274 F. A. Ferret — Floating Islands of Halemaumau. 



so incessant and so titanic a warfare, solid masses may be com- 

 pacted and floated on the surface of the liquid lava. 



But the formation of a central cone at Halemaumau is not a 

 very frequent occurrence while large, floating islands are com- 

 paratively common and it is clear that we must look to another 

 cause for the origin of the majority of these interesting struc- 

 tures. 



The island shown in flg. 1 was clearly seen to consist mainly 

 of a mass of stratified, crystalline rock similar in appearance to 



Fig. 1. 



Fig. 1. The Halemaumau Lava Lake with Floating Island, July, 1911. 



that of the crater walls, and more particularly to that of the 

 "black ledge" — an inner wall consolidated to the main wall 

 during a former high level of the lava lake. This clue to the 

 origin of the island was supported by the testimony of several 

 residents, who affirmed that the mass of rock fell from the 

 northeast sector of the black ledge in the early summer of 

 1910. The records, moreover, show several accounts of the 

 formation of islands in this manner, of which I shall quote but 

 one: — Mr. L. A. Thurston — an enthusiastic and indefatigable 

 local observer, to whom the present writer is indebted for a 

 mass of information and for innumerable courtesies — in his 

 vivid description of the great subsidence in July, 1894,* wrote 

 as follows : k< Most of the falling rocks were immediately swal- 

 lowed up by the lake, but when one of the great downfalls 

 referred to occurred, it would not immediately sink, but 

 would float off across the lake, a great floating island of rock." 

 * Brigham, op. cit., p. 187. 



