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+The Project Gutenberg EBook of Scientific American Supplement, No. 441,
+June 14, 1884., by Various
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Scientific American Supplement, No. 441, June 14, 1884.
+
+Author: Various
+
+Release Date: May 16, 2005 [EBook #15833]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK SCIENTIFIC AMERICAN ***
+
+
+
+
+Produced by Juliet Sutherland and the Online Distributed
+Proofreading Team at www.pgdp.net.
+
+
+
+
+
+[Illustration]
+
+
+
+
+SCIENTIFIC AMERICAN SUPPLEMENT NO. 441
+
+
+
+
+NEW YORK, JUNE 14, 1884
+
+Scientific American Supplement. Vol. XVII., No. 441.
+
+Scientific American established 1845
+
+Scientific American Supplement, $5 a year.
+
+Scientific American and Supplement, $7 a year.
+
+       *       *       *       *       *
+
+
+
+
+TABLE OF CONTENTS.
+
+
+I.   CHEMISTRY AND METALLURGY.--On Electrolysis.--Precipitation
+     of lead, thallium, silver, bismuth, manganese, etc.--By H.
+     SCHUCHT
+
+     The Electro-Chemical Equivalent of Silver
+
+     Zircon.--How it can be rendered soluble.--By F. STOLBA
+
+     A New Process for Making Wrought Iron Directly from the Ore.
+     --Comparison with other processes.--With descriptions and
+     engravings of the apparatus used
+
+     Some Remarks on the Determination of Hardness in Water
+
+     On the changes which Take Place in the Conversion of Hay
+     into Ensilage.--By F.J. Lloyd
+
+II.  ENGINEERING AND MECHANICS.--Faure's Machine for
+     Decorticating Sugar Cane.--With full description
+     and 13 figures
+
+     The Generation of Steam and the Thermodynamic Problems
+     Involved.--By WM. ANDERSON.--Apparatus used in the
+     experimental determination of the heat of combustion and
+     the laws which govern its development.--Ingredients of
+     fuel.--Potential energy of fuel.--With 7 figures and
+     several tables
+
+     Planetary Wheel Trains.--Rotations of the wheels relatively
+     to the train arm.--By Prof. C.W. MACCORD
+
+     The Pantanemone.--A New Windwheel.--1 engraving
+
+     Relvas's New Life Boat.--With engraving
+
+     Experiments with Double Barreled Guns and Rifles.
+     --Cause of the divergence of the charge.--4 figures
+
+     Improved Ball Turning Machine.--1 figure
+
+     Cooling Apparatus for Injection Water.--With engraving
+
+     Corrugated Disk Pulleys.--1 engraving
+
+III. TECHNOLOGY.--A New Standard Light
+
+     Dr. Feussner's New Polarizing Prism.--Points of difference
+     between the old and new prisms.--By P.R. SLEEMAN
+
+     Density and Pressure of Detonating Gas
+
+IV.  ELECTRICITY, LIGHT, ETC.--Early History of the Telegraph.
+     --Pyrsia, or the system of telegraphy among the Greeks.
+     --Communication by means of characters and the telescope.
+     --Introduction of the magnetic telegraph between Baltimore
+     and Washington
+
+     The Kravogl Electro Motor and its Conversion Into a Dynamo
+     Electric Machine.--5 figures
+
+     Bornhardt's Electric Machine for Blasting in Mines.
+     --15 figures
+
+     Pritchett's Electric Fire Alarm.--1 figure
+
+     A Standard Thermopile
+
+     Telephonic Transmission without Receivers.--Some of the
+     apparatus exhibited at the annual meeting of the French
+     Society of Physics.--Telephonic transmission through a
+     chain of persons
+
+     Diffraction Phenomena during Total Solar Eclipses.--By G.D.
+     Hiscox
+
+V.   BOTANY AND HORTICULTURE.--Gum Diseases in Trees.--
+     Cause and contagion of the same
+
+     Drinkstone Park.--Trees and plants cultivated therein.--
+     With 2 engravings
+
+VI.  MEDICINE AND HYGIENE.--Miryachit.--A newly-discovered
+     disease of the nervous system, and its analogues.--By WM. A.
+     HAMMOND
+
+VII. MISCELLANEOUS.--Turkish Baths for Horses.--With
+     diagram.
+
+       *       *       *       *       *
+
+
+
+
+FAURE'S MACHINE FOR DECORTICATING SUGAR-CANE.
+
+
+The object of the apparatus shown in the accompanying engraving is to
+effect a separation of the tough epidermis of the sugar-cane from the
+internal spongy pith which is to be pressed. Its function consists in
+isolating and separating the cells from their cortex, and in putting
+them in direct contact with the rollers or cylinders of the mill.
+After their passage into the apparatus, which is naturally placed in a
+line with the endless chain that carries them to the mill, the canes
+arrive in less compact layers, pass through much narrower spaces, and
+finally undergo a more efficient pressure, which is shown by an
+abundant flow of juice. The first trials of the machine were made in
+1879 at the Pointe Simon Works, at Martinique, with the small type
+that was shown at the Paris Exhibition of 1878. These experiments,
+which were applied to a work of 3,000 kilos of cane per hour, gave
+entire satisfaction, and decided the owners of three of the colonial
+works (Pointe Simon, Larcinty, and Marin) to adopt it for the season
+of 1880.
+
+The apparatus is shown in longitudinal section in Fig. 1, and in plan
+in Fig. 2.
+
+Fig. 3 gives a transverse section passing through the line 3-4, and
+Fig. 4 an external view on the side whence the decorticated canes make
+their exit from the apparatus.
+
+[Illustration: FAURE'S MACHINE FOR DECORTICATING SUGAR CANE.]
+
+The other figures relate to details that will be referred to further
+along.
+
+_The Decorticating Cylinder._--The principal part of the apparatus is
+a hollow drum, A, of cast iron, 430 mm. in internal diameter by 1.41
+m. in length, which is keyed at its two extremities to the shaft, a.
+Externally, this drum (which is represented apart in transverse
+section in Fig. 5) has the form of an octagonal prism with well
+dressed projections between which are fixed the eight plates, C, that
+constitute the decorticating cylinder. These plates, which are of
+tempered cast iron, and one of which is shown in transverse section in
+Fig. 7, when once in place form a cylindrical surface provided with 48
+helicoidal, dentate channels. The length of these plates is 470 mm.
+There are three of them in the direction of the generatrices of the
+cylinder, and this makes a total of 24. All are strengthened by ribs
+(as shown in Fig. 8), and each is fixed by 4 bolts, _c_, 20mm. in
+diameter. The pitch of the helices of each tooth is very elongated,
+and reaches about 7.52 m. The depth of the toothing is 18 mm.
+
+_Frame and Endless Chain._--The cylinder thus constructed rotates with
+a velocity of 50 revolutions per minute over a cylindrical vessel, B',
+cast in a piece with the frame, B. This vessel is lined with two
+series of tempered cast iron plates, D and D', called exit and
+entrance plates, which rest thereon, through the intermedium of well
+dressed pedicels, and which are held in place by six 20-millimeter
+bolts. Their length is 708 mm. The entrance plates, D, are provided
+with 6 spiral channels, whose pitch is equal to that of the channels
+of the decorticating cylinder, C, and in the same direction. The depth
+of the toothing is 10 mm.
+
+The exit plates, D', are provided with 7 spiral channels of the same
+pitch and direction as those of the preceding, but the depth of which
+increases from 2 to 10 mm. The axis of the decorticating cylinder does
+not coincide with that of the vessel, B', so that the free interval
+for the passage of the cane continues to diminish from the entrance to
+the exit.
+
+The passage of the cane to the decorticator gives rise to a small
+quantity of juice, which flows through two orifices, _b'_, into a sort
+of cast iron trough, G, suspended beneath the vessel. The cane, which
+is brought to the apparatus by an endless belt, empties in a conduit
+formed of an inclined bottom, E, of plate iron, and two cast iron
+sides provided with ribs. These sides rest upon the two ends of the
+vessel, B', and are cross-braced by two flat bars, _e_, to which is
+bolted the bottom, E. This conduit is prolonged beyond the
+decorticating cylinder by an inclined chute, F, the bottom of which is
+made of plate iron 7 mm. thick and the sides of the same material 9
+mm. thick. The hollow frame, B, whose general form is like that of a
+saddle, carries the bearings, _b_, in which revolves the shaft, _a_.
+One of these bearings is represented in detail in Figs. 9 and 10. It
+will be seen that the cap is held by bolts with sunken heads, and that
+the bearing on the bushes is through horizontal surfaces only. In a
+piece with this frame are cast two similar brackets, B�, which support
+the axle, _h_, of the endless chain. To this axle, whose diameter is
+100 mm., are keyed, toward the extremities, the pinions, H, to which
+correspond the endless pitch chains, _i_. These latter are formed, as
+may be seen in Figs. 11 and 12, of two series of links. The shorter of
+these latter are only 100 mm. in length, while the longer are 210 mm.,
+and are hollowed out so as to receive the butts of the boards, I. The
+chain thus formed passes over two pitch pinions, J, like the pinions,
+H, that are mounted at the extremities of an axle, _j_, that revolves
+in bearings, I', whose position with regard to the apparatus is
+capable of being varied so as to slacken or tauten the chain, I. This
+arrangement is shown in elevation in Fig. 13.
+
+_Transmission._--The driving shaft, _k_, revolves in a pillow block,
+K, cast in a piece with the frame, B. It is usually actuated by a
+special motor, and carries a fly-wheel (not shown in the figure for
+want of space). It receives in addition a cog-wheel, L, which
+transmits its motion to the decorticating cylinder through, the
+intermedium of a large wooden-toothed gear wheel, L'. The shaft, _a_,
+whose diameter is 228 mm., actuates in its turn, through the pinions,
+M' and M, the pitch pinion, N, upon whose prolonged hub is keyed the
+pinion, M. This latter is mounted loosely upon the intermediate axle,
+_m_. Motion is transmitted to the driving shaft, _h_, of the endless
+chain, I, by an ordinary pitch chain, through a gearing which is shown
+in Fig. 12. The pitch pinion, N', is cast in a piece with a hollow
+friction cone, N�, which is mounted loosely upon the shaft, _h_, and
+to which corresponds a second friction cone, O. This latter is
+connected by a key to a socket, _o_, upon which it slides, and which
+is itself keyed to the shaft, _h_. The hub of the cone, O, is
+connected by a ring with a bronze nut, _p_, mounted at the threaded
+end of the shaft, _h_, and carrying a hand-wheel, P. It is only
+necessary to turn this latter in one direction or the other in order
+to throw the two cones into or out of gear.
+
+If we allow that the motor has a velocity of 70 revolutions per
+minute, the decorticating cylinder will run at the rate of 50, and the
+sugar-cane will move forward at the rate of 12 meters per minute.
+
+This new machine is a very simple and powerful one. The decortication
+is effected with wonderful rapidity, and the canes, opened throughout
+their entire length and at all points of their circumference, leave
+the apparatus in a state that allows of no doubt as to what the result
+of the pressure will be that they have to undergo. There is no
+tearing, no trituration, no loss of juice, but merely a simple
+preparation for a rational pressure effected under most favorable
+conditions.
+
+The apparatus, which is made in several sizes, has already received
+numerous applications in Martinique, Trinidad, Cuba, Antigua, St.
+Domingo, Peru, Australia, the Mauritius Islands, and
+Brazil.--_Publication Industrielle._
+
+       *       *       *       *       *
+
+
+
+
+MOVING A BRIDGE.
+
+
+An interesting piece of engineering work has recently been
+accomplished at Bristol, England, which consisted in the moving of a
+foot-bridge 134 feet in length, bodily, down the river a considerable
+distance. The pontoons by means of which the bridge was floated to its
+new position consisted of four 80-ton barges, braced together so as to
+form one solid structure 64 feet in width, and were placed in position
+soon after the tide commenced to rise. At six o'clock A.M. the top of
+the stages, which was 24 feet above the water, touched the under part
+of the bridge, and in a quarter of an hour later both ends rose from
+their foundations. When the tide had risen 4 ft. the stage and bridge
+were floated to the new position, when at 8.30 the girders dropped on
+to their beds.
+
+       *       *       *       *       *
+
+
+
+
+THE GENERATION OF STEAM, AND THE THERMODYNAMIC PROBLEMS
+INVOLVED.[1]
+
+   [Footnote 1: Lecture delivered at the Institution of Civil
+   Engineers, session 1883-84. For the illustrations we are indebted
+   to the courtesy of Mr. J. Forrest, the secretary.]
+
+By Mr. WILLIAM ANDERSON, M.I.C.E.
+
+
+It will not be necessary to commence this lecture by explaining the
+origin of fuel; it will be sufficient if I remind you that it is to
+the action of the complex rays of the sun upon the foliage of plants
+that we mainly owe our supply of combustibles. The tree trunks and
+branches of our forests, as well as the subterranean deposits of coal
+and naphtha, at one time formed portions of the atmosphere in the form
+of carbonic acid gas; that gas was decomposed by the energy of the
+solar rays, the carbon and the oxygen were placed in positions of
+advantage with respect to each other--endowed with potential energy;
+and it is my duty this evening to show how we can best make use of
+these relations, and by once more combining the constituents of fuel
+with the oxygen of the air, reverse the action which caused the growth
+of the plants, that is to say, by destroying the plant reproduce the
+heat and light which fostered it. The energy which can be set free by
+this process cannot be greater than that derived originally from the
+sun, and which, acting through the frail mechanism of green leaves,
+tore asunder the strong bonds of chemical affinity wherein the carbon
+and oxygen were hound, converting the former into the ligneous
+portions of the plants and setting the latter free for other uses. The
+power thus silently exerted is enormous; for every ton of carbon
+separated in twelve hours necessitates an expenditure of energy
+represented by at least 1,058 horse power, but the action is spread
+over an enormous area of leaf surface, rendered necessary by the small
+proportion of carbonic acid contained in the air, by measure only
+1/2000 part, and hence the action is silent and imperceptible. It is
+now conceded on all hands that what is termed heat is the energy of
+molecular motion, and that this motion is convertible into various
+kinds and obeys the general laws relating to motion. Two substances
+brought within the range of chemical affinity unite with more or less
+violence; the motion of transition of the particles is transformed,
+wholly or in part, into a vibratory or rotary motion, either of the
+particles themselves or the interatomic ether; and according to the
+quality of the motions we are as a rule, besides other effects, made
+conscious of heat or light, or of both. When these emanations come to
+be examined they are found to be complex in the extreme, intimately
+bound up together, and yet capable of being separated and analyzed.
+
+As soon as the law of definite chemical combination was firmly
+established, the circumstance that changes of temperature accompanied
+most chemical combinations was noticed, and chemists were not long in
+suspecting that the amount of heat developed or absorbed by chemical
+reaction should be as much a property of the substances entering into
+combination as their atomic weights. Solid ground for this expectation
+lies in the dynamic theory of heat. A body of water at a given height
+is competent by its fall to produce a definite and invariable quantity
+of heat or work, and in the same way two substances falling together
+in chemical union acquire a definite amount of kinetic energy, which,
+if not expended in the work of molecular changes, may also by suitable
+arrangements be made to manifest a definite and invariable quantity of
+heat.
+
+At the end of last century Lavoisier and Laplace, and after them, down
+to our own time, Dulong, Desprez, Favre and Silbermann, Andrews,
+Berthelot, Thomson, and others, devoted much time and labor to the
+experimental determination of the heat of combustion and the laws
+which governed its development. Messrs. Favre and Silbermann, in
+particular, between the years 1845 and 1852, carried out a splendid
+series of experiments by means of the apparatus partly represented in
+Fig. 1 (opposite), which is a drawing one-third the natural size of
+the calorimeter employed. It consisted essentially of a combustion
+chamber formed of thin copper, gilt internally. The upper part of the
+chamber was fitted with a cover through which the combustible could be
+introduced, with a pipe for a gas jet, with a peep hole closed by
+adiathermanous but transparent substances, alum and glass, and with a
+branch leading to a thin copper coil surrounding the lower part of the
+chamber and descending below it. The whole of this portion of the
+apparatus was plunged into a thin copper vessel, silvered internally
+and filled with water, which was kept thoroughly mixed by means of
+agitators. This second vessel stood inside a third one, the sides and
+bottom of which were covered with the skins of swans with the down on,
+and the whole was immersed in a fourth vessel tilled with water, kept
+at the average temperature of the laboratory. Suitable thermometers of
+great delicacy were provided, and all manner of precautions were taken
+to prevent loss of heat.
+
+[Illustration: THE GENERATION OF STEAM. Fig 1.]
+
+It is impossible not to admire the ingenuity and skill exhibited in
+the details of the apparatus, in the various accessories for
+generating and storing the gases used, and for absorbing and weighing
+the products of combustion; but it is a matter of regret that the
+experiments should have been carried out on so small a scale. For
+example, the little cage which held the solid fuel tested was only 5/8
+inch diameter by barely 2 inches high, and held only 38 grains of
+charcoal, the combustion occupying about sixteen minutes. Favre and
+Silbermann adopted the plan of ascertaining the weight of the
+substances consumed by calculation from the weight of the products of
+combustion. Carbonic acid was absorbed by caustic potash, as also was
+carbonic oxide, after having been oxidized to carbonic acid by heated
+oxide of copper, and the vapor of water was absorbed by concentrated
+sulphuric acid. The adoption of this system showed that it was in any
+case necessary to analyze the products of combustion in order to
+detect imperfect action. Thus, in the case of substances containing
+carbon, carbonic oxide was always present to a variable extent with
+the carbonic acid, and corrections were necessary in order to
+determine the total heat due to the complete combination of the
+substance with oxygen. Another advantage gained was that the
+absorption of the products of combustion prevents any sensible
+alteration in the volumes during the process, so that corrections for
+the heat absorbed in the work of displacing the atmosphere were not
+required. The experiments on various substances were repeated many
+times. The mean results for those in which we are immediately
+interested are given in Table I., next column.
+
+Comparison with later determinations have established their
+substantial accuracy. The general conclusion arrived at is thus
+stated:
+
+"As a rule there is an equality between the heat disengaged or
+absorbed in the acts, respectively, of chemical combination or
+decomposition of the same elements, so that the heat evolved during
+the combination of two simple or com-pound substances is equal to the
+heat absorbed at the time of their chemical segregation."
+
+       TABLE I.--SUBSTANCES ENTERING INTO THE COMPOSITION OF FUEL.
+
+  -----------------------+-------------+-----------+-------------------+
+                         |                         | Heat evolved in   |
+                         |     Symbol and Atomic   |the Combustion of  |
+                         |           Weight.       |  1 lb. of Fuel.   |
+                         +------------+------------+--------+----------+
+                         |            |            |        |In Pounds |
+                         |            |            |  In    | of Water |
+                         |            |            |British |Evaporated|
+                         |   Before   |    After   |Thermal | from and |
+                         | Combustion | Combustion | Units. | at 212�. |
+                         +------------+------------+--------+----------+
+  Hydrogen burned        | H        1 | H2O     18 | 62,032 |  64.21   |
+    in oxygen.           |            |            |        |          |
+  -----------------------+------------+------------+--------+----------+
+  Carbon burned to       | C       12 | CO      28 |  4,451 |   4.61   |
+    carbonic oxide.      |            |            |        |          |
+  -----------------------+------------+------------+--------+----------+
+  Carbon burned to       | C       12 | CO2     44 | 14,544 |  15.06   |
+    carbonic acid.       |            |            |        |          |
+  -----------------------+------------+------------+--------+----------+
+  Carbonic oxide burned  | CO      28 | CO2     44 |  4,326 |   4.48   |
+    to carbonic acid.    |            |            |        |          |
+  -----------------------+------------+------------+--------+----------+
+  Olefiant gas (ethylene)| C2H4    28 | 2CO2   124 | 21,343 |  22.09   |
+    burnt in oxygen.     |            | 2H2O       |        |          |
+  -----------------------+------------+------------+--------+----------+
+  Marsh gas (methane)    | CH4     16 | 2CO2    80 | 23,513 |  24.34   |
+  burnt in oxygen.       |            | 2H2O       |        |          |
+  -----------------------+------------+------------+--------+----------+
+
+Composition of air--
+
+  by volume 0.788 N + 0.197 O + 0.001 CO2 + 0.014 H2O
+  ----------------------------------------------------
+  by weight 0.771 N + 0.218 O + 0.009 CO2 + 0.017 H2O
+
+This law is, however, subject to some apparent exceptions. Carbon
+burned in protoxide of nitrogen, or laughing gas, N_{2}O, produces
+about 38 per cent. more heat than the same substance burned in pure
+oxygen, notwithstanding that the work of decomposing the protoxide of
+nitrogen has to be performed. In marsh gas, or methane, CH_{4}, again,
+the energy of combustion is considerably less than that due to the
+burning of its carbon and hydrogen separately. These exceptions
+probably arise from the circumstance that the energy of chemical
+action is absorbed to a greater or less degree in effecting molecular
+changes, as, for example, the combustion of 1 pound of nitrogen to
+form protoxide of nitrogen results in the absorption of 1,157 units of
+heat. Berthelot states, as one of the fundamental principles of
+thermochemistry, "that the quantity of heat evolved is the measure of
+the sum of the chemical and physical work accomplished in the
+reaction"; and such a law will no doubt account for the phenomena
+above noted. The equivalent heat of combustion of the compounds we
+have practically to deal with has been experimentally determined, and
+therefore constitutes a secure basis on which to establish
+calculations of the caloric value of fuel; and in doing so, with
+respect to substances composed of carbon, hydrogen, and oxygen, it is
+convenient to reduce the hydrogen to its heat-producing equivalent of
+carbon. The heat of combustion of hydrogen being 62,032 units, that of
+carbon 14,544 units, it follows that 4.265 times the weight of
+hydrogen will represent an equivalent amount of carbon. With respect
+to the oxygen, it is found that it exists in combination with the
+hydrogen in the form of water, and, being combined already, abstracts
+its combining equivalent of hydrogen from the efficient ingredients of
+the fuel; and hence hydrogen, to the extent of 1/8 of the weight of
+the oxygen, must be deducted. The general formula then becomes:
+
+       Heat of combustion = 14,544 {C + 4.265 (H-(O/8))},
+
+and water evaporated from and at 212�, taking 966 units as the heat
+necessary to evaporate 1 pound of water,
+
+       lb. evaporated = 15.06 {C + 4.265 (H-(O/8))},
+
+carbon, hydrogen, and oxygen being taken at their weight per cent. in
+the fuel. Strictly speaking, marsh gas should be separately
+determined. It often happens that available energy is not in a form in
+which it can be applied directly to our needs. The water flowing down
+from the mountains in the neighborhood of the Alpine tunnels was
+competent to provide the power necessary for boring through them, but
+it was not in a form in which it could be directly applied. The
+kinetic energy of the water had first to be changed into the potential
+energy of air under pressure, then, in that form, by suitable
+mechanism, it was used with signal success to disintegrate and
+excavate the hard rock of the tunnels. The energy resulting from
+combustion is also incapable of being directly transformed into useful
+motive power; it must first be converted into potential force of steam
+or air at high temperature and pressure, and then applied by means of
+suitable heat engines to produce the motions we require. It is
+probably to this circumstance that we must attribute the slowness of
+the human race to take advantage of the energy of combustion. The
+history of the steam engine hardly dates back 200 years, a very small
+fraction of the centuries during which man has existed, even since
+historic times.
+
+The apparatus by means of which the potential energy of fuel with
+respect to oxygen is converted into the potential energy of steam, we
+call a steam boiler; and although it has neither cylinder nor piston,
+crank nor fly wheel, I claim for it that it is a veritable heat
+engine, because it transmits the undulations and vibrations caused by
+the energy of chemical combination in the fuel to the water in the
+boiler; these motions expend themselves in overcoming the liquid
+cohesion of the water and imparting to its molecules that vigor of
+motion which converts them into the molecules of a gas which,
+impinging on the surfaces which confine it and form the steam space,
+declare their presence and energy in the shape of pressure and
+temperature. A steam pumping engine, which furnishes water under high
+pressure to raise loads by means of hydraulic cranes, is not more
+truly a heat engine than a simple boiler, for the latter converts the
+latent energy of fuel into the latent energy of steam, just as the
+pumping engine converts the latent energy of steam into the latent
+energy of the pumped-up accumulator or the hoisted weight.
+
+If I am justified in taking this view, then I am justified in applying
+to my heat engine the general principles laid down in 1824 by Sadi
+Carnot, namely, that the proportion of work which can be obtained out
+of any substance working between two temperatures depends entirely and
+solely upon the difference between the temperatures at the beginning
+and end of the operation; that is to say, if T be the higher
+temperature at the beginning, and _t_ the lower temperature at the end
+of the action, then the maximum possible work to be got out of the
+substance will be a function of (T-_t_). The greatest range of
+temperature possible or conceivable is from the absolute temperature
+of the substance at the commencement of the operation down to absolute
+zero of temperature, and the fraction of this which can be utilized is
+the ratio which the range of temperature through which the substance
+is working bears to the absolute temperature at the commencement of
+the action. If W = the greatest amount of effect to be expected, T and
+_t_ the absolute temperatures, and H the total quantity of heat
+(expressed in foot pounds or in water evaporated, as the case may be)
+potential in the substance at the higher temperature, T, at the
+beginning of the operation, then Carnot's law is expressed by the
+equation:
+
+         / T - t \
+   W = H( ------- )
+         \   T   /
+
+I will illustrate this important doctrine in the manner which Carnot
+himself suggested.
+
+[Illustration: THE GENERATION OF STEAM. Fig 2.]
+
+Fig. 2 represents a hillside rising from the sea. Some distance up
+there is a lake, L, fed by streams coming down from a still higher
+level. Lower down on the slope is a millpond, P, the tail race from
+which falls into the sea. At the millpond is established a factory,
+the turbine driving which is supplied with water by a pipe descending
+from the lake, L. Datum is the mean sea level; the level of the lake
+is T, and of the millpond _t_. Q is the weight of water falling
+through the turbine per minute. The mean sea level is the lowest level
+to which the water can possibly fall; hence its greatest potential
+energy, that of its position in the lake, = QT = H. The water is
+working between the absolute levels, T and _t_; hence, according to
+Carnot, the maximum effect, W, to be expected is--
+
+         / T - t \
+   W = H( ------- )
+         \   T   /
+                                / T - t \
+but H = QT [therefore]  W = Q T( ------- )
+                                \   T   /
+
+   W = Q (T - t),
+
+that is to say, the greatest amount of work which can be expected is
+found by multiplying the weight of water into the clear fall, which
+is, of course, self-evident.
+
+Now, how can the quantity of work to be got out of a given weight of
+water be increased without in any way improving the efficiency of the
+turbine? In two ways:
+
+1. By collecting the water higher up the mountain, and by that means
+increasing T.
+
+2. By placing the turbine lower down, nearer the sea, and by that
+means reducing _t_.
+
+Now, the sea level corresponds to the absolute zero of temperature,
+and the heights T and _t_ to the maximum and minimum temperatures
+between which the substance is working; therefore similarly, the way
+to increase the efficiency of a heat engine, such as a boiler, is to
+raise the temperature of the furnace to the utmost, and reduce the
+heat of the smoke to the lowest possible point. It should be noted, in
+addition, that it is immaterial what liquid there may be in the lake;
+whether water, oil, mercury, or what not, the law will equally apply,
+and so in a heat engine, the nature of the working substance, provided
+that it does not change its physical state during a cycle, does not
+affect the question of efficiency with which the heat being expended
+is so utilized. To make this matter clearer, and give it a practical
+bearing, I will give the symbols a numerical value, and for this
+purpose I will, for the sake of simplicity, suppose that the fuel used
+is pure carbon, such as coke or charcoal, the heat of combustion of
+which is 14,544 units, that the specific heat of air, and of the
+products of combustion at constant pressure, is 0.238, that only
+sufficient air is passed through the fire to supply the quantity of
+oxygen theoretically required for the combustion of the carbon, and
+that the temperature of the air is at 60� Fahrenheit = 520� absolute.
+The symbol T represents the absolute temperature of the furnace, a
+value which is easily calculated in the following manner: 1 lb. of
+carbon requires 2-2/3 lb. of oxygen to convert it into carbonic acid,
+and this quantity is furnished by 12.2 lb. of air, the result being
+13.2 lb. of gases, heated by 14,544 units of heat due to the energy of
+combustion; therefore:
+
+                14,544 units
+  T = 520� + ------------------ = 5,150� absolute.
+              13.2 lb. X 0.238
+
+The lower temperature, _t_, we may take as that of the feed water, say
+at 100� or 560� absolute, for by means of artificial draught and
+sufficiently extending the heating surface, the temperature of the
+smoke may be reduced to very nearly that of the feed water. Under such
+circumstances the proportion of heat which can be realized is
+
+       5,150� - 560�
+    = --------------- = 0.891;
+           5,150�
+
+that is to say, under the extremely favorable if not impracticable
+conditions assumed, there must be a loss of 11 per cent. Next, to give
+a numerical value to the potential energy, H, to be derived from a
+pound of carbon, calculating from absolute zero, the specific heat of
+carbon being 0.25, and absolute temperature of air 520�:
+
+                                              Units.
+  1 lb. of carbon X 0.25 X 520              =    130
+  12.2 of air X 0.238 X 520                 =  1,485
+  Heat of combustion                        = 14,544
+                                              ------
+                                              16,159
+  Deduct heat equivalent to work of       \
+    displacing atmosphere by products of   }
+    combustion raised from 60� to 100�,    }      32
+    or from 149.8 cubic feet to 161.3      }
+    cubic feet,                           /
+                                              ------
+          Total units of heat available       16,127
+
+Equal to 16.69 lb. of water evaporated from and at 212�. Hence the
+greatest possible evaporation from and at 212� from a lb. of carbon--
+
+       16,159 u. X 0.891 - 32 u.
+  W = --------------------------- = 14.87 lb.
+               966 u.
+
+I will now take a definite case, and compare the potential energy of a
+certain kind of fuel with the results actually obtained. For this
+purpose the boiler of the eight-horse portable engine, which gained
+the first prize at the Cardiff show of the Royal Agricultural Society
+in 1872, will serve very well, because the trials, all the details of
+which are set forth very fully in vol. ix. of the _Journal_ of the
+Society, were carried out with great care and skill by Sir Frederick
+Bramwell and the late Mr. Menelaus; indeed, the only fact left
+undetermined was the temperature of the furnace, an omission due to
+the want of a trustworthy pyrometer, a want which has not been
+satisfied to this day.[2]
+
+   [Footnote 2: In the fifty-second volume of the _Proceedings_
+   (1887-78), page 154, will be found a remarkable experiment on the
+   evaporative power of a vertical boiler with internal circulating
+   pipes. The experiment was conducted by Sir Frederick Bramwell and
+   Dr. Russell, and is remarkable in this respect, that the quantity
+   of air admitted to the fuel, the loss by convection and
+   radiation, and the composition of the smoke were determined. The
+   facts observed were as follows:
+
+   Steam pressure 53 lb................................... = 300.6� F.
+                                                               lb.
+   Fuel--Water in coke and wood...........................    26.08
+         Ash..............................................    10.53
+         Hydrogen, oxygen, nitrogen, and sulphur..........     7.18
+                                                             ------
+                Total non-combustible.....................    43.79
+         Carbon, being useful combustible.................   194.46
+                                                             ------
+                Total fuel................................   238.25
+
+   Air per pound of carbon................................   17-1/8 lb.
+   Time of experiment.....................................  4 h. 12 min.
+   Water evaporated from 60� into steam at 53 lb. pressure   1,620 lb.
+   Heat lost by radiation and convection..................  70,430 units.
+   Mean temperature of chimney............................    700� F.
+    "        "       " air................................     70� F.
+
+   No combustible gas was found in the chimney.
+
+   I will apply Carnot's doctrine to this case.
+
+   Potential energy of the fuel with respect to absolute zero:
+                                                               Units.
+     239.25 lb. � 530� abs. � 0.238 ...................... =   30,053
+     194.46 lb. � 17-1/8 � 530� � 0.238,
+         the weight and heat of air.......................    420,660
+     194.46 � 14,544 units heat of combustion of carbon...  2,828,200
+                                                            ---------
+                Total energy                                3,278,813
+     Heat absorbed in evaporating 26.08 lb. of water
+       in fuel............................................    -29,888
+                                                            ---------
+                Available energy..........................  3,248,425
+
+   Temperature of furnace--
+
+   The whole of the fuel was heated up, but the heat absorbed in the
+   evaporation of the water lowered the temperature of the furnace,
+   and must be deducted from the heat of combustion.
+
+                                                                Units.
+     Heat of combustion...................................  2,828,200
+       "   " evaporation of 26.08 lb. water...............    -29,888
+                                                            ---------
+                Available heat of combustion..............  2,798,312
+
+     Dividing by 238.25 lb. gives the heat per 1 lb.
+       of fuel used................................... = 11,745 units.
+     And temperature of furnace:
+     11,745 units/(18.125 lb. � 0.238) + 530�......... = 3,253�
+     Temperature of chimney 700� + 460�............... = 1,160�
+     Maximum duty (3,253� - 1,160�)/3,253�............ = 0.643�
+
+   Work of displacing atmosphere by smoke at 700�:
+                                                         Cubic feet.
+      Volumes of gases at  70�........................    = 228.3
+        "      "   "    " 700�........................    = 499.8
+                                                            -----
+                Increase of volume....................      271.5
+
+                                                             Units.
+     Work done=
+     (194.46 lb. � 271.5 cub. ft. � 144 sq. in. � 15 lb.)
+      /722 units ..................................... =   147,720
+     Maximum amount of work to be expected =
+       3,248,425 � 0.643.............................. = 2,101,700
+     Deduct work of displacing atmosphere............. =   147,720
+                                                         ---------
+                Available work........................   1,953,980
+
+   Actual work done:
+                                                             Units.
+     1,620 lb. of water raised from 60� and turned
+       into steam at 53 lb..... ...................... = 1,855,900
+     Loss by radiation and convection.................      70,430
+     10-1/2 lb. ashes left, say at 500�...............       1,129
+                                                         ---------
+                Total work actually done..............   1,927,459
+     Unaccounted for..................................      26,521
+                                                         ---------
+     Calculated available work........................   1,953,980
+
+   The unaccounted-for work, therefore, amounts to only 1� per cent.
+   of the calculated available work.
+
+   Sir Frederick Bramwell ingeniously arranged his data in the form
+   of a balance sheet, and showed 253,979 units unaccounted for; but
+   if from this we deduct the work lost in displacing the air, the
+   unaccounted-for heat falls to less than 4 per cent. of the total
+   heat of combustion. These results show how extremely accurate the
+   observations must have been, and that the loss mainly arises from
+   convection and radiation from the boiler.]
+
+The data necessary for our purpose are:
+
+Steam pressure 80 lb. temperature                    324� = 784� absolute.
+Mean temperature of smoke                            389� = 849�    "
+Water evaporated per 1 lb of coal, from and at 212�  11.83 lb.
+Temperature of the air                                60� = 520� absolute.
+     "      of feed water                            209� = 669�    "
+Heating surface                                      220 square feet.
+Grate surface                                        3.29 feet.
+Coal burnt per hour                                  41 lb.
+
+The fuel used was a smokeless Welsh coal, from the Llangennech
+colleries. It was analyzed by Mr. Snelus, of the Dowlais Ironworks,
+and in Table II. are exhibited the details of its composition, and the
+weight and volume of air required for its combustion. The total heat
+of combustion in 1 lb of water evaporated:
+
+      = 15.06 � (0.8497 + 4.265 � (0.426 - 0.035/8))
+      = 15.24 lb. of water from and at 212�
+      = 14,727 units of heat.
+
+           TABLE II.--PROPERTIES OF LLANGENNECH COAL.
+
+  ---------------------+----------+------------+---------------------+
+                       |          |            |                     |
+                       |          |            |    Products of      |
+                       |          |  Oxygen    | Combustion at 32� F.|
+                       | Analyses | required   +--------+------------+
+                       | of 1 lb. |    for     |        |            |
+                       | of Coal. | Combustion.| Cubic  |  Volume    |
+                       |          | Pounds.    | feet.  | per cent.  |
+  ---------------------+----------+------------+--------+------------+
+   Carbon...........   |  0.8497  |  2.266     |  25.3  |     11.1   |
+   Hydrogen.........   |  0.0426  |  0.309     |   7.6  |      3.4   |
+   Oxygen...........   |  0.0350  |    ---     |   ---  |      ---   |
+   Sulphur..........   |  0.0042  |    ---     |   ---  | _    ---   |
+   Nitrogen.........   |  0.1045  |    ---     |   0.18 |  |         |
+   Ash..............   |  0.0540  |    ---     |   ---  |  |         |
+                       +----------+------------+        |  |  85.5   |
+                       |          |            |        |  |         |
+    Total...........   |  1.0000  |  2.572     |   ---  |  |         |
+  9-1/3.lb nitrogen    |    ---   |    ---     | 118.9  |  |         |
+  6 lb. excess of air. |    ---   |    ---     |  71.4  | _|         |
+                       +----------+------------+--------+------------+
+  Total cubic feet of  |          |            |        |            |
+  products per 1 lb.   |          |            |        |            |
+  of coal...........   |    --    |    --      | 226.4  |    100.0   |
+  ---------------------+----------+------------+--------+------------+
+
+The temperature of the furnace not having been determined, we must
+calculate it on the supposition, which will be justified later on,
+that 50 per cent more air was admitted than was theoretically
+necessary to supply the oxygen required for perfect combustion. This
+would make 18 lb. of air per 1 lb. of coal; consequently 19 lb. of
+gases would be heated by 14,727 units of heat. Hence:
+
+         14,727 u.
+  T = ---------------- = 3,257�
+       19 lb. � 0.238
+
+above the temperatures of the air, or 3,777� absolute. The temperature
+of the smoke, _t_, was 849� absolute; hence the maximum duty would be
+
+      3,777� - 849�
+     --------------- = 0.7752.
+          3,777�
+
+The specific heat of coal is very nearly that of gases at constant
+pressure, and may, without sensible error, be taken as such. The
+potential energy of 1 lb. of coal, therefore, with reference to the
+oxygen with which it will combine, and calculated from absolute zero,
+is:
+
+                                                              Units.
+19 lb. of coal and air at the temperature
+  of the air contained 19 lb. � 520� � 0.238                   2,350
+Heat of combustion                                            14,727
+                                                             -------
+                                                              17,078
+Deduct heat expended in displacing atmosphere 151 cubic feet   - 422
+                                                              ------
+            Total potential energy                            16,656
+
+Hence work to be expected from the boiler:
+
+                    / 3,777� - 849� \
+  = 17,078 units X ( --------------- ) - 422 units
+                    \     3,777�    /
+    ---------------------------------------------- = 13.27 lb.
+                         966 units
+
+of water evaporated from and at 212�, corresponding to 12,819 units.
+The actual result obtained was 11.83 lb.; hence the efficiency of this
+boiler was
+
+    11.83
+   ------- = 0.892.
+    13.27
+
+I have already claimed for a boiler that it is a veritable heat
+engine, and I have ventured to construct an indicator diagram to
+illustrate its working. The rate of transfer of heat from the furnace
+to the water in the boiler, at any given point, is some way
+proportional to the difference of temperature, and the quantity of
+heat in the gases is proportional to their temperatures. Draw a base
+line representing -460� Fahr., the absolute zero of temperature. At
+one end erect an ordinate, upon which set off T = 3,777�, the
+temperature of the furnace. At 849� = _t_, on the scale of
+temperature, draw a line parallel to the base, and mark on it a length
+proportional to the heating surface of the boiler; join T by a
+diagonal with the extremity of this line, and drop a perpendicular on
+to the zero line. The temperature of the water in the boiler being
+uniform, the ordinates bounded by the sloping line, and by the line,
+_t_, will at any point be approximately proportional to the rate of
+transmission of heat, and the shaded area above _t_ will be
+proportional to the quantity of heat imparted to the water. Join T by
+another diagonal with extremity of the heating surface on the zero
+line, then the larger triangle, standing on the zero line, will
+represent the whole of the heat of combustion, and the ratio of the
+two triangles will be as the lengths of their respective bases, that
+is, as (T - _t_) / T, which is the expression we have already used. The
+heating surface was 220 square feet, and it was competent to transmit
+the energy developed by 41 lb. of coal consumed per hour = 12,819 u. �
+41 u. = 525,572 units, equal to an average of 2,389 units per square
+foot per hour; this value will correspond to the mean pressure in an
+ordinary diagram, for it is a measure of the energy with which
+molecular motion is transferred from the heated gases to the
+boiler-plate, and so to the water. The mean rate of transmission,
+multiplied by the area of heating surface, gives the area of the
+shaded portion of the figure, which is the total work which should
+have been done, that is to say, the work of evaporating 544 lb. of
+water per hour. The actual work done, however, was only 485 lb. To
+give the speculations we have indulged in a practical turn, it will be
+necessary to examine in detail the terms of Carnot's formula. Carnot
+labored under great disadvantages. He adhered to the emission theory
+of heat; he was unacquainted with its dynamic equivalent; he did not
+know the reason of the difference between the specific heat of air at
+constant pressure and at constant volume, the idea of an absolute zero
+of temperature had not been broached; but the genius of the man, while
+it made him lament the want of knowledge which he felt must be
+attainable, also enabled him to penetrate the gloom by which he was
+surrounded, and enunciate propositions respecting the theory of heat
+engines, which the knowledge we now possess enables us to admit as
+true. His propositions are:
+
+1. The motive power of heat is independent of the agents employed to
+develop it, and its quantity is determined solely by the temperature
+of the bodies between which the final transfer of caloric takes place.
+
+2. The temperature of the agent must in the first instance be raised
+to the highest degree possible in order to obtain a great fall of
+caloric, and as a consequence a large production of motive power.
+
+3. For the same reason the cooling of the agent must be carried to as
+low a degree as possible.
+
+4. Matters must be so arranged that the passage of the elastic agent
+from the higher to the lower temperature must be due to an increase of
+volume, that is to say, the cooling of the agent must be caused by its
+rarefaction.
+
+This last proposition indicates the defective information which Carnot
+possessed. He knew that expansion of the elastic agent was accompanied
+by a fall of temperature, but he did not know that that fall was due
+to the conversion of heat into work. We should state this clause more
+correctly by saying that "the cooling of the agent must be caused by
+the external work it performs." In accordance with these propositions,
+it is immaterial what the heated gases or vapors in the furnace of a
+boiler may be, provided that they cool by doing external work and, in
+passing over the boiler surfaces, impart their heat energy to the
+water. The temperature of the furnace, it follows, must be kept as
+high as possible. The process of combustion is usually complex. First,
+in the case of coal, close to the fire-bars complete combustion of the
+red hot carbon takes place, and the heat so developed distills the
+volatile hydrocarbons and moisture in the upper layers of the fuel.
+The inflammable gases ignite on or near the surface of the fuel, if
+there be a sufficient supply of air, and burn with a bright flame for
+a considerable distance around the boiler. If the layer of fuel be
+thin, the carbonic acid formed in the first instance passes through
+the fuel and mixes with the other gases. If, however, the layer of
+fuel be thick, and the supply of air through the bars insufficient,
+the carbonic acid is decomposed by the red hot coke, and twice the
+volume of carbonic oxide is produced, and this, making its way through
+the fuel, burns with a pale blue flame on the surface, the result, as
+far as evolution of heat is concerned, being the same as if the
+intermediate decomposition of carbonic acid had not taken place. This
+property of coal has been taken advantage of by the late Sir W.
+Siemens in his gas producer, where the supply of air is purposely
+limited, in order that neither the hydrocarbons separated by
+distillation, nor the carbonic oxide formed in the thick layer of
+fuel, may be consumed in the producer, but remain in the form of crude
+gas, to be utilized in his regenerative furnaces.
+
+[Illustration: THE GENERATION OF STEAM. Fig 3.]
+
+[Illustration: THE GENERATION OF STEAM. Fig 4.]
+
+[Illustration: THE GENERATION OF STEAM. Fig 5.]
+
+[Illustration: THE GENERATION OF STEAM. Fig 6.]
+
+[Illustration: THE GENERATION OF STEAM. Fig 7.]
+
+_(To be continued.)_
+
+       *       *       *       *       *
+
+[Continued from SUPPLEMENT No. 437, page 6970.]
+
+
+
+
+PLANETARY WHEEL-TRAINS.
+
+By Prof. C.W. MACCORD, Sc.D.
+
+
+II.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 14]
+
+It has already been shown that the rotations of all the wheels of a
+planetary train, relatively to the train-arm, are the same when the
+arm is in motion as they would be if it were fixed. Now, in Fig. 14,
+let A be the first and F the last wheel of an _incomplete_ train, that
+is, one having but one sun-wheel. As before, let these be so connected
+by intermediate gearing that, when T is stationary, a rotation of A
+through _m_ degrees shall drive F through _n_ degrees: and also as
+before, let T in the same time move through _a_ degrees. Then, if _m'_
+represent the total motion of A, we have again,
+
+       m' = m + a, or m = m' - a.
+
+This is, clearly, the motion of A relatively to the fixed frame of the
+machine; and is measured from a fixed vertical line through the
+center of A. Now, if we wish to express the total motion of F
+relatively to the same fixed frame, we must measure it from a vertical
+line through the center of F, wherever that maybe; which gives in this
+case:
+
+      n' = n + a, or n = n' - a.
+
+but with respect to the train-arm when at rest, we have:
+
+      ang. vel. A     n
+      ------------ = ---, whence again
+      ang. vel. F     m
+
+        n' - a     n
+        ------ = --- .
+        m' - a     m
+
+This is the manner in which the equation is deduced by Prof. Willis,
+who expressly states that it applies whether the last wheel F is or is
+not concentric with the first wheel A, and also that the train may be
+composed of any combinations which transmit rotation with both a
+constant velocity ratio and a constant directional relation. He
+designates the quantities _m'_, _n'_, _absolute revolutions_, as
+distinguished from the _relative revolutions_ (that is, revolutions
+relatively to the train-arm), indicated by the quantities _m_, _n_:
+adding, "Hence it appears that the absolute revolutions of the wheels
+of epicyclic trains are equal to the sum of their relative revolutions
+to the arm, and of the arm itself, when they take place in the same
+direction, and equal to the difference of these revolutions when in
+the opposite direction."
+
+In this deduction of the formula, as in that of Prof. Rankine, all the
+motions are supposed to have the same direction, corresponding to that
+of the hands of the clock; and in its application to any given train,
+the signs of the terms must be changed in case of any contrary motion,
+as explained in the preceding article.
+
+And both the deduction and the application, in reference to these
+incomplete trains in which the last wheel is carried by the
+train-arm, clearly involve and depend upon the resolving of a motion
+of revolution into the components of a circular translation and a
+rotation, in the manner previously discussed.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 15]
+
+To illustrate: Take the simple case of two equal wheels, Fig. 15, of
+which the central one A is fixed. Supposing first A for the moment
+released and the arm to be fixed, we see that the two wheels will turn
+in opposite directions with equal velocities, which gives _n_/_m_ = -1;
+but when A is fixed and T revolves, we have _m'_ = 0, whence in the
+general formula
+
+  n' - a
+  ------   = -1, or n' = 2 a;
+    -a
+
+which means, being interpreted, that F makes two rotations about its
+axis during one revolution of T, and in the same direction. Again, let
+A and F be equal in the 3-wheel train, Fig. 16, the former being fixed
+as before. In this case we have:
+
+   n
+  --- = 1, m' = 0, which gives
+   m
+
+   n' - a
+  ------- = 1, [therefore] n' = 0;
+    -a
+
+that is to say, the wheel F, which now evidently has a motion of
+circular translation, does not rotate at all about its axis during the
+revolution of the train-arm.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 16]
+
+All this is perfectly consistent, clearly, with the hypothesis that
+the motion of circular translation is a simple one, and the motion of
+revolution about a fixed axis is a compound one.
+
+Whether the hypothesis was made to substantiate the formula, or the
+formula constructed to suit the hypothesis, is not a matter of
+consequence. In either case, no difficulty will arise so long as the
+equation is applied only to cases in which, as in those here
+mentioned, that motion of revolution _can_ be resolved into those
+components.
+
+When the definition of an epicyclic train is restricted as it is by
+Prof. Rankine, the consideration of the hypothesis in question is
+entirely eliminated, and whether it be accepted or rejected, the whole
+matter is reduced to merely adding the motion of the train-arm to the
+rotation of each sun-wheel.
+
+But in attempting to apply this formula in analyzing the action of an
+incomplete train, we are required to add this motion of the train-arm,
+not only to that of a sun-wheel, but to that of a planet-wheel. This
+is evidently possible in the examples shown in Figs. 15 and 16,
+because the motions to be added are in all respects similar: the
+trains are composed of spur-wheels, and the motions, whether of
+revolution, translation, or rotation, _take place in parallel planes
+perpendicular to parallel axes_. This condition, which we have
+emphasized, be it observed, must hold true with regard to the motions
+of the first and last wheels and the train-arm, in order to make this
+addition possible. It is not essential that spur-wheels should be used
+exclusively or even at all; for instance, in Fig. 16, A and F may be
+made bevel or screw-wheels, without affecting the action or the
+analysis; but the train-arm in all cases revolves around the central
+axis of the system, that is, about the axis of A, and to this the axis
+of F _must_ be parallel, in order to render the deduction of the
+formula, as made by Prof. Willis, and also by Prof. Goodeve, correct,
+or even possible.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 17]
+
+This will be seen by an examination of Fig. 17; in which A and B are
+two equal spur-wheels, E and F two equal bevel wheels, B and E being
+secured to the same shaft, and A being fixed to the frame H. As the
+arm T goes round, B will also turn in its bearings in the same
+direction: let this direction be that of the clock, when the apparatus
+is viewed from above, then the motion of F will also have the same
+direction, when viewed from the central vertical axis, as shown at F':
+and let these directions be considered as positive. It is perfectly
+clear that F will turn in its bearings, in the direction indicated, at
+a rate precisely equal to that of the train-arm. Let P be a pointer
+carried by F, and R a dial fixed to T; and let the pointer be vertical
+when OO is the plane containing the axes of A, B, and E. Then, when F
+has gone through any angle a measured from OO, the pointer will have
+turned from its original vertical position through an equal angle, as
+shown also at F'.
+
+Now, there is no conceivable sense in which the motion of T can be
+said to be added to the rotation of F about its axis, and the
+expression "absolute revolution," as applied to the motion of the last
+wheel in this train, is absolutely meaningless.
+
+Nevertheless, Prof. Goodeve states (Elements of Mechanism, p. 165)
+that "We may of course apply the general formula in the case of bevel
+wheels just as in that of spur wheels." Let us try the experiment;
+when the train-arm is stationary, and A released and turned to the
+right, F turns to the left at the same rate, whence:
+
+    n
+   --- = -1; also m' = 0 when A is fixed,
+    m
+
+and the equation becomes
+
+  n' - a
+  ------ = -1, [therefore] n' = 2a:
+   - a
+
+or in other words F turns _twice_ on its axis during one revolution of
+T: a result too palpably absurd to require any comment. We have seen
+that this identical result was obtained in the case of Fig. 15, and it
+would, of course, be the same were the formula applied to Figs. 5 and
+6; whereas it has never, so far as we are aware, been pretended that a
+miter or a bevel wheel will make more than one rotation about its axis
+in rolling once around an equal fixed one.
+
+Again, if the formula be general, it should apply equally well to a
+train of screw wheels: let us take, for example, the single pair shown
+in Fig. 8, of which, when T is fixed, the velocity ratio is unity. The
+directional relation, however, depends upon the direction in which the
+wheels are twisted: so that in applying the formula, we shall have
+_n/m_ = +1, if the helices of both wheels are right handed, and
+_n_/_m_ = -1, if they are both left handed. Thus the formula leads to
+the surprising conclusion, that when A is fixed and T revolves, the
+planet-wheel B will revolve about its axis twice as fast as T moves,
+in one case, while in the other it will not revolve at all.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 18]
+
+A favorite illustration of the peculiarities of epicyclic mechanism,
+introduced both by Prof. Willis and Prof. Goodeve, is found in the
+contrivance known as Ferguson's Mechanical Paradox, shown in Fig. 18.
+This consists of a fixed sun-wheel A, engaging with a planet-wheel B
+of the same diameter. Upon the shaft of B are secured the three thin
+wheels E, G, I, each having 20 teeth, and in gear with the three
+others F, H, K, which turn freely upon a stud fixed in the train-arm,
+and have respectively 19, 20, and 21 teeth. In applying the general
+formula, we have the following results:
+
+                    n     20     n' - a                         1
+  For the wheel F, --- = ---- = ---------, [therefore] n' = - ---- a.
+                    m     19       -a                          19
+
+                    n         n' - a
+   "   "    "   H, --- = 1 = --------, [therefore] n' = 0.
+                    m           -a
+
+                    n     20     n' - a                         1
+   "   "    "   K, --- = ---- = ---------, [therefore] n' = + ---- a.
+                    m     21       -a                          21
+
+The paradoxical appearance, then, consists in this, that although the
+drivers of the three last wheels each have the same number of teeth,
+yet the central one, H, having a motion of circular translation,
+remains always parallel to itself, and relatively to it the upper one
+seems to turn in the same direction as the train-arm, and the lower in
+the contrary direction. And the appearance is accepted, too, as a
+reality; being explained, agreeably to the analysis just given, by
+saying that H has no absolute rotation about its axis, while the other
+wheels have; that of F being positive and that of K negative.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 18]
+
+The Mechanical Paradox, it is clear, may be regarded as composed of
+three separate trains, each of which is precisely like that of Fig.
+16: and that, again, differs from the one of Fig. 15 only in the
+addition of a third wheel. Now, we submit that the train shown in Fig.
+17 is mechanically equivalent to that of Fig. 15; the velocity ratio
+and the directional relation being the same in both. And if in Fig. 17
+we remove the index P, and fix upon its shaft three wheels like E, G,
+and I of Fig. 18, we shall have a combination mechanically equivalent
+to Ferguson's Paradox, the three last wheels rotating in vertical
+planes about horizontal axes. The relative motions of those three
+wheels will be the same, obviously, as in Fig. 18; and according to
+the formula their absolute motions are the same, and we are invited to
+perceive that the central one does not rotate at all about its axis.
+
+But it _does_ rotate, nevertheless; and this unquestioned fact is of
+itself enough to show that there is something wrong with the formula
+as applied to trains like those in question. What that something is,
+we think, has been made clear by what precedes; since it is impossible
+in any sense to add together motions which are unlike, it will be seen
+that in order to obtain an intelligible result in cases like these,
+the equation must be of the form _n'_/(_m'_ - _a_) = _n_/_m_. We shall
+then have:
+
+                    n     20     n'                       20
+  For the wheel F, --- = ---- = ----, [therefore] n' = - ---- a;
+                    m     19     -a                       19
+
+                    n         n'
+  For the wheel H, --- = 1 = ----, [therefore] n' = -a;
+                    m         -a
+
+                    n     20     n'                       20
+  For the wheel K, --- = ---- = ----, [therefore] n' = - ---- a,
+                    m     21     -a                       21
+
+which corresponds with the actual state of things; all three wheels
+rotate in the same direction, the central one at the same rate as the
+train arm, one a little more rapidly and the third a little more
+slowly.
+
+It is, then, absolutely necessary to make this modification in the
+general formula, in order to apply it in determining the rotations of
+any wheel of an epicyclic train whose axis is not parallel to that of
+the sun-wheels. And in this modified form it applies equally well to
+the original arrangement of Ferguson's paradox, if we abandon the
+artificial distinction between "absolute" and "relative" rotations of
+the planet-wheels, and regard a spur-wheel, like any other, as
+rotating on its axis when it turns in its bearings; the action of the
+device shown in Fig. 18 being thus explained by saying that the wheel
+H turns once backward during each forward revolution of the train-arm,
+while F turns a little more and K a little less than once, in the same
+direction. In this way the classification and analysis of these
+combinations are made more simple and consistent, and the
+incongruities above pointed out are avoided; since, without regard to
+the kind of gearing employed or the relative positions of the axes, we
+have the two equations:
+
+       n' - a     n
+   I. -------- = ---, for all complete trains;
+       m' - a     m
+
+          n'      n
+  II. -------- = ---, for all incomplete trains.
+       m' - a     m
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 19]
+
+As another example of the difference in the application of these
+formul�, let us take Watt's sun and planet wheels, Fig. 19. This
+device, as is well known, was employed by the illustrious inventor as
+a substitute for the crank, which some one had succeeded in patenting.
+It consists merely of two wheels A and F connected by the link T; A
+being keyed on the shaft of the engine and F being rigidly secured to
+the connecting-rod. Suppose the rod to be of infinite length, so as to
+remain always parallel to itself, and the two wheels to be of equal
+size.
+
+Then, according to Prof. Willis' analysis, we shall have--
+
+    n' - a     n                               -s
+   -------- = --- = -1, n' = 0, [therefore] -------- = -1, whence
+    m' - a     m                              m' - a
+
+          -a = a - m', or m = 2a.
+
+The other view of the question is, that F turns once backward in its
+bearings during each forward revolution of T; whence in Eq. 2 we
+have--
+
+       n'      n
+   -------- = --- = -1, n' = -a,
+    m' - a     m
+
+                 -a
+  [therefore] -------- -1, which gives -a = a - m', or m' = 2a,
+               m' - a
+
+as before.
+
+It is next to be remarked, that the errors which arise from applying
+Eq. I. to incomplete trains may in some cases counterbalance and
+neutralize each other, so that the final result is correct.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 20]
+
+For example, take the combination shown in Fig. 20. This consists of a
+train-arm T revolving about the vertical axis OO of the fixed wheel A,
+which is equal in diameter to F, which receives its motion by the
+intervention of one idle wheel carried by a stud S fixed in the arm.
+The second train-arm T' is fixed to the shaft of F and turns with it;
+A' is secured to the arm T, and F' is actuated by A' also through a
+single idler carried by T'.
+
+We have here a compound train, consisting of two simple planetary
+trains, A--F and A'--F'; and its action is to be determined by
+considering them separately. First suppose T' to be removed and find
+the motion of F; next suppose F to be removed and T fixed, and find
+the rotation of F'; and finally combine these results, noting that the
+motion of T' is the same as that of F, and the motion of A' the same
+as that of T.
+
+Then, according to the analysis of Prof. Willis, we shall have
+(substituting the symbol _t_ for _a_ in the equation of the second
+train, in order to avoid confusion):
+
+                  n         n' - a
+  1. Train A--F. --- = 1 = --------; m' = 0,
+                  m         m' - a
+
+                            n' - a
+      whence               -------- = 1, n' = 0, = rot. of F.
+                               a
+
+                    n         n' - t
+  2. Train A'--F'. --- = 1 = --------; m' = 0,
+                    m         m' - t
+
+                              n' - t
+     whence again           -------- = 1, t = 0, = rot. of F'.
+                                -t
+
+Of these results, the first is explicable as being the _absolute_
+rotation of F, but the second is not; and it will be readily seen that
+the former would have been equally absurd, had the axis LL been
+inclined instead of vertical. But in either case we should find the
+errors neutralized upon combining the two, for according to the theory
+now under consideration, the wheel A', being fixed to T, turns once
+upon its axis each time that train arm revolves, and in the same
+direction; and the revolutions of T' equal the rotations of F, whence
+finally in train A'--F' we have:
+
+      n         n' - t
+  3. --- = 1 = --------; in which t = 0, m' = a,
+      m         m' - t
+
+                n' - 0
+which gives    --------- = 1, or n' = a.
+                 a - 0
+
+This is, unquestionably, correct; and indeed it is quite obvious that
+the effect upon F' is the same, whether we say that during a
+revolution of T the wheel A' turns once forward and T' not at all, or
+adopt the other view and assert that T' turns once backward and A' not
+at all. But the latter view has the advantage of giving concordant
+results when the trains are considered separately, and that without
+regard to the relative positions of the axes or the kind of gearing
+employed. Analyzing the action upon this hypothesis, we have:
+
+  In train A--F:
+
+    n            n'                         n'
+   --- = 1 = --------; m' = 0, [therefore] ---- = 1, or n' = -a;
+    m         m' - a                        -a
+
+  In train A'--F':
+
+    n'           n'                         n'
+   --- = 1 = --------; m' = 0, [therefore] ---- = 1, or n' = -t;
+    m         m' - t                       -t
+
+In combining, we have in the latter train m' = 0, t = -a, whence
+
+    n           n'           n'
+   --- = 1 = -------- gives ---- = 1, or n' = a, as before.
+    m         m' - t         +a
+
+Now it happens that the only examples given by Prof. Willis of
+incomplete trains in which the axis of a planet-wheel whose motion is
+to be determined is not parallel to the central axis of the system,
+are similar to the one just discussed; the wheel in question being
+carried by a secondary train-arm which derives its motion from a wheel
+of the primary train.
+
+The application of his general equation in these cases gives results
+which agree with observed facts; and it would seem that this
+circumstance, in connection doubtless with the complexity of these
+compound trains, led him to the too hasty conclusion that the formula
+would hold true in all cases; although we are still left to wonder at
+his overlooking the fact that in these very cases the "absolute" and
+the "relative" rotations of the last wheel are identical.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 21]
+
+In Fig. 21 is shown a combination consisting also of two distinct
+trains, in which, however, there is but one train-arm T turning freely
+upon the horizontal shaft OO, to which shaft the wheels A', F, are
+secured; the train-arm has two studs, upon which turn the idlers B B',
+and also carries the bearings of the last wheel F'; the first wheel A
+is annular, and fixed to the frame of the machine. Let it be required
+to determine the results of one revolution of the crank H, the numbers
+of teeth being assigned as follows:
+
+      A = 60, F = 30, A' = 60, F' = 10.
+
+We shall then have, for the train ABF (Eq. I.),
+
+      n       60          n' - a
+     --- = - ---- = -2 = --------, in which n' = 1, m' = 0,
+      m       30          m' - a'
+
+             1 - a                            1
+whence -2 = -------, 2a = 1 - a, 3a = 1, a = ---.
+               -a                             3
+
+And for the train A'B'F' (Eq. II.),
+
+      n     60           n'                   1
+     --- = ---- = 6 = --------, in which a = ---, m' = 1,
+      m     10         m' - a'                3
+
+                           n'
+whence            6 = -----------, or n' = 4.
+                       1 - (1/3)
+
+That is, the last wheel F' turns _four_ times about the axis LL during
+one revolution of the crank H. But according to Profs. Willis and
+Goodeve, we should have for the second train:
+
+      n     60         n' - a                 1
+     --- = ---- = 6 = --------, in which a = ---, m' = 1,
+      m     10         m' - a'                3
+
+                n' - (1/3)
+which gives 6 = -----------, n' - (1/3) = 4, n' = 4-1/3,
+                 1 - (1/3)
+
+or _four and one-third_ revolutions of F' for one of H.
+
+This result, no doubt, might be near enough to the truth to serve all
+practical purposes in the application of this mechanism to its
+original object, which was that of paring apples, impaled upon the
+fork K; but it can hardly be regarded as entirely satisfactory in a
+general way; nor can the analysis which renders such a result
+possible.
+
+       *       *       *       *       *
+
+
+
+
+THE PANTANEMONE.
+
+
+The need of irrigating prairies, inundating vines, drying marshes, and
+accumulating electricity cheaply has, for some time past, led to a
+search for some means of utilizing the forces of nature better than
+has ever hitherto been done. Wind, which figures in the first rank as
+a force, has thus far, with all the mills known to us, rendered
+services that are much inferior to those that we have a right to
+expect from it with improved apparatus; for the work produced,
+whatever the velocity of the wind, has never been greater than that
+that could be effected by wind of seven meters per second. But, thanks
+to the experiments of recent years, we are now obtaining an effective
+performance double that which we did with apparatus on the old system.
+
+Desirous of making known the efforts that have been made in this
+direction, we lately described Mr. Dumont's atmospheric turbine. In
+speaking of this apparatus we stated that aerial motors generally stop
+or are destroyed in high winds. Recently, Mr. Sanderson has
+communicated to us the result of some experiments that he has been
+making for years back by means of an apparatus which he styles a
+pantanemone.
+
+The engraving that we give of this machine shows merely a cabinet
+model of it; and it goes without saying that it is simply designed to
+exhibit the principle upon which its construction is based.
+
+[Illustration: THE PANTANEMONE.]
+
+Two plane surfaces in the form of semicircles are mounted at right
+angles to each other upon a horizontal shaft, and at an angle of 45�
+with respect to the latter. It results from this that the apparatus
+will operate (even without being set) whatever be the direction of the
+wind, except when it blows perpendicularly upon the axle, thus
+permitting (owing to the impossibility of reducing the surfaces) of
+three-score days more work per year being obtained than can be with
+other mills. Three distinct apparatus have been successively
+constructed. The first of these has been running for nine years in the
+vicinity of Poissy, where it lifts about 40,000 liters of water to a
+height of 20 meters every 24 hours, in a wind of a velocity of from 7
+to 8 meters per second. The second raises about 150,000 liters of
+water to the Villejuif reservoir, at a height of 10 meters, every 24
+hours, in a wind of from 5 to 6 meters. The third supplies the
+laboratory of the Montsouris observatory.
+
+The first is not directible, the second may be directed by hand, and
+the third is directed automatically. These three machines defied the
+hurricane of the 26th of last January.--_La Nature._
+
+       *       *       *       *       *
+
+
+
+
+RELVAS'S NEW LIFE-BOAT.
+
+
+The Spanish and Portuguese papers have recently made known some
+interesting experiments that have been made by Mr. Carlos Relvas with
+a new life-boat which parts the waves with great facility and exhibits
+remarkable stability. This boat, which is shown in front view in one
+of the corners of our engraving, is T-shaped, and consists of a very
+thin keel connected with the side-timbers by iron rods. Cushions of
+cork and canvas are adapted to the upper part, and, when the boat is
+on the sea, it has the appearance of an ordinary canoe, although, as
+may be seen, it differs essentially therefrom in the submerged part.
+When the sea is heavy, says Mr. Relvas, and the high waves are
+tumbling over each other, they pass over my boat, and are powerless to
+capsize it. My boat clears waves that others are obliged to recoil
+before. It has the advantage of being able to move forward, whatever
+be the fury of the sea, and is capable, besides, of approaching rocks
+without any danger of its being broken.
+
+[Illustration: RELVAS'S NEW LIFE BOAT.]
+A committee was appointed by the Portuguese government to examine this
+new life-boat, and comparative experiments were made with it and an
+ordinary life-boat at Porto on a very rough sea. Mr. Relvas's boat was
+manned by eight rowers all provided with cork girdles, while the
+government life-boat was manned by twelve rowers and a pilot, all
+likewise wearing cork girdles. The chief of the maritime department,
+an engineer of the Portuguese navy and a Portuguese deputy were
+present at the trial in a pilot boat. The three boats proceeded to the
+entrance of the bar, where the sea was roughest, and numerous
+spectators collected upon the shore and wharfs followed their
+evolutions from afar.
+
+The experiments began at half past three o'clock in the afternoon. The
+two life-boats shot forward to seek the most furious waves, and were
+seen from afar to surmount the billows and then suddenly disappear. It
+was a spectacle as moving as it was curious. It was observed that Mr.
+Relvas's boat cleft the waves, while the other floated upon their
+surface like a nut-shell. After an hour's navigation the two boats
+returned to their starting point.
+
+The official committee that presided over these experiments has again
+found in this new boat decided advantages, and has pointed out to its
+inventor a few slight modifications that will render it still more
+efficient.--_La Nature._
+
+       *       *       *       *       *
+
+
+
+
+EXPERIMENTS WITH DOUBLE-BARRELED GUNS AND RIFLES.
+
+
+The series of experiments we are about to describe has recently been
+made by Mr. Horatio Phillips, a practical gun maker of London. The
+results will no doubt prove of interest to those concerned in the use
+or manufacture of firearms.
+
+The reason that the two barrels of a shot gun or rifle will, if put
+together parallel, throw their charges in diverging lines has never
+yet been satisfactorily accounted for, although many plausible and
+ingenious theories have been advanced for the purpose. The natural
+supposition would be that this divergence resulted from the axes of
+the barrels not being in the same vertical plane as the center line of
+the stock. That this is not the true explanation of the fact, the
+following experiment would tend to prove.
+
+[Illustration: EXPERIMENTS WITH DOUBLE-BARRELLED GUNS.]
+
+Fig. 1 represents a single barrel fitted with sights and firmly
+attached to a heavy block of beech. This was placed on an ordinary
+rifle rest, being fastened thereto by a pin at the corner, A, the
+block and barrel being free to revolve upon the pin as a center.
+Several shots were fired both with the pin in position and with it
+removed, the barrel being carefully pointed at the target each time.
+No practical difference in the accuracy of fire was discernible under
+either condition. When the pin was holding the corner of the block,
+the recoil caused the barrel to move from right to left in a circular
+path; but when the pin was removed, so that the block was not attached
+to the rest in any way, the recoil took place in a line with the axis
+of the bore. It will be observed that the conditions which are present
+when a double barreled gun is fired in the ordinary way from the
+shoulder were in some respects much exaggerated in the apparatus, for
+the pin was a distance of 3 in. laterally from the axis of the barrel,
+whereas the center of resistance of the stock of a gun against the
+shoulder would ordinarily be about one-sixth of this distance from the
+axis of the barrel. This experiment would apparently tend to prove
+that the recoil does not appreciably affect the path of the
+projectile, as it would seem that the latter must clear the muzzle
+before any considerable movement of the barrel takes place.
+
+With a view to obtain a further confirmation of the result of this
+experiment, it was repeated in a different form by a number of shots
+being fired from a "cross-eyed" rifle,[1] in which the sights were
+fixed in the center of the rib. Very accurate shooting was obtained
+with this arm.
+
+   [Footnote 1: A cross-eyed rifle is one made with a crooked stock
+   for the purpose of shooting from the right shoulder, aim being
+   taken with the left eye.]
+
+A second theory, often broached, in order to account for the
+divergence of the charge, is that the barrel which is not being fired,
+by its _vis inertia_ in some way causes the shot to diverge. In order
+to test this, Mr. Phillips took a single rifle and secured it near the
+muzzle to a heavy block of metal, when the accuracy of the shooting
+was in no way impaired.
+
+So far the experiments were of a negative character, and the next step
+was made with a view to discover the actual cause of the divergence
+referred to. A single barrel was now taken, to which a template was
+fitted, in order to record its exact length. The barrel was then
+subjected to a heavy internal hydrostatic pressure. Under this
+treatment it expanded circumferentially and at the same time was
+reduced in length. This, it was considered, gave a clew to the
+solution of the problem. A pair of barrels was now taken and a
+template fitted accurately to the side of the right-hand one. As the
+template fitted the barrel when the latter was not subject to internal
+pressure, upon such pressure being applied any alterations that might
+ensue in the length or contour of the barrel could be duly noted. The
+right-hand barrel was then subjected to internal hydrostatic pressure.
+The result is shown in an exaggerated form in Fig. 2. It will be seen
+that both barrels are bent into an arched form. This would be caused
+by the barrel under pressure becoming extended circumferentially, and
+thereby reduced in length, because the metal that is required to
+supply the increased circumference is taken to some extent from the
+length, although the substance of metal in the walls of the barrel by
+its expansion contributes also to the increased diameter. A simple
+illustration of this effect is supplied by subjecting an India-rubber
+tube to internal pressure. Supposing the material to be sufficiently
+elastic and the pressure strong enough, the tube would ultimately
+assume a spherical form. It is a well known fact that heavy barrels
+with light charges give less divergence than light barrels with heavy
+charges.
+
+After the above experiments it was hoped that, if a pair of barrels
+were put together parallel and soldered only for a space of 3 in. at
+the breech end, and were then coupled by two encircling rings joined
+together as in Fig. 4, the left-hand ring only being soldered to the
+barrel, very accurate shooting would be obtained. For, it was argued,
+that by these means the barrel under fire would be able to contract
+without affecting or being affected by the other barrel; that on the
+right-hand, it will be seen by the illustration, was the one to slide
+in its ring.
+
+A pair of able 0.500 bore express rifle barrels were accordingly
+fitted in this way. Fig. 3 shows the arrangement with the rings in
+position. Upon firing these barrels with ordinary express charges it
+was found that the lines of fire from each barrel respectively crossed
+each other, the bullet from the right-hand barrel striking the target
+10 in. to the left of the bull's eye, while the left barrel placed its
+projectile a similar distance in the opposite direction; or, as would
+be technically said, the barrels crossed 20 in. at 100 yards, the
+latter distance being the range at which the experiment was made.
+These last results have been accounted for in the following manner:
+The two barrels were rigidly joined for a space of 3 in., and for that
+distance they would behave in a manner similar to that illustrated in
+Fig. 2, and were they not coupled at the muzzles by the connecting
+rings they would shoot very wide, the charges taking diverging
+courses. When the connecting rings are fitted on, the barrel not being
+fired will remain practically straight, and, as it is coupled to the
+barrel being fired by the rings, the muzzle of the latter will be
+restrained from pointing outward.
+
+The result will be as shown in an exaggerated manner by the dotted
+lines on the right barrel in Fig. 3.
+
+It would appear from these experiments that when very accurate
+shooting is required at long ranges with double-barreled rifles, they
+should be mounted in a manner similar to that adopted in the
+manufacture of the Nordenfelt machine gun, in which weapon the barrels
+are fitted into a plate at the extreme breech end, the muzzles
+projecting through holes bored to receive them in a metal plate. No
+unequal expansion would then take place, and the barrels would be free
+to become shorter independently of each other. We give the above
+experiments on the authority of their author, who, we believe, has
+taken great pains to render them as exhaustive as possible, so far as
+they go.--_Engineering._
+
+       *       *       *       *       *
+
+
+
+
+BALL TURNING MACHINE.
+
+
+The distinguishing feature in the ball turning machine shown opposite
+is that the tool is stationary, while the work revolves in two
+directions simultaneously. In the case of an ordinary spherical
+object, such as brass clack ball, the casting is made from a perfect
+pattern having two small caps or shanks, in which the centers are also
+marked to avoid centering by hand. It is fixed in the machine between
+two centers carried on a face plate or chuck, with which they revolve.
+One of these centers, when the machine is in motion, receives a
+continuous rotary motion about its axis from a wormwheel, D. This is
+driven by a worm, C, carried on a shaft at the back of the chuck, and
+driven itself by a wormwheel, B, which gears with a screw which rides
+loosely upon the mandrel, and is kept from rotating by a finger on the
+headstock. This center, in its rotation, carries with it the ball,
+which is thus slowly moved round an axis parallel to the face plate,
+at the same time that it revolves about the axis of the mandrel, the
+result being that the tool cuts upon the ball a scroll, of which each
+convolution is approximately a circle, and lies in a plane parallel to
+the line of centers.
+
+When the chuck is set for one size of ball, which may be done in a few
+minutes, any quantity of that diameter may be turned without further
+adjustment. A roughing cut for a 2 in. ball may be done in one minute,
+and a finishing cut leaving the ball quite bright in the same time.
+The two paps are cut off within one-sixteenth of an inch and then
+broken off, and the ball finished in the usual way. On account of the
+work being geometrically true, the finishing by the ferrule tool is
+done in one quarter of the time usually required.
+
+[Illustration: IMPROVED BALL TURNING MACHINE.]
+
+The chuck may be applied to an ordinary lathe or may be combined with
+a special machine tool, as show in our illustration. In the latter
+case everything is arranged in the most handy way for rapid working,
+and six brass balls of 2 in. in diameter can be turned and finished in
+an hour. The machine is specially adapted for turning ball valves for
+pumps, pulsometers, and the like, and in the larger sizes for turning
+governor balls and spherical nuts for armor plates, and is
+manufactured by Messrs. Wilkinson and Lister, of Bradford Road Iron
+Works, Keighley.--_Engineering._
+
+       *       *       *       *       *
+
+
+
+
+COOLING APPARATUS FOR INJECTION WATER.
+
+
+It often happens in towns and where manufactories are crowded
+together, that the supply of water for condensing purposes is very
+small, and consequently that it attains an inconveniently high
+temperature under unfavorable conditions of weather, resulting in the
+deterioration of the vacuum and a consequent increase in the
+consumption of fuel. To remedy or to diminish this difficulty, Messrs.
+Boase and Miller, of London, have brought out the water cooler
+illustrated above. This consists, says _Engineering_, of a revolving
+basket of wire gauze surrounding an inner stationary vessel pierced
+with numerous small holes, through which the heated water discharged
+by the air pump finds its way into the basket, to be thrown out in the
+form of fine spray to a distance of 20 ft. at each side. The drops are
+received in the tank or pond, and in their rapid passage through the
+air are sufficiently cooled to be again injected into the condenser.
+
+The illustration shows a cooler having a basket three feet in
+diameter, revolving at 300 revolutions per minute, and discharging
+into a tank 40 ft. square. It requires 3 to 4 indicated horse-power to
+drive it, and will cool 300 gallons per minute. The following decrease
+of temperature has been observed in actual practice: Water entering at
+95 deg. fell 20 deg. in temperature; water entering at 100 deg. to 110
+deg. fell 25 deg.; and water entering at 110 deg. to 120 deg. fell 30
+deg. The machine with which these trials were made was so placed that
+the top of the basket was four ft. from the surface of the water in
+the pond. With a greater elevation, as shown in the engraving, better
+results can be obtained.
+
+[Illustration: IMPROVED WATER COOLING APPARATUS.]
+
+The advantages claimed for the cooler are that by its means the
+temperature of the injection water can be reduced, the cost and size
+of cooling ponds can be diminished, and condensing engines can be
+employed where hitherto they have not been possible. The apparatus has
+been for two years in operation at several large factories, and there
+is every reason to believe that its use will extend, as it supplies a
+real want in a very simple and ingenious manner. Messrs. Duncan
+Brothers, of Dundee and 32 Queen Victoria Street, E.C., are the
+manufacturers.
+
+       *       *       *       *       *
+
+
+
+
+CORRUGATED DISK PULLEYS.
+
+
+This is a pulley recently introduced by Messrs. J. and E. Hall, of
+Dartford Eng. With the exception of the boss, which is cast, it is
+composed entirely of steel or sheet iron. In place of the usual arms a
+continuous web of corrugated sheet metal connects the boss to the rim;
+this web is attached to the boss by means of Spence's metal. Inside
+the rim, which is flanged inward, a double hoop iron ring is fixed for
+strengthening purposes. The advantageous disposition of metal obtained
+by means of the corrugated web enables the pulley to be made of a
+given strength with less weight of material, and from this cause and
+also on account of being accurately balanced these pulleys are well
+adapted for high speeds.
+
+[Illustration]
+
+       *       *       *       *       *
+
+[KANSAS CITY REVIEW.]
+
+
+
+
+EARLY HISTORY OF THE TELEGRAPH.
+
+
+Although the electric telegraph is, comparatively speaking, a recent
+invention, yet methods of communication at a distance, by means of
+signals, have probably existed in all ages and in all nations. There
+is reason to believe that among the Greeks a system of telegraphy was
+in use, as the burning of Troy was certainly known in Greece very soon
+after it happened, and before any person had returned from Troy.
+Polybius names the different instruments used by the ancients for
+communicating information--"pyrsia," because the signals were always
+made by means of fire lights. At first they communicated information
+of events in an imperfect manner, but a new method was invented by
+Cleoxenus, which was much improved by Polybius, as he himself informs
+us, and which may be described as follows:
+
+Take the letters of the alphabet and arrange them on a board in five
+columns, each column containing five letters; then the man who signals
+would hold up with his left hand a number of torches which would
+represent the number of the column from which the letter is to be
+taken, and with his right hand a number of torches that will represent
+the particular letter in that column that is to be taken. It is thus
+easy to understand how the letters of a short sentence are
+communicated from station to station as far as required. This is the
+pyrsia or telegraph of Polybius.
+
+It seems that the Romans had a method of telegraphing in their walled
+cities, either by a hollow formed in the masonry, or by a tube fixed
+thereto so as to confine the sound, in order to convey information to
+any part they liked. This method of communicating is in the present
+age frequently employed in the well known speaking tubes. It does not
+appear that the moderns had thought of such a thing as a telegraph
+until 1661, when the Marquis of Worcester, in his "Century of
+Inventions," affirmed that he had discovered a method by which a man
+could hold discourse with his correspondent as far as they could
+reach, by night as well as by day; he did not, however, describe this
+invention.
+
+Dr. Hooke delivered a discourse before the Royal Society in 1684,
+showing how to communicate at great distances. In this discourse he
+asserts the possibility of conveying intelligence from one place to
+another at a distance of 120 miles as rapidly as a man can write what
+he would have sent. He takes to his aid the then recent invention of
+the telescope, and explains how characters exposed at one station on
+the top of one hill may be made visible to the next station on the top
+of the next hill. He invented twenty-four simple characters, each
+formed of a combination of three deal boards, each character
+representing a letter by the use of cords; these characters were
+pushed from behind a screen and exposed, and then withdrawn behind the
+screen again. It was not, however, until the French revolution that
+the telegraph was applied to practical purposes; but about the end of
+1703 telegraphic communication was established between Paris and the
+frontiers, and shortly afterward telegraphs were introduced into
+England.
+
+The history of the invention and introduction of the electric
+telegraph by Prof. Morse is one of inexhaustible interest, and every
+incident relating to it is worthy of preservation. The incidents
+described below will be found of special interest. The article is from
+the pen of the late Judge Neilson Poe, and was the last paper written
+by him. He prepared it during his recent illness, the letter embodied
+in it from Mr. Latrobe being of course obtained at the time of its
+date. It is as follows:
+
+On the 5th of April, 1843, when the monthly meeting of the directors
+of the Baltimore & Ohio Railroad Company was about to adjourn, the
+President, the Hon. Louis McLane, rose with a paper in his hand which
+he said he had almost overlooked, and which the Secretary would read.
+It proved to be an application from Prof. Morse for the privilege of
+laying the wires of his electric telegraph along the line of the
+railroad between Baltimore and Washington, and was accompanied by a
+communication from B.H. Latrobe, Esq., Chief Engineer, recommending
+the project as worthy of encouragement.
+
+On motion of John Spear Nicholas, seconded by the Hon. John P.
+Kennedy, the following resolution was then considered:
+
+_Resolved_, "That the President be authorized to afford Mr. Morse such
+facilities as may be requisite to give his invention a proper trial
+upon the Washington road, provided in his opinion and in that of the
+engineer it can be done without injury to the road and without
+embarrassment to the operations of the company, and provided Mr. Morse
+will concede to the company the use of the telegraph upon the road
+without expense, and reserving to the company the right of
+discontinuing the use if, _upon experiment_, it should prove _in any
+manner injurious_."
+
+"Whatever," said Mr. McLane, "may be our individual opinions as to the
+feasibility of Mr. Morse's invention, it seems to me that it is our
+duty to concede to him the privilege he asks, and to lend him all the
+aid in our power, especially as the resolution carefully protects the
+company against all present or future injury to its works, and secures
+us the right of requiring its removal at any time."
+
+[In view of the fact that no railroad can now be run safely without
+the aid of the telegraph, the cautious care with which the right to
+remove it if it should become a nuisance was reserved, strikes one at
+this day as nearly ludicrous.]
+
+A short pause ensued, and the assent of the company was about to be
+assumed, when one of the older directors, famed for the vigilance with
+which he watched even the most trivial measure, begged to be heard.
