« AnteriorContinuar »
ballast remaining, which we judge it prudent to keep for the descent. Besides, it is useless to try to mount higher with instruments which have become mute; the mercury is congealed. We could, at most, only strive to maintain ourselves for some time at the same height, but, although the appendage is raised to prevent the escape of gas by its orifice, the balloon begins to descend. We proceed to secure portions of the air, and, though the tube of one of the receptacles is broken in attempting to turn the stop-cock, the other is filled without accident. But the cold paralyzes all our efforts; observations have become impossible; our fingers are disqualified for every operation. We resign ourselves to a descent.
" The thermometer with a glass surface marks +20.50 ; that with a silvered surface +1°.91.
“ 5h 16m.-The barometer oscillates from 598.5 millimeters to 618.0 millimeters, because we throw over our ballast, and this arrests our descent; the temperature is 10.8; the height varies from 1,973 to 1,707 meters.
The oscillations are prolonged by the discharge of the last portions of our ballast. We are now only occupied with moderating the descent by sacrificing all that we have at our disposal, except the instruments, and we place the thermometers in their cases.
“ 5h 30m.- We touch the earth at the hamlet of Peux, a commune of Saint Denis les Rebris, arrondissement of Coulommiers, (Seine et Marne,) at some paces from the residence of M. Brulfert, mayor of the commune, 70 kilometers distant from Paris.
We had the good fortune to break no instrument in our descent. The village afforded but a single vehicle to carry us to the Strasbourg railroad, 18 kilometers distant, and the transfer was rendered troublesome by a violent storm of wind and rain; the horse fell, breaking two of the instruments, which we greatly desired to carry safe to Paris, namely, the balloon for air, and the instrument indicating the minimum of barometric pressure. Fortunately the minimum thermometer of M. Walferdin, with his seal, was conveyed intact to the College of France. Here the seal was removed by MM. Regnault and Walferdin, and the minimum of temperature determined, by direct experiment, was found to be - 399.67, consequently very little different from the lowest temperature observed by ourselves on the thermometer of the barometer."
In rendering my report to the Academy of Sciences, I remarked that the fact of the presence of a cloud composed of small particles of ice having a temperature of about -40° in mid-summer, at a height of from 6,000 to 7,000 meters above the surface of Europe, is the greatest discovery which meteorology has
for a long time recorded. This discovery explains how these icy particles may become the nucleus of hailstones of considerable volume, for we readily coniprehend how they may condense around them and solidify the aqueous vapors contained in the atmospheric strata in which they float; it likewise demonstrates the truth of the hypothesis of Mariotte, who attributed the existence of halos, parhelia, and paraselenes, to crystals of ice suspended in the air. In fine, the presence of a widely-extended cloud of great coldness very well accounts for the sudden changes of temperature which so often and unexpectedly affect our climates. MM. Barral and Bixio, in discussing the meteorological observations made in Europe at the time, including the day preceding and the day following their memorable ascension, were enabled to establish the occurrence of sudden and general accessions of cold, which bore undoubtedly a direct relation to the arrival of the intensely frigorific masses of vapor
which were then propagating themselves from the northeast to the southwest.
VI.-VOYAGES OF JOHN WELSH.
In July, 1852, the committee of directors of the observatory of Kew, near London, resolved on the execution of a series of aeronautic ascensions with a view to the investigation of the meteorological and physical phenomena which develop themselves in the most elevated regions of the terrestrial atmosphere. This resolution was approved by the council of the British Association for the Advancement of Science. Instruments were immediately prepared, consisting of a barometer of Gay Lussac, dry and wet thermometers, an aspirator, a condensing hygrometer of Regnault, a hygrometer of Daniell, a polariscope and glass tubes to collect the air. The balloon made use of was that of M. Green, who constantly accompanied M. John Welsh, to whom the observations were intrusted ; illuminating gas was employed for inflation. Four ascensions took place, August 17 and 26, October 21, November 10, 1852. In the first two voyages M. Nicklin also accompanied M. Welsh. The place of departure was the garden of Vauxhall.
