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THE AERIAL STEAM CARRIAGE. When it was announced some time ago, by the ordinary monthly lists of patents granted, that Air. Henson had in- vented a machine capable of conveying despatches and pas- sengers through the air, the general impression was, that some moody and enthusiastic projector was about to exhibit the produce of his day dreams. Our readers may, therefore, be somewhat surprised to learn that this is in truth no visionary scheme, but a design of very scientific conception, carefully and perseveriugly wrought out. It would perhaps be too much to affirm (what yet we cannot deny) that the machine in its present state will certainly succeed; but the least which can be said is, that the inventor has most skilfully removed the difficulties which have hitherto debarred us the possession of the long coveted faculty of flight, and has made its eventual, perhaps early, attainment a matter of little less than cer- tainty. All former attempts of this kind have failed through the want of a source of power whose energy bore a suiffciently high ratio to the weight of the requisite machinery. Could this source of power have been found, there was ingenuity enough to turn it to the desired account. Mr. Henson, in overcoming the difficulty, has first divided it. To set a ma- chine agoing, and bring it up to a given velocity, is one thing; to maintain that velocity against opposing forces is another. Now, in the case bef<NCi|ettbti power necessary for starting is much greater than {EarWqatr<Hl for maintaining the flight. Mr. Henson, therefore, starts his aerial car- riage by means of an apparatus which be does not carry with him, and then embarks only the smaller power and lighter machinery, which are sufficient for keeping up the ACizma! velocity. But even this happy device would not have succeeded if the inventor had not also effected an extraordinary reduction in the weight of his steam-engine. Our engineering readers will he somewhat surprised to learn that the engine of 20 horses' power now in preparation for the aerial carriage weighs with its condenser and requisite water but 6001b. To the united effect of these different branches of this im- portant invention must we attribute our present prospect of making our paths in the air. THE MACHINE. We proceed now to describe the machine itself, and its mode of flight. Its car, enclosed on all sides, and containing the passengers, managers, burden, and steam-engine, is sus- pended to the middle of a framework, which is so constructed as to combine great strength with extreme lightness, and is covered with any woven texture which is moderately light and close. This main frame or expanded surface, which is 150 feet long by 30 feet wide, serves in the most important respects as wings; yet it is perfectly jointle.'S and without vibratory motion. It advances through the air with one of its long sides foremost and a little elevated. To the middle of the other long side is joined the tail, of 50 feet in length, beneath which is the rudder. These important appendages effectually control the flight as to elevation and direction, and are governed by cords proceeding from the car. Situated at the back edge of the main frame are two sets of vanes or propellers, ol 20 feet in diameter, driven by the steam engine. THE START. We have already said that the velocity of the machine is imparted at its starting. This is effected by its being made to descend an inclined plane: during the descent the cover- ing of the wings is reefed, but before the machine reaches the bottom that covering is rapidly spread: by this time the velocity acquired by the descent is so great that the resistance produced by the oblique impact of the sloping under surface of the wings on the air is sufficient to sustain the entire weight of the machine, just as a brisk wind upholds a kite. But while the pneumatic resistance thus procured by the velocity prevents the falling of the carriage, it opposes also its forward flight. To overcome this latter and smaller resist- ance is the office of the steam-engine. The chief peculiarities of this important member of the carriage are the respective constructions of its boiler and con- denser. The former consists of hollow inverted truncated cones, arranged above and around the furnace; they are about 50 in number, and large enough to afford 100 square feet of evaporating surface, of which half is exposed to ra- diating heat- The condenser is an assemblage of small pipes exposed to the stream of air produced by the flight of the ma- chine. It is found to produce a vacuum of from 51b. to 8lb. to the square inch. The steam is employed in two cylinders, and is cut off at one-fourth of the stroke. Our engineering readers will be able to gather from these particulars, that the steam-engine is of about 20-horse power, supposing the evap- orating power of the boiler to be equal, foot for foot, to that of the locomotive steam-engine. Less certain is the determination of the resistance to be overcome. Mechanical science is notoriously defective in all that relates to the oblique impact of solids and fluids, and is particularly so on the points involved in this subject. Ex- periments do not supply the lack of sound theory for, not only has their purpose been to ascertain the effects of large angles of impact to the neglect of the smaller ones here con- cerned, but the objects of the experimenters (Robins, Hutton, Borda, &c.) have always required the determination of the resistance in the direction of the moving body to the neglect of that which is perpendicular to that direction; while here their effects are so intimately connected that one cannot be determined without first knowing the other; and of that which is to be first known—viz., that which supports the vehicle, we have no information on which the smallest reliance can be placed. Mr. Henson, we understand, has formed his con- clusions from the best observations he could make on the flight of birds, and we think he has done wisely. We are informed, however, that the resources of mechanical art are by no means exhausted by the present construction of Air. Henson's engine, and that recent inventions are available by which its power may be doubled with little increase of weight. The area of the sustaining surface will be, we understand, not less than 4,500 square feet; the weight to be sustained, including the carriage and its total burden, is estimated at 3,000lb. The load is said to be considerably less per square foot than that of many birds. It may assist the conceptions of our non-mechanical readers, to add that the general appear- ance of the machine is that of a gigantic bird with stationary wings; that the mechanical principles concerned in its sup- port are strongly exemplified in the case of a kite; and that its progress is maintained by an application of power like that which propels a steam-boat. In the operations of nature, particularly in the flight of birds, will be found many striking illustrations of the principles on which the inventor has proceeded. Whatever may be the immediate issue of the present at- tempt, we think it is impossible not to award to the in- ventor the highest credit due to the removal of the great difficulties which have hitherto defeated all similar inven- E tions nor do we doubt, that in following out the path he has opened, complete success will eventually be obtained: whether that success will be, as we wish, early and entire, or whether it will be delayed and gradual, depends on the facts as to oblique pneumatic resistance, which have yet to be as- certained. It is, however, high time to begin to consider in the spirit of careful inquiry and cheerful hope what will be the changes, commercial, social, and political, which the posses- ion of this new-born power will necessarily bring about.