CHAP, xviir. 



DOME-SHAPED ERRATIC. 



359 



I observed one of the green blocks, twenty-four feet long, 

 poised upon another about nineteen feet in length. The 

 largest of all on the west flank of m, or Dupey's Mount, 

 called the Alderman, is about ninety feet in diameter, 



FiK. 51. 



Erratic dome-sliaped block of compact chloritic rock {n, map, iig. 50), near 

 the Richmond Meeting-house, Berkshire, Massachusetts, lat. 42° 25' N. 

 Length, fifty-two feet ; width, forty feet ; height above the soil, fifteen feet. 



Fig. 52. 



Section showing position of the block, fig. 51. 



a The large block. Fig. 51, and h, map, p. 357. 



b Fragment detached from the same. 



c Unstratified drift with boulders. 



d Silurian limestone in inclined stratification. 



and nearly three hundred feet in circumference. We counted 

 at some j)oints between forty and fifty blocks visible at once, 

 the smallest of them larger than a camel. 



24 



