Basic Rocks of Northeastern Maryland. — Leonard. 171 
FeO 2.58 3.24 6.12 5.83 8.61 7.29 7.92 3.43 
NiO, CoO none 0.01 0.01 0.01 0.03 0.71 
MnO 0.10 C.18 0.15 28 0.18 0.22 0.09 
CaO 3.74 4.89 7.39 8.50 11.68 11.42 13.12 
SrO trace trace trace none none none 
BaO 0.08 trace trace none none none 
MgO 0.50 2.19 2.33 4.35 5.01 10.05 20.78 39.02 
K2O 1.48 2.05 1.01 1.08 0.15 0.05 0.07 
NaoO 2.81 2.65 2.11 1.83 1.24 0.51 0.11 
LioO trace trace trace trace trace trace 
^^^ii^^^^ ! 106 0.16 0.21 0.18 0.11 0.10 0.14] 
105 C J (. 12.10 
H2O a^bovc I -j^ QQ ^21 2.01 1.90 0.57 0.87J 
P2O5 0.10 0.37 0.21 0.52 trace trace 
FeS2 trace 0.03 0.25 0.11 0.03 
CO2 none none none 0.25 0.10 
CI undet. undet. undet. undet. undet 
Fe304 
Fl undet. undet. undet. undet. undet. 3.02 
99.74 100.32 100.07 100.17 100.42 99.98 100.47 100.00 
Sp. gr 2.89 2.90 3.03 2.98 3.34 2.66 
I. Granite from the Port Deposit quarries. 
II. Biotite-granite from the railroad cut at Rowlandsville. 
III. Quartz-mica-hornblende-dioryte. Near the foundry on Stone 
run. 
IV. A more basic variety of the same. Porter Bridge on Octoraro 
creek. 
V. Hornblende-dioryte poor in quartz. Three-quarters of a mile 
northwest of Rising Sun. 
VI. Noryte. One mile west of Oak Grove schoolhouse. 
VII. Websteryte. Oakwood. 
VIII. Serpentine. Broad creek quarry in northeastern Harford county. 
Analyses I and II are taken from G. P. Grimsley's paper 
on the granites of Cecil county.* I. was made by Mr. William 
Bromwell in the chemical laboratory of the Johns Hopkins 
University; II. -VII. were made by W. F. Hillebrand, of the 
United States Geological Survey, and A'll. is by F. A. Genth. 
It will be observed that the rocks of the series range in com- 
position from that of a granite to a pyroxenyte and serpentine. 
A comparison of these analyses shows that as the silica de- 
creases there is an increase in the magnesia, the latter constitu- 
ent being especially characteristic for rocks of this character. 
The alumina increases from the most acid member of the series 
♦Jour. Cincinnati "Soc. Nat. Hist.. Vol. 17. pp. 59-67; 78-114. Cincin- 
nati, 1894. 