+
+He admitted that the rights and interests of the work were all
+carefully guarded by the terms of the resolution, and that the company
+was not called upon to lay out any of its means for the promotion of
+the scheme. But notwithstanding all this, he did not feel, as a
+conscientious man, that he could, without further examination, give
+his vote for the resolution. He knew that this idea of Mr. Morse,
+however plausible it might appear to theorists and dreamers, and
+so-called men of science, was regarded by all practical people as
+destined, like many other similar projects, to certain failure, and
+must consequently result in loss and possibly ruin to Mr. Morse. For
+one, he felt conscientiously scrupulous in giving a vote which would
+aid or tempt a visionary enthusiast to ruin himself.
+
+Fortunately, the views of this cautious, practical man did not
+prevail. A few words from the mover of the resolution, Mr. Nicholas,
+who still lives to behold the wonders he helped to create, and from
+Mr. Kennedy, without whose aid the appropriation would not have passed
+the House of Representatives, relieved the other directors from all
+fear of contributing to Mr. Morse's ruin, and the resolution was
+adopted. Of the President and thirty directors who took part in this
+transaction, only three, Samuel W. Smith, John Spear Nicholas, and the
+writer, survive. Under it Morse at once entered upon that test of his
+invention whose fruits are now enjoyed by the people of all the
+continents.
+
+It was not, however, until the spring of 1844 that he had his line and
+its appointments in such a condition as to allow the transmission of
+messages between the two cities, and it was in May of that year that
+the incident occurred which has chiefly led to the writing of this
+paper.
+
+
+MR. LATROBE'S RECOLLECTIONS.
+
+MY DEAR MR. POE: Agreeably to my promise, this morning I put
+on paper my recollection of the introduction of the magnetic telegraph
+between Baltimore and Washington. I was counsel of the Baltimore &
+Ohio Railroad Co. at the time, and calling on Mr. Louis McLane, the
+President, on some professional matter, was asked in the course of
+conversation whether I knew anything about an electric telegraph which
+the inventor, who had obtained an appropriation from Congress, wanted
+to lay down on the Washington branch of the road. He said he expected
+Mr. Morse, the inventor, to call on him, when he would introduce me to
+him, and would be glad if I took an opportunity to go over the subject
+with him and afterward let him, Mr. McLane, know what I thought about
+it. While we were yet speaking, Mr. Morse made his appearance, and
+when Mr. McLane introduced me he referred to the fact that, as I had
+been educated at West Point, I might the more readily understand the
+scientific bearings of Mr. Morse's invention. The President's office
+being no place for prolonged conversation, it was agreed that Mr.
+Morse should take tea at my dwelling, when we would go over the whole
+subject. We met accordingly, and it was late in the night before we
+parted. Mr. Morse went over the history of his invention from the
+beginning with an interest and enthusiasm that had survived the
+wearying toil of an application to Congress, and with the aid of
+diagrams drawn on the instant made me master of the matter, and wrote
+for me the telegraphic alphabet which is still in use over the world.
+Not a small part of what Mr. Morse said on this occasion had reference
+to the future of his invention, its influence upon communities and
+individuals, and I remember regarding as the wild speculations of an
+active imagination what he prophesied in this connection, and which I
+have lived to see even more than realized. Nor was his conversation
+confined to his invention. A distinguished artist, an educated
+gentleman, an observant traveler, it was delightful to hear him talk,
+and at this late day I recall few more pleasant evenings than the only
+one I passed in his company.
+
+Of course, my first visit the next morning was to Mr. McLane to make
+my report. By this time I had become almost as enthusiastic as Mr.
+Morse himself, and repeated what had passed between us. I soon saw
+that Mr. McLane was becoming as eager for the construction of the line
+to Washington as Mr. Morse could desire. He entered warmly into the
+spirit of the thing, and laughed heartily, if not incredulously, when
+I told him that although he had been Minister to England, Secretary of
+State, and Secretary of the Treasury, his name would be forgotten,
+while that of Morse would never cease to be remembered with gratitude
+and praise. We then considered the question as to the right of the
+company to permit the line to be laid in the bed of the road--the plan
+of construction at that time being to bury in a trench some eight or
+ten inches deep a half inch leaden tube containing the wrapped wire
+that was to form the electric circuit. About this there was, in my
+opinion, no doubt, and it was not long after that the work of
+construction commenced. I met Mr. Morse from time to time while he
+lived, and often recurred to the evening's discussion at my house in
+Baltimore.
+
+The above is the substance of what I have more than once related to
+other persons. I hope you will persist in your design of putting on
+paper your own very interesting recollections in this connection, and
+if what I have contributed of mine is of service to you, I shall be
+much pleased.
+
+                                  Most truly yours,
+                                    JOHN H.B. LATROBE.
+March 3, 1881.
+
+       *       *       *       *       *
+
+
+
+
+THE KRAVOGL ELECTRIC MOTOR.
+
+
+At the origin of every science, of whatever nature it may be, there is
+always a fruitless period, of greater or less length, characterized by
+the warfare of a few superior minds against general apathy. The finest
+discoveries pass unperceived, so to speak, since they cannot cross the
+limits of a narrow circle; and it often happens that they fall into
+oblivion before they have been seriously judged. Meanwhile, a slow
+progress is imperceptibly made, and, in measure as theoretical
+principles more clearly disengage themselves, a few industrial
+applications spring up and have the effect of awakening curiosity. An
+impulse is thus given, and from this moment a movement in advance goes
+on increasing at a headlong pace from day to day.
+
+With electricity this period has been of comparatively short duration,
+since scarcely a century and a half separate us from the first
+experiments made in this line of research. Now that it has truly taken
+its place in a rank with the other sciences, we like to go back to the
+hesitations of the first hour, and trace, step by step, the history of
+the progress made, so as to assign to each one that portion of the
+merit that belongs to him in the common work. When we thus cast a
+retrospective glance we find ourselves in the presence of one strange
+fact, and that is the simultaneousness of discoveries. That an
+absolutely original idea, fertile in practical consequences, should
+rise at a given moment in a fine brain is well; we admire the
+discovery, and, in spite of us, a little surprise mingles with our
+admiration. But is it not a truly curious thing that _several_
+individuals should have had at nearly the same time that idea that was
+so astonishing in one? This, however, is a fact that the history of
+electrical inventions offers more than one example of. No one ignores
+the fact that the invention of the telephone gave rise to a notorious
+lawsuit, two inventors having had this ingenious apparatus patented on
+the same day and at nearly the same hour. This is one example among a
+thousand. In the history of dynamo-electric machines it is an equally
+delicate matter to fix upon the one to whom belongs the honor of
+having first clearly conceived the possibility of engendering
+continuous currents.
+
+We do not wish to take up this debate nor to go over the history of
+the question again. Every one knows that the first continuous current
+electric generator whose form was practical is due to Zenobius Gramme,
+and dates back to July, 1871, an epoch at which appeared a memoir
+(entitled "Note upon a magneto-electric machine that produces
+continuous currents") that was read to the Academy of Sciences by Mr.
+Jamin. Ten years previous, Pacinotti had had a glimpse of the
+phenomenon, and of its practical realization, but was unfortunately
+unable to appreciate the importance of his discovery and the benefit
+that might be reaped from it. It is of slight consequence whether
+Gramme knew of this experiment or not, for the glory that attaches to
+his name could not be diminished for all that. But an interesting fact
+that we propose to dwell upon now has recently been brought to light
+in an electrical review published at Vienna.[1] It results from
+documents whose authenticity cannot be doubted that, as far back as
+1867, Mr. L. Pfaundler, a professor at Innsbruck, very clearly
+announced the reversibility of a magneto-electric motor constructed by
+Kravogl, a mechanician of the same place, and that he succeeded some
+time before Gramme in obtaining continuous currents.
+
+   [Footnote 1: _Zeitschrift des Electrotechnischen Vereines_ in
+   _Wien_, July, 1883.]
+
+The Kravogl motor that figured at the Universal Exhibition of 1867 is
+but little known, and it is now very difficult to obtain drawings of
+it. What is certain is that this motor is an application of the
+properties of the solenoid, and, from this standpoint, resembles the
+Bessolo motor that was patented in 1855. We may figure the apparatus
+to our mind very well if we suppose that in the Gramme ring a half and
+almost two-thirds of the core are removed, and the spirals are movable
+around the said core. If a current be sent into a portion of the
+spirals only, and in such a way that only half of the core be exposed,
+the latter will move with respect to the bobbin or the bobbin with
+respect to the core, according as we suppose the solenoid or the
+bobbin fixed. In the first case we have a Bessolo motor, and in the
+second a Kravogl one.
+
+In order to obtain a continuous motion it is only necessary to allow
+the current to circulate successively in the different portions of the
+solenoid. It is difficult to keep the core in place, since it is
+unreachable, being placed in the interior of the bobbin. Kravogl
+solved this difficulty by constructing a hollow core into which he
+poured melted lead. This heavy piece, mounted upon rollers, assumed a
+position of equilibrium that resulted from its weight, from friction,
+and from magnetic attraction. But for a current of given intensity
+this position, once reached, did not vary, and so necessitated a
+simple adjustment of the rubbers. Under such circumstances, with a
+somewhat large number of sections, the polarity of the core was nearly
+constant. The spirals as a whole were attached to a soft iron armature
+that had the effect of closing up the lines of forces and forming a
+shell, so to speak.
+
+Like Bessolo, Kravogl never thought of making anything but a motor,
+and did not perceive that his machine was reversible. It results from
+some correspondence between Dr. A. Von Waltenhofen and Mr. L.
+Pfaundler at this epoch that the latter clearly saw the possibility of
+utilizing this motor as a current generator. Under date of November 9,
+1867, he wrote, in speaking of the Kravogl motor, which had just been
+taken to Innsbruck in order to send it to Paris. "I regret that I
+shall not be able to see it any more, for I should have liked to try
+to make it act in an opposite direction, that is to say, to produce a
+current or an electric light by means of mechanical work." A little
+more than two years later these experiments were carried out on a
+larger motor constructed by Kravogl in 1869, and Mr. Pfaundler was
+enabled to write as follows: "Upon running the machine by hand we
+obtain a current whose energy is that of one Bunsen element." This
+letter is dated February 11, 1870, that is to say, it is a year
+anterior to the note of Gramme.
+
+[Illustration: FIG. 1.]
+
+In the presence of the historic interest that attaches to the
+question, we do not think it will be out of place to reproduce here
+the considerations that guided Prof. Pfaundler in the researches that
+led him to convert the Kravogl motor into a dynamo-electric machine.
+Let us consider two magnetized bars, _db_ and _bd'_, placed end to end
+and surrounded by a cylindrical armature forming a shell, this
+armature being likewise supposed to be a permanent magnet and to
+present poles of contrary direction opposite the poles of the bars.
+For the sake of greater simplicity this shell is represented by a part
+only in the figure, _s n n s_. If, into a magnetic field thus
+formed, we pass a spiral from left to right, the spiral will be
+traversed by a current whose direction will change according to the
+way in which the moving is done. It is only necessary to apply Lenz's
+law to see that a reversal of the currents will occur at the points,
+_a_ and _c_, the direction of the current being represented by arrows
+in the figure. If we suppose a continual displacement of the spirals
+from left to right, we shall collect a continuous current by placing
+two rubbers at _a_ and _c_. Either the core or the shell may be
+replaced by a piece of soft iron. In such a case this piece will move
+with the spiral and keep its poles that are developed by induction
+fixed in space. From this, in order to reach a dynamo-electric machine
+it is necessary to try to develop the energy of the magnetic field by
+the action of the current itself. If we suppose the core to be of soft
+iron, and make a closer study of the action of the current as regards
+the polarity that occurs under the influence of the poles, _s_, _n_,
+_s_, we shall see that from _d_ to _a_ and from _b_ to _c_ the current
+is contrary, while that from _a_ to _b_ and from _c_ to _d'_ it is
+favorable to the development of such polarity. In short, with a spiral
+moving from _d_ to _d'_ the resulting effect is _nil_, a fact,
+moreover, that is self-evident. Under such circumstances, if we
+suppose the shell, as well as the core, to be of soft iron, we shall
+obtain a feeble current due to the presence of remanent magnetism; but
+this magnetism will not be able to continue increasing under the
+influence of the current. To solve this difficulty two means present
+themselves: (1) to cause a, favorable magnetic current and act upon
+the armature, and (2) to suppress such portions of the current in the
+spirals as are injurious in effect. The first solution was thought of
+by Gramme in 1871, and is represented diagramatically in Fig. 2. The
+second is due to Prof. Pfaundler, and dates back to 1870. The core is
+cut through the center (Fig. 3), and the portion to the right is
+suppressed; the current is interrupted between _da_ and _cd'_, and is
+closed only between _a_ and _c_ (_v_, Fig. 1). It results from this
+arrangement that, under the action of the current, the polarity due to
+remanent magnetism does nothing but increase. It suffices then for but
+little remanent magnetism to prime the machine; the polarity of the
+shell continues to increase, and the energy of the magnetic field, and
+consequently of the current, has for a limit only the saturation of
+the soft iron. If, now, we curve the core, the spirals, and the
+armature into a circle, we have a Gramme or a Pfaundler machine,
+according as we consider Fig. 2 or Fig. 3.
+
+[Illustration: FIG. 2.]
+
+[Illustration: FIG. 3.]
+
+This latter apparatus has in this case the form shown in Fig. 4.
+
+[Illustration: FIG. 4.]
+
+The spiral, _s m b_, is movable, and the core, N _o s_, is kept in a
+position of equilibrium by virtue of its weight, and is provided with
+rollers. For the sake of greater clearness, the front part of the
+armature is supposed to be removed. The current does not circulate in
+the spirals to the right of the diameter, W O, which latter is not
+absolutely vertical. The position of the rubbers and armature is
+regulated once for all. We do not know just what were the means
+devised by Kravogl to suppress the current in the spheres to the
+right. At all events, it is probable that the system has grown old
+since Gramme invented his collector. In the application of the Kravogl
+motor to the generation of continuous currents, Professor Pfaundler
+now proposes to ingeniously utilize the Gramme collector. In such a
+case the arrangement shown in Fig. 5 would be adopted. Let us suppose
+an ordinary collector having as many plates as there are sections in
+the ring, these plates being connected as usual with the entrance and
+exit wires of the sections. The diametrically opposite touches that
+are in the line, W O, are divided, and one of the halves is connected
+at the entrance, _c a'_ (Fig. 4), with the corresponding section,
+while the other communicates with the exit, _c' a_, of the neighboring
+section. Each of these halves is prolonged by a piece of metal bent
+into the form of an arc of a circle and embracing a little less than a
+semi-circumference. Between these prolongations there is an insulating
+part. In the rotary motion of the spiral, at least one of the touches
+is always outside of the arc comprised between the brushes, R. In
+order to secure a continuity of the circuit in the effective arc, W S_ o_,
+it is only necessary to arrange a rubber, M, in such a way as to
+establish a communication between the two parts of the divided touch
+as soon as this latter enters the arc under consideration.
+
+In order to produce a current in the direction of the arrows shown in
+Fig. 4, the spiral and axle must revolve from right to left. In this
+case the rubber, M, occupies the position shown in the same figure,
+the brushes embracing an arc of a little less than 180�. As soon as
+the lower touch comes in contact with the brush, R, when the
+revolution is being effected from left to right, the rubber, M,
+establishes a communication between the two halves that have until now
+been isolated, and the current is no longer interrupted. The second
+touch during this time is at any point whatever of the arc, W N _o_,
+and the spirals corresponding to the latter arc outside of the
+circuit. In short, thanks to the rubber, M, we have an ordinary Gramme
+collector in that portion of the circuit comprised between the
+brushes, and a collector with a breakage of the circuit in the portion
+to the right.
+
+[Illustration: FIG. 5.]
+
+This type of machine is entirely theoretical. In the apparatus used
+for Prof. Pfaundler's experiments in 1870, the armature revolved with
+the solenoid. The core and armature were of soft iron, and the core
+was arranged in a manner analogous to the preceding, and remained in
+place under the action of its weight, and the shell, forming a
+complete circle, revolved with poles fixed in space.
+
+Practically, the machine that we have just described would prove
+inconvenient to realize, and would present serious inconveniences. In
+the first place, it seems to us quite difficult to transmit the motion
+of the solenoid to the axle, supposing the former to revolve within
+the armature. In the second place, considerable friction would surely
+occur between the spirals and core, and the axle, being submitted to a
+lateral stress, would be placed in a poor condition for work. It is
+even allowable to doubt whether such a type could be practically got
+up. At all events, no trial has as yet been made of it.
+
+Compared with the Gramme machine, from an absolutely theoretical point
+of view, the Pfaundler apparatus presents undoubted advantages. A
+theoretically perfect dynamo electric machine would be one in which
+there was a complete reciprocity between the magnetizing action of the
+current and the inductive action of the magnetic field. Now, such is
+not the case in the Gramme machine. In this apparatus the soft iron
+core is at the same time a magnet through favorable induction and a
+disadvantageous electro-magnet. This double polarization is only
+remedied to a certain extent by the adjustment of the brushes. In the
+Pfaundler machine, on the contrary, the electro-magnetism and
+magnetism through induction act in the same direction, and concur in
+effecting a polarization that favors the production of the current.
+Looked at it in this light, the latter machine more nearly approaches
+the type of perfection than does that of Gramme.
+
+But we must not forget that such qualities are purely theoretical. In
+practice the best machine is that in which the copper is best
+utilized, that is to say, that which with a given weight of this metal
+furnishes the most work. Now, this is certainly not the case in the
+Pfaundler machine, for here half or more than half of the ring is
+inert--a defect which is apparent at first sight. It results from this
+that as soon as we propose to obtain an electromotive force, however
+slight it be, we must get it with machines of large dimensions. Now,
+it is permissible to believe that under such circumstances (taking
+into consideration the complication of mechanical means that the
+construction of such apparatus necessitates, and the great friction
+that occurs) it would be impossible to obtain practical rotary
+velocities. Comparing his machine with Gramme's, Prof. Pfaundler
+expresses the idea that between them there is the same analogy as
+there is between a constant pressure and an expansion engine. With
+cylinders of equal diameters the work performed by the former of these
+is greater than that done by the second, but in the latter the
+expansive force of the steam is better utilized. This comparison seems
+to us to be more ingenious than exact. Would it not be coming nearer
+to the truth if we were to suppose a case of a hydraulic motor whose
+performance continued diminishing with the height of the fall, and
+would it not be advantageous under such circumstances to utilize only
+a portion of the fall for the purpose of increasing the motor's
+performance?
+
+This machine, however, as before stated, has never as yet been
+constructed, so that experimental data relative to its mode of working
+are wanting. It is especially interesting as regards its origin, which
+dates back to an epoch at which researches on the dynamo electric
+machine were at their heat. It is in its historical aspect that it is
+proper to regard it, and it is from such a point of view that we have
+deemed it well to say a few words about it in this place.--_La Lumiere
+Electrique._
+
+       *       *       *       *       *
+
+
+
+
+BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES.
+
+
+We shall not attempt to pass in review the several apparatus that have
+hitherto been devised for igniting blasts in mining operations, but
+shall simply describe in this place a machine recently invented for
+this purpose by Mr. Bornhardt, an engineer to the Grand Duke of
+Brunswick.
+
+This apparatus (shown in the accompanying engravings) consists
+essentially of two hard-rubber disks, A (Figs. 2 and 3), keyed to an
+iron axle, and of two rubbers, B, that are formed of skin and are held
+against the disks by small springs, R; motion is communicated to the
+axle, _a_, by means of a pair of gearings, _a_ and _b_, and a crank,
+_f_.
+
+[Illustration: BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES.]
+
+Each disk revolves between two metallic rings, _c_, provided with
+points that attract and collect in Leyden jars, D, the electricity
+produced by the friction. For discharging the condensers there is
+employed a manipulator formed of a rod, mm, which can be acted upon,
+from the exterior, by means of a button, _k_. Upon bringing the ball,
+_m_, of the rod in contact with the ball, _p_, of the condenser, the
+lever (which then takes the position shown by the dotted line)
+continues to remain in connection with a small ring, _q_, through a
+special spring. Another ring, _t_, is connected in the same way with
+the external armature of the condenser. Upon connecting the rings, _p_
+and _t_, by a wire to which cartridges are attached, any number of the
+latter may be ignited.
+
+The parts that we have just enumerated are inclosed in a tin box
+covered with a wooden casing, P. Between the two there is inserted a
+sheet of hard rubber in order to prevent a loss of electricity; the
+whole is held in place by strong springs.
+
+In order to show the normal state of the condenser, a scale consisting
+of 15 metallic buttons to give the dimensions of the sparks, is
+arranged at X. This scale is capable of being connected with the
+rings, _q_ and _t_, by means of chains; when the spark obtained after 15
+or 20 revolutions considerably exceeds the intervals of the scale, it
+is a sure thing that the machine is in a proper state.
+
+In order to prepare the apparatus for carriage, the winch is taken off
+and placed in the compartment, _m_, which is closed by means of a
+door, Q.
+
+Figs. 5 and 6 show the arrangement of the dynamite cartridges and
+wires in the blast hole. Figs. 7 to 10 show different arrangements of
+the igniting wires. Figs. 11 and 12 give the general arrangement for
+igniting a number of cartridges simultaneously by means of the
+electric machine. Fig. 13 shows the arrangement where powder is
+employed. Fig. 14 shows the arrangement of a horizontal
+hole.--_Annales Industrielles._
+
+       *       *       *       *       *
+
+
+
+
+IMPROVED ELECTRIC FIRE ALARM.
+
+
+The object of this apparatus is to close an electric circuit when the
+temperature of a room rises above a certain point. Many devices have
+been invented for effecting this object, each of which have their own
+advantages or disadvantages. The invention of Mr. Pritchett enables
+the required result to be obtained in a very satisfactory manner. The
+apparatus consists (as shown by the figure) of a long glass vessel
+containing air; connected to this vessel there is a glass tube filled
+with mercury. The whole is mounted on a metal cradle, which turns on
+pivots. According to the position which the glass vessel and its
+adjuncts occupy in the cradle (this position being adjustable by means
+of a thumb-screw, seen at the upper part of the cradle), so will the
+same have a tendency to rock longitudinally over to one side or the
+other. Now, if we suppose the position to be such that the right hand
+end of the glass vessel is depressed, and the left hand end raised,
+then if the vessel becomes subjected to an elevation of temperature,
+the air inside the same will become expanded, and the mercury column
+in the tube will be driven over to the left, and will rise in the
+turned up end of the tube. This will cause the left hand branch of the
+glass vessel, and its attachments, to become increased in weight,
+while the right hand branch will become proportionally lighter; the
+consequence of this will be that the vessel and its cradle will cant
+over, and by falling on an electrical contact will close a circuit and
+sound an alarm. It is obvious that the apparatus is equally well
+adapted for indicating a diminution as well as an increase of
+temperature, for if the electrical contact be placed under the right
+hand portion of the cradle, and the latter be adjusted so that in its
+normal position its left hand portion is depressed, then when the
+glass vessel becomes cooled, the air in it will contract, and the
+mercury will fall in the turned-up portion of the tube before referred
+to, and will rise in the limb connected to the vessel, consequently
+the cradle and glass vessel will cant over in the reverse way to that
+which it did in the first case.
+
+Owing to the surface which the glass vessel exposes, the air inside
+quickly responds to any external change of temperature, consequently
+the apparatus is very sensitive. Another important feature is the fact
+that the cradle and vessel in canting over acquires a certain
+momentum, and thus the contact made becomes very certain.
+
+[Illustration: PRITCHETT'S ELECTRIC FIRE ALARM.]
+
+Mr. Pritchett proposes that his apparatus shall give external evidence
+outside the house by ringing a gong, and by dropping a semaphore arm
+released by an electromagnet. He also proposes (as has often been
+suggested) that a water supply shall be automatically turned
+on.--_Electrical Review._
+
+       *       *       *       *       *
+
+
+
+
+A STANDARD THERMOPILE.
+
+
+Dr. G. Gore, F.R.S., has invented an improved thermopile for
+measuring small electromotive forces. It consists of about 300 pairs
+of horizontal, slender, parallel wires of iron and German silver, the
+former being covered with cotton. They are mounted on a wooden frame.
+About 1� in. of the opposite ends of the wires are bent downward to a
+vertical position to enable them to dip into liquids at different
+temperatures contained in long narrow troughs; the liquids being
+non-conductors, such as melted paraffin for the hot junctions, and the
+non-volatile petroleum, known as thin machinery oil. The electromotive
+force obtained varies with the temperature; a pile of 295 pairs having
+a resistance of 95.6 ohms at 16 deg. Cent. gave with a difference of
+temperature of 100 deg. Cent. an electromotive force of 0.7729 volts,
+or with 130 deg. Cent. an electromotive force of 1.005 volt. Each
+element, therefore, equaled 0.0000262 volt for each degree Cent.
+difference of temperature. On having been verified with a standard
+voltaic cell the apparatus becomes itself a standard, especially for
+small electromotive forces. It is capable of measuring the 1/34861
+part of a volt. For higher electromotive forces than a volt, several
+of these piles would have to be connected in series. The fractional
+electromotive force is obtained by means of a sliding contact which
+cuts out so many pairs as is required.
+
+       *       *       *       *       *
+
+
+
+
+TELEPHONIC TRANSMISSION WITHOUT RECEIVERS.
+
+
+The annual meeting of the French Society of Physics, the success of
+which is continually increasing, took place this year in the salons of
+the Observatory, which were kindly placed at the Society's disposal by
+Admiral Mouchez.
+
+There were three consecutive sessions, the one of Tuesday, April 15,
+being set apart for the members of the Association, the one of the
+16th for the invited guests of Admiral Mouchez, and that of the 17th
+for the invited guests of the Society. The salons were partially
+lighted by the Siemens differential arc, continuous current lamps, and
+partially by the Swan incandescent lamp supplied by a distributing
+machine that permitted of the lamps being lighted and extinguished at
+will without changing the normal operation of all the rest. Many
+apparatus figured at this exhibition, but we shall on the present
+occasion merely call attention to those that presented a certain
+character of novelty or of originality.
+
+Among the apparatus that we shall reserve a description of for the
+present was Messrs. Richard Bros.' registering thermometer designed
+for the Concarneau laboratory, an instrument which, when sunk at one
+mile from the coast, and to a depth of 40 meters, will give a diagram
+of the temperature of the ocean at that depth; and Mr. Hospitalier's
+continuous electrical indicators, designed for making known from a
+distance such mechanical or physical phenomena as velocities, levels,
+temperatures, pressures, etc.
+
+Among the most important of the apparatus exhibited we must reckon Mr.
+Cailletet's devices for liquefying gases, and those of Mr. Mascart for
+determining the ohm. The results obtained by Mr. Mascart (which have
+been submitted to the Committee on Unities of the Congress of
+Electricians now in session at Paris), are sensibly concordant with
+those obtained independently in England by Lord Rayleigh. Everything
+leads to the hope, then, that a rapid and definite solution will be
+given of this important question of electric unities, and that nothing
+further will prevent the international development of the C.G.S.
+system.
+
+Mr. Jules Duboscq made a number of very successful projections, and we
+particularly remarked the peculiar experiment made in conjunction with
+Mr. Parinaud, that gave in projection two like spectra produced by the
+same prism, and which, through superposition, were capable of
+increasing the intensity of the colors, or, on the contrary, of
+reconstituting white light.
+
+Among the optical applications we may cite Mr. Leon Laurent's
+apparatus for controlling plane, parallel, perpendicular, and oblique
+surfaces, and magic mirrors obtained with an ordinary light; Mr. S.P.
+Thompson's apparatus for demonstrating the propagation of
+electro-magnetic waves in ether (according to Maxwell's theory), as
+well as some new polarizing prisms; and a mode of lighting the
+microscope (presented by Mr. Yvon), that was quite analogous to the
+one employed more than a year ago by Dr. Van Heurck, director of the
+Botanical Garden of Anvers.
+
+Acoustics were represented by an electro-magnetic brake siren of Mr.
+Bourbouze; Konig's apparatus for the synthesis of sounds; and Mr. S.P.
+Thompson's cymatograph--a pendulum apparatus for demonstrating the
+phenomena of beats.
+
+It was electricity again that occupied the largest space in the
+programme of the session.
+
+Apparatus for teaching are assuming greater and greater importance
+every day, and the exhibit of Mr. Ducretet included a large number of
+the most interesting of these. The house of Breguet exhibited on a
+reduced scale the magnificent experiments of Gaston Plante, wherein
+320 leaden wire secondary elements charged for quantity with 3 Daniell
+elements, and afterward coupled for tension, served to charge a
+rheostatic machine formed of 50 condensers coupled for quantity. These
+latter, coupled anew for tension, furnished upon being discharged a
+spark due to a difference of potential of about 32,000 volts that
+presented all the characters of the spark produced by induction coils
+on the machines so improperly called "static." Finally, we may cite
+the apparatus arranged by Mr. S.P. Thompson for studying the
+development of currents in magneto-electric machines. The inventor
+studies the influence of the forms of the inductors and armatures of
+machines by means of an arrangement that allows him to change the
+rings or armatures at will and to take out the induced bobbins in
+order to sound every part of the magnetic field. Upon giving the
+armature an angular motion limited by two stops, there develops a
+certain quantity of electricity that may be measured by causing it to
+traverse an appropriate ballistic galvanometer. Messrs. Deprez and
+D'Arsonval's galvanometer answers very well for this purpose, and its
+aperiodicity, which causes it quickly to return to zero as soon as the
+induced current ceases, permits of a large number of readings being
+taken within a very short space of time.
+
+Measuring apparatus were represented by a new and very elegant
+arrangement of Sir William Thomson's reflecting galvanometers, due to
+Mr. J. Carpentier. The mounting adopted by Mr. Carpentier permits of
+an easy removal of the bobbins and of an instantaneous substitution
+therefor. The galvanometric part, composed of the needles and mirror,
+therefore remains entirely free, thus allowing of its being verified,
+and making it convenient to attach the silken fiber. Mr. Carpentier
+has, moreover, adopted for all the minor apparatus a transparent
+celluloid scale which simplifies them, facilitates observations, and
+renders the use of reflection almost industrial.
+
+We shall complete our enumeration of the measuring apparatus by citing
+Ducretet's non-oscillating galvanometer, Sir William Thomson's
+amperemeters, voltameters, ohmmeters, and mhosmeters, constructed and
+exhibited by Breguet, and a new aperiodic galvanoscope of Mr. Maiche.
+Mr. Baudot exhibited the recent improvements that he has made in his
+multiplex printing telegraph, and M. Boudet of Paris showed a new
+system of telephone transmission by submarine cables.
+
+[Illustration: FIG. 1.--DIAGRAM EXHIBITING THE ARRANGEMENT FOR
+TELEPHONIC TRANSMISSIONS WITHOUT A RECEIVER.]
+
+Finally, we shall conclude our enumeration by referring to the
+curiosities. The house of Siemens exhibited a miniature electric
+railway actuated by a new model of Reynier accumulators; M. Maiche
+operated a system of musical telephonic auditions that differed only
+in detail from those instituted by Mr. Ader at the exhibition of 1881;
+and Mr. Hospitalier presented a new form of an experiment devised by
+Mr. Giltay, consisting of a telephonic transmission of sounds without
+the use of receivers. Mr. Giltay's experiment is nothing but Mr.
+Dunand's speaking condenser without the condenser. A glance at Fig. 1
+will show how things are arranged for the experiment. The transmitting
+system comprises two distinct circuits, viz.: (1) one formed of a
+pile, P, of 2 or 3 Leclanche elements, or of 1 or 2 small sized
+accumulators, an Ader microphane transmitter, M, and the inducting
+wire of a small induction coil, B; and (2) the other formed of the
+induced wire of the coil, B, of a pile, P', of 10 or 12 Leclanche
+elements, and of a line whose extremities terminate at R, in two
+ordinary electro-medical handles. With this arrangement the experiment
+performed is as follows: When any one speaks or sings in front of the
+transmitter, T, while two persons, A and B, each having one hand
+gloved, are holding the handles in the ungloved hand, it is only
+necessary for A to place his gloved hand upon B's ear, or for the
+latter to place his hand upon A's, or for each to place his hand on
+the other's ear simultaneously, in order that A or B, or A and B
+simultaneously, may hear a voice issuing from the glove. Under these
+circumstances, Mr. Giltay's experiment is explained like Dunand's
+speaking condenser--the hand of A and the ear of B here constituting
+the armature of an elementary condenser in which the glove performs
+the role of dielectric.
+
+Upon repeating this experiment at the laboratory of the School of
+Physics and Industrial Chemistry of Paris, it has been found that the
+glove maybe replaced by a sheet of plain or paraffined paper. In this
+case, when two persons are holding the handles, and have their ears
+applied, one against the other, if a sheet of paper be interposed,
+airs or words will be heard to proceed therefrom. Finally, it has been
+found possible to entirely suppress the paper, or dielectric, and to
+hear directly, by simply interposing the auditor or auditors in the
+circuit. One of the most curious forms of the experiment is the one
+shown in Fig. 2. Here a third person, C, hears the hands of A and B
+speak when a circuit is formed by means of three persons, A, B, and C,
+the two former, A and B, each holding one of the wires of the circuit
+and applying his free hand to the ear of C. Although the experiment is
+one that requires entire silence, and could not on that account be
+performed at the laboratory, a sort of telephonic chain can be formed
+in which five or six persons may hear at the same time. A, putting his
+hand on the ear of B, the latter putting his to that of C, and so on
+up to the last person, who closes the circuit by grasping one of the
+handles, the other one being held by A.
+
+[Illustration: EXPERIMENT ON TELEPHONIC TRANSMISSION WITHOUT
+RECEIVING APPARATUS.]
+
+It is difficult in the present state of science to explain very
+clearly how these telephonic transmissions are effected without a
+receiver. All that we can conclude from it so far is that the ear is
+an instrument of incomparable delicacy and of exquisite sensitiveness,
+since it perceives vibrations in which the energy developer,
+particularly in the telephonic chain, is exceedingly feeble.
+
+Without any desire to seek an application for an experiment that is
+simply curious, we yet believe that there is here a phenomenon of a
+nature to be studied by physicists. Discoveries in telephony and
+microphony have certainly opened up to science, as regards both theory
+and practice, new horizons that still promise other surprises for the
+future. But to return to the observatory: The success obtained by the
+exhibition of the French Society of Physics shows that these reunions
+respond to a genuine need--that of instructing in and popularizing
+science. While warmly congratulating the organizers of these meetings,
+we may express a wish that the good example set by the Society of
+Physics may be followed by other societies. We are convinced in
+advance that an equal success awaits them.--_La Nature._
+
+       *       *       *       *       *
+
+
+
+
+ON THE ARRANGEMENT OF GROUND CONDUCTORS.
+
+
+In telegraphy, as well as in the question of lightning rods, attention
+has been but incidentally paid to the improvement of ground
+conductors, and this point has not been the object of that careful
+study that has been bestowed upon the establishment of aerial lines.
+It is only recently that the interest created by lightning rods has
+given rise to new forms of conductors differing from those formerly
+used. The publications of the Prussian Academy of Sciences of from
+1876 to 1880 contain some information of special importance in regard
+to this. It is stated therein that the effect of ground conductors may
+be notably increased by the division of the earth plates and the use
+of metallic rods, without necessitating a greater output of material.
+These facts, however, have not as yet been put to profit in practice
+for the reason, perhaps, that the considerations, which have remained
+general, have not at once permitted of obtaining forms what could be
+employed with perfect knowledge of the results. This is what led Mr.
+Ulbricht, of Dresden, to make calculations for a few forms of
+conductors, and to test their approximate values. The results of these
+researches are printed in the _Elektrotechnischen Zeitschrift_ for
+1883 (p. 18).
+
+[Illustration]
+
+The equations found show, in the first place, that there exist three
+means of obtaining a considerable effect, as regards the ground
+conductor, with a slight expenditure of material: The cylindrical
+electrode may be drawn out into the form of a bar or wire; the plate
+may be rendered narrow, and elongated in the form of a ribbon; and,
+besides, the annular plate may be enlarged in lessening the metallic
+surface.
+
+Finally, a short, open cylinder with a vertical axis may be formed by
+curving a narrow plate or ribbon. It is not necessary to see the
+formula to recognize the fact that this cylinder must behave like a
+ribbon and a flat ring. The radius increasing, and the surface
+remaining constant, the resistance of the earth here likewise
+approaches zero.
+
+As the resistance of the earth is inversely proportional to the
+diameter of the plates, the zero resistance can also be reached by
+dividing a plate _ad infinitum_. As the parts of the plate may be
+brought quite close to each other without perceptibly interfering with
+the action, a _network_ has finally been reached by a division carried
+very far, yet limited, and by connecting the parts with one another by
+conducting cylinders.
+
+If we seek to determine what forms of ground conductors are efficient
+and economical under given conditions, we shall have to begin by
+informing ourselves as to the choice of material to be used for the
+electrode, and shall then have to ascertain whether putting it in the
+ground will or will not necessitate much outlay. The most suitable
+material is copper, which may be used with advantage, in that it lasts
+pretty well underground, and that the facility which it may be worked
+permits of easily giving it more appropriate forms than those that can
+be obtained with cast iron, which is of itself less costly.
+
+If the burying in the ground requires little or no labor, as when
+there exist ponds, rivers, and wells, or subterranean strata of water
+near the surface of the earth, elongated forms of conductors will be
+employed, such as the solid or hollow cylinder, the wire, the ribbon,
+the narrow ring, and the network. Plates approaching a square or
+circular shape are not advantageous. But if the ground has to be dug
+deeply in order to sink the conductor, the form of the electrode must
+be more condensed, and selected in such a way that the necessary
+action may be obtained with a minimum output of copper and labor. For
+great depths, and when the ground will permit of boring, an elongated
+and narrow cylinder will be used. Such a system, however, can only be
+employed when the cylinder is surrounded by spring water, since,
+without that, an intimate contact with earth that is only moist,
+cannot be obtained with certainty. In earth that is only moist and for
+moderate depths, preference may be given to an electrode laid down
+flat. The digging necessary in this case is onerous, it is true, but
+it permits of very accurately determining the state of the earth
+beneath and of obtaining a very perfect adherence of the electrode
+therewith. Two forms, the annular ribbon or the flat ring and the
+network, present themselves, according to calculations, as a
+substitute for copper plates, which are so expensive; and these forms
+are satisfactory on condition that the labor of digging be not notably
+increased. These forms should always have a diameter a little greater
+than that of the plate. The flat ring and the network, however, offer
+one weak point, which they possess in common with the plate, and that
+is, their dimensions cannot be easily adapted to the nature of the
+ground met with without a notable increase in the expense. Now, if the
+ground should offer a conductivity less than what was anticipated, and
+it were desired to increase the plate, say by one-third, it would be
+impossible to do so as a consequence of the closed form.
+
+One important advantage is realized in this respect by combining the
+ring and the network in the form of a reticulated ring having a
+diameter of from 1 to 1� meters. On cutting this ring at a given place
+and according to a certain radius we obtain the reticulated ribbon
+shown in the accompanying figure. The thickness of the wires is 2.5
+mm., and their weight is 0.475 kilo. per meter. L, L, and L are the
+points at which the conducting cable is soldered. A reticulated ribbon
+of copper can be made in advance of any length whatever, and,
+according to local exigencies, it may be easily curved and given the
+form of a flat or cylindrical ring of varying width. Even though the
+ribbon has already been cut for a ring of given diameter, it may be
+still further enlarged by drawing it out and leaving a bit of the ring
+open, so as to thus obtain a nearly corresponding diminution in the
+resistance. Such a resistance may be still further diminished by
+rendering the ring higher, that is to say, by employing an annular
+cylindrical form.
+
+After assuring himself, by experiments on a small scale, that
+calculation and observation gave concordant results for the flat ring,
+the author made an experiment on a larger scale with the annular
+network. For practical reasons he employed for this purpose a copper
+wire 2.5 mm. in diameter, which may be expected to last as long as one
+of iron plate 2 mm. in thickness. Calculation showed that in a ribbon
+160 mm. wide, meshes 40 mm. in breadth were advantageous and favorable
+as regards rigidity. A reticulated ribbon like this, 4 meters in
+length, was made and formed into a flat ring having an external
+diameter of 1.42 m. and an internal one of 1.10 m. The resistance of
+this ring was found to be W = 0.3485 (1/_k_), and that of a plate one
+meter square, W0 = 0.368 (1/_k_).
+
+As the conductivity of the earth is very variable, and as we cannot
+have an absolute guarantee that the ramming will be uniform, it seemed
+proper to make the measurements of the resistance by fixing the plate
+and the ring in succession to the lower surface of a small raft, in
+such a way that the contact with the water should correspond as well
+as possible to the suppositions made for the calculation. As a second
+ground conductor, a system of water pipes was used, and, after this, a
+lightning rod conductor, etc.
+
+Repeated and varied experiments gave, for the calculation of the
+values of the resistances, equations so concordant that the following
+results may be considered very approximate.
+
+The square plate had a resistance of 35.5 Siemens units, and the
+reticulated ring one of 32.5. From the first figure we deduce k =
+1/91.12, that is to say, the specific conductivity of river-water is
+1:91120000. Calculation, then, gives as the resistance of the earth in
+Siemens units:
+
+                                    Calculated. Observed.
+       Square plate.                   33.5       33.5
+       Annular ring.                   31.76      32.5
+
+These figures prove the accuracy of the calculations that had been
+made in an approximate way.
+
+The experiments were performed upon the Elba, above Dresden. Other
+experiments still had reference to the influence of immersion. In
+order to diminish polarization, only instantaneous currents from the
+measuring pile were employed. It was to be supposed that the current
+of water through which the bubbles of gas were removed from the
+electrodes would not have permitted of a notable resistance of
+polarization. Later measurements, made upon a ribbon buried, like the
+plates, in the earth, gave likewise most favorable results.
+
+As a result of these experiments, the State railways of Saxony have,
+in such cases as were practicable, introduced the annular network of
+copper. There are some manufacturers, too, who seem desirous of
+adopting this system, although it has hardly emerged from the period
+of experiment. The pecuniary advantages that will result from an
+application of it ought, it would seem, to dispel a large proportion
+of the criticisms directed against the erection of lightning rods,
+from the standpoint of expense, and contribute to extend an
+arrangement which may be considered as a very happy one.
+
+If we compare the square plate with the equivalent annular network,
+constructed as above indicated, and which should possess, according to
+the author an external diameter of 1.26 m. and of 3.45 m., we find
+that:
+
+    The square plate, 1 mm. thick weighs 8.9 kilos.
+                 "    2  "    "     "   17.8   "
+    The annular network             "    1.64  "
+
+The cost of reticulated ribbon per meter amounts to about 4.4 francs,
+supposing it to be arranged as shown in the cut.
+
+As term of comparison, we may admit that the following forms are
+nearly the equivalent of a horizontal, unburied plate one meter
+square.
+
+                                   Length. Diameter.
+    Vertical cylinder buried       1.40 m.  0.13  m.
+        "       "      "           1.80 m.  0.06  m.
+    Vertical bar       "           2.60 m.  0.013 m.
+    Horizontal bar     "           5.20 m.  0.013 m.
+
+Horizontal flat ring 1.32 m. in external diameter, and 1.08 m.
+internal.
+
+Horizontal network 1.01 m. square, and having meshes of the same size
+as those of the reticulated ribbon.
+
+Horizontal reticulated ribbon 3 m. in length and of the structure
+described.
+
+Horizontal annular ring 1.26 m. in external diameter, 0.94 m.
+internal.
+
+In conclusion, let us meet an objection that might be made to the
+accuracy of the hypotheses that serve as a base to the preceding
+calculations, in cases where ground plates for lightning rods and not
+for telegraphs are concerned. Between the two ground plates of a
+telegraph line there is generally a distance such that the curves of
+the current undergo no deviation in the vicinity of one of the
+electrodes (the only part important for integrations) through the
+influence of the other. But it might be admitted that such would prove
+the case with a lightning rod in a storm, at the time of the passage
+of the fluid into the earth. The ground plate here is one of the
+electrodes, and the other is replaced by the surface of the earth
+strongly charged to a great distance under the storm clouds. If we
+suppose (what may be admitted in a good lightning rod) that there no
+longer occurs any spark from the point downward, the curves of the
+current, in starting perpendicularly from the ground plate, would be
+obliged to leave their rectilinear trajectory and strike the surface
+of the earth at right angles. When the electricity flows through a
+plane surface into an infinite body, it is only when such surface
+presents a very great development that the respective potentials
+decrease very slowly in the vicinity of the said surface. No notable
+modification occurs, then, in the curves of equal potential, in the
+vicinity of the ground plate through the action of this extended
+charge, nor consequently any modification in the curves of the
+current; but the electricity which spreads has but a short distance to
+travel in order to overcome the most important resistances.
+
+The calculations of resistances given above have, then, the same value
+for discharges of atmospheric electricity.--_Bull. du Musee de
+l'Industrie._
+
+       *       *       *       *       *
+
+
+
+
+ON ELECTROLYSIS.
+
+By H. SCHUCHT.
+
+
+Concerning the separations which take place at the positive pole, the
+composition of the peroxides, and the manner of their determination,
+relatively little has been done.
+
+If solutions of the salts of lead, thallium, silver, bismuth, nickel,
+and cobalt are decomposed by the current between platinum electrodes,
+metal is deposited at the negative, and oxide at the positive
+electrode. Manganese is precipitated only as peroxide. The formation
+of peroxide is, of course, effected by the ozone found in the
+electrolytic oxygen at the positive pole; the oxide existing in
+solution is brought to a higher degree of oxidation, and is separated
+out. Its formation may be decreased or entirely prevented by the
+addition of readily oxidizible bodies, such as organic acids, lactose,
+glycerine, and preferably by an excess of oxalic acid; but only until
+the organic matter is transformed into carbonic acid. In this manner
+Classen separates other metals from manganese in order to prevent the
+saline solutions from being retained by the peroxide.
+
+With solutions of silver, bismuth, nickel, and cobalt, it is often
+practicable to prevent the separation of oxide by giving the current a
+greater resistance--increasing the distance between the electrodes.
+
+The proportion between the quantities of metal and of peroxide
+deposited is not constant, and even if we disregard the concentration
+of the solution, the strength of the current and secondary influences
+(action of nascent hydrogen) is different in acid and in alkaline
+solutions. In acid solutions much peroxide is formed; in alkaline
+liquids, little or none. The reason of the difference is that ozone is
+evolved principally in acid solutions, but appears in small quantities
+only in alkaline liquids, or under certain circumstances not at all.
+The quantity of peroxide deposited depends also on the temperature of
+the saline solution; at ordinary temperatures the author obtained more
+peroxide--the solution, the time, and the strength of current being
+equal--than from a heated liquid. The cause is that ozone is destroyed
+by heat and converted into ordinary oxygen. With the exception of lead
+and thallium the quantity of metal deposited from an acid solution is
+always greater than that of the peroxide.
+
+_Lead._--Luckow has shown that from acid solutions--no matter what may
+be the acid--lead is deposited at the anode as a mixture of anhydrous
+and hydrated peroxide of variable composition. Only very strongly acid
+solutions let all their lead fall down as peroxide; the precipitation
+is rapid immediately on closing the circuit, and complete separation
+is effected only in presence of at least 10 per cent. of free nitric
+acid. As the current becomes stronger with the increase of free acid,
+there is deposited upon the first compact layer a new stratum of
+loosely adhering peroxide.
+
+In presence of small quantities of other metals which are thrown down
+by the current in the metallic state, such as copper, mercury, etc.,
+peroxide alone is deposited from a solution of lead containing small
+quantities only of free nitric acid.
+
+The lead peroxide deposited is at first light brown or dark red, and
+becomes constantly darker and finally taking a velvet-black. As its
+stratification upon the platinum is unequal, it forms beautifully
+colored rings.
+
+Experiments show that the quantity of peroxide deposited depends on
+the nature of the solution and the strength of the current. In case of
+very feeble currents and slight acidity, its quantity is so small that
+it does not need to be taken into consideration. If the lead solution
+is very dilute scarcely any current is observed, lead solutions _per
+se_ being very bad conductors of electricity.
+
+Faintly acid concentrated lead solutions give loose peroxide along
+with much spongy metallic lead. Free alkali decreases the separation
+of peroxide; feebly alkaline solutions, concentrated and dilute, yield
+relatively much peroxide along with metallic lead, while strongly
+alkaline solutions deposit no peroxide.
+
+Dried lead peroxide is so sparingly hygroscopic that it may be weighed
+as such; its weight remains constant upon the balance for a long time.
+In order to apply the peroxide for quantitative determinations, a
+large surface must be exposed to action. As positive electrode a
+platinum capsule is convenient, and a platinum disk as negative pole.
+The capsule shape is necessary because the peroxide when deposited in
+large quantities adheres only partially, and falls in part in thin
+loose scales. It is necessary to siphon off the nitric solution,
+since, like all peroxides, that of lead is not absolutely insoluble in
+nitric acid. The methods of Riche and May give results which are
+always too high, since portions of saline solution are retained by the
+spongy deposit and can be but very imperfectly removed by washing.
+This is especially the case in presence of free alkali.
+
+The author has proceeded as follows: The lead peroxide is dried in the
+capsule, and there is passed over it pure dry gaseous sulphurous acid
+in a strong current from a rather narrow delivery tube. Lead sulphate
+is formed with evolution of heat; it is let cool under the exsiccator,
+and weighed as such. Or he ignites the peroxide along with finely
+pulverized ammonium sulphite; the mass must have a pure white color.
+After the conclusion of the reaction it is ignited for about 20
+minutes. The results are too high. The proportion of actual lead
+peroxide in the deposit ranges from 94 to 94.76 per cent. The peroxide
+precipitated from a nitric solution may, under certain circumstances,
+be anhydrous. This result is due to the secondary influences at the
+positive pole, where the free acid gradually withdraws water from the
+peroxide.
+
+The peroxide thrown down from alkaline solutions retains alkali so
+obstinately that it cannot be removed by washing; the peroxide plays
+here the part of an acid. The lead nitrate mechanically inclosed in
+the peroxide is resolved by ignition into oxide, hyponitric acid, and
+oxygen; this small proportion of lead oxide does not exert an
+important influence on the final result. The quantity of matter
+mechanically inclosed is relatively high, as in the precipitation of
+much lead peroxide there is relatively more saline matter occluded
+than when a few centigrammes are deposited. The peroxide incloses also
+more foreign matter if it is thrown down upon a small surface than if
+it is deposited in a thin layer over a broad surface. From numerous
+analyses the author concludes that in presence of much free nitric
+acid the proportion of water is increased; with free alkali the
+reverse holds good.
+
+_Thallium_ behaves similarly to lead. From a nitric acid solution it
+is thrown down, according to the proportion of free acid, either as
+sesquioxide only or in small quantities as silvery, metallic leaflets;
+from alkaline solutions it is deposited as sesquioxide and metal, the
+latter of a lead-gray color. Thallium solutions conduct the electric
+current badly. Thallium oxide resembles lead peroxide in color; at a
+strong heat it melts, becomes darker, and is converted into peroxide,
+in which state it can be weighed.
+
+_Silver._--All solutions of silver salts, except the nitrate, and
+those containing a very large quantity of free nitric acid or
+nitrates, deposit electrolytically merely metallic silver. In the
+above mentioned exceptional cases there is formed a small quantity of
+peroxide which adheres to the anode as a blackish-gray deposit. The
+greatest quantity of peroxide is obtained on employing a concentrated,
+strongly acid solution of the nitrate, and a strong current. If the
+solution is very dilute we obtain no peroxide, or mere traces which
+disappear again toward the end of the process. The peroxide is
+deposited at first in small, dark, shining octahedral crystals;
+subsequently, in an amorphous state. At 110� it evolves oxygen
+suddenly, and is converted into metallic silver. It dissolves in
+ammonia with a violent escape of nitrogen. In nitric acid it dissolves
+without decomposition and with a red color.
+
+The author uses a galvanic current for reducing silver residues,
+consisting of sulphocyanide. The salt is mixed with sulphuric acid in
+a roomy platinum capsule, and a fine platinum wire gauze is used as
+positive electrode.
+
+_Bismuth._--The current resolves bismuth solutions into metal and
+bismutic acid. The latter is deposited at the positive pole, and in
+thin layers appears of a golden-yellow, but in thick strata is darker,
+approaching to red. Its formation is very gradual, and in time it
+disappears again, owing to secondary actions of the current. On
+ignition it becomes lemon yellow, and transitorily darker, even brown,
+and passes into the sexquioxide.
+
+_Nickel and Cobalt._--On the electrolysis of the ammonical solution
+the sesquioxide appears at the positive pole. Its formation is
+prevented by an excess of ammonia. The author never obtains more than
+3� per cent. of the quantity of the metal. The sesquioxides dissolve
+in ammonia without escape of nitrogen, and are usually anhydrous.
+
+_Manganese._--Manganese is the only metal which is precipitated only
+as peroxide. It is deposited at once on closing the circuit, and is at
+first brown, then black and shining. Organic acids, ferrous oxide,
+chromic oxide, ammonium salts, etc., prevent the formation of peroxide
+and the red color produced by permanganic acid. In very dilute
+strongly acid nitric solutions there is formed only permanganic acid,
+which according to Riche is plainly visible in solutions containing
+1/1000000 grm. manganese. On electrolyzing a manganiferous solution of
+copper nitrate, red permanganic acid appeared in a stratum floating
+above the platinum disk coated with brown peroxide. No manganese
+peroxide was deposited. The peroxide adheres firmly to the platinum
+when the proportion of free acid is small, not exceeding 3 per cent.,
+and the current is not too strong. If the action of the current is
+prolonged after the peroxide is thrown down, it falls off in lamin�.
+According to Riche, in a nitric solution the manganese is deposited as
+peroxide, also at the negative pole. This formation is not directly
+due to the current, but is a precipitate occasioned by the production
+of ammonia by the reduction of nitric acid. To determine the manganese
+in peroxide electrolytically precipitated, it is heated to bright
+redness in the platinum capsule until the weight becomes constant. The
+results are too high.
+
+_Selenium and Tellurium._--Both these bodies are readily and
+completely reduced by the current either in acid or alkaline
+solutions. Selenium is thrown down at first of a fine brownish red,
+which gradually becomes darker. The deposit of tellurium is of a
+bluish black color. If the current is feeble, the deposit of selenium
+is moderately compact; that of tellurium is always loose, and it often
+floats on the liquid. A strong current precipitates both as powders.
+The positive pole is coated during electrolysis with a film of a dark
+color in case of selenium, but of a lemon yellow with tellurium. As in
+case of arsenic and antimony, the hydrogen evolved at the negative
+pole combines with the reduced substances, forming hydrogen, selenide,
+or telluride, which remain in part in solution in the liquid. The
+reduced metal separates out at the anode in a friable
+condition.--_Zeitschrift fur Analytische Chemie, and Chemical News._
+
+       *       *       *       *       *
+
+
+
+
+THE ELECTRO-CHEMICAL EQUIVALENT OF SILVER.
+
+
+
+A very careful and important determination of the electrochemical
+equivalent of silver has been made at the observatory of the Physical
+Institute of W�rzbourg, and the results are that an ampere current
+flowing for a second, or a coulomb of electricity deposits 1.1183
+milligrammes of silver or 0.3281 milligramme of copper, and decomposes
+0.09328 milligramme of water, a result agreeing closely with that of
+Lord Rayleigh recently communicated to the Physical Society. An ampere
+therefore deposits 4.0259 grammes of silver per hour; Kohlrausch's
+value is 4.0824, a value hitherto accepted universally. This value is
+so useful in measuring electric currents with accuracy, and free from
+the disturbances of magnetism, etc., that it is eminently satisfactory
+to find the German value agree with that of Lord Rayleigh, which will
+probably be adopted by English electricians.
+
+       *       *       *       *       *
+
+
+
+
+A NEW STANDARD LIGHT.
+
+
+Herr Hefner-Alteneck has suggested a new standard light for
+photometric purposes, which promises to be very simple and effective
+in operation. The light is produced by an open flame of amyl-acetate
+burning from a wick of cotton fiber which fills a tube of German
+silver 1 in. long and 316 mils. internal diameter; the external
+diameter being 324 mils. The flame is 1.58 in. high from top to
+bottom; and it should be lighted at least ten minutes before using the
+light for testing. A cylindrical glass chimney surrounds it to ward
+off air currents. About 2 per cent. of the light is absorbed by the
+glass. The power of the flame is that of a standard English candle;
+and experiments have shown that amyl acetate, which besides is not
+expensive, is the best fuel for steadiness and brilliance. Neither the
+substitution of commercial amyl-acetate for pure nor the use of a wick
+of cotton thread for loose cotton fiber alters the illuminating power;
+but the wick should be trimmed square across the mouth of the tube,
+for if it project and droop the illuminating power is increased.
+
+       *       *       *       *       *
+
+[NATURE.]
+
+
+
+
+DR. FEUSSNER'S NEW POLARIZING PRISM.
+
+
+In a recent number of the _Zeitschrift fur Instrumentenkunde_ (iv.,
+42-50, February, 1884), Dr. K. Feussner of Karlsruhe has given a
+detailed description of a polarizing prism lately devised by him,
+which presents several points of novelty, and for which certain
+advantages are claimed. The paper also contains an account, although
+not an exhaustive one, of the various polarizing prisms which have
+from time to time been constructed by means of different combinations
+of Iceland spar. The literature of this subject is scattered and
+somewhat difficult of access, and moreover only a small part of it has
+hitherto been translated into English; and it would appear therefore
+that a brief abstract of the paper may not be without service to those
+among the readers of _Nature_ who may be unacquainted with the
+original memoirs, or who may not have the necessary references at
+hand.
+
+Following the order adopted by Dr. Feussner, the subject may be
+divided into two parts:
+
+
+I.--OLDER FORMS OF POLARIZING PRISMS.
+
+In comparing the various forms of polarizing prisms, the main points
+which need attention are--the angular extent of the field of view, the
+direction of the emergent polarized ray, whether it is shifted to one
+side of, or remains symmetrical to the long axis of the prism; the
+proportion which the length of the prism bears to its breadth; and
+lastly, the position of the terminal faces, whether perpendicular or
+inclined to the long axis. These requirements are fulfilled in
+different degrees by the following methods of construction:
+
+[Illustration: Fig. 1., Fig. 2., and Fig. 3.]
+
+1. _The Nicol Prism_ (_Edin. New Phil. Journal_, 1828, vi., 83).--This
+(Fig. 1), as is well known, is constructed from a rhombohedron of
+Iceland spar, the length of which must be fully three times as great
+as the width. The end faces are cut off in such a manner that the
+angle of 72� which they originally form with the lateral edge of the
+rhombohedron is reduced to 68�. The prism is then cut in two in a
+plane perpendicular to the new end surfaces, the section being carried
+obliquely from one obtuse corner of the prism to the other, in the
+direction of its length. The surfaces of this section, after having
+been carefully polished, are cemented together again by means of
+Canada balsam. A ray of light, on entering the prism, is separated by
+the double refraction of the calc-spar into an ordinary and an
+extraordinary ray; the former undergoes total reflection at the layer
+of balsam at an incidence which allows the extraordinary ray to be
+transmitted; the latter, therefore, passes through unchanged. This
+principle of obtaining a single polarized ray by means of total
+reflection of the other is common to all the forms of prism now to be
+described.
+
+Dr. Feussner gives a mathematical analysis of the paths taken by the
+two polarized rays within the Nicol prism, and finds that the emergent
+extraordinary ray can include an angular field of 29�, but that this
+extreme value holds good only for rays incident upon that portion of
+the end surface which is near to the obtuse corner, and that from
+thence it gradually decreases until the field includes an angle of
+only about half the previous amount. He finds, moreover, that,
+although of course the ray emerges parallel to its direction of
+incidence, yet that the zone of polarized light is shifted to one side
+of the central line. Also that the great length of the Nicol--3.28
+times its breadth--is not only an inconvenience, but owing to the
+large pieces of spar thus required for its construction, prisms of any
+but small size become very expensive. To this it may be added that
+there is a considerable loss of light by reflection from the first
+surface, owing to its inclined position in regard to the long axis of
+the prism.
+
+[Illustration: Fig. 4., Fig. 5., and Fig. 6.]
+
+It is with the view of obviating these defects that the modifications
+represented in Figs. 2 to 6 have been devised.
+
+2. _The Shortened Nicol Prism_.--This arrangement of the Nicol prism
+is constructed by Dr. Steeg and Reuter of Homburg v.d.H. For the sake
+of facility of manufacture, the end surfaces are cleavage planes, and
+the oblique cut, instead of being perpendicular, makes with these an
+angle of about 84�. By this alteration the prism becomes shorter, and
+is now only 2.83 times its breadth; but if Canada balsam is still used
+as the cement, the field will occupy a very unsymmetrical position in
+regard to the long axis. If balsam of copaiba is made use of, the
+index of refraction of which is 1.50, a symmetrical field of about 24�
+will be obtained. A prism of this kind has also been designed by Prof.
+B. Hasert of Eisenach (_Pogg. Ann._, cxiii., 189), but its performance
+appears to be inferior to the above.
+
+3. _The Nicol Prism with Perpendicular Ends._--The terminal surfaces
+in this prism are perpendicular to the long axis, and the sectional
+cut makes with them an angle of about 75�. The length of the prism is
+3.75 times its breadth, and if the cement has an index of refraction
+of 1.525, the field is symmetrically disposed, and includes an angle
+of 27�. Prisms of this kind have been manufactured by Dr. Steeg, Mr.
+C.D. Ahrens, and others.
+
+4. _The Foucault Prism_ (_Comptes Rendus_, 1857, xlv., 238).--This
+construction differs from all those hitherto mentioned, in that a film
+of air is employed between the two cut surfaces as the totally
+reflecting medium instead of a layer of cement. The two halves of the
+prism are kept in position, without touching each other, by means of
+the mounting. The length of the prism is in this way much reduced, and
+amounts to only 1.528 times its breadth. The end surfaces are cleavage
+planes, and the sectional cut makes with them an angle of 59�. The
+field, however, includes not more than about 8�, so that this prism
+can be used only in the case of nearly parallel rays; and in addition
+to this the pictures which may be seen through it are to some extent
+veiled and indistinct, owing to repeated internal reflection.
+
+5. _The Hartnack Prism_ (_Ann. de Ch. et de Physique_, ser. iv., vii.,
+181).--This form of prism was devised in 1866 by MM. Hartnack and
+Prazmowiski; the original memoir is a valuable one; a translation of
+it, with some additions, has lately been published (_Journ. of the R.
+Microscopical Soc._, June, 1883, 428). It is considered by Dr.
+Feussner to be the most perfect prism capable of being prepared from
+calc-spar. The ends of the prism are perpendicular to its length; the
+section carried through it is in a plane perpendicular to the
+principal axis of the crystal. The cementing medium is linseed oil,
+the index of refraction of which is 1.485. This form of prism is
+certainly not so well known in this country as it deserves to be; a
+very excellent one, supplied to the present writer by Dr. Steeg is of
+rectangular form throughout, the terminal surfaces are 19 � 15 mm.,
+and the length 41 mm. The lateral shifting of the field is scarcely
+perceptible, the prism is perfectly colorless and transparent, and its
+performance is far superior to that of the ordinary Nicol. The field
+of view afforded by this construction depends upon the cementing
+substance used, and also upon the inclination of the sectional cut in
+regard to the end of the prism; it may vary from 20� to 41�. If the
+utmost extent of field is not required, the prism may be shortened by
+lessening the angle of the section, at the expense, however, of
+interfering with the symmetrical disposition of the field.
+
+6. _The Glan Prism_ (Carl's "Repertorium," xvi., 570, and xvii.,
+195).--This is a modification of the Foucault, and in a similar manner
+includes a film of air between the sectional surfaces. The end
+surfaces and also the cut carried through the prism are parallel to
+the principal axis of the calc-spar. The ends are normal to the
+length, and the field includes about 8�. This prism is very short, and
+may indeed be even shorter than it is broad. It is subject to the same
+defect as that mentioned in the case of the Foucault, although perhaps
+not quite to the same extent.
+
+
+II.--THE NEW POLARIZING PRISM.
+
+This prism differs very considerably from the preceding forms, and
+consists of a thin plate of a doubly refracting crystal cemented
+between two wedge-shaped pieces of glass, the terminal faces of which
+are normal to the length. The external form of the prism may thus be
+similar to the Hartnack, the calc-spar being replaced by glass. The
+indices of refraction of the glass and of the cementing medium should
+correspond with the greater index of refraction of the crystal, and
+the directions of greatest and least elasticity in the latter must
+stand in a plane perpendicular to the direction of the section. One of
+the advantages claimed for the new prism is that, it dispenses with
+the large and valuable pieces of spar hitherto found necessary; a
+further advantage being that other crystalline substances may be used
+in this prism instead of calc-spar. The latter advantage, however,
+occurs only when the difference between the indices of refraction for
+the ordinary and extraordinary rays in the particular crystal made use
+of is greater than in calc-spar. When this is the case, the field
+becomes enlarged, and the length of the prism is reduced.
+
+[Illustration: Fig. 7.]
+
+The substance which Dr. Feussner has employed as being most suitable
+for the separating crystal plate is nitrate of soda (_natronsalpeter_),
+in which the above-mentioned values are [omega] = 1.587 and [eta] =
+1.336. It crystallizes in similar form to calcite, and in both cases
+thin plates obtained by cleavage may be used.
+
+As the cementing substance for the nitrate of soda, a mixture of gum
+dammar with monobromonaphthalene was used, which afforded an index of
+refraction of 1.58. In the case of thin plates of calcite, a solid
+cementing substance of sufficiently high refractive power was not
+available, and a fluid medium was therefore employed. For this purpose
+the whole prism was inclosed in a short glass tube with airtight ends,
+which was filled with monobromonaphthalene. In an experimental prism a
+mixture of balsam of tolu was made use of, giving a cement with an
+index of refraction of 1.62, but the low refractive power resulted in
+a very considerable reduction of the field. The extent and disposition
+of the field may be varied by altering the inclination at which the
+crystal lamina is inserted (Fig. 7), and thereby reducing the length
+of the prism, as in the case of the Hartnack.
+
+In order to obviate the effects of reflection from the internal side
+surfaces if the prism, the wedge-shaped blocks of glass of which it is
+built up may be made much broader than would otherwise be necessary;
+the edges of this extra width are cut obliquely and suitably
+blackened.
+
+The accompanying diagram (Fig. 8) represents a prism of cylindrical
+external form constructed in this manner, the lower surface being that
+of the incident light. In this the field amounts to 30�, and the
+breadth is about double the length.
+
+[Illustration: Fig. 8.]
+
+Dr. Feussner remarks that a prism similar in some respects to his new
+arrangement was devised in 1869 by M. Jamin (_Comptes Rendus_,
+lxviii., 221), who used a thin plate of calc-spar inclosed in a cell
+filled with bisulphide of carbon; and also by Dr. Zenker, who replaced
+the liquid in M. Jamin's construction by wedges of flint glass.
+
+Among others, the carefully considered modifications of the Nicol
+prism which have recently been devised by Prof. S.P. Thompson (_Phil.
+Mag._, November, 1881, 349, and _Jour. R. Micros. Soc._, August, 1883,
+575), and by Mr. R.T. Glazebrook (_Phil. Mag._, May, 1883, 352), do
+not appear to have been known to Dr. Feussner.
+
+The following tabular view of different forms of polarizing prisms is
+taken from the conclusion of Dr. Feussner's paper:
+
+  ---------------------------------------+------+---------+------+------
+                                         |      |Inclina- |Ratio |
+                                         |      |tion of  | of   |
+                                         |      |section  |length|
+                                         |      |in regard| to   |
+                                         |      |to long  |clear |
+                                         |Field.|axis.    |width.|Fig.
+  ---------------------------------------+------+---------+------+------
+  I. THE OLD POLARISING PRISMS.          |  �   |    �    |      |
+      1. Nicol's prism.                  | 29   |   22    | 3.28 | 1
+      2. Shortened Nicol prism--         |      |         |      |
+          a. Cemented with Canada balsam.| 13   |   25    | 2.83 | 2
+          b. Cemented with copaiba  "    | 24   |   25    | 2.83 | 2
+      3. Nicol with perpendicular ends-- |      |         |      |
+          a. With Canada balsam.         | 20   |   15    | 3.73 | 3
+          b. With cement of index of     |      |         |      |
+              refraction of 1.525.       | 27   |   15    | 3.73 | 3
+      4. Foucault's prism.               |  8   |   40    | 1.528| 4
+      5. Hartnack's prism--              |      |         |      |
+          a. Original form.              | 35   |   15.9  | 3.51 |5 _a b_
+          b. With largest field.         | 41.9 |   13.9  | 4.04 |5 _a a_
+          c. With field of 30�.          | 30   |   17.4  | 3.19 |5 _a c_
+          d. With field of 20�.          | 20   |   20.3  | 2.70 |5 _a d_
+      6. Glan's prism.                   |  7.9 |   50.3  | 0.831| 6
+                                         |      |         |      |
+  II. THE NEW POLARISING PRISM.          |      |         |      |
+      1. With calc-spar: largest field.  | 44   |   13.2  | 4.26 |5 _a a_
+      2.       "         field of 30�.   | 30   |   17.4  | 3.19 |5 _a c_
+      3.       "         field of 20�.   | 20   |   20.3  | 2.70 |5 _a d_
+      4. With nitrate of soda:           |      |         |      |
+               "         largest field.  | 54   |   16.7  | 3.53 |7 _a a_
+      5.       "         field of 30�.   | 30   |   24    | 2.25 |7 _a b_
+      6.       "         field of 20�.   | 20   |   27    | 1.96 |7 _a c_
+  ---------------------------------------+------+---------+------+------
+
+As an analyzing prism of about 6 mm. clear width, and 13.5 mm. long,
+the new prism is stated by its inventor to be of the most essential
+service, and it would certainly appear that the arrangement is rather
+better adapted for small prisms than for those of considerable size.
+Any means by which a beam of polarized light of large diameter--say 3
+to 3� inches--could be obtained with all the convenience of a Nicol
+would be a real advance, for spar of sufficient size and purity for
+such a purpose has become so scarce and therefore so valuable that
+large prisms are difficult to procure at all. So far as an analyzer is
+concerned, the experience of the writer of this notice would lead to
+the opinion that improvements are to be looked for rather in the way
+of the discovery of an artificial crystal which absorbs one of the
+polarized rays than by further modifications depending upon total
+reflection. The researches of Dr. Herapath on iodosulphate of quinine
+(_Phil. Mag._, March, 1852, 161, and November, 1853, 346) are in this
+direction; but crystals of the so-called herapathite require great
+manipulative skill for their production. If these could be readily
+obtained of sufficient size, they would be invaluable as analyzers.
+
+This opinion is supported by the existence of an inconvenience which
+attends every form of analyzing prism. It is frequently, and
+especially in projecting apparatus, required to be placed at the focus
+of a system of lenses, so that the rays may cross in the interior of
+the prism. This is an unfavorable position for a prismatic analyzer,
+and in the case of a powerful beam of light, such as that from the
+electric arc, the crossing of the rays within the prism is not
+unattended with danger to the cementing substance, and to the surfaces
+in contact with it.
+
+PHILIP R. SLEEMAN.
+
+       *       *       *       *       *
+
+
+
+
+ZIRCON.
+
+By F. STOLBA.
+
+
+Finely ground zircon is quickly rendered soluble if fused with a
+mixture of potassium borofluoride and potassium carbonate. The author
+takes two parts of the former to three of the latter, and prepares an
+intimate, finely divided mixture, which is kept ready for use.
+
+Of this mixture four parts are taken to one of zircon, thoroughly
+mixed, and melted in a platinum crucible at a red heat. The mass fuses
+readily, froths at first and gives off bubbles of gas, and flows then
+quietly, forming a very fluid melt. If the zircon is finely ground, 15
+minutes are sufficient for this operation. The loss of weight is 16
+per cent., and is not notably increased on prolonged fusion. It
+corresponds approximately to the weight of the carbonic anhydride
+present in the potassium carbonate.
+
+As pungent vapors are given off during fusion, the operation should be
+conducted under a draught hood. The activity of the mixture in
+attacking zircon appears from the following experiment: Two zircon
+crystals, each weighing � grm., were introduced into the melted
+mixture and subjected to prolonged heat. In a short time they
+decreased perceptibly in size; each of them broke up into two
+fragments, and within an hour they were entirely dissolved. The melted
+mass is poured upon a dry metal plate, and when congealed is thrown
+into water. It is at once intersected with a number of fissures, which
+facilitate pulverization. This process is the more necessary as the
+unbroken mass is very slowly attacked by water even on prolonged
+boiling. The powder is boiled in a large quantity of water so as to
+remove everything soluble. There is obtained a faintly alkaline
+solution and a sediment insoluble in water. From the filtrate alkalies
+throw down zirconium hydroxide, free from iron.
+
+The portion insoluble in water is readily dissolved in hydrofluoric
+acid, and is converted into zircon potassium fluoride. The chief bulk
+of the zirconium is found in the aqueous solution in the state of
+double fluorides. The platinum crucible is not in the least attacked
+during melting. On the contrary, dirty platinum crucibles may be
+advantageously cleaned by melting in them a little of the above
+mentioned mixture.
+
+If finely divided zircon is boiled for a long time with caustic lye,
+it is perceptibly attacked. It is very probable that in this manner
+zircon might be entirely dissolved under a pressure of 10 atmospheres.
+
+Potassium borofluoride may be readily prepared from cryolite.
+Crucibles of nickel seem especially well adapted for the fusion of
+zircon in caustic alkalies.--_Ber. Boehm. Gesell. Wissenschaft;
+Chem. News_.
+
+       *       *       *       *       *
+
+
+
+
+A PROCESS FOR MAKING WROUGHT IRON DIRECT FROM THE ORE.[1]
+
+   [Footnote 1: A paper read at the Cincinnati Meeting of the
+   American Institute of Mining Engineers, by Willard P. Ward, A.M.,
+   M.E., February, 1884.]
+
+
+The numerous direct processes which have been patented and brought
+before the iron masters of the world, differ materially from that now
+introduced by Mr. Wilson. After a careful examination of his process,
+I am convinced that Mr. Wilson has succeeded in producing good blooms
+from iron ore, and I think that I am able to point out theoretically
+the chief reasons of the success of his method.
+
+Without going deeply into the history of the metal, I may mention the
+well known fact that wrought iron was extensively used in almost all
+quarters of the globe, before pig or cast iron was ever produced.
+Without entering into the details of the processes by which this
+wrought iron was made, it suffices for my present purpose to say that
+they were crude, wasteful, and expensive, so that they can be employed
+to-day only in a very few localities favored with good and cheap ore,
+fuel, and labor.
+
+The construction of larger furnaces and the employment of higher
+temperatures led to the production of a highly carbonized, fusible
+metal, without any special design on the part of the manufacturers in
+producing it. This pig iron, however, could be used only for a few
+purposes for which metallic iron was needed; but it was produced
+cheaply and with little loss of metal, and the attempt to decarbonize
+this product and bring it into a state in which it could be hammered
+and welded was soon successfully made. This process of decarbonization,
+or some modification of it, has successfully held the field against
+all so-called, direct processes up to the present time. Why? Because
+the old fashioned bloomeries and Catalan forges could produce blooms
+only at a high cost, and because the new processes introduced failed
+to turn out good blooms. Those produced were invariably "red short,"
+that is, they contained unreduced oxide of iron, which prevented the
+contact of the metallic particles, and rendered the welding together
+of these particles to form a solid bloom impossible.
+
+The process of puddling cast iron, and transforming it by
+decarbonization into wrought iron, has, as everybody knows, been in
+successful practical operation for many years, and the direct process
+referred to so closely resembles this, that a short description of the
+theory of puddling is not out of place here.
+
+The material operated on in puddling is iron containing from 2� to 4
+per cent. of carbon. During the first stage of the process this iron
+is melted down to a fluid bath in the bottom of a reverberatory
+furnace. Then the oxidation of the carbon contained in the iron
+commences, and at the same time a fluid, basic cinder, or slag, is
+produced, which covers a portion of the surface of the metal bath, and
+prevents too hasty oxidation. This slag results from the union of
+oxides of iron with the sand adhering to the pigs, and the silica
+resulting from the oxidation of the silicon contained in the iron.
+
+This cinder now plays a very important part in the process. It takes
+up the oxides of iron formed by the contact of the oxidizing flame
+with the exposed portion of the metal bath, and at the same time the
+carbon of the iron, coming in contact with the under surface of the
+cinder covering, where it is protected from oxidizing influences,
+reduces these oxides from the cinder and restores them to the bath in
+metallic form. This alternate oxidation of exposed metal, and its
+reduction by the carbon of the cast iron, continues till the carbon is
+nearly exhausted, when the iron assumes a pasty condition, or "comes
+to nature," as the puddlers call this change. The charge is then
+worked up into balls, and removed for treatment in the squeezer, and
+then hammered or rolled. In the Wilson process the conditions which we
+have noted in the puddling operation are very closely approximated.
+Iron ore reduced to a coarse sand is mixed with the proper proportion
+of charcoal or coke dust, and the mixture fed into upright retorts
+placed in the chimney of the puddling furnace. By exposure for 24
+hours to the heat of the waste gases from the furnace, in the presence
+of solid carbon, a considerable portion of the oxygen of the ore is
+removed, but little or no metallic iron is formed. The ore is then
+drawn from the deoxidizer into the rear or second hearth of the
+puddling furnace, situated below it, where it is exposed for 20
+minutes to a much higher temperature than that of the deoxidizer. Here
+the presence of the solid carbon, mixed with the ore, prevents any
+oxidizing action, and the temperature of the mass is raised to a point
+at which the cinder begins to form. Then the charge is carried forward
+by the workmen to the front hearth, in which the temperature of a
+puddling furnace prevails. Here the cinder melts, and at the same
+time the solid carbon reacts on the oxygen remaining combined with the
+ore, and forms metallic iron; but by this time the molten cinder is
+present to prevent undue oxidation of the metal formed, and solid
+carbon is still present in the mixture to play the same role, of
+reducing protoxide of iron from the cinder, as the carbon of the cast
+iron does in the ordinary puddling process. I have said that the cast
+iron used as the material for puddling contains about 3 per cent. of
+carbon; but in this process sufficient carbon is added to effect the
+reduction of the ore to a metallic state, and leave enough in the mass
+to play the part of the carbon of the cast iron when the metallic
+stage has been reached.
+
+It would be interesting to compare the Wilson with the numerous other
+direct processes to which allusion has already been made, but there
+have been so many of them, and the data concerning them are so
+incomplete, that this is impossible. Two processes, however, the Blair
+and the Siemens, have attracted sufficient attention, and are
+sufficiently modern to deserve notice. In the Blair process a metallic
+iron sponge was made from the ore in a closed retort, this sponge
+cooled down in receptacles from which the air was excluded, to the
+temperature of the atmosphere, then charged into a puddling furnace
+and heated for working. In this way (and the same plan essentially has
+been followed by other inventors), the metallic iron, in the finest
+possible state of subdivision, is subjected to the more or less
+oxidizing influences of the flame, without liquid slag to save it from
+oxidation, and with no carbon present to again reduce the iron oxides
+from the cinder after it is formed. The loss of metal is consequently
+very large, but oxides of iron being left in the metal the blooms are
+invariably "red short."
+
+In the Siemens process pieces of ore of the size of beans or peas,
+mixed with lime or other fluxing material, form the charge, which is
+introduced into a rotating furnace; and when this charge has become
+heated to a bright-red heat, small coal of uniform size is added in
+sufficient quantity to effect the reduction of the ore.
+
+The size of the pieces of the material employed prevents the intimate
+mixture of the particles of iron with the particles of carbon, and
+hence we would, on theoretical grounds, anticipate just what practice
+has proved, viz., that the reduction is incomplete, and the resulting
+metal being charged with oxides is red-short. In practice, blooms made
+by this process have been so red-short that they could not be hammered
+at all.
+
+It would be impracticable in this process to employ ore and carbon in
+as fine particles as Wilson does, as a very large portion of the
+charge would be carried off by the draught, and a sticking of the
+material to the sides of the rotating furnace could scarcely be
+avoided. I do not imagine that a division of the material into
+anything like the supposed size of molecules is necessary; we know
+that the graphitic carbon in the pig-iron employed in puddling is not
+so finely divided, but it is much smaller particles than bean or pea
+size, and by approximating the size of the graphite particles in pig
+iron, Wilson has succeeded in obtaining good results.
+
+If we examine the utilization of the heat developed by the combustion
+of a given quantity of coal in this process, and compare it with the
+result of the combustion of an equivalent amount of fuel in a blast
+furnace, we shall soon see the theoretical economy of the process. The
+coal is burned on the grate of the puddling-furnace, to carbonic acid,
+and the flame is more fully utilized than in an ordinary
+puddling-furnace, for besides the ordinary hearth there is the second
+or rear hearth, where additional heat is taken up, and then the
+products of combustion are further utilized in heating the retorts in
+which the ore is partly reduced. After this the heat is still further
+utilized by passing it under the boilers for the generation of steam,
+and the heat lost in the gases, when they finally escape, is very
+small. In a blast furnace the carbon is at first burned only to
+carbonic oxide, and the products of combustion issue mainly in this
+form from the top of the furnace. Then a portion of the heat resulting
+from the subsequent burning of these gases is pretty well utilized in
+making steam to supply the power required about the works, but the
+rest of the gas can only be utilized for heating the blast, and here
+there is an enormous waste, the amount of heat returned to the furnace
+by the heated blast being very small in proportion to the amount
+generated by the burning of that portion of carbonic oxide expended in
+heating it, and the gases escape from both the hot-blast and the
+boilers at a high temperature.
+
+In the direct process under consideration the fuel burned is more
+completely utilized than in the puddling process, to which the cast
+iron from the blast furnace is subjected to convert it into wrought
+iron.
+
+The economy claimed for this process, over the blast furnace and
+puddling practice for the production of wrought iron, is that nearly
+all the fuel used in the puddling operation is saved, and that with
+about the same amount of fuel used in the blast furnace to produce a
+ton of pig iron, a ton of wrought iron blooms can be made. I had no
+opportunity of weighing the charges of ore and coal used, but I saw
+the process in actual operation at Rockaway, N.J. The iron produced
+was hammered up into good solid blooms, containing but little cinder.
+The muck-bar made from the blooms was fibrous in fracture, and showed
+every appearance of good iron. I am informed by the manager of the
+Sanderson Brothers' steel works, at Syracuse, N.Y., that they
+purchased blooms made by the Wilson process in 1881-1882, that _none_
+of them showed red-shortness, and that they discontinued their use
+only on account of the injurious action of the titanium they contained
+on the melting pots. These blooms were made from magnetic sands from
+the Long Island and Connecticut coasts.
+
+[Illustration: NEW PROCESS FOR MAKING WROUGHT IRON FROM THE ORE.]
+
+The drawing given shows the construction of the furnace employed. I
+quote from the published description:
+
+    "The upper part, or deoxidizer, is supported on a strong
+    mantel plate resting on four cast iron columns.
+
+    "The retorts and flues are made entirely of fire-brick, from
+    special patterns. The outside is protected by a wrought iron
+    jacket made of No. 14 iron. The puddling furnace is of the
+    ordinary construction, except in the working bottom, which is
+    made longer to accommodate two charges of ore, and thus
+    utilize more of the waste heat in reducing the ore to metallic
+    iron.
