260 Froceedings of the Royal Physical Society. 



were even the familiar pot-holes worn out in its bed, — and 

 to judge by the number and size of the boulders, in time of 

 spate it must be of considerable volume. 



It forks some distance inland and from the ridge between 

 the two tributaries, but some way below the summit of the 

 island, there rises up a large rounded column of rock, which 

 has been named by some of the sealers, who have from time 

 to time lived on the island, " The Apostle." This appeared, 

 from a distance, to be the stump of the plug of a volcanic 

 vent, but without closer inspection it was impossible to be 

 sure of its nature. It may be either a " Tower of Pelee " or 

 one of those phonolite bosses so common in the volcanic 

 islands of the South Atlantic, e.g., " Lot " and " Lot's Wife " 

 at St Helena, the " Peak " of Fernando Noronha, and the 

 " Nine-pin Eock " on South Trinidad. Its appearance was 

 not at all unlike the pictures of the latter. 



Dykes do not form very prominent scenic features, so far 

 as was seen, save in one of the hanging valleys near the 

 north-east corner of the island, where large detached wall- 

 like pieces stand out prominently on both sides of the valley. 

 Smaller vertical dykes can, however, be traced up the face 

 of the cliffs in various places. 



Around a considerable part of the island there is a rough 

 bouldery beach at the foot of the cliffs, with here and 

 there small screes resting on it. Numerous sea-caves occur 

 on the south and east coasts at a height of 10 to 15 feet 

 above sea-level, and the ground on which stand the ruined 

 huts at the landing-place is a small raised beach of coarse 

 pebbles, through which the stream has cut a bed. There has 

 evidently been, therefore, a slight alteration of sea-level in 

 favour of the land, and it is interesting to note that in the 

 South Orkneys there has also been a recent elevation of 

 about the same extent. 



The first thing that attracted one's attention on landing 

 was the lower part of the cliff on the left bank of the stream, 

 where a bright yellow semicircular patch of rock, some 30 to 

 40 feet in radius, formed a prominent contrast to the darker 

 rock surrounding it. This was found to be a fine grained 

 tuff or peperino, containing abundant black crystals of augite 



