north extremity of the island. It form a sinuous ridge 

 of volcanic rock clift into blocks either fixed or loose, 

 and interrupted only or rather declining in level, where 

 the road across the island now runs. 



The hill or mountain rising from the volcanic plain 

 to the height of 370 feet above the sea. formed entirely 

 of volcanic rock presenting a more or less pseudo-stra- 

 titied appearance, is traversed on its southern face by 

 deep gullies or fissures, and in some parts perpendicu- 

 lar rocks. It is terminated on its eastern extremity by 

 two pointed elevations, and declines on its w^estern side 

 almost perpendicularly to the sea. The highest part 

 of the hill forms a small plateau on which the light- 

 house has been erected. Ou the northern side towards 

 the land the descent is steep but covered wdth a thin 

 layer of volcanic earth and grass, as are also many of 

 the steep slopes on the southward or seaward side. 



On the summit of this hill a little to the east of the 

 light -house is a ridge of fixed and very large volcanic 

 blocks forming a considerable segment of a large cir- 

 cle delineated with great exactitude on Mr Corby's 

 excellent map of Flat and Gabriel Islands ; from which 

 the maps, coloured to illustrate the geological forma- 

 tion, now before you, have been copied on an enlarged 

 scale. Can this ridge have been part of the crater of 

 a submarine volcano as suggested by Capt. Stokes ? or 

 is it more probable that it formed the summit of a sub- 

 marine hill, which has been fissured by the action of 

 currents of water ? 



The rock here and elsewhere, ou this and Gabriel 

 Islands varies considerably in colour and consistence. 

 In some parts no traces of stratification can be disco- 

 vered, while in others the spurious stratification is very 

 obvious. Much of the rock is of a dark brown or blu- 

 ish-black colour, perfectly solid, very hard, and homoge-i 

 ueous in texture. Other masses have the same general 

 characters, but are spongy and porous, and hollowed 

 by numerous cavities produced by the extrication of 

 gazes or vapours while in a semi-fused condition. Others 

 again, especially the stratified rocks arc inferior in den^ 

 sity and hardness, and of a reddish or ferruginous co- 

 lour. Many of these rocks contain ^mall crystals of 



