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Excerpt from The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, Vol. 36: July-December, 1868 <p>The grand simplicity of the idea of the conservation of force, together with the tendency to generalize which inuences most inquirers in scientific matters, would naturally lead to the belief that if mechanical energy is directly convertible into heat, heat should be also directly convertible into mechanical energy, and, of course, in the same proportion. Hence it is assumed that when a hot perfect gas performs work by expansion in a cylinder supposed to be neutral to the thermometric effects of heat, and having a piston moving without friction, it must naturally lose as much heat in raising a weight of 7 72 pounds one foot as would raise the temperature of one pound of liquid water 1 de gree of Fahrenheit's scale. By the same reasoning, steam, in performing work in vessels supposed to be equally neutral to heat, should lose exactly the same quantity of heat in doing the same quantity of work; and as perfect steam (neither super heated nor containing water in suspension) cannot lose heat without undergoing a corresponding amount of condensation, it is assumed that in the working of the steam-engine as much steam is condensed (theoretically) as corresponds to the amount of work performed in the proportion of Joule's equivalent, and consequently that the quantitative heat of the steam passing into the condenser is by so much less than the total heat of the steam furnished by the boiler to the engine. <p>More than thirty years ago Seguin, in his interesting work On the Influence of Railways, ' endeavoured to trace the dyna mical relation which he saw must exist between the heat applied to the boiler and. The energy developed by the engine; and it is remarkable that, in many experiments made by him on the actual working of steam-engines, with the express purpose of proving the disappearance of quantitative heat which he thought must be converted