t'SEFUIi rRODJJCTS FROM COAL. ^^J 



siied in the earthen jar at N, by that means the pipes will 

 not clog up in half a century. These jars must be some- 

 times removed and emptied, fresh water pat in, as also the 

 water in the vessel H must be changed, to keep it clean and 

 sweet; and the water in the purifier C should be changed The water to 

 every two or three days: by these means the gas will be de-^^^j^J^'^j®"^^^ 

 prived of all its smell, at least as far as washing will effect 

 itj and the apparatus will be clean. 



The stop. cock at O is for the use of a master, if heCock for lock- 

 wishes to lock up the gas in the reservoir, to prevent his^"| g^j[,^^^g^'_, 

 workman &c. wasting it in his absence; as also if any pipeing the lights. 

 should leak, or a cock be out of order, in any part of the 

 premises, by turning this cock ail the gas is kept in the re- 

 servoir while the pipe is repaired, or any other alteration 

 made; it also extinguishes all the lights when turned, if 

 any are left burning by careless workmen, nor can they be 

 lighted until it is opened again. 



The whole of this apparatus is simple, and not liable to Conduct of the 

 be put out of order in such a way, but that any person may^"^"^^* 

 put it to rights again. All the art required to make the gas 

 is to take off the cover of the pot, and, without removing 

 the pot, to take out the coke, and fill it with fresh coal; 

 wedge the cover down by putting an iron wedge between 

 the bewels or ears and the elbow of the vessel, and, if re- 

 quired, plaster a little clay or loam round the cover, to keep 

 it air-tight ; a fire is then to be made under it, and the whole 

 is done. The boy, or man, who does it, must now and 

 then look at the fire, and keep it up, until the pot is hot, 

 and the gas is made. Now in works where lights are want- 

 ed almost always, I would recommend two fire-places, and 

 two pots, so that when one pot is burned out, the other pot 

 may be ready to act; for this purpose the purifier must be 

 provided with two of the water.joints B, one communicat- 

 ing with each pot, and the elbow-pipe of each pot must have 

 a stop-cock, as V. When one pot is burning, the cock in 

 the other pipe must be stopped, that the gas may not find 

 its way out of the purifier; and when all the gas is extract- 

 ed from that pot, the cock V, leading from it, must be 

 stopped, and the pot left to cool ; while a fire is put under 

 the other pot, its cock is opened, and a supply of gas from 



Si^ppLEMENT — Vol. XXXI. Z it 



