314 J. D. Dana on American Geological History. 
are a region in N ys New York, others about and beyond 
e Superior, and a large territory stretching from Labrador 
westward, as recognized by Messrs. Foster and W hitney and Prof, 
Hall, and the e geologists of Canada.* 
The Silurian or Molluscan Age next opens. The lowest rock 
sandstone, one of the most widely spread rocks of the conti- 
nent, seiaiind from New England and Canada south and west, 
an ‘reaching beyond. the Mississippi,—how far is not known. 
And this first leaf in the record of life is like a title page to the 
whole volume, long afterwards completed; for the nature of the 
story is here declared in a few comprehensive enunciations. 
1. The rock, from its thin, even layers, and very great extent, 
shows the wide action of the ocean in distributing and working 
over the sands of which it was made; and the ocean ever after- 
ward vical ba most active agenc sae makin 
2. Moreover, ripple-marks, sch as are made o resent 
seledcredal or in ' shallow waters, abound in the oka! both t wee 
the east and west, and there are other evidences also of modera 
depths, and of emerged land.t They all announce the oad 
fact, that even then, in that early day, when life first began to 
light up the globe, the continent had its existence,—not in 
in the Veron of life which appear in the earliest 
thes ot ahs Pes al rock, three of the four great branches of 
the Animal Kingdom are represented,—Mollusks, Trilobites 
among antl tes, id Corals and Crinoids among Radiates,— 
a sufficient representation of life for a. title- ‘page. The New 
* The Azoic lands, above the ocean at this time, re d by Messrs, Foster and 
scperies in the Report referred to, were that of th a he Nene n Lake 
i hight the 
souri iron-m 
other islands. Mr. White has more re shown that the bene dae of g 
pre-Siluri 
On the Geslogieat i map of northern North America, Isbister in 
the Quarterly Journal of the Geological Societ for Tee ae: hee << Azxoic is 
shown to extend in a narrow band northwestward from Canada to he Arctic sea 
between Hudson’s Bay and the Winnipeg | f lakes. 
+ Other marks of shallow water alluded to e obli 
lamination characterising many subordinate a Wayeia fh Agile an ae peg 3 
changing currents, like the ebb and flow of t tides, or variations in tidal or other cur- 
rents, or the occasional action of storm wayes. This se ht gon Kew ell as 
ds 
a @ ga a Ke bundantly in the Potsdam san hight oe: 
ions’s Geol. Rep. p. 104, 180); in Canada - a ve 
elsewhere) ; so th of Lak 3 ee oe + Reports 1861 “5 Pt 
e Superior (Foster and Wi t it. p. 118); in the 
gas Mini (Owen, Survey of Ws sconsin, Pid yt yo th ‘ Pebnsylvan ia ia and 
irginia (Professors H. D. and Rogers), 
