93 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL, 



[March, 



Iile a correspondent as myself, will be .illowed to add inudi weight Ut 

 the eritiiisii) of Mr. Leeds; nor sliould I venture on these reiimrUs, 

 hilt that opinions — and very decided imcs — h.ive heeci expressed hy so 

 many person*, whose riglit to pass sentence is nut more than mine. 



Tlie d 'fee's of the strnrture should have been criticised with a more 

 candid re fen nee to the imperative necessities width interfered with 

 the full exiTcise <if the arcliilect's taste; and the merits of the portico 

 (parti- ul.irly as rejiards its (dan) of tlie entrance liall, and of the 

 <re"eral proportions of the several conip irtments of the ficaile, 

 separately considered, slioiild have bi'en allowed. Gr.intrd. the central 

 cupola is small, its tambour much loo plain, and the tno smaller 

 cupola* or turrets unnecessary. The cornice of the portico, too, cer- 

 tainly lacks that prondnence and richness which the C Tintliian 

 coUiinns (particularly as thry are Ibited) rquire ; but the p irtico 

 dtherui.-^e, in Pi;ard lo its low- pitched pediment (lerliapsit may lie too 

 low) a'd the just approximation of its columns, is worthy of infinitely 

 more admiration than tho St. M.irtiiiians have yet besiowed upon it ; 

 a- d I 'ordially a^ree ivith the writer, whose minute ana ysis wou'd 

 nnder any furtlier comments uraluiloiis, that the " faia le, if erected 

 some years earlier, would have been probably as tnuch extolled as it 

 has now bi'en decri'd." 



]My chief pnrpose in now addrcssinu' y >u, is tosup^g'st such remedial 

 nieisures as I conceive to be — at a vrrv little expense — practieub'c ; 

 and I tlierefore, with all defert-nce (as to an unquestionable superior 

 whom, in spiteotthe world, I deliglit to honour) snbiuit to the archi- 

 tect the adjoined sUeteh, simply showing: bow, by raisiiii; atlic stories 

 over the central and extreme compartments ; by tr.insposing the 

 columns now in the centre of the wings, and by placing a pila-ter attic 

 order round the (arahour of the dome, an altered ell'ect wmild be pro- 

 duced, which the public might deem an improvement. The dome will 

 still perhaps remain too small (the dotted line inelosinsf it being more 

 accordant with my own notions of proportion), but it will certainly 

 not be so objectionable on the score of plainness. If the dome could 

 be entirely reconstructed, it might possibly he made at once available, 

 for increased accommodation and elfect ; but I am speculating only 

 on what may be irathered from the small engravings before inc, and 

 saw too little of the building when in London some time back, to ven- 

 ture on anything more than mere suggestions. 



Your obedient servant, 



GEORGE WICiHTWICK. 



Plymouth, Feb., 1839. 



[VVe regret that it is out of onr power to comply with the request of 

 our correspondent as lo the insertion of a wo<id-cnt, as it would form a 

 precedent which would not tail in other cases of sHsgestions to entail 

 on us great inconvenience and expense. We think his proposed alb ra- 

 tions would be calculated t ; produce the ell'ect he describes, but they 

 would have a tendency to alter the character of the building from its 

 present classicality.] — Edit. Civ. Eng. §• Arch. Journal. 



RAILWAY CURVES. 



Sib, — Having been lately employed setting out railway curves, like 

 your correspondent, " A Sub" (in your January number), I cannot 

 help offering a few observations on bis plan ; althongb 1 fear I am 

 not one of the " more experienced readers" that be expected would 

 take it up. He says, he thinks " it would be an improvement upon 

 the system of running directly from a straight line to a curve of li, 2, 

 or ij miles radius, if a curve of 3, 4, or o miles radius, for a short 

 distance, were made use of to connect them." 



Now to me it appears that the true principle is this : — When you must 

 change your line of direction in a railroad, do so with as iiiuable a 

 curvature as possible ; for we know that if the curvature is not equa- 

 ble, some parts of it must be sharper than if the same radius were 

 used all through. This, I think, would be a sufficient reason for 

 rejecting his plan at the outset. 



But even if without injury we could have a gradual increase of 

 curvature — Cvi bono ? Is it to acmsloni the engines to a curvilinear 

 path ? Surely when an engine is at a point just entering on a curve, 

 it is pretty clear that its action on that curve will not be affected by 

 the nature of the path it vi3.s preciously describing, since its tendency 

 just then is in the direction of the tangent, which is quite independent 

 of that path. 



