The Dominion of the Air Part 11

It will have been gathered from what has been already stated that the balloonist is commonly in much uncertainty as to his precise course when he is above the clouds, or when unable from darkness to see the earth beneath him. With a view of overcoming this disadvantage some original experiments were suggested by a distinguished officer, who during the seventies had begun to interest himself in aeronautics.

This was Captain Burnaby. His method was to employ two small silk parachutes, which, if required, might carry burning magnesium wires, and which were to be attached to each other by a length of silk thread.

On dropping one parachute, it would first partake of the motion of the balloon, but would presently drop below, when the second parachute would be dismissed, and then an imaginary line drawn between the two bodies was supposed to betray the balloon's course. It should be mentioned, however, that if a careful study is made of the course of many descending parachutes it will be found that their behaviour is too uncertain to be relied upon for such a purpose as the above. They will often float behind the balloon's wake, but sometimes again will be found in front, and sometimes striking off in some side direction, so wayward and complex are the currents which control such small bodies. Mr.

Glaisher has stated that a balloon's course above the clouds may be detected by observing the grapnel, supposed to be hanging below the car, as this would be seen to be out of the vertical as the balloon drifted, and thus serve to indicate the course. However this may be, the most experienced sky sailors will be found to be in perplexity as to their direction, as also their speed, when view of the earth is obscured.

But Captain Burnaby is a.s.sociated notably with the adventurous side of ballooning, the most famous of his aerial exploits being, perhaps, that of crossing the English Channel alone from Dover on March 23rd, 1882.

Outwardly, he made presence of sailing to Paris by sky to dine there that evening; inwardly, he had determined to start simply with a wind which bid fair for a cross-Channel trip, and to take whatever chances it might bring him.

Thus, at 10.30 a.m., just as the mail packet left the pier, he cast off with a lifting power which rapidly carried him to a height of 2,000 feet, when he found his course to be towards Folkestone. But by shortly after 11 o'clock he had decided that he was changing his direction, and when, as he judged, some seven miles from Boulogne, the wind was carrying him not across, but down the Channel. Then, for nearly four hours, the balloon s.h.i.+fted about with no improvement in the outlook, after which the wind fell calm, and the balloon remained motionless at 2,000 feet above the sea. This state of things continuing for an hour, the Captain resolved on the heroic expedient of casting out all his ballast and philosophically abiding the issue. The manoeuvre turned out a happy one, for the balloon, shooting up to 11,000 feet, caught a current, on which it was rapidly carried towards and over the main land; and, when twelve miles beyond Dieppe, it became easy to descend to a lower level by manipulation of the valve, and finally to make a successful landing in open country beyond.

A few years before, an attempt to cross the Channel from the other side ended far more disastrously. Jules Duruof, already mentioned as having piloted the first runaway balloon from beleaguered Paris, had determined on an attempt to cross over to England from Calais; and, duly advertising the event, a large concourse a.s.sembled on the day announced, clamouring loudly for the ascent. But the wind proved unsuitable, setting out over the North Sea, and the mayor thought fit to interfere, and had the car removed so as to prevent proceedings. On this the crowd grew impatient, and Duruof, determining to keep faith with them, succeeded by an artifice in regaining his car, which he hastily carried back to the balloon, and immediately taking his seat, and accompanied by his wife, the intrepid pair commenced their bold flight just as the shades of evening were settling down. Shortly the balloon disappeared into the gathering darkness, and then for three days Calais knew no more of balloon or balloonists.

Neither could the voyagers see aught for certain of their own course, and thus through the long night hours their attention was wholly needed, without chance of sleep, in closely watching their situation, lest unawares they should be borne down on the waves. When morning broke they discovered that they were still being carried out over the sea on a furious gale, being apparently off the Danish coast, with the distant mountains of Norway dimly visible on the starboard bow. It was at this point, and possibly owing to the chill commonly experienced aloft soon after dawn, that the balloon suddenly took a downward course and plunged into the sea, happily, however, fairly in the track of vessels. Presently a s.h.i.+p came in sight, but cruelly kept on its course, leaving the castaways in despair, with their car fast succ.u.mbing to the waves.

