Other means are
had recourse to when the force required is great, and the space
through which it is to act is small. The hydraulic press of
Bramah can, by the exertion of one man, produce a pressure of
1,500 atmospheres; and with such an instrument a hollow cylinder
of wrought iron three inches thick has been burst. In rivetting
together the iron plates, out of which steam-engine boilers are
made, it is necessary to produce as close a joint as possible.
This is accomplished by using the rivets red-hot: while they are
in that state the two plates of iron are rivetted together, and
the contraction which the rivet undergoes in cooling draws them
together with a force which is only limited by the tenacity of
the metal of which the rivet itself is made.
59. It is not alone in the greater operations of the engineer
or the manufacturer, that those vast powers which man has called
into action, in availing himself of the agency of steam, are
fully developed. Wherever the individual operation demanding
little force for its own performance is to be multiplied in
almost endless repetition, commensurate power is required.
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