Again, your correspondent says, " that iirojcctiles (where the 

 resistance is equal) assume the parabolic curve," by which he pro- 

 poses an approximation. Now the resistance heiny constant is not the 

 causeof a projectile's describing a parabola, but because gravity, which 

 acts upon it, is a constant force, producing a constantly accelerated 

 velocity, so that the distances gone in a vertical direction are as the 

 squares of those gone in a horizontal (counting from the highest 

 foint), -vvhich is not a very similar case to that of an engine moving 



along a railway. But even if we were to draw an inference from the 

 motion of a projectile, I would do it thus : — We know that the curva- 

 ture of its path is not constant, neither is its velocity — the latter being 

 least when the former is greatcs'. ; now, the velocity of an engine 

 should be constant, if possible^ — therefore, let the curvature of its path 

 be so also. — I remain, Sir, your most obedient servant, 



Feb. 19, 1839. R. W. T. 



A METHOD FOR STRIKING GOTHIC ARCHES. 



Sir, — I beg leave to make public, through the medium of your 

 Journal, the following method, which I discovered some years ago, and 

 which I believe to be original, for Striking Gothic Arches, more, 

 particularly that which has been termed the Tudor arch : — 



Having determined the height and breadth of the arch, draw a 

 horizontal line on a whitened wall ; make the length of this line twice 

 the height of the arch, and from the centre of the line, let fall a perpen- 

 dicular, to which give one half the width of the arch. Let nails be 

 driven at the two extremities of the horizontal line ; to one of these 

 fix an end of a chain somewhat heavy, but composed of short links, and, 

 passing the other end over the other nail, draw np the chain till the 

 bottom of the curve correspond with the extremity of the perpendicular, 

 and when in that position make the chain fast to the nail over which 

 it was passed. This done, trace upon the wall, with charcoal or other- 

 wise, one half of the curve formed by the freely suspended chain. This 

 curve, placed in such a manner as that the lower or more curved part 

 may rest upon the impost, will form one half of the required Tudor 

 arch, the other half being its counterpait — thus : — 



1. 



Let A B (in fig 1) be the breadth of the required arch, and C D its 

 height. Set oft' on the wall (fig •2) E F=2 C D ; from the centre G, 

 of E F, let fall G =H— The chain being fastened at E, and then 



passed over F, and drawn np until the bottom of the curve correspond 

 with H, make fast at F. Now the curve E H or F H placed so as that 

 the more curved part fall on the impost ; and the extreme E or F at 

 the point C (fig 1), will be half of the required Tudor arch. By this 

 bisection and arrangement of a Catenary, gotbic arches of various agree- 

 able curvature may be most easily and expeditiously traced. 

 I am. Sir, your most obedient, 



13th Feb. 1839. J. K- JACKSON, Col. 



[VVe have taken the liberty of altering onr correspondent's arrange- 

 ment of the figures, by making two answer the purpose of three, which 

 we hope he will excuse, particularly as it does not interfere with the 

 description of his ingenious and simple method of setting out the arch ; 

 a method which, we are sure, will be appreciated by the profession. — 

 Editor.] 



MONTROSE ■VVET DOCK. 



Jteport pf James Walker, Esq., Chit Engineer, 

 The Site. — Having risitcd Jlontroso, in ooininm.v with Mr. Leslie, early 

 in Peceinber last, I surveyed tlie sites and pUuis of Docks proposcil by tliat 

 cuRincer, viz.,— the Horologe Hill site, and the other h-tnccn Meiiiliiin Plaio 

 anil the patent SHp, or farther down the river than the Horologe Hill ; anil I 

 have no hesitation in preferring the lowui- situation. It places the entrnuce 

 in a wilier ami better part of the riyer, where the tcUly-tiile will reniler the 

 euturing of the ships very easy ; it inlorferis Irss with the present wliarfage ; 

 and (which I think very 'important) gives the opportunity of oxteiuling the 

 Docks as occasion mayrequire upon the links — a property which is uncovered 

 and belongs to the town. I consider this site also, whether as respects ap- 

 proach from sea, entrance to the Dock, or the Dock itself, peculiarly eligible. 

 FliiST, AS to the approach PiioM Ska. — Having had reference to an 

 apparently very accurate survey by Mr. Buclianau pf JSJinburgh, and having 



