UNDULATORY FORCES. Lie HT. 



[GAB-BIT KKEUs. 



strong resemblance to a double engine : it consists of a 



cylinder divided by a plate in the centre into two sepa- 

 rate cylindrical compartment <, which are closed at the 

 opposite ends \>y mct.d discs; those dines scrre the 

 purpose uf pistons, and they are kept in their places by a 

 kind of universal joint adapted to each. The space 

 through which the duos move, and consequently^ the means 

 of measurement, is governed by metal arms and rods; 

 which space, when onco adjusted, cannot vary. To avoid 

 tlu friction occasioned by a piston working in a cylinder, 

 a band of leather is attached so as to act as a hinge. 

 Tliis folds with the motion of the discs, but it is not in 

 any way concerned in measuring the gas ; so that if it 

 were to contract or expand, the registration of the proper 

 quantity of gas would not be affected ; for such a change 

 would only decrease or increase the capacity of the hinge, 

 leaving the disc still at liberty to move through the 

 required space. The leather is also attached in such a 

 manner as to avoid folds, and thus to render it more 

 durable. 



Gas-burners. Scarcely anything connected with the 

 subject of gas illumination has commanded more attcnt i >n 

 than the means" whereby gas may be burnt to the best 

 advantage ; and although the greatest ingenuity has been 

 displayed in the construction of many of the burners 

 which have at different times been invented, yet none of 

 them possesses that universal applicability for which they 

 have in most cases been so highly vaunted. The reason 

 of this is obvious : different kinds of gas require different 

 forms of burners, in order to effect perfect combustion. 

 As a rule, it may be stated, that the rich cannel gases are 

 best consumed from burners with very fine apertures: 

 while the poorer gases namely, those which contain 

 less than live or six per cent, of condensible hydro- 

 carbons are burnt with most advantage from 1 

 apertures. Again, in the former case, provision should 

 be made for a large supply of atmospheric air, as by 

 spreading out the flame by means of an internal button, 

 or by using tall glasses ; whereas, in the latter case, the 

 opposite condition should be observed. It is mani- 

 thereforc, that no single burner can be constructed 

 so as to secure both of these requirements; ami, con- 

 sequently, that any burner which is well suited for one 

 kind of gas, is altogether unfit for the other. 



Another point of importance to which we may refer in 

 peaking of this subject, is the following : that when 

 several jets issue from the same burner, and blend 

 together or coalesce, the light is always improved ; for it 

 is the property of one jet to assist another by exalting its 

 temperature ; and thus a greater heat and a brighter flame 

 are the result of the union more light being given out 

 than is the sum of the individual jets. It is on this 

 account that the Argand burner, the fish-tail, the 

 (Jaiiniont, and the Gardner, have obtained preference 

 over many other forms of burners. 



Lastly, it may be stated, that in whatever way gas is 

 consumed, the maximum effect, as regards its illuminating 

 power, is always produced by burning the gas just short 

 of its smoking-poiut : for if it bo burnt with too much 

 air, the particles of carbon are consumed; and we thus 

 obtain a diminishing light, until the flame becomes of a 

 pale-blue colour. On the other hand, if it be burnt with 

 too small a supply < >horic air, the particles of 



carbon will not be sufficiently consumed, anil they will 

 escape as soot thereby cooling the flame, and making it 

 of a dingy yellow tint. Our object, therefore, should 

 always be to burn the gas in 'such a manner that the 

 particles of carbon may be t'n>t intensely heated, so as to 

 produce a white light; and then, as they reach the 

 exterior of the flame, they ought to be consumed entirely, 

 so as to avoid the evolution of soot. < if the dill 

 varieties of burners now in use, the following are the 

 most important : 



I. Tli< fimiil'- j't is produced from a burner pierced . 

 with a single hole. This mode of consuming gas is not 

 considered to be cleanly or economical ; . 'fur 



certain purposes of illumination, as whi-iv we wish to 

 prod-H'o different kinds of devices, it is rarely empl 

 Occasionally it is used in the laboratory of the chemist , 



for experiments with the blowpipe, as it is found to give 

 a much hotter and clearer flame with this instrument 

 than any other form of jet. The average consumpn 

 a jet the thirty-third of an inch in diameter, with a flame 

 four inches high, is about one cubic foot per hour. With 

 richer gases the quantity is a little less, and with very 

 poor gases it is somewhat more. As we have already 

 said, Dr. Fyfe prefers a jet of this description for the 

 purpose of estimating the illuminating power of gas ; and, 

 in a general way, it is equal to from one to one-and-a-half, 

 or two sperm caudles. 



