41 
open to objection, I selected, in the first instance, the highest 
value in each month of the six years, and taking the means 
obtained the following numbers, a projection of which is 
shown in curve No. 1 of diagram C. 
o o 
January 
164 
July 
.... 211 
February 
20*5 
August 
.... 20-3 
March 
193 
September 
21-8 
April 
22*6 
October 
19*6 
May 
20*9 
November ..... 
17-2 
June 
20T 
December 
15*3 
This curve exhibits two principal maxima in April and 
September, and a low minimum in December. 
Taking next the means derived 
from the three highest values in 
each month, and then those of the 
five highest, we have curves No. 2 
and No. 3. The slight irregularities 
in the first curve have now dis- 
appeared, and curve 3 has two well 
defined maxima in April and Sep- 
tember, a principal minimum in 
December, and secondary minimum 
in June. 
Proceeding now a step farther and taking the ten highest 
values in each month, we have curve No. 4. The first 
maximum still occurs in April, but a slight change has 
taken place in the time of the second, which now occurs in 
the latter part of August instead of the middle of Septem- 
ber; but no change has taken place in the times of the 
two minima. 
Finally, taking the ten lowest values in each month we 
have curve No. 5. Here the first maximum has almost 
disappeared, though still occurring in April, and the second 
