530 



GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



This rule is not without exceptions, since the pass which separates 

 Mount Tom from the next peak trends a little north of east, and the next 

 passage north trends east and west. President Hitchcock argued as follows 

 concerning the matter:^ 



If these notches had been determined by anything in direct relation with the 

 trap of the mountain, the most probable cause would have been a fissuiiug of the 

 bed of trap during its upheaval, and as this Assuring would have occurred most 

 naturally at right angles to the axis of the chain, the Assures would have con- 

 verged on a point south of the mountain, somewhere about the northwest corner of 

 Ludlow. 



So he concluded that if the first notches he noticed (those cutting at 

 right angles) were caused by Assuring, those farther west would be also 



at right angles to the chain there 

 and parallel with the dip there; 

 and when he found this was not 

 the case, he explained them as a 

 strange result of the great north- 

 ern diluvial cuiTent which did 

 duty then in place of the ice cur- 

 rent of more modern theories.^ 



The larger notches seem to 

 have been caused by the system 

 of faults which cut the range, 

 and to liave been enlarged by 

 pre-Glacial streams (see PI. XI, 

 p. 510) in case of two or three 

 of the deeper ones. Where, as is 

 often the case, these faults fail to run north and south, the notches may 

 have been remodeled by the ice and given a new direction, and the great 

 number of smaller notches, all parallel with the direction of the ice, do 

 not seem explicable as a result of water action, but rather as the work of 

 the ice acting on the irregular rim of the trap sheet, which emphasized 

 irregularities where this rim ran athwart the course of the ice, as in the 

 Holyoke range, and smoothed them down where the rim ran with the 

 ice, as in Mount Tom. 



/ZFT 



-East slope of a large glaciated groove bebind the bo 

 ing alley on Mount Holyoke. 



' Geology of Massachusetts, 1841, p. 389. 



