104 Mr: Smeatoiis Works > &c 



that Mr. Michel had contemplated the identity of the Bri- 

 tish strata over wide spaces *. The "sand" of Newark 

 is seen on its S.E. side near Baldcrton : the wt red clay" of 

 Tux ford is noticed as the produce of "several" other 

 places, and is the gypseous earth, or red marie, which 

 forms so conspicuous a figure across a large portion of the 

 middle and western parts of England. Sherwood Forest 

 < ( pebbles and gravel," over the northern skirt of which, 

 this road passes between Tuxford anil Doncaster, is noticed 

 by Mr. Michel, as being " unequal " in thickness ; and if 

 his observations had been further extended, it would doubt- 

 less have appeared clear to him, that the same ought not 

 to have been taken into his list of strata, anv more than 

 the numerous other patches of alluvium on the surface 

 which he must have passed in this road, and has not 

 noticed ; and particularly so, if 1 am right in conjecturing, 

 that the " very fine white sand," which he mentions, as of 

 " uncertain" thickness, is enveloped, ds an accidental bed 

 in the if red clay," (wluch he had before mentioned) si- 

 milar to what we find at Norman ton on the S. of Derby, 

 and some few other places, for the occurrence is rather rare, 

 J believe, and should therefore wish much to learn, the 

 precise spot or pits to which Mr. Michel here alludes 3 it 

 being a part of the country which I have never visited. 



The " lime" of Brotherton being associated with that of 

 Roche-Abbey, 25 miles S.S.E. of it, shows again, that 

 Mr. Michel had discovered some at least of those geolo- 

 gical principles, which the labours of Mr. William Smith 

 very soon after tended to confirm, and to render them of 

 the utmost practical use and importance. 



Mr. Michel was also aware, that the coal-strata known 

 in Yorkshire, are under-measures to the yellow lime, above 

 mentioned : it must however be observed, that the thick* 

 nesses in the above list are most of them (except perhaps 

 the chalk, the golt, and the Balderlon sand) greatly under* 

 rated ; while many very thick or important strata (of which 

 J intend to give a short account in my Derbyshire Report) 

 are omitted altogether ; as the Bagshot-heath sand, the 



* The lyas or blue lias limestone {laving been much the object of Air. 

 Smeaton's notice, on account of its important quality of making a durable 

 mortar which sets suddenly and very hard, even under sea- water, as he 

 proved in the building- of the Eddystone light-hoti.'e. and others of his 

 great works; and with whose appearance at Aberthaw and Watchet on 

 the opposite shores of the Bristol Channel, and numerous other places, he 

 was so well acquainted, was probably the reason, why so very lacunic a 

 fnention of the^e strata is here made by Mr. Smeaton. 



London 



