Page:Encyclopædia Britannica, Ninth Edition, v. 10.djvu/112

Rh 10:? GAS the elevator mechanism are set in operation by being ] at present conducted is a consideration of much weight in mounted on a spindle which passes through and outside the cylinder, and is turned either by a weight attached to a length of steel wire or, where convenient, by hydraulic power. The turrets contain (1) a gas-holder which sup- plies gas while the machine is being wound up, should any light be then burning, and a governor to regulate the pressure of the issuing gas. The apparatus works only when gas is being burned, and moves in proportion to the demand on it up to its limit of production. There is therefore no necessity for storing, as indeed would be i1n- practicable with this form of carburetted gas. The function of the blower is not only, by its revolution, to press forward the gas i uto the supply pipes, but also to carburet the air by exposing continually renewed thin ﬁlms of the liquids to its inﬂuence on the moist metallic surfaces. The revolu- tion of the blower, moreover, maintains an unceasing agitation in the gasolin, vaporizes the liquid in an equal and uniform manner, and keeps the entire volume at the same temperature throughout. The quantity of gasolin operated on being comparatively large, the tempera- ture of the liquid decreases only slowly, and is in ordinary conditions sufﬁciently recouped from the external air to keep it in good working order throughout any length of time. M. Tessie du Motay, who for many years advocated a modiﬁed system of lime—light, latterly abandoned that system in favour of a form of carburetted gas. His system necessitates two sets of pipes and a special form of burner,—- one pipe supplying ordinary coal-gas or highly carburetted hydrogen, and the other leading in a supply of oxygen, whereby a powerful, steady, white light is maintained at the burner. Philipps of Cologne has also utilized oxygen in a comparatively pure state for burning in a lamp with a wick a mixture of heav * hydrocarbons, which in common air would burn with a very smoky ﬂame. Other sources of gas, such as tar, and even faecal matters, have been proposed ; and many modiﬁed forms of gaseous illumination have been brought forward which, even to name here, would occupy space out of proportion to their importance. THE FUTURE or COAL-GAS. The processes involved in the preparation, distribution, and consumption of coal-gas still remain essentially the same as when the system was ﬁrst elaborated; but in all details of the industry numerous improvements have been introduced, resulting in marked economy and efﬁciency of the system. In the meantime new applications of import- ance have been found for coal-gas in connexion with heating and cooking, and as a motive power in gas—engines. Further, collateral industries have been superadded to the gas manufacture, which in themselves are of such value and importance that, were the distillation of coal as a source of artiﬁcial light to cease, it would certainly continue to be practised as a source of the raw materials of the coal-tar colours, and of carbolic acid, &c. Were coal-gas to cease to be made primarily and principally for artiﬁcial illumina- tion, and to become more a heating and cooking agent, or were it to fall into the position of being a mere collateral product of the manufacture of tar, it is certain that the manufacturing processes would be very materially modiﬁed. Costly cannel-gas, with its high illuminating power, is no better suited for a gas engine than common gas ; and for heating purposes a much greater yield of gas might be obtained, which, in burning, would evolve more heat than is sought in making illuminating gas. But as matters now stand, the fact that illumination, heat, motive power, and dye-stuffs are all obtained by means of the manufacture as dealing with rival systems of artiﬁcial lighting. Throughout the whole experience of gas manufacture the efforts of inventors have been directed, not only to improve the manufacture of coal-gas, but also to supersede its ordi- nary processes, and to supplant it by gas yielded by other raw materials or by new systems of illumination. The persistent efforts which have been made to improve coal-gas, and the success which many of the plans exhibit in their experimental stage, warrant the conclusion that the pro- cesses and results of the manufacture are still susceptible of much improvement. When it is considered how exceed- ingly small is the total proportion of illuminants in coal-gas to the bulk of the materials dealt with, it is not diﬁicult t-) imagine that modiﬁcations of processes may be devised whereby a great increase of lighting effect might be practi- cally available, and at the same time a greater percenta-_»‘c of the total heat-giving power of the coal secured for domestic and manufacturing purposes. Notwithstanding the confessed imperfections of the system of coal gas-mak- 'ing,—the evil odours which attach to the works, the yet 1nore offensive exhalations given off from streets through which the main-pipes are led, the destructive accidents which occasionally occur from gas explosions, and the heat and sulphurous fumes evolved during its combustion,——not one of the numerous substitutes which have been proposed has been able to stand in competition against it in any large town or city where coal is a marketable commodity. As against the system of electric lighting, which is now being brought into competi- tion with it, the ultimate fate of gas may be diﬁferent. It - may be regarded as already demonstrated that for busy thoroughfares—almost, it may be said, for open-air lighting generally and for large halls and enclosed spaces, electric lighting will, in the near future, supersede gas. The advantages of the electric light for such positions in bril- liancy, penetration, and purity are so manifest that its use must ultimately prevail, irrespective of the question of com- parative cost, and of the fact that municipalities and wealthy corporations have an enormous pecuniary stake in gas- property. That the electric light will be equally available for domestic illumination is, however, not yet so certain; and until it is demonstrated that a current may be sub- divided practically without limit, that the supply can adapt itself to the demand with the same ease that the pressure of gas is regulated, and that the lights can be raised and lowered equally with gas—lights—till these and other con- ditions are satisﬁed, the disuse of gas-lighting is still out of sight. Should these conditions, however, be satisfied, there can be little doubt that gas-lighting will enter on a period of severe competition and struggle for existence; and in the end the material which at one time was regarded as a most troublesome and annoying waste—- the gas—tar——will, in all probability, exercise a decisive inﬂuence on the continuance of the gas manufacture. Bibliograplq/.—Clegg, A Practical Treatise on the Jfrmufacture and DistrA'but«'ma qf Coal-Gas, new edition, London, 1869; llnghes, A Treatise on 0113- lVorl:s and 1|[an'u_factur2'ng Uoal-(Ins, 5th edition by Richards, London, 1875; Richards, A I’rar'tz'ml Trmtis-e on the 1|[a'n-ufactm'c and Dist-ribution of Coal-Gas, London, 1877 ; Accum, Practical Treatise on Gas-Light, 4th ed., 1818; Journal for Gas- Lz'g}ut£7z.g, London ; Bowditch, The Analg/sis, Tcclmical Val-ualion, and Purz:/ication of Coal-Gas, London, 1867; Banister, Gus .l[am'- jntlation, new cd. by Sugg, London, 1867 ; Servier, Tra2‘te’]n'atiquc de la fabrication ct de la clistribztlion tlu gas d'écIaz‘rage, Paris, 1868 ; Payen, Précis do Uhemie indewtricllc, 6th edition, Paris, 1877; Schilling, Ilandlmch der Steinkoklmz- Gas-Bcleuchtzm g, Munich, 1860; Diehl and Illgen, Gasbcleuciztmzg and Gas-t'm‘b7'nuch., Iserlohn, 1872; llgen, Die G'asz'7ulush°z'c dcr Grgrnwart, Leipsic, 1874 ; Holley, Tcchvzologie, vol. i., Brunswick, 1862; Vagner’s JaIu‘csImrz'¢-lat der chanisch/m Tcch.noIo_c/ic, Leipsic; Journal fiir G'asbelc-zcclmmg mid rerwamlte Bcleuchtzmgsart, Munich; lteissig, Hmzdburh dcr Hal: and To’/f Gr -Fulnikation, Munich, 1863. (J. PA.)