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+The Project Gutenberg EBook of Gas Burners, by Owen Merriman
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Gas Burners
+       Old and New
+
+Author: Owen Merriman
+
+Release Date: November 5, 2011 [EBook #37928]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK GAS BURNERS ***
+
+
+
+
+Produced by Chris Curnow and the Online Distributed
+Proofreading Team at http://www.pgdp.net (This file was
+produced from images generously made available by The
+Internet Archive)
+
+
+
+
+
+
+GAS BURNERS
+
+OLD AND NEW.
+
+
+
+GAS BURNERS
+
+OLD AND NEW.
+
+A Historical and Descriptive Treatise
+
+ON THE
+
+PROGRESS OF INVENTION IN GAS LIGHTING;
+
+EMBRACING AN ACCOUNT
+
+OF THE
+
+THEORY OF LUMINOUS COMBUSTION.
+
+
+
+BY
+
+"OWEN MERRIMAN."
+
+
+_Reprinted from the_ JOURNAL OF GAS LIGHTING.
+
+
+London:
+WALTER KING,
+11, BOLT COURT, FLEET STREET, E. C.
+
+
+1884.
+
+W. KING AND SELL, PRINTERS,
+12, GOUGH SQUARE, FLEET STREET,
+LONDON.
+
+
+
+
+Transcriber's Note: Figure 11 and Figure 12 are identical.
+
+
+
+PREFACE.
+
+
+The little work here presented to the public appeared originally in
+the pages of the _Journal of Gas Lighting_. In the hope that it
+may thereby become of service to a wider circle of readers, it has
+been revised and done into its present shape. The object of the writer
+will be attained if it is the means of lessening, in any degree, the
+suspicion and prejudice (born of ignorance) which, alas! yet prevail
+with regard to gas and gas lighting.
+
+
+
+
+CONTENTS.
+
+
+                                                       PAGE
+
+INTRODUCTION                                              9
+
+THE FIRST GAS-BURNER                                     13
+
+THE BATSWING BURNER                                      15
+
+THE UNION-JET OR FISHTAIL BURNER                         17
+
+HOW LIGHT IS PRODUCED FROM COAL GAS                      20
+
+IMPROVEMENTS IN FLAT-FLAME BURNERS                       25
+
+BRÖNNER'S BURNERS                                        31
+
+THE HOLLOW-TOP BURNER                                    35
+
+BRAY'S BURNERS                                           38
+
+ARGAND BURNERS                                           44
+
+SUGG'S ARGANDS                                           48
+
+THE DOUGLASS BURNER                                      52
+
+GOVERNOR BURNERS                                         55
+
+REGENERATIVE BURNERS                                     61
+
+INCANDESCENT BURNERS                                     73
+
+CONCLUSION                                               79
+
+
+
+
+CHAPTER I.
+
+INTRODUCTION.
+
+
+[Sidenote: Gas consumers and gas producers.]
+
+The subject of gas-burners and the development of light from coal gas
+is of considerable interest, alike to the consumer and the producer of
+gas. When it is known that one burner may develop twice as much light
+as another, for the same consumption of gas--the first cost of the one
+being no higher than that of the other--its importance to the former
+will scarcely be disputed. To the gas consumer it is obviously of great
+value to know how he may most effectively and economically develop the
+illuminating power of the gas which is supplied to him; and so obtain
+the fullest return, in lighting effect, for the money which he expends.
+Not quite so obvious is its relation to the latter. To a person totally
+unacquainted with the recent history of gas lighting, and ignorant of
+the policy which has guided the most prosperous gas undertakings to
+their successful issues, it may appear that the manufacturer of gas is
+not closely concerned with the utilization of the commodity which he
+supplies. Such an one might argue, and with a certain show of reason,
+that the sole business of the gas maker is with its production; that
+after providing, in the consumer's service-pipe, a full and continuous
+supply of gas, of the stipulated quality, his care ends; and that
+henceforth the utilization and management of the illuminant rests with
+the consumer himself. But, by any one who is at all conversant with the
+subject, it will be readily conceded that the interest of the
+manufacturer of gas, in this matter, is only second to that of the
+consumer. In the gas industry, as in any other business undertaking,
+the concern prospers or declines according as the interests of the
+customers are considered or neglected. This has been conclusively
+demonstrated in the history of many gas undertakings. So long as their
+management was conducted in exclusive and selfish regard solely to
+their own internal affairs--looking with supreme indifference or
+careless apathy upon the needs of the consumers--so long was their
+career marked by difficulties and embarrassments. No sooner, however,
+were the claims of the consumers recognized, and efforts put forth to
+further their interests, than the prospects of the concern brightened;
+and by adhering to, and extending the same line of action, the goal of
+commercial prosperity was eventually reached.
+
+Seeing, therefore, that the subject is of so supreme importance to
+consumers of gas, and that the interests of the consumer are closely
+interwoven with those of the manufacturer, it is eminently desirable
+that there should be more generally diffused a correct knowledge of the
+principles of economical gas consumption, and of the extent to which
+these principles are applied in the various burners which, from time to
+time, have been invented. No further apology ought therefore to be
+required in presenting to the reader the following disquisition on
+gas-burners. It may, however, be of advantage for me to state in brief,
+at the commencement, what are the objects I have in view, and what the
+chief considerations which have led me to write this treatise.
+
+[Sidenote: Waste of gas.]
+
+I purpose, then, to tell of the progress that has been made in
+apparatus for the development of light from coal gas; to relate how
+the crude and imperfect devices of the early inventors have been
+gradually improved upon; and, while not ignoring the drawbacks connected
+with recently invented burners, or the defects inherent to their
+construction, to show, in the superior achievements of these burners,
+how great an advance has been made upon the apparatus formerly in use.
+It will be, also, my endeavour to make plain the little understood
+phenomenon of the production of light by the combustion of coal gas;
+and to show the extent to which the illuminating power developed is
+dependent upon the burner employed. That there is need for such
+information as I propose to furnish must be sufficiently obvious to any
+one who has considered the waste of gas which takes place through
+ignorance of the laws of its combustion, and through the use of
+defective burners. In a report presented to the Board of Trade by the
+London Gas Referees in 1871, it was stated that a number of burners had
+been tested, taken from various places of business in the Metropolis;
+the major portion of which gave out only one-half, and some of them not
+more than one-fourth, of the illuminating power capable of being
+developed from the gas. Although, since the time that report was
+penned, considerable progress has been made in the construction of
+burners, and in the more general adoption of efficient burners by the
+public, much yet remains to be done. Doubtless it would still be within
+the mark to assert that fully one-fifth of the gas consumed by the
+public might be saved by the adoption of better burners, and by the
+observance of the conditions necessary for their satisfactory
+operation; and when it is borne in mind that the gas-rental of the
+United Kingdom amounts to a sum of certainly not less than £9,000,000
+per annum, the saving which might be effected assumes truly great
+proportions.
+
+The field on which I propose to enter can hardly be said to be already
+occupied. Nowhere that I know of is the subject of gas-burners fully
+treated of in a manner available for the general reader. With the
+exception of the admirable chapter contributed by Mr. R. H. Patterson
+to "King's Treatise on Coal Gas," I am not aware that the subject
+has been dealt with to any complete extent by recent writers. But,
+admirable as is that contribution to the literature of the subject,
+being written for technical readers, it is neither so popular in style
+nor so elementary in character as to fulfil the purpose which I have in
+view in writing the present series of articles. Briefly stated, my sole
+purpose is to make the subject of the combustion of gas for the
+production of light intelligible to the simplest; and to present an
+interesting account of the progress of invention in the perfection of
+gas-burners. While passing lightly over many modifications of apparatus
+which have been of but limited or temporary service, I shall not
+scruple to dwell at length upon such burners as have done much to
+further the extension of gas lighting, or whose construction exhibits
+a considerable advance upon previous attainments. And while it will
+be my endeavour to clothe my remarks in such language as shall be
+"understanded of the people," in speaking of the theory of combustion I
+hope to be sufficiently explicit to enable my readers to form a clear
+conception of the scientific principles underlying the phenomena of
+which I treat.
+
+[Sidenote: Progress of gas lighting.]
+
+A further justification--if such, indeed, were needed--for the
+appearance of this treatise might be found in the remarkable impetus
+which has been given, within recent years, to the perfection of the
+details of gas manufacture and the improvement of gas-burners. Of
+course, I refer to the beneficial consequences to the gas industry
+which have followed the brief, if conspicuous, career of electricity as
+an illuminating agent. That the interest in improved illumination which
+has been aroused by the short-lived popularity of the electric light,
+and the extravagant claims put forward on its behalf, have stimulated
+to the development of the resources of gas lighting, is sufficiently
+obvious to the most superficial observer. And not only has the
+manufacturer of gas been benefited, but the public have reaped no
+inconsiderable advantage. At the present day, gas is sold at a far
+cheaper rate, as well as of a higher quality, than at any former
+period. Nor is the advent of cheap gas the only direction in which the
+public have gained. Although not so patent to the majority, the
+improvements that have been effected in the methods of burning gas, so
+as to obtain the fullest advantage from its use, are calculated to
+confer benefits equally real, and not less valuable. It is hardly too
+much to say that the last few years have witnessed a greater advance in
+the apparatus employed in the combustion of gas than had been effected
+during the whole previous history of gas lighting. This being so, it
+may not be unacceptable if I attempt to pass in review some of the
+various burners that have been invented and used for obtaining light
+from coal gas; showing the successive improvements that are exhibited
+in their construction, and the extent to which they apply the
+principles of combustion. It may be that what I have to relate will
+awaken some minds to the consciousness that gas lighting has not
+altogether retired into obscurity on the advent of electricity--nay,
+that it has even assumed a bolder front; and, with increased resources
+and accession of strength, is prepared firmly to maintain its position
+as at once the most convenient, economical, and reliable of artificial
+illuminants.
+
+
+
+
+CHAPTER II.
+
+FLAT-FLAME BURNERS.
+
+
+THE FIRST GAS-BURNER.
+
+The first gas-burner was a very simple and unpretentious contrivance.
+In one of the earliest works on gas lighting[1] we read: "The
+extremities of the pipes have small apertures, out of which the gas
+issues; and the streams of gas, being lighted at those apertures, burn
+with a clear and steady flame as long as the supply of gas continues."
+Familiar as it is to us, and from its familiarity unnoticed, the
+phenomenon presented by the flame thus produced continuing to burn "as
+long as the supply of gas continued," was doubtless, to the first
+experimenters, a wonderful sight. Though we may smile at the question,
+it is not difficult to understand the incredulity of the honourable
+member who, when Murdock was examined before a Committee of the House
+of Commons, in 1809, asked the witness: "Do you mean to tell us that it
+will be possible to have a light _without a wick_?" "Yes; I do indeed,"
+replied Murdock. "Ah, my friend," replied the member, "you are trying
+to prove too much."
+
+          [1] Accum's "Treatise on Gas-Lights." Third edition, 1816.
+
+[Sidenote: The dawn of gas lighting.]
+
+It was but natural, seeing that oil-lamps and candles were the only
+forms of artificial illumination in use prior to the introduction of
+gas lighting, that the earliest attempts at illumination by gas should
+be in imitation of the effects produced by those means. Accordingly we
+find that one of the first gas-burners employed was the Argand,
+modelled upon the oil-lamp of that name, which had been found to give
+superior results; while in more general use, and for some time almost
+the sole apparatus available, were single jets, giving a flame similar
+in appearance to that of a common candle, together with various
+combinations of these jets. A fair idea of the mode of illumination
+practised during the earliest period of gas lighting may be gleaned
+from the following extract from a paper describing the lighting of
+Messrs. Phillips and Lee's cotton-mill at Manchester, read before the
+Royal Society, in 1808, by Mr. William Murdock:--
+
+    The gas-burners are of two kinds. The one is upon the principle of
+    the Argand lamp, and resembles it in appearance; the other is a
+    small curved tube with a conical end, having three circular
+    apertures or perforations, of about 1-30th of an inch in diameter,
+    one at the point of the cone, and two lateral ones, through which
+    the gas issues, forming three divergent jets of flame, somewhat
+    like a fleur-de-lis. The shape and general appearance of this tube
+    has procured for it, among the workmen, the name of the "cockspur"
+    burner.
+
+  [Illustration: FIG. 1.--EARLY GAS-BURNERS.
+                 (From Accum's "Treatise on Gas-Lights.")]
+
+Nor was much advance made upon these arrangements down to the year
+1816, judging from Accum's "Treatise" (before cited), as the subjoined
+extract from that work, together with the above illustrations, will
+show:--
+
+    The burners are formed in various ways--either a tube ending with a
+    simple orifice, at which the gas issues in a stream, and if once
+    lighted will continue to burn with the most steady and regular
+    light imaginable, as long as the gas is supplied; or two concentric
+    tubes of brass or sheet iron are placed at a distance of a small
+    fraction of an inch from each other, and closed at the bottom. The
+    gas which enters between these cylinders, when lighted, forms an
+    Argand lamp, which is supplied by an internal and external current
+    of air in the usual manner. Or the two concentric tubes are closed
+    at the top with a ring, having small perforations, out of which the
+    gas can issue; thus forming small distinct streams of light.
+
+It is interesting, in view of the present demand for increased
+illumination, and for burners of high illuminating power, to note the
+amount of light produced by the burners then in use. In Mr. Murdock's
+paper we find it stated that each of the Argands in use at Messrs.
+Phillips and Lee's establishment gave "a light equal to that of 4
+candles (mould candles of 6 to the pound);" and each of the cockspurs
+"a light equal to 2-1/4 of the same candles." From which meagre results
+we conclude that, besides being burnt in an ignorant and wasteful
+manner, the gas consumed was wofully deficient in illuminating power.
+
+
+THE BATSWING BURNER.
+
+[Sidenote: Who invented the batswing burner?]
+
+A notable advance was made when the batswing burner was invented. To
+whom we are indebted for this invention seems involved in some doubt.
+Although Clegg, in the historical introduction to his valuable work,[2]
+says, very distinctly, that "the batswing burner was introduced by a
+Mr. Stone, an intelligent workman employed by Mr. Winsor," it is not so
+much as mentioned by Accum, even in the third edition of his
+"Treatise;" and Accum, it may be remarked, was for some time closely
+associated with Winsor in the promotion of the latter's ambitious and
+visionary schemes. Yet, if Clegg's statement be correct, it would
+almost appear to fix the date of the introduction of this burner as
+prior to 1816. But to whomsoever is due the credit of its invention,
+certain is it that the batswing burner was a considerable improvement
+upon the old cockspur. Producing a better light for the gas consumed,
+it assisted to demonstrate still further the superiority of gas
+lighting over other methods of illumination; and as it could be
+supplied at a trifling cost, and contained no delicately adjusted nor
+easily injured parts, it enabled the benefits of the new method of
+lighting to be extended to wherever artificial light was required.
+
+          [2] Clegg's "Treatise on Coal Gas," 1841, p. 21.
+
+  [Illustration: FIG. 2.--BATSWING BURNER.]
+
+[Sidenote: Superiority of the batswing over the cockspur burner.]
+
+From the cockspur and single jet burners the gas ascended in streams,
+rising into the air until it came in contact with sufficient oxygen to
+completely consume it. In order that this might take place without
+producing a flame of an inordinate length, and without much smoke, the
+orifices were restricted to a very small size; and the gas issuing from
+these at considerable pressure tended to draw in, and mix with the air
+in its course. Besides the loss of illuminating power caused by this
+mixture of air with the gas flame (similar to what takes place in a
+Bunsen burner), the cooling influence upon the small body of flame of
+the mass of metal composing the burner, operated still further to
+reduce the quantity of light which the gas was calculated to yield.
+With the batswing the gas was spread out producing, when ignited, a
+thin sheet of flame, by which means the gas was enabled to combine more
+readily with the air necessary to effect complete combustion. The size
+of the flame being, in comparison with that of the cockspur, so much
+larger proportionately to the metal burner, the cooling effect of the
+latter was not so apparent. The increased size of flame, also, of
+itself, tended to improve the illuminating power; each portion of flame
+contributing to elevate and sustain the temperature of the whole, and
+so to heighten the intensity of incandescence to which the light-giving
+particles were raised.
+
+[Sidenote: Batswing and Argand burners compared.]
+
+Even with the Argands of that day, the batswing compared not
+unfavourably. The former burner, having the regulation of its air
+supply under complete control, gives the best results when the gas is
+supplied to it at a low pressure; as then the requisite quantity of air
+to ensure complete combustion of the gas can be delicately adjusted by
+means of a chimney of suitable length. When the gas and air have been
+nicely adjusted to each other, the flame becomes extremely sensitive to
+any change of pressure in the gas supply; a diminution of the supply,
+by reducing the quantity of gas issuing from the burner without at the
+same time proportionately diminishing the supply of air, tends to
+destroy the illuminating power by the cooling action of the surplus
+air; while an increased pressure, by allowing more gas to issue than
+the air can consume, causes the flame to smoke. But at the time to
+which I now refer the principles of combustion were little understood,
+still less applied in the construction of burners. Besides this, the
+pressure of the gas in the mains was excessive; and there being no
+method adopted of controlling it at the burner, the construction of a
+good Argand was, under the circumstances, almost impossible. The
+batswing was not so prejudicially affected by an excess of pressure.
+Pressure to some extent was, indeed, required to enable the flame to
+attain its normal shape; while any excess forced the gas through the
+flame without permitting it to be raised to incandescence before being
+consumed, and although necessitating loss of light, caused no
+inconvenience like a smoking flame. Another important advantage which
+the batswing possessed over the Argand burner was its simplicity of
+construction; and the absence of accessories, such as the glass
+chimney--dispensing with the cleaning and attention which the latter
+required. Had the benefits of gas lighting been dependent upon the use
+of apparatus so fragile, and requiring so much care and attention as
+the Argand, the range of its applicability must have been considerably
+limited, and its prospects of commercial success much less assured. The
+introduction of a series of cheap but effective burners, however,
+altered the conditions of gas lighting, and marked the commencement of
+a new era in artificial illumination. The possibility of obtaining, by
+means of a burner so simple and apparently insignificant as the
+batswing, results little, if at all, inferior to what could be obtained
+by the use of the most complicated and expensive, was of advantage
+alike to the consumer and the producer of gas. To the former it gave
+the benefits of an increased illumination, without requiring any
+corresponding outlay; to the latter it promised a growing extension of
+the use of coal gas, and thus furnished the surest guarantee of future
+progress and prosperity.
+
+
+THE UNION-JET, OR FISHTAIL BURNER.
+
+[Sidenote: Who invented the union-jet burner?]
+
+The batswing had been for some years in extensive use before a burner
+was produced worthy in any degree to compare with it in respect to
+simplicity and efficiency. The invention of the union-jet, or fishtail
+burner, furnished a competitor equally simple; little, if at all,
+inferior as regards efficiency; and, to some extent, superior to the
+former burner in general adaptability. Although so much behind in point
+of time, the new burner speedily rivalled the older batswing in popular
+favour; and in its various modifications and improvements may be said,
+without fear of contradiction, to have received a wider application
+than any other gas-burner. As in the case of the batswing, so with
+regard to this burner: few details are recorded of its invention. But,
+slight as is the information available, such as we have is more
+satisfactory and more authentic than the meagre notice of Clegg, which
+is all that is known of the invention of the former burner. It appears
+to be established beyond doubt that the union-jet is the joint
+invention of Mr. James B. Neilson, the inventor of the hot-blast, and
+Mr. James Milne, of Glasgow, founder of the engineering firm of Milne
+and Son. About the year 1820, or soon after (as in that year Mr.
+Neilson was appointed Manager of the Glasgow Gas-Works), these
+gentlemen were experimenting with gas-burners, when they discovered
+that by allowing two jets of gas, of equal size, to impinge upon each
+other at a certain angle, a flat-flame was produced, with increased
+light. This was the origin of the union-jet; so called from the manner
+in which the flame is produced. At first separate nipples were employed
+for the two jets; but, very soon, Mr. Milne hit upon the expedient of
+drilling two holes, at the required angle, in the same nipple. In this
+manner, with slight modifications, the burner has continued to be
+constructed down to the present day.
+
+  [Illustration: FIG. 3.--FISHTAIL BURNER.]
+
+The explanation of the preference accorded to this burner over its
+predecessor, the batswing, is to be found chiefly, I think, in the very
+different shapes of the respective flames produced by the two burners.
+The batswing, in its original form, produced a flame of great width,
+but of no corresponding height. The extremities of the flame,
+stretching out from the burner so far on either hand, were easily
+affected by an agitation of, or commotion in the surrounding
+atmosphere; a slight draught or current of air causing the flame to
+smoke at these points. The extreme width of flame also precluded the
+use of this burner in globes. The flame produced by the union-jet
+burner, as first constructed, was very different to the one just
+described. Longer than that of the batswing, and considerably narrower
+(but widening gradually from its base, at the burner, to its apex), it
+presented somewhat nearly the appearance of an isosceles triangle; or
+more closely, perhaps (with its slightly-forked apex), the tail of a
+fish, from which resemblance it is commonly designated the fishtail
+burner. This form of flame was better adapted for use in globes, and
+also better withstood the effects of draughts. And it is perhaps not
+unreasonable to suppose that as in shape it approached more closely to
+the kind of flame with which the people had been familiar in oil lamps,
+the flame produced by the union-jet burner was more agreeable to the
+eye than that of the batswing, and that this seemingly trivial
+consideration will account, to some extent at least, for the undue
+favour shown towards it. For it must not be assumed, because of the
+widespread popularity to which the union-jet so early attained, and
+which it has continued to enjoy, that it was of necessity a better
+burner (in the sense of developing more light for the gas consumed)
+than the one which preceded it. On the contrary, in this regard it was
+not quite so effective as the batswing. Nor is this result surprising,
+looking at the different methods adopted in the two burners for
+producing the same effects of light and flame.
+
+[Sidenote: Union-jet and batswing burners compared.]
+
+From the batswing burner the gas issued in a thin but widely-extending
+stream, presenting, when ignited, a continuous sheet of flame; its
+height and width depending upon the pressure at which the gas was
+supplied, but always offering an unbroken surface of flame to the air.
+Although, from the excessive pressures which, in the early days of gas
+lighting, were generally employed, the flame drew upon its surface too
+much air for the attainment of the fullest lighting efficiency
+obtainable from the gas; yet the form given to the issuing stream of
+gas precluded the air from entering the interior of the flame, and
+still further reducing its illuminating power. With the union-jet
+burner the conditions were greatly changed; and this latter evil, of
+the introduction of cold air into the interior of the flame, was one of
+the consequences entailed by the means it employed for producing its
+flame. From this burner the gas issued in two narrow streams, like
+single jets, which, directly after emerging from the burner, impinged
+upon each other at a given angle; the mutual shock given to the streams
+of gas when thus arrested causing them to spread out in a lateral
+direction, and (the high velocity at which the gas issued being
+expended) to unite, and ascend in a sluggish stream until consumed.
+That injury to the illuminating power of the flame should result from
+causes connected with the manner of producing it will be understood on
+considering some of the phenomena associated with the production of a
+gas flame.
+
+[Sidenote: How air is drawn upon a gas flame.]
+
+When a jet or stream of gas issues into a still atmosphere, it produces
+in its immediate neighbourhood, on all sides, an area of low pressure,
+to occupy which the contiguous air rushes in. Induced air currents are
+thus set up in close proximity to, and having the same direction as the
+issuing stream of gas, and varying in force with the pressure, or
+velocity, at which the gas issues. The non-luminous flame of the Bunsen
+burner, and of the so-called "atmospheric" burner employed in gas
+cooking and heating stoves (which is produced by burning a mixture of
+gas and air), is obtained by taking advantage of this tendency of a
+stream of gas, issuing under pressure, to draw air upon itself; and it
+is to the same circumstance that ordinary illuminating flames owe the
+continuous supply of air necessary to keep up combustion. For the
+effect is heightened when the gas is inflamed; because, the gaseous
+products of combustion being expanded by the intense heat to which they
+are subjected, their velocity of ascension is vastly increased. Having
+regard to these considerations, it will be clearly perceived how that,
+in producing the flame of the union-jet burner, the two streams of gas,
+in the act of combining together, drew into the very midst of the flame
+a portion of the air with which they were surrounded; and this air,
+reducing the temperature of the flame, and diluting the illuminating
+gas by the inert nitrogen introduced, as well as by its oxygen causing
+a too early oxidation of the carbon particles in the flame, operated to
+reduce the illuminating power otherwise obtainable from the gas.
+
+The foregoing remarks, it must be borne in mind, refer to the union-jet
+burner in its original form. Numerous improvements have been effected,
+from time to time, in its construction, as well as in that of the
+batswing, which, by reducing its liability thus to convey air into the
+flame, have increased its efficiency; while, at the same time, the
+shape of the flame has been improved. Indeed, the result of successive
+improvements in the construction of both burners has been so to modify
+the shape of their respective flames that, in their latest and most
+improved form, the flames produced by the two burners are practically
+identical in appearance, although the manner of their production
+remains as widely diverse as at the first. The improvements that led up
+to, and the causes that produced this result, will be more fully
+explained in the sequel.
+
+
+HOW LIGHT IS PRODUCED FROM COAL GAS.
+
+I have before remarked that, in the early period of its use, one of the
+chief obstacles to the development of the lighting power of coal gas
+was the excessive pressure at which it was generally supplied. To
+understand the action of pressure in influencing the amount of light
+which a given quantity of gas will afford, it is necessary to know
+something of the nature and properties of flame. Moreover, the
+conditions upon which is dependent the illuminating power of a gas
+flame are so intimately related to each other, that the precise
+functions due to each cannot well be separated from the complete effect
+produced by the combined operation of all. I shall not, therefore, be
+needlessly digressing from my subject if, at this juncture, I explain
+the manner in which combustion takes place in the flame of an ordinary
+gas-burner. In doing this, I shall endeavour to clothe my remarks in
+very plain language; using no more technicalities than are absolutely
+required by the exigencies of the subject. In this way I hope to make
+my meaning clear to the simplest. At the same time, without pretending
+to be scientifically complete, the explanation of the phenomena of
+combustion which I shall furnish will, I trust, be sufficiently
+explicit to enable the reader to form a right estimate of the
+principles which regulate the production of light when coal gas is
+consumed. The end chiefly kept in view is to show clearly the extent to
+which the degree of light evolved is dependent upon the burner
+employed, and the manner in which the gas is consumed. If my remarks
+are the means of causing the reader to look with intelligent interest
+upon the familiar phenomena of gaslight, they will not have been
+written altogether in vain.
+
+[Sidenote: What is coal gas?]
+
+Seeing that this treatise is compiled especially for those whose
+knowledge as to what coal gas consists of is extremely limited, it may
+be of advantage to preface my observations on its combustion, and the
+production of light therefrom, by a few remarks as to its composition.
+Coal gas, as generally supplied, is made up of a variety of distinct
+gases; of which, however, only some three or four exist in any
+considerable proportion. About 50 per cent., by volume (or half of the
+whole), is hydrogen; from 30 to 40 per cent. consists of marsh gas;
+while carbonic oxide is usually present to the extent of from 5 to 15
+per cent. These three gases, which constitute the great bulk of what is
+known as common gas--that is, gas made from ordinary bituminous coal,
+as distinguished from that produced from the more costly cannel--are of
+little or no value as regards the amount of light they are capable of
+affording. The flames produced by the burning of the two former gases
+evolve much heat, but are of very feeble illuminating power. The latter
+gives a flame of a deep blue colour, producing scarcely any light, but,
+like the other two, an intense heat. The power of coal gas to yield a
+luminous flame is dependent upon the small quantity of heavy
+hydrocarbons which it contains--a constituent, or series of
+constituents, of which common gas only contains a proportion varying
+between 3 and 7 per cent., although in cannel gas it reaches as high as
+15 or 20 per cent. These heavy hydrocarbons are gases composed, like
+marsh gas, of carbon and hydrogen; but containing in their composition,
+for each unit of volume, a greater aggregate of the two elements, as
+well as a relatively higher proportion of carbon, than exists in marsh
+gas. One of the simplest members of the series, and that which is
+usually present in by far the largest amount, is called olefiant gas.
+It contains twice as much carbon, combined with only the same quantity
+of hydrogen, as is contained in marsh gas. But besides olefiant gas
+there are minute quantities of other gases of the same series, having
+an analogous composition, but differing in the amount and relative
+proportions they contain of the two elements of which they are
+composed. All the gases of this series, when properly burnt, are
+capable of affording a brightly luminous flame; but when consumed alone
+it is somewhat difficult, on account of the high proportion of carbon
+which they contain, to effect their combustion without the production
+of smoke. It is, then, to the heavy hydrocarbons which are part of
+it--insignificant as their amount may appear--that the luminosity of a
+gas flame is solely due. The other constituents which I have mentioned
+as forming so much larger a proportion of the whole, besides
+contributing to the heat of the flame, serve only to dilute these
+richer gases, and so promote their more complete combustion.
+
+[Sidenote: How gas burns.]
+
+The various simple gases which constitute ordinary coal gas do not all
+burn together in the flame; the temperature required to effect their
+ignition being lower for some of them than for others. Thus, hydrogen
+is the first to burn, taking fire readily as soon as it issues from the
+burner; while the combustion of the heavy hydrocarbons does not
+commence until they enter the hotter portions of the flame, and is not
+completed until they reach its farthest extremity. Neither is the
+process of combustion in both cases the same. The former gas is at once
+completely consumed; the latter first undergo decomposition by the heat
+of the flame, being resolved into their elements--hydrogen and
+carbon--before being fully consumed. This decomposition of the
+hydrocarbons is a factor of supreme importance in the development of
+the lighting power of the flame. The hydrogen they contain, being more
+easily ignited than the carbon, burns first; and the latter is set
+free, in the solid form, as minute particles of soot. These particles
+of solid carbon, being liberated in the midst of the flame, are
+immediately subjected to its most intense heat; they thus become
+white-hot before they reach the outer verge of the flame, and come in
+contact with sufficient oxygen to effect their complete combustion.
+The amount of light developed by any coal-gas flame is directly
+proportional to the degree of intensity to which the temperature of
+these carbon particles is raised, and the length of time they remain
+in the flame before being finally consumed. It becomes, therefore, a
+matter of considerable importance to know the conditions which are
+most conducive to the early liberation in the flame of free carbon,
+and the attainment by it of an exalted temperature.
+
+[Sidenote: What is a gas flame?]
+
+Looking at the flame (say) of a common slit burner, it is seen to be
+divided into two sharply defined and wholly distinct portions. First,
+there is--immediately surrounding the burner head, and extending to
+some distance from it--a dark, transparent area, which, on closer
+examination, is found to consist of unignited gas enclosed in a thin
+envelope of bright blue flame. Second, there is (beyond this central
+area) a zone, or belt, of brightly luminous flame, white and opaque;
+the latter property indicating the presence of solid matter at this
+part of the flame. That the dark central portion of the flame consists
+chiefly of unignited gas may be shown in various ways, in addition to
+the evidence afforded by its complete transparency. Thus, if a small
+glass tube be taken, and its lower end inserted in the flame at this
+point, the unburnt gas will pass up the tube, and may be lighted at its
+upper extremity. A splinter of wood thrust through this portion of the
+flame is charred first at the two edges of the flame; while, in like
+manner, a piece of platinum foil remains dull in the centre of the
+flame, and glows only at the points of contact with the outer air. The
+presence of solid carbon in the luminous portion of the flame may be
+shown by inserting therein any cold substance (such as a piece of metal
+or porcelain), which, reducing the temperature of the heated particles
+of carbon below the point at which they are consumed, becomes instantly
+coated on its under surface with a deposit of soot. Or, if the flame be
+suddenly cooled by gently blowing upon its surface, the same result is
+brought about; clouds of soot are given off, and the flame "smokes."[3]
+
+          [3] The behaviour of gas flames when exposed to the action
+          of the wind (as exemplified in the naked lights of open
+          markets and similar situations) affords an instructive
+          illustration of the theory of luminous combustion. A sudden
+          gust causes the flame to smoke, by reducing the temperature
+          of the liberated carbon below the point at which it can
+          combine with the oxygen of the air. A continuous wind
+          blowing upon the flame destroys its luminosity altogether,
+          because the heat-intensity of the flame is lowered below the
+          temperature necessary to decompose the hydrocarbons;
+          consequently, these latter burn without the preliminary
+          separation of carbon, and a non-luminous flame is
+          produced--exactly as in the Bunsen or "atmospheric" burner.
+
+  [Illustration: FIG. 4.--SHOWING THE TWO ZONES OF THE FLAME, AND
+  THE METHOD OF DEMONSTRATING THE PRESENCE OF UNBURNT GAS IN THE
+  FLAME.]
+
+[Sidenote: How the flame is cooled.]
+
+The existence, in the midst of the flame, of an area of unconsumed gas
+is due to the cold gas, as it issues from the burner, cooling the
+interior of the flame below the temperature required for its ignition,
+as well as to its not at once meeting with sufficient air for complete
+combustion. The causes which affect the luminous zone of the flame are
+not so readily explained. It has been stated that the luminosity of the
+flame is due to the particles of carbon, which are separated out of the
+hydrocarbons in the gas, being raised to a white heat. To decompose the
+hydrocarbons, a very high temperature is required; and, on account of
+the cooling effect of the stream of cold gas, this is not attained
+except at some distance from the burner. The abstraction of heat by the
+burner itself is also a cause of the reduction of the temperature of
+the flame; and, on this account, burners of porcelain, steatite, or
+similar composition, being bad conductors of heat, have an advantage
+over those made of metal. So considerable is the cooling influence of
+the gas stream, that, within certain limits, the distance, from the
+burner head, at which the luminosity of a flame commences, is
+proportionate to the velocity with which the gas issues; or, in other
+words, the pressure at which it is delivered from the burner. The
+effect is heightened by the tendency (which has been before remarked)
+of a stream of gas, issuing under pressure, to draw upon itself and mix
+with the surrounding air. Thus, with each increment of pressure the
+luminous zone of the flame is farther removed, until a point is reached
+at which the gas is so mixed with air before being consumed that the
+luminosity of the flame is completely destroyed.
+
+[Sidenote: Effects of pressure in the gas supply.]
+
+But it must not be assumed, because of the foregoing remarks, that the
+pressure at which the gas issues from the burner is altogether an
+unmixed evil. In flat-flame burners it fulfils the important function
+of promoting intensity of combustion, by bringing the white-hot
+particles of carbon into intimate and rapid contact with the air that
+is necessary for complete combustion. In Argand burners this duty is
+discharged by the glass chimney; but with flat-flame burners it
+devolves entirely upon the pressure at which the gas issues from the
+burner. It will be seen, therefore, that the pressure of the gas is a
+factor of considerable importance in determining the amount of light
+afforded by a gas flame, as it is a matter requiring careful adjustment
+with each and every burner. On the one hand, with an excessive pressure
+the intensity of combustion is increased; but the separated carbon does
+not remain so long in the flame. The area of luminosity is thereby
+decreased, and the total light yielded is reduced. On the other hand,
+with insufficient pressure the combustion is not energetic enough to
+raise the particles of carbon to a white heat; consequently, the
+illuminating power of the flame is feeble, or else the carbon escapes
+unconsumed as smoke.
+
+The thickness of the flame produced by any burner has also an important
+bearing upon the degree of light afforded; and this property of
+thickness, again, is dependent upon the width of slit, in the case of
+batswings (or, in the case of union-jets, upon the size of orifices),
+and the pressure at which the gas is supplied. The thickness of the
+flame yielded by any burner will obviously vary inversely with the
+pressure at which the gas is supplied to it. With a thin flame, all
+parts of the flame are so completely exposed to the air, that the
+particles of carbon are no sooner raised to the temperature required to
+enable them to give out light than they are entirely consumed. With a
+thicker flame the carbon separated in the midst of the flame exists for
+a sensibly longer period of time in the white-hot state before it
+reaches the outside of the flame, and meets with sufficient oxygen for
+its complete combustion. Thus we find that the best flat-flame burners
+have comparatively wide orifices; while the pressure at which the gas
+is delivered from the burner is carefully reduced to the lowest point
+at which a firm flame is obtained, without smoke. Similarly, in the
+best Argands the pressure is considerably diminished within the burner,
+and the gas allowed to issue gently through relatively large holes;
+while the chimney is carefully adapted to draw upon the surface of the
+flame just sufficient air to completely consume the quantity of gas
+which the burner is calculated to deliver.
+
+
+IMPROVEMENTS IN FLAT-FLAME BURNERS.
+
+Although, there is no doubt, they were made empirically, and in
+ignorance of the real effects of pressure upon the flame, the first
+steps towards increasing the efficiency of flat-flame burners were in
+the right direction of reducing the excessive pressure at which the gas
+was formerly allowed to burn. They consisted in the adoption of simple
+arrangements for obstructing the passage of the gas through the burner,
+and so retarding its flow. The crudeness of the means which were
+employed is sufficient evidence that the end aimed at was, at best, but
+dimly discerned. The body of the burner was stuffed with wool, or
+pieces of wire gauze; which impeded the progress of the gas; reduced
+the quantity that would otherwise have been consumed; and,
+consequently, diminished the velocity with which it issued from the
+burner. Unfortunately, owing to the imperfect methods in use at that
+day for condensing and purifying the gas, the burners so constructed
+became choked with the tarry matters held in suspension, and carried
+forward by the gas; and so, after a comparatively short period of
+service, were rendered entirely inoperative. But, altogether apart from
+the inconvenience and loss thus entailed (which, when improved modes of
+manufacture had removed the cause, ceased to be experienced), the
+arrangement was ill adapted for the purpose which it was designed to
+serve. The rough and uneven nature of the material employed to stuff
+the burner caused the gas to eddy and swirl as it issued into the
+atmosphere, and prevented it being supplied equally to all parts of the
+flame. The consequence was that the advantages which ought to have been
+derived from the diminished pressure were neutralized by the unsteady
+flow acquired by the stream of gas; and the illuminating power
+developed by the flame was little improvement upon what could
+previously be obtained by the manipulation of the tap controlling the
+supply of gas to the burner. Besides which, from its unevenness, the
+appearance of the flame was not so satisfactory. It was not until the
+principles which regulate the production of light from coal gas came to
+be known and observed in the construction of burners, that a
+modification of the old idea was arrived at, which enabled the benefits
+of a reduced pressure to be obtained without any of the attendant evils
+hitherto experienced.
+
+[Sidenote: The first real improvement of the union-jet burner.]
+
+A modification in the construction of the union-jet which, though
+slight, was nevertheless a real improvement, appears to have been made
+at an early period in the history of this burner. Instead of having the
+top of the burner perfectly flat, it was made slightly concave; more
+especially at its centre, where the two jets of gas emerge. The effect
+of this alteration was to enable the stream of gas to spread out
+better; and thus to cause the flame to become broader at its base. The
+shape of the flame was thereby improved; and (what is of more
+consequence) its illuminating power increased, because air was not
+drawn so readily into the midst of the flame. The value of the
+arrangement is shown by the fact that it has been retained ever since,
+and is made use of in the latest and most improved burners of this
+class.
+
+Prior to 1860, numerous novel contrivances were introduced as
+"improved" burners; but all were not equally valuable with the simple
+arrangement just described. The construction of many of them, indeed,
+betrayed a lamentable ignorance of the first principles of gas
+combustion. For instance, one is described as "a fishtail with four
+converging holes; and there is an aperture in the centre of the burner
+for the admission of atmospheric air into the flame!" Another was a
+batswing with two or more slits, producing a series of flames
+amalgamated into one; by which means it was supposed that an improved
+duty was obtained from the gas--unmindful, or, more probably, in
+ignorance of the fact that the same quantity of gas, properly consumed
+through one slit, would yield a better light.
+
+[Sidenote: The double-flame burner.]
+
+A burner which, at different times, and under various names, has been
+brought repeatedly into notice is the double-flame; consisting of two
+batswing or union-jet burners set at an angle to each other, so that
+their flames converge, and merge into one. When two gas flames are made
+to coalesce in this manner, a greater amount of light is developed than
+the sum of that yielded by the separate flames; provided that, in the
+combined flame, the gas is properly consumed, without smoke. The reason
+for this increase is twofold. First, the increased quantity of gas
+burnt in one flame enables a higher average temperature to be
+maintained; and, in addition, a smaller surface of flame is exposed to
+the cooling action of the atmosphere than when the same quantity of gas
+is consumed in two flames. Second, the pressure at which the gas burns
+is diminished, because the initial velocity with which the streams of
+gas issue from the two burners is expended in impinging against each
+other, and a thicker flame results; the apparatus being, as far as its
+effect is concerned, a union-jet burner on a large scale. The increase
+of light so obtained appears to have been noticed at an early period;
+as a burner embodying the same principle is described and figured in
+"Clegg's Treatise," published in 1848. In Clegg's burner the gas issued
+from two perforated parallel plates inclined to each other; but at a
+more recent period two fishtail burners were employed, being mounted on
+separate tubes which branched out to a short distance from each other.
+Occasionally, for experimental and show purposes, it has been
+constructed with the two branches hinged together, so as to show the
+different effects produced when the two burners are used separately and
+in combination. At the present day it is made, by various makers, as
+one burner with two nipples, as shown in the annexed illustration;
+which doubtless is its most perfect form.
+
+  [Illustration: FIG. 5.--DUPLEX BURNER.]
+
+The advantages of the double flame are not so obvious under the
+conditions which obtain at the present day as at the period when it was
+first introduced. The increase of light it affords is most apparent
+when the gas is being consumed at an excessive pressure. Although, in
+general, it may be taken that any two flames, when combined, will
+develop a higher duty, per cubic foot of gas consumed, than separately;
+yet it would appear that this is not so in every case. When the gas is
+being consumed at the critical pressure which gives the best results,
+the flames are so near the smoking point that the slight diminution of
+pressure experienced when the streams of gas impinge upon each other is
+sufficient to cause the combined flame to smoke. Moreover, to such a
+stage of perfection have the ordinary flat-flame burners now been
+brought, that, for all ordinary consumptions, it may be safely affirmed
+that equal, if not superior results can be obtained with a single as
+with a double flame. Where, however, larger quantities of gas are
+required to be dealt with than can be effectively consumed in a single
+burner, the principle of combining two or more burners together, so
+that their flames shall mutually assist each other, may be
+advantageously employed; as is seen in the combination of flat-flame
+burners in the large lamps now employed in improved street lighting.
+
+  [Illustration: FIG. 6.--SCHOLL'S PLATINUM LIGHT PERFECTER.]
+
+[Sidenote: Scholl's "Platinum Light Perfecter."]
+
+An ingenious device for improving the efficiency of union-jet burners
+was brought out some twenty years ago by a Mr. Scholl, of London, and
+known as Scholl's "Platinum Light Perfecter," which is shown in the
+accompanying illustration. It consisted of a little brass ring,
+carrying a plate of platinum about 0·4 inch long by 0·15 inch wide. The
+ring fitted on to the top of the burner in such a manner that the
+platinum plate was held, in a vertical position, between the two
+orifices from which the gas emerged. The jets of gas, instead of
+impinging upon each other, impinged against the plate, and united above
+to form the flame. By the interposition of the metal plate, the
+velocity of the gas was much reduced; and a thicker and more sluggish
+flame was produced, with the result of increasing its illuminating
+power. When the apparatus was used upon a burner having very small
+orifices, and delivering its gas at a high pressure, the increase of
+light obtained was very striking; but with lower pressures the
+advantage derived from its use was correspondingly diminished. This is
+very clearly shown by the following table, which is extracted from a
+report, by Captain Webber and Mr. Rowden, on experiments upon
+gas-burners, carried out at the Paris Universal Exhibition, 1867.[4]
+
+          [4] See _Journal of Gas Lighting_, Vol. XVIII., p. 88.
+
+  --------------------------+-------+--------+---------------------+--------
+  Kind of Burner.           |Cubic  |Pressure| Illuminating Power. |
+                            |Feet of|  in    +----------+----------+Increase
+                            |Gas    |Inches. |Without   |With      |  per
+                            |per    |        |Perfecter.|Perfecter.| Cent.
+                            |Hour.  |        |          |          |
+  --------------------------+-------+--------+----------+----------+--------
+  Leoni's fishtail, No. 2 . |  3    | 0·84   | 1·3      |  4·1     | 215
+  Leoni's fishtail, No. 3 . |  {3   | 0·46   | 2·4      |  4·6     |  91
+                            |  {4   | 0·70   | 2·8      |  6·5     | 132
+                            | {3    | 0·31   | 3·4      |  5·0     |  47
+  Leoni's fishtail, No. 4 . | {4    | 0·47   | 4·5      |  7·6     |  68
+                            | {5    | 0·71   | 5·0      |  9·2     |  84
+                            |  {4   | 0·42   | 5·3      |  6·9     |  30
+  Leoni's fishtail, No. 5 . |  {5   | 0·60   | 6·1      |  8·3     |  36
+                            |  {6   | 0·81   | 7·1      | 10·0     |  40[5]
+  Leoni's fishtail, No. 6 . | {4    | 0·31   | 6·2      |  8·0     |  29[6]
+                            | {5    | 0·46   | 8·0      | 10·4     |  30[7]
+  --------------------------+-------+--------+----------+----------+--------
+
+          [5] Flame flickers.
+
+          [6] Do.
+
+          [7] Flame flickers a great deal.
+
+Burners were also made with the metal plate forming part of the burner
+head; and, instead of being of platinum, it was sometimes formed of
+thin steel, or other commoner metal. Where platinum was used, some
+advantage probably accrued from its becoming incandescent; but, of
+course, any benefit arising from this source was not obtained when
+steel was employed. The remarks which have been made respecting the
+limited applicability of the double-flame burner will apply, with equal
+force, to the apparatus under notice. Although it effected an undoubted
+improvement when applied to burners ill adapted to the pressure at
+which the gas was supplied, equally good results could be obtained
+without its aid, when a burner was employed suited to the quality and
+pressure of the gas supplied.
+
+[Sidenote: Leoni's flat-flame burners.]
+
+Perhaps the most efficient flat-flame burners available prior to 1867
+were those made by Mr. S. Leoni, of London. One of these is shown in
+fig. 7. This maker produced both batswing and union-jets; various sizes
+being made of each burner. Besides affording fairly good results from
+the gas consumed, the burners were supplied at a very moderate price.
+Their distinguishing feature was the peculiar substance of which the
+burner-tips were formed. This was a material invented by Mr. Leoni, and
+named by him "adamas." (The precise composition of "adamas" is a trade
+secret; but it appears to consist of a mixture of various minerals or
+earths, moulded in a clayey or plastic condition, and then burnt.)
+Previous to his invention, the tip of the burner, or the burner head,
+had been made, almost exclusively, of iron or brass. There were,
+however, some grave defects inherent in the use of metal for this
+purpose. The orifices of union-jets and the slits of batswings in
+course of time became much obstructed by the corrosion of the metal;
+and the efforts made to remove the obstruction only served to destroy
+the burner more quickly, by increasing the size and injuring the
+precise shape of the apertures. The "adamas" tips, on the other hand,
+perfectly withstood the high temperature to which they were exposed,
+were quite incorrodible, and were sufficiently hard to endure a
+considerable degree of even rough usage. By constructing the tip of
+this material, the efficiency of the burner was improved in many ways.
+The liability of the burner to corrosion being removed, and the
+inconvenience due to this cause done away with, the life of the burner
+was prolonged, and the expense of renewal consequently reduced. But, in
+addition to these advantages, there was yet another direction in which
+the "adamas" tip contributed to enhance the utility of the burner. This
+was in maintaining a higher temperature of the flame; and arose from
+its inferior capacity, compared with metal, for conducting heat from
+the flame. That the advantage derived from this source, although
+unimportant, was not altogether imaginary, will be apparent when it is
+mentioned that metal burners, when in operation, usually attain to a
+temperature of from 400° to 500° Fahr.--an indication of the amount of
+heat being continuously abstracted from the flame. The adoption of a
+non-conducting material for the burner-tip, while it did not entirely
+prevent, considerably reduced the loss of heat.
+
+  [Illustration: FIG. 7.--LEONI'S FLAT-FLAME BURNER.]
+
+Two varieties of each class of burner were made by Mr. Leoni. In the
+one burner, the "adamas" tip was inserted into an iron stem; in the
+other, the tip was inserted in a brass body, which fitted on to the
+iron stem. Between the brass body and the iron stem of the latter
+burner there was affixed a layer of wool, designed to check the
+pressure at which the gas was supplied. Owing, very probably, to the
+unsuitability of the material (wool) used for this purpose, the result
+was not satisfactory; as, according to the statements of Messrs. Webber
+and Rowden, in the report previously cited, no difference could be
+detected, in many experiments, between the results yielded by the
+burner with or without the layer of wool. Some light is shed upon this
+apparent anomaly by certain experiments made by the writer to determine
+the pressure at which gas issues from various burners. With one of
+Leoni's No. 4 union-jets, under an initial pressure of 1 inch (the
+pressure at the inlet when the burner is in operation), the pressure at
+the outlet of the burner, when the layer of wool was employed, was 0·11
+inch; but from the same burner, when the layer of wool was removed, the
+gas issued at a pressure of only 0·07 inch. Thus the effect of
+inserting the layer of wool in the burner was exactly the opposite of
+that which it was intended to produce; the pressure of the issuing gas
+stream being increased instead of diminished.
+
+
+BRÖNNER'S BURNERS.
+
+The credit of having produced the first flat-flame burners designed
+upon scientifically correct principles belongs undoubtedly to Herr
+Julius Brönner, of Frankfort-on-the-Maine. Long before the date of his
+invention, efforts had been made to reduce the pressure of the gas
+within the burner. But these endeavours were carried out in so
+hap-hazard a fashion as to lead to the belief that no definite
+conception was entertained as to what was really required. As we have
+seen, layers of wool had been employed; but the area of the
+interstices, or the gas-way through the material, was a matter of the
+merest accident. And there was not the slightest guarantee that the
+same conditions should prevail in any two burners. Herr Brönner
+shrewdly detected the cause of former failures, as he clearly perceived
+the end which it was requisite to attain, and towards which previous
+inventors had been but blindly groping. Having formed a right estimate
+of the requirements to be fulfilled, and the difficulties to be
+surmounted, he set about accomplishing the desired result by other
+means. There were two causes which had chiefly contributed to the
+unsuccessful issues of previous attempts. One was the uncertain and
+indefinite operation of the means employed for diminishing the
+pressure; the other was the inadequate provision for enabling the gas
+to lose the current, or swirl, acquired in passing the diminishing
+arrangement, and come to a state of comparative rest before issuing
+into the atmosphere. Both these errors were successfully avoided in
+Brönner's invention--the former by making the inlet to the burner of
+restricted and definite dimensions, and of less area than the outlet,
+or slit; the latter by enlarging the chamber, or place of expansion
+within the burner, as well as by the different arrangement adopted for
+diminishing the pressure.
+
+  [Illustration: A TOP.
+                 B TOP.
+                 FIG. 8.--BRÖNNER'S BURNERS.]
+
+[Sidenote: Construction of Brönner's burners.]
+
+The general appearance of Brönner's burner is pear-shaped; and in size
+it is considerably larger than an ordinary burner designed to pass an
+equal quantity of gas. It consists of a cylindrical brass body
+surmounted by a steatite top, and tapering to a very small diameter at
+its lower end, or inlet; the latter being closed by a plug of steatite,
+in which is a rectangular slot, or aperture, of accurately defined
+dimensions. The size of this aperture determines the quantity of gas
+which, at any particular pressure, is admitted to the burner; and the
+slit, or outlet of the burner, being of greater area than the inlet,
+ensures the gas being delivered from the burner at a lower pressure
+than that at which it enters it. By varying the respective dimensions
+of these two openings, and their relation to each other, the burner may
+be regulated to deliver its gas at any required pressure short of the
+initial pressure at the entrance to the burner. The enlargement of the
+cylindrical body provides an expansion chamber, wherein the velocity of
+the stream of gas which rushes through the narrow opening at the inlet
+of the burner is checked, and any agitation or unsteadiness which may
+have been imparted to it is subdued before the gas issues into the
+atmosphere and is consumed. There are two kinds of tops for the
+burners, which are distinguished by the letters A and B. The B top is
+of the ordinary semi-spherical type, giving a true batswing-shaped
+flame; the A top is flatter, almost square in form, and yields a flame
+taller than, but not so broad as the former. In consequence of this
+difference in the shape of its flame, the latter burner is better
+adapted for use in globes. The general appearance of the burners, and
+their distinguishing peculiarities, will be clearly understood from the
+illustrations.
+
+[Sidenote: Properties of steatite.]
+
+The material of which the more important parts of the burner are
+constructed is eminently adapted for the purpose. Steatite is a mineral
+which, as found in nature, is so soft as to be readily turned in a
+lathe, and shaped to any design; but when heated up to about 2000°
+Fahr. it becomes almost as hard and durable as flint, while perfectly
+retaining its form and colour. These properties peculiarly qualify it
+for receiving a slit or orifice, which, though of minute proportions,
+must be accurately formed to precise dimensions. Besides which, like
+"adamas," its capacity for conducting heat away from the flame is so
+limited that, in this respect, it has a considerable advantage over
+metal for the purpose of being formed into gas-burners.
+
+[Sidenote: Varied adaptability of the Brönner burner.]
+
+The following tables, which are extracted from the report of the
+Committee of the British Association appointed to investigate the means
+for the development of light from coal gas of different qualities,[8]
+exhibit the very satisfactory results obtained by the use of these
+burners. In Table I., the gas operated upon was cannel gas (such as is
+generally supplied in Scotland), and possessed an illuminating power,
+when employed in the standard burner, of 26 candles per 5 cubic feet.
+Table II. contains the results of determinations with common gas (such
+as is used in London, and generally throughout the greater part of
+England); 5 cubic feet of which, in the standard burner, gave an
+illuminating power of 16 candles. The first and second columns of the
+tables refer to the different sizes of the tops and bottoms of the
+particular burners employed; there being in all some 16 sizes of the
+one, and 11 sizes of the other. These, being interchangeable, permit of
+a great variety of combinations; and enable a burner to be selected
+suited to any particular quality or pressure of gas. For as with
+pressure, so with illuminating power: In order to obtain the utmost
+lighting efficiency, different burners are required for gases differing
+in quality or their degree of richness. A burner which, with gas of one
+quality, will yield excellent results, may, under the same conditions
+of pressure and supply, be totally unsuited to gas of another quality.
+That this should be so will be evident from a consideration of what has
+been said as to the theory of burning gas to the best advantage; and,
+in brief, results from the richer gas containing in its composition a
+greater proportion of carbon, and so requiring an increased supply of
+air for its thorough combustion. This increased supply of air can only
+be obtained (with flat-flame burners) by causing the gas to issue into
+the atmosphere at a higher pressure; and so it comes about that,
+compared with the quantity of gas to be delivered through them, the
+slits of batswing and the orifices of union-jet burners must be
+considerably narrower when intended for cannel gas than when common gas
+is to be consumed. In other words, in order to develop its full
+illuminating power, it is essential that the pressure at which the gas
+issues from the burner should be proportioned to its quality. The gist
+of the matter is set forth in the general statement that "the poorer
+the quality of the gas, the lower must be the pressure at which it is
+consumed; and _vice versâ_."
+
+          [8] See _Journal of Gas Lighting_, Vol. XXXII., p. 423,
+          and Vol. XXXVI., p. 376.
+
+  TABLE I.
+
+  -----------------------------------+-----------------------------------
+         |    AT 0·5-INCH   |    AT 1·0-INCH      |    AT 1·5-INCH
+         |      PRESSURE.   |      PRESSURE.      |      PRESSURE.
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+  No.    |No. |Cubic|Illumi-|Illumi- |No.    |No. |Cubic|Illumi-|Illumi-
+  of     |of  |Feet |nating |nating  |of     |of  |Feet |nating |nating
+  Burner.|Top.|per  |Power. |Power   |Burner.|Top.|per  |Power. |Power
+         |    |Hour.|       |per Five|       |    |Hour.|       |per Five
+         |    |     |       |Cub. Ft.|       |    |     |       |Cub. Ft.
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+     2   |  2 | 1·20|  5·07 | 24·13  |   2   |  2 | 1·40|  5·25 | 18·75
+     2   |  3 | 1·40|  6·64 | 23·71  |   2   |  3 | 1·95|  7·37 | 18·90
+     2   |  4 | --  | Smokes|  --    |   2   |  4 | 2·30| 10·33 | 22·46
+     2   |  5 | --  |   "   |  --    |   2   |  5 | 2·40| 11·24 | 23·42
+     2   |  6 | --  |   "   |  --    |   2   |  6 | --  | Smokes|  --
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+   2-1/2 |  2 | 1·40|   5·53| 19·75  | 2-1/2 |  2 | 1·90|  8·30 | 21·84
+   2-1/2 |  3 | 1·70|   8·48| 24·94  | 2-1/2 |  3 | 2·30| 10·14 | 22·04
+   2-1/2 |  4 | 2·03|  10·33| 25·49  | 2-1/2 |  4 | 2·70| 12·08 | 22·37
+   2-1/2 |  5 | --  | Smokes|  --    | 2-1/2 |  5 | 2·85| 14·29 | 25·07
+   2-1/2 |  6 | --  |   "   |  --    | 2-1/2 |  6 | 3·00| 15·21 | 25·35
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+     3   |  2 | 1·45|   6·27| 21·62  |   3   |  2 | 2·00|  8·48 | 21·20
+     3   |  3 | 1·90|   8·66| 22·79  |   3   |  3 | 2·40| 11·34 | 23·63
+     3   |  4 | 2·13|  11·24| 26·39  |   3   |  4 | 2·80| 14·84 | 26·50
+     3   |  5 | --  | Smokes|  --    |   3   |  5 | 3·15| 17·04 | 27·20
+     3   |  6 | --  |   "   |  --    |   3   |  6 | 3·25| 18·07 | 27·80
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+   3-1/2 |  2 | 1·50|   5·81| 19·36  | 3-1/2 |  2 | 2·12|  8·85 | 20·87
+   3-1/2 |  3 | 1·95|   8·30| 21·28  | 3-1/2 |  3 | 2·55| 12·63 | 24·76
+   3-1/2 |  4 | 2·55|  12·08| 23·68  | 3-1/2 |  4 | 3·00| 14·47 | 26·12
+   3-1/2 |  5 | 2·80|  14·38| 25·68  | 3-1/2 |  5 | 3·50| 18·07 | 25·81
+   3-1/2 |  6 | 3·00|  15·58| 25·97  | 3-1/2 |  6 | 3·60| 19·45 | 27·01
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+     4   |  2 | 1·60|   6·36| 19·87  |   4   |  2 | 2·30|  9·77 | 21·24
+     4   |  3 | 2·10|  10·69| 25·45  |   4   |  3 | 2·90| 13·83 | 23·84
+     4   |  4 | 2·65|  13·37| 25·23  |   4   |  4 | 3·30| 17·06 | 25·85
+     4   |  5 | 3·45|  17·61| 25·52  |   4   |  5 | 4·10| 21·57 | 26·30
+     4   |  6 | 3·55|  18·07| 25·45  |   4   |  6 | 4·20| 22·40 | 26·66
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+     5   |  2 | 1·77|   7·38| 20·85  |   5   |  2 | 2·60|  9·68 | 18·81
+     5   |  3 | 2·30|  11·90| 25·87  |   5   |  3 | 3·30| 13·64 | 20·67
+     5   |  4 | 3·30|  15·40| 23·33  |   5   |  4 | 4·00| 19·91 | 24·14
+     5   |  5 | 4·10|  20·74| 25·29  |   5   |  5 | 5·00| 25·36 | 25·36
+     5   |  6 | 4·30|  22·68| 26·37  |   5   |  6 | 5·30| 27·66 | 26·10
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+
+  TABLE II.
+
+  ----+----+----------------------+---------------------+------------------
+      |    |    AT 0·5-INCH     |    AT 1·0-INCH      |    AT 1·5-INCH
+           |      PRESSURE.     |      PRESSURE.      |      PRESSURE.
+      |    +-----+-------+------+-----+-------+-------+-----+-------+------
+  No. |No. |Cubic|Illumi-|Illum.|Cubic|Illumi-|Illum. |Cubic|Illumi-|Illum.
+  of  |of  |Feet |nating |Power |Feet |nating |Power  |Feet |nating |Power
+  Top.|Bot-|per  |Power. |per   |per  |Power. |per    |per  |Power. |per
+      |tom.|Hour.|       |Five  |Hour.|       |Five   |Hour.|       |Five
+           |     |       |Cub.  |     |       |Cub.   |     |       |Cub.
