98 BEPORX — 1882. 



The oscillation of the pendulum is generally parallel to valleys or 

 chains of mountains in the neighbourhood. The oscillations are indepen- 

 dent of local tremors, velocity and direction of wind, rain, change of 

 temperature, and atmospheric electricity. 



Pendulums of different lengths betray the movements of the soil in 

 different manners, according to the agreement or disagreement of their 

 free-periods with the period of the terrestrial vibrations. 



The disturbances are not strictly simultaneous in the different towns 

 of Italy, but succeed one another at short intervals. 



After earthquakes the ' tromometric ' or microseismic movements are 

 especially apt to be in a vertical direction. They are always so when the 

 earthquake is local, but the vertical movements are sometimes absent 

 when the shock occurs elsewhei'e. Sometimes there is no movement at 

 all, even when the shock occurs quite close at hand. 



The positions of the sun and moon appear to have some influence on 

 the movements of the pendulum, but the disturbances are especially fre- 

 qnent when the barometer is low. 



The curves of ' the monthly means of the tromometric movement ' 

 exhibit the same forms in the various towns of Italy, even those which 

 are distant from one another. 



The maximum of disturbance occurs near the winter solstice and 

 the minimum near the summer solstice ; this agrees with Mallet's results 

 about earthquakes. 



At Florence a period of earthquakes is presaged by the magnitude 

 and frequency of pendulous movements in a vertical direction. These 

 movements are observable at intervals and during several hours after 



At page 103 of the first part of the ' Bulletino ' for 1878 (?), there is 

 a review of a work by Giulio Grablovitz, ' Dell' attrazione luni-solare in 

 relatione coi fenomeni mareo-sismici,' MUano, Tipografia degli Ingegneri, 



1877. 



In this work it appears that M. Grablovitz attributes a considerable 

 part of the deviations of the vertical to bodily tides in the earth, but as 

 he apparently enters into no computations to show the competency of 

 this cause to produce the observed effects, it does not seem necessary to 

 make any further comment on his views. 



At page 99 of the volume for September-December, 1878, Eossi 

 writes on the use of the microphone for the purpose of observing earth- 

 quakes (' II microfono nella meteorologia endogena '). He begins by 

 "•ivino- an account of a correspondence, beginning in 187'i>, between him- 

 self and Count Giovanni Mocenigo,' of Vicenza, who seems to have been 

 very near to the discovery of the microphone. When the invention of 

 the microphone was announced, Mocenigo and Armellini adopted it for 

 their experiments, and came to the conclusion that the mysterious noises 

 which they heard arose from minute earthquakes or microisms. 



Rossi then determined to undertake observations in his cavern at 

 Rocca di Papa, with a microphone, made of silver instead of carbon, 

 mounted on a stone beam. The sensitiveness of the instrument could be 

 regulated, and he found that it was not much influenced by external 

 noises. 



The instrument was placed 20 meters underground, and remote from 



' Count jMocenigo has recently published at Yicenza a book on his observations. 

 It is reviewed in Nature for July 6, 1882. 



