272 



THE GEOLOGIST. 



with it, and hence the coating of sulphate of lime, for which I was totally 

 unable to account, until Dr. Bowerbank was kind enough to impart to me some 

 of the vast information he has amassed on the nature and habits of sponges, 

 recent and fossil. — W. B. Kestevan, Upper HoIIot^ ay. 



On the Vertical Veins of Dark Limestone in Red Shale at 

 Templemore. — Dear Sir, — Permit me to offer an explanation for the occur- 

 rence of those " irregular vertical veins or thin dykes of dark grey compost 

 limestone, which cross a nearly horizontal bed of red sb.ale near the base of the 

 old red sandstone of the neighbourhood of Templemore," to which attention 

 has been directed by your correspondent A. B. W., in the April number of 

 " The Geologist." 



Let us suppose that the accompanying diagram, fig. 1, represents the face of 

 this bed. 



Lign. l.—a, Sandstone; b. Shale; c c, Limestone miid filling up fissm'es; d e. Limit of 



denudation. 



After the deposition of the shale b, and while it was yet in the state of mud, 

 the sea bottom at this place became suddenly elevated above the waters, and 

 subjected to rapid dessication, which produced numerous cracks and fissures 

 over its surface ; and these after a time were doubtless increased in dimensions 

 by subsequent atmospheric action. The land was then submerged ; but during 

 tlic interval of this upheaval and dessication, the sea around this particular 

 area had ceased to deposit ferrugio-argillaceous mud as weU as sand, owing, 

 d()ul)tlcss, to local changes of currents, the result possibly of those movements 

 in tiie hind which I have just supposed. Its sediment now consisted entirely 

 of such highly calcareous materials as would be capable of forming limestone 

 only, and this, of course, filled up these cracks and fissures, and any other irre- 

 gularities which existed over Avhat was then the bottom of the sea. 



It is remarkable that in the neighbourhood of Templemore absolute beds of 

 pure dark grey limestone are frequently, found interstratified with the old red 

 sandst ones, and we may therefore rationally suppose that the shale which I am 

 describing may have been at one time covered by a bed of such limestone as I 

 have alhuhnl to, at whioli period of its history the section at this locality may 

 liavo been t liat which 1 have represented in the diagram fig. 2. 



After a time, the calcareous mud not only ceased to be deposited here, but 

 another great and material change took place in the relative distribution of 

 land and water. The sea bottom became sufiiciently elevated to be brought 



