March i6, 191 i] 



NATURE 



91 



actions in which light is not concerned, since the concen- 

 tration of the catalyst is then without influence on the 

 final equilibrium between isomers. Other characteristics 

 of photo-chemical action were shown by the investigation 

 of the bromination of toluene under the influence of light. 

 This action is extraordinarily sensitive to the presence of 

 oxygen, which appears to give rise to oxidised bromine- 

 compounds which carry on the action after the light has 

 been removed ; bromination in the side chain can, indeed, 

 be effected almost violently in the dark if the material 

 is subjected to the action of slightly ozonised oxygen, 

 which thus acts as a most efficient " carrier " of bromine 

 to the side chain. When these disturbing effects were got 

 rid of by exclusion of oxygen and the addition of a little 

 iodine, the velocity of bromination was found to be in- 

 dependent of the concentration of the bromine, i.e. equal 

 quantities of bromine were used in equal times throughout 

 the action. The action of various wave-lengths of light 

 was determined with the help of a mercury lamp and light- 

 filters, but all wave-lengths absorbed by the bromine 

 appeared to take part equally in the photo-chemical action. 



An account of a Garratt locomotive made by Messrs. 

 Beyer, Peacock and Co., Ltd., of Manchester, for the 

 Darjeeling-Himalayan Railway, appears in The Engineer 

 for March lo. This railway is of 2 feet gauge, and pre- 

 sents peculiar difficulties on account of the steep ascent 

 and frequent loops or spirals and reverses, one of the 

 latter having gradients of i in 28. Curves of 70 feet 

 radius are numerous. The specification for the locomotive 

 included the condition that it should be able to travel over 

 revise curves of 60 feet radius with a length of tangent 

 between the curves of 20 feet only. The engine consists 

 of a girder frame, which is pivoted and supported at its 

 extreme ends on four-wheeled bogies. Each bogie is a 

 miniature locomotive sans boiler. The boiler supplying 

 both is carried between the bogies on the girder frame. 

 As therev are no wheels under the boiler, the size of boiler 

 is practically unrestricted. There are four cylinders each 

 ii-inch diameter by 14-inch stroke, and fitted with 

 Walschaert's valve gear. 



Prof. Emil Fischer's lecture on " Neuere Erfolge und 

 Probleme der Chemie," of which a translation appeared in 

 Nature of February 23, has been published by the firm of 

 Julius Springer, Berlin, price 0.80 mark. 



OUR ASTRONOMICAL COLUMN. 



The Spectrum and Orbit of o Persei. — In No. 10, 

 vol. ii., of the Publications of the Allegheny Observatory, 

 Mr. Frank C. Jordan discusses the s{>ectrum and orbit of 

 the spectroscopic binary o Persei. From a discussion of 

 seventy plates, taken with the Mellon spectrograph during 

 1908-9, he finds that, instead of a radial velocity of 

 — 3 km., as found by Vogel, the centre of the system has 

 a radial velocity of -|- 18-5 km. ; the orbit is practically 

 circular, and the period is 4-4192 days. 



The most striking fact educed by Mr. Jordan, however, 

 is that the H and K lines of calcium do not appear to 

 participate in the displacements due to motion in the line 

 of sight shown by the other lines. In other words, whilst 

 helium, hydrogen, magnesium, and carbon lines in the 

 star's spectra indicate that the star is revolving in a 

 circular orbit, the H and K lines indicate that the calcium 

 vapour producing them is moving with a constant velocity 

 away from us. Prof. Hartmann found the same pheno- 

 menon in the spectrum of 5 Orionis, and, as the apparent 

 velocity derived from the K line differed by 7 km. from 

 the velocity of the centre of the system, he suggested that 

 the calcium absorption took place in a medium lying 

 between us and the star ; such .a suggestion is strengthened 



NO. 2159, VOL. 86] 



by the fact that most stars exhibiting this peculiarity lie 

 in nebulous regions. But Mr. Jordan is inclined to ques- 

 tion the difference of 7 km., which might be obviated by 

 adopting other standard values for the wave-length of K, 

 and, very tentatively, suggests that a clue to the pheno- 

 menon may be found in the fact that, of eleven stars ex- 

 hibiting the peculiarity, ten are strong helium stars. 



