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+Project Gutenberg (https://www.gutenberg.org) public repository for
+eBook #51481 (https://www.gutenberg.org/ebooks/51481)
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-The Project Gutenberg EBook of Flying Machines Today, by William Duane Ennis
-
-This eBook is for the use of anyone anywhere in the United States and most
-other parts of the world 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.  If you are not located in the United States, you'll have
-to check the laws of the country where you are located before using this ebook.
-
-Title: Flying Machines Today
-
-Author: William Duane Ennis
-
-Release Date: March 17, 2016 [EBook #51481]
-
-Language: English
-
-Character set encoding: ISO-8859-1
-
-*** START OF THIS PROJECT GUTENBERG EBOOK FLYING MACHINES TODAY ***
-
-
-
-
-Produced by Chris Curnow, Ralph Carmichael and the Online
-Distributed Proofreading Team at http://www.pgdp.net (This
-file was produced from images generously made available
-by The Internet Archive)
-
-
-
-
-
-
-FLYING MACHINES TODAY
-
-
-
-
-"Hitherto aviation has been almost monopolized by that much-overpraised
-and much-overtrusted person, 'the practical man.' It is much in need
-of the services of the theorist--the engineer with his mathematical
-calculations of how a flying machine ought to be built and of how the
-material used in its construction should be distributed to give the
-greatest possible amount of strength and efficiency."
-
-                         --From the _New York Times_, January 16, 1911.
-
-
-  [Illustration: THE FALL OF ICARUS]
-
-
-
-
-FLYING MACHINES TODAY
-
- BY
- WILLIAM DUANE ENNIS
-
- _Professor of Mechanical Engineering in the Polytechnic
-  Institute of Brooklyn_
-
-_123 ILLUSTRATIONS_
-
-  [Illustration: VAN NOSTRAND LOGO]
-
-  NEW YORK
-  D. VAN NOSTRAND COMPANY
-  23 MURRAY AND          1911          27 WARREN STS.
-
-
-
-
-  _Copyright, 1911, by_
-  D. VAN NOSTRAND COMPANY
-
-
-THE · PLIMPTON · PRESS · NORWOOD · MASS · U · S · A
-
-
-
-
- To
- MY MOTHER
-
-
-
-
-PREFACE
-
-
-Speaking with some experience, the writer has found that instruction
-in the principles underlying the science and sport of aviation must be
-vitalized by some contemporaneous study of what is being accomplished
-in the air. No one of the revolutionizing inventions of man has
-progressed as rapidly as aerial navigation. The "truths" of today are
-the absurdities of tomorrow.
-
-The suggestion that some grasp of the principles and a very fair
-knowledge of the current practices in aeronautics may be had without
-special technical knowledge came almost automatically. If this book
-is comprehensible to the lay reader, and if it conveys to him even a
-small proportion of the writer's conviction that flying machines are to
-profoundly influence our living in the next generation, it will have
-accomplished its author's purpose.
-
-  POLYTECHNIC INSTITUTE OF BROOKLYN,
-   NEW YORK, April, 1911.
-
-
-
-
-CONTENTS
-
-
-                                                          PAGE
- THE DELIGHTS AND DANGERS OF FLYING.--Dangers of
- Aviation.--What it is Like to Fly                           1
-
- SOARING FLIGHT BY MAN.--What Holds it Up?--Lifting
- Power.--Why so Many Sails?--Steering                       17
-
- TURNING CORNERS.--What Happens when Making a Turn.--
- Lateral Stability.--Wing Warping.--Automatic Control.--
- The Gyroscope.--Wind Gusts                                 33
-
- AIR AND THE WIND.--Sailing Balloons.--Field and Speed      43
-
- GAS AND BALLAST.--Buoyancy in Air.--Ascending and
- Descending.--The Ballonet.--The Equilibrator               57
-
- DIRIGIBLE BALLOONS AND OTHER KINDS.--Shapes.--
- Dimensions.--Fabrics.--Framing.--Keeping the Keel
- Horizontal.--Stability.--Rudders and Planes.--Arrangement
- and Accessories.--Amateur Dirigibles.--The Fort
- Omaha Plant.--Balloon Progress                             71
-
- THE QUESTION OF POWER.--Resistance of Aeroplanes.--
- Resistance of Dirigibles.--Independent Speed and
- Time-Table.--The Cost of Speed.--The Propeller            101
-
- GETTING UP AND DOWN; MODELS AND GLIDERS;
- AEROPLANE DETAILS.--Launching.--Descending.--
- Gliders.--Models.--Balancing.--Weights.--
- Miscellaneous.--Things to Look After                      121
-
- SOME AEROPLANES.--SOME ACCOMPLISHMENTS                    143
-
- THE POSSIBILITIES IN AVIATION.--The Case of the
- Dirigible.--The Orthopter.--The Helicopter.--Composite
- Types.--What is Promised                                  170
-
- AERIAL WARFARE                                            189
-
-
-
-
- LIST OF ILLUSTRATIONS
-
-
-                                                         PAGE
-
-  The Fall of Icarus                           _Frontispiece_
-  The Aviator                                               3
-  The Santos-Dumont "_Demoiselle_"                          4
-  View from a Balloon                                       9
-  Anatomy of a Bird's Wing                                 10
-  Flight of a Bird                                         11
-  In a Meteoric Shower                                     13
-  How a Boat Tacks                                         15
-  Octave Chanute                                           18
-  Pressure of the Wind                                     19
-  Forces Acting on a Kite                                  20
-  Sustaining Force in the Aeroplane                        23
-  Direct Lifting and Resisting Forces                      24
-  Shapes of Planes                                         26
-  Balancing Sail                                           28
-  Roe's Triplane at Wembley                                30
-  Action of the Steering Rudder                            31
-  Recent Type of Wright Biplane                            31
-  Circular Flight                                          33
-  The Aileron                                              35
-  Wing Tipping                                             36
-  Wing Warping                                             37
-  The Gyroscope                                            39
-  Diurnal Temperatures at Different Heights                45
-  Seasonal Variation in Wind Velocities                    47
-  The Wind Rose for Mt. Weather, Va.                       49
-  Diagram of Parts of a Drifting Balloon                   51
-  Glidden and Stevens Getting Away in the "_Boston_"       52
-  Relative and Absolute Balloon Velocities                 53
-  Field and Speed                                          53
-  Influence of Wind on Possible Course                     54
-  Count Zeppelin                                           55
-  Buoyant Power of Wood                                    57
-  One Cubic Foot of Wood Loaded in Water                   58
-  Buoyant Power of Hydrogen                                59
-  Lebaudy's "_Jaune_"                                      60
-  Air Balloon                                              62
-  Screw Propeller for Altitude Control                     66
-  Balloon with Ballonets                                   67
-  Construction of the Zeppelin Balloon                     68
-  The Equilibrator                                         69
-  Henry Giffard's Dirigible                                71
-  Dirigible of Dupuy de Lome                               72
-  Tissandier Brothers' Dirigible Balloon                   73
-  The "_Baldwin_"                                          74
-  The "_Zeppelin_" on Lake Constance                       75
-  The "_Patrie_"                                           77
-  Manufacturing the Envelope of a Balloon                  79
-  Andrée's Balloon, "_L'Oernen_"                           80
-  Wreck of the "_Zeppelin_"                                82
-  Car of the "_Zeppelin_"                                  84
-  Stern View of the "_Zeppelin_"                           86
-  The "_Clément-Bayard_"                                   87
-  The "_Ville de Paris_"                                   88
-  Car of the "_Liberté_"                                   89
-  The "_Zodiac No. 2_"                                     92
-  United States Signal Corps Balloon Plant at Fort Omaha   93
-  The "_Caroline_"                                         94
-  The Ascent at Versailles, 1783                           95
-  Proposed Dirigible                                       96
-  The "_République_"                                       97
-  The First Flight for the Gordon-Bennett Cup              99
-  The Gnome Motor                                         102
-  Screw Propeller                                         103
-  One of the Motors of the "_Zeppelin_"                   104
-  The Four-Cycle Engine                                   105
-  Action of Two-Cycle Engine                              106
-  Motor and Propeller                                     108
-  Two-Cylinder Opposed Engine                             110
-  Four-Cylinder Vertical Engine                           110
-  Head End Shapes                                         113
-  The Santos-Dumont Dirigible No. 2                       115
-  In the Bay of Monaco: Santos-Dumont                     117
-  Wright Biplane on Starting Rail                         121
-  Launching System for Wright Aeroplane                   122
-  The Nieuport Monoplane                                  124
-  A Biplane                                               125
-  Ely at Los Angeles                                      126
-  Trajectory During Descent                               127
-  Descending                                              128
-  The Witteman Glider                                     130
-  French Monoplane                                        132
-  A Problem in Steering                                   133
-  Lejeune Biplane                                         134
-  Tellier Monoplane                                       135
-  A Monoplane                                             137
-  Cars and Framework                                      139
-  Some Details                                            139
-  Recent French Machines                                  141
-  Orville Wright at Fort Myer                             143
-  The First Flight Across the Channel                     144
-  Wright Motor                                            145
-  Voisin-Farman Biplane                                   147
-  The Champagne Grand Prize Flight                        148
-  Farman's First Biplane                                  149
-  The "_June Bug_"                                        150
-  Curtiss Biplane                                         151
-  Curtiss' Hydro-Aeroplane at San Diego Bay               152
-  Flying Over the Water                                   153
-  Blériot-Voisin Cellular Biplane with Pontoons           154
-  Latham's "_Antoinette_"                                 155
-  James J. Ward at Lewiston Fair                          156
-  Marcel Penot in the "_Mohawk_"                          157
-  Santos-Dumont's "_Demoiselle_"                          159
-  Blériot Monoplane                                       160
-  Latham's Fall into the Channel                          161
-  De Lesseps Crossing the Channel                         163
-  The Maxim Aeroplane                                     164
-  Langley's Aeroplane                                     165
-  Robart Monoplane                                        166
-  Vina Monoplane                                          167
-  Blanc Monoplane                                         170
-  Melvin Vaniman Triplane                                 171
-  Jean de Crawhez Triplane                                171
-  A Triplane                                              172
-  Giraudon's Wheel Aeroplane                              175
-  Bréguet Gyroplane (Helicopter)                          177
-  Wellman's "_America_"                                   181
-  The German Emperor Watching the Progress of Aviation    189
-  Automatic Gun for Attacking Airships                    193
-  Gun for Shooting at Aeroplanes                          197
-  Santos-Dumont Circling the Eiffel Tower                 199
-  Latham, Farman and Paulhan                              202
-
-
-
-
-FLYING MACHINES TODAY
-
-
-
-
-THE DELIGHTS AND DANGERS OF FLYING
-
-
-Few things have more charm for man than flight. The soaring of a bird
-is beautiful and the gliding of a yacht before the wind has something
-of the same beauty. The child's swing; the exercise of skating on
-good ice; a sixty-mile-an-hour spurt on a smooth road in a motor car;
-even the slightly passé bicycle: these things have all in their time
-appealed to us because they produce the illusion of flight--of progress
-through the intangible air with all but separation from the prosaic
-earth.
-
-But these sensations have been only illusions. To actually leave the
-earth and wander at will in aerial space--this has been, scarcely a
-hope, perhaps rarely even a distinct dream. From the days of Dædalus
-and Icarus, of Oriental flying horses and magic carpets, down to
-"Darius Green and his flying machine," free flight and frenzy were
-not far apart. We were learnedly told, only a few years since, that
-sustention by heavier-than-air machines was impossible without the
-discovery, first, of some new matter or some new force. It is now
-(1911) only eight years since Wilbur Wright at Kitty Hawk, with the
-aid of the new (?) matter--aluminum--and the "new" force--the gasoline
-engine--in three successive flights proved that a man could travel
-through the air and safely descend, in a machine weighing many times
-as much as the air it displaced. It is only five years since two
-designers--Surcouf and Lebaudy--built dirigible balloons approximating
-present forms, the _Ville de Paris_ and _La Patrie_. It is only now
-that we average people may confidently contemplate the prospect of an
-aerial voyage for ourselves before we die. A contemplation not without
-its shudder, perhaps; but yet not altogether more daring than that of
-our grandsires who first rode on steel rails behind a steam locomotive.
-
-
-The Dangers of Aviation
-
-We are very sure to be informed of the fact when an aviator is
-killed. Comparatively little stir is made nowadays over an automobile
-fatality, and the ordinary railroad accident receives bare mention. For
-instruction and warning, accidents to air craft cannot be given too
-much publicity; but if we wish any accurate conception of the danger we
-must pay regard to factors of proportion. There are perhaps a thousand
-aeroplanes and about sixty dirigible balloons in the world. About 500
-men--amateurs and professionals--are continuously engaged in aviation.
-The Aero Club of France has issued in that country nearly 300 licenses.
-In the United States, licenses are held by about thirty individuals.
-We can form no intelligent estimate as to the number of unlicensed
-amateurs of all ages who are constantly experimenting with gliders at
-more or less peril to life and limb.
-
-A French authority has ascertained the death rate among air-men to
-have been--to date--about 6%. This is equivalent to about one life for
-4000 miles of flight: but we must remember that accidents will vary
-rather with the number of ascents and descents than with the mileage.
-Four thousand miles in 100 flights would be much less perilous, under
-present conditions, than 4000 miles in 1000 flights.
-
-  [Illustration: THE AVIATOR]
-
-There were 26 fatal aeroplane accidents between September 17, 1908,
-and December 3, 1910. Yet in that period there were many thousands of
-ascents: 1300 were made in one week at the Rheims tournament alone.
-Of the 26 accidents, 1 was due to a wind squall, 3 to collision,
-6 (apparently) to confusion of the aviator, and 12 to mechanical
-breakage. An analysis of 40 British accidents shows 13 to have been
-due to engine failures, 10 to alighting on bad ground, 6 to wind
-gusts, 5 to breakage of the propeller, and 6 to fire and miscellaneous
-causes. These casualties were not all fatal, although the percentage of
-fatalities in aeronautic accidents is high. The most serious results
-were those due to alighting on bad ground; long grass and standing
-grain being very likely to trip the machine and throw the occupant.
-French aviators are now strapping themselves to their seats in order to
-avoid this last danger.
-
-  [Illustration: THE SANTOS-DUMONT "DEMOISELLE"
-  (From _The Aeroplane_, by Hubbard, Ledeboer and Turner)]
-
-Practically all of the accidents occur to those who are flying; but
-spectators may endanger themselves. During one of the flights of
-Mauvais at Madrid, in March of the present year, the bystanders rushed
-through the barriers and out on the field before the machine had well
-started. A woman was decapitated by the propeller, and four other
-persons were seriously injured.
-
-Nearly all accidents result from one of three causes: bad design,
-inferior mechanical construction, and the taking of unnecessary risks
-by the operator. Scientific design at the present writing is perhaps
-impossible. Our knowledge of the laws of air resistance and sustention
-is neither accurate nor complete. Much additional study and experiment
-must be carried on; and some better method of experimenting must be
-devised than that which sends a man up in the air and waits to see what
-happens. A thorough scientific analysis will not only make aviation
-safer, it will aid toward making it commercially important. Further
-data on propeller proportions and efficiencies, and on strains in the
-material of screws under aerial conditions, will do much to standardize
-power plant equipment. The excessive number of engine breakdowns
-is obviously related to the extremely light weight of the engines
-employed: better design may actually increase these weights over those
-customary at present. Great weight reduction is no longer regarded
-as essential at present speeds in aerial navigation: we have perhaps
-already gone too far in this respect.
-
-Bad workmanship has been more or less unavoidable, since no one has
-yet had ten years' experience in building aeroplanes. The men who have
-developed the art have usually been sportsmen rather than mechanics,
-and only time is necessary to show the impropriety of using "safety
-pins" and bent wire nails for connections.
-
-The taking of risks has been an essential feature. When one man earns
-$100,000 in a year by dare-devil flights, when the public flocks in
-hordes--and pays good prices--to see a man risk his neck, he will
-usually aim to satisfy it. This is not developing aerial navigation:
-this is circus riding--looping-the-loop performances which appeal to
-some savage instinct in us but lead us nowhere. Men have climbed two
-miles into the clouds, for no good purpose whatever. All that we need
-to know of high altitude conditions is already known or may be learned
-by ascents in anchored balloons. Records up to heights of sixteen miles
-have been obtained by sounding balloons.
-
-If these high altitudes may under certain conditions be desirable for
-particular types of balloon, they are essentially undesirable for the
-aeroplane. The supporting power of a heavier-than-air machine decreases
-in precisely inverse ratio with the altitude. To fly high will then
-involve either more supporting surface and therefore a structurally
-weaker machine, or greater speed and consequently a larger motor. It
-is true that the resistance to propulsion decreases at high altitudes,
-just as the supporting power decreases: and on this account, given only
-a sufficient margin of supporting power, we might expect a standard
-machine to work about as well at a two-mile elevation as at a height of
-200 feet; but rarefaction of the air at the higher altitudes decreases
-the weight of carbureted mixture drawn into the motor, and consequently
-its output. Any air-man who attempts to reach great heights in a
-machine not built for such purpose is courting disaster.
-
-Flights over cities, spectacular as they are, and popular as they are
-likely to remain, are doubly dangerous on account of the irregular air
-currents and absence of safe landing places. They have at last been
-officially discountenanced as not likely to advance the sport.
-
-All flights are exhibition flights. The day of a quiet,
-mind-your-own-business type of aerial journey has not yet arrived.
-Exhibition performances of any sort are generally hazardous. There
-were nine men killed in one recent automobile meet. If the automobile
-were used exclusively for races and contests, the percentage of
-fatalities might easily exceed that in aviation. It is claimed that no
-inexperienced aviator has ever been killed. This may not be true, but
-there is no doubt that the larger number of accidents has occurred to
-the better-known men from whom the public expects something daring.
-
-Probably the best summing up of the danger of aviation may be obtained
-from the insurance companies. The courts have decided that an
-individual does not forfeit his life insurance by making an occasional
-balloon trip. Regular classified rates for aeroplane and balloon
-operators are in force in France and Germany. It is reported that Mr.
-Grahame-White carries a life insurance policy at 35% premium--about
-the same rate as that paid by a "crowned head." Another aviator of a
-less professional type has been refused insurance even at 40% premium.
-Policies of insurance may be obtained covering damage to machines by
-fire or during transportation and by collisions with other machines;
-and covering liability for injuries to persons other than the aviator.
-
-On the whole, flying is an ultra-hazardous _occupation_; but an
-_occasional_ flight by a competent person or by a passenger with a
-careful pilot is simply a thrilling experience, practically no more
-dangerous than many things we do without hesitation. Nearly all
-accidents have been due to preventable causes; and it is simply a
-matter of science, skill, perseverance, and determination to make an
-aerial excursion under proper conditions as safe as a journey in a
-motor car. Men who for valuable prizes undertake spectacular feats will
-be killed as frequently in aviation as in bicycle or even in automobile
-racing; but probably not very much more frequently, after design and
-workmanship in flying machines shall have been perfected. The total
-number of deaths in aviation up to February 9, 1911, is stated to have
-been forty-two.
-
-
-What It Is Like to Fly
-
-We are fond of comparing flying machines with birds, with fish,
-and with ships: and there are useful analogies with all three. A
-drifting balloon is like a becalmed ship or a dead fish. It moves at
-the speed of the aerial fluid about it and the occupants perceive no
-movement whatever. The earth's surface below appears to move in the
-opposite direction to that in which the wind carries the balloon. With
-a dirigible balloon or flying machine, the sensation is that of being
-exposed to a violent wind, against which (by observation of landmarks)
-we find that we progress. It is the same experience as that obtained
-when standing in an exposed position on a steamship, and we wonder if a
-bird or a fish gradually gets so accustomed to the opposing current as
-to be unconscious of it. But in spite of jar of motors and machinery,
-there is a freedom of movement, a detachment from earth-associations,
-in air flight, that distinguishes it absolutely from the churning of a
-powerful vessel through the waves.
-
-  [Illustration: VIEW FROM A BALLOON]
-
-  [Illustration: ANATOMY OF A BIRD'S WING
-  (From Walker's _Aerial Navigation_)]
-
-  [Illustration: FLIGHT OF A BIRD]
-
-Birds fly in one of three ways. The most familiar bird flight is
-by a rapid wing movement which has been called oar-like, but which
-is precisely equivalent to the usual movement of the arms of a man
-in swimming. The edge of the wing moves forward, cutting the air; on
-the return stroke the leading edge is depressed so as to present a
-nearly flat surface to the air and thus propel the bird forward. A
-slight downward direction of this stroke serves to impel the flight
-sufficiently upward to offset the effect of gravity. Any man can learn
-to swim, but no man can fly, because neither in his muscular frame nor
-by any device which he can attach thereto can he exert a sufficient
-pressure to overcome his own weight against as imponderable a fluid
-as air. If air were as heavy as water, instead of 700 times lighter,
-it would be as easy to fly as to swim. The bird can fly because of
-the great surface, powerful construction, and rapid movement of its
-wings, in proportion to the weight of its body. But compared with
-the rest of the animal kingdom, flying birds are all of small size.
-Helmholz considered that the vulture represented the heaviest body that
-could possibly be raised and kept aloft by the exercise of muscular
-power, and it is understood that vultures have considerable difficulty
-in ascending; so much so that unless in a position to take a short
-preliminary run they are easily captured.
-
-Every one has noticed a second type of bird flight--soaring. It is this
-flight which is exactly imitated in a glider. An aeroplane differs
-from a soaring bird only in that it carries with it a producer of
-forward impetus--the propeller--so that the soaring flight may last
-indefinitely: whereas a soaring bird gradually loses speed and descends.
-
-  [Illustration: IN A METEORIC SHOWER]
-
-A third and rare type of bird flight has been called _sailing_. The
-bird faces the wind, and with wings outspread and their forward edge
-elevated rises while being forced backward under the action of the
-breeze. As soon as the wind somewhat subsides, the bird turns and
-_soars_ in the desired direction. Flight is thus accomplished without
-muscular effort other than that necessary to properly incline the
-wings and to make the turns. It is practicable only in squally winds,
-and the birds which practice "sailing"--the albatross and frigate
-bird--are those which live in the lower and more disturbed regions of
-the atmosphere. This form of flight has been approximately imitated in
-the man[oe]uvering of aeroplanes.
-
-Comparison of flying machines and ships suggests many points of
-difference. Water is a fluid of great density, with a definite upper
-surface, on which marine structures naturally rest. A vessel in the air
-may be at any elevation in the surrounding rarefied fluid, and great
-attention is necessary to keep it at the elevation desired. The air has
-no surface. The air ship is like a submarine--the dirigible balloon
-of the sea--and perhaps rather more safe. An ordinary ship is only
-partially immersed; the resistance of the fluid medium is exerted over
-a portion only of its head end: but the submarine or the flying machine
-is wholly exposed to this resistance. The submarine is subjected to
-ocean currents of a very few miles per hour, at most; the currents to
-which the flying machine may be exposed exceed a mile a minute. Put a
-submarine in the Whirlpool Rapids at Niagara and you will have possible
-air ship conditions.
-
-A marine vessel may _tack_, _i.e._, may sail partially against the
-wind that propels it, by skillful utilization of the resistance to
-sidewise movement of the ship through the water: but the flying machine
-is wholly immersed in a single fluid, and a head wind is nothing else
-than a head wind, producing an absolute subtraction from the proper
-speed of the vessel.
-
-  [Illustration: HOW A BOAT TACKS
-  The wind always exerts a pressure, perpendicular to the sail,
-  which tends to drift the boat sidewise (R) and also to propel
-  it forward (L). Sidewise movement is resisted by the hull.
-  An air ship cannot tack because there is no such resistance
-  to drift.]
-
-Aerial navigation is thus a new art, particularly when heavier-than-air
-machines are used. We have no heavier-than-water _ships_. The flying
-machine must work out its own salvation.
-
-
-
-
-SOARING FLIGHT BY MAN
-
-
-Flying machines have been classified as follows:--
-
-     Lighter than Air
-  Fixed balloon,
-  Drifting balloon,
-  Sailing balloon,
-  Dirigible balloon
-        rigid (Zeppelin),
-        ballonetted.
-
-     Heavier than Air
-  Orthopter,
-  Helicopter,
-  Aeroplane
-        monoplane,
-        multiplane.
-
-We will fall in with the present current of popular interest and
-consider the aeroplane--that mechanical grasshopper--first.
-
-
-What Holds It Up?
-
-  [Illustration: OCTAVE CHANUTE (DIED 1910)]
-
-To the researches of Chanute and Langley must be ascribed much of
-American progress in aviation.
-
-When a flat surface like the side of a house is exposed to the breeze,
-the velocity of the wind exerts a force or pressure directly against
-the surface. This principle is taken into account in the design of
-buildings, bridges, and other structures. The pressure exerted per
-square foot of surface is equal (approximately) to the square of the
-wind velocity in miles per hour, divided by 300. Thus, if the wind
-velocity is thirty miles, the pressure against a house wall on which it
-acts directly is 30 × 30 ÷ 300 = 3 pounds per square foot: if the wind
-velocity is sixty miles, the pressure is 60 × 60 ÷ 300 = 12 pounds:
-if the velocity is ninety miles, the pressure is 90 × 90 ÷ 300 = 27
-pounds, and so on.
-
-  [Illustration: PRESSURE OF THE WIND]
-
-If the wind blows obliquely toward the surface, instead of directly,
-the pressure at any given velocity is reduced, but may still be
-considerable. Thus, in the sketch, let _ab_ represent a wall, toward
-which we are looking downward, and let the arrow _V_ represent the
-direction of the wind. The air particles will follow some such paths
-as those indicated, being deflected so as to finally escape around
-the ends of the wall. The result is that a pressure is produced which
-may be considered to act along the dotted line _P_, perpendicular to
-the wall. This is the invariable law: that no matter how oblique the
-surface may be, with reference to the direction of the wind, there is
-always a pressure produced against the surface by the wind, and this
-pressure always acts _in a direction perpendicular to the surface_. The
-amount of pressure will depend upon the wind velocity and the obliquity
-or inclination of the surface (_ab_) with the wind (_V_).
-
-Now let us consider a kite--the "immediate ancestor" of the aeroplane.
-The surface _ab_ is that of the kite itself, held by its string _cd_.
-We are standing at one side and looking at the _edge_ of the kite. The
-wind is moving horizontally against the face of the kite, and produces
-a pressure _P_ directly against the latter. The pressure tends both to
-move it toward the left and to lift it. If the tendency to move toward
-the left be overcome by the string, then the tendency toward lifting
-may be offset--and in practice _is_ offset--by the weight of the kite
-and tail.
-
-  [Illustration: FORCES ACTING ON A KITE]
-
-We may represent the two tendencies to movement produced by the force
-_P_, by drawing additional dotted lines, one horizontally to the left
-(_R_) and the other vertically (_L_); and it is known that if we let
-the length of the line _P_ represent to some convenient scale the
-amount of direct pressure, then the lengths of _R_ and _L_ will also
-represent to the same scale the amounts of horizontal and vertical
-force due to the pressure. If the weight of kite and tail exceeds the
-vertical force _L_, the kite will descend: if these weights are less
-than that force, the kite will ascend. If they are precisely equal to
-it, the kite will neither ascend nor descend. The ratio of _L_ to _R_
-is determined by the slope of _P_; and this is fixed by the slope of
-_ab_; so that we have the most important conclusion: _not only does
-the amount of direct pressure (P) depend upon the obliquity of the
-surface with the breeze (as has already been shown), but the relation
-of vertical force (which sustains the kite) to horizontal force also
-depends on the same obliquity_. For example, if the kite were flying
-almost directly above the boy who held the string, so that _ab_ became
-almost horizontal, _P_ would be nearly vertical and _L_ would be much
-greater than _R_. On the other hand, if _ab_ were nearly vertical, the
-kite flying at low elevation, the string and the direct pressure would
-be nearly horizontal and _L_ would be much less than _R_. The force _L_
-which lifts the kite seems to increase while _R_ decreases, as the kite
-ascends: but _L_ may not actually increase, because it depends upon the
-amount of direct pressure, _P_, as well as upon the direction of this
-pressure; and the amount of direct pressure steadily decreases during
-ascent, on account of the increasing obliquity of _ab_ with _V_. All of
-this is of course dependent on the assumption that the kite always has
-the same inclination to the string, and the described resolution of the
-forces, although answering for illustrative purposes, is technically
-incorrect.
-
-It seems to be the wind velocity, then, which holds up the kite: but
-in reality the string is just as necessary as the wind. If there is
-no string, and the wind blows the kite with it, the kite comes down,
-because the pressure is wholly due to a relative velocity as between
-kite and wind. The wind exerts a pressure against the rear of a railway
-train, if it happens to be blowing in that direction, and if we
-stood on the rear platform of a stationary train we should feel that
-pressure: but if the train is started up and caused to move at the same
-speed as the wind there would be no pressure whatever.
-
-One of the very first heavier-than-air flights ever recorded is said
-to have been made by a Japanese who dropped bombs from an immense
-man-carrying kite during the Satsuma rebellion of 1869. The kite as
-a flying machine has, however, two drawbacks: it needs the wind--it
-cannot fly in a calm--and it stands still. One early effort to improve
-on this situation was made in 1856, when a man was towed in a sort of
-kite which was hauled by a vehicle moving on the ground. In February
-of the present year, Lieut. John Rodgers, U.S.N., was lifted 400 feet
-from the deck of the cruiser _Pennsylvania_ by a train of eleven large
-kites, the vessel steaming at twelve knots against an eight-knot
-breeze. The aviator made observations and took photographs for about
-fifteen minutes, while suspended from a tail cable about 100 feet
-astern. In the absence of a sufficient natural breeze, an artificial
-wind was thus produced by the motion imparted to the kite; and the
-device permitted of reaching some destination. The next step was
-obviously to get rid of the tractive vehicle and tow rope by carrying
-propelling machinery on the kite. This had been accomplished by Langley
-in 1896, who flew a thirty-pound model nearly a mile, using a steam
-engine for power. The gasoline engine, first employed by Santos-Dumont
-(in a dirigible balloon) in 1901, has made possible the present day
-_aeroplane_.
-
-  [Illustration: SUSTAINING FORCE IN THE AEROPLANE]
-
-What "keeps it up", in the case of this device, is likewise its
-velocity. Looking from the side, _ab_ is the sail of the aeroplane,
-which is moving toward the right at such speed as to produce the
-equivalent of an air velocity _V_ to the left. This velocity causes the
-direct pressure _P_, equivalent to a lifting force _L_ and a retarding
-force _R_. The latter is the force which must be overcome by the motor:
-the former must suffice to overcome the whole weight of the apparatus.
-Travel in an aeroplane is like skating rapidly over very thin ice: the
-air literally "doesn't have time to get away from underneath."
-
-  [Illustration: DIRECT, LIFTING, AND RESISTING FORCES
-  If the pressure is 10 lbs. when the wind blows directly toward the
-  surface (at an angle of 90 degrees), then the forces for other angles
-  of direction are as shown on the diagram. The _amounts_ of all forces
-  depend upon the wind velocity: that assumed in drawing the diagram
-  was about 55 miles per hour. But the _relations_ of the forces are
-  the same for the various angles, no matter what the velocity.]
-
-If we designate the angle made by the wings (_ab_) with the horizontal
-(_V_) as _B_, then _P_ increases as _B_ increases, while (as has been
-stated) the ratio of _L_ to _R_ decreases. When the angle _B_ is a
-right angle, the wings being in the position _a´b´_, _P_ has its
-maximum value for direct wind--1/300 of the square of the velocity,
-in pounds per square foot; but _L_ is zero and _R_ is equal to _P_.
-The plane would have no lifting power. When the angle _B_ becomes
-zero, position _a´´b´´_, wings being horizontal, _P_ becomes zero
-and (so far as we can now judge) the plane has neither lifting power
-nor retarding force. At some intermediate position, like _ab_, there
-will be appreciable lifting and retarding forces. The chart shows the
-approximate lifting force, in pounds per square foot, for various
-angles. This force becomes a maximum at an angle of 45° (half a
-right angle). We are not yet prepared to consider why in all actual
-aeroplanes the angle of inclination is much less than this. The reason
-will be shown presently. At this stage of the discussion we may note
-that the lifting power per square foot of sail area varies with
-
-  the square of the velocity, _and_
-  the angle of inclination.
-
-The total lifting power of the whole plane will also vary with its
-area. As we do not wish this whole lifting power to be consumed in
-overcoming the dead weight of the machine itself, we must keep the
-parts light, and in particular must use for the wings a fabric of light
-weight per unit of surface. These fabrics are frequently the same as
-those used for the envelopes of balloons.
-
-Since the total supporting power varies both with the sail area and
-with the velocity, we may attain a given capacity either by employing
-large sails or by using high speed. The size of sails for a given
-machine varies inversely as the square of the speed. The original
-Wright machine had 500 square feet of wings and a speed of forty
-miles per hour. At eighty miles per hour the necessary sail area for
-this machine would be only 125 square feet; and at 160 miles per hour
-it would be only 31-1/4 square feet: while if we attempted to run the
-machine at ten miles per hour we should need a sail area of 8000 square
-feet. This explains why the aeroplane cannot go slowly.
-
-It would seem as if when two or more superposed sails were used, as in
-biplanes, the full effect of the air would not be realized, one sail
-becalming the other. Experiments have shown this to be the case; but
-there is no great reduction in lifting power unless the distance apart
-is considerably less than the width of the planes.
-
-In all present aeroplanes the sails are concaved on the under side.
-This serves to keep the air from escaping from underneath as rapidly
-as it otherwise would, and increases the lifting power from one-fourth
-to one-half over that given by our 1/300 rule: the divisor becoming
-roughly about 230 instead of 300.
-
-  [Illustration: SHAPES OF PLANES]
-
-Why are the wings placed crosswise of the machine, when the other
-arrangement--the greatest dimension in the line of flight--would seem
-to be stronger? This is also done in order to "keep the air from
-escaping from underneath." The sketch shows how much less easily the
-air will get away from below a wing of the bird-like spread-out form
-than from one relatively long and narrow but of the same area.
-
-A sustaining force of two pounds per square foot of area has been
-common in ordinary aeroplanes and is perhaps comparable with the
-results of bird studies: but this figure is steadily increasing as
-velocities increase.
-
-
-Why so Many Sails?
-
-Thus far a single wing or pair of wings would seem to fully answer
-for practicable flight: yet every actual aeroplane has several small
-wings at various points. The necessity for one of these had already
-been discovered in the kite, which is built with a balancing tail. In
-the sketch on page 18 it appears that the particles of air which are
-near the upper edge of the surface are more obstructed in their effort
-to get around and past than those near the lower edge. They have to
-turn almost completely about, while the others are merely deflected.
-This means that on the whole the upper air particles will exert more
-pressure than the lower particles and that the "center of pressure"
-(the point where the entire force of the wind may be assumed to act)
-will be, not at the center of the surface, but at a point some distance
-_above_ this center. This action is described as the "displacement of
-the center of pressure." It is known that the displacement is greatest
-for least inclinations of surface (as might be surmised from the
-sketch already referred to), and that it is always proportional to the
-dimension of the surface in the direction of movement; _i.e._, to the
-length of the line _ab_.
-
-  [Illustration: BALANCING SAIL]
-
-If the weight _W_ of the aeroplane acts downward at the center of the
-wing (at _o_ in the accompanying sketch), while the direct pressure
-_P_ acts at some point _c_ farther along toward the upper edge of
-the wing, the two forces _W_ and _P_ tend to revolve the whole wing
-in the direction indicated by the curved arrow. This rotation, in an
-aeroplane, is resisted by the use of a tail plane or planes, such as
-_mn_. The velocity produces a direct pressure _P´_ on the tail plane,
-which opposes, like a lever, any rotation due to the action of _P_.
-It may be considered a matter of rather nice calculation to get the
-area and location of the tail plane just right: but we must remember
-that the amount of pressure _P´_ can be greatly varied by changing
-the inclination of the surface _mn_. This change of inclination is
-effected by the operator, who has access to wires which are attached to
-the pivoted tail plane. It is of course permissible to place the tail
-plane _in front_ of the main planes--as in the original Wright machine
-illustrated: but in this case, with the relative positions of _W_ and
-_P_ already shown, the forward edge of the tail plane would have to be
-depressed instead of elevated. The illustration shows the tail built as
-a biplane, just as are the principal wings (page 141).
-
-Suppose the machine to be started with the tail plane in a horizontal
-position. As its speed increases, it rises and at the same time (if
-the weight is suspended from the center of the main planes) tilts
-backward. The tilting can be stopped by swinging the tail plane on its
-pivot so as to oppose the rotative tendency. If this control is not
-carried too far, the main planes will be allowed to maintain some of
-their excessive inclination and ascent will continue. When the desired
-altitude has been attained, the inclination of the main planes will, by
-further swinging of the tail plane, be reduced to the normal amount,
-at which the supporting power is precisely equal to the load; and the
-machine will be in vertical equilibrium: an equilibrium which demands
-at every moment, however, the attention of the operator.
-
-In many machines, ascent and tilting are separately controlled by using
-two sets of transverse planes, one set placed forward, and the other
-set aft, of the main planes. In any case, quick ascent can be produced
-only by an increase in the lifting force _L_ (see sketch, page 24) of
-the main planes: and this force is increased by enlarging the angle of
-inclination of the main planes, that is, by a controlled and partial
-tilting. The forward transverse wing which produces this tilting is
-therefore called the _elevating rudder_ or elevating plane. The rear
-transverse plane which checks the tilting and steadies the machine is
-often described as the _stabilizing plane_. _Descent_ is of course
-produced by _decreasing_ the angle of inclination of the main planes.
-
-  [Illustration: ROE'S TRIPLANE AT WEMBLEY
-  (From Brewer's _Art of Aviation_)]
-
-
-Steering
-
-If we need extra sails for stability and ascent or descent, we need
-them also for changes of horizontal direction. Let _ab_ be the top view
-of the main plane of a machine, following the course _xy_. At _rs_
-is a vertical plane called the _steering rudder_. This is pivoted,
-and controlled by the operator by means of the wires _t_, _u_. Let
-the rudder be suddenly shifted to the position _r´s´_. It will then
-be subjected to a pressure _P´_ which will swing the whole machine
-into the new position shown by the dotted lines, its course becoming
-_x´y´_. The steering rudder may of course be double, forming a vertical
-biplane, as in the Wright machine shown below.
-
-  [Illustration: ACTION OF THE STEERING RUDDER]
-
-Successful steering necessitates lateral resistance to drift, _i.e._,
-a fulcrum. This is provided, to some extent, by the stays and frame of
-the machine; and in a much more ample way by the vertical planes of the
-original Voisin cellular biplane. A recent Wright machine had vertical
-planes forward probably intended for this purpose.
-
-  [Illustration: RECENT TYPE OF WRIGHT BIPLANE]
-
-It now begins to appear that the aviator has a great many things to
-look after. There are many more things requiring his attention than
-have yet been suggested. No one has any business to attempt flying
-unless he is superlatively cool-headed and has the happy faculty of
-instinctively doing the right thing in an emergency. Give a chauffeur
-a high power automobile running at maximum speed on a rough and
-unfamiliar road, and you have some conception of the position of the
-operator of an aeroplane. It is perhaps not too much to say that to
-make the two positions fairly comparable we should _blindfold_ the
-chauffeur.
-
-Broadly speaking, designers may be classed in one of two groups--those
-who, like the Wrights, believe in training the aviator so as to
-qualify him to properly handle his complicated machine; and those
-who aim to simplify the whole question of control so that to acquire
-the necessary ability will not be impossible for the average man. If
-aviation is to become a popular sport, the latter ideal must prevail.
-The machines must be more automatic and the aviator must have time
-to enjoy the scenery. In France, where amateur aviation is of some
-importance, progress has already been made in this direction. The
-universal steering head, for example, which not only revolves like that
-of an automobile, but is hinged to permit of additional movements,
-provides for simultaneous control of the steering rudder and the main
-plane warping, while scarcely demanding the conscious thought of the
-operator.
-
-
-
-
-TURNING CORNERS
-
-
-A year elapsed after the first successful flight at Kitty Hawk before
-the aviator became able to describe a circle in the air. A later date,
-1907, is recorded for the first European half-circular flight: and the
-first complete circuit, on the other side of the water, was made a year
-after that; by both biplane and monoplane. It was in the same year that
-Louis Blériot made the pioneer cross-country trip of twenty-one miles,
-stopping at will _en route_ and returning to his starting point.
-
-
-What Happens When Making a Turn
-
-  [Illustration: CIRCULAR FLIGHT]
-
-We are looking downward on an aeroplane _ab_ which has been moving
-along the straight path _cd_. At _d_ it begins to describe the circle
-_de_, the radius of which is _od_, around the center _o_. The outer
-portion of the plane, at the edge _b_, must then move faster than the
-inner edge _a_. We have seen that the direct air pressure on the plane
-is proportional to the square of the velocity. The direct pressure
-_P_ (see sketch on page 22) will then be greater at the outer than at
-the inner limb; the lifting force _L_ will also be greater and the
-outer limb will tend to rise, so that the plane (viewed from the rear)
-will take the inclined position shown in the lower view: and this
-inclination will increase as long as the outer limb travels faster than
-the inner limb; that is, as long as the orbit continues to be curved.
-Very soon, then, the plane will be completely tipped over.
-
-Necessarily, the two velocities have the ratio _om_:_om´_; the
-respective lifting forces must then be proportional to the squares of
-these distances. The difference of lifting forces, and the tendency to
-overturn, will be more important as the distances most greatly differ:
-which is the case when the distance _om_ is small as compared with
-_mm´_. The shorter the radius of curvature, the more dangerous, for a
-given machine, is a circling flight: and in rounding a curve of given
-radius the most danger is attached to the machine of greatest spread of
-wing.
-
-
-Lateral Stability
-
-This particular difficulty has considerably delayed the development
-of the aeroplane. It may, however, be overcome by very simple
-methods--simple, at least as far as their mechanical features are
-concerned. If the outer limb of the plane is tilted upward, it is
-because the wind pressure is greater there. The wind pressure is
-greater because the velocity is greater. We have only to increase the
-wind pressure at the inner limb, in order to restore equilibrium. This
-cannot be done by adjusting the velocity, because the velocity is fixed
-by the curvature of path required: but the total wind pressure depends
-upon the _sail area_ as well as the velocity; so that by increasing the
-surface at the inner limb we may equalize the value of _L_, the lifting
-force, at the two ends of the plane. This increase of surface must be
-a temporary affair, to be discontinued when moving along a straight
-course.
-
-  [Illustration: THE AILERON]
-
-Let us stand in the rear of an aeroplane, the main wing of which is
-represented by _ab_. Let the small fan-shaped wings _c_ and _d_ be
-attached near the ends, and let the control wires, _e_, _f_, passing
-to the operator at _g_, be employed to close and unclasp the fans. If
-these fans are given a forward inclination at the top, as indicated in
-the end view, they will when spread out exert an extra lifting force.
-A fan will be placed at each end. They will be ordinarily folded up:
-but when rounding a curve the aviator will open the fan on the inner or
-more slowly moving limb of the main plane. This represents one of the
-first forms of the _aileron_ or wing-tip for lateral control.
-
-The more common present form of aileron is that shown in the lower
-sketch, at _s_ and _t_. The method of control is the same.
-
-  [Illustration: WING TIPPING]
-
-The cellular Voisin biplanes illustrate an attempt at self-sufficing
-control, without the interposition of the aviator. Between the upper
-and lower sails of the machine there were fore and aft vertical
-partitions. The idea was that when the machine started to revolve, the
-velocity of rotation would produce a pressure against these partitions
-which would obstruct the tipping. But rotation may take place slowly,
-so as to produce an insufficient pressure for control, and yet be amply
-sufficient to wreck the apparatus. The use of extra vertical rudder
-planes, hinged on a horizontal longitudinal axis, is open to the same
-objection.
-
-
-Wing Warping
-
-In some monoplanes with the inverted _V_ wing arrangement, a dipping
-of one wing answers, so to speak, to increase its concavity and thus
-to augment the lifting force on that side. The sketch shows the normal
-and distorted arrangement of wings: the inner limb being the one bent
-down in rounding a curve. An equivalent plan was to change the angle
-of inclination of one-half the sail by swinging it about a horizontal
-pivot at the center or at the rear edge: some machines have been built
-with sails divided in the center. The obvious objection to both of
-these plans is that too much mechanism is necessary in order to distort
-what amounts to nearly half the whole machine. They remind one of
-Charles Lamb's story of the discovery of roast pig.
-
-  [Illustration: WING WARPING]
-
-The distinctive feature of the Wright machines lies in the warping
-or distorting of the _ends only_ of the main planes. This is made
-possible, not by hinging the wings in halves, but by the flexibility
-of the framework, which is sufficiently pliable to permit of a
-considerable bending without danger. The operator, by pulling on a
-stout wire linkage, may tip up (or down) the corners _cc´_ of the sails
-at one limb, thus decreasing or increasing the effective surface acted
-on by the wind, as the case may require. The only objection is that
-the scheme provides one more thing for the aviator to think about and
-manipulate.
-
-
-Automatic Control
-
-Let us consider again the condition of things when rounding a curve,
-as in the sketch on page 32. As long as the machine is moving forward
-in a straight line, the operator sits upright. When it begins to tip,
-he will unconsciously tip himself the other way, as represented by
-the line _xy_ in the rear view. Any bicyclist will recognize this as
-plausible. Why not take advantage of this involuntary movement to
-provide a stabilizing force? If operating wires are attached to the
-aviator's belt and from thence connected with ailerons or wing-warping
-devices, then by a proper proportioning of levers and surfaces to the
-probable swaying of the man, the control may become automatic. The idea
-is not new; it has even been made the subject of a patent.
-
-
-The Gyroscope
-
-  [Illustration: THE GYROSCOPE]
-
-This device for automatic control is being steadily developed and may
-ultimately supersede all others. It uses the inertia of a fast-moving
-fly wheel for control, in a manner not unlike that contemplated in
-proposed methods of automatic balancing by the action of a suspended
-pendulum. Every one has seen the toy gyroscope and perhaps has wondered
-at its mysterious ways. The mathematical analysis of its action fills
-volumes: but some idea of what it does, and why, may perhaps be
-gathered at the expense of a very small amount of careful attention.
-The wheel _acbd_, a thin disc, is spinning rapidly about the axle _o_.
-In the side view, _ab_ shows the edge of the wheel, and _oo´_ the
-axle. This axle is not fixed, but may be conceived as held in some
-one's fingers. Now suppose the right-hand end of the axle (_o´_) to
-be suddenly moved toward us (away from the paper) and the left-hand
-(_o_) to be moved away. The wheel will now appear in both views as an
-ellipse, and it has been so represented, as _afbe_. Now, any particle,
-like _x_, on the rim of the wheel, will have been regularly moving
-in the circular orbit _cb_. The tendency of any body in motion is to
-move indefinitely in a straight line. The cohesion of the metal of
-the disc prevents the particle _x_ from flying off at a straight line
-tangent, _xy_, and it is constrained, therefore, to move in a circular
-orbit. Unless some additional constraint is imposed, it will at least
-remain in this orbit and will try to remain in its plane of rotation.
-When the disc is tipped, the plane of rotation is changed, and the
-particle is required, instead of (so to speak) remaining in the plane
-of the paper--in the side view--to approach and pass through that plane
-at _b_ and afterward to continue receding from us. Under ordinary
-circumstances, this is just what it would do: but if, as in the
-gyroscope, the axle _oo´_ is perfectly free to move in any direction,
-the particle _x_ will refuse to change its direction of rotation.
-Its position has been shifted: it no longer lies in the plane of the
-paper: but it will at least persist in rotating in a parallel plane:
-and this persistence forces the revolving disc to swing into the new
-position indicated by the curve _hg_, the axis being tipped into the
-position _pq_. The whole effect of all particles like _x_ in the entire
-wheel will be found to produce precisely this condition of things: if
-we undertake to change the plane of rotation by shifting the axle in
-a horizontal plane, the device itself will (if not prevented) make
-a further change in the plane of rotation by shifting the axle in a
-vertical plane.
-
-A revolving disc mounted on the gyroscopic framework therefore resists
-influences tending to change its plane of rotation. If the device
-is placed on a steamship, so that when the vessel rolls a change of
-rotative plane is produced, the action of the gyroscope will resist
-the rolling tendency of the vessel. All that is necessary is to have
-the wheel revolving in a fore and aft plane on the center line of the
-vessel, the axle being transverse and firmly attached to the vessel
-itself. A small amount of power (consumed in revolving the wheel) gives
-a marked steadying effect. The same location and arrangement on an
-aeroplane will suffice to overcome tendencies to transverse rotation
-when rounding curves. The device itself is automatic, and requires no
-attention, but it does unfortunately require power to drive it and it
-adds some weight.
-
-The gyroscope is being tested at the present time on some of the
-aeroplanes at the temporary army camps near San Antonio, Texas.
-
-
-Wind Gusts
-
-This feature of aeronautics is particularly important, because any
-device which will give automatic stability when turning corners will go
-far toward making aviation a safe amusement. Inequalities of velocity
-exist not only on curves, but also when the wind is blowing at anything
-but uniform velocity across the whole front of the machine. The
-slightest "flaw" in the wind means an at least temporary variation in
-lifting force of the two arms. Here is a pregnant source of danger, and
-one which cannot be left for the aviator to meet by conscious thought
-and action. It is this, then, that blindfolds him: he cannot see the
-wind conditions in advance. The conditions are upon him, and may have
-done their destructive work, before he can prepare to control them. We
-must now study what these conditions are and what their influence may
-be on various forms of aerial navigation: after which, a return to our
-present subject will be possible.
-
-
-
-
-AIR AND THE WIND
-
-The air that surrounds us weighs about one-thirteenth of a pound per
-cubic foot and exerts a pressure, at sea level, of nearly fifteen
-pounds per square inch. Its temperature varies from 30° below to 100°
-above the Fahrenheit zero. The pressure of the air decreases about
-one-half pound for each thousand feet of altitude; at the top of Mt.
-Blanc it would be, therefore, only about six pounds per square inch.
-The temperature also decreases with the altitude. The weight of a cubic
-foot, or _density_, which, as has been stated, is one-thirteenth of a
-pound ordinarily, varies with the pressure and with the temperature.
-The variation with pressure may be described by saying that the
-_quotient_ of the pressure by the density is constant: one varies in
-the same ratio as the other. Thus, at the top of Mt. Blanc (if the
-temperature were the same as at sea level), the density of air would be
-about 6/15 × 1/13 = 2/65: less than half what it is at sea level. As to
-temperature, if we call our Fahrenheit zero 460°, and correspondingly
-describe other temperatures--for instance, say that water boils at
-672°--then (pressure being unchanged) the _product_ of the density
-and the temperature is constant. If the density at sea level and zero
-temperature is one-thirteenth pound, then that at sea level and 460°
-Fahrenheit would be
-
-  (0 + 460)/(460 + 460) × 1/13 = 1/26.
-
-These relations are particularly important in the design of all
-balloons, and in computations relating to aeroplane flight at
-high altitudes. We shall be prepared to appreciate some of their
-applications presently.
-
-Generally speaking, the atmosphere is always in motion, and moving air
-is called wind. Our meteorologists first studied winds near the surface
-of the ground: it is only of late years that high altitude measurements
-have been considered practically desirable. Now, records are obtained
-by the aid of kites up to a height of nearly four miles: estimates of
-cloud movements have given data on wind velocities at heights above six
-miles: and much greater heights have been obtained by free balloons
-equipped with instruments for recording temperatures, pressures,
-altitude, time, and other data.
-
-When the Eiffel Tower was completed, it was found that the average wind
-velocity at its summit was about four times that at the base. Since
-that time, much attention has been given to the contrasting conditions
-of surface and upper breezes as to direction and velocity.
-
-Air is easily impeded in its movement, and the well-known uncertainties
-of the weather are closely related to local variations in atmospheric
-pressure and temperature. When near the surface of the ground,
-impingement against irregularities therein--hills, cliffs, and
-buildings--makes the atmospheric currents turbulent and irregular.
-Where there are no surface irregularities, as on a smooth plain or
-over water, the friction of the air particles passing over the surface
-still results in a stratification of velocities. Even on a mountain
-top, the direction and speed of the wind are less steady than in the
-open where measured by a captive balloon. The stronger the wind,
-the greater, relatively, is the irregularity produced by surface
-conditions. Further, the earth's surface and its features form a vast
-sponge for sun heat, which they transfer in turn to the air in an
-irregular way, producing those convectional currents peculiar to low
-altitudes, the upper limit of which is marked by the elevation of the
-cumulus clouds. Near the surface, therefore, wind velocities are lowest
-in the early morning, rising to a maximum in the afternoon.
-
-  [Illustration: DIURNAL TEMPERATURES AT DIFFERENT HEIGHTS
-  (From Rotch's _The Conquest of the Air_)]
-
-Every locality has its so-called "prevailing winds." Considering the
-compass as having eight points, one of those points may describe
-as many as 40% of all the winds at a given place. The direction of
-prevalence varies with the season. The range of wind velocities is
-also a matter of local peculiarity. In Paris, the wind speed exceeds
-thirty-four miles per hour on only sixty-eight days in the average
-year, and exceeds fifty-four miles on only fifteen days. Observations
-at Boston show that the velocity of the wind exceeds twenty miles per
-hour on half the days in winter and on only one-sixth the days in
-summer. Our largest present dirigible balloons have independent speeds
-of about thirty-four miles per hour and are therefore available (at
-some degree of effectiveness) for nearly ten months of the year, in the
-vicinity of Paris. In a region of low wind velocities--like western
-Washington, in this country--they would be available a much greater
-proportion of the time. To make the dirigible able to at least move
-nearly every day in the average year--in Paris--it must be given a
-speed of about fifty-five miles per hour.
-
-Figures as to wind velocity mean little to one unaccustomed to using
-them. A five-mile breeze is just "pleasant." Twelve miles means a brisk
-gale. Thirty miles is a high wind: fifty miles a serious storm (these
-are the winds the aviator constantly meets): one hundred miles is
-perhaps about the maximum hurricane velocity.
-
-As we ascend from the surface of the earth, the wind velocity steadily
-increases; and the excess velocity of winter winds over summer winds
-is as steadily augmented. Thus, Professor Rotch found the following
-variations:
-
-  Altitude in Feet      Annual Average
-                Wind Velocity, Feet per Second
-          656               23.15
-        1,800               32.10
-        3,280               35.
-        8,190               41.
-       11,440               50.8
-       17,680               81.7
-       20,970               89.
-       31,100              117.5
-
-                          Average Wind Velocities,
-  Altitude in Feet          Feet per Second
-                            Summer          Winter
-     656 to 3,280            24.55           28.80
-   3,280 to 9,810            26.85           48.17
-   9,810 to 16,400           34.65           71.00
-  16,400 to 22,950           62.60          161.5
-  22,950 to 29,500           77.00          177.0
-
-  [Illustration: DIURNAL TEMPERATURES AT DIFFERENT HEIGHTS]
-
-These results are shown in a more striking way by the chart. At a five
-or six mile height, double-barreled hurricanes at speeds exceeding 200
-miles per hour are not merely possible; they are part of the regular
-order of things, during the winter months.
