Bihliography. 185 



wardly, bearing before it immense masses of debris, and depositing 

 them far to the south of their original places. Around the city of 

 Providence and on the island of Rhode Island are found bowlders of 

 porphyritic iron ore, that have been transported many miles from their 

 native bed in the iron mine hill in Cumberland ; the bowlders near 

 Providence being two or three feet in diameter, decreasing in size as 

 we go south, until they are not larger than a cannon ball. "The width 

 of the line of deposition is about eight or ten miles." None of the 

 bowlders of the Cumberland iron are found to the north of the iron 

 mine hill, while to the south they are so abundantly scattered in the 

 soil that most of the fences are constructed of them. Diluvial 

 scratches and striae are very numerous, and the direction is generally 

 N. 5° E., S. 5° W. — the variation being about 7° 30' W. — so that the 

 direction is very nearly in the meridional line, thus indicating the 

 course of the ancient current which has polished the hard rocks more 

 or less. 



Dr. Jackson carefully collected and analyzed the useful minerals, 

 and their extent was measured or estimated with great care. The ex- 

 ploration for coal in Cumberland has been abandoned, after penetra- 

 ting twenty eight feet through loose materials, and the entire shaft 

 was sixty seven feet deep. 



Diamond hill is composed of quartz rock, partially agatized, and 

 containing jasper, druses of quartz crystals, phosphate of lime, and 

 veins of red haematite iron ore, and is much visited by mineralogists 

 on account of the beautiful specimens of agate, chalcedony, and quartz 

 crystals, that abound in it, " and which are especially beautiful at its 

 summit, where they can be easily broken off from the huge detached 

 masses of rock," as we had occasion many years ago to observe. 



The iron mine hill is a mass of porphyritic magnetic iron ore, 462 

 feet in length, 132 feet in width, and 104 feet in height, above the ad- 

 joining meadow; containing, at the rate of 240^ lbs. to the cubic foot, 

 6,342,336 lbs., and composed of oxides of iron 40 per cent., silex 23, 

 titanium 15, alumina 13.10, magnesia 4, manganese 2. This hill of 

 ore seems to have been protruded through the granite and gneiss con- 

 temporaneously with the serpentine veins in the vicinity. Its origin 

 would appear to have been the same with that of the iron mines of 

 Missouri. 



Near Sneech pond is a remarkable bed of manganese, whose com- 

 position is silex 26.4, protoxide of iron 35.9, protoxide of manganese 

 32.8, carbonic acid 5.2. 



Beacon hill, in Cumberland, so called from its displaying a beacon 

 light in the American revolution, is composed of granite. 

 Vol. XL, No. 1.— Oct.-Dec. 1840. 24 



