AvuGustT 18, 1899. ] 
workings. The examination of the Butte 
district was undertaken in 1896, and the 
Butte Special folio has been published. 
The Tintic district in Utah was surveyed 
in the following season, and the results ap- 
pear in the 19th Annual Report under the 
title of ‘The Geology and Mining Industry 
of the Tintic District, Utah,’ by Geo. W. 
Tower, Jr., and Geo. Otis Smith. 
The Deadwood district in the Black Hills 
of South Dakota next claimed attention, and 
areal and economic surveys are now in 
progress there. Apart from the economic in- 
terest, the region presents geologic features 
of comprehensive and significant character. 
The literature of the subject of laccoliths 
will receive an important addition when a 
report on the structural relations of the 
rocks in the Spearfish and Sturgis quad- 
rangles is published. It is anticipated that 
this season will suffice to finish the neces- 
sary field work. 
In Montana the work begun by Mr. 
Hague in the Yellowstone Park has, during 
a number of years, been extended north- 
ward nearly to the boundary of British 
Columbia, and surveys on the scale of 2 
miles to the inch have replaced those on the 
formerly adopted scale of 4 miles to the 
inch. The Fort Benton and Little Belt 
Mountain quadrangles, covering together 
nearly 7,000 square miles, have been sur- 
veyed in connection with studies of the 
Neihart mining district. They will be 
published as folios of the Geologic Atlas. 
More detailed accounts of the geologic ob- 
servations in Montana appear in the 19th 
Annual Report, Geology and Mineral Re- 
sources of the Judith Mountains of Mon- 
tana, by W. H. Weed and L. VY. Pirsson, 
and are contained in an elaborate article in 
the 20th Annual, ‘The Geology and Mining 
Districts of the Little Belt Mountains,’ 
by the same authors. This last is almost 
a monographic work, both in size and 
detail. Detailed areal surveys have been 
SCIENCE. 209 
carried out in the Boulder and Helena. 
Special quadrangles, and topographic sur- 
veys in preparation for geologic work have 
been conducted in the Bitter Root, Valley. 
The discovery by Mr. Walcott of pre-Cam- 
brian fossils in the Belt terrane of Montana 
lends additional interest to the north- 
western extension of the Rocky Mountains, 
of which these rocks form a large part. 
Mr. Hague’s monographic work upon the 
Yellowstone National Park has been ener- 
getically pushed, and the volumes are well 
advanced. The surveys of the Absaroka 
Rauge to the east of the Yellowstone Park 
are represented in the Absaroka folio, which 
will shortly be issued from the press. The 
remarkable phenomena presented by vol- 
canic breccias laid in horizontal attitudes 
over a wide area, and by post-Miocene in- 
trusives, have been discussed by Mr. Hague 
in his Presidential Address to the Geological 
Society of Washington, but are more fully 
illustrated and described in the Absaroka - 
folio. 
The Boise mining district, Idaho, at- 
tracted attention to a region which has 
since been the subject of surveys during 
several successive field seasons. Among 
the results is the determination of the prob- 
ably post-Paleozoic age of a large granite 
area formerly considered to be Archean, 
and the elucidation of interesting episodes 
in the history of Snake River. <A portion 
of these results are published in the 18th 
Annual as a paper entitled The Mining 
Districts of the Idaho Basin and the Boise 
Ridge, Idaho, by Waldemar Lindgren, and 
in the Boise folio, No. 45, and the 20th An- 
nual contains an article entitled The Silver 
City, De Lamar and other Mining Districts 
in Idaho, by the same author. The work of 
the present field season is designed through 
reconnaissance to obtain a general knowl- 
edge of the areal geology of central and 
northern Idaho up to and ineluding the Ceur 
d’Alene district of eastern Washington. 
