38 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



1890, Vol. II), where res^ults of over 30,000 pound.s were obtained; but it is 

 far beyond the requirements of buikling. 



"Cubes of the rock were also boiled in acid. One which was thus 

 treated for five hours in boiling dilute HCl (1 part HCl of specific gravity 

 1.20 to 20 parts HoO) lost 0.59 per cent in weight. A second cube treated 

 in the same way in boiling dilute H2SO4 (1 part H2SO4 of specific gravity 

 1.84 to 20 parts HoO) gave a loss of 0.48 per cent. Both these results indi- 

 cate a great resistance to natural solvents. Two large cubes were placed in 

 a muffle and maintained at a bright red for half an hour. One was allowed 

 to cool just below redness and then plunged in cold water. It caused 

 one crack that extended half through. The other cube was allowed to 

 cool slowly in the air, and showed a thin external crumbling layer. When 

 these results are compared with somewhat similar tests of other granites, as 

 set forth bv Mr. G. P. Merrill in his valuable work. Stones for Construction 

 and Ornament, and with others in Vol. I of the Final Report of the Geo- 

 logical Survey of Minnesota, and others by Dr. A. W. Jackson in the recent 

 amiual reports of the State mineralogist of California, it appears that the 

 Chester "^^ stone endured well." 



THE GKT:ISS at SrrELBTJRNE. 



The oval area of gneiss on the Deerfield River, at Shelbume Falls, 

 has long attracted attention as a very striking illustration of erosion." It is 

 a regular quaquaversal. The gneisses in the center of the area are in the 

 main horizontal, though much contoi'ted. Toward the borders they dip 

 under a bed of hornblende-schist, which frames them beautifully, and this 

 schist in turn dips outward on all sides beneath the mica-schists, and these 

 dip outward also, with gradually increasing inclination. 



The ero.sion which woi-e through the newer beds domed over the gneiss 

 has cut more rapidly into it, so that the gneiss occupies now the bottom of a 

 deep circular basin and rises high up the sides of the surrounding hills, where 

 it is capped by the newer beds. This basin is cut across by the Deerfield 

 River and its tributary, the North River. 



The rock is very largely a biotite-gneiss of medium grain, granitoid and 

 light-gray, as at the quarry by the railroad on the western boundary of the 



' This should be Becket; the quarries of the company are in Becket and the workshops in Chester. 

 -E.Hitchcock. "Ten thousand feet of vertical thickness have disappeared.'' Elementary 

 Geolo^'v, isno, p 121. 



