On Sun-heat and Radiation. 99 
These nine equations furnish 36 combinations for finding & and 
R, and of these, 33 give consistent results; but three combina- 
tions, viz. :— 
(0°—10°), (0° 20°), and (10°—20°), 
give results inconsistent with the others, in consequence of the 
cause already stated. The mean values of k and R deduced from 
the remaining 33 combinations are— 
k=0°7285. 
R= 34-385 feet of ice. 
If we throw out altogether the latitudes 0° and 10°, and calculate 
from the remaining 21 combinations (from 20° to 80°), we find— 
R= 35-475 feet of ice. 
The agreement between the results calculated from all latitudes, 
and those found by omitting the low latitudes, is not quite so close 
in the Northern as in the Southern Hemisphere; but our formula 
is fully justified, and we are entitled to conclude that the annual 
heat lost by radiation in the Northern Hemisphere may be 35 feet 
of ice melted. 
It follows, that the mean annual radiation of heat from the 
whole earth is equivalent to melt a coating of ice 28°5 feet in 
thickness; but as the sun-heat received is equivalent to 80 feet 
of ice, we have 51°5 feet of ice representing heat not accounted 
for as heat, for the mean temperature of the earth’s surface is not 
increased. 
This balance of heat is expended in two ways :— 
1. It is converted into the Geological work done by rainfall 
and rivers. 
2. It is converted into Chemical and Vital work done by the 
vegetable and animal organisms that clothe the surface 
of the earth. 
The Geological work done by rainfall and rivers can be shown 
to absorb a very small portion of the surplus sun-heat. 
The Mechanical work done in crushing to fine powder a cubic 
foot of rock can be estimated from the following data, taken from 
Scien. Proc. R.D.S., Vou. uu. Pr. 1. H2 
