Purposes of Exposition News

=Generalization=This is one of the most effective devices in the public speaker's repertory.

Take a hollow cylinder, the bottom closed while the top remains open, and pour in water to the height of a few inches. Next cover the water with a flat plate or piston, which fits the interior of the cylinder perfectly; then apply heat to the water, and we shall witness the following phenomena. After the lapse of some minutes the water will begin to boil, and the steam accumulating at the upper surface will make room for itself by raising the piston slightly. As the boiling continues, more and more steam will be formed, and raise the piston higher and higher, till all the water is boiled away, and nothing but steam is left in the cylinder. Now this machine, consisting of cylinder, piston, water, and fire, is the steam-engine in its most elementary form. For a steam-engine may be defined as an apparatus for doing work by means of heat applied to water; and since raising such a weight as the piston is a form of doing work, this apparatus, clumsy and inconvenient though it may be, answers the definition precisely.

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