52-' 



NA TURE 



[April 2, 1903 



OUR ASTRONOMICAL COLUMN. 



A New Star in Gemini. — A communication received from 

 Prof. H. II. Turner on March 25 announced lhat the image 

 of a Nova, or a variable, had been discovered on a photo- 

 graph taken at the University Observatory, Oxford, on 

 March 16. The position of the object was given as 



R.A. =6h. 37m. 4.S'qs., Dec. = +30° 2' ?q" (1900), 



which is situated in the constellation Gemini near to the 

 border of Auriga, and about half-way between & and e 

 Geminorum, a little preceding the straight line joining 

 them. This position was confirmed by an observation made 

 at Oxford on the evening of March 24. A telegram from 

 the Kiel Centralstelle confirmed the discovery. 



In a second communication from Oxford it was announced 

 that Mr. Newall had observed the spectrum with a direct 

 vision spectroscope attached to the Sheepshanks equatorial 

 al Cambridge, and had little doubt that the object was a 

 Nova. Up found that bright lines — both numerous and 

 strong — were present, those in the green part of the spec- 

 trum being especially bright. 



In a letter to the Times of Saturday, March 28, Prof. 

 Turner stated that the object was not bright enough for its 

 image to appear on plates taken on February 24 and earlier, 

 and as no apparent movement had taken place between 

 March 16 and 24, it was certainly not a planet. 



The magnitude of the new star is about 7, and, as il is at 

 present near to the zenith during a greater part of the 

 evening, it should be easv to observe, given favourable 

 meteorological conditions. The accompanying chart shows 

 the approximate position of the Nova in regard lo the 

 surrounding stars. 



\ Circular (No. 58) from the Kiel Centralstelle announces 

 that Prof. Hartmann, at Potsdam, examined the visual 

 spectrum on March 27. lie found the hydrogen lines H/3 

 and 11a to be present, the latter appearing especially bright ; 

 the yellow part of the spectrum is extremely faint as com- 

 pared with the blue, which contains many bright lines 

 superimposed on a continuous spectrum. The spectrum 

 hails to the conclusion that the star is either a Nova or a 

 variable of the Mira type. 



Prof. Hale, at Yerkes Observatory, observed the Nova 

 on March 2775 (G.M.T.), and found its position to be 

 a = t)h. 37111. 4,1s., B = +3o c 2' 38", and its magnitude S3, 

 The spectrum contains bright lines (or bands), and the colour 

 of the No\ a is red. 



The Solar Constant. — In a paper read before the 

 American Association for the Advancement of Science on 

 December 30, Prof. S. P. Langley discussed the values 

 which have hitherto been obtained for the constant of si lar 

 radiation, and gave an outline of the course of study of this 

 onstant that it is proposed to carry out in the immediate 

 future at the .Smithsonian Astrophysical Observatory. 



1 he author, in his opening remarks, drew attention to 

 the vital importance to humanity of obtaining definite know- 



ledge of the magnitude, nature and possible variations of 

 this radiation, and stated that whilst many other astro- 

 nomical problems are of great interest from a purely scien- 

 tific point of view, this one problem is of intensely practical 

 importance ; he then summarised this view in the following 

 statement : — " I recognise that every nebula might be 

 wiped out of the sky to-night without affecting the price 

 of a labourer's dinner, while a small change i.n the solar 

 radiation may conceivably cause the deaths of numberless 

 men in an Indian famine." 



Thus recognising the grave importance of a minute study 

 of solar physics, Prof. Langley devoted a great deal of 

 attention to its problems whilst connected with the Alle- 

 gheny Observatory and the Mount Whitney expedition, and 

 with his bolometer made a long series of observations which 

 led to the conclusion that the values obtained by Pouillet 

 and other observers were far too small. By measuring the 

 solar radiations wave-length by wave-length, he obtained 

 values varying from 3'o to 3'5, thus nearly doubling the 

 classical value, 1*76 calories, obtained by Pouillet. 



I sing the bolometric method it is now possible to obtain 

 results in fifteen minutes which it previously took two days 

 to obtain, and the Smithsonian Observatory nroposes to com- 

 mence, in the immediate future, a series of observations in 

 order to determine (a) the coefficients of atmospheric trans- 

 mission under all conditions, and (/>) the coefficients of 

 transmission of the various parts of the apparatus. In 

 doing this the observers will become familiar with the ex- 

 perimental methods which, it is hoped, will be used later 

 at more elevated stations where the atmospheric conditions 

 are much more favourable, and they will also obtain values 

 more nearly approximate to the true values than those 

 hitherto obtained {Astrophysical Journal, vol. xvii. No. 2). 



The Magnesium Spectrum Line at a 4481. — Sir William 

 and Lady Huggins communicate to the March number of 

 the Astrophysical Journal the preliminary results obtained 

 by them in a series of experiments made in order to deter- 

 mine under what laboratory conditions the line at a 4481 in 

 the magnesium spectrum assumes the sharp, narrow appear- 

 ance it has in many stellar spectra. 4 



The authors have arrived at the conclusion that the 

 quantity and the electromotive force of the electricity which 

 aits during the spark discharge between magnesium poles, 

 have only a small influence on the character of this line, but 

 that the suddenness of the blow of the discharge determines 

 its character. 



In a plate which accompanies the article is shown a re- 

 production of the spark spectrum where the discharge of 

 the secondary took place directly between the magnesium 

 poles, the jar having been removed from the circuit ; in 

 this case the blow of the discharge is less sudden, through 

 the incoming of the full self-induction of the coil itself, and 

 the line assumes the sharp appearance seen in stellar spectra. 



Other spectra which are reproduced show the difference 

 in the appearance of this line under various conditions of 

 spark discharge. 



THE EMANATIONS OF RADIUM. 1 



A SOLUTION of almost pure radium nitrate which had 

 "^^ been used for spectrographic work was evaporated to 

 dryness in a dish, and the crystalline residue examined in a 

 dark room. It was feebly luminous. 



A screen of platinocyanide of barium brought near the 

 residue glowed with a green light, the intensity varying with 

 the distance separating them. The phosphorescence disap- 

 peared as soon as the screen was removed from the influence 

 of the radium. 



A screen of Sidot's hexagonal biende (zinc sulphide), said 

 to be useful for detecting polonium radiations, was almost as 

 luminous as the platinocyanide screen in presence of radium, 

 hut there was more residual phosphorescence, lasting from a 

 few minutes to half an hour or more according to the 

 strength and duration of the initial excitement. 



The persistence of radio-activity on glass vessels which 



NO. 1744, VOL. 67] 



1 By Sir William Cruokes, F.k.S. 

 March 19. 



Read at the Royal Society on 



