XX. Remarks on Farey's Account of the Stratification of the Limestone District of Derbyshire

Philosophical Magazine Series 3

ISSN: 1941-5966 (Print) 1941-5974 (Online) Journal homepage: http://www.tandfonline.com/loi/tphm14

XX. Remarks on Farey's Account of the stratification of the limestone district of derbyshire

W. Hopkins Esq. M.A.

To cite this article: W. Hopkins Esq. M.A. (1834) XX. Remarks on Farey's Account of the stratification of the limestone district of derbyshire , Philosophical Magazine Series 3, 5:26, 121-131, DOI: 10.1080/14786443408648421

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Download by: [University of California Santa Barbara] Date: 16 June 2016, At: 05:44 Mr. Hopkins on the Stratification of Derb~yshire. l°1 and inclosing a firm and longitudinal fibre, or rather a hun- dle of longitudinal fibres united into one cord, like the fila- ments that compose the nerves of animals, and which termi- nate uhimately in soft, bibulous, and club-shaped appendages designated by the appellation of spongiolce. Thus we trace in plants the foundation of three grand orders, depending upon the relative simplicity or complexity of the structure of the caudex~ anti presumed to exhaust the subject. They agree in point of number, but not in point of specific extent, with the arrangements of modern botanists, by which plants are reduced to three grand orders depending upon tlle structure of their seeds--the aeotyledonous, the monocoty- ledonous, and the dicotyledonous. Whether or not these groupings of threes give ally support to Professor Burnett's system of triads, I am not able to say ; but what we learn, unequivocally, from the foregoing investigation is, that the decomposite organs of all plants, to whatever division belonging, are reducible to one or other of the tbllowing con- stituent parts~epidermis, pulp, pith, cortical layers, ligneous layers, fibre~to the analysis of which we now proceed. [To be continued.]

XX. tlemarks on Farey's Account of the Stratification of the Limestone District of Derb#shire. B.y W. HoPKIns, Esq., M. A., Mathematical Lecturer of St.Peter' s College, Ca mbridge, and Fellow of the Geological and Cambridge Philosophical Societies. To the Editors of the Philosophical Magazine and Journal Gentlemen, ~/I R. CONYBEAI~E,, in the latter part of his "Inquiry how far De Beaumont s theory is applicable to the mountain chains of this country," which appeared in the Number of the Ptlilosophical Magazine for June, in speaking of the elevated chain of hills which ranges N. and S. through our northern counties, has expressed considerable doubts as to the accuracy of Farey's account of the geology of the limestone district of Derbyshire, which forms the southern extremity of the chain ;

Downloaded by [University of California Santa Barbara] at 05:44 16 June 2016 and this I observe has led you to refer, in a note, to an abstract, published in the Phil. Mag. fbr January, of an account which I laid before the Cambridge Philosophical Society of an investigation I had recently made of one or two important points in the stratification of that county. During the spring of tile present year I have had an opportunity of extending my investigation over the greater part of the district; and as 7hirdSeries. Vol. 5. No. 26. A~. 1834. R 122 Mr. Hopkins's Remarks on Farey's Account of the I have now so fully satisfied myself of the entire erroneousness of Farey's views of its stratification, I will, with your permis- sion, enter with some detail into a refutation of them. Before I notice those points on which Farey and myself differ so widely, I will mention one in which we are entirely agreed, viz. the regular interstratification of the toadstone with the limestone. The direct evidence of this is aftbrded by those cliffs in which the faef is matter of observation; and the indirect evidence of it must be sought in tile circumstance of our being able to found on this hypothesis a generalization which shall clearly and distinctly embrace all the particular phaznomena which the stratification of the district presents to us. The validity of this latter evidence must, of course, de- pend on that which can be offered in proof of the generalization contended for; but as the examination of this evidence would necessarily involve the complete discussion of the subject, into which it is far from my intention to enter at present, I must content myself with stating my conviction of the fact of this interstratification of the toadstone. Any opinion of its uneonformability with the limestone beds, professing to rely upon observation, can only, I think, be founded on a superficial examination or on an imperfect conception of the subject. I mention my conviction on this point more particularly in consequence of Mr. Conybeare's having suggested, in the paper above alluded to, the possible unconformability of the toadstone, from its having, perhaps, been thrust up among the limestone beds at a period posterior to their formation. In addition, however, to the reasons above mentioned, I conceive that any such idea must be completely negatived by the total absence of all indications of that mechanical violence which must necessarily attend the forcible intrusion of a mass of igneous rock among masses previously deposited. ] will proceed, however, to the exposition of what I con- eeive to be erroneous in Farey's account of the district. He has asserted (and it should be recollected that on this subject he has made many assertions, but has given no proofs,) that there exist in the limestone district of Derbyshire three distinct beds oftoadstone. The limestone occupying the surface, and lying above the frst or highest toadstone--that