+           |     |       |Ft.   |     |       |Ft.    |     |       |Ft.
+  ----+----+-----+-------+------+-----+-------+-------+-----+-------+------
+  A2  | 1  | --  |  --   |  --  | 1·5 |   2·7 |  9·0  | 2·0 |   4·0 | 10·0
+   "  | 2  | 1·6 |  2·9  |  9·1 | 2·4 |   5·2 | 10·8  | 3·1 |   6·8 | 11·0
+   "  | 2½ | 2·0 |  3·9  |  9·8 | 2·9 |   6·8 | 11·7  | 3·8 |   9·4 | 12·4
+  A3  | 3  | 2·1 |  4·4  | 10·5 | 3·2 |   7·8 | 12·2  | 4·4 |  10·6 | 12·0
+   "  | 3½ | 2·5 |  4·8  |  9·6 | 3·8 |   9·2 | 12·1  | 4·9 |  12·2 | 12·4
+   "  | 4  | 2·5 |  5·4  | 10·8 | 3·8 |   9·6 | 12·7  | 5·2 |  13·6 | 13·1
+   "  | 4½ | 3·0 |  6·4  | 10·7 | 4·5 |  10·8 | 12·0  | 5·9 |  14·8 | 12·5
+   "  | 5  | 3·2 |  7·7  |  2·0 | 5·1 |  13·2 | 13·0  | 6·8 |  18·0 | 13·2
+   "  | 6  | 3·7 |  8·7  | 11·8 | 5·8 |  15·5 | 13·3  | 7·7 |  21·0 | 13·6
+   "  | 7  | 3·5 |  8·6  | 12·3 | 5·9 |  16·0 | 13·6  | 8·4 |  23·0 | 13·7
+   "  | 8  | 3·7 |  9·0  | 12·2 | 6·2 |  16·8 | 13·5  | 8·6 |  23·4 | 13·6
+  B1  | 1  | --  |  --   |  --  | 1·3 |   2·3 |  8·8  | 1·8 |   3·5 |  9·7
+  B2  | 2  | 1·3 |  2·3  |  8·8 | 2·1 |   4·4 | 10·5  | 2·8 |   6·4 | 11·4
+   "  | 2½ | 1·6 |  3·0  |  9·4 | 2·5 |   6·0 | 12·0  | 3·4 |   8·4 | 12·4
+  B3  | 3  | 2·0 |  3·8  |  9·0 | 3·0 |   7·2 | 12·0  | 4·1 |  10·1 | 12·3
+   "  | 3½ | 2·3 |  4·3  |  9·3 | 3·4 |   7·7 | 11·3  | 4·5 |  11·0 | 12·2
+  B4  | 4  | 2·3 |  4·7  |  0·2 | 3·6 |   8·8 | 12·2  | 5·0 |  13·0 | 13·0
+   "  | 4½ | 2·7 |  5·9  | 10·9 | 4·3 |  10·4 | 12·1  | 5·6 |  15·0 | 13·4
+  B5  | 5  | 3·1 |  7·0  | 11·3 | 4·9 |  12·9 | 13·2  | 6·5 |  18·0 | 13·8
+  B6  | 6  | 3·8 |  9·6  | 12·6 | 5·9 |  16·4 | 13·8  | 8·0 |  23·0 | 14·4
+  B7  | 7  | 4·0 | 10·2  | 12·8 | 6·6 |  19·0 | 14·4  | 9·0 |  26·0 | 14·4
+  B8  | 8  | 4·7 | 11·8  | 12·6 | 7·3 |  22·0 | 15·1  | 9·6 |  30·0 | 15·7
+  ----+----+-----+-------+------+-----+-------+-------+-----+-------+------
+
+[Sidenote: Pressure of gas with the Brönner burner.]
+
+Doubtless the chief cause of the remarkable efficiency of the Brönner
+over previous burners is to be found in the pressure at which the
+gas flows from the burner and is consumed. In the course of some
+experiments made to determine the pressure at which gas is delivered
+from various burners, the writer found that from a No. 4 Brönner, with
+an initial pressure--_i.e._, the pressure at the inlet when the burner
+is in operation--of 1 inch, the gas issued at a pressure of only 0·05
+inch; and with an initial pressure of 0·5 inch, the outlet pressure was
+only 0·03 inch. On the other hand, a No. 4 steatite flat-flame burner,
+without any arrangement for retarding the flow of the gas, under the
+same initial pressure gave at the outlet 0·16 inch and 0·05 inch
+respectively. The absence of anything within the burner to cause the
+gas to swirl, or to issue with an unsteady flow, must also be credited
+with contributing, in no slight degree, to the favourable results
+yielded by these burners.
+
+
+THE HOLLOW-TOP BURNER.
+
+In the hollow-top burner we have one of the most notable improvements
+which have been effected in flat-flame burners. A simple modification
+of the batswing--the earliest of flat-flame burners--it is not more
+complicated in its details than is that burner. Yet, simple as it
+is, its construction exhibits an important advance upon the original
+batswing. Indeed, this burner may be said to embody the only
+considerable improvement that has been made in the distinctive features
+of the batswing since the introduction of the latter burner, which, as
+we have seen, took place as early as the year 1816.
+
+[Sidenote: The hollow-top an improved batswing burner.]
+
+In its outward form, the hollow-top burner differs little, if at all,
+from the batswing; but a slight modification which has been adopted in
+the arrangement of its interior has produced a very marked result in
+improving the shape of the flame yielded by the burner, and, to some
+extent, in the results, as regards illuminating power, which it is
+capable of affording. In this burner, as its name implies, the
+interior of the top or head of the burner is hollowed out, forming an
+enlargement of the cavity or chamber within the burner, and (what is
+chiefly important) making the shell of the dome-shaped burner head of
+equal thickness throughout. In the ordinary batswing, in consequence
+of the varying thickness of the burner at this part, the slit is much
+deeper in the middle than at any other part of its length, and
+gradually decreases in depth towards each end. As the resistance to
+the passage of the gas, or the friction which it encounters, increases
+with the depth of the slit, the gas passes out from the burner at the
+ends of the slit more readily than in the middle; producing a
+wide-stretching flame, of scanty height in proportion to its width.
+From the same cause the flame is not of equal thickness throughout;
+being thinner in the middle than at the ends. Moreover, the outer
+extremities of the flame, extending so far beyond the body of the
+burner, are unable to retain the form given to them by the lateral
+flow of the gas at the ends of the slit; the resistance, presented by
+the atmosphere, together with the natural tendency of the gas to
+ascend, causing the under portion of the flame to fold back upon
+itself. As one result of this combination of untoward circumstances,
+the flame is liable to smoke with a slight agitation of the
+surrounding air.
+
+In the hollow-top burner, the slit is of equal depth throughout its
+length; and the resistance offered to the passage of the gas being the
+same in all parts of the slit, the gas flows through the middle as
+readily as at the ends--nay, in reality rather more so, owing to the
+innate ascensive power of the gas, due to its being lighter than air.
+The peculiar hollowing-out of the head of the burner, also, withdraws
+the ends of the slit out of the direct course or current of the gas
+through the burner; so that the tendency of the stream of gas to issue
+at these points, in preference to going through the middle of the
+slit, is further checked. The consequence is that the shape of the
+flame is considerably improved; it being taller, more compact, and not
+so broad as that of the batswing. In addition, the flame being of
+equal thickness throughout, its illuminating power is somewhat
+improved; while, from its compactness, it is better enabled to resist
+atmospheric influences. With this alteration in the shape of the flame
+all original resemblance to a batswing is entirely destroyed; but the
+appearance of the flame of the new burner is much more agreeable to
+the eye than that of the older batswing.
+
+  [Illustration: FIG. 9.--ORIGINAL HOLLOW-TOP BURNER.
+                 (From Wadsworth's Specification.)]
+
+[Sidenote: Who invented the hollow-top burner.]
+
+As has been exemplified in so many instances in the history of
+invention, the hollow-top burner was not appreciated at its true value
+until long after it had been brought into existence. It appears to
+have been originally invented by Joseph and James Wadsworth, of Marple
+and Salford, and was patented by them in 1860. According to the
+specification of the inventors, the burners might be made either
+in solid or sheet metal, as will be seen from the accompanying
+illustrations, copied from the drawings in the specification. But
+there were difficulties in the way of casting the burners in solid
+metal which do not seem to have been surmounted; and those produced
+under the patent appear to have been made exclusively of sheet brass.
+For many years these burners were made and sold without their
+peculiarities attracting any marked attention; which would seem to
+imply that their faulty construction precluded the attainment of all
+the advantages afforded by the burner as we know it.
+
+[Sidenote: Sugg's hollow-top burner.]
+
+The superior results which the hollow-top burner was calculated to
+afford did not become fully apparent until the burner was made of
+non-conducting material, and greater care exercised in its
+construction. This appears to have been done in Germany earlier than
+in this country. But, in England, it was undoubtedly Mr. Sugg who
+first turned his attention to the improvement of the burner, and
+demonstrated its merits. Mr. Sugg commenced the manufacture of this
+burner in steatite in the year 1868; and since that time the burner
+has been extensively employed, and its advantages widely recognized.
+The superiority of hollow-top burners produced by Mr. Sugg to those
+previously manufactured, is chiefly the result of their being made in
+steatite instead of in metal. With this material, greater exactness
+and uniformity are obtained in the shape and dimensions of the burner
+than when metal is employed; besides which there is (what has been
+before referred to) the advantage arising from its inferior conductive
+capacity for heat, and its non-liability to corrosion. Another
+improvement, also due to Mr. Sugg, and which is productive of
+noticeable results, consists in cutting the slit of the burner with
+a circular saw, applied from above, so as to make the ends of the
+slit curved instead of horizontal; by which means the tendency of
+the gas to issue laterally at the ends of the slit, and form horns
+to the flame, is lessened. Mr. Sugg's table-top burner (which was
+introduced in 1880), in addition to the characteristic features
+of the hollow-top, has a rim-like projection from the burner, below
+the slit; its object being to protect the flame from the disturbing
+influence of the uprush of air in its immediate vicinity, and so
+preserve its shape unaltered, while diminishing its liability to
+smoke. Prior to Mr. Sugg--namely, in the early part of 1879--Mr. Bray
+had successfully obviated this injurious action upon the flame of the
+ascending current of air, by affixing to the burner two arms of brass,
+so placed as to be immediately under the projecting wings of the
+flame.
+
+  [Illustration: 1868 BURNER.
+                 1874 BURNER.
+                 TABLE-TOP BURNER.
+                 FIG. 10.--SUGG'S HOLLOW-TOP BURNERS.]
+
+
+BRAY'S BURNERS.
+
+The burners of Messrs. George Bray and Co. have deservedly acquired a
+world-wide reputation, and are in extensive use wherever gas lighting
+is known. Their distinguishing characteristic, and that which has won
+for them the high repute in which they are held, is the union of
+cheapness with remarkable efficiency. In all the various descriptions
+and classes of burners which are produced by this firm, the
+characteristic referred to is preserved; although it is needless to
+add that the different varieties are not equally efficient. Of the
+three forms of flat-flame burners we have been considering--batswing,
+union-jet, and hollow-top--the one which, more than any other, has
+been the speciality of the firm is the union-jet; and it is with the
+development of this class of burner that the name of Bray is most
+intimately and honourably associated.
+
+  [Illustration: UNION-JET.
+                 HOLLOW-TOP OR SLIT-UNION.[9]
+                 BATSWING.
+                 FIG. 11.--BRAY'S "REGULATOR" BURNERS.]
+
+          [9] The name "slit-union," by which Mr. Bray prefers to
+          designate this burner, he states to be derived from the
+          resemblance of its flame to that of the union-jet burner;
+          while it is produced by means of a slit.
+
+[Sidenote: Bray's "regulator" burner.]
+
+[Sidenote: Bray's "special" burner.]
+
+The "regulator" union-jet, which was the first notable burner produced
+by Messrs. Bray, has received, perhaps, a wider application than any
+other single gas-burner. It consists of a cylindrical brass case,
+screwed at one end for insertion into the fittings, and at the other
+containing a tip of "enamel"--a material invented by Mr. Bray, and
+apparently of somewhat similar composition to the "adamas" of Mr.
+Leoni--the "enamel" tip being perforated, in the usual manner, with
+two holes, set at an angle to each other, for the outflow of the gas.
+The distinctive feature of this burner is the introduction into the
+lower part of the brass case of a layer, or layers, of muslin;
+designed to check in some degree, and to steady the current or flow of
+the gas through the burner. At the time of its introduction, this
+burner compared very favourably, as regards the results it yielded,
+with other burners in common use; and its fairly good performances,
+together with the very low price at which it can be sold, cause it
+still to be extensively employed wherever the attainment, from the gas
+consumed, of the highest obtainable results may be subordinated to
+cheapness, or in situations where, from delicacy of construction or
+from the care and attention demanded, a more efficient burner may not
+be so suitable. But in the matter of developing the illuminating power
+of the gas employed, the "regulator" is far surpassed by the more
+recently introduced "special" burner of the same makers.
+
+  [Illustration: UNION-JET.
+                 HOLLOW-TOP OR SLIT-UNION.
+                 BATSWING.
+                 FIG. 12.--BRAY'S "SPECIAL" BURNERS.]
+
+Mr. Bray's series of "special" burners--embracing union-jet,
+hollow-top, and batswing--are constructed upon the principle of, and
+in form are somewhat similar to Brönner's burners, which have already
+been fully described. Apart from its being of greater bulk, the main
+divergence in the construction of the "special" burner from that of
+the earlier "regulator" is the introduction, into the lower part of
+the brass case, of a plug or washer of enamel, pierced by a small
+circular hole for the admission of gas into the burner; the diameter
+of this hole determining the quantity of gas which, at any particular
+pressure, is admitted into the burner. Just above the enamel washer, a
+layer of muslin is inserted, as in the "regulator" burner; which, in
+this case, is for the purpose of subduing the agitation, or swirl,
+acquired by the current of gas in passing through the narrow aperture
+in the washer. A tip of enamel, made of the particular description
+(union-jet, hollow-top, or batswing) required, fitting into the upper
+part of the brass case, completes the burner. The objects aimed at in
+the "special" burner are to cause the gas to be consumed at the lowest
+pressure compatible with the maintenance of a firm flame, and with the
+least agitation, or swirl, in the current of gas as it issues from
+the burner. The former is attained, as in Brönner's burners, by
+diminishing the area of the opening admitting into the burner, without
+a corresponding diminution of the orifices through which the gas
+issues into the atmosphere; the latter, by the interposition of
+the layer of muslin which is immediately above the diminishing
+arrangement, as well as by the enlargement of the gas chamber in
+the upper part of the burner. The improvement thus effected in the
+illuminating power developed from the gas is well shown in the
+following tables extracted from an exhaustive series of tests of
+gas-burners carried out by Mr. T. Fairley, F.R.S.E., Borough Analyst
+of Leeds, and embodied by him in a report presented to the Leeds
+Corporation. The full text of the report will be found in the _Journal
+of Gas Lighting_ for February 6, 1883.
+
+  _Medium Lighting Power Union-Jets._
+
+  -----------------------------------+-----------------------------------
+        "Regulator" Burners.         |      "Special" Burners.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+  No.   |Pres- |Cubic|Illumi-|Illumi-|No.   |Pres- |Cubic|Illumi-|Illumi-
+  of    |sure  |Feet |nating |nating |of    |sure  |Feet |nating |nating
+  Burner|in    |per  |Power  |Power  |Burner|in    |per  |Power  |Power
+        |Inches|Hour |in     |per 5  |      |Inches|Hour |in     |per 5
+        |      |     |Stand. |Cubic  |      |      |     |Stand. |Cubic
+        |      |     |Candls.|Feet.  |      |      |     |Candls.|Feet.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+     3  |  0·5 | 3·50|   6·8 |  9·7  |   3  |  0·5 | 3·43|  11·3 | 16·4
+     3  |  1·0 | 4·80|   6·9 |  7·2  |   3  |  1·0 | 4·90|  15·6 | 15·8
+     3  |  1·5 | 6·20|   7·5 |  6·05 |   3  |  1·5 | 6·03|  17·6 | 14·6
+     4  |  0·5 | 4·65|  12·2 | 13·1  |   4  |  0·5 | 3·73|  13·3 | 17·8
+     4  |  1·0 | 6·67|  14·2 | 10·6  |   4  |  1·0 | 5·15|  17·4 | 16·9
+     4  |  1·5 | 8·16|  14·2 |  8·8  |   4  |  1·5 | 6·57|  22·4 | 17·1
+     5  |  0·5 | 5·72|  17·0 | 14·9  |   5  |  0·5 | 4·80|  17·6 | 18·3
+     5  |  1·0 | 7·97|  20·0 | 12·6  |   5  |  1·0 | 6·67|  24·4 | 18·3
+     5  |  1·5 | 9·73|  21·8 | 11·2  |   5  |  1·5 | 8·30|  30·0 | 18·2
+     6  |  0·5 | 5·90|  18·0 | 15·2  |   6  |  0·5 | 5·48|  20·1 | 18·3
+     6  |  1·0 | 8·35|  23·0 | 13·8  |   6  |  1·0 | 7·65|  28·4 | 18·6
+     6  |  1·5 |10·60|  28·0 | 13·2  |   6  |  1·5 | 9·20|  34·2 | 18·7
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+
+  _Medium Lighting Power Slit-Unions._
+
+  -----------------------------------+-----------------------------------
+        "Regulator" Burners.         |      "Special" Burners.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+  No.   |Pres- |Cubic|Illumi-|Illumi-|No.   |Pres- |Cubic|Illumi-|Illumi-
+  of    |sure  |Feet |nating |nating |of    |sure  |Feet |nating |nating
+  Burner|in    |per  |Power  |Power  |Burner|in    |per  |Power  |Power
+        |Inches|Hour |in     |per 5  |      |Inches|Hour |in     |per 5
+        |      |     |Stand. |Cubic  |      |      |     |Stand. |Cubic
+        |      |     |Candls.|Feet.  |      |      |     |Candls.|Feet.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+    3   | 0·5  | 4·22|  13·8 |  16·4 |   3  |  0·5 | 3·04|  10·8 | 17·8
+    3   | 1·0  | 6·37|  20·2 |  15·9 |   3  |  1·0 | 4·61|  16·4 | 17·6
+    3   | 1·5  | 8·14|  25·8 |  15·9 |   3  |  1·5 | 5·88|  19·9 | 16·9
+    4   | 0·5  | 4·25|  14·8 |  17·4 |   4  |  0·5 | 3·82|  14·2 | 18·6
+    4   | 1·0  | 5·88|  20·6 |  17·5 |   4  |  1·0 | 5·69|  20·8 | 18·3
+    4   | 1·5  | 7·95|  26·5 |  16·6 |   4  |  1·5 | 7·35|  25·6 | 17·5
+    5   | 0·5  | 5·25|  19·0 |  18·2 |   5  |  0·5 | 4·12|  15·4 | 18·7
+    5   | 1·0  | 8·14|  28·4 |  17·45|   5  |  1·0 | 6·37|  23·4 | 18·4
+    5   | 1·5  |10·20|  36·4 |  17·8 |   5  |  1·5 | 7·94|  28·5 | 18·0
+    6   | 0·5  | 5·67|  22·2 |  19·6 |   6  |  0·5 | 5·00|  19·6 | 19·6
+    6   | 1·0  | 8·60|  33·6 |  19·4 |   6  |  1·0 | 7·55|  29·0 | 19·2
+    6   | 1·5  |11·10|  39·5 |  17·8 |   6  |  1·5 | 9·70|  37·0 | 19·1
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+
+  _Medium Lighting Power Batswings._
+
+  -----------------------------------+-----------------------------------
+        "Regulator" Burners.         |      "Special" Burners.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+  No.   |Pres- |Cubic|Illumi-|Illumi-|No.   |Pres- |Cubic|Illumi-|Illumi-
+  of    |sure  |Feet |nating |nating |of    |sure  |Feet |nating |nating
+  Burner|in    |per  |Power  |Power  |Burner|in    |per  |Power  |Power
+        |Inches|Hour |in     |per 5  |      |Inches|Hour |in     |per 5
+        |      |     |Stand. |Cubic  |      |      |     |Stand. |Cubic
+        |      |     |Candls.|Feet.  |      |      |     |Candls.|Feet.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+     3  |  0·5 | 4·16|  12·6 |  15·1 |   3  |  0·5 | 3·37|  12·4 | 18·4
+     3  |  1·0 | 5·64|  16·6 |  14·8 |   3  |  1·0 | 5·25|  20·4 | 19·4
+     3  |  1·5 | 7·83|  21·0 |  13·4 |   3  |  1·5 | 7·13|  24·0 | 16·8
+     4  |  0·5 | 4·26|  14·0 |  16·4 |   4  |  0·5 | 3·67|  13·0 | 17·7
+     4  |  1·0 | 6·74|  21·2 |  15·6 |   4  |  1·0 | 5·55|  20·6 | 18·6
+     4  |  1·5 | 7·81|  24·0 |  15·3 |   4  |  1·5 | 7·13|  26·0 | 18·2
+     5  |  0·5 | 4·76|  15·4 |  16·2 |   5  |  0·5 | 3·86|  14·6 | 18·9
+     5  |  1·0 | 6·93|  20·4 |  14·7 |   5  |  1·0 | 5·85|  22·6 | 19·4
+     5  |  1·5 | 8·72|  25·8 |  14·7 |   5  |  1·5 | 7·53|  28·0 | 18·6
+     6  |  0·5 | 6·04|  20·0 |  16·5 |   6  |  0·5 | 4·86|  19·4 | 20·0
+     6  |  1·0 | 8·82|  29·4 |  16·6 |   6  |  1·0 | 7·53|  31·6 | 21·0
+     6  |  1·5 |11·10|  31·6 |  14·2 |   6  |  1·5 | 9·60|  39·0 | 20·4
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+
+The quality of the gas operated upon averaged about 19 candles when
+tested with the Standard London Argand Burner.
+
+In a former part of this treatise it was remarked that the flames
+produced by the modern representatives[10] of the batswing and fishtail
+burners have lost the original resemblance to the objects whence the
+names of those burners were derived; and that the two flames have
+gradually approached each other in shape, until, in their latest
+developments, they are practically identical. We have seen how that,
+by the invention of the hollow-top, a burner is obtained apparently,
+to all outward appearance, the same as the batswing, yet giving a
+greatly improved form of flame. We have now to learn how the fishtail,
+or union-jet burner has been modified so as to yield a flame closely
+agreeing with that produced by the improved slit burner.
+
+          [10] Although the true batswing is still in common use, I
+          look upon the hollow-top as being its "modern representative;"
+          seeing that, in a great many instances, it has superseded
+          the former burner--of which, indeed, it is only an improved
+          form.
+
+[Sidenote: How the union-jet burner has been improved.]
+
+As first constructed, the union-jet burner gave a tall, narrow flame;
+its extremity being forked and jagged like the tail of a fish. Besides
+being unsightly, this form of flame was ill-adapted to develop, to
+anything like its full extent, the illuminating power of the gas. In
+order to obtain the best results, as regards illuminating power, the
+heat-intensity of the flame must be very high, so as to bring up the
+temperature of the particles of carbon liberated in the flame to the
+necessary degree of incandescence. To this end there must be
+concentration of the flame, in order to utilize to the full the heat
+of combustion. With the tall flame produced by the original union-jet
+burner there was too much exposure to the atmosphere for the flame to
+attain to the requisite intensity of heat; as well as considerable
+liability of the gas being brought too early into intimate contact
+with air, and so oxidized, or fully consumed, before its carbon had
+been raised to the temperature necessary to enable it to give out
+light. With the burner in its improved form the height of the flame is
+much curtailed, while it is broadened, and made more even and compact.
+This alteration has been chiefly brought about by two modifications in
+the construction of the burner-tip--first, by hollowing out its flat
+upper surface; and, second, by altering the angle at which the two
+streams of gas emerge from the burner. By scooping out the central
+portion of the flat top of the burner, so as to form a hollow or
+depression where the gas emerges, the flat sheet of flame which is
+formed when the two streams of gas impinge upon each other obtains a
+broader base, and at the same time is preserved from drawing air into
+its midst. But the chief share of the improvement is due to the
+alteration in the angle formed by the two channels in the burner-tip.
+It will be readily apparent that the more obtuse this angle--that is,
+the nearer the two streams of gas are to impinging against each other
+in a horizontal line--the more will the flame tend to spread out, or
+the lower the pressure required to obtain any desired spread of flame.
+It is by taking advantage of this circumstance that Mr. Bray has been
+enabled to improve the union-jet burner. Twenty years ago this burner
+was usually made with the two channels in the burner-tip placed at an
+angle of about 60°. In Bray's "regulator" burner, introduced in 1869,
+they were placed at an angle of 90°; with the result of obtaining a
+more satisfactory flame, both as regards its appearance and
+illuminating power. In the "special" burner, which was not brought out
+till 1876, the angle is increased to 120°; thus enabling the necessary
+spread of flame to be obtained with the gas issuing at a low pressure.
+Another minor improvement in the latter burner consists in making the
+holes in the burner-tip elliptical instead of circular.
+
+
+
+
+CHAPTER III.
+
+ARGAND BURNERS.
+
+
+[Sidenote: The premier gas-burner.]
+
+The premier position among gas-burners undoubtedly belongs to the
+Argand; and it is from no unwillingness to recognize its claims, much
+less from ignorance of its merits, that I have left the consideration
+of this burner until now. It occupies this honourable position as much
+by virtue of the importance it has acquired through being accepted by
+Parliament as the test burner, and the peculiar relation in which it
+consequently stands to other burners, as for any marked superiority in
+operation. For while, in general, the Argand gives superior results to
+other burners, this is not always the case. There are circumstances
+and conditions to which the Argand is quite inapplicable, and where a
+simpler and less pretentious burner will give excellent results.
+Indeed, some of the simple flat-flame burners which we have had under
+notice have now been brought to such a stage of perfection, that, when
+intelligently used, they not unsuccessfully rival the Argand. But it
+has been in the direction of demonstrating the illuminating power
+which it was possible to obtain from gas, and stimulating to the
+attainment, by other and simpler burners, of the same level of
+excellence, that the influence of the Argand has been most beneficial.
+For, by reason of its peculiar construction, and more especially its
+mode of obtaining the air necessary for combustion, the Argand lends
+itself, more readily than any other burner, to the work of
+investigating and experimenting upon the conditions necessary for
+economical combustion, and the development of the highest illuminating
+power from the gas consumed. In this burner, the air supply to the
+flame is under complete control; and thus one of the chief elements of
+uncertainty and difficulty which are experienced in dealing with other
+burners is eliminated. The delivery of gas to different parts of the
+flame is also more susceptible of variation; and the results of such
+variation more fully exposed to observation. The consequence has been
+that the most remarkable advances in developing improved illuminating
+power from coal gas have been made with this burner. But after the
+possibility of obtaining an improved duty from the gas has been
+demonstrated by means of the Argand, and the conditions necessary for
+its attainment determined, equally good results have been achieved by
+other burners.
+
+  [Illustration: PLAN OF GLASS-HOLDER AND BURNER TOP.
+                 SECTION OF BURNER.
+                 FIG. 13.--ARGAND BURNER.]
+
+In thus showing the benefits to be derived from a more scientific mode
+of combustion, and leading the way to the fuller attainment, by other
+burners, of the illuminating power obtainable from the gas, the Argand
+burner has acted as a pioneer in the development of gas lighting. For,
+on account of its complexity, and its delicacy of construction, this
+burner has never been, nor, indeed, can ever hope to be generally
+employed. Besides the inconvenience and expense entailed by the
+cleaning and renewal, when broken, of the glass chimney which is
+indispensable to this burner, its very perfection as a burner
+precludes its being adopted under the conditions which appertain to
+the great majority of situations in which gaslight is required. For
+while, under the particular conditions as to pressure of gas, &c., for
+which it has been constructed, the Argand may give results surpassing
+any other burner, a very slight divergence from these conditions is
+productive of far more damaging results to the illuminating power of
+the flame than is the case with other and less efficient burners. The
+cause of this seeming anomaly will be apparent when we come to
+consider in detail the construction of the Argand, and the conditions
+which must be observed to ensure its satisfactory operation. For the
+present it will suffice merely to make mention of what appear to be
+well-established facts--viz., that the most perfect burners are the
+least adapted for use under uncertain and varying conditions; and that
+in proportion to the efficiency of a burner, under the conditions for
+which it has been constructed, is the injury to the illuminating power
+of its flame which is experienced when these conditions are departed
+from.
+
+[Sidenote: What is an Argand burner?]
+
+Resolved into its simplest form, the Argand burner may be said to
+consist of a hollow ring of metal, or other suitable material,
+provided with the necessary tubes or connections for communicating
+between its interior and the gas supply, and perforated on its upper
+surface with a number of holes for the emission of the gas. Through
+these holes the gas issues in a series of jets, which immediately
+coalesce to form one cylindrical sheet of flame. The burner is
+surmounted, and the flame enclosed, by a glass chimney, which is
+supported on a light gallery connected with the burner; the chimney
+serving the double purpose of shielding the flame from draughts, or
+currents of air (thus enabling the gas to burn uniformly and
+steadily), and of drawing upon the surface of the flame the supply of
+air necessary for its proper and complete combustion. For in the
+Argand the air supply is produced under conditions totally different
+from those which govern its production in all the other burners we
+have had under consideration. In flat-flame burners, the quantity of
+air supplied to the flame is determined by the pressure of the gas;
+or, in other words, the velocity with which it issues from the burner.
+In Argand burners, on the contrary, the air supply is obtained quite
+independently of the pressure at which the gas issues; and the
+conditions most effective for the economical combustion of the gas,
+and the development from it of the highest illuminating power
+attainable, are only secured when the pressure of gas is reduced to a
+minimum.
+
+It has been shown, in speaking of flat-flame burners, how the
+illuminating power of the flames yielded by such burners is
+injuriously affected by an excess of pressure in the gas, as it issues
+into the atmosphere, causing a too great intermingling of gas and air.
+With such burners, however, some degree of pressure is needed, in
+order, by bringing the flame into contact with sufficient of the
+oxygen of the air, to promote the requisite intensity of combustion;
+whereas with the Argand the draught that is produced through the
+agency of the glass chimney enables the necessary supply of air to be
+obtained for the support of the flame without adventitious aid from
+the pressure of the gas. Consequently, one of the chief objects to be
+aimed at in the construction of the latter burner is to so reduce the
+pressure of the gas within the burner that it may issue with little or
+no greater velocity than that due to its own specific lightness. In
+some of the best Argands this object is attained very successfully;
+and the ingenious devices which have been made use of to gain this end
+will be duly described in the sequel. But, in addition to causing the
+gas to issue from the burner at the minimum of pressure, it must be
+delivered evenly and equally at all parts of the ring of holes; so
+that there shall not be an excess of gas supplied to one portion of
+the flame, and an insufficiency to others. Then the area of the
+opening in the centre of the ring, through which the air supply is
+obtained to the inner surface of the flame, as well as the length and
+diameter of the glass chimney, must be so proportioned that the exact
+quantity of air needed to enable the flame to yield its maximum
+results shall be drawn upon it. These, and other equally essential
+requirements, have to be taken into consideration, and provided for,
+in constructing an efficient Argand burner. It is no wonder,
+therefore, that the development of the powers of this burner has taken
+up so much time and labour and inventive skill; and the remarkable
+degree of efficiency to which it has now been brought testifies to the
+thought and the accurate knowledge of the principles of combustion
+which have been brought to bear upon it.
+
+[Sidenote: The earliest Argands.]
+
+It is, however, only within comparatively recent years that its true
+principles of construction have been at all fully recognized, as
+evinced by the burners which have been produced. For a long period,
+Argand burners were made upon wholly empirical and arbitrary rules.
+During the early years of gas lighting, the makers of gas apparatus,
+and such persons as professed to have a special knowledge of the
+production and utilization of the new illuminant, appear to have been
+ignorant of even the most obvious of the conditions required for the
+successful working of the burner. In one of the earliest works which
+appeared relating to gas lighting,[11] we find the Argand burner
+described as consisting of "two concentric tubes closed at the top
+with a ring having small perforations, out of which the gas can issue;
+thus forming small distinct streams of light." According to this
+description, the burner referred to cannot have been an Argand in the
+strictest sense of the word; but, in reality, must have consisted
+chiefly of a series of single jets placed in a circle, and surrounded
+by a glass chimney. But the great improvement in the amount of light
+developed, which resulted from bringing the jets of flame closer
+together, so as to cause them to coalesce and produce one homogeneous
+mass of flame, could not long escape notice; and accordingly we find
+that in "Clegg's Treatise," which appeared twenty-five years later,
+the proper disposition of the holes in the ring, necessary for the
+successful operation of the burner, is clearly recognized. In this
+work, speaking of the Argand burner, it is remarked (p. 193) that "the
+distance between the holes in the drilled ring should be so much that
+the jet of gas issuing from each shall, when ignited, just unite with
+its neighbour."
+
+          [11] Accum's "Treatise on Gas-Lights."
+
+Before a really efficient burner could be produced, there were,
+however, to be successfully encountered other problems, the precise
+nature of which was not so clearly apparent as that of the one above
+referred to; otherwise their solution would not have been so long
+delayed. Of these, the most important, and at the same time the most
+difficult, were two--namely, the right adjustment of the air supply,
+and the most advantageous pressure at which to consume the gas. In the
+earliest Argands, not the slightest provision was made for diminishing
+the pressure of the gas before it was consumed. It was thought that
+everything had been accomplished that was necessary if the holes for
+its emission were sufficiently minute to allow of no more than the
+required quantity of gas passing through them at the extreme pressure
+at which it was supplied to the burner. The consequence was that the
+gas, issuing from the burner at a very high velocity, became so
+intermingled with air before it was consumed, that its flame was
+excessively cooled; and only a small fraction of the illuminating
+power available was developed. Then as to the air supply. In nearly
+every burner produced prior to Mr. W. Sugg's invention of the "London"
+Argand in 1868, this was greatly in excess of the requirements; nor is
+it to be wondered at. Had the supply of air been delicately adjusted,
+while yet there was no provision for diminishing the pressure of gas
+at the burner, the flame would have been liable to smoke on any sudden
+increase in the pressure of gas in the mains; and the annoyance and
+inconvenience occasioned by a smoking flame were greater drawbacks
+than the loss of light experienced through having the air supply
+greatly in excess. Thus, although during this period there were many
+so-called "improved" burners brought into notice, in none of them were
+these two cardinal requirements in the production of an efficient
+burner clearly recognized and seriously grappled with; and,
+consequently, the high level of excellence to which the Argand is
+capable of being brought was not attained.
+
+
+SUGG'S ARGANDS.
+
+[Sidenote: The 'London' Argand.]
+
+The invention by Mr. W. Sugg, in 1868, of the famous "London" Argand
+constitutes an important epoch in the history of gas lighting. Prior
+to that time, the construction of this class of burners had been
+carried out in a wholly empirical manner; and such improvements as had
+been effected must be looked upon as being rather the fortuitous
+issues of hap-hazard endeavours, than as resulting from the
+acquirement of clearer views as to the conditions to be complied with
+in order to ensure the successful operation of the burners. The
+invention of the "London" Argand was the first earnest attempt to
+abandon the former chance methods, and to proceed upon more scientific
+lines. Its construction shows that its inventor possessed a thorough
+acquaintance with the principles of combustion; while, in many
+particulars, it exhibits an intelligent discernment, and a successful
+application of the precise means required to attain a desired end. In
+this burner, the extreme importance of causing the gas to issue at a
+low pressure is for the first time clearly recognized; and the manner
+in which this object is so successfully attained is as simple as it is
+ingenious. At the entrance to the burner the gas is divided among
+three narrow tubes, the combined capacity of which is much smaller
+than that of the pipe supplying the burner. Through these tubes the
+gas is conducted into a concentric cylindrical chamber (forming the
+main body of the burner), where its rapid flow is checked; the
+current, or swirl, which it may have acquired, is subdued; and the gas
+comes to a state of comparative rest before it issues into the
+atmosphere and is consumed. The top rim of this concentric cylinder is
+pierced with 24 holes, the aggregate area of which is considerably
+greater than that of the three supply-tubes; thus ensuring that the
+gas shall be delivered at a much lower pressure than that at which it
+enters the burner. By dividing the gas into three streams, which enter
+the cylindrical chamber at equidistant points in its circumference,
+the supply is equally distributed throughout the entire ring of holes;
+and a flame of even and regular shape is the result.
+
+The arrangement by which, in this burner, the air supply is obtained
+and regulated is as noteworthy as are the means adopted for
+controlling the pressure of the gas. The opening within the circular
+ring of holes is much smaller than in previous Argands; thereby
+proportionately reducing the quantity of air supplied to the inner
+surface of the flame. The space between the cylindrical body of the
+burner and the glass chimney is occupied by a truncated cone of thin
+metal, the upper edge of which is on a level with, and reaches to
+within a very short distance of the rim of the burner; while its base
+rests upon the gallery supporting the chimney. By means of this cone,
+all the air entering between the burner and the chimney is directed
+upon the immediate surface of the flame; thereby promoting intensity
+of combustion, and a higher illuminating power of the flame. Then the
+chimney itself is of such dimensions that, with the quantity of gas
+for which the burner has been constructed, just sufficient air is
+drawn upon the flame to completely consume the gas by the time the top
+of the chimney is reached; a flame of such length as to nearly reach
+to the top of the chimney, without smoking, being the most effective
+and economical for the quantity of gas consumed.
+
+  [Illustration: FIG. 14.--SUGG'S "LONDON" ARGAND.
+                 (_Full Size._)]
+
+Another matter which tended not a little to enhance the results
+yielded by this burner was an alteration in the material of which the
+body of the burner was constructed. In previous Argands, this had, in
+almost every instance, been metal; whereas in the "London" burner
+steatite was employed. How the illuminating power of the flame is
+affected by the material of which the burner is constructed has been
+gone into so fully before (in relation to flat-flame burners), that it
+is unnecessary to dwell upon the matter here; only remarking that as
+in Argands the contact surface between the burner and the flame is
+relatively so much greater than in flat-flame burners, the cooling of
+the flame due to this cause is proportionately increased.
+
+[Sidenote: The standard test burner.]
+
+[Sidenote: The improved "London" Argand.]
+
+So great was the improvement effected by this burner in the
+illuminating power developed from the gas consumed, so obvious its
+superiority to every previous Argand, that it was immediately adopted
+by the Metropolitan Gas Referees as the standard burner for testing
+ordinary coal gas within the area of their jurisdiction; and from that
+time down to the present it has continued to be prescribed in Acts of
+Parliament as the burner to be employed in testing ordinary coal gas,
+not only in the Metropolis, but generally throughout the United
+Kingdom. But although, as the standard test-burner, the original
+"London" Argand can still be obtained, it has been far surpassed, in
+the results yielded, by a new series of Argands, in which the same
+ingenious inventor has still further applied the principles first put
+into practice in the former burner. In this newer series of burners,
+the details of construction before adopted are modified in two or
+three particulars; but without departing from the general principles
+embodied in the arrangement of the earlier burner. Thus the holes in
+the ring are considerably larger, while the three supply-tubes remain
+of exactly the same capacity as before; by which means the gas is
+delivered at a much lower pressure. As the increased size of holes
+necessitates that the cylindrical body of the burner should be of
+enlarged diameter, the opening in the centre becomes of greater area
+than before. Were it to remain so, it would permit too large a
+quantity of air to be drawn upon the inner surface of the flame; to
+obviate which result a metal spike rises in the centre, reducing the
+area of the opening, and proportionately diminishing the quantity of
+air which would otherwise be admitted at this part of the burner. The
+arrangement for regulating the air supply to the outer surface of the
+flame is likewise modified, but in a different direction. The upper
+edge of the cone is brought nearer to the rim of the burner, and
+slightly curved, so as to direct the air more completely upon the
+flame; while the base of the cone, instead of extending to the glass
+chimney in an unbroken surface, is pierced by a number of holes, which
+admit air between the cone and the chimney. The action of this third
+current of air is to keep the chimney cool, and to steady the flame;
+and, in addition, it may be that it provides a supply of air to
+support and intensify combustion at the upper extremity of the flame.
+The combined effect of these alterations is to cause the burner to
+develop from 7 to 12 per cent. more light from the gas consumed, than
+is yielded by the original "London" Argand.
+
+[Sidenote: Silber's Argand burner.]
+
+The Silber Argand, which is a remarkably efficient burner, in the main
+features of its construction is very closely related to Mr. Sugg's
+later Argands just described. The air is directed on to the outer
+surface of the flame, as in those burners, by a curved deflector, of
+which the upper edge is, however, at a higher level than in Mr. Sugg's
+burners. Air is also admitted between the deflector and the glass
+chimney. The most striking divergence in its construction from that of
+Mr. Sugg's burners is contained within the opening in the centre of
+the burner. Instead of a solid metal spike, there is a brass tube,
+through which, as well as between its circumference and the
+cylindrical body of the burner, air can enter to feed the inner
+surface of the flame. In addition to promoting the steadiness of the
+flame, it would appear that the air entering through this inner tube
+supports the combustion of the gas at the tail of the flame. The
+arrangements for diminishing the pressure of the gas within the
+burner, and for ensuring its equable distribution to all parts of the
+ring of holes, though quite different, seem to be scarcely less
+complete than those employed in the "London" burner. From the nipple
+which connects the burner to the gas supply, the gas enters (by four
+minute perforations) into a horizontal chamber, where its velocity is
+checked, and whence it is conveyed into the cylindrical chamber
+forming the main body of the burner. The very satisfactory
+performances of the burner (which are in advance of those of the
+standard Argand) sufficiently attest the correctness of its
+construction.
+
+[Sidenote: Multiple Argands.]
+
+For consuming large quantities of gas, double or treble Argands are
+constructed. These consist, in effect, of two or three Argand burners
+placed concentrically to each other within one chimney. Mr. Sugg
+has produced a series of burners of this class, designed to pass
+quantities of gas ranging from 15 to 55 cubic feet per hour; and, in
+some instances, exceeding even the latter figure. These burners, with
+ordinary (16-candle) coal gas, give a light equal to 4 candles per
+cubic foot of gas consumed; which is a considerably better result than
+is afforded by the standard burner. The cause of their yielding
+results so superior to the ordinary Argand is found in the
+circumstance that their flames present a much smaller surface area to
+the cooling action of the air, in proportion to the quantity of gas
+consumed. The arrangement of these burners differs from that of the
+improved single Argands, which have been described, only in that there
+are two or more steatite cylinders, each fed by its own supply-tubes,
+and having its own distinct ring of holes; while the space between the
+cylinders is so proportioned as to admit no more than the quantity of
+air required to produce the necessary intensity of combustion.
+
+  [Illustration: FIG. 15.--THE DOUGLASS ARGAND.
+                 (_A A, Focal Plane, or Belt of Strongest Light._)]
+
+
+THE DOUGLASS BURNER.
+
+The multiple or concentric Argand invented by Mr. (now Sir) J. N.
+Douglass, the Engineer to the Trinity House, may be mentioned here.
+This burner is of the type of those last noticed, but possesses
+certain peculiar features which give it a distinct claim to novelty.
+As will be seen by the accompanying illustration, the concentric
+cylinders of which the burner is composed terminate at different
+heights; their tops forming a regular gradation of steps, of which the
+innermost is the highest. These cylinders are of considerable depth,
+permitting the gas and air to be heated by contact with their surfaces
+before the point of ignition is reached. The essential feature of the
+invention, however, is a series of deflectors of peculiar shape,
+which, in addition to directing air on to the surfaces of the flames,
+are so formed "as to force the outer flame or flames on to the inner
+flame or flames in the manner illustrated." By this means the flames
+are concentrated and united into one, and combustion is quickened;
+and, a greater intensity of heat being thus attained, the illuminating
+power is much augmented. When this burner was first brought into
+notice, in 1881, high hopes were entertained as to its future. The
+results which it was said to afford, being far in advance of anything
+previously obtained from a simple Argand, seemed to promise for the
+burner a speedy and unequivocal success. At the North-East Coast
+Marine Exhibition, held in 1882, a burner with ten rings was
+exhibited, which was reported to develop, from 16-candle gas, 6
+candles per cubic foot--a truly remarkable result to be given by so
+simple a burner. But, notwithstanding its apparently successful
+introduction, the burner has made little or no headway in the
+direction of its practical application. Indeed, it may almost be said
+to have faded altogether out of public view. This would seem to imply
+that there are difficulties in the way of its successful working, when
+brought under ordinary conditions, which were not foreseen at the time
+of its invention.
+
+
+
+
+CHAPTER IV.
+
+GOVERNOR-BURNERS.
+
+
+[Sidenote: Effects of excessive pressure with Argand and flat-flame
+burners.]
+
+Throughout this treatise, much has been said of the relation which the
+pressure of gas, at the point of its delivery from the burner, bears
+to the illuminating power of the flame yielded--sufficient to show
+that the maintenance of a low and equable pressure in the gas supply
+is one of the conditions most imperative to be observed for the
+attainment of economy in combustion. Ordinarily, however, this
+condition does not obtain at the consumers' burners. The exigencies of
+distribution require that, in order to maintain a sufficient supply
+wherever gas is needed, a much higher pressure should be kept in the
+mains than is requisite for developing, at the burner, the best
+results from the gas consumed. Moreover, the pressure at any one point
+is subject to continual fluctuations from the variations in the
+consumption of gas going on in the neighbourhood. For instance, where
+a number of burners are in operation in a house, consuming about the
+exact quantities of gas for which they have been constructed, when
+part of them are shut off the gas supply to the remainder is in excess
+of what is required; and, consequently, the burners do not develop the
+same proportion of light from the gas consumed as formerly. Where a
+large consumption of gas is suddenly discontinued (as in the business
+parts of a town, when the shops and warehouses are closed), the
+increase of pressure that is experienced at the burners which remain
+in operation is very manifest. The effect of this increase in the
+pressure of the gas supply is seen in different directions in Argand
+and flat-flame burners. In the former, it causes the flame to smoke,
+by permitting more gas to pass through the burner than can be properly
+consumed; in the latter, by cooling the flame below the temperature
+required for effective combustion, it reduces, in proportion to the
+extent to which it is higher than the original pressure, the
+illuminating power developed per cubic foot of gas consumed.
+
+[Sidenote: The gas regulator.]
+
+Seeing that economy in combustion can only be attained under the
+conditions of an equable pressure, it becomes necessary to subdue the
+fluctuations above referred to, or at least to prevent their reaching
+the burner. To this end the regulator, or governor, is employed. In
+this instrument, a bell dipping into, and sealed in liquid--or else a
+flexible leather diaphragm--is actuated by the pressure of the
+entering gas, and so connected with a valve as to reduce the area of
+the opening which permits gas to enter the instrument in proportion to
+the pressure of gas at the inlet; by which means an equable pressure
+is maintained at the outlet, no matter what the quantity of gas which
+is being consumed, or how the pressure may vary in the inlet-pipe. By
+the aid of a governor, fixed on the service-pipe at the entrance to a
+building, the pressure of gas at the various burners is rendered
+fairly uniform; yet, even then, perfect equality of pressure is not
+obtained. The slight friction which the gas experiences in flowing
+through the pipes causes the burners to be supplied at somewhat lower
+pressures, the farther they are removed from the burner. And, again,
+owing to its low specific gravity, gas tends to gain in pressure with
+an increased elevation; each rise of 10 feet adding about 1-10th of an
+inch to its pressure. From this cause a higher pressure is experienced
+in the upper than in the lower rooms of a building. This peculiarity
+was observed at an early period in the history of gas lighting; as
+Clegg mentions that, in cotton-mills, check-taps were employed to
+regulate the pressure of gas at each floor.[12] In order, therefore, to
+obtain the desired regularity of pressure in the gas supply, governors
+must be employed for each storey; or, what is better still, each
+burner must have its own separate governor. And this brings us back to
+the subject with which we are more closely concerned.
+
+          [12] Clegg's "Treatise on Coal Gas," 1st Ed., p. 197.
+
+The governor-burner, as its name implies, consists of a governor, as
+described above (but, of course, on a smaller scale) combined with a
+gas-burner; the governor being adjusted so as, whatever excess of
+pressure there may be in the gas-supply pipes, to permit only the
+quantity of gas to pass which the burner is intended to consume.
+Obviously, the principle herein contained is capable of receiving
+numerous applications. It can be, and is applied with equal success to
+Argand and flat-flame burners; while the modifications which obtain in
+the manner of constructing the regulating portion of the apparatus are
+almost as numerous and as varied as are the burners themselves. As the
+main features exhibited by one are common to all, it is unnecessary to
+go into the details of their several constructions. It will suffice to
+take two or three of the most successful, or the best known, as
+representatives of the whole.
+
+[Sidenote: Giroud's Rheometer.]
+
+Among the first in order of time--and still retaining no unworthy
+position in order of merit--is the "rheometer," or "flow-measurer," of
+M. Giroud. In this instrument a light metal bell is sealed in
+glycerine contained in a cylindrical case; the bottom of this latter
+containing the inlet-pipe, screwed for connecting to the ordinary
+fittings, while from the centre of its cover rises a tube leading to
+the burner. The bell is pierced by a small hole for the passage of the
+gas, and is surmounted by a cone-shaped projection, which constitutes
+the valve of the instrument. As the pressure of the entering gas lifts
+the bell, it causes this cone-valve to enter the mouth of the tube
+leading to the burner; reducing the area of the opening in proportion
+to the pressure of gas acting upon the under side of the bell, and so
+permitting only the required quantity of gas to pass to the burner. It
+might be thought that the presence of liquid would constitute an
+objection to the use of the instrument; but, as glycerine does not
+evaporate, when once the instrument is fixed and properly adjusted, it
+needs no further attention. With an excessive initial pressure, there
+is, however, a liability of the gas to bubble through the sealing
+liquid, and so destroy the efficiency of the instrument; but this
+might be obviated by increasing the depth of the bell, and so giving
+it a greater seal. The instrument is very reliable for the purpose
+which it is intended to fulfil; delivering, through a considerable
+range of pressure beyond that required to raise the bell, the exact
+quantity of gas for which it has been adjusted. It may be added that
+the rheometer has an advantage over many instruments of its class, in
+that it presents so little obstruction to the downward rays of the
+flame.
+
+  [Illustration: FIG. 16.--GIROUD'S RHEOMETER.]
+
+[Sidenote: Sugg's Christiania governor-burner.]
+
+Mr. William Sugg, in his regulator or governor, adopts an entirely
+different arrangement to the foregoing. The valve is placed at the
+inlet of the governor; and not at its outlet, as in the instrument
+just described. Instead of a metal bell, a diaphragm of thin and very
+flexible leather is employed, which is raised by the pressure of the
+entering gas, and, in turn, actuates the valve; closing the entrance
+to the governor in proportion to the pressure of gas acting upon it.
+The orifice communicating between the under and the upper side of
+the leather diaphragm is controlled by a screw, whereby the quantity
+of gas delivered to the burner can be regulated according to
+requirements; but when once it has been adjusted to give any desired
+pressure of gas at the burner, this pressure will be strictly
+maintained, no matter with what excess of pressure (within reasonable
+limits) the gas may be supplied to the instrument. The improved
+"London" Argands produced by Mr. Sugg (the details of the construction
+of which have been already described) are too delicately adjusted to
+be applied with advantage directly to the ordinary consumer's
+gas-fittings, or wherever any variation in the pressure of the gas
+supply is likely to be experienced. However, with the addition to them
+of the above governor, their use becomes as easy and simple as that of
+other burners; and thus the gas consumer is enabled to obtain the
+benefit of the most improved apparatus without being called upon to
+exercise the constant care and attention which, without the aid of the
+governor, would be necessitated. Besides being applied to Argands,
+this governor is successfully applied by its inventor to his
+flat-flame burners. In conjunction with a simple steatite burner of
+the latter class, it has received a very extended application, under
+the name of the Christiania governor-burner.
+
+[Sidenote: Sugg's Steatite-float governor-burner.]
+
+Recently, however, a new type of governor, for application to burners,
+has been brought out by the same manufacturer, the construction of
+which is very different to that of the instrument referred to above;
+and as it is somewhat simpler in its details, and withal appears to be
+cheaper in construction, it seems destined to supersede the former
+instrument. In this new governor, instead of a leather diaphragm,
+there is a bell (or float) of steatite, which is free to move, in the
+manner of a piston, within an inner cylindrical chamber contained
+within the outer case of the instrument. Attached to the centre of the
+float, and on its upper surface, is a tube sliding within another tube
+of somewhat larger area; the latter forming a continuation of the
+inner cylindrical chamber. The smaller tube is open at both ends, and
+thus communicates from below to above the float; the outer tube is
+closed at the top, but has an orifice in its side. The action of the
+instrument is as follows:--The gas, entering below the float, passes
+through the inner tube to the upper part of the cylindrical chamber,
+and thence, through the orifice in the outer tube, to the burner. As
+the pressure of the entering gas exceeds that required to overcome the
+weight of the float, the latter is raised; the tube which is attached
+to it being propelled farther into the outer tube in which it slides,
+and, in so doing, partially closes the orifice in the side of the
+latter. In this way, according to the pressure of the gas acting upon
+the under side of the float, the area of the opening through which it
+must flow to get to the burner is reduced; and so the quantity of gas
+which issues from the burner remains the same under all pressures
+above that required to actuate the float. The instrument appears to be
+as reliable as it is simple, and to contain few parts calculated to
+get out of order; but, of course, whether or not it will retain its
+good qualities after long-continued use can only be proved by
+experience.
+
+  [Illustration: FIG. 17.--SUGG'S STEATITE-FLOAT GOVERNOR.]
+
+[Sidenote: Peebles's needle governor-burner.]
+
+[Sidenote: Efficiency of the needle governor-burner.]
+
+Another instrument of this class--the last which I shall notice--is
+Peebles's needle governor-burner. For simplicity combined with
+remarkable efficiency, it is undoubtedly ahead of all its compeers.
+Somewhat similar in principle to Giroud's rheometer, it differs from
+that instrument in many of the details of its construction; and while
+dispensing with the use of liquid, maintains equal efficiency in
+operation. It was described as follows by Dr. W. Wallace, in a lecture
+on "Gas Illumination," delivered before the Society of Arts in
+January, 1879:[13]--"In a little cylinder stands a so-called needle, on
+the point of which rests a flanged cone of exceedingly thin metal. At
+one side of the cylinder there is a small tube leading away the gas,
+and the orifice of which is influenced in area by the action of the
+cone. The instrument, by means of a screw leading into the side tube,
+can be made to deliver any desired number of cubic feet, which it does
+with surprising accuracy, provided that the pressure of the gas is not
+less than 6-10ths of an inch." As to the efficiency of the instrument,
+Dr. Wallace proceeded to state:--"In trials that I have made, I have
+not found the variations of volume at different pressures to exceed 1
+per cent." For situations where this extreme nicety of operation is
+not absolutely essential, or where the rate of consumption is to be
+invariable, the instrument is constructed in a somewhat modified and
+simpler form. The small tube on the side of the instrument is
+dispensed with, and the gas permitted to pass through perforations in
+the lower part of the cone. With this alteration there is a nearer
+approach to the construction of the rheometer; but, as in that
+instrument, there is no provision for altering the rate of consumption
+to suit different circumstances.
+
+          [13] See _Journal of Gas Lighting_, Vol. XXXIII., p. 162.
+
+  [Illustration: FIG. 18.--PEEBLES'S NEEDLE GOVERNOR.]
+
+
+
+
+CHAPTER V.
+
+REGENERATIVE BURNERS.
+
+
+[Sidenote: Temperature of a gas flame.]
+
+As was remarked in the introduction to this treatise, recent years
+have witnessed a very considerable advance in the construction of
+gas-burners, and in the amount of light capable of being developed
+from each cubic foot of gas consumed. Undoubtedly the most noticeable
+feature of this advance is the successful application of the
+regenerative, or, as it would be more appropriately designated,
+recuperative system. Briefly stated, this consists in utilizing the
+heat of the products of combustion from the gas flame (which otherwise
+would be dissipated into the atmosphere) to raise the temperature of
+the gas before it is ignited; and, likewise, of the air necessary for
+combustion. The temperature of an illuminating gas flame is usually
+estimated to be between 2000° and 2400° Fahr.; and as the products of
+combustion must leave the flame at a temperature little, if at all,
+inferior to the former figure, it must be evident that there is an
+ample margin of heat for employment in this direction. A considerable
+proportion of the large amount of heat conveyed by those products of
+combustion which, under ordinary circumstances, is imparted to the
+surrounding atmosphere--often elevating its temperature to an
+unnecessary and prejudicial extent--is, by this method, returned to
+the flame; intensifying the process of combustion, and augmenting, in
+a remarkable degree, the illuminating power developed from the gas
+consumed. Thus the ultimate effect of the operation is to produce a
+concentration of heat in the flame, and the conversion of superfluous
+heat into beneficial light. Within a comparatively recent period, the
+utility of this process was strongly disputed; and it was stoutly
+maintained, by many persons, that as the immediate effect of ignition
+was to cause a temperature of more than 2000° Fahr. to be attained,
+the heating of the gas and air prior to their combustion could produce
+little or no beneficial effect upon the illuminating power of the
+flame. However, the falsity of this view of the case is conclusively
+demonstrated by practical experiment; the remarkably high results
+yielded by burners that have been constructed upon the regenerative
+system sufficiently attesting the correctness of the principles upon
+which they are founded.
+
+Although, in general, both the gas and air supplies are heated, it is
+chiefly due to the latter that the beneficial effect noticed is
+produced; and this for two reasons. First, because the quantity of air
+is so much greater than the gas it is required to consume; being, at
+the nearest approach to theoretical perfection, fully six times its
+volume. Second, because four-fifths in volume of the air consists of
+inert nitrogen, which does not contribute anything to the heat of the
+flame, but, when applied in its normal, cold condition, abstracts no
+inconsiderable proportion of heat from it. Yet the heating of the gas
+itself is not without very appreciable influence. In an ordinary
+gas flame there is always an area of non-illumination around, and
+extending to a variable distance from the burner head. This is caused
+partly by the conduction of heat from the flame by the burner; but, in
+a greater degree, by the cooling action of the issuing stream of cold
+gas, as is shown by its extending farther from the burner in
+proportion to the pressure or velocity with which the gas issues. The
+prejudicial effect due to the former is obviated to a great extent by
+constructing the burner of steatite, or other non-conducting material.
+To remedy the latter, nothing will avail but the heating of the gas
+supply.
+
+[Sidenote: Effects of heating the gas and air.]
+
+The effect of heating the gas is to enlarge the area of the
+illuminating portion of the flame, and, in a minor degree, to enhance
+the intensity of incandescence to which the carbonaceous particles are
+raised. When the gas issues from the burner at a temperature little
+inferior to the temperature of ignition, the hydrocarbons it contains
+are immediately decomposed; the liberated particles of carbon are
+raised to the temperature of incandescence; and the illuminating area
+of the flame is extended downwards, even to the surface of the burner.
+The heating of the air operates chiefly to produce and maintain a more
+elevated temperature of the flame; and, in this manner, contributes to
+the development of a higher illuminating power from the same area of
+flame. In the case of ordinary gas flames, the cold atmosphere by
+which they are surrounded, by abstracting heat from the flame,
+prevents the most favourable conditions for the development of light
+from being attained. When, however, the air immediately surrounding
+the flame has been previously heated, the particles of carbon (the
+incandescence of which furnishes the desired illuminating power)
+attain to a much more exalted temperature; and, consequently, give out
+a greater degree of light.
+
+But there is yet another direction in which the prior heating of the
+air supply contributes to the development of improved illuminating
+power. Being heated, its density is lowered; so that in any given
+volume of air there is less weight of oxygen than when cold. The
+consequence is that as less oxygen is presented to a given surface
+area of flame, the separated particles of carbon remain for a longer
+period of time in the incandescent condition before being entirely
+consumed. Thus there are three distinct results produced by heating
+the gas and air before combustion--namely, first, the particles of
+carbon are liberated earlier in the flame; second, they are raised to
+a more exalted temperature; and, third, they remain for a longer time
+in the incandescent condition. The combined effect of all three is the
+improved illuminating power developed from the gas consumed.
+
+  [Illustration: FIG. 19.--BOWDITCH'S REGENERATIVE GAS-BURNER.]
+
+[Sidenote: Bowditch's regenerative burner.]
