350 E. M. KINDLE 
(Fig. 5). Such a drift pile checks the current and furnishes the 
beginning of the conditions essential to island formation. The 
river makes a deposit of silt below it, and this, in time, may connect 
with another similarly formed ‘sland by downstream growth. 
These low knobs prevail up to the mouth of the main outlet of the 
Peace. Above the mouth of the Peace the knobs of granite increase 
in elevation till 25 feet is an average height. Still higher up the 
Slave River the granite knobs increase in height toward Little Lake 
and Lake Athabasca, just north, until an elevation of 150 feet or 
more is reached. In Peace River the same type of island construc- 
tion and destruction which characterizes the lower Slave is seen. 
Fic. 5.—Island composed of drift timber, Slave River 
Great numbers of spruce trees are being undermined constantly 
and thrown into the river. This timber from the cut banks of the 
Peace and Slave is the source of the enormous quantities of drift 
logs which line the shores of Great Slave Lake (Fig. 3). Some 
of the logs accumulate on the low, granite-island knobs and form 
islands, some of which appear, at high water, to consist exclusively 
of logs (Fig. 5). Trees whose roots are heavily Joaded with earth 
and stones often strand in shoal water and form the nuclei of new 
islands. 
The delta of Athabasca River near the western end of Athabasca 
Lake is very similar to that of Slave River in Great Slave Lake. 
The lake water in front of it is only 2 to 4 feet deep for a considerable 
distance except along a narrow, crooked channel. The banks rise 
above the river (late-summer stage) less than 1 foot for 3 or 4 
miles. Higher up from the lake they rise gradually to about 3 
