308 
Proceedings of Eoyal Society of Edinburgh . [sess. 
Table showing the time in hours reckoned from culmination at which 
for given values of the sun’s declination , as shoim in the top 
row , the radiation crossing unit horizontal surface in lat. 56° 
N. lias value as shown in the first column. 
B. 
+ 23° 27' 
+ 20° 
+ 12° 
0° 
-12° 
-20° 
-23° 27' 
Sun’s 
declination. 
0-552 
0 
•516 
0 
•512 
1*57 
0-81 
•433 
0 
•421 
2*92 
2*43 
•331 
3-89 
3-48 
2-49 
0 
hours 
•296 
4-7 
V measured 
from cul- 
•245 
4*34 
3-51 
1-77 
0 
•145 
mination. 
*0914 
2-03 
•06 
6-6 
6*2 
5-41 
4*22 
2-63 
•0554 
0 
•051 
0 
•0073 
7-54 
7*11 
6-27 
5*13 
3*83 
2-61 
2-54: 
0 
8*66 
8*11 
7*18 
6 
478 
3-82 
3*79 
J 
From the graphical representations of these seven sets of numbers 
we can estimate the areas and so evaluate the integral Judk 
through half a day. With the minute as the unit of time in- 
volved, we find the following numbers expressing the relative 
radiations during half a day for the different declinations of the 
sun, the unit being the amount that would cross unit area per- 
pendicularly were there no absorption in the atmosphere. 
Declination. 
Half-daily heat- 
ing (relative). 
Daily heating 
(absolute). 
+ 23° 27' 
141-2 
847-2 
+ 20 
125-4 
752-4 
+ 12 
95*5 
573 
0 
51-8 
310-8 
-12 
20-7 
124-2 
-20 
5-48 
32-9 
-23 27 
5-06 
30-4 
Multiplying the numbers in the second column by twice the 
