The Century of Inventions of the Marquis of Worcester / from the Original MS., with Historical and Explanatory Notes and a Biographical Memoir

by Marquis of Edward Somerset Worcester

No. LXXVII.

How to make a man to fly: which I have tried with a little boy of ten years old, in a barn, from one end to the other, on a hay-mow.

NOTE.

Innumerable are the schemes that have been proposed by the learned at different periods, to enable man to support himself in the air by the means of artificial wings, &c. and some, indeed, of these ingenious contrivances have formed the labours of the most distinguished mechanical geniuses, which are recorded in the early annals of science.

Bacon, and an Italian priest named Francisco Lana, endeavoured to accomplish it by means of two thin hollow globes, exhausted of air, which being considerably lighter than that fluid, were intended to sustain a chair suspended to their lower extremity, and on which the aeronaut might be seated. But Dr. Hook, in a work published some time after the Prodromo of Lana, plainly showed the fallacy of the attempt, though without in the least attempting to deny the possibility of eventually effecting this object.

Bishop Wilkins, who was also a disciple of the flying system, describes a species of land-sailing vessels or chariots, which were then commonly used in China: and it is rather a curious fact that a German Count, possessing as much of modesty as the generality of foreign mechanics, has lately given to the public, as his own, an invention which has been known in Europe, and occasionally employed in Asia, for the last four hundred years.

But of all the plans that have hitherto been devised, those only which have mechanic power as their basis appear to have any chance of success. This may be considered as an unerring datum to guide the future experimentalist, the certainty of which is fully demonstrated by a comparison of the powers of the human frame with those of the feathered tribe: for it has been calculated by an ingenious anatomist, that the muscles which move the wings downwards in a bird in many instances, constitute not less than the sixth part of the weight of the whole body; while those of a man are not one hundredth part so large. By the use of springs, however, wound to a certain degree of tension, prior to embarking upon the intended expedition, and acting upon cranks working the wings, the same power as that possessed by the feathered race may be obtained, and the springs may be readily made to draw more than fifty times their weight. By this means a whalebone, or other light carriage, may be raised, though it would be but for a short time, as it would not be in the power of the aëronaut to wind the springs so quick as the machine would require.

From this, then, it will be seen that, to produce the effect necessary for this species of navigation, it is only requisite to have a first mover, which will produce more power, in a given time, in proportion to its weight, than the animal system of muscles.

High pressure steam-engines have been made to operate by expansion only, and they, it appears, might be constructed so as to be light enough for this purpose. In that case, however, it will be evident that the usual plan of a large boiler must be given up, and the principle of injecting a proper charge of water into a series of tubes, forming the cavity of the fire, must be adopted in lieu of it.

The following estimate will show the probable weight of such an engine with its charge for one hour.

		lbs.
The engine itself, from 90 to		100
Weight of inflamed coals in a	}
cavity presenting about 4 feet	}	25
surface of tube	}
Supply of coal for 1 hour		6
Water for ditto, allowing steam	}
of one atmosphere to be 1/1800	}	32
the specific gravity of water	}
		163

It may at first view appear superfluous to inquire further relative to a first mover for aërial navigation; but lightness is of so much value in this instance, that it is proper to notice the probability that exists of using the expansion of air by the sudden combustion of inflammable powders or fluids with great advantage. The French have experimentally shown the great power produced by igniting inflammable fluids in close vessels; and several years ago, an engine was made in this country to work in a similar manner, by the inflammation of spirit of tar.

It appears that eighty drops of this fluid raised eight hundred weight to the height of 22 inches; hence a one-horse power may consume from 10 to 12 pounds per hour, and the engine itself need not exceed 50 pounds weight.

