131 
eight years’ averages, the greatest difference between the 
amounts of rain which fell in the lower and higher gauges 
occurs in January, decreases gradually in difference till 
May, when it attains a minimum. This minimum main- 
tains itself till August, when there is a slight increase; then 
after a slight decrease in September, the increase becomes 
constant to J anuary again. On the theory first enunciated 
by Mr. Baxendell that the excess of rainfall in the lower 
gauge is due to the particles of invisible vapour in the air 
between it and the higher gauge coalescing with the falling 
rain-drops, the results seem to show that in the spring and 
early summer months there is relatively less of this vapour 
in the air below a height of 34ft., and there is relatively 
more of it in the winter months and particularly in J anuary. 
Monthly and annual ratios of the excess of rainfall 
measured at 3ft. from the ground over the amount measured 
at 34ft. from the ground ; together with the amount of the 
mean humidity of the atmosphere, full saturation being 
represented by unity. 
Ratios of such 
rainfall for 1875. 
Ratios of such rain- 
fall for an average 
of 8 years, from 
1868 to 1875. 
Mean humidity of 
the atmosphere 
for 8 years, from 
1868 to 1875. 
January 
”643 
•705 
•871 
February 
”709 
•753 
•855 
March 
*835 
•784 
•836 
April 
•697 
•845 
•765 
May 
•871 
•901 
•755 
June 
•840 
•879 
•747 
July 
•930 
•896 
•759 
August 
•934 
•851 
•793 
September 
•894 
•856 
•777 
October 
‘929 
•836 
•840 
November 
•841 
•785 
•853 
December 
•720 
•800 
•872 
Annual Ratios 
•820 
•824 
•810 
That I might demonstrate as far as possible that this is 
the true way to account for the difference of rainfall at the 
two heights above the ground, I took out the representatives 
I had for the last 8 years of the relative amount of moisture 
in the atmosphere. These results were obtained from a 
