428 Mr. Farcy's Remarks on Mr. BakeiveWs Lectures. 



by Mr. Thomas Bird, I believe, in Eyam, is a very com- 

 plete instance of this filling up of cavems by subterranean 

 currents, instead of their being formed thereby. 



Respecting the opening of the fissures occupied by mJ- 

 neral veins, Mr. B. (p. 31 i) appears, like Dr. James Miller, 

 when speaking of the Wenitrian Theory (as I have ob- 

 served in the note, p. 74 of my Report) to overlook the 

 causes assigned, and principally insisted on bv M. Wtr- 

 r.er himself, in his " new Theory" of Veins, lately trans- 

 lated, viz. slips " in rainy seasons," and the yielding and 

 cracking of the mass by ils own weight, when the rock 

 was " at first wet and possessed little solidity," and part 

 of it fell to the free side !. The suggestions which Mr. 

 Bake well offers, at the bottom of page 315, as to the pro- 

 bable voltaic influence which the sides or cheeks of the 

 Vein have had on the metallic deposits within it, is in- 

 genious, and accords well with most of the facts which I 

 know, particularly that remarkable one, that the bearing 

 measures (Rep. i. 24G), or particular beds of Rock between 

 which the ore is principally lodged in the vein, were in se- 

 veral of the most productive Mines in Derbyshire, consider' 

 ally inclined to the horizon, and are so in the Gang and some 

 others, that are yet workmg: indeed, where the Limestone 

 laps round an irregular lump of Toadstone in the floor of 

 the Rock, as in Ashover Velley, Crich, Matlock High-Tor 

 and Masson Hills, &c., the bearing-measures therein, are 

 found to conform to this shape of the floor, with very va- 

 rious and sometimes sudden changes in their inclination to 

 the horizon : and furnish a good proof, in accordance with 

 every other ascertained fact, that these Limestone Rocks 

 could not have been lent into their present form by in- 

 jected Lava between them, as Mr. B. appears, I think, 

 disposed to concede to Mr. Whitchnrst : since few persons 

 would grant, that the crystals of spar and ore in a vein 

 could have been sojt and capable of bending, without the 

 least fracture or distortion being observable in them; what- 

 ever a superficial knowledge of stony depositions, might 

 dispose them to concede, with respect to the rocks that 

 contain the veins. 



I am, sir^^ 



Your obedient servant, 



Westiniaster, June 14, 1812. JoHN FaREV Senior. 



LXIV. On 



