99 
and the Mode of its Communication. 
lieat which passes off through a given surface must be as the 
times elapsed, all other circumstances being the same, we can 
determine how much of the heat given off by the instrument, 
in those experiments in which its ends were covered, passed 
through the sides of the instrument ; and, consequently, how 
much of it must have made its way through its ends and neck, 
notwithstanding their being covered. 
The instrument with its ends and neck covered up with eider- 
down, furs, &c. was found to cool through the standard interval 
of 10 degrees in ,55^ minutes. Now, as only 5885 parts of heat 
were found to pass through the naked vertical sides of the in- 
strument in 4,5^ minutes, no more than 7015 parts could have 
passed through the same surface in 55-I minutes ; consequently, 
the remainder of the heat lost by the instrument, in the experi- 
ment in question, amounting to 2985 parts, must necessarily 
have made its way through the covered ends and neck of the 
instrument, in the given period, minutes. 
Taking it for granted that these computations are well founded, 
we may now proceed to a more exact determination of the re- 
lative quantities of heat which made their way through the sides 
of the instrument No. 2, when its sides were exposed naked to 
the air, and when they were covered with the different substances 
which appeared to facilitate the escape of the heat. 
In the experiment No. 11, when the sides of the instrument 
were made quite black, by holding it over the flame of a wax 
candle, the instrument cooled through the standard interval of 
10 degrees in 36 1 minutes. 
In that time, a quantity of heat = 1942 parts, must have 
passed off through the covered ends and neck of the instrument; 
for, if a quantity = 2985 parts could pass off that way in 55! 
O 2 
