October 28, 19 15] 



NATURE 



237 



. agent, and the total elimination of iron. The nature 

 ^of the disintegration of platinum and its alloys is 

 if briefly discussed. 



I The announcements of Messrs. Crosby Lockwood 

 and Son include : — A translation of Prof. Klingen- 

 berg's Large Electric Power Stations, illustrated ; Oil- 

 Field Development, by A. Beeby Thompson ; Air 

 Screws : an Analytical Study in the Application of 

 the Analogy of an Aerofoil having a Rectilinear 

 Motion, by M. A, S. Riach ; and new editions of 

 Naval Architect's and Shipbuilder's Pocket Book of 

 Formulae, Rules, and Tables (with a section on Aero- 

 nautics), by C. Mackrow and L. Woollard; Mechan- 

 ical Handling of Material, by G. F. Zimmer. 



Messrs. George Allen and Unwin, Ltd., will pub- 

 lish shortly : — Table of Compound Interest and Anti- 

 logarithms, by J. J. Stuckey, and a translation, by 

 Dr. E. L. Schaub, of Prof. W. Wundt's Elements of 

 Folk Psychology : Outlines of a Psychological History 

 of the Development of Mankind. 



OVR ASTRONOMICAL COLUMN. 



The Great Meteor of October 5.- -A large number 



of descriptions of this object has reached Mr. W. F. 



Denning as the result of an appeal for observations 



published in some of the leading journals of the west 



of England. Mr. Denning sends us the following 



summar}- of the observations : — The meteor appears 



■ to have been widely seen over the S.W. region of 



'"^ngland, and there were many observers in South 



Vales. Most of the spectators first saw a brilliant 



llumination of the sky and landscape, and, looking 



Ip to ascertain the cause, the end of the meteor or 



luminous streak it left was at once perceived. To 



lany of the observers in Cornwall and Devon the 



>sition of the object was in the X. by E. sky, and 



le streak remained visible for periods varying between 



vo and twenty minutes. 



The light evolved from the fireball at the instant 

 its greatest outburst is said to have exceeded that 

 the full moon, but there are not many really accu- 

 ite accounts of its path amongst the stars. At first 

 streak was projected like a glowing bar among 

 stars between the pointers in Ursa Major and the 

 Pole star, but it quickly became contorted and curled 

 either into a ring with appendages or into an 

 regular ellipse, expanding as time went on, and 

 jcoming fainter. 



Using many of the best observations of the metec-r 



|[or comparison, the height seems to have been from 82 



_55 miles from over Lampeter to Neath, South Wales. 



"le length of the visible course was about 42 miles, 



id velocity about 35 miles per second. Radiant at 



+ 72°; but this feature is rather doubtful, and it 



hoped that further observations of the flight mav 



Jt be acquired so that the position may be tested. 



eastern side of the streak expanded so'quickly and 



nth a motion decidedly eastwards that its velocitv 



lust have been equivalent to about 90 miles per houi'. 



Proper Motions Measured by the Blink-Micro- 



:OPE. — There can be no doubt that stereoscopic or 



i-stereoscopic methods are destined to become 



_ very great importance in astronomical work. Thus 



:at the Lowell Observatory, Lampland has employed 



Pulfrich's device, the blink-microscope, for detecting 



variables and asteroids ; at Yerkes, Slocum has shown 



that it is equally well adapted for finding proper 



motions, and the instrument has been enthusiastically 



adopted at the Union Observatory, Johannesburg. 



NO. 2400, VOL. 96] 



The director, Mr. R. T. A. Innes, can even see this 

 instrument with standard transparent charts replacing 

 the unwieldy durchmusterung catalogues. Already many 

 variable stars have been discovered by its use, asteroids 

 have been successfully picked up, and a good be- 

 ginning has now been made in its application to the 

 I question of proper motions. In Circular No. 25, 

 i Unioh Observatory, Mr. Innes and Mr. J. V6ute, an 

 assistant from the Leyden Observatory, who has been 

 working at the Cape, both describe methods by which 

 the proper motions of a number of stars in the great 

 w Centauri cluster have been measured. The former 

 not only detects, but also measures the displacements 

 with the "blink," whilst Mr. Voute only uses it to 

 make the selection, and then proceeds to take differen- 

 tial micrometric measures. The plates employed 

 (astrographic) had been taken separated by an interval 

 of 2385 years. Of the 2000 stars on the plate, 30 

 presented measurable displacements (motions exceed- 

 ing an annual value of oo4"-oo6''), whilst for fifty 

 others the indications were doubtful. 



The Light-Curve of XX Cygni. — Several recently 

 published papers concerning stellar variability have 

 possessed somewhat exceptional attraction, not only 

 in the variety of methods exemplified, but chiefly in 

 consequence of the notable astrophysical importance 

 of the stellar bodies investigated. Another such 

 memoir appears in the September number of the 

 Astrophysical Journal, Dr. Harlow Shapley and 

 Martha B. Shapley presenting an account of the em- 

 ployment of the latest methods of photographic actino- 

 metry in the study of the light curve of XX Cygni. 

 Previous work indicated that this star was to be 

 regarded as an abnormal Cepheid variable, exceptional 

 not only by reason of its short period — the most rapid 

 known— but also because it had been shown by Kron 

 to present a greater amplitude of light-change visually 

 than photographically. Employing the Mount Wilson 

 6o-in. refractor on four nights, upwards of 300 photo- 

 graphs of the star on ordinary plates alternately with 

 isochromatic plates with yellow screen were secured, 

 providing the material for a photographic and photo- 

 visual investigation of its fluctuating light. The 

 results obtained show that the shape of the mean 

 light-curve, and also its range, are both variable. 

 The visual range does not exceed the photographic 

 but apparently is somewhat smaller. It is concluded 

 that the maxima, although occurring at regular inter- 

 vals, are disturbances varying in character, the mini- 

 mum being the sensibly constant condition of the 

 star. The value of the colour index indicates an 

 average spectrum of the F type rather than A as 

 classified at Harvard. 



Atmospheric Effects of Kathode Rays. — M. J. 

 Maurer, of the Central Met^rological Bureau, Zurich, 

 describes (No. 4813, Asironomische Nachrichten) for 

 the first time what is possibly an atmospheric effect 

 due to solar kathode rays. Having formed the opinion 

 that times of exceptional solar activity would be 

 especially favourable for decisive observations of a 

 long-suspected phenomenon, arrangements were 

 accordingly made with Prof. Wolfer, who supplied 

 information regarding the rapid development of solar 

 activity about the middle of last June. The result 

 was that between 2 and 3 p.m. on June 16, with a 

 blue sky, in addition to the water-vapour halo of 70°, 

 there was also observed a distinct brown aureole 

 having a maximum breadth of about 15°. Prof. 

 Wolfer also noted that some optical effect, comparable 

 with the interposition of a slight veil of vapour, had 

 interfered with his solar observations. It is" further 

 pointed out that Prof. Barnard recorded an auroral 

 display on the night of June 16. 



