GEOLOGY-CAUSE AND EFFECT OF LOW TEMPERATURE. 
43 
holding, as they do, such peculiar and constant relation to the areas which are drained through 
them, cannot possibly he regarded as rifts formed by volcanic action in the harriers which they 
traverse. The conclusion seems irresistible that they have been formed principally, if not 
entirely, by currents of water, of which the present streams are representatives. 
Another of the deeply graven records from which we are attempting to deduce the ancient 
history of the western coast is found in the great depth of the channels by which these streams 
terminate in the Pacific. The deep and narrow fiords which mark the northern portion of the 
western coast, of which those opposite the island of Vancouver, on the coast of Washington 
Territory, are good examples, have been described by Professor Dana, in his Geology of the 
Exploring Expedition. The mouth of the Columbia exhibits similar features. For a hundred 
miles it forms an arm of the sea of great and uniform depth. 
The channel of the Golden Gate has a maximum depth of nearly fifty fathoms, being greatest 
immediately in the line of the axis of the chain through which it is cut, while the bar without 
and the bay within are silted up to within less than ten fathoms of the surface. 
The Straits of Carquines have a maximum depth of eighteen fathoms, and in the line of the 
range which bounds them an average depth of fourteen. 
It is evident that glaciers could now be formed in the Cascade mountains only by a great 
depression of temperature, and it is perhaps doubtful whether glaciers would now form to the 
extent indicated by the traces of their former existence, which has been described, even with a 
depression of temperature so low as to precipitate and congeal all the vapor which floats above 
them. Without, however, raising that question, we may be at least certain that with the former 
existence of glaciers in the Cascades, the average temperature was much lower than at present. 
This must have been dependent upon one of two causes : either a great and radical difference in 
the climate of the coast without a change of elevation, or, the climate remaining the same, by 
the elevation of the coast to a general altitude several thousand feet higher than at present. 
Of the condition required by the first of these hypotheses we have no other evidence than that 
of the glaciers themselves, while of the former elevation of the coast, in the sub-mrial excavation 
of the fiords at the north in the deep channel of the Columbia, and, as it seems to me, in that 
of the Golden Gate, we have cumulative and conclusive proof. The effect of such an elevation 
as would be required to cover the slopes and valleys of the Cascades with glaciers, would be 
exhibited in various ways. The amount of moisture precipitated upon the sides of these moun¬ 
tains would then be much greater than now. Instead of presenting isolated peaks rising above 
the line of congelation, they would form an unbroken wall, of which the summit, white 
with perpetual frost, would rob of all its moisture the wind, then as now, blowing over it from 
the Pacific. This precipitation, though greatest on the western slopes, and forming by its con¬ 
gelation sheets of ice which would reach far down its sides, crowding themselves into the 
angular valleys which now lead toward the Pacific, would also extend its influence to the eastern 
slope, fill many of its basins, now dry, with water, give greater volume and efficiency to the 
streams, and enable them to score so deeply the surfaces of the plateau, and force mountain 
barriers to reach the ocean, cutting deep channels in its shores where we now find them. 
