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phate of Lime from Hurdstown, N. J. These deposits are 

 of great value for the manufacture of porcelain and phos- 

 phorus, and especially for agricultural purposes. 



Mr. Alger presented some fine minerals from Grafton, 

 N. H., a piece of Beryl, {aqua marina,) from a crystal 

 weighing two and a half tons, occurring in a bed of quartz, 

 in a gneiss formation, interspersed with beds of white fel- 

 spar containing thirteen per cent, of potash. Specimens 

 of the quartz and felspar, of trapezohedral garnet, and of 

 copper pyrites with garnet, were also presented ; and sheets 

 of prismatic mica containing compressed crystals of garnet 

 and tourmaline. Mr. Alger alluded to another magnificent 

 crystal of beryl, on land belonging to him in that locality, 

 weighing over five tons, and measuring two feet eight inches 

 in its greatest diameter, the largest crystal of any sub- 

 stance ever described. 



Dr. C. T. Jackson drew the attention of the Society to 

 the compressed crystals of tourmaline, as they were com- 

 pressed in the very direction necessary for a perfect polari- 

 zation apparatus, for which purpose, in the microscope, 

 they were admirably adapted and were considerably used. 

 Crystals of quartz were also found of exceeding thinness, 

 like plates of glass. This interpenetration of the minerals in- 

 dicates that they were once all plastic, and had crystallized 

 simultaneously. Sir C. Lyell inquired, if these crystals had 

 at first their natural form, and, if so, how they were after- 

 wards compressed. Dr. Jackson replied, that they must 

 have either assumed this form while in a plastic state, or 

 have been thus flattened by aggregation of particles at the 

 sides, where there was least pressure. 



Dr. C. T. Jackson gave a detailed account of the geology 

 and mineralogy of the mine of red oxide of zinc in Sussex 

 County, at Franklin, N. J., and described the various pro- 

 cesses employed in the manufacture of the white oxide, 

 or zinc paint. 



