PARACHUTE

(Fr. parer, to ward off, and chute, fall; a guard against falling.) An apparatus resembling the common umbrella, but of far greater extent, intended to enable an aeronaut, in case of alarm, to drrp from his balloon to the ground without sustaining inj-iry. This is effected by means of the resistance of the atmosphere. When the parachute is detached from the balloon, and abandoned with its load in the air, it must proceed at first, from the continued action of gravity, with an accelerated motion, until the increased velocity produces a resistance equal to the force of attraction, or the weight of the apparatus with its load. After this equilibrium has been attained, the parachute will descend with a nearly uniform velocity. According to theory, this terminal velocity, supposing the surface of the parachute to be flat, is equal to that which a heavy body would acquire in falling through the altitude of a column of air incumbent on that surface, and having the same weight as the whole apparatus. A circular parachute having a diameter of 30 feet, and weighing with its load 225 pounds, would acquire a terminal velocity of about 13 feet per second; and a person descending with it at this rate would receive the same shock on reaching the ground as if he dropped freely from a height of 2| feet. (For the method of solving this problem, see Mutton's Mathematical Tracts, vol. iii. p. 316.) The actual resistance of the air is, however, greater than is given by theory, and is besides augmented by the concavity of the parachute, which occasions an accumulation of the fluid; but, on account of the action of the wind, the axis of the parachute will probably become inclined to the vertical, in which case the resistance will suffer a diminution. One of the most remarkable instances of descent from a great height with a parachute is that of Garner in, a French man, who ascended in a balloon from an enclosure, near North Audley Street, in London, on the 2d of September, 1802. After hovering seven or eight minutes in the atmosphere, he cut the cord by which his parachute was attached to the balloon. It instantly expanded, and for some seconds descended with an accelerating velocity, till it became to ed extremely, and took such wide oscillations that the basket or car was at times thrown almost into a horizontal position. The intrepid aeronaut narrowly escaped destruction by being precipitated on the houses in St. Pancras, and at last fortunately came to the ground in a neighbouring field. He seemed to be much agitated, and trembled exceedingly at the moment he was released from the car. {Ency. Brit., " Aeron.iutics.") A recent experiment of this kind, made by Mr.Cockin^, was attended with fatal consequences. Having concefved a notion that the vibrations might be avoided by giving the machine a difTerent form, this projector constructed one in the form of an inverted umbrella, that is, having the concave side uppermost, and bound to a strong wooden hoop to prevent its collapse in the descent. The diameter of the hoop was 34 feet; and there was also a hole of 6 feet in diameter in the middle of the parachute, which, it was supposed, would also contribute to give greater steadine . Having attached himself to this machine, he ascended from Vauxhall Gardens on the 24th of July, 18.37. On being cut away from the balloon the parachute descended rapidly, and with violent oscillations: the hoop broke, and the unfortunate projector fell, dreadfully mangled, at Lee, near Blackheatn. The persons in the car of the balloon were also placed in greai danger, having narrowly escaped Bufl'oration from the quantity of gas expelled in conscoueiire of the great velocity with which the balloon narled upwards immediately on being liberated from the parachute. They sufl'ered extreme pain, and-for a time 884 PARADISE. were deprived of sight; but fortunately they had carried up with them a large bag filled with atmospheric air, by means of which they were enabled to breathe. Without this, they would probably have perished. [s. 897]