1883.] NATURAL SCIENCES OF PHILADELPHIA. 241 



The following, received tlirongli the Mineralogical and Geo- 

 logical Section, was also ordered to be printed : — 



NOTES ON THE GE0L03Y OF CHESTER VALLEY AND VICINITY. 

 BY THEO. T>. RAND. 



In a recent reply to criticisms by Dr. Frazer of statements in , 

 regard to the serpentine on, ci'ops, etc., described in Vol. C 6 of 

 the Second Geol. Survej' of Pennsylvania, I stated that I would 

 exhibit before the Academy specimens from the outcrops in 

 question. Dr. Frazer stated (Am. Nat., Sept., 1883, p. 525) : "At 

 the same time it must not be forgotten that what one observer 

 would regard as evidence of a serpentine outcrop, another would 

 not. * * * 2t would seem to be only thus that such wide 

 divergencies as are here noted are explicable." 



I have here specimens from the serpentine outcrops which I 

 had stated were overlooked in C 6, and specimens from two out- 

 crops represented in C 6 to be serpentine, which I questioned. I 

 think they speak for themselves, but if au}^ member has any doubt 

 or question, I trust the matter may be so discussed as to elicit 

 the truth. 



I desire also to call attention to certain statements in the survej'' 

 of Chester Co., C 4, recently published, statements with which 

 my observations do not agree. 



1. The non-existence of Potsdam sandstone, or a sandstone very 

 closely resembling Potsdam, south of Chester Valle}'. 



C 4 says, pp. 34, L24 : " The quartzite failed altogether on the 

 southern side of the valley.'' " No Potsdam sandstone has been 

 detected anywhere along the southern edge of the limestone 

 area." 



I have here specimens from Samuel Tyson's, on north flank of 

 South Valle}'^ Hill, near King of Prussia station, Chester Valley, 

 land from three localities in Cream Vallc}'^ (between the South 

 Valley Hill and the Radnor syenitic gneiss range), one, on the 

 Brooks farm, about 100 yards west of the line dividing Delaware 

 county from Montgomery and 300 yards northeast of the south- 

 west corner of Upper Merion township ; another, one-half mile 

 west of this, near and south of the limestone on Stacker's place, 

 and the third the Pennsj-lvania Railroad cut northwest of Wayne 

 station, just north of the trap, in which cut Dr. Frazer, p. 283, 



