[ M4 ] 



In the prefent age this enquiry has been revived, and purfued 

 with all the fruitlefs enthufiafm of antiquity, affording the 

 cleareft proof that the fpeculative reafonings of mankind for 

 three thoufand years, are unequal to the tafk of deciding a 

 queftion which attentive experiments would probably have 

 refolved in a much fhorter period of time. 



The Count dc BufFon has indeed ventured to affert that the 

 temperature of the earth has been for many ages a decreafing 

 quantity ; but a flight view of the fteps by which that gentle- 

 man conduded himfelf to this hafty opinion will eafily fatisfy 

 one that neither his experiments, nor his reafonings, are 

 adequate to the conclufions which he has deduced from them j 

 fince it is obvious that any proofs derived from the cooling 

 of heated bodies on the earth's furface, in a medium of known 

 denfity, and a determinate capacity for receiving heat, become 

 extremely deceitful when applied to the diminution of tempera- 

 ture which may take place in a body fituated, as the earth is, 

 either in vacuo, or in a medium whofe denfity and capacity for 

 heat is altogether indefinite. 



From oblervations on the warmth of the earth itfelf, on 

 the heat of various fprings of water, and on the eruptions of 

 volcanoes, many philofophers have been led to conclude the 

 exiftence of a central fire, by which thcfe phaenomena might 

 be explained ; and, were this conclufion well founded, it might 

 feem that the temperature of the earth's furface ought to be 

 an encreafing quantity : but it is certain that the accumulation 

 of heat communicated to the furface of the earth in fummer, 



will 



