April, 1903 .] 
Some Climatic Conditions of Ohio. 
407 
the same direction as that of the hands of a clock. Thus the 
winds in advance of a “Low,” as the low-pressure areas are 
termed, are warmer, and with us in Ohio usually southerly or 
southwesterly, while the winds in advance of the high-pressure 
area following the rainy “ Low ” are from the north or northwest 
and colder. It is probably due to such cold northwest winds 
blowing over a region left moist and warm by the preceding storm 
that the areas of low temperatures can be traced in a northwest 
to southeast direction, and so likewise the area of high relative 
humidity, if determined indirectly by the same cause, would 
follow the same direction. 
In July, which we may take as being about the middle of the 
growing season, Ohio again presents some interesting problems 
in connection with its relative humidity. The main body of the 
State has an average of between sixty-five and seventy per cent. 
(Map XI). The highest per cent, is in the southeast, while in 
the western part, and extending over southern Indiana as well, is 
a section with a relative humidity for July of less than sixty-five 
per cent. For July this is the driest region in the United States 
east of Kansas or Nebraska. The region is not in the right posi- 
tion, with prevailing southwest winds, to derive any benefit from 
the Great Lakes, and the atmosphere is apparently pretty well 
dried out after its passage over the broad, level region to the west. 
The following tables were taken from the Report of the Chief 
of the U. S. Weather Bureau, 1901-1902, and include the period 
1888 to 1901 : 
MONTHLY AND ANNUAL MEAN RELATIVE HUMIDITY. 
Stations. 
Average Per Cent, in 
Each Month 
Least 
~ Monthly 
5 Per Cent. 
Greatest 
Monthly 
Per Cent. 
c 
* — 1 
V 
X 
Mai. 
Apr. 
>» 
a 
S 
. | 
= £ 
< 
a 
V 
tn 
U 
O 
> 
0 
2 
6 
a/ 
Annual 
Month. 
Amt. 
Month. 
Amt. 
Toledo 
82.4 
80.4 
"5 8 
69. I 
69.0 
69.967 1 
70.1 
72 2 
73 3 
77-6 
79 9 
73-9 July 
67.1 
Jan. 
82 4 
Sandusky .... 
7 Q 8 
7S.6 
70.4 
69.4 
69 1 
70.967 7 
69 4 
70 4 
71 0 
74 8 
76 6 
74 4 July 
67 7 
Jan. 
79 8 
Columbus 
80.2 
78.o 
73 8 
66.7 
67.9 
69 1 66.9 
69.9 
7° 3 
71 8 
77 0 
7Q0 
72 6 July 
66 q 
Ian. 
82.0 
Cleveland 
77 6 
77 2 
75 1 
70.0 
71 1 
70 6 68 . 2 
70 5 
72 8 
72 4 
74.o 
75 0 
72 9 Ju'y 
68 2 
Jan. 
77 6 
Cincinnati 
76.6 
73 .<> 
70.0 
62.0 
64 4 
64 . 8 64 8 
66. S 
68.0 
68 q 
72 9 
75 4 
69 0 Apr. 
62.0 
Jan. 
76.6 
Detroit 
82 7 
80.6 
76,4 
69.6 
69 s 
69 . 6 66 . 9 
69 S 
73 4 
74.8 
78.8 
81.3 
74 4 July 
66 g 
Jan. 
82.7 
Pittsburg 
78.9 
77-2 
75 0 
68 4 
69.2 
69.7,67.8 
69 0 
71 1 
69.I 
74.8 
75 9 
72 2 July 
67.8 
Jan. 
78 9 
Indianapolis . . 
77-9 
76.2 
70.9 
64.4 
66.0 
66 5 62.8 
a 5 i 
67 0 
67-7 
71 8 
75 0 
69 2 July 
62.8 
Jan. 
77-9 
Erie 
80 9 
82.4 
79-5 
77.1 
74 4 
73 - o 6 9 3 
71 1 
73-3 
73 1 
76 6 
78 9 
75 5 July 
69 3 
Feb. 
82 4 
Now, with regard to the application of some of the foregoing 
conclusions to ecological work, it must be remembered that defi- 
ciencies of one factor may often be counterbalanced by a surplus of 
another factor. It is thus necessary to consider the factors col- 
lectively as well as individually. In the ecology of Ohio it is 
