ON SEISMOLOGICAL INVESTIGATION. 205 



frequent, it is reasonable to suppose that sedimentation and erosion and 

 other causes which lead up to the critical conditions are geologically 



rapid. 



Briefly, the foregoing notes and facts indicate that beneath the oceans 

 certain important geological changes are more rapid than they are upon 

 land, whilst new sources from which information respecting these changes 

 may be obtained are pointed out to the student of dynamical geology. 



The more important of these sources are the experiences of the cable 

 engineer and the records of seismographs, which are sensitive to unfeli 

 movements. When a number of these instruments have been established 

 round the world, on the borders of great oceans, and on oceanic islandsy 

 it is diificult to overestimate the practical and scientific results which will 

 follow. 



The greater number of records, as it has been shown, would refer to- 

 disturbances which originated beneath the sea. From the times at which 

 earth-waves arrived at different stations, as, for example, on the two sides 

 of the Atlantic, it would be possible to localise their origins, and in time 

 districts would be indicated which it would be well for those who lay 

 cables to avoid. Work of this nature has, by means of ordinary seismo- 

 graphs, been partially accomplished for Japan, and the seismic maps of 

 that country ' show that sub-oceanic disturbances originating near to the 

 coast are herded in groups. Should a trans-Pacific cable be landed in. 

 that country, to effect this through the middle of one of these groups- 

 would be inviting its destruction. 



If we had the means of knowing that when an interruption occurred 

 in a cable at the same time an unfelt earthquake had been recorded, we- 

 should then be in a position to attribute the fault to its proper cause.. 

 The practically simultaneous failure of three Atlantic cables in 1884 led 

 to the hypothesis that they had been broken by the grapnels of a 

 repairing vessel ; fortunately for the owners of this vessel, it could not be- 

 substantiated. 



From the 'Electrician ' of August 20 and October 12, 1888, we learn 

 that the simultaneous interruption of the two cables connecting Java and 

 Australia in 1888 cut off the latter from the outside world for nineteen 

 days, and gave a pretext for calling out the military and naval reserves to- 

 meet the contingency of war having broken out. In 1890 three cables 

 Avere simultaneously broken, and telegraphic communication with Australia, 

 was cut off for nine days. On these occasions, had there been established 

 in Australia a proper instrument for recording unfelt movements of the' 

 ground, it is extremely likely that the cause of the interruption would 

 have been recognised as due to seismic action, and the fear of war and the- 

 probable accompanying commercial paralysis would have been averted. 

 Other direct benefits, which have already been derived from the records; 

 of instruments such as it is here proposed to establish round the world, 

 are that they enable us to extend, correct, and even to cast doubt upon 

 certain classes of telegraphic information published in our newspapers. 



Late in June last year we learned from our newspapers that a great 

 disaster had taken place in North Japan, and that nearly 30,000 peoplfr 

 had lost their lives. Seismograms taken in the Isle of Wight not only 

 indicated how many maxima of motion had taken place, but showed that 

 there had been an error in transmission of two days, the catastrophe; 



' See Seismological Jortrnal, vol. ir. 



