March 



[918] 



NATURE 



General Sir William Robertson, who, in the course of 

 an address, pointed out the debt which the Army owes 

 to medical science and skilful nursing. In past cam- 

 paigns the mortality from sickness and epidemic 

 disease was great, and was accepted as more or less 

 'inn-prcventable ; but in the present war, with millions 

 men engaged in many different theatres of opera- 

 ns, some of them notoriously unhealthy, there has 

 not been a singk> epidemic of any kind. The achieve- 

 j ments of the Medical Service in this war constitute 

 a bright spot on a picture which in many respects can 

 regarded only with sorrow and sadness. 



A VERY important memorandum is issued bv the 

 Board of Agriculture and Fisheries as the s'edond 

 interim report pf the Fresh-water Fish Committee. 

 It deals with the economic value of the British eel 

 fisheries, and deserves the widest publicity during the 

 coming months. There are enormous runs of elvers 

 in Great Britain and Ireland, so much so that many 

 millions of these fish were formerly exported alive to 

 Germany, for cultivation, from one catching dep6t on 

 the Severn. This depot is now closed, and the Committee 

 suggests that it should be taken over. The eel is the 

 only popular fresh-water fish in these islands which is 

 at the same time potentially highly abundant. The 

 Committee is preparing schemes for intensive cultiva- 

 tion, now and after the war, and suggests the prob- 

 ability of a larg*> export trade in the future. All 

 persons interested in schemes of immediate eel culture 

 should procure this report and advice from the Board 

 of Agriculture and Fisheries (43 Parliament Street, 

 London, S.VV.i) or from the Fresh-water Fish Com- 

 mittee. The address of the secretary of the latter is 

 the Hon. A. S. Northcote, 54A Parliament Street, Lon- 

 don, S.W.I. 



Many of the accepted ideas regarding the electric arc 

 in to be undergoing some revision. At the meeting 



I he Illuminating Engineering Society held on Febru- 

 ary 26 Lt.-Com. Haydn T. Harrison mentioned several 

 interesting respects in which some of the latest high- 

 candle-power arc searchlights differ from the older 

 and simpler types. In the new lamps the intrinsic bril- 

 liancy attained is as much as 250,000-300,000 c.p. per 

 square inch, as compared with 80,000-90,000, which 

 was formerly considered the limit likely to be attained. 

 It was pointed out by Mr. A. P. Trotter so long ago 

 - 1892 that the candle-power in any direction from a 

 arc crater can be determined with fair accuracy 



>ni Lambert's lav^-, and that the polar curve of light 

 distribution (neglecting the shadow cast by the nega- 

 tive carbon) is approximately a circle. This law is so 

 'infinite that if photometric measurements, when 

 plotted, yield a different curve it is proof that the 

 -^<iurce of light is not a plane surface, but convex. 

 In the high-candle-power searchlight lamp developed 

 <iuring the last few years this phenomenon occurs 

 despite the fact that there is a very deep crater. It 

 therefore appears that the gaseous contents of the 

 crater actually boil over, and thus change the plane 

 surface into a convex-shaped source of light. 



Dr. Hugo de Vries, professor of botany in the 



liversity of Amsterdam, has just completed his 



intieth year. His long connection with the Uni- 



i >ity has been marked by patient and successful in- 



Mstij^ations on "sporting" among plants, especially 



in Oenothera Lamarckiana, a plant which had become 



naturalised in Holland. His work with OEnothera 



began in i8<)5, and an article upon it appeared in 



Nature of November 26, 1908 (vol. Ixxix., p. loi), 



when the Hortus Botanicus at Amsterdam was the 



subject of a contribution to our series of " Scientific 



Contres." Out of the work and the experiments that 



NO. 2523, VOL. lOl] 



had led up to it the 'mutation theory" of evolution 

 originated and developed. Prof, de Vries gave an 

 account of this theory and of his researches in the 

 Masters memorial lectures, which he delivered Ix'fore 

 the Royal Horticultural Society in 1909 (he was the 

 first Masters memorial lecturer), and his great book, 

 "Die Mutationstheorie," has been ably translated into 

 English by Prof. J. B. Farmer and .V'. D. Darbishire. 

 The fundamental idea of unit characters upon which 

 the whole argument rests has been at the back of 

 almost all recent research into heredity in plants, and 

 the development of Mendel's work, which had been 

 so long overlooked, was prepared for, and aided not a 

 little by, the researches de Vries made with CEnothera 

 and other plants. This work has had a profound effect 

 upon our outlook towards, and knowledge of, the origin 

 and development of horticultural varieties of pUints. 

 In order to mark its apprecijitipn of the great value 

 of this work the council of the Royal Horticultural 

 Society has conferred upon Prof, de Vries one of the 

 Veitch memorial medals — a gold medal awarded only 

 to those whose researches have had, or are likely to 

 have, great influence in the advancement of horticul- 

 ture. 



An article in La Nature for February 16, under the 

 title " Eflicacite des Bombardements Terrestres et 

 .\6riens," is worthy of note. The writer remarks that 

 the frequency of air raids has caused no little specula- 

 tion as to the probability of f>ersonaI danger during 

 such raids. He proceeds -to state the manner in which 

 the laws of probabilitA- can be applied to estimate the 

 chance of a shell falling at any particular spot near 

 the target when the mean errors in range and direction 

 are known. Turning to the question of bombardment 

 from the air, figures are quoted from the Aeroplane 

 giving the chances of a person receiving injury, and 

 calculated on the assumption that a certain definite 

 area surrounding the point of impact of a bomb is 

 dangerous, and that bombs are equally likely to fall 

 I at any place in I^ndon. The results of these calcula- 

 tions were given in the Aeroplane as a table, which 

 La Xature reproduces. The chance of danger is given 

 as one in 150,000 in open spaces for each bomb 

 dropped, while in a well-built house the chance is of 

 the order of one in 50,000,000. These figures were 

 based on the casualties during raids over London. 

 One obvious weakness of the argument is that the 

 bombs are not equally likely to fall anywhere, .so that 

 the danger is proportionatelv greater to those living 

 near well-defined targets. The writer in La Nature, 

 in applying these figures to Paris, expresses the opinion 

 that the chances of injury are greater in that city than 

 in Ivondon. He considers that the protection due to 

 buildings has been ov^er-estimated in the Aeroplane, 

 especially if the buildings are not Avell constructed. 

 The density of buildings is greater in Paris, and the 

 houses are usually higher and more densely peopled. 

 Making allowance for these facts, the French writer 

 considers that the dangers in Paris are about twice 

 as great as in London during an aerial bombardment. 



Some remarks made in the House of Commons on 

 February 21 by Sir Watson Cheyne, dealing with the 

 question of "The Medical .Aspect of Flying," or, as it 

 would be -more correctly described, "The Physiology 

 of the Airman," have attracted wide attention. While 

 all men of science would doubtless support the in- 

 stitution of a special service to devote attention to the 

 troubles which happen to the airman on account of his 

 ascent to high altitudes, it cannot be too strongly 

 pointed out that the problem is essentially one for the 

 physiologist. Naturally, the airman is liable to the 

 numerous other ailments that beset us all, so that the 

 air medical service requires the inclusion of men with 



