ACTION OF THESE FORCES IN THE ARTIC OCEAN 2 1 -J 



addition to which all the important tributari(!S that enter its 

 channel below the mouth of Lake Ontario pass throiiL,di smaller 

 but sufficient natural catch-pools, that retain the debris. The 

 result is that the vast tide of the St. Lawrence waters comes 

 to tile sea level almost without burden of sediment, and 

 nothing like a delta deposit appears at the mouth of the 

 stream. 



Owing- to certain peculiarides in their conditions, the 

 laro-e rivers which flow into the Arctic Ocean, the Macken- 

 zie of North America, and the Lena, the Obi and the Yenisei 

 of Asia, discharge much larger amounts of sediment than any 

 other streams of high latitudes. The cause of this is peculiar. 

 In the winter season the ice forms in the lower and more 

 northern portion of these streams to such thickness that they 

 are often frozen to their very bottoms, so that when the spring 

 floods send down a great tide of water from the southern trib- 

 utaries the current is unable to break up the ice which fills the 

 accustomed channel of the river, and the inundations sweep far 

 and wide on either side of their fit path. In these movements 

 the}' erode a great deal of earthy matter and bear it to the 

 mouth of the streams. The result is that the mud deposits 

 in the delta districts about the Arctic Ocean are much more 

 extensive than in other parts of the northern realm, but as the 

 harborages of this sea-shore have no commercial value the 

 effect of these mud accumulations is of no economic impor- 

 tance. 



If the sea-shore maintains this position for any considerable 

 eeoloo-ic time, the effect of ri\er action would be to make the 

 mouth of every stream discharging into the ocean the seat of a 

 delta, and as almost all our ports have tributary rivers, the num- 

 ber of harbors, except such as the delta channels afford, would 



