44 2 



NATURE 



[December ig, 1912 



strains, and includes 35 per cent, to rice, 10 per cent, 

 to wheat. The acreage devoted to cane-sugar has 

 remained steady at i per cent., but that devoted to 

 cotton, which is about one-twentieth of the cropped 

 area, shows an increase for the last quinquennium 

 as compared with that whicli preceded it. Indigo 

 culture has steadily declined during the ten years, 

 until the acreage in the last season was but one-third 

 of the acreage ten years previously ; this decline has 

 been most marked during the last five j'ears in Madras, 

 and least marked in Bengal. The acreage given up 

 to opium has declined also within the five years to 

 about two-thirds of that of the earlier period. The 

 acreage devoted to coffee is also smaller, and those 

 given up to tea and tobacco have been increased. 

 Tables are given regarding the average yield per 

 acre of certain crops in certain districts; these show 

 that irrigated land gives an increased yield over un- 

 irrigated land for rice in Madras (20 per cent.), Pun- 

 jab (40 per cent.), and for wheat in the United 

 Provinces (45 per cent.), and in Bombay (100 per 

 cent.). 



When ultra-violet light falls on an electro-positive 

 metal, the metal emits negative electrons, and the 

 phenomenon has received the name of the photo-electric 

 effect. Two theories as to the mechanism by which the 

 effect is brought about have been suggested at various 

 times. The first regards the electrons of the metal 

 as in harmonic oscillation and ascribes the emission to 

 resonance due to the light frequency; the other, and 

 in some respects the better, takes them as describing 

 elliptic orbits like planets and regards the emission as 

 due to conversion of the orbits into parabolas owing 

 to the absorption of light. In the Verhandlnngen of 

 the German Physical Society for October 30, Dr. K. 

 Herrmann shows that neither theory is in itself alto- 

 gether satisfactory, and concludes that in all prob- 

 ability both causes are at work, resonance in the case 

 of the selective effect, and the other in the normal 

 effect. 



A PAPER by Prof. Luigi Palazzo, extracted from 

 vol. xxxii., part i., of the Annali dell' Vfficio Centrale 

 di Meteorologia e Geodinamica, deals with magnetic 

 observations made in 1908 and 1909 by Prof. Palazzo 

 himself, and in 1907 to 1909 by an Italian surveying 

 vessel, along the coast of Italian Somaliland and 

 British East Africa. It includes a magnetic chart for 

 the epoch January i, 1909, giving lines of equal 

 declination, inclination, and horizontal force for the 

 coastal district from 6° N. latitude to a little south of 

 the equator. The chart and an abbreviated account 

 of the observational material also appear in mono- 

 graph No. 17 relating to colonial affairs, published in 

 September, 1912, by the Italian Foreign Office. In 

 a preface to No. 4 of these same monographs, Prof. 

 Palazzo advocates the establishment of a magnetic 

 observatory in Tripoli. This proposal, he says, met 

 with considerable encouragement at a meeting of the 

 International Magnetic Commission, held in 1910, in 

 Berlin, and recent political events would seem to 

 favour its realisation. 



Messrs. Burroughs, Wellcome and Co. have sent 

 us the 1913 edition of their photographic exposure 

 NO. 2251, VOL, 90] 



record and diary, which is, as usual, neat and handy. 

 There are many photographers to whom this little 

 pocket-book is most necessary, and they will no doubt 

 be glad to hear of this early issue, for does it not 

 comprise a useful gift to a photographic friend? The 

 concentrated and high standard of excellence of the 

 contents of this diary in former years does not leave 

 much room for any great additions or alterations in 

 the present issue, but where possible, such as in the 

 tables of film plate and paper speeds, the most recent 

 data have been inserted. The pocket-book, as usual, 

 includes that excellent and easily worked exposure 

 calculator which may be regarded as the main feature 

 of the issue, a feature of great value to thosr; who .-sre 

 acquainted with it. Three separate diaries are issued, 

 namely for the northern hemisphere and tropics, 

 southern hemisphere and tropics, and for the United 

 States of America, and all are got up in their tasteful 

 style for the reasonable sum of is. 



Under the title " Kreislaufvorgange in der Erd- 

 geschichte," Mr. Gustav Fischer, of Jena, has pub- 

 lished (price 1.50 marks, pp. 39) an address by Prof. 

 Gottlob Lincli delivered before the University of Jena 

 in June last. It is an interesting review, based on 

 the most recent results, of the probable course of the 

 formation of the earth and its atmosphere, dealing 

 more particularly with the reasons for the present 

 proportion of oxygen and nitrogen in tlie air, the 

 composition of sea-water, and the origin of limestone 

 rocks. The principal cyclic changes, both organic and 

 inorganic, which occur under present terrestrial con- 

 ditions are discussed, and a prophetic glance thrown 

 on the future course of the world's history. Although 

 the subject is highly speculative, it is treated with 

 due regard to quantitative calculation and the most 

 trustworthy geochemical data are employed. One 

 noteworthy suggestion put forward is that by the 

 progressive oxidation of the ferrous iron in the eruptive 

 rocks the atmosphere will be gradually depleted of its 

 oxygen, until insufficient remains to support the pre- 

 sent existing forms of life. 



.•\ rifle-barrel is very sensitive to transverse stress, 

 and vibrations are produced in it by the explosion of 

 the charge, by the friction between the bullet and 

 the barrel, and by the reaction between the bullet and 

 the rifling. Mr. Francis Carnegie has read a paper 

 at the Institution of Civil Engineers on December 3 

 giving an account of his experiments on these vibra- 

 tions and drawing conclusions therefrom. In the case 

 of a o'303 in. Mark III. Lee-Enfield rifle, the natural 

 vibration of the barrel was first found by removing 

 all its attachments. The attachments were then added 

 one after another and the effect of each on the vibra- 

 tions examined by photographic means. The position 

 on the vibration curve at which the bullet leaves the 

 muzzle is discussed, and the author favours the point 

 of maximum displacement, as being likely to obtain 

 a much less scattered group on the target. Experi- 

 ments were also made with different designs of barrel, 

 and it was found that the exterior shape of the barrel 

 materially affected the vibrations. Experiments with 

 different pitches of rifling indicate marked effects on 

 the vibrations, but tlie results do not establish definite 



