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 
Culpepper 1. 
a 
Wenman l. Miles 
t — j , i i i i _j 
Abingdon I. 
Tower I. 
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 
