178

General Description.

follows. The annulus is in the first place half fill-ed with water, either admitted cold, and heated bysuffering the steam to flow into it through the pipee, or admitted in a heated state from the boiler.On the steam valve being opened, the steam entersthe hole l in the mask, Fig. 4. through the pipe l,Fig. 5. and passes thence through the hole in theface which happens to be opposite to the aperturein the mask, and enters the annulus j then risingthrough the water, it is stopped by the valve d,immediately above the radius by which it entered,which will then be closed. The steam resisted bythe valve, acts against the surface of the water be-low it, and pressing it downwards, proportionablyraises it on the opposite side of the annulus, untilthe pressure of the column of water acting againstthe closed valve, through the medium of the steam,is sufficient to overcome the resistance. The trokeis now made to revolve, and, as it revolves, each ofthe holes in the face communicates in successionwith the hole l, and, by this construction, one en-tire hole in the face, or parts of two equal in propor-tion to one, is always in communication with thehole l; so that there is a continual flow of steaminto the annulus, causing the water, through its me-dium, to exert a constant and uniform pressure onthe valves as they ascend. The holes in the face,as they pass in succession from the hole l to the holei are entirely closed by the space between them ;and, immediately on communicating with the hole