Review of Owen’s Geological Report on Wisconsin, Lowa, etc. GF 
the drift. And what is remarkable, these calcareous roeks, 
throughout this vast range, are, for the most part, highly charged 
with magnesia, containing from 15 to 20 per cent. of this earth, 
These magnesio-calcareous beds, more than any other forma- 
tion, impress upon the landscape the peculiar picturesque scenery 
so characteristic of the Upper Mississippi country in Wisconsin 
and Iowa. They are moreover the lead-bearing rocks of these 
States, from whence so much mineral wealth has been derived. 
From the recorded statistics in the table on page 61, it appears 
that the veins of Galena, worked in the upper magnesian lime- 
stone, in the Mineral Point district of Wisconsin and part of the 
Du Buque district of Iowa, yielded in 1847 upwards of fifty-four 
millions of pounds of lead, and, as it is justly remarked, this 
amount would undoubtedly have been much increased up to the 
present time, but for the inducements offered to miners to emigrate 
- to California. 
‘The whole of these two vast formations—as well siliceous as 
calcareous—with the exception of the coralline and pentamerus 
beds, are referred to the lower Silurian period of Murchison. The 
upper and lower Magnesian limestone formations are separated 
by a subordinate bed “of sandstone , varying from 40 to 100 feet in 
thickness, often composed of limpid grains of quartz, upon which 
rest two beds of fossiliferous limestone with a non-fossiliferous 
band intervening. In all 30 to 40 feet in thickness. Analyses 
showed the lowest of them to be the purest limestone of the 
Upper Mississippi country, containing only between six and seven 
per cent. of magnesia. These layers lie at the base of the upper 
magnesian limestone jertaaton, and are described as richer in 
organic remains than any of the overlying or underlying beds. 
Many of the species are identical with those occurring in the 
blue Sevadiace of the Ohio Valley and the Trenton limestone of 
or 
The 2d chapter i is devoted to the formations belonging to the 
Devonian period, which are confined chiefly to the valley of 
Cedar River and its tributaries. They consist mostly of pure cal- 
labor-saving eoekiiees in his sowing and harvest erations 
cumbered with stumps, which forma serious obstruction in the 
newly cleared forest lands of Ohio and Indiana. 
The cay beds of this formation appear, from the _— 
character of the organic remains, to correspond in age to the 
ane teniestone of New York; the upper to the Hamilton 
oup. 
