98 



THE ATLANTIC. 



[chap. II. 



white enamel -like incrustation described by Mr. Darwin was 

 observed on the southern rock only, the liaunt of the booby. 

 The northern rock is chiefly composed of what appears to be 



Darwin's yellowish harsh stone, split up into numerous frag- 

 ments which somewliat resemble large weathered crystals of 

 orthoclase. All these rocks give off alkaline water when heated 



