1830.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



337 



The first of our travellers will have seen only these north-western 

 portions of our country which are composed of rocks belonging to the 

 prima y and transition series; the second will have traversed those 

 fossil portions of the new red sandstone formation, which are made up 

 of the detritus of more ancient rocks, and have beneath and near them, 

 inestimable treasures of mineral coal, while the third will have con- 

 fined his route to wolds of limestone and downs of chalk, which are 

 best adapted for sheep walks and the growth of corn. 



We will now, with your permission, take the various counties be- 

 ginning with the southern coasts, and proceeding in a northerly 

 direction, will describe the chief formations which present themselves. 

 Beginning with the I^and's End, we have in the co\inty of Cornwall 

 the primary formations, the granite and the sienite, with schistose 

 rocks, and similarly ancient formations ; in the adjoining county of 

 Devonshire we find rocks of the grcywaeke and transition series ; and 

 passing into Wales, and thence to the border comities of Scotland, will 

 meet with rocks of similarly ancient origin ; in Dorsetshire we liave 

 the lias and the oclite, in Hampshire and the Isle of Wight we have 

 the tertiary formations, which also extend into Sussex ; at Brighton 

 we meet the chalk which extends to Beachy liead, beyond which 

 the Wealden strata terminates at the coast ; the chalk again appear- 

 'ing on the coast of Kent. At the Isle of Sheppey we meet with the 

 tertiary beds, which foim a part of the London basin. In the county of 

 Sussex we have the remarkable and peculiar Wealden deposits, which 

 have been ascertained by my distinguished friend Dr. Mantell, to be 

 the bed of an ancient and mighty river, which overflowed through the 

 vallies of Kent and Sussex, constituting the drainage of an extensive 

 tract of country. 



The road from Bath to Oxford, and thence by Stamford to Lincoln, 

 affords an instance of similarity in the character and cultivation of the 

 soil and the occupations of the people, which attends the line in which 

 the oolite traverses England from Weymouth to Scarborough. The 

 road from Dorchester, through Salisbury to Basingstoke, or from Dun- 

 stable to Royston, Cambridge and Newmarket, and thence into Nor- 

 folk, aflTords a like imiformity which characterise the line of chalk 

 from near Bridport in Dorsetshire, to Flamborough Head on the coast 

 of Yorkshire. In the same line of direction or line of bearing of the 

 strata across England, a journey might be made from Lyme Regis to 

 Whitby, almost entirely upon the lias formation ; and from Weymouth 

 to the Humber without once leaving the Oxford clay of the oolite for- 

 mation. Indeed almost any route taking a north-east and south-west 

 direction across England, will for the most part pass continuously 

 along the same formation, while a line from north-east to south-west 

 at right angles to the former line, will nowhere continue on the same 

 stratum beyond a few miles. Such a line which displays the greatest 

 variety in the strata, will give the best information of the order of super- 

 position, and various condition of the very numerous strata that traverse 

 our islandin a succession of narrow belts, the main direction of which is 

 nearly north-east and south-west. This line has uflbrded to Mr. Coney- 

 beare the instructive section from Newhaven and Brighton to White- 

 haven, published in his Geology of England and Wales, along which 

 nearly seventy changes of strata t;ike place. 



