6am 



NATURE 



[July 15, 1920 



of another element which exists in the form of two 

 isotopes differing much less in their atomic weights 

 than those of chlorine. Furthermore, if we put 

 A=f{t), and if f{t) can be expanded in the analytical 

 series, 



/(o) + /./'(o) + J'^/"(o) + ,etc, 



and /'(o) is zero as Nernst assumes, then it must be 

 explained how the series 



/(o) + ^/"(o) + ,etc., 



can become almost equal to f.Rloge4 between wide 

 limits of temperature. , • , 



In fact, if the isotopes are inseparable by chemical 

 means, I think that the most natural conclusion to 

 draw is that the difference in the entropies of the 

 reactants and resultants of a chemical change taking 

 place at zero temperature is a finite quantity which 

 depends on the type of the change, and also, of 

 course, on the num'ber of molecules transformed. 



Jesus College, Oxford. D. L. Chapman. 



Anti-Gas Fans. 



Owing to my absence from home I did not see 

 Prof. Allmand's letter in Nature of June lo on my 

 indictment of the War Office until too late to reply 

 to it last week, but I hope you will now allow me to 

 put before your readers a few of the points he has 

 missed. 



First, may I reoeat that I had no personal interest 

 in the number of 'fans sent out, since I neither asked 

 for nor would accept payment or reward of any kind or 

 description for their use during the war. I attributed 

 the suffering and loss of life, which I deplore and 

 Prof. AUmand denies, even more to the lack of 

 training, and consequent ignorance of what the fans 

 could do, than to their scarcity. 



From this letter I gather that his own knowledge 

 concerning them is of the slightest. He seems never 

 to have heard of the clearing of trenches with them, 

 the purpose to which they were principally put; but 

 he allows that they were "found useful " for clearing 

 shelters and dug-outs that would otherwise have 

 remained dangerous for "hours, or even days," after 

 a gas attack. We have only to picture our men, 

 after hours of hard fighting, perhaps wounded or 

 already gassed, compelled to remain in the open, 

 whatever the weather, with the remains of gas still 

 there, to realise the vital importance of clearing every 

 space, dug-out, and shelter the moment it was 

 possible. Yet for a whole year (May, 1915, to May, 

 1916) the use of the fans with which it could always 

 have been done in a few minutes was held up by the 

 wilful obstruction of War Office officials. It must be 

 remembered, too, that at the beginning of that year 

 the respirators were still quite crude and untrust- 

 worthy, and that even by the end of it they were very 

 far from perfect. Is it too much to say, then, that 

 "much suffering and loss of life could have been 

 avoided " had the fans been accepted, and the troops 

 properly trained to use them, nine months earlier, as 

 they could so well have been? On this point Prof. 

 Allmand is silent. 



He says that, later, fires were found to be as 

 efficacious as, and less fatiguing than, fans. They 

 were not as efficacious, but they were certainly less 

 fatiguing, as I have said, when the materials were 

 ready to hand ; and it was perfectly right to use them 

 when practicable. But each time a space was cleared 

 by firej fresh dry wood and paper were required. Now 

 it is common knowledge that there were wide areas 

 which, over long periods, were so wet that dry wood 

 for even one clearing would have been hard to find, 

 NO. 2646, VOL. 105] 



let alone many. Is it an exaggeration to say that 

 "much suffering and loss of life could have been 

 avoided " if those responsible had remembered this, 

 and had provided not only plenty of fans for every 

 area, but also men trained to use them? On this 

 point also Prof. Allmand is silenr. 



"Working an Ayrton fan, even in the most approved 

 fashion " — my italics^he says, " . . • is a tiring task." 

 Prof. Allmand will, I am sure, be surprised to learn 

 that there are at least three approved fashions, and 

 that the efficiency of the fans depends almost more on 

 the ability of the officer in charge to cTioose the right 

 method for the particular space, and to place and 

 move his men properly, than on the skill of the 

 wielders ; moreover, the approved methods are not 

 less fatiguing than the wrong ones, only infinitely 

 more efficient. This ignorance on the part of an 

 authority on anti-gas methods is not unique; it is 

 typical. Let me show how it arises. 



As soon as the fans were accepted I warned the 

 War Office that, if they were to be of any value, 

 officers and men alike must have two or three days' 

 practical training in their use; and, at the request of 

 the Commander-in-Chief, my assistant went to France 

 to show how the training should be carried out. At 

 first, after he left, it may have been fairly well done ; 

 but ia time those who had seen for themselves what 

 the fans could do died or became scattered ; and after 

 that the training degenerated at best into an hour or 

 two of exercise in the stroke for trench-clearing, and 

 at worst into the mere e::ihibition and naming of a 

 fan, while numbers of men never even saw one at all. 

 Major Gillespie, D.S.O., who practically saved his 

 battery by means of the fans, when a howitzer battery 

 within a hundred yards of it was wiped out, wrote to 

 the Times of May 4: "Even after the introduction 

 of the fans in limited quantities, I never met an 

 officer or man who had been properly instructed in 

 their use." This ignorance, for which the War Office 

 is responsible, extended from the highest to the lowest 

 officials in the Anti-Gas Service. The only men who 

 did not share it were those officers who were clever 

 enough and interested enough to make out for them- 

 selves what could be done with the fans. Small 

 wonder, then, that most officers regarded them simply 

 as nuisances, and that some of the men treated them 

 as fuel. 



This same ignorance and want of imagination led 

 to the idea that the fans were useless for dealing with 

 mustard gas. In describing the saving of his battery 

 Major Gillespie wrote: "The gas hung about for 

 days afterwards, but by judicious flapping at frequent 

 intervals we kept our quarters fairly free from it." 

 This is the evidence of a "fighting soldier." It is 

 odd that those other fighting soldiers quoted by Prof. 

 Allmand should not have thought of this very simple 

 way of ridding themselves of a vapour that came off 

 slowly and took some time to reach a dangerous 

 concentration. 



Finally, is not Prof. Allmand in his last sentence 

 confusing scientific methods with the methods of 

 some scientific men? In directing attention to the 

 dire effects of the unscientific methods of the War 

 Office in connection with anti-gas fans, I was adding 

 my quota to the efforts of those who are trying to 

 "ensure the application of scientific methods to mili- 

 tary problems." The fact that it was scientific men 

 who were responsible for those unscientific methods 

 is surely no reason for condoning them, but rather for 

 censuring them the more severely. 



Hertha Ayrton. 



41 Norfolk Square, W.2, June 22. 



At the risk of the accusation of shirking inquiry, 

 I repeat that I have no intention of entering into a 



