The Dominion of the Air Part 4

Despite all efforts, however, it was soon evident that the c.u.mbersome nature of the huge parachute would prevent its being carried up quite so high as the inventor desired. Mr. c.o.c.king had stipulated for an elevation of 7,000 feet, and, as things were, only 5,000 feet could be reached, at any rate, before darkness set in. This fact was communicated to Mr. c.o.c.king, who promptly intimated his intention of leaving, only requesting to know whereabouts he was, to which query Mr. Spencer replied that they were on a level with Greenwich. The brief colloquy that ensued is thus given by Mr. Green:--

"I asked him if he felt quite comfortable, and if the practical trial bore out his calculation. Mr. c.o.c.king replied, 'Yes, I never felt more comfortable or more delighted in my life,' presently adding, 'Well, now I think I shall leave you.' I answered, 'I wish you a very "Good Night!"

and a safe descent if you are determined to make it and not use the tackle' (a contrivance for enabling him to retreat up into the balloon if he desired). Mr. c.o.c.king's only reply was, 'Good-night, Spencer; Good-night, Green!' Mr. c.o.c.king then pulled the rope that was to liberate himself, but too feebly, and a moment afterwards more violently, and in an instant the balloon shot upwards with the velocity of a sky rocket. The effect upon us at this moment was almost beyond description. The immense machine which suspended us between heaven and earth, whilst it appeared to be forced upwards with terrific violence and rapidity through unknown and untravelled regions amidst the howlings of a fearful hurricane, rolled about as though revelling in a freedom for which it had long struggled, but of which until that moment it had been kept in utter ignorance. It, at length, as if somewhat fatigued by its exertions, gradually a.s.sumed the motions of a snake working its way with extraordinary speed towards a given object. During this frightful operation the gas was rushing in torrents from the upper and lower valve, but more particularly from the latter, as the density of the atmosphere through which we were forcing our progress pressed so heavily on the valve at the top of the balloon as to admit of but a comparatively small escape by this aperture. At this juncture, had it not been for the application to our mouths of two pipes leading into an air bag, with which we had furnished ourselves previous to starting, we must within a minute have been suffocated, and so, but by different means, have shared the melancholy fate of our friend. This bag was formed of silk, sufficiently capacious to contain 100 gallons of atmospheric air. Prior to our ascent, the bag was inflated with the a.s.sistance of a pair of bellows with fifty gallons of air, so allowing for any expansion which might be produced in the upper regions. Into the end of this bag were introduced two flexible tubes, and the moment we felt ourselves to be going up in the manner just described, Mr. Spencer, as well as myself, placed either of them in our mouths. By this simple contrivance we preserved ourselves from instantaneous suffocation, a result which must have ensued from the apparently endless volume of gas with which the car was enveloped. The gas, notwithstanding all our precautions, from the violence of its operation on the human frame, almost immediately deprived us of sight, and we were both, as far as our visionary powers were concerned, in a state of total darkness for four or five minutes."

Messrs. Green and Spencer eventually reached earth in safety near Maidstone, knowing nothing of the fate of their late companion. But of this we are sufficiently informed through a Mr. R. Underwood, who was on horseback near Blackheath and watching the aeronauts at the moment when the parachute was separated from the balloon. He noticed that the former descended with the utmost rapidity, at the same time swaying fearfully from side to side, until the basket and its occupant, actually parting from the parachute, fell together to earth through several hundred feet and were dashed to pieces.

It would appear that the liberation of the parachute from below the balloon had been carried out without hitch; indeed, all so far had worked well, and the wind at the time was but a gentle breeze. The misadventure, therefore, must be entirely attributed to the faulty manner in which the parachute was constructed. There could, of course, be only one issue to the sheer drop from such a height, which became the unfortunate Mr. c.o.c.king's fate, but the very interesting question will have to be discussed as to the chances in favour of the aeronaut who, within his wicker car, while still duly attached to the balloon, may meet with a precipitate descent.

We may here fitly mention an early perilous experience of Mr. Green, due simply to the malice of someone never discovered. It appears that while Green's balloon, previous to an ascent, was on the ground, the cords attaching the car had been partly severed in such a way as to escape detection. So that as soon as the balloon rose the car commenced breaking away, and its occupants, Mr. Green and Mr. Griffiths, had to clutch at the ring, to which with difficulty they continued to cling.

