The Dominion of the Air Part 15

"For the first few minutes all went well, and the motor seemed to be working satisfactorily. The air s.h.i.+p answered the helm readily, and admiring exclamations rose from the crowd.... But as the vessel rose higher she was seen to fall off from the wind, while the aeronauts could be seen vainly endeavouring to keep her head on. Then M. Severo commenced throwing out ballast.... All this time the s.h.i.+p was gradually soaring higher and higher until, just as it was over the Montparna.s.se Cemetery, at the height of 2,000 feet, a sheet of flame was seen to shoot up from one of the motors, and instantly the immense silk envelope containing 9,000 cubic feet of hydrogen was enveloped in leaping tongues of fire.... As soon as the flames came in contact with the gas a tremendous explosion followed, and in an instant all that was left of the air s.h.i.+p fell to the earth." Both aeronauts were dashed to pieces.

It was thought that the fatality was caused through faulty construction, the escape valve for the gas being situated only about nine feet from the motor. It was announced by Count de la Vaulx that during the summer of 1901 he would attempt to cross the Mediterranean by a balloon, provisioned for three weeks, maintaining communication with the coast during his voyage by wireless telegraphy and other methods of signalling. He was to make use of the "Herve Deviator," or steering apparatus, which may be described as a series of cupshaped plates dipping in the water at the end of a trail rope. By means of controlling cords worked from the car, the whole series of plates could be turned at an angle to the direction of the wind, by which the balloon's course would be altered. Count de la Vaulx attempted this grand journey on October 12th, starting from Toulon with the intention of reaching Algiers, taking the precaution, however, of having a cruiser in attendance. When fifty miles out from Ma.r.s.eilles a pa.s.sing steamer received from the balloon the signal, "All's well"; but the wind had veered round to the east, and, remaining persistently in this quarter, the Count abandoned his venture, and, signalling to the cruiser, succeeded in alighting on her deck, not, however, before he had completed the splendid and record voyage of 41 hours' duration.

CHAPTER XXVII. THE POSSIBILITIES OF BALLOONS IN WARFARE.

Clearly the time has not yet arrived when the flying machine will be serviceable in war. Yet we are not without those theorisers who, at the present moment, would seriously propose schemes for conveying dynamite and other explosives by air s.h.i.+p, or dropping them over hostile forces or fortresses, or even fleets at sea. They go yet further, and gravely discuss the point whether such warfare would be legitimate. We, however, may say at once, emphatically, that any such scheme is simply impracticable. It must be abundantly evident that, so far, no form of dirigible air s.h.i.+p exists which could be relied on to carry out any required manoeuvre in such atmospheric conditions as generally prevail.

If, even in calm and favourable weather, more often than not motors break down, or gear carries away, what hope is there for any aerial craft which would attempt to battle with such wind currents as commonly blow aloft?

And when we turn to the balloon proper, are chances greatly improved?

The eminently practical aeronaut, John Wise, as was told in Chapter XII., prepared a scheme for the reduction of Vera Cruz by the agency of a balloon. Let us glance at it. A single balloon was to suffice, measuring 100 feet in diameter, and capable of raising in the gross 30,000 lbs. To manoeuvre this monstrous engine he calculates he would require a cable five miles long, by means of which he hoped, in some manner, to work his way directly over the fortress, and to remain poised at that point at the height of a mile in the sky. Once granted that he could arrive and maintain himself at that position, the throwing out of combustibles would be simple, though even then the spot where they would alight after the drop of a mile would be by no means certain. It is also obvious that a vast amount of gas would have to be sacrificed to compensate for the prodigal discharge of ballast in the form of missiles.

The idea of manoeuvring a balloon in a wind, and poising it in the manner suggested, is, of course, preposterous; and when one considers the attempt to aim bombs from a moving balloon high in air the case becomes yet more absurd. Any such missile would partake of the motion of the balloon itself, and it would be impossible to tell where it would strike the earth.

