« PreviousContinue »
tion or division of the line, being made self- Soon after Mr. Clegg had taken out his acting, there will be no occasion for stopping, patent, he exhibited a model 30 feet long at or even for retarding the movement of the Paris; and a second model, 120 feet long, train, in passing from one division of the pipe 10 another, as the air is successively exhausted was erected in 1840, by Messrs. Samuda at by the stationary power placed at the proper their manufactory in Southwark, which exintervals. The carriages may, therefore, pass
cited much attention. In the autumn of continuously, at any required velocity, as if the same year a space of ground at Wormdrawn by a locomotive engine; and it is ne- holt Scrubs, half a mile long, was placed by cessary to keep this circumstance in mind, as the directors of the Thames Junction Railby any other system of traction by stationary way Company at the disposal of Messrs. a change at each engine is'unavoidable."— Clegg and Samuda, (who co-operated in Pages 9-10.
carrying out the invention,) for the purpose
of laying down a line of railway on the atIt is difficult to appreciate fully the sim- mospheric principle; and in May, 1840, plicity and beauty of this invention, and the this experimental line was opened. An facility and regularity with which the tube event so interesting attracted a large conand valves act, without examining the appa- issue of the experiment then to be tried,
course of persons to the spot; and by the ratus or plans of its construction. The exhaustion of the main tube, and the pro- would probably be shown the practicability pulsion of the piston and carriages attach- or failure of the invention : several memed, are easily comprehended; but the mode bers of the Cabinet, and a large number of of passing from one section of the pipe to persons of rank and eminent engineers were another, above alluded to, requires more present. The success which from the first attention : this is explained in the descrip- attended these experiments realized the extion given by M. Teisserenc in his Report pectations of Messrs. Clegg and Samuda; to the French Government, to which we they were repeated several times each week shall presently allude:
during a twelvemonth, and continued less
frequently a second year. Engineers and “Quand on sort de la sphère d'action d'une ma- persons connected with railway companies chine pneumatique, pour entrer dans la sphère came from Paris, Petersburg, Vienna, Berd'action de l'appareil pneumatique suivant, il lin and other parts of the continent, as well est donc convenable que l'air du tube dans le- as from every part of the British dominions, quel on entre soit dejà raréfié; mais alors le tube to examine the apparatus and witness its est fermé à ses deux extrémités. Nouvelle diffi
operation. The results of these expericulté pour éviter le choc du piston arrivant avec toute sa vitesse acquise contre la sou
ments appeared in a pamphlet in 1840, pape de clôture, pour ouvrir cette soupape
which was reprinted in an extended form avec un petit effort, de manière à donner pas- in 1841. We shall refer to the points of sage au piston, sans donner passage à l'air ex- chief interest. térieur, sans arrêter, sans ralentir seulement le The inclination of the line was 1 in 120; convoi. Ici il a fallu encore recourir à une the vacuum-pipe half a mile long and 9 disposition fort ingénieuse. La soupape de inches internal diameter ; the exhausting, MM. Clegg et Samuda s'ouvre au moment où le piston ferme déjà le tube, et par l'action pump was 37} inches diameter and 22 mème du piston ; l'effort est presque nul, la inches stroke, worked by a steam-engine of rentrée de l'air n'en est pas augmentée. Quant 16-horse power. à la sortie du piston d'un tube, elle ne donne lieu non plus à aucun choc, bien qu'une sou
“For the purpose of experim ent, a series of pape de cloture se trouve aussi à l'extrémité du posts were fixed along the half mile every two tuyau, et voici comment: l'appareil pneumat
chains, and a barometric gauge was attached ique placé sur le côté du chemin communique at each end of the pipe, for the purpose of asavec le tube de propulsion par un tube aspira- certaining the degree to which the pipe was
Il a suffi de placer ce tuyau aspirateur exhausted. A vacuum equal to a column of à quelques mètres en deçà de l'extrémité fer- mercury eighteen inches high was obtained in mée par la soupape de sortie pour rendre toute
about one minute, and both gauges indicated rencontre entre le piston et cette soupape im- the same extent of vacuum at the same inpossible. Dès que le piston a dépassé le tube
stant." aspirateur, l'air n'étant plus enlevé devant lui se comprime de plus en plus, augmente pro; tained during six months, it was found that
Following out the registered results obla pression intérieure étant supérieure à la a main pipe of 18 inches diameter would be pression atmosphérique, la soupape s'ouvre sufficiently large for a traffic of 5000 tons a d'elle-même." ---M. Teisserenc's Report, p. 112. day, viz. 2500 each way, supposing the in
clination of the line to average 1 in 100.* (one hour every week; the composition now in But among the most important of the facts the valve-groove has never been changed; deduced from these experiments are the fol- and 56 lbs. weight only has been added to lowing, which refer to the effects of wear which consists of wax and tallow, is is. per lb."
