BAHIA, BRAZIL. 297 



posed of matter which has been organized : he de- 

 tects in it some siUceous-shielded, fresh-water in- 

 fusoria, and no less than twenty-five different kinds 

 of the siliceous tissue of plants, chiefly of grasses. 

 From the absence of all carbonaceous matter, Pro- 

 fessor Ehrenberg believes that these organic bod- 

 ies have passed through the volcanic fire, and have 

 been erupted in the state in which we now see 

 them. The appearance of the layers induced me 

 to believe that they had been deposited mider wa- 

 ter, though, from the extreme dryness of the cli- 

 mate, I was forced to imagine that toiTents of rain 

 had probably fallen during some great eruption, and 

 that thus a temporary lake had been formed into 

 which the ashes fell. But it may now be suspect- 

 ed that the lake was not a temporary one. Any- 

 how, we may feel sure that at some former epoch 

 the climate and productions of Ascension were 

 very different from what they now are. Where 

 on the face of the eai-th can we find a sjDOt on which 

 close investigation will not discover signs of that 

 endless cycle of change to which this earth has 

 been, is, and will be subjected '? 



On leaving Ascension we sailed for Bahia, on the 

 coast of Brazil, in order to complete the chrono- 

 metrical measurement of the world. We arrived 

 there on August 1st, and stayed four days, during 

 which I took several long walks. I was glad to 

 find my enjoyment in tropical scenery had not de- 

 creased from the want of novelty, even in the slight- 

 est degree. The elements of the scenery are so sim- 

 ple, that they are worth mentioning, as a proof on 

 what trifling circumstances exquisite natural beau- 

 ty depends. 



The country may be described as a level plain 

 of about three hundred feet in elevation, which in 

 all parts has been worn into flat-bottomed valleys. 



