136 



Miles and $ 2 ie ^ ( l 5' 6 nl t0 the level ° f Lak e 



Kilometres. Ontario. A deep gorge is cut here in the 

 Pre-Cambrian gneisses making one of the 

 most beautiful spots on the inland water-ways 

 of Canada. 



Resuming the journey in a north-easterly 



direction on the east side 



9 m. Blake's Quarry, of the canal, for a dis- 



14-4 km. tance of 4 miles, (6-4 km.) 



Blake's quarry is reached. This quarry is 

 in Potsdam (Upper Cambrian) sandstone, 

 and is noted for the peculiar concretions it 

 contains. There are innumerable spherical 

 to elliptical sandstone concretions, but the 

 most peculiar ones are long cylindrical forms 

 which are popularly called "Fossil tree- 

 trunks". These stand in vertical position, 

 and the writer would suggest that they re- 

 present structural forms laid in eddies, con- 

 temporaneously with the surrounding sands. 

 That this sandstone was laid down in 

 moving water is indicated by the abundance 

 of "cross-bedding" shown here. The red 

 Potsdam sandstone yields an excellent build- 

 ing stone in most parts of the quarry. 

 17 m. Barriefield. — At Barriefield may be seen 



27-2 km. a "qua-qua-versal", where Pre-Cambrian 

 gneiss forms the core with Ordovician lime- 

 stones dipping away from it in all directions. 

 A short distance farther south an intrusive 

 granite dyke of Laurentian age is exposed. 

 This dyke has cut through the gneisses, and 

 along its contact a number of pneumatolitic 

 minerals have developed, for example, fluorite, 

 tourmaline, pyrite, as well as hornblende and 

 chlorite. The dyke itself shows well-devel- 

 oped joint planes, along which these minerals 

 have collected. Excellent glacial gouges and 

 troughs have been preserved here, as well as 

 glacial striation. Southward from this point 

 on the shore of the St. Lawrence river, a 

 classic example of basal conglomerate is 

 exposed, where the limestones are filled with 

 boulders of the underlying Pre-Cambrian. 