+
+So far back as the year 1854, the principle of heating the air supply
+to an Argand burner, by means of waste heat from the flame, was
+partially applied, with some success, by the Rev. W. R. Bowditch,
+M.A., of Wakefield. Mr. Bowditch's burner, which is shown in the
+accompanying diagram, contained, in addition to the ordinary chimney,
+an outer glass chimney, which extended for some distance below the
+inner one, and was closed at the bottom; so that all the air needed to
+support the combustion of the gas was required to pass down the
+annular space between the chimneys, and in its passage became
+intensely heated by contact with the hot surface of the inner chimney,
+as well as by radiation from the flame itself. This burner contained
+many defects. Amongst others, the inner chimney could not long
+withstand the intense heat to which it was subjected, and, in
+consequence, had to be frequently renewed; the heating of the air was
+not effected solely by the products of combustion, but, perhaps in a
+greater degree, by the abstraction of heat from the flame itself;
+while, at best, this heating was but partial. Yet, these defects
+notwithstanding, the burner showed very clearly the beneficial results
+attending even a partial application of the principle; as, in the
+illuminating power it developed from the gas consumed, a clear gain of
+67 per cent. over the ordinary Argand burner was obtained. Although
+the drawbacks connected with the construction of Mr. Bowditch's burner
+prevented its ever receiving general, or even extensive adoption, its
+simplicity has gained for it the distinction of being freely copied by
+so-called inventors of a later day.
+
+[Sidenote: Invention of the Siemens regenerative burner.]
+
+It was left to Herr Friedrich Siemens, of Dresden, to produce a burner
+which, while applying the principle of regenerative heating in the
+most scientific and complete manner, should also be adapted to the
+ordinary conditions of gas lighting. After much experimenting on the
+subject, a burner embodying the essential features of the regenerative
+system was invented by this gentleman in 1879; and so great was the
+advance which its performances manifested over anything previously
+attained, so wide the prospect of further achievements which was
+opened out, that it may fairly be said to have inaugurated a new era
+in gas illumination. In this burner the products of combustion were
+made to give up a considerable portion of their heat to the gas and
+air, as the latter passed to the point of ignition; the flame itself
+not being called upon to contribute in any degree to this result.
+Although, as was but natural, the first attempts towards the
+construction of such a burner were very crude, and but partially
+successful in their results, the inventor persevered in his endeavours
+to work out his ideas into practical and thoroughly satisfactory
+shape. It was not until after it had gone through many modifications
+that the burner acquired the peculiar form which now distinguishes it,
+and attained to its present stage of perfection. Before proceeding to
+describe an example of the burner as now constructed, it is necessary
+to state that the principles embodied in Herr Siemens's invention are
+equally well adapted--and, indeed, are applied with equal success--to
+the construction of flat-flame and Argand burners; but as the
+distinctive features of the invention are common to both classes of
+burners, it will be quite sufficient to describe in detail one of the
+latter type.
+
+A prominent feature in the appearance of the Siemens burner, as will
+be seen from the annexed illustration, is a large metal chimney, for
+creating a draught to carry away the products of combustion. The
+entrance to this chimney is situated a little above the apex of the
+flame; but there is a branch flue connecting the main chimney with the
+interior of the burner. The body of the burner is of metal, and its
+interior is divided into three concentric chambers. Of these, the
+innermost is open at the top, and is surmounted by a porcelain
+cylinder, which, when the gas is lighted, is surrounded by the flame.
+This chamber is closed at the bottom, but communicates at the side
+with the before-mentioned branch tube, or flue, leading to the main
+chimney. The intermediate chamber communicates, at its lower
+extremity, with the gas supply; and terminates, a short distance from
+the top of the burner, in a number of small metal tubes, which convey
+the gas to the point of ignition. The outer chamber is open both at
+top and bottom, and is for conveying air to support the combustion of
+the gas. In order to promote greater intensity of combustion, there is
+a notched deflector at the summit of the latter chamber, and another
+on the lower part of the porcelain cylinder, which cause the air to
+impinge more directly upon both sides of the flame. There is also an
+arrangement for introducing air between the outer casing of the air
+chamber and the glass chimney which encloses the flame; its object
+being to keep the chimney cool.
+
+  [Illustration: ELEVATION.
+                 ENLARGED SECTION OF COMBUSTION CHAMBERS.
+                 FIG. 20.--SIEMENS'S REGENERATIVE GAS-BURNER.]
+
+[Sidenote: Action of the Siemens burner.]
+
+The action of the burner is as follows:--When the gas is ignited at
+the ring of tubes, the heated air and products of combustion, which
+rise from the flame, create a draught in the main chimney. Through the
+communication established by means of the lateral flue, a partial
+vacuum, or area of low pressure, is induced in the innermost chamber
+of the burner, and within the porcelain cylinder which surmounts it.
+As the flame terminates close to the mouth of the latter, the greater
+portion of the products of combustion, instead of going into the main
+chimney, are sucked into the porcelain cylinder; and thus a current is
+set up through the interior of the burner, and by the lateral flue, to
+the main chimney. The heat carried away by the products of combustion
+is communicated, through the walls of the chambers, to the entering
+gas and air; and by this means the latter are heated to a very high
+temperature before they issue from the burner and are consumed. The
+consequence is that a much greater intensity of combustion is
+maintained; the carbon particles are separated earlier in the flame,
+and are raised to a more exalted temperature; and the ultimate effect
+is a higher yield in illuminating power per cubic foot of gas
+consumed. Independent tests by various experienced photometrists have
+conclusively shown that a light equivalent to that from 5 to 6 candles
+is obtained per cubic foot, from gas which, in the standard "London"
+Argand, yields a light of only from 3 to 3-1/2 candles.
+
+[Sidenote: Defects of the Siemens burner.]
+
+While the advantages of the Siemens burner are many and obvious, it is
+not without its disadvantages. These partly arise from causes
+connected with the very observance of the conditions necessary to
+secure the efficiency of the burner. With every advance in the more
+efficient operation of gas-burners, increased care and attention are
+demanded in their employment, in order to obtain the benefits they are
+calculated to yield. Indeed, it would almost appear that the nearer
+the approach to perfection which is made in the construction of a
+burner, the greater must be the drawbacks to its general adoption.
+Thus, in the burner under notice, if the gas supply is allowed to
+become in excess, the tail of the flame enters the porcelain cylinder,
+and soot is deposited in the interior of the burner; obstructing the
+passages, and impairing the burner's action. Then, to cause the burner
+to yield its highest results, it is necessary that the air supply be
+accurately adjusted to the quantity of gas being consumed. To this end
+the entrance to the air chamber, at the bottom of the burner, is
+covered by a perforated semi-circular cup, by turning which the
+quantity of air entering the burner can be increased or diminished as
+required. Moreover, the bulky construction of the burner, with its
+accompaniment of chimney and flue, and its complicated arrangement of
+tubes and chambers, imparts to it a somewhat clumsy and inelegant
+appearance, which is calculated to impair the favour with which its
+remarkable performances cause it to be regarded. But these drawbacks
+are far outweighed by the undoubted advantages conferred by the
+burner--in improved illumination combined with economy of combustion,
+and the facilities it affords for securing perfect ventilation.
+
+Encouraged by the success of Herr Siemens, other inventors have
+followed in his footsteps; with the result that there are now a
+variety of burners before the public, embodying the same principles,
+but differing in the details of their construction and in the measure
+of their efficiency. Of these may be mentioned Grimston's, Thorp's,
+and Clark's; and without describing in detail the construction of the
+several burners (of which further particulars will be found in the
+"Register of Patents" in the _Journal of Gas Lighting_[14]), it must
+suffice to refer to the salient points and distinctive features of
+each.
+
+          [14] See Vol. XL., pp. 786, 950; and Vol. XLII, p. 836.
+
+[Sidenote: Grimston's regenerative burner.]
+
+Grimston's burner (shown on the next page) consists, in effect, of an
+Argand burner turned upside down; the gas issuing from the bottom ends
+of a number of small tubes placed in a circle. The jets of
+flame--first directed downwards from the mouths of these tubes--by a
+conoidal deflector in the centre of the ring, are caused to spread
+outwards, and assume a horizontal direction; and by their amalgamation
+with each other a continuous sheet or ring of flame is produced. The
+horizontal direction of the flame is maintained by its passing
+underneath a metal flange, faced with white porcelain, or other
+refractory material; the supply of gas being adjusted so that the
+flame just terminates at the outer edge of this flange. Before
+entering the chimney, the products of combustion are caused to flow
+through a number of vertical tubes contained in a cylinder, which is
+concentric to an inner cylinder containing the gas-supply tubes. The
+outer cylinder is traversed by the air needed for the support of
+combustion, which is to become heated before reaching the point of
+ignition; and in order the more completely to enable the products of
+combustion to impart their heat to the entering air, the cylinder is
+further intersected by strips of wire gauze, which pass around and
+between the tubes (see fig. 22, on next page). By these means the air
+is intensely heated; and, passing among the narrow burner tubes
+through which the gas is conveyed, gives up a portion of its heat to
+the latter before the point of ignition is reached. Thus, in a very
+simple manner, both air and gas are raised to a considerable
+temperature before combustion takes place.
+
+With regard to the efficiency of the burner, at the exhibition of gas
+appliances held at Stockport in 1882 (where a gold medal was awarded
+to it, as well as to Thorp's burner, to be referred to hereafter),
+with a consumption per hour of 9·84 cubic feet of 17·5 candle gas, an
+illuminating power of 60·67 candles was obtained (equal to 6·16
+candles per cubic foot); while, on another occasion, when the burner
+was consuming 8·94 cubic feet per hour, an illuminating power of 51·5
+candles (equal to 5·76 candles per cubic foot) was obtained from gas
+of the same quality. It is claimed for this burner that equally good
+results are obtained with small sizes as with large; and this, if
+borne out in actual practice, should go far towards ensuring the
+success and extensive adoption of the burner.
+
+  [Illustration: FIG. 21.--GRIMSTON'S REGENERATIVE GAS-BURNER.]
+
+  [Illustration: FIG. 22.--GRIMSTON'S BURNER.
+                 PLAN, SHOWING REGENERATING ARRANGEMENT.]
+
+  [Illustration: FIG. 23.--THORP'S REGENERATIVE GAS-BURNER.]
+
+[Sidenote: Thorp's regenerative burner.]
+
+Thorp's burner produces a cylindrical flame, like that of the Argand,
+but without the aid of a glass chimney which is a necessary adjunct to
+the latter burner. By means of a deflector on the inner side of the
+flame, the latter is made to curve outwards and assume a somewhat
+convex form, so as to obviate the shadow which otherwise would be cast
+by the gas chamber at the bottom of the burner. Above the flame is a
+cylindrical chimney, divided by a vertical partition into two
+concentric chambers, which are intersected by a series of metal gills,
+or projections, continued through both chambers. The outer chamber is
+for conveying away the products of combustion; the inner one for the
+passage of air to feed the flame; while down the centre of the inner
+chamber there passes a tube conveying the gas to the point of
+ignition. The hot products of combustion pass up from the flame
+through the outer chamber, and give up the greater portion of their
+heat to the projections; by which it is conducted into the inner
+chamber, and transferred to the incoming air. A common imperfection of
+regenerative burners is that, in consequence of the diminished rate at
+which the gas flows through the burner when expanded by heat, when
+starting the burner the gas must be only partially turned on, and the
+quantity gradually increased as the burner becomes heated; thus
+necessitating considerable attention. To prevent the need for this
+attention, there is in Thorp's burner an ingenious contrivance for
+automatically regulating the quantity of gas admitted to the flame.
+The central gas-tube, which is referred to above, contains a brass
+rod, fixed at one end, and at the other connected to a valve
+controlling the quantity of gas that enters the tube. At first, when
+the gas is lighted, this valve is almost closed; but as the rod
+becomes heated it elongates, gradually opening the valve until the
+full quantity of gas is admitted which the burner is intended to
+consume. At the Stockport exhibition, Thorp's burner was tested with
+the following results, as recorded in the Judges' report. After it had
+burned about two hours, "it gave an illuminating power of 183 standard
+candles, while burning 27 cubic feet of gas per hour (equal to 6·77
+standard candles per cubic foot), with gas of 3·5 candles per cubic
+foot.... In another experiment with the same quality of gas, after
+burning half an hour it yielded, under similar conditions, 154 candles
+with a consumption of 25·29 cubic feet per hour, which gave an
+illuminating power of 6·02 candles per cubic foot."
+
+[Sidenote: Clark's regenerative burner.]
+
+There is nothing in Clark's burner that calls for special notice. In
+its main features it appears to be constructed upon similar lines to
+Grimston's burner, although the coincidence is doubtless only
+accidental.[15] It must, however, be added that in the details of its
+construction it is much simpler than the latter burner; and certainly
+it appears to lose very little in efficiency from its greater
+simplicity, as the following extract from a report by Mr. F. W.
+Hartley, the well-known photometrist, will show:--"With a consumption
+rate of 5·3 cubic feet of gas per hour, the amount of light yielded
+horizontally was equal to 29·79 times that of a standard candle. The
+light yielded per cubic foot of gas burned per hour was therefore
+equal to 5·62 times that of a standard candle." And the amount of
+light delivered immediately downwards is said to be "very sensibly
+greater than the amount of light delivered horizontally." Like the
+Grimston burner, it is of the inverted Argand form; the gas issuing
+from a chamber at the bottom of a tube which descends through the
+centre of the burner. The products of combustion escape through a
+chimney; and in so doing give up a portion of their heat to the
+entering air, which is conveyed to the point of ignition through
+horizontal tubes that intersect the chimney. The burner is enclosed in
+a suitable lantern, the lower half of which consists of a
+semi-globular glass; a similar arrangement being adopted in connection
+with the Grimston and Thorp burners.
+
+          [15] In justice to Mr. Clark it should be mentioned that,
+          since the above appeared in the _Journal of Gas Lighting_,
+          the attention of the writer has been called to the fact
+          (which had been overlooked by him) that Clark's patent was
+          taken out some months before that of either Grimston or
+          Thorp.
+
+  [Illustration: FIG. 24.--CLARK'S REGENERATIVE GAS-BURNER.]
+
+The three burners last mentioned have not been before the public
+sufficiently long to enable a reliable opinion to be formed as to
+their value in actual and prolonged use. Although there is no reason
+for supposing that such will occur in the present instance, it so
+often happens that the results indicated by apparatus in the
+experimental stage, or while still under the control of the inventor,
+are not borne out in practice, that it would be unwise to express any
+decided opinion as to their ultimate worth from existing information.
+It is, however, to be earnestly hoped that the marked favour with
+which they have been received will not be impaired on improved
+acquaintance; but that further experience will justify the
+anticipations that have been excited by the excellent performances of
+the burners hitherto, and demonstrate at once their durability and
+real usefulness.
+
+
+Since writing the above, considerable activity has been shown by
+inventors in producing new burners upon the regenerative principle, or
+in improving upon existing models. Of course, as yet it is too early
+to arrive at a satisfactory estimate of their actual value or relative
+worth; but it may be hoped that, from the increased attention being
+devoted to the subject, some real and practical results will flow, by
+which the gas-consuming public will be the gainers. So far, the most
+promising of this class of burners that has been brought into actual
+use, since the introduction of the Siemens burner, is the one
+represented below.
+
+  [Illustration: FIG. 25.--BOWER AND THORP'S REGENERATIVE GAS-BURNER.]
+
+It is a modification, in the direction of greater simplicity, of
+Thorp's former burner, illustrated and described on p. 69 of this
+treatise; and as its construction is based upon the same lines as that
+burner, further description is not required.
+
+
+
+
+CHAPTER VI.
+
+INCANDESCENT BURNERS.
+
+
+A review of gas-burners would scarcely be complete without some
+reference to the incandescent burners of M. Clamond and Mr. Lewis.
+Although their dependence upon an artificially produced blast or
+current of air removes them from the list of appliances applicable to
+ordinary conditions, the remarkable results which they afford, not
+less than their originality, demand for them at least a passing
+notice. The production of light by the agency of these burners is
+brought about in a manner altogether different, and is due to quite
+other causes than those which are concerned in the production of an
+ordinary illuminating gas flame. In the latter case, the illuminating
+power developed is solely due to the hydrocarbons contained in the
+gas, which are decomposed by the heat of the flame, the separated
+carbon being raised to a white heat. In the former, the illuminating
+power is not obtained directly from the gas; but advantage is taken of
+the heat of the flame, enhanced by the application of a blast of air,
+to raise to incandescence some refractory foreign material, which
+latter is thus made to give out light. In the Clamond burner this
+refractory substance is a basket composed of magnesia, spun into
+threads; in the Lewis burner it is a cage of platinum wire.
+
+To the unthinking reader it may perhaps appear somewhat surprising
+that results so remarkable as are yielded by these burners should be
+obtained, while disregarding, as a source of light, the hydrocarbons
+contained in gas, and employing them, in common with the other
+constituents, solely as a source of heat. An explanation, however, is
+readily forthcoming. As was shown in a former part of this
+treatise,[16] the great bulk of ordinary coal gas consists of
+constituents which, in the act of combustion, produce considerable
+heat, but scarcely any light; the illuminating power developed in an
+ordinary gas flame being almost wholly dependent upon the very small
+proportion of heavy hydrocarbons which the gas contains. Thus, the
+quantity of heat-producing elements contained in the gas being quite
+disproportionate to the light-yielding hydrocarbons, there is always
+produced, in an ordinary gas flame, more heat than is necessary for
+effectively consuming the free carbon, which is liberated in the flame
+by the decomposition of the heavy hydrocarbons. This is shown by the
+fact that coal gas can usually be naphthalized--that is, impregnated
+with the vapour of naphtha--to a considerable extent before the limit
+of effective combustion is reached. The object aimed at in the
+incandescent burners about to be described is to utilize, in the
+development of illuminating power, the combined heat produced by the
+combustion of all the constituents of the gas. To this end the heat
+of combustion is brought to bear upon, and caused to raise to
+incandescence, some refractory material, extraneous to, but brought
+within the operation of the flame.
+
+          [16] See Chap. II., p. 21.
+
+[Sidenote: Effect of injecting a blast of air into a gas flame.]
+
+A further explanation of the superior results yielded by these burners
+may be found in the employment of an artificial blast or current of
+air. Indeed, without some such arrangement the desired end could not
+be attained. The heat developed by the unaided flame is diffused over
+too wide an area to raise the temperature of the heated substance to
+the necessary degree of incandescence to enable it to give out
+sufficient light. By injecting a current of air into its midst, the
+flame is condensed into a smaller compass; and is brought to bear more
+directly upon the precise locality where its heat may be most
+effectively employed. Thus, although the total quantity of heat
+developed remains exactly the same as before, it is concentrated upon
+a smaller surface of the refractory substance; and the latter is
+consequently more intensely heated, or, in other words, raised to a
+more exalted temperature. The very superior illuminating power which
+is thereby obtained is due to the circumstance that the quantity of
+light yielded by an incandescent body increases in a higher ratio than
+the temperature to which it is raised.
+
+[Sidenote: Lewis's incandescent gas-burner.]
+
+Proceeding now to describe the burners. The one invented by Mr. Lewis
+(various forms of which are illustrated on the next page) consists of
+an upright tube, connected at its base to the gas supply, and
+surmounted by a cap or cage of platinum wire gauze; which latter
+constitutes a combustion chamber, as it is there that the mixture of
+gas and air is consumed. Into the lower part of the upright tube the
+nozzle of an air-pipe is inserted, through which a supply of air can
+be injected, under pressure, into the burner, after the manner of a
+blowpipe. There are also small branch tubes leading into the upright
+gas-tube, and open to the atmosphere. Through these an additional
+quantity of air enters the burner; being drawn or sucked in by the
+agency of the main current, which flows through the upright tube. The
+resemblance to an ordinary Bunsen burner is, therefore, very close.
+The mixture of gas and air thus produced, when ignited, burns at the
+platinum cap; the heat which is developed causing the latter to become
+highly incandescent, and so to give out a brilliant light. To prevent
+the conduction of heat from the incandescent platinum, through the
+upright tube, a non-conducting material--such, for instance, as
+steatite or porcelain--is interposed between the gauze cap and the
+metal tube.
+
+  [Illustration: FIG. 26.--LEWIS'S INCANDESCENT GAS-BURNER.]
+
+The light produced by this burner is said to approximate more closely
+to daylight than that yielded by an ordinary gas flame (the colours of
+textile fabrics, for instance, being shown as well by its aid as by
+daylight); while, on account of its resulting from the incandescence
+of a fixed body, instead of being emitted from a flame, it is
+unaffected by a gust of wind, and maintains perfect steadiness under
+every condition of weather. The illuminating power developed is stated
+to be equal to 5 standard candles per cubic foot of gas consumed.
+
+[Sidenote: Clamond's incandescent gas-burner.]
+
+M. Clamond's burner, which is shown in fig. 27, is a much more
+complicated apparatus than the preceding one, and not so easily
+described; but its main features may be briefly enumerated as
+follows:--The air (which, as in Mr. Lewis's burner, is supplied under
+pressure) is divided, as it enters the apparatus, into two portions.
+One portion is at once mixed with the gas; the remainder being
+conveyed, through a peculiarly constructed tube composed of small
+pieces of refractory material, to the combustion chamber, or "wick,"
+as it is termed, of the burner. This "wick" is a small conical basket,
+made of a kind of lacework of spun magnesia, which, when raised to
+incandescence by the heat produced by the combustion of the gas,
+furnishes the desired illumination. The mixture of gas and air is
+subdivided, by a "distributor," into two portions, one of which goes
+direct to the magnesia "wick," there to be burnt, while the other is
+distributed among a number of tubes, forming so-called "auxiliary
+burners," the flames of which are utilized to heat the chief air
+supply; being directed upon the sides of the before-mentioned tube of
+refractory material, through which it is conveyed. By this means the
+air is raised to a very high temperature (1000° C., or 1800° Fahr., it
+is said) before it impinges upon the flame. The result is the
+production of a most intense heat within the magnesia basket; the
+latter being raised to brilliant incandescence, and so developing a
+high illuminating power.
+
+  [Illustration: FIG. 27.--CLAMOND'S INCANDESCENT GAS-BURNER.]
+
+The magnesia basket must be renewed after being in use a period of
+from 40 to 60 hours, as it gradually deteriorates by the action of the
+intense heat to which it is subjected; but as the cost is said to be
+insignificant, this should not be a great drawback. The basket is
+placed at the base of the burner, in order to obviate the shadow which
+would otherwise be cast by the apparatus; and it is attached to the
+main body of the apparatus by platinum wires. As to illuminating
+power, the only particulars which have been made public refer to the
+first two models constructed; one of which was said to develop a light
+equal to that from 6·208 candles, and the other to 9·72 candles per
+cubic foot of gas consumed.
+
+  [Illustration: FIG. 28.--CLAMOND'S IMPROVED INCANDESCENT BURNER.]
+
+[Sidenote: Clamond's new burner.]
+
+In a recently designed modification of the burner (which is shown in
+the accompanying illustration) M. Clamond dispenses with an artificial
+supply of air under pressure, and endeavours to obtain similar results
+by other and simpler means. To this end the position of the magnesia
+"wick" is reversed (it being placed at the top of the apparatus); the
+current of gas is allowed to draw in upon itself a quantity of air by
+a precisely similar arrangement to that adopted in the Bunsen burner;
+while an additional supply of air is drawn upon the flame by the
+accelerated draught produced by the aid of a glass chimney. As in the
+more complicated and complete burner, the air supply is heated by
+means of auxiliary burners in the interior of the apparatus. It has
+been stated, on the authority of M. Clamond, that this modified burner
+develops, from the gas consumed, a duty of about 6 candles per cubic
+foot; being equal to the results yielded by the more complicated
+apparatus. Should this be borne out in practice, M. Clamond will
+have achieved a noteworthy success. It is, however, advisable to
+reserve expressing any definite opinion of its merits until further
+information is received, or until the burner has been tried in this
+country.
+
+
+
+
+CHAPTER VII.
+
+CONCLUSION.
+
+
+The burners last mentioned may be said to mark the extent of the
+progress that has been made, down to the present time, in the
+construction of apparatus for developing light from coal gas; and they
+remind me that I have arrived at the conclusion of my subject. From
+the unpretending gas-jet described by Accum--burning, with
+wonder-provoking steadiness and constancy, "so long as the supply of
+gas continued"--to the complicated apparatus of M. Clamond, is a long
+stretch of invention; embracing the labours of many distinct and
+original workers in the same field, and including numerous variations
+in the details of burners that have not been touched upon in the
+foregoing remarks. As was announced in the introduction, I have dealt
+in this treatise only with the more important or the more successful
+of the modifications that have been made from time to time in the
+construction of the gas-burner. In addition to the burners that have
+been referred to, there have been invented many others, which could
+not be adequately noticed without prolonging the treatise to an undue
+length. Some of these (the fruit of much thought and careful
+experiment) have obtained, in the commercial success that has attended
+them, no more than their merited reward; others (devoid of any real
+merit, and in their construction disregarding the most elementary
+principles of economic combustion) have been brought into somewhat
+extensive use by the misleading statements and false representations
+of their inventors, and are only tolerated through the ignorance of
+the public; while not a few of the latter class of burners have
+speedily found the oblivion which they richly deserved. Sufficient,
+however, has been said to show that many real improvements have been
+effected in the construction of gas-burners, and to prove that, with
+the apparatus now available, a far higher duty may be obtained from
+the gas consumed than was possible only a few years ago.
+
+But although the great advance that has been made in the construction
+of gas-burners is undoubted, the benefits which ought to result
+therefrom have not been realized by the gas-consuming public; nor are
+they likely to be to their full extent. While the ingenious and
+effective inventions for utilizing the waste heat of combustion, and
+for lighting by incandescence, may, and doubtless will, in the course
+of a few years, be far more extensively adopted than at present, it is
+hardly to be expected that they will be generally employed. Two causes
+operate to preclude the latter result--namely, their first cost, and
+the care and attention demanded in their employment. It seems
+tolerably certain that for a long time yet the great bulk of coal gas,
+used for lighting purposes, will be consumed through the simple
+flat-flame burners that have done so much hitherto for the furtherance
+of gas lighting. Fortunately so much has been done towards the
+perfection of this class of burners, that, for a very slight
+expenditure, results may now be obtained far in advance of what could
+formerly be produced only by the most costly and delicate apparatus.
+For ordinary situations and requirements, the improved flat-flame
+burners produced by Bray, Brönner, and Sugg, when intelligently
+employed, leave scarcely anything to be desired. _When intelligently
+employed_, I repeat, and with cautious emphasis; for the best of
+burners will be extravagant and ineffective if employed without due
+regard to the conditions for which it was made. That which is most
+needed at the present day, and which will best ensure the continued
+use of coal gas for the purposes of illumination, is the more general
+diffusion amongst gas consumers of a knowledge of the principles of
+combustion, and of the simple precautions to be taken and conditions
+to be fulfilled in the employment of gas-burners. The apparatus that
+is available is both varied and effective; what is wanted is the
+knowledge to use it aright. By contributing to the freer dissemination
+of that knowledge, purveyors of gas will confer no inconsiderable
+benefits upon their customers, and, at the same time, will assuredly
+promote their own interests.
+
+
+
+
+
+
+End of the Project Gutenberg EBook of Gas Burners, by Owen Merriman
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+<pre>
+
+The Project Gutenberg EBook of Gas Burners, by Owen Merriman
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Gas Burners
+       Old and New
+
+Author: Owen Merriman
+
+Release Date: November 5, 2011 [EBook #37928]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK GAS BURNERS ***
+
+
+
+
+Produced by Chris Curnow 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 class="ctr"><img src="images/head.jpg" alt="Gas Burners Old and New" width="500" height="216"></p>
+
+
+
+<h1>
+GAS BURNERS
+</h1>
+
+<h2>
+OLD AND NEW.
+</h2>
+
+<p class="ctr"><img src="images/historical.jpg" alt="A Historical and Descriptive Treatise
+" width="400" height="43">
+</p>
+
+<h4>
+ON THE
+</h4>
+
+<h2>
+PROGRESS OF INVENTION IN GAS LIGHTING;
+</h2>
+
+<h3>
+EMBRACING AN ACCOUNT
+</h3>
+
+<h4>
+OF THE
+</h4>
+
+<h3>
+THEORY OF LUMINOUS COMBUSTION.
+</h3>
+
+<br>
+
+<h3>
+BY
+</h3>
+
+<h2>
+"OWEN MERRIMAN."
+</h2>
+
+<br>
+<h4>
+<i>Reprinted from the</i> <span class="sc">Journal of Gas Lighting</span>.
+</h4>
+
+<br>
+<h4>
+London:<br>
+WALTER KING,<br>
+11, BOLT COURT, FLEET STREET, E. C.
+</h4>
+
+<h4>
+1884.
+</h4>
+
+<h4>
+W. KING AND SELL, PRINTERS,<br>
+12, GOUGH SQUARE, FLEET STREET,<br>
+LONDON.
+</h4>
+
+<hr class="med">
+
+
+<p class="section">
+PREFACE.
+</p>
+<p class="decoration"><img src="images/deco2.jpg" alt="Decoration" width="150" height="26"></p>
+
+<p>
+The little work here presented to the public appeared originally in
+the pages of the <i>Journal of Gas Lighting</i>. In the hope that it
+may thereby become of service to a wider circle of readers, it has
+been revised and done into its present shape. The object of the writer
+will be attained if it is the means of lessening, in any degree, the
+suspicion and prejudice (born of ignorance) which, alas! yet prevail
+with regard to gas and gas lighting.
+</p>
+
+
+<hr class="med">
+
+
+<p class="section">
+CONTENTS.
+</p>
+
+<p class="decoration"><img src="images/deco2.jpg" alt="Decoration" width="150" height="26"></p>
+
+<table summary="Contents">
+
+<tr>
+<td class="txt">&nbsp;</td>
+<td class="pg"><small>PAGE</small></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">Introduction</span></td>
+<td class="pg"><a href="#9">9</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">The First Gas-Burner</span></td>
+<td class="pg"><a href="#13">13</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">The Batswing Burner</span></td>
+<td class="pg"><a href="#15">15</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">The Union-Jet or Fishtail Burner</span></td>
+<td class="pg"><a href="#17">17</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">How Light is Produced from Coal Gas</span></td>
+<td class="pg"><a href="#20">20</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">Improvements in Flat-Flame Burners</span></td>
+<td class="pg"><a href="#25">25</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">Br&#246;nner's Burners</span></td>
+<td class="pg"><a href="#31">31</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">The Hollow-Top Burner</span></td>
+<td class="pg"><a href="#35">35</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">Bray's Burners</span></td>
+<td class="pg"><a href="#38">38</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">Argand Burners</span></td>
+<td class="pg"><a href="#44">44</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">Sugg's Argands</span></td>
+<td class="pg"><a href="#48">48</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">The Douglass Burner</span></td>
+<td class="pg"><a href="#52">52</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">Governor Burners</span></td>
+<td class="pg"><a href="#55">55</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">Regenerative Burners</span></td>
+<td class="pg"><a href="#61">61</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">Incandescent Burners</span></td>
+<td class="pg"><a href="#73">73</a></td>
+</tr>
+
+<tr>
+<td class="txt"><span class="sc">Conclusion</span></td>
+<td class="pg"><a href="#79">79</a></td>
+</tr>
+</table>
+
+<hr class="med">
+
+<a name="9">&nbsp;</a>
+<p class="chapter">CHAPTER I.
+</p>
+
+<p class="ctr">
+<img src="images/t1.jpg" alt="Introduction." width="229" height="54">
+</p>
+
+
+
+<p>
+The subject of gas-burners and the development of light from coal gas
+<span class="sidenote">
+Gas consumers and gas producers.
+</span>
+is of considerable interest, alike to the consumer and the producer of
+gas. When it is known that one burner may develop twice as much light
+as another, for the same consumption of gas&#8212;the first cost of the one
+being no higher than that of the other&#8212;its importance to the former
+will scarcely be disputed. To the gas consumer it is obviously of great
+value to know how he may most effectively and economically develop the
+illuminating power of the gas which is supplied to him; and so obtain
+the fullest return, in lighting effect, for the money which he expends.
+Not quite so obvious is its relation to the latter. To a person totally
+unacquainted with the recent history of gas lighting, and ignorant of
+the policy which has guided the most prosperous gas undertakings to
+their successful issues, it may appear that the manufacturer of gas is
+not closely concerned with the utilization of the commodity which he
+supplies. Such an one might argue, and with a certain show of reason,
+that the sole business of the gas maker is with its production; that
+after providing, in the consumer's service-pipe, a full and continuous
+supply of gas, of the stipulated quality, his care ends; and that
+henceforth the utilization and management of the illuminant rests with
+the consumer himself. But, by any one who is at all conversant with the
+subject, it will be readily conceded that the interest of the
+manufacturer of gas, in this matter, is only second to that of the
+consumer. In the gas industry, as in any other business undertaking,
+the concern prospers or declines according as the interests of the
+customers are considered or neglected. This has been conclusively
+demonstrated in the history of many gas undertakings. So long as their
+management was conducted in exclusive and selfish regard solely to
+their own internal affairs&#8212;looking with supreme indifference or
+careless apathy upon the needs of the consumers&#8212;so long was their
+career marked by difficulties and embarrassments. No sooner, however,
+were the claims of the consumers recognized, and efforts put forth to
+further their interests, than the prospects of the concern brightened;
+and by adhering to, and extending the same line of action, the goal of
+commercial prosperity was eventually reached.
+</p>
+
+<p>
+Seeing, therefore, that the subject is of so supreme importance to
+consumers of gas, and that the interests of the consumer are closely
+interwoven with those of the manufacturer, it is eminently desirable
+that there should be more generally diffused a correct knowledge of the
+principles of economical gas consumption, and of the extent to which
+these principles are applied in the various burners which, from time to
+time, have been invented. No further apology ought therefore to be
+required in presenting to the reader the following disquisition on
+gas-burners. It may, however, be of advantage for me to state in brief,
+at the commencement, what are the objects I have in view, and what the
+chief considerations which have led me to write this treatise.
+</p>
+
+
+<p>
+I purpose, then, to tell of the progress that has been made in
+apparatus for the development of light from coal gas; to relate how
+the crude and imperfect devices of the early inventors have been
+gradually improved upon; and, while not ignoring the drawbacks connected
+with recently invented burners, or the defects inherent to their
+construction, to show, in the superior achievements of these burners,
+how great an advance has been made upon the apparatus formerly in use.
+It will be, also, my endeavour to make plain the little understood
+phenomenon of the production of light by the combustion of coal gas;
+and to show the extent to which the illuminating power developed is
+dependent upon the burner employed. That there is need for such
+information as I propose to furnish must be sufficiently obvious to any
+one who has considered the waste of gas which takes place through
+<span class="sidenote"> Waste of gas.</span>
+ignorance of the laws of its combustion, and through the use of
+defective burners. In a report presented to the Board of Trade by the
+London Gas Referees in 1871, it was stated that a number of burners had
+been tested, taken from various places of business in the Metropolis;
+the major portion of which gave out only one-half, and some of them not
+more than one-fourth, of the illuminating power capable of being
+developed from the gas. Although, since the time that report was
+penned, considerable progress has been made in the construction of
+burners, and in the more general adoption of efficient burners by the
+public, much yet remains to be done. Doubtless it would still be within
+the mark to assert that fully one-fifth of the gas consumed by the
+public might be saved by the adoption of better burners, and by the
+observance of the conditions necessary for their satisfactory
+operation; and when it is borne in mind that the gas-rental of the
+United Kingdom amounts to a sum of certainly not less than &#163;9,000,000
+per annum, the saving which might be effected assumes truly great
+proportions.
+</p>
+
+<p>
+The field on which I propose to enter can hardly be said to be already
+occupied. Nowhere that I know of is the subject of gas-burners fully
+treated of in a manner available for the general reader. With the
+exception of the admirable chapter contributed by Mr. R. H. Patterson
+to "King's Treatise on Coal Gas," I am not aware that the subject has
+been dealt with to any complete extent by recent writers. But,
+admirable as is that contribution to the literature of the subject,
+being written for technical readers, it is neither so popular in style
+nor so elementary in character as to fulfil the purpose which I have in
+view in writing the present series of articles. Briefly stated, my sole
+purpose is to make the subject of the combustion of gas for the
+production of light intelligible to the simplest; and to present an
+interesting account of the progress of invention in the perfection of
+gas-burners. While passing lightly over many modifications of apparatus
+which have been of but limited or temporary service, I shall not
+scruple to dwell at length upon such burners as have done much to
+further the extension of gas lighting, or whose construction exhibits a
+considerable advance upon previous attainments. And while it will
+be my endeavour to clothe my remarks in such language as shall be
+"understanded of the people," in speaking of the theory of combustion I
+hope to be sufficiently explicit to enable my readers to form a clear
+conception of the scientific principles underlying the phenomena of
+which I treat.
+</p>
+
+
+<p>
+A further justification&#8212;if such, indeed, were needed&#8212;for the
+<span class="sidenote"> Progress of gas lighting.</span>
+appearance of this treatise might be found in the remarkable impetus
+which has been given, within recent years, to the perfection of the
+details of gas manufacture and the improvement of gas-burners. Of
+course, I refer to the beneficial consequences to the gas industry
+which have followed the brief, if conspicuous, career of electricity as
+an illuminating agent. That the interest in improved illumination which
+has been aroused by the short-lived popularity of the electric light,
+and the extravagant claims put forward on its behalf, have stimulated
+to the development of the resources of gas lighting, is sufficiently
+obvious to the most superficial observer. And not only has the
+manufacturer of gas been benefited, but the public have reaped no
+inconsiderable advantage. At the present day, gas is sold at a far
+cheaper rate, as well as of a higher quality, than at any former
+period. Nor is the advent of cheap gas the only direction in which the
+public have gained. Although not so patent to the majority, the
+improvements that have been effected in the methods of burning gas, so
+as to obtain the fullest advantage from its use, are calculated to
+confer benefits equally real, and not less valuable. It is hardly too
+much to say that the last few years have witnessed a greater advance in
+the apparatus employed in the combustion of gas than had been effected
+during the whole previous history of gas lighting. This being so, it
+may not be unacceptable if I attempt to pass in review some of the
+various burners that have been invented and used for obtaining light
+from coal gas; showing the successive improvements that are exhibited
+in their construction, and the extent to which they apply the
+principles of combustion. It may be that what I have to relate will
+awaken some minds to the consciousness that gas lighting has not
+altogether retired into obscurity on the advent of electricity&#8212;nay,
+that it has even assumed a bolder front; and, with increased resources
+and accession of strength, is prepared firmly to maintain its position
+as at once the most convenient, economical, and reliable of artificial
+illuminants.
+</p>
+
+
+
+
+<a name="13">&nbsp;</a>
+<p class="chapter">
+CHAPTER II.
+</p>
+
+<p class="ctr">
+<img src="images/t2.jpg" alt="Flat-Flame Burners." width="317" height="54">
+</p>
+
+<p class="head">
+THE FIRST GAS-BURNER.
+</p>
+
+<p>
+The first gas-burner was a very simple and unpretentious contrivance.
+In one of the earliest works on gas lighting<a href="#note1" name="noteref1">
+<small>[1]</small></a> we read: "The
+extremities of the pipes have small apertures, out of which the gas
+issues; and the streams of gas, being lighted at those apertures, burn
+with a clear and steady flame as long as the supply of gas continues."
+Familiar as it is to us, and from its familiarity unnoticed, the
+phenomenon presented by the flame thus produced continuing to burn "as
+long as the supply of gas continued," was doubtless, to the first
+experimenters, a wonderful sight. Though we may smile at the question,
+it is not difficult to understand the incredulity of the honourable
+member who, when Murdock was examined before a Committee of the House
+of Commons, in 1809, asked the witness: "Do you mean to tell us that it
+will be possible to have a light <i>without a wick</i>?" "Yes; I do
+indeed," replied Murdock. "Ah, my friend," replied the member, "you are
+trying to prove too much."
+</p>
+
+
+<p>
+It was but natural, seeing that oil-lamps and candles were the only
+<span class="sidenote"> The dawn of gas lighting.</span>
+forms of artificial illumination in use prior to the introduction of
+gas lighting, that the earliest attempts at illumination by gas should
+be in imitation of the effects produced by those means. Accordingly we
+find that one of the first gas-burners employed was the Argand,
+modelled upon the oil-lamp of that name, which had been found to give
+superior results; while in more general use, and for some time almost
+the sole apparatus available, were single jets, giving a flame similar
+in appearance to that of a common candle, together with various
+combinations of these jets. A fair idea of the mode of illumination
+practised during the earliest period of gas lighting may be gleaned
+from the following extract from a paper describing the lighting of
+Messrs. Phillips and Lee's cotton-mill at Manchester, read before the
+Royal Society, in 1808, by Mr. William Murdock:&#8212;
+</p>
+<div class="blockquote">
+<p>
+    The gas-burners are of two kinds. The one is upon the principle of
+    the Argand lamp, and resembles it in appearance; the other is a
+    small curved tube with a conical end, having three circular
+    apertures or perforations, of about 1-30th of an inch in diameter,
+    one at the point of the cone, and two lateral ones, through which
+    the gas issues, forming three divergent jets of flame, somewhat
+    like a fleur-de-lis. The shape and general appearance of this tube
+    has procured for it, among the workmen, the name of the "cockspur"
+    burner.
+</p>
+</div>
+<div class="figcenter"><img src="images/001.jpg" alt="Early Gas-Burners" width="360" height="356"></div>
+<p class="caption"><span class="sc">Fig. 1.&#8212;Early Gas-Burners.</span>
+<br>(From Accum's "Treatise on Gas-Lights.")
+</p>
+
+<p>
+Nor was much advance made upon these arrangements down to the year
+1816, judging from Accum's "Treatise" (before cited), as the subjoined
+extract from that work, together with the above illustrations, will
+show:&#8212;
+</p>
+<div class="blockquote">
+<p>
+The burners are formed in various ways&#8212;either a tube ending with
+a simple orifice, at which the gas issues in a stream, and if once
+lighted will continue to burn with the most steady and regular light
+imaginable, as long as the gas is supplied; or two concentric tubes of
+brass or sheet iron are placed at a distance of a small fraction of an
+inch from each other, and closed at the bottom. The gas which enters
+between these cylinders, when lighted, forms an Argand lamp, which is
+supplied by an internal and external current of air in the usual
+manner. Or the two concentric tubes are closed at the top with a ring,
+having small perforations, out of which the gas can issue; thus forming
+small distinct streams of light.
+</p>
+</div>
+<p>
+It is interesting, in view of the present demand for increased
+illumination, and for burners of high illuminating power, to note the
+amount of light produced by the burners then in use. In Mr. Murdock's
+paper we find it stated that each of the Argands in use at Messrs.
+Phillips and Lee's establishment gave "a light equal to that of 4
+candles (mould candles of 6 to the pound);" and each of the cockspurs
+"a light equal to 2&#188; of the same candles." From which meagre results
+we conclude that, besides being burnt in an ignorant and wasteful
+manner, the gas consumed was wofully deficient in illuminating power.
+</p>
+
+<a name="15">&nbsp;</a>
+<p class="subhead">
+THE BATSWING BURNER.
+</p>
+
+
+<p>
+<span class="sidenote"> Who invented the batswing burner?</span>
+A notable advance was made when the batswing burner was invented. To
+whom we are indebted for this invention seems involved in some doubt.
+Although Clegg, in the historical introduction to his valuable work,<a href="#note2" name="noteref2">
+<small>[2]</small></a>
+says, very distinctly, that "the batswing burner was introduced by a
+Mr. Stone, an intelligent workman employed by Mr. Winsor," it is not so
+much as mentioned by Accum, even in the third edition of his
+"Treatise;" and Accum, it may be remarked, was for some time closely
+associated with Winsor in the promotion of the latter's ambitious and
+visionary schemes. Yet, if Clegg's statement be correct, it would
+almost appear to fix the date of the introduction of this burner as
+prior to 1816. But to whomsoever is due the credit of its invention,
+certain is it that the batswing burner was a considerable improvement
+upon the old cockspur. Producing a better light for the gas consumed,
+it assisted to demonstrate still further the superiority of gas
+lighting over other methods of illumination; and as it could be
+supplied at a trifling cost, and contained no delicately adjusted nor
+easily injured parts, it enabled the benefits of the new method of
+lighting to be extended to wherever artificial light was required.
+</p>
+
+<div class="figcenter"><img src="images/002.jpg" alt="Batswing Burner" width="286" height="168"></div>
+<p class="caption"><span class="sc">Fig. 2.&#8212;Batswing Burner.</span>
+</p>
+
+
+<p>
+From the cockspur and single jet burners the gas ascended in streams,
+<span class="sidenote"> Superiority of the batswing over the cockspur burner.</span>
+rising into the air until it came in contact with sufficient oxygen to
+completely consume it. In order that this might take place without
+producing a flame of an inordinate length, and without much smoke, the
+orifices were restricted to a very small size; and the gas issuing from
+these at considerable pressure tended to draw in, and mix with the air
+in its course. Besides the loss of illuminating power caused by this
+mixture of air with the gas flame (similar to what takes place in a
+Bunsen burner), the cooling influence upon the small body of flame of
+the mass of metal composing the burner, operated still further to
+reduce the quantity of light which the gas was calculated to yield.
+With the batswing the gas was spread out producing, when ignited, a
+thin sheet of flame, by which means the gas was enabled to combine more
+readily with the air necessary to effect complete combustion. The size
+of the flame being, in comparison with that of the cockspur, so much
+larger proportionately to the metal burner, the cooling effect of the
+latter was not so apparent. The increased size of flame, also, of
+itself, tended to improve the illuminating power; each portion of flame
+contributing to elevate and sustain the temperature of the whole, and
+so to heighten the intensity of incandescence to which the light-giving
+particles were raised.
+</p>
+
+
+<p>
+Even with the Argands of that day, the batswing compared not
+unfavourably. The former burner, having the regulation of its air
+supply under complete control, gives the best results when the gas is
+<span class="sidenote"> Batswing and Argand burners compared.</span>
+supplied to it at a low pressure; as then the requisite quantity of air
+to ensure complete combustion of the gas can be delicately adjusted by
+means of a chimney of suitable length. When the gas and air have been
+nicely adjusted to each other, the flame becomes extremely sensitive to
+any change of pressure in the gas supply; a diminution of the supply,
+by reducing the quantity of gas issuing from the burner without at the
+same time proportionately diminishing the supply of air, tends to
+destroy the illuminating power by the cooling action of the surplus
+air; while an increased pressure, by allowing more gas to issue than
+the air can consume, causes the flame to smoke. But at the time to
+which I now refer the principles of combustion were little understood,
+still less applied in the construction of burners. Besides this, the
+pressure of the gas in the mains was excessive; and there being no
+method adopted of controlling it at the burner, the construction of a
+good Argand was, under the circumstances, almost impossible. The
+batswing was not so prejudicially affected by an excess of pressure.
+Pressure to some extent was, indeed, required to enable the flame to
+attain its normal shape; while any excess forced the gas through the
+flame without permitting it to be raised to incandescence before being
+consumed, and although necessitating loss of light, caused no
+inconvenience like a smoking flame. Another important advantage which
+the batswing possessed over the Argand burner was its simplicity of
+construction; and the absence of accessories, such as the glass
+chimney&#8212;dispensing with the cleaning and attention which the latter
+required. Had the benefits of gas lighting been dependent upon the use
+of apparatus so fragile, and requiring so much care and attention as
+the Argand, the range of its applicability must have been considerably
+limited, and its prospects of commercial success much less assured. The
+introduction of a series of cheap but effective burners, however,
+altered the conditions of gas lighting, and marked the commencement of
+a new era in artificial illumination. The possibility of obtaining, by
+means of a burner so simple and apparently insignificant as the
+batswing, results little, if at all, inferior to what could be obtained
+by the use of the most complicated and expensive, was of advantage
+alike to the consumer and the producer of gas. To the former it gave
+the benefits of an increased illumination, without requiring any
+corresponding outlay; to the latter it promised a growing extension of
+the use of coal gas, and thus furnished the surest guarantee of future
+progress and prosperity.
+</p>
+
+<a name="17">&nbsp;</a>
+<p class="subhead">
+THE UNION-JET, OR FISHTAIL BURNER.
+</p>
+
+
+<p>
+The batswing had been for some years in extensive use before a burner
+was produced worthy in any degree to compare with it in respect to
+simplicity and efficiency. The invention of the union-jet, or fishtail
+burner, furnished a competitor equally simple; little, if at all,
+inferior as regards efficiency; and, to some extent, superior to the
+former burner in general adaptability. Although so much behind in point
+of time, the new burner speedily rivalled the older batswing in popular
+favour; and in its various modifications and improvements may be said,
+without fear of contradiction, to have received a wider application
+than any other gas-burner. As in the case of the batswing, so with
+regard to this burner: few details are recorded of its invention. But,
+slight as is the information available, such as we have is more
+satisfactory and more authentic than the meagre notice of Clegg, which
+is all that is known of the invention of the former burner. It appears
+to be established beyond doubt that the union-jet is the joint
+<span class="sidenote"> Who invented the union-jet burner?</span>
+invention of Mr. James B. Neilson, the inventor of the hot-blast, and
+Mr. James Milne, of Glasgow, founder of the engineering firm of Milne
+and Son. About the year 1820, or soon after (as in that year Mr.
+Neilson was appointed Manager of the Glasgow Gas-Works), these
+gentlemen were experimenting with gas-burners, when they discovered
+that by allowing two jets of gas, of equal size, to impinge upon each
+other at a certain angle, a flat-flame was produced, with increased
+light. This was the origin of the union-jet; so called from the manner
+in which the flame is produced. At first separate nipples were employed
+for the two jets; but, very soon, Mr. Milne hit upon the expedient of
+drilling two holes, at the required angle, in the same nipple. In this
+manner, with slight modifications, the burner has continued to be
+constructed down to the present day.
+</p>
+
+<div class="figcenter"><img src="images/003.jpg" alt="Fishtail Burner" width="199" height="240"></div>
+<p class="caption"><span class="sc">Fig. 3.&#8212;Fishtail Burner.</span>
+</p>
+
+<p>
+The explanation of the preference accorded to this burner over its
+predecessor, the batswing, is to be found chiefly, I think, in the very
+different shapes of the respective flames produced by the two burners.
+The batswing, in its original form, produced a flame of great width,
+but of no corresponding height. The extremities of the flame,
+stretching out from the burner so far on either hand, were easily
+affected by an agitation of, or commotion in the surrounding
+atmosphere; a slight draught or current of air causing the flame to
+smoke at these points. The extreme width of flame also precluded the
+use of this burner in globes. The flame produced by the union-jet
+burner, as first constructed, was very different to the one just
+described. Longer than that of the batswing, and considerably narrower
+(but widening gradually from its base, at the burner, to its apex), it
+presented somewhat nearly the appearance of an isosceles triangle; or
+more closely, perhaps (with its slightly-forked apex), the tail of a
+fish, from which resemblance it is commonly designated the fishtail
+burner. This form of flame was better adapted for use in globes, and
+also better withstood the effects of draughts. And it is perhaps not
+unreasonable to suppose that as in shape it approached more closely to
+the kind of flame with which the people had been familiar in oil lamps,
+the flame produced by the union-jet burner was more agreeable to the
+eye than that of the batswing, and that this seemingly trivial
+consideration will account, to some extent at least, for the undue
+favour shown towards it. For it must not be assumed, because of the
+widespread popularity to which the union-jet so early attained, and
+which it has continued to enjoy, that it was of necessity a better
+burner (in the sense of developing more light for the gas consumed)
+than the one which preceded it. On the contrary, in this regard it was
+not quite so effective as the batswing. Nor is this result surprising,
+looking at the different methods adopted in the two burners for
+producing the same effects of light and flame.
+</p>
+
+
+<p>
+From the batswing burner the gas issued in a thin but widely-extending
+stream, presenting, when ignited, a continuous sheet of flame; its
+height and width depending upon the pressure at which the gas was
+supplied, but always offering an unbroken surface of flame to the air.
+Although, from the excessive pressures which, in the early days of gas
+lighting, were generally employed, the flame drew upon its surface too
+much air for the attainment of the fullest lighting efficiency
+obtainable from the gas; yet the form given to the issuing stream of
+<span class="sidenote"> Union-jet and batswing burners compared.</span>
+gas precluded the air from entering the interior of the flame, and
+still further reducing its illuminating power. With the union-jet
+burner the conditions were greatly changed; and this latter evil, of
+the introduction of cold air into the interior of the flame, was one of
+the consequences entailed by the means it employed for producing its
+flame. From this burner the gas issued in two narrow streams, like
+single jets, which, directly after emerging from the burner, impinged
+upon each other at a given angle; the mutual shock given to the streams
+of gas when thus arrested causing them to spread out in a lateral
+direction, and (the high velocity at which the gas issued being
+expended) to unite, and ascend in a sluggish stream until consumed.
+That injury to the illuminating power of the flame should result from
+causes connected with the manner of producing it will be understood on
+considering some of the phenomena associated with the production of a
+gas flame.
+</p>
+
+
+<p>
+When a jet or stream of gas issues into a still atmosphere, it produces
+in its immediate neighbourhood, on all sides, an area of low pressure,
+to occupy which the contiguous air rushes in. Induced air currents are
+thus set up in close proximity to, and having the same direction as the
+issuing stream of gas, and varying in force with the pressure, or
+velocity, at which the gas issues. The non-luminous flame of the Bunsen
+burner, and of the so-called "atmospheric" burner employed in gas
+<span class="sidenote"> How air is drawn upon a gas flame.</span>
+cooking and heating stoves (which is produced by burning a mixture of
+gas and air), is obtained by taking advantage of this tendency of a
+stream of gas, issuing under pressure, to draw air upon itself; and it
+is to the same circumstance that ordinary illuminating flames owe the
+continuous supply of air necessary to keep up combustion. For the
+effect is heightened when the gas is inflamed; because, the gaseous
+products of combustion being expanded by the intense heat to which they
+are subjected, their velocity of ascension is vastly increased. Having
+regard to these considerations, it will be clearly perceived how that,
+in producing the flame of the union-jet burner, the two streams of gas,
+in the act of combining together, drew into the very midst of the flame
+a portion of the air with which they were surrounded; and this air,
+reducing the temperature of the flame, and diluting the illuminating
+gas by the inert nitrogen introduced, as well as by its oxygen causing
+a too early oxidation of the carbon particles in the flame, operated to
+reduce the illuminating power otherwise obtainable from the gas.
+</p>
+
+<p>
+The foregoing remarks, it must be borne in mind, refer to the union-jet
+burner in its original form. Numerous improvements have been effected,
+from time to time, in its construction, as well as in that of the
+batswing, which, by reducing its liability thus to convey air into the
+flame, have increased its efficiency; while, at the same time, the
+shape of the flame has been improved. Indeed, the result of successive
+improvements in the construction of both burners has been so to modify
+the shape of their respective flames that, in their latest and most
+improved form, the flames produced by the two burners are practically
+identical in appearance, although the manner of their production
+remains as widely diverse as at the first. The improvements that led up
+to, and the causes that produced this result, will be more fully
+explained in the sequel.
+</p>
+
+<a name="20">&nbsp;</a>
+<p class="subhead">
+HOW LIGHT IS PRODUCED FROM COAL GAS.
+</p>
+
+<p>
+I have before remarked that, in the early period of its use, one of the
+chief obstacles to the development of the lighting power of coal gas
+was the excessive pressure at which it was generally supplied. To
+understand the action of pressure in influencing the amount of light
+which a given quantity of gas will afford, it is necessary to know
+something of the nature and properties of flame. Moreover, the
+conditions upon which is dependent the illuminating power of a gas
+flame are so intimately related to each other, that the precise
+functions due to each cannot well be separated from the complete effect
+produced by the combined operation of all. I shall not, therefore, be
+needlessly digressing from my subject if, at this juncture, I explain
+the manner in which combustion takes place in the flame of an ordinary
+gas-burner. In doing this, I shall endeavour to clothe my remarks in
+very plain language; using no more technicalities than are absolutely
+required by the exigencies of the subject. In this way I hope to make
+my meaning clear to the simplest. At the same time, without pretending
+to be scientifically complete, the explanation of the phenomena of
+combustion which I shall furnish will, I trust, be sufficiently
+explicit to enable the reader to form a right estimate of the
+principles which regulate the production of light when coal gas is
+consumed. The end chiefly kept in view is to show clearly the extent to
+which the degree of light evolved is dependent upon the burner
+employed, and the manner in which the gas is consumed. If my remarks
+are the means of causing the reader to look with intelligent interest
+upon the familiar phenomena of gaslight, they will not have been
+written altogether in vain.
+</p>
+
+
+<p>
+Seeing that this treatise is compiled especially for those whose
+knowledge as to what coal gas consists of is extremely limited, it may
+be of advantage to preface my observations on its combustion, and the
+production of light therefrom, by a few remarks as to its composition.
+<span class="sidenote"> What is coal gas?</span>
+Coal gas, as generally supplied, is made up of a variety of distinct
+gases; of which, however, only some three or four exist in any
+considerable proportion. About 50 per cent., by volume (or half of the
+whole), is hydrogen; from 30 to 40 per cent. consists of marsh gas;
+while carbonic oxide is usually present to the extent of from 5 to 15
+per cent. These three gases, which constitute the great bulk of what is
+known as common gas&#8212;that is, gas made from ordinary bituminous coal,
+as distinguished from that produced from the more costly cannel&#8212;are of
+little or no value as regards the amount of light they are capable of
+affording. The flames produced by the burning of the two former gases
+evolve much heat, but are of very feeble illuminating power. The latter
+gives a flame of a deep blue colour, producing scarcely any light, but,
+like the other two, an intense heat. The power of coal gas to yield a
+luminous flame is dependent upon the small quantity of heavy
+hydrocarbons which it contains&#8212;a constituent, or series of
+constituents, of which common gas only contains a proportion varying
+between 3 and 7 per cent., although in cannel gas it reaches as high as
+15 or 20 per cent. These heavy hydrocarbons are gases composed, like
+marsh gas, of carbon and hydrogen; but containing in their composition,
+for each unit of volume, a greater aggregate of the two elements, as
+well as a relatively higher proportion of carbon, than exists in marsh
+gas. One of the simplest members of the series, and that which is
+usually present in by far the largest amount, is called olefiant gas.
+It contains twice as much carbon, combined with only the same quantity
+of hydrogen, as is contained in marsh gas. But besides olefiant gas
+there are minute quantities of other gases of the same series, having
+an analogous composition, but differing in the amount and relative
+proportions they contain of the two elements of which they are
+composed. All the gases of this series, when properly burnt, are
+capable of affording a brightly luminous flame; but when consumed alone
+it is somewhat difficult, on account of the high proportion of carbon
+which they contain, to effect their combustion without the production
+of smoke. It is, then, to the heavy hydrocarbons which are part of
+it&#8212;insignificant as their amount may appear&#8212;that the luminosity of a
+gas flame is solely due. The other constituents which I have mentioned
+as forming so much larger a proportion of the whole, besides
+contributing to the heat of the flame, serve only to dilute these
+richer gases, and so promote their more complete combustion.
+</p>
+
+
+<p>
+The various simple gases which constitute ordinary coal gas do not all
+burn together in the flame; the temperature required to effect their
+ignition being lower for some of them than for others. Thus, hydrogen
+is the first to burn, taking fire readily as soon as it issues from the
+burner; while the combustion of the heavy hydrocarbons does not
+commence until they enter the hotter portions of the flame, and is not
+completed until they reach its farthest extremity. Neither is the
+process of combustion in both cases the same. The former gas is at once
+<span class="sidenote"> How gas burns.</span>
+completely consumed; the latter first undergo decomposition by the heat
+of the flame, being resolved into their elements&#8212;hydrogen and
+carbon&#8212;before being fully consumed. This decomposition of the
+hydrocarbons is a factor of supreme importance in the development of
+the lighting power of the flame. The hydrogen they contain, being more
+easily ignited than the carbon, burns first; and the latter is set
+free, in the solid form, as minute particles of soot. These particles
+of solid carbon, being liberated in the midst of the flame, are
+immediately subjected to its most intense heat; they thus become
+white-hot before they reach the outer verge of the flame, and come in
+contact with sufficient oxygen to effect their complete combustion.
+The amount of light developed by any coal-gas flame is directly
+proportional to the degree of intensity to which the temperature of
+these carbon particles is raised, and the length of time they remain
+in the flame before being finally consumed. It becomes, therefore, a
+matter of considerable importance to know the conditions which are
+most conducive to the early liberation in the flame of free carbon,
+and the attainment by it of an exalted temperature.
