the dominion of the air-第34部分
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ans unreasonable to levy。 The recognised tariff seems to have been 20 centimes for 4 grammes； or at the rate of not greatly more than a shilling per English ounce。 Surely hardly on a par with famein prices in a time of siege。
It has already been stated that the defenders of Paris did not derive substantial assistance from the services of such a reconnoitring balloon as is generally used in warfare at every available opportunity。 It is possible that the peculiar circumstances of the investment of the town rendered such reconnaissance of comparatively small value。 But； at any rate； it seems clear that due opportunity was not given to this strategic method。 M。 Giffard； who at the commencement of the siege was in Paris； and whose experience with a captive balloon was second to none； made early overtures to the Government； offering to build for L40；000 a suitable balloon； capable of raising forty persons to a heightm of 3；000 feet。 Forty aerial scouts； it may be said； are hardly needed for purposes of outlook at one time； but it appears that this was not the consideration which stood in the way of M。 Giffard's offer being accepted。 According to M。 de Fonvielle； the Government refused the experienced aeronaut's proposal on the ground that he required a place in the Champs Elysees； 〃which it would be necessary to clear of a few shrubs〃！
CHAPTER XIX。 THE TRAGEDY OF THE ZENITH。〃THE NAVIGABLE BALLOON
The mechanical air ship had； by this time； as may be inferred； begun seriously to occupy the attention of both theoretical and practical aeronauts。 One of the earliest machines deserving of special mention was designed by M。 Giffard； and consisted of an elongated balloon； 104 feet in length and 39 feet in greatest diameter； furnished with a triangular rudder； and a steam engine operating a screw。 The fire of the engine； which burned coke； was skilfully protected； and the fuel and water required were taken into calculation as so much ballast to be gradually expended。 In this vessel； inflated only with coal gas； and somewhat unmanageable and difficult to balance； the enthusiastic inventor ascended alone from the Hippodrome and executed sundry desired movements； not unsuccessfully。 But the trial was not of long duration； and the descent proved both rapid and perilous。 Had the trial been made in such a perfect calm as that which prevailed when certain subsequent inventions were tested； it was considered that M。 Giffard's vessel would have been as navigable as a boat in the water。 This unrivalled mechanician； after having made great advances in the direction of high speed engines of sufficient lightness； proceeded to design a vastly improved dirigible balloon； when his endeavours were frustrated by blindness。
As has been already stated； M。 Dupuy de Lome； at the end of the siege of Paris； was engaged in building a navigable balloon； which； owing to the unsettled state of affairs in France； did not receive its trial till two years later。 This balloon； which was inflated with pure hydrogen； was of greater capacity than that of M。 Giffard； being cigar shaped and measuring 118 feet by 48 feet。 It was also provided with an ingenious arrangement consisting of an internal air bag； capable of being either inflated or discharged； for the purpose of keeping the principal envelope always distended； and thus offering the least possible resistance to the wind。 The propelling power was the manual labour of eight men working the screw； and the steerage was provided for by a triangular rudder。 The trial； which was carried out without mishap； took place in February； 1872； in the Fort of Vincennes； under the personal direction of the inventor； when it was found that the vessel readily obeyed the helm； and was capable of a speed exceeding six miles an hour。
It was not till nine years after this that the next important trial with air ships was made。 The brothers Tissandier will then be found taking the lead； and an appalling incident in the aeronautical career of one of these has now to be recorded。
In the spring of 1875； and with the co…operation of French scientific societies； it was determined to make two experimental voyages in a balloon called the 〃Zenith；〃 one of these to be of long duration； the other of great height。 The first of these had been successfully accomplished in a flight of twenty…four hours' duration from Paris to Bordeaux。 It was now April the 15th； and the lofty flight was embarked upon by M。 Gaston Tissandier； accompanied by MM。 Croce…Spinelli and Sivel。 Under competent advice； provision for respiration on emergency was provided in three small balloons； filled with a mixture of air and oxygen； and fitted with indiarubber hose pipes； which would allow the mixture； when inhaled； to pass first through a wash bottle containing aromatic fluid。 The experiments determined on included an analysis of the proportion of carbonic acid gas at different heights by means of special apparatus； spectroscopic observations； and the readings registered by certain barometers and thermometers。 A novel and valuable experiment； also arranged； was that of testing the internal temperature of the balloon as compared with that of the external air。