Downloaded by [University of California Santa Barbara] at 05:44 16 June 2016 between the first and second toadstones--that between the second and third--and that beneath the third--he has termed respectively the3grst, second, third, and fourth limestones. He states that these beds of toadstone have continuous bassets, that of the third or lowest bed commencing on the north near Casfleton, and ranging by ~Vormhill, Chalmerton, Pike Hall, and tile Grange to Bonsai Dale; and those of the two other Stratification of lhe Limestone District olDer@shire. 12.~ beds ranging nearly parallel to the above basset at short di- stances to the west of it. Let us first consider the two latter bassets, i. e. those of his first and second toadstones. He asserts that they commence on the north at the great fault (which he assumes to run N. and S. between Castleton and Litton,) not far from Wind- mill Houses, the first passing near the village of Litton and the second near Tideswell. Now of the existence of a toadstone basset anywhere to the north of Litton, where these are said to commence, I have not been able to find the most remote indication, either in my own examination of the spot, or in the information I have derived from the most intelligent miners in the neighbourhood; and moreover I can myself" bear positive testimony to the fact that the toadstone near Tideswell, which Farey asserts to belong to the second bed, belongs to the same as that at Litton, which he has assigned to the first, for I have most distinctly traced the toadstone without the smallest interruption from the one place to the other. It is manifestly brought up by the E. and W. fault which has elevated Litton Edge. Again, (if I understand him rightly, which is sometimes no easv matter~ even with the aid of his able commentator*,) Farey says, that the first basset passes nearly at the southern extremity of Crossbrook Dale, and from thence to Fin Copt Hill; and that the second passes fi'om near Tideswell to the southern extremity of Tideswell Dale next the Wye, ranging thence easterly along the sides of Miller's Dale and Monsal Dale till it descends to the level of the river Wye, at the mouth of Crossbrook Dale, and that crossing the river at that point, it returns westerly along the opposite side of the valley to the top of Priestcliff Lowe. Now, in the first place, I deny the possibility of tracing any continuous basset from Litton to the south end of Crossbrook Dale, or from the point where the toadstone appears north of Tideswell to the southern extremity of Tideswell Dale; nor is there the slightest indication in either case of any faults by which the bassets between those places respectively might be hidden. In the second place, the toadstone which appears in the southern part of Crossbrook Dale is not the western ex- Downloaded by [University of California Santa Barbara] at 05:44 16 June 2016 tremity or basset of the bed to which it belongs, for nothing can be more manifest than that the bed passes across the dale, of which for some distance it occupies the whole of the lower part, ascending in exactly a similar manner on both 6 See "Geology of England and Wales," in which Mr. Conybeare has given an exposition of Farey's views far more intelligible than that which Farey himself has given of them. R2 124 Mr. Hopkins's Remarks on Farey's Account of the sides of it to the height (where the upper surface of tile bed is most elevated,) of perhaps 200 feet. It has manifestly been raised to this position by an E. and W. fault which ranges nearly parallel to the valley of the Wye, and is here about 300 or 400 yards from it. The toadstone is here seen, fi'om the bottom of the dale to the height just mentioned, to abut directly against the limestone, which forms, as it were, a solid wall intervening between the toadstone and tile valley of the Wye, thus concealing the raised edge of the toadstone as we proceed westerly along the latter valley till we come to Litton Mill, where the intervening wall becomes too low for that purpose, and accordingly the toadstone then reappears, its upper surfhce being high in the side of the valley, at an elevation exactly corresponding to its position in Crossbrook Dale. From this place it is easily traced to the southern extremity of Tideswell Dale, tile point at which Farey asserted tile toadstone to belong to his second bed ; whereas the facts I have now stated establish the identity of the beds at Tides- well Dale and Crossbrook Dale as clearly as I have esta- blished a similar identity at Litton and Tideswell, as above mentioned. It must be carefully observed here, that the partial toadstone basset I have just described nowhere descends down the side of Monsal Dale or Miller's Dale to the level of the river, as it must necessarily have done had there been a continuous complete basset crossing the river at the mouth of Crossbrook Dale, as Farey describes ; and in like manner on the south of tile river the toadstone ranges at a considerable elevation along the side of the valley, as on the opposite side, but nowhere, as far as I have been able to ascertain, does it descend continuously to the margin of tile river. I conceive this toadstone to have been elevated by a fault exactly similar to that on tile N. side of the river, and exactly parallel to it. According to this view of the subject the valley of the Wye, from Chee Tor to the point near Longstone, must have been originally formed by two parallel faults, ¢00 or 500 yards as under~ the strata being elevated on the N. side of the more northern, and on the S. side of the more southern fault, leaving the intermediate portion in nearly its original position.

