1865.] WALLACE — FLOS PEEEI. 413 



2. On the Growth of Flos Ferri, or Coealloidal Arragonite. 

 By W. Wallace, Esq. 



[Communicated by W. W. Smyth, Esq., T.E.S., Sec. G.S.] 

 [Abridged.] 



In giving a sketch of the physical features of the Meldon district in 

 "Westmoreland, Mr. "Wallace stated that the water- shed of the Mel- 

 don range of mountains corresponds with an anticlinal axis which 

 probably ranges at nearly equal distances from the Eiver Tees and 

 one of its tributaries — the Maizebeck. 



The denudation of the country to the east of the Great Penine 

 fault has evidently been regulated by the unequal elevation of the 

 strata. The highest mountains are chiselled out of an immense mass 

 of stratified rocks, and left standing on the ridges, or axes of highest 

 elevation, of the beds. The denuding forces have produced the 

 greatest effect where they have formed the valleys ; or, in other 

 words, in a general view, the greatest amount of denudation has been 

 effected where the rocks have been the least elevated from their ori- 

 ginal horizontal position. 



On each side of the Meldon hills lead-veins are found ; and the 

 formation of these veins is evidently connected with the anticlinal 

 axis, the direction of which corresponds with that of these hills. On 

 the north side, the principal vein of the Silver Band and Dunfell 

 Mines dislocates the strata some 16 or 20 fathoms, the side next the 

 axis being elevated. The veins on the contrary side probably dis- 

 locate the strata less ; the amount of their throw has not, however, 

 been exactly ascertained. 



All the veins of the Silver Band Mine and the flats of the Dufton 

 Fell Mine contain much sulphate of barytes. In some parts of the 

 Silver Band vein I have found the width of this substance to be not 

 less than 21 feet. Nodules of lead-ore are enclosed in the barytes ; 

 and this mineral occasionally encloses ribs of lead-ore of very irre- 

 gular width. From a number of observations I am inclined to sup- 

 pose that the presence of iron in the barytes has been a condition 

 favourable to the deposition of lead-ore. 



When the Great Limestone was formed, its position would be ho- 

 rizontal, or nearly so, throughout the whole extent of the mining 

 districts of Alston Moor, Weardale, Teesdale, &c. It has, however, 

 been wrenched into very unequal positions. At Nenthead it is ele- 

 vated about 1450 feet above the sea ; in the Silver Band Mine, and 

 on the south side of the principal vein, 2400 feet. This difference 

 in elevation of nearly 1000 feet is connected vrith very different 

 kinds of- phenomena. In the Silver Band Mine the Great Limestone 

 is much broken by joints in which pure air circulates, so that 

 artificial ventilation is seldom needed where mining-works are made. 

 In the Nenthead district the Great Limestone is only jointed near 

 the surface ; and, but for the numerous veins, it would form unbroken 

 sheets of rock in the centres of the surrounding mountains. It has 

 been stated that " limestone strata near the summits of mountain- 

 ranges, even when under considerable pressure, are found to contain 



VOL. XXI.— PART I. 2 F 



