The Rideau Lakes. 235 



Bay and continues at intervals to Brockville. There is 

 thus a widespread distribution of it in patches or small 

 areas nearly across the Laurentian isthmus which connects 

 the Adirondack^ with the Laurentian country to the north- 

 ward. And in this locality where glacial action has been 

 so marked, we can imagine that these softer rocks may at 

 one time have had a greater development than now ap- 

 pears. 



Laurentian Rocks. 



Writing generally of the Laurentian rocks in the Coun- 

 ties of Lanark, Leeds and Frontenac, the late Mr. H. G. 

 Yennor in the Geological Survey Report for 1870, charac- 

 terizes them as made up of granitoid gneisses, composed of 

 flesh colored feldspar, with grey quartz, greenish horn- 

 blende, and some mica, and much cut up by granitic veins. 

 They have, in places, great crystalline limestone bands 

 which can be traced continuously through two or three 

 townships, and sometimes they include broad areas of 

 granitic rocks containing red orthoclase and white quartz. 



The economic minerals met with in the neighborhood of 

 the Rideau lakes are iron ore in large quantity at several 

 points, lead and yellow sulphuret of copper but not, thus 

 far, in paying quantities, phosphate of lime at numerous 

 points, mica, marble, granite for paving blocks, and thick 

 bedded sandstone for building material. The iron ore 

 generally, has assayed from 52 per cent, to 60 per cent, of 

 metallic iron, but is occasionally associated with 6 per 

 cent, to 12 per cent, of titanic acid and some sulphur. 



The leading physical features of the country — the lakes, 

 the islands, the low overlooking hills — are all due to the 

 Laurentian rocks, and to the line of direction which these 

 hills or great ridges have taken. At Brewer's Mills on the 

 Cataraqui River the direction is about N. 20° E. From 

 this point to Seeley's Bay their course is about N. 34° E., 

 whilst south-east of Seeley's Bay there are ridges lying N. 

 30° E. A long, conspicuous gully here which has afforded 

 a probable opening to the engineers for location, takes, 

 however, a course, for a considerable distance, of N. 82° E. 



