41 
are so muddied by decomposition products as to be scarcely 
recognizable. A few augite particles are still unchanged. No 
essential differences. 
Dike 9.—Like 10, but a trifle coarser in texture. The hand 
specimen shows small black segregations of what is apparently 
hornblende ; but these do not appear in the section. 
Dike 8.—Very compact, with no macroscopic constituents ; 
color, dark gray, nearly black. The sample was taken from the 
edge of the dike at the contact with melaphyr. It offers no 
characters worthy of note to distinguish it from 9. 
Dike 7.—Coarse and distinctly crystalline; color, greenish. 
This is one of the coarsest rocks of the series. Under the micro- 
scope it shows large plates of reddish brown augites, often en- 
closing the lath-shaped plagioclases and producing the typical 
ophitie structure. The feldspars here are sufficiently fresh to 
show twinning striæ. [топ oxide is very abundant, in large 
grains, with much pyrite and some apatite. The section shows to 
excellent advantage the various stages of augitic alteration into 
viridite. The rock resembles 22 more closely than any of the 
preceding. 
Dike 26.— Very fine, compact and homogeneous. Color, dark 
gray, somewhat greenish. This rock is greatly altered ; being 
essentially an aggregate of viridite scales, and fibres and gran- 
ules of iron oxide, interspersed with epidote. A few cavities or 
pseudo-amygdules occur, the cavity wall being lined with vir- 
idite, while the central portion is occupied by calcite. The feld- 
spars are very obscure; and the iron oxide in part titaniferous. 
Dike 29.— l'exture of medium fineness, with large segregations 
of black hornblende. Color, uneven, black, greenish and yellow- 
ish green; the last tint being due to epidote veins. The augite 
is greatly altered; and there is much viridite and epidote, the 
latter in scattered granules and veins, The feldspars are ob- 