In the first ascension, August 17, the expeditionists set forth at 49 minutes after three in the evening, and again touched the earth at 20 minutes after five, 23 leagues north of London. They reached the height of 5,947 meters. The lowest pressure they obtained was 364.5 millimeters, and the minimum temperature -13°.2. On the earth the barometer indicated 755.1 millimeters, and the thermometer +21°.8. A cloud covered the horizon, its inferior limit was reached at about 762 meters, and its superior limit at 3,963 meters. The balloon then penetrated into pure air, but at a great distance above there spread a dense cloudy mass. Snow, consisting of star-shaped flakes, fell from time to time on the balloon.
The second ascension, August 26, commenced at 4 hours 43 minutes in the evening, and terminated at 7 hours 35 minutes; the descent took place 10 leagues W.NW. of London. The balloon rose to a height of 6,096 meters, and the lowest temperature observed was – 100.3. On the earth the pressure was 760.9 millimeters, and the temperature +19.1. A few clouds were suspended in the atmosphere at a height of about 900 meters; above, the sky was clear and of a bright blue.
The third ascension took place October 21, at 2 hours 45 minutes; the voyagers descended at 4 hours 20 minutes, about 12 leagues to the east of London. They ascended only to a height of 3,853 meters; the least pressure observed was 475.5 millimeters, the lowest temperature -30.8. On the earth the barometer marked 759.2 millimeters, the thermometer +14°.2. Between 254 and 853 meters, the balloon encountered detached and irregular clouds; at about 915 meters it entered a continuous bed of cloud, whose upper surface terminated at 1,093 meters.' On its emergence from the cloud the balloon projected on its nearly level expanse a shadow surrounded with fringes. The light, directly reflected by the cloud, examined with the polariscope, presented no trace of polarization.
The greatest height at which M. Welsh arrived was attained in his fourth voyage, performed the 10th of November. The ascent took place at 2 hours 21 minutes, and the descent, near Folkstone, 23 leagues E.SE. of London, at 3 hours 45 minutes. The height reached was 6,989 meters; minimum temperature observed -23°.6; minimum pressure 310.9 millimeters. On the earth the barometer indicated 761.1 millimeters, and the thermometer +90.6. A first cloud was encountered at 254 meters, whose upper surface reached a height of 600 meters. There occurred next a space of 620 meters, free from all sensible vapor; but, at a height of 1,220 meters, a new cloud was met with, which ter. minated at 4,494 meters. Beyond this there were only a few cirri at a very great height.
We see that the English aeronauts only once approached, though without attaining, the height of 7,000 meters, reached by Gay Lussac, and by Barral and Bixio. The very low temperature of -2306, observed by Welsh in his last ascension, would certainly have appeared extraordinary if our countrymen,
expedition of July 27, 1850, had not encountered a cloud having a much lower temperature. The air collected by Mr. Welsh was analyzed by M. Miller, who found its composition the same with that of normal air. The hygrometrical observations which Mr. Welsh made with care, and in great num. ber, by help of the psychrometer and hygrometer of M. Regnault, did not indicate any considerable dryness. On the contrary, even in the highest regions, the relative atmospheric humidity approached saturation.
VII.--THE GREATEST HEIGHTS REACHED, AND THE TEMPERATURES OBSERVED,
IN THE UPPER REGIONS OF THE ATMOSPHERE.
