186 A POPULAR EXPOSITION OF THE 
Lower Silurian Series :—This series comprises, in ascending order, 
the following subdivisions :—1, The Potsdam Group ; 2, the Caleci- 
ferous Group; 38, The Chazy Formation; 4, The Trenton Group; 
5, The Utica Slate Formation; and 6, The Hudson River Formation. 
Note :—The Calciferous and Chazy strata, as regards their occurrence in the 
neighbourhood of Quebee and throughont the Eastern Townships, are united by 
Sir William Logan under the term of the Quebec Group. It would also, per- 
haps, be more in conformity with Nature to unite the three latter divisions, as 
given above, and to arrange the whole as in the annexed Table. The term 
“ Ontario Group” might be adopted for the proposed union of these higher 
formations. 
Hudson River Formation. 
: Utica Formation. 
Ontario? Group: 1 Trenton Formation. 
| Bird’s Eye and Black River Formation. 
The higher beds of the 
Orsi Group {Suny ing Forman ("Wiper Corer bning 
‘ strata of L. Superior (# ) 
The bottom beds of tha 
Upper Copper-bearing 
strata of L. Superior (?) 
ries ren (Oran Beauharnois Formation, 
yeaah P-) Kaministiquia Formation. (?) 
The Potsdam Group :—This subdivision, until a comparatively 
recent period, was known as the Potsdam Sandstone. Its stratified 
deposits may be arranged under the heads of: deep-sea strata; shal- 
low-sea or shore-line deposits; and altered rocks. Of the deep-sea 
strata of the Potsdam epoch, merely uncertain indications have at 
present been obtained. Sir William Logan has suggested that some 
dark slates which are found to occupy a lower geological position 
than the Quebec beds of Point Levis,* may very possibly represent 
some of the deep-sea deposits of that period; whilst it is certain 
that the ordinary sandstones, of the epoch, were shore-line or coast 
deposits. This is proved by the presence of ripple marks, and tracks 
of crustacea or other animals, as well as by the general nature of the 
sediments of which these sandstones consist.’ The slates, however, 
may be of contemporaneous formation with the sandstones: » point 
at present unsettled. Another series of slate rocks and slaty con- 
glomerates, somewhat resembling those of the Huronian series, 
associated with beds of chert (a flint-like variety of quartz, some- 
times coloured black from the presence of anthracitic matter), grey 
dolomites, (weathering red), interstratified trap beds, and some 
* In the pronunciation of this word the final letter is mute. Hence the word is often 
written Lévi. 
