1843.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



129 



body onward ; the effort of the animal being resolvable into these two parts 

 — viz. the action on the load, and that required to move itself by. It may 

 be gathered from writers on this subject that the force a horse is capable 

 of exerting, is that equal to about one-seventh or one-eighth part of his 

 own weight : or that, on an ascent of one in seven or one in eight, the exer- 

 tion required to overcome his own gravity, is a force equal to that he is able 

 to exert on a load on a level plane. Taking the average weight of a horse, 

 and considering that he is capable of occasionally exerting great extra power 

 on the load, still it seems to be satisfactorily ascertained,- that nearly seven 

 parts out of eight of the muscular power of a horse is required to drag 

 Ids own weight forward, leaving, of course, only one part applicable to 

 the load. But the criterion of a horse's power in practice is not the 

 occasional effort of which the animal is capable at a dead pull, or for a 

 short period : we must estimate his strength by what he can do daily, and 

 day after day for a long period, and without breaking him down prematurely. 

 If a horse is to travel at the rate of 10 miles an hour, his power of pulling 

 is greatly diminished, and he can work only an hour or so in the day : at 

 two miles an hour he may. give out a power of 1.30 lb. on the load : at 10 

 miles he has scarcely 331b. to spare, and at 12 miles an hour, he can seldom 

 be expected to do more than move himself. This was on the average of 

 horses— all beyond were exceptions Thus, the application of horses to 

 railways ?s the motive-power was very limited: and in laying out lines 

 where they are to be used, to full effect, gravity should be arranged to be 

 always with the load, or, at least, not against it; the rate of travelling only 

 2 or 2-1- miles per hour, and the traffic uniform. Mr. Vignoles proceeded to 

 an interesting comparison between locomotive and stationary power up in- 

 clined planes, taking the inclination of 1 in .30 as a maximum, and showed 

 that when the traffic was small, ami the loads consequently comparatively ligiit, 

 and the daila number of trains not great, locomotive engines, as the motive- 

 power, (taking into consideration all circumstances of first cost, and working 

 expenses — particularly the latter, of which the locomotive power was but a 

 small part), would not be so expensive as stationary engines, while they would 

 be certainly more convenient ; and that, with all the best modern improve- 

 ments in the locomotive engines, the system of working with large cylinders, 

 using the steam expansively on the level and falling parts of the railway, 

 improved boilers, &c, planes of 1 in 50 might be practically worked: the only 

 material drawback being, occasional slipping of the wheels en the ascent, 

 and the necessity of great caution and careful application of the brakes on 

 descents ; but on the whole, the balance, under the above circumstances, was 

 much in favour of the locomotive system. The Professor then entered into 

 a very long and minute comparison of the present system of working the 

 Blackwall Railway by stationary engines, with ropes and pullies, with what 

 would be the case if the motive power were locomotive engines— and by 

 tables, showed that while the working of the Blackwall Railway (3£ miles) 

 on the stationary system, was costing about seventy-two pence per mile per 

 train, the cost of working the Greenwich Railway (3^ miles) was only about 

 forty pence : — but, Mr. Vignoles admitted, that by the former, great accom- 

 modation to the public was afforded by the numerous intermediate stations. 

 while on the latter, there was only one stoppage. In concluding the general 

 comparison between the two principles of mechanical motive-power, the 

 Professor observed that on the locomotive system, a minimum of power need 

 only be provided in the first instance and the number of engines might be 

 increased gradually as the traffic required, which was a great consideration 

 when the first expenditure of capital had to be kept down to the very lowest 

 terms, at all future risks. On the stationary system, provision had to be 

 made, from the outset, for the maximum anticipated trade, which of course 

 increased the first outlay on the railway establishment, and depended on the 

 ultimate economy of future working to make up the difference. Having con- 

 cluded the notice of various descriptions of motive-power employed on rail- 

 ways, of which the preceding is but a mere outline, some general remarks 

 were made on the principles of laying out railways, in reference to the 

 several systems respectively. 



In a concluding general summary, Mr. Vignoles observed, that in his first 

 course, at the latter end of 1841, he had fully considered the practical rules 

 for earthwork and constructions :— these were not peculiar to railways; the 

 theory and practice of bridge-building, applied to all internal communication, 

 and would be most conveniently considered in a separate illustrated course, 

 but he wished to recall to the class generally, that in proceeding to lay out 

 railways in ihe first instance, the engineer ought to enter much more deli- 

 berately into those previous inquiries, so absolutely necessary, than had 

 hitherto been done. A system of applying the same general rule of perfect 

 gradients alike to lines, of the least as well as of the greatest traffic, had 

 too much prevailed, and until more rational ideas were substituted, the 

 public would shrink from embarking in enterprises subject to all the contin- 

 gencies of extra cost beyond estimates which had characterised almost every 

 railway in this country. The earthwork and its consequences, regulated the 

 cost, particularly as regarded contingencies, and the utmost consideration 

 should be bestowed as to how far it was justifiable to encounter the expense 

 of these operations. The average cost of earthwork, and all consequent 



works of art, &c, on the English railways was nearly £15,000 per mile, or 

 about 50 per cent, of the whole capital expenditure. Mr. Vignoles was de- 

 cidedly of opinion that in all future lines in this country, and pari,.-,, 

 tlie continent, the corresponding outlay ought not t<> exceed £5000 per mi/,-, and 

 that beyond that sum perfection of gradient would be bought too dearly. 

