620 
NATURE 
[JANUARY 29, 1914 
associated rocks by photographs taken in the tunnels 
of the mines. 
Mining districts in a hitherto unmapped region in 
Elko County, Nevada, are described by F. C. Schrader 
in Bull. 497 (1912). The gold ores of Jarbridge, which 
are here beautifully illustrated, are attributed (p. 63) 
to the rise of waters at a high temperature, follow- 
ing on the eruption of Miocene rhyolites. The metallic 
ores are sometimes referred to as ‘‘mineral’’ and 
sometimes as ‘‘ metal values,” terms which seem out 
of place in a scientific treatise. A. Knopf (Bull. 504, 
1912) describes briefly the Sitka mining district, 
Alaska, where gold in quartz reefs and gypsum are 
the valuable materials. The gold, as well as certain 
copper ores, is regarded (p. 17) as connected with the 
uprise of intrusive diorite. 
F. H. Moffit and S. R. Capps (Bull. 448, 1911) show 
very interestingly how slowly moving rock-glaciers 
succeed true glaciers where warmer conditions now 
prevail in Alaska. Snow-slides, of course, assist in 
Fic. 2.—Diabase dyke in fault-plane in Cainozoic (Chickaloon Coal-measure) strata, Castle Mountain, Alaska. 
From Bull. soo, U.S. Geol. Survey. 
moving the material, but rock undoubtedly now 
predominates in the flow. The illustration here repro- 
duced (Fig. 1) is one of several instructive plates. Gold 
is now the main product of the Nizina district, though 
chalcosine and native copper offer attractions. 
Alaska claims continued notice. Bulletin 485, by 
G. C. Martin and F. J. Katz, describes the Iliamna 
region, where Triassic cherts are associated, as seems 
almost inevitable, with ‘‘green rocks” of yoleanic 
origin. The same authors, in Bulletin 500, deal with 
the coal-bearing Lower Matanuska Valley, above 
Cook Inlet in lat. 62°, The coals are-in Cainozoic 
strata, and are probably of Eocene age (p. 52). Basic 
lavas have intruded through these beds, and form 
conspicuous features on the bare hillsides (Fig. 2). 
The development of Alaskan areas is also seen in 
Bulletins 449, 498, and 502. In Bulletin 467 (1911), 
W. W. Attwood deals with the coals and possible gold 
ores of the Alaska Peninsula, and furnishes several very 
interesting photographs of the coast. Bulletin 520, by 
a number of authors, brings our knowledge of the 
NO. ‘2309, VOL. 92] 
mineral resources of Alaska up to date. The review 
(pp. 45-88) of the possibilities of railway construction 
between the Pacific coast and the interior is of special 
interest, and the sketch-map provided, with ‘coal 
reported’ marked on the seaboard of the north-east 
passage, is-the sort of thing to captivate a Frobisher 
or a Cabot. The Cainozoic coal of the Bonnifield 
region is reported on in Bulletin 501, which also 
contains interesting notes on _ glaciation. Other 
economic papers on Alaska have been already noticed 
in Nature (vol. xc., 1913, p. 659). 
Professional Paper 71 (1912), constituting a large 
memoir on the stratigraphy of North America, by Bailey 
Willis, and accompanied by a coloured geological 
map of North America, on the scale of 1: 5,000,000, is 
of such wide educational importance that it has 
already received special mention (Natur, vol. xci., 
p. 93). Changes in nomenclature are somewhat rapid 
in the United States, and, since this great index was 
published, C. D. Walcott (Smithsonian Miscell. Col- 
lections, vol. Ivii., No. 7o, 
September, 1912) gives 
reasons for withdrawing his 
terms Georgian for Lower 
Cambrian and Saratogian for 
Upper Cambrian, and replac- 
ing them by Waucoban and 
St. Croixan respectively. 
Both these new names offer 
puzzles in pronunciation for 
the stranger. . ‘St. Croixan” 
was first published by Wal- 
cott as a stratigraphical term 
in the preceding number of 
the Collections, p. 257, in 
which some very interesting 
tracks of Upper Cambrian 
trilobites are illustrated. 
Four of the recent Profes- 
sional Papers deal with 
western districts. No. 70, by 
A. H. Brooks, describes the 
difficult survey of the Mount 
McKinley region in Alaska 
in 1902, where almost all the 
geological systems are repre- 
sented. From the historical 
summary on pp. 29-32, it 
seems doubtful if any ex- 
plorers had reached the sum- 
mit of Mount McKinley 
(20,300 ft.) by the close of 
tg10. The decay of the up- 
land is shown’ by the 
immense areas of post-Pliocene detritus recorded on 
the preliminary geological map. The maps add con- 
siderably to our knowledge of the topography of the 
divide between Cook Inlet and the Yukon system. 
In No. 73 W. Lindgren discusses the Tertiary 
gravels of the Sierra Nevada of California, well 
known_as the scene of hydraulic gold-mining. The 
Great Valley of California has received detritus from 
the rising continental land ever since the opening of 
Cretaceous times, the shore-gravels becoming purely 
fluviatile during the Pliocene period (p. 28). J. M. 
Boutwell (p. 54) has had an opportunity of resifting 
the first-hand evidence as to the antiquity of the 
Calaveras skull, which at one time obtained a cele- 
brity akin to that of the bones—also from Calaveras 
—which ‘‘were found within a tunnel near the tene- 
ment of Jones.” 
Professional Paper 74, by W. H. Weed, describes 
the Butte District, Montana, and is bound 
in cloth, a mode of presentation which makes 
it far more corvenient than most of these large and 
ee 
