THE AMERICAN ENTOMOLOGIST. 



241 



nois, — the year in which Dr. Shimer ob- 

 served them dying of some disease. Each 

 of these three years follows a preceding dry 

 period of two or three years. 



Fourthly. — According to this representa- 

 tion, 1878 should be below the average ; 

 1879 above it; 1880 and i88i dry; and 

 the chinch bugs probably appear in 1881. 



I have not yet received the records of 

 1878-9, but expect to examine them before 

 the report is published. That those who 

 have the records and desire to make the 

 comparison may do so, I here state that 

 for the average from 1873 to 1877 I use 

 the Signal Service records for Chicago, 

 Dubuque, Davenport and St. Louis, count- 

 ing the year from January to December. 



As I do not wish to take up too much 

 of your space, the last point I call attention 

 to is the fact that this exhibit shows a de- 

 crease in the amount of rainfall. 



If we divide the series into sections, and 

 take the mean or average of these divis- 

 ions, the fact of a decrease becomes ap- 

 parent. 



Dividing into two sections the average 

 is as follows : 



1840 to 1858 39.58 inches. 



1859101877 36.86 



Dividing into three sections : 



1840 to 1851 

 1852 to 1864 

 1865 to 1877 



40.97 

 36.79 

 37.10 



inches. 



Dividing into sections of seven years : 



1842 to 1848 

 1849 to 1855 

 1856 to 1862 

 1863 to 1869 

 1870 to 1876 



41.37 inches. 

 39.12 

 36.04 

 37.26 



35-82 



Dr. Draper's examination of the rain- 

 fall in New York City, or any point on the 

 sea-coast or larger lakes, cannot form a 

 fair test in reference to the increase or de- 

 crease of rain precipitation. The only rec- 

 ords by which this question can be prop- 

 erly tested are those of the interior of the 

 country. 



In the accompanying diagram the rain- 

 fall is given in absolute amounts and in- 

 dicated by a heavy line ; the temperature 

 is given in variations from the mean (50°. 



[Fig. 120.1 



1S40 



— 4i 



-46 

 -i6. 



-SO 

 -SI 

 -32 

 -S3 

 -54 

 -SS 

 -56 

 -57 

 -68 



-62 

 -63 

 -64 

 -66 

 -66 

 -67 

 -68 

 -&) 

 -70 

 -71 

 -72 

 -73 

 -74 



-76 

 -76 

 J877 



