All About Engines
Forfatter: Edward Cressy
År: 1918
Forlag: Cassell and Company, LTD
Sted: London, New York, Toronto and Melbourne
Sider: 352
UDK: 621 1
With a coloured Frontispiece, and 182 halftone Illustrations and Diagrams.
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32 All About Engines
sized one. But in 1711 he undertook to construct
one for a colliery near Wolverhampton. In trying
to make this engine work to his satisfaction, he was
led to an important improvement. Both in the
small and the large engine he had tried a tank of
water round the cylinder, and had naturally found
the method very wasteful of steam. Further, in order
to make the piston air-tight, he had a shallow layer
of water on the top of it. He noticed that occasion-
ally the engine made a few strokes much more quickly
.than usual, and on inquiring into the cause found
that it was due to a small hole in the piston by
means of which a little water every now and then
reached the interior of the cylinder. This suggested
to him the desirability of condensing the steam by
a jet inside the cylinder, and he adopted this plan
with great advantage.
You can imagine the eagerness with which he
watched every movement, and how he bent his
thoughts to discover any little alteration which would
improve the machine upon which he had laboured
for many years. But the next step came from a boy
named Humphrey Potter, who was less interested
in the engine than in obtaining more time for play.
He was engaged to turn the taps admitting steam
and water alternately to the cylinder, and, tiring of
the monotony of this task, he conceived the idea
of fastening the taps to the moving beam in §uch a
way that the engine opened and closed them itself.
The result was surprising, for the speed of the engine
was increased from six or eight to fifteen or sixteen