Meanwhile, the car remaining suspended by one cord only, the balloon was caused to hang awry, with the result that its upper netting began giving way, allowing the balloon proper gradually to escape through the bursting meshes, thus threatening the distracted voyagers with terrible disaster. The disaster, in fact, actually came to pa.s.s ere the party completed their descent, "the balloon, rushing through the opening in the net-work with a tremendous explosion, and the two pa.s.sengers clinging to the rest of the gear, falling through a height said to be near a hundred feet. Both, though only with much time and difficulty, recovered from the shock."

In 1840, three years after the tragic adventure connected with Mr.

c.o.c.king's parachute trial, we find Charles Green giving his views as to the practicability of carrying out a ballooning enterprise which should far excel all others that had hitherto been attempted. This was nothing less than the crossing of the Atlantic from America to England. There is no shadow of doubt that the adventurous aeronaut was wholly in earnest in the readiness he expressed to embark on the undertaking should adequate funds be forthcoming; and he discusses the possibilities with singular clearness and candour. He maintains that the actual difficulties resolve themselves into two only: first, the maintenance of the balloon in the sky for the requisite period of time; and, secondly, the adequate control of its direction in s.p.a.ce. With respect to the first difficulty, he points out the fact to which we have already referred, namely, that it is impossible to avoid the fluctuations of level in a balloon's course, "by which it constantly becomes alternately subjected to escape of gas by expansion, and consequent loss of ballast, to furnish an equivalent diminution of weight." Taking his own balloon of 80,000 cubic feet by way of example, he shows that this, fully inflated on the earth, would lose 8,000 cubic feet of gas by expansion in ascending only 3,000 feet. Moreover, the approach of night or pa.s.sage through cloud or falling rain would occasion chilling of the gas or acc.u.mulation of moisture on the silk, in either case necessitating the loss of ballast, the store of which is always the true measure of the balloon's life.

To combat the above difficulty Green sanguinely relies on his favourite device of a trail or guide rope, whose function, being that of relieving the balloon of a material weight as it approaches the earth, could, he supposed, be made to act yet more efficiently when over the sea in the following manner. Its length, suspended from the ring, being not less than 2,000 feet, it should have attached at its lower end at certain intervals a number of small, stout waterproof canvas bags, the apertures of which should be contrived to admit water, but to oppose its return.

Between these bags were to be conical floats, to support any length of the rope that might descend on the sea. Now, should the balloon commence descending, it would simply deposit a certain portion of rope on the water until it regained equilibrium at no great decrease of alt.i.tude, and would thus continue its course until alteration of conditions should cause it to recommence rising, when the weight of water now collected in the bags would play its part in preventing the balloon from soaring up into s.p.a.ce. With such a contrivance Green allowed himself to imagine that he could keep a properly made balloon at practically the same alt.i.tude for a period of three months if required.

The difficulty of maintaining a due course was next discussed, and somewhat speedily disposed of. Here Green relied on the results of his own observation, gathered during 275 ascents, and stated his conviction that there prevails a uniformity of upper wind currents that would enable him to carry out his bold projects successfully. His contention is best given in his own words:

"Under whatever circ.u.mstances," he says, "I made my ascent, however contrary the direction of the winds below, I uniformly found that at a certain elevation, varying occasionally, but always within 10,000 feet of the earth, a current from the west or rather from the north of west, invariably travailed, nor do I recollect a single instance in which a different result ensued." Green's complete scheme is now sufficiently evident. He was to cross the Atlantic practically by the sole a.s.sistance of upper currents and his guide rope, but on this latter expedient, should adverse conditions prevail, he yet further relied, for he conceived that the rope could have attached to its floating end a water drag, which would hold the balloon in check until favouring gales returned.

Funds, apparently, were not forthcoming to allow of Mr. Green's putting his bold method to the test; but we find him still adhering with so much zeal to his project that, five years later, he made, though again unsuccessfully, a second proposal to cross the Atlantic by balloon. He still continued to make many and most enterprising ascents, and one of a specially sensational nature must be briefly mentioned before we pa.s.s on to regard the exploits of other aeronauts.

