a represents the side of a warehouse; b a cylinder truly bored, and fixed ver tically to the wall ; c a piston fitting air-tight in the same cylinder, and sus pended from a rope or chain passing over the jib k ; g a load attached to the rope ; d a double-barrelled air-pump worked by the two cranks which may be turned by hand or by steam ; a a pipe of communication between the air pumps and the cylinder, and fitted with a cock f. Now if the pumps be set in motion, the air in the cylinder will become more and more rarefied, and the pressure of the external air will at length so far exceed the internal pressure, as to cause the piston to descend, and, consequently, to raise the load g. But this would be an exceedingly inconvenient form ; for the machine, in its powers, would be confined within very narrow limits by the largest cylinders which could be constructed ; but in the excellent arrangements of Mr. Hague, which we now proceed to describe, it will be seen that any load, however great, may be raised to any required height. In the subjoined engraving a represents a working cylinder vibrating upon gudgeons, one of which has passages leading to the top and bottom of the cylinder ; b piston rod connected to the crank ; d d guide rods ; e pinion on axis of the crank, driving f a toothed wheel on the axis of the drum g; i the valve-box, in which the hollow gudgeon of the cylin der turns, and, admitting the atmosphere to press upon one side of the piston whilst the air is drawn from the opposite side by an air-pump worked by a steam engine ; k the spanner for reversing and regulating the motions of the machine ; 1 pipe leading to the air-pump ; m fly-wheel.
The above figure represents a swing-round crane, upon the same principles as the former, and may be supposed to form one of a range round a dock basin. a is a hollow cast-iron post, upon which the crane turns, and is firmly imbedded in masonry ; from the upper end proceeds a pipe b turning airtight in a stuffing-box, and communicating with a cylinder d by means of a three-way cock c. The cylinder vibrates upon gudgeons, in one of which are formed two hollow passages, the one leading to the top, and the other to the bottom, of the cylinder. A pipe e proceeds from an aperture f in the crane post to an air pump, worked by a steam-engine, or any other power, and which may be situated in any part of the docks, the air being rarified alternately above and below the piston of the vibrating cylinder, whilst the atmosphere presses upon the opposite side of the piston ; the alternate motion of the latter turns the crank g and the piston h, which drives the wheel k fixed upon the axis of the chain barrel 1, and thus raises the load ; m is a fly-wheel, by means of which the reciprocating motion of the cylinder imparts a rotatory action to the crank.
The last example we shall give of the application of Mr. Hague's patent, is that of a tilting or powerful forge-hammer, which is raised by the atmosphere pressing upon a piston connected to the hammer, (the air on the opposite side being rarefied by means of an air-pump situated at a distance,) and which falls, by its own weight, upon the admission of the atmosphere above the piston.
a b is the hammer turning upon a fulcrum at b ; c the anvil; d a cylinder, situated immediately over the hammer; e the piston, connected with the hammer by the bar f, and the k a slide valve, worked by the lever 1, which is struck by a pin on the bar f; when the piston arrives at the to of the cylinder, which depresses the valve so as to shut off the communication with the air pump, and admit the atmosphere, permitting the hammer and piston to fall by their own weight. Towards the close of the descent, the hammer, by means of a line attached to it and to the lever I, reverses the position of the lever 1 and of the slide-valve, thus re-opening the communication between the cylinder and air-pump. k is the pipe leading from the cylinder to the air-pump, and m a cock for shutting off the communication with the air-pump when the hammer is not at work ; n n spanners for opening and the cock.
Pneumatic Transport.—In the year 1824, the ingenious Mr. John Valiance, of Brighton, took out a patent for a mode of employing the natural pressure of the atmosphere, operating upon a partial vacuum, for the purpose of transporting persons and goods with extraordinary rapidity from place to place. He proposed to construct hollow cylinders of cast-iron, sufficiently large to allow carriages with passengers and goods to pass through them. A. series of these cylinders were to be united, and extend from town to town, and the junctions made sufficiently air-tight to admit of a rarefaction of the air within the tube, by the continued action of powerful exhausting machinery at one end. The carnages, • which were to travel inside of this tube, were to be of the same cylindrical form, and very nearly of the same transverse dimensions, so as to constitute, in effect, pistons, which were to be impelled by the air rushing in at one end of the trunk, to restore the equilibrium, or fill up the vacuous space mechanically produced on the opposite side of the pistons. A model, on a sufficiently large scale to test the of the principle and mode of action, was set up an the patentee's premises at Brighton, and many persons were thus blows through the tube. Notwithstanding this demonstration of the correctness of the principle, sufficient subscriptions were not obtained to carry the plan into effect on a greater scale. A notion was very generally entertained that the scheme, if feasible, could not be carried into practice on an extensive scale, and at a cost that would repay the subscribers; to this circumstance may also lie added, a fear that the extraordinary mode proposed, of travelling in the interior of a tube, would not accord with the taste of the public. The latter objection has, however, been obviated by a novel arrangement of mechanism, which has recently been the subject of a patent granted to Mr. Henry Pinkua, whose invention consists in transferring the action produced upon a piston or diaphragm, moving in the interior of a tunnel or tube, to its exterior, by con necting a vehicle or machine, (termed the dynamic traveller,) situated within the tube, with a car or