112 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
As this table was intended only to illust i ate the rhapter on chronology, 
it does not indicate the years of invasion of the temporary region. \V< 
therefore call attention to the fact that the years of great locust invasions 
of these regions, to which we shall chiefly limit the present discussion, 
were 187G, 1874, and 1SGG. The year 18G4 was also marked by the ap- 
pearance of numerous invading swarms in the northwest, but the locust 
distribution was nothing like so general over the west as in 18GG. Accord- 
ing to Mr. Alexander Taylor, 1855 was also a noted locust year, especially 
in the intcrmontane area, on the Pacific slope, and in Mexico ; but he 
speaks also of them as abundant in that and the following year in 
Nebraska, Kansas, and Minnesota Territories. As the 'meteorological 
records that reach back as far as 1855 are too meager to be of any real 
value, we shall of necessity confine our investigations to the period 
embracing 18G4, 18GG, 1874, and 1876. 
The following table of rainfall for the years 18G0-186G, at the stations 
named is taken chiefly from Schott's Table of Eatios. 205 The figures, 
except in the bottom line, are the ratios of the rainfall in the different 
years mentioned, to the mean annual rainfall of the station named at 
the head of the column. The bottom line shows the mean rainfall in 
inches at the different stations. A few omissions in Schott's table have 
been filled out from the record in the Reports of the Agricultural Depart- 
ment: 
Table I. — Eatios of rainfall for the years 1860-1666. 
Year. 
1860 
1861 
1862 
1863 
1864 
1865 
1866 
Annual mean in inches. 
P3 
1.22 
L 29 
.57 
.69 
.48 
1. 00 
1.X0 
23.11 
.66 
.90 
L 17 
.73 
.56 
1.36 
L 00' 
.77 
.74 
.89 
.72 
.74 
1. 06 
L 00 
25. 69 41. 96 
.80 
1.15 
1.05 
1.01 
.75 
L 08 
1. 08 
L 00 
L 24 
.80 
.71 
.90 
L 04 
.88 
.79 
1.11 
32.24 42.88 42. IS 
.61 
.86 
.93 
.96 
.51 
L 61 
L52 
31.74 
1.34 
.86 
1.16 
.61 
.94 
1.15 
28. 62 
L 08 
1.35 
1.16 
a -~ 
C5.3 
.07 
.77 
.87 
L00 
.85t 
.93t 
L 03t 
3 
a 
? 
•a 
.68 
.92 
1.13 
.81 
.87 
L 33 
1. 36 
17.34 25.55 30.48 
.78 
1.02 
.95 
.87 
.73 
L 02 
L13 
3L 25 
* Ratio of the nearest stations for the year. Those of 1866, Fort Ripley and Fort Ridgley are the 
average 'within less than . 01 of those stations in Minnesota 'west of the Mississippi, 
t Ratios of the Bellevue records. 
A careful study of this table brings out several interesting facts, of 
which we may mention the following as most important. The mean 
ratio of 1864 is the smallest of the series, and as all the ratios for that 
year fall below the average of the several stations, it, so far as dryness 
is concerned, was favorable to the increase and migrations of the locusts ; 
and, as heretofore stated, they did appear in portions of the Northwest, 
206 Tables and Results of the Precipitations of Rain and Snow in the United States, 147-152. 