It was in 1841 on the occasion of a fete at Cremorne House, when Mr.

Green, using his famous Na.s.sau balloon, ascended with a Mr. Macdonnell.

The wind was blowing with such extreme violence that Rainham, in Ess.e.x, about twenty miles distant, was reached in little more than a quarter of an hour, and here, on nearing the earth, the grapnel, finding good hold, gave a wrench to the balloon that broke the ring and jerked the car completely upside down, the aeronauts only escaping precipitation by holding hard to the ropes. A terrific steeplechase ensued, in which the travellers were dragged through stout fencing and other obstacles till the balloon, fairly emptied of gas, finally came to rest, but not until some severe injuries had been received.

CHAPTER VIII. JOHN WISE--THE AMERICAN AERONAUT.

By this period the domination of the air was being pursued in a fresh part of the world. England and her Continental neighbours had vied with each in adding to the roll of conquests, and it could hardly other be supposed that America would stand by without taking part in the campaign which was now being revived with so much fresh energy in the skies.

The American champion who stepped forward was Mr. John Wise, of Lancaster, Pa., whose career, commencing in the year 1835, we must now for a while follow. Few attempts at ballooning of any kind had up to that time been made in all America. There is a record that in December, 1783, Messrs. Rittenhouse and Hopkins, Members of the Philosophical Academy of Philadelphia, inst.i.tuted experiments with an aerial machine consisting of a cage to which forty-seven small balloons were harnessed.

In this strange craft a carpenter, by name Wilc.o.x, was induced to ascend, which, it is said, he did successfully, remaining in the air for ten minutes, when, finding himself near a river, he sought to come to earth again by opening several of his balloons. This brought about an awkward descent, attended, however, by no more serious accident than a dislocated wrist. Mr. Wise, on the other hand, states that Blanchard had won the distinction of making the first ascent in the New World in 1793 in Philadelphia on which occasion Washington was a spectator; and a few years afterwards other Frenchmen gave exhibitions, which, however, led to no real development of the new art on this, the further side of the Atlantic. Thus the endeavours we are about to describe were those of an independent and, at the same time, highly, practical experimentalist, and on this account have a special value of their own.

The records that Wise has left of his investigations begin at the earliest stage, and possess the charm of an obvious and somewhat quaint reality. They commence with certain crude calculations which would seem to place no limit to the capabilities of a balloon. Thus, he points out that one of "the very moderate size of 400 feet diameter" would convey 13,000 men. "No wonder, then," he continues, "the citizens of London became alarmed during the French War, when they mistook the appearance of a vast flock of birds coming towards the Metropolis for Napoleon's army apparently coming down upon them with this new contrivance."

Proceeding to practical measures, Wise's first care was to procure some proper material of which to build an experimental balloon of sufficient size to lift and convey himself alone. For this he chose ordinary long-cloth, rendered gas-tight by coats of suitable varnish, the preparation of which became with him, as, indeed, it remains to this day, a problem of chief importance and difficulty. Perhaps it hardly needs pointing out that the varnish of a balloon must not only be sufficiently elastic not to crack or scale off with folding or unavoidable rough usage, but it must also be of a nature to resist the common tendency of such substances to become adherent or "tacky." Wise determined on bird lime thinned with linseed oil and ordinary driers.

With this preparation he coated his material several times both before and after the making up, and having procured a net, of which he speaks with pride, and a primitive sort of car, of which he bitterly complains, he thought himself sufficiently equipped to embark on an actual ascent, which he found a task of much greater practical difficulty than the mere manufacture of his air ship. For the inflation by hydrogen of so small a balloon as his was he made more than ample provision in procuring no less than fifteen casks of 130 gallons capacity each. He also duly secured a suitable filling ground at the corner of Ninth and Green Streets, Philadelphia, but he made a miscalculation as to the time the inflation would demand, and this led to unforeseen complications, for as yet he knew not the way of a crowd which comes to witness a balloon ascent.

Having all things in readiness, and prudently waiting for fair weather, he embarked on his grand experiment on the 2nd of May, 1835, announcing 4 p.m. as the hour of departure. But by that time the inflation, having only proceeded for three hours, the balloon was but half full, and then the populace began to behave as in such circ.u.mstances they always will.