carriage without, (denominated the governor,) to which the train of transport carriages are attached. A working model of this invention is at present being exhibited in Wigmore-street, Cavendish-square; and a joint stock company, called "The National Pneumatic Railway Association," is in progress of formation ; the avowed object of which is to carry the plan into effect on all the principal roads of the kingdom. This singular mode of trans port having thus gained considerable celebrity, and the principle upon which it is founded being essentially correct, we shall (notwithstandhlg the mechanical difficulties apparently to be surmounted) introduce a brief description of the in vention under this head, reserving a more extended consideration of the subject for the article Ren.wey. The pneumatic railway admits of several methods of application, in each of which the dimensions, economy, and details, vary. On a line of road where the transit is very great, as, for example, between Liverpool and Manchester, a double line would be required, the cylinders of which, the patentee states, should be 38 inches in diameter, and so moulded, as to be of the average thickness of three-quarters of an inch ; that is, the lower semi circumference to be three-quarters of an inoh, and enlarged into a series of rings three feet apart, so as to be inch thick where the rings occur; • thus giving the lower semi-circumference an average thickness of seven-eighths of an inch. The upper semi-circumference need not be of a greater average thickness than five-eighths of an inch, when disposed into similar rings. On a single line of road, where the transit is considerable, the size of the cylinders may be increased to 40 inches diameter, and be of a proportionate thickness ; but when the pneumatic system is combined with a common railroad, that is, laid between the ordinary rails, as a medium for transmitting motive power to carriages running in the usual manner on rails fixed upon blocks, the cylinder not having to sustain the weight or action of the loaded carriages, may be reduced to 28 inches diameter, and half an inch thick : and when the system is applied to draw or propel barges on canals, (which is also contemplated by the patentee,) a cylinder of only 22 inches diameter, laid down in the towing path, he considers to be fully adequate. The length of the pneumatic tube will be equal to the whole length of the railway or canal to which it may be applied, and it should be cast in portions of the greatest length possible, in smooth metal moulds, so that their inner sides should be very even and true, and they are to be connected by the ordinary socket joint. Fig. I of the annexed wood-cute exhibits a perspective sketch of a portion of a line of pneumatic railway, laid down, exhibiting the " governor drawing a train of carriages along it. The upper half only of the air tunnel a a is seen, the other half being imbedded in a semicircular trench ; on the edges of which trench rest strong projecting ledges, which are cast to the outsides of the tunnel, in a longitudinal direction. These ledges are about three inches wide on their upper surfaces, and constitute the railway upon which the wheels h h of the governor or drag, and those of the train, run. To explain the mode adopted of com
municating the motive force generated in the interior of the tunnel to the governor on the outside, we must refer the reader to fig. which represents a sectional perspective of a portion of the tunnel ; wherein it will be seen the) a strong flat bar f is bolted to the governor, so as to depend vertically througli a longitudinal chase made in the top of the tunnel, and reaching to the centre of it. Here it is firmly fastened to a species of carriage, of the form of a velo cipede, which operates as a guide and stiffening-frame to the piston or diaphragm c, that receives the impulse of the atmosphere ; the expanding piston having a conical steel ring around its periphery, one foot wide, and placed at an angle of about 15° from the surface of the cyhnder, against which one edge of the cone acts with a slight pressure of the air, so as to conform to any slight inequality of the cylinder. A more exact comprehension of these arrangements will be afforded by the subjoined Fig. 3, which exhibits a transverse section of tha pneumatic railway, an end elevation of the governor ; its connexions and position ; also the rear wheel of the dynamic traveller; its position within the cylinder ; the guide rail (cast to the interior of the cylinder) on which it runs; and the piston in advance. a a a is the cylinder, the lower semi-circumference of which is of greater thickness than the upper, to enable it to withstand the greater strain on this part, to which it is subjected by the weight of the carriages rolling upon the projecting ledges or rails bb; cec shows the area of the piston strengthened by cross bars; d d d d stay rods, connecting the piston to the frame of the dynamic traveller, the hind wheel only e of which can be seen in this view. f exhibits an edge view of the bar that connects the dynamic traveller to the governor g, of which h h are the running wheels, connected by a cranked axletree. In connexion with the vertical arm f are inflexible horizontal arms, from which are suspended by pivots or vertical axles, anti-friction wheels i whose peripheries roll on the outer sides of the longitudinal chase, and keep the vertical arm in the centre, so as to prevent its touching on either side. This figure also shows the shape of the longitudinal chase or aperture,. through which the connexion is made from the interior to the exterior; this chase is cast with the cylinders, and is necessarily continued the whole length of the tunnel. In order that the running wheels of the governor, as well as those of the train of carriages that follow it, may be kept truly upon the centre line of the projecting rails, and never rub against the sides of the tunnel, metallic arms are projected from their frames, carrying anti-friction wheels, the peripheries of which roll against the outer sides of the longitudinal chase and underneath the flange : this latter circumstance affords a great security against upsetting. And for the purpose of keeping the peripheries of these anti-friction