Downloaded by [University of California Santa Barbara] at 05:44 16 June 2016 In this intermediate portion the lower part of the present valley has been formed, as I conceive, by erosion. The small inclination of the lines of stratification, and their almost un- broken continuity in the precipitous rocks which rise immediately from the margin of the river between Crossbrook Dale and the upper end of Miller's Dale, attest the slight disturbance which the portion of the limestone beds between the Stratification ¢f the Limestone District ~'Derbgshire. 125 faults has suffered, while on either side of the valley, beyond the faults, we find such undoubted indications of immense dislocations. The formation of this curious and beautiful vale, cutting eompletely through the elevated central ridge of tile district, perpendicularly to its direction, is thus simply accounted for. I have entered with some detail into the explanation of it tbr the purpose of comparing it with the necessary deductions fi'om Farey's view of the subject. He asserts, as I have before mentioned, that the basset of tlle second toadstone crosses the Wye at the mouth of Crossbrook Dale*, in which case the limestone forming the N. side of Monsal Dale, immediately E. of this point, must be the second, and as such Farey has in fact described it. But this limestone is seen in Crossbrook Dale, at tile fimlt ahout S00 or 400 yards from the Wye, to abut directly against his )¢rst toadstone, as above described. Hence we must conclude that the limestone on the south side of this fimlt (instead of that on the north side, as I conceive,) has been elevated, and to an immense height, since the 3frst limestone and frst toadstone are no longer superincumbent upon it. And yet it is in this mass of limestone thus elevated above the adjoining part, according to Farey, that the present deep valley of the Wye has been excavated. How the river first selected such a course is most marvellous. The explanation I have myself given of the formation of this valley will at least appear to have the testimony of hydrostatical principles in its favour. It is almost incredible that so industrious an observer as Farey must have been, should have failed to note any one of the longitudinal |hults in the district bordering the Wye, though they are .so fi'equent and characteristic, tbllowing, almost to mathematical accm'acy the law of para]lehsm. We might suppose fi'om his account of this interesting tract that the stratified masses which it comprises remain, relatively at least to each olher, in the regular and undisturbed order in which they were first deposited, although in its external cha- racters we cannot fail to mark the most obvious indications of violent dislocation. This is not, however, the only instance * A patch of toadstone which is seen at this point at the level of the Downloaded by [University of California Santa Barbara] at 05:44 16 June 2016 Wye has, no doubt, led to this erroneous notion. It must not be con- founded with that before mentioned in the southern part of Crossbrook Dale as belonging, according to Farey, to his first bed. According to my own view of the subject it belongs to the undisturbed portion of limestone and toadstone lying between the two parallel faults described above. Other patches show themselves at several places along the valley, indi- cating that this undisturbed portion of the toadstone lies just beneath the bed of the river. 126 Mr. Hopkins's Remarks on Farey's Account of the in which our geologist has shown such an aptitude to make " the crooked straight~ and the rough places plain." But to proceed with Farey's imaginary bassets. The first basset passes, he says, from Crossbrook Dale to Fin Copt Hilt. I assert in answer, that there is no continuous basset between those points, nor can I find the slightest evidence of any N. and S. t~ault which might conceal it. From Fin Copt Hill it is said to range south-westerly by Flagg and Moneyash to Gratton Dale near Elton ; but on what authority the assertion can possibly rest, I cannot form the most remote idea. I have carefnlly examined several parts of this range, and have made most diligent inquiry respecting the basset among the most intelligent miners at Moneyash, and have never been able to discover the slightest evidence of its existence between Fin Copt Hill and Gratton Dale. In like manner the supposed second basset is said to range from Priestcliff Lowe west of ]¢loneyash, at a short distance from the first ; but where it was conceived to pass over the E. and W. range of hill between Taddington and the basin in which Moneyash is situated, I could never understand either from Farey's work or from Mr. Conybeare's interpretation of it. I have, however, most positive evidence that such is not the line which the basset from Priestcliff Lowe follows, having distinctly traced it from the summit of the Lowe continuously to the E. and immediately to the S. of Taddington to the basset by Chilmerton (considered by Farey as the third basset,) on the one hand, and by the W. of Taddington and Blackwell on the other, to the foot of the Lowe, fi'om the summit of which I had set out; thus absolutely demonstrating that the toadstone found at the foot of the Lowe as we descend to the V~:ye belongs to the same bed as that at its summit, though Farey has asserted the latter to belong to the second, and the former to the third bed. I can offer no explanation of these discrepancies on simple matters of fact between Farey's statements and my own. I can only hold myself responsible for the facts I have stated. From Gratton Dale to Masson Lowe and Matlock High Tor, the bassets I have traced agree more nearly, though still imperfectly as regards the second of them ; but in his account