-
-The winds of the upper air, though vastly more powerful, are far less
-irregular than those near the surface: and the directions of prevailing
-winds are changed. If 50% of the winds, at a given location on the
-surface, are from the southwest, then at as moderate an elevation
-as even 1000 feet, the prevailing direction will cease to be from
-southwest; it may become from west-southwest; and the proportion of
-total winds coming from this direction will not be 50%. These factors
-are represented in meteorological papers by what is known as the _wind
-rose_. From the samples shown, we may note that 40% of the surface
-winds at Mount Weather are from the northwest; while at some elevation
-not stated the most prevalent of the winds (22% of the total) are
-westerly. The direction of prevalence has changed through one-eighth
-of the possible circle, and in a _counter-clockwise_ direction. This
-is contrary to the usual variation described by the so-called Broun's
-Law, which asserts that as we ascend the direction of prevalence
-rotates around the circle like the hands of a watch; being, say, from
-northwest at the surface, from north at some elevation, from northeast
-at a still higher elevation, and so on. At a great height, the change
-in direction may become total: that is, the high altitude winds blow
-in the exactly opposite direction to that of the surface winds. In
-the temperate regions, most of the high altitude winds are from the
-west: in the tropics, the surface winds blow _toward_ the west and
-toward the equator; being northeasterly in the northern hemisphere
-and southeasterly in the southern: and there are undoubtedly equally
-prevalent high-altitude counter-trades.
-
-  [Illustration: THE WIND ROSE FOR MOUNT WEATHER, VA.
-  (From the _Bulletin_ of the Mount Weather Observatory, II, 6)]
-
-The best flying height for an aeroplane over a flat field out in the
-country is perhaps quite low--200 or 300 feet: but for cross-country
-trips, where hills, rivers, and buildings disturb the air currents, a
-much higher elevation is necessary; perhaps 2000 or 3000 feet, but in
-no case more than a mile. The same altitude is suitable for dirigible
-balloons. At these elevations we have the conditions of reasonable
-warmth, dryness, and moderate wind velocities.
-
-
-Sailing Balloons
-
-In classifying air craft, the sailing balloon was mentioned as a type
-intermediate between the drifting balloon and the dirigible. No such
-type has before been recognized: but it may prove to have its field,
-just as the sailing vessel on the sea has bridged the gap between the
-raft and the steamship. It is true that tacking is impossible, so that
-our sailing balloons must always run before the wind: but they possess
-this great advantage over marine sailing craft, that by varying their
-altitude they may always be able to find a favorable wind. This implies
-adequate altitude control, which is one of the problems not yet solved
-for lighter-than-air flying machines: but when it has been solved we
-shall go far toward attaining a dirigible balloon without motor or
-propeller; a true sailing craft.
-
-  [Illustration: DIAGRAM OF PARTS OF A DRIFTING BALLOON]
-
-This means more study and careful utilization of stratified atmospheric
-currents. Professor Rotch suggests the utilization of the upper
-westerly wind drift across the American continent and the Atlantic
-Ocean, which would carry a balloon from San Francisco to southern
-Europe at a speed of about fifty feet per second--thirty-four miles
-per hour. Then by transporting the balloon to northern Africa, the
-northeast surface trade wind would drive it back to the West Indies at
-twenty-five miles per hour. This without any motive power: and since
-present day dirigibles are all short of motive power for complete
-dirigibility, we must either make them much more powerful or else adopt
-the sailing principle, which will permit of actually decreasing present
-sizes of motors, or even possibly of omitting them altogether. Our next
-study is, then, logically, one of altitude control in balloons.
-
-  [Illustration: GLIDDEN AND STEVENS GETTING AWAY IN THE "BOSTON"
-  (Leo Stevens, N.Y.)]
-
-
-Field and Speed
-
-  [Illustration: RELATIVE AND ABSOLUTE BALLOON VELOCITIES]
-
-  [Illustration: FIELD AND SPEED]
-
-An _aerostat_ (non-dirigible balloon), unless anchored, drifts at the
-speed of the wind. To the occupants, it seems to stand still, while
-the surface of the earth below appears to move in a direction opposite
-to that of the wind. In the sketch, if the independent velocity of a
-_dirigible_ balloon be _PB_, the wind velocity _PV_, then the actual
-course pursued is _PR_, although the balloon always points in the
-direction _PB_, as shown at 1 and 2. If the speed of the wind exceed
-that of the balloon, there will be some directions in which the latter
-cannot progress. Thus, let _PV_ be the wind velocity and _TV_ the
-independent speed of the balloon. The tangents _PX_, _PX´_, include the
-whole "field of action" possible. The wind direction may change during
-flight, so that the initial objective point may become unattainable,
-or an initially unattainable point may be brought within the field. The
-present need is to increase independent speeds from thirty or forty
-to fifty or sixty miles per hour, so that the balloon will be truly
-dirigible (even if at low effectiveness) during practically the whole
-year.
-
-  [Illustration: INFLUENCE OF WIND ON POSSIBLE COURSE]
-
-Suppose a dirigible to start on a trip from New York to Albany,
-150 miles away. Let the wind be a twenty-five mile breeze from the
-southwest. The wind alone tends to carry the balloon from New York to
-the point _d_ in four hours. If the balloon meanwhile be headed due
-west, it would need an independent velocity of its own having the same
-ratio to that of the wind as that of _de_ to _fd_, or about seventeen
-and one-half miles per hour. Suppose its independent speed to be only
-twelve and one-half miles; then after four hours it will be at the
-position _b_, assuming it to have been continually headed due west, as
-indicated at _a_. It will have traveled northward the distance _fe_,
-apparently about sixty-nine miles.
-
-  [Illustration: COUNT ZEPPELIN]
-
-After this four hours of flight, the wind suddenly changes to
-south-southwest. It now tends to carry the balloon to _g_ in the next
-four hours. Meanwhile the balloon, heading west, overcomes the easterly
-drift, and the balloon actually lands at _c_. Unless there is some
-further favorable shift of the wind it cannot reach Albany. If, during
-the second four hours, its independent speed could have been increased
-to about fifteen and a half miles it would have just made it. The
-actual course has been _fbc_: a drifting balloon would have followed
-the course _fdh_, _dh_ being a course parallel to _bg_.
-
-
-
-
-GAS AND BALLAST
-
-
-A cubical block of wood measuring twelve inches on a side floats on
-water because it is lighter than water; it weighs, if yellow pine,
-thirty-eight pounds, whereas the same volume of water weighs about
-sixty-two pounds. Any substance weighing more than sixty-two pounds to
-the cubic foot would sink in water.
-
-  [Illustration: BUOYANT POWER OF WOOD]
-
-If our block of wood be drilled, and _lead_ poured in the hole, the
-total size of wood-and-lead block being kept constantly at one cubic
-foot, the block will sink as soon as its whole weight exceeds sixty-two
-pounds. Ignoring the wood removed by boring (as, compared with the lead
-which replaces it, an insignificant amount), the weight of lead plugged
-in may reach twenty-four pounds before the block will sink.
-
-This figure, twenty-four pounds, the difference between sixty-two and
-thirty-eight pounds, then represents the maximum buoyant power of a
-cubic foot of wood in water. It is the difference between the weight of
-the wood block and the weight of the water it displaces. If any weight
-less than this is added to that of the wood, the block will float,
-projecting above the water's surface more or less, according to the
-amount of weight buoyed up. It will not rise entirely from the water,
-because to do this it would need to be lighter, not only than water,
-but than air.
-
-  [Illustration: ONE CUBIC FOOT OF WOOD LOADED IN WATER]
-
-
-Buoyancy in Air
-
-There are _gases_, if not woods, lighter than air: among them, coal gas
-and hydrogen. A "bubble" of any of these gases, if isolated from the
-surrounding atmosphere, cannot sink but must rise. At the same pressure
-and temperature, hydrogen weighs about one-fifteenth as much as air;
-coal gas, about one-third as much. If a bubble of either of these gases
-be isolated in the atmosphere, it must continually rise, just as wood
-immersed in water will rise when liberated. But the wood will stop
-when it reaches the surface of the water, while there is no reason
-to suppose that the hydrogen or coal gas bubbles will ever stop. The
-hydrogen bubble can be made to remain stationary if it is weighted down
-with something of about fourteen times its own weight (thirteen and
-one-half times, accurately). Perhaps it would be better to say that it
-would still continue to rise slowly because that additional something
-would itself displace some additional air; but if the added weight is a
-solid body, its own buoyancy in air is negligible.
-
-  [Illustration: BUOYANT POWER OF HYDROGEN]
-
-Our first principle is, then, that at the same pressure and
-temperature, any gas lighter than air, if properly confined, will exert
-a net lifting power of (_n_-1) times its own weight, where _n_ is the
-ratio of weights of air and gas per cubic foot.
-
-  [Illustration: LEBAUDY'S "JAUNE"]
-
-If the pressures and temperatures are different, this principle is
-modified. In a balloon, the gas is under a pressure slightly in
-excess of that of the external atmosphere: this decreases its lifting
-power, because the weight of a given volume of gas is greater as the
-pressure to which it is subjected is increased. The weight of a given
-volume we have called the _density_: and, as has been stated, if the
-temperature be unchanged, the density varies directly as the pressure.
-
-The pressure in a balloon is only about 1% greater than that of
-the atmosphere at sea level, so that this factor has only a slight
-influence on the lifting power. That it leads to certain difficulties
-in economy of gas will, however, soon be seen.
-
-The temperature of the gas in a balloon, one might think, would
-naturally be the same as that of the air outside: but the surface
-of the balloon envelope has an absorbing capacity for heat, and on
-a bright sunny day the gas may be considerably warmed thereby. This
-action increases the lifting power, since increase of temperature (the
-pressure remaining fixed) decreases the density of a gas. To avoid
-this possibly objectionable increase in lifting power, balloons are
-sometimes painted with a non-absorbent color. One of the first Lebaudy
-balloons received a popular nickname in Paris on account of the yellow
-hue of its envelope.
-
-Suppose we wish a balloon to carry a total weight, including that of
-the envelope itself, of a ton. If of hydrogen, it will have to contain
-one fifteenth of this weight or about 133 pounds of that gas, occupying
-a space of about 23,000 cubic feet. If coal gas is used, the size
-of the balloon would have to be much greater. If hot air is used--as
-has sometimes been the case--let us assume the temperature of the air
-inside the envelope such that the density is just half that of the
-outside air. This would require a temperature probably about 500°.
-The air needed would be just a ton, and the balloon would be of about
-52,000 cubic feet. It would soon lose its lifting power as the air
-cooled; and such a balloon would be useful only for short flights.
-
-  [Illustration: AIR BALLOON
-  (Photo by Paul Thompson, N.Y.)
-  Built by some Germans in the backwoods of South Africa]
-
-The 23,000 cubic foot hydrogen balloon, designed to carry a ton, would
-just answer to sustain the weight. If anchored at sea level, it would
-neither fall to the ground nor tug upward on its holding-down ropes.
-In order to ascend, something more is necessary. This "something more"
-might be some addition to the size and to the amount of hydrogen. Let
-us assume that we, instead, drop one hundred pounds of our load. Thus
-relieved of so much ballast, the balloon starts upward, under the net
-lifting force of one hundred pounds. It is easy to calculate how far
-it will go. It will not ascend indefinitely, because, as the altitude
-increases, the pressure (and consequently the density) of the external
-atmosphere decreases. At about a 2000-foot elevation, this decrease
-in density will have been sufficient to decrease the buoyant power of
-the hydrogen to about 1900 pounds, and the balloon will cease to rise,
-remaining at this level while it moves before the wind.
-
-There are several factors to complicate any calculations. Any
-expansion of the gas bag--stretching due to an increase in internal
-pressure--would be one; but the envelope fabrics do not stretch much;
-there is indeed a very good reason why they must not be allowed to
-stretch. The pressure in the gas bag is a factor. If there is no
-stretching of the bag, this pressure will vary directly with the
-temperature of the gas, and might easily become excessive when the sun
-shines on the envelope.
-
-A more serious matter is the increased difference between the internal
-pressure of the gas and the external pressure of the atmosphere at high
-altitudes. Atmospheric pressure decreases as we ascend. The difference
-between gas pressure and air pressure thus increases, and it is this
-difference of pressure which tends to burst the envelope. Suppose the
-difference of pressure at sea level to have been two-tenths of a pound.
-For a balloon of twenty feet diameter, this would give a stress on
-the fabric, per lineal inch, of twenty-four pounds. At an altitude of
-2000 feet, the atmospheric pressure would decrease by one pound, the
-difference of pressures would become one and two-tenths pounds, and the
-stress on the fabric would be 144 pounds per lineal inch--an absolutely
-unpermissible strain. There is only one remedy: to allow some of the
-gas to escape through the safety valve; and this will decrease our
-altitude.
-
-
-Ascending and Descending
-
-To ascend, then, we must discard ballast: and we cannot ascend beyond
-a certain limit on account of the limit of allowable pressure on the
-envelope fabric. To again descend, we must discharge some of the gas
-which gives us lifting power. Every change of altitude thus involves
-a loss either of gas or of ballast. Our vertical field of control
-may then be represented by a series of oscillations of gradually
-decreasing magnitude until finally all power to ascend is gone. And
-even this situation, serious as it is, is made worse by the gradual but
-steady leakage of gas through the envelope fabric. Here, in a word,
-is the whole problem of altitude regulation. Air has no surface of
-equilibrium like water. Some device supplementary to ballast and the
-safety valve is absolutely necessary for practicable flight in any
-balloon not staked to the ground.
-
-A writer of romance has equipped his aeronautic heroes with a complete
-gas-generating plant so that all losses might be made up; and in
-addition, heating arrangements were provided so that when the gas
-supply had been partially expended its lifting power could be augmented
-by warming it so as to decrease its density below even the normal.
-There might be something to say in favor of this latter device, if used
-in connection with a collapsible gas envelope.
-
-Methods of mechanically varying the size of the balloon, so as by
-compressing the gas to cause descent and by giving it more room to
-increase its lifting power and produce ascent, have been at least
-suggested. The idea of a vacuum balloon, in which a rigid hollow shell
-would be exhausted of its contents by a continually working pump, may
-appear commendable. Such a balloon would have maximum lifting power for
-its size; but the weight of any rigid shell would be considerable, and
-the pressure tending to rupture it would be about 100 times that in
-ordinary gas balloons.
-
-It has been proposed to carry stored gas at high pressure (perhaps
-in the liquefied condition) as a supplementary method of prolonging
-the voyage while facilitating vertical movements: but hydrogen gas
-at a pressure of a ton to the square inch in steel cylinders would
-give an ultimate lifting power of only about one-tenth the weight of
-the cylinders which contain it. These cylinders might be regarded as
-somewhat better than ordinary ballast: but to throw them away, with
-their gas charge, as ballast, would seem too tragic. Liquefied gas
-might possibly appear rather more desirable, but would be altogether
-too expensive.
-
-  [Illustration: SCREW PROPELLER FOR ALTITUDE CONTROL]
-
-If a screw propeller can be used on a steamship, a dirigible balloon,
-or an aeroplane to produce forward motion, there is no reason why it
-could not also be used to produce upward motion in any balloon; and the
-propeller with its operating machinery would be a substitute for twice
-its equivalent in ballast, since it could produce motion either upward
-or downward. Weight for weight, however, the propeller and engine give
-only (in one computed case) about half the lifting power of hydrogen.
-If we are to use the screw for ascent, we might well use a helicopter,
-heavier than air, rather than a balloon.
-
-
-The Ballonet
-
-The present standard method of improving altitude regulation involves
-the use of the ballonet, or compartment air bag, inside the main
-envelope. For stability and effective propulsion, it is important that
-the balloon preserve its shape, no matter how much gas be allowed to
-escape. Dirigible balloons are divided into two types, according to
-the method employed for maintaining the shape. In the Zeppelin type, a
-rigid internal metal framework supports the gas envelope. This forms
-a series of seventeen compartments, each isolated from the others. No
-matter what the pressure of gas, the shape of the balloon is unchanged.
-
-In the more common form of balloon, the internal air ballonet is empty,
-or nearly so, when the main envelope is full. As gas is vented from the
-latter, air is pumped into the former. This compresses the remaining
-gas and thus preserves the normal form of the balloon outline.
-
-  [Illustration: BALLOON WITH BALLONETS]
-
-But the air ballonet does more than this. It provides an opportunity
-for keeping the balloon on a level keel, for by using a number of
-compartments the air can be circulated from one to another as the case
-may require, thus altering the distribution of weights. Besides this,
-if the pressure in the air ballonet be initially somewhat greater
-than that of the external atmosphere, a considerable ascent may be
-produced by merely venting this air ballonet. This involves no loss of
-gas; and when it is again desired to descend, air may be pumped into
-the ballonet. If any considerable amount of gas should be vented, to
-produce quick and rapid descent, the pumping of air into the ballonet
-maintains the shape of the balloon and also facilitates the descent.
-
-  [Illustration: CONSTRUCTION OF THE ZEPPELIN BALLOON]
-
-
-The Equilibrator
-
-  [Illustration: THE EQUILIBRATOR IN NEUTRAL POSITION]
-
-Suppose a timber block of one square foot area, ten feet long, weighing
-380 pounds, to be suspended from the balloon in the ocean, and let
-mechanism be provided by which this block may be raised or lowered
-at pleasure. When completely immersed in water it exerts an upward
-pressure (lifting force) of 240 pounds, which may be used to supplement
-the lifting power of the balloon. If wholly withdrawn from the water,
-it pulls down the balloon with its weight of 380 pounds. It seems to be
-equivalent, therefore, to about 620 pounds of ballast. When immersed a
-little over six feet--the upper four feet being out of the water--it
-exerts neither lifting nor depressing effect. The amount of either
-may be perfectly adjusted between the limits stated by varying the
-immersion.
-
-In the Wellman-Vaniman equilibrator attached to the balloon _America_,
-which last year carried six men (and a cat) a thousand miles in three
-days over the Atlantic Ocean, a string of tanks partly filled with fuel
-was used in place of the timber block. As the tanks were emptied, the
-degree of control was increased; and this should apparently have given
-ideal results, equilibration being augmented as the gas supply was lost
-by leakage: but the unsailorlike disregard of conditions resulting from
-the strains transferred from a choppy sea to the delicate gas bag led
-to disaster, and it is doubtful whether this method of control can ever
-be made practicable. The _America's_ trip was largely one of a drifting
-rather than of a dirigible balloon. The equilibrator could be used only
-in flights over water in any case: and if we are to look to water for
-our buoyancy, why not look wholly to water and build a ship instead of
-a balloon?
-
-
-
-
-DIRIGIBLE BALLOONS AND OTHER KINDS
-
-
-Shapes
-
-  [Illustration: HENRY GIFFARD'S DIRIGIBLE
-  (The first with steam power)]
-
-The cylindrical Zeppelin balloon with approximately conical ends
-has already been shown (page 68). Those balloons in which the shape
-is maintained by internal pressure of air are usually _pisciform_,
-that is, fish-shaped. Studies have actually been made of the contour
-lines of various fishes and equivalent symmetrical forms derived,
-the outline of the balloon being formed by a pair of approximately
-parabolic curves.
-
-  [Illustration: DIRIGIBLE OF DUPUY DE LOME
-  (Man Power)]
-
-The first flight in a power driven balloon was made by Giffard in 1852.
-This balloon had an independent speed of about ten feet per second, but
-was without appliances for steering. A ballonetted balloon of 120,000
-cubic feet capacity was directed by man power in 1872: eight men turned
-a screw thirty feet in diameter which gave a speed of about seven miles
-per hour. Electric motors and storage batteries were used for dirigible
-balloons in 1883-'84: in the latter year, Renard and Krebs built the
-first fish-shaped balloon. The first dirigible driven by an internal
-combustion motor was used by Santos-Dumont in 1901.
-
-  [Illustration: TISSANDIER BROTHERS' DIRIGIBLE BALLOON
-  (Electric Motor)]
-
-
-Dimensions
-
-The displacements of present dirigibles vary from 20,000 cubic feet (in
-the United States Signal Corps airship) up to 460,000 cubic feet (in
-the Zeppelin). The former balloon has a carrying capacity only about
-equivalent to that of a Wright biplane. While anchored or drifting
-balloons are usually spherical, all dirigibles are elongated, with
-a length of from four to eleven diameters. The Zeppelin represents
-an extreme elongation, the length being 450 feet and the diameter
-forty-two feet. At the other extreme, some of the English military
-dirigibles are thirty-one feet in diameter and only 112 feet long.
-Ballonet capacities may run up to one-fifth the gas volume. All present
-dirigibles have gasoline engines driving propellers from eight to
-twenty feet in diameter. The larger propellers are connected with
-the motors by gearing, and make from 250 to 700 turns per minute.
-The smaller propellers are direct connected and make about 1200
-revolutions. Speeds are usually from fifteen to thirty miles per hour.
-
-  [Illustration: THE BALDWIN
-  Dirigible of the United States Signal Corps]
-
-The present-day elongated shape is the result of the effort to
-decrease the proportion of propulsion resistance due to the pressure
-of the air against the head of the balloon. This has led also to the
-pointed ends now universal; and to avoid eddy resistance about the
-rear it is just as important to point the stern as the bow. As far as
-head end resistance alone is concerned, the longer the balloon the
-better: but the friction of the air along the side of the envelope
-also produces resistance, so that the balloon must not be too much
-elongated. Excessive elongation also produces structural weakness. From
-the standpoint of stress on the fabric of the envelope, the greatest
-strain is that which tends to break the material along a longitudinal
-line, and this is true no matter what the length, as long as the seams
-are equally strong in both directions and the load is so suspended as
-not to produce excessive bending strain on the whole balloon. In the
-_Patrie_ (page 77), some distortion due to loading is apparent. The
-stress per lineal inch of fabric is obtained by multiplying the net
-pressure by half the diameter of the envelope (in inches).
-
-  [Illustration: THE ZEPPELIN ENTERING ITS HANGAR ON LAKE CONSTANCE]
-
-Ample steering power (provided by vertical planes, as in
-heavier-than-air machines) is absolutely necessary in dirigibles: else
-the head could not be held up to the wind and the propelling machinery
-would become ineffective.
-
-
-Fabrics
-
-The material for the envelope and ballonets should be light, strong,
-unaffected by moisture or the atmosphere, non-cracking, non-stretching,
-and not acted upon by variations in temperature. The same
-specifications apply to the material for the wings of an aeroplane. In
-addition, for use in dirigible balloons, fabrics must be impermeable,
-resistent to chemical action of the gas, and not subject to spontaneous
-combustion. The materials used are vulcanized silk, gold beater's
-skin, Japanese silk and rubber, and cotton and rubber compositions.
-In many French balloons, a middle layer of rubber has layers of
-cotton on each side, the whole thickness being the two hundred and
-fiftieth part of an inch. In the _Patrie_, this was supplemented by
-an outside non-heat-absorbent layer of lead chromate and an inside
-coating of rubber, all rubber being vulcanized. The inner rubber layer
-was intended to protect the fabric against the destructive action of
-impurities in the gas.
-
-  [Illustration: THE "PATRIE." DESTROYED BY A STORM]
-
-Fabrics are obtainable in various colors, painted, varnished, or wholly
-uncoated. The rubber and cotton mixtures are regularly woven in France
-and Germany for aeroplanes and balloons. The cars and machinery are
-frequently shielded by a fabricated wall. Weights of envelope materials
-range from one twenty-third to one-fourteenth pound per square foot,
-and breaking stresses from twenty-eight to one hundred and thirty
-pounds. Pressures (net) in the main envelope are from three-fifths to
-one and a quarter _ounces_ per square inch, those in the ballonets
-being somewhat less. The _Patrie_ of 1907 had an envelope guaranteed
-not to allow the leakage of more than half a cubic inch of hydrogen per
-square foot of surface per twenty-four hours.
-
-  [Illustration: MANUFACTURING THE ENVELOPE OF A BALLOON]
-
-  [Illustration: INSPECTING THE ENVELOPE OF ANDRÉE'S BALLOON "L'OERNEN"]
-
-The best method of cutting the fabric is to arrange for building up the
-envelope by a series of strips about the circumference, the seams being
-at the bottom. The two warps of the cloth should cross at an angle so
-as to localize a rip or tear. Bands of cloth are usually pasted over
-the seams, inside and out, with a rubber solution; this is to prevent
-leakage at the stitches.
-
-
-Framing
-
-In the _Zeppelin_, the rigid aluminum frame is braced every forty-five
-feet by transverse diametral rods which make the cross-sections
-resemble a bicycle wheel (page 68). This cross-section is not circular,
-but sixteen-sided. The pressure is resisted by the framework itself,
-the envelope being required to be impervious only. The seventeen
-compartments are separated by partitions of sheet aluminum. There is a
-system of complete longitudinal bracing between these partitions. Under
-the main framework, the cars and machinery are carried by a truss about
-six feet deep which runs the entire length. The cars are boat-shaped,
-twenty feet long and six feet wide, three and one-half feet high,
-enclosed in aluminum sheathing. These cars, placed about one hundred
-feet from the ends, are for the operating force and machinery. The
-third car, carrying passengers, is built into the keel.
-
-  [Illustration: WRECK OF THE "ZEPPELIN"]
-
-In non-rigid balloons like the _Patrie_, the connecting frame must be
-carefully attached to the envelope. In this particular machine, cloth
-flaps were sewed to the bag, and nickel steel tubes then laced in
-the flaps. With these tubes as a base, a light framework of tubes
-and wires, covered with a laced-on waterproof cloth, was built up
-for supporting the load. Braces ran between the various stabilizing
-and controlling surfaces and the gas bag; these were for the most
-part very fine wire cables. The weight of the car was concentrated
-on about seventy feet of the total length of 200 feet. This accounts
-for the deformation of the envelope shown in the illustration (page
-77). The frame and car of this balloon were readily dismantled for
-transportation.
-
-In some of the English dirigibles the cars were suspended by network
-passing over the top of the balloon.
-
-
-Keeping the Keel Horizontal
-
-In the _Zeppelin_, a sliding weight could be moved along the keel so as
-to cause the center of gravity to coincide with the center of upward
-pressure in spite of variations in weight and position of gas, fuel,
-and ballast. In the German balloon _Parseval_, the car itself was
-movable on a longitudinal suspending cable which carried supporting
-sheaves. This balloon has figured in recent press notices. It was
-somewhat damaged by a collision with its shed in March: the sixteen
-passengers escaped unharmed. A few days later, emergency deflation by
-the rip-strip was made necessary during a severe storm. In the ordinary
-non-rigid balloon, the pumping of air between the ballonets aids in
-controlling longitudinal equilibrium. The pump may be arranged for
-either hand or motor operation: that in the _Clément-Bayard_ had a
-capacity of 1800 liters per minute against the pressure of a little
-over three-fifths of an ounce. The _Parseval_ has two ballonets. Into
-the rear of these air is pumped at starting. This raises the bow and
-facilitates ascent on the principle of the inclined surface of an
-aeroplane. After some elevation is attained, the forward ballonet is
-also filled.
-
-  [Illustration: CAR OF THE ZEPPELIN
-  (From the _Transactions_ of the American Society of
-  Mechanical Engineers)]
-
-
-Stability
-
-Besides proper distribution of the loads, correct vertical location of
-the propeller is important if the balloon is to travel on a level keel.
-In some early balloons, two envelopes side by side had the propeller
-at the height of the axes of the gas bags and midway between them. The
-modern forms carry the car, motor, and propeller below the balloon
-proper. The air resistance is mostly that of the bow of the envelope:
-but there is some resistance due to the car, and the propeller shaft
-should properly be at the equivalent center of all resistance, which
-will be between car and axis of gas bag and nearer the latter than
-the former. With a single envelope and propeller, this arrangement
-is impracticable. By using four (or even two) propellers, as in the
-_Zeppelin_ machine (page 68), it can be accomplished. If only one
-propeller is employed, horizontal rudder planes must be disposed at
-such angles and in such positions as to compensate for the improper
-position of the tractive force. Even on the _Zeppelin_, such planes
-were employed with advantage (pages 66 and 73).
-
-Perfect stability also involves freedom from rolling. This is usually
-inherent in a balloon, because the center of mass is well below the
-center of buoyancy: but in machines of the non-rigid type the absence
-of a ballonet might lead to both rolling and pitching when the gas was
-partially exhausted.
-
-  [Illustration: STERN VIEW OF THE ZEPPELIN]
-
-What is called "route stability" describes the condition of straight
-flight. The balloon must point directly in its (independent) course.
-This involves the use of a steering rudder, and, in addition, of fixed
-vertical planes, which, on the principle of the vertical partitions
-of Voisin, probably give some automatic steadiness to the course. To
-avoid the difficulty or impossibility of holding the head up to the
-wind at high speeds, an _empennage_ or feathering tail is a feature of
-all present balloons. The empennage of the _Patrie_ (page 77) consisted
-of pairs of vertical and horizontal planes at the extreme stern. In
-the _France_, thirty-two feet in maximum diameter and nearly 200 feet
-long, empennage planes aggregating about 400 square feet were placed
-somewhat forward of the stern. In the _Clément-Bayard_, the empennage
-consisted of cylindro-conical ballonets projecting aft from the stern.
-A rather peculiar grouping of such ballonets was used about the
-prolonged stern of the _Ville de Paris_.
-
-  [Illustration: THE "CLÉMENT-BAYARD"]
-
-  [Illustration: THE "VILLE DE PARIS"]
-
-
-Rudders and Planes
-
-The dirigible has thus several air-resisting or gliding surfaces.
-The approximately "horizontal" (actually somewhat inclined) planes
-permit of considerable ascent and descent by the expenditure of power
-rather than gas, and thus somewhat influence the problem of altitude
-control. Each of the four sets of horizontal rudder planes on the
-_Zeppelin_, for example, has, at thirty-five miles per hour, with an
-inclination equal to one-sixth a right angle, a lifting power of nearly
-a ton; about equal to that of all of the gas in one of the sixteen
-compartments.
-
-  [Illustration: CAR OF THE "LIBERTÉ"]
-
-Movable rudders may be either hand or motor-operated. The double
-vertical steering rudder of the _Ville de Paris_ had an area of 150
-square feet. The horizontally pivoted rudders for vertical direction
-had an area of 130 square feet.
-
-
-Arrangement and Accessories
-
-The motor in the _Ville de Paris_ was at the front of the car, the
-operator behind it. This car had the excessive weight of nearly 700
-pounds. The _Patrie_ employed a non-combustible shield over the motor,
-for the protection of the envelope: its steering wheel was in front and
-the motor about in the middle of the car. The gasoline tank was under
-the car, compressed air being used to force the fuel up to the motor,
-which discharged its exhaust downward at the rear through a spark
-arrester. Motors have battery and magneto ignition and decompression
-cocks, and are often carried on a spring-supported chassis. The
-interesting _Parseval_ propeller has four cloth blades which hang limp
-when not revolving. When the motor is running, these blades, which are
-weighted with lead at the proper points, assume the desired form.
-
-Balloons usually carry guide ropes at head and stern, the aggregate
-weight of which may easily exceed a hundred pounds. In descending, the
-bow rope is first made fast, and the airship then stands with its head
-to the wind, to be hauled in by the stern rope. For the large French
-military balloons, this requires a force of about thirty men. The
-_Zeppelin_ descends in water, being lowered until the cars float, when
-it is docked like a ship (see page 84). Landing skids are sometimes
-used, as with aeroplanes.
-
-The balloon must have escape valves in the main envelope and ballonets.
-In addition it has a "rip-strip" at the bottom by which a large cut
-can be made and the gas quickly vented for the purpose of an emergency
-descent. Common equipment includes a siren, megaphone, anchor pins,
-fire extinguisher, acetylene search light, telephotographic apparatus,
-registering and indicating gages and other instruments, anemometer,
-possibly carrier pigeons; besides fuel, oil and water for the motor,
-and the necessary supplies for the crew. The glycerine floated compass
-of Moisant must now also be included if we are to contemplate genuine
-navigation without constant recourse to landmarks.
-
-
-Amateur Dirigibles
-
-The French Zodiac types of "aerial runabout" displace 700 cubic
-meters, carrying one passenger with coal gas or two passengers with a
-mixture of coal gas and hydrogen. The motor is four-cylinder, sixteen
-horse-power, water-cooled. The stern screw, of seven feet diameter,
-makes 600 turns per minute, giving an independent speed of nineteen
-miles per hour. The machine can remain aloft three hours with 165
-pounds of supplies. It costs $5000. Hydrogen costs not far from a cent
-per cubic foot (twenty cents per cubic meter) so that the question
-of gas leakage may be at least as important as the tire question with
-automobiles.
-
-  [Illustration: THE ZODIAC NO. 2
-  May be deflated and easily transported]
-
-
-The Fort Omaha Plant
-
-The Signal Corps post at Fort Omaha has a plant comprising a steel
-balloon house of size sufficient to house one of the largest dirigibles
-built, an electrolytic plant for generating hydrogen gas, having a
-capacity of 3000 cubic feet per hour, a 50,000 cubic foot gas storage
-tank, and the compressing and carrying equipment involved in preparing
-gas for shipment at high pressure in steel cylinders.
-
-  [Illustration: UNITED STATES SIGNAL CORPS BALLOON PLANT AT
-  FORT OMAHA, NEB.
-  (From the _Transactions_ of the American Society of
-  Mechanical Engineers)]
-
-
-Balloon Progress
-
-  [Illustration: THE "CAROLINE" OF ROBERT BROTHERS, 1784
-  The ascent terminated tragically]
-
-The first aerial buoy of Montgolfier brothers, in 1783, led to the
-suggestion of Meussier that two envelopes be used; the inner of an
-impervious material to prevent gas leakage, and the outer for strength.
-There was perhaps a foreshadowing of the Zeppelin idea. Captive and
-drifting balloons were used during the wars of the French Revolution:
-they became a part of standard equipment in our own War of Secession
-and in the Franco-Prussian conflict. The years 1906 to 1908 recorded
-rapid progress in the development of the dirigible: the record-breaking
-_Zeppelin_ trip was in 1909 and Wellman's _America_ exploit in
-October, 1910. Unfortunately, dirigibles have had a bad record for
-stanchness: the _Patrie_, _République_, _Zeppelin_ (_I_ and _II_),
-_Deutschland_, _Clément-Bayard_--all have gone to that bourne whence no
-balloon returns.
-
-  [Illustration: THE ASCENT AT VERSAILLES, 1783
-  The first balloon carrying living beings in the air]
-
-  [Illustration: PROPOSED DIRIGIBLE
-  Investors were lacking to bring about the realization of this project]
-
-It is gratifying to record that Count Zeppelin's latest machine, the
-_Deutschland II_, is now in operation. During the present month (April,
-1911), flights have been made covering 90 miles and upward at speeds
-exceeding 20 miles per hour with the wind unfavorable. This balloon
-is intended for use as a passenger excursion vehicle during the coming
-summer, under contract with the municipality of Düsseldorf.
-
-  [Illustration: THE "RÉPUBLIQUE"]
-
-At the present moment, Neale, in England, is reported to be
-building a dirigible for a speed of a hundred miles per hour. The
-Siemens-Schuckart non-rigid machine, nearly 400 feet long and of 500
-horse-power, is being tried out at Berlin: it is said to carry fifty
-passengers.[A] Fabrice, of Munich, is experimenting with the _Inchard_,
-with a view to crossing the Atlantic at an early date. Mr. Vaniman,
-partner of Wellman on the _America_ expedition, is planning a new
-dirigible which it is proposed to fly across the ocean before July 4.
-The engine, according to press reports, will develop 200 horse-power,
-and the envelope will be more elongated than that of the _America_.
-And meanwhile a Chicago despatch describes a projected fifty-passenger
-machine, to have a gross lifting power of twenty-five tons!
-
-  [Illustration: THE FIRST FLIGHT FOR THE GORDON-BENNET CUP.
-  Won by Lieut. Frank P. Lahm, U.S.A., 1906. Figures on the map denote
-  distances in kilometers. The cup has been offered annually by Mr.
-  James Gordon-Bennet for international competition under such
-  conditions as may be prescribed by the International Aeronautic
-  Federation.]
-
-Germany has a slight lead in number of dirigible balloons--sixteen
-in commission and ten building. France follows closely with fourteen
-active and eleven authorized. This accounts for two-thirds of all the
-dirigible balloons in the world. Great Britain, Italy, and Russia
-rank in the order named. The United States has one balloon of the
-smallest size. Spain has, or had, one dirigible. As to aeroplanes,
-however, the United States and England rank equally, having each about
-one-fourth as many machines as France (which seems, therefore, to
-maintain a "four-power standard"). Germany, Russia, and Italy follow,
-in order, the United States. These figures include all machines,
-whether privately or nationally owned. Until lately, our own government
-operated but one aeroplane. A recent appropriation by Congress of
-$125,000 has led to arrangements for the purchase of a few additional
-biplanes of the Wright and Curtiss types; and a training school for
-army officers has been regularly conducted at San Diego, Cal., during
-the past winter. The Curtiss machine to be purchased is said to carry
-700 pounds of dead weight with a sail area of 500 square feet. It is
-completely demountable and equipped with pontoons.
-
-
-
-
-THE QUESTION OF POWER
-
-
-In the year 1810, a steam engine weighed something over a ton to
-the horse-power. This was reduced to about 200 pounds in 1880. The
-steam-driven dirigible balloon of Giffard, in 1852, carried a complete
-power plant weighing a little over 100 pounds per horse-power; about
-the weight of a modern locomotive. The unsuccessful Maxim flying
-machine of 1894 brought this weight down to less than 20 pounds. The
-gasoline engine on the original Wright machines weighed about 5 pounds
-to the horse-power; those on some recent French machines not far from 2
-pounds.
-
-Pig iron is worth perhaps a cent a pound. An ordinary steam or gas
-engine may cost eight cents a pound; a steam turbine, perhaps forty
-cents. A high grade automobile or a piano may sell for a dollar a
-pound; the Gnome aeroplane motor is priced at about twenty dollars a
-pound. This is considerably more than the price of silver. The motor
-and accessories account for from two-thirds to nine-tenths of the total
-cost of an aeroplane.
-
-A man weighing 150 pounds can develop at the outside about one-eighth
-of a horse-power. It would require 1200 pounds of man to exert one
-horse-power. Considered as an engine, then, a man is (weight for
-weight) only one six-hundredth as effective as a Gnome motor. In the
-original Wright aeroplane, a weight of half a ton was sustained at the
-expenditure of about twenty-five horse-power. The motor weight was
-about one-eighth of the total weight. If traction had been produced by
-man-power, 30,000 pounds of man would have been necessary: thirty times
-the whole weight supported.
-
-  [Illustration: THE GNOME MOTOR
-  (Aeromotion Company of America)]
-
-Under the most favorable conditions, to support his own weight of
-150 pounds (at very high gliding velocity and a slight angle of
-inclination, disregarding the weight of sails necessary), a man would
-need to have the strength of about fifteen men. No such thing as an
-aerial bicycle, therefore, appears possible. The man can not emulate
-the bird.
-
-  [Illustration: SCREW PROPELLER (American Propeller Company)]
-
-The power plant of an air craft includes motor, water and water tank,
-radiator and piping, shaft and bearings, propeller, controlling wheels
-and levers, carbureter, fuel, lubricating oil and tanks therefor. Some
-of the weight may eventually be eliminated by employing a two-cycle
-motor (which gives more power for its size) or by using rotary
-air-cooled cylinders. Propellers are made light by employing wood or
-skeleton construction. One eight-foot screw of white oak and spruce,
-weighing from twelve to sixteen pounds, is claimed to give over 400
-pounds of propelling force at a thousand turns per minute.
-
-  [Illustration: ONE OF THE MOTORS OF THE ZEPPELIN]
-
-The cut shows the action of the so-called "four-cycle" motor. Four
-strokes are required to produce an impulse on the piston and return
-the parts to their original positions. On the first, or suction
-stroke, the combustible mixture is drawn into the cylinder, the inlet
-valve being open and the outlet valve closed. On the second stroke,
-both valves are closed and the mixture is highly compressed. At about
-the end of this stroke, a spark ignites the charge, a still greater
-pressure is produced in consequence, and the energy of the gas now
-forces the piston outward on its third or "working" stroke, the valves
-remaining closed. Finally, the outlet valve is opened and a fourth
-stroke sweeps the burnt gas out of the cylinder.
-
-  [Illustration: ACTION OF THE FOUR-CYCLE ENGINE]
-
-In the "two-cycle" engine, the piston first moves to the left,
-compressing a charge already present in the cylinder at _F_, and
-meanwhile drawing a fresh supply through the valve _A_ and passages
-_C_ to the space _D_. On the return stroke, the exploded gas in _F_
-expands, doing its work, while that in _D_ is slightly compressed, the
-valve _A_ being now closed. When the piston, moving toward the right,
-opens the passage _E_, the burnt gas rushes out. A little later, when
-the passage _I_ is exposed, the fresh compressed gas in _D_ rushes
-through _C_, _B_, and _I_ to _F_. The operation may now be repeated.
-Only two strokes have been necessary. The cylinder develops power twice
-as rapidly as before: but at the cost of some waste of gas, since the
-inlet (_I_) and outlet (_E_) passages are for a brief interval _both
-open at once_: a condition not altogether remedied by the use of a
-deflector at _G_. A two-cycle cylinder should give nearly twice the
-power of a four-cycle cylinder of the same size, and the two-cycle
-engine should weigh less, per horse-power; but it requires from 10 to
-30% more fuel, and fuel also counts in the total weight.
-
-  [Illustration: ACTION OF TWO-CYCLE ENGINE]
-
-The high temperatures in the cylinder would soon make the cast-iron
-walls red-hot, unless the latter where artificially cooled. The
-usual method of cooling is to make the walls hollow and circulate
-water through them. This involves a pump, a quantity of water, and a
-"radiator" (cooling machine) so that the water can be used over and
-over again. To cool by air blowing over the surface of the cylinder is
-relatively ineffective: but has been made possible in automobiles by
-building fins on the cylinders so as to increase the amount of cooling
-surface. When the motors are worked at high capacity, or when two-cycle
-motors are used, the heat is generated so rapidly that this method of
-cooling is regarded as inapplicable. By rapidly rotating the cylinders
-themselves through the air, as in motors like the Gnome, air cooling is
-made sufficiently adequate, but the expenditure of power in producing
-this rotation has perhaps not been sufficiently regarded.
-
-  [Illustration: MOTOR AND PROPELLER
-  (Detroit Aeronautic Construction Co.)]
-
-Possible progress in weight economy is destined to be limited by the
-necessity for reserve motor equipment.
-
-The engine used is usually the four-cycle, single-acting, four-cylinder
-gasoline motor of the automobile, designed for great lightness. The
-power from each cylinder of such a motor is approximately that obtained
-by dividing the square of the diameter in inches by the figure 2-1/2.
-Thus a five-inch cylinder should give ten horse-power--at normal piston
-speed. On account of friction losses and the wastefulness of a screw
-propeller, not more than half this power is actually available for
-propulsion.
-
-The whole power plant of the _Clément-Bayard_ weighed about eleven
-pounds to the horse-power. This balloon was 184 feet long and 35
-feet in maximum diameter, displacing about 100,000 cubic feet. It
-carried six passengers, about seventy gallons of fuel, four gallons of
-lubricating oil, fifteen gallons of water, 600 pounds of ballast, and
-130 pounds of ropes. The motor developed 100 horse-power at a thousand
-revolutions per minute. About eight gallons of fuel and one gallon of
-oil were consumed per hour when running at the full independent speed
-of thirty-seven miles per hour.
-
-The Wellman balloon _America_ is said to have consumed half a ton of
-gasoline per twenty-four hours: an eight days' supply was carried. The
-gas leakage in this balloon was estimated to have been equivalent to a
-loss of 500 pounds of lifting power per day.
-
-The largest of dirigibles, the _Zeppelin_, had two motors of 170
-horse-power each. It made, in 1909, a trip of over 800 miles in
-thirty-eight hours.
-
-The engine of the original Voisin cellular biplanes was an
-eight-cylinder Antoinette of fifty horse-power, set near the rear
-edge of the lower of the main planes. The Wright motors are placed near
-the front edge. A twenty-five horse-power motor at 1400 revolutions
-propelled the Fort Myer machine, which was built to carry two
-passengers, with fuel for a 125 mile flight: the total weight of the
-whole flying apparatus being about half a ton.
-
-  [Illustration: TWO-CYLINDER OPPOSED ENGINE.
-  (From _Aircraft_)]
-
-  [Illustration: FOUR-CYLINDER VERTICAL ENGINE
-  (The Dean Manufacturing Co.)]
-
-The eight-cylinder Antoinette motor on a Farman biplane, weighing 175
-pounds, developed thirty-eight horse-power at 1050 revolutions. The
-total weight of the machine was nearly 1200 pounds, and its speed
-twenty-eight miles per hour.
-
-The eight-cylinder Curtiss motor on the _June Bug_ was air cooled. This
-aeroplane weighed 650 pounds and made thirty-nine miles per hour, the
-engine developing twenty-five horse-power at 1200 turns.
-
-
-Resistance of Aeroplanes
-
-The chart on page 24 (see also the diagram of page 23) shows that the
-lifting power of an aeroplane increases as the angle of inclination
-increases, up to a certain limit. The resistance to propulsion also
-increases, however: and the ratio of lifting power to resistance is
-greatest at a very small angle--about five or six degrees. Since the
-motor power and weight are ruling factors in design, it is important to
-fly at about this angle. The supporting force is then about two pounds,
-and the resistance about three-tenths of a pound, per square foot of
-sail area, if the velocity is that assumed in plotting the chart:
-namely, about fifty-five miles per hour.
-
-But the resistance _R_ indicated on pages 23 and 24 is not the
-only resistance to propulsion. In addition, we have the frictional
-resistance of the air sliding along the sail surface. The amount of
-this resistance is independent of the angle of inclination: it depends
-directly upon the area of the planes, and in an indirect way on their
-dimensions in the direction of movement. It also varies nearly with
-the square of the velocity. At any velocity, then, the addition of
-this frictional resistance, which does not depend on the angle of
-inclination, modifies our views as to the desirable angle: and the
-total resistance reaches a minimum (in proportion to the weight
-supported) when the angle is about three degrees and the velocity about
-fifty miles per hour.
-
-This is not quite the best condition, however. The skin friction does
-not vary exactly with the square of the velocity: and when the true law
-of variation is taken into account, it is found that the _horse-power_
-is a minimum at an angle of about five degrees and a speed of about
-forty miles per hour. The weight supported per horse-power may then be
-theoretically nearly a hundred pounds: and the frictional resistance is
-about one-third the direct pressure resistance. This must be regarded
-as the approximate condition of best effectiveness: not the exact
-condition, because in arriving at this result we have regarded the
-sails as square flat planes whereas in reality they are arched and of
-rectangular form.
-
-At the most effective condition, the resistance to propulsion is only
-about one-tenth the weight supported. Evidently the air is helping the
-motor.
-
-
-Resistance of Dirigibles
-
-If the bow of a balloon were cut off square, its head end resistance
-would be that given by the rule already cited (page 19): one
-three-hundredth pound per square foot, multiplied by the square of
-the velocity. But by pointing the bow an enormous reduction of this
-pressure is possible. If the head end is a hemisphere (as in the
-English military dirigible), the reduction is about one-third. If it
-is a sharp cone, the reduction may be as much as four-fifths. Unless
-the stern is also tapered, however, there will be a considerable eddy
-resistance at that point.
-
-  [Illustration: HEAD END SHAPES]
-
-If head end resistance were the only consideration, then for a balloon
-of given diameter and end shape it would be independent of the length
-and capacity. The longer the balloon, the better. Again, since the
-volume of any solid body increases more rapidly than its surface (as
-the linear dimensions are increased), large balloons would have a
-distinct advantage over small ones. The smallest dirigible ever built
-was that of Santos-Dumont, of about 5000 cubic feet.
-
-Large balloons, however, are structurally weak: and more is lost by
-the extra bracing necessary than is gained by reduction of head end
-resistance. It is probable that the Zeppelin represents the limit of
-progress in this direction; and even in that balloon, if it had not
-been that the adoption of a rigid type necessitated great structural
-strength, it is doubtful if as great a length would have been fixed
-upon, in proportion to the diameter.
-
-The frictional resistance of the air gliding along the surface of the
-envelope, moreover, invalidates any too arbitrary conclusions. This,
-as in the aeroplane, varies nearly as the square of the velocity, and
-is usually considerably greater than the direct head end resistance.
-Should the steering gear break, however, and the wind strike the _side_
-of the balloon, the pressure of the wind against this greatly increased
-area would absolutely deprive it of dirigibility.
-
-A stationary, drifting, or "sailing" balloon may as well have the
-spherical as well as any other shape: it makes the wind a friend
-instead of a foe and requires nothing in the way of control other than
-regulation of altitude.
-
-
-Independent Speed and Time Table
-
-The air pressure, direct and frictional resistances, and power depend
-upon the _relative_ velocity of flying machine and air. It is this
-relative velocity, not the velocity of the balloon as compared with a
-point on the earth's surface, that marks the limit of progression.
-Hence the speed of the wind is an overwhelming factor to be reckoned
-with in developing an aerial time table. If we wish to travel east at
-an effective speed of thirty miles per hour, while the wind is blowing
-due west at a speed of ten miles, our machine must have an independent
-speed of forty miles. On the other hand, if we wish to travel west, an
-independent speed of twenty miles per hour will answer.
-
-  [Illustration: THE SANTOS-DUMONT DIRIGIBLE NO. 2 (1909)]
-
-Again, if the wind is blowing north at thirty miles per hour, and the
-minimum (relative) velocity at which an aeroplane will sustain its load
-is forty miles per hour, we cannot progress northward any more slowly
-than at seventy miles' speed. And we have this peculiar condition of
-things: suppose the wind to be blowing north at fifty miles per hour.
-The aeroplane designed for a forty mile speed may then face this wind
-and sustain itself while actually moving backward at an absolute speed
-(as seen from the earth) of ten miles per hour.
-
-We are at the mercy of the wind, and wind velocities may reach a
-hundred miles an hour. The inherent disadvantage of aerial flight is
-in what engineers call its "low load factor." That is, the ratio of
-normal performance required to possible abnormal performance necessary
-under adverse conditions is extremely low. To make a balloon truly
-dirigible throughout the year involves, at Paris, for example, as
-we have seen, a speed exceeding fifty-four miles per hour: and even
-then, during one-tenth the year, the _effective_ speed would not
-exceed twenty miles per hour. A time table which required a schedule
-speed reduction of 60% on one day out of ten would be obviously
-unsatisfactory.
-
-  [Illustration: IN THE BAY OF MONACO SANTOS-DUMONT'S NO. 6
-  The flights terminated with a fall into the sea,
-  happily without injury to the operator]
-
-Further, if we aim at excessively high independent speeds for our
-dirigible balloons, in order to become independent of wind conditions,
-we soon reach velocities at which the gas bag is unnecessary: that
-is, a simple wing surface would at those speeds give ample support.
-The increased difficulty of maintaining rigidity of the envelope, and
-of steering, at the great pressures which would accompany these high
-velocities would also operate against the dirigible type.
-
-With the aeroplane, higher speed means less sail area for a given
-weight and a stronger machine. Much higher speeds are probable. We have
-already a safe margin as to weight per horse-power of motor, and many
-aeroplane motors are for stanchness purposely made heavier than they
-absolutely need to be.
-
-
-The Cost of Speed
-
-Since the whole resistance, in either type of flying machine, is
-approximately proportional to the square of the velocity; and since
-horse-power (work) is the product of resistance and velocity, the
-horse-power of an air craft of any sort varies about as the cube of the
-speed. To increase present speeds of dirigible balloons from thirty to
-sixty miles per hour would then mean eight times as much horse-power,
-eight times as much motor weight, eight times as rapid a rate of fuel
-consumption, and (since the speed has been doubled) four times as rapid
-a consumption of fuel in proportion to the distance traveled. Either
-the radius of action must be decreased, or the weight of fuel carried
-must be greatly increased, if higher velocities are to be attained.
-Present (independent) aeroplane speeds are usually about fifty miles
-per hour, and there is not the necessity for a great increase which
-exists with the lighter-than-air machines. We have already succeeded in
-carrying and propelling fifty pounds of total load or fifteen pounds
-of passenger load per horse-power of motor, with aeroplanes; the ratio
-of net load to horse-power in the dirigible is considerably lower; but
-the question of weight in relation to power is of relatively smaller
-importance in the latter machine, where support is afforded by the gas
-and not by the engine.
-
-
-The Propeller
-
-Very little effort has been made to utilize paddle wheels for aerial
-propulsion; the screw is almost universally employed. Every one knows
-that when a bolt turns in a stationary nut, it moves forward a distance
-equal to the _pitch_ (lengthwise distance between two adjacent threads)
-at every revolution. A screw propeller is a bolt partly cut away for
-lightness, and the "nut" in which it works is water or air. It does
-not move forward quite as much as its pitch, at each revolution,
-because any fluid is more or less slippery as compared with a nut of
-solid metal. The difference between the pitch and the actual forward
-movement of the vessel at each revolution is called the "slip," or
-"slip ratio." It is never less than ten or twelve per cent in marine
-work, and with aerial screws is much greater. Within certain limits,
-the less the slip, the greater the efficiency of the propeller. Small
-screws have relatively greater slips and less efficiency, but are
-lighter. The maximum efficiency of a screw propeller in water is under
-80%. According to Langley's experiments, the usual efficiency in air
-is only about 50%. This means that only half the power of the motor
-will be actually available for producing forward movement--a conclusion
-already foreshadowed.
-
-In common practice, the pitch of aerial screws is not far from equal
-to the diameter. The rate of forward movement, if there were no slip,
-would be proportional to the pitch and the number of revolutions per
-minute. If the latter be increased, the former may be decreased.
-Screws direct-connected to the motors and running at high speeds will
-therefore be of smaller pitch and diameter than those run at reduced
-speed by gearing, as in the machine illustrated on page 134. The number
-of blades is usually two, although this gives less perfect balance than
-would a larger number. The propeller is in many monoplanes placed in
-_front_: this interferes, unfortunately, with the air currents against
-the supporting surfaces.
-
-There is always some loss of power in the bearings and
-power-transmitting devices between the motor and propeller. This may
-decrease the power usefully exerted even to _less_ than half that
-developed by the motor.
-
-
-
-
-GETTING UP AND DOWN: MODELS AND GLIDERS: AEROPLANE DETAILS
-
-
-Launching
-
-The Wright machines (at least in their original form) have usually
-been started by the impetus of a falling weight, which propels them
-along skids until the velocity suffices to produce ascent. The
-preferred designs among French machines have contemplated self-starting
-equipment. This involves mounting the machine on pneumatic-tired
-bicycle wheels so that it can run along the ground. If a fairly long
-stretch of good, wide, straight road is available, it is usually
-possible to ascend. The effect of altitude and atmospheric density on
-sustaining power is forcibly illustrated by the fact that at Salt Lake
-City one of the aviators was unable to rise from the ground.
