the Weight ascribed to Heat. 189 
with as little variation as possible, and the contents of the bottles 
A and B appearing, by their inclosed thermometers, to be 
exactly at the same temperature, the bottles were all wiped with 
a very clean dry cambric handkerchief; and, being afterwards 
suffered to remain exposed to the free air of the room a couple 
of hours longer, in order that any inequalities in the quantities 
of heat, — or of the moisture attached to their surfaces, — which 
might have been occasioned by the wiping, might be corrected 
by the operation of the atmosphere by which they were sur- 
rounded, they were all weighed, and were brought into the 
most exact equilibrium with each other, by means of small 
pieces of very fine silver wire, attached to the necks of those 
of the bottles which were the lightest. 
This being done, the bottles were all removed into a room in 
which the air was at 30°, where they were suffered to remain, 
perfectly at rest and undisturbed, forty-eight hours; the bottles 
A and B being suspended to the arms of the balance, and the 
bottle C suspended, at an equal height, to the arm of a stand 
constructed for that purpose, and placed as near the balance as 
possible, and a very sensible thermometer suspended by the 
side of it. 
At the end of forty-eight hours, — during which time the 
apparatus was left in this situation, — I entered the room, open- 
ing the door very gently, for fear of disturbing the balance ; 
when I had the pleasure to find the three thermometers, — viz. 
that in the bottle A, (which was now inclosed in a solid cake 
of ice,) — that in the bottle B, — and that suspended in the open 
air of the room, all standing at the same point, 29 0 F, and the 
bottles A and B remaining in the most perfect equilibrium. 
To assure myself that the play of the balance was free, I 
MDCCXCIX. C C 
