Page:Reflections on the Motive Power of Heat.djvu/250

226 We can then establish the general proposition that motive power is, in quantity, invariable in nature; that it is, correctly speaking, never either produced or destroyed. It is true that it changes form, that is, it produces sometimes one sort of motion, sometimes another, but it is never annihilated.

According to some ideas that I have formed on the theory of heat, the production of a unit of motive power necessitates the destruction of 2.70 units of heats.

A machine which would produce 20 units of motive power per kilogram of coal ought to destroy $$\tfrac{20 \times 2.70}{7000}$$ of the heat developed by the combustion. $$\tfrac{20 \times 2.70}{7000} = \tfrac{8}{1000}$$ about; that is, less than $$\tfrac{1}{100}$$. (Each unit of motive power, or dyname, representing the weight of one cubic metre of water raised to the height of one metre.)

To repeat Rumford's experiments in the drilling of a metal in water, but to measure the motive power consumed at the same time as the heat