Conversion of Light into Heat. 
5 
The conclusion to be drawn from these experiments would 
appear to be that the absorption or cessation of the light vibra- 
tions was the cause of the increased temperature, or in other words 
the vibrations of light-motion were changed in proportion as they 
were stopped into a correlated force, namely, heat. 
Another experiment was made to test the rate of cooling of 
different colored liquids. 
The three tubes, one of ink and two of water, were placed in 
a vessel of water heated to i io° F., and when heated up to that 
point were placed under equal conditions. After five minutes all 
three had cooled down uniformly, and at the end of a half hour all 
stood at 74 0 F. 
From this experiment it was evident that direct vibrations from 
the black fluid and from water did not differ, and that the cooling 
took place probably from the contact of the tubes and their con- 
tents with the surrounding air ; that the heat was abstracted chiefly 
by a medium acting equally upon the tubes ; that dark substances 
or fluids do not radiate more rapidly than colorless fluids, and 
that the heat does not pass off in the kind of vibrations which 
constitute light its correlated force, but follows the law of direct 
contact. 