Help, nevertheless, was really at hand. The captain of an English fis.h.i.+ng smack, the Grand Charge, had sighted the sinking balloon, and was already bearing down to the rescue. It is said that when, at length, a boat came alongside as near as it was possible, Madame Duruof was unable to make the necessary effort to jump on board, and her husband had to throw her into the arms of the sailors. A fitting sequel to the story comes from Paris, where the heroic couple, after a sojourn in England, were given a splendid reception and a purse of money, with which M. Duruof forthwith constructed a new balloon, named the "Ville de Calais."

On the 4th of March, 1882, the ardent amateur balloonist, Mr. Simmons, had a narrow escape in circ.u.mstances somewhat similar to the above. He was attempting, in company with Colonel Brine, to cross the Channel from Canterbury, when a change of wind carried them out towards the North Sea. Falling in the water, they abandoned their balloon, but were rescued by the mail packet Foam.

The same amateur aeronaut met with an exciting experience not long after, when in company with Sir Claude C. de Crespigny. The two adventurers left Maldon, in Ess.e.x, at 11 p.m., on an August night, and, sailing at a great height out to sea, lost all sight of land till 6 a.m. the next morning, when, at 17,000 feet alt.i.tude, they sighted the opposite coast and descended in safety near Flus.h.i.+ng.

Yet another adventure at sea, and one which proved fatal and unspeakably regrettable, occurred about this time, namely, on the 10th of December, 1881, when Captain Templer, Mr. W. Powell, M.P., and Mr. Agg-Gardner ascended from Bath. We prefer to give the account as it appears in a leading article in the Times for December 13th of that year.

After sailing over Glas...o...b..ry, "Crewkerne was presently sighted, then Beaminster. The roar of the sea gave the next indication of the locality to which the balloon had drifted and the first hint of the possible perils of the voyage. A descent was now effected to within a few hundred feet of earth, and an endeavour was made to ascertain the exact position they had reached. The course taken by the balloon between Beaminster and the sea is not stated in Captain Templer's letter. The wind, as far as we can gather, must have s.h.i.+fted, or different currents of air must have been found at the different alt.i.tudes. What Captain Templer says is that they coasted along to Symonsbury, pa.s.sing, it would seem, in an easterly direction and keeping still very near to the earth. Soon after they had left Symonsbury, Captain Templer shouted to a man below to tell them how far they were from Bridport, and he received for answer that Bridport was about a mile off. The pace at which the balloon was moving had now increased to thirty-five miles an hour. The sea was dangerously close, and a few minutes in a southerly current of air would have been enough to carry them over it. They seem, however, to have been confident in their own powers of management. They threw out ballast, and rose to a height of 1,500 feet, and thence came down again only just in time, touching the ground at a distance of about 150 yards from the cliff. The balloon here dragged for a few feet, and Captain Templer, who had been letting off the gas, rolled out of the car, still holding the valve line in his hand. This was the last chance of a safe escape for anybody.

The balloon, with its weight lightened, went up about eight feet. Mr.

Agg-Gardner dropped out and broke his leg. Mr. Powell now remained as the sole occupant of the car. Captain Templer, who had still hold of the rope, shouted to Mr. Powell to come down the line. This he attempted to do, but in a few seconds, and before he could commence his perilous descent, the line was torn out of Captain Templer's hands. All communication with the earth was cut off, and the balloon rose rapidly, taking Mr. Powell with it in a south-easterly direction out to sea."

It was a few seasons previous to this, namely, on the 8th of July, 1874, when Mr. Simmons was concerned in a balloon fatality of a peculiarly distressing nature. A Belgian, Vincent de Groof, styling himself the "Flying Man," announced his intention of descending in a parachute from a balloon piloted by Mr. Simmons, who was to start from Cremorne Gardens. The balloon duly ascended, with De Groof in his machine suspended below, and when over St. Luke's Church, and at a height estimated at 80 feet, it is thought that the unfortunate man overbalanced himself after detaching his apparatus, and fell forward, clinging to the ropes. The machine failed to open, and De Groof was precipitated into Robert Street, Chelsea, expiring almost immediately.

The porter of Chelsea Infirmary, who was watching the balloon, a.s.serted that he fancied the falling man called out twice, "Drop into the churchyard; look out!" Mr. Simmons, shooting upwards in his balloon, thus suddenly lightened, to a great height, became insensible, and when he recovered consciousness found himself over Victoria Park. He made a descent, without mishap, on a line of railway in Ess.e.x.

