July 2, 1908J 



NA TURE 



207 



OVR ASTRONOMICAL COLUMN. 



AsTKONOiMICAL OCCURRENCES IN JULY : — 

 July 4. Opposition of Juno. 



7. Uranus in opposition to the Sun. 

 ,, Satuin. Outer minor axis of outer ring =5"'68. 

 9. I2h. 57m. Minimum of Algol (;3 Persei). 

 12. 9h. 46m. ,, ,, ,, 



16. loh. 59m. to I2h. 3m. Moon occults t^ Aquarii 



(mag. 4-3). 

 18. i6h. ilm. Saturn in conjunction with Moon. Saturn 



3° 2' N. 

 22. i6h. 35m. Western elongation of Saturn's Satellite 



Titan. 

 25. loh. Mercury at greatest elongation, 19° so' W. 

 27-31. Epoch of the .■\quarid and early-Perseid meteors. 



29. I5h. Vesta 0° I' S. of Moon. 



,, Venus. Illuminated portion of the disc =0"I53- 



30. i6h. Eastern elongation of Saturn's Satellite Titan^- 



A Bright Meteor. — A magnificent meteor, with a long 

 path and very slow motion, was observed on June 28 

 iih. 12m. by Mr. Denning at Bristol, and by the Rev. 

 John Brown at Brighton. At Bristol, the apparent course 

 was recorded as from 276° + 23° to i° + 48=°, while at 

 Brighton the object passed just under the stars 3 and 7 

 of Ursa Major, and just above Cor Caroli, the direction 

 being from $ Scorpii. 



Mr. Denning has investigated the real path, and found 

 the heights eighty-seven to fifty-four miles over Dorchester, 

 Borset, to Kineton, Warwick. Length of observed flight 

 123 miles, and velocity 175 miles per second. Radiant 

 point 240° — 20°, and about 10" W. of the usual radiant 

 of the June shower of Scorpild fireballs. The meteor had 

 a bright train of sparks, and sailed along a considerable 

 arc (70°), the duration at Bristol being estimated as seven 

 seconds and at Brighton six to eight seconds. 



Computed Magnitudes for Halley's Comet before 

 Perihelion. — In No. 4254 of the Astronomische Nach- 

 richten (p. 99, June 13) Prof. J. Holetschek discusses the 

 probable magnitudes of Halley's comet during the two 

 oppositions which are to come before it arrives at peri- 

 helion. Monthly ephemerides show the probable positions 

 of the comet for October, 1908, to March, 1909, according 

 to the assumptions that perihelion passage will take place 

 on May 16, 1910, thirty days earlier or thirty days later, 

 and the geocentric and heliocentric distances are also 

 shown. Then follows the table giving the probable magni- 

 tudes for the same period, and also for September and 

 October, 1909. From this we see that for October 2, 1908, 

 the probable magnitude is 18-2, the comet increasing in 

 brightness until, on October 2, 1909, its magnitude should 

 be 14-6. 



The Revised Harvard Photometry. — We have just 

 received a copy of vol. 1. of the Annals of the Astronomical 

 Observatory of Harvard College, in which is published the 

 revised Harvard photometry. This comprises a catalogue 

 of the positions, photometric magnitudes, and spectra of 

 the 9 no stars, mainly of magnitude 6-50 and brighter, 

 which were observed with the 2-inch and 4-inch meridian 

 photometers, in all parts of the sky, during the years 1879 

 to 1906. Some idea of the magnitude of the work may be 

 gathered from the fact that the observations involved a total 

 number of 1,082,060 photometric settings. In the catalogue 

 itself the stars are given consecutive numbers, and are 

 arranged in order of R..\. as usual. Then follows the 

 designation for each star in other catalogues, the position 

 for 1900, the magnitude, the residuals, and the combina- 

 tion of letters and figures which denotes the spectral type. 

 It is proposed by Prof. Pickering that the abbreviation 

 H.R. shall be used when referring to a star's designation 

 in the present catalogue. Several pages of " remarks " 

 which follow the catalogue proper give valuable notes 

 concerning stars which are in any way peculiar. 



