MILITARY BALLOONING IN THE YEAR OF JUBILEE.
One of the latest and most interesting phases of this subject relates to Lord Wolseley’s maiden ascent from the grounds at Lidsing, near Chatham, and to various active preparations on the Continent which have a character of their own, and are essentially dissimilar to the experiments in Great Britain.
An illustrious man undergoing his initiation in the balloon car, forms an event which is not of every day occurrence, and must prove very encouraging to the intrepid engineer officers, and also to the general public, who like to see the leading authority go now and again to the front for the sake of thoroughly inspecting, and of obtaining some practical acquaintance with any new branch of science which may be on trial.
The General’s declaration that “he believed himself in novelties,” must have produced conflicting opinions in the minds of many more conservative brother officers; but what must have been the effect of the next assertion? namely, “the more novelties the better.”
Lord Wolseley believed in what Napoleon said: “You must change your tactics frequently.”
The first impression made by his ascent of 500 feet, elicited the General’s approval.
In the course of a conversation with one of his staff, Lord Wolseley stated that “had he been able to employ balloons in the earlier stages of the Soudan campaign, the affair would not have lasted as many months as it did years.”
We get therefore a very high testimony as to the value of the balloon for military objects, and as the exploits of our war balloons do not amount, at present, to anything particularly noteworthy, the General’s encouraging remarks will have an excellent effect, it may fairly be presumed.
The most recent effort in this line, near Dover, was not successful.
The balloon “Sentinel” was filled and essayed to watch the volunteers, but was forced to retire with the most eccentric capers—owing to the freaks of rude Boreas, which was, after all, merely imparting useful instruction, though not particularly pleasing, probably, to the officer who occupied the seat of honour.
It is, doubtless, a matter to rejoice over, that he was not blown out over the adjacent coast line; had he been driven away down Channel in a small skin balloon under the influence of a north-easterly wind, he might have touched the extreme corner of the French coast, or been sent down betwixt the Channel Islands.
Happily, however, there was no fresh fatality to lament over, and the instructions imparted by the clerk of the weather as to the impracticability of captive ascents during strong winds will not be lost, and may prove of the greatest importance, so that it is well worth while referring to it as a warning for future caution.
As the writer of this book holds it to be his province, and his duty as a practical man to review both sides of public opinion respecting his speciality, he considers it right to state, that the representatives of the press, like the representatives of our constituencies in parliament, do not all take one and the same view about military ballooning; neither do superior officers or the rank-and-file, who, in these advanced days are quite capable of drawing their own conclusions.
A paragraph which I read in the Court Society Review, was to this effect.
“I have very little faith in military balloons for the purposes of observation. In the Soudan no atmospheric conditions, and many were tried, were found to be suitable, for even when the air was dead-still, and brilliantly clear, the balloon waggled to such an extent as to make telescopic observation impossible, or, at any rate, practically useless. At the Easter Monday fight, an infinitely more futile attempt was made to employ the balloon in a stiffish breeze, and the result was, of course, as worthless as the experiment was dangerous.
“All the same, for signalling, especially at night, captive balloons might be made of immense use.”
Secondly, we have another rather discouraging experience, which ought not to be forgotten or omitted in these pages.
It is in McClellan’s own story, about their doings on April 11th, 1862, and is rather amusing than complimentary to the cause I have so long advocated.
“I am just recovering,” the writer observes, “from a terrible scare. Early this morning I was awakened by a despatch from Fitz-John’s head-quarters, stating that Fitz had made an ascension in the balloon this morning, and that it had broken away and come to the ground some three miles south-west, which would be within the enemy’s lines.
“You can imagine how I felt. I at once sent off to the various pickets to find out what they knew, and tried to do something to save him, but the order had no sooner gone, than in walks Fitz, just as cool as usual. He had luckily come down near my own camp, after actually passing over that of the enemy.
“You may rest assured of one thing,” was the remark: “you won’t catch me in the confounded balloon, nor will I allow any other General in it.”
On the converse side, it should be mentioned that in a telegram received at Washington during the Civil War, it was stated, “that all the information received from balloons, deserters, prisoners, &c., agrees in the statement that the mass of the rebel troops were still in the immediate vicinity of Richmond, ready to defend it.”
