422 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Deoembkr, 



tion of those interested in the siiliject, in a form helter adaptcil to use than 

 that of verbal description. He lioped it would be found that tlieir experi- 

 ments had gone far to fill up one of the great desiderata of jiractical science. 

 Sir Jolm Robison stated, that the whole merit of imagining and conducting 

 he experiments belonged to Mr. Russell. — .Mr. Arch. Smith made some ob- 

 servations, disputing the matliematical accuracy of one of the illustrations 

 used bv Mr. Russell. — .Mr. Russell exjilained that the physical effect dilfered 

 in this instance from the niathematiral theoiT. — The Key. Mr. Brodie had 

 arrived, by calculation, at nearly the same results as Mr. Russell had by ex- 

 periment. Mr. Brodie hoiied Mr. Russell would ditect his attention to the 

 phenomena at very high velocities, such as fi'om 25 to 30 miles an hour. Mr. 

 Brodie's calculations h.ive led to such curious conchisinns. as to make him 

 stispect some mistake : he was, therefore, anxious that Mr. Russell should 

 prove their accuracy by his delicate exiierinients. 



" On the Economy of Railways in resjiect of Gradients." By Mr. Vignoles. 

 Jlr. Vignoles stated that this was another subject, in addition to the former 

 one on timber bridges, selected from a general work ou the I'rinciples and 

 Economy of Railways, which he was preparing for publication. Looking to 

 the great cost of railways, he had turned his attention to a comi)arison of the 

 result of the working of railways, with the price paid for various degrees of 

 perfection. He disclaimed asserting that sh.irp curves or steep gradients were 

 preferable to straight and level lines, but he would endeavour to show th .t 

 good practicable lines might be and had Ijeen constructed, on which trains 

 sufficient for the traffic and public ':ccommodatioa could and did move at the 

 same, or nearly the same velocities. \nd with little, if any, additional expense. 

 Ou an average, the hitherto ascei ..iiucd cost of the principal lines might be 

 divided thus : — 



Land 10 per cent. 



Stations and carrying establishment 20 „ 



Management 10 „ 



Iron 10 „ 



Works of construction proper 50 „ 



100 

 though, of course, these items differed considerably in various railways, but 

 in general it might he said that the works of construction constituted one- 

 half of the whole first cost. He left out, on the present occasion, all con- 

 sideration of the saving of any of the items, except as to the works of con- 

 struction ; though it would not be difficult to show a reduction on these, to 

 the extent of at least one-half. Mr. ^'ignoles stated that he had analyzed 

 railway expenses of working, and had reduced them to a mileage, — that is, 

 the average expense per mile, per train, as deduced from several years' ex- 

 perience, and observations of various railways under different circumstances, 

 and with greatly difl'erent gradients, some of which lines were enumerated. 

 The result on passenger and light traffic lines was, that the total deductions 

 for expenditure from gross receipts was 3«. per mile per train ; 2s. (td. being 

 the least, and 3s. id. the highest ; and that this average seemed to hold good, 

 irrespective of gradients or curves. Particular lines might, from local circum- 

 stances, differ in detail, but he was satisfied fliat the following detail was a 

 fair average approximation : — 



s. d. 



Daily cost of locomotive power and repairs 1 6 



Annual depreciation, sinking fund, and interest on stock, tools, shops, 



and establishment 6 



Daily and annual cost in carriage department 4 



(iovernnient duty, office expenses, police, clerks, guards, management, 



and maintenance of railway 8 



3 



It was not found practicable to distinguish the additional expense, if any, 

 arising from curves or gradients ; but as three-fourths of railway expenses 

 were quite independent of these curves, such addition must be small ; espe- 

 cially as, on the North Union Railway, a line which had 5 miles out of 22 in 

 the gradients of 1 in 100, or nearly 53 feet per mile, the total expenses were 

 less than on the Grand Junction Railway, and several other lines. Mr. Vig- 

 noles then proceeded to illustrate, by diagrams, the mode in which the 

 economy might be made in the works of construction, ou what he called the 

 Jirst sysfetn, by the occasional introduction of inclines of 50 and even CO feet 

 per mile, if not of too great a length ; and again, on the second systeem, by 

 introducing entire series of severe gradients, such as those of 30, 35, and 40 

 feet. On the first system, he had executed the Korth Union Railway ; and 

 had also thus designed all the goveinment railways to the south and west of 

 England. On the second system was the Bolton and Manchester Railway, 

 by the late Mr. Nimmo, Mr. Macneill's government railway lines to the north 

 districts of Ireland; and that engineer had lately altered the Dublin and Kil- 

 kenny, and the Dublin and Drogheda Railways, from better but more expen- 

 sive gradients, to those on the second system ; and Mr. Vignoles was about 

 to apply it to the DubUn and Kingstown Railway ; and he had set out the 

 whole extent of the Sheffield ami Manchester Railway, for 40 miles, on an 

 average gradient of nearly 10 feet ))er mile, mixed with occasional incUnations 

 of 1 in 100, and with curves of one-third mile radius. That work was now 

 under execution by Mr. Locke, who had succeeded Mr. Vignoles an engineer, 

 and who fully concurred in the general principles, — which, as also the details, 

 and the introdnction of timber viaducts on a large scale for economy, Mr. 



Nicholas Wood ajiproved. Mr. Gibbs had also .idnptcd the saiu'! svstcm on 

 the first ten miles eastward of the Newcastle and Carlisle Railway. Mr. 