To give an example which is often enough tried in balloon travel when the ground below is clear. A gla.s.s bottle (presumably empty) is cast overboard and its fall watched. It is seen not to be left behind, but to keep pace with the balloon, shrinking gradually to an object too small to be discerned, except when every now and then a ray of sunlight reflected off it reveals it for a moment as it continues to plunge downwards. After a very few seconds the impression is that it is about to reach the earth, and the eye forms a guess at some spot which it will strike; but the spot is quickly pa.s.sed, and the bottle travels far beyond across a field, over the further fence, and vastly further yet; indeed, inasmuch as to fall a mile in air a heavy body may take over twenty seconds--and twenty seconds is long to those who watch--it is often impossible to tell to two or three fields where it will finally settle.

All this while the risk that a balloon would run of being riddled by bullets, shrapnel, or pom-poms has not been taken into account, and as to the estimate of this risk there is some difference of opinion. The balloon corps and the artillery apparently approach the question with different bias. On the one hand, it is stated with perfect truth that a free balloon, which is generally either rising or falling, as well as moving across country, is a hard object to hit, and a marksman would only strike it with a chance or blundering shot; but, on the other hand let us take the following report of three years ago.

The German artillery had been testing the efficiency of a quick-firing gun when used against a balloon, and they decided that the latter would have no chance of escape except at night. A German kite-balloon was kept moving at an alt.i.tude of 600 metres, and the guns trained upon it were distant 3,000 metres. It was then stated that after the third discharge of the rapid firing battery the range was found, when all was at once over with the balloon; for, not only was it hit with every discharge, but it was presently set on fire and annihilated.

But, in any case, the antique mode of keeping a balloon moored at any spot as a post of observation must be abandoned in modern warfare. Major Baden-Powell, speaking from personal experience in South Africa, has shown how dangerous, or else how useless, such a form of reconnaissance has become. "I remember," he says, "at the battle of Magersfontein my company was lying down in extended order towards the left of our line.

We were perfectly safe from musketry fire, as we lay, perhaps, two miles from the Boer trenches, which were being sh.e.l.led by some of our guns close by. The enemy's artillery was practically silent. Presently, on looking round, I descried our balloon away out behind us about two miles off. Then she steadily rose and made several trips to a good height, but what could be seen from that distance? When a large number of our troops were ranged up within 800 yards of the trenches, and many more at all points behind them, what useful information could be obtained by means of the balloon four miles off?"

The same eminent authority insists on the necessity of an observing war balloon making short ascents. The balloon, in his opinion, should be allowed to ascend rapidly to its full height, and with as little delay as possible be hauled down again. Under these conditions it may then be well worth testing whether the primitive form of balloon, the Montgolfier, might not be the most valuable. Instead of being made, as the war balloon is now, of fragile material, and filled with costly gas difficult to procure, and which has to be conveyed in heavy and c.u.mbersome cylinders, a hot air balloon could be rapidly carried by hand anywhere where a few men could push their way. It is of strong material, readily mended if torn, and could be inflated for short ascents, if not by mere brush wood, then by a portable blast furnace and petroleum.

But there is a further use for balloons in warfare not yet exploited.

The Siege of Paris showed the utility of free balloons, and occasions arise when their use might be still further extended. The writer pointed out that it might have been very possible for an aeronaut of experience, by choosing the right weather and the right position along the British lines, to have skilfully manoeuvred a free balloon by means of upper currents, so as to convey all-important intelligence to besieged Mafeking, and he proved that it would have sufficed if the balloon could have been "tacked" across the sky to within some fifteen miles of the desired goal.

The mode of signalling which he proposed was by means of a "collapsing drum," an instrument of occasional use in the Navy. A modification of this instrument, as employed by the writer, consisted of a light, spherical, drum-shaped frame of large size, which, when covered with dark material and hung in the clear below the car of a lofty balloon, could be well seen either against blue sky or grey at a great distance.

The so-called drum could, by a very simple contrivance, readily worked from the car, be made to collapse into a very inconspicuous object, and thus be capable of displaying Morse Code signals. A long pause with the drum extended--like the long wave of a signalling flag--would denote a "dash," and a short pause a "dot," and these motions would be at once intelligible to anyone acquainted with the now universal Morse Code system.

