168 GLACIOLOGY 



rounded by low debris-covered hills, and receives its name because of the well- 

 marked vestiges of at least three terraces on the slojDes of these hills. None of 

 the terraces are very much above the ^aresent level of the lake, being only a few 

 feet ajiart. The lake is fringed with a certain amount of the algous plant so 

 common at Cape Royds, and large bunches of the same plant were weathered out 

 of the surface by reason of the ablation of the lake ice. Before the end of August, 

 at least 3 or 4 inches must have been removed by ablation since the preceding 

 summer. 



Parts of this lake were very deep and of very pure and clear ice, and at these 

 places the inclusions in the ice were plainly visible at a great depth. It was here 

 that the photograph of a snow-tabloid half a foot in diameter was secured, and 

 these snow-tabloids were very common. These tabloids were usually cavities 

 formed by gases, in some cases perhaps set free from the algas, and partly 

 filled with powdery ice. Many pieces of alga were visible enclosed in the ice, and 

 above them generally were streams of small bubbles showing up clearly against the 

 clear lake ice because they contained a quantity of finely-divided ice particles 

 growing like an efflorescence on the inside of their ice-walls. This efflorescence in 

 some of the larger bubbles examined seems to be due to the expulsion at low 

 temperatures of the water-vapour taken up at high temperatures, a process which 

 would have small result at first, but after many repetitions seems quite adequate 

 to produce this small amount of rime. 



Another occurrence unusually common here was the interstratification of fairly 

 large stretches of rippled snow between layers of ice. All those seen here seemed 

 to be at the same level, and at 3 or 4 feet below the surface, but the estimation 

 of depth is only approximate, for we dug no trenches in the lakes. 



It was near Terrace Lake that a thick deposit of dead alga of the type occupy- 

 ing lakes was found at a height of 40 feet above any present lake surface. It seems 

 probable that this deposit, which was 2 or 3 feet thick, and covered with a 

 layer several feet thick of moraine gravel, was the remains of an old lake-bottom 

 elevated and denuded. 



Deep Lake. Dee]! Lake was bounded on its east and west sides by cliffs of 

 highly -jointed kenyte, with the joints radiating in fan shape. To the north of the 

 lake was the ridge which was capped by mirabilite, and to the soiith was a gradually 

 shelving plain of moraine matter. The cliffs at the side dipped almost pei-pendicu- 

 larly beneath the ice, and it seems probable, since we could see no bottom, although 

 the lake was very clear, that the depth here is at least 15 or 20 feet. Its surface 

 is about 40 feet above sea-level. This lake was one of the earliest of the fresh- 

 water ice lakes to melt, for already before the departure of the Western Party on 

 December 9, 1908, a fringe of water had formed at the foot of the kenyte cliffs. 

 Unfortunately the extent of the thaw was not ascertained. 



Sunk Lake. This lake received its name because the present surface of the ice 



