84 The Irish Naturalist. 



GBOLOGY. 



Perforations in Carboniferous IvImestone. — I have seen the 

 perforated limestone described by Rev. Mr. Close in situ on the shores 

 of Lough Corrib, near Oughterard. So far as I could observe, the holes 

 were perpendicular to the exposed surface, but this would not necessarily 

 mean that they were at right angles to the bedding. I was anxious to 

 ascertain the true cause of these holes, and for this purpose I visited the 

 Geological Museum of Queen's College, Galway, There I saw a good 

 specimen described as an "example of the chemical and mechanical 

 action of water on limestone." This was in Professor King's time, and I 

 am sure he was satisfied before attaching the descriptive note to the 

 specimen. — O. Fallon, Ardara, Co. Donegal. 



I forward a specimen of perforated limestone, much of which has been 

 turned up by the blasting operations carried on by the harbour authori- 

 ties in the bed of the river here. The rock is from two to four feet under 

 low water at spring tides, but the perforated stone seems to come from 

 about two feet below the upper strata of rock. — Joseph M. McBride, 

 Westport. 



The geological notes on Limestone perforations in this and last issue 

 considerably interest me. Personally I had always considered such as 

 due to aqueous action. A few years back I remember coming on such 

 indentations upon smooth exposed Limestone Rocks, Queen's Co. To the 

 best of my recollection the holes varied from a little less than three- 

 quarter inch to one and a-half inches in diameter, and from two inches 

 to four inches in depth. In all cases they were perfectly round, gently 

 tapering towards the bottom. Their circularity is a necessity of aqueous 

 action, their tapering can hardly be explained by it, while their varying 

 diameters and depths suggest forces of greater or lessmagnitude — possibly 

 molluscs of different sizes } Varying depth cannot be explained by 

 action of water, for, if due to denudation, the holes should regularly 

 decrease or increase in depth a uniform series — or at least more uni- 

 formly than they do, — T. H. Walpole, Dublin. 



I have much pleasure in forwarding for inspection a fragment of the 

 perforated limestone. I believe that when these perforations are ex- 

 amined, there will be no doubt that they were formed by a mussel or 

 other organised being, whose work is quite distinct from any effect which 

 could be produced by inanimate agency. When speculating on what 

 caused these curious holes, I certainly thought of the weathering action 

 of water, etc., but I had very soon to abandon this view for the following 

 reasons among others: — Firstly, there is too much of a "family likeness" 

 about these holes for me to believe that they were produced otherwise 

 than by an animal; secondly, though the rock is wrinkled, scored, and 

 bored by the tooth of time, it is easy to distinguish the work of the intel- 

 ligent little creature from the ordinary denudation of the stone; and 

 thirdly, the holes are confined to a foot or two at the top of the stone, as 

 if the animal could onl}' live and work at a certain depth of water ; per- 

 haps the lower part of the stone was protected by some deposit of mud, 

 but the scratching and weathering extend there. 



For these reasons I have come to the conclusion that these strange 

 perforations can only have been formed by some animal living in the- dis- 

 tant past, as the boring-mussel of the present day is known to produce 

 similar work, but perhaps on a lesser scale. 



In answer to Mr. Close's question, I should say that the perforations do 

 not seem to follow any set rule; the stone appears to have been attacked 

 in all directions. The only rule which seems to prevail is that where the 

 holes enter the stone horizontally, they always turn upwards soon after 

 entry. — Owen Smith, Nobber, Co. Meath. 



[We acknowledge with many thanks the receipt of specimens from 

 Mr. Smith and Mr. McBride, and hope to return to this interesting sub- 

 ject in our next number. — Kds.] 