The Parall.4Xes of Nebul.e. — From a re-discussibn of 

 Prof. Wilsing's results for the parallaxes of the two 

 tnebulae G.C. 4964 and N.G.C. 7027, Herr Einar Huss, of 

 Stockholm, derives new definitive values which, in each 

 ca^;!.. show a reduction of the negative values obtained by 

 Prof. Wilsing. For G.C. 4064 the latter observer found 



N'O. 201S, VOL. 78] 



the parallax — o"-o83 +o"-025, whereas Herr Huss derives 

 the value — o"-o63 +o"-o50 ; for N'.G.C. 7027 the respective 

 values are — o"'i72 +o".o68 and — o"'ii9±o"'02i. "Taking 

 into account the facts that the observations were made at 

 about the same epoch, and that the objects are in the 

 same part of the sky, Herr Huss considers that there is 

 evidence that, of the two, the nebula N.G.C. 7027 is the 

 more remote (Astronomische Nachrichten, No. 4254, 

 p. 96). 



Occultation of Jupiter's Satellite II. by S.itellite I. 

 In No. 4255 of the Astronomische Nachrichten (p. 119, 

 June 18) Prof. Hartmann places on record the results 

 obtained from observations of the occultation of J. ii. by 

 J. i. on February 24. The observations were made with 

 the 50 cm. refractor of the Potsdam Observatory, a power 

 of 450 being used, and the best value for the time of the 

 middle of the conjunction is given as gh. 45m. 32s. + 5s. 

 (M.E.T.). 



Solar Prominences in 1907. — Prof. Ricci's summary of 

 the results of the prominence observations made at the 

 Catania Observatory during 1907 appears in No. 5, vol. 

 xxxvii. (p. 83), of the Memorie delta Societd degli Spettro- 

 scopisti Italiani ; the usual data regarding the latitudes, 

 heights, and extensions at the base are given, and the 

 complete results summarised. The mean heliographic 

 latitude, for both hemispheres, was 29°.4, being 1° less 

 than in 1906 ; a notable maximum occurred in the third 

 quarter in latitude 8o°-85° south. In the northern hemi- 

 sphere, for the whole year, there were two well-defined 

 maxima (in latitudes so^-eo" and 20°-30°), and in the 

 southern hemisphere there were three (latitudes io°-20°, 

 4o°-5o°, and So'-go"). During the first five months the 

 number of prominences in the northern hemisphere pre- 

 ponderated, but for the last seven months the southern 

 hemisphere showed the greater numbers ; the numbers- 

 observed for the whole year were 381 and 447 respectively. 



The Temperature and Structure of the Sun. — In a 

 lecture delivered before the Philosophical Society of 

 Washington, and now printed as a bulletin of the society 

 (vol. XV., pp. 75-101, May), Dr. O. Lummer gave an 

 interesting and suggestive resume of our present know- 

 ledge concerning the probable temperature and structure 

 of the sun. From a discussion of the laws of radiation 

 as applied to the observed solar values, he arrives at the 

 conclusion that the temperature may, with reasonable 

 certainty, be assumed to be about 7000°. As such a 

 temperature surpasses the critical temperature of all 

 terrestrial substances. Dr. Lummer concludes that a sharp 

 limit between a liquid and a gaseous mass on the sun is 

 physically impossible. On the basis of this conclusion he 

 discusses the probable structure of the sun's envelopes, and 

 finds that most of the spectral phenomena observed, e.g. 

 the broadening of lines in sun-spots and the distortion and 

 displacement of various lines in prominences, can be 

 accounted for by the assumption that they are produced 

 by anomalous dispersion in the various layers of the sun's 

 atmosphere. 



THE ROYAL SOCIETY CONVERS.iZIONE. 



'T'HE annual conversazione to which ladies as well as 

 gentlemen are invited by the Royal Society was held 

 in the society's rooms at Burlington House on Monday. 

 Most of the objects of scientific interest exhibited on this 

 occasion were the same as those shown at the conversazione 

 in May, and already described in these columns (May 21, 

 p. 58). A few additional exhibits may, however, be re- 

 ferred to here to supplement the previous article. .^s 

 before, we summarise the descriptions in the oflficial cata- 

 logue, after arranging together related subjects. 



Dr. George E. Hale and Mr. Ferdinand EUerman : 

 Astrophysical photographs taken at Mount Wilson Solar 

 Observatory, Pasadena, California. — Tlie Director of the 

 Meteorological Office : Zoetropic apparatus exhibiting the 

 progress of a travelling storm-centre and the circulation of 

 air associated therewith. By means of a series of maps, 

 upon which the isobaric lines and corresponding' steps of the 

 trajectories are drawn, and an ordinary zoetropic apparatus, 

 viz. a revolving drum with slits through which the 