As a pioneer myself in the service of military ballooning, I heartily wish that something more had been carried out in the decidedly important neighbourhood of Suakim.
I was constantly suggesting plans; among others, to take out an apparatus and holder for the generation of coal gas, feeling persuaded that at a short notice, an enterprising private firm would have sent out an equipment with the necessary men and coals, to generate gas on the old quick and cheap plan, in addition to the compressed hydrogen system. There are, certainly, some advantages in employing the lighter gas, but several counter and compensating results might be adduced on the other side, one of which is, that in a hot climate, pure hydrogen will escape quicker than the denser production, and, I have no hesitation in saying, that a small skin balloon behaves itself in a breeze with an infinitely less steady action, than a more enlarged surface with greater vertical power imparted to it, which is one out of many of those secrets of success, which men of long experience are well aware of, and I do believe that a certain amount of co-operation between civilian experts, and the military engineers would be attended with good results.
I am not referring particularly to the English school of balloonists, but to foreign corps as well.
It is a regrettable fact that one cannot perceive in the whole list of balloon transactions in warfare, either at home or abroad, any deeds that are at present conspicuously worth chronicling. The splendid exodus of hastily organised balloonists, chiefly sailors, who went out of Paris during the Franco-German War, can scarcely be called military ballooning.
There was no strategy, exceptional skill, or discoveries to mark and dignify their departure or descent; only a most valuable and timely postal and parcels delivery transmission.
This was excellent auxiliary aid, and altogether sui generis, but it was not manœuvring with the enemy or rendering fresh intelligence which could not be gained by ordinary scouts, I mean in a strictly military sense. The winged messengers (pigeons) were certainly helped in their work by having a lift up on their outward journey; but what we should like to hear of, when balloons show up in war time, is that something important has been seen and reported which would have escaped notice but for the argus-eyed aëronauts.
A considerable amount of bewilderment, as we have said, accompanies a novice’s first glance of the earth’s surface, when villages, fields, towns and fortresses, are seen under a new aspect, with minimised proportions reduced to the model size, and seen from above instead of horizontally.
It requires a trained observer to make heads, tails, and relative proportions out of the new map, and if any altitude has to be attained, very small machines will not do, they may be light and of little capacity, but they are unable to offer a powerful upward tug, which is indispensable for steadying the balloon when telescopic observations have to be made.
The action of diminutive machines of this kind may not inaptly be compared to the jerking, fitful movement, of certain small birds, such as a tomtit, or a titlark, as contrasted with the soaring power of an eagle, or the steadied poise of a hawk.
The balloon, under which Lord Wolseley took a bird’s-eye view, is described as “a magnificent spic and span new aërial machine, constructed of the new preparation of bullock’s skin, and capable of containing 10,000 feet of compressed gas,” by which is meant, I presume, 10,000 feet of hydrogen gas that has been compressed and subsequently liberated into the said balloon.
If I were questioned as to the value of this kind of material for the objects intended by the designers, I should, certainly, not speak disparagingly of it, because I think that skin may be very good in its way, but I believe that a certain quality of silk, all things considered, is more reliable, and if it is heavier than skin, it is more readily repaired in case of fracture, and would better resist the shrivelling effects of a hot atmosphere, and of sudden gusts of wind. Silk is also less tempting to the gnawing of insects.
If it is supposed that the use of skin is a new adaptation, I can remove any false impression of that sort by stating that half a century since, I saw and handled a huge balloon composed of similar animal substance, which was called Egg’s folly. The gunmaker had built an enormous fish shaped affair, and it had, fish like, an air bladder to assist it in rising and descending. I was asked to buy the lot which had been laid by for some years, but it was not to my taste; later on, however, after Mr. Barnum had brought over the dwarf, Tom Thumb, to this country, an exhibition was got up at the Surrey Zoological Gardens, and Mr. C. Green was asked to provide a suitable balloon to take up Tom Thumb for a captive ascent.
The air bladder then cropped up, as it would lift fifty or sixty pounds when filled with ordinary gas, and I well remember witnessing the ascent, and shaking hands with the occupant of the little car.
