done on board H.M.S. c Challenger. 3 619 



worn rock at the crest, which gives it its castellated look, consists of a 

 light-coloured ground, in which are enclosed pieces of the recent scoria- 

 ceous lava which occurs immediately beneath it and large crystals of 

 augite. These crystals, though apparently perfect when imbedded in the 

 rock, were not found otherwise than broken when weathered out ; and in 

 places inside these natural battlements, where there was free play for the 

 usually boisterous wind, all the lighter sand had been blown away, leaving 

 the ground covered by a jet-black gravel. Both these crystals and the 

 rocks show the abrading effect of blown sand, the crystals having lost 

 their regularity of form and the rocks having acquired a more definite 

 shape than would have been the case had the weathering proceeded 

 equally on all sides. Here, however, and still more remarkably so in 

 Heard Island, the constant and violent westerly winds, wherever they 

 have an opportunity of charging themselves with sand, sculpture the 

 rocks into shapes of apparently unnatural regularity. From this hill 

 another similar but smaller one could be seen close to the base of the 

 " Sugar-loaf." It resembled more a circle of Druidical stones protruding 

 through the moorland than a hill ; my time, however, was too limited to 

 admit of my visiting either it or the imposing Sugar-loaf, the structure 

 of which appeared from a distance to be quite peculiar. 



On entering Greenland Harbour, which at its head is only separated 

 by a narrow neck of land from Royal Sound, the eye is at once struck by 

 the strange protrusions of light grey rock through the ordinary horizontal 

 basaltic beds which form the hill-ranges. The most extensive of them, 

 which occurs on the summit of the range on the western side of the 

 harbour, has at a distance a very strong resemblance to a ruined castle. 

 I was able to examine two of them, one on the summit and one down 

 nearer the landing-place, both on the west side of the harbour. The 

 rock in both of them is identical, and consists of a light, greenish-white 

 phonolite protruding through the horizontal beds of augitic rock. These 

 cylindrical masses of phonolite are columnar at the outer edges, the 

 columns lying horizontally and being arranged radially. This columnar 

 structure, however, disappears a few feet from the outside, and the rock 

 is simply massive. The effect of weathering has been to split it up into 

 loose blocks, which lie thickly scattered over the ground enclosed. The 

 whole outside line being constructed of horizontal columns, forms a sort 

 of natural cyclopian wall, much more capable of resisting the degrading 

 influence of the weather than the massive inside ; hence we might expect 

 that as they always protrude on a hill slope, the rock being disintegrated 

 in the centre would slip down the hill, forming a heap or talus of rubbish 

 below, and overwhelming the wall encircling the lower edge, but at the 

 same time falling away from the wall of the upper edge, which, thanks 

 to its artificial structure, is able to keep together its fragments ; and, in 

 fact, this is what we observe. The upper wall of the more distant one, 

 which stands out a prominent object on the summit of the ridge, is over 



