vessel as the air escapes. In order to back the vessel, the air is forced out through pipes directed towards the bow of the vessel. The improved steam-engine consists of a horizontal cylinder through the centre of which a main shaft passes, carrying two vibrating vertical fans, which together fill the diameter of the cylinders, and greatly resemble a Bramah's pump. On one side of this cylinder is another of equal size, and similarly constructed, which forms the air-pump for propelling the vessel, while on the opposite side is the air-pump of the steam-engine. The shafts are all connected so as to move together. On admitting steam to the engine, the fans make a vibratory movement, each motion of the air-pump forcing a portion of air into the channel before mentioned, along which it passes in broken currents, which the patentees consider more advantageous than a continuous current of air. Ibid. Specification of a Patent granted to THOMAS WILLIAM BOOKER, of Melin Griffith's Works, near Cardiff, for improvements in the Manufacture of Iron. August 21, 1841. For the purpose of converting cast iron from its crude state, into wrought or malleable iron, an open refinery, or furnace, is connected with a reverberatory, or puddling furnace, by a passage which terminates in its neck. The refining furnace having been sufficiently heated, a charge of about nine hundred weight of cast-iron is thrown in, and melted down in the ordinary way; when the refining process is complete, the whole charge of metal is run off into the puddling furnace, previously heated to a proper degree. The iron is then puddled in the usual manner, and divided into lumps or balls of a convenient size, which are passed to the rolling cylinders, &c., to be finished. The principal novelty in the process consists in causing the heated metal of the refining furnace to pass directly into a puddling furnace without being permitted to become cold. Progress of Civil Engineering. Baldwin's Geared Truck Locomotive Engine. Ibid. Through the kindness of Mr. Baldwin, we are enabled to lay before our readers in the present number, an engraving of this new arrange. ment of the machinery of a Locomotive, by means of which, the wheels of the leading truck (so valuable in a curved way) are converted into drivers, without interfering with their other useful properties. We also subjoin the letter of the Superintendent of the Reading railroad, describing a large performance made by this Locomotive on that railway; and at page 178 we insert the report of the committee of Science and the Arts, upon the merits of the peculiar arrangement of parts, by which the adhesion of all the wheels is obtained.* • For the specification of Mr. Baldwin's patent, for the mode of accomplishing this object, see the number of this Journal for February, 1842, page 136. PHILADELPHIA, February 12, 1842. Messrs. BALDWIN & VAIL; Gentlemen,-I send you inclosed, a statement of the performance of your new six wheeled, geared engine, which you will perceive is in every way satisfactory. The train weighed 1084 tons, of 2,240 lbs., more than that hauled by your "Hichens and Harrison" engine in February last, on our road.* Statement of the performance of a six wheeled engine, built by Messrs· BALDWIN & VAIL, on the Philadelphia, Reading and Pottsville Railroad, February 12, 1842. This engine has six wheels and outside connexions. The large drivers (forty-four inches in diameter,) are behind the fire box, and connected with the four truck wheels, (thirty-three inches in diameter,) by cog gearing, in such a way as to obtain the adhesion of the whole weight of the engine, with little additional friction, and at the same time allow the requisite play in curves. Her weight, in running order, is 30,000 lbs.; on her large drivers, 11,775lbs.; or 5,887lbs. on each. On the truck wheel 18,225lbs. or 4,565lbs. on each, and her cylinders are thirteen inches diameter and sixteen inches stroke. This engine hauled, on the above date, a train of 117 loaded cars, weighing in all 590 tons, from Reading to the inclined plane, on the Columbia railroad, fifty-four miles, in five hours and twenty-two minutes, being at the rate of over ten miles per hour the whole way. She consumed 2 cords of wood, and evaporated 3,110 gallons of water, with the above train. Weight of freight, 375 tons, of 2,240 lbs.; consisting of 259 tons of coal, twenty-two tons of iron and nails, and ninety-four tons of sundry other merchandize, including fifty-three live hogs, ten hhds. of whiskey, 188 bbls. flour, ship stuff, butter, &c. Weight of cars, 215 tons, making a total weight, not including engine and tender, of 590 tons of 2,240lbs. Whole length of train, 1,402 feet, or eighty-two feet over a quarter of a mile. The above train was transported in the ordinary freight business of the road, and was run without any previous preparation of engines, cars or fuel for the performance. The engine was closely watched at all the starts of the train, and not the least slipping of any of her wheels could be perceived. She worked remarkably well throughout the trip, turning curves of 819 feet radius, with ease to her machinery, and no perceptible increase of friction in her gearing. Her speed with the train on a level, was found to be nine miles per hour. Whole length of level, over which the above train was hauled, twenty-eight miles; longest continuous level, 8 miles; total fall, from the point where the train was started to where it stopped, 210 feet. The above train is unprecedented in length and weight, in Europe or America. G. A. NICHOLLS, Superintendent of transportation on the Philadelphia, Reading, and Pottsville railroad. U. S. Gazette, Feb. 14th. See the number of this Journal for May, 1841, page 319. C. EVANS, Esq: Cadwallader Evans' Safety Valve. Letter from Professor JOSEPH HENRY. Princeton, N. J., Feb. 25th, 1842. Dear Sir:-I have deferred answering your letter relative to your Safety Apparatus until I could find time to make some experiments with the model you sent me, but I have been unable to give the subject any attention until within a few days past. I have for the last few years been in the habit of mentioning to my class the advantages of using the fusible metal inclosed in a tube surrounded by the steam, for the purpose of setting off an "alarm" in case of the undue heating of the boiler, as proposed by my friend, Professor Bache; but I was not aware of the fact, until I was informed of it by Professor Bache himself, that you had independently applied the same principle to set in operation a self-acting apparatus for relieving the safety valve in case of danger. I have made a number of experiments with your apparatus, the results of which are perfectly satisfactory. To determine if the discharge of the steam always takes place at the same pressure, the composition of the fusible metal remaining the same, I attached to the boiler a manometer gauge, and found that in each case the discharge took place at about a pressure of thirty-three pounds per square inch. The indications of the gauge did not vary from this more than a pound on either side in any of the experiments, although the quantity of water in the boilers was not precisely the same in all cases. I also have made some experiments on surcharged steam; for this purpose the water was suffered to get low in the boiler, and then the fire was removed from the bottom to the sides, so as to heat the metal above the water line, and surcharge the steam. Under these circumstances the fusible metal gave way at a pressure of about sixteen pounds. These results appear so satisfactory, that I do not hesitate to state that I consider the plan of using the fusible metal, inclosed in a tube, exposed to the steam, and your arrangement for relieving the safety valve at the approach of danger, as the best contrivance which has been proposed to the public as a means of preventing the disastrous explosions from steam. With my best wishes for your success in introducing your invention into general use, I remain respectfully yours, &c., JOSEPH HENRY. Observations on the effect of wind on the Suspension Bridge over the Menai Strait, more especially with reference to the injuries which its roadways sustained during the storm of January 1839. By W. A. PROVIS. From the Proceedings of the Institution of Civil Engineers. In the month of December, 1825, when the original construction of the bridge was nearly completed, several severe gales occurred, and |