[ 26 ] 



II. ^n Account of the Great Derlysliire Denudation. By 

 Mr. J. Fakey Senior. In a Letter to the Right Hon. 

 Sir Joseph Banks, Bart. K.B. P.R.S* 



Sir, X HAD but recently entered on the survey of Derby- 

 shire and its environs, which under your kind patronage I 

 WAS induced to commence in the autumn of I8O7, and had 

 only cursorily examined the strata, in my way from Cham- 

 wood Forest and Brecdon in Leicestershire, in order to meet 

 you at Overton Hall, before I perceived clearly, that those 

 principles which contemplate the terrestrial strata as ter- 

 minating or ending in one direction (simple and important 

 as they are), which 1 had learned under Mr.Williain Smith 

 in 1801, and which he has so successfully applied in the 

 filling up of his ma()S of the strata in the south-east and 

 east, and some of the middle parts of England, would fail 

 me, in their application to the strata of Derbyshire, without 

 takino^ into consideration along with them,' not only the 

 denudation, or local stripping off, of patches of strata, eome 

 of immense extent and thickness, and even more consider- 

 able than those which I had discovered to be missing f 

 from off the Wealds of Kent, Sussex, and Surry, and had ex- 

 plained to you, by a rough section across this great southern 

 denudation in I8O6, and such as the valley of Ashover then 

 appeared to present, a more perfect instance of, around us: 

 but that previouslv to such denudations of the Derbyshire 

 strata, immense dislocations or vertical derangements of 

 very large piles of strata, separated by the fissures, called 

 faults by the miners, needed also to be taken into account, 

 fur explaining the appearances of the strata and surface of 

 the district, which I was then about to explore : faults, ex- 

 ccedins immensely in their extent and quantity of lift otl 

 one side (or sink on the other) any which had occurred to 

 Mr. Smith, in the tracing of the south-eastern strata of 

 England, where no faults had been discovered, so consider- 

 able as to cut off entirely the connection of the strata, or in 

 other vvords, to bring strata in contact on the surface, whose 

 places in the series were too distant to be known, and '•eadily 

 traced in their order, in the neighbourhood. And in con- 

 sequence, I judged it necessary, on my return to town, when 

 the winter arrived, to set about the consideration of strati- 



• From the Philosophical Transactions for ISIl, part ii. 



\ And such as Dr. William Richardson had found to have been removed 

 in several places, from nfF the basaltic area in the counties of Derry and 

 Antrim in Irela.-.d, and has named rU-ruplicns, in his very admirable paper 

 on this district, ia the Philosopliical Transactions for 1^08. 



fied 