On the 19th of August, 1887, occurred an important total eclipse of the sun, the track of which lay across Germany, Russia, Western Siberia, and j.a.pan. At all suitable stations along the shadow track astronomers from all parts of the world established themselves; but at many eclipses observers had had bad fortune owing to the phenomenon at the critical moment being obscured. And on this account one astronomer determined on measures which should render his chances of a clear view a practical certainty. Professor Mendeleef, in Russia, resolved to engage a balloon, and by rising above the cloud barrier, should there be one, to have the eclipse all to himself. It was an example of fine enthusiasm, which, moreover, was presently put to a severe and unexpected test, for the balloon, when inflated, proved unable to take up both the aeronaut and the astronomer, whereupon the latter, though wholly inexperienced, had no alternative but to ascend alone, which, either by accident or choice, he actually did. Shooting up into s.p.a.ce, he soon reached an alt.i.tude of 11,500 feet, where he obtained, even if he did not enjoy, an un.o.bstructed view of the Corona. It may be supposed, however, that, owing to the novelty of his situation, his scientific observations may not have been so complete as they would have been on terra firma.

In the same month an attempt to reach a record height was made by MM.

Jovis and Mallet at Paris, with the net result that an elevation of 23,000 feet was reached. It will have been noted that the difficulty through physical exhaustion of inhaling oxygen from either a bag or cylinder is a serious matter not easily overcome, and it has been suggested that the helmet invented by M. Fleuss might prove of value.

This contrivance, which has scarcely attracted the attention it has merited, provides a receptacle for respiration, containing oxygen and certain purifying media, by means of which the inventor was able to remain for hours under water without any communication with the outward air.

About the period at which we have now arrived two fatal accidents befel English aeronauts. We have related how Maldon, in Ess.e.x, was a.s.sociated with one of the more adventurous exploits in Mr. Simmons's career. It was fated also to be a.s.sociated with the voyage with which his career closed. On August 27th, 1888, he ascended from Olympia in company with Mr. Field, of West Brighton, and Mr. Myers, of the Natural History Museum, with the intention, if practicable, of crossing to Flanders; and the voyage proceeded happily until the neighbourhood of Maldon was reached, when, as the sea coast was in sight, and it was already past five o'clock, it appeared prudent to Mr. Simmons to descend and moor the balloon for the night. Some labourers some three miles from Maldon sighted the balloon coming up at speed, and at the same time descending until its grapnel commenced tearing through a field of barley, when ballast was thrown out, causing the balloon to rise again towards and over some tall elms, which became the cause of the disaster which followed. The grapnel, catching in the upper boughs of one of these trees, held fast, while the balloon, borne by the force of a strong wind, was repeatedly blown down to earth with violence, rebounding each time to a considerable height, only to be flung down again on the same spot. After three or four impacts the balloon is reported to have burst with a loud noise, when high in the air, the silk being blown about over the field, and the car and its occupants dashed to the ground. Help was unavailing till this final catastrophe, and when, at length, the labourers were able to extricate the party, Mr. Simmons was found with a fractured skull and both companions badly injured.

Four summers later, June 30th, 1892, Captain Dale, the aeronaut to the Crystal Palace, was announced to make an ascent from the usual balloon grounds, weather permitting. Through the night and morning a violent storm prevailed, and it was contemplated that the exhibition would be withdrawn; but the wind abating in the afternoon, the inflation was proceeded with, and the ascent took place shortly before 6 p.m., not, however, before a large rent had been discovered and repaired as far as possible by Mrs. Dale. As pa.s.sengers, there ascended the Captain's son William, aged nineteen, Mr. J. Macintosh, and Mr. Cecil Shadbolt. When the balloon had reached an alt.i.tude estimated at 600 feet the onlookers were horrified to see it suddenly collapse, a large rent having developed near the top part of the silk, from which the gas "rushed out in a dense ma.s.s, allowing the balloon to fall like a rag." The occupants of the car were seen to be throwing out everything madly, even wrenching the b.u.t.tons from their clothing. All, however, with little avail, for the balloon fell "with a sickening thud," midway between the Maze and lower lake. All were found alive; but Captain Dale, who had alighted on his back, died in a few minutes; Mr. Shadbolt succ.u.mbed later, and both remaining pa.s.sengers sustained terrible injuries.

