538 Intelligence and Miscellaneous Articles. 



Descriptions of all the Classes, Orders, Families, and Genera of Fossil 

 Animals, found in the Strata of the British Isles ; to be completed 

 in four or five Parts, forming one volume, 8vo, of about 500 pages, 

 with nearly 1000 Wood Engravings. 



LXXXIV. Intelligence and Miscellaneous Articles. 



ON A REMARKABLE DEPOSIT OF TIN-ORE AT THE PROVIDENCE 

 MINES NEAR ST. IVES^ CORNWALL. BY WILLIAM JORY HEN- 

 WOOD, F.R.S., F.G.S.* 



rpiHE Providence Mines, in the parish of Lelant, comprise the mines 

 A formerly known as Wheal Speed, Wheal Laity, Wheal Com- 

 fort, and Wheal Providence, long worked on the eastern side of the 

 hill which slopes from KnilPs monument to the sea. 



(«.) Observations on the eastern workings in the slate, and on the 

 western within the granite formation, have already appeared in the 

 Royal Cornwall Geological Society's Transactions f. The interme- 

 diate tract now to be described is wholly in granite, of which the upper 

 beds aie composed of a basis of grayish felspar and quartz, imbedding 

 medium-sized crystals of white felspar, as well as numerous small 

 groups of schorl in radiating crystals : but near the productive parts 

 of the lodes the rock is mostly rather coarse-grained, its basis is 

 greenish-gray felspar, black mica, and quartz ; and the included por- 

 phyritic crystals of felspar are either of a pale buft', a pink, or a red- 

 dish-brown hue. 



(i.) The veins are : — 



The Cross-Com-se or Trawn, which beai-s about 22° W. of N., and dips E.J 



The "\\Tieal Comfort lode 15°W. ofN., ... W. 



andWlieal Laity lode or lodes ... 17° S. of W., ... S. 



Connected with the Wheal Comfort lode there is a " Carbona§," 

 to which further reference will be made presently. 



It may be here stated generally, that the Cross-course is from one 

 foot and a half to two feet in breadth, and is composed of disinte- 

 grated fine-grained granite, divided by numerous joints parallel to 

 the " ivalls ;" as well as by many other curved and irregular ones 

 which intersect each other in every imaginable manner, and are 

 filled with oxide of iron, and closely but unconformably striated. 



The Wheal Comfort lode varies in width from a few inches to more 

 than six feet. At a distance from the Wheal Laity lodes it is of 

 granite very thinly impregnated with tin-ore ; the remainder con- 

 sists of quartz, schorl-rock (capel), brown iron-ore, and greenish 



* From the Transactions of the Royal Geological Society of Cornwall, 

 vol. vii. 



t Vol. V. pp. lG-20, plate 2. fig. 7, Tables 21 and 22. 



'I The " directions " have reference to true north, the " dips " are from 

 the horizon. 



§ I have already described a similar, though a much smaller formation, 

 in one of these mines.— Corn. Geol. Trans, vol. v. Table 22. 



