BULLETIN 
No. III. 
ARTICLE I. 
CONVERSION OF LIGHT INTO HEAT. 
By LeB. Botsford, M. D. 
' ( Read 27th January , 1884). 
T HERE are but few physical facts more definitely settled and 
accepted, than that of the conversion of -motion into heat. 
So thoroughly is this understood, that, given the volume of matter, 
and the Velocity of movement, the amount of heat evolved from 
a sudden stopping of the moving mass can be very accurately 
ascertained. 
The great cold which exists in the upper air sufficiently shows 
that the rays from the sun do not produce any sensible rise in the 
temperature of the atmosphere, and that it is chiefly when the 
rays of light approach the surface of the earth that heat becomes 
developed, first in the objects against which the light strikes, then 
indirectly in the air by contact with those substances which have 
been heated by the sun’s rays. Air also may be artificially heated. 
No doubt can enter the mind but that heat is developed by the 
action of the direct rays, and man and beast alike seek shelter 
from its effects in the cooler shades. 
Light, we all know, is the result of vibrations in a medium in- 
finitesimal in its tenuity, and passes along with great velocity. If 
these vibrations should be stopped by any material substance, 
then they must either cease to exist altogether, or manifest some 
condition of force which could be stated as their equivalent. 
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