Provided with an apparatus of the kind, the writer made an ascent from Newbury at a time when the military camps were lying on Salisbury Plain at a distance of nearly twenty miles to the south-west. The ground wind up to 2,500 feet on starting was nearly due north, and would have defeated the attempt; again, the air stream blowing above that height was nearly due east, which again would have proved unsuitable. But it was manifestly possible to utilise the two currents, and with good luck to zig-zag one's course so as to come within easy signalling distance of the various camps; and, as a matter of fact, we actually pa.s.sed immediately over Bulford Camp, with which we exchanged signals, while two other camps lay close to right and left of us. Fortune favouring us, we had actually hit our mark, though it would have been sufficient for the experiment had our course lain within ten miles right or left.

Yet a further use for the balloon in warfare remains untried in this country. Acting under the advice of experts in the Service, the writer, in the early part of the present year, suggested to the Admiralty the desirability of experimenting with balloons as a means of detecting submarine engines of war. It is well known that reefs and shoals can generally be seen from a cliff or mast head far more clearly than from the deck or other position near the surface of the water. Would not, then, a balloon, if skilfully manoeuvred, serve as a valuable post of observation? The Admiralty, in acknowledging the communication, promised to give the matter their attention; but by the month of June the Press had announcements of how the self-same experiments had been successfully carried through by French authorities, while a few days later the Admiralty wrote, "For the present no need is seen for the use of a captive balloon to detect submarines."

Among many and varied ballooning incidents which have occurred to the writer, there are some which may not unprofitably be compared with certain experiences already recorded of other aeronauts. Thunderstorms, as witnessed from a balloon, have already been casually described, and it may reasonably be hoped that the observations which have, under varying circ.u.mstances, been made at high alt.i.tudes may throw some additional light on this familiar, though somewhat perplexing, phenomenon.

To begin with, it seems a moot point whether a balloon caught in a thunderstorm is, or is not, in any special danger of being struck. It has been argued that immunity under such circ.u.mstances must depend upon whether a sufficiently long time has elapsed since the balloon left the earth to allow of its becoming positively electrified by induction from the clouds or by rain falling upon its surface. But there are many other points to be considered. There is the constant escape of gas from the mouth; there is the ma.s.s of pointed metal in the anchor; and, again, it is conceivable that a balloon rapidly descending out of a thunderstorm might carry with it a charge residing on its moistened surface which might manifest itself disastrously as the balloon reached the earth.

Instances seem to have been not infrequent of balloons encountering thunderstorms; but, unfortunately, in most cases the observers have not had any scientific training, or the accounts which are to hand are those of the type of journalist who is chiefly in quest of sensational copy.

Thus there is an account from America of a Professor King who made an ascent from Burlington, Iowa, just as a thunderstorm was approaching, with the result that, instead of scudding away with the wind before the storm, he was actually, as if by some attraction, drawn into it. On this his aim was to pierce through the cloud above, and then follows a description which it is hard to realise:--"There came down in front of him, and apparently not more than 50 feet distant, a grand discharge of electricity." Then he feels the car lifted, the gas suddenly expands to overflowing, and the balloon is hurled through the cloud with inconceivable velocity, this happening several times, with tremendous oscillations of the car, until the balloon is borne to earth in a torrent of rain. We fancy that many practical balloonists will hardly endorse this description.

But we have another, relating to one of the most distinguished aeronauts, M. Eugene G.o.dard, who, in an ascent with local journalists, was caught in a thunderstorm. Here we are told--presumably by the journalists--that "twice the lightning flashed within a few yards of the terror-stricken crew."

Once again, in an ascent at Derby, a spectator writes:--"The lightning played upon the sphere of the balloon, lighting it up and making things visible through it." This, however, one must suppose, can hardly apply to the balloon when liberated.

