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"VI. — Recent Observations on SuUerranean Temperature in the Clifford 

 Amalgamated Mines. — By Sir Frederick Martin Williams, 

 Bart., M.P., F.G.S., &c., &c. 



Eead at the Spring Meeting, lltli May, 1870. 



THE district iii which the Clifford Amalgamated Mines are 

 worked has been frequently described,'"^ but never better than 

 by Mr. Warington Wilkinson Smyth, F.E.S., who says, ''The 

 constituent rock of this region is mostly the clay-slate or killas, 

 which, abutting against the granite dome of Carn Marth, dips 

 away from that hill towards the east, and has not been unbottomed 

 in the deepest mines about to be mentioned, although there can 

 be no reasonable doubt that the granite would be found occurring 

 again beneath it. The clay-slate is intersected by dykes of elvan 

 or granitic-porphyry, coursing in an east and west direction ; by 

 lodes or mineral-veins, having on the whole a very similar line of 

 strike ; and by cross-courses or non-metalliferous veins, running 

 north and south. The more notable mines of this district have 

 been Poldice, Wheal Jewell, Tin^ Tang, Wheal Squire, the Con- 

 solidated Mines, the United Mines, and Wheal Clifford, worked 

 with various success to depths of from 1,000 to 1,900 feet from 

 the surface. Certain of them are at present in abeyance ; others 



• Borlase, Natural History of Cormoall, p. 206 ; Pryce, Mineralogia 

 Cornubiensis, pp. 8, 9, 11, 12, 192, PL vii ; Berger, Geol. Travis. O.S., i, p. 72 ; 

 Phillips (William), ibid, ii, p. 156, PL vi ; Williams, ibid, iv, p. 143, PL vii, 

 Fig. 1; Thomas (Eichard), Survey of the Mining District from Chasewater to 

 Camborne, pp. 1 — 76, Geological Map and Sections ; Carne, Cormoall Geol. 

 Trans., ii, pp. 44 — 128, PL 2, 3 ; ibid, iii, p. 81 ; Hawkins, ibid, ii, pp. 225 — 

 230, PL 4 ; Henwood, ibid, iii, pp. 324—31, v, pp. 69—92*, PL vii, viii ; 

 Boase, ibid, iv, pp. 29j)— 1, 305—7 ; Fox, Phil. Trans. (1830), pp. 407—9,-10, 

 11, 13, 14 ; De la Beche, Report on the Geology of Cormoall, Devon, and West 

 Somerset, pp. 93, 176, 305 — 6, — 39, — 40; 'Bwxic, Quarterly Mining Revieio,t^o, 

 vii, p. 20 ; Hopkins (Evan) Geology and Terrestrial Magnetism, pp. 46 — 50, 

 PL viii ; Thomas (Charles) Remarks on the Geology of Cormoall and Devon, 

 pp. 4, 19 ; Salmon, Mining and Smelting Magazine, v, p. 329 ; Baruett, 

 Reports of the Royal Cornwall Polytechnic Society, xxxvii, pp. 53 — 6. 



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