+
+    "The operation of the furnace is as follows: The pulverized
+    ore is mixed with 20 per cent. of pulverized charcoal or coke,
+    and is fed into an elevator which discharges into the hopper
+    on the deoxidizer leading into the retorts marked C. These
+    retorts are proportioned so that they will hold ore enough to
+    run the puddling furnace 24 hours, the time required for
+    perfect deoxidation. After the retorts are filled, a fire is
+    started in the furnace, and the products of combustion pass up
+    through the main flue, or well, B, where they are deflected by
+    the arch, and pass out through suitable openings, as indicated
+    by arrows, into the down-takes marked E, and out through an
+    annular flue, where they are passed under a boiler.
+
+    "It will be noticed that the ore is exposed to the waste heat
+    on three sides of the retorts, and owing to the great surface
+    so exposed, the ore is very thoroughly deoxidized, and reduced
+    in the retorts before it is introduced into the puddling
+    furnace for final reduction. The curved cast iron pipes marked
+    D are provided with slides, and are for the purpose of
+    introducing the deoxidized ore into the second bottom of the
+    furnace. As before stated, the furnace is intended to
+    accommodate two charges of ore, and as fast as it is balled up
+    and taken out of the working bottom, the charge remaining in
+    the second bottom is worked up in the place occupied by the
+    first charge, and a _new_ charge is introduced. As fast as the
+    ore is drawn out from the retorts the elevator supplies a new
+    lot, so that the retorts are always filled, thus making the
+    process continuous."
+
+The temperature of the charge in the deoxidizer is from 800� to 1,000�
+F.--_Amer. Engineer._
+
+       *       *       *       *       *
+
+
+
+
+SOME REMARKS ON THE DETERMINATION OF HARDNESS IN WATERS.
+
+By HERBERT JACKSON.
+
+
+Having had occasion some short time ago to examine a hard water which
+owed half its hardness to salts of magnesium, I noticed that the soap
+test, applied in the usual way, gave a result which differed very much
+from that obtained by the quantitative estimation of calcium and
+magnesium. A perfectly normal lather was obtained when soap had been
+added in quantities sufficient to neutralize 14� of hardness, whereas
+the water contained salts of calcium and magnesium equivalent, on
+Clark's scale, to a hardness of 27�.
+
+Although I was aware that similar observations had been made before, I
+thought that it might be useful to determine the conditions under
+which the soap test could not be depended upon for reliable results.
+
+I found with waters containing calcium or magnesium alone that,
+whenever salts of either of these metals were in solution in
+quantities sufficient to give 23� of hardness on Clark's scale, no
+dependence could be placed upon the results given by the soap test. In
+the case of waters containing salts of both calcium and magnesium, I
+found that if the salts of the latter metal were in solution in
+quantities sufficient to give more than 10� of hardness, no evidence
+could be obtained of their presence so long as the salts of calcium in
+the same water exceeded 6�; in such a case a perfect and permanent
+lather was produced when soap had been added equivalent to 7� of
+hardness.
+
+If any water be diluted so as to reduce the proportions of the salts
+of calcium and magnesium below those stated above, perfectly reliable
+results will of course be obtained.
+
+Instead of dilution I found that heating the water to about 70� C. was
+sufficient to cause a complete reaction between the soap and the salts
+of calcium and magnesium, even if these were present in far larger
+quantities than any given here.
+
+The experiments so far had all been made with a solution of Castile
+soap of the strength suggested by Mr. Wanklyn in his book on "Water
+Analysis." My attention was next directed to the use of any one of the
+compounds of which such a soap is composed. I commenced with sodium
+oleate, and found that by employing this substance in a moderately
+pure condition, perfectly reliable results could be obtained in very
+hard waters without the trouble of either diluting or heating. I was
+unable to try sodium stearate directly because of the slight
+solubility of this substance in cold water or dilute alcohol; but I
+found that a mixture of sodium oleate and stearate behaved in exactly
+the same manner as the Castile soap.
+
+I am not prepared at present to state the exact reaction which takes
+place between salts of calcium and magnesium and a compound soap
+containing sodium oleate and stearate. I publish these results because
+I have not noticed anywhere the fact that some waters show a greater
+hardness with soap when their temperatures approach the boiling point
+than they do at the average temperature of the air, it being, I
+believe, the ordinary impression that cold water wastes more soap than
+hot water before a good and useful lather can be obtained, whereas
+with very many waters the case is quite the reverse. Neither am I
+aware at present whether it is well known that the use of sodium
+oleate unmixed with sodium stearate dispenses with the process of
+dilution even in very hard waters.--_Chem. News._
+
+       *       *       *       *       *
+
+
+
+
+THE DENSITY AND PRESSURE OF DETONATING GAS MIXTURES.
+
+
+MM. Berthelot and Vielle have recently been studying the influence of
+the density of detonating gaseous mixtures upon the pressure
+developed. The measure of pressure developed by the same gaseous
+system, taken under two initial states of different density to which
+the same quantity of heat is communicated, is an important matter in
+thermodynamics. If the pressures vary in the same ratio as the
+densities, we may conclude, independently of all special hypotheses on
+the laws of gases, first, that the specific heat of the system is
+independent of its density (that is to say, of its initial pressure),
+and depends only on the absolute temperature, whatever that may mean;
+and secondly, that the relative variation of the pressure at constant
+volume, produced by the introduction of a determinate quantity of
+heat, is also independent of the pressure, and a function only of the
+temperature. Lastly, the pressure itself will vary proportionally with
+the absolute temperature, as defined by the theory of a perfect gas,
+and will serve to determine it. MM. Berthelot and Vielle operated with
+a bomb, at first kept at ordinary temperatures in the air, and
+afterward heated in an oil bath to 153 deg. Cent. They also employed
+isomeric mixtures of the gases; methylic ether, cyanogen, hydrogen,
+acetylene, and other gases were experimented upon, and the general
+conclusions are as follows: 1. The same quantity of heat being
+furnished to a gaseous system, the pressure of the system varies
+proportionally to the density of the system. 2. The specific heat of
+the gas is sensibly independent of the density as well toward very
+high temperatures as about deg. Cent. This is all true for densities
+near to those that the gas possesses cold under normal pressure, and
+which varied in the experiment to double the original value. 3. The
+pressure increases with the quantity of heat furnished to the same
+system. 4. The apparent specific heat increases parallel with this
+quantity of heat. These conclusions are independent of all hypotheses
+on the nature and laws of gases, and were simply drawn from the
+experiments in question.
+
+       *       *       *       *       *
+
+
+
+
+TURKISH BATHS FOR HORSES.
+
+
+The Turkish bath has become an established institution in this
+country; men of all classes now use it for sanitary as well as
+remedial purposes. Athletes of various descriptions find it invaluable
+in "training," and all the distinguished jockeys and light weights
+keep themselves in condition by its use.
+
+It was thought probable that what was good for man might also be good
+for the horse, and the fact has been proved. Messrs. Pickford, the
+eminent carriers, in their hospital for horses at Finchley, have had a
+bath in operation over eleven years, and find the horses derive great
+benefit from its use. The bath is put in operation three days a week,
+and is administered to over twenty horses in this time. The value of
+the bath having been thus proved, it is rather strange that it has not
+been more generally adopted by the large carrying firms. However, the
+Great Northern Railway Company at their new hospital for horses at
+Totteridge, are erecting a very complete Turkish bath. It consists of
+three rooms. First, a large wash room or grooming room, from which is
+entered the first hot room, or tepidarium, from 140� to 150� Fahr.;
+from this room, the horse, after being thoroughly acclimated, can, if
+necessary, pass to the hottest room, or calidarium, from 160� to 170�
+Fahr., and without any turning round can pass on into the grooming and
+washing room again. This last room is slightly heated from the two
+other rooms, and in each are stocks in which the animal can he
+fastened if required. The heating is done most economically by
+Constantine's convoluted stove, and thorough ventilation is secured
+from the large volume of hot air constantly supplied, which passes
+through the baths, and as it becomes vitiated is drawn off by
+specially designed outlets. The wash room is supplied with hot and
+cold water, which can, of course, be mixed to any required
+temperature.--_Building News._
+
+[Illustration]
+
+   ||
+   |+-------------------------------------------------------+
+   |+-------------------++---__-------____------------__---+|
+   ||                   ||FOUL AIR  FOUL AIR       FOUL AIR||
+   ||                   ||                                 ||
+   ||                   ||                                 ||
+   ||                   ||         ==============          ||
+   ||                  /     /                             ||
+   ||                 /     /       1ST HOT ROOM           ||
+   ||                /     /                               ||
+   ||               /     /        ==============          ||
+   ||                   ||                                 ||
+   /         =======+   ||                                 ||
+  /                ||   ||                          CURTAIN||
+       WASHING ROOM||   |+===========================     =||
+  \                ||   ||                                 ||
+   \         =======+   ||                                 ||
+   ||                   ||                                 ||
+   ||               \     \        ==============          ||
+   ||                \     \                               ||
+   ||                 \     \       2ND HOT ROOM           ||  FRESH
+   ||                  \     \                             || / AIR
+   ||                   ||         ==============          ||==
+   ||                   ||                          +======||  |
+   ||                   ||                          | WARM ||  |
+   ||                   ||FOUL AIR          FOUL AIR| AIR  ||  |
+   |+-------------------++---__--+===+---------__----------+|==
+   |+----------------------------|_|_|---------------------+|
+   ||      |     ||||| |                                   ||
+   ||      |     ||||| |                                   ||
+   ||      |============           S T O K E R Y           ||
+   ||                 ||                                   ||
+   ||                 ||                                   ||
+   ||                 |+-----------------------------------||
+                      +-------------------------------------+
+
+
+       *       *       *       *       *
+
+
+
+
+MIRYACHIT, A NEWLY DESCRIBED DISEASE OF THE NERVOUS SYSTEM, AND
+ITS ANALOGUES.[1]
+
+   [Footnote 1: Read before the New York Neurological Society,
+   February 5, 1884.]
+
+By WILLIAM A. HAMMOND, M.D., Surgeon-General, U.S. Army (Retired
+List); Professor of Diseases of the Mind and Nervous System in the New
+York Post-Graduate Medical School and Hospital.
+
+
+In a very interesting account of a journey from the Pacific Ocean
+through Asia to the United States, by Lieutenant B.H. Buckingham and
+Ensigns George C. Foulk and Walter McLean,[2] United States navy, I
+find an affection of the nervous system described which, on account of
+its remarkable characteristics, as well as by reason of certain known
+analogies, I think should be brought to the special notice of the
+medical profession. I quote from the work referred to, the following
+account of this disease. The party is on the Ussuri River not far from
+its junction with the Amur in Eastern Siberia: "While we were walking
+on the bank here we observed our messmate, the captain of the general
+staff (of the Russian army), approach the steward of the boat
+suddenly, and, without any apparent reason or remark, clap his hands
+before his face; instantly the steward clapped _his_ hands in the same
+manner, put on an angry look, and passed on. The incident was somewhat
+curious, as it involved a degree of familiarity with the steward
+hardly to have been expected. After this we observed a number of queer
+performances of the steward, and finally comprehended the situation.
+It seemed that he was afflicted with a peculiar mental or nervous
+disease, which forced him to imitate everything suddenly presented to
+his senses. Thus, when the captain slapped the paddle-box suddenly in
+the presence of the steward, the latter instantly gave it a similar
+thump; or, if any noise were made suddenly, he seemed compelled
+against his will to imitate it instantly, and with remarkable
+accuracy. To annoy him, some of the passengers imitated pigs grunting,
+or called out absurd names; others clapped their hands and shouted,
+jumped, or threw their hats on the deck suddenly, and the poor
+steward, suddenly startled, would echo them all precisely, and
+sometimes several consecutively. Frequently he would expostulate,
+begging people not to startle him, and again would grow furiously
+angry, but even in the midst of his passion he would helplessly
+imitate some ridiculous shout or motion directed at him by his
+pitiless tormenters. Frequently he shut himself up in his pantry,
+which was without windows, and locked the door, but even there he
+could be heard answering the grunts, shouts, or pounds on the bulkhead
+outside. He was a man of middle age, fair physique, rather intelligent
+in facial expression, and without the slightest indication in
+appearance of his disability. As we descended the bank to go on board
+the steamer, some one gave a loud shout and threw his cap on the
+ground; looking about for the steward, for the shout was evidently
+made for his benefit, we saw him violently throw his cap, with a
+shout, into a chicken-coop, into which he was about to put the result
+of his foraging expedition among the houses of the stanitza.
+
+   [Footnote 2: "Observations upon the Korean Coast, Japanese-Korean
+   Ports, and Siberia, made during a journey from the Asiatic
+   Station to the United States, through Siberia to Europe, June 3
+   to September 8, 1882." Published by the United States Navy
+   Department, Washington, 1883, pp. 51.]
+
+"We afterward witnessed an incident which illustrated the extent of
+his disability. The captain of the steamer, running up to him,
+suddenly clapping his hands at the same time, accidentally slipped and
+fell hard on the deck; without having been touched by the captain, the
+steward instantly clapped his bands and shouted, and then, in
+powerless imitation, he too fell as hard and almost precisely in the
+same manner and position as the captain. In speaking of the steward's
+disorder, the captain of the general staff stated that it was not
+uncommon in Siberia; that he had seen a number of cases of it, and
+that it was commonest about Yakutsk, where the winter cold is extreme.
+Both sexes were subject to it, but men much less than women. It was
+known to Russians by the name of 'miryachit'".
+
+So far as I am aware--and I have looked carefully through several
+books of travel in Siberia--no account of this curious disease has
+been hitherto published.
+
+The description given by the naval officers at once, however, brings
+to mind the remarks made by the late Dr. George M. Beard, before the
+meeting of the American Neurological Association in 1880, relative to
+the "Jumpers" or "Jumping Frenchmen" of Maine and northern New
+Hampshire.[3]
+
+   [Footnote 3: "Journal of Nervous and Mental Diseases," vol. vii.,
+   1880, p. 487.]
+
+In June, 1880, Dr. Beard visited Moosehead Lake, found the "Jumpers,"
+and experimented with them. He ascertained that whatever order was
+given them was at once obeyed. Thus, one of the jumpers who was
+sitting in a chair with a knife in his hand was told to throw it, and
+he threw it quickly, so that it stuck in a beam opposite; at the same
+time he repeated the order to throw it with a cry of alarm not unlike
+that of hysteria or epilepsy. He also threw away his pipe, which he
+was filling with tobacco, when he was slapped upon the shoulder. Two
+jumpers standing near each other were told to strike, and they struck
+each other very forcibly. One jumper, when standing by a window, was
+suddenly commanded by a person on the other side of the window to
+jump, and he jumped up half a foot from the floor, repeating the
+order. When the commands are uttered in a quick, loud voice, the
+jumper repeats the order. When told to strike he strikes, when told to
+throw he throws whatever he may happen to have in his hand. Dr. Beard
+tried this power of repetition with the first part of the first line
+of Virgil's "�neid" and the first part of the first line of Homer's
+"Iliad," and out-of-the-way words of the English language with which
+the jumper could not be familiar, and he repeated or echoed the sound
+of the word as it came to him in a quick, sharp voice, at the same
+time he jumped, or struck, or threw, or raised his shoulders, or made
+some other violent muscular motion. They could not help repeating the
+word or sound that came from the person that ordered them, any more
+than they could help striking, dropping, throwing, jumping, or
+starting; all of these phenomena were indeed but parts of the general
+condition known as jumping. It was not necessary that the sound should
+come from a human being; any sudden or unexpected noise, as the
+explosion of a gun or pistol, the falling of a window, or the slamming
+of a door--provided it was unexpected and loud enough--would cause
+these jumpers to exhibit some one or all of these phenomena. One of
+these jumpers came very near cutting his throat, while shaving, on
+hearing a door slam. They had been known to strike their fists against a
+red-hot stove, to jump into the fire and into water. They could not
+help striking their best friend if near them when ordered. The noise
+of a steam whistle was especially obnoxious to them. One of these
+jumpers, when taking some bromide of sodium in a tumbler, was told to
+throw it, and he dashed the tumbler upon the floor. It was dangerous
+to startle them in any way when they had an ax or an knife in their
+hands. All of the jumpers agreed that it tired them to be jumped, and
+they dreaded it, but they were constantly annoyed by their companions.
+
+From this description it will at once, I think, be perceived that
+there are striking analogies between "miryachit" and this disorder of
+the "Jumping Frenchmen" of Maine. Indeed, it appears to me that, if
+the two affections were carefully studied, it would be found that they
+were identical, or that, at any rate, the phenomena of the one could
+readily be developed into those of the others. It is not stated that
+the subjects of miryachit do what they are told to do. They require an
+example to reach their brains through the sense of sight or that of
+hearing, whereas the "Jumpers" do not apparently perform an act which
+is executed before them, but they require a command. It seems,
+however, that a "Jumper" starts whenever any sudden noise reaches his
+ears.
+
+In both classes of cases a suggestion of some kind is required, and
+then the act takes place independently of the will. There is another
+analogous condition known by the Germans as _Schlaftrunkenheit_, and
+to English and American neurologists as somnolentia, or
+sleep-drunkenness. In this state an individual, on being suddenly
+awakened, commits some incongruous act of violence, ofttimes a murder.
+Sometimes this appears to be excited by a dream, but in others no such
+cause could be discovered.
+
+Thus, a sentry fell asleep during his watch, and, being suddenly
+aroused by the officer in command, attacked the latter with his sword,
+and would have killed him but for the interposition of the bystanders.
+The result of the medical examination was that the act was
+involuntary, being the result of a violent confusion of mind
+consequent upon the sudden awaking from a profound sleep. Other cases
+are cited by Wharton and Stille in their work on medical
+jurisprudence, by Hoffbauer, and by myself in "Sleep and its
+Derangements."
+
+The following cases among others have occurred in my own experience:
+
+A gentleman was roused one night by his wife, who heard the
+street-door bell ring. He got up, and, without paying attention to
+what she said, dragged the sheets off of the bed, tore them hurriedly
+into strips, and proceeded to tie the pieces together. She finally
+succeeded in bringing him to himself, when he said he had thought the
+house was on fire, and he was providing means for their escape. He did
+not recollect having had any dream of the kind, but was under the
+impression that the idea had occurred to him at the instant of his
+awaking.
+
+Another was suddenly aroused from a sound sleep by the slamming of a
+window-shutter by the wind. He sprang instantly from his bed, and,
+seizing a chair that was near, hurled it with all his strength against
+the window. The noise of the breaking of glass fully awakened him. He
+explained that he imagined some one was trying to get into the room
+and had let his pistol fall on the floor, thereby producing the noise
+which had startled him.
+
+In another case a man dreamed that he heard a voice telling him to
+jump out of the window. He at once arose, threw open the sash, and
+jumped to the ground below, fortunately only a distance of about ten
+feet, so that he was not injured beyond receiving a violent shock.
+Such a case as this appears to me to be very similar to those
+described by Dr. Beard in all its essential aspects.
+
+A few years ago I had a gentleman under my charge who would attempt to
+execute any order given him while he was asleep by a person
+whispering into his ear. Thus, if told in this way to shout, he
+shouted as loud as he could; if ordered to get up, he at once jumped
+from the bed; if directed to repeat certain words, he said them, and
+so on.
+
+I am not able to give any certain explanation of the phenomena of
+miryachit or of the "Jumpers," or of certain of those cases of
+sleep-drunkenness which seem to be of like character. But they all
+appear to be due to the fact a motor impulse is excited by perceptions
+without the necessary concurrence of the volition of the individual to
+cause the discharge. They are, therefore, analogous to reflex actions,
+and especially to certain epileptic paroxysms due to reflex
+irritations. It would seem as though the nerve cells were very much in
+the condition of a package of dynamite or nitro glycerin, in which a
+very slight impression is sufficient to effect a discharge of nerve
+force. They differ, however, from the epileptic paroxysm in the fact
+that the discharge is consonant with the perception--which is in these
+cases an irritation--and is hence an apparently logical act, whereas
+in epilepsy the discharge is more violent, is illogical, and does not
+cease with the cessation of the irritation.
+
+Certainly the whole subject is of sufficient importance to demand the
+careful study of competent observers.
+
+       *       *       *       *       *
+
+
+
+
+THE GUM DISEASE IN TREES.[1]
+
+  [Footnote 1: Communicated to the _Medical Times_ by Sir James Paget.]
+
+
+An essay by Dr. Beijerinck, on the contagion of the gum disease in
+plants, lately published by the Royal Academy of Sciences at
+Amsterdam, contains some useful facts. The gum disease (_gummosis,
+gum-flux)_ is only too well known to all who grow peaches, apricots,
+plums, cherries, or other stone fruits. A similar disease produces gum
+arabic, gum tragacanth, and probably many resins and gum resins. It
+shows itself openly in the exudation of thick and sticky or hard and
+dry lumps of gum, which cling on branches of any of these trees where
+they have been cracked or wounded through the bark. Dr. Beijerinck was
+induced to make experimental inoculations of the gum disease by
+suspicions that, like some others observed in plants, it was due to
+bacteria. He ascertained that it is in a high degree contagious, and
+can easily be produced by inserting the gum under the edge of a wound
+through the bark of any of the trees above named. The observation that
+heated or long boiled pieces of gum lose their contagious property
+made it most probable that a living organism was concerned in the
+contagions; and he then found that only those pieces of the gum
+conveyed contagion in which, whether with or without bacteria, there
+were spores of a relatively highly organized fungus, belonging to the
+class of Ascomycetes; and that these spores, inserted by themselves
+under the bark, produced the same pathological changes as did the
+pieces of gum. The fungus thus detected, was examined by Professor
+Oudemans, who ascertained it to be a new species of Coryneum, and has
+named it _Coryneum Beijerincki_. The inoculation experiments are best
+made by means of incisions through the bark of young branches of
+healthy peach trees or cherry trees, and by slightly raising the cut
+edge of the bark and putting under it little bits of gum from a
+diseased tree of the same kind. In nearly every instance these wounds
+become the seats of acute gum disease, while similar wounds in the
+same or other branches of the same tree, into which no gum is
+inserted, remain healthy, unless, by chance, gum be washed into them
+during rain. The inoculation fails only when the inserted pieces of
+gum contain no Coryneum. By similar inoculations similar diseases can
+be produced in plum, almond, and apricot trees, and with the gum of
+any one of these trees any other can be infected; but of many other
+substances which Beijerinck tried, not one produced any similar
+disease. The inoculation with the gum is commonly followed by the
+death of more or less of the adjacent structures; first of the bark,
+then of the wood. Small branches or leaf stalks thus infected in
+winter, or in many places at the same time, may be completely killed;
+but, in the more instructive experiments the first symptom of the gum
+disease is the appearance of a beautiful red color around the wound.
+It comes out in spots like those which often appear spontaneously on
+the green young branches of peach trees that have the gum disease; and
+in these spots it is usual to find Coryneum stromata or mycelium
+filaments. The color is due to the formation of a red pigment in one
+or more of the layers of the cells of the bark. But in its further
+progress the disease extends beyond the parts at which the Coryneum or
+any structures derived from it can be found; and this extension,
+Beijerinck believes, is due to the production of a fluid of the nature
+of a ferment, produced by the Coryneum, and penetrating the adjacent
+structures. This, acting on the cell walls, the starch granules, and
+other constituents of the cells, transforms them into gum, and even
+changes into gum the Coryneum itself, reminding the observer of the
+self-digestion of a stomach.
+
+In the cells of the cambium, the same fluid penetrating unites with
+the protoplasm, and so alters it that the cells produced from it form,
+not good normal wood, but a morbid parenchymatous structure. The cells
+of this parenchyma, well known among the features of gum disease, are
+cubical or polyhedral, thin walled, and rich in protoplasm. This, in
+its turn, is transformed into gum, such as fills the gum channels and
+other cavities found in wood, and sometimes regarded as gum glands.
+And from this also the new ferment fluid constantly produced, and
+tracking along the tissues of the branches, conveys the Coryneum
+infection beyond the places in which its mycelium can be found.
+
+       *       *       *       *       *
+
+
+
+
+DRINKSTONE PARK.
+
+
+Drinkstone has long been distinguished on account of the successful
+cultivation of remarkable plants. It lies some eight miles southeast
+from Bury St. Edmund's, and is the seat of T.H. Powell, Esq. The
+mansion or hall is a large old-fashioned edifice, a large portion of
+its south front being covered by a magnificent specimen of the
+Magnolia grandiflora, not less than 40 feet in height, while other
+portions of its walls are covered with the finest varieties of
+climbing roses and other suitable plants. The surrounding country,
+although somewhat flat, is well wooded, and the soil is a rich loam
+upon a substratum of gravel, and is consequently admirably suited to
+the development of the finer kinds of coniferous and other ornamental
+trees and shrubs, so that the park and grounds contain a fine and well
+selected assortment of such plants.
+
+[Illustration: THE SNOWFLAKE, LEUCOJUM VERNUM, AT DRINKSTONE
+PARK.]
+
+Coniferous trees are sometimes considered as out of place in park
+scenery; this, however, does not hold good at Drinkstone, where Mr.
+Powell has been displayed excellent taste in the way of improving the
+landscape and creating a really charming effect by so skillfully
+blending the dressed grounds with the rich greensward of the park
+that it is not easy to tell where the one terminates or the other
+commences.
+
+The park, which covers some 200 acres, including a fine lake over
+eight acres in extent, contains also various large groups or clumps of
+such species as the Sequoia gigantea, Taxodium sempervirens, Cedres
+deodora, Picea douglasii, Pinsapo, etc., interspersed with groups of
+ornamental deciduous trees, producing a warm and very pleasing effect
+at all seasons of the year. Among species which are conspicuous in the
+grounds are fine, well-grown examples of Araucaria imbricata, some 30
+feet high; Cedrus deodara, 60 feet in height; Abies pinsapo, 40 feet;
+and fine specimens of Abies grandis, A. nobilis, and A. nordmanniana,
+etc., together with Abies albertiana or mertensiana, a fine,
+free-growing species; also Libocedrus gigantea, Thuiopsis borealis,
+Thuia lobbii, Juniperus recurva, Taxas adpressa, fine plants; with
+fine golden yews and equally fine examples of the various kinds of
+variegated hollies, etc.
+
+[Illustration: ODONTOGLOSSUM ROSSI MAJOR VAR. RUBESCENS, AT DRINKSTONE
+PARK.]
+
+Particular attention is here paid to early spring flowers. Drinkstone
+is also celebrated as a fruit growing establishment, more particularly
+as regards the grape vine; the weight and quality of the crops of
+grapes which are annually produced here are very remarkable.--_The
+Gardeners' Chronicle._
+
+       *       *       *       *       *
+
+
+
+
+ON THE CHANGES WHICH TAKE PLACE IN THE CONVERSION OF HAY INTO
+ENSILAGE.
+
+By FREDK. JAS. LLOYD, F.C.S., Lecturer on Agriculture, King's
+College.
+
+
+The recently published number of the _Royal Agricultural Society's
+Journal_ contains some information upon the subject of silage which
+appears to me of considerable interest to those chemists who are at
+present investigating the changes which take place in the conversion
+of grass into silage. The data[1] are, so far as I know, unique, and
+though the analytical work is not my own, yet it is that of an
+agricultural chemist, Mr. A. Smetham, of Liverpool, whose work I know
+from personal experience to be thoroughly careful and reliable. I have
+therefore no hesitation in basing my remarks upon it.
+
+   [Footnote 1: _Royal Agricultural Society's Journal_, vol. xx.,
+   part i., pp. 175 and 380.]
+
+We have here for the first time an accurate account of the quantity of
+grass put into a silo, of the quantity of silage taken out, and of the
+exact composition both of the grass and resulting silage. I desire
+merely to place myself in the position of, so to speak, a "chemical
+accountant."
+
+The ensilage has been analyzed at three depths, or rather in three
+layers, the first being 1 foot, the second 1 ft. to 1 ft. 6 in., and
+the third 1 ft. 6 in. to 2 ft. from the bottom of the silo. By
+doubling the figures of the bottom layer analysis, adding these to the
+second and third layer analysis, and dividing by 4, we obtain a fair
+representation of the average composition of the silage taken
+throughout the silo, for by so doing we obtain the average of the
+analyses of each 6-inch layer of silage. The results of the analyses
+are as follows, calculated on the dry matter. The moisture was
+practically the same, being 70.48 per cent, in the grass and 72.97 in
+the silage.
+
+
+         _Composition of Grass and Silage (dried at 100�C.)._
+
+                                         Grass.       Ensilage.
+ Fat (ether extract)                       2.80            5.38
+ Soluble albuminous compounds              3.06            5.98
+ Insoluble albuminous compounds            6.94            3.77
+ Mucilage, sugar, and extractives, etc.   11.65            4.98
+ Digestible fiber                         36.24           33.37
+ Indigestible woody fiber                 32.33           31.79
+                                         -------         -------
+                                          93.02           85.27
+ Soluble mineral matters                   5.24           12.62
+ Insoluble mineral matters                 1.74            2.11
+                                         -------         -------
+                                         100.00          100.00
+
+The striking difference in the mineral matter of the grass and silage
+I will merely draw attention to; it is not due to the salt added to
+the silage. I may say, however, that other analysts and I myself have
+found similar striking differences. For instance, Prof. Kinch[2]
+found in grass 8.50 per cent. mineral matter, in silage 10.10 per
+cent., which, as be points out, is equivalent, to a "loss of about 18
+per cent. of combustible constituents"--a loss which we have no proof
+of having taken place. In Mr. Smetham's sample the loss would have to
+be 50 per cent., which did not occur, and in fact is not possible.
+What is the explanation?
+
+  [Footnote 2: _Journ. Chem. Society_, March, 1884, p. 124.]
+
+I am, however, considering now the organic constituents. Calculating
+the percentages of these in the grass and silage, we obtain the
+following figures:
+
+          _Percentage Composition of Organic Compounds._
+
+                                 Grass.           Ensilage.
+  Fat (ether extract)               3.01               6.31
+  Soluble albuminous compounds      8.29}             {7.01
+                                        }10.75   11.43{
+  Insoluble "            "          7.46}             {4.42
+
+  Mucilage, sugar, and extractives 12.52               5.84
+  Digestible fiber                 38.96              39.14
+  Indigestible woody fiber         34.76              37.28
+                                 -------            -------
+                                  100.00             100.00
+
+The difference in the total nitrogen in the grass and silage is equal
+to 0.68 per cent. of albuminoids. Practically it is a matter of
+impossibility that the nitrogen could have increased in the silo, and
+it will be a very safe premise upon which to base any further
+calculations that the total amount of nitrogen in the silage was
+identical with that in the grass. There may have been a loss, but
+that is not yet proved. Arguing then upon the first hypothesis, it is
+evident that 100 parts of the organic matters of silage represent more
+than 100 parts of the organic matter of grass, and by the equation we
+obtain 10.75:11.43 :: 100:106 approximately. If now we calculate the
+composition of 106 parts organic matter of grass, it will represent
+exactly the organic matter which has gone to form 100 parts of that
+present in silage.
+
+The following table gives these results, and also the loss or gain in
+the various constitutents arising from the conversion into silage:
+
+                 _Organic Matter_.
+
+                               In 106 pts. In 100 pts. Loss or
+                                  Grass.     Silage.     Gain.
+
+Fat (ether extract)               3.19        6.31      +3.12
+Soluble albuminous compounds      3.49        7.01      +3.52
+Insoluble "           "           7.91        4.42      -3.49
+Mucilage                         13.27        5.84      -7.43
+Digestible Fiber                 41.30       39.14      -2.16
+Indigestible woody fiber         36.84       37.28      +0.44
+                                -------     -------
+                                106.00      100.00
+
+These calculations show, provided my reasoning be correct, that the
+chief changes which take place are in the albuminous compounds, which
+has already been pointed out by Professors Voelcker, Kinch, and
+others; and in the starch, gum, mucilage, sugar, and those numerous
+bodies termed extractives, which was to be expected. But they show
+most conclusively that the "decrease in the amount of indigestible
+fiber and increase in digestible" so much spoken of is, so far as our
+present very imperfect methods of analyzing these compounds permit us
+to judge, a myth; and I have not yet found any sufficient evidence to
+support this statement. A loss, then, of 6 parts of organic matter out
+of every 106 parts put into the silo has in this instance taken place,
+due chiefly to the decomposition of starch, sugar, and mucilage, etc.
+And as the grass contained 70 parts of water when put into the silo,
+the total loss would only be 1.7 per cent. of the total weight. This
+theoretical deduction was found by practical experience correct, for
+Mr. Smith, agent to Lord Egerton, upon whose estate this silage was
+made, in his report to Mr. Jenkins says the "actual weight out of the
+silo corresponds exactly with the weight we put into the same."
+
+In my judgment these figures are of interest to the agricultural
+chemist for many reasons. First, they will clear the ground for future
+workers and eliminate from their researches what would have greatly
+complicated them--changes in the cellulose bodies.
+
+Secondly, they are of interest because our present methods of
+distinguishing between and estimating digestible and indigestible
+fiber is most rough, and probably inaccurate, and may not in the least
+represent the power of an animal--say a cow--to digest these various
+substances; and most of us know that when a new method of analysis
+becomes a necessity, a new method is generally discovered. Lastly,
+they are of interest to the agriculturist, for they point out, I
+believe for the first time, the exact amount of loss which grass--or
+at least one sample--has undergone in conversion into silage, and also
+that much of the nitrogenous matter is changed, and so far as we know
+at present, lost its nutritive value. This, however, is only comparing
+silage with grass. What is wanted is to compare silage with hay--both
+made out of the same grass. Then, and then only, will it be possible
+to sum up the relative advantages or disadvantages of the two methods
+of preserving grass as food for cattle.--_Chem. News_.
+
+       *       *       *       *       *
+
+
+
+
+THE ILLUMINATING POWER OF ETHYLENE.
+
+
+Dr. Percy Frankland has obtained results which may be thus briefly
+summarized: (1.) That pure ethylene, when burnt at the rate of 5 cubic
+feet per hour from a Referee's Argand burner, emits a light of 68.5
+standard candles. (2.) That the illuminating power of equal volumes of
+mixtures of ethylene with either hydrogen carbonic oxide or
+marsh-gas is less than that of pure ethylene. (3.) That when the
+proportion of ethylene in such mixtures is above 63 per cent. the
+illuminating power of the mixture is but slightly affected by the
+nature of the diluent. When, on the other hand, the proportion of
+ethylene in such mixtures is low, the illuminating power of the
+mixture is considerably the highest when marsh-gas is the diluent, and
+the lowest when the ethylene is mixed with carbonic oxide. (4.) That
+if 5 cubic feet of ethylene be uniformly consumed irrespectively of
+the composition of the mixture, the calculated illuminating power is
+in every case equal to or actually greater than that of pure ethylene
+until a certain degree of dilution is attained. This intrinsic
+luminosity of ethylene remains almost constant when the latter is
+diluted with carbonic oxide, until the ethylene forms only 40 per
+cent. of the mixture, after which it rapidly diminishes to zero when
+the ethylene forms only 20 per cent. of the mixture. When the ethylene
+is diluted with hydrogen, its intrinsic luminosity rises to 81 candles
+when the ethylene constitutes 30 per cent. of the mixture, after which
+it rapidly falls to zero when the ethylene amounts to only 10 per
+cent. In the case of mixtures of ethylene and marsh-gas, the intrinsic
+luminosity of the former is augmented with increasing rapidity as the
+proportion of marsh gas rises, the intrinsic luminosity of ethylene,
+in a mixture containing 10 per cent. of the latter, being between 170
+and 180 candles.
+
+       *       *       *       *       *
+
+
+
+
+DIFFRACTION PHENOMENA DURING TOTAL SOLAR ECLIPSES.[1]
+
+   [Footnote 1: A paper read before the American Astronomical
+   Society, May 5, 1884.]
+
+By G.D. Hiscox.
+
+
+The reality of the sun's corona having been cast in doubt by a leading
+observer of the last total eclipse, who, from the erratic display
+observed in the spectroscope, has declared it a subjective phenomenon
+of diffraction, has led me to an examination and inquiry as to the
+bearing of an obscurely considered and heretofore only casually
+observed phenomenon seen to take place during total solar eclipses.
+This phenomenon, it seems to me, ought to account for, and will
+possibly satisfy, the spectroscopic conditions observed just before,
+during, and after totality; which has probably led to the epithet used
+by some leading observers--"the fickle corona." The peculiar
+phenomenon observed in the spectroscope, the flickering bands or lines
+of the solar spectrum flashing upon and across the coronal spectrum,
+has caused no little speculation among observers.
+
+The diffraction or interference bands projected by the passage of a
+strong beam of light by a solid body, as discovered long since by
+Grimaldi, and investigated later by Newton, Fresnel, and Fraunhofer,
+are explained and illustrated in our text books; but the grand display
+of this phenomenon in a total solar eclipse, where the sun is the
+source of light and the moon the intercepting body, has as yet
+received but little attention from observers, and is not mentioned to
+my knowledge in our text books.
+
+In the instructions issued from the United States Naval Observatory
+and the Signal Office at Washington for the observation of the eclipse
+of July 29, 1878, attention was casually directed to this phenomenon,
+and a few of the observers at Pike's Peak, Central City, Denver, and
+other places have given lucid and interesting descriptions of the
+flight of the diffraction bands as seen coursing over the face of the
+earth at the speed of the moon's shadow, at the apparent enormous
+velocity of thirty-three miles per minute, or fifty times the speed of
+a fast railway train.
+
+From a known optical illusion derived from interference or fits of
+perception, as illustrated in quick moving shadows, this great speed
+was not realized to the eye, as the observed motion of these shadows
+was apparently far less rapid than their reality.
+
+The ultra or diffraction bands outside of the shadow were distinctly
+seen and described by Mr. J.E. Keeler at Central City, both before and
+after totality. He estimates the shadow bands at 8 inches wide and 4
+feet apart.
+
+Professor E.S. Holden, also at Central City, estimated the dark bands
+as about 3 feet apart, and variable.
+
+From estimates which he obtained from other observers of his party,
+the distances between the bands varied from 6 to l� feet, but so
+quickly did they pass that they baffled all attempts to count even the
+number that passed in one second.
+
+He observed the time of continuance of their passage from west to east
+as forty-eight seconds, which indicates a width of 33 miles of
+diffraction bands stretching outward from the edge of the shadow to
+the number of many thousands.
+
+Mr. G.W. Hill, at Denver, a little to the north of the central track
+of the shadow, observed the infra or bands within the shadow, alluding
+to the fact that they must be moving at the same rate as the shadow,
+although their apparent motion was much slower, or like the shadows of
+flying clouds. He attributes the discrepancy to optical illusion.
+
+At Virginia City the _colors_ of the _ultra_ bands were observed, and
+estimated at five seconds' duration from the edge of the shadow, which
+is equal to about 4 miles in width. These are known to be the
+strongest color bands in the diffraction spectrum, which accounts for
+their being generally observed.
+
+Mr. W.H. Bush, observing at Central City, in a communication to Prof.
+Holden alludes to the brilliancy of the colors of these bands as seen
+through small clouds floating near the sun's place during totality,
+and of the rapid change of their rainbow colors as observed dashing
+across the clouds with the rapidity of thought.
+
+All of these bands, both ultra and infra, as seen in optical
+experiments, are colored in reverse order, being from violet to red
+for each band outward and inward from the edge of the shadow.
+
+It is very probable that the velocity of the passage of all the bands
+during a total eclipse very much modifies the distinctness of the
+colors or possibly obliterates them by optically blending so as to
+produce the dull white and black bands which occupied so large a
+portion of this grand panorama.
+
+The phenomenon of these faint colored bands, with the observed light
+and dark shadows, may be attributed to one or all of the following
+causes:
+
+1. A change in the direction of a small portion of the sun's light
+passing by the solid body of the moon, it being deflected outward by
+repulsion or reflection from its surface, and other portions being
+deflected inward after passing the body by mutual repulsion of its own
+elements toward a _light vacuum_ or space devoid of the element of
+vibration.
+
+2. The colored spectral bands being the direct result of the property
+of interference, or the want of correspondence of the wave lengths due
+to divergence; the same phenomenon being also observed in convergent
+light. This is practically illustrated in the hazy definition of the
+reduced aperture of telescopes, and its peculiarities shown in the
+spectral rings within and beyond the focus.
+
+3. Chromatic dispersion by our atmosphere, together with selective
+absorption, also by our atmosphere and its vapors, have been suggested
+as causes in this curious and complicated phenomena.
+
+In none of the reports descriptive of the phenomena of polarization of
+the corona is there the slightest allusion to the influence that the
+diffraction bands may possibly have in modifying or producing the
+various conditions of polarization observed; although these
+observations have been made and commented upon during the past
+twenty-five years.
+
+Investigations now in progress of the modifying relation of the
+phenomenon of diffraction in its effect upon not only the physical
+aspect of the corona, but also in some strange spectroscopic anomalies
+that have been observed near the sun at other times than during a
+total solar eclipse, will, it is hoped, result in a fuller
+interpretation of the physical nature of one of the grandest elements
+of creation--_light_; let there be more of it.
+
+       *       *       *       *       *
+
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+
+The Project Gutenberg EBook of Scientific American Supplement, No. 441,
+June 14, 1884., by Various
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Scientific American Supplement, No. 441, June 14, 1884.
+
+Author: Various
+
+Release Date: May 16, 2005 [EBook #15833]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK SCIENTIFIC AMERICAN ***
+
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+
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+Produced by Juliet Sutherland and the Online Distributed
+Proofreading Team at www.pgdp.net.
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+</pre>
+
+<p class="ctr" style="margin-left: -10%; margin-right: -10%;"><a href="./images/title.png">
+<img src="./images/title_th.png" alt="Issue Title" /></a></p>
+<h1>SCIENTIFIC AMERICAN SUPPLEMENT NO. 441</h1>
+<h2>NEW YORK, JUNE 14, 1884</h2>
+<h4>Scientific American Supplement. Vol. XVII, No. 441.</h4>
+<h4>Scientific American established 1845</h4>
+<h4>Scientific American Supplement, $5 a year.</h4>
+<h4>Scientific American and Supplement, $7 a year.</h4>
+<hr />
+<table summary="Contents" border="0" cellspacing="5">
+<tr>
+<th colspan="2">TABLE OF CONTENTS.</th>
+</tr>
+<tr>
+<td valign="top">I.</td>
+<td><a href="#art01">
+CHEMISTRY AND METALLURGY.&mdash;On Electrolysis.&mdash;Precipitation
+     of lead, thallium, silver, bismuth, manganese, etc.&mdash;By H.
+     SCHUCHT</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art02">
+The Electro-Chemical Equivalent of Silver
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art03">
+ Zircon.&mdash;How it can be rendered soluble.&mdash;By F. STOLBA
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art04">
+A New Process for Making Wrought Iron Directly from the Ore.
+     &mdash;Comparison with other processes.&mdash;With descriptions and
+     engravings of the apparatus used</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art05">
+Some Remarks on the Determination of Hardness in Water</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art06">
+On the changes which Take Place in the Conversion of Hay
+     into Ensilage.&mdash;By F.J. Lloyd</a></td>
+</tr>
+<tr>
+<td valign="top">II.</td>
+<td><a href="#art07">
+ENGINEERING AND MECHANICS.&mdash;Faure's Machine for
+     Decorticating Sugar Cane.&mdash;With full description
+     and 13 figures
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art08">
+The Generation of Steam and the Thermodynamic Problems
+     Involved.&mdash;By WM. ANDERSON.&mdash;Apparatus used in the
+     experimental determination of the heat of combustion and
+     the laws which govern its development.&mdash;Ingredients of
+     fuel.&mdash;Potential energy of fuel.&mdash;With 7 figures and
+     several tables
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art09">
+Planetary Wheel Trains.&mdash;Rotations of the wheels relatively
+     to the train arm.&mdash;By Prof. C.W. MACCORD
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art10">
+The Pantanemone.&mdash;A New Windwheel.&mdash;1 engraving
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art11">
+Relvas's New Life Boat.&mdash;With engraving
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art12">
+ Experiments with Double Barreled Guns and Rifles.
+     &mdash;Cause of the divergence of the charge.&mdash;4 figures
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art13">
+Improved Ball Turning Machine.&mdash;1 figure
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art14">
+Cooling Apparatus for Injection Water.&mdash;With engraving
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art15">
+Corrugated Disk Pulleys.&mdash;1 engraving
+</a></td>
+</tr>
+<tr>
+<td valign="top">III.</td>
+<td><a href="#art16">
+TECHNOLOGY.&mdash;A New Standard Light
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art17">
+Dr. Feussner's New Polarizing Prism.&mdash;Points of difference
+     between the old and new prisms.&mdash;By P.R. SLEEMAN
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art18">
+Density and Pressure of Detonating Gas
+</a></td>
+</tr>
+<tr>
+<td valign="top">IV.</td>
+<td><a href="#art19">
+ ELECTRICITY, LIGHT, ETC.&mdash;Early History of the Telegraph.
+     &mdash;Pyrsia, or the system of telegraphy among the Greeks.
+     &mdash;Communication by means of characters and the telescope.
+     &mdash;Introduction of the magnetic telegraph between Baltimore
+     and Washington
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art20">
+ The Kravogl Electro Motor and its Conversion Into a Dynamo
+     Electric Machine.&mdash;5 figures
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art21">
+Bornhardt's Electric Machine for Blasting in Mines.
+     &mdash;15 figures
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art22">
+Pritchett's Electric Fire Alarm.&mdash;1 figure
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art23">
+A Standard Thermopile
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art24">
+Telephonic Transmission without Receivers.&mdash;Some of the
+     apparatus exhibited at the annual meeting of the French
+     Society of Physics.&mdash;Telephonic transmission through a
+     chain of persons
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art25">
+Diffraction Phenomena during Total Solar Eclipses.&mdash;By G.D.
+     Hiscox
+</a></td>
+</tr>
+<tr>
+<td valign="top">V.</td>
+<td><a href="#art26">
+BOTANY AND HORTICULTURE.&mdash;Gum Diseases in Trees.&mdash;
+     Cause and contagion of the same</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art27">
+Drinkstone Park.&mdash;Trees and plants cultivated therein.&mdash;
+     With 2 engravings
+</a></td>
+</tr>
+<tr>
+<td valign="top">VI.</td>
+<td><a href="#art28">
+MEDICINE AND HYGIENE.&mdash;Miryachit.&mdash;A newly-discovered
+     disease of the nervous system, and its analogues.&mdash;By WM. A.
+     HAMMOND
+</a></td>
+</tr>
+
+<tr>
+<td valign="top">VII.</td>
+<td><a href="#art29">
+MISCELLANEOUS.&mdash;Turkish Baths for Horses.&mdash;With
+     diagram.
+</a></td>
+</tr>
+<tr>
+<td></td>
+<td><a href="#art30">
+<ins title="Transcriber's Note: This article not in original Table of Contents.">
+On The Arrangement Of Ground Conductors.</ins>
+</a></td>
+</tr>
+</table>
+
+
+
+<hr />
+
+
+<h2><a name="Page_7031" id="Page_7031"></a><a name="art07" id="art07"></a>FAURE'S MACHINE FOR DECORTICATING SUGAR-CANE.</h2>
+
+<p>The object of the apparatus shown in the accompanying engraving is to
+effect a separation of the tough epidermis of the sugar-cane from the
+internal spongy pith which is to be pressed. Its function consists in
+isolating and separating the cells from their cortex, and in putting
+them in direct contact with the rollers or cylinders of the mill.
+After their passage into the apparatus, which is naturally placed in a
+line with the endless chain that carries them to the mill, the canes
+arrive in less compact layers, pass through much narrower spaces, and
+finally undergo a more efficient pressure, which is shown by an
+abundant flow of juice. The first trials of the machine were made in
+1879 at the Pointe Simon Works, at Martinique, with the small type
+that was shown at the Paris Exhibition of 1878. These experiments,
+which were applied to a work of 3,000 kilos of cane per hour, gave
+entire satisfaction, and decided the owners of three of the colonial
+works (Pointe Simon, Larcinty, and Marin) to adopt it for the season
+of 1880.</p>
+
+<p>The apparatus is shown in longitudinal section in Fig. 1, and in plan
+in Fig. 2.</p>
+
+<p>Fig. 3 gives a transverse section passing through the line 3-4, and
+Fig. 4 an external view on the side whence the decorticated canes make
+their exit from the apparatus.</p>
+
+<p class="ctr"><a href="./images/1a.png"><img src="./images/1a_th.png" alt="FAURE'S MACHINE FOR DECORTICATING SUGAR CANE." /></a><br /> FAURE'S MACHINE FOR DECORTICATING SUGAR CANE.</p>
+
+<p>The other figures relate to details that will be referred to further
+along.</p>
+
+<p><i>The Decorticating Cylinder.</i>&mdash;The principal part of the apparatus is
+a hollow drum, A, of cast iron, 430 mm. in internal diameter by 1.41
+m. in length, which is keyed at its two extremities to the shaft, a.
+Externally, this drum (which is represented apart in transverse
+section in Fig. 5) has the form of an octagonal prism with well
+dressed projections between which are fixed the eight plates, C, that
+constitute the decorticating cylinder. These plates, which are of
+tempered cast iron, and one of which is shown in transverse section in
+Fig. 7, when once in place form a cylindrical surface provided with 48
+helicoidal, dentate channels. The length of these plates is 470 mm.
+There are three of them in the direction of the generatrices of the
+cylinder, and this makes a total of 24. All are strengthened by ribs
+(as shown in Fig. 8), and each is fixed by 4 bolts, <i>c</i>, 20mm. in
+diameter. The pitch of the helices of each tooth is very elongated,
+and reaches about 7.52 m. The depth of the toothing is 18 mm.</p>
+
+<p><i>Frame and Endless Chain.</i>&mdash;The cylinder thus constructed rotates with
+a velocity of 50 revolutions per minute over a cylindrical vessel, B',
+cast in a piece with the frame, B. This vessel is lined with two
+series of tempered cast iron plates, D and D', called exit and
+entrance plates, which rest thereon, through the intermedium of well
+dressed pedicels, and which are held in place by six 20-millimeter
+bolts. Their length is 708 mm. The entrance plates, D, are provided
+with 6 spiral channels, whose pitch is equal to that of the channels
+of the decorticating cylinder, C, and in the same direction. The depth
+of the toothing is 10 mm.</p>
+
+<p>The exit plates, D', are provided with 7 spiral channels of the same
+pitch and direction as those of the preceding, but the depth of which
+increases from 2 to 10 mm. The axis of the decorticating cylinder does
+not coincide with that of the vessel, B', so that the free interval
+for the passage of the cane continues to diminish from the entrance to
+the exit.</p>
+
+<p>The passage of the cane to the decorticator gives rise to a small
+quantity of juice, which flows through two orifices, <i>b'</i>, into a sort
+of cast iron trough, G, suspended beneath the vessel. The cane, which
+is brought to the apparatus by an endless belt, empties in a conduit
+formed of an inclined bottom, E, of plate iron, and two cast iron
+sides provided with ribs. These sides rest upon the two ends of the
+vessel, B', and are cross-braced by two flat bars, <i>e</i>, to which is
+bolted the bottom, E. This conduit is prolonged beyond the
+decorticating cylinder by an inclined chute, F, the bottom of which is
+made of plate iron 7 mm. thick and the sides of the same material 9
+mm. thick. The hollow frame, B, whose general form is like that of a
+saddle, carries the bearings, <i>b</i>, in which revolves the shaft, <i>a</i>.
+One of these bearings is represented in detail in Figs. 9 and 10. It
+will be seen that the cap is held by bolts with sunken heads, and that
+the bearing on the bushes is through horizontal surfaces only. In a
+piece with this frame are cast two similar brackets, B�, which support
+the axle, <i>h</i>, of the endless chain. To this axle, whose diameter is
+100 mm., are keyed, toward the extremities, the pinions, H, to which
+correspond the endless pitch chains, <i>i</i>. These latter are formed, as
+may be seen in Figs. 11 and 12, of two series of links. The shorter of
+these latter are only 100 mm. in length, while the longer are 210 mm.,
+and are hollowed out so as to receive the butts of the boards, I. The
+chain thus formed passes over two pitch pinions, J, like the pinions,
+H, that are mounted at the extremities of an axle, <i>j</i>, that revolves
+in bearings, I', whose position with regard to the apparatus is
+capable of being varied so as to slacken or tauten the chain, I. This
+arrangement is shown in elevation in Fig. 13.</p>
+
+<p><i>Transmission.</i>&mdash;The driving shaft, <i>k</i>, revolves in a pillow block,
+K, cast in a piece with the frame, B. It is usually actuated by a
+special motor, and carries a fly-wheel (not shown in the figure for
+want of space). It receives in addition a cog-wheel, L, which
+transmits its motion to the decorticating cylinder through, the
+intermedium of a large wooden-toothed gear wheel, L'. The shaft, <i>a</i>,
+whose diameter is 228 mm., actuates in its turn, through the pinions,
+M' and M, the pitch pinion, N, upon whose prolonged hub is keyed the
+pinion, M. This latter is mounted loosely upon the intermediate axle,
+<i>m</i>. Motion is transmitted to the driving shaft, <i>h</i>, of the endless
+chain, I, by an ordinary pitch chain, through a gearing which is shown
+in Fig. 12. The pitch pinion, N', is cast in a piece with a hollow
+friction cone, N�, which is mounted loosely upon the shaft, <i>h</i>, and
+to which corresponds a second friction cone, O. This latter is
+connected by a key to a socket, <i>o</i>, upon which it slides, and which
+is itself keyed to the shaft, <i>h</i>. The hub of the cone, O, is
+connected by a ring with a bronze nut, <i>p</i>, mounted at the threaded
+end of the shaft, <i>h</i>, and carrying a hand-wheel, P. It is only
+necessary to turn this latter in one direction or the other in order
+to throw the two cones into or out of gear.</p>
+
+<p>If we allow that the motor has a velocity of 70 revolutions per
+minute, the decorticating cylinder will run at the rate of 50, and the
+sugar-cane will move forward at the rate of 12 meters per minute.</p>
+
+<p>This new machine is a very simple and powerful one. The decortication
+is effected with wonderful rapidity, and the canes, opened throughout
+their entire length and at all points of their circumference, leave
+the apparatus in a state that allows of no doubt as to what the result
+of the pressure will be that they have to undergo. There is no
+tearing, no trituration, no loss of juice, but merely a simple
+preparation for a rational pressure effected under most favorable
+conditions.</p>
+
+<p>The apparatus, which is made in several sizes, has already received
+numerous applications in Martinique, Trinidad, Cuba, Antigua, St.
+Domingo, Peru, Australia, the Mauritius Islands, and
+Brazil.&mdash;<i>Publication Industrielle.</i></p>
+
+<hr />
+
+<h3>MOVING A BRIDGE.</h3>
+
+
+<p>An interesting piece of engineering work has recently been
+accomplished at Bristol, England, which consisted in the moving of a
+foot-bridge 134 feet in length, bodily, down the river a considerable
+distance. The pontoons by means of which the bridge was floated to its
+new position consisted of four 80-ton barges, braced together so as to
+form one solid structure 64 feet in width, and were placed in position
+soon after the tide commenced to rise. At six o'clock A.M. the top of
+the stages, which was 24 feet above the water, touched the under part
+of the bridge, and in a quarter of an hour later both ends rose from
+their foundations. When the tide had risen 4 ft. the stage and bridge
+were floated to the new position, when at 8.30 the girders dropped on
+to their beds.</p>
+
+<hr />
+
+
+<h2><a name="Page_7032" id="Page_7032"></a><a name="art08" id="art08"></a>THE GENERATION OF STEAM, AND THE THERMODYNAMIC PROBLEMS
+INVOLVED.<a name="FNanchor_1" id="FNanchor_1"></a><a href="#Footnote_1"><sup>1</sup></a></h2>
+
+
+<h3>By Mr. WILLIAM ANDERSON, M.I.C.E.</h3>
+
+
+<p>It will not be necessary to commence this lecture by explaining the
+origin of fuel; it will be sufficient if I remind you that it is to
+the action of the complex rays of the sun upon the foliage of plants
+that we mainly owe our supply of combustibles. The tree trunks and
+branches of our forests, as well as the subterranean deposits of coal
+and naphtha, at one time formed portions of the atmosphere in the form
+of carbonic acid gas; that gas was decomposed by the energy of the
+solar rays, the carbon and the oxygen were placed in positions of
+advantage with respect to each other&mdash;endowed with potential energy;
+and it is my duty this evening to show how we can best make use of
+these relations, and by once more combining the constituents of fuel
+with the oxygen of the air, reverse the action which caused the growth
+of the plants, that is to say, by destroying the plant reproduce the
+heat and light which fostered it. The energy which can be set free by
+this process cannot be greater than that derived originally from the
+sun, and which, acting through the frail mechanism of green leaves,
+tore asunder the strong bonds of chemical affinity wherein the carbon
+and oxygen were hound, converting the former into the ligneous
+portions of the plants and setting the latter free for other uses. The
+power thus silently exerted is enormous; for every ton of carbon
+separated in twelve hours necessitates an expenditure of energy
+represented by at least 1,058 horse power, but the action is spread
+over an enormous area of leaf surface, rendered necessary by the small
+proportion of carbonic acid contained in the air, by measure only
+1/2000 part, and hence the action is silent and imperceptible. It is
+now conceded on all hands that what is termed heat is the energy of
+molecular motion, and that this motion is convertible into various
+kinds and obeys the general laws relating to motion. Two substances
+brought within the range of chemical affinity unite with more or less
+violence; the motion of transition of the particles is transformed,
+wholly or in part, into a vibratory or rotary motion, either of the
+particles themselves or the interatomic ether; and according to the
+quality of the motions we are as a rule, besides other effects, made
+conscious of heat or light, or of both. When these emanations come to
+be examined they are found to be complex in the extreme, intimately
+bound up together, and yet capable of being separated and analyzed.</p>
+
+<p>As soon as the law of definite chemical combination was firmly
+established, the circumstance that changes of temperature accompanied
+most chemical combinations was noticed, and chemists were not long in
+suspecting that the amount of heat developed or absorbed by chemical
+reaction should be as much a property of the substances entering into
+combination as their atomic weights. Solid ground for this expectation
+lies in the dynamic theory of heat. A body of water at a given height
+is competent by its fall to produce a definite and invariable quantity
+of heat or work, and in the same way two substances falling together
+in chemical union acquire a definite amount of kinetic energy, which,
+if not expended in the work of molecular changes, may also by suitable
+arrangements be made to manifest a definite and invariable quantity of
+heat.</p>
+
+<p>At the end of last century Lavoisier and Laplace, and after them, down
+to our own time, Dulong, Desprez, Favre and Silbermann, Andrews,
+Berthelot, Thomson, and others, devoted much time and labor to the
+experimental determination of the heat of combustion and the laws
+which governed its development. Messrs. Favre and Silbermann, in
+particular, between the years 1845 and 1852, carried out a splendid
+series of experiments by means of the apparatus partly represented in
+Fig. 1 (opposite), which is a drawing one-third the natural size of
+the calorimeter employed. It consisted essentially of a combustion
+chamber formed of thin copper, gilt internally. The upper part of the
+chamber was fitted with a cover through which the combustible could be
+introduced, with a pipe for a gas jet, with a peep hole closed by
+adiathermanous but transparent substances, alum and glass, and with a
+branch leading to a thin copper coil surrounding the lower part of the
+chamber and descending below it. The whole of this portion of the
+apparatus was plunged into a thin copper vessel, silvered internally
+and filled with water, which was kept thoroughly mixed by means of
+agitators. This second vessel stood inside a third one, the sides and
+bottom of which were covered with the skins of swans with the down on,
+and the whole was immersed in a fourth vessel tilled with water, kept
+at the average temperature of the laboratory. Suitable thermometers of
+great delicacy were provided, and all manner of precautions were taken
+to prevent loss of heat.</p>
+
+<p class="ctr"><a href="./images/3a-1.png"><img src="./images/3a-1_th.png" alt="THE GENERATION OF STEAM. Fig 1." /></a><br /> THE GENERATION OF STEAM. Fig 1.</p>
+
+<p>It is impossible not to admire the ingenuity and skill exhibited in
+the details of the apparatus, in the various accessories for
+generating and storing the gases used, and for absorbing and weighing
+the products of combustion; but it is a matter of regret that the
+experiments should have been carried out on so small a scale. For
+example, the little cage which held the solid fuel tested was only 5/8
+inch diameter by barely 2 inches high, and held only 38 grains of
+charcoal, the combustion occupying about sixteen minutes. Favre and
+Silbermann adopted the plan of ascertaining the weight of the
+substances consumed by calculation from the weight of the products of
+combustion. Carbonic acid was absorbed by caustic potash, as also was
+carbonic oxide, after having been oxidized to carbonic acid by heated
+oxide of copper, and the vapor of water was absorbed by concentrated
+sulphuric acid. The adoption of this system showed that it was in any
+case necessary to analyze the products of combustion in order to,m
+detect imperfect action. Thus, in the case of substances containing
+carbon, carbonic oxide was always present to a variable extent with
+the carbonic acid, and corrections were necessary in order to
+determine the total heat due to the complete combination of the
+substance with oxygen. Another advantage gained was that the
+absorption of the products of combustion prevents any sensible
+alteration in the volumes during the process, so that corrections for
+the heat absorbed in the work of displacing the atmosphere were not
+required. The experiments on various substances were repeated many
+times. The mean results for those in which we are immediately
+interested are given in Table I., next column.</p>
+
+<p>Comparison with later determinations have established their
+substantial accuracy. The general conclusion arrived at is thus
+stated:</p>
+
+<p>&quot;As a rule there is an equality between the heat disengaged or
+absorbed in the acts, respectively, of chemical combination or
+decomposition of the same elements, so that the heat evolved during
+the combination of two simple or com-pound substances is equal to the
+heat absorbed at the time of their chemical segregation.&quot;</p>
+
+
+<p class="ctr">TABLE I.&mdash;SUBSTANCES ENTERING INTO THE COMPOSITION OF FUEL.</p>
+
+<div class="ctr">
+<table border="1" cellpadding="4" cellspacing="0" summary="">
+<colgroup span="7"><col align="left" span="2" /><col align="right" /><col align="left" /><col align="right" span="3" /></colgroup>
+<tr><td rowspan="2"><br /></td><th colspan="4" align="center">Symbol and Atomic Weight.</th><th colspan="2" align="center">Heat evolved in<br /> the Combustion of<br />1 lb. of Fuel.</th></tr>
+<tr><th colspan="2">Before Combustion</th><th colspan="2">After Combustion</th><th align="center">In British<br /> Thermal<br />Units.</th><th align="center">In Pounds<br />of Water<br />Evaporated<br />from and<br /> at 212�.</th></tr>
+<tr><td>Hydrogen burned in oxygen.</td><td>H</td><td>1</td><td>H<sub>2</sub>O</td><td>18</td><td>62,032</td><td>64.21</td></tr>
+<tr><td>Carbon burned to carbonic oxide.</td><td>C</td><td>12</td><td>CO</td><td>28</td><td>4,451</td><td>4.61</td></tr>
+<tr><td>Carbon burned to carbonic acid.</td><td>C</td><td>12</td><td>CO<sub>2</sub></td><td>44</td><td>14,544</td><td>15.06</td></tr>
+<tr><td>Carbonic oxide burned to carbonic acid.</td><td>CO</td><td>28</td><td>CO<sub>2</sub></td><td>44</td><td>4,326</td><td>4.48</td></tr>
+<tr><td>Olefiant gas (ethylene) burnt in oxygen.</td><td>C<sub>2</sub>H<sub>4</sub><br />2H<sub>2</sub>O</td><td>28</td><td>2CO<sub>2</sub></td><td>124</td><td>21,343</td><td>22.09</td></tr>
+<tr><td>Marsh gas (methane) burnt in oxygen.</td><td>CH<sub>4</sub></td><td>16</td><td>2CO<sub>2</sub><br />2H<sub>2</sub>O</td><td>80</td><td>23,513</td><td>24.34</td></tr>
+</table></div>
+
+<p>Composition of air&mdash;</p>
+
+<div class="ctr">
+<table summary="">
+<tr><td rowspan="2"><span class="xxl">{</span></td><td>by volume 0.788 N + 0.197 O + 0.001 CO<sub>2</sub> + 0.014 H<sub>2</sub>O</td></tr>
+<tr><td>by weight 0.771 N + 0.218 O + 0.009 CO<sub>2</sub> + 0.017 H<sub>2</sub>O</td></tr>
+</table></div>
+
+<p>This law is, however, subject to some apparent exceptions. Carbon
+burned in protoxide of nitrogen, or laughing gas, N<sub>2</sub>O, produces
+about 38 per cent. more heat than the same substance burned in pure
+oxygen, notwithstanding that the work of decomposing the protoxide of
+nitrogen has to be performed. In marsh gas, or methane, CH<sub>4</sub>, again,
+the energy of combustion is considerably less than that due to the
+burning of its carbon and hydrogen separately. These exceptions
+probably arise from the circumstance that the energy of chemical
+action is absorbed to a greater or less degree in effecting molecular
+changes, as, for example, the combustion of 1 pound of nitrogen to
+form protoxide of nitrogen results in the absorption of 1,157 units of
+heat. Berthelot states, as one of the fundamental principles of
+thermochemistry, &quot;that the quantity of heat evolved is the measure of
+the sum of the chemical and physical work accomplished in the
+reaction&quot;; and such a law will no doubt account for the phenomena
+above noted. The equivalent heat of combustion of the compounds we
+have practically to deal with has been experimentally determined, and
+therefore constitutes a secure basis on which to establish
+calculations of the caloric value of fuel; and in doing so, with
+respect to substances composed of carbon, hydrogen, and oxygen, it is
+convenient to reduce the hydrogen to its heat-producing equivalent of
+carbon. The heat of combustion of hydrogen being 62,032 units, that of
+carbon 14,544 units, it follows that 4.265 times the weight of
+hydrogen will represent an equivalent amount of carbon. With respect
+to the oxygen, it is found that it exists in combination with the
+hydrogen in the form of water, and, being combined already, abstracts
+its combining equivalent of hydrogen from the efficient ingredients of
+the fuel; and hence hydrogen, to the extent of 1/8 of the weight of
+the oxygen, must be deducted. The general formula then becomes:</p>
+
+<p class="ctr">Heat of combustion = 14,544 {C + 4.265 (H-(O/8))},</p>
+
+<p>and water evaporated from and at 212�, taking 966 units as the heat
+necessary to evaporate 1 pound of water,</p>
+
+<p class="ctr">lb. evaporated = 15.06 {C + 4.265 (H-(O/8))},</p>
+
+<p>carbon, hydrogen, and oxygen being taken at their weight per cent. in
+the fuel. Strictly speaking, marsh gas should be separately
+determined. It often happens that available energy is not in a form in
+which it can be applied directly to our needs. The water flowing down
+from the mountains in the neighborhood of the Alpine tunnels was
+competent to provide the power necessary for boring through them, but
+it was not in a form in which it could be directly applied. The
+kinetic energy of the water had first to be changed into the potential
+energy of air under pressure, then, in that form, by suitable
+mechanism, it was used with signal success to disintegrate and
+excavate the hard rock of the tunnels. The energy resulting from
+combustion is also incapable of being directly transformed into useful
+motive power; it must first be converted into potential force of steam
+or air at high temperature and pressure, and then applied by means of
+suitable heat engines to produce the motions we require. It is
+probably to this circumstance that we must attribute the slowness of
+the human race to take advantage of the energy of combustion. The
+history of the steam engine hardly dates back 200 years, a very small
+fraction of the centuries during which man has existed, even since
+historic times.</p>
+
+<p>The apparatus by means of which the potential energy of fuel with
+respect to oxygen is converted into the potential energy of steam, we
+call a steam boiler; and although it has neither cylinder nor piston,
+crank nor fly wheel, I claim for it that it is a veritable heat
+engine, because it transmits the undulations and vibrations caused by
+the energy of chemical combination in the fuel to the water in the
+boiler; these motions expend themselves in overcoming the liquid
+cohesion of the water and imparting to its molecules that vigor of
+motion which converts them into the molecules of a gas which,
+impinging on the surfaces which confine it and form the steam space,
+declare their presence and energy in the shape of pressure and
+temperature. A steam pumping engine, which furnishes water under high
+pressure to raise loads by means of hydraulic cranes, is not more
+truly a heat engine than a simple boiler, for the latter converts the
+latent energy of fuel into the latent energy of steam, just as the
+pumping engine converts the latent energy of steam into the latent
+energy of the pumped-up accumulator or the hoisted weight.</p>
+
+<p>If I am justified in taking this view, then I am justified in applying
+to my heat engine the general principles laid down in 1824 by Sadi
+Carnot, namely, that the proportion of work which can be obtained out
+of any substance working between two temperatures depends entirely and
+solely upon the difference between the temperatures at the beginning
+and end of the operation; that is to say, if T be the higher
+temperature at the beginning, and <i>t</i> the lower temperature at the end
+of the action, then the maximum possible work to be got out of the
+substance will be a function of (T-<i>t</i>). The greatest range of
+temperature possible or conceivable is from the absolute temperature
+of the substance at the commencement of the operation down to absolute
+zero of temperature, and the fraction of this which can be utilized is
+the ratio which the range of temperature through which the substance
+is working bears to the absolute temperature at the commencement of
+the action. If W = the greatest amount of effect to be expected, T and
+<i>t</i> the absolute temperatures, and H the total quantity of heat
+(expressed in foot pounds or in water evaporated, as the case may be)
+potential in the substance at the higher temperature, T, at the
+beginning of the operation, then Carnot's law is expressed by the
+equation:</p>
+
+<div class="ctr">
+<table summary="Equation">
+<colgroup span="3" align="center"></colgroup>
+<tr><td rowspan="2">W = H <span class="xxl">(</span></td>
+<td><span class="underline">T - <i>t</i></span></td>
+<td rowspan="2"><span class="xxl">)</span></td></tr>
+<tr><td>T</td></tr>
+</table></div>
+
+
+<p>I will illustrate this important doctrine in the manner which Carnot
+himself suggested.</p>
+
+<p class="ctr"><a href="./images/3a-2.png"><img src="./images/3a-2_th.png" alt=" THE GENERATION OF STEAM. Fig 2." /></a><br /> THE GENERATION OF STEAM. Fig 2.</p>
+
+<p>Fig. 2 represents a hillside rising from the sea. Some distance up
+there is a lake, L, fed by streams coming down from a still higher
+level. Lower down on the slope is a millpond, P, the tail race from
+which falls into the sea. At the millpond is established a factory,
+the turbine driving which is supplied with water by a pipe descending
+from the lake, L. Datum is the mean sea level; the level of the lake
+is T, and of the millpond <i>t</i>. Q is the weight of water falling
+through the turbine per minute. The mean sea level is the lowest level
+to which the water can possibly fall; hence its greatest potential
+energy, that of its position in the lake, = QT = H. The water is
+working between the absolute levels, T and <i>t</i>; hence, according to
+Carnot, the maximum effect, W, to be expected is&mdash;</p>
+
+<div class="ctr">
+<table summary="Equation">
+<colgroup span="4" align="left"></colgroup>
+<tr><td></td><td>W = H <span class="xxl">(</span></td>
+<td align="center"><span class="underline">T - <i>t</i></span><br />T</td>
+<td><span class="xxl">)</span></td></tr>
+<tr><td rowspan="2" valign="bottom">but H = QT &there4;</td><td rowspan="2" valign="bottom">W = QT <span class="xxl">(</span></td>
+<td><span class="underline">T - <i>t</i></span></td>
+<td rowspan="2" valign="bottom"><span class="xxl">)</span></td></tr>
+<tr><td align="center">T</td></tr>
+<tr><td></td><td colspan="2" align="left">W = Q (T - <i>t</i>),</td></tr>
+</table></div>
+
+
+<p>that is to say, the greatest amount of work which can be expected is
+found by multiplying the weight of water into the clear fall, which
+is, of course, self-evident.</p>
+
+<p>Now, how can the quantity of work to be got out of a given weight of
+water be increased without in any way improving the efficiency of the
+turbine? In two ways:</p>
+
+<div class="indlist"><p>1. By collecting the water higher up the mountain, and by that means
+increasing T.</p>
+
+<p>2. By placing the turbine lower down, nearer the sea, and by that
+means reducing <i>t</i>.</p></div>
+
+<p>Now, the sea level corresponds to the absolute zero of temperature,
+and the heights T and <i>t</i> to the maximum and minimum temperatures
+between which the substance is working; therefore similarly, the way
+to increase the efficiency of a heat engine, such as a boiler, is to
+raise the temperature of the furnace to the utmost, and reduce the
+heat of the smoke to the lowest possible point. It should be noted, in
+addition, that it is immaterial what liquid there may be in the lake;
+whether water, oil, mercury, or what not, the law will equally apply,
+and so in a heat engine, the nature of the working substance, provided
+that it does not change its physical state during a cycle, does not
+affect the question of efficiency with which the heat being expended
+is so utilized. To make this matter clearer, and give it a practical
+bearing, I will give the symbols a numerical value, and for this
+purpose I will, for the sake of simplicity, suppose that the fuel used
+is pure carbon, such as coke or charcoal, the heat of combustion of
+which is 14,544 units, that the specific heat of air, and of the
+products of combustion at constant pressure, is 0.238, that only
+sufficient air is passed through the fire to supply the quantity of
+oxygen theoretically required for the combustion of the carbon, and
+that the temperature of the air is at 60� Fahrenheit = 520� absolute.
+The symbol T represents the absolute temperature of the furnace, a
+value which is easily calculated in the following manner: 1 lb. of
+carbon requires 2-2/3 lb. of oxygen to convert it into carbonic acid,
+and this quantity is furnished by 12.2 lb. of air, the result being
+13.2 lb. of gases, heated by 14,544 units of heat due to the energy of
+combustion; therefore:</p>
+
+<div class="ctr">
+<table summary="Equation">
+<tr><td rowspan="2"> T = 520� + </td><td>14,544 units</td>
+<td rowspan="2"> = 5,150� absolute.</td></tr>
+<tr><td><span class="overline">13.2 lb. � 0.238</span></td></tr>
+</table></div>
+
+<p>The lower temperature, <i>t</i>, we may take as that of the feed water, say
+at 100� or 560� absolute, for by means of artificial draught and
+sufficiently extending the heating surface, the temperature of the
+smoke may be reduced to very nearly that of the feed water. Under such
+circumstances the proportion of heat which can be realized is</p>
+
+<div class="ctr">
+<table summary="Equation">
+<tr><td rowspan="2"> = </td><td><span class="underline">5,150� - 560�</span></td>
+<td rowspan="2"> = 0.891;</td></tr>
+<tr><td>5,150�</td></tr>
+</table></div>
+
+<p>that is to say, under the extremely favorable if not impracticable
+conditions assumed, there must be a loss of 11 per cent. Next, to give
+a numerical value to the potential energy, H, to be derived from a
+pound of carbon, calculating from absolute zero, the specific heat of
+carbon being 0.25, and absolute temperature of air 520�:</p>
+
+
+<div class="ctr">
+<table border="0" summary="" width="80%">
+<colgroup span="3"><col align="left"/><col align="right"/><col align="right"/></colgroup>
+<tr><td colspan="2"></td><td>Units.</td></tr>
+<tr><td>1 lb. of carbon � 0.25 � 520</td><td>=</td><td>130</td></tr>
+<tr><td>12.2 of air � 0.238 � 520</td><td>=</td><td>1,485</td></tr>
+<tr><td>Heat of combustion</td><td>=</td><td>14,544</td></tr>
+<tr><td colspan="2"></td><td><span class="overline">16,159</span></td></tr>
+<tr><td>Deduct heat equivalent to work of displacing atmosphere by products of combustion raised from 60� to 100�, or from 149.8 cubic feet to 161.3 cubic feet,</td><td></td><td>32</td></tr>
+<tr><td>Total units of heat available</td><td></td><td><span class="overline">16,127</span></td></tr>
+</table></div>
+
+<p>Equal to 16.69 lb. of water evaporated from and at 212�. Hence the
+greatest possible evaporation from and at 212� from a lb. of carbon&mdash;</p>
+
+<div class="ctr">
+<table border="0" summary="Equation">
+<tr>
+<td rowspan="2">W =</td><td>
+<span class="underline"> 16,159 u. � 0.891 - 32 u.</span></td>
+<td rowspan="2">= 14.87 lb.</td></tr>
+<tr><td>966 u.</td></tr>
+</table></div>
+
+<p>I will now take a definite case, and compare the potential energy of a
+certain kind of fuel with the results actually obtained. For this
+purpose the boiler of the eight-horse portable engine, which gained
+the first prize at the Cardiff show of the Royal Agricultural Society
+in 1872, will serve very well, because the trials, all the details of
+which are set forth very fully in vol. ix. of the <i>Journal</i> of the
+Society, were carried out with great care and skill by Sir Frederick
+Bramwell and the late Mr. Menelaus; <a name="Page_7033" id="Page_7033"></a>indeed, the only fact left
+undetermined was the temperature of the furnace, an omission due to
+the want of a trustworthy pyrometer, a want which has not been
+satisfied to this day.<a name="FNanchor_2" id="FNanchor_2"></a><a href="#Footnote_2"><sup>2</sup></a> The data necessary for our purpose are:</p>
+
+<div class="ctr">
+<table border="0" summary="">
+<colgroup><col align="left" /><col align="right" /><col align="center" /></colgroup>
+<tr><td>Steam pressure 80 lb. temperature</td><td>324� = 784�</td><td>absolute.</td></tr>
+<tr><td>Mean temperature of smoke</td><td>389� = 849�</td><td>&quot;</td></tr>
+<tr><td>Water evaporated per 1 lb of coal, from and at 212�</td><td>11.83 lb.</td></tr>
+<tr><td>Temperature of the air</td><td>60� = 520�</td><td>absolute.</td></tr>
+<tr><td>Temperature of feed water</td><td>209� = 669�</td><td>&quot;</td></tr>
+<tr><td>Heating surface</td><td>220 square feet.</td></tr>
+<tr><td>Grate surface</td><td>3.29 feet.</td></tr>
+<tr><td>Coal burnt per hour</td><td>41 lb.</td></tr>
+</table></div>
+
+<p>The fuel used was a smokeless Welsh coal, from the Llangennech
+colleries. It was analyzed by Mr. Snelus, of the Dowlais Ironworks,
+and in Table II. are exhibited the details of its composition, and the
+weight and volume of air required for its combustion. The total heat
+of combustion in 1 lb of water evaporated:</p>
+
+<div class="ind">
+<p>
+      = 15.06 � (0.8497 + 4.265 � (0.426 - 0.035/8)) <br />
+      = 15.24 lb. of water from and at 212�<br />
+      = 14,727 units of heat.
+</p></div>
+
+<p class="ctr">TABLE II.&mdash;PROPERTIES OF LLANGENNECH COAL.</p>
+
+<div class="ctr">
+<table border="1" summary="" width="90%">
+<colgroup span="5"><col align="left" /><col span="4" align="right" /></colgroup>
+<tr><th rowspan="2">&nbsp;</th><th rowspan="2" align="center">Analyses of 1 lb. of Coal.</th><th rowspan="2">Oxygen required for Combustion.<br />Pounds.</th><th colspan="2">Products of Combustion at 32� F.</th></tr>
+<tr><th>Cubic feet.</th><th>Volume per cent.</th></tr>
+<tr><td>Carbon</td><td>0.8497</td><td>2.266</td><td>25.3</td><td>11.1</td></tr>
+<tr><td>Hydrogen</td><td>0.0426</td><td>0.309</td><td>7.6</td><td>3.4</td></tr>
+<tr><td>Oxygen</td><td>0.0350</td><td>&mdash;</td><td>&mdash;</td><td>&mdash;</td></tr>
+<tr><td>Sulphur</td><td>0.0042</td><td>&mdash;</td><td>&mdash;</td><td>&mdash;</td></tr>
+<tr><td>Nitrogen</td><td>0.1045</td><td>&mdash;</td><td>0.18</td><td rowspan="5" valign="middle"><span class="xxl">}</span>85.5</td></tr>
+<tr><td>Ash</td><td>0.0540</td><td>&mdash;</td><td>&mdash;</td></tr>
+<tr><td>Total</td><td>1.0000</td><td>2.572</td><td>&mdash;</td></tr>
+<tr><td>9-1/3.lb nitrogen</td><td>&mdash;</td><td>&mdash;</td><td>118.9</td></tr>
+<tr><td>6 lb. excess of air.</td><td>&mdash;</td><td>&mdash;</td><td>71.4</td></tr>
+<tr><td>Total cubic feet of products per 1 lb. of coal</td><td>&mdash;</td><td>&mdash;</td><td>226.4</td><td>100.0</td></tr>
+</table></div>
+
+<p>The temperature of the furnace not having been determined, we must
+calculate it on the supposition, which will be justified later on,
+that 50 per cent more air was admitted than was theoretically
+necessary to supply the oxygen required for perfect combustion. This
+would make 18 lb. of air per 1 lb. of coal; consequently 19 lb. of
+gases would be heated by 14,727 units of heat. Hence:</p>
+
+<div class="ctr">
+<table border="0" summary="Equation">
+<tr>
+<td rowspan="2">T =</td>
+<td>14,727 u.</td>
+<td rowspan="2">= 3,257�</td></tr>
+<tr><td><span class="overline">19 lb. � 0.238</span></td></tr>
+</table></div>
+
+<p>above the temperatures of the air, or 3,777� absolute. The temperature
+of the smoke, <i>t</i>, was 849� absolute; hence the maximum duty would be</p>
+
+<div class="ctr">
+<table border="0" summary="Equation">
+<tr>
+<td>
+<span class="underline">3,777� - 849�</span></td>
+<td rowspan="2">= 0.7752.</td></tr>
+<tr><td>3,777�</td></tr>
+</table></div>
+
+<p>The specific heat of coal is very nearly that of gases at constant
+pressure, and may, without sensible error, be taken as such. The
+potential energy of 1 lb. of coal, therefore, with reference to the
+oxygen with which it will combine, and calculated from absolute zero,
+is:</p>
+
+<div class="ctr">
+<table border="0" summary="">
+<colgroup><col align="left" /><col align="right" /></colgroup>
+<tr><td></td><td>Units.</td></tr>
+<tr><td>19 lb. of coal and air at the temperature of the air contained 19 lb. � 520� � 0.238</td><td>2,350</td></tr>
+<tr><td>Heat of combustion</td><td><span class="underline">14,727</span></td></tr>
+<tr><td></td><td>17,078</td></tr>
+<tr><td>Deduct heat expended in displacing atmosphere 151 cubic feet</td><td><span class="underline">- 422</span></td></tr>
+<tr><td align="center">Total potential energy</td><td>16,656</td></tr>
+</table></div>
+
+<p>Hence work to be expected from the boiler:</p>
+
+<div class="ctr">
+<table border="0" summary="Equation">
+<tr><td></td>
+<td rowspan="2">17,078 units � <span class="xxl">(</span></td>
+<td>
+<span class="underline">3,777� - 849�</span></td>
+<td rowspan="2"><span class="xxl">)</span> - 422 units</td>
+</tr>
+<tr><td></td><td>3,777�</td></tr>
+<tr><td>=</td><td colspan="3">&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;&mdash;</td>
+<td>= 13.27 lb.</td></tr>
+<tr><td></td><td colspan="3">966 units</td></tr>
+</table></div>
+
+<p>of water evaporated from and at 212�, corresponding to 12,819 units.
