Walker's Statistical Atlas of the United States. 167 
minishes eastward to the eastern base of the Apallachian sys- 
tem, amounting to 80° in northern New England, but south of 
New York it is usually less than 70°. The hot line of 85° in 
eastern Dakota is north of the cold line of —20, and passing 
eastward, successively cuts every cold line to +20, which it 
crosses in eastern Delaware. The hot line of 90°, which is 
first traced above Fort Benton, crosses the Ohio River near 
that of the Ohio. During the cold week, nearly all the Ohio 
pores was between +5° and +20°, while in that of the Mis- 
ri the average was rie zero to —20 and lower. Space 
forbids a further comparison of these two — or any no- 
tice of others we intended to have dwelt u 
This last chart is of much interest to the studanid in biology. 
In Dakota (beyond which the lines are not traced) we have a 
difference of 105° F., and over large areas of the plains, a differ- 
ence of 100° F. On the 91st meridian, the hot line of 90° is 
330 miles north of the ~ line of +10°; they cross each other 
near Cincinnati: and on the 83d meridian they are again 340 
miles apart but in the reveal order. Again, the hot line of 
85° and the line of +20° are together; in fact they cross in 
southeastern Delaware. They separate westward, the cold 
line crossing extreme southern Arkansas, the hot line pee 
up to Dakota, more than 950 miles north. Again, in the lon- 
or 1385 miles from the maximum line of 90°. Passing west- 
ward, the former descends to lat. 27° in Texas, the latter rises 
to lat. 48° in Montana, equivalent to a distance of about 1 
miles on the meridian. These climatic peculiarities, taken in 
connection with the nature of the ‘storms of winter and the 
sudden changes of t occurring there, must 
have much greater influence on the distribution of life than ao 
annual means of temperature and rain-fall. It is, perhaps, 
tically there the controlling condition. That a dry an hot 
climate may have a flora and fauna rich in species is Ulustrated 
by South Africa. But this “ middle region” is poor in species, 
=a whole of it is without forests as shown in the ‘‘ Map of 
, nds.” 
The excellent geological map, compiled by Professors C. B. 
Hitchcock and W. P. Blake, we have already noticed. On it, 
the “ oo. and Permian” are shown as a single mem- 
ber. That portion lying east of the 100th meridian forms a 
broad doakly eos belt, like a huge inverted letter S, reach- 
ing from aries York to Texas, with i wee outlying patches, the 
which is in Michigan. e upper division of the 
Cazhan fice series, “ the Coal acy is shown on a large 
