NEIGHBOURHOOD OF CORK, 95 



been, in a great measure, abstracted, and the silice- 

 ous matter left behind, in the form of a light po- 

 rous mass. In this state, my acute friend Mr Davy, 

 the Professor of Chemistry in the Royal Institution 

 of Cork, found the specific gravity of a very porous 

 piece, to be 2.07, and of a more compact specimen, 

 2.208. He has tried its effects as a material for 

 polishing metals, and had reason to be satisfied with 

 the results. The siliceous limestone thus decom- 

 posed, approaches the mineral termed float-stone, 

 transitions to which may frequently be observed 

 in the weathered fragments of the floetz lime- 

 stones. 



The surface of these limestone rocks is, in many 

 places, covered with the Lichen immersus of 

 Withering, the shields of which, by means of some 

 solvent, are sunk in the rock. In every crevice 

 and quarry, the Helix rufescens and virgata, were 

 common. 



In this limestone numerous remains of the tes- 

 taceous mollusca are found imbedded. Some of 

 these exhibit very striking peculiarities of structure, 

 and may probably characterise the formation to 

 which they belong. I attempted to collect as many 

 species as possible, and was kindly assisted by Mr 

 Wright of the Cork Institution, who has formed 

 a very instructive cabinet of these petrifactions. 

 Many of these have been figured by Sowerby in 

 his " Mineral Conchology," from specimens sent 

 by Mr Wright. 