+The actual result obtained was 11.83 lb.; hence the efficiency of this
+boiler was</p>
+
+<div class="ctr">
+<table border="0" summary="equation">
+<tr><td><span class="underline">11.83</span></td><td rowspan="2">= 0.892.</td></tr>
+<tr><td>13.27</td></tr>
+</table></div>
+
+<p>I have already claimed for a boiler that it is a veritable heat
+engine, and I have ventured to construct an indicator diagram to
+illustrate its working. The rate of transfer of heat from the furnace
+to the water in the boiler, at any given point, is some way
+proportional to the difference of temperature, and the quantity of
+heat in the gases is proportional to their temperatures. Draw a base
+line representing -460� Fahr., the absolute zero of temperature. At
+one end erect an ordinate, upon which set off T = 3,777�, the
+temperature of the furnace. At 849� = <i>t</i>, on the scale of
+temperature, draw a line parallel to the base, and mark on it a length
+proportional to the heating surface of the boiler; join T by a
+diagonal with the extremity of this line, and drop a perpendicular on
+to the zero line. The temperature of the water in the boiler being
+uniform, the ordinates bounded by the sloping line, and by the line,
+<i>t</i>, will at any point be approximately proportional to the rate of
+transmission of heat, and the shaded area above <i>t</i> will be
+proportional to the quantity of heat imparted to the water. Join T by
+another diagonal with extremity of the heating surface on the zero
+line, then the larger triangle, standing on the zero line, will
+represent the whole of the heat of combustion, and the ratio of the
+two triangles will be as the lengths of their respective bases, that
+is, as (T-<i>t</i>) / T, which is the expression we have already used. The
+heating surface was 220 square feet, and it was competent to transmit
+the energy developed by 41 lb. of coal consumed per hour = 12,819 u. �
+41 u. = 525,572 units, equal to an average of 2,389 units per square
+foot per hour; this value will correspond to the mean pressure in an
+ordinary diagram, for it is a measure of the energy with which
+molecular motion is transferred from the heated gases to the
+boiler-plate, and so to the water. The mean rate of transmission,
+multiplied by the area of heating surface, gives the area of the
+shaded portion of the figure, which is the total work which should
+have been done, that is to say, the work of evaporating 544 lb. of
+water per hour. The actual work done, however, was only 485 lb. To
+give the speculations we have indulged in a practical turn, it will be
+necessary to examine in detail the terms of Carnot's formula. Carnot
+labored under great disadvantages. He adhered to the emission theory
+of heat; he was unacquainted with its dynamic equivalent; he did not
+know the reason of the difference between the specific heat of air at
+constant pressure and at constant volume, the idea of an absolute zero
+of temperature had not been broached; but the genius of the man, while
+it made him lament the want of knowledge which he felt must be
+attainable, also enabled him to penetrate the gloom by which he was
+surrounded, and enunciate propositions respecting the theory of heat
+engines, which the knowledge we now possess enables us to admit as
+true. His propositions are:</p>
+
+<div class="indlist"><p>1. The motive power of heat is independent of the agents employed to
+develop it, and its quantity is determined solely by the temperature
+of the bodies between which the final transfer of caloric takes place.</p>
+
+<p><a name="Page_7034" id="Page_7034"></a>2. The temperature of the agent must in the first instance be raised
+to the highest degree possible in order to obtain a great fall of
+caloric, and as a consequence a large production of motive power.</p>
+
+<p>3. For the same reason the cooling of the agent must be carried to as
+low a degree as possible.</p>
+
+<p>4. Matters must be so arranged that the passage of the elastic agent
+from the higher to the lower temperature must be due to an increase of
+volume, that is to say, the cooling of the agent must be caused by its
+rarefaction.</p></div>
+
+<p>This last proposition indicates the defective information which Carnot
+possessed. He knew that expansion of the elastic agent was accompanied
+by a fall of temperature, but he did not know that that fall was due
+to the conversion of heat into work. We should state this clause more
+correctly by saying that &quot;the cooling of the agent must be caused by
+the external work it performs.&quot; In accordance with these propositions,
+it is immaterial what the heated gases or vapors in the furnace of a
+boiler may be, provided that they cool by doing external work and, in
+passing over the boiler surfaces, impart their heat energy to the
+water. The temperature of the furnace, it follows, must be kept as
+high as possible. The process of combustion is usually complex. First,
+in the case of coal, close to the fire-bars complete combustion of the
+red hot carbon takes place, and the heat so developed distills the
+volatile hydrocarbons and moisture in the upper layers of the fuel.
+The inflammable gases ignite on or near the surface of the fuel, if
+there be a sufficient supply of air, and burn with a bright flame for
+a considerable distance around the boiler. If the layer of fuel be
+thin, the carbonic acid formed in the first instance passes through
+the fuel and mixes with the other gases. If, however, the layer of
+fuel be thick, and the supply of air through the bars insufficient,
+the carbonic acid is decomposed by the red hot coke, and twice the
+volume of carbonic oxide is produced, and this, making its way through
+the fuel, burns with a pale blue flame on the surface, the result, as
+far as evolution of heat is concerned, being the same as if the
+intermediate decomposition of carbonic acid had not taken place. This
+property of coal has been taken advantage of by the late Sir W.
+Siemens in his gas producer, where the supply of air is purposely
+limited, in order that neither the hydrocarbons separated by
+distillation, nor the carbonic oxide formed in the thick layer of
+fuel, may be consumed in the producer, but remain in the form of crude
+gas, to be utilized in his regenerative furnaces.</p>
+
+<p class="ctr"><a href="./images/3a-3.png"><img src="./images/3a-3_th.png" alt=" THE GENERATION OF STEAM. Fig 3." /></a><br /> THE GENERATION OF STEAM. Fig 3.</p>
+
+<p class="ctr"><a href="./images/3a-4.png"><img src="./images/3a-4_th.png" alt=" THE GENERATION OF STEAM. Fig 4." /></a><br /> THE GENERATION OF STEAM. Fig 4.</p>
+
+<p class="ctr"><a href="./images/3a-5.png"><img src="./images/3a-5_th.png" alt=" THE GENERATION OF STEAM. Fig 5." /></a><br /> THE GENERATION OF STEAM. Fig 5.</p>
+
+<p class="ctr"><img src="./images/3a-6.png" alt="THE GENERATION OF STEAM. Fig 6." /><br />THE GENERATION OF STEAM. Fig 6.</p>
+
+<p class="ctr"><a href="./images/3a-7.png"><img src="./images/3a-7_th.png" alt="THE GENERATION OF STEAM. Fig 7." /></a><br /> THE GENERATION OF STEAM. Fig 7.</p>
+
+<p class="ctr"><i>(To be continued.)</i></p>
+
+
+<div class="note"><p><a name="Footnote_1" id="Footnote_1"></a><a href="#FNanchor_1">[1]</a></p>
+<p>Lecture delivered at the Institution of Civil Engineers,
+session 1883-84. For the illustrations we are indebted to the courtesy
+of Mr. J. Forrest, the secretary.</p>
+
+<p><a name="Footnote_2" id="Footnote_2"></a><a href="#FNanchor_2">[2]</a></p>
+<p>In the fifty-second volume of the <i>Proceedings</i>
+(1887-78), page 154, will be found a remarkable experiment on the
+evaporative power of a vertical boiler with internal circulating
+pipes. The experiment was conducted by Sir Frederick Bramwell and Dr.
+Russell, and is remarkable in this respect, that the quantity of air
+admitted to the fuel, the loss by convection and radiation, and the
+composition of the smoke were determined. The facts observed were as
+follows:</p>
+
+<div class="ctr">
+<table border="0" summary="" width="90%">
+<colgroup span="2"><col align="left" /><col align="right" width="100px" /></colgroup>
+<tr><td>Steam pressure 53 lb</td><td>= 300.6� F.</td></tr>
+<tr><td></td><td>lb.</td></tr>
+<tr><td>Fuel&mdash;Water in coke and wood</td><td>26.08</td></tr>
+<tr><td><span class="indlist">Ash</span></td><td>10.53</td></tr>
+<tr><td><span class="indlist">Hydrogen, oxygen, nitrogen, and sulphur</span></td><td>7.18</td></tr>
+<tr><td></td><td>&mdash;&mdash;&mdash;</td></tr>
+<tr><td><span class="indlist"><span class="indlist">Total non-combustible</span></span></td><td>43.79</td></tr>
+<tr><td><span class="indlist">Carbon, being useful combustible</span></td><td>194.46</td></tr>
+<tr><td></td><td>&mdash;&mdash;&mdash;</td></tr>
+<tr><td><span class="indlist">Total fuel</span></td><td>238.25</td></tr>
+<tr><td>&nbsp;</td></tr>
+<tr><td>Air per pound of carbon</td><td>17-1/8 lb.</td></tr>
+<tr><td>Time of experiment</td><td>4 h. 12 min.</td></tr>
+<tr><td>Water evaporated from 60� into steam at 53 lb. pressure</td><td>1,620 lb.</td></tr>
+<tr><td>Heat lost by radiation and convection</td><td>70,430 units.</td></tr>
+<tr><td>Mean temperature of chimney</td><td>700� F.</td></tr>
+<tr><td>Mean temperature of air</td><td>70� F.</td></tr>
+</table></div>
+
+<p>No combustible gas was found in the chimney.</p>
+
+<p>I will apply Carnot's doctrine to this case.</p>
+
+<p>Potential energy of the fuel with respect to absolute zero:</p>
+
+<div class="ctr">
+<table border="0" summary="" width="90%">
+<colgroup span="2"><col align="left" /><col align="right" width="100px" /></colgroup>
+<tr><td></td><td>Units.</td></tr>
+<tr><td>239.25 lb. � 530� abs. � 0.238</td><td>= 30,053</td></tr>
+<tr><td>194.46 lb. � 17-1/8 � 530� � 0.238, the weight and heat of air  </td><td>420,660</td></tr>
+<tr><td>194.46 � 14,544 units heat of combustion of carbon  </td><td>2,828,200</td></tr>
+<tr><td></td><td>&mdash;&mdash;&mdash;&mdash;</td></tr>
+<tr><td><span class="indlist">Total energy</span></td><td>3,278,813</td></tr>
+<tr><td>Heat absorbed in evaporating 26.08 lb. of water in fuel  </td><td>-29,888</td></tr>
+<tr><td></td><td>&mdash;&mdash;&mdash;&mdash;</td></tr>
+<tr><td><span class="indlist">Available energy</span></td><td>3,248,425</td></tr>
+</table></div>
+
+<p>Temperature of furnace&mdash;</p>
+
+<p>The whole of the fuel was heated up, but the heat absorbed in the
+evaporation of the water lowered the temperature of the furnace, and
+must be deducted from the heat of combustion.</p>
+
+<div class="ctr">
+<table border="0" summary="" width="90%">
+<colgroup span="2"><col align="left" /><col align="right" width="100px" /></colgroup>
+<tr><td></td><td>Units.</td></tr>
+<tr><td>Heat of combustion</td><td>2,828,200</td></tr>
+<tr><td>Heat of evaporation of 26.08 lb. water</td><td>-29,888</td></tr>
+<tr><td></td><td>&mdash;&mdash;&mdash;</td></tr>
+<tr><td><span class="indlist">Available heat of combustion</span></td><td>2,798,312</td></tr>
+<tr><td>Dividing by 238.25 lb. gives the heat per 1 lb. of fuel used</td><td>= 11,745 units.</td></tr>
+</table></div>
+
+<p>And temperature of furnace:</p>
+
+<div class="ctr">
+<table border="0" summary="" width="90%">
+<colgroup span="3"><col align="left" span="2" /><col align="right" width="100px" /></colgroup>
+<tr><td align="center">11,745 units<br /><span class="overline">(18.125 lb. � 0.238)</span></td><td> + 530�</td><td>= 3,253�</td></tr>
+<tr><td colspan="2" align="left">Temperature of chimney 700� + 460�</td><td>= 1,160�</td></tr>
+<tr><td>Maximum duty</td><td align="center"><span class="underline">(3,253� - 1,160�)</span><br />3,253�</td><td>= 0.643�</td></tr>
+</table></div>
+
+<p>Work of displacing atmosphere by smoke at 700�:</p>
+
+<div class="ctr">
+<table border="0" summary="" width="90%">
+<colgroup span="2"><col align="left" /><col align="right" width="100px" /></colgroup>
+<tr><td></td><td>Cubic feet.</td></tr>
+<tr><td>Volumes of gases at &nbsp;70�</td><td>= 228.3</td></tr>
+<tr><td>Volumes of gases at 700�</td><td>= 499.8</td></tr>
+<tr><td></td><td>&mdash;&mdash;&mdash;</td></tr>
+<tr><td><span class="indlist">Increase of volume</span></td><td>271.5</td></tr>
+<tr><td>&nbsp;</td></tr>
+<tr><td>Work done= </td><td>Units.</td></tr>
+<tr><td align="center"><span class="underline">(194.46 lb. � 271.5 cub. ft. � 144 sq. in. � 15 lb.)</span><br /> 722 units</td><td>= 147,720</td></tr>
+<tr><td>Maximum amount of work to be expected = 3,248,425 � 0.643</td><td>= 2,101,700</td></tr>
+<tr><td>Deduct work of displacing atmosphere</td><td>= 147,720</td></tr>
+<tr><td></td><td>&mdash;&mdash;&mdash;&mdash;</td></tr>
+<tr><td><span class="indlist">Available work</span></td><td>1,953,980</td></tr>
+</table></div>
+
+<p>Actual work done:</p>
+
+<div class="ctr">
+<table border="0" summary="" width="90%">
+<colgroup span="2"><col align="left" /><col align="right" width="100px" /></colgroup>
+<tr><td></td><td>Units.</td></tr>
+<tr><td>1,620 lb. of water raised from 60� and turned into steam at 53 lb</td><td>= 1,855,900</td></tr>
+<tr><td>Loss by radiation and convection</td><td>70,430</td></tr>
+<tr><td>10� lb. ashes left, say at 500�</td><td>1,129</td></tr>
+<tr><td></td><td>&mdash;&mdash;&mdash;&mdash;</td></tr>
+<tr><td><span class="indlist">Total work actually done</span></td><td>1,927,459</td></tr>
+<tr><td>Unaccounted for</td><td>26,521</td></tr>
+<tr><td></td><td>&mdash;&mdash;&mdash;&mdash;</td></tr>
+<tr><td><span class="indlist">Calculated available work</span></td><td>1,953,980</td></tr>
+</table></div>
+
+<p>The unaccounted-for work, therefore, amounts to only 1� per cent. of
+the calculated available work.</p>
+
+<p>Sir Frederick Bramwell ingeniously arranged his data in the form of a
+balance sheet, and showed 253,979 units unaccounted for; but if from
+this we deduct the work lost in displacing the air, the
+unaccounted-for heat falls to less than 4 per cent. of the total heat
+of combustion. These results show how extremely accurate the
+observations must have been, and that the loss mainly arises from
+convection and radiation from the boiler.</p></div>
+
+<hr />
+
+<p class="ctr">[Continued from SUPPLEMENT No. 437, page 6970.]</p>
+
+
+<h2><a name="art09" id="art09"></a>PLANETARY WHEEL-TRAINS.</h2>
+
+<h3>By Prof. C.W. MACCORD, Sc.D.</h3>
+
+
+<h3>II.</h3>
+
+<p class="ctr"><img src="./images/4-14.png" alt="PLANETARY WHEEL TRAINS. Fig. 14" /><br />PLANETARY WHEEL TRAINS. Fig. 14</p>
+
+<p>It has already been shown that the rotations of all the wheels of a
+planetary train, relatively to the train-arm, are the same when the
+arm is in motion as they would be if it were fixed. Now, in Fig. 14,
+let A be the first and F the last wheel of an <i>incomplete</i> train, that
+is, one having but one sun-wheel. As before, let these be so connected
+by intermediate gearing that, when T is stationary, a rotation of A
+through <i>m</i> degrees shall drive F through <i>n</i> degrees: and also as
+before, let T in the same time move through <i>a</i> degrees. Then, if <i>m'</i>
+represent the total motion of A, we have again,</p>
+
+<p class="ctr"> <i>m'</i> = <i>m</i> + <i>a</i>, or <i>m</i> = <i>m'</i> - <i>a</i>.</p>
+
+<p>This is, clearly, the motion of A relatively to the fixed frame of the
+machine; and is measured from a fixed vertical line through the
+center of A. Now, if we wish to express the total motion of F
+relatively to the same fixed frame, we must measure it from a vertical
+line through the center of F, wherever that maybe; which gives in this
+case:</p>
+
+<p class="ctr"><i>n'</i> = <i>n</i> + <i>a</i>, or <i>n</i> = <i>n'</i> - <i>a</i>.</p>
+
+<p>but with respect to the train-arm when at rest, we have:</p>
+
+<div class="ctr">
+<table summary="equation">
+<tr><td><span class="underline">ang. vel. A</span><br /> ang. vel. F</td>
+<td> = </td><td><span class="underline"><i>n</i></span><br /><i>m</i></td><td>, whence again,</td></tr>
+<tr><td><span class="underline"><i>n'</i> - <i>a</i></span><br /><i>m'</i> - <i>a</i></td>
+<td> = </td><td><span class="underline"><i>n</i></span><br /><i>m</i></td><td align="left">.</td></tr>
+</table>
+</div>
+
+<p>This is the manner in which the equation is deduced by Prof. Willis,
+who expressly states that it applies whether the last wheel F is or is
+not concentric with the first wheel A, and also that the train may be
+composed of any combinations which transmit rotation with both a
+constant velocity ratio and a constant directional relation. He
+designates the quantities <i>m'</i>, <i>n'</i>, <i>absolute revolutions</i>, as
+distinguished from the <i>relative revolutions</i> (that is, revolutions
+relatively to the train-arm), indicated by the quantities <i>m</i>, n:
+adding, &quot;Hence it appears that the absolute revolutions of the wheels
+of epicyclic trains are equal to the sum of their relative revolutions
+to the arm, and of the arm itself, when they take place in the same
+direction, and equal to the difference of these revolutions when in
+the opposite direction.&quot;</p>
+
+<p>In this deduction of the formula, as in that of Prof. Rankine, all the
+motions are supposed to have the same direction, corresponding to that
+of the hands of the clock; and in its application to any given train,
+the signs of the terms must be changed in case of any contrary motion,
+as explained in the preceding article.</p>
+
+<p>And both the deduction and the application, in reference to these
+incomplete trains in which the last wheel is carried <a name="Page_7035" id="Page_7035"></a>by the
+train-arm, clearly involve and depend upon the resolving of a motion
+of revolution into the components of a circular translation and a
+rotation, in the manner previously discussed.</p>
+
+<p class="ctr"><img src="./images/4-15.png" alt="PLANETARY WHEEL TRAINS. Fig. 15" /><br />PLANETARY WHEEL TRAINS. Fig. 15</p>
+
+<p>To illustrate: Take the simple case of two equal wheels, Fig. 15, of
+which the central one A is fixed. Supposing first A for the moment
+released and the arm to be fixed, we see that the two wheels will turn
+in opposite directions with equal velocities, which gives <i>n</i>/<i>m</i> = -1;
+but when A is fixed and T revolves, we have <i>m'</i> = 0, whence in the
+general formula</p>
+
+<div class="ctr">
+<table summary="equation">
+<tr><td><span class="underline"><i>n'</i> - <i>a</i></span><br /><i>-a</i></td>
+<td align="left">  = -1, or <i>n'</i> = 2 <i>a</i>; </td></tr>
+</table></div>
+
+
+<p>which means, being interpreted, that F makes two rotations about its
+axis during one revolution of T, and in the same direction. Again, let
+A and F be equal in the 3-wheel train, Fig. 16, the former being fixed
+as before. In this case we have:</p>
+
+<div class="ctr">
+<table summary="equation">
+<colgroup span="2"><col align="center" /><col align="left" /></colgroup>
+<tr><td><span class="underline"><i>n</i></span><br /><i>m</i></td>
+<td> = 1, <i>m'</i> = 0, which gives</td></tr>
+<tr><td>&nbsp;</td></tr>
+<tr><td><span class="underline"><i>n'</i> - <i>a</i></span><br /><i>-a</i></td>
+<td> = 1, &there4; <i>n'</i> = 0;</td></tr>
+</table></div>
+
+<p>that is to say, the wheel F, which now evidently has a motion of
+circular translation, does not rotate at all about its axis during the
+revolution of the train-arm.</p>
+
+<p class="ctr"><img src="./images/4-16.png" alt="PLANETARY WHEEL TRAINS. Fig. 16" /><br />PLANETARY WHEEL TRAINS. Fig. 16</p>
+
+<p>All this is perfectly consistent, clearly, with the hypothesis that
+the motion of circular translation is a simple one, and the motion of
+revolution about a fixed axis is a compound one.</p>
+
+<p>Whether the hypothesis was made to substantiate the formula, or the
+formula constructed to suit the hypothesis, is not a matter of
+consequence. In either case, no difficulty will arise so long as the
+equation is applied only to cases in which, as in those here
+mentioned, that motion of revolution <i>can</i> be resolved into those
+components.</p>
+
+<p>When the definition of an epicyclic train is restricted as it is by
+Prof. Rankine, the consideration of the hypothesis in question is
+entirely eliminated, and whether it be accepted or rejected, the whole
+matter is reduced to merely adding the motion of the train-arm to the
+rotation of each sun-wheel.</p>
+
+<p>But in attempting to apply this formula in analyzing the action of an
+incomplete train, we are required to add this motion of the train-arm,
+not only to that of a sun-wheel, but to that of a planet-wheel. This
+is evidently possible in the examples shown in Figs. 15 and 16,
+because the motions to be added are in all respects similar: the
+trains are composed of spur-wheels, and the motions, whether of
+revolution, translation, or rotation, <i>take place in parallel planes
+perpendicular to parallel axes</i>. This condition, which we have
+emphasized, be it observed, must hold true with regard to the motions
+of the first and last wheels and the train-arm, in order to make this
+addition possible. It is not essential that spur-wheels should be used
+exclusively or even at all; for instance, in Fig. 16, A and F may be
+made bevel or screw-wheels, without affecting the action or the
+analysis; but the train-arm in all cases revolves around the central
+axis of the system, that is, about the axis of A, and to this the axis
+of F <i>must</i> be parallel, in order to render the deduction of the
+formula, as made by Prof. Willis, and also by Prof. Goodeve, correct,
+or even possible.</p>
+
+<p class="ctr"><img src="./images/4-17.png" alt="PLANETARY WHEEL TRAINS. Fig. 17" /><br />PLANETARY WHEEL TRAINS. Fig. 17</p>
+
+<p>This will be seen by an examination of Fig. 17; in which A and B are
+two equal spur-wheels, E and F two equal bevel wheels, B and E being
+secured to the same shaft, and A being fixed to the frame H. As the
+arm T goes round, B will also turn in its bearings in the same
+direction: let this direction be that of the clock, when the apparatus
+is viewed from above, then the motion of F will also have the same
+direction, when viewed from the central vertical axis, as shown at F':
+and let these directions be considered as positive. It is perfectly
+clear that F will turn in its bearings, in the direction indicated, at
+a rate precisely equal to that of the train-arm. Let P be a pointer
+carried by F, and R a dial fixed to T; and let the pointer be vertical
+when OO is the plane containing the axes of A, B, and E. Then, when F
+has gone through any angle a measured from OO, the pointer will have
+turned from its original vertical position through an equal angle, as
+shown also at F'.</p>
+
+<p>Now, there is no conceivable sense in which the motion of T can be
+said to be added to the rotation of F about its axis, and the
+expression &quot;absolute revolution,&quot; as applied to the motion of the last
+wheel in this train, is absolutely meaningless.</p>
+
+<p>Nevertheless, Prof. Goodeve states (Elements of Mechanism, p. 165)
+that &quot;We may of course apply the general formula in the case of bevel
+wheels just as in that of spur wheels.&quot; Let us try the experiment;
+when the train-arm is stationary, and A released and turned to the
+right, F turns to the left at the same rate, whence:</p>
+
+<div class="ctr">
+<table summary="equation">
+<tr><td><span class="underline"><i>n</i></span><br /><i>m</i></td>
+<td> = -1; also <i>m'</i>= 0 when A is fixed,</td></tr>
+</table></div>
+
+<p>and the equation becomes</p>
+
+<div class="ctr">
+<table summary="equation">
+<tr><td><span class="underline"><i>n'</i> - <i>a</i></span><br /> - <i>a</i></td>
+<td> = -1, &there4; <i>n</i>' = 2 <i>a</i>:</td></tr>
+</table></div>
+
+<p>or in other words F turns <i>twice</i> on its axis during one revolution of
+T: a result too palpably absurd to require any comment. We have seen
+that this identical result was obtained in the case of Fig. 15, and it
+would, of course, be the same were the formula applied to Figs. 5 and
+6; whereas it has never, so far as we are aware, been pretended that a
+miter or a bevel wheel will make more than one rotation about its axis
+in rolling once around an equal fixed one.</p>
+
+<p>Again, if the formula be general, it should apply equally well to a
+train of screw wheels: let us take, for example, the single pair shown
+in Fig. 8, of which, when T is fixed, the velocity ratio is unity. The
+directional relation, however, depends upon the direction in which the
+wheels are twisted: so that in applying the formula, we shall have
+<i>n/m</i> = +1, if the helices of both wheels are right handed, and <i>n</i>/<i>m</i>
+= -1, if they are both left handed. Thus the formula leads to the
+surprising conclusion, that when A is fixed and T revolves, the
+planet-wheel B will revolve about its axis twice as fast as T moves,
+in one case, while in the other it will not revolve at all.</p>
+
+<p class="ctr"><img src="./images/4-18.png" alt="PLANETARY WHEEL TRAINS. Fig. 18" /><br />PLANETARY WHEEL TRAINS. Fig. 18</p>
+
+<p>A favorite illustration of the peculiarities of epicyclic mechanism,
+introduced both by Prof. Willis and Prof. Goodeve, is found in the
+contrivance known as Ferguson's Mechanical Paradox, shown in Fig. 18.
+This consists of a fixed sun-wheel A, engaging with a planet-wheel B
+of the same diameter. Upon the shaft of B are secured the three thin
+wheels E, G, I, each having 20 teeth, and in gear with the three
+others F, H, K, which turn freely upon a stud fixed in the train-arm,
+and have respectively 19, 20, and 21 teeth. In applying the general
+formula, we have the following results:</p>
+
+<div class="ctr"><table summary="equation">
+<tr><td>For the wheel</td><td>F,</td><td></td><td><span class="underline"><i>n</i></span><br /><i>m</i></td>
+<td> = </td><td><span class="underline">20</span><br />19</td>
+<td> = </td><td><span class="underline"><i>n'</i> - <i>a</i></span><br /><i>-a</i></td>
+<td>&there4; <i>n'</i> =</td><td>-</td><td>1<br /><span class="overline">19</span></td><td><i>a</i>.</td></tr>
+
+<tr><td>&nbsp;</td></tr>
+<tr><td>&quot;</td><td>H,</td><td></td><td><span class="underline"><i>n</i></span><br /><i>m</i></td><td> = </td><td>1</td>
+<td> = </td><td><span class="underline"><i>n'</i> - <i>a</i></span><br /><i>-a</i></td>
+<td>&there4; <i>n'</i> =</td><td>0.</td></tr>
+
+<tr><td>&quot;</td><td>K,</td><td></td><td><span class="underline"><i>n</i></span><br /><i>m</i></td>
+<td> = </td><td><span class="underline">21</span><br />20</td>
+<td> = </td><td><span class="underline"><i>n'</i> - <i>a</i></span><br /><i>-a</i></td>
+<td>&there4; <i>n'</i> =</td><td>+</td><td>1<br /><span class="overline">21</span></td><td><i>a</i>.</td></tr>
+</table></div>
+
+
+<p>The paradoxical appearance, then, consists in this, that although the
+drivers of the three last wheels each have the same number of teeth,
+yet the central one, H, having a motion of circular translation,
+remains always parallel to itself, and relatively to it the upper one
+seems to turn in the same direction as the train-arm, and the lower in
+the contrary direction. And the appearance is accepted, too, as a
+reality; being explained, agreeably to the analysis just given, by
+saying that H has no absolute rotation about its axis, while the other
+wheels have; that of F being positive and that of K negative.</p>
+
+<p>The Mechanical Paradox, it is clear, may be regarded as composed of
+three separate trains, each of which is precisely like that of Fig.
+16: and that, again, differs from the one of Fig. 15 only in the
+addition of a third wheel. Now, we submit that the train shown in Fig.
+17 is mechanically equivalent to that of Fig. 15; the velocity ratio
+and the directional relation being the same in both. And if in Fig. 17
+we remove the index P, and fix upon its shaft three wheels like E, G,
+and I of Fig. 18, we shall have a combination mechanically equivalent
+to Ferguson's Paradox, the three last wheels rotating in vertical
+planes about horizontal axes. The relative motions of those three
+wheels will be the same, obviously, as in Fig. 18; and according to
+the formula their absolute motions are the same, and we are invited to
+perceive that the central one does not rotate at all about its axis.</p>
+
+<p>But it <i>does</i> rotate, nevertheless; and this unquestioned fact is of
+itself enough to show that there is something wrong with the formula
+as applied to trains like those in question. What that something is,
+we think, has been made clear by what precedes; since it is impossible
+in any sense to add together motions which are unlike, it will be seen
+that in order to obtain an intelligible result in cases like these,
+the equation must be of the form <i>n'</i>/(<i>m'</i>-<i>a</i>) = <i>n</i>/<i>m</i>. We shall then have:</p>
+
+<div class="ctr">
+<table border="0" summary="equation">
+<tr><td>For the wheel F,</td>
+<td><span class="underline"><i>n</i></span><br /><i>m</i></td>
+<td>=</td>
+<td><span class="underline">20</span><br />19</td>
+<td>=</td>
+<td><span class="underline"><i>n'</i></span><br /><i>-a</i></td>
+<td>, &there4; <i>n'</i> = - </td>
+<td><span class="underline">20</span><br />19</td>
+<td><i>a</i>.</td></tr>
+<tr><td>&nbsp;</td></tr>
+<tr><td>For the wheel H,</td>
+<td><span class="underline"><i>n</i></span><br /><i>m</i></td>
+<td>=</td>
+<td>1</td>
+<td>=</td>
+<td><span class="underline"><i>n'</i></span><br /><i>-a</i></td>
+<td>, &there4; <i>n'</i> = -</td><td><i>a</i>;</td></tr>
+<tr><td>&nbsp;</td></tr>
+<tr><td>For the wheel K,</td>
+<td><span class="underline"><i>n</i></span><br /><i>m</i></td>
+<td>=</td>
+<td><span class="underline">21</span><br />20</td>
+<td>=</td>
+<td><span class="underline"><i>n'</i></span><br /><i>-a</i></td>
+<td>, &there4; <i>n'</i> = -</td>
+<td><span class="underline">21</span><br />20</td>
+<td><i>a</i>,</td></tr>
+</table></div>
+
+
+<p>which corresponds with the actual state of things; all three wheels
+rotate in the same direction, the central one at the same rate as the
+train arm, one a little more rapidly and the third a little more
+slowly.</p>
+
+<p>It is, then, absolutely necessary to make this modification in the
+general formula, in order to apply it in determining the rotations of
+any wheel of an epicyclic train whose axis is not parallel to that of
+the sun-wheels. And in this modified form it applies equally well to
+the original arrangement of Ferguson's paradox, if we abandon the
+artificial distinction between &quot;absolute&quot; and &quot;relative&quot; rotations of
+the planet-wheels, and regard a spur-wheel, like any other, as
+rotating on its axis when it turns in its bearings; the action of the
+device shown in Fig. 18 being thus explained by saying that the wheel
+H turns once backward during each forward revolution of the train-arm,
+while F turns a little more and K a little less than once, in the same
+direction. In this way the classification and analysis of these
+combinations are made more simple and consistent, and the
+incongruities above pointed out are avoided; since, without regard to
+the kind of gearing employed or the relative positions of the axes, we
+have the two equations:</p>
+
+<div class="ctr">
+<table summary="equation">
+<tr><td>I.</td><td><span class="underline"><i>n'</i> - <i>a</i></span><br /><i>m'</i> - <i>a</i></td>
+<td>=</td><td><span class="underline"><i>n</i></span><br /><i>m</i></td><td>, for all complete trains;</td></tr>
+<tr><td>&nbsp;</td></tr>
+<tr><td>II.</td><td><span class="underline"><i>n'</i></span><br /><i>m'</i> - <i>a</i></td>
+<td>=</td><td><span class="underline"><i>n</i></span><br /><i>m</i></td><td>, for all incomplete trains.</td></tr>
+</table></div>
+
+<p class="ctr"><img src="./images/4-19.png" alt="PLANETARY WHEEL TRAINS. Fig. 19" /><br />PLANETARY WHEEL TRAINS. Fig. 19</p>
+
+<p>As another example of the difference in the application of these
+formul&aelig;, let us take Watt's sun and planet wheels, Fig. 19. This
+device, as is well known, was employed by the illustrious inventor as
+a substitute for the crank, which some one had succeeded in patenting.
+It consists merely of two wheels A and F connected by the link T; A
+being keyed on the shaft of the engine and F being rigidly secured to
+the connecting-rod. Suppose the rod to be of infinite length, so as to
+remain always parallel to itself, and the two wheels to be of equal
+size.</p>
+
+<p>Then, according to Prof. Willis' analysis, we shall have&mdash;</p>
+
+<div class="ctr">
+<table summary="Equation">
+<tr><td><span class="underline"><i>n'</i> - <i>a</i></span><br /><i>m'</i> - <i>a</i></td>
+<td>=</td>
+<td><span class="underline"><i>n</i></span><br /><i>m</i></td>
+<td>= -1, <i>n'</i> = 0, &there4; </td>
+<td><i>-a</i><br /><span class="overline"><i>m'</i> - <i>a</i></span></td>
+<td>= -1, whence</td></tr>
+</table>
+<p class="ctr"><i>-a</i> = <i>a</i> - <i>m'</i>, or <i>m</i> = 2<i>a</i>.</p></div>
+
+
+<p>The other view of the question is, that F turns once backward in its
+bearings during each forward revolution of T; whence in Eq. 2 we
+have&mdash;</p>
+
+<div class="ctr"><table summary="Equation">
+<tr><td><i>n'</i><br /><span class="overline"><i>m'</i> - <i>a</i></span></td>
+<td>=</td>
+<td><span class="underline"><i>n</i></span><br /><i>m</i></td>
+<td>= -1, <i>n'</i> = - <i>a</i>,</td></tr>
+</table></div>
+
+<div class="ctr">
+<table summary="">
+<tr><td> &there4;</td>
+<td><i>-a</i><br /><span class="overline"><i>m'</i> - <i>a</i></span></td>
+<td>= -1 which gives <i>-a</i> = <i>a</i> - <i>m'</i>, or <i>m'</i> = 2<i>a</i>,</td></tr>
+</table>
+</div>
+
+<p>as before.</p>
+
+<p>It is next to be remarked, that the errors which arise from applying
+Eq. I. to incomplete trains may in some cases counterbalance and
+neutralize each other, so that the final result is correct.</p>
+
+<p class="ctr"><img src="./images/4-20.png" alt="PLANETARY WHEEL TRAINS. Fig. 20" /><br />PLANETARY WHEEL TRAINS. Fig. 20</p>
+
+<p>For example, take the combination shown in Fig. 20. This consists of a
+train-arm T revolving about the vertical axis OO of the fixed wheel A,
+which is equal in diameter to F, which receives its motion by the
+intervention of one idle wheel carried by a stud S fixed in the arm.
+The second train-arm T' is fixed to the shaft of F and turns with it;
+A' is secured to the arm T, and F' is actuated by A' also through a
+single idler carried by T'.</p>
+
+<p>We have here a compound train, consisting of two simple planetary
+trains, A&mdash;F and A'&mdash;F'; and its action is to be determined by
+considering them separately. First suppose T' to be removed and find
+the motion of F; next suppose F to be removed and T fixed, and find
+the rotation of F'; and finally combine these results, noting that the
+motion of T' is the same as that of F, and the motion of A' the same
+as that of T.</p>
+
+<p>Then, according to the analysis of Prof. Willis, we shall have
+(substituting the symbol <i>t</i> for <i>a</i> in the equation of the second
+train, in order to avoid confusion):</p>
+
+<div class="ctr">
+<table summary="">
+<colgroup span="5"><col align="left" /><col align="center" />
+<col align="left" /><col align="center" /><col align="left" /></colgroup>
+<tr><td rowspan="2" valign="middle"> 1. Train A&mdash;F.</td>
+<td><span class="underline"><i>n</i></span></td><td rowspan="2" valign="middle"> = 1 = </td>
+<td><span class="underline"><i>m'</i> - <i>a</i></span></td><td rowspan="2" valign="middle">; <i>m'</i> = 0,</td></tr>
+<tr><td><i>m</i></td><td><i>m'</i> - <i>a</i></td></tr>
+<tr><td rowspan="2" valign="middle">whence</td><td colspan="2"></td>
+<td><span class="underline"><i>n'</i> - <i>a</i></span></td>
+<td rowspan="2" valign="middle">= 1, <i>n'</i> = 0, = rot. of F.</td></tr>
+<tr><td colspan="2"></td><td><i>- a</i></td></tr>
+<tr><td rowspan="2" valign="middle"> 2. Train A'&mdash;F'.</td>
+<td><span class="underline"><i>n</i></span></td><td rowspan="2" valign="middle"> = 1 = </td>
+<td><span class="underline"><i>m'</i> - <i>t</i></span></td><td rowspan="2" valign="middle">; <i>m'</i> = 0,</td></tr>
+<tr><td><i>m</i></td><td><i>m'</i> - <i>t</i></td></tr>
+<tr><td rowspan="2" valign="middle">whence again</td><td colspan="2"></td>
+<td><span class="underline"><i>n'</i> - <i>t</i></span></td>
+<td rowspan="2" valign="middle">= 1, <i>t</i> = 0, = rot. of F'.</td></tr>
+<tr><td colspan="2"></td><td><i>- t</i></td></tr>
+</table></div>
+
+<p>Of these results, the first is explicable as being the <i>absolute</i>
+rotation of F, but the second is not; and it will be readily seen that
+the former would have been equally absurd, had the axis LL been
+inclined instead of vertical. But in either case we should find the
+errors neutralized upon combining the two, for according to the theory
+now under consideration, the wheel A', being fixed to T, turns once
+upon its axis each time that train arm revolves, and in the same
+direction; and the revolutions of T' equal the rotations of F, whence
+finally in train A'&mdash;F' we have:</p>
+
+<div class="ctr"><table summary="">
+<tr><td rowspan="2" valign="middle"> 3.</td>
+<td><span class="underline"><i>n</i></span></td>
+<td rowspan="2" valign="middle"> = 1 = </td>
+<td><span class="underline"><i>n'</i> - <i>t</i></span></td>
+<td rowspan="2" valign="middle">; in which <i>t</i> = 0, <i>m'</i> = <i>a</i>,</td></tr>
+<tr><td><i>m</i></td><td><i>m'</i> - <i>t</i></td></tr>
+<tr><td colspan="3" rowspan="2" valign="middle">which gives</td>
+<td><span class="underline"><i>n'</i> - 0</span></td>
+<td rowspan="2" valign="middle" align="left">= 1, or <i>n'</i> = <i>a</i>.</td></tr>
+<tr><td><i>a</i> - 0</td></tr></table></div>
+
+
+<p>This is, unquestionably, correct; and indeed it is quite obvious that
+the effect upon F' is the same, whether we say that during a
+revolution of T the wheel A' turns once forward and T' not at all, or
+adopt the other view and assert that T' turns once backward and A' not
+at all. But the latter view has the advantage of giving concordant
+results when the trains are considered separately, and that without
+regard to the relative positions of the axes or the kind of gearing
+employed. Analyzing the action upon this hypothesis, we have:</p>
+
+
+<div class="ctr"><table summary="">
+<colgroup span="5"><col align="left" /><col align="center" />
+<col align="left" /><col align="center" /><col align="left" /></colgroup>
+<tr><td rowspan="2" valign="middle">In train A&mdash;F:</td>
+<td><i>n</i></td><td rowspan="2" valign="middle"> = 1 = </td>
+<td><i>n'</i></td>
+<td rowspan="2" valign="middle">; <i>m'</i> = 0,  &there4;</td>
+<td><i>n'</i></td>
+<td rowspan="2" valign="middle"> = 1, or <i>n'</i> = <i>-a</i>;</td></tr>
+<tr><td><span class="overline"><i>m</i></span></td>
+<td><span class="overline"><i>m'</i> - <i>a</i></span></td>
+<td><span class="overline"><i>-a</i></span></td></tr>
+<tr><td rowspan="2" valign="middle">In train A'&mdash;F':</td>
+<td><i>n'</i></td><td rowspan="2" valign="middle"> = 1 = </td>
+<td><i>n'</i></td>
+<td rowspan="2" valign="middle">; <i>m'</i> = 0,  &there4;</td>
+<td><i>n'</i></td>
+<td rowspan="2" valign="middle"> = 1, or <i>n'</i> = <i>-t</i>;</td></tr>
+<tr><td><span class="overline"><i>m</i></span></td>
+<td><span class="overline"><i>m'</i> - <i>t</i></span></td>
+<td><span class="overline"><i>-t</i></span></td></tr>
+</table></div>
+
+<p>In combining, we have in the latter train <i>m'</i> = 0, <i>t</i> = <i>-a</i>, whence</p>
+
+<div class="ctr"><table summary="">
+<colgroup span="6"><col align="center" /><col align="left" />
+<col align="center" /><col align="left" /><col align="center" /><col align="left" />
+</colgroup>
+<tr><td><i>n</i><br /><span class="overline"><i>m</i></span></td><td>= 1 =</td>
+<td><i>n'</i><br /><span class="overline"><i>m'</i> - <i>t</i></span></td>
+<td>gives</td><td><i>n'</i><br /><span class="overline"><i>+a</i></span></td>
+<td> = 1, or <i>n'</i> = <i>a</i>, as before.</td></tr>
+</table></div>
+
+<p>Now it happens that the only examples given by Prof. Willis of
+incomplete trains in which the axis of a planet-wheel whose motion is
+to be determined is not parallel to the central axis of the system,
+are similar to the one just discussed; the wheel in question being
+carried by a secondary train-arm which derives its motion from a wheel
+of the primary train.</p>
+
+<p>The application of his general equation in these cases gives results
+which agree with observed facts; and it would seem that this
+circumstance, in connection doubtless with the complexity of these
+compound trains, led him to the too hasty conclusion that the formula
+would hold true in all cases; although we are still left to wonder at
+his overlooking the fact that in these very cases the &quot;absolute&quot; and
+the &quot;relative&quot; rotations of the last wheel are identical.</p>
+
+<p class="ctr"><img src="./images/4-21.png" alt="PLANETARY WHEEL TRAINS. Fig. 21" /><br />PLANETARY WHEEL TRAINS. Fig. 21</p>
+
+<p>In Fig. 21 is shown a combination consisting also of two distinct
+trains, in which, however, there is but one train-arm T turning freely
+upon the horizontal shaft OO, to which shaft the wheels A', F, are
+secured; the train-arm has two studs, upon which turn the idlers B B',
+and also carries the bearings of the last wheel F'; the first wheel A
+is annular, and fixed to the frame of the machine. Let it be required
+to determine the results of one revolution of the crank H, the numbers
+of teeth being assigned as follows:</p>
+
+<p class="center">A = 60, F = 30, A' = 60, F' = 10.</p>
+
+<p>We shall then have, for the train ABF (Eq. I.),</p>
+
+<div class="ctr">
+<table summary="">
+<colgroup span="6"><col align="center" /><col align="left" />
+<col align="center" /><col align="left" /><col align="center" />
+<col align="left" /></colgroup>
+<tr><td><i>n</i></td><td rowspan="2" valign="middle"> = -</td><td>60</td>
+<td rowspan="2" valign="middle"> = -2 = </td><td><i>n'</i> - <i>a</i></td>
+<td rowspan="2" valign="middle">, in which <i>n'</i> = 1, <i>m'</i> = 0,</td></tr>
+<tr><td><span class="overline"><i>m</i></span></td><td><span class="overline">30</span></td>
+<td><span class="overline"><i>m'</i> - <i>a'</i></span></td></tr>
+</table></div>
+
+
+<div class="ctr"><table summary="">
+<colgroup span="4"><col align="left" />
+<col align="center" /><col span="2" align="left" /></colgroup>
+<tr><td>whence -2 = </td>
+<td><span class="underline">1 - <i>a</i></span><br />-<i>a</i></td>
+<td>, 2<i>a</i> = 1 - <i>a</i>, 3<i>a</i> - 1, <i>a</i> =</td>
+<td><span class="underline">1</span><br />3</td><td>.</td></tr>
+</table></div>
+
+
+<p>And for the train A'B'F' (Eq. II.),</p>
+
+<div class="ctr"><table summary="">
+<tr><td><i>n</i></td>
+<td rowspan="2" valign="middle"> = </td>
+<td>60</td>
+<td rowspan="2" valign="middle"> = 6 = </td>
+<td><i>n'</i></td>
+<td rowspan="2" valign="middle">, in which <i>a</i> =</td>
+<td>1</td>
+<td rowspan="2" valign="middle">, <i>m'</i> = 1,</td></tr>
+<tr><td><span class="overline"><i>m</i></span></td>
+<td><span class="overline">10</span></td>
+<td><span class="overline"><i>m'</i> - <i>a'</i></span></td>
+<td><span class="overline">3</span></td></tr>
+</table></div>
+
+<div class="ctr"><table summary="">
+<tr><td rowspan="2" valign="middle">whence&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 6 = </td>
+<td><i>n'</i></td>
+<td rowspan="2" valign="middle">, or <i>n'</i> = 4.</td></tr>
+<tr><td><span class="overline">1 - (1/3)</span></td></tr>
+</table></div>
+
+<p>That is, the last wheel F' turns <i>four</i> times about the axis LL during
+one revolution of the crank H. But according to Profs. Willis and
+Goodeve, we should have for the second train:</p>
+
+<div class="ctr"><table summary="">
+<tr><td><i>n</i></td>
+<td rowspan="2" valign="middle"> = </td>
+<td>60</td>
+<td rowspan="2" valign="middle"> = 6 = </td>
+<td><i>n'</i> - <i>a</i></td>
+<td rowspan="2" valign="middle">, in which <i>a</i> =</td>
+<td>1</td>
+<td rowspan="2" valign="middle">, <i>m'</i> = 1,</td></tr>
+<tr><td><span class="overline"><i>m</i></span></td>
+<td><span class="overline">10</span></td>
+<td><span class="overline"><i>m'</i> - <i>a'</i></span></td>
+<td><span class="overline">3</span></td></tr>
+</table>
+
+<table summary="">
+<colgroup span="7"><col align="left" /><col align="center" />
+<col align="left" /><col align="center" /><col align="left" /><col span="2" align="center" />
+</colgroup>
+<tr><td rowspan="2" valign="middle">which gives 6 =</td>
+<td><span class="underline"><i>n'</i> - (1/3)</span></td>
+<td rowspan="2" valign="middle">, <i>n'</i> - </td>
+<td><span class="underline">1</span></td>
+<td rowspan="2" valign="middle"> = 4, <i>n'</i> = 4</td>
+<td><span class="underline">1</span></td><td>,</td></tr>
+<tr><td>1 - (1/3)</td><td>3</td><td>3</td></tr>
+</table></div>
+
+<p>or <i>four and one-third</i> revolutions of F' for one of H.</p>
+
+<p>This result, no doubt, might be near enough to the truth to serve all
+practical purposes in the application of this mechanism to its
+original object, which was that of paring apples, impaled upon the
+fork K; but it can hardly be regarded as entirely satisfactory in a
+general way; nor can the analysis which renders such a result
+possible.</p>
+
+<hr />
+
+
+<h2><a name="art10" id="art10"></a>THE PANTANEMONE.</h2>
+
+
+<p>The need of irrigating prairies, inundating vines, drying marshes, and
+accumulating electricity cheaply has, for some time past, led to a
+search for some means of utilizing the forces of nature better than
+has ever hitherto been done. Wind, which figures in the first rank as
+a force, has thus far, with all the mills known to us, rendered
+services that are much inferior to those that we have a right to
+expect from it with improved apparatus; for the work produced,
+whatever the velocity of the wind, has never been greater than that
+that could be effected by wind of seven meters per second. But, thanks
+to the experiments of recent years, we are now obtaining an effective
+performance double that which we did with apparatus on the old system.</p>
+
+<p>Desirous of making known the efforts that have been made in this
+direction, we lately described Mr. Dumont's atmospheric <a name="Page_7036" id="Page_7036"></a>turbine. In
+speaking of this apparatus we stated that aerial motors generally stop
+or are destroyed in high winds. Recently, Mr. Sanderson has
+communicated to us the result of some experiments that he has been
+making for years back by means of an apparatus which he styles a
+pantanemone.</p>
+
+<p>The engraving that we give of this machine shows merely a cabinet
+model of it; and it goes without saying that it is simply designed to
+exhibit the principle upon which its construction is based.</p>
+
+<p class="ctr"><a href="./images/6a.png"><img src="./images/6a_th.png" alt=" THE PANTANEMONE." /></a><br /> THE PANTANEMONE.</p>
+
+<p>Two plane surfaces in the form of semicircles are mounted at right
+angles to each other upon a horizontal shaft, and at an angle of 45�
+with respect to the latter. It results from this that the apparatus
+will operate (even without being set) whatever be the direction of the
+wind, except when it blows perpendicularly upon the axle, thus
+permitting (owing to the impossibility of reducing the surfaces) of
+three-score days more work per year being obtained than can be with
+other mills. Three distinct apparatus have been successively
+constructed. The first of these has been running for nine years in the
+vicinity of Poissy, where it lifts about 40,000 liters of water to a
+height of 20 meters every 24 hours, in a wind of a velocity of from 7
+to 8 meters per second. The second raises about 150,000 liters of
+water to the Villejuif reservoir, at a height of 10 meters, every 24
+hours, in a wind of from 5 to 6 meters. The third supplies the
+laboratory of the Montsouris observatory.</p>
+
+<p>The first is not directible, the second may be directed by hand, and
+the third is directed automatically. These three machines defied the
+hurricane of the 26th of last January.&mdash;<i>La Nature.</i></p>
+
+<hr />
+
+<h2><a name="art11" id="art11"></a>RELVAS'S NEW LIFE-BOAT.</h2>
+
+
+<p>The Spanish and Portuguese papers have recently made known some
+interesting experiments that have been made by Mr. Carlos Relvas with
+a new life-boat which parts the waves with great facility and exhibits
+remarkable stability. This boat, which is shown in front view in one
+of the corners of our engraving, is T-shaped, and consists of a very
+thin keel connected with the side-timbers by iron rods. Cushions of
+cork and canvas are adapted to the upper part, and, when the boat is
+on the sea, it has the appearance of an ordinary canoe, although, as
+may be seen, it differs essentially therefrom in the submerged part.
+When the sea is heavy, says Mr. Relvas, and the high waves are
+tumbling over each other, they pass over my boat, and are powerless to
+capsize it. My boat clears waves that others are obliged to recoil
+before. It has the advantage of being able to move forward, whatever
+be the fury of the sea, and is capable, besides, of approaching rocks
+without any danger of its being broken.</p>
+
+<p class="ctr"><a href="./images/6b.png"><img src="./images/6b_th.png" alt=" RELVAS'S NEW LIFE BOAT." /></a><br /> RELVAS'S NEW LIFE BOAT.</p>
+<p>A committee was appointed by the Portuguese government to examine this
+new life-boat, and comparative experiments were made with it and an
+ordinary life-boat at Porto on a very rough sea. Mr. Relvas's boat was
+manned by eight rowers all provided with cork girdles, while the
+government life-boat was manned by twelve rowers and a pilot, all
+likewise wearing cork girdles. The chief of the maritime department,
+an engineer of the Portuguese navy and a Portuguese deputy were
+present at the trial in a pilot boat. The three boats proceeded to the
+entrance of the bar, where the sea was roughest, and numerous
+spectators collected upon the shore and wharfs followed their
+evolutions from afar.</p>
+
+<p>The experiments began at half past three o'clock in the afternoon. The
+two life-boats shot forward to seek the most furious waves, and were
+seen from afar to surmount the billows and then suddenly disappear. It
+was a spectacle as moving as it was curious. It was observed that Mr.
+Relvas's boat cleft the waves, while the other floated upon their
+surface like a nut-shell. After an hour's navigation the two boats
+returned to their starting point.</p>
+
+<p>The official committee that presided over these experiments has again
+found in this new boat decided advantages, and has pointed out to its
+inventor a few slight modifications that will render it still more
+efficient.&mdash;<i>La Nature.</i></p>
+
+<hr />
+
+
+
+
+<h2><a name="art12" id="art12"></a>EXPERIMENTS WITH DOUBLE-BARRELED GUNS AND RIFLES.</h2>
+
+
+<p>The series of experiments we are about to describe has recently been
+made by Mr. Horatio Phillips, a practical gun maker of London. The
+results will no doubt prove of interest to those concerned in the use
+or manufacture of firearms.</p>
+
+<p>The reason that the two barrels of a shot gun or rifle will, if put
+together parallel, throw their charges in diverging lines has never
+yet been satisfactorily accounted for, although many plausible and
+ingenious theories have been advanced for the purpose. The natural
+supposition would be that this divergence resulted from the axes of
+the barrels not being in the same vertical plane as the center line of
+the stock. That this is not the true explanation of the fact, the
+following experiment would tend to prove.</p>
+
+<p class="ctr"><img src="./images/6c.png" alt="EXPERIMENTS WITH DOUBLE-BARRELLED GUNS." /><br />EXPERIMENTS WITH DOUBLE-BARRELLED GUNS.</p>
+
+<p>Fig. 1 represents a single barrel fitted with sights and firmly
+attached to a heavy block of beech. This was placed on an ordinary
+rifle rest, being fastened thereto by a pin at the corner, A, the
+block and barrel being free to revolve upon the pin as a center.
+Several shots were fired both with the pin in position and with it
+removed, the barrel being carefully pointed at the target each time.
+No practical difference in the accuracy of fire was discernible under
+either condition. When the pin was holding the corner of the block,
+the recoil caused the barrel to move from right to left in a circular
+path; but when the pin was removed, so that the block was not attached
+to the rest in any way, the recoil took place in a line with the axis
+of the bore. It will be observed that the conditions which are present
+when a double barreled gun is fired in the ordinary way from the
+shoulder were in some respects much exaggerated in the apparatus, for
+the pin was a distance of 3 in. laterally from the axis of the barrel,
+whereas the center of resistance of the stock of a gun against the
+shoulder would ordinarily be about one-sixth of this distance from the
+axis of the barrel. This experiment would apparently tend to prove
+that the recoil does not appreciably affect the path of the
+projectile, as it would seem that the latter must clear the muzzle
+before any considerable movement of the barrel takes place.</p>
+
+<p>With a view to obtain a further confirmation of the result of this
+experiment, it was repeated in a different form by a number of shots
+being fired from a &quot;cross-eyed&quot; rifle,<a name="FNanchor_3" id="FNanchor_3"></a><a href="#Footnote_3"><sup>1</sup></a> in which the sights were
+fixed in the center of the rib. Very accurate shooting was obtained
+with this arm.</p>
+
+<p>A second theory, often broached, in order to account for the
+divergence of the charge, is that the barrel which is not being fired,
+by its <i>vis inertia</i> in some way causes the shot to diverge. In order
+to test this, Mr. Phillips took a single rifle and secured it near the
+muzzle to a heavy block of metal, when the accuracy of the shooting
+was in no way impaired.</p>
+
+<p>So far the experiments were of a negative character, and the next step
+was made with a view to discover the actual cause of the divergence
+referred to. A single barrel was now taken, to which a template was
+fitted, in order to record its exact length. The barrel was then
+subjected to a heavy internal hydrostatic pressure. Under this
+treatment it expanded circumferentially and at the same time was
+reduced in length. This, it was considered, gave a clew to the
+solution of the problem. A pair of barrels was now taken and a
+template fitted accurately to the side of the right-hand one. As the
+template fitted the barrel when the latter was not subject to internal
+pressure, upon such pressure being applied any alterations that might
+ensue in the length or contour of the barrel could be duly noted. The
+right-hand barrel was then subjected to internal hydrostatic pressure.
+The result is shown in an exaggerated form in Fig. 2. It will be seen
+that both barrels are bent into an arched form. This would be caused
+by the barrel under pressure becoming extended circumferentially, and
+thereby reduced in length, because the metal that is required to
+supply the increased circumference is taken to some extent from the
+length, although the substance of metal in the walls of the barrel by
+its expansion contributes also to the increased diameter. A simple
+illustration of this effect is supplied by subjecting an India-rubber
+tube to internal pressure. Supposing the material to be sufficiently
+elastic and the pressure strong enough, the tube would ultimately
+assume a spherical form. It is a well known fact that heavy barrels
+with light charges give less divergence than light barrels with heavy
+charges.</p>
+
+<p>After the above experiments it was hoped that, if a pair of barrels
+were put together parallel and soldered only for a space of 3 in. at
+the breech end, and were then coupled by two encircling rings joined
+together as in Fig. 4, the left-hand ring only being soldered to the
+barrel, very accurate shooting would be obtained. For, it was argued,
+that by these means the barrel under fire would be able to contract
+without affecting or being affected by the other barrel; that on the
+right-hand, it will be seen by the illustration, was the one to slide
+in its ring.</p>
+
+<p>A pair of able 0.500 bore express rifle barrels were accordingly
+fitted in this way. Fig. 3 shows the arrangement with the rings in
+position. Upon firing these barrels with ordinary express charges it
+was found that the lines of fire from each barrel respectively crossed
+each other, the bullet from the right-hand barrel striking the target
+10 in. to the left of the bull's eye, while the left barrel placed its
+projectile a similar distance in the opposite direction; or, as would
+be technically said, the barrels crossed 20 in. at 100 yards, the
+latter distance being the range at which the experiment was made.
+These last results have been accounted for in the following manner:
+The two barrels were rigidly joined for a space of 3 in., and for that
+distance they would behave in a manner similar to that illustrated in
+Fig. 2, and were they not coupled at the muzzles by the connecting
+rings they would shoot very wide, the charges taking diverging
+courses. When the connecting rings are fitted on, the barrel not being
+fired will remain practically straight, and, as it is coupled to the
+barrel being fired by the rings, the muzzle of the latter will be
+restrained from pointing outward.</p>
+
+<p>The result will be as shown in an exaggerated manner by the dotted
+lines on the right barrel in Fig. 3.</p>
+
+<p>It would appear from these experiments that when very accurate
+shooting is required at long ranges with double-barreled rifles, they
+should be mounted in a manner similar to that adopted in the
+manufacture of the Nordenfelt machine gun, in which weapon the barrels
+are fitted into a plate at the extreme breech end, the muzzles
+projecting through holes bored to receive them in a metal plate. No
+unequal expansion would then take place, and the barrels would be free
+to become shorter independently of each other. We give the above
+experiments on the authority of their author, who, we believe, has
+taken great pains to render them as exhaustive as possible, so far as
+they go.&mdash;<i>Engineering.</i></p>
+
+
+<div class="note"><p><a name="Footnote_3" id="Footnote_3"></a><a href="#FNanchor_3">[1]</a></p>
+<p>A cross-eyed rifle is one made with a crooked stock for
+the purpose of shooting from the right shoulder, aim being taken with
+the left eye.</p></div>
+
+<hr />
+
+
+<h2><a name="art13" id="art13"></a>BALL TURNING MACHINE.</h2>
+
+
+<p>The distinguishing feature in the ball turning machine shown opposite
+is that the tool is stationary, while the work revolves in two
+directions simultaneously. In the case of an ordinary spherical
+object, such as brass clack ball, the casting is made from a perfect
+pattern having two small caps or shanks, in which the centers are also
+marked to avoid centering by hand. It is fixed in the machine between
+two centers carried on a face plate or chuck, with which they revolve.
+One of these centers, when the machine is in motion,<a name="Page_7037" id="Page_7037"></a> receives a
+continuous rotary motion about its axis from a wormwheel, D. This is
+driven by a worm, C, carried on a shaft at the back of the chuck, and
+driven itself by a wormwheel, B, which gears with a screw which rides
+loosely upon the mandrel, and is kept from rotating by a finger on the
+headstock. This center, in its rotation, carries with it the ball,
+which is thus slowly moved round an axis parallel to the face plate,
+at the same time that it revolves about the axis of the mandrel, the
+result being that the tool cuts upon the ball a scroll, of which each
+convolution is approximately a circle, and lies in a plane parallel to
+the line of centers.</p>
+
+<p>When the chuck is set for one size of ball, which may be done in a few
+minutes, any quantity of that diameter may be turned without further
+adjustment. A roughing cut for a 2 in. ball may be done in one minute,
+and a finishing cut leaving the ball quite bright in the same time.
+The two paps are cut off within one-sixteenth of an inch and then
+broken off, and the ball finished in the usual way. On account of the
+work being geometrically true, the finishing by the ferrule tool is
+done in one quarter of the time usually required.</p>
+
+<p class="ctr"><a href="./images/7a.png"><img src="./images/7a_th.png" alt="IMPROVED BALL TURNING MACHINE." /></a><br /> IMPROVED BALL TURNING MACHINE.</p>
+
+<p>The chuck may be applied to an ordinary lathe or may be combined with
+a special machine tool, as show in our illustration. In the latter
+case everything is arranged in the most handy way for rapid working,
+and six brass balls of 2 in. in diameter can be turned and finished in
+an hour. The machine is specially adapted for turning ball valves for
+pumps, pulsometers, and the like, and in the larger sizes for turning
+governor balls and spherical nuts for armor plates, and is
+manufactured by Messrs. Wilkinson and Lister, of Bradford Road Iron
+Works, Keighley.&mdash;<i>Engineering.</i></p>
+
+<hr />
+
+
+
+
+<h2><a name="art14" id="art14"></a>COOLING APPARATUS FOR INJECTION WATER.</h2>
+
+
+<p>It often happens in towns and where manufactories are crowded
+together, that the supply of water for condensing purposes is very
+small, and consequently that it attains an inconveniently high
+temperature under unfavorable conditions of weather, resulting in the
+deterioration of the vacuum and a consequent increase in the
+consumption of fuel. To remedy or to diminish this difficulty, Messrs.
+Boase and Miller, of London, have brought out the water cooler
+illustrated above. This consists, says <i>Engineering</i>, of a revolving
+basket of wire gauze surrounding an inner stationary vessel pierced
+with numerous small holes, through which the heated water discharged
+by the air pump finds its way into the basket, to be thrown out in the
+form of fine spray to a distance of 20 ft. at each side. The drops are
+received in the tank or pond, and in their rapid passage through the
+air are sufficiently cooled to be again injected into the condenser.</p>
+
+<p>The illustration shows a cooler having a basket three feet in
+diameter, revolving at 300 revolutions per minute, and discharging
+into a tank 40 ft. square. It requires 3 to 4 indicated horse-power to
+drive it, and will cool 300 gallons per minute. The following decrease
+of temperature has been observed in actual practice: Water entering at
+95 deg. fell 20 deg. in temperature; water entering at 100 deg. to 110
+deg. fell 25 deg.; and water entering at 110 deg. to 120 deg. fell 30
+deg. The machine with which these trials were made was so placed that
+the top of the basket was four ft. from the surface of the water in
+the pond. With a greater elevation, as shown in the engraving, better
+results can be obtained.</p>
+
+<p class="ctr"><a href="./images/7b.png"><img src="./images/7b_th.png" alt="IMPROVED WATER COOLING APPARATUS." /></a><br />IMPROVED WATER COOLING APPARATUS.</p>
+
+<p>The advantages claimed for the cooler are that by its means the
+temperature of the injection water can be reduced, the cost and size
+of cooling ponds can be diminished, and condensing engines can be
+employed where hitherto they have not been possible. The apparatus has
+been for two years in operation at several large factories, and there
+is every reason to believe that its use will extend, as it supplies a
+real want in a very simple and ingenious manner. Messrs. Duncan
+Brothers, of Dundee and 32 Queen Victoria Street, E.C., are the
+manufacturers.</p>
+
+<hr />
+
+
+
+
+<h2><a name="art15" id="art15"></a>CORRUGATED DISK PULLEYS.</h2>
+
+
+<p>This is a pulley recently introduced by Messrs. J. and E. Hall, of
+Dartford Eng. With the exception of the boss, which is cast, it is
+composed entirely of steel or sheet iron. In place of the usual arms a
+continuous web of corrugated sheet metal connects the boss to the rim;
+this web is attached to the boss by means of Spence's metal. Inside
+the rim, which is flanged inward, a double hoop iron ring is fixed for
+strengthening purposes. The advantageous disposition of metal obtained
+by means of the corrugated web enables the pulley to be made of a
+given strength with less weight of material, and from this cause and
+also on account of being accurately balanced these pulleys are well
+adapted for high speeds.</p>
+
+<p class="ctr"><img src="./images/7c.png" alt="DISK PULLEY" /></p>
+
+<hr />
+
+<h3>[KANSAS CITY REVIEW.]</h3>
+
+
+
+
+<h2><a name="art19" id="art19"></a>EARLY HISTORY OF THE TELEGRAPH.</h2>
+
+
+<p>Although the electric telegraph is, comparatively speaking, a recent
+invention, yet methods of communication at a distance, by means of
+signals, have probably existed in all ages and in all nations. There
+is reason to believe that among the Greeks a system of telegraphy was
+in use, as the burning of Troy was certainly known in Greece very soon
+after it happened, and before any person had returned from Troy.
+Polybius names the different instruments used by the ancients for
+communicating information&mdash;&quot;pyrsia,&quot; because the signals were always
+made by means of fire lights. At first they communicated information
+of events in an imperfect manner, but a new method was invented by
+Cleoxenus, which was much improved by Polybius, as he himself informs
+us, and which may be described as follows:</p>
+
+<p>Take the letters of the alphabet and arrange them on a board in five
+columns, each column containing five letters; then the man who signals
+would hold up with his left hand a number of torches which would
+represent the number of the column from which the letter is to be
+taken, and with his right hand a number of torches that will represent
+the particular letter in that column that is to be taken. It is thus
+easy to understand how the letters of a short sentence are
+communicated from station to station as far as required. This is the
+pyrsia or telegraph of Polybius.</p>
+
+<p>It seems that the Romans had a method of telegraphing in their walled
+cities, either by a hollow formed in the masonry, or by a tube fixed
+thereto so as to confine the sound, in order to convey information to
+any part they liked. This method of communicating is in the present
+age frequently employed in the well known speaking tubes. It does not
+appear that the moderns had thought of such a thing as a telegraph
+until 1661, when the Marquis of Worcester, in his &quot;Century of
+Inventions,&quot; affirmed that he had discovered a method by which a man
+could hold discourse with his correspondent as far as they could
+reach, by night as well as by day; he did not, however, describe this
+invention.</p>
+
+<p>Dr. Hooke delivered a discourse before the Royal Society in 1684,
+showing how to communicate at great distances. In this discourse he
+asserts the possibility of conveying intelligence from one place to
+another at a distance of 120 miles as rapidly as a man can write what
+he would have sent. He takes to his aid the then recent invention of
+the telescope, and explains how characters exposed at one station on
+the top of one hill may be made visible to the next station on the top
+of the next hill. He invented twenty-four simple characters, each
+formed of a combination of three deal boards, each character
+representing a letter by the use of cords; these characters were
+pushed from behind a screen and exposed, and then withdrawn behind the
+screen again. It was not, however, until the French revolution that
+the telegraph was applied to practical purposes; but about the end of
+1703 telegraphic communication was established between Paris and the
+frontiers, and shortly afterward telegraphs were introduced into
+England.</p>
+
+<p>The history of the invention and introduction of the electric
+telegraph by Prof. Morse is one of inexhaustible interest, and every
+incident relating to it is worthy of preservation. The incidents
+described below will be found of special interest. The article is from
+the pen of the late Judge Neilson Poe, and was the last paper written
+by him. He prepared it during his recent illness, the letter embodied
+in it from Mr. Latrobe being of course obtained at the time of its
+date. It is as follows:</p>
+
+<p>On the 5th of April, 1843, when the monthly meeting of the directors
+of the Baltimore &amp; Ohio Railroad Company was about to adjourn, the
+President, the Hon. Louis McLane, rose with a paper in his hand which
+he said he had almost overlooked, and which the Secretary would read.
+It proved to be an application from Prof. Morse for the privilege of
+laying the wires of his electric telegraph along the line of the
+railroad between Baltimore and Washington, and was accompanied by a
+communication from B.H. Latrobe, Esq., Chief Engineer, recommending
+the project as worthy of encouragement.</p>
+
+<p>On motion of John Spear Nicholas, seconded by the Hon. John P.
+Kennedy, the following resolution was then considered:</p>
+
+<p><i>Resolved</i>, &quot;That the President be authorized to afford Mr. Morse such
+facilities as may be requisite to give his invention a proper trial
+upon the Washington road, provided in his opinion and in that of the
+engineer it can be done without injury to the road and without
+embarrassment to the operations of the company, and provided Mr. Morse
+will concede to the company the use of the telegraph upon the road
+without expense, and reserving to the company the right of
+discontinuing the use if, <i>upon experiment</i>, it should prove <i>in any
+manner injurious</i>.&quot;</p>
+
+<p>&quot;Whatever,&quot; said Mr. McLane, &quot;may be our individual opinions as to the
+feasibility of Mr. Morse's invention, it seems to me that it is our
+duty to concede to him the privilege he asks, and to lend him all the
+aid in our power, especially as the resolution carefully protects the
+company against all present or future injury to its works, and secures
+us the right of requiring its removal at any time.&quot;</p>
+
+<p>[In view of the fact that no railroad can now be run safely without
+the aid of the telegraph, the cautious care with which the right to
+remove it if it should become a nuisance was reserved, strikes one at
+this day as nearly ludicrous.]</p>
+
+<p>A short pause ensued, and the assent of the company was about to be
+assumed, when one of the older directors, famed for the vigilance with
+which he watched even the most trivial measure, begged to be heard.</p>
+
+<p>He admitted that the rights and interests of the work were all
+carefully guarded by the terms of the resolution, and that the company
+was not called upon to lay out any of its means for the promotion of
+the scheme. But notwithstanding all this, he did not feel, as a
+conscientious man, that he could, without further examination, give
+his vote for the resolution. He knew that this idea of Mr. Morse,
+however plausible it might appear to theorists and dreamers, and
+so-called men of science, was regarded by all practical people as
+destined, like many other similar projects, to certain failure, and
+must consequently result in loss and possibly ruin to Mr. Morse. For
+one, he felt conscientiously scrupulous in giving a vote which would
+aid or tempt a visionary enthusiast to ruin himself.</p>
+
+<p>Fortunately, the views of this cautious, practical man did not
+prevail. A few words from the mover of the resolution, Mr. Nicholas,
+who still lives to behold the wonders he helped to create, and from
+Mr. Kennedy, without whose aid the appropriation would not have passed
+the House of Representatives, relieved the other directors from all
+fear of contributing to Mr. Morse's ruin, and the resolution was
+adopted. Of the President and thirty directors who took part in this
+transaction, only three, Samuel W. Smith, John Spear Nicholas, and the
+writer, survive. Under it Morse at once entered upon that test of his
+invention whose fruits are now enjoyed by the people of all the
+continents.</p>
+
+<p>It was not, however, until the spring of 1844 that he had his line and
+its appointments in such a condition as to allow the transmission of
+messages between the two cities, and it was in May of that year that
+the incident occurred which has chiefly led to the writing of this
+paper.</p>
+
+
+<h3>MR. LATROBE'S RECOLLECTIONS.</h3>
+
+<p>MY DEAR MR. POE: Agreeably to my promise, this morning I put
+on paper my recollection of the introduction of the magnetic telegraph
+between Baltimore and Washington. I was counsel of the Baltimore &amp;
+Ohio Railroad Co. at the time, and calling on Mr. Louis McLane, the
+President, on some professional matter, was asked in the course of
+conversation whether I knew anything about an electric telegraph which
+the inventor, who had obtained an appropriation from Congress, wanted
+to lay down on the Washington branch of the road. He said he expected
+Mr. Morse, the inventor, to call on him, when he would introduce me to
+him, and would be glad if I took an opportunity to go over the subject
+with him and afterward let him, Mr. McLane, know what I thought about
+it. While we were yet speaking, Mr. Morse made his appearance, and
+when Mr. McLane introduced me he referred to the fact that, as I had
+been educated at West Point, I might the more readily understand the
+scientific bearings of Mr. Morse's invention. The President's office
+being no place for prolonged conversation, it was agreed that Mr.
+Morse should take tea at my dwelling, when we would go over the whole
+subject. We met accordingly, and it was late in the night before we
+parted. Mr. Morse went over the history of his invention from the
+beginning with an interest and enthusiasm that had survived the
+wearying toil of an application to Congress, and with the aid of
+diagrams drawn on the instant made me master of the matter, and wrote
+for me the telegraphic alphabet which is still in use over the world.
+Not a small part of what Mr. Morse said on this occasion had reference
+to the future of his invention, its influence upon communities and
+individuals, and I remember regarding as the wild speculations of an
+active imagination what he prophesied in this connection, and which I
+have lived to see even more than realized. Nor was his conversation
+confined to his invention. A distinguished artist, an educated
+gentleman, an observant traveler, it was delightful <a name="Page_7038" id="Page_7038"></a>to hear him talk,
+and at this late day I recall few more pleasant evenings than the only
+one I passed in his company.</p>
+
+<p>Of course, my first visit the next morning was to Mr. McLane to make
+my report. By this time I had become almost as enthusiastic as Mr.
+Morse himself, and repeated what had passed between us. I soon saw
+that Mr. McLane was becoming as eager for the construction of the line
+to Washington as Mr. Morse could desire. He entered warmly into the
+spirit of the thing, and laughed heartily, if not incredulously, when
+I told him that although he had been Minister to England, Secretary of
+State, and Secretary of the Treasury, his name would be forgotten,
+while that of Morse would never cease to be remembered with gratitude
+and praise. We then considered the question as to the right of the
+company to permit the line to be laid in the bed of the road&mdash;the plan
+of construction at that time being to bury in a trench some eight or
+ten inches deep a half inch leaden tube containing the wrapped wire
+that was to form the electric circuit. About this there was, in my
+opinion, no doubt, and it was not long after that the work of
+construction commenced. I met Mr. Morse from time to time while he
+lived, and often recurred to the evening's discussion at my house in
+Baltimore.</p>
+
+<p>The above is the substance of what I have more than once related to
+other persons. I hope you will persist in your design of putting on
+paper your own very interesting recollections in this connection, and
+if what I have contributed of mine is of service to you, I shall be
+much pleased.</p>
+
+
+<p class="signature">      Most truly yours,<br /><br />
+     JOHN H.B. LATROBE.</p>
+<p>March 3, 1881.</p>
+
+
+<hr />
+
+
+<h2><a name="art20" id="art20"></a>THE KRAVOGL ELECTRIC MOTOR.</h2>
+
+<p>At the origin of every science, of whatever nature it may be, there is
+always a fruitless period, of greater or less length, characterized by
+the warfare of a few superior minds against general apathy. The finest
+discoveries pass unperceived, so to speak, since they cannot cross the
+limits of a narrow circle; and it often happens that they fall into
+oblivion before they have been seriously judged. Meanwhile, a slow
+progress is imperceptibly made, and, in measure as theoretical
+principles more clearly disengage themselves, a few industrial
+applications spring up and have the effect of awakening curiosity. An
+impulse is thus given, and from this moment a movement in advance goes
+on increasing at a headlong pace from day to day.</p>
+
+<p>With electricity this period has been of comparatively short duration,
+since scarcely a century and a half separate us from the first
+experiments made in this line of research. Now that it has truly taken
+its place in a rank with the other sciences, we like to go back to the
+hesitations of the first hour, and trace, step by step, the history of
+the progress made, so as to assign to each one that portion of the
+merit that belongs to him in the common work. When we thus cast a
+retrospective glance we find ourselves in the presence of one strange
+fact, and that is the simultaneousness of discoveries. That an
+absolutely original idea, fertile in practical consequences, should
+rise at a given moment in a fine brain is well; we admire the
+discovery, and, in spite of us, a little surprise mingles with our
+admiration. But is it not a truly curious thing that <i>several</i>
+individuals should have had at nearly the same time that idea that was
+so astonishing in one? This, however, is a fact that the history of
+electrical inventions offers more than one example of. No one ignores
+the fact that the invention of the telephone gave rise to a notorious
+lawsuit, two inventors having had this ingenious apparatus patented on
+the same day and at nearly the same hour. This is one example among a
+thousand. In the history of dynamo-electric machines it is an equally
+delicate matter to fix upon the one to whom belongs the honor of
+having first clearly conceived the possibility of engendering
+continuous currents.</p>
+
+<p>We do not wish to take up this debate nor to go over the history of
+the question again. Every one knows that the first continuous current
+electric generator whose form was practical is due to Zenobius Gramme,
+and dates back to July, 1871, an epoch at which appeared a memoir
+(entitled &quot;Note upon a magneto-electric machine that produces
+continuous currents&quot;) that was read to the Academy of Sciences by Mr.
+Jamin. Ten years previous, Pacinotti had had a glimpse of the
+phenomenon, and of its practical realization, but was unfortunately
+unable to appreciate the importance of his discovery and the benefit
+that might be reaped from it. It is of slight consequence whether
+Gramme knew of this experiment or not, for the glory that attaches to
+his name could not be diminished for all that. But an interesting fact
+that we propose to dwell upon now has recently been brought to light
+in an electrical review published at Vienna.<a name="FNanchor_4" id="FNanchor_4"></a><a href="#Footnote_4"><sup>1</sup></a> It results from
+documents whose authenticity cannot be doubted that, as far back as
+1867, Mr. L. Pfaundler, a professor at Innsbruck, very clearly
+announced the reversibility of a magneto-electric motor constructed by
+Kravogl, a mechanician of the same place, and that he succeeded some
+time before Gramme in obtaining continuous currents.</p>
+
+<p>The Kravogl motor that figured at the Universal Exhibition of 1867 is
+but little known, and it is now very difficult to obtain drawings of
+it. What is certain is that this motor is an application of the
+properties of the solenoid, and, from this standpoint, resembles the
+Bessolo motor that was patented in 1855. We may figure the apparatus
+to our mind very well if we suppose that in the Gramme ring a half and
+almost two-thirds of the core are removed, and the spirals are movable
+around the said core. If a current be sent into a portion of the
+spirals only, and in such a way that only half of the core be exposed,
+the latter will move with respect to the bobbin or the bobbin with
+respect to the core, according as we suppose the solenoid or the
+bobbin fixed. In the first case we have a Bessolo motor, and in the
+second a Kravogl one.</p>
+
+<p>In order to obtain a continuous motion it is only necessary to allow
+the current to circulate successively in the different portions of the
+solenoid. It is difficult to keep the core in place, since it is
+unreachable, being placed in the interior of the bobbin. Kravogl
+solved this difficulty by constructing a hollow core into which he
+poured melted lead. This heavy piece, mounted upon rollers, assumed a
+position of equilibrium that resulted from its weight, from friction,
+and from magnetic attraction. But for a current of given intensity
+this position, once reached, did not vary, and so necessitated a
+simple adjustment of the rubbers. Under such circumstances, with a
+somewhat large number of sections, the polarity of the core was nearly
+constant. The spirals as a whole were attached to a soft iron armature
+that had the effect of closing up the lines of forces and forming a
+shell, so to speak.</p>
+
+<p>Like Bessolo, Kravogl never thought of making anything but a motor,
+and did not perceive that his machine was reversible. It results from
+some correspondence between Dr. A. Von Waltenhofen and Mr. L.
+Pfaundler at this epoch that the latter clearly saw the possibility of
+utilizing this motor as a current generator. Under date of November 9,
+1867, he wrote, in speaking of the Kravogl motor, which had just been
+taken to Innsbruck in order to send it to Paris. &quot;I regret that I
+shall not be able to see it any more, for I should have liked to try
+to make it act in an opposite direction, that is to say, to produce a
+current or an electric light by means of mechanical work.&quot; A little
+more than two years later these experiments were carried out on a
+larger motor constructed by Kravogl in 1869, and Mr. Pfaundler was
+enabled to write as follows: &quot;Upon running the machine by hand we
+obtain a current whose energy is that of one Bunsen element.&quot; This
+letter is dated February 11, 1870, that is to say, it is a year
+anterior to the note of Gramme.</p>
+
+<p class="ctr"><img src="./images/8a.png" alt="FIG. 1." /><br />FIG. 1.</p>
+
+<p>In the presence of the historic interest that attaches to the
+question, we do not think it will be out of place to reproduce here
+the considerations that guided Prof. Pfaundler in the researches that
+led him to convert the Kravogl motor into a dynamo-electric machine.
+Let us consider two magnetized bars, <i>db</i> and <i>bd'</i>, placed end to end
+and surrounded by a cylindrical armature forming a shell, this
+armature being likewise supposed to be a permanent magnet and to
+present poles of contrary direction opposite the poles of the bars.
