1845.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



149 



of the problem. 'It must be more agreeable,' says lie, with great 

 naivett; to travel in the open air than in a dark tube, si-tting aside the 

 pleasure of seeing the country througli which one is passing.' Med- 

 hurst proposed to transmit the action of a piston contained in thotube 

 to carriages placed above it.by a longitudinal opening closed by means 

 of an ingenious apparatus which he called the water-valve. This ap- 

 paratus required that the tube and railroad should be on a constant 

 level ; it was abandoned. 



"The American engineer Pinkus took out a patent in 1834 for a 

 valve of rope, which did not succeed better than the water-valve. 



" Lastlv, Messrs. Clegg and Samuda proposed a new valve, tried at 

 Chaillot "in ls38, two years after with more success at Wormwood 

 Scrubbs, near London, and more recently applied to a railway of about 

 two miles in length from Kingston Dalkey, in Ireland. 



"To resume, then, the history of the invention of atmospheric rail- 

 ways :— The first idea belongs "to Papin : Medhurst opened the way 

 to the complete solution of the problem : Messrs. Clegg and Samuda 

 proved the praciicability of the invention, to avail ourselves of an 

 English term, also of French origin. We ourselves dare to claim the 

 honour of having completed— of having realised the idea ofrapin— 

 of having utilised it. 



" Extract from the Report of lite Sittings of the '^cadanie des Sciences.' 

 "M. Arago submitted to the Academy a small model of the new 

 valve, invented by M. Hallette, for the pneumatic tube which forms 

 the principal part of the apparatus of the atmospheric railways. M. 

 Hallette places above the propulsion tube two longitudinal semi-cylin- 

 ders, or rather two grooves, fixed alongside the slit or aperture of the 

 tube, with their concavities opposite. Each of these grooves contains 

 elastic tubing, to be filled with air or water. When these tubings filled 

 with air are sufficiently expanded, they touch each other in part of 

 their surface, act as the lips of the human mouth, and so, completely 

 intercept the communication between the interior and exterior of the 

 tube. When the piston is in motion, the arm, which unites it to the 

 carriages, glides between the two elastic tubes, which close imme- 

 diately after its passage. This arm, which penetrates by its wedge — 

 form between the two tubes, passes between them with very little 

 friction; nevertheless M. Hallette, to ensure their durability, covers 

 those portions of the tubes which come in contact with leather. — M. 

 Arago observed that a system of pneumatic tubes fixed along the quay 

 of the Seine would cost much less to construct than a towing path, and 

 that the employment of steam to draw boats had many great advan- 

 tages over the employment of horses." 



Explanation of the apparatus, 

 " The propulsion-tube is always placed above the ground, exactly 

 between the two rails; but the tube differs from that oif Messrs. Clegg 

 and Samuda, 1st. in form, 2nd. in dimensions, 3rd. in the manner in 

 which it is attached to the ground, 4th. and principally, in the manner 

 of closing the longitudinal tube. 



" 1. The form of the tube is indicated in the plate by a transverse 

 section'during the passage of the piston. 



"2. The diameter is extended to Om- 50 (about 1 ft. 7 in.) to make 

 provision, in the first instance, for all future requirements. 



" 3. In place of being attached to the cross-sleepers which carry the 

 rails, and which are consequently liable to be disturbed, the tube is 

 isolated and independent of the cross-sleepers; it is fixed, as may be 

 seen by the figure, on a line of piles, of a length and strength to be 

 determinedby the nature of the soil; the top of each pile has a groove 

 cut in it which contains a blade projecting from the tube. It is there- 

 fore very easy to rectify the parallelism of the tube ; to move the 

 blocks a little on either side all that is required is to ram down addi- 

 tional earth; a blow or two on the head of the pile will sink it 

 slightly ; and a wedge placed under the vertical blade will raise it 

 a little. 



" 4. The method of closing the tube is borrowed from nature, instead 

 of being exclusively mechanical. Man has the faculty of breathing, 

 and of retaining or breathing out the air. The respiratory orifices 

 are opem-d or closed at will by the nostrils and lips. A pencil, or the 

 stalk of a flower, can be placed between the lips without ;idmitting the 

 air. To follow this model it was necessary to introduce lips to the 

 longitudinal orifice of the tube. On the edges of the opening in the 

 propulsion-tube are placed two other small tubes, which would be 

 tangent to each other if they were entire, but which are defalcated in 

 the direction of their length, so as to form as it were two troughs with 

 their openings opposite to each other. Into these troughs are intro- 

 duced two hollow tubes, of some substance impermeable to air and 

 water, and capable of retaining compressed air. When filled with 

 either of these two elements, or both mixed, the tubes expand, touch 

 each other in part of their surface, and exercise a mutual compression 

 dependent on the degree of internal pressvire, which may be always 



regulated as required. These tubes act as lips j they are artificial but 

 real veritable lips, which permit without difficulty, and almost without 

 friclion, the most rapid motion of the arm of the piston without sulTer- 

 iii" the air thereby to enter the propulsion-tube. The tube is inter- 

 rupted at the stations for the construction of siding tubes. Stationary 

 engines are established at intervals of about 5 miles. 