They were incredulous, and presently grew troublesome. In vain the harnessing of the car was proceeded with as though all were well. For all was not well, and when the aeronaut stepped into his car with only fifteen pounds of sand and a few instruments he must have done so with much misgiving. Still, he had friends around who might have been useful had they been less eager to help. But these simply crowded round him, giving him no elbow room, nor opportunity for trying the "lift" of his all-too-empty globe. Moreover, some would endeavour to throw the machine upward, while others as strenuously strove to keep it down, and at last the former party prevailed, and the balloon, being fairly cast into the air, grazed a neighbouring chimney and then plunged into an adjacent plot, not, however, before the distracted traveller had flung away all his little stock of sand. There now was brief opportunity for free action, and to the first bystander who came running up Wise gave the task of holding the car in check. To the next he handed out his instruments, his coat, and also his boots, hoping thus to get away; but his chance had not yet come, for once again the crowd swarmed round him, keeping him prisoner with good-natured but mistaken interference, and drowning his voice with excited shouting. Somehow, by word and gesture, he gave his persecutors to understand that he wished to speak, and then he begged them only to give him a chance, whereupon the crowd fell back, forming a ring, and leaving only one man holding the car. It was a moment of suspense, for Wise calculated that he had only parted with some eighteen pounds since his first ineffectual start from the filling ground; but it was enough, and in another moment he was sailing up clear above the crowd. So great, as has been already shewn, is often the effect of parting with the last few pounds of dead weight in a well-balanced balloon.

Such was the first "send off" of the future great balloonist, destined to become the pioneer in aeronautics on the far side of the Atlantic.

The balloon ascended to upwards of a mile, floating gradually away, but at its highest point it reached a conflict of currents, causing eddies from which Wise escaped by a slight decrease of weight, effected by merely cutting away the wreaths of flowers that were tied about his car.

A further small subst.i.tute for ballast he extemporised in the metal tube inserted in the neck of his fabric, and this he cast out when over the breadth of the Delaware, and he describes it as falling with a rustling sound, and striking the water with a splash plainly heard at more than a mile in the sky. After an hour and a quarter the balloon spontaneously and steadily settled to earth.

An ascent carried out later in the same summer led to a mishap, which taught the young aeronaut an all-important lesson. Using the same balloon and the same mode of inflation, he got safely and satisfactorily away from his station in the town of Lebanon, Pa., and soon found himself over a toll gate in the open country, where the gate keeper in banter called up to him for his due. To this summons Wise, with heedless alacrity, responded in a manner which might well have cost him dear. He threw out a bag of sand to represent his toll, and, though he estimated this at only six pounds, it so greatly accelerated his ascent that he shortly found himself at a greater alt.i.tude than he ever after attained.

He pa.s.sed through mist into upper sunshine, where he experienced extreme cold and ear-ache, at which time, seeking the natural escape from such trouble, he found to his dismay that the valve rope was out of reach.

Thus he was compelled to allow the balloon to ascend yet higher, at its own will; and then a terrible event happened.

By mischance the neck of his balloon, which should have been open, was out of reach and folded inwards in such a way as to prevent the free escape of the gas, which, at this great alt.i.tude, struggled for egress with a loud humming noise, giving him apprehensions of an accident which very shortly occurred, namely, the bursting of the lower part of his balloon with a loud report. It happened, however, that no extreme loss of gas ensued, and he commenced descending with a speed which, though considerable, was not very excessive. Still, he was eager to alight in safety, until a chance occurrence made him a second time that afternoon guilty of an act of boyish impetuosity. A party of volunteers firing a salute in his honour as he neared the ground, he instantly flung out papers, ballast, anything he could lay his hands on, and once again soared to a great height with his damaged balloon. He could then do no more, and presently subsiding to earth again, he acquired the welcome knowledge that even in such precarious circ.u.mstances a balloon may make a long fall with safety to its freight.

