GLACIAL NOTCHES. 529 



mass of the ice over Hampshire County was S. 35° E., while the 

 lowest portions in the broad depression of the Connecticut Valley moved 

 with that valley from north to south, and even west of south along- the 

 Mount Tom range. While this explanation is surrounded with difficulties, 

 it does explain in a very satisfactory way many peculiarities of the character 

 and distribution of the till in the valley, as will be made clear in the next 

 sections. 



GliACI^VL T^OTCHES. 



Another remarkable series of phenomena, which we may possibly refer, 

 in whole or part, to the direct action of the ice upon the rocky floor over 

 which it moved, is to be found in the succession of notches of varying- depth 

 Avhich cut the Holyoke chain transversely in its east-west portion and 

 give it the appearance of a sierra in miniature. One of these cuts the 

 ridge to its base, forming the notch tlu-ough which the river flows. Two 

 cut down deep into the heart of the mountain, forming low cols, 

 thi-ough the western of which the road runs.^ Others are shallower, and 

 one may find a quite complete series connecting them with the ordi- 

 nary glacial grooves and scratches. The larger notches are themselves 

 scratched and polished, and the direction of the scratches coincides with 

 the axis of the notches themselves. 



Another circumstance harmonizes with the idea that they were formed 

 by a force like that of moving ice, the direction of whose action was in great 

 degree independent of the relative hardness and direction of the rido-e. 

 The Holyoke range lies like a blowpipe with the mouthpiece pointing south 

 and the point directed east. So long as the chain runs east and west the 

 groo"\-es cross it at right angles, running, as did the ice in the vallev, north 

 and south, while as the ridge swings round from west to south the succeeding 

 notches run parallel to the first and cut the chain more and more obliquely 

 until the last coincides with the southward prolongation of the mountain 

 and splits it; and one looking at the trap from the west — in Southampton 

 or Easthampton, for instance — sees the almost vertical cliff of trap bounded 

 above by a line which deviates little from horizontahty, instead of the 

 serrate sky line of the Holyoke range proper as seen from Amherst. 



'This used to be called the East Crack, the deep notch just east of the Holyoke Mountain House 

 being known as the West Crack, and there was once a road through this also; and the deepest depres- 

 sion between these was the Low Place. 

 MON XXIX 34 



