REPORT ON THE PETROLOGY OF OCEANIC ISLANDS. Ill 



to the shore. The volcanic manifestations, which gave birth to Kerguelen Island, have 

 now entered on a stage of repose. According to the fishermen, an active volcano still 

 exists on the west coast, and in this region also mineral oils and thermal springs are 

 found. 



Low plains are absent, as in all volcanic islands, and valleys with a flat bottom are 

 uncommon. The heights run in lines forming chains, and the small extent of plain is 

 also covered with rocks or mounds connected together. The tabular form is most 

 common for the eminences with which Kerguelen is, in a certain sense, covered. 

 These heights are cut into perpendicular-walled terraces. This arrangement is almost 

 always observed in the case of ranges of hills not exceeding 1000 feet in height. The 

 mountains are sometimes formed by the superposition of five or ten terraces, in 

 other places as many as twenty have been counted. The terminal plateau and the 

 terraces are covered with the debris and alteration-products of the volcanic masses, 

 geodes from amygdaloidal rocks, and nodules of olivine, such as are found in basalt. 

 What has been said applies particularly to the mountains near the coast. The less 

 explored heights of the interior attain an altitude of about 1500 feet, and are composed 

 of solid rocks carved and terraced like those of the coast. Mount Ross, with its double 

 peak, and Mount Crozier belong to the mountains of the interior. According to Professor 

 Eoth, these jagged summits are formed of two kinds of rock, — dolerite and trachyte. 



We shall now proceed to describe the different localities of the island from which 

 specimens have been collected, indicating at the same time their principal topographical 

 features and the local observations relating specially to the rocks under description. 

 As we stated before, the north-east coast is the only one which has hitherto been 

 explored. In the descriptions we shall follow the coasts, from Christmas Harbour at 

 the northern extremity to Greenland Harbour on the south-east of the island. 

 Describing in succession the rocks of each locality, we will specially lay stress on those 

 parts of the island where the Challenger collected specimens. These localities are 

 designated in our description by the names adopted in the chart of Kerguelen, 

 accompanying this Report (Map V.). 



Starting from the northern extremity and going eastwards, Christmas Harbour is 

 the first place we meet with. This bay was named by Cook, who anchored there on 

 Christmas Day, 1776. It is a fine example of a Kerguelen fjord on a small scale, a 

 deep indentation surrounded by mountains with perpendicular cliffs. On each side 

 the land runs out in narrow precipitous promontories. At the northern part of the 

 bay the ground falls more gradually, so that it is possible to land from a boat. At 

 the point of the southern tongue of land stands the well-known Arch Rock, which 

 was formerly united to the island. Now the waves have perforated the central part 

 of this wall of rock, while its base and summit remain connected with the land, forming 

 a natural arch leading to a pile of rocks surrounded by the waves. Above the 



