HOMEWARD BOUND 189 



According to Dr. George M. Dawson, the 

 geologist: "This ash deposit appears to be 

 entirely due to a single period of eruption. 

 It is homogeneous in character wherever seen, 

 forming a single layer not divided by interca- 

 lations of other material, and has been spread 

 everywhere in the entire area characterized by 

 it. It is much more recent in date than the 

 white silt deposits which are the last of those 

 properly referable to the glacial series, having 

 been deposited after the river valleys were ex- 

 cavated in the glacial materials, and at a time 

 when the rivers had cut down nearly quite to 

 their present levels — a fact rendered evident 

 by the circumstance that it overlies the depos- 

 its of river and valley — gravels and sands in 

 all cases, except in those low river flats where 

 these deposits sometimes cover it a depth of 

 several feet. In most places it is overlain 

 merely by the surface soil with a depth of six 

 inches to two feet, and in a few instances it 

 was noted as constituting the actual surface 

 of terrace of moderate height, the present for- 

 est being rooted in it. The ash appears to 

 have fallen tranquilly, much in the manner of 

 snow deposited from a calm atmosphere. The 

 examination of scraped banks along the two 

 rivers (the Pelly and the Yukon) showed it 



