ON EARTH TREMOKrf. 147 



7h. 45m. P.M. On both occasions the tromometer oscillated so much that 

 it was not possible to determine the amplitude. 



Mineo ('Boll. Meteor.'), 37° 15' N., 14° 42' E. April 20, 5h. 26m. 

 (± some seconds), p.m. April 27, 7h. 53m. p.m. 



Portici ('Boll. Meteor.'), 40° 50' K, 14° 19' E. April 27, 7h. 51m. 9s. 

 p.m., movement indicated by a Brassart seismograph. 



Fe^feiri (' Boll. Meteor.'), 41° 41' N., 12° 47' E. April 20, 5h. 26m. p.m. 



Eocca di Papa (Dr. A. Cancani and 'Boll. Meteor.'), 41° 54' N., 

 12° 29' E. April 20, 5h. 20m. p.m., the beginning of the pulsations indi- 

 cated by the ' tromometro avvisatore.' The Brassart seismograph displaced 

 at 5h. 22m. ± 20s. April 27, 7h. 45m. p.m., the arrival of the pulsa- 

 tions announced by the ' tromometro avvisatore.' The great seismograph 

 (7 metres in length and 100 kilogrammes in mass) shows the beginning of 

 small earthquakes in the S.E.-N.AY. componeiit at 7h. 47m. 30s. At 

 about 7h. 49m. 30s. the large oscillations in the S.E.-N,W. component 

 began, and at 7h. 49m. 49s. in the N.E.-S.W. component. These large 

 oscillations had a period of 7 '2 seconds, and present a principal maximum in 

 the N.E.-S.W. component at 7h. 50in. 40s., that of the other component not 

 being well defined. This great undulatory movement ceased at 7h. 57m. 20s. 

 in the N.E.-S.W. component, and at about 8h. 2m. 20s. in the S.E.-N.W. 

 component. 



Pome (Professor Tacchini and ' Boll. Meteor.'), 41° 54' N., 12° 29' E. 

 April 20, beginning of the movement about 5h. 20m. 20s. p.m. in the 

 N.W.-S.E. component, about 5h. 22m. Os. in the JST.E.-S.W. component. 

 The movement gradually increased until the following maxima were pre- 

 sented : 5h. 25m. 35s., 5h. 26m. Os., 5h. 26m. 55s. (principal maximum), 

 5h. 28m. 20s., 5h. 29m. Os., after which the traces irregularly and slowly 

 decreased, the end of the movement taking place at about 5h. 33m. 15s. 

 in the N.W.-S.E. component, and about 5h. 35m. 10s. in the N.E.-S.W. 

 component. April 27, the beginning of the movement in both components 

 at about 7h. 47m. 50s. p.m. ; a series of maxima, first increasing and 

 then decreasing, at 7h. 50m. 55s., 7h. 51m. 40s. (principal maximum), 

 7h. 52m. 10s., 7h. 52m. 25s., 7h. 53m. Os., 7h. 53m. 45s , 7h. 55m. 55s., and 

 7h. 57m. 10s. ; the end of the movement in both components may be taken 

 at about 8h. 6m. 20s., but not improbably it was prolonged still further. 



Siena (' Boll. Meteor.'), 43° 19' N., 11° 20' E. April 20, 5h. 23m. 40s. 

 (± about 10s.) P.M., -beginning of the movement in the N.N.E.-S.S.W. 

 component, as registered by the Vicentini seismograph ; the oscillations 

 gradually increased in amplitude until they attained the following 

 maxima : between oh. 25m. 40s. and 5h. 26m. 40s. (two principal 

 maxima), at 5h. 26m. 58s., 5h. 28m. 4s., and 5h. 28m. 40s. ; the 

 oscillations then slowly disappeared, the total duration being about fifteen 

 minutes. During the first seven minutes the average period of the oscil- 

 lations in the E.iS.E.-W.N.W. component was about five seconds, and in 

 the other, during the first ten minutes, about four seconds. At about 

 5h. 49m. 40s. there was a group of fourteen small oscillations, lasting for 

 one minute. April 27, about 7h. 47m. 40s. p.m., beginning of the oscil- 

 lations, which increased suddenly in amplitude ; the first maximum at 

 7h. 51m., after which there were four others, the principal maximum 

 being at 7h. 53m. 6s. During an interval of 552 seconds sixty-five oscil- 

 lations were counted in the N.N.E.-S.S.W. component, and sixty-one in 

 the E.S.E.-W.N.W. component, giving an average period of eight and a 

 half seconds for each complete oscillation. 



l2 



