We have not yet noticed the other steam vessel V′, which, as far as we have described, would have remained filled with common atmospheric air, the pressure of which on the valve A′ would have prevented the water raised in the suction pipe S from passing through it. However, this is not the case; for, during the entire process which has been described in V, similar effects have been produced in V′, which we have only omitted to notice to avoid the confusion which the two processes might produce. It will be remembered, that after the steam, in the first instance, having flowed from the boiler [Pg055] through T, has blown the air out of V through B, the communication between T and the boiler is closed. Now the same motion of the regulator which closes this, opens the communication between T′ and the boiler; for the sliding plate R (_fig._ 11.) is moved from the one tube to the other, and at the same time, as we have already stated, the condensing pipe is brought to play on V. While, therefore, a vacuum is being formed in V by condensation, the steam, flowing through T′, blows out the air through B′, as already described in the other vessel V; and while the air in S is rushing up through A into V, followed by the water raised in S by the atmospheric pressure, the vessel V′ is being filled with steam, and the air is completely expelled from it. The communication between T and the boiler is now again opened, and the communication between T′ and the boiler closed by moving the regulator R (_fig._ 11.) from the tube T to T′; at the same time the condensing pipe is removed from over V, and brought to play upon V′. While the steam once more expels the air from V through B, a vacuum is formed by condensation in V′, into which the water in S rushes through the valve A′. In the mean time V is again filled with steam. The communication between T and the boiler is now closed, and that between T′ and the boiler is opened, and the condensing pipe removed from V′, and brought to play on V. While the steam from the boiler forces the water in V′ through B′ into the force-pipe F, a vacuum is being produced in V, into which water is raised by the atmospheric pressure. Thus each of the vessels V V′ is alternately filled from S, and the water thence forced into F. The same steam which forces the water from the vessels into F, having done its duty, is condensed, and brings up the water from S, by giving effect to the atmospheric pressure.