1842.] 



?THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



0.5 



MR. VIQNOLES' LECTURES OX CIVIL EKGINEERIN'G, AT THE 

 LONDON" UNIVERSITY COLLEGE. 



( Continued from page 60.) 



Lecti-re VIL J.nn.5. 1842.— Tlie Professor ccmmonced liy stating that he 

 had then readied the tliird division of the firs! courso, and his present lecture 

 would L* upon retaining walls. The meaning of the tecl nical term.s of " rc- 

 taininvr" and "sustaining"' walls was— when a wall was used eilluT to support 

 water or earth arlificially put together; but when it was used to supp rt 

 natural earth, it was often called a "breast-work." As the term "batir" 

 would often be maiie use of in that and the following lecture, he proceeded 

 to explain that the batir was the base of a triangle, formed by the slope of 

 the wall and perpendiculars of the other two sides — thui a batinng wall 

 was a 'loping wall. The introduction of retaining walls was very ancient; 

 in Italy there were several of great antiquity, formed of concrete, rubble, 

 8;c., an.l even some parts of the great wall of China were built in that way. 

 Retaining walls were generally introduced at the ends of bridges, to connect 

 the aluiments ot the bridge w ith the natural ground ; but in these cases they 

 were ca led " w ing walls." In forming roads retaining walls were sometimes 

 carried along the sides of the valleys— the road itself having to be cut at 

 times .i^ung the sides of hills so precipitous, that half was embankment and 

 half cutting. In the celebrated road formed by Napoleon across the Alps. 

 there were many instances of work of this kind, and good lessons c uld be 

 learnt from the failures which had taken place, the reasons for which were 

 generally very apparent. In Telford's grand road through AVales, there were 

 many instances of retaining walls, and one in particular, where the road h.ad 

 to pass along the side of a hill which was nearly perpendicular. The great 

 cutting' from Camden-tonn to Euston-square was another instance, but, from 

 certain causes, which he very ably expbiined, the walls were giving way in 

 many places. He then proceeded to lay down, by numerous diagrams, seven 

 forms of retaining walls mailc use of, and pointed out, by mathematical for- 

 mula and practical e.\i)eriments that had been made, and which the diagrams 

 explained, the best forms for use. In No. I the batir was represented as being 

 equal on each side of the wall ; in No. 2 the batir was on the side next the 

 earth to be supiiorled ; No. 3 was a parallel batiring wall ; in No. 4 the 

 batir w.as next the earth, but at the bottom of the wall, No. 5, the batir was 

 on the outside, at the top ; No. Gwas a parallel and [lerpendicular wall, with 

 no batir on either side; and No. 7 had theb.itir at the outer side of the wall, 

 and next the earth the slope was cut in steps ; these seven diagrams showed 

 tlie common forms of retaining walls. The grand points to be considered 

 were — 1st, the \alue of the pressure that the earth exercised against retain- 

 ing walls ; and, 2nd, the description and dimension of the n all nccessiry to 

 oiler sufficient resiit.ince to that pressure. It was found that if you take 

 away the wall, the earth will for a short space of time retain its position, but, 

 after exj osure, it will lx>gin wiih crumbling at the edges, and ultimately gain 

 a slo| e so .as to lie at the angle, which is called the " angle of repose." This 

 requires, m building retaining walls, that the angle of repose of the descrip- 

 tion of earth to be supported should be ascertained : this done, the pressure 

 to be resisted might be calculated, and the dimensions of the wa 1 be decided 

 upon accordingly. Of all the descriplions of retaining walls. No. 3 was the 

 one which oflertd the most support with the least quantity of material, and 

 which had, by experiments made at Dublin, under the direction of Sir J. 

 Durgoyne and the Board of Public Voiks of Ireland, been fully proved. The 

 Profe.^^or then explained the nature of the several experiments, and the effects 

 uiion ;he walls, exemplifying them by very instructive diagrams. The atten- 

 tion of tlie students was next called to the cunilinear batir, and several very 

 interesting cases were adduced of failure in that plan, from v.arious caus s, 

 but principally from water, lie then allulcd to two or three failures of bis 

 own. and fully explained to the students the causes of them, and the nie.ins 

 be should have adopted in the first instance for their prevention. The occa- 

 sional supporting of walls was judicious in various instances; suppose there 

 Was a ease, that, wliilc the earth was in an unsettled state, the pressure 

 against the wall was double what it would be when it had settled ; in such a 

 case he would recommend supporting walls until the settlement took place- 

 not to go to double I lie expense fot'w temporary purpose, lie then mentioned 

 a very remarkable instance of an abutment, which was practically a retain- 



ng wall, giving way. Me had to make an arch of twenty feet span lor a river, 

 through an embankment eighty feet high ; the foundation «as rock, but a 

 sudden liitch look place in the body of the (ml>ankment,anil the earth forced 

 its way through very many feet of saiul backing, drove the .ibutmenl or re- 

 taining wall clean oil the rock, and tnoved the whole twelve or thirteen feet. 

 Several giH)d rules were then laid down to calculate the do^cliptiotl of wall to 

 be used, and melhiHl of giving a temporary support until the ear h settled ; 

 nnd the learned lecturer, in eonclrsloii. stated tb:it hbs next lecture wi uld lie 

 given on ^^'orm«oad Scrubbs. where there were some most remarkable 



instances of failures in retaining walls, the reason of which he couU better 

 explain on the spot th .n by diagrams. 



