Page:Popular Science Monthly Volume 12.djvu/36

26 particularly the deep pits of Cornwall, free from water, and the failure of every attempt previously made to provide effective and economical pumping machinery, were noted by Savery, who, July 25, 1698, patented the design of the first engine which ever was actually employed in this work.



A working model was submitted to the Royal Society of London, in 1699, and successful experiments were made with it.

This engine is shown in Fig. 8, as described by Savery himself in 1702, in the "Miner's Friend."

L L is the boiler, in which steam is raised, and through the pipes O O it is alternately let into the vessels P P.

Suppose it to pass into the left-hand vessel first. The valve M being closed and r being opened, the water contained in P is driven out and up the pipe S to the desired height, where it is discharged.

The valve r is then closed, and also the valve in the pipe O. The valve M is next opened, and condensing water is turned upon the exterior of P by the cock Y, leading water from the cistern X. As the steam contained in P is condensed, forming a vacuum, a fresh charge of water is driven by atmospheric pressure up the pipe T.

Meantime, steam from the boiler has been let into the right-hand vessel P, the cock W having been first closed and R opened. The charge of water is driven out through the lower pipe and the cock R, and up the pipe S as before, while the other vessel is refilling preparatory to acting in its turn.