A History of the Growth of the Steam-Engine

by Robert Henry Thurston

Dynamics, or kinetics, which treats of simple motion as an effect of the action of forces.

Energetics, which treats of modifications of energy under the action of forces, and of its transformation from one mode of manifestation to another, and from one body to another.

Under the latter of these four divisions of mechanical philosophy is comprehended that latest of the minor sciences, of which the heat-engines, and especially the steam-engine, illustrate the most important applications—Thermo-dynamics. This science is simply a wider generalization of principles which, as we have seen, have been established one at a time, and by philosophers widely separated both geographically and historically, by both space and time, and which have been slowly aggregated to form one after another of the sciences, and out of which, as we now are beginning to see, we are slowly evolving wider generalizations, and thus tending toward a condition of scientific knowledge which renders more and more probable the truth of Cicero’s declaration: “One eternal and immutable law embraces all things and all times.” At the basis of the whole science of energetics lies a principle which was enunciated before Science had a birthplace or a name:

All that exists, whether matter or force, and in whatever form, is indestructible, except by the Infinite Power which has created it.

That matter is indestructible by finite power became admitted as soon as the chemists, led by their great teacher Lavoisier, began to apply the balance, and were thus able to show that in all chemical change there occurs only a modification of form or of combination of elements, and no loss of matter ever takes place. The “persistence” of energy was a later discovery, consequent largely upon the experimental determination of the convertibility of heat-energy into other forms and into mechanical work, for which we are indebted to Rumford and Davy, and to the determination of the quantivalence anticipated by Newton, shown and calculated approximately by Colding and Mayer, and measured with great probable accuracy by Joule.

Benjamin Thompson, Count Rumford.

The great fact of the conservation of energy was loosely stated by Newton, who asserted that the work of friction and the vis viva of the system or body arrested by friction were equivalent. In 1798, Benjamin Thompson, Count Rumford, an American who was then in the Bavarian service, presented a paper[105] to the Royal Society of Great Britain, in which he stated the results of an experiment which he had recently made, proving the immateriality of heat and the transformation of mechanical into heat energy. This paper is of very great historical interest, as the now accepted doctrine of the persistence of energy is a generalization which arose out of a series of investigations, the most important of which are those which resulted in the determination of the existence of a definite quantivalent relation between these two forms of energy and a measurement of its value, now known as the “mechanical equivalent of heat.” His experiment consisted in the determination of the quantity of heat produced by the boring of a cannon at the arsenal at Munich.

Rumford, after showing that this heat could not have been derived from any of the surrounding objects, or by compression of the materials employed or acted upon, says: “It appears to me extremely difficult, if not impossible, to form any distinct idea of anything capable of being excited and communicated in the manner that heat was excited and communicated in these experiments, except it be motion.”[106] He then goes on to urge a zealous and persistent investigation of the laws which govern this motion. He estimates the heat produced by a power which he states could easily be exerted by one horse, and makes it equal to the “combustion of nine wax candles, each three-quarters of an inch in diameter,” and equivalent to the elevation of “25.68 pounds of ice-cold water” to the boiling-point, or 4,784.4 heat-units.[107] The time was stated at “150 minutes.” Taking the actual power of Rumford’s Bavarian “one horse” as the most probable figure, 25,000 pounds raised one foot high per minute,[108] this gives the “mechanical equivalent” of the foot-pound as 783.8 heat-units, differing but 1.5 per cent. from the now accepted value.