fcEOLOGY OF THE VICINITY QF DUBLIN. 289 



8. The granular sulphate of barytes, hitherto very rare, has Sranular sul- 

 phate of 

 barytes. 



been found, as the Rev. Mr. Hincks of Cork informs rc»e, by V^^^^^of 



Dr. V/ood of that city, on the seashore, near Clonakilty, 

 whence a specimen in the Museum of Dublin Collegej 

 (No. 653) has probably been obtained: it is accompanied 

 by iron pyrites. 



9. Wavellite. This remarkable mineral has recently been Wavellite. 

 found in the county of Cork, at Springhill near Tractou 

 Abbey, about tert miles south-eastward from the city. The 

 Rev. Mr. Hincks of the Cork Institution, from whom the 

 specimens that I hav^ seen were obtained, informs me, that 

 it was found at a small distance from the surface, near the 

 base of a hill composed of flinty slate, and that he has seen 

 it adhering to a piece of rock of that description. But it 

 ijas occurred principally detached in the form of globular 

 nodules, irregularly grouped together, and of various sizes^ 

 the longest about an inch in diameter, externally coated 

 with a yellowish brown earthy crust, and within conjposed 

 of radiating crystalline spiculse, the characters of which 

 agree ve^y nearly with those of the wavellite from Devon- 

 shire, described by Mr. Davy; indeed some of the speci- 

 mens from the county of Cork are scarcely to be distin- 

 guished from some of those obtained at that place. 



The most distinct specimen, that I have seeri, was a nodule 

 about three fourths of an inch in diameter, in part affected 

 by decomposition, and containing some small spongy cavi- 

 ties. On its external surface indistinct dihedral terminations 

 of the crystalline shoots are discernible; and internally, 

 where it is not decomposed, its lustre is higher and more 

 glassy than is common in the Devonshire fossil. The 

 specific gravity of that part of it, which was very pure and 

 nearly transparent, was 2*34. 



The nodules areinsomeinstancesdecomposed throughout; 

 the spiculse, havir^glost their lustre, acquire a dull gray or 

 brownish colour, and become much softer than when un- 

 changed ; and Mr. Hincks has seen some of them altoge- 

 ther in the state of clay, apparently from the effect of de- 

 composition. 



It would appear that the fluoric acid, ©f which Mr. Davy 



has ascertained the presence in the wavellite from Devon- 



VoL. XXXI.— Apeil 1812, U shire 



