14 



KNOWLEDGE & SCIENTIFIC NEWS. 



[Jan., 1905. 



R^efraction in Planetary Occultations. 



A lunar occultation is usually an instantaneous phenomenon, 

 the moon possessing no atmosphere sufficient to cause a sensi- 

 ble refraction of the light of the star occulted. But several 

 of the planets evidently possess considerable atmospheres, 

 and it might at first sight be expected that an occultation of 

 a star by one of them should show a noticeable effect ; a re- 

 tardation of the disappearance and an acceleration of the 

 reappearance. Dr. T. J. J. See in No. 39S4 of the .Istroiw- 

 michc- Kachriihtctt shows that in general there is a zone of 

 irradiation round the disc of a planet many times the greatest 

 admissible depth of the atmosphere. A daylight occultation 

 would be free from this irradiation effect, but the observation 

 of such an event under good conditions must be most r.ire ; 

 whilst in an occultation at the dark limb in the case of Mars 

 or \'enus the limb of the planet would be unseen, and " it is 

 difficult to see how any result of value could be obtained." 



The Greenwich-Paris Longitude. 



M. Loewy, in a communication to the Paris .\cademie des 

 Sciences gives the final result of the determination of the 

 difference of longitude between the two Observatories which 

 was carried out by MM. Bigourdan and Lancelin in 1902. 

 Some small differences were noted between the values obtained 

 in September, 1902, and those in .April and May, which are 

 ascribed to slight changes in personal equation. The mean 

 result gives the difference of longitude as 9m. 20-974S., the 

 value found independently by the two English observers, 

 Messrs. r>yson and Mollis, being 9m. 20-g4S. ; a difference of 

 only the thirtieth of a second of time. The difference of 

 longitude between the two meridians may therefore be 

 considered as now known with most gratifying precision. 



Sunspot Spectra. 



The Rev. A. L. Cortie, S.J., gives in the Astrophysical 

 Journal for November an interesting summary of his obser- 

 vations of sunspot spectra during the years 1883- 1901. His 

 spectroscope was an automatic twelve-prism instrument by 

 Browning, each prism being of 60 refracting angle. The 

 region examined was the red and yellow ; from B to D ; and 

 349 lines are contained in the catalogue of widened lines — the 

 individual observations being 54S6 in number. 



The summary of results shows the important part played by 

 the faint lines of vanadium and titanium in the spectra 

 of sunspots. Lines which in the earlier observations were 

 classed as of unknown origin have since been found to 

 be due to vanadium or titanium. These faint lines are 

 always at all times of the sunspot period among the most 

 widened lines ; X 6243"o6 of vanadium being particularly 

 noticeable. Father Cortie finds no evidence of the " cross- 

 ing points " when these vanadium and titanium lines give 

 way to lines of iron, such as Sir Norman Lockyer has in- 

 sisted upon so strongly; nor is he inclined to admit that there 

 is warrant for concluding that there is an essential difference 

 of character or temperature between maximum and minimum 

 spots. He regards the widening of some of the oxygen lines, 

 especially in the a Vjand, as a real phenomenon, but considers 

 that the apparent evidence for the widening of lines accredited 

 to water vapour requires support from further research before 

 it can be definitely received. 



♦ ♦ » 



The Astronomical and Scientific Bequests 

 of Mr. Frank McClean. 



Mr. Frank McClean, F.K.S., has made the following be- 

 quests: 1^5000 to the University of Cambridge, to be expended 

 in improving the instrumental equipment of the Newall Ob- 

 servatory; ;{'5ooo to the University of^Birmingbam for physical 

 science ; £2000 to the Koyal Society ; ;f 2000 to the Koyal 

 Astronomical Observatory; /'2000 to the Koyal Institution; 

 and to the University of Cambridge, for presentation to the 

 Fitzwilliam Museum, all the testator's illuminated or other 

 manuscripts and early printed books, and all objects of 

 media:val or early art which the Director of the Museum may 

 select as being of permanent interest to the Museum. 



