GEOLOGY OF MOUNT DESERT. 57 



history of a region requires an examination of the records 

 of denudation, as well as of those of accumulation. It is 

 likely that Nature gave quite as much time to wearing 

 down as to building up the Island ; and we may well follow 

 her example in the division of our sections. 



The reasons for believing that the Island and the adjacent 

 mainland have lost much of the rock mass that once existed 

 above their present surface may be briefly stated. We first 

 notice that, if the tilted beds of the stratified and volcanic 

 series were again extended upwards into the air from their 

 present denuded edges, a great increase would be given to 

 the altitude of the surface. This is not merely a local mat- 

 ter. The same conclusion is reached all along the New 

 England coast, and far inland. The rocks of the whole 

 region are greatly disordered, much as rocks are in lofty 

 mountains, and the edges of the strata as now revealed 

 are by no means the original edges. How far they once 

 extended upwards cannot be stated ; but the distance 

 should be estimated in thousands of feet rather than in 

 hundreds. 



The evidence thus derived from the attitude of the 

 bedded rocks is confirmed by the features of the intrusive 

 rocks, — the diorites, the granite, and the trap dikes. None 

 of these exhibit any trace of surface extrusion, such as is 

 so plainly manifested in the more ancient felsites. Hence 

 we must suppose that, since the felsites were extruded, a 

 great accumulation of superincumbent materials was loaded 

 upon the region, and that it was upwards into this heavy 

 accumulation that the intrusive rocks were thrust. It is 

 quite probable that during the time of accumulation and 

 intrusion the whole region stood lower than it now does, 

 even so low that its surface then was near or below sea 

 level. As long as this low stand was maintained, further 

 accumulation would be natural enough, and denudation 

 would be postponed. No limits of quantity or time can 



