152 GLACIOLOGY 



working. The superficial dimensions of the trench were 3 feet by 7 feet, and the 

 ice proved to be 5 feet deep. Tliere was water luader the ice, but the supply was 

 limited, as shown by the fact that when tapped it only rose quickly to within 2 feet 

 6 inches of the top of the ice, subsequently rising another 6 inches in an hour. 

 This rise was probably due to a slight sagging of the ice, and also to the release of 

 some of the water held under pressure in the bottom G inches of tlie ice, and which 

 would only disengage itself slowly. There was scarcely a foot of liquid left under 

 the 5 feet of ice, and from the slowness with which the water rose in the trench 

 it seems probable that we tapped the lake at one of the few places where a little 

 brine solution was left unfrozen. This brine solution was at the remarkably low 

 temperature of 21° F., and some which we bottled we left to stand for some time, 

 when a ring of oily material about I inch thick with a greenish fluorescence was 

 formed at the top. This was formed of tiny globules, each about ^^ of an inch in 

 diameter, with a refractive index lower than that of water. It was afterwards masked 

 by a brownish -yellow scum, with a thickness of quite an inch in parts, and a quantity 

 of evil-smelling gas was given oft'. A quantity of the ooze from the bottom of the 

 lake was also collected. 



On Fig. 55 is shown the shaft sunk by one of us in this lake ice in June 1908. 



Descending Section. 



A. Ten inches of ice with numerous air bubbles. (Four inches of fairly clear 



ice then a layer of bubbles, 3 inches of ice and then a layer of bulables, 

 then layers from an inch and a half to half an inch separated by regularly 

 arranged rows of bubbles. ) 



B. Three feet 2 inches of typical lake ice, very bubbly, and with some 



bubbles drawn out. A falsely fibrous structure becomes more and more 

 apparent as the lower layers are reached, its cause being ajaparently 

 streams of very fine bubbles in a vertical direction. The bubbles are 

 fairly vniiformly distributed. 



C. At 4 feet the ice became yellow and discoloured, with a very unpleasant 



smell, due to gases given off". It was also very salt and moist, and all three 



characteristics increased as the work proceeded. 

 Tijpe A. The structure of this ice is very interesting, and apjjears to be due to 

 atmospheric conditions. In the late summer, when the lake began to freeze over, 

 the layer of ice formed when the sun was low was at first entirely removed when 

 the sun's rays impinged on the lake at a steeper angle. As the winter approached, 

 and the hours when the sun was high enough to afifect the lake decreased, the ice 

 became permanent, and apjjarently the first permanent layer of ice formed was suftl- 

 ciently thick to leave a layer of 4 inches at the end of the succeeding day's thaw. Dur- 

 ing the succeeding period of comparative warmth before another frost set in, and when 

 the first layer of ice was being removed (as thaw at tlie time was dominating freezing), 

 a number of gas bubbles, disengaged by the decay of the organic matter at the 



