I 2 GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 



the narrowness of the system, its proximity to the Pacific, the higher latitude, 

 the arrangement of the Cordilleran ranges with respect to height, and the position 

 of the region with reference to the ordinary paths of the great cyclonic areas. 

 If these areas of low pressure commonly crossed the continent so that the path 

 of their centres lay well within the United States, the prevailing winds would be 

 easterly over this region. Such winds would be colder in the winter and warmer 

 in the summer than those which now prevail and capable of supplying relatively 

 little precipitation. There can be but little doubt that any great shifting of 

 the paths of the cyclonic areas, either to the north or the south, would lead to 

 a great reduction in the size of the glaciers of this region, and perhaps to their 

 complete extinction. 



b. Chinook winds. One of the most interesting and important climatic 

 factors of this section is connected with the prevailing westerly winds and the 

 north to south trend of the main mountain ranges, giving rise to the so-called 

 "Chinooks." These winds must have been long familiar to the aborigines 

 and voyageurs, but were first noted by Mackenzie about the year 1790 in the 

 region of the Athabasca and Saskatchewan rivers, bringing clear, mild weather 

 in the winter and spring. ' He ascribed their warmth, very naturally, to the 

 nearness of the warm currents of the Pacific, their progress over the snowfields 

 being assumed to be too rapid to permit of their being cooled. The same 

 winds are known in Montana and still farther south in Colorado, where they 

 are known as "zephyrs " and "snow eaters. " They also occur in South America 

 with the passage of westerly winds over the Andes, having been described by 

 Bishop in the vicinity of San Juan, Argentine Republic, under the name 

 "zonda. "2 Here they were supposed to derive their warmth from volcanic 

 sources. The chief characteristics of these, and similar winds are their 

 wannth and drjTiess and consequent accompaniment of bright sky. The}' 

 are most conspicuous in the winter and spring, but occur also in the summer and 

 fall. Standing upon the Victoria Glacier, in midsummer, opposite the nose of 

 Mt. Lefroy, one frequently notes gusts of balmy air sweeping down from the 

 elevated snowfields and puzzles over the source of the warmth. The following 

 graphic description of these winds will serve to get before the reader their 

 climatic importance. 



"The extreme severity of the winters in certain parts of our northwestern 

 states, among the Rocky Mountains and along their eastern base, is much 

 tempered by the prevalence of a mild westerly wind, locally called the chinook. 

 Its name is derived from that of the tribe of Clainook Indians, living near Puget's 

 Sound. It is said first to have been applied by the early Hudson Bay trappers 

 and voyageurs, who, meeting the wind while travelling towards the Pacific 

 coast, and finding it particularly strong and warm as they approached the lands 

 ot this particular tribe, called it the chinook wind. 



"It is described as a soft, bakny wind, varying in velocity from a gentle 



' Voyages on tlte' River St. Lawrence and through the Continent of North America to the Frozen and Pacific 

 Oceans in the Years 1789 and 1793, London, 1801, p. 138. 



2 A Thousand Mile Walk across South America. Boston, 1869. N. H. Bishop. 