I was informed afterwards by the veteran himself, that Captain Currie, who was a frequent voyager at that time, wished to train and lose weight, so that the skin balloon would take him up, if filled with hydrogen instead of coal gas.
I do not think the trial came off, but I can vouch for it, that the so-called bullock’s skin is by no means a novel departure.
We thus learn that history repeats itself, even in an art which is practically little more than a century old.
If we turn from the balloon force at home, and direct a glance towards the continent, as much difference is to be observed in their aërostatic pretensions, as there is between our small and compact army, when compared with the millions of bayonets (and good ones no doubt) that are ready to do battle whenever the dogs of war shall be let loose for slaughter.
In England, preference is shown for exceedingly small bullock’s skin balloons.
In France they are cigar or cannon shaped, with steering power and propelling machinery attached. I am referring, now, to the war balloons at Meudon.
Germany inclines to medium sized spherical balloons, composed of silk by preference—and I think they are right—to the calico or muslin balloons in store at Chatham or Lidsing.
Russia, if we may believe newspaper accounts, is provided with an air torpedo, besides Montgolfier, and gas balloons. The torpedo air ship can take up eight hundredweight of dynamite, the application of which I have already pictured.
An American novelty consists of an electro dynamic air ship, in the form of a cigar cut lengthways, which presents a flat underside, and a rounded upper; it is constructed of seven independent cells, which are divided longitudinally, making fourteen separate compartments in all.
Among the attractions proposed for the Paris exhibition of 1889, is a captive balloon, having a capacity of 1,800,000 cubic feet, which will take up one hundred passengers.
Then comes the most wonderful invention of all, a balloon which is to surpass in speed the Flying Scotchman. The German Government is stated to have purchased this monster for a million marks, and the constructor is to have a handsome pension for life. I do not believe it!
Now, if these formidable rivals are bent on mischief, and find an opportunity of indulging their destructive propensities, there will be lively and sensational diversions overhead, no less than frightful work beneath, particularly if the torpedoes act their part as expected.
Many scientific men, and all the professional aëronauts, with whom I am acquainted, regard this tall talk, not altogether in a literal and serious light, but as a scare and exchange of swagger between those powers who desire to be thought most efficient in modern appliances for warfare. Be that as it may, there can be no doubt that vast sums of money have been expended, and extensive preparations made, in aërostatic material.
There is something about all this boasting and threatening which is calculated to disturb the serenity of susceptible persons, when they read of hundreds of pounds of dynamite and chemical compounds being cast down upon contending armies, and about forts blown up, especially when it is remembered that no shields or ramparts are ever raised, or dreamt of, to resist a vertical onslaught from the regions above. This mode of attack would, to all intents and purposes, prove a novelty, and the question is, whether the lieutenants of our far seeing general, who approves of new tactics, are prepared to resist this kind of thing should a detachment of air torpedoes swarm like wasps or locusts upon our numerically small army, or should they even seek out our tiny war balloons and demolish them with a fell swoop of explosives.
The bare idea of such an ignominious extinction brings us to the vital question of how such intruders could be sent to the right about, or brought low by arms of precision.
Lieutenant B. Baden-Powell, in his able lecture at the Royal United Service Institution, took the danger into consideration; not I think under any apprehension about the descent of dynamite shells, but simply of the customary missiles which are discharged from cannon and small arms. We may infer that air torpedoes and such like were not dreaded.
Mr. Baden-Powell starts from an apt and thrilling commencement when he says—
“First then, the chance of being wrecked by shots from the enemy.
“It must be remembered,” he goes on to say, “that the balloon would generally be some way behind the first line, and that the enemy would hardly, especially during the heat of battle, pay much attention to it. It is well to remember that if only hit by a few bullets it would not be much damaged, and could be quickly repaired. Both at Frankfort and at Frankenthal the balloons were penetrated by bullets, at the latter place by nine, but the balloon remained up three-quarters of an hour after. In some experiments made at Tours, a balloon was penetrated by bullets at 1,000 yards, but the escape of gas was very slow, and the balloon remained up some time longer.
