ON THE VOLCANIC PHENOMENA OF JAPAN. 



219 



fal on record. Rocks, from 40 to 80 feet in some of their dimensions, 

 ■were hurtled through the air in all directions. Towns and villages were 

 buried. One stone is said to have measured 264 by 120 feet. It fell in 

 a river, and looked like an island. Records of this eruption are still to be 

 seen, in the form of enormous blocks of stone scattered over the Oiwake 

 plain, and in a lava stream 63 kilometres in length. 



Earth-tremors. 

 Introductory notes relating to the work done in Italy. — During the past 

 year considerable time has been devoted to a critical examination of the 

 earth- tremor records obtained from the automatic tromometer described 

 in the report to the British Association for 1885. These records, together 

 with the results which they have furnished, will be published in detail by 

 the Seismological Society of Japan. As an introduction to an epitome 

 of the results obtained in Japan, a few words may be said respecting the 

 work now in progress in the Italian Peninsula, where, through the efforts 

 of Professor M. S. de Rossi, twenty -seven stations for the observation of 

 microseismical movements have been established. At the central station in 

 Rome a dailj^map is issued on which the following phenomena are indicated: 



1. Isobars at 1 millimetre apart. 



2. Microseismical activity in different pai-ts of the kingdom. 



3. The number and intensity of earthquakes. 



4. The state of activity at volcanoes. 



5. The state of hot springs. 



6. The increase or decrease in the water of wells. 



From the tabular matter accompanying the maps one can read the 

 state of microseismic activity at any particular station, or the average state 

 of activity for the whole kingdom for any particular day or for a whole 

 decade of ten days, the conclusion having been arrived at in Italy that 

 microseismical storms recur decadically. 



January 1885. 



As illustrative of this decadic recurrence I give the preceding table 

 compiled from the notes of Professor Rossi as published in the ' Bullettino 

 del Valcanismo Italiano ' (anno xiii. fas. 1-3, pp. 5-7). 



