560 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



it had been broken off from the trap ledges immediately above it, but its exact 

 correspondence with Oreb and Etam iu characters, and want of resemblance to 

 the trap of Holyoke, make it more probable that it was brought into . its present 

 position by drift agency and originated in the same region as those on Warner. 



THE SENTINEL. 



As we ascend Mount Boreas, looking northerly up the valley on its east side, 

 * * * we see a prominent bowlder lying near the base. We find it to be com- 

 posed of gneiss and lying on gneiss, although the stratification on both is very 

 indistinct. It weighs something less perhaps than 200 tons, although not accurately 

 measured. 



THE ROCKING STONE. 



Some years ago a bowlder of several tons weight, capable of being rocked a little 

 by one man, lay on a farm then owned by Mr. Grout, about a mile north of Pelham 

 Center, on the road to Shutesbury. 



OTHER BOWLDERS. 



The finest l)o\vlder ever found in the valley is the one now lying in 

 front of the Woods cabinet, Avhere it was brought by the class of 1857, as 

 the inscription upon it indicates. Its former north end now faces south. 

 (See PL XXXIII.) It was uncovered in lowering the road in front of the 

 residence of the late Edward Dickinson, and, judging from the excavations 

 here for the waterworks, it was derived from the lower till. It is a large, 

 coarse, red sandstone, in size 78 by G6 by 33 inches, the four sides planed 

 down to a flat convex surface and striated longitudinally, the ends for the 

 most part still rough and irregular. It exhibits exactly, on a large scale, 

 the form of the most perfectly polished glacial stones. The striae of the 

 upper surface when it was fii-,st exposed ran north-south, as do the striae in 

 the valley, and it may be that the ice passed over it after it was iixed in 

 the till, thus polishing its fourth side, which was naturally at first mistaken 

 for a ledge. A full description of it was published l)y President Hitchcock.^ 



The largest specimen of the buff quartzite, which is so abundant in 

 smaller masses throughout the valley, is the one mentioned on page 542, 

 in the yard of the Whitney homestead, on King street, in Northampton, 

 which came from the Denniston jjlace, near Florence. This quartzite, I 

 think, came into the valley farther north from Vermont and then drifted 

 down in the valley with the altered direction of the ice. 



'Am. Jour. Sci., 2il series, Vol. XXII, 1857, p. 397. 



