Ivi PEOCEEDLyGS OP THE GEOLOGICAL SOCIETY, 'vol. IxXYui, 



of the cormexion between it and the earthquake proper : the 

 subject is an interesting one. and a review of the evidence, to- 

 gether with the deductions which can be drawn fi'om it, would 

 fill the time available : but it is not my intention to do more than 

 to attempt, by analogy, to illustrate and explain the nature of 

 the connexion of the bathyseism with its two independent results. 



Xot many years have passed since, in the south-eastern comer 

 of England, we heard what were knovni as the guns of Flanders ; 

 and the description was correct. The sound — it was more a sensa- 

 tion than a soimd — which was heard in Kent and Sussex was 

 midoubtedly produced by the report of gi'eat guns, by the explosion, 

 that is, of the charge in the gun itself : but, had the explosion 

 done no more than give rise to the sound-waves which travelled 

 far in every direction, it wonld have little ti'oubled the enemy. 

 Simultaneously, however, with the production of the report, and 

 by the same explosion, a projectile was sent flying through the 

 air, and, after a trajectory of some miles, itself exploded, causing 

 the damage which was the purpose of its despatch. The effect of 

 this second explosion was severe but local, and at a short distance 

 away neither sound nor shock was sensible. 



Here we have a very complete analogy, the explosion of the gun 

 represents the bathyseism ; the report and sound-waves, ti"a veiling 

 afar, correspond to the disturbance which, propagated through 

 the substance of the Earth, ^ives rise to the lons^-distance records : 

 the explosion of the shell to those dislocations in the outer crust 

 which produce the destructive earthquake : and the trajectory to 

 the connexion, of which the character is as yet unknown, between 

 the bathyseism and the surface-shock. 



If this interpretation be accepted, it becomes evident that the 

 distant records represent something which is distinct from the 

 earthquake, as originally understood, and that the study of them, 

 with the deductions drawn fi-om that study, have little or no 

 bearing on the problems of geology, as we usually limit the scope 

 of that science. It is otherwise with the earthquake proper ; 

 originating in, and affecting, the outermost crust of the Earth, it 

 has long, and rightly, been regarded as one of the depai-tments of 

 geology, both as regards cause and chai"cicter, and it is with this 

 aspect of the subject alone that I shall deal. 



The character of earthquakes is known to an extent sufficient 

 for my pm'pose : they are elastic waves, transmitted through the 



