674 



DERBYSHIRE. 



Derby- 

 shire. 



Mineralo. 



Annesley, at Kirkby, Hacknal, and to the west of 

 Teversal ; shortly after which it leaves Nottinghamshire, 

 and appears in Derbyshire at Hardwich. From thence 

 it passes by Alt Hucknal, Bolsover, to the west of 

 Clown and Barlborough, and forward into Yorkshire. 

 The line which it describes is very irregular, and there 

 are some circumstances attending its geological history 

 not yet satisfactorily explained. Our knowledge of the 

 mill- stone grit is much more complete, the basset-edge 

 of this stratum being the most distinctly and accurately 

 denned of any in the county. Its first occurrence, to 

 the southward, is at Little Eaton, about three miles to 

 the north of Derby. It may from thence be traced to 

 the west of Holbrook, at Belper, west of Heage ; east of 

 Crich, at Tansley ; east of Darley in the Dale ; east of 

 Becley, on the ridge at the back of Chatsworth house ; 

 east of Curbar, at Fox house, and to the east of Hathers- 

 age ; shortly beyond which point it crosses into York- 

 shire. On the eastern side of all these places, therefore, 

 bounded by the yellow lime as before particularized, 

 lies the whole of the Derbyshire coal field ; and to the 

 west, the range of limestone and amygdaloid rocks, 

 which remain yet to be described. The facility with 

 which the geology of the county may be studied, by 

 having these points fixed on the memory, must be im- 

 mediately obvious ; and the present sketch, in particu- 

 lar, will derive a very material assistance from it, in the 

 sort of connecting link which it will supply to the 

 scattered remarks here offered in explanation of the 

 principal mineral features of this interesting neighbour- 

 hood. 



In leaving the mill-stone grit, we next come to a con- 

 siderable, but irregular formation, called, by Mr Farey, 

 the lime-stone shale. Its thickness varies in different 

 parts of the county from a hundred and forty to a 

 hundred and seventy yards ; and it is occasionally ac- 

 companied with beds of sandstone, sandstone slate, and 

 black or dark blue limestone. Ironstone is also found 

 in it, in some places, in considerable quantity ; but the 

 distance at which this is situated from coal, prevents it 

 from being converted to any profitable use. If is in one of 

 tile beds attendant on this formation, that the tripoli, or 

 rotten-stone of Derbyshire, is contained. This mineral 

 occurs only with the black limestone, forming a coat on 

 its upper surface of different thicknesses, and appears 

 to be the result of a decomposition which the latter sub- 

 stance has undergone. However improbable such a 

 change may be considered, specimens are in the pos- 

 session of the writer of these remarks, obtained from 

 ihe vicinity of Bakewell, in which the transition from 

 one to the other is so distinctly shewn, that it seems 

 impossible otherwise to account for the phenomena. 

 Analysis, it is true, presents at first sight some formi- 

 dable objections ; but they constitute by much the lesser 

 difficulty. Indeed, the change may be supposed to be 

 wholly effected by the solution of the carbonate of 

 lime in the water which filters through the rock, and 

 which thus leaves the silex occupying its original situa- 

 tion. 



Under the shale just described, lies the first great 

 limestone rock of Derbyshire. This, in the neighbour- 

 hood of Crich, is quarried to an immense extent, for the 

 various uses of agriculture and the arts. The lime 

 yielded by it is of a most beautiful whiteness, and fur- 

 nishes the bleachers of most of the neighbouring coun- 

 ties with the base of their bleaching liquor, for which 

 it is peculiarly applicable, in consequence of the total 

 absence of .all metallic matter, and especially of iron. 

 Beneath this, is a stratum of amygdaloid, or toadslonc, 



Derby, 

 shire. 



as it is here termed, of which there are three distinct 

 beds in the county alternating with limestone. They 

 all cross the celebrated vale of Matlock, and either ~ ' v-""^ 

 emerge, or basset, in the vale itself, or on the declivity Miner^Ie- 

 of the ridge which bounds its western side. This was gy, 

 first described by the ingenious Mr Whitehurst, who 

 has given a section, in the second plate to his work, 

 shewing the position of the whole range, in the neigh- 

 bourhood of Matlock, from the mill-stone grit down- 

 wards. The lowest stratum he has there marked, and 

 indeed the lowest which is yet known in Derbyshire, 

 is a fourth bed of limestone, lying under the third- 

 toadstone. The total thickness of these is about six I 

 hundred and fifty yards; the particulars of which ares> 

 follows : 



Mill-stone grit 120 yards. 



Great shale 150 . . . 



First limestone 50 . . . 



. . . Toadstone . 20 . . 



Second limestone 50 . . . 



.... Toadstone 30 . . . 



Third limestone 70 . . . 



.... Toadstone SO . . . 



Fourth limestone 130 . . .. 



650 



There is one error in Mr Whitehurst's delineation of the . 

 strata at this point, arising from his having supposed, 

 a dislocation or fault to exist in that part of the vale . 

 which formed the bed of the river Derwent. This Mr 

 Farey has succeeded in proving to be a mistake,, 

 the angle which the different rocks make with the ho- 

 rizon being the same on each side cf the valley. 



The whole of the lead smelted in the county, is fur- . 

 nished by veins, which' traverse the beds of limestone 

 here mentioned. There is not an instance, it is belie- . 

 ved, where the amygdaloid has ever yielded a single . 

 vein. Hard specimens have been found, in late 

 years, containing small quantities of galena disseminated 

 through them; but these are of very rare occurrence, and , 

 appear to be of a newer formation than- the strata now 

 under inquiry. One of the most curious and instruc- 

 tive phenomena connected with the history of the pre- 

 sent series of rocks, is the occurrence of the veins, winch 

 are found at right angles to the dip of the limestone. 

 These exist in each of the four beds, in the same rela- 

 tive situation ; so that if the toadstone were removed, 

 they would form one continued vein. The amygda- 

 loid, however, has no corresponding appearance. Im- 

 mediately at its surface the vein terminates ; and miners . 

 are now aware that they must pierce the whole sub- . 

 stance of the rock, and reach the subjacent limestone, 

 before the object of their search will re-appear. . 



The lead ore yielded most abundantly in Derbyshire 

 is the galena, or lead glance. White and green lead . 

 ore are also got in considerable quantity, and are now ■ 

 worked in the smelting furnaces. This, however, has 

 only been done within these few years. For many 

 centuries they were thrown aside with the sulphate of 

 barytes, (a cawlc, as the miners term it,) under the^ 

 belief that they were abke destitute of metallic matter ; 

 and many thousand tons are accumulated near the old . 

 workings, which, since the composition of these mine- . 

 rals was discovered, have all been re-explored, and con- 

 tinue, in many places, still to yield a profitable em- 

 ployment. A new species of lead ore was, some years 

 ago, described by Mr Chenevix, as having been found: 



