1844.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



340 



REPORT ON THE ATMOSPHERIC RAILWAY. 



To the Committee of Manaijement of the Cromford and Higlt Peak Railwaij. 



Gentlemen — Agreeably to the instructions which I received at the 

 meeting, held on the 7tli of March last, I proceeded shortly afterwards, ac- 

 companied by Mr. Brittlebank, to Dublin, to examine the Amospheric Rail- 

 way between Kingstown and Dalkey, and to ascertain whether or not the 

 principle might be applied with advantage to our inclined planes. In our 

 investigition we received every attention from the gentlemen connected with 

 the undertaking, and were not only allowed to examine every part of it mi- 

 nutely, but were also furnished with every information derived from their own 

 experience. 



For the information of those gentlemen who may not be conversant with the 

 principle of the invention, I will explain its peculiarities in contrast with 

 those of other railways, as carried out, and in daily operation at Kingstown. 

 On ordinary railways, the train or load is moved along by means of an en- 

 gine, attached thereto, and moving with it ; on the contrary, on the Atmos- 

 pheric principle, the load is moved by means of a stationarii engine, at a 

 considerable distance from, and totally unconnected with it; differing, how- 

 ever, not oidy from railways where the locomotive engine is used, but also 

 from those on which the stationary engine is the propelling power ; inas- 

 much, as the rope is entirely dispensed with, and its place supplied by the 

 pressure of the Atmosphere. This therefore, forms the peculiar feature of 

 the system, and constitutes the difference between it and all other modes of 

 propulsion on railways. 



The means by which the principle is put in practice, are simply these : — 

 Between the rails, and along the entire length of an ordinary single line 

 of railway, a pipe is laid of, say, fifteen inches diameter. This is connected 

 at one end by a steam engine, the power of which, is applied to a large air 

 pump, which being set to work, pumps out or exhausts the air from the interior 

 of the pipe. Within this pipe is a piston, or plug, which works freely along 

 its entire length; but, nevertheless, so tight that but little air can pass from 

 one side to the other. This being so far understood, it is clear, that by 

 pumping out the air from the front side of the piston, the pressure of the 

 atmosphere on the bacic of, or behind it, will force it forward with a velocity 

 dependant, 1st, on the degree of rarifaction of the air in front of the piston ; 

 2nd, on the weight of the load to be drawn ; and 3rd, on the inclination of 

 the railway. The great difficulty however, and that which yet remains to be 

 explained, is, how to communicate the power which is inside the pipe, to the 

 load which is outside. To accomplish this, there is a longitudinal opening 

 or slot on the upper side of the pipe, which is continued throughout its en- 

 tire length. In this opening there is a bar of iron, which is attached below 

 to the piston within the pipe ; and, above, to the leading carriage of the 

 Iraiu, or rather one used exclusively for that purpose, to which the train is 

 attached ; so that if the former moves along the latter must move with it. 

 It is evident, however, that during the time the engine is at work, exhausting 

 the air from the pipe, the opening or slot of that portion of it, which is be- 

 tween the engine and the piston, must be closed perfectly, or as nearly as 

 possible, air tight, otherwise a vacuum could not be formed. This is effected 

 by means of a leather valve, hinged on one side of the opening, over which 

 it falls, and extending its entire length, perfectly covers and closes the whole 

 of it. This valve is covered with iron plates both on its upper and undei 

 sides, for the purpose of strengthening it, and is rendered more perfectly air 

 tight by means of a composition of wax and tallow, into which the outer edge 

 falls when closed. A heater attached to the carriage completes the process 

 by melting the composition as it runs along its surface, and effectually seals 

 it in readiness for re-exhaustion. 



There are other valves, hut of a different description, which close across 

 the pipe, and by means of which, it is separated into divisions ; one of these 

 is placed at that end of the pipe which is opposite to the engine, so that 

 when closed, the pumping can commence, and a vacuum be formed at any 

 time, so as to be in constant readiness. When the train is about starting, 

 and the air pump has produced a sufEcient vacuum, as indicated by the baro- 

 meter, the travelling carriage, with the train attached, is moved by hand 

 until the piston enters the open end of the pipe, within a short distance of 

 which the closed separating valve is placed. This valve, immediately on the 

 entrance of the piston, falls down, by means of a self-acting apparatus, and 

 the pressure of the atmosphere is instantly transferred from it to the piston, 

 and motion forthwith commences. 



During the passage of the train, the longitudinal leather valve has to be 

 raised or opened, to allow the bar before spoken of, as connecting the piston 

 wit/iin the pipe to the train on the outside, to pass ; this is done by means 

 of a roller attached to the piston frame, within the pipe, which is placed a 

 little in advance of the bar, but behind the piston; and which, as it passes 

 along, raises the valve just sufficient to allow the bar to pass, which being 

 done, the valve falls into its place again, and is immediately pressed down by 

 another roller which follows for that purpose ; the heater follows and seals 

 the composiliion. and the whole is then ready for the next train. 