But a graphic description of a very different character given in the "Quarterly Journal of the Royal Meteorological Society" for January, 1901, is of real value. It appears that three lieutenants of the Prussian Balloon Corps took charge of a balloon that ascended at Berlin, and, when at a height of 2,300 feet, became enveloped in the mist, through which only occasional glimpses of earth were seen. At this point a sharp, crackling sound was heard at the ring, like the sparking of a huge electrical machine, and, looking up, the voyagers beheld sparks apparently some half-inch thick, and over two feet in length, playing from the ring. Thunder was heard, but--and this may have significance--only before and after the above phenomenon.

Another instructive experience is recorded of the younger Green in an ascent which he made from Frankfort-on-the-Maine. On this occasion he relates that he encountered a thunderstorm, and at a height of 4,400 feet found himself at the level where the storm clouds were discharging themselves in a deluge. He seems to have had no difficulty in ascending through the storm into the clear sky above, where a breeze from another quarter quickly carried him away from the storm centre.

This co-existence, or conflict of opposite currents, is held to be the common characteristic, if not the main cause, of thunderstorms, and tallies with the following personal experience. It was in typical July weather of 1900 that the writer and his son, accompanied by Admiral Sir Edmund Fremantle and Mr. Percival Spencer, made an evening ascent from Newbury. It had been a day of storms, but about 5 p.m., after what appeared to be a clearing shower, the sky brightened, and we sailed up into a cloudless heaven. The wind, at 3,000 feet, was travelling at some thirty miles an hour, and ere the distance of ten miles had been covered a formidable thunder pack was seen approaching and coming up dead against the wind. Nothing could be more evident than that the balloon was travelling rapidly with a lower wind, while the storm was being borne equally rapidly on an upper and diametrically opposite current. It proved one of the most severe thunderstorms remembered in the country.

It brooded for five hours over Devizes, a few miles ahead. A homestead on our right was struck and burned to the ground, while on our left two soldiers were killed on Salisbury Plain. The sky immediately overhead was, of course, hidden by the large globe of the balloon, but around and beneath us the storm seemed to gather in a blue grey mist, which quickly broadened and deepened till, almost before we could realise it, we found ourselves in the very heart of the storm, the lightning playing all around us, and the sharp hail stinging our faces.

The countrymen below described the balloon as apparently enveloped by the lightning, but with ourselves, though the flashes were incessant, and on all sides, the reverberations of the thunder were not remarkable, being rather brief explosions in which they resembled the thunder claps not infrequently described by travellers on mountain heights.

The balloon was now descending from a double cause: the weight of moisture suddenly acc.u.mulated on its surface, and the very obvious downrush of cold air that accompanied the storm of pelting hail. With a very limited store of ballast, it seemed impossible to make a further ascent, nor was this desirable. The signalling experiments on which we were intent could not be carried on in such weather. The only course was to descend, and though this was not at once practicable, owing to Savernake Forest being beneath us, we effected a safe landing in the first available clearing.

As has been mentioned, Mr. Glaisher and other observers have recorded several remarkable instances of opposite wind currents being met with at moderate alt.i.tudes. None, however, can have been more noteworthy or surprising than the following experience Of the writer on Whit Monday of 1899. The ascent was under an overcast sky, from the Crystal Palace at 3 p.m., at which hour a cold drizzle was settling in with a moderate breeze from the east. Thus, starting from the usual filling ground near the north tower, the balloon sailed over the body of the Palace, and thence over the suburbs towards the west till lost in the mist. We then ascended through 1,500 feet of dense, wetting cloud, and, emerging in bright suns.h.i.+ne, continued to drift for two hours at an average alt.i.tude of some 3,000 feet; 1,000 feet below us was the ill-defined, ever changing upper surface of the dense cloud floor, and it was no longer possible to determine our course, which we therefore a.s.sumed to have remained unchanged. At length, however, as a measure of prudence, we determined to descend through the clouds sufficiently to learn something of our whereabouts, which we reasonably expected to be somewhere in Surrey or Berks. On emerging, however, below the cloud, the first object that loomed out of the mist immediately below us was a cargo vessel, in the rigging of which our trail rope was entangling itself. Only by degrees the fact dawned upon us that we were in the estuary of the Thames, and beating up towards London once again with an cast wind. Thus it became evident that at the higher level, unknown to ourselves, we had been headed back on our course, for two hours, by a wind diametrically opposed to that blowing on the ground.

