2.5 i On Alum' Shales 



incUiratccI clay, which contain native alum; geodes of iron- 

 stone that contain vaplulia ; pieces of petrified, charred and 

 bituminated ivoody ox jet : red iron-stone, in strata of a few- 

 inches to two tcct thick, four or five in number, at about 

 200 feet from the top ot" the shale: calcareous spar, about 

 half an inch thick, in the vertical slincs and end-joints of the 

 shale above mentioned : whin-dykes arc said also to traverse 

 these strata, and to have charred the coals in their vicinity? 

 The specific gravity of the alum-shale is about 2*48 ; it 

 decomposes into clay on long exposure : its upper part is 

 richest in sulphur, and produces about oiic ton of alum 

 from 130 tons of shale, or 00*77 percent.: the lower part of 

 the shale is very bituminous, hard and slaty ; a spontaneous 

 and slow combustion ensues when the alum-shale is mixed 

 and sprinkled with sea-water. 



Such arc the interesting geological facts, which Mr. 

 Winter has laid before the public, respecting the aluminous 

 shale strata of Whitby ; concerning which, it is further 

 desirable to know, the names of the different species of im- 

 bedded shells and other organic remains, with reference to 

 published descriptions and plates of them, or drawings and 

 descriptions of such as have not yet been described by na- 

 turalists ; and an account of the strata that underlay the 

 alum-shale, as well as of those which overlay the ferru- 

 ginous sand-stone. To ascertain these last particulars, it 

 may be necessary to examine the extremities of the alum- 

 shale on the sea- shore, and to trace its edges or boundaries 

 for some miles inland ; carefully distinguishing between 

 the alluviaL matters, properly so called, consisting of or 

 containing rounded stones and broken and heterogeneous 

 mechanical mixtures, and the regular stratified matters, 

 which will somewhere be found in a regular range, covering 

 the ferruginous rock and other strata which Mr. Winter 

 has described ; the nature and peculiar fossils of which 

 strata, it will be very desirable to obtain an account of. 



In Derbyshire, some arc of opinion, that the great or 

 limestone Shale which there covers the mineral limestone 

 and basaltic strata, as shown in Plate if of your thirty-first 

 volume"^, (and of Vvhich Mam Tor is composed,) is the 

 same soil or assemblage of strata, which produces alum at 



* And is de^^rlbed by Mr. Whitehurst in his "Inquiry conccMiing the 

 £arth," iid edit. p. 18:5; v^here however he is wroii^ in saying, that thissJialc 

 contains no vegetable imprcsbioiis, since such occur at Shaw-Engine mine 

 there mentioned, and numerous other places. Mr. Mawc, in his '* Minera- 

 Jogy of Derbyshire," p. i!-3, has copied this error, and added a still greater 

 oce, vi2. tbat litis shale " is not stratiiicd." 



Whiiby 