Ascending at 11。30 a。m。 under a warm sun； the balloon had by 1 p。m。 reached an altitude of 16；000 feet； when the external air was at freezing point； the gas high in the balloon being 72 degrees； and at the centre 66 degrees。 Ere this height had been fully reached； however； the voyagers had begun to breathe oxygen。 At 11。57； an hour previously； Spinelli had written in his notebook； 〃Slight pain in the earssomewhat oppressedit is the gas。〃 At 23；000 feet Sivel wrote in his notebook； 〃I am inhaling oxygenthe effect is excellent；〃 after which he proceeded to urge the balloon higher by a discharge of ballast。 The rest of the terrible narrative has now to be taken from the notes of M。 Tissandier； and as these constitute one of the most thrilling narratives in aeronautical records we transcribe them nearly in full； as given by Mr。 Glaisher：
〃At 23；000 feet we were standing up in the car。 Sivel； who had given up for a moment； is re…invigorated。 Croce…Spinelli is motionless in front of me。。。。 I felt stupefied and frozen。 I wished to put on my fur gloves； but； without being conscious of it； the action of taking them from my pocket necessitated an effort that I could no longer make。。。。 I copy； verbatim； the following lines which were written by me； although I have no very distinct remembrance of doing so。 They are traced in a hardly legible manner by a hand trembling with cold： 'My hands are frozen。 I am all right。 We are all all right。 Fog in the horizon； with little rounded cirrus。 We are ascending。 Croce pants； he inhales oxygen。 Sivel closes his eyes。 Croce also closes his eyes。。。。 Sivel throws out ballast'these last words are hardly readable。 Sivel seized his knife and cut successively three cords； and the three bags emptied themselves and we ascended rapidly。 The last remembrance of this ascent which remains clear to me relates to a moment earlier。 Croce…Spinelli was seated； holding in one hand a wash bottle of oxygen gas。 His head was slightly inclined and he seemed oppressed。 I had still strength to tap the aneroid barometer to facilitate the movement of the needle。 Sivel had just raised his hand towards the sky。 As for myself； I remained perfectly still； without suspecting that I had； perhaps； already lost the power of moving。 About the height of 25；000 feet the condition of stupefaction which ensues is extraordinary。 The mind and body weaken by degrees； and imperceptibly； without consciousness of it。 No suffering is then experienced； on the contrary； an inner joy is felt like an irradiation from the surrounding flood of light。 One becomes indifferent。 One thinks no more of the perilous position or of danger。 One ascends； and is happy to ascend。 The vertigo of the upper regions is not an idle word； but； so far as I can judge from my personal impression； vertigo appears at the last moment； it immediately precedes annihilation； sudden； unexpected； and irresistible。
〃When Sivel cut away the bags of ballast at the height of about 24；000 feet； I seemed to remember that he was sitting at the bottom of the car； and nearly in the same position as Croce…Spinelli。 For my part； I was in the angle of the car； thanks to which support I was able to hold up； but I soon felt too weak even to turn my head to look at my companions。 Soon I wished to take hold of the tube of oxygen； but it was impossible to raise my arm。 My mind； nevertheless； was quite clear。 I wished to explain； 'We are 8；000 metres high'； but my tongue was； as it were； paralysed。 All at once I closed my eyes； and； sinking down inert； became insensible。 This was about 1。30 p。m。 At 2。8 p。m。 I awoke for a moment； and found the balloon rapidly descending。 I was able to cut away a bag of ballast to check the speed and write in my notebook the following lines； which I copy：
〃 'We are descending。 Temperature； 3 degrees。 I throw out ballast。 Barometer； 12。4 inches。 We are descending。 Sivel and Croce still in a fainting state at the bottom of the car。 Descending very rapidly。'
〃Hardly had I written these lines when a kind of trembling seized me； and I fell back weakened again。 There was a violent wind from below； upwards； denoting a very rapid descent。 After some minutes I felt myself shaken by the arm； and I recognised Croce； who had revived。 'Throw out ballast；' he said to me； 'we are descending '； but I could hardly open my eyes； and did not see whether Sivel was awake。 I called to mind that Croce unfastened the aspirator； which he then threw overboard； and then he threw out ballast； rugs； etc。
〃All this is an extremely confused remembrance； quickly extinguished； for again I fell back inert more completely than before； and it seemed to me that I was dying。 What happened？ It is certain that the balloon； relieved of a great weight of ballast； at once ascended to the higher regions。
〃At 3。30 p。m。 I opened my eyes again。 I felt dreadfully giddy and oppressed； but gradually came to myself。 The balloon was descending with frightful speed and making great oscillations。 I crept along on my