Mr. Wise's zeal and indomitable spirit of enterprise led to speedy developments of the art which he had espoused; the road to success being frequently pointed out by failure or mishap. He quickly discarded the linen balloon for one of silk on which he tried a new varnish composed of linseed oil and india-rubber, and, dressing several gores with this, he rolled them up and left them through a night in a drying loft, with the result that the next day they were disintegrated and on the point of bursting into flame by spontaneous combustion. Fresh silk and other varnish were then tried, but with indifferent success. Next he endeavoured to dispense with sewing, and united the gores of yet another balloon by the mere adhesiveness of the varnish and application of a hot iron. This led to a gaping seam developing at the moment of an ascent, and then there followed a hasty and hazardous descent on a house-top and an exciting rescue by a gentleman who appeared opportunely at a third storey window. Further, another balloon had been destroyed, and Wise badly burned, at a descent, owing to a naked light having been brought near the escaping gas. It is then without wonder that we find him after this temporarily bankrupt, and resorting to his skill in instrument-making to recover his fortunes. Only, however, for a few months, after which he is before the public once more as a professional aeronaut. He now adopts coal gas for inflation, and incidents of an impressive nature crowd into his career, forcing important facts upon him. The special characteristics of his own country present peculiar difficulties; broad rivers and vast forests become serious obstacles.

He is caught in the embrace of a whirlwind; he narrowly escapes falling into a forest fire; he is precipitated, but harmlessly, into a pine wood. Among other experiments, he makes a small copy of Mr. c.o.c.king's parachute, and drops it to earth with a cat as pa.s.senger, proving thereby that that unfortunate gentleman's principle was really less in fault than the actual slenderness of the material used in his machine.

We now approach one of Wise's boldest, and at the same time most valuable, experiments. It was the summer of 1839, and once again the old trouble of spontaneous combustion had destroyed a silk balloon which was to have ascended at Easton, Pa. Undeterred, however, Wise resolutely advertised a fresh attempt, and, with only a clear month before the engagement, determined on hastily rigging up a cambric muslin balloon, soaking it in linseed oil and essaying the best exhibition that this improvised experiment could afford. It was intended to become a memorable one, inasmuch as, should he meet with no hindrance, his determination was nothing less than that of bursting this balloon at a great height, having firmly convinced himself that the machine in these circ.u.mstances would form itself into a natural parachute, and bring him to earth with every chance in favour of safety. In his own words, "Scientific calculations were on his side with a certainty as great and principles as comprehensive as that a pocket-handkerchief will not fall as rapidly to the ground when thrown out of a third storey window as will a brick."

His balloon was specially contrived for the experiment in hand, having cords sewn to the upper parts of its seams, and then led down through the neck, where they were secured within reach, their office being that of rending the whole head of the balloon should this be desired. On this occasion a cat and a dog were taken up, one of these being let fall from a height of 2,000 feet in a c.o.c.king's parachute, and landing in safety, the other being similarly dismissed at an alt.i.tude of 4,000 feet in an oiled silk balloon made in the form of a collapsed balloon, which, after falling a little distance, expanded sufficiently to allow of its descending with a safe though somewhat vibratory motion. Its behaviour, at any rate, fully determined Wise on carrying out his own experiment.

Being constructed entirely for the main object in view, the balloon had no true opening in the neck beyond an orifice of about an inch, and by the time a height of 13,000 feet had been reached the gas was streaming violently through this small hole, the entire globe being expanded nearly to bursting point, and the cords designed for rending the balloon very tense. At this critical period Wise owns to having experienced considerable nervous excitement, and observing far down a thunderstorm in progress he began to waver in his mind, and inclined towards relieving the balloon of its strain, and so abandoning his experiment, at least for the present. He remembers pulling out his watch to make a note of the hour, and, while thus occupied, the straining cords, growing tenser every moment, suddenly took charge of the experiment and burst the balloon of their own accord. The gas now rushed from the huge rent above tumultuously and in some ten seconds had entirely escaped, causing the balloon to descend rapidly, until the lower part of the muslin, doubling in upwards, formed a species of parachute after the manner intended. The balloon now came down with zig-zag descent, and finally the car, striking the earth obliquely, tossed its occupant out into a field unharmed. Shortly after this Wise experimented with further success with an exploded balloon.

