184 GLACIOLOGY 



tures, and had drops of the brine dependent from their lower ends. On the occasion 

 mentioned, the middle of June 1908, when the temperature was about —30^ F., the 

 brine had frozen as a white enamel-like cryohydrate. 



During the winter we observed that horizontal stratification was imparted to 

 the sea ice in the neighbourhood of the tide cracks by the following process : — with 

 the rise of the tide, at a time when the sea ice was pressed hard against the shore 

 by wind or currents, so that the sea ice was not free to rise with the tide, sea water 

 would overflow the surface of the sea ice for some distance on the seaward side of the 

 tide crack. This layer of water would then freeze. The process being many times 

 repeated, a deposit of laminated ice became superimposed upon the true sea ice. 

 Plate LV. Fig. 3 shows the appearance of such laminated ice from near Flagstaff 

 Point. 



A somewhat analogous phenomenon was observed by the Western Party. They 

 observed in summer time that the sea ice at McMurdo Sound was traversed by 

 pressure ridges parallel to the edge of the piedmont ice. Nearest the ice-foot 

 numerous slabs of well-laminated ice were observed, the origin of which was probably 

 similar to that just described. They observed that local depression of the sea ice 

 near the tide crack probably takes place on the western side of McMurdo Sound 

 on a large scale. Along the " jainnacled ice" (perhaps a floating piedmont heavily 

 loaded in places with moraine) is situated a band of ice, which is probably sea ice 

 three or four years old. The junction line between this ice and the new ice of last 

 year was marked by a pronounced ice-foot 2 or 3 feet high. About 1 mile to the 

 E.S.E. of where the Western Party descended there was an area along this ice-foot 

 extending for a distance of 2 or 3 miles of intensely blue, apparently wind-swept, ice 

 with no snow on it whatever. They had hardly advanced more than a few steps on 

 to it when it began to crack and bend in an alarming manner, and they realised that 

 it was merely a thin crust of ice, which had evidently formed during the last two 

 cloudy days over what had before been a pool of open sea water. At first they were 

 inclined to think that they had struck a salt water pool, such as that reported by the 

 Discovery off Cape Armitage. The latter was attributed to the thawing of a swift 

 current of relatively warm sea water flowing over a shoal ; but in this case, on 

 testing the ice in several places with ice axes, they found that there was a thin 

 upper skin of ice on top followed by a few inches of water below, and then apparently 

 by a solid mass of ice of unknown thickness ; at any rate sufficiently thick to resist 

 any efforts to penetrate through it with the point of the ice axe, although they were 

 several yards away from the edge of this belt of clear, freshly-formed ice. The 

 water intervening between the two ice layers was nowhere more than a few inches 

 in depth. 



It seems probable that, owing to the pressure from the south-east and north- 

 west, this ice had been thrown into very long gentle undulations, of which the area 

 described was one of the troughs, and that this trough was subsequently floated by 



