154 GLACIOLOGY 



trench, but the yellow ice started at 2 feet 6 inches and the ice was almost 5 feet 



6 inches thick, reaching to within 3 or 4 inches of the lake bottom. 



In making this section two master cracks were used to lighten the labour at 

 a place where they crossed at right angles, and incidentally it was proved that they 

 were open right to the bottom of the lake, as the trench was scarcely 3 feet deep 

 when the brine solution oozed up very quickly along both of the cracks, and it was 

 necessary to desist and cut a trench within a trench. The work was much inter- 

 rupted by other duties, but the bottom 18 inches was taken out on August 6 th, 

 when the section exposed was as follows : — 



A. Ten inches of laminated ice as in Trench 1. 



B. Twenty inches of colourless ice, opaque, with fine bubbles and salt extrusions. 



C. Thirty-six inches of ice similar to above, but of yellow colour and very 

 malodorous. 



After the ice was broken through the water rose only 24 inches in 

 the trench. Specimens of ice from the sides of the shaft at different depths were 

 examined by Mawsou, and bottles of the brine solution were collected. The latter 

 was similar in colour and consistency to that of the former trench, but nothing like 

 as much gas was given off. 



It seems likely, therefore, from consideration of this last fact, and the little 

 height to which the water rose in the trench, that this second trench was cut down 

 into the same reservoir of the brine which we tapped last time, that this solution is 

 the last concentrate produced from the water of the whole lake, and that the part 

 of the lake in which we trenched is the deepest. 



Temperatures taken on July 1st were — 



The temperature of the brine solution taken immediately we broke through the 

 ice on August 6th was —17° F., probably one of the lowest temperatures ever re- 

 corded for so large a body of water under natural conditions. 



Clear Lake. Clear Lake is situated to the north-west of Blue Lake, and in the 

 western fork of the northern continuation of the Blue Lake Valley. Its name was 

 given to it because of the remarkable clearness of the upper layers of ice. There 

 were few striking topographical features immediately near the lake, but one was 

 a steeply-rounded kenyte knoll, whose sides sloped rapidly down right underneath 

 the lake, and a few yards out from which, to judge from the contour of the lake 

 basin, the deepest part of the lake should be situated, for everywhere else the slojae 



