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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 10, 



are found to be more or less occupied by deposits which are terraced 

 with greater regularity. 



On descending the western slope, these deposits were first observed 

 in the lower part of the valley of Vermilion River, where they are 

 formed of the same glistening, white, calcareous mud that was seen in 

 the valley of the North Saskatchewan ; but it is in the wide valleys 

 of the Kootanie and Upper Columbia Rivers that these terraces are 

 best developed in the Rocky Mountains. These rivers run in oppo- 

 site directions through the same great valley which lies parallel with 

 the mountain-axis for nearly 250 miles, and which throughout is 

 skirted by terraces forming a succession of platforms, often rising to 

 600 feet above the river. These extend into the side-valleys, pre- 

 serving their horizontal character, but their composition is often 

 changed. At various points these deposits were seen to be distinctly 

 stratified, and in some cases they must have been disturbed between 

 the time of their formation and that of their being finally moulded 

 into terraces. Thus where the Kicking-horse River joins the Colum- 

 bia, and where both valleys present perfect terraces at five different 

 levels, the highest, forming a wide shelf 540 feet above the river, 

 the appearance which is exhibited in fig. 3 was observed, where 

 the stream has worn away the bank. 



Fig. 3. — Terraces in the Valley of Kicking-horse River, Roclcy 

 Mountains. 



Shingle. 



Slate-rock. 



The erosion of these deposits, and the production of steep and 

 quickly succeeding terraces (both being processes which may have 

 been simultaneously effected on successive shore-lines either of the 

 sea or of inland lakes) have been much more perfect in the valley of 

 Columbia, as far south as latitude 51°, than in the remainder of the 

 Columbia valley, which extends for a degree further to the south, 

 or throughout that portion of the same great trough which is oc- 

 cupied by the Kootanie River ; for there the deposits remain com- 

 paratively undisturbed, and form great stretches of prairie, only 

 cut through by a narrow but deep channel for the river. The 

 change of appearance in the valley from this cause is very abrupt 

 and striking. North of latitude 51° the terrace-steps succeed one 

 another rapidly, with the tread, or horizontal surface of the step, 

 narrow and furrowed ; and the traveller's progress is here impeded 

 by the dense growth of forest of a northern type, consisting of varie- 