+For the sake of greater simplicity this shell is represented by a part
+only in the figure, <i>s&nbsp;n&nbsp;n&nbsp;s</i>. If, into a magnetic field thus
+formed, we pass a spiral from left to right, the spiral will be
+traversed by a current whose direction will change according to the
+way in which the moving is done. It is only necessary to apply Lenz's
+law to see that a reversal of the currents will occur at the points,
+<i>a</i> and <i>c</i>, the direction of the current being represented by arrows
+in the figure. If we suppose a continual displacement of the spirals
+from left to right, we shall collect a continuous current by placing
+two rubbers at <i>a</i> and <i>c</i>. Either the core or the shell may be
+replaced by a piece of soft iron. In such a case this piece will move
+with the spiral and keep its poles that are developed by induction
+fixed in space. From this, in order to reach a dynamo-electric machine
+it is necessary to try to develop the energy of the magnetic field by
+the action of the current itself. If we suppose the core to be of soft
+iron, and make a closer study of the action of the current as regards
+the polarity that occurs under the influence of the poles, <i>s</i>, <i>n</i>,
+<i>s</i>, we shall see that from <i>d</i> to <i>a</i> and from <i>b</i> to <i>c</i> the current
+is contrary, while that from <i>a</i> to <i>b</i> and from <i>c</i> to <i>d'</i> it is
+favorable to the development of such polarity. In short, with a spiral
+moving from <i>d</i> to <i>d'</i> the resulting effect is <i>nil</i>, a fact,
+moreover, that is self-evident. Under such circumstances, if we
+suppose the shell, as well as the core, to be of soft iron, we shall
+obtain a feeble current due to the presence of remanent magnetism; but
+this magnetism will not be able to continue increasing under the
+influence of the current. To solve this difficulty two means present
+themselves: (1) to cause a, favorable magnetic current and act upon
+the armature, and (2) to suppress such portions of the current in the
+spirals as are injurious in effect. The first solution was thought of
+by Gramme in 1871, and is represented diagramatically in Fig. 2. The
+second is due to Prof. Pfaundler, and dates back to 1870. The core is
+cut through the center (Fig. 3), and the portion to the right is
+suppressed; the current is interrupted between <i>da</i> and <i>cd'</i>, and is
+closed only between <i>a</i> and <i>c</i> (<i>v</i>, Fig. 1). It results from this
+arrangement that, under the action of the current, the polarity due to
+remanent magnetism does nothing but increase. It suffices then for but
+little remanent magnetism to prime the machine; the polarity of the
+shell continues to increase, and the energy of the magnetic field, and
+consequently of the current, has for a limit only the saturation of
+the soft iron. If, now, we curve the core, the spirals, and the
+armature into a circle, we have a Gramme or a Pfaundler machine,
+according as we consider Fig. 2 or Fig. 3.</p>
+
+<p class="ctr"><img src="./images/8b.png" alt="FIG. 2." /><br />FIG. 2.</p>
+
+<p class="ctr"><img src="./images/8c.png" alt="FIG. 3." /><br />FIG. 3.</p>
+
+<p>This latter apparatus has in this case the form shown in Fig. 4.</p>
+
+<p class="ctr"><img src="./images/8d.png" alt="FIG. 4." /><br />FIG. 4.</p>
+
+<p>The spiral, <i>s&nbsp;m&nbsp;b</i>, is movable, and the core, N&nbsp;<i>o&nbsp;s</i>, is kept in a
+position of equilibrium by virtue of its weight, and is provided with
+rollers. For the sake of greater clearness, the front part of the
+armature is supposed to be removed. The current does not circulate in
+the spirals to the right of the diameter, W&nbsp;O, which latter is not
+absolutely vertical. The position of the rubbers and armature is
+regulated once for all. We do not know just what were the means
+devised by Kravogl to suppress the current in the spheres to the
+right. At all events, it is probable that the system has grown old
+since Gramme invented his collector. In the application of the Kravogl
+motor to the generation of continuous currents, Professor Pfaundler
+now proposes to ingeniously utilize the Gramme collector. In such a
+case the arrangement shown in Fig. 5 would be adopted. Let us suppose
+an ordinary collector having as many plates as there are sections in
+the ring, these plates being connected as usual with the entrance and
+exit wires of the sections. The diametrically opposite touches that
+are in the line, W&nbsp;O, are divided, and one of the halves is connected
+at the entrance, <i>c&nbsp;a'</i> (Fig. 4), with the corresponding section,
+while the other communicates with the exit, <i>c'&nbsp;a</i>, of the neighboring
+section. Each of these halves is prolonged by a piece of metal bent
+into the form of an arc of a circle and embracing a little less than a
+semi-circumference. Between these prolongations there is an insulating
+part. In the rotary motion of the spiral, at least one of the touches
+is always outside of the arc comprised between the brushes, R. In
+order to secure a continuity of the circuit in the effective arc, W&nbsp;S<i>&nbsp;o</i>,
+it is only necessary to arrange a rubber, M, in such a way as to
+establish a communication between the two parts of the divided touch
+as soon as this latter enters the arc under consideration.</p>
+
+<p>In order to produce a current in the direction of the arrows shown in
+Fig. 4, the spiral and axle must revolve from right to left. In this
+case the rubber, M, occupies the position shown in the same figure,
+the brushes embracing an arc of a little less than 180�. As soon as
+the lower touch comes in contact with the brush, R, when the
+revolution is being effected from left to right, the rubber, M,
+establishes a communication between the two halves that have until now
+been isolated, and the current is no longer interrupted. The second
+touch during this time is at any point whatever of the arc, W&nbsp;N&nbsp;<i>o</i>,
+and the spirals corresponding to the latter arc outside of the
+circuit. In short, thanks to the rubber, M, we have an ordinary Gramme
+collector in that portion of the circuit comprised between the
+brushes, and a collector with a breakage of the circuit in the portion
+to the right.</p>
+
+<p class="ctr"><img src="./images/8e.png" alt="FIG. 5." /><br />FIG. 5.</p>
+
+<p>This type of machine is entirely theoretical. In the apparatus used
+for Prof. Pfaundler's experiments in 1870, the armature revolved with
+the solenoid. The core and armature were of soft iron, and the core
+was arranged in a manner analogous to the preceding, and remained in
+place under the action of its weight, and the shell, forming a
+complete circle, revolved with poles fixed in space.</p>
+
+<p>Practically, the machine that we have just described would prove
+inconvenient to realize, and would present serious inconveniences. In
+the first place, it seems to us quite difficult to transmit the motion
+of the solenoid to the axle, supposing the former to revolve within
+the armature. In the second place, considerable friction would surely
+occur between the spirals and core, and the axle, being submitted to a
+lateral stress, would be placed in a poor condition for work. It is
+even allowable to doubt whether such a type <a name="Page_7039" id="Page_7039"></a>could be practically got
+up. At all events, no trial has as yet been made of it.</p>
+
+<p>Compared with the Gramme machine, from an absolutely theoretical point
+of view, the Pfaundler apparatus presents undoubted advantages. A
+theoretically perfect dynamo electric machine would be one in which
+there was a complete reciprocity between the magnetizing action of the
+current and the inductive action of the magnetic field. Now, such is
+not the case in the Gramme machine. In this apparatus the soft iron
+core is at the same time a magnet through favorable induction and a
+disadvantageous electro-magnet. This double polarization is only
+remedied to a certain extent by the adjustment of the brushes. In the
+Pfaundler machine, on the contrary, the electro-magnetism and
+magnetism through induction act in the same direction, and concur in
+effecting a polarization that favors the production of the current.
+Looked at it in this light, the latter machine more nearly approaches
+the type of perfection than does that of Gramme.</p>
+
+<p>But we must not forget that such qualities are purely theoretical. In
+practice the best machine is that in which the copper is best
+utilized, that is to say, that which with a given weight of this metal
+furnishes the most work. Now, this is certainly not the case in the
+Pfaundler machine, for here half or more than half of the ring is
+inert&mdash;a defect which is apparent at first sight. It results from this
+that as soon as we propose to obtain an electromotive force, however
+slight it be, we must get it with machines of large dimensions. Now,
+it is permissible to believe that under such circumstances (taking
+into consideration the complication of mechanical means that the
+construction of such apparatus necessitates, and the great friction
+that occurs) it would be impossible to obtain practical rotary
+velocities. Comparing his machine with Gramme's, Prof. Pfaundler
+expresses the idea that between them there is the same analogy as
+there is between a constant pressure and an expansion engine. With
+cylinders of equal diameters the work performed by the former of these
+is greater than that done by the second, but in the latter the
+expansive force of the steam is better utilized. This comparison seems
+to us to be more ingenious than exact. Would it not be coming nearer
+to the truth if we were to suppose a case of a hydraulic motor whose
+performance continued diminishing with the height of the fall, and
+would it not be advantageous under such circumstances to utilize only
+a portion of the fall for the purpose of increasing the motor's
+performance?</p>
+
+<p>This machine, however, as before stated, has never as yet been
+constructed, so that experimental data relative to its mode of working
+are wanting. It is especially interesting as regards its origin, which
+dates back to an epoch at which researches on the dynamo electric
+machine were at their heat. It is in its historical aspect that it is
+proper to regard it, and it is from such a point of view that we have
+deemed it well to say a few words about it in this place.&mdash;<i>La Lumiere
+Electrique.</i></p>
+
+<div class="note"><p><a name="Footnote_4" id="Footnote_4"></a><a href="#FNanchor_4">[1]</a></p>
+<p><i>Zeitschrift des Electrotechnischen Vereines</i> in <i>Wien</i>,
+July, 1883.</p></div>
+
+<hr />
+
+
+<h2><a name="art21" id="art21"></a>BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES.</h2>
+
+
+<p>We shall not attempt to pass in review the several apparatus that have
+hitherto been devised for igniting blasts in mining operations, but
+shall simply describe in this place a machine recently invented for
+this purpose by Mr. Bornhardt, an engineer to the Grand Duke of
+Brunswick.</p>
+
+<p>This apparatus (shown in the accompanying engravings) consists
+essentially of two hard-rubber disks, A (Figs. 2 and 3), keyed to an
+iron axle, and of two rubbers, B, that are formed of skin and are held
+against the disks by small springs, R; motion is communicated to the
+axle, <i>a</i>, by means of a pair of gearings, <i>a</i> and <i>b</i>, and a crank,
+<i>f</i>.</p>
+
+<p class="ctr"><a href="./images/9a.png"><img src="./images/9a_th.png" alt=" BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES." /></a><br /> BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES.</p>
+
+<p>Each disk revolves between two metallic rings, <i>c</i>, provided with
+points that attract and collect in Leyden jars, D, the electricity
+produced by the friction. For discharging the condensers there is
+employed a manipulator formed of a rod, mm, which can be acted upon,
+from the exterior, by means of a button, <i>k</i>. Upon bringing the ball,
+<i>m</i>, of the rod in contact with the ball, <i>p</i>, of the condenser, the
+lever (which then takes the position shown by the dotted line)
+continues to remain in connection with a small ring, <i>q</i>, through a
+special spring. Another ring, <i>t</i>, is connected in the same way with
+the external armature of the condenser. Upon connecting the rings, <i>p</i>
+and <i>t</i>, by a wire to which cartridges are attached, any number of the
+latter may be ignited.</p>
+
+<p>The parts that we have just enumerated are inclosed in a tin box
+covered with a wooden casing, P. Between the two there is inserted a
+sheet of hard rubber in order to prevent a loss of electricity; the
+whole is held in place by strong springs.</p>
+
+<p>In order to show the normal state of the condenser, a scale consisting
+of 15 metallic buttons to give the dimensions of the sparks, is
+arranged at X. This scale is capable of being connected with the
+rings, <i>q</i> and <i>t</i>, by means of chains; when the spark obtained after 15
+or 20 revolutions considerably exceeds the intervals of the scale, it
+is a sure thing that the machine is in a proper state.</p>
+
+<p>In order to prepare the apparatus for carriage, the winch is taken off
+and placed in the compartment, <i>m</i>, which is closed by means of a
+door, Q.</p>
+
+<p>Figs. 5 and 6 show the arrangement of the dynamite cartridges and
+wires in the blast hole. Figs. 7 to 10 show different arrangements of
+the igniting wires. Figs. 11 and 12 give the general arrangement for
+igniting a number of cartridges simultaneously by means of the
+electric machine. Fig. 13 shows the arrangement where powder is
+employed. Fig. 14 shows the arrangement of a horizontal
+hole.&mdash;<i>Annales Industrielles.</i></p>
+
+<hr />
+
+
+
+
+<h2><a name="art22" id="art22"></a>IMPROVED ELECTRIC FIRE ALARM.</h2>
+
+
+<p>The object of this apparatus is to close an electric circuit when the
+temperature of a room rises above a certain point. Many devices have
+been invented for effecting this object, each of which have their own
+advantages or disadvantages. The invention of Mr. Pritchett enables
+the required result to be obtained in a very satisfactory manner. The
+apparatus consists (as shown by the figure) of a long glass vessel
+containing air; connected to this vessel there is a glass tube filled
+with mercury. The whole is mounted on a metal cradle, which turns on
+pivots. According to the position which the glass vessel and its
+adjuncts occupy in the cradle (this position being adjustable by means
+of a thumb-screw, seen at the upper part of the cradle), so will the
+same have a tendency to rock longitudinally over to one side or the
+other. Now, if we suppose the position to be such that the right hand
+end of the glass vessel is depressed, and the left hand end raised,
+then if the vessel becomes subjected to an elevation of temperature,
+the air inside the same will become expanded, and the mercury column
+in the tube will be driven over to the left, and will rise in the
+turned up end of the tube. This will cause the left hand branch of the
+glass vessel, and its attachments, to become increased in weight,
+while the right hand branch will become proportionally lighter; the
+consequence of this will be that the vessel and its cradle will cant
+over, and by falling on an electrical contact will close a circuit and
+sound an alarm. It is obvious that the apparatus is equally well
+adapted for indicating a diminution as well as an increase of
+temperature, for if the electrical contact be placed under the right
+hand portion of the cradle, and the latter be adjusted so that in its
+normal position its left hand portion is depressed, then when the
+glass vessel becomes cooled, the air in it will contract, and the
+mercury will fall in the turned-up portion of the tube before referred
+to, and will rise in the limb connected to the vessel, consequently
+the cradle and glass vessel will cant over in the reverse way to that
+which it did in the first case.</p>
+
+<p>Owing to the surface which the glass vessel exposes, the air inside
+quickly responds to any external change of temperature, consequently
+the apparatus is very sensitive. Another important feature is the fact
+that the cradle and vessel in canting over acquires a certain
+momentum, and thus the contact made becomes very certain.</p>
+
+<p class="ctr"><img src="./images/9b.png" alt="PRITCHETT'S ELECTRIC FIRE ALARM." /><br />PRITCHETT'S ELECTRIC FIRE ALARM.</p>
+
+<p>Mr. Pritchett proposes that his apparatus shall give external evidence
+outside the house by ringing a gong, and by dropping a semaphore arm
+released by an electromagnet. He also proposes (as has often been
+suggested) that a water supply shall be automatically turned
+on.&mdash;<i>Electrical Review.</i></p>
+
+<hr />
+
+
+
+
+<h2><a name="art23" id="art23"></a>A STANDARD THERMOPILE.</h2>
+
+
+<p>Dr. G. Gore, F.R.S., has invented an improved thermopile for
+measuring small electromotive forces. It consists of about 300 pairs
+of horizontal, slender, parallel wires of iron and German silver, the
+former being covered with cotton. They are mounted on a wooden frame.
+About 1� in. of the opposite ends of the wires are bent downward to a
+vertical position to enable them to dip into liquids at different
+temperatures contained in long narrow troughs; the liquids being
+non-conductors, such as melted paraffin for the hot junctions, and the
+non-volatile petroleum, known as thin machinery oil. The electromotive
+force obtained varies with the temperature; a pile of 295 pairs having
+a resistance of 95.6 ohms at 16 deg. Cent. gave with a difference of
+temperature of 100 deg. Cent. an electromotive force of 0.7729 volts,
+or with 130 deg. Cent. an electromotive force of 1.005 volt. Each
+element, therefore, equaled 0.0000262 volt for each degree Cent.
+difference of temperature. On having been verified with a standard
+voltaic cell the apparatus becomes itself a standard, especially for
+small electromotive forces. It is capable of measuring the 1/34861
+part of a volt. For higher electromotive forces than a volt, several
+of these piles would have to be connected in series. The fractional
+electromotive force is obtained by means of a sliding contact which
+cuts out so many pairs as is required.</p>
+
+<hr />
+
+
+
+
+<h2><a name="Page_7040" id="Page_7040"></a><a name="art24" id="art24"></a>TELEPHONIC TRANSMISSION WITHOUT RECEIVERS.</h2>
+
+
+<p>The annual meeting of the French Society of Physics, the success of
+which is continually increasing, took place this year in the salons of
+the Observatory, which were kindly placed at the Society's disposal by
+Admiral Mouchez.</p>
+
+<p>There were three consecutive sessions, the one of Tuesday, April 15,
+being set apart for the members of the Association, the one of the
+16th for the invited guests of Admiral Mouchez, and that of the 17th
+for the invited guests of the Society. The salons were partially
+lighted by the Siemens differential arc, continuous current lamps, and
+partially by the Swan incandescent lamp supplied by a distributing
+machine that permitted of the lamps being lighted and extinguished at
+will without changing the normal operation of all the rest. Many
+apparatus figured at this exhibition, but we shall on the present
+occasion merely call attention to those that presented a certain
+character of novelty or of originality.</p>
+
+<p>Among the apparatus that we shall reserve a description of for the
+present was Messrs. Richard Bros.' registering thermometer designed
+for the Concarneau laboratory, an instrument which, when sunk at one
+mile from the coast, and to a depth of 40 meters, will give a diagram
+of the temperature of the ocean at that depth; and Mr. Hospitalier's
+continuous electrical indicators, designed for making known from a
+distance such mechanical or physical phenomena as velocities, levels,
+temperatures, pressures, etc.</p>
+
+<p>Among the most important of the apparatus exhibited we must reckon Mr.
+Cailletet's devices for liquefying gases, and those of Mr. Mascart for
+determining the ohm. The results obtained by Mr. Mascart (which have
+been submitted to the Committee on Unities of the Congress of
+Electricians now in session at Paris), are sensibly concordant with
+those obtained independently in England by Lord Rayleigh. Everything
+leads to the hope, then, that a rapid and definite solution will be
+given of this important question of electric unities, and that nothing
+further will prevent the international development of the C.G.S.
+system.</p>
+
+<p>Mr. Jules Duboscq** made a number of very successful projections, and we
+particularly remarked the peculiar experiment made in conjunction with
+Mr. Parinaud, that gave in projection two like spectra produced by the
+same prism, and which, through superposition, were capable of
+increasing the intensity of the colors, or, on the contrary, of
+reconstituting white light.</p>
+
+<p>Among the optical applications we may cite Mr. Leon Laurent's
+apparatus for controlling plane, parallel, perpendicular, and oblique
+surfaces, and magic mirrors obtained with an ordinary light; Mr. S.P.
+Thompson's apparatus for demonstrating the propagation of
+electro-magnetic waves in ether (according to Maxwell's theory), as
+well as some new polarizing prisms; and a mode of lighting the
+microscope (presented by Mr. Yvon), that was quite analogous to the
+one employed more than a year ago by Dr. Van Heurck, director of the
+Botanical Garden of Anvers.</p>
+
+<p>Acoustics were represented by an electro-magnetic brake siren of Mr.
+Bourbouze; Konig's apparatus for the synthesis of sounds; and Mr. S.P.
+Thompson's cymatograph&mdash;a pendulum apparatus for demonstrating the
+phenomena of beats.</p>
+
+<p>It was electricity again that occupied the largest space in the
+programme of the session.</p>
+
+<p>Apparatus for teaching are assuming greater and greater importance
+every day, and the exhibit of Mr. Ducretet included a large number of
+the most interesting of these. The house of Breguet exhibited on a
+reduced scale the magnificent experiments of Gaston Plante, wherein
+320 leaden wire secondary elements charged for quantity with 3 Daniell
+elements, and afterward coupled for tension, served to charge a
+rheostatic machine formed of 50 condensers coupled for quantity. These
+latter, coupled anew for tension, furnished upon being discharged a
+spark due to a difference of potential of about 32,000 volts that
+presented all the characters of the spark produced by induction coils
+on the machines so improperly called &quot;static.&quot; Finally, we may cite
+the apparatus arranged by Mr. S.P. Thompson for studying the
+development of currents in magneto-electric machines. The inventor
+studies the influence of the forms of the inductors and armatures of
+machines by means of an arrangement that allows him to change the
+rings or armatures at will and to take out the induced bobbins in
+order to sound every part of the magnetic field. Upon giving the
+armature an angular motion limited by two stops, there develops a
+certain quantity of electricity that may be measured by causing it to
+traverse an appropriate ballistic galvanometer. Messrs. Deprez and
+D'Arsonval's galvanometer answers very well for this purpose, and its
+aperiodicity, which causes it quickly to return to zero as soon as the
+induced current ceases, permits of a large number of readings being
+taken within a very short space of time.</p>
+
+<p>Measuring apparatus were represented by a new and very elegant
+arrangement of Sir William Thomson's reflecting galvanometers, due to
+Mr. J. Carpentier. The mounting adopted by Mr. Carpentier permits of
+an easy removal of the bobbins and of an instantaneous substitution
+therefor. The galvanometric part, composed of the needles and mirror,
+therefore remains entirely free, thus allowing of its being verified,
+and making it convenient to attach the silken fiber. Mr. Carpentier
+has, moreover, adopted for all the minor apparatus a transparent
+celluloid scale which simplifies them, facilitates observations, and
+renders the use of reflection almost industrial.</p>
+
+<p>We shall complete our enumeration of the measuring apparatus by citing
+Ducretet's non-oscillating galvanometer, Sir William Thomson's
+amperemeters, voltameters, ohmmeters, and mhosmeters, constructed and
+exhibited by Breguet, and a new aperiodic galvanoscope of Mr. Maiche.
+Mr. Baudot exhibited the recent improvements that he has made in his
+multiplex printing telegraph, and M. Boudet of Paris showed a new
+system of telephone transmission by submarine cables.</p>
+
+<p class="ctr"><img src="./images/10b.png" alt="FIG. 1.&mdash;DIAGRAM EXHIBITING THE ARRANGEMENT" /><br />
+FIG. 1.&mdash;DIAGRAM EXHIBITING THE ARRANGEMENT FOR TELEPHONIC TRANSMISSIONS WITHOUT A RECEIVER.</p>
+
+<p>Finally, we shall conclude our enumeration by referring to the
+curiosities. The house of Siemens exhibited a miniature electric
+railway actuated by a new model of Reynier accumulators; M. Maiche
+operated a system of musical telephonic auditions that differed only
+in detail from those instituted by Mr. Ader at the exhibition of 1881;
+and Mr. Hospitalier presented a new form of an experiment devised by
+Mr. Giltay, consisting of a telephonic transmission of sounds without
+the use of receivers. Mr. Giltay's experiment is nothing but Mr.
+Dunand's speaking condenser without the condenser. A glance at Fig. 1
+will show how things are arranged for the experiment. The transmitting
+system comprises two distinct circuits, viz.: (1) one formed of a
+pile, P, of 2 or 3 Leclanche elements, or of 1 or 2 small sized
+accumulators, an Ader microphane transmitter, M, and the inducting
+wire of a small induction coil, B; and (2) the other formed of the
+induced wire of the coil, B, of a pile, P', of 10 or 12 Leclanche
+elements, and of a line whose extremities terminate at R, in two
+ordinary electro-medical handles. With this arrangement the experiment
+performed is as follows: When any one speaks or sings in front of the
+transmitter, T, while two persons, A and B, each having one hand
+gloved, are holding the handles in the ungloved hand, it is only
+necessary for A to place his gloved hand upon B's ear, or for the
+latter to place his hand upon A's, or for each to place his hand on
+the other's ear simultaneously, in order that A or B, or A and B
+simultaneously, may hear a voice issuing from the glove. Under these
+circumstances, Mr. Giltay's experiment is explained like Dunand's
+speaking condenser&mdash;the hand of A and the ear of B here constituting
+the armature of an elementary condenser in which the glove performs
+the role of dielectric.</p>
+
+<p>Upon repeating this experiment at the laboratory of the School of
+Physics and Industrial Chemistry of Paris, it has been found that the
+glove maybe replaced by a sheet of plain or paraffined paper. In this
+case, when two persons are holding the handles, and have their ears
+applied, one against the other, if a sheet of paper be interposed,
+airs or words will be heard to proceed therefrom. Finally, it has been
+found possible to entirely suppress the paper, or dielectric, and to
+hear directly, by simply interposing the auditor or auditors in the
+circuit. One of the most curious forms of the experiment is the one
+shown in Fig. 2. Here a third person, C, hears the hands of A and B
+speak when a circuit is formed by means of three persons, A, B, and C,
+the two former, A and B, each holding one of the wires of the circuit
+and applying his free hand to the ear of C. Although the experiment is
+one that requires entire silence, and could not on that account be
+performed at the laboratory, a sort of telephonic chain can be formed
+in which five or six persons may hear at the same time. A, putting his
+hand on the ear of B, the latter putting his to that of C, and so on
+up to the last person, who closes the circuit by grasping one of the
+handles, the other one being held by A.</p>
+
+<p class="ctr"><a href="./images/10a.png"><img src="./images/10a_th.png" alt=" EXPERIMENT ON TELEPHONIC TRANSMISSION WITHOUT" /></a>
+<br />EXPERIMENT ON TELEPHONIC TRANSMISSION WITHOUT RECEIVING APPARATUS.</p>
+
+<p>It is difficult in the present state of science to explain very
+clearly how these telephonic transmissions are effected without a
+receiver. All that we can conclude from it so far is that the ear is
+an instrument of incomparable delicacy and of exquisite sensitiveness,
+since it perceives vibrations in which the energy developer,
+particularly in the telephonic chain, is exceedingly feeble.</p>
+
+<p>Without any desire to seek an application for an experiment that is
+simply curious, we yet believe that there is here a phenomenon of a
+nature to be studied by physicists. Discoveries in telephony and
+microphony have certainly opened up to science, as regards both theory
+and practice, new horizons that still promise other surprises for the
+future. But to return to the observatory: The success obtained by the
+exhibition of the French Society of Physics shows that these reunions
+respond to a genuine need&mdash;that of instructing in and popularizing
+science. While warmly congratulating the organizers of these meetings,
+we may express a wish that the good example set by the Society of
+Physics may be followed by other societies. We are convinced in
+advance that an equal success awaits them.&mdash;<i>La Nature.</i></p>
+
+<hr />
+
+
+<h2><a name="art30" id="art30"></a>ON THE ARRANGEMENT OF GROUND CONDUCTORS.</h2>
+
+
+<p>In telegraphy, as well as in the question of lightning rods, attention
+has been but incidentally paid to the improvement of ground
+conductors, and this point has not been the object of that careful
+study that has been bestowed upon the establishment of aerial lines.
+It is only recently that the interest created by lightning rods has
+given rise to new forms of conductors differing from those formerly
+used. The publications of the Prussian Academy of Sciences of from
+1876 to 1880 contain some information of special importance in regard
+to this. It is stated therein that the effect of ground conductors may
+be notably increased by the division of the earth plates and the use
+of metallic rods, without necessitating a greater output of material.
+These facts, however, have not as yet been put to profit in practice
+for the reason, perhaps, that the considerations, which have remained
+general, have not at once permitted of obtaining forms what could be
+employed with perfect knowledge of the results. This is what led Mr.
+Ulbricht, of Dresden, to make calculations for a few forms of
+conductors, and to test their approximate values. The results of these
+researches are printed in the <i>Elektrotechnischen Zeitschrift</i> for
+1883 (p. 18).</p>
+
+<p class="ctr"><img src="./images/10c.png" alt="" /></p>
+
+<p>The equations found show, in the first place, that there exist three
+means of obtaining a considerable effect, as regards the ground
+conductor, with a slight expenditure of material: The cylindrical
+electrode may be drawn out into the form of a bar or wire; the plate
+may be rendered narrow, and elongated in the form of a ribbon; and,
+besides, the annular plate may be enlarged in lessening the metallic
+surface.</p>
+
+<p>Finally, a short, open cylinder with a vertical axis may be formed by
+curving a narrow plate or ribbon. It is not necessary to see the
+formula to recognize the fact that this cylinder must behave like a
+ribbon and a flat ring. The radius increasing, and the surface
+remaining constant, the resistance of the earth here likewise
+approaches zero.</p>
+
+<p>As the resistance of the earth is inversely proportional to the
+diameter of the plates, the zero resistance can also be reached by
+dividing a plate <i>ad infinitum</i>. As the parts of the plate may be
+brought quite close to each other without perceptibly interfering with
+the action, a <i>network</i> has finally been reached by a division carried
+very far, yet limited, and by connecting the parts with one another by
+conducting cylinders.</p>
+
+<p>If we seek to determine what forms of ground conductors are efficient
+and economical under given conditions, we shall have to begin by
+informing ourselves as to the choice of material to be used for the
+electrode, and shall then have to ascertain whether putting it in the
+ground will or will not necessitate much outlay. The most suitable
+material is copper, which may be used with advantage, in that it lasts
+pretty well underground, and that the facility which it may be worked
+permits of easily giving it more appropriate forms than those that can
+be obtained with cast iron, which is of itself less costly.</p>
+
+<p>If the burying in the ground requires little or no labor, as when
+there exist ponds, rivers, and wells, or subterranean strata of water
+near the surface of the earth, elongated forms of conductors will be
+employed, such as the solid or hollow cylinder, the wire, the ribbon,
+the narrow ring, and the network. Plates approaching a square or
+circular shape are not advantageous. But if the ground has to be dug
+deeply in order to sink the conductor, the form of the electrode must
+be more condensed, and selected in such a way that the necessary
+action may be obtained with a minimum output of copper and labor. For
+great depths, and when the ground will permit of boring, an elongated
+and narrow cylinder will be used. Such a system, however, can only be
+employed when the cylinder is surrounded by spring water, since,
+without that, an intimate contact with earth that is only moist,
+cannot be obtained with certainty. In earth that is only moist and for
+moderate depths, preference may be given to an electrode laid down
+flat. The digging necessary in this case is onerous, it is true, but
+it permits of very accurately determining the state of the earth
+beneath and of obtaining a very perfect adherence of the electrode
+therewith. Two forms, the annular ribbon or the flat ring and the
+network, present themselves, according to calculations, as a
+substitute for copper plates, which are so expensive; and these forms
+are satisfactory on condition that the labor of digging be not notably
+increased. These forms should always have a diameter a little greater
+than that of the plate. The flat ring and the network, however, offer
+one weak point, which they possess in common with the plate, and that
+is, their dimensions cannot be easily adapted <a name="Page_7041" id="Page_7041"></a>to the nature of the
+ground met with without a notable increase in the expense. Now, if the
+ground should offer a conductivity less than what was anticipated, and
+it were desired to increase the plate, say by one-third, it would be
+impossible to do so as a consequence of the closed form.</p>
+
+<p>One important advantage is realized in this respect by combining the
+ring and the network in the form of a reticulated ring having a
+diameter of from 1 to 1� meters. On cutting this ring at a given place
+and according to a certain radius we obtain the reticulated ribbon
+shown in the accompanying figure. The thickness of the wires is 2.5
+mm., and their weight is 0.475 kilo. per meter. L, L, and L are the
+points at which the conducting cable is soldered. A reticulated ribbon
+of copper can be made in advance of any length whatever, and,
+according to local exigencies, it may be easily curved and given the
+form of a flat or cylindrical ring of varying width. Even though the
+ribbon has already been cut for a ring of given diameter, it may be
+still further enlarged by drawing it out and leaving a bit of the ring
+open, so as to thus obtain a nearly corresponding diminution in the
+resistance. Such a resistance may be still further diminished by
+rendering the ring higher, that is to say, by employing an annular
+cylindrical form.</p>
+
+<p>After assuring himself, by experiments on a small scale, that
+calculation and observation gave concordant results for the flat ring,
+the author made an experiment on a larger scale with the annular
+network. For practical reasons he employed for this purpose a copper
+wire 2.5 mm. in diameter, which may be expected to last as long as one
+of iron plate 2 mm. in thickness. Calculation showed that in a ribbon
+160 mm. wide, meshes 40 mm. in breadth were advantageous and favorable
+as regards rigidity. A reticulated ribbon like this, 4 meters in
+length, was made and formed into a flat ring having an external
+diameter of 1.42 m. and an internal one of 1.10 m. The resistance of
+this ring was found to be W = 0.3485 1/<i>k</i>, and that of a plate one
+meter square, W<sub>0</sub> = 0.368 1/<i>k</i>.</p>
+
+<p>As the conductivity of the earth is very variable, and as we cannot
+have an absolute guarantee that the ramming will be uniform, it seemed
+proper to make the measurements of the resistance by fixing the plate
+and the ring in succession to the lower surface of a small raft, in
+such a way that the contact with the water should correspond as well
+as possible to the suppositions made for the calculation. As a second
+ground conductor, a system of water pipes was used, and, after this, a
+lightning rod conductor, etc.</p>
+
+<p>Repeated and varied experiments gave, for the calculation of the
+values of the resistances, equations so concordant that the following
+results may be considered very approximate.</p>
+
+<p>The square plate had a resistance of 35.5 Siemens units, and the
+reticulated ring one of 32.5. From the first figure we deduce k =
+1/91.12, that is to say, the specific conductivity of river-water is
+1:91120000. Calculation, then, gives as the resistance of the earth in
+Siemens units:</p>
+
+<div class="ctr">
+<table border="0" cellpadding="4" cellspacing="0" summary="">
+<colgroup span="3" align="left"></colgroup>
+<tr><td></td><th>Calculated</th><th>Observed.</th></tr>
+<tr><td>Square plate.</td><td>&nbsp;&nbsp;33.5</td><td>&nbsp;&nbsp;33.5</td></tr>
+<tr><td>Annular ring.</td><td>&nbsp;&nbsp;31.76</td><td>&nbsp;&nbsp;32.5</td></tr>
+</table></div>
+
+<p>These figures prove the accuracy of the calculations that had been
+made in an approximate way.</p>
+
+<p>The experiments were performed upon the Elba, above Dresden. Other
+experiments still had reference to the influence of immersion. In
+order to diminish polarization, only instantaneous currents from the
+measuring pile were employed. It was to be supposed that the current
+of water through which the bubbles of gas were removed from the
+electrodes would not have permitted of a notable resistance of
+polarization. Later measurements, made upon a ribbon buried, like the
+plates, in the earth, gave likewise most favorable results.</p>
+
+<p>As a result of these experiments, the State railways of Saxony have,
+in such cases as were practicable, introduced the annular network of
+copper. There are some manufacturers, too, who seem desirous of
+adopting this system, although it has hardly emerged from the period
+of experiment. The pecuniary advantages that will result from an
+application of it ought, it would seem, to dispel a large proportion
+of the criticisms directed against the erection of lightning rods,
+from the standpoint of expense, and contribute to extend an
+arrangement which may be considered as a very happy one.</p>
+
+<p>If we compare the square plate with the equivalent annular network,
+constructed as above indicated, and which should possess, according to
+the author an external diameter of 1.26 m. and of 3.45 m., we find
+that:</p>
+
+<div class="ctr"><table summary="">
+<colgroup span="3" align="left"></colgroup>
+<tr><td>The square plate,</td><td>1  mm. thick</td><td>weighs  8.9 kilos.</td></tr>
+<tr><td align="center">&quot;</td><td>2  mm. thick</td><td>weighs  17.8 kilos.</td></tr>
+<tr><td colspan="2">The annular network</td><td>weighs   1.64 kilos.</td></tr>
+</table></div>
+
+<p>The cost of reticulated ribbon per meter amounts to about 4.4 francs,
+supposing it to be arranged as shown in the cut.</p>
+
+<p>As term of comparison, we may admit that the following forms are
+nearly the equivalent of a horizontal, unburied plate one meter
+square.</p>
+
+<div class="ctr">
+<table border="0" cellpadding="4" cellspacing="0" summary="">
+<colgroup span="4"><col align="left" /><col align="center" /><col align="right" span="2" /></colgroup>
+<tr><td></td><td></td><th>Length.</th><th>Diameter.</th></tr>
+<tr><td>Vertical cylinder</td><td>buried</td><td>1.40 m.</td><td>0.13 m.</td></tr>
+<tr><td align="center">&quot;</td><td>&quot;</td><td>1.80 m.</td><td>0.06 m.</td></tr>
+<tr><td>Vertical bar</td><td>&quot;</td><td>2.60 m.</td><td>0.013 m.</td></tr>
+<tr><td>Horizontal bar</td><td>&quot;</td><td>5.20 m.</td><td>0.013 m.</td></tr>
+</table></div>
+
+
+<p>Horizontal flat ring 1.32 m. in external diameter, and 1.08 m.
+internal.</p>
+
+<p>Horizontal network 1.01 m. square, and having meshes of the same size
+as those of the reticulated ribbon.</p>
+
+<p>Horizontal reticulated ribbon 3 m. in length and of the structure
+described.</p>
+
+<p>Horizontal annular ring 1.26 m. in external diameter, 0.94 m.
+internal.</p>
+
+<p>In conclusion, let us meet an objection that might be made to the
+accuracy of the hypotheses that serve as a base to the preceding
+calculations, in cases where ground plates for lightning rods and not
+for telegraphs are concerned. Between the two ground plates of a
+telegraph line there is generally a distance such that the curves of
+the current undergo no deviation in the vicinity of one of the
+electrodes (the only part important for integrations) through the
+influence of the other. But it might be admitted that such would prove
+the case with a lightning rod in a storm, at the time of the passage
+of the fluid into the earth. The ground plate here is one of the
+electrodes, and the other is replaced by the surface of the earth
+strongly charged to a great distance under the storm clouds. If we
+suppose (what may be admitted in a good lightning rod) that there no
+longer occurs any spark from the point downward, the curves of the
+current, in starting perpendicularly from the ground plate, would be
+obliged to leave their rectilinear trajectory and strike the surface
+of the earth at right angles. When the electricity flows through a
+plane surface into an infinite body, it is only when such surface
+presents a very great development that the respective potentials
+decrease very slowly in the vicinity of the said surface. No notable
+modification occurs, then, in the curves of equal potential, in the
+vicinity of the ground plate through the action of this extended
+charge, nor consequently any modification in the curves of the
+current; but the electricity which spreads has but a short distance to
+travel in order to overcome the most important resistances.</p>
+
+<p>The calculations of resistances given above have, then, the same value
+for discharges of atmospheric electricity.&mdash;<i>Bull. du Musee de
+l'Industrie.</i></p>
+
+<hr />
+
+
+
+
+<h2><a name="art01" id="art01"></a>ON ELECTROLYSIS.</h2>
+
+<h3>By H. SCHUCHT.</h3>
+
+
+<p>Concerning the separations which take place at the positive pole, the
+composition of the peroxides, and the manner of their determination,
+relatively little has been done.</p>
+
+<p>If solutions of the salts of lead, thallium, silver, bismuth, nickel,
+and cobalt are decomposed by the current between platinum electrodes,
+metal is deposited at the negative, and oxide at the positive
+electrode. Manganese is precipitated only as peroxide. The formation
+of peroxide is, of course, effected by the ozone found in the
+electrolytic oxygen at the positive pole; the oxide existing in
+solution is brought to a higher degree of oxidation, and is separated
+out. Its formation may be decreased or entirely prevented by the
+addition of readily oxidizible bodies, such as organic acids, lactose,
+glycerine, and preferably by an excess of oxalic acid; but only until
+the organic matter is transformed into carbonic acid. In this manner
+Classen separates other metals from manganese in order to prevent the
+saline solutions from being retained by the peroxide.</p>
+
+<p>With solutions of silver, bismuth, nickel, and cobalt, it is often
+practicable to prevent the separation of oxide by giving the current a
+greater resistance&mdash;increasing the distance between the electrodes.</p>
+
+<p>The proportion between the quantities of metal and of peroxide
+deposited is not constant, and even if we disregard the concentration
+of the solution, the strength of the current and secondary influences
+(action of nascent hydrogen) is different in acid and in alkaline
+solutions. In acid solutions much peroxide is formed; in alkaline
+liquids, little or none. The reason of the difference is that ozone is
+evolved principally in acid solutions, but appears in small quantities
+only in alkaline liquids, or under certain circumstances not at all.
+The quantity of peroxide deposited depends also on the temperature of
+the saline solution; at ordinary temperatures the author obtained more
+peroxide&mdash;the solution, the time, and the strength of current being
+equal&mdash;than from a heated liquid. The cause is that ozone is destroyed
+by heat and converted into ordinary oxygen. With the exception of lead
+and thallium the quantity of metal deposited from an acid solution is
+always greater than that of the peroxide.</p>
+
+<p><i>Lead.</i>&mdash;Luckow has shown that from acid solutions&mdash;no matter what may
+be the acid&mdash;lead is deposited at the anode as a mixture of anhydrous
+and hydrated peroxide of variable composition. Only very strongly acid
+solutions let all their lead fall down as peroxide; the precipitation
+is rapid immediately on closing the circuit, and complete separation
+is effected only in presence of at least 10 per cent. of free nitric
+acid. As the current becomes stronger with the increase of free acid,
+there is deposited upon the first compact layer a new stratum of
+loosely adhering peroxide.</p>
+
+<p>In presence of small quantities of other metals which are thrown down
+by the current in the metallic state, such as copper, mercury, etc.,
+peroxide alone is deposited from a solution of lead containing small
+quantities only of free nitric acid.</p>
+
+<p>The lead peroxide deposited is at first light brown or dark red, and
+becomes constantly darker and finally taking a velvet-black. As its
+stratification upon the platinum is unequal, it forms beautifully
+colored rings.</p>
+
+<p>Experiments show that the quantity of peroxide deposited depends on
+the nature of the solution and the strength of the current. In case of
+very feeble currents and slight acidity, its quantity is so small that
+it does not need to be taken into consideration. If the lead solution
+is very dilute scarcely any current is observed, lead solutions <i>per
+se</i> being very bad conductors of electricity.</p>
+
+<p>Faintly acid concentrated lead solutions give loose peroxide along
+with much spongy metallic lead. Free alkali decreases the separation
+of peroxide; feebly alkaline solutions, concentrated and dilute, yield
+relatively much peroxide along with metallic lead, while strongly
+alkaline solutions deposit no peroxide.</p>
+
+<p>Dried lead peroxide is so sparingly hygroscopic that it may be weighed
+as such; its weight remains constant upon the balance for a long time.
+In order to apply the peroxide for quantitative determinations, a
+large surface must be exposed to action. As positive electrode a
+platinum capsule is convenient, and a platinum disk as negative pole.
+The capsule shape is necessary because the peroxide when deposited in
+large quantities adheres only partially, and falls in part in thin
+loose scales. It is necessary to siphon off the nitric solution,
+since, like all peroxides, that of lead is not absolutely insoluble in
+nitric acid. The methods of Riche and May give results which are
+always too high, since portions of saline solution are retained by the
+spongy deposit and can be but very imperfectly removed by washing.
+This is especially the case in presence of free alkali.</p>
+
+<p>The author has proceeded as follows: The lead peroxide is dried in the
+capsule, and there is passed over it pure dry gaseous sulphurous acid
+in a strong current from a rather narrow delivery tube. Lead sulphate
+is formed with evolution of heat; it is let cool under the exsiccator,
+and weighed as such. Or he ignites the peroxide along with finely
+pulverized ammonium sulphite; the mass must have a pure white color.
+After the conclusion of the reaction it is ignited for about 20
+minutes. The results are too high. The proportion of actual lead
+peroxide in the deposit ranges from 94 to 94.76 per cent. The peroxide
+precipitated from a nitric solution may, under certain circumstances,
+be anhydrous. This result is due to the secondary influences at the
+positive pole, where the free acid gradually withdraws water from the
+peroxide.</p>
+
+<p>The peroxide thrown down from alkaline solutions retains alkali so
+obstinately that it cannot be removed by washing; the peroxide plays
+here the part of an acid. The lead nitrate mechanically inclosed in
+the peroxide is resolved by ignition into oxide, hyponitric acid, and
+oxygen; this small proportion of lead oxide does not exert an
+important influence on the final result. The quantity of matter
+mechanically inclosed is relatively high, as in the precipitation of
+much lead peroxide there is relatively more saline matter occluded
+than when a few centigrammes are deposited. The peroxide incloses also
+more foreign matter if it is thrown down upon a small surface than if
+it is deposited in a thin layer over a broad surface. From numerous
+analyses the author concludes that in presence of much free nitric
+acid the proportion of water is increased; with free alkali the
+reverse holds good.</p>
+
+<p><i>Thallium</i> behaves similarly to lead. From a nitric acid solution it
+is thrown down, according to the proportion of free acid, either as
+sesquioxide only or in small quantities as silvery, metallic leaflets;
+from alkaline solutions it is deposited as sesquioxide and metal, the
+latter of a lead-gray color. Thallium solutions conduct the electric
+current badly. Thallium oxide resembles lead peroxide in color; at a
+strong heat it melts, becomes darker, and is converted into peroxide,
+in which state it can be weighed.</p>
+
+<p><i>Silver.</i>&mdash;All solutions of silver salts, except the nitrate, and
+those containing a very large quantity of free nitric acid or
+nitrates, deposit electrolytically merely metallic silver. In the
+above mentioned exceptional cases there is formed a small quantity of
+peroxide which adheres to the anode as a blackish-gray deposit. The
+greatest quantity of peroxide is obtained on employing a concentrated,
+strongly acid solution of the nitrate, and a strong current. If the
+solution is very dilute we obtain no peroxide, or mere traces which
+disappear again toward the end of the process. The peroxide is
+deposited at first in small, dark, shining octahedral crystals;
+subsequently, in an amorphous state. At 110� it evolves oxygen
+suddenly, and is converted into metallic silver. It dissolves in
+ammonia with a violent escape of nitrogen. In nitric acid it dissolves
+without decomposition and with a red color.</p>
+
+<p>The author uses a galvanic current for reducing silver residues,
+consisting of sulphocyanide. The salt is mixed with sulphuric acid in
+a roomy platinum capsule, and a fine platinum wire gauze is used as
+positive electrode.</p>
+
+<p><i>Bismuth.</i>&mdash;The current resolves bismuth solutions into metal and
+bismutic acid. The latter is deposited at the positive pole, and in
+thin layers appears of a golden-yellow, but in thick strata is darker,
+approaching to red. Its formation is very gradual, and in time it
+disappears again, owing to secondary actions of the current. On
+ignition it becomes lemon yellow, and transitorily darker, even brown,
+and passes into the sexquioxide.</p>
+
+<p><i>Nickel and Cobalt.</i>&mdash;On the electrolysis of the ammonical solution
+the sesquioxide appears at the positive pole. Its formation is
+prevented by an excess of ammonia. The author never obtains more than
+3� per cent. of the quantity of the metal. The sesquioxides dissolve
+in ammonia without escape of nitrogen, and are usually anhydrous.</p>
+
+<p><i>Manganese.</i>&mdash;Manganese is the only metal which is precipitated only
+as peroxide. It is deposited at once on closing the circuit, and is at
+first brown, then black and shining. Organic acids, ferrous oxide,
+chromic oxide, ammonium salts, etc., prevent the formation of peroxide
+and the red color produced by permanganic acid. In very dilute
+strongly acid nitric solutions there is formed only permanganic acid,
+which according to Riche is plainly visible in solutions containing
+1/1000000 grm. manganese. On electrolyzing a manganiferous solution of
+copper nitrate, red permanganic acid appeared in a stratum floating
+above the platinum disk coated with brown peroxide. No manganese
+peroxide was deposited. The peroxide adheres firmly to the platinum
+when the proportion of free acid is small, not exceeding 3 per cent.,
+and the current is not too strong. If the action of the current is
+prolonged after the peroxide is thrown down, it falls off in lamin&aelig;.
+According to Riche, in a nitric solution the manganese is deposited as
+peroxide, also at the negative pole. This formation is not directly
+due to the current, but is a precipitate occasioned by the production
+of ammonia by the reduction of nitric acid. To determine the manganese
+in peroxide electrolytically precipitated, it is heated to bright
+redness in the platinum capsule until the weight becomes constant. The
+results are too high.</p>
+
+<p><i>Selenium and Tellurium.</i>&mdash;Both these bodies are readily and
+completely reduced by the current either in acid or alkaline
+solutions. Selenium is thrown down at first of a fine brownish red,
+which gradually becomes darker. The deposit of tellurium is of a
+bluish black color. If the current is feeble, the deposit of selenium
+is moderately compact; that of tellurium is always loose, and it often
+floats on the liquid. A strong current precipitates both as powders.
+The positive pole is coated during electrolysis with a film of a dark
+color in case of selenium, but of a lemon yellow with tellurium. As in
+case of arsenic and antimony, the hydrogen evolved at the negative
+pole combines with the reduced substances, forming hydrogen, selenide,
+or telluride, which remain in part in solution in the liquid. The
+reduced metal separates out at the anode in a friable
+condition.&mdash;<i>Zeitschrift fur Analytische Chemie, and Chemical News.</i></p>
+
+<hr />
+
+
+<h2><a name="art02" id="art02"></a>THE ELECTRO-CHEMICAL EQUIVALENT OF SILVER.</h2>
+
+
+<p>A very careful and important determination of the electrochemical
+equivalent of silver has been made at the observatory of the Physical
+Institute of W�rzbourg, and the results are that an ampere current
+flowing for a second, or a coulomb of electricity deposits 1.1183
+milligrammes of silver or 0.3281 milligramme of copper, and decomposes
+0.09328 milligramme of water, a result agreeing closely with that of
+Lord Rayleigh recently communicated to the Physical Society. An ampere
+therefore deposits 4.0259 grammes of silver per hour; Kohlrausch's
+value is 4.0824, a value hitherto accepted universally. This value is
+so useful in measuring electric currents with accuracy, and free from
+the disturbances of magnetism, etc., that it is eminently satisfactory
+to find the German value agree with that of Lord Rayleigh, which will
+probably be adopted by English electricians.</p>
+
+<hr />
+
+
+<h2><a name="art16" id="art16"></a>A NEW STANDARD LIGHT.</h2>
+
+
+<p>Herr Hefner-Alteneck has suggested a new standard light for
+photometric purposes, which promises to be very simple and effective
+in operation. The light is produced by an open flame of amyl-acetate
+burning from a wick of cotton fiber which fills a tube of German
+silver 1 in. long and 316 mils. internal diameter; the external
+diameter being 324 mils. The flame is 1.58 in. high from top to
+bottom; and it should be lighted at least ten minutes before using the
+light for testing. A cylindrical glass chimney surrounds it to ward
+off air currents. About 2 per cent. of the light is absorbed by the
+glass. The power of the flame is that of a standard English candle;
+and experiments have shown that amyl acetate, which besides is not
+expensive, is the best fuel for steadiness and brilliance. Neither the
+substitution of commercial amyl-acetate for pure nor the use of a wick
+of cotton thread for loose cotton fiber alters the illuminating power;
+but the wick should be trimmed square across the mouth of the tube,
+for if it project and droop the illuminating power is increased.</p>
+
+<hr />
+
+<p class="ctr">[NATURE.]</p>
+
+
+
+
+<h2><a name="Page_7042" id="Page_7042"></a><a name="art17" id="art17"></a>DR. FEUSSNER'S NEW POLARIZING PRISM.</h2>
+
+
+<p>In a recent number of the <i>Zeitschrift fur Instrumentenkunde</i> (iv.,
+42-50, February, 1884), Dr. K. Feussner of Karlsruhe has given a
+detailed description of a polarizing prism lately devised by him,
+which presents several points of novelty, and for which certain
+advantages are claimed. The paper also contains an account, although
+not an exhaustive one, of the various polarizing prisms which have
+from time to time been constructed by means of different combinations
+of Iceland spar. The literature of this subject is scattered and
+somewhat difficult of access, and moreover only a small part of it has
+hitherto been translated into English; and it would appear therefore
+that a brief abstract of the paper may not be without service to those
+among the readers of <i>Nature</i> who may be unacquainted with the
+original memoirs, or who may not have the necessary references at
+hand.</p>
+
+<p>Following the order adopted by Dr. Feussner, the subject may be
+divided into two parts:</p>
+
+
+<h3>I.&mdash;OLDER FORMS OF POLARIZING PRISMS.</h3>
+
+<p>In comparing the various forms of polarizing prisms, the main points
+which need attention are&mdash;the angular extent of the field of view, the
+direction of the emergent polarized ray, whether it is shifted to one
+side of, or remains symmetrical to the long axis of the prism; the
+proportion which the length of the prism bears to its breadth; and
+lastly, the position of the terminal faces, whether perpendicular or
+inclined to the long axis. These requirements are fulfilled in
+different degrees by the following methods of construction:</p>
+
+<p class="ctr"><img src="./images/12a.png" alt="Fig. 1., Fig. 2., and Fig. 3." /><br />Figs. 1., 2., and 3.</p>
+
+<p>1. <i>The Nicol Prism</i> (<i>Edin. New Phil. Journal</i>, 1828, vi., 83).&mdash;This
+(Fig. 1), as is well known, is constructed from a rhombohedron of
+Iceland spar, the length of which must be fully three times as great
+as the width. The end faces are cut off in such a manner that the
+angle of 72� which they originally form with the lateral edge of the
+rhombohedron is reduced to 68�. The prism is then cut in two in a
+plane perpendicular to the new end surfaces, the section being carried
+obliquely from one obtuse corner of the prism to the other, in the
+direction of its length. The surfaces of this section, after having
+been carefully polished, are cemented together again by means of
+Canada balsam. A ray of light, on entering the prism, is separated by
+the double refraction of the calc-spar into an ordinary and an
+extraordinary ray; the former undergoes total reflection at the layer
+of balsam at an incidence which allows the extraordinary ray to be
+transmitted; the latter, therefore, passes through unchanged. This
+principle of obtaining a single polarized ray by means of total
+reflection of the other is common to all the forms of prism now to be
+described.</p>
+
+<p>Dr. Feussner gives a mathematical analysis of the paths taken by the
+two polarized rays within the Nicol prism, and finds that the emergent
+extraordinary ray can include an angular field of 29�, but that this
+extreme value holds good only for rays incident upon that portion of
+the end surface which is near to the obtuse corner, and that from
+thence it gradually decreases until the field includes an angle of
+only about half the previous amount. He finds, moreover, that,
+although of course the ray emerges parallel to its direction of
+incidence, yet that the zone of polarized light is shifted to one side
+of the central line. Also that the great length of the Nicol&mdash;3.28
+times its breadth&mdash;is not only an inconvenience, but owing to the
+large pieces of spar thus required for its construction, prisms of any
+but small size become very expensive. To this it may be added that
+there is a considerable loss of light by reflection from the first
+surface, owing to its inclined position in regard to the long axis of
+the prism.</p>
+
+<p class="ctr"><img src="./images/12b.png" alt="Fig. 4., Fig. 5., and Fig. 6." /><br />Figs. 4., 5., and 6.</p>
+
+<p>It is with the view of obviating these defects that the modifications
+represented in Figs. 2 to 6 have been devised.</p>
+
+<p>2. <i>The Shortened Nicol Prism</i>.&mdash;This arrangement of the Nicol prism
+is constructed by Dr. Steeg and Reuter of Homburg v.d.H. For the sake
+of facility of manufacture, the end surfaces are cleavage planes, and
+the oblique cut, instead of being perpendicular, makes with these an
+angle of about 84�. By this alteration the prism becomes shorter, and
+is now only 2.83 times its breadth; but if Canada balsam is still used
+as the cement, the field will occupy a very unsymmetrical position in
+regard to the long axis. If balsam of copaiba is made use of, the
+index of refraction of which is 1.50, a symmetrical field of about 24�
+will be obtained. A prism of this kind has also been designed by Prof.
+B. Hasert of Eisenach (<i>Pogg. Ann.</i>, cxiii., 189), but its performance
+appears to be inferior to the above.</p>
+
+<p>3. <i>The Nicol Prism with Perpendicular Ends.</i>&mdash;The terminal surfaces
+in this prism are perpendicular to the long axis, and the sectional
+cut makes with them an angle of about 75�. The length of the prism is
+3.75 times its breadth, and if the cement has an index of refraction
+of 1.525, the field is symmetrically disposed, and includes an angle
+of 27�. Prisms of this kind have been manufactured by Dr. Steeg, Mr.
+C.D. Ahrens, and others.</p>
+
+<p>4. <i>The Foucault Prism</i> (<i>Comptes Rendus</i>, 1857, xlv., 238).&mdash;This
+construction differs from all those hitherto mentioned, in that a film
+of air is employed between the two cut surfaces as the totally
+reflecting medium instead of a layer of cement. The two halves of the
+prism are kept in position, without touching each other, by means of
+the mounting. The length of the prism is in this way much reduced, and
+amounts to only 1.528 times its breadth. The end surfaces are cleavage
+planes, and the sectional cut makes with them an angle of 59�. The
+field, however, includes not more than about 8�, so that this prism
+can be used only in the case of nearly parallel rays; and in addition
+to this the pictures which may be seen through it are to some extent
+veiled and indistinct, owing to repeated internal reflection.</p>
+
+<p>5. <i>The Hartnack Prism</i> (<i>Ann. de Ch. et de Physique</i>, ser. iv., vii.,
+181).&mdash;This form of prism was devised in 1866 by MM. Hartnack and
+Prazmowiski; the original memoir is a valuable one; a translation of
+it, with some additions, has lately been published (<i>Journ. of the R.
+Microscopical Soc.</i>, June, 1883, 428). It is considered by Dr.
+Feussner to be the most perfect prism capable of being prepared from
+calc-spar. The ends of the prism are perpendicular to its length; the
+section carried through it is in a plane perpendicular to the
+principal axis of the crystal. The cementing medium is linseed oil,
+the index of refraction of which is 1.485. This form of prism is
+certainly not so well known in this country as it deserves to be; a
+very excellent one, supplied to the present writer by Dr. Steeg is of
+rectangular form throughout, the terminal surfaces are 19 � 15 mm.,
+and the length 41 mm. The lateral shifting of the field is scarcely
+perceptible, the prism is perfectly colorless and transparent, and its
+performance is far superior to that of the ordinary Nicol. The field
+of view afforded by this construction depends upon the cementing
+substance used, and also upon the inclination of the sectional cut in
+regard to the end of the prism; it may vary from 20� to 41�. If the
+utmost extent of field is not required, the prism may be shortened by
+lessening the angle of the section, at the expense, however, of
+interfering with the symmetrical disposition of the field.</p>
+
+<p>6. <i>The Glan Prism</i> (Carl's &quot;Repertorium,&quot; xvi., 570, and xvii.,
+195).&mdash;This is a modification of the Foucault, and in a similar manner
+includes a film of air between the sectional surfaces. The end
+surfaces and also the cut carried through the prism are parallel to
+the principal axis of the calc-spar. The ends are normal to the
+length, and the field includes about 8�. This prism is very short, and
+may indeed be even shorter than it is broad. It is subject to the same
+defect as that mentioned in the case of the Foucault, although perhaps
+not quite to the same extent.</p>
+
+
+<h3>II.&mdash;THE NEW POLARIZING PRISM.</h3>
+
+<p>This prism differs very considerably from the preceding forms, and
+consists of a thin plate of a doubly refracting crystal cemented
+between two wedge-shaped pieces of glass, the terminal faces of which
+are normal to the length. The external form of the prism may thus be
+similar to the Hartnack, the calc-spar being replaced by glass. The
+indices of refraction of the glass and of the cementing medium should
+correspond with the greater index of refraction of the crystal, and
+the directions of greatest and least elasticity in the latter must
+stand in a plane perpendicular to the direction of the section. One of
+the advantages claimed for the new prism is that, it dispenses with
+the large and valuable pieces of spar hitherto found necessary; a
+further advantage being that other crystalline substances may be used
+in this prism instead of calc-spar. The latter advantage, however,
+occurs only when the difference between the indices of refraction for
+the ordinary and extraordinary rays in the particular crystal made use
+of is greater than in calc-spar. When this is the case, the field
+becomes enlarged, and the length of the prism is reduced.</p>
+
+<p class="ctr"><img src="./images/12c-7.png" alt="Fig. 7." /><br />Fig. 7.</p>
+
+<p>The substance which Dr. Feussner has employed as being most suitable
+for the separating crystal plate is nitrate of soda
+(<i>natronsalpeter</i>), in which the above-mentioned values are &omega; =
+1.587 and &eta; = 1.336. It crystallizes in similar form to calcite,
+and in both cases thin plates obtained by cleavage may be used.</p>
+
+<p>As the cementing substance for the nitrate of soda, a mixture of gum
+dammar with monobromonaphthalene was used, which afforded an index of
+refraction of 1.58. In the case of thin plates of calcite, a solid
+cementing substance of sufficiently high refractive power was not
+available, and a fluid medium was therefore employed. For this purpose
+the whole prism was inclosed in a short glass tube with airtight ends,
+which was filled with monobromonaphthalene. In an experimental prism a
+mixture of balsam of tolu was made use of, giving a cement with an
+index of refraction of 1.62, but the low refractive power resulted in
+a very considerable reduction of the field. The extent and disposition
+of the field may be varied by altering the inclination at which the
+crystal lamina is inserted (Fig. 7), and thereby reducing the length
+of the prism, as in the case of the Hartnack.</p>
+
+<p>In order to obviate the effects of reflection from the internal side
+surfaces if the prism, the wedge-shaped blocks of glass of which it is
+built up may be made much broader than would otherwise be necessary;
+the edges of this extra width are cut obliquely and suitably
+blackened.</p>
+
+<p>The accompanying diagram (Fig. 8) represents a prism of cylindrical
+external form constructed in this manner, the lower surface being that
+of the incident light. In this the field amounts to 30�, and the
+breadth is about double the length.</p>
+
+<p class="ctr"><img src="./images/12c-8.png" alt="Fig. 8." /><br />Fig. 8.</p>
+
+<p>Dr. Feussner remarks that a prism similar in some respects to his new
+arrangement was devised in 1869 by M. Jamin (<i>Comptes Rendus</i>,
+lxviii., 221), who used a thin plate of calc-spar inclosed in a cell
+filled with bisulphide of carbon; and also by Dr. Zenker, who replaced
+the liquid in M. Jamin's construction by wedges of flint glass.</p>
+
+<p>Among others, the carefully considered modifications of the Nicol
+prism which have recently been devised by Prof. S.P. Thompson (<i>Phil.
+Mag.</i>, November, 1881, 349, and <i>Jour. R. Micros. Soc.</i>, August, 1883,
+575), and by Mr. R.T. Glazebrook (<i>Phil. Mag.</i>, May, 1883, 352), do
+not appear to have been known to Dr. Feussner.</p>
+
+<p>The following tabular view of different forms of polarizing prisms is
+taken from the conclusion of Dr. Feussner's paper:</p>
+
+<div class="ctr">
+<table border="1" cellpadding="4" cellspacing="0" summary="">
+<colgroup span="6"><col span="2" align="left" /><col span="3" align="right" /><col align="left" /></colgroup>
+<tr><td colspan="2">&nbsp;</td><th>Field.</th><th>Inclination of <br />section in <br /> regard to <br />long axis.</th><th>Ratio of<br /> length to <br />clear width.</th><th>Fig.</th></tr>
+<tr><td colspan="2" align="left">I. THE OLD POLARISING PRISMS.</td><td>�</td><td>�</td><td colspan="2">&nbsp;</td></tr>
+<tr><td colspan="2"><span class="indlist">1. Nicol's prism.</span></td><td>29</td><td>22</td><td>3.28</td><td>1</td></tr>
+<tr><td colspan="6"><span class="indlist">2. Shortened Nicol prism&mdash;</span></td></tr>
+<tr><td rowspan="2">&nbsp;</td><td><i>a.</i> Cemented with Canada balsam.</td><td>13</td><td>25</td><td>2.83</td><td>2</td></tr>
+<tr><td><i>b.</i> Cemented with copaiba balsam.</td><td>24</td><td>25</td><td>2.83</td><td>2</td></tr>
+<tr><td colspan="6"><span class="indlist">3. Nicol with perpendicular ends&mdash;</span></td></tr>
+<tr><td rowspan="2">&nbsp;</td><td><i>a.</i> With Canada balsam.</td><td>20</td><td>15</td><td>3.73</td><td>3</td></tr>
+<tr><td><i>b.</i> With cement of index <br />of refraction of 1.525.</td><td>27</td><td>15</td><td>3.73</td><td>3</td></tr>
+<tr><td colspan="2"><span class="indlist">4. Foucault's prism.</span></td><td>8</td><td>40</td><td>1.528</td><td>4</td></tr>
+<tr><td colspan="6"><span class="indlist">5. Hartnack's prism&mdash;</span></td></tr>
+<tr><td rowspan="4">&nbsp;</td><td><i>a.</i> Original form.</td><td>35</td><td>15.9</td><td>3.51</td><td>5<i>a</i><i>b</i></td></tr>
+<tr><td><i>b.</i> With largest field.</td><td>41.9</td><td>13.9</td><td>4.04</td><td>5<i>a</i><i>a</i></td></tr>
+<tr><td><i>c.</i> With field of 30�.</td><td>30</td><td>17.4</td><td>3.19</td><td>5<i>a</i><i>c</i></td></tr>
+<tr><td><i>d.</i> With field of 20�.</td><td>20</td><td>20.3</td><td>2.70</td><td>5<i>a</i><i>d</i></td></tr>
+<tr><td colspan="2"><span class="indlist">6. Glan's prism.</span></td><td>7.9</td><td>50.3</td><td>0.831</td><td>6</td></tr>
+<tr><td colspan="6" align="left">II. THE NEW POLARISING PRISM.</td></tr>
+<tr><td><span class="indlist">1. With calc-spar:</span></td><td>largest field.</td><td>44</td><td>13.2</td><td>4.26</td><td>5<i>a</i><i>a</i></td></tr>
+<tr><td><span class="indlist">2. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&quot;</span></td><td>field of 30�.</td><td>30</td><td>17.4</td><td>3.19</td><td>5<i>a</i><i>c</i></td></tr>
+<tr><td><span class="indlist">3. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&quot;</span></td><td>field of 20�.</td><td>20</td><td>20.3</td><td>2.70</td><td>5<i>a</i><i>d</i></td></tr>
+<tr><td><span class="indlist">4. With nitrate of soda:</span></td><td>largest field.</td><td>54</td><td>16.7</td><td>3.53</td><td>7<i>a</i><i>a</i></td></tr>
+<tr><td><span class="indlist">5. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&quot;</span></td><td>field of 30�.</td><td>30</td><td>24</td><td>2.25</td><td>7<i>a</i><i>b</i></td></tr>
+<tr><td><span class="indlist">6. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&quot;</span></td><td>field of 20�.</td><td>20</td><td>27</td><td>1.96</td><td>7<i>a</i><i>c</i></td></tr>
+</table></div>
+
+
+<p>As an analyzing prism of about 6 mm. clear width, and 13.5 mm. long,
+the new prism is stated by its inventor to be of the most essential
+service, and it would certainly appear that the arrangement is rather
+better adapted for small prisms than for those of considerable size.
+Any means by which a beam of polarized light of large diameter&mdash;say 3
+to 3� inches&mdash;could be obtained with all the convenience of a Nicol
+would be a real advance, for spar of sufficient size and purity for
+such a purpose has become so scarce and therefore so valuable that
+large prisms are difficult to procure at all. So far as an analyzer is
+concerned, the experience of the writer of this notice would lead to
+the opinion that improvements are to be looked for rather in the way
+of the discovery of an artificial crystal which absorbs one of the
+polarized rays than by further modifications depending upon total
+reflection. The researches of Dr. Herapath on iodosulphate of quinine
+(<i>Phil. Mag.</i>, March, 1852, 161, and November, 1853, 346) are in this
+direction; but crystals of the so-called herapathite require great
+manipulative skill for their production. If these could be readily
+obtained of sufficient size, they would be invaluable as analyzers.</p>
+
+<p>This opinion is supported by the existence of an inconvenience which
+attends every form of analyzing prism. It is frequently, and
+especially in projecting apparatus, required to be placed at the focus
+of a system of lenses, so that the rays may cross in the interior of
+the prism. This is an unfavorable position for a prismatic analyzer,
+and in the case of a powerful beam of light, such as that from the
+electric arc, the crossing of the rays within the prism is not
+unattended with danger to the cementing substance, and to the surfaces
+in contact with it.</p>
+
+<p class="signature">PHILIP R. SLEEMAN.</p>
+
+<hr />
+
+
+
+
+<h2><a name="art03" id="art03"></a>ZIRCON.</h2>
+
+<h3>By F. STOLBA.</h3>
+
+
+<p>Finely ground zircon is quickly rendered soluble if fused with a
+mixture of potassium borofluoride and potassium carbonate. The author
+takes two parts of the former to three of the latter, and prepares an
+intimate, finely divided mixture, which is kept ready for use.</p>
+
+<p>Of this mixture four parts are taken to one of zircon, thoroughly
+mixed, and melted in a platinum crucible at a red heat. The mass fuses
+readily, froths at first and gives off bubbles of gas, and flows then
+quietly, forming a very fluid melt. If the zircon is finely ground, 15
+minutes are sufficient for this operation. The loss of weight is 16
+per cent., and is not notably increased on prolonged fusion. It
+corresponds approximately to the weight of the carbonic anhydride
+present in the potassium carbonate.</p>
+
+<p>As pungent vapors are given off during fusion, the operation should be
+conducted under a draught hood. The activity of the mixture in
+attacking zircon appears from the following experiment: Two zircon
+crystals, each weighing � grm., were introduced into the melted
+mixture and subjected to prolonged heat. In a short time they
+decreased perceptibly in size; each of them broke up into two
+fragments, and within an hour they were entirely dissolved. The melted
+mass is poured upon a dry metal plate, and when congealed is thrown
+into water. It is at once intersected with a number of fissures, which
+facilitate pulverization. This process is the more necessary as the
+unbroken mass is very slowly attacked by water even on prolonged
+boiling. The powder <a name="Page_7043" id="Page_7043"></a>is boiled in a large quantity of water so as to
+remove everything soluble. There is obtained a faintly alkaline
+solution and a sediment insoluble in water. From the filtrate alkalies
+throw down zirconium hydroxide, free from iron.</p>
+
+<p>The portion insoluble in water is readily dissolved in hydrofluoric
+acid, and is converted into zircon potassium fluoride. The chief bulk
+of the zirconium is found in the aqueous solution in the state of
+double fluorides. The platinum crucible is not in the least attacked
+during melting. On the contrary, dirty platinum crucibles may be
+advantageously cleaned by melting in them a little of the above
+mentioned mixture.</p>
+
+<p>If finely divided zircon is boiled for a long time with caustic lye,
+it is perceptibly attacked. It is very probable that in this manner
+zircon might be entirely dissolved under a pressure of 10 atmospheres.</p>
+
+<p>Potassium borofluoride may be readily prepared from cryolite.
+Crucibles of nickel seem especially well adapted for the fusion of
+zircon in caustic alkalies.&mdash;<i>Ber. B&oelig;hm. Gesell. Wissenschaft;
+Chem. News</i>.</p>
+
+<hr />
+
+
+
+
+<h2><a name="art04" id="art04"></a>A PROCESS FOR MAKING WROUGHT IRON DIRECT FROM THE ORE.<a name="FNanchor_5" id="FNanchor_5"></a><a href="#Footnote_5"><sup>1</sup></a></h2>
+
+<p>The numerous direct processes which have been patented and brought
+before the iron masters of the world, differ materially from that now
+introduced by Mr. Wilson. After a careful examination of his process,
+I am convinced that Mr. Wilson has succeeded in producing good blooms
+from iron ore, and I think that I am able to point out theoretically
+the chief reasons of the success of his method.</p>
+
+<p>Without going deeply into the history of the metal, I may mention the
+well known fact that wrought iron was extensively used in almost all
+quarters of the globe, before pig or cast iron was ever produced.
+Without entering into the details of the processes by which this
+wrought iron was made, it suffices for my present purpose to say that
+they were crude, wasteful, and expensive, so that they can be employed
+to-day only in a very few localities favored with good and cheap ore,
+fuel, and labor.</p>
+
+<p>The construction of larger furnaces and the employment of higher
+temperatures led to the production of a highly carbonized, fusible
+metal, without any special design on the part of the manufacturers in
+producing it. This pig iron, however, could be used only for a few
+purposes for which metallic iron was needed; but it was produced
+cheaply and with little loss of metal, and the attempt to decarbonize
+this product and bring it into a state in which it could be hammered
+and welded was soon successfully made. This process of decarbonization,
+or some modification of it, has successfully held the field against
+all so-called, direct processes up to the present time. Why? Because
+the old fashioned bloomeries and Catalan forges could produce blooms
+only at a high cost, and because the new processes introduced failed
+to turn out good blooms. Those produced were invariably &quot;red short,&quot;
+that is, they contained unreduced oxide of iron, which prevented the
+contact of the metallic particles, and rendered the welding together
+of these particles to form a solid bloom impossible.</p>
+
+<p>The process of puddling cast iron, and transforming it by
+decarbonization into wrought iron, has, as everybody knows, been in
+successful practical operation for many years, and the direct process
+referred to so closely resembles this, that a short description of the
+theory of puddling is not out of place here.</p>
+
+<p>The material operated on in puddling is iron containing from 2� to 4
+per cent. of carbon. During the first stage of the process this iron
+is melted down to a fluid bath in the bottom of a reverberatory
+furnace. Then the oxidation of the carbon contained in the iron
+commences, and at the same time a fluid, basic cinder, or slag, is
+produced, which covers a portion of the surface of the metal bath, and
+prevents too hasty oxidation. This slag results from the union of
+oxides of iron with the sand adhering to the pigs, and the silica
+resulting from the oxidation of the silicon contained in the iron.</p>
+
+<p>This cinder now plays a very important part in the process. It takes
+up the oxides of iron formed by the contact of the oxidizing flame
+with the exposed portion of the metal bath, and at the same time the
+carbon of the iron, coming in contact with the under surface of the
+cinder covering, where it is protected from oxidizing influences,
+reduces these oxides from the cinder and restores them to the bath in
+metallic form. This alternate oxidation of exposed metal, and its
+reduction by the carbon of the cast iron, continues till the carbon is
+nearly exhausted, when the iron assumes a pasty condition, or &quot;comes
+to nature,&quot; as the puddlers call this change. The charge is then
+worked up into balls, and removed for treatment in the squeezer, and
+then hammered or rolled. In the Wilson process the conditions which we
+have noted in the puddling operation are very closely approximated.
+Iron ore reduced to a coarse sand is mixed with the proper proportion
+of charcoal or coke dust, and the mixture fed into upright retorts
+placed in the chimney of the puddling furnace. By exposure for 24
+hours to the heat of the waste gases from the furnace, in the presence
+of solid carbon, a considerable portion of the oxygen of the ore is
+removed, but little or no metallic iron is formed. The ore is then
+drawn from the deoxidizer into the rear or second hearth of the
+puddling furnace, situated below it, where it is exposed for 20
+minutes to a much higher temperature than that of the deoxidizer. Here
+the presence of the solid carbon, mixed with the ore, prevents any
+oxidizing action, and the temperature of the mass is raised to a point
+at which the cinder begins to form. Then the charge is carried forward
+by the workmen to the front hearth, in which the temperature of a
+puddling furnace prevails. Here the cinder melts, and at the same
+time the solid carbon reacts on the oxygen remaining combined with the
+ore, and forms metallic iron; but by this time the molten cinder is
+present to prevent undue oxidation of the metal formed, and solid
+carbon is still present in the mixture to play the same role, of
+reducing protoxide of iron from the cinder, as the carbon of the cast
+iron does in the ordinary puddling process. I have said that the cast
+iron used as the material for puddling contains about 3 per cent. of
+carbon; but in this process sufficient carbon is added to effect the
+reduction of the ore to a metallic state, and leave enough in the mass
+to play the part of the carbon of the cast iron when the metallic
+stage has been reached.</p>
+
+<p>It would be interesting to compare the Wilson with the numerous other
+direct processes to which allusion has already been made, but there
+have been so many of them, and the data concerning them are so
+incomplete, that this is impossible. Two processes, however, the Blair
+and the Siemens, have attracted sufficient attention, and are
+sufficiently modern to deserve notice. In the Blair process a metallic
+iron sponge was made from the ore in a closed retort, this sponge
+cooled down in receptacles from which the air was excluded, to the
+temperature of the atmosphere, then charged into a puddling furnace
+and heated for working. In this way (and the same plan essentially has
+been followed by other inventors), the metallic iron, in the finest
+possible state of subdivision, is subjected to the more or less
+oxidizing influences of the flame, without liquid slag to save it from
+oxidation, and with no carbon present to again reduce the iron oxides
+from the cinder after it is formed. The loss of metal is consequently
+very large, but oxides of iron being left in the metal the blooms are
+invariably &quot;red short.&quot;</p>
+
+<p>In the Siemens process pieces of ore of the size of beans or peas,
+mixed with lime or other fluxing material, form the charge, which is
+introduced into a rotating furnace; and when this charge has become
+heated to a bright-red heat, small coal of uniform size is added in
+sufficient quantity to effect the reduction of the ore.</p>
+
+<p>The size of the pieces of the material employed prevents the intimate
+mixture of the particles of iron with the particles of carbon, and
+hence we would, on theoretical grounds, anticipate just what practice
+has proved, viz., that the reduction is incomplete, and the resulting
+metal being charged with oxides is red-short. In practice, blooms made
+by this process have been so red-short that they could not be hammered
+at all.</p>
+
+<p>It would be impracticable in this process to employ ore and carbon in
+as fine particles as Wilson does, as a very large portion of the
+charge would be carried off by the draught, and a sticking of the
+material to the sides of the rotating furnace could scarcely be
+avoided. I do not imagine that a division of the material into
+anything like the supposed size of molecules is necessary; we know
+that the graphitic carbon in the pig-iron employed in puddling is not
+so finely divided, but it is much smaller particles than bean or pea
+size, and by approximating the size of the graphite particles in pig
+iron, Wilson has succeeded in obtaining good results.</p>
+
+<p>If we examine the utilization of the heat developed by the combustion
+of a given quantity of coal in this process, and compare it with the
+result of the combustion of an equivalent amount of fuel in a blast
+furnace, we shall soon see the theoretical economy of the process. The
+coal is burned on the grate of the puddling-furnace, to carbonic acid,
+and the flame is more fully utilized than in an ordinary
+puddling-furnace, for besides the ordinary hearth there is the second
+or rear hearth, where additional heat is taken up, and then the
+products of combustion are further utilized in heating the retorts in
+which the ore is partly reduced. After this the heat is still further
+utilized by passing it under the boilers for the generation of steam,
+and the heat lost in the gases, when they finally escape, is very
+small. In a blast furnace the carbon is at first burned only to
+carbonic oxide, and the products of combustion issue mainly in this
+form from the top of the furnace. Then a portion of the heat resulting
+from the subsequent burning of these gases is pretty well utilized in
+making steam to supply the power required about the works, but the
+rest of the gas can only be utilized for heating the blast, and here
+there is an enormous waste, the amount of heat returned to the furnace
+by the heated blast being very small in proportion to the amount
+generated by the burning of that portion of carbonic oxide expended in
+heating it, and the gases escape from both the hot-blast and the
+boilers at a high temperature.</p>
+
+<p>In the direct process under consideration the fuel burned is more
+completely utilized than in the puddling process, to which the cast
+iron from the blast furnace is subjected to convert it into wrought
+iron.</p>
+
+<p>The economy claimed for this process, over the blast furnace and
+puddling practice for the production of wrought iron, is that nearly
+all the fuel used in the puddling operation is saved, and that with
+about the same amount of fuel used in the blast furnace to produce a
+ton of pig iron, a ton of wrought iron blooms can be made. I had no
+opportunity of weighing the charges of ore and coal used, but I saw
+the process in actual operation at Rockaway, N.J. The iron produced
+was hammered up into good solid blooms, containing but little cinder.
