DERBYSHIRE. 



673 



Derby- 

 shire. 



no part of Derbyshire can be properly considered as 

 belonging to it. In speaking generally of the rock for- 

 mations of the county, their dip may be said to be 

 south-east. The highest strata of Derbyshire will from 

 hence be expected on its southern boundary. 



The uppermost regularly stratified mass in Derby- 

 shire, and that consequently which occupies its south- 

 ern boundary, is a reddish marl. This covers a large 

 extent of surface, and possesses an additional claim to 

 attention, from the gypsum, which, in particular places, 

 is abundantly imbedded in it. At Chellaston, near 

 Derby, this mineral has been got in great quantities- 

 from a very distant date ; and in two other situatians 

 in the same neighbourhood, it has also been worked, 

 but to a less considerable extent. In all these places, 

 it occurs in a tract of land considerably, and abruptly, 

 elevated above the surrounding country. This bed 

 contains fossils or petrifactions, such as gryphites, ano- 

 mice, belemnites, mylili, and pentacrinites. With these 

 are mixed fragments, and detached masses of rock, 

 brought from a distant part of the country, such as 

 limestone, chalk, coal, fuller's earth, and' a variety of 

 others. In one instance, a block of limestone, evidently 

 belonging to the uppermost of the four limestone strata 

 of Derbyshire, the nearest occurrence of which is fifteen 

 or sixteen miles from this point, was seen lying here, 

 which was equal to at least five-and-twenty hundred 

 weight (112 lbs. x 25. ) Nearly the whole of the gyp- 

 sum furnished from these situations is of the sort de- 

 nominated by mineralogists compact gypsum. Speci- 

 mens of the foliated and Jibrous varieties occasionally 

 occur, forming a thin bed of four or five inches thick, 

 which lies a short distance above the former; but these, 

 from a strange and unaccountable prejudice, are re- 

 jected by plasterers and others who use this mineral, 

 under the impression that they are destitute of the pro- 

 perties possessed by the compact gypsum. The com- 

 mon name for this substance is plaster and alabaster, 

 and its price is from 7s. to 9s. per ton, (120lbs. x 20) 

 according to quality. 



The next stratum which presents itself in Derby- 

 shire, under the red marl, is the yellow, or magnesian 

 limestone. This, however, instead of appearing in the 

 southern districts, as might have been expected, does 

 not occur till we reach Hardwich and Pleasley; but 

 attends the eastern boundary of the county for about 

 fifteen miles previously, just within the edge of Not- 

 tinghamshire. 



Immediately under the yellow lime, lie the extensive 

 and important range of rocks constituting the coal series 

 of Derbyshire, Yorkshire, and, it may be perhaps 

 added, of Lancashire. These principally consist of al- 

 ternations of sandstone, clay, bituminous shale, slate- 

 clay, and coal, in different states of induration. The 

 number of sandstone rocks in Derbyshire is about 

 twenty, and of coal beds about thirty, the latter of 

 which vary in thickness from six inches to eleven feet. 

 The total thickness of the coal measures in this county 

 is, as nearly as can be estimated, about twenty-five 

 yards. Their general dip is towards the south-east ; 

 but the dislocations and other accidents to which the 

 coal field has been exposed, have produced many ex- 

 ceptions. Notwithstanding this, however, the order of 

 succession in the different rocks may be so confidently 

 relied upon, that the difficulty, in a practical point of 

 view, becomes very much reduced ; for wherever any 

 particular stratum can be identified, those which ac- 

 company it may be immediately inferred. The value 



VOL. VII. part n. 



Derby- 

 shire. 



of this knowledge, both in the present, and in the 

 neighbouring counties, has, in many instances, been 

 most abundantly proved to its possessors, by the ad- ~~ v 

 vantages they have been able to make of it in specu- Mineralo 

 lations respecting coal property. This was very striking- SY' 

 ly shewn in Staffordshire, (the formations of which are 

 widely different from those now under examination,) 

 where an entirely new series of coals have, within these 

 few years, been discovered, and brought into work, 

 solely by the light which this species of information 

 has supplied. The benefits have not been confined to 

 the individual alone who first disclosed those hidden 

 treasures, but has extended to the whole population of 

 the neighbourhood, and to the kingdom generally. 



The whole of the ironstone by which the iron works 

 of Derbyshire are supplied, is furnished from the beds 

 of slate and clay called bind, which alternate with the 

 coal. It lies imbedded in these in the form of nodules, 

 and for the most part, consists of the reniform iron- 

 stone, and common clay iron-stone, described by Profes- 

 sor Jameson. The latter occurs under various extrane- 

 ous forms, such as of muscles, reeds, and ferns. The 

 number of blast furnaces in Derbyshire now (1814),. 

 all of which, it is believed, are worked with coke, is 

 about twenty. Several of these are out of blast from 

 the depressed state of the iron trade, and will, in all 

 probability, continue so, until our intercourse with 

 America is revived, not from its direct, but from its in- 

 direct influence. The processes employed in the ma- 

 nufacture of iron in this district, do not appear to dif- 

 fer, in any essential point, from those practised with the 

 same materials in other situations. The mechanical 

 aid is in most, if not in every instance, furnished by. 

 steam, and the pressure with which the air is thrown 

 into the furnace, on the average, perhaps may be con- 

 sidered as equal to about two pounds and a half on the 

 square inch. To those interested in the manufacture of 

 iron, it may be useful to add, that most of the furnaces 

 in this county are worked with a bright tugen, aris- 

 ing from their being principally employed in produ- 

 cing soft metal. In returning from this digression, it- 

 remains only, before quitting the present subjects of in- 

 quiry, to say a few words concerning some other gene- 

 ral appearances of the Derbyshire coal-field, it being 

 impossible, within the space allotted for these remarks, 

 to convey such a particular account of it as would be 

 requisite for a complete geological acquaintance with its 

 subordinate members. The total depth of the strata 

 composing it, from the under surface of the magnesian 

 limestone to the lowest sandstone, inclusive, is from 

 seven hundred and fifty to eight hundred yards. The 

 last rock alone, which is a coarse quartzose compound, 

 measures a hundred and twenty yards, and is the one 

 called, by MrWhitehurst, {Inquiry concerning the Earth), 

 and by Mr Farey, the mill-stone grit. It is much in 

 use in the county for the making of mill-stones, (whence 

 its name,) and also for the hearths of blast furnaces. 

 Wherever it occurs, therefore, the coal may be consider- 

 ed as having all disappeared, and an intimate acquaint- 

 ance, both with this, and with the yellow lime-stone, 

 becomes, in consequence, a valuable sort of knowledge, 

 since these two strata include the whole of the treasures 

 of ironstone and coal furnished by the district. The 

 first appearance of the limestone here mentioned, with- 

 in the limits of the present inquiry, is between Walla- 

 ton and Bilborough in Nottinghamshire. Proceeding 

 norths ard, its basset-edge afterwards occurs to the west 

 of Stretley and of Nuttal, at Greasley, to the west of 

 4q 



