2 6o 



NA TURE 



\yan. 13, i! 



At the siege of Paris this use of balloons was demonstrated most 

 efficiently. At the time when the Parisians fonnJ themselves 

 cut off from all means of communication there were but a few 

 balloons in Paris, but the successful escape of some aeronauts in 

 these few was considered encouraging enough to establish an 

 aerial highway involving a more wholesale manufacture of 

 balloons than has ever been undertaken, the disused railway- 

 stations being converted into balloon manufactories and train- 

 ing-schools for aeronauts. During four months 66 balloons left 

 Paris — 54'being specially made for the administration of Posts and 

 Telegraphs — 160 persons were carried over the Prussian lines, 

 3,000,000 letters reached their destination, 360 pigeons were 

 taken up, of which, however, only 57 came back, but these 

 latter brought 100,000 messages. These facts show that free 

 balloons are useful in war. The utility of a free balloon would 

 be largely increased if it could be steered against a considerable 

 wind. Attempts have been made to navigate balloons on two 

 principles : (i) by using the various currents of the air ; (2) by 

 some kind of mechanical propulsion. I will say just a word or 

 two on each of these heads. 



(l) As regards mechanical propulsion. There are some persons 

 who, when they hear any suggestion regarding a steerable balloon, 

 denounce the idea as impossible ever to be accomplished. I 

 think it a wiser course to reserve a definite opinion as to whether 

 such a thing is possible in the future, as the experiments worth 

 anything which have been made in this direction have been few 

 and far between, and it is unwise to draw conclusions on a basis 

 of inadequate facts. I will, however, say this much, that those 

 who have the task in hand have a difficult problem before them, 

 and that the engineer who first steers a balloon against a strong 

 wind by mechanical propulsion will deserve a high place amongst 

 the heroes of science. I will enumerate some of the difficulties 

 in the way of steering a balloon against the wind by mechanical 

 propul-ion, and then proceed to give you a short description of 

 some ijf the latest experiments that have been made. 



There is an essential difference of condition between navi- 

 gating the water and navigating the air. In the former we have 

 a body moving within the limits of two media, air .and water. 

 These two media have different densities and elasticities, con- 

 sequently resistances. In air-navigation the body moves in one 

 medium only, which renders the motion of a paddle-wheel 

 entirely useless in that one medium — a paddle-wheel moving in 

 the air would effect nothing — therefore, the only available 

 means of propulsion in air-navigation is the screw : this cuts into 

 the medium. Now it stands to reason that this medium must be 

 in a state of comparative rest, or else the work of the screw will 

 be overpowered. A moderate wind is sufficient to overpower a 

 strong screw, hence the obstacle to air-navigation by mechanical 

 propulsion. Capt. Renard has recently sent in to the French 

 Academy an account of his experiments with his so-called 

 navigable balloon La France, at Meudon. His experiments 

 were decidedly interesting — in fact, they were in advance of 

 anything yet accomplished in balloon guidance, but there has, I 

 think, been a tendency to exaggerate the results obtained. I 

 think anyone who re.ads carefully the accounts of those experi- 

 ments which appeared in La Nature will see that the old 

 difficulty with the screw still remains. The experiments to 

 which I refer took place in comparatively calm weather. It is 

 said that out of seven performances the balloon returned five 

 times to the place whence it started. This is certainly more 

 than most balloons do. To accomplish this, much care and 

 ingenuity must have been exercised ; but on reading the ac- 

 counts, we find that great care w.as taken for the selection of 

 that kind of weather that would not make the work of the screw 

 nil. A whole month, in fact, had to elapse between the first 

 ascent mentioned and the second, owing to unfitness of weather. 

 On the day of the second experiment the wind blew from the 

 north-north-we>t from Paris at a velocity of from 3 to 3"5o 

 metres per second, st.arting from Meudon. The balloon was 

 directed towards Paris at 4.25 p.m. It crossed the railway-line 

 at 4.55, reached the Seine at 5 o'clock ; at 5.12 the balloon 

 entered i\i^ enceinte by Bastion 65. Then the aeronauts decided 

 to go home. The balloon was easily turned, and, .aided now 

 by the aerial current, rea:hed the exact spot whence it had 

 started. The journey going had taken 47 minutes, the journey 

 back took 1 1 minutes. Such experiments as these, to my mind, 

 deserve praise, because they were conducted in a scientific 

 manner, .and because some results were attained ; although the 

 result of navigating a balloon against a wind of consider- 

 able power certainly did not come to pass. One must, it 



seems, still be content with mere bread-crumbs of aerial 

 navigation. 



