Concluding Remarks. 539 



fied rocks, along extensive lines, and not from circular craters, as lava 

 is now erupted from volcanoes. A change of this kind having been 

 effected, all would remain quiet until the secular refrigeration had pro- 

 duced other cavities; when a renewal of the same process would take 

 place. And I think it easy to conceive, that a long series of such 

 changes might take place without so sensibly diminishing the magni- 

 tude of the globe, that astronomers should be able to perceive their 

 effects on the earths rotatory motion through decades of centuries. 

 For the elevation would nearly equal the depression. 



From this view of the subject, it would appear that gravity has 

 been the principal force employed to elevate systems of mountains. 

 This, in consequence of the diminished size of the internal nucleus 

 of the globe, would produce a lateral pressure on both sides of that 

 portion of the crast which was depressed, sufficient to elevate adjoin- 

 ing portions ; and to force up melted matter beneath and even through 

 the ridges ; and thus the ultimate effects would he precisely like that 

 of an' expansive force within the earth ; except that it would operate 

 along extended lines and not in circular foci. 



I am aware that many of the views of Beaumont, which I have 

 attempted briefly to develope, have been, and are now, ably and 

 warmly opposed by Boue and other geologists no less distinguished. 

 All, however, agree, I believe, that different formations, and consequent- 

 ly different mountain masses, have been elevated at different epochs ; 

 which I regard as the fundamental and most important principle con- 

 cerned. Even if it be proved that distant parallel mountain chains were 

 not of synchronous elevation, (which is the principal point at issue,) it 

 cannot materially affect the value of Beaumonts researches. He cer- 

 tainly has the merit of bringing together all that was known on this sub- 

 ject and of deducing from thence some masterly generalizations, 

 which must be regarded as forming an interesting epoch in geology. 



Concluding Remarks. 



In drawing to a conclusion this protracted Report on the Geology 

 of Massachusetts, it is natural to pause and look back upon my labor. 

 And I freely acknowledge that its great deficiency and imperfection 

 are its most striking features. I cannot, indeed, accuse myself of a 

 want of diligence and effort to accomplish the objects of my appoint- 

 ment. It is now a little more than three years since I received my 

 commission; and during that period, in addition to the ordinary la- 

 bors of my profession, I have traveled 4550 miles for geological pur- 