+The muck-bar made from the blooms was fibrous in fracture, and showed
+every appearance of good iron. I am informed by the manager of the
+Sanderson Brothers' steel works, at Syracuse, N.Y., that they
+purchased blooms made by the Wilson process in 1881-1882, that <i>none</i>
+of them showed red-shortness, and that they discontinued their use
+only on account of the injurious action of the titanium they contained
+on the melting pots. These blooms were made from magnetic sands from
+the Long Island and Connecticut coasts.</p>
+
+<p class="ctr"><a href="./images/13a.png"><img src="./images/13a_th.png" alt=" NEW PROCESS FOR MAKING WROUGHT IRON FROM THE ORE." /></a><br /> NEW PROCESS FOR MAKING WROUGHT IRON FROM THE ORE.</p>
+
+<p>The drawing given shows the construction of the furnace employed. I
+quote from the published description:</p>
+
+<div class="indlist">
+<p> &quot;The upper part, or deoxidizer, is supported on a strong
+    mantel plate resting on four cast iron columns.</p>
+
+<p>    &quot;The retorts and flues are made entirely of fire-brick, from
+    special patterns. The outside is protected by a wrought iron
+    jacket made of No. 14 iron. The puddling furnace is of the
+    ordinary construction, except in the working bottom, which is
+    made longer to accommodate two charges of ore, and thus
+    utilize more of the waste heat in reducing the ore to metallic
+    iron.</p>
+
+<p>    &quot;The operation of the furnace is as follows: The pulverized
+    ore is mixed with 20 per cent. of pulverized charcoal or coke,
+    and is fed into an elevator which discharges into the hopper
+    on the deoxidizer leading into the retorts marked C. These
+    retorts are proportioned so that they will hold ore enough to
+    run the puddling furnace 24 hours, the time required for
+    perfect deoxidation. After the retorts are filled, a fire is
+    started in the furnace, and the products of combustion pass up
+    through the main flue, or well, B, where they are deflected by
+    the arch, and pass out through suitable openings, as indicated
+    by arrows, into the down-takes marked<a name="Page_7044" id="Page_7044"></a> E, and out through an
+    annular flue, where they are passed under a boiler.</p>
+
+<p>    &quot;It will be noticed that the ore is exposed to the waste heat
+    on three sides of the retorts, and owing to the great surface
+    so exposed, the ore is very thoroughly deoxidized, and reduced
+    in the retorts before it is introduced into the puddling
+    furnace for final reduction. The curved cast iron pipes marked
+    D are provided with slides, and are for the purpose of
+    introducing the deoxidized ore into the second bottom of the
+    furnace. As before stated, the furnace is intended to
+    accommodate two charges of ore, and as fast as it is balled up
+    and taken out of the working bottom, the charge remaining in
+    the second bottom is worked up in the place occupied by the
+    first charge, and a <i>new</i> charge is introduced. As fast as the
+    ore is drawn out from the retorts the elevator supplies a new
+    lot, so that the retorts are always filled, thus making the
+    process continuous.&quot;</p>
+</div>
+
+<p>The temperature of the charge in the deoxidizer is from 800� to 1,000�
+F.&mdash;<i>Amer. Engineer.</i></p>
+
+
+<div class="note"><p><a name="Footnote_5" id="Footnote_5"></a><a href="#FNanchor_5">[1]</a></p>
+<p>A paper read at the Cincinnati Meeting of the American
+Institute of Mining Engineers, by Willard P. Ward, A.M., M.E.,
+February, 1884.</p></div>
+
+<hr />
+
+
+<h2><a name="art05" id="art05"></a>SOME REMARKS ON THE DETERMINATION OF HARDNESS IN WATERS.</h2>
+
+<h3>By HERBERT JACKSON.</h3>
+
+
+<p>Having had occasion some short time ago to examine a hard water which
+owed half its hardness to salts of magnesium, I noticed that the soap
+test, applied in the usual way, gave a result which differed very much
+from that obtained by the quantitative estimation of calcium and
+magnesium. A perfectly normal lather was obtained when soap had been
+added in quantities sufficient to neutralize 14� of hardness, whereas
+the water contained salts of calcium and magnesium equivalent, on
+Clark's scale, to a hardness of 27�.</p>
+
+<p>Although I was aware that similar observations had been made before, I
+thought that it might be useful to determine the conditions under
+which the soap test could not be depended upon for reliable results.</p>
+
+<p>I found with waters containing calcium or magnesium alone that,
+whenever salts of either of these metals were in solution in
+quantities sufficient to give 23� of hardness on Clark's scale, no
+dependence could be placed upon the results given by the soap test. In
+the case of waters containing salts of both calcium and magnesium, I
+found that if the salts of the latter metal were in solution in
+quantities sufficient to give more than 10� of hardness, no evidence
+could be obtained of their presence so long as the salts of calcium in
+the same water exceeded 6�; in such a case a perfect and permanent
+lather was produced when soap had been added equivalent to 7� of
+hardness.</p>
+
+<p>If any water be diluted so as to reduce the proportions of the salts
+of calcium and magnesium below those stated above, perfectly reliable
+results will of course be obtained.</p>
+
+<p>Instead of dilution I found that heating the water to about 70� C. was
+sufficient to cause a complete reaction between the soap and the salts
+of calcium and magnesium, even if these were present in far larger
+quantities than any given here.</p>
+
+<p>The experiments so far had all been made with a solution of Castile
+soap of the strength suggested by Mr. Wanklyn in his book on &quot;Water
+Analysis.&quot; My attention was next directed to the use of any one of the
+compounds of which such a soap is composed. I commenced with sodium
+oleate, and found that by employing this substance in a moderately
+pure condition, perfectly reliable results could be obtained in very
+hard waters without the trouble of either diluting or heating. I was
+unable to try sodium stearate directly because of the slight
+solubility of this substance in cold water or dilute alcohol; but I
+found that a mixture of sodium oleate and stearate behaved in exactly
+the same manner as the Castile soap.</p>
+
+<p>I am not prepared at present to state the exact reaction which takes
+place between salts of calcium and magnesium and a compound soap
+containing sodium oleate and stearate. I publish these results because
+I have not noticed anywhere the fact that some waters show a greater
+hardness with soap when their temperatures approach the boiling point
+than they do at the average temperature of the air, it being, I
+believe, the ordinary impression that cold water wastes more soap than
+hot water before a good and useful lather can be obtained, whereas
+with very many waters the case is quite the reverse. Neither am I
+aware at present whether it is well known that the use of sodium
+oleate unmixed with sodium stearate dispenses with the process of
+dilution even in very hard waters.&mdash;<i>Chem. News.</i></p>
+
+<hr />
+
+
+<h2><a name="art18" id="art18"></a>THE DENSITY AND PRESSURE OF DETONATING GAS MIXTURES.</h2>
+
+
+<p>MM. Berthelot and Vielle have recently been studying the influence of
+the density of detonating gaseous mixtures upon the pressure
+developed. The measure of pressure developed by the same gaseous
+system, taken under two initial states of different density to which
+the same quantity of heat is communicated, is an important matter in
+thermodynamics. If the pressures vary in the same ratio as the
+densities, we may conclude, independently of all special hypotheses on
+the laws of gases, first, that the specific heat of the system is
+independent of its density (that is to say, of its initial pressure),
+and depends only on the absolute temperature, whatever that may mean;
+and secondly, that the relative variation of the pressure at constant
+volume, produced by the introduction of a determinate quantity of
+heat, is also independent of the pressure, and a function only of the
+temperature. Lastly, the pressure itself will vary proportionally with
+the absolute temperature, as defined by the theory of a perfect gas,
+and will serve to determine it. MM. Berthelot and Vielle operated with
+a bomb, at first kept at ordinary temperatures in the air, and
+afterward heated in an oil bath to 153 deg. Cent. They also employed
+isomeric mixtures of the gases; methylic ether, cyanogen, hydrogen,
+acetylene, and other gases were experimented upon, and the general
+conclusions are as follows: 1. The same quantity of heat being
+furnished to a gaseous system, the pressure of the system varies
+proportionally to the density of the system. 2. The specific heat of
+the gas is sensibly independent of the density as well toward very
+high temperatures as about deg. Cent. This is all true for densities
+near to those that the gas possesses cold under normal pressure, and
+which varied in the experiment to double the original value. 3. The
+pressure increases with the quantity of heat furnished to the same
+system. 4. The apparent specific heat increases parallel with this
+quantity of heat. These conclusions are independent of all hypotheses
+on the nature and laws of gases, and were simply drawn from the
+experiments in question.</p>
+
+<hr />
+
+
+<h2><a name="art29" id="art29"></a>TURKISH BATHS FOR HORSES.</h2>
+
+<p>The Turkish bath has become an established institution in this
+country; men of all classes now use it for sanitary as well as
+remedial purposes. Athletes of various descriptions find it invaluable
+in &quot;training,&quot; and all the distinguished jockeys and light weights
+keep themselves in condition by its use.</p>
+
+<p>It was thought probable that what was good for man might also be good
+for the horse, and the fact has been proved. Messrs. Pickford, the
+eminent carriers, in their hospital for horses at Finchley, have had a
+bath in operation over eleven years, and find the horses derive great
+benefit from its use. The bath is put in operation three days a week,
+and is administered to over twenty horses in this time. The value of
+the bath having been thus proved, it is rather strange that it has not
+been more generally adopted by the large carrying firms. However, the
+Great Northern Railway Company at their new hospital for horses at
+Totteridge, are erecting a very complete Turkish bath. It consists of
+three rooms. First, a large wash room or grooming room, from which is
+entered the first hot room, or tepidarium, from 140� to 150� Fahr.;
+from this room, the horse, after being thoroughly acclimated, can, if
+necessary, pass to the hottest room, or calidarium, from 160� to 170�
+Fahr., and without any turning round can pass on into the grooming and
+washing room again. This last room is slightly heated from the two
+other rooms, and in each are stocks in which the animal can he
+fastened if required. The heating is done most economically by
+Constantine's convoluted stove, and thorough ventilation is secured
+from the large volume of hot air constantly supplied, which passes
+through the baths, and as it becomes vitiated is drawn off by
+specially designed outlets. The wash room is supplied with hot and
+cold water, which can, of course, be mixed to any required
+temperature.&mdash;<i>Building News.</i></p>
+
+<p class="ctr"><img src="./images/14a.png" alt="Diagram of Horse Bath" /></p>
+
+
+<hr />
+
+
+<h2><a name="art28" id="art28"></a>MIRYACHIT, A NEWLY DESCRIBED DISEASE OF THE NERVOUS SYSTEM, AND
+ITS ANALOGUES.<a name="FNanchor_6" id="FNanchor_6"></a><a href="#Footnote_6"><sup>1</sup></a></h2>
+
+<h3>By WILLIAM A. HAMMOND, M.D., Surgeon-General, U.S. Army (Retired
+List); Professor of Diseases of the Mind and Nervous System in the New
+York Post-Graduate Medical School and Hospital.</h3>
+
+
+<p>In a very interesting account of a journey from the Pacific Ocean
+through Asia to the United States, by Lieutenant B.H. Buckingham and
+Ensigns George C. Foulk and Walter McLean,<a name="FNanchor_7" id="FNanchor_7"></a><a href="#Footnote_7"><sup>2</sup></a> United States navy, I
+find an affection of the nervous system described which, on account of
+its remarkable characteristics, as well as by reason of certain known
+analogies, I think should be brought to the special notice of the
+medical profession. I quote from the work referred to, the following
+account of this disease. The party is on the Ussuri River not far from
+its junction with the Amur in Eastern Siberia: &quot;While we were walking
+on the bank here we observed our messmate, the captain of the general
+staff (of the Russian army), approach the steward of the boat
+suddenly, and, without any apparent reason or remark, clap his hands
+before his face; instantly the steward clapped <i>his</i> hands in the same
+manner, put on an angry look, and passed on. The incident was somewhat
+curious, as it involved a degree of familiarity with the steward
+hardly to have been expected. After this we observed a number of queer
+performances of the steward, and finally comprehended the situation.
+It seemed that he was afflicted with a peculiar mental or nervous
+disease, which forced him to imitate everything suddenly presented to
+his senses. Thus, when the captain slapped the paddle-box suddenly in
+the presence of the steward, the latter instantly gave it a similar
+thump; or, if any noise were made suddenly, he seemed compelled
+against his will to imitate it instantly, and with remarkable
+accuracy. To annoy him, some of the passengers imitated pigs grunting,
+or called out absurd names; others clapped their hands and shouted,
+jumped, or threw their hats on the deck suddenly, and the poor
+steward, suddenly startled, would echo them all precisely, and
+sometimes several consecutively. Frequently he would expostulate,
+begging people not to startle him, and again would grow furiously
+angry, but even in the midst of his passion he would helplessly
+imitate some ridiculous shout or motion directed at him by his
+pitiless tormenters. Frequently he shut himself up in his pantry,
+which was without windows, and locked the door, but even there he
+could be heard answering the grunts, shouts, or pounds on the bulkhead
+outside. He was a man of middle age, fair physique, rather intelligent
+in facial expression, and without the slightest indication in
+appearance of his disability. As we descended the bank to go on board
+the steamer, some one gave a loud shout and threw his cap on the
+ground; looking about for the steward, for the shout was evidently
+made for his benefit, we saw him violently throw his cap, with a
+shout, into a chicken-coop, into which he was about to put the result
+of his foraging expedition among the houses of the stanitza.</p>
+
+<p>&quot;We afterward witnessed an incident which illustrated the extent of
+his disability. The captain of the steamer, running up to him,
+suddenly clapping his hands at the same time, accidentally slipped and
+fell hard on the deck; without having been touched by the captain, the
+steward instantly clapped his bands and shouted, and then, in
+powerless imitation, he too fell as hard and almost precisely in the
+same manner and position as the captain. In speaking of the steward's
+disorder, the captain of the general staff stated that it was not
+uncommon in Siberia; that he had seen a number of cases of it, and
+that it was commonest about Yakutsk, where the winter cold is extreme.
+Both sexes were subject to it, but men much less than women. It was
+known to Russians by the name of 'miryachit'&quot;.</p>
+
+<p>So far as I am aware&mdash;and I have looked carefully through several
+books of travel in Siberia&mdash;no account of this curious disease has
+been hitherto published.</p>
+
+<p>The description given by the naval officers at once, however, brings
+to mind the remarks made by the late Dr. George M. Beard, before the
+meeting of the American Neurological Association in 1880, relative to
+the &quot;Jumpers&quot; or &quot;Jumping Frenchmen&quot; of Maine and northern New
+Hampshire.<a name="FNanchor_8" id="FNanchor_8"></a><a href="#Footnote_8"><sup>3</sup></a></p>
+
+<p>In June, 1880, Dr. Beard visited Moosehead Lake, found the &quot;Jumpers,&quot;
+and experimented with them. He ascertained that whatever order was
+given them was at once obeyed. Thus, one of the jumpers who was
+sitting in a chair with a knife in his hand was told to throw it, and
+he threw it quickly, so that it stuck in a beam opposite; at the same
+time he repeated the order to throw it with a cry of alarm not unlike
+that of hysteria or epilepsy. He also threw away his pipe, which he
+was filling with tobacco, when he was slapped upon the shoulder. Two
+jumpers standing near each other were told to strike, and they struck
+each other very forcibly. One jumper, when standing by a window, was
+suddenly commanded by a person on the other side of the window to
+jump, and he jumped up half a foot from the floor, repeating the
+order. When the commands are uttered in a quick, loud voice, the
+jumper repeats the order. When told to strike he strikes, when told to
+throw he throws whatever he may happen to have in his hand. Dr. Beard
+tried this power of repetition with the first part of the first line
+of Virgil's &quot;&AElig;neid&quot; and the first part of the first line of Homer's
+&quot;Iliad,&quot; and out-of-the-way words of the English language with which
+the jumper could not be familiar, and he repeated or echoed the sound
+of the word as it came to him in a quick, sharp voice, at the same
+time he jumped, or struck, or threw, or raised his shoulders, or made
+some other violent muscular motion. They could not help repeating the
+word or sound that came from the person that ordered them, any more
+than they could help striking, dropping, throwing, jumping, or
+starting; all of these phenomena were indeed but parts of the general
+condition known as jumping. It was not necessary that the sound should
+come from a human being; any sudden or unexpected noise, as the
+explosion of a gun or pistol, the falling of a window, or the slamming
+of a door&mdash;provided it was unexpected and loud enough&mdash;would cause
+these jumpers to exhibit some one or all of these phenomena. One of
+these jumpers came very near cutting his throat, while shaving, on
+hearing a door slam. They had been known to strike their fists against a
+red-hot stove, to jump into the fire and into water. They could not
+help striking their best friend if near them when ordered. The noise
+of a steam whistle was especially obnoxious to them. One of these
+jumpers, when taking some bromide of sodium in a tumbler, was told to
+throw it, and he dashed the tumbler upon the floor. It was dangerous
+to startle them in any way when they had an ax or an knife in their
+hands. All of the jumpers agreed that it tired them to be jumped, and
+they dreaded it, but they were constantly annoyed by their companions.</p>
+
+<p>From this description it will at once, I think, be perceived that
+there are striking analogies between &quot;miryachit&quot; and this disorder of
+the &quot;Jumping Frenchmen&quot; of Maine. Indeed, it appears to me that, if
+the two affections were carefully studied, it would be found that they
+were identical, or that, at any rate, the phenomena of the one could
+readily be developed into those of the others. It is not stated that
+the subjects of miryachit do what they are told to do. They require an
+example to reach their brains through the sense of sight or that of
+hearing, whereas the &quot;Jumpers&quot; do not apparently perform an act which
+is executed before them, but they require a command. It seems,
+however, that a &quot;Jumper&quot; starts whenever any sudden noise reaches his
+ears.</p>
+
+<p>In both classes of cases a suggestion of some kind is required, and
+then the act takes place independently of the will. There is another
+analogous condition known by the Germans as <i>Schlaftrunkenheit</i>, and
+to English and American neurologists as somnolentia, or
+sleep-drunkenness. In this state an individual, on being suddenly
+awakened, commits some incongruous act of violence, ofttimes a murder.
+Sometimes this appears to be excited by a dream, but in others no such
+cause could be discovered.</p>
+
+<p>Thus, a sentry fell asleep during his watch, and, being suddenly
+aroused by the officer in command, attacked the latter with his sword,
+and would have killed him but for the interposition of the bystanders.
+The result of the medical examination was that the act was
+involuntary, being the result of a violent confusion of mind
+consequent upon the sudden awaking from a profound sleep. Other cases
+are cited by Wharton and Stille in their work on medical
+jurisprudence, by Hoffbauer, and by myself in &quot;Sleep and its
+Derangements.&quot;</p>
+
+<p>The following cases among others have occurred in my own experience:</p>
+
+<p>A gentleman was roused one night by his wife, who heard the
+street-door bell ring. He got up, and, without paying attention to
+what she said, dragged the sheets off of the bed, tore them hurriedly
+into strips, and proceeded to tie the pieces together. She finally
+succeeded in bringing him to himself, when he said he had thought the
+house was on fire, and he was providing means for their escape. He did
+not recollect having had any dream of the kind, but was under the
+impression that the idea had occurred to him at the instant of his
+awaking.</p>
+
+<p>Another was suddenly aroused from a sound sleep by the slamming of a
+window-shutter by the wind. He sprang instantly from his bed, and,
+seizing a chair that was near, hurled it with all his strength against
+the window. The noise of the breaking of glass fully awakened him. He
+explained that he imagined some one was trying to get into the room
+and had let his pistol fall on the floor, thereby producing the noise
+which had startled him.</p>
+
+<p>In another case a man dreamed that he heard a voice telling him to
+jump out of the window. He at once arose, threw open the sash, and
+jumped to the ground below, fortunately only a distance of about ten
+feet, so that he was not injured beyond receiving a violent shock.
+Such a case as this appears to me to be very similar to those
+described by Dr. Beard in all its essential aspects.</p>
+
+<p>A few years ago I had a gentleman under my charge who would attempt to
+execute any order given him while he was <a name="Page_7045" id="Page_7045"></a>asleep by a person
+whispering into his ear. Thus, if told in this way to shout, he
+shouted as loud as he could; if ordered to get up, he at once jumped
+from the bed; if directed to repeat certain words, he said them, and
+so on.</p>
+
+<p>I am not able to give any certain explanation of the phenomena of
+miryachit or of the &quot;Jumpers,&quot; or of certain of those cases of
+sleep-drunkenness which seem to be of like character. But they all
+appear to be due to the fact a motor impulse is excited by perceptions
+without the necessary concurrence of the volition of the individual to
+cause the discharge. They are, therefore, analogous to reflex actions,
+and especially to certain epileptic paroxysms due to reflex
+irritations. It would seem as though the nerve cells were very much in
+the condition of a package of dynamite or nitro glycerin, in which a
+very slight impression is sufficient to effect a discharge of nerve
+force. They differ, however, from the epileptic paroxysm in the fact
+that the discharge is consonant with the perception&mdash;which is in these
+cases an irritation&mdash;and is hence an apparently logical act, whereas
+in epilepsy the discharge is more violent, is illogical, and does not
+cease with the cessation of the irritation.</p>
+
+<p>Certainly the whole subject is of sufficient importance to demand the
+careful study of competent observers.</p>
+
+<div class="note">
+<p><a name="Footnote_6" id="Footnote_6"></a><a href="#FNanchor_6">[1]</a></p>
+<p>Read before the New York Neurological Society, February
+5, 1884.</p>
+
+<p><a name="Footnote_7" id="Footnote_7"></a><a href="#FNanchor_7">[2]</a></p>
+<p>&quot;Observations upon the Korean Coast, Japanese-Korean
+Ports, and Siberia, made during a journey from the Asiatic Station to
+the United States, through Siberia to Europe, June 3 to September 8,
+1882.&quot; Published by the United States Navy Department, Washington,
+1883, pp. 51.</p>
+
+<p><a name="Footnote_8" id="Footnote_8"></a><a href="#FNanchor_8">[3]</a></p>
+<p>&quot;Journal of Nervous and Mental Diseases,&quot; vol. vii.,
+1880, p. 487.</p></div>
+
+<hr />
+
+<h2><a name="art26" id="art26"></a>THE GUM DISEASE IN TREES.<a name="FNanchor_9" id="FNanchor_9"></a><a href="#Footnote_9"><sup>1</sup></a></h2>
+
+<p>An essay by Dr. Beijerinck, on the contagion of the gum disease in
+plants, lately published by the Royal Academy of Sciences at
+Amsterdam, contains some useful facts. The gum disease (<i>gummosis,
+gum-flux)</i> is only too well known to all who grow peaches, apricots,
+plums, cherries, or other stone fruits. A similar disease produces gum
+arabic, gum tragacanth, and probably many resins and gum resins. It
+shows itself openly in the exudation of thick and sticky or hard and
+dry lumps of gum, which cling on branches of any of these trees where
+they have been cracked or wounded through the bark. Dr. Beijerinck was
+induced to make experimental inoculations of the gum disease by
+suspicions that, like some others observed in plants, it was due to
+bacteria. He ascertained that it is in a high degree contagious, and
+can easily be produced by inserting the gum under the edge of a wound
+through the bark of any of the trees above named. The observation that
+heated or long boiled pieces of gum lose their contagious property
+made it most probable that a living organism was concerned in the
+contagions; and he then found that only those pieces of the gum
+conveyed contagion in which, whether with or without bacteria, there
+were spores of a relatively highly organized fungus, belonging to the
+class of Ascomycetes; and that these spores, inserted by themselves
+under the bark, produced the same pathological changes as did the
+pieces of gum. The fungus thus detected, was examined by Professor
+Oudemans, who ascertained it to be a new species of Coryneum, and has
+named it <i>Coryneum Beijerincki</i>. The inoculation experiments are best
+made by means of incisions through the bark of young branches of
+healthy peach trees or cherry trees, and by slightly raising the cut
+edge of the bark and putting under it little bits of gum from a
+diseased tree of the same kind. In nearly every instance these wounds
+become the seats of acute gum disease, while similar wounds in the
+same or other branches of the same tree, into which no gum is
+inserted, remain healthy, unless, by chance, gum be washed into them
+during rain. The inoculation fails only when the inserted pieces of
+gum contain no Coryneum. By similar inoculations similar diseases can
+be produced in plum, almond, and apricot trees, and with the gum of
+any one of these trees any other can be infected; but of many other
+substances which Beijerinck tried, not one produced any similar
+disease. The inoculation with the gum is commonly followed by the
+death of more or less of the adjacent structures; first of the bark,
+then of the wood. Small branches or leaf stalks thus infected in
+winter, or in many places at the same time, may be completely killed;
+but, in the more instructive experiments the first symptom of the gum
+disease is the appearance of a beautiful red color around the wound.
+It comes out in spots like those which often appear spontaneously on
+the green young branches of peach trees that have the gum disease; and
+in these spots it is usual to find Coryneum stromata or mycelium
+filaments. The color is due to the formation of a red pigment in one
+or more of the layers of the cells of the bark. But in its further
+progress the disease extends beyond the parts at which the Coryneum or
+any structures derived from it can be found; and this extension,
+Beijerinck believes, is due to the production of a fluid of the nature
+of a ferment, produced by the Coryneum, and penetrating the adjacent
+structures. This, acting on the cell walls, the starch granules, and
+other constituents of the cells, transforms them into gum, and even
+changes into gum the Coryneum itself, reminding the observer of the
+self-digestion of a stomach.</p>
+
+<p>In the cells of the cambium, the same fluid penetrating unites with
+the protoplasm, and so alters it that the cells produced from it form,
+not good normal wood, but a morbid parenchymatous structure. The cells
+of this parenchyma, well known among the features of gum disease, are
+cubical or polyhedral, thin walled, and rich in protoplasm. This, in
+its turn, is transformed into gum, such as fills the gum channels and
+other cavities found in wood, and sometimes regarded as gum glands.
+And from this also the new ferment fluid constantly produced, and
+tracking along the tissues of the branches, conveys the Coryneum
+infection beyond the places in which its mycelium can be found.</p>
+
+<div class="note">
+<p><a name="Footnote_9" id="Footnote_9"></a><a href="#FNanchor_9">[1]</a></p>
+<p>Communicated to the <i>Medical Times</i> by Sir James Paget.</p></div>
+
+<hr />
+
+<h2><a name="art27" id="art27"></a>DRINKSTONE PARK.</h2>
+
+<p>Drinkstone has long been distinguished on account of the successful
+cultivation of remarkable plants. It lies some eight miles southeast
+from Bury St. Edmund's, and is the seat of T.H. Powell, Esq. The
+mansion or hall is a large old-fashioned edifice, a large portion of
+its south front being covered by a magnificent specimen of the
+Magnolia grandiflora, not less than 40 feet in height, while other
+portions of its walls are covered with the finest varieties of
+climbing roses and other suitable plants. The surrounding country,
+although somewhat flat, is well wooded, and the soil is a rich loam
+upon a substratum of gravel, and is consequently admirably suited to
+the development of the finer kinds of coniferous and other ornamental
+trees and shrubs, so that the park and grounds contain a fine and well
+selected assortment of such plants.</p>
+
+<p class="ctr"><a href="./images/15a.png"><img src="./images/15a_th.png" alt=" THE SNOWFLAKE, LEUCOJUM VERNUM, AT DRINKSTONE" /></a><br />
+THE SNOWFLAKE, LEUCOJUM VERNUM, AT DRINKSTONE PARK.</p>
+
+<p>Coniferous trees are sometimes considered as out of place in park
+scenery; this, however, does not hold good at Drinkstone, where Mr.
+Powell has been displayed excellent taste in the way of improving the
+landscape and creating a really charming effect by so skillfully
+blending the dressed grounds with the rich greensward of the park
+that it is not easy to tell where the one terminates or the other
+commences.</p>
+
+<p>The park, which covers some 200 acres, including a fine lake over
+eight acres in extent, contains also various large groups or clumps of
+such species as the Sequoia gigantea, Taxodium sempervirens, Cedres
+deodora, Picea douglasii, Pinsapo, etc., interspersed with groups of
+ornamental deciduous trees, producing a warm and very pleasing effect
+at all seasons of the year. Among species which are conspicuous in the
+grounds are fine, well-grown examples of Araucaria imbricata, some 30
+feet high; Cedrus deodara, 60 feet in height; Abies pinsapo, 40 feet;
+and fine specimens of Abies grandis, A. nobilis, and A. nordmanniana,
+etc., together with Abies albertiana or mertensiana, a fine,
+free-growing species; also Libocedrus gigantea, Thuiopsis borealis,
+Thuia lobbii, Juniperus recurva, Taxas adpressa, fine plants; with
+fine golden yews and equally fine examples of the various kinds of
+variegated hollies, etc.</p>
+
+<p class="ctr">
+<a href="./images/15b.png"><img src="images/15b_th.png" width="474" height="400" alt="ODONTOGLOSSUM ROSSI MAJOR VAR. RUBESCENS, AT DRINKSTONE
+PARK." title="" /></a><br />ODONTOGLOSSUM ROSSI MAJOR VAR. RUBESCENS, AT DRINKSTONE
+PARK.</p>
+
+
+<p>Particular attention is here paid to early spring flowers. Drinkstone
+is also celebrated as a fruit growing establishment, more particularly
+as regards the grape vine; the weight and quality of the crops of
+grapes which are annually produced here are very remarkable.&mdash;<i>The
+Gardeners' Chronicle.</i></p>
+
+<hr />
+
+
+
+
+<h2><a name="art06" id="art06"></a>ON THE CHANGES WHICH TAKE PLACE IN THE CONVERSION OF HAY INTO
+ENSILAGE.</h2>
+
+<h3>By FREDK. JAS. LLOYD, F.C.S., Lecturer on Agriculture, King's
+College.</h3>
+
+
+<p>The recently published number of the <i>Royal Agricultural Society's
+Journal</i> contains some information upon the subject of silage which
+appears to me of considerable interest to those chemists who are at
+present investigating the changes which take place in the conversion
+of grass into silage. The data<a name="FNanchor_10" id="FNanchor_10"></a><a href="#Footnote_10"><sup>1</sup></a> are, so far as I know, unique, and
+though the analytical work is not my own, yet it is that of an
+agricultural chemist, Mr. A. Smetham, of Liverpool, whose work I know
+from personal experience to be thoroughly careful and reliable. I have
+therefore no hesitation in basing my remarks upon it.</p>
+
+<p>We have here for the first time an accurate account of the quantity of
+grass put into a silo, of the quantity of silage taken out, and of the
+exact composition both of the grass and resulting silage. I desire
+merely to place myself in the position of, so to speak, a &quot;chemical
+accountant.&quot;</p>
+
+<p>The ensilage has been analyzed at three depths, or rather <a name="Page_7046" id="Page_7046"></a>in three
+layers, the first being 1 foot, the second 1 ft. to 1 ft. 6 in., and
+the third 1 ft. 6 in. to 2 ft. from the bottom of the silo. By
+doubling the figures of the bottom layer analysis, adding these to the
+second and third layer analysis, and dividing by 4, we obtain a fair
+representation of the average composition of the silage taken
+throughout the silo, for by so doing we obtain the average of the
+analyses of each 6-inch layer of silage. The results of the analyses
+are as follows, calculated on the dry matter. The moisture was
+practically the same, being 70.48 per cent, in the grass and 72.97 in
+the silage.</p>
+
+
+<p class="ctr"><i>Composition of Grass and Silage (dried at 100�C.).</i></p>
+
+<div class="ctr">
+<table border="0" width="75%" summary="">
+<colgroup span="3"><col align="left" /><col align="right" span="2" /></colgroup>
+<tr><td></td><th>Grass.</th><th>Ensilage.</th></tr>
+<tr><td>Fat (ether extract)</td><td>2.80</td><td>5.38</td></tr>
+<tr><td>Soluble albuminous compounds</td><td>3.06</td><td>5.98</td></tr>
+<tr><td>Insoluble albuminous compounds</td><td>6.94</td><td>3.77</td></tr>
+<tr><td>Mucilage, sugar, and extractives, etc.</td><td>11.65</td><td>4.98</td></tr>
+<tr><td>Digestible fiber</td><td>36.24</td><td>33.37</td></tr>
+<tr><td>Indigestible woody fiber</td><td>32.33</td><td>31.79</td></tr>
+<tr><td></td><td>&mdash;&mdash;</td><td>&mdash;&mdash;</td></tr>
+<tr><td></td><td>93.02</td><td>85.27</td></tr>
+<tr><td>Soluble mineral matters</td><td>5.24</td><td>12.62</td></tr>
+<tr><td>Insoluble mineral matters</td><td>1.74</td><td>2.11</td></tr>
+<tr><td></td><td>&mdash;&mdash;</td><td>&mdash;&mdash;</td></tr>
+<tr><td></td><td>100.00</td><td>100.00</td></tr>
+</table></div>
+
+<p>The striking difference in the mineral matter of the grass and silage
+I will merely draw attention to; it is not due to the salt added to
+the silage. I may say, however, that other analysts and I myself have
+found similar striking differences. For instance, Prof. Kinch <a name="FNanchor_11" id="FNanchor_11"></a><a href="#Footnote_11"><sup>2</sup></a>
+found in grass 8.50 per cent. mineral matter, in silage 10.10 per
+cent., which, as be points out, is equivalent, to a &quot;loss of about 18
+per cent. of combustible constituents&quot;&mdash;a loss which we have no proof
+of having taken place. In Mr. Smetham's sample the loss would have to
+be 50 per cent., which did not occur, and in fact is not possible.
+What is the explanation?</p>
+
+<p>I am, however, considering now the organic constituents. Calculating
+the percentages of these in the grass and silage, we obtain the
+following figures:</p>
+
+<p class="ctr"><i>Percentage Composition of Organic Compounds.</i></p>
+
+<div class="ctr">
+<table border="0" summary="" width="75%">
+<colgroup span="4"><col align="left" /><col align="right" /><col align="center" /><col align="right" />
+</colgroup>
+<tr><td></td><th>Grass.</th><td></td><th>Ensilage.</th></tr>
+<tr><td>Fat (ether extract)</td><td>3.01</td><td></td><td>6.31</td></tr>
+<tr><td>Soluble albuminous compounds</td><td>8.29</td>
+<td rowspan="2" valign="middle"><span class="large">} 10.75&nbsp;&nbsp;&nbsp; 11.43 {</span></td>
+<td>7.01</td></tr>
+<tr><td>Insoluble albuminous compounds</td><td>7.46</td><td>4.42</td></tr>
+<tr><td>Mucilage, sugar, and extractives</td><td>12.52</td><td></td><td>5.84</td></tr>
+<tr><td>Digestible fiber</td><td>38.96</td><td></td><td>39.14</td></tr>
+<tr><td>Indigestible woody fiber</td><td>34.76</td><td></td><td>37.28</td></tr>
+<tr><td></td><td>&mdash;&mdash;&mdash;</td><td></td><td>&mdash;&mdash;&mdash;</td></tr>
+<tr><td></td><td>100.00</td><td></td><td>100.00</td></tr>
+</table></div>
+
+<p>The difference in the total nitrogen in the grass and silage is equal
+to 0.68 per cent. of albuminoids. Practically it is a matter of
+impossibility that the nitrogen could have increased in the silo, and
+it will be a very safe premise upon which to base any further
+calculations that the total amount of nitrogen in the silage was
+identical with that in the grass. There may have been a loss, but
+that is not yet proved. Arguing then upon the first hypothesis, it is
+evident that 100 parts of the organic matters of silage represent more
+than 100 parts of the organic matter of grass, and by the equation we
+obtain 10.75:11.43 :: 100:106 approximately. If now we calculate the
+composition of 106 parts organic matter of grass, it will represent
+exactly the organic matter which has gone to form 100 parts of that
+present in silage.</p>
+
+<p>The following table gives these results, and also the loss or gain in
+the various constitutents arising from the conversion into silage:</p>
+
+<p class="ctr"><i>Organic Matter.</i></p>
+
+
+<div class="ctr">
+<table border="0" width="75%" summary="">
+<colgroup span="4"><col align="left" /><col span="3" align="right" /></colgroup>
+<tr><td></td><th>In 106 pts.<br />Grass.</th><th>In 100 pts.<br />Silage.</th><th>Loss or<br /> Gain.</th></tr>
+<tr><td>Fat (ether extract)</td><td>3.19</td><td>6.31</td><td>+3.12</td></tr>
+<tr><td>Soluble albuminous compounds</td><td>3.49</td><td>7.01</td><td>+3.52</td></tr>
+<tr><td>Insoluble albuminous compounds</td><td>7.91</td><td>4.42</td><td>-3.49</td></tr>
+<tr><td>Mucilage</td><td>13.27</td><td>5.84</td><td>-7.43</td></tr>
+<tr><td>Digestible Fiber</td><td>41.30</td><td>39.14</td><td>-2.16</td></tr>
+<tr><td>Indigestible woody fiber</td><td>36.84</td><td>37.28</td><td>+0.44</td></tr>
+<tr><td></td><td>&mdash;&mdash;&mdash;</td><td>&mdash;&mdash;&mdash;</td></tr>
+<tr><td></td><td>106.00</td><td>100.00</td></tr>
+</table></div>
+
+<p>These calculations show, provided my reasoning be correct, that the
+chief changes which take place are in the albuminous compounds, which
+has already been pointed out by Professors Voelcker, Kinch, and
+others; and in the starch, gum, mucilage, sugar, and those numerous
+bodies termed extractives, which was to be expected. But they show
+most conclusively that the &quot;decrease in the amount of indigestible
+fiber and increase in digestible&quot; so much spoken of is, so far as our
+present very imperfect methods of analyzing these compounds permit us
+to judge, a myth; and I have not yet found any sufficient evidence to
+support this statement. A loss, then, of 6 parts of organic matter out
+of every 106 parts put into the silo has in this instance taken place,
+due chiefly to the decomposition of starch, sugar, and mucilage, etc.
+And as the grass contained 70 parts of water when put into the silo,
+the total loss would only be 1.7 per cent. of the total weight. This
+theoretical deduction was found by practical experience correct, for
+Mr. Smith, agent to Lord Egerton, upon whose estate this silage was
+made, in his report to Mr. Jenkins says the &quot;actual weight out of the
+silo corresponds exactly with the weight we put into the same.&quot;</p>
+
+<p>In my judgment these figures are of interest to the agricultural
+chemist for many reasons. First, they will clear the ground for future
+workers and eliminate from their researches what would have greatly
+complicated them&mdash;changes in the cellulose bodies.</p>
+
+<p>Secondly, they are of interest because our present methods of
+distinguishing between and estimating digestible and indigestible
+fiber is most rough, and probably inaccurate, and may not in the least
+represent the power of an animal&mdash;say a cow&mdash;to digest these various
+substances; and most of us know that when a new method of analysis
+becomes a necessity, a new method is generally discovered. Lastly,
+they are of interest to the agriculturist, for they point out, I
+believe for the first time, the exact amount of loss which grass&mdash;or
+at least one sample&mdash;has undergone in conversion into silage, and also
+that much of the nitrogenous matter is changed, and so far as we know
+at present, lost its nutritive value. This, however, is only comparing
+silage with grass. What is wanted is to compare silage with hay&mdash;both
+made out of the same grass. Then, and then only, will it be possible
+to sum up the relative advantages or disadvantages of the two methods
+of preserving grass as food for cattle.&mdash;<i>Chem. News</i>.</p>
+
+<div class="note"><p><a name="Footnote_10" id="Footnote_10"></a><a href="#FNanchor_10">[1]</a></p>
+<p><i>Royal Agricultural Society's Journal</i>, vol. xx., part
+i., pp. 175 and 380.</p>
+
+<p><a name="Footnote_11" id="Footnote_11"></a><a href="#FNanchor_11">[2]</a></p>
+<p><i>Journ. Chem. Society</i>, March, 1884, p. 124.</p></div>
+
+<hr />
+
+
+<h3>THE ILLUMINATING POWER OF ETHYLENE.</h3>
+
+<p>Dr. Percy Frankland has obtained results which may be thus briefly
+summarized: (1.) That pure ethylene, when burnt at the rate of 5 cubic
+feet per hour from a Referee's Argand burner, emits a light of 68.5
+standard candles. (2.) That the illuminating power of equal volumes of
+mixtures of ethylene with either hydrogen carbonic oxide or
+marsh-gas is less than that of pure ethylene. (3.) That when the
+proportion of ethylene in such mixtures is above 63 per cent. the
+illuminating power of the mixture is but slightly affected by the
+nature of the diluent. When, on the other hand, the proportion of
+ethylene in such mixtures is low, the illuminating power of the
+mixture is considerably the highest when marsh-gas is the diluent, and
+the lowest when the ethylene is mixed with carbonic oxide. (4.) That
+if 5 cubic feet of ethylene be uniformly consumed irrespectively of
+the composition of the mixture, the calculated illuminating power is
+in every case equal to or actually greater than that of pure ethylene
+until a certain degree of dilution is attained. This intrinsic
+luminosity of ethylene remains almost constant when the latter is
+diluted with carbonic oxide, until the ethylene forms only 40 per
+cent. of the mixture, after which it rapidly diminishes to zero when
+the ethylene forms only 20 per cent. of the mixture. When the ethylene
+is diluted with hydrogen, its intrinsic luminosity rises to 81 candles
+when the ethylene constitutes 30 per cent. of the mixture, after which
+it rapidly falls to zero when the ethylene amounts to only 10 per
+cent. In the case of mixtures of ethylene and marsh-gas, the intrinsic
+luminosity of the former is augmented with increasing rapidity as the
+proportion of marsh gas rises, the intrinsic luminosity of ethylene,
+in a mixture containing 10 per cent. of the latter, being between 170
+and 180 candles.</p>
+
+<hr />
+
+
+
+
+<h2><a name="art25" id="art25"></a>DIFFRACTION PHENOMENA DURING TOTAL SOLAR ECLIPSES.<a name="FNanchor_12" id="FNanchor_12"></a><a href="#Footnote_12"><sup>1</sup></a></h2>
+
+<h3>By G.D. Hiscox.</h3>
+
+
+<p>The reality of the sun's corona having been cast in doubt by a leading
+observer of the last total eclipse, who, from the erratic display
+observed in the spectroscope, has declared it a subjective phenomenon
+of diffraction, has led me to an examination and inquiry as to the
+bearing of an obscurely considered and heretofore only casually
+observed phenomenon seen to take place during total solar eclipses.
+This phenomenon, it seems to me, ought to account for, and will
+possibly satisfy, the spectroscopic conditions observed just before,
+during, and after totality; which has probably led to the epithet used
+by some leading observers&mdash;&quot;the fickle corona.&quot; The peculiar
+phenomenon observed in the spectroscope, the flickering bands or lines
+of the solar spectrum flashing upon and across the coronal spectrum,
+has caused no little speculation among observers.</p>
+
+<p>The diffraction or interference bands projected by the passage of a
+strong beam of light by a solid body, as discovered long since by
+Grimaldi, and investigated later by Newton, Fresnel, and Fraunhofer,
+are explained and illustrated in our text books; but the grand display
+of this phenomenon in a total solar eclipse, where the sun is the
+source of light and the moon the intercepting body, has as yet
+received but little attention from observers, and is not mentioned to
+my knowledge in our text books.</p>
+
+<p>In the instructions issued from the United States Naval Observatory
+and the Signal Office at Washington for the observation of the eclipse
+of July 29, 1878, attention was casually directed to this phenomenon,
+and a few of the observers at Pike's Peak, Central City, Denver, and
+other places have given lucid and interesting descriptions of the
+flight of the diffraction bands as seen coursing over the face of the
+earth at the speed of the moon's shadow, at the apparent enormous
+velocity of thirty-three miles per minute, or fifty times the speed of
+a fast railway train.</p>
+
+<p>From a known optical illusion derived from interference or fits of
+perception, as illustrated in quick moving shadows, this great speed
+was not realized to the eye, as the observed motion of these shadows
+was apparently far less rapid than their reality.</p>
+
+<p>The ultra or diffraction bands outside of the shadow were distinctly
+seen and described by Mr. J.E. Keeler at Central City, both before and
+after totality. He estimates the shadow bands at 8 inches wide and 4
+feet apart.</p>
+
+<p>Professor E.S. Holden, also at Central City, estimated the dark bands
+as about 3 feet apart, and variable.</p>
+
+<p>From estimates which he obtained from other observers of his party,
+the distances between the bands varied from 6 to l� feet, but so
+quickly did they pass that they baffled all attempts to count even the
+number that passed in one second.</p>
+
+<p>He observed the time of continuance of their passage from west to east
+as forty-eight seconds, which indicates a width of 33 miles of
+diffraction bands stretching outward from the edge of the shadow to
+the number of many thousands.</p>
+
+<p>Mr. G.W. Hill, at Denver, a little to the north of the central track
+of the shadow, observed the infra or bands within the shadow, alluding
+to the fact that they must be moving at the same rate as the shadow,
+although their apparent motion was much slower, or like the shadows of
+flying clouds. He attributes the discrepancy to optical illusion.</p>
+
+<p>At Virginia City the <i>colors</i> of the <i>ultra</i> bands were observed, and
+estimated at five seconds' duration from the edge of the shadow, which
+is equal to about 4 miles in width. These are known to be the
+strongest color bands in the diffraction spectrum, which accounts for
+their being generally observed.</p>
+
+<p>Mr. W.H. Bush, observing at Central City, in a communication to Prof.
+Holden alludes to the brilliancy of the colors of these bands as seen
+through small clouds floating near the sun's place during totality,
+and of the rapid change of their rainbow colors as observed dashing
+across the clouds with the rapidity of thought.</p>
+
+<p>All of these bands, both ultra and infra, as seen in optical
+experiments, are colored in reverse order, being from violet to red
+for each band outward and inward from the edge of the shadow.</p>
+
+<p>It is very probable that the velocity of the passage of all the bands
+during a total eclipse very much modifies the distinctness of the
+colors or possibly obliterates them by optically blending so as to
+produce the dull white and black bands which occupied so large a
+portion of this grand panorama.</p>
+
+<p>The phenomenon of these faint colored bands, with the observed light
+and dark shadows, may be attributed to one or all of the following
+causes:</p>
+
+<p>1. A change in the direction of a small portion of the sun's light
+passing by the solid body of the moon, it being deflected outward by
+repulsion or reflection from its surface, and other portions being
+deflected inward after passing the body by mutual repulsion of its own
+elements toward a <i>light vacuum</i> or space devoid of the element of
+vibration.</p>
+
+<p>2. The colored spectral bands being the direct result of the property
+of interference, or the want of correspondence of the wave lengths due
+to divergence; the same phenomenon being also observed in convergent
+light. This is practically illustrated in the hazy definition of the
+reduced aperture of telescopes, and its peculiarities shown in the
+spectral rings within and beyond the focus.</p>
+
+<p>3. Chromatic dispersion by our atmosphere, together with selective
+absorption, also by our atmosphere and its vapors, have been suggested
+as causes in this curious and complicated phenomena.</p>
+
+<p>In none of the reports descriptive of the phenomena of polarization of
+the corona is there the slightest allusion to the influence that the
+diffraction bands may possibly have in modifying or producing the
+various conditions of polarization observed; although these
+observations have been made and commented upon during the past
+twenty-five years.</p>
+
+<p>Investigations now in progress of the modifying relation of the
+phenomenon of diffraction in its effect upon not only the physical
+aspect of the corona, but also in some strange spectroscopic anomalies
+that have been observed near the sun at other times than during a
+total solar eclipse, will, it is hoped, result in a fuller
+interpretation of the physical nature of one of the grandest elements
+of creation&mdash;<i>light</i>; let there be more of it.</p>
+
+<div class="note"><p><a name="Footnote_12" id="Footnote_12"></a><a href="#FNanchor_12">[1]</a></p>
+<p>A paper read before the American Astronomical Society,
+May 5, 1884.</p></div>
+
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@@ -0,0 +1,5041 @@
+The Project Gutenberg EBook of Scientific American Supplement, No. 441,
+June 14, 1884., by Various
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Scientific American Supplement, No. 441, June 14, 1884.
+
+Author: Various
+
+Release Date: May 16, 2005 [EBook #15833]
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK SCIENTIFIC AMERICAN ***
+
+
+
+
+Produced by Juliet Sutherland and the Online Distributed
+Proofreading Team at www.pgdp.net.
+
+
+
+
+
+[Illustration]
+
+
+
+
+SCIENTIFIC AMERICAN SUPPLEMENT NO. 441
+
+
+
+
+NEW YORK, JUNE 14, 1884
+
+Scientific American Supplement. Vol. XVII., No. 441.
+
+Scientific American established 1845
+
+Scientific American Supplement, $5 a year.
+
+Scientific American and Supplement, $7 a year.
+
+       *       *       *       *       *
+
+
+
+
+TABLE OF CONTENTS.
+
+
+I.   CHEMISTRY AND METALLURGY.--On Electrolysis.--Precipitation
+     of lead, thallium, silver, bismuth, manganese, etc.--By H.
+     SCHUCHT
+
+     The Electro-Chemical Equivalent of Silver
+
+     Zircon.--How it can be rendered soluble.--By F. STOLBA
+
+     A New Process for Making Wrought Iron Directly from the Ore.
+     --Comparison with other processes.--With descriptions and
+     engravings of the apparatus used
+
+     Some Remarks on the Determination of Hardness in Water
+
+     On the changes which Take Place in the Conversion of Hay
+     into Ensilage.--By F.J. Lloyd
+
+II.  ENGINEERING AND MECHANICS.--Faure's Machine for
+     Decorticating Sugar Cane.--With full description
+     and 13 figures
+
+     The Generation of Steam and the Thermodynamic Problems
+     Involved.--By WM. ANDERSON.--Apparatus used in the
+     experimental determination of the heat of combustion and
+     the laws which govern its development.--Ingredients of
+     fuel.--Potential energy of fuel.--With 7 figures and
+     several tables
+
+     Planetary Wheel Trains.--Rotations of the wheels relatively
+     to the train arm.--By Prof. C.W. MACCORD
+
+     The Pantanemone.--A New Windwheel.--1 engraving
+
+     Relvas's New Life Boat.--With engraving
+
+     Experiments with Double Barreled Guns and Rifles.
+     --Cause of the divergence of the charge.--4 figures
+
+     Improved Ball Turning Machine.--1 figure
+
+     Cooling Apparatus for Injection Water.--With engraving
+
+     Corrugated Disk Pulleys.--1 engraving
+
+III. TECHNOLOGY.--A New Standard Light
+
+     Dr. Feussner's New Polarizing Prism.--Points of difference
+     between the old and new prisms.--By P.R. SLEEMAN
+
+     Density and Pressure of Detonating Gas
+
+IV.  ELECTRICITY, LIGHT, ETC.--Early History of the Telegraph.
+     --Pyrsia, or the system of telegraphy among the Greeks.
+     --Communication by means of characters and the telescope.
+     --Introduction of the magnetic telegraph between Baltimore
+     and Washington
+
+     The Kravogl Electro Motor and its Conversion Into a Dynamo
+     Electric Machine.--5 figures
+
+     Bornhardt's Electric Machine for Blasting in Mines.
+     --15 figures
+
+     Pritchett's Electric Fire Alarm.--1 figure
+
+     A Standard Thermopile
+
+     Telephonic Transmission without Receivers.--Some of the
+     apparatus exhibited at the annual meeting of the French
+     Society of Physics.--Telephonic transmission through a
+     chain of persons
+
+     Diffraction Phenomena during Total Solar Eclipses.--By G.D.
+     Hiscox
+
+V.   BOTANY AND HORTICULTURE.--Gum Diseases in Trees.--
+     Cause and contagion of the same
+
+     Drinkstone Park.--Trees and plants cultivated therein.--
+     With 2 engravings
+
+VI.  MEDICINE AND HYGIENE.--Miryachit.--A newly-discovered
+     disease of the nervous system, and its analogues.--By WM. A.
+     HAMMOND
+
+VII. MISCELLANEOUS.--Turkish Baths for Horses.--With
+     diagram.
+
+       *       *       *       *       *
+
+
+
+
+FAURE'S MACHINE FOR DECORTICATING SUGAR-CANE.
+
+
+The object of the apparatus shown in the accompanying engraving is to
+effect a separation of the tough epidermis of the sugar-cane from the
+internal spongy pith which is to be pressed. Its function consists in
+isolating and separating the cells from their cortex, and in putting
+them in direct contact with the rollers or cylinders of the mill.
+After their passage into the apparatus, which is naturally placed in a
+line with the endless chain that carries them to the mill, the canes
+arrive in less compact layers, pass through much narrower spaces, and
+finally undergo a more efficient pressure, which is shown by an
+abundant flow of juice. The first trials of the machine were made in
+1879 at the Pointe Simon Works, at Martinique, with the small type
+that was shown at the Paris Exhibition of 1878. These experiments,
+which were applied to a work of 3,000 kilos of cane per hour, gave
+entire satisfaction, and decided the owners of three of the colonial
+works (Pointe Simon, Larcinty, and Marin) to adopt it for the season
+of 1880.
+
+The apparatus is shown in longitudinal section in Fig. 1, and in plan
+in Fig. 2.
+
+Fig. 3 gives a transverse section passing through the line 3-4, and
+Fig. 4 an external view on the side whence the decorticated canes make
+their exit from the apparatus.
+
+[Illustration: FAURE'S MACHINE FOR DECORTICATING SUGAR CANE.]
+
+The other figures relate to details that will be referred to further
+along.
+
+_The Decorticating Cylinder._--The principal part of the apparatus is
+a hollow drum, A, of cast iron, 430 mm. in internal diameter by 1.41
+m. in length, which is keyed at its two extremities to the shaft, a.
+Externally, this drum (which is represented apart in transverse
+section in Fig. 5) has the form of an octagonal prism with well
+dressed projections between which are fixed the eight plates, C, that
+constitute the decorticating cylinder. These plates, which are of
+tempered cast iron, and one of which is shown in transverse section in
+Fig. 7, when once in place form a cylindrical surface provided with 48
+helicoidal, dentate channels. The length of these plates is 470 mm.
+There are three of them in the direction of the generatrices of the
+cylinder, and this makes a total of 24. All are strengthened by ribs
+(as shown in Fig. 8), and each is fixed by 4 bolts, _c_, 20mm. in
+diameter. The pitch of the helices of each tooth is very elongated,
+and reaches about 7.52 m. The depth of the toothing is 18 mm.
+
+_Frame and Endless Chain._--The cylinder thus constructed rotates with
+a velocity of 50 revolutions per minute over a cylindrical vessel, B',
+cast in a piece with the frame, B. This vessel is lined with two
+series of tempered cast iron plates, D and D', called exit and
+entrance plates, which rest thereon, through the intermedium of well
+dressed pedicels, and which are held in place by six 20-millimeter
+bolts. Their length is 708 mm. The entrance plates, D, are provided
+with 6 spiral channels, whose pitch is equal to that of the channels
+of the decorticating cylinder, C, and in the same direction. The depth
+of the toothing is 10 mm.
+
+The exit plates, D', are provided with 7 spiral channels of the same
+pitch and direction as those of the preceding, but the depth of which
+increases from 2 to 10 mm. The axis of the decorticating cylinder does
+not coincide with that of the vessel, B', so that the free interval
+for the passage of the cane continues to diminish from the entrance to
+the exit.
+
+The passage of the cane to the decorticator gives rise to a small
+quantity of juice, which flows through two orifices, _b'_, into a sort
+of cast iron trough, G, suspended beneath the vessel. The cane, which
+is brought to the apparatus by an endless belt, empties in a conduit
+formed of an inclined bottom, E, of plate iron, and two cast iron
+sides provided with ribs. These sides rest upon the two ends of the
+vessel, B', and are cross-braced by two flat bars, _e_, to which is
+bolted the bottom, E. This conduit is prolonged beyond the
+decorticating cylinder by an inclined chute, F, the bottom of which is
+made of plate iron 7 mm. thick and the sides of the same material 9
+mm. thick. The hollow frame, B, whose general form is like that of a
+saddle, carries the bearings, _b_, in which revolves the shaft, _a_.
+One of these bearings is represented in detail in Figs. 9 and 10. It
+will be seen that the cap is held by bolts with sunken heads, and that
+the bearing on the bushes is through horizontal surfaces only. In a
+piece with this frame are cast two similar brackets, B squared, which support
+the axle, _h_, of the endless chain. To this axle, whose diameter is
+100 mm., are keyed, toward the extremities, the pinions, H, to which
+correspond the endless pitch chains, _i_. These latter are formed, as
+may be seen in Figs. 11 and 12, of two series of links. The shorter of
+these latter are only 100 mm. in length, while the longer are 210 mm.,
+and are hollowed out so as to receive the butts of the boards, I. The
+chain thus formed passes over two pitch pinions, J, like the pinions,
+H, that are mounted at the extremities of an axle, _j_, that revolves
+in bearings, I', whose position with regard to the apparatus is
+capable of being varied so as to slacken or tauten the chain, I. This
+arrangement is shown in elevation in Fig. 13.
+
+_Transmission._--The driving shaft, _k_, revolves in a pillow block,
+K, cast in a piece with the frame, B. It is usually actuated by a
+special motor, and carries a fly-wheel (not shown in the figure for
+want of space). It receives in addition a cog-wheel, L, which
+transmits its motion to the decorticating cylinder through, the
+intermedium of a large wooden-toothed gear wheel, L'. The shaft, _a_,
+whose diameter is 228 mm., actuates in its turn, through the pinions,
+M' and M, the pitch pinion, N, upon whose prolonged hub is keyed the
+pinion, M. This latter is mounted loosely upon the intermediate axle,
+_m_. Motion is transmitted to the driving shaft, _h_, of the endless
+chain, I, by an ordinary pitch chain, through a gearing which is shown
+in Fig. 12. The pitch pinion, N', is cast in a piece with a hollow
+friction cone, N squared, which is mounted loosely upon the shaft, _h_, and
+to which corresponds a second friction cone, O. This latter is
+connected by a key to a socket, _o_, upon which it slides, and which
+is itself keyed to the shaft, _h_. The hub of the cone, O, is
+connected by a ring with a bronze nut, _p_, mounted at the threaded
+end of the shaft, _h_, and carrying a hand-wheel, P. It is only
+necessary to turn this latter in one direction or the other in order
+to throw the two cones into or out of gear.
+
+If we allow that the motor has a velocity of 70 revolutions per
+minute, the decorticating cylinder will run at the rate of 50, and the
+sugar-cane will move forward at the rate of 12 meters per minute.
+
+This new machine is a very simple and powerful one. The decortication
+is effected with wonderful rapidity, and the canes, opened throughout
+their entire length and at all points of their circumference, leave
+the apparatus in a state that allows of no doubt as to what the result
+of the pressure will be that they have to undergo. There is no
+tearing, no trituration, no loss of juice, but merely a simple
+preparation for a rational pressure effected under most favorable
+conditions.
+
+The apparatus, which is made in several sizes, has already received
+numerous applications in Martinique, Trinidad, Cuba, Antigua, St.
+Domingo, Peru, Australia, the Mauritius Islands, and
+Brazil.--_Publication Industrielle._
+
+       *       *       *       *       *
+
+
+
+
+MOVING A BRIDGE.
+
+
+An interesting piece of engineering work has recently been
+accomplished at Bristol, England, which consisted in the moving of a
+foot-bridge 134 feet in length, bodily, down the river a considerable
+distance. The pontoons by means of which the bridge was floated to its
+new position consisted of four 80-ton barges, braced together so as to
+form one solid structure 64 feet in width, and were placed in position
+soon after the tide commenced to rise. At six o'clock A.M. the top of
+the stages, which was 24 feet above the water, touched the under part
+of the bridge, and in a quarter of an hour later both ends rose from
+their foundations. When the tide had risen 4 ft. the stage and bridge
+were floated to the new position, when at 8.30 the girders dropped on
+to their beds.
+
+       *       *       *       *       *
+
+
+
+
+THE GENERATION OF STEAM, AND THE THERMODYNAMIC PROBLEMS
+INVOLVED.[1]
+
+   [Footnote 1: Lecture delivered at the Institution of Civil
+   Engineers, session 1883-84. For the illustrations we are indebted
+   to the courtesy of Mr. J. Forrest, the secretary.]
+
+By Mr. WILLIAM ANDERSON, M.I.C.E.
+
+
+It will not be necessary to commence this lecture by explaining the
+origin of fuel; it will be sufficient if I remind you that it is to
+the action of the complex rays of the sun upon the foliage of plants
+that we mainly owe our supply of combustibles. The tree trunks and
+branches of our forests, as well as the subterranean deposits of coal
+and naphtha, at one time formed portions of the atmosphere in the form
+of carbonic acid gas; that gas was decomposed by the energy of the
+solar rays, the carbon and the oxygen were placed in positions of
+advantage with respect to each other--endowed with potential energy;
+and it is my duty this evening to show how we can best make use of
+these relations, and by once more combining the constituents of fuel
+with the oxygen of the air, reverse the action which caused the growth
+of the plants, that is to say, by destroying the plant reproduce the
+heat and light which fostered it. The energy which can be set free by
+this process cannot be greater than that derived originally from the
+sun, and which, acting through the frail mechanism of green leaves,
+tore asunder the strong bonds of chemical affinity wherein the carbon
+and oxygen were hound, converting the former into the ligneous
+portions of the plants and setting the latter free for other uses. The
+power thus silently exerted is enormous; for every ton of carbon
+separated in twelve hours necessitates an expenditure of energy
+represented by at least 1,058 horse power, but the action is spread
+over an enormous area of leaf surface, rendered necessary by the small
+proportion of carbonic acid contained in the air, by measure only
+1/2000 part, and hence the action is silent and imperceptible. It is
+now conceded on all hands that what is termed heat is the energy of
+molecular motion, and that this motion is convertible into various
+kinds and obeys the general laws relating to motion. Two substances
+brought within the range of chemical affinity unite with more or less
+violence; the motion of transition of the particles is transformed,
+wholly or in part, into a vibratory or rotary motion, either of the
+particles themselves or the interatomic ether; and according to the
+quality of the motions we are as a rule, besides other effects, made
+conscious of heat or light, or of both. When these emanations come to
+be examined they are found to be complex in the extreme, intimately
+bound up together, and yet capable of being separated and analyzed.
+
+As soon as the law of definite chemical combination was firmly
+established, the circumstance that changes of temperature accompanied
+most chemical combinations was noticed, and chemists were not long in
+suspecting that the amount of heat developed or absorbed by chemical
+reaction should be as much a property of the substances entering into
+combination as their atomic weights. Solid ground for this expectation
+lies in the dynamic theory of heat. A body of water at a given height
+is competent by its fall to produce a definite and invariable quantity
+of heat or work, and in the same way two substances falling together
+in chemical union acquire a definite amount of kinetic energy, which,
+if not expended in the work of molecular changes, may also by suitable
+arrangements be made to manifest a definite and invariable quantity of
+heat.
+
+At the end of last century Lavoisier and Laplace, and after them, down
+to our own time, Dulong, Desprez, Favre and Silbermann, Andrews,
+Berthelot, Thomson, and others, devoted much time and labor to the
+experimental determination of the heat of combustion and the laws
+which governed its development. Messrs. Favre and Silbermann, in
+particular, between the years 1845 and 1852, carried out a splendid
+series of experiments by means of the apparatus partly represented in
+Fig. 1 (opposite), which is a drawing one-third the natural size of
+the calorimeter employed. It consisted essentially of a combustion
+chamber formed of thin copper, gilt internally. The upper part of the
+chamber was fitted with a cover through which the combustible could be
+introduced, with a pipe for a gas jet, with a peep hole closed by
+adiathermanous but transparent substances, alum and glass, and with a
+branch leading to a thin copper coil surrounding the lower part of the
+chamber and descending below it. The whole of this portion of the
+apparatus was plunged into a thin copper vessel, silvered internally
+and filled with water, which was kept thoroughly mixed by means of
+agitators. This second vessel stood inside a third one, the sides and
+bottom of which were covered with the skins of swans with the down on,
+and the whole was immersed in a fourth vessel tilled with water, kept
+at the average temperature of the laboratory. Suitable thermometers of
+great delicacy were provided, and all manner of precautions were taken
+to prevent loss of heat.
+
+[Illustration: THE GENERATION OF STEAM. Fig 1.]
+
+It is impossible not to admire the ingenuity and skill exhibited in
+the details of the apparatus, in the various accessories for
+generating and storing the gases used, and for absorbing and weighing
+the products of combustion; but it is a matter of regret that the
+experiments should have been carried out on so small a scale. For
+example, the little cage which held the solid fuel tested was only 5/8
+inch diameter by barely 2 inches high, and held only 38 grains of
+charcoal, the combustion occupying about sixteen minutes. Favre and
+Silbermann adopted the plan of ascertaining the weight of the
+substances consumed by calculation from the weight of the products of
+combustion. Carbonic acid was absorbed by caustic potash, as also was
+carbonic oxide, after having been oxidized to carbonic acid by heated
+oxide of copper, and the vapor of water was absorbed by concentrated
+sulphuric acid. The adoption of this system showed that it was in any
+case necessary to analyze the products of combustion in order to
+detect imperfect action. Thus, in the case of substances containing
+carbon, carbonic oxide was always present to a variable extent with
+the carbonic acid, and corrections were necessary in order to
+determine the total heat due to the complete combination of the
+substance with oxygen. Another advantage gained was that the
+absorption of the products of combustion prevents any sensible
+alteration in the volumes during the process, so that corrections for
+the heat absorbed in the work of displacing the atmosphere were not
+required. The experiments on various substances were repeated many
+times. The mean results for those in which we are immediately
+interested are given in Table I., next column.
+
+Comparison with later determinations have established their
+substantial accuracy. The general conclusion arrived at is thus
+stated:
+
+"As a rule there is an equality between the heat disengaged or
+absorbed in the acts, respectively, of chemical combination or
+decomposition of the same elements, so that the heat evolved during
+the combination of two simple or com-pound substances is equal to the
+heat absorbed at the time of their chemical segregation."
+
+       TABLE I.--SUBSTANCES ENTERING INTO THE COMPOSITION OF FUEL.
+
+  -----------------------+-------------+-----------+-------------------+
+                         |                         | Heat evolved in   |
+                         |     Symbol and Atomic   |the Combustion of  |
+                         |           Weight.       |  1 lb. of Fuel.   |
+                         +------------+------------+--------+----------+
+                         |            |            |        |In Pounds |
+                         |            |            |  In    | of Water |
+                         |            |            |British |Evaporated|
+                         |   Before   |    After   |Thermal | from and |
+                         | Combustion | Combustion | Units. | at 212 deg.. |
+                         +------------+------------+--------+----------+
+  Hydrogen burned        | H        1 | H2O     18 | 62,032 |  64.21   |
+    in oxygen.           |            |            |        |          |
+  -----------------------+------------+------------+--------+----------+
+  Carbon burned to       | C       12 | CO      28 |  4,451 |   4.61   |
+    carbonic oxide.      |            |            |        |          |
+  -----------------------+------------+------------+--------+----------+
+  Carbon burned to       | C       12 | CO2     44 | 14,544 |  15.06   |
+    carbonic acid.       |            |            |        |          |
+  -----------------------+------------+------------+--------+----------+
+  Carbonic oxide burned  | CO      28 | CO2     44 |  4,326 |   4.48   |
+    to carbonic acid.    |            |            |        |          |
+  -----------------------+------------+------------+--------+----------+
+  Olefiant gas (ethylene)| C2H4    28 | 2CO2   124 | 21,343 |  22.09   |
+    burnt in oxygen.     |            | 2H2O       |        |          |
+  -----------------------+------------+------------+--------+----------+
+  Marsh gas (methane)    | CH4     16 | 2CO2    80 | 23,513 |  24.34   |
+  burnt in oxygen.       |            | 2H2O       |        |          |
+  -----------------------+------------+------------+--------+----------+
+
+Composition of air--
+
+  by volume 0.788 N + 0.197 O + 0.001 CO2 + 0.014 H2O
+  ----------------------------------------------------
+  by weight 0.771 N + 0.218 O + 0.009 CO2 + 0.017 H2O
+
+This law is, however, subject to some apparent exceptions. Carbon
+burned in protoxide of nitrogen, or laughing gas, N_{2}O, produces
+about 38 per cent. more heat than the same substance burned in pure
+oxygen, notwithstanding that the work of decomposing the protoxide of
+nitrogen has to be performed. In marsh gas, or methane, CH_{4}, again,
+the energy of combustion is considerably less than that due to the
+burning of its carbon and hydrogen separately. These exceptions
+probably arise from the circumstance that the energy of chemical
+action is absorbed to a greater or less degree in effecting molecular
+changes, as, for example, the combustion of 1 pound of nitrogen to
+form protoxide of nitrogen results in the absorption of 1,157 units of
+heat. Berthelot states, as one of the fundamental principles of
+thermochemistry, "that the quantity of heat evolved is the measure of
+the sum of the chemical and physical work accomplished in the
+reaction"; and such a law will no doubt account for the phenomena
+above noted. The equivalent heat of combustion of the compounds we
+have practically to deal with has been experimentally determined, and
+therefore constitutes a secure basis on which to establish
+calculations of the caloric value of fuel; and in doing so, with
+respect to substances composed of carbon, hydrogen, and oxygen, it is
+convenient to reduce the hydrogen to its heat-producing equivalent of
+carbon. The heat of combustion of hydrogen being 62,032 units, that of
+carbon 14,544 units, it follows that 4.265 times the weight of
+hydrogen will represent an equivalent amount of carbon. With respect
+to the oxygen, it is found that it exists in combination with the
+hydrogen in the form of water, and, being combined already, abstracts
+its combining equivalent of hydrogen from the efficient ingredients of
+the fuel; and hence hydrogen, to the extent of 1/8 of the weight of
+the oxygen, must be deducted. The general formula then becomes:
+
+       Heat of combustion = 14,544 {C + 4.265 (H-(O/8))},
+
+and water evaporated from and at 212 deg., taking 966 units as the heat
+necessary to evaporate 1 pound of water,
+
+       lb. evaporated = 15.06 {C + 4.265 (H-(O/8))},
+
+carbon, hydrogen, and oxygen being taken at their weight per cent. in
+the fuel. Strictly speaking, marsh gas should be separately
+determined. It often happens that available energy is not in a form in
+which it can be applied directly to our needs. The water flowing down
+from the mountains in the neighborhood of the Alpine tunnels was
+competent to provide the power necessary for boring through them, but
+it was not in a form in which it could be directly applied. The
+kinetic energy of the water had first to be changed into the potential
+energy of air under pressure, then, in that form, by suitable
+mechanism, it was used with signal success to disintegrate and
+excavate the hard rock of the tunnels. The energy resulting from
+combustion is also incapable of being directly transformed into useful
+motive power; it must first be converted into potential force of steam
+or air at high temperature and pressure, and then applied by means of
+suitable heat engines to produce the motions we require. It is
+probably to this circumstance that we must attribute the slowness of
+the human race to take advantage of the energy of combustion. The
+history of the steam engine hardly dates back 200 years, a very small
+fraction of the centuries during which man has existed, even since
+historic times.
+
+The apparatus by means of which the potential energy of fuel with
+respect to oxygen is converted into the potential energy of steam, we
+call a steam boiler; and although it has neither cylinder nor piston,
+crank nor fly wheel, I claim for it that it is a veritable heat
+engine, because it transmits the undulations and vibrations caused by
+the energy of chemical combination in the fuel to the water in the
+boiler; these motions expend themselves in overcoming the liquid
+cohesion of the water and imparting to its molecules that vigor of
+motion which converts them into the molecules of a gas which,
+impinging on the surfaces which confine it and form the steam space,
+declare their presence and energy in the shape of pressure and
+temperature. A steam pumping engine, which furnishes water under high
+pressure to raise loads by means of hydraulic cranes, is not more
+truly a heat engine than a simple boiler, for the latter converts the
+latent energy of fuel into the latent energy of steam, just as the
+pumping engine converts the latent energy of steam into the latent
+energy of the pumped-up accumulator or the hoisted weight.
+
+If I am justified in taking this view, then I am justified in applying
+to my heat engine the general principles laid down in 1824 by Sadi
+Carnot, namely, that the proportion of work which can be obtained out
+of any substance working between two temperatures depends entirely and
+solely upon the difference between the temperatures at the beginning
+and end of the operation; that is to say, if T be the higher
+temperature at the beginning, and _t_ the lower temperature at the end
+of the action, then the maximum possible work to be got out of the
+substance will be a function of (T-_t_). The greatest range of
+temperature possible or conceivable is from the absolute temperature
+of the substance at the commencement of the operation down to absolute
+zero of temperature, and the fraction of this which can be utilized is
+the ratio which the range of temperature through which the substance
+is working bears to the absolute temperature at the commencement of
+the action. If W = the greatest amount of effect to be expected, T and
+_t_ the absolute temperatures, and H the total quantity of heat
+(expressed in foot pounds or in water evaporated, as the case may be)
+potential in the substance at the higher temperature, T, at the
+beginning of the operation, then Carnot's law is expressed by the
+equation:
+
+         / T - t \
+   W = H( ------- )
+         \   T   /
+
+I will illustrate this important doctrine in the manner which Carnot
+himself suggested.
+
+[Illustration: THE GENERATION OF STEAM. Fig 2.]
+
+Fig. 2 represents a hillside rising from the sea. Some distance up
+there is a lake, L, fed by streams coming down from a still higher
+level. Lower down on the slope is a millpond, P, the tail race from
+which falls into the sea. At the millpond is established a factory,
+the turbine driving which is supplied with water by a pipe descending
+from the lake, L. Datum is the mean sea level; the level of the lake
+is T, and of the millpond _t_. Q is the weight of water falling
+through the turbine per minute. The mean sea level is the lowest level
+to which the water can possibly fall; hence its greatest potential
+energy, that of its position in the lake, = QT = H. The water is
+working between the absolute levels, T and _t_; hence, according to
+Carnot, the maximum effect, W, to be expected is--
+
+         / T - t \
+   W = H( ------- )
+         \   T   /
+                                / T - t \
+but H = QT [therefore]  W = Q T( ------- )
+                                \   T   /
+
+   W = Q (T - t),
+
+that is to say, the greatest amount of work which can be expected is
+found by multiplying the weight of water into the clear fall, which
+is, of course, self-evident.
+
+Now, how can the quantity of work to be got out of a given weight of
+water be increased without in any way improving the efficiency of the
+turbine? In two ways:
+
+1. By collecting the water higher up the mountain, and by that means
+increasing T.
+
+2. By placing the turbine lower down, nearer the sea, and by that
+means reducing _t_.
+
+Now, the sea level corresponds to the absolute zero of temperature,
+and the heights T and _t_ to the maximum and minimum temperatures
+between which the substance is working; therefore similarly, the way
+to increase the efficiency of a heat engine, such as a boiler, is to
+raise the temperature of the furnace to the utmost, and reduce the
+heat of the smoke to the lowest possible point. It should be noted, in
+addition, that it is immaterial what liquid there may be in the lake;
+whether water, oil, mercury, or what not, the law will equally apply,
+and so in a heat engine, the nature of the working substance, provided
+that it does not change its physical state during a cycle, does not
+affect the question of efficiency with which the heat being expended
+is so utilized. To make this matter clearer, and give it a practical
+bearing, I will give the symbols a numerical value, and for this
+purpose I will, for the sake of simplicity, suppose that the fuel used
+is pure carbon, such as coke or charcoal, the heat of combustion of
+which is 14,544 units, that the specific heat of air, and of the
+products of combustion at constant pressure, is 0.238, that only
+sufficient air is passed through the fire to supply the quantity of
+oxygen theoretically required for the combustion of the carbon, and
+that the temperature of the air is at 60 deg. Fahrenheit = 520 deg. absolute.
+The symbol T represents the absolute temperature of the furnace, a
+value which is easily calculated in the following manner: 1 lb. of
+carbon requires 2-2/3 lb. of oxygen to convert it into carbonic acid,
+and this quantity is furnished by 12.2 lb. of air, the result being
+13.2 lb. of gases, heated by 14,544 units of heat due to the energy of
+combustion; therefore:
+
+                14,544 units
+  T = 520 deg. + ------------------ = 5,150 deg. absolute.
+              13.2 lb. X 0.238
+
+The lower temperature, _t_, we may take as that of the feed water, say
+at 100 deg. or 560 deg. absolute, for by means of artificial draught and
+sufficiently extending the heating surface, the temperature of the
+smoke may be reduced to very nearly that of the feed water. Under such
+circumstances the proportion of heat which can be realized is
+
+       5,150 deg. - 560 deg.
+    = --------------- = 0.891;
+           5,150 deg.
+
+that is to say, under the extremely favorable if not impracticable
+conditions assumed, there must be a loss of 11 per cent. Next, to give
+a numerical value to the potential energy, H, to be derived from a
+pound of carbon, calculating from absolute zero, the specific heat of
+carbon being 0.25, and absolute temperature of air 520 deg.:
+
+                                              Units.
+  1 lb. of carbon X 0.25 X 520              =    130
+  12.2 of air X 0.238 X 520                 =  1,485
+  Heat of combustion                        = 14,544
+                                              ------
+                                              16,159
+  Deduct heat equivalent to work of       \
+    displacing atmosphere by products of   }
+    combustion raised from 60 deg. to 100 deg.,    }      32
+    or from 149.8 cubic feet to 161.3      }
+    cubic feet,                           /
+                                              ------
+          Total units of heat available       16,127
+
+Equal to 16.69 lb. of water evaporated from and at 212 deg.. Hence the
+greatest possible evaporation from and at 212 deg. from a lb. of carbon--
+
+       16,159 u. X 0.891 - 32 u.
+  W = --------------------------- = 14.87 lb.
+               966 u.
+
+I will now take a definite case, and compare the potential energy of a
+certain kind of fuel with the results actually obtained. For this
+purpose the boiler of the eight-horse portable engine, which gained
+the first prize at the Cardiff show of the Royal Agricultural Society
+in 1872, will serve very well, because the trials, all the details of
+which are set forth very fully in vol. ix. of the _Journal_ of the
+Society, were carried out with great care and skill by Sir Frederick
+Bramwell and the late Mr. Menelaus; indeed, the only fact left
+undetermined was the temperature of the furnace, an omission due to
+the want of a trustworthy pyrometer, a want which has not been
+satisfied to this day.[2]
+
+   [Footnote 2: In the fifty-second volume of the _Proceedings_
+   (1887-78), page 154, will be found a remarkable experiment on the
+   evaporative power of a vertical boiler with internal circulating
+   pipes. The experiment was conducted by Sir Frederick Bramwell and
+   Dr. Russell, and is remarkable in this respect, that the quantity
+   of air admitted to the fuel, the loss by convection and
+   radiation, and the composition of the smoke were determined. The
+   facts observed were as follows:
+
+   Steam pressure 53 lb................................... = 300.6 deg. F.
+                                                               lb.
+   Fuel--Water in coke and wood...........................    26.08
+         Ash..............................................    10.53
+         Hydrogen, oxygen, nitrogen, and sulphur..........     7.18
+                                                             ------
+                Total non-combustible.....................    43.79
+         Carbon, being useful combustible.................   194.46
+                                                             ------
+                Total fuel................................   238.25
+
+   Air per pound of carbon................................   17-1/8 lb.
+   Time of experiment.....................................  4 h. 12 min.
+   Water evaporated from 60 deg. into steam at 53 lb. pressure   1,620 lb.
+   Heat lost by radiation and convection..................  70,430 units.
+   Mean temperature of chimney............................    700 deg. F.
+    "        "       " air................................     70 deg. F.
+
+   No combustible gas was found in the chimney.
+
+   I will apply Carnot's doctrine to this case.
+
+   Potential energy of the fuel with respect to absolute zero:
+                                                               Units.
+     239.25 lb. x 530 deg. abs. x 0.238 ...................... =   30,053
+     194.46 lb. x 17-1/8 x 530 deg. x 0.238,
+         the weight and heat of air.......................    420,660
+     194.46 x 14,544 units heat of combustion of carbon...  2,828,200
+                                                            ---------
+                Total energy                                3,278,813
+     Heat absorbed in evaporating 26.08 lb. of water
+       in fuel............................................    -29,888
+                                                            ---------
+                Available energy..........................  3,248,425
+
+   Temperature of furnace--
+
+   The whole of the fuel was heated up, but the heat absorbed in the
+   evaporation of the water lowered the temperature of the furnace,
+   and must be deducted from the heat of combustion.
+
+                                                                Units.
+     Heat of combustion...................................  2,828,200
+       "   " evaporation of 26.08 lb. water...............    -29,888
+                                                            ---------
+                Available heat of combustion..............  2,798,312
+
+     Dividing by 238.25 lb. gives the heat per 1 lb.
+       of fuel used................................... = 11,745 units.
+     And temperature of furnace:
+     11,745 units/(18.125 lb. x 0.238) + 530 deg.......... = 3,253 deg.
+     Temperature of chimney 700 deg. + 460 deg................ = 1,160 deg.
+     Maximum duty (3,253 deg. - 1,160 deg.)/3,253 deg............. = 0.643 deg.
+
+   Work of displacing atmosphere by smoke at 700 deg.:
+                                                         Cubic feet.
+      Volumes of gases at  70 deg.........................    = 228.3
+        "      "   "    " 700 deg.........................    = 499.8
+                                                            -----
+                Increase of volume....................      271.5
+
+                                                             Units.
+     Work done=
+     (194.46 lb. x 271.5 cub. ft. x 144 sq. in. x 15 lb.)
+      /722 units ..................................... =   147,720
+     Maximum amount of work to be expected =
+       3,248,425 x 0.643.............................. = 2,101,700
+     Deduct work of displacing atmosphere............. =   147,720
+                                                         ---------
+                Available work........................   1,953,980
+
+   Actual work done:
+                                                             Units.
+     1,620 lb. of water raised from 60 deg. and turned
+       into steam at 53 lb..... ...................... = 1,855,900
+     Loss by radiation and convection.................      70,430
+     10-1/2 lb. ashes left, say at 500 deg................       1,129
+                                                         ---------
+                Total work actually done..............   1,927,459
+     Unaccounted for..................................      26,521
+                                                         ---------
+     Calculated available work........................   1,953,980
+
+   The unaccounted-for work, therefore, amounts to only 11/2 per cent.
+   of the calculated available work.
+
+   Sir Frederick Bramwell ingeniously arranged his data in the form
+   of a balance sheet, and showed 253,979 units unaccounted for; but
+   if from this we deduct the work lost in displacing the air, the
+   unaccounted-for heat falls to less than 4 per cent. of the total
+   heat of combustion. These results show how extremely accurate the
+   observations must have been, and that the loss mainly arises from
+   convection and radiation from the boiler.]
+
+The data necessary for our purpose are:
+
+Steam pressure 80 lb. temperature                    324 deg. = 784 deg. absolute.
+Mean temperature of smoke                            389 deg. = 849 deg.    "
+Water evaporated per 1 lb of coal, from and at 212 deg.  11.83 lb.
+Temperature of the air                                60 deg. = 520 deg. absolute.
+     "      of feed water                            209 deg. = 669 deg.    "
+Heating surface                                      220 square feet.
+Grate surface                                        3.29 feet.
+Coal burnt per hour                                  41 lb.
+
+The fuel used was a smokeless Welsh coal, from the Llangennech
+colleries. It was analyzed by Mr. Snelus, of the Dowlais Ironworks,
+and in Table II. are exhibited the details of its composition, and the
+weight and volume of air required for its combustion. The total heat
+of combustion in 1 lb of water evaporated:
+
+      = 15.06 x (0.8497 + 4.265 x (0.426 - 0.035/8))
+      = 15.24 lb. of water from and at 212 deg.
+      = 14,727 units of heat.
+
+           TABLE II.--PROPERTIES OF LLANGENNECH COAL.
+
+  ---------------------+----------+------------+---------------------+
+                       |          |            |                     |
+                       |          |            |    Products of      |
+                       |          |  Oxygen    | Combustion at 32 deg. F.|
+                       | Analyses | required   +--------+------------+
+                       | of 1 lb. |    for     |        |            |
+                       | of Coal. | Combustion.| Cubic  |  Volume    |
+                       |          | Pounds.    | feet.  | per cent.  |
+  ---------------------+----------+------------+--------+------------+
+   Carbon...........   |  0.8497  |  2.266     |  25.3  |     11.1   |
+   Hydrogen.........   |  0.0426  |  0.309     |   7.6  |      3.4   |
+   Oxygen...........   |  0.0350  |    ---     |   ---  |      ---   |
+   Sulphur..........   |  0.0042  |    ---     |   ---  | _    ---   |
+   Nitrogen.........   |  0.1045  |    ---     |   0.18 |  |         |
+   Ash..............   |  0.0540  |    ---     |   ---  |  |         |
+                       +----------+------------+        |  |  85.5   |
+                       |          |            |        |  |         |
+    Total...........   |  1.0000  |  2.572     |   ---  |  |         |
+  9-1/3.lb nitrogen    |    ---   |    ---     | 118.9  |  |         |
+  6 lb. excess of air. |    ---   |    ---     |  71.4  | _|         |
+                       +----------+------------+--------+------------+
+  Total cubic feet of  |          |            |        |            |
+  products per 1 lb.   |          |            |        |            |
+  of coal...........   |    --    |    --      | 226.4  |    100.0   |
+  ---------------------+----------+------------+--------+------------+
+
+The temperature of the furnace not having been determined, we must
+calculate it on the supposition, which will be justified later on,
+that 50 per cent more air was admitted than was theoretically
+necessary to supply the oxygen required for perfect combustion. This
+would make 18 lb. of air per 1 lb. of coal; consequently 19 lb. of
+gases would be heated by 14,727 units of heat. Hence:
+
+         14,727 u.
+  T = ---------------- = 3,257 deg.
+       19 lb. x 0.238
+
+above the temperatures of the air, or 3,777 deg. absolute. The temperature
+of the smoke, _t_, was 849 deg. absolute; hence the maximum duty would be
+
+      3,777 deg. - 849 deg.
+     --------------- = 0.7752.
+          3,777 deg.
+
+The specific heat of coal is very nearly that of gases at constant
+pressure, and may, without sensible error, be taken as such. The
+potential energy of 1 lb. of coal, therefore, with reference to the
+oxygen with which it will combine, and calculated from absolute zero,
+is:
+
+                                                              Units.
+19 lb. of coal and air at the temperature
+  of the air contained 19 lb. x 520 deg. x 0.238                   2,350
+Heat of combustion                                            14,727
+                                                             -------
+                                                              17,078
+Deduct heat expended in displacing atmosphere 151 cubic feet   - 422
+                                                              ------
+            Total potential energy                            16,656
+
+Hence work to be expected from the boiler:
+
+                    / 3,777 deg. - 849 deg. \
+  = 17,078 units X ( --------------- ) - 422 units
+                    \     3,777 deg.    /
+    ---------------------------------------------- = 13.27 lb.
+                         966 units
+
+of water evaporated from and at 212 deg., corresponding to 12,819 units.
+The actual result obtained was 11.83 lb.; hence the efficiency of this
+boiler was
+
+    11.83
+   ------- = 0.892.
+    13.27
+
+I have already claimed for a boiler that it is a veritable heat
+engine, and I have ventured to construct an indicator diagram to
+illustrate its working. The rate of transfer of heat from the furnace
+to the water in the boiler, at any given point, is some way
+proportional to the difference of temperature, and the quantity of
+heat in the gases is proportional to their temperatures. Draw a base
+line representing -460 deg. Fahr., the absolute zero of temperature. At
+one end erect an ordinate, upon which set off T = 3,777 deg., the
+temperature of the furnace. At 849 deg. = _t_, on the scale of
+temperature, draw a line parallel to the base, and mark on it a length
+proportional to the heating surface of the boiler; join T by a
+diagonal with the extremity of this line, and drop a perpendicular on
+to the zero line. The temperature of the water in the boiler being
+uniform, the ordinates bounded by the sloping line, and by the line,
+_t_, will at any point be approximately proportional to the rate of
+transmission of heat, and the shaded area above _t_ will be
+proportional to the quantity of heat imparted to the water. Join T by
+another diagonal with extremity of the heating surface on the zero
+line, then the larger triangle, standing on the zero line, will
+represent the whole of the heat of combustion, and the ratio of the
+two triangles will be as the lengths of their respective bases, that
+is, as (T - _t_) / T, which is the expression we have already used. The
+heating surface was 220 square feet, and it was competent to transmit
+the energy developed by 41 lb. of coal consumed per hour = 12,819 u. x
+41 u. = 525,572 units, equal to an average of 2,389 units per square
+foot per hour; this value will correspond to the mean pressure in an
+ordinary diagram, for it is a measure of the energy with which
+molecular motion is transferred from the heated gases to the
+boiler-plate, and so to the water. The mean rate of transmission,
+multiplied by the area of heating surface, gives the area of the
+shaded portion of the figure, which is the total work which should
+have been done, that is to say, the work of evaporating 544 lb. of
+water per hour. The actual work done, however, was only 485 lb. To
+give the speculations we have indulged in a practical turn, it will be
+necessary to examine in detail the terms of Carnot's formula. Carnot
+labored under great disadvantages. He adhered to the emission theory
+of heat; he was unacquainted with its dynamic equivalent; he did not
+know the reason of the difference between the specific heat of air at
+constant pressure and at constant volume, the idea of an absolute zero
+of temperature had not been broached; but the genius of the man, while
+it made him lament the want of knowledge which he felt must be
+attainable, also enabled him to penetrate the gloom by which he was
+surrounded, and enunciate propositions respecting the theory of heat
+engines, which the knowledge we now possess enables us to admit as
+true. His propositions are:
+
+1. The motive power of heat is independent of the agents employed to
+develop it, and its quantity is determined solely by the temperature
+of the bodies between which the final transfer of caloric takes place.