“Secondly—and now comes a case in point which should not be lightly passed over, it is this—
“In 1880 the Siege Operations’ Committee made an experiment at Dungeness with rather more disastrous results for the balloon. An eight-inch howitzer was directed on a captive balloon 2,000 yards off, and 800 feet high. The first shot was unsuccessful, the exact range not being known. The second shell, however, burst just in front of the balloon and tore it open. But even then it took fifteen minutes to descend, so that the aëronauts would have been safe.” Later tests have also taken place.
Many persons would think, and as many more might argue with some show of common sense on their side, that the actual safety of a party of balloonists after their machine had been torn open by a shell from an eight-inch howitzer was perilous in the extreme; but the lecturer had no such fears probably, as he went on with unmoved visage, I daresay, to remark that “bullets made of spongy platinum had been suggested as a means of igniting the hydrogen in a balloon by mere contact.”
But these stirring and well nigh nerve-testing quotations need not be dwelt upon to any further extent, they suffice to show that the risks, without taking into consideration the doings of those horrid torpedoes, have been fairly weighed.
If the dynamiters put in an appearance, and manage by skilful steering to be in at close quarters, then all I have to say is Heaven help those who may be in their power.
While contemplating this all important phase of aërostatics, I sometimes wonder whether these and other equally important ideas have ever entered into the fertile brains of those, whose province it is to lead and direct the military balloon tactics. There are, I have no hesitation in saying, at this critical period of our national history, uses for balloons even in this country, considering its position and possible surroundings, which I could point out if they would be listened to, and which at no distant period may be found unprovided for when most needed.
I recollect when first I talked over with Major Grover, R.E., who went up with me, my plan for using small and large balloons for destructive purposes, I had such a friendly but scathing glance that I at once interpreted his meaning to the effect that “anything of that sort would not be countenanced at head-quarters.”
Well, I have lived to draw attention to the very suggestions which were lightly esteemed a quarter of a century since, but I will not allude to any fresh conceptions at the present time.
Sir Edward Birkbeck, M.P., has done useful service in narrating not long since his experiences with me in the year 1862. Observations for military purposes were gone into, and our ascent made in the presence of His Royal Highness the Prince of Wales and the Duke of Sutherland was narrated with spirit. Instructive comments followed, and war balloons were referred to which have since been spoken of in a pleasing letter, wherein Sir Edward gave evidence that he still has a taste for scientific ballooning.
REMARKABLE ASCENTS
DURING THIS CENTURY.
A T no time during my own recollection, has an attempt, to reach a great height, been heralded with greater stir and interest than the voyage by Messrs. Jovis and Mallet from Paris, on August 13th, 1887.
In England, scientific men, professional aëronauts, and the public, regarded it with favour and admiration, that is, so far as their spirited intentions were interpreted on this side of the channel; and I may take upon myself to say, that it was viewed with no envious feelings, it being clear, that two enterprising men were desirous of trying their hands at adding lustre to the annals of aëronautics, and, that like a great many travellers in new and untried latitudes, these courageous aëronauts would do their best for their employers, and their own credit, or perish in the struggle, which last they were not wholly unprepared for, having disposed of their bodies in case of a fatal issue.
Of course, the press as a faithful mirror of public opinion, was not entirely in accord with their aims, about which some wrote severely and disparagingly, as it seemed to them, that the most apparent motive for the ascent, was to settle at what height animal life could exist; and other reviewers went so far as to insinuate, that pigeons and guinea-pigs were all very well, but in reality, it was a thinly veiled international bit of rivalry, as to who should go highest, Frenchmen or Englishmen.
Well, even if there existed a limited amount of this sort of thing, it was only friendly rivalry, which no true Briton could possibly object to, or be afraid of; it was not, however, to be expected that in France or England another expedition, which might be ill-fated like Sivel’s and Crose Spenelli’s, would be recognized without protest and free writing. Still, on the whole, Captain Jovis and Lieut. Mallet were well received, and I have little hesitation in saying that if an aëronaut, in this country, had on his own account or on that of a newspaper proprietor, done the like, he would have been, in all probability, denounced for his pains, as such an undertaking would not do here, unless a scientific society, or some pre-eminent physicist were to embark in totally fresh experiments.
