MARYLAND GEOLOGICAL SURVEY 203 



picion, that the Port Deposit granite will not withstand atmospheric 

 agencies for any great period of time. This deceptive appearance 

 arises from the fact that the crystalline rocks southward from Phila- 

 delphia have not been scoured and cleaned by the action of glacial 

 ice as in more northern latitudes. Thus the overlying waste repre- 

 sents the decomposed products of several geological epochs. 



The number of quarries about Port Deposit has never been very 

 large, although now and then attempts have been made to establish 

 rivals to the large quarries which are at present operated by the 

 McClenahan Granite Company. 



FRENCHTOWN. 



At the eastern end of the high suspension bridge of the Baltimore 

 and Ohio railroad over the Susquehanna river there is a small quarry 

 opened in a schistose granite, which is very similar to that worked 

 at Port Deposit. This quarry was probably first opened during the 

 construction of the railroad bridge, 1 but nothing of economic import- 

 ance was done here until the firm of Wm. Gray and Sons of Phila- 

 delphia became interested in 1894. At this time the capital invested 

 was about $8,000, a sum which represents but part of the present 

 investments. No work of any particular moment was done by the 

 present owners until the autumn of 1896, when the receipt of some 

 moderate sized contracts encouraged the further opening of the 

 quarry, which now bids fair to establish a well organized industry at 

 Frenchtown. The only buildings of importance which have been 

 built from the Frenchtown rock are the Cold Storage Warehouse and 

 an extension of the Baldwin Locomotive Works in Philadelphia. 



The location of the quarry topographically and geologically is simi- 

 lar to that of the quarries at Port Deposit. The ground is stripped 

 upon the side of a hill and the quarry has worked down to the level 

 of the low bench, along which runs the Port Deposit and Columbia 

 Railroad. The jointing of the rock is similar to that at Port Deposit, 

 and there are here three prominent sets of joints intersecting approxi- 

 mately at right angles. Members of the same series are so placed 



1 The main piers of the bridge are built of Port Deposit granite. 



