206 , REPORT— 1898. 



It is worthy of note that we have here instances where higher velo- 

 cities have been obtained from the records of instruments with frictional 

 writing indices than from those where the records have been photogi'aphic, 

 from which it must be inferred that the former indicated earlier phases 

 of motion than the latter. 



At Rome the long waves had a period of 10 seconds and a maximum 

 amplitude of 12". The complete length of these waves, as computed from 

 the above data, would be 54 kms., and the height of their crests about 

 half a metre. 



When in Italy (see last section of this report) I saw the original 

 seismograms of this earthquake at nearly all the stations I visited. 



The preliminary tremors and the greater portion of the succeeding heavy 

 motion, as given by two different instruments, are reproduced (figs. 1, 2 and 

 3) from the ' BoUettino della Societa Sismologica Italiana,' vol. iii. No. 9. 

 They are appended to a paper by Dr. Cancani, describing his horizontal 

 pendulums and the Assam earthquake. The upper figures show the 

 E.-W. and the N.-S. motion as recorded by the large horizontal pendu- 

 lums (for a description of which see p. 265). The lower figure gives the 

 corresponding motion, as obtained from an ordinary pendulum of 250 kgs. 

 and 15 m. in length, the movements of which are multiplied 12-5 times. 

 The original diagrams are about two-and-a-half times greater than the 

 present reproduction. 



The horizontal pendulums when writing have a complete period of 

 22 seconds. With the Indian earthquake the maximum range of motion 

 was for the N.-S. component 5-5 cm., and for the E.-W. component 

 4 cm. 



The maximum change in the vertical for the N.-S. component was 13". 

 The 15 m. pendulum showed a change of 12", whilst with a third instru- 

 ment, a simple pendulum, 7 m. in length, it was 10" . For the large 

 waves the complete period was 18 seconds. For these waves, with a 

 velocity of 27 kms. per sec, their length becomes 48-6 kms. 



If ^=length of wave, and a=the maximum angle of tilting, then 



height of a wave = - — tan a = 45 cm. 



No. 106, June 12, 1897. 



H. M. S. 



Shide . . . . 19 53 19 Duration 10 mins. 



Strassburg . . . 19 23 27 to 8 hrs. 35 min. 7 sees, with maxi- 

 mum at 7 hrs. 51 mins. 33 sees. 

 and 8 hrs. min. 31 sees. 



Not recorded in Italy or Russia. 



JVo. 107, June 13, 1897. 



H. M. S. If. 



Shide 7 39 33 Duration 7 



Strassburg 7 28 55 



Not recorded in Italy or Russia. 



No. 112, June 24, 1897. 



A disturbance was recorded in Ischia, Padua, and Rome, but it com- 

 menced about 20 hrs. 30 mins,, and not at 19 hrs. 34 mins. 53 sees., as 

 noted at Shide. 