-
-  [Illustration: WRIGHT BIPLANE ON STARTING RAIL, SHOWING PYLON AND
-  WEIGHT]
-
-To accelerate a machine from rest to a given velocity in a given time
-or distance involves the use of propulsive force additional to that
-necessary to maintain the velocity attained. Apparently, therefore, any
-self-starting machine must have not only the extra weight of framework
-and wheels but also extra motor power.
-
-  [Illustration: LAUNCHING SYSTEM FOR WRIGHT AEROPLANE
-  (From Brewer's _Art of Aviation_)]
-
-Upon closer examination of the matter, we may find a particularly
-fortunate condition of things in the aeroplane. Both sustaining power
-and resistance vary with the inclination of the planes, as indicated
-by the chart on page 24. It is entirely possible to start with no such
-inclination, so that the direct wind resistance is eliminated. The
-motor must then overcome only air friction, in addition to providing
-an accelerating force. The machine runs along the ground, its velocity
-rapidly increasing. As soon as the necessary speed (or one somewhat
-greater) is attained, the planes are tilted and the aeroplane rises
-from the ground.
-
-  [Illustration: THE NIEUPORT MONOPLANE
-  Self-Starting with an 18 hp. motor (From _The Air Scout_)]
-
-The velocity necessary to just sustain the load at a given angle of
-inclination is called the _critical_ or _soaring_ velocity. For a given
-machine, there is an angle of inclination (about half a right angle)
-at which the minimum speed is necessary. This speed is called the
-"least soaring velocity." If the velocity is now increased, the angle
-of inclination may be reduced and the planes will soar through the
-air almost edgewise, apparently with diminished resistance and power
-consumption. This decrease in power as the speed increases is called
-_Langley's Paradox_, from its discoverer, who, however, pointed out
-that the rule does not hold in practice when frictional resistances
-are included. We cannot expect to actually save power by moving more
-rapidly than at present; but we should have to provide much more power
-if we tried to move much more slowly.
-
-  [Illustration: A BIPLANE
-  (From _Aircraft_)]
-
-  [Illustration: ELY AT LOS ANGELES
-  (Photo by American Press Association)]
-
-Economical and practicable starting of an aeroplane thus requires a
-free launching space, along which the machine may accelerate with
-nearly flat planes: a downward slope would be an aid. When the planes
-are tilted for ascent, after attaining full speed, quick control is
-necessary to avoid the possibility of a back-somersault. A fairly
-wide launching platform of 200 feet length would ordinarily suffice.
-The flight made by Ely in January of this year, from San Francisco
-to the deck of the cruiser _Pennsylvania_ and back, demonstrated the
-possibility of starting from a limited area. The wooden platform built
-over the after deck of the warship was 130 feet long, and sloped. On
-the return trip, the aeroplane ran down this slope, dropped somewhat,
-and then ascended successfully.
-
-If the effort is made to ascend at low velocities, then the motor
-power must be sufficient to propel the machine at an extreme angle of
-inclination--perhaps the third of a right angle, approximating to the
-angle of least velocity for a given load. According to Chatley, this
-method of starting by Farman at Issy-les-Moulineaux involved the use of
-a motor of fifty horse-power: while Roe's machine at Brooklands rose,
-it is said, with only a six horse-power motor.
-
-
-Descending
-
-  [Illustration: TRAJECTORY DURING DESCENT]
-
-What happens when the motor stops? The velocity of the machine
-gradually decreases: the resistance to forward movement stops its
-forward movement and the excess of weight over upward pressure due to
-velocity causes it to descend. It behaves like a projectile, but the
-details of behavior are seriously complicated by the variation in head
-resistance and sustaining force due to changes in the angle of the
-planes. The "angle of inclination" is now not the angle made by the
-planes with the horizontal, but the angle which they make with the path
-of flight. Theory indicates that this should be about two-thirds the
-angle which the path itself makes with the horizontal: that is, the
-planes themselves are inclined downward toward the front. The forces
-which determine the descent are fixed by the velocity and the angle
-between the planes and the path of flight. Manipulation of the rudders
-and main planes or even the motor may be practised to ensure lancing
-to best advantage; but in spite of these (or perhaps on account of
-these) scarcely any part of aviation offers more dangers, demands more
-genius on the part of the operator, and has been less satisfactorily
-analyzed than the question of "getting down." It is easy to stay up
-and not very hard to "get up," weather conditions being favorable; but
-it is an "all-sufficient job" to _come down_. Under the new rules of
-the International Aeronautic Federation, a test flight for a pilot's
-license must terminate with a descent (motor stopped) in which the
-aviator is to land within fifty yards of the observers and come to
-a full stop inside of fifty yards therefrom. The elevation at the
-beginning of descent must be at least 150 feet.
-
-  [Illustration: DESCENDING]
-
-
-Gliders
-
-If the motor and its appurtenances, and some of the purely auxiliary
-planes, be omitted, we have a _glider_. The glider is not a toy; some
-of the most important problems of balancing may perhaps be some day
-solved by its aid. Any boy may build one and fly therewith, although
-a large kite promises greater interest. The cost is trifling, if the
-framework is of bamboo and the surfaces are cotton. Areas of glider
-surfaces frequently exceed 100 square feet. This amount of surface
-is about right for a person of moderate weight if the machine itself
-does not weigh over fifty pounds. By running down a slope, sufficient
-velocity may be attained to cause ascent; or in a favorable wind (up
-the slope) a considerable backward flight may be experienced. Excessive
-heights have led to fatal accidents in gliding experiments.
-
-  [Illustration: THE WITTEMAN GLIDER]
-
-
-Models
-
-The building of flying models has become of commercial importance.
-It is not difficult to attain a high ratio of surface to weight,
-but it is almost impossible to get motor power in the small units
-necessary without exceeding the permissible limit of motor weight. No
-gasoline engine or electric motor can be made sufficiently light for
-a toy model. Clockwork springs, if especially designed, may give the
-necessary power for short flights, but no better form of power is known
-just now than the twisted rubber band. For the small boy, a biplane
-with sails about eighteen inches by four feet, eighteen inches apart,
-anchored under his shoulders by six-foot cords while he rides his
-bicycle, will give no small amount of experience in balancing and will
-support enough of a load to make the experiment interesting.
-
-
-Some Details: Balancing
-
-  [Illustration: FRENCH MONOPLANE
-  (From _Aircraft_)]
-
-It is easily possible to compute the areas, angles, and positions
-of auxiliary planes to give desired controlling or stabilizing
-effects; but the computation involves the use of accurate data as to
-positions of the various weights, and on the whole it is simpler to
-correct preliminary calculations by actually supporting the machine
-at suitable points and observing its balance. Stability is especially
-uncertain at very small angles of inclination, and such angles are
-to be avoided whether in ordinary operation or in descent. The
-necessity for rotating main planes in order to produce ascent is
-disadvantageous on this ground; but the proposed use of sliding or
-jockey weights for supplementary balancing appears to be open to
-objections no less serious. Steering may be perceptibly assisted, in
-as delicately a balanced device as the aeroplane, by the inclination
-of the body of the operator, just as in a bicycle. The direction of
-the wind in relation to the required course may seriously influence
-the steering power. Suppose the course to be northeast, the wind east,
-the independent speed of the machine and that of the wind being the
-same. The car will head due north. By bringing the rudder in position
-(_a_), the course may be changed to north, or nearly so, the wind
-exerting a powerful pressure on the rudder; but if a more easterly or
-east-northeast course be desired, and the rudder be thrown into the
-usual position therefor (_b_), it will exert no influence whatever,
-because it is moving before the wind and precisely at the speed of the
-wind.
-
-  [Illustration: A PROBLEM IN STEERING]
-
-It might be thought that, following analogies of marine engineering,
-the center of gravity of an aeroplane should be kept low. The effect
-of any unbalanced pressure or force against the widely extended sails
-of the machine is to rotate the whole apparatus about its center of
-gravity. The further the force from the center of gravity, the
-more powerful is the force in producing rotation. The defect in most
-aeroplanes (especially biplanes) is that the center of gravity is _too_
-low. If it could be made to coincide with the center of disturbing
-pressure, there would be no unbalancing effect from the latter. It is
-claimed that the steadiest machines are those having a high center of
-gravity; and the claim, from these considerations, appears reasonable.
-
-  [Illustration: LEJEUNE BIPLANE (385 LBS., 10-12 HP.)]
-
-
-Weights
-
-It has been found not difficult to keep down the weight of framework
-and supporting surfaces to about a pound per square foot. The most
-common ratio of surface to total weight is about one to two: so that
-the machinery and operator will require one square foot of surface
-for each pound of their weight. On this basis, the smallest possible
-man-carrying aeroplane would have a surface scarcely below 250 square
-feet. Most biplanes have twice this surface: a thousand square feet
-seems to be the limit without structural weakness. Some recent French
-machines, designed for high speeds, show a greatly increased ratio
-of weight to surface. The _Hanriot_, a monoplane with wings upwardly
-inclined toward the outer edge, carries over 800 pounds on less than
-300 square feet. The Farman monoplane of only 180 square feet sustains
-over 600 pounds. The same aviator's racing biplane is stated to support
-nearly 900 pounds on less than 400 square feet.
-
-  [Illustration: THE TELLIER TWO-SEAT SIX-CYLINDER MONOPLANE AT
-  THE PARIS SHOW
-  One of this type has been sold to the Russian Government
-  (From _Aircraft_)]
-
-Motor weights can be brought down to about two pounds per horse-power,
-but such extreme lightness is not always needed and may lead to
-unreliability of operation. The effect of an accumulation of ice,
-sleet, snow, rain, or dew might be serious in connection with flights
-in high altitudes or during bad weather. After one of his last year's
-flights at Étampes Mr. Farman is said to have descended with an extra
-load of nearly 200 pounds on this account. With ample motor power,
-great flexibility in weight sustention is made possible by varying the
-inclination of the planes. In January of this year, Sommer at Douzy
-carried six passengers in a large biplane on a cross-country flight:
-and within the week afterward a monoplane operated by Le Martin flew
-for five minutes with the aeronaut and seven passengers, at Pau. The
-total weight lifted was about half a ton, and some of the passengers
-must have been rather light. The two-passenger Fort Myer biplane of
-the Wright brothers is understood to have carried about this total
-weight. These records have, however, been surpassed since they were
-noted. Bréguet, at Douai, in a deeply-arched biplane of new design,
-carried eleven passengers, the total load being 2602 pounds, and that
-of aeronaut and passengers alone 1390 pounds. The flight was a short
-one, at low altitude; but the same aviator last year made a long flight
-with five passengers, and carried a load of 1262 pounds at 62 miles per
-hour. And as if in reply to this feat, Sommer carried a live load of
-1436 pounds (13 passengers) for nearly a mile, a day or two later, at
-Mouzon. One feels less certain than formerly, now, in the snap judgment
-that the heavier-than-air machine will never develop the capacity for
-heavy loads.
-
-  [Illustration: A MONOPLANE
-  (From _Aircraft_)]
-
-
-Miscellaneous
-
-French aviators are fond of employing a carefully designed car for the
-operator and control mechanism. The Wright designs practically ignore
-the car: the aviator sits on the forward edge of the lower plane with
-his legs hanging over.
-
-It has been found that auxiliary planes must not be too close to the
-main wings: a gap of a distance about 50% greater than the width of
-the widest adjacent plane must be maintained if interference with the
-supporting air currents is to be avoided. Main planes are now always
-arched; auxiliary planes, not as universally. The concave under surface
-of supporting wings has its analogy in the wing of the bird and had
-long years since been applied in the parachute.
-
-  [Illustration: CARS AND FRAMEWORK]
-
-The car (if used) and all parts of the framework should be of "wind
-splitter" construction, if useless resistance is to be avoided. The
-ribs and braces of the frame are of course stronger, weight for weight,
-in this shape, since a narrow deep beam is always relatively stronger
-than one of square or round section. Excessive frictional resistance is
-to be avoided by using a smoothly finished fabric for the wings, and
-the method of attaching this fabric to the frame should be one that
-keeps it as flat as possible at all joints.
-
-  [Illustration: SOME DETAILS]
-
-The sketches give the novel details of some machines recently exhibited
-at the Grand Central Palace in New York. The stabilizing planes were
-invariably found in the rear, in all machines exhibited.
-
-
-The Things to Look After
-
-The operator of an aeroplane has to do the work of at least two men. No
-vessel in water would be allowed to attain such speeds as are common
-with air craft, unless provided with both pilot and engineer. The
-aviator is his own pilot and his own engineer. He must both manage his
-propelling machinery and steer. Separate control for vertical rudders,
-elevating rudders and ailerons, for starting the engine; the adjustment
-of the carbureter, the spark, and the throttle to get the best results
-from the motor; attention to lubrication and constant watchfulness of
-the water-circulating system: these are a few of the things for him to
-consider; to say nothing of the laying of his course and the necessary
-anticipation of wind and altitude conditions.
-
-These things demand great resourcefulness, but--for their best
-control--involve also no small amount of scientific knowledge. For
-example, certain adjustments at the motor may considerably increase its
-power, a possibly necessary increase under critical conditions: but if
-such adjustments also decrease the motor efficiency there must be a
-nice analysis of the two effects so that extra power may not be gained
-at too great a cost in radius of action.
-
-  [Illustration: SOME RECENT FRENCH MACHINES (From _Aircraft_)]
-
-The whole matter of flight involves both sportsman's and engineers
-problems. Wind gusts produce the same effects as "turning corners";
-or worse--rapidly changing the whole balance of the machines and
-requiring immediate action at two or three points of control. Both
-ascent and descent are influenced by complicated laws and are scarcely
-rendered safe--under present conditions--by the most ample experience.
-A lateral air current bewilders the steering and also demands special
-promptness and skill. To avoid disturbing surface winds, even over open
-country, a minimum flying height of 300 feet is considered necessary.
-This height, furthermore, gives more choice in the matter of landing
-ground than a lower elevation.
-
-When complete and automatic balance shall have been attained--as it
-must be attained--we may expect to see small amateur aeroplanes flying
-along country roads at low elevations--perhaps with a guiding wheel
-actually in contact with the ground. They will cost far less than even
-a small automobile, and the expense for upkeep will be infinitely less.
-The grasshopper will have become a water-spider.
-
-
-
-
-SOME AEROPLANES--SOME ACCOMPLISHMENTS
-
-
-  [Illustration: ORVILLE WRIGHT AT FORT MYER, VA., 1908]
-
-  [Illustration: THE FIRST BALLOON FLIGHT ACROSS THE BRITISH CHANNEL
-  More than a century before Blériot's feat, Blanchard crossed from
-  Dover to Calais]
-
-The Wright biplane has already been shown (see pages 31, 37, 121, 122).
-It was distinguished by the absence of a wheel frame or car and by the
-wing-warping method of stabilizing. Later Wright machines have the
-spring frame and wheels for self-starting. The best known aeroplane of
-this design was built to meet specifications of the United States
-Signal Corps issued in 1907. It was tried out during 1908 at Fort
-Myer, Va., while one of the Wright brothers was breaking all records
-in Europe: making over a hundred flights in all, first carrying a
-passenger and attaining the then highest altitude (360 feet) and
-greatest distance of flight (seventy-seven miles).
-
-  [Illustration: WRIGHT MOTOR. DIMENSIONS IN MILLIMETERS
-  (From Petit's _How to Build an Aeroplane_)]
-
-The ownership of the Wrights in the wing-warping method of control is
-still the subject of litigation. The French infringers, it is stated,
-concede priority of application to the Wright firm, but maintain that
-such publicity was given the device that it was in general use before
-it was patented.
-
-The Fort Myer machine had sails of forty feet spread, six and one-half
-feet deep, with front elevating planes three by sixteen feet. It made
-about forty miles per hour with two passengers. The apparatus was
-specified to carry a passenger weight of 350 pounds, with fuel for a
-125-mile flight. The main planes were six feet apart. The steering
-rudder (double) was of planes one foot deep and nearly six feet high.
-The four-cylinder-four-cycle, water-cooled motor developed twenty-five
-horse-power at 1400 revolutions. The two propellers, eight and one-half
-feet in diameter, made 400 revolutions.
-
-The flight by Mr. Wilbur Wright from the Statue of Liberty to the tomb
-of General Grant, in New York, 1909, and the exploits of his brother
-in the same year, when a new altitude record of 1600 feet was made
-and H.R.H. the Crown Prince of Germany was taken up as a passenger,
-are only specimens of the later work done by these pioneers in aerial
-navigation.
-
-Like the Wrights, the Voisin firm from the beginning adhered firmly to
-the biplane type of machine. The sketch gives dimensions of one of the
-early cellular forms built for H. Farman (see illustration, page 147).
-The metal screw makes about a thousand revolutions. The wings are of
-india rubber sheeting on an ash frame, the whole frame and car body
-being of wood, the latter covered with canvas and thirty inches wide by
-ten feet long. The engine weighed 175 pounds. The whole weight of this
-machine was nearly 1200 pounds; that built later for Delagrange was
-brought under a thousand pounds. The ratio of weight to main surface in
-the Farman aeroplane was about 2-3/4 to 1.
-
-A modified cellular biplane also built for Farman had a main wing area
-of 560 square feet, the planes being seventy-nine inches wide and only
-fifty-nine inches apart. The tail was an open box, seventy-nine inches
-wide and of about ten feet spread. The cellular partitions in this tail
-were pivoted along the vertical front edges so as to serve as steering
-rudders. The elevating rudder was in front. The total weight was about
-the same as that of the first machine and the usual speed twenty-eight
-miles per hour.
-
-  [Illustration: VOISIN-FARMAN BIPLANE]
-
-Henry Farman has been flying publicly since 1907. He made the first
-circular flight of one kilometer, and attained a speed of about a mile
-a minute, in the year following. In 1909 he accomplished a trip of
-nearly 150 miles, remaining four hours in the air. Farman was probably
-the first man to ascend with two passengers.
-
-  [Illustration: THE CHAMPAGNE GRAND PRIZE WON BY HENRY FARMAN
-  80 Kilometers in 3 hours]
-
-  [Illustration: FARMAN'S FIRST BIPLANE AT ISSY-LES-MOULINEAUX
-  Returning to the Hangar After a Flight]
-
-The _June Bug_, one of the first Curtiss machines, is shown below. This
-was one of the lightest of biplanes, having a wing spread of forty-two
-feet and an area of 370 square feet. The wings were transversely
-arched, being furthest apart at the center: an arrangement which has
-not been continued. It had a box tail, with a steering rudder of about
-six square feet area, _above_ the tail. The horizontal rudder, in
-front, had a surface of twenty square feet. Four triangular ailerons
-were used for stability. The machine had a landing frame and wheels,
-made about forty miles per hour, and weighed, in operation, 650 pounds.
-
-  [Illustration: THE "JUNE BUG"]
-
-Mr. Curtiss first attained prominence in aviation circles by winning
-the _Scientific American_ cup by his flight at the speed of fifty-seven
-miles per hour, in 1908. In the following year he exhibited intricate
-curved flights at Mineola, and circled Governor's Island in New York
-harbor. In 1910 he made his famous flight from Albany to New York,
-stopping _en route_, as prearranged. At Atlantic City he flew fifty
-miles over salt water. A flight of seventy miles over Lake Erie was
-accomplished in September of the same year, the return trip being
-made the following day. On January 26, 1911, Curtiss repeatedly
-ascended and descended, with the aid of hydroplanes, in San Diego bay,
-California: perhaps one of the most important of recent achievements.
-It is understood that Mr. Curtiss is now attempting to duplicate some
-of these performances under the high-altitude conditions of Great
-Salt Lake. According to press reports, he has been invited to give a
-similar demonstration before the German naval authorities at Kiel.
-
-  [Illustration: CURTIS BIPLANE
-  (Photo by Levick, N.Y.)]
-
-  [Illustration: CURTISS' HYDRO-AEROPLANE AT SAN DIEGO GETTING UNDER WAY
-  (From the _Columbian Magazine_)]
-
-The _aeroscaphe_ of Ravard was a machine designed to move either on
-water or in air. It was an aeroplane with pontoons or floaters. The
-supporting surface aggregated 400 square feet, and the gross weight
-was about 1100 pounds. A fifty horse-power Gnome seven-cylinder motor
-at 1200 revolutions drove two propellers of eight and ten and one-half
-feet diameter respectively: the propellers being mounted one behind
-the other on the same shaft.
-
-  [Illustration: FLYING OVER THE WATER AT FIFTY MILES PER HOUR
-  Curtiss at San Diego Bay
-  (From the _Columbian Magazine_)]
-
-Ely's great shore-to-warship flight was made without the aid of the
-pontoons which he carried. Ropes were stretched across the landing
-platform, running over sheaves and made fast to heavy sand bags. As a
-further precaution, a canvas barrier was stretched across the forward
-end of the platform. The descent brought the machine to the platform at
-a distance of forty feet from the upper end: grappling hooks hanging
-from the framework of the aeroplane then caught the weighted ropes, and
-the speed was checked (within about sixty feet) so gradually that "not
-a wire or bolt of the biplane was injured."
-
-  [Illustration: BLÉRIOT-VOISIN CELLULAR BIPLANE WITH PONTOONS
-  Hauled by a Motor Boat]
-
-  [Illustration: LATHAM'S "ANTOINETTE"]
-
-  [Illustration: JAMES J. WARD AT LEWISTON FAIR, IDAHO
-  (Photo copyright 1910 by Burns)
-  Flying Machine Mfg. Co. Biplane (30 hp. Motor)]
-
-  [Illustration: MARCEL PENOT IN THE MOHAWK BIPLANE,
-  Mineola to Hicksville, L. I.
-  26 miles cross-country in 30 minutes (50 hp. Harriman Engine)]
-
-Recent combinations of aeroplane and automobile, and aeroplane with
-motor boat, have been exhibited. One of the latter devices is like any
-monoplane, except that the lower part is a water-tight aluminum boat
-body carrying three passengers. It is expected to start of itself from
-the water and to fly at a low height like a flying fish at a speed of
-about seventy-five miles per hour. Should anything go wrong, it is
-capable of floating on the water.
-
-In the San Diego Curtiss flights, the machine skimmed along the surface
-of the bay, then rose to a height of a hundred feet, moved about two
-miles through the air in a circular course, and finally alighted
-close to its starting-point in the water. Turns were made in water as
-well as in air, a speed of forty miles per hour being attained while
-"skimming." The "hydroplanes" used are rigid flat surfaces which
-utilize the pressure of the water for sustention, just as the main
-wings utilize air pressure. On account of the great density of water,
-no great amount of surface is required: but it must be so distributed
-as to balance the machine. The use of pontoons makes it possible to
-rest upon the water and to start from rest. A trip like Ely's could
-be made without a landing platform, with this type of machine; the
-aeroplane could either remain alongside the war vessel or be hoisted
-aboard until ready to venture away again.
-
-There are various other biplanes attracting public attention in this
-country. In France the tendency is all toward the monoplane form, and
-many of the "records" have, during the past couple of years, passed
-from the former to the latter type of machine. The monoplane is simpler
-and usually cheaper. The biplane may be designed for greater economy
-in weight and power. Farman has lately experimented with the monoplane
-type of machine: the large number of French designs in this class
-discourages any attempt at complete description.
-
-  [Illustration: SANTOS-DUMONT'S "DEMOISELLE"]
-
-The smallest of aeroplanes is the Santos-Dumont _Demoiselle_. The
-original machine is said to have supported 260 pounds on 100 square
-feet of area, making a speed of sixty miles per hour. Its proprietor
-was the first aviator in Europe of the heavier-than-air class. After
-having done pioneer work with dirigible balloons, he won the Deutsch
-prize for a hundred meter aeroplane flight (the first outside of the
-United States) in 1906; the speed being twenty-three miles per hour.
-His first flight, of 400 feet, in a monoplane was made in 1907.
-
-  [Illustration: BLÉRIOT MONOPLANE]
-
-The master of the monoplane has been Louis Blériot. Starting in
-1907 with short flights in a Langley type of machine, he made his
-celebrated cross-country run, and the first circling flights ever
-achieved in a monoplane, the following year. On July 25, 1909, he
-crossed the British Channel, thirty-two miles, in thirty-seven minutes.
-
-  [Illustration: LATHAM'S FALL INTO THE CHANNEL]
-
-The Channel crossing has become a favorite feat. Mr. Latham, only two
-days after Blériot, all but completed it in his Antoinette monoplane.
-De Lesseps, in a Blériot machine, was more fortunate. Sopwith, last
-year, won the de Forest prize of $20,000 by a flight of 174 miles
-from England into Belgium. The ill-fated Rolls made the round trip
-between England and France. Grace, contesting for the same prize,
-reached Belgium, was driven back to Calais, started on the return
-voyage, and vanished--all save some few doubtful relics lately found.
-Moisant reached London from Paris--the first trip on record between
-these cities without change of conveyance: and one which has just been
-duplicated by Pierre Prier, who, on April 12, made the London to Paris
-journey, 290 miles, in 236 minutes, without a stop. This does not,
-however, make the record for a continuous flight: which was attained by
-Tabuteau, who at Buc, on Dec. 30, 1910, flew around the aerodrome for
-465 minutes at the speed of 48-1/2 miles per hour.
-
-Other famous crossings include those of the Irish Sea, 52 miles, by
-Loraine; Long Island Sound, 25 miles, by Harmon; and Lake Geneva, 40
-miles, by Defaux.
-
-It was just about a century ago that Cayley first described a soaring
-machine, heavier than air, of a form remarkably similar to that of the
-modern aeroplane. Aside from Henson's unsuccessful attempt to build
-such a machine, in 1842, and Wenham's first gliding experiments with a
-triplane in 1857, soaring flight made no real progress until Langley's
-experiments. That investigator, with Maxim and others, ascertained
-those laws of aerial sustention the application of which led to success
-in 1903.
-
-  [Illustration: DE LESSEPS IN A BLÉRIOT CROSSING THE CHANNEL
-  (Photo by Levick, N.Y.)]
-
-The eight years since have held the crowded hours of aviation. Before
-this book is printed, it may be rendered obsolete by new developments.
-The exploits of Paulhan, of R. E. Peltèrie since 1907, Bell's work with
-his tetrahedral kites--all have been either stimulating or directly
-fruitful. Delagrange began to break speed records in 1908. A year
-later he attained a speed of fifty miles. The first woman to enjoy an
-aeroplane voyage was Mme. Delagrange, in Turin, in 1908.
-
-  [Illustration: THE MAXIM AEROPLANE]
-
-  [Illustration: LANGLEY'S AEROPLANE (1896)
-  Steam driven]
-
-The first flight in England by an English-built machine was made in
-January, 1909. That year, Count de Lambert flew over Paris, and in
-1910 Grahame-White circled his machine over the city of Boston. The
-year 1910 surpassed all its predecessors in increasing the range and
-control of aeroplanes; over 1500 ascents were made by Wright machines
-alone; but 1911 promises to show even greater results. Three men made
-cross-country flights from Belmont Park to the Statue of Liberty and
-back, in New York;[B] at least five men attained altitudes exceeding
-9,000 feet. Hamilton made the run from New York to Philadelphia and
-return, in June. The unfortunate Chavez all but abolished the fames of
-Hannibal and Napoleon by crossing the icy barrier of the Alps, from
-Switzerland to Italy--in forty minutes!
-
-  [Illustration: ROBART MONOPLANE.]
-
-Tabuteau, almost on New Year's eve, broke all distance records by a
-flight of 363 miles in less than eight hours; while Barrier at Memphis
-probably reached a speed of eighty-eight miles per hour (timing
-unofficial). With the new year came reports of inconceivable speeds by
-a machine skidding along the ice of Lake Erie; the successful receipt
-by Willard and McCurdy of wireless messages from the earth to their
-aeroplanes; and the proposal by the United States Signal Corps for the
-use of flying machines for carrying Alaskan mails.
-
-  [Illustration: VINA MONOPLANE.]
-
-McCurdy all but succeeded in his attempt to fly from Key West to
-Havana, surpassing previous records by remaining aloft above salt water
-while traveling eighty miles. Lieutenant Bague, in March, started from
-Antibes, near Nice, for Corsica. After a 124-mile flight, breaking all
-records for sea journeys by air, he reached the islet of Gorgona, near
-Leghorn, Italy, landing on bad ground and badly damaging his machine.
-The time of flight was 5-1/2 hours. Bellinger completed the 500-mile
-"accommodation train" flight from Vincennes to Pau; Vedrine, on April
-12, by making the same journey in 415 minutes of actual flying time,
-won the Béarn prize of $4000; Say attained a speed of 74 miles per hour
-in circular flights at Issy-les-Moulineaux. Aeroplane flights have been
-made in Japan, India, Peru, and China.
-
-One of the most spectacular of recent achievements is that of Renaux,
-competing for the Michelin Grand Prize. A purse of $20,000 was offered
-in 1909 by M. Michelin, the French tire manufacturer, for the first
-successful flight from Paris to Clermont-Ferrand--260 miles--in less
-than six hours. The prize was to stand for ten years. It was prescribed
-that the aviator must, at the end of the journey, circle the tower of
-the Cathedral and alight on the summit of the Puy de Dome--elevation
-4500 feet--on a landing place measuring only 40 by 100 yards,
-surrounded by broken and rugged ground and usually obscured by fog.
-
-The flight was attempted last year by Weymann, who fell short of the
-goal by only a few miles. Leon Morane met with a serious accident,
-a little later, while attempting the trip with his brother as a
-passenger. Renaux completed the journey with ease in his Farman
-biplane, carrying a passenger, his time being 308 minutes.
-
-This Michelin Grand Prize is not to be confused with the Michelin
-Trophy of $4000 offered yearly for the longest flight in a closed
-circuit.
-
-Speeds have increased 50% during the past year; even with passengers,
-machines have moved more than a mile a minute: average motor capacities
-have been doubled or tripled. The French men and machines hold the
-records for speed, duration, distance, and (perhaps) altitude. The
-highest altitude claimed is probably that attained by Garros at Mexico
-City, early this year--12,052 feet above sea level. The world's speed
-record for a two-man flight appears to be that of Foulois and Parmalee,
-made at Laredo, Texas, March 3, 1911: 106 miles, cross-country, in 127
-minutes. Three-fourths of all flights made up to this time have been
-made in France--a fair proportion, however, in American machines.
-
-
-NOTE
-
-The rapidity with which history is made in aeronautics is forcibly
-suggested by the revision of text made necessary by recent news.
-The new _Deutschland_ has met the fate of its predecessors; the
-Paris-Rome-Turin flight is at this moment under way; and Lieutenant
-Bayne, attempting once more his France-to-Corsica flight, has--for the
-time being at least--disappeared.
-
-
-
-
-THE POSSIBILITIES IN AVIATION
-
-
-Men now fly and will probably keep on flying; but aviation is still
-too hazardous to become the popular sport of the average man. The
-overwhelmingly important problem with the aeroplane is that of
-stability. These machines must have a better lateral balance when
-turning corners or when subjected to wind gusts: and the balance must
-be automatically, not manually, produced.
-
-  [Illustration: BLANC MONOPLANE]
-
-Other necessary improvements are of minor urgency and in some cases
-will be easy to accomplish. Better mechanical construction, especially
-in the details of attachments, needs only persistence and common sense.
-Structural strength will be increased; the wide spread of wing presents
-difficulties here, which may be solved either by increasing the number
-of superimposed surfaces, as in triplanes, or in some other manner.
-Greater carrying capacity--two men instead of one--may be insisted
-upon: and this leads to the difficult question of motor weights.
-The revolving air-cooled motor may offer further possibilities: the
-two-cycle idea will help if a short radius of action is permissible:
-but a weight of less than two pounds to the horse-power seems
-to imply, almost essentially, a lack of ruggedness and surety of
-operation. A promising field for investigation is in the direction of
-increasing propeller efficiencies. If such an increase can be effected,
-the whole of the power difficulty will be greatly simplified.
-
-  [Illustration: MELVIN VANIMAN TRIPLANE]
-
-  [Illustration: JEAN DE CRAWHEZ TRIPLANE]
-
-  [Illustration: A TRIPLANE]
-
-This same motor question controls the proposal for increased speed.
-The use of a reserve motor would again increase weights; though not
-necessarily in proportion to the aggregate engine capacity. Perhaps
-something may be accomplished with a gasoline turbine, when one
-is developed. In any case, no sudden increase in speeds seems to
-be probable; any further lightening of motors must be undertaken
-with deliberation and science. If much higher maximum speeds are
-attained, there will be an opportunity to vary the speed to suit the
-requirements. Then clutches, gears, brakes, and speed-changing devices
-of various sorts will become necessary, and the problem of weights of
-journal bearings--already no small matter--will be made still more
-serious. And with variable speed must probably come variable sail
-area--in preference to tilting--so that the fabric must be reefed on
-its frame. Certainly two men, it would seem, will be needed!
-
-Better methods for starting are required. The hydroplane idea promises
-much in this respect. With a better understanding and control of the
-conditions associated with successful and safe descent--perhaps with
-improved appliances therefor--the problem of ascent will also be partly
-solved. If such result can be achieved, these measures of control must
-be made automatic.
-
-The building of complete aeroplanes to standard designs would be
-extremely profitable at present prices, which range from $2500 to
-$5000. Perhaps the most profitable part would be in the building of the
-motor. The framing and fabric of an ordinary monoplane could easily
-be constructed at a cost below $300. The propeller may cost $50 more.
-The expense for wires, ropes, etc., is trifling; and unless special
-scientific instruments and accessories are required, all of the rest
-of the value lies in the motor and its accessories. Within reasonable
-limits, present costs of motors vary about with the horse-power. The
-amateur designer must therefore be careful to keep down weight and
-power unless he proposes to spend money quite freely.
-
-
-The Case of the Dirigible
-
-Not very much is being heard of performances of dirigible balloons just
-at present. They have shown themselves to be lacking in stanchness
-and effectiveness under reasonable variations of weather. We must
-have fabrics that are stronger for their weight and more impervious.
-Envelopes must be so built structurally as to resist deformation at
-high speeds, without having any greatly increased weight. A cheap way
-of preparing pure hydrogen gas is to be desired.
-
-Most important of all, the balloon must have a higher speed, to make it
-truly dirigible. This, with sufficient steering power, will protect it
-against the destructive accidents that have terminated so many balloon
-careers. Here again arises the whole question of power in relation
-to motor weight, though not as formidably as is the case with the
-aeroplane. The required higher speeds are possible now, at the cost
-merely of careful structural design, reduced radius of action, and
-reduced passenger carrying capacity.
-
-Better altitude control will be attained with better fabrics and
-the use of plane fin surfaces at high speeds. The employment of a
-vertically-acting propeller as a somewhat wasteful but perhaps finally
-necessary measure of safety may also be regarded as probable.
-
-  [Illustration: GIRAUDON'S WHEEL AEROPLANE]
-
-
-The Orthopter
-
-The _aviplane_, _ornithoptère_ or _orthopter_ is a flying machine with
-bird-like flapping wings, which has received occasional attention
-from time to time, as the result of a too blind adherence to Nature's
-analogies. Every mechanical principle is in favor of the screw as
-compared with any reciprocating method of propulsion. There have been
-few actual examples of this type: a model was exhibited at the Grand
-Central Palace in New York in January of this year.
-
-The mechanism of an orthopter would be relatively complex, and the
-flapping wings would have to "feather" on their return stroke. The
-flapping speed would have to be very high or the surface area very
-great. This last requirement would lead to structural difficulties.
-Propulsion would not be uniform, unless additional complications were
-introduced. The machine would be the most difficult of any type to
-balance. The motion of a bird's wing is extremely complicated in its
-details--one that it would be as difficult to imitate in a mechanical
-device as it would be for us to obtain the structural strength of an
-eagle's wing in fabric and metal, with anything like the same extent of
-surface and limit of weight. According to Pettigrew, the efficiency of
-bird and insect flight depends largely upon the elasticity of the wing.
-Chatley gives the ratio of area to weight as varying from fifty (gnat)
-to one-half (Australian crane) square feet per pound. The usual ratio
-in aeroplanes is from one-third to one-half.
-
-About the only advantages perceptible with the orthopter type of
-machine would be, first, the ability "to start from rest without
-a preliminary surface glide"; and second, more independence of
-irregularity in air currents, since the propulsive force is exerted
-over a greater extent than is that of a screw propeller.
-
-
-The Helicopter
-
-The _gyroplane_ or _helicopter_ was the type of flying machine
-regarded by Lord Kelvin as alone likely to survive. It lifts itself
-by screw propellers acting vertically. This form was suggested in
-1852. When only a single screw was used, the whole machine rotated
-about its vertical axis. It was attempted to offset this by the use
-of vertical fin-planes: but these led to instability in the presence
-of irregular air currents. One early form had two oppositely-pitched
-screws driven by a complete steam engine and boiler plant. One of the
-Cornu helicopters had adjustable inclined planes under the two large
-vertically propelling screws. The air which slipped past the screws
-imposed a pressure on the inclined planes which was utilized to produce
-horizontal movement in any desired direction--if the wind was not too
-adverse. A gasoline engine was carried in a sort of well between the
-screws.
-
-  [Illustration: BRÉGUET GYROPLANE DURING CONSTRUCTION
-  (Helicopter type)]
-
-The helicopter may be regarded as the limiting type of aeroplane, the
-sail area being reduced nearly to zero; the wings becoming mere fins,
-the smaller the better. It therefore requires maximum motor power and
-is particularly dependent upon the development of an excessively light
-motor. It is launched and descends under perfect control, without
-regard to horizontal velocity. It has very little exposed surface and
-is therefore both easy to steer and independent of wind conditions. By
-properly arranging the screws it can be amply balanced: but it must
-have a particularly stout and strong frame.
-
-The development of this machine hinges largely on the propeller. It is
-not only necessary to develop _power_ (which means force multiplied by
-velocity) but actual propulsive vertical _force_: and this must exceed
-or at least equal the whole weight of the machine. From ten to forty
-pounds of lifting force per horse-power have been actually attained:
-and with motors weighing less than five pounds there is evidently some
-margin. The propellers are of special design, usually with very large
-blades. Four are commonly used: one, so to speak, at each "corner" of
-the machine. The helicopter is absolutely dependent upon its motors.
-It cannot descend safely if the power fails. If it is to do anything
-but ascend and descend it must have additional propulsive machinery for
-producing horizontal movement.
-
-
-Composite Types
-
-The aeroplane is thus particularly weak as to stability, launching,
-and descending: but it is economical in power because it uses the
-air to hold itself up. The dirigible balloon is lacking in power and
-speed, but can ascend and descend safely, even if only by wasteful
-methods; and it can carry heavy weights, which are impossible with the
-structurally fragile aeroplane. The helicopter is wasteful in power,
-but is stable and sure in ascending and descending, providing only that
-the motor power does not fail.
-
-Why, then, not combine the types? An aeroplane-dirigible would
-be open to only one objection: on the ground of stability. The
-dirigible-helicopter would have as its only disadvantage a certain
-wastefulness of power, while the aeroplane-helicopter would seem to
-have no drawback whatever.
-
-All three combinations have been, or are being, tried. An Italian
-engineer officer has designed a balloon-aeroplane. The balloon is
-greatly flattened, or lens-shaped, and floats on its side, presenting
-its edge to the horizon--if inclination be disregarded. With some
-inclination, the machine acts like an aeroplane and is partially
-self-sustaining at any reasonable velocity.
-
-The use of a vertically-acting screw on a dirigible combines the
-features of that type and the helicopter. This arrangement has also
-been the subject of design (as in Captain Miller's flexible balloon)
-if not of construction. The combination of helicopter and aeroplane
-seems especially promising: the vertical propellers being employed for
-starting and descending, as an emergency safety feature and perhaps for
-aid in stabilizing. The fact that composite types of flying machine
-have been suggested is perhaps, however, an indication that the
-ultimate type has not yet been established.
-
-
-What is Promised
-
-The flying machine will probably become the vehicle of the explorer.
-If Stanley had been able to use a small high-powered dirigible in
-the search for Livingstone, the journey would have been one of hours
-as compared with months, the food and general comfort of the party
-would have been equal in quality to those attainable at home, and the
-expense in money and in human life would have been relatively trifling.
-
-  [Illustration: WELLMAN'S AMERICA
-  (From Wellman's _Aerial Age_)]
-
-Most readers will remember the fate of Andrée, and the projected polar
-expeditions of Wellman in 1907 and 1909. Misfortune accompanied both
-attempts; but one has only to read Peary's story of the dogged tramp
-over the Greenland ice blink to realize that danger and misfortune
-in no less degree have accompanied other plans of Arctic pioneering.
-With proper design and the right men, it does not seem unreasonable to
-expect that a hundred flying machines may soar above Earth's invisible
-axial points during the next dozen years.[C]
-
-The report of Count Zeppelin's Spitzbergen expedition of last year
-has just been made public. This was undertaken to ascertain the
-adaptability of flying machines for Arctic navigation. Besides speed
-and radius of action, the conclusive factors include that of freedom
-from such breakdowns as cannot be made good on the road.
-
-For exploration in other regions, the balloon or the aeroplane is
-sure to be employed. Rapidity of progress without fatigue or danger
-will replace the floundering through swamps, shivering with ague, and
-bickering with hostile natives now associated with tropical and other
-expeditions. The stereoscopic camera with its scientific adjuncts will
-permit of almost automatic map-making, more comprehensive and accurate
-than any now attempted in other than the most settled sections. It
-is not too much to expect that arrangements will be perfected for
-conducting complete topographical surveys without more than occasional
-descents. If extremely high altitudes must be attained--over a
-mile--the machines will be of special design; but as far as can now be
-anticipated, there will be no insurmountable difficulties. The virgin
-peaks of Ruwenzori and the Himalayas may become easily accessible--even
-to women and children if they desire it. We may obtain direct evidence
-as to the contested ascent of Mt. McKinley. A report has been current
-that a Blériot monoplane has been purchased for use in the inspection
-of construction work for an oil pipe line across the Persian desert;
-the aeroplane being regarded as "more expeditious and effectual" than
-an automobile.
-
-The flying machine is the only land vehicle which requires no
-"permanent way." Trains must have rails, bicycles and automobiles
-must have good roads. Even the pedestrian gets along better on a
-path. The ships of the air and the sea demand no improvement of the
-fluids in which they float. To carry mails, parcels, persons, and even
-light freight--these applications, if made commercially practicable
-tomorrow,[D] would surprise no one; their possibility has already
-been amply demonstrated. With the dirigible as the transatlantic
-liner and the aeroplane as the naphtha launch of the air, the whole
-range of applications is commanded. Hangars and landing stages--the
-latter perhaps on the roofs of buildings, revolutionizing our domestic
-architecture--may spring up as rapidly as garages have done. And the
-aeroplane is potentially (with the exception of the motorcycle) the
-cheapest of self-propelled vehicles.
-
-Governments have already considered the possibilities of aerial
-smuggling. Perhaps our custom-house officers will soon have to watch a
-fence instead of a line: to barricade in two dimensions instead of one.
-They will need to be provided with United States Revenue aeroplanes.
-But how are aerial frontiers to be marked? And does a nation own the
-air above it, or is this, like the high seas, "by natural right, common
-to all"? Can a flying-machine blockade-runner above the three-mile
-height claim extraterritoriality?
-
-The flying machine is no longer the delusion of the "crank," because
-it has developed a great industry. A now antiquated statement put
-the capitalization of aeroplane manufactories in France at a million
-dollars, and the development expenditure to date at six millions.
-There are dozens of builders, in New York City alone, of monoplanes,
-biplanes, gliders, and models. A permanent exhibition of air craft is
-just being inaugurated. We have now even an aeronautic "trust," since
-the million-dollar capitalization of the Maxim, Blériot, Grahame-White
-firm.
-
-According to the New York _Sun_, over $500,000 has been subscribed for
-aviation prizes in 1911. The most valuable prizes are for new records
-in cross-country flights. The Paris _Journal_ has offered $70,000 for
-the best speed in a circling race from Paris to Berlin, Brussels,
-London, and back to Paris--1500 miles. Supplementary prizes from other
-sources have increased the total stake in this race to $100,000. A
-purse of $50,000 is offered by the London _Daily Mail_ for the "Circuit
-of Britain" race, from London up the east coast to Edinburgh, across
-to Glasgow, and home by way of the west coast, Exeter, and the Isle of
-Wight; a thousand miles, to be completed in two weeks, beginning July
-22, with descents only at predetermined points. This contest will be
-open (at an entrance fee of $500) to any licensee of the International
-Federation. A German circuit, from Berlin to Bremen, Magdeburg,
-Düsseldorf, Aix-la-Chapelle, Dresden, and back to the starting point,
-is proposed by the _Zeitung am Mittag_ of Berlin, a prize of $25,000
-having been offered. In this country, a comparatively small prize
-has been established for a run from San Francisco to New York, _via_
-Chicago. Besides a meet at Bridgeport, May 18-20, together with those
-to be held by several of the colleges and the ones at Bennings and
-Chicago, there will be, it is still hoped, a national tournament at
-Belmont Park at the end of the same month. Here probably a dozen
-aviators will contest in qualification for the international meet in
-England, to which three American representatives should be sent as
-competitors for the championship trophy now held by Mr. Grahame-White.
-It is anticipated that the chances in the international races favor
-the French aviators, some of whom--in particular, Leblanc--have been
-making sensational records at Pau. Flights between aviation fields in
-different cities are the leading feature in the American program for
-the year. A trip is proposed from Washington to Belmont Park, _via_
-Atlantic City, the New Jersey coast, and lower New York bay. The
-distance is 250 miles and the time will probably be less than that of
-the best passenger trains between Washington and New York. If held,
-this race will probably take place late in May. It is wisely concluded
-that the advancement of aviation depends upon cross-country runs under
-good control and at reasonable speeds and heights rather than upon
-exhibition flights in enclosures. It is to be hoped that commercial
-interests will not be sufficiently powerful to hinder this development.
-
-We shall of course have the usual international championship balloon
-race, preceded by elimination contests. From present indications Omaha
-is likely to be chosen as the point of departure.
-
-The need for scientific study of aerial problems is recognized. The
-sum of $350,000 has been offered the University of Paris to found an
-aeronautic institute. In Germany, the university at Göttingen has for
-years maintained an aerodynamic laboratory. Lord Rayleigh, in England,
-is at the head of a committee of ten eminent scientists and engineers
-which has, under the authority of Parliament, prepared a program of
-necessary theoretical and experimental investigations in aerostatics
-and aerodynamics. Our American colleges have organized student aviation
-societies and in some of them systematic instruction is given in the
-principles underlying the art. A permanent aeronautic laboratory, to be
-located at Washington, D.C., is being promoted.
-
-Aviation as a sport is under the control of the International
-Aeronautic Federation, having its headquarters at Paris. Bodies
-like the Royal Aero Club of England and the Aero Club of America
-are subsidiaries to the Federation. In addition, we have in this
-country other clubs, like the Aeronautic Society, the United States
-Aeronautical Reserve, etc. The National Council of the Aero Clubs of
-America is a sort of supreme court for all of these, having control of
-meets and contests; but it has no affiliation with the International
-body, which is represented here by the Aero Club of America. The
-Canadian Auto and Aero Club supervises aviation in the Dominion.
-
-Aviation has developed new legal problems: problems of liability for
-accidents to others; the matter of supervision of airship operators.
-Bills to license and regulate air craft have been introduced in at
-least two state legislatures.
-
-Schools for instruction in flying as an art or sport are being
-promoted. It is understood that the Wright firm is prepared to organize
-classes of about a dozen men, supplying an aeroplane for their
-instruction. Each man pays a small fee, which is remitted should he
-afterward purchase a machine. Mr. Grahame-White, at Pau, in the south
-of France, conducts a school of aviation, and the arrangements are now
-being duplicated in England. Instruction is given on Blériot monoplanes
-and Farman biplanes, at a cost of a hundred guineas for either. The
-pupil is coached until he can make a three-mile flight; meanwhile, he
-is held partially responsible for damage and is required to take out a
-"third-party" insurance policy.
-
-There is no lack of aeronautic literature. Major Squier's paper in the
-_Transactions_ of the American Society of Mechanical Engineers, 1908,
-gave an eighteen-page list of books and magazine articles of fair
-completeness up to its date; Professor Chatley's book, _Aeroplanes_,
-1911, discusses some recent publications; the Brooklyn Public Library
-in New York issued in 1910 (misdated 1909) a manual of fourteen pages
-critically referring to the then available literature, and itself
-containing a list of some dozen bibliographies.
-
-
-Aerial Warfare
-
-  [Illustration: THE GERMAN EMPEROR WATCHING THE PROGRESS OF AVIATION]
-
-The use of air craft as military auxiliaries is not new. As early
-as 1812 the Russians, before retreating from Moscow, attempted to
-drop bombs from balloons: an attempt carried to success by Austrian
-engineers in 1849. Both contestants in our own War of Secession
-employed captive and drifting balloons. President Lincoln organized a
-regular aeronautic auxiliary staff in which one Lowe held the official
-rank of chief aeronaut. This same gentleman (who had accomplished a
-reconnaissance of 350 miles in eight hours in a 25,000 cubic foot
-drifting balloon) was subjected to adverse criticism on account of a
-weakness for making ascents while wearing the formal "Prince Albert"
-coat and silk hat! A portable gas-generating plant was employed by
-the Union army. We are told that General Stoneman, in 1862, directed
-artillery fire from a balloon, which was repeatedly fired at by the
-enemy, but not once hit. The Confederates were less amply equipped.
-Their balloon was a patchwork of silk skirts contributed (one doubts
-not, with patriotic alacrity) by the daughters of the Confederacy.
-
-It is not forgotten that communication between besieged Paris and the
-external world was kept up for some months during 1870-71 by balloons
-exclusively. Mail was carried on a truly commercial scale: pet animals
-and--the anticlimax is unintended--164 persons, including M. Gambetta,
-escaped in some sixty-five flights. Balloons were frequently employed
-in the Franco-Prussian contest; and they were seldom put _hors de
-combat_ by the enemy.
-
-During our war with Spain, aerial craft were employed in at least
-one instance, namely, at San Juan, Porto Rico, for reconnoitering
-entrenchments. Frequent ascents were made from Ladysmith, during the
-Boer war. The balloons were often fired at, but never badly damaged.
-Cronje's army was on one occasion located by the aid of a British
-scout-balloon. Artillery fire was frequently directed from aerial
-observations. Both sides employed balloons in the epic conflict between
-Russia and Japan.
-
-A declaration introduced at the second international peace conference
-at the Hague proposed to prohibit, for a limited period, the discharge
-of projectiles or explosives from flying machines of any sort. The
-United States was the only first-class power which endorsed the
-declaration. It does not appear likely, therefore, that international
-law will discountenance the employment of aerial craft in international
-disputes. The building of airships goes on with increasing eagerness.
-Last year the Italian chamber appropriated $5,000,000 for the
-construction and maintenance of flying machines.
-
-A press report dated February 4 stated that a German aeronaut had
-been spending some weeks at Panama, studying the air currents of the
-Canal Zone. No flying machine may in Germany approach more closely
-than within six miles of a fort, unless specially licensed. At the
-Krupp works in Essen there are being tested two new guns for shooting
-at aeroplanes and dirigibles. One is mounted on an armored motor
-truck. The other is a swivel-mounted gun on a flat-topped four-wheeled
-carriage.
-
-The United States battleship _Connecticut_ cost $9,000,000. It
-displaces 18,000 tons, uses 17,000 horse-power and 1000 men, and makes
-twenty miles an hour. An aeroplane of unusual size with nearly three
-times this speed, employing from one to three men with an engine of 100
-horse-power, would weigh one ton and might cost $5000. A Dreadnought
-costs $16,000,000, complete, and may last--it is difficult to say, but
-few claim more than ten years. It depreciates, perhaps, at the rate
-of $2,000,000 a year. Aeroplanes built to standard designs in large
-quantities would cost certainly not over $1000 each. The ratio of cost
-is 16,000 to 1. Would the largest Dreadnought, exposed unaided to the
-attack of 16,000 flying machines, be in an entirely enviable situation?
-
-An aeroplane is a fragile and costly thing to hazard at one blow: but
-not more fragile or costly than a Whitehead torpedo. The aeroplane
-soldier takes tremendous risks; but perhaps not greater risks than
-those taken by the crew of a submarine. There is never any lack of
-daring men when daring is the thing needed.
-
-All experience goes to show that an object in the air is hard to
-hit. The flying machine is safer from attack where it works than it
-is on the ground. The aim necessary to impart a crippling blow to an
-aeroplane must be one of unprecedented accuracy. The dirigible balloon
-gives a larger mark, but could not be immediately crippled by almost
-any projectile. It could take a good pounding and still get away.
-Interesting speculations might be made as to the outcome of an aerial
-battle between the two types of craft. The aeroplane might have a
-sharp cutting beak with which to ram its more cumbersome adversary,
-but this would involve some risk to its own stability: and the balloon
-could easily escape by a quick ascent. It has been suggested that each
-dirigible would need an aeroplane escort force for its defense against
-ramming. Any collision between two opposing heavier-than-air machines
-could not, it would seem, be other than disastrous: but perhaps
-the dirigible could rescue the wrecks. Possibly gas-inflated life
-buoys might be attached to the individual combatants. In the French
-man[oe]uvers, a small aeroplane circled the dirigible with ease, flying
-not only around it, but in vertical circles over and under it.
-
-  [Illustration: 7.5 CENTIMETER GERMAN AUTOMATIC GUN FOR ATTACKING
-  AIRSHIPS
-  (From Brewer's _Art of Aviation_)]
-
-The French war office has exploited both types of machine. In
-Germany, the dirigible has until recently received nearly all the
-attention of strategists: but the results of a recent aerial war
-game have apparently suggested a change in policy, and the Germans
-are now, without neglecting the balloon, actively developing its
-heavier-than-air competitor. England seems to be muddled as to its
-aerial policy, while the United States has been waiting and for the
-most part doing nothing. Now, however, the mobilizations in Texas have
-been associated with a considerable amount of aeroplane enthusiasm.
-A half-dozen machines, it is expected, will soon be housed in the
-aerodrome at San Antonio. Experiments are anticipated in the carrying
-of light ammunition and emergency supplies, and one of the promised
-man[oe]uvers is to be the locating of concealed bodies of troops by air
-scouts. Thirty army officers are to be detailed for aeroplane service
-this year; five training schools are to be established.
-
-If flying machines are relatively unsusceptible to attack, there is
-also some question as to their effectiveness _in_ attack. Rifles have
-been discharged from moving balloons with some degree of accuracy in
-aim; but long-range marksmanship with any but hand weapons involves the
-mastery of several difficult factors additional to those present in
-gunnery at sea. The recoil of guns might endanger stability; and it is
-difficult to estimate the possible effects of a powerful concussion,
-with its resulting surges of air, in the immediate vicinity of a
-delicately balanced aerial vessel.
