A marvellous escape took place in 1808, when two Italians ascended in a gas balloon from Padua and attained a great height, estimated as approaching 30,000 feet. Here the balloon burst, and came precipitately to the ground; and yet, despite the terrific fall, the aeronauts escaped with their lives. The explanation of this seeming impossibility was, no doubt, the tendency which a balloon, emptied of its gas, possesses to form a natural parachute. During a rapid fall the lower part of the silk will, if loose, collapse into the upper portion to form a kind of open umbrella, and thus very effectually break the descent. Many balloonists have owed their safety in similar accidents to this fortunate fact. The bursting of balloons when at high altitudes has already been referred to as happening on several previous occasions. It is a danger which is always present when a balloon is aloft, unless due precautions are taken, and the neglect of these precautions has probably led to more ballooning accidents than any other cause. The explanation is simply the varying pressure exerted upon the bag of gas by the weight of the atmosphere. When an inflated balloon is resting upon the ground, the vast ocean of air above it is pressing upon it with a weight of approximately fifteen pounds to the square inch, and it is this pressure which prevents the enclosed gas from expanding beyond a certain limit. The balloon then rises high into the air, where the weight of atmosphere pressing upon it is much diminished. The higher it rises the less the pressure becomes, and the gas it holds soon expands so much that, unless a vent is provided for it, the balloon will burst. At the present day the neck of a balloon is always left wide open when the balloon is in the air, to allow of the escape of the gas during the ascent. A perilous adventure befell Mr. Sadler, an English aeronaut, in 1812, whilst attempting to cross the Irish Channel. He started from Dublin with a wind which he hoped would carry him to Liverpool, but had gone only a short distance when he discovered a rent, which seemed to be increasing, in the silk of his balloon. Climbing the rigging with difficulty, he contrived to tie up the hole with his neckcloth. He was by this time over the sea, and having passed near the Isle of Man, found himself, as evening was approaching, close to the coast of North Wales. Here he endeavoured to seek a landing, but just at the critical moment the wind shifted, as it frequently does in this treacherous Channel, and he was quickly blown out to sea again. There he remained for another hour vainly endeavouring to make the land, and then, despairing of the attempt and seeing five ships beneath him, he came boldly down on the water, trusting they would come to his assistance.