EARTH TREMOES. 323 



With the microphone Rossi hears sounds which he 

 describes as roarings, explosions, occurring isolated or in 

 volleys, metallic and bell-like sounds, ticking, &c., which, 

 he says, revealed natural telluric phenomena. Sometimes 

 these have been intolerably loud. At Vesuvius the ver- 

 tical shocks corresponded with a sound like volleys of 

 musketry, whilst the undulatory shocks gave the roaring. 

 Some of these sounds could be imitated artificially by 

 rubbing together the conducting wires in the same 

 manner in which the rocks must rub against each other 

 in an earthquake. Other sounds were imitated by placing 

 the microphone on a vessel of boiling water, or by putting 

 it on a marble slab and scratching and tapping the under 

 side of it. 



These, then, are some of the more important results 

 which have been arrived at by the study of microseismic 

 motions. One point which seems worthy of attention is 

 that they appear to be more law-abiding than their more 

 violent relations, the earthquakes, and as phenomena in 

 which natural laws are to be traced they are certainly 

 deserving our attention. As to whether they will ever 

 become the means of forewarning ourselves against earth- 

 quakes is yet problematical. Their systematic study, 

 however, will enable us to trace the progress of a micro- 

 seismic storm from point to point, and it is not impossible 

 that we may yet be enabled to foretell where the storm 

 may reach its climax as an earthquake. These, I believe, 

 are the views of Professor di Rossi, who is at the present 

 time engaged in the establishment of a system of micro- 

 seismic observations throughout Italy. 



Before the earthquake of San Remo (Dec. 6, 1874) 

 Rossi's tromometer was in a state of agitation, and similar 

 disturbances were observed at Livorno, Florence, and 

 Bologna. 