(2) As regards the second means of navigating the air, by a fit 

 selection of those varying currents that are frequently overlying 

 one another blowing in different directions over the same spot. 

 I think a closer and more methodical study of those currents 

 might lead to satisfactory results. Up to the present time but 

 little has been ascertained concerning them. Unfortunately for 

 aeronautical science its Glaishers have been few, its mountebanks 

 numerous. It is true there has always been a difficulty m the 

 way of studying the aerial currents from a balloon, namely, the 

 difficulty of keeping the balloon at a certain elevation, .\fter 

 expending ballast to make the balloon rise to a certain elev.ation 

 for the sake of reaching a particular current, seme change of 

 temperature produced by the sun or clouds will often affect the 

 delicately-balanced machine, and .alter its altitude. If it has 

 risen higher, gas must be sacrificed to reach the lower level ; if 

 it has descended, more ballast must be expended. In this way 

 g£is and ballast, which a celebrated aeronaut has called the 

 "life-blood of the balloon," is quickly exhausted. It is these 

 facts that make the successful experiment carried out by M. 

 Lhoste last Auguit so worthy of note. In his voyage across 

 the Channel he made use of an apparatus which he called a 

 "Jlotteiirfreiii." This acted as a kind of floating anchor or 

 brake. It was a cylindrical iron vessel with a conical air- 

 chamber at the top, I metre 60 centimetres in length, 22 centi- 

 metres in width, weighing 10 kilogrammes when empty, and 60 

 kilogrammes when filled with salt water. The flotteur was 

 attached to a bar underneath the balloon, on which a small sail 

 was hoisted. The important function of \h\s flotteur is, that by 

 its means the s.ame altitude of the balloon can be maintained 

 when the favourable current is once found. By means of this 

 flotteur the water itself can be drawn up into a reservoir in the 

 balloon and utilised as ballast, after sunrise, when the expansion 

 of the gas by the heat of the sun's rays would otherwise cause 

 the b.alloon to shoot upwards. By this method of adjusting the 

 altitude of the balloon, several important observations of the 

 various currents of air about which we know so little might be 

 taken, and it would, I think, be well if Governments org.anised 

 experiments with these various currents, as well as with 

 elaborate screws worked with power inadequate for the purpose 

 of propelling a balloon against a powerful wind. Perhaps the 

 atirial machine of the future may be directed by utilising in a 

 thoroughly scientific manner these varying currents. In such a 

 system of aerial locomotion perhaps the screw may be used as a 

 kind of makeshift in a dead calm, when a change of level is not 

 desirable, like the oars when there is no wind to fill the sails. 



One of the most practical uses of b.alloons in war is for sig- 

 nalling. The utility of balloon-signalling consists in the eleva- 

 tion obtainable. Any accepted method of signalling may be 

 used in the car of .an ordinary captive balloon, e.g. flag-signalling 

 or lantern-signalling. But signalling from the car of a balloon 

 necessitates the use of a balloon of considerable size to secure 

 the required lifting-power. This limits the practicability of such 

 a method. About a year and a half ago it occurred to me to so 

 apply electricity to a cap'ive balloon that a method of flashing 

 signals from-a balloon is practicable while the operator remains on 

 the ground. Thus the weight of the operator is obviated, and 

 consequently the balloon can be of such a size as to be extremely 

 portable. It is my wish to thoroughly explain to you this 

 method. In the interior of a balloon which is made of a 

 material that is perfectly tr.anslucent and filled with hydrogen or 

 coal-gas are placed several incandescent electric lamps. The 

 lamps are in metallic circuit with a source of electricity on the 

 ground. In the circuit on the ground is an apparatus for m.iking 

 and breaking contact rapidly. By varying the duration of the 

 flashes of light in the balloon, it is possible to signal according 

 to the Morse or any other code. To thus place a source of light 

 in the midst of the gas inside a balloon would not have been 

 possible until the development of the electric light. Many per- 

 sons even now seem to think the proceeding of showing a light 

 inside a balloon a dangerous one. Therefore, before I describe 

 my invention in detail, I will show you a few experiments, after 

 which I think you will realise that the placing of the incan- 

 descent lamp in'-ide a balloon is not attended with danger. 

 [Experiment shown.] If I take a jar of hydrogen in my h.inds, 

 and insert a taper at the mouth, the gas catches fire, but the 

 taper goes out when I thrust it upwards in the jar. Vou see, 

 hydrogen gas takes fire under certain conditions, but is incapable 

 of itself of supporting combustion. The flame you have seen 