Probably a much cheaper engine of this sort might be produced by gas-light apparatus, and by firing the inflammable air generated, with a due portion of common air, under a piston. Upon some of these principles it is perfectly clear that force can be obtained by a much lighter apparatus than the muscles of animals or birds, and therefore in such proportion may aërial vehicles be loaded with inactive matter. Even the high pressure steam-engine doing the work of six men, and only weighing equal to one, will readily raise five men into the air, but by increasing the magnitude of the engine ten, fifty; or even five hundred men may equally well be conveyed.

Having rendered the accomplishment of this object probable upon the general view of the subject, it will now be necessary to point out the principles of the art itself. The whole problem is confined within these limits, viz. To make a surface support a given weight by the application of power to the resistance of the surrounding atmosphere.

Many experiments have been made upon the direct resistance of air by Mr. Robins, Mr. Rouse, Mr. Edgeworth, Mr. Smeaton, and others. The result of Mr. Smeaton's experiments and observations was, that a surface of one square foot met with a resistance of one pound, when it travelled perpendicularly to itself through air at a velocity of 21 feet per second.

Having ascertained this point, had our tables of angular resistance been complete, the size of the surface necessary for any given weight would easily have been determined. Theory, which gives the resistance of a surface opposed to the same current in different angles, to be as the squares of the sine of the angle of incidence, is of no use in this case; as it appears, from the experiments of the French Academy, that in acute angles, the resistance varies much more nearly to the direct ratio of the sines, than as the squares of the sines of the angles of incidence. The flight of birds will prove to an attentive observer, that, with a concave wing apparently parallel to the horizontal path of the bird, the same support, and of course resistance, is obtained. And hence it appears that, under extremely acute angles with concave surfaces, the resistance is nearly similar in them all.

Six degrees was the most acute angle, the resistance of which was determined by the valuable experiments of the French Academy; and it gave 4/10 of the resistance, which the same surface would have received from the same current when perpendicular to itself. Hence then a superficial foot, forming an angle of six degrees with the horizon, would, if carried forward horizontally (as a bird in the act of skimming) with a velocity of 23·6 feet per second, receive a pressure of 4/10 of a pound perpendicular to itself. And if we allow the resistance to increase as the square of the velocity, at 27·3 feet per second it would receive a pressure of one pound.

The flight of the corvus frugilegus, or rook, during any part of which it can skim at pleasure, is (from an average of many observations) about 34·5 feet per second. The concavity of the wing may account for the greater resistance here received, than the experiments upon plain surfaces would indicate.

The angle made use of in the crow's wing is much more acute than six degrees: but in the observations that will be grounded upon these data, it may safely be stated that every foot of such curved surface, as will be used in aërial navigation, will receive a resistance of one pound, perpendicular to itself, when carried through the air in an angle of six degrees with the line of its path, at a velocity of about 34 or 35 feet per second.

The next object is to apply what has been advanced to the theory of aërial navigation; and the following description will convey a just idea of the best method of effecting it. Suppose a sail to be made of thin cloth, of a firm texture, containing two hundred square feet; and that the weight of the man and the apparatus is 200 pounds. Then if the wind blow with a velocity of 35 feet per second, in a certain direction, at the same time that a cord in that direction sustains a tension of 21 lbs. from being fixed to the machine, the whole apparatus will be suspended in the air. But it is perfectly indifferent whether the wind blow against the plane, or the plane be propelled by any means against the air with an unequal velocity. Hence, if this machine were drawn forward by the cord under a tension of 21 lbs. and with a velocity of 35 feet per second, the whole would be suspended in an horizontal path. Now, if, instead of this cord, any other propelling power were generated in the same direction, and with the same intensity, an equivalent effect would be produced, and aërial navigation accomplished. Vide Bishop Wilkins's Math. Magic.—Hook's Philosophical Collections.—Sir G. Cayley on Aërial Navigation.

		lbs.
The engine itself, from 90 to		100
Weight of inflamed coals in a	}
cavity presenting about 4 feet	}	25
surface of tube	}
Supply of coal for 1 hour		6
Water for ditto, allowing steam	}
of one atmosphere to be 1/1800	}	32
the specific gravity of water	}
		163