408 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[December, 



lifted up out of the groove two or tlirce inches higli, in any particular place 

 of the side that is not rivcttcil ; and, wlien kH down again, tlie edge will fall 

 into the groove, by tlie sjiring and weight of the plate, and stop close as lie- 

 fore. 



Therefore, if there is a large and light iron wheel fixed in the front of the 

 interior carriage, and close to the side wall on which the plate shuts into the 

 groove; and if this wheel is planted to stand two inches higher than the un- 

 der side of the covering plate, this wheel, as it passes along, will constantly 

 lift up the plates, and make an opening of two inches wide, or more, and 8 

 or 10 feet long; and, when the wheel has passed, the plate will fall down 

 into the groove, and close the joint, as before. 



Through this o]iening, a bar of iron may pass, that is fixed to the interior 

 carriage, may project over the side wall, and the outer end may be attached 

 to the exterior carriage by a chain or strap, and pidl it along upon its own 

 wheels and wheel track, which should lie along by the side of the wall of the 

 canal. 



The iron bar will not touch any thing as it passes through the opening, for 

 the iron covering may be lifted up two or three inches high ; but the bar 

 need not be more than one inch in thickness. 



In page 24, he says — 



The same principle, and the same form, may be advantageously applied to 

 convey goods and passengers in the ojien air, upon a common road, at the 

 same rate of a mile in a minute, or sixty miles per hour ; and without any 

 obstruction, except, at times, contrary winds, which may retard its progress, 

 and heavy snow, which may obstruct it. 



If a square iron tube be formed, 2 feet on each side. 4 feet in area, with 

 three sides, and one-half of the top, of cast iron, the other half of the top 

 made of plate iron or copper, to lift up and shut down in a groove in the cast 

 iron semi-top plate, as before described; and if a strong and light box or 

 frame be made to run upon wheels, within the tube, and an iron arm made 

 to pass out, through the opening made by lifting up the plate, as before 

 described, this arm may give motion to a carriage in the open air. and upon 

 the common road, without any rail-way, if the pressure within the tube is 

 made strong enough for the purpose. 



The opening of the iron plate shoidd be made in the middle of the top, so 

 that the iron arm may pass out, and stand upright a few inches above the 

 top, to which the strap should be attached, to communicate motion to the 

 carriage. 



The frame or box, within the tube, should be 10 or 12 feet long, and must 

 be guided by wheels, on all sides, as large as can be admitted, and as truly 

 formed and planted as possible ; the nundier will be 14 or 1 6. 



A piston, or vane, must be formed near the middle of the frame, to inter- 

 cept the air, and must be leathered all round, so as lightly or barely to 

 touch the sides of the tube. 



!, The inside, or middle of this vane, should be open, and the opening filled 

 up and closed by a valve, suspended by an axis across the middle of the open- 

 ing, so that this valve, by turning on its axis, may open the vane, and suifer 

 the air to pass through, and prevent its impulse ujion the vane and carriage, 

 or, by closing the valve, intercept the air, and give it motion. 



By this means, the conductor of the carriage may restrain and limit the 

 velocity, and stop the carriage, at any time and at any place, by a communi- 

 cation from the valve, through the opening, to the conductor on the outside ; 

 and this will he done without the least violence, shock, or chance of disor- 

 dering any thing, either within or without. 



Fig. 2 represents the vane within its frame m, m,m,m; the outside edge 



FiK. 2. 



Fig. 4. 



of the vane, a, b, c, d, is leathered all round, and the middle part, o, p, q, r, 

 is open, and is to be closed by the double valve, that is to turn upon its ver- 

 tical axis e, e. The valve will shut, half on one side of the vane a, b, c, d. 

 and half on the other ; when it is shut, the air will be intercepted, and the 

 impulse of the air will be given to the carriage ; but, when the valve is turned 

 a quarter of a circle, it presents its edge to the air, and leaves the interior of 

 the vane open for the air to pass by unobstructed, when the carriage will 

 gradually be stopped, by the friction of the road and the resistance of the 



outward .lir. It m.iy be put in motion again, as soon and as gradually, by 

 closing the valve. 



m, in, m, m, is the box, or open frame, that is to )iass through the tube, 

 on the wheels «, n, », n, n, to support the vane, and tlie iron arm, and to be 

 inii»elled by the air in the tube. 



rig. 3 is a section of the iron tube, with the wrought iron 

 semi-top, a, b, rivetted to the flanch, and represented as Ufted 

 up by the projection of the wheel under it; and of the 

 crooked iron arm w,as it is to come out through the opening, 

 and stand up for the carriage to be attached to it. 



