We shall now briefly describe what has been generally termed "Hallette's system of atmospheric railway;" although, strictly speaking, the system is not new, being in fact a combination of Mr. Pinkus's two plans, and the improvements consisting of modifications of different parts of the apparatus, chiefly the continuous valve, the piston, and the mode of connecting a pneumatic locomotive engine with the pneumatic main, as proposed by Mr. Pinkus in his patent of 1836. Mr. Hallette's improvements form the subjects of two patents in this country, which were taken in the name of Mr. W. Newton. In his first patent Mr. Hallette employs a piston, travelling in the air tube as proposed in Mr. Pinkus's first plan; but the longitudinal valve is on the principle of that proposed in Mr. Pinkus's second plan, already described, in which the slit is closed by two elastic plates of metal, extending the length of the tube; these plates in Mr. Hallette's plan being replaced by flexible hose, filled with air or water, or a portion of both.
Fig. 1 represents a transverse section of the tube, and of the arm by which the piston is connected with the leading carriage of the train; fig. 2 is a longitudinal section of the tube and piston; and fig. 3 is a plan of the tube and of the piston arm. a is the tube, having a slit or opening for the passage of the piston arm, extending along its upper side, and strengthened below by a rib, b. Along each side of the slit extends a semicircular trough or recess c c, cast upon the tube, and in each recess is lodged an air tight flexible tube or hose d d, filled with compressed air, and any suitable liquid; and the two hose lying in close contact with each other close hermetically the longitudinal slit. The travelling piston is composed of a short tube e, attached to a forked leverf, which receives within its fork the hollow arm g, and is jointed thereto by the pin h. The piston carries at its circumference two cupped leathers secured by rings at i i, to form an air tight joint with the interior of the atmospheric main, and two pieces of brass at k k, which fill up the breadth of the slit, and prevent the passage of the air at that part into the vacuum in front of the piston.
The piston is open at the fore end, but at the back it is closed by hinge valves m m, which are connected by rods to the lever n n (within the hoHow arm), by means of which they can be raised when it is requisite to destroy the vacuum, in order to prevent the advance of the train. The piston is free to turn upon the pin h, being counterbalanced by the weight of the leverf, and the latter has several collars of stout leather, screwed up between two rings at o o, to deaden the concussions which might arise from any irregularities in the level of the main. The hollow arm g, is made of wrought iron, and in its horizontal section has the form of a weaver's shuttle, as is shown in the plan. This arm is connected to the leading carriage by a hinged clamp p, attached to a stout bar of wood g, secured to the under side of the frame of the carriage. The atmospheric tube is not attached to the transverse sleepers which carry the rails, but is supported upon a number of vertical posts s, driven into the ground midway between the rails, and having a notch in the upper end to receive the rib of the tube, and it is steadied laterally by chairs t, bolted to the sleepers.
Mr. Hallette's second plan resembles in principle that of Mr. Pinkus, in which a pneumatic locomotive was substituted for a steam locomotive, the pneumatic engines communicating with the pneumatic main, in which a vacuum was to be maintained; but Mr. Hallette proposes, instead of a vacuum, to employ compressed air. Mr. Hallette's chief improvements in the details of the plan consist, firstly, in the valve or apparatus for closing the longitudinal opening in the tube; and secondly, an apparatus whereby the locomotives may be supplied with compressed air, without creating too much friction, and thereby injuring those parts of the longitudinal valve with which the instrument comes in contact.
The accompanying figure represents a transverse section of the pneumatic tube, and the connecting apparatus a, is the pneumatic tube, formed of sheet iron, and supported by chairs b. The longitudinal groove is closed by means of two long cushions, c, the surfaces of which, when at rest, are by their own elasticity maintained in close contact with each other, and thereby prevent the passage of air between them, except when forced apart for the purpose of allowing the compressed air to enter the locomotive engines. These cushions are made of leather, and filled with a composition of gelatine and molasses, or any other suitable compound; and the edges of the tube are pinched between the doubled-over edge of the tube, and an iron band, d' is a hollow disc, from 3 to 5 feet in diameter, and in its transverse section resembling a double convex lens. It is mounted on hollow axles g, which work in stuffing boxes, attached to the locomotive, and form a communication between the disc and the locomotive engines. Near the periphery of the disc are a number of small apertures e, closed on the inside by valves of soft leather f.
