1883.] NATURAL SCIENCES OF PHILADELPHIA. 243 



this possibly be construed to be more than that converging lines 

 must meet? 



4. P. 84 : " The southern oflge of the South Valley Hill belt of talc 

 mica slates is defined upon the map b}^ a chain of dots and stripes 

 of two colors, representing outcrops of serpentine, and outcrops 

 of crj'stalline limestone. Were these outcrops ranged in more 

 than one line, the task of explaining their appearance would be 

 far easier. * * * It looks as if the serpentine might be a 

 subsequent modification of the limestone. No case is recorded 

 of the serpentine and crystalline limestone of our line being seen 

 in contact." I do not dispute the last sentence, but the speci- 

 mens show a variety of rocks in Radnor between the serpentine 

 and limestone, which there occupy, as shown on my map, approxi- 

 matively parallel positions a thousand feet and more apart — con- 

 clusive evidence that in that part of the line at least they have no 

 possible connection. 



The map in C 4 shows, as clearly as possible on so small a scale, 

 that the line of limestone outcrops is north of the line of serpen- 

 tine outcrops; all the limestone outcrops shown are west of the 

 west end of the serpentine outcrop-. 



There is some evidence tiiat tiiis serpentine belt is an altered 

 enstatite. 



T show a specimen from near Devon Inn, Easttown township, 

 whicli seems almost certainly' altered enstatite ; and specimens of 

 undoubted enstatite from the Lafayette belt, the ser|)entine of 

 which so strongly resembles that of the Radnor belt, both in 

 structure and accompanying minerals. 



5. The statement, p. 282 : '' The east end of this (the Easttown 

 and Williamstovvn serpentine belt) continues much further into 

 Montgomery county." 



This is certainly an error, caused, perhaps, b}' confusing this 

 belt with that north of it, as was done in C 6. This belt ceases 

 abruptly on the land of Hon. D. J. Morell, in Radnor township, 

 Delaware county, where the contour suggests the possibility of a 

 fault. The lithological difference of the belts may be seen b}'^ the 

 'specimens produced. The northerly belt begins on the land of 

 Brooke, about one-fourth mile northwest of the easterly end of the 

 Radnor outcrop, east of Radnor station. 



5. On p. 138, a Mr. Morely is quoted, without comment, as 

 stating that the Conshohocken trap follows the summit of Bethel 



