An efficient mode of working an engine with an uniformity of force, by meana of a fluid that is constantly diminishing in its elasticity, is, we believe a problem not yet solved. Another patent for precisely the same obj , ect as was granted on the let of June following, to Mr. W. Mann, of Effra-road, Brixton, Surrey, who was of course uninformed at the time of hie having been anticipated. Nevertheless Mr. Mann pursued his undertaking, published a pamphlet descriptive of his plans, accompanied by drawings, and endeavoured to raise a company to carry his project into operation. Whether be actually carried it experimentally into practice we are uncertain, but a drawing of the carriage and reservoirs of compressed air are given in the 5th Vol. N. S. of the Register of Ark :— " Mr. Mann proposes, like his predecessors, to employ a series of strong metallic recipients, similar to the cylindrical vessels used for portable gas, into which thirty or more atmospheres are to be condensed by the • ower of a steam engine, water mill, or other adequate prime mover. A s "dent number of these vessels are stowed in a case adapted for the purpose, which is to be fixed underneath the canine ; a tube, communicating with all the recipients, is to convey the compressed air to two working cylinders, having the apparatus com mon to high pressure steam-engines, the piston rods of which wiII give motion to a crank on the axis of the hind running wheels. It is proposed to work expansively, and to vary the cutting off the stroke, according to the degree of elasticity of the air.
" The velocity Mr. Mann proposed to travel, was 14 miles in the hour, which he calculates will require 2000 cubic feet, of the natural density, to propel a carriage weighing, with its load, two tone. When the roads are in a bad state, it is intended to charge the vessels with a greater number of atmospheres, to overcome the increased resistance.
" The patentee states, that the carriage is contrasted(?) to carry 75 cubic feet of compressed air, which, at a density of thirty-two attnospheres, is sufficient to propel it 14 miles; and if the air were compressed to be equal to 48 atmo spheres, that quantity would propel the carriage 23 miles; and if to 64 atmo spheres, 34 miles. The average cost of the power is calculated at one penny per mile ; that is, if a steam-engine be employed to effect the compression of the air into the recipients, the cost in coals of such steam power, to condense a volume of sir sufficient, by its subsequent expansion, to propel a carriage one mile, is one penny. Mr. Mann, however, must know that this would only form tee item in the expense of working a carriage. The proposition of propelling by a process of this kind, is certainly specious; but those who have given the subject their best attention, consider that no practical means have yet been devised to compensate for the constantly decreasing expansive force of the air in the recipients." A misnsion railway, combining the characteristic features of Mr. Palmer's and Mr. Fisher's, previously described, was patented by Mr. Maxwell Dick, of Irving, in Ayrshire, on the 21st of May, 1829; doubtless, in ignorance of those precedents, as we were personally assured by the latter patentee. The chief
object of this gentleman was, as is stated in the title of his patent, " for the conveyance of passengers, letters, intelligence, packages, and other goods, with great velocity. The means which he adopts for this purpose, are designed to obviate the necessity and enormous expense of cutting and embanking resorted to on railways of the ordinary kind. The rail is supported, like Mr. Palmer's, upon vertical pillars, but carrying a double track for the carriages, like Mr. Fisher's. Mr. Dick has, however, added, what he denominates " safety rails," one on each side of the track, against which anti-friction wheels, attached to the carriages, are made to act, in case of the carriages receiving from any cause an impulse up wards. The patent likewise embraces a curious combination of wheel-work, for communicating a high velocity to the• A large and well constructed working model of this invention was pu iely exhibited for several weeks at Charing Cross, London, in 1830, and drew crowds of visitors, who were surprised and delighted at the velocity with which the carriages darted along the wire rails across the room, by the application of a small force. The notoriety of this invention, as well as the capability of its being usefully applied under many circumstances and situations, for light loads at high velocities, seems to require from us something more than this brief historical notice. Accordingly we proceed to give a few, out of the many details and modifications, which the prolific mind of the inventor has thrown together in his specification. From this document we learn that the patentee especially designed his invention for traversing undulating, rugged, and abrupt ground, the crossing of rivers, mosses, marshes, &c. Pillars are to be erected of brick or stone with lime, at given dis tances apart, suppose fifty yards ; between each of these may be placed four or five cast metal pillars, according to circumstances, for bestowing the requisite stability and keeping the rail free from undulations. On the top of each of the pillars is to be fastened a frame, to which the rails are to be secured, and to the frames are connected grooved friction wheels or pulleys, between which the drag-line is conducted. The rails are to be made of the best wrought iron, such as is used for chain cables, and they are to be duly connected together in great lengths, and secured to the frames in such manner as to make the top sur face smooth, and free from all obstruction to the motion of the carriages. Between each frame there are to be introduced three or four cast-iron braces, to prevent vibration and stiffen the structure. The method proposed for dragging the carriage along the railway, is by fixed, or stationary engines acting with drag-lines or ropes attached to the carriage, which, if the railway be double, (as in the subjoined illustration) will act in an endless round ; but if the line of railway be single, then the engine will be interchangeable and reciprocal.