Quaestiones Convivales

I SUPPOSE you may remember what Aristotle says in his problems, of little stones and pieces of iron, how it hath been observed by some that being thrown into the water

they temper and cool it. This is no more than barely asserted by him; but we will go farther and enquire into the reason of it, the discovery of which will be a matter of difficulty. Yes, says I, it will so, and it is much if we hit upon it; for do but consider, first of all, do not you suppose that the air which comes in from without cools the water? But now air has a great deal more power and force, when it beats against stones and pieces of iron. For they do not, like brazen and earthen vessels, suffer it to pass through; but, by reason of their solid bulk, beat it back and reflect it into the water, so that upon all parts the cold works very strongly. And hence it comes to pass that rivers in the winter are colder than the sea, because the cold air has a power over them, which by reason of its depth it has not over the sea, where it is scattered without any reflection. But it is probable that for another reason thinner waters may be made colder by the air than thicker, because they are not so strong to resist its force. Now whetstones and pebbles make the water thinner by drawing to them all the mud and other grosser substances that be mixed with it, that so by taking the ’strength from it it may the more easily be wrought upon by the cold. But besides, lead is naturally cold, as that which, being dissolved in vinegar, makes the coldest of all poisons, called white-lead; and stones, by reason of their density, raise cold in the bottom of the water. For every stone is nothing else but a congealed lump of frozen earth, though some more or less than others; and therefore it is no absurdity to say that stones and lead, by reflecting the air, increase the coldness of the water.

Yes, said I, it is a very strange thing, if true. But it is not so; and we cozen ourselves by presently concluding a thing to be hot if it have a faculty of causing heat, when yet we see that the same garment causes heat in winter, and cold in summer. Thus the nurse in the tragedy,

In garments thin doth Niobe’s children fold,

And sometimes heats and sometimes cools the babes.

The Germans indeed make use of clothes only against the cold, the Ethiopians only against the heat; but they are useful to us upon both accounts. Why therefore should we rather say the clothes are hot, because they cause heat, than cold, because they cause cold? Nay, if we must be tried by sense, it will be found that they are more cold than hot. For at the first putting on of a coat it is cold, and so is our bed when we lie down; but afterwards they grow hot with the heat of our bodies, because they both keep in the heat and keep out the cold. Indeed, feverish persons and others that have a violent heat upon them often change their clothes, because they perceive that fresh ones at the first putting on are much colder; but within a very little time their bodies make them as hot as the others. In like manner, as a garment heated makes us hot, so a covering cooled keeps snow cold. Now that which causes this cold is the continual emanations of a subtile spirit the snow has in it, which spirit, as long as it remains in the snow, keeps it compact and close; but, after once it is gone, the snow melts and dissolves into water, and instantly loses its whiteness, occasioned by a mixture of this spirit with a frothy moisture. Therefore at the same time, by the help of these clothes, the cold is kept in, and the external air is shut out, lest it should thaw the concrete body of the snow. The reason why they make use of cloth that has not yet been at the fuller’s is this, because that in such cloth the hair and coarse flocks keep it off from pressing too hard upon the snow, and bruising it. So chaff lying lightly upon it does not dissolve the body of the snow, besides the chaff lies close and shuts out the warm air, and keeps in the natural cold of the snow. Now that snow melts by the evaporating of this spirit, we are ascertained by sense; for when snow melts it raises a vapor.