376 Oil the Geological Structure 



tions of these very curious and Unique Instruments ; and 

 hoping, that Mr. L. may receive ample remuneration ior his 

 ingenuity and labours, in the Sale of his Work and his 

 Organs. 



I remain sir, 



Your obedient servant, 



12, Upper Crown Street, Westminster, JoHN FaREY Sen. 



16th May, 1812. 



LVl. Notice respecting the Geological Structure of the Vi- 

 cinilij of Dublin; with an Account of some rare Minerals 

 J'ovfid in Ireland. % William Fitton, 3f. D. Com- 

 municated by L. Horner, Esq. Secretary to the Geologi- 

 cal Society. 



[Continued from p. 311.] 



JL HE following substances, v^ith the exception of the last 

 two, have been found within the district to which the pre- 

 ceding observations relate. 



1. FesTivian — (/f/oa-a5e, Haiiy.) This mineral was observed 

 by Mr. Stephens, in specimens found by me at Kilraneiagh 

 in the county of Wicklow ; where it occurs in irregular cry- 

 stalline mssses, in a rock composed of common garnet of a 

 reddish brown colour, of quartz, for the most part greenish, 

 apparently from the aJmi.xture of a lamellar fossil of that 

 hue, and a small quantity of yellowish white felspar. The 

 dodecahedral figure of the garnet was vcrv distinct iu se- 

 veral of these specimens ; but the form of the Vesuvian was 

 not so well exhibited, some indistinct prisms only being 

 observable; and in general, the crystalline shoots of the 

 latter mineral had assumed a diverging or stelliform arrange- 

 ment, an appearance which I have not observed in speci- 

 mens of this substance from other places; but their easy 

 fusibility, lustre, colour, and other characters, were suffi- 

 ciently decisive of their nature. 



I could not discover the original situation of the com- 

 pound above mentioned at Kiiranclagh ; but the size, the 

 great weight, and angular form of the blocks consisting of 

 it, render it probable that they were not far removed from 

 their natural place: and the country m that neighbourhood 

 is composed of primitive substances, among which Garnet 

 rock is described hy mineralogists, as constituting beds. 



It is remarkable, that a compound much resembling that 

 which I have now described, occurs also in the county of 

 Donegal ; from whence specimens in the cabinet of the 

 Dublin Society, and that of Dublin College (No. 30), were 



obtained. 