-
-But aside from purely combative functions, air craft may be
-superlatively useful as messengers. To send despatches rapidly and
-without interference, or to carry a general 100 miles in as many
-minutes--these accomplishments would render impossible the romance
-of a "Sheridan's Ride," but might have a romance of their own. With
-the new sense added to human equipment by wireless communication,
-the results of observations may be signaled to friends over miles of
-distance without intervening permanent connections of however fragile a
-nature.
-
-Flying machines would seem to be the safest of scouts. They could pass
-over the enemy's country with as little direct danger--perhaps as
-unobserved--as a spy in disguise; yet their occupants would scarcely
-be subjected to the penalty accompanying discovery of a spy. They
-could easily study the movements of an opposing armed force: a study
-now frequently associated with great loss of life and hampering of
-effective handling of troops. They could watch for hostile fleets with
-relatively high effectiveness (under usual conditions), commanding
-distant approaches to a long coast line at slight cost. From their
-elevated position, they could most readily detect hostile submarines
-threatening their own naval fleet. Maximum effective reconnaissance in
-minimum time would be their chief characteristic: in fact, the high
-speeds might actually constitute an objection, if they interfered with
-thorough observation. But if air craft had been available at Santiago
-in 1898, Lieutenant Blue's expedition would have been unnecessary, and
-there would have been for no moment any doubt that Admiral Cervera's
-fleet was actually bottled up behind the Morro. No besieged fortress
-need any longer be deprived of communication with--or even some
-medical or other supplies from--its friends. Suppose that Napoleon had
-been provided with a flying machine at Elba--or even at St. Helena!
-
-The applications to rapid surveying of unknown ground that have been
-suggested as possible in civil life would be equally possible in time
-of war. Even if the scene of conflict were in an unmapped portion of
-the enemy's territory, the map could be quickly made, the location of
-temporary defenses and entrenchments ascertained, and the advantage
-of superior knowledge of the ground completely overcome prior to an
-engagement. The searchlight and the compass for true navigation on long
-flights over unknown country would be the indispensable aids in such
-applications.
-
-During the current mobilization of the United States Army at Texas, a
-dispatch was carried 21 miles on a map-and-compass flight, the round
-trip occupying less than two hours and being made without incident. The
-machine flew at a height of 1500 feet and was sighted several miles off.
-
-A dirigible balloon, it has been suggested, is comparatively safe while
-moving in the air, but is subjected to severe strains when anchored to
-the ground, if exposed. It must have either safe harbors of refuge or
-actual shelter buildings--dry docks, so to speak. In an enemy's country
-a ravine or even a deep railway cut might answer in an emergency, but
-the greatest reliance would have to be placed on quick return trips
-from a suitable base. The balloon would be, perhaps, a more effective
-weapon in defense than in attack. Major Squier regards a flying height
-of one mile as giving reasonable security against hostile projectiles
-in the daytime. A lower elevation would be sufficient at night. Given a
-suitable telephotographic apparatus, all necessary observations could
-easily be made from this altitude. Even in the enemy's territory,
-descent to the earth might be possible at night under reasonably
-favorable conditions. Two sizes of balloon would seem to be indicated:
-the scouting work described would be done by a small machine having the
-greatest possible radius of action. Frontiers would be no barrier to
-it. Sent from England in the night it could hover over a Kiel canal or
-an island of Heligoland at sunrise, there to observe in most leisurely
-fashion an enemy's mobilizations.
-
-  [Illustration: GERMAN GUN FOR SHOOTING AT AEROPLANES
-  (From Brewer's _Art of Aviation_)]
-
-At the London meeting of the Institute of Naval Architects, in April,
-1911, the opinion was expressed that the only effective way of meeting
-attack from a flying machine at sea would be by a counter-attack from
-the same type of craft. The ship designers concluded that the aeroplane
-would no more limit the sizes of battleships than the torpedo has
-limited them.
-
-For the more serious work of fighting, larger balloons would be needed,
-with net carrying capacities perhaps upward from one ton. Such a
-machine could launch explosives and combustibles against the enemy's
-forts, dry docks, arsenals, magazines, and battleships. It could easily
-and completely destroy his railroads and bridges; perhaps even his
-capital itself, including the buildings housing his chief executive
-and war office staff. Nothing--it would seem--could effectually combat
-it save air craft of its own kind. The battles of the future may be
-battles of the air.
-
-There are of course difficulties in the way of dropping missiles
-of any great size from flying machines. Curtiss and others have
-shown that accuracy of aim is possible. Eight-pound shrapnel shells
-have been dropped from an aeroplane with measurably good effect,
-without upsetting the vessel; but at best the sudden liberation of
-a considerable weight will introduce stabilizing and controlling
-difficulties. The passengers who made junketing trips about Paris on
-the _Clément-Bayard_ complained that they were not allowed to throw
-even a chicken-bone overboard! But it does not seem too much to expect
-that these purely mechanical difficulties will be overcome by purely
-mechanical remedies. An automatic venting of a gas ballonet of just
-sufficient size to compensate for the weight of the dropped shell would
-answer in a balloon: a similar automatic change in propeller speed and
-angle of planes would suffice with the aeroplane. There is no doubt
-but that air craft may be made efficient agents of destruction on a
-colossal scale.
-
-  [Illustration: SANTOS-DUMONT CIRCLING THE EIFFEL TOWER
-  (From Walker's _Aerial Navigation_)]
-
-A Swedish engineer officer has invented an aerial torpedo,
-automatically propelled and balanced like an ordinary submarine
-torpedo. It is stated to have an effective radius of three miles while
-carrying two and one-half pounds of explosive at the speed of a bullet.
-One can see no reason why such torpedoes of the largest size are not
-entirely practicable: though much lower speeds than that stated should
-be sufficient.
-
-According to press reports, the Krupps have developed a non-recoiling
-torpedo, having a range exceeding 5000 yards. The percussion device is
-locked at the start, to prevent premature explosion: unlocking occurs
-only after a certain velocity has been attained.
-
-Major Squier apparently contends that the prohibition of offensive
-aerial operations is unfair, unless with it there goes the reciprocal
-provision that a war balloon shall not be fired at from below. Again,
-there seems to be no good reason why aerial mines dropped from above
-should be forbidden, while submarine mines--the most dangerous naval
-weapons--are allowed. Modern strategy aims to capture rather than to
-destroy: the man[oe]uvering of the enemy into untenable situations by
-the rapid mobilization of troops being the end of present-day highly
-organized staffs. Whether the dirigible (certainly not the aeroplane)
-will ever become an effective vehicle for transport of large bodies of
-troops cannot yet be foreseen.
-
-Differences in national temper and tradition, and the conflict of
-commercial enterprise, perhaps the very recentness of the growth of a
-spirit of national unity on the one hand, are rapidly bringing the two
-foremost powers of Europe into keen competition: a competition which
-is resulting in a bloodless revolution in England, necessitated by the
-financial requirements of its naval program. Germany, by its strategic
-geographical position, its dominating military organization, and the
-enforced frugality, resourcefulness, and efficiency of its people,
-possesses what must be regarded as the most invincible army in the
-world. Its avowed purpose is an equally invincible navy. Whether the
-Gibraltar-Power can keep its ascendancy may well be doubted. The one
-doubtful--and at the same time perhaps hopeful--factor lies in the
-possibilities of aerial navigation.
-
-  [Illustration: LATHAM, FARMAN, AND PAULHAN]
-
-If one battleship, in terms of dollars, represents 16,000 airships,
-and if one or a dozen of the latter can destroy the former--a feat
-not perhaps beyond the bounds of possibility--if the fortress that
-represents the skill and labor of generations may be razed by twoscore
-men operating from aloft, then the nations may beat their spears into
-pruning-hooks and their swords into plowshares: then the battle ceases
-to hinge on the power of the purse. Let war be made so costly that
-nations can no more afford it than sane men can wrestle on the brink
-of a precipice. Let armed international strife be viewed as it really
-is--senseless as the now dying duello. Let the navy that represents
-the wealth, the best engineering, the highest courage and skill, of
-our age, be powerless at the attack of a swarm of trifling gnats like
-Gulliver bound by Lilliputians--what happens then? It is a _reductio ad
-absurdum_. Destructive war becomes so superlatively destructive as to
-destroy itself.
-
-There is only one other way. Let the two rival Powers on whom the peace
-of the world depends settle their difficulties--surely the earth must
-be big enough for both!--and then as one would gently but firmly take
-away from a small boy his too destructive toy rifle, spike the guns
-and scuttle the ships, their own and all the rest, leaving to some
-unambitious and neutral power the prosaic task of policing the world.
-Here is a work for red blood and national self-consciousness. If war
-were ever needed for man's best development, other things will answer
-now. The torn bodies and desolated homes of millions of men have paid
-the price demanded. No imaged hell can surpass the unnamed horrors that
-our fathers braved.
-
-"Enforced disarmament!" Why not? Force (and public opinion) have
-abolished private duels. Why not national duels as well? Civilization's
-control of savagery always begins with compulsion. For a generation,
-no first-class power has had home experience in a serious armed
-conflict. We should not willingly contemplate such experience now. We
-have too much to do in the world to fight.
-
-       *       *       *       *       *
-
-The writer has felt some hesitancy in letting these words stand as
-the conclusion of a book on flying machines: but as with the old
-Roman who terminated every oration with a defiance of Carthage, the
-conviction prevails that no other question of the day is of comparable
-importance; and on a matter of overwhelming consequence like this
-no word can ever be out of place. The five chief powers spent for
-war purposes (officially, as Professor Johnson puts it, for the
-"preservation of peace") about $1,000,000,000 in the year 1908. In
-the worst period of the Napoleonic operations the French military and
-naval budget was less than $100,000,000 annually. Great Britain, on
-the present peace footing, is spending for armament more rapidly than
-from 1793 to 1815. The gigantic "War of the Spanish Succession" (which
-changed the map of Europe) cost England less than a present year's
-military expenditure. Since the types for these pages have been set,
-the promise of international peace has been distinctly strengthened.
-President Taft has suggested that as, first, questions of individual
-privilege, and, finally, even those of individual honor, have been
-by common consent submitted to adjudication, so also may those
-so-called "issues involving national honor" be disposed of without
-dishonor by international arbitration. Sir Edward Grey, who does not
-hesitate to say that increase of armaments may end in the destruction
-of civilization unless stopped by revolt of the masses against the
-increasing burdens of taxation, has electrified Europe by his reception
-of the Taft pronouncement. England and the United States rule one-third
-the inhabitants of the earth. It is true that a defensive alliance
-might be more advantageous to the former and disagreeably entangling to
-the latter; but a binding treaty of arbitration between these powers
-would nevertheless be a worthy climax to our present era. And if it
-led to alliance against a third nation which had refused to arbitrate
-(led--as Sir Edward Grey suggests--by the logic of events and not by
-subterranean device) would not such be the fitting and conclusive
-outcome?
-
-The Taft-Grey program--one would wish to call it that--has had all
-reputable endorsement; in England, no factional opposition may be
-expected. Our own jingoes are strangely silent. Mr. Dillon's fear that
-compulsory disarmament would militate against the weaker nations is
-offset by the hearty adherence of Denmark. A resolution in favor of the
-establishment of an international police force has passed the House of
-Commons by a heavy majority. It looks now as if we might hope before
-long to re-date our centuries. We have had Olympiads and Years of Rome,
-B.C. and A.D. Perhaps next the dream of thoughtful men may find its
-realization in the new (and, we may hope, English) prefix, Y.P.--Year
-of Peace.
-
-
-
-
-FOOTNOTES
-
-[A] According to press reports, temporary water ballast will
-be taken on during the daytime, to offset the ascensional effect of the
-hot sun on the envelope.
-
-[B] The contestants for the Ryan prize of $10,000 were
-Moisant, Count de Lesseps, and Grahame-White. Owing to bad weather,
-there was no general participation in the preliminary qualifying
-events, and some question exists as to whether such qualification was
-not tacitly waived; particularly in view of the fact that the prize was
-awarded to the technically unqualified competitor, Mr. Moisant, who
-made the fastest time. This award was challenged by Mr. Grahame-White,
-and upon review by the International Aeronautic Federation the prize
-was given to de Lesseps, the slowest of the contestants, Grahame-White
-being disqualified for having fouled a pylon at the start. This
-gentleman has again appealed the case, and a final decision cannot be
-expected before the meeting of the Federation in October, 1911.
-
-[C] The high wind velocities of the southern circumpolar
-regions may be an insurmountable obstacle in the Antarctic. Yet Mawson
-expects to take with him a 2-passenger monoplane having a 180-mile
-radius of action on the expedition proposed for this year.
-
-[D] It seems that tomorrow has come; for an aeroplane is being
-regularly used (according to a reported interview with Dr. Alexander
-Graham Bell) for carrying mails in India.
-
-
-
-
-Books on Aeronautics
-
-
- =FLYING MACHINES TO-DAY.= By WILLIAM D. ENNIS, M. E., Professor of
-   Mechanical Engineering, Polytechnic Institute, Brooklyn. 12mo.,
-   cloth, 218 pp., 123 illustrations =$1.50 net=
-   =CONTENTS=: THE DELIGHTS AND DANGERS OF FLYING--Dangers of
-   Aviation--What it is Like to Fly. SOARING FLIGHT BY MAN--What Holds
-   it Up. Lifting Power. Why so Many Sails. Steering. TURNING
-   CORNERS--What Happens When Making a Turn. Lateral Stability. Wing
-   Warping. Automatic Control. The Gyroscope. Wind Gusts. AIR AND THE
-   WIND--Sailing Balloons. Field and Speed. GAS AND BALLAST--Buoyancy in
-   Air. Ascending and Descending. The Ballonet. The Equilibrator.
-   DIRIGIBLE BALLOONS AND OTHER KINDS--Shapes. Dimensions. Fabrics.
-   Framing. Keeping the Keel Horizontal. Stability. Rudders and Planes.
-   Arrangement and Accessories. Amateur Dirigibles. Fort Omaha Plant.
-   Balloon Progress. QUESTION OF POWER--Resistance of Aeroplanes.
-   Resistance of Dirigibles. Independent Speed and Timetable. Cost of
-   Speed. Propeller. GETTING UP AND DOWN; MODELS AND GLIDERS; AEROPLANE
-   DETAILS--Launching. Descending. Gliders. Models. Balancing. Weights.
-   Miscellaneous. Things to Look After. SOME AEROPLANES--SOME
-   ACCOMPLISHMENTS. THE POSSIBILITIES IN AVIATION--Case of the
-   Dirigible. The Orthopter. The Helicopter. Composite Types. What is
-   Promised. AERIAL WARFARE.
-
- =AERIAL FLIGHT. Vol. 1. Aerodynamics.= By F. W. LANCHESTER. 8vo.,
-   cloth, 438 pp., 162 illustrations =$6.00 net=
-   =CONTENTS=: Fluid Resistance and Its Associated Phenomena. Viscosity
-   and Skin Friction. The Hydrodynamics of Analytical Theory. Wing
-   Form and Motion in the Periphery. The Aeroplane. The Normal Plane.
-   The Inclined Aeroplane. The Economics of Flight. The Aerofoil. On
-   Propulsion, the Screw Propeller, and the Power Expended in Flight.
-   Experimental Aerodynamics. Glossary. Appendices.
- =Vol. II. Aerodonetics.= By F. W. LANCHESTER. 8vo., cloth, 433 pp.,
-   208 illustrations =$6.00 net=
-   =CONTENTS=: Free Flight. General Principles and Phenomena. The Phugoid
-   Theory--The Equations of the Flight Path. The Phugoid 1852-1872.
-   Dirigible Balloons from 1883-1897; 1898-1906. Flying Machine
-   Theory--The Flight Path Plotted. Elementary Deductions from the
-   Phugoid Theory. Stability of the Flight Path as Affected by Resistance
-   and Moment of Inertia. Experimental Evidence and Verification of the
-   Phugoid Theory. Lateral and Directional Stability. Review of Chapters
-   I to VII and General Conclusions. Soaring. Experimental. Aerodonetics.
-
- =AERIAL NAVIGATION. A practical handbook on the construction of
-  dirigible balloons, aerostats, aeroplanes and aeromotors=, by
-  FREDERICK WALKER. 12mo., cloth, 151 pp., 100 illustrations
-  =$3.00 net.=
-  =CONTENTS=: Laws of Flight. Aerostatics. Aerostats. Aerodynamics.
-  Screw Propulsion. Paddles and Aeroplanes. Motive Power. Structure of
-  Airships and Materials. Airships. Appendix.
-
- =AEROPLANE PATENTS.= By ROBERT M. NEILSON. 8vo., cloth, 101 pp., 77
-  illustrations =$2.00 net=
-  =CONTENTS=: Advice to Inventors. Review of British Patents. British
-  Patents and Applications for Patents from 1860 to 1910, arranged in
-  Order of Application. British Patentees, arranged alphabetically.
-  United States Patents from 1896 to 1909, arranged in order of issue.
-  United States Patentees, arranged alphabetically.
-
- =THE PRINCIPLES OF AEROPLANE CONSTRUCTION.= By RANKIN KENNEDY, C. E.
-  8vo., cloth, 145 pp., 51 diagrams =$1.50 net=
-  =CONTENTS=: Elementary Mechanics and Physics. Principles of Inclined
-  Planes. Air and Its Properties. Principles of the Aeroplane. The
-  Curves of the Aeroplane. Centers of Gravity: Balancing; Steering. The
-  Propeller. The Hélicoptère. The Wing Propeller. The Engine. The Future
-  of the Aeroplane.
-
- =HOW TO DESIGN AN AEROPLANE.= By HERBERT CHATLEY. 16mo., boards, 109
-  pp., illustrated (Van Nostrand's Science Series) =50 cents=
-  =CONTENTS=: The Aeroplane. Air Pressure. Weight. Propellers and
-  Motors. Balancing. Construction. Difficulties. Future Developments.
-  Cost. Other Flying-Machines (Gyroplane and Orinthoptere).
-
- =HOW TO BUILD AN AEROPLANE.= By ROBERT PETIT. Translated from the
-  French by T. O'B. Hubbard and J. H. Ledeboer. 8vo., cloth, 131 pp., 93
-  illustrations =$1.50 net=
-  =CONTENTS=: General Principles of Aeroplane Design. Theory and
-  Calculation. Resistance, Lift, Power, Calculations for the Design of
-  an Aeroplane, Application of Power, Design of Propeller, Arrangements
-  of Surfaces, Stability, Center of Gravity, etc. Materials.
-  Construction of Propellers. Arrangements for Starting and Landing.
-  Controls. Placing Motor. The Planes. Curvatures. Motors.
-
- =AIRSHIPS, PAST AND PRESENT. Together with chapters on the use of
-  balloons in connection with meteorology, photography, and the carrier
-  pigeon.= By A. HILDEBRANDT, Captain and Instructor in the Prussian
-  Balloon Corps. Translated by W. H. Story. 8vo., cloth, 361 pp., 222
-  illustrations =$3.50 net=
-  =CONTENTS=: Early History of the Art. Invention of the Air Balloon.
-  Montgolfieres, Charlieres, and Rozieres. Theory of the Balloon.
-  Development of the Dirigible Balloon. History of the Dirigible
-  Balloon, 1852-1872. Dirigible Balloons from 1883-1897; 1898-1906.
-  Flying Machines. Kites. Parachutes. Development of Military
-  Ballooning. Ballooning in Franco-Prussian War. Modern Organization
-  of Military Ballooning in France, Germany, England and Russia.
-  Military Ballooning in Other Countries. Balloon Construction and the
-  Preparation of the Gas. Instruments. Ballooning as a Sport. Scientific
-  Ballooning. Balloon Photography. Photographic Outfit for Balloon Work.
-  Interpretation of Photographs. Hectography by Means of Kites and
-  Rockets. Carrier Pigeons for Balloons. Balloon Law.
-
-  [Illustration: VAN NOSTRAND LOGO]
-
-
-D. VAN NOSTRAND CO., Publishers
-
-23 MURRAY and 27 WARREN STREETS, NEW YORK
-
-
-
-
-Transcriber's Note: Italics are delimited by underscores; bold by equal
-signs. Four occurrences of the oe-ligature in the word man[oe]uver
-are left as [oe]. The four footnotes have been moved to the end of the
-book. A few words were judged to be printer errors and were changed.
-These include two occurrences of horse-power in the unhyphenated form,
-the spelling of Tabuteau as Tabuteaw on p. 162, and the spelling of
-hélicoptère as helicoptéré on p.208. On a few of the
-figure captions, missing accents were added to some French names.
-
-
-
-
-
-
-
-End of Project Gutenberg's Flying Machines Today, by William Duane Ennis
-
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-
-<pre>
-
-The Project Gutenberg EBook of Flying Machines Today, by William Duane Ennis
-
-This eBook is for the use of anyone anywhere in the United States and most
-other parts of the world 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.  If you are not located in the United States, you'll have
-to check the laws of the country where you are located before using this ebook.
-
-Title: Flying Machines Today
-
-Author: William Duane Ennis
-
-Release Date: March 17, 2016 [EBook #51481]
-
-Language: English
-
-Character set encoding: ISO-8859-1
-
-*** START OF THIS PROJECT GUTENBERG EBOOK FLYING MACHINES TODAY ***
-
-
-
-
-Produced by Chris Curnow, Ralph Carmichael and the Online
-Distributed Proofreading Team at http://www.pgdp.net (This
-file was produced from images generously made available
-by The Internet Archive)
-
-
-
-
-
-
-</pre>
-
-
-<p><span class="pagenum"><a name="Page_i" id="Page_i">[Pg i]</a></span></p>
-<h1>FLYING MACHINES TODAY</h1>
-
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_ii" id="Page_ii">[Pg ii]</a></span></p>
-<h2 class="no_text">Introductory Note</h2>
-<p id="intronote">
-&ldquo;Hitherto aviation has been almost monopolized by that much-overpraised
-and much-overtrusted person, &lsquo;the practical man.&rsquo; It is much in
-need of the services of the theorist&mdash;the engineer with his mathematical
-calculations of how a flying machine ought to be built and of how the
-material used in its construction should be distributed to give the greatest
-possible amount of strength and efficiency.&rdquo; </p>
-<p id="intronoteCitation">
-&mdash;From the <cite>New York Times</cite>, January 16, 1911.
-</p>
-
-<p><span class="pagenumh"><a name="Page_iii" id="Page_iii">[Pg iii]</a></span></p>
-
-<!-- FRONTISPIECE -->
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_iv" id="Page_iv">[Pg iv]</a></span></p>
-<h2 class="no_text">Frontispiece - The Fall of Icarus</h2>
-<div class="figcenter" style="width: 600px">
-<img src="images/front.jpg" alt="The Fall of Icarus"
-     width="600" height="367"/>
-</div>
-
-<!-- TITLE PAGE -->
-<hr class="chapter_rule" />
-<p class="break"><span class="pagenum"><a name="Page_v" id="Page_v">[Pg v]</a></span></p>
-<div>   <!-- adding class="box" puts a box about the title page -->
-<p id="titlebox">FLYING MACHINES TODAY</p>
-
-<p id="bybox">BY</p>
-
-<p id="authorbox">WILLIAM &nbsp; DUANE &nbsp; ENNIS</p>
-
-<p id="affiliationbox">Professor of Mechanical Engineering in the Polytechnic
-Institute of Brooklyn</p>
-
-<p id="illustrationbox">123 ILLUSTRATIONS</p>
-
-<div class="figcenter" style="width: 100px">
-<img src="images/logo.jpg" alt="Van Nostrand logo"
-     width="120" height="120"/>
-</div>
-
-<p id="publisherbox1">NEW YORK</p>
-
-<p id="publisherbox2">D. VAN NOSTRAND COMPANY</p>
-
-<table summary="Van Nostrand address">
-<tr> <td class="tdl"><span class="sc">23 Murray and</span></td>
-<td class="tdc">1911</td>
-<td class="tdr"> <span class="sc">27 Warren Sts.</span></td>  </tr>
-</table>
-</div>
-
-<!-- COPYRIGHT PAGE -->
-<hr class="chapter_rule" />
-<p class="break"><span class="pagenum"><a name="Page_vi" id="Page_vi">[Pg vi]</a></span></p>
-<h2 class="no_text">Copyright Page</h2>
-<p id="copyright">
-<i>Copyright, 1911, by</i><br />
-<span class="sc"> D. Van Nostrand Company</span></p>
-<p id="copyrightAddress" class="center">
-THE · PLIMPTON · PRESS · NORWOOD · MASS · U · S · A
-</p>
-
-
-
-<!-- DEDICATION PAGE -->
-<hr class="chapter_rule" />
-<p class="break"><span class="pagenum"><a name="Page_vii" id="Page_vii">[Pg vii]</a></span></p>
-<h2 class="no_text">Dedication Page</h2>
-
-<p id="dedication">To</p>   <!-- original was set in an Old English Gothic font -->
-<p class="sc center">MY MOTHER</p>
-
-
-<p><span class="pagenumh"><a name="Page_viii" id="Page_viii">[Pg viii]</a></span></p>
-
-<!-- PREFACE PAGE -->
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_ix" id="Page_ix">[Pg ix]</a></span></p>
-<h2>PREFACE</h2>
-
-<p>Speaking with some experience, the writer has found
-that instruction in the principles underlying the science
-and sport of aviation must be vitalized by some contemporaneous
-study of what is being accomplished in the air.
-No one of the revolutionizing inventions of man has progressed
-as rapidly as aerial navigation. The &ldquo;truths&rdquo; of
-today are the absurdities of tomorrow.</p>
-
-<p>The suggestion that some grasp of the principles and a
-very fair knowledge of the current practices in aeronautics
-may be had without special technical knowledge came
-almost automatically. If this book is comprehensible to
-the lay reader, and if it conveys to him even a small proportion
-of the writer&rsquo;s conviction that flying machines are
-to profoundly influence our living in the next generation,
-it will have accomplished its author&rsquo;s purpose.</p>
-
-<p>
-<span class="sc"><br />Polytechnic Institute of Brooklyn,<br />
- &nbsp; &nbsp; &nbsp; New York</span>, April, 1911.<br />
-</p>
-
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_xi" id="Page_xi">[Pg xi]</a></span></p>
-<h2>CONTENTS</h2>
-<table summary="Table of Contents">
-
-<tr><td> </td> <td class="page_no small">PAGE</td></tr>
-
-<tr>
-<td class="chaptertext">THE DELIGHTS AND DANGERS OF FLYING.&mdash;
-<span class="sc">Dangers of Aviation.&mdash;What it is Like to Fly</span></td>
-<td class="page_no"><a href="#Page_1">1</a></td>
-</tr>
-
-<tr><td class="chaptertext">SOARING FLIGHT BY MAN.&mdash;
-<span class="sc">What Holds it Up? &mdash; Lifting Power.&mdash;Why so Many Sails?&mdash;Steering</span></td>
-<td class="page_no"><a href="#Page_17">17</a></td>
-</tr>
-
-<tr>
-<td class="chaptertext">TURNING CORNERS.&mdash;<span class="sc">What Happens when Making a Turn.&mdash;Lateral Stability.&mdash;
-Wing Warping.&mdash;Automatic Control.&mdash;The Gyroscope.&mdash;Wind Gusts</span></td>
-<td class="page_no"><a href="#Page_33">33</a></td>
-</tr>
-
-<tr>
-<td class="chaptertext">AIR AND THE WIND.&mdash;<span class="sc">Sailing Balloons.&mdash;Field and Speed</span></td>
-<td class="page_no"><a href="#Page_43">43</a></td>
-</tr>
-
-<tr>
-<td class="chaptertext">GAS AND BALLAST.&mdash;<span class="sc">Buoyancy in Air.&mdash;Ascending and
-Descending.&mdash;The Ballonet.&mdash;The Equilibrator</span></td>
-<td class="page_no"><a href="#Page_57">57</a></td>
-</tr>
-
-<tr>
-<td class="chaptertext">DIRIGIBLE BALLOONS AND OTHER KINDS.&mdash;
-<span class="sc">Shapes.&mdash;Dimensions.&mdash;Fabrics.&mdash;Framing.&mdash;
-Keeping the Keel Horizontal.&mdash;Stability.&mdash;Rudders and Planes.&mdash;
-Arrangement and Accessories.&mdash;Amateur Dirigibles.&mdash;
-The Fort Omaha Plant.&mdash;Balloon Progress</span></td>
-<td class="page_no"><a href="#Page_71">71</a></td>
-</tr>
-
-<tr>
-<td class="chaptertext">THE QUESTION OF POWER.&mdash;
-<span class="sc">Resistance of Aeroplanes.&mdash;Resistance of Dirigibles.&mdash;
-Independent Speed and Time-Table.&mdash;The Cost of Speed.&mdash;The Propeller</span></td>
-<td class="page_no"><a href="#Page_101">101</a></td>
-</tr>
-
-<tr>
-<td class="chaptertext">GETTING UP AND DOWN; MODELS AND GLIDERS;
-AEROPLANE DETAILS.&mdash;<span class="sc">Launching.&mdash;Descending.&mdash;Gliders.&mdash;
-Models.&mdash;Balancing.&mdash;Weights.&mdash;Miscellaneous.&mdash;Things
-to Look After</span></td>
-<td class="page_no"><a href="#Page_121">121</a></td>
-</tr>
-
-<tr>
-<td class="chaptertext">SOME AEROPLANES.&mdash;SOME ACCOMPLISHMENTS</td>
-<td class="page_no"><a href="#Page_143">143</a></td>
-</tr>
-
-<tr>
-<td class="chaptertext">THE POSSIBILITIES IN AVIATION.&mdash;
-<span class="sc">The Case of the Dirigible.&mdash;The Orthopter.&mdash;
-The Helicopter.&mdash;Composite Types.&mdash;What is Promised</span></td>
-<td class="page_no"><a href="#Page_170">170</a></td>
-</tr>
-
-<tr>
-<td class="chaptertext">AERIAL WARFARE</td>
-<td class="page_no"><a href="#Page_189">189</a></td>
-</tr>
-</table>
-
-<p><span class="pagenumh"><a name="Page_xii" id="Page_xii">[Pg xii]</a></span></p>
-
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_xiii" id="Page_xiii">[Pg xiii]</a></span></p>
-<h2>LIST OF ILLUSTRATIONS</h2>
-
-<table summary="List of Illustrations">
-
-<tr><td> </td> <td class="page_no small">PAGE</td> </tr>
-<tr>
-<td>The Fall of Icarus</td> <td class="page_no"><i>Frontispiece</i></td></tr>
-<tr>
-<td>The Aviator</td>
-<td class="page_no"><a href="#Page_3">3</a></td></tr>
-<tr>
-<td>The Santos-Dumont &ldquo;<i>Demoiselle</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_4">4</a></td></tr>
-<tr>
-<td>View from a Balloon</td>
-<td class="page_no"><a href="#Page_9">9</a></td></tr>
-<tr>
-<td>Anatomy of a Bird&rsquo;s Wing</td>
-<td class="page_no"><a href="#Page_10">10</a></td></tr>
-<tr>
-<td>Flight of a Bird</td>
-<td class="page_no"><a href="#Page_11">11</a></td></tr>
-<tr>
-<td>In a Meteoric Shower</td>
-<td class="page_no"><a href="#Page_13">13</a></td></tr>
-<tr>
-<td>How a Boat Tacks</td>
-<td class="page_no"><a href="#Page_15">15</a></td></tr>
-<tr>
-<td>Octave Chanute</td>
-<td class="page_no"><a href="#Page_18">18</a></td></tr>
-<tr>
-<td>Pressure of the Wind</td>
-<td class="page_no"><a href="#Page_19">19</a></td></tr>
-<tr>
-<td>Forces Acting on a Kite</td>
-<td class="page_no"><a href="#Page_20">20</a></td></tr>
-<tr>
-<td>Sustaining Force in the Aeroplane</td>
-<td class="page_no"><a href="#Page_23">23</a></td></tr>
-<tr>
-<td>Direct Lifting and Resisting Forces</td>
-<td class="page_no"><a href="#Page_24">24</a></td></tr>
-<tr>
-<td>Shapes of Planes</td>
-<td class="page_no"><a href="#Page_26">26</a></td></tr>
-<tr>
-<td>Balancing Sail</td>
-<td class="page_no"><a href="#Page_28">28</a></td></tr>
-<tr>
-<td>Roe&rsquo;s Triplane at Wembley</td>
-<td class="page_no"><a href="#Page_30">30</a></td></tr>
-<tr>
-<td>Action of the Steering Rudder</td>
-<td class="page_no"><a href="#Page_31">31</a></td></tr>
-<tr>
-<td>Recent Type of Wright Biplane</td>
-<td class="page_no"><a href="#Page_31">31</a></td></tr>
-<tr>
-<td>Circular Flight</td>
-<td class="page_no"><a href="#Page_33">33</a></td></tr>
-<tr>
-<td>The Aileron</td>
-<td class="page_no"><a href="#Page_35">35</a></td></tr>
-<tr>
-<td>Wing Tipping</td>
-<td class="page_no"><a href="#Page_36">36</a></td></tr>
-<tr>
-<td>Wing Warping</td>
-<td class="page_no"><a href="#Page_37">37</a></td></tr>
-<tr>
-<td>The Gyroscope</td>
-<td class="page_no"><a href="#Page_39">39</a></td></tr>
-<tr>
-<td>Diurnal Temperatures at Different Heights</td>
-<td class="page_no"><a href="#Page_45">45</a></td></tr>
-<tr>
-<td>Seasonal Variation in Wind Velocities</td>
-<td class="page_no"><a href="#Page_47">47</a></td></tr>
-<tr>
-<td>The Wind Rose for Mt. Weather, Va.</td>
-<td class="page_no"><a href="#Page_49">49</a></td></tr>
-<tr>
-<td>Diagram of Parts of a Drifting Balloon</td>
-<td class="page_no"><a href="#Page_51">51</a></td></tr>
-<tr>
-<td>Glidden and Stevens Getting Away in the &ldquo;<i>Boston</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_52">52</a></td></tr>
-<tr>
-<td>Relative and Absolute Balloon Velocities</td>
-<td class="page_no"><a href="#Page_53">53</a></td></tr>
-<tr>
-<td>Field and Speed</td>
-<td class="page_no"><a href="#Page_53">53</a></td></tr>
-<tr>
-<td>Influence of Wind on Possible Course</td>
-<td class="page_no"><a href="#Page_54">54</a></td></tr>
-<tr>
-<td>Count Zeppelin</td>
-<td class="page_no"><a href="#Page_55">55</a></td></tr>
-<tr>
-<td>Buoyant Power of Wood</td>
-<td class="page_no"><a href="#Page_57">57</a></td></tr>
-<tr>
-<td>One Cubic Foot of Wood Loaded in Water</td>
-<td class="page_no"><a href="#Page_58">58</a></td></tr>
-<tr>
-<td>Buoyant Power of Hydrogen</td>
-<td class="page_no"><a href="#Page_59">59</a></td></tr>
-<tr>
-<td>Lebaudy&rsquo;s &ldquo;<i>Jaune</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_60">60</a></td></tr>
-<tr>
-<td>Air Balloon</td>
-<td class="page_no"><a href="#Page_62">62</a></td></tr>
-<tr>
-<td>Screw Propeller for Altitude Control</td>
-<td class="page_no"><a href="#Page_66">66</a></td></tr>
-<tr>
-<td>Balloon with Ballonets</td>
-<td class="page_no"><a href="#Page_67">67</a></td></tr>
-<tr>
-<td>Construction of the Zeppelin Balloon</td>
-<td class="page_no"><a href="#Page_68">68</a></td></tr>
-<tr>
-<td>The Equilibrator</td>
-<td class="page_no"><a href="#Page_69">69</a></td></tr>
-<tr>
-<td>Henry Giffard&rsquo;s Dirigible</td>
-<td class="page_no"><a href="#Page_71">71</a></td></tr>
-<tr>
-<td>Dirigible of Dupuy de Lome</td>
-<td class="page_no"><a href="#Page_72">72</a></td></tr>
-<tr>
-<td>Tissandier Brothers&rsquo; Dirigible Balloon</td>
-<td class="page_no"><a href="#Page_73">73</a></td></tr>
-<tr>
-<td>The &ldquo;<i>Baldwin</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_74">74</a></td></tr>
-<tr>
-<td>The &ldquo;<i>Zeppelin</i>&rdquo; on Lake Constance</td>
-<td class="page_no"><a href="#Page_75">75</a></td></tr>
-<tr>
-<td>The &ldquo;<i>Patrie</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_77">77</a></td></tr>
-<tr>
-<td>Manufacturing the Envelope of a Balloon</td>
-<td class="page_no"><a href="#Page_79">79</a></td></tr>
-<tr>
-<td>Andrée&rsquo;s Balloon, &ldquo;<i>L&rsquo;Oernen</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_80">80</a></td></tr>
-<tr>
-<td>Wreck of the &ldquo;<i>Zeppelin</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_82">82</a></td></tr>
-<tr>
-<td>Car of the &ldquo;<i>Zeppelin</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_84">84</a></td></tr>
-<tr>
-<td>Stern View of the &ldquo;<i>Zeppelin</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_86">86</a></td></tr>
-<tr>
-<td>The &ldquo;<i>Clément-Bayard</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_87">87</a></td></tr>
-<tr>
-<td>The &ldquo;<i>Ville de Paris</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_88">88</a></td></tr>
-<tr>
-<td>Car of the &ldquo;<i>Liberté</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_89">89</a></td></tr>
-<tr>
-<td>The &ldquo;<i>Zodiac No. 2</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_92">92</a></td></tr>
-<tr>
-<td>United States Signal Corps Balloon Plant at Fort Omaha</td>
-<td class="page_no"><a href="#Page_93">93</a></td></tr>
-<tr>
-<td>The &ldquo;<i>Caroline</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_94">94</a></td></tr>
-<tr>
-<td>The Ascent at Versailles, 1783</td>
-<td class="page_no"><a href="#Page_95">95</a></td></tr>
-<tr>
-<td>Proposed Dirigible</td>
-<td class="page_no"><a href="#Page_96">96</a></td></tr>
-<tr>
-<td>The &ldquo;<i>République</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_97">97</a></td></tr>
-<tr>
-<td>The First Flight for the Gordon-Bennett Cup</td>
-<td class="page_no"><a href="#Page_99">99</a></td></tr>
-<tr>
-<td>The Gnome Motor</td>
-<td class="page_no"><a href="#Page_102">102</a></td></tr>
-<tr>
-<td>Screw Propeller</td>
-<td class="page_no"><a href="#Page_103">103</a></td></tr>
-<tr>
-<td>One of the Motors of the &ldquo;<i>Zeppelin</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_104">104</a></td></tr>
-<tr>
-<td>The Four-Cycle Engine</td>
-<td class="page_no"><a href="#Page_105">105</a></td></tr>
-<tr>
-<td>Action of Two-Cycle Engine</td>
-<td class="page_no"><a href="#Page_106">106</a></td></tr>
-<tr>
-<td>Motor and Propeller</td>
-<td class="page_no"><a href="#Page_108">108</a></td></tr>
-<tr>
-<td>Two-Cylinder Opposed Engine</td>
-<td class="page_no"><a href="#Page_110">110</a></td></tr>
-<tr>
-<td>Four-Cylinder Vertical Engine</td>
-<td class="page_no"><a href="#Page_110">110</a></td></tr>
-<tr>
-<td>Head End Shapes</td>
-<td class="page_no"><a href="#Page_113">113</a></td></tr>
-<tr>
-<td>The Santos-Dumont Dirigible No. 2</td>
-<td class="page_no"><a href="#Page_115">115</a></td></tr>
-<tr>
-<td>In the Bay of Monaco: Santos-Dumont</td>
-<td class="page_no"><a href="#Page_117">117</a></td></tr>
-<tr>
-<td>Wright Biplane on Starting Rail</td>
-<td class="page_no"><a href="#Page_121">121</a></td></tr>
-<tr>
-<td>Launching System for Wright Aeroplane</td>
-<td class="page_no"><a href="#Page_122">122</a></td></tr>
-<tr>
-<td>The Nieuport Monoplane</td>
-<td class="page_no"><a href="#Page_124">124</a></td></tr>
-<tr>
-<td>A Biplane</td>
-<td class="page_no"><a href="#Page_125">125</a></td></tr>
-<tr>
-<td>Ely at Los Angeles</td>
-<td class="page_no"><a href="#Page_126">126</a></td></tr>
-<tr>
-<td>Trajectory During Descent</td>
-<td class="page_no"><a href="#Page_127">127</a></td></tr>
-<tr>
-<td>Descending</td>
-<td class="page_no"><a href="#Page_128">128</a></td></tr>
-<tr>
-<td>The Witteman Glider</td>
-<td class="page_no"><a href="#Page_130">130</a></td></tr>
-<tr>
-<td>French Monoplane</td>
-<td class="page_no"><a href="#Page_132">132</a></td></tr>
-<tr>
-<td>A Problem in Steering</td>
-<td class="page_no"><a href="#Page_133">133</a></td></tr>
-<tr>
-<td>Lejeune Biplane</td>
-<td class="page_no"><a href="#Page_134">134</a></td></tr>
-<tr>
-<td>Tellier Monoplane</td>
-<td class="page_no"><a href="#Page_135">135</a></td></tr>
-<tr>
-<td>A Monoplane</td>
-<td class="page_no"><a href="#Page_137">137</a></td></tr>
-<tr>
-<td>Cars and Framework</td>
-<td class="page_no"><a href="#Page_139">139</a></td></tr>
-<tr>
-<td>Some Details</td>
-<td class="page_no"><a href="#Page_139">139</a></td></tr>
-<tr>
-<td>Recent French Machines</td>
-<td class="page_no"><a href="#Page_141">141</a></td></tr>
-<tr>
-<td>Orville Wright at Fort Myer</td>
-<td class="page_no"><a href="#Page_143">143</a></td></tr>
-<tr>
-<td>The First Flight Across the Channel</td>
-<td class="page_no"><a href="#Page_144">144</a></td></tr>
-<tr>
-<td>Wright Motor</td>
-<td class="page_no"><a href="#Page_145">145</a></td></tr>
-<tr>
-<td>Voisin-Farman Biplane</td>
-<td class="page_no"><a href="#Page_147">147</a></td></tr>
-<tr>
-<td>The Champagne Grand Prize Flight</td>
-<td class="page_no"><a href="#Page_148">148</a></td></tr>
-<tr>
-<td>Farman&rsquo;s First Biplane</td>
-<td class="page_no"><a href="#Page_149">149</a></td></tr>
-<tr>
-<td>The &ldquo;<i>June Bug</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_150">150</a></td></tr>
-<tr>
-<td>Curtiss Biplane</td>
-<td class="page_no"><a href="#Page_151">151</a></td></tr>
-<tr>
-<td>Curtiss&rsquo; Hydro-Aeroplane at San Diego Bay</td>
-<td class="page_no"><a href="#Page_152">152</a></td></tr>
-<tr>
-<td>Flying Over the Water</td>
-<td class="page_no"><a href="#Page_153">153</a></td></tr>
-<tr>
-<td>Blériot-Voisin Cellular Biplane with Pontoons</td>
-<td class="page_no"><a href="#Page_154">154</a></td></tr>
-<tr>
-<td>Latham&rsquo;s &ldquo;<i>Antoinette</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_155">155</a></td></tr>
-<tr>
-<td>James J. Ward at Lewiston Fair</td>
-<td class="page_no"><a href="#Page_156">156</a></td></tr>
-<tr>
-<td>Marcel Penot in the &ldquo;<i>Mohawk</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_157">157</a></td></tr>
-<tr>
-<td>Santos-Dumont&rsquo;s &ldquo;<i>Demoiselle</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_159">159</a></td></tr>
-<tr>
-<td>Blériot Monoplane</td>
-<td class="page_no"><a href="#Page_160">160</a></td></tr>
-<tr>
-<td>Latham&rsquo;s Fall into the Channel</td>
-<td class="page_no"><a href="#Page_161">161</a></td></tr>
-<tr>
-<td>De Lesseps Crossing the Channel</td>
-<td class="page_no"><a href="#Page_163">163</a></td></tr>
-<tr>
-<td>The Maxim Aeroplane</td>
-<td class="page_no"><a href="#Page_164">164</a></td></tr>
-<tr>
-<td>Langley&rsquo;s Aeroplane</td>
-<td class="page_no"><a href="#Page_165">165</a></td></tr>
-<tr>
-<td>Robart Monoplane</td>
-<td class="page_no"><a href="#Page_166">166</a></td></tr>
-<tr>
-<td>Vina Monoplane</td>
-<td class="page_no"><a href="#Page_167">167</a></td></tr>
-<tr>
-<td>Blanc Monoplane</td>
-<td class="page_no"><a href="#Page_170">170</a></td></tr>
-<tr>
-<td>Melvin Vaniman Triplane</td>
-<td class="page_no"><a href="#Page_171">171</a></td></tr>
-<tr>
-<td>Jean de Crawhez Triplane</td>
-<td class="page_no"><a href="#Page_171">171</a></td></tr>
-<tr>
-<td>A Triplane</td>
-<td class="page_no"><a href="#Page_172">172</a></td></tr>
-<tr>
-<td>Giraudon&rsquo;s Wheel Aeroplane</td>
-<td class="page_no"><a href="#Page_175">175</a></td></tr>
-<tr>
-<td>Bréguet Gyroplane (Helicopter)</td>
-<td class="page_no"><a href="#Page_177">177</a></td></tr>
-<tr>
-<td>Wellman&rsquo;s &ldquo;<i>America</i>&rdquo;</td>
-<td class="page_no"><a href="#Page_181">181</a></td></tr>
-<tr>
-<td>The German Emperor Watching the Progress of Aviation</td>
-<td class="page_no"><a href="#Page_189">189</a></td></tr>
-<tr>
-<td>Automatic Gun for Attacking Airships</td>
-<td class="page_no"><a href="#Page_193">193</a></td></tr>
-<tr>
-<td>Gun for Shooting at Aeroplanes</td>
-<td class="page_no"><a href="#Page_197">197</a></td></tr>
-<tr>
-<td>Santos-Dumont Circling the Eiffel Tower</td>
-<td class="page_no"><a href="#Page_199">199</a></td></tr>
-<tr>
-<td>Latham, Farman and Paulhan</td>
-<td class="page_no"><a href="#Page_202">202</a></td></tr>
-
-</table>
-
-
-
-
-
-<!-- BEGIN PAGE ONE OF THE BOOK -->
-<hr class="chapter_rule" />
-<div>
-<p><span class="pagenum"><a name="Page_1" id="Page_1">[Pg 1]</a></span></p>
-<p id="pageonetitle" class="break">FLYING MACHINES TODAY</p>
-<h2 class="nobreak">THE DELIGHTS AND DANGERS OF FLYING</h2></div>
-
-<p>Few things have more charm for man than flight. The
-soaring of a bird is beautiful and the gliding of a yacht
-before the wind has something of the same beauty. The
-child&rsquo;s swing; the exercise of skating on good ice; a sixty-mile-an-hour
-spurt on a smooth road in a motor car; even
-the slightly passé bicycle: these things have all in their
-time appealed to us because they produce the illusion of
-flight&mdash;of progress through the intangible air with all
-but separation from the prosaic earth.</p>
-
-<p>But these sensations have been only illusions. To actually
-leave the earth and wander at will in aerial space&mdash;this
-has been, scarcely a hope, perhaps rarely even a distinct
-dream. From the days of Dædalus and Icarus, of
-Oriental flying horses and magic carpets, down to &ldquo;Darius
-Green and his flying machine,&rdquo; free flight and frenzy were
-not far apart. We were learnedly told, only a few years
-since, that sustention by heavier-than-air machines was
-impossible without the discovery, first, of some new
-matter or some new force. It is now (1911) only eight
-years since Wilbur Wright at Kitty Hawk, with the aid of
-the new (?) matter&mdash;aluminum&mdash;and the &ldquo;new&rdquo; force&mdash;the
-gasoline engine&mdash;in three successive flights proved
-that a man could travel through the air and safely descend,<span class="pagenum"><a name="Page_2" id="Page_2">[Pg 2]</a></span>
-in a machine weighing many times as much as the air it
-displaced. It is only five years since two designers&mdash;Surcouf
-and Lebaudy&mdash;built dirigible balloons approximating
-present forms, the <i>Ville de Paris</i> and <i>La Patrie</i>.
-It is only now that we average people may confidently
-contemplate the prospect of an aerial voyage for ourselves
-before we die. A contemplation not without its shudder,
-perhaps; but yet not altogether more daring than that of
-our grandsires who first rode on steel rails behind a steam
-locomotive.</p>
-
-
-<h3>The Dangers of Aviation</h3>
-
-<p>We are very sure to be informed of the fact when an
-aviator is killed. Comparatively little stir is made nowadays
-over an automobile fatality, and the ordinary railroad
-accident receives bare mention. For instruction and
-warning, accidents to air craft cannot be given too much
-publicity; but if we wish any accurate conception of
-the danger we must pay regard to factors of proportion.
-There are perhaps a thousand aeroplanes and about
-sixty dirigible balloons in the world. About 500 men&mdash;amateurs
-and professionals&mdash;are continuously engaged
-in aviation. The Aero Club of France has issued in
-that country nearly 300 licenses. In the United States,
-licenses are held by about thirty individuals. We can
-form no intelligent estimate as to the number of unlicensed
-amateurs of all ages who are constantly experimenting
-with gliders at more or less peril to life and limb.</p>
-
-<p>A French authority has ascertained the death rate<span class="pagenum"><a name="Page_3" id="Page_3">[Pg 3]</a></span>
-among air-men to have been&mdash;to date&mdash;about 6%.
-This is equivalent to about one life for 4000 miles of flight:
-but we must remember that accidents will vary rather
-with the number of ascents and descents than with the
-mileage. Four thousand miles in 100 flights would be
-much less perilous, under present conditions, than 4000
-miles in 1000 flights.</p>
-
-<div class="figcenter" style="width: 378px">
-<img src="images/pg003.jpg" alt="The Aviator"
-     width="378" height="552"/>
-</div>
-
-<p>There were 26 fatal aeroplane accidents between September
-17, 1908, and December 3, 1910. Yet in that
-period there were many thousands of ascents: 1300 were
-made in one week at the Rheims tournament alone. Of<span class="pagenum"><a name="Page_4" id="Page_4">[Pg 4]</a></span>
-the 26 accidents, 1 was due to a wind squall, 3 to collision,
-6 (apparently) to confusion of the aviator, and 12 to mechanical
-breakage. An analysis of 40 British accidents
-shows 13 to have been due to engine failures, 10 to alighting
-on bad ground, 6 to wind gusts, 5 to breakage of the
-propeller, and 6 to fire and miscellaneous causes. These
-casualties were not all fatal, although the percentage of
-fatalities in aeronautic accidents is high. The most serious
-results were those due to alighting on bad ground; long
-grass and standing grain being very likely to trip the
-machine and throw the occupant. French aviators are
-now strapping themselves to their seats in order to avoid
-this last danger.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg004.jpg" alt="The Santos-Dumont Demoiselle"
-     width="600" height="399"/>
-<div class="caption">The Santos-Dumont <i>&ldquo;Demoiselle&rdquo;</i><br />
-  <span class="normal">(From <cite>The Aeroplane</cite>,
-     by Hubbard, Ledeboer and Turner)</span></div>
-</div>
-
-<p><span class="pagenum"><a name="Page_5" id="Page_5">[Pg 5]</a></span></p>
-
-<p>Practically all of the accidents occur to those who are
-flying; but spectators may endanger themselves. During
-one of the flights of Mauvais at Madrid, in March
-of the present year, the bystanders rushed through the
-barriers and out on the field before the machine had well
-started. A woman was decapitated by the propeller,
-and four other persons were seriously injured.</p>
-
-<p>Nearly all accidents result from one of three causes: bad
-design, inferior mechanical construction, and the taking of
-unnecessary risks by the operator. Scientific design at
-the present writing is perhaps impossible. Our knowledge
-of the laws of air resistance and sustention is neither
-accurate nor complete. Much additional study and experiment
-must be carried on; and some better method of experimenting
-must be devised than that which sends a man up
-in the air and waits to see what happens. A thorough
-scientific analysis will not only make aviation safer, it will
-aid toward making it commercially important. Further
-data on propeller proportions and efficiencies, and on
-strains in the material of screws under aerial conditions,
-will do much to standardize power plant equipment. The
-excessive number of engine breakdowns is obviously related
-to the extremely light weight of the engines employed:
-better design may actually increase these weights over
-those customary at present. Great weight reduction is no
-longer regarded as essential at present speeds in aerial
-navigation: we have perhaps already gone too far in this
-respect.</p>
-
-<p><span class="pagenum"><a name="Page_6" id="Page_6">[Pg 6]</a></span></p>
-
-<p>Bad workmanship has been more or less unavoidable,
-since no one has yet had ten years&rsquo; experience in building
-aeroplanes. The men who have developed the art have
-usually been sportsmen rather than mechanics, and only
-time is necessary to show the impropriety of using &ldquo;safety
-pins&rdquo; and bent wire nails for connections.</p>
-
-<p>The taking of risks has been an essential feature. When
-one man earns $100,000 in a year by dare-devil flights,
-when the public flocks in hordes&mdash;and pays good prices&mdash;to
-see a man risk his neck, he will usually aim to satisfy
-it. This is not developing aerial navigation: this is circus
-riding&mdash;looping-the-loop performances which appeal
-to some savage instinct in us but lead us nowhere. Men
-have climbed two miles into the clouds, for no good purpose
-whatever. All that we need to know of high altitude
-conditions is already known or may be learned by ascents
-in anchored balloons. Records up to heights of sixteen
-miles have been obtained by sounding balloons.</p>
-
-<p>If these high altitudes may under certain conditions be
-desirable for particular types of balloon, they are essentially
-undesirable for the aeroplane. The supporting power of a
-heavier-than-air machine decreases in precisely inverse
-ratio with the altitude. To fly high will then involve
-either more supporting surface and therefore a structurally
-weaker machine, or greater speed and consequently a larger
-motor. It is true that the resistance to propulsion
-decreases at high altitudes, just as the supporting power
-decreases: and on this account, given only a sufficient<span class="pagenum"><a name="Page_7" id="Page_7">[Pg 7]</a></span>
-margin of supporting power, we might expect a standard
-machine to work about as well at a two-mile elevation as
-at a height of 200 feet; but rarefaction of the air at the
-higher altitudes decreases the weight of carbureted mixture
-drawn into the motor, and consequently its output.
-Any air-man who attempts to reach great heights in a
-machine not built for such purpose is courting disaster.</p>
-
-<p>Flights over cities, spectacular as they are, and popular as
-they are likely to remain, are doubly dangerous on account
-of the irregular air currents and absence of safe landing
-places. They have at last been officially discountenanced
-as not likely to advance the sport.</p>
-
-<p>All flights are exhibition flights. The day of a quiet,
-mind-your-own-business type of aerial journey has not
-yet arrived. Exhibition performances of any sort are
-generally hazardous. There were nine men killed in one
-recent automobile meet. If the automobile were used
-exclusively for races and contests, the percentage of fatalities
-might easily exceed that in aviation. It is claimed that
-no inexperienced aviator has ever been killed. This may
-not be true, but there is no doubt that the larger number
-of accidents has occurred to the better-known men from
-whom the public expects something daring.</p>
-
-<p>Probably the best summing up of the danger of aviation
-may be obtained from the insurance companies. The
-courts have decided that an individual does not forfeit
-his life insurance by making an occasional balloon trip.