Few balloon mishaps, unattended with fatal results, have proved more exciting than the following. A large party had ascended from Belfast, in a monster balloon, under the guidance of Mr. c.o.xwell, on a day which was very unfit for the purpose by reason of stormy weather. A more serious trouble than the wind, however, lay in several of the pa.s.sengers themselves, who seem to have been highly excitable Irishmen, incapable at the critical moment of quietly obeying orders.

The princ.i.p.al hero of the story, a German. Mr. Runge, in writing afterwards to the Ulster Observer, entirely exonerates Mr. c.o.xwell from any blame, attributing his mischances solely to the reprehensible conduct of his companions. On approaching the ground, Mr. c.o.xwell gave clear instructions. The pa.s.sengers were to sit down in an unconstrained position facing each other, and be prepared for some heavy shocks. Above all things they were to be careful to get out one by one, and on no account to leave hold of the car. Many of the pa.s.sengers, however, refused to sit down, and, according to Mr. Runge, "behaved in the wildest manner, losing completely their self-control. Seizing the valve rope themselves, they tore it away from its attachment, the stronger pus.h.i.+ng back the weaker, and refusing to lend help when they had got out. In consequence of this the car, relieved of their weight, tore away from the grasp of Mr. c.o.xwell and those who still clung to it, and rose above the trees, with Mr. Runge and one other pa.s.senger, Mr. Halferty, alone within. As the balloon came earthwards again, they shouted to the countrymen for succour, but without the slightest avail, and presently, the anchor catching, the car struck the earth with a shock which threw Mr. Halferty out on the ground, leaving Mr. Runge to rise again into the air, this time alone." He thus continues the story:--

"The balloon moved on, very soon, in a horizontal direction straight towards the sea, which we were then rapidly nearing. Coming to a farm, I shouted out to the people standing there. Some women, with their quick humane instincts, were the first to perceive my danger, and exhorted the men to hurry to my a.s.sistance, they themselves running as fast as they could to tender what little help they might be able to give me. The anchor stuck in a willow tree. I shouted out to the people below to secure the cable and anchor by ropes, which they did. The evening was now beautifully still, the breeze had died away, and the balloon was swinging calmly at her moorings above the farmhouse. One of the men asked me whether I had a rope with me, and how I intended to get out.

I told them only to take care of the cable, because the balloon would settle down by herself before long. I was congratulating myself on a speedy escape from my dangerous position. I had not counted on the wind.

A breeze in about six or eight minutes sprang up, tossed the balloon about like a large sail, then a crash, and--the anchor was loose again.

It tore through the trees, flinging limbs and branches about like matches. It struck the roof of the farmhouse, splintering the chimneys and tiles like gla.s.s.

"On I went; I came near another farm; shouted out for help, and told the men to secure the anchor to the foot of a large tree close by. The anchor was soon made fast, but this was only a momentary relief. The breeze again filled the half-empty balloon like a sail, there was a severe strain on the cable, then a dull sound, and a severe concussion of the basket--the cable, strange fatality, had broken, and the anchor, my last and only hope, was gone. I was now carried on in a straight direction towards the sea, which was but a short distance ahead. The anchor being lost I gave up all hope. I sat down resigned in the car, and prepared for the end. All at once I discovered that a side current was drifting me towards the mountain; the car struck the ground, and was das.h.i.+ng along at a fearful rate, knocking down stone fences and breaking everything it came in contact with in its wild career. By-and-by the knocks became less frequent. We were pa.s.sing over a cultivated country, and the car was, as it were skimming the surface and grazing the top of the hedges. I saw a thick hawthorn hedge at some distance before me, and the balloon rapidly sweeping towards it. That was my only chance. I rushed to the edge of the car and flung myself down upon the hedge."

CHAPTER XXI. THE COMING OF THE FLYING MACHINE.

In the early nineties the air s.h.i.+p was engaging the attention of many inventors, and was making important strides in the hands of Mr. Maxim.

