262 



NATURE 



[November 5, 1914 



original propulsive plant, wings, and rudders, and 

 with 40 per cent, extra aggregate weight due to floats 

 and their attachments. An account of these experi- 

 ments is given in the Scientific American for October 

 10. 



Messrs. G, Michaud and F. Tristan, writing in the 

 Scientific American, describe photographs and observa- 

 tions on the absorbing power of different flowers for 

 invisible light. They find that the majority of flowers 

 come out dark when photographed in ultra-violet light, 

 but that a certain number of yellow flowers reflect 

 the ultra-violet rays in a marked degree. In the case 

 of the Compositae this property is only exhibited by 

 the exterior corollas. On the other hand, most flowers 

 of any colour appear to reflect infra-red light to an 

 equal degree. 



In the South African Journal of Science for Septem- 

 ber (vol. x., 14) Mr. Pedro Luis de Bellegarde da Silva 

 advocates the use of wireless telegraphy in connection 

 with the surveying operations now in progress in the 

 province of Mozambique. At present these operations 

 involve considerable delay owing to the peculiar nature 

 of the country, and it is suggested that a distributing 

 station at some place, such as Louren^o Marques 

 together with small portable wireless outfits would 

 enable the survey to determine the longitudes of many 

 points in the province with greater expedition and 

 accuracy than is possible with the present use of 

 chronometers. 



"The Propagation of Disturbances in Dispersive 

 Media" forms the title of No. 17 of the "Cambridge 

 Tracts in Mathematics and Mathematical Physics," 

 by T. H. Havelock (Cambridge University Press, 1914; 

 pp. viii + 87; price 35. 6d. net). In it the author 

 applies Fourier analysis to investigate the changes of 

 form of a disturbance propagated in a medium in 

 which the wave velocity is a given function of the 

 wave-length. The theory of groups of waves of the 

 most general type is thus discussed, and applications 

 to optical problems are considered. 



Part 213 of the Proceedings of the American Philo- 

 sophical Society contains a paper by Prof. A. E. 

 Kennelly and Mr. H. S. Sanborn, read before the 

 society on April 24, which gives the results of a 

 research carried out at Harvard University in 19 11 on 

 the effect of air pressure on the heat carried away 

 from a hot wire by an air current blowing across it. 

 In the original experiments of Prof. Kennelly and his 

 pupils in 1909 it was shown that the watts which had 

 to be spent in the wire to keep its temperature con- 

 stant (400° or 500° C.) when air blew across it at a 

 speed V between 200 and 2000 cm. p er sec. varied as 

 >s/v, but at lower speeds as ^-^ + 30. As Boussinesq 

 in 190 1 showed that the heat loss should also vary 

 as the square root of the density of the fluid used, the 

 present observations were made in a tank at various 

 pressures, and it was found that for pressures above 

 atmospheric the law held, but at lower pressures the 

 power of the density was more nearly 0-4. They con- 

 clude that the constant of their heated wire wind 

 velocity measurer or anemometer requires to be cor- 

 NO. 2349, VOL. 94] 



rected for both temperature and pressure of the air. 

 The effect of moisture in the air appears, however, 

 to be small. 



For many years there has been periodical agitation 

 for the construction throughout the country of large 

 granaries in order that there might be no possibility of 

 a famine in the event of war. So far as the war has 

 gone, the pressure of the Navy has shown that those 

 who contended in favour of absolute ensurance of the 

 command of the sea, in preference to such tentative 

 measures, were right. Nevertheless, the immense 

 granaries, which are increasing in number at our great 

 shipping ports, are welcome on account of the facili- 

 ties they afford for the discharge and distribution of 

 grain, and for ensuring an adequate supply at the 

 outset of war. The latest of these granaries, built by 

 the Clyde Navigation Trustees at Glasgow, is described 

 in Engineering for October 30. This granary has a 

 total length of 312 ft., a width inside of 72 ft., and a 

 total storage capacity for 31,000 tons of grain. While 

 not so large as corresponding arrangements in Canada 

 and the United States, the structural details of the 

 Glasgow granary and the design of its machinery for 

 discharging grain from ships and distributing it into 

 and out of silos, are thoroughly representative of the 

 best practice of the day, and of great and prolonged 

 experience. 



A LIST of the titles of English, American, French, 

 and German medical and other scientific periodicals, 

 together with prices of subscription, including postage 

 to any part of the world, has been issued by Mr. H. K. 

 Lewis, 136 Gower Street, London. Though only the 

 leading publications are included, the list contains 

 nearly 300 names. The periodicals published in Ger- 

 many cannot be supplied during the war. The list 

 will prove of particular service to librarians and of 

 interest to medical men generally. 



OUR ASTRONOMICAL COLUMN. 



A New Comet. — M. Bigourdan communicates to the 

 Coinptes rendus for October 27 (vol. clix.. No. 17) the 

 substance of a telegram received from M. Com^s Sola, 

 director of the Fabra Observatory, Barcelona, record- 

 ing the discovery of a comet in a region of the sky 

 recently occupied by Encke's comet. Its position on 

 October 25 at i6h. mean Barcelona time is given 

 approximately as R.A. iih. 27m., and declination 

 + 50° 36', and the movement is in a south-south-east 

 direction at the rate of 5° a day. The comet is stated 

 to be visible with a pair of opera-glasses. 



The Comet Recently Observed at the C.'U'e. — In 

 this column on October 8 (p. 151) we recorded the 

 appearance of a bright comet observed at the Royal 

 Observatory, Cape Town, and published an ephemeris 

 up to October 13, computed by Mr. Wood, of 

 Johannesburg. The comet was stated to be fading, 

 and at the same time to be rapidly decreasing its 

 southern declination. This object has now been 

 recorded from Barcelona, where it was photographed 

 on October 17 last (Com-ptes rendus, vol. clix., No. 16, 

 October 19). The note by M. Comis So\k, presented 

 by M. Bigourdan, to the French Academy, records its 

 position as being R.A. 2ih. 53m. 12s., declination 

 -3° 14 at 8h. 9m., Barcelona mean time, the place 



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