 Reference to Emjravings, Plate XII. 

 Fig. 1 a longitudinal view, and fig. 2 a transverse view, showing the con- 

 nection of the carriage with the propulsion tube and the exhaustion tube. 

 I'ii;. 3 is a top view of the propulsion tube, with part removed to show the 

 entrance valve and the piston in its progress; the entrance of the tube is 

 has a trumpet mouth, to allow of the entry of the piston during its passage. 

 Fig. 4 is a aide view of the propulsion tube, part being removed to show a 

 section of the piston with its regulating cock. Fig. 5 is an enlarged section 

 of the lube and piston. 



A, are piles upon which the propidsion tube is fixed ; 15, cross sleepers to 

 carry the rails ; C, the exhaustion tube, furnished with a valve, F, like a sluice 

 cock, to cither close or open a communication with the propelling tube ; 

 T), the propulsion tube; E, the entrance valve ; F, sluice valve; G, piston ; 

 II, the connecting arm ; I, regulating cock ; J, key to cock, regulated by the 

 conductor sitting on the front seat of the carriage, K. 



Operation. — Before the train arrives at the entrance of the propul- 

 sion tube, the valve, F, of the exhaustion tube is opened, and the 

 en"ines are set to work the air-pump, for the purpose of exhausting 

 the air from the propulsion tube to the necessary degree of rarefac- 

 tion, this being obtained, the train is then put in motion by allowing 

 the piston to enter the propulsion tube, which by its passage opens 

 the entrance valve, and on its leaving closes the exhaustion valve 

 without any assistant being required. If it be desired to arrest the 

 progress of the train when coming to a station, or for any other cause, 

 the conductor who sits in the front of the carriage opens the regulat- 

 ing cock, I, in the piston, G, which allows the air to rush in to the 

 front of the piston and arrest its progress, and at the same time he 

 applies the break. In a similar manner the conductor is enabled to re- 

 gulate the velocity of the train going down inclined planes. When 

 the train is not in motion the valves of the exhaustion tube at each 

 end, and also the two entrance valves, are closed ; the piston is kept 

 in equilibrium on the entrance side by the pressure of the atmosphere 

 remaining in the tube and the breaks, and on the other side by the 

 natural pressure of the atmosphere. When the train is to start again 

 the valve of the exhaustion tube on the advance side of the piston is 

 opened, and the entrance valve at the opposite end is also opened, when 

 the air is suflSicently rarefied, and the breaks released from the carriage, 

 the train proceeds at the required velocity. The conductor is at 

 all times enabled by the cock, 1, to regulate the velocity of the train ; 

 there is also a barometer, L, placed before him, with a scale to indi- 

 cate the state of rarefaction of the air in the tube. 

 Comparative Expense. 

 "The ten railways executed in France have cost on the average 

 .£30,000 per mile, according to M. le Comte Daru. The three great 

 lines which have been completed have cost on the average ,£24,000 a 

 mile, according to the Manorial de Rouen, cited in the Monileitr Uni- 

 ttrsel of the 9lh of February 1844. It is known that the estimate of 

 £20,000 a mile adopted by the law of June llth has been found too 

 small. The railway by the present system would be laid down by the 

 side of a public road or canal. The expense of moving earth would 

 therefore be the same as for small roads. The construction of an 

 ordinary road costs in France, according to M. Comte Daru, £9G0 a 



mile. o'^firt 



Embankments, sleepers, rails .. .. •• 2,300 



Stations and various buildings 640 



Propulsion-tube and accessories .. .. .. 10,240 



Engines, pneumatic apparatus it 4,000 for every 



5 miles ; for one mile . . . . • • • • °^^ 



Carriages . , . . . . ^^0 



£14,620 

 "Say £15,000 a mile. It will be seen that the real economy of the 

 system is estimated below its true amount when taken at 30 per cent 

 of the cost of railroads for locomotive engines." 



The advocates of the atmospheric propulsion principle generally 

 draw their comparison of the expenses by allowing only a single line 

 of rails on the atmospheric principle, against a railway with double 

 lines of ways on the locomotive princijile. This is making a false 

 assumption, for the atmospheric system, in order to obtain any degree 

 of certainty in the traffic, requires a double line of ways, two engines 

 at each station, and so forth : in such case the economy of the system 

 at once vanishes ; in fact the comparative expenses of the construc- 

 tion of the railways on the atmospheric and locomotive priafc'jl.es 

 , will be greatly against the former. _ 



' 20 



