196 J. R. Mayer on Celestial Dynamics. 
the sun—in fact, in all places where his rays do not reach the 
surface, the temperature of the earth would soon be as low as 
that of the universe, if the atmosphere were removed, or if it did 
not exist. Hven the powerful solar rays in the tropics would be 
unable to preserve water in its liquid state. 
Between the great cold which would reign at all times and in 
all places, and the moderate warmth which in reality exists on 
our globe, intermediate temperatures may be imagined; and it 
is easily seen that the mean temperature would decrease if the 
atmosphere were to become more and more rare. Such a rare 
faction of a valve-like acting atmosphere actually takes place as 
we ascend higher and higher above the level of the sea, and it 
is accordingly and necessarily accompanied by a corresponding 
diminution of temperature. 
perature of low altitudes is nevertheless higher than it 8 ™ 
more elevated positions, is explained by the fact that the atmo 
sphere stops to a far greater egree the calorific rays emanating 
from the earth than it does those from the sun. 
VI. The Constancy of the Sun’s Mass. 
Newton, as is well known, considered light to be the emission 
of luminous particles from the sun. the continued emissit 
of light this great philosopher saw a cause tending to ey 
the solar mass; and he assumed, in order to make good this (0% 
comets and other cosmical masses to be continually falling into 
tral body. ids 