+</p>
+
+
+<p>
+Looking at the flame (say) of a common slit burner, it is seen to be
+divided into two sharply defined and wholly distinct portions. First,
+there is&#8212;immediately surrounding the burner head, and extending to
+some distance from it&#8212;a dark, transparent area, which, on closer
+examination, is found to consist of unignited gas enclosed in a thin
+envelope of bright blue flame. Second, there is (beyond this central
+area) a zone, or belt, of brightly luminous flame, white and opaque;
+the latter property indicating the presence of solid matter at this
+<span class="sidenote"> What is a gas flame?</span>
+part of the flame. That the dark central portion of the flame consists
+chiefly of unignited gas may be shown in various ways, in addition to
+the evidence afforded by its complete transparency. Thus, if a small
+glass tube be taken, and its lower end inserted in the flame at this
+point, the unburnt gas will pass up the tube, and may be lighted at its
+upper extremity. A splinter of wood thrust through this portion of the
+flame is charred first at the two edges of the flame; while, in like
+manner, a piece of platinum foil remains dull in the centre of the
+flame, and glows only at the points of contact with the outer air. The
+presence of solid carbon in the luminous portion of the flame may be
+shown by inserting therein any cold substance (such as a piece of metal
+or porcelain), which, reducing the temperature of the heated particles
+of carbon below the point at which they are consumed, becomes instantly
+coated on its under surface with a deposit of soot. Or, if the flame be
+suddenly cooled by gently blowing upon its surface, the same result is
+brought about; clouds of soot are given off, and the flame "smokes."<a href="#note3" name="noteref3">
+<small>[3]</small></a>
+</p>
+
+<div class="figcenter"><img src="images/004.jpg" alt="Showing the Two Zones of the Flame, and
+  the Method of Demonstrating the Presence of Unburnt Gas in the
+  Flame" width="485" height="320"></div>
+<p class="caption"><span class="sc">Fig. 4.&#8212;Showing the Two Zones
+of the Flame, and the Method of Demonstrating the Presence of Unburnt
+Gas in the Flame.</span>
+</p>
+
+
+<p>
+The existence, in the midst of the flame, of an area of unconsumed gas
+is due to the cold gas, as it issues from the burner, cooling the
+interior of the flame below the temperature required for its ignition,
+as well as to its not at once meeting with sufficient air for complete
+combustion. The causes which affect the luminous zone of the flame are
+not so readily explained. It has been stated that the luminosity of the
+flame is due to the particles of carbon, which are separated out of the
+hydrocarbons in the gas, being raised to a white heat. To decompose the
+hydrocarbons, a very high temperature is required; and, on account of
+the cooling effect of the stream of cold gas, this is not attained
+except at some distance from the burner. The abstraction of heat by the
+burner itself is also a cause of the reduction of the temperature of
+<span class="sidenote"> How the flame is cooled.</span>
+the flame; and, on this account, burners of porcelain, steatite, or
+similar composition, being bad conductors of heat, have an advantage
+over those made of metal. So considerable is the cooling influence of
+the gas stream, that, within certain limits, the distance, from the
+burner head, at which the luminosity of a flame commences, is
+proportionate to the velocity with which the gas issues; or, in other
+words, the pressure at which it is delivered from the burner. The
+effect is heightened by the tendency (which has been before remarked)
+of a stream of gas, issuing under pressure, to draw upon itself and mix
+with the surrounding air. Thus, with each increment of pressure the
+luminous zone of the flame is farther removed, until a point is reached
+at which the gas is so mixed with air before being consumed that the
+luminosity of the flame is completely destroyed.
+</p>
+
+
+<p>
+But it must not be assumed, because of the foregoing remarks, that the
+pressure at which the gas issues from the burner is altogether an
+unmixed evil. In flat-flame burners it fulfils the important function
+of promoting intensity of combustion, by bringing the white-hot
+particles of carbon into intimate and rapid contact with the air that
+is necessary for complete combustion. In Argand burners this duty is
+discharged by the glass chimney; but with flat-flame burners it
+devolves entirely upon the pressure at which the gas issues from the
+<span class="sidenote"> Effects of pressure in the gas supply.</span>
+burner. It will be seen, therefore, that the pressure of the gas is a
+factor of considerable importance in determining the amount of light
+afforded by a gas flame, as it is a matter requiring careful adjustment
+with each and every burner. On the one hand, with an excessive pressure
+the intensity of combustion is increased; but the separated carbon does
+not remain so long in the flame. The area of luminosity is thereby
+decreased, and the total light yielded is reduced. On the other hand,
+with insufficient pressure the combustion is not energetic enough to
+raise the particles of carbon to a white heat; consequently, the
+illuminating power of the flame is feeble, or else the carbon escapes
+unconsumed as smoke.
+</p>
+
+<p>
+The thickness of the flame produced by any burner has also an important
+bearing upon the degree of light afforded; and this property of
+thickness, again, is dependent upon the width of slit, in the case of
+batswings (or, in the case of union-jets, upon the size of orifices),
+and the pressure at which the gas is supplied. The thickness of the
+flame yielded by any burner will obviously vary inversely with the
+pressure at which the gas is supplied to it. With a thin flame, all
+parts of the flame are so completely exposed to the air, that the
+particles of carbon are no sooner raised to the temperature required to
+enable them to give out light than they are entirely consumed. With a
+thicker flame the carbon separated in the midst of the flame exists for
+a sensibly longer period of time in the white-hot state before it
+reaches the outside of the flame, and meets with sufficient oxygen for
+its complete combustion. Thus we find that the best flat-flame burners
+have comparatively wide orifices; while the pressure at which the gas
+is delivered from the burner is carefully reduced to the lowest point
+at which a firm flame is obtained, without smoke. Similarly, in the
+best Argands the pressure is considerably diminished within the burner,
+and the gas allowed to issue gently through relatively large holes;
+while the chimney is carefully adapted to draw upon the surface of the
+flame just sufficient air to completely consume the quantity of gas
+which the burner is calculated to deliver.
+</p>
+
+<a name="25">&nbsp;</a>
+<p class="subhead">
+IMPROVEMENTS IN FLAT-FLAME BURNERS.
+</p>
+
+<p>
+Although, there is no doubt, they were made empirically, and in
+ignorance of the real effects of pressure upon the flame, the first
+steps towards increasing the efficiency of flat-flame burners were in
+the right direction of reducing the excessive pressure at which the gas
+was formerly allowed to burn. They consisted in the adoption of simple
+arrangements for obstructing the passage of the gas through the burner,
+and so retarding its flow. The crudeness of the means which were
+employed is sufficient evidence that the end aimed at was, at best, but
+dimly discerned. The body of the burner was stuffed with wool, or
+pieces of wire gauze; which impeded the progress of the gas; reduced
+the quantity that would otherwise have been consumed; and,
+consequently, diminished the velocity with which it issued from the
+burner. Unfortunately, owing to the imperfect methods in use at that
+day for condensing and purifying the gas, the burners so constructed
+became choked with the tarry matters held in suspension, and carried
+forward by the gas; and so, after a comparatively short period of
+service, were rendered entirely inoperative. But, altogether apart from
+the inconvenience and loss thus entailed (which, when improved modes of
+manufacture had removed the cause, ceased to be experienced), the
+arrangement was ill adapted for the purpose which it was designed to
+serve. The rough and uneven nature of the material employed to stuff
+the burner caused the gas to eddy and swirl as it issued into the
+atmosphere, and prevented it being supplied equally to all parts of the
+flame. The consequence was that the advantages which ought to have been
+derived from the diminished pressure were neutralized by the unsteady
+flow acquired by the stream of gas; and the illuminating power
+developed by the flame was little improvement upon what could
+previously be obtained by the manipulation of the tap controlling the
+supply of gas to the burner. Besides which, from its unevenness, the
+appearance of the flame was not so satisfactory. It was not until the
+principles which regulate the production of light from coal gas came to
+be known and observed in the construction of burners, that a
+modification of the old idea was arrived at, which enabled the benefits
+of a reduced pressure to be obtained without any of the attendant evils
+hitherto experienced.
+</p>
+
+
+<p>
+<span class="sidenote"> The first real improvement of the union-jet burner.</span>
+A modification in the construction of the union-jet which, though
+slight, was nevertheless a real improvement, appears to have been made
+at an early period in the history of this burner. Instead of having the
+top of the burner perfectly flat, it was made slightly concave; more
+especially at its centre, where the two jets of gas emerge. The effect
+of this alteration was to enable the stream of gas to spread out
+better; and thus to cause the flame to become broader at its base. The
+shape of the flame was thereby improved; and (what is of more
+consequence) its illuminating power increased, because air was not
+drawn so readily into the midst of the flame. The value of the
+arrangement is shown by the fact that it has been retained ever since,
+and is made use of in the latest and most improved burners of this
+class.
+</p>
+
+<p>
+Prior to 1860, numerous novel contrivances were introduced as
+"improved" burners; but all were not equally valuable with the simple
+arrangement just described. The construction of many of them, indeed,
+betrayed a lamentable ignorance of the first principles of gas
+combustion. For instance, one is described as "a fishtail with four
+converging holes; and there is an aperture in the centre of the burner
+for the admission of atmospheric air into the flame!" Another was a
+batswing with two or more slits, producing a series of flames
+amalgamated into one; by which means it was supposed that an improved
+duty was obtained from the gas&#8212;unmindful, or, more probably, in
+ignorance of the fact that the same quantity of gas, properly consumed
+through one slit, would yield a better light.
+</p>
+
+
+<p>
+<span class="sidenote"> The double-flame burner.</span>
+A burner which, at different times, and under various names, has been
+brought repeatedly into notice is the double-flame; consisting of two
+batswing or union-jet burners set at an angle to each other, so that
+their flames converge, and merge into one. When two gas flames are made
+to coalesce in this manner, a greater amount of light is developed than
+the sum of that yielded by the separate flames; provided that, in the
+combined flame, the gas is properly consumed, without smoke. The reason
+for this increase is twofold. First, the increased quantity of gas
+burnt in one flame enables a higher average temperature to be
+maintained; and, in addition, a smaller surface of flame is exposed to
+the cooling action of the atmosphere than when the same quantity of gas
+is consumed in two flames. Second, the pressure at which the gas burns
+is diminished, because the initial velocity with which the streams of
+gas issue from the two burners is expended in impinging against each
+other, and a thicker flame results; the apparatus being, as far as its
+effect is concerned, a union-jet burner on a large scale. The increase
+of light so obtained appears to have been noticed at an early period;
+as a burner embodying the same principle is described and figured in
+"Clegg's Treatise," published in 1848. In Clegg's burner the gas issued
+from two perforated parallel plates inclined to each other; but at a
+more recent period two fishtail burners were employed, being mounted on
+separate tubes which branched out to a short distance from each other.
+Occasionally, for experimental and show purposes, it has been
+constructed with the two branches hinged together, so as to show the
+different effects produced when the two burners are used separately and
+in combination. At the present day it is made, by various makers, as
+one burner with two nipples, as shown in the annexed illustration;
+which doubtless is its most perfect form.
+</p>
+
+<div class="figcenter"><img src="images/005.jpg" alt="Duplex Burner" width="215" height="320"></div>
+<p class="caption"><span class="sc">Fig. 5.&#8212;Duplex Burner.</span>
+</p>
+
+<p>
+The advantages of the double flame are not so obvious under the
+conditions which obtain at the present day as at the period when it was
+first introduced. The increase of light it affords is most apparent
+when the gas is being consumed at an excessive pressure. Although, in
+general, it may be taken that any two flames, when combined, will
+develop a higher duty, per cubic foot of gas consumed, than separately;
+yet it would appear that this is not so in every case. When the gas is
+being consumed at the critical pressure which gives the best results,
+the flames are so near the smoking point that the slight diminution of
+pressure experienced when the streams of gas impinge upon each other is
+sufficient to cause the combined flame to smoke. Moreover, to such a
+stage of perfection have the ordinary flat-flame burners now been
+brought, that, for all ordinary consumptions, it may be safely affirmed
+that equal, if not superior results can be obtained with a single as
+with a double flame. Where, however, larger quantities of gas are
+required to be dealt with than can be effectively consumed in a single
+burner, the principle of combining two or more burners together, so
+that their flames shall mutually assist each other, may be
+advantageously employed; as is seen in the combination of flat-flame
+burners in the large lamps now employed in improved street lighting.
+</p>
+
+<div class="figcenter"><img src="images/006.jpg" alt="Scholl's Platinum Light Perfecter" width="328" height="303"></div>
+<p class="caption"><span class="sc">Fig. 6.&#8212;Scholl's Platinum Light Perfecter.</span>
+</p>
+
+
+<p>
+<span class="sidenote"> Scholl's "Platinum Light Perfecter."</span>
+An ingenious device for improving the efficiency of union-jet burners
+was brought out some twenty years ago by a Mr. Scholl, of London, and
+known as Scholl's "Platinum Light Perfecter," which is shown in the
+accompanying illustration. It consisted of a little brass ring,
+carrying a plate of platinum about 0&#183;4 inch long by 0&#183;15 inch wide. The
+ring fitted on to the top of the burner in such a manner that the
+platinum plate was held, in a vertical position, between the two
+orifices from which the gas emerged. The jets of gas, instead of
+impinging upon each other, impinged against the plate, and united above
+to form the flame. By the interposition of the metal plate, the
+velocity of the gas was much reduced; and a thicker and more sluggish
+flame was produced, with the result of increasing its illuminating
+power. When the apparatus was used upon a burner having very small
+orifices, and delivering its gas at a high pressure, the increase of
+light obtained was very striking; but with lower pressures the
+advantage derived from its use was correspondingly diminished. This is
+very clearly shown by the following table, which is extracted from a
+report, by Captain Webber and Mr. Rowden, on experiments upon
+gas-burners, carried out at the Paris Universal Exhibition, 1867.<a href="#note4" name="noteref4">
+<small>[4]</small></a>
+</p>
+
+<table summary="Kind of Burner">
+<tr>
+<td class="cbtbbbl" colspan="3">&nbsp;</td>
+<td class="cbtbbbl" colspan="2">Illuminating Power.</td>
+<td class="cbtbbbr">&nbsp;</td>
+</tr>
+
+<tr>
+<td class="cbbbl">Kind of Burner.</td>
+<td class="cbbbl">Cubic Feet<br>of Gas<br>per Hour.</td>
+<td class="cbbbl">Pressure<br>in<br>Inches.</td>
+<td class="cbbbl">Without<br>Perfecter.</td>
+<td class="cbbbl">With<br>Perfecter.</td>
+<td class="chead2">Increase<br>per<br>Cent.</td>
+</tr>
+
+<tr>
+<td class="bbbl">Leoni's fishtail, No. 2</td>
+<td class="cbbbl">3</td>
+<td class="cbbbl">0&#183;84</td>
+<td class="cbbbl">1&#183;3</td>
+<td class="rbbbl">4&#183;1</td>
+<td class="rbbblbr">215</td>
+</tr>
+
+<tr>
+<td class="bbbl" rowspan="2">Leoni's fishtail, No. 3</td>
+<td class="cbl">3</td>
+<td class="cbl">0&#183;46</td>
+<td class="cbl">2&#183;4</td>
+<td class="rbl">4&#183;6</td>
+<td class="rblbr">91</td>
+</tr>
+
+<tr>
+<td class="cbbbl">4</td>
+<td class="cbbbl">0&#183;70</td>
+<td class="cbbbl">2&#183;8</td>
+<td class="rbbbl">6&#183;5</td>
+<td class="rbbblbr">132</td>
+</tr>
+
+
+<tr>
+<td class="bbbl" rowspan="2">Leoni's fishtail, No. 4</td>
+<td class="cbl">4</td>
+<td class="cbl">0&#183;47</td>
+<td class="cbl">4&#183;5</td>
+<td class="rbl">7&#183;6</td>
+<td class="rblbr">68</td>
+</tr>
+
+<tr>
+<td class="cbbbl">5</td>
+<td class="cbbbl">0&#183;71</td>
+<td class="cbbbl">5&#183;0</td>
+<td class="rbbbl">9&#183;2</td>
+<td class="rbbblbr">84</td>
+</tr>
+
+<tr>
+<td class="bbbl" rowspan="3">Leoni's fishtail, No. 5</td>
+<td class="cbl">4</td>
+<td class="cbl">0&#183;42</td>
+<td class="cbl">5&#183;3</td>
+<td class="rbl">6&#183;9</td>
+<td class="rblbr">30</td>
+</tr>
+
+<tr>
+<td class="cbl">5</td>
+<td class="cbl">0&#183;60</td>
+<td class="cbl">6&#183;1</td>
+<td class="rbl">8&#183;3</td>
+<td class="rblbr">36</td>
+</tr>
+
+<tr>
+<td class="cbbbl">6</td>
+<td class="cbbbl">0&#183;81</td>
+<td class="cbbbl">7&#183;1</td>
+<td class="rbbbl">10&#183;0</td>
+<td class="rbbblbr">40<a href="#note5" name="noteref5"><small>[5]</small></a></td>
+</tr>
+
+<tr>
+<td class="bbbl" rowspan="2">Leoni's fishtail, No. 6</td>
+<td class="cbl">4</td>
+<td class="cbl">0&#183;31</td>
+<td class="cbl">6&#183;2</td>
+<td class="rbl">8&#183;0</td>
+<td class="rblbr">29<a href="#note6" name="noteref6"><small>[6]</small></a></td>
+</tr>
+
+<tr>
+<td class="cbbbl">5</td>
+<td class="cbbbl">0&#183;46</td>
+<td class="cbbbl">8&#183;0</td>
+<td class="rbbbl">10&#183;4</td>
+<td class="rbbblbr">30<a href="#note7" name="noteref7"><small>[7]</small></a></td>
+</tr>
+
+</table>
+
+<p>
+Burners were also made with the metal plate forming part of the burner
+head; and, instead of being of platinum, it was sometimes formed of
+thin steel, or other commoner metal. Where platinum was used, some
+advantage probably accrued from its becoming incandescent; but, of
+course, any benefit arising from this source was not obtained when
+steel was employed. The remarks which have been made respecting the
+limited applicability of the double-flame burner will apply, with equal
+force, to the apparatus under notice. Although it effected an undoubted
+improvement when applied to burners ill adapted to the pressure at
+which the gas was supplied, equally good results could be obtained
+without its aid, when a burner was employed suited to the quality and
+pressure of the gas supplied.
+</p>
+
+
+<p>
+<span class="sidenote"> Leoni's flat-flame burners.</span>
+Perhaps the most efficient flat-flame burners available prior to 1867
+were those made by Mr. S. Leoni, of London. One of these is shown in
+fig. 7. This maker produced both batswing and union-jets; various sizes
+being made of each burner. Besides affording fairly good results from
+the gas consumed, the burners were supplied at a very moderate price.
+Their distinguishing feature was the peculiar substance of which the
+burner-tips were formed. This was a material invented by Mr. Leoni, and
+named by him "adamas." (The precise composition of "adamas" is a trade
+secret; but it appears to consist of a mixture of various minerals or
+earths, moulded in a clayey or plastic condition, and then burnt.)
+Previous to his invention, the tip of the burner, or the burner head,
+had been made, almost exclusively, of iron or brass. There were,
+however, some grave defects inherent in the use of metal for this
+purpose. The orifices of union-jets and the slits of batswings in
+course of time became much obstructed by the corrosion of the metal;
+and the efforts made to remove the obstruction only served to destroy
+the burner more quickly, by increasing the size and injuring the
+precise shape of the apertures. The "adamas" tips, on the other hand,
+perfectly withstood the high temperature to which they were exposed,
+were quite incorrodible, and were sufficiently hard to endure a
+considerable degree of even rough usage. By constructing the tip of
+this material, the efficiency of the burner was improved in many ways.
+The liability of the burner to corrosion being removed, and the
+inconvenience due to this cause done away with, the life of the burner
+was prolonged, and the expense of renewal consequently reduced. But, in
+addition to these advantages, there was yet another direction in which
+the "adamas" tip contributed to enhance the utility of the burner. This
+was in maintaining a higher temperature of the flame; and arose from
+its inferior capacity, compared with metal, for conducting heat from
+the flame. That the advantage derived from this source, although
+unimportant, was not altogether imaginary, will be apparent when it is
+mentioned that metal burners, when in operation, usually attain to a
+temperature of from 400&#176; to 500&#176; Fahr.&#8212;an indication of the amount of
+heat being continuously abstracted from the flame. The adoption of a
+non-conducting material for the burner-tip, while it did not entirely
+prevent, considerably reduced the loss of heat.
+</p>
+
+<div class="figcenter"><img src="images/007.jpg" alt="Leoni's Flat-Flame Burner" width="255" height="320"></div>
+<p class="caption"><span class="sc">Fig. 7.&#8212;Leoni's Flat-Flame Burner.</span>
+</p>
+
+<p>
+Two varieties of each class of burner were made by Mr. Leoni. In the
+one burner, the "adamas" tip was inserted into an iron stem; in the
+other, the tip was inserted in a brass body, which fitted on to the
+iron stem. Between the brass body and the iron stem of the latter
+burner there was affixed a layer of wool, designed to check the
+pressure at which the gas was supplied. Owing, very probably, to the
+unsuitability of the material (wool) used for this purpose, the result
+was not satisfactory; as, according to the statements of Messrs. Webber
+and Rowden, in the report previously cited, no difference could be
+detected, in many experiments, between the results yielded by the
+burner with or without the layer of wool. Some light is shed upon this
+apparent anomaly by certain experiments made by the writer to determine
+the pressure at which gas issues from various burners. With one of
+Leoni's No. 4 union-jets, under an initial pressure of 1 inch (the
+pressure at the inlet when the burner is in operation), the pressure at
+the outlet of the burner, when the layer of wool was employed, was 0&#183;11
+inch; but from the same burner, when the layer of wool was removed, the
+gas issued at a pressure of only 0&#183;07 inch. Thus the effect of
+inserting the layer of wool in the burner was exactly the opposite of
+that which it was intended to produce; the pressure of the issuing gas
+stream being increased instead of diminished.
+</p>
+
+<a name="31">&nbsp;</a>
+<p class="subhead">
+BR&#214;NNER'S BURNERS.
+</p>
+
+<p>
+The credit of having produced the first flat-flame burners designed
+upon scientifically correct principles belongs undoubtedly to Herr
+Julius Br&#246;nner, of Frankfort-on-the-Maine. Long before the date of his
+invention, efforts had been made to reduce the pressure of the gas
+within the burner. But these endeavours were carried out in so
+hap-hazard a fashion as to lead to the belief that no definite
+conception was entertained as to what was really required. As we have
+seen, layers of wool had been employed; but the area of the
+interstices, or the gas-way through the material, was a matter of the
+merest accident. And there was not the slightest guarantee that the
+same conditions should prevail in any two burners. Herr Br&#246;nner
+shrewdly detected the cause of former failures, as he clearly perceived
+the end which it was requisite to attain, and towards which previous
+inventors had been but blindly groping. Having formed a right estimate
+of the requirements to be fulfilled, and the difficulties to be
+surmounted, he set about accomplishing the desired result by other
+means. There were two causes which had chiefly contributed to the
+unsuccessful issues of previous attempts. One was the uncertain and
+indefinite operation of the means employed for diminishing the
+pressure; the other was the inadequate provision for enabling the gas
+to lose the current, or swirl, acquired in passing the diminishing
+arrangement, and come to a state of comparative rest before issuing
+into the atmosphere. Both these errors were successfully avoided in
+Br&#246;nner's invention&#8212;the former by making the inlet to the burner of
+restricted and definite dimensions, and of less area than the outlet,
+or slit; the latter by enlarging the chamber, or place of expansion
+within the burner, as well as by the different arrangement adopted for
+diminishing the pressure.
+</p>
+
+<div class="figcenter"><img src="images/008.jpg" alt="Br&#246;nner's Burners" width="245" height="336"></div>
+<p class="caption"><span class="sc">A Top.</span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="sc">B Top.</span>
+<br><span class="sc">Fig. 8.&#8212;Br&#246;nner's Burners.</span>
+</p>
+
+
+<p>
+The general appearance of Br&#246;nner's burner is pear-shaped; and in size
+it is considerably larger than an ordinary burner designed to pass an
+equal quantity of gas. It consists of a cylindrical brass body
+surmounted by a steatite top, and tapering to a very small diameter at
+<span class="sidenote"> Construction of Br&#246;nner's burners.</span>
+its lower end, or inlet; the latter being closed by a plug of steatite,
+in which is a rectangular slot, or aperture, of accurately defined
+dimensions. The size of this aperture determines the quantity of gas
+which, at any particular pressure, is admitted to the burner; and the
+slit, or outlet of the burner, being of greater area than the inlet,
+ensures the gas being delivered from the burner at a lower pressure
+than that at which it enters it. By varying the respective dimensions
+of these two openings, and their relation to each other, the burner may
+be regulated to deliver its gas at any required pressure short of the
+initial pressure at the entrance to the burner. The enlargement of the
+cylindrical body provides an expansion chamber, wherein the velocity of
+the stream of gas which rushes through the narrow opening at the inlet
+of the burner is checked, and any agitation or unsteadiness which may
+have been imparted to it is subdued before the gas issues into the
+atmosphere and is consumed. There are two kinds of tops for the
+burners, which are distinguished by the letters A and B. The B top is
+of the ordinary semi-spherical type, giving a true batswing-shaped
+flame; the A top is flatter, almost square in form, and yields a flame
+taller than, but not so broad as the former. In consequence of this
+difference in the shape of its flame, the latter burner is better
+adapted for use in globes. The general appearance of the burners, and
+their distinguishing peculiarities, will be clearly understood from the
+illustrations.
+</p>
+
+
+<p>
+<span class="sidenote"> Properties of steatite.</span>
+The material of which the more important parts of the burner are
+constructed is eminently adapted for the purpose. Steatite is a mineral
+which, as found in nature, is so soft as to be readily turned in a
+lathe, and shaped to any design; but when heated up to about 2000&#176;
+Fahr. it becomes almost as hard and durable as flint, while perfectly
+retaining its form and colour. These properties peculiarly qualify it
+for receiving a slit or orifice, which, though of minute proportions,
+must be accurately formed to precise dimensions. Besides which, like
+"adamas," its capacity for conducting heat away from the flame is so
+limited that, in this respect, it has a considerable advantage over
+metal for the purpose of being formed into gas-burners.
+</p>
+
+
+<p>
+The following tables, which are extracted from the report of the
+Committee of the British Association appointed to investigate the means
+for the development of light from coal gas of different qualities,<a href="#note8" name="noteref8">
+<small>[8]</small></a>
+exhibit the very satisfactory results obtained by the use of these
+burners. In Table I., the gas operated upon was cannel gas (such as is
+generally supplied in Scotland), and possessed an illuminating power,
+when employed in the standard burner, of 26 candles per 5 cubic feet.
+Table II. contains the results of determinations with common gas (such
+as is used in London, and generally throughout the greater part of
+England); 5 cubic feet of which, in the standard burner, gave an
+illuminating power of 16 candles. The first and second columns of the
+<span class="sidenote"> Varied adaptability of the Br&#246;nner burner.</span>
+tables refer to the different sizes of the tops and bottoms of the
+particular burners employed; there being in all some 16 sizes of the
+one, and 11 sizes of the other. These, being interchangeable, permit of
+a great variety of combinations; and enable a burner to be selected
+suited to any particular quality or pressure of gas. For as with
+pressure, so with illuminating power: In order to obtain the utmost
+lighting efficiency, different burners are required for gases differing
+in quality or their degree of richness. A burner which, with gas of one
+quality, will yield excellent results, may, under the same conditions
+of pressure and supply, be totally unsuited to gas of another quality.
+That this should be so will be evident from a consideration of what has
+been said as to the theory of burning gas to the best advantage; and,
+in brief, results from the richer gas containing in its composition a
+greater proportion of carbon, and so requiring an increased supply of
+air for its thorough combustion. This increased supply of air can only
+be obtained (with flat-flame burners) by causing the gas to issue into
+the atmosphere at a higher pressure; and so it comes about that,
+compared with the quantity of gas to be delivered through them, the
+slits of batswing and the orifices of union-jet burners must be
+considerably narrower when intended for cannel gas than when common gas
+is to be consumed. In other words, in order to develop its full
+illuminating power, it is essential that the pressure at which the gas
+issues from the burner should be proportioned to its quality. The gist
+of the matter is set forth in the general statement that "the poorer
+the quality of the gas, the lower must be the pressure at which it is
+consumed; and <i>vice vers&#226;</i>."
+</p>
+
+<p class="ctr">
+<span class="sc">Table I.</span>
+</p>
+
+<table summary="Table 1">
+
+<tr>
+<td class="cbtbbbr" colspan="5"><span class="sc">At 1&#183;0-Inch Pressure.</span></td>
+<td class="cbtbbbl" colspan="5"><span class="sc">At 1&#183;5-Inch Pressure.</span></td>
+</tr>
+
+<tr>
+<td class="cbbbr">No.<br>of<br>Burner.</td>
+<td class="cbbbr">No.<br>of<br>Top.</td>
+<td class="cbbbr">Cubic<br>Feet<br>per<br>Hour.</td>
+<td class="cbbbr">Illumi-<br>nating<br>Power.</td>
+<td class="cbbbr">Illumi-<br>nating<br>Power<br>per<br>Five<br>Cub.<br>Ft.</td>
+
+<td class="cbbblbr">No.<br>of<br>Burner.</td>
+<td class="cbbbr">No.<br>of<br>Top.</td>
+<td class="cbbbr">Cubic<br>Feet<br>per<br>Hour.</td>
+<td class="cbbbr">Illumi-<br>nating<br>Power.</td>
+<td class="cbb">Illumi-<br>nating<br>Power<br>per<br>Five<br>Cub.<br>Ft.</td>
+</tr>
+
+<tr>
+<td class="cbr">2</td>
+<td class="cbr">2</td>
+<td class="cbr">1&#183;20</td>
+<td class="cbr">5&#183;07</td>
+<td class="cbr">24&#183;13</td>
+
+<td class="cblbr">2</td>
+<td class="cbr">2</td>
+<td class="cbr">1&#183;40</td>
+<td class="cbr">5&#183;25</td>
+<td class="c">18&#183;75</td>
+</tr>
+
+<tr>
+<td class="cbr">2</td>
+<td class="cbr">3</td>
+<td class="cbr">1&#183;40</td>
+<td class="cbr">6&#183;64</td>
+<td class="cbr">23&#183;71</td>
+
+<td class="cblbr">2</td>
+<td class="cbr">3</td>
+<td class="cbr">1&#183;95</td>
+<td class="cbr">7&#183;37</td>
+<td class="c">18&#183;90</td>
+</tr>
+
+<tr>
+<td class="cbr">2</td>
+<td class="cbr">4</td>
+<td class="cbr">&#8212;</td>
+<td class="cbr">Smokes</td>
+<td class="cbr">&#8212;</td>
+
+<td class="cblbr">2</td>
+<td class="cbr">4</td>
+<td class="cbr">2&#183;30</td>
+<td class="cbr">10&#183;33</td>
+<td class="c">22&#183;46</td>
+</tr>
+
+<tr>
+<td class="cbr">2</td>
+<td class="cbr">5</td>
+<td class="cbr">&#8212;</td>
+<td class="cbr">"</td>
+<td class="cbr">&#8212;</td>
+
+<td class="cblbr">2</td>
+<td class="cbr">5</td>
+<td class="cbr">2&#183;40</td>
+<td class="cbr">11&#183;24</td>
+<td class="c">23&#183;42</td>
+</tr>
+
+<tr>
+<td class="cbbbr">2</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">&#8212;</td>
+<td class="cbbbr">"</td>
+<td class="cbbbr">&#8212;</td>
+
+<td class="cbbblbr">2</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">&#8212;</td>
+<td class="cbbbr">Smokes</td>
+<td class="cbb">&#8212;</td>
+</tr>
+
+<tr>
+<td class="cbr">2&#189;</td>
+<td class="cbr">2</td>
+<td class="cbr">1&#183;40</td>
+<td class="cbr">5&#183;53</td>
+<td class="cbr">19&#183;75</td>
+
+<td class="cblbr">2&#189;</td>
+<td class="cbr">2</td>
+<td class="cbr">1&#183;90</td>
+<td class="cbr">8&#183;30</td>
+<td class="c">21&#183;84</td>
+</tr>
+
+<tr>
+<td class="cbr">2&#189;</td>
+<td class="cbr">3</td>
+<td class="cbr">1&#183;70</td>
+<td class="cbr">8&#183;48</td>
+<td class="cbr">24&#183;94</td>
+
+<td class="cblbr">2&#189;</td>
+<td class="cbr">3</td>
+<td class="cbr">2&#183;30</td>
+<td class="cbr">10&#183;14</td>
+<td class="c">22&#183;04</td>
+</tr>
+
+<tr>
+<td class="cbr">2&#189;</td>
+<td class="cbr">4</td>
+<td class="cbr">2&#183;03</td>
+<td class="cbr">10&#183;33</td>
+<td class="cbr">25&#183;49</td>
+
+<td class="cblbr">2&#189;</td>
+<td class="cbr">4</td>
+<td class="cbr">2&#183;70</td>
+<td class="cbr">12&#183;08</td>
+<td class="c">22&#183;37</td>
+</tr>
+
+<tr>
+<td class="cbr">2&#189;</td>
+<td class="cbr">5</td>
+<td class="cbr">&#8212;</td>
+<td class="cbr">Smokes</td>
+<td class="cbr">&#8212;</td>
+
+<td class="cblbr">2&#189;</td>
+<td class="cbr">5</td>
+<td class="cbr">2&#183;85</td>
+<td class="cbr">14&#183;29</td>
+<td class="c">25&#183;07</td>
+</tr>
+
+<tr>
+<td class="cbbbr">2&#189;</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">&#8212;</td>
+<td class="cbbbr">"</td>
+<td class="cbbbr">&#8212;</td>
+
+<td class="cbbblbr">2&#189;</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">3&#183;00</td>
+<td class="cbbbr">15&#183;21</td>
+<td class="cbb">25&#183;35</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">2</td>
+<td class="cbr">1&#183;45</td>
+<td class="cbr">6&#183;27</td>
+<td class="cbr">21&#183;62</td>
+
+<td class="cblbr">3</td>
+<td class="cbr">2</td>
+<td class="cbr">2&#183;00</td>
+<td class="cbr">8&#183;48</td>
+<td class=c>21&#183;20</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">3</td>
+<td class="cbr">1&#183;90</td>
+<td class="cbr">8&#183;66</td>
+<td class="cbr">22&#183;79</td>
+
+<td class="cblbr">3</td>
+<td class="cbr">3</td>
+<td class="cbr">2&#183;40</td>
+<td class="cbr">11&#183;34</td>
+<td class="c">23&#183;63</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">4</td>
+<td class="cbr">2&#183;13</td>
+<td class="cbr">11&#183;24</td>
+<td class="cbr">26&#183;39</td>
+
+<td class="cblbr">3</td>
+<td class="cbr">4</td>
+<td class="cbr">2&#183;80</td>
+<td class="cbr">14&#183;84</td>
+<td class="c">26&#183;50</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">5</td>
+<td class="cbr">&#8212;</td>
+<td class="cbr">Smokes</td>
+<td class="cbr">&#8212;</td>
+
+<td class="cblbr">3</td>
+<td class="cbr">5</td>
+<td class="cbr">3&#183;15</td>
+<td class="cbr">17&#183;04</td>
+<td class="c">27&#183;20</td>
+</tr>
+
+<tr>
+<td class="cbbbr">3</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">&#8212;</td>
+<td class="cbbbr">"</td>
+<td class="cbbbr">&#8212;</td>
+
+<td class="cbbblbr">3</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">3&#183;25</td>
+<td class="cbbbr">18&#183;07</td>
+<td class="cbb">27&#183;80</td>
+</tr>
+
+<tr>
+<td class="cbr">3&#189;</td>
+<td class="cbr">2</td>
+<td class="cbr">1&#183;50</td>
+<td class="cbr">5&#183;81</td>
+<td class="cbr">19&#183;36</td>
+
+<td class="cblbr">3&#189;</td>
+<td class="cbr">2</td>
+<td class="cbr">2&#183;12</td>
+<td class="cbr">8&#183;85</td>
+<td class="c">20&#183;87</td>
+</tr>
+
+<tr>
+<td class="cbr">3&#189;</td>
+<td class="cbr">3</td>
+<td class="cbr">1&#183;95</td>
+<td class="cbr">8&#183;30</td>
+<td class="cbr">21&#183;28</td>
+
+<td class="cblbr">3&#189;</td>
+<td class="cbr">3</td>
+<td class="cbr">2&#183;55</td>
+<td class="cbr">12&#183;63</td>
+<td class="c">24&#183;76</td>
+</tr>
+
+<tr>
+<td class="cbr">3&#189;</td>
+<td class="cbr">4</td>
+<td class="cbr">2&#183;55</td>
+<td class="cbr">12&#183;08</td>
+<td class="cbr">23&#183;68</td>
+
+<td class="cblbr">3&#189;</td>
+<td class="cbr">4</td>
+<td class="cbr">3&#183;00</td>
+<td class="cbr">14&#183;47</td>
+<td class="c">26&#183;12</td>
+</tr>
+
+<tr>
+<td class="cbr">3&#189;</td>
+<td class="cbr">5</td>
+<td class="cbr">2&#183;80</td>
+<td class="cbr">14&#183;38</td>
+<td class="cbr">25&#183;68</td>
+
+<td class="cblbr">3&#189;</td>
+<td class="cbr">5</td>
+<td class="cbr">3&#183;50</td>
+<td class="cbr">18&#183;07</td>
+<td class="c">25&#183;81</td>
+</tr>
+
+<tr>
+<td class="cbbbr">3&#189;</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">3&#183;00</td>
+<td class="cbbbr">15&#183;58</td>
+<td class="cbbbr">25&#183;97</td>
+
+<td class="cbbblbr">3&#189;</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">3&#183;60</td>
+<td class="cbbbr">19&#183;45</td>
+<td class="cbb">27&#183;01</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">2</td>
+<td class="cbr">1&#183;60</td>
+<td class="cbr">6&#183;36</td>
+<td class="cbr">19&#183;87</td>
+
+<td class="cblbr">4</td>
+<td class="cbr">2</td>
+<td class="cbr">2&#183;30</td>
+<td class="cbr">9&#183;77</td>
+<td class="c">21&#183;24</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">3</td>
+<td class="cbr">2&#183;10</td>
+<td class="cbr">10&#183;69</td>
+<td class="cbr">25&#183;45</td>
+
+<td class="cblbr">4</td>
+<td class="cbr">3</td>
+<td class="cbr">2&#183;90</td>
+<td class="cbr">13&#183;83</td>
+<td class="c">23&#183;84</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">4</td>
+<td class="cbr">2&#183;65</td>
+<td class="cbr">13&#183;37</td>
+<td class="cbr">25&#183;23</td>
+
+<td class="cblbr">4</td>
+<td class="cbr">4</td>
+<td class="cbr">3&#183;30</td>
+<td class="cbr">17&#183;06</td>
+<td class="c">25&#183;85</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">5</td>
+<td class="cbr">3&#183;45</td>
+<td class="cbr">17&#183;61</td>
+<td class="cbr">25&#183;52</td>
+
+<td class="cblbr">4</td>
+<td class="cbr">5</td>
+<td class="cbr">4&#183;10</td>
+<td class="cbr">21&#183;57</td>
+<td class="cbr">26&#183;30</td>
+</tr>
+
+<tr>
+<td class="cbbbr">4</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">3&#183;55</td>
+<td class="cbbbr">18&#183;07</td>
+<td class="cbbbr">25&#183;45</td>
+
+<td class="cbbblbr">4</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">4&#183;20</td>
+<td class="cbbbr">22&#183;40</td>
+<td class="cbb">26&#183;66</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">2</td>
+<td class="cbr">1&#183;77</td>
+<td class="cbr">7&#183;38</td>
+<td class="cbr">20&#183;85</td>
+
+<td class="cblbr">5</td>
+<td class="cbr">2</td>
+<td class="cbr">2&#183;60</td>
+<td class="cbr">9&#183;68</td>
+<td class="c">18&#183;81</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">3</td>
+<td class="cbr">2&#183;30</td>
+<td class="cbr">11&#183;90</td>
+<td class="cbr">25&#183;87</td>
+
+<td class="cblbr">5</td>
+<td class="cbr">3</td>
+<td class="cbr">3&#183;30</td>
+<td class="cbr">13&#183;64</td>
+<td class="c">20&#183;67</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">4</td>
+<td class="cbr">3&#183;30</td>
+<td class="cbr">15&#183;40</td>
+<td class="cbr">23&#183;33</td>
+
+<td class="cblbr">5</td>
+<td class="cbr">4</td>
+<td class="cbr">4&#183;00</td>
+<td class="cbr">19&#183;91</td>
+<td class="c">24&#183;14</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">5</td>
+<td class="cbr">4&#183;10</td>
+<td class="cbr">20&#183;74</td>
+<td class="cbr">25&#183;29</td>
+
+<td class="cblbr">5</td>
+<td class="cbr">5</td>
+<td class="cbr">5&#183;00</td>
+<td class="cbr">25&#183;36</td>
+<td class="c">25&#183;36</td>
+</tr>
+
+<tr>
+<td class="cbbbr">5</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">4&#183;30</td>
+<td class="cbbbr">22&#183;68</td>
+<td class="cbbbr">26&#183;37</td>
+
+<td class="cbbblbr">5</td>
+<td class="cbbbr">6</td>
+<td class="cbbbr">5&#183;30</td>
+<td class="cbbbr">27&#183;66</td>
+<td class="cbb">26&#183;10</td>
+</tr>
+</table>
+<br>
+<p class="ctr">
+<span class="sc">Table II.</span>
+</p>
+
+<table summary="Table 2">
+
+<tr>
+<td class="cbtbbbr" colspan="5"><span class="sc">At 0&#183;5-Inch Pressure.</span></td>
+<td class="cbtbbbr" colspan="3"><span class="sc">At 1&#183;0-Inch Pressure.</span></td>
+<td class="cbtbbbl" colspan="3"><span class="sc">At 1&#183;5-Inch Pressure.</span></td>
+</tr>
+
+<tr>
+<td class="cbbbr">No.<br>of<br>Top.</td>
+<td class="cbbbr">No.<br>of<br>Bottom.</td>
+<td class="cbbbr">Cubic<br>Feet<br>per<br>Hour.</td>
+<td class="cbbbr">Illumi-<br>nating Power.</td>
+<td class="cbbbr">Illum.<br>Power<br>per<br>Five<br>Cub.<br>Ft.</td>
+<td class="cbbbr">Cubic<br>Feet<br>per<br>Hour.</td>
+<td class="cbbbr">Illumi-<br>nating Power.</td>
+<td class="cbbbr">Illum.<br>Power<br>per<br>Five<br>Cub. Ft.</td>
+<td class="cbbbr">Cubic<br>Feet<br>per<br>Hour.</td>
+<td class="cbbbr">Illumi-<br>nating Power.</td>
+<td class="cbb">Illum.<br>Power<br>per<br>Five<br>Cub. Ft.</td>
+</tr>
+
+<tr>
+<td class="cbr">A2</td>
+<td class="cbr">1</td>
+<td class="cbr">&#8212;</td>
+<td class="cbr">&#8212;</td>
+<td class="cbr">&#8212;</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">2&#183;7</td>
+<td class="cbr">9&#183;0</td>
+<td class="cbr">2&#183;0</td>
+<td class="cbr">4&#183;0</td>
+<td class="c">10&#183;0</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">2</td>
+<td class="cbr">1&#183;6</td>
+<td class="cbr">2&#183;9</td>
+<td class="cbr">9&#183;1</td>
+<td class="cbr">2&#183;4</td>
+<td class="cbr">5&#183;2</td>
+<td class="cbr">10&#183;8</td>
+<td class="cbr">3&#183;1</td>
+<td class="cbr">6&#183;8</td>
+<td class="c">11&#183;0</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">2&#189;</td>
+<td class="cbr">2&#183;0</td>
+<td class="cbr">3&#183;9</td>
+<td class="cbr">9&#183;8</td>
+<td class="cbr">2&#183;9</td>
+<td class="cbr">6&#183;8</td>
+<td class="cbr">11&#183;7</td>
+<td class="cbr">3&#183;8</td>
+<td class="cbr">9&#183;4</td>
+<td class="c">12&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">A3</td>
+<td class="cbr">3</td>
+<td class="cbr">2&#183;1</td>
+<td class="cbr">4&#183;4</td>
+<td class="cbr">10&#183;5</td>
+<td class="cbr">3&#183;2</td>
+<td class="cbr">7&#183;8</td>
+<td class="cbr">12&#183;2</td>
+<td class="cbr">4&#183;4</td>
+<td class="cbr">10&#183;6</td>
+<td class="c">12&#183;0</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">3&#189;</td>
+<td class="cbr">2&#183;5</td>
+<td class="cbr">4&#183;8</td>
+<td class="cbr">9&#183;6</td>
+<td class="cbr">3&#183;8</td>
+<td class="cbr">9&#183;2</td>
+<td class="cbr">12&#183;1</td>
+<td class="cbr">4&#183;9</td>
+<td class="cbr">12&#183;2</td>
+<td class="c">12&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">4</td>
+<td class="cbr">2&#183;5</td>
+<td class="cbr">5&#183;4</td>
+<td class="cbr">10&#183;8</td>
+<td class="cbr">3&#183;8</td>
+<td class="cbr">9&#183;6</td>
+<td class="cbr">12&#183;7</td>
+<td class="cbr">5&#183;2</td>
+<td class="cbr">13&#183;6</td>
+<td class="c">13&#183;1</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">4&#189;</td>
+<td class="cbr">3&#183;0</td>
+<td class="cbr">6&#183;4</td>
+<td class="cbr">10&#183;7</td>
+<td class="cbr">4&#183;5</td>
+<td class="cbr">10&#183;8</td>
+<td class="cbr">12&#183;0</td>
+<td class="cbr">5&#183;9</td>
+<td class="cbr">14&#183;8</td>
+<td class="c">12&#183;5</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">5</td>
+<td class="cbr">3&#183;2</td>
+<td class="cbr">7&#183;7</td>
+<td class="cbr">2&#183;0</td>
+<td class="cbr">5&#183;1</td>
+<td class="cbr">13&#183;2</td>
+<td class="cbr">13&#183;0</td>
+<td class="cbr">6&#183;8</td>
+<td class="cbr">18&#183;0</td>
+<td class="c">13&#183;2</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">6</td>
+<td class="cbr">3&#183;7</td>
+<td class="cbr">8&#183;7</td>
+<td class="cbr">11&#183;8</td>
+<td class="cbr">5&#183;8</td>
+<td class="cbr">15&#183;5</td>
+<td class="cbr">13&#183;3</td>
+<td class="cbr">7&#183;7</td>
+<td class="cbr">21&#183;0  </td>
+<td class="c">13&#183;6</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">7</td>
+<td class="cbr">3&#183;5</td>
+<td class="cbr">8&#183;6</td>
+<td class="cbr">12&#183;3</td>
+<td class="cbr">5&#183;9</td>
+<td class="cbr">16&#183;0</td>
+<td class="cbr">13&#183;6 </td>
+<td class="cbr">  8&#183;4</td>
+<td class="cbr">23&#183;0</td>
+<td class="c">13&#183;7</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">8</td>
+<td class="cbr">3&#183;7</td>
+<td class="cbr">9&#183;0</td>
+<td class="cbr">12&#183;2</td>
+<td class="cbr">6&#183;2</td>
+<td class="cbr">16&#183;8</td>
+<td class="cbr">13&#183;5</td>
+<td class="cbr">8&#183;6</td>
+<td class="cbr">23&#183;4</td>
+<td class="c">13&#183;6</td>
+</tr>
+
+<tr>
+<td class="cbr">B1</td>
+<td class="cbr">1</td>
+<td class="cbr">&#8212;</td>
+<td class="cbr">&#8212;</td>
+<td class="cbr">&#8212;</td>
+<td class="cbr">1&#183;3</td>
+<td class="cbr">2&#183;3</td>
+<td class="cbr">8&#183;8</td>
+<td class="cbr">1&#183;8</td>
+<td class="cbr">3&#183;5</td>
+<td class="c">9&#183;7</td>
+</tr>
+
+<tr>
+<td class="cbr">B2</td>
+<td class="cbr">2</td>
+<td class="cbr">1&#183;3</td>
+<td class="cbr">2&#183;3</td>
+<td class="cbr">8&#183;8</td>
+<td class="cbr">2&#183;1</td>
+<td class="cbr">4&#183;4</td>
+<td class="cbr">10&#183;5</td>
+<td class="cbr">2&#183;8</td>
+<td class="cbr">6&#183;4</td>
+<td class="c">11&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">2&#189;</td>
+<td class="cbr">1&#183;6</td>
+<td class="cbr">3&#183;0</td>
+<td class="cbr">9&#183;4</td>
+<td class="cbr">2&#183;5</td>
+<td class="cbr">6&#183;0</td>
+<td class="cbr">12&#183;0</td>
+<td class="cbr">3&#183;4</td>
+<td class="cbr">8&#183;4</td>
+<td class="c">12&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">B3</td>
+<td class="cbr">3</td>
+<td class="cbr">2&#183;0</td>
+<td class="cbr">3&#183;8</td>
+<td class="cbr">9&#183;0</td>
+<td class="cbr">3&#183;0</td>
+<td class="cbr">7&#183;2</td>
+<td class="cbr">12&#183;0</td>
+<td class="cbr">4&#183;1</td>
+<td class="cbr">10&#183;1</td>
+<td class="c">12&#183;3</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">3&#189;</td>
+<td class="cbr">2&#183;3</td>
+<td class="cbr">4&#183;3</td>
+<td class="cbr">9&#183;3</td>
+<td class="cbr">3&#183;4</td>
+<td class="cbr">7&#183;7</td>
+<td class="cbr">11&#183;3</td>
+<td class="cbr">4&#183;5</td>
+<td class="cbr">11&#183;0</td>
+<td class="c">12&#183;2</td>
+</tr>
+
+<tr>
+<td class="cbr">B4</td>
+<td class="cbr">4</td>
+<td class="cbr">2&#183;3</td>
+<td class="cbr">4&#183;7</td>
+<td class="cbr">0&#183;2</td>
+<td class="cbr">3&#183;6</td>
+<td class="cbr">8&#183;8</td>
+<td class="cbr">12&#183;2</td>
+<td class="cbr">5&#183;0</td>
+<td class="cbr">13&#183;0</td>
+<td class="c">13&#183;0</td>
+</tr>
+
+<tr>
+<td class="cbr">"</td>
+<td class="cbr">4&#189;</td>
+<td class="cbr">2&#183;7</td>
+<td class="cbr">5&#183;9</td>
+<td class="cbr">10&#183;9</td>
+<td class="cbr">4&#183;3</td>
+<td class="cbr">10&#183;4</td>
+<td class="cbr">12&#183;1</td>
+<td class="cbr">5&#183;6</td>
+<td class="cbr">15&#183;0</td>
+<td class="c">13&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">B5</td>
+<td class="cbr">5</td>
+<td class="cbr">3&#183;1</td>
+<td class="cbr">7&#183;0</td>
+<td class="cbr">11&#183;3</td>
+<td class="cbr">4&#183;9</td>
+<td class="cbr">12&#183;9</td>
+<td class="cbr">13&#183;2</td>
+<td class="cbr">6&#183;5</td>
+<td class="cbr">18&#183;0</td>
+<td class="c">13&#183;8</td>
+</tr>
+
+<tr>
+<td class="cbr">B6</td>
+<td class="cbr">6</td>
+<td class="cbr">3&#183;8</td>
+<td class="cbr">9&#183;6</td>
+<td class="cbr">12&#183;6</td>
+<td class="cbr">5&#183;9</td>
+<td class="cbr">16&#183;4</td>
+<td class="cbr">13&#183;8</td>
+<td class="cbr">8&#183;0</td>
+<td class="cbr">23&#183;0</td>
+<td class="c">14&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">B7</td>
+<td class="cbr">7</td>
+<td class="cbr">4&#183;0</td>
+<td class="cbr">10&#183;2</td>
+<td class="cbr">12&#183;8</td>
+<td class="cbr">6&#183;6</td>
+<td class="cbr">19&#183;0</td>
+<td class="cbr">14&#183;4</td>
+<td class="cbr">9&#183;0</td>
+<td class="cbr">26&#183;0</td>
+<td class="c">14&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">B8</td>
+<td class="cbr">8</td>
+<td class="cbr">4&#183;7</td>
+<td class="cbr">11&#183;8</td>
+<td class="cbr">12&#183;6</td>
+<td class="cbr">7&#183;3</td>
+<td class="cbr">22&#183;0</td>
+<td class="cbr">15&#183;1</td>
+<td class="cbr">9&#183;6</td>
+<td class="cbr">30&#183;0</td>
+<td class="c">15&#183;7</td>
+</tr>
+</table>
+
+
+<p>
+Doubtless the chief cause of the remarkable efficiency of the Br&#246;nner
+over previous burners is to be found in the pressure at which the
+<span class="sidenote"> Pressure of gas with the Br&#246;nner burner.</span>
+gas flows from the burner and is consumed. In the course of some
+experiments made to determine the pressure at which gas is delivered
+from various burners, the writer found that from a No. 4 Br&#246;nner, with
+an initial pressure&#8212;<i>i.e.</i>, the pressure at the inlet when the
+burner is in operation&#8212;of 1 inch, the gas issued at a pressure of
+only 0&#183;05 inch; and with an initial pressure of 0&#183;5 inch, the outlet
+pressure was only 0&#183;03 inch. On the other hand, a No. 4 steatite
+flat-flame burner, without any arrangement for retarding the flow of
+the gas, under the same initial pressure gave at the outlet 0&#183;16 inch
+and 0&#183;05 inch respectively. The absence of anything within the burner
+to cause the gas to swirl, or to issue with an unsteady flow, must also
+be credited with contributing, in no slight degree, to the favourable
+results yielded by these burners.
+</p>
+
+<a name="35">&nbsp;</a>
+<p class="subhead">
+THE HOLLOW-TOP BURNER.
+</p>
+
+<p>
+In the hollow-top burner we have one of the most notable improvements
+which have been effected in flat-flame burners. A simple modification
+of the batswing&#8212;the earliest of flat-flame burners&#8212;it is not more
+complicated in its details than is that burner. Yet, simple as it
+is, its construction exhibits an important advance upon the original
+batswing. Indeed, this burner may be said to embody the only
+considerable improvement that has been made in the distinctive features
+of the batswing since the introduction of the latter burner, which, as
+we have seen, took place as early as the year 1816.
+</p>
+
+
+<p>
+<span class="sidenote"> The hollow-top an improved batswing burner.</span>
+In its outward form, the hollow-top burner differs little, if at all,
+from the batswing; but a slight modification which has been adopted in
+the arrangement of its interior has produced a very marked result in
+improving the shape of the flame yielded by the burner, and, to some
+extent, in the results, as regards illuminating power, which it is
+capable of affording. In this burner, as its name implies, the
+interior of the top or head of the burner is hollowed out, forming an
+enlargement of the cavity or chamber within the burner, and (what is
+chiefly important) making the shell of the dome-shaped burner head of
+equal thickness throughout. In the ordinary batswing, in consequence
+of the varying thickness of the burner at this part, the slit is much
+deeper in the middle than at any other part of its length, and
+gradually decreases in depth towards each end. As the resistance to
+the passage of the gas, or the friction which it encounters, increases
+with the depth of the slit, the gas passes out from the burner at the
+ends of the slit more readily than in the middle; producing a
+wide-stretching flame, of scanty height in proportion to its width.
+From the same cause the flame is not of equal thickness throughout;
+being thinner in the middle than at the ends. Moreover, the outer
+extremities of the flame, extending so far beyond the body of the
+burner, are unable to retain the form given to them by the lateral
+flow of the gas at the ends of the slit; the resistance, presented by
+the atmosphere, together with the natural tendency of the gas to
+ascend, causing the under portion of the flame to fold back upon
+itself. As one result of this combination of untoward circumstances,
+the flame is liable to smoke with a slight agitation of the
+surrounding air.
+</p>
+
+<p>
+In the hollow-top burner, the slit is of equal depth throughout its
+length; and the resistance offered to the passage of the gas being the
+same in all parts of the slit, the gas flows through the middle as
+readily as at the ends&#8212;nay, in reality rather more so, owing to the
+innate ascensive power of the gas, due to its being lighter than air.
+The peculiar hollowing-out of the head of the burner, also, withdraws
+the ends of the slit out of the direct course or current of the gas
+through the burner; so that the tendency of the stream of gas to issue
+at these points, in preference to going through the middle of the
+slit, is further checked. The consequence is that the shape of the
+flame is considerably improved; it being taller, more compact, and not
+so broad as that of the batswing. In addition, the flame being of
+equal thickness throughout, its illuminating power is somewhat
+improved; while, from its compactness, it is better enabled to resist
+atmospheric influences. With this alteration in the shape of the flame
+all original resemblance to a batswing is entirely destroyed; but the
+appearance of the flame of the new burner is much more agreeable to
+the eye than that of the older batswing.
+</p>
+
+<div class="figcenter"><img src="images/009.jpg" alt="Original Hollow-Top Burner" width="388" height="320"></div>
+<p class="caption"><span class="sc">Fig. 9.&#8212;Original Hollow-Top Burner.</span>
+<br>(From Wadsworth's Specification.)
+</p>
+
+
+<p>
+As has been exemplified in so many instances in the history of
+invention, the hollow-top burner was not appreciated at its true value
+until long after it had been brought into existence. It appears to
+have been originally invented by Joseph and James Wadsworth, of Marple
+and Salford, and was patented by them in 1860. According to the
+specification of the inventors, the burners might be made either
+in solid or sheet metal, as will be seen from the accompanying
+illustrations, copied from the drawings in the specification. But
+<span class="sidenote"> Who invented the hollow-top burner.</span>
+there were difficulties in the way of casting the burners in solid
+metal which do not seem to have been surmounted; and those produced
+under the patent appear to have been made exclusively of sheet brass.
+For many years these burners were made and sold without their
+peculiarities attracting any marked attention; which would seem to
+imply that their faulty construction precluded the attainment of all
+the advantages afforded by the burner as we know it.
+</p>
+
+
+<p>
+The superior results which the hollow-top burner was calculated to
+afford did not become fully apparent until the burner was made of
+non-conducting material, and greater care exercised in its
+construction. This appears to have been done in Germany earlier than
+in this country. But, in England, it was undoubtedly Mr. Sugg who
+first turned his attention to the improvement of the burner, and
+demonstrated its merits. Mr. Sugg commenced the manufacture of this
+burner in steatite in the year 1868; and since that time the burner
+has been extensively employed, and its advantages widely recognized.
+The superiority of hollow-top burners produced by Mr. Sugg to those
+previously manufactured, is chiefly the result of their being made in
+steatite instead of in metal. With this material, greater exactness
+and uniformity are obtained in the shape and dimensions of the burner
+than when metal is employed; besides which there is (what has been
+before referred to) the advantage arising from its inferior conductive
+capacity for heat, and its non-liability to corrosion. Another
+<span class="sidenote"> Sugg's hollow-top burner.</span>
+improvement, also due to Mr. Sugg, and which is productive of
+noticeable results, consists in cutting the slit of the burner with a
+circular saw, applied from above, so as to make the ends of the slit
+curved instead of horizontal; by which means the tendency of the gas
+to issue laterally at the ends of the slit, and form horns to the
+flame, is lessened. Mr. Sugg's table-top burner (which was introduced
+in 1880), in addition to the characteristic features of the
+hollow-top, has a rim-like projection from the burner, below the slit;
+its object being to protect the flame from the disturbing influence of
+the uprush of air in its immediate vicinity, and so preserve its shape
+unaltered, while diminishing its liability to smoke. Prior to Mr.
+Sugg&#8212;namely, in the early part of 1879&#8212;Mr. Bray had successfully
+obviated this injurious action upon the flame of the ascending current
+of air, by affixing to the burner two arms of brass, so placed as to
+be immediately under the projecting wings of the flame.
+</p>
+
+<div class="figcenter"><img src="images/010.jpg" alt="Three different burners" width="320" height="140"></div>
+<p class="caption"><span class="sc">1868 Burner.</span>
+&#8212;<span class="sc">1874 Burner.</span>
+&#8212;<span class="sc">Table-Top Burner.</span>
+<br><span class="sc">Fig. 10.&#8212;Sugg's Hollow-Top Burners.</span>
+</p>
+
+<a name="38">&nbsp;</a>
+<p class="subhead">
+BRAY'S BURNERS.
