182 MINERAL PRODUCTS. 



them. The opinions of working colliers on this point have too often 

 been preferred to the legitimate deductions of science, and even yet 

 persons will perhaps be found willing to credit the delusive tale of 

 finding good coal by going deeper. But the warning must be given, 

 though it be disregarded ; and from all the natural exhibitions on the 

 coast, as well as from the result of every experiment inland, I am com- 

 pelled to state, that any hope of discovering seams of coal more than 

 eighteen inches or two feet in thickness, in any part of the strata above 

 the upper lias or alum shale, is entirely unsupported by reason and 

 experience. That the coal measures of Durham and western Yorkshire 

 exist (covered by magnesian limestone and red sandstone) beneath the 

 lias, is probable, but the practicability of reaching them by pits, even in 

 Cleveland, or near York, is very questionable, and the expense of the 

 experiment may be ruinous. 



Of several thin and variable seams of coal which appear among the 

 sandstone rocks above the lias, only the lower one immediately above the 

 dogger, and the upper one not far beneath the gray limestone, have been 

 found worth the expense of working. The upper seam is the most 

 regular, and has been worked at Clou gh ton Wyke, May becks, Goadland, 

 Glaizedale, Danby, Blakehoe, Rudland, Coxwold, Newborough Park, 

 Colton, &c. : that this and the lower seam may be opened in new 

 places, is highly probable, and such attempts may be productive of much 

 local advantage, but they should be guided by geological induction, and 

 not abandoned to ignorance and empiricism. 



The manufacture of ALUM from the upper lias shale, has furnished 

 extensive employment and considerable emolument, but there appears 

 little encouragement to establish works in new situations. The principal 

 material in the process does not retain its essential characters much 

 further south than the present establishments ; and the difficulty of 

 transporting materials to a distance will probably confine the trade to 

 the vicinity of the Peak, Lyth, Kettleness, Boulby, Rockcliff, and 

 Guisborough. 



