The rapidity of the descent is arrested by the large surface which the parachute presents to the air. When the aeronaut wishes to descend by the parachute, all that is required is, after he has slipped down from the car of the balloon to that of the parachute, to loosen the rope which binds the latter to the former, which is done by means of a pulley. In an instant the aeronaut is launched into space with a rapidity in comparison with which the wild flights of the balloon are but gentle oscillations. But in a few moments, the air rushing into the folds of the parachute, forces them open like an umbrella, and immediately, owing to the wide surface which this contrivance presents to the atmosphere, the violence of the descent is arrested, and the aeronaut falls gently to the ground, without receiving too rude a shock. The virtues of the parachute were first tried upon animals. Thus, Blanchard allowed his dog to fall in one from a height of 6,500 feet. A gust of wind caught the falling parachute, and swept it away up above the clouds. Afterwards, the aeronaut in his balloon fell in with the dog in the parachute, both of them high up in the cloudy reaches of the sky, and the poor animal manifested by his barking his joy at seeing his master. A new current separated the aerial voyagers, but the parachute, with its canine passenger, reached the ground safely a short time after Blanchard had landed from his balloon. Experience has proved that, in the case of a descending parachute, if the rapidity of the descent is doubled the resistance of the air is quadrupled; if the rapidity is triple the resistance is increased ninefold; or, to speak in language of science, the resistance of the air is increased by the square of the swiftness of the body in motion. This resistance increases in proportion as the parachute spreads, and thus the uniformity of its fall is established a minute after it has been disengaged from the balloon. We can, therefore, check the descent of a body by giving it a surface capable of distension by the action of the air. Garnerin, in the year 1802, conceived the bold design of letting himself fall from a height of 1,200 feet, and he accomplished the exploit before the Parisians. When he had reached the height he had fixed beforehand, he cut the rope which connected the parachute with the balloon. At first the fall was terribly rapid; but as soon as the parachute spread out the rapidity was considerably diminished. The machine made, however, enormous oscillations. The air, gathering end compressed under it, would sometimes escape by one side sometimes by the other, thus shaking and whirling the parachute about with a violence which, however great, had happily no unfortunate effect. The origin of the parachute is more remote than is generally supposed, as there was a figure of one which appeared among a collection of machines at Venice, in 1617.