Dikes near Kennehunkport^ Maitie. — Kemp. 135 
striking, but a careful search failed to discover any cassiterite. 
These veins were undoubtedly occasioned by the active circu- 
lation due to the intrusion of the granite, accompanied per- 
haps by boracic and fluoric fumerole action. 
The remaining dikes are in most cases forms of the olivine- 
diabase t3"pe, but of a somewhat varying structure, owing in 
part at least to their varying width. They are most frequently 
holocrystalline, j^et porphyritic ones arc also present, and the 
ground mass is somewhat glass\\ I have selected as the type, 
the holocr3'^stalline form, and will consider the others as struc- 
tural deviations from it. This is shown in dikes 11, 13, 15, 17, 
19, 21, 22, 23, 24, 29, 30, 34, 35, 48, 51, 55, 56, 60, 61, 63, 67, 75, 
76, 77, 78, 80, 81, 82, 83, 86, 87, 89, 91. Of these 48 and 56 are 
the best. Thej" consist of augite, plagioclase, olivine, and 
magnetite as essentials. With these is found very often (dikes 
11, 22, 34, 48, 55, 56, 60, 63, 81) brown basaltic hornblende, 
both as an undoubted idiomorphic component, and as an 
equally indubitable paramorph from the augite. Biotite was 
noted in but three, and then in a very subordinate capacity. 
Dike 91 alone contains any great amount. Pyrite also is 
present. 
The augite is of the usual rose tint, and resembles very 
closely the augite of certain New Jersey triassic diabases and 
the Campton Falls olivine diabase of Hawes. No pleochroism 
could be detected. It shows the usual cleavages, but often in 
addition other partings parallel with the pinacoids. It occurs 
in two generations : the older and rather exceptional shows 
the eight-sided cross-section of ooP, ooPoo and ooPra and is 1-2 
mm. across ; the latter is most frequently seen, and appears 
as irregular masses, about 0.2-0.3 X 0. 5 m m., forming the 
largest part of the rock. Twinninig is rare, but sometimes is 
often repeated on the same crystal. In dike 75 twins were 
noted parallel with ooPm and twenty differently oriented layers 
were counted within 0.5 m m. The augite frequently alters to 
a feebly pleochroic chlorite. 
The plagioclase is in the usual lath-shaped crystals of quite 
irregular outline, being in the more coarsely crystalline speci- 
mens stocky and broad, — in the more finely crystalline, in 
very slender rods. It falls an easy prey to alteration, which 
has often proceeded so far as to reduce the feldspar to a kaol- 
inized mass. Sometimes a dark green nucleus a]>pears with- 
