200 REVIEWS—GEOLOGICAL SURVEY OF IOWA. 
such localities covered with an abundant growth of timber.”” Where 
the so-called “groves ’’ occur upon higher levels of the prairies, 
there is always a partial acccumulation of drift and other coarse 
materials, in place of true prairie-sediment; and the same is observ- 
able, according to Mr. Whitney, wherever timber is found upon the 
bottom-prairies of the Mississippi and Missouri valleys south of 
Towa. 
In the concluding and principal portion of Mr. Whitney’s Report, 
numerous analyses are given of the dolomites, limestones, coals, and 
other economic substances, of the State; and the great lead region 
is described with much detail. The lead ore lies essentially in the 
Galena limestone, in “gash’’ or shrinkage veins, and in caverns, 
openings, or pockets, all of which are cut off at comparatively small 
depths beneath the surface. The whole of this portion of the Report 
is drawn up in an exceedingly clear and able manner, and will well 
repay the perusal of those interested in mining operations. 
We have already alluded to the beautifully executed plates, in 
illustration of the Paleontology of the survey, engraved under the 
superintendence of Professor Hall. The letter-press to these is 
exceedingly copious, and contains many additional diagrams illustra- 
tive of crinoid structures. Another advantageous feature, as 
compared with the descriptions in the published volumes of the 
Paleeontology of New York, is the definition of the various genera, 
given in connection with the characters of their respective species. 
All the deseribed forms, however, belong to the Devonian and — 
Carboniferous formations: the Silurian fossils, met with during the 
survey, having been previously figured in Dr. Owen’s Report on the 
geology of Wisconsin, and in other publications. A few plates of 
the more characteristic of these fossils would contribute nevertheless 
to the utility of the present work, without any very material addition 
to its cost ; and we trust the legislature of Iowa will afford the 
means of effecting this, in the volume which is yet to appear. To 
the enlightened legislature of this far western State—a State added 
but yesterday, as it were, to the Union—too much credit cannot be 
accorded for these goodly and important volumes, so usefui to 
agriculture and practical art, and so liberally presented to the 
seientifie world. 
E. J. C. 
