Philosophical Magazine Series 1

ISSN: 1941-5796 (Print) 1941-580X (Online) Journal homepage: http://www.tandfonline.com/loi/tphm12

VII. On the stratification of England; the intended Thames archways, &c.

John Farey Esq.

To cite this article: John Farey Esq. (1806) VII. On the stratification of England; the intended Thames archways, &c. , Philosophical Magazine Series 1, 25:97, 44-49, DOI: 10.1080/14786440608563406

To link to this article: http://dx.doi.org/10.1080/14786440608563406

Published online: 18 May 2009.

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VII, On the Stratification of England; the intended Thames .4rchu,ays, ~c. By Jon~ Fxtt~Y~ Esq. To Mr. Tilloch. SIR, A I~Eo.~RD for the interests of science has long_oeeasloned me and others to regret, that a truly valuable and extensive body of facts on the stratification of England, Wales, and part of Scotland, the labour of 14 years or more, spent in the most intense application to the subject by a gentleman of Bath (Mr. tVil~iara Smith, engineer, now resident in Buck- ingham street, Strand, London), should remain useless on his hands, for waaet of sufficient public encouragement :to induce him to publish his Maps, Seetionsb Drawings and Descriptions of extraneous Fossils and other particulars, most of which are new, and appear quite essential to the placing of the Geology of our own country, and perhaps of the whole terraqueous Globe, among the accurate sciences. Mr. Smith has traced the out-crop of a stratum of Chalk, that is~ it~ appearance on the surface of the land, or rather in th~ -hangings of certain ranges of o~r Eaxglizh hills for near 700 miles in length! The exact uniformity of appearances of this out-crop in innumerable instances, corroborated by the sinking of wells and other works of art upon or in this stratum, in the greatest variety of situations, has fully warranted the eonclusions~; that this immense mass of mat- ter consists of a vast number of layers of chalk°` and siliceous substances, the latter in almost every variety of form, from that of solid black flint, to a white and fine sand or grit-stone; the whole of which layers (except of flints) have in general so much the appearance of chalk for 409 feet or more in thicknes%" as hitherto to have passed under that denomina- Downloaded by [University of California Santa Barbara] at 16:05 20 June 2016 tion, and which it may perhaps be well still to retain as a general name for this assemblage of strata. In like manner the out-crop has been traced' of an immense succession of argillaceous, siliceous and ferrugiuous matters lying up6n the above chalk stratum, wherever the same is found to have any regular strata upon it in England i which strata Mr. Smith On the Strat~ficatlon of England, ~Yc. 4s Mr. Smith may be well entitled to denominate the London daft, from the circumstance of the metropolis and its en- virons (where alluvial gravel, sand~ &e. or peat do not in- tervene) standing immediately upon a very considerable and remarkable red clay layer or stratum, forming part of this uppermost assemblage of the British strata. It is not my present intention, nor would it be proper towards my friend Mr. Smith~ to attempb were I able, completely to develop the theory which the immense body of facts in his posses- sion (alld numerous others in my own~ collected before and since 18Ol, when I t]rst became acquainted with Mr. Smith) go to establish: suffice it to say, that the most eon!plete and certain rules have been, or may in every instance be~ de- duced for aseei'taining the relative position (which pro- bably never varies) of each distinct stratum, however thin, with regard to those above and below it in the series (or natural order of the strata, as Mr. Smith called it in his first printed prospectus) ; rules equally general have, or will on sufficient inquiry, be found, for identifying each partio eular stratum, either by the knowledge of its relative po- sition with other known strata in its vicinity, by the pe- culiar organized remains imbedded in ib and not to be found in the adjoining strata, or by the peculiar nature and properties of the matter composing the stratum itself. By a reference to the rules above alluded to, and the considera- tion of other well-established and unvarying particulars, the alluvial matters can be certainly distinguished ~ by which term are here meant, the fragments of the regular strata~ more or less mixed with each other, or-with extraneous matters, and rounded or worn, lying upon the regular strata (for such are rarely or probably never seen in or under the strata) and are thee found deposited, apparently by the action

