ioo Count Rumford’s Enquiry concerning the Nature of Heat , 
minutes, the quantity above-mentioned (= 194,2 parts) must 
have escaped in 3 frj- minutes. 
This quantity, = 194,2 parts, taken from the whole quantity, 
= 10000 parts, lost by the instrument in cooling through the 
interval in question, leaves 8058 parts, for the quantity which 
made its escape through the sides of the instrument, in the expe- 
riment in question. 
Now, if a quantity of heat = 7015 parts, requires 55^ minutes 
to make its way through the naked sides of the instrument, (as 
we have just seen,) it would require 63^ minutes, for the quantity 
in question, = 8058 parts, to pass off through the same surface. 
But, when that surface was blackened over the flame of a 
candle, that quantity of heat passed off through it in 3 6f minutes. 
Hence it appears, that the velocity with which heat is given 
off from the naked surface of a heated metal exposed to cool in 
the air, is to the velocity with which it is given off by the same 
metal when its surface is blackened in the manner above de- 
scribed, as 36-i to or as 565 4, to 10000, very nearly; for 
the velocities are as the times of cooling, inversely. 
Again, in the experiment No. 6 , the sides of the instrument 
No. 2 being covered with four coatings of spirit varnish, the 
instrument was found to cool through the given interval of 10 
degrees in 30^ minutes. 
In that time, a quantity of heat 1627 parts, must have 
made its way through the covered ends of the instrument ; and 
the remainder, = 8373 parts, must have made its way through 
its varnished sides. 
This quantity, = 8373 parts, would have required 66 ± minutes, 
to have made its way through the naked sides of the instrument ; 
and, as it actually made its way through the varnished sides of 