It is worthy of remark that, to the present time, man has not ascended into the atmosphere as high as the aerial stratum which surrounds the loftiest mountain summits of the Old and New World. Kintschindinga and Aconcagua, the former 8,592, the latter 7,291 meters high. In the ascent of mountains, barely 6,000 meters may be assigned as the height to which human effort has attained. In June, 1802, my illustrious friend, Alexander Humboldt, accompanied by M. Bonpland, ascended Chimborazo to the altitude of 5,878 meters. In December, 1831, another of my friends, M. Boussingault, accompanied by Colonel Hall, climbed the same mountain to the height of 6,004 meters above the level of the sea. If we add to these two celebrated excursions the aeronautic voyages of Lhoest and Robertson, July 18, 1803; of Gay Lussac, September 16, 1804; of MM. Barral and Bixio, July 27, 1850; of M. Welsh, August 26 and November 10, 1852, we have the sum of all the enterprises in which man has succeeded in maintaining his position for a few instants in the strata of air situated from 6,000 to 7,000 meters above the mean level of the seas. The following table recapitulates the thermometric and barometric observations made under these rare circumstances :
Lowest barometrie Lowest pressures observed. temperatures
(Reduced to 0°.) observed
Humboldt and Bonpland..... June 24, 1802
July 18, 1803
Sept. 16, 1804 Boussingault and Colonel Hall.. Doc. 16, 1831 Barral and Bixio...
July 27, 1850 Welsh.
Aug. 26, 1852 Welsh .
Nov. 10, 1852
5, 878 6,831 7,016 6,004 7, 049 6, 096 6,989
376.7 336.0 328.8 371.1 315.0 371.1 310.9
1.6 - 6,9 - 9,5 + 7.8
These figures certainly demonstrate that, in high atmospheric regions, the thermometric variations are not less considerable than on the surface of the earth, and that, in any case, if there be a stratum of constant temperature in the terrestrial atmosphere, the fact of its existence is only admissible as regards an elevation probably much greater than any yet reached. Is it practicable to transcend this limitary height of 7,000 meters, by which all ascensions hitherto undertaken have been bounded? There is but one consideration which can make us hesitate to answer affirmatively. We know not if man's physical constitution could adapt itself to a pressure much lighter than that of 311 millimeters, about twofifths of the mean pressure observed on the sea-shore.
AN ACCOUNT OF BALLOON ASCENSIONS.
BY MR. JAMES GLAISHER.
[From the London Atheneum, October, 1864.)
The committee on balloon experiments was appointed last year for the following purposes : To examine the electrical condition of the air at different heights; to verify the law of the decrease of temperature; and to compare the constants in different states of the atmosphere. With respect to the first of these objects no progress had been made, with the exception of preparing an instrument and apparatus for the investigation. At the request of the committee Mr. Fleming Jenkin undertook the construction of the best instrument for the purpose, and one was finished towards the end of 1863, but it was constructed to be used with fire. It has since had to be adapted for water, a constant flow of which is necessary in electrical experiments in balloons. This apparatus Mr. Glaisher was requested by the committee not to use, as they felt that these instruments, if exerting no influence while the balloon was rising, might, when it was falling, throw considerable doubt on the experiments relating to humidity. With respect to the second of these objects, the verifying the law of the decrease of temperature in different states of the atmosphere, the committee considered would be best attained by taking as many observations as possible at times in the year, and at times in the day, at which no experiments had been made, for the purpose of determining whether the laws which hold good at noon apply equally well at all other times of the day. The committee have always pressed the importance of magnetic observations in the higher regions of the air—the Astronomer Royal suggesting the use of a horizontal magnet, and taking the times of its vibration at different elevations, a method which is seldom practicable, owing to the almost constant revolution of the balloon. To obviate this, Dr. Lloyd suggested the use of a dipping-needle, placed horizontally when on the ground, by means of a magnet above it, so that, when in the balloon, the deviation from horizontality might be noticed, and which deviation would be independent of rotary motion of the balloon. The latter method has not yet been tried, Dr. Lloyd wishing some experiments to be made before the instrument was constructed. At Newcastle a very general wish being expressed that very high ascents should not again be attempted, none above five miles had since been made. Mr. Glaisher then gave an account of the ascents made by him during the past year. The first was from Newcastle, on the 31st of August. The balloon left the earth at 6h. 11m. p. m., with a north wind, and descended at five minutes past 7, at Pittington, near Durham. The decrease of temperature within the first 200
