July 8, 1922] 



NA TURE 



59 



The problem of soil aeration and the way in which 

 it works injury to plants is much under discussion, 

 but it appears certain that in some soils the lack of 

 oxygen and the accumulation of carbon-dioxide are 

 primary factors, while the organic acids and salts 

 arising from ana^robiosis may play some part. In 

 other cases acidity brings salts of aluminium, iron, 



or manganese into solution, which then exert a toxic 

 effect. 



Finally, after putting forward the present position 

 of affairs with regard to toxic exudates and soil 

 toxins, the author concludes his valuable survey 

 with a comprehensive bibliography which contains 

 more than seven hundred references. W. E. B. 



Radio Direction Finding in Flying Machines. 



T"HERE is little doubt that radio direction finders 

 * and other radio devices will soon be in regular 

 use to enable aeroplanes to land at night, during 

 fogs or at other times of poor visibility. The usual 

 method is to transmit signals from an antenna in 

 the landing field to the direction-finder on the aero- 

 plane. This, however, gives merely the direction 

 of the landing-field and provides no indication to the 

 navigator of his distance from his destination. 



Some years ago the Bureau of Standards in 

 America experimented with induction signalling. A 

 large horizontal single turn coil, 600 by 800 feet, 

 was erected at the landing-stage. It was tuned to 

 resonance at a frequency of 500 so that it produced a 

 very powerful alternating magnetic field over a wide 

 area in the neighbourhood. It was found that 

 induction effects could be detected at considerable 

 distances when the aeroplane was at a low altitude, 

 but at the height of a mile they could be detected 

 only throughout a small area directly over the coil. 

 The tests showed that what was wanted was a hollow 

 conical beam of radiation, the vertex of the beam 

 being on the landing ground. At low altitudes it 

 was very important that the signal should be audible 

 over only a very limited range. 



This has been effected by means of two equal 

 coaxial coils with their planes horizontal and at 

 different altitudes. The current, which has a radio- 

 frequency of 300,000, flows in opposite directions 

 in the two coils. Under these conditions the signals 

 are received at the aeroplane only when the machine 

 is in the immediate neighbourhood and approaching 

 or receding from the station. 



Gregory Breit, a physicist of the Bureau of Stan- 

 dards, has worked out mathematically the nature of 

 the field from the two horizontal coils. It is proved 

 that the maximum intensity of the signals occurs 

 when the angle which the line joining the aeroplane with 

 the landing-stage makes with the vertical is approxi- 

 mately 30 . The region of space within which the 

 signal can be detected is nearly the space between 

 two inverted coaxial cones with their axes vertical 

 and their common apex at the transmitting station. 

 The signals are inaudible directly overhead and 

 rapidly die away when the aeroplane passes through 

 the conical surface where the sound is a maximum. 

 The lower the aeroplane also the louder the noise. 

 The theoretical results have proved of great value in 

 designing stations for emitting landing signals, and 

 should be of considerable practical importance. 



Industrial Research in India. 



/^\NE of the bye-products of the new constitution 

 ^-^ legalised by the Government of India Act of 

 1919 was the transfer of certain " heads of business," 

 previously administered by the bureaucratic regime, 

 to the control of popularly elected Ministers in each 

 province. The subjects so transferred included 

 agriculture, forests, and the development of in- 

 dustries, with, therefore, the scientific and technical 

 services attached to these departments. Realising 

 that " decentralisation of authority and responsibility 

 must necessarily tend to give rise to local variations 

 in policy, apart altogether from those variations that 

 follow local diversity in natural resources," Sir 

 Thomas Holland, when designing the new Depart- 

 ment of Industries and Labour in 1920, elaborated 

 a system which would facilitate concerted action 

 among the provinces while leaving them free to 

 develop in any way that seemed to their respective 

 legislatures best suited to their special needs. The 

 new Ministers were, in the first instance, provided 

 with a monthly circular summarising the information, 

 often of a semi-confidential nature, collected by the 

 Intelligence Branch of the Munitions Board. Out 

 of these circulars grew the agenda of half-yearly 

 conferences, followed by a quarterly Journal and a 

 series of Bulletins suitable for publication. 



During 1921 four parts of the first volume of the 

 Journal, amounting to 568 pages, well illustrated 

 and fully indexed, were issued, and we have now 

 received the first part of the new volume for 1922, to- 

 gether with twenty-three Bulletins on special subjects. 

 The first part of the Journal published in 192 1 was 

 noticed last year in Nature of April 7 (vol. 107, 

 p. 179), and it is satisfactory to observe that trie 

 qualitv of the papers and the fundamental object of 

 the publication have both been faithfully maintained. 



NO. 2749, VOL. I IO] 



Some of the articles, like those by Dr. E. R. Watson 

 and Mr. Mukerji on the alkaline " bad lands " of the 

 United Provinces, by Mr. B. M. Das on the tan-stuffs 

 of the mangrove swamps on the Gangetic delta, by 

 Mr. Appleyard on the manufacture of acetone and 

 butyl alcohol, and by Messrs. Gadre and Mukerji on 

 rose otto, include the results of original research ; 

 but generally the articles and notes have an industrial 

 rather than a scientific bias, avoiding the ground 

 covered by those scientific and technical departments 

 that have established j ournals of their own. Problems 

 of factory welfare, which are beginning to assume 

 embarrassing importance in India, occupy a con- 

 spicuous place among papers describing local ven- 

 tures in glass manufacture, paper-making, tanning, 

 pottery, oil- extraction, perfume distillation, wire- 

 drawing, textile manufacture, and mineral enter- 

 prises. 



The progress reports provided quarterly by the 

 provincial Directors of Industries show the efforts 

 being made to carry out the recommendations of 

 the Industrial Commission which delivered its report 

 towards the end of 191 8. The reports generally give 

 some justification for the claim made by Lord 

 Chelmsford in his article in the United Empire 

 for December last (vol. xii. p. 778) that " never has 

 effect been given more expeditiously " to a Com- 

 mission's report. Differences of provincial outlook, 

 however, still retard the adoption of the excellent 

 scheme of chemical research drawn up by Prof. 

 Thorpe's Committee in 1920 ; and without some 

 such organisation to this end, by co-operation among 

 the provinces, the industries of India must always 

 retain their primitive " configuration " and remain 

 distinctly behind, for example, those of a country 

 like Japan. 



