MISCELLANEA. 595 



closely upon the appearance of tlie ice-slieet. This fact has led some 

 geologists to suspect that there must have been some physical con- 

 nexion between the appearance of the ice and the sinking of the 

 land. In an able paper lately read before the Greological Society, 

 Mr. Jamieson suggests that the submergence might have been caused 

 by the earth's crust having yielded under the enormous weight of 

 the ice. 



While pondering over the subject, a few days ago, what I sup- 

 pose to have been the true cause of the submergence suggested 

 itself to my mind. The cause was a purely mechanical one, of ex- 

 treme beauty and simplicity, The submergence was a necessary 

 result of the influence of the weight of the ice-sheet on the earth's 

 centre of gravity. The whole affair is so simple and ob\dous, that 

 it is singular that the cause should have so long escaped obser- 

 vation. 



The surface of the ocean always adjusts itself in relation to the 

 earth's centre of gravity, no matter what the form of the solid mass 

 of earth may happen to be. Now, if a large portion of the water of 

 the ocean be converted into solid ice, and placed, for example, aroimd 

 the northern Polar regions, it will necessarily change the position 

 of the earth's centre of gravity. The centre of gravity Avill be re- 

 moved a little to the north of its former position. The water of the 

 ocean will then forsake the old centre, and adjust itself in relation to 

 the new. The surface of the ocean will, therefore, rise towards the 

 North Pole, and fall towards the South ; in other words, there will 

 be, in relation to the sea-level, a depression of the land on the northern 

 hemisphere, and an elevation on the southern. The surface of the 

 land, it is true, will not sink nearer to the earth's centre of gravity, 

 as is generally supposed, but the centre of gravity will rise nearer to 

 the surface. The land will not sink under the sea ; but, what is the 

 same thing, the sea will, in consequence of the change in the earth's 

 centre of gravity, rise upon the land. The extent of the rise of the 

 ocean level, or, what is equally the same, the extent of the submer- 

 gence, will be in proportion to the weight of the ice-sheet. The 

 weiglit or the size of the ice- sheet being known, we can determine, 

 with the utmost certainty, the extent of the submergence ; or, con- 

 versely, the extent of the submergence being known, we can deter- 

 mine both the weight and size of the ice-sheet. It is singular why 

 physicists should have not perceived the physical impossibihty of an 

 ice-Bbeet, several thousands of feet in thickness, being placed upon 