The Medals A^varded by the Royal 



Society. 



The Copley Medal has been awarded to Sir William Crookes 

 for his experimental researches in chemistry; the Rumford 

 Medal to Professor Ernest Rutherford for his researches on 

 the properties of radio-active matter ; one Royal Medal to 

 Professor W. Burnside, on the ground of the number, originality, 

 and importance of his contributions to mathematical science ; 

 the other Koyal Medal to Colonel David Bruce for his success- 

 ful researches into the causation of a number of important 

 diseases affecting man and animals ; the Davy Medal to Pro- 

 fessor W. H. Perkin, jun., for his researches in the domain of 

 synthetic organic chemistry ; the Darwin Medal to Mr. William 

 Bateson for his researches on heredity and variation ; the 

 Sylvester Medal to Professor Georg Cantor for his researches 

 in pure mathematics; and the Hughes Medal to Sir Joseph 

 Swan for his invention of the incandescent electric lamp and 

 his other inventions and improvements in the practical 

 applications of electricity. 



BOTANICAL. 



S. A. Skan. 



It is announced in the December number of the Botanical 

 Magaziiu- that Sir J. D. Hooker, who has been the editor of 

 this famous periodical for the long term of forty years, retires 

 from that position with the completion of the volume for 1904, 

 on account of his great age, Sir Joseph now being in his eighty- 

 eighth year. It is further stated that a new series begins in 

 January, 1905, with Sir William Thiselton-Dyer, K.C.M.G., 

 Director of the Koyal Botanic Gardens, Kew, as editor. For 

 some time past Mr. W. Botting Hemsley, F.R.S., has given 

 Sir J. D. Hooker a great deal of assistance in carrying on the 

 work, most of the text in the last volume having been contri- 

 buted by him. The Botanical Maf;aziitc has now appeared 

 uninterruptedly for n 8 years. Mr. Hemsley. in his interest- 

 ing history of the work, which was published in the Gaydeiurs' 

 Chronicle in 1887, refers to it as " having long outlived the 

 numerous rivals and imitators which its successful career gave 

 rise to from time to time. Indeed, it is doubtful if it is not 

 the only illustrated serial ever published that has enjoyed a 

 century of unbroken vitality." 



In the Comptcs Rcndus, Vol. CXXXVIII., p. 293, Messrs. 

 Bouilhac and Giustiniani have an interesting article on the 

 important question of the utilisation of free nitrogen by 

 various higher plants through the medium of certain fresh- 

 water alg<E (A'os^if />H»f/ i/oj-Hif and Auahana) associated with 

 bacteria. Nitrogen, one of the essential constituents of plant 

 food — the development of proteid substances depending on 

 its presence — though so abundant in the atmosphere, is shown 

 by experimenters, amongst whom may be mentioned De 

 Saussure, Boussingault, Lawes and Gilbert, to be inaccessible 

 to plants in its uncombined state, and that the majority of 

 them are dependent for their supply of the gas to nitrogenous 

 manures incorporated with the soil in reach of their roots. 

 Leguminosa; are remarkable in being able to make use of the 

 atmospheric nitrogen, which is fixed and rendered diffusible 

 for them by the agency of bacteria infesting the nodules often 

 found in abundance on their roots. The writers referred to at 

 the beginning of this note show that other plants besides 

 Leguminosa;, such as buckwheat, mustard, cress and maize.will 

 thrive when the source of nitrogenous food is restricted to the 

 nitrogen of the air, so long as certain algie and bacteria are 

 present in the soil. These appear to be able to convert the 

 gas into a form accessible to the plant in the same way as do 

 the bacteria in the root-nodules of the Leguminosa;. Messrs. 

 Deherain and Demoussy had previously ascertained that even 

 a IcKimiinous plant (t.iipiniis) would flourish in soil deprived 

 of nitrogenous ingredients, and without developing nodules on 

 its roots, if alga; were present. 



