34 Inquiry concerning the Nature of Heat, 



If, for instance, in the experiment of the nth March, 

 (the details of which have just been given) the time 

 when the instrument No. 2, in cooling, passed the 

 important point of 94 had not been observed, this 

 neglect might have been supplied, by computation, in 

 the following manner. 



It is CD = 94f> the nearest observed temperature 

 higher than EF ( 94), and GH = 90^, the nearest 

 observed temperature below that of 94 ; and CG = 15 

 minutes, or 900 seconds = the time elapsed between 

 the two observations. 



It is log. 94! = 1.9765792 

 And log. 9 o 1.9554472 



Log. CD log. GH = 0.021 1320 



And 0.0211320 is to 900 (= CG) as i 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 seconds = 2 minutes and 27 seconds; which dif- 

 fers very little from i\ minutes, the observed time. 



If, from the temperature observed at nh. 30 min. = 

 86{, and the temperature observed at nh. 45 min. = 

 and the time which elapsed between these two 



perature of the air in which it is placed, were its velocity of cooling at the point D to 

 be continued uniformly from that point; and, as the subtangent of the logarithmic 

 curve is constant, if PQ were the logarithmic curve, it would follow that the velocity 

 with which a hot body cools in a fluid medium is everywhere 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. 



