at the Surface of the Earth. 17S 



stibversive of its accumulation in the interior. Either the dif- 

 fusion alone, therefore, or the diffusion attended with the final 

 result of equilibrium of temperature, is sufficient for the refuta- 

 tion of the hypothesis. Both I conceive are established. And 

 I would still regard the argument in the light in which 1 first 

 advanced it, as a demonstration of the fallacy of the leading 

 principle of the Huttonian system, which assumes the existence 

 of an internal heat operating at renewed periods for indefinite 

 time. 



There are some other points of view under which the subject 

 may be considered, in which the difficulties attending the assump- 

 tion of an internal heat, when connected with the law which 

 Mr. Playfair has illustrated, appear in a very strong light. 



It has always been found difficult to give any account of ihQ 

 origin of the supposed interna! heat, to the operation of which 

 the consolidation of minerab, and the elevation of the habitable 

 lan^ from the bed of the ocean, have been ascribed, if the view 

 be restricted to the production even of one world, such an iii- 

 tcusity and continuance of heat are necessary for this single ef- 

 fect, that no adequate cause can be even hypothetically assigned 

 for it. If it be extended to the successive production of thvee 

 or four worlds, each embracing a period between its formalioii 

 and destruction in which millions of years must elapse, — an event 

 which, according to the theory, is not only possible, but has 

 actually occurred, — the h.eat requi^'cd is altogether beyond what 

 the imagination can conceive. But if, in addition to this, calorie 

 is also diffused from the interior, and discharged from the cir- 

 cumference of the globe into unlimited space, we are lost in the 

 magnitude of the result, and are unable to acquire a just con- 

 ception of the force of the argument, from the impossibility of 

 contemplating clearly the difficulty in all its extent. 



The difficulty, from the intensity of the heat which must be 

 jtssumed to exist, is not less great than that from its continuance 

 and waste. It is sufficiently apparent, when we consider tliat 

 the highest mountains of the globe run in extensive chains, and 

 are so connected, that they must have been formed at one time, 

 and that they are composed of materials which a very intea<<€ 

 heat does not fuse. But this is nothing compared with the statt- 

 Mient which nmst be made, in consequence of the law, that the 

 internal temperature is a decreasing one from the niterior to ihe 

 circumference of the globe. 



!f we can discover the rate of thin decrease, bv knov»'ing the 

 temperature which exists at two distant points, we may of coarse 

 form some calculation of the intensity of the heat which exists 

 at the commencement of the series. Now this we have the 

 means of delermini/.g with considcrablo precision, At tlie bot- 



toiii 



