42 — Scientific Intelligence. 
SCIENTIFIC INTELLIGENCE. 
I. PHysics AND CHEMISTRY. 
ar 
reason of this is obvious. Nearly all the land is in the northern 
hemisphere, while the southern hemisphere is for the most part 
: the northern or land-hemisphere, for rea- 
sons to which I need not here refer, becomes heated in summer 
and cooled in winter to a far greater extent than the surface of 
the southern or water hemisphere. Consequently when we add 
the July or midsummer temperature of the northern to the July 
temperature of the southern hemisphere, we must get a higher 
number than when we add the January or midwinter temperature 
: e 
northern hemisphere is 48°-9, which, added to 59°5, the mean 
January temperature of the southern hemisphere, gives only 
108°°4, or a mean of 54°-2. Consequently the air over the surface 
of the globe is hotter in July by 8° than in January, notwith- 
standing the effects of eccentricity. It is obvious that, were 1t 
not for the counteracting effects of eccentricity, the difference 
would be much greater. Ten thousand years ago, when eccen- 
tricity and the distribution of land and water combined to pro- 
duce the same effect, the difference must have been far greater 
an 8° 
But it will be asked, How can this affect the air over the equa- 
tor, which is not situated more on the one hemisphere than on.the 
other? It is true that those causes have but little direct effect on 
the air at the equator, but indirectly they have a very powerfu 
influence. The air is continually flowing in to the equatorial re- 
gions from both hemispheres. In fact, the air which we find 