Downloaded by [University of California Santa Barbara] at 05:44 16 June 2016 of Masson Lowe he has fidlen into exactly the same error as at Priestcliff Lowe, and the exposition of it is effeeted exactly in the same manner. The constitution of this curious hill, however, is too intricate for me now to enter into any descrip- tion of it*. * In my first examination of this intricate hill (which I was obliged to make hastily) I conceived the toadstone at Bonsal to be the #rst. A more Strat~cation of the Limestone District of Derbqshh'e. 127 It would be useless for me to dwell upon other points in which Farey has fallen into errors exactly similar to those I have already pointed out, and from the same eause--a total neglect of the great distinction between a partial and a complete basset. Those of which I have more particularly spoken in the vicinity of the Wye are manifestly of the former, instead of being, as he has represented them, of the latter class ; and hence we have the important conclusion that the basset immediately to the west of them, from Copt Hill to Chilmerton, must belong to tile same and highest bed, instead of being the third, as Farey has represented. I have no doubt too of this basset being only a partial one, terminating shortly after crossing the Ashborne and Buxton road, to the south of Chil- merton. Hence, again, I conclude that the limestone west of this line of basset is thefirst limestone, instead of being the fourth, according to Farey's notions. The toadstone ranging N. and S. between Dove Hole and the Wye, about two miles :E. of Buxton, must, again, be the highest, and the limestone on the surface at this western boundary of the district must have been of contemporaneous formation with that on the eastern side, and passes (in this north-western portion of the boundary which I have more particularly examined) under the shale and grit hills with a gentle dip to the west. Here, then, Farey and myself are completely at issue respecting that portion of what he calls the great limestone fault which ranges, according to his account, along this western boundary of the district, and which, on his supposmon of the fourth limestone occupying the surface, must necessarily be estimated at nearly ~000 feet, not merely in particular places, but along every part of its range. Now though I have not yet examined the whole of this boundary with the attention which I hope shortly to devote to it, I have examined a considerable portion of it north of Buxton, and I can only observe (as I have already observed respecting some other statements of Farey's,) that I am totally at a loss to conceive on what evidence his assertions respecting this fault can rest. That partial faults exist along this boundary as in other parts of the district, I doubt not; but I will venture to assert that no evidence can be found of any such continuous fault as that Downloaded by [University of California Santa Barbara] at 05:44 16 June 2016 contended for; and I confess that it appears to me most marvellous that Farey should have persisted in a theory which involved as a necessary consequence the existence of this enor-- mous fault, in opposition, as I believe, to all the direct evi-

