Its nature

Next to the phenomena of gravity, those of heat are, unquestionably, the most universal in the province of Physics. Throughout the economy of terrestrial nature, dead or living, the function of heat is as important as that of gravity, of which it is the chief antagonist. The consideration of gravity presides over the geometrical and mechanical study of bodies : while that of heat prevails in its turn, when we investigate deeper modifications, relating to either the state of aggregation or the composition of molecules : and finally, vitality is subordinated to it. The intelligent application of heat constitutes the chief action of man upon nature. Thus, after barology, thermology is, of all the parts of physics, the one which most deserves our study.

Its history

The earliest scientific observations in thermology are almost as old as the discoveries of Stevinus and Galileo on gravity, the invention of the thermometer having taken place at the beginning of the seventeenth century: but, owing to the complication of its phenomena, it has always been far distanced by barology. At the end of the seventeenth century, the indications of the thermometer could not be compared, for want of two fixed points, the necessity for which was, at that time, pointed out by Newton. The greatest difference between the two studies, however, was in their spirit.