+</p>
+
+<p>
+The burners of Messrs. George Bray and Co. have deservedly acquired a
+world-wide reputation, and are in extensive use wherever gas lighting
+is known. Their distinguishing characteristic, and that which has won
+for them the high repute in which they are held, is the union of
+cheapness with remarkable efficiency. In all the various descriptions
+and classes of burners which are produced by this firm, the
+characteristic referred to is preserved; although it is needless to
+add that the different varieties are not equally efficient. Of the
+three forms of flat-flame burners we have been considering&#8212;batswing,
+union-jet, and hollow-top&#8212;the one which, more than any other, has
+been the speciality of the firm is the union-jet; and it is with the
+development of this class of burner that the name of Bray is most
+intimately and honourably associated.
+</p>
+
+<div class="figcenter"><img src="images/011.jpg" alt="Three burners" width="273" height="175"></div>
+<p class="caption"><span class="sc">Union-Jet.</span>
+&#8212;<span class="sc">Hollow-Top or Slit-Union.</span><a href="#note9" name="noteref9">
+<small>[9]</small></a>
+&#8212;<span class="sc">Batswing.</span>
+<br><span class="sc">Fig. 11.&#8212;Bray's "Regulator" Burners.</span>
+</p>
+
+
+
+<p>
+<span class="sidenote"> Bray's "regulator" burner.</span>
+The "regulator" union-jet, which was the first notable burner produced
+by Messrs. Bray, has received, perhaps, a wider application than any
+other single gas-burner. It consists of a cylindrical brass case,
+screwed at one end for insertion into the fittings, and at the other
+containing a tip of "enamel"&#8212;a material invented by Mr. Bray, and
+apparently of somewhat similar composition to the "adamas" of Mr.
+Leoni&#8212;the "enamel" tip being perforated, in the usual manner, with
+two holes, set at an angle to each other, for the outflow of the gas.
+The distinctive feature of this burner is the introduction into the
+lower part of the brass case of a layer, or layers, of muslin;
+designed to check in some degree, and to steady the current or flow of
+the gas through the burner. At the time of its introduction, this
+burner compared very favourably, as regards the results it yielded,
+with other burners in common use; and its fairly good performances,
+<span class="sidenote"> Bray's "special" burner.</span>
+together with the very low price at which it can be sold, cause it
+still to be extensively employed wherever the attainment, from the gas
+consumed, of the highest obtainable results may be subordinated to
+cheapness, or in situations where, from delicacy of construction or
+from the care and attention demanded, a more efficient burner may not
+be so suitable. But in the matter of developing the illuminating power
+of the gas employed, the "regulator" is far surpassed by the more
+recently introduced "special" burner of the same makers.
+</p>
+
+<div class="figcenter"><img src="images/012.jpg" alt="Three burners" width="285" height="215"></div>
+<p class="caption"><span class="sc">Union-Jet.</span>
+&#8212;<span class="sc">Hollow-Top or Slit-Union.</span>
+&#8212;<span class="sc">Batswing.</span>
+<br><span class="sc">Fig. 12.&#8212;Bray's "Special" Burners.</span>
+</p>
+
+<p>
+Mr. Bray's series of "special" burners&#8212;embracing union-jet,
+hollow-top, and batswing&#8212;are constructed upon the principle of, and
+in form are somewhat similar to Br&#246;nner's burners, which have already
+been fully described. Apart from its being of greater bulk, the main
+divergence in the construction of the "special" burner from that of
+the earlier "regulator" is the introduction, into the lower part of
+the brass case, of a plug or washer of enamel, pierced by a small
+circular hole for the admission of gas into the burner; the diameter
+of this hole determining the quantity of gas which, at any particular
+pressure, is admitted into the burner. Just above the enamel washer, a
+layer of muslin is inserted, as in the "regulator" burner; which, in
+this case, is for the purpose of subduing the agitation, or swirl,
+acquired by the current of gas in passing through the narrow aperture
+in the washer. A tip of enamel, made of the particular description
+(union-jet, hollow-top, or batswing) required, fitting into the upper
+part of the brass case, completes the burner. The objects aimed at in
+the "special" burner are to cause the gas to be consumed at the lowest
+pressure compatible with the maintenance of a firm flame, and with the
+least agitation, or swirl, in the current of gas as it issues from
+the burner. The former is attained, as in Br&#246;nner's burners, by
+diminishing the area of the opening admitting into the burner, without
+a corresponding diminution of the orifices through which the gas
+issues into the atmosphere; the latter, by the interposition of
+the layer of muslin which is immediately above the diminishing
+arrangement, as well as by the enlargement of the gas chamber in the
+upper part of the burner. The improvement thus effected in the
+illuminating power developed from the gas is well shown in the
+following tables extracted from an exhaustive series of tests of
+gas-burners carried out by Mr. T. Fairley, F.R.S.E., Borough Analyst
+of Leeds, and embodied by him in a report presented to the Leeds
+Corporation. The full text of the report will be found in the
+<i>Journal of Gas Lighting</i> for February 6, 1883.
+</p>
+
+<p class="ctr">
+<i>Medium Lighting Power Union-Jets.</i>
+</p>
+<table summary="Medium Lighting Power Union-Jets">
+
+<tr>
+<td class="cbtbbbr" colspan="5">"Regulator" Burners.</td>
+<td class="cbtbbbl" colspan="5">"Special" Burners.</td>
+</tr>
+
+<tr>
+<td class="cbbbr">No.<br>of<br>Burner</td>
+<td class="cbbbr">Pres-<br>sure<br>in<br>Inches</td>
+<td class="cbbbr">Cubic<br>Feet<br>per<br>Hour</td>
+<td class="cbbbr">Illumi-<br>nating<br>Power<br>in<br>Stand.<br>Candls.</td>
+<td class="cbbbr">Illumi-<br>Power<br>per 5<br>Cubic<br>Feet.</td>
+<td class="cbtbbbl">No.<br>of<br>Burner</td>
+<td class="cbbbr">Pres-<br>sure<br>in<br>Inches</td>
+<td class="cbbbr">Cubic<br>Feet<br>per<br>Hour</td>
+<td class="cbbbr">Illumi-<br>nating<br>Power<br>in<br>Stand.<br>Candls.</td>
+<td class="cbb">Illumi-<br>Power<br>per 5<br>Cubic<br>Feet.</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">3&#183;50</td>
+<td class="cbr">6&#183;8</td>
+<td class="cbr">9&#183;7</td>
+<td class="cblbr">3</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">3&#183;43</td>
+<td class="cbr">11&#183;3</td>
+<td class="c">16&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">4&#183;80</td>
+<td class="cbr">6&#183;9</td>
+<td class="cbr">7&#183;2</td>
+<td class="cblbr">3</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">4&#183;90</td>
+<td class="cbr">15&#183;6</td>
+<td class="c">15&#183;8</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">6&#183;20</td>
+<td class="cbr">7&#183;5</td>
+<td class="cbr">6&#183;05</td>
+<td class="cblbr">3</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">6&#183;03</td>
+<td class="cbr">17&#183;6</td>
+<td class="c">14&#183;6</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">4&#183;65</td>
+<td class="cbr">12&#183;2</td>
+<td class="cbr">13&#183;1</td>
+<td class="cblbr">4</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">3&#183;73</td>
+<td class="cbr">13&#183;3</td>
+<td class="c">17&#183;8</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">6&#183;67</td>
+<td class="cbr">14&#183;2</td>
+<td class="cbr">10&#183;6</td>
+<td class="cblbr">4</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">5&#183;15</td>
+<td class="cbr">17&#183;4</td>
+<td class="c">16&#183;9</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">8&#183;16</td>
+<td class="cbr">14&#183;2</td>
+<td class="cbr">8&#183;8</td>
+<td class="cblbr">4</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">6&#183;57</td>
+<td class="cbr">22&#183;4</td>
+<td class="c">17&#183;1</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">5&#183;72</td>
+<td class="cbr">17&#183;0</td>
+<td class="cbr">14&#183;9</td>
+<td class="cblbr">5</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">4&#183;80</td>
+<td class="cbr">17&#183;6</td>
+<td class="c">18&#183;3</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">7&#183;97</td>
+<td class="cbr">20&#183;0</td>
+<td class="cbr">12&#183;6</td>
+<td class="cblbr">5</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">6&#183;67</td>
+<td class="cbr">24&#183;4</td>
+<td class="c">18&#183;3</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">9&#183;73</td>
+<td class="cbr">21&#183;8</td>
+<td class="cbr">11&#183;2</td>
+<td class="cblbr">5</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">8&#183;30</td>
+<td class="cbr">30&#183;0</td>
+<td class="c">18&#183;2</td>
+</tr>
+
+<tr>
+<td class="cbr">6</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">5&#183;90</td>
+<td class="cbr">18&#183;0</td>
+<td class="cbr">15&#183;2</td>
+<td class="cblbr">6</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">5&#183;48</td>
+<td class="cbr">20&#183;1</td>
+<td class="c">18&#183;3</td>
+</tr>
+
+<tr>
+<td class="cbr">6</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">8&#183;35</td>
+<td class="cbr">23&#183;0</td>
+<td class="cbr">13&#183;8</td>
+<td class="cblbr">6</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">7&#183;65</td>
+<td class="cbr">28&#183;4</td>
+<td class="c">18&#183;6</td>
+</tr>
+
+<tr>
+<td class="cbr">6</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">10&#183;60</td>
+<td class="cbr">28&#183;0</td>
+<td class="cbr">13&#183;2</td>
+<td class="cblbr">6</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">9&#183;20</td>
+<td class="cbr">34&#183;2</td>
+<td class="c">18&#183;7</td>
+</tr>
+</table>
+<br>
+<p class="ctr">
+<i>Medium Lighting Power Slit-Unions.</i>
+</p>
+<table summary="Medium Lighting Power Slit-Unions">
+
+<tr>
+<td class="cbtbbbr" colspan="5">"Regulator" Burners.</td>
+<td class="cbtbbbl" colspan="5">"Special" Burners.</td>
+</tr>
+
+<tr>
+<td class="cbbbr">No.<br>of<br>Burner</td>
+<td class="cbbbr">Pres-<br>sure<br>in<br>Inches</td>
+<td class="cbbbr">Cubic<br>Feet<br>per<br>Hour</td>
+<td class="cbbbr">Illumi-<br>nating<br>Power<br>in<br>Stand.<br>Candls.</td>
+<td class="cbbbr">Illumi-<br>Power<br>per 5<br>Cubic<br>Feet.</td>
+<td class="cbtbbbl">No.<br>of<br>Burner</td>
+<td class="cbbbr">Pres-<br>sure<br>in<br>Inches</td>
+<td class="cbbbr">Cubic<br>Feet<br>per<br>Hour</td>
+<td class="cbbbr">Illumi-<br>nating<br>Power<br>in<br>Stand.<br>Candls.</td>
+<td class="cbb">Illumi-<br>Power<br>per 5<br>Cubic<br>Feet.</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">4&#183;22</td>
+<td class="cbr">13&#183;8</td>
+<td class="cbr">16&#183;4</td>
+<td class="cblbr">3</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">3&#183;04</td>
+<td class="cbr">10&#183;8</td>
+<td class="c">17&#183;8</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">6&#183;37</td>
+<td class="cbr">20&#183;2</td>
+<td class="cbr">15&#183;9</td>
+<td class="cblbr">3</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">4&#183;61</td>
+<td class="cbr">16&#183;4</td>
+<td class="c">17&#183;6</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">8&#183;14</td>
+<td class="cbr">25&#183;8</td>
+<td class="cbr">15&#183;9</td>
+<td class="cblbr">3</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">5&#183;88</td>
+<td class="cbr">19&#183;9</td>
+<td class="c">16&#183;9</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">4&#183;25</td>
+<td class="cbr">14&#183;8</td>
+<td class="cbr">17&#183;4</td>
+<td class=cblbr>4</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">3&#183;82</td>
+<td class="cbr">14&#183;2</td>
+<td class="c">18&#183;6</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">5&#183;88</td>
+<td class="cbr">20&#183;6</td>
+<td class="cbr">17&#183;5</td>
+<td class="cblbr">4</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">5&#183;69</td>
+<td class="cbr">20&#183;8</td>
+<td class="c">18&#183;3</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">7&#183;95</td>
+<td class="cbr">26&#183;5</td>
+<td class="cbr">16&#183;6</td>
+<td class="cblbr">4</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">7&#183;35</td>
+<td class="cbr">25&#183;6</td>
+<td class="c">17&#183;5</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">5&#183;25</td>
+<td class="cbr">19&#183;0</td>
+<td class="cbr">18&#183;2</td>
+<td class="cblbr">5</td>
+<td class="cblbr">0&#183;5</td>
+<td class="cbr">4&#183;12</td>
+<td class="cbr">15&#183;4</td>
+<td class="c">18&#183;7</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">8&#183;14</td>
+<td class="cbr">28&#183;4</td>
+<td class="cbr">17&#183;45</td>
+<td class="cblbr">5</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">6&#183;37</td>
+<td class="cbr">23&#183;4</td>
+<td class="c">18&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">10&#183;20</td>
+<td class="cbr">36&#183;4</td>
+<td class="cbr">17&#183;8</td>
+<td class="cblbr">5</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">7&#183;94</td>
+<td class="cbr">28&#183;5</td>
+<td class="c">18&#183;0</td>
+</tr>
+
+<tr>
+<td class="cbr">6</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">5&#183;67</td>
+<td class="cbr">22&#183;2</td>
+<td class="cbr">19&#183;6</td>
+<td class="cblbr">6</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">5&#183;00</td>
+<td class="cbr">19&#183;6</td>
+<td class="c">19&#183;6</td>
+</tr>
+
+<tr>
+<td class="cbr">6</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">8&#183;60</td>
+<td class="cbr">33&#183;6</td>
+<td class="cbr">19&#183;4</td>
+<td class="cblbr">6</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">7&#183;55</td>
+<td class="cbr">29&#183;0</td>
+<td class="c">19&#183;2</td>
+</tr>
+
+<tr>
+<td class="cbr">6</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">11&#183;10</td>
+<td class="cbr">39&#183;5</td>
+<td class="cbr">17&#183;8</td>
+<td class="cblbr">6</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">9&#183;70</td>
+<td class="cbr">37&#183;0</td>
+<td class="c">19&#183;1</td>
+</tr>
+</table>
+<br>
+<p class="ctr">
+<i>Medium Lighting Power Batswings.</i>
+</p>
+<table summary="Medium Lighting Power Batswings">
+
+<tr>
+<td class="cbtbbbr" colspan="5">"Regulator" Burners.</td>
+<td class="cbtbbbl" colspan="5">"Special" Burners.</td>
+</tr>
+
+<tr>
+<td class="cbbbr">No.<br>of<br>Burner</td>
+<td class="cbbbr">Pres-<br>sure<br>in<br>Inches</td>
+<td class="cbbbr">Cubic<br>Feet<br>per<br>Hour</td>
+<td class="cbbbr">Illumi-<br>nating<br>Power<br>in<br>Stand.<br>Candls.</td>
+<td class="cbbbr">Illumi-<br>Power<br>per 5<br>Cubic<br>Feet.</td>
+<td class="cbtbbbl">No.<br>of<br>Burner</td>
+<td class="cbbbr">Pres-<br>sure<br>in<br>Inches</td>
+<td class="cbbbr">Cubic<br>Feet<br>per<br>Hour</td>
+<td class="cbbbr">Illumi-<br>nating<br>Power<br>in<br>Stand.<br>Candls.</td>
+<td class="cbb">Illumi-<br>Power<br>per 5<br>Cubic<br>Feet.</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">4&#183;16</td>
+<td class="cbr">12&#183;6</td>
+<td class="cbr">15&#183;1</td>
+<td class="cblbr">3</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">3&#183;37</td>
+<td class="cbr">12&#183;4</td>
+<td class="c">18&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">5&#183;64</td>
+<td class="cbr">16&#183;6</td>
+<td class="cbr">14&#183;8</td>
+<td class="cblbr">3</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">5&#183;25</td>
+<td class="cbr">20&#183;4</td>
+<td class="c">19&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">3</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">7&#183;83</td>
+<td class="cbr">21&#183;0</td>
+<td class="cbr">13&#183;4</td>
+<td class="cblbr">3</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">7&#183;13</td>
+<td class="cbr">24&#183;0</td>
+<td class="c">16&#183;8</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">4&#183;26</td>
+<td class="cbr">14&#183;0</td>
+<td class="cbr">16&#183;4</td>
+<td class="cblbr">4</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">3&#183;67</td>
+<td class="cbr">13&#183;0</td>
+<td class="c">17&#183;7</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">6&#183;74</td>
+<td class="cbr">21&#183;2</td>
+<td class="cbr">15&#183;6</td>
+<td class="cblbr">4</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">5&#183;55</td>
+<td class="cbr">20&#183;6</td>
+<td class="c">18&#183;6</td>
+</tr>
+
+<tr>
+<td class="cbr">4</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">7&#183;81</td>
+<td class="cbr">24&#183;0</td>
+<td class="cbr">15&#183;3</td>
+<td class=cblbr>4</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">7&#183;13</td>
+<td class="cbr">26&#183;0</td>
+<td class="c">18&#183;2</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">4&#183;76</td>
+<td class="cbr">15&#183;4</td>
+<td class="cbr">16&#183;2</td>
+<td class="cblbr">5</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">3&#183;86</td>
+<td class="cbr">14&#183;6</td>
+<td class="c">18&#183;9</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">6&#183;93</td>
+<td class="cbr">20&#183;4</td>
+<td class="cbr">14&#183;7</td>
+<td class="cblbr">5</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">5&#183;85</td>
+<td class="cbr">22&#183;6</td>
+<td class="c">19&#183;4</td>
+</tr>
+
+<tr>
+<td class="cbr">5</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">8&#183;72</td>
+<td class="cbr">25&#183;8</td>
+<td class="cbr">14&#183;7</td>
+<td class="cblbr">5</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">7&#183;53</td>
+<td class="cbr">28&#183;0</td>
+<td class="c">18&#183;6</td>
+</tr>
+
+<tr>
+<td class="cbr">6</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">6&#183;04</td>
+<td class="cbr">20&#183;0</td>
+<td class="cbr">16&#183;5</td>
+<td class="cblbr">6</td>
+<td class="cbr">0&#183;5</td>
+<td class="cbr">4&#183;86</td>
+<td class="cbr">19&#183;4</td>
+<td class="c">20&#183;0</td>
+</tr>
+
+<tr>
+<td class="cbr">6</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">8&#183;82</td>
+<td class="cbr">29&#183;4</td>
+<td class="cbr">16&#183;6</td>
+<td class="cblbr">6</td>
+<td class="cbr">1&#183;0</td>
+<td class="cbr">7&#183;53</td>
+<td class="cbr">31&#183;6</td>
+<td class="c">21&#183;0</td>
+</tr>
+
+<tr>
+<td class="cbr">6</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">11&#183;10</td>
+<td class="cbr">31&#183;6</td>
+<td class="cbr">14&#183;2</td>
+<td class="cblbr">6</td>
+<td class="cbr">1&#183;5</td>
+<td class="cbr">9&#183;60</td>
+<td class="cbr">39&#183;0</td>
+<td class="c">20&#183;4</td>
+</tr>
+</table>
+
+<p>
+The quality of the gas operated upon averaged about 19 candles when
+tested with the Standard London Argand Burner.
+</p>
+
+<p>
+In a former part of this treatise it was remarked that the flames
+produced by the modern representatives<a href="#note10" name="noteref10">
+<small>[10]</small></a> of the batswing and fishtail
+burners have lost the original resemblance to the objects whence the
+names of those burners were derived; and that the two flames have
+gradually approached each other in shape, until, in their latest
+developments, they are practically identical. We have seen how that,
+by the invention of the hollow-top, a burner is obtained apparently,
+to all outward appearance, the same as the batswing, yet giving a
+greatly improved form of flame. We have now to learn how the fishtail,
+or union-jet burner has been modified so as to yield a flame closely
+agreeing with that produced by the improved slit burner.
+</p>
+
+
+<p>
+<span class="sidenote"> How the union-jet burner has been improved.</span>
+As first constructed, the union-jet burner gave a tall, narrow flame;
+its extremity being forked and jagged like the tail of a fish. Besides
+being unsightly, this form of flame was ill-adapted to develop, to
+anything like its full extent, the illuminating power of the gas. In
+order to obtain the best results, as regards illuminating power, the
+heat-intensity of the flame must be very high, so as to bring up the
+temperature of the particles of carbon liberated in the flame to the
+necessary degree of incandescence. To this end there must be
+concentration of the flame, in order to utilize to the full the heat
+of combustion. With the tall flame produced by the original union-jet
+burner there was too much exposure to the atmosphere for the flame to
+attain to the requisite intensity of heat; as well as considerable
+liability of the gas being brought too early into intimate contact
+with air, and so oxidized, or fully consumed, before its carbon had
+been raised to the temperature necessary to enable it to give out
+light. With the burner in its improved form the height of the flame is
+much curtailed, while it is broadened, and made more even and compact.
+This alteration has been chiefly brought about by two modifications in
+the construction of the burner-tip&#8212;first, by hollowing out its flat
+upper surface; and, second, by altering the angle at which the two
+streams of gas emerge from the burner. By scooping out the central
+portion of the flat top of the burner, so as to form a hollow or
+depression where the gas emerges, the flat sheet of flame which is
+formed when the two streams of gas impinge upon each other obtains a
+broader base, and at the same time is preserved from drawing air into
+its midst. But the chief share of the improvement is due to the
+alteration in the angle formed by the two channels in the burner-tip.
+It will be readily apparent that the more obtuse this angle&#8212;that is,
+the nearer the two streams of gas are to impinging against each other
+in a horizontal line&#8212;the more will the flame tend to spread out, or
+the lower the pressure required to obtain any desired spread of flame.
+It is by taking advantage of this circumstance that Mr. Bray has been
+enabled to improve the union-jet burner. Twenty years ago this burner
+was usually made with the two channels in the burner-tip placed at an
+angle of about 60&#176;. In Bray's "regulator" burner, introduced in 1869,
+they were placed at an angle of 90&#176;; with the result of obtaining a
+more satisfactory flame, both as regards its appearance and
+illuminating power. In the "special" burner, which was not brought out
+till 1876, the angle is increased to 120&#176;; thus enabling the necessary
+spread of flame to be obtained with the gas issuing at a low pressure.
+Another minor improvement in the latter burner consists in making the
+holes in the burner-tip elliptical instead of circular.
+</p>
+
+
+
+
+<a name="44">&nbsp;</a>
+<p class="chapter">
+CHAPTER III.
+</p>
+
+<p class="ctr">
+<img src="images/t3.jpg" alt="Argand Burners.&quot;" width="276" height="54"></p>
+
+
+
+<p>
+<span class="sidenote"> The premier gas-burner.</span>
+The premier position among gas-burners undoubtedly belongs to the
+Argand; and it is from no unwillingness to recognize its claims, much
+less from ignorance of its merits, that I have left the consideration
+of this burner until now. It occupies this honourable position as much
+by virtue of the importance it has acquired through being accepted by
+Parliament as the test burner, and the peculiar relation in which it
+consequently stands to other burners, as for any marked superiority in
+operation. For while, in general, the Argand gives superior results to
+other burners, this is not always the case. There are circumstances
+and conditions to which the Argand is quite inapplicable, and where a
+simpler and less pretentious burner will give excellent results.
+Indeed, some of the simple flat-flame burners which we have had under
+notice have now been brought to such a stage of perfection, that, when
+intelligently used, they not unsuccessfully rival the Argand. But it
+has been in the direction of demonstrating the illuminating power
+which it was possible to obtain from gas, and stimulating to the
+attainment, by other and simpler burners, of the same level of
+excellence, that the influence of the Argand has been most beneficial.
+For, by reason of its peculiar construction, and more especially its
+mode of obtaining the air necessary for combustion, the Argand lends
+itself, more readily than any other burner, to the work of
+investigating and experimenting upon the conditions necessary for
+economical combustion, and the development of the highest illuminating
+power from the gas consumed. In this burner, the air supply to the
+flame is under complete control; and thus one of the chief elements of
+uncertainty and difficulty which are experienced in dealing with other
+burners is eliminated. The delivery of gas to different parts of the
+flame is also more susceptible of variation; and the results of such
+variation more fully exposed to observation. The consequence has been
+that the most remarkable advances in developing improved illuminating
+power from coal gas have been made with this burner. But after the
+possibility of obtaining an improved duty from the gas has been
+demonstrated by means of the Argand, and the conditions necessary for
+its attainment determined, equally good results have been achieved by
+other burners.
+</p>
+
+<div class="figcenter"><img src="images/013.jpg" alt="Plan of Glass-Holder and Burner Top" width="335" height="254"></div>
+<p class="caption"><span class="sc">Plan of Glass-Holder and Burner Top.</span>
+&#8212;<span class="sc">Section of Burner.</span>
+<br><span class="sc">Fig. 13.&#8212;Argand Burner.</span>
+</p>
+
+<p>
+In thus showing the benefits to be derived from a more scientific mode
+of combustion, and leading the way to the fuller attainment, by other
+burners, of the illuminating power obtainable from the gas, the Argand
+burner has acted as a pioneer in the development of gas lighting. For,
+on account of its complexity, and its delicacy of construction, this
+burner has never been, nor, indeed, can ever hope to be generally
+employed. Besides the inconvenience and expense entailed by the
+cleaning and renewal, when broken, of the glass chimney which is
+indispensable to this burner, its very perfection as a burner
+precludes its being adopted under the conditions which appertain to
+the great majority of situations in which gaslight is required. For
+while, under the particular conditions as to pressure of gas, &#38;c., for
+which it has been constructed, the Argand may give results surpassing
+any other burner, a very slight divergence from these conditions is
+productive of far more damaging results to the illuminating power of
+the flame than is the case with other and less efficient burners. The
+cause of this seeming anomaly will be apparent when we come to
+consider in detail the construction of the Argand, and the conditions
+which must be observed to ensure its satisfactory operation. For the
+present it will suffice merely to make mention of what appear to be
+well-established facts&#8212;viz., that the most perfect burners are the
+least adapted for use under uncertain and varying conditions; and that
+in proportion to the efficiency of a burner, under the conditions for
+which it has been constructed, is the injury to the illuminating power
+of its flame which is experienced when these conditions are departed
+from.
+</p>
+
+
+<p>
+<span class="sidenote"> What is an Argand burner?</span>
+Resolved into its simplest form, the Argand burner may be said to
+consist of a hollow ring of metal, or other suitable material,
+provided with the necessary tubes or connections for communicating
+between its interior and the gas supply, and perforated on its upper
+surface with a number of holes for the emission of the gas. Through
+these holes the gas issues in a series of jets, which immediately
+coalesce to form one cylindrical sheet of flame. The burner is
+surmounted, and the flame enclosed, by a glass chimney, which is
+supported on a light gallery connected with the burner; the chimney
+serving the double purpose of shielding the flame from draughts, or
+currents of air (thus enabling the gas to burn uniformly and
+steadily), and of drawing upon the surface of the flame the supply of
+air necessary for its proper and complete combustion. For in the
+Argand the air supply is produced under conditions totally different
+from those which govern its production in all the other burners we
+have had under consideration. In flat-flame burners, the quantity of
+air supplied to the flame is determined by the pressure of the gas;
+or, in other words, the velocity with which it issues from the burner.
+In Argand burners, on the contrary, the air supply is obtained quite
+independently of the pressure at which the gas issues; and the
+conditions most effective for the economical combustion of the gas,
+and the development from it of the highest illuminating power
+attainable, are only secured when the pressure of gas is reduced to a
+minimum.
+</p>
+
+<p>
+It has been shown, in speaking of flat-flame burners, how the
+illuminating power of the flames yielded by such burners is
+injuriously affected by an excess of pressure in the gas, as it issues
+into the atmosphere, causing a too great intermingling of gas and air.
+With such burners, however, some degree of pressure is needed, in
+order, by bringing the flame into contact with sufficient of the
+oxygen of the air, to promote the requisite intensity of combustion;
+whereas with the Argand the draught that is produced through the
+agency of the glass chimney enables the necessary supply of air to be
+obtained for the support of the flame without adventitious aid from
+the pressure of the gas. Consequently, one of the chief objects to be
+aimed at in the construction of the latter burner is to so reduce the
+pressure of the gas within the burner that it may issue with little or
+no greater velocity than that due to its own specific lightness. In
+some of the best Argands this object is attained very successfully;
+and the ingenious devices which have been made use of to gain this end
+will be duly described in the sequel. But, in addition to causing the
+gas to issue from the burner at the minimum of pressure, it must be
+delivered evenly and equally at all parts of the ring of holes; so
+that there shall not be an excess of gas supplied to one portion of
+the flame, and an insufficiency to others. Then the area of the
+opening in the centre of the ring, through which the air supply is
+obtained to the inner surface of the flame, as well as the length and
+diameter of the glass chimney, must be so proportioned that the exact
+quantity of air needed to enable the flame to yield its maximum
+results shall be drawn upon it. These, and other equally essential
+requirements, have to be taken into consideration, and provided for,
+in constructing an efficient Argand burner. It is no wonder,
+therefore, that the development of the powers of this burner has taken
+up so much time and labour and inventive skill; and the remarkable
+degree of efficiency to which it has now been brought testifies to the
+thought and the accurate knowledge of the principles of combustion
+which have been brought to bear upon it.
+</p>
+
+
+<p>
+It is, however, only within comparatively recent years that its true
+principles of construction have been at all fully recognized, as
+evinced by the burners which have been produced. For a long period,
+<span class="sidenote"> The earliest Argands.</span>
+Argand burners were made upon wholly empirical and arbitrary rules.
+During the early years of gas lighting, the makers of gas apparatus,
+and such persons as professed to have a special knowledge of the
+production and utilization of the new illuminant, appear to have been
+ignorant of even the most obvious of the conditions required for the
+successful working of the burner. In one of the earliest works which
+appeared relating to gas lighting,<a href="#note11" name="noteref11">
+<small>[11]</small></a> we find the Argand burner
+described as consisting of "two concentric tubes closed at the top
+with a ring having small perforations, out of which the gas can issue;
+thus forming small distinct streams of light." According to this
+description, the burner referred to cannot have been an Argand in the
+strictest sense of the word; but, in reality, must have consisted
+chiefly of a series of single jets placed in a circle, and surrounded
+by a glass chimney. But the great improvement in the amount of light
+developed, which resulted from bringing the jets of flame closer
+together, so as to cause them to coalesce and produce one homogeneous
+mass of flame, could not long escape notice; and accordingly we find
+that in "Clegg's Treatise," which appeared twenty-five years later,
+the proper disposition of the holes in the ring, necessary for the
+successful operation of the burner, is clearly recognized. In this
+work, speaking of the Argand burner, it is remarked (p. 193) that "the
+distance between the holes in the drilled ring should be so much that
+the jet of gas issuing from each shall, when ignited, just unite with
+its neighbour."
+</p>
+
+<p>
+Before a really efficient burner could be produced, there were,
+however, to be successfully encountered other problems, the precise
+nature of which was not so clearly apparent as that of the one above
+referred to; otherwise their solution would not have been so long
+delayed. Of these, the most important, and at the same time the most
+difficult, were two&#8212;namely, the right adjustment of the air supply,
+and the most advantageous pressure at which to consume the gas. In the
+earliest Argands, not the slightest provision was made for diminishing
+the pressure of the gas before it was consumed. It was thought that
+everything had been accomplished that was necessary if the holes for
+its emission were sufficiently minute to allow of no more than the
+required quantity of gas passing through them at the extreme pressure
+at which it was supplied to the burner. The consequence was that the
+gas, issuing from the burner at a very high velocity, became so
+intermingled with air before it was consumed, that its flame was
+excessively cooled; and only a small fraction of the illuminating
+power available was developed. Then as to the air supply. In nearly
+every burner produced prior to Mr. W. Sugg's invention of the "London"
+Argand in 1868, this was greatly in excess of the requirements; nor is
+it to be wondered at. Had the supply of air been delicately adjusted,
+while yet there was no provision for diminishing the pressure of gas
+at the burner, the flame would have been liable to smoke on any sudden
+increase in the pressure of gas in the mains; and the annoyance and
+inconvenience occasioned by a smoking flame were greater drawbacks
+than the loss of light experienced through having the air supply
+greatly in excess. Thus, although during this period there were many
+so-called "improved" burners brought into notice, in none of them were
+these two cardinal requirements in the production of an efficient
+burner clearly recognized and seriously grappled with; and,
+consequently, the high level of excellence to which the Argand is
+capable of being brought was not attained.
+</p>
+
+<a name="48">&nbsp;</a>
+<p class="subhead">
+SUGG'S ARGANDS.
+</p>
+
+<span class="sidenote"> The 'London' Argand.</span>
+
+<p>
+The invention by Mr. W. Sugg, in 1868, of the famous "London" Argand
+constitutes an important epoch in the history of gas lighting. Prior
+to that time, the construction of this class of burners had been
+carried out in a wholly empirical manner; and such improvements as had
+been effected must be looked upon as being rather the fortuitous
+issues of hap-hazard endeavours, than as resulting from the
+acquirement of clearer views as to the conditions to be complied with
+in order to ensure the successful operation of the burners. The
+invention of the "London" Argand was the first earnest attempt to
+abandon the former chance methods, and to proceed upon more scientific
+lines. Its construction shows that its inventor possessed a thorough
+acquaintance with the principles of combustion; while, in many
+particulars, it exhibits an intelligent discernment, and a successful
+application of the precise means required to attain a desired end. In
+this burner, the extreme importance of causing the gas to issue at a
+low pressure is for the first time clearly recognized; and the manner
+in which this object is so successfully attained is as simple as it is
+ingenious. At the entrance to the burner the gas is divided among
+three narrow tubes, the combined capacity of which is much smaller
+than that of the pipe supplying the burner. Through these tubes the
+gas is conducted into a concentric cylindrical chamber (forming the
+main body of the burner), where its rapid flow is checked; the
+current, or swirl, which it may have acquired, is subdued; and the gas
+comes to a state of comparative rest before it issues into the
+atmosphere and is consumed. The top rim of this concentric cylinder is
+pierced with 24 holes, the aggregate area of which is considerably
+greater than that of the three supply-tubes; thus ensuring that the
+gas shall be delivered at a much lower pressure than that at which it
+enters the burner. By dividing the gas into three streams, which enter
+the cylindrical chamber at equidistant points in its circumference,
+the supply is equally distributed throughout the entire ring of holes;
+and a flame of even and regular shape is the result.
+</p>
+
+<p>
+The arrangement by which, in this burner, the air supply is obtained
+and regulated is as noteworthy as are the means adopted for
+controlling the pressure of the gas. The opening within the circular
+ring of holes is much smaller than in previous Argands; thereby
+proportionately reducing the quantity of air supplied to the inner
+surface of the flame. The space between the cylindrical body of the
+burner and the glass chimney is occupied by a truncated cone of thin
+metal, the upper edge of which is on a level with, and reaches to
+within a very short distance of the rim of the burner; while its base
+rests upon the gallery supporting the chimney. By means of this cone,
+all the air entering between the burner and the chimney is directed
+upon the immediate surface of the flame; thereby promoting intensity
+of combustion, and a higher illuminating power of the flame. Then the
+chimney itself is of such dimensions that, with the quantity of gas
+for which the burner has been constructed, just sufficient air is
+drawn upon the flame to completely consume the gas by the time the top
+of the chimney is reached; a flame of such length as to nearly reach
+to the top of the chimney, without smoking, being the most effective
+and economical for the quantity of gas consumed.
+</p>
+
+<div class="figcenter"><img src="images/014.jpg" alt="Sugg's &quot;London&quot; Argand" width="300" height="364"></div>
+<p class="caption"><span class="sc">Fig. 14.&#8212;Sugg's "London" Argand.</span>
+<br>(<i>Full Size.</i>)
+</p>
+
+<p>
+Another matter which tended not a little to enhance the results
+yielded by this burner was an alteration in the material of which the
+body of the burner was constructed. In previous Argands, this had, in
+almost every instance, been metal; whereas in the "London" burner
+steatite was employed. How the illuminating power of the flame is
+affected by the material of which the burner is constructed has been
+gone into so fully before (in relation to flat-flame burners), that it
+is unnecessary to dwell upon the matter here; only remarking that as
+in Argands the contact surface between the burner and the flame is
+relatively so much greater than in flat-flame burners, the cooling of
+the flame due to this cause is proportionately increased.
+</p>
+
+
+
+<p>
+So great was the improvement effected by this burner in the
+illuminating power developed from the gas consumed, so obvious its
+superiority to every previous Argand, that it was immediately adopted
+by the Metropolitan Gas Referees as the standard burner for testing
+ordinary coal gas within the area of their jurisdiction; and from that
+time down to the present it has continued to be prescribed in Acts of
+Parliament as the burner to be employed in testing ordinary coal gas,
+not only in the Metropolis, but generally throughout the United
+<span class="sidenote"> The standard test burner.</span>
+Kingdom. But although, as the standard test-burner, the original
+"London" Argand can still be obtained, it has been far surpassed, in
+the results yielded, by a new series of Argands, in which the same
+ingenious inventor has still further applied the principles first put
+into practice in the former burner. In this newer series of burners,
+the details of construction before adopted are modified in two or
+three particulars; but without departing from the general principles
+embodied in the arrangement of the earlier burner. Thus the holes in
+the ring are considerably larger, while the three supply-tubes remain
+of exactly the same capacity as before; by which means the gas is
+delivered at a much lower pressure. As the increased size of holes
+necessitates that the cylindrical body of the burner should be of
+enlarged diameter, the opening in the centre becomes of greater area
+<span class="sidenote"> The improved "London" Argand.</span>
+than before. Were it to remain so, it would permit too large a
+quantity of air to be drawn upon the inner surface of the flame; to
+obviate which result a metal spike rises in the centre, reducing the
+area of the opening, and proportionately diminishing the quantity of
+air which would otherwise be admitted at this part of the burner. The
+arrangement for regulating the air supply to the outer surface of the
+flame is likewise modified, but in a different direction. The upper
+edge of the cone is brought nearer to the rim of the burner, and
+slightly curved, so as to direct the air more completely upon the
+flame; while the base of the cone, instead of extending to the glass
+chimney in an unbroken surface, is pierced by a number of holes, which
+admit air between the cone and the chimney. The action of this third
+current of air is to keep the chimney cool, and to steady the flame;
+and, in addition, it may be that it provides a supply of air to
+support and intensify combustion at the upper extremity of the flame.
+The combined effect of these alterations is to cause the burner to
+develop from 7 to 12 per cent. more light from the gas consumed, than
+is yielded by the original "London" Argand.
+</p>
+
+
+<p>
+<span class="sidenote"> Silber's Argand burner.</span>
+The Silber Argand, which is a remarkably efficient burner, in the main
+features of its construction is very closely related to Mr. Sugg's
+later Argands just described. The air is directed on to the outer
+surface of the flame, as in those burners, by a curved deflector, of
+which the upper edge is, however, at a higher level than in Mr. Sugg's
+burners. Air is also admitted between the deflector and the glass
+chimney. The most striking divergence in its construction from that of
+Mr. Sugg's burners is contained within the opening in the centre of
+the burner. Instead of a solid metal spike, there is a brass tube,
+through which, as well as between its circumference and the
+cylindrical body of the burner, air can enter to feed the inner
+surface of the flame. In addition to promoting the steadiness of the
+flame, it would appear that the air entering through this inner tube
+supports the combustion of the gas at the tail of the flame. The
+arrangements for diminishing the pressure of the gas within the
+burner, and for ensuring its equable distribution to all parts of the
+ring of holes, though quite different, seem to be scarcely less
+complete than those employed in the "London" burner. From the nipple
+which connects the burner to the gas supply, the gas enters (by four
+minute perforations) into a horizontal chamber, where its velocity is
+checked, and whence it is conveyed into the cylindrical chamber
+forming the main body of the burner. The very satisfactory
+performances of the burner (which are in advance of those of the
+standard Argand) sufficiently attest the correctness of its
+construction.
+</p>
+
+
+<p>
+<span class="sidenote"> Multiple Argands.</span>
+For consuming large quantities of gas, double or treble Argands are
+constructed. These consist, in effect, of two or three Argand burners
+placed concentrically to each other within one chimney. Mr. Sugg has
+produced a series of burners of this class, designed to pass
+quantities of gas ranging from 15 to 55 cubic feet per hour; and, in
+some instances, exceeding even the latter figure. These burners, with
+ordinary (16-candle) coal gas, give a light equal to 4 candles per
+cubic foot of gas consumed; which is a considerably better result than
+is afforded by the standard burner. The cause of their yielding
+results so superior to the ordinary Argand is found in the
+circumstance that their flames present a much smaller surface area to
+the cooling action of the air, in proportion to the quantity of gas
+consumed. The arrangement of these burners differs from that of the
+improved single Argands, which have been described, only in that there
+are two or more steatite cylinders, each fed by its own supply-tubes,
+and having its own distinct ring of holes; while the space between the
+cylinders is so proportioned as to admit no more than the quantity of
+air required to produce the necessary intensity of combustion.
+</p>
+
+<div class="figcenter"><img src="images/015.jpg" alt="The Douglass Argand" width="382" height="410"></div>
+<p class="caption"><span class="sc">Fig. 15.&#8212;The Douglass Argand.</span>
+<br>(<i>A A, Focal Plane, or Belt of Strongest Light.</i>)
+</p>
+
+<a name="52">&nbsp;</a>
+<p class="subhead">
+THE DOUGLASS BURNER.
+</p>
+
+<p>
+The multiple or concentric Argand invented by Mr. (now Sir) J. N.
+Douglass, the Engineer to the Trinity House, may be mentioned here.
+This burner is of the type of those last noticed, but possesses
+certain peculiar features which give it a distinct claim to novelty.
+As will be seen by the accompanying illustration, the concentric
+cylinders of which the burner is composed terminate at different
+heights; their tops forming a regular gradation of steps, of which the
+innermost is the highest. These cylinders are of considerable depth,
+permitting the gas and air to be heated by contact with their surfaces
+before the point of ignition is reached. The essential feature of the
+invention, however, is a series of deflectors of peculiar shape,
+which, in addition to directing air on to the surfaces of the flames,
+are so formed "as to force the outer flame or flames on to the inner
+flame or flames in the manner illustrated." By this means the flames
+are concentrated and united into one, and combustion is quickened;
+and, a greater intensity of heat being thus attained, the illuminating
+power is much augmented. When this burner was first brought into
+notice, in 1881, high hopes were entertained as to its future. The
+results which it was said to afford, being far in advance of anything
+previously obtained from a simple Argand, seemed to promise for the
+burner a speedy and unequivocal success. At the North-East Coast
+Marine Exhibition, held in 1882, a burner with ten rings was
+exhibited, which was reported to develop, from 16-candle gas, 6
+candles per cubic foot&#8212;a truly remarkable result to be given by so
+simple a burner. But, notwithstanding its apparently successful
+introduction, the burner has made little or no headway in the
+direction of its practical application. Indeed, it may almost be said
+to have faded altogether out of public view. This would seem to imply
+that there are difficulties in the way of its successful working, when
+brought under ordinary conditions, which were not foreseen at the time
+of its invention.
+</p>
+
+
+
+
+<a name="55">&nbsp;</a>
+<p class="chapter">
+CHAPTER IV.
+</p>
+
+<p class="ctr">
+<img src="images/t4.jpg" alt="Governor-Burners." width="317" height="54">
+</p>
+
+
+<p>
+Throughout this treatise, much has been said of the relation which the
+pressure of gas, at the point of its delivery from the burner, bears
+to the illuminating power of the flame yielded&#8212;sufficient to show
+that the maintenance of a low and equable pressure in the gas supply
+is one of the conditions most imperative to be observed for the
+attainment of economy in combustion. Ordinarily, however, this
+condition does not obtain at the consumers' burners. The exigencies of
+distribution require that, in order to maintain a sufficient supply
+wherever gas is needed, a much higher pressure should be kept in the
+mains than is requisite for developing, at the burner, the best
+<span class="sidenote"> Effects of excessive pressure with Argand and
+flat-flame burners.</span>
+results from the gas consumed. Moreover, the pressure at any one point
+is subject to continual fluctuations from the variations in the
+consumption of gas going on in the neighbourhood. For instance, where
+a number of burners are in operation in a house, consuming about the
+exact quantities of gas for which they have been constructed, when
+part of them are shut off the gas supply to the remainder is in excess
+of what is required; and, consequently, the burners do not develop the
+same proportion of light from the gas consumed as formerly. Where a
+large consumption of gas is suddenly discontinued (as in the business
+parts of a town, when the shops and warehouses are closed), the
+increase of pressure that is experienced at the burners which remain
+in operation is very manifest. The effect of this increase in the
+pressure of the gas supply is seen in different directions in Argand
+and flat-flame burners. In the former, it causes the flame to smoke,
+by permitting more gas to pass through the burner than can be properly
+consumed; in the latter, by cooling the flame below the temperature
+required for effective combustion, it reduces, in proportion to the
+extent to which it is higher than the original pressure, the
+illuminating power developed per cubic foot of gas consumed.
+</p>
+
+
+<p>
+<span class="sidenote"> The gas regulator.</span>
+Seeing that economy in combustion can only be attained under the
+conditions of an equable pressure, it becomes necessary to subdue the
+fluctuations above referred to, or at least to prevent their reaching
+the burner. To this end the regulator, or governor, is employed. In
+this instrument, a bell dipping into, and sealed in liquid&#8212;or else a
+flexible leather diaphragm&#8212;is actuated by the pressure of the
+entering gas, and so connected with a valve as to reduce the area of
+the opening which permits gas to enter the instrument in proportion to
+the pressure of gas at the inlet; by which means an equable pressure
+is maintained at the outlet, no matter what the quantity of gas which
+is being consumed, or how the pressure may vary in the inlet-pipe. By
+the aid of a governor, fixed on the service-pipe at the entrance to a
+building, the pressure of gas at the various burners is rendered
+fairly uniform; yet, even then, perfect equality of pressure is not
+obtained. The slight friction which the gas experiences in flowing
+through the pipes causes the burners to be supplied at somewhat lower
+pressures, the farther they are removed from the burner. And, again,
+owing to its low specific gravity, gas tends to gain in pressure with
+an increased elevation; each rise of 10 feet adding about 1-10th of an
+inch to its pressure. From this cause a higher pressure is experienced
+in the upper than in the lower rooms of a building. This peculiarity
+was observed at an early period in the history of gas lighting; as
+Clegg mentions that, in cotton-mills, check-taps were employed to
+regulate the pressure of gas at each floor.<a href="#note12" name="noteref12">
+<small>[12]</small></a> In order, therefore, to
+obtain the desired regularity of pressure in the gas supply, governors
+must be employed for each storey; or, what is better still, each
+burner must have its own separate governor. And this brings us back to
+the subject with which we are more closely concerned.
+</p>
+
+<p>
+The governor-burner, as its name implies, consists of a governor, as
+described above (but, of course, on a smaller scale) combined with a
+gas-burner; the governor being adjusted so as, whatever excess of
+pressure there may be in the gas-supply pipes, to permit only the
+quantity of gas to pass which the burner is intended to consume.
+Obviously, the principle herein contained is capable of receiving
+numerous applications. It can be, and is applied with equal success to
+Argand and flat-flame burners; while the modifications which obtain in
+the manner of constructing the regulating portion of the apparatus are
+almost as numerous and as varied as are the burners themselves. As the
+main features exhibited by one are common to all, it is unnecessary to
+go into the details of their several constructions. It will suffice to
+take two or three of the most successful, or the best known, as
+representatives of the whole.
+</p>
+
+
+<p>
+<span class="sidenote"> Giroud's Rheometer.</span>
+Among the first in order of time&#8212;and still retaining no unworthy
+position in order of merit&#8212;is the "rheometer," or "flow-measurer," of
+M. Giroud. In this instrument a light metal bell is sealed in
+glycerine contained in a cylindrical case; the bottom of this latter
+containing the inlet-pipe, screwed for connecting to the ordinary
+fittings, while from the centre of its cover rises a tube leading to
+the burner. The bell is pierced by a small hole for the passage of the
+gas, and is surmounted by a cone-shaped projection, which constitutes
+the valve of the instrument. As the pressure of the entering gas lifts
+the bell, it causes this cone-valve to enter the mouth of the tube
+leading to the burner; reducing the area of the opening in proportion
+to the pressure of gas acting upon the under side of the bell, and so
+permitting only the required quantity of gas to pass to the burner. It
+might be thought that the presence of liquid would constitute an
+objection to the use of the instrument; but, as glycerine does not
+evaporate, when once the instrument is fixed and properly adjusted, it
+needs no further attention. With an excessive initial pressure, there
+is, however, a liability of the gas to bubble through the sealing
+liquid, and so destroy the efficiency of the instrument; but this
+might be obviated by increasing the depth of the bell, and so giving
+it a greater seal. The instrument is very reliable for the purpose
+which it is intended to fulfil; delivering, through a considerable
+range of pressure beyond that required to raise the bell, the exact
+quantity of gas for which it has been adjusted. It may be added that
+the rheometer has an advantage over many instruments of its class, in
+that it presents so little obstruction to the downward rays of the
+flame.
+</p>
+
+<div class="figcenter"><img src="images/021.jpg" alt="Giroud's Rheometer" width="325" height="300"></div>
+<p class="caption"><span class="sc">Fig. 16.&#8212;Giroud's Rheometer.</span>
+</p>
+
+
+<p>
+<span class="sidenote"> Sugg's Christiania governor-burner.</span>
+Mr. William Sugg, in his regulator or governor, adopts an entirely
+different arrangement to the foregoing. The valve is placed at the
+inlet of the governor; and not at its outlet, as in the instrument
+just described. Instead of a metal bell, a diaphragm of thin and very
+flexible leather is employed, which is raised by the pressure of the
+entering gas, and, in turn, actuates the valve; closing the entrance
+to the governor in proportion to the pressure of gas acting upon it.
+The orifice communicating between the under and the upper side of the
+leather diaphragm is controlled by a screw, whereby the quantity of
+gas delivered to the burner can be regulated according to
+requirements; but when once it has been adjusted to give any desired
+pressure of gas at the burner, this pressure will be strictly
+maintained, no matter with what excess of pressure (within reasonable
+limits) the gas may be supplied to the instrument. The improved
+"London" Argands produced by Mr. Sugg (the details of the construction
+of which have been already described) are too delicately adjusted to
+be applied with advantage directly to the ordinary consumer's
+gas-fittings, or wherever any variation in the pressure of the gas
+supply is likely to be experienced. However, with the addition to them
+of the above governor, their use becomes as easy and simple as that of
+other burners; and thus the gas consumer is enabled to obtain the
+benefit of the most improved apparatus without being called upon to
+exercise the constant care and attention which, without the aid of the
+governor, would be necessitated. Besides being applied to Argands,
+this governor is successfully applied by its inventor to his
+flat-flame burners. In conjunction with a simple steatite burner of
+the latter class, it has received a very extended application, under
+the name of the Christiania governor-burner.
+</p>
+
+
+<p>
+Recently, however, a new type of governor, for application to burners,
+has been brought out by the same manufacturer, the construction of
+which is very different to that of the instrument referred to above;
+and as it is somewhat simpler in its details, and withal appears to be
+cheaper in construction, it seems destined to supersede the former
+instrument. In this new governor, instead of a leather diaphragm,
+there is a bell (or float) of steatite, which is free to move, in the
+manner of a piston, within an inner cylindrical chamber contained
+within the outer case of the instrument. Attached to the centre of the
+<span class="sidenote"> Sugg's Steatite-float governor-burner.</span>
+float, and on its upper surface, is a tube sliding within another tube
+of somewhat larger area; the latter forming a continuation of the
+inner cylindrical chamber. The smaller tube is open at both ends, and
+thus communicates from below to above the float; the outer tube is
+closed at the top, but has an orifice in its side. The action of the
+instrument is as follows:&#8212;The gas, entering below the float, passes
+through the inner tube to the upper part of the cylindrical chamber,
+and thence, through the orifice in the outer tube, to the burner. As
+the pressure of the entering gas exceeds that required to overcome the
+weight of the float, the latter is raised; the tube which is attached
+to it being propelled farther into the outer tube in which it slides,
+and, in so doing, partially closes the orifice in the side of the
+latter. In this way, according to the pressure of the gas acting upon
+the under side of the float, the area of the opening through which it
+must flow to get to the burner is reduced; and so the quantity of gas
+which issues from the burner remains the same under all pressures
+above that required to actuate the float. The instrument appears to be
+as reliable as it is simple, and to contain few parts calculated to
+get out of order; but, of course, whether or not it will retain its
+good qualities after long-continued use can only be proved by
+experience.
+</p>
+
+<div class="figcenter"><img src="images/017.jpg" alt="Sugg's Steatite-Float Governor" width="183" height="289"></div>
+<p class="caption"><span class="sc">Fig. 17.&#8212;Sugg's Steatite-Float Governor.</span>
+</p>
+
+
+
+<p>
+<span class="sidenote"> Peebles's needle governor-burner.</span>
+Another instrument of this class&#8212;the last which I shall notice&#8212;is
+Peebles's needle governor-burner. For simplicity combined with
+remarkable efficiency, it is undoubtedly ahead of all its compeers.
+Somewhat similar in principle to Giroud's rheometer, it differs from
+that instrument in many of the details of its construction; and while
+dispensing with the use of liquid, maintains equal efficiency in
+operation. It was described as follows by Dr. W. Wallace, in a lecture
+on "Gas Illumination," delivered before the Society of Arts in
+January, 1879:<a href="#note13" name="noteref13">
+<small>[13]</small></a>&#8212;"In a little cylinder stands a so-called needle, on
+the point of which rests a flanged cone of exceedingly thin metal. At
+one side of the cylinder there is a small tube leading away the gas,
+and the orifice of which is influenced in area by the action of the
+cone. The instrument, by means of a screw leading into the side tube,
+can be made to deliver any desired number of cubic feet, which it does
+with surprising accuracy, provided that the pressure of the gas is not
+<span class="sidenote"> Efficiency of the needle governor-burner.</span>
+less than 6-10ths of an inch." As to the efficiency of the instrument,
+Dr. Wallace proceeded to state:&#8212;"In trials that I have made, I have
+not found the variations of volume at different pressures to exceed 1
+per cent." For situations where this extreme nicety of operation is
+not absolutely essential, or where the rate of consumption is to be
+invariable, the instrument is constructed in a somewhat modified and
+simpler form. The small tube on the side of the instrument is
+dispensed with, and the gas permitted to pass through perforations in
+the lower part of the cone. With this alteration there is a nearer
+approach to the construction of the rheometer; but, as in that
+instrument, there is no provision for altering the rate of consumption
+to suit different circumstances.
+</p>
+
+<div class="figcenter"><img src="images/018.jpg" alt="Peebles's Needle Governor" width="142" height="288"></div>
+<p class="caption"><span class="sc">Fig. 18.&#8212;Peebles's Needle Governor.</span>
+</p>
+
+
+
+
+<a name="61">&nbsp;</a>
+<p class="chapter">
+CHAPTER V.
+</p>
+
+<p class="ctr">
+<img src="images/t5.jpg" alt="Regenerative Burners." width="372" height="54">
+</p>
+
+
+<p>
+As was remarked in the introduction to this treatise, recent years
+have witnessed a very considerable advance in the construction of
+gas-burners, and in the amount of light capable of being developed
+from each cubic foot of gas consumed. Undoubtedly the most noticeable
+feature of this advance is the successful application of the
+regenerative, or, as it would be more appropriately designated,
+recuperative system. Briefly stated, this consists in utilizing the
+heat of the products of combustion from the gas flame (which otherwise
+would be dissipated into the atmosphere) to raise the temperature of
+the gas before it is ignited; and, likewise, of the air necessary for
+combustion. The temperature of an illuminating gas flame is usually
+<span class="sidenote"> Temperature of a gas flame.</span>
+estimated to be between 2000&#176; and 2400&#176; Fahr.; and as the products of
+combustion must leave the flame at a temperature little, if at all,
+inferior to the former figure, it must be evident that there is an
+ample margin of heat for employment in this direction. A considerable
+proportion of the large amount of heat conveyed by those products of
+combustion which, under ordinary circumstances, is imparted to the
+surrounding atmosphere&#8212;often elevating its temperature to an
+unnecessary and prejudicial extent&#8212;is, by this method, returned to
+the flame; intensifying the process of combustion, and augmenting, in
+a remarkable degree, the illuminating power developed from the gas
+consumed. Thus the ultimate effect of the operation is to produce a
+concentration of heat in the flame, and the conversion of superfluous
+heat into beneficial light. Within a comparatively recent period, the
+utility of this process was strongly disputed; and it was stoutly
+maintained, by many persons, that as the immediate effect of ignition
+was to cause a temperature of more than 2000&#176; Fahr. to be attained,
+the heating of the gas and air prior to their combustion could produce
+little or no beneficial effect upon the illuminating power of the
+flame. However, the falsity of this view of the case is conclusively
+demonstrated by practical experiment; the remarkably high results
+yielded by burners that have been constructed upon the regenerative
+system sufficiently attesting the correctness of the principles upon
+which they are founded.
+</p>
+
+<p>
+Although, in general, both the gas and air supplies are heated, it is
+chiefly due to the latter that the beneficial effect noticed is
+produced; and this for two reasons. First, because the quantity of air
+is so much greater than the gas it is required to consume; being, at
+the nearest approach to theoretical perfection, fully six times its
+volume. Second, because four-fifths in volume of the air consists of
+inert nitrogen, which does not contribute anything to the heat of the
+flame, but, when applied in its normal, cold condition, abstracts no
+inconsiderable proportion of heat from it. Yet the heating of the gas
+itself is not without very appreciable influence. In an ordinary
+gas flame there is always an area of non-illumination around, and
+extending to a variable distance from the burner head. This is caused
+partly by the conduction of heat from the flame by the burner; but, in
+a greater degree, by the cooling action of the issuing stream of cold
+gas, as is shown by its extending farther from the burner in
+proportion to the pressure or velocity with which the gas issues. The
+prejudicial effect due to the former is obviated to a great extent by
+constructing the burner of steatite, or other non-conducting material.
+To remedy the latter, nothing will avail but the heating of the gas
+supply.
+</p>
+
+
+<p>
+<span class="sidenote"> Effects of heating the gas and air.</span>
+The effect of heating the gas is to enlarge the area of the
+illuminating portion of the flame, and, in a minor degree, to enhance
+the intensity of incandescence to which the carbonaceous particles are
+raised. When the gas issues from the burner at a temperature little
+inferior to the temperature of ignition, the hydrocarbons it contains
+are immediately decomposed; the liberated particles of carbon are
+raised to the temperature of incandescence; and the illuminating area
+of the flame is extended downwards, even to the surface of the burner.
+The heating of the air operates chiefly to produce and maintain a more
+elevated temperature of the flame; and, in this manner, contributes to
+the development of a higher illuminating power from the same area of
+flame. In the case of ordinary gas flames, the cold atmosphere by
+which they are surrounded, by abstracting heat from the flame,
+prevents the most favourable conditions for the development of light
+from being attained. When, however, the air immediately surrounding
+the flame has been previously heated, the particles of carbon (the
+incandescence of which furnishes the desired illuminating power)
+attain to a much more exalted temperature; and, consequently, give out
+a greater degree of light.
+</p>
+
+<p>
+But there is yet another direction in which the prior heating of the
+air supply contributes to the development of improved illuminating
+power. Being heated, its density is lowered; so that in any given
+volume of air there is less weight of oxygen than when cold. The
+consequence is that as less oxygen is presented to a given surface
+area of flame, the separated particles of carbon remain for a longer
+period of time in the incandescent condition before being entirely
+consumed. Thus there are three distinct results produced by heating
+the gas and air before combustion&#8212;namely, first, the particles of
+carbon are liberated earlier in the flame; second, they are raised to
+a more exalted temperature; and, third, they remain for a longer time
+in the incandescent condition. The combined effect of all three is the
+improved illuminating power developed from the gas consumed.
