104 ART. 3. — B. KOÏÛ; 



little or no trembling (air-concussions), accompanied the breaking 

 open of the cooled ping of the lava vent, followed by the cracking 

 and clinking noise of the overflowing lava-stream. 



The volcanic earthquakes without eruption (fourth column) 

 showed a marked tendency of standing in opposition to the fre- 

 quency of stronger outbursts (column II). To the writer the 

 numbers of the fourth column seem to have been the movements 

 to and fro of magma in a reservoir more than 1000 ?7i. deep from 

 the vents. Consequently, these ' endo volcanic earthquakes ' have 

 closer relation to the stronger outbursts as compared wâth the 

 weaker surficial activity (column III), tliough the relations are 

 remote with either. 



iY. Mass and Dimensions of Lava. — The lava-efiusing volcanoes are 

 very rare in modern Japan, in contrast to surficial straggling explo- 

 sive eruptions. The rocks are a basic type of andésites (auganites) 

 of intermediate acidity. In Sakura-jima, lavas are poured out from 

 the Yuno-hira vents on the western slope as w^ell as from the eas- 

 tern, Nabé-yama vents. Both have independent lava fields and both 

 flowed directly into the sea, just like the recent Sawaiian flows. 



In the following the writer gives the dimensions and the 

 mass of lavas, which are necessarily of the nature of a first ap- 

 proximation to truth, besides he gives the numbers computed by 

 his colleagues for comparison. We find a not inconsiderable dis- 

 crepancy in the columns, owing to the estimation firstly, of thick- 

 ness assumed by different writers after their personal judgment, 

 and secondly, of the extension of submarine flows. The writer is 

 favored with the data of the new soundings^^ of Mr. Fujishiro's 



1) The soundings were taken at the end of April, 1914, and the calculations given here are 

 all based on the data at hand at that time. Since then, some changes were brought about 

 especially on the eastern field (Text-fig. 24) by constant movements and secondary flows of the 

 lava-front seawards. The marked changes occurred in regard to areal extent if a comparison is 

 made between the area marked • Marine Lava Field ' from the siirvey of April. 1914, and that 

 outlined with a heavy line, with the remark ' Sept. 1915,' the latter b3ing the result of the 

 renewed land-surveying done by the Prefectural office of Kagoshima. 



