MUSEUM OF COMPARATIVE ZOOLOGY. 25 



bear smooth surfaces, and the beds of limestone which outcrop in the 

 valleys are rounded and water-worn, none of these rocks exhibit well- 

 marked striae. This peculiarity is probably due to the great amount of 

 decomposition which the surface of these rocks has undergone. 



In the case of the mica schists and argillites, the slight amount of 

 decomposition which they have suffered, and the coarseness of the striations 

 which they have received, have prevented the obliteration of the markings. 



Though there is a great difference in direction between certain widely 

 separated sets of strias, yet it is generally true that the stria) situated 

 upon the same N. E. and S. W. line, have, if not separated by a great 

 distance, nearly the same direction. 



4. SUPERFICIAL DEPOSITS UNDERLYING THE TRAINS. 



The superficial deposits of the region consist of unstratified gravels 

 made up of water-worn fragments of all sizes, and composed of limestone, 

 quartz, quartzite, mica schist, chloritic schist, and chloritic sandstone. In 

 a cut on the Boston and Albany Railroad, three quarters of a mile N. E. 

 of Richmond Station, are completely rounded and polished boulders, 

 some of which -have a length of four or five feet. They are composed of 

 limestone and of chloritic schist, and a few exhibit well-marked parallel 

 striae. The thickness of the drift deposits diminishes from the base 

 towards the crest upon each of the three ranges in the region, the sum- 

 raits or crests being in nearly all cases free from this formation, though 

 in several instances the bed-rock is concealed by a scanty soil bearing a 

 thick vegetable growth. 



The following table gives the thicknesses of the drift deposits in vari- 

 ous localities. 



Table of Thicknesses of the Drift. 



(1.) Channel of brook between North and South *' Families " of Ca- 

 naan Shakers 20 feet. 



(2.) Channel of same brook in ravine between Flat Rock and Merri- 



nian's Mount 25 " 



(3.) Chaiuiel of brook near head of ravine between Merriman's and 



Dupey's Mounts 8 " 



(4.) Channel of brook \ m. east of summit of Perry's Peak 8 " 



(5.) Channel of brook \ m. north of Haskell's, in the Haskell Valley (at 



least) 6 " 



(6.) Channel of same brook ^ m. nearly south of Haskell's 12 " 



(7.) Channel of brook ^ m. S. S. E. of summit of Perry's Peak 3 " 



(8.) Channel of same brook \ m. N. N, W. of Miss Pearson's 8 " 



