1846. 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



203 



quis of Worcester's celebrated " Centurie of Inventions." The marquis 

 mii^t have lici-n an eMniurdiimry man, for, by his own account, he eliected 

 several physical iiiipossibililies. 



The coiiliniiatiun of the memoir of tlie Thames Tunnel follows. The 

 account of ihe repeated discouraging failures to whicli Sir 1. Brunei was 

 aubjected iu the progress of Ins great work, and the courage witli which 

 he persevered, is very inleresling. There are not, however, in the present 

 Dumber any of tho;-e adniiralile plates, representing the mechanical con- 

 trivance employed by Hrnnel in the Thames Tunnel, which rendered the 

 former portions of this memoir of speciliu value to the engineer. 



The letterpress description of the Krankf irt and Wisbadeu railway does 

 nut possess an interest cummeusurale with the excellence of the engrav- 

 ings by which it is illustrated, for the ground traversed by the railway is 

 so level that there are few, if any, engineering works worthy of detailed 

 description. We can speak from personal knowledge of the excellent 

 regulations by which this railway is nwiiaged, and the convenience of di- 

 viding the pas-ieiigers iii\o four clauses, all of whom travel much more 

 cheaply than ihey would iu linglaad, and are seated in comfortable car- 

 riages defended from the weather and the smoke aud hot cinders of the 

 engine. In (lermany, the comforts of the poor are less lallud about than 

 in England, but we are not certain that they are less attended to. 



The new dock at Suudt-rland is designed by Mr Stephenson and Sir. 

 Murray, and is to be 27 acies in extent. The following extract from the 

 report of iMr. Walker, who was commissioned by the Lords of the Admi- 

 ralty to examine the plan proposed, will explain the principal novelty in 

 Ihe design : — 



"The lift of a spring tide heing only 14 feet 6 inches, the dock is to be 

 6 feet under low water, giving 20 leet (i inches water in the dock on a spring, 

 and 17 feet on a neap tide. The above depths can he maintained in the 

 dock, liut the riepih at the bar at the harbour mouth is two feet less, so that 

 with the " scud " of sea during a north-east gale a vesel drawing more than 

 14 feet cannot venture over the bar with safety. To have the dock so much 

 deeper than the approaih to it would be of little use, and yet, from the great 

 draught of ships from foreign ports, it would be very <idvisalile to have not 

 less than 17 feet at neap and 20 at spring tides. The engineers propose to 

 accomplish this by sending laden vessels chiefly out at the south end through 

 a tidal basin of 4.j acres, with two dpenings, one having gates of 6t) feet, 

 and the other of 45 feet, iielween the dock and it and other siluilar gates 

 between the basin and the outer entrance. The outer entrance or rather 

 exit points south, south-east nearly,* and is to he formed by means of rough 

 breakwaters, one on tlie east ride, nearly parallel with the entrance, and the 

 other on the west side, neaily square with it. This southern passage is pro- 

 posed to lie as deep as the dock, and to kept to that level by dredging and 

 icourhia. The very important feature of the plan (the southern passage), 

 is, so tar as I remeinber, uetv ; and if it can be effected as proposed, will he 

 a great convenienee, by giving laden ships two to four feet more water than 

 can at present he depended on ; starting them in the riglit direction for the 

 •outh, when the wind is fair, also leaving the Wear or harbour entrance clear 

 for the present harbour, and the entrance of light ships into the docks." 



On Staking out Railway Curves. By George Heald, Carlisle, 1846. 



pp. 7. 



This is a small lithographed pamphlet of seven pages, of which the ex- 

 tract given below will give a sufficiently correct idea. The author's plans 

 of setting out curves seems correct; however the investigation does not 

 require any wonderful amount of geometrical ingenuity, and we hope that 

 the time is not far distant when every engineer and surveyor will know 

 enough mathematics to solve so simple a problem for himself, without hav- 

 ing recourse to books. This remark is however made without disparage" 

 nient of the treatise before us. 



The curve described in the following extract is strictly speaking a para- 

 bola—the curvature of a parabola near its vertex resembles that of a circle 

 with sufficient accuracy fur the purpose here proposed, if the ofl'sets be 

 small, and the radius of curvature very large. 



** Having by the practice and examination of several methods of staking 

 out railway curves arrived at the comlusion that it is best eflfected by em- 

 ploying the theodolite ; and several friends having requested a detail of the 

 system that I have pursued for that purpose. 1 have had the following 

 summary of the principles lithographed for the in^ormaliun of those who 

 may be desirous of becoming acquainted with the system. Suffice it to say 

 as its recommendation that the system insures the curves being truly cir- 

 cular, ami greatly economises the labour that is often requisite to drive the 

 curve through a distant given poiut from which little or no variation can 

 be allowed ; which is a case of frequent occurrence, and upon some sys- 

 tems one whose practical execution is very tedious. 