 Vignoles went on to state, that, on either one or both of these systems, in- 

 troduced as miglit he considered most advantageous by the directing engineer, 

 lines of railway might be laid out so as not to exceed 10,000/. per mile, being 

 jiarticularly applicable where fertile, populous, and manufacturing districts, 

 or the metropolis, with the extremes of the empire, had to be connected 

 through difficult and unproductive districts. Mr. Vignoles concluded by re- 

 marking, that when a continued stream of heavy Iraftic justified the ex]>ense, 

 he saw no reason to \ary from the general rules adopted hitherto by engineers 

 for laying out railways, or from his own former opinions and jn^actice. But 

 it was forced on him by daily experience, that, to accommodate the public 

 convenience, the Post Office arrangements, and business in general, it was 

 scarcely once in twenty times that a locomotive engine went out with more 

 than half its load, and in general the engines were only worked up to two- 

 fifths of their full power : he was, therefore, conclusively of opinion, that it 

 was much cheaper to put ou additional engines on extraordinary occasions; 

 and on such principle railways shoidd be constructed through the more re- 

 mote parts of the country, so as to be made in the cheapest possible manner. 

 The possession of all \hc profit alle lines of railway by private companies, was 

 likely to throw on the government theon«s of constructing their lines through 

 such districts, in which case economy was desu'able : or, if not to be con- 

 structed by the government, then was economy still more important; for 

 Scotland, Ireland, Wales, and western and eastern England would want rail- 

 ways, until some such system as those now promulgated could be brought to 

 bear in the laying out lines of internal conimimicatiou. 



Mr. Roherfs entirely concurred with Mr. A'ignoles with regard to the gra- 

 dients and curves, as also to the propriety of the economy of adopting timber 

 bridges, and so reducing the price of conveyance to the public. — Mr. Vignoles 

 being asked whether, in the gradients of 1 in 100, on the North Union line, 

 any practical danger was to be apprehended, stated that no danger whatever 

 was apprehended ; and tliat, on these gradients of 1 in 100, the trains tra- 

 velled doivn at full speed, or about forty miles per hour. 



Mr. Jeftreys described a fire-grate, exhibited in the model-room, which 

 may be placed, he said, so far forwards as to be (pnte out of the chimnej', 

 and radiate a two-fold quantity of heat into the apartment ; and yet there 

 shall be no tendency to send smoke into the room. By an addition, in ac- 

 cordance with the same principle, fresh air is introduced, comfortably warm- 

 ed before it enters the room. 



" Timber Bridget." 



Mr. Mitchell observed, that Mr. Vignoles liaving drawn attention to the 

 subject of Timber Bridges, with reference to their application to the econo- 

 mical construction of Railways, he begged to report the result of some ex- 

 perience in works of this nature in the Highlands of Scotland, .\bout twelve 

 years ago he had erected a bridge across the Spey, consisting of an arch of 

 100 feet span ; another about six years since of two arches of 100 feet span, 

 with stone abutments and piers ; a third across the Dee, of five arches of 75 

 feet span, with timber piers; besides a number of others of smaller dimensions. 

 Economy was the chief object in building bridges of this material. It was 

 found they were one-third less expensive ; that across the Dee with timber 

 piers less than lialf: the period of duration he found to be from thirty to forty 

 years ; the accumvdated value of the saving being more than equivalent to 

 rebuilding the structure. In his opinion, viaducts of this material might be 

 beneficially applied in the construction of railways, of course being suitably 

 constructed to resist the violent action and heavy weights of railway trains. 

 He was glad to hear that Mr. Vignoles considered that railways might be 

 constructed with gradients so much steeper than what has been hitherto con- 

 sidered practically advantageous. Of course, there could be but one opinion 

 about the propriety of a level and direct line both for safety and speed : but 

 the subject was of great importance to Scotland, where neither the country 

 admits nor the traffic demands such perfect construction. He thought prac- 

 tical exjicriraents should be made on the amount of locomotive traction at 

 different inclinations, and with difl'erent rates of speed ; it appears that hitherto 

 engineers had acted more by theory than observation. One fact he would 

 mention. On a railway recently constructed, he found, that with inclinations 

 of from 1 in 70 to 1 in 100, locomoti\es travelled nearly at full speed, and at 

 one point, an inclined jdaiic of half a mile with a gradient of 1 in 22, a train 

 of loaded carriages, with a gross weight of thirty-five tons, was drawn up 

 with ease, of course at a reduced speed, but not such as to affect tlie general 

 rate of travelling ; the carriages also passed along curves with radii less than 

 500 feet. 



" On the application of Native Alloy for Compass Pivots." By Capt. E. J. 

 Johnson, R.N. 



Among those portions of a ship's compass which most affect its working, 

 are the jiivots and caps on which the needle and card traverse, and which, 

 like the balance of a chronometer (but of far more importance to the practi- 

 cal navigator), should not only be fitted witli the most scrupulous attention 

 to accuracy, but be made of materials capable of maintaining a given form 

 under the trials to which such instruments are necessarily exi)Osed. Having 

 examined a great variety of compasses wliich had been used at sea, wiierein 

 Capt. Johnson noticed that their pivots were generally injured, and often by 

 rust, he searched numerous records of experiments for its |)revention, and for 

 improving the quality of steel in other respects, by means of alloys of plati- 

 num, palladium, silver, &c. (he alluded particlarly to the experiments of Dr. 