+
+2. The temperature of the agent must in the first instance be raised
+to the highest degree possible in order to obtain a great fall of
+caloric, and as a consequence a large production of motive power.
+
+3. For the same reason the cooling of the agent must be carried to as
+low a degree as possible.
+
+4. Matters must be so arranged that the passage of the elastic agent
+from the higher to the lower temperature must be due to an increase of
+volume, that is to say, the cooling of the agent must be caused by its
+rarefaction.
+
+This last proposition indicates the defective information which Carnot
+possessed. He knew that expansion of the elastic agent was accompanied
+by a fall of temperature, but he did not know that that fall was due
+to the conversion of heat into work. We should state this clause more
+correctly by saying that "the cooling of the agent must be caused by
+the external work it performs." In accordance with these propositions,
+it is immaterial what the heated gases or vapors in the furnace of a
+boiler may be, provided that they cool by doing external work and, in
+passing over the boiler surfaces, impart their heat energy to the
+water. The temperature of the furnace, it follows, must be kept as
+high as possible. The process of combustion is usually complex. First,
+in the case of coal, close to the fire-bars complete combustion of the
+red hot carbon takes place, and the heat so developed distills the
+volatile hydrocarbons and moisture in the upper layers of the fuel.
+The inflammable gases ignite on or near the surface of the fuel, if
+there be a sufficient supply of air, and burn with a bright flame for
+a considerable distance around the boiler. If the layer of fuel be
+thin, the carbonic acid formed in the first instance passes through
+the fuel and mixes with the other gases. If, however, the layer of
+fuel be thick, and the supply of air through the bars insufficient,
+the carbonic acid is decomposed by the red hot coke, and twice the
+volume of carbonic oxide is produced, and this, making its way through
+the fuel, burns with a pale blue flame on the surface, the result, as
+far as evolution of heat is concerned, being the same as if the
+intermediate decomposition of carbonic acid had not taken place. This
+property of coal has been taken advantage of by the late Sir W.
+Siemens in his gas producer, where the supply of air is purposely
+limited, in order that neither the hydrocarbons separated by
+distillation, nor the carbonic oxide formed in the thick layer of
+fuel, may be consumed in the producer, but remain in the form of crude
+gas, to be utilized in his regenerative furnaces.
+
+[Illustration: THE GENERATION OF STEAM. Fig 3.]
+
+[Illustration: THE GENERATION OF STEAM. Fig 4.]
+
+[Illustration: THE GENERATION OF STEAM. Fig 5.]
+
+[Illustration: THE GENERATION OF STEAM. Fig 6.]
+
+[Illustration: THE GENERATION OF STEAM. Fig 7.]
+
+_(To be continued.)_
+
+       *       *       *       *       *
+
+[Continued from SUPPLEMENT No. 437, page 6970.]
+
+
+
+
+PLANETARY WHEEL-TRAINS.
+
+By Prof. C.W. MACCORD, Sc.D.
+
+
+II.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 14]
+
+It has already been shown that the rotations of all the wheels of a
+planetary train, relatively to the train-arm, are the same when the
+arm is in motion as they would be if it were fixed. Now, in Fig. 14,
+let A be the first and F the last wheel of an _incomplete_ train, that
+is, one having but one sun-wheel. As before, let these be so connected
+by intermediate gearing that, when T is stationary, a rotation of A
+through _m_ degrees shall drive F through _n_ degrees: and also as
+before, let T in the same time move through _a_ degrees. Then, if _m'_
+represent the total motion of A, we have again,
+
+       m' = m + a, or m = m' - a.
+
+This is, clearly, the motion of A relatively to the fixed frame of the
+machine; and is measured from a fixed vertical line through the
+center of A. Now, if we wish to express the total motion of F
+relatively to the same fixed frame, we must measure it from a vertical
+line through the center of F, wherever that maybe; which gives in this
+case:
+
+      n' = n + a, or n = n' - a.
+
+but with respect to the train-arm when at rest, we have:
+
+      ang. vel. A     n
+      ------------ = ---, whence again
+      ang. vel. F     m
+
+        n' - a     n
+        ------ = --- .
+        m' - a     m
+
+This is the manner in which the equation is deduced by Prof. Willis,
+who expressly states that it applies whether the last wheel F is or is
+not concentric with the first wheel A, and also that the train may be
+composed of any combinations which transmit rotation with both a
+constant velocity ratio and a constant directional relation. He
+designates the quantities _m'_, _n'_, _absolute revolutions_, as
+distinguished from the _relative revolutions_ (that is, revolutions
+relatively to the train-arm), indicated by the quantities _m_, _n_:
+adding, "Hence it appears that the absolute revolutions of the wheels
+of epicyclic trains are equal to the sum of their relative revolutions
+to the arm, and of the arm itself, when they take place in the same
+direction, and equal to the difference of these revolutions when in
+the opposite direction."
+
+In this deduction of the formula, as in that of Prof. Rankine, all the
+motions are supposed to have the same direction, corresponding to that
+of the hands of the clock; and in its application to any given train,
+the signs of the terms must be changed in case of any contrary motion,
+as explained in the preceding article.
+
+And both the deduction and the application, in reference to these
+incomplete trains in which the last wheel is carried by the
+train-arm, clearly involve and depend upon the resolving of a motion
+of revolution into the components of a circular translation and a
+rotation, in the manner previously discussed.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 15]
+
+To illustrate: Take the simple case of two equal wheels, Fig. 15, of
+which the central one A is fixed. Supposing first A for the moment
+released and the arm to be fixed, we see that the two wheels will turn
+in opposite directions with equal velocities, which gives _n_/_m_ = -1;
+but when A is fixed and T revolves, we have _m'_ = 0, whence in the
+general formula
+
+  n' - a
+  ------   = -1, or n' = 2 a;
+    -a
+
+which means, being interpreted, that F makes two rotations about its
+axis during one revolution of T, and in the same direction. Again, let
+A and F be equal in the 3-wheel train, Fig. 16, the former being fixed
+as before. In this case we have:
+
+   n
+  --- = 1, m' = 0, which gives
+   m
+
+   n' - a
+  ------- = 1, [therefore] n' = 0;
+    -a
+
+that is to say, the wheel F, which now evidently has a motion of
+circular translation, does not rotate at all about its axis during the
+revolution of the train-arm.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 16]
+
+All this is perfectly consistent, clearly, with the hypothesis that
+the motion of circular translation is a simple one, and the motion of
+revolution about a fixed axis is a compound one.
+
+Whether the hypothesis was made to substantiate the formula, or the
+formula constructed to suit the hypothesis, is not a matter of
+consequence. In either case, no difficulty will arise so long as the
+equation is applied only to cases in which, as in those here
+mentioned, that motion of revolution _can_ be resolved into those
+components.
+
+When the definition of an epicyclic train is restricted as it is by
+Prof. Rankine, the consideration of the hypothesis in question is
+entirely eliminated, and whether it be accepted or rejected, the whole
+matter is reduced to merely adding the motion of the train-arm to the
+rotation of each sun-wheel.
+
+But in attempting to apply this formula in analyzing the action of an
+incomplete train, we are required to add this motion of the train-arm,
+not only to that of a sun-wheel, but to that of a planet-wheel. This
+is evidently possible in the examples shown in Figs. 15 and 16,
+because the motions to be added are in all respects similar: the
+trains are composed of spur-wheels, and the motions, whether of
+revolution, translation, or rotation, _take place in parallel planes
+perpendicular to parallel axes_. This condition, which we have
+emphasized, be it observed, must hold true with regard to the motions
+of the first and last wheels and the train-arm, in order to make this
+addition possible. It is not essential that spur-wheels should be used
+exclusively or even at all; for instance, in Fig. 16, A and F may be
+made bevel or screw-wheels, without affecting the action or the
+analysis; but the train-arm in all cases revolves around the central
+axis of the system, that is, about the axis of A, and to this the axis
+of F _must_ be parallel, in order to render the deduction of the
+formula, as made by Prof. Willis, and also by Prof. Goodeve, correct,
+or even possible.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 17]
+
+This will be seen by an examination of Fig. 17; in which A and B are
+two equal spur-wheels, E and F two equal bevel wheels, B and E being
+secured to the same shaft, and A being fixed to the frame H. As the
+arm T goes round, B will also turn in its bearings in the same
+direction: let this direction be that of the clock, when the apparatus
+is viewed from above, then the motion of F will also have the same
+direction, when viewed from the central vertical axis, as shown at F':
+and let these directions be considered as positive. It is perfectly
+clear that F will turn in its bearings, in the direction indicated, at
+a rate precisely equal to that of the train-arm. Let P be a pointer
+carried by F, and R a dial fixed to T; and let the pointer be vertical
+when OO is the plane containing the axes of A, B, and E. Then, when F
+has gone through any angle a measured from OO, the pointer will have
+turned from its original vertical position through an equal angle, as
+shown also at F'.
+
+Now, there is no conceivable sense in which the motion of T can be
+said to be added to the rotation of F about its axis, and the
+expression "absolute revolution," as applied to the motion of the last
+wheel in this train, is absolutely meaningless.
+
+Nevertheless, Prof. Goodeve states (Elements of Mechanism, p. 165)
+that "We may of course apply the general formula in the case of bevel
+wheels just as in that of spur wheels." Let us try the experiment;
+when the train-arm is stationary, and A released and turned to the
+right, F turns to the left at the same rate, whence:
+
+    n
+   --- = -1; also m' = 0 when A is fixed,
+    m
+
+and the equation becomes
+
+  n' - a
+  ------ = -1, [therefore] n' = 2a:
+   - a
+
+or in other words F turns _twice_ on its axis during one revolution of
+T: a result too palpably absurd to require any comment. We have seen
+that this identical result was obtained in the case of Fig. 15, and it
+would, of course, be the same were the formula applied to Figs. 5 and
+6; whereas it has never, so far as we are aware, been pretended that a
+miter or a bevel wheel will make more than one rotation about its axis
+in rolling once around an equal fixed one.
+
+Again, if the formula be general, it should apply equally well to a
+train of screw wheels: let us take, for example, the single pair shown
+in Fig. 8, of which, when T is fixed, the velocity ratio is unity. The
+directional relation, however, depends upon the direction in which the
+wheels are twisted: so that in applying the formula, we shall have
+_n/m_ = +1, if the helices of both wheels are right handed, and
+_n_/_m_ = -1, if they are both left handed. Thus the formula leads to
+the surprising conclusion, that when A is fixed and T revolves, the
+planet-wheel B will revolve about its axis twice as fast as T moves,
+in one case, while in the other it will not revolve at all.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 18]
+
+A favorite illustration of the peculiarities of epicyclic mechanism,
+introduced both by Prof. Willis and Prof. Goodeve, is found in the
+contrivance known as Ferguson's Mechanical Paradox, shown in Fig. 18.
+This consists of a fixed sun-wheel A, engaging with a planet-wheel B
+of the same diameter. Upon the shaft of B are secured the three thin
+wheels E, G, I, each having 20 teeth, and in gear with the three
+others F, H, K, which turn freely upon a stud fixed in the train-arm,
+and have respectively 19, 20, and 21 teeth. In applying the general
+formula, we have the following results:
+
+                    n     20     n' - a                         1
+  For the wheel F, --- = ---- = ---------, [therefore] n' = - ---- a.
+                    m     19       -a                          19
+
+                    n         n' - a
+   "   "    "   H, --- = 1 = --------, [therefore] n' = 0.
+                    m           -a
+
+                    n     20     n' - a                         1
+   "   "    "   K, --- = ---- = ---------, [therefore] n' = + ---- a.
+                    m     21       -a                          21
+
+The paradoxical appearance, then, consists in this, that although the
+drivers of the three last wheels each have the same number of teeth,
+yet the central one, H, having a motion of circular translation,
+remains always parallel to itself, and relatively to it the upper one
+seems to turn in the same direction as the train-arm, and the lower in
+the contrary direction. And the appearance is accepted, too, as a
+reality; being explained, agreeably to the analysis just given, by
+saying that H has no absolute rotation about its axis, while the other
+wheels have; that of F being positive and that of K negative.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 18]
+
+The Mechanical Paradox, it is clear, may be regarded as composed of
+three separate trains, each of which is precisely like that of Fig.
+16: and that, again, differs from the one of Fig. 15 only in the
+addition of a third wheel. Now, we submit that the train shown in Fig.
+17 is mechanically equivalent to that of Fig. 15; the velocity ratio
+and the directional relation being the same in both. And if in Fig. 17
+we remove the index P, and fix upon its shaft three wheels like E, G,
+and I of Fig. 18, we shall have a combination mechanically equivalent
+to Ferguson's Paradox, the three last wheels rotating in vertical
+planes about horizontal axes. The relative motions of those three
+wheels will be the same, obviously, as in Fig. 18; and according to
+the formula their absolute motions are the same, and we are invited to
+perceive that the central one does not rotate at all about its axis.
+
+But it _does_ rotate, nevertheless; and this unquestioned fact is of
+itself enough to show that there is something wrong with the formula
+as applied to trains like those in question. What that something is,
+we think, has been made clear by what precedes; since it is impossible
+in any sense to add together motions which are unlike, it will be seen
+that in order to obtain an intelligible result in cases like these,
+the equation must be of the form _n'_/(_m'_ - _a_) = _n_/_m_. We shall
+then have:
+
+                    n     20     n'                       20
+  For the wheel F, --- = ---- = ----, [therefore] n' = - ---- a;
+                    m     19     -a                       19
+
+                    n         n'
+  For the wheel H, --- = 1 = ----, [therefore] n' = -a;
+                    m         -a
+
+                    n     20     n'                       20
+  For the wheel K, --- = ---- = ----, [therefore] n' = - ---- a,
+                    m     21     -a                       21
+
+which corresponds with the actual state of things; all three wheels
+rotate in the same direction, the central one at the same rate as the
+train arm, one a little more rapidly and the third a little more
+slowly.
+
+It is, then, absolutely necessary to make this modification in the
+general formula, in order to apply it in determining the rotations of
+any wheel of an epicyclic train whose axis is not parallel to that of
+the sun-wheels. And in this modified form it applies equally well to
+the original arrangement of Ferguson's paradox, if we abandon the
+artificial distinction between "absolute" and "relative" rotations of
+the planet-wheels, and regard a spur-wheel, like any other, as
+rotating on its axis when it turns in its bearings; the action of the
+device shown in Fig. 18 being thus explained by saying that the wheel
+H turns once backward during each forward revolution of the train-arm,
+while F turns a little more and K a little less than once, in the same
+direction. In this way the classification and analysis of these
+combinations are made more simple and consistent, and the
+incongruities above pointed out are avoided; since, without regard to
+the kind of gearing employed or the relative positions of the axes, we
+have the two equations:
+
+       n' - a     n
+   I. -------- = ---, for all complete trains;
+       m' - a     m
+
+          n'      n
+  II. -------- = ---, for all incomplete trains.
+       m' - a     m
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 19]
+
+As another example of the difference in the application of these
+formulae, let us take Watt's sun and planet wheels, Fig. 19. This
+device, as is well known, was employed by the illustrious inventor as
+a substitute for the crank, which some one had succeeded in patenting.
+It consists merely of two wheels A and F connected by the link T; A
+being keyed on the shaft of the engine and F being rigidly secured to
+the connecting-rod. Suppose the rod to be of infinite length, so as to
+remain always parallel to itself, and the two wheels to be of equal
+size.
+
+Then, according to Prof. Willis' analysis, we shall have--
+
+    n' - a     n                               -s
+   -------- = --- = -1, n' = 0, [therefore] -------- = -1, whence
+    m' - a     m                              m' - a
+
+          -a = a - m', or m = 2a.
+
+The other view of the question is, that F turns once backward in its
+bearings during each forward revolution of T; whence in Eq. 2 we
+have--
+
+       n'      n
+   -------- = --- = -1, n' = -a,
+    m' - a     m
+
+                 -a
+  [therefore] -------- -1, which gives -a = a - m', or m' = 2a,
+               m' - a
+
+as before.
+
+It is next to be remarked, that the errors which arise from applying
+Eq. I. to incomplete trains may in some cases counterbalance and
+neutralize each other, so that the final result is correct.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 20]
+
+For example, take the combination shown in Fig. 20. This consists of a
+train-arm T revolving about the vertical axis OO of the fixed wheel A,
+which is equal in diameter to F, which receives its motion by the
+intervention of one idle wheel carried by a stud S fixed in the arm.
+The second train-arm T' is fixed to the shaft of F and turns with it;
+A' is secured to the arm T, and F' is actuated by A' also through a
+single idler carried by T'.
+
+We have here a compound train, consisting of two simple planetary
+trains, A--F and A'--F'; and its action is to be determined by
+considering them separately. First suppose T' to be removed and find
+the motion of F; next suppose F to be removed and T fixed, and find
+the rotation of F'; and finally combine these results, noting that the
+motion of T' is the same as that of F, and the motion of A' the same
+as that of T.
+
+Then, according to the analysis of Prof. Willis, we shall have
+(substituting the symbol _t_ for _a_ in the equation of the second
+train, in order to avoid confusion):
+
+                  n         n' - a
+  1. Train A--F. --- = 1 = --------; m' = 0,
+                  m         m' - a
+
+                            n' - a
+      whence               -------- = 1, n' = 0, = rot. of F.
+                               a
+
+                    n         n' - t
+  2. Train A'--F'. --- = 1 = --------; m' = 0,
+                    m         m' - t
+
+                              n' - t
+     whence again           -------- = 1, t = 0, = rot. of F'.
+                                -t
+
+Of these results, the first is explicable as being the _absolute_
+rotation of F, but the second is not; and it will be readily seen that
+the former would have been equally absurd, had the axis LL been
+inclined instead of vertical. But in either case we should find the
+errors neutralized upon combining the two, for according to the theory
+now under consideration, the wheel A', being fixed to T, turns once
+upon its axis each time that train arm revolves, and in the same
+direction; and the revolutions of T' equal the rotations of F, whence
+finally in train A'--F' we have:
+
+      n         n' - t
+  3. --- = 1 = --------; in which t = 0, m' = a,
+      m         m' - t
+
+                n' - 0
+which gives    --------- = 1, or n' = a.
+                 a - 0
+
+This is, unquestionably, correct; and indeed it is quite obvious that
+the effect upon F' is the same, whether we say that during a
+revolution of T the wheel A' turns once forward and T' not at all, or
+adopt the other view and assert that T' turns once backward and A' not
+at all. But the latter view has the advantage of giving concordant
+results when the trains are considered separately, and that without
+regard to the relative positions of the axes or the kind of gearing
+employed. Analyzing the action upon this hypothesis, we have:
+
+  In train A--F:
+
+    n            n'                         n'
+   --- = 1 = --------; m' = 0, [therefore] ---- = 1, or n' = -a;
+    m         m' - a                        -a
+
+  In train A'--F':
+
+    n'           n'                         n'
+   --- = 1 = --------; m' = 0, [therefore] ---- = 1, or n' = -t;
+    m         m' - t                       -t
+
+In combining, we have in the latter train m' = 0, t = -a, whence
+
+    n           n'           n'
+   --- = 1 = -------- gives ---- = 1, or n' = a, as before.
+    m         m' - t         +a
+
+Now it happens that the only examples given by Prof. Willis of
+incomplete trains in which the axis of a planet-wheel whose motion is
+to be determined is not parallel to the central axis of the system,
+are similar to the one just discussed; the wheel in question being
+carried by a secondary train-arm which derives its motion from a wheel
+of the primary train.
+
+The application of his general equation in these cases gives results
+which agree with observed facts; and it would seem that this
+circumstance, in connection doubtless with the complexity of these
+compound trains, led him to the too hasty conclusion that the formula
+would hold true in all cases; although we are still left to wonder at
+his overlooking the fact that in these very cases the "absolute" and
+the "relative" rotations of the last wheel are identical.
+
+[Illustration: PLANETARY WHEEL TRAINS. Fig. 21]
+
+In Fig. 21 is shown a combination consisting also of two distinct
+trains, in which, however, there is but one train-arm T turning freely
+upon the horizontal shaft OO, to which shaft the wheels A', F, are
+secured; the train-arm has two studs, upon which turn the idlers B B',
+and also carries the bearings of the last wheel F'; the first wheel A
+is annular, and fixed to the frame of the machine. Let it be required
+to determine the results of one revolution of the crank H, the numbers
+of teeth being assigned as follows:
+
+      A = 60, F = 30, A' = 60, F' = 10.
+
+We shall then have, for the train ABF (Eq. I.),
+
+      n       60          n' - a
+     --- = - ---- = -2 = --------, in which n' = 1, m' = 0,
+      m       30          m' - a'
+
+             1 - a                            1
+whence -2 = -------, 2a = 1 - a, 3a = 1, a = ---.
+               -a                             3
+
+And for the train A'B'F' (Eq. II.),
+
+      n     60           n'                   1
+     --- = ---- = 6 = --------, in which a = ---, m' = 1,
+      m     10         m' - a'                3
+
+                           n'
+whence            6 = -----------, or n' = 4.
+                       1 - (1/3)
+
+That is, the last wheel F' turns _four_ times about the axis LL during
+one revolution of the crank H. But according to Profs. Willis and
+Goodeve, we should have for the second train:
+
+      n     60         n' - a                 1
+     --- = ---- = 6 = --------, in which a = ---, m' = 1,
+      m     10         m' - a'                3
+
+                n' - (1/3)
+which gives 6 = -----------, n' - (1/3) = 4, n' = 4-1/3,
+                 1 - (1/3)
+
+or _four and one-third_ revolutions of F' for one of H.
+
+This result, no doubt, might be near enough to the truth to serve all
+practical purposes in the application of this mechanism to its
+original object, which was that of paring apples, impaled upon the
+fork K; but it can hardly be regarded as entirely satisfactory in a
+general way; nor can the analysis which renders such a result
+possible.
+
+       *       *       *       *       *
+
+
+
+
+THE PANTANEMONE.
+
+
+The need of irrigating prairies, inundating vines, drying marshes, and
+accumulating electricity cheaply has, for some time past, led to a
+search for some means of utilizing the forces of nature better than
+has ever hitherto been done. Wind, which figures in the first rank as
+a force, has thus far, with all the mills known to us, rendered
+services that are much inferior to those that we have a right to
+expect from it with improved apparatus; for the work produced,
+whatever the velocity of the wind, has never been greater than that
+that could be effected by wind of seven meters per second. But, thanks
+to the experiments of recent years, we are now obtaining an effective
+performance double that which we did with apparatus on the old system.
+
+Desirous of making known the efforts that have been made in this
+direction, we lately described Mr. Dumont's atmospheric turbine. In
+speaking of this apparatus we stated that aerial motors generally stop
+or are destroyed in high winds. Recently, Mr. Sanderson has
+communicated to us the result of some experiments that he has been
+making for years back by means of an apparatus which he styles a
+pantanemone.
+
+The engraving that we give of this machine shows merely a cabinet
+model of it; and it goes without saying that it is simply designed to
+exhibit the principle upon which its construction is based.
+
+[Illustration: THE PANTANEMONE.]
+
+Two plane surfaces in the form of semicircles are mounted at right
+angles to each other upon a horizontal shaft, and at an angle of 45 deg.
+with respect to the latter. It results from this that the apparatus
+will operate (even without being set) whatever be the direction of the
+wind, except when it blows perpendicularly upon the axle, thus
+permitting (owing to the impossibility of reducing the surfaces) of
+three-score days more work per year being obtained than can be with
+other mills. Three distinct apparatus have been successively
+constructed. The first of these has been running for nine years in the
+vicinity of Poissy, where it lifts about 40,000 liters of water to a
+height of 20 meters every 24 hours, in a wind of a velocity of from 7
+to 8 meters per second. The second raises about 150,000 liters of
+water to the Villejuif reservoir, at a height of 10 meters, every 24
+hours, in a wind of from 5 to 6 meters. The third supplies the
+laboratory of the Montsouris observatory.
+
+The first is not directible, the second may be directed by hand, and
+the third is directed automatically. These three machines defied the
+hurricane of the 26th of last January.--_La Nature._
+
+       *       *       *       *       *
+
+
+
+
+RELVAS'S NEW LIFE-BOAT.
+
+
+The Spanish and Portuguese papers have recently made known some
+interesting experiments that have been made by Mr. Carlos Relvas with
+a new life-boat which parts the waves with great facility and exhibits
+remarkable stability. This boat, which is shown in front view in one
+of the corners of our engraving, is T-shaped, and consists of a very
+thin keel connected with the side-timbers by iron rods. Cushions of
+cork and canvas are adapted to the upper part, and, when the boat is
+on the sea, it has the appearance of an ordinary canoe, although, as
+may be seen, it differs essentially therefrom in the submerged part.
+When the sea is heavy, says Mr. Relvas, and the high waves are
+tumbling over each other, they pass over my boat, and are powerless to
+capsize it. My boat clears waves that others are obliged to recoil
+before. It has the advantage of being able to move forward, whatever
+be the fury of the sea, and is capable, besides, of approaching rocks
+without any danger of its being broken.
+
+[Illustration: RELVAS'S NEW LIFE BOAT.]
+A committee was appointed by the Portuguese government to examine this
+new life-boat, and comparative experiments were made with it and an
+ordinary life-boat at Porto on a very rough sea. Mr. Relvas's boat was
+manned by eight rowers all provided with cork girdles, while the
+government life-boat was manned by twelve rowers and a pilot, all
+likewise wearing cork girdles. The chief of the maritime department,
+an engineer of the Portuguese navy and a Portuguese deputy were
+present at the trial in a pilot boat. The three boats proceeded to the
+entrance of the bar, where the sea was roughest, and numerous
+spectators collected upon the shore and wharfs followed their
+evolutions from afar.
+
+The experiments began at half past three o'clock in the afternoon. The
+two life-boats shot forward to seek the most furious waves, and were
+seen from afar to surmount the billows and then suddenly disappear. It
+was a spectacle as moving as it was curious. It was observed that Mr.
+Relvas's boat cleft the waves, while the other floated upon their
+surface like a nut-shell. After an hour's navigation the two boats
+returned to their starting point.
+
+The official committee that presided over these experiments has again
+found in this new boat decided advantages, and has pointed out to its
+inventor a few slight modifications that will render it still more
+efficient.--_La Nature._
+
+       *       *       *       *       *
+
+
+
+
+EXPERIMENTS WITH DOUBLE-BARRELED GUNS AND RIFLES.
+
+
+The series of experiments we are about to describe has recently been
+made by Mr. Horatio Phillips, a practical gun maker of London. The
+results will no doubt prove of interest to those concerned in the use
+or manufacture of firearms.
+
+The reason that the two barrels of a shot gun or rifle will, if put
+together parallel, throw their charges in diverging lines has never
+yet been satisfactorily accounted for, although many plausible and
+ingenious theories have been advanced for the purpose. The natural
+supposition would be that this divergence resulted from the axes of
+the barrels not being in the same vertical plane as the center line of
+the stock. That this is not the true explanation of the fact, the
+following experiment would tend to prove.
+
+[Illustration: EXPERIMENTS WITH DOUBLE-BARRELLED GUNS.]
+
+Fig. 1 represents a single barrel fitted with sights and firmly
+attached to a heavy block of beech. This was placed on an ordinary
+rifle rest, being fastened thereto by a pin at the corner, A, the
+block and barrel being free to revolve upon the pin as a center.
+Several shots were fired both with the pin in position and with it
+removed, the barrel being carefully pointed at the target each time.
+No practical difference in the accuracy of fire was discernible under
+either condition. When the pin was holding the corner of the block,
+the recoil caused the barrel to move from right to left in a circular
+path; but when the pin was removed, so that the block was not attached
+to the rest in any way, the recoil took place in a line with the axis
+of the bore. It will be observed that the conditions which are present
+when a double barreled gun is fired in the ordinary way from the
+shoulder were in some respects much exaggerated in the apparatus, for
+the pin was a distance of 3 in. laterally from the axis of the barrel,
+whereas the center of resistance of the stock of a gun against the
+shoulder would ordinarily be about one-sixth of this distance from the
+axis of the barrel. This experiment would apparently tend to prove
+that the recoil does not appreciably affect the path of the
+projectile, as it would seem that the latter must clear the muzzle
+before any considerable movement of the barrel takes place.
+
+With a view to obtain a further confirmation of the result of this
+experiment, it was repeated in a different form by a number of shots
+being fired from a "cross-eyed" rifle,[1] in which the sights were
+fixed in the center of the rib. Very accurate shooting was obtained
+with this arm.
+
+   [Footnote 1: A cross-eyed rifle is one made with a crooked stock
+   for the purpose of shooting from the right shoulder, aim being
+   taken with the left eye.]
+
+A second theory, often broached, in order to account for the
+divergence of the charge, is that the barrel which is not being fired,
+by its _vis inertia_ in some way causes the shot to diverge. In order
+to test this, Mr. Phillips took a single rifle and secured it near the
+muzzle to a heavy block of metal, when the accuracy of the shooting
+was in no way impaired.
+
+So far the experiments were of a negative character, and the next step
+was made with a view to discover the actual cause of the divergence
+referred to. A single barrel was now taken, to which a template was
+fitted, in order to record its exact length. The barrel was then
+subjected to a heavy internal hydrostatic pressure. Under this
+treatment it expanded circumferentially and at the same time was
+reduced in length. This, it was considered, gave a clew to the
+solution of the problem. A pair of barrels was now taken and a
+template fitted accurately to the side of the right-hand one. As the
+template fitted the barrel when the latter was not subject to internal
+pressure, upon such pressure being applied any alterations that might
+ensue in the length or contour of the barrel could be duly noted. The
+right-hand barrel was then subjected to internal hydrostatic pressure.
+The result is shown in an exaggerated form in Fig. 2. It will be seen
+that both barrels are bent into an arched form. This would be caused
+by the barrel under pressure becoming extended circumferentially, and
+thereby reduced in length, because the metal that is required to
+supply the increased circumference is taken to some extent from the
+length, although the substance of metal in the walls of the barrel by
+its expansion contributes also to the increased diameter. A simple
+illustration of this effect is supplied by subjecting an India-rubber
+tube to internal pressure. Supposing the material to be sufficiently
+elastic and the pressure strong enough, the tube would ultimately
+assume a spherical form. It is a well known fact that heavy barrels
+with light charges give less divergence than light barrels with heavy
+charges.
+
+After the above experiments it was hoped that, if a pair of barrels
+were put together parallel and soldered only for a space of 3 in. at
+the breech end, and were then coupled by two encircling rings joined
+together as in Fig. 4, the left-hand ring only being soldered to the
+barrel, very accurate shooting would be obtained. For, it was argued,
+that by these means the barrel under fire would be able to contract
+without affecting or being affected by the other barrel; that on the
+right-hand, it will be seen by the illustration, was the one to slide
+in its ring.
+
+A pair of able 0.500 bore express rifle barrels were accordingly
+fitted in this way. Fig. 3 shows the arrangement with the rings in
+position. Upon firing these barrels with ordinary express charges it
+was found that the lines of fire from each barrel respectively crossed
+each other, the bullet from the right-hand barrel striking the target
+10 in. to the left of the bull's eye, while the left barrel placed its
+projectile a similar distance in the opposite direction; or, as would
+be technically said, the barrels crossed 20 in. at 100 yards, the
+latter distance being the range at which the experiment was made.
+These last results have been accounted for in the following manner:
+The two barrels were rigidly joined for a space of 3 in., and for that
+distance they would behave in a manner similar to that illustrated in
+Fig. 2, and were they not coupled at the muzzles by the connecting
+rings they would shoot very wide, the charges taking diverging
+courses. When the connecting rings are fitted on, the barrel not being
+fired will remain practically straight, and, as it is coupled to the
+barrel being fired by the rings, the muzzle of the latter will be
+restrained from pointing outward.
+
+The result will be as shown in an exaggerated manner by the dotted
+lines on the right barrel in Fig. 3.
+
+It would appear from these experiments that when very accurate
+shooting is required at long ranges with double-barreled rifles, they
+should be mounted in a manner similar to that adopted in the
+manufacture of the Nordenfelt machine gun, in which weapon the barrels
+are fitted into a plate at the extreme breech end, the muzzles
+projecting through holes bored to receive them in a metal plate. No
+unequal expansion would then take place, and the barrels would be free
+to become shorter independently of each other. We give the above
+experiments on the authority of their author, who, we believe, has
+taken great pains to render them as exhaustive as possible, so far as
+they go.--_Engineering._
+
+       *       *       *       *       *
+
+
+
+
+BALL TURNING MACHINE.
+
+
+The distinguishing feature in the ball turning machine shown opposite
+is that the tool is stationary, while the work revolves in two
+directions simultaneously. In the case of an ordinary spherical
+object, such as brass clack ball, the casting is made from a perfect
+pattern having two small caps or shanks, in which the centers are also
+marked to avoid centering by hand. It is fixed in the machine between
+two centers carried on a face plate or chuck, with which they revolve.
+One of these centers, when the machine is in motion, receives a
+continuous rotary motion about its axis from a wormwheel, D. This is
+driven by a worm, C, carried on a shaft at the back of the chuck, and
+driven itself by a wormwheel, B, which gears with a screw which rides
+loosely upon the mandrel, and is kept from rotating by a finger on the
+headstock. This center, in its rotation, carries with it the ball,
+which is thus slowly moved round an axis parallel to the face plate,
+at the same time that it revolves about the axis of the mandrel, the
+result being that the tool cuts upon the ball a scroll, of which each
+convolution is approximately a circle, and lies in a plane parallel to
+the line of centers.
+
+When the chuck is set for one size of ball, which may be done in a few
+minutes, any quantity of that diameter may be turned without further
+adjustment. A roughing cut for a 2 in. ball may be done in one minute,
+and a finishing cut leaving the ball quite bright in the same time.
+The two paps are cut off within one-sixteenth of an inch and then
+broken off, and the ball finished in the usual way. On account of the
+work being geometrically true, the finishing by the ferrule tool is
+done in one quarter of the time usually required.
+
+[Illustration: IMPROVED BALL TURNING MACHINE.]
+
+The chuck may be applied to an ordinary lathe or may be combined with
+a special machine tool, as show in our illustration. In the latter
+case everything is arranged in the most handy way for rapid working,
+and six brass balls of 2 in. in diameter can be turned and finished in
+an hour. The machine is specially adapted for turning ball valves for
+pumps, pulsometers, and the like, and in the larger sizes for turning
+governor balls and spherical nuts for armor plates, and is
+manufactured by Messrs. Wilkinson and Lister, of Bradford Road Iron
+Works, Keighley.--_Engineering._
+
+       *       *       *       *       *
+
+
+
+
+COOLING APPARATUS FOR INJECTION WATER.
+
+
+It often happens in towns and where manufactories are crowded
+together, that the supply of water for condensing purposes is very
+small, and consequently that it attains an inconveniently high
+temperature under unfavorable conditions of weather, resulting in the
+deterioration of the vacuum and a consequent increase in the
+consumption of fuel. To remedy or to diminish this difficulty, Messrs.
+Boase and Miller, of London, have brought out the water cooler
+illustrated above. This consists, says _Engineering_, of a revolving
+basket of wire gauze surrounding an inner stationary vessel pierced
+with numerous small holes, through which the heated water discharged
+by the air pump finds its way into the basket, to be thrown out in the
+form of fine spray to a distance of 20 ft. at each side. The drops are
+received in the tank or pond, and in their rapid passage through the
+air are sufficiently cooled to be again injected into the condenser.
+
+The illustration shows a cooler having a basket three feet in
+diameter, revolving at 300 revolutions per minute, and discharging
+into a tank 40 ft. square. It requires 3 to 4 indicated horse-power to
+drive it, and will cool 300 gallons per minute. The following decrease
+of temperature has been observed in actual practice: Water entering at
+95 deg. fell 20 deg. in temperature; water entering at 100 deg. to 110
+deg. fell 25 deg.; and water entering at 110 deg. to 120 deg. fell 30
+deg. The machine with which these trials were made was so placed that
+the top of the basket was four ft. from the surface of the water in
+the pond. With a greater elevation, as shown in the engraving, better
+results can be obtained.
+
+[Illustration: IMPROVED WATER COOLING APPARATUS.]
+
+The advantages claimed for the cooler are that by its means the
+temperature of the injection water can be reduced, the cost and size
+of cooling ponds can be diminished, and condensing engines can be
+employed where hitherto they have not been possible. The apparatus has
+been for two years in operation at several large factories, and there
+is every reason to believe that its use will extend, as it supplies a
+real want in a very simple and ingenious manner. Messrs. Duncan
+Brothers, of Dundee and 32 Queen Victoria Street, E.C., are the
+manufacturers.
+
+       *       *       *       *       *
+
+
+
+
+CORRUGATED DISK PULLEYS.
+
+
+This is a pulley recently introduced by Messrs. J. and E. Hall, of
+Dartford Eng. With the exception of the boss, which is cast, it is
+composed entirely of steel or sheet iron. In place of the usual arms a
+continuous web of corrugated sheet metal connects the boss to the rim;
+this web is attached to the boss by means of Spence's metal. Inside
+the rim, which is flanged inward, a double hoop iron ring is fixed for
+strengthening purposes. The advantageous disposition of metal obtained
+by means of the corrugated web enables the pulley to be made of a
+given strength with less weight of material, and from this cause and
+also on account of being accurately balanced these pulleys are well
+adapted for high speeds.
+
+[Illustration]
+
+       *       *       *       *       *
+
+[KANSAS CITY REVIEW.]
+
+
+
+
+EARLY HISTORY OF THE TELEGRAPH.
+
+
+Although the electric telegraph is, comparatively speaking, a recent
+invention, yet methods of communication at a distance, by means of
+signals, have probably existed in all ages and in all nations. There
+is reason to believe that among the Greeks a system of telegraphy was
+in use, as the burning of Troy was certainly known in Greece very soon
+after it happened, and before any person had returned from Troy.
+Polybius names the different instruments used by the ancients for
+communicating information--"pyrsia," because the signals were always
+made by means of fire lights. At first they communicated information
+of events in an imperfect manner, but a new method was invented by
+Cleoxenus, which was much improved by Polybius, as he himself informs
+us, and which may be described as follows:
+
+Take the letters of the alphabet and arrange them on a board in five
+columns, each column containing five letters; then the man who signals
+would hold up with his left hand a number of torches which would
+represent the number of the column from which the letter is to be
+taken, and with his right hand a number of torches that will represent
+the particular letter in that column that is to be taken. It is thus
+easy to understand how the letters of a short sentence are
+communicated from station to station as far as required. This is the
+pyrsia or telegraph of Polybius.
+
+It seems that the Romans had a method of telegraphing in their walled
+cities, either by a hollow formed in the masonry, or by a tube fixed
+thereto so as to confine the sound, in order to convey information to
+any part they liked. This method of communicating is in the present
+age frequently employed in the well known speaking tubes. It does not
+appear that the moderns had thought of such a thing as a telegraph
+until 1661, when the Marquis of Worcester, in his "Century of
+Inventions," affirmed that he had discovered a method by which a man
+could hold discourse with his correspondent as far as they could
+reach, by night as well as by day; he did not, however, describe this
+invention.
+
+Dr. Hooke delivered a discourse before the Royal Society in 1684,
+showing how to communicate at great distances. In this discourse he
+asserts the possibility of conveying intelligence from one place to
+another at a distance of 120 miles as rapidly as a man can write what
+he would have sent. He takes to his aid the then recent invention of
+the telescope, and explains how characters exposed at one station on
+the top of one hill may be made visible to the next station on the top
+of the next hill. He invented twenty-four simple characters, each
+formed of a combination of three deal boards, each character
+representing a letter by the use of cords; these characters were
+pushed from behind a screen and exposed, and then withdrawn behind the
+screen again. It was not, however, until the French revolution that
+the telegraph was applied to practical purposes; but about the end of
+1703 telegraphic communication was established between Paris and the
+frontiers, and shortly afterward telegraphs were introduced into
+England.
+
+The history of the invention and introduction of the electric
+telegraph by Prof. Morse is one of inexhaustible interest, and every
+incident relating to it is worthy of preservation. The incidents
+described below will be found of special interest. The article is from
+the pen of the late Judge Neilson Poe, and was the last paper written
+by him. He prepared it during his recent illness, the letter embodied
+in it from Mr. Latrobe being of course obtained at the time of its
+date. It is as follows:
+
+On the 5th of April, 1843, when the monthly meeting of the directors
+of the Baltimore & Ohio Railroad Company was about to adjourn, the
+President, the Hon. Louis McLane, rose with a paper in his hand which
+he said he had almost overlooked, and which the Secretary would read.
+It proved to be an application from Prof. Morse for the privilege of
+laying the wires of his electric telegraph along the line of the
+railroad between Baltimore and Washington, and was accompanied by a
+communication from B.H. Latrobe, Esq., Chief Engineer, recommending
+the project as worthy of encouragement.
+
+On motion of John Spear Nicholas, seconded by the Hon. John P.
+Kennedy, the following resolution was then considered:
+
+_Resolved_, "That the President be authorized to afford Mr. Morse such
+facilities as may be requisite to give his invention a proper trial
+upon the Washington road, provided in his opinion and in that of the
+engineer it can be done without injury to the road and without
+embarrassment to the operations of the company, and provided Mr. Morse
+will concede to the company the use of the telegraph upon the road
+without expense, and reserving to the company the right of
+discontinuing the use if, _upon experiment_, it should prove _in any
+manner injurious_."
+
+"Whatever," said Mr. McLane, "may be our individual opinions as to the
+feasibility of Mr. Morse's invention, it seems to me that it is our
+duty to concede to him the privilege he asks, and to lend him all the
+aid in our power, especially as the resolution carefully protects the
+company against all present or future injury to its works, and secures
+us the right of requiring its removal at any time."
+
+[In view of the fact that no railroad can now be run safely without
+the aid of the telegraph, the cautious care with which the right to
+remove it if it should become a nuisance was reserved, strikes one at
+this day as nearly ludicrous.]
+
+A short pause ensued, and the assent of the company was about to be
+assumed, when one of the older directors, famed for the vigilance with
+which he watched even the most trivial measure, begged to be heard.
+
+He admitted that the rights and interests of the work were all
+carefully guarded by the terms of the resolution, and that the company
+was not called upon to lay out any of its means for the promotion of
+the scheme. But notwithstanding all this, he did not feel, as a
+conscientious man, that he could, without further examination, give
+his vote for the resolution. He knew that this idea of Mr. Morse,
+however plausible it might appear to theorists and dreamers, and
+so-called men of science, was regarded by all practical people as
+destined, like many other similar projects, to certain failure, and
+must consequently result in loss and possibly ruin to Mr. Morse. For
+one, he felt conscientiously scrupulous in giving a vote which would
+aid or tempt a visionary enthusiast to ruin himself.
+
+Fortunately, the views of this cautious, practical man did not
+prevail. A few words from the mover of the resolution, Mr. Nicholas,
+who still lives to behold the wonders he helped to create, and from
+Mr. Kennedy, without whose aid the appropriation would not have passed
+the House of Representatives, relieved the other directors from all
+fear of contributing to Mr. Morse's ruin, and the resolution was
+adopted. Of the President and thirty directors who took part in this
+transaction, only three, Samuel W. Smith, John Spear Nicholas, and the
+writer, survive. Under it Morse at once entered upon that test of his
+invention whose fruits are now enjoyed by the people of all the
+continents.
+
+It was not, however, until the spring of 1844 that he had his line and
+its appointments in such a condition as to allow the transmission of
+messages between the two cities, and it was in May of that year that
+the incident occurred which has chiefly led to the writing of this
+paper.
+
+
+MR. LATROBE'S RECOLLECTIONS.
+
+MY DEAR MR. POE: Agreeably to my promise, this morning I put
+on paper my recollection of the introduction of the magnetic telegraph
+between Baltimore and Washington. I was counsel of the Baltimore &
+Ohio Railroad Co. at the time, and calling on Mr. Louis McLane, the
+President, on some professional matter, was asked in the course of
+conversation whether I knew anything about an electric telegraph which
+the inventor, who had obtained an appropriation from Congress, wanted
+to lay down on the Washington branch of the road. He said he expected
+Mr. Morse, the inventor, to call on him, when he would introduce me to
+him, and would be glad if I took an opportunity to go over the subject
+with him and afterward let him, Mr. McLane, know what I thought about
+it. While we were yet speaking, Mr. Morse made his appearance, and
+when Mr. McLane introduced me he referred to the fact that, as I had
+been educated at West Point, I might the more readily understand the
+scientific bearings of Mr. Morse's invention. The President's office
+being no place for prolonged conversation, it was agreed that Mr.
+Morse should take tea at my dwelling, when we would go over the whole
+subject. We met accordingly, and it was late in the night before we
+parted. Mr. Morse went over the history of his invention from the
+beginning with an interest and enthusiasm that had survived the
+wearying toil of an application to Congress, and with the aid of
+diagrams drawn on the instant made me master of the matter, and wrote
+for me the telegraphic alphabet which is still in use over the world.
+Not a small part of what Mr. Morse said on this occasion had reference
+to the future of his invention, its influence upon communities and
+individuals, and I remember regarding as the wild speculations of an
+active imagination what he prophesied in this connection, and which I
+have lived to see even more than realized. Nor was his conversation
+confined to his invention. A distinguished artist, an educated
+gentleman, an observant traveler, it was delightful to hear him talk,
+and at this late day I recall few more pleasant evenings than the only
+one I passed in his company.
+
+Of course, my first visit the next morning was to Mr. McLane to make
+my report. By this time I had become almost as enthusiastic as Mr.
+Morse himself, and repeated what had passed between us. I soon saw
+that Mr. McLane was becoming as eager for the construction of the line
+to Washington as Mr. Morse could desire. He entered warmly into the
+spirit of the thing, and laughed heartily, if not incredulously, when
+I told him that although he had been Minister to England, Secretary of
+State, and Secretary of the Treasury, his name would be forgotten,
+while that of Morse would never cease to be remembered with gratitude
+and praise. We then considered the question as to the right of the
+company to permit the line to be laid in the bed of the road--the plan
+of construction at that time being to bury in a trench some eight or
+ten inches deep a half inch leaden tube containing the wrapped wire
+that was to form the electric circuit. About this there was, in my
+opinion, no doubt, and it was not long after that the work of
+construction commenced. I met Mr. Morse from time to time while he
+lived, and often recurred to the evening's discussion at my house in
+Baltimore.
+
+The above is the substance of what I have more than once related to
+other persons. I hope you will persist in your design of putting on
+paper your own very interesting recollections in this connection, and
+if what I have contributed of mine is of service to you, I shall be
+much pleased.
+
+                                  Most truly yours,
+                                    JOHN H.B. LATROBE.
+March 3, 1881.
+
+       *       *       *       *       *
+
+
+
+
+THE KRAVOGL ELECTRIC MOTOR.
+
+
+At the origin of every science, of whatever nature it may be, there is
+always a fruitless period, of greater or less length, characterized by
+the warfare of a few superior minds against general apathy. The finest
+discoveries pass unperceived, so to speak, since they cannot cross the
+limits of a narrow circle; and it often happens that they fall into
+oblivion before they have been seriously judged. Meanwhile, a slow
+progress is imperceptibly made, and, in measure as theoretical
+principles more clearly disengage themselves, a few industrial
+applications spring up and have the effect of awakening curiosity. An
+impulse is thus given, and from this moment a movement in advance goes
+on increasing at a headlong pace from day to day.
+
+With electricity this period has been of comparatively short duration,
+since scarcely a century and a half separate us from the first
+experiments made in this line of research. Now that it has truly taken
+its place in a rank with the other sciences, we like to go back to the
+hesitations of the first hour, and trace, step by step, the history of
+the progress made, so as to assign to each one that portion of the
+merit that belongs to him in the common work. When we thus cast a
+retrospective glance we find ourselves in the presence of one strange
+fact, and that is the simultaneousness of discoveries. That an
+absolutely original idea, fertile in practical consequences, should
+rise at a given moment in a fine brain is well; we admire the
+discovery, and, in spite of us, a little surprise mingles with our
+admiration. But is it not a truly curious thing that _several_
+individuals should have had at nearly the same time that idea that was
+so astonishing in one? This, however, is a fact that the history of
+electrical inventions offers more than one example of. No one ignores
+the fact that the invention of the telephone gave rise to a notorious
+lawsuit, two inventors having had this ingenious apparatus patented on
+the same day and at nearly the same hour. This is one example among a
+thousand. In the history of dynamo-electric machines it is an equally
+delicate matter to fix upon the one to whom belongs the honor of
+having first clearly conceived the possibility of engendering
+continuous currents.
+
+We do not wish to take up this debate nor to go over the history of
+the question again. Every one knows that the first continuous current
+electric generator whose form was practical is due to Zenobius Gramme,
+and dates back to July, 1871, an epoch at which appeared a memoir
+(entitled "Note upon a magneto-electric machine that produces
+continuous currents") that was read to the Academy of Sciences by Mr.
+Jamin. Ten years previous, Pacinotti had had a glimpse of the
+phenomenon, and of its practical realization, but was unfortunately
+unable to appreciate the importance of his discovery and the benefit
+that might be reaped from it. It is of slight consequence whether
+Gramme knew of this experiment or not, for the glory that attaches to
+his name could not be diminished for all that. But an interesting fact
+that we propose to dwell upon now has recently been brought to light
+in an electrical review published at Vienna.[1] It results from
+documents whose authenticity cannot be doubted that, as far back as
+1867, Mr. L. Pfaundler, a professor at Innsbruck, very clearly
+announced the reversibility of a magneto-electric motor constructed by
+Kravogl, a mechanician of the same place, and that he succeeded some
+time before Gramme in obtaining continuous currents.
+
+   [Footnote 1: _Zeitschrift des Electrotechnischen Vereines_ in
+   _Wien_, July, 1883.]
+
+The Kravogl motor that figured at the Universal Exhibition of 1867 is
+but little known, and it is now very difficult to obtain drawings of
+it. What is certain is that this motor is an application of the
+properties of the solenoid, and, from this standpoint, resembles the
+Bessolo motor that was patented in 1855. We may figure the apparatus
+to our mind very well if we suppose that in the Gramme ring a half and
+almost two-thirds of the core are removed, and the spirals are movable
+around the said core. If a current be sent into a portion of the
+spirals only, and in such a way that only half of the core be exposed,
+the latter will move with respect to the bobbin or the bobbin with
+respect to the core, according as we suppose the solenoid or the
+bobbin fixed. In the first case we have a Bessolo motor, and in the
+second a Kravogl one.
+
+In order to obtain a continuous motion it is only necessary to allow
+the current to circulate successively in the different portions of the
+solenoid. It is difficult to keep the core in place, since it is
+unreachable, being placed in the interior of the bobbin. Kravogl
+solved this difficulty by constructing a hollow core into which he
+poured melted lead. This heavy piece, mounted upon rollers, assumed a
+position of equilibrium that resulted from its weight, from friction,
+and from magnetic attraction. But for a current of given intensity
+this position, once reached, did not vary, and so necessitated a
+simple adjustment of the rubbers. Under such circumstances, with a
+somewhat large number of sections, the polarity of the core was nearly
+constant. The spirals as a whole were attached to a soft iron armature
+that had the effect of closing up the lines of forces and forming a
+shell, so to speak.
+
+Like Bessolo, Kravogl never thought of making anything but a motor,
+and did not perceive that his machine was reversible. It results from
+some correspondence between Dr. A. Von Waltenhofen and Mr. L.
+Pfaundler at this epoch that the latter clearly saw the possibility of
+utilizing this motor as a current generator. Under date of November 9,
+1867, he wrote, in speaking of the Kravogl motor, which had just been
+taken to Innsbruck in order to send it to Paris. "I regret that I
+shall not be able to see it any more, for I should have liked to try
+to make it act in an opposite direction, that is to say, to produce a
+current or an electric light by means of mechanical work." A little
+more than two years later these experiments were carried out on a
+larger motor constructed by Kravogl in 1869, and Mr. Pfaundler was
+enabled to write as follows: "Upon running the machine by hand we
+obtain a current whose energy is that of one Bunsen element." This
+letter is dated February 11, 1870, that is to say, it is a year
+anterior to the note of Gramme.
+
+[Illustration: FIG. 1.]
+
+In the presence of the historic interest that attaches to the
+question, we do not think it will be out of place to reproduce here
+the considerations that guided Prof. Pfaundler in the researches that
+led him to convert the Kravogl motor into a dynamo-electric machine.
+Let us consider two magnetized bars, _db_ and _bd'_, placed end to end
+and surrounded by a cylindrical armature forming a shell, this
+armature being likewise supposed to be a permanent magnet and to
+present poles of contrary direction opposite the poles of the bars.
+For the sake of greater simplicity this shell is represented by a part
+only in the figure, _s n n s_. If, into a magnetic field thus
+formed, we pass a spiral from left to right, the spiral will be
+traversed by a current whose direction will change according to the
+way in which the moving is done. It is only necessary to apply Lenz's
+law to see that a reversal of the currents will occur at the points,
+_a_ and _c_, the direction of the current being represented by arrows
+in the figure. If we suppose a continual displacement of the spirals
+from left to right, we shall collect a continuous current by placing
+two rubbers at _a_ and _c_. Either the core or the shell may be
+replaced by a piece of soft iron. In such a case this piece will move
+with the spiral and keep its poles that are developed by induction
+fixed in space. From this, in order to reach a dynamo-electric machine
+it is necessary to try to develop the energy of the magnetic field by
+the action of the current itself. If we suppose the core to be of soft
+iron, and make a closer study of the action of the current as regards
+the polarity that occurs under the influence of the poles, _s_, _n_,
+_s_, we shall see that from _d_ to _a_ and from _b_ to _c_ the current
+is contrary, while that from _a_ to _b_ and from _c_ to _d'_ it is
+favorable to the development of such polarity. In short, with a spiral
+moving from _d_ to _d'_ the resulting effect is _nil_, a fact,
+moreover, that is self-evident. Under such circumstances, if we
+suppose the shell, as well as the core, to be of soft iron, we shall
+obtain a feeble current due to the presence of remanent magnetism; but
+this magnetism will not be able to continue increasing under the
+influence of the current. To solve this difficulty two means present
+themselves: (1) to cause a, favorable magnetic current and act upon
+the armature, and (2) to suppress such portions of the current in the
+spirals as are injurious in effect. The first solution was thought of
+by Gramme in 1871, and is represented diagramatically in Fig. 2. The
+second is due to Prof. Pfaundler, and dates back to 1870. The core is
+cut through the center (Fig. 3), and the portion to the right is
+suppressed; the current is interrupted between _da_ and _cd'_, and is
+closed only between _a_ and _c_ (_v_, Fig. 1). It results from this
+arrangement that, under the action of the current, the polarity due to
+remanent magnetism does nothing but increase. It suffices then for but
+little remanent magnetism to prime the machine; the polarity of the
+shell continues to increase, and the energy of the magnetic field, and
+consequently of the current, has for a limit only the saturation of
+the soft iron. If, now, we curve the core, the spirals, and the
+armature into a circle, we have a Gramme or a Pfaundler machine,
+according as we consider Fig. 2 or Fig. 3.
+
+[Illustration: FIG. 2.]
+
+[Illustration: FIG. 3.]
+
+This latter apparatus has in this case the form shown in Fig. 4.
+
+[Illustration: FIG. 4.]
+
+The spiral, _s m b_, is movable, and the core, N _o s_, is kept in a
+position of equilibrium by virtue of its weight, and is provided with
+rollers. For the sake of greater clearness, the front part of the
+armature is supposed to be removed. The current does not circulate in
+the spirals to the right of the diameter, W O, which latter is not
+absolutely vertical. The position of the rubbers and armature is
+regulated once for all. We do not know just what were the means
+devised by Kravogl to suppress the current in the spheres to the
+right. At all events, it is probable that the system has grown old
+since Gramme invented his collector. In the application of the Kravogl
+motor to the generation of continuous currents, Professor Pfaundler
+now proposes to ingeniously utilize the Gramme collector. In such a
+case the arrangement shown in Fig. 5 would be adopted. Let us suppose
+an ordinary collector having as many plates as there are sections in
+the ring, these plates being connected as usual with the entrance and
+exit wires of the sections. The diametrically opposite touches that
+are in the line, W O, are divided, and one of the halves is connected
+at the entrance, _c a'_ (Fig. 4), with the corresponding section,
+while the other communicates with the exit, _c' a_, of the neighboring
+section. Each of these halves is prolonged by a piece of metal bent
+into the form of an arc of a circle and embracing a little less than a
+semi-circumference. Between these prolongations there is an insulating
+part. In the rotary motion of the spiral, at least one of the touches
+is always outside of the arc comprised between the brushes, R. In
+order to secure a continuity of the circuit in the effective arc, W S_ o_,
+it is only necessary to arrange a rubber, M, in such a way as to
+establish a communication between the two parts of the divided touch
+as soon as this latter enters the arc under consideration.
+
+In order to produce a current in the direction of the arrows shown in
+Fig. 4, the spiral and axle must revolve from right to left. In this
+case the rubber, M, occupies the position shown in the same figure,
+the brushes embracing an arc of a little less than 180 deg.. As soon as
+the lower touch comes in contact with the brush, R, when the
+revolution is being effected from left to right, the rubber, M,
+establishes a communication between the two halves that have until now
+been isolated, and the current is no longer interrupted. The second
+touch during this time is at any point whatever of the arc, W N _o_,
+and the spirals corresponding to the latter arc outside of the
+circuit. In short, thanks to the rubber, M, we have an ordinary Gramme
+collector in that portion of the circuit comprised between the
+brushes, and a collector with a breakage of the circuit in the portion
+to the right.
+
+[Illustration: FIG. 5.]
+
+This type of machine is entirely theoretical. In the apparatus used
+for Prof. Pfaundler's experiments in 1870, the armature revolved with
+the solenoid. The core and armature were of soft iron, and the core
+was arranged in a manner analogous to the preceding, and remained in
+place under the action of its weight, and the shell, forming a
+complete circle, revolved with poles fixed in space.
+
+Practically, the machine that we have just described would prove
+inconvenient to realize, and would present serious inconveniences. In
+the first place, it seems to us quite difficult to transmit the motion
+of the solenoid to the axle, supposing the former to revolve within
+the armature. In the second place, considerable friction would surely
+occur between the spirals and core, and the axle, being submitted to a
+lateral stress, would be placed in a poor condition for work. It is
+even allowable to doubt whether such a type could be practically got
+up. At all events, no trial has as yet been made of it.
+
+Compared with the Gramme machine, from an absolutely theoretical point
+of view, the Pfaundler apparatus presents undoubted advantages. A
+theoretically perfect dynamo electric machine would be one in which
+there was a complete reciprocity between the magnetizing action of the
+current and the inductive action of the magnetic field. Now, such is
+not the case in the Gramme machine. In this apparatus the soft iron
+core is at the same time a magnet through favorable induction and a
+disadvantageous electro-magnet. This double polarization is only
+remedied to a certain extent by the adjustment of the brushes. In the
+Pfaundler machine, on the contrary, the electro-magnetism and
+magnetism through induction act in the same direction, and concur in
+effecting a polarization that favors the production of the current.
+Looked at it in this light, the latter machine more nearly approaches
+the type of perfection than does that of Gramme.
+
+But we must not forget that such qualities are purely theoretical. In
+practice the best machine is that in which the copper is best
+utilized, that is to say, that which with a given weight of this metal
+furnishes the most work. Now, this is certainly not the case in the
+Pfaundler machine, for here half or more than half of the ring is
+inert--a defect which is apparent at first sight. It results from this
+that as soon as we propose to obtain an electromotive force, however
+slight it be, we must get it with machines of large dimensions. Now,
+it is permissible to believe that under such circumstances (taking
+into consideration the complication of mechanical means that the
+construction of such apparatus necessitates, and the great friction
+that occurs) it would be impossible to obtain practical rotary
+velocities. Comparing his machine with Gramme's, Prof. Pfaundler
+expresses the idea that between them there is the same analogy as
+there is between a constant pressure and an expansion engine. With
+cylinders of equal diameters the work performed by the former of these
+is greater than that done by the second, but in the latter the
+expansive force of the steam is better utilized. This comparison seems
+to us to be more ingenious than exact. Would it not be coming nearer
+to the truth if we were to suppose a case of a hydraulic motor whose
+performance continued diminishing with the height of the fall, and
+would it not be advantageous under such circumstances to utilize only
+a portion of the fall for the purpose of increasing the motor's
+performance?
+
+This machine, however, as before stated, has never as yet been
+constructed, so that experimental data relative to its mode of working
+are wanting. It is especially interesting as regards its origin, which
+dates back to an epoch at which researches on the dynamo electric
+machine were at their heat. It is in its historical aspect that it is
+proper to regard it, and it is from such a point of view that we have
+deemed it well to say a few words about it in this place.--_La Lumiere
+Electrique._
+
+       *       *       *       *       *
+
+
+
+
+BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES.
+
+
+We shall not attempt to pass in review the several apparatus that have
+hitherto been devised for igniting blasts in mining operations, but
+shall simply describe in this place a machine recently invented for
+this purpose by Mr. Bornhardt, an engineer to the Grand Duke of
+Brunswick.
+
+This apparatus (shown in the accompanying engravings) consists
+essentially of two hard-rubber disks, A (Figs. 2 and 3), keyed to an
+iron axle, and of two rubbers, B, that are formed of skin and are held
+against the disks by small springs, R; motion is communicated to the
+axle, _a_, by means of a pair of gearings, _a_ and _b_, and a crank,
+_f_.
+
+[Illustration: BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES.]
+
+Each disk revolves between two metallic rings, _c_, provided with
+points that attract and collect in Leyden jars, D, the electricity
+produced by the friction. For discharging the condensers there is
+employed a manipulator formed of a rod, mm, which can be acted upon,
+from the exterior, by means of a button, _k_. Upon bringing the ball,
+_m_, of the rod in contact with the ball, _p_, of the condenser, the
+lever (which then takes the position shown by the dotted line)
+continues to remain in connection with a small ring, _q_, through a
+special spring. Another ring, _t_, is connected in the same way with
+the external armature of the condenser. Upon connecting the rings, _p_
+and _t_, by a wire to which cartridges are attached, any number of the
+latter may be ignited.
+
+The parts that we have just enumerated are inclosed in a tin box
+covered with a wooden casing, P. Between the two there is inserted a
+sheet of hard rubber in order to prevent a loss of electricity; the
+whole is held in place by strong springs.
+
+In order to show the normal state of the condenser, a scale consisting
+of 15 metallic buttons to give the dimensions of the sparks, is
+arranged at X. This scale is capable of being connected with the
+rings, _q_ and _t_, by means of chains; when the spark obtained after 15
+or 20 revolutions considerably exceeds the intervals of the scale, it
+is a sure thing that the machine is in a proper state.
+
+In order to prepare the apparatus for carriage, the winch is taken off
+and placed in the compartment, _m_, which is closed by means of a
+door, Q.
+
+Figs. 5 and 6 show the arrangement of the dynamite cartridges and
+wires in the blast hole. Figs. 7 to 10 show different arrangements of
+the igniting wires. Figs. 11 and 12 give the general arrangement for
+igniting a number of cartridges simultaneously by means of the
+electric machine. Fig. 13 shows the arrangement where powder is
+employed. Fig. 14 shows the arrangement of a horizontal
+hole.--_Annales Industrielles._
+
+       *       *       *       *       *
+
+
+
+
+IMPROVED ELECTRIC FIRE ALARM.
+
+
+The object of this apparatus is to close an electric circuit when the
+temperature of a room rises above a certain point. Many devices have
+been invented for effecting this object, each of which have their own
+advantages or disadvantages. The invention of Mr. Pritchett enables
+the required result to be obtained in a very satisfactory manner. The
+apparatus consists (as shown by the figure) of a long glass vessel
+containing air; connected to this vessel there is a glass tube filled
+with mercury. The whole is mounted on a metal cradle, which turns on
+pivots. According to the position which the glass vessel and its
+adjuncts occupy in the cradle (this position being adjustable by means
+of a thumb-screw, seen at the upper part of the cradle), so will the
+same have a tendency to rock longitudinally over to one side or the
+other. Now, if we suppose the position to be such that the right hand
+end of the glass vessel is depressed, and the left hand end raised,
+then if the vessel becomes subjected to an elevation of temperature,
+the air inside the same will become expanded, and the mercury column
+in the tube will be driven over to the left, and will rise in the
+turned up end of the tube. This will cause the left hand branch of the
+glass vessel, and its attachments, to become increased in weight,
+while the right hand branch will become proportionally lighter; the
+consequence of this will be that the vessel and its cradle will cant
+over, and by falling on an electrical contact will close a circuit and
+sound an alarm. It is obvious that the apparatus is equally well
+adapted for indicating a diminution as well as an increase of
+temperature, for if the electrical contact be placed under the right
+hand portion of the cradle, and the latter be adjusted so that in its
+normal position its left hand portion is depressed, then when the
+glass vessel becomes cooled, the air in it will contract, and the
+mercury will fall in the turned-up portion of the tube before referred
+to, and will rise in the limb connected to the vessel, consequently
+the cradle and glass vessel will cant over in the reverse way to that
+which it did in the first case.
+
+Owing to the surface which the glass vessel exposes, the air inside
+quickly responds to any external change of temperature, consequently
+the apparatus is very sensitive. Another important feature is the fact
+that the cradle and vessel in canting over acquires a certain
+momentum, and thus the contact made becomes very certain.
+
+[Illustration: PRITCHETT'S ELECTRIC FIRE ALARM.]
+
+Mr. Pritchett proposes that his apparatus shall give external evidence
+outside the house by ringing a gong, and by dropping a semaphore arm
+released by an electromagnet. He also proposes (as has often been
+suggested) that a water supply shall be automatically turned
+on.--_Electrical Review._
+
+       *       *       *       *       *
+
+
+
+
+A STANDARD THERMOPILE.
+
+
+Dr. G. Gore, F.R.S., has invented an improved thermopile for
+measuring small electromotive forces. It consists of about 300 pairs
+of horizontal, slender, parallel wires of iron and German silver, the
+former being covered with cotton. They are mounted on a wooden frame.
+About 11/2 in. of the opposite ends of the wires are bent downward to a
+vertical position to enable them to dip into liquids at different
+temperatures contained in long narrow troughs; the liquids being
+non-conductors, such as melted paraffin for the hot junctions, and the
+non-volatile petroleum, known as thin machinery oil. The electromotive
+force obtained varies with the temperature; a pile of 295 pairs having
+a resistance of 95.6 ohms at 16 deg. Cent. gave with a difference of
+temperature of 100 deg. Cent. an electromotive force of 0.7729 volts,
+or with 130 deg. Cent. an electromotive force of 1.005 volt. Each
+element, therefore, equaled 0.0000262 volt for each degree Cent.
+difference of temperature. On having been verified with a standard
+voltaic cell the apparatus becomes itself a standard, especially for
+small electromotive forces. It is capable of measuring the 1/34861
+part of a volt. For higher electromotive forces than a volt, several
+of these piles would have to be connected in series. The fractional
+electromotive force is obtained by means of a sliding contact which
+cuts out so many pairs as is required.
+
+       *       *       *       *       *
+
+
+
+
+TELEPHONIC TRANSMISSION WITHOUT RECEIVERS.
+
+
+The annual meeting of the French Society of Physics, the success of
+which is continually increasing, took place this year in the salons of
+the Observatory, which were kindly placed at the Society's disposal by
+Admiral Mouchez.
+
+There were three consecutive sessions, the one of Tuesday, April 15,
+being set apart for the members of the Association, the one of the
+16th for the invited guests of Admiral Mouchez, and that of the 17th
+for the invited guests of the Society. The salons were partially
+lighted by the Siemens differential arc, continuous current lamps, and
+partially by the Swan incandescent lamp supplied by a distributing
+machine that permitted of the lamps being lighted and extinguished at
+will without changing the normal operation of all the rest. Many
+apparatus figured at this exhibition, but we shall on the present
+occasion merely call attention to those that presented a certain
+character of novelty or of originality.
+
+Among the apparatus that we shall reserve a description of for the
+present was Messrs. Richard Bros.' registering thermometer designed
+for the Concarneau laboratory, an instrument which, when sunk at one
+mile from the coast, and to a depth of 40 meters, will give a diagram
+of the temperature of the ocean at that depth; and Mr. Hospitalier's
+continuous electrical indicators, designed for making known from a
+distance such mechanical or physical phenomena as velocities, levels,
+temperatures, pressures, etc.
+
+Among the most important of the apparatus exhibited we must reckon Mr.
+Cailletet's devices for liquefying gases, and those of Mr. Mascart for
+determining the ohm. The results obtained by Mr. Mascart (which have
+been submitted to the Committee on Unities of the Congress of
+Electricians now in session at Paris), are sensibly concordant with
+those obtained independently in England by Lord Rayleigh. Everything
+leads to the hope, then, that a rapid and definite solution will be
+given of this important question of electric unities, and that nothing
+further will prevent the international development of the C.G.S.
+system.
+
+Mr. Jules Duboscq made a number of very successful projections, and we
+particularly remarked the peculiar experiment made in conjunction with
+Mr. Parinaud, that gave in projection two like spectra produced by the
+same prism, and which, through superposition, were capable of
+increasing the intensity of the colors, or, on the contrary, of
+reconstituting white light.
+
+Among the optical applications we may cite Mr. Leon Laurent's
+apparatus for controlling plane, parallel, perpendicular, and oblique
+surfaces, and magic mirrors obtained with an ordinary light; Mr. S.P.
+Thompson's apparatus for demonstrating the propagation of
+electro-magnetic waves in ether (according to Maxwell's theory), as
+well as some new polarizing prisms; and a mode of lighting the
+microscope (presented by Mr. Yvon), that was quite analogous to the
+one employed more than a year ago by Dr. Van Heurck, director of the
+Botanical Garden of Anvers.
+
+Acoustics were represented by an electro-magnetic brake siren of Mr.
+Bourbouze; Konig's apparatus for the synthesis of sounds; and Mr. S.P.
+Thompson's cymatograph--a pendulum apparatus for demonstrating the
+phenomena of beats.
+
+It was electricity again that occupied the largest space in the
+programme of the session.
+
+Apparatus for teaching are assuming greater and greater importance
+every day, and the exhibit of Mr. Ducretet included a large number of
+the most interesting of these. The house of Breguet exhibited on a
+reduced scale the magnificent experiments of Gaston Plante, wherein
+320 leaden wire secondary elements charged for quantity with 3 Daniell
+elements, and afterward coupled for tension, served to charge a
+rheostatic machine formed of 50 condensers coupled for quantity. These
+latter, coupled anew for tension, furnished upon being discharged a
+spark due to a difference of potential of about 32,000 volts that
+presented all the characters of the spark produced by induction coils
+on the machines so improperly called "static." Finally, we may cite
+the apparatus arranged by Mr. S.P. Thompson for studying the
+development of currents in magneto-electric machines. The inventor
+studies the influence of the forms of the inductors and armatures of
+machines by means of an arrangement that allows him to change the
+rings or armatures at will and to take out the induced bobbins in
+order to sound every part of the magnetic field. Upon giving the
+armature an angular motion limited by two stops, there develops a
+certain quantity of electricity that may be measured by causing it to
+traverse an appropriate ballistic galvanometer. Messrs. Deprez and
+D'Arsonval's galvanometer answers very well for this purpose, and its
+aperiodicity, which causes it quickly to return to zero as soon as the
+induced current ceases, permits of a large number of readings being
+taken within a very short space of time.
+
+Measuring apparatus were represented by a new and very elegant
+arrangement of Sir William Thomson's reflecting galvanometers, due to
+Mr. J. Carpentier. The mounting adopted by Mr. Carpentier permits of
+an easy removal of the bobbins and of an instantaneous substitution
+therefor. The galvanometric part, composed of the needles and mirror,
+therefore remains entirely free, thus allowing of its being verified,
+and making it convenient to attach the silken fiber. Mr. Carpentier
+has, moreover, adopted for all the minor apparatus a transparent
+celluloid scale which simplifies them, facilitates observations, and
+renders the use of reflection almost industrial.
+
+We shall complete our enumeration of the measuring apparatus by citing
+Ducretet's non-oscillating galvanometer, Sir William Thomson's
+amperemeters, voltameters, ohmmeters, and mhosmeters, constructed and
+exhibited by Breguet, and a new aperiodic galvanoscope of Mr. Maiche.
+Mr. Baudot exhibited the recent improvements that he has made in his
+multiplex printing telegraph, and M. Boudet of Paris showed a new
+system of telephone transmission by submarine cables.
+
+[Illustration: FIG. 1.--DIAGRAM EXHIBITING THE ARRANGEMENT FOR
+TELEPHONIC TRANSMISSIONS WITHOUT A RECEIVER.]
+
+Finally, we shall conclude our enumeration by referring to the
+curiosities. The house of Siemens exhibited a miniature electric
+railway actuated by a new model of Reynier accumulators; M. Maiche
+operated a system of musical telephonic auditions that differed only
+in detail from those instituted by Mr. Ader at the exhibition of 1881;
+and Mr. Hospitalier presented a new form of an experiment devised by
+Mr. Giltay, consisting of a telephonic transmission of sounds without
+the use of receivers. Mr. Giltay's experiment is nothing but Mr.
+Dunand's speaking condenser without the condenser. A glance at Fig. 1
+will show how things are arranged for the experiment. The transmitting
+system comprises two distinct circuits, viz.: (1) one formed of a
+pile, P, of 2 or 3 Leclanche elements, or of 1 or 2 small sized
+accumulators, an Ader microphane transmitter, M, and the inducting
+wire of a small induction coil, B; and (2) the other formed of the
+induced wire of the coil, B, of a pile, P', of 10 or 12 Leclanche
+elements, and of a line whose extremities terminate at R, in two
+ordinary electro-medical handles. With this arrangement the experiment
+performed is as follows: When any one speaks or sings in front of the
+transmitter, T, while two persons, A and B, each having one hand
+gloved, are holding the handles in the ungloved hand, it is only
+necessary for A to place his gloved hand upon B's ear, or for the
+latter to place his hand upon A's, or for each to place his hand on
+the other's ear simultaneously, in order that A or B, or A and B
+simultaneously, may hear a voice issuing from the glove. Under these
+circumstances, Mr. Giltay's experiment is explained like Dunand's
+speaking condenser--the hand of A and the ear of B here constituting
+the armature of an elementary condenser in which the glove performs
+the role of dielectric.
+
+Upon repeating this experiment at the laboratory of the School of
+Physics and Industrial Chemistry of Paris, it has been found that the
+glove maybe replaced by a sheet of plain or paraffined paper. In this
+case, when two persons are holding the handles, and have their ears
+applied, one against the other, if a sheet of paper be interposed,
+airs or words will be heard to proceed therefrom. Finally, it has been
+found possible to entirely suppress the paper, or dielectric, and to
+hear directly, by simply interposing the auditor or auditors in the
+circuit. One of the most curious forms of the experiment is the one
+shown in Fig. 2. Here a third person, C, hears the hands of A and B
+speak when a circuit is formed by means of three persons, A, B, and C,
+the two former, A and B, each holding one of the wires of the circuit
+and applying his free hand to the ear of C. Although the experiment is
+one that requires entire silence, and could not on that account be
+performed at the laboratory, a sort of telephonic chain can be formed
+in which five or six persons may hear at the same time. A, putting his
+hand on the ear of B, the latter putting his to that of C, and so on
+up to the last person, who closes the circuit by grasping one of the
+handles, the other one being held by A.
+
+[Illustration: EXPERIMENT ON TELEPHONIC TRANSMISSION WITHOUT
+RECEIVING APPARATUS.]
+
+It is difficult in the present state of science to explain very
+clearly how these telephonic transmissions are effected without a
+receiver. All that we can conclude from it so far is that the ear is
+an instrument of incomparable delicacy and of exquisite sensitiveness,
+since it perceives vibrations in which the energy developer,
+particularly in the telephonic chain, is exceedingly feeble.
+
+Without any desire to seek an application for an experiment that is
+simply curious, we yet believe that there is here a phenomenon of a
+nature to be studied by physicists. Discoveries in telephony and
+microphony have certainly opened up to science, as regards both theory
+and practice, new horizons that still promise other surprises for the
+future. But to return to the observatory: The success obtained by the
+exhibition of the French Society of Physics shows that these reunions
+respond to a genuine need--that of instructing in and popularizing
+science. While warmly congratulating the organizers of these meetings,
+we may express a wish that the good example set by the Society of
+Physics may be followed by other societies. We are convinced in
+advance that an equal success awaits them.--_La Nature._
+
+       *       *       *       *       *
+
+
+
+
+ON THE ARRANGEMENT OF GROUND CONDUCTORS.
+
+
+In telegraphy, as well as in the question of lightning rods, attention
+has been but incidentally paid to the improvement of ground
+conductors, and this point has not been the object of that careful
+study that has been bestowed upon the establishment of aerial lines.
+It is only recently that the interest created by lightning rods has
+given rise to new forms of conductors differing from those formerly
+used. The publications of the Prussian Academy of Sciences of from
+1876 to 1880 contain some information of special importance in regard
+to this. It is stated therein that the effect of ground conductors may
+be notably increased by the division of the earth plates and the use
+of metallic rods, without necessitating a greater output of material.
+These facts, however, have not as yet been put to profit in practice
+for the reason, perhaps, that the considerations, which have remained
+general, have not at once permitted of obtaining forms what could be
+employed with perfect knowledge of the results. This is what led Mr.
+Ulbricht, of Dresden, to make calculations for a few forms of
+conductors, and to test their approximate values. The results of these
+researches are printed in the _Elektrotechnischen Zeitschrift_ for
+1883 (p. 18).
+
+[Illustration]
+
+The equations found show, in the first place, that there exist three
+means of obtaining a considerable effect, as regards the ground
+conductor, with a slight expenditure of material: The cylindrical
+electrode may be drawn out into the form of a bar or wire; the plate
+may be rendered narrow, and elongated in the form of a ribbon; and,
+besides, the annular plate may be enlarged in lessening the metallic
+surface.
+
+Finally, a short, open cylinder with a vertical axis may be formed by
+curving a narrow plate or ribbon. It is not necessary to see the
+formula to recognize the fact that this cylinder must behave like a
+ribbon and a flat ring. The radius increasing, and the surface
+remaining constant, the resistance of the earth here likewise
+approaches zero.
+
+As the resistance of the earth is inversely proportional to the
+diameter of the plates, the zero resistance can also be reached by
+dividing a plate _ad infinitum_. As the parts of the plate may be
+brought quite close to each other without perceptibly interfering with
+the action, a _network_ has finally been reached by a division carried
+very far, yet limited, and by connecting the parts with one another by
+conducting cylinders.
+
+If we seek to determine what forms of ground conductors are efficient
+and economical under given conditions, we shall have to begin by
+informing ourselves as to the choice of material to be used for the
+electrode, and shall then have to ascertain whether putting it in the
+ground will or will not necessitate much outlay. The most suitable
+material is copper, which may be used with advantage, in that it lasts
+pretty well underground, and that the facility which it may be worked
+permits of easily giving it more appropriate forms than those that can
+be obtained with cast iron, which is of itself less costly.
+
+If the burying in the ground requires little or no labor, as when
+there exist ponds, rivers, and wells, or subterranean strata of water
+near the surface of the earth, elongated forms of conductors will be
+employed, such as the solid or hollow cylinder, the wire, the ribbon,
+the narrow ring, and the network. Plates approaching a square or
+circular shape are not advantageous. But if the ground has to be dug
+deeply in order to sink the conductor, the form of the electrode must
+be more condensed, and selected in such a way that the necessary
+action may be obtained with a minimum output of copper and labor. For
+great depths, and when the ground will permit of boring, an elongated
+and narrow cylinder will be used. Such a system, however, can only be
+employed when the cylinder is surrounded by spring water, since,
+without that, an intimate contact with earth that is only moist,
+cannot be obtained with certainty. In earth that is only moist and for
+moderate depths, preference may be given to an electrode laid down
+flat. The digging necessary in this case is onerous, it is true, but
+it permits of very accurately determining the state of the earth
+beneath and of obtaining a very perfect adherence of the electrode
+therewith. Two forms, the annular ribbon or the flat ring and the
+network, present themselves, according to calculations, as a
+substitute for copper plates, which are so expensive; and these forms
+are satisfactory on condition that the labor of digging be not notably
+increased. These forms should always have a diameter a little greater
+than that of the plate. The flat ring and the network, however, offer
+one weak point, which they possess in common with the plate, and that
+is, their dimensions cannot be easily adapted to the nature of the
+ground met with without a notable increase in the expense. Now, if the
+ground should offer a conductivity less than what was anticipated, and
+it were desired to increase the plate, say by one-third, it would be
+impossible to do so as a consequence of the closed form.
+
+One important advantage is realized in this respect by combining the
+ring and the network in the form of a reticulated ring having a
+diameter of from 1 to 11/2 meters. On cutting this ring at a given place
+and according to a certain radius we obtain the reticulated ribbon
+shown in the accompanying figure. The thickness of the wires is 2.5
+mm., and their weight is 0.475 kilo. per meter. L, L, and L are the
+points at which the conducting cable is soldered. A reticulated ribbon
+of copper can be made in advance of any length whatever, and,
+according to local exigencies, it may be easily curved and given the
+form of a flat or cylindrical ring of varying width. Even though the
+ribbon has already been cut for a ring of given diameter, it may be
+still further enlarged by drawing it out and leaving a bit of the ring
+open, so as to thus obtain a nearly corresponding diminution in the
+resistance. Such a resistance may be still further diminished by
+rendering the ring higher, that is to say, by employing an annular
+cylindrical form.
+
+After assuring himself, by experiments on a small scale, that
+calculation and observation gave concordant results for the flat ring,
+the author made an experiment on a larger scale with the annular
+network. For practical reasons he employed for this purpose a copper
+wire 2.5 mm. in diameter, which may be expected to last as long as one
+of iron plate 2 mm. in thickness. Calculation showed that in a ribbon
+160 mm. wide, meshes 40 mm. in breadth were advantageous and favorable
+as regards rigidity. A reticulated ribbon like this, 4 meters in
+length, was made and formed into a flat ring having an external
+diameter of 1.42 m. and an internal one of 1.10 m. The resistance of
+this ring was found to be W = 0.3485 (1/_k_), and that of a plate one
+meter square, W0 = 0.368 (1/_k_).
+
+As the conductivity of the earth is very variable, and as we cannot
+have an absolute guarantee that the ramming will be uniform, it seemed
+proper to make the measurements of the resistance by fixing the plate
+and the ring in succession to the lower surface of a small raft, in
+such a way that the contact with the water should correspond as well
+as possible to the suppositions made for the calculation. As a second
+ground conductor, a system of water pipes was used, and, after this, a
+lightning rod conductor, etc.
+
+Repeated and varied experiments gave, for the calculation of the
+values of the resistances, equations so concordant that the following
+results may be considered very approximate.
+
+The square plate had a resistance of 35.5 Siemens units, and the
+reticulated ring one of 32.5. From the first figure we deduce k =
+1/91.12, that is to say, the specific conductivity of river-water is
+1:91120000. Calculation, then, gives as the resistance of the earth in
+Siemens units:
+
+                                    Calculated. Observed.
