59^ 



NATURE 



[February 29, 19 12 



•charge, (2) the " semi-brusque " discharge, and (3) the 

 " brusque " discharge, of which the respective durations 

 are of the order of 001 sec, ooooi sec, and oooooi sec, 

 and M. Millochau briefly describes the different types of 

 pectra produced in various gases by each. Thus in CO, 

 ilie first produces the " Swan " spectrum, while the second 

 produces the spectrum of carbonic oxide in place of the 

 "Swan." With the "brusque" discharge, "line" 

 spectra are produced, the lines of hydrogen and helium 

 being always broad. Finally, M. Millochau arrives at the 

 most important conclusion that his results favour the 

 dissociation hypothesis, inasmuch as they appear to show 

 that the production of the various spectra depend upon the 

 temperature of the vibrating molecule and upon the dis- 

 sociation effects which correspond to this temperature. 



OVR ASTRONOMICAL COLUMN. 

 Astronomical Occurrences for March : — 

 "March 2. 2h. om. Mercury in superior conjunction with the 

 Sun. 

 4. 5h. Dm. Mars at quadrature to the Sun. 

 4. i6h. cm. Jupiter at quadrature to the .Sun. 

 9. 22h. 36m. Jupiter in conjunction with the Moon 



(Jupiter 4° 59' N.). 

 13. I9h. 12m. Uranus in conjunction with the Moon 



(Uranus 4° 43' N.). 

 15. igh. 6m. Venus in conjunction with the Moon 

 (Venus 3° 43' N.). 



19. J6h. 44m. Mercury in conjunction with the Moon 



(Mercury 1° 47' N.). 



20. iih. 30m. Sun enters Sign of Aries ; Spring 



Equinox. 

 22. 6h. 14m. Saturn in conjunction with the Moon 



(Saturn 1° 36' N.). 

 24. 2oh. 30m. Mars in conjunction with the Moon 



(Mars 2° 44' S.). 



26. l6h. 19m. Neptune in conjunction with the Moon 



(Neptune 5" 53' S.). 



27. I4h. om. Mercury at greatest elongation east of 



the Sun. (i8°5i'E.). 

 31. I7h. cm. Venus in aphelion. 



The Eclipse of the Sun on April 17. — In a memoir 

 prepared by the Madrid Observatory there is an excellent 

 account of the conditions for the total and annular eclipse 

 which will be visible in the peninsula on April 17 next. 

 Intended for popular information, the memoir contains not 

 only the data calculated for the eclipse in general and for 

 several favourable localities. But also gives an account of 

 the geometry of eclipses, the methods of calculation, the 

 results, and some excellent diagrams and maps showing 

 the track of the shadow. 



As an example of the application of the method of 

 calculating the values for any particular place, Cacabelos 

 (long. = 6° 42' 57" W. of Greenwich; lat.=42° 35' 53" N.) 

 is selected, and for this place it is found that totality will 

 last 4-6 seconds, the middle of the eclipse occurring at 

 23h. 48m. 54-7S. Other places where the eclipse will be 

 total were selected, and, in order to ensure accuracy, a 

 commission was appointed to determine their geographical 

 coordinates. They are Barco de Valdeorras and \'erin, 

 and tlieir positions were found to be : — long. 3° 17' 43-5" 

 W. of Madrid, lat. 42° 25' 5.4* N., and long. 3° 45' 12-0'' 

 W. of Madrid, lat. 41° 56' 290" N., respectively. The 

 track of the eclipse across the peninsula is shown on a 

 large-scale map (i : 500,000) at the end of the memoir, the 

 central line passing from immediately north of Ovar, in 

 Portugal, to Oviedo, and leaving the northern coast 

 slightly to the east of Gijon. 



The Early Babylonian Eclipse of the Sun. — In a paper 

 appearing in part iii., vol. ii., of the Transactions of the 

 Royal Society of South Africa, Mr. Nevill discusses at 

 length the ve.xed question of the date to be assigned to the 

 eclipse of the sun recorded on Tablet No. 35968 of the 

 British Museum collection, which Dr. Cowell has identified 

 with the eclipse of —1062, July 31. He describes the 

 broken tablet, and discusses Mr. King's reading of the 

 same from several aspects, arriving at the conclusion that 

 tiic internal evidence does not preclude a date in the 



NO. 2209, VOL. 88] 



twelfth century b.c, or even earlier. .After examining 

 every eclipse occurring between 1250 and 920 B.C., Mr! 

