398 GALAPAGOS ARCHIPELAGO chap. 



tion. Some of the craters surmounting the larger islands are of 

 immense size, and they rise to a height of between three and 

 four thousand feet. Their flanks are studded by innumerable 

 smaller orifices. I scarcely hesitate to affirm that there must 

 be in the whole archipelago at least two thousand craters. 

 These consist either of lava and scoriae, or of finely-stratified, 

 sandstone -like tuff. Most of the latter are beautifully 

 symmetrical ; they owe their origin to eruptions of volcanic mud 

 without any lava : it is a remarkable circumstance that every 



Ciilpepp^r 1. 

 Weiivian I. 60 Miles 



Abingdon I. 



Tower L 



Narhorough ^.!^ ^^^ ^''\p 'o" 



%tekVJ«'»es /. 



^to.. 



t, luilc/LUigahle I, 



Albemarle I. ^.^ _Cf^ JP ^*!^ f%, ^f'r 



Barriimton 1. ' 



Charles 1. 



Hood's I. 

 GALAPAGOS ARCHIPELAGO. 



one of the twenty-eight tuff-craters which were examined had 

 their southern sides either much lower than the other sides, or 

 quite broken down and removed. As all these craters 

 apparently have been formed when standing in the sea, and 

 as the waves from the trade wind and the swell from the open 

 Pacific here unite their forces on the southern coasts of all the 

 islands, this singular uniformity in the broken state of the craters, 

 composed of the soft and yielding tuff, is easily explained. 



Considering that these islands are placed directly under the 

 equator, the climate is far from being excessively hot ; this 

 seems chiefly caused by the singularly low temperature of the 



