454 



NATURE 



[June io, 1920 



fan to remove gas from shelters could really be 

 effectual only after first dealing with the area round 

 the shelter. That is one reason for the relative decline 

 in the fortunes of the Ayr ton fan. I say relative, as 

 large numbers of such fans were issued oven during 

 the winter of 1917-18, and, for all I can remember, 

 still later. Other reasons were the natural and rooted 

 objections of the regimental officer and soldier respec- 

 tively to be responsible for, or to load himself with, 

 stores of (to him) problematical value, and the growing 

 favour shown to the alternative fire method. (It was 

 said, perhaps not without malice, that Ayrton fans 

 were often used for clearing shelters from gas — bv 

 fire!) 



However that may be, there was no demand "by 

 troops for the fans towards the end of the war ; on the 

 contrary, we were besought to withdraw them. I 

 know this myself from many personal interviews with 

 regimental officers and from reports furnished by Gas 

 personnel of every type of unit and formation. There 

 were, of course, up to the end of the war gas casual- 

 ties caused by men sleeping in shelters which might 

 have been successfully cleared of gas either by the 

 fan or by fire. Thev were, however, owing to the 

 particular properties of "mustard gas," a small pro- 

 portion of the whole ; and fatigue and ignorance and 

 the exigencies of the battle were their causes. 



I must, therefore, characterise as quite unfounded 

 the view that much suffering and loss of life could 

 have been avoided by increasing the provision of Mrs. 

 Ayrton 's fan. Regimental and Gas Services personnel 

 were both far too anxious to reduce gas casualties 

 in every way practicable. It was ultimately the 

 fighting soldier who decided, after weighing all the 

 facts of the situation, that the fan, useful in sound 

 and well-established trenches, was scarcely "worth 

 while " during the advances and retirements of 

 1917-18 or in the mud and pill-boxes of the Ypres 

 salient — this apart from the question of " mustard 

 gas." Mrs. Avrton is verv obviouslv sincere, but, like 

 another distinguished civilian who has recently written 

 on camouflae"e. is not quite an fait with the realities 

 of the battlefield. Exaggerated attacks of this nature 

 on the War Office are liable to defeat their own ends, 

 and also to neutralise the efforts of others who are 

 trying to ensure the application of scientific methods 

 to militarv problems in a more systematic manner 

 than has been the case in the past. 



A. J. Allmand. 

 (Late Chemical Adviser to Fourth and to 

 Second Army Headquarters.) 



King's College, W.C.2, June 7. 



Attainment of High Levels in the Atmosphere. 



I MUST confess that I am very scepticiil as to a 

 sounding balloon having reached 37,000 metres or a 

 pilot balloon 39,000 metres, as mentioned in Nature 

 for June 3, p. 437, although such heights would be 

 possible if sufficiently large balloons were employed. 



A sounding balloon as commonly used is a small 

 india-rubber balloon expanded by hydrogen to 

 about twice its natural diameter, and then 

 securely tied up. The rubber stretches as the 

 balloon ascends, until finally it can stretch no further 

 and the balloon bursts. Under the supposition that 

 the pressure and temperature of the gas inside are 

 the same as those of the air outside, and under 

 average conditions of temperature for Europe, the 

 following rules hold : The starting diameter is 

 doubled at a little more than 16 km., trebled at a little 

 more than 24 km., and quadrupled at 30 km. Since 

 the starting diameter is about double the natural 

 diameter, this means that at 30 km. the rubber has 



NO. 2641, VOL. 105] 



stretched eightfold linearly and its thickness been 

 reduced sixty-fourfold. I do not think any rubber that 

 will stand this treatment can be found. 



On the other hand, a precise calculation of a great 

 height is in practice impossible. We can only measure 

 the pressure, and when the air pressure is greatlv 

 reduced a very small error in the pressure makes ;i 

 large error in the height. 



For a pilot balloon, if the balloon is near the zenith 

 and the base line for the theodolites a long one, there 

 is not so much risk of error ; but if, as is usuallv 

 the case, the balloon has drifted a long wav, 

 particularly if it has drifted in the direction towards 

 which the base line points, then a small error in the 

 setting of the theodolites or in reading the angles will 

 make a f»reat error in the height. 



It is desirable that when/thie recorded height has 

 reached an abnormal value the computer should give 

 full details and state his reasons for believing it to be 

 Gfenuine, otherwise one is apt to think some mistake 

 has crept in. W^. H. Dines. 



Benson, Wallingford, Berks, June 4. 



Central Wireless Station for Astronomy. 



In the "Astronomical Column" of Nature of 

 May 2y it is stated that " Prof. Kobold, editor of 

 Astr. Nachrichten, and director of the Central- 

 stelle, delegated the latter work to Prof. Stromgren, 

 Copenhagen, during the war, but has now resumed 

 it, and announces in Astr. Nach., 5044, that 

 arrangements have been made for the distribution of 

 astronomical information by wireless telegraphy from 

 the Nauen station." 



It will be remembered that, in pursuance of resolu- 

 tions adopted by the International Scientific Academies 

 at London and Paris in 1918, there was established 

 at an international conference held at Brussels in 

 July, 1919, among other Commissions, a Commission 

 of Astronomical Telegrams, with a central bureau 

 at the Royal Observatory of Belgium (Uccle), to re- 

 place Kiel, for the purpose of receiving, centralising, 

 and dispatching information concerning astronomical 

 discoveries, observations, and calculations, either by 

 telegram or post, to the various institutions or private 

 persons subscribing to it. 



Surely with such an organisation in full working 

 order this Commission should undertake the dispatcli 

 bv wireless of ;istronomical information of great 

 urgency, such as the appearance of a new star, etc., 

 if such information is going to be distributed by wire- 

 less at all ! 



Practically every observatory in Western Europe now 

 takes in the time and weather signals from the Eiffel 

 Tower, and any news of an astronomical nature could 

 be easily transmitted to that station from the central 

 bureau at Uccle (or Brussels) and re-transmitted from 

 the Eiffel Tower at, say, lo.ooh. and i6.ooh., the 

 standard times of transmission of the time and weather 

 signals. 



Before the war the Central Bureau of Astronomical 

 Telegrams was located at Kiel, but this organi.sation 

 has ceased to exist from an international point of 

 view. There seems no object, therefore, in reviving 

 it at Nauen (near Berlin) purelv for the sake of this 

 wireless astronomical information, when this mode 

 of disnatch can be as easily adopted in Western Europe 

 for this purpose. 



Prof. Kobold seems not only to ignore the existence 

 of the new International Central Bureau in Belgium, 

 but also assumes that the war has made "no differ- 

 ence." William J. S. Lockver. 



Hill Observatorv. Sidmouth, S. Devon, 

 Mav 28. 



