52 THE ROYAL SOCIETY OF CANADA 
which runs along its south side from 150 to 250 feet above the level of 
the river. The gravels in the terrace are, as a rule, from 10 to 30 feet 
or more in thickness and are quite loose and uncemented. In fact, 
they are so easily broken down and so dry and well drained that it is 
difficult at times to believe that they are actually somewhat older than 
the tighter and more compact gravels near the river. 
These upper gravels, therefore, apparently represent an old flood- 
plain deposit of the White Channel period or Second Cycle of Erosion. 
Like the rest of the White Channel gravel, they have a small quantity 
of gold distributed through them, but up to the present time no pay- 
streak has been found on this terrace, so that probably the bottom of 
the V-shaped valley of that early terrace period ran to the North of 
them. 
Gravels of the Third Cycle of Erosion. These gravels are found in 
the bottoms of the more recent valleys and on the terraces on the sides 
of these valleys below the level of the White Channel gravels. 
As we have seen, the streams flowing Northward into the Klondike 
river have cut gorge-like valleys into the bottoms of the old mature 
valleys of the Second Cycle, while those flowing southward into the In- 
dian river have not been able to cut such gorges but have continued to 
flow in the old valleys, and for the most part at the old levels. 
In the Klondike tributaries the new valleys are narrow, and there 
has been little opportunity for the development of terraces in them, but 
nevertheless a few small terraces were developed and have not since 
been worn away. Across some of these the pay-streak was formed, 
and rich and productive mines have been worked on them. 
The gravel on them is somewhat similar in character to that of the 
White Channel, but, as might be expected in pebbles and loose rock 
particles which had been cut down by the mechanical action of running 
water, rather than by the weathering of atmospheric agencies, the 
pebbles are much fresher and more nearly approximate to the average 
character of the rocks of the adjoining country. For instance, quartz 
pebbles do not entirely preponderate, but associated with them are a 
large number of schist and other rocks which occur within the water- 
sheds of the individual streams. 
Such terrace gravel is not usually more than 10 or 15 feet thick, 
and is often covered by a deep bed of moss and decayed vegetable ma- 
terial similar to that found covering the bottoms of the valleys. 
On the tributaries of Indian river, the lower reaches of the streams 
still flow over the top of the White Channel gravel, but as these streams 
are ascended, and as the gradient increases, the gravel of the White 
Channel period is found to have been washed away and the water is 
