308 On the Geological Structure 



of the globe*. I am informed by Mr. Jameson that he has 

 seen in Lusatia detached conical summits composed of that 

 substance; and that the summits ot the same figure in the 

 mountains separating Caithness horn Sutherland are like- 

 wise formed of it ; as are also the Paps of Jura in the Westera 

 Islesfj and according to Dr. Ber<.'er ihc muv\i\Vd\v\ Dimilull 

 near the town of Portsoy ii. Scotlnnd. 



The princiiial mines which have hi'herto been npened 

 within the mountainous district near Dnhhn, are thohc of 

 copper ore ai Cmne/'ar/e and Baih/riiurfagh, ihe nielalHfe- 

 rous waters of which were described in the Philosophical 

 Transactions so long ago as in the year 1737 J ; and of 

 lead at Gievmahir^, at G etirlalogk, at Dalkn/, and at 

 Balhjconts near the Scalp. The ^tieam works commonly 

 called " the Gold-nnine" were situate on the north cast 

 side of the mountain Croglian Kinshela on the southern 

 verge of the county ot Wickiow ; and gold has been found 

 within that county at another mountain named Cnighan- 

 MoJra, about eight English miles to the north of that 

 place ||. 



The occurrence of Tinstone at the " Gold-mine, where 

 it has been obtained in fragments^, is a tact which de- 

 serves particular attention ; for the probability of the dis- 

 covery of veins of that valuable ore wi;hin a tract of pri- 

 mitive country so extensive as that of Dublin and Wick- 

 low, appears from this circumstance to be considerable. 



Porcelain ea'^th resulting from the decomposition of 

 felspar, has been found at Ktlranelagh in the county of 

 Wickiow, in puntv nearly equal to the Cornish " China 

 clay:" and granite is found in a decomposed state so 

 commonly in other parts of that county, that this valuable 

 production may with nmeh probability be expected to oc- 

 cur there in other places, and in considerable quantity. 



* Siliceous earth in the form of this mineral, and consequently nearly 

 pore, seems to constitute a much greater portion ot the earth's surface than 

 some mineralogists have supposed Humboldt states that near Caxamarca 

 in Peru, a mass of more than nine thousand feet in thickness is exclusively 

 composed of quartz : — he has not mentioned the form of the summits. 

 Jalteiw Pliv.w/iii:,p. 128. 



+ See Walker's CEconomical History of the Hebrides, vol. ii. p. 392. 



\ Vols, xb ii- and xiviii. 



§ The sales of lead from ore riised and smelted at the Glenmalur mine, 

 amounted du'ing the year ending Lerember 3ist, 1811, to no less than 

 9819/. I6s. 2d. Irish currency: the weight of metal sold was 6680 cwts. 

 2. qrs. ^ 



|l Gold is said to have been found alfo at the King s river, near the village 

 of Holywood, in the county of Wickiow. 



^ Report on the Gold-mine by Messrs. Mills and Weaver. Trans, of Dub- 

 lin Society, vol. iii. 



The 



