246 A NATURALIST ON THE "CHALLENGER." 



One small berg was passed at a distance which was of 

 remarkable colour. It looked just like a huge crystal of sul- 

 phate of copper, being all intensely blue, but it seemed as if 

 attached to, and forming part of, another berg of normal colour 

 (coloured plate, fig. 7). Possibly it was part of the formerly sub- 

 merged base, and of more than ordinary density. Only one other 

 such berg was seen. The intensity of the blue light received from 

 the bergs ordinarily is such that the grey sky behind them 

 appears distinctly reddened, assuming the complementary tint, 

 and the reddening appears most intense close to the berg. 



At night bergs appear as if they had a very slight luminous 

 glow, almost as if they were to very small extent phosphorescent. 



The sea at the foot of the bergs usually looks of a dark indigo 

 colour, partly, no doubt, out of contrast to the brighter blue of 

 the ice. Where spurs and platforms run out under water from 

 the bases of the berg cliffs, the shallow water is seen to be 

 lighted up by reflection of the light from these. 



The surf beats on the coast of an iceberg as on a rocky shore, 

 and washes and dashes in and out of the gullies and caverns, 

 and up against the cliffs. Washing in and out of the caves, it 

 makes a resounding roar, which, when many bergs surround the 

 ship, is very loud. So heavy is the surf on the bergs, and so 

 steep are they as a rule, that we did not see one on which we 

 could well have landed from a boat. 



As the waves wash up into the wash-lines of the bergs they 

 form icicles, which are to be seen hanging in rows from the 

 upper border of these grooves. 



A line of fragments is always to be seen drifting away from 

 a large berg. These are termed wash-pieces. They are very 

 instructive as showing the vast relative extent of submerged ice 

 required to float a small portion above water ; the parts of the 

 fragments below water being visible from a ship's deck. 



The scenic effects produced by large numbers of icebergs, 

 some in the foreground, others scattered at all distances to the 

 horizon and beyond it, are very varied and remarkable, de- 

 pending on the varying effects of light and atmosphere. 



On one occasion, as we were approaching the pack ice, some 

 distant bergs were seen to assume a most intense black colour. 



