342 J. S. Newoerry — Surface Geology of the country 



markings from the snow line to a point ^,500 feet lower, where 

 they pass under the alluvium of McKenzie's Fork.* 



It has been claimed by Lecoq {Les Glaciers et les Climats) 

 and following him b} T Professor Whitney and others {Later Cli- 

 matic Changes), that the great development of glaciers during 

 the Ice Period, such as those of the Canadian highlands, the 

 Rocky Mountains, the Cascades and Sierra Nevada, was not the 

 effect of a cold but a warm period, which increased the precipi- 

 tation and consequently the snow-fall at all places where the 

 temperature was low enough to cause it to take the form of 

 snow. If this was all, however, the most extensive glaciers 

 should be in the Alpine districts of the tropics or temperate 

 zones wherever the precipitation is most abundant and the tem- 

 perature low enough to produce perpetual snow. But the great 

 glaciers of the present time are not on the Andes, the Himalayas 

 or the Alps, but on Greenland and the Antarctic Continent 

 where the climate is very cold and the amount of precipitation 

 small. 



We also find on the summits of the Cascades a demonstration 

 of the fallacy of this view; since here some of the mountains 

 rise 14,000 feet above the sea and the line of perpetual snow is 

 not over 7,000 feet, while the annual precipitation is greater 

 than in almost any other portion of our country. In fact the 

 snow accumulates in such quantity that even in mid-summer it 

 reaches down to where it is met and opposed by a vigorous 

 forest growth — the product of a high temperature It is evident 

 that no elevation of temperature, though it should increase the 

 evaporation on the Pacific and the rain-fall on the coast, would 

 cause the renewal of the ancient glaciers; but with a depression 

 of temperature which should continue the present winter con- 

 ditions through the year, the precipitation remaining the same, 

 the accumulation would soon cover the mountain summits with 

 snow and ice and bring the glaciers down to their old limits. 



THE LOWER COLUMBIA. 



The country bordering the Lower Columbia is too well known 

 to require description. I am impelled, however, to refer to one 

 or two points in its physical structure which are of special in- 

 terest when brought into connection with facts of similar import 

 observed in the region about Puget's Sound. I have said that 

 the Lower Columbia is an arm of the sea. It is in fact a deep 

 river valley which has been flooded by an influx of the sea 

 caused by subsidence. This brings tide-water to the foot of the 

 falls of the Willamette at Oregon City, and to the Cascades. 



It requires no argument to prove that such a channel could 

 not have been cut unless by a rapid stream flowing into the 

 * Pacific Railroad Report, vol. vi, Part II, Geology, p. 42. 



