CURRENT PRE-CAMBRIAN LITERATURE 853 
different places along the Upper Ottawa River section. Concerning 
many of the intermediate gneisses, it may be said that while in their 
general aspect they resemble stratified sedimentary rocks, their study 
under the microscope shows them to have presumably a different 
origin, so that it is possible that the true altered aqueous portion may 
be confined to the areas of crystalline limestone with their associated 
bands of quartzite and grayish quartzose and hornblende gneiss. The 
crystalline limestones are particularly developed along the Ottawa 
River section, from the vicinity of Deschenes Lake, west of Ottawa 
city, to the village of Bryson, in which section they are frequently cut 
by large areas of granitic and dioritic rocks. At one place, near the 
Chats, the limestone is overlain by a considerable breadth of Huronian- 
looking schists, etc., which have been described under the name of 
Hastings series. The limestone has its most westerly outcrop on the 
Ottawa in the vicinity of Coulonge Lake, a short distance west of 
the Black River. From here west to the mouth of the Mattawa the 
limestone occurs as separate belts occupying synclinals in the upper 
stratified gneisses. 
The rocks along the route of the Mattawa and French Rivers to 
Lake Huron are chiefly those which have been regarded as Laurentian 
gneisses. There is very little of the crystalline limestone which forms 
such an abundant constituent of the Laurentian farther east, and this, 
as well as the apparent inferior position of the gneisses, according to 
their banding, caused them early to be placed at the very base of the 
geological series, and called the Lower Laurentian series. Crystalline 
limestone occurs at Talon Lake, on the east shore of the Great Mani- 
tou or Newman Island in the eastern part of Lake Nipissing, as well 
as on two of the small islands composing this group, and on Iron 
Island. All the evidence seems to point to the fact that the limestone 
has been caught up in the gneisses during its eruption. 
The foliation of the gneisses is produced either by (r) alternation 
of light and dark bands, or (2) by the more or less parallel distribution 
of the component minerals. In many of the plutonic rocks, and 
particularly in the granites and similar rocks, there is a marked ten- 
dency for the bisilicates to aggregate themselves in certain belts or 
patches (called Auscheidungen in the granites). The result of pres- 
sure on a rock characterized by the presence of these masses would 
be the flattening of the dark areas into more or less lenticular 
areas. Again, many of the dark bands are seen to have had their 
