51 
development, and we find, by examining the history, that they did 
make their appearance in the spring of 1862, in considerable num¬ 
bers, but were cut off by the rains. 
An examination of the line of temperature shows no such 
periodicity as that found in the rainfall curve; it is therefore im¬ 
possible to predict, with any degree of certainty, whether a given 
future year will or will not be marked by the appearance of Chinch- 
bugs in injurious numbers over the designated area. Judging from 
the periodicity shown by the rainfall curve, as before stated, 1880 
and 1881 should be dry years, and if the temperature of the latter 
is above the average, we may, according to what has been already 
shown, expect these insects. A wet Spring may destroy them; 
otherwise we may expect them in injurious numbers. It is not our 
aim, in presenting these facts and conclusions, to bring forward any 
claims as a weather prophet, as our only object at present is to call 
attention to them, that they may be compared with future observa¬ 
tions, in order to see whether this apparent periodicity is only acci¬ 
dental, or a meteorological law applicable to the area alluded to. 
As the amount of rainfall has a very important bearing on the 
agricultural interests of our State, it will not be amiss for me to 
call attention to some other facts brought out by means of these 
and other similar curves. 
As will be observed, the series commences with 1840 and ends 
with 1877, making 68 years. The general average annual rainfall 
for this entire series, as before stated, is 38.80 inches. In order to 
ascertain whether there has been an increase or decrease, we may 
divide the series into sections of different lengths, and, taking the 
average of these, compare them with one another. ^ 
Dividing the series into two sections, we find the average annual 
rainfall of these to be as follows: 
1st. Sec.—1840 to 1858. 39.58 inches. 
2d Sec.—1859 to 1877. 36.86 
Dividing into three sections, the averages will be as follows: 
1st Sec.—1840 to 1851. 40.97 inches. 
2d Sec.—1852 to 1864. 36.79 
3d Sec.—1865 to 1877. 37.10 
Dividing into sections of seven years each, so as to correspond 
with the septenary periods, the several averages will be as follows: 
1st. Sec.—1842 to 1848. 41.37 inches. 
2d Sec.-1849 to 1855. 39.12 
3d Sec.—1856 to 1862. 36.04 
4th Sec.—1863 to 1869 . 37.26 
5th Sec.—1870 to 1877 . 35.82 
A single glance at these figures is sufficient to show that the 
rainfall in the latter part of the series is less than that of the ear¬ 
lier portion; in other words, that the rainfall has been decreas¬ 
ing. 
When divided into two sections, the average rainfall of the latter 
half of the series is 2.72 inches less than that of the first half. 
When divided into three sections, the average of the last section'is 
