8 14 THE POPULAR SCIENCE MONTHLY. 



not exert an influence on tlie distribution of rain through the 

 seasons, as tliey 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 de- 

 serve 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 stor- 

 ing up of the heat of the sun which is now jjartly dissipated 

 by radiation at night, and would furnish a source of constant 

 warmth. 



BAD AIR AND BAD HEALTH. 



By HAEOLD wager and AUBEEON HEKBEET. 



THE 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 oc- 

 casionally 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 in- 

 different. 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. 



