76 



THAT S IT : 



smoke and flames. The mouth of the retort is 

 now closed by its lid, which extinguishes the 

 flame by shutting off the air, and leaves no 

 escape for the dense vapours arising from the 

 coal, except by the outlet pipe ; they rush 

 through this tube, and are heard bubbling up 

 into the hydraulic main until the charge is ex- 

 hausted. The retort then contains the de- 

 hydrogenized matter of coal, which is distin- 

 guished by the name of coke, and consists of 

 carbon." 



The hydrogen, being driven off, 

 escapes through outlet pipes, B B, 

 which ascend from the ends of 

 the retorts and enter the hydraulic 

 main, C C. The latter is par- 

 tially filled with water, and the 

 ends of the outlet pipes, 18, enter 

 the hydraulic main, 19, and dip be- 

 neath the water, 20, 

 through which the 

 gas bubbles and rises 

 to the top. This 

 cleanses the gas, 

 and also stops the 

 mouths of the outlet- 

 pipe, 18, when no 

 more gas comes 

 from the retort, and when the 

 latter is opened to be emptied of 

 coke and refilled with coals. From 

 the hydraulic main, C C, the gas 

 passes through pipes away from 

 the retort house, 321, to the tar 

 cistern, 2 in which the tar and 



J 6' 7 8 9 10 



324. 



other deposits from the gas are 

 collected; from the tar cistern 

 an ascending pipe, 3, leads to the 

 condenser, 4, to which there are 

 attached a series of tubes, 5, 6, 7, 



8, 9, 10 ; in these the warm gas 

 ascends to the top, and becoming 

 cooled, falls to the bottom, while 

 warm gas takes the upper place. 

 In this way a circulation is kept 

 up in these tubes, by which the 

 gas becomes condensed and cooled ; 

 it then passes, in some instances, 

 to an upright cylindrical tube, 11, 

 filled with brushwood, through 

 which it continues on its way to 

 the chemical purifier, 12, where 

 it passes through lime, either dry 

 or mixed with water to the con, 

 sistence of cream. In other 

 cases the 

 gas passes 

 through a 

 scrubber, 13, 

 where a 

 stream of 

 water runs is 

 over a thick 

 layer of 

 pieces of coJce, 14 ; the gas enters 

 at the bottom, 15, and bubbling 

 through the coke and water to 

 the top, the coke absorbs various 

 impurities, and the gas passes 

 through a pipe, 16, to the reser- 

 voir, or gasometer. 



Gas is also made from oil in 

 a similar manner. The simple 

 apparatus, 1, for making which 

 upon a small scale, will assist to 

 explain the greater system. A 

 small cylinder, 2, is fitted into a 

 furnace, 3, where it is made red- 

 hot. A reservoir, 4, filled with 

 oil or fat is suspended to the 

 chimney of the furnace, 5, and 

 when the fat is melted it runs 

 from a small tap, 6, into a syphon, 

 7, whence it goes into the red-hot 

 cylinder, 2, and is converted into 

 gas, which escapes by the pipe, 0, 



325. 



