GAS LIGHT. 



369 



from M. Le Bon, exhibited gas illuminations at Lon- 

 don, in the Lyceum ; and, in 1808, a gas apparatus 

 was erected at the factory of Messrs Philips and Lee 

 of Manchester, under the direction of Mr Murdoch, 

 who, the same year, was honoured with the Rumford 

 medal by the royal society for the paper on gas light, 

 which he furnished for their transactions of that year. 

 Mr Winsor had, by specious promises and false state- 

 ments, raised the sum of .50,000 from a number of 

 subscribers who formed themselves into a company, 

 called a national light and heat company. In raising 

 this sum, he was assisted in imposing upon the pub- 

 lic in drawing out erroneous statements of pretended 

 facts, by Mr Frederic Accum ; but with the money 

 Mr Winsor lighted Pall-Mali, and thus proved the 

 practicability of lighting the streets of cities by gas. 

 Since this time, gas has been more extensively 

 employed every succeeding year, and throughout 

 this kingdom almost all factories and large towns 

 are lighted by it. The chief improvements upon 

 gas apparatus, since Mr Murdoch's erection at 

 Manchester, have been made by Mr Cleg, who has 

 also furnished the most correct specimens of calcu- 

 lation. 



Gas, for the purpose of illumination, is obtained, 

 in general, from coal, and sometimes from oil. In 

 detailing the process, we shall devote our attention 

 chiefly to the formation of coal gas. 



In plate XXXVIII. we have given a view of an 

 improved gas apparatus, well adapted for supplying 

 a factory where light may be required from between 

 four and five hundred jets. In describing this en- 

 graving we shall follow the order of the process of 

 coal gas manufacture. 



The first operation is the decomposition of the coal 

 by heat, which is effected by subjecting the coal, en- 

 closed in a cast iron vessel called a retort, to the action 

 of a furnace. In general the retorts are made in the 

 form of hollow cylinders, and lie in the furnace with 

 their axes in a horizontal direction. It has been 

 found, however, that although the cylindrical shape 

 is the most conducive to durability, it is inferior to 

 that form of the retort where the cross section is an 

 ellipse, which last, though not so durable, evolves 

 the gas much more rapidly, in which desirable qua- 

 lity the saddle shaped retort, the cross section of 

 which is seen at A, is the best of all. In the engrav- 

 ing we have represented one furnace as only heating 

 one retort, an arrangement which seems preferable 

 to that of placing two or three retorts in one furnace, 

 which is sometimes done with the view of economis- 

 ing fuel. In order that the heat may be distributed 

 as equally as possible, the flue of the furnace is led 

 along the retort to the front, and then returns to the 

 back, where the heated air escapes into the chimney, 

 and to preserve the retort as much as possible from 

 the destructive effect of the bright red heat which is 

 necessary for the decomposition of the coal, it is 

 cased round with an arch of fire bricks, as may be 

 seen at A in the drawing. The quantity of gas, as 

 likewise its quality, vary during the progress of 

 decomposing the coal. At first carbonic acid is 

 evolved, mingled with a little steam, if the coals 

 have not been previously well dried. Carburetted 

 hydrogen, olefiant gas, and sulphuretted hydrogen 

 then follow, which become less and less abundant 

 as the process advances, until nothing is produced 

 but hydrogen and carbonic oxide. The time required 

 for the decomposition of the coal, depends upon its 

 quality, cannel coal being the most easily decom- 

 posed. The interval of recharging the retorts, varies 

 from three and a half to six and a half, or even eight 

 hours. 



The following table, by Mr Peckston, exhibits the 

 ratio at which the gas is evolved from Bewicke and 

 . in. 



Crastor's Wall's-end coal, when the retorts are worked 

 at eight hours' charges : 



Cubic feet Sum. 



During the 1st hour are generated, . 2000. 



2d, . . . . 1495 3495 



3d, .... 1387 4882 



4th, .... 1279 6161 



5th, .... 1189 7350 



6th, .... 991 8341 



7th, . . . .884 9225 



8th, .... 775 10000 



From the top of the retorts, pipes B B, called dip 

 pipes, arise ; which, having reached to a consider- 

 able height, return downwards and enter the hydrau- 

 lic or condensing main, C. The condensing main is 

 a cast-iron cylinder, or pipe, lying in a horizontal 

 direction ; being supported by pillars on front of the 

 furnaces. The main, C, is constantly kept half full 

 of water, and the dipping pipes are made to termi- 

 nate in it, at a depth of about two inches below the sur- 

 face of the fluid which it contains. By this arrange- 

 ment, two important ends are attained ; for, when 

 the gas which is generated in the retort ascends the 

 dip pipe, B, and passes into the water in the con- 

 densing main, C, then the tar and other useless mat- 

 ter arising from the retorts are in a great measure 

 condensed, and separated from the gas which rises 

 above the surface of the water in the main, and passes 

 out by the pipe, D D, in a state of much greater 

 purity than that in which it was produced in the 

 retort. But, besides this advantage, the condensing 

 main enables us to open and clean any of the retorts, 

 without any possibility of the gas returning through 

 the dip pipe ; since, before the gas in the condensing 

 main could pass up through the pipe B, it would 

 require to exert a pressure on the surface of the fluid 

 on the main, sufficient to raise a column of water to 

 the top of the dip pipe, wluch shows the necessity of 

 carrying these pipes to a considerable height before 

 they return to the main. 



The gas, partially purified, passes out of the main 

 C, and down the pipe D D, depositing the tar in the 

 vessel E. From the tar vessel, , a pipe, F, is led 

 to a cooler, G G, which is a sort of oblong rectan- 

 gular chest, kept about half full of water. The gas 

 is introduced into this vessel for the purpose of being 

 cooled, and, in order to do this the more effectually, the 

 gas is made to come into contact with the greatest 

 possible surface of water, by an arrangement of par- 

 titions, seen endwise in the plate. These are fas- 

 tened to the top of the cooler, and reach nearly to the 

 bottom ; one half of them are fastened to one side of 

 the vessel, and the other half to the other side, as 

 may be seen in the annexed ground-plan ; where, the 

 gas being introduced at one end, must cross the ves- 

 sel at every compartment before it can enter the 

 next. 



After the gas has been cooled, by traversing from 

 side to side of the cooler on the surface of the water, 

 it passes out of this vessel by the pipe I, and enters 

 the purifier H. This is a close vessel, in which 

 shelves are placed, formed of sieves of wire-cloth. 

 On these sieves, layers of dry pulverised quicklime 

 are laid, and the gas, in rising through them, is puri- 

 fied to a considerable extent by the combination of 

 the lime with the carbonic acid and sulphuretted 

 hydrogen. The lid of the purifier is kept air-tight, 

 by inverting a vessel over it, whose bottom rests 

 in water. The gas passes out of the ourifying ves- 

 2 A 