We have described the south-eastern portion of our island. The 

 tract extending from London to the sea in a south and south-easterly 

 direction, is occupied by the various deposits of the tertiary, the 

 chalk, and the Wealden. Of these the tertiary beds, deposits analo- 

 gous in date and character to those of London occur in the craig form- 

 ation, so called of Norfolk and Suffolk ; the chalk appears again in 

 Wiltshire, Oxfordshire, Bedfordshire, Cambridgeshire, Norfolk and 

 Yorkshire ; the Wealden formation is confined to Kent and Sussex, 

 with some few indications in Wiltshire, and with regard to the last 

 of the secondary strata, they are disposed in the manner I have 

 described in narrow belts, traversing the island from south-west to 

 north-east, but developed of course in a mamier so varied as to render 

 them extremely irregular in their relative situation and character, one 

 particular formation being contracted in its course through one county, 

 expanded in another, lost in a third, and reappearing in a fourth. Tlie 

 best general idea, I repeat, which w^e can best convey to a popular 

 audience, being that the older rocks are developed on the west, and 

 in proportion as we proceed north till we reach the great coal fields of 

 Northumberland and Durham, and the transition beds of Cumberland, 

 and the primary rocks of the borders and of Scotland, and the whole 

 of the strata of our island, as I have before described, forming a de- 

 scending scale, which commencing with the tertiary series, the upper 

 or latest deposits in the south proceeds onward to the deeper rocks in 

 the northern districts of our island, and comprising, as before stated, a 

 variety of geological deposits to be found elsewhere, only diffused 

 over areas of far wider extent. This variety of deposits of course 

 wdiile it provides generally the recpiisite supplies for the chief wants 

 i\nd necessities of mankind, yields aUmditut sopplies for the purposes 



of the architect, and when to the materials already known and em- 

 ployed, shall be added those which have been discovered and brought 

 into notice by the labours of the commission to wdiich I have before 

 had occasion to allude, you will perceive gentlemen, that the geolo- 

 gical deposits of our native land, are such as will supply ample ma- 

 terials for the exercise of your taste and skill. That in this as in 

 every other respect your beautiful and highly valuable art may be 

 cultivated to the honour of our native land, and the embellishment of 

 its splendid capital, is the sincere wish of the humble individual who 

 now presumes to address you. 



A brief but luminous and interesting description of the chalk forma- 

 tion which the lecturer described as the bed of an ancient sea abounding 

 in the usual marine exuviae, weeds, corals, shells, and fish, formed the 

 conclusion of the discourse of this evening. 



RAILWAY CURVES. 



Siu — I would have trespassed on \'our columns before this, to 

 answer the remarks in your April number signed J. Ely, but that, 

 having been on leave of absence for some time, it, as well as your 

 May number, lay most innocently by, neither cut nor read, until my 

 return on the twenty-first of the latter month, when it was too late to 

 send anything even for your June number. 



Mr. lily asserts the incorrectness of a statement of mine, and founds 

 his assertion on the supposition that the object of " A Sub." was, "to 

 begin curving sooner, and make the radii of portions of his curve 

 greater." On referring, however, to "A Sub." 's letter, I can see 

 nothing about beginning sooner, and surely there can be no reason why 

 a constant curvature might not be commenced jtisl as soon as "A 

 Sub." 's or Mr. Ely's plan of a gradually increasing curvature ; and if 

 the two kinds were to conunence together, (which is the real case to 

 be considered,) my observation " that if the curvature is not equable, 

 some part of it must be sharper than if the same radius were used all 

 through," is perfectly correct. A figure wouUI make it quite clear, 

 but I don't like to encumber you with one. 



Mr. E. also dissents from another assertion of mine, viz. " that wdien 

 an engine is entering upon a curve, if will nut be affected by the nature 

 of the path it was previously describing;" and brings forward a fact 

 to disprove it; still, however, I must maintain my assertion, but I only 

 supposed the case of an engine travelling alone. I don't nor never did 

 mean to sav, that the action of a /rain upon the engine dragsino- it, 

 does not depend upon the relative positions; oi the paths they are both 

 describing; it certainly does-; and in the case he mentions, it will 

 easily be seen, that the drag of the train upon the engine, it being on 

 the commencement of a curve, is more oblique wdieii the former is on a 

 straight line, than when it is on a curve of opposite curvature (forming 

 an SJ. In fict, in an S curve, the commencing rail of the one is in 

 direction with the concluding rail of the other. This obliquity of 

 strain at once accounts for the difference of wear and tear he mentions,- 

 it being only at the comnitnctnient of a curve. 



In the latter part of his comiiumicalion, in endeavouring to carrv 

 out the similarity which "A Sub." took lor granted that there existed 

 between an engine upon a railway and a iirojecfile, Mr. Ely seems to 

 have mistaken_/;7c//o« iurgravi/y, for he slales'that "gravity acts upon a 

 locomotive with the same effect as upon a projectile, viz. to bring it 

 io a litate of rest. Now gravity, on the contrary, tends to keep every 



2 C a 