The tube being filled with compressed air, and the disc being inserted between the cushions, the air will force open the valves f, and instantly fill the disk with air of the same density, and as the disk revolves and finally passes out into the atmosphere, the compressed air within the disc closes the valves, f, in which it is assisted by a spring. As the engine advances along the rails, the disc revolves between the cushions, which recede as it advances and close upon it behind, so as to preclude the escape of the compressed air within the tube, into the atmosphere; and to reduce the friction between the disc and the cushions, the latter are lubricated with a mixture of suet and powdered talc. The pneumatic tube is divided-into sections of about 150 yards long, and at the end of every section, a yard or two, with its cushions, is sloped down to the revolving disc, to enter and leave the tube more gradually. We conclude our account of the atmospheric modes of propulsion, by a description of Taylor and Conder's patent electro-magnetic railway. This invention consists in the application of electro-magnetic power, to connect the piston carriage of a train with the driving piston within the tube.
Fig. 1 is a longitudinal section, and Fig. 2 a cross section of an atmospheric railway tube, and piston carriage, showing the manner in which the connexion is effected. t is the tube, in the top of which there is a longitudinal slit or opening as usual, but much narrower; c is a continuous air tight cover which is bolted down upon the longitudinal slit. The tube t is of iron, but the cover c is made of copper, brass, or some other substance not susceptible of the electro-magnetic influence, and bolted to the tube by copper bolts; d is the driving piston, which consists of two end discs d d, of the same diameter as the interior of- the tube (or nearly so), connected by a rod r, which carries (as here shown) four upright square pieces a a a a, called armatures, which project upwards through the top slit in the tube, and fit into the square space within the cover c. These armatures are made on the upper part of some substance not susceptible of the electromagnetic influence, as brass or wood, but capped at the top by pieces of iron, secured by copper bolts. p is the piston carriage, to the bottom of which there is attached (instead of the usual piston connecting rod) four electro-magnets m m m m of the peculiar form shown in Fig. 2, each of which presents its two extremities or poles to the sides of the cover c.
The power of the magnets may be increased by inclosing them in a tube or case of iron, leaving the extremities or poles open g is a galvanic battery placed in the piston carriage, and which may be of any approved form and of any required power; w w are wires by which the battery is connected with the electro-magnets m m m m. The mode of action is as follows. Motion being given to the piston by exhaustion (more or less) from the tube of the air in front of the piston, and the magnets being at the same time connected with and excited by the battery, the magnets act by induction on the iron armatures aaaa attached to the piston rod, as they come within the sphere of their attraction, (the cover c offering no obstruction to that attraction, as it is of a substance not susceptible of electromagnetic influence,) whereby the magnets and the armatures become virtually coupled together, and draw along with them whatever carriages may be attached to the carriage which holds the magnets and battery. When it is desired to disconnect a train from the piston, this is effected instantaneously, by disconnecting the wires of the battery from the magnets.
Instead of using one electro-magnet for each armature of the form before described, two ordinary horse-shoe magnets may be employed, care being taken that the positive pole of the one magnet shall be placed opposite the negative pole of the other.
To allow air to pass through the piston as may occasionally be required, the discs d d of the piston are provided with valves v v, which are respectively connected to vertical iron spindles s, which terminate within the cover c immediately opposite small electro-magnets n n affixed beneath the carriages; so that when it is desired to open either valve, all that is necessary is to excite the magnet which commands the spindle of the valve (by connecting it to the galvanic battery), on which the magnet will draw the spindle upwards, and thereby open the valve.