290 PROCEEDINGS OF SECTION C. 



glacial epoch. This frozen mass is the most recent formation of the 

 district, and contains the bones of several extinct mammals of the 

 quaternary period, together with those of some living species and the 

 wood of a few kinds of trees which still grow in the district. Among 

 the animal remains are bones and numerous large tusks of the 

 mammoth, bones and horns of a great extinct bison, and of the exisi> 

 ing American bison, the moose, the reindeer or cariboo, a bear, and 

 an extinct horse, of which Mr. J. B. Tyrrell found only a few bones. 

 A well-made copper spear-head, which the ^vl■iter saw at Dawson, was 

 found at some depth in this deposit. 



Great Depth of Frozen Ground. . 



No animal or plant remains have been met with in any of the 

 old gravels underlying this newest deposit. 



This mass of unstratified material has resulted from the super- 

 ficial decay of the rocks in the interval between the Pliocene and the 

 lotest glacial period. It is thickest on the lower levels and thinnest 

 on the tops of the hills and ridges, as if it had gradually slidden 

 down as it was formed, and accumulated in the valley bottoms. It 

 is all permanently frozen to a great depth which, however, varies con- 

 siderably according to situation. Borings at different places gave the 

 following results : — Upon the ridge south of Eldorado Creek the 

 bottom of the frozen rrfass was reached at 60 ft. from the surface, 

 while in the valley of this creek unfrozen ground was first indicated 

 by running water a little below 200 ft. On the plateau between the 

 Klondike River and Bonanza Creek unfrozen ground was reached at 

 175 ft. 



At the time of the writer's visit to Dawson, in 1905, a boring in 

 progress near the centre of the town, and not far from the Klondike 

 River, was do-wn considerably more than 100 ft., and Avas still in 

 frozen ground. In some of the excavations made by the miners in 

 other parts of the district, portions of the frozen " ground " consisted 

 of ice mixed with some earth. It is improbable that the ground would 

 freeze to such great depths in the present climate of the Klondike. 

 Where the living moss, or the deeper covering of muck is removed 

 from the surface, the earth thaws in summer to a depth of 6 to 10 ft., 

 but this becomes completely frozen again during the following winter, 

 as it lies between the cold air and the imderlying frozen earth, which 

 has a temperature below 32° Fahr. Where the surface covering of 

 vegetable matter is undisturbed the ground does not thaw all summer. 



A record of the temperatures was being kept at the bore-hole 

 above referred to in Dawson town, and it was found that the maximum 

 cold had been reached at about lO'O ft. from the surface. It was the 

 opinion of the intelligent operator, with whom I conversed on the 

 subject, that this was the general condition wherever the frozen 

 ground had its full development. Since the usual depth of the frozen 

 layer throughout the district appears to be about 200 ft., this would 

 seem to show that the climate of the Klondike has so far improved 

 since the last Glacial period, that the summer's thawing now pene- 

 trates to as great a depth as the winter's freezing. The great thick- 

 ness of the frozen ground, and the low temperature of its mid-depth, 

 indicate that the permanently frozen condition is a legacy from a 