+</p>
+
+
+<div class="figcenter"><img src="images/019.jpg" alt="Bowditch's Regenerative Gas-Burner" width="141" height="328"></div>
+<p class="caption"><span class="sc">Fig. 19.&#8212;Bowditch's Regenerative Gas-Burner.</span>
+</p>
+
+<p>
+So far back as the year 1854, the principle of heating the air supply
+to an Argand burner, by means of waste heat from the flame, was
+partially applied, with some success, by the Rev. W. R. Bowditch,
+<span class="sidenote"> Bowditch's regenerative burner.</span>
+M.A., of Wakefield. Mr. Bowditch's burner, which is shown in the
+accompanying diagram, contained, in addition to the ordinary chimney,
+an outer glass chimney, which extended for some distance below the
+inner one, and was closed at the bottom; so that all the air needed to
+support the combustion of the gas was required to pass down the
+annular space between the chimneys, and in its passage became
+intensely heated by contact with the hot surface of the inner chimney,
+as well as by radiation from the flame itself. This burner contained
+many defects. Amongst others, the inner chimney could not long
+withstand the intense heat to which it was subjected, and, in
+consequence, had to be frequently renewed; the heating of the air was
+not effected solely by the products of combustion, but, perhaps in a
+greater degree, by the abstraction of heat from the flame itself;
+while, at best, this heating was but partial. Yet, these defects
+notwithstanding, the burner showed very clearly the beneficial results
+attending even a partial application of the principle; as, in the
+illuminating power it developed from the gas consumed, a clear gain of
+67 per cent. over the ordinary Argand burner was obtained. Although
+the drawbacks connected with the construction of Mr. Bowditch's burner
+prevented its ever receiving general, or even extensive adoption, its
+simplicity has gained for it the distinction of being freely copied by
+so-called inventors of a later day.
+</p>
+
+
+<p>
+It was left to Herr Friedrich Siemens, of Dresden, to produce a burner
+which, while applying the principle of regenerative heating in the
+most scientific and complete manner, should also be adapted to the
+ordinary conditions of gas lighting. After much experimenting on the
+<span class="sidenote"> Invention of the Siemens regenerative burner.</span>
+subject, a burner embodying the essential features of the regenerative
+system was invented by this gentleman in 1879; and so great was the
+advance which its performances manifested over anything previously
+attained, so wide the prospect of further achievements which was
+opened out, that it may fairly be said to have inaugurated a new era
+in gas illumination. In this burner the products of combustion were
+made to give up a considerable portion of their heat to the gas and
+air, as the latter passed to the point of ignition; the flame itself
+not being called upon to contribute in any degree to this result.
+Although, as was but natural, the first attempts towards the
+construction of such a burner were very crude, and but partially
+successful in their results, the inventor persevered in his endeavours
+to work out his ideas into practical and thoroughly satisfactory
+shape. It was not until after it had gone through many modifications
+that the burner acquired the peculiar form which now distinguishes it,
+and attained to its present stage of perfection. Before proceeding to
+describe an example of the burner as now constructed, it is necessary
+to state that the principles embodied in Herr Siemens's invention are
+equally well adapted&#8212;and, indeed, are applied with equal success&#8212;to
+the construction of flat-flame and Argand burners; but as the
+distinctive features of the invention are common to both classes of
+burners, it will be quite sufficient to describe in detail one of the
+latter type.
+</p>
+
+<p>
+A prominent feature in the appearance of the Siemens burner, as will
+be seen from the annexed illustration, is a large metal chimney, for
+creating a draught to carry away the products of combustion. The
+entrance to this chimney is situated a little above the apex of the
+flame; but there is a branch flue connecting the main chimney with the
+interior of the burner. The body of the burner is of metal, and its
+interior is divided into three concentric chambers. Of these, the
+innermost is open at the top, and is surmounted by a porcelain
+cylinder, which, when the gas is lighted, is surrounded by the flame.
+This chamber is closed at the bottom, but communicates at the side
+with the before-mentioned branch tube, or flue, leading to the main
+chimney. The intermediate chamber communicates, at its lower
+extremity, with the gas supply; and terminates, a short distance from
+the top of the burner, in a number of small metal tubes, which convey
+the gas to the point of ignition. The outer chamber is open both at
+top and bottom, and is for conveying air to support the combustion of
+the gas. In order to promote greater intensity of combustion, there is
+a notched deflector at the summit of the latter chamber, and another
+on the lower part of the porcelain cylinder, which cause the air to
+impinge more directly upon both sides of the flame. There is also an
+arrangement for introducing air between the outer casing of the air
+chamber and the glass chimney which encloses the flame; its object
+being to keep the chimney cool.
+</p>
+
+<div class="figcenter"><img src="images/020.jpg" alt="Siemens's Regenerative Gas-Burner" width="356" height="327"></div>
+<p class="caption"><span class="sc">Elevation.</span>
+&#8212;<span class="sc">Enlarged Section of Combustion Chambers.</span>
+<br><span class="sc">Fig. 20.&#8212;Siemens's Regenerative Gas-Burner.</span>
+</p>
+
+
+<p>
+<span class="sidenote"> Action of the Siemens burner.</span>
+The action of the burner is as follows:&#8212;When the gas is ignited at
+the ring of tubes, the heated air and products of combustion, which
+rise from the flame, create a draught in the main chimney. Through the
+communication established by means of the lateral flue, a partial
+vacuum, or area of low pressure, is induced in the innermost chamber
+of the burner, and within the porcelain cylinder which surmounts it.
+As the flame terminates close to the mouth of the latter, the greater
+portion of the products of combustion, instead of going into the main
+chimney, are sucked into the porcelain cylinder; and thus a current is
+set up through the interior of the burner, and by the lateral flue, to
+the main chimney. The heat carried away by the products of combustion
+is communicated, through the walls of the chambers, to the entering
+gas and air; and by this means the latter are heated to a very high
+temperature before they issue from the burner and are consumed. The
+consequence is that a much greater intensity of combustion is
+maintained; the carbon particles are separated earlier in the flame,
+and are raised to a more exalted temperature; and the ultimate effect
+is a higher yield in illuminating power per cubic foot of gas
+consumed. Independent tests by various experienced photometrists have
+conclusively shown that a light equivalent to that from 5 to 6 candles
+is obtained per cubic foot, from gas which, in the standard "London"
+Argand, yields a light of only from 3 to 3&#189; candles.
+</p>
+
+
+<p>
+While the advantages of the Siemens burner are many and obvious, it is
+not without its disadvantages. These partly arise from causes
+connected with the very observance of the conditions necessary to
+<span class="sidenote"> Defects of the Siemens burner.</span>
+secure the efficiency of the burner. With every advance in the more
+efficient operation of gas-burners, increased care and attention are
+demanded in their employment, in order to obtain the benefits they are
+calculated to yield. Indeed, it would almost appear that the nearer
+the approach to perfection which is made in the construction of a
+burner, the greater must be the drawbacks to its general adoption.
+Thus, in the burner under notice, if the gas supply is allowed to
+become in excess, the tail of the flame enters the porcelain cylinder,
+and soot is deposited in the interior of the burner; obstructing the
+passages, and impairing the burner's action. Then, to cause the burner
+to yield its highest results, it is necessary that the air supply be
+accurately adjusted to the quantity of gas being consumed. To this end
+the entrance to the air chamber, at the bottom of the burner, is
+covered by a perforated semi-circular cup, by turning which the
+quantity of air entering the burner can be increased or diminished as
+required. Moreover, the bulky construction of the burner, with its
+accompaniment of chimney and flue, and its complicated arrangement of
+tubes and chambers, imparts to it a somewhat clumsy and inelegant
+appearance, which is calculated to impair the favour with which its
+remarkable performances cause it to be regarded. But these drawbacks
+are far outweighed by the undoubted advantages conferred by the
+burner&#8212;in improved illumination combined with economy of combustion,
+and the facilities it affords for securing perfect ventilation.
+</p>
+
+<p>
+Encouraged by the success of Herr Siemens, other inventors have
+followed in his footsteps; with the result that there are now a
+variety of burners before the public, embodying the same principles,
+but differing in the details of their construction and in the measure
+of their efficiency. Of these may be mentioned Grimston's, Thorp's,
+and Clark's; and without describing in detail the construction of the
+several burners (of which further particulars will be found in the
+"Register of Patents" in the <i>Journal of Gas Lighting</i><a href="#note14" name="noteref14">
+<small>[14]</small></a>), it
+must suffice to refer to the salient points and distinctive features
+of each.
+</p>
+
+
+<p>
+<span class="sidenote"> Grimston's regenerative burner.</span>
+Grimston's burner (shown on the next page) consists, in effect, of an
+Argand burner turned upside down; the gas issuing from the bottom ends
+of a number of small tubes placed in a circle. The jets of
+flame&#8212;first directed downwards from the mouths of these tubes&#8212;by a
+conoidal deflector in the centre of the ring, are caused to spread
+outwards, and assume a horizontal direction; and by their amalgamation
+with each other a continuous sheet or ring of flame is produced. The
+horizontal direction of the flame is maintained by its passing
+underneath a metal flange, faced with white porcelain, or other
+refractory material; the supply of gas being adjusted so that the
+flame just terminates at the outer edge of this flange. Before
+entering the chimney, the products of combustion are caused to flow
+through a number of vertical tubes contained in a cylinder, which is
+concentric to an inner cylinder containing the gas-supply tubes. The
+outer cylinder is traversed by the air needed for the support of
+combustion, which is to become heated before reaching the point of
+ignition; and in order the more completely to enable the products of
+combustion to impart their heat to the entering air, the cylinder is
+further intersected by strips of wire gauze, which pass around and
+between the tubes (see fig. 22, on next page). By these means the air
+is intensely heated; and, passing among the narrow burner tubes
+through which the gas is conveyed, gives up a portion of its heat to
+the latter before the point of ignition is reached. Thus, in a very
+simple manner, both air and gas are raised to a considerable
+temperature before combustion takes place.
+</p>
+
+<p>
+With regard to the efficiency of the burner, at the exhibition of gas
+appliances held at Stockport in 1882 (where a gold medal was awarded
+to it, as well as to Thorp's burner, to be referred to hereafter),
+with a consumption per hour of 9&#183;84 cubic feet of 17&#183;5 candle gas, an
+illuminating power of 60&#183;67 candles was obtained (equal to 6&#183;16
+candles per cubic foot); while, on another occasion, when the burner
+was consuming 8&#183;94 cubic feet per hour, an illuminating power of 51&#183;5
+candles (equal to 5&#183;76 candles per cubic foot) was obtained from gas
+of the same quality. It is claimed for this burner that equally good
+results are obtained with small sizes as with large; and this, if
+borne out in actual practice, should go far towards ensuring the
+success and extensive adoption of the burner.
+</p>
+
+<div class="figcenter"><img src="images/021.jpg" alt="Grimston's Regenerative Gas-Burner" width="325" height="300"></div>
+<p class="caption"><span class="sc">Fig. 21.&#8212;Grimston's Regenerative Gas-Burner.</span>
+</p>
+
+<div class="figcenter"><img src="images/022.jpg" alt="Grimston's Burner" width="240" height="234"></div>
+<p class="caption"><span class="sc">Fig. 22.&#8212;Grimston's Burner.</span>
+<br><span class="sc">Plan, showing Regenerating Arrangement.</span>
+</p>
+
+<div class="figcenter"><img src="images/023.jpg" alt="Thorp's Regenerative Gas-Burner" width="240" height="286"></div>
+<p class="caption"><span class="sc">Fig. 23.&#8212;Thorp's Regenerative Gas-Burner.</span>
+</p>
+
+
+<p>
+<span class="sidenote"> Thorp's regenerative burner.</span>
+Thorp's burner produces a cylindrical flame, like that of the Argand,
+but without the aid of a glass chimney which is a necessary adjunct to
+the latter burner. By means of a deflector on the inner side of the
+flame, the latter is made to curve outwards and assume a somewhat
+convex form, so as to obviate the shadow which otherwise would be cast
+by the gas chamber at the bottom of the burner. Above the flame is a
+cylindrical chimney, divided by a vertical partition into two
+concentric chambers, which are intersected by a series of metal gills,
+or projections, continued through both chambers. The outer chamber is
+for conveying away the products of combustion; the inner one for the
+passage of air to feed the flame; while down the centre of the inner
+chamber there passes a tube conveying the gas to the point of
+ignition. The hot products of combustion pass up from the flame
+through the outer chamber, and give up the greater portion of their
+heat to the projections; by which it is conducted into the inner
+chamber, and transferred to the incoming air. A common imperfection of
+regenerative burners is that, in consequence of the diminished rate at
+which the gas flows through the burner when expanded by heat, when
+starting the burner the gas must be only partially turned on, and the
+quantity gradually increased as the burner becomes heated; thus
+necessitating considerable attention. To prevent the need for this
+attention, there is in Thorp's burner an ingenious contrivance for
+automatically regulating the quantity of gas admitted to the flame.
+The central gas-tube, which is referred to above, contains a brass
+rod, fixed at one end, and at the other connected to a valve
+controlling the quantity of gas that enters the tube. At first, when
+the gas is lighted, this valve is almost closed; but as the rod
+becomes heated it elongates, gradually opening the valve until the
+full quantity of gas is admitted which the burner is intended to
+consume. At the Stockport exhibition, Thorp's burner was tested with
+the following results, as recorded in the Judges' report. After it had
+burned about two hours, "it gave an illuminating power of 183 standard
+candles, while burning 27 cubic feet of gas per hour (equal to 6&#183;77
+standard candles per cubic foot), with gas of 3&#183;5 candles per cubic
+foot.... In another experiment with the same quality of gas, after
+burning half an hour it yielded, under similar conditions, 154 candles
+with a consumption of 25&#183;29 cubic feet per hour, which gave an
+illuminating power of 6&#183;02 candles per cubic foot."
+</p>
+
+
+<p>
+<span class="sidenote"> Clark's regenerative burner.</span>
+There is nothing in Clark's burner that calls for special notice. In
+its main features it appears to be constructed upon similar lines to
+Grimston's burner, although the coincidence is doubtless only
+accidental.<a href="#note15" name="noteref15">
+<small>[15]</small></a> It must, however, be added that in the details of its
+construction it is much simpler than the latter burner; and certainly
+it appears to lose very little in efficiency from its greater
+simplicity, as the following extract from a report by Mr. F. W.
+Hartley, the well-known photometrist, will show:&#8212;"With a consumption
+rate of 5&#183;3 cubic feet of gas per hour, the amount of light yielded
+horizontally was equal to 29&#183;79 times that of a standard candle. The
+light yielded per cubic foot of gas burned per hour was therefore
+equal to 5&#183;62 times that of a standard candle." And the amount of
+light delivered immediately downwards is said to be "very sensibly
+greater than the amount of light delivered horizontally." Like the
+Grimston burner, it is of the inverted Argand form; the gas issuing
+from a chamber at the bottom of a tube which descends through the
+centre of the burner. The products of combustion escape through a
+chimney; and in so doing give up a portion of their heat to the
+entering air, which is conveyed to the point of ignition through
+horizontal tubes that intersect the chimney. The burner is enclosed in
+a suitable lantern, the lower half of which consists of a
+semi-globular glass; a similar arrangement being adopted in connection
+with the Grimston and Thorp burners.
+</p>
+
+<div class="figcenter"><img src="images/024.jpg" alt="Clark's Regenerative Gas-Burner" width="316" height="300"></div>
+<p class="caption"><span class="sc">Fig. 24.&#8212;Clark's Regenerative Gas-Burner.</span>
+</p>
+
+<p>
+The three burners last mentioned have not been before the public
+sufficiently long to enable a reliable opinion to be formed as to
+their value in actual and prolonged use. Although there is no reason
+for supposing that such will occur in the present instance, it so
+often happens that the results indicated by apparatus in the
+experimental stage, or while still under the control of the inventor,
+are not borne out in practice, that it would be unwise to express any
+decided opinion as to their ultimate worth from existing information.
+It is, however, to be earnestly hoped that the marked favour with
+which they have been received will not be impaired on improved
+acquaintance; but that further experience will justify the
+anticipations that have been excited by the excellent performances of
+the burners hitherto, and demonstrate at once their durability and
+real usefulness.
+</p>
+
+<p>&nbsp;</p>
+
+<p>
+Since writing the above, considerable activity has been shown by
+inventors in producing new burners upon the regenerative principle, or
+in improving upon existing models. Of course, as yet it is too early
+to arrive at a satisfactory estimate of their actual value or relative
+worth; but it may be hoped that, from the increased attention being
+devoted to the subject, some real and practical results will flow, by
+which the gas-consuming public will be the gainers. So far, the most
+promising of this class of burners that has been brought into actual
+use, since the introduction of the Siemens burner, is the one
+represented below.
+</p>
+
+<div class="figcenter"><img src="images/025.jpg" alt="Bower and Thorp's Regenerative Gas-Burner" width="397" height="340"></div>
+<p class="caption"><span class="sc">Fig. 25.&#8212;Bower and Thorp's Regenerative Gas-Burner.</span>
+</p>
+
+<p>
+It is a modification, in the direction of greater simplicity, of
+Thorp's former burner, illustrated and described on p. 69 of this
+treatise; and as its construction is based upon the same lines as that
+burner, further description is not required.
+</p>
+
+
+
+
+<a name="73">&nbsp;</a>
+<p class="chapter">
+CHAPTER VI.
+</p>
+
+<p class="ctr">
+<img src="images/t6.jpg" alt="Incandescent Burners." width="372" height="54"></p>
+
+
+<p>
+A review of gas-burners would scarcely be complete without some
+reference to the incandescent burners of M. Clamond and Mr. Lewis.
+Although their dependence upon an artificially produced blast or
+current of air removes them from the list of appliances applicable to
+ordinary conditions, the remarkable results which they afford, not
+less than their originality, demand for them at least a passing
+notice. The production of light by the agency of these burners is
+brought about in a manner altogether different, and is due to quite
+other causes than those which are concerned in the production of an
+ordinary illuminating gas flame. In the latter case, the illuminating
+power developed is solely due to the hydrocarbons contained in the
+gas, which are decomposed by the heat of the flame, the separated
+carbon being raised to a white heat. In the former, the illuminating
+power is not obtained directly from the gas; but advantage is taken of
+the heat of the flame, enhanced by the application of a blast of air,
+to raise to incandescence some refractory foreign material, which
+latter is thus made to give out light. In the Clamond burner this
+refractory substance is a basket composed of magnesia, spun into
+threads; in the Lewis burner it is a cage of platinum wire.
+</p>
+
+<p>
+To the unthinking reader it may perhaps appear somewhat surprising
+that results so remarkable as are yielded by these burners should be
+obtained, while disregarding, as a source of light, the hydrocarbons
+contained in gas, and employing them, in common with the other
+constituents, solely as a source of heat. An explanation, however, is
+readily forthcoming. As was shown in a former part of this
+treatise,<a href="#note16" name="noteref16">
+<small>[16]</small></a> the great bulk of ordinary coal gas consists of
+constituents which, in the act of combustion, produce considerable
+heat, but scarcely any light; the illuminating power developed in an
+ordinary gas flame being almost wholly dependent upon the very small
+proportion of heavy hydrocarbons which the gas contains. Thus, the
+quantity of heat-producing elements contained in the gas being quite
+disproportionate to the light-yielding hydrocarbons, there is always
+produced, in an ordinary gas flame, more heat than is necessary for
+effectively consuming the free carbon, which is liberated in the flame
+by the decomposition of the heavy hydrocarbons. This is shown by the
+fact that coal gas can usually be naphthalized&#8212;that is, impregnated
+with the vapour of naphtha&#8212;to a considerable extent before the limit
+of effective combustion is reached. The object aimed at in the
+incandescent burners about to be described is to utilize, in the
+development of illuminating power, the combined heat produced by the
+combustion of all the constituents of the gas. To this end the heat of
+combustion is brought to bear upon, and caused to raise to
+incandescence, some refractory material, extraneous to, but brought
+within the operation of the flame.
+</p>
+
+
+<p>
+<span class="sidenote"> Effect of injecting a blast of air into a gas flame.</span>
+A further explanation of the superior results yielded by these burners
+may be found in the employment of an artificial blast or current of
+air. Indeed, without some such arrangement the desired end could not
+be attained. The heat developed by the unaided flame is diffused over
+too wide an area to raise the temperature of the heated substance to
+the necessary degree of incandescence to enable it to give out
+sufficient light. By injecting a current of air into its midst, the
+flame is condensed into a smaller compass; and is brought to bear more
+directly upon the precise locality where its heat may be most
+effectively employed. Thus, although the total quantity of heat
+developed remains exactly the same as before, it is concentrated upon
+a smaller surface of the refractory substance; and the latter is
+consequently more intensely heated, or, in other words, raised to a
+more exalted temperature. The very superior illuminating power which
+is thereby obtained is due to the circumstance that the quantity of
+light yielded by an incandescent body increases in a higher ratio than
+the temperature to which it is raised.
+</p>
+
+
+<p>
+<span class="sidenote"> Lewis's incandescent gas-burner.</span>
+Proceeding now to describe the burners. The one invented by Mr. Lewis
+(various forms of which are illustrated on the next page) consists of
+an upright tube, connected at its base to the gas supply, and
+surmounted by a cap or cage of platinum wire gauze; which latter
+constitutes a combustion chamber, as it is there that the mixture of
+gas and air is consumed. Into the lower part of the upright tube the
+nozzle of an air-pipe is inserted, through which a supply of air can
+be injected, under pressure, into the burner, after the manner of a
+blowpipe. There are also small branch tubes leading into the upright
+gas-tube, and open to the atmosphere. Through these an additional
+quantity of air enters the burner; being drawn or sucked in by the
+agency of the main current, which flows through the upright tube. The
+resemblance to an ordinary Bunsen burner is, therefore, very close.
+The mixture of gas and air thus produced, when ignited, burns at the
+platinum cap; the heat which is developed causing the latter to become
+highly incandescent, and so to give out a brilliant light. To prevent
+the conduction of heat from the incandescent platinum, through the
+upright tube, a non-conducting material&#8212;such, for instance, as
+steatite or porcelain&#8212;is interposed between the gauze cap and the
+metal tube.
+</p>
+
+<div class="figcenter"><img src="images/026.jpg" alt="Lewis's Incandescent Gas-Burner" width="324" height="310"></div>
+<p class="caption"><span class="sc">Fig. 26.&#8212;Lewis's Incandescent Gas-Burner.</span>
+</p>
+
+<p>
+The light produced by this burner is said to approximate more closely
+to daylight than that yielded by an ordinary gas flame (the colours of
+textile fabrics, for instance, being shown as well by its aid as by
+daylight); while, on account of its resulting from the incandescence
+of a fixed body, instead of being emitted from a flame, it is
+unaffected by a gust of wind, and maintains perfect steadiness under
+every condition of weather. The illuminating power developed is stated
+to be equal to 5 standard candles per cubic foot of gas consumed.
+</p>
+
+
+<p>
+<span class="sidenote"> Clamond's incandescent gas-burner.</span>
+M. Clamond's burner, which is shown in fig. 27, is a much more
+complicated apparatus than the preceding one, and not so easily
+described; but its main features may be briefly enumerated as
+follows:&#8212;The air (which, as in Mr. Lewis's burner, is supplied under
+pressure) is divided, as it enters the apparatus, into two portions.
+One portion is at once mixed with the gas; the remainder being
+conveyed, through a peculiarly constructed tube composed of small
+pieces of refractory material, to the combustion chamber, or "wick,"
+as it is termed, of the burner. This "wick" is a small conical basket,
+made of a kind of lacework of spun magnesia, which, when raised to
+incandescence by the heat produced by the combustion of the gas,
+furnishes the desired illumination. The mixture of gas and air is
+subdivided, by a "distributor," into two portions, one of which goes
+direct to the magnesia "wick," there to be burnt, while the other is
+distributed among a number of tubes, forming so-called "auxiliary
+burners," the flames of which are utilized to heat the chief air
+supply; being directed upon the sides of the before-mentioned tube of
+refractory material, through which it is conveyed. By this means the
+air is raised to a very high temperature (1000&#176; C., or 1800&#176; Fahr., it
+is said) before it impinges upon the flame. The result is the
+production of a most intense heat within the magnesia basket; the
+latter being raised to brilliant incandescence, and so developing a
+high illuminating power.
+</p>
+
+<div class="figcenter"><img src="images/027.jpg" alt="Clamond's Incandescent Gas-Burner" width="180" height="360"></div>
+<p class="caption"><span class="sc">Fig. 27.&#8212;Clamond's Incandescent Gas-Burner.</span>
+</p>
+
+<p>
+The magnesia basket must be renewed after being in use a period of
+from 40 to 60 hours, as it gradually deteriorates by the action of the
+intense heat to which it is subjected; but as the cost is said to be
+insignificant, this should not be a great drawback. The basket is
+placed at the base of the burner, in order to obviate the shadow which
+would otherwise be cast by the apparatus; and it is attached to the
+main body of the apparatus by platinum wires. As to illuminating
+power, the only particulars which have been made public refer to the
+first two models constructed; one of which was said to develop a light
+equal to that from 6&#183;208 candles, and the other to 9&#183;72 candles per
+cubic foot of gas consumed.
+</p>
+
+
+<div class="figcenter"><img src="images/028.jpg" alt="Clamond's Improved Incandescent Burner" width="314" height="475"></div>
+<p class="caption"><span class="sc">Fig. 28.&#8212;Clamond's Improved Incandescent Burner.</span>
+</p>
+
+<p>
+<span class="sidenote"> Clamond's new burner.</span>
+In a recently designed modification of the burner (which is shown in
+the accompanying illustration) M. Clamond dispenses with an artificial
+supply of air under pressure, and endeavours to obtain similar results
+by other and simpler means. To this end the position of the magnesia
+"wick" is reversed (it being placed at the top of the apparatus); the
+current of gas is allowed to draw in upon itself a quantity of air by
+a precisely similar arrangement to that adopted in the Bunsen burner;
+while an additional supply of air is drawn upon the flame by the
+accelerated draught produced by the aid of a glass chimney. As in the
+more complicated and complete burner, the air supply is heated by
+means of auxiliary burners in the interior of the apparatus. It has
+been stated, on the authority of M. Clamond, that this modified burner
+develops, from the gas consumed, a duty of about 6 candles per cubic
+foot; being equal to the results yielded by the more complicated
+apparatus. Should this be borne out in practice, M. Clamond will have
+achieved a noteworthy success. It is, however, advisable to reserve
+expressing any definite opinion of its merits until further
+information is received, or until the burner has been tried in this
+country.
+</p>
+
+
+
+
+<a name="79">&nbsp;</a>
+<p class="chapter">
+CHAPTER VII.
+</p>
+
+<p class="ctr">
+<img src="images/t7.jpg" alt="Conclusion." width="200" height="54"></p>
+
+
+<p>
+The burners last mentioned may be said to mark the extent of the
+progress that has been made, down to the present time, in the
+construction of apparatus for developing light from coal gas; and they
+remind me that I have arrived at the conclusion of my subject. From
+the unpretending gas-jet described by Accum&#8212;burning, with
+wonder-provoking steadiness and constancy, "so long as the supply of
+gas continued"&#8212;to the complicated apparatus of M. Clamond, is a long
+stretch of invention; embracing the labours of many distinct and
+original workers in the same field, and including numerous variations
+in the details of burners that have not been touched upon in the
+foregoing remarks. As was announced in the introduction, I have dealt
+in this treatise only with the more important or the more successful
+of the modifications that have been made from time to time in the
+construction of the gas-burner. In addition to the burners that have
+been referred to, there have been invented many others, which could
+not be adequately noticed without prolonging the treatise to an undue
+length. Some of these (the fruit of much thought and careful
+experiment) have obtained, in the commercial success that has attended
+them, no more than their merited reward; others (devoid of any real
+merit, and in their construction disregarding the most elementary
+principles of economic combustion) have been brought into somewhat
+extensive use by the misleading statements and false representations
+of their inventors, and are only tolerated through the ignorance of
+the public; while not a few of the latter class of burners have
+speedily found the oblivion which they richly deserved. Sufficient,
+however, has been said to show that many real improvements have been
+effected in the construction of gas-burners, and to prove that, with
+the apparatus now available, a far higher duty may be obtained from
+the gas consumed than was possible only a few years ago.
+</p>
+
+<p>
+But although the great advance that has been made in the construction
+of gas-burners is undoubted, the benefits which ought to result
+therefrom have not been realized by the gas-consuming public; nor are
+they likely to be to their full extent. While the ingenious and
+effective inventions for utilizing the waste heat of combustion, and
+for lighting by incandescence, may, and doubtless will, in the course
+of a few years, be far more extensively adopted than at present, it is
+hardly to be expected that they will be generally employed. Two causes
+operate to preclude the latter result&#8212;namely, their first cost, and
+the care and attention demanded in their employment. It seems
+tolerably certain that for a long time yet the great bulk of coal gas,
+used for lighting purposes, will be consumed through the simple
+flat-flame burners that have done so much hitherto for the furtherance
+of gas lighting. Fortunately so much has been done towards the
+perfection of this class of burners, that, for a very slight
+expenditure, results may now be obtained far in advance of what could
+formerly be produced only by the most costly and delicate apparatus.
+For ordinary situations and requirements, the improved flat-flame
+burners produced by Bray, Br&#246;nner, and Sugg, when intelligently
+employed, leave scarcely anything to be desired. <i>When intelligently
+employed</i>, I repeat, and with cautious emphasis; for the best of
+burners will be extravagant and ineffective if employed without due
+regard to the conditions for which it was made. That which is most
+needed at the present day, and which will best ensure the continued
+use of coal gas for the purposes of illumination, is the more general
+diffusion amongst gas consumers of a knowledge of the principles of
+combustion, and of the simple precautions to be taken and conditions
+to be fulfilled in the employment of gas-burners. The apparatus that
+is available is both varied and effective; what is wanted is the
+knowledge to use it aright. By contributing to the freer dissemination
+of that knowledge, purveyors of gas will confer no inconsiderable
+benefits upon their customers, and, at the same time, will assuredly
+promote their own interests.
+</p>
+<br>
+<div class="tn">
+<p class="ctr">
+Transcriber's Note: Figure 11 and Figure 12 are identical.
+</p></div>
+
+
+<hr class="med">
+<p class="ctr">
+<b>Footnotes</b>
+</p>
+
+<p class="fn">
+<a name="note1" href="#noteref1">&nbsp;&nbsp;[1]</a> Flame flickers.
+</p>
+
+
+<p class="fn">
+<a name="note2" href="#noteref2">&nbsp;&nbsp;[2]</a> Clegg's "Treatise on Coal Gas," 1841, p. 21.
+</p>
+
+<p class="fn">
+<a name="note3" href="#noteref3">&nbsp;&nbsp;[3]</a> The behaviour of gas flames when exposed to the action of
+the wind (as exemplified in the naked lights of open markets and
+similar situations) affords an instructive illustration of the theory
+of luminous combustion. A sudden gust causes the flame to smoke, by
+reducing the temperature of the liberated carbon below the point at
+which it can combine with the oxygen of the air. A continuous wind
+blowing upon the flame destroys its luminosity altogether, because the
+heat-intensity of the flame is lowered below the temperature necessary
+to decompose the hydrocarbons; consequently, these latter burn without
+the preliminary separation of carbon, and a non-luminous flame is
+produced&#8212;exactly as in the Bunsen or "atmospheric" burner.
+</p>
+
+<p class="fn">
+<a name="note4" href="#noteref4">&nbsp;&nbsp;[4]</a> See <i>Journal of Gas Lighting</i>, Vol. XVIII., p. 88.
+</p>
+
+<p class="fn">
+<a name="note5" href="#noteref5">&nbsp;&nbsp;[5]</a> Flame flickers.
+</p>
+
+<p class="fn">
+<a name="note6" href="#noteref6">&nbsp;&nbsp;[6]</a> Do.
+</p>
+
+<p class="fn">
+<a name="note7" href="#noteref7">&nbsp;&nbsp;[7]</a> Flame flickers a great deal.
+</p>
+
+<p class="fn">
+<a name="note8" href="#noteref8">&nbsp;&nbsp;[8]</a> See <i>Journal of Gas Lighting</i>, Vol. XXXII., p. 423,
+and Vol. XXXVI., p. 376.
+</p>
+
+<p class="fn">
+<a name="note9" href="#noteref9">&nbsp;&nbsp;[9]</a> The name "slit-union," by which Mr. Bray prefers to
+designate this burner, he states to be derived from the resemblance of
+its flame to that of the union-jet burner; while it is produced by
+means of a slit.
+</p>
+
+<p class="fn">
+<a name="note10" href="#noteref10">[10]</a> Although the true batswing is still in common use, I look
+upon the hollow-top as being its "modern representative;" seeing that,
+in a great many instances, it has superseded the former burner&#8212;of
+which, indeed, it is only an improved form.
+</p>
+
+<p class="fn">
+<a name="note11" href="#noteref11">[11]</a> Accum's "Treatise on Gas-Lights."
+</p>
+
+<p class="fn">
+<a name="note12" href="#noteref12">[12]</a> Clegg's "Treatise on Coal Gas," 1st Ed., p. 197.
+</p>
+
+<p class="fn">
+<a name="note13" href="#noteref13">[13]</a> See <i>Journal of Gas Lighting</i>, Vol. XXXIII., p. 162.
+</p>
+
+<p class="fn">
+<a name="note14" href="#noteref14">[14]</a> See Vol. XL., pp. 786, 950; and Vol. XLII, p. 836.
+</p>
+
+<p class="fn">
+<a name="note15" href="#noteref15">[15]</a> In justice to Mr. Clark it should be mentioned that,
+since the above appeared in the <i>Journal of Gas Lighting</i>, the
+attention of the writer has been called to the fact (which had been
+overlooked by him) that Clark's patent was taken out some months
+before that of either Grimston or Thorp.
+</p>
+
+<p class="fn">
+<a name="note16" href="#noteref16">[16]</a> See Chap. II., p. 21.
+</p>
+
+
+
+
+
+
+
+<pre>
+
+
+
+
+
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+The Project Gutenberg EBook of Gas Burners, by Owen Merriman
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Gas Burners
+       Old and New
+
+Author: Owen Merriman
+
+Release Date: November 5, 2011 [EBook #37928]
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK GAS BURNERS ***
+
+
+
+
+Produced by Chris Curnow and the Online Distributed
+Proofreading Team at http://www.pgdp.net (This file was
+produced from images generously made available by The
+Internet Archive)
+
+
+
+
+
+
+GAS BURNERS
+
+OLD AND NEW.
+
+
+
+GAS BURNERS
+
+OLD AND NEW.
+
+A Historical and Descriptive Treatise
+
+ON THE
+
+PROGRESS OF INVENTION IN GAS LIGHTING;
+
+EMBRACING AN ACCOUNT
+
+OF THE
+
+THEORY OF LUMINOUS COMBUSTION.
+
+
+
+BY
+
+"OWEN MERRIMAN."
+
+
+_Reprinted from the_ JOURNAL OF GAS LIGHTING.
+
+
+London:
+WALTER KING,
+11, BOLT COURT, FLEET STREET, E. C.
+
+
+1884.
+
+W. KING AND SELL, PRINTERS,
+12, GOUGH SQUARE, FLEET STREET,
+LONDON.
+
+
+
+
+Transcriber's Note: Figure 11 and Figure 12 are identical.
+
+
+
+PREFACE.
+
+
+The little work here presented to the public appeared originally in
+the pages of the _Journal of Gas Lighting_. In the hope that it
+may thereby become of service to a wider circle of readers, it has
+been revised and done into its present shape. The object of the writer
+will be attained if it is the means of lessening, in any degree, the
+suspicion and prejudice (born of ignorance) which, alas! yet prevail
+with regard to gas and gas lighting.
+
+
+
+
+CONTENTS.
+
+
+                                                       PAGE
+
+INTRODUCTION                                              9
+
+THE FIRST GAS-BURNER                                     13
+
+THE BATSWING BURNER                                      15
+
+THE UNION-JET OR FISHTAIL BURNER                         17
+
+HOW LIGHT IS PRODUCED FROM COAL GAS                      20
+
+IMPROVEMENTS IN FLAT-FLAME BURNERS                       25
+
+BROeNNER'S BURNERS                                        31
+
+THE HOLLOW-TOP BURNER                                    35
+
+BRAY'S BURNERS                                           38
+
+ARGAND BURNERS                                           44
+
+SUGG'S ARGANDS                                           48
+
+THE DOUGLASS BURNER                                      52
+
+GOVERNOR BURNERS                                         55
+
+REGENERATIVE BURNERS                                     61
+
+INCANDESCENT BURNERS                                     73
+
+CONCLUSION                                               79
+
+
+
+
+CHAPTER I.
+
+INTRODUCTION.
+
+
+[Sidenote: Gas consumers and gas producers.]
+
+The subject of gas-burners and the development of light from coal gas
+is of considerable interest, alike to the consumer and the producer of
+gas. When it is known that one burner may develop twice as much light
+as another, for the same consumption of gas--the first cost of the one
+being no higher than that of the other--its importance to the former
+will scarcely be disputed. To the gas consumer it is obviously of great
+value to know how he may most effectively and economically develop the
+illuminating power of the gas which is supplied to him; and so obtain
+the fullest return, in lighting effect, for the money which he expends.
+Not quite so obvious is its relation to the latter. To a person totally
+unacquainted with the recent history of gas lighting, and ignorant of
+the policy which has guided the most prosperous gas undertakings to
+their successful issues, it may appear that the manufacturer of gas is
+not closely concerned with the utilization of the commodity which he
+supplies. Such an one might argue, and with a certain show of reason,
+that the sole business of the gas maker is with its production; that
+after providing, in the consumer's service-pipe, a full and continuous
+supply of gas, of the stipulated quality, his care ends; and that
+henceforth the utilization and management of the illuminant rests with
+the consumer himself. But, by any one who is at all conversant with the
+subject, it will be readily conceded that the interest of the
+manufacturer of gas, in this matter, is only second to that of the
+consumer. In the gas industry, as in any other business undertaking,
+the concern prospers or declines according as the interests of the
+customers are considered or neglected. This has been conclusively
+demonstrated in the history of many gas undertakings. So long as their
+management was conducted in exclusive and selfish regard solely to
+their own internal affairs--looking with supreme indifference or
+careless apathy upon the needs of the consumers--so long was their
+career marked by difficulties and embarrassments. No sooner, however,
+were the claims of the consumers recognized, and efforts put forth to
+further their interests, than the prospects of the concern brightened;
+and by adhering to, and extending the same line of action, the goal of
+commercial prosperity was eventually reached.
+
+Seeing, therefore, that the subject is of so supreme importance to
+consumers of gas, and that the interests of the consumer are closely
+interwoven with those of the manufacturer, it is eminently desirable
+that there should be more generally diffused a correct knowledge of the
+principles of economical gas consumption, and of the extent to which
+these principles are applied in the various burners which, from time to
+time, have been invented. No further apology ought therefore to be
+required in presenting to the reader the following disquisition on
+gas-burners. It may, however, be of advantage for me to state in brief,
+at the commencement, what are the objects I have in view, and what the
+chief considerations which have led me to write this treatise.
+
+[Sidenote: Waste of gas.]
+
+I purpose, then, to tell of the progress that has been made in
+apparatus for the development of light from coal gas; to relate how
+the crude and imperfect devices of the early inventors have been
+gradually improved upon; and, while not ignoring the drawbacks connected
+with recently invented burners, or the defects inherent to their
+construction, to show, in the superior achievements of these burners,
+how great an advance has been made upon the apparatus formerly in use.
+It will be, also, my endeavour to make plain the little understood
+phenomenon of the production of light by the combustion of coal gas;
+and to show the extent to which the illuminating power developed is
+dependent upon the burner employed. That there is need for such
+information as I propose to furnish must be sufficiently obvious to any
+one who has considered the waste of gas which takes place through
+ignorance of the laws of its combustion, and through the use of
+defective burners. In a report presented to the Board of Trade by the
+London Gas Referees in 1871, it was stated that a number of burners had
+been tested, taken from various places of business in the Metropolis;
+the major portion of which gave out only one-half, and some of them not
+more than one-fourth, of the illuminating power capable of being
+developed from the gas. Although, since the time that report was
+penned, considerable progress has been made in the construction of
+burners, and in the more general adoption of efficient burners by the
+public, much yet remains to be done. Doubtless it would still be within
+the mark to assert that fully one-fifth of the gas consumed by the
+public might be saved by the adoption of better burners, and by the
+observance of the conditions necessary for their satisfactory
+operation; and when it is borne in mind that the gas-rental of the
+United Kingdom amounts to a sum of certainly not less than L9,000,000
+per annum, the saving which might be effected assumes truly great
+proportions.
+
+The field on which I propose to enter can hardly be said to be already
+occupied. Nowhere that I know of is the subject of gas-burners fully
+treated of in a manner available for the general reader. With the
+exception of the admirable chapter contributed by Mr. R. H. Patterson
+to "King's Treatise on Coal Gas," I am not aware that the subject
+has been dealt with to any complete extent by recent writers. But,
+admirable as is that contribution to the literature of the subject,
+being written for technical readers, it is neither so popular in style
+nor so elementary in character as to fulfil the purpose which I have in
+view in writing the present series of articles. Briefly stated, my sole
+purpose is to make the subject of the combustion of gas for the
+production of light intelligible to the simplest; and to present an
+interesting account of the progress of invention in the perfection of
+gas-burners. While passing lightly over many modifications of apparatus
+which have been of but limited or temporary service, I shall not
+scruple to dwell at length upon such burners as have done much to
+further the extension of gas lighting, or whose construction exhibits
+a considerable advance upon previous attainments. And while it will
+be my endeavour to clothe my remarks in such language as shall be
+"understanded of the people," in speaking of the theory of combustion I
+hope to be sufficiently explicit to enable my readers to form a clear
+conception of the scientific principles underlying the phenomena of
+which I treat.
+
+[Sidenote: Progress of gas lighting.]
+
+A further justification--if such, indeed, were needed--for the
+appearance of this treatise might be found in the remarkable impetus
+which has been given, within recent years, to the perfection of the
+details of gas manufacture and the improvement of gas-burners. Of
+course, I refer to the beneficial consequences to the gas industry
+which have followed the brief, if conspicuous, career of electricity as
+an illuminating agent. That the interest in improved illumination which
+has been aroused by the short-lived popularity of the electric light,
+and the extravagant claims put forward on its behalf, have stimulated
+to the development of the resources of gas lighting, is sufficiently
+obvious to the most superficial observer. And not only has the
+manufacturer of gas been benefited, but the public have reaped no
+inconsiderable advantage. At the present day, gas is sold at a far
+cheaper rate, as well as of a higher quality, than at any former
+period. Nor is the advent of cheap gas the only direction in which the
+public have gained. Although not so patent to the majority, the
+improvements that have been effected in the methods of burning gas, so
+as to obtain the fullest advantage from its use, are calculated to
+confer benefits equally real, and not less valuable. It is hardly too
+much to say that the last few years have witnessed a greater advance in
+the apparatus employed in the combustion of gas than had been effected
+during the whole previous history of gas lighting. This being so, it
+may not be unacceptable if I attempt to pass in review some of the
+various burners that have been invented and used for obtaining light
+from coal gas; showing the successive improvements that are exhibited
+in their construction, and the extent to which they apply the
+principles of combustion. It may be that what I have to relate will
+awaken some minds to the consciousness that gas lighting has not
+altogether retired into obscurity on the advent of electricity--nay,
+that it has even assumed a bolder front; and, with increased resources
+and accession of strength, is prepared firmly to maintain its position
+as at once the most convenient, economical, and reliable of artificial
+illuminants.
+
+
+
+
+CHAPTER II.
+
+FLAT-FLAME BURNERS.
+
+
+THE FIRST GAS-BURNER.
+
+The first gas-burner was a very simple and unpretentious contrivance.
+In one of the earliest works on gas lighting[1] we read: "The
+extremities of the pipes have small apertures, out of which the gas
+issues; and the streams of gas, being lighted at those apertures, burn
+with a clear and steady flame as long as the supply of gas continues."
+Familiar as it is to us, and from its familiarity unnoticed, the
+phenomenon presented by the flame thus produced continuing to burn "as
+long as the supply of gas continued," was doubtless, to the first
+experimenters, a wonderful sight. Though we may smile at the question,
+it is not difficult to understand the incredulity of the honourable
+member who, when Murdock was examined before a Committee of the House
+of Commons, in 1809, asked the witness: "Do you mean to tell us that it
+will be possible to have a light _without a wick_?" "Yes; I do indeed,"
+replied Murdock. "Ah, my friend," replied the member, "you are trying
+to prove too much."
+
+          [1] Accum's "Treatise on Gas-Lights." Third edition, 1816.
+
+[Sidenote: The dawn of gas lighting.]
+
+It was but natural, seeing that oil-lamps and candles were the only
+forms of artificial illumination in use prior to the introduction of
+gas lighting, that the earliest attempts at illumination by gas should
+be in imitation of the effects produced by those means. Accordingly we
+find that one of the first gas-burners employed was the Argand,
+modelled upon the oil-lamp of that name, which had been found to give
+superior results; while in more general use, and for some time almost
+the sole apparatus available, were single jets, giving a flame similar
+in appearance to that of a common candle, together with various
+combinations of these jets. A fair idea of the mode of illumination
+practised during the earliest period of gas lighting may be gleaned
+from the following extract from a paper describing the lighting of
+Messrs. Phillips and Lee's cotton-mill at Manchester, read before the
+Royal Society, in 1808, by Mr. William Murdock:--
+
+    The gas-burners are of two kinds. The one is upon the principle of
+    the Argand lamp, and resembles it in appearance; the other is a
+    small curved tube with a conical end, having three circular
+    apertures or perforations, of about 1-30th of an inch in diameter,
+    one at the point of the cone, and two lateral ones, through which
+    the gas issues, forming three divergent jets of flame, somewhat
+    like a fleur-de-lis. The shape and general appearance of this tube
+    has procured for it, among the workmen, the name of the "cockspur"
+    burner.
+
+  [Illustration: FIG. 1.--EARLY GAS-BURNERS.
+                 (From Accum's "Treatise on Gas-Lights.")]
+
+Nor was much advance made upon these arrangements down to the year
+1816, judging from Accum's "Treatise" (before cited), as the subjoined
+extract from that work, together with the above illustrations, will
+show:--
+
+    The burners are formed in various ways--either a tube ending with a
+    simple orifice, at which the gas issues in a stream, and if once
+    lighted will continue to burn with the most steady and regular
+    light imaginable, as long as the gas is supplied; or two concentric
+    tubes of brass or sheet iron are placed at a distance of a small
+    fraction of an inch from each other, and closed at the bottom. The
+    gas which enters between these cylinders, when lighted, forms an
+    Argand lamp, which is supplied by an internal and external current
+    of air in the usual manner. Or the two concentric tubes are closed
+    at the top with a ring, having small perforations, out of which the
+    gas can issue; thus forming small distinct streams of light.
+
+It is interesting, in view of the present demand for increased
+illumination, and for burners of high illuminating power, to note the
+amount of light produced by the burners then in use. In Mr. Murdock's
+paper we find it stated that each of the Argands in use at Messrs.
+Phillips and Lee's establishment gave "a light equal to that of 4
+candles (mould candles of 6 to the pound);" and each of the cockspurs
+"a light equal to 2-1/4 of the same candles." From which meagre results
+we conclude that, besides being burnt in an ignorant and wasteful
+manner, the gas consumed was wofully deficient in illuminating power.
+
+
+THE BATSWING BURNER.
+
+[Sidenote: Who invented the batswing burner?]
+
+A notable advance was made when the batswing burner was invented. To
+whom we are indebted for this invention seems involved in some doubt.
+Although Clegg, in the historical introduction to his valuable work,[2]
+says, very distinctly, that "the batswing burner was introduced by a
+Mr. Stone, an intelligent workman employed by Mr. Winsor," it is not so
+much as mentioned by Accum, even in the third edition of his
+"Treatise;" and Accum, it may be remarked, was for some time closely
+associated with Winsor in the promotion of the latter's ambitious and
+visionary schemes. Yet, if Clegg's statement be correct, it would
+almost appear to fix the date of the introduction of this burner as
+prior to 1816. But to whomsoever is due the credit of its invention,
+certain is it that the batswing burner was a considerable improvement
+upon the old cockspur. Producing a better light for the gas consumed,
+it assisted to demonstrate still further the superiority of gas
+lighting over other methods of illumination; and as it could be
+supplied at a trifling cost, and contained no delicately adjusted nor
+easily injured parts, it enabled the benefits of the new method of
+lighting to be extended to wherever artificial light was required.
+
+          [2] Clegg's "Treatise on Coal Gas," 1841, p. 21.
+
+  [Illustration: FIG. 2.--BATSWING BURNER.]
+
+[Sidenote: Superiority of the batswing over the cockspur burner.]
+
+From the cockspur and single jet burners the gas ascended in streams,
+rising into the air until it came in contact with sufficient oxygen to
+completely consume it. In order that this might take place without
+producing a flame of an inordinate length, and without much smoke, the
+orifices were restricted to a very small size; and the gas issuing from
+these at considerable pressure tended to draw in, and mix with the air
+in its course. Besides the loss of illuminating power caused by this
+mixture of air with the gas flame (similar to what takes place in a
+Bunsen burner), the cooling influence upon the small body of flame of
+the mass of metal composing the burner, operated still further to
+reduce the quantity of light which the gas was calculated to yield.
+With the batswing the gas was spread out producing, when ignited, a
+thin sheet of flame, by which means the gas was enabled to combine more
+readily with the air necessary to effect complete combustion. The size
+of the flame being, in comparison with that of the cockspur, so much
+larger proportionately to the metal burner, the cooling effect of the
+latter was not so apparent. The increased size of flame, also, of
+itself, tended to improve the illuminating power; each portion of flame
+contributing to elevate and sustain the temperature of the whole, and
+so to heighten the intensity of incandescence to which the light-giving
+particles were raised.
+
+[Sidenote: Batswing and Argand burners compared.]
+
+Even with the Argands of that day, the batswing compared not
+unfavourably. The former burner, having the regulation of its air
+supply under complete control, gives the best results when the gas is
+supplied to it at a low pressure; as then the requisite quantity of air
+to ensure complete combustion of the gas can be delicately adjusted by
+means of a chimney of suitable length. When the gas and air have been
+nicely adjusted to each other, the flame becomes extremely sensitive to
+any change of pressure in the gas supply; a diminution of the supply,
+by reducing the quantity of gas issuing from the burner without at the
+same time proportionately diminishing the supply of air, tends to
+destroy the illuminating power by the cooling action of the surplus
+air; while an increased pressure, by allowing more gas to issue than
+the air can consume, causes the flame to smoke. But at the time to
+which I now refer the principles of combustion were little understood,
+still less applied in the construction of burners. Besides this, the
+pressure of the gas in the mains was excessive; and there being no
+method adopted of controlling it at the burner, the construction of a
+good Argand was, under the circumstances, almost impossible. The
+batswing was not so prejudicially affected by an excess of pressure.
+Pressure to some extent was, indeed, required to enable the flame to
+attain its normal shape; while any excess forced the gas through the
+flame without permitting it to be raised to incandescence before being
+consumed, and although necessitating loss of light, caused no
+inconvenience like a smoking flame. Another important advantage which
+the batswing possessed over the Argand burner was its simplicity of
+construction; and the absence of accessories, such as the glass
+chimney--dispensing with the cleaning and attention which the latter
+required. Had the benefits of gas lighting been dependent upon the use
+of apparatus so fragile, and requiring so much care and attention as
+the Argand, the range of its applicability must have been considerably
+limited, and its prospects of commercial success much less assured. The
+introduction of a series of cheap but effective burners, however,
+altered the conditions of gas lighting, and marked the commencement of
+a new era in artificial illumination. The possibility of obtaining, by
+means of a burner so simple and apparently insignificant as the
+batswing, results little, if at all, inferior to what could be obtained
+by the use of the most complicated and expensive, was of advantage
+alike to the consumer and the producer of gas. To the former it gave
+the benefits of an increased illumination, without requiring any
+corresponding outlay; to the latter it promised a growing extension of
+the use of coal gas, and thus furnished the surest guarantee of future
+progress and prosperity.
+
+
+THE UNION-JET, OR FISHTAIL BURNER.
+
+[Sidenote: Who invented the union-jet burner?]
+
+The batswing had been for some years in extensive use before a burner
+was produced worthy in any degree to compare with it in respect to
+simplicity and efficiency. The invention of the union-jet, or fishtail
+burner, furnished a competitor equally simple; little, if at all,
+inferior as regards efficiency; and, to some extent, superior to the
+former burner in general adaptability. Although so much behind in point
+of time, the new burner speedily rivalled the older batswing in popular
+favour; and in its various modifications and improvements may be said,
+without fear of contradiction, to have received a wider application
+than any other gas-burner. As in the case of the batswing, so with
+regard to this burner: few details are recorded of its invention. But,
+slight as is the information available, such as we have is more
+satisfactory and more authentic than the meagre notice of Clegg, which
+is all that is known of the invention of the former burner. It appears
+to be established beyond doubt that the union-jet is the joint
+invention of Mr. James B. Neilson, the inventor of the hot-blast, and
+Mr. James Milne, of Glasgow, founder of the engineering firm of Milne
+and Son. About the year 1820, or soon after (as in that year Mr.
+Neilson was appointed Manager of the Glasgow Gas-Works), these
+gentlemen were experimenting with gas-burners, when they discovered
+that by allowing two jets of gas, of equal size, to impinge upon each
+other at a certain angle, a flat-flame was produced, with increased
+light. This was the origin of the union-jet; so called from the manner
+in which the flame is produced. At first separate nipples were employed
+for the two jets; but, very soon, Mr. Milne hit upon the expedient of
+drilling two holes, at the required angle, in the same nipple. In this
+manner, with slight modifications, the burner has continued to be
+constructed down to the present day.
+
+  [Illustration: FIG. 3.--FISHTAIL BURNER.]
+
+The explanation of the preference accorded to this burner over its
+predecessor, the batswing, is to be found chiefly, I think, in the very
+different shapes of the respective flames produced by the two burners.
+The batswing, in its original form, produced a flame of great width,
+but of no corresponding height. The extremities of the flame,
+stretching out from the burner so far on either hand, were easily
+affected by an agitation of, or commotion in the surrounding
+atmosphere; a slight draught or current of air causing the flame to
+smoke at these points. The extreme width of flame also precluded the
+use of this burner in globes. The flame produced by the union-jet
+burner, as first constructed, was very different to the one just
+described. Longer than that of the batswing, and considerably narrower
+(but widening gradually from its base, at the burner, to its apex), it
+presented somewhat nearly the appearance of an isosceles triangle; or
+more closely, perhaps (with its slightly-forked apex), the tail of a
+fish, from which resemblance it is commonly designated the fishtail
+burner. This form of flame was better adapted for use in globes, and
+also better withstood the effects of draughts. And it is perhaps not
+unreasonable to suppose that as in shape it approached more closely to
+the kind of flame with which the people had been familiar in oil lamps,
+the flame produced by the union-jet burner was more agreeable to the
+eye than that of the batswing, and that this seemingly trivial
+consideration will account, to some extent at least, for the undue
+favour shown towards it. For it must not be assumed, because of the
+widespread popularity to which the union-jet so early attained, and
+which it has continued to enjoy, that it was of necessity a better
+burner (in the sense of developing more light for the gas consumed)
+than the one which preceded it. On the contrary, in this regard it was
+not quite so effective as the batswing. Nor is this result surprising,
+looking at the different methods adopted in the two burners for
+producing the same effects of light and flame.
+
+[Sidenote: Union-jet and batswing burners compared.]
+
+From the batswing burner the gas issued in a thin but widely-extending
+stream, presenting, when ignited, a continuous sheet of flame; its
+height and width depending upon the pressure at which the gas was
+supplied, but always offering an unbroken surface of flame to the air.
+Although, from the excessive pressures which, in the early days of gas
+lighting, were generally employed, the flame drew upon its surface too
+much air for the attainment of the fullest lighting efficiency
+obtainable from the gas; yet the form given to the issuing stream of
+gas precluded the air from entering the interior of the flame, and
+still further reducing its illuminating power. With the union-jet
+burner the conditions were greatly changed; and this latter evil, of
+the introduction of cold air into the interior of the flame, was one of
+the consequences entailed by the means it employed for producing its
+flame. From this burner the gas issued in two narrow streams, like
+single jets, which, directly after emerging from the burner, impinged
+upon each other at a given angle; the mutual shock given to the streams
+of gas when thus arrested causing them to spread out in a lateral
+direction, and (the high velocity at which the gas issued being
+expended) to unite, and ascend in a sluggish stream until consumed.
+That injury to the illuminating power of the flame should result from
+causes connected with the manner of producing it will be understood on
+considering some of the phenomena associated with the production of a
+gas flame.
+
+[Sidenote: How air is drawn upon a gas flame.]
+
+When a jet or stream of gas issues into a still atmosphere, it produces
+in its immediate neighbourhood, on all sides, an area of low pressure,
+to occupy which the contiguous air rushes in. Induced air currents are
+thus set up in close proximity to, and having the same direction as the
+issuing stream of gas, and varying in force with the pressure, or
+velocity, at which the gas issues. The non-luminous flame of the Bunsen
+burner, and of the so-called "atmospheric" burner employed in gas
+cooking and heating stoves (which is produced by burning a mixture of
+gas and air), is obtained by taking advantage of this tendency of a
+stream of gas, issuing under pressure, to draw air upon itself; and it
+is to the same circumstance that ordinary illuminating flames owe the
+continuous supply of air necessary to keep up combustion. For the
+effect is heightened when the gas is inflamed; because, the gaseous
+products of combustion being expanded by the intense heat to which they
+are subjected, their velocity of ascension is vastly increased. Having
+regard to these considerations, it will be clearly perceived how that,
+in producing the flame of the union-jet burner, the two streams of gas,
+in the act of combining together, drew into the very midst of the flame
+a portion of the air with which they were surrounded; and this air,
+reducing the temperature of the flame, and diluting the illuminating
+gas by the inert nitrogen introduced, as well as by its oxygen causing
+a too early oxidation of the carbon particles in the flame, operated to
+reduce the illuminating power otherwise obtainable from the gas.
+
+The foregoing remarks, it must be borne in mind, refer to the union-jet
+burner in its original form. Numerous improvements have been effected,
+from time to time, in its construction, as well as in that of the
+batswing, which, by reducing its liability thus to convey air into the
+flame, have increased its efficiency; while, at the same time, the
+shape of the flame has been improved. Indeed, the result of successive
+improvements in the construction of both burners has been so to modify
+the shape of their respective flames that, in their latest and most
+improved form, the flames produced by the two burners are practically
+identical in appearance, although the manner of their production
+remains as widely diverse as at the first. The improvements that led up
+to, and the causes that produced this result, will be more fully
+explained in the sequel.
+
+
+HOW LIGHT IS PRODUCED FROM COAL GAS.
+
+I have before remarked that, in the early period of its use, one of the
+chief obstacles to the development of the lighting power of coal gas
+was the excessive pressure at which it was generally supplied. To
+understand the action of pressure in influencing the amount of light
+which a given quantity of gas will afford, it is necessary to know
+something of the nature and properties of flame. Moreover, the
+conditions upon which is dependent the illuminating power of a gas
+flame are so intimately related to each other, that the precise
+functions due to each cannot well be separated from the complete effect
+produced by the combined operation of all. I shall not, therefore, be
+needlessly digressing from my subject if, at this juncture, I explain
+the manner in which combustion takes place in the flame of an ordinary
+gas-burner. In doing this, I shall endeavour to clothe my remarks in
+very plain language; using no more technicalities than are absolutely
+required by the exigencies of the subject. In this way I hope to make
+my meaning clear to the simplest. At the same time, without pretending
+to be scientifically complete, the explanation of the phenomena of
+combustion which I shall furnish will, I trust, be sufficiently
+explicit to enable the reader to form a right estimate of the
+principles which regulate the production of light when coal gas is
+consumed. The end chiefly kept in view is to show clearly the extent to
+which the degree of light evolved is dependent upon the burner
+employed, and the manner in which the gas is consumed. If my remarks
+are the means of causing the reader to look with intelligent interest
+upon the familiar phenomena of gaslight, they will not have been
+written altogether in vain.
+
+[Sidenote: What is coal gas?]
+
+Seeing that this treatise is compiled especially for those whose
+knowledge as to what coal gas consists of is extremely limited, it may
+be of advantage to preface my observations on its combustion, and the
+production of light therefrom, by a few remarks as to its composition.
