Periodicity of Earthquakes. 



469 



Italy. 



10. M. F. de Montessus de Ballore, Arch, des Sci. phys. et 

 not. vol. xxii. 1889, tables. 



Duration of record: Acireale to Verona, Dec. 1872-1887; 

 Vesuvius, 1863-1884. Number of earth-tremors: Acireale, 

 364 ; Bologna and S. Luca, 636 ; Cascia, 505 ; Corleone, 584; 

 Rocca di Papa, 388 ; Rome, 2346 ; Velletri, 1491 ; Verona, 

 700 ; Vesuvius, 547 ; Italy, 8177. 



In the same table M. de Montessus gives the hourly num- 

 bers of tremors at four other observatories (Alvito, Belluno, 

 Narni, and Spinea di Mestre), but the total numbers of 

 tremors are so small (123, 180, 144, and 159) that I have 

 have not made use of them separately. They are, however, 

 included in the total for all Italy. 



Observatory. 



1st comp. 

 (24 hours). 



2nd comp. 

 (12 hours). 



3rd comp. 



(8 hours). 



4th comp. 

 (6 hours). 



Ampl. 



Epoch. 

 n m 



Ampl. 



Epoch. 

 h. m 



Ampl. 



Epoch. 

 h m 



Ampl. 



Epoch, 

 h m 





■583 

 •705 

 •259 

 •398 

 •523 

 613 

 •307 

 •238 

 •494 

 •324 



P.M. 



45 



8 



A.M. 



1 27 

 13 



11 22 



P.M. 



36 



25 



A.M 



11 32 



P.M. 



11 



25 



•119 

 •166 

 •091 

 •305 

 •159 

 •143 

 •113 

 •270 

 •371 

 •112 



A.M. 



11 45 

 6 56 

 9 11 

 1 14 



11 22 



10 25 



11 



10 7 

 1 35 



11 14 





041 

 081 

 166 

 217 

 342 

 097 

 164 

 137 

 052 

 045 



A.M. 



17 

 7 41 

 4 38 



3 16 



4 10 



1 37 

 43 



55 



5 59 



1 46 



•142 



A.M. 



2 51 

 5 25 



3 35 



3 3 

 2 44 



4 6 



2 25 



3 56 

 3 43 

 3 47 



Bologna & S. Luca . 

 Cascia 





009 

 230 

 093 

 103 

 150 

 060 

 366 

 038 

 113 



Corleone 



Rocca di Papa 



Rome 



Velletri 



Verona 



Vesuvius < 



Italy 















The nine Italian records thus agree in exhibiting a marked 

 diurnal period, the epoch in seven cases being about noon, 

 and in the other two cases not far from midnight. Reference 

 has already been made to M. de Montessus's explanation of 

 the preponderance of slight tremors during the day. There 

 is much to be said in favour of this explanation. The obser- 

 vatory on Vesuvius is only a few yards from the main road, 

 along which there is a great deal of heavy traffic about mid- 

 day. During the interval embraced by M. de Montessus's 



Phil. Mag. S. 5. Vol. 42. No. 259. Dec. 1896. 2 L 



