USEFUL PRODUCTS FROM COAL. 335 



when the lid or cover of the pot is put on, the bewels or 

 ears come over the elbow of the pipe that is on the lid, and 

 a wedge is put between them and this elbow, to keep down 

 the cover air-tight, and a little clay or loam may be luted 

 in the joint, if any gas should escape round the cover of ihe 

 pot. The other elbow B goes into a water-joint, formed Purification of 

 of a tube affixed to the cover of the purifier C ; and another ^^^ ^^' 

 tube, which passes through the lid of the purifier: the eU 

 bow-pipe then goes over the inner tube, and when put on, 

 the jointing is made good by pouring water into the space 

 between the tubes, which renders it air-tight. The gas, as 

 the arrows show, passes down into the purifier C, which is 

 rather more than half full of water ; the use of this water- 

 joint is for the convenience of removing the lid rf, to which 

 this pipe is attached. The purifier C is a wooden trough, 

 with a sheet-iron top, to which the tubes are soldered, and 

 it is fastened to the trough to keep all secure and air-tight. 

 The sheets of iron, e,/, g, k, i, k, are alternately soldered 

 to the iron top, and fastened to the wooden bottom. Now 

 when the trough is half filled with water, the gas passes 

 into it at B ; and, as it can only find its way out again at R, 

 it must pass through the water. The inner pipe B reaches 

 under the surface of the water in the trough ; now when the 

 gas is forced into the water, it would rise to the top of the 

 pnrifier, and go along in a body to the end, and out at the 

 pipe R, if the sheets of iron, e, /, g-, A, i, and k, Mhich 

 stand across the trough, with openings in them alternately 

 at top and bottom, did not stop it, force it to descend dowa 

 into the water, and hinder it from going any way but 

 through these apertures, purifying it all the time it is pass- 

 ing through the whole body of water, until it is properly 

 washed ; it then escapes through the pipe R at the end of the 

 trough C, passes down the pipe S, and is carried up into 

 the reservoir or gazometer K. In the bottom of the purifier 

 is an aperture, closed by a plug at D, to let off the amraonia- 

 cal water and tar as it is deposited, and the pipe, with the 

 cock E at the top of the purifier, is to burn away the spare 

 gas, when not to be used. 



There is a stop. cock placed in the main pipe at F, that Method of 



. ^, . . ». II J • 1 • 1 . burning the SU- 



IT hen the reservoir is full, and gas is making, and cannot p^j.^^^^j'^j. ^^^^ 



be 



