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XXXII. On the B'lffui'ion of Heat at the Surface of the Earth, 

 By John Murray, M.D, F.R.S. Ed* 



An argument which I had stated against the Huttonian Theory 

 of the Earth, in so far as it relates to the operation of a centra] 

 heat, was honoured some time ago with a reply by a d.stmguished 

 member of the Society. Respect for the opmion of Mr. Flaytair 

 led me to consider attentively the reasoning he employea ; and 

 Tstill feeling some confidence in the grounds on which the original 

 argument rests, I propose to offer a few observations witn regard 

 to it. The question further involves the consideration ot tne 

 mode in which heat is distributed at the surface of the gloiie. 

 i'iiis, when minutelv investigated, presents a very perfect arrange- 

 nent, by which the' escape of caloric is prevented, while its equal 

 distribution is more effectually attained ; and tiie subject, under 

 this point of view, may have some interest, independent ot its 

 relation to any controversial discussion. 



The argument which I had adv^mced is. That if a heat exict 

 in the interior part of the earth, operating for an indefinite pe- 

 riod, as is assumed in the Huttonian theory, it cannot for such 

 .1 period remain locally accumulated. It must diffuse itse.t 

 tinough the entire mass, and become at length equal, or nearly 

 so, over the whole. An equilibrium of temperature must there- 

 fore be established, incompatible with that system of indehnitely 

 renewed operations which is represented as the great excellence 

 of the system. This has always appeared to me conclusive x and 

 an argument such as this, derived a prion, and directed to the 

 first principles of a geological theory, if successful, is of greater 

 weight than arguments derived from its adaptation to natural 

 piiffinomena, which, even when they appear to be just, amount 

 only to probabiUtv, and,, from our imperfect knowledge ot the re- 

 lations of the mineral iangdoiu, leave often some degree ot un- 

 certainty f. . , 



To obviate this argument, the following reasoning has lieen 

 employed by Mr. Playfair. The ditfusion of temperature he 

 remarks, is a consequcHicc of the tendency of heat to pass from 



• From the Transaclions of tlic Royal Society of Edinburgh. 



i 1 out-i.t to rcin-.u-k, that this view of t!ie constant existence of a cen- 

 fa' heat ii n..t co..sidei-ecl by i>.lt the defenders of Dr. liuttou s system as 

 « neccs.ary part of it, nor do they even regard it as r. position which he him- 

 self inaiuiaincd. They suppose the existence only ot interior local heat, 

 tvhich mav cease for a ti-ne, and he .a^ain renewed; and to this hypotheeis 

 r ,e abovf argument docs not so strictlv apply. I must only add, Xiat it 

 evon this view of the sul.jeci he adopted, much of the difficulty will still 

 rr.uain in its original force, it becomes liable too, it I mistake not, to 

 other objections iicculiar to itscif, cfjfl-'Hy important; and by adopiuij; it, 

 J * ' £ ^ uiucn 



