White Limestones of Sussex County, JV. -/. — JVuson. 163 
in studying the limestone area in northern New Jersey, and 
the facts observed in the field led to serious doubts as to the 
correctness of the views previously held. This led to a de- 
tailed investigation of the area, especially in the vicinity of 
Franklin Furnace, which resulted in accumulating a series of 
related facts which prove conclusively the post-Archaean age 
of all of the limestones and quartzites in this region. These 
results were published by the writer in 1890,* but owing to 
the great length of time during which the former view had 
generally been held, and during which it had come to be con- 
sidered as a positive fact, these conclusions met with a tardy 
acceptance and are still doubted by some. Additional papers 
on this subject have been published by the writer;! and re- 
cently Kemp and Hollick, in an excellent paper* on the north- 
ern portion of the same area extending into New York state, 
reach the same conclusions as a result of their very careful 
work in the field and in the laboratory. It therefore seems to 
be an appropriate time for a concise summary of the facts 
which prove that the white limestones of Sussex county, N. 
J., including the deposits of franklinite and zinc ores, are of 
Cambrian age. This it is proposed to do by establishing the 
truth of the following statements: 
1. The white limestones are continuous with the blue limestones (now 
accepted as of Cambrian age) and every degree of transition may be 
found between them. 
2. Both have the same dip and strike 
3. Both are conformable with a quartzite also containing Cambrian 
fossils. 
4. Both arc unconformable with the gneiss upon which I hey rest. 
5. Both have in sum total the same chemical composition and are 
magnesian. 
6. The altered crystalline condition of the white limestone is due to 
the intrusion of igneous masses and to regional metamorphism, while 
the blue limestone never contains such igneous injections. 
7. The presence of certain minerals, especially chondrodite, is not in- 
dical ive of geological aye. 
1. The continuity. In crossing the strike of the limestones 
from the white to the blue, where there is a continuous expos- 
ure, one of two things is always to be observed: either (") 
*Ann. Rep. State Geol. of N. J., 1890. 
(•Americas Geologist, April. 1801; s.pi . 1891 . March. 1894. Trans 
Am. Inst. .Min. En., Feb.. 1894. 
I A no. N. V. Acad. Sci., vol. vii. 1893, 