supply the waste; the cost of this composition, and tear on the apparatus :
- Page 11. ..... “ The workings of the system are equally perfect during all seasons,—through
The success of these experiments, and the height of summer and in the severest win the general attention which was drawn to ter that we have known for many years: in no the subject, forced it upon the notice of the single instance during the whole time has any Government. Mr. Pim, who took a warm derangement of the machinery taken place, to interest in the promotion of so important an prevent, or even to delay for one minute, the enterprise, printed a detailed description of starting of the trains. The main pipe and valve have considerably improved by work
the atmospheric railway, the great public ing; the composition for sealing the valve has advantages which its adoption held out, become so much more firmly bedded in its and urged the subject strongly on the atplace, that while in June last we were only tention of the Board of Trade. In conse able to obtain a vacuum equal to a column of quence of this appeal, Sir Frederick Smith mercury 19 to 20 inches high, we now obtain and Professor Barlow were appointed to from 22 to 24 inches, and occasionally 25. The examine the experimental works at Wormspeed, originally from 20 to 30 miles per hour, holt Scrubs, and to furnish a report upon now ranges from 30 to 45. The whole attendance the valve and main received during this the applicability of the system. This docuperiod was that of a single laborer for about ment, addressed to the Earl of Ripon, was
* The Patentees give the following details :- presented to Parliament, and is dated Feb“ A main pipe, 18 inches diameter, will contain a
ruary 15, 1842. It contents consist chiefly piston of 254 inches area : the usual pressure on
of calculations on the details of working, this piston, produced by exhausting the pipe, too purely scientific for our examination should be 8 lbs, per square inch (as this is the here. We cannot, however, but notice the most economical degree of vacuum to work at, partiality of the general remarks, the eviand a large margin is left for obtaining higher dent desire to suggest every doubt and to vacuums to draw trains heavier than usual on emergencies,-a tractive force of 2032 pounds is minimize every advantage of the atmosthus obtained, which will draw a train weighing pheric system. Notwithstanding this bias, 45 tons, at 30 miles per hour, up an incline rising however, the admissions forced upon its 1 in 100. Two and a half miles of this pipe will authors are decisive. The chief points on contain 23,324 cubic feet of air, goths of which, or
which questions naturally present them12,439 cubic feet, must be pumped out to effect a vacuum equal to 8 lbs. per square inch; the air- selves, and to which we shall first confine pump for this purpose should be 5 feet 7 inches our attention, are the following: we quote diameter, or 247 feet area, and its piston should them from the Parliamentary Report :move through 220 feet per minute, thus discharg. ing at the rate of 24 7 X 220 = 5434 cubic feet per trains of carriages may be worked by means
“ It is no longer a question whether per minute when the vacuum has advanced to 16 of atmospheric pressure ; the points now inches mercury, or 8 lbs. per square inch, the to be decided are: mean quantity discharged being thus 3985 feet “1. Whether this principle admit of its per minute: therefore = 3-1 minutes, the being advantageously applied to greater distime required to exhaust the pipe ; and as the area of the pump-piston is 14 times as great as that in tances than half a mile, which is the length the pipe, so the velocity of the latter will be 14 of the present experimental line" (at Wormtimes as great as that of the former, or 220 feet holt Scrubs]. per minute X 14
3080 feet per minute, or 35 “2. The probable expense of constructmiles per hour. But in consequence of the imperfect action of an air-pump, slight leakages, ing a railway on this principle, and of supetc., this velocity will be reduced to 30 miles plying the locomotive power. per hour, and the time requisite to make the “ 3. The relative economy in working vacuum increased to 4 minutes : the train will such a line, as compared with a railway thus move over the 2 1-2 miles section in 5 minworked by locomotive engines. utes, and it can be prepared for the next train in
" 4. The degree of safety which the at4 minutes more,-together 9 minutes ; 15 min. utes is therefore ample time to allow between mospheric system affords, as compared with each train, and supposing the working day to other locomotive means." consist of 14 hours, 56 trains can be started in The first of these points appears to be each direction, or 2520 tons, making a total of 5000 tons per day. The fixed engine to perform this decided, by the successful results obtained duty will be 110 horses' power, equivalent to 22 on the railway from Kingstown to Dalkey, horses' power per mile in each direction." extending nearly two miles, which has been