When it is necessary to produce a greatly diffused light, 

 it may be accomplished by means of one or more rows of 

 single jets. These may be distributed around the cornice 

 or mouldings of a room, and the effect is remarkably 

 pleasant and agreeable, for there is a flood of light 

 without the least glare or shadow. The only objection t,. 

 it is its great cost and its liability to evolve smoke ; but 

 if these were overcome, and our rooms constructed so as 

 to have a row of lights around a panel in the ceiling, 

 there is no doubt that the effect would be much more 

 pleasing than that which results from our present mode 

 of burning gas; besides which, the panel might be so 

 arranged as to convey away the products of combustioii, 

 and thus the effect would also be more salutary. 



2. The Cockspur Burner is a burner with three or more 

 jets radiating oft' from it, and burning separately. The 

 light from such a burner is only equal to the sum of the 

 individual jets; for as thoy do not coalesce, they cannot 

 in any way assist each other. It is one of the worst 

 forms of burner that can be employed. A burner with 

 three jets, consuming three cubic feet per hour of ordinary 

 London gas, gives a light of from five to six candles. 



3. The, Fish-tail or Union Burner is so named because 

 of the form of its flame, and because of the manner in 

 wliich it is produced by the union of two jets. It is 

 formed by drilling two holes at an angle of about 00. 

 The jots are directed into each other; and as they 

 coalesce, they spread out so as to produce a flat sheet of 

 flame of the form of a fish-tail : by this means the in- 

 tensity of the light is greatly increased. The holes are 

 drilled largo or small, according to the quality of the gas 

 to be employed. In the case of cannel gas, the holes are 

 small ; and for common London gas they are rather 1. 

 The former are known by the name of Lancashire or 

 Scotch fish-tails, and the latter as London jots. Each 

 sort is numbered 1, 2, 3, or 4, according to the size of the 

 holes ; and these numbers are indicated by means of little 

 rings turned on the body of the jet. No. 1 is the smallest. 

 These burners consume from two to four cubic feet of 

 gas per hour ; and with cannel gas they give the light of 

 from eight to fourteen candles, and with common gas, of 

 from four to ten. 



4. Johnson's Burner is a fish-tail with four converging 

 holes ; and there is an aperture through the centre of tho 

 burner for the admission of atmospheric air into the flame. 



6. Billow's or Gardner'* Burner. Tliis is a com- 

 bination of two fish-tail or bat's- wing burners, arranged so 

 as to produce one flat flame (Fig. 129). The flames 

 impinge on each other, and thus increase the 

 illuminating power by about thirty per cent 

 These burners are usually constructed of two 

 fish-tails; and occasionally, for experimental 

 purposes, they are attached to a hinge-joint, 

 so that the flames may be burnt separately 

 or together. As in the case of the ordinary 

 fish-toils, they are numbered 1. '_', :'., ami 4. 

 No. 1 consumes about three cubic feet per hour, and No. 

 4 about five. 



G. The I Burner is so named on account of 



the shape of tho flame. It is one of the oldest forms of 

 gas-burners; it is constructed with a slit instead of two 

 - for tho exit of gas; and the flame is broader, and 

 not so high as the fish tail. These burners are easily 

 managed, and on this account they are generally supplied 

 to the public lamps. They bum from three to five cubic 



er hour ; and, with a consumption of four 

 per hour, they give tho light of about nine sperm candles 

 of standard quality. 



Yin. \13. 