wheels always in contact with the chase, whatever curves may be made in the line of railway, their axles turn in slots, and are pressed inward by springs. Into the trough, an elastic flexible padded chain, called by the patentee, the valvular cord, is fitted the whole length of the tunnel, forming, as it were, a continuous valve. In the annexed figure, this valve is shown in section on a greater scale, with the flexible cord 1 in its place. The sides of this cord, when not compressed, have a curved figure, as represented by the dotted lines ; it is surrounded with a coat of felt, and on the top is attached a jointed band m of iron, resembling a con tinuous series of hinge-flaps, the joints admitting of the utmost pliability to the cord, and affording a compensation for the expansion or contraction of the metallic portion of the band ; the other materials of the valvular cord are of too soft and yielding a nature to require any provision against the changes of temperature, and these are smeared over, or saturated with, unctuous matter, to keep them soft and more effectually air-tight. By reference to Fig. 2 it will be seen that the piston precedes the dynamic traveller in the tunnel ; and by reference to Fig. 1 it will be perceived that there is a small wheel in the centre, (shewn also at k, Fig. 3,) with the valvular cord 1 passing over its periphery, while there is another similar wheel in front, and a third at the hind part, which constantly keeps the valvular cord in its trough. The office of the centre wheel is, therefore, simply to keep continually lifting out the valvular cord from its seat, and thereby expose the back of the piston to the full and direct action of the proximate atmosphere ; the fore wheel, by its pressure upon the valvular cord, preserving the partial vacuum effected before the piston, and the bind wheel, by its pressure, restoring the valvular cord to its previous station. To enable the conductor to retard or stop the progress of the vehicle at pleasure, the patentee pros to form a valve in the lower quadrant of the piston, to be opened or closed at by means of a lever, or a chain and pulleys. With a view to facilitate the operation of transit, and enable various parts of the same line of the pneumatic tunnel to be used simultaneously, the patentee proposes to divide it into sections, (of convenient lengths, which may be determined by the stations of the operating engines,) by intercepting station valves, which may be made similar in form and construction to the common gas valves usually applied to mains ; and the connexion may, in this case also, be similar. The patentee, however, prefers station valves of the nature of vertically sliding shutters, running down into sills below the line of the tunnel, as these admit of readier working than the gas main valves. Stationary exhausting engines, or air-pumps, are to be put in action by attached local steam engines, or other con venient first mover; communications between the exhausting engine and the pneumatic tunnel to be made by means of lateral tubes ; and the connexions are to be made- in the common manner upon the lower side, at the distance of about 200 feet from the station valve, and on the side of it that lies nearest to the station whence the governor, with its train of carriages, is to be drawn. The stations for the engines may be at 3, 4, or 5 miles apart, according to the power of the engines, the capacity of the pneumatic tunnel, the degree of -arefaction necessary, the average weight to be conveyed, the velocity required, and the height of any inclined plane to be surmounted. As the power to be produced is by the pressure of the atmosphere acting against the piston, in advance of the dynamic traveller, by the rarefaction within the tube before it, the pressure will depend upon the degree of rarefaction ; and that may be con stantly ascertained by means of barometers placed at the different stations, which will indicate the approach of the governor and its train, and about its distance from the station. A barometer placed on the governor, and commu nicating by a small tube with the interior of the pneumatic cylinder, and through the piston to its vacuum side, will likewise indicate the degree of rarefaction, and, consequently, the pressure upon the piston, the sufficiency of power to propel, and the time for moving off. Action being given to the exhausting engines connected with the section of the tube through which propulsion is to be effected, the station valve being closed, and the air abstracted from that end of the section of the pneumatic cylinder, rarefaction will take place throughout the whole of the included atmosphere contained in the space lying between the station valve and the piston, which is attached to the dynamic traveller. The partial vacuum thus effected at the station will cause the included column of air to move rapidly towards it; and the incumbent atmosphere pressing upon the valvular cord, will tend to aid the action of the weight of the cord in making the pneumatic valve sufficiently close to prevent the ingress of the external air, and preserve the required degree of rarefaction on the vacuum side of the piston. The unincluded atmosphere rushing into the cylinder through the aperture in the pneumatic valve over the dynamic traveller, (which is laid open by the lifting of the valvular cord over the central wheel of the governor, as before mentioned,) and impinging on the plenum side of the piston, will produce a pressure pro portional to the degree of rarefaction on its opposite side, and consequently draw the train of carriages connected thereto after it. On the near approach of a train to a station valve, the latter will be quickly let down into its recess, to allow the former to pass. The valve may then be again raised; and the same engine continuing to abstract the air, as before, from the same section of the railway, it will be again soon prepared for another train in like manner; while the train that had passed into the next section is being operated upon in like manner by the engine belonging to it, and so on, from one section to the other, throughout the whole line of railway. For further remarks on this interesting proposition, we must refer the reader to the article RAILWAY.