2 GEORGE V. SESSIONAL PAPER No. 25a A. 1912 



CHAPTER I. 



INTRODUCTION, 



Area Covered. — In 1901 the writer was commissioned by the Canadian 

 Minister of the Interior to undertake the geological examination of the mountains 

 crossed by the Boundary Line between Canada and the United States, at the 

 Forty-ninth Parallel. Field work was begun in July of that year and continued 

 through the different summer seasons to and including that of 1906. During 

 the summer of 1901 reconnaissance surveys on the American side of the same 

 line were led by Messrs. Bailey Willis, F. Leslie Ransome, and George Otis 

 Smith, members of the United States Geological Survey. No further geological 

 work in connection with the Boundary survey was carried on by the United 

 States Government, and the map sheets prepared by the United States topo- 

 graphers were placed at the disposal of the writer as geologist (for Canada) to 

 the International Boundary Commission. The present report represents the 

 principal results of the study made during the six field seasons. 



The geological examination covered a belt along the Forty-ninth Parallel, 

 from the Strait of Georgia to the Great Plains. The belt is 400 miles long and 

 varies from 5 to 10 miles in width, with a total area of about 2,500 square miles. 

 Its width was controlled, in part, by that of the map sheets prepared by the topo- 

 graphers of the Commission parties ; in part, by the necessity of depending on the 

 trails which those parties built into the Boundary belt. As a rule, this moun- 

 tainous belt is heavily wooded and, without trails, is almost inaccessible to 

 pack-animals. During the first three seasons accurate topographic maps on the 

 required scale were not available, and in 1902 and 1903 the writer used, as 

 topographic base, an enlarged copy of the West Kootenay sheet of the Canadian 

 Geological Survey. In that relatively accessible part of the Boundary belt 

 (from Grand Forks to Porthill, eighty miles to the eastward) it was found 

 possible to cover a zone ten miles in width. 



Conditions of Work in the Field. — No geologically trained assistant was 

 employed in any part of the field. The work was, therefore, slow. Each 

 traverse generally meant a more or less taxing mountain climb through brush 

 or brule. The geology could not be worked out in the detail which this moun- 

 tain belt deserves. For long stretches the rock exposures were found to be 

 poor. Such was the case for the heavily drift-covered mountains between 

 Osoyoos lake and Christina lake, and, again, for nearly all of the 60-mile sec- 

 tion between the two crossings of the Kootenay river, at Gateway and Porthill. 

 Some confidence is felt in the maps aud structure sections of the Rocky 

 Mountains proper (from Waterton lake to Gateway), of part of the Selkirk 



25a— Vol. ii— 1 



