Professor Emerson on HalVs Geological Collections. 571 



auother, aud inclosing large crystals of all the other constituents, especially 

 garnet and hornblende. Often several garnets or large crystals of hornblende 

 lie wholly or partly inclosed in a single mica crystal, or, in the case of the horn- 

 blende, run entirely across and divide the crystal into several parts. 



Besides these larger inclosures, there occur in great numbers long tlat micro- 

 lites, irregularly arranged, and which seem to be themselves of mi(iaceous nature, 

 long fine apatite needles, and rarely grains of magnetite or blood-red scales of 

 hematite. The blood-red color occurs where the cleavage lines are lacking, and 

 the P face is parallel to the section i)lane, while crystals cut i^arallel to the 

 principal axis, and showing strongly the cleavage lines, are light brownish yel- 

 low. In the latter case the mineral is strongly dichroic. The mineral is remark- 

 ably fresh and clear in appearance, but is bordered by blackish-green fibrous 

 viridite. 



The hornblende occurs in groups of elongated crystals, often fibrous and 

 brush-like at their ends. It is mostly grass green, sometimes grass green and 

 smoke brown at one end aud colorless at the other. It accompanies the rubellan, 

 but is less abundant. 



A blackish to grayish-green fibrous viridite surrounds many of the garnets, 

 and is accumulated abundantly in the neighborhood of the rubellan and horn- 

 blende, from which one would not easily distinguish it if it were not for its slight 

 absorption. 



Several small portions of quartz and very rarely a grain of magnetite com- 

 plete the list of the minerals observed. 



102. Trap-granulite. 



Not to be distinguished microscopically from the preceding rock, except in 

 containing finely-disseminated pyrite. 



Thin sections show the garnets to be more decomposed, so that there is no 

 clear rim left ; also the smaller garnets inclosed in the larger are much decom- 

 posed. In the mica, which is exactly like that in the foregoing, very many small, 

 perfectly clear, hexagonal cross-sections of apatite occur. Single plates of diallage 

 occur. The section contains aggregations of hornblende, grass green or smoke 

 browu at one end and colorless at the other, x)rojecting into calcite, which fills 

 free spaces in the mica, and is transparent, shoAving the cleavage sharply. With 

 the hornblende is associated spinel, in separate octahedra, sharply built out and 

 in crystalline groups of a deep cobalt to plum-blue color. 



103. Trap-granulite. 



This is a coarser grained variety, but difiers in no other respect microscopic- 

 ally from No. 101. The garnets, which are the principal ingredient, are distinctly 