The Atmospheric Railway, at Kingstown, is 1-J miles in length, and in that 

 distance, rises by variable gradients i)l feet, which is equal to 1 in 115, or 

 about 52 feet per mile. It has a main or pipe of 15 inches diameter, and is 

 exhausted by an air pump of G7 inches diameter, and S.J feet stroke ; worked 

 by a steam engine of 100 horse power, making about 20 strokes, and dis- 

 charging upwards gf 5000 cubic feet of air per minute. The degree of ex- 



haustion varies with the load ; but for ordinary passenger trains, it ranges on 

 the barometer from 12 to 16 inches of mercury, which is equivalent to a 

 pressure of from 6 to 8 pounds per square inch. The trains weigh from 15 

 to 20 tons, and the time occupied in working the engine for each, is about 

 G minutes ; that is, 2^ minutes in exhausting the main, and 3-i in working 

 the train up the IJ miles. Hence the mean rate of travelling is about 30 

 miles an hour, but the greatest speed occurs about the middle of the journey, 

 at which point the train moves at a rate of 40 miles an hour. The railway 

 does not appear to be by any means adapted for high velocities, there being 

 curves upon it which have a radius of not more than 500 feet ; but this I be- 

 lieve was unavoidable, the railway having to follow the line of an old tram 

 road, which had been used for the conveyance of stone from the (juarries at 

 Dalkey ; as a mere experiment, however it is valuable, inasmuch as it proves 

 that curves of so short a radius may be traversed at a speed of from 30 to 40 

 miles an hour without danger. 



Without entering into the subject of the Atmospheric Railway, beyond the 

 legitimate object which we have in view, I may here remark that the 

 application of the principle to a long, single line of railway, with an exten- 

 sive, irregular, and miscellaneous traffic, would appear to me, in the present 

 state of our knowledge of its capabilities, an experiment of doubtful success ; 

 confined however, to such lines as would not require that trains should be 

 travelling in opposite directions at the same time, and to situations where 

 good locomotive gradients, could not at a reasonable expense be obtained ; 

 the invention offers advantages which are not found in, nor could be accom- 

 plished so well, so safely, or so economically by any other with which we are 

 at present acquainted. But, before making any further remarks on this part 

 of the subject, I will proceed in considering it with reference to its applica- 

 tion to our Inclined Planes. 



In order to shorten and simplify the enquiry, I purposely omitted entering 

 upon anything which might be considered as common to both systems, and 

 confined myself to those points only, in wliich they might be expected to 

 differ. Limiting my investigation therefore exclusively to the mode of ap- 

 plying the power; 1 directed my attention, first, to its mechauical practica- 

 bility ; secondly, to the comparitive loss of power ; thirdly, to the working 

 expenses, near and tear, &c. ; fourthly, to llie requisite permanent outlay ; 

 and lastly, to its comparative advantages and disadvantages. 



As regards the first subject of enquiry, namely, its mechanical practicabi- 

 lity ; I found that the working parts of such as are most subject to wear, 

 were by no means of a complicated character, nor such as would require 

 either elaborate workmanship, or other than the most common materials in 

 their construction ; consequently, neither from their form or material, are 

 they such as, under ordinary circumstances, would easily be deranged, or 

 soon worn out, or require other than common workmen and labourers for 

 their repair, renewal, or management. 



Exclusive of minute details, the only parts subject to wear are the piston, 

 and the valve which covers the pipe ; the latter being merely a strip of 

 leather between iron plates, protected from the influence of the weather by 

 the composition of wax and tallow, and merely raised a httle out of its placft 

 once for each train, can scarcely be said to be subject to wear of any kind. 

 The same may almost be said of the piston, which is simple and strong, and 

 requires no further attention than the application of a little grease occasion- 

 ally, and the renewal once a week, or so, of the leather packing, which can 

 be done by an ordinary workman, or even an intelligent labourer. On the 

 whole, therefore, there is nothing whatever in the system which would re- 

 quire a superior description of men to those which we now employ, nor any 

 thing which they could not comprelieud and manage as well as their present 

 employment. 



The second object of my enquiry, and one which I considered of great im- 

 portance, was to ascertain the precise lose of power, from leakage. I was 

 the more anxious for satisfactory information on this head, because the sub- 

 stitution of a rope of air, for one of hemp or iron, has been much dwelt 

 upon, and the difference of their weight and friction considered as an addi- 

 tion to the nett available power : but however plausible this may appear, it 

 is possible that a loss of power may arise to as great an extent from pumping 

 out the superfluous air from a pipe, as in moving a heavy chain or rope ; 

 and if it should be found that the loss from leakage in the one case is equal 

 to the loss from friction in the other, it would be evident that in this respect 

 no advantage would be gained by one as compared with the other. The loss 

 from leakage on the atmospheric system (supposing the permanent joints to 

 be perfectly tight) can only arise, first, from the longitudinal valve ; second, 

 from the travelling piston; and third, from the air pump piston. 



The loss from the latter, whatever its amount, which however cannot be 

 great, is permanent and irremediable. That arising from the travelling pis- 

 ton, is also, to a certain extent, permanent, but less in proportion as the 

 velocity increases and the degree of exhaustion is diminished, while that from 

 the longitudinal valve, which I consider the source of by far the greatest part, 

 is proportioned to its length, and the degree of exhaustion of the main, 

 dimiuishing of course as the piston approaches the engine : the loss, how- 

 ever, from this cause depends much on the attention paid to the state of the 

 valve and the sealing composition. On our inclined planes, the loss of power, 

 wliich arises from the weight and friction of the chain and other causes, 

 amounts to about thirty per cent. ; and, judging from information which I 

 obtained at Kingstown, that arising from leakage on the atmospheric system 

 is as nearly the same as possible. This estimate of the loss is confirmed by 

 some experiments made by Mr. Stephenson, the particulars of which were 

 given me by the engineer of the railway, in one of which the loss from 