ecently completed : these are still more tion, we now possess satisfactory data upon atisfactory than the former experiments on which to form a calculation. In the first 1 line of half a mile; but we shall have place, on the atmospheric system one line occasion to refer to them hereafter. We of rails is proved to be sufficient, and half shall here quote the observations of Mr. the expense of rails is thus at once saved. Samuda on this point :
But in addition to this, the weight of the “In answer to the first objection we would rail may be reduced very considerably, in say, in every case where a train has been consequence of the weight of the locomostarted, the pipe has first been exhausted to 18 tive engine (from fifteen to twenty tons) inches of mercury or upwards. ..... From being got rid of. the barometric gauges fixed at both ends of M. Mallet, in his recent Report to the the pipe, the vacuum is ascertained to be French Government, (to which we shall formed to an equal extent throughout the refer hereafter), makes another valuable ence of time. The pipe laid down is 9 inches suggestion, which will probably lead to a diameter, and half a mile long, and a pressure
further saving :-“ Could we not besides equal to a column of mercury 18 inches high (as is done on the road from Kingstown to is obtained in one minute by an air-pump 373 Dalkey, where the trains run more than 500 inches diameter, moving through 165 feet per mètres by momentum, the piston out of the minute. Now it is obvious that, if the trans- pipe) have long interruptions of the main verse section of the pipe be increased to any pipes, at the ends of which the trains arrivextent, and the area of the air-pump propor: ving at new mains should regain their lost altered, -i. e. hall a mile of pipe will be ex- speed. Great economy would follow such hausted in one minute; and supposing the air- an arrangement.
Of the different combipump has to exhaust 3 miles, it will perform nations which might thus be formed, much ihe operation in 6 minutes; it is also obvious yet remains to be said.”—Page 44. that if the area of the air-pump be increased
Another considerable saving is effected in a greater proportion than tliat of the pipe, in the expense of forming the road. Those the exhaustion will be performed more rapidly, who have studied the cost of constructing or vice versa. These results are matters of absolute certainıy, as convincingly clear as that railways, know well how large an item this the power of a steam-engine must be regula- forms. A slight inclination in the course ted by the area of the piston on which the renders a succession of embankments, cut
No person of scientific attain. tings, viaducts, etc., necessary, which have ments will for one moment doubt that, if a not only to be made in the first instance, steam-engine were made with a cylinder twice but to be maintained and repaired. The the area of the largest cylinder ever set to work, the power obtained would be in propor
cost of this is too obvious, to any one who tion to the increased area. And so with the air-has travelled on our present lines of railpumps before alluded to; the excess of work way, to need indication. is immediately arrived at, that an air-pump 6 M. Mallet, in speaking of the width of feet 3 inches diameter will perform over an- way required on the present system, says :other of 3 feet 14 inch diameter, the speed of the pistons being the same in both instances.
“This width, more than quadruple that of So plain and self-evident is this result, that we the road, is rendered necessary by-First, the believe the most skeptical will admit it to be foundation of the slopes required by the cutcorrect; and this being granted, the applica- tings and embankments. Secondly, the spoil bility of the system 10 a line of any length banks. Thirdly, the side roads. Fourthly, must follow; for whatever the length of rail the drains or ditches; and Fifthly and lastly, road be, whether 3, or 30, or 300 miles,-no the sidings for stations on the line. Of these different effects have to be produced. The five causes the principal is the foundations for working a road 30 miles long would be the the slopes, which are often very considerable. same thing as working 10 roads each 3 miles The necessity of great radii of curvature, and long. Every 3 miles an engine and air-pump especially that of small inclinations,
leads inis fixed, which exhausts its own portion of pipe evitably to this. With the Atmospheric sysbefore the train arrives ; thus, as the train ad- tem, the earthworks, and consequently the exyances, it receives power from each succeed- tent of the slopes, will be much less consideraing engine in turn (and without any stoppage, ble. To estimate the cost of compensation on unless required, until it arrives at its final des this system at five-ninths of that on the orditination), and the air-pumps continuing to nary railroads would be to overrate this part work, after the train has passed, on the section of the expense.”—Page 40. they act
upon, re-exhaust it in readiness for the next.”