It is not a little remarkable that this pioneer of aeronautics in American--a contemporary of Charles Green in England, but working and investigating single-handed on perfectly independent lines--should have arrived at the same conclusions as did Green himself as to the possibility, which, in his opinion, amounted to a certainty, of being able to cross the Atlantic by balloon if only adequate funds were forth-coming. So intent was he on his bold scheme that, in the summer of 1843, he handed to the Lancaster Intelligencer a proclamation, which he desired might be conveyed to all publishers of newspapers on the globe.

It contained, among other clauses, the following:--

"Having from a long experience in aeronautics been convinced that a constant and regular current of air is blowing at all times from west to east, with a velocity of from twenty to forty and even sixty miles per hour, according to its height from the earth, and having discovered a composition which renders silk or muslin impervious to hydrogen gas, so that a balloon may be kept afloat for many weeks, I feel confident with these advantages that a trip across the Atlantic will not be attended with as much real danger as by the common mode of transition. The balloon is to be 100 feet in diameter, giving it a net ascending power of 25,000 lbs." It was further stated that the crew would consist of three persons, including a sea navigator, and a scientific landsman.

The specifications for the transatlantic vessel were also to include a seaworthy boat in place of the ordinary car. The sum requisite for this enterprise was, at the time, not realised; but it should be mentioned that several years later a sufficient sum of money was actually subscribed. In the summer of 1873 the proprietors of the New York Daily Graphic provided for the construction of a balloon of no less than 400,000 cubic feet capacity, and calculated to lift 14,000 lbs. It was, however, made of bad material; and, becoming torn in inflation, Wise condemned and declined to use it. A few months later, when it had been repaired, one Donaldson and two other adventurers, attempting a voyage with this ill-formed monster, ascended from New York, and were fortunate in coming down safely, though not without peril, somewhere in Connecticut.

Failing in his grand endeavour, Wise continued to follow the career of a professional aeronaut for some years longer, of which he has left a full record, terminating with the spring of 1848. His ascents were always marked by carefulness of detail, and a coolness and courage in trying circ.u.mstances that secured him uniform success and universal regard. He was, moreover, always a close and intelligent observer, and many of his memoranda are of scientific value.

His description of an encounter with a storm-cloud in the June of 1843 has an interest of its own, and may not be considered overdrawn. It was an ascent from Carlisle, Pa., to celebrate the anniversary of Bunker's Hill, and Wise was anxious to gratify the large concourse of people a.s.sembled, and thus was tempted, soon after leaving the ground, to dive up into a huge black cloud of peculiarly forbidding aspect. This cloud appeared to remain stationary while he swept beneath it, and, having reached its central position, he observed that its under surface was concave towards the earth, and at that moment he became swept upwards in a vortex that set his balloon spinning and swinging violently, while he himself was afflicted with violent nausea and a feeling of suffocation.

The cold experienced now became intense, and the cordage became glazed with ice, yet this had no effect in checking the upward whirling of the balloon. Sunshine was beyond the upper limits of the cloud; but this was no sooner reached than the balloon, escaping from the uprush, plunged down several hundred feet, only to be whirled up again, and this reciprocal motion was repeated eight or ten times during an interval of twenty minutes, in all of which time no expenditure of gas or discharge of ballast enabled the aeronaut to regain any control over his vessel.

Statements concerning a thunderstorm witnessed at short range by Wise will compare with other accounts. The thunder "rattled" without any reverberations, and when the storm was pa.s.sing, and some dense clouds moving in the upper currents, the "surface of the lower stratum swelled up suddenly like a boiling cauldron, which was immediately followed by the most brilliant ebullition of sparkling coruscations." Green, in his stormy ascent from Newbury, England, witnessed a thunderstorm below him, as will be remembered, while an upper cloud stratum lay at his own level. It was then that Green observed that "at every discharge of thunder all the detached pillars of clouds within the distance of a mile around became attracted."

The author will have occasion, in due place, to give personal experiences of an encounter with a thunderstorm which will compare with the foregoing description.

CHAPTER IX. EARLY METHODS AND IDEAS.

Before proceeding to introduce the chief actors and their achievements in the period next before us, it will be instructive to glance at some of the princ.i.p.al ideas and methods in favour with aeronauts up to the date now reached. It will be seen that Wise in America, contrary to the practice of Green in our own country, had a strong attachment to the antique mode of inflation with hydrogen prepared by the vitriolic process; and his balloons were specially made and varnished for the use of this gas. The advantage which he thus bought at the expense of much trouble and the providing of c.u.mbersome equipment was obvious enough, and may be well expressed by a formula which holds good to-day, namely, that whereas 1,000 cubic feet of hydrogen is capable of lifting 7 lbs., the same quant.i.ty of coal gas of ordinary quality will raise but 35 lbs.

