Chapter C: D E F are the four printing cylinders, named in the order of their (32)

The gasometer may be separated from the purifier by an intermediate vessel, such as is represented _fig._ 491., with which the two gas pipes are connected. A is the cylindrical vessel of cast iron, _a_, the end of the gas pipe which comes from the purifier, immersed a few inches deep into the liquid with which the vessel is about two-thirds filled; _b_ is the gas-pipe which leads into the gasometer, _c_ is a perpendicular tube, placed over the bottom of the vessel, and reaching to within one-third of the top, through which the liquid is introduced into the vessel, and through which it escapes when it overflows the level _d_. In this tube the liquid stands towards the inner level higher, in proportion to the pressure of the gas in the gasometer. The fluid which is condensed in the gas pipe, _b_, and in its prolongation from the gasometer, runs off into the vessel A; and therefore the latter must be laid so low that the said tube may have the requisite declivity. A straight stop-cock may also be attached to the side over the bottom, to draw off any sediment.