2G0 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[August, 



the leather between the plates and the bar to act as a hinge, similar 

 to a common pnmp valve ; the other edge of the valve falls into a 

 groove which contains a composition of beeswax and tallow : this com- 

 position is solid at the temperature of the atmosphere, and becomes 

 fluid when heated a few degrees above it. Over this valve is a pro- 

 tecting cover, I, which serves to preserve it from snow or rain, formed 

 of thin plates of iron about five feet long hinged with leather, and the 

 end of each plate underlaps the next in the direction of the piston's 

 motion, thus ensuring the lifting of each in succession. To the under- 

 side of the first carriage in each train is attached the piston, B, and its 

 appurtenances ; a rod passing horizontally from the piston is attached 

 to a connecting arm, c, about six feet behind the piston. This con- 

 necting arm passes through the continuous groove in the pipe, and 

 being fixed to the carriage, imparts motion to the train as the tube be- 

 comes exhausted ; to the piston rod are also attached four steel wheels, 

 H ir, (two in advance and two behind the connecting arm,1 which serve 

 to lift t!ie valve, and form a space for the passage of the connecting 

 arm, and also for the admission of air to the back of the piston; 

 another steel wheel, D, is attached to the carriage, regulated by a 

 spring, which serves to ensure the perfect closing of the valve, by run- 

 ning over the top plates immediately after the arm has passed. A 

 cop])er tube or heater, N, about ten feet long, constantly kept hot by a 

 small stove, z, also fixed to the under side of the carriage, passes over 

 and melts the surface of the composition (wdiich has been broken by 

 lifting the valve,) which upon cooling becomes solid, and hermetically 

 seals the valve. Thus each train in passing leaves the pipe in a fit 

 state to receive the next train. 



The continuous pipe is divided into suitable sections (according to 

 the respective distance of the fixed steam engines) by separating valves, 

 y"and Q, whidi are opened by the train as it goes along: these valves 

 are so constructed that no stoppage or diminution of speed is necessary 

 in passing from one section to another. The exit separating valve, Q, 

 or that at the end of the section nearest to its steam engine, is opened 

 by the compression of air in front of the piston, which necessari'y takes 

 place after it has passed the branch which communicates with the air- 

 pump ; the entrance separating valve,/, (that near the commencement 

 of the next section of pipe,) is an equilibrium or balance valve, and 

 opens immediately the piston has entered the pipe. The main pipe 

 is put together with deep socket joints, in each of which an annular 

 space is left about the middle of the packing, and filled with a semi- 

 fluid : thus any possible leakage of air into the pipe is prevented. 



From the result of the experiments already made, the inventors cal- 

 culate that a main pipe of eighteen inches diameter will be sufficiently 

 large for a traffic of 5,0OU tons per day, viz., 2,500 tons in each direc- 

 tion, supposing the gradients of the road to average 1 in 100. 



Note. — A main pipe, 18 inches diameter, will contain a piston of 254 

 inches area : the usual pressure on this piston, produced by exhausting the 

 pipe, should he 8 lb. per square inch (as this is the most economical degree 

 of vacuum to work at, and a large margin is left for obtaining higher vacuums 

 to draw trains heavier than usual on emergencies) — a tractive force of 2,032 

 pounds is thus obtained, which will draw a train weighing 45 tons, at 30 

 miles per honr up an incline rising 1 in 100. Two and a half miles of this 

 pipe will contain 23,324 cubic feet of air, i{j of which, or 12,439 cubic feet, 

 must he pumped out to effect a vacuum equal to 8 lb. per square inch ; the 

 air pumji for this purpose should he 5 feet 7 in. diameter, or 24-7 feet area, 

 and its jjiston should move through 220 feet ])er minute, thus discharging at 

 the rate of 24-7 x 220 = 5,434 cubic feet per minute at first, and at the rate 

 of 2,536 cubic feet per minute when the vacuum has advanced to 16 inches 

 mercur)', or 8 lb. per square inch, the mean quantity discharged being thus 

 3,985 feet per minute; therefore VTi¥¥'= 3'1 minutes, the time requireil to 

 exhaust the pipe; and as the area of the pump piston is 14 times as great as 

 that in the pipe, so the velocity of the latter wdl he 14 times as great as that 

 of the former, or 220 feet per minute x 14 = 3,080 feet per minute, or 35 

 miles per hour : hut in consequence of the imperfect action of an air-pump, 

 slight leakages, &c., this velocity will he reduced to 30 miles per hour, and 

 the time requisite to make the vacuum increased to 4 minutes : the train will 

 thus move over the 2 J miles section in 5 minutes, and it can he prepared for 

 the next train in 4 minutes more, together 9 minutes; 15 minutes is there- 

 fore ample time to allow between each train, and supposing the working day 

 to consist of 14 hours, 56 trains can he started in each direction or 2,520 

 tons, making a total of 5,000 tons per day. The fixed engine to perform this 

 duty will he 110 horses power, equivalent to 22 horses power per mile in 

 each direction. 



