October 26, 191 1] 



NATURE 



56i 



nine are recorded from Siam in the recent account pro- 

 vided by Mr. F. D. Ryan and Dr. A. F. G. Kerr in the 

 Journal of the Siam Society (vol. viii., part i.). Of six 

 Dipterocarpus, D. hiberculatus and D. obtusi- 

 folius are the most important, as they form in some locali- 

 ties almost pure, open jungle forests. D. tuberculatus is 

 best developed on red clay; D. obtusifolius becomes 

 dominant on sandy soil, while Shorca siamensis may also 

 develop into forest on stony ground. Different forms, re- 

 spectively tomentose and glabrous, were observed for 

 the tomentose form is associated with 

 higher and drier situations. A peculiar feature is the 

 ige of water by D. obtusifolius, so that if the stem be 

 cut and turned upside down, a sufficiency is obtained to be 

 able to shooting parties. 



OWING to the propensities of native growers and the 

 traditions of the industry, the improvement and increase 

 of cotton cultivation in India is a complicated problem ; 

 but, judging from the note compiled by Mr. B. Coventry, 

 and published as Bulletin N'o. 26 of the Agricultural Re- 

 search Institute, Pusa, appreciable success has already been 

 attained with some measures, while others are proceeding 

 favourably. The yield of Broach and other better-class 

 native varieties has been improved by seed selection ; 

 coincidently stores have been established for distributing 

 the pure improved seed. Promising results have been 

 obtained by hybridisation at Surat and elsewhere. In Sind 

 a good-class American cotton has been profitably raised, 

 and Egyptian metafifi is being tried where canal irriga- 

 tion is feasible. A signal failure is noted in the case of 

 experiments with tree cottons, which have therefore been 

 discontinued. 



The September number of The American Journal of 

 Science contains an account, by Mr. O. A. Derby, of a 

 big diamond recently obtained from the Bagagem district 

 of Minas Geraes, where the famous " star of the south " 

 was found. That stone weighed 255 carats ; and the same 

 locality also yielded the " Dresden diamond," with a 

 weight when uncut of 1192 carats; the new stone, 

 " estrella de Minas," weighs 175 carats. All three 

 diamonds are elliptical in shape, with curved faces. It is 

 mentioned in the same note that the largest diamond 

 known from Brazil was one found in 1906, the weight of 

 which was estimated at 600 carats. Its owner, being 

 doubtful whether it was really a diamond, caused it to be 

 struck with a heavy hammer on an anvil, in the belief 

 that if genuine it would be uninjured ! Fragments weigh- 

 ing about 100 carats were saved, from which one diamond 

 - S carats was cut. 



The valuable meteorological charts published by the 

 U.S. Weather Bureau for the large oceans and the great 

 American lakes for November have been received. In 

 addition to the usual statistical and other useful informa- 

 tion contained on the face of the charts, the reverse sides 

 of those of the North Atlantic and North Pacific contain 

 articles on the sea surface and air temperatures, currents, 

 &c. It is shown, inter alia, that high barometric pressure 

 usually prevails over the central portion of the North 

 Atlantic, the crest lying between longitudes 25 and 40° W., 

 having slightly increased since October. Low barometric 

 pressure obtains north of 55 , between longitudes 20° and 

 50 W., having decreased since October. The increased 

 steepness of the barometric gradient causes frequent storms 

 over the Transatlantic routes. 



A summary of the weather issued by the Meteorological 

 Office shows that the rainfall for last week was again 

 NO. 2191, VOL. 87] 



generally below the average, the only really appreciable 

 excess being 048 inch in the south of Ireland. Contrary 

 to recent experience, the duration of bright sunshine was 

 below the average over the entire kingdom. The aggre- 

 gate rainfall for the seven weeks of autumn as yet expired 

 is below the average over the entire kingdom, except in 

 the Channel Islands, where there is a slight excess, amount- 

 ing to 0-09 inch. The deficiency in the west of Scotland 

 is 3-59 inches, and in the north of Scotland 3-54 inches. 

 The deficiency of rainfall since the commencement of the 

 year is very great ; in the north of Ireland it amounts to 

 876 inches, the west of Scotland 788 inches, the south- 

 west of England 776 inches, and the Midland counties 

 770 inches. In the south-east of England the deficiency 

 is 572 inches, where the excess of sunshine is 335 hours, 

 which is the greatest excess in any part of the kingdom. 

 The heavy rains of the present week will decrease some- 

 what the accumulated deficiency of rainfall. 



According to several communications which have been 

 made to the Physikalische Zeitschrift recently, Drs. Elster 

 and Geitel have succeeded in increasing the sensitiveness 

 of the potassium photoelectric cell very materially by pass- 

 ing an electric discharge for a short time through the 

 hydrogen in the tube. The potassium becomes covered 

 with a greenish-blue film, which appears to give off 

 negative electrons when illuminated much more readily 

 than the metal itself. If the hydrogen remains in the 

 tube the film disappears, and the sensitiveness of the cell 

 falls. By replacing the hydrogen after the formation of 

 the film by argon, the film becomes permanent and the 

 sensitiveness constant. By covering the ordinary potassium 

 kathode with a film of colloidal potassium a cell may be 

 made sensitive to the infra-red rays. As an example of 

 the use to which these sensitive cells may be put, the 

 measurement of the decrease of the light from the moon 

 during the eclipse of November 16, 1910, may be cited. 

 With 232 volts on the cell full moonlight gave a current 

 of 350X10- 9 ampere, which sank to 220x10-' as the 

 moon entered the umbra, and to zero before totalitv was 

 reached, owing to the passage of clouds. 



The Sociedad Matematica Espanola is to be congratu- 

 lated on the success that is attending its efforts to remove 

 a reproach from the annals of Spanish science. It was 

 founded in April last, and has already published three 

 numbers of its Rivista, a periodical which should play a 

 notable part in the awakening and sustaining of mathe- 

 matical interests throughout the peninsula. Each number 

 opens with a biography and portrait, contains articles on 

 pure and applied mathematics, reviews of current mathe- 

 matical literature, articles on the history and methodology 

 of the science, and a column for queries and answers. 

 The society proposes to publish for the benefit of its 

 members translations of foreign works on mathematics. 

 This, when finances allow, is to be at less than cost price. 

 On the same terms the society will supply to members 

 translations of articles from foreign periodicals. A depart- 

 ment has also been organised for the supply to members of 

 references from the vast body of mathematical literature. 

 The outlook is full of promise, especially when we 

 remember that a much larger audience than Spain can at 

 present produce awaits the appeal of the Sociedad in the 

 intellectual centres south of the United States and north 

 of the line joining Buenos Ayres and Valparaiso. The 

 new society is a vigorous bantling. Time alone will show 

 if it will rise to its opportunities. All information may 

 be obtained from D. Jose Mingot, San Bernardo, 51, 

 Madrid. 