-Regular classified rates for aeroplane and balloon operators<span class="pagenum"><a name="Page_8" id="Page_8">[Pg 8]</a></span>
-are in force in France and Germany. It is reported that
-Mr. Grahame-White carries a life insurance policy at 35%
-premium&mdash;about the same rate as that paid by a &ldquo;crowned
-head.&rdquo; Another aviator of a less professional type has
-been refused insurance even at 40% premium. Policies
-of insurance may be obtained covering damage to machines
-by fire or during transportation and by collisions
-with other machines; and covering liability for injuries to
-persons other than the aviator.</p>
-
-<p>On the whole, flying is an ultra-hazardous <em>occupation</em>;
-but an <em>occasional</em> flight by a competent person or by a
-passenger with a careful pilot is simply a thrilling experience,
-practically no more dangerous than many things
-we do without hesitation. Nearly all accidents have been
-due to preventable causes; and it is simply a matter of
-science, skill, perseverance, and determination to make an
-aerial excursion under proper conditions as safe as a journey
-in a motor car. Men who for valuable prizes undertake
-spectacular feats will be killed as frequently in aviation as
-in bicycle or even in automobile racing; but probably not
-very much more frequently, after design and workmanship
-in flying machines shall have been perfected. The total
-number of deaths in aviation up to February 9, 1911, is
-stated to have been forty-two.</p>
-
-<h3>What It Is Like to Fly</h3>
-
-<p>We are fond of comparing flying machines with birds,
-with fish, and with ships: and there are useful analogies
-with all three. A drifting balloon is like a becalmed ship
-or a dead fish. It moves at the speed of the aerial fluid
-about it and the occupants perceive no movement whatever.
-The earth&rsquo;s surface below appears to move in the
-opposite direction to that in which the wind carries the
-balloon. With a dirigible balloon or flying machine, the
-sensation is that of being exposed to a violent wind, against
-which (by observation of landmarks) we find that we
-progress. It is the same experience as that obtained when
-standing in an exposed position on a steamship, and we
-wonder if a bird or a fish gradually gets so accustomed to
-the opposing current as to be unconscious of it. But in
-spite of jar of motors and machinery, there is a freedom of
-movement, a detachment from earth-associations, in air
-flight, that distinguishes it absolutely from the churning
-of a powerful vessel through the waves.</p>
-
-<p><span class="pagenum"><a name="Page_9" id="Page_9">[Pg 9]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg009.jpg" alt="View from a Balloon"
-     width="600" height="375"/>
-<div class="caption">View from a Balloon</div>
-</div>
-
-<hr />
-
-<p><span class="pagenum"><a name="Page_10" id="Page_10">[Pg 10]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg010.jpg" alt="Anatomy of a Bird&rsquo;s Wing"
-     width="600" height="336"/>
-<div class="caption">Anatomy of a Bird&rsquo;s Wing<br />
-  <span class="normal">(From Walker&rsquo;s <cite>Aerial Navigation</cite>)
-  </span></div>
-</div>
-
-<hr />
-
-<p><span class="pagenum"><a name="Page_11" id="Page_11">[Pg 11]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg011.jpg" alt="Flight of a Bird"
-     width="600" height="324"/></div>
-<div class="caption">Flight of a Bird</div>
-
-<p>Birds fly in one of three ways. The most familiar bird
-   <span class="pagenum"><a name="Page_12" id="Page_12">[Pg 12]</a></span>
-flight is by a rapid wing movement which has been called
-oar-like, but which is precisely equivalent to the usual
-movement of the arms of a man in swimming. The edge
-of the wing moves forward, cutting the air; on the return
-stroke the leading edge is depressed so as to present a
-nearly flat surface to the air and thus propel the bird forward.
-A slight downward direction of this stroke serves
-to impel the flight sufficiently upward to offset the effect
-of gravity. Any man can learn to swim, but no man can
-fly, because neither in his muscular frame nor by any device
-which he can attach thereto can he exert a sufficient pressure
-to overcome his own weight against as imponderable
-a fluid as air. If air were as heavy as water, instead of
-700 times lighter, it would be as easy to fly as to swim.
-The bird can fly because of the great surface, powerful
-construction, and rapid movement of its wings, in proportion
-to the weight of its body. But compared with the
-rest of the animal kingdom, flying birds are all of small size.
-Helmholz considered that the vulture represented the
-heaviest body that could possibly be raised and kept aloft
-by the exercise of muscular power, and it is understood
-that vultures have considerable difficulty in ascending;
-so much so that unless in a position to take a short preliminary
-run they are easily captured.</p>
-
-<p>Every one has noticed a second type of bird flight&mdash;soaring.
-It is this flight which is exactly imitated in a
-glider. An aeroplane differs from a soaring bird only in
-that it carries with it a producer of forward impetus&mdash;the<span class="pagenum"><a name="Page_13" id="Page_13">[Pg 13]</a></span>
-propeller&mdash;so that the soaring flight may last indefinitely:
-whereas a soaring bird gradually loses speed and descends.</p>
-
-<div class="figcenter" style="width: 392px">
-<img src="images/pg013.jpg" alt="In a Metoric Shower"
-     width="392" height="500"/></div>
-<div class="caption">In a Meteoric Shower</div>
-
-<p>A third and rare type of bird flight has been called <em>sailing</em>.
-The bird faces the wind, and with wings outspread and
-their forward edge elevated rises while being forced backward
-under the action of the breeze. As soon as the wind<span class="pagenum"><a name="Page_14" id="Page_14">[Pg 14]</a></span>
-somewhat subsides, the bird turns and <em>soars</em> in the desired
-direction. Flight is thus accomplished without muscular
-effort other than that necessary to properly incline the wings
-and to make the turns. It is practicable only in squally
-winds, and the birds which practice &ldquo;sailing&rdquo;&mdash;the
-albatross and frigate bird&mdash;are those which live in the
-lower and more disturbed regions of the atmosphere. This
-form of flight has been approximately imitated in the
-man&oelig;uvering of aeroplanes.</p>
-
-<p>Comparison of flying machines and ships suggests many
-points of difference. Water is a fluid of great density, with
-a definite upper surface, on which marine structures
-naturally rest. A vessel in the air may be at any elevation
-in the surrounding rarefied fluid, and great attention is
-necessary to keep it at the elevation desired. The air
-has no surface. The air ship is like a submarine&mdash;the
-dirigible balloon of the sea&mdash;and perhaps rather more
-safe. An ordinary ship is only partially immersed; the
-resistance of the fluid medium is exerted over a portion
-only of its head end: but the submarine or the flying
-machine is wholly exposed to this resistance. The submarine
-is subjected to ocean currents of a very few miles
-per hour, at most; the currents to which the flying machine
-may be exposed exceed a mile a minute. Put a submarine
-in the Whirlpool Rapids at Niagara and you will have
-possible air ship conditions.</p>
-
-<p>A marine vessel may <em>tack</em>, <i>i.e.</i>, may sail partially against
-the wind that propels it, by skillful utilization of the resistance
-<span class="pagenum"><a name="Page_15" id="Page_15">[Pg 15]</a></span>
-to sidewise movement of the ship through the water:
-but the flying machine is wholly immersed in a single
-fluid, and a head wind is nothing else than a head wind,
-producing an absolute subtraction from the proper speed
-of the vessel.</p>
-
-<p><span class="pagenum"><a name="Page_16" id="Page_16">[Pg 16]</a></span></p>
-<div class="figcenter" style="width: 385px">
-<img src="images/pg015.jpg" alt="How a Boat Tacks"
-     width="385" height="500"/></div>
-<div class="caption">How a Boat Tacks</div>
-
-<p class="note">The wind always exerts a pressure, perpendicular
-to the sail, which tends to
-drift the boat sidewise (R) and also to propel
-it forward (L). Sidewise movement
-is resisted by the hull.
-An air ship cannot tack
-because there is no such
-resistance to drift.</p>
-
-<p>Aerial navigation is thus a new art, particularly when
-heavier-than-air machines are used. We have no heavier-than-water
-<em>ships</em>. The flying machine must work out its
-own salvation.</p>
-
-<div>
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_17" id="Page_17">[Pg 17]</a></span></p>
-<h2>SOARING FLIGHT BY MAN</h2></div>
-
-
-<p>Flying machines have been classified as follows:&mdash;</p>
-
-<p class="sc center">Lighter than Air</p>
-<ul>
-<li>Fixed balloon,</li>
-<li>Drifting balloon,</li>
-<li>Sailing balloon,</li>
-<li>Dirigible balloon
-  <ul class="sublist">
-  <li>rigid (Zeppelin),</li>
-  <li>ballonetted.</li>
-  </ul></li>
-</ul>
-
-<p class="sc center">Heavier than Air</p>
-<ul>
-<li>Orthopter,</li>
-<li>Helicopter,</li>
-<li>Aeroplane
-  <ul class="sublist">
-  <li>monoplane,</li>
-  <li>multiplane.</li>
-  </ul></li>
-</ul>
-
-<p>We will fall in with the present current of popular interest
-and consider the aeroplane&mdash;that mechanical grasshopper&mdash;first.</p>
-
-
-<h3 class="break">What Holds It Up?</h3>
-
-<p><span class="pagenum"><a name="Page_18" id="Page_18">[Pg 18]</a></span></p>
-<div class="figcenter" style="width: 288px">
-<img src="images/pg018.jpg" alt=" Octave Chanute (died 1910)"
-     width="288" height="550"/></div>
-<div class="caption">Octave Chanute <span class="normal">(died 1910)</span><br />
-  <span class="normal">To the researches of Chanute and Langley must be
-  ascribed much of American progress in aviation.</span></div>
-
-<p>When a flat surface like the side of a house is exposed to
-the breeze, the velocity of the wind exerts a force or pressure
-directly against the surface. This principle is taken
-into account in the design of buildings, bridges, and other<span class="pagenum"><a name="Page_19" id="Page_19">[Pg 19]</a></span>
-structures. The pressure exerted per square foot of surface
-is equal (approximately) to the square of the wind
-velocity in miles per hour, divided by 300. Thus, if the
-wind velocity is thirty miles, the pressure against a house
-wall on which it acts directly is 30 × 30 ÷ 300 = 3 pounds
-per square foot: if the wind velocity is sixty miles, the
-pressure is 60 × 60 ÷ 300 = 12 pounds: if the velocity is
-ninety miles, the pressure is 90 × 90 ÷ 300 = 27 pounds,
-and so on.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg019.jpg" alt="Pressure of the Wind"
-     width="600" height="376"/>
-</div>
-<p class="caption">Pressure of the Wind</p>
-
-<p>If the wind blows obliquely toward the surface, instead
-of directly, the pressure at any given velocity is reduced,
-but may still be considerable. Thus, in the sketch, let <i>ab</i>
-represent a wall, toward which we are looking downward,
-and let the arrow <i>V</i> represent the direction of the wind.
-The air particles will follow some such paths as those
-indicated, being deflected so as to finally escape around
-the ends of the wall. The result is that a pressure is produced
-which may be considered to act along the dotted<span class="pagenum"><a name="Page_20" id="Page_20">[Pg 20]</a></span>
-line <i>P</i>, perpendicular to the wall. This is the invariable
-law: that no matter how oblique the surface may be, with
-reference to the direction of the wind, there is always a
-pressure produced against the surface by the wind, and
-this pressure always acts <em>in a direction perpendicular to the
-surface</em>. The amount of pressure will depend upon the
-wind velocity and the obliquity or inclination of the surface
-(<i>ab</i>) with the wind (<i>V</i>).</p>
-
-<p>Now let us consider a kite&mdash;the &ldquo;immediate ancestor&rdquo;
-of the aeroplane. The surface <i>ab</i> is that of the kite itself,
-held by its string <i>cd</i>. We are standing at one side and
-looking at the <em>edge</em> of the kite. The wind is moving
-horizontally against the face of the kite, and produces a
-pressure <i>P</i> directly against the latter. The pressure tends
-both to move it toward the left and to lift it. If the tendency
-to move toward the left be overcome by the string,
-then the tendency toward lifting may be offset&mdash;and in
-practice <em>is</em> offset&mdash;by the weight of the kite and tail.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg020.jpg" alt="Forces Acting on a Kite"
-     width="600" height="412"/>
-</div>
-<div class="caption">Forces Acting on a Kite</div>
-
-<p>We may represent the two tendencies to movement
-produced by the force <i>P</i>, by drawing additional dotted
-lines, one horizontally to the left (<i>R</i>) and the other vertically (<i>L</i>);<span class="pagenum"><a name="Page_21" id="Page_21">[Pg 21]</a></span>
-and it is known that if we let the length of the
-line <i>P</i> represent to some convenient scale the amount of
-direct pressure, then the lengths of <i>R</i> and <i>L</i> will also
-represent to the same scale the amounts of horizontal and
-vertical force due to the pressure. If the weight of kite and
-tail exceeds the vertical force <i>L</i>, the kite will descend: if
-these weights are less than that force, the kite will ascend.
-If they are precisely equal to it, the kite will neither ascend
-nor descend. The ratio of <i>L</i> to <i>R</i> is determined by the
-slope of <i>P</i>; and this is fixed by the slope of <i>ab</i>; so that we
-have the most important conclusion: <em>not only does the
-amount of direct pressure (P) depend upon the obliquity of
-the surface with the breeze (as has already been shown), but
-the relation of vertical force (which sustains the kite) to horizontal
-force also depends on the same obliquity</em>. For example,
-if the kite were flying almost directly above the boy who
-held the string, so that <i>ab</i> became almost horizontal, <i>P</i>
-would be nearly vertical and <i>L</i> would be much greater
-than <i>R</i>. On the other hand, if <i>ab</i> were nearly vertical, the
-kite flying at low elevation, the string and the direct pressure
-would be nearly horizontal and <i>L</i> would be much less
-than <i>R</i>. The force <i>L</i> which lifts the kite seems to increase
-while <i>R</i> decreases, as the kite ascends: but <i>L</i> may not
-actually increase, because it depends upon the amount of
-direct pressure, <i>P</i>, as well as upon the direction of this
-pressure; and the amount of direct pressure steadily
-decreases during ascent, on account of the increasing
-obliquity of <i>ab</i> with <i>V</i>. All of this is of course dependent<span class="pagenum"><a name="Page_22" id="Page_22">[Pg 22]</a></span>
-on the assumption that the kite always has the same
-inclination to the string, and the described resolution of
-the forces, although answering for illustrative purposes,
-is technically incorrect.</p>
-
-<p>It seems to be the wind velocity, then, which holds up the
-kite: but in reality the string is just as necessary as the
-wind. If there is no string, and the wind blows the kite
-with it, the kite comes down, because the pressure is wholly
-due to a relative velocity as between kite and wind. The
-wind exerts a pressure against the rear of a railway train,
-if it happens to be blowing in that direction, and if we
-stood on the rear platform of a stationary train we should
-feel that pressure: but if the train is started up and caused
-to move at the same speed as the wind there would be no
-pressure whatever.</p>
-
-<p>One of the very first heavier-than-air flights ever recorded
-is said to have been made by a Japanese who dropped
-bombs from an immense man-carrying kite during the
-Satsuma rebellion of 1869. The kite as a flying machine
-has, however, two drawbacks: it needs the wind&mdash;it cannot
-fly in a calm&mdash;and it stands still. One early effort
-to improve on this situation was made in 1856, when a
-man was towed in a sort of kite which was hauled by a
-vehicle moving on the ground. In February of the present
-year, Lieut. John Rodgers, U.S.N., was lifted 400 feet
-from the deck of the cruiser <i>Pennsylvania</i> by a train of
-eleven large kites, the vessel steaming at twelve knots
-against an eight-knot breeze. The aviator made observations<span class="pagenum"><a name="Page_23" id="Page_23">[Pg 23]</a></span>
-and took photographs for about fifteen minutes,
-while suspended from a tail cable about 100 feet astern.
-In the absence of a sufficient natural breeze, an artificial
-wind was thus produced by the motion imparted to the
-kite; and the device permitted of reaching some destination.
-The next step was obviously to get rid of the tractive
-vehicle and tow rope by carrying propelling machinery
-on the kite. This had been accomplished by Langley in
-1896, who flew a thirty-pound model nearly a mile, using a
-steam engine for power. The gasoline engine, first employed
-by Santos-Dumont (in a dirigible balloon) in 1901,
-has made possible the present day <em>aeroplane</em>.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg023.jpg" alt="Sustaining Force in the Aeroplane"
-     width="600" height="500"/></div>
-<div class="caption">Sustaining Force in the Aeroplane</div>
-
-<p>What &ldquo;keeps it up&rdquo;, in the case of this device, is likewise
-its velocity. Looking from the side, <i>ab</i> is the sail of the
-aeroplane, which is moving toward the right at such speed
-as to produce the equivalent of an air velocity <i>V</i> to the
-left. This velocity causes the direct pressure <i>P</i>, equivalent
-to a lifting force <i>L</i> and a retarding force <i>R</i>. The latter is
-the force which must be overcome by the motor: the<span class="pagenum"><a name="Page_24" id="Page_24">[Pg 24]</a></span>
-former must suffice to overcome the whole weight of the
-apparatus. Travel in an aeroplane is like skating rapidly
-over very thin ice: the air literally &ldquo;doesn&rsquo;t have time to
-get away from underneath.&rdquo;</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg024.jpg" alt="Direct, Lifting, and Resisting Forces"
-     width="600" height="402"/></div>
-<div class="caption">Direct, Lifting, and Resisting Forces</div>
-
-<p class="note">
-If the pressure is 10 lbs. when the wind blows directly toward the
-surface (at an angle of 90 degrees), then the forces for other angles of
-direction are as shown on the diagram. The <em>amounts</em> of all forces depend
-upon the wind velocity: that assumed in drawing the diagram
-was about 55 miles per hour. But the <em>relations</em> of the forces are the
-same for the various angles, no matter what the velocity.
-</p>
-
-<p>If we designate the angle made by the wings (<i>ab</i>) with
-the horizontal (<i>V</i>) as <i>B</i>, then <i>P</i> increases as <i>B</i> increases,
-while (as has been stated) the ratio of <i>L</i> to <i>R</i> decreases.
-When the angle <i>B</i> is a right angle, the wings being in the
-position <i>a´b´</i>, <i>P</i> has its maximum value for direct wind&mdash;1/300
-of the square of the velocity, in pounds per square foot;
-but <i>L</i> is zero and <i>R</i> is equal to <i>P</i>. The plane would have no<span class="pagenum"><a name="Page_25" id="Page_25">[Pg 25]</a></span>
-lifting power. When the angle <i>B</i> becomes zero, position
-<i>a´´b´´</i>, wings being horizontal, <i>P</i> becomes zero and (so far
-as we can now judge) the plane has neither lifting power
-nor retarding force. At some intermediate position, like
-<i>ab</i>, there will be appreciable lifting and retarding forces.
-The chart shows the approximate lifting force, in pounds
-per square foot, for various angles. This force becomes a
-maximum at an angle of 45° (half a right angle). We are
-not yet prepared to consider why in all actual aeroplanes
-the angle of inclination is much less than this. The reason
-will be shown presently. At this stage of the discussion
-we may note that the lifting power per square foot of sail
-area varies with</p>
-
-<p id="p25note">
-the square of the velocity, <em>and</em><br />
-the angle of inclination.</p>
-
-<p>The total lifting power of the whole plane will also vary
-with its area. As we do not wish this whole lifting power
-to be consumed in overcoming the dead weight of the machine
-itself, we must keep the parts light, and in particular
-must use for the wings a fabric of light weight per unit of
-surface. These fabrics are frequently the same as those
-used for the envelopes of balloons.</p>
-
-<p>Since the total supporting power varies both with the
-sail area and with the velocity, we may attain a given
-capacity either by employing large sails or by using high
-speed. The size of sails for a given machine varies inversely
-as the square of the speed. The original Wright
-machine had 500 square feet of wings and a speed of forty
-<span class="pagenum"><a name="Page_26" id="Page_26">[Pg 26]</a></span>
-miles per hour. At eighty miles per hour the necessary sail
-area for this machine would be only 125 square feet; and
-at 160 miles per hour it would be only 31-1/4 square feet:
-while if we attempted to run the machine at ten miles per
-hour we should need a sail area of 8000 square feet. This
-explains why the aeroplane cannot go slowly.</p>
-
-<p>It would seem as if when two or more superposed sails
-were used, as in biplanes, the full effect of the air would
-not be realized, one sail becalming the other. Experiments
-have shown this to be the case; but there is no great reduction
-in lifting power unless the distance apart is considerably
-less than the width of the planes.</p>
-
-<p>In all present aeroplanes the sails are concaved on the
-under side. This serves to keep the air from escaping
-from underneath as rapidly as it otherwise would, and
-increases the lifting power from one-fourth to one-half over
-that given by our 1/300 rule: the divisor becoming roughly
-about 230 instead of 300.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg026.jpg" alt="Shapes of Planes"
-     width="600" height="257"/>
-</div>
-<div class="caption">Shapes of Planes</div>
-
-<p>Why are the wings placed crosswise of the machine,
-when the other arrangement&mdash;the greatest dimension
-in the line of flight&mdash;would seem to be stronger? This
-<span class="pagenum"><a name="Page_27" id="Page_27">[Pg 27]</a></span>
-is also done in order to &ldquo;keep the air from escaping from
-underneath.&rdquo; The sketch shows how much less easily
-the air will get away from below a wing of the bird-like
-spread-out form than from one relatively long and narrow
-but of the same area.</p>
-
-<p>A sustaining force of two pounds per square foot of area
-has been common in ordinary aeroplanes and is perhaps
-comparable with the results of bird studies: but this figure
-is steadily increasing as velocities increase.</p>
-
-
-<h3>Why so Many Sails?</h3>
-
-<p>Thus far a single wing or pair of wings would seem to
-fully answer for practicable flight: yet every actual aeroplane
-has several small wings at various points. The
-necessity for one of these had already been discovered in the
-kite, which is built with a balancing tail. In the sketch
-on page 18 it appears that the particles of air which are
-near the upper edge of the surface are more obstructed
-in their effort to get around and past than those near the
-lower edge. They have to turn almost completely about,
-while the others are merely deflected. This means that on
-the whole the upper air particles will exert more pressure
-than the lower particles and that the &ldquo;center of pressure&rdquo;
-(the point where the entire force of the wind may be
-assumed to act) will be, not at the center of the surface, but
-at a point some distance <em>above</em> this center. This action is
-described as the &ldquo;displacement of the center of pressure.&rdquo;
-It is known that the displacement is greatest for least<span class="pagenum"><a name="Page_28" id="Page_28">[Pg 28]</a></span>
-inclinations of surface (as might be surmised from the
-sketch already referred to), and that it is always proportional
-to the dimension of the surface in the direction of
-movement; <i>i.e.</i>, to the length of the line <i>ab</i>.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg028.jpg" alt="Balancing Sail"
-     width="600" height="305"/>
-</div>
-<div class="caption">Balancing Sail</div>
-
-<p>If the weight <i>W</i> of the aeroplane acts downward at the
-center of the wing (at <i>o</i> in the accompanying sketch),
-while the direct pressure <i>P</i> acts at some point <i>c</i> farther
-along toward the upper edge of the wing, the two forces <i>W</i>
-and <i>P</i> tend to revolve the whole wing in the direction
-indicated by the curved arrow. This rotation, in an aeroplane,
-is resisted by the use of a tail plane or planes, such
-as <i>mn</i>. The velocity produces a direct pressure <i>P´</i> on the
-tail plane, which opposes, like a lever, any rotation due to
-the action of <i>P</i>. It may be considered a matter of rather
-nice calculation to get the area and location of the tail
-plane just right: but we must remember that the amount
-of pressure <i>P´</i> can be greatly varied by changing the inclination
-of the surface <i>mn</i>. This change of inclination is
-effected by the operator, who has access to wires which are
-attached to the pivoted tail plane. It is of course permissible
-to place the tail plane <em>in front</em> of the main planes&mdash;as<span class="pagenum"><a name="Page_29" id="Page_29">[Pg 29]</a></span>
-in the original Wright machine illustrated: but in this
-case, with the relative positions of <i>W</i> and <i>P</i> already shown,
-the forward edge of the tail plane would have to be depressed
-instead of elevated. The illustration shows the
-tail built as a biplane, just as are the principal wings
-(page <a href="#Page_141">141</a>).</p>
-
-<p>Suppose the machine to be started with the tail plane in a
-horizontal position. As its speed increases, it rises and at
-the same time (if the weight is suspended from the center
-of the main planes) tilts backward. The tilting can be
-stopped by swinging the tail plane on its pivot so as to
-oppose the rotative tendency. If this control is not carried
-too far, the main planes will be allowed to maintain some
-of their excessive inclination and ascent will continue.
-When the desired altitude has been attained, the inclination
-of the main planes will, by further swinging of the tail
-plane, be reduced to the normal amount, at which the
-supporting power is precisely equal to the load; and the
-machine will be in vertical equilibrium: an equilibrium
-which demands at every moment, however, the attention
-of the operator.</p>
-
-<p>In many machines, ascent and tilting are separately
-controlled by using two sets of transverse planes, one set
-placed forward, and the other set aft, of the main planes.
-In any case, quick ascent can be produced only by an
-increase in the lifting force <i>L</i> (see sketch, page <a href="#Page_24">24</a>) of the
-main planes: and this force is increased by enlarging the
-angle of inclination of the main planes, that is, by a controlled<span class="pagenum"><a name="Page_30" id="Page_30">[Pg 30]</a></span>
-and partial tilting. The forward transverse wing
-which produces this tilting is therefore called the <em>elevating
-rudder</em> or elevating plane. The rear transverse plane
-which checks the tilting and steadies the machine is often
-described as the <em>stabilizing plane</em>. <em>Descent</em> is of course
-produced by <em>decreasing</em> the angle of inclination of the main
-planes.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg030.jpg" alt="Roe&rsquo;s Triplane at Wembley"
-     width="600" height="391"/>
-</div>
-<div class="caption">Roe&rsquo;s Triplane at Wembley<br />
-<span class="normal">(From Brewer&rsquo;s <cite>Art of Aviation</cite>)</span></div>
-
-
-<h3>Steering</h3>
-
-<p>If we need extra sails for stability and ascent or descent,
-we need them also for changes of horizontal direction.
-Let <i>ab</i> be the top view of the main plane of a machine,
-following the course <i>xy</i>. At <i>rs</i> is a vertical plane called the
-<em>steering rudder</em>. This is pivoted, and controlled by the<span class="pagenum"><a name="Page_31" id="Page_31">[Pg 31]</a></span>
-operator by means of the wires <i>t</i>, <i>u</i>. Let the rudder be
-suddenly shifted to the position <i>r´s´</i>. It will then be subjected
-to a pressure <i>P´</i> which will swing the whole machine
-into the new position shown by the dotted lines, its course
-becoming <i>x´y´</i>. The steering rudder may of course be
-double, forming a vertical biplane, as in the Wright machine
-shown below.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg031a.jpg" alt="Action of the Steering Rudder"
-     width="600" height="280"/>
-</div>
-<div class="caption">Action of the Steering Rudder</div>
-
-<p>Successful steering necessitates lateral resistance to
-drift, <i>i.e.</i>, a fulcrum. This is provided, to some extent, by
-the stays and frame of the machine; and in a much more
-ample way by the vertical planes of the original Voisin
-cellular biplane. A recent Wright machine had vertical
-planes forward probably intended for this purpose.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg031b.jpg" alt="Recent Type of Wright Biplane"
-     width="600" height="174"/>
-</div>
-<div class="caption">Recent Type of Wright Biplane</div>
-
-<p><span class="pagenum"><a name="Page_32" id="Page_32">[Pg 32]</a></span></p>
-
-<p>It now begins to appear that the aviator has a great
-many things to look after. There are many more things
-requiring his attention than have yet been suggested. No
-one has any business to attempt flying unless he is superlatively
-cool-headed and has the happy faculty of instinctively
-doing the right thing in an emergency. Give a
-chauffeur a high power automobile running at maximum
-speed on a rough and unfamiliar road, and you have some
-conception of the position of the operator of an aeroplane.
-It is perhaps not too much to say that to make the two
-positions fairly comparable we should <em>blindfold</em> the chauffeur.</p>
-
-<p>Broadly speaking, designers may be classed in one of
-two groups&mdash;those who, like the Wrights, believe in
-training the aviator so as to qualify him to properly handle
-his complicated machine; and those who aim to simplify
-the whole question of control so that to acquire the necessary
-ability will not be impossible for the average man.
-If aviation is to become a popular sport, the latter ideal
-must prevail. The machines must be more automatic
-and the aviator must have time to enjoy the scenery. In
-France, where amateur aviation is of some importance,
-progress has already been made in this direction. The universal
-steering head, for example, which not only revolves
-like that of an automobile, but is hinged to permit of
-additional movements, provides for simultaneous control
-of the steering rudder and the main plane warping, while
-scarcely demanding the conscious thought of the operator.</p>
-
-<div>
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_33" id="Page_33">[Pg 33]</a></span></p>
-<h2>TURNING CORNERS</h2></div>
-
-<p>A year elapsed after the first successful flight at Kitty
-Hawk before the aviator became able to describe a circle
-in the air. A later date, 1907, is recorded for the first
-European half-circular flight: and the first complete
-circuit, on the other side of the water, was made a year
-after that; by both biplane and monoplane. It was in
-the same year that Louis Blériot made the pioneer cross-country
-trip of twenty-one miles, stopping at will <i>en route</i>
-and returning to his starting point.</p>
-
-
-<h3>What Happens When Making a Turn</h3>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg033.jpg" alt="Circular Flight"
-     width="600" height="364"/>
-</div>
-
-<p>We are looking downward on an aeroplane <i>ab</i> which
-has been moving along the straight path <i>cd</i>. At <i>d</i> it begins
-to describe the circle <i>de</i>, the radius of which is <i>od</i>, around<span class="pagenum"><a name="Page_34" id="Page_34">[Pg 34]</a></span>
-the center <i>o</i>. The outer portion of the plane, at the edge
-<i>b</i>, must then move faster than the inner edge <i>a</i>. We have
-seen that the direct air pressure on the plane is proportional
-to the square of the velocity. The direct pressure
-<i>P</i> (see sketch on page <a href="#Page_22">22</a>) will then be greater at the outer
-than at the inner limb; the lifting force <i>L</i> will also be greater
-and the outer limb will tend to rise, so that the plane
-(viewed from the rear) will take the inclined position shown
-in the lower view: and this inclination will increase as long
-as the outer limb travels faster than the inner limb; that
-is, as long as the orbit continues to be curved. Very soon,
-then, the plane will be completely tipped over.</p>
-
-<p>Necessarily, the two velocities have the ratio <i>om</i>:<i>om´</i>;
-the respective lifting forces must then be proportional to
-the squares of these distances. The difference of lifting
-forces, and the tendency to overturn, will be more important
-as the distances most greatly differ: which is the
-case when the distance <i>om</i> is small as compared with <i>mm´</i>.
-The shorter the radius of curvature, the more dangerous,
-for a given machine, is a circling flight: and in rounding a
-curve of given radius the most danger is attached to the
-machine of greatest spread of wing.</p>
-
-
-<h3>Lateral Stability</h3>
-
-<p>This particular difficulty has considerably delayed the
-development of the aeroplane. It may, however, be overcome
-by very simple methods&mdash;simple, at least as far as
-their mechanical features are concerned. If the outer<span class="pagenum"><a name="Page_35" id="Page_35">[Pg 35]</a></span>
-limb of the plane is tilted upward, it is because the wind
-pressure is greater there. The wind pressure is greater
-because the velocity is greater. We have only to increase
-the wind pressure at the inner limb, in order to restore
-equilibrium. This cannot be done by adjusting the velocity,
-because the velocity is fixed by the curvature of path required:
-but the total wind pressure depends upon the <em>sail
-area</em> as well as the velocity; so that by increasing the surface
-at the inner limb we may equalize the value of <i>L</i>, the
-lifting force, at the two ends of the plane. This increase
-of surface must be a temporary affair, to be discontinued
-when moving along a straight course.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg035.jpg" alt="The Aileron"
-     width="600" height="279"/>
-</div>
-<div class="caption">The Aileron</div>
-
-<p>Let us stand in the rear of an aeroplane, the main wing
-of which is represented by <i>ab</i>. Let the small fan-shaped
-wings <i>c</i> and <i>d</i> be attached near the ends, and let the control
-wires, <i>e</i>, <i>f</i>, passing to the operator at <i>g</i>, be employed to close
-and unclasp the fans. If these fans are given a forward
-inclination at the top, as indicated in the end view, they
-will when spread out exert an extra lifting force. A fan<span class="pagenum"><a name="Page_36" id="Page_36">[Pg 36]</a></span>
-will be placed at each end. They will be ordinarily folded
-up: but when rounding a curve the aviator will open the
-fan on the inner or more slowly moving limb of the main
-plane. This represents one of the first forms of the <i>aileron</i>
-or wing-tip for lateral control.</p>
-
-<p>The more common present form of aileron is that shown
-in the lower sketch, at <i>s</i> and <i>t</i>. The method of control is
-the same.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg036.jpg" alt="Wing Tipping"
-    width="600" height="163"/>
-</div>
-<div class="caption">Wing Tipping</div>
-
-<p>The cellular Voisin biplanes illustrate an attempt at
-self-sufficing control, without the interposition of the aviator.
-Between the upper and lower sails of the machine
-there were fore and aft vertical partitions. The idea was
-that when the machine started to revolve, the velocity of
-rotation would produce a pressure against these partitions
-which would obstruct the tipping. But rotation may take
-place slowly, so as to produce an insufficient pressure for
-control, and yet be amply sufficient to wreck the apparatus.
-The use of extra vertical rudder planes, hinged on a horizontal
-longitudinal axis, is open to the same objection.</p>
-
-
-<h3>Wing Warping</h3>
-
-<p>In some monoplanes with the inverted <i>V</i> wing arrangement,
-a dipping of one wing answers, so to speak, to increase<span class="pagenum"><a name="Page_37" id="Page_37">[Pg 37]</a></span>
-its concavity and thus to augment the lifting force on that
-side. The sketch shows the normal and distorted arrangement
-of wings: the inner limb being the one bent down in
-rounding a curve. An equivalent plan was to change the
-angle of inclination of one-half the sail by swinging it
-about a horizontal pivot at the center or at the rear
-edge: some machines have been built with sails divided
-in the center. The obvious objection to both of these
-plans is that too much mechanism is necessary in order
-to distort what amounts to nearly half the whole machine.
-They remind one of Charles Lamb&rsquo;s story of the
-discovery of roast pig.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg037.jpg" alt="Wing Warping"
-     width="600" height="395"/>
-</div>
-<div class="caption">Wing Warping</div>
-
-<p>The distinctive feature of the Wright machines lies in
-the warping or distorting of the <em>ends only</em> of the main
-planes. This is made possible, not by hinging the wings in
-halves, but by the flexibility of the framework, which is
-sufficiently pliable to permit of a considerable bending
-without danger. The operator, by pulling on a stout wire
-linkage, may tip up (or down) the corners <i>cc´</i> of the sails
-at one limb, thus decreasing or increasing the effective
-surface acted on by the wind, as the case may require.<span class="pagenum"><a name="Page_38" id="Page_38">[Pg 38]</a></span>
-The only objection is that the scheme provides one more
-thing for the aviator to think about and manipulate.</p>
-
-
-<h3>Automatic Control</h3>
-
-<p>Let us consider again the condition of things when
-rounding a curve, as in the sketch on page <a href="#Page_32">32</a>. As long
-as the machine is moving forward in a straight line, the
-operator sits upright. When it begins to tip, he will unconsciously
-tip himself the other way, as represented by
-the line <i>xy</i> in the rear view. Any bicyclist will recognize
-this as plausible. Why not take advantage of this involuntary
-movement to provide a stabilizing force? If operating
-wires are attached to the aviator&rsquo;s belt and from thence
-connected with ailerons or wing-warping devices, then by
-a proper proportioning of levers and surfaces to the probable
-swaying of the man, the control may become automatic.
-The idea is not new; it has even been made the subject of
-a patent.</p>
-
-
-<h3 class="break">The Gyroscope</h3>
-
-<div class="figcenter" style="width: 460px">
-<img src="images/pg039.jpg" alt="The Gyroscope"
-     width="460" height="500"/>
-</div>
-<div class="caption">The Gyroscope</div>
-
-<p>This device for automatic control is being steadily
-developed and may ultimately supersede all others. It
-uses the inertia of a fast-moving fly wheel for control, in a
-manner not unlike that contemplated in proposed methods
-of automatic balancing by the action of a suspended pendulum.
-Every one has seen the toy gyroscope and perhaps
-has wondered at its mysterious ways. The mathematical
-analysis of its action fills volumes: but some idea of what
-it does, and why, may perhaps be gathered at the expense<span class="pagenum"><a name="Page_39" id="Page_39">[Pg 39]</a></span>
-of a very small amount of careful attention. The wheel
-<i>acbd</i>, a thin disc, is spinning rapidly about the axle <i>o</i>. In
-the side view, <i>ab</i> shows the edge of the wheel, and <i>oo´</i> the
-axle. This axle is not fixed, but may be conceived as held
-in some one&rsquo;s fingers. Now suppose the right-hand end
-of the axle (<i>o´</i>) to be suddenly moved toward us (away
-from the paper) and the left-hand (<i>o</i>) to be moved away.<span class="pagenum"><a name="Page_40" id="Page_40">[Pg 40]</a></span>
-The wheel will now appear in both views as an ellipse, and
-it has been so represented, as <i>afbe</i>. Now, any particle, like
-<i>x</i>, on the rim of the wheel, will have been regularly moving
-in the circular orbit <i>cb</i>. The tendency of any body in
-motion is to move indefinitely in a straight line. The
-cohesion of the metal of the disc prevents the particle <i>x</i>
-from flying off at a straight line tangent, <i>xy</i>, and it is constrained,
-therefore, to move in a circular orbit. Unless
-some additional constraint is imposed, it will at least
-remain in this orbit and will try to remain in its plane of
-rotation. When the disc is tipped, the plane of rotation
-is changed, and the particle is required, instead of (so to
-speak) remaining in the plane of the paper&mdash;in the side
-view&mdash;to approach and pass through that plane at <i>b</i> and
-afterward to continue receding from us. Under ordinary
-circumstances, this is just what it would do: but if, as in
-the gyroscope, the axle <i>oo´</i> is perfectly free to move in any
-direction, the particle <i>x</i> will refuse to change its direction
-of rotation. Its position has been shifted: it no longer
-lies in the plane of the paper: but it will at least persist
-in rotating in a parallel plane: and this persistence forces
-the revolving disc to swing into the new position indicated
-by the curve <i>hg</i>, the axis being tipped into the
-position <i>pq</i>. The whole effect of all particles like <i>x</i>
-in the entire wheel will be found to produce precisely
-this condition of things: if we undertake to change the
-plane of rotation by shifting the axle in a horizontal
-plane, the device itself will (if not prevented) make a<span class="pagenum"><a name="Page_41" id="Page_41">[Pg 41]</a></span>
-further change in the plane of rotation by shifting the
-axle in a vertical plane.</p>
-
-<p>A revolving disc mounted on the gyroscopic framework
-therefore resists influences tending to change its plane of
-rotation. If the device is placed on a steamship, so that
-when the vessel rolls a change of rotative plane is produced,
-the action of the gyroscope will resist the rolling tendency
-of the vessel. All that is necessary is to have the wheel
-revolving in a fore and aft plane on the center line of the
-vessel, the axle being transverse and firmly attached to
-the vessel itself. A small amount of power (consumed in
-revolving the wheel) gives a marked steadying effect. The
-same location and arrangement on an aeroplane will suffice
-to overcome tendencies to transverse rotation when rounding
-curves. The device itself is automatic, and requires
-no attention, but it does unfortunately require power to
-drive it and it adds some weight.</p>
-
-<p>The gyroscope is being tested at the present time on
-some of the aeroplanes at the temporary army camps
-near San Antonio, Texas.</p>
-
-
-<h3>Wind Gusts</h3>
-
-<p>This feature of aeronautics is particularly important,
-because any device which will give automatic stability
-when turning corners will go far toward making aviation
-a safe amusement. Inequalities of velocity exist not only
-on curves, but also when the wind is blowing at anything
-but uniform velocity across the whole front of the machine.<span class="pagenum"><a name="Page_42" id="Page_42">[Pg 42]</a></span>
-The slightest &ldquo;flaw&rdquo; in the wind means an at least temporary
-variation in lifting force of the two arms. Here is a
-pregnant source of danger, and one which cannot be left
-for the aviator to meet by conscious thought and action.
-It is this, then, that blindfolds him: he cannot see the
-wind conditions in advance. The conditions are upon
-him, and may have done their destructive work, before
-he can prepare to control them. We must now study
-what these conditions are and what their influence may
-be on various forms of aerial navigation: after which,
-a return to our present subject will be possible.</p>
-
-<div>
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_43" id="Page_43">[Pg 43]</a></span></p>
-<h2>AIR AND THE WIND</h2></div>
-
-<p>The air that surrounds us weighs about one-thirteenth
-of a pound per cubic foot and exerts a pressure, at sea
-level, of nearly fifteen pounds per square inch. Its temperature
-varies from 30° below to 100° above the Fahrenheit
-zero. The pressure of the air decreases about one-half
-pound for each thousand feet of altitude; at the top
-of Mt. Blanc it would be, therefore, only about six pounds
-per square inch. The temperature also decreases with the
-altitude. The weight of a cubic foot, or <em>density</em>, which,
-as has been stated, is one-thirteenth of a pound ordinarily,
-varies with the pressure and with the temperature. The
-variation with pressure may be described by saying that
-the <em>quotient</em> of the pressure by the density is constant:
-one varies in the same ratio as the other. Thus, at the
-top of Mt. Blanc (if the temperature were the same as at
-sea level), the density of air would be about 6/15 × 1/13 = 2/65:
-less than half what it is at sea level. As to temperature,
-if we call our Fahrenheit zero 460°, and correspondingly
-describe other temperatures&mdash;for instance, say that water
-boils at 672°&mdash;then (pressure being unchanged) the <em>product</em>
-of the density and the temperature is constant. If the
-density at sea level and zero temperature is one-thirteenth
-pound, then that at sea level and 460° Fahrenheit would be</p>
-
-<p><span class="pagenum"><a name="Page_44" id="Page_44">[Pg 44]</a></span></p>
-
-<p class="center">
-(0 + 460) / (460 + 460) × 1/13 = 1/26.<br />
-</p>
-
-<p>These relations are particularly important in the design
-of all balloons, and in computations relating to aeroplane
-flight at high altitudes. We shall be prepared to appreciate
-some of their applications presently.</p>
-
-<p>Generally speaking, the atmosphere is always in motion,
-and moving air is called wind. Our meteorologists first
-studied winds near the surface of the ground: it is only
-of late years that high altitude measurements have been
-considered practically desirable. Now, records are obtained
-by the aid of kites up to a height of nearly four
-miles: estimates of cloud movements have given data
-on wind velocities at heights above six miles: and much
-greater heights have been obtained by free balloons equipped
-with instruments for recording temperatures, pressures,
-altitude, time, and other data.</p>
-
-<p>When the Eiffel Tower was completed, it was found that
-the average wind velocity at its summit was about four
-times that at the base. Since that time, much attention
-has been given to the contrasting conditions of surface and
-upper breezes as to direction and velocity.</p>
-
-<p>Air is easily impeded in its movement, and the well-known
-uncertainties of the weather are closely related to
-local variations in atmospheric pressure and temperature.
-When near the surface of the ground, impingement against
-irregularities therein&mdash;hills, cliffs, and buildings&mdash;makes
-the atmospheric currents turbulent and irregular. Where<span class="pagenum"><a name="Page_45" id="Page_45">[Pg 45]</a></span>
-there are no surface irregularities, as on a smooth plain
-or over water, the friction of the air particles passing over
-the surface still results in a stratification of velocities.
-Even on a mountain top, the direction and speed of the
-wind are less steady than in the open where measured by
-a captive balloon. The stronger the wind, the greater,
-relatively, is the irregularity produced by surface conditions.
-Further, the earth&rsquo;s surface and its features form a
-vast sponge for sun heat, which they transfer in turn to the
-air in an irregular way, producing those convectional currents
-peculiar to low altitudes, the upper limit of which is
-marked by the elevation of the cumulus clouds. Near the
-surface, therefore, wind velocities are lowest in the early
-morning, rising to a maximum in the afternoon.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg045.jpg" alt="Diurnal Temperatures at Different Heights"
-     width="600" height="395"/>
-</div>
-<div class="caption">Diurnal Temperatures at Different Heights<br />
-<span class="normal">
-(From Rotch&rsquo;s <cite>The Conquest of the Air</cite>)
-</span>
-</div>
-
-<p>Every locality has its so-called &ldquo;prevailing winds.&rdquo;
-Considering the compass as having eight points, one of<span class="pagenum"><a name="Page_46" id="Page_46">[Pg 46]</a></span>
-those points may describe as many as 40% of all the winds
-at a given place. The direction of prevalence varies with
-the season. The range of wind velocities is also a matter of
-local peculiarity. In Paris, the wind speed exceeds thirty-four
-miles per hour on only sixty-eight days in the average
-year, and exceeds fifty-four miles on only fifteen days.
-Observations at Boston show that the velocity of the wind
-exceeds twenty miles per hour on half the days in winter
-and on only one-sixth the days in summer. Our largest
-present dirigible balloons have independent speeds of
-about thirty-four miles per hour and are therefore available
-(at some degree of effectiveness) for nearly ten months of
-the year, in the vicinity of Paris. In a region of low wind
-velocities&mdash;like western Washington, in this country&mdash;they
-would be available a much greater proportion of the
-time. To make the dirigible able to at least move nearly
-every day in the average year&mdash;in Paris&mdash;it must be
-given a speed of about fifty-five miles per hour.</p>
-
-<p>Figures as to wind velocity mean little to one unaccustomed
-to using them. A five-mile breeze is just &ldquo;pleasant.&rdquo;
-Twelve miles means a brisk gale. Thirty miles
-is a high wind: fifty miles a serious storm (these are the
-winds the aviator constantly meets): one hundred miles
-is perhaps about the maximum hurricane velocity.</p>
-
-<p>As we ascend from the surface of the earth, the wind
-velocity steadily increases; and the excess velocity of
-winter winds over summer winds is as steadily augmented.
-Thus, Professor Rotch found the following variations:</p>
-
-<p><span class="pagenum break"><a name="Page_47" id="Page_47">[Pg 47]</a></span></p>
-
-<table summary="Table of Annual Average Wind Velocity">
-<tr><td class="w20"></td><td class="w10"></td><td class="w20"></td>
-    <td class="w20"></td><td class="w10"></td><td class="w20"></td></tr>
-<tr><td class="tdc sc" colspan="3">Altitude in Feet</td>
-<td class="tdc sc" colspan="3">Annual Average Wind</td></tr>
-<tr><td class="tdc sc" colspan="3"> </td>
-<td class="tdc sc" colspan="3">Velocity, Feet per Second</td></tr>
-
-<tr><td> </td><td class="tdr">   656</td><td> </td> <td> </td><td>&nbsp; 23.15</td><td> </td></tr>
-<tr><td> </td><td class="tdr"> 1,800</td><td> </td> <td> </td><td>&nbsp; 32.10</td><td> </td></tr>
-<tr><td> </td><td class="tdr"> 3,280</td><td> </td> <td> </td><td>&nbsp; 35.  </td><td> </td></tr>
-<tr><td> </td><td class="tdr"> 8,190</td><td> </td> <td> </td><td>&nbsp; 41.  </td><td> </td></tr>
-<tr><td> </td><td class="tdr">11,440</td><td> </td> <td> </td><td>&nbsp; 50.8 </td><td> </td></tr>
-<tr><td> </td><td class="tdr">17,680</td><td> </td> <td> </td><td>&nbsp; 81.7 </td><td> </td></tr>
-<tr><td> </td><td class="tdr">20,970</td><td> </td> <td> </td><td>&nbsp; 89.  </td><td> </td></tr>
-<tr><td> </td><td class="tdr">31,100</td><td> </td> <td> </td><td>117.5 </td><td> </td></tr>
-
-</table>
-
-<hr />
-
-<table summary="Summer and Winter Wind Velocities" >
-<tr><td class="w5"></td><td class="w30"></td><td class="w5"></td>
-    <td class="w5"></td><td class="w20"></td><td class="w5"></td>
-    <td class="w5"></td><td class="w20"></td><td class="w5"></td></tr>
-<tr><td></td><td class="sc tdr">Altitude in Feet</td><td></td>
-    <td> </td>
-    <td class="sc tdc" colspan="5">Average Wind Velocities,<br /> Feet per Second</td></tr>
-<tr><td colspan="4"></td>
-    <td>Summer</td> <td colspan="2"></td> <td>Winter</td><td></td></tr>
-<tr> <td></td><td class="tdr">656 to&nbsp; 3,280</td><td></td>
-     <td></td><td>24.55</td><td></td> <td></td><td>28.80</td><td></td></tr>
-<tr> <td></td><td class="tdr">3,280 to&nbsp; 9,810</td><td></td>
-     <td></td><td>26.85</td><td></td> <td></td><td>48.17</td><td></td></tr>
-<tr> <td></td><td class="tdr">9,810 to 16,400</td><td></td>
-     <td></td><td>34.65</td><td></td> <td></td><td>71.00</td><td></td></tr>
-<tr> <td></td><td class="tdr">16,400 to 22,950</td><td></td>
-     <td></td><td>62.60</td><td></td> <td></td><td>161.5</td><td></td></tr>
-<tr> <td></td><td class="tdr">22,950 to 29,500</td><td></td>
-     <td></td><td>77.00</td><td></td> <td></td><td>177.0</td><td></td></tr>
-</table>
-
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg047.jpg" alt="Seasonal Variation in Wind Velocities"
-     width="600" height="571"/>
-</div>
-
-<p>These results are shown in a more striking way by the
-chart. At a five or six mile height, double-barreled hurricanes
-at speeds exceeding 200 miles per hour are not<span class="pagenum"><a name="Page_48" id="Page_48">[Pg 48]</a></span>
-merely possible; they are part of the regular order of
-things, during the winter months.</p>
-
-<p>The winds of the upper air, though vastly more powerful,
-are far less irregular than those near the surface: and
-the directions of prevailing winds are changed. If 50%
-of the winds, at a given location on the surface, are from
-the southwest, then at as moderate an elevation as even
-1000 feet, the prevailing direction will cease to be from
-southwest; it may become from west-southwest; and the
-proportion of total winds coming from this direction will
-not be 50%. These factors are represented in meteorological
-papers by what is known as the <em>wind rose</em>. From the
-samples shown, we may note that 40% of the surface
-winds at Mount Weather are from the northwest; while
-at some elevation not stated the most prevalent of the
-winds (22% of the total) are westerly. The direction of
-prevalence has changed through one-eighth of the possible
-circle, and in a <em>counter-clockwise</em> direction. This is contrary
-to the usual variation described by the so-called
-Broun&rsquo;s Law, which asserts that as we ascend the direction
-of prevalence rotates around the circle like the hands
-of a watch; being, say, from northwest at the surface,
-from north at some elevation, from northeast at a still
-higher elevation, and so on. At a great height, the change
-in direction may become total: that is, the high altitude
-winds blow in the exactly opposite direction to that of the
-surface winds. In the temperate regions, most of the
-high altitude winds are from the west: in the tropics,
-the surface winds blow <em>toward</em> the west and toward the
-equator; being northeasterly in the northern hemisphere
-and southeasterly in the southern: and there are undoubtedly
-equally prevalent high-altitude counter-trades.</p>
-
-<p><span class="pagenum"><a name="Page_49" id="Page_49">[Pg 49]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg049.jpg" alt="The Wind Rose for Mount Weather, Va."
-     width="600" height="319"/>
-</div>
-<div class="caption"> The Wind Rose for Mount Weather, Va.<br />
-<span class="normal">
-(From the <cite>Bulletin</cite> of the Mount Weather Observatory, II, 6)
-</span>
-</div>
-
-<p>
-<span class="pagenum"><a name="Page_50" id="Page_50">[Pg 50]</a></span>
-The best flying height for an aeroplane over a flat field
-out in the country is perhaps quite low&mdash;200 or 300 feet:
-but for cross-country trips, where hills, rivers, and buildings
-disturb the air currents, a much higher elevation is necessary;
-perhaps 2000 or 3000 feet, but in no case more than
-a mile. The same altitude is suitable for dirigible balloons.
-At these elevations we have the conditions of reasonable
-warmth, dryness, and moderate wind velocities.</p>
-
-
-<h3>Sailing Balloons</h3>
-
-<p>In classifying air craft, the sailing balloon was mentioned
-as a type intermediate between the drifting balloon and
-the dirigible. No such type has before been recognized:
-but it may prove to have its field, just as the sailing vessel
-on the sea has bridged the gap between the raft and the
-steamship. It is true that tacking is impossible, so that
-our sailing balloons must always run before the wind: but
-they possess this great advantage over marine sailing craft,
-that by varying their altitude they may always be able to
-find a favorable wind. This implies adequate altitude
-control, which is one of the problems not yet solved for
-lighter-than-air flying machines: but when it has been
-solved we shall go far toward attaining a dirigible balloon
-without motor or propeller; a true sailing craft.</p>
-
-<p><span class="pagenum"><a name="Page_51" id="Page_51">[Pg 51]</a></span></p>
-
-<div class="figcenter" style="width: 504px">
-<img src="images/pg051.jpg" alt="Diagram of Parts of a Drifting Balloon"
-     width="504" height="500"/>
-</div>
-<div class="caption">Diagram of Parts of a Drifting Balloon</div>
-
-
-<p>This means more study and careful utilization of stratified
-atmospheric currents. Professor Rotch suggests the
-utilization of the upper westerly wind drift across the
-American continent and the Atlantic Ocean, which would
-carry a balloon from San Francisco to southern Europe at
-a speed of about fifty feet per second&mdash;thirty-four miles
-per hour. Then by transporting the balloon to northern
-Africa, the northeast surface trade wind would drive it
-back to the West Indies at twenty-five miles per hour.