The next item to be considered is the comparative cost of the two 

 systems. 



1st. The necessity of liaving the railway comparatively level, causes 

 the present enormous outlay fur earth-work, viaducts and tunnelling: 

 it also increases the cost of land, not only by lengthening the line to 

 save cutting and embankment, by the quantity wasted on each side of 

 the road wherever an endjankment or cutting is required. Thus if an 

 embankment or cutting has to be made of thirty feet, at least sixty feet 



of land must be covered on each side of tlie railvvav in order to obtain 

 sufficient slope, making a width of 120 feet, besides the roa<l, except 

 where they occur in stone oi chalk. The comparative expense of this 

 item between the two systems can be ascertained by referring to the 

 average cost of forming a turnpike road and that of the ptinci])al rad- 

 ways now in operation.* 



LOCOMOTIVE SYSTEM. 



Per mile. 

 Taking five of the principal Railroads as the basis of the 



calculation, their average expense of formation has 



exceeded £36,000 



And the original stock of Locomotives 1,600 



£■37,000 



ATMOSPHERIC SYSTEM. Per mUc. 



The average expense of forming a turnpike road through- 

 out England has been 3,000 per mile, hut for the 



atmospheric railroad, say £4,000 



Allow extra for road-bridges 2,000 



Rails, chairs, sleepers, and laying down 2,500 



JIain i)ii)e and apparatus complete (on a scale for trans- 

 porting 360 tons per hour, or 5,000 tons per day of 

 fourteen hours, on a road with gradients of 1 in 100) 5,200 



Fixed engines, air pumps, and engine-houses 1,400 



TraveUing pistons 20 



£15,120 

 Saving per mile in forming and furnishing on the At- 

 mospheric system 22,480 



£37,600 



Annual expenses of working per mile, when conveying fivo thousand 

 tons per d.iy. (This is beyond the average quantity conveyed on the 

 Liverpool and Manchester Railroad) : — ■ 



LOCOMOTIVE SYSTEM. 



Per mile. 



5 per cent, interest on capital sunk £37,600 £1,880 



Maintenance of way 450 



Locomotive department, including coke 1,800 



£4,130 



ATMOSPHERIC SYSTEM. 



Per mile. 



5 per cent, interest on capital sunk, viz., £15,120. . . . £756 



Maintenance of w*ay, and attendance on mains 300 



Wear and tear of fixed engines, 5 per cent, of cost . . 70 



Coal -75 lb. per ton per mile, 214 tons, at 20s 214 



M'ages to engine men and stokers 60 



Wages to train conductors 26 



Renewal of travelling apparatus and composition, and 



sundries 200 



£1,626 

 Annual saving per mile on the Atmospheric system . . 2,504 



£4,130 



Total expenses per ton per mile on the Locomotive system 1-54 pence. 



Ditto ditto ditto on the Atmospheric ditto 0'6 do. 

 Exclusive of carriages and management, which may he taken as the same 

 on both systems. 



From the above description, and the calculations made by the inge- 

 nious inventors, together with the success of the experiments which 

 have been made, almost daily, for the last month, our readers will be 

 able to form some judgment as to the probable introduction of this new 

 system into general use ; we sincerely hope that the inventors will be 

 able to obtain an ample reward fur the great expence and labour they 

 have devoted to the first ex|ieriment, which has, to say the le;ist of it, 

 been carried out by them in a very spirited manner. 



* The calculations are founded on the reports of diflisrent companies whose 

 railways are complete or in a forward state. 



CORRECTION— CANDIDUS. 



Allow me, Sir, to correct an error in F.isciculns, No. 16, hy your Corres- 

 pondent Candidns, in last month's Journal, he there states that the Medal 

 was given by the Institute to the late Sir J. Soane. The Medal was by public 

 subscription, as doubtless you remember. 



