292 



NATURE 



[June 12, 19 19 



that in future the designation "Mount Wilson Ob- 

 servatory" will be emplo3'ed, as it is in Prof. Hale's 

 report for 19 18. 



Sun-spots as Electric Vortices. — Adopting the 

 hypothesis that sun-spots are vortices in which elec- 

 trified particles produced by ionisation in the solar 

 atmosphere are whirled at high velocity and thereby 

 give rise to magnetic fields, Prof. Hale has built up 

 a research in which he determines the polarity of the 

 field or direction of rotation of the vortex by observa- 

 tion of the Zeeman effect in the spectrum of the spot. 

 In the early stages of this research, before the mini- 

 mum of 1912, it was found that in the case of groups 

 which consist mainly of two large spots these com- 

 ponents were of opposite polarity, and that, in general, 

 the polarities of the leading spots, and consequently 

 of the following spots, were of opposite sign in 

 the northern and southern hemispheres of the sun. 

 After the minimum the surprising fact emerged that 

 the polarities were reversed in both hemispheres — 

 that is to say, the preceding spots of northern bi-polar 

 groups which before the minimum were of the same 

 polarity as the north magnetic pole of the earth were 

 of the opposite polarity after the minimum. This 

 state of things endured, and the interesting question 

 arose whether a similar reversal would occur at or 

 near the sun-spot maximurn, but in Prof. Hale's report 

 for 19 18 it is stated that no general change of polarity 

 has been observed since the maximum, which occurred 

 in the latter half of 1917. 



SCIENCE AND WAR. ■ 



ON Thursday, June 5, in the Senate House of the 

 University of Cambridge, before a distinguished 

 audience. Lord Moulton delivered the Rede lecture on 

 science and war. After pointing out generally how 

 the advances in scientific knowledge had revolutionised 

 the methods of warfare since the last great European 

 conflict in 1870-71, the lecturer dealt specifically with 

 some of the more conspicuous examples of what had 

 been achieved during the present war through the 

 application of science to military problems. Beginning 

 with explosives, he recalled the discovery some seventy 

 years ago of guncotton and nitroglycerine, and showed 

 how it led to the production of the smokeless powders 

 that have revolutionised tactics both by land and sea. 

 At first it was found impossible to use guncotton and 

 nitroglycerine for anything but blasting or like 

 destructive purposes until the discovery was made 

 that, by the aid of certain volatile solvents, the two 

 substances could be incorporated so as to produce a 

 material resembling gelatine, which could be formed 

 into pieces of any shape or size. While these gela- 

 tinised powders burn with extreme rapidity, they 

 are poor conductors of heat. Thus when the charge 

 is fired all the pieces begin to burn on the surface, 

 and the combustion spreads itself through each piece 

 of the material more rapidly than the high tempera- 

 ture can pass inwards by conduction of heat. Hence 

 the pieces always burn from the outside, and by 

 making the amount of the surface large or small com- 

 pared with the bulk the rate of burning of the powder 

 can be controlled. , 



Besides providing a perfect propellant, science had 

 also given the high explosives needed for shells. These 

 are distinguished by the high .rate of rise of the pres- 

 sure which they produce on explosion. The_ rate at 

 which the pressure comes on in a 6-in. gun is about 

 10,000 tons per square inch per second, so that it 

 rises to the full pressure of 15 to 20 tons in some- 

 thing under the five-hundredth part of a second. In 

 a good high explosive the rate of rise per second \vas 

 several millions of tons per square inch, and the period 



NO. 2589, VOL. 103] 



was a fraction of a thousandth part of a second. Hence 

 the shattering effect of these high explosives. High 

 explosives show the remarkable peculiarity that there 

 are two distinct ways in which they can explode. 

 One gives rise to a comparatively mild explosion 

 which opens out the shell, but does little more; the 

 other IS a fierce detonation by which the shell is rent 

 to pieces. The cause of this is not understood but 

 It IS undoubtedly connected with the intensity of the 

 initial disturbance \*hich sets the explosive off. Bv 

 the commencement of the present war we had learnt 

 how to detonate with fair, but not absolute, certaintv 

 the high explosives then used in the Service. But 

 the prospect of the supply of toluene failing to equal 

 the enormous demands of our shells necessitated a 

 change of high explosive, and the one that was taken 

 required special study before detonation could be en- 

 sured. It was achieved through the unremitting 

 labours of those scientific workers who, little known 

 to the public, have had to face and solve the in- 

 numerable problems that have presented themselves 

 during the war. Through their labours we arrived 

 at a degree of excellence which reduced the propor- 

 tion of shells which failed to detonate from all causes 

 to so small a figure that it was, the lecturer believed, 

 little more than one-fifth of that of our adversaries. 



Lord Moulton then referred to the changes in artil- 

 lery which the new explosives had brought about, men- 

 tioning our howitzers, which, at ranges such as eight 

 to^ fifteen miles, could be relied on to fire shot after shot 

 with a variation of a few yards only, and also making 

 some interesting statements with regard to the long- 

 range gun which the Germans used to bombard Paris. 

 Amongst other things, he pointed out that the dis- 

 tance passed over by the projectile was so great that 

 if the Germans had taken the trouble to aim at anv 

 particular building they must have allowed nearl'v 

 half a mile for the fact that during the flight the 

 rotation of the earth would to that extent carrv the 

 target further towards the east than it would carrv 

 the gun. 



The most hateful chapter of the work of science in 

 the war was the introduction of chemical warfare. 

 The first gas attack was on April 22, 1915, and it was 

 not until the following September that we were able 

 in any way to retaliate. "But our immediate reply 

 was one that did honour to science. Due to the 

 splendid work of the late Col. Harrison, a system of 

 defence by gas-masks was established, in which we 

 were for the greater part of the war far ahead of our 

 adversaries, who succeeded in coming up to us only 

 by learning and copying our methods. 



Finally, the lecturer paid an eloquent tribute to the 

 assistance rendered by science in the war in dealing 

 with disease and wounds, with particular reference to 

 the success which had attended the use of anti-tetanus 

 serum, to the reduction of the rate of mortality in 

 spotted fever to one-tenth of its former value, and to- 

 the complete elucidation of the mode of transmission 

 of bilharziasis, a disease with which we were faced 

 through the presence of large contingents of our troops 

 in Lower Egypt. Lord Moulton 's conclusion was that 

 one overmastering lesson was to be derived from the 

 contemplation of all that science had done in the war. 

 She had made mankind too formidable a being to be 

 permitted to have recourse to it. The uncontrolled 

 indulgence on the part either of a nation or of an 

 individual in the exercise of the power that science 

 had placed within reach was too directly fatal to 

 civilisation itself. It was easy to criticise the League 

 of Nations and to point out the diflRculties, and even 

 impossibilities, with which it was faced, but we should 

 never forget that some combined action of that type 

 was an imperative necessity. 



