520 



NA TURE 



[September 25, 1890 



OUR ASTRONOMICAL COLUMN. 

 Objects for the Spectroscope. 

 Sidereal Time at Greenwich at lo p.m. on September 25 

 22h. 1 8m. 40s. 



Remarks. 



(i) According to the observations of Huggin and D' Arrest, 

 this nebula has a continuous spectrum, but further observations 

 for "irregularities" or bright flutings should be made. The 

 nebula is described as "Bright; pretty large; pretty much 

 elongated in the direction 160°; suddenly much brighter in the 

 middle." 



(2) Duner compares the spectrum of this star of Group II. 

 wfith that of o Herculis, and states that "it is one of the finest 

 in the northern sky." The bands 2-9, including 6, are very 

 wide and dark, and the spectrum is one which may be advan- 

 tageously studied. Light-curves of spectra of this type are 

 valuable, as they show the relative extent of carbon radiation, 

 and therefore serve as a cross check in the classification which is 

 made on other grounds. 



(3) The spectrum of this star is one of Group II., in which 

 bands 2, 3, and 7 are dark but not very wide, and bands 4, 5, 

 and 8 are feeble and narrow. Duner thinks it almost inter- 

 mediate between Group II. and Group III., but in this he is 

 probably mistaken, as the description agrees almost exactly with 

 that of 75 Cygni (see p. 511), which turns out to belong to an 

 early and not a late species of the group. In that case the bright' 

 carbon flutings are predominant, and it will probably be found 

 that this applies also to the star in question. Here, again, a 

 light-curve of the spectrum compared with that of a star like (2) 

 should emphasize this point. 



(4) This star has a spectrum which is almost Group IV., the 

 hydrogen lines being considerably broad, but, at the same time, 

 b and D are seen without much difficulty. Its proper place on 

 the temperature curve is therefore the last stage of Group III. 

 It may be remarked that with the same thickness of F in a star 

 of Group v., the metallic lines would not be so prominent. One 

 need only compare Aldebaran and Capella to see this difference 

 in the intensities of the metallic lines in Groups III. and V. 



(5) A star of Group IV. 



(6) In the spectrum of this star of Group VI. no secondary 

 bands were seen with certainty by Duner, and although the 

 green and yellow zones are very bright, the blue light is very 

 feeble. It seems as if in some of these stars there is more con- 

 tinuous absorption than in others, and comparative light-curves 

 of the spectra of stars of the group might throw light upon this 

 point. This again would probably enable us to determine the 

 relative temperatures of the different stars. The intensity 

 of the blue zone certainly does not depend altogether upon 

 magnitude. 



(7) The approaching maximum of this variable (October 4), 

 will offer another opportunity of determining the character of its 

 spectrum. It is much to be regretted that 50 many variables 

 have as yet unknown spectra, and the sooner they are observed 

 the better. T Herculis has a period of about 165 days, and 

 ranges from 6"9-8'3 at maximum to Ii'4-I2'7 at minimum 

 (Gore). A. Fowler. 



Solar Activity from January to June 1890. — Prof. 

 Tacchini has just presented to the Paris Academy of Sciences a 

 note on the distribution in latitude of solar phenomena observed 

 by him during the first half of this year {Coinptes rendui, 

 September 15). Hydrogen prominences have been more frequent 

 in the southern hemisphere than in the northern, and reached a 

 maximum of frequency in the zone included between the latitudes 

 40°-5o°. This was also the case in 1889 (Comptes rcndus, 

 May 5, 1890). During the second quarter of this year pro- 

 minences have been observed very near to the poles, which 



indicates that solar activity is on the increase. Faculse show 

 maxima of occurrence at the same distance from the equator in 

 both hemispheres, viz. 20°-3o°. The maximum frequency in 

 the northern hemisphere is more marked, however, than in the 

 southern. The distribution of groups of spots is the same as 

 that of faculse, hence Prof. Tacchini concludes that we have 

 reached a period of change in the distribution in latitude of solar 

 phenomena ; for whilst prominences have maintained a pre- 

 dominance in the southern hemisphere, faculre and spots have 

 been more frequent in the northern. The absolute number of 

 groups of spots during the second quarter of this year was greater 

 than that of the first quarter, thus indicating that the minimum 

 period has definitely passed. 



The Telluric Spectrum. — In the current number of 

 V Astronoviie M. Janssen gives a short account of his work in 

 Algeria on the telluric spectrum. The object of the expedition 

 was to photograph the solar spectrum on isochromatic plates- 

 when the sun was respectively on the meridian and horizon. By 

 the use of such plates, having maxima of sensibility at the less 

 refrangible end of the spectrum, the increase in intensity of the 

 most important telluric lines, which accompanied a decrease in 

 the sun's altitude, may be strikingly demonstrated. The ob- 

 servations were made from a small fort near Biskra, situated on 

 the edge of the Sahara, and having an uninterrupted view 

 towards the south. The solar spectrum was obtained by means 

 of a Rowland's grating, and many photographs were taken 

 during the three months of observation. Their discussion is not 

 yet completed, but M. Janssen notes that without the purity of 

 the sky at the place of observation and the continuance of fine 

 weather it would have been impossible to obtain any useful 

 results. An excursion was made to Tuggurt in order to study 

 the solar spectrum from one of the driest places on our globe. 

 Some photographic observations of mirages were also made at 

 the same time, and are said to throw much light on the nature 

 of the conditions necessary for the production of these singular 

 phenomena. 



The Perseid Meteors. — In Co?nples rendus for September 

 15, Prof. Denza gives an account of the observations, made in 

 Italy from August 9 to 11 under the direction of the Italian 

 Association for the Observation of Meteors. From the results 

 obtained at the thirty stations it is concluded : — 



(i) The number of luminous meteors, especially on August 

 1 1 and 12, was greater than in preceding years, and has relatively 

 attained a maximum. This appears to prove that the earth has 

 cut through a condensation in the meteoritic ring. 



(2) The meteoritic shower, which formerly began on August 

 10, appears to have suffered a retardation, and now begins on 

 August II. 



(3) The following are the numbers of meteors observed at 

 some of the stations : Vatican Observatory, 197 1 ; Florence, 

 1749; Aprica, 1740; Gaeta, 1305; San Martino in Pensili, 

 1276 ; Moncalieri, 1036. 



(4) The radiant of the principal shower was found to have the 

 same position between Perseus and Cassiopeia as has previously 

 been noted. 



(5) Other radiants were also observed, and notably in Ursa 

 Major and Ursa Minor, Cygnus and Andromeda. 



(6) Most of the meteors seen had the yellow colour charac- 

 teristic of this swarm. 



•(7) The shower was a remarkable one this year, not only 

 because of the great number of meteors, but also because of 

 their large size. 



Natal Observatory. — From the annual report of the 

 Government Astronomer of this Observatory for 1889 it appears 

 that the principal work in progress is a comparison of the 

 declinations deduced from observations made at Observatories 

 in the northern and southern hemispheres by a comparison by 

 Talco's method of the zenith distances of northern stars and 

 circumpolars both above and below the pole. Some irnportant 

 results have also been obtained from an investigation into the 

 present theory of lunar motion. The meteorological observa- 

 tions made during 1889 have been tabulated, and will be found 

 useful. 



NO. 109 1, VOL. 42] 



THE NARRABURRA METEOR. 

 ^HE Narraburra meteor was found in the year 1854, by Mr. 

 O'Brien, in lat. 34° 10' S., long. 147° 43' E., which is a point 

 the Narraburra Creek about 12 miles east of Temora. When 



