78 A NATURALIST ON THE "CHALLENGER." 



clinkstone, as is also St. Michael's Mount, which is a conical mass 

 300 feet in height. 



Eat Island and Booby Island are formed of a calcareous 

 sandstone, an JEolian formation like that of Bermuda, but here 

 containing volcanic particles intermixed. This rock is weathered 

 in a closely similar manner to that at Bermuda, the exposed 

 surface being covered with irregular projecting pinnacles with 

 excessively sharp honeycombed surfaces, in places on Bat 

 Island as much as two feet in height. 



On the western side of Bat Island, close to the shore, a beach 

 of large oval pebbles of phonolith is embedded in tins sand rock. 

 In Blatform Island the sand rock overlies columnar volcanic rock. 

 The main island is thickly wooded, and appears beautifully green 

 from the sea. 



The principal trees are what Webster, who visited the island 

 in 1828, calls the Laurelled Bar a, which has dark green laurel- 

 like leaves, and an abundant milky juice, but the exact nature of 

 which is unknown, since I did not succeed in procuring a 

 specimen, and a Euphorbiaceous tree, or rather tall shrub, called 

 by Webster, Jatropha or Binhao (Japhopha gossypifolicC). 



It has a pink flower, and at the time of our visit had only 

 single tufts of young leaves immediately beneath the inflo- 

 rescence, although in full flower. Its bare stems and branches 

 render it a striking object amongst the green of the creepers 

 when the forest is viewed from the sea. Webster says that it 

 casts its leaves in July and August, that is, at the commencement 

 of the dry season. It is evidently the tree mentioned by Darwin 

 as occurring on the Beak. 



There is a dry and a rainy season on the islands. The rainy 

 season is from January to July, and the dry from July to 

 December. In the dry season there is occasionally want of 

 water, but it often falls heavily during this season, as it did during 

 our stay, on September 2nd. 



Fernando do Norhona is used by the Brazilians as a convict 

 settlement. Close to the base of the Beak is the citadel or small 

 fort, on which the Brazilian flag was seen flying as we approached 

 the shore, and beneath this are the convict buildings, a group of 

 low huts, with the governor's house, a small church, and a long 