detailed examination has convinced me that if there be two toadstones here, it is the second. 128 Mr. Hopkins's Remarks on Farey's Accozmt of lhe deuce and obvious appearances in that part of the boundary to which I have more particularly referred. That a great N. and S. thult, however, does exist, I have no doubt, though inferior in importance and very different in position to that which Farey imagined. It is this thult which has brought to the surface the toadstone basset already mentioned as extending from Copt Hill to the south of Chilmer- ton, and has produced that central elevated ridge which forms the principal feature in the external character of the district. Of this I believe that I shall be able on some future occasion to offer the most indisputable evidence. Farey's account of the great E. and W. tZault at the southern extremity of the limestone agrees with my own observations as titr as they have yet extended, which is not far west of Hopton ; but whether any N. and S. fault meets this further westward I have not yet ascertained. At the northern extremity of the district, instead of a fault ranging along the whole extreme boundary, an E. and W. one ranges from the north side of Copt Hill, where it meets the great N. and S. f~mlt, to Castleton. That described by Farey as extending from Castleton nearly to Litton, is, I believe, totally unsupported by the slightest evidence. If we would allow to a geologist on the one hand unli- mited power of introducing thults, and on the other an un- controlled command of denuding agents, he must be greatly wanting in ingenuity if he could not devise almost numherless systems of stratification for a district like Derbyshire. These, however, are not powers to be delegated to any geologist merely tbr the purpose of suppm'ting his own theory; but we have seen, notwithstanding, how boldly Farey has asserted the existence of thults without reference to the evidence of facts; and in his denuding hypotheses we find a character of still greater hardihood. It is manifest that according to his theory, hisjfrst, second, and third limestones, together with his ffgrst, seco~zd, and third toadstones, must necessarily have been swept away by some means from an extensive tract of court-, try, and this too without leaving a trace of the mighty operation behind. Probably he considered also that the shale and gritstone had shared the same fate; but for all this, and for

Downloaded by [University of California Santa Barbara] at 05:44 16 June 2016 much more that still continues to puzzle geologists, he conceived he had found an adequate cause in the extraordinary hypothesis of a large satellite revolving at so small a distance from the earth as must have rendered him a most trouble- some neighbour; for he accuses him of being, by his powerfifl attraction, the source of all those disturbances of which such manifest indications still exist on the fi~ce of the earth, and. Sh'atification of the Limestone District of Derb~sMre. 120 among other tllings of ]laving carried off the Derbyshire limestones. He appears, according to the same philosopher, to have terminated his existence by precipating himself to the earth, thus, after having long disturbed the peace of his pri- mary, violating in his last act the universal laws of motion*. Now it is very true that theoretical absurdities are not necessarily associated with imperfect statements of facts, or in all cases with incorrect generalizations of them ; and moreover I do not think that geological blunders of five-and-twenty years ago demand any great severity of criticism; but absurdities such as those to which I have just alluded are quite intoler- able, even though their date were very long prior to. the.com- mencement of the present century, and assuredly respire us with little reverence for the philosophical opinions of the per- son who fell into them, or for any particular views with which he associated them. From the representation I have given of Farey's opinions of the stratification of this limestone part of Derbyshire, it might almost appear that they are scarcely worth the trouble I have taken to refute them. It musts however, be recollected that such refutation can only rest on a much more detailed examination of the district than geologists in general can have an opportunity of giving it, and that, in fact, these opinions have, to a certain degree, stood the test of such cursory in- vestigations as some of our most eminent geologists have made of it; that Farey has been frequently appealed to on this subject during the last twenty years; and moreover that Mr. Conybeare, in the " Geology of England and Wales," Ca work distinguished for its general accuracy in the geological details of this country,) whatever doubts he may have entertained as to Farey's accuracy on particular points, has nevertheless considered him sufficient authority for a detailed account of the district in question. For these reasons I shall not, perhaps, appear to have given an undue importance to the refutation of the opinions against which I have been contending. I shall conclude with a short abstract of the views I have myself formed on the stratification of this limestone district, premising, however, that my examination of some of its details is not yet complete.

