164 GLACIOLOGY 



lower few inches. This type of ice shows marked resemblance to type A. in 

 Green Lake, and is probably produced in a similar way. 

 B. From 18 inches to 2 feet the ice was of a similar type, but yellow and malo- 

 dorous, and again the resemblance to the section of Green Lake is to be 

 remarked. 

 C A layer 9 inches thick of a kind of algous peat, which proved on melting to 

 be composed of numerous small fragments of decayed alga. 



D. The layer C. was followed by a thin 

 layer of ice fairly free from alga, 

 and containing a series of small 

 snow-tabloids and partially ice- 

 filled gas bubbles. This layer in 

 its turn was succeeded by 1 foot 



3 inches of regularly stratified 

 layers of the algous peat, separated 

 by very thin seams of fairly clean 

 ice, and ending in a layer, about 



4 inches thick, which contained 

 rather more grit than the upper 

 layers. The presence of this peat 

 was explained by the abundance 

 of living alga scattered througli 

 the ice at different levels. 



When sinking this trench a main crack 

 was used as one side of the trench in order 

 to accelerate the work. This crack had 

 originally been an inch and a half in 

 diameter, but had been filled, with the 

 exception of an eighth of an inch, with ice 

 in extremely thin vertical layers, formed 

 evidently earlier in the autumn by condensation of the vapour from the water and 

 salt ice beneath. The crack only extended, at the time the trench was sunk, 

 to a depth of 18 inches; beyond that depth it had evidently been entirely filled, 

 either by the ice from this vapour, or from the oozing up of the brine along its 

 leneth. 



Fig. 55. Section of ice and .ilgous peat at 

 Coast Lake near Cape Royds 



Temperatures. 



Air temperature 

 Surface 



1 foot 



2 feet 



3 feet 



- 4'5° F. 



-1.5-5° F. 



-160° F. 



-16-0° F. 



-15'0°F. 



3 feet 10 inches -12-5° F. 



