262 



NA TURE 



\_ycw. 13, 1887 



preparatory to the ascent for purposes of signalling. The army •■ in the skies would have told the tale of the events below— a tale 

 on the other side of the mountains has already sent up a that would have been eagerly read— and perhaps that bravt 

 similar balloon. The next scene shows a nearer balloon | general would then have left Khartoum, a conqueror, and with 

 ascended to a certain height. Now the two balloons are about i his life spared for the future service of his country, 

 to communicate. You see the flashes of light from the balloon. ! 

 Although this invention is not two years old, it has already a , 



7l 



short history. It was exhibited in model in the War Depart 

 ment of the Inventions E.xhibition, and while on exhibition 

 there the method \ias referred for Government trial under a 

 Committee of the Royal Engineers at Chatham. During the 

 time the model was being exhibited at South Kensington, some 

 experiments were tried with a balloon of 4000 cubic feet capacity 

 at the Albert Palace. In this balloon were placed six lamps 

 worked to 16 or 20 candle-power. The six lamps took a cur- 

 rent of some 9 amperes, and the electromotive force was 24 

 volts. The source of electric power then used was 25 cells of 

 the Electrical Power Storage Company. 

 During this Exhibition the value of the 

 method for long-distance signalling was well 

 tested, the flashes of light from the balloon 

 being observed as far as Uxbridge, a distance 

 of sixteen miles. This was effected by less 

 than 100 candle-power. I used the same 

 apparatus for the Government trial at Chat- 

 ham, after which trial I received an order 

 from the War Office to supply some of my 

 apparatus to the Royal Engineers. The 

 system was again tried at Aldershot under 

 the Signalling Department. On the day 

 fixed for the trial there was a snowstorm and 

 a fog, two very unfavourable conditions in 

 a system of signalling, but signals were read 

 and answered from my balloon, in >pite of 

 snow and fog, by the signallers stationed 

 some few miles off. As I mentioned the 

 other day at a meeting of the Aeron.auticaI 

 Society, I wish, as the inventor of this system, 

 to see it tried to its utmost capacity, and I 

 puqrose to put the system myself shortly to 

 the most rigorous of tests. One of those 

 tests will be, I hope, to signal over the 

 Channel, i.e. to send up the balloon on some 

 site on the English coast, probably Dover, 

 and observe whether the balloon can be seen 

 on the French coast. The Channel is by no 

 means the most favourable expanse for sig- 

 nalling, for there are frequent fogs in it to 

 obscure the view. The Channel, however, 

 is a time-honoured and popular measure of 

 distance, and I must repeat here the wish 

 1 expressed lately at the meeting of the 

 Aeronautical Society, that, if the flashes of 

 light can be observed over that expanse, I 

 hope the public will look upon the accom- 

 plishment, not as a sensational feat, but as 

 showing the practical value of balloon-sig- 

 nalling. Up till lately I have only considered 

 my system as being useful to the army. I 

 think, however, it would be also useful to 

 the navy. I have schemed a method of 

 employing these balloons on board ship. 

 Their greatest use in the navy would be, I 

 think, for coast-signalling — signalling round 

 corners ; I have been asked to submit this 

 scheme to the Admiralty, and am preparing 

 to do so. The picture now before you repre- 

 sents its use in the navy on board a ship 

 stationed in a bay, which vessel wishes to 

 communicate with another at the other side of the cliffs which 

 form the bay. It is, as you see, night-time. The ship that is 

 not visible to you sends up the balloon, and now the two balloons 

 commence signalling to each other. [Experiment shown.] 



You may perhaps be inclined to think that I ought to mention 

 some one particular occasion in history when this balloon would 

 have been useful. I do not think we need look far back to find 

 one example. But a short while ago there was a brave general 

 shut up in a besieged city with a few followers. Near at hand 

 there were friends ready to help, but ignorant of the immediate 

 necessity of that help. Need I name that general and that city ? 

 Now, if from Khartoum there could have arisen such an electric 

 signalling-balloon as I have described to-day, its flashes of light 



SOCIETIES AND ACADEMIES 



London 



Royal Society, January 6. — "Preliminary Note on the 

 Continuity of the Liquid and Gaseous States of Matter." By 

 William Ramsay, Ph.D., and Sydney Young, D.Sc. 



For several years past we have been engaged in an examina- 

 tion of the behaviour of liquids and gases through wide ranges of 

 temperature and pressure. The results of our experiments with 

 ethyl alcohol have recently been published in the Pliilosophicai 





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Transactions ; those with acetic acid in the Transactions of the 

 Chemical Society ; and the Royal Society have in their hands a 

 similar investigation on ether. We have also finished a study of 

 the thermal properties of methyl alcohol. 



In consequence of a recent publication by Wroblewski, of 

 which we have seen only the abstract [Baichte, 18S6, p. 728, 

 abstracts), we deem it advisable to communicate a short .notice 

 of an examination in which we are at present engaged. 



We find that with the above-mentioned substances, acetic acid 

 excepted, whether they are in the liquid or gaseous state, pro- 

 vided volume be kept constant, a simple relation holds between 

 pressure and temperature. It is/ = bT - a. This is evidently 

 a simple modification of Boyle's and Gay-Lussac's laws ; for at 



