June 21, 1906] 



NA TURE 



185 



and infra-red to pass. M. Stefanik has arrived at thp 

 conclusion that if only a limited region of ihe spr-tlruni be 

 allowed to enter the spectroscope this region is seen much 

 bitier than if the total light were employed, for, despite 

 the large absorption by the numerous pieces of glass in- 

 cluded in his apparatus, he was able to observe and to 

 map easily the spectrum down to i /*. The group Z was 

 always easily visible, also X, and the lines jr, (,", o-, and t 

 more rarely. It appears from the variations in the intensi- 

 ties of the lines that some of them are of telluric origin. 

 .According to the Annuaxre of the Bureau dcs Longitudes 

 the infra-red is visible to 0-795 /i, but by the employment 

 of the screens M. Stefanik has extended the limit to a' 

 least 0900 /n. 



The Oxford University Junior Scientific Club is to be 

 congratulated on the May number of its Transactions. 

 Trof. H. \. Miers gives an interesting account of his 

 recent investigations, in collaboration with Miss Isaacs, of 

 spontaneous crystallisation and the nature of supersaturated 

 solutions, while a paper by Mr. M. H. Godby, on the 

 place of natural science in education, is full of good things, 

 and deserves notice of a larger public. 



In a note in the Pliysikalisclic Zeitschrift f\o. S, p. 257) 

 Dr>. Stefan Meyer and Egon von Schweidler point out 

 that Madame Curie, in a criticism of their work, referred 

 to in X.\TURE (vol. Ixxiii., p. 549), misinterpreted the 

 tenor of their original communication in assuming that 

 they considered polonium to consist of a mixture of 

 radium D, radium E, and radium F. The conclusion they 

 actually formed (Proceedings of the Vienna Academy of 

 Sciences, February 1) was in reality the same as that 

 arrived at by Madame Curie, namely, that polonium is 

 identical with radium F. In another paper (Vienna 

 Academy of Sciences, Anseiger, No. 12) Drs. Meyer and 

 von Schweidler confirm, however, the view that radio-lead 

 is a mixture of radium D, radium E, and raclium F, and 

 describe the separation of these substances by electrolysis. 

 Several determinations of the constant of decay of radium E 

 were made as a means of characterising this substance, 

 and the nature of a new- radio-active product from actinium 

 is discussed. 



The transformation of oxygen into ozone at high tempera- 

 tures is the subject of a paper by Messrs. Franz Fischer 

 and Fritz Braehmer in the Physikalische Zeitschrift 

 (No. 9). It is shown that w-hen a platinum wire or a 

 Nernst filament is rendered incandescent whilst surrounded 

 by liquid oxygen, or when an arc lamp or hydrogen fiame 

 is played upon liquid oxygen, ozone is formed. When the 

 action is prolonged the amount of ozone formed increases ; 

 in one experiment i per cent, by weight of the o.xygen 

 used underwent condensation. E.xperiments are adduced 

 to prove that the formation of ozone in these cases is 

 solely a thermal phenomenon, and is not to be referred 

 to an ozonising ultra-violet radiation. When any of the 

 methods of heating described are adopted in ordinary air, 

 nitric oxide appears to be the sole product ; in such a case 

 the ozone is not cooled and removed from the sphere of 

 action sufliciently quickly to prevent its decomposition. It 

 is well known that when a hydrogen flame burning in 

 oxygen is played upon water or ice hydrogen peroxide is 

 formed in minute quantity ; it is interesting to note that 

 when hydrogen is burnt in liquid oxygen no hydrogen 

 peroxide can be detected. In the former case water is 

 oxidised to hydrogen peroxide, in the latter molecular 

 oxvgen is converted into ozone. 

 NO 1 91 2, VOL. 74] 



OUR ASTRONOMICAL COLUMN. 



Discussion of Faclx^e Observations. — An interesting 

 discussion of the observations of facul.Te, in which Prof. 

