PYRONOMICS. 99 
tle vapor arising from the water will be condensed so rapidly as quickly to 
convert the water into ice. 
e. The Steam-Engine. 
The steam-engine serves in general to convert the vapor of water into a 
motive power. As early as the year 1687 Papin constructed an apparatus, 
which may be considered the earliest steam-engine on record. It is repre- 
sented on pl. 19, fig. 26. It consists of a glass tube with a bulb blown at 
one end containing some water. A piston, p, moves air-tight up and down 
the tube. If while the piston is depressed the bulb be heated, the steam will 
force it up to the top; then, if dipped in cold water, the steam will become 
condensed, and a vacuum being produced, the piston will be depressed by 
the incumbent pressure of the atmosphere. Papin employed an iron cylin- 
der instead of a glass tube. Savery made the first practical application of 
the steam-engine: he employed it in removing water from the bottom of 
mines; which was also the application of Newcomen’s atmospheric engine. 
This latter was constructed according to the principles of Papin’s engine, 
except that he admitted cold water into the cylinder to condense the steam. 
Watt made the great improvement of attaching a receiver, separate from 
the cylinder, to condense the steam. To him we also owe a great number 
of other important improvements; and with justice he is considered as the 
inventor of the steam-engine in its present perfected form. 
A sectional view of Watt’s steam-engine is exhibited in pl. 19, fig. 27. 
Here A is the cylinder, air-tight below and above, in which the p:ston, C, 
moves. The steam, generated in a boiler, enters through a pipe. Z, and 
thus is introduced into the cylinder alternately at the upper and lower ends 
at E and O. If it enter above, as in the figure, the steam beneath the piston 
escapes at O, and enters the condenser, I, through the pipe H, where it is 
condensed. There is thus a rarefied space beneath the piston, which must 
consequently descend when pressed on by the steam above. The condenser, 
I, stands in a cistern partly filled with cold water; there is a pump, K, to 
remove the water from the condenser, and likewise the air which rapidly accu- 
mulates there. This is called the air-pump. It brings the water from the 
condenser into the receiver. R, whence it flows through the pipe S to be 
partly employed in feeding the boiler. The water required for the boiler is 
brought through the pipe M to a pump, and, by means of this, through the 
pipe M’ to the boiler. This latter pump, called the hot water pump, like 
the air-pump, is kept in motion by the engine itself; thus, the pump rod, L, 
is attached towards one end of the great beam or lever set in motion by the 
piston, C, and is elevated or depressed with the elevation or jepression of thr 
end of the beam. During elevation the suction valve opens, and during 
depression the valve x. On the other side of the beam, not visible in the 
figure, is a pump rod, by which cold water is raised in the pipe T’, and brought 
through the tube U into the cistern in which is placed the condenser. 
By means of the piston rod an alternating upward and downward motion 
ICONOGRAPHIC ENCYCLOP Z£DIA.—VOL. I. 18 ais 
