Review of Recent Geological Literafjire. 61 
also very serviceable by other survej-ors and engineers and by teachers 
in technical schools. w. r. 
Reconnoissance maj) of the United States, showing the distribution of the 
Geologic Systems, so far as known. Compiled from data in the possession 
of the U. S. Geological Survey, by W J McGee, 1893. This set of twelve 
maps, which are classed together as plate II of the forthcoming Four- 
teenth Annual Report of this surve\' (for 1892-'{)3), is issued in advance 
of that report. The scale is about 110 miles to an inch, being the same 
with that of the geologic map compiled by Prof. C. H. Hitchcock about 
ten years ago. Professor Hitchcock's map has geologic coloring extended 
provisionally over the entire United States, and across the. border of Can- 
ada to thelimitof the sheet; butthe present mapomits coloring from Can- 
ada, and from areas where the e.xact boundaries of the formations have 
not yet been traced. Thus a large region of western Montana, Idaho, 
Oregon, and southern Washington, comprising the great volcanic area 
cro-ssed by the Snake and Columbia rivers, remain uncolored on Mr. 
McGee's map. 
Another and more regrettable departure from the earlier map is the 
omission of the Cretaceous color from a large tract of eastern North 
and South Dakota, giving to it only the designation of glacial drift. 
This tract was rightly called Cretaceous by Hitchcock; and the same 
Cretaceous formations, according to Prof. N. H. Winchell in the front- 
ispiece map of the Geology of Minnesota, Vol. iir, Part t, also continue 
eastward, beneath the drift, upon the western half of that state. In 
this opinion the present reviewer confidently accords, and would .tlso 
include the northwestern quarter of Iowa in the eastern extension of 
the Cretaceous area. 
Besides the comprehensive geologic map, with its contour lines, this 
series comprises an uncolored map with only contours, and ten other 
maps showing respectivelj' the areas of (l)the Pleistocene ice and water 
deposits, these alone being colored; (2) Neocene and Eocene formations; 
(3) the <''retaceous; (1) the Jura-Trias; {'->) the Carboniferous; ((>) the 
Devonian; (7) the Silurian; (8) the Cambrian; (9) the Algonkiaii and 
.Arclicaii: and (10) igneous rocks. The Pleistocene formations arc dis- 
I)layed h\' overprinted dots. The scheme of colors is very tasteful, with 
mostly lighter tints than on Prof. Hitchcock's map. 
A further im[)rovement, very helpful for convenient reference and 
study, is the more fretjuent insertion of names of cities, towns, rivers, 
lakes, bays, capes, etc. Among these the name of lake Itasca is 
wrongly spelled, with k; its derivation being from the Latin words 
reritas ;\\\(\ caput, by Procrustean elision of the initial and final syllables. 
w. V. 
rnterloessial I'll! near Sioiw Cifg, Iowa. By J. I*.. Todd and If. Fostkk 
Bain. (Proceedings of the Iowa Academy of Sciences, vol. ii, I89."), p]). 
20-23.) At the hight, of about l.")0 feet above the Big Sioux and Missouri 
rivers, a deposit of typical boulder-clay or till, having an observed max- 
imum thickness of six feet, is underlain and overlain by ordinary loess. 
