Halemaumau Lava Lake. 3i9 



paper* — with some of whose conclusions regarding Kileauean 

 phenomena the present writer does not, however, quite agree 

 — is of the opinion that convection, in the sense of the proper 

 motion of a mass of highly vesiculated lava, may "stir the 

 magma column to great depth and with considerable rapidity." 

 The idea of the extension of the circulation to the conduit 

 would be very convenient as making easy the question of heat 

 maintenance and especially as tending to explain the well- 

 known migration of conduit and crater by the down now of 

 cooled and passive material at one side and the rising of hot 

 and active lava at the other. Where all is conjecture, how- 

 ever, it may be but fair to state that there seems to be some 

 reason for believing the actual exchange of lava between con- 

 duit and crater to be quite limited — sufficiently so to permit 

 the material in the crater basin to acquire, by being ceaselessly 

 worked over in contact with air and water and made the 

 recipient of the mass of gas vesicles rising from the conduit, a 

 different consistency to that of the lava in the conduit. 



However this may be, it seems certain that the fundamental 

 cause of heat maintenance in the entire lava column, as well as 

 of all the dynamic phenomena, lies in the supply of juvenile gas, 

 and that the immediate cause of the circulation in the crater 

 lake is the formation of heavy surface layers which tend to 

 sink. 



Posillipo, Naples, Feb. 7, 1913. 



* '"The Nature of Volcanic Action,'* Keginald A. Daly, American Academy 

 of Arts and Sciences, vol. xlvii, No. 3. 



