96 PROCEEDINGS OF THE ACADEMY OF [1890. 



One mass, five or six feet long, was nearly pure talc schist at one 

 end, while at the other, much quartz remained and to the eye the 

 rock looked like unaltered Laurentian.^ 



Northwestward of this quarry all visible rocks are Laurentian for 

 about two hundred feet to a quarry of similar talcose i-ock quarried 

 on a slope up and into the hill somewhat over one hundred feet. 

 The quai-ry when visited had not been wrought for some time and 

 large masses of the south wall had fallen in. These masses were 

 Laurentian, the north wall was the same. Some of the fallen 

 masses showed a change from syenite, or more strictly granulite, into 

 steatite. 



Northwestward from this, the Laurentian was apparent for three 

 hundred to four hundred feet, where another and much larger out- 

 crop of steatite is quarried. The contacts here were not visible. 



Northwestward from this followed two hundred to three hundred 

 feet of Laurentian including one very prominent overhanging cliff 

 and then another exposure of steatite, in which was a considerable 

 quarry. Northwestward of this the Laurentian again appeared. 

 The dips were not clear but from what could be observed are not far 

 from vertical. The hill adjacent to these quarries probably exceeds 

 four hundred feet in height. It seems incredible that these four 

 outcrops are an overlying stratum in three successive compressed 

 synclinals. It is much more rational to conclude that they are in- 

 terbedded in the Laurentian. 



On the Bushkill, which cuts the same hill about one and a half 

 miles from the Delaware the outcrop is not so distinct but here also 

 the steatite and serpentine are between walls of Laurentian, and in 

 these hard unaltered Laurentian rocks may occasionally be found 

 masses of rock apparently changing into steatite and serpentine. 



Dr. Hunt in his INIineral Physiology and Physiography seems to 

 regard the change of gneiss into serpentine or steatite as almost 

 an absurdity, and before visiting this locality I should have 

 agreed with him, but here we certainly have Laurentian gneiss 

 changing into steatite, or steatite changing into Laurentian gneiss. 



Considering the Delaware, Chester and Montgomery county ser- 

 pentines in detail we find as follows : 



At the northeastern end of the Raclnor-West Chester belt 

 there is Laurentian on the strike line, and on both sides of the 

 belt, but. the exposure does not show the walls in place. About a 



1 Apiece of this is in the collection of the Academy. 



