191 1-] REID— ISOSTASY AND MOUNTAIN RANGES. 451 



recently been raised; and the great depths of the latter to the fact 

 that they are in the act of sinking, or have only recently sunk. As 

 the centres of the great majority of strong earthquakes are along 

 the boundaries of high mountain ranges, or of great ocean deeps, 

 it seems most probable that the forces which have produced these 

 very interesting features of the earth's surface are still in active 

 operation. 