Two recent developments of the hot-air war balloon suggest great possibilities in the near future. One takes the form of a small captive, carrying aloft a photographic camera directed and operated electrically from the ground. The other is a self-contained pa.s.senger balloon of large dimensions, carrying in complete safety a special petroleum burner of great power. These new and important departures are mainly due to the mechanical genius of Mr. J. N. Maskelyne, who has patented and perfected them in conjunction with the writer.

CHAPTER XXVIII. THE CONSt.i.tUTION OF THE AIR.

Some fair idea of the conditions prevailing in the upper air may have been gathered from the many and various observations already recorded.

Stating the case broadly, we may a.s.sert that the same atmospheric changes with which we are familiar at the level of the earth are to be found also at all accessible heights, equally extensive and equally sudden.

Standing on an open heath on a gusty day, we may often note the rhythmic buffeting of the wind, resembling the a.s.sault of rolling billows of air. The evidence of these billows has been actually traced far aloft in balloon travel, when aeronauts, looking down on a wind-swept surface of cloud, have observed this surface to be thrown into a series of rolls of vapour, which were but vast and veritable waves of air. The interval between successive crests of these waves has on one occasion been estimated at approximately half a mile. We have seen how these air streams sometimes hold wide and independent sway at different levels.

We have seen, too, how they sometimes meet and mingle, not infrequently attended with electrical disturbance

Through broad drifts of air minor air streams would seem often literally to "thread" their way, breaking up into filaments or wandering rills of air. In the voyage across Salisbury Plain lately described, while the balloon was being carried with the more sluggish current, a number of small parachutes were dropped out at frequent intervals and carefully watched. These would commonly attend the balloon for a little while, until, getting into some minor air stream, they would suddenly and rapidly diverge at such wide angles as to suggest that crossing our actual course there were side paths, down which the smaller bodies became wafted.

On another occasion the writer met with strongly marked and altogether exceptional evidence of the vehemence and persistence of these minor aerial streamlets. It was on an occasion in April weather, when a heavy overcast sky blotted out the upper heavens. In the cloud levels the wind was somewhat sluggish, and for an hour we travelled at an average speed of a little over twenty miles an hour, never higher than 3,000 feet.

At this point, while flying over Hertfords.h.i.+re, we threw out sufficient ballast to cause the balloon to rise clear of the hazy lower air, and coming under the full influence of the sun, then in the meridian, we shot upwards at considerable speed, and soon attained an alt.i.tude of three miles. But for a considerable portion of this climb--while, in fact, we were ascending through little less than a mile of our upward course--we were a.s.sailed by impetuous cross currents, which whistled through car and rigging and smote us fairly on the cheek. It was altogether a novel experience, and the more remarkable from the fact that our main onward course was not appreciably diverted.

Then we got above these currents, and remained at our maximum level, while we floated, still at only a moderate speed, the length of a county. The descent then began, and once again, while we dropped through the same disturbed region, the same far-reaching and obtrusive cross-current a.s.sailed us. It was quite obvious that the vehement currents were too slender to tell largely upon the huge surface of the balloon, as it was being swept steadily onwards by the main wind, which never varied in direction from ground levels up to the greatest height attained.

This experience is but confirmation of the story of the wind told by the wind gauges on the Forth Bridge. Here the maximum pressure measured on the large gauge of 300 square feet is commonly considerably less than that on the smaller gauge, suggesting that the latter must be due to threads of air of limited area and high velocity.

Further and very valuable light is thrown on the peculiar ways of the wind, now being considered, by Professor Langley in the special researches of his to which reference has already been made. This eminent observer and mathematician, suspecting that the old-fas.h.i.+oned instruments, which only told what the wind had been doing every hour, or at best every minute, gave but a most imperfect record, constructed delicate gauges, which would respond to every impulse and give readings from second to second.

