148 GLACIOLOGY 



1. The wind brings salt to the soil and to the lakes in two main ways. In the 

 short summer, dm'ing the heavy blizzard of February 17th, 18th, and 19th of 1908, 

 the sea spray in a frozen state was carried by the wind for considerable distances in- 

 land. Such action as this, although the high winds during this season of the year 

 are few in number, must have no inconsiderable effect on the waters of those 

 lakes which melt in summer, for not only do they receive the spray which is 

 dropped immediately on them, but also a large quantity of that which falls on the 

 slopes of the hills surrounding them. The latter is carried into them by small 

 streams of thaw-water in the summer. In that portion of the year, when the sea is 

 frozen over, the method of transport is different, but the quantitative result must be 

 even greater. Every blizzard brings quantities of drift snow which has been lying 

 on the sea ice, and has been infiltrated with the salt extruded from between the 

 crystals of the sea ice, and some of this snow (although large quantities pass on 

 beyond Cape Eoyds towards Cape Bird and the Ross Sea) is formed into drifts on 

 the lee side of the hills and ridges, and subsequently in the thaw season goes to swell 

 the amount of water in the lakes. 



2. The second cause appears to be less significant in the Cape Ptoyds area, as 

 here the denudation seems to be more mechanical than chemical. The chemical 

 leaching by the thaw-water is much better illustrated in the Western INIountains of 

 McMurdo Sound, and will be considered in the section dealing with that portion of 

 our researches. Nevertheless, it is probable that a certain amount, at any rate of 

 the soda salts, is leached out from the kenyte during the short period when the thaw 

 is sufficiently effective to produce rivulets of water leading down from the snow-drifts 

 to the lakes. 



The waters of the lakes may be further mineralised by other local causes, which 

 will be dealt with when considering them separately. 



The main glacial groove in which the larger lakes are situated passes from the 

 head of Backdoor Bay along the length of Blue Lake, and sends a branch to the 

 coast by way of Clear Lake and Coast Lake, while the main valley continues as a 

 broad depression filled with morainic material in a north and south direction. (See 

 Plate XLI. Fig. 1.) Two lakes near Cape Barne, Sunk Lake and Deep Lake, 

 appear to be situated in a continuation of the same valley, whilst the other im- 

 portant grooves appear to run more or less parallel with this one, as, for instance, 

 that which the tripartite Terrace Lake occupies. (See Plate XLI. Fig. 2.) 



The remaining lakes or tarns are situated in the depressions which are essentially 

 characteristic results of the phase of denudation which is so typically illustrated here. 

 All angles and craggy projections have been rounded by the Great Ice Sheet, and a 

 mantle of morainic matter of varying thickness has been deposited on top of the 

 country rock, while through this mantle bosses of the more resistant types of kenyte 

 project here and there. 



Green Lake. Green Lake lies about half-way between Blacksand Beach and 