+       Square plate.                   33.5       33.5
+       Annular ring.                   31.76      32.5
+
+These figures prove the accuracy of the calculations that had been
+made in an approximate way.
+
+The experiments were performed upon the Elba, above Dresden. Other
+experiments still had reference to the influence of immersion. In
+order to diminish polarization, only instantaneous currents from the
+measuring pile were employed. It was to be supposed that the current
+of water through which the bubbles of gas were removed from the
+electrodes would not have permitted of a notable resistance of
+polarization. Later measurements, made upon a ribbon buried, like the
+plates, in the earth, gave likewise most favorable results.
+
+As a result of these experiments, the State railways of Saxony have,
+in such cases as were practicable, introduced the annular network of
+copper. There are some manufacturers, too, who seem desirous of
+adopting this system, although it has hardly emerged from the period
+of experiment. The pecuniary advantages that will result from an
+application of it ought, it would seem, to dispel a large proportion
+of the criticisms directed against the erection of lightning rods,
+from the standpoint of expense, and contribute to extend an
+arrangement which may be considered as a very happy one.
+
+If we compare the square plate with the equivalent annular network,
+constructed as above indicated, and which should possess, according to
+the author an external diameter of 1.26 m. and of 3.45 m., we find
+that:
+
+    The square plate, 1 mm. thick weighs 8.9 kilos.
+                 "    2  "    "     "   17.8   "
+    The annular network             "    1.64  "
+
+The cost of reticulated ribbon per meter amounts to about 4.4 francs,
+supposing it to be arranged as shown in the cut.
+
+As term of comparison, we may admit that the following forms are
+nearly the equivalent of a horizontal, unburied plate one meter
+square.
+
+                                   Length. Diameter.
+    Vertical cylinder buried       1.40 m.  0.13  m.
+        "       "      "           1.80 m.  0.06  m.
+    Vertical bar       "           2.60 m.  0.013 m.
+    Horizontal bar     "           5.20 m.  0.013 m.
+
+Horizontal flat ring 1.32 m. in external diameter, and 1.08 m.
+internal.
+
+Horizontal network 1.01 m. square, and having meshes of the same size
+as those of the reticulated ribbon.
+
+Horizontal reticulated ribbon 3 m. in length and of the structure
+described.
+
+Horizontal annular ring 1.26 m. in external diameter, 0.94 m.
+internal.
+
+In conclusion, let us meet an objection that might be made to the
+accuracy of the hypotheses that serve as a base to the preceding
+calculations, in cases where ground plates for lightning rods and not
+for telegraphs are concerned. Between the two ground plates of a
+telegraph line there is generally a distance such that the curves of
+the current undergo no deviation in the vicinity of one of the
+electrodes (the only part important for integrations) through the
+influence of the other. But it might be admitted that such would prove
+the case with a lightning rod in a storm, at the time of the passage
+of the fluid into the earth. The ground plate here is one of the
+electrodes, and the other is replaced by the surface of the earth
+strongly charged to a great distance under the storm clouds. If we
+suppose (what may be admitted in a good lightning rod) that there no
+longer occurs any spark from the point downward, the curves of the
+current, in starting perpendicularly from the ground plate, would be
+obliged to leave their rectilinear trajectory and strike the surface
+of the earth at right angles. When the electricity flows through a
+plane surface into an infinite body, it is only when such surface
+presents a very great development that the respective potentials
+decrease very slowly in the vicinity of the said surface. No notable
+modification occurs, then, in the curves of equal potential, in the
+vicinity of the ground plate through the action of this extended
+charge, nor consequently any modification in the curves of the
+current; but the electricity which spreads has but a short distance to
+travel in order to overcome the most important resistances.
+
+The calculations of resistances given above have, then, the same value
+for discharges of atmospheric electricity.--_Bull. du Musee de
+l'Industrie._
+
+       *       *       *       *       *
+
+
+
+
+ON ELECTROLYSIS.
+
+By H. SCHUCHT.
+
+
+Concerning the separations which take place at the positive pole, the
+composition of the peroxides, and the manner of their determination,
+relatively little has been done.
+
+If solutions of the salts of lead, thallium, silver, bismuth, nickel,
+and cobalt are decomposed by the current between platinum electrodes,
+metal is deposited at the negative, and oxide at the positive
+electrode. Manganese is precipitated only as peroxide. The formation
+of peroxide is, of course, effected by the ozone found in the
+electrolytic oxygen at the positive pole; the oxide existing in
+solution is brought to a higher degree of oxidation, and is separated
+out. Its formation may be decreased or entirely prevented by the
+addition of readily oxidizible bodies, such as organic acids, lactose,
+glycerine, and preferably by an excess of oxalic acid; but only until
+the organic matter is transformed into carbonic acid. In this manner
+Classen separates other metals from manganese in order to prevent the
+saline solutions from being retained by the peroxide.
+
+With solutions of silver, bismuth, nickel, and cobalt, it is often
+practicable to prevent the separation of oxide by giving the current a
+greater resistance--increasing the distance between the electrodes.
+
+The proportion between the quantities of metal and of peroxide
+deposited is not constant, and even if we disregard the concentration
+of the solution, the strength of the current and secondary influences
+(action of nascent hydrogen) is different in acid and in alkaline
+solutions. In acid solutions much peroxide is formed; in alkaline
+liquids, little or none. The reason of the difference is that ozone is
+evolved principally in acid solutions, but appears in small quantities
+only in alkaline liquids, or under certain circumstances not at all.
+The quantity of peroxide deposited depends also on the temperature of
+the saline solution; at ordinary temperatures the author obtained more
+peroxide--the solution, the time, and the strength of current being
+equal--than from a heated liquid. The cause is that ozone is destroyed
+by heat and converted into ordinary oxygen. With the exception of lead
+and thallium the quantity of metal deposited from an acid solution is
+always greater than that of the peroxide.
+
+_Lead._--Luckow has shown that from acid solutions--no matter what may
+be the acid--lead is deposited at the anode as a mixture of anhydrous
+and hydrated peroxide of variable composition. Only very strongly acid
+solutions let all their lead fall down as peroxide; the precipitation
+is rapid immediately on closing the circuit, and complete separation
+is effected only in presence of at least 10 per cent. of free nitric
+acid. As the current becomes stronger with the increase of free acid,
+there is deposited upon the first compact layer a new stratum of
+loosely adhering peroxide.
+
+In presence of small quantities of other metals which are thrown down
+by the current in the metallic state, such as copper, mercury, etc.,
+peroxide alone is deposited from a solution of lead containing small
+quantities only of free nitric acid.
+
+The lead peroxide deposited is at first light brown or dark red, and
+becomes constantly darker and finally taking a velvet-black. As its
+stratification upon the platinum is unequal, it forms beautifully
+colored rings.
+
+Experiments show that the quantity of peroxide deposited depends on
+the nature of the solution and the strength of the current. In case of
+very feeble currents and slight acidity, its quantity is so small that
+it does not need to be taken into consideration. If the lead solution
+is very dilute scarcely any current is observed, lead solutions _per
+se_ being very bad conductors of electricity.
+
+Faintly acid concentrated lead solutions give loose peroxide along
+with much spongy metallic lead. Free alkali decreases the separation
+of peroxide; feebly alkaline solutions, concentrated and dilute, yield
+relatively much peroxide along with metallic lead, while strongly
+alkaline solutions deposit no peroxide.
+
+Dried lead peroxide is so sparingly hygroscopic that it may be weighed
+as such; its weight remains constant upon the balance for a long time.
+In order to apply the peroxide for quantitative determinations, a
+large surface must be exposed to action. As positive electrode a
+platinum capsule is convenient, and a platinum disk as negative pole.
+The capsule shape is necessary because the peroxide when deposited in
+large quantities adheres only partially, and falls in part in thin
+loose scales. It is necessary to siphon off the nitric solution,
+since, like all peroxides, that of lead is not absolutely insoluble in
+nitric acid. The methods of Riche and May give results which are
+always too high, since portions of saline solution are retained by the
+spongy deposit and can be but very imperfectly removed by washing.
+This is especially the case in presence of free alkali.
+
+The author has proceeded as follows: The lead peroxide is dried in the
+capsule, and there is passed over it pure dry gaseous sulphurous acid
+in a strong current from a rather narrow delivery tube. Lead sulphate
+is formed with evolution of heat; it is let cool under the exsiccator,
+and weighed as such. Or he ignites the peroxide along with finely
+pulverized ammonium sulphite; the mass must have a pure white color.
+After the conclusion of the reaction it is ignited for about 20
+minutes. The results are too high. The proportion of actual lead
+peroxide in the deposit ranges from 94 to 94.76 per cent. The peroxide
+precipitated from a nitric solution may, under certain circumstances,
+be anhydrous. This result is due to the secondary influences at the
+positive pole, where the free acid gradually withdraws water from the
+peroxide.
+
+The peroxide thrown down from alkaline solutions retains alkali so
+obstinately that it cannot be removed by washing; the peroxide plays
+here the part of an acid. The lead nitrate mechanically inclosed in
+the peroxide is resolved by ignition into oxide, hyponitric acid, and
+oxygen; this small proportion of lead oxide does not exert an
+important influence on the final result. The quantity of matter
+mechanically inclosed is relatively high, as in the precipitation of
+much lead peroxide there is relatively more saline matter occluded
+than when a few centigrammes are deposited. The peroxide incloses also
+more foreign matter if it is thrown down upon a small surface than if
+it is deposited in a thin layer over a broad surface. From numerous
+analyses the author concludes that in presence of much free nitric
+acid the proportion of water is increased; with free alkali the
+reverse holds good.
+
+_Thallium_ behaves similarly to lead. From a nitric acid solution it
+is thrown down, according to the proportion of free acid, either as
+sesquioxide only or in small quantities as silvery, metallic leaflets;
+from alkaline solutions it is deposited as sesquioxide and metal, the
+latter of a lead-gray color. Thallium solutions conduct the electric
+current badly. Thallium oxide resembles lead peroxide in color; at a
+strong heat it melts, becomes darker, and is converted into peroxide,
+in which state it can be weighed.
+
+_Silver._--All solutions of silver salts, except the nitrate, and
+those containing a very large quantity of free nitric acid or
+nitrates, deposit electrolytically merely metallic silver. In the
+above mentioned exceptional cases there is formed a small quantity of
+peroxide which adheres to the anode as a blackish-gray deposit. The
+greatest quantity of peroxide is obtained on employing a concentrated,
+strongly acid solution of the nitrate, and a strong current. If the
+solution is very dilute we obtain no peroxide, or mere traces which
+disappear again toward the end of the process. The peroxide is
+deposited at first in small, dark, shining octahedral crystals;
+subsequently, in an amorphous state. At 110 deg. it evolves oxygen
+suddenly, and is converted into metallic silver. It dissolves in
+ammonia with a violent escape of nitrogen. In nitric acid it dissolves
+without decomposition and with a red color.
+
+The author uses a galvanic current for reducing silver residues,
+consisting of sulphocyanide. The salt is mixed with sulphuric acid in
+a roomy platinum capsule, and a fine platinum wire gauze is used as
+positive electrode.
+
+_Bismuth._--The current resolves bismuth solutions into metal and
+bismutic acid. The latter is deposited at the positive pole, and in
+thin layers appears of a golden-yellow, but in thick strata is darker,
+approaching to red. Its formation is very gradual, and in time it
+disappears again, owing to secondary actions of the current. On
+ignition it becomes lemon yellow, and transitorily darker, even brown,
+and passes into the sexquioxide.
+
+_Nickel and Cobalt._--On the electrolysis of the ammonical solution
+the sesquioxide appears at the positive pole. Its formation is
+prevented by an excess of ammonia. The author never obtains more than
+31/2 per cent. of the quantity of the metal. The sesquioxides dissolve
+in ammonia without escape of nitrogen, and are usually anhydrous.
+
+_Manganese._--Manganese is the only metal which is precipitated only
+as peroxide. It is deposited at once on closing the circuit, and is at
+first brown, then black and shining. Organic acids, ferrous oxide,
+chromic oxide, ammonium salts, etc., prevent the formation of peroxide
+and the red color produced by permanganic acid. In very dilute
+strongly acid nitric solutions there is formed only permanganic acid,
+which according to Riche is plainly visible in solutions containing
+1/1000000 grm. manganese. On electrolyzing a manganiferous solution of
+copper nitrate, red permanganic acid appeared in a stratum floating
+above the platinum disk coated with brown peroxide. No manganese
+peroxide was deposited. The peroxide adheres firmly to the platinum
+when the proportion of free acid is small, not exceeding 3 per cent.,
+and the current is not too strong. If the action of the current is
+prolonged after the peroxide is thrown down, it falls off in laminae.
+According to Riche, in a nitric solution the manganese is deposited as
+peroxide, also at the negative pole. This formation is not directly
+due to the current, but is a precipitate occasioned by the production
+of ammonia by the reduction of nitric acid. To determine the manganese
+in peroxide electrolytically precipitated, it is heated to bright
+redness in the platinum capsule until the weight becomes constant. The
+results are too high.
+
+_Selenium and Tellurium._--Both these bodies are readily and
+completely reduced by the current either in acid or alkaline
+solutions. Selenium is thrown down at first of a fine brownish red,
+which gradually becomes darker. The deposit of tellurium is of a
+bluish black color. If the current is feeble, the deposit of selenium
+is moderately compact; that of tellurium is always loose, and it often
+floats on the liquid. A strong current precipitates both as powders.
+The positive pole is coated during electrolysis with a film of a dark
+color in case of selenium, but of a lemon yellow with tellurium. As in
+case of arsenic and antimony, the hydrogen evolved at the negative
+pole combines with the reduced substances, forming hydrogen, selenide,
+or telluride, which remain in part in solution in the liquid. The
+reduced metal separates out at the anode in a friable
+condition.--_Zeitschrift fur Analytische Chemie, and Chemical News._
+
+       *       *       *       *       *
+
+
+
+
+THE ELECTRO-CHEMICAL EQUIVALENT OF SILVER.
+
+
+
+A very careful and important determination of the electrochemical
+equivalent of silver has been made at the observatory of the Physical
+Institute of Wuerzbourg, and the results are that an ampere current
+flowing for a second, or a coulomb of electricity deposits 1.1183
+milligrammes of silver or 0.3281 milligramme of copper, and decomposes
+0.09328 milligramme of water, a result agreeing closely with that of
+Lord Rayleigh recently communicated to the Physical Society. An ampere
+therefore deposits 4.0259 grammes of silver per hour; Kohlrausch's
+value is 4.0824, a value hitherto accepted universally. This value is
+so useful in measuring electric currents with accuracy, and free from
+the disturbances of magnetism, etc., that it is eminently satisfactory
+to find the German value agree with that of Lord Rayleigh, which will
+probably be adopted by English electricians.
+
+       *       *       *       *       *
+
+
+
+
+A NEW STANDARD LIGHT.
+
+
+Herr Hefner-Alteneck has suggested a new standard light for
+photometric purposes, which promises to be very simple and effective
+in operation. The light is produced by an open flame of amyl-acetate
+burning from a wick of cotton fiber which fills a tube of German
+silver 1 in. long and 316 mils. internal diameter; the external
+diameter being 324 mils. The flame is 1.58 in. high from top to
+bottom; and it should be lighted at least ten minutes before using the
+light for testing. A cylindrical glass chimney surrounds it to ward
+off air currents. About 2 per cent. of the light is absorbed by the
+glass. The power of the flame is that of a standard English candle;
+and experiments have shown that amyl acetate, which besides is not
+expensive, is the best fuel for steadiness and brilliance. Neither the
+substitution of commercial amyl-acetate for pure nor the use of a wick
+of cotton thread for loose cotton fiber alters the illuminating power;
+but the wick should be trimmed square across the mouth of the tube,
+for if it project and droop the illuminating power is increased.
+
+       *       *       *       *       *
+
+[NATURE.]
+
+
+
+
+DR. FEUSSNER'S NEW POLARIZING PRISM.
+
+
+In a recent number of the _Zeitschrift fur Instrumentenkunde_ (iv.,
+42-50, February, 1884), Dr. K. Feussner of Karlsruhe has given a
+detailed description of a polarizing prism lately devised by him,
+which presents several points of novelty, and for which certain
+advantages are claimed. The paper also contains an account, although
+not an exhaustive one, of the various polarizing prisms which have
+from time to time been constructed by means of different combinations
+of Iceland spar. The literature of this subject is scattered and
+somewhat difficult of access, and moreover only a small part of it has
+hitherto been translated into English; and it would appear therefore
+that a brief abstract of the paper may not be without service to those
+among the readers of _Nature_ who may be unacquainted with the
+original memoirs, or who may not have the necessary references at
+hand.
+
+Following the order adopted by Dr. Feussner, the subject may be
+divided into two parts:
+
+
+I.--OLDER FORMS OF POLARIZING PRISMS.
+
+In comparing the various forms of polarizing prisms, the main points
+which need attention are--the angular extent of the field of view, the
+direction of the emergent polarized ray, whether it is shifted to one
+side of, or remains symmetrical to the long axis of the prism; the
+proportion which the length of the prism bears to its breadth; and
+lastly, the position of the terminal faces, whether perpendicular or
+inclined to the long axis. These requirements are fulfilled in
+different degrees by the following methods of construction:
+
+[Illustration: Fig. 1., Fig. 2., and Fig. 3.]
+
+1. _The Nicol Prism_ (_Edin. New Phil. Journal_, 1828, vi., 83).--This
+(Fig. 1), as is well known, is constructed from a rhombohedron of
+Iceland spar, the length of which must be fully three times as great
+as the width. The end faces are cut off in such a manner that the
+angle of 72 deg. which they originally form with the lateral edge of the
+rhombohedron is reduced to 68 deg.. The prism is then cut in two in a
+plane perpendicular to the new end surfaces, the section being carried
+obliquely from one obtuse corner of the prism to the other, in the
+direction of its length. The surfaces of this section, after having
+been carefully polished, are cemented together again by means of
+Canada balsam. A ray of light, on entering the prism, is separated by
+the double refraction of the calc-spar into an ordinary and an
+extraordinary ray; the former undergoes total reflection at the layer
+of balsam at an incidence which allows the extraordinary ray to be
+transmitted; the latter, therefore, passes through unchanged. This
+principle of obtaining a single polarized ray by means of total
+reflection of the other is common to all the forms of prism now to be
+described.
+
+Dr. Feussner gives a mathematical analysis of the paths taken by the
+two polarized rays within the Nicol prism, and finds that the emergent
+extraordinary ray can include an angular field of 29 deg., but that this
+extreme value holds good only for rays incident upon that portion of
+the end surface which is near to the obtuse corner, and that from
+thence it gradually decreases until the field includes an angle of
+only about half the previous amount. He finds, moreover, that,
+although of course the ray emerges parallel to its direction of
+incidence, yet that the zone of polarized light is shifted to one side
+of the central line. Also that the great length of the Nicol--3.28
+times its breadth--is not only an inconvenience, but owing to the
+large pieces of spar thus required for its construction, prisms of any
+but small size become very expensive. To this it may be added that
+there is a considerable loss of light by reflection from the first
+surface, owing to its inclined position in regard to the long axis of
+the prism.
+
+[Illustration: Fig. 4., Fig. 5., and Fig. 6.]
+
+It is with the view of obviating these defects that the modifications
+represented in Figs. 2 to 6 have been devised.
+
+2. _The Shortened Nicol Prism_.--This arrangement of the Nicol prism
+is constructed by Dr. Steeg and Reuter of Homburg v.d.H. For the sake
+of facility of manufacture, the end surfaces are cleavage planes, and
+the oblique cut, instead of being perpendicular, makes with these an
+angle of about 84 deg.. By this alteration the prism becomes shorter, and
+is now only 2.83 times its breadth; but if Canada balsam is still used
+as the cement, the field will occupy a very unsymmetrical position in
+regard to the long axis. If balsam of copaiba is made use of, the
+index of refraction of which is 1.50, a symmetrical field of about 24 deg.
+will be obtained. A prism of this kind has also been designed by Prof.
+B. Hasert of Eisenach (_Pogg. Ann._, cxiii., 189), but its performance
+appears to be inferior to the above.
+
+3. _The Nicol Prism with Perpendicular Ends._--The terminal surfaces
+in this prism are perpendicular to the long axis, and the sectional
+cut makes with them an angle of about 75 deg.. The length of the prism is
+3.75 times its breadth, and if the cement has an index of refraction
+of 1.525, the field is symmetrically disposed, and includes an angle
+of 27 deg.. Prisms of this kind have been manufactured by Dr. Steeg, Mr.
+C.D. Ahrens, and others.
+
+4. _The Foucault Prism_ (_Comptes Rendus_, 1857, xlv., 238).--This
+construction differs from all those hitherto mentioned, in that a film
+of air is employed between the two cut surfaces as the totally
+reflecting medium instead of a layer of cement. The two halves of the
+prism are kept in position, without touching each other, by means of
+the mounting. The length of the prism is in this way much reduced, and
+amounts to only 1.528 times its breadth. The end surfaces are cleavage
+planes, and the sectional cut makes with them an angle of 59 deg.. The
+field, however, includes not more than about 8 deg., so that this prism
+can be used only in the case of nearly parallel rays; and in addition
+to this the pictures which may be seen through it are to some extent
+veiled and indistinct, owing to repeated internal reflection.
+
+5. _The Hartnack Prism_ (_Ann. de Ch. et de Physique_, ser. iv., vii.,
+181).--This form of prism was devised in 1866 by MM. Hartnack and
+Prazmowiski; the original memoir is a valuable one; a translation of
+it, with some additions, has lately been published (_Journ. of the R.
+Microscopical Soc._, June, 1883, 428). It is considered by Dr.
+Feussner to be the most perfect prism capable of being prepared from
+calc-spar. The ends of the prism are perpendicular to its length; the
+section carried through it is in a plane perpendicular to the
+principal axis of the crystal. The cementing medium is linseed oil,
+the index of refraction of which is 1.485. This form of prism is
+certainly not so well known in this country as it deserves to be; a
+very excellent one, supplied to the present writer by Dr. Steeg is of
+rectangular form throughout, the terminal surfaces are 19 x 15 mm.,
+and the length 41 mm. The lateral shifting of the field is scarcely
+perceptible, the prism is perfectly colorless and transparent, and its
+performance is far superior to that of the ordinary Nicol. The field
+of view afforded by this construction depends upon the cementing
+substance used, and also upon the inclination of the sectional cut in
+regard to the end of the prism; it may vary from 20 deg. to 41 deg.. If the
+utmost extent of field is not required, the prism may be shortened by
+lessening the angle of the section, at the expense, however, of
+interfering with the symmetrical disposition of the field.
+
+6. _The Glan Prism_ (Carl's "Repertorium," xvi., 570, and xvii.,
+195).--This is a modification of the Foucault, and in a similar manner
+includes a film of air between the sectional surfaces. The end
+surfaces and also the cut carried through the prism are parallel to
+the principal axis of the calc-spar. The ends are normal to the
+length, and the field includes about 8 deg.. This prism is very short, and
+may indeed be even shorter than it is broad. It is subject to the same
+defect as that mentioned in the case of the Foucault, although perhaps
+not quite to the same extent.
+
+
+II.--THE NEW POLARIZING PRISM.
+
+This prism differs very considerably from the preceding forms, and
+consists of a thin plate of a doubly refracting crystal cemented
+between two wedge-shaped pieces of glass, the terminal faces of which
+are normal to the length. The external form of the prism may thus be
+similar to the Hartnack, the calc-spar being replaced by glass. The
+indices of refraction of the glass and of the cementing medium should
+correspond with the greater index of refraction of the crystal, and
+the directions of greatest and least elasticity in the latter must
+stand in a plane perpendicular to the direction of the section. One of
+the advantages claimed for the new prism is that, it dispenses with
+the large and valuable pieces of spar hitherto found necessary; a
+further advantage being that other crystalline substances may be used
+in this prism instead of calc-spar. The latter advantage, however,
+occurs only when the difference between the indices of refraction for
+the ordinary and extraordinary rays in the particular crystal made use
+of is greater than in calc-spar. When this is the case, the field
+becomes enlarged, and the length of the prism is reduced.
+
+[Illustration: Fig. 7.]
+
+The substance which Dr. Feussner has employed as being most suitable
+for the separating crystal plate is nitrate of soda (_natronsalpeter_),
+in which the above-mentioned values are [omega] = 1.587 and [eta] =
+1.336. It crystallizes in similar form to calcite, and in both cases
+thin plates obtained by cleavage may be used.
+
+As the cementing substance for the nitrate of soda, a mixture of gum
+dammar with monobromonaphthalene was used, which afforded an index of
+refraction of 1.58. In the case of thin plates of calcite, a solid
+cementing substance of sufficiently high refractive power was not
+available, and a fluid medium was therefore employed. For this purpose
+the whole prism was inclosed in a short glass tube with airtight ends,
+which was filled with monobromonaphthalene. In an experimental prism a
+mixture of balsam of tolu was made use of, giving a cement with an
+index of refraction of 1.62, but the low refractive power resulted in
+a very considerable reduction of the field. The extent and disposition
+of the field may be varied by altering the inclination at which the
+crystal lamina is inserted (Fig. 7), and thereby reducing the length
+of the prism, as in the case of the Hartnack.
+
+In order to obviate the effects of reflection from the internal side
+surfaces if the prism, the wedge-shaped blocks of glass of which it is
+built up may be made much broader than would otherwise be necessary;
+the edges of this extra width are cut obliquely and suitably
+blackened.
+
+The accompanying diagram (Fig. 8) represents a prism of cylindrical
+external form constructed in this manner, the lower surface being that
+of the incident light. In this the field amounts to 30 deg., and the
+breadth is about double the length.
+
+[Illustration: Fig. 8.]
+
+Dr. Feussner remarks that a prism similar in some respects to his new
+arrangement was devised in 1869 by M. Jamin (_Comptes Rendus_,
+lxviii., 221), who used a thin plate of calc-spar inclosed in a cell
+filled with bisulphide of carbon; and also by Dr. Zenker, who replaced
+the liquid in M. Jamin's construction by wedges of flint glass.
+
+Among others, the carefully considered modifications of the Nicol
+prism which have recently been devised by Prof. S.P. Thompson (_Phil.
+Mag._, November, 1881, 349, and _Jour. R. Micros. Soc._, August, 1883,
+575), and by Mr. R.T. Glazebrook (_Phil. Mag._, May, 1883, 352), do
+not appear to have been known to Dr. Feussner.
+
+The following tabular view of different forms of polarizing prisms is
+taken from the conclusion of Dr. Feussner's paper:
+
+  ---------------------------------------+------+---------+------+------
+                                         |      |Inclina- |Ratio |
+                                         |      |tion of  | of   |
+                                         |      |section  |length|
+                                         |      |in regard| to   |
+                                         |      |to long  |clear |
+                                         |Field.|axis.    |width.|Fig.
+  ---------------------------------------+------+---------+------+------
+  I. THE OLD POLARISING PRISMS.          |   deg.   |     deg.    |      |
+      1. Nicol's prism.                  | 29   |   22    | 3.28 | 1
+      2. Shortened Nicol prism--         |      |         |      |
+          a. Cemented with Canada balsam.| 13   |   25    | 2.83 | 2
+          b. Cemented with copaiba  "    | 24   |   25    | 2.83 | 2
+      3. Nicol with perpendicular ends-- |      |         |      |
+          a. With Canada balsam.         | 20   |   15    | 3.73 | 3
+          b. With cement of index of     |      |         |      |
+              refraction of 1.525.       | 27   |   15    | 3.73 | 3
+      4. Foucault's prism.               |  8   |   40    | 1.528| 4
+      5. Hartnack's prism--              |      |         |      |
+          a. Original form.              | 35   |   15.9  | 3.51 |5 _a b_
+          b. With largest field.         | 41.9 |   13.9  | 4.04 |5 _a a_
+          c. With field of 30 deg..          | 30   |   17.4  | 3.19 |5 _a c_
+          d. With field of 20 deg..          | 20   |   20.3  | 2.70 |5 _a d_
+      6. Glan's prism.                   |  7.9 |   50.3  | 0.831| 6
+                                         |      |         |      |
+  II. THE NEW POLARISING PRISM.          |      |         |      |
+      1. With calc-spar: largest field.  | 44   |   13.2  | 4.26 |5 _a a_
+      2.       "         field of 30 deg..   | 30   |   17.4  | 3.19 |5 _a c_
+      3.       "         field of 20 deg..   | 20   |   20.3  | 2.70 |5 _a d_
+      4. With nitrate of soda:           |      |         |      |
+               "         largest field.  | 54   |   16.7  | 3.53 |7 _a a_
+      5.       "         field of 30 deg..   | 30   |   24    | 2.25 |7 _a b_
+      6.       "         field of 20 deg..   | 20   |   27    | 1.96 |7 _a c_
+  ---------------------------------------+------+---------+------+------
+
+As an analyzing prism of about 6 mm. clear width, and 13.5 mm. long,
+the new prism is stated by its inventor to be of the most essential
+service, and it would certainly appear that the arrangement is rather
+better adapted for small prisms than for those of considerable size.
+Any means by which a beam of polarized light of large diameter--say 3
+to 31/2 inches--could be obtained with all the convenience of a Nicol
+would be a real advance, for spar of sufficient size and purity for
+such a purpose has become so scarce and therefore so valuable that
+large prisms are difficult to procure at all. So far as an analyzer is
+concerned, the experience of the writer of this notice would lead to
+the opinion that improvements are to be looked for rather in the way
+of the discovery of an artificial crystal which absorbs one of the
+polarized rays than by further modifications depending upon total
+reflection. The researches of Dr. Herapath on iodosulphate of quinine
+(_Phil. Mag._, March, 1852, 161, and November, 1853, 346) are in this
+direction; but crystals of the so-called herapathite require great
+manipulative skill for their production. If these could be readily
+obtained of sufficient size, they would be invaluable as analyzers.
+
+This opinion is supported by the existence of an inconvenience which
+attends every form of analyzing prism. It is frequently, and
+especially in projecting apparatus, required to be placed at the focus
+of a system of lenses, so that the rays may cross in the interior of
+the prism. This is an unfavorable position for a prismatic analyzer,
+and in the case of a powerful beam of light, such as that from the
+electric arc, the crossing of the rays within the prism is not
+unattended with danger to the cementing substance, and to the surfaces
+in contact with it.
+
+PHILIP R. SLEEMAN.
+
+       *       *       *       *       *
+
+
+
+
+ZIRCON.
+
+By F. STOLBA.
+
+
+Finely ground zircon is quickly rendered soluble if fused with a
+mixture of potassium borofluoride and potassium carbonate. The author
+takes two parts of the former to three of the latter, and prepares an
+intimate, finely divided mixture, which is kept ready for use.
+
+Of this mixture four parts are taken to one of zircon, thoroughly
+mixed, and melted in a platinum crucible at a red heat. The mass fuses
+readily, froths at first and gives off bubbles of gas, and flows then
+quietly, forming a very fluid melt. If the zircon is finely ground, 15
+minutes are sufficient for this operation. The loss of weight is 16
+per cent., and is not notably increased on prolonged fusion. It
+corresponds approximately to the weight of the carbonic anhydride
+present in the potassium carbonate.
+
+As pungent vapors are given off during fusion, the operation should be
+conducted under a draught hood. The activity of the mixture in
+attacking zircon appears from the following experiment: Two zircon
+crystals, each weighing 1/2 grm., were introduced into the melted
+mixture and subjected to prolonged heat. In a short time they
+decreased perceptibly in size; each of them broke up into two
+fragments, and within an hour they were entirely dissolved. The melted
+mass is poured upon a dry metal plate, and when congealed is thrown
+into water. It is at once intersected with a number of fissures, which
+facilitate pulverization. This process is the more necessary as the
+unbroken mass is very slowly attacked by water even on prolonged
+boiling. The powder is boiled in a large quantity of water so as to
+remove everything soluble. There is obtained a faintly alkaline
+solution and a sediment insoluble in water. From the filtrate alkalies
+throw down zirconium hydroxide, free from iron.
+
+The portion insoluble in water is readily dissolved in hydrofluoric
+acid, and is converted into zircon potassium fluoride. The chief bulk
+of the zirconium is found in the aqueous solution in the state of
+double fluorides. The platinum crucible is not in the least attacked
+during melting. On the contrary, dirty platinum crucibles may be
+advantageously cleaned by melting in them a little of the above
+mentioned mixture.
+
+If finely divided zircon is boiled for a long time with caustic lye,
+it is perceptibly attacked. It is very probable that in this manner
+zircon might be entirely dissolved under a pressure of 10 atmospheres.
+
+Potassium borofluoride may be readily prepared from cryolite.
+Crucibles of nickel seem especially well adapted for the fusion of
+zircon in caustic alkalies.--_Ber. Boehm. Gesell. Wissenschaft;
+Chem. News_.
+
+       *       *       *       *       *
+
+
+
+
+A PROCESS FOR MAKING WROUGHT IRON DIRECT FROM THE ORE.[1]
+
+   [Footnote 1: A paper read at the Cincinnati Meeting of the
+   American Institute of Mining Engineers, by Willard P. Ward, A.M.,
+   M.E., February, 1884.]
+
+
+The numerous direct processes which have been patented and brought
+before the iron masters of the world, differ materially from that now
+introduced by Mr. Wilson. After a careful examination of his process,
+I am convinced that Mr. Wilson has succeeded in producing good blooms
+from iron ore, and I think that I am able to point out theoretically
+the chief reasons of the success of his method.
+
+Without going deeply into the history of the metal, I may mention the
+well known fact that wrought iron was extensively used in almost all
+quarters of the globe, before pig or cast iron was ever produced.
+Without entering into the details of the processes by which this
+wrought iron was made, it suffices for my present purpose to say that
+they were crude, wasteful, and expensive, so that they can be employed
+to-day only in a very few localities favored with good and cheap ore,
+fuel, and labor.
+
+The construction of larger furnaces and the employment of higher
+temperatures led to the production of a highly carbonized, fusible
+metal, without any special design on the part of the manufacturers in
+producing it. This pig iron, however, could be used only for a few
+purposes for which metallic iron was needed; but it was produced
+cheaply and with little loss of metal, and the attempt to decarbonize
+this product and bring it into a state in which it could be hammered
+and welded was soon successfully made. This process of decarbonization,
+or some modification of it, has successfully held the field against
+all so-called, direct processes up to the present time. Why? Because
+the old fashioned bloomeries and Catalan forges could produce blooms
+only at a high cost, and because the new processes introduced failed
+to turn out good blooms. Those produced were invariably "red short,"
+that is, they contained unreduced oxide of iron, which prevented the
+contact of the metallic particles, and rendered the welding together
+of these particles to form a solid bloom impossible.
+
+The process of puddling cast iron, and transforming it by
+decarbonization into wrought iron, has, as everybody knows, been in
+successful practical operation for many years, and the direct process
+referred to so closely resembles this, that a short description of the
+theory of puddling is not out of place here.
+
+The material operated on in puddling is iron containing from 21/2 to 4
+per cent. of carbon. During the first stage of the process this iron
+is melted down to a fluid bath in the bottom of a reverberatory
+furnace. Then the oxidation of the carbon contained in the iron
+commences, and at the same time a fluid, basic cinder, or slag, is
+produced, which covers a portion of the surface of the metal bath, and
+prevents too hasty oxidation. This slag results from the union of
+oxides of iron with the sand adhering to the pigs, and the silica
+resulting from the oxidation of the silicon contained in the iron.
+
+This cinder now plays a very important part in the process. It takes
+up the oxides of iron formed by the contact of the oxidizing flame
+with the exposed portion of the metal bath, and at the same time the
+carbon of the iron, coming in contact with the under surface of the
+cinder covering, where it is protected from oxidizing influences,
+reduces these oxides from the cinder and restores them to the bath in
+metallic form. This alternate oxidation of exposed metal, and its
+reduction by the carbon of the cast iron, continues till the carbon is
+nearly exhausted, when the iron assumes a pasty condition, or "comes
+to nature," as the puddlers call this change. The charge is then
+worked up into balls, and removed for treatment in the squeezer, and
+then hammered or rolled. In the Wilson process the conditions which we
+have noted in the puddling operation are very closely approximated.
+Iron ore reduced to a coarse sand is mixed with the proper proportion
+of charcoal or coke dust, and the mixture fed into upright retorts
+placed in the chimney of the puddling furnace. By exposure for 24
+hours to the heat of the waste gases from the furnace, in the presence
+of solid carbon, a considerable portion of the oxygen of the ore is
+removed, but little or no metallic iron is formed. The ore is then
+drawn from the deoxidizer into the rear or second hearth of the
+puddling furnace, situated below it, where it is exposed for 20
+minutes to a much higher temperature than that of the deoxidizer. Here
+the presence of the solid carbon, mixed with the ore, prevents any
+oxidizing action, and the temperature of the mass is raised to a point
+at which the cinder begins to form. Then the charge is carried forward
+by the workmen to the front hearth, in which the temperature of a
+puddling furnace prevails. Here the cinder melts, and at the same
+time the solid carbon reacts on the oxygen remaining combined with the
+ore, and forms metallic iron; but by this time the molten cinder is
+present to prevent undue oxidation of the metal formed, and solid
+carbon is still present in the mixture to play the same role, of
+reducing protoxide of iron from the cinder, as the carbon of the cast
+iron does in the ordinary puddling process. I have said that the cast
+iron used as the material for puddling contains about 3 per cent. of
+carbon; but in this process sufficient carbon is added to effect the
+reduction of the ore to a metallic state, and leave enough in the mass
+to play the part of the carbon of the cast iron when the metallic
+stage has been reached.
+
+It would be interesting to compare the Wilson with the numerous other
+direct processes to which allusion has already been made, but there
+have been so many of them, and the data concerning them are so
+incomplete, that this is impossible. Two processes, however, the Blair
+and the Siemens, have attracted sufficient attention, and are
+sufficiently modern to deserve notice. In the Blair process a metallic
+iron sponge was made from the ore in a closed retort, this sponge
+cooled down in receptacles from which the air was excluded, to the
+temperature of the atmosphere, then charged into a puddling furnace
+and heated for working. In this way (and the same plan essentially has
+been followed by other inventors), the metallic iron, in the finest
+possible state of subdivision, is subjected to the more or less
+oxidizing influences of the flame, without liquid slag to save it from
+oxidation, and with no carbon present to again reduce the iron oxides
+from the cinder after it is formed. The loss of metal is consequently
+very large, but oxides of iron being left in the metal the blooms are
+invariably "red short."
+
+In the Siemens process pieces of ore of the size of beans or peas,
+mixed with lime or other fluxing material, form the charge, which is
+introduced into a rotating furnace; and when this charge has become
+heated to a bright-red heat, small coal of uniform size is added in
+sufficient quantity to effect the reduction of the ore.
+
+The size of the pieces of the material employed prevents the intimate
+mixture of the particles of iron with the particles of carbon, and
+hence we would, on theoretical grounds, anticipate just what practice
+has proved, viz., that the reduction is incomplete, and the resulting
+metal being charged with oxides is red-short. In practice, blooms made
+by this process have been so red-short that they could not be hammered
+at all.
+
+It would be impracticable in this process to employ ore and carbon in
+as fine particles as Wilson does, as a very large portion of the
+charge would be carried off by the draught, and a sticking of the
+material to the sides of the rotating furnace could scarcely be
+avoided. I do not imagine that a division of the material into
+anything like the supposed size of molecules is necessary; we know
+that the graphitic carbon in the pig-iron employed in puddling is not
+so finely divided, but it is much smaller particles than bean or pea
+size, and by approximating the size of the graphite particles in pig
+iron, Wilson has succeeded in obtaining good results.
+
+If we examine the utilization of the heat developed by the combustion
+of a given quantity of coal in this process, and compare it with the
+result of the combustion of an equivalent amount of fuel in a blast
+furnace, we shall soon see the theoretical economy of the process. The
+coal is burned on the grate of the puddling-furnace, to carbonic acid,
+and the flame is more fully utilized than in an ordinary
+puddling-furnace, for besides the ordinary hearth there is the second
+or rear hearth, where additional heat is taken up, and then the
+products of combustion are further utilized in heating the retorts in
+which the ore is partly reduced. After this the heat is still further
+utilized by passing it under the boilers for the generation of steam,
+and the heat lost in the gases, when they finally escape, is very
+small. In a blast furnace the carbon is at first burned only to
+carbonic oxide, and the products of combustion issue mainly in this
+form from the top of the furnace. Then a portion of the heat resulting
+from the subsequent burning of these gases is pretty well utilized in
+making steam to supply the power required about the works, but the
+rest of the gas can only be utilized for heating the blast, and here
+there is an enormous waste, the amount of heat returned to the furnace
+by the heated blast being very small in proportion to the amount
+generated by the burning of that portion of carbonic oxide expended in
+heating it, and the gases escape from both the hot-blast and the
+boilers at a high temperature.
+
+In the direct process under consideration the fuel burned is more
+completely utilized than in the puddling process, to which the cast
+iron from the blast furnace is subjected to convert it into wrought
+iron.
+
+The economy claimed for this process, over the blast furnace and
+puddling practice for the production of wrought iron, is that nearly
+all the fuel used in the puddling operation is saved, and that with
+about the same amount of fuel used in the blast furnace to produce a
+ton of pig iron, a ton of wrought iron blooms can be made. I had no
+opportunity of weighing the charges of ore and coal used, but I saw
+the process in actual operation at Rockaway, N.J. The iron produced
+was hammered up into good solid blooms, containing but little cinder.
+The muck-bar made from the blooms was fibrous in fracture, and showed
+every appearance of good iron. I am informed by the manager of the
+Sanderson Brothers' steel works, at Syracuse, N.Y., that they
+purchased blooms made by the Wilson process in 1881-1882, that _none_
+of them showed red-shortness, and that they discontinued their use
+only on account of the injurious action of the titanium they contained
+on the melting pots. These blooms were made from magnetic sands from
+the Long Island and Connecticut coasts.
+
+[Illustration: NEW PROCESS FOR MAKING WROUGHT IRON FROM THE ORE.]
+
+The drawing given shows the construction of the furnace employed. I
+quote from the published description:
+
+    "The upper part, or deoxidizer, is supported on a strong
+    mantel plate resting on four cast iron columns.
+
+    "The retorts and flues are made entirely of fire-brick, from
+    special patterns. The outside is protected by a wrought iron
+    jacket made of No. 14 iron. The puddling furnace is of the
+    ordinary construction, except in the working bottom, which is
+    made longer to accommodate two charges of ore, and thus
+    utilize more of the waste heat in reducing the ore to metallic
+    iron.
+
+    "The operation of the furnace is as follows: The pulverized
+    ore is mixed with 20 per cent. of pulverized charcoal or coke,
+    and is fed into an elevator which discharges into the hopper
+    on the deoxidizer leading into the retorts marked C. These
+    retorts are proportioned so that they will hold ore enough to
+    run the puddling furnace 24 hours, the time required for
+    perfect deoxidation. After the retorts are filled, a fire is
+    started in the furnace, and the products of combustion pass up
+    through the main flue, or well, B, where they are deflected by
+    the arch, and pass out through suitable openings, as indicated
+    by arrows, into the down-takes marked E, and out through an
+    annular flue, where they are passed under a boiler.
+
+    "It will be noticed that the ore is exposed to the waste heat
+    on three sides of the retorts, and owing to the great surface
+    so exposed, the ore is very thoroughly deoxidized, and reduced
+    in the retorts before it is introduced into the puddling
+    furnace for final reduction. The curved cast iron pipes marked
+    D are provided with slides, and are for the purpose of
+    introducing the deoxidized ore into the second bottom of the
+    furnace. As before stated, the furnace is intended to
+    accommodate two charges of ore, and as fast as it is balled up
+    and taken out of the working bottom, the charge remaining in
+    the second bottom is worked up in the place occupied by the
+    first charge, and a _new_ charge is introduced. As fast as the
+    ore is drawn out from the retorts the elevator supplies a new
+    lot, so that the retorts are always filled, thus making the
+    process continuous."
+
+The temperature of the charge in the deoxidizer is from 800 deg. to 1,000 deg.
+F.--_Amer. Engineer._
+
+       *       *       *       *       *
+
+
+
+
+SOME REMARKS ON THE DETERMINATION OF HARDNESS IN WATERS.
+
+By HERBERT JACKSON.
+
+
+Having had occasion some short time ago to examine a hard water which
+owed half its hardness to salts of magnesium, I noticed that the soap
+test, applied in the usual way, gave a result which differed very much
+from that obtained by the quantitative estimation of calcium and
+magnesium. A perfectly normal lather was obtained when soap had been
+added in quantities sufficient to neutralize 14 deg. of hardness, whereas
+the water contained salts of calcium and magnesium equivalent, on
+Clark's scale, to a hardness of 27 deg..
+
+Although I was aware that similar observations had been made before, I
+thought that it might be useful to determine the conditions under
+which the soap test could not be depended upon for reliable results.
+
+I found with waters containing calcium or magnesium alone that,
+whenever salts of either of these metals were in solution in
+quantities sufficient to give 23 deg. of hardness on Clark's scale, no
+dependence could be placed upon the results given by the soap test. In
+the case of waters containing salts of both calcium and magnesium, I
+found that if the salts of the latter metal were in solution in
+quantities sufficient to give more than 10 deg. of hardness, no evidence
+could be obtained of their presence so long as the salts of calcium in
+the same water exceeded 6 deg.; in such a case a perfect and permanent
+lather was produced when soap had been added equivalent to 7 deg. of
+hardness.
+
+If any water be diluted so as to reduce the proportions of the salts
+of calcium and magnesium below those stated above, perfectly reliable
+results will of course be obtained.
+
+Instead of dilution I found that heating the water to about 70 deg. C. was
+sufficient to cause a complete reaction between the soap and the salts
+of calcium and magnesium, even if these were present in far larger
+quantities than any given here.
+
+The experiments so far had all been made with a solution of Castile
+soap of the strength suggested by Mr. Wanklyn in his book on "Water
+Analysis." My attention was next directed to the use of any one of the
+compounds of which such a soap is composed. I commenced with sodium
+oleate, and found that by employing this substance in a moderately
+pure condition, perfectly reliable results could be obtained in very
+hard waters without the trouble of either diluting or heating. I was
+unable to try sodium stearate directly because of the slight
+solubility of this substance in cold water or dilute alcohol; but I
+found that a mixture of sodium oleate and stearate behaved in exactly
+the same manner as the Castile soap.
+
+I am not prepared at present to state the exact reaction which takes
+place between salts of calcium and magnesium and a compound soap
+containing sodium oleate and stearate. I publish these results because
+I have not noticed anywhere the fact that some waters show a greater
+hardness with soap when their temperatures approach the boiling point
+than they do at the average temperature of the air, it being, I
+believe, the ordinary impression that cold water wastes more soap than
+hot water before a good and useful lather can be obtained, whereas
+with very many waters the case is quite the reverse. Neither am I
+aware at present whether it is well known that the use of sodium
+oleate unmixed with sodium stearate dispenses with the process of
+dilution even in very hard waters.--_Chem. News._
+
+       *       *       *       *       *
+
+
+
+
+THE DENSITY AND PRESSURE OF DETONATING GAS MIXTURES.
+
+
+MM. Berthelot and Vielle have recently been studying the influence of
+the density of detonating gaseous mixtures upon the pressure
+developed. The measure of pressure developed by the same gaseous
+system, taken under two initial states of different density to which
+the same quantity of heat is communicated, is an important matter in
+thermodynamics. If the pressures vary in the same ratio as the
+densities, we may conclude, independently of all special hypotheses on
+the laws of gases, first, that the specific heat of the system is
+independent of its density (that is to say, of its initial pressure),
+and depends only on the absolute temperature, whatever that may mean;
+and secondly, that the relative variation of the pressure at constant
+volume, produced by the introduction of a determinate quantity of
+heat, is also independent of the pressure, and a function only of the
+temperature. Lastly, the pressure itself will vary proportionally with
+the absolute temperature, as defined by the theory of a perfect gas,
+and will serve to determine it. MM. Berthelot and Vielle operated with
+a bomb, at first kept at ordinary temperatures in the air, and
+afterward heated in an oil bath to 153 deg. Cent. They also employed
+isomeric mixtures of the gases; methylic ether, cyanogen, hydrogen,
+acetylene, and other gases were experimented upon, and the general
+conclusions are as follows: 1. The same quantity of heat being
+furnished to a gaseous system, the pressure of the system varies
+proportionally to the density of the system. 2. The specific heat of
+the gas is sensibly independent of the density as well toward very
+high temperatures as about deg. Cent. This is all true for densities
+near to those that the gas possesses cold under normal pressure, and
+which varied in the experiment to double the original value. 3. The
+pressure increases with the quantity of heat furnished to the same
+system. 4. The apparent specific heat increases parallel with this
+quantity of heat. These conclusions are independent of all hypotheses
+on the nature and laws of gases, and were simply drawn from the
+experiments in question.
+
+       *       *       *       *       *
+
+
+
+
+TURKISH BATHS FOR HORSES.
+
+
+The Turkish bath has become an established institution in this
+country; men of all classes now use it for sanitary as well as
+remedial purposes. Athletes of various descriptions find it invaluable
+in "training," and all the distinguished jockeys and light weights
+keep themselves in condition by its use.
+
+It was thought probable that what was good for man might also be good
+for the horse, and the fact has been proved. Messrs. Pickford, the
+eminent carriers, in their hospital for horses at Finchley, have had a
+bath in operation over eleven years, and find the horses derive great
+benefit from its use. The bath is put in operation three days a week,
+and is administered to over twenty horses in this time. The value of
+the bath having been thus proved, it is rather strange that it has not
+been more generally adopted by the large carrying firms. However, the
+Great Northern Railway Company at their new hospital for horses at
+Totteridge, are erecting a very complete Turkish bath. It consists of
+three rooms. First, a large wash room or grooming room, from which is
+entered the first hot room, or tepidarium, from 140 deg. to 150 deg. Fahr.;
+from this room, the horse, after being thoroughly acclimated, can, if
+necessary, pass to the hottest room, or calidarium, from 160 deg. to 170 deg.
+Fahr., and without any turning round can pass on into the grooming and
+washing room again. This last room is slightly heated from the two
+other rooms, and in each are stocks in which the animal can he
+fastened if required. The heating is done most economically by
+Constantine's convoluted stove, and thorough ventilation is secured
+from the large volume of hot air constantly supplied, which passes
+through the baths, and as it becomes vitiated is drawn off by
+specially designed outlets. The wash room is supplied with hot and
+cold water, which can, of course, be mixed to any required
+temperature.--_Building News._
+
+[Illustration]
+
+   ||
+   |+-------------------------------------------------------+
+   |+-------------------++---__-------____------------__---+|
+   ||                   ||FOUL AIR  FOUL AIR       FOUL AIR||
+   ||                   ||                                 ||
+   ||                   ||                                 ||
+   ||                   ||         ==============          ||
+   ||                  /     /                             ||
+   ||                 /     /       1ST HOT ROOM           ||
+   ||                /     /                               ||
+   ||               /     /        ==============          ||
+   ||                   ||                                 ||
+   /         =======+   ||                                 ||
+  /                ||   ||                          CURTAIN||
+       WASHING ROOM||   |+===========================     =||
+  \                ||   ||                                 ||
+   \         =======+   ||                                 ||
+   ||                   ||                                 ||
+   ||               \     \        ==============          ||
+   ||                \     \                               ||
+   ||                 \     \       2ND HOT ROOM           ||  FRESH
+   ||                  \     \                             || / AIR
+   ||                   ||         ==============          ||==
+   ||                   ||                          +======||  |
+   ||                   ||                          | WARM ||  |
+   ||                   ||FOUL AIR          FOUL AIR| AIR  ||  |
+   |+-------------------++---__--+===+---------__----------+|==
+   |+----------------------------|_|_|---------------------+|
+   ||      |     ||||| |                                   ||
+   ||      |     ||||| |                                   ||
+   ||      |============           S T O K E R Y           ||
+   ||                 ||                                   ||
+   ||                 ||                                   ||
+   ||                 |+-----------------------------------||
+                      +-------------------------------------+
+
+
+       *       *       *       *       *
+
+
+
+
+MIRYACHIT, A NEWLY DESCRIBED DISEASE OF THE NERVOUS SYSTEM, AND
+ITS ANALOGUES.[1]
+
+   [Footnote 1: Read before the New York Neurological Society,
+   February 5, 1884.]
+
+By WILLIAM A. HAMMOND, M.D., Surgeon-General, U.S. Army (Retired
+List); Professor of Diseases of the Mind and Nervous System in the New
+York Post-Graduate Medical School and Hospital.
+
+
+In a very interesting account of a journey from the Pacific Ocean
+through Asia to the United States, by Lieutenant B.H. Buckingham and
+Ensigns George C. Foulk and Walter McLean,[2] United States navy, I
+find an affection of the nervous system described which, on account of
+its remarkable characteristics, as well as by reason of certain known
+analogies, I think should be brought to the special notice of the
+medical profession. I quote from the work referred to, the following
+account of this disease. The party is on the Ussuri River not far from
+its junction with the Amur in Eastern Siberia: "While we were walking
+on the bank here we observed our messmate, the captain of the general
+staff (of the Russian army), approach the steward of the boat
+suddenly, and, without any apparent reason or remark, clap his hands
+before his face; instantly the steward clapped _his_ hands in the same
+manner, put on an angry look, and passed on. The incident was somewhat
+curious, as it involved a degree of familiarity with the steward
+hardly to have been expected. After this we observed a number of queer
+performances of the steward, and finally comprehended the situation.
+It seemed that he was afflicted with a peculiar mental or nervous
+disease, which forced him to imitate everything suddenly presented to
+his senses. Thus, when the captain slapped the paddle-box suddenly in
+the presence of the steward, the latter instantly gave it a similar
+thump; or, if any noise were made suddenly, he seemed compelled
+against his will to imitate it instantly, and with remarkable
+accuracy. To annoy him, some of the passengers imitated pigs grunting,
+or called out absurd names; others clapped their hands and shouted,
+jumped, or threw their hats on the deck suddenly, and the poor
+steward, suddenly startled, would echo them all precisely, and
+sometimes several consecutively. Frequently he would expostulate,
+begging people not to startle him, and again would grow furiously
+angry, but even in the midst of his passion he would helplessly
+imitate some ridiculous shout or motion directed at him by his
+pitiless tormenters. Frequently he shut himself up in his pantry,
+which was without windows, and locked the door, but even there he
+could be heard answering the grunts, shouts, or pounds on the bulkhead
+outside. He was a man of middle age, fair physique, rather intelligent
+in facial expression, and without the slightest indication in
+appearance of his disability. As we descended the bank to go on board
+the steamer, some one gave a loud shout and threw his cap on the
+ground; looking about for the steward, for the shout was evidently
+made for his benefit, we saw him violently throw his cap, with a
+shout, into a chicken-coop, into which he was about to put the result
+of his foraging expedition among the houses of the stanitza.
+
+   [Footnote 2: "Observations upon the Korean Coast, Japanese-Korean
+   Ports, and Siberia, made during a journey from the Asiatic
+   Station to the United States, through Siberia to Europe, June 3
+   to September 8, 1882." Published by the United States Navy
+   Department, Washington, 1883, pp. 51.]
+
+"We afterward witnessed an incident which illustrated the extent of
+his disability. The captain of the steamer, running up to him,
+suddenly clapping his hands at the same time, accidentally slipped and
+fell hard on the deck; without having been touched by the captain, the
+steward instantly clapped his bands and shouted, and then, in
+powerless imitation, he too fell as hard and almost precisely in the
+same manner and position as the captain. In speaking of the steward's
+disorder, the captain of the general staff stated that it was not
+uncommon in Siberia; that he had seen a number of cases of it, and
+that it was commonest about Yakutsk, where the winter cold is extreme.
+Both sexes were subject to it, but men much less than women. It was
+known to Russians by the name of 'miryachit'".
+
+So far as I am aware--and I have looked carefully through several
+books of travel in Siberia--no account of this curious disease has
+been hitherto published.
+
+The description given by the naval officers at once, however, brings
+to mind the remarks made by the late Dr. George M. Beard, before the
+meeting of the American Neurological Association in 1880, relative to
+the "Jumpers" or "Jumping Frenchmen" of Maine and northern New
+Hampshire.[3]
+
+   [Footnote 3: "Journal of Nervous and Mental Diseases," vol. vii.,
+   1880, p. 487.]
+
+In June, 1880, Dr. Beard visited Moosehead Lake, found the "Jumpers,"
+and experimented with them. He ascertained that whatever order was
+given them was at once obeyed. Thus, one of the jumpers who was
+sitting in a chair with a knife in his hand was told to throw it, and
+he threw it quickly, so that it stuck in a beam opposite; at the same
+time he repeated the order to throw it with a cry of alarm not unlike
+that of hysteria or epilepsy. He also threw away his pipe, which he
+was filling with tobacco, when he was slapped upon the shoulder. Two
+jumpers standing near each other were told to strike, and they struck
+each other very forcibly. One jumper, when standing by a window, was
+suddenly commanded by a person on the other side of the window to
+jump, and he jumped up half a foot from the floor, repeating the
+order. When the commands are uttered in a quick, loud voice, the
+jumper repeats the order. When told to strike he strikes, when told to
+throw he throws whatever he may happen to have in his hand. Dr. Beard
+tried this power of repetition with the first part of the first line
+of Virgil's "AEneid" and the first part of the first line of Homer's
+"Iliad," and out-of-the-way words of the English language with which
+the jumper could not be familiar, and he repeated or echoed the sound
+of the word as it came to him in a quick, sharp voice, at the same
+time he jumped, or struck, or threw, or raised his shoulders, or made
+some other violent muscular motion. They could not help repeating the
+word or sound that came from the person that ordered them, any more
+than they could help striking, dropping, throwing, jumping, or
+starting; all of these phenomena were indeed but parts of the general
+condition known as jumping. It was not necessary that the sound should
+come from a human being; any sudden or unexpected noise, as the
+explosion of a gun or pistol, the falling of a window, or the slamming
+of a door--provided it was unexpected and loud enough--would cause
+these jumpers to exhibit some one or all of these phenomena. One of
+these jumpers came very near cutting his throat, while shaving, on
+hearing a door slam. They had been known to strike their fists against a
+red-hot stove, to jump into the fire and into water. They could not
+help striking their best friend if near them when ordered. The noise
+of a steam whistle was especially obnoxious to them. One of these
+jumpers, when taking some bromide of sodium in a tumbler, was told to
+throw it, and he dashed the tumbler upon the floor. It was dangerous
+to startle them in any way when they had an ax or an knife in their
+hands. All of the jumpers agreed that it tired them to be jumped, and
+they dreaded it, but they were constantly annoyed by their companions.
+
+From this description it will at once, I think, be perceived that
+there are striking analogies between "miryachit" and this disorder of
+the "Jumping Frenchmen" of Maine. Indeed, it appears to me that, if
+the two affections were carefully studied, it would be found that they
+were identical, or that, at any rate, the phenomena of the one could
+readily be developed into those of the others. It is not stated that
+the subjects of miryachit do what they are told to do. They require an
+example to reach their brains through the sense of sight or that of
+hearing, whereas the "Jumpers" do not apparently perform an act which
+is executed before them, but they require a command. It seems,
+however, that a "Jumper" starts whenever any sudden noise reaches his
+ears.
+
+In both classes of cases a suggestion of some kind is required, and
+then the act takes place independently of the will. There is another
+analogous condition known by the Germans as _Schlaftrunkenheit_, and
+to English and American neurologists as somnolentia, or
+sleep-drunkenness. In this state an individual, on being suddenly
+awakened, commits some incongruous act of violence, ofttimes a murder.
+Sometimes this appears to be excited by a dream, but in others no such
+cause could be discovered.
+
+Thus, a sentry fell asleep during his watch, and, being suddenly
+aroused by the officer in command, attacked the latter with his sword,
+and would have killed him but for the interposition of the bystanders.
+The result of the medical examination was that the act was
+involuntary, being the result of a violent confusion of mind
+consequent upon the sudden awaking from a profound sleep. Other cases
+are cited by Wharton and Stille in their work on medical
+jurisprudence, by Hoffbauer, and by myself in "Sleep and its
+Derangements."
+
+The following cases among others have occurred in my own experience:
+
+A gentleman was roused one night by his wife, who heard the
+street-door bell ring. He got up, and, without paying attention to
+what she said, dragged the sheets off of the bed, tore them hurriedly
+into strips, and proceeded to tie the pieces together. She finally
+succeeded in bringing him to himself, when he said he had thought the
+house was on fire, and he was providing means for their escape. He did
+not recollect having had any dream of the kind, but was under the
+impression that the idea had occurred to him at the instant of his
+awaking.
+
+Another was suddenly aroused from a sound sleep by the slamming of a
+window-shutter by the wind. He sprang instantly from his bed, and,
+seizing a chair that was near, hurled it with all his strength against
+the window. The noise of the breaking of glass fully awakened him. He
+explained that he imagined some one was trying to get into the room
+and had let his pistol fall on the floor, thereby producing the noise
+which had startled him.
+
+In another case a man dreamed that he heard a voice telling him to
+jump out of the window. He at once arose, threw open the sash, and
+jumped to the ground below, fortunately only a distance of about ten
+feet, so that he was not injured beyond receiving a violent shock.
+Such a case as this appears to me to be very similar to those
+described by Dr. Beard in all its essential aspects.
+
+A few years ago I had a gentleman under my charge who would attempt to
+execute any order given him while he was asleep by a person
+whispering into his ear. Thus, if told in this way to shout, he
+shouted as loud as he could; if ordered to get up, he at once jumped
+from the bed; if directed to repeat certain words, he said them, and
+so on.
+
+I am not able to give any certain explanation of the phenomena of
+miryachit or of the "Jumpers," or of certain of those cases of
+sleep-drunkenness which seem to be of like character. But they all
+appear to be due to the fact a motor impulse is excited by perceptions
+without the necessary concurrence of the volition of the individual to
+cause the discharge. They are, therefore, analogous to reflex actions,
+and especially to certain epileptic paroxysms due to reflex
+irritations. It would seem as though the nerve cells were very much in
+the condition of a package of dynamite or nitro glycerin, in which a
+very slight impression is sufficient to effect a discharge of nerve
+force. They differ, however, from the epileptic paroxysm in the fact
+that the discharge is consonant with the perception--which is in these
+cases an irritation--and is hence an apparently logical act, whereas
+in epilepsy the discharge is more violent, is illogical, and does not
+cease with the cessation of the irritation.
+
+Certainly the whole subject is of sufficient importance to demand the
+careful study of competent observers.
+
+       *       *       *       *       *
+
+
+
+
+THE GUM DISEASE IN TREES.[1]
+
+  [Footnote 1: Communicated to the _Medical Times_ by Sir James Paget.]
+
+
+An essay by Dr. Beijerinck, on the contagion of the gum disease in
+plants, lately published by the Royal Academy of Sciences at
+Amsterdam, contains some useful facts. The gum disease (_gummosis,
+gum-flux)_ is only too well known to all who grow peaches, apricots,
+plums, cherries, or other stone fruits. A similar disease produces gum
+arabic, gum tragacanth, and probably many resins and gum resins. It
+shows itself openly in the exudation of thick and sticky or hard and
+dry lumps of gum, which cling on branches of any of these trees where
+they have been cracked or wounded through the bark. Dr. Beijerinck was
+induced to make experimental inoculations of the gum disease by
+suspicions that, like some others observed in plants, it was due to
+bacteria. He ascertained that it is in a high degree contagious, and
+can easily be produced by inserting the gum under the edge of a wound
+through the bark of any of the trees above named. The observation that
+heated or long boiled pieces of gum lose their contagious property
+made it most probable that a living organism was concerned in the
+contagions; and he then found that only those pieces of the gum
+conveyed contagion in which, whether with or without bacteria, there
+were spores of a relatively highly organized fungus, belonging to the
+class of Ascomycetes; and that these spores, inserted by themselves
+under the bark, produced the same pathological changes as did the
+pieces of gum. The fungus thus detected, was examined by Professor
+Oudemans, who ascertained it to be a new species of Coryneum, and has
+named it _Coryneum Beijerincki_. The inoculation experiments are best
+made by means of incisions through the bark of young branches of
+healthy peach trees or cherry trees, and by slightly raising the cut
+edge of the bark and putting under it little bits of gum from a
+diseased tree of the same kind. In nearly every instance these wounds
+become the seats of acute gum disease, while similar wounds in the
+same or other branches of the same tree, into which no gum is
+inserted, remain healthy, unless, by chance, gum be washed into them
+during rain. The inoculation fails only when the inserted pieces of
+gum contain no Coryneum. By similar inoculations similar diseases can
+be produced in plum, almond, and apricot trees, and with the gum of
+any one of these trees any other can be infected; but of many other
+substances which Beijerinck tried, not one produced any similar
+disease. The inoculation with the gum is commonly followed by the
+death of more or less of the adjacent structures; first of the bark,
+then of the wood. Small branches or leaf stalks thus infected in
+winter, or in many places at the same time, may be completely killed;
+but, in the more instructive experiments the first symptom of the gum
+disease is the appearance of a beautiful red color around the wound.
+It comes out in spots like those which often appear spontaneously on
+the green young branches of peach trees that have the gum disease; and
+in these spots it is usual to find Coryneum stromata or mycelium
+filaments. The color is due to the formation of a red pigment in one
+or more of the layers of the cells of the bark. But in its further
+progress the disease extends beyond the parts at which the Coryneum or
+any structures derived from it can be found; and this extension,
+Beijerinck believes, is due to the production of a fluid of the nature
+of a ferment, produced by the Coryneum, and penetrating the adjacent
+structures. This, acting on the cell walls, the starch granules, and
+other constituents of the cells, transforms them into gum, and even
+changes into gum the Coryneum itself, reminding the observer of the
+self-digestion of a stomach.
+
+In the cells of the cambium, the same fluid penetrating unites with
+the protoplasm, and so alters it that the cells produced from it form,
+not good normal wood, but a morbid parenchymatous structure. The cells
+of this parenchyma, well known among the features of gum disease, are
+cubical or polyhedral, thin walled, and rich in protoplasm. This, in
+its turn, is transformed into gum, such as fills the gum channels and
+other cavities found in wood, and sometimes regarded as gum glands.
+And from this also the new ferment fluid constantly produced, and
+tracking along the tissues of the branches, conveys the Coryneum
+infection beyond the places in which its mycelium can be found.
+
+       *       *       *       *       *
+
+
+
+
+DRINKSTONE PARK.
+
+
+Drinkstone has long been distinguished on account of the successful
+cultivation of remarkable plants. It lies some eight miles southeast
+from Bury St. Edmund's, and is the seat of T.H. Powell, Esq. The
+mansion or hall is a large old-fashioned edifice, a large portion of
+its south front being covered by a magnificent specimen of the
+Magnolia grandiflora, not less than 40 feet in height, while other
+portions of its walls are covered with the finest varieties of
+climbing roses and other suitable plants. The surrounding country,
+although somewhat flat, is well wooded, and the soil is a rich loam
+upon a substratum of gravel, and is consequently admirably suited to
+the development of the finer kinds of coniferous and other ornamental
+trees and shrubs, so that the park and grounds contain a fine and well
+selected assortment of such plants.
+
+[Illustration: THE SNOWFLAKE, LEUCOJUM VERNUM, AT DRINKSTONE
+PARK.]
+
+Coniferous trees are sometimes considered as out of place in park
+scenery; this, however, does not hold good at Drinkstone, where Mr.
+Powell has been displayed excellent taste in the way of improving the
+landscape and creating a really charming effect by so skillfully
+blending the dressed grounds with the rich greensward of the park
+that it is not easy to tell where the one terminates or the other
+commences.
+
+The park, which covers some 200 acres, including a fine lake over
+eight acres in extent, contains also various large groups or clumps of
+such species as the Sequoia gigantea, Taxodium sempervirens, Cedres
+deodora, Picea douglasii, Pinsapo, etc., interspersed with groups of
+ornamental deciduous trees, producing a warm and very pleasing effect
+at all seasons of the year. Among species which are conspicuous in the
+grounds are fine, well-grown examples of Araucaria imbricata, some 30
+feet high; Cedrus deodara, 60 feet in height; Abies pinsapo, 40 feet;
+and fine specimens of Abies grandis, A. nobilis, and A. nordmanniana,
+etc., together with Abies albertiana or mertensiana, a fine,
+free-growing species; also Libocedrus gigantea, Thuiopsis borealis,
+Thuia lobbii, Juniperus recurva, Taxas adpressa, fine plants; with
+fine golden yews and equally fine examples of the various kinds of
+variegated hollies, etc.
+
+[Illustration: ODONTOGLOSSUM ROSSI MAJOR VAR. RUBESCENS, AT DRINKSTONE
+PARK.]
+
+Particular attention is here paid to early spring flowers. Drinkstone
+is also celebrated as a fruit growing establishment, more particularly
+as regards the grape vine; the weight and quality of the crops of
+grapes which are annually produced here are very remarkable.--_The
+Gardeners' Chronicle._
+
+       *       *       *       *       *
+
+
+
+
+ON THE CHANGES WHICH TAKE PLACE IN THE CONVERSION OF HAY INTO
+ENSILAGE.
+
+By FREDK. JAS. LLOYD, F.C.S., Lecturer on Agriculture, King's
+College.
+
+
+The recently published number of the _Royal Agricultural Society's
+Journal_ contains some information upon the subject of silage which
+appears to me of considerable interest to those chemists who are at
+present investigating the changes which take place in the conversion
+of grass into silage. The data[1] are, so far as I know, unique, and
+though the analytical work is not my own, yet it is that of an
+agricultural chemist, Mr. A. Smetham, of Liverpool, whose work I know
+from personal experience to be thoroughly careful and reliable. I have
+therefore no hesitation in basing my remarks upon it.
+
+   [Footnote 1: _Royal Agricultural Society's Journal_, vol. xx.,
+   part i., pp. 175 and 380.]
+
+We have here for the first time an accurate account of the quantity of
+grass put into a silo, of the quantity of silage taken out, and of the
+exact composition both of the grass and resulting silage. I desire
+merely to place myself in the position of, so to speak, a "chemical
+accountant."
+
+The ensilage has been analyzed at three depths, or rather in three
+layers, the first being 1 foot, the second 1 ft. to 1 ft. 6 in., and
+the third 1 ft. 6 in. to 2 ft. from the bottom of the silo. By
+doubling the figures of the bottom layer analysis, adding these to the
+second and third layer analysis, and dividing by 4, we obtain a fair
+representation of the average composition of the silage taken
+throughout the silo, for by so doing we obtain the average of the
+analyses of each 6-inch layer of silage. The results of the analyses
+are as follows, calculated on the dry matter. The moisture was
+practically the same, being 70.48 per cent, in the grass and 72.97 in
+the silage.
+
+
+         _Composition of Grass and Silage (dried at 100 deg.C.)._
+
+                                         Grass.       Ensilage.
+ Fat (ether extract)                       2.80            5.38
+ Soluble albuminous compounds              3.06            5.98
+ Insoluble albuminous compounds            6.94            3.77
+ Mucilage, sugar, and extractives, etc.   11.65            4.98
+ Digestible fiber                         36.24           33.37
+ Indigestible woody fiber                 32.33           31.79
+                                         -------         -------
+                                          93.02           85.27
+ Soluble mineral matters                   5.24           12.62
+ Insoluble mineral matters                 1.74            2.11
+                                         -------         -------
+                                         100.00          100.00
+
+The striking difference in the mineral matter of the grass and silage
+I will merely draw attention to; it is not due to the salt added to
+the silage. I may say, however, that other analysts and I myself have
+found similar striking differences. For instance, Prof. Kinch[2]
+found in grass 8.50 per cent. mineral matter, in silage 10.10 per
+cent., which, as be points out, is equivalent, to a "loss of about 18
+per cent. of combustible constituents"--a loss which we have no proof
+of having taken place. In Mr. Smetham's sample the loss would have to
+be 50 per cent., which did not occur, and in fact is not possible.
+What is the explanation?
+
+  [Footnote 2: _Journ. Chem. Society_, March, 1884, p. 124.]
+
+I am, however, considering now the organic constituents. Calculating
+the percentages of these in the grass and silage, we obtain the
+following figures:
+
+          _Percentage Composition of Organic Compounds._
+
+                                 Grass.           Ensilage.
+  Fat (ether extract)               3.01               6.31
+  Soluble albuminous compounds      8.29}             {7.01
+                                        }10.75   11.43{
+  Insoluble "            "          7.46}             {4.42
+
+  Mucilage, sugar, and extractives 12.52               5.84
+  Digestible fiber                 38.96              39.14
+  Indigestible woody fiber         34.76              37.28
+                                 -------            -------
+                                  100.00             100.00
+
+The difference in the total nitrogen in the grass and silage is equal
+to 0.68 per cent. of albuminoids. Practically it is a matter of
+impossibility that the nitrogen could have increased in the silo, and
+it will be a very safe premise upon which to base any further
+calculations that the total amount of nitrogen in the silage was
+identical with that in the grass. There may have been a loss, but
+that is not yet proved. Arguing then upon the first hypothesis, it is
+evident that 100 parts of the organic matters of silage represent more
+than 100 parts of the organic matter of grass, and by the equation we
+obtain 10.75:11.43 :: 100:106 approximately. If now we calculate the
+composition of 106 parts organic matter of grass, it will represent
+exactly the organic matter which has gone to form 100 parts of that
+present in silage.
+
+The following table gives these results, and also the loss or gain in
+the various constitutents arising from the conversion into silage:
+
+                 _Organic Matter_.
+
+                               In 106 pts. In 100 pts. Loss or
+                                  Grass.     Silage.     Gain.
+
+Fat (ether extract)               3.19        6.31      +3.12
+Soluble albuminous compounds      3.49        7.01      +3.52
+Insoluble "           "           7.91        4.42      -3.49
+Mucilage                         13.27        5.84      -7.43
+Digestible Fiber                 41.30       39.14      -2.16
+Indigestible woody fiber         36.84       37.28      +0.44
+                                -------     -------
+                                106.00      100.00
+
+These calculations show, provided my reasoning be correct, that the
+chief changes which take place are in the albuminous compounds, which
+has already been pointed out by Professors Voelcker, Kinch, and
+others; and in the starch, gum, mucilage, sugar, and those numerous
+bodies termed extractives, which was to be expected. But they show
+most conclusively that the "decrease in the amount of indigestible
+fiber and increase in digestible" so much spoken of is, so far as our
+present very imperfect methods of analyzing these compounds permit us
+to judge, a myth; and I have not yet found any sufficient evidence to
+support this statement. A loss, then, of 6 parts of organic matter out
+of every 106 parts put into the silo has in this instance taken place,
+due chiefly to the decomposition of starch, sugar, and mucilage, etc.
+And as the grass contained 70 parts of water when put into the silo,
+the total loss would only be 1.7 per cent. of the total weight. This
+theoretical deduction was found by practical experience correct, for
+Mr. Smith, agent to Lord Egerton, upon whose estate this silage was
+made, in his report to Mr. Jenkins says the "actual weight out of the
+silo corresponds exactly with the weight we put into the same."
+
+In my judgment these figures are of interest to the agricultural
+chemist for many reasons. First, they will clear the ground for future
+workers and eliminate from their researches what would have greatly
+complicated them--changes in the cellulose bodies.
+
+Secondly, they are of interest because our present methods of
+distinguishing between and estimating digestible and indigestible
+fiber is most rough, and probably inaccurate, and may not in the least
+represent the power of an animal--say a cow--to digest these various
+substances; and most of us know that when a new method of analysis
+becomes a necessity, a new method is generally discovered. Lastly,
+they are of interest to the agriculturist, for they point out, I
+believe for the first time, the exact amount of loss which grass--or
+at least one sample--has undergone in conversion into silage, and also
+that much of the nitrogenous matter is changed, and so far as we know
+at present, lost its nutritive value. This, however, is only comparing
+silage with grass. What is wanted is to compare silage with hay--both
+made out of the same grass. Then, and then only, will it be possible
+to sum up the relative advantages or disadvantages of the two methods
+of preserving grass as food for cattle.--_Chem. News_.
+
+       *       *       *       *       *
+
+
+
+
+THE ILLUMINATING POWER OF ETHYLENE.
+
+
+Dr. Percy Frankland has obtained results which may be thus briefly
+summarized: (1.) That pure ethylene, when burnt at the rate of 5 cubic
+feet per hour from a Referee's Argand burner, emits a light of 68.5
+standard candles. (2.) That the illuminating power of equal volumes of
+mixtures of ethylene with either hydrogen carbonic oxide or
+marsh-gas is less than that of pure ethylene. (3.) That when the
+proportion of ethylene in such mixtures is above 63 per cent. the
+illuminating power of the mixture is but slightly affected by the
+nature of the diluent. When, on the other hand, the proportion of
+ethylene in such mixtures is low, the illuminating power of the
+mixture is considerably the highest when marsh-gas is the diluent, and
+the lowest when the ethylene is mixed with carbonic oxide. (4.) That
+if 5 cubic feet of ethylene be uniformly consumed irrespectively of
+the composition of the mixture, the calculated illuminating power is
+in every case equal to or actually greater than that of pure ethylene
+until a certain degree of dilution is attained. This intrinsic
+luminosity of ethylene remains almost constant when the latter is
+diluted with carbonic oxide, until the ethylene forms only 40 per
+cent. of the mixture, after which it rapidly diminishes to zero when
+the ethylene forms only 20 per cent. of the mixture. When the ethylene
+is diluted with hydrogen, its intrinsic luminosity rises to 81 candles
+when the ethylene constitutes 30 per cent. of the mixture, after which
+it rapidly falls to zero when the ethylene amounts to only 10 per
+cent. In the case of mixtures of ethylene and marsh-gas, the intrinsic
+luminosity of the former is augmented with increasing rapidity as the
+proportion of marsh gas rises, the intrinsic luminosity of ethylene,
+in a mixture containing 10 per cent. of the latter, being between 170
+and 180 candles.
+
+       *       *       *       *       *
+
+
+
+
+DIFFRACTION PHENOMENA DURING TOTAL SOLAR ECLIPSES.[1]
+
+   [Footnote 1: A paper read before the American Astronomical
+   Society, May 5, 1884.]
+
+By G.D. Hiscox.
+
+
+The reality of the sun's corona having been cast in doubt by a leading
+observer of the last total eclipse, who, from the erratic display
+observed in the spectroscope, has declared it a subjective phenomenon
+of diffraction, has led me to an examination and inquiry as to the
+bearing of an obscurely considered and heretofore only casually
+observed phenomenon seen to take place during total solar eclipses.
+This phenomenon, it seems to me, ought to account for, and will
+possibly satisfy, the spectroscopic conditions observed just before,
+during, and after totality; which has probably led to the epithet used
+by some leading observers--"the fickle corona." The peculiar
+phenomenon observed in the spectroscope, the flickering bands or lines
+of the solar spectrum flashing upon and across the coronal spectrum,
+has caused no little speculation among observers.
+
+The diffraction or interference bands projected by the passage of a
+strong beam of light by a solid body, as discovered long since by
+Grimaldi, and investigated later by Newton, Fresnel, and Fraunhofer,
+are explained and illustrated in our text books; but the grand display
+of this phenomenon in a total solar eclipse, where the sun is the
+source of light and the moon the intercepting body, has as yet
+received but little attention from observers, and is not mentioned to
+my knowledge in our text books.
+
+In the instructions issued from the United States Naval Observatory
+and the Signal Office at Washington for the observation of the eclipse
+of July 29, 1878, attention was casually directed to this phenomenon,
+and a few of the observers at Pike's Peak, Central City, Denver, and
+other places have given lucid and interesting descriptions of the
+flight of the diffraction bands as seen coursing over the face of the
+earth at the speed of the moon's shadow, at the apparent enormous
+velocity of thirty-three miles per minute, or fifty times the speed of
+a fast railway train.
+
+From a known optical illusion derived from interference or fits of
+perception, as illustrated in quick moving shadows, this great speed
+was not realized to the eye, as the observed motion of these shadows
+was apparently far less rapid than their reality.
+
+The ultra or diffraction bands outside of the shadow were distinctly
+seen and described by Mr. J.E. Keeler at Central City, both before and
+after totality. He estimates the shadow bands at 8 inches wide and 4
+feet apart.
+
+Professor E.S. Holden, also at Central City, estimated the dark bands
+as about 3 feet apart, and variable.
+
+From estimates which he obtained from other observers of his party,
+the distances between the bands varied from 6 to l1/2 feet, but so
+quickly did they pass that they baffled all attempts to count even the
+number that passed in one second.
+
+He observed the time of continuance of their passage from west to east
+as forty-eight seconds, which indicates a width of 33 miles of
+diffraction bands stretching outward from the edge of the shadow to
+the number of many thousands.
+
+Mr. G.W. Hill, at Denver, a little to the north of the central track
+of the shadow, observed the infra or bands within the shadow, alluding
+to the fact that they must be moving at the same rate as the shadow,
+although their apparent motion was much slower, or like the shadows of
+flying clouds. He attributes the discrepancy to optical illusion.
+
+At Virginia City the _colors_ of the _ultra_ bands were observed, and
+estimated at five seconds' duration from the edge of the shadow, which
+is equal to about 4 miles in width. These are known to be the
+strongest color bands in the diffraction spectrum, which accounts for
+their being generally observed.
+
+Mr. W.H. Bush, observing at Central City, in a communication to Prof.
+Holden alludes to the brilliancy of the colors of these bands as seen
+through small clouds floating near the sun's place during totality,
+and of the rapid change of their rainbow colors as observed dashing
+across the clouds with the rapidity of thought.
+
+All of these bands, both ultra and infra, as seen in optical
+experiments, are colored in reverse order, being from violet to red
+for each band outward and inward from the edge of the shadow.
+
+It is very probable that the velocity of the passage of all the bands
+during a total eclipse very much modifies the distinctness of the
+colors or possibly obliterates them by optically blending so as to
+produce the dull white and black bands which occupied so large a
+portion of this grand panorama.
+
+The phenomenon of these faint colored bands, with the observed light
+and dark shadows, may be attributed to one or all of the following
+causes:
+
+1. A change in the direction of a small portion of the sun's light
+passing by the solid body of the moon, it being deflected outward by
+repulsion or reflection from its surface, and other portions being
+deflected inward after passing the body by mutual repulsion of its own
+elements toward a _light vacuum_ or space devoid of the element of
+vibration.
+
+2. The colored spectral bands being the direct result of the property
+of interference, or the want of correspondence of the wave lengths due
+to divergence; the same phenomenon being also observed in convergent
+light. This is practically illustrated in the hazy definition of the
+reduced aperture of telescopes, and its peculiarities shown in the
+spectral rings within and beyond the focus.
+
+3. Chromatic dispersion by our atmosphere, together with selective
+absorption, also by our atmosphere and its vapors, have been suggested
+as causes in this curious and complicated phenomena.
+
+In none of the reports descriptive of the phenomena of polarization of
+the corona is there the slightest allusion to the influence that the
+diffraction bands may possibly have in modifying or producing the
+various conditions of polarization observed; although these
+observations have been made and commented upon during the past
+twenty-five years.
+
+Investigations now in progress of the modifying relation of the
+phenomenon of diffraction in its effect upon not only the physical
+aspect of the corona, but also in some strange spectroscopic anomalies
+that have been observed near the sun at other times than during a
+total solar eclipse, will, it is hoped, result in a fuller
+interpretation of the physical nature of one of the grandest elements
+of creation--_light_; let there be more of it.
+
+       *       *       *       *       *
+
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