146 ON THE REVOLUTIONS 



whole of the North Sea. His idea is, that a change has be6n 

 gradually going forward in the position of the centre of gravity of 

 the earth, which has been moving to the southward, and that an 

 equivalent rise is experienced in the southern hemisphere. 

 That when the North Sea stood at its highest level, these gra- 

 nitic blocks had been transported across the Baltic, by means^ 

 of the winds, on floats of ice, and settling in their present pla- 

 ces, had been left by the retiring waters. 



M. DE Luc, in a very satisfactoiy manner, in my opinion, re- 

 futes one essential part of this system, by shewing, from the 

 form of the new lands, and from other circumstances, that no 

 change in level whatever has taken place on the surface of that 

 sea for many ages back, and, indeed, ever since the surround- 

 inf country has possessed its present form. As to the other 

 part of his system, which relates to the transportation of these 

 blocks by means of ice, we shall soon have occasion to resume 

 its consideration. ' 



Besides the consequences resulting from these particular 

 phenomena, there are other material branches of Dr Button's: 

 theory connected with the same views, which in my opinion 

 require to be carefully revised. Tlie theory which he has ad- 

 vanced respecting the formation of valleys, by mere diurnal 

 actions, appears to me liable to great objections, and I cannot 

 help agreeing with M. de Luc, in much that he has urged 

 against Mr Playfaib on this point I also concur with my 

 friend Sir George Mackenzie, in some general views, sug- 

 gested to him by the aspect of certain rocks in Iceland, and 

 in rejecting the slow operations of the atmosphere {Travels 

 in Iceland., p. 39.) 



The difficulty is peculiarly great where a lake occupies the 

 bottom of the valley, and is very conspicuous in the case of the 

 lake of Geneva lately mentioned. For, grjvnting all that has 



been 



