the dominion of the air-第31章
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aluable aid to the uses of philosophy； and rescue it from the impending degradation of continuing a toy fit only to be exhibited or to administer to the pleasures of the curious and lovers of adventure。〃
The words of the same authority as to the possible practical development of the balloon as an aerial machine should likewise be quoted； and will appear almost prophetic。 〃In England the subject of aero…station has made but little progress； and no valuable invention has arisen to facilitate travelling in the air。 In all my ascents I used the balloon as I found it。 The desire which influenced me was to ascend to the higher regions and travel by its means in furtherance of a better knowledge of atmospheric phenomena。 Neither its management nor its improvement formed a part of my plan。 I soon found that balloon travelling was at the mercy of the wind； and I saw no probability of any method of steering balloons being obtained。 It even appeared to me that the balloon itself； admirable for vertical ascents； was not necessarily a first step in aerial navigation； and might possibly have no share in the solution of the problem。 It was this conviction that led to the formation of the Aeronautical Society a few years since under the presidency of the Duke of Argyll。 In the number of communications made to this society it is evident that many minds are taxing their ingenuity to discover a mode of navigating the air； all kinds of imaginary projects have been suggested； some showing great mechanical ingenuity； but all indicating the want of more knowledge of the atmosphere itself。 The first great aim of this society is the connecting the velocity of the air with its pressure on plane surfaces at various inclinations。
〃There seems no prospect of obtaining this relation otherwise than by a careful series of experiments。〃
CHAPTER XIV。 THE HIGHEST ASCENT ON RECORD。
Mr。 Glaisher's instrumental outfit was on an elaborate and costly scale； and the programme of experimental work drawn up for him by the Committee of the British Association did not err on the side of too much modesty。 In the first place the temperature and moisture of the atmosphere were to be examined。 Observations on mountain sides had determined that thermometers showed a decrease of 1 degree F。 for every 300 feet； and the accuracy of this law was particularly to be tested。 Also； investigations were to be made as to the distribution of vapour below the clouds； in them； and above them。 Then careful observations respecting the dew point were to be undertaken at all accessible heights； and； more particularly； up to those heights where man may be resident or troops may be located。 The comparatively new instrument； the aneroid barometer； extremely valuable； if only trustworthy； by reason of its sensibility； portability and safety； was to be tested and compared with the behaviour of a reliable mercurial barometer。 Electrical conditions were to be examined； the presence of ozone tested； the vibration of a magnet was again to be resorted to to determine how far the magnetism of the earth might be affected by height。 The solar spectrum was to be observed； air was to be collected at different heights for analysis； clouds； also upper currents； were to be reported on。 Further observations were to be made on sound； on solar radiation； on the actinic action of the sun； and on atmospheric phenomena in general。
All this must be regarded as a large order where only a very limited number of ascents were contemplated； and it may be mentioned that some of the methods of investigation； as； for instance； the use of ozone papers； would now be generally considered obsolete； while the mechanical aspiration of thermometers by a stream of air； which； as we have pointed out； was introduced by Welsh； and which is strongly insisted on at the present day； was considered unnecessary by Mr。 Glaisher in the case of wet and dry bulb hygrometers。 The entire list of instruments； as minutely described by the talented observer； numbered twenty…two articles； among which were such irreproachable items as a bottle of water and a pair of scissors。
The following is a condensed account； gathered from Mr。 Glaisher's own narrative； of his first ascent； which has been already briefly sketched in these pages by the hand of Mr。 Coxwell。 Very great difficulties were experienced in the inflation； which operation appeared as if it would never be completed； for a terrible W。S。W。 wind was constantly blowing； and the movements of the balloon were so great and so rapid that it was impossible to fix a single instrument in its position before quitting the earth； a position of affairs which； says Mr。 Glaisher； 〃was by no means cheering to a novice who had never before put his foot in the car of a balloon；〃 and when； at last； at 9。42 a。m。； Mr。 Coxwell cast off； there was no upward motion； the car simply dragging on its side till the expiration of a whole minute； when the balloon lifted； and in six minutes reached the first cloud at an altitude of 4；467 feet。 This cloud was passed at 5；802 feet； and further cloud encountered at 2；000 feet further aloft。 Four minutes later； the ascent proceeding； the sun shone out brightly； expanding the balloon into a perfect globe and displaying a magnificent view； which； however； the incipient voyager did not allow himself to enjoy until the instruments were arranged in due order； by which time a height of 10；000 feet was recorded。
Mr。 Glaisher apparently now had opportunity for observing the clouds； which he describes as very beautiful； and he records the hearing of a band of music at a height of 12；709 feet； which was attained in exactly twenty minutes from the start。 A minute later the earth was sighted through a break in the clouds； and at 16；914 feet the clouds were far below； the sky above being perfectly cloudless； and of an intense Prussian blue。
By this time Mr。 Glaisher had received his first surprise； as imparted by the record of his instruments。 At starting； the temperature of the air had stood at 59 degrees。 Then at 4；000 feet this was reduced to 45 degrees； and； further； to 26 degrees at 10；000 feet； when it remained stationary through an ascent of 3；000 feet more； during which period both travellers added to their clothing； anticipating much accession of cold。 However； at 15；500 feet the temperature had actually risen to 31 degrees； increasing to no less than 42 degrees at 19；500 feet。
Astonishing as this discovery was； it was not the end of the wonder； for two minutes later； on somewhat descending； the temperature commenced decreasing so rapidly as to show a fall of 27 degrees in 26 minutes。 As to personal experiences； Mr。 Glaisher should be left to tell his own story。 〃At the height of 18；844 feet 18 vibrations of a horizontal magnet occupied 26。8 seconds； and at the same height my pulse beat at the rate of 100 pulsations per minute。 At 19；415 feet palpitation of the heart became perceptible； the beating of the chronometer seemed very loud； and my breathing became affected。 At 19；435 feet my pulse had accelerated； and it was with increasing difficulty that I could read the instruments； the palpitation of the heart was very perceptible； the hands and lips assumed a dark bluish colour； but not the face。 At 20；238 feet 28 vibrations of a horizontal magnet occupied 43 seconds。 At 21；792 feet I experienced a feeling analogous to sea…sickness； though there was neither pitching nor rolling in the balloon； and through this illness I was unable to watch the instrument long enough to lower the temperature to get a deposit of dew。 The sky at this elevation was of a very deep blue colour； and the clouds were far below us。 At 22；357 feet I endeavoured to make the magnet vibrate； but could not； it moved through arcs of about 20 degrees； and then settled suddenly。
〃Our descent began a little after 11 a。m。； Mr。 Coxwell experiencing considerable uneasiness at our too close vicinity to the Wash。 We came down quickly from a height of 16；300 feet to one of 12；400 feet in one minute； at this elevation we entered into a dense cloud which proved to be no less than 8；000 feet in thickness and whilst passing through this the balloon was invisible from t
