SOUNDS CONNECTED WITH THE EARTHQUAKE. 113 



The sounds referred to here, like those associated with the 

 former earthquakes, were local in their distribution, the areas over 

 which they were heard were a Long way from the epicentre! tract, 

 and the explosions followed the shock. 



Mr. Ripley, Sub-divisional Officer of Magwe, reported that on 



May 16th he was at a place called luvwagvi 



Noises heard in the in fche fifyothit township. when peculiar, 

 Macrwe District on May ±11 \ -\ 1 t 1 i , • 



, 6 ^g | 912 . ' fcnougn not very loud sounds of Long dura! ion 



were heard from the north. The inhabitants 



of the neighbourhood could not understand the noises and had 



never heard them before. Such mysterious noises known under 



the general name of "brontides' 1 and locally as " Barisal guns ", 



•■ mist-poefi'eurs", " marinas", etc.. may possibly be. earthsounds 



following in the wake, but after a prolonged interval of time, of 



some past and almost forgotton shock.) 1 ) 



The questions may be asked how do such sound vibrations 

 Origin of earthquake originate, and how do they reach any parti- 

 sounds, cular locality in advance of the shock itself ? 



A view which appears to find some favour is that earthquakes 

 and earthsounds are manifestations, differing only in degree and 

 in the mode in which mankind perceives them, of one and the 

 same phenomenon. The excentricity of the sound areas when 

 referred to the isoseismal lines, in the cases of those earthquakes 

 concerning which Sufficient data exist to enable such comparative 

 studies to be made, together with the general precedence of the 

 sound, is held to be explained by assuming the generation of two 

 sets of vibrations in different regions of the focus. The portion 

 from which the sound vibrations proceed lies outside tin 1 other, 

 and principally in the upper and lateral margins of the seismic 

 locus. ( 2 ) 



Seismic waves tiaversc the earth's crust very much faster than 

 sound waves are transmitted in air. It is therefore impossible for 

 sounds produced in the latter medium, above the seat of the 

 the disturbance, to reach distant points in advance of the seismic 

 vibrations themselves. United testimony of witnesses is too strong 

 for tin 1 fact to be doubted that the sounds are really generally 

 heard in advance of the felt shock. The Bounds, therefore, must 

 be made by vibrations communicated to the atmosphere by 



1 c. Davison : The Origin of Earthquakes, p. 121. 



2 Davison : Lor. cil.. p. l-^i- 



