BOWLDERS ALONG THE COAST. 113 



buildings or any of the finish was afi'ectecl by moisture, and 

 during the past summer's residence there the objection was 

 not observed. 



In the construction of stone buildings, it is important that 

 an air-space at least four inches in depth should be arranged 

 between the wall and the ceiling, and with this the air within 

 is uniformly dry and comfortable. 



I hope, gentlemen, I have not wearied you with this topic. 

 I have endeavored to group together in popular form, some 

 of the facts and principles of modern geological and chemical 

 science which have a bearing upon the history of bowlder 

 rocks, and if I have excited so much interest in the subject 

 as to lead you to make further investigations, one of the 

 objects had in view will be attained. Perhaps we may learn, 

 from what has been stated, that the most common objects 

 found upon our farms have a history full of interest, and 

 that no substance with which we are brought in contact in 

 our daily labor is unworthy of our attention and study. 



Mr. Vincent, of Edgartown. More than a half century 

 since, I heard it stated that there was a bowlder on the north- 

 westerly side of Martha's Vineyard, which, it was said, had 

 its counterpart on the main land. It was affirmed, that, 

 having evidently been split off from some other portion of 

 rock, no such portion was to be found in the vicinity ; but 

 that, upon examination, the split side corresponded exactly 

 with one side of the rock referred to on the main land, both 

 as to size and shape. I heard it from very respectable gentle- 

 men ; but, never having seen and compared the two myself, 

 of course I cannot vouch for the reality. Science might 

 profit from a substantiation of the alleged fact, as it would 

 furnish an unmistakable evidence of the glacial theory, taken 

 in connection with supposed as well as known changes along 

 the coast of Massachusetts, caused by the wear of the ocean 

 by force of winds and tides. 



I assume that this island, with some smaller neighboring 

 islands, was a part of the main land ; that it probably became 

 separated from it first by the water obtaining a narrow run 

 through some of the lower parts of the land, which run of 

 water in time grew by the action of the known powerful tide 



15 



