100 PROCEEDINGS OF THE ACADEMY OF [l'S90. 



hundred feet into the hill, exhibiting a stratum of crystalline lime- 

 stone probably 60 feet wide bounded on the northwest by garnetiferous 

 mica schists, with feldspar nodules, most closely resembling those of 

 Cream Valley, Radnor. On the southeast is a rock closely resem- 

 bling the Laurentian, containing interbedded limestone. This is not 

 far north of undoubted Laurentian, and is either that rock, or as 

 Dr. Frazer has suggested,^ a more recent formation made up of the 

 fragments of the underlying rocks. In this quarry a satisfactory 

 exposure gave strike N. 40° E. dip 55° S. E. Northwest of this outcrop 

 are 100 feet of the schists, and then a very small exposure of sac- 

 charoidal limestone, apparently an anticlinal in the schists. The 

 steatite outcrop is 450 feet N. 50° E. from the southerly limestone, 

 K. 65° E. from the northerly. 



A short distance northwest are the hydromica schists of the 

 South (Chester) Valley Hill. 



Dr. Frazer^ thinks it probable that the serpentine of this belt is a 

 metasomatized portion of the hydromica schists with which he regards 

 it as lying in contact ; but towards the northeast we find between the 

 hydromica and this serpentine, limestone, Rogers' altered primal, 

 garnetiferous micaschists,Potsdam sandstone and steatite, the garnet- 

 iferous mica schists much more nearly continuous (apparently) than 

 the serpentine. North of Radnor station fully a thousand feet of the 

 above rocks intervene between the hydromica schists and the serpen- 

 tine. I have nowhere seen the hydromica schists of the South Valley 

 Hill in contact with the serj^entine. 



The LaFayette Belt. 

 On the southeast side of the Laurentian anticlinal is the LaFay- 

 ette belt, but along nearly its whole course there intervenes visibly 

 between it and the Laurentian a schistose rock, including crystals 

 of mica like the feldspar crystals in a porphyry and more rarely 

 visible a thin bedded gneiss resembling the altered primal of Rogers 

 so largely exposed on the northwest side of the anticlinal. The 

 schist is very uniform and persistent but it is nowhere well exposed. 

 At times, as on the southwest bank of Meadow Brook north of 



1 C 4 p. 294. 



2 " These resulis seem to lend a high degree of probability to the theory that at 

 least this beh (Ralnor-West Chester) is a metasomatized product of a layer or 

 layers of the hydromica schists in contact with which it lies and with whicii its rela- 

 tions are abundantly made out by very different processes of comparison, viz., 

 stratigraphically, geographically and chemically." Trans. Am. Inst. M. E. Troy 

 Meeting, Oct. 1883. 