-This without any motive power: and since present day
-dirigibles are all short of motive power for complete<span class="pagenum"><a name="Page_52" id="Page_52">[Pg 52]</a></span>
-dirigibility, we must either make them much more powerful
-or else adopt the sailing principle, which will permit of
-actually decreasing present sizes of motors, or even possibly
-of omitting them altogether. Our next study is, then,
-logically, one of altitude control in balloons.</p>
-
-
-
-<div class="figcenter" style="width: 332px">
-<img src="images/pg052.jpg" alt="Glidden and Stevens Getting Away in the Boston"
-     width="332" height="502"/>
-</div>
-<div class="caption">Glidden and Stevens Getting Away in the <i>"Boston"</i><br />
-  <span class="normal">(Leo Stevens, N.Y.)</span>
-</div>
-
-<p><span class="pagenum"><a name="Page_53" id="Page_53">[Pg 53]</a></span></p>
-<h3 class="break">Field and Speed</h3>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg053a.jpg" alt="Relative and Absolute Balloon Velocities"
-     width="600" height="272"/>
-</div>
-
-<hr />
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg053b.jpg" alt="Field and Speed"
-     width="600" height="358"/>
-</div>
-
-<p>An <em>aerostat</em> (non-dirigible balloon), unless anchored,
-drifts at the speed of the wind. To the occupants, it seems
-to stand still, while the surface of the earth below appears
-to move in a direction opposite to that of the wind. In
-the sketch, if the independent velocity of a <em>dirigible</em> balloon
-be <i>PB</i>, the wind velocity <i>PV</i>, then the actual course pursued
-is <i>PR</i>, although the balloon always points in the
-direction <i>PB</i>, as shown at 1 and 2. If the speed of the wind
-exceed that of the balloon, there will be some directions
-in which the latter cannot progress. Thus, let <i>PV</i> be the
-wind velocity and <i>TV</i> the independent speed of the balloon.
-The tangents <i>PX</i>, <i>PX´</i>, include the whole &ldquo;field of action&rdquo;
-possible. The wind direction may change during flight,<span class="pagenum"><a name="Page_54" id="Page_54">[Pg 54]</a></span>
-so that the initial objective point may become unattainable,
-or an initially unattainable point may be brought
-within the field. The present need is to increase independent
-speeds from thirty or forty to fifty or sixty miles
-per hour, so that the balloon will be truly dirigible (even if
-at low effectiveness) during practically the whole year.</p>
-
-
-<div class="figcenter" style="width: 470px">
-<img src="images/pg054.jpg" alt="Influence of Wind on Possible Course"
-     width="470" height="500"/>
-</div>
-
-<p>Suppose a dirigible to start on a trip from New York
-to Albany, 150 miles away. Let the wind be a twenty-five
-mile breeze from the southwest. The wind alone tends to
-carry the balloon from New York to the point <i>d</i> in four
-hours. If the balloon meanwhile be headed due west, it
-would need an independent velocity of its own having the
-same ratio to that of the wind as that of <i>de</i> to <i>fd</i>, or about
-seventeen and one-half miles per hour. Suppose its independent<span class="pagenum"><a name="Page_55" id="Page_55">[Pg 55]</a></span>
-speed to be only twelve and one-half miles; then
-after four hours it will be at the position <i>b</i>, assuming
-it to have been continually headed due west, as indicated
-at <i>a</i>. It will have traveled northward the distance <i>fe</i>,
-apparently about sixty-nine miles.</p>
-
-<div class="figcenter" style="width: 392px">
-<img src="images/pg055.jpg" alt="Count Zeppelin"
-     width="392" height="500"/>
-</div>
-<div class="caption">Count Zeppelin</div>
-
-<p>After this four hours of flight, the wind suddenly changes
-to south-southwest. It now tends to carry the balloon to<span class="pagenum"><a name="Page_56" id="Page_56">[Pg 56]</a></span>
-<i>g</i> in the next four hours. Meanwhile the balloon, heading
-west, overcomes the easterly drift, and the balloon actually
-lands at <i>c</i>. Unless there is some further favorable shift
-of the wind it cannot reach Albany. If, during the second
-four hours, its independent speed could have been increased
-to about fifteen and a half miles it would have just made it.
-The actual course has been <i>fbc</i>: a drifting balloon would
-have followed the course <i>fdh</i>, <i>dh</i> being a course parallel
-to <i>bg</i>.</p>
-
-<div>
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_57" id="Page_57">[Pg 57]</a></span></p>
-<h2>GAS AND BALLAST</h2></div>
-
-<p>A cubical block of wood measuring twelve inches on a
-side floats on water because it is lighter than water; it
-weighs, if yellow pine, thirty-eight pounds, whereas the
-same volume of water weighs about sixty-two pounds.
-Any substance weighing more than sixty-two pounds to
-the cubic foot would sink in water.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg057.jpg" alt="Buoyant Power of Wood"
-     width="600" height="355"/>
-</div>
-<div class="caption">Buoyant Power of Wood</div>
-
-<p>If our block of wood be drilled, and <em>lead</em> poured in the
-hole, the total size of wood-and-lead block being kept constantly
-at one cubic foot, the block will sink as soon as its
-whole weight exceeds sixty-two pounds. Ignoring the
-wood removed by boring (as, compared with the lead
-which replaces it, an insignificant amount), the weight of
-lead plugged in may reach twenty-four pounds before the
-block will sink.</p>
-
-<p>This figure, twenty-four pounds, the difference between<span class="pagenum"><a name="Page_58" id="Page_58">[Pg 58]</a></span>
-sixty-two and thirty-eight pounds, then represents the
-maximum buoyant power of a cubic foot of wood in water.
-It is the difference between the weight of the wood block
-and the weight of the water it displaces. If any weight
-less than this is added to that of the wood, the block will
-float, projecting above the water&rsquo;s surface more or less,
-according to the amount of weight buoyed up. It will not
-rise entirely from the water, because to do this it would
-need to be lighter, not only than water, but than air.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg058.jpg" alt="One Cubic Foot of Wood Loaded in Water"
-     width="600" height="228"/>
-</div>
-<div class="caption">One Cubic Foot of Wood Loaded in Water</div>
-
-<h3>Buoyancy in Air</h3>
-
-<p>There are <em>gases</em>, if not woods, lighter than air: among
-them, coal gas and hydrogen. A &ldquo;bubble&rdquo; of any of these
-gases, if isolated from the surrounding atmosphere, cannot
-sink but must rise. At the same pressure and temperature,
-hydrogen weighs about one-fifteenth as much as air;
-coal gas, about one-third as much. If a bubble of either
-of these gases be isolated in the atmosphere, it must continually
-rise, just as wood immersed in water will rise when<span class="pagenum"><a name="Page_59" id="Page_59">[Pg 59]</a></span>
-liberated. But the wood will stop when it reaches the surface
-of the water, while there is no reason to suppose that
-the hydrogen or coal gas bubbles will ever stop. The hydrogen
-bubble can be made to remain stationary if it is weighted
-down with something of about fourteen times its own
-weight (thirteen and one-half times, accurately). Perhaps
-it would be better to say that it would still continue to rise
-slowly because that additional something would itself displace
-some additional air; but if the added weight is a
-solid body, its own buoyancy in air is negligible.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg059.jpg" alt="Buoyant Power of Hydrogen"
-     width="600" height="502"/>
-</div>
-<div class="caption">Buoyant Power of Hydrogen</div>
-
-<p>Our first principle is, then, that at the same pressure
-and temperature, any gas lighter than air, if properly
-confined, will exert a net lifting power of (<i>n</i>-1) times
-its own weight, where <i>n</i> is the ratio of weights of air and
-gas per cubic foot.</p>
-
-<p><span class="pagenum"><a name="Page_60" id="Page_60">[Pg 60]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg060.jpg" alt="Lebaudy's Jaune"
-     width="600" height="360"/>
-</div>
-<div class="caption">Lebaudy&rsquo;s &ldquo;Jaune&rdquo;</div>
-
-<p>If the pressures and temperatures are different, this
-principle is modified. In a balloon, the gas is under a<span class="pagenum"><a name="Page_61" id="Page_61">[Pg 61]</a></span>
-pressure slightly in excess of that of the external atmosphere:
-this decreases its lifting power, because the weight
-of a given volume of gas is greater as the pressure to which
-it is subjected is increased. The weight of a given volume
-we have called the <em>density</em>: and, as has been stated, if the
-temperature be unchanged, the density varies directly as
-the pressure.</p>
-
-<p>The pressure in a balloon is only about 1% greater than
-that of the atmosphere at sea level, so that this factor has
-only a slight influence on the lifting power. That it leads
-to certain difficulties in economy of gas will, however, soon
-be seen.</p>
-
-<p>The temperature of the gas in a balloon, one might
-think, would naturally be the same as that of the air outside:
-but the surface of the balloon envelope has an absorbing
-capacity for heat, and on a bright sunny day the gas
-may be considerably warmed thereby. This action increases
-the lifting power, since increase of temperature
-(the pressure remaining fixed) decreases the density of a
-gas. To avoid this possibly objectionable increase in
-lifting power, balloons are sometimes painted with a non-absorbent
-color. One of the first Lebaudy balloons received
-a popular nickname in Paris on account of the yellow
-hue of its envelope.</p>
-
-<p>Suppose we wish a balloon to carry a total weight,
-including that of the envelope itself, of a ton. If of hydrogen,
-it will have to contain one fifteenth of this weight or
-about 133 pounds of that gas, occupying a space of about<span class="pagenum"><a name="Page_62" id="Page_62">[Pg 62]</a></span>
-23,000 cubic feet. If coal gas is used, the size of the
-balloon would have to be much greater. If hot air is used&mdash;as
-has sometimes been the case&mdash;let us assume the
-temperature of the air inside the envelope such that the
-density is just half that of the outside air. This would
-require a temperature probably about 500°. The air
-needed would be just a ton, and the balloon would be
-of about 52,000 cubic feet. It would soon lose its lifting
-power as the air cooled; and such a balloon would be
-useful only for short flights.</p>
-
-<div class="figcenter" style="width: 602px">
-<img src="images/pg062.jpg" alt="Air Balloon"
-     width="602" height="594"/>
-</div>
-<div>
-(Photo by Paul Thompson, N.Y.)<br />
-</div>
-<div class="caption">Air Balloon<br />
-<span class="normal">Built by some Germans in the backwoods of South Africa
-</span>
-</div>
-
-<p>The 23,000 cubic foot hydrogen balloon, designed to
-carry a ton, would just answer to sustain the weight. If<span class="pagenum"><a name="Page_63" id="Page_63">[Pg 63]</a></span>
-anchored at sea level, it would neither fall to the ground
-nor tug upward on its holding-down ropes. In order to
-ascend, something more is necessary. This &ldquo;something
-more&rdquo; might be some addition to the size and to the
-amount of hydrogen. Let us assume that we, instead, drop
-one hundred pounds of our load. Thus relieved of so much
-ballast, the balloon starts upward, under the net lifting
-force of one hundred pounds. It is easy to calculate how
-far it will go. It will not ascend indefinitely, because, as
-the altitude increases, the pressure (and consequently the
-density) of the external atmosphere decreases. At about
-a 2000-foot elevation, this decrease in density will have
-been sufficient to decrease the buoyant power of the hydrogen
-to about 1900 pounds, and the balloon will cease to
-rise, remaining at this level while it moves before the
-wind.</p>
-
-<p>There are several factors to complicate any calculations.
-Any expansion of the gas bag&mdash;stretching due to an increase
-in internal pressure&mdash;would be one; but the envelope
-fabrics do not stretch much; there is indeed a very good
-reason why they must not be allowed to stretch. The
-pressure in the gas bag is a factor. If there is no stretching
-of the bag, this pressure will vary directly with the temperature
-of the gas, and might easily become excessive
-when the sun shines on the envelope.</p>
-
-<p>A more serious matter is the increased difference between
-the internal pressure of the gas and the external pressure
-of the atmosphere at high altitudes. Atmospheric pressure<span class="pagenum"><a name="Page_64" id="Page_64">[Pg 64]</a></span>
-decreases as we ascend. The difference between gas
-pressure and air pressure thus increases, and it is this
-difference of pressure which tends to burst the envelope.
-Suppose the difference of pressure at sea level to have
-been two-tenths of a pound. For a balloon of twenty feet
-diameter, this would give a stress on the fabric, per lineal
-inch, of twenty-four pounds. At an altitude of 2000 feet,
-the atmospheric pressure would decrease by one pound,
-the difference of pressures would become one and two-tenths
-pounds, and the stress on the fabric would be 144 pounds
-per lineal inch&mdash;an absolutely unpermissible strain.
-There is only one remedy: to allow some of the gas to
-escape through the safety valve; and this will decrease our
-altitude.</p>
-
-
-<h3>Ascending and Descending</h3>
-
-<p>To ascend, then, we must discard ballast: and we cannot
-ascend beyond a certain limit on account of the limit
-of allowable pressure on the envelope fabric. To again
-descend, we must discharge some of the gas which gives
-us lifting power. Every change of altitude thus involves
-a loss either of gas or of ballast. Our vertical field of
-control may then be represented by a series of oscillations
-of gradually decreasing magnitude until finally all power
-to ascend is gone. And even this situation, serious as it
-is, is made worse by the gradual but steady leakage of
-gas through the envelope fabric. Here, in a word, is the
-whole problem of altitude regulation. Air has no surface<span class="pagenum"><a name="Page_65" id="Page_65">[Pg 65]</a></span>
-of equilibrium like water. Some device supplementary to
-ballast and the safety valve is absolutely necessary for
-practicable flight in any balloon not staked to the ground.</p>
-
-<p>A writer of romance has equipped his aeronautic heroes
-with a complete gas-generating plant so that all losses
-might be made up; and in addition, heating arrangements
-were provided so that when the gas supply had been partially
-expended its lifting power could be augmented by
-warming it so as to decrease its density below even the
-normal. There might be something to say in favor of
-this latter device, if used in connection with a collapsible
-gas envelope.</p>
-
-<p>Methods of mechanically varying the size of the balloon,
-so as by compressing the gas to cause descent and by giving
-it more room to increase its lifting power and produce
-ascent, have been at least suggested. The idea of a vacuum
-balloon, in which a rigid hollow shell would be exhausted
-of its contents by a continually working pump, may appear
-commendable. Such a balloon would have maximum
-lifting power for its size; but the weight of any rigid shell
-would be considerable, and the pressure tending to rupture
-it would be about 100 times that in ordinary gas balloons.</p>
-
-<p>It has been proposed to carry stored gas at high pressure
-(perhaps in the liquefied condition) as a supplementary
-method of prolonging the voyage while facilitating vertical
-movements: but hydrogen gas at a pressure of a ton to the
-square inch in steel cylinders would give an ultimate lifting
-power of only about one-tenth the weight of the cylinders<span class="pagenum"><a name="Page_66" id="Page_66">[Pg 66]</a></span>
-which contain it. These cylinders might be regarded
-as somewhat better than ordinary ballast: but to throw
-them away, with their gas charge, as ballast, would seem
-too tragic. Liquefied gas might possibly appear rather
-more desirable, but would be altogether too expensive.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg066.jpg" alt="Screw Propeller for Altitude Control"
-     width="600" height="202"/>
-</div>
-<div class="caption">Screw Propeller for Altitude Control</div>
-
-<p>If a screw propeller can be used on a steamship, a dirigible
-balloon, or an aeroplane to produce forward motion, there
-is no reason why it could not also be used to produce upward
-motion in any balloon; and the propeller with its
-operating machinery would be a substitute for twice its
-equivalent in ballast, since it could produce motion either
-upward or downward. Weight for weight, however, the
-propeller and engine give only (in one computed case)
-about half the lifting power of hydrogen. If we are to use
-the screw for ascent, we might well use a helicopter, heavier
-than air, rather than a balloon.</p>
-
-
-<h3>The Ballonet</h3>
-
-<p>The present standard method of improving altitude
-regulation involves the use of the ballonet, or compartment<span class="pagenum"><a name="Page_67" id="Page_67">[Pg 67]</a></span>
-air bag, inside the main envelope. For stability and
-effective propulsion, it is important that the balloon preserve
-its shape, no matter how much gas be allowed to
-escape. Dirigible balloons are divided into two types,
-according to the method employed for maintaining the
-shape. In the Zeppelin type, a rigid internal metal framework
-supports the gas envelope. This forms a series of
-seventeen compartments, each isolated from the others.
-No matter what the pressure of gas, the shape of the
-balloon is unchanged.</p>
-
-<p>In the more common form of balloon, the internal
-air ballonet is empty, or nearly so, when the main
-envelope is full. As gas is vented from the latter,
-air is pumped into the former. This compresses the
-remaining gas and thus preserves the normal form of the
-balloon outline.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg067.jpg" alt="Balloon with Ballonets"
-     width="600" height="183"/>
-</div>
-<div class="caption">Balloon with Ballonets</div>
-
-<p>But the air ballonet does more than this. It provides
-an opportunity for keeping the balloon on a level keel,
-for by using a number of compartments the air can be
-circulated from one to another as the case may require,
-thus altering the distribution of weights. Besides this, if
-the pressure in the air ballonet be initially somewhat
-greater than that of the external atmosphere, a considerable
-ascent may be produced by merely venting this air
-ballonet. This involves no loss of gas; and when it is
-again desired to descend, air may be pumped into the ballonet.
-If any considerable amount of gas should be
-vented, to produce quick and rapid descent, the pumping
-of air into the ballonet maintains the shape of the balloon
-and also facilitates the descent.</p>
-
-<p><span class="pagenum"><a name="Page_68" id="Page_68">[Pg 68]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg068.jpg" alt="Construction of the Zeppelin Balloon"
-     width="600" height="267"/>
-</div>
-<div class="caption">Construction of the Zeppelin Balloon</div>
-
-
-<p><span class="pagenum"><a name="Page_69" id="Page_69">[Pg 69]</a></span></p>
-<h3 class="break">The Equilibrator</h3>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg069.jpg" alt="The Equilibrator in Neutral Position"
-     width="600" height="582"/>
-</div>
-<div class="caption">The Equilibrator in Neutral Position</div>
-
-<p>Suppose a timber block of one square foot area, ten feet
-long, weighing 380 pounds, to be suspended from the
-balloon in the ocean, and let mechanism be provided by
-which this block may be raised or lowered at pleasure.
-When completely immersed in water it exerts an upward<span class="pagenum"><a name="Page_70" id="Page_70">[Pg 70]</a></span>
-pressure (lifting force) of 240 pounds, which may be used
-to supplement the lifting power of the balloon. If wholly
-withdrawn from the water, it pulls down the balloon with
-its weight of 380 pounds. It seems to be equivalent, therefore,
-to about 620 pounds of ballast. When immersed a
-little over six feet&mdash;the upper four feet being out of the
-water&mdash;it exerts neither lifting nor depressing effect.
-The amount of either may be perfectly adjusted between
-the limits stated by varying the immersion.</p>
-
-<p>In the Wellman-Vaniman equilibrator attached to the
-balloon <i>America</i>, which last year carried six men (and a cat)
-a thousand miles in three days over the Atlantic Ocean, a
-string of tanks partly filled with fuel was used in place of
-the timber block. As the tanks were emptied, the degree
-of control was increased; and this should apparently
-have given ideal results, equilibration being augmented as
-the gas supply was lost by leakage: but the unsailorlike
-disregard of conditions resulting from the strains transferred
-from a choppy sea to the delicate gas bag led to
-disaster, and it is doubtful whether this method of control
-can ever be made practicable. The <i>America&rsquo;s</i> trip was
-largely one of a drifting rather than of a dirigible balloon.
-The equilibrator could be used only in flights over water
-in any case: and if we are to look to water for our buoyancy,
-why not look wholly to water and build a ship instead
-of a balloon?</p>
-
-<div>
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_71" id="Page_71">[Pg 71]</a></span></p>
-<h2>DIRIGIBLE BALLOONS AND OTHER KINDS</h2></div>
-
-<h3>Shapes</h3>
-
-<div class="figcenter" style="width: 602px">
-<img src="images/pg071.jpg" alt="Henry Giffard&rsquo;s Dirigible"
-     width="602" height="498"/>
-</div>
-<div class="caption">Henry Giffard&rsquo;s Dirigible<br />
-   <span class="normal">(The first with steam power)</span></div>
-
-<p>The cylindrical Zeppelin balloon with approximately
-conical ends has already been shown (page <a href="#Page_68">68</a>). Those
-balloons in which the shape is maintained by internal
-pressure of air are usually <em>pisciform</em>, that is, fish-shaped.
-Studies have actually been made of the contour lines of
-various fishes and equivalent symmetrical forms derived,<span class="pagenum"><a name="Page_72" id="Page_72">[Pg 72]</a></span>
-the outline of the balloon being formed by a pair of
-approximately parabolic curves.</p>
-
-
-<div class="figcenter" style="width: 602px">
-<img src="images/pg072.jpg" alt="Dirigible of Dupuy de Lome"
-     width="602" height="540"/>
-</div>
-<div class="caption">Dirigible of Dupuy de Lome<br />
-<span class="normal">(Man Power)</span></div>
-
-<p>The first flight in a power driven balloon was made by
-Giffard in 1852. This balloon had an independent speed
-of about ten feet per second, but was without appliances
-for steering. A ballonetted balloon of 120,000 cubic feet
-capacity was directed by man power in 1872: eight men
-turned a screw thirty feet in diameter which gave a speed
-of about seven miles per hour. Electric motors and
-storage batteries were used for dirigible balloons in 1883-&rsquo;84:
-in the latter year, Renard and Krebs built the first<span class="pagenum"><a name="Page_73" id="Page_73">[Pg 73]</a></span>
-fish-shaped balloon. The first dirigible driven by an
-internal combustion motor was used by Santos-Dumont
-in 1901.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg073.jpg" alt="Tissandier Brothers' Dirigible Balloon"
-     width="600" height="428"/>
-</div>
-<div class="caption">Tissandier Brothers&rsquo; Dirigible Balloon<br />
-<span class="normal">(Electric Motor)</span></div>
-
-
-<h3>Dimensions</h3>
-
-<p>The displacements of present dirigibles vary from 20,000
-cubic feet (in the United States Signal Corps airship) up
-to 460,000 cubic feet (in the Zeppelin). The former balloon
-has a carrying capacity only about equivalent to that of
-a Wright biplane. While anchored or drifting balloons
-are usually spherical, all dirigibles are elongated, with a
-length of from four to eleven diameters. The Zeppelin
-represents an extreme elongation, the length being 450
-feet and the diameter forty-two feet. At the other extreme,
-<span class="pagenum"><a name="Page_74" id="Page_74">[Pg 74]</a></span>
-some of the English military dirigibles are thirty-one feet
-in diameter and only 112 feet long. Ballonet capacities
-may run up to one-fifth the gas volume. All present
-dirigibles have gasoline engines driving propellers from
-eight to twenty feet in diameter. The larger propellers
-are connected with the motors by gearing, and make from
-250 to 700 turns per minute. The smaller propellers are
-direct connected and make about 1200 revolutions. Speeds
-are usually from fifteen to thirty miles per hour.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg074.jpg" alt="The Baldwin"
-     width="600" height="523"/>
-</div>
-<div class="caption">The Baldwin<br />
-<span class="normal">Dirigible of the United States Signal Corps</span>
-</div>
-
-<p>The present-day elongated shape is the result of the effort
-to decrease the proportion of propulsion resistance due to
-the pressure of the air against the head of the balloon.
-This has led also to the pointed ends now universal; and to
-avoid eddy resistance about the rear it is just as important
-to point the stern as the bow. As far as head end resistance
-alone is concerned, the longer the balloon the better: but
-the friction of the air along the side of the envelope also
-produces resistance, so that the balloon must not be too
-much elongated. Excessive elongation also produces
-structural weakness. From the standpoint of stress on the
-fabric of the envelope, the greatest strain is that which
-tends to break the material along a longitudinal line, and
-this is true no matter what the length, as long as the seams
-are equally strong in both directions and the load is so
-suspended as not to produce excessive bending strain on
-the whole balloon. In the <i>Patrie</i> (page <a href="#Page_77">77</a>), some distortion
-due to loading is apparent. The stress per lineal
-inch of fabric is obtained by multiplying the net pressure
-by half the diameter of the envelope (in inches).</p>
-
-<p><span class="pagenum"><a name="Page_75" id="Page_75">[Pg 75]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg075.jpg"
-     alt="The Zeppelin Entering Its Hangar on Lake Constance"
-     width="600" height="324"/>
-</div>
-<div class="caption">The Zeppelin Entering Its Hangar on Lake Constance</div>
-
-<p>
-<span class="pagenum"><a name="Page_76" id="Page_76">[Pg 76]</a></span>
-Ample steering power (provided by vertical planes, as
-in heavier-than-air machines) is absolutely necessary in
-dirigibles: else the head could not be held up to the wind
-and the propelling machinery would become ineffective.</p>
-
-<p><span class="pagenum"><a name="Page_77" id="Page_77">[Pg 77]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg077.jpg" alt="The 'Patrie.' Destroyed by a Storm"
-     width="600" height="349"/>
-</div>
-<div class="caption">The &ldquo;Patrie.&rdquo; Destroyed by a Storm</div>
-
-
-<h3>Fabrics</h3>
-
-<p>The material for the envelope and ballonets should be
-light, strong, unaffected by moisture or the atmosphere,
-non-cracking, non-stretching, and not acted upon by variations
-<span class="pagenum"><a name="Page_78" id="Page_78">[Pg 78]</a></span>
-in temperature. The same specifications apply to
-the material for the wings of an aeroplane. In addition,
-for use in dirigible balloons, fabrics must be impermeable,
-resistent to chemical action of the gas, and not subject to
-spontaneous combustion. The materials used are vulcanized
-silk, gold beater&rsquo;s skin, Japanese silk and rubber, and
-cotton and rubber compositions. In many French balloons,
-a middle layer of rubber has layers of cotton on each side,
-the whole thickness being the two hundred and fiftieth
-part of an inch. In the <i>Patrie</i>, this was supplemented by
-an outside non-heat-absorbent layer of lead chromate and
-an inside coating of rubber, all rubber being vulcanized.
-The inner rubber layer was intended to protect the fabric
-against the destructive action of impurities in the gas.</p>
-
-<p>Fabrics are obtainable in various colors, painted, varnished,
-or wholly uncoated. The rubber and cotton mixtures
-are regularly woven in France and Germany for
-aeroplanes and balloons. The cars and machinery are
-frequently shielded by a fabricated wall. Weights of
-envelope materials range from one twenty-third to one-fourteenth
-pound per square foot, and breaking stresses
-from twenty-eight to one hundred and thirty pounds.
-Pressures (net) in the main envelope are from three-fifths
-to one and a quarter <em>ounces</em> per square inch, those in the
-ballonets being somewhat less. The <i>Patrie</i> of 1907 had an
-envelope guaranteed not to allow the leakage of more
-than half a cubic inch of hydrogen per square foot of surface
-per twenty-four hours.</p>
-
-<p><span class="pagenum"><a name="Page_79" id="Page_79">[Pg 79]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg079.jpg" alt="Manufacturing the Envelope of a Balloon"
-     width="600" height="409"/>
-</div>
-<div class="caption">Manufacturing the Envelope of a Balloon</div>
-
-<hr />
-
-<p><span class="pagenum"><a name="Page_80" id="Page_80">[Pg 80]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg080.jpg" alt=" Inspecting the Envelope of Andrée's Balloon 'L'Oernen'"
-     width="600" height="387"/>
-</div>
-<div class="caption">
-  Inspecting the Envelope of Andrée&rsquo;s Balloon &ldquo;L&rsquo;Oernen&rdquo;
-</div>
-
-<p><span class="pagenum"><a name="Page_81" id="Page_81">[Pg 81]</a></span></p>
-
-<p>The best method of cutting the fabric is to arrange for
-building up the envelope by a series of strips about the circumference,
-the seams being at the bottom. The two
-warps of the cloth should cross at an angle so as to localize
-a rip or tear. Bands of cloth are usually pasted over the
-seams, inside and out, with a rubber solution; this is to
-prevent leakage at the stitches.</p>
-
-
-<h3>Framing</h3>
-
-<p>In the <i>Zeppelin</i>, the rigid aluminum frame is braced
-every forty-five feet by transverse diametral rods which
-make the cross-sections resemble a bicycle wheel (page <a href="#Page_68">68</a>).
-This cross-section is not circular, but sixteen-sided. The
-pressure is resisted by the framework itself, the envelope
-being required to be impervious only. The seventeen compartments
-are separated by partitions of sheet aluminum.
-There is a system of complete longitudinal bracing between
-these partitions. Under the main framework, the cars and
-machinery are carried by a truss about six feet deep which
-runs the entire length. The cars are boat-shaped, twenty
-feet long and six feet wide, three and one-half feet high,
-enclosed in aluminum sheathing. These cars, placed about
-one hundred feet from the ends, are for the operating force
-and machinery. The third car, carrying passengers, is
-built into the keel.</p>
-
-<p><span class="pagenum"><a name="Page_82" id="Page_82">[Pg 82]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg082.jpg" alt="Wreck of the 'Zeppelin'"
-     width="600" height="330"/>
-</div>
-<div class="caption">Wreck of the &ldquo;Zeppelin&rdquo;</div>
-
-<p>In non-rigid balloons like the <i>Patrie</i>, the connecting
-frame must be carefully attached to the envelope. In this
-particular machine, cloth flaps were sewed to the bag, and<span class="pagenum"><a name="Page_83" id="Page_83">[Pg 83]</a></span>
-nickel steel tubes then laced in the flaps. With these
-tubes as a base, a light framework of tubes and wires,
-covered with a laced-on waterproof cloth, was built up for
-supporting the load. Braces ran between the various
-stabilizing and controlling surfaces and the gas bag; these
-were for the most part very fine wire cables. The weight
-of the car was concentrated on about seventy feet of the
-total length of 200 feet. This accounts for the deformation
-of the envelope shown in the illustration (page <a href="#Page_77">77</a>). The
-frame and car of this balloon were readily dismantled for
-transportation.</p>
-
-<p>In some of the English dirigibles the cars were suspended
-by network passing over the top of the balloon.</p>
-
-
-<h3>Keeping the Keel Horizontal</h3>
-
-<p>In the <i>Zeppelin</i>, a sliding weight could be moved along
-the keel so as to cause the center of gravity to coincide with
-the center of upward pressure in spite of variations in
-weight and position of gas, fuel, and ballast. In the German
-balloon <i>Parseval</i>, the car itself was movable on a
-longitudinal suspending cable which carried supporting
-sheaves. This balloon has figured in recent press notices.
-It was somewhat damaged by a collision with its shed in
-March: the sixteen passengers escaped unharmed. A few
-days later, emergency deflation by the rip-strip was made
-necessary during a severe storm. In the ordinary non-rigid
-balloon, the pumping of air between the ballonets aids in
-controlling longitudinal equilibrium. The pump may be
-arranged for either hand or motor operation: that in the
-<i>Clément-Bayard</i> had a capacity of 1800 liters per minute
-against the pressure of a little over three-fifths of an ounce.
-The <i>Parseval</i> has two ballonets. Into the rear of these air
-is pumped at starting. This raises the bow and facilitates
-ascent on the principle of the inclined surface of an aeroplane.
-After some elevation is attained, the forward ballonet
-is also filled.</p>
-
-<p><span class="pagenum"><a name="Page_84" id="Page_84">[Pg 84]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg084.jpg" alt="Car of the Zeppelin"
-     width="600" height="353"/>
-</div>
-<div class="caption">Car of the Zeppelin<br />
-<span class="normal">
- (From the <cite>Transactions</cite> of the American Society of Mechanical Engineers)
-</span>
-</div>
-
-<p><span class="pagenum"><a name="Page_85" id="Page_85">[Pg 85]</a></span></p>
-<h3>Stability</h3>
-
-<p>Besides proper distribution of the loads, correct vertical
-location of the propeller is important if the balloon is to
-travel on a level keel. In some early balloons, two envelopes
-side by side had the propeller at the height of the axes
-of the gas bags and midway between them. The modern
-forms carry the car, motor, and propeller below the balloon
-proper. The air resistance is mostly that of the bow of the
-envelope: but there is some resistance due to the car, and
-the propeller shaft should properly be at the equivalent
-center of all resistance, which will be between car and axis
-of gas bag and nearer the latter than the former. With a
-single envelope and propeller, this arrangement is impracticable.
-By using four (or even two) propellers, as in the
-<i>Zeppelin</i> machine (page <a href="#Page_68">68</a>), it can be accomplished. If
-only one propeller is employed, horizontal rudder planes
-must be disposed at such angles and in such positions as to
-compensate for the improper position of the tractive force.
-Even on the <i>Zeppelin</i>, such planes were employed with
-advantage (pages <a href="#Page_66">66</a> and <a href="#Page_73">73</a>).</p>
-
-<p><span class="pagenum"><a name="Page_86" id="Page_86">[Pg 86]</a></span></p>
-
-<p>Perfect stability also involves freedom from rolling.
-This is usually inherent in a balloon, because the center of
-mass is well below the center of buoyancy: but in machines
-of the non-rigid type the absence of a ballonet might lead
-to both rolling and pitching when the gas was partially
-exhausted.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg086.jpg" alt="Stern View of the Zeppelin"
-     width="600" height="597"/>
-</div>
-<div class="caption">Stern View of the Zeppelin</div>
-
-<p>What is called &ldquo;route stability&rdquo; describes the condition
-of straight flight. The balloon must point directly in its
-(independent) course. This involves the use of a steering<span class="pagenum"><a name="Page_87" id="Page_87">[Pg 87]</a></span>
-rudder, and, in addition, of fixed vertical planes, which, on
-the principle of the vertical partitions of Voisin, probably
-give some automatic steadiness to the course. To avoid
-the difficulty or impossibility of holding the head up to
-the wind at high speeds, an <em>empennage</em> or feathering tail
-is a feature of all present balloons. The empennage of the
-<i>Patrie</i> (page <a href="#Page_77">77</a>) consisted of pairs of vertical and horizontal
-planes at the extreme stern. In the <i>France</i>, thirty-two
-feet in maximum diameter and nearly 200 feet long, empennage
-planes aggregating about 400 square feet were
-placed somewhat forward of the stern. In the <i>Clément-Bayard</i>,
-the empennage consisted of cylindro-conical ballonets
-projecting aft from the stern. A rather peculiar
-grouping of such ballonets was used about the prolonged
-stern of the <i>Ville de Paris</i>.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg087.jpg" alt="The 'Clément-Bayard'"
-     width="600" height="456"/>
-</div>
-<div class="caption">The &ldquo;Clément-Bayard&rdquo;</div>
-
-<hr />
-
-<p><span class="pagenum"><a name="Page_88" id="Page_88">[Pg 88]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg088.jpg" alt="The 'Ville de Paris'"
-     width="600" height="336"/>
-</div>
-<div class="caption">The &ldquo;Ville de Paris&rdquo;</div>
-
-<p><span class="pagenum"><a name="Page_89" id="Page_89">[Pg 89]</a></span></p>
-<h3 class="break">Rudders and Planes</h3>
-
-<p>The dirigible has thus several air-resisting or gliding
-surfaces. The approximately &ldquo;horizontal&rdquo; (actually somewhat
-inclined) planes permit of considerable ascent and
-descent by the expenditure of power rather than gas, and
-thus somewhat influence the problem of altitude control.
-Each of the four sets of horizontal rudder planes on the
-<i>Zeppelin</i>, for example, has, at thirty-five miles per hour,
-<span class="pagenum"><a name="Page_90" id="Page_90">[Pg 90]</a></span>
-with an inclination equal to one-sixth a right angle, a
-lifting power of nearly a ton; about equal to that of all
-of the gas in one of the sixteen compartments.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg089.jpg" alt="Car of the 'Liberté'"
-     width="600" height="455"/>
-</div>
-<div class="caption">Car of the &ldquo;Liberté&rdquo;</div>
-
-<p>Movable rudders may be either hand or motor-operated.
-The double vertical steering rudder of the <i>Ville de Paris</i>
-had an area of 150 square feet. The horizontally pivoted
-rudders for vertical direction had an area of 130 square
-feet.</p>
-
-
-<h3>Arrangement and Accessories</h3>
-
-<p>The motor in the <i>Ville de Paris</i> was at the front of the
-car, the operator behind it. This car had the excessive
-weight of nearly 700 pounds. The <i>Patrie</i> employed a non-combustible
-shield over the motor, for the protection of the
-envelope: its steering wheel was in front and the motor
-about in the middle of the car. The gasoline tank was
-under the car, compressed air being used to force the
-fuel up to the motor, which discharged its exhaust downward
-at the rear through a spark arrester. Motors have
-battery and magneto ignition and decompression cocks,
-and are often carried on a spring-supported chassis. The
-interesting <i>Parseval</i> propeller has four cloth blades which
-hang limp when not revolving. When the motor is running,
-these blades, which are weighted with lead at the
-proper points, assume the desired form.</p>
-
-<p>Balloons usually carry guide ropes at head and stern,
-the aggregate weight of which may easily exceed a hundred
-pounds. In descending, the bow rope is first made fast,
-and the airship then stands with its head to the wind, to be<span class="pagenum"><a name="Page_91" id="Page_91">[Pg 91]</a></span>
-hauled in by the stern rope. For the large French military
-balloons, this requires a force of about thirty men. The
-<i>Zeppelin</i> descends in water, being lowered until the cars
-float, when it is docked like a ship (see page <a href="#Page_84">84</a>). Landing
-skids are sometimes used, as with aeroplanes.</p>
-
-<p>The balloon must have escape valves in the main envelope
-and ballonets. In addition it has a &ldquo;rip-strip&rdquo; at the bottom
-by which a large cut can be made and the gas quickly
-vented for the purpose of an emergency descent. Common
-equipment includes a siren, megaphone, anchor pins, fire
-extinguisher, acetylene search light, telephotographic apparatus,
-registering and indicating gages and other instruments,
-anemometer, possibly carrier pigeons; besides fuel,
-oil and water for the motor, and the necessary supplies for
-the crew. The glycerine floated compass of Moisant must
-now also be included if we are to contemplate genuine
-navigation without constant recourse to landmarks.</p>
-
-
-<h3>Amateur Dirigibles</h3>
-
-<p>The French Zodiac types of &ldquo;aerial runabout&rdquo; displace
-700 cubic meters, carrying one passenger with coal gas or
-two passengers with a mixture of coal gas and hydrogen.
-The motor is four-cylinder, sixteen horse-power, water-cooled.
-The stern screw, of seven feet diameter, makes
-600 turns per minute, giving an independent speed of
-nineteen miles per hour. The machine can remain aloft
-three hours with 165 pounds of supplies. It costs $5000.
-Hydrogen costs not far from a cent per cubic foot (twenty
-<span class="pagenum"><a name="Page_92" id="Page_92">[Pg 92]</a></span>
-cents per cubic meter) so that the question of gas leakage
-may be at least as important as the tire question with
-automobiles.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg092.jpg" alt="The Zodiac No. 2"
-     width="600" height="428"/>
-</div>
-<div class="caption">The Zodiac No. 2<br />
-<span class="normal">May be deflated and easily transported</span></div>
-
-
-<h3>The Fort Omaha Plant</h3>
-
-<p>The Signal Corps post at Fort Omaha has a plant comprising
-a steel balloon house of size sufficient to house one
-of the largest dirigibles built, an electrolytic plant for
-generating hydrogen gas, having a capacity of 3000 cubic
-feet per hour, a 50,000 cubic foot gas storage tank, and
-the compressing and carrying equipment involved in preparing
-gas for shipment at high pressure in steel cylinders.</p>
-
-<p><span class="pagenum"><a name="Page_93" id="Page_93">[Pg 93]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg093.jpg" alt="United States Signal Corps Balloon Plant at Fort Omaha, Neb."
-     width="600" height="409"/>
-</div>
-<div class="caption">United States Signal Corps Balloon Plant at Fort Omaha, Neb.<br />
-<span class="normal">(From the <cite>Transactions</cite> of the American
-   Society of Mechanical Engineers)</span></div>
-
-<div><span class="pagenum"><a name="Page_94" id="Page_94">[Pg 94]</a></span></div>
-<h3 class="break">Balloon Progress</h3>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg094.jpg" alt="The 'Caroline' of Robert Brothers, 1784"
-     width="600" height="573"/>
-</div>
-<div class="caption">The &ldquo;Caroline&rdquo; of Robert Brothers, 1784<br />
-<span class="normal">The ascent terminated tragically</span></div>
-
-<p>The first aerial buoy of Montgolfier brothers, in 1783,
-led to the suggestion of Meussier that two envelopes be
-used; the inner of an impervious material to prevent gas
-leakage, and the outer for strength. There was perhaps
-a foreshadowing of the Zeppelin idea. Captive and drifting
-balloons were used during the wars of the French
-Revolution: they became a part of standard equipment
-in our own War of Secession and in the Franco-Prussian
-conflict. The years 1906 to 1908 recorded rapid progress
-in the development of the dirigible: the record-breaking
-<i>Zeppelin</i> trip was in 1909 and Wellman&rsquo;s <i>America</i> exploit
-in October, 1910. Unfortunately, dirigibles have had a
-a bad record for stanchness: the <i>Patrie</i>, <i>République</i>,
-<i>Zeppelin</i> (<i>I</i> and <i>II</i>), <i>Deutschland</i>, <i>Clément-Bayard</i>&mdash;all
-have gone to that bourne whence no balloon returns.</p>
-
-<p><span class="pagenum"><a name="Page_95" id="Page_95">[Pg 95]</a></span></p>
-<div class="figcenter" style="width: 338px">
-<img src="images/pg095.jpg" alt="The Ascent at Versailles, 1783"
-     width="338" height="500"/>
-</div>
-<div class="caption">The Ascent at Versailles, 1783<br />
-  <span class="normal">The first balloon carrying living beings in the air</span>
-</div>
-
-<hr />
-
-<div class="figcenter" style="width: 375px">
-<img src="images/pg096.jpg" alt="Proposed Dirigible"
-     width="375" height="502"/>
-</div>
-<div class="caption"><span class="normal">
-  Investors were lacking to bring about the realization of this project</span>
-</div>
-
-<p>
-<span class="pagenum"><a name="Page_96" id="Page_96">[Pg 96]</a></span>
-It is gratifying to record that Count Zeppelin&rsquo;s latest
-machine, the <i>Deutschland II</i>, is now in operation. During
-the present month (April, 1911), flights have been made
-covering 90 miles and upward at speeds exceeding 20 miles
-per hour with the wind unfavorable. This balloon is intended
-for use as a passenger excursion vehicle during the
-coming summer, under contract with the municipality of
-Düsseldorf.</p>
-
-<p><span class="pagenum"><a name="Page_97" id="Page_97">[Pg 97]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg097.jpg" alt="The 'République'"
-     width="600" height="228"/>
-</div>
-<div class="caption">The &ldquo;République&rdquo;</div>
-
-<p>
-<span class="pagenum"><a name="Page_98" id="Page_98">[Pg 98]</a></span>
-At the present moment, Neale, in England, is reported
-to be building a dirigible for a speed of a hundred miles per
-hour. The Siemens-Schuckart non-rigid machine, nearly
-400 feet long and of 500 horse-power, is being tried out at
-Berlin: it is said to carry fifty passengers.
-<a name="FNanchor_1" id="FNanchor_1"></a>
-<a href="#Footnote_1" class="fnanchor">1</a>
-Fabrice, of
-Munich, is experimenting with the <i>Inchard</i>, with a view to
-crossing the Atlantic at an early date. Mr. Vaniman,
-partner of Wellman on the <i>America</i> expedition, is planning
-a new dirigible which it is proposed to fly across the ocean
-before July 4. The engine, according to press reports,
-will develop 200 horse-power, and the envelope will be
-more elongated than that of the <i>America</i>. And meanwhile
-a Chicago despatch describes a projected fifty-passenger
-machine, to have a gross lifting power of twenty-five tons!</p>
-
-<p><span class="pagenum"><a name="Page_99" id="Page_99">[Pg 99]</a></span></p>
-<div class="figcenter" style="width: 349px">
-<img src="images/pg099.jpg" alt="The First Flight for the Gordon-Bennet Cup."
-     width="349" height="500"/>
-</div>
-<div class="caption">The First Flight for the Gordon-Bennet Cup.</div>
-<p class="note">
-Won by Lieut. Frank P. Lahm, U.S.A., 1906. Figures on the map denote
-distances in kilometers. The cup has been offered annually by Mr.
-James Gordon-Bennet for international competition under such conditions
-as may be prescribed by the International Aeronautic Federation.</p>
-
-<p>Germany has a slight lead in number of dirigible balloons&mdash;sixteen
-in commission and ten building. France follows
-closely with fourteen active and eleven authorized.
-This accounts for two-thirds of all the dirigible balloons in
-the world. Great Britain, Italy, and Russia rank in the
-order named. The United States has one balloon of the
-smallest size. Spain has, or had, one dirigible. As to<span class="pagenum"><a name="Page_100" id="Page_100">[Pg 100]</a></span>
-aeroplanes, however, the United States and England rank
-equally, having each about one-fourth as many machines
-as France (which seems, therefore, to maintain a &ldquo;four-power
-standard&rdquo;). Germany, Russia, and Italy follow,
-in order, the United States. These figures include all
-machines, whether privately or nationally owned. Until
-lately, our own government operated but one aeroplane.
-A recent appropriation by Congress of $125,000 has led to
-arrangements for the purchase of a few additional biplanes
-of the Wright and Curtiss types; and a training
-school for army officers has been regularly conducted at
-San Diego, Cal., during the past winter. The Curtiss
-machine to be purchased is said to carry 700 pounds of
-dead weight with a sail area of 500 square feet. It is
-completely demountable and equipped with pontoons.</p>
-
-<div>
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_101" id="Page_101">[Pg 101]</a></span></p>
-<h2>THE QUESTION OF POWER</h2></div>
-
-<p>In the year 1810, a steam engine weighed something
-over a ton to the horse-power. This was reduced to about
-200 pounds in 1880. The steam-driven dirigible balloon
-of Giffard, in 1852, carried a complete power plant weighing
-a little over 100 pounds per horse-power; about the
-weight of a modern locomotive. The unsuccessful Maxim
-flying machine of 1894 brought this weight down to less
-than 20 pounds. The gasoline engine on the original
-Wright machines weighed about 5 pounds to the horse-power;
-those on some recent French machines not far
-from 2 pounds.</p>
-
-<p>Pig iron is worth perhaps a cent a pound. An ordinary
-steam or gas engine may cost eight cents a pound; a steam
-turbine, perhaps forty cents. A high grade automobile
-or a piano may sell for a dollar a pound; the Gnome aeroplane
-motor is priced at about twenty dollars a pound.
-This is considerably more than the price of silver. The
-motor and accessories account for from two-thirds to nine-tenths
-of the total cost of an aeroplane.</p>
-
-<p>A man weighing 150 pounds can develop at the outside
-about one-eighth of a horse-power. It would require
-1200 pounds of man to exert one horse-power. Considered
-as an engine, then, a man is (weight for weight) only<span class="pagenum"><a name="Page_102" id="Page_102">[Pg 102]</a></span>
-one six-hundredth as effective as a Gnome motor. In the
-original Wright aeroplane, a weight of half a ton was
-sustained at the expenditure of about twenty-five horse-power.
-The motor weight was about one-eighth of the
-total weight. If traction had been produced by man-power,
-30,000 pounds of man would have been necessary: thirty
-times the whole weight supported.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg102.jpg" alt="The Gnome Motor"
-     width="600" height="556"/>
-</div>
-<div class="caption">The Gnome Motor<br />
-  <span class="normal">(Aeromotion Company of America)</span></div>
-
-<p>Under the most favorable conditions, to support his
-own weight of 150 pounds (at very high gliding velocity
-and a slight angle of inclination, disregarding the weight
-of sails necessary), a man would need to have the strength<span class="pagenum"><a name="Page_103" id="Page_103">[Pg 103]</a></span>
-of about fifteen men. No such thing as an aerial bicycle,
-therefore, appears possible. The man can not emulate
-the bird.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg103.jpg" alt="Screw Propeller"
-     width="600" height="108"/>
-</div>
-<div class="caption">Screw Propeller &nbsp;
-  <span class="normal">(American Propeller Company)</span></div>
-
-<p>The power plant of an air craft includes motor, water
-and water tank, radiator and piping, shaft and bearings,
-<span class="pagenum"><a name="Page_104" id="Page_104">[Pg 104]</a></span>
-propeller, controlling wheels and levers, carbureter, fuel,
-lubricating oil and tanks therefor. Some of the weight may
-eventually be eliminated by employing a two-cycle motor
-(which gives more power for its size) or by using rotary
-air-cooled cylinders. Propellers are made light by employing
-wood or skeleton construction. One eight-foot screw of
-white oak and spruce, weighing from twelve to sixteen
-pounds, is claimed to give over 400 pounds of propelling
-force at a thousand turns per minute.</p>
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg104.jpg" alt="One of the Motors of the Zeppelin"
-     width="600" height="509"/>
-</div>
-<div class="caption">One of the Motors of the Zeppelin</div>
-
-<p>The cut shows the action of the so-called &ldquo;four-cycle&rdquo;
-motor. Four strokes are required to produce an impulse
-on the piston and return the parts to their original positions.
-On the first, or suction stroke, the combustible
-mixture is drawn into the cylinder, the inlet valve being
-open and the outlet valve closed. On the second stroke,
-both valves are closed and the mixture is highly compressed.
-At about the end of this stroke, a spark ignites the charge,
-a still greater pressure is produced in consequence, and the
-energy of the gas now forces the piston outward on its
-third or &ldquo;working&rdquo; stroke, the valves remaining closed.
-Finally, the outlet valve is opened and a fourth stroke
-sweeps the burnt gas out of the cylinder.</p>
-
-
-<p><span class="pagenum"><a name="Page_105" id="Page_105">[Pg 105]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg105.jpg" alt="Action of the Four-Cycle Engine"
-     width="600" height="548"/>
-</div>
-<div class="caption">Action of the Four-Cycle Engine</div>
-
-<p>
-<span class="pagenum"><a name="Page_106" id="Page_106">[Pg 106]</a></span>
-In the &ldquo;two-cycle&rdquo; engine, the piston first moves to
-the left, compressing a charge already present in the cylinder
-at <i>F</i>, and meanwhile drawing a fresh supply through
-the valve <i>A</i> and passages <i>C</i> to the space <i>D</i>. On the
-return stroke, the exploded gas in <i>F</i> expands, doing its<span class="pagenum"><a name="Page_107" id="Page_107">[Pg 107]</a></span>
-work, while that in <i>D</i> is slightly compressed, the valve <i>A</i>
-being now closed. When the piston, moving toward the
-right, opens the passage <i>E</i>, the burnt gas rushes out. A
-little later, when the passage <i>I</i> is exposed, the fresh compressed
-gas in <i>D</i> rushes through <i>C</i>, <i>B</i>, and <i>I</i> to <i>F</i>. The operation
-may now be repeated. Only two strokes have been
-necessary. The cylinder develops power twice as rapidly
-as before: but at the cost of some waste of gas, since the
-inlet (<i>I</i>) and outlet (<i>E</i>) passages are for a brief interval
-<i>both open at once</i>: a condition not altogether remedied by
-the use of a deflector at <i>G</i>. A two-cycle cylinder should
-give nearly twice the power of a four-cycle cylinder of the
-same size, and the two-cycle engine should weigh less,
-per horse-power; but it requires from 10 to 30% more
-fuel, and fuel also counts in the total weight.</p>
-
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg106.jpg" alt="Action of Two-Cycle Engine"
-     width="600" height="362"/>
-</div>
-<div class="caption">Action of Two-Cycle Engine</div>
-
-<p>The high temperatures in the cylinder would soon make
-the cast-iron walls red-hot, unless the latter where artificially
-cooled. The usual method of cooling is to make
-the walls hollow and circulate water through them. This
-involves a pump, a quantity of water, and a &ldquo;radiator&rdquo;
-(cooling machine) so that the water can be used over and
-over again. To cool by air blowing over the surface of
-the cylinder is relatively ineffective: but has been made
-possible in automobiles by building fins on the cylinders
-so as to increase the amount of cooling surface. When the
-motors are worked at high capacity, or when two-cycle
-motors are used, the heat is generated so rapidly that this
-method of cooling is regarded as inapplicable. By rapidly<span class="pagenum"><a name="Page_108" id="Page_108">[Pg 108]</a></span>
-rotating the cylinders themselves through the air, as in
-motors like the Gnome, air cooling is made sufficiently
-adequate, but the expenditure of power in producing this
-rotation has perhaps not been sufficiently regarded.</p>
-
-
-<div class="figcenter" style="width: 461px">
-<img src="images/pg108.jpg" alt="Motor and Propeller"
-     width="461" height="500"/>
-</div>
-<div class="caption">Motor and Propeller<br />
-<span class="normal">(Detroit Aeronautic Construction Co.)</span></div>
-
-<p>Possible progress in weight economy is destined to be
-limited by the necessity for reserve motor equipment.</p>
-
-<p>The engine used is usually the four-cycle, single-acting,
-four-cylinder gasoline motor of the automobile, designed<span class="pagenum"><a name="Page_109" id="Page_109">[Pg 109]</a></span>
-for great lightness. The power from each cylinder of
-such a motor is approximately that obtained by dividing
-the square of the diameter in inches by the figure 2-1/2.
-Thus a five-inch cylinder should give ten horse-power&mdash;at
-normal piston speed. On account of friction losses
-and the wastefulness of a screw propeller, not more than
-half this power is actually available for propulsion.</p>
-
-<p>The whole power plant of the <i>Clément-Bayard</i> weighed
-about eleven pounds to the horse-power. This balloon
-was 184 feet long and 35 feet in maximum diameter,
-displacing about 100,000 cubic feet. It carried six passengers,
-about seventy gallons of fuel, four gallons of
-lubricating oil, fifteen gallons of water, 600 pounds of
-ballast, and 130 pounds of ropes. The motor developed
-100 horse-power at a thousand revolutions per minute.
-About eight gallons of fuel and one gallon of oil were consumed
-per hour when running at the full independent
-speed of thirty-seven miles per hour.</p>
-
-<p>The Wellman balloon <i>America</i> is said to have consumed
-half a ton of gasoline per twenty-four hours: an eight days&rsquo;
-supply was carried. The gas leakage in this balloon was
-estimated to have been equivalent to a loss of 500 pounds
-of lifting power per day.</p>
-
-<p>The largest of dirigibles, the <i>Zeppelin</i>, had two motors
-of 170 horse-power each. It made, in 1909, a trip of over
-800 miles in thirty-eight hours.</p>
-
-<p>The engine of the original Voisin cellular biplanes was
-an eight-cylinder Antoinette of fifty horse-power, set near
-the rear edge of the lower of the main planes. The
-Wright motors are placed near the front edge. A twenty-five
-horse-power motor at 1400 revolutions propelled
-the Fort Myer machine, which was built to carry two
-passengers, with fuel for a 125 mile flight: the total
-weight of the whole flying apparatus being about half
-a ton.</p>
-
-
-<p><span class="pagenum"><a name="Page_110" id="Page_110">[Pg 110]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg110a.jpg" alt="Two-Cylinder Opposed Engine."
