852 C. K. LEITH 
On the upturned edges of the Archean rocks, both gneiss and 
anorthosite, the Potsdam sandstone and other Cambro-Silurian rocks 
repose in flat and undisturbed beds. 
Ells and Barlow* describe the physical features and geology of the 
proposed Ottawa Canal between the St. Lawrence River and Lake 
Huron. The proposed canal for several hundred miles traverses for the 
most part Archean rocks nearly at right angles to the strike of their 
schistosity or banding. The work of Logan, Murray, Lawson, and 
Adams, and others of the important workers on the Canadian crystal- 
line is briefly summarized. 
The Grenville series of the Original Laurentian area probably 
illustrates the most perfect section of Laurentian rocks which we can 
yet recognize. This section shows various kinds of gneisses, foliated 
and stratified, with foliated and massive granites and syenites, pyrox- 
enic, dioritic, hornblendic, and quartzose rocks, and quartzite and 
limestone. In the basal beds of the limestone and quartzite, supposed 
to constitute the upper member of the series, are interstratified bands 
of rusty quartzose gneiss, which from the available evidence is believed 
to form an integral part of the limestone series. This portion presents 
in its banded arrangement of quartzose and calcareous rocks, the 
usual aspect of true altered sedimentary strata. The same well banded 
arrangement is also visible in some of the directly underlying gneiss ; 
but in the case of the great mass of this gneiss, the microscopic 
examination shows the evidence of an aqueous origin to be wanting. 
Some portions of the igneous rocks are undoubtedly older than the 
limestones, and most probably represent the lowest, portions of the 
earth’s crust known to us. Other portions are clearly established to 
be of more recent age than the crystalline limestone. The oldest 
gneisses are foliated, rather than stratified, but in their foliation they 
underlie the regular series of stratified hornblende and other gneisses 
which occur frequently between the fundamental gneiss and the 
crystalline limestone and quartzite series at the summit of the section. 
To this fundamental series may be assigned the rocks of Trembling 
Mountain, those forming the anticlinals north of Lachute, rocks from 
various places throughout the Grenville district, and large areas at 
*The physical features and geology of the route of the “proposed Ottawa Canal 
between the St. Lawrence River and Lake Huron, by R. W. ELts and A. E. BARLow. 
Proc. and Trans. Roy. Soc. of Canada, 2d ser., Vol. I, Sec. IV, 1895, pp. 163-190. 
With sketch map. 
