Chemical and Physical Notes 



77 



therefore y l = f , and in each interval of ten seconds the loss 

 of heat is | of the amount which was present at the beginning 

 of it. Therefore, if in each succeeding interval of ten seconds 

 the same amount of heat were lost, the whole of the excess of 

 heat would disappear in seven such intervals, or in seventy 

 seconds. Therefore, the arithmetical result which we arrive 

 at from observations made at intervals of ten seconds is that 

 the term of cooling of the thermometer is seventy seconds. 



But if 0*0669 is the logarithmic difference for ten seconds, 

 then 0-00669 is the logarithmic difference for one second, 

 0x300669 for one-tenth of a second, 0-0000669 for one-hundredth 

 of a second, and so on. The resulting terms of cooling 

 derived from these different intervals and logarithmic diffe- 

 rences, and the method of arriving at them, will be apparent 

 from the following table : 



TABLE X. 



The rule 1 for finding the term of cooling referred to the 

 shortest possible intervals of time, and the smallest logarithmic 

 differences, from observed values of dd and dl is : Divide the 

 modulus of the system of logarithms, 0-434295, by the logarithmic 

 difference dl, and multiply the quotient by the interval of time 

 dQ. The product is the term of cooling expressed in the same 



1 Experimental Inquiry into the Nature of Heat, by John Leslie. 

 1804. Page 265. 



Edinburgh, 



