a 3 6 Count Rumford’s Enquiry concerning the Nature of Heat , 
the flat part of its bottom : this flat part was about 8 inches in 
diameter. 
The two conical vessels were now filled with boiling hot water, 
and the times of their cooling were carefully observed. 
From the above description of the apparatus used in this 
experiment, it is evident, that the vessel which was suspended 
over the ice, could not be reached by any streams of cold air that 
might be occasioned by that ice, or by the cooled sides of the 
vessel which contained it ; for the air which, coming into contact 
with the sides of that vessel, was cooled by it, becoming speci- 
fically heavier than it was before, naturally descended, and 
spread itself out on the floor of the room ; and the perforated 
circular sheet of paper, which was laid down horizontally on 
the platter, effectually prevented any of the air so cooled from 
being thrown upwards against the bottom of the conical vessel, 
(placed immediately over the platter,) by any occasional undu- 
lation of the air in the room. 
To preserve the air of the room in a state of perfect quietness, 
not only the doors and windows, but even the window -shutters 
of the room, were kept shut ; so much light only being admitted 
occasionally, as was necessary to observe the thermometers 
which were placed in the conical vessels. 
In order to guard still more effectually the bottoms of the 
vessels wjiich were cooling, from the effects of occasional undu- 
lations in the air of the room, over each of these vessels there 
was drawn a cylindrical covering of very fine thin post paper ; 
the lower open end of which projected just half an inch below the 
horizontal level of the flat bottom of the vessel. These cylin- 
drical coverings of post paper were made to fit, as exactly as 
