217 
the mean monthly differences between the maximum tem- 
perature in the shade and that in the sun 
years 1859 to 1864. They are as follows : — 
during the six 
January 
5-51° 
July 
13-81° 
February 
9*16° 
August 
.......14-03° 
March ... 
.10*08° 
September 
......13-71° 
April . . . 
13-23° 
October . . 
9-66° 
May 
..12-90° 
November 
...... 8-00° 
June 
12-93° 
December.. 
4-50° 
Here are 
represented two 
maxima of 
solar radiation 
which occur in April and August, and two minima in May 
and December. Below I represent the mean monthly 
amounts of ozone for five years, from 1862 to 1867 : — 
January 
... 1-15° 
July 
1-29° 
February 
... 1-44° 
August 
1-34° 
March 
... 1-85° 
September 
1-01° 
April 
... 2-51° 
October 
. 0-80° 
May 
... 2-00° 
November ...... 
. 0-88° 
June 
... 1-48° 
December 
. 1-25° 
From the foregoing table two 
maxima will be 
seen iden- 
tical with those of Solar Radiation, viz. one in 
April and 
another in August. The minima are not satisfactory. There 
are reasons for this. The first four years’ observations were 
made near the village where the amounts, for the reasons 
already given, were small and fitful ; and the test papers 
used were not so sensitive as those I have since used. The 
amounts I have obtained for the last year and a half are 
more than double the amounts I obtained at my previous 
station. I am much farther from the village, several feet 
higher, and use very sensitive test papers. I anticipate 
that future observations at my present station will far more 
fully concur with the Solar Radiation deductions above 
quoted. In proof of this, I give below the mean monthly 
amounts of ozone for 1867. 
