Page:Popular Science Monthly Volume 11.djvu/208

196

E shall devote this evening to the consideration of some hygienic functions of the house. On the whole, the house has the same hygienic object as our clothing: it has not only to keep up the intercourse with the atmosphere surrounding us, but to regulate it according to our wants. No more than our clothing ought the house to be a contrivance for excluding us from the air outside. In some of their forms we can also trace a certain mutual transition. The cloak and the tent are cousins. The heavy circular cloak of former times might well be styled a portable tent, and the tent a fixed cloak; both have their necessary openings. So the hat may be considered the roof of our clothing, and the roof the head-gear of the house.

We may then naturally suppose that those materials which are advantageous for the building of our habitations must stand in some-what the same relations to air, water, and heat, as the materials we use for our clothing. Walls allow air to pass through them, and they must do so to a certain degree, if we are to preserve our health within them with some comfort, and without injury. Current opinion is certainly opposed to my assertion about the permeability of walls to air, even more so than to that about the permeability of our clothing; but it is easy to show that current opinion labors under an error which has no other basis than the insensibility of our senses to the movement of the air, if the same is less than nineteen inches per second. This is the cause of the fallacy that no motion of the air takes place. Just as well might we deny the earth's rotation round its axis at the rate of more than a quarter of a mile per second, because we are not in the least aware of this tremendous velocity. Only very late and slowly have our minds opened to the conviction that after all the earth moves round the sun, and not the sun round the earth, and that our eyes had all the while been mistaken. There must exist something of a higher nature, of a greater power, than our sensuous perceptions, and that is science, which examines and probes our perceptions. Science has not the least power over Nature; she cannot command any alteration in Nature, cannot give it any