GENERAL STRUCTURE ANJ> CORRELATION. 



13 



been excavated as the well-known Berkshire sand. About 100 feet east of 

 this we find an outcrop of vitreous quartzite. The next outcrops — older 

 and 300 or 400 feet eastward and dipping 50° easterly — show a schistose 

 quartzite overlain by an older and more slaty bed of the same; and this br- 

 avery coarsely feldspathic quartzite followed by another bed of schistose 

 quartzite, and this by a feldspathic biotite-schist. Representing these in 

 their normal succession we have — 



Stockbridge limestone. 

 Flaggy quartz-schists. 

 Schistose calcareous quartzite. 

 Sandy quartzite (friable). 

 Vitreous quartzite. 

 Covered (300 or 400 feet). 

 Schistose quartzite. 

 Schistose quartzite, more slaty. 

 Very feldspathic quartzite. 

 Schistose quartzite. 

 Feldspathic biotite-schist. 



Grryl.tch ML, 



GrcylocJi Schist . 



_Btjll"tyspif>t ljtrritstori*: . 

 Berkshire Sch Csl. 



SloddbrCcUiiiLarws/zn. 





=^^_- Hoosac Schist, 



Qunj-tei/e Coif/hrmeratt. . 

 Majn/br-cl Grwits. 



Fiu :; ( '"nvhitr.l , nlumiiLs nf the liuos ic and Greyloeh 1 



We now had both the Hoosac and Greylock columns complete, and 

 both springing from the same conformably underlying Cambrian quartzite 

 (see Fig. 3). 



A glance shows one point of difference — the entire absence of limestone 

 in the Hoosac column. But on the other hand, we have the observed con-^ 



