Wet steam, steam holding water mechanically suspended, the water being in the form of spray.
Specific gravity of steam is ·625 as compared to air under the same pressure.
The properties which make it so valuable are:
1. The ease with which we can condense it.
2. Its great expansive power.
3. The small space in which it shrinks when it is condensed either in a vacuum chamber or the air.
A cubic inch of water turned into steam at the pressure of the atmosphere will expand into 1,669 cubic inches.
THE DAVIDSON.
The Davidson pump is shown complete in [Fig. 248]; the valve motion consists principally of a valve, valve pistons, valve pin and cam. The main valve is operated by a positive mechanical connection between it and the main piston rod, also by the action of steam on the valve pistons. The engraving, [Fig. 249], shows the details of valve gear and steam cylinder. The steam end consists of the cylinder, M, valve, A, and valve pistons, B and B. These pistons are connected with sufficient space between them for the valve, A, covering the steam ports, F and F1, Fig. 250.