254 Professors W. E. Ayrton and J. Perry on 



from the experiments. For example, the curve AAA lies 



between the following exisothermals: — 



. o o 



when £=1200, between the exisothermals for 19*3 and 18*69 



„ 1500 „ „ „ 18-69 „ 18*08 



„ 2100 „ „ „ 17-76 „ 17-15 



•? 



V 



5? 



J* 



J* 



*? 



7? 



V 



2400 „ „ „ 16-94 „ 16-60 



» 2700 „ „ „ ]6-6 „ 16-4. 



If this is true, then the ordinates of the curve AAA are 

 greater than the ordinates of the exisothermal for 16°"4 C. by 

 distances which are approximately slightly less than 



(23*97\ 

 1 — R/xqq ) or 1*53 (say therefore equal to 1*50 for t = 1200), 



and slightly less than 



0-2^-1^^) or 0-184 (say therefore equal to0-18for £ = 2700). 



Consequently, as in an exisothermal curve, 



kg? 



m— -j- rvi > 



it follows that in our experiment m is very nearly equal to 

 40-37-16-4-1-50 



log 



to 20-75-16-4-0-18 ft#nmio 

 — or 0*00112, 



and 



1500 log e 



N = 417e 2 ' 00 '* 



= 85-79 



N 



£-= 0-808; 



from which in the usual way it may be found that 

 a =130°'47, 

 K= 0-00590, 

 E = 0-00252. 



We see, therefore, that by these four methods of treating 

 the curves A^A, aaa (fig. 2), which have been rendered 

 necessary by the want of constancy of the external tempera- 

 ture, we have obtained the following results for K and E : — 





