334 



NATURE 



[Feb. 22, 1872 



AERIAL NA VIGA TION IN FRANCE * 



•yilERE has been a most interesting sitting at the Academy 

 ■'■ of Sciences, at which M. Dunuy de Lome read a report on 

 his newly tried and apparently successful system for steering air 

 balloons. M. de Lome is one of the most eminent — if he is not the 

 most eminent — of living French engineers. He was the first to 

 apply steam to ships of war, and lie was one of the earliest de- 

 signers of ironclad frigates. The piercing of a tunnel under the 

 English Channel is another of M. Dupuy de Lome's long- 

 cherished projects, and he is one of the engineers who are about 

 to commence that gigantic enterprise. During the siege of Paris 

 by the Prassians, M. Dupuy de Lome offered to construct a 

 balloon which should have steering powers of its own, and so 

 not be totally at the mercy of the winds. That some sort of 

 guiding power was required for the balloons which were de- 

 spatched from Paris durintj its investment by the Germans is 

 shown by the fact that, out of sixty balloons sent out during that 

 period, no less than fifteen failed to caay their contents to a 

 place of safety, some falling into the sea and several into the 

 hands of the Prussians. After much tiresome delay, M. Dupuy 

 de Lome's plans were accepted by the Government of National 

 Defence, a credit of 40,000 francs (1,600/.) was opened for him, 

 and he began to construct his balloon at the Palais de I'lndus- 

 trie, in the Champs Elysees. So great was the difficulty, how- 

 ever, in constructing an immense balloon on a totally new system, 

 in a city completely cut off from the rest of the civilised world, 

 that M. Dupuy de Lome's huge machine was not ready until just 

 four days before the capitulation. When that event took place, the 

 balloon had to be packed up and hidden away from the prying eyes 

 of the Germans when they partially occupied Paris. Then came 

 the Commune, and all the disorganisation which followed. It 

 was only after much difficulty that M. Dupuy de Lome obtained 

 permission to make use of the buildings of the Fort Neuf at 

 Vincennes, whence, on the 2nd inst. , he started on his trial trip. 

 Before proceeding to quote from M. Dupuy de Lome's most in- 

 teresting report, it may be as well to say a few words as to the 

 end which the eminent aeronaut has proposed to himself. He 

 does not pretend to be able to make independent progress in the 

 teeth of the wind, but only to deviate from the direct set of the 

 wind when running before it. He does not hope ever to be able 

 to beat to windward, but only to tack to right or left with the 

 wind. A sailor would say that M. Dupuy de Lome wanted to 

 be always running free with the wind on the quarter. So if the 

 wind set straight from Paris to Brussels, an ordinary balloon 

 could only land at some point between Paris and Brussels, or 

 else beyond the Belgian capital. But with a balloon constructed 

 on M. Dupuy de Lome's system, the areonaut might steer his 

 course either on the port or starboard tack, and might descend 

 at London or Cologne, as he saw fit. 



Having said this much, let me try to describe the balloon 

 which M. Dupuy de Lome makes use of. Let your 

 readers imagine a gigantic egg of inflated silk, the longer 

 axis being horizontal ; to this egg is attached an oblong 

 car, something the shape of a punt. The motive of the 

 inventor in choosing the ovoid form was at once to obtain 

 greater stability for the car than could be hoped for with 

 the old balloons, and at the same time to give the least possible 

 hold to the wind. The diameter of the balloon is about two- 

 fifths of its horizontal length from point to point. I take the 

 'following dimensions from M. Dupuy de Lome's highly interest- 

 ing report, read before the Academy of Sciences, only changing 

 French metres into feet for the convenience of EngUsh readers. 



Total length from end to end . . . . 1 1 S ft. 6 in. 



Diameter at the point of greatest circum- 

 ference 49 ft. 2 in. 



Diameter of the screw 29 ft. 6 in. 



Number of blades 2 



Number of turns of the screw in a mi- 

 nute, when the balloon is going eight 

 kilometres (five miles) an hour faster 



than the wind 21 



M. Dupuy de Lome thus describes the rudder by which his 

 balloon is steered : — "The rudder is a plain triangular surface. 