The semi-top of cast-iron, o, /;, is to he screwed upon 

 the tube by the flanch p, aiul, at the edge o, is a small pro- 

 jection, which the edge of the wrought iron is to cover, to 

 prevent the rain or dust from entering into the tube. 



Fig. 4 represents a part of tlie tube, with the semi-top as lifted up at m, 

 and the section of the crooked iron arm, w, as it is to pass out of tlie open- 

 ing, besides the wheel that lifts it. 



The iron tube slioukl lie in the ground, with the top of it a few inches 

 above the surface ; and the carriage should run over it, with the wheels on 

 each side ; then the iron arm n, would draw the carriage in the fairest posi- 

 tion. 



The opening being, in this plan, made in the middle of the top of the tube, 

 instead of the side, the lifting wheel will act either way, without being re- 

 moved ; but the iron arm that passes through the opening (to draw the car- 

 riage), as well as the arm that is to pass through (to open and shut the valve), 

 must be changed to the other side, when the motion is changed to a contrary 

 direction. 



If the carriage is attached to the regulating arm that is to pass through the 

 opening, and tliat arm is supported by the main bar. the effect will be, that, 

 if by any accident the chain should let go its hold of the arm, the inside valve 

 would instantly fly open ; and the vane, being no longer impelled, would soon 

 stop of itself, and the chain might be replaced. 



In summing up tliis invention he remarks, 



Although the perfection of this work is not to be olitained but by time, 

 skill, experience, and the wealth of a nation, yet, upon a smaller scale, and 

 less rapidity, the expense will be moderate, and within reach ; and the value 

 of it, compared with the present mode of conveyance, would be abundantly 

 advantageous and desirable. 



Here then is a clear and full explanation of a mechanical arrange- 

 ment for employing the power of the atmosphere against a vacuum 

 inside a tube, and communicating the power so obtained to carriages 

 moving on a road on the outside. 



No impartial person, and not even Mr. Pinkus can read these pas- 

 sages without being convinced that this most ingenious, though unfor- 

 tunate inventor Medhurst, had brought the atmospheric system to the 

 point where it was taken up by Messrs. Clegg and Samuda, and that 

 his great practical failure was, that he could not, and did not make 

 the valve air-tight, upon doing which the entire success of tlie system 

 depended. 



And now that we have shown what Medhurst did, and what he 

 failed in, viz., "in making a continuous communication from the inside 

 of the pipe to the carriage tight enough to allow a useful degree of 

 rarifaction to be produced ;" we will examine what progress the in- 

 vention has made since then. 



On the 3rd January, 1839, Clegg and Samuda obtained a patent 

 "for a new improvement in valves and the combination of them with 

 machinery." This valve, says the inventor, " works in a hinge of 

 leather, (or other flexible material wliich is practically air-tiglit), simi- 

 lar to the valves commonly used in air-pumps. The extremity or 

 edge of these valves is caused to fall into a trough containing a com- 

 position of beeswax and tallow, or beeswax and oil, or any substance 

 or composition of substances wliich is solid at the temperature of the 

 atmosphere, and becomes fluid when heated a few degress above it ; 

 after the valve is closed, and its extremity is laying in the trough, the 

 tallow is heated sufficiently to seal up or cement together, the fracture 

 round the edge or edges of the valve which the previous opening of 

 it had caused, and the heat being removed the tallow again becomes 

 hard and forms an air-tight joint or cement between the extremity of 

 the valve and the trough. When it is requisite to open the valve, it 

 is done by lifting it out of the tallow with or without the application 

 of heat, and the before named process of sealing it or rendering it air- 

 tight is repeated every time it is closed. 



The inventor then goes on to describe how, by means of this valve 

 in combination with a line of partially exhausted tubes, it may be 

 rendered useful to move weights on railways. The combination em- 

 ployed being described precisely similar to that invented and published 

 by Medhurst. The only claim set up in the patent being " the method 

 of constructing and using valves as above described." The success of 

 this valve has been demonstrated by six months experience on the 

 Thames Junction Railway, and as the whole combination there em- 

 ployed, except the valve and mude of sealing it, is precisely that invent- 