The Determination of Latitude. — While the Talcott- 

 Horrebow method of determining latitude is the most 

 important from the point of view of accuracy and facility 

 of application, it generally necessitates the use of a 

 specially constructed instrument, the zenith telescope. But 

 in No. 4481 of the Astronomische Nachrichten Mr. Kiyo- 

 fusa Sotome, of the Tokio Observatory, explains how the 

 method may be used in connection with an ordinary field 

 theodolite. Three wires, one vertical and two others 45° 

 from the vertical, cross at the centre of the field of the 

 telescope, and are carried by a reticle in the focal plane. 

 Then a pair of stars are observed, circle east and circle 

 west, and the time-intervals between the transits are noted. 

 Knowing the declinations of the stars, Talcott's method 

 gives the latitude, after the application of various correc- 

 tions. Mr. Sotome explains the method in detail with 

 formulas, and shows that reasonable errors in the time 

 intervals will not seriously vitiate the results. A series 

 of seven observations at Tokio gave a mean error of 

 ±0-80", with a probable error of a single observation of 

 ±1-63". 



The Relation between the Separation and the Magni- 

 tude OF Visual Double Stars. — In No. 176 of the Lick 

 Observatory Bulletins, Dr. R. ,G. Aitken analyses the 

 degree of separation and the magnitudes of the double 

 stars, brighter than magnitude 9-5 and closer than 5-0", 

 given in several large catalogues, and finds that the 

 numbers of doubles consistently increase as one passes 

 from the wider to the closer pairs. He also finds that the 

 number of doubles of every distance-class under 5-0" in- 

 creases with increasing numerical magnitude ; for instance, 

 for B.D. stars as bright as magnitude 8-o the proportion 

 of doubles separated by less than 5-0" is about i in 13^, 

 but for B.D. stars between magnitudes 80 and 9-0 the 

 proportion is only i in 25. 



H alley's Comet. — Already the periods of observation, 

 both before and after perihelion, of Halley's comet, have 

 easily exceeded those of any previous return ; but observa- 

 tions are still being made at many observatories, and are 

 likely to be continued for some time. M. Gonnessiat re- 

 ports, in Astronomische Nachrichten, Nos. 4480-1, that on 

 December 7 the magnitude was about 13-5, and that on 

 February 25 it was 14-0. 



In No. 4478 of the same journal Herr M. Ernst places 

 on record his observations of the comet's magnitude on a 

 number of dates extending from September 12, 1909, to 

 June 30, 1910 ; his magnitudes for May 16 and 22, 1910, 

 are — o-i and —0-2 respectively. 



The Path of Comet 1886 I. — More than one hundred 

 columns of the Astronomische Nachrichten, Nos. 4477-8, 

 are taken up by an exhaustive discussion, by Dr. Erich 

 Redlich, of the available observations of the large comet 

 1886 I. After giving and discussing each observation in 

 detail. Dr. Redlich derives a set of elements which give 

 the eccentricity of the orbit as 1-0004461 ±00000141. 



Nova Lacert^. — The faintness of this nova and the 

 almost persistent cloudiness of our skies have prevented 

 any extensive recent observations. In No. 4476 of the 

 Astronomische Nachrichten, however. Prof. Millosevich 

 reports that on February 10 the magnitude was 8-8. 



Earthshine on the Moon.— To the casual observer of 

 the heavens, the earthshine on the moon is deeply 

 mysterious. On the evening of March 4, when our satel- 

 lite was in conjunction with Saturn, the earthshine, as 

 seen from Leeds, was unusually distinct, and many people, 

 says Mr. J. H. Elgie in The Yorkshire Post, were led to 

 believe that an eclipse was in progress. Mr. Elgie's 

 observations showed that in the twilight the glow was of 

 ashen hue, but that it deepened into olive as darkness 

 came on. 



