158 



laiomlues. more numerous as the main Keweenawan area 

 around Lake Nipigon is approached. They 

 have a pronounced columnar and parallel 

 jointing, which gives rise in them to a much 

 more precipitous relief than is seen in the 

 Laurentian. 



334-9 m. Allen Water — Altitude 1,332 ft. (4,062 m.). 



535-8 km. Between Kawa and Allen Water river, the 

 gneiss contains numerous angular and ribbon- 

 like inclusions of hornblende gneiss, derived 

 from the Keewatin. 



About a mile and a half (2-4 km.) west of 

 Kawa, Keweenawan diabase may be seen lying 

 directly upon Laurentian gneiss. At this point, 

 on the north side of the railway, a clifif of 

 diabase rises abruptly from a comparatively 

 flat Laurentian floor. 



362-4 m. Ogoki — Altitude 1,273 ft. (388-2 m.). From 



579-8 km. Cameo to Ogoki the forest has been burned, the 

 gneiss is almost completely bare of soil, and the 

 country is excessively bleak-looking. Between 

 Kawa and Jacobs, however, a number of con- 

 spicuous gravel hills rise directly from this bare 

 rock surface. 



The precipitous topography characteristic 

 of the Keweenawan sills is exemplified between 

 Jacobs and Ogoki, where the railway skirts a 

 small but rugged canyon carvedin this formation. 



391 m. Armstrong — Altitude 1,113 ft. (339-4 m.). 



625 - 6 km. The Laurentian gneiss disappe?rs under a man tie 

 of boulder clay four miles (6-4 km.) east of 

 Armstrong and, from this point to Lake 

 Nipigon, solid rocks are infrequently exposed. 

 Low sand hills and muskegs, intersected by 

 sluggish creeks, take the place of the hummocky 

 rock surface and rock-bound lakes. Near 

 Wagaming the boulder clay merges into a 

 comparatively flat plain underlain by the, 

 stratified sand and clay of glacial Lake Warren. 

 There are few excavations along the railway 

 in which these lacustrine depof its are favourably 

 exposed, but natural sections are exposed by 

 the streams flowing toward Lake Nipigon, 

 which are rapidly deepening their channels 



