Petrography of SJicfford Mountain. — Dresser. 213 
ing aside quantitative calculations of the output of these 
two rocks, or considering them equal, which may reasonably 
be done, the chemical character of the primary magma was 
about that of the pulaskyte. 
For convenience in reference their chemrcal anatyses are 
repeated with the mean between the essexyte and the nord- 
markyte. 
I 
II 
III 
IV 
SiOs 
53.15 
65.43 
59.96 
59.290 
TiOs 
1.52 
.16 
.66 
.840 
AI2O3 
17.64 
16.96 
19.12 
17.300 
FeoOs 
3.10 
1.55 
1.85 
2.-325 
FeO 
4.65 
1.53 
1.73 
3.090 
MnO 
.46 
.40 
.49 
.430 
CaO 
5.66 
1.36 
2.24 
. 3.510 
BaO 
.13 
none 
.12 
.065 
MgO 
2.94 -- 
.22 
.65 
1.580 
KoO 
3.10 
5 36 
4.91 
4.230 
NasO 
5.00 
5.95 
6.98 
5 475 
P2O5 
.65 
.02 
.14 
.335 
CO2 
.39 
none 
none 
.195 
SO3 
.28 
.06 
.08 
.170 
CI 
.07 
.04 
.14 
.055 
H2O 
1.10 
.82 
1.10 
.960 
99.86 99.84 100.17 99.850 
I. Essexyte. 
II. Nordmarkyte. 
III. Pulaskyte. 
IV. Mean between Essexyte and Nordmarkyte. 
In order of intrusion the successive chemical variations 
have accordingly been : 
1. Alore basic than the pulaskyte magma = essexyte. 
2. More acidic than the pulaskyte magma = nordmarkyte. 
3. The normal, or pulaskyte 
4. More basic =: Camptonyke dykes. 
5. More acidic = Bostonyte dykes. 
