Cosmos, Vol. 5

and the needle approaches most closely to the vertical direction when, in winter, the northern hemisphere of the Earth stands nearest to the sun. This fact—discovered only in recent years—of an indubitable connection between the magnetism of our planet and the mighty magnetic force of the distant central body of our system, gives a cosmic character to an important group of earthly phenomena in the broadest sense of the word.

As we have just touched upon an electro-chemical process which seems to proceed like a perpetual thunderstorm within the solar body, exciting light and heat; so must we also consider the important new view concerning a universal activity of matter: heat; whether the same be communicated from without, or evoked through impact, friction, change in volume, and chemical effects. I refer to the mechanical theory of heat Now known as thermodynamics, developed in many ways and with a great expenditure of ingenuity—that endeavor, now become so vital, to trace all effects of heat and electricity back to the concept of motion. Every heating of a body corresponds to the generation of a mechanical force ¹), a certain measurable work. Every quantity of heat has its work-equivalent: so that in general it would seem to be subject to little doubt that heat can be transformed into work—that is, into a mechanical effect—and conversely, that mechanical work can appear as heat. However, in detail, the reduction of all temperature phenomena (the communication of heat, latent heat, and specific heat) remains hitherto exposed to many somewhat arbitrary assumptions: even if we, without abandoning the Carnot principle Refers to Nicolas Léonard Sadi Carnot's reflections on the motive power of fire, fundamental to the Second Law of Thermodynamics of