 It is made of unvarnished calico, and is kept in its place by a 

 horizontal yard six metres long at its lower extremity. It can 



* Reprinted from the Daily News, 



turn easily on its forward extremity. The height of the rudder 

 is five metres, and it has a superfices of fifteen metres." The 

 car is next described — it is of wicker-work, and of sufficient 

 size to contain comfortably the windlass for the screw, and eight 

 men to work it ; tlic ventilator with which to manage the small 

 b.illoon — we shall have to speak of this presently— and the man 

 who attends to it. In all, fourteen persons can be carried in the 

 car. The driving screw is directly carried by the car. The shaft 

 of the screw is a hollow steel tube. This shaft is constructed so 

 as to allow of the screw being easily dismounted when a landing 

 is effected. The rudder is fixed to the balloon itself, and the 

 screw, as we said, is below it, and immediately attached to the 

 car. Two blades only are used in the screw instead of four, 

 because when the ground is touched the two blades can be 

 placed horizontally, so as to escape injury. Were there four 

 blades, the screw would be almost certain to be broken when- 

 ever a landing was effected. The windlass which turns the screw 

 is worked by four, o', if necessary, eight men, in a similar manner 

 to the steering wheel of a ship — only the wheel is placed parallel 

 to the axis of the car, instead of at right angles to it, in order to 

 lessen the rolling occasioned by the movements of the men working 

 the windlass. The material of which the envelope of the balloon 

 is composed is white silk, weighing 52 grammes, not quite 2 oz. 

 to the square metre, and a coarser lining weighing 40 grammes 

 the square metre, and seven coatsof india-rubber, which together 

 weigh iSo grammes, a little over 6 oz. the square metre. Thus 

 the whole weight of the external web of the balloon is 273 

 grammes, about 9 oz. to the square metre. In order to render 

 the web of the balloon totally impermeable to the hydrogen gas 

 with which it is inflated, the silk Avas pain'ed over with a sort of 

 gelatinous compound, invented by M. Dupuy de Lome. The 

 total weight of the two balloons when ready to start was 570 

 kilogrammes, or ra'her more than half a ton. The web of the 

 balloon was reckoned to be capable of supporting a pressure 

 of over 2,000 pounds to the square yard. I have mentioned the 

 smaller balloon ; this is, more correctly speaking, only a division 

 as it were of the larger balloon. It is formed by means of an 

 inner skin, separating the bottom of the balloon from the rest. 

 This compartment occupies about one-tenth of the whole cubic 

 space of the balloon, and serves to keep it stiff, and of the re- 

 quired shape. By these means i\I. Dupuy de Lome has attained 

 the two ends he proposed to himself, viz., first, permanence in 

 the shape of the balloon ; and, secondly, he has been able to 

 give the whole apparatus an axis decidedly parallel to that of the 

 force of propulsion. 



liaving thus endeavoured to give some account of the new 

 aerial navigator — no easy matter without diagrams — it only re- 

 mains for us to say a few words about M. Dupuy de Lome's 

 first experimental trip. There was half a gale of wind blowing 

 at the time he started, and the screw had been slightly damaged. 

 The spirited inventor did not hesitate, however, to make his 

 contemplated ascent. The end justified his confidence ; for not 

 only was he able to land near Noyon, in the Department of the 

 Oise, some seventy miles north-east of Paris, but his balloon 

 more than answered his expectations. The screw, when worked 

 by four men, drove the balloon eight kilometres (about five miles) 

 an hour quicker than the rate at which the wind was blowing ; 

 so that M. Dupuy de I.-ome not only " went like the wind," but 

 actually went faster than the wind. By the use of the rudder 

 the course of the balloon could be altered eleven degrees either 

 way from the set of the wind, making a total deviation of twenty- 

 two degrees. This is, of course, the greatest and most noteworthy 

 result obtained by the new aerial machine. It may possibly be 

 asked, What is the use of the screw when the wind carries your 

 balloon at the rate of fifty-four kilometres, or nearly forty miles 

 an hour? The answer is, that without the screw the rudder 

 would be of little or no use. Every one knows that a ship with- 

 out way on her steerage-way, as it is called, is nearly impossible 

 to steer. And a balloon which has not, like a ship, a second 

 element for the rudder to work on, is still more at the mercy of 

 the wind. The next question is whether the screw cannot be 

 turned by steam instead of by manual labour. But fire and 

 hydrogen gas are bad neighbours, and the introduction of a steam- 

 engine into the car — although it was hazarded some twenty years 

 ago by one of our countrymen, Mr. Henry Giffard — would expose 

 the aeronauts to the dangers of an explosion, followed by a descent 

 to the earth, doubling in rapidity every sixteen feet, in accord- 

 ance with the law of gravitation. Even with a steam-engine on 

 board, there does not seem much cause to fear the "airy navies" 

 of the inventor of ironclad ships just at present. 