The lighter gas came into all Wise's calculations for bolder schemes.

Thus, when he discusses the possibility of using a metal balloon, his figures work out as follows: If a balloon of 200 feet diameter were constructed out of copper, weighing one pound to the square foot; if, moreover, some six tons were allowed for the weight of car and fastenings, an available lifting power would remain capable of raising 45 tons to an alt.i.tude of two miles. This calculation may appear somewhat startling, yet it is not only substantially correct, but Wise entertained no doubt as to the practicability of such a machine. For its inflation he suggests inserting a muslin balloon filled with air within the copper globe, and then pa.s.sing hydrogen gas between the muslin and copper surfaces, which would exclude the inner balloon as the copper one filled up.

His method of preparing hydrogen was practically that still adopted in the field, and seems in his hands to have been seldom attended with difficulty. With eight common 130-gallon rum puncheons he could reckon on evolving 5,000 cubic feet of gas in an hour, using his elements in the following proportions: water, 560 lbs.; sulphuric acid (sp. g.

1.85), 144 lbs.; iron turnings, 125 lbs. The gas, as given off, was cooled and purified by being pa.s.sed through a head of water kept cool and containing lime in solution. Contrasted with this, we find it estimated, according to the practice of this time, that a ton of good bituminous coal should yield 10,000 cubic feet of carburetted hydrogen fit for lighting purposes, and a further quant.i.ty which, though useless as an illuminant, is still of excellent quality for the aeronaut.

It would even seem from a statement of Mr. Monck Mason that the value of c.o.ke in his day largely compensated for the cost of producing coal gas, so that in a large number of Green's ascents no charge whatever was made for gas by the companies that supplied him.

Some, at least, of the methods formerly recommended for the management of free balloons must in these days be modified. Green, as we have seen, was in favour of a trail rope of inordinate length, which he recommended both as an aid to steering and for a saving of ballast. In special circ.u.mstances, and more particularly over the sea, this may be reckoned a serviceable adjunct, but over land its use, in this country at least, would be open to serious objection. The writer has seen the consternation, not to say havoc, that a trail rope may occasion when crossing a town, or even private grounds, and the actual damage done to a garden of hops, or to telegraph or telephone wires, may be very serious indeed. Moreover, the statement made by some early pract.i.tioners that a trail rope will not catch so as to hold fast in a wood or the like, is not to be relied on, for an instance could be mentioned coming under the writer's knowledge where such a rope was the source of so much trouble in a high wind that it had to be cut away.

The trouble arose in this way. The rope dragged harmlessly enough along the open ground. It would, likewise, negotiate exceedingly well a single tree or a whole plantation, catching and releasing itself with only such moderate tugs at the car as were not disturbing; but, presently, its end, which had been caught and again released by one tree, swung free in air through a considerable gap to another tree, where, striking a horizontal bough, it coiled itself several times around, and thus held the balloon fast, which now, with the strength of the wind, was borne to the earth again and again, rebounding high in air after each impact, until freedom was gained only by the sacrifice of a portion of the rope.

Wise recommends a pendant line of 600 or 800 feet, capable of bearing a strain of 100 lbs., and with characteristic ingenuity suggests a special use which can be made of it, namely, that of having light ribbons tied on at every hundred feet, by means of which the drifts of lower currents may be detected. In this suggestion there is, indeed, a great deal of sound sense; for there is, as will be shown hereafter, very much value to be attached to a knowledge of those air rivers that are flowing, often wholly unsuspected, at various heights. Small parachutes, crumpled paper, and other such-like bodies as are commonly thrown out and relied on to declare the lower drifts, are not wholly trustworthy, for this reason--that air-streams are often very slender, mere filaments, as they are sometimes called, and these, though setting in some definite direction, and capable of entrapping and wafting away some small body which may come within their influence, may not affect the travel of so big an object as a balloon, which can only partake of some more general air movement.