52 



lean phase of the iron formation. This variety is exposed 

 near the centre of the west face of the bluff, where there is 

 a slide of talus material. 



The attitude of the beds is well shown near the waters 

 edge, where there is an abundant development of the 

 lime silicates, which have weathered into marked relief. 



Fossiliferous Steeprock limestone, Trueman point, Steep- 

 rock lake, Ontario. 



A dyke of quite unaltered diabase cuts the Laurentian 

 about 500 feet (152 m.) north of the northern landing, and 

 probably represents a vent through which some part of 

 the sills or flows in the Steeprock series reached their 

 present position. Numerous basic, dyke-like masses cut 

 the granite in this neighbourhood. 



