. Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900--Twenty-First Annual Report of the United States Geological Society. ^ Dr. W. F. Hillebrand, withthe following results: Analysis of rock from smniiiit of Pine Hill, near South Britain, Connecticut. Per cent. Per cent. SiO, 52. 40 .873 MgO TiO^ . Iv,0 40 AI2O, 55 .000 .133 Na.,0 FeA .004 Li.,0 None. FeO 9. 79 « H,0 (belowH.,0 (above 105°) 62 .OKi 105°) NiO Tr. .12 MnO .26 CO, None. CaO .179 ,| ?--- 13 SrO None. Tr. {-) BaO The Levy-Brogger dia
. Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900--Twenty-First Annual Report of the United States Geological Society. ^ Dr. W. F. Hillebrand, withthe following results: Analysis of rock from smniiiit of Pine Hill, near South Britain, Connecticut. Per cent. Per cent. SiO, 52. 40 .873 MgO TiO^ . Iv,0 40 AI2O, 55 .000 .133 Na.,0 FeA .004 Li.,0 None. FeO 9. 79 « H,0 (belowH.,0 (above 105°) 62 .OKi 105°) NiO Tr. .12 MnO .26 CO, None. CaO .179 ,| ?--- 13 SrO None. Tr. {-) BaO The Levy-Brogger diagram of this analysis is shown in tig. Si. The rock of the upper layers of this sheet of is not only moreopen textured and more weathered than that which has just beendescribed from the lower zone, but other differences are Fig. 2-1.—Brilgger diagram to show the composition of the main basalt. Blebs of black rock glass or tachylite several millimeters in diametermay be observed in the rock from some localities, as, for example, atthe road corner southwest of the Oak Tree House at Southbury, andin the road of the Kaghuid area. These glassy blebs turnbrown and gray on strong ignition, l)ut do not fuse. On examination in microscopic sections the texture of this rock isseen to be general!} finer and the feldspar laths of the second genera-tion more numerous and more acicular than in the rock from the lowerzone, a felty texture being the residt. The feldspars of the first generation are much altered, in many a central core having the shape of theentire crystal being occupied ])v green uralitic and chloritic material. oNot corrected for pyrrhotite nor for VoOj, if present. b Pyrrhotite calculated as pyrite. 76 NEWARK SYSTEM OF POMPERAUG VALLEY, CONN. The peripheral zone of these phenocrysts, and t
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