186 A NATURALIST ON THE "CHALLENGER." 



investigated, and there is no doubt that it is entirely so formed, 

 the beds of coal alone excepted, and certain beds of red earth, 

 which are of the same origin as the coal, but merely different in 

 that they have undergone a more intense heating. 



The island has undergone immense denudation, and on its 

 whole north-eastern and southern regions there is no trace 

 of any volcanic cone or signs of comparatively modern volcanic 

 action, as at Marion Island. Every appearance bespeaks con- 

 siderable antiquity. 



Nevertheless it seems to be certain that there exists towards 

 the south-west of the island, a still active volcano with hot 

 springs in its neighbourhood. We fell in with an American 

 whaling captain, Captain Fuller, who has been often on the 

 weather shore, and is well acquainted with the position of the 

 volcano, and though he had not been actually at it himself, some 

 of his men had ; and in Tristan da Cunha we received indepen- 

 dent testimony in the matter from old sealers. 



The appearance of the island in the region of the volcano 

 must thus be very different from that of the north-eastern and 

 south-eastern portions. 



As necessarily follows from the presence of fjords, the whole 

 of the lower rock surface of the island shows most marked 

 evidence of glaciation. 



Christmas Harbour, almost on the extreme north of the 

 island, is a small example of one of the fjords. It is a deep 

 inlet with dark frowning cliffs on either hand at its entrance. 

 The land on either side runs out into long narrow promontories, 

 which separate the harbour from another similar fjord on the 

 south and from a bay on the north. The promontories thus 

 formed are high and bounded throughout almost their entire 

 stretch by sheer precipices on either hand. On the northern 

 side only of Christmas Harbour, somewhat above its mouth, does 

 the land rise in a steep broken slope, which can be ascended 

 directly from the sea. 



At the termination seawards of the southern promontory, is 

 the well-known arched rock of Christmas Harbour, a roughly 

 rectangular oblong mass, evidently formerly continuous directly 

 with the rest of the promontory, but now separated from it, 



