170 
CONTRIBUTIONS TO THE GEOLOGY OF MAINE. 
[BULL. 165. 
measure. No other mineral rises above the groundmass, and the 
whole section otherwise shows a uniform aggregate of feldspar laths, 
which are stout rectangular to long irregular in shape, and among 
them are embedded more or less rounded grains of quite fresh, color- 
less pyroxene. The structure of the groundmass is therefore not the 
ordinary ophitic type common to diabases, but corresponds to the 
granulitic type of Judd. 1 The feldspar mierolites show twinning, but 
could not be satisfactorily measured, and their basic character is calcu- 
lated from the analysis. A quantity of the rock powder was tested for 
nepheline, but it yielded no gelatinous silica. 
Analysis. — The following analysis (I) of a specimen from the largest 
dike was made by Dr. W. F. Hillebrand, of the United States Geo- 
logical Survey. 
Analyses of diabase. 
Constituent. 
I. 
II. 
in. 
IV. 
V. 
Si0 2 
Per cent. 
49.64 
15. 07 
1.66 
8.82 
5. 43 
7.23 
4.19 
.89 
.45 
2.81 
2.32 
None. 
Trace. 
.04 
Trace. 
.25 
.02 
.05 
Trace. 
.29 
.32 
? 
? 
r (-43S) 
I .79 
Per cent. 
49.27 
15.87 
1.93 
10.17 
5.90 
7.46 
3.45 
.74 
\ 3. 92 
Per cent. 
52.37 
15.06 
2.34 
9. 82 
5.38 
7.33 
4.04 
.92 
2.24 
.21 
Per cent. 
51.80 
14. 21 
3.55 
8.26 
7.63 
10.68 
2.15 
.39 
.63 
Per cent. 
49. 25 
16.97 
| 15.21 
3.00 
7.17 
4.91 
2.01 
.30 
1.41 
Al.,0, 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 — 105 
H 2 O + 105..1 
Ti0 2 
Zr0 2 . 
Cr.,0, 
V.,0, ' 
NiO.. 
MnO 
.35 
.32 
.42 
Trace. 
BaO 
SrO 
Li 2 
P 2 5 
.14 
.76 
Trace. 
CO., 
1.12 
CI 
Fl 
FeS 2 
Total 
100. 27 
100.18 
100. 03 
99.86 
100.99 
1 Judd, Gabbros, etc., in Scotland and Ireland; Quart. Jour, Qeol. Soc, Vol, XLII, 1886, 
