88 Count Rumford’s Enquiry concerning the Nature of Heat, 
If, for instance, in the experiment of the 11th March, (the 
details of which have just been given,) the time when the instru- 
ment No. 2, in cooling, passed the important point of 94 0 , had 
not been observed, this neglect might have been supplied, by 
computation, in the following manner. 
It is CD = 94^°, the nearest observed temperature higher than 
EF (=±= 94 0 ) and GH = 90^-°, the nearest observed temperature 
below that of 94 0 ; and CG = 15 minutes, or 900 seconds, = the 
time elapsed between the two observations. 
It is log. 94f = 1.976579 2 
And log. 90^ = 1.9554472 
Log. CD — log. GH = 0.0211320 
And 0.0211320 is to 900 (=CG) as 1 to 42590 = m. 
And again, log. 94^= 1.9765792 
Log. 94 = 1 -9731279 
Log. CD — log. EF = 0.0034513 
42590 x 0.0034513 (— m x log. CD — log. EF) =-= 147 se- 
conds, = 2 minutes and 27 seconds ; which differs very little 
from 2-§- minutes, the observed time. 
If, from the temperature observed at 1 i h 30 min. = 86^°, and 
the temperature observed at n h 45 min. = 82^°, and the time 
which elapsed between these two observations, (=15 minutes) 
we were to determine, by computation, the time when the instru- 
ment was at the temperature of 84°, (the lower point of the 
standard interval of 10 degrees answering to the temperature of 
with which a hot body cools in a fluid medium, is every where such, that were that 
velocity to be continued uniformly, the body would be cooled down to the temperature 
of the medium, in the same time, whatever might be the excess of the temperature of 
the hot body above that of the medium, at the moment when its velocity of cooling 
became uniform. 
