1T2 GLACIOLOGY 



layers of snow. The Plate shows one of the larger of tliese tabular bergs of what 

 may be termed shelf ice capped by snow. 



This formed one of the fleet above described. 



Plate XLV. Fig. 1 shows the stratified cliaracter of the snow in one of these 

 bergs, which had become tilted as the result of differential corrosion in the sea water. 



The height of this last berg appeared to be about 60 feet. The older bergs not 

 only exhibited traces of tilting, but also extensive wave-worn gi-ooves at their base. 

 Such a structure is well illustrated in Fig. 2 of an iceberg close to which the 

 Nimrod passed in Koss Sea in the third week of January 1908. 



While the solvent action of sea water, combined with the mechanical erosive 

 force of the waves, tends to rapidly destroy these bergs, the work of destruction is 

 to a limited extent further accelerated by the collision of the bergs with each other 

 during blizzards. The effect of such collision in crushing up the layers of snow and 

 neve, of which the upper portion of the berg is formed, is illustrated in Plate XLVI. 



It is very noticeable that the sides of bergs facing the north become strongly 

 etched in the warm beams of the noonday sun. In fact, for a great part of the twenty- 

 four hours during the time of midnight sun, such faces showed evidence of more or less 

 continued thawing. The icicles dependent from this berg are clearly shown in the 

 photograph. At the base of the berg is seen the fringe of icicles formed along the 

 wave-worn grove. If much dust was present on the surface of bergs, the effect of 

 thawing became more pronounced. Such cases were of course most frequent amongst 

 bergs of blue ice derived from land glaciers. An interesting berg of this kind was 

 sighted near Cape Bernacchi by the Northern Party. The berg was about 70 feet 

 in height, and the face directed towards the north was beautifully fluted, the structure 

 having some resemblance to the pipes of an organ. A close examination of this 

 structure revealed the fact that the fluting was the work of comparatively small 

 quantities of rock dust together with fine pebbles. In the first instance these appear 

 to have been distributed with tolerable uniformity in a thin layer over the surface of 

 the berg. In places more heat would be absorbed by this layer of rock material 

 than in others, on account either of difference in the colour of the rock, or in the 

 thickness of the layer of rock debris, and as a result small thaw hollows would be 

 produced into which the rock dust and pebbles would glide. The thaw-water from 

 these conical depressions, if they were situated near the northern face of the berg, 

 would sooner or later overflow in a tiny rill, and cut down for itself a channel in the 

 northern face of the berg, down which it would fall in tiny cascades. It would 

 carry down with it some of the dust and small pebbles, and these, arrested in their 

 downward progress on small projections of the ice-cliflf, have further accelerated the 

 process of thaw and completed the grooving process. The surface of this particular 

 berg was, therefore, much pitted with typical "dust wells." 



Bergs formed of true blue glacier ice were comparatively uncommon. Altogether 

 only a few were sighted in the journey of 200 miles from Cape Royds to the 



