32 REPORT — 1844. 



the loadstone beds, and it is mentioned as not surprising that beds so uncertain not 

 only in thickness, but in locality, should daunt the enterprise of the miner, since a 

 mere bed of clay varying from a few inches to afoot in thickness in one mine, becomes 

 in the next mine twelve or fourteen fathoms thick, and in another a hard compact rock. 

 The object of the paper was to prove this uncertainty, and to show that there are at least 

 two if not three distinct beds of the singular i-ock called toadstone. 



The author, alluding to the opinion of Mr. Hopkins, that when two beds of toad- 

 stone have been thought to exist, a fault has re-introduced the one, and thereby occa- 

 sioned the mistake (an opinion since somewhat modified), states that in a section of 

 Crick Cliff, what is at one shaft a thin bed of clay a foot thick, becomes within a 

 short distance fourteen feet thick, and contains large nodules of compact toadstone, 

 while the thick bed of toadstone actually sunk through at one shaft diminishes to a 

 thin bed at the other mine, and this is clearly discernible, since the workings are con- 

 nected and the trace of each bed is never lost sight of. 



The author then proceeds to allude to different clayey beds uncertain in thickness, and 

 ■when thickest, containing blocks of hard toadstone. One of these, the " great clay " of 

 the Wirksworth district, is identified with another at Crick, by the situation of three beds 

 of clay beneath. These clays are said to be well-known to the working miner and 

 to be easily recognizable when they have been once seen. They are called (1) the 

 " twenty-fathom clay," (2) the "bearing clay," occurring about seventeen fathoms 

 below the former, and (3) the " tumbling clay," about five fathoms below the bearing 

 clay, and remarkable for its xmdulating character. 



It is stated that at Smitterton a thick bed of toadstone of twelve fathoms replaces 

 a thia bed of clay at Crick and Wirksworth, there being at this place (Smitterton) 

 a second toadstone similar to those at Crick and Wirksworth with a limestone resting 

 upon it, also similar in character and containing similar fossils. There is also another 

 bed, to all appearance another toadstone, but this was not made out distinctly ; it is at 

 the same distance from the toadstone as the twenty-fathom clay at the other places. 



Account of the Grassington Lead Mines, illustrating a Model of the Mine. 

 By S. Eddy. 



The model which this communication was intended to illustrate represented a portion 

 of the Grassington Lead Mines near Skipton in the West Riding of Yorkshire, the 

 property of the Duke of Devonshire, at whose request the model was exhibited. The 

 mines are in the carboniferous series of strata, from which two-thirds of the whole 

 quantity of lead raised aimually in England is obtained. 



It is well known that most of the lead veins in this formation in England are prin- 

 cipally valuable when passing through the limestone bed, but to this general rule the 

 Grassington mines form an exception, nearly the whole produce being obtained in the 

 gritty beds, alternating with the limestone and shale. It is to be observed, however, 

 that the veins, although numerous and extending over a large tract of moorland, are for 

 the most part small and not very productive. It was considered that as a thick bed of 

 limestone (thirt3'-six fathoms) succeeds the shale and gritstone in which the veins are 

 ■worked, and is succeeded by a bed of shale, the produce would increase on reaching 

 the limestone, but this has not proved to be the case. A trial is now going on for the 

 purpose of exploring some of the principal veins below the shale. 



Nearly all the veins in the Grassington district are what are termed " Fault veins," 

 that is, a vertical displacement of the strata has taken place, so that the same beds are 

 found at different levels on the two sides of the vein, and the subsidence of the strata 

 is generally on that side to which the veins incline, the amount of inclination or under- 

 lay of the vein being invariably much greater in the argillaceous beds than in the grit 

 or limestone. 



A depression of a few feet or two or three fathoms is considered most favourable 

 for lead ore, but the displacement is sometimes much greater, causing grit or limestone 

 on one side of the vein to be opposite to argillaceous beds on the other. In such cases 

 the veins are rarely productive, although the principal vein shown in the model is an 

 exception to this rule. 



The general matrix of the ore (the veinstone) is calcareous spar, fluor spar, barytes, 

 and occasionally calamine, and when the amount of the fault is so considerable as to 