 In reference to the gauge of railways, Mr. Vignoles stated, distinctly, that 

 theoretical investigations and practical results led him to consider a six fool 

 gauge the best ; but the present 4:J foot gauge was certainly rather cheaper. 

 In respect of curves, he observed, that they were much less disadvantageous 

 than had been first supposed : that a half mile radius was now everywhere 

 admitted : and that he himself did not hesitate to adopt a quarter mile 

 radius whenever expense could be materially saved ; and if the atmospheric 

 system of motive power should be found to succeed on a large scale, the 

 curves might, on lines thus worked, be safely made still sharper. In regard 

 to the systems of constructing the upper works, he had in a recent lecture, 

 entered so lully into the comparison, that he need only now say, that if the 

 expensive and complicated system of heavy rails and chairs, and cross sleep- 

 ers, were preferred by engineers, then the ingenious improvements of Mr. 

 May, of Ipswich, in chairs and fastenings, applied by Mr. Cubitt on the 

 Soulh Eastern (Dover) Railway, with great care in laying, draining, and 

 ballasting, made that system perfect and complete. The Professor, however, 

 decidedly gave the preference to the less costly, and the more simple system 

 of lighter rails, without chairs, laid on continuous longitudinal balks of 

 timber of sufficient scantling, and fastened on Evans's principle, modified in 

 the manner shown by the models exhibited to the class; and several en- 

 gineers were adopting this opinion. On the continent of Europe, where 

 iron was dear, and timber cheap and abundant, Mr. Vignoles calculated a 

 saving of full £2000 per mile of double road would accrue from the adoption of 

 the latter system — which ottered a vast national economy. In reference to 

 the subject of working drawings, plans, and sections, the Professor it 

 the class of the importance he attached to having all such previously made 

 out on a large scale, that the cubic quantities might be accurately obtained, 

 and the just prices considered ; and thus, in proceeding to make the esti- 

 mates, nothing would be left to conjecture, and as little as possible left to be 

 afterwards altered. The period of time for the execution of the works 

 should be extended as far as consistently could be done. The two great 

 sources of the extra expenditure on railways had been, the extreme haste 

 with which the works had been pushed on, and the changes of every kind 

 from the original designs. These points being all carefully considered, even 

 before the plan was brought before the public in general, the estimates might 

 be better depended on. Mr. Vignoles then went through all the great items 

 of expenditure generally arising on first construction, and explained how the 

 accounts of measurements should be made out and kept under very distinct 

 general beads, subdivided into minor items, from the purchase of the land to 

 the last finish to the stations, and the entire fitting up and furnishing of the 

 carrying establishments. Sufficient experience had been attained in all these 

 matters to enable the engineer, in future, if the above rules were faithfully 

 followed out, to place himself beyond all chance of reproach for making er- 

 roneous estimates. In conclusion, the Professor observed, that he had se- 

 lected railways at the request of the class, as the theme for the course just 

 concluded ; but although so much consideration had been given to the sub- 

 ject, lie had only been able to touch in a very general way upon the chief 

 points ; yet it was to be hoped a sufficient idea had been given of the prin- 

 ciples of construction, and of their general application, to create an interest 

 in their minds. Should any of the students hereafter be employed to exe- 

 cute a railway, he trusted they would recollect these lectures with advan- 

 tage, while they would also probably better understand and appreciate them : 

 at the same time, he must not neglect to impress upon them, that it was not 

 at the college, in the lecture-room, or even in the office of an engineer, that 

 all the duties and knowledge necessary could be taught : the young aspirant 

 must pass much time in the work-shop, indeed, he must become a workman, 

 and acquire the use and skill in the handling of tools, and the erection of 

 mechanism of every kind— and passing to the actual works, ought to learn 

 to be able to direct personally the labour of the mason, the carpenter, and 

 the smith. " Above all," said Mr. Vignoles, "the student in engineering 

 must carry into life with him the constant remembrance of what I have so 

 repeatedly enforced, that the reputation of an engineer in this country is 

 based upon the success of his works, of his mechanism, and of all the efforts 

 of his mind and hand, in respect to, and in proportion to their being pro- 

 ductive of commercial and beneficial results, to those who, at his suggestion, 

 may undertake to provide the necessary funds : and he should consider how 

 this result can be best obtained, rather than study the splendour of his un- 

 dertakings. It is for Ihe architect to attend to the decorative and the beau- 

 tiful ; it is sufficient for the engineer to study proportions, and rely on the 

 simple grandeur of his works as a whole. It is related that Napoleon once 

 observed to the celebrated Carnot, " Lis ingenieuts doiient toujours avoir ■/, . 

 ide'es magnifiques ;" this is true as to their first conceptions, but in the rea- 

 lization, they must be sobered down by the rules of economy and judgment. 

 After the first burst of talent, after image and form has been given by the 



