in SPHERICAL BODIES. 359 



long as the intenfity and magnitude of the central fire conti- 

 nue the fame. 



9. It remains for us to determine the value of a, which, 

 though conftant, is not yet given, or known from obferva- 

 tion. 



At the furface of the globe we may fuppofe the mean tem- 

 perature to be known : let T be that temperature, and let R — 

 the radius of the globe. Then, when xzR, h — T, and by 



fubftituting in the general formula, we have T — H-j (~ )» 



and a - = 3(T-H) = 3 Rr(H-T) > 

 I i R — r 



R~~"r 



Rr(H-T) /i 1 



Thus h — H 



\x r J 



R — r 



= H _RKH-T) /i_iY 

 K — r \r xj 



Hence alfo by reduction 



h - RT — ^ H , R r (H — T) 

 "~ R — r + ~T^T^rY> 



From this equation, it is evident, that h — r H r 



R — r * 



the excefs of the temperature at any diflance x from the 



centre, above a certain given temperature, is inverfely as x. 



But the conftrudion of the hyperbola which is the locus of the 



preceding 