As an instance of this very natural spirit of emulation, which is to be met with among enthusiastic air travellers, I may mention, that after I had initiated the late lamented Mr. Walter Powell, M.P., by taking him a long trip from Ashford, in Kent, to Crediton, in Devonshire, he wished, among other chivalrous schemes, not only to go straight to Rome without let or hindrance, which was most plucky and ambitious, but he wanted, without being duly acclimatised, to go seven miles high. I took upon myself to discountenance this and other suggestions, and was most likely considered a slow old coach for my pains, but I rather prided myself upon being properly cautious, and as I considered my patron’s views rather too advanced for me at my time of life, I gladly allowed that gentleman to pass into other hands, and what occurred afterwards is a matter not easily forgotten.
In Messrs. Jovis and Mallet’s ascent, there was a conspicuous omission in the first place, in not giving the size of their balloon. This was neglectful and ominous, as it is by figures and facts, that a fair and proper estimate can be formed as to the competency of the aëronaut and his balloon to do the work he takes in hand.
M. Wilfrid de Fonvielle, by correct calculations, found it too small for the intended elevation.
Whether aëronauts of the highest rank, such as the Tissandiers, Camille Flammarion, and de Fonvielle, were too polite and forbearing, as to impossibilities, I am not aware. The latter authority is known to be free from all party prejudices, to have an opinion of his own, and to utter it when necessary.
De Fonvielle may well have had doubts, I remember that Green had, as to the heights attained by Robertson and Gay-Lussac, the former being credited with having risen over 7,000 metres, while the latter reached 23,000 feet—higher, be it observed, than the 22,960 feet reached by Jovis.
Green never could make out, to use his own words, “how it was that they did it with balloons, as small as were quoted in the accounts of Robertson’s and Gay-Lussac’s experiments.”
“Certainly,” as the veteran observed, “they used hydrogen, but there must have been very little left of it on returning to the earth, if the diameters of their small balloons were no more than stated,” that is as Green added with emphasis, “if they touched 22,000 or 23,000 feet.”
By the light of our present investigations and deductions, it appears that many of the accounts of the early ascents in this century, viz., in 1803 and 4, are unreliable statements, and not altogether excusable.
For instance, Robertson, in his journey from Hamburg, said that “his head swelled, and that blood came from his nose.”
M. L’Hoest, his companion, was violently affected in a similar way; he could not get his hat on.
Mr. Glaisher’s head and mine were covered with caps, but I did not notice any cerebral expansion, being very intent upon the expansion of the gas; in short, we were always sticking to more important business.
“At their greatest elevation they could scarcely hear each other speak.”
Now I found at seven miles high, and at five and six, that in the absence of all sounds it was not necessary to speak much above a whisper, and that palpitations, watch-ticks, &c., were audible with an increase of sound the higher I got.
Robertson and his friend “could scarcely resist a strong inclination to sleep.”
I not only knew the great importance of keeping wide awake, but felt no desire to do otherwise.
Robertson’s balloon contained only 9,000 cubic feet of hydrogen.
It weighed, with all its apparatus, 5 pood 2 pounds, or a little over 200 pounds, and the weight of the whole was 18 pood 3 pounds.
Now, unless these figures are incorrect, a man like Charles Green might well feel doubtful.
M. Gay-Lussac on September 15th, 1804, when he attained 7016 metres, though well clothed, began to feel cold, he was still “far from experiencing such uneasiness as to oblige him to descend,” his pulse and respiration were accelerated; these were all the inconveniences he felt, and they read to my thinking more correct and natural than Robertson’s.
Green had no belief in what may be styled miraculous ballooning, by that I mean in going up very high or extremely far in a very diminutive balloon.
Practically speaking, irrespective of exact mathematical determinations, a sure and certain test is the amount of ballast taken, together with the volume of gas in the balloon at starting, and the space left for expansion, supposing that the ascent is made with only a partial inflation.
It is useless to boast of distance or height, unless sand equal to the occasion can be taken in the car; and if the diameter and depth of the machine is not in conformity with well established rules, no confidence should be placed in unsupported vapourings, as all the accessories to which I refer must be in order and bear comparison, one with another.
