128 Galapagos Archipelago. paeil 



islets. 1 and now exist as mere crescents quite open to 

 the south, with occasionally a few points of rock mark- 

 ing their former circumference ; of the remaining six- 

 teen, some form promontories, and others stand at a 

 little distance inland from the shore ; but all, have 

 their southern sides either the lowest, or quite broken 

 down. Two, however, of the sixteen bad their northern 

 sides also low, whilst their eastern and western sides 

 were perfect. I did not see, or hear of. a single ex- 

 ception to the rule, of these craters being broken down 

 or low on the side, which faces a point of the horizon 

 between SE. and SW. This rule does not apply to 

 craters composed of lava and scoriae. The explanation 

 is simple : at this Archipelago, the waves from the 

 trade-wind, and the swell propagated from the distant 

 parts of the open ocean, coincide in direction, (which 

 is not the case in many parts of the Pacific,) and with 

 their united forces attack the southern sides of all the 

 islands ; and consequently the southern slope, even 

 when entirely formed of hard basaltic rock, is invariably 

 steeper than the northern slope. As the tuff-craters 

 are composed of a soft material, and as probably all, or 

 nearly all. have at some period stood immersed in the 

 sea. we need not wonder that they should invariably 

 exhibit on their exposed sides the effects of this great 

 denuding power. Judging from the worn condition of 

 many of these craters, it is probable that some have 

 been entirely washed away. As there is no reason to 

 suppose, that the craters formed of scoriae and lava 



1 These consist of the three Crossman Islets, the largest of which 

 is 600 feet in height ; Enchanted Island ; Gardner Island (760 feet 

 high) ; Champion Island (381 feet high) ; Enderby Island ; Brattle 

 Island; two islets near Indefatigable Island; and one near James 

 Island. A second crater near James Island (with a salt lake in its 

 centre) has its southern side only about twenty feet high, whilst the 

 other parts of the circumference are about 300 feet in height. 



