ON SEISMOLOGICAL INVESTIGATION. 175 



Examination of Cases where the Velocity has been Abnormally High. 



Shock No. 1. — This was recorded at three stations in Japan Ijy hori- 

 zontal pendulums recording on photographic surfaces. From the fact that 

 ordinary seismographs did not record an earthquake on that day, and 

 because each photogram began with gentle tremors, it is safe to assume 

 that they represented an earthquake originating at a great distance. 

 Unfortunately, the note-books containing the clock corrections were burned, 

 but taking the time determinations direct from the photograms, they lead 

 to the conclusion that motion was propagated to Japan from a place 

 almost at its antipodes at a rate varying between 16 and 19 kms. per 

 second. 



The greatest merit in this record is that it falls in line with what we 

 should expect from records taken over shorter ranges. 



Shock 17. — Like other Strassburg records, this was obtained on paper 

 moving at a rate of about 1 mm. in three minutes. Independently of this, 

 however, we see that for the same shock at four other observatories 

 velocities of 9-7, 11"1, 11'2, and ITS kms. per second have been calculated 

 (Nos. 15, 6, 8, and 12), and it is therefore highly probable that the 

 determination for Strassburg of 14-2 kms. is too high. 



Shock 28. — We have here another case of a record from a surface 

 moving at a rate of 1 mm. in about three minutes, whilst the epicentre 

 may have been distant from Tokio. 



Shock 37 . — Because a delicate seismograph at Catania was disturbed 

 2 minutes 40 seconds before the one at Padua suggests the idea that 

 these Italian records possibly refer to a local disturbance, and not to the 

 one in Asia Minor. This point has been discussed by Professor M. G. 

 Agamennone (see ' Bollet. A. Soc. Sis. Italiana,' vol. ii.. No. 8). 



Shock 35. — This estimate is based upon a most careful and elaborate 

 analysis of records, none of which, however, were obtained fi'om the 

 automatic indications of seismographs. 



Abnormally Low Velocities. 



Shocks 9 and 23. — We have here two observations for the same shock, 

 and we find that the photograms obtained at Strassburg and Nicolaiew 

 were ' schwach und wenig scharf,' and for the former there was an 

 ' unbestimmter anfang,' from which it may be concluded that the com- 

 mencement of movement at these places was not determined. 



Shock 21. — From the Nicolaiew record it appears that the commence- 

 ment of this disturbance is thus noted : ' 5-02 h. (?) Anfang der Storung.' 

 The uncertainty here expressed possibly explains the low velocity 

 recorded. 



Shock 16. — Here again there appears to have been difficulty in 

 determining the commencement of movement, owing to the undefined 

 character of the photogram. 



Shock 25.^ — This was observed not onh* at Nicolaiew, but also at 

 Strassburg, the velocities being 3-72 and 4-2 kms. per second respectively. 

 Although von Rebeur in his ' Horizontalpendel-Beobachtungen,' p. 492, 

 tells us that these velocities are based upon tlie observation of the time at 

 which the first weak movement is visible, from a table on p. 443 they 

 appear to have been determined from the observation of the instant at 

 which there was a sudden increase in motion, and are used with other 



