1 88 The Irish Naturalist, September, 1908. 



GEOLOGY. 



Sounds of Seismic Disturbance. 



On a fine, calm day in summer an observer seated on the sandhills at 

 the mouth of the Boyne will be very likely to hear from time to time 

 sounds like distant peals of thunder. For many years I have been listen- 

 ing to and puzzing over these mysterious noises, and I wish to ask if 

 anyone can explain them. They sound like muffled explosions or distant 

 peals of thunder, are never loud, and sometimes almost inaudible (rather 

 to be felt than heard), never very long, but longer as a rule than the 

 sound of a heavy gun. They are only to be heard in fine and calm 

 weather, but that may be because wind and noise ma}- render them in- 

 audible. They often go on at intervals for a whole day, notably on May 

 27 and 29 last. I have heard them all along the E. coast from Wicklow 

 to Carlingford. They always seem to come from the sea, and, at the 

 mouth of the EoA'ne, from the E. to S.E. The common explanations of 

 these sounds are quite inadequate : distant thunderstorms, guns at sea, 

 fog signals, quarry explosions, &c, all quite incompatible with the condi- 

 tions. These sounds appear to resemble the noises known in Ital}- as 

 " Brontidi," which are heard over a great part of that country, and have 

 lately been enquired into by the Director of the Seismological Obser- 

 vator}' of Urbino. He seems to think that the cause is the same as that 

 of earthquakes, and that the phenomenon has its origin in the soil rather 

 than in the air. Professor Grenville Cole thinks the sounds "point to 

 something like the Brontidi or the famous Berisal or Borisal guns of 

 India," and he also thinks that "books on earthquakes mention these 

 phenomena, which are now commonly attributed to earth movements 

 along lines of faulting." I am writing this note at his suggestion. Mr. 

 Lloyd Praeger tells me that, as is well known, similar sounds are 

 heard about Lough Neagh, and that he himself has heard them. Both 

 of these gentlemen consider the subject to be one of great interest and 

 well worthy of discussion and observation, and I hope readers of the /m// 

 Naturalist will help to throw light on it. I would venture to suggest that 

 hearers of these sounds should note the circumstances, and especially 

 the direction from which they come. A few cross bearings taken along 

 the coast would locate them effectually. Yachtsmen should note them 

 if heard I have often heard them when far at sea, but I don't think the}- 

 would be audible on a steamer. It will also be necessary for observers to 

 remember that one, or even a dozen distant muffled sounds may not 

 belong to this class of sounds at all, but may really be the reverberations 

 of a distant storm, or of gun firing, or quarry explosions, or some such 

 cause. Care will be necessary to discriminate. The direction, too, is not 

 always eas)' to determine. I hope some observers will take this matter 

 up and help to cast some light on an obscure and interesting pheno- 

 menon. C' 



G. H. PentiRnd. 



Black Hall, Drogheda. 



