174 BULLETIN OF THE 



similar iu character aud arrangement to the same minerals outside that we 

 have to suppose they were all formed together where we now find them. 

 This is the well known character of these pseudo-porphyritic feldspars 

 in phyllite-gueiss or feldspar-phyllite in general, aud in the present case 

 their character as albite has been proved by chemical and optical analy- 

 sis. That they should have some connection with the grains of true 

 detrital feldspar found in the less metamorphosed phyllites of this region 

 is easy to see, but difficult to prove. 



It should be mentioned that the Hoosac conglomerate in its fine 

 schistose portions contains little glassy feldspars with albitic characters. 



This conglomerate occurs at intervals for more than a hundred 

 miles to the north, well into the centre of Vermont, lying between the 

 Cambrian quartzite of the Taconic region and the underlying gneisses 

 on the east. 



One of the most striking localities is on Bear Mountain in Walling- 

 ford, a few miles southeast of Rutland, Vermont, which was described 

 and figured in the " Geology of Vermont," Volume T. pages 32 and 34. 

 The conglomerate character is exhibited in wonderful perfection, the 

 pebbles varying from almost boulder size to that of the grains of the 

 finest sandstone. They are principally quartz (often blue) and feld- 

 spar ; the latter are generally of a dull white or reddish color, due 

 to kaolinization. One of the large feldspars, tested by the ordinary 

 methods, proved to be microcline. In the Hoosac conglomei'ate this 

 feldspar also occurs in the pebbles and in the underlying coarse gneiss 

 from which they were derived. In the finer grained layers of the Bear 

 Mountain rock the cement predominates, so that the rock is a crystal- 

 line schist containing little pea-sized angular grains of quartz and feld- 

 spar. This cement rock here and at other localities glitters with small 

 glassy feldspars, as does the albite schist of Hoosac Tunnel. 



In the finer grained portions of this conglomerate schist the detrital 

 feldspars show interesting changes, whicli may throw some light on the 

 formation of albite schists. The descriptions which follow are based on 

 material from one hand specimen, so tli;it it will be understood that the 

 changes observed are ])rogressive only by comparison, feldspars side by 

 side having been aff'ected to a varying degree l)y the forces of metamor- 

 phism, obliterating partially or else completely the original characters. 



In the hand specimen the rock is a silvery green schist, the color 

 due to large scales of a light green muscovite, which are arranged in 

 pai'allel layers, and enclose l)etwecn the meshes little elongated masses 

 of quartz, and little glassy feldspars, which are barely visible with the 