feet of the earth in this ascent was very remarkable, no such rapid decrease having been found in any other ascents. On the ground the temperature was 64°, and by the time 200 feet had been attained, a decrease of 8 degrees had taken place, the temperature being 56°. From this height to 1,200 feet there was but little change, and above this the temperature decreased from 2° to 3.1° in each succeeding 1,000 feet up to 7,000 feet, when the balloon entered a relatively warmer current of air. The second ascent, on the 29th of September, 1863, was from Wolverhampton. The gas on this occasion had been prepared in July expressly for a high ascent intended to have taken place before the Newcastle meeting, but circumstances prevented this being made, and the gas was oblig. ingly stored in the gasometer by the directors of the gas-works. The balloon left at 7h. 43m. a. m., wind SW. At 8,200 feet there were two layers of clouds below the balloon and very dense clouds above. When at 11,000 feet the clouds were still a mile higher; there was a sea of blue-tinged cloud below, and peeps of the earth was seen through the breaks. At 13,000 feet high clouds were still above; but after this they began to dissipate, and at 9h. 38m., at 14,000 feet, the sun shone brightly. Ten minutes afterwards the travellers discovered the Wash at a distance of only ten miles, and were compelled to descend. southwest gale was blowing, and so strong was the wind that on the grapnels taking the ground near Sleaford, at 10h. 30m., the balloon was rent from top to bottom. In this ascent warm currents were met with at 8,000 and 13,500 feet. In the descent a warm current was passed through, extending from 14,000 to 9,000 feet. Temperature at the ground on leaving 48°; at time of descent 53o. On passing out of the mist at 3,000 feet the humidity declined to 58° at 8,000 fect. Here there were dense clouds above and below. At 9,000 feet the humidity was 71°, and then the air became suddenly dry. The third ascent was made from the Crystal Palace, at 4h. 29m. p. m., on the 9th of October. In sev. enteen minutes it was 7,300 feet high, and directly over London Bridge, and all the vast number of buildings, comprising the whole of London, could be clearly
There were neither warm nor cold currents met with on this day. The secretary of state for war having granted permission to the committee to avail themselves of the facilities afforded in the Royal Arsenal, at Woolwich, the ascent of the 12th of January was made from thence. It was intended to have been made on the 21st of December previous, and from time to time the balloon had been partially inflated. It left at 2h. 7m. p. m., and in 14 minutes had crossed the Tilbury railway, and was over Ilainault forest. At 3h. 31m. the height of 12,000 feet was attained, when the balloon began to descend, and touched the ground at 4h. 10m. at Lakenheath. On the carth the wind was SE. At 1,300 feet a strong SW. current was entered, in which the balloon continued up to 4,000 feet, when the wind changed to S. At 8,000 feet the wind changed to S.SW., and afterwards to S.SE. At 11,000 feet fine granular snow was met with, and the balloon passed through snot on descending till within 8,000 feet of the earth. Clouds were entered at 7,000 feet, which merged at about 6,000 feet into mist. This ascent is the only one ever made in January for scientific purposes. The fifth ascent was designed to have been mide as near the 21st of March as possible, but through adverse weather was deferred to the 6th of April. The balloon left Woolwich at 4h. 7m. p. m., with a SE. wind, ascending evenly at the rate of 1,000 feet in about three minutes, till 11,000 feet was attained at 4h. 37m. It descended into Wilderness Park, near Sevenoaks, in Kent. Its course was most remarkable, having passed over the Thames into Essex. The balloon, unknown to the aeronauts, must have repassed the river and moved in a directly opposite direction, and so continued till it approached the earth, when it again moved in the same direction as at first. The ascent is remarkable for the small decrease in temperature with increase of elevation. The air, at the period of starting, was 45.1°, and did not decline at all till after reaching 300 feet, after which it decreased gradually to 33° at 4,300. A warm current was then en