88 Review of Owen's Geological Report on Wisconsin, Iowa, ete. 
derfully successful experiment which will doubtless be the means — 
of its introduction whenever the form and character of the sub- 
ject admits of its application. All structure visible to the naked 
eye can be brought out by this process; and even minuter struc- 
ture, indistinctly visible to the unassisted eye, can be worked up 
by a skillful artist, after the plate comes from the machine, as 
may be seen by inspecting figs. 4, 11, 13 and 20 of Tab. IIB, 
and figs. 16, 19, and 21 of Tab. IITA.” 
The plates engraved from daguerreotypes of the originals are 
also admirably executed, especially Tab. XII, XII A, and XIIB. 
Altogether we have seldom, if ever, seen engravings which pre- 
sent so life-like an effect; if such an expression be admissible, 
in figures of fossil remains. 
The first chapter of the Report embraces a description of the 
protozoic or most ancient fossiliferous strata belonging to the pa 
leozoic period. ‘The developments in regard to the organic con- 
tents of these rocks, in the valley of the Mississippi, are amongst 
the most important discoveries and contributions of the survey i0 
a scientific point of view. 
On this head we extract the following: 
‘Tt had been usually believed, up to the date of my Annual Report 
of 1848, that the lowest members of the sandstone formation of which 
Tam now speaking, were devoid of fossils. The geologists of our owt 
country had set down the Lingula beds of the New York Potsdam 
as the equivalent of the above-named Lingula beds. I am now able to 
exhibit a new and interesting geological feature with regard to this 
formation. 
The present survey has brought to light the fact, that in Western 
America are found strata underlying coarse Lingula grits, and at 4 
depth of seventy-five to one hundred feet beneath them, which are 
* In the chloritic and ferruginous slates here metioned no organic remains hav? 
n discovered. In these rocks Iam unable any analogy, in lithological 
character, to Professor Emmons’s “ Taconic System.” Whatever may occur elsewher® 
it does not appear that in the Valley of the Upper Mississippi, any fossil-beari03 
rocks, deserving the name of a distinct sys occur intervening between the igneo™ 
rocks and the base of the sandstones re be to the Silurian peri 
