1890.] NATURAL SCIENCES OF PHILADELPHIA. 95 



The ^Media outcrop as delineated on Mr. Hall's map would be 

 nearly continuous on its northwestern edge with the Blue Hill out- 

 crop of the LaFayette belt and on its southwestern with the outcrops 

 southeast of the great Marple outcrop. 



This region is much covered with soil and it may be possible that 

 the two parallel belts exist Avith a schist area between. The re- 

 sults of a careful examination of this outcrop are given hereafter. 



The close connection of one series of these serpentine areas with 

 the margin of the Laurentian being apparent, it would seem that the 

 serpentine at Chestnut Hill on the Delaware, one mile north of 

 Easton should afford us a key, the exposures there being much 

 greater and better than any in Delaware or Chester County. 

 As to these in addition to the quotations above given the Second 

 Oeological Survey states as follows: 



D^ p. 252 (A). "Along the southern escarpment of Chestnut Hill steatite and 

 serpentine extend from the Delaware river to a point about one-half mile west of 

 Bu>hkill creek. The belt has a width of about four hundred feet. 



The serpentine and steatite have generally a greenish color; associated with the 

 steatite massive, coarse quartzose feldspathic rock (granulite) occurs. 



The rock is different in character from the feldspathic rocks of the gneissic belt 

 which form the mass of Chestnut Hill. The feldspathic rock associated with the 

 steatite belongs evidently to the steatite belt.'' 



D^ p. 256 (A). "On the southern slope of Chestnut Hill the Upper Primal 

 slates (hydro-mica slates) appear to have been altered into steatite and serpentine 

 (§251). No limonite occurs on the flanks of Chestnut Hill." 



D^ p. 253. " The steatite and serpentines of this belt appear to be equivalent to 

 the slates overlying the Potsdam sandstone. (Upper Primal Slates.) I see no e.\- 

 planation for the alteration of the hydro-mica slates of the Upper Primal into 

 steatite and serpentine in this locality." (Rogers, p. 94-5.) 



D^ p. 58- " Whether the serpentine and other magnesian minerals found at the 

 base of the formation along the south flank of Chestnut Hill, north of Easton, be- 

 long to this formation" (Chazy and Calciferous Limestone) " or not is still an open 

 question." 



Visits to the locality forced me to a conclusion differing 

 from the above. Passing up the west bank of the Delaware from 

 Easton the limestone appears for a distance of nearly a mile dipping 

 southeastwardly 60° to 80° then 200 feet are under cover, and then 

 a narrow bed of steatite appears. The southeast wall is not visible, 

 the northwest wall is Laurentian and were this the only exposure 

 there might be no reason to question the conclusion that the steatite 

 is an altered slate between the Laurentian and the limestone. 



East of this quarry may be seen Laurentian in place and the con- 

 tact with the talc schist may be seen. 



Immediately north of it is another quarry apparently within the 

 Laurentian, and here may be .seen masses of tons weight having all the 

 appearance of Laurentian but converted in ])art or in whole into tale. 