-     width="600" height="339"/>
-</div>
-<div class="caption">Two-Cylinder Opposed Engine.<br />
-  <span class="normal">(From <cite>Aircraft</cite>)</span></div>
-
-<hr />
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg110b.jpg" alt="Four-Cylinder Vertical Engine"
-     width="600" height="419"/>
-</div>
-<div class="caption">Four-Cylinder Vertical Engine<br />
-(The Dean Manufacturing Co.)</div>
-
-<p>
-<span class="pagenum"><a name="Page_111" id="Page_111">[Pg 111]</a></span>
-The eight-cylinder Antoinette motor on a Farman biplane,
-weighing 175 pounds, developed thirty-eight horse-power
-at 1050 revolutions. The total weight of the machine
-was nearly 1200 pounds, and its speed twenty-eight
-miles per hour.</p>
-
-<p>The eight-cylinder Curtiss motor on the <i>June Bug</i> was
-air cooled. This aeroplane weighed 650 pounds and made
-thirty-nine miles per hour, the engine developing twenty-five
-horse-power at 1200 turns.</p>
-
-
-<h3>Resistance of Aeroplanes</h3>
-
-<p>The chart on page <a href="#Page_24">24</a> (see also the diagram of page
-<a href="#Page_23">23</a>) shows that the lifting power of an aeroplane increases
-as the angle of inclination increases, up to a certain limit.
-The resistance to propulsion also increases, however: and
-the ratio of lifting power to resistance is greatest at a very
-small angle&mdash;about five or six degrees. Since the motor
-power and weight are ruling factors in design, it is important
-to fly at about this angle. The supporting force is
-then about two pounds, and the resistance about three-tenths
-of a pound, per square foot of sail area, if the velocity<span class="pagenum"><a name="Page_112" id="Page_112">[Pg 112]</a></span>
-is that assumed in plotting the chart: namely, about
-fifty-five miles per hour.</p>
-
-<p>But the resistance <i>R</i> indicated on pages <a href="#Page_23">23</a>
-and <a href="#Page_24">24</a> is not
-the only resistance to propulsion. In addition, we have
-the frictional resistance of the air sliding along the sail surface.
-The amount of this resistance is independent of the
-angle of inclination: it depends directly upon the area of
-the planes, and in an indirect way on their dimensions in
-the direction of movement. It also varies nearly with the
-square of the velocity. At any velocity, then, the addition
-of this frictional resistance, which does not depend on the
-angle of inclination, modifies our views as to the desirable
-angle: and the total resistance reaches a minimum (in proportion
-to the weight supported) when the angle is about
-three degrees and the velocity about fifty miles per hour.</p>
-
-<p>This is not quite the best condition, however. The skin
-friction does not vary exactly with the square of the velocity:
-and when the true law of variation is taken into account,
-it is found that the <em>horse-power</em> is a minimum at
-an angle of about five degrees and a speed of about forty
-miles per hour. The weight supported per horse-power
-may then be theoretically nearly a hundred pounds: and the
-frictional resistance is about one-third the direct pressure
-resistance. This must be regarded as the approximate
-condition of best effectiveness: not the exact condition,
-because in arriving at this result we have regarded the
-sails as square flat planes whereas in reality they are
-arched and of rectangular form.</p>
-
-<p><span class="pagenum"><a name="Page_113" id="Page_113">[Pg 113]</a></span></p>
-
-<p>At the most effective condition, the resistance to propulsion
-is only about one-tenth the weight supported.
-Evidently the air is helping the motor.</p>
-
-
-<h3>Resistance of Dirigibles</h3>
-
-<p>If the bow of a balloon were cut off square, its head end
-resistance would be that given by the rule already cited
-(page <a href="#Page_19">19</a>): one three-hundredth pound per square foot,
-multiplied by the square of the velocity. But by pointing
-the bow an enormous reduction of this pressure is possible.
-If the head end is a hemisphere (as in the English
-military dirigible), the reduction is about one-third. If
-it is a sharp cone, the reduction may be as much as four-fifths.
-Unless the stern is also tapered, however, there
-will be a considerable eddy resistance at that point.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg113.jpg" alt="Head End Shapes"
-     width="600" height="141"/>
-</div>
-<div class="caption">Head End Shapes</div>
-
-<p>If head end resistance were the only consideration, then
-for a balloon of given diameter and end shape it would be
-independent of the length and capacity. The longer the
-balloon, the better. Again, since the volume of any solid
-body increases more rapidly than its surface (as the linear
-dimensions are increased), large balloons would have
-a distinct advantage over small ones. The smallest<span class="pagenum"><a name="Page_114" id="Page_114">[Pg 114]</a></span>
-dirigible ever built was that of Santos-Dumont, of about
-5000 cubic feet.</p>
-
-<p>Large balloons, however, are structurally weak: and
-more is lost by the extra bracing necessary than is gained
-by reduction of head end resistance. It is probable that
-the Zeppelin represents the limit of progress in this direction;
-and even in that balloon, if it had not been that the
-adoption of a rigid type necessitated great structural
-strength, it is doubtful if as great a length would have been
-fixed upon, in proportion to the diameter.</p>
-
-<p>The frictional resistance of the air gliding along the surface
-of the envelope, moreover, invalidates any too arbitrary
-conclusions. This, as in the aeroplane, varies nearly
-as the square of the velocity, and is usually considerably
-greater than the direct head end resistance. Should the
-steering gear break, however, and the wind strike the <em>side</em>
-of the balloon, the pressure of the wind against this greatly
-increased area would absolutely deprive it of dirigibility.</p>
-
-<p>A stationary, drifting, or &ldquo;sailing&rdquo; balloon may as well
-have the spherical as well as any other shape: it makes the
-wind a friend instead of a foe and requires nothing in the
-way of control other than regulation of altitude.</p>
-
-
-<h3>Independent Speed and Time Table</h3>
-
-<p>The air pressure, direct and frictional resistances, and
-power depend upon the <em>relative</em> velocity of flying machine
-and air. It is this relative velocity, not the velocity of
-the balloon as compared with a point on the earth&rsquo;s surface,
-that marks the limit of progression. Hence the speed
-of the wind is an overwhelming factor to be reckoned with
-in developing an aerial time table. If we wish to travel
-east at an effective speed of thirty miles per hour, while the
-wind is blowing due west at a speed of ten miles, our machine
-must have an independent speed of forty miles.
-On the other hand, if we wish to travel west, an independent
-speed of twenty miles per hour will answer.</p>
-
-
-<p><span class="pagenum"><a name="Page_115" id="Page_115">[Pg 115]</a></span><br /></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg115.jpg" alt="The Santos-Dumont No. 2 (1909)"
-     width="600" height="385"/>
-</div>
-<div class="caption">The Santos-Dumont No. 2 (1909)</div>
-
-<p>
-<span class="pagenum"><a name="Page_116" id="Page_116">[Pg 116]</a></span>
-Again, if the wind is blowing north at thirty miles per
-hour, and the minimum (relative) velocity at which an
-aeroplane will sustain its load is forty miles per hour, we
-cannot progress northward any more slowly than at seventy
-miles&rsquo; speed. And we have this peculiar condition
-of things: suppose the wind to be blowing north at fifty
-miles per hour. The aeroplane designed for a forty mile
-speed may then face this wind and sustain itself while
-actually moving backward at an absolute speed (as seen
-from the earth) of ten miles per hour.</p>
-
-<p>We are at the mercy of the wind, and wind velocities
-may reach a hundred miles an hour. The inherent disadvantage
-of aerial flight is in what engineers call its
-&ldquo;low load factor.&rdquo; That is, the ratio of normal performance
-required to possible abnormal performance necessary
-under adverse conditions is extremely low. To make a
-balloon truly dirigible throughout the year involves, at
-Paris, for example, as we have seen, a speed exceeding
-fifty-four miles per hour: and even then, during one-tenth
-the year, the <em>effective</em> speed would not exceed twenty miles
-per hour. A time table which required a schedule speed
-reduction of 60% on one day out of ten would be obviously
-unsatisfactory.</p>
-
-<p><span class="pagenum"><a name="Page_117" id="Page_117">[Pg 117]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg117.jpg" alt="In the Bay of Monaco Santos-Dumont's No. 6"
-     width="600" height="284"/>
-</div>
-<div class="caption">In the Bay of Monaco Santos-Dumont&rsquo;s No. 6<br />
-  <span class="normal">The flights terminated with a fall into the sea,
-                       happily without injury to the operator</span></div>
-
-<p>
-<span class="pagenum"><a name="Page_118" id="Page_118">[Pg 118]</a></span>
-Further, if we aim at excessively high independent
-speeds for our dirigible balloons, in order to become independent
-of wind conditions, we soon reach velocities at
-which the gas bag is unnecessary: that is, a simple wing
-surface would at those speeds give ample support. The
-increased difficulty of maintaining rigidity of the envelope,
-and of steering, at the great pressures which would accompany
-these high velocities would also operate against the
-dirigible type.</p>
-
-<p>With the aeroplane, higher speed means less sail area
-for a given weight and a stronger machine. Much higher
-speeds are probable. We have already a safe margin as
-to weight per horse-power of motor, and many aeroplane
-motors are for stanchness purposely made heavier than
-they absolutely need to be.</p>
-
-
-<h3>The Cost of Speed</h3>
-
-<p>Since the whole resistance, in either type of flying machine,
-is approximately proportional to the square of the
-velocity; and since horse-power (work) is the product of
-resistance and velocity, the horse-power of an air craft
-of any sort varies about as the cube of the speed. To
-increase present speeds of dirigible balloons from thirty
-to sixty miles per hour would then mean eight times as
-much horse-power, eight times as much motor weight,
-<span class="pagenum"><a name="Page_119" id="Page_119">[Pg 119]</a></span>
-eight times as rapid a rate of fuel consumption, and (since
-the speed has been doubled) four times as rapid a consumption
-of fuel in proportion to the distance traveled.
-Either the radius of action must be decreased, or the weight
-of fuel carried must be greatly increased, if higher velocities
-are to be attained. Present (independent) aeroplane
-speeds are usually about fifty miles per hour, and there is
-not the necessity for a great increase which exists with the
-lighter-than-air machines. We have already succeeded in
-carrying and propelling fifty pounds of total load or fifteen
-pounds of passenger load per horse-power of motor, with
-aeroplanes; the ratio of net load to horse-power in the dirigible
-is considerably lower; but the question of weight in
-relation to power is of relatively smaller importance in the
-latter machine, where support is afforded by the gas and
-not by the engine.</p>
-
-
-<h3>The Propeller</h3>
-
-<p>Very little effort has been made to utilize paddle wheels
-for aerial propulsion; the screw is almost universally employed.
-Every one knows that when a bolt turns in a
-stationary nut, it moves forward a distance equal to the
-<em>pitch</em> (lengthwise distance between two adjacent threads)
-at every revolution. A screw propeller is a bolt partly
-cut away for lightness, and the &ldquo;nut&rdquo; in which it works
-is water or air. It does not move forward quite as much as
-its pitch, at each revolution, because any fluid is more or
-less slippery as compared with a nut of solid metal. The
-difference between the pitch and the actual forward movement<span class="pagenum"><a name="Page_120" id="Page_120">[Pg 120]</a></span>
-of the vessel at each revolution is called the &ldquo;slip,&rdquo;
-or &ldquo;slip ratio.&rdquo; It is never less than ten or twelve per cent
-in marine work, and with aerial screws is much greater.
-Within certain limits, the less the slip, the greater the
-efficiency of the propeller. Small screws have relatively
-greater slips and less efficiency, but are lighter. The maximum
-efficiency of a screw propeller in water is under 80%.
-According to Langley&rsquo;s experiments, the usual efficiency in
-air is only about 50%. This means that only half the power
-of the motor will be actually available for producing forward
-movement&mdash;a conclusion already foreshadowed.</p>
-
-<p>In common practice, the pitch of aerial screws is not
-far from equal to the diameter. The rate of forward movement,
-if there were no slip, would be proportional to the
-pitch and the number of revolutions per minute. If the
-latter be increased, the former may be decreased. Screws
-direct-connected to the motors and running at high speeds
-will therefore be of smaller pitch and diameter than those
-run at reduced speed by gearing, as in the machine illustrated
-on page <a href="#Page_134">134</a>. The number of blades is usually two,
-although this gives less perfect balance than would a larger
-number. The propeller is in many monoplanes placed in
-<em>front</em>: this interferes, unfortunately, with the air currents
-against the supporting surfaces.</p>
-
-<p>There is always some loss of power in the bearings and
-power-transmitting devices between the motor and propeller.
-This may decrease the power usefully exerted
-even to <em>less</em> than half that developed by the motor.</p>
-
-<div>
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_121" id="Page_121">[Pg 121]</a></span></p>
-<h2>GETTING UP AND DOWN: MODELS AND GLIDERS: AEROPLANE DETAILS</h2></div>
-
-
-<h3>Launching</h3>
-
-<p>The Wright machines (at least in their original form)
-have usually been started by the impetus of a falling weight,
-which propels them along skids until the velocity suffices
-to produce ascent. The preferred designs among French
-machines have contemplated self-starting equipment.
-This involves mounting the machine on pneumatic-tired
-bicycle wheels so that it can run along the ground. If a
-fairly long stretch of good, wide, straight road is available,
-it is usually possible to ascend. The effect of altitude
-and atmospheric density on sustaining power is
-forcibly illustrated by the fact that at Salt Lake City
-one of the aviators was unable to rise from the ground.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg121.jpg"
-     width="600" height="152"
-     alt="Wright Biplane on Starting Rail, showing Pylon and Weight" />
-
-</div>
-<div class="caption">Wright Biplane on Starting Rail, showing Pylon and Weight
-</div>
-
-<p>To accelerate a machine from rest to a given velocity
-in a given time or distance involves the use of propulsive
-force additional to that necessary to maintain the velocity
-attained. Apparently, therefore, any self-starting machine
-must have not only the extra weight of framework and
-wheels but also extra motor power.</p>
-
-
-
-<p><span class="pagenum"><a name="Page_122" id="Page_122">[Pg 122]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg122.jpg" alt="Launching System for Wright Aeroplane"
-     width="600" height="246"/>
-</div>
-<div class="caption">Launching System for Wright Aeroplane<br />
-  <span class="normal">(From Brewer&rsquo;s <cite>Art of Aviation</cite>)</span>
-</div>
-
-<p>
-<span class="pagenum"><a name="Page_123" id="Page_123">[Pg 123]</a></span>
-Upon closer examination of the matter, we may find a
-particularly fortunate condition of things in the aeroplane.
-Both sustaining power and resistance vary with the inclination
-of the planes, as indicated by the chart on page <a href="#Page_24">24</a>.
-It is entirely possible to start with no such inclination, so
-that the direct wind resistance is eliminated. The motor
-must then overcome only air friction, in addition to providing
-an accelerating force. The machine runs along the
-ground, its velocity rapidly increasing. As soon as the
-necessary speed (or one somewhat greater) is attained,
-the planes are tilted and the aeroplane rises from the
-ground.</p>
-
-
-<p><span class="pagenum"><a name="Page_124" id="Page_124">[Pg 124]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg124.jpg" alt="The Nieuport Monoplane"
-     width="600" height="251"/>
-</div>
-<div class="caption">The Nieuport Monoplane<br />
-  <span class="normal">Self-Starting with an 18 hp. motor &nbsp;
-        (From <cite>The Air Scout</cite>)</span></div>
-
-<p>The velocity necessary to just sustain the load at a
-given angle of inclination is called the <em>critical</em> or <em>soaring</em>
-velocity. For a given machine, there is an angle of inclination
-(about half a right angle) at which the minimum
-speed is necessary. This speed is called the &ldquo;least soaring
-velocity.&rdquo; If the velocity is now increased, the angle of
-inclination may be reduced and the planes will soar through
-the air almost edgewise, apparently with diminished resistance
-and power consumption. This decrease in power
-as the speed increases is called <em>Langley&rsquo;s Paradox</em>, from
-its discoverer, who, however, pointed out that the rule
-does not hold in practice when frictional resistances are<span class="pagenum"><a name="Page_125" id="Page_125">[Pg 125]</a></span>
-included. We cannot expect to actually save power by
-moving more rapidly than at present; but we should have
-to provide much more power if we tried to move much
-more slowly.</p>
-
-<div class="figcenter" style="width: 359px">
-<img src="images/pg125.jpg" alt="A Biplane"
-     width="359" height="500"/>
-</div>
-<div class="caption">A Biplane<br />
-  <span class="normal">(From <cite>Aircraft</cite>)</span></div>
-
-<p><span class="pagenum"><a name="Page_126" id="Page_126">[Pg 126]</a></span></p>
-<p>Economical and practicable starting of an aeroplane thus
-requires a free launching space, along which the machine
-may accelerate with nearly flat planes: a downward slope
-would be an aid. When the planes are tilted for ascent,
-after attaining full speed, quick control is necessary to
-avoid the possibility of a back-somersault. A fairly wide
-launching platform of 200 feet length would ordinarily
-suffice. The flight made by Ely in January of this year,
-from San Francisco to the deck of the cruiser <i>Pennsylvania</i>
-and back, demonstrated the possibility of starting from a
-limited area. The wooden platform built over the after
-
-deck of the warship was 130 feet long, and sloped. On
-the return trip, the aeroplane ran down this slope, dropped
-somewhat, and then ascended successfully.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg126.jpg" alt="Ely at Los Angeles"
-     width="600" height="486"/>
-</div>
-<p>
-(Photo by American Press Association)
-</p>
-
-<div class="caption">Ely at Los Angeles</div>
-
-<p>
-<span class="pagenum"><a name="Page_127" id="Page_127">[Pg 127]</a></span>
-If the effort is made to ascend at low velocities, then the
-motor power must be sufficient to propel the machine at
-an extreme angle of inclination&mdash;perhaps the third of a
-right angle, approximating to the angle of least velocity
-for a given load. According to Chatley, this method of
-starting by Farman at Issy-les-Moulineaux involved the
-use of a motor of fifty horse-power: while Roe&rsquo;s machine
-at Brooklands rose, it is said, with only a six horse-power
-motor.</p>
-
-
-<h3 class="break">Descending</h3>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg127.jpg" alt=""
-     width="600" height="283"/>
-</div>
-
-<p>What happens when the motor stops? The velocity
-of the machine gradually decreases: the resistance to
-forward movement stops its forward movement and the
-excess of weight over upward pressure due to velocity
-causes it to descend. It behaves like a projectile, but
-the details of behavior are seriously complicated by the
-variation in head resistance and sustaining force due to
-changes in the angle of the planes. The &ldquo;angle of inclination&rdquo;
-is now not the angle made by the planes with the
-horizontal, but the angle which they make with the path
-of flight. Theory indicates that this should be about two-thirds
-the angle which the path itself makes with the
-horizontal: that is, the planes themselves are inclined
-downward toward the front. The forces which determine
-the descent are fixed by the velocity and the angle between
-the planes and the path of flight. Manipulation of the
-rudders and main planes or even the motor may be practised
-to ensure lancing to best advantage; but in spite of
-these (or perhaps on account of these) scarcely any part
-of aviation offers more dangers, demands more genius on
-the part of the operator, and has been less satisfactorily
-analyzed than the question of &ldquo;getting down.&rdquo; It is
-easy to stay up and not very hard to &ldquo;get up,&rdquo; weather
-conditions being favorable; but it is an &ldquo;all-sufficient
-job&rdquo; to <em>come down</em>. Under the new rules of the International
-Aeronautic Federation, a test flight for a pilot&rsquo;s
-license must terminate with a descent (motor stopped)
-in which the aviator is to land within fifty yards of the
-observers and come to a full stop inside of fifty yards therefrom.
-The elevation at the beginning of descent must
-be at least 150 feet.</p>
-
-
-<p><span class="pagenum"><a name="Page_128" id="Page_128">[Pg 128]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg128.jpg" alt="Descending"
-     width="600" height="352"/>
-</div>
-<div class="caption">Descending</div>
-
-<p><span class="pagenum"><a name="Page_129" id="Page_129">[Pg 129]</a></span></p>
-<h3>Gliders</h3>
-
-<p>If the motor and its appurtenances, and some of the
-purely auxiliary planes, be omitted, we have a <em>glider</em>. The
-glider is not a toy; some of the most important problems<span class="pagenum"><a name="Page_130" id="Page_130">[Pg 130]</a></span>
-of balancing may perhaps be some day solved by its aid.
-Any boy may build one and fly therewith, although a
-large kite promises greater interest. The cost is trifling,
-if the framework is of bamboo and the surfaces are cotton.
-Areas of glider surfaces frequently exceed 100 square feet.
-This amount of surface is about right for a person of moderate
-weight if the machine itself does not weigh over
-fifty pounds. By running down a slope, sufficient velocity
-may be attained to cause ascent; or in a favorable wind
-(up the slope) a considerable backward flight may be
-experienced. Excessive heights have led to fatal accidents
-in gliding experiments.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg130.jpg" alt="The Witteman Glider"
-     width="600" height="490"/>
-</div>
-<div class="caption">The Witteman Glider</div>
-
-<p><span class="pagenum"><a name="Page_131" id="Page_131">[Pg 131]</a></span></p>
-<h3>Models</h3>
-
-<p>The building of flying models has become of commercial
-importance. It is not difficult to attain a high ratio of
-surface to weight, but it is almost impossible to get motor
-power in the small units necessary without exceeding the
-permissible limit of motor weight. No gasoline engine
-or electric motor can be made sufficiently light for a toy
-model. Clockwork springs, if especially designed, may
-give the necessary power for short flights, but no better
-form of power is known just now than the twisted rubber
-band. For the small boy, a biplane with sails about
-eighteen inches by four feet, eighteen inches apart,
-anchored under his shoulders by six-foot cords while he
-rides his bicycle, will give no small amount of experience
-in balancing and will support enough of a load to make
-the experiment interesting.</p>
-
-<h3 class="break">Some Details: Balancing</h3>
-
-<div class="figcenter" style="width: 298px">
-<img src="images/pg132.jpg" alt="French Monoplane"
-     width="298" height="500"/>
-</div>
-<div class="caption">French Monoplane<br />
-  <span class="normal">(From <cite>Aircraft</cite>)</span></div>
-
-<p>It is easily possible to compute the areas, angles, and
-positions of auxiliary planes to give desired controlling or
-stabilizing effects; but the computation involves the use
-of accurate data as to positions of the various weights, and
-on the whole it is simpler to correct preliminary calculations
-by actually supporting the machine at suitable
-points and observing its balance. Stability is especially
-uncertain at very small angles of inclination, and such angles
-are to be avoided whether in ordinary operation or in<span class="pagenum"><a name="Page_132" id="Page_132">[Pg 132]</a></span>
-descent. The necessity for rotating main planes in order
-to produce ascent is disadvantageous on this ground; but
-the proposed use of sliding or jockey weights for supplementary
-balancing appears to be open to objections no
-less serious. Steering may be perceptibly assisted, in as
-delicately a balanced device as the aeroplane, by the
-<span class="pagenum"><a name="Page_133" id="Page_133">[Pg 133]</a></span>
-inclination of the body of the operator, just as in a bicycle.
-The direction of the wind in relation to the required course
-may seriously influence the steering power. Suppose the
-course to be northeast, the wind east, the independent
-speed of the machine and that of the wind being the same.
-The car will head due north. By bringing the rudder in
-position (<i>a</i>), the course may be changed to north, or
-nearly so, the wind exerting a powerful pressure on the
-rudder; but if a more easterly or east-northeast course
-be desired, and the rudder be thrown into the usual position
-therefor (<i>b</i>), it will exert no influence whatever,
-because it is moving before the wind and precisely at the
-speed of the wind.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg133.jpg" alt="A Problem in Steering"
-     width="600" height="516"/>
-</div>
-
-<p>It might be thought that, following analogies of marine
-engineering, the center of gravity of an aeroplane should
-be kept low. The effect of any unbalanced pressure or
-force against the widely extended sails of the machine is
-to rotate the whole apparatus about its center of gravity.
-The further the force from the center of gravity, the more
-powerful is the force in producing rotation. The defect
-in most aeroplanes (especially biplanes) is that the center
-of gravity is <em>too</em> low. If it could be made to coincide with
-the center of disturbing pressure, there would be no unbalancing
-effect from the latter. It is claimed that the
-steadiest machines are those having a high center of gravity;
-and the claim, from these considerations, appears
-reasonable.</p>
-
-<p><span class="pagenum"><a name="Page_134" id="Page_134">[Pg 134]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg134.jpg" alt="Lejeune Biplane"
-     width="600" height="228"/>
-</div>
-<div class="caption">Lejeune Biplane
-  <span class="normal">(385 lbs., 10-12 hp.)</span></div>
-
-<p><span class="pagenum"><a name="Page_135" id="Page_135">[Pg 135]</a></span></p>
-<h3>Weights</h3>
-
-<p>It has been found not difficult to keep down the weight
-of framework and supporting surfaces to about a pound
-per square foot. The most common ratio of surface to
-total weight is about one to two: so that the machinery
-and operator will require one square foot of surface for
-each pound of their weight. On this basis, the smallest
-possible man-carrying aeroplane would have a surface<span class="pagenum"><a name="Page_136" id="Page_136">[Pg 136]</a></span>
-scarcely below 250 square feet. Most biplanes have twice
-this surface: a thousand square feet seems to be the
-limit without structural weakness. Some recent French
-machines, designed for high speeds, show a greatly increased
-ratio of weight to surface. The <i>Hanriot</i>, a monoplane
-with wings upwardly inclined toward the outer
-edge, carries over 800 pounds on less than 300 square feet.
-The Farman monoplane of only 180 square feet sustains
-over 600 pounds. The same aviator&rsquo;s racing biplane is
-stated to support nearly 900 pounds on less than 400
-square feet.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg135.jpg" alt="The Tellier Two-seat Six-cylinder Monoplane"
-     width="600" height="288"/>
-</div>
-<div class="caption">The Tellier Two-seat Six-cylinder Monoplane at the
-Paris Show<br />
-  <span class="normal">One of this type has been sold to the Russian Government<br />
-(From <cite>Aircraft</cite>)</span></div>
-
-<p>Motor weights can be brought down to about two pounds
-per horse-power, but such extreme lightness is not always
-needed and may lead to unreliability of operation. The
-effect of an accumulation of ice, sleet, snow, rain, or dew
-might be serious in connection with flights in high altitudes
-or during bad weather. After one of his last year&rsquo;s
-flights at Étampes Mr. Farman is said to have descended
-with an extra load of nearly 200 pounds on this account.
-With ample motor power, great flexibility in weight sustention
-is made possible by varying the inclination of the
-planes. In January of this year, Sommer at Douzy carried
-six passengers in a large biplane on a cross-country
-flight: and within the week afterward a monoplane operated
-by Le Martin flew for five minutes with the aeronaut
-and seven passengers, at Pau. The total weight lifted
-was about half a ton, and some of the passengers must
-have been rather light. The two-passenger Fort Myer<span class="pagenum"><a name="Page_137" id="Page_137">[Pg 137]</a></span>
-biplane of the Wright brothers is understood to have carried
-about this total weight. These records have, however,
-been surpassed since they were noted. Bréguet, at
-Douai, in a deeply-arched biplane of new design, carried<span class="pagenum"><a name="Page_138" id="Page_138">[Pg 138]</a></span>
-eleven passengers, the total load being 2602 pounds, and
-that of aeronaut and passengers alone 1390 pounds. The
-flight was a short one, at low altitude; but the same aviator
-last year made a long flight with five passengers, and carried
-a load of 1262 pounds at 62 miles per hour. And as if
-in reply to this feat, Sommer carried a live load of 1436
-pounds (13 passengers) for nearly a mile, a day or two
-later, at Mouzon. One feels less certain than formerly,
-now, in the snap judgment that the heavier-than-air
-machine will never develop the capacity for heavy loads.</p>
-
-<div class="figcenter" style="width: 400px">
-<img src="images/pg137.jpg" alt="A Monoplane"
-     width="400" height="600"/>
-</div>
-<div class="caption">A Monoplane<br />
-  <span class="normal">(From <cite>Aircraft</cite>)</span></div>
-
-
-<h3>Miscellaneous</h3>
-
-<p>French aviators are fond of employing a carefully designed
-car for the operator and control mechanism. The
-Wright designs practically ignore the car: the aviator sits
-on the forward edge of the lower plane with his legs hanging
-over.</p>
-
-<p>It has been found that auxiliary planes must not be
-too close to the main wings: a gap of a distance about
-50% greater than the width of the widest adjacent plane
-must be maintained if interference with the supporting air
-currents is to be avoided. Main planes are now always
-arched; auxiliary planes, not as universally. The concave
-under surface of supporting wings has its analogy in the
-wing of the bird and had long years since been applied in
-the parachute.</p>
-
-<div class="figcenter" style="width: 544px">
-<img src="images/pg139a.jpg" alt="Cars and Framework"
-     width="544" height="500"/>
-</div>
-
-<p>The car (if used) and all parts of the framework should
-be of &ldquo;wind splitter&rdquo; construction, if useless resistance is<span class="pagenum"><a name="Page_139" id="Page_139">[Pg 139]</a></span>
-to be avoided. The ribs and braces of the frame are of
-course stronger, weight for weight, in this shape, since a
-narrow deep beam is always relatively stronger than one
-of square or round section. Excessive frictional resistance
-is to be avoided by using a smoothly finished fabric
-for the wings, and the method of attaching this fabric
-to the frame should be one that keeps it as flat as possible
-at all joints.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg139b.jpg" alt="Some Details"
-     width="600" height="409"/>
-</div>
-
-<p>The sketches give the novel details of some machines
-recently exhibited at the Grand Central Palace in New<span class="pagenum"><a name="Page_140" id="Page_140">[Pg 140]</a></span>
-York. The stabilizing planes were invariably found in
-the rear, in all machines exhibited.</p>
-
-
-<h3>The Things to Look After</h3>
-
-<p>The operator of an aeroplane has to do the work of at
-least two men. No vessel in water would be allowed to
-attain such speeds as are common with air craft, unless
-provided with both pilot and engineer. The aviator is
-his own pilot and his own engineer. He must both manage
-his propelling machinery and steer. Separate control
-for vertical rudders, elevating rudders and ailerons, for
-starting the engine; the adjustment of the carbureter, the
-spark, and the throttle to get the best results from the
-motor; attention to lubrication and constant watchfulness
-of the water-circulating system: these are a few of the things
-for him to consider; to say nothing of the laying of his
-course and the necessary anticipation of wind and altitude
-conditions.</p>
-
-<p>These things demand great resourcefulness, but&mdash;for
-their best control&mdash;involve also no small amount of scientific
-knowledge. For example, certain adjustments at
-the motor may considerably increase its power, a possibly
-necessary increase under critical conditions: but if such
-adjustments also decrease the motor efficiency there must
-be a nice analysis of the two effects so that extra power
-may not be gained at too great a cost in radius of action.</p>
-
-
-
-<p><span class="pagenum"><a name="Page_141" id="Page_141">[Pg 141]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg141.jpg" alt="Some Recent French Machines"
-     width="600" height="361"/>
-</div>
-<div class="caption">Some Recent French Machines
-  <span class="normal">(From <cite>Aircraft</cite>)</span></div>
-
-<p>The whole matter of flight involves both sportsman&rsquo;s
-and engineers problems. Wind gusts produce the same<span class="pagenum"><a name="Page_142" id="Page_142">[Pg 142]</a></span>
-effects as &ldquo;turning corners&rdquo;; or worse&mdash;rapidly changing
-the whole balance of the machines and requiring immediate
-action at two or three points of control. Both
-ascent and descent are influenced by complicated laws and
-are scarcely rendered safe&mdash;under present conditions&mdash;by
-the most ample experience. A lateral air current
-bewilders the steering and also demands special promptness
-and skill. To avoid disturbing surface winds, even
-over open country, a minimum flying height of 300 feet
-is considered necessary. This height, furthermore, gives
-more choice in the matter of landing ground than a lower
-elevation.</p>
-
-<p>When complete and automatic balance shall have been
-attained&mdash;as it must be attained&mdash;we may expect to
-see small amateur aeroplanes flying along country roads
-at low elevations&mdash;perhaps with a guiding wheel actually
-in contact with the ground. They will cost far less than
-even a small automobile, and the expense for upkeep will
-be infinitely less. The grasshopper will have become a
-water-spider.</p>
-
-<div>
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_143" id="Page_143">[Pg 143]</a></span></p>
-<h2>SOME AEROPLANES&mdash;SOME ACCOMPLISHMENTS</h2></div>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg143.jpg" alt="Orville Wright at Fort Myer, Va., 1908"
-     width="600" height="450"/>
-</div>
-<div class="caption">Orville Wright at Fort Myer, Va., 1908</div>
-
-<hr />
-
-<p><span class="pagenum"><a name="Page_144" id="Page_144">[Pg 144]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg144.jpg" alt="The First Balloon Flight Across the British Channel"
-     width="600" height="285"/>
-</div>
-<div class="caption">The First Balloon Flight Across the British Channel<br />
-   <span class="normal">More than a century before Blériot&rsquo;s feat,
-    Blanchard crossed from Dover to Calais</span></div>
-
-<p>The Wright biplane has already been shown (see pages
-<a href="#Page_31">31</a>, <a href="#Page_37">37</a>,
-<a href="#Page_121">121</a>, <a href="#Page_122">122</a>).
-It was distinguished by the absence
-of a wheel frame or car and by the wing-warping method of
-stabilizing. Later Wright machines have the spring frame
-and wheels for self-starting. The best known aeroplane
-of this design was built to meet specifications of the United<span class="pagenum"><a name="Page_145" id="Page_145">[Pg 145]</a></span>
-States Signal Corps issued in 1907. It was tried out
-during 1908 at Fort Myer, Va., while one of the Wright
-brothers was breaking all records in Europe: making
-over a hundred flights in all, first carrying a passenger
-and attaining the then highest altitude (360 feet) and
-greatest distance of flight (seventy-seven miles).</p>
-
-<div class="figcenter" style="width: 335px">
-<img src="images/pg145.jpg" alt="Wright Motor."
-     width="335" height="500"/>
-</div>
-<div class="caption">Wright Motor.
-   <span class="normal"> Dimensions in millimeters</span><br />
-   <span class="normal">(From Petit&rsquo;s <cite>How to Build an Aeroplane</cite>)</span>
-</div>
-
-<p>The ownership of the Wrights in the wing-warping<span class="pagenum"><a name="Page_146" id="Page_146">[Pg 146]</a></span>
-method of control is still the subject of litigation. The
-French infringers, it is stated, concede priority of application
-to the Wright firm, but maintain that such publicity
-was given the device that it was in general use
-before it was patented.</p>
-
-<p>The Fort Myer machine had sails of forty feet spread,
-six and one-half feet deep, with front elevating planes
-three by sixteen feet. It made about forty miles per hour
-with two passengers. The apparatus was specified to
-carry a passenger weight of 350 pounds, with fuel for a
-125-mile flight. The main planes were six feet apart.
-The steering rudder (double) was of planes one foot deep
-and nearly six feet high. The four-cylinder-four-cycle,
-water-cooled motor developed twenty-five horse-power at
-1400 revolutions. The two propellers, eight and one-half
-feet in diameter, made 400 revolutions.</p>
-
-<p>The flight by Mr. Wilbur Wright from the Statue of
-Liberty to the tomb of General Grant, in New York, 1909,
-and the exploits of his brother in the same year, when a new
-altitude record of 1600 feet was made and H.R.H. the
-Crown Prince of Germany was taken up as a passenger,
-are only specimens of the later work done by these pioneers
-in aerial navigation.</p>
-
-<p>Like the Wrights, the Voisin firm from the beginning
-adhered firmly to the biplane type of machine. The
-sketch gives dimensions of one of the early cellular forms
-built for H. Farman (see illustration, page <a href="#Page_147">147</a>). The
-metal screw makes about a thousand revolutions. The<span class="pagenum"><a name="Page_147" id="Page_147">[Pg 147]</a></span>
-wings are of india rubber sheeting on an ash frame, the
-whole frame and car body being of wood, the latter covered
-with canvas and thirty inches wide by ten feet long.
-The engine weighed 175 pounds. The whole weight of
-this machine was nearly 1200 pounds; that built later for
-Delagrange was brought under a thousand pounds. The
-ratio of weight to main surface in the Farman aeroplane
-was about 2-3/4 to 1.</p>
-
-<p>A modified cellular biplane also built for Farman had a
-main wing area of 560 square feet, the planes being seventy-nine
-inches wide and only fifty-nine inches apart.
-The tail was an open box, seventy-nine inches wide and of
-about ten feet spread. The cellular partitions in this tail
-were pivoted along the vertical front edges so as to serve
-as steering rudders. The elevating rudder was in front.
-The total weight was about the same as that of the first
-machine and the usual speed twenty-eight miles per hour.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg147.jpg" alt="Voisin-Farman Biplane"
-     width="600" height="268"/>
-</div>
-<div class="caption">Voisin-Farman Biplane</div>
-
-<p>Henry Farman has been flying publicly since 1907. He<span class="pagenum"><a name="Page_148" id="Page_148">[Pg 148]</a></span>
-made the first circular flight of one kilometer, and attained
-a speed of about a mile a minute, in the year following.
-In 1909 he accomplished a trip of nearly 150 miles, remaining
-four hours in the air. Farman was probably the first
-man to ascend with two passengers.</p>
-
-<div class="figcenter" style="width: 426px">
-<img src="images/pg148.jpg" alt="The Champagne Grand Prize Won by Henry Farman"
-     width="426" height="500"/>
-</div>
-<div class="caption">The Champagne Grand Prize Won by Henry Farman<br />
-  <span class="normal">80 Kilometers in 3 hours</span></div>
-
-<hr />
-
-<p><span class="pagenum"><a name="Page_149" id="Page_149">[Pg 149]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg149.jpg" alt="Farman's First Biplane at Issy-les-Moulineaux Returning to the Hangar after a Flight"
-     width="600" height="379"/>
-</div>
-<div class="caption">
-Farman&rsquo;s First Biplane at Issy-les-Moulineaux Returning to the Hangar after a Flight
-</div>
-
-<p><span class="pagenum"><a name="Page_150" id="Page_150">[Pg 150]</a></span></p>
-
-<p>The <i>June Bug</i>, one of the first Curtiss machines, is
-shown below. This was one of the lightest of biplanes,
-having a wing spread of forty-two feet and an area of
-370 square feet. The wings were transversely arched,
-being furthest apart at the center: an arrangement which
-has not been continued. It had a box tail, with a steering
-rudder of about six square feet area, <em>above</em> the tail.
-The horizontal rudder, in front, had a surface of twenty
-square feet. Four triangular ailerons were used for stability.
-The machine had a landing frame and wheels, made
-about forty miles per hour, and weighed, in operation,
-650 pounds.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg150.jpg" alt="The 'June Bug'"
-     width="600" height="354"/>
-</div>
-<div class="caption">The &ldquo;June Bug&rdquo;</div>
-
-<p>Mr. Curtiss first attained prominence in aviation circles
-by winning the <cite>Scientific American</cite> cup by his flight at
-the speed of fifty-seven miles per hour, in 1908. In the
-following year he exhibited intricate curved flights at
-Mineola, and circled Governor&rsquo;s Island in New York<span class="pagenum"><a name="Page_151" id="Page_151">[Pg 151]</a></span>
-harbor. In 1910 he made his famous flight from Albany
-to New York, stopping <i>en route</i>, as prearranged. At
-Atlantic City he flew fifty miles over salt water. A flight
-of seventy miles over Lake Erie was accomplished in September
-of the same year, the return trip being made the
-following day. On January 26, 1911, Curtiss repeatedly
-ascended and descended, with the aid of hydroplanes, in
-San Diego bay, California: perhaps one of the most important
-of recent achievements. It is understood that
-Mr. Curtiss is now attempting to duplicate some of these
-performances under the high-altitude conditions of Great
-Salt Lake. According to press reports, he has been invited<span class="pagenum"><a name="Page_152" id="Page_152">[Pg 152]</a></span>
-to give a similar demonstration before the German naval
-authorities at Kiel.</p>
-
-<div class="figcenter" style="width: 491px">
-<img src="images/pg151.jpg" alt="Curtis Biplane"
-     width="491" height="500"/>
-</div>
-
-<p>
-(Photo by Levick, N.Y.)
-</p>
-<div class="caption">Curtis Biplane</div>
-
-<hr />
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg152.jpg"
-     width="600" height="549"
-     alt="Curtiss' Hydro-Aeroplane at San Diego Getting under Way" />
-
-</div>
-<div class="caption">Curtiss&rsquo; Hydro-Aeroplane at San Diego Getting under Way<br />
-  <span class="normal">(From the <cite>Columbian Magazine</cite>)</span></div>
-
-<p>The <em>aeroscaphe</em> of Ravard was a machine designed to
-move either on water or in air. It was an aeroplane with
-pontoons or floaters. The supporting surface aggregated
-400 square feet, and the gross weight was about 1100
-pounds. A fifty horse-power Gnome seven-cylinder motor
-at 1200 revolutions drove two propellers of eight and
-ten and one-half feet diameter respectively: the propellers<span class="pagenum"><a name="Page_153" id="Page_153">[Pg 153]</a></span>
-being mounted one behind the other on the same
-shaft.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg153.jpg" alt="Flying over the Water at Fifty Miles per Hour"
-     width="600" height="382"/>
-</div>
-<div class="caption">Flying over the Water at Fifty Miles per Hour<br />
-  <span class="normal">Curtiss at San Diego Bay</span><br />
-  <span class="normal">(From the <cite>Columbian Magazine</cite>)</span></div>
-
-<p>Ely&rsquo;s great shore-to-warship flight was made without
-the aid of the pontoons which he carried. Ropes were
-stretched across the landing platform, running over sheaves
-and made fast to heavy sand bags. As a further precaution,
-a canvas barrier was stretched across the forward
-end of the platform. The descent brought the machine
-to the platform at a distance of forty feet from the upper
-end: grappling hooks hanging from the framework of the
-aeroplane then caught the weighted ropes, and the speed
-was checked (within about sixty feet) so gradually that
-&ldquo;not a wire or bolt of the biplane was injured.&rdquo;</p>
-
-<p><span class="pagenum"><a name="Page_154" id="Page_154">[Pg 154]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg154.jpg"
-     alt="Blériot-Voisin Cellular Biplane with Pontoons"
-     width="600" height="315"/>
-</div>
-<div class="caption">Blériot-Voisin Cellular Biplane with Pontoons<br />
-  <span class="normal">Hauled by a Motor Boat</span></div>
-
-<hr />
-<p><span class="pagenum"><a name="Page_155" id="Page_155">[Pg 155]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg155.jpg" alt="Latham's 'Antoinette'"
-     width="600" height="265"/>
-</div>
-<div class="caption">Latham&rsquo;s &ldquo;Antoinette&rdquo;</div>
-
-<hr />
-
-<p><span class="pagenum"><a name="Page_156" id="Page_156">[Pg 156]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg156.jpg" alt="James J. Ward at Lewiston Fair, Idaho"
-     width="600" height="374"/>
-</div>
-<div class="caption">James J. Ward at Lewiston Fair, Idaho<br />
-  <span class="normal">Flying Machine Mfg. Co. Biplane (30 hp. Motor)</span></div>
-
-<hr />
-
-<p><span class="pagenum"><a name="Page_157" id="Page_157">[Pg 157]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg157.jpg" alt="Marcel Penot in the Mohawk Biplane"
-     width="600" height="374"/>
-</div>
-<div class="caption">Marcel Penot in the Mohawk Biplane
-  <span class="normal">Mineola to Hicksville, L. I.</span><br />
-  <span class="normal">26 miles cross-country in 30 minutes (50 hp. Harriman Engine)</span>
-</div>
-
-<p><span class="pagenum"><a name="Page_158" id="Page_158">[Pg 158]</a></span></p>
-
-<p>Recent combinations of aeroplane and automobile,
-and aeroplane with motor boat, have been exhibited.
-One of the latter devices is like any monoplane, except
-that the lower part is a water-tight aluminum boat body
-carrying three passengers. It is expected to start of itself
-from the water and to fly at a low height like a flying
-fish at a speed of about seventy-five miles per hour.
-Should anything go wrong, it is capable of floating on
-the water.</p>
-
-<p>In the San Diego Curtiss flights, the machine skimmed
-along the surface of the bay, then rose to a height of a
-hundred feet, moved about two miles through the air in a
-circular course, and finally alighted close to its starting-point
-in the water. Turns were made in water as well as
-in air, a speed of forty miles per hour being attained while
-&ldquo;skimming.&rdquo; The &ldquo;hydroplanes&rdquo; used are rigid flat
-surfaces which utilize the pressure of the water for sustention,
-just as the main wings utilize air pressure. On
-account of the great density of water, no great amount of
-surface is required: but it must be so distributed as to
-balance the machine. The use of pontoons makes it possible
-to rest upon the water and to start from rest. A trip
-like Ely&rsquo;s could be made without a landing platform, with
-this type of machine; the aeroplane could either remain
-alongside the war vessel or be hoisted aboard until ready
-to venture away again.</p>
-
-<p>There are various other biplanes attracting public attention
-in this country. In France the tendency is all toward
-<span class="pagenum"><a name="Page_159" id="Page_159">[Pg 159]</a></span>
-the monoplane form, and many of the &ldquo;records&rdquo; have, during
-the past couple of years, passed from the former to
-the latter type of machine. The monoplane is simpler
-and usually cheaper. The biplane may be designed for<span class="pagenum"><a name="Page_160" id="Page_160">[Pg 160]</a></span>
-greater economy in weight and power. Farman has
-lately experimented with the monoplane type of machine:
-the large number of French designs in this class discourages
-any attempt at complete description.</p>
-
-<div class="figcenter" style="width: 391px">
-<img src="images/pg159.jpg" alt="Santos-Dumont's 'Demoiselle'"
-     width="391" height="500"/>
-</div>
-<div class="caption">Santos-Dumont&rsquo;s &ldquo;Demoiselle&rdquo;</div>
-
-<p>The smallest of aeroplanes is the Santos-Dumont <i>Demoiselle</i>.
-The original machine is said to have supported
-260 pounds on 100 square feet of area, making a speed of
-sixty miles per hour. Its proprietor was the first aviator
-in Europe of the heavier-than-air class. After having
-done pioneer work with dirigible balloons, he won the
-Deutsch prize for a hundred meter aeroplane flight (the
-first outside of the United States) in 1906; the speed being
-twenty-three miles per hour. His first flight, of 400 feet,
-in a monoplane was made in 1907.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg160.jpg" alt="Blériot Monoplane"
-     width="600" height="314"/>
-</div>
-<div class="caption">Blériot Monoplane</div>
-
-<p>The master of the monoplane has been Louis Blériot.
-Starting in 1907 with short flights in a Langley type of<span class="pagenum"><a name="Page_161" id="Page_161">[Pg 161]</a></span>
-machine, he made his celebrated cross-country run, and
-the first circling flights ever achieved in a monoplane, the
-following year. On July 25, 1909, he crossed the British
-Channel, thirty-two miles, in thirty-seven minutes.</p>
-
-<div class="figcenter" style="width: 466px">
-<img src="images/pg161.jpg" alt="Latham's Fall into the Channel"
-     width="466" height="500"/>
-</div>
-<div class="caption">Latham&rsquo;s Fall into the Channel</div>
-
-<p>The Channel crossing has become a favorite feat. Mr.<span class="pagenum"><a name="Page_162" id="Page_162">[Pg 162]</a></span>
-Latham, only two days after Blériot, all but completed
-it in his Antoinette monoplane. De Lesseps, in a
-Blériot machine, was more fortunate. Sopwith, last
-year, won the de Forest prize of $20,000 by a flight of
-174 miles from England into Belgium. The ill-fated
-Rolls made the round trip between England and France.
-Grace, contesting for the same prize, reached Belgium,
-was driven back to Calais, started on the return voyage,
-and vanished&mdash;all save some few doubtful relics lately
-found. Moisant reached London from Paris&mdash;the first
-trip on record between these cities without change of
-conveyance: and one which has just been duplicated by
-Pierre Prier, who, on April 12, made the London to Paris
-journey, 290 miles, in 236 minutes, without a stop. This
-does not, however, make the record for a continuous flight:
-which was attained by Tabuteau, who at Buc, on Dec. 30,
-1910, flew around the aerodrome for 465 minutes at the
-speed of 48-1/2 miles per hour.</p>
-
-<p>Other famous crossings include those of the Irish Sea,
-52 miles, by Loraine; Long Island Sound, 25 miles, by
-Harmon; and Lake Geneva, 40 miles, by Defaux.</p>
-
-<p>It was just about a century ago that Cayley first described
-a soaring machine, heavier than air, of a form remarkably
-similar to that of the modern aeroplane. Aside
-from Henson&rsquo;s unsuccessful attempt to build such a machine,
-in 1842, and Wenham&rsquo;s first gliding experiments
-with a triplane in 1857, soaring flight made no real progress
-until Langley&rsquo;s experiments. That investigator, with
-Maxim and others, ascertained those laws of aerial sustention
-the application of which led to success in 1903.</p>
-
-<p><span class="pagenum"><a name="Page_163" id="Page_163">[Pg 163]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg163.jpg" alt="De Lesseps in a Blériot Crossing the Channel"
-     width="600" height="366"/>
-</div>
-<p>
-(Photo by Levick, N.Y.)
-</p>
-
-<div class="caption">De Lesseps in a Blériot Crossing the Channel</div>
-
-<p>
-<span class="pagenum"><a name="Page_164" id="Page_164">[Pg 164]</a></span>
-The eight years since have held the crowded hours of
-aviation. Before this book is printed, it may be rendered
-obsolete by new developments. The exploits of Paulhan,
-of R. E. Peltèrie since 1907, Bell&rsquo;s work with his tetrahedral
-kites&mdash;all have been either stimulating or directly
-fruitful. Delagrange began to break speed records in 1908.
-A year later he attained a speed of fifty miles. The first
-woman to enjoy an aeroplane voyage was Mme. Delagrange,
-in Turin, in 1908.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg164.jpg" alt="The Maxim Aeroplane"
-     width="600" height="337"/>
-</div>
-<div class="caption">The Maxim Aeroplane</div>
-
-<hr />
-
-<p><span class="pagenum"><a name="Page_165" id="Page_165">[Pg 165]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg165.jpg" alt="Langley's Aeroplane (1896)"
-     width="600" height="245"/>
-</div>
-<div class="caption">Langley&rsquo;s Aeroplane (1896)<br />
-  <span class="normal">Steam driven</span></div>
-
-<p>The first flight in England by an English-built machine
-was made in January, 1909. That year, Count de Lambert
-flew over Paris, and in 1910 Grahame-White circled
-his machine over the city of Boston. The year 1910 surpassed
-<span class="pagenum"><a name="Page_166" id="Page_166">[Pg 166]</a></span>
-all its predecessors in increasing the range and
-control of aeroplanes; over 1500 ascents were made by
-Wright machines alone; but 1911 promises to show even
-greater results. Three men made cross-country flights
-from Belmont Park to the Statue of Liberty and back,
-in New York;
-<a name="FNanchor_2" id="FNanchor_2"></a>
-<a href="#Footnote_2" class="fnanchor">2</a>
-at least five men attained altitudes exceeding
-9,000 feet. Hamilton made the run from New York
-to Philadelphia and return, in June. The unfortunate
-Chavez all but abolished the fames of Hannibal and Napoleon<span class="pagenum"><a name="Page_167" id="Page_167">[Pg 167]</a></span>
-by crossing the icy barrier of the Alps, from Switzerland
-to Italy&mdash;in forty minutes!</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg166.jpg" alt="Robart Monoplane."
-     width="600" height="307"/>
-</div>
-<div class="caption">Robart Monoplane.</div>
-
-<p>Tabuteau, almost on New Year&rsquo;s eve, broke all distance
-records by a flight of 363 miles in less than eight hours;
-while Barrier at Memphis probably reached a speed of
-eighty-eight miles per hour (timing unofficial). With the
-new year came reports of inconceivable speeds by a machine
-skidding along the ice of Lake Erie; the successful
-receipt by Willard and McCurdy of wireless messages
-from the earth to their aeroplanes; and the proposal by
-the United States Signal Corps for the use of flying
-machines for carrying Alaskan mails.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg167.jpg" alt="Vina Monoplane."
-     width="600" height="317"/>
-</div>
-<div class="caption">Vina Monoplane.</div>
-
-<p>McCurdy all but succeeded in his attempt to fly from
-Key West to Havana, surpassing previous records by
-remaining aloft above salt water while traveling eighty
-miles. Lieutenant Bague, in March, started from Antibes,
-near Nice, for Corsica. After a 124-mile flight, breaking all
-records for sea journeys by air, he reached the islet of Gorgona,<span class="pagenum"><a name="Page_168" id="Page_168">[Pg 168]</a></span>
-near Leghorn, Italy, landing on bad ground and badly
-damaging his machine. The time of flight was 5-1/2 hours.
-Bellinger completed the 500-mile &ldquo;accommodation train&rdquo;
-flight from Vincennes to Pau; Vedrine, on April 12, by
-making the same journey in 415 minutes of actual flying
-time, won the Béarn prize of $4000; Say attained a speed
-of 74 miles per hour in circular flights at Issy-les-Moulineaux.
-Aeroplane flights have been made in Japan, India,
-Peru, and China.</p>
-
-<p>One of the most spectacular of recent achievements is
-that of Renaux, competing for the Michelin Grand Prize.
-A purse of $20,000 was offered in 1909 by M. Michelin, the
-French tire manufacturer, for the first successful flight
-from Paris to Clermont-Ferrand&mdash;260 miles&mdash;in less
-than six hours. The prize was to stand for ten years. It
-was prescribed that the aviator must, at the end of the
-journey, circle the tower of the Cathedral and alight on
-the summit of the Puy de Dome&mdash;elevation 4500 feet&mdash;on
-a landing place measuring only 40 by 100 yards, surrounded
-by broken and rugged ground and usually obscured
-by fog.</p>
-
-<p>The flight was attempted last year by Weymann, who
-fell short of the goal by only a few miles. Leon Morane
-met with a serious accident, a little later, while attempting
-the trip with his brother as a passenger. Renaux completed
-the journey with ease in his Farman biplane, carrying a
-passenger, his time being 308 minutes.</p>
-
-<p>This Michelin Grand Prize is not to be confused with the<span class="pagenum"><a name="Page_169" id="Page_169">[Pg 169]</a></span>
-Michelin Trophy of $4000 offered yearly for the longest
-flight in a closed circuit.</p>
-
-<p>Speeds have increased 50% during the past year; even
-with passengers, machines have moved more than a mile
-a minute: average motor capacities have been doubled
-or tripled. The French men and machines hold the records
-for speed, duration, distance, and (perhaps) altitude.
-The highest altitude claimed is probably that attained by
-Garros at Mexico City, early this year&mdash;12,052 feet above
-sea level. The world&rsquo;s speed record for a two-man flight
-appears to be that of Foulois and Parmalee, made at Laredo,
-Texas, March 3, 1911: 106 miles, cross-country, in 127 minutes.