THE ATMOSrilERlC KAILW.W. 



Lf.cti-iie VIII. Jan. 10, 1842.— TliiB being intended as a practical illus- 

 tration of some interesting and important jioints, the lecture was delivered on 

 the works of the railways situated at, or near. Wormwood Scrubbs, in place 

 of being given, as usual, in the Ircture room of University College. 



The fust point to which Mr. A'ignoles directed the attention of the class 

 was to ilie atmospheric railway, or rather, a portion of railway laid down on 

 that principle for experimental purposes, u[<on the line belonging to the 

 West London Railway Company. The length of this experimental line is 

 half a mile, and, according to the Professor's statement, it fully answered 

 the pnrpose ; and he, at some length and with great ingenuity, explained 

 the principles of the system. The iron tube fir^t attracted attention; it is 

 nine inches in diameter, w ith a grooved slit along the upper surface, which is 

 closed by means of a valve ot le.ither, slrengihened by plates of iron, flat on 

 the outside, and forming the segment of a circle on the inside, so as to com- 

 plete the diameter of the tube when it is shut ; at the edge of the valve it a 

 composilion of bees'-wax and tallow, which renders the tube air tight. Next 

 was examined the carriage, to which was attached a piston, fitting into the 

 tube, and a very ingenious contrivance was shown, by which the valve was 

 first opened, and afterwanls closed down, immediately after the piston had 

 passed, however great the velocity of the carriage. The imjiossibilily of pro- 

 curing a perfect vacuum had long been assigne<l as the great objection t(> 

 this principle of ] roducing locomotion ; but Professor Vignoles showed that a 

 good working half vacuum was. by the simple contrivance he had explained, 

 quite attainable, and sufficient for practical purposes. The engine and air- 

 pump were next severally examined and explained, and the lecturer then gave 

 some very interesting CNplanations of matters connected with the present 

 experimental railway ; he stated that the air from the half mile of tube could 

 be extracted in about one minute, while it \>ould take nearly eight minutes 

 for the leakage of the valve and air-tube to admit the air to fill the tube. In 

 consequence of the imperfections in the present line, vibich had been merely 

 laid down for experiment, the leakage was very much more considerable than 

 when a perfect line should be formed for service ; and the formation of a rail- 

 way on the atmospheric principle would not exceeJ, perhaps, one-third of 

 the cost of many of the great lines hitherto contracted for, as it would do 

 away with much of the cutting and embankment, ihe slips of which had 

 recently been so troulilesume and dangerous, by the trains being able, on 

 this method, to ascend eonsi.lerable acclivities. Tlie present experimental 

 line had a rise of about one foot in 110, and he had gone along at the rate of 

 forty-five miles an hour, notwithst nding the imperfections of the machinery 

 and the wretched state of the line. He pointed out that it would be practicably 

 impossible for a locomotive to travel upon such a line, as it would be off the 

 rails immediately, in consequence of their being so uneven and loose ; yet he 

 hiid travelled at the rate he before mentioned, with jierfect ease and safety, 

 and. furthermore, the extreme simplicity of the machinery rendered it very 

 unlikely to get out of order. A feiv weeks back the line n.is required suddenly 

 for some experiment, and, although the tube was half full of ice, in less than 

 half an hour everything was in readiness, and the trial was very satisfacton . 

 The power obtained by the present small tube is 500 lb., with an atmospheric 

 pressure of about 8 lb. per inch only. The engine employed to work ihe air- 

 pump is sixteen or eighteen horse-power, and the economy of stationary 

 over locomotive power was admitted by every body. He concluded his 

 remarks upon this interesting, and what promises to be most useful applica- 

 tion of the power of atmospheric pressure, by det.ailing, at some length, the 

 minutiffi of the saving that would be elTectcd by its general ailoption, and 

 stating that two miles were to be laid down upon the Dublin and Kingstown 

 Railway, to try the experiment upon a larger scale, with a tube fifteen inches 

 in diameter, and more perfect apparatus. The Professor then, .as the party 

 walked along the line, pointed out to the class various slips that had taken 

 place, some of w hieh were slight and others extensive ; one part in particular, 

 situated between the Great Western and London and Himiingham Uaihiays 

 (which arc here within a quarter of a mile of each other), attracted general 

 atlenliun, the wliok-, for nearly 100 yards, lieing a perfect ch.aos A r.inark- 

 ablo instance of a failure of a retaining wall here presented itself, it havin« 

 for about forty-five yards, l-een actually pusliwl forward ofl ilie fuund.ation. 

 to a distance of eight or ten feel, the wall still standing, which apiieared to 

 U alx.ut four feel thick, strongly built of brick and concrete, and strength- 

 ened with bands of iron nnd wood. The causes of this destruction were 

 explained by Mr. Vignoles as arising from the lodgment of water, which, 

 having no outlet, had settled the earili against the back of the retaining wall, 

 turning the clay into mud. and. by the great additional weight, f.rr.ng ii 

 into the position in wliicb it now appe:ir>. If the water had lieen cut oil in 

 time ihis would not have liappmeil, and that water was the occssion of this 

 accident seimcd very apparent. The lecturer then pi inted out the manner of 

 supi>orting retaining walls, several portions uflhe London and Birmingbam and 



