242 PROCEEDINGS OF THE ACADEMY OF [1880. 



pentine into quartz, very strikingly shown near a quarry of 

 serpentine rock on tiie farm of John Stacker, about a tlaird of a 

 mile N. W. of Radnor Station, P. R. R., Delaware Co., Pa. 



The outcrop of the serpentine is accompanied by a rock, locally 

 called " Ironstone," which however is a cellular quartz, generally 

 stained by oxide of iron. It occurs as loose masses in the soil, 

 generally of small size, but sometimes of over a hundred pounds 

 weight ; the cavities are frequently lined with drusy (piartz. This 

 rock is of common occurrence in connection with serpentine belts, 

 but that it has arisen from a decomposition of the serpentine, 

 has, he believed, not been observed elsewhere. On the south side of 

 Stacker's quarry a few feet below the original surface of the ground, 

 is a bed of soft serpentine much cracked ; a foot or two above, 

 these cracks are found lined with chalcedonic quartz, of paper-like 

 thinness ; above, the quartz thickens, the serpentine becomes more 

 and more decomposed, until near the surface the quartz onl3^ re- 

 mains, with the cavities empty, or filled with what appears to be 

 oxide of iron with alumina. It is an instance of pseudomorphism 

 on a large scale, the progress of which can be traced, step by 

 step, from almost unaltered serpentine to almost pure quartz. 



Well-water. — In this connection the analysis of the water of a 

 well 50 feet deep in the serpentine, about 400 hundred feet from 

 the quarry, but under the same quartz outcrop, may not be 

 xniinteresting. 



In a gallon of 70,000 grains, — mean of three analj^ses : — 



Grains, per Gall. Parts in 1,000,000. 



.5.665 80.8 



A New Locality for Siderite. — Mr. H. C. Lewis announced 

 Dunbar, Faj'ette Co., Penna., as a new locality for Siderite. It 

 there occurs in finely crj'stallized specimens in the interior of 

 nodules of amorphous Siderite. These nodules or concretions 

 are of various and often curious shapes. Doubly terminated 

 limpid quartz crystals and minute but ver}^ perfect crystals of 

 Pyrite are associated with those of Siderite, forming handsome 

 specimens. 



Magnetite Markings in Muscovite. — Mr. Lewis made some 

 remarks on the markings in the Muscovite of Brandy wine 

 Hundred, Delaware. He proved that these markings were Mag 

 netite, by exhibiting their attractability by the magnet, and said 



