ii8 



NATURE 



[March 24, 192 1 



very clearly shown. The price of the instrument, 

 with the necessary charts and plant, is 55I. 



The Meteorological Magazine for January contains 

 a communication from Sir Napier Shaw concerning 

 the possibility of dissipating fog by artificial heating, 

 the subject having been suggested to him by an 

 inquirer who alleged that he "had seen fog disperse 

 over a football ground as the game proceeded." Sir 

 Napier Shaw is clearly very dubious of the possibility 

 of dissipating fog artificially, especially as in a fog the 

 air is in motion and not absolutely still, as is generally 

 supposed. A preliminary survey of the rainfall of 

 1920 is given ; it is said to be divided into two well- 

 marked periods, the first seven months being generally 

 wet and the five later months generally dry. The total 

 for the year was above the average in the west, but 

 there was a deficiency along the east coast of Great 

 Britain. The greatest excess was in Wales, where 

 in places the total was 30 per cent, above the average. 

 For the British Isles as a whole the rainfall in 1920 

 is estimated as 109 per cent, of the average. The 

 Thames Valley rainfall map for December shows the 

 greatest rainfall during that month to have occurred 

 in the southern areas, in parts of Hampshire and 

 Sussex, where it exceeded 4 in., whilst in the north, 

 around Cambridge, the rainfall was 1-5 in. or less. 



A PAPER by Prof. Gabriel Petit published in La 

 Nature of October 16, 1920, gives an interesting 

 account of the effect of radio-activity on the fertility 

 of the soil. From the results of experiments on 

 geraniums, chrysanthemums, etc., the author con- 

 cludes that there is no doubt that radio-active sub- 

 stances exert a very favourable influence on the 

 growth of plants. The experiments show that the 

 treatment is harmful if the radio-active substance is 

 present in too great quantity. Researches are there- 

 fore being continued in different parts of the country 

 to decide on the optimum dose and on the best method 

 of application ; to discover which of the three kinds 

 of rays — the a, y8, or 7 — are the most valuable, and 

 whether the rays act on the plant directly or in- 

 directly via the soil or via the micro-organisms in the 

 soil ; and, finally, to decide whether radio-activity has 

 any influence on nitrogen fixation. It is clear that 

 there is an almost unlimited field for experiments, 

 and, in the author's opinion, there will undoubtedly be 

 a great gain for agriculture from the scientific applica- 

 tion of radio-active substances. 



At the meeting of the Illuminating Engineering 

 Society on March 17 Major" K. Garrard read a paper 

 entitled " Motor-car Headlights : Ideal Requirements 

 and Practical Solutions." It was pointed out that 

 the problem involves a compromise between two 

 almost irreconcilable points of view, that of the driver 

 of a car who requires a powerful beam impinging on 

 distant persons and vehicles and that of approaching 

 persons or drivers of other vehicles who are apt to 

 be dazzled by the intense light of such a beam. On 

 the whole, the best practical solution appears to lie 

 in keeping all light below the eye-level, at the same 

 time giving maximum intensity just below the boun- 

 dary. Several headlights in which an attempt was 

 made to realise this condition were shown at the 



NO. 2682, VOL. 107] 



meeting. The lecturer suggested that the ideal beam 

 should consist of (i) a bright, penetrating part, very 

 shallow and relatively wide, projected along the road 

 surface below eye-level ; (2) a much wider beam, not 

 so bright, illuminating hedges, etc., also all below 

 eye-level ; and (3) a generally diffused beam of very 

 low intensity close to the car. He contended that 

 these requirements cannot be met by any simple 

 device or attachment to the ordinary parabolic head- 

 lamp, but only by some form of optical projecting 

 apparatus employing at least one lens, which should 

 not be materially more complex or expensive than the 

 headlight of the present day. 



The Bulletin de la Societe d' encouragement pour 

 rindustrie nationale for January contains the complete 

 text of the public lecture given by Lt.-Col. Renard in 

 February, 1920, on "The Evolution of Aeronautics 

 during the War." Col. Renard points out that while 

 in the war of 1870-71 the ordinary balloon played an 

 important part, in the recent war its utility was in- 

 significant. On the other hand, the captive balloon, 

 which had been scrapped as out of date by the French 

 military authorities in 191 1, was used by the Germans 

 from the very beginning of the war as a means of 

 observation. Before the end of the war captive bal- 

 loons of 800 to 1000 cubic metres capacity were in 

 constant use. In the same way the development of 

 the dirigible had only reached the stage represented 

 by a volume of 8000 cubic metres in France in 19 14, 

 while in Germany Zeppelins of three times that volume 

 had been constructed. The aeroplane had, on the 

 contrary, been developed in France with enthusiasm, 

 and speeds of 120 km. per hour attained. During the 

 war this speed was doubled. Col. Renard urges on 

 his country the importance of developing civil aviation 

 as the best preparation for the next war, which he 

 believes will open by the aerial bombardment of all 

 the principal cities of one of the belligerents. 



The March issue of the Philosophical Magazine 

 contains an article by Sir J. J. Thomson on the struc- 

 ture of the molecule and chemical combination, which 

 collects together and amplifies the statements the 

 author has made in his Royal Institution lectures 

 during the past few years. He points out that the 

 nuclear atom with revolving electrons is unstable, and 

 replaces it by a positive nucleus with electrons in 

 equilibrium around it, the equilibrium being secured 

 by the law of action of nucleus and electron being 

 taken as an attraction according to the inverse square 

 of the distance at considerable distances, but as a repul- 

 sion at small distances. In these circumstances it fs 

 shown that one electron arranges itself at the distance 

 from the nucleus at which attraction changes to repul. 

 sion, two arrange themselves on opposite sides of the 

 nucleus, three at the corners of an equilateral triangle, 

 four at the corners of a tetrahedron, and so on up to 

 eight electrons, which arrange themselves in regular 

 order on the surface of a sphere with the nucleus at 

 the centre. When there are more than eight electrons, 

 the first eight form an inner, and the rest an outer, 

 layer, the number of the latter determining the 

 valency of the atom. The properties of the atoms 

 and molecules which are accounted for on this theory 

 are numerous, and the theory seems most fertile. 



