16 GEOLOGICAL AREAS OF CANADA. 



wooded district, iinderlaid by hard crystalline rocks, and lying at an 

 average elevation of from 1,000 to 1,500 feet above the sea — Lake 

 Huron being 578 feet, and Lake Superior 600 feet above the sea 

 level. Gneissoid Laurentian strata occupy the greater portion of its 

 area ; but these are overlaid along a large portion of the north shore 

 of Lake Hu.ron, and in other localities (as in the country adjacent to 

 Thunder Bay, &c.) by belts of Huronian slates, semi-crystalline con- 

 glomerates, and other metamorphic strata ; and intrusive masses of 

 granite and trappean rock appear in many places. A higher series 

 of strata, known provisionally as the " Upper Copper-bearing rooks 

 of Lake Superior," overlie these Huronian and Laurentian formations 

 around Thunder Bay and elsewhere in the Lake Superior region. 

 They consist of an under series, mostly of dark slates, and' a higher 

 series of indurated marls and calcereous sandstones, the whole 

 traversed or overlaid by enormous masses of trap, as seen at Thunder 

 Cape, &c. Finally, Glacial boulders, clays, and gravels, and Post- 

 Glacial sands, &c., in many places in the form of high terraces, are 

 distributed over the region generally. The Laurentian rocks of the 

 district appear to be destitute of economic minerals, but the Huronian 

 and higher beds are penetrated by numerous metalliferous veins con- 

 taining copper-pyrites, native silver, silver glance, galena, and other 

 ores. Beds and veins of haematite and magnetic iron ore are also 

 present in the Huronian strata of the region ; and native gold has 

 been found in rocks of the same age in the Lake Shebandowan 

 country. The copper pyrites and zinc blende of the higher strata 

 around Thunder Bay are.also more or less auriferous. 



PROVINCE OF MANITOBA, 



AND 



REGION OF THE NORTH-WEST TERRITORY. 



The geology of this vast area — extending from the western 

 boundary-lme of Ontario (not yet permanently established) to the 

 Rocky Mountains — is only known at present in its broa,d6r or more 

 general features, but it appears to indicate a natural subdivision 

 of the region into four leading districts. These comprise : — (1) The 

 Eastern or Laurentian District ; (2) The Eastern Prairie or Lake 

 Manitoba District ; (3) The Central Prairie District; and (4) The 

 Mountain District. 



(1.) The Eastern or Laurentian District. — An elevated rocky 

 region, more or less densely wooded : a continuation of the Lake 