In a voyage this year by German officers from Berlin, the exact number of bags of ballast they took up led me to guess the capacity of the balloon, allowing for the number of passengers, and the supposed weight of the whole; I found that I was pretty near the mark, and that the expenditure of sand was about in proportion to my own when I took Mr. Walter Powell a journey of 250 miles.
The balloon itself is no bad indicator of what can be achieved, especially in vertical motion, that is by showing the extent of expansion when the silk is throughout fully distended, and if it be so, by the force with which the gas rushes out of the safety valve; it in this way helps and checks barometrical readings, and may at times approximately take the place of that instrument for a rough-and-ready intimation of the height. For example, if a balloon mounts up when only half full at starting, and afterwards rises so high that gas escapes from the neck, then it must be between three and four miles high, roughly speaking.
It is of no use for a novice or an unscientific aëronaut to tell a fanciful tale about his lofty flights to fabulous elevations, when he is known to have taken only a moderate amount of ballast, and only one person besides himself in the car.
If one hears a story that a small aërial affair has been up miles high, or hundreds of miles horizontally, even at a low altitude, do not take it for granted that you have been told the truth, you can easily try and prove it for yourself. Just ask a few questions as to its size, next get at its displacement of air, as you would judge in like manner of a ship’s displacement of water when it has to carry so many thousand tons of cargo.
If you hear that a balloon of thirty or even forty feet in diameter has been 20,000 feet high when filled with coal gas, shake your head and fly to figures, remembering that the following simple calculations will enable you to judge for yourself. Make, in fact, yourself a balloon of tissue or Chinese paper, and bear in mind at the outset the proportion that the diameter bears to the circumference of a circle.
Say you make it of three feet diameter, or thirty-six inches.
In order to find the circumference, which is three times and one-seventh the diameter, multiply the diameter thirty-six by 3·1416—
| Then 3·1416 | |
| 36 | inches. |
| ——— | |
| 188496 | |
| 94248 | |
| ———— | |
| 113·0976 | |
| ======= |
Secondly.—By multiplying this circumference 113, by the diameter 36, it gives the superficial surface.
| 113 | |
| 36 | |
| —— | |
| 678 | |
| 339 | |
| —— | |
| Number of superficial inches on the surface | 4068 |
| === | |
This multiplied by one-sixth gives the contents in cubic inches—
| 4068 |
| 6 |
| ——— |
| 24408 |
| ===== |
Then if 24408, the contents of a balloon three feet in diameter is divided by 1728, the number of cubic inches in a foot, you have fourteen cubic feet as the capacity of a three feet balloon, thus—
| 1728) | 24408 | (14 cubic feet |
| 1728 | ||
| —— | ||
| 7128 | and | |
| 6912 | ||
| —— | ||
| 216 | inches over. | |
| ==== | ||
If you want to find the internal capacity of a balloon three feet in diameter, first multiply the three feet by three feet to give the circumference (nine feet), which gives twenty-seven, the surface.
Then multiply by 5236 to ascertain the cubic contents.
| 5236 | |
| 27 | |
| ——— | |
| 36652 | |
| 10472 | |
| ———— | |
| 14·1372 | being 14 cubic feet and a fraction. |
| ======= | |
| 14 |
I will just give one more simple calculation of the capacity and superficial surface of a balloon thirty-three—instead of three—feet in diameter.
| 33 | |
| 33 | |
| —— | |
| 99 | |
| 99 | |
| —— | |
| 1089 | circumference. |
| 33 | diameter. |
| ——— | |
| 35937 | surface. |
| ·5236 | decimal numbers. |
| ——— | |
| 215622 | |
| 107811 | |
| 71874 | |
| 179685 | |
| ————— | |
| 18816·6132 | cubic contents. |
| ========= |
Carburetted hydrogen or coal gas, should raise from 402 pounds, as 1,000 feet of light gas should raise 40 pounds to the 1,000 cubic feet.
If the reader is desirous of calculating either for model balloons, or, as to the size, capacity, and power of larger balloons, take note of this concise and abridged table of the diameters, surfaces, and capacities, together with the ascensive power for every foot capacity for hydrogen, so that if coal gas is used, allowance must be made accordingly.