Downloaded by [University of California Santa Barbara] at 16:05 20 June 2016 o~ violent currents of water (assisted perhaps by the general principle of gravity, in circumstances which have never yet been contemplated among the physical inquiries of mathe- maticians), the manner of these alluvial deposits being per- f~tly different from~ and apparently regulated by laws quite dissimilar from those which obtained when the de- position of the strata took place. A further remark it is essenti~l 46 On the Stratification of England, e~sential to make, and which relates to the truly enormoug and violent breaking up, which the strata have almost uni- versally undergone (probably owing to their gravity under the circumstances above alluded to)~ the effects of which are well known to miners, and to all others who extensively open the soil in directions nearly horizontal, by the name of faults, troubles, dykes, fissures, &c. &c. I was led, Sir, ori the present occasion, to make the above remarks, from having lately, for the sake of information~ visited the works going on near the Horse Ferry, !n Rother- hithe~ (about 2÷ miles below London Bridge) for making an archway under the Thames river, intended for the passage of horses and carriages, in case, on executing the perpen- dicular shaft, now in hand, and a drift or drain therefrom under the river, it shall be judged practicable at this place to tunnel and form an archway under its bed, upon a suf- ficiently high level for carriages to descend down into it~ and ascend again at the opposite end, by sloping roads of easy and convenient lengths. Should the result of the present experimen~ appear against a carriage archway at the Horse Ferry, it is still hoped by Mr. Robert l/'azie, the projector an d superintendant of the works, that a Smaller arch may be-here formed under the bed of the river, at a depth not inconvenient to foot-passengers, who are to descend to the same by a circular or well staircase at one end, and ascend by ttte like means from the other end. Mr. Vazie, with a liberality highly creditable to himself and to those who employ him, showed me the plans and sections of the proposed works," and of the borings which he made, together with specimens of some of the matters obtained thereby, at different depths on each side of the river at this place. These were denominated as follows : viz. On the North side. Downloaded by [University of California Santa Barbara] at 16:05 20 June 2016 On the South Side. Feet. 6 From high water level to the surface of the ground. 9 Brown clay. Feet. (Belowhlgh-water mark.) 21 Gravel. 12 Gravel. 19_Strong blue clay. 33_ Stroflg blue clay. 55 45 Chalk. the intended Thames _/h'chways, ~c. 47 On the South Side. On the North Side. Feet. Feet. 55 (Brought over) 45 8 Chalk. 7 Light blue and brown stratum resembling sand. 4 Concreted rock. a Sand. 16 Green dry sand. 4 Variegated blue and brown hard clay. 3 In firm gray wet sand. In wct sand.

86 61 The fiver in this place being 772~ feet wide at high water of spr!ng tides, and then S8 feet 10 inches deep in the middle. I have already, sir, declared myself convinced* of the practicability and usefulness of forming archways under Rivers in almost any situations, and it is principally from a desire to contribute my mite towards promoting this highly useful mode of communication that I have troubled you herewith. The shaft or well at present sinking in Rotherhithe, is, as Mr. Vazie informs me, intended, in the 'first instance, for ascertaining, more fully thanboring can do, the nature and condition (as to springs of water) of the strata or alluvial matters under the south bank of the river; and, during the progress thereof, I beg to call the attention of Mr. Vazie and those concerned, to the circumstance of preserving frequent and ample sped- mens of all the matters sunk through, with reference to the exact depth and thickness of each, and the state of the wa- ter, as ascertained by the strokes of the engine-pump from time to time. I beg further to mention, that, as far as my recollection of Mr. Smith's map now serves me, the top of the great Chalk stratum above mentioned, is to be found on

