1 JQ On the Diffusion of Heat 



torn of the sea, or within a short dist;ince from it, the heat from 

 the interior must be at a degree of intensity sufficient to produee 

 mineral fu!?ion and consoHdation from the disintegrated nnaterials 

 of a former land, which may be estimated from our know'odge 

 of the fusibility of these bodies. It is propagated from this on- 

 wards, with such a decrease that at the surface there is no 

 sensible liigli teniperature. Its difTusion from the central regions 

 to the bottom of the sea must of course have been at a similar 

 rate of diminution. If we were to calculate the rate of pro- 

 gression, and compare it with the distances in the two portions 

 of space, — that fiom the central region to the bottom of the sea, 

 and that from the bottom cf the sea to the surface of the land, — 

 we shall find an intensity of heat in the interior, compared with 

 which the heat necessary to melt mountains of quartz, formerly 

 supposed to present so great a difficulty, is a mere atom in the 

 scale, scarcely affording even a point of comparison. 



Some idea may be formed of this, by recurring to the illustra- 

 tion of the iron bnr, with a decreasing temperature, making the 

 most liberal allowance in favour of the Huttonian hypothesis, 

 with regard to the respective portions of space. Thus, the bar 

 being one thousand inches in length, if its temperature at the one 

 extremity be 50% and if within live inches of this it is at a white 

 heat, then the heat increasing at the same rate, through every 

 succeeding five inches, what must be its intensity at the other 

 extremity ? No effort of the imagination can form the most 

 remote eonce])l ion of it, nor can any argument he wanting to 

 prove, that no such heat can exist in the interior of the earth. 



If, to avoid the ditliculty, a less rapid decrement of tempera- 

 ture be supposed; then, from a heat of that intensity which must 

 be assumed to exist at the bottom of the ocean, to produce the 

 effects ascril>ed to it, the decrease in the short space between 

 that and the surface cannot he such as to bring the temperature 

 within that which is at all compatible with the established osco- 

 iiomy of nature. The difficulty is, therefore, insurmoimtable ; 

 it must occur on the one hand or on the other ; and it is not 

 merely connected with Mr. Playfair's argument ; but, as that 

 argimient is founded on a law perfectly just with regard to the 

 diffusion of temperature, it is a difficulty which necessarily fol- 

 lows from the assumption of a central heat, or of any internal 

 heat such as that which must be assumed in the Huttonian 

 theory, — a heat which is to operate around the whole circum- 

 ference of the globe, continue its operations for such immense 

 periods, and renew it for indefinite time. 



Leaving the consideration of this subject, in so far as it is 

 connected with the argument ou the Huttonian theory, I mav 



add 



