214 Supposed causes of the Elevation of' the Land. 



merged, or that, during the process, the subjacent beds shrunk 

 in consequence of a reduction of the temperature, and to such 

 an extent that the contraction in a vertical line equalled the dis- 

 tance from the level of the highest tops of the continent to that 

 of the surrounding ocean. In like manner, before we can ad- 

 mit the elevation of a continent, we must admit either that, at a 

 period immediately preceding that catastrophe, there happened 

 an inroad of sustaining matter equal in thickness and in extent 

 to the continent about to be uplifted, or that, during the pro- 

 cess, the subjacent beds expanded in consequence of an increase 

 of temperature, and to such an extent that the expansion in a 

 vertical line equalled the distance from the level of the highest 

 tops of the continent to that of the surrounding ocean. These, 

 therefore, are the events which we are taught to credit, as having 

 taken place again and again, notwithstanding the tendency which 

 caloric has to diffuse itself, and the apparently unaltered dimen- 

 sions of the fissures and local caverns by which the strata are so 

 often separated or intersected. 



I will not expend more of your time in arguing against such 

 doctrines. Ail men are more or less lovers of the marvellous, 

 but few, I think, will upon reflection approve such marvels as 

 these. 



Solids, fluids and aeriform substances exist, we know, in the 

 interior of the earth, and expand by heat, which exists there 

 likewise. All of these, therefore, are fit agents of elevation^ 

 subject to certain conditions. 



Dr Daubeny attributes the liquefaction of lava, the throwing 

 up of ashes, and all other phenomena of disturbance attendant 

 on volcanic eruptions, to the action of water upon the metallic 

 bases. This cause is not opposed to experience, and appears 

 well proportioned to the efi^ect, which is sudden, violent, occa- 

 sional, temporary, accompanied by heat and by flame. To me, 

 at least, it seems far more satisfactory than the explanation of 

 those who ascribe the eff*ect to the elastic power of subterranean 

 fires, repressed in one place and relieved in another, or to the 

 undulations of a heated nucleus. 



A heated central mtcleus is a mere invention of fancy, trace- 

 able, I believe, to no other source than the hope of obtaining a 

 good argument from the multiplication of bad ones. To the 