-Three-fourths of all flights made up to this time have
-been made in France&mdash;a fair proportion, however, in
-American machines.</p>
-
-<p class="center">NOTE</p>
-
-<p id="p169note">
-The rapidity with which history is made in aeronautics is forcibly
-suggested by the revision of text made necessary by recent
-news. The new <i>Deutschland</i> has met the fate of its predecessors;
-the Paris-Rome-Turin flight is at this moment under way; and
-Lieutenant Bayne, attempting once more his France-to-Corsica
-flight, has&mdash;for the time being at least&mdash;disappeared.</p>
-
-<div>
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_170" id="Page_170">[Pg 170]</a></span></p>
-<h2>THE POSSIBILITIES IN AVIATION</h2></div>
-
-<p>Men now fly and will probably keep on flying; but aviation
-is still too hazardous to become the popular sport of
-the average man. The overwhelmingly important problem
-with the aeroplane is that of stability. These machines
-must have a better lateral balance when turning corners
-or when subjected to wind gusts: and the balance must
-be automatically, not manually, produced.</p>
-
-
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg170.jpg" alt="Blanc Monoplane"
-     width="600" height="323"/>
-</div>
-<div class="caption">Blanc Monoplane</div>
-
-<p>Other necessary improvements are of minor urgency and
-in some cases will be easy to accomplish. Better mechanical
-construction, especially in the details of attachments,
-needs only persistence and common sense. Structural
-strength will be increased; the wide spread of wing presents
-difficulties here, which may be solved either by<span class="pagenum"><a name="Page_171" id="Page_171">[Pg 171]</a></span>
-increasing the number of superimposed surfaces, as in triplanes,
-or in some other manner. Greater carrying capacity&mdash;two
-men instead of one&mdash;may be insisted upon:
-and this leads to the difficult question of motor weights.
-The revolving air-cooled motor may offer further possibilities:
-the two-cycle idea will help if a short radius of action
-is permissible: but a weight of less than two pounds to<span class="pagenum"><a name="Page_172" id="Page_172">[Pg 172]</a></span>
-the horse-power seems to imply, almost essentially, a lack
-of ruggedness and surety of operation. A promising field
-for investigation is in the direction of increasing propeller
-efficiencies. If such an increase can be effected, the whole
-of the power difficulty will be greatly simplified.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg171a.jpg" alt="Melvin Vaniman Triplane"
-     width="600" height="317"/>
-</div>
-<div class="caption">Melvin Vaniman Triplane</div>
-
-<hr />
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg171b.jpg" alt="Jean de Crawhez Triplane"
-     width="600" height="357"/>
-</div>
-<div class="caption">Jean de Crawhez Triplane</div>
-
-<hr />
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg172.jpg" alt="A Triplane"
-     width="600" height="317"/>
-</div>
-<div class="caption">A Triplane</div>
-
-
-<p><span class="pagenum"><a name="Page_173" id="Page_173">[Pg 173]</a></span></p>
-
-<p>This same motor question controls the proposal for
-increased speed. The use of a reserve motor would again
-increase weights; though not necessarily in proportion to
-the aggregate engine capacity. Perhaps something may
-be accomplished with a gasoline turbine, when one is
-developed. In any case, no sudden increase in speeds
-seems to be probable; any further lightening of motors
-must be undertaken with deliberation and science. If
-much higher maximum speeds are attained, there will be
-an opportunity to vary the speed to suit the requirements.
-Then clutches, gears, brakes, and speed-changing devices
-of various sorts will become necessary, and the problem of
-weights of journal bearings&mdash;already no small matter&mdash;will
-be made still more serious. And with variable speed
-must probably come variable sail area&mdash;in preference to
-tilting&mdash;so that the fabric must be reefed on its frame.
-Certainly two men, it would seem, will be needed!</p>
-
-<p>Better methods for starting are required. The hydroplane
-idea promises much in this respect. With a better
-understanding and control of the conditions associated
-with successful and safe descent&mdash;perhaps with improved
-appliances therefor&mdash;the problem of ascent will also be
-partly solved. If such result can be achieved, these
-measures of control must be made automatic.</p>
-
-<p>The building of complete aeroplanes to standard designs
-would be extremely profitable at present prices, which
-range from $2500 to $5000. Perhaps the most profitable
-part would be in the building of the motor. The framing<span class="pagenum"><a name="Page_174" id="Page_174">[Pg 174]</a></span>
-and fabric of an ordinary monoplane could easily be constructed
-at a cost below $300. The propeller may cost
-$50 more. The expense for wires, ropes, etc., is trifling;
-and unless special scientific instruments and accessories
-are required, all of the rest of the value lies in the motor
-and its accessories. Within reasonable limits, present costs
-of motors vary about with the horse-power. The amateur
-designer must therefore be careful to keep down weight and
-power unless he proposes to spend money quite freely.</p>
-
-
-<h3>The Case of the Dirigible</h3>
-
-<p>Not very much is being heard of performances of dirigible
-balloons just at present. They have shown themselves
-to be lacking in stanchness and effectiveness under
-reasonable variations of weather. We must have fabrics
-that are stronger for their weight and more impervious.
-Envelopes must be so built structurally as to resist deformation
-at high speeds, without having any greatly increased
-weight. A cheap way of preparing pure hydrogen gas
-is to be desired.</p>
-
-<p>Most important of all, the balloon must have a higher
-speed, to make it truly dirigible. This, with sufficient
-steering power, will protect it against the destructive
-accidents that have terminated so many balloon careers.
-Here again arises the whole question of power in relation
-to motor weight, though not as formidably as is the case
-with the aeroplane. The required higher speeds are possible
-now, at the cost merely of careful structural design,<span class="pagenum"><a name="Page_175" id="Page_175">[Pg 175]</a></span>
-reduced radius of action, and reduced passenger carrying
-capacity.</p>
-
-<p>Better altitude control will be attained with better fabrics
-and the use of plane fin surfaces at high speeds. The
-employment of a vertically-acting propeller as a somewhat
-wasteful but perhaps finally necessary measure of safety
-may also be regarded as probable.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg175.jpg" alt="Giraudon's Wheel Aeroplane"
-     width="600" height="361"/>
-</div>
-<div class="caption">Giraudon&rsquo;s Wheel Aeroplane</div>
-
-<h3>The Orthopter</h3>
-
-<p>The <em>aviplane</em>, <em>ornithoptère</em> or <em>orthopter</em> is a flying machine
-with bird-like flapping wings, which has received occasional
-attention from time to time, as the result of a too
-blind adherence to Nature&rsquo;s analogies. Every mechanical
-principle is in favor of the screw as compared with any
-reciprocating method of propulsion. There have been
-few actual examples of this type: a model was exhibited
-at the Grand Central Palace in New York in January of
-this year.</p>
-
-<p><span class="pagenum"><a name="Page_176" id="Page_176">[Pg 176]</a></span></p>
-
-<p>The mechanism of an orthopter would be relatively
-complex, and the flapping wings would have to &ldquo;feather&rdquo;
-on their return stroke. The flapping speed would have to
-be very high or the surface area very great. This last
-requirement would lead to structural difficulties. Propulsion
-would not be uniform, unless additional complications
-were introduced. The machine would be the most
-difficult of any type to balance. The motion of a bird&rsquo;s
-wing is extremely complicated in its details&mdash;one that it
-would be as difficult to imitate in a mechanical device as
-it would be for us to obtain the structural strength of an
-eagle&rsquo;s wing in fabric and metal, with anything like the
-same extent of surface and limit of weight. According to
-Pettigrew, the efficiency of bird and insect flight depends
-largely upon the elasticity of the wing. Chatley gives the
-ratio of area to weight as varying from fifty (gnat) to
-one-half (Australian crane) square feet per pound. The
-usual ratio in aeroplanes is from one-third to one-half.</p>
-
-<p>About the only advantages perceptible with the orthopter
-type of machine would be, first, the ability &ldquo;to start
-from rest without a preliminary surface glide&rdquo;; and second,
-more independence of irregularity in air currents,
-since the propulsive force is exerted over a greater extent
-than is that of a screw propeller.</p>
-
-
-<h3>The Helicopter</h3>
-
-<p>The <em>gyroplane</em> or <em>helicopter</em> was the type of flying machine
-regarded by Lord Kelvin as alone likely to survive. It
-
-lifts itself by screw propellers acting vertically. This
-form was suggested in 1852. When only a single screw
-was used, the whole machine rotated about its vertical
-axis. It was attempted to offset this by the use of vertical
-fin-planes: but these led to instability in the presence of
-irregular air currents. One early form had two oppositely-pitched
-screws driven by a complete steam engine and
-boiler plant. One of the Cornu helicopters had adjustable
-inclined planes under the two large vertically propelling
-screws. The air which slipped past the screws imposed
-a pressure on the inclined planes which was utilized to
-produce horizontal movement in any desired direction&mdash;if
-the wind was not too adverse. A gasoline engine was
-carried in a sort of well between the screws.</p>
-
-<p><span class="pagenum"><a name="Page_177" id="Page_177">[Pg 177]</a></span></p>
-<div class="figcenter" style="width: 600px">
-<img src="images/pg177.jpg" alt="Bréguet Gyroplane During Construction"
-     width="600" height="211"/>
-</div>
-<div class="caption">Bréguet Gyroplane During Construction<br />
-  <span class="normal">(Helicopter type)</span></div>
-
-<p>
-<span class="pagenum"><a name="Page_178" id="Page_178">[Pg 178]</a></span>
-The helicopter may be regarded as the limiting type of
-aeroplane, the sail area being reduced nearly to zero; the
-wings becoming mere fins, the smaller the better. It
-therefore requires maximum motor power and is particularly
-dependent upon the development of an excessively
-light motor. It is launched and descends under perfect
-control, without regard to horizontal velocity. It has
-very little exposed surface and is therefore both easy to
-steer and independent of wind conditions. By properly
-arranging the screws it can be amply balanced: but it must
-have a particularly stout and strong frame.</p>
-
-<p>The development of this machine hinges largely on the
-propeller. It is not only necessary to develop <em>power</em>
-(which means force multiplied by velocity) but actual<span class="pagenum"><a name="Page_179" id="Page_179">[Pg 179]</a></span>
-propulsive vertical <em>force</em>: and this must exceed or at least
-equal the whole weight of the machine. From ten to
-forty pounds of lifting force per horse-power have been
-actually attained: and with motors weighing less than five
-pounds there is evidently some margin. The propellers
-are of special design, usually with very large blades. Four
-are commonly used: one, so to speak, at each &ldquo;corner&rdquo;
-of the machine. The helicopter is absolutely dependent
-upon its motors. It cannot descend safely if the power
-fails. If it is to do anything but ascend and descend it
-must have additional propulsive machinery for producing
-horizontal movement.</p>
-
-
-<h3 class="break">Composite Types</h3>
-
-<p>The aeroplane is thus particularly weak as to stability,
-launching, and descending: but it is economical in power
-because it uses the air to hold itself up. The dirigible
-balloon is lacking in power and speed, but can ascend and
-descend safely, even if only by wasteful methods; and it
-can carry heavy weights, which are impossible with the
-structurally fragile aeroplane. The helicopter is wasteful
-in power, but is stable and sure in ascending and
-descending, providing only that the motor power does not
-fail.</p>
-
-<p>Why, then, not combine the types? An aeroplane-dirigible
-would be open to only one objection: on the
-ground of stability. The dirigible-helicopter would have
-as its only disadvantage a certain wastefulness of power,
-<span class="pagenum"><a name="Page_180" id="Page_180">[Pg 180]</a></span>
-while the aeroplane-helicopter would seem to have no
-drawback whatever.</p>
-
-<p>All three combinations have been, or are being, tried.
-An Italian engineer officer has designed a balloon-aeroplane.
-The balloon is greatly flattened, or lens-shaped,
-and floats on its side, presenting its edge to the horizon&mdash;if
-inclination be disregarded. With some inclination, the
-machine acts like an aeroplane and is partially self-sustaining
-at any reasonable velocity.</p>
-
-<p>The use of a vertically-acting screw on a dirigible combines
-the features of that type and the helicopter. This
-arrangement has also been the subject of design (as in
-Captain Miller&rsquo;s flexible balloon) if not of construction.
-The combination of helicopter and aeroplane seems especially
-promising: the vertical propellers being employed for
-starting and descending, as an emergency safety feature
-and perhaps for aid in stabilizing. The fact that composite
-types of flying machine have been suggested is perhaps,
-however, an indication that the ultimate type has not
-yet been established.</p>
-
-
-<h3>What is Promised</h3>
-
-<p>The flying machine will probably become the vehicle
-of the explorer. If Stanley had been able to use a small
-high-powered dirigible in the search for Livingstone, the
-journey would have been one of hours as compared with
-months, the food and general comfort of the party would
-have been equal in quality to those attainable at home,<span class="pagenum"><a name="Page_181" id="Page_181">[Pg 181]</a></span>
-and the expense in money and in human life would
-have been relatively trifling.</p>
-
-
-
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg181.jpg" alt="Wellman's America"
-     width="600" height="324"/>
-</div>
-<div class="caption">Wellman&rsquo;s America<br />
-  <span class="normal">(From Wellman&rsquo;s <cite>Aerial Age</cite>)</span>
-</div>
-
-<p>Most readers will remember the fate of Andrée, and the
-projected polar expeditions of Wellman in 1907 and 1909.
-Misfortune accompanied both attempts; but one has only
-to read Peary&rsquo;s story of the dogged tramp over the Greenland
-ice blink to realize that danger and misfortune in
-no less degree have accompanied other plans of Arctic
-pioneering. With proper design and the right men, it
-does not seem unreasonable to expect that a hundred
-flying machines may soar above Earth&rsquo;s invisible axial
-points during the next dozen years.
-<a name="FNanchor_3" id="FNanchor_3"></a>
-<a href="#Footnote_3" class="fnanchor">3</a></p>
-<p><span class="pagenum"><a name="Page_182" id="Page_182">[Pg 182]</a></span></p>
-
-<p>The report of Count Zeppelin&rsquo;s Spitzbergen expedition
-of last year has just been made public. This
-was undertaken to ascertain the adaptability of flying
-machines for Arctic navigation. Besides speed and radius
-of action, the conclusive factors include that of
-freedom from such breakdowns as cannot be made good
-on the road.</p>
-
-<p>For exploration in other regions, the balloon or the aeroplane
-is sure to be employed. Rapidity of progress without
-fatigue or danger will replace the floundering through
-swamps, shivering with ague, and bickering with hostile
-natives now associated with tropical and other expeditions.
-The stereoscopic camera with its scientific adjuncts will
-permit of almost automatic map-making, more comprehensive
-and accurate than any now attempted in other
-than the most settled sections. It is not too much to
-expect that arrangements will be perfected for conducting
-complete topographical surveys without more than occasional
-descents. If extremely high altitudes must be
-attained&mdash;over a mile&mdash;the machines will be of special
-design; but as far as can now be anticipated, there will
-be no insurmountable difficulties. The virgin peaks of
-Ruwenzori and the Himalayas may become easily accessible&mdash;even
-to women and children if they desire it. We
-may obtain direct evidence as to the contested ascent of
-Mt. McKinley. A report has been current that a Blériot
-monoplane has been purchased for use in the inspection
-of construction work for an oil pipe line across the Persian<span class="pagenum"><a name="Page_183" id="Page_183">[Pg 183]</a></span>
-desert; the aeroplane being regarded as &ldquo;more expeditious
-and effectual&rdquo; than an automobile.</p>
-
-<p>The flying machine is the only land vehicle which
-requires no &ldquo;permanent way.&rdquo; Trains must have rails,
-bicycles and automobiles must have good roads. Even
-the pedestrian gets along better on a path. The ships of
-the air and the sea demand no improvement of the fluids
-in which they float. To carry mails, parcels, persons, and
-even light freight&mdash;these applications, if made commercially
-practicable tomorrow,
-<a name="FNanchor_4" id="FNanchor_4"></a>
-<a href="#Footnote_4" class="fnanchor">4</a>
-would surprise no one; their
-possibility has already been amply demonstrated. With
-the dirigible as the transatlantic liner and the aeroplane
-as the naphtha launch of the air, the whole range of applications
-is commanded. Hangars and landing stages&mdash;the
-latter perhaps on the roofs of buildings, revolutionizing
-our domestic architecture&mdash;may spring up as rapidly
-as garages have done. And the aeroplane is potentially
-(with the exception of the motorcycle) the cheapest of
-self-propelled vehicles.</p>
-
-<p>Governments have already considered the possibilities
-of aerial smuggling. Perhaps our custom-house officers
-will soon have to watch a fence instead of a line: to barricade
-in two dimensions instead of one. They will need
-to be provided with United States Revenue aeroplanes.
-But how are aerial frontiers to be marked? And does a<span class="pagenum"><a name="Page_184" id="Page_184">[Pg 184]</a></span>
-nation own the air above it, or is this, like the high seas,
-&ldquo;by natural right, common to all&rdquo;? Can a flying-machine
-blockade-runner above the three-mile height claim extraterritoriality?</p>
-
-<p>The flying machine is no longer the delusion of the
-&ldquo;crank,&rdquo; because it has developed a great industry. A
-now antiquated statement put the capitalization of aeroplane
-manufactories in France at a million dollars, and the
-development expenditure to date at six millions. There
-are dozens of builders, in New York City alone, of monoplanes,
-biplanes, gliders, and models. A permanent exhibition
-of air craft is just being inaugurated. We have now
-even an aeronautic &ldquo;trust,&rdquo; since the million-dollar capitalization
-of the Maxim, Blériot, Grahame-White firm.</p>
-
-<p>According to the New York <cite>Sun</cite>, over $500,000 has been
-subscribed for aviation prizes in 1911. The most valuable
-prizes are for new records in cross-country flights. The
-Paris <i>Journal</i> has offered $70,000 for the best speed in a
-circling race from Paris to Berlin, Brussels, London, and
-back to Paris&mdash;1500 miles. Supplementary prizes from
-other sources have increased the total stake in this race to
-$100,000. A purse of $50,000 is offered by the London
-<cite>Daily Mail</cite> for the &ldquo;Circuit of Britain&rdquo; race, from London
-up the east coast to Edinburgh, across to Glasgow, and
-home by way of the west coast, Exeter, and the Isle of
-Wight; a thousand miles, to be completed in two weeks,
-beginning July 22, with descents only at predetermined
-points. This contest will be open (at an entrance fee of<span class="pagenum"><a name="Page_185" id="Page_185">[Pg 185]</a></span>
-$500) to any licensee of the International Federation. A
-German circuit, from Berlin to Bremen, Magdeburg, Düsseldorf,
-Aix-la-Chapelle, Dresden, and back to the starting
-point, is proposed by the <cite>Zeitung am Mittag</cite> of Berlin, a
-prize of $25,000 having been offered. In this country, a
-comparatively small prize has been established for a run
-from San Francisco to New York, <i>via</i> Chicago. Besides a
-meet at Bridgeport, May 18-20, together with those to be
-held by several of the colleges and the ones at Bennings
-and Chicago, there will be, it is still hoped, a national
-tournament at Belmont Park at the end of the same month.
-Here probably a dozen aviators will contest in qualification
-for the international meet in England, to which three
-American representatives should be sent as competitors
-for the championship trophy now held by Mr. Grahame-White.
-It is anticipated that the chances in the international
-races favor the French aviators, some of whom&mdash;in
-particular, Leblanc&mdash;have been making sensational
-records at Pau. Flights between aviation fields in different
-cities are the leading feature in the American program for
-the year. A trip is proposed from Washington to Belmont
-Park, <i>via</i> Atlantic City, the New Jersey coast, and lower
-New York bay. The distance is 250 miles and the time
-will probably be less than that of the best passenger trains
-between Washington and New York. If held, this race
-will probably take place late in May. It is wisely concluded
-that the advancement of aviation depends upon cross-country
-runs under good control and at reasonable speeds<span class="pagenum"><a name="Page_186" id="Page_186">[Pg 186]</a></span>
-and heights rather than upon exhibition flights in enclosures.
-It is to be hoped that commercial interests will not
-be sufficiently powerful to hinder this development.</p>
-
-<p>We shall of course have the usual international championship
-balloon race, preceded by elimination contests. From
-present indications Omaha is likely to be chosen as the
-point of departure.</p>
-
-<p>The need for scientific study of aerial problems is
-recognized. The sum of $350,000 has been offered the
-University of Paris to found an aeronautic institute. In
-Germany, the university at Göttingen has for years maintained
-an aerodynamic laboratory. Lord Rayleigh, in
-England, is at the head of a committee of ten eminent
-scientists and engineers which has, under the authority
-of Parliament, prepared a program of necessary theoretical
-and experimental investigations in aerostatics and aerodynamics.
-Our American colleges have organized student
-aviation societies and in some of them systematic instruction
-is given in the principles underlying the art. A permanent
-aeronautic laboratory, to be located at Washington,
-D.C., is being promoted.</p>
-
-<p>Aviation as a sport is under the control of the International
-Aeronautic Federation, having its headquarters at
-Paris. Bodies like the Royal Aero Club of England and
-the Aero Club of America are subsidiaries to the Federation.
-In addition, we have in this country other clubs, like
-the Aeronautic Society, the United States Aeronautical
-Reserve, etc. The National Council of the Aero Clubs of<span class="pagenum"><a name="Page_187" id="Page_187">[Pg 187]</a></span>
-America is a sort of supreme court for all of these, having
-control of meets and contests; but it has no affiliation
-with the International body, which is represented here by
-the Aero Club of America. The Canadian Auto and Aero
-Club supervises aviation in the Dominion.</p>
-
-<p>Aviation has developed new legal problems: problems
-of liability for accidents to others; the matter of supervision
-of airship operators. Bills to license and regulate
-air craft have been introduced in at least two state legislatures.</p>
-
-<p>Schools for instruction in flying as an art or sport are
-being promoted. It is understood that the Wright firm
-is prepared to organize classes of about a dozen men, supplying
-an aeroplane for their instruction. Each man pays
-a small fee, which is remitted should he afterward purchase
-a machine. Mr. Grahame-White, at Pau, in the
-south of France, conducts a school of aviation, and the
-arrangements are now being duplicated in England. Instruction
-is given on Blériot monoplanes and Farman
-biplanes, at a cost of a hundred guineas for either. The
-pupil is coached until he can make a three-mile flight;
-meanwhile, he is held partially responsible for damage
-and is required to take out a &ldquo;third-party&rdquo; insurance
-policy.</p>
-
-<p>There is no lack of aeronautic literature. Major Squier&rsquo;s
-paper in the <cite>Transactions</cite> of the American Society of
-Mechanical Engineers, 1908, gave an eighteen-page list
-of books and magazine articles of fair completeness up<span class="pagenum"><a name="Page_188" id="Page_188">[Pg 188]</a></span>
-to its date; Professor Chatley&rsquo;s book, <cite>Aeroplanes</cite>, 1911,
-discusses some recent publications; the Brooklyn Public
-Library in New York issued in 1910 (misdated 1909) a
-manual of fourteen pages critically referring to the then
-available literature, and itself containing a list of some
-dozen bibliographies.</p>
-
-<div>
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_189" id="Page_189">[Pg 189]</a></span></p>
-<h2>AERIAL WARFARE</h2></div>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg189.jpg" alt="The German Emperor Watching the Progress of Aviation"
-     width="600" height="584"/>
-</div>
-<div class="caption">The German Emperor Watching the Progress of Aviation</div>
-
-<p>The use of air craft as military auxiliaries is not new.
-As early as 1812 the Russians, before retreating from Moscow,
-attempted to drop bombs from balloons: an attempt
-carried to success by Austrian engineers in 1849. Both
-contestants in our own War of Secession employed captive
-and drifting balloons. President Lincoln organized a
-regular aeronautic auxiliary staff in which one Lowe held
-the official rank of chief aeronaut. This same gentleman
-(who had accomplished a reconnaissance of 350 miles in
-eight hours in a 25,000 cubic foot drifting balloon) was<span class="pagenum"><a name="Page_190" id="Page_190">[Pg 190]</a></span>
-subjected to adverse criticism on account of a weakness
-for making ascents while wearing the formal &ldquo;Prince
-Albert&rdquo; coat and silk hat! A portable gas-generating
-plant was employed by the Union army. We are told
-that General Stoneman, in 1862, directed artillery fire
-from a balloon, which was repeatedly fired at by the
-enemy, but not once hit. The Confederates were less
-amply equipped. Their balloon was a patchwork of silk
-skirts contributed (one doubts not, with patriotic alacrity)
-by the daughters of the Confederacy.</p>
-
-<p>It is not forgotten that communication between besieged
-Paris and the external world was kept up for some
-months during 1870-71 by balloons exclusively. Mail
-was carried on a truly commercial scale: pet animals
-and&mdash;the anticlimax is unintended&mdash;164 persons, including
-M. Gambetta, escaped in some sixty-five flights.
-Balloons were frequently employed in the Franco-Prussian
-contest; and they were seldom put <i>hors de combat</i> by the
-enemy.</p>
-
-<p>During our war with Spain, aerial craft were employed
-in at least one instance, namely, at San Juan, Porto Rico,
-for reconnoitering entrenchments. Frequent ascents were
-made from Ladysmith, during the Boer war. The balloons
-were often fired at, but never badly damaged. Cronje&rsquo;s
-army was on one occasion located by the aid of a British
-scout-balloon. Artillery fire was frequently directed from
-aerial observations. Both sides employed balloons in
-the epic conflict between Russia and Japan.</p>
-
-<p><span class="pagenum"><a name="Page_191" id="Page_191">[Pg 191]</a></span></p>
-
-<p>A declaration introduced at the second international
-peace conference at the Hague proposed to prohibit, for
-a limited period, the discharge of projectiles or explosives
-from flying machines of any sort. The United States was
-the only first-class power which endorsed the declaration.
-It does not appear likely, therefore, that international law
-will discountenance the employment of aerial craft in
-international disputes. The building of airships goes on
-with increasing eagerness. Last year the Italian chamber
-appropriated $5,000,000 for the construction and maintenance
-of flying machines.</p>
-
-<p>A press report dated February 4 stated that a German
-aeronaut had been spending some weeks at Panama,
-studying the air currents of the Canal Zone. No flying
-machine may in Germany approach more closely than
-within six miles of a fort, unless specially licensed. At
-the Krupp works in Essen there are being tested two
-new guns for shooting at aeroplanes and dirigibles. One
-is mounted on an armored motor truck. The other is a
-swivel-mounted gun on a flat-topped four-wheeled carriage.</p>
-
-<p>The United States battleship <i>Connecticut</i> cost $9,000,000.
-It displaces 18,000 tons, uses 17,000 horse-power and
-1000 men, and makes twenty miles an hour. An aeroplane
-of unusual size with nearly three times this speed,
-employing from one to three men with an engine of 100
-horse-power, would weigh one ton and might cost $5000.
-A Dreadnought costs $16,000,000, complete, and may last&mdash;it
-is difficult to say, but few claim more than ten<span class="pagenum"><a name="Page_192" id="Page_192">[Pg 192]</a></span>
-years. It depreciates, perhaps, at the rate of $2,000,000 a
-year. Aeroplanes built to standard designs in large quantities
-would cost certainly not over $1000 each. The
-ratio of cost is 16,000 to 1. Would the largest Dreadnought,
-exposed unaided to the attack of 16,000 flying
-machines, be in an entirely enviable situation?</p>
-
-<p>An aeroplane is a fragile and costly thing to hazard at
-one blow: but not more fragile or costly than a Whitehead
-torpedo. The aeroplane soldier takes tremendous risks;
-but perhaps not greater risks than those taken by the crew
-of a submarine. There is never any lack of daring men
-when daring is the thing needed.</p>
-
-<p>All experience goes to show that an object in the air is
-hard to hit. The flying machine is safer from attack
-where it works than it is on the ground. The aim necessary
-to impart a crippling blow to an aeroplane must be
-one of unprecedented accuracy. The dirigible balloon
-gives a larger mark, but could not be immediately crippled
-by almost any projectile. It could take a good pounding
-and still get away. Interesting speculations might be made
-as to the outcome of an aerial battle between the two types
-of craft. The aeroplane might have a sharp cutting
-beak with which to ram its more cumbersome adversary,
-but this would involve some risk to its own stability: and
-the balloon could easily escape by a quick ascent. It has
-been suggested that each dirigible would need an aeroplane
-escort force for its defense against ramming. Any
-collision between two opposing heavier-than-air machines<span class="pagenum"><a name="Page_193" id="Page_193">[Pg 193]</a></span>
-could not, it would seem, be other than disastrous: but
-perhaps the dirigible could rescue the wrecks. Possibly
-gas-inflated life buoys might be attached to the individual
-combatants. In the French man&oelig;uvers, a small aeroplane
-circled the dirigible with ease, flying not only around
-it, but in vertical circles over and under it.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg193.jpg" alt="7.5 Centimeter German Automatic Gun for Attacking Airships"
-     width="600" height="466"/>
-</div>
-<div class="caption">7.5 Centimeter German Automatic Gun for Attacking Airships<br />
-  <span class="normal">(From Brewer&rsquo;s <cite>Art of Aviation</cite>)</span>
-</div>
-
-<p>The French war office has exploited both types of
-machine. In Germany, the dirigible has until recently
-received nearly all the attention of strategists: but the
-results of a recent aerial war game have apparently suggested
-a change in policy, and the Germans are now,<span class="pagenum"><a name="Page_194" id="Page_194">[Pg 194]</a></span>
-without neglecting the balloon, actively developing its
-heavier-than-air competitor. England seems to be muddled
-as to its aerial policy, while the United States has been
-waiting and for the most part doing nothing. Now, however,
-the mobilizations in Texas have been associated with
-a considerable amount of aeroplane enthusiasm. A half-dozen
-machines, it is expected, will soon be housed in the
-aerodrome at San Antonio. Experiments are anticipated
-in the carrying of light ammunition and emergency supplies,
-and one of the promised man&oelig;uvers is to be the locating
-of concealed bodies of troops by air scouts. Thirty army
-officers are to be detailed for aeroplane service this year;
-five training schools are to be established.</p>
-
-<p>If flying machines are relatively unsusceptible to attack,
-there is also some question as to their effectiveness <em>in</em>
-attack. Rifles have been discharged from moving balloons
-with some degree of accuracy in aim; but long-range
-marksmanship with any but hand weapons involves the
-mastery of several difficult factors additional to those
-present in gunnery at sea. The recoil of guns might
-endanger stability; and it is difficult to estimate the
-possible effects of a powerful concussion, with its resulting
-surges of air, in the immediate vicinity of a delicately
-balanced aerial vessel.</p>
-
-<p>But aside from purely combative functions, air craft
-may be superlatively useful as messengers. To send
-despatches rapidly and without interference, or to carry
-a general 100 miles in as many minutes&mdash;these accomplishments<span class="pagenum"><a name="Page_195" id="Page_195">[Pg 195]</a></span>
-would render impossible the romance of a
-&ldquo;Sheridan&rsquo;s Ride,&rdquo; but might have a romance of their
-own. With the new sense added to human equipment by
-wireless communication, the results of observations may be
-signaled to friends over miles of distance without intervening
-permanent connections of however fragile a nature.</p>
-
-<p>Flying machines would seem to be the safest of scouts.
-They could pass over the enemy&rsquo;s country with as little
-direct danger&mdash;perhaps as unobserved&mdash;as a spy in
-disguise; yet their occupants would scarcely be subjected
-to the penalty accompanying discovery of a spy. They
-could easily study the movements of an opposing armed
-force: a study now frequently associated with great loss
-of life and hampering of effective handling of troops.
-They could watch for hostile fleets with relatively high
-effectiveness (under usual conditions), commanding distant
-approaches to a long coast line at slight cost. From
-their elevated position, they could most readily detect
-hostile submarines threatening their own naval fleet.
-Maximum effective reconnaissance in minimum time would
-be their chief characteristic: in fact, the high speeds might
-actually constitute an objection, if they interfered with
-thorough observation. But if air craft had been available
-at Santiago in 1898, Lieutenant Blue&rsquo;s expedition
-would have been unnecessary, and there would have been
-for no moment any doubt that Admiral Cervera&rsquo;s fleet
-was actually bottled up behind the Morro. No besieged
-fortress need any longer be deprived of communication<span class="pagenum"><a name="Page_196" id="Page_196">[Pg 196]</a></span>
-with&mdash;or even some medical or other supplies from&mdash;its
-friends. Suppose that Napoleon had been provided
-with a flying machine at Elba&mdash;or even at St. Helena!</p>
-
-<p>The applications to rapid surveying of unknown ground
-that have been suggested as possible in civil life would
-be equally possible in time of war. Even if the scene of
-conflict were in an unmapped portion of the enemy&rsquo;s territory,
-the map could be quickly made, the location of temporary
-defenses and entrenchments ascertained, and the
-advantage of superior knowledge of the ground completely
-overcome prior to an engagement. The searchlight and
-the compass for true navigation on long flights over unknown
-country would be the indispensable aids in such
-applications.</p>
-
-<p>During the current mobilization of the United States
-Army at Texas, a dispatch was carried 21 miles on a map-and-compass
-flight, the round trip occupying less than two
-hours and being made without incident. The machine
-flew at a height of 1500 feet and was sighted several miles
-off.</p>
-
-<p>A dirigible balloon, it has been suggested, is comparatively
-safe while moving in the air, but is subjected to
-severe strains when anchored to the ground, if exposed.
-It must have either safe harbors of refuge or actual shelter
-buildings&mdash;dry docks, so to speak. In an enemy&rsquo;s country
-a ravine or even a deep railway cut might answer in an
-emergency, but the greatest reliance would have to be
-placed on quick return trips from a suitable base. The<span class="pagenum"><a name="Page_197" id="Page_197">[Pg 197]</a></span>
-balloon would be, perhaps, a more effective weapon in
-defense than in attack. Major Squier regards a flying
-height of one mile as giving reasonable security against
-hostile projectiles in the daytime. A lower elevation
-would be sufficient at night. Given a suitable telephotographic
-apparatus, all necessary observations could easily
-be made from this altitude. Even in the enemy&rsquo;s territory,
-descent to the earth might be possible at night under reasonably<span class="pagenum"><a name="Page_198" id="Page_198">[Pg 198]</a></span>
-favorable conditions. Two sizes of balloon would
-seem to be indicated: the scouting work described would
-be done by a small machine having the greatest possible
-radius of action. Frontiers would be no barrier to it.
-Sent from England in the night it could hover over a Kiel
-canal or an island of Heligoland at sunrise, there to observe
-in most leisurely fashion an enemy&rsquo;s mobilizations.</p>
-
-<div class="figcenter" style="width: 253px">
-<img src="images/pg197.jpg" alt="German Gun for Shooting at Aeroplanes"
-     width="253" height="500"/>
-</div>
-<div class="caption">German Gun for Shooting at Aeroplanes<br />
-  <span class="normal">(From Brewer&rsquo;s <cite>Art of Aviation</cite>)
-  </span>
-</div>
-
-<p>At the London meeting of the Institute of Naval Architects,
-in April, 1911, the opinion was expressed that the only
-effective way of meeting attack from a flying machine at
-sea would be by a counter-attack from the same type of
-craft. The ship designers concluded that the aeroplane
-would no more limit the sizes of battleships than the
-torpedo has limited them.</p>
-
-<p>For the more serious work of fighting, larger balloons
-would be needed, with net carrying capacities perhaps
-upward from one ton. Such a machine could launch
-explosives and combustibles against the enemy&rsquo;s forts, dry
-docks, arsenals, magazines, and battleships. It could easily
-and completely destroy his railroads and bridges; perhaps
-even his capital itself, including the buildings housing his
-chief executive and war office staff. Nothing&mdash;it would
-seem&mdash;could effectually combat it save air craft of its own
-kind. The battles of the future may be battles of the air.</p>
-
-<p>There are of course difficulties in the way of dropping
-missiles of any great size from flying machines. Curtiss
-and others have shown that accuracy of aim is possible.
-Eight-pound shrapnel shells have been dropped from an
-aeroplane with measurably good effect, without upsetting
-the vessel; but at best the sudden liberation of a considerable
-weight will introduce stabilizing and controlling difficulties.
-The passengers who made junketing trips about
-Paris on the <i>Clément-Bayard</i> complained that they were
-not allowed to throw even a chicken-bone overboard! But
-it does not seem too much to expect that these purely
-mechanical difficulties will be overcome by purely mechanical
-remedies. An automatic venting of a gas ballonet
-of just sufficient size to compensate for the weight of the
-dropped shell would answer in a balloon: a similar automatic
-change in propeller speed and angle of planes would
-suffice with the aeroplane. There is no doubt but that
-air craft may be made efficient agents of destruction on a
-colossal scale.</p>
-
-<p><span class="pagenum"><a name="Page_199" id="Page_199">[Pg 199]</a></span></p>
-<div class="figcenter" style="width: 342px">
-<img src="images/pg199.jpg" alt="Santos-Dumont Circling the Eiffel Tower"
-     width="342" height="500"/>
-</div>
-<div class="caption">Santos-Dumont Circling the Eiffel Tower<br />
-  <span class="normal">(From Walker&rsquo;s <cite>Aerial Navigation</cite>)
-  </span>
-</div>
-
-<p>
-<span class="pagenum"><a name="Page_200" id="Page_200">[Pg 200]</a></span>
-A Swedish engineer officer has invented an aerial torpedo,
-automatically propelled and balanced like an ordinary
-submarine torpedo. It is stated to have an effective
-radius of three miles while carrying two and one-half
-pounds of explosive at the speed of a bullet. One can see
-no reason why such torpedoes of the largest size are not
-entirely practicable: though much lower speeds than that
-stated should be sufficient.</p>
-
-<p>According to press reports, the Krupps have developed
-a non-recoiling torpedo, having a range exceeding 5000
-yards. The percussion device is locked at the start, to
-prevent premature explosion: unlocking occurs only after
-a certain velocity has been attained.</p>
-
-<p><span class="pagenum"><a name="Page_201" id="Page_201">[Pg 201]</a></span></p>
-
-<p>Major Squier apparently contends that the prohibition
-of offensive aerial operations is unfair, unless with it
-there goes the reciprocal provision that a war balloon
-shall not be fired at from below. Again, there seems
-to be no good reason why aerial mines dropped from
-above should be forbidden, while submarine mines&mdash;the
-most dangerous naval weapons&mdash;are allowed. Modern
-strategy aims to capture rather than to destroy:
-the man&oelig;uvering of the enemy into untenable situations
-by the rapid mobilization of troops being the end of
-present-day highly organized staffs. Whether the dirigible
-(certainly not the aeroplane) will ever become an
-effective vehicle for transport of large bodies of troops
-cannot yet be foreseen.</p>
-
-<p>Differences in national temper and tradition, and the
-conflict of commercial enterprise, perhaps the very recentness
-of the growth of a spirit of national unity on the one
-hand, are rapidly bringing the two foremost powers of
-Europe into keen competition: a competition which is
-resulting in a bloodless revolution in England, necessitated
-by the financial requirements of its naval program. Germany,
-by its strategic geographical position, its dominating
-military organization, and the enforced frugality, resourcefulness,
-and efficiency of its people, possesses what must
-be regarded as the most invincible army in the world. Its
-avowed purpose is an equally invincible navy. Whether
-the Gibraltar-Power can keep its ascendancy may well
-be doubted. The one doubtful&mdash;and at the same time<span class="pagenum"><a name="Page_202" id="Page_202">[Pg 202]</a></span>
-perhaps hopeful&mdash;factor lies in the possibilities of aerial
-navigation.</p>
-
-<div class="figcenter" style="width: 600px">
-<img src="images/pg202.jpg" alt=""
-     width="600" height="513"/>
-</div>
-<div class="caption">Latham, Farman, and Paulhan</div>
-
-<p>If one battleship, in terms of dollars, represents 16,000
-airships, and if one or a dozen of the latter can destroy the
-former&mdash;a feat not perhaps beyond the bounds of possibility&mdash;if
-the fortress that represents the skill and labor
-of generations may be razed by twoscore men operating
-from aloft, then the nations may beat their spears into
-pruning-hooks and their swords into plowshares: then the<span class="pagenum"><a name="Page_203" id="Page_203">[Pg 203]</a></span>
-battle ceases to hinge on the power of the purse. Let
-war be made so costly that nations can no more afford it
-than sane men can wrestle on the brink of a precipice.
-Let armed international strife be viewed as it really is&mdash;senseless
-as the now dying duello. Let the navy that
-represents the wealth, the best engineering, the highest
-courage and skill, of our age, be powerless at the attack of
-a swarm of trifling gnats like Gulliver bound by Lilliputians&mdash;what
-happens then? It is a <i>reductio ad absurdum</i>.
-Destructive war becomes so superlatively destructive as to
-destroy itself.</p>
-
-<p>There is only one other way. Let the two rival
-Powers on whom the peace of the world depends settle
-their difficulties&mdash;surely the earth must be big
-enough for both!&mdash;and then as one would gently but
-firmly take away from a small boy his too destructive
-toy rifle, spike the guns and scuttle the ships, their own
-and all the rest, leaving to some unambitious and neutral
-power the prosaic task of policing the world. Here is a
-work for red blood and national self-consciousness. If
-war were ever needed for man&rsquo;s best development, other
-things will answer now. The torn bodies and desolated
-homes of millions of men have paid the price demanded.
-No imaged hell can surpass the unnamed horrors that
-our fathers braved.</p>
-
-<p>&ldquo;Enforced disarmament!&rdquo; Why not? Force (and public
-opinion) have abolished private duels. Why not national
-duels as well? Civilization&rsquo;s control of savagery<span class="pagenum"><a name="Page_204" id="Page_204">[Pg 204]</a></span>
-always begins with compulsion. For a generation, no
-first-class power has had home experience in a serious
-armed conflict. We should not willingly contemplate
-such experience now. We have too much to do in the world
-to fight.</p>
-
-<hr class="tb" />
-
-<p>The writer has felt some hesitancy in letting these words
-stand as the conclusion of a book on flying machines: but
-as with the old Roman who terminated every oration with
-a defiance of Carthage, the conviction prevails that no
-other question of the day is of comparable importance;
-and on a matter of overwhelming consequence like this no
-word can ever be out of place. The five chief powers spent
-for war purposes (officially, as Professor Johnson puts it,
-for the &ldquo;preservation of peace&rdquo;) about $1,000,000,000 in the
-year 1908. In the worst period of the Napoleonic operations
-the French military and naval budget was less than
-$100,000,000 annually. Great Britain, on the present peace
-footing, is spending for armament more rapidly than from
-1793 to 1815. The gigantic &ldquo;War of the Spanish Succession&rdquo;
-(which changed the map of Europe) cost England less
-than a present year&rsquo;s military expenditure. Since the
-types for these pages have been set, the promise of international
-peace has been distinctly strengthened. President
-Taft has suggested that as, first, questions of individual
-privilege, and, finally, even those of individual honor, have
-been by common consent submitted to adjudication, so
-also may those so-called &ldquo;issues involving national honor&rdquo;<span class="pagenum"><a name="Page_205" id="Page_205">[Pg 205]</a></span>
-be disposed of without dishonor by international arbitration.
-Sir Edward Grey, who does not hesitate to say that increase
-of armaments may end in the destruction of civilization
-unless stopped by revolt of the masses against the increasing
-burdens of taxation, has electrified Europe by his reception
-of the Taft pronouncement. England and the United
-States rule one-third the inhabitants of the earth. It is
-true that a defensive alliance might be more advantageous
-to the former and disagreeably entangling to the latter;
-but a binding treaty of arbitration between these powers
-would nevertheless be a worthy climax to our present era.
-And if it led to alliance against a third nation which had
-refused to arbitrate (led&mdash;as Sir Edward Grey suggests&mdash;by
-the logic of events and not by subterranean device)
-would not such be the fitting and conclusive outcome?</p>
-
-<p>The Taft-Grey program&mdash;one would wish to call it
-that&mdash;has had all reputable endorsement; in England,
-no factional opposition may be expected. Our own jingoes
-are strangely silent. Mr. Dillon&rsquo;s fear that compulsory
-disarmament would militate against the weaker nations is
-offset by the hearty adherence of Denmark. A resolution
-in favor of the establishment of an international police force
-has passed the House of Commons by a heavy majority.
-It looks now as if we might hope before long to re-date our
-centuries. We have had Olympiads and Years of Rome,
-<span class="sc">B.C.</span> and <span class="sc">A.D.</span> Perhaps next the dream of thoughtful
-men may find its realization in the new (and, we may
-hope, English) prefix, Y.P.&mdash;Year of Peace.</p>
-
-<hr class="chapter_rule" />
-<h2>Footnotes</h2>
-
-<p><a name="Footnote_1" id="Footnote_1"></a>
-<a href="#FNanchor_1"><span>1.</span></a>
-According to press reports, temporary water ballast will be taken on
-during the daytime, to offset the ascensional effect of the hot sun on the
-envelope.</p>
-
-<p><a name="Footnote_2" id="Footnote_2"></a>
-<a href="#FNanchor_2">2.</a>
-The contestants for the Ryan prize of $10,000 were Moisant, Count
-de Lesseps, and Grahame-White. Owing to bad weather, there was no
-general participation in the preliminary qualifying events, and some question
-exists as to whether such qualification was not tacitly waived; particularly
-in view of the fact that the prize was awarded to the technically
-unqualified competitor, Mr. Moisant, who made the fastest time. This
-award was challenged by Mr. Grahame-White, and upon review by the
-International Aeronautic Federation the prize was given to de Lesseps, the
-slowest of the contestants, Grahame-White being disqualified for having
-fouled a pylon at the start. This gentleman has again appealed the case,
-and a final decision cannot be expected before the meeting of the Federation
-in October, 1911.</p>
-
-<p><a name="Footnote_3" id="Footnote_3"></a>
-<a href="#FNanchor_3">3.</a>
-The high wind velocities of the southern circumpolar regions may be
-an insurmountable obstacle in the Antarctic. Yet Mawson expects to
-take with him a 2-passenger monoplane having a 180-mile radius of action
-on the expedition proposed for this year.</p>
-
-<p><a name="Footnote_4" id="Footnote_4"></a>
-<a href="#FNanchor_4">4.</a>
-It seems that tomorrow has come; for an aeroplane is being regularly
-used (according to a reported interview with Dr. Alexander Graham
-Bell) for carrying mails in India.</p>
-
-
-
-
-<hr class="chapter_rule" />
-<p><span class="pagenum"><a name="Page_206" id="Page_206">[Pg 206]</a></span></p>
-<h2 class="no_text">Van Nostrand Books on Aeronautics</h2>
-
-<table id="booklist1" summary="Van Nostrand Books on Aeronautics">
-<tr><td class="tdl">Books</td>
-    <td class="tdc">on</td>
-    <td class="tdr">Aeronautics</td></tr>
-</table>
-
-
-<p class="booklist">
-<b>FLYING MACHINES TO-DAY.</b> By WILLIAM D. ENNIS, M. E., Professor
-of Mechanical Engineering, Polytechnic Institute, Brooklyn.
-12mo., cloth, 218 pp., 123 illustrations <b>$1.50 net</b><br />
-<b>CONTENTS</b>: <span class="sc">The Delights and Dangers of Flying</span>--Dangers of Aviation--What
-it is Like to Fly. <span class="sc">Soaring Flight by Man</span>--What Holds it Up. Lifting Power. Why
-so Many Sails. Steering. <span class="sc">Turning Corners</span>--What Happens When Making a Turn.
-Lateral Stability. Wing Warping. Automatic Control. The Gyroscope. Wind Gusts.
-<span class="sc">Air and the Wind</span>--Sailing Balloons. Field and Speed. <span class="sc">Gas and Ballast</span>--Buoyancy
-in Air. Ascending and Descending. The Ballonet. The Equilibrator.
-<span class="sc">Dirigible Balloons and Other Kinds</span>--Shapes. Dimensions. Fabrics. Framing.
-Keeping the Keel Horizontal. Stability. Rudders and Planes. Arrangement and
-Accessories. Amateur Dirigibles. Fort Omaha Plant. Balloon Progress. <span class="sc">Question
-of Power</span>--Resistance of Aeroplanes. Resistance of Dirigibles. Independent Speed
-and Timetable. Cost of Speed. Propeller. <span class="sc">Getting Up and Down; Models and
-Gliders; Aeroplane Details</span>--Launching. Descending. Gliders. Models.
-Balancing. Weights. Miscellaneous. Things to Look After. <span class="sc">Some Aeroplanes--Some
-Accomplishments. The Possibilities in Aviation</span>--Case of the Dirigible. The
-Orthopter. The Helicopter. Composite Types. What is Promised. <span class="sc">Aerial Warfare.</span>
-</p>
-
-
-<p class="booklist">
-<b>AERIAL FLIGHT. Vol. 1. Aerodynamics.</b> By F. W. LANCHESTER.
-8vo., cloth, 438 pp., 162 illustrations <b>$6.00 net</b><br />
-<b>CONTENTS</b>: Fluid Resistance and Its Associated Phenomena. Viscosity and Skin
-Friction. The Hydrodynamics of Analytical Theory. Wing Form and Motion in the
-Periphery. The Aeroplane. The Normal Plane. The Inclined Aeroplane. The
-Economics of Flight. The Aerofoil. On Propulsion, the Screw Propeller, and the
-Power Expended in Flight. Experimental Aerodynamics. Glossary. Appendices.
-</p>
-
-
-<p class="booklist">
-<b>Vol. II. Aerodonetics.</b> By F. W. LANCHESTER.
-8vo., cloth, 433 pp., 208 illustrations <b>$6.00 net</b><br />
-<b>CONTENTS</b>: Free Flight. General Principles and Phenomena. The Phugoid
-Theory--The Equations of the Flight Path. The Phugoid 1852-1872. Dirigible
-Balloons from 1883-1897; 1898-1906. Flying Machine Theory--The Flight Path
-Plotted. Elementary Deductions from the Phugoid Theory. Stability of the Flight
-Path as Affected by Resistance and Moment of Inertia. Experimental Evidence
-and Verification of the Phugoid Theory. Lateral and Directional Stability. Review of
-Chapters I to VII and General Conclusions. Soaring. Experimental. Aerodonetics.
-</p>
-
-
-<p class="booklist">
-<b>AERIAL NAVIGATION. A practical handbook on the construction
-of dirigible balloons, aerostats, aeroplanes and aeromotors</b>, by
-FREDERICK WALKER. 12mo., cloth, 151 pp., 100 illustrations <b>$3.00 net.</b><br />
-<b>CONTENTS</b>: Laws of Flight. Aerostatics. Aerostats. Aerodynamics. Screw
-Propulsion. Paddles and Aeroplanes. Motive Power. Structure of Airships and
-Materials. Airships. Appendix.
-</p>
-
-
-<p class="booklist">
-<b>AEROPLANE PATENTS.</b> By ROBERT M. NEILSON. 8vo., cloth, 101
-pp., 77 illustrations <b>$2.00 net</b><br />
-<b>CONTENTS</b>: Advice to Inventors. Review of British Patents. British Patents and
-Applications for Patents from 1860 to 1910, arranged in Order of Application. British
-Patentees, arranged alphabetically. United States Patents from 1896 to 1909, arranged
-in order of issue. United States Patentees, arranged alphabetically.
-</p>
-
-<p class="pagenum"><a name="Page_207" id="Page_207">[Pg 207]</a></p>
-<p class="booklist">
-<b>THE PRINCIPLES OF AEROPLANE CONSTRUCTION.</b> By RANKIN
-KENNEDY, C. E. 8vo., cloth, 145 pp., 51 diagrams <b>$1.50 net</b><br />
-<b>CONTENTS</b>: Elementary Mechanics and Physics. Principles of Inclined Planes.
-Air and Its Properties. Principles of the Aeroplane. The Curves of the Aeroplane.
-Centers of Gravity: Balancing; Steering. The Propeller. The Hélicoptère. The Wing
-Propeller. The Engine. The Future of the Aeroplane.
-</p>
-
-
-<p class="booklist">
-<b>HOW TO DESIGN AN AEROPLANE.</b> By HERBERT CHATLEY.
-16mo., boards, 109 pp., illustrated (Van Nostrand&rsquo;s Science Series) <b>50 cents</b><br />
-<b>CONTENTS</b>: The Aeroplane. Air Pressure. Weight. Propellers and Motors.
-Balancing. Construction. Difficulties. Future Developments. Cost. Other Flying-Machines
-(Gyroplane and Orinthoptere).
-</p>
-
-
-<p class="booklist">
-<b>HOW TO BUILD AN AEROPLANE.</b> By ROBERT PETIT. Translated
-from the French by T. O&rsquo;B. Hubbard and J. H. Ledeboer. 8vo., cloth, 131 pp.,
-93 illustrations <b>$1.50 net</b><br />
-<b>CONTENTS</b>: General Principles of Aeroplane Design. Theory and Calculation.
-Resistance, Lift, Power, Calculations for the Design of an Aeroplane, Application of
-Power, Design of Propeller, Arrangements of Surfaces, Stability, Center of Gravity, etc.
-Materials. Construction of Propellers. Arrangements for Starting and Landing. Controls.
-Placing Motor. The Planes. Curvatures. Motors.
-</p>
-
-
-<p class="booklist">
-<b>AIRSHIPS, PAST AND PRESENT. Together with chapters on the
-use of balloons in connection with meteorology, photography,
-and the carrier pigeon.</b> By A. HILDEBRANDT, Captain and Instructor
-in the Prussian Balloon Corps. Translated by W. H. Story. 8vo., cloth, 361 pp.,
-222 illustrations <b>$3.50 net</b><br />
-<b>CONTENTS</b>: Early History of the Art. Invention of the Air Balloon. Montgolfieres,
-Charlieres, and Rozieres. Theory of the Balloon. Development of the Dirigible Balloon.
-History of the Dirigible Balloon, 1852-1872. Dirigible Balloons from 1883-1897;
-1898-1906. Flying Machines. Kites. Parachutes. Development of Military Ballooning.
-Ballooning in Franco-Prussian War. Modern Organization of Military Ballooning in
-France, Germany, England and Russia. Military Ballooning in Other Countries. Balloon
-Construction and the Preparation of the Gas. Instruments. Ballooning as a Sport.
-Scientific Ballooning. Balloon Photography. Photographic Outfit for Balloon Work.
-Interpretation of Photographs. Hectography by Means of Kites and Rockets. Carrier
-Pigeons for Balloons. Balloon Law.
-</p>
-
-<div class="figcenter"  style="width: 120px;" >
-<img src="images/logo.jpg" alt="Van Nostrand logo"
-     width="120" height="120"/>
-</div>
-
-<p id="booklist2">D. &nbsp; VAN &nbsp; NOSTRAND &nbsp; CO., &nbsp; Publishers</p>
-
-<p id="booklist3">23 MURRAY &nbsp; and &nbsp; 27 WARREN STREETS, &nbsp; NEW YORK</p>
-
-<hr class="chapter_rule" />
-<h2>Transcriber's Note</h2>
-<p class="transnote">The four footnotes have been moved to the end of the book. A few words
-were judged to be printer errors and were changed. These include two
-occurrences of horse-power in the unhyphenated form, the spelling of
-Tabuteau as Tabuteaw on p. 162, and the spelling of
-hélicoptère as helicoptéré on p.208. On a few of the figure captions, missing
-accents were added to some French names.</p>
-
-
-
-
-
-
-
-
-<pre>
-
-
-
-
-
-End of Project Gutenberg's Flying Machines Today, by William Duane Ennis
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