101 
these elements for the years 1859-64 at Oxford, and their 
ratios, are as follows : — 
Maximum 
in Sun less 
Maximum 
in Shade. 
Temperature 
of Air less 
Temperature 
of Evaporation. 
i 
Ratio. 
1859 
12-85 
2-67 
4-81 
1860 
10-78 
1-98 
5-44 
1861 
11-24 
2-49 
4-51 
1862 
9-37 
2-72 
3-44 
1863 
9-78 
2-87 
3-40 
1864 
9-81 
2-73 
3-59 
A projection of the ratios gives a curve closely resembling 
the curve No I, diagram B (p. 39), and therefore strongly 
supporting the view that the calorific intensity of the sun’s 
rays varies in a period corresponding with the solar spot 
period. 
If instead of the difference between the mean tempertures 
of the air and of evaporation we employ the difference be- 
tween the mean temperatures of the air and of the dew point 
we obtain the following ratios. 
1859 
2-33 
1860 
2-57 
1861 
2-17 
1862 ! 
1-66 
1863 : 
1-65 
1864 1 
1-72 
It will be seen that the curve representing these ratios is 
identical in form with that representing the last series of 
ratios, as indeed might have been expected. 
Proceeding now to apply the same method to the treat- 
