272 Mr. Farey on the Pontefract Sandstone Rock. [April, 



Northumberland; besides which, I have there mentioned the 

 probability, that this same rock underlies the magnesias lime- 

 stone in Salop and in Cumberland counties ; and, perhaps, it 

 exists also under that of Abberley, in Worcestershire ; but these 

 last very contorted rocks, and others such on the north of Dudley, 

 at and southward of Breedon, in Leicestershire, and at Wild 

 Park, in Derbyshire,* require, I am of opinion, a great deal 

 more of careful investigation than has yet been bestowed upon 

 them, before anything satisfactory can be concluded concerning 



them. 



Mr. Conybeare's observation in p. 137 is perfectly just, as to 

 the highest seams of coal, and the strata of the regular series 

 accompanying and overlying them, not being, perhaps, displayed 

 on the surface, in any part of the British Islands ; and it is 

 equally true, that the parts or places are, in very few of our 

 extensive coal-fields, yet ascertained, where the series is the most 

 complete, or where the highest of their conformable carboniferous 

 strata are visible. 



In the year 1816, the late Duke of Buccleugh employed me 

 professionally, among other matters, to ascertain this point, as 

 to the Midlothian coal-field ; the full details of which investiga- 

 tion remain in the hands of his Grace's intelligent mineral agent, 

 Mr. James M'Laren,t of Dalkeith ; showing, that the town of 

 Fisher-row, near to Musselburgh, stands on the highest stratum, 

 of above 5000 feet thick of coal-measures, including 84 seams of 

 coal ! J as has been inferred, from a systematic comparison of 

 2374 spots or places of observation, in the pits, boreings, levels, 

 and quarries, or visible bassets of the strata of that district ; 

 whence, the extremes and the average thicknesses of the greater 

 part of 337 alternating strata are ascertained, amounting toge- 

 ther to the total thickness above named. 



I have frequently pointed out to my mineral friends resident 



* If the Breedon and Wild Park limestones (Derb. Rep. i. 158) belong to the lotcer 

 magnesian rock, may not the gypsum hummocks of Chellaston, Aston, and Ballington 

 (Rep. i. 149, &c.) intermediately situated, in a strata trough, belong to the gypseous 

 red marl, resting immediately upon that rock, answering to the gypsum near Fair- 

 burn, in Yorkshire (Phil. Mag. vol. xxxix. p. 102), which, in Bolium Farm Well, and 

 many others thereabouts, has proved pure and crystallized, several yards thick? — and 

 may not the absence in Derbyshire and Yorkshire, of salt springs and rock salt, which 

 last in Cheshire, underlies gypsum, arise from the latter belonging (as locally imbedded 

 masses) to the upper or great red marl, overlying the very irregularly coarse gritstone, 

 which, on Sherwood Forest and in other situations, I mistakenly represented as " gravel 

 rock," in most of my early writings ? The Birchwood Park, and the Nev.'bold Astbury 

 limestones, occurring in small denudations, from whence no basset edges could be traced, 

 were, in 1811, hesitatingly referred by me to the yellow limestone series (Derb. Rep. i. 

 409 and 401), when, but for a complete error, as to " an upper series of coals above 

 the yellow limestone " (see my Index), of which I had often been told, I should have 

 associated them, either with the shale limestone, or with the first limestone rock. 



+ And other copies in my possession. I am happy in this opportunity to mention, 

 that Mr. M'Laren is now carrying into effect the instructions which he received from 

 me, by making similar surveys of the districts hi which his Grace's other mineral pro- 

 perties are situated. 



J See Mr. Westgarth Forster's Treatise on a Section of Strata, p. 89, 2d. Edit. 