And again :
• Passing now to works of art, I shall re2. With respect to the cost of construc-mark that a great number among them, as
bridges, under which the railroad passes, willing calculations which the present system, be considerably reduced in their dimensions with its stringent conditions, does not admit Instead of' a height of 5m. 50 under the crown. of.” To overcome the resistance of a load these bridges will need to have no more than 3m, 50 at most, since it will not be necessary up a steep hill, the power of the engine to leave passage for the chimneys of the loco must be increased ; and it is only a quesmotives. The quantity of embankment at the tion, in each particular instance, whether approaches to these bridges will be propor- this will be more expensive than tunnelling tionally less.”—— Page 41.
or embanking. The Parliamentary Re
porters remark, that “to work steep inThe fact has never been questioned, that clines by means of larger tubes would inthe atmospheric railway admits of much volve the necessity of stopping the train at steeper gradients; and, without entering on the foot of such planes, and of again overthe wide field of calculations of economy coming the inertia of the load ; in both inand public advantage which this simple fact stances causing a loss of time.” This obopens, we shall limit our remarks to one jection is answered by Mr. Bergin as folpoint of view, and leave our readers to follows:low out the deducible reasonings. A locomotive engine weighing 17 tons will only "Assume for a moment, which however I draw a load of about 30 tons up an inclined altogether deny, that it was necessary to vary plane of 1 in 100 at the rate of 20 miles an the size of the main on every ascent, and io hour. If required to draw any additional stop the train at the foot thereof, for the purweight, at this small speed, another engine pose of changing the piston, I should say the
cases are very few indeed in which the engimust be attached,—that is, the cost of work
neer, when laying out a line of railway, could ing must be doubled. This is alluded to not so arrange his plans that these stopping by M. Teisserenc:
places should be the most desirable for stations,
and thus render the accommodation afforded “Ne pouvant diviser les trains, ni créer à to the public perfectly compatible with the effivolonté des trains supplementaires, aussitôt cient and economical working of the line. But qu'un convoi est trop chargé, il faut atteler I do not agree in supposing it necessary to deux locomotives, c'est-à-dire doubler les frais change the dimensions of the main on every de transport. Les accidents sur les trains steep incline ........the less the exhaustion in menés à très-grande vitesse ont d'autant plus the main, the greater the quantity of air exde gravité que le nombre des voitures attelées tracted at each stroke of the pump in proporest plus considérable. Non seulement ils frap-tion to the power expended; or, in other words, pent un plus grand nombre de personnes, mais the less the exhaustion (within proper limits) la masse en mouvement étant plus grande, les the diameter of the main being proportionately chocs, en cas d'arrêt brusque, sont plus difficiles increased, the greater the economy of the sysà amortir, plus désastreux dans leurs consé- tem ; and in this assertion I am fully borne out quences.”- Page 107.
by the Reporters' investigation. Further, this
reduction of vacuum does not materially affect We now turn to the atmospheric princi- the velocity of travelling, which is essentially ple. The stationary engine of 100 horse- dependent on the discharging power of the power, now at work on the Dalkey railway, when looking out a line of railway, and start
air-pump. Such being the fact, an engineer, draws 72 tons at 20 miles an hour, along a
ing with the knowledge tha: he is not restricted line of 13 miles upon a gradient of 1 in to levels or even to moderate gradients, would 100. The Parliamentary Reporters admit find few districts in which he would not be that, whilst “a great part of the power of able to form the railway almost on the very the heavy locomotive engine is expended surface of the country; for he would be at in overcoming its own gravity and resist- liberty to avail himself of almost any ascent; ance, it is equally true that, on the atmo- the only consequence of his doing so being an spheric principle, the whole additional force increased expenditure of power, precisely in spheric principle, the whole additional force the ratio of the increased resistance." is exerted on the load itself.” This advantage of the atmospheric principle consequently admits the power of working lines There are many other incidental advaneconomically on a large range of gradients tages, of an importance scarcely yet apprefrom which locomotive power is necessarily ciable, which are obtained by the simple excluded; the question of limit is, in fact, command of steeper gradients. It will be one not of power, but of economical calcu- seen that this opens at once a much wider lation. “The atmospheric system,” says and more free choice to the engineer in the M. Mallet, "is, so to speak, master of the course of his line, and the expenses of comacclivities, and affords opportunities of mak-pensation for the value of property may fre
quently be affected and considerably re- of fifty to sixty miles an hour, upon an orE duced or avoided.
dinary line, as at twenty miles, with the Independent, however, of mere economi- remarkable advantage, that increase of cal considerations, we remark the incalcu- speed does not increase the cost.
