13 District traversed hy the 



A vein of granular limestone nearly approaching in 

 appearance to dolaraite, runs through the calcareous 

 formation, which is also intersected with broad veins of 

 quartz and hornblende. This hornblende in many instances 

 is vesicular, the vesicles tilled with crystals of calcareous 

 spar ; there also occurred masses of quartz, containing 

 nodules of the calcareous rock. At one place was observed 

 a broad vien of epidote, running through the calcareous 

 spar with an upper strata of quartz resting upon it ; thin 

 veins of calcareous spar passed through this epidote. 



We occasionally fell in with the calcareous formation, 

 until we reached Lac du Sable, where we again noticed it 

 on the north shore, underlying a rock of light grey lime- 

 stone containing in its composition an admixture of silecious 

 matter, and some small orbicular crystals of milk colored 

 quartz. These rocks are situate close to the edge of the 

 lakes and rising immediately above them is a hill of sienite 

 thinly covered with sand. The sienite is of a dark color, 

 apparently stained with the oxide of iron. 



Between Lac du Sable and the River Ottawa, we alter- 

 nately fell in with the calcareous spar, and sienite, the 

 hills being invariably composed of the latter. At the foot 

 of the Cedar Portage, a few miles below Lac du Sable, the 

 calcareous spar occurred, forming the bed of the river, 

 but intersected with broad veins of silecious limestone, 

 abounding in large crystals of talcy mica and white iron 

 pyrites. The portage, which is rather above the level of 

 the river, runs over a rock of sienite. About ten yards 

 from the west shore rises a small hill of sienite, about two 

 hundred feet in circumference, covered with moss and 

 trees : the channel between it and the main shore consists 

 of the calcareous spar, abounding with mica; near the 



