252 



THE VOYAGE OF H.M.S. CHALLENGER. 



With respect to men-of-war calling, there need be no apprehension of danger. Gales 

 of wind are, of course, common at all seasons, but the islanders can nearly always com- 

 municate with ships if they stand close in, and now-a-days, with steam ever at command, 

 there is no chance of a vessel sharing the " Julia's " fate. One precaution should, how- 

 ever, always be taken by vessels anchoring — steam should invariably be kept up, and 

 the cable ready for slipping at a moment's warning. 



The cliffs of the main island show a very regular stratification, and are composed 

 throughout of a series of beds lying nearly horizontally, but dipping slightly towards the 

 shores, at least they appear to do so east and west of the anchorage. The beds, which 

 are conspicuously marked, are alternately of hard basalt and looser scoriaceous lava, with 

 occasional beds of a red tufa. The whole section is traversed by numerous dikes, mostly 



m->*'M-BJ*-Mi& 



Fig. 99. — Settlement of "Edinburgh," Tristan da Cunlia. {From a Photograph.) 



vertical and usually narrow in appearance, and is not unlike that exposed in the Grand 

 Cural at Madeira. The rock specimens collected were large grained felspathic basalts some- 

 time bordered with layers of black basaltic glass (sideromelan) passing to palagonite, 

 basaltic tufa, augite-andesite, pyroxenite, and amphibolic ancles ite containing sanidine. 



Streams, or rather cascades, which come dashing down to the sea during the constant 

 heavy rains, have eaten their way into the cliffs, and their beds form conspicuous features 

 in the view as narrow gullies, descending the rocks in a series of irregular steps.' At the 

 foot of the cliffs, immediately opposite the anchorage, are debris slopes and irregular rocky 

 and sandy ground, forming a narrow strip of low shore land. 



The settlement lies on a broader and more even stretch of low land which extends 



