272 The American Geologist October, is97 
Rocks, in 56 pages, by Samuel Walker Beyer : Artesian Wells of Iowa, 
in 31t5 pa^es, by William Harmon Norton ; and Relations of the Wis- 
consin and Kansan Drift Sheets in Central Iowa, and Related Phenom- 
ena, in 48 pages, by H. Foster Bain. 
Prof. Leonard describes the mines of Dubuque, Clayton, and Allam- 
akee counties, in northeastern Iowa, on the west border of the Upper 
Mississippi lead and zinc district. The ores are galena, smithsouite, 
and sphalerite, occuriug in crevices of the Galena limestone. The ore 
concentration is attributed to lateral secretion from the limestone by 
infiltrating sui'face waters ; and the original source of the ores, as Whit- 
ney long ago suggested, is held to have been the ancient sea, at whose 
bottom the limestone was formed, the sea itself having received its me- 
tallic salts from the decay of the Archean rocks. 
The Sioux quartzite. described by Dr. Beyer, extends only one or two 
miles into the northwest corner of Iowa, so far as it is seen in outcrops. 
The localities here chiefly described are between six and fifteen miles 
farther north, in Minnehaha county, South Dakota, where the quartzite 
is succeeded above by thinly bedded quartz-slates, which vary in texture 
from line-grained homogeneous "pipestone" to argillaceous quartzite. 
An extensive mass of diabase, which is thought to have been intruded 
between bedding planes of the slates, is exposed along a distance of 
about a mile in the valley of Split Rock creek; and the author pi-esents 
the results of his study of its mineral composition and alteration 
products. 
The artesian field of Iowa is shown by Prof. Norton to be a part of a 
much larger basin which reaches southward into Missouri and eastward 
into Illinois. Its main area of intake from rains is on the north, where 
the St. Croix and St. Peter sandstones outcrop in the southern parts of 
Wisconsin and Minnesota. The altitudes to which the artesian flows 
rise have a somewhat regular gradient from 1200 feet above the sea in 
northwestern Iowa to 700 feet in its southeastern part. Records of the 
Iowa wells, and details of their relations to the stratigraphy of the re- 
gion, are followed by a discussion of the chemistry of artesian waters, 
notes of their use as a public supply, and a bibliography for the state. 
This is a very thorough and admirable memoir, which will be of great 
value as a guide to the further development of the artesian water supply. 
In the last paper of the volume Mr. Bain gives results of his studies 
of the glacial drift in central Iowa, includiisg the southern end of the 
Minnesota and Iowa lobe of the ice-sheet in its Wisconsin or moraine- 
forming stage. A synopsis of the successive stages of the Glacial period, 
as recognized in Iowa by Prof. Calvin, appeared in the last April num- 
ber of this magazine (pages 270-272), and Mr. Bain here discusses the 
ratios of these stages. He agrees substantially with the ratios pvil)lished 
by Prof. Chamberlin a year ago in the Journal of Geology (vol. iv, pp. 
872-876). R-of. N. H. Winchell's estimate of the Postglacial period as 
7,800 years, based on the recession of St. Anthony's falls, is accepted ; 
but for the previous time of retreat of the ice-sheet from Des Moines 
to Minneapolis an undetermined addition is required. This duration 
since the maximum extension of the Wisconsin ice-sheet is thought to 
