How thy garments are warm, when he quieteth the earth by the south wind? How thy garments are warm - What are warmth and cold? How difficult this question! Is heat incontestably a substance, and is cold none? I am afraid we are in the dark on both these subjects. The existence of caloric, as a substance, is supposed to be demonstrated. Much, satisfactorily, has been said on this subject; but is it yet beyond doubt? I fear not. But supposing this question to be set at rest, is it demonstrated that cold is only a quality, the mere absence of heat? If it be demonstrated that there is such a substance as caloric, is it equally certain that there is no such substance as frigoric? But how do our garments keep us warm? By preventing the too great dissipation of the natural heat. And why is it that certain substances, worked into clothing, keep us warmer than others? Because they are bad conductors of caloric. Some substances conduct off the caloric or natural heat from the body; others do not conduct it at all, or imperfectly; hence those keep us warmest which, being bad conductors of caloric, do not permit the natural heat to be thrown off. In these things we know but little, after endless cares, anxieties, and experiments!
But is the question yet satisfactorily answered, why the north wind brings cold, and the south wind heat? If it be so to my readers, it is not so to me; yet I know the reasons which are alleged.