THE CONWAY SCHISTS. 191 



tion following, and the curious relations of the bed to the base of the 

 Triassic are discussed in Chapter XII, under the head of "The Mount Toby 

 conglomerate:" 



PETROGRAPHICAL DESCRIPTION OF LIMESTONE AND AMPIIIBOLITE. THE LIMESTONES. THE ANVILS. 

 THK PASSAGE OF LIMESTONE INTO AMPnillOLlTF.. 



(rt) Carbonaceous limestone from Whately. From the mass at the Ijridge 

 west of the village, thrust up thi-ough the argillite (described on p. 196); a 

 dark-gray, nearly black, compact, traplike rock, weatliering deeply to a 

 red-brown, porous and friable mass. 



Under the microscope it is seen to be a granular mixture of quartz 

 and calcite, the latter often multiple-twinned, and the whole darkened by 

 coaly matter in fine gi'ains. In this groundmass are developed varying 

 quantities of muscovite and biotite, the latter more loaded with coal dust 

 than the general mass, indicating early crystallization, when the whole 

 was more coaly. 



(1)) Micaceous protuherances on the limestone anvils from^ Goshen Q). (See 

 PI. XXXIII.) This section was cut from a small warty protuberance, an 

 inch across, from the central limestone portion of an "anvil," which stands 

 in front of the geological building at Amherst, to determine the cause of 

 the regular projections on the weathered surfaces of the limestone portion 

 of the "anvils." On the fresh surface the projections appeared exactly like 

 the rest of the limestone. Under the microscope there proved to be in 

 them considerable accumulations of a greenish muscovite, with here and 

 there a few scales of red biotite. The muscovite was filled with needles 

 of rutile. There was also considerable feebly pleochroic hornblende in 

 notched plates. 



(c) Base of same anvil. This seems to have been a passage bed from 

 the sandstone to the limestone. It is nearly 4 inches thick, and is made up 

 of a green, fibrous, matted hornblende, filled with quartz grains which are 

 in part rounded and apparently original, in part turbercitlous and caused by 

 secondary infiltration, and in part in scales so sharply angular that they may 

 have been crushed in place. Very many of these quartz grains are crowded 

 wnth coal dust in the center and are clear outside, indicating secondary 

 enlargement, and the same is tnie of the large hornblendes. A few much- 

 corroded ffrains of calcite remain. There are also grains and well-formed 



