395 
GEOLOGICAL WORK IN CANADA AND 
AUSTRALASIA. 
pe Geological Survey.. of Canada publishes in 
Memoir 72 an account of *‘The Artesian Wells 
of Montreal,’ which is suggestive to investigators 
in other limestone districts. Out of 179 deep wells, 
only about twenty yield less than 5000 gallons a day. 
The water. usually comes in greatest abundance from 
depths of 300 to 1000 ft., and rises to within 30 ft. 
of the surface. .The chance of finding a good supply 
below tooo ft. is small, and it seems that the source 
of the water (p. 26) is the rain that falls on the 
St. Lawrence highlands and lowlands and creeps into 
the Palzozoic sediments. This water moves in the 
limestone along fissures and cracks, and is held up 
at no particular horizon; the closing of the fissures 
as the depth increases is held to explain its practical 
absence below tooo ft. The author, C. L. Cumming, 
discusses the origin ani possible interactions of the 
dissolved salts; the proportion of sodium carbonate 
is high for water in sedimentary deposits (p. 48), and 
‘this salt may be derived from flow over the crystalline 
rocks of the’ Laurentian highlands. 
Fic. 1.—The Rocky Mountain Trench, looking east across the Kootenay River near Cranbrook, B.C. 
From ‘‘ Geology of Cranbrook Map-Area, British Columbia.” 
Four considerable memoirs deal with districts in 
British Columbia, and are accompanied by geological 
maps conveniently folded in pockets at the end. 
Memoir 55, by J. A. Allan, on the “Geology of 
Field Map-area, B.C. and Alberta,” covers 
the mountainous district on the west slope of the 
Rocky Mountains, where Mt. Goodsir rises to 
11,676 ft., with residual glaciers on its steep north-east 
descent. One of the most famous stretches of the 
Canadian Pacific Railway lies within the area, and 
the continuous Cambrian section studied by Dr. C. D. 
Walcott in recent years occurs on Mt. Bosworth, in 
the north-east corner of the map. A mass of igneous 
rocks rich in alkalies was intruded through the older 
Palzozoic strata in post-Cretaceous times, and has 
been cut into by the valley of the Ice River. The 
richness of the prevalent nepheline-syenite in lime is 
attributed (p. 186) to its absorption of limestone at the 
contact-zone. The author points out (p. 42) the neces- 
sity for distinguishing cirques formed by local ex- 
cavation at high levels, by the action of Russell’s 
““mountain-side”’ type of glacier, from those left 
behind as hanging valleys. This. distinction is even 
NO. 2464, VOL. 98] 
NATURE 
“the borders of Alaska. 
|] ANUARY 18, 1917 
now worthy of emphasis, although Matthes’s work on 
“nivation”’ in .the Bighorn. Mountains has. justly 
attracted attention. — ; 
Toxada Island, the elongated and steeply flanked 
ridge that rises from the Strait. of Georgia, north- 
west of Vancouver, i$ described by R. G. McConnell 
(Memoir 58). The main rock is a great body of 
porphyrite of Lower Jurassic age, which shows pillow- 
structure (plates iv. and v.), here called nodular 
structure, though it seems to be an intrusive mass. 
Magnetite lenses, which sometimes form low hills, 
have encouraged mining. . They are held to be contact- 
products (p..77), connected with the younger intrusive 
rocks, which are in part of Lower Cretaceous age. 
The Cranbrook map-area has been studied by S. J. 
Schofield (Memoir 76), on account of the development 
of gold-mining in lodes in the eastern part of the 
Kootenay electoral division. The district is well served- 
by failways, which connect it southward with Mon- 
tana, and northward with the main Canadian highway 
west of Field. It includes the south end of the 
“Rocky Mountain Trench” (p. 10), which extends to 
Kootenay River runs southward, amid parklike and 
largely alluvial country, while deeply 
} dissected mountains of pre-Cambrian 
sediments rise beyond Cranbrook on 
ne the west. The Rocky Mountains on 
the east présent the appearance of a 
distinct range, their crests of re- 
markably even altitude _ being 
touched here and there with snow 
(Fig. 1). The composite Purcell 
. sills (p. 75), with upper zones of 
».+-| micropegmatitic granite and lower 
: ‘| gravitational zones of gabbro, have 
much interest for petrographers. 
The singular course of the Koote- 
nay River brings it round the Pur- 
cell Range again into British Colum- 
bia, along the flooded valley known 
as Kootenay Lake, and westward 
out of this hollow to join, and 
largely to form, the rapid Columbia 
River descending on Washington 
and Oregon. Rossland (Memoir 77) 
lies on the. upper part of the Colum- 
bia, close to the International Boun- 
dary, which cares for none of the 
things of physical geography. The 
alpine landscapes here lie away upon 
the east, and the town has’ grown 
up in the last twenty-five years among glacially 
moulded and often wooded hills. From its sulphide 
ores the output of copper rose to a maximum in 1902. 
Gold is extracted from massive pyrrhotine and copper 
pyrites, in which it is occasionally visible in a free 
form. C. W. Drysdale, in this memoir of 317 pages, 
deals with mining matters first. The ores made their 
appearance (p. 92) in fissures in connection with the 
intrusive rocks of the Jurassic mountain-building 
stage, and secondary enrichment, including the rise 
of gold, occurred during the Miocene disturbances. 
The author inclines (p. 186) towards a ‘' three-cycle 
hypothesis’ of the development of the surface-features 
around Rossland, beginning with the dissection of the 
Cretaceous peneplane, of which very few traces now 
remain. The Laramide upheavals were the cause of 
this dissection, which continued through Eocene times. 
Movements in the Oligocene period led to the destruc- 
tion of much of the Eocene deposits by renewed 
erosion; and then Miocene diastrophism, accompanied 
by the introduction of mineral ores, provided a surface 
in which broad fairly mature features were established 
by the close of the Pliocene period. Renewed upwarp- 
. 
4 
In this tectonic feature the ~ 
