PROPELLING DEVICES—“The Queen of the South, a large steamship belonging to the General Screw Steam Company (England), broke the fan of her screw on one of her recent voyages, and Mr. Field, of the firm of Maudsley & Field, of London—able engineers —who was consulted respecting the new screw, put in one with a decreasing width of fan or blade, and an increase ot four feet pitch. The new screw was reduced 1600 lbs., and yet the ship ran with the same speed making ten revolutions less per minute. With the new screw she made 104 miles per hour, with the old one only 9 knots. FEATHERING PADDLE WHEELS—The steamship Parana, (which was to have been the Arabia, but was sold to the West India Mail Co., after the Amazon was burned), was fitted with Morgans Feathering Paddle Wheels, and it was supposed that she would surpass all the steamships in the world in point of speed ; she made two very fast passages, but the London Artizan states that the feathering wheels have been taken out of her, and the old common kind put in, and that she goes much better. Two other steamships, the Orinoco and Madalena, which were fitted with feathering wheels also, are about to be altered in the same way. THE NEW YORK AND ERIE RAILOAD—The American Railroad Journal handles the directors of this railroad with great severity, asserting that $-6,722,260 have been spent for which no account has been rendered. It says that as much money has been spent and not accounted for, as was first estimated for the original cost of the whole road. It insinuates something about a secret service fund. We do not know what can be the meaning of it, although from the statements published, it appears that the said company has managed its affairs in a most extraordinary manner. We hope the Directors will be able to make all things clear and explicit. To PREVENT CANDLES GUTTERING—A scientific correspondent informs us that by using the frustrum of a cone of wire gauze or perforated metal on the shoulder of a candle, it will keep the candle from flickering and the grease from guttering. This is certainly a good device for such a purpose. BURNING FLUID AND CAMPBENE—A Bos- , ton correspondent requests us to explain the difference—tor the benefit of many—between camphene and the spirit gas (explosive fluid) sold in our stores, as many people suppose camphene to be explosive, and do not know the difference between it and the spirit gas. j Camphene is highly rectified spirits of turpentine, contains no alcohol, and is not explosive. It will not burn in a common lamp without a chimney, as it contains C.10, H.8—a very large portion of carbon, and emits much smoke, which is only prevented by using a long chimney to supply a great quantity of oxygen to support combustion. The spirit gas is a mixture of rectified camphene, with about five or six times its quantity, by measure, of alcohol. They are mixed together in a cold state. It is the volatile nature of the alcohol which is the cause of danger. SQUARE CYLINDERS—We have seen extracts in various papers telling how an engineer in Paris had constructed a steam engine with a square cylinder, and consequently with a square piston. We confess to a knowledge of what a square box is, but a square cylinder is something really new—we do not know what it is. The idea of a square piston working in a rectangular box is really worthy of the enlightenment of the year one instead of the nineteenth century. One great advantage of the reciprocating over the rotary engine, is the form of piston and cylinder. The round disc working in the round cylinder are the best known forms for working smoothly, uniformly, and lor rendering the piston easily packed to work steam-tight. ENGLISH PATENT LAWS—A Bill is now before Parliament to amend several clauses of the late Patent Law Amendment Act : it provides for the payment of stamp duties for fees on letters patent. This will expedite the business of procuring a patent. Proper stamps are to be provided for the purpose by the Inland Revenue Commissioners. We will apprize our readers of the nature and provisions of the Bill when it passes, if it does pass. A NEW GREEN DYK—The Chinese employ a substance ot a vegetable origin, which contains no indigo and which dyes cotton fabrics, prepared with a mordaunt of alum, a beautiful I green. M. Peroz, of Paris, has recently obtained some of this substance, and has made some successful experiments with it. We possesss no such dye in America,but Bancroft mentions that such a substance, has been long known in Africa.