REVIEWS. 
415 
the south-western corner of the State. All these gentlemen seem to have 
done their work in a most conscientious manner, and although probably 
many details still remain to he investigated, the result of their labours fur- 
nishes a very good idea of the geological phenomena of this region. Its 
structure, indeed, is tolerably simple. In the northern part of the State 
there is an immense mass of crystalline rocks, which are for the present re- 
ferred to the Laurentian. These are partially overlain by quartzites, slates, 
&c., identified with the Huronian, and like it containing considerable quantities 
of iron ores ; and both these archsean formations make their appearance now 
and then through the more recent rocks of the other parts of the state. Even 
these newer formations are all of very ancient date. In central Wisconsin 
no rocks are met with younger than the Lower Silurian Trenton and Galena 
limestones ; whilst the eastern division contains the Cincinnati, Niagara, and 
Lower Helderberg groups, and also exhibits a small development of the Hamil- 
ton group of the Devonian. Above these Palaeozoic rocks there is nothing 
except the Drift and the Champlain deposits. Mr. C. W. Wright appends 
to the second section descriptions of the microscopic characters of a great 
number of the crystalline rocks. Besides describing the geology of the 
country, each author furnishes details of the topographical character and 
hydrology, and of the soils and vegetation of the region surveyed by him, so 
that the physical geography of the country is pretty well worked out, and 
the whole is admirably illustrated by the magnificent atlas of 14 large 
coloured maps and sections which accompanies the volume. The book itself 
is also profusely illustrated with plates and woodcuts. 
Not to be behindhand with its neighbour on the other side of the 
Mississippi, the State of Minnesota has also its survey, directed by Professor 
N. H. Winchell, which is placed under the care of the Board of Regents of 
the University of Minneapolis. It has the title of the Geological and Natural 
History Survey of Minnesota, and its fifth Annual Report* has just reached 
us. This includes reports on the geology and surface features of Houston 
and Hennepin counties, in which the phenomena presented by the drifts are 
especially dwelt upon, and the question of the time occupied in the recession 
of the Palis of St. Anthony, which was briefly referred to in our last num- 
ber (p. 319), is treated in considerable detail. The botanist, Dr. A. E. 
Johnson, contributes a list of the known fungi of Minnesota, which is of 
interest to the student of the geographical distribution of those plants ; and 
the Entomologist furnishes a long report on the evil-doings of that scourge 
of the American agriculturist, the Rocky Mountain locust. The other con- 
tributions are chiefly of local interest, except the description of a new species 
of Cyclops (C. longicornis) by Mr. C. L. Herrick. The illustrations consist 
of a few woodcuts and several maps, some of which are coloured. 
The report of the United States Commission of Pish and Fisheries for 
1875-76f, which has recently appeared, relates more specially than some 
* 11 The Geological and Natural History Survey of Minnesota. The fifth 
annual report for the year 1876.” 8vo. St. Paul, Pioneer Press Companv, 
1877. 
t “ U.S. Commission of Fish and Fisheries.” Part IV. Report of the 
Commission for 1875-76. 8vo. Washington Government Printing Office, 
1878. 