Downloaded by [University of California Santa Barbara] at 05:44 16 June 2016 1. The toadstone is interstratified with the limestone. It cannot. I conceive, have been forcibly protruded among the limestone beds, but must have been diffused over the surface of the country at the time of its emission (assuming it to be of igneous origin). See Phil. Mag. for 1807, vol. xxviii.; and for 1808, vol. xxxi. TMrd ,~eries. Vol. ~;. No. ~6. Aug. 18,~4. S 130 Mr. Hopkins's Remarks on Farey's Account of the 2. The period of the disturbance or disturbances which produced the present dislocations of the superficial strata must have been long posterior to that of the production of the toadstone, since the beds of toadstone have suffered exactly the same dislocation as the limestone. :3. One and the same bed of toadstone pervades the whole district N. of Middleton Moor (by Youlgrave), the limestone above it, occupying the surface, being of contemporaneous formation in every part of it*. There is no valid evidence of the existence of a second bed beneath. ¢. In the portion of the district S. of Middleton Moor, I have not yet obtained evidence perfectly conclusive as to there being one or two beds of toadstone. If there be two, it would seem almost necessary that the lower one should be contemporaneous with the one above described, the upper one being probably of very limited extent. 5. The principal transverse or N. and S. fault is that already described as extending from Copt Hill to the S. of Chelmerton, the strata on the E. of it being elevated. Many other partial ones, however, exist along the eastern side of the district from Bakewell to Cromford and Wirksworth, and along the north western boundary. In the former, where the dip is easterly, the E. side is almost without exception the most elevated ; and in the latter, where the dip is westerly, the W. side is the elevated one. Of the south-western side I cannot yet speak in detail. These faults are not distinguished, like the longitudinal E. and W. faults, by strict rectilinearity and persistency in their direction. They are rather formed of a number of partial faults, the directions of which are nearly parallel, and of which the extremities do not exactly meet. 6. The great E. and W. faults are numerous, and their common direction coincides with the mean dip of the strata. They are remarkable for their rectilinearity and parallelism to each other. 7. Each of these longitudinal faults is accompanied by one of those fissures which are become so well known to us as mineral veins, this fissure being generally though not universally on the elevated side of the fault, to which they are near and

Downloaded by [University of California Santa Barbara] at 05:44 16 June 2016 parallel. Conversely, each of the large rake veins, about fifteen or six-

* It was only on renewing my investigation in the spring that I came to this conclusion. Before I had examined Farey's third basset, I took for granted its continuity, and therefore regarded it as the complete basset of the first toadstone, and consequently the limestone beyond it to the W. as the second. Stratifcation of the Limestone District of Derlwshire. 131 teen in number, which form together the great system of parallel veins characteristic of the distriet~ is accompanied through at least a eonsiderable Tart of its course b9 a fault. 8. A small system of parallel veins is sometimes found independent of the general system, but having this character in common with it,--that the common direction of the system coincides with the Tarticular dip of the strata in which it is formed. 9. Though fissures, I have no doubt, accompany the transverse as well as the longitudinal faults, they much more rarely become good mineral veins, and I know of none that are eon- tinuous as such for any considerable distance. Instances, however, are not wanting of productive veins of this class. 10. Many small veins exist in the direction of which I have detected no general law. These cross veins, however, are for the most part incomparably smaller as d~ssures than the great E. and W. veins above mentioned. 11. All the great springs of this district are found in con- junction with the great faults. I do not at this moment recol- lect an exception to this rule ; for, I believe, in every instance where I observed a powerful spring I had independent evidence of the existence of a great fault. The water is also generally observed to proceed from the upper surface of the toadstone, as might be expected from the circumstance of its being, unable to penetrate it. The circumstances attending the posmons of these springs, when carefully examined, offer a curious corro- boration of the fact of the regular interstratification of the toadstone beds. 1~. I have observed no indications of a central point from which the toadstone might be conceived to have flowed as from a crater; nor have I yet observed any very.distinct appear- anees of an altered state of the limestone at its junction with the toadstone. My attention, however, has not yet been so particularly directed to this latter point. Should any of your readers have detected instances of this kind, I should feel obliged for any information respecting them. We may remark that this view of the subject does not involve, as an essential part of it, the supposition of any great and extensive denudation, but merely that local and partial

Downloaded by [University of California Santa Barbara] at 05:44 16 June 2016 operation of denuding causes which must be recognised in almost every district. I remain, Gentlemen, yours, &c. W. HOPKINS. St. Peter's College, Cambridge, July 18, 183,t.