CHAP. XVIII. 



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 above ninety feet in diameter, 



Fig. 51 



Erratic dome-shaped block of compact chloritic rock (n map, 

 fig. 50), near the Eichmond 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 n 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 points between forty and fifty blocks visible at once, 

 the smallest of them larger than a camel. 



