808 THE JOURNAL OF GEOLOGY. 



focus, that of the Kaimeni on Methana. Here we have an exam- 

 ple of that type of eruption so happily called by Fouque 1 " cumulo 

 volcanoes." The type specimen of this class of volcanoes is the 

 cone of Giorgio Kaimeni in Santorini, produced by the great 

 eruption which began in February, 1866, and whose formation 

 was closely watched and studied by scientific observers from the 

 beginning to the end. 2 The succession and character of the 

 phenomena in this eruption were briefly as follows : The erup- 

 tion began as a submarine outpouring of lava and lava blocks, 

 accompanied by few or no explosions. As the mass reached 

 the surface of the sea it was seen that the outflow consisted of a 

 stream of solid angular lava blocks, pouring out slowly and with 

 no explosions till they gradually heaped themselves above sea 

 level, forming a "cone" quite different from any of the well- 

 known types, there being no crater, no stratification of any kind, 

 no tuff, scoriae, nor ashes, and no flow of liquid lava. It was 

 simply the quiet exudation of a mass of solid angular blocks of 

 eruptive rock, whose rate of progress was slow, not forming 

 streams such as liquid lava forms, but a comparatively short and 

 high agglomeration of loose blocks. Such a cone is also quite 

 different from the also craterless typical Kiippen of the Rhine, 

 pnys of Auvergne or mamelons of the Island of Reunion, which 

 are due to the exudation of liquid but pasty material. 



A suggestion put forward by Professor J. D. Dana 3 in regard 

 to certain lava streams of Mauna Loa and Kilauea, offers a good 

 explanation of the structure just described. The lava streams 

 called in Hawaii aa, are likewise composed of loose angular 

 blocks, and Dana suggests that this structure is due to the lava 

 stream flowing over a region containing subterranean moisture in 

 quantity sufficient to cool and fracture the lava and not be evap- 

 orated by the first hot portions of the stream. 4 In the case of 



Fouque: Santorin, Paris, 1879, p. xv. 



2 Cf. Fouque: Santorin, Cap. II. 



3 Dana: Characteristics of Volcanoes. New York, 1890, p. 243. 



4 1 have observed such an action in the glass works at Murano, where a large 

 mass of molten glass was poured into water, with the result that it was cracked into- 

 large pieces, much resembling the lava blocks of Giorgio Kaimeni. 