Downloaded by [University of California Santa Barbara] at 16:05 20 June 2016 the surface at no great distance south of the head of the Croydon canal, about ten miles from London : also, that at the foot of Ridge Hill, 16-~ miles from London, on the road to St. Albans, the same stratum appears again; the surface between these two places (passing through the metropolis) being occupied by the whole or the lowermost of the strata * Dr. l~ees's Cyclopaedia, article Canal, sect. Thames River, &c. comprehended 4S On the Stratifieatlon of England, comprehended in the London clay. I have mentioned the above two points, one sufficiently near in direction to the south and the other to the north of the proposed archway, as a guide to the inquiries which I am going to suggest ; but ka all probability some other line, nearly north and south, (par- ticularly on the north side of London,) may be found more eligible, in which I beg "to recommend that it should be mi- nutely inquired by means of the many different Wells which have been sunk, by the recent cuttings of the Croydon Canal and other excavations, as vJell as bythe croppingof the several strata which compose the London clay, both at its southern and northern edge, what are the nature, the actual succession, and thicknesses of the several strata, which may be expected to exist under the vale of the Thames at London, after the alluvial matters therein have all been sunk through, and the strata reached. During the last autumn, I, and.others, had an opportunity of making part of the above inquiries on the line of the Croydon canal, and am enabled to state, that~ pro- ceeding northward from Sydenham town to near Bro~kley- Green, the canal will be found all the way cut in a thick stratum of very. strong red day, whose eharacteristle mark seems to he, two or more remarkable layers of ludus Helmontii, or clay-balls ; which clay-ball stratum forms the surface in most parts near London that I have examined, except where either gravel or alluvial matters exist thereon, or where an excavation or abrasion of the surface has taken place, and exposed strata which are to be found lower in the series, In going southward from Broekley-Green, and descending from the surface of the stratum above described (for the course of one mile and a half', or rather less,) to the foot of Plough-garliek Hill, near the London and Greenwich road, a great number of the upper strata of the London clay may

Downloaded by [University of California Santa Barbara] at 16:05 20 June 2016 be traced in succession, and ample specimens of each may be obtained from the new banks of the canal. It may be necessary here to mention, that the exposure of the edges of the strata, in the cutting of the canal between Brockley and the Greenwich road, and in numerous other places on the southern side of the Thames vale, seems owing to an enor- mous dislocation or lift of the strata in those places, and to an amazing abrasion or wearing away of the edges of the uppermost the intended Thames ~lrchway#; &c. 49 tlppermost of those strata. The dislocations above men- tioned present to naturalists a most favourable opportunity, by ascending from the several chalk-pits in Greenwich, Chalton, WoolwieIi, &e. towards the top of Shooter's Hill, of distinctly tracing, as I apprehend, every stratum in the Londori diay. I have ventured to suggest these, as among the fiumerous methods which might be taken to ascertain, Whether regular strata have already or may hereafter be reached by the borings or sinkings for the Rotherhithe arch- way : justice, perhaps, requires of me to sR~,, iti this place, that the borings above given, and specimerig shown to me by Mr. Vazie, present to me none of the chai'aeters of the undisturbed London strata, but decidedly those of alluvial matters ; and which matters, I have too much reason to fear, extend to still vastly greater depths at Rotherhithe. I have hinted elsewhere, that had the regular o'r clay-ball stratum appeared at the surface on eae'h bank of the river, still, before an ex- pensive tunneling is undertaken, it would be prudenttobore at short intervals across the river sufficiently far into the clay to ascertain whether any fissures filled with alluvial matters exist therein under the river, which it may be extremely dif- ficult if not impossible to work through. It has long ap- peared probable to me, that the vale of the Thamds, from Charing-Cross to the Tower on the north side, and from the foot of Camberwell Hill to the foot of Plough-Garliek Hill on the south, has l~een occasioned by two fissures, one along each of those lines or nearly, and that the whole of the strata between those lines are sunk down, perhaps, to a depth far below practicable boring or well-sinking, and that this chasm (a similar and remarkable instance of which I have traced at ~Voburn, in Bedfordshire,) has been filled up, almost to its present level, by successive alluvial deposits Of

Downloaded by [University of California Santa Barbara] at 16:05 20 June 2016 sand, clay, and other matters washed from the neighbouring eminences ; and that, in after and more quiet periods, the growth of peat, and the gradual subsidence of mad, have completed the filling up of the valley to its present state. Having far exceeded the limits which I proposed to myself when I began this letter, I beg to conclude, and am, ~2, Upper Crown-street, Westminster, Yotlrs~ ~c. '21st May, 1806. ,JOHN FARE~_'. Vo]. £5, No. 97. June 1806. D VIII. Me-