 Nevill, by several processes of elimination, finds that, with- 

 out assuming any secular acceleration of the sun's motion, 

 the eclipses which fit the various conditions, of time, date, 

 place, &c., best are those of June 5, 1217, May 18, 1123, 

 and .May 31, 956 B.C., and of these three the first most 

 closely corresponds with theory and observation. 



Finally, he points out that Dr. Cowell's hypothesis of 

 secular acceleration, permitting a number of ancient 

 eclipses to be recognised, constitutes a strong case if no 

 other hypothesis can be found, but its adoption raises 

 several questions which for the present cannot be satis- 

 factorily answered. 



The Proper Motions of the Stars in the Clusters 

 h AND X Persei. — Vol. v. of the Recherches Astro- 

 nomiqtics de I'Observatoire d'Utrecht is devoted to a thesis 

 prepared by M. A. van Maanen dealing with an investiga- 

 tion of the proper motions of 1418 stars in and near the 

 famous double cluster h and x Persei. 



The object of the investigation was twofold : first, to 

 find the proper motion of the two clusters ; secondly, to 

 determine the frequency of the proper motion according to 

 its amount and to the magnitudes of the stars for this 

 region of the sky. From a number of plates six were 

 selected, two pairs taken by Kostinsky in 1896 and 190S, 

 and one pair by Donner in 1892 and 1909, and among the 

 conclusions arrived at it is maintained that this method 

 of using pairs of plates is not inferior to that where the 

 images are impressed upon the same plate at different 

 epochs. The proper motions resulting from the discussion 

 are so small as to render it impossible to make out which 

 stars are, and which are not, members of the groups. In 

 determining the frequency of the proper motions, it was 

 found that, of the 763 stars considered, 300 had P.M.'s 

 betw-een 0010" and ooiq", while only 142 had motions 

 less than o-oio" ; no sufficient reason has yet been found 

 for the relatively small number of small proper motions. 



The Terrestrial Magnetic Effects of Solar Radi.\- 

 tion. — In an extract from del el Terre (No. 12, 1911) Dr. 

 A. Brester discusses the causes which produce the diurnal 

 oscillation of the magnetic needle and other terrestrial 

 magnetism effects. In the place of the vortices produced 

 by the heating effects of the solar radiation, he would 

 substitute vortices produced by solar kathode rays, and 

 he shows how the action of these would be concentrated in 

 the neighbourhood of the earth's poles where the greatest 

 oscillations of the needle are recorded. Further, he points 

 out that electrical tourbillons would not be disturbed by 

 ordinary atmospheric disturbances, and thus would give 

 regular changes such as are observed, and also that, the 

 electrical state of the sun depending on the solar activity, 

 his theory would account for the observed relation between 

 the diurnal oscillations of the needle and the number of 

 sun-spots. 



Absorption of Light in Space. — The Januan,- number 

 of the Monthly Notices contains an interesting paper by 

 Mr. F. G. Brown, in which the author discusses the 

 absorption of light in interstellar space. Taking all the 

 nebulae given in the N.G.C., he found approximate 

 measures of the intrinsic brightness of each by comparing 

 the total brightness, or conspicuousness, as given in the 

 N.G.C. with the diameter. Although this method of deal- 

 ing with the subject cannot be regarded as final, the results 

 are very striking, and indicate that the small nebula; 

 appear less bright per unit area than do the large nebulae, 

 or, in other words, the probably distant are fainter than 

 the probably near. Mi. Brown's preliminary investigation 

 also suggests that the absorption is different in different 

 directions through space. 



.An Observer's Handbook. — " The Observer's Hand- 

 book for iqi2," published by the Royal Astronomical 

 Society of Canada, is a valuable compendium of the data 

 likely to be required by the isolated amateur. It contains 

 various ephemerides and tables, useful star-charts, notes 

 on the constellations and phenomena for each month, 

 tables showing the times of sunrise and sunset for each 

 day in latitudes 44°-52°, and brief accounts of the eight 

 comets of iqii. The handbook contains sixty-four pages, 

 and is sold for 25 cents at the society's rooms, 198 College 

 ' Street, Toronto. 



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