INFLUENCE OF THE RAINFALL ON THE LOCUST. 113 
especially in Nebraska, Iowa, Minnesota and Manitoba. This was also 
a year of visitation in Utah, Montana, parts of Dakota, Colorado, and 
the northern portion of New Mexico. Bnt in numbers and general dis- 
tribution in the region east of the mountains, it was far exceeded by the 
locust invasion of 18GG ; in fact it is not usually counted as one of the 
great locust years. 
Before passing to other points suggested by this table we desire to 
present other evidence showing the unusually favorable conditions of 
this year for the increase and spread of the locusts so far as dryness 
is concerned. 
First we call attention to the fact that there had been a gradual 
decrease in the rainfall the two preceding years, as will be seen by refer- 
ence to the column of means. In 18G2 the mean of all the stations was 
.95 ; in 1863 it was .87, falling in 1864 to .73. 
Does the character of 1864, as shown by these figures, correspond 
with that of the year throughout the West ? By reference to Schott's 
tables, we find these ratios given for that year in the following States and 
Territories. The names of the stations are not mentioned here, as our 
object is only to show the general character of the season in reference 
to humidity, as compared with the mean annual rainfall. Each ratio 
represents the rainfall of a station for 1864, in the same manner as given 
in the forecoiner tables : 
Texas, .81. 
Tennessee, .89. 
Kentucky, .93. 
Ohio, .96, 1.19, .74, .96. 
Michigan, .86. 
Indiana, .79, .87. 
Illinois, .79, .83. 
Wisconsin, .98. 
Minnesota, .48, .56, .75, .61. 
Iowa, .74, .86, .75. 
Missouri, .79, .87, .96, .94. 
Kansas, .51, .51, .66. 
New Mexico, .76, 1.25. 
California, .99, .81, .91, .86. 
Washington Ter., .81, .69. 
Oregon, .91, 78. 
Idaho, .82. 
Utah, 1.00, 1.20. 
Dakota, .87. 
Nebraska, .70. 
The general average of these ratios is .83, or 17 per cent, less than the 
usual rainfall throughout the entire West; and what is rather unusual, 
and indicative of the general prevalence of the dry season over the en- 
tire western portion of the United States, is that, with the exception of 
one station in Ohio, one in New Mexico, which is estimated, and the two 
in Utah, the records all show less than the average precipitation. So 
far, therefore, as the amount of moisture is concerned, this was evidently 
a favorable year for the locusts. 
Now let us turn to the record of temperature and see whether that 
was favorable or unfavorable. For this we have recourse to the re- 
ports of the Agricultural Department as the only data at hand adapted 
to our purpose. As our object is to compare the meteorology of 1864 
with that of 1866, we present, in the following table, in parallel columns, 
the record of monthly means of temperature of the two years in Minne- 
sota, Iowa, Nebraska, Kansas, and Missouri. 
8 L 