+Coal gas, as generally supplied, is made up of a variety of distinct
+gases; of which, however, only some three or four exist in any
+considerable proportion. About 50 per cent., by volume (or half of the
+whole), is hydrogen; from 30 to 40 per cent. consists of marsh gas;
+while carbonic oxide is usually present to the extent of from 5 to 15
+per cent. These three gases, which constitute the great bulk of what is
+known as common gas--that is, gas made from ordinary bituminous coal,
+as distinguished from that produced from the more costly cannel--are of
+little or no value as regards the amount of light they are capable of
+affording. The flames produced by the burning of the two former gases
+evolve much heat, but are of very feeble illuminating power. The latter
+gives a flame of a deep blue colour, producing scarcely any light, but,
+like the other two, an intense heat. The power of coal gas to yield a
+luminous flame is dependent upon the small quantity of heavy
+hydrocarbons which it contains--a constituent, or series of
+constituents, of which common gas only contains a proportion varying
+between 3 and 7 per cent., although in cannel gas it reaches as high as
+15 or 20 per cent. These heavy hydrocarbons are gases composed, like
+marsh gas, of carbon and hydrogen; but containing in their composition,
+for each unit of volume, a greater aggregate of the two elements, as
+well as a relatively higher proportion of carbon, than exists in marsh
+gas. One of the simplest members of the series, and that which is
+usually present in by far the largest amount, is called olefiant gas.
+It contains twice as much carbon, combined with only the same quantity
+of hydrogen, as is contained in marsh gas. But besides olefiant gas
+there are minute quantities of other gases of the same series, having
+an analogous composition, but differing in the amount and relative
+proportions they contain of the two elements of which they are
+composed. All the gases of this series, when properly burnt, are
+capable of affording a brightly luminous flame; but when consumed alone
+it is somewhat difficult, on account of the high proportion of carbon
+which they contain, to effect their combustion without the production
+of smoke. It is, then, to the heavy hydrocarbons which are part of
+it--insignificant as their amount may appear--that the luminosity of a
+gas flame is solely due. The other constituents which I have mentioned
+as forming so much larger a proportion of the whole, besides
+contributing to the heat of the flame, serve only to dilute these
+richer gases, and so promote their more complete combustion.
+
+[Sidenote: How gas burns.]
+
+The various simple gases which constitute ordinary coal gas do not all
+burn together in the flame; the temperature required to effect their
+ignition being lower for some of them than for others. Thus, hydrogen
+is the first to burn, taking fire readily as soon as it issues from the
+burner; while the combustion of the heavy hydrocarbons does not
+commence until they enter the hotter portions of the flame, and is not
+completed until they reach its farthest extremity. Neither is the
+process of combustion in both cases the same. The former gas is at once
+completely consumed; the latter first undergo decomposition by the heat
+of the flame, being resolved into their elements--hydrogen and
+carbon--before being fully consumed. This decomposition of the
+hydrocarbons is a factor of supreme importance in the development of
+the lighting power of the flame. The hydrogen they contain, being more
+easily ignited than the carbon, burns first; and the latter is set
+free, in the solid form, as minute particles of soot. These particles
+of solid carbon, being liberated in the midst of the flame, are
+immediately subjected to its most intense heat; they thus become
+white-hot before they reach the outer verge of the flame, and come in
+contact with sufficient oxygen to effect their complete combustion.
+The amount of light developed by any coal-gas flame is directly
+proportional to the degree of intensity to which the temperature of
+these carbon particles is raised, and the length of time they remain
+in the flame before being finally consumed. It becomes, therefore, a
+matter of considerable importance to know the conditions which are
+most conducive to the early liberation in the flame of free carbon,
+and the attainment by it of an exalted temperature.
+
+[Sidenote: What is a gas flame?]
+
+Looking at the flame (say) of a common slit burner, it is seen to be
+divided into two sharply defined and wholly distinct portions. First,
+there is--immediately surrounding the burner head, and extending to
+some distance from it--a dark, transparent area, which, on closer
+examination, is found to consist of unignited gas enclosed in a thin
+envelope of bright blue flame. Second, there is (beyond this central
+area) a zone, or belt, of brightly luminous flame, white and opaque;
+the latter property indicating the presence of solid matter at this
+part of the flame. That the dark central portion of the flame consists
+chiefly of unignited gas may be shown in various ways, in addition to
+the evidence afforded by its complete transparency. Thus, if a small
+glass tube be taken, and its lower end inserted in the flame at this
+point, the unburnt gas will pass up the tube, and may be lighted at its
+upper extremity. A splinter of wood thrust through this portion of the
+flame is charred first at the two edges of the flame; while, in like
+manner, a piece of platinum foil remains dull in the centre of the
+flame, and glows only at the points of contact with the outer air. The
+presence of solid carbon in the luminous portion of the flame may be
+shown by inserting therein any cold substance (such as a piece of metal
+or porcelain), which, reducing the temperature of the heated particles
+of carbon below the point at which they are consumed, becomes instantly
+coated on its under surface with a deposit of soot. Or, if the flame be
+suddenly cooled by gently blowing upon its surface, the same result is
+brought about; clouds of soot are given off, and the flame "smokes."[3]
+
+          [3] The behaviour of gas flames when exposed to the action
+          of the wind (as exemplified in the naked lights of open
+          markets and similar situations) affords an instructive
+          illustration of the theory of luminous combustion. A sudden
+          gust causes the flame to smoke, by reducing the temperature
+          of the liberated carbon below the point at which it can
+          combine with the oxygen of the air. A continuous wind
+          blowing upon the flame destroys its luminosity altogether,
+          because the heat-intensity of the flame is lowered below the
+          temperature necessary to decompose the hydrocarbons;
+          consequently, these latter burn without the preliminary
+          separation of carbon, and a non-luminous flame is
+          produced--exactly as in the Bunsen or "atmospheric" burner.
+
+  [Illustration: FIG. 4.--SHOWING THE TWO ZONES OF THE FLAME, AND
+  THE METHOD OF DEMONSTRATING THE PRESENCE OF UNBURNT GAS IN THE
+  FLAME.]
+
+[Sidenote: How the flame is cooled.]
+
+The existence, in the midst of the flame, of an area of unconsumed gas
+is due to the cold gas, as it issues from the burner, cooling the
+interior of the flame below the temperature required for its ignition,
+as well as to its not at once meeting with sufficient air for complete
+combustion. The causes which affect the luminous zone of the flame are
+not so readily explained. It has been stated that the luminosity of the
+flame is due to the particles of carbon, which are separated out of the
+hydrocarbons in the gas, being raised to a white heat. To decompose the
+hydrocarbons, a very high temperature is required; and, on account of
+the cooling effect of the stream of cold gas, this is not attained
+except at some distance from the burner. The abstraction of heat by the
+burner itself is also a cause of the reduction of the temperature of
+the flame; and, on this account, burners of porcelain, steatite, or
+similar composition, being bad conductors of heat, have an advantage
+over those made of metal. So considerable is the cooling influence of
+the gas stream, that, within certain limits, the distance, from the
+burner head, at which the luminosity of a flame commences, is
+proportionate to the velocity with which the gas issues; or, in other
+words, the pressure at which it is delivered from the burner. The
+effect is heightened by the tendency (which has been before remarked)
+of a stream of gas, issuing under pressure, to draw upon itself and mix
+with the surrounding air. Thus, with each increment of pressure the
+luminous zone of the flame is farther removed, until a point is reached
+at which the gas is so mixed with air before being consumed that the
+luminosity of the flame is completely destroyed.
+
+[Sidenote: Effects of pressure in the gas supply.]
+
+But it must not be assumed, because of the foregoing remarks, that the
+pressure at which the gas issues from the burner is altogether an
+unmixed evil. In flat-flame burners it fulfils the important function
+of promoting intensity of combustion, by bringing the white-hot
+particles of carbon into intimate and rapid contact with the air that
+is necessary for complete combustion. In Argand burners this duty is
+discharged by the glass chimney; but with flat-flame burners it
+devolves entirely upon the pressure at which the gas issues from the
+burner. It will be seen, therefore, that the pressure of the gas is a
+factor of considerable importance in determining the amount of light
+afforded by a gas flame, as it is a matter requiring careful adjustment
+with each and every burner. On the one hand, with an excessive pressure
+the intensity of combustion is increased; but the separated carbon does
+not remain so long in the flame. The area of luminosity is thereby
+decreased, and the total light yielded is reduced. On the other hand,
+with insufficient pressure the combustion is not energetic enough to
+raise the particles of carbon to a white heat; consequently, the
+illuminating power of the flame is feeble, or else the carbon escapes
+unconsumed as smoke.
+
+The thickness of the flame produced by any burner has also an important
+bearing upon the degree of light afforded; and this property of
+thickness, again, is dependent upon the width of slit, in the case of
+batswings (or, in the case of union-jets, upon the size of orifices),
+and the pressure at which the gas is supplied. The thickness of the
+flame yielded by any burner will obviously vary inversely with the
+pressure at which the gas is supplied to it. With a thin flame, all
+parts of the flame are so completely exposed to the air, that the
+particles of carbon are no sooner raised to the temperature required to
+enable them to give out light than they are entirely consumed. With a
+thicker flame the carbon separated in the midst of the flame exists for
+a sensibly longer period of time in the white-hot state before it
+reaches the outside of the flame, and meets with sufficient oxygen for
+its complete combustion. Thus we find that the best flat-flame burners
+have comparatively wide orifices; while the pressure at which the gas
+is delivered from the burner is carefully reduced to the lowest point
+at which a firm flame is obtained, without smoke. Similarly, in the
+best Argands the pressure is considerably diminished within the burner,
+and the gas allowed to issue gently through relatively large holes;
+while the chimney is carefully adapted to draw upon the surface of the
+flame just sufficient air to completely consume the quantity of gas
+which the burner is calculated to deliver.
+
+
+IMPROVEMENTS IN FLAT-FLAME BURNERS.
+
+Although, there is no doubt, they were made empirically, and in
+ignorance of the real effects of pressure upon the flame, the first
+steps towards increasing the efficiency of flat-flame burners were in
+the right direction of reducing the excessive pressure at which the gas
+was formerly allowed to burn. They consisted in the adoption of simple
+arrangements for obstructing the passage of the gas through the burner,
+and so retarding its flow. The crudeness of the means which were
+employed is sufficient evidence that the end aimed at was, at best, but
+dimly discerned. The body of the burner was stuffed with wool, or
+pieces of wire gauze; which impeded the progress of the gas; reduced
+the quantity that would otherwise have been consumed; and,
+consequently, diminished the velocity with which it issued from the
+burner. Unfortunately, owing to the imperfect methods in use at that
+day for condensing and purifying the gas, the burners so constructed
+became choked with the tarry matters held in suspension, and carried
+forward by the gas; and so, after a comparatively short period of
+service, were rendered entirely inoperative. But, altogether apart from
+the inconvenience and loss thus entailed (which, when improved modes of
+manufacture had removed the cause, ceased to be experienced), the
+arrangement was ill adapted for the purpose which it was designed to
+serve. The rough and uneven nature of the material employed to stuff
+the burner caused the gas to eddy and swirl as it issued into the
+atmosphere, and prevented it being supplied equally to all parts of the
+flame. The consequence was that the advantages which ought to have been
+derived from the diminished pressure were neutralized by the unsteady
+flow acquired by the stream of gas; and the illuminating power
+developed by the flame was little improvement upon what could
+previously be obtained by the manipulation of the tap controlling the
+supply of gas to the burner. Besides which, from its unevenness, the
+appearance of the flame was not so satisfactory. It was not until the
+principles which regulate the production of light from coal gas came to
+be known and observed in the construction of burners, that a
+modification of the old idea was arrived at, which enabled the benefits
+of a reduced pressure to be obtained without any of the attendant evils
+hitherto experienced.
+
+[Sidenote: The first real improvement of the union-jet burner.]
+
+A modification in the construction of the union-jet which, though
+slight, was nevertheless a real improvement, appears to have been made
+at an early period in the history of this burner. Instead of having the
+top of the burner perfectly flat, it was made slightly concave; more
+especially at its centre, where the two jets of gas emerge. The effect
+of this alteration was to enable the stream of gas to spread out
+better; and thus to cause the flame to become broader at its base. The
+shape of the flame was thereby improved; and (what is of more
+consequence) its illuminating power increased, because air was not
+drawn so readily into the midst of the flame. The value of the
+arrangement is shown by the fact that it has been retained ever since,
+and is made use of in the latest and most improved burners of this
+class.
+
+Prior to 1860, numerous novel contrivances were introduced as
+"improved" burners; but all were not equally valuable with the simple
+arrangement just described. The construction of many of them, indeed,
+betrayed a lamentable ignorance of the first principles of gas
+combustion. For instance, one is described as "a fishtail with four
+converging holes; and there is an aperture in the centre of the burner
+for the admission of atmospheric air into the flame!" Another was a
+batswing with two or more slits, producing a series of flames
+amalgamated into one; by which means it was supposed that an improved
+duty was obtained from the gas--unmindful, or, more probably, in
+ignorance of the fact that the same quantity of gas, properly consumed
+through one slit, would yield a better light.
+
+[Sidenote: The double-flame burner.]
+
+A burner which, at different times, and under various names, has been
+brought repeatedly into notice is the double-flame; consisting of two
+batswing or union-jet burners set at an angle to each other, so that
+their flames converge, and merge into one. When two gas flames are made
+to coalesce in this manner, a greater amount of light is developed than
+the sum of that yielded by the separate flames; provided that, in the
+combined flame, the gas is properly consumed, without smoke. The reason
+for this increase is twofold. First, the increased quantity of gas
+burnt in one flame enables a higher average temperature to be
+maintained; and, in addition, a smaller surface of flame is exposed to
+the cooling action of the atmosphere than when the same quantity of gas
+is consumed in two flames. Second, the pressure at which the gas burns
+is diminished, because the initial velocity with which the streams of
+gas issue from the two burners is expended in impinging against each
+other, and a thicker flame results; the apparatus being, as far as its
+effect is concerned, a union-jet burner on a large scale. The increase
+of light so obtained appears to have been noticed at an early period;
+as a burner embodying the same principle is described and figured in
+"Clegg's Treatise," published in 1848. In Clegg's burner the gas issued
+from two perforated parallel plates inclined to each other; but at a
+more recent period two fishtail burners were employed, being mounted on
+separate tubes which branched out to a short distance from each other.
+Occasionally, for experimental and show purposes, it has been
+constructed with the two branches hinged together, so as to show the
+different effects produced when the two burners are used separately and
+in combination. At the present day it is made, by various makers, as
+one burner with two nipples, as shown in the annexed illustration;
+which doubtless is its most perfect form.
+
+  [Illustration: FIG. 5.--DUPLEX BURNER.]
+
+The advantages of the double flame are not so obvious under the
+conditions which obtain at the present day as at the period when it was
+first introduced. The increase of light it affords is most apparent
+when the gas is being consumed at an excessive pressure. Although, in
+general, it may be taken that any two flames, when combined, will
+develop a higher duty, per cubic foot of gas consumed, than separately;
+yet it would appear that this is not so in every case. When the gas is
+being consumed at the critical pressure which gives the best results,
+the flames are so near the smoking point that the slight diminution of
+pressure experienced when the streams of gas impinge upon each other is
+sufficient to cause the combined flame to smoke. Moreover, to such a
+stage of perfection have the ordinary flat-flame burners now been
+brought, that, for all ordinary consumptions, it may be safely affirmed
+that equal, if not superior results can be obtained with a single as
+with a double flame. Where, however, larger quantities of gas are
+required to be dealt with than can be effectively consumed in a single
+burner, the principle of combining two or more burners together, so
+that their flames shall mutually assist each other, may be
+advantageously employed; as is seen in the combination of flat-flame
+burners in the large lamps now employed in improved street lighting.
+
+  [Illustration: FIG. 6.--SCHOLL'S PLATINUM LIGHT PERFECTER.]
+
+[Sidenote: Scholl's "Platinum Light Perfecter."]
+
+An ingenious device for improving the efficiency of union-jet burners
+was brought out some twenty years ago by a Mr. Scholl, of London, and
+known as Scholl's "Platinum Light Perfecter," which is shown in the
+accompanying illustration. It consisted of a little brass ring,
+carrying a plate of platinum about 0.4 inch long by 0.15 inch wide. The
+ring fitted on to the top of the burner in such a manner that the
+platinum plate was held, in a vertical position, between the two
+orifices from which the gas emerged. The jets of gas, instead of
+impinging upon each other, impinged against the plate, and united above
+to form the flame. By the interposition of the metal plate, the
+velocity of the gas was much reduced; and a thicker and more sluggish
+flame was produced, with the result of increasing its illuminating
+power. When the apparatus was used upon a burner having very small
+orifices, and delivering its gas at a high pressure, the increase of
+light obtained was very striking; but with lower pressures the
+advantage derived from its use was correspondingly diminished. This is
+very clearly shown by the following table, which is extracted from a
+report, by Captain Webber and Mr. Rowden, on experiments upon
+gas-burners, carried out at the Paris Universal Exhibition, 1867.[4]
+
+          [4] See _Journal of Gas Lighting_, Vol. XVIII., p. 88.
+
+  --------------------------+-------+--------+---------------------+--------
+  Kind of Burner.           |Cubic  |Pressure| Illuminating Power. |
+                            |Feet of|  in    +----------+----------+Increase
+                            |Gas    |Inches. |Without   |With      |  per
+                            |per    |        |Perfecter.|Perfecter.| Cent.
+                            |Hour.  |        |          |          |
+  --------------------------+-------+--------+----------+----------+--------
+  Leoni's fishtail, No. 2 . |  3    | 0.84   | 1.3      |  4.1     | 215
+  Leoni's fishtail, No. 3 . |  {3   | 0.46   | 2.4      |  4.6     |  91
+                            |  {4   | 0.70   | 2.8      |  6.5     | 132
+                            | {3    | 0.31   | 3.4      |  5.0     |  47
+  Leoni's fishtail, No. 4 . | {4    | 0.47   | 4.5      |  7.6     |  68
+                            | {5    | 0.71   | 5.0      |  9.2     |  84
+                            |  {4   | 0.42   | 5.3      |  6.9     |  30
+  Leoni's fishtail, No. 5 . |  {5   | 0.60   | 6.1      |  8.3     |  36
+                            |  {6   | 0.81   | 7.1      | 10.0     |  40[5]
+  Leoni's fishtail, No. 6 . | {4    | 0.31   | 6.2      |  8.0     |  29[6]
+                            | {5    | 0.46   | 8.0      | 10.4     |  30[7]
+  --------------------------+-------+--------+----------+----------+--------
+
+          [5] Flame flickers.
+
+          [6] Do.
+
+          [7] Flame flickers a great deal.
+
+Burners were also made with the metal plate forming part of the burner
+head; and, instead of being of platinum, it was sometimes formed of
+thin steel, or other commoner metal. Where platinum was used, some
+advantage probably accrued from its becoming incandescent; but, of
+course, any benefit arising from this source was not obtained when
+steel was employed. The remarks which have been made respecting the
+limited applicability of the double-flame burner will apply, with equal
+force, to the apparatus under notice. Although it effected an undoubted
+improvement when applied to burners ill adapted to the pressure at
+which the gas was supplied, equally good results could be obtained
+without its aid, when a burner was employed suited to the quality and
+pressure of the gas supplied.
+
+[Sidenote: Leoni's flat-flame burners.]
+
+Perhaps the most efficient flat-flame burners available prior to 1867
+were those made by Mr. S. Leoni, of London. One of these is shown in
+fig. 7. This maker produced both batswing and union-jets; various sizes
+being made of each burner. Besides affording fairly good results from
+the gas consumed, the burners were supplied at a very moderate price.
+Their distinguishing feature was the peculiar substance of which the
+burner-tips were formed. This was a material invented by Mr. Leoni, and
+named by him "adamas." (The precise composition of "adamas" is a trade
+secret; but it appears to consist of a mixture of various minerals or
+earths, moulded in a clayey or plastic condition, and then burnt.)
+Previous to his invention, the tip of the burner, or the burner head,
+had been made, almost exclusively, of iron or brass. There were,
+however, some grave defects inherent in the use of metal for this
+purpose. The orifices of union-jets and the slits of batswings in
+course of time became much obstructed by the corrosion of the metal;
+and the efforts made to remove the obstruction only served to destroy
+the burner more quickly, by increasing the size and injuring the
+precise shape of the apertures. The "adamas" tips, on the other hand,
+perfectly withstood the high temperature to which they were exposed,
+were quite incorrodible, and were sufficiently hard to endure a
+considerable degree of even rough usage. By constructing the tip of
+this material, the efficiency of the burner was improved in many ways.
+The liability of the burner to corrosion being removed, and the
+inconvenience due to this cause done away with, the life of the burner
+was prolonged, and the expense of renewal consequently reduced. But, in
+addition to these advantages, there was yet another direction in which
+the "adamas" tip contributed to enhance the utility of the burner. This
+was in maintaining a higher temperature of the flame; and arose from
+its inferior capacity, compared with metal, for conducting heat from
+the flame. That the advantage derived from this source, although
+unimportant, was not altogether imaginary, will be apparent when it is
+mentioned that metal burners, when in operation, usually attain to a
+temperature of from 400 deg. to 500 deg. Fahr.--an indication of the amount of
+heat being continuously abstracted from the flame. The adoption of a
+non-conducting material for the burner-tip, while it did not entirely
+prevent, considerably reduced the loss of heat.
+
+  [Illustration: FIG. 7.--LEONI'S FLAT-FLAME BURNER.]
+
+Two varieties of each class of burner were made by Mr. Leoni. In the
+one burner, the "adamas" tip was inserted into an iron stem; in the
+other, the tip was inserted in a brass body, which fitted on to the
+iron stem. Between the brass body and the iron stem of the latter
+burner there was affixed a layer of wool, designed to check the
+pressure at which the gas was supplied. Owing, very probably, to the
+unsuitability of the material (wool) used for this purpose, the result
+was not satisfactory; as, according to the statements of Messrs. Webber
+and Rowden, in the report previously cited, no difference could be
+detected, in many experiments, between the results yielded by the
+burner with or without the layer of wool. Some light is shed upon this
+apparent anomaly by certain experiments made by the writer to determine
+the pressure at which gas issues from various burners. With one of
+Leoni's No. 4 union-jets, under an initial pressure of 1 inch (the
+pressure at the inlet when the burner is in operation), the pressure at
+the outlet of the burner, when the layer of wool was employed, was 0.11
+inch; but from the same burner, when the layer of wool was removed, the
+gas issued at a pressure of only 0.07 inch. Thus the effect of
+inserting the layer of wool in the burner was exactly the opposite of
+that which it was intended to produce; the pressure of the issuing gas
+stream being increased instead of diminished.
+
+
+BROeNNER'S BURNERS.
+
+The credit of having produced the first flat-flame burners designed
+upon scientifically correct principles belongs undoubtedly to Herr
+Julius Broenner, of Frankfort-on-the-Maine. Long before the date of his
+invention, efforts had been made to reduce the pressure of the gas
+within the burner. But these endeavours were carried out in so
+hap-hazard a fashion as to lead to the belief that no definite
+conception was entertained as to what was really required. As we have
+seen, layers of wool had been employed; but the area of the
+interstices, or the gas-way through the material, was a matter of the
+merest accident. And there was not the slightest guarantee that the
+same conditions should prevail in any two burners. Herr Broenner
+shrewdly detected the cause of former failures, as he clearly perceived
+the end which it was requisite to attain, and towards which previous
+inventors had been but blindly groping. Having formed a right estimate
+of the requirements to be fulfilled, and the difficulties to be
+surmounted, he set about accomplishing the desired result by other
+means. There were two causes which had chiefly contributed to the
+unsuccessful issues of previous attempts. One was the uncertain and
+indefinite operation of the means employed for diminishing the
+pressure; the other was the inadequate provision for enabling the gas
+to lose the current, or swirl, acquired in passing the diminishing
+arrangement, and come to a state of comparative rest before issuing
+into the atmosphere. Both these errors were successfully avoided in
+Broenner's invention--the former by making the inlet to the burner of
+restricted and definite dimensions, and of less area than the outlet,
+or slit; the latter by enlarging the chamber, or place of expansion
+within the burner, as well as by the different arrangement adopted for
+diminishing the pressure.
+
+  [Illustration: A TOP.
+                 B TOP.
+                 FIG. 8.--BROeNNER'S BURNERS.]
+
+[Sidenote: Construction of Broenner's burners.]
+
+The general appearance of Broenner's burner is pear-shaped; and in size
+it is considerably larger than an ordinary burner designed to pass an
+equal quantity of gas. It consists of a cylindrical brass body
+surmounted by a steatite top, and tapering to a very small diameter at
+its lower end, or inlet; the latter being closed by a plug of steatite,
+in which is a rectangular slot, or aperture, of accurately defined
+dimensions. The size of this aperture determines the quantity of gas
+which, at any particular pressure, is admitted to the burner; and the
+slit, or outlet of the burner, being of greater area than the inlet,
+ensures the gas being delivered from the burner at a lower pressure
+than that at which it enters it. By varying the respective dimensions
+of these two openings, and their relation to each other, the burner may
+be regulated to deliver its gas at any required pressure short of the
+initial pressure at the entrance to the burner. The enlargement of the
+cylindrical body provides an expansion chamber, wherein the velocity of
+the stream of gas which rushes through the narrow opening at the inlet
+of the burner is checked, and any agitation or unsteadiness which may
+have been imparted to it is subdued before the gas issues into the
+atmosphere and is consumed. There are two kinds of tops for the
+burners, which are distinguished by the letters A and B. The B top is
+of the ordinary semi-spherical type, giving a true batswing-shaped
+flame; the A top is flatter, almost square in form, and yields a flame
+taller than, but not so broad as the former. In consequence of this
+difference in the shape of its flame, the latter burner is better
+adapted for use in globes. The general appearance of the burners, and
+their distinguishing peculiarities, will be clearly understood from the
+illustrations.
+
+[Sidenote: Properties of steatite.]
+
+The material of which the more important parts of the burner are
+constructed is eminently adapted for the purpose. Steatite is a mineral
+which, as found in nature, is so soft as to be readily turned in a
+lathe, and shaped to any design; but when heated up to about 2000 deg.
+Fahr. it becomes almost as hard and durable as flint, while perfectly
+retaining its form and colour. These properties peculiarly qualify it
+for receiving a slit or orifice, which, though of minute proportions,
+must be accurately formed to precise dimensions. Besides which, like
+"adamas," its capacity for conducting heat away from the flame is so
+limited that, in this respect, it has a considerable advantage over
+metal for the purpose of being formed into gas-burners.
+
+[Sidenote: Varied adaptability of the Broenner burner.]
+
+The following tables, which are extracted from the report of the
+Committee of the British Association appointed to investigate the means
+for the development of light from coal gas of different qualities,[8]
+exhibit the very satisfactory results obtained by the use of these
+burners. In Table I., the gas operated upon was cannel gas (such as is
+generally supplied in Scotland), and possessed an illuminating power,
+when employed in the standard burner, of 26 candles per 5 cubic feet.
+Table II. contains the results of determinations with common gas (such
+as is used in London, and generally throughout the greater part of
+England); 5 cubic feet of which, in the standard burner, gave an
+illuminating power of 16 candles. The first and second columns of the
+tables refer to the different sizes of the tops and bottoms of the
+particular burners employed; there being in all some 16 sizes of the
+one, and 11 sizes of the other. These, being interchangeable, permit of
+a great variety of combinations; and enable a burner to be selected
+suited to any particular quality or pressure of gas. For as with
+pressure, so with illuminating power: In order to obtain the utmost
+lighting efficiency, different burners are required for gases differing
+in quality or their degree of richness. A burner which, with gas of one
+quality, will yield excellent results, may, under the same conditions
+of pressure and supply, be totally unsuited to gas of another quality.
+That this should be so will be evident from a consideration of what has
+been said as to the theory of burning gas to the best advantage; and,
+in brief, results from the richer gas containing in its composition a
+greater proportion of carbon, and so requiring an increased supply of
+air for its thorough combustion. This increased supply of air can only
+be obtained (with flat-flame burners) by causing the gas to issue into
+the atmosphere at a higher pressure; and so it comes about that,
+compared with the quantity of gas to be delivered through them, the
+slits of batswing and the orifices of union-jet burners must be
+considerably narrower when intended for cannel gas than when common gas
+is to be consumed. In other words, in order to develop its full
+illuminating power, it is essential that the pressure at which the gas
+issues from the burner should be proportioned to its quality. The gist
+of the matter is set forth in the general statement that "the poorer
+the quality of the gas, the lower must be the pressure at which it is
+consumed; and _vice versa_."
+
+          [8] See _Journal of Gas Lighting_, Vol. XXXII., p. 423,
+          and Vol. XXXVI., p. 376.
+
+  TABLE I.
+
+  -----------------------------------+-----------------------------------
+         |    AT 0.5-INCH   |    AT 1.0-INCH      |    AT 1.5-INCH
+         |      PRESSURE.   |      PRESSURE.      |      PRESSURE.
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+  No.    |No. |Cubic|Illumi-|Illumi- |No.    |No. |Cubic|Illumi-|Illumi-
+  of     |of  |Feet |nating |nating  |of     |of  |Feet |nating |nating
+  Burner.|Top.|per  |Power. |Power   |Burner.|Top.|per  |Power. |Power
+         |    |Hour.|       |per Five|       |    |Hour.|       |per Five
+         |    |     |       |Cub. Ft.|       |    |     |       |Cub. Ft.
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+     2   |  2 | 1.20|  5.07 | 24.13  |   2   |  2 | 1.40|  5.25 | 18.75
+     2   |  3 | 1.40|  6.64 | 23.71  |   2   |  3 | 1.95|  7.37 | 18.90
+     2   |  4 | --  | Smokes|  --    |   2   |  4 | 2.30| 10.33 | 22.46
+     2   |  5 | --  |   "   |  --    |   2   |  5 | 2.40| 11.24 | 23.42
+     2   |  6 | --  |   "   |  --    |   2   |  6 | --  | Smokes|  --
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+   2-1/2 |  2 | 1.40|   5.53| 19.75  | 2-1/2 |  2 | 1.90|  8.30 | 21.84
+   2-1/2 |  3 | 1.70|   8.48| 24.94  | 2-1/2 |  3 | 2.30| 10.14 | 22.04
+   2-1/2 |  4 | 2.03|  10.33| 25.49  | 2-1/2 |  4 | 2.70| 12.08 | 22.37
+   2-1/2 |  5 | --  | Smokes|  --    | 2-1/2 |  5 | 2.85| 14.29 | 25.07
+   2-1/2 |  6 | --  |   "   |  --    | 2-1/2 |  6 | 3.00| 15.21 | 25.35
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+     3   |  2 | 1.45|   6.27| 21.62  |   3   |  2 | 2.00|  8.48 | 21.20
+     3   |  3 | 1.90|   8.66| 22.79  |   3   |  3 | 2.40| 11.34 | 23.63
+     3   |  4 | 2.13|  11.24| 26.39  |   3   |  4 | 2.80| 14.84 | 26.50
+     3   |  5 | --  | Smokes|  --    |   3   |  5 | 3.15| 17.04 | 27.20
+     3   |  6 | --  |   "   |  --    |   3   |  6 | 3.25| 18.07 | 27.80
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+   3-1/2 |  2 | 1.50|   5.81| 19.36  | 3-1/2 |  2 | 2.12|  8.85 | 20.87
+   3-1/2 |  3 | 1.95|   8.30| 21.28  | 3-1/2 |  3 | 2.55| 12.63 | 24.76
+   3-1/2 |  4 | 2.55|  12.08| 23.68  | 3-1/2 |  4 | 3.00| 14.47 | 26.12
+   3-1/2 |  5 | 2.80|  14.38| 25.68  | 3-1/2 |  5 | 3.50| 18.07 | 25.81
+   3-1/2 |  6 | 3.00|  15.58| 25.97  | 3-1/2 |  6 | 3.60| 19.45 | 27.01
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+     4   |  2 | 1.60|   6.36| 19.87  |   4   |  2 | 2.30|  9.77 | 21.24
+     4   |  3 | 2.10|  10.69| 25.45  |   4   |  3 | 2.90| 13.83 | 23.84
+     4   |  4 | 2.65|  13.37| 25.23  |   4   |  4 | 3.30| 17.06 | 25.85
+     4   |  5 | 3.45|  17.61| 25.52  |   4   |  5 | 4.10| 21.57 | 26.30
+     4   |  6 | 3.55|  18.07| 25.45  |   4   |  6 | 4.20| 22.40 | 26.66
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+     5   |  2 | 1.77|   7.38| 20.85  |   5   |  2 | 2.60|  9.68 | 18.81
+     5   |  3 | 2.30|  11.90| 25.87  |   5   |  3 | 3.30| 13.64 | 20.67
+     5   |  4 | 3.30|  15.40| 23.33  |   5   |  4 | 4.00| 19.91 | 24.14
+     5   |  5 | 4.10|  20.74| 25.29  |   5   |  5 | 5.00| 25.36 | 25.36
+     5   |  6 | 4.30|  22.68| 26.37  |   5   |  6 | 5.30| 27.66 | 26.10
+  -------+----+-----+-------+--------+-------+----+-----+-------+--------
+
+  TABLE II.
+
+  ----+----+----------------------+---------------------+------------------
+      |    |    AT 0.5-INCH     |    AT 1.0-INCH      |    AT 1.5-INCH
+           |      PRESSURE.     |      PRESSURE.      |      PRESSURE.
+      |    +-----+-------+------+-----+-------+-------+-----+-------+------
+  No. |No. |Cubic|Illumi-|Illum.|Cubic|Illumi-|Illum. |Cubic|Illumi-|Illum.
+  of  |of  |Feet |nating |Power |Feet |nating |Power  |Feet |nating |Power
+  Top.|Bot-|per  |Power. |per   |per  |Power. |per    |per  |Power. |per
+      |tom.|Hour.|       |Five  |Hour.|       |Five   |Hour.|       |Five
+           |     |       |Cub.  |     |       |Cub.   |     |       |Cub.
+           |     |       |Ft.   |     |       |Ft.    |     |       |Ft.
+  ----+----+-----+-------+------+-----+-------+-------+-----+-------+------
+  A2  | 1  | --  |  --   |  --  | 1.5 |   2.7 |  9.0  | 2.0 |   4.0 | 10.0
+   "  | 2  | 1.6 |  2.9  |  9.1 | 2.4 |   5.2 | 10.8  | 3.1 |   6.8 | 11.0
+   "  | 21/2 | 2.0 |  3.9  |  9.8 | 2.9 |   6.8 | 11.7  | 3.8 |   9.4 | 12.4
+  A3  | 3  | 2.1 |  4.4  | 10.5 | 3.2 |   7.8 | 12.2  | 4.4 |  10.6 | 12.0
+   "  | 31/2 | 2.5 |  4.8  |  9.6 | 3.8 |   9.2 | 12.1  | 4.9 |  12.2 | 12.4
+   "  | 4  | 2.5 |  5.4  | 10.8 | 3.8 |   9.6 | 12.7  | 5.2 |  13.6 | 13.1
+   "  | 41/2 | 3.0 |  6.4  | 10.7 | 4.5 |  10.8 | 12.0  | 5.9 |  14.8 | 12.5
+   "  | 5  | 3.2 |  7.7  |  2.0 | 5.1 |  13.2 | 13.0  | 6.8 |  18.0 | 13.2
+   "  | 6  | 3.7 |  8.7  | 11.8 | 5.8 |  15.5 | 13.3  | 7.7 |  21.0 | 13.6
+   "  | 7  | 3.5 |  8.6  | 12.3 | 5.9 |  16.0 | 13.6  | 8.4 |  23.0 | 13.7
+   "  | 8  | 3.7 |  9.0  | 12.2 | 6.2 |  16.8 | 13.5  | 8.6 |  23.4 | 13.6
+  B1  | 1  | --  |  --   |  --  | 1.3 |   2.3 |  8.8  | 1.8 |   3.5 |  9.7
+  B2  | 2  | 1.3 |  2.3  |  8.8 | 2.1 |   4.4 | 10.5  | 2.8 |   6.4 | 11.4
+   "  | 21/2 | 1.6 |  3.0  |  9.4 | 2.5 |   6.0 | 12.0  | 3.4 |   8.4 | 12.4
+  B3  | 3  | 2.0 |  3.8  |  9.0 | 3.0 |   7.2 | 12.0  | 4.1 |  10.1 | 12.3
+   "  | 31/2 | 2.3 |  4.3  |  9.3 | 3.4 |   7.7 | 11.3  | 4.5 |  11.0 | 12.2
+  B4  | 4  | 2.3 |  4.7  |  0.2 | 3.6 |   8.8 | 12.2  | 5.0 |  13.0 | 13.0
+   "  | 41/2 | 2.7 |  5.9  | 10.9 | 4.3 |  10.4 | 12.1  | 5.6 |  15.0 | 13.4
+  B5  | 5  | 3.1 |  7.0  | 11.3 | 4.9 |  12.9 | 13.2  | 6.5 |  18.0 | 13.8
+  B6  | 6  | 3.8 |  9.6  | 12.6 | 5.9 |  16.4 | 13.8  | 8.0 |  23.0 | 14.4
+  B7  | 7  | 4.0 | 10.2  | 12.8 | 6.6 |  19.0 | 14.4  | 9.0 |  26.0 | 14.4
+  B8  | 8  | 4.7 | 11.8  | 12.6 | 7.3 |  22.0 | 15.1  | 9.6 |  30.0 | 15.7
+  ----+----+-----+-------+------+-----+-------+-------+-----+-------+------
+
+[Sidenote: Pressure of gas with the Broenner burner.]
+
+Doubtless the chief cause of the remarkable efficiency of the Broenner
+over previous burners is to be found in the pressure at which the
+gas flows from the burner and is consumed. In the course of some
+experiments made to determine the pressure at which gas is delivered
+from various burners, the writer found that from a No. 4 Broenner, with
+an initial pressure--_i.e._, the pressure at the inlet when the burner
+is in operation--of 1 inch, the gas issued at a pressure of only 0.05
+inch; and with an initial pressure of 0.5 inch, the outlet pressure was
+only 0.03 inch. On the other hand, a No. 4 steatite flat-flame burner,
+without any arrangement for retarding the flow of the gas, under the
+same initial pressure gave at the outlet 0.16 inch and 0.05 inch
+respectively. The absence of anything within the burner to cause the
+gas to swirl, or to issue with an unsteady flow, must also be credited
+with contributing, in no slight degree, to the favourable results
+yielded by these burners.
+
+
+THE HOLLOW-TOP BURNER.
+
+In the hollow-top burner we have one of the most notable improvements
+which have been effected in flat-flame burners. A simple modification
+of the batswing--the earliest of flat-flame burners--it is not more
+complicated in its details than is that burner. Yet, simple as it
+is, its construction exhibits an important advance upon the original
+batswing. Indeed, this burner may be said to embody the only
+considerable improvement that has been made in the distinctive features
+of the batswing since the introduction of the latter burner, which, as
+we have seen, took place as early as the year 1816.
+
+[Sidenote: The hollow-top an improved batswing burner.]
+
+In its outward form, the hollow-top burner differs little, if at all,
+from the batswing; but a slight modification which has been adopted in
+the arrangement of its interior has produced a very marked result in
+improving the shape of the flame yielded by the burner, and, to some
+extent, in the results, as regards illuminating power, which it is
+capable of affording. In this burner, as its name implies, the
+interior of the top or head of the burner is hollowed out, forming an
+enlargement of the cavity or chamber within the burner, and (what is
+chiefly important) making the shell of the dome-shaped burner head of
+equal thickness throughout. In the ordinary batswing, in consequence
+of the varying thickness of the burner at this part, the slit is much
+deeper in the middle than at any other part of its length, and
+gradually decreases in depth towards each end. As the resistance to
+the passage of the gas, or the friction which it encounters, increases
+with the depth of the slit, the gas passes out from the burner at the
+ends of the slit more readily than in the middle; producing a
+wide-stretching flame, of scanty height in proportion to its width.
+From the same cause the flame is not of equal thickness throughout;
+being thinner in the middle than at the ends. Moreover, the outer
+extremities of the flame, extending so far beyond the body of the
+burner, are unable to retain the form given to them by the lateral
+flow of the gas at the ends of the slit; the resistance, presented by
+the atmosphere, together with the natural tendency of the gas to
+ascend, causing the under portion of the flame to fold back upon
+itself. As one result of this combination of untoward circumstances,
+the flame is liable to smoke with a slight agitation of the
+surrounding air.
+
+In the hollow-top burner, the slit is of equal depth throughout its
+length; and the resistance offered to the passage of the gas being the
+same in all parts of the slit, the gas flows through the middle as
+readily as at the ends--nay, in reality rather more so, owing to the
+innate ascensive power of the gas, due to its being lighter than air.
+The peculiar hollowing-out of the head of the burner, also, withdraws
+the ends of the slit out of the direct course or current of the gas
+through the burner; so that the tendency of the stream of gas to issue
+at these points, in preference to going through the middle of the
+slit, is further checked. The consequence is that the shape of the
+flame is considerably improved; it being taller, more compact, and not
+so broad as that of the batswing. In addition, the flame being of
+equal thickness throughout, its illuminating power is somewhat
+improved; while, from its compactness, it is better enabled to resist
+atmospheric influences. With this alteration in the shape of the flame
+all original resemblance to a batswing is entirely destroyed; but the
+appearance of the flame of the new burner is much more agreeable to
+the eye than that of the older batswing.
+
+  [Illustration: FIG. 9.--ORIGINAL HOLLOW-TOP BURNER.
+                 (From Wadsworth's Specification.)]
+
+[Sidenote: Who invented the hollow-top burner.]
+
+As has been exemplified in so many instances in the history of
+invention, the hollow-top burner was not appreciated at its true value
+until long after it had been brought into existence. It appears to
+have been originally invented by Joseph and James Wadsworth, of Marple
+and Salford, and was patented by them in 1860. According to the
+specification of the inventors, the burners might be made either
+in solid or sheet metal, as will be seen from the accompanying
+illustrations, copied from the drawings in the specification. But
+there were difficulties in the way of casting the burners in solid
+metal which do not seem to have been surmounted; and those produced
+under the patent appear to have been made exclusively of sheet brass.
+For many years these burners were made and sold without their
+peculiarities attracting any marked attention; which would seem to
+imply that their faulty construction precluded the attainment of all
+the advantages afforded by the burner as we know it.
+
+[Sidenote: Sugg's hollow-top burner.]
+
+The superior results which the hollow-top burner was calculated to
+afford did not become fully apparent until the burner was made of
+non-conducting material, and greater care exercised in its
+construction. This appears to have been done in Germany earlier than
+in this country. But, in England, it was undoubtedly Mr. Sugg who
+first turned his attention to the improvement of the burner, and
+demonstrated its merits. Mr. Sugg commenced the manufacture of this
+burner in steatite in the year 1868; and since that time the burner
+has been extensively employed, and its advantages widely recognized.
+The superiority of hollow-top burners produced by Mr. Sugg to those
+previously manufactured, is chiefly the result of their being made in
+steatite instead of in metal. With this material, greater exactness
+and uniformity are obtained in the shape and dimensions of the burner
+than when metal is employed; besides which there is (what has been
+before referred to) the advantage arising from its inferior conductive
+capacity for heat, and its non-liability to corrosion. Another
+improvement, also due to Mr. Sugg, and which is productive of
+noticeable results, consists in cutting the slit of the burner with
+a circular saw, applied from above, so as to make the ends of the
+slit curved instead of horizontal; by which means the tendency of
+the gas to issue laterally at the ends of the slit, and form horns
+to the flame, is lessened. Mr. Sugg's table-top burner (which was
+introduced in 1880), in addition to the characteristic features
+of the hollow-top, has a rim-like projection from the burner, below
+the slit; its object being to protect the flame from the disturbing
+influence of the uprush of air in its immediate vicinity, and so
+preserve its shape unaltered, while diminishing its liability to
+smoke. Prior to Mr. Sugg--namely, in the early part of 1879--Mr. Bray
+had successfully obviated this injurious action upon the flame of the
+ascending current of air, by affixing to the burner two arms of brass,
+so placed as to be immediately under the projecting wings of the
+flame.
+
+  [Illustration: 1868 BURNER.
+                 1874 BURNER.
+                 TABLE-TOP BURNER.
+                 FIG. 10.--SUGG'S HOLLOW-TOP BURNERS.]
+
+
+BRAY'S BURNERS.
+
+The burners of Messrs. George Bray and Co. have deservedly acquired a
+world-wide reputation, and are in extensive use wherever gas lighting
+is known. Their distinguishing characteristic, and that which has won
+for them the high repute in which they are held, is the union of
+cheapness with remarkable efficiency. In all the various descriptions
+and classes of burners which are produced by this firm, the
+characteristic referred to is preserved; although it is needless to
+add that the different varieties are not equally efficient. Of the
+three forms of flat-flame burners we have been considering--batswing,
+union-jet, and hollow-top--the one which, more than any other, has
+been the speciality of the firm is the union-jet; and it is with the
+development of this class of burner that the name of Bray is most
+intimately and honourably associated.
+
+  [Illustration: UNION-JET.
+                 HOLLOW-TOP OR SLIT-UNION.[9]
+                 BATSWING.
+                 FIG. 11.--BRAY'S "REGULATOR" BURNERS.]
+
+          [9] The name "slit-union," by which Mr. Bray prefers to
+          designate this burner, he states to be derived from the
+          resemblance of its flame to that of the union-jet burner;
+          while it is produced by means of a slit.
+
+[Sidenote: Bray's "regulator" burner.]
+
+[Sidenote: Bray's "special" burner.]
+
+The "regulator" union-jet, which was the first notable burner produced
+by Messrs. Bray, has received, perhaps, a wider application than any
+other single gas-burner. It consists of a cylindrical brass case,
+screwed at one end for insertion into the fittings, and at the other
+containing a tip of "enamel"--a material invented by Mr. Bray, and
+apparently of somewhat similar composition to the "adamas" of Mr.
+Leoni--the "enamel" tip being perforated, in the usual manner, with
+two holes, set at an angle to each other, for the outflow of the gas.
+The distinctive feature of this burner is the introduction into the
+lower part of the brass case of a layer, or layers, of muslin;
+designed to check in some degree, and to steady the current or flow of
+the gas through the burner. At the time of its introduction, this
+burner compared very favourably, as regards the results it yielded,
+with other burners in common use; and its fairly good performances,
+together with the very low price at which it can be sold, cause it
+still to be extensively employed wherever the attainment, from the gas
+consumed, of the highest obtainable results may be subordinated to
+cheapness, or in situations where, from delicacy of construction or
+from the care and attention demanded, a more efficient burner may not
+be so suitable. But in the matter of developing the illuminating power
+of the gas employed, the "regulator" is far surpassed by the more
+recently introduced "special" burner of the same makers.
+
+  [Illustration: UNION-JET.
+                 HOLLOW-TOP OR SLIT-UNION.
+                 BATSWING.
+                 FIG. 12.--BRAY'S "SPECIAL" BURNERS.]
+
+Mr. Bray's series of "special" burners--embracing union-jet,
+hollow-top, and batswing--are constructed upon the principle of, and
+in form are somewhat similar to Broenner's burners, which have already
+been fully described. Apart from its being of greater bulk, the main
+divergence in the construction of the "special" burner from that of
+the earlier "regulator" is the introduction, into the lower part of
+the brass case, of a plug or washer of enamel, pierced by a small
+circular hole for the admission of gas into the burner; the diameter
+of this hole determining the quantity of gas which, at any particular
+pressure, is admitted into the burner. Just above the enamel washer, a
+layer of muslin is inserted, as in the "regulator" burner; which, in
+this case, is for the purpose of subduing the agitation, or swirl,
+acquired by the current of gas in passing through the narrow aperture
+in the washer. A tip of enamel, made of the particular description
+(union-jet, hollow-top, or batswing) required, fitting into the upper
+part of the brass case, completes the burner. The objects aimed at in
+the "special" burner are to cause the gas to be consumed at the lowest
+pressure compatible with the maintenance of a firm flame, and with the
+least agitation, or swirl, in the current of gas as it issues from
+the burner. The former is attained, as in Broenner's burners, by
+diminishing the area of the opening admitting into the burner, without
+a corresponding diminution of the orifices through which the gas
+issues into the atmosphere; the latter, by the interposition of
+the layer of muslin which is immediately above the diminishing
+arrangement, as well as by the enlargement of the gas chamber in
+the upper part of the burner. The improvement thus effected in the
+illuminating power developed from the gas is well shown in the
+following tables extracted from an exhaustive series of tests of
+gas-burners carried out by Mr. T. Fairley, F.R.S.E., Borough Analyst
+of Leeds, and embodied by him in a report presented to the Leeds
+Corporation. The full text of the report will be found in the _Journal
+of Gas Lighting_ for February 6, 1883.
+
+  _Medium Lighting Power Union-Jets._
+
+  -----------------------------------+-----------------------------------
+        "Regulator" Burners.         |      "Special" Burners.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+  No.   |Pres- |Cubic|Illumi-|Illumi-|No.   |Pres- |Cubic|Illumi-|Illumi-
+  of    |sure  |Feet |nating |nating |of    |sure  |Feet |nating |nating
+  Burner|in    |per  |Power  |Power  |Burner|in    |per  |Power  |Power
+        |Inches|Hour |in     |per 5  |      |Inches|Hour |in     |per 5
+        |      |     |Stand. |Cubic  |      |      |     |Stand. |Cubic
+        |      |     |Candls.|Feet.  |      |      |     |Candls.|Feet.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+     3  |  0.5 | 3.50|   6.8 |  9.7  |   3  |  0.5 | 3.43|  11.3 | 16.4
+     3  |  1.0 | 4.80|   6.9 |  7.2  |   3  |  1.0 | 4.90|  15.6 | 15.8
+     3  |  1.5 | 6.20|   7.5 |  6.05 |   3  |  1.5 | 6.03|  17.6 | 14.6
+     4  |  0.5 | 4.65|  12.2 | 13.1  |   4  |  0.5 | 3.73|  13.3 | 17.8
+     4  |  1.0 | 6.67|  14.2 | 10.6  |   4  |  1.0 | 5.15|  17.4 | 16.9
+     4  |  1.5 | 8.16|  14.2 |  8.8  |   4  |  1.5 | 6.57|  22.4 | 17.1
+     5  |  0.5 | 5.72|  17.0 | 14.9  |   5  |  0.5 | 4.80|  17.6 | 18.3
+     5  |  1.0 | 7.97|  20.0 | 12.6  |   5  |  1.0 | 6.67|  24.4 | 18.3
+     5  |  1.5 | 9.73|  21.8 | 11.2  |   5  |  1.5 | 8.30|  30.0 | 18.2
+     6  |  0.5 | 5.90|  18.0 | 15.2  |   6  |  0.5 | 5.48|  20.1 | 18.3
+     6  |  1.0 | 8.35|  23.0 | 13.8  |   6  |  1.0 | 7.65|  28.4 | 18.6
+     6  |  1.5 |10.60|  28.0 | 13.2  |   6  |  1.5 | 9.20|  34.2 | 18.7
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+
+  _Medium Lighting Power Slit-Unions._
+
+  -----------------------------------+-----------------------------------
+        "Regulator" Burners.         |      "Special" Burners.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+  No.   |Pres- |Cubic|Illumi-|Illumi-|No.   |Pres- |Cubic|Illumi-|Illumi-
+  of    |sure  |Feet |nating |nating |of    |sure  |Feet |nating |nating
+  Burner|in    |per  |Power  |Power  |Burner|in    |per  |Power  |Power
+        |Inches|Hour |in     |per 5  |      |Inches|Hour |in     |per 5
+        |      |     |Stand. |Cubic  |      |      |     |Stand. |Cubic
+        |      |     |Candls.|Feet.  |      |      |     |Candls.|Feet.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+    3   | 0.5  | 4.22|  13.8 |  16.4 |   3  |  0.5 | 3.04|  10.8 | 17.8
+    3   | 1.0  | 6.37|  20.2 |  15.9 |   3  |  1.0 | 4.61|  16.4 | 17.6
+    3   | 1.5  | 8.14|  25.8 |  15.9 |   3  |  1.5 | 5.88|  19.9 | 16.9
+    4   | 0.5  | 4.25|  14.8 |  17.4 |   4  |  0.5 | 3.82|  14.2 | 18.6
+    4   | 1.0  | 5.88|  20.6 |  17.5 |   4  |  1.0 | 5.69|  20.8 | 18.3
+    4   | 1.5  | 7.95|  26.5 |  16.6 |   4  |  1.5 | 7.35|  25.6 | 17.5
+    5   | 0.5  | 5.25|  19.0 |  18.2 |   5  |  0.5 | 4.12|  15.4 | 18.7
+    5   | 1.0  | 8.14|  28.4 |  17.45|   5  |  1.0 | 6.37|  23.4 | 18.4
+    5   | 1.5  |10.20|  36.4 |  17.8 |   5  |  1.5 | 7.94|  28.5 | 18.0
+    6   | 0.5  | 5.67|  22.2 |  19.6 |   6  |  0.5 | 5.00|  19.6 | 19.6
+    6   | 1.0  | 8.60|  33.6 |  19.4 |   6  |  1.0 | 7.55|  29.0 | 19.2
+    6   | 1.5  |11.10|  39.5 |  17.8 |   6  |  1.5 | 9.70|  37.0 | 19.1
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+
+  _Medium Lighting Power Batswings._
+
+  -----------------------------------+-----------------------------------
+        "Regulator" Burners.         |      "Special" Burners.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+  No.   |Pres- |Cubic|Illumi-|Illumi-|No.   |Pres- |Cubic|Illumi-|Illumi-
+  of    |sure  |Feet |nating |nating |of    |sure  |Feet |nating |nating
+  Burner|in    |per  |Power  |Power  |Burner|in    |per  |Power  |Power
+        |Inches|Hour |in     |per 5  |      |Inches|Hour |in     |per 5
+        |      |     |Stand. |Cubic  |      |      |     |Stand. |Cubic
+        |      |     |Candls.|Feet.  |      |      |     |Candls.|Feet.
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+     3  |  0.5 | 4.16|  12.6 |  15.1 |   3  |  0.5 | 3.37|  12.4 | 18.4
+     3  |  1.0 | 5.64|  16.6 |  14.8 |   3  |  1.0 | 5.25|  20.4 | 19.4
+     3  |  1.5 | 7.83|  21.0 |  13.4 |   3  |  1.5 | 7.13|  24.0 | 16.8
+     4  |  0.5 | 4.26|  14.0 |  16.4 |   4  |  0.5 | 3.67|  13.0 | 17.7
+     4  |  1.0 | 6.74|  21.2 |  15.6 |   4  |  1.0 | 5.55|  20.6 | 18.6
+     4  |  1.5 | 7.81|  24.0 |  15.3 |   4  |  1.5 | 7.13|  26.0 | 18.2
+     5  |  0.5 | 4.76|  15.4 |  16.2 |   5  |  0.5 | 3.86|  14.6 | 18.9
+     5  |  1.0 | 6.93|  20.4 |  14.7 |   5  |  1.0 | 5.85|  22.6 | 19.4
+     5  |  1.5 | 8.72|  25.8 |  14.7 |   5  |  1.5 | 7.53|  28.0 | 18.6
+     6  |  0.5 | 6.04|  20.0 |  16.5 |   6  |  0.5 | 4.86|  19.4 | 20.0
+     6  |  1.0 | 8.82|  29.4 |  16.6 |   6  |  1.0 | 7.53|  31.6 | 21.0
+     6  |  1.5 |11.10|  31.6 |  14.2 |   6  |  1.5 | 9.60|  39.0 | 20.4
+  ------+------+-----+-------+-------+------+------+-----+-------+-------
+
+The quality of the gas operated upon averaged about 19 candles when
+tested with the Standard London Argand Burner.
+
+In a former part of this treatise it was remarked that the flames
+produced by the modern representatives[10] of the batswing and fishtail
+burners have lost the original resemblance to the objects whence the
+names of those burners were derived; and that the two flames have
+gradually approached each other in shape, until, in their latest
+developments, they are practically identical. We have seen how that,
+by the invention of the hollow-top, a burner is obtained apparently,
+to all outward appearance, the same as the batswing, yet giving a
+greatly improved form of flame. We have now to learn how the fishtail,
+or union-jet burner has been modified so as to yield a flame closely
+agreeing with that produced by the improved slit burner.
+
+          [10] Although the true batswing is still in common use, I
+          look upon the hollow-top as being its "modern representative;"
+          seeing that, in a great many instances, it has superseded
+          the former burner--of which, indeed, it is only an improved
+          form.
+
+[Sidenote: How the union-jet burner has been improved.]
+
+As first constructed, the union-jet burner gave a tall, narrow flame;
+its extremity being forked and jagged like the tail of a fish. Besides
+being unsightly, this form of flame was ill-adapted to develop, to
+anything like its full extent, the illuminating power of the gas. In
+order to obtain the best results, as regards illuminating power, the
+heat-intensity of the flame must be very high, so as to bring up the
+temperature of the particles of carbon liberated in the flame to the
+necessary degree of incandescence. To this end there must be
+concentration of the flame, in order to utilize to the full the heat
+of combustion. With the tall flame produced by the original union-jet
+burner there was too much exposure to the atmosphere for the flame to
+attain to the requisite intensity of heat; as well as considerable
+liability of the gas being brought too early into intimate contact
+with air, and so oxidized, or fully consumed, before its carbon had
+been raised to the temperature necessary to enable it to give out
+light. With the burner in its improved form the height of the flame is
+much curtailed, while it is broadened, and made more even and compact.
+This alteration has been chiefly brought about by two modifications in
+the construction of the burner-tip--first, by hollowing out its flat
+upper surface; and, second, by altering the angle at which the two
+streams of gas emerge from the burner. By scooping out the central
+portion of the flat top of the burner, so as to form a hollow or
+depression where the gas emerges, the flat sheet of flame which is
+formed when the two streams of gas impinge upon each other obtains a
+broader base, and at the same time is preserved from drawing air into
+its midst. But the chief share of the improvement is due to the
+alteration in the angle formed by the two channels in the burner-tip.
+It will be readily apparent that the more obtuse this angle--that is,
+the nearer the two streams of gas are to impinging against each other
+in a horizontal line--the more will the flame tend to spread out, or
+the lower the pressure required to obtain any desired spread of flame.
+It is by taking advantage of this circumstance that Mr. Bray has been
+enabled to improve the union-jet burner. Twenty years ago this burner
+was usually made with the two channels in the burner-tip placed at an
+angle of about 60 deg.. In Bray's "regulator" burner, introduced in 1869,
+they were placed at an angle of 90 deg.; with the result of obtaining a
+more satisfactory flame, both as regards its appearance and
+illuminating power. In the "special" burner, which was not brought out
+till 1876, the angle is increased to 120 deg.; thus enabling the necessary
+spread of flame to be obtained with the gas issuing at a low pressure.
+Another minor improvement in the latter burner consists in making the
+holes in the burner-tip elliptical instead of circular.
+
+
+
+
+CHAPTER III.
+
+ARGAND BURNERS.
+
+
+[Sidenote: The premier gas-burner.]
+
+The premier position among gas-burners undoubtedly belongs to the
+Argand; and it is from no unwillingness to recognize its claims, much
+less from ignorance of its merits, that I have left the consideration
+of this burner until now. It occupies this honourable position as much
+by virtue of the importance it has acquired through being accepted by
+Parliament as the test burner, and the peculiar relation in which it
+consequently stands to other burners, as for any marked superiority in
+operation. For while, in general, the Argand gives superior results to
+other burners, this is not always the case. There are circumstances
+and conditions to which the Argand is quite inapplicable, and where a
+simpler and less pretentious burner will give excellent results.
+Indeed, some of the simple flat-flame burners which we have had under
+notice have now been brought to such a stage of perfection, that, when
+intelligently used, they not unsuccessfully rival the Argand. But it
+has been in the direction of demonstrating the illuminating power
+which it was possible to obtain from gas, and stimulating to the
+attainment, by other and simpler burners, of the same level of
+excellence, that the influence of the Argand has been most beneficial.
+For, by reason of its peculiar construction, and more especially its
+mode of obtaining the air necessary for combustion, the Argand lends
+itself, more readily than any other burner, to the work of
+investigating and experimenting upon the conditions necessary for
+economical combustion, and the development of the highest illuminating
+power from the gas consumed. In this burner, the air supply to the
+flame is under complete control; and thus one of the chief elements of
+uncertainty and difficulty which are experienced in dealing with other
+burners is eliminated. The delivery of gas to different parts of the
+flame is also more susceptible of variation; and the results of such
+variation more fully exposed to observation. The consequence has been
+that the most remarkable advances in developing improved illuminating
+power from coal gas have been made with this burner. But after the
+possibility of obtaining an improved duty from the gas has been
+demonstrated by means of the Argand, and the conditions necessary for
+its attainment determined, equally good results have been achieved by
+other burners.
+
+  [Illustration: PLAN OF GLASS-HOLDER AND BURNER TOP.
+                 SECTION OF BURNER.
