April, 1903.] Some Climatic Conditions of Ohi'\ 



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 

 southwesterl}', 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 iudirectl}- by the same cause, would 

 follow the same direction. 



In July, which we ma}' take as being about the middle of the 

 growing season, Ohio again presents some interesting problems 

 in connection wath 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 prett}- 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 : 



MONTHI^Y AND ANNUAL MKAN RELATIVE HUMIDITY. 



Stations. 



Toledo 



Sandusky . . 

 Columbus . . . 

 Cleveland 

 Cincinnati .. 



Detroit 



Pittsburg. . . . 

 Indianapolis 

 Erie 



Average Per Cent, in Each Month. 



77 



73 



80 



77.2 



76.2 



82.4 



< 



"5 -5 '69. 

 70.4169 



73.866, 



75 I 

 70.0 

 76.4 

 75-0 

 70.9 

 79-5 



I 69. 

 69 



(S7.9 

 71. 1 

 64.4 

 69.5 

 69.2 

 66.0 

 74-4 



69.967 

 70.967 



69 I 66. 



70 6 68 . 

 64 . 8 64 

 69.666. 

 69.7 67. 

 66.562. 

 73- 0,69 



be 

 <! 



1 70 



769 

 969 



2 70 

 8,66 

 9169 

 869 

 8165 

 371 



a 



72.2 



70.4 

 70 3 

 72 8 

 68.068 

 73-474 



o 71 .4 



67 o 



73-3 



,6,79 9 

 8,76 6 

 o|79.o 

 .0750 

 9'75 4 

 ,8j8i.3 



■8 75 9 

 5I75 o 

 6,78 9 



Least 

 g ) Monthly 

 li ' Per Cent. 



73- 

 74 

 72 

 72 

 69 

 74 

 72 

 69 

 75-5i 



July 

 July 

 July 

 July 

 Apr 



67.1 

 67.7 

 66.9 

 68 2 

 62.0 



Greatest 

 Monthly 

 Per Cent. 



July 166 9 

 Julv 167.8 

 July 162.8 

 July 69.3 



Jan. 

 Jan. 

 Jan. 

 Jan. 

 Jan. 

 Jan. 

 Jan. 

 Jan. 

 Feb. 



a 

 < 



82.4 

 79.8 



82. 



77.6 

 76.6 

 82.7 

 78.9 



77-9 

 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 maj' often be counterbalanced b}- 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 



