486 APPEI^DIX 



branch, below which it becomes more conspicuous, forming the 

 whole banks of the stream, with the ezception of a few feet of 

 limestone at the base, for a distance of many miles. These 

 banks are sometimes about one hundred and fifty feet in height, 

 and frequently maintain an elevation of about one hundred 

 feet for considerable distances. Except where they have been 

 long exposed to the weather, they generally look as black as 

 coal. A thick tar is often seen draining out of the deposit, and 

 in numerous places on the ground at the foot of either bank, 

 or on terraces lower than their summits, this tar collects in 

 pools or flows in sluggish streams to lower levels among the 

 peaty materials in the woods. The surface of these accumula- 

 tions of tar is usually covered with a hardened pitchy crust. 

 The boatmen on the river break through this crust in order to 

 collect the underlying tar, which they boil down and use for 

 pitching their craft. Some parts of the banks are rendered 

 plastic en masse from being over-saturated with the asphalt, 

 and in warm weather they slide gradually down into the bed 

 of the river, incorporating the boulders and pebbles in their 

 course." 



BITUMINOUS SAND-ROCK. 



Prom the Athabasca Eiver, about six miles below its conflu- 

 ence with the Clearwater; collected by Dr. E. Bell. This 

 specimen was compact and homogeneous in appearance, of a 

 dull, dark, brownish-black colour. Specific gravity at 60° F. 

 3.040. At the temperature of 50° F. it is quite firm, barely, 

 if at all, yielding to pressure, and does not soil the hand; at 

 70° P. it gives somewhat to the touch, and it is slightly sticky; 

 at 100° P. it becomes quite soft, and eminently soils the fingers. 

 It is scarcely acted on by alcohol in the cold, and but very 

 slightly at a boiling temperature; but ether, oil of turpentine, 

 kerosene, benzine (petroleum spirit), benzol (coal-tar naphtha) 

 and bi-sulphide of carbon, more especially the last two named, 

 readily dissolve the bituminous matter, with formation of dark 

 brown coloured solutions, and leaving a pure, or almost pure, 

 siliceous residue in the form of sand, of which apparently the 

 bitumen had constituted the sole binding medium. 



The composition of this specimen of the rock was found to 

 be as follows: 



Bitumen 12.42 



Water, mechanically included 5.85 



Siliceous sand 81.73 



100. 