+                 FIG. 13.--ARGAND BURNER.]
+
+In thus showing the benefits to be derived from a more scientific mode
+of combustion, and leading the way to the fuller attainment, by other
+burners, of the illuminating power obtainable from the gas, the Argand
+burner has acted as a pioneer in the development of gas lighting. For,
+on account of its complexity, and its delicacy of construction, this
+burner has never been, nor, indeed, can ever hope to be generally
+employed. Besides the inconvenience and expense entailed by the
+cleaning and renewal, when broken, of the glass chimney which is
+indispensable to this burner, its very perfection as a burner
+precludes its being adopted under the conditions which appertain to
+the great majority of situations in which gaslight is required. For
+while, under the particular conditions as to pressure of gas, &c., for
+which it has been constructed, the Argand may give results surpassing
+any other burner, a very slight divergence from these conditions is
+productive of far more damaging results to the illuminating power of
+the flame than is the case with other and less efficient burners. The
+cause of this seeming anomaly will be apparent when we come to
+consider in detail the construction of the Argand, and the conditions
+which must be observed to ensure its satisfactory operation. For the
+present it will suffice merely to make mention of what appear to be
+well-established facts--viz., that the most perfect burners are the
+least adapted for use under uncertain and varying conditions; and that
+in proportion to the efficiency of a burner, under the conditions for
+which it has been constructed, is the injury to the illuminating power
+of its flame which is experienced when these conditions are departed
+from.
+
+[Sidenote: What is an Argand burner?]
+
+Resolved into its simplest form, the Argand burner may be said to
+consist of a hollow ring of metal, or other suitable material,
+provided with the necessary tubes or connections for communicating
+between its interior and the gas supply, and perforated on its upper
+surface with a number of holes for the emission of the gas. Through
+these holes the gas issues in a series of jets, which immediately
+coalesce to form one cylindrical sheet of flame. The burner is
+surmounted, and the flame enclosed, by a glass chimney, which is
+supported on a light gallery connected with the burner; the chimney
+serving the double purpose of shielding the flame from draughts, or
+currents of air (thus enabling the gas to burn uniformly and
+steadily), and of drawing upon the surface of the flame the supply of
+air necessary for its proper and complete combustion. For in the
+Argand the air supply is produced under conditions totally different
+from those which govern its production in all the other burners we
+have had under consideration. In flat-flame burners, the quantity of
+air supplied to the flame is determined by the pressure of the gas;
+or, in other words, the velocity with which it issues from the burner.
+In Argand burners, on the contrary, the air supply is obtained quite
+independently of the pressure at which the gas issues; and the
+conditions most effective for the economical combustion of the gas,
+and the development from it of the highest illuminating power
+attainable, are only secured when the pressure of gas is reduced to a
+minimum.
+
+It has been shown, in speaking of flat-flame burners, how the
+illuminating power of the flames yielded by such burners is
+injuriously affected by an excess of pressure in the gas, as it issues
+into the atmosphere, causing a too great intermingling of gas and air.
+With such burners, however, some degree of pressure is needed, in
+order, by bringing the flame into contact with sufficient of the
+oxygen of the air, to promote the requisite intensity of combustion;
+whereas with the Argand the draught that is produced through the
+agency of the glass chimney enables the necessary supply of air to be
+obtained for the support of the flame without adventitious aid from
+the pressure of the gas. Consequently, one of the chief objects to be
+aimed at in the construction of the latter burner is to so reduce the
+pressure of the gas within the burner that it may issue with little or
+no greater velocity than that due to its own specific lightness. In
+some of the best Argands this object is attained very successfully;
+and the ingenious devices which have been made use of to gain this end
+will be duly described in the sequel. But, in addition to causing the
+gas to issue from the burner at the minimum of pressure, it must be
+delivered evenly and equally at all parts of the ring of holes; so
+that there shall not be an excess of gas supplied to one portion of
+the flame, and an insufficiency to others. Then the area of the
+opening in the centre of the ring, through which the air supply is
+obtained to the inner surface of the flame, as well as the length and
+diameter of the glass chimney, must be so proportioned that the exact
+quantity of air needed to enable the flame to yield its maximum
+results shall be drawn upon it. These, and other equally essential
+requirements, have to be taken into consideration, and provided for,
+in constructing an efficient Argand burner. It is no wonder,
+therefore, that the development of the powers of this burner has taken
+up so much time and labour and inventive skill; and the remarkable
+degree of efficiency to which it has now been brought testifies to the
+thought and the accurate knowledge of the principles of combustion
+which have been brought to bear upon it.
+
+[Sidenote: The earliest Argands.]
+
+It is, however, only within comparatively recent years that its true
+principles of construction have been at all fully recognized, as
+evinced by the burners which have been produced. For a long period,
+Argand burners were made upon wholly empirical and arbitrary rules.
+During the early years of gas lighting, the makers of gas apparatus,
+and such persons as professed to have a special knowledge of the
+production and utilization of the new illuminant, appear to have been
+ignorant of even the most obvious of the conditions required for the
+successful working of the burner. In one of the earliest works which
+appeared relating to gas lighting,[11] we find the Argand burner
+described as consisting of "two concentric tubes closed at the top
+with a ring having small perforations, out of which the gas can issue;
+thus forming small distinct streams of light." According to this
+description, the burner referred to cannot have been an Argand in the
+strictest sense of the word; but, in reality, must have consisted
+chiefly of a series of single jets placed in a circle, and surrounded
+by a glass chimney. But the great improvement in the amount of light
+developed, which resulted from bringing the jets of flame closer
+together, so as to cause them to coalesce and produce one homogeneous
+mass of flame, could not long escape notice; and accordingly we find
+that in "Clegg's Treatise," which appeared twenty-five years later,
+the proper disposition of the holes in the ring, necessary for the
+successful operation of the burner, is clearly recognized. In this
+work, speaking of the Argand burner, it is remarked (p. 193) that "the
+distance between the holes in the drilled ring should be so much that
+the jet of gas issuing from each shall, when ignited, just unite with
+its neighbour."
+
+          [11] Accum's "Treatise on Gas-Lights."
+
+Before a really efficient burner could be produced, there were,
+however, to be successfully encountered other problems, the precise
+nature of which was not so clearly apparent as that of the one above
+referred to; otherwise their solution would not have been so long
+delayed. Of these, the most important, and at the same time the most
+difficult, were two--namely, the right adjustment of the air supply,
+and the most advantageous pressure at which to consume the gas. In the
+earliest Argands, not the slightest provision was made for diminishing
+the pressure of the gas before it was consumed. It was thought that
+everything had been accomplished that was necessary if the holes for
+its emission were sufficiently minute to allow of no more than the
+required quantity of gas passing through them at the extreme pressure
+at which it was supplied to the burner. The consequence was that the
+gas, issuing from the burner at a very high velocity, became so
+intermingled with air before it was consumed, that its flame was
+excessively cooled; and only a small fraction of the illuminating
+power available was developed. Then as to the air supply. In nearly
+every burner produced prior to Mr. W. Sugg's invention of the "London"
+Argand in 1868, this was greatly in excess of the requirements; nor is
+it to be wondered at. Had the supply of air been delicately adjusted,
+while yet there was no provision for diminishing the pressure of gas
+at the burner, the flame would have been liable to smoke on any sudden
+increase in the pressure of gas in the mains; and the annoyance and
+inconvenience occasioned by a smoking flame were greater drawbacks
+than the loss of light experienced through having the air supply
+greatly in excess. Thus, although during this period there were many
+so-called "improved" burners brought into notice, in none of them were
+these two cardinal requirements in the production of an efficient
+burner clearly recognized and seriously grappled with; and,
+consequently, the high level of excellence to which the Argand is
+capable of being brought was not attained.
+
+
+SUGG'S ARGANDS.
+
+[Sidenote: The 'London' Argand.]
+
+The invention by Mr. W. Sugg, in 1868, of the famous "London" Argand
+constitutes an important epoch in the history of gas lighting. Prior
+to that time, the construction of this class of burners had been
+carried out in a wholly empirical manner; and such improvements as had
+been effected must be looked upon as being rather the fortuitous
+issues of hap-hazard endeavours, than as resulting from the
+acquirement of clearer views as to the conditions to be complied with
+in order to ensure the successful operation of the burners. The
+invention of the "London" Argand was the first earnest attempt to
+abandon the former chance methods, and to proceed upon more scientific
+lines. Its construction shows that its inventor possessed a thorough
+acquaintance with the principles of combustion; while, in many
+particulars, it exhibits an intelligent discernment, and a successful
+application of the precise means required to attain a desired end. In
+this burner, the extreme importance of causing the gas to issue at a
+low pressure is for the first time clearly recognized; and the manner
+in which this object is so successfully attained is as simple as it is
+ingenious. At the entrance to the burner the gas is divided among
+three narrow tubes, the combined capacity of which is much smaller
+than that of the pipe supplying the burner. Through these tubes the
+gas is conducted into a concentric cylindrical chamber (forming the
+main body of the burner), where its rapid flow is checked; the
+current, or swirl, which it may have acquired, is subdued; and the gas
+comes to a state of comparative rest before it issues into the
+atmosphere and is consumed. The top rim of this concentric cylinder is
+pierced with 24 holes, the aggregate area of which is considerably
+greater than that of the three supply-tubes; thus ensuring that the
+gas shall be delivered at a much lower pressure than that at which it
+enters the burner. By dividing the gas into three streams, which enter
+the cylindrical chamber at equidistant points in its circumference,
+the supply is equally distributed throughout the entire ring of holes;
+and a flame of even and regular shape is the result.
+
+The arrangement by which, in this burner, the air supply is obtained
+and regulated is as noteworthy as are the means adopted for
+controlling the pressure of the gas. The opening within the circular
+ring of holes is much smaller than in previous Argands; thereby
+proportionately reducing the quantity of air supplied to the inner
+surface of the flame. The space between the cylindrical body of the
+burner and the glass chimney is occupied by a truncated cone of thin
+metal, the upper edge of which is on a level with, and reaches to
+within a very short distance of the rim of the burner; while its base
+rests upon the gallery supporting the chimney. By means of this cone,
+all the air entering between the burner and the chimney is directed
+upon the immediate surface of the flame; thereby promoting intensity
+of combustion, and a higher illuminating power of the flame. Then the
+chimney itself is of such dimensions that, with the quantity of gas
+for which the burner has been constructed, just sufficient air is
+drawn upon the flame to completely consume the gas by the time the top
+of the chimney is reached; a flame of such length as to nearly reach
+to the top of the chimney, without smoking, being the most effective
+and economical for the quantity of gas consumed.
+
+  [Illustration: FIG. 14.--SUGG'S "LONDON" ARGAND.
+                 (_Full Size._)]
+
+Another matter which tended not a little to enhance the results
+yielded by this burner was an alteration in the material of which the
+body of the burner was constructed. In previous Argands, this had, in
+almost every instance, been metal; whereas in the "London" burner
+steatite was employed. How the illuminating power of the flame is
+affected by the material of which the burner is constructed has been
+gone into so fully before (in relation to flat-flame burners), that it
+is unnecessary to dwell upon the matter here; only remarking that as
+in Argands the contact surface between the burner and the flame is
+relatively so much greater than in flat-flame burners, the cooling of
+the flame due to this cause is proportionately increased.
+
+[Sidenote: The standard test burner.]
+
+[Sidenote: The improved "London" Argand.]
+
+So great was the improvement effected by this burner in the
+illuminating power developed from the gas consumed, so obvious its
+superiority to every previous Argand, that it was immediately adopted
+by the Metropolitan Gas Referees as the standard burner for testing
+ordinary coal gas within the area of their jurisdiction; and from that
+time down to the present it has continued to be prescribed in Acts of
+Parliament as the burner to be employed in testing ordinary coal gas,
+not only in the Metropolis, but generally throughout the United
+Kingdom. But although, as the standard test-burner, the original
+"London" Argand can still be obtained, it has been far surpassed, in
+the results yielded, by a new series of Argands, in which the same
+ingenious inventor has still further applied the principles first put
+into practice in the former burner. In this newer series of burners,
+the details of construction before adopted are modified in two or
+three particulars; but without departing from the general principles
+embodied in the arrangement of the earlier burner. Thus the holes in
+the ring are considerably larger, while the three supply-tubes remain
+of exactly the same capacity as before; by which means the gas is
+delivered at a much lower pressure. As the increased size of holes
+necessitates that the cylindrical body of the burner should be of
+enlarged diameter, the opening in the centre becomes of greater area
+than before. Were it to remain so, it would permit too large a
+quantity of air to be drawn upon the inner surface of the flame; to
+obviate which result a metal spike rises in the centre, reducing the
+area of the opening, and proportionately diminishing the quantity of
+air which would otherwise be admitted at this part of the burner. The
+arrangement for regulating the air supply to the outer surface of the
+flame is likewise modified, but in a different direction. The upper
+edge of the cone is brought nearer to the rim of the burner, and
+slightly curved, so as to direct the air more completely upon the
+flame; while the base of the cone, instead of extending to the glass
+chimney in an unbroken surface, is pierced by a number of holes, which
+admit air between the cone and the chimney. The action of this third
+current of air is to keep the chimney cool, and to steady the flame;
+and, in addition, it may be that it provides a supply of air to
+support and intensify combustion at the upper extremity of the flame.
+The combined effect of these alterations is to cause the burner to
+develop from 7 to 12 per cent. more light from the gas consumed, than
+is yielded by the original "London" Argand.
+
+[Sidenote: Silber's Argand burner.]
+
+The Silber Argand, which is a remarkably efficient burner, in the main
+features of its construction is very closely related to Mr. Sugg's
+later Argands just described. The air is directed on to the outer
+surface of the flame, as in those burners, by a curved deflector, of
+which the upper edge is, however, at a higher level than in Mr. Sugg's
+burners. Air is also admitted between the deflector and the glass
+chimney. The most striking divergence in its construction from that of
+Mr. Sugg's burners is contained within the opening in the centre of
+the burner. Instead of a solid metal spike, there is a brass tube,
+through which, as well as between its circumference and the
+cylindrical body of the burner, air can enter to feed the inner
+surface of the flame. In addition to promoting the steadiness of the
+flame, it would appear that the air entering through this inner tube
+supports the combustion of the gas at the tail of the flame. The
+arrangements for diminishing the pressure of the gas within the
+burner, and for ensuring its equable distribution to all parts of the
+ring of holes, though quite different, seem to be scarcely less
+complete than those employed in the "London" burner. From the nipple
+which connects the burner to the gas supply, the gas enters (by four
+minute perforations) into a horizontal chamber, where its velocity is
+checked, and whence it is conveyed into the cylindrical chamber
+forming the main body of the burner. The very satisfactory
+performances of the burner (which are in advance of those of the
+standard Argand) sufficiently attest the correctness of its
+construction.
+
+[Sidenote: Multiple Argands.]
+
+For consuming large quantities of gas, double or treble Argands are
+constructed. These consist, in effect, of two or three Argand burners
+placed concentrically to each other within one chimney. Mr. Sugg
+has produced a series of burners of this class, designed to pass
+quantities of gas ranging from 15 to 55 cubic feet per hour; and, in
+some instances, exceeding even the latter figure. These burners, with
+ordinary (16-candle) coal gas, give a light equal to 4 candles per
+cubic foot of gas consumed; which is a considerably better result than
+is afforded by the standard burner. The cause of their yielding
+results so superior to the ordinary Argand is found in the
+circumstance that their flames present a much smaller surface area to
+the cooling action of the air, in proportion to the quantity of gas
+consumed. The arrangement of these burners differs from that of the
+improved single Argands, which have been described, only in that there
+are two or more steatite cylinders, each fed by its own supply-tubes,
+and having its own distinct ring of holes; while the space between the
+cylinders is so proportioned as to admit no more than the quantity of
+air required to produce the necessary intensity of combustion.
+
+  [Illustration: FIG. 15.--THE DOUGLASS ARGAND.
+                 (_A A, Focal Plane, or Belt of Strongest Light._)]
+
+
+THE DOUGLASS BURNER.
+
+The multiple or concentric Argand invented by Mr. (now Sir) J. N.
+Douglass, the Engineer to the Trinity House, may be mentioned here.
+This burner is of the type of those last noticed, but possesses
+certain peculiar features which give it a distinct claim to novelty.
+As will be seen by the accompanying illustration, the concentric
+cylinders of which the burner is composed terminate at different
+heights; their tops forming a regular gradation of steps, of which the
+innermost is the highest. These cylinders are of considerable depth,
+permitting the gas and air to be heated by contact with their surfaces
+before the point of ignition is reached. The essential feature of the
+invention, however, is a series of deflectors of peculiar shape,
+which, in addition to directing air on to the surfaces of the flames,
+are so formed "as to force the outer flame or flames on to the inner
+flame or flames in the manner illustrated." By this means the flames
+are concentrated and united into one, and combustion is quickened;
+and, a greater intensity of heat being thus attained, the illuminating
+power is much augmented. When this burner was first brought into
+notice, in 1881, high hopes were entertained as to its future. The
+results which it was said to afford, being far in advance of anything
+previously obtained from a simple Argand, seemed to promise for the
+burner a speedy and unequivocal success. At the North-East Coast
+Marine Exhibition, held in 1882, a burner with ten rings was
+exhibited, which was reported to develop, from 16-candle gas, 6
+candles per cubic foot--a truly remarkable result to be given by so
+simple a burner. But, notwithstanding its apparently successful
+introduction, the burner has made little or no headway in the
+direction of its practical application. Indeed, it may almost be said
+to have faded altogether out of public view. This would seem to imply
+that there are difficulties in the way of its successful working, when
+brought under ordinary conditions, which were not foreseen at the time
+of its invention.
+
+
+
+
+CHAPTER IV.
+
+GOVERNOR-BURNERS.
+
+
+[Sidenote: Effects of excessive pressure with Argand and flat-flame
+burners.]
+
+Throughout this treatise, much has been said of the relation which the
+pressure of gas, at the point of its delivery from the burner, bears
+to the illuminating power of the flame yielded--sufficient to show
+that the maintenance of a low and equable pressure in the gas supply
+is one of the conditions most imperative to be observed for the
+attainment of economy in combustion. Ordinarily, however, this
+condition does not obtain at the consumers' burners. The exigencies of
+distribution require that, in order to maintain a sufficient supply
+wherever gas is needed, a much higher pressure should be kept in the
+mains than is requisite for developing, at the burner, the best
+results from the gas consumed. Moreover, the pressure at any one point
+is subject to continual fluctuations from the variations in the
+consumption of gas going on in the neighbourhood. For instance, where
+a number of burners are in operation in a house, consuming about the
+exact quantities of gas for which they have been constructed, when
+part of them are shut off the gas supply to the remainder is in excess
+of what is required; and, consequently, the burners do not develop the
+same proportion of light from the gas consumed as formerly. Where a
+large consumption of gas is suddenly discontinued (as in the business
+parts of a town, when the shops and warehouses are closed), the
+increase of pressure that is experienced at the burners which remain
+in operation is very manifest. The effect of this increase in the
+pressure of the gas supply is seen in different directions in Argand
+and flat-flame burners. In the former, it causes the flame to smoke,
+by permitting more gas to pass through the burner than can be properly
+consumed; in the latter, by cooling the flame below the temperature
+required for effective combustion, it reduces, in proportion to the
+extent to which it is higher than the original pressure, the
+illuminating power developed per cubic foot of gas consumed.
+
+[Sidenote: The gas regulator.]
+
+Seeing that economy in combustion can only be attained under the
+conditions of an equable pressure, it becomes necessary to subdue the
+fluctuations above referred to, or at least to prevent their reaching
+the burner. To this end the regulator, or governor, is employed. In
+this instrument, a bell dipping into, and sealed in liquid--or else a
+flexible leather diaphragm--is actuated by the pressure of the
+entering gas, and so connected with a valve as to reduce the area of
+the opening which permits gas to enter the instrument in proportion to
+the pressure of gas at the inlet; by which means an equable pressure
+is maintained at the outlet, no matter what the quantity of gas which
+is being consumed, or how the pressure may vary in the inlet-pipe. By
+the aid of a governor, fixed on the service-pipe at the entrance to a
+building, the pressure of gas at the various burners is rendered
+fairly uniform; yet, even then, perfect equality of pressure is not
+obtained. The slight friction which the gas experiences in flowing
+through the pipes causes the burners to be supplied at somewhat lower
+pressures, the farther they are removed from the burner. And, again,
+owing to its low specific gravity, gas tends to gain in pressure with
+an increased elevation; each rise of 10 feet adding about 1-10th of an
+inch to its pressure. From this cause a higher pressure is experienced
+in the upper than in the lower rooms of a building. This peculiarity
+was observed at an early period in the history of gas lighting; as
+Clegg mentions that, in cotton-mills, check-taps were employed to
+regulate the pressure of gas at each floor.[12] In order, therefore, to
+obtain the desired regularity of pressure in the gas supply, governors
+must be employed for each storey; or, what is better still, each
+burner must have its own separate governor. And this brings us back to
+the subject with which we are more closely concerned.
+
+          [12] Clegg's "Treatise on Coal Gas," 1st Ed., p. 197.
+
+The governor-burner, as its name implies, consists of a governor, as
+described above (but, of course, on a smaller scale) combined with a
+gas-burner; the governor being adjusted so as, whatever excess of
+pressure there may be in the gas-supply pipes, to permit only the
+quantity of gas to pass which the burner is intended to consume.
+Obviously, the principle herein contained is capable of receiving
+numerous applications. It can be, and is applied with equal success to
+Argand and flat-flame burners; while the modifications which obtain in
+the manner of constructing the regulating portion of the apparatus are
+almost as numerous and as varied as are the burners themselves. As the
+main features exhibited by one are common to all, it is unnecessary to
+go into the details of their several constructions. It will suffice to
+take two or three of the most successful, or the best known, as
+representatives of the whole.
+
+[Sidenote: Giroud's Rheometer.]
+
+Among the first in order of time--and still retaining no unworthy
+position in order of merit--is the "rheometer," or "flow-measurer," of
+M. Giroud. In this instrument a light metal bell is sealed in
+glycerine contained in a cylindrical case; the bottom of this latter
+containing the inlet-pipe, screwed for connecting to the ordinary
+fittings, while from the centre of its cover rises a tube leading to
+the burner. The bell is pierced by a small hole for the passage of the
+gas, and is surmounted by a cone-shaped projection, which constitutes
+the valve of the instrument. As the pressure of the entering gas lifts
+the bell, it causes this cone-valve to enter the mouth of the tube
+leading to the burner; reducing the area of the opening in proportion
+to the pressure of gas acting upon the under side of the bell, and so
+permitting only the required quantity of gas to pass to the burner. It
+might be thought that the presence of liquid would constitute an
+objection to the use of the instrument; but, as glycerine does not
+evaporate, when once the instrument is fixed and properly adjusted, it
+needs no further attention. With an excessive initial pressure, there
+is, however, a liability of the gas to bubble through the sealing
+liquid, and so destroy the efficiency of the instrument; but this
+might be obviated by increasing the depth of the bell, and so giving
+it a greater seal. The instrument is very reliable for the purpose
+which it is intended to fulfil; delivering, through a considerable
+range of pressure beyond that required to raise the bell, the exact
+quantity of gas for which it has been adjusted. It may be added that
+the rheometer has an advantage over many instruments of its class, in
+that it presents so little obstruction to the downward rays of the
+flame.
+
+  [Illustration: FIG. 16.--GIROUD'S RHEOMETER.]
+
+[Sidenote: Sugg's Christiania governor-burner.]
+
+Mr. William Sugg, in his regulator or governor, adopts an entirely
+different arrangement to the foregoing. The valve is placed at the
+inlet of the governor; and not at its outlet, as in the instrument
+just described. Instead of a metal bell, a diaphragm of thin and very
+flexible leather is employed, which is raised by the pressure of the
+entering gas, and, in turn, actuates the valve; closing the entrance
+to the governor in proportion to the pressure of gas acting upon it.
+The orifice communicating between the under and the upper side of
+the leather diaphragm is controlled by a screw, whereby the quantity
+of gas delivered to the burner can be regulated according to
+requirements; but when once it has been adjusted to give any desired
+pressure of gas at the burner, this pressure will be strictly
+maintained, no matter with what excess of pressure (within reasonable
+limits) the gas may be supplied to the instrument. The improved
+"London" Argands produced by Mr. Sugg (the details of the construction
+of which have been already described) are too delicately adjusted to
+be applied with advantage directly to the ordinary consumer's
+gas-fittings, or wherever any variation in the pressure of the gas
+supply is likely to be experienced. However, with the addition to them
+of the above governor, their use becomes as easy and simple as that of
+other burners; and thus the gas consumer is enabled to obtain the
+benefit of the most improved apparatus without being called upon to
+exercise the constant care and attention which, without the aid of the
+governor, would be necessitated. Besides being applied to Argands,
+this governor is successfully applied by its inventor to his
+flat-flame burners. In conjunction with a simple steatite burner of
+the latter class, it has received a very extended application, under
+the name of the Christiania governor-burner.
+
+[Sidenote: Sugg's Steatite-float governor-burner.]
+
+Recently, however, a new type of governor, for application to burners,
+has been brought out by the same manufacturer, the construction of
+which is very different to that of the instrument referred to above;
+and as it is somewhat simpler in its details, and withal appears to be
+cheaper in construction, it seems destined to supersede the former
+instrument. In this new governor, instead of a leather diaphragm,
+there is a bell (or float) of steatite, which is free to move, in the
+manner of a piston, within an inner cylindrical chamber contained
+within the outer case of the instrument. Attached to the centre of the
+float, and on its upper surface, is a tube sliding within another tube
+of somewhat larger area; the latter forming a continuation of the
+inner cylindrical chamber. The smaller tube is open at both ends, and
+thus communicates from below to above the float; the outer tube is
+closed at the top, but has an orifice in its side. The action of the
+instrument is as follows:--The gas, entering below the float, passes
+through the inner tube to the upper part of the cylindrical chamber,
+and thence, through the orifice in the outer tube, to the burner. As
+the pressure of the entering gas exceeds that required to overcome the
+weight of the float, the latter is raised; the tube which is attached
+to it being propelled farther into the outer tube in which it slides,
+and, in so doing, partially closes the orifice in the side of the
+latter. In this way, according to the pressure of the gas acting upon
+the under side of the float, the area of the opening through which it
+must flow to get to the burner is reduced; and so the quantity of gas
+which issues from the burner remains the same under all pressures
+above that required to actuate the float. The instrument appears to be
+as reliable as it is simple, and to contain few parts calculated to
+get out of order; but, of course, whether or not it will retain its
+good qualities after long-continued use can only be proved by
+experience.
+
+  [Illustration: FIG. 17.--SUGG'S STEATITE-FLOAT GOVERNOR.]
+
+[Sidenote: Peebles's needle governor-burner.]
+
+[Sidenote: Efficiency of the needle governor-burner.]
+
+Another instrument of this class--the last which I shall notice--is
+Peebles's needle governor-burner. For simplicity combined with
+remarkable efficiency, it is undoubtedly ahead of all its compeers.
+Somewhat similar in principle to Giroud's rheometer, it differs from
+that instrument in many of the details of its construction; and while
+dispensing with the use of liquid, maintains equal efficiency in
+operation. It was described as follows by Dr. W. Wallace, in a lecture
+on "Gas Illumination," delivered before the Society of Arts in
+January, 1879:[13]--"In a little cylinder stands a so-called needle, on
+the point of which rests a flanged cone of exceedingly thin metal. At
+one side of the cylinder there is a small tube leading away the gas,
+and the orifice of which is influenced in area by the action of the
+cone. The instrument, by means of a screw leading into the side tube,
+can be made to deliver any desired number of cubic feet, which it does
+with surprising accuracy, provided that the pressure of the gas is not
+less than 6-10ths of an inch." As to the efficiency of the instrument,
+Dr. Wallace proceeded to state:--"In trials that I have made, I have
+not found the variations of volume at different pressures to exceed 1
+per cent." For situations where this extreme nicety of operation is
+not absolutely essential, or where the rate of consumption is to be
+invariable, the instrument is constructed in a somewhat modified and
+simpler form. The small tube on the side of the instrument is
+dispensed with, and the gas permitted to pass through perforations in
+the lower part of the cone. With this alteration there is a nearer
+approach to the construction of the rheometer; but, as in that
+instrument, there is no provision for altering the rate of consumption
+to suit different circumstances.
+
+          [13] See _Journal of Gas Lighting_, Vol. XXXIII., p. 162.
+
+  [Illustration: FIG. 18.--PEEBLES'S NEEDLE GOVERNOR.]
+
+
+
+
+CHAPTER V.
+
+REGENERATIVE BURNERS.
+
+
+[Sidenote: Temperature of a gas flame.]
+
+As was remarked in the introduction to this treatise, recent years
+have witnessed a very considerable advance in the construction of
+gas-burners, and in the amount of light capable of being developed
+from each cubic foot of gas consumed. Undoubtedly the most noticeable
+feature of this advance is the successful application of the
+regenerative, or, as it would be more appropriately designated,
+recuperative system. Briefly stated, this consists in utilizing the
+heat of the products of combustion from the gas flame (which otherwise
+would be dissipated into the atmosphere) to raise the temperature of
+the gas before it is ignited; and, likewise, of the air necessary for
+combustion. The temperature of an illuminating gas flame is usually
+estimated to be between 2000 deg. and 2400 deg. Fahr.; and as the products of
+combustion must leave the flame at a temperature little, if at all,
+inferior to the former figure, it must be evident that there is an
+ample margin of heat for employment in this direction. A considerable
+proportion of the large amount of heat conveyed by those products of
+combustion which, under ordinary circumstances, is imparted to the
+surrounding atmosphere--often elevating its temperature to an
+unnecessary and prejudicial extent--is, by this method, returned to
+the flame; intensifying the process of combustion, and augmenting, in
+a remarkable degree, the illuminating power developed from the gas
+consumed. Thus the ultimate effect of the operation is to produce a
+concentration of heat in the flame, and the conversion of superfluous
+heat into beneficial light. Within a comparatively recent period, the
+utility of this process was strongly disputed; and it was stoutly
+maintained, by many persons, that as the immediate effect of ignition
+was to cause a temperature of more than 2000 deg. Fahr. to be attained,
+the heating of the gas and air prior to their combustion could produce
+little or no beneficial effect upon the illuminating power of the
+flame. However, the falsity of this view of the case is conclusively
+demonstrated by practical experiment; the remarkably high results
+yielded by burners that have been constructed upon the regenerative
+system sufficiently attesting the correctness of the principles upon
+which they are founded.
+
+Although, in general, both the gas and air supplies are heated, it is
+chiefly due to the latter that the beneficial effect noticed is
+produced; and this for two reasons. First, because the quantity of air
+is so much greater than the gas it is required to consume; being, at
+the nearest approach to theoretical perfection, fully six times its
+volume. Second, because four-fifths in volume of the air consists of
+inert nitrogen, which does not contribute anything to the heat of the
+flame, but, when applied in its normal, cold condition, abstracts no
+inconsiderable proportion of heat from it. Yet the heating of the gas
+itself is not without very appreciable influence. In an ordinary
+gas flame there is always an area of non-illumination around, and
+extending to a variable distance from the burner head. This is caused
+partly by the conduction of heat from the flame by the burner; but, in
+a greater degree, by the cooling action of the issuing stream of cold
+gas, as is shown by its extending farther from the burner in
+proportion to the pressure or velocity with which the gas issues. The
+prejudicial effect due to the former is obviated to a great extent by
+constructing the burner of steatite, or other non-conducting material.
+To remedy the latter, nothing will avail but the heating of the gas
+supply.
+
+[Sidenote: Effects of heating the gas and air.]
+
+The effect of heating the gas is to enlarge the area of the
+illuminating portion of the flame, and, in a minor degree, to enhance
+the intensity of incandescence to which the carbonaceous particles are
+raised. When the gas issues from the burner at a temperature little
+inferior to the temperature of ignition, the hydrocarbons it contains
+are immediately decomposed; the liberated particles of carbon are
+raised to the temperature of incandescence; and the illuminating area
+of the flame is extended downwards, even to the surface of the burner.
+The heating of the air operates chiefly to produce and maintain a more
+elevated temperature of the flame; and, in this manner, contributes to
+the development of a higher illuminating power from the same area of
+flame. In the case of ordinary gas flames, the cold atmosphere by
+which they are surrounded, by abstracting heat from the flame,
+prevents the most favourable conditions for the development of light
+from being attained. When, however, the air immediately surrounding
+the flame has been previously heated, the particles of carbon (the
+incandescence of which furnishes the desired illuminating power)
+attain to a much more exalted temperature; and, consequently, give out
+a greater degree of light.
+
+But there is yet another direction in which the prior heating of the
+air supply contributes to the development of improved illuminating
+power. Being heated, its density is lowered; so that in any given
+volume of air there is less weight of oxygen than when cold. The
+consequence is that as less oxygen is presented to a given surface
+area of flame, the separated particles of carbon remain for a longer
+period of time in the incandescent condition before being entirely
+consumed. Thus there are three distinct results produced by heating
+the gas and air before combustion--namely, first, the particles of
+carbon are liberated earlier in the flame; second, they are raised to
+a more exalted temperature; and, third, they remain for a longer time
+in the incandescent condition. The combined effect of all three is the
+improved illuminating power developed from the gas consumed.
+
+  [Illustration: FIG. 19.--BOWDITCH'S REGENERATIVE GAS-BURNER.]
+
+[Sidenote: Bowditch's regenerative burner.]
+
+So far back as the year 1854, the principle of heating the air supply
+to an Argand burner, by means of waste heat from the flame, was
+partially applied, with some success, by the Rev. W. R. Bowditch,
+M.A., of Wakefield. Mr. Bowditch's burner, which is shown in the
+accompanying diagram, contained, in addition to the ordinary chimney,
+an outer glass chimney, which extended for some distance below the
+inner one, and was closed at the bottom; so that all the air needed to
+support the combustion of the gas was required to pass down the
+annular space between the chimneys, and in its passage became
+intensely heated by contact with the hot surface of the inner chimney,
+as well as by radiation from the flame itself. This burner contained
+many defects. Amongst others, the inner chimney could not long
+withstand the intense heat to which it was subjected, and, in
+consequence, had to be frequently renewed; the heating of the air was
+not effected solely by the products of combustion, but, perhaps in a
+greater degree, by the abstraction of heat from the flame itself;
+while, at best, this heating was but partial. Yet, these defects
+notwithstanding, the burner showed very clearly the beneficial results
+attending even a partial application of the principle; as, in the
+illuminating power it developed from the gas consumed, a clear gain of
+67 per cent. over the ordinary Argand burner was obtained. Although
+the drawbacks connected with the construction of Mr. Bowditch's burner
+prevented its ever receiving general, or even extensive adoption, its
+simplicity has gained for it the distinction of being freely copied by
+so-called inventors of a later day.
+
+[Sidenote: Invention of the Siemens regenerative burner.]
+
+It was left to Herr Friedrich Siemens, of Dresden, to produce a burner
+which, while applying the principle of regenerative heating in the
+most scientific and complete manner, should also be adapted to the
+ordinary conditions of gas lighting. After much experimenting on the
+subject, a burner embodying the essential features of the regenerative
+system was invented by this gentleman in 1879; and so great was the
+advance which its performances manifested over anything previously
+attained, so wide the prospect of further achievements which was
+opened out, that it may fairly be said to have inaugurated a new era
+in gas illumination. In this burner the products of combustion were
+made to give up a considerable portion of their heat to the gas and
+air, as the latter passed to the point of ignition; the flame itself
+not being called upon to contribute in any degree to this result.
+Although, as was but natural, the first attempts towards the
+construction of such a burner were very crude, and but partially
+successful in their results, the inventor persevered in his endeavours
+to work out his ideas into practical and thoroughly satisfactory
+shape. It was not until after it had gone through many modifications
+that the burner acquired the peculiar form which now distinguishes it,
+and attained to its present stage of perfection. Before proceeding to
+describe an example of the burner as now constructed, it is necessary
+to state that the principles embodied in Herr Siemens's invention are
+equally well adapted--and, indeed, are applied with equal success--to
+the construction of flat-flame and Argand burners; but as the
+distinctive features of the invention are common to both classes of
+burners, it will be quite sufficient to describe in detail one of the
+latter type.
+
+A prominent feature in the appearance of the Siemens burner, as will
+be seen from the annexed illustration, is a large metal chimney, for
+creating a draught to carry away the products of combustion. The
+entrance to this chimney is situated a little above the apex of the
+flame; but there is a branch flue connecting the main chimney with the
+interior of the burner. The body of the burner is of metal, and its
+interior is divided into three concentric chambers. Of these, the
+innermost is open at the top, and is surmounted by a porcelain
+cylinder, which, when the gas is lighted, is surrounded by the flame.
+This chamber is closed at the bottom, but communicates at the side
+with the before-mentioned branch tube, or flue, leading to the main
+chimney. The intermediate chamber communicates, at its lower
+extremity, with the gas supply; and terminates, a short distance from
+the top of the burner, in a number of small metal tubes, which convey
+the gas to the point of ignition. The outer chamber is open both at
+top and bottom, and is for conveying air to support the combustion of
+the gas. In order to promote greater intensity of combustion, there is
+a notched deflector at the summit of the latter chamber, and another
+on the lower part of the porcelain cylinder, which cause the air to
+impinge more directly upon both sides of the flame. There is also an
+arrangement for introducing air between the outer casing of the air
+chamber and the glass chimney which encloses the flame; its object
+being to keep the chimney cool.
+
+  [Illustration: ELEVATION.
+                 ENLARGED SECTION OF COMBUSTION CHAMBERS.
+                 FIG. 20.--SIEMENS'S REGENERATIVE GAS-BURNER.]
+
+[Sidenote: Action of the Siemens burner.]
+
+The action of the burner is as follows:--When the gas is ignited at
+the ring of tubes, the heated air and products of combustion, which
+rise from the flame, create a draught in the main chimney. Through the
+communication established by means of the lateral flue, a partial
+vacuum, or area of low pressure, is induced in the innermost chamber
+of the burner, and within the porcelain cylinder which surmounts it.
+As the flame terminates close to the mouth of the latter, the greater
+portion of the products of combustion, instead of going into the main
+chimney, are sucked into the porcelain cylinder; and thus a current is
+set up through the interior of the burner, and by the lateral flue, to
+the main chimney. The heat carried away by the products of combustion
+is communicated, through the walls of the chambers, to the entering
+gas and air; and by this means the latter are heated to a very high
+temperature before they issue from the burner and are consumed. The
+consequence is that a much greater intensity of combustion is
+maintained; the carbon particles are separated earlier in the flame,
+and are raised to a more exalted temperature; and the ultimate effect
+is a higher yield in illuminating power per cubic foot of gas
+consumed. Independent tests by various experienced photometrists have
+conclusively shown that a light equivalent to that from 5 to 6 candles
+is obtained per cubic foot, from gas which, in the standard "London"
+Argand, yields a light of only from 3 to 3-1/2 candles.
+
+[Sidenote: Defects of the Siemens burner.]
+
+While the advantages of the Siemens burner are many and obvious, it is
+not without its disadvantages. These partly arise from causes
+connected with the very observance of the conditions necessary to
+secure the efficiency of the burner. With every advance in the more
+efficient operation of gas-burners, increased care and attention are
+demanded in their employment, in order to obtain the benefits they are
+calculated to yield. Indeed, it would almost appear that the nearer
+the approach to perfection which is made in the construction of a
+burner, the greater must be the drawbacks to its general adoption.
+Thus, in the burner under notice, if the gas supply is allowed to
+become in excess, the tail of the flame enters the porcelain cylinder,
+and soot is deposited in the interior of the burner; obstructing the
+passages, and impairing the burner's action. Then, to cause the burner
+to yield its highest results, it is necessary that the air supply be
+accurately adjusted to the quantity of gas being consumed. To this end
+the entrance to the air chamber, at the bottom of the burner, is
+covered by a perforated semi-circular cup, by turning which the
+quantity of air entering the burner can be increased or diminished as
+required. Moreover, the bulky construction of the burner, with its
+accompaniment of chimney and flue, and its complicated arrangement of
+tubes and chambers, imparts to it a somewhat clumsy and inelegant
+appearance, which is calculated to impair the favour with which its
+remarkable performances cause it to be regarded. But these drawbacks
+are far outweighed by the undoubted advantages conferred by the
+burner--in improved illumination combined with economy of combustion,
+and the facilities it affords for securing perfect ventilation.
+
+Encouraged by the success of Herr Siemens, other inventors have
+followed in his footsteps; with the result that there are now a
+variety of burners before the public, embodying the same principles,
+but differing in the details of their construction and in the measure
+of their efficiency. Of these may be mentioned Grimston's, Thorp's,
+and Clark's; and without describing in detail the construction of the
+several burners (of which further particulars will be found in the
+"Register of Patents" in the _Journal of Gas Lighting_[14]), it must
+suffice to refer to the salient points and distinctive features of
+each.
+
+          [14] See Vol. XL., pp. 786, 950; and Vol. XLII, p. 836.
+
+[Sidenote: Grimston's regenerative burner.]
+
+Grimston's burner (shown on the next page) consists, in effect, of an
+Argand burner turned upside down; the gas issuing from the bottom ends
+of a number of small tubes placed in a circle. The jets of
+flame--first directed downwards from the mouths of these tubes--by a
+conoidal deflector in the centre of the ring, are caused to spread
+outwards, and assume a horizontal direction; and by their amalgamation
+with each other a continuous sheet or ring of flame is produced. The
+horizontal direction of the flame is maintained by its passing
+underneath a metal flange, faced with white porcelain, or other
+refractory material; the supply of gas being adjusted so that the
+flame just terminates at the outer edge of this flange. Before
+entering the chimney, the products of combustion are caused to flow
+through a number of vertical tubes contained in a cylinder, which is
+concentric to an inner cylinder containing the gas-supply tubes. The
+outer cylinder is traversed by the air needed for the support of
+combustion, which is to become heated before reaching the point of
+ignition; and in order the more completely to enable the products of
+combustion to impart their heat to the entering air, the cylinder is
+further intersected by strips of wire gauze, which pass around and
+between the tubes (see fig. 22, on next page). By these means the air
+is intensely heated; and, passing among the narrow burner tubes
+through which the gas is conveyed, gives up a portion of its heat to
+the latter before the point of ignition is reached. Thus, in a very
+simple manner, both air and gas are raised to a considerable
+temperature before combustion takes place.
+
+With regard to the efficiency of the burner, at the exhibition of gas
+appliances held at Stockport in 1882 (where a gold medal was awarded
+to it, as well as to Thorp's burner, to be referred to hereafter),
+with a consumption per hour of 9.84 cubic feet of 17.5 candle gas, an
+illuminating power of 60.67 candles was obtained (equal to 6.16
+candles per cubic foot); while, on another occasion, when the burner
+was consuming 8.94 cubic feet per hour, an illuminating power of 51.5
+candles (equal to 5.76 candles per cubic foot) was obtained from gas
+of the same quality. It is claimed for this burner that equally good
+results are obtained with small sizes as with large; and this, if
+borne out in actual practice, should go far towards ensuring the
+success and extensive adoption of the burner.
+
+  [Illustration: FIG. 21.--GRIMSTON'S REGENERATIVE GAS-BURNER.]
+
+  [Illustration: FIG. 22.--GRIMSTON'S BURNER.
+                 PLAN, SHOWING REGENERATING ARRANGEMENT.]
+
+  [Illustration: FIG. 23.--THORP'S REGENERATIVE GAS-BURNER.]
+
+[Sidenote: Thorp's regenerative burner.]
+
+Thorp's burner produces a cylindrical flame, like that of the Argand,
+but without the aid of a glass chimney which is a necessary adjunct to
+the latter burner. By means of a deflector on the inner side of the
+flame, the latter is made to curve outwards and assume a somewhat
+convex form, so as to obviate the shadow which otherwise would be cast
+by the gas chamber at the bottom of the burner. Above the flame is a
+cylindrical chimney, divided by a vertical partition into two
+concentric chambers, which are intersected by a series of metal gills,
+or projections, continued through both chambers. The outer chamber is
+for conveying away the products of combustion; the inner one for the
+passage of air to feed the flame; while down the centre of the inner
+chamber there passes a tube conveying the gas to the point of
+ignition. The hot products of combustion pass up from the flame
+through the outer chamber, and give up the greater portion of their
+heat to the projections; by which it is conducted into the inner
+chamber, and transferred to the incoming air. A common imperfection of
+regenerative burners is that, in consequence of the diminished rate at
+which the gas flows through the burner when expanded by heat, when
+starting the burner the gas must be only partially turned on, and the
+quantity gradually increased as the burner becomes heated; thus
+necessitating considerable attention. To prevent the need for this
+attention, there is in Thorp's burner an ingenious contrivance for
+automatically regulating the quantity of gas admitted to the flame.
+The central gas-tube, which is referred to above, contains a brass
+rod, fixed at one end, and at the other connected to a valve
+controlling the quantity of gas that enters the tube. At first, when
+the gas is lighted, this valve is almost closed; but as the rod
+becomes heated it elongates, gradually opening the valve until the
+full quantity of gas is admitted which the burner is intended to
+consume. At the Stockport exhibition, Thorp's burner was tested with
+the following results, as recorded in the Judges' report. After it had
+burned about two hours, "it gave an illuminating power of 183 standard
+candles, while burning 27 cubic feet of gas per hour (equal to 6.77
+standard candles per cubic foot), with gas of 3.5 candles per cubic
+foot.... In another experiment with the same quality of gas, after
+burning half an hour it yielded, under similar conditions, 154 candles
+with a consumption of 25.29 cubic feet per hour, which gave an
+illuminating power of 6.02 candles per cubic foot."
+
+[Sidenote: Clark's regenerative burner.]
+
+There is nothing in Clark's burner that calls for special notice. In
+its main features it appears to be constructed upon similar lines to
+Grimston's burner, although the coincidence is doubtless only
+accidental.[15] It must, however, be added that in the details of its
+construction it is much simpler than the latter burner; and certainly
+it appears to lose very little in efficiency from its greater
+simplicity, as the following extract from a report by Mr. F. W.
+Hartley, the well-known photometrist, will show:--"With a consumption
+rate of 5.3 cubic feet of gas per hour, the amount of light yielded
+horizontally was equal to 29.79 times that of a standard candle. The
+light yielded per cubic foot of gas burned per hour was therefore
+equal to 5.62 times that of a standard candle." And the amount of
+light delivered immediately downwards is said to be "very sensibly
+greater than the amount of light delivered horizontally." Like the
+Grimston burner, it is of the inverted Argand form; the gas issuing
+from a chamber at the bottom of a tube which descends through the
+centre of the burner. The products of combustion escape through a
+chimney; and in so doing give up a portion of their heat to the
+entering air, which is conveyed to the point of ignition through
+horizontal tubes that intersect the chimney. The burner is enclosed in
+a suitable lantern, the lower half of which consists of a
+semi-globular glass; a similar arrangement being adopted in connection
+with the Grimston and Thorp burners.
+
+          [15] In justice to Mr. Clark it should be mentioned that,
+          since the above appeared in the _Journal of Gas Lighting_,
+          the attention of the writer has been called to the fact
+          (which had been overlooked by him) that Clark's patent was
+          taken out some months before that of either Grimston or
+          Thorp.
+
+  [Illustration: FIG. 24.--CLARK'S REGENERATIVE GAS-BURNER.]
+
+The three burners last mentioned have not been before the public
+sufficiently long to enable a reliable opinion to be formed as to
+their value in actual and prolonged use. Although there is no reason
+for supposing that such will occur in the present instance, it so
+often happens that the results indicated by apparatus in the
+experimental stage, or while still under the control of the inventor,
+are not borne out in practice, that it would be unwise to express any
+decided opinion as to their ultimate worth from existing information.
+It is, however, to be earnestly hoped that the marked favour with
+which they have been received will not be impaired on improved
+acquaintance; but that further experience will justify the
+anticipations that have been excited by the excellent performances of
+the burners hitherto, and demonstrate at once their durability and
+real usefulness.
+
+
+Since writing the above, considerable activity has been shown by
+inventors in producing new burners upon the regenerative principle, or
+in improving upon existing models. Of course, as yet it is too early
+to arrive at a satisfactory estimate of their actual value or relative
+worth; but it may be hoped that, from the increased attention being
+devoted to the subject, some real and practical results will flow, by
+which the gas-consuming public will be the gainers. So far, the most
+promising of this class of burners that has been brought into actual
+use, since the introduction of the Siemens burner, is the one
+represented below.
+
+  [Illustration: FIG. 25.--BOWER AND THORP'S REGENERATIVE GAS-BURNER.]
+
+It is a modification, in the direction of greater simplicity, of
+Thorp's former burner, illustrated and described on p. 69 of this
+treatise; and as its construction is based upon the same lines as that
+burner, further description is not required.
+
+
+
+
+CHAPTER VI.
+
+INCANDESCENT BURNERS.
+
+
+A review of gas-burners would scarcely be complete without some
+reference to the incandescent burners of M. Clamond and Mr. Lewis.
+Although their dependence upon an artificially produced blast or
+current of air removes them from the list of appliances applicable to
+ordinary conditions, the remarkable results which they afford, not
+less than their originality, demand for them at least a passing
+notice. The production of light by the agency of these burners is
+brought about in a manner altogether different, and is due to quite
+other causes than those which are concerned in the production of an
+ordinary illuminating gas flame. In the latter case, the illuminating
+power developed is solely due to the hydrocarbons contained in the
+gas, which are decomposed by the heat of the flame, the separated
+carbon being raised to a white heat. In the former, the illuminating
+power is not obtained directly from the gas; but advantage is taken of
+the heat of the flame, enhanced by the application of a blast of air,
+to raise to incandescence some refractory foreign material, which
+latter is thus made to give out light. In the Clamond burner this
+refractory substance is a basket composed of magnesia, spun into
+threads; in the Lewis burner it is a cage of platinum wire.
+
+To the unthinking reader it may perhaps appear somewhat surprising
+that results so remarkable as are yielded by these burners should be
+obtained, while disregarding, as a source of light, the hydrocarbons
+contained in gas, and employing them, in common with the other
+constituents, solely as a source of heat. An explanation, however, is
+readily forthcoming. As was shown in a former part of this
+treatise,[16] the great bulk of ordinary coal gas consists of
+constituents which, in the act of combustion, produce considerable
+heat, but scarcely any light; the illuminating power developed in an
+ordinary gas flame being almost wholly dependent upon the very small
+proportion of heavy hydrocarbons which the gas contains. Thus, the
+quantity of heat-producing elements contained in the gas being quite
+disproportionate to the light-yielding hydrocarbons, there is always
+produced, in an ordinary gas flame, more heat than is necessary for
+effectively consuming the free carbon, which is liberated in the flame
+by the decomposition of the heavy hydrocarbons. This is shown by the
+fact that coal gas can usually be naphthalized--that is, impregnated
+with the vapour of naphtha--to a considerable extent before the limit
+of effective combustion is reached. The object aimed at in the
+incandescent burners about to be described is to utilize, in the
+development of illuminating power, the combined heat produced by the
+combustion of all the constituents of the gas. To this end the heat
+of combustion is brought to bear upon, and caused to raise to
+incandescence, some refractory material, extraneous to, but brought
+within the operation of the flame.
+
+          [16] See Chap. II., p. 21.
+
+[Sidenote: Effect of injecting a blast of air into a gas flame.]
+
+A further explanation of the superior results yielded by these burners
+may be found in the employment of an artificial blast or current of
+air. Indeed, without some such arrangement the desired end could not
+be attained. The heat developed by the unaided flame is diffused over
+too wide an area to raise the temperature of the heated substance to
+the necessary degree of incandescence to enable it to give out
+sufficient light. By injecting a current of air into its midst, the
+flame is condensed into a smaller compass; and is brought to bear more
+directly upon the precise locality where its heat may be most
+effectively employed. Thus, although the total quantity of heat
+developed remains exactly the same as before, it is concentrated upon
+a smaller surface of the refractory substance; and the latter is
+consequently more intensely heated, or, in other words, raised to a
+more exalted temperature. The very superior illuminating power which
+is thereby obtained is due to the circumstance that the quantity of
+light yielded by an incandescent body increases in a higher ratio than
+the temperature to which it is raised.
+
+[Sidenote: Lewis's incandescent gas-burner.]
+
+Proceeding now to describe the burners. The one invented by Mr. Lewis
+(various forms of which are illustrated on the next page) consists of
+an upright tube, connected at its base to the gas supply, and
+surmounted by a cap or cage of platinum wire gauze; which latter
+constitutes a combustion chamber, as it is there that the mixture of
+gas and air is consumed. Into the lower part of the upright tube the
+nozzle of an air-pipe is inserted, through which a supply of air can
+be injected, under pressure, into the burner, after the manner of a
+blowpipe. There are also small branch tubes leading into the upright
+gas-tube, and open to the atmosphere. Through these an additional
+quantity of air enters the burner; being drawn or sucked in by the
+agency of the main current, which flows through the upright tube. The
+resemblance to an ordinary Bunsen burner is, therefore, very close.
+The mixture of gas and air thus produced, when ignited, burns at the
+platinum cap; the heat which is developed causing the latter to become
+highly incandescent, and so to give out a brilliant light. To prevent
+the conduction of heat from the incandescent platinum, through the
+upright tube, a non-conducting material--such, for instance, as
+steatite or porcelain--is interposed between the gauze cap and the
+metal tube.
+
+  [Illustration: FIG. 26.--LEWIS'S INCANDESCENT GAS-BURNER.]
+
+The light produced by this burner is said to approximate more closely
+to daylight than that yielded by an ordinary gas flame (the colours of
+textile fabrics, for instance, being shown as well by its aid as by
+daylight); while, on account of its resulting from the incandescence
+of a fixed body, instead of being emitted from a flame, it is
+unaffected by a gust of wind, and maintains perfect steadiness under
+every condition of weather. The illuminating power developed is stated
+to be equal to 5 standard candles per cubic foot of gas consumed.
+
+[Sidenote: Clamond's incandescent gas-burner.]
+
+M. Clamond's burner, which is shown in fig. 27, is a much more
+complicated apparatus than the preceding one, and not so easily
+described; but its main features may be briefly enumerated as
+follows:--The air (which, as in Mr. Lewis's burner, is supplied under
+pressure) is divided, as it enters the apparatus, into two portions.
+One portion is at once mixed with the gas; the remainder being
+conveyed, through a peculiarly constructed tube composed of small
+pieces of refractory material, to the combustion chamber, or "wick,"
+as it is termed, of the burner. This "wick" is a small conical basket,
+made of a kind of lacework of spun magnesia, which, when raised to
+incandescence by the heat produced by the combustion of the gas,
+furnishes the desired illumination. The mixture of gas and air is
+subdivided, by a "distributor," into two portions, one of which goes
+direct to the magnesia "wick," there to be burnt, while the other is
+distributed among a number of tubes, forming so-called "auxiliary
+burners," the flames of which are utilized to heat the chief air
+supply; being directed upon the sides of the before-mentioned tube of
+refractory material, through which it is conveyed. By this means the
+air is raised to a very high temperature (1000 deg. C., or 1800 deg. Fahr., it
+is said) before it impinges upon the flame. The result is the
+production of a most intense heat within the magnesia basket; the
+latter being raised to brilliant incandescence, and so developing a
+high illuminating power.
+
+  [Illustration: FIG. 27.--CLAMOND'S INCANDESCENT GAS-BURNER.]
+
+The magnesia basket must be renewed after being in use a period of
+from 40 to 60 hours, as it gradually deteriorates by the action of the
+intense heat to which it is subjected; but as the cost is said to be
+insignificant, this should not be a great drawback. The basket is
+placed at the base of the burner, in order to obviate the shadow which
+would otherwise be cast by the apparatus; and it is attached to the
+main body of the apparatus by platinum wires. As to illuminating
+power, the only particulars which have been made public refer to the
+first two models constructed; one of which was said to develop a light
+equal to that from 6.208 candles, and the other to 9.72 candles per
+cubic foot of gas consumed.
+
+  [Illustration: FIG. 28.--CLAMOND'S IMPROVED INCANDESCENT BURNER.]
+
+[Sidenote: Clamond's new burner.]
+
+In a recently designed modification of the burner (which is shown in
+the accompanying illustration) M. Clamond dispenses with an artificial
+supply of air under pressure, and endeavours to obtain similar results
+by other and simpler means. To this end the position of the magnesia
+"wick" is reversed (it being placed at the top of the apparatus); the
+current of gas is allowed to draw in upon itself a quantity of air by
+a precisely similar arrangement to that adopted in the Bunsen burner;
+while an additional supply of air is drawn upon the flame by the
+accelerated draught produced by the aid of a glass chimney. As in the
+more complicated and complete burner, the air supply is heated by
+means of auxiliary burners in the interior of the apparatus. It has
+been stated, on the authority of M. Clamond, that this modified burner
+develops, from the gas consumed, a duty of about 6 candles per cubic
+foot; being equal to the results yielded by the more complicated
+apparatus. Should this be borne out in practice, M. Clamond will
+have achieved a noteworthy success. It is, however, advisable to
+reserve expressing any definite opinion of its merits until further
+information is received, or until the burner has been tried in this
+country.
+
+
+
+
+CHAPTER VII.
+
+CONCLUSION.
+
+
+The burners last mentioned may be said to mark the extent of the
+progress that has been made, down to the present time, in the
+construction of apparatus for developing light from coal gas; and they
+remind me that I have arrived at the conclusion of my subject. From
+the unpretending gas-jet described by Accum--burning, with
+wonder-provoking steadiness and constancy, "so long as the supply of
+gas continued"--to the complicated apparatus of M. Clamond, is a long
+stretch of invention; embracing the labours of many distinct and
+original workers in the same field, and including numerous variations
+in the details of burners that have not been touched upon in the
+foregoing remarks. As was announced in the introduction, I have dealt
+in this treatise only with the more important or the more successful
+of the modifications that have been made from time to time in the
+construction of the gas-burner. In addition to the burners that have
+been referred to, there have been invented many others, which could
+not be adequately noticed without prolonging the treatise to an undue
+length. Some of these (the fruit of much thought and careful
+experiment) have obtained, in the commercial success that has attended
+them, no more than their merited reward; others (devoid of any real
+merit, and in their construction disregarding the most elementary
+principles of economic combustion) have been brought into somewhat
+extensive use by the misleading statements and false representations
+of their inventors, and are only tolerated through the ignorance of
+the public; while not a few of the latter class of burners have
+speedily found the oblivion which they richly deserved. Sufficient,
+however, has been said to show that many real improvements have been
+effected in the construction of gas-burners, and to prove that, with
+the apparatus now available, a far higher duty may be obtained from
+the gas consumed than was possible only a few years ago.
+
+But although the great advance that has been made in the construction
+of gas-burners is undoubted, the benefits which ought to result
+therefrom have not been realized by the gas-consuming public; nor are
+they likely to be to their full extent. While the ingenious and
+effective inventions for utilizing the waste heat of combustion, and
+for lighting by incandescence, may, and doubtless will, in the course
+of a few years, be far more extensively adopted than at present, it is
+hardly to be expected that they will be generally employed. Two causes
+operate to preclude the latter result--namely, their first cost, and
+the care and attention demanded in their employment. It seems
+tolerably certain that for a long time yet the great bulk of coal gas,
+used for lighting purposes, will be consumed through the simple
+flat-flame burners that have done so much hitherto for the furtherance
+of gas lighting. Fortunately so much has been done towards the
+perfection of this class of burners, that, for a very slight
+expenditure, results may now be obtained far in advance of what could
+formerly be produced only by the most costly and delicate apparatus.
+For ordinary situations and requirements, the improved flat-flame
+burners produced by Bray, Broenner, and Sugg, when intelligently
+employed, leave scarcely anything to be desired. _When intelligently
+employed_, I repeat, and with cautious emphasis; for the best of
+burners will be extravagant and ineffective if employed without due
+regard to the conditions for which it was made. That which is most
+needed at the present day, and which will best ensure the continued
+use of coal gas for the purposes of illumination, is the more general
+diffusion amongst gas consumers of a knowledge of the principles of
+combustion, and of the simple precautions to be taken and conditions
+to be fulfilled in the employment of gas-burners. The apparatus that
+is available is both varied and effective; what is wanted is the
+knowledge to use it aright. By contributing to the freer dissemination
+of that knowledge, purveyors of gas will confer no inconsiderable
+benefits upon their customers, and, at the same time, will assuredly
+promote their own interests.
+
+
+
+
+
+
+End of the Project Gutenberg EBook of Gas Burners, by Owen Merriman
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