166 REPORT— 1895. 



In examining this diagram it must be remembered that near to an 

 origin tlie difference in time between the maximum phases of an earth- 

 quake and its actual commencement may be only a few seconds, while at 

 a great distance the I'ecords of sensitive instruments show that the same 

 interval may be many minutes. When instruments of such sensibility 

 are near to an origin, my own observations seem to show tliat they are 

 not set into any sensible amount of motion before the ordinary seismo- 

 scopes or seismographs, and thei'efore for places comparatively near to 

 the origin of a disturbance, when observations were made with the latter 

 type of instrument, I should be inclined to think that the phases of 

 maximum motion might be approximately coincident with the times of 

 commencement of movement. 



An inspection of the diagram points towards the following results : — ■ 



No. 1. The velocity for the first 5")0 km. is greater than it is to a 

 point which is more remote. 



No. 2. This is the only disturbance for whicli observations are made 

 at points comparatively near to the epicentre, for which they show a 

 very high velocity. Between stations distant 300 aiid 1,100 km. from 

 the origin the velocity decreases, but beyond this limit it apparently 

 increases. 



No. 3. The chief difference between this and No. 2 is that the point of 

 inflexion of a free curve drawn between the points of observation, instead 

 of being at a distance of 1,100 km. from the epicentre, is at about 

 1,300 km. from tliat point. 



No. -t. The velocity is apparently greater at a distance from the epi- 

 centre than near to it. 



No. 5. This resembles No. 4. 



If we omit the one case which shows a high velocity in the immediate 

 neighbourhood of the ^irigin — which, however, is in perfect accordance 

 with results obtained with artificially produced disturbances — there 

 remains the clearly marked observation that to Catania and Mineo the 

 velocities are, as compared Avith the rate of propagation to more distant 

 stations, relatively low. Professor A. Ricco, who discusses these observa- 

 tions, gives us every reason to believe that tlie time observations at 

 Catania are correct, while those at Mineo may bs in error, owing to the 

 manner in which it receives the time signals from Eome, which finally 

 reach the observatory by circolare. 



Professor Ricco concludes that the low velocity between Zante and 

 Catania may Ije accounted for by the fact that the motion was entirely 

 transmitted tln'ough watei-, because the velocity recorded of 1,439 km. per 

 second practically coincides with that of a sound wave in water. Professor 

 Ricco adds that Bertelli lias shown that the shocks of eartliquakes felt on 

 shipboard and the sound waves have been simultaneous. From one of 

 Abbot's experiments, howe^'er, we have seen that a wave velocity obtained 

 from a water path was greatly increased. 



The following is Agamennone's table of velocities, which, although 

 they represent averages, show that the lowest is the one on August i, 

 which had the shortest range : — 



