684 B. K. EMERSON CIRQUES AND TERRACES OF MOUNT TOBY. 



up by four incipient hanging valleys, "k-n/' which could not be repre- 

 sented on the figure. 



The objections to this glacial hypothesis are certainly serious. Mount 

 Toby is a mount rather than a mountain. I have seen very small gla- 

 ciers in Yakutat Bay, Alaska, and farther north, but I doubt if any quite 

 as small as these have been found. 



Again the Worcester County plateau, 1,200 feet high, comes up to 

 within 3 miles of the mountain on the east. Mount Toby is 1,265 feet 

 high, and 12 miles to the west begins the Berkshire County plateau at 

 1,400 feet. It may be urged that the ice gathering over these high areas 

 would become confluent with that of Mount Toby before much independ- 

 ent work had been done to the mountain itself. This has not quite so 

 much force as the former objection, since as the ice moved from the 

 northwest the great vertical-walled westward facing trap ridge of Deer- 

 field Mountain (which stands west of Mount Toby, extends north through 

 Greenfield, and bends round to the east in Gill) certainly did fend off the 

 ice from Mount Toby in a considerable degree, as the direction of the 

 ice scratches show, and may have protected it until the main Berk- 

 •shire ice had gained a considerable thickness. Both here and at the 

 Holyoke range the ice impinged very obliquely against the trap ridge and 

 went south at its foot a long way before it rode obliquely over it, as a 

 carriage wheel escapes from a trolley track. From this cause the soft 

 sandstones stand several hundred feet higher east of the Holyoke range 

 than west of it, and preserve the preglacial stream beds, and this protec- 

 tion is the main cause of the height of Mount Toby. 



It is certainly very difficult to realize on the ground how these closely 

 approximated corries can have been formed by ordinary water erosion. 

 If they were thus formed the time required must have been very great, 

 since the supply of water must have been very small. Faulting, how- 

 ever, may have had more influence than is admitted in the above de- 

 scription, since faults are hard to locate in these monotonous conglom- 

 erates where the trap is wanting. 



The Tebeaces 



One needs to consider also the moderating and modifying influence of 

 this trap barrier on the impact of the continental ice against Mount 

 Toby in studying the second peculiarity of the mountain — that is, its 

 rock-cut terraces. 



The whole western wall of the mountain on all the ridges and inter- 

 vening slopes between the cirques has been cut into a series of great rocky 