This unrivalled mechanician, in stating the case, premises that a motive power has to be discovered which can develop at least as much power in proportion to its weight as a bird is able to develop. He a.s.serts that a heavy bird, with relatively small wings--such as a goose--carries about 150 lb. to the horse power, while the albatross or the vulture, possessed of proportionately greater winged surface, can carry about 250 lbs. per horse power.

Professor Langley, of Was.h.i.+ngton, working contemporaneously, but independently of Mr. Maxim, had tried exhaustive experiments on a rotating arm (characteristically designated by Mr. Maxim a "merry-go-round"), thirty feet long, applying screw propellers. He used, for the most part, small planes, carrying loads of only two or three pounds, and, under these circ.u.mstances, the weight carried was at the rate of 250 lbs. per horse power. His important statements with regard to these trials are that one-horse power will transport a larger weight at twenty miles an hour than at ten, and a still larger at forty miles than at twenty, and so on; that "the sustaining pressure of the air on a plane moving at a small angle of inclination to a horizontal path is many times greater than would result from the formula implicitly given by Newton, while, whereas in land or marine transport increased speed is maintained only by a disproportionate expenditure of power within the limits of experiment, in aerial horizontal transport the higher speeds are more economical of power than the lower ones."

This Mr. Maxim is evidently ready to endorse, stating, in his own words, that birds obtain the greater part of their support by moving forward with sufficient velocity so as to be constantly resting on new air, the inertia of which has not been disturbed. Mr. Maxim's trials were on a scale comparable with all his mechanical achievements. He employed for his experiments a rotating arm, sweeping out a circle, the circ.u.mference of which was 200 feet. To the end of this arm he attached a cigar-shaped apparatus, driven by a screw, and arranged in such a manner that aero-planes could be attached to it at any angle. These planes were on a large scale, carrying weights of from 20 lbs. to 100 lbs. With this contrivance he found that, whatever push the screw communicated to the aero-plane, "the plane would lift in a vertical direction from ten to fifteen times as much as the horizontal push that it received from the screw, and which depended upon the angle at which the plane was set, and the speed at which the apparatus was travelling through the air." Next, having determined by experiment the power required to perform artificial flight, Mr. Maxim applied himself to designing the requisite motor.

"I constructed," he states, "two sets of compound engines of tempered steel, all the parts being made very light and strong, and a steam generator of peculiar construction, the greater part of the heating surface consisting of small and thin copper tubes. For fuel I employed naphtha."

This Mr. Maxim wrote in 1892, adding that he was then experimenting with a large machine, having a spread of over 100 feet. Labour, skill, and money were lavishly devoted henceforward to the great task undertaken, and it was not long before the giant flying machine, the outcome of so much patient experimenting, was completed and put to a practical trial.

Its weight was 7,500 lbs. The screw propellers were nearly 18 feet in diameter, each with two blades, while the engines were capable of being run up to 360 horse power. The entire machine was mounted on an inner railway track of 9 feet and an outer of 35 feet gauge, while above there was a reversed rail along which the machine would begin to run so soon as with increase of speed it commenced to lift itself off the inner track.

In one of the latest experiments it was found that when a speed of 42 miles an hour was attained all the wheels were running on the upper track, and revolving in the opposite direction from those on the lower track. However, after running about 1,000 feet, an axle tree doubled up, and immediately afterwards the upper track broke away, and the machine, becoming liberated, floated in the air, "giving those on board a sensation of being in a boat."

The experiment proved conclusively to the inventor that a machine could be made on a large scale, in which the lifting effect should be considerably greater than the weight of the machine, and this, too, when a steam engine was the motor. When, therefore, in the years shortly following, the steam engine was for the purposes of aerial locomotion superseded by the lighter and more suitable petrol engine, the construction of a navigable air s.h.i.+p became vastly more practicable.

Still, in Sir H. Maxim's opinion, lately expressed, "those who seek to navigate the air by machines lighter than the air have come, practically, to the end of their tether," while, on the other hand, "those who seek to navigate the air with machines heavier than the air have not even made a start as yet, and the possibilities before them are very great indeed."

As to the a.s.sertion that the aerial navigators last mentioned "have not even made a start as yet," we can only say that Sir H. Maxim speaks with far too much modesty. His own colossal labours in the direction of that mode of aerial flight, which he considers to be alone feasible, are of the first importance and value, and, as far as they have gone, exhaustive. Had his experiments been simply confined to his cla.s.sical investigations of the proper form of the screw propeller his name would still have been handed down as a true pioneer in aeronautics. His work, however, covers far wider ground, and he has, in a variety of ways, furnished practical and reliable data, which must always be an indispensable guide to every future worker in the same field.

