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HUTTONIAN THEORY. 



187 



It is true, that it is not by the folar rays that 

 fubterraneous heat is produced ; but ftill, from 

 this inftance, we fee, that there is no incongrui- 

 ty in fuppofmg the produdlion of heat to be in- 

 dependent of combuftible bodies, and of vital air. 

 We are indeed, in all cafes, flrangers to the ori- 

 gin of heat : philofophers difpute, at this mo- 

 jiient, concerning the fource of that which is 

 produced by burning ; and much more are they 



at a lofs to determine, What upholds the light 

 and heat of" the great luminary, which animates 

 all nature by its influence. If we would form 

 any opinion on this fubjed, we fliall do well 

 to attend to the fuggeftions of that great philo- 

 fopher, who was hardly lefs dillinguiflied from 

 others by his doubts and conjediures, than by 

 his molt rigorous and profound inveftigations. 

 *' May not great, denfe, and fixed bodies, when 

 heated beyond a certain degree, emit light fo 

 copioufly, as, by the emiffion and reaction of 



and the refledtions and refradiions of 

 its rays within its pores, to grow ftill hotter, till 

 it comes to a certain period of heat, fuch as is 

 that of the fun ? And, are not the fun and fix- 

 ed ftars great earths, vehemently hot, whofe heat 

 is conferved by the greatnefs of the bodies, and 

 the mutual action and re-adion between them 

 and the light which they emit * ?" 



167, Some 



Its 



light, 



* NewtOH's Optics, ubifu^rd 