In this way he established the fact that the wind, far from being a body of even approximate uniformity, is under most ordinary conditions irregular almost beyond conception. Further, that the greater the speed the greater the fluctuations, so that a high wind has to be regarded as "air moving in a tumultuous ma.s.s," the velocity at one moment perhaps forty miles an hour, then diminis.h.i.+ng to an almost instantaneous calm, and then resuming. "In fact, in the very nature of the case, wind is not the result of one simple cause, but of an infinite number of impulses and changes, perhaps long pa.s.sed, which are preserved in it, and which die only slowly away."

When we come to take observations of temperature we find the conditions in the atmosphere above us to be at first sight not a little complex, and altogether different in day and night hours. From observations already recorded in this volume--notably those of Gay Lussac, Welsh, and Glaisher--it has been made to appear that, in ascending into the sky in daytime, the temperature usually falls according to a general law; but there are found regions where the fall of temperature becomes arrested, such regions being commonly, though by no means invariably, a.s.sociated with visible cloud. It is probable, however, that it would be more correct not to interpret the presence of cloud as causing manifestation of cold, but rather to regard the meeting of warm and cold currents as the cause of cloud.

The writer has experimented in the upper regions with a special form of air thermometer of great sensibility, designed to respond rapidly to slight variations of temperature. Testing this instrument on one occasion in a room of equable warmth, and without draughts, he was puzzled by seeing the index in a capillary tube suddenly mounting rapidly, due to some cause which was not apparent, till it was noticed that the parlour cat, attracted by the proceedings, had approached near the apparatus. The behaviour of this instrument when slung in the clear some distance over the side of the balloon car, and carefully watched, suggests by its fitful, sudden, and rapid changes that warmer currents are often making their way in such slender wandering rills as have been already pictured as permeating the broader air streams. During night hours conditions are reversed. The warmer air radiated off the earth through the day has then ascended. It will be found at different heights, lying in pools or strata, possibly resembling in form, could they be seen, ma.s.ses of visible cloud.

The writer has gathered from night voyages instructive and suggestive facts with reference to the ascent of air streams, due to differences of temperature, particularly over London and the suburbs, and it is conceivable that in such ascending streams may lie a means of dealing successfully with visitations of smoke and fog.

One lesson taught by balloon travel has been that fog or haze will come or go in obedience to temperature variations at low levels. Thus thick haze has lain over London, more particularly over the lower parts, at sundown. Then through night hours, as the temperature of the lower air has become equalised, the haze has completely disappeared, but only to rea.s.sert itself at dawn.

A description of the very impressive experience of a night sail over London has been reserved, but should not be altogether omitted.

Glaisher, writing of the spectacle as he observed it nearly forty years ago, describes London seen at night from a balloon at a distance as resembling a vast conflagration. When actually over the town, a main thoroughfare like the Commercial Road shone up like a line of brilliant fire; but, travelling westward, Oxford Street presented an appearance which puzzled him. "Here the two thickly studded rows of brilliant lights were seen on either side of the street, with a narrow, dark s.p.a.ce between, and this dark s.p.a.ce was bounded, as it were, on both sides by a bright fringe like frosted silver." Presently he discovered that this rich effect was caused by the bright illumination of the shop lights on the pavements.

London, as seen from a balloon on a clear moonlight night in August a year ago (1901), wore a somewhat altered appearance. There were the fairy lamps tracing out the streets, which, though dark centred, wore their silver lining; but in irregular patches a whiter light from electric arc lamps broadened and brightened and shone out like some pyrotechnic display above the black housetops. Through the vast town ran a blank, black channel, the river, winding on into distance, crossed here and there by bridges showing as bright bands, and with bright spots occasionally to mark where lay the river craft. But what was most striking was the silence. Though the noise of London traffic as heard from a balloon has diminished of late years owing to the better paving, yet in day hours the roar of the streets is heard up to a great height as a hard, harsh, grinding din. But at night, after the last 'bus has ceased to ply, and before the market carts begin lumbering in, the balloonist, as he sails over the town, might imagine that he was traversing a City of the Dead.