Professor Langley, in attacking the same problem, first studied the principle and behaviour of a well-known toy--the model invented by Penaud, which, driven by the tension of india-rubber, sustains itself in the air for a few seconds. He constructed over thirty modifications of this model, and spent many months in trying from these to as certain what he terms the "laws of balancing leading to horizontal flight." His best endeavours at first, however, showed that he needed three or four feet of sustaining surface to a pound of weight, whereas he calculated that a bird could soar with a surface of less than half a foot to the pound. He next proceeded to steam-driven models in which for a time he found an insuperable difficulty in keeping down the weight, which, in practice, always exceeded his calculation; and it was not till the end of 1893 that he felt himself prepared for a fair trial. At this time he had prepared a model weighing between nine and ten pounds, and he needed only a suitable launching apparatus to be used over water. The model would, like a bird, require an initial velocity imparted to it, and the discovery of a suitable apparatus gave him great trouble. For the rest the facilities for launching were supplied by a houseboat moored on the Potomac. Foiled again and again by many difficulties, it was not till after repeated failures and the lapse of many months, when, as the Professor himself puts it, hope was low, that success finally came. It was in the early part of 1896 that a successful flight was accomplished in the presence of Dr. Bell, of telephone fame, and the following is a brief epitome of the account that this accomplished scientist contributed to the columns of Nature:--

"The flying machine, built, apparently, almost entirely of metal, was driven by an engine said to weigh, with fuel and water, about 25 lbs., the supporting surface from tip to tip being 12 or 14 feet. Starting from a platform about 20 feet high, the machine rose at first directly in the face of the wind, moving with great steadiness, and subsequently wheeling in large curves until steam was exhausted, when, from a height of 80 or 100 feet, it shortly settled down. The experiment was then repeated with similar results. Its motion was so steady that a gla.s.s of water might have remained unspilled. The actual length of flight each time, which lasted for a minute and a half, exceeded half a mile, while the velocity was between twenty and twenty-five miles an hour in a course that was constantly taking it 'up hill.' A yet more successful flight was subsequently made."

But flight of another nature was being courageously attempted at this time. Otto Lilienthal, of Berlin, in imitation of the motion of birds, constructed a flying apparatus which he operated himself, and with which he could float down from considerable elevations. "The feat," he warns tyros, "requires practice. In the beginning the height should be moderate, and the wings not too large, or the wind will soon show that it is not to be trifled with." The inventor commenced with all due caution, making his first attempt over a gra.s.s plot from a spring board one metre high, and subsequently increasing this height to two and a half metres, from which elevation he could safely cross the entire gra.s.s plot. Later he launched himself from the lower ridges of a hill 250 feet high, when he sailed to a distance of over 250 yards, and this time he writes enthusiastically of his self-taught accomplishment:--

"To those who, from a modest beginning and with gradually increased extent and elevation of flight have gained full control over the apparatus, it is not in the least dangerous to cross deep and broad ravines. It is a difficult task to convey to one who has never enjoyed aerial flight a clear perception of the exhilarating pleasure of this elastic motion. The elevation above the ground loses its terrors, because we have learned by experience what sure dependence may be placed upon the buoyancy of the air."

As a commentary to the above we extract the following:--"We have to record the death of Otto Lilienthal, whose soaring machine, during a gliding flight, suddenly tilted over at a height of about 60 feet, by which mishap he met an untimely death on August 9th, 1896." Mr. O.

Chanute, C.E. of Chicago, took up the study of gliding flight at the point where Lilienthal left it, and, later, Professor Fitzgerald and others. Besides that invented by Penaud, other aero-plane models demanding mention had been produced by Tatin, Moy, Stringfellow, and Lawrence Hargrave, of Australia, the subsequent inventor of the well-known cellular kite. These models, for the most part, aim at the mechanical solution of the problem connected with the soaring flight of a bird.

