The Correlation and Conservation of Forces

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1876 edition. Excerpt: ...in fact ever returns or can return to a state of existence identical with a previous state. But the field is too illimitable for me to venture further. The inevitable dissipation or throwing off a portion of the initial force presents a great experimental difficulty in the way of establishing the equivalents of the various natural forces. In the steam-engine, for instance, the heat of the furnace not only expands the water and thereby produces the motion of the piston, but it also expands the iron of the boil er, of the cylinder and all surrounding bodies. The force expended in expanding this iron to a very small extent is equal to that which expands the vapour to a very large extent: this expansion of the iron is capable, in its turn, of producing a great mechanical force, which is practically lost. Could all the force be applied to the vapour, an enormous addition of power would be gained for the same expenditure: and per- haps even with our present means more might be done in utilising the expansion of the iron. Another great difficulty in experimentally ascertaining the dynamic equivalents of different forces arises from the effects of disruption, or the overcoming an existing force. Thus, when a part of the initial force employed is engaged in twisting or tearing asunder matter previously held together by cohesive attraction, or in overcoming gravitation or inertia, the same amount of heat or electricity would not be evolved as if such obstacle were non-existent, and the initial force were wholly employed in producing, not in opposing. There is a difficulty apparently extreme in devising experiments in which some portion of the force is not so employed. The initial force, however, that has been employed for such disruption is not lost, ..