In some lable advantage of effecting the possibility respects, the tendency of increase of speed of railroads in countries where locomotive is even to lessen cost; for instance, it has power must ever remain inapplicable.- been shown that the leakage is diminished
Mountains may be bored, valleys may be in proportion to speed, and a saving is thus $ bridged with viaducts, or filled up with em- effected. Assuming, therefore, on the other 1 bankments, but the power to effect this hand, that the traffic on a line renders it g does not depend merely upon skill and the desirable to start trains every quarter in• a command of capital ; it is restricted within stead of every half hour, it is easily accom
the limits of prudential economy, of that plished. The statement of the Parliameni foresight in man which regulates expendi- tary Reporters shows how the economy on
ture by anticipated profit, which plants the atmospheric system would increase in the grain, that it may increase and multi- such cases. And here we must remark a
ply. These gigantic works will only be singular advantage of employing stationary y undertaken where the existing or antici- engines, alluded to by M. Teisserenc.*
pated traffic justifies the speculation; and The cost of a locomotive engine, in action, we may hence estimate, in some degree, is nearly the same whatever load it draws; the value of an invention which offers so and the cost of repairs is proportionably wide an extension of these advantages of smaller upon an engine of large size and communication, whilst it holds out increased power; such a motive power can therefore inducements of profit to enterprising capi- be only profitably worked with large trains, talists to promote the public benefit. and this very fact tends to limit considera
3. We now proceed to the relative ex- bly the number of daily trains, and consepenses of working, on which point the Par- quently the advantages of railway travelliamentary Reporters make the following ling. A necessary regard to public securemarks:
rity leads to the same conclusion. The “ This a question to which no general an
rapid succession of trains upon a line is a swer can be given, because it depends entirely constant source of danger, and delays are on the daily amount of traffic. We have no
therefore unavoidable. Upon an atmosphein doubt that a stationary engine properly pro- ric railway, on the contrary, the greater the
portioned, according to the rules we have in- number of trains started in a day (without dicated for a pipe three miles long, would be reference to their load), the more economiable to work trains on a line every quarter of cal is the system of working. By the regan hour, or every half hour, each way, during istered experiments on the Dalkey railway, the day (say of 12 hours), amounting to 144 miles. Now to work this distance by a loco- a train with a load of seventy-two tons, motive engine, at the moderate estimate of Is. takes five minutes and thirty-three seconds 4d. per mile, would amount to 91. 188., say 101. to perform the journey of a mile and three per day; whereas the stationary engine power quarters. Now, as upon this system no would not cost one half that sum, and conse- two trains can possibly move at once on quently a saving in working expenses would the same section of pipe, no delay is rearise of 18001. or 20001. per annum. But if only half this duty were required, the expenses
quired in starting the trains, to avoid danof ihe two ways of working would be much ger from their overtaking one another. As nearer equal; and again, if only half the lat- soon, therefore, as one train has passed off ter duty were to be performed, that is, of trains a section, the tube is ready to be exhausted starting only every two hours each way, the again (which is effected in about three to advantages would be on the side of the loco- five minutes), and to receive the next train motive engine. The fact is, that in one case immediately. Upon these facts it is easy the expenses per diem will be nearly the
to form any calculations; motives of econosame, whether working at intervals of an hour or at every quarter hour; whereas in the other my would lead to the starting of as many, the charge is nearly proportional to the work instead of as few trains as possible; and actually performed." —Report, p. 5.
whilst no accident could by any chance
occur from a rapid succession of trains, it This we assume to be correct; at the is needless to remark that the public would same time it will be borne in mind that, by be incalculably benefited. ascertained facts, the atmospheric railway * See his Report to the French Government, is now shown to work as easily at the rate p. 107.
+ Ibid, p. 107.