The theoretical solution of the same problem had been attacked by Professor Langley in a masterly monograph, ent.i.tled "The Internal Work of the Wind." By painstaking experiment with delicate instruments, specially constructed, the Professor shows that wind in general, so far from being, as was commonly a.s.sumed, mere air put in motion with an approximately uniform velocity in the same strata, is, in reality, variable and irregular in its movements beyond anything which had been antic.i.p.ated, being made up, in fact, of a succession of brief pulsations in different directions, and of great complexity. These pulsations, he argues, if of sufficient amplitude and frequency, would be capable, by reason of their own "internal work," of sustaining or even raising a suitably curved surface which was being carried along by the main mean air stream. This would account for the phenomenon of "soaring." Lord Rayleigh, discussing the same problem, premises that when a bird is soaring the air cannot be moving uniformly and horizontally. Then comes the natural question, Is it moving in ascending currents? Lord Rayleigh has frequently noticed such currents, particularly above a cliff facing the wind. Again, to quote another eminent authority, Major Baden-Powell, on an occasion when flying one of his own kites, found it getting to so high an angle that it presently rose absolutely overhead, with the string perpendicular. He then took up a heavy piece of wood, which, when tied to the string, began to rise in the air. He satisfied himself that this curious result was solely due to a strong uptake of the air.

But, again, Lord Rayleigh, lending support to Professor Langley's argument, points out that the apparent cause of soaring may be the non-uniformity of the wind. The upper currents are generally stronger than the lower, and it is mechanically possible for a bird, taking advantage of two adjacent air streams, different in velocity, to maintain itself in air without effort on its own part.

Lord Rayleigh, proceeding to give his views on artificial flight, declares the main problem of the flying machine to be the problem of the aerial plane. He states the case thus:--"Supposing a plane surface to be falling vertically at the rate of four miles an hour, and also moving horizontally at the rate of twenty miles an hour, it might have been supposed that the horizontal motion would make no difference to the pressure on its under surface which the falling plane must experience.

We are told, however, that in actual trial the horizontal motion much increases the pressure under the falling plane, and it is this fact on which the possibility of natural and artificial flight depends."

Ere this opinion had been stated by Lord Rayleigh in his discourse on "Flight," at the Royal Inst.i.tution, there were already at work upon the aero-plane a small army of inventors, of whom it will be only possible in a future chapter to mention some. Due reference, however, should here be made to Mr. W. F. Wenham, of Boston, U.S.A., who had been at work on artificial flight for many years, and to whose labours in determining whether man's power is sufficient to raise his own weight Lord Rayleigh paid a high tribute. As far back as 1866 Mr. Wenham had published a paper on aerial locomotion, in which he shows that any imitation by man of the far-extended wings of a bird might be impracticable, the alternative being to arrange the necessary length of wing as a series of aero-planes, a conception far in advance of many theorists of his time.

But there had been developments in aerostation in other lines, and it is time to turn from the somewhat tedious technicalities of mechanical flight and the theory or practice of soaring, to another important means for traversing the air--the parachute. This aerial machine, long laid aside, was to lend its aid to the navigation of the air with a reliability never before realised. Professor Baldwin, as he was termed, an American aeronaut, arrived in England in the summer of 1888, and commenced giving a series of exhibitions from the Alexandra Palace with a parachute of his own invention, which, in actual performance, seems to have been the most perfect instrument of the kind up to that time devised. It was said to be about 18 feet in diameter, whereas that of Garnerin, already mentioned, had a diameter of some 30 feet, and was distinctly top-heavy, owing to its being thus inadequately ballasted; for it was calculated that its enormous size would have served for the safe descent, not of one man, but of four or five. Baldwin's parachute, on the contrary, was reckoned to give safe descent to 250 lbs., which would include weight of man and apparatus, and reduce the ultimate fall to one not exceeding 8 feet. The parachute was attached to the ring of a small balloon of 12,000 cubic feet, and the Professor ascended, sitting on a mere sling of rope, which did duty for a car.

Mr. Thomas Moy, who investigated the mechanics of the contrivance, estimated that after a drop of 16 feet, the upward pressure, amounting to over 2 lb. per square foot, would act on a surface of not less than 254 square feet. There was, at the time, much foolish comment on the great distance which the parachute fell before it opened, a complete delusion due to the fact that observers failed to see that at the moment of separation the balloon itself sprang upward.