H5 
and the Mode of its Communication. 
produced by currents of cold air occasioned in the room by the 
presence of the cold body, I now repeated the experiment with 
the following variations. 
The thermoscope was laid down on one side, so that the two 
ends of its tube, to which its balls were attached, ihfetead of being 
vertical, were now in a horizontal position ; and the cold body, 
instead of being presented to the ball of the instrument on one 
side of it, and on the same horizontal level with it, was now 
placed directly under it, and at the distance of 6 inches. 
This cold body, instead of being a metallic substance, was a 
solid cake of ice, circular, flat, and about 3 inches thick, and 
8 inches in diameter. It was placed in a shallow earthen dish, 
about g inches in diameter below, 12 inches in diameter above, 
at its brim, and 4 inches deep. The cake of ice being laid down 
on the bottom of the dish, the top of the dish was covered by a 
circular piece of thick paper, 14 inches in diameter, which had a 
circular hole in its centre, just 6 inches in diameter. 
This earthen dish, containing the ice, and thus covered, was 
placed perpendicularly under one of the balls of the thermo- 
scope, at such a distance that the centre of the upper surface of 
the flat cake of ice was 6 inches below the ball. 
The result of this experiment was just what might have been 
expected : the ice was no sooner placed under the ball of the 
instrument, than the bubble of spirit of wine began to move 
towards that side where the cold body was placed; and it did not 
remain stationary, till after it had advanced more than an inch 
in the tube. 
Exper . No. 1 g. Desirous of discovering whether the surface 
of a liquid emits frigorific or calorific rays, as solid toiies have 
been found to do, I now removed the cake of ice from the 
