Popular scientific lectures

of mechanical processes, especially the performance of work, with changes of thermal conditions by the invention of the steam-engine, and by its great technical imp

development in question was not connected w

ust fall from a higher level to a lower level to put a mill-wheel in motion. Differences of temperature, accordingly, represent forces able to do work exactly as do differences of height in heavy bodies. Carnot pictures to himself an ideal process in which no heat flows away unused, that is, without doing work. With a given expenditure of heat, accordingly, this process furnishes the maximum of work. An analogue of the process would be a mill-wheel which scoop

W, but in B under the same circumstances it should perform a greater quantity of work W + W'; then, we could join B in the sense assigned and A in the reverse sense into a single process

arnot here excludes for the first time from the province of general physics the possibility of a perpetual motion. But it follows, then, that the quantity of work W, produced by the passage of a quantity of heat Q from

as an adherent of the theory of Black, according to which the sum-total of the quantity of heat in the world is constant, but so far as his investigations have been hitherto considered the decision on this point is of no consequence. Carnot's principle led to the most remarkable results. W. Thomson (1848) founded upon it the ingen

s of the venous blood. In agreement with Liebig's theory of animal heat he connected this fact with the diminished loss of heat in warmer climates, and with the diminished expenditure of organic combustibles. The total expenditure of heat of a man

xplosive gas formed, is reproduced. If the current runs an electromotor, a portion of the heat again disappears, which, on the consumption of the work by friction, again makes its appearance. Accordingly, both the heat produced and the work produced, appeared to Joule also as connected with the consumption of material. The thought was therefore present, both to Mayer and to Joule, of regarding heat and

5 kilogramme-metres of work could be performed, and vice versa. Joule, on the other hand, by a long series of delicate and varied experim

e can measure all physical changes of condition, no matter how different they may be, with the same common measure, and say: the sum-total of all energy remains constant. Thi

"If a quantity of heat Q' is transformed into work in a reversible process, another quantity of heat Q of the absolute[55] temperature T1 is lowered to the absolute temperature T2." Here Q' is dependent only on Q, T1, T2, but is independent of the substances used and of the character of

Q) = (T1-

divided by the sum of the transformed and transferred heats (the tota

-T2