These springs
of nature differ in some respects from the steel springs formed
by our art; for in the compression of the natural springs a vast
quantity of latent heat is forced out, and in their return to the
state of gas an equal quantity is absorbed. May not this very
property be employed with advantage in their application?
Part of the mechanical difficulty to be overcome in
constructing apparatus connected with liquefied gases, will
consist in the structure of the valves and packing necessary to
retain the fluids under the great pressure to which they must be
submitted. The effect of heat on these gases has not yet been
sufficiently tried, to lead us to any very precise notions of the
additional power which its application to them will supply.
The elasticity of air is sometimes employed as a spring,
instead of steel: in one of the large printing-machines in London
the momentum of a considerable mass of matter is destroyed by
making it condense the air included in a cylinder, by means of a
piston against which it impinges.
352. The effect of competition in cheapening articles of
manufacture sometimes operates in rendering them less durable.
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