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from their position belong unmistakably to distinct systems. 
In grouping the rocks as below I have, therefore, but followed 
the notes of Professor Crosby. 
FIRST SERIES. 
Dike 3. —Rock finely porphyritic with greenish feldspars ; 
macroscopic pyrite; color greenish. This is a very typical 
diabase, with irregular and sharply wedge-shaped augites, lath- 
shaped plagioclases and numerous grains of iron oxide. The 
augites are undergoing a chloritic alteration ; and the feldspars 
аге во badly kaolinized that the twinning strie are completely 
obscured. The iron oxides are in part magnetite and in part 
show the whitish alteration characteristic of menaccanite. Pyrite 
occurs in brassy yellow irregular clumps. Small, irregular, 
brown and strongly dichroic scales attached to the altered au- 
gites are evidently secondary hornblende. The porphyritic 
feldspars are so thoroughly kaolinized that nothing whatever can 
be learned of their original nature. Scattering grains of epi- 
dote, kaolin, opacite and viridite complete the list of recognizable 
constituents. 
Dike 5.— Very fine grained and compact; macroscopic 
Pyrite ; color greenish. This presents no distinctions in any 
Way essential. oth augites and feldspars are more decom- 
posed ; and there is a corresponding increase in the propor- 
tions of epidote, viridite, calcite, ete. A few small apatites 
appear in this slide. 
Dike 22.— Medium fine in texture but distinctly crystalline, 
and color greenish. This differs from the preceding only 
in being slightly coarser in texture. The iron oxides, judged 
by their irregular forms and whitish decomposition products are 
largely titaniferous. 
Dike 25.— Very fine-grained and compact; a few greenish 
feldspars " : 
Ispars porphyritically developed; and color greenish. The 
