THE nOOSAC SCHIST. 71 



As it blends southwiirdly with the Rowe schist, wliicli becomes feld- 

 spathic, and as it is here also doubled by its reappearance in East Grranville, 

 the whole of its southern portion was associated with the gneiss below by 

 President Hitchcock,* though in his first publication he suggests doubtfully 

 "the passage of the mica-schists into gneiss along the line of strike," and 

 reiterates the idea more decidedly in the first report on the geology of 

 Massachusetts.- He continues, however, to color his map in accordance 

 with the lithological character of the rock, representing the gneiss as a 

 broad wedge, tapering northward, and the mica-schist as a wedge of about 

 equal size, tapering southward and scarcely reaching the south line of 

 the State. Prof C. H. Hitchcock, from a study of the data given by his 

 father, and of Percival's report, has in part con-ected this in a map published 

 in Walling's Atlas of the State of Massachusetts.' 



SECTION ALONG THE UOSTON AND ALBANY RAILROAD. 



The variety ^Ji'esented by the schist from below upward is well 

 illustrated by a continuation of the section along the railroad from the 

 point reached upon page 32. Just east of Bancroft station, where Factory 

 Brook joins the Westfield River, the lowest bank of Hoosac schist rests 

 upon the granitoid Becket gneiss with clear unconformity. It is a well- 

 defined hydromica-schist, light-gray, quartzose and thin-fissile, but porphy- 

 ritic with an abundance of small albite crystals, which are of rounded 

 outline and are filled with the quartz grains in the midst of which they 

 have formed. 



Twenty rods east, at the beginning of the cutting, the green-spotted 

 hydromica-schist carries large, fine garnets (oo 0), and alternates through 

 the cut with sandy gneissoid layers — layers which are gneiss in composition, 

 but of an arenaceous texture, like that of the Devonian feldspathic quartz- 

 ites described later from Bernardston, rather than that of the older gneisses. 

 The ajipearance of the rock is as if a later development of feldspar and mica 

 in a sandstone had transformed the rock into a gneiss which retains a sandy 

 texture very difterent from that of the lower gneisses, where the constituents 

 are closely interwoven. 



On passing the second bridge the hydromica-schist, still feldspathic, is 



' Geology of the Connecticut: Am. Jour. Soi., Ist series, Vol. VI, 1828, p. 19. 

 ' Geology of Massacliusetts, 1835, p. 332. 

 ' Boston, 1871. 



