476 F. A. Perret — Subsidence Phenomena at Kilauea. 



solid rock, by a process of almost infinite subdivision, sank 

 with imperceptible motion in a sort of " slow flow " during 

 several weeks of time and presenting the appearance repro- 

 duced in fig. 6. The weight of this mass of rock depressed 

 the shore several meters, causing overflows from the lake at 

 this side, in spite of the general lowering of the lava level. 



By the end of September the result of this great, though 

 gradual, subsidence of the lava column was a change from the 



Fig. 6. 



Fig. 6. Showing gradual subsidence and "slow now" of south black 

 ledge. Seen from the west. 



previous pit-like chasm with vertical walls and flat floor, to a 

 cup-shaped cavity formed of debris at the angle of repose, and 

 more nearly resembling the prevailing form of volcanic crater, 

 while the almost total demolition of all recent consolidations 

 left a clean page, so to speak, for the record of a future period 

 of high lava.* 



The alternating of elevation, with construction by consolida- 

 tion, and of subsidence, with demolition by collapse, is thus 

 seen to be as characteristic of this as of the other so-called 

 widely variable types of volcanoes — a fact which can but 

 strengthen that increasingly evident bond of fundamental simi- 

 larity over which so complicated a system of minor and con- 

 sequent and inevitable variations have been reared. 

 Posillipo, Naples, February, 1913. 



* This was initiated soon after the writer left the islands. 