 Mascari compares the frequency and intensity of these 

 phenomena with the solar activity as indicated by sun- 

 spots and the variation of the total luminous radiation from 

 the solar disc, appears in No. 5, vol. xxxv., of the Memorie 

 della Socicta degli Sticttroscopisti Italiaiii. 



Since 1894 the groups of facula; on the solar disc have 

 been observed, and their number and intensity recorded, 

 on everv day that the atmospheric conditions were favour- 

 able. The intensities were classified in five groups, viz. 

 brightest (V.V.), bright (V.), ordinary, weak (d.), and 

 weakest (d.d.). 



Analysing the results thus obtained, Prof. Mascari finds 

 that tiie third class (and possibly the second and third 

 classes) decreased in frequency from that year of sun- 

 spot maximum until 1901, sun-spot minimum, and then 

 increased regularly up to the 1905 maximum. The (d.) 

 and (d.d.) classes varied in the inverse sense. 



Assigning numerical values to these classes, from 5 for 

 the (V.V.j to I for the [d.d.). and t.aking the grouped 

 mean for each year as the relative annual brightness of 

 the faculae, Prof. Mascari finds that this mean brightness 

 also varies with the sun-spot activity, being 2-83 in 1894, 

 i-SS in 1901, and 297 in 1905. Combining, as a product, 

 the mean frequency of the facuU-e for each year with their 

 relative mean brightness a similar result is obtained, the 

 respective values being 2980 in 1894, 462 in 1901, and 

 1963 in 1905. 



These results, combined with those obtained by himself 

 in 1901 and Tacchini in 1878 showing that the chromo- 

 spheric phenomena were less bright at sun-spot minima 

 than at maxima, led Prof. Mascari to the conclusion that 

 the luminous radiation of the sun is greater at the spot 

 maxima than it is at the epochs of minima. 



New Method for the Discovery of Asteroids. — In 

 No. 4, vol. xxiii., of the Astrophysical Journal, Mr. J. H. 

 Metcalf, of Taunton (Mass.), describes a method which he 

 has employed successfully in the photographic discovery 

 of asteroids. 



This method is really an adaptation of that employed in 

 the photography of comets, where the observer, instead of 

 following the guiding star in the usual way, regularly 

 moves the photographic plate during the exposure so that 

 it follows the object which he hopes to photograph, and 

 thus obtains a well-defined single image of that particular 

 object, whilst the surrounding stars are represented on the 

 plate by trails. 



By moving his plate in a direction parallel to the ecliptic 

 at a rate previously computed for an ideal asteroid, ^Ir. 

 Metcalf has obtained some excellent, well-defined circular 

 images of several known faint asteroids, and has also 

 discovered some new ones. For example, one of the re- 

 productions which accompany his paper shows a pair of 

 images of an asteroid of the thirteenth magnitude which 

 he discovered on March 22. 



Radi.al Velocity of a Dracoxis. — A brief note by Herr 

 H. LudendorfT, published in No. 408S of the Astronomischc 

 Nachrichten, confirms the variability of the radial velocity 

 of a Draconis announced by the Lick observers. Accord- 

 ing to the laliter, the radial velocity on June 16, 1902. 

 was o km., and on May 4, 1903, and June 19. 1904. •' "'^s 



— 42 km.; values of -43 km. and -40 km. were also 

 obtained. 



On two plates secured with the Potsdam spectrograph 

 (iv.) on May 23 and 24, 1903, the displacement of the lines 

 \ 4481 and H7 gave the radial velocity of this star as 



— 17 km. and —14 km. respectively. 



Useful Tables and Formul.b for Astronomical Com- 

 putations. — No. 15 of the Publications of the Groningen 

 .Astronomical Laboratory contains a number of tables for 

 photographic parallax-observations, prepared by Dr. W. 

 de Sitter. Each table gives the parallax factors, for each 

 hour of R.A., for every 10° of latitude, and also shows 

 the limiting dates between which a star of the stated R..^. 

 may be observed photographically. 



No. 16 of the same "publications is given in the same 

 volume, and contains a number of trigonometrical formulae 