First, for miniature paper or skin balloons.
| Feet, Diameter. | Surface in Square. | Capacities in Cubic Feet. | Pounds Ascensive Power. | |||
| 1 | 3 | 1⁄10 | 0 | 1⁄2 | 0 | 2⁄32 |
| 3 | 28 | 14 | 1 | in nearly a pound. | ||
| 6 | 113 | 113 | 7 | |||
| 10 | 314 | 523 | 33 | |||
| 20 | 1,257 | 4,189 | 261 | |||
| LARGER BALLOONS. | ||||||
| 30 | 2,827 | 14,137 | 884 | |||
| 40 | 5,026 | 33,510 | 2,094 | |||
| 50 | 7,854 | 65,450 | 4,091 | |||
| 80 | 20,106 | 268,083 | 16,755 | |||
| 100 | 31,416 | 523,599 | 32,725 | |||
The striking advantage of enlarging balloons, arises from the fact, that their powers increase faster than their surfaces. When the diameter is doubled, four times as much material is required, but you get eight times as much capacity.
I have now offered a few plain calculations in order to assist those who feel interested in the subject, they may be extended and more scientifically pursued in another volume of my experiences, when they will be required, perhaps, for illustration of other ascents.
I am often asked, how high will a balloon go? Will it mount higher and higher until gas is let off to stop it?
My answer is, that when a balloon, after inflation, is brought to an even balance, in other words, when so much ballast is placed in the car, that it shows a very slight tendency to move upwards, then the required ascending power is increased by putting out more sand, say to the amount of twenty, thirty, or forty pounds, according to circumstances, I mean the strength of wind at the time, and the proximity of adjacent objects, such as trees and buildings.
With either of these limited number of weights removed, the balloon cannot rise very high, unless there is either a large space for expansion, or a very much larger quantity of sand is put out subsequently.
I will simply try this position by asking the reader to suppose that A and B, two rival aëronauts, are about to engage at one and the same time with two balloons of similar capacities to reach an elevation, say of six miles, and that both balloonists have balloons that will contain each 100,000 cubic feet of coal gas, and that they each take up one person, so that the weight of their respective balloons, each having to raise two persons, will altogether be 1,000 pounds for A’s and the same for B’s machine.
A’s balloon is to be quite filled with gas that lifts forty pounds the 1,000 feet, but B’s balloon is to be only half filled.
On testing the lifting power, A’s being full, that is containing 100,000 cubic feet of gas, will, after deducting the weight of balloon and two persons calculated at 1,000 pounds, with 3,000 pounds weight of ballast.
But B’s balloon would only have a 1,000 pounds of sand as compared with A’s, because B’s is only half full, having only 50,000 feet of gas in it.
Well, under these apparently opposite conditions, which balloon, do you suppose, would attain the greatest height?
I should say, paradoxical as it may appear, that they would reach about the same height, because the space left for expansion in B’s balloon, owing to its half filled state, would admit of the gas doubling its volume, while A’s balloon, being filled at starting, would from the first irrecoverably lose gas from the neck, although it remained full to the safety valve.
B’s would hold its own 50,000 feet, and it would quickly increase and multiply up to 100,000 cubic feet, and thus equal A’s balloon.
The store of ballast would soon be equal. A’s 3,000 pounds would, at three and three quarter miles high, be reduced to the level of B’s, which was 1,000 pounds at starting, with only 50,000 cubic feet of gas.
I have frequently adopted this system, but as I shall advert in the next part of my experiences to cases in point, I prefer now to refer to two of Mr. Green’s high ascents in proof of the practicability and objects of this method, which saves labour in casting out so much sand, and saves expense as well.
The two voyages of Green, which were made in the years 1838-9, have altogether escaped notice in the recent reviews of the most remarkable scientific ascents in the present century.
Robertson’s, Gay-Lussac’s, Bixio’s, and Barral’s having been mentioned, but not those of Green, which came after the ascents of above experimenters, and long before the fatal one by Croce Spinelli and Sivel, and that lately made by Captain Jovis and Lieutenant Mallet.