* The beariDgs are all by corapats. 



" The first principle is, that in circles of Ihe magnitude of those used for 

 railway curves, if a tangent be drawn to them, the olfsets from the tangent 

 to the curve increase according to the squares of their distances from the 

 point of contact 



Thus let the junction of a curve and tangent be at ; then, if equal dis- 

 tances be set oil from at the points 1, 2, 3, 4, 5, and 6, which may repre- 

 sent chains, the otrsel from the laiigent to the curve at the 2od, 3rd 4th, 

 5th, and 0th will be respectively 4, 9, 10, 2j, aud 30 (or 2" 3^ 42' 5» 

 and U") limes the offset at the ist chain. ' > . • 



" This is one of those close approximations which, though not rigidly 

 correct as an abstract mathematical proposition, is much too uear the truth 

 to permit any discrepancy to appear after the most critical examination ; 

 It being understood that when the radius is as snail as twenty chains, the 

 length of the tangent io restricted to three chains, and when it is three miles 

 radius It is restricted to eight chaius, it is between these limits that rail- 

 way curves are supposed to range. 



" In Ihe praciical slaking out of curves the offsets from the tangent to 

 the circle at each chain length, expressed in inches, or feet and inches are 

 made use of, aud from ihe preceding paragraph it will be seen that having 

 the oS'set from the tangent lor one chaiu length given, the succeediug chaius 

 will be deduced from it by miilliplyiiig by 4, 9, 10, 23, &c. 



" It perhaps will not be amiss at this stage to point out a rule for finding 

 these offsets, which is panicularly cunveuieiit when the radius is some 

 aliquot part of a mile, like the principle euunciated iu section 2, to which 

 it IS so closely allied, it is practically correct, but not mathematically true. 

 Its somewhat singular phraseology runs thus — from the square of the tan- 

 gent in chains subtract Us ,Jjlh part ; divide the remainder by the diameter 

 of ihe circle in miles, aud ten times the quotient is the required oti'set in 

 inches. 



A Treatise on the Steam Engine. By the Artizan Club. Parts XXIV. 

 and XXV. Longmau : 1S40. 



As these are the concluding parts of the treatise, we may as well say a 

 few words respecting its general character, notwithstanding that the work 

 has already been frequently noticed in these pages. 



Excepting an excellent folio plate giving views of 14 of the most cele- 

 brated varieties of direct action marine engines, the present numbers con- 

 tain little that possesses independent interest, for they are chiefly occupied 

 by the index. We have however the introduction, by the editor, Mr. 

 Bourne, aud the character which he gives his own performance is on the 

 whole so nearly correct, that we are content that it should be taken as an 

 expression of our Judgment on the work. 



"The circumstance of having been published in monthly numbers fur- 

 nishes, of itself, au explanation of many imperfections ; for it can hardly 

 be expected that works produced under the exigencies of periodical pub- 

 lication should be distinguished by the perfections which belong to literary 

 leisure aud fastidious ePaboratioo. I have been obliged to confide the 

 greater portion of the theoretical part of the present work to some mathe- 

 matical assistants, whose algebra has, I fear sometimes risen lo a needless 

 luxuriance, and iu whose superfine speculatious the engineer may perhaps 

 discern the hand of a tyro. In spue, however, of its iniperfeclioiis I be- 

 lieve that the present Treatise on the Steam Engine is likely to prove the 

 most useful yet published ; and it is the only one, 1 believe, which can be 

 regarded as of a really practical character. Although falling far short of 

 my conceptions of what such a work should be, 1 believe that it substan- 

 tially fulfils the promise held out iu the prospectus; and having now col- 

 lected the rough materials, I irust to be able, should another edition be 

 called for, to clear them of the drojs by which they are now didgured, and 

 present them ia a form that will in some measure justify ihe public appro- 

 bation. 



'• The preliminary and practical portions of the work have, for the most 

 part, been executed by me, the disquisitions upon the slide valve and 

 parallel motion are taken from the 'Artizan,' aud oiher portions of the 

 work are by various members of Ihe Artizan fraternity. In the praciical 

 part of the work I have been able to obtain but little assistance from pre- 

 Mous auihors, and many of the subjects discussed are now brought for the 

 first time bef(»re Ihe public. Mr. Farcy's work, though of great merit, 

 gives but little iuforniation of any kind touching modern engines; and 

 Tredgold's work is chiefly made up of mathematical sublimities, whicii 

 have but little relation lo practice." 



The acknowledgement of the theoielical errors is made in a manner 

 which disarms criticism. As far as we could judge the errors arose from 

 an attempt to coiubiue the theory of De Pambour with that of Tredgold — 

 that is, the true with the false. We have uo besitatioa in saying that 



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