358 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



ceals the shore conglomerates. This till stretches half across the Westfield 

 Valley and extends a long way south, and, curiously, in the portion adjoin- 

 ing the bluflf of crystalline rocks it is made up almost wholly of the arkose, 

 while its thicker central portion is composed of coarse granitic materials. 



The Triassic shore conglomerates are largely concealed. Only in one 

 place (Mrs. S. Gillett's), near where the Grranville road goes over Sodom 

 Mountain, in the southwest portion of Southwick, is the rock seen in place, 

 within 50 rods of the base of the bluff. It is here a coarse, flaggy arkose, 

 the mass of the rock a coarse, buff, feldspathic sand, with a few far-traveled 

 pebbles of quartz 1 to 3 inches long. Skirting the base of the bluff for 

 miles the al^undant fragments in the till show that this is the prevailing 

 rock. It is often so well cemented and so little worn that it closely 

 resembles a granite. Stretching east across Westfield and Southwick to the 

 raih-oad the rock is uniformly a loosely cemented mass of unworn granitic 

 debris, quite deep red in the interior, but bleached and kaolinized at the 

 surface, and very often dug into for road material It is commonly more 

 or less spotted with well-rounded and therefore far-traveled quartz and 

 granite pebbles 1 to 4 inches across. 



THE MOUNT TOBY CONGLOMERATE, OR THE SLATE AND QUARTZITE 

 CONGLOMERATE. 



This rock never anywhere sinks to the dimensions of a sandstone, but 

 varies from a conglomerate with its coarse pebbles 2 inches long to one 

 where the larger constituents are from 2 to 4 feet in length. The mass of 

 the rock is very largely and often wholly made up of comminuted arg-illite, 

 quartz-schist, and vein quartz, with the larger pebbles of the same material. 



In many cases, as along the eastern slope of Mount Toby and in Gill, 

 it deserves the name of a giant conglomerate, blocks from 1 to 2 feet long 

 being stuck as closely as they can lie in a coarse gravel from which all sand 

 has been washed. An arrangement of the constituents, often very partial, 

 with their flat sm'faces parallel to a common plane and a rude stratification 

 in coarser and finer beds is the only structure. The rock occupies the east 

 shore of the basin except in the central portion. 



CONTACT AND DISTRIBUTION. 



The most northern outcrop of the Trias occurs a half mile north of 

 Northfield, where the Winchester road starts. It is a coarse conglomerate, 

 which appears in continuous outcrops west of the village street, and Toay 



