ALGONKIAN ROCKS IN VERMONT. 423 



the State. Between the areas indicated upon their map,^ the 

 writer has observed it or its metamorphosed equivalent, so it is 

 known to extend in an unbroken line from near North Benning- 

 ton the entire length of the State as a persistent characteristic 

 horizon. At the Massachusetts line it is wanting where the 

 Olenellus quartzite reposes discordantly upon a granitoid gneiss. 

 On the east side of the range it is described by the above- 

 mentioned authors as occurring in a narrow band running across 

 the towns of Plymouth and Ludlow, and is correlated with the 

 conglomerate horizon of the Rutland Valley. It is largely upon 

 this eastern occurrence of the conglomerate that the anticlinal 

 nature of the Green Mountains was hypothecated by them. The 

 phenomena of stretching of quartz and gniess pebbles in this 

 horizon and their destruction thereby, furnished the elder Hitch- 

 cock with the necessary confirmatory data for his then revolu- 

 tionary ideas concerning the production of gneisses from con- 

 glomerates by metamorphism. About one mile north of 

 Tyson's Furnace in Plymouth and on the south slope of Bear 

 Mountain in Wallingford occur the now classical localities where 

 the conglomerate was most carefully studied by him and where 

 nearly all his illustrations were obtained. It is doubtful if two 

 areas can be found in metamorphic regions where the change of 

 sedimentary rocks to crystalline gneiss is better or more satis- 

 factorily shown. It was with fear and hesitancy that the ques- 

 tion of this new effect of metamorphism was discussed, but the 

 carefully-elaborated arguments advanced show that a keen appre- 

 ciation of the proper interpretation of the phenomena revealed 

 there was felt by the author of this most valuable contribution 

 to the science of geology. 



The first area described (the Wallingford locality^) is situ- 

 ated about where the 1500 feet contour makes a sudden jog to 

 the south. Here the elongation and flattening of the pebbles, 

 their contorted character and the transition of the rock to gneiss 

 are remarked upon. 



'Opus. cit. PI. I., Vol. II. 

 ^Opus. cit,, Vol. I., pp. 32 to 44. 



