2G0 The American Geolotjiat. April, 1895 
ii's and aiilliiirs. wi(l\ (latcs, inarkiiij;' stages of iiolcwdrthv i'.\lciisi(ni of 
Ihc sciiMRT and cslablislimcut of its chief principles. l\>v each of Ilie 
great I'ras and ])eri()ds, tiie aiitliorsliip and (hite of first- use of tiieir 
])resent names, willi Iheir synonymy, are noted, alfording useful clues 
for the student in enlfring any special studies of stratigraphy or pale- 
ontology. 
'{"he gi'and di\ isions of the ndIuiuc. and the oi-der of their considei'a- 
tioii. are ph \ siograph ic, structural, dynamical, and historical geology. 
In the prid'ace I'rof. Daiui says: "As the rewi'itten l)ook shows, new 
l)riMciples, new theories, and widely diverse opinions on various sub- 
jects are among the later contributions, along with a profusion of new 
facts relating to ;ill de[iartments of I he science. The Cambrian forma- 
tion has lieen traced through a large part of the continent, and the 
number of its fossils has been increased, cliielly by ('. I). Walcolt, from 
a few to humlreds. The Api)alachian Mountain structure has been 
shown by Clarence King, Dr. (i. M. Dawson, and \l. C McConn(dl, to 
have been repeated in the great post-Cretaceous mountain-making of 
the Rocky Mount.ain region. The Reptiles, iiirds, and Mammals of the 
Mesozoic and Tertiary have coidinued coming from the rocks until the, 
species recognized much outnumber those of anv other continent. Tlu> 
c'afions and other results of erosion in the west have llirown new light, 
through their investigators, on the work of the waters, liesides, the 
science of pel rologv has elucidated much of the obscure in the const itu- 
lion. relations, and origin of rocks." 
It was not to be e.xpected that this summary of Noi'th American geol- 
ogy, by one who has held so prominent a part in its deNclopmeiit, would 
accord wil h the views of othiu- prominent geologists in all details, or 
even in some important correlations and opinions concerning the origin 
of debated formations, 'i'aking two or three of the author's interpreta- 
tions, where they <lilfer from those held by others who have done mucli 
field work on the formations under consideration, we may note the ref- 
erence of ihe Keweenawan series to the Middle or Lower Cambrian, in- 
stead of the .Mgonkian system, which latter is not accepted for its 
pi-oposed place Ix'tweeii the Cambrian and Arcluean; the assignment of 
the Lafayette formation to the Pleisloci'iie period, and to freshwater 
deposition h\ Hooded ri\ ers, i nstead of the I'liocene ;ige and mai'ine 
origin which have lieen much claimed for it: anil theopinion that lake 
Agassi/., in the basin of the Red river of the North and of the great 
]\Linitol)a lakes, was due to a laiul barrier on the north, as was thought 
by (Jen. (i. K. Warren, instead of to thi' retreating ice-sheet, as was 
suggested in 1872 by Prof. X. U. Wiiudiell. This lake was \hv largest 
one of many due in common either to land or ice barriers. Professor 
Dana I hinks t hat the fullness of thi' Chaniplain subsidence, al tlu' end 
of the ( Jlacial perio;l, was attained after, not before, the linu'of lake 
Agassi/,, and after the expanded Late (Jlacial represenlal i\cs of the 
great lakes I i-ibu(ary to till' St. Lawrence. 'I'hough the I'eviewer can- 
not agree with this opinion, il is most heartily welcomed as an impor- 
