the dominion of the air-第30节
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nstruments； to the immediate destruction of some of them。
Another result of this abrupt departure was a very rapid rise； which took the balloon a height of 3；000 feet in three minutes' space； and another 4；000 feet higher in six minutes more。 Seven thousand feet vertically in nine minutes is fast pace； but the voyagers were to know higher speed yet that day when the vertical motion was to be in the reverse and wrong direction。 At the height now reached they were in cloud； and while thus enveloped the temperature； as often happens； remained practically stationary at about 32 degrees； while that of the dew point increased several degrees。 But； on passing out of the cloud； the two temperatures were very suddenly separated； the latter decreasing rapidly under a deep blue upper sky that was now without a cloud。 Shortly after this the temperature dropped suddenly some 8 degrees； and then； during the next 12；000 feet； crept slowly down by small stages。 Presently the balloon； reaching more than twenty thousand feet； or； roughly； four miles； and still ascending； the thermometer was taken with small fits of rising and falling alternately till an altitude of 24；000 feet was recorded； at which point other and more serious matters intruded themselves。
The earth had been for a considerable time lost to view； and the rate and direction of recent progress had become merely conjectural。 What might be taking place in these obscured and lofty regions？ It would be as well to discover。 So the valve was opened rather freely； with the result that the balloon dropped a mile in three minutes。 Then another mile slower； by a shade。 Then at 12；000 feet a cloud layer was reached； and shortly after the voyagers broke through into the clear below。
At that moment Mr。 Glaisher； who was busy with his instruments； heard Mr。 Coxwell make an exclamation which caused him to look over the car； and he writes； 〃The sea seemed to be under us。 Mr。 Coxwell again exclaimed； 'There's not a moment to spare： we must save the land at all risks。 Leave the instruments。' Mr。 Coxwell almost hung to the valve line； and told me to do the same； and not to mind its cutting my hand。 It was a bold decision opening the valve in this way； and it was boldly carried out。〃 As may be supposed； the bold decision ended with a crash。 The whole time of descending the four and a quarter miles was a quarter of an hour； the last two miles taking four minutes only。 For all that； there was no penalty beyond a few bruises and the wrecking of the instruments； and when land was reached there was no rebound； the balloon simply lay inert hard by the margin of the sea。 This terrific experience in its salient details is strangely similar to that already recorded by Albert Smith。
In further experimental labours conducted during the summer of this year； many interesting facts stand out prominently among a voluminous mass of observations。 In an ascent in an east wind from the Crystal Palace in early July it was found that the upper limit of that wind was reached at 2；400 feet； at which level an air…stream from the north was encountered； but at 3；000 feet higher the wind again changed to a current from the N。N。W。 At the height； then； of little more than half a mile； these upper currents were travelling leisurely； but what was more noteworthy was their humidity； which greatly increased with altitude； and a fact which may often be noted here obtruded itself； namely； when the aeronauts were at the upperlimits of the east wind； flat…bottomed cumulus clouds were floating at their level。 These clouds were entirely within the influence of the upper or north wind； so that their under sides were in contact with the east wind； i。e。 with a much drier air； which at once dissipated all vapour in contact with it； and thus presented the appearance of flat…bottomed clouds。 It is a common experience to find the lower surface of a cloud mowed off flat by an east wind blowing beneath it。
At the end of June a voyage from Wolverton was accomplished； which yielded remarkable results of much real value and interest。 The previous night had been perfectly calm； and through nearly the whole morning the sun shone in a clear blue sky； without a symptom of wind or coming change。 Shortly before noon； however； clouds appeared aloft； and the sky assumed an altered aspect。 Then the state of things quickly changed。 Wind currents reached the earth blowing strongly； and the half…filled balloon began to lurch to such an extent that the inflation could only with difficulty be proceeded with。 Fifty men were unable to hold it in sufficient restraint to prevent rude bumping of the car on the ground； and when； at length； arrangements were complete and release effected； rapid discharge of ballast alone saved collision with neighbouring buildings。
It was now that the disturbance overhead came under investigation； and； considering the short period it had been in progress； proved most remarkable； the more so the further it was explored。 At 4；000 feet they plunged into the cloud canopy； through which as it was painfully cold； they； sought to penetrate into the clear above； feeling confident of finding themselves； according to their usual experience； in bright blue sky； with the sun brilliantly shining。 On the contrary； however； the region they now entered was further obscured with another canopy of cloud far up。 It was while they were traversing this clear interval that a sound unwonted in balloon travel assailed their ears。 This was the 〃sighing； or rather moaning； of the wind as preceding a storm。〃 Rustling of the silk within the cordage is often heard aloft； being due to expansion of gas or similar cause； but the aeronauts soon convinced themselves that what they heard was attributable to nothing else than the actual conflict of air currents beneath。 Then they reached foga dry fogand； passing through it； entered a further fog； but wetting this time； and within the next 1；000 feet they were once again in fog that was dry； and then； reaching three miles high and seeing struggling sunbeams； they looked around and saw cloud everywhere； below； above； and far clouds on their own level。 The whole sky had filled in most completely since the hours but recently passed； when they had been expatiating on the perfect serenity of the empty heavens。
Still they climbed upwards； and in the next 2；000 feet had entered further fog； dry at first； but turning wetter as they rose。 At four miles high they found themselves on a level with clouds； whose dark masses and fringed edges proved them to be veritable rain clouds； and； while still observing them； the fog surged up again and shut out the view； and by the time they had surmounted it they were no less than 23；000 feet up； or higher than the loftiest of the Andes。 Even here； with cloud masses still piling high overhead； the eager observer； bent on further quests； was for pursuing the voyage； but Mr。 Coxwell interposed with an emphatic； 〃Too short of sand！〃 and the downward journey had to be commenced。 Then phenomena similar to those already described were experienced againfog banks （sometimes wet； sometimes dry）； rain showers； and cloud strata of piercing cold。 Presently； too； a new wonder for a midsummer afternoona snow scene all around； and spicules of ice settling and remaining frozen on the coatsleeve。 Finally dropping to earth helplessly through the last 5；000 feet； with all ballast spent； Ely Cathedral was passed at close quarters； yet even that vast pile was hidden in the gloom that now lay over all the land。
It was just a month later； and day broke with thoroughly dirty weather； a heavy sky； and falling showers。 This was the day of all others that Mr。 Glaisher was waiting for； having determined on making special investigations concerning the formation of rain in the clouds themselves。 It had long been noticed that； in an ordinary way； if there be two rain gauges placed； one near the surface of the ground； and another at a somewhat higher elevation； then the lower gauge will collect most water。 Does； then； rain condense in some appreciable quantity out of the lowest level？ Again； during rain； is the air saturated completely； and what regulates the quality of rainfall； for rain sometimes falls in large drops and sometimes in minute particles？ These were questions which Mr。 Glaisher sought to solve； and there was another。
Charles Green had stated as his conviction that whenever rain was falling from an overcast sky there would always be found a higher canopy of cloud over…hanging the lower stratum。 On the day； then； which we are now describing； Mr。 Glaisher wished to put this his theory to the test； and； if correct； then he desired to measure the space between the cloud layers； to gauge their thickness； and to see if above the second stratum the sun was shining。 The main details of the ascent read thus：
In ten seconds they were in mist； and in ten seconds more were level with the cloud。 At 1；200 feet they were out of the rain； though not yet out of the cloud。 Emerging from the lower cloud at 2；300 feet； they saw； what Green would have foretold； an upper stratum of dark cloud above。 Then they made excursions up and down； trying high and low to verify these
