124' Tlic American Geologist. August, i899 
Wolff and Brooks have very carefully studied the white limestone 
of New Jersey, on which Mr. F. L. Nason wrote several papers in the 
American Geologist for the years 1891 and 1894 (vols. vii. viii, xiii, 
und xiv). It is found to be of pre-Cambrian age, distinct from the 
Wallkill or blue limestone, which is Cambrian, the two occurring in 
contact at some localities. 
San Clemente island, the southernmost ofif the coast of southern 
California, having a length of nearly twenty-one miles, a maximum 
width of about four miles, and a maximum altitude of 1,964 feet, is 
shown by W. S. T. Smith to be a tilted fault block. The rocks are 
almost entirely lava flows, with intercalated volcanic breccias and ash 
deposits, together regarded as of Miocene age; and the faulting which 
formed this crust-block appears to have taken place near the end of 
Miocene time. During a Pliocene depression, San Clemente stood 
about 1,500 feet lower than now, and conspicuous wave-cut terraces 
at that hight and at many lower levels attest the stages of its reeleva- 
tion. 
Professor Shaler describes the drift formations of the Cape Cod 
peninsula and the neighboring islands on the south and southwest, 
with discussion of their mode of origin, correlation, and the attendant 
epeirogenic movements of the region. The theme is one of great 
interest to glacialists, and the reviewer contributes an article upon it 
in the foregoing pages, based largely on his early examination of the 
same areas. 
Part III, Economic Geology, has six papers, of which the first 
two (by Becker on the gold fields of southern Alaska, and by Spurr 
on the Yukon gold district) have been previously reviewed. Notes of 
the others are as follows. 
The southern coal fields of the Puget Sound basin, described by 
Willis, lie within twenty-five miles eastward of Seattle and Tacoma. 
This Puget formation of faulted, tilted, and folded sandstones, con- 
taining the coal seams, has an exposed thickness of 5,800 feet, and it is 
thought that its total thickness may be 9,000 feet or more. Its age is 
not clearly ascertained by stratigraphic relations, but its fossil leaf 
impressions indicate, according to Knowlton, that it is largely Eocene, 
perhaps continuing to the Miocene. The coal deposits range in quality 
from lignite to anthracite and coke, the lignite having been locally 
thus transformed by the influence of igneous rocks. 
The Judith mountains, occupying an area eighteen miles long and 
three to eight miles wide, with peaks rising about 2,500 feet above the 
plains, which there are 3,500 feet above the sea, had, as shown in the 
paper by Weed and Pirsson, a laccolithic origin near the close of 
Cretaceous time. Following the laccolithic uplifts, ore-bearing solu- 
tions brought gold into the rocks contiguous to the volcanic intru- 
sions, as revealed by subsequent denudation. 
Lindgren describes the geology and mining districts of an area of 
about 13,500 square miles, surrounding Boise in western Idaho. The 
primary gold ores, carrying also silver, are all contained in granitic 
rocks and associated dikes. The granite, of undetermined age. per- 
