284 PROCEEDINGS OF SECTION C. 



orthoclase being the principal ones, together with a smaller proportion 

 of honilDlende and a little biotite or phlogopite. Scattered small 

 crystals of magnetite may be occasionally detected. 



In this respect the Lower Laurentian contrasts with the Upper, 

 in which there is a great variety of minerals, including ores of 

 numerous metals, which, however, do not often occur in economic 

 quantities, with the exception of iron, lead, and rarely copper. 

 Structurally the Lower Laui'entian may be described as consisting of 

 heavy granitic gneiss or slightly laminated granite, which may be 

 imperfectly banded owing to alternating belts of different shades of 

 gray, pink, and light red. Although the average of the local strikes 

 of these belts may show that a certain general direction prevails in a 

 g:ven area, the course of the lamination is generally quite local or 

 ill-defined, with frequent changes, or it may be contorted. Again^ 

 by means of the alteration of shades, the bands may sometimes be 

 found to form irregular parallel cuiwes or zig-zags, and sometimes 

 they follow imperfect concentric ellipses of low or high eccentricity. 



Upper Laurea'tian. 



Tlie Upper or Newer division of the Laurentian system is made 

 up principally of a variety of well-foliated gneisses, arranged in 

 distinct bands, also beds of ciystalline limestones and dolomites, some 

 of which are of great thickness, together with anorthosites, norites, 

 pyroxenites, granites, massive and schistose greenstones, &c. 

 Minerals of man}'' kinds are found in the series. Over 150 different 

 species have been collected in the townships opposite to the city of 

 Ottawa. Among the economic minerals which these rocks have so 

 far produced in commercial quantities are ores of iron, lead, and in 

 a few cases of copper; also apatite, mica, fibrous serpentine, barite, 

 cc-iestite, marble, and a variety of semi-precious stones. There is little 

 doubt that some of the gneisses represent altered sediments. The 

 parallelism of the members of the series and the structural arrange- 

 ment or geographical distribution of their outcrops resemble those of 

 altered and disturbed sedimentary rocks of other formations. In some 

 localities the anrangement is tolerably regular, but in others it is 

 considerably disturbed or corrugated. 



The total area of the Upper division is less tlian that of the 

 Lower, but the boundaries between them are only imperfectly known. 



HURONIAN AND KeEWATIN. 



In the eastern half of the Dominion, or rather that greater part of 

 it whicli lies eastward of the Mackenzie River, some large and many 

 smaller areas are occupied by a great pyroclastic series, the different 

 parts of which, until i-ecent years, were provisionally grouped under 

 the name Huronian. Before they could be satisfactorily divided, this 

 name was understood to embrace all the rock-formations between the 

 Upper Laurentian and the lowest Cambrian. As far as this series was 

 concerned, while the Canadian geologists gave their attention mostly 

 to the discovery and tracing out of the geographical distribution of 

 tlie Huronian areas in our vast territories, a few of them in later 

 years, as well as some of the United States geologists, devoted them- 

 selves to a closer study of restricted areas in the Lake Superior 

 region. They found tliat the lower part of the seiies consisted of 



