The Dominion of the Air [110]
well-considered and practical method of employing Montgolfier reconnoitring balloons, portable, readily inflated, and especially suited to the war in South Africa. Perhaps the last letters of a private nature penned by Mr. Coxwell were to the writer and his daughter, full of friendly and valuable suggestion, and more particularly commenting on a recent scientific aerial voyage, which proved to be not only sensational, but established a record in English ballooning.
The great train of the November meteors, known as the Leonids, which at regular periods of thirty-three years had in the past encountered the earth's atmosphere, was due, and over-due. The cause of this, and of their finally eluding observation, need only be very briefly touched on here. The actual meteoric train is known to travel in an elongated ellipse, the far end of which lies near the confines of the solar system, while at a point near the hither end the earth's orbit runs slantingly athwart it, forming, as it were, a level crossing common to the two orbits, the earth taking some five or six hours in transit. Calculation shows that the meteor train is to be expected at this crossing every thirty-three and a third years, while the train is extended to such an enormous length--taking more than a year to draw clear--that the earth must needs encounter it ere it gets by, possibly even two years running. There could be no absolute certainty about the exact year, nor the exact night when the earth and the meteors would foregather, owing to the uncertain disturbance which the latter must suffer from the pull of the planetary bodies in the long journey out and home again among them. As is now known, this disturbing effect had actually dispersed the train.
The shower, which was well seen in 1866, was pretty confidently expected in 1899, and to guard against the mischance of cloudy weather, it was arranged that the writer should, on behalf of the Times newspaper, make an ascent on the right night to secure observations. Moreover, it was arranged that he should have, as chief assistant, his own daughter, an enthusiastic lady aeronaut, who had also taken part in previous astronomical work.
Unfortunately there were two nights, those of November 14th and 15th, when the expected shower seemed equally probable, and, taking counsel with the best authorities in the astronomical world, it seemed that the only course to avoid disappointment would be to have a balloon filled and moored in readiness for an immediate start, either on the first night or on the second.
This settled the matter from the astronomical side, but there was the aeronautical side also to be considered. A balloon of 56,000 cubic feet capacity was the largest available for the occasion, and a night ascent with three passengers and instruments would need plenty of lifting power to meet chance emergencies. Thus it seemed that a possible delay of forty-eight hours might entail a greater leakage of gas than could be afforded.
The leakage might be expected chiefly to occur at the valve in the head of the balloon, it being extremely difficult to render any form of mechanical valve gas tight, however carefully its joints be stopped with luting. On this account, therefore, it was determined that the balloon should be fitted with what is known as a solid or rending valve, consisting simply of balloon fabric tied hard and fast over the entire upper outlet, after the fashion of a jam pot cover. The outlet itself was a gaping hole of over 2 feet across; but by the time its covering had been carefully varnished over all leakage was sufficiently prevented, the one drawback to this method being the fact that the liberation of gas now admitted of no regulation. Pulling the valve line would simply mean opening the entire wide aperture, which could in no way be closed again.
The management of such a valve consists in allowing the balloon to sink spontaneously earthwards, and when it has settled near the ground, having chosen a desirable landing place, to tear open the so-called valve once and
The great train of the November meteors, known as the Leonids, which at regular periods of thirty-three years had in the past encountered the earth's atmosphere, was due, and over-due. The cause of this, and of their finally eluding observation, need only be very briefly touched on here. The actual meteoric train is known to travel in an elongated ellipse, the far end of which lies near the confines of the solar system, while at a point near the hither end the earth's orbit runs slantingly athwart it, forming, as it were, a level crossing common to the two orbits, the earth taking some five or six hours in transit. Calculation shows that the meteor train is to be expected at this crossing every thirty-three and a third years, while the train is extended to such an enormous length--taking more than a year to draw clear--that the earth must needs encounter it ere it gets by, possibly even two years running. There could be no absolute certainty about the exact year, nor the exact night when the earth and the meteors would foregather, owing to the uncertain disturbance which the latter must suffer from the pull of the planetary bodies in the long journey out and home again among them. As is now known, this disturbing effect had actually dispersed the train.
The shower, which was well seen in 1866, was pretty confidently expected in 1899, and to guard against the mischance of cloudy weather, it was arranged that the writer should, on behalf of the Times newspaper, make an ascent on the right night to secure observations. Moreover, it was arranged that he should have, as chief assistant, his own daughter, an enthusiastic lady aeronaut, who had also taken part in previous astronomical work.
Unfortunately there were two nights, those of November 14th and 15th, when the expected shower seemed equally probable, and, taking counsel with the best authorities in the astronomical world, it seemed that the only course to avoid disappointment would be to have a balloon filled and moored in readiness for an immediate start, either on the first night or on the second.
This settled the matter from the astronomical side, but there was the aeronautical side also to be considered. A balloon of 56,000 cubic feet capacity was the largest available for the occasion, and a night ascent with three passengers and instruments would need plenty of lifting power to meet chance emergencies. Thus it seemed that a possible delay of forty-eight hours might entail a greater leakage of gas than could be afforded.
The leakage might be expected chiefly to occur at the valve in the head of the balloon, it being extremely difficult to render any form of mechanical valve gas tight, however carefully its joints be stopped with luting. On this account, therefore, it was determined that the balloon should be fitted with what is known as a solid or rending valve, consisting simply of balloon fabric tied hard and fast over the entire upper outlet, after the fashion of a jam pot cover. The outlet itself was a gaping hole of over 2 feet across; but by the time its covering had been carefully varnished over all leakage was sufficiently prevented, the one drawback to this method being the fact that the liberation of gas now admitted of no regulation. Pulling the valve line would simply mean opening the entire wide aperture, which could in no way be closed again.
The management of such a valve consists in allowing the balloon to sink spontaneously earthwards, and when it has settled near the ground, having chosen a desirable landing place, to tear open the so-called valve once and