Hide Articles List

2 articles on this Page

[No title]


The Atmospheric Railway The problem which Messrs. Clegg and Samuda had to solve, and which they have so far solved most successfully, was the practicability of effecting the propulsion of carriages upon a railway, by the mechanical exhaustion of the air, from one end of a set of pipes, and a preponder- ant pressure of the atmosphere at the other. Mr. Medhurst and Mr. Pinkins had both tried to accom- plish this, but both failed. The obvious difficulty in the case was not so much to accomplish the required degree of exhaustion, as how to connect the carriages, outside of the pipes, with the moving force established by the exhausting process within. So formidable did this difficulty seem to Mr. Vallance, another well- known experimentalist in this line, that despairing altogether of overcoming it, he proposed to make the pipes large enough to contain the carriages and pas- sengers inside, and to produce an exhaustion in front of them so complete that they should be projected in a twinkling from London to Brighton, or vice versa! On the practicability of such a scheme it is unneces- sary to waste a single word. The way in which Messrs. Clegg and Samuda have got over the difficul- ty, we shall now briefly describe. An air channel consisting of a series of pipes about 9 inches in diameter, connected together, by air-tight joints, is laid down between the two lines of the rails on which the carriages travel, and at the top of this air channel, but rather to the one side, there is a small slit or opening, which is covered with a continuous leather valve, one edge of which is fastened down, and the other drops into a trough or groove filled with a composition of bess' wax and tallow which is solid at the ordinary temperature of the atmosphere, but is only very slightly adhesive, and becomes quitu fluid when heated a few degrees above that tempera- ture. As long as this valve remains fixed in its seat no access of air can of course take place through tho slit or opening. A piston which works lengthwise in the air channel has a vertical arm which works into the slit, upon the leather valve which covers that slit being lifted (which is easily effected by alittle pressure), and is connected with a driving carriage placed on the rails outside in the usual way. The air channel is divided by separating valves into suitable length* for exhaustion, and each length has a steam-erigim; and air pump of its own to exhaust it. The inventors propose at first to try lengths of about a mile, but to increase or diminish the distance, according as expe- rience shall determine the one or the other course to be the most economical. For the half mile ou which they are experimenting, one engine of 1 G horse fpower is found amply sufficient. Supposing, then, one of the separating valves of a section of the air chamber- that behind the pistonâto be opened, and the at- mosphere freely admitted in that direction, while the valve of the opposite side is closed, and a steam-engine and air pump applied to exhaust the air from the intermediate space, this result necessarily follows:- The piston is moved forward by the pressure of the atmosphere, and the vertical arm which rises from it. follows in the slit or top, forcing aside, as it advances, the leather valve, and drawing after it, the driving carriage, with which it is immediately connected. Close behind the vertical arm there comes a small wheel, which presses the leather valve down as far as the arm clears it; and after that wheel cornea a heating iron, (heated from a small furnace in the driving carriage,) which re-melts the bee's-wax and tallow, that had been broken up by the lifting of the valve, and makes the valve once more air-tight, and ready for a repetition of the preceding process by any succeeding carriage or train. In two trips, the average speed realised was 30 miles an hour; in a third 35 miles and in a fourth, when Prince Albert was present, no less than 40. The weight of the driven carriage and persons upoa it, varied from 5 to 8 tons. The 15th Centuryâ" It was" says M. Guizot, "a period of voyages, travels, enterprizes, discoveries, and inventions of every kind. It was the time of the Portuguese expeditions along the coasts of Africa, of the discovery of the new passage to India by the Cape of Good Hope, by Vasco de Gama; of the discovery of America by Christopher Columbus; of the wonderful extension of European Commerce. A thousand new inventions started up; others already known, but confined within a narrow sphere, became popular and in general use. Gunpowder changed the system of war; the compass changed the system of navigation. Painting in oil was invented, and filled Europe with master-pieces of art. Engraving on copper, invented in 1406, multiplied, and diffused them. Paper made of linen became common. Finally, between 1436 and 1452 was invented printing- printing, the theme of so many declamations and common-places, but to whose merits and effects no common-places or declamations will ever be able to to justice." IMPORTANT DISCOVERY.-Mr. John Wimbridge, of Presteign, has discovered a chemical process by means of which steel may be so hardened as to cut glass more easily than the diamond.