On the 4th of September, 1838, the celebrated Nassau balloon, which at that time was the property of Messrs. Gye & Hughes, the proprietors of Vauxhall Gardens, ascended from them with Mr. Green, Mr. Edward Spencer, and Mr. Rush of Elsenham Hall, Essex, the latter gentleman having engaged the balloon for experimental purposes, and more particularly on this occasion for ascertaining the greatest altitude that could with safety be attained with three persons in the car; and further to ascertain the changes of temperature that would take place at different elevations, as well as the variations of the currents of air; and finally, to establish the important fact, as to whether the same difficulties with regard to respiration in a very rarified atmosphere would be experienced by persons rising in a balloon to any great altitude, as have been felt by persons who have ascended lofty mountains, and by previous aërial travellers in balloons to great heights.
They left the earth at twenty-five minutes before 7 p.m. with two barometers standing at thirty inches each.
One of these instruments, as well as a thermometer, was furnished by Mr. Rush, constructed on the most accurate principles, and made expressly for the purpose.
The thermometer stood at 66° Fahrenheit.
The following were the variations:—
| Barometer. | Thermometer. | |||
| 30 | inches. | 66 | degrees. | |
| 23 | ” | 56 | ” | |
| 21 | ” | 53 | ” | |
| 19 | ” | 46 | ” | |
| 18 | ” | 42 | ” | |
| 17 | ” | 39 | ” | |
| 16 | ” | 35 | ” | |
| 15 | ” | 25 | ” | |
| Greatest altitude | 14·70 | ” | 25 | ” |
On first rising they took a north-westerly direction; at 2,500 it changed to the north, and shortly afterwards to north-east.
Their journey was pursued towards Epping, and they were discharging ballast all the time. Leaving Dunmow to their left they attained their greatest altitude, namely, 19,335 feet, or three and a half miles and 855 feet.
In consequence of the great quantity of sand discharged after clearing the Metropolis their ascent became very rapid, and, from the great expansion of the inflating power, the gas rushed out from the lower valve in considerable torrents.
The velocity of their upward progress caused the balloon to rotate in a spiral motion with astonishing rapidity.
During their trip about 1,200 pounds of ballast was discharged, but they reserved 100 pounds by which to regulate the descent.
During their descent, when at 1,200 feet from the earth, a heavy fall of snow was encountered, accompanied by a sudden and very great reduction of temperature, the thermometer dropping to 22°, or 10° below freezing point. The mercury in the barometer at this moment had risen to nineteen inches.
I mention this circumstance for the purpose of showing that sometimes sudden changes of temperature have been experienced, not only by Green, but by Bixio and Barral later on in the present century.
The fatigue of the muscular powers, occasioned by exertion in emptying ballast, did not occasion any serious inconvenience in respect to difficulty in respiration.
We shall see, in the next ascent which was still higher, that the plan I have already exemplified as to allowing considerable space for expansion was resorted to, and this saved both the necessity for and the depression consequent upon hard work, although a large volume of gas was literally wasted, which might, in an economical point of view, have been prevented; but it will serve to show that a large balloon partially inflated, with a reduced amount of sand, is for all practical and scientific purposes preferable to a fully inflated balloon, that is, for very high ascents.
The ordinary way of examining the specific gravity of the different gases is by a simple method founded on the principles of pneumatics, for discovering the relative specific gravities of the aëriform fluids.
This consists in observing the time that a given portion of the gas, under a determined pressure, takes to escape through a very small aperture. The density of the gaseous fluid must be inversely as the square of the interval that elapses.
The weight of the balloon and all appendages must evidently compress the included gas, and thereby render it in some degree denser.
To compute this minute effect, we have only to consider that the pressure of a column of atmosphere at the mean temperature, and near the level of the sea, is 1632 pounds on a circle of a foot in diameter.
Thus, in a balloon of sixty feet in diameter, if we suppose the whole load to have been 6000 pounds, the compression of the bag would only amount to five-thirds of a pound for each circle of a foot in diameter in the horizontal action, or corresponding to the 979th part of the entire pressure of the atmosphere.
But the weight of the confined gas (hydrogen) being 1200 pounds, its buoyancy must have suffered a diminution of somewhat more than a pound or one-eleventh from the circumference opposed to it.
But as I have purposely abstained from giving in this first elementary part any computations of an abstruse order by more learned and capable writers than myself, I shall reserve further remarks on this particular head for my subsequent volume.