117 
the summer months, and particularly in June, there is rela- 
tively less of this vapour in the air below a height of 34 
feet, and that there is relatively more of it in the winter 
months, and particularly in January. Hence the maximum 
of dry air on the ground is in June, and the minimum in 
January, This can only be due to a very rapid convection 
of warm air with its attendant vapour from the surface of 
the ground upward. A consideration of this law in its 
action upon public health cannot be too much regarded. 
Monthly and Annual Katios of the Excess of Eainfall measheed 
AT 3 feet from the aEOHND OVER THE AMOUNT MEASURED AT 34 
FEET FROM THE UEOUND. 
Ratios of such 
rainfall for 
1873. 
Ratios of such 
rainfall for an 
average of 6 yeai’s 
from 1868 to 
1873. 
Ja^nuary 
•732 
•715 
February 
•642 
•749 
March 
•805 
•786 
April 
•889 
•859 
May 
•875 
•846 
June 
•914 
•894 
July 
•870 
•887 
August 
•808 
•850 
September 
•865 
•858 
October 
•821 
•829 
November 
•799 
•763 
December 
•736 
•838 
Annual ratios... 
•813 
•822 
In the next table I give the fall of rain during the day 
from 8 a.m. to 8 p.m., and the fall during the night from 
8 p.m. to 8 a.m. The amount of rain that fell during the 
day exceeded, as usual, the fall during the night, and this 
happened in every month of the year excepting January, 
February, and December. The total excess of the day over 
the night fall for last year was .2'846 inches. In 1871 the 
excess was 4T36 inches, and in 1872 it was 1*891 inches. 
