[88] _Cobalt._ _Huel Sparnon_ Tin and Copper Mine in the Parish of Redruth, is the only mine in the county that ever produced any considerable quantity of Cobalt; one fragment raised from it weighed 1333 lbs. [89] _Silver._ In the Copper Lode of Huel Ann, there occurred a distinct vein of _black_ and _grey Silver ore_, with _Native Silver_, from two to five inches wide with a wall of Quartz, on each side. It was however very short. See Mr. Carne's paper on the Silver Mines of Cornwall, _Transactions of the Royal Geological Society of Cornwall_, _vol._ i. _p._ 118. [90] Only one Lode in Cornwall has, however, been found of this size, and that only for the length of 20 fathoms in _Relistian_. In _Nangiles_ the lode is, in some parts, 30 feet wide. [91] As the Counting House of Dolcoath has been determined to be 360 feet above the level of the sea, the mine extends 1050 feet below it; which is probably deeper under the sea level than any mine in the globe. [92] Clay-slate is provincially called _Killas_; and Porphyry is known by the name of _Elvan_. [93] For a full account of this subject, the reader must consult Mr. Carne's laborious paper, "_On the Veins of Cornwall_," in the 2nd Volume of the Transactions of the Royal Geological Society of Cornwall. [94] We must refer the reader to a Paper, "On the Veins of Cornwall," by _W. Phillips, Esq._, published in the 2nd vol. of the Transactions of the London Geological Society; and also to a Paper, "On the relative Age of Veins," by _Joseph Carne, Esq._ in the 2nd vol. of the Cornish Transactions. [95] We shall pass over, as being too absurd to require any serious refutation, the former belief in the power of the _Virgula Divinatoria_ to discover Lodes. A power less poetical but not less fabulous then the story of the _Virga Fatalis_ that conducted Æneas to the Shades. [96] _Grass_ is the technical name for the surface on all occasions. [97] The great Copper Mine, called _Crennis_, was discovered by some casual observers in the cliff. [98] From _Aditus_, a passage? [99] The application of this machine in the county is estimated as saving the labour of 10,000 men; whilst the powers of the different steam-engines are considered as at least equivalent to 40,000 more. [100] See Dr. Forbes's Paper "On the Temperature of Mines," in the second volume of the Transactions of the Cornish Society. [101] The annual cost of gunpowder, used in the mines of the county, amounts to more than thirty thousand pounds. [102] Transactions of the Royal Geological Society of Cornwall, vol. 2, page 162. [103] The quantity of water discharged by the pumps from many of the Cornish mines is very considerable; thus _Huel Abraham_ discharges from the depth of 1440 feet, about 2,092,320 gallons every 24 hours; _Dolcoath_, from nearly the same depth, 535,173 gallons in the same time; and _Huel Vor_, from the depth of 950 feet, 1,692,660 gallons.