lO GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 



any tendency towards a westerly movement being checked b>^ the ice in the 

 Cascade and Bow valleys. The westerly movement noted by Dr. Ogilvie was 

 simply a minor episode toward the close of the Pleistocene glaciation. 



4. Climatic Data. 



a. Geographic distribution of moisture. The climatic conditions of this 

 section of country are peculiarly dependent upon the physiographic features 

 above outlined, combined with its proximity to the Pacific. The centers of 

 the areas of low pressure commonly move in from the ocean to the northward 

 of the region, give rise" to westerly winds which convey the warmth and moisture 

 of the Pacific currents across British Columbia and Alberta. At Nanaimo, 

 upon Vancouver Island, separated from the mainland by 30 miles of strait, 

 the precipitation records available show a rain- and snowfall combined ot 41.36 

 inches, only 5 per cent, of which falls as snow. Opposite, upon the mainland, 

 the total precipitation at Vancouver rises to 63.06 inches, with 4 per cent, 

 falling as snow. This increase is due to the Coast Ranges, having here a north- 

 west-southeast trend, which compel the westerly winds to ascend their westerly 

 slopes, by which rise the air is cooled and its capacity for holding moisture 

 thereby diminished. At Agassiz, in the lower Frazer Valley, the precipitation 

 is but slightly less, although it is located some 70 miles from the Strait of Georgia, 

 up the broad open valley, and about 50 feet above sea- level. Records are 

 available here since 1890, with the exception of the years 1891 and 1899, and 

 give for the 14-year series an average precipitation of 62.02 inches, 6 per cent. 

 of which falls as snow. Over the broad interior plateau which lies between the 

 Coast and Gold ranges, the temperature is colder and the precipitation relatively 

 slight. At Kamloops, with an elevation of 1,160 feet and in latitude 50° 41', 

 the combined rain- and snowball averages biit 10.66 inches. Passing eastward 

 the air currents impinge upon the westerly slopes of the Gold Range, are again 

 compelled to ascend to still higher altitudes, with the attendant loss of moisture. 

 In consequence, the station of Griffin Lake, located in this range at an elevation 

 of 1,511 feet, and 90 miles east of Kamloops, receives an average precipitation 

 of 34.37 inches, or over three times as much as the latter place. Crossing the 

 Columbia a still higher barrier is encountered in the impressive Selkirk system 

 of ranges, and a correspondingly increased amount of moisture extracted from 

 the still laden air currents. The records in the Selkirks are unfortunately 

 meager, but they indicate a precipitation almost as great as that of Vancouver 

 and Agassiz, and considerably in excess of Nanaimo and Victoria out in the 

 Pacific. The station of Glacier House is located just west of the main crest 

 of the Selkirks, in latitude 51° 16' and at an elevation above tide of 4,093 feet. 

 The average total precipitation here is 56.68 inches, of which 77 percent, falls 

 as snow. If the entire amount were precipitated as snow, as is practically the 

 case upon the peaks and elevated n^v^ fields, this would represent an average 

 fall of over 47 feet. This heavy snowfall in the Selkirks and Gold Range has 



