Page:Popular Science Monthly Volume 40.djvu/836

 not exert an influence on the distribution of rain through the seasons, as they certainly do on that of ground moisture, does not appear to have been yet adequately investigated.

In connection with the influence upon climate of the relations of land and water, the speculations respecting the probable effect upon the climate of Europe of flooding the Desert of Sahara deserve to be noticed. It has usually been taken for granted that a cooler condition would follow. But Prof. Hennessey argued several years ago that, as vapor, rather than dry air, is the chief vehicle of wind-borne heat, the result would be the opposite of this. While the midday heats of the desert are intense, the nights are cold. Hence a uniformly warm breeze can not come from there. The warm southwest winds of central and southern Europe have been found to be connected with the currents of the Atlantic, and not to come from the desert. The substitution of water for barren sands and rocks would be followed by the storing up of the heat of the sun which is now partly dissipated by radiation at night, and would furnish a source of constant warmth.



HE purpose of this paper is to utter a warning against the careless way in which the great mass of people, poor and rich, ignorant and learned, allow the air of their living-rooms to be in an impure condition, and to point out the great sacrifice of energy and health which results from this carelessness. We shall try to show that there is strong ground for believing that not only a large part of the ever-increasing trouble of bronchial and lung affections, but also a very large part of that vague and subtle ill-health which troubles our modern lives in varying forms, is to be placed to the account of the impure air which we so habitually breathe.

As we wish to make the paper plain to every one, we shall occasionally go back to the A B C of certain matters involved. The air which we breathe is made up of two gases, one active, one indifferent. The active gas, oxygen, on which life depends, is in the proportion of about one fifth (twenty-one per cent) of the whole; the indifferent gas, nitrogen, which tempers and dilutes its active partner, is in the proportion of four fifths (seventy-nine per cent), and with these two gases is found a small quantity—varying according to the purity of the air—of carbonic acid, about three to four parts in 10,000 parts, or 0·04 per cent, and in addition a minute quantity of a peculiarly active form of oxygen.