554 



NATURE 



[Oct. 4, 1888 



was very dark, or was moving with the same speed amongst the 

 stars as the moon, but in the opposite direction, in which case 

 it would have been mistaken for a star. 



Photometric Observations of Asteroids.— It has fre- 

 quently been suggested that the asteroids, shining by reflected 

 light, and subject, it might be assumed, only to variations the 

 amount of which could be calculated for any required date, would 

 prove specially useful as standards of brightness in the photo- 

 metric observation of the fainter stars. Mr. Henry M. Park- 

 hurst has carried out recently a series of observations on several 

 of these bodies, which throws considerable light on their suit- 

 ability for such a purpose. His method of observation was to 

 note the time which the asteroid took to disappear after passing 

 a transit-wire, the telescope being stationary, and the light of 

 the asteroid or comparison-star suffering diminution either by a 

 wedge or more frequently by a deflector — a piece of glass with 

 nearly parallel sides, placed in the telescope tube, about one- 

 seventh of the way from the focus, and covering half the field. 

 The results of Mr. Farkhurst's observations, which embraced 

 eighteen asteroids, and extended over nearly nine months — 

 April to December 1887 — are given in No. 3 of vol. xviii. 

 of the Annals of the Harvard College Observatory, and show 

 that the asteroids are not appreciably self-luminous, and that 

 the sun undergoes no noteworthy fluctuations in light in periods 

 of a few days ; nor, as a comparison with observations made in 

 some former years would indicate, in more lengthened periods. 

 But they also show that the phase-correction is not covered by 

 allowing simply for the decrease in the area illuminated— a further 

 correction is needed, and one peculiar to each asteroid. In two 

 case-, also, Harmonia and Iris, several of the observations 

 stand out in strong contrast to the rest, and appear to indicate a 

 variation due to axial rotation, the planet probably being 

 irregular in shape, or its surface in reflecting power. No varia- 

 tion depending, as in the case of Saturn's ring, on the position 

 of the asteroid in its 01 bit, and the relative position of the earth, 

 has been noticed, but this inquiry has only been extended to the 

 four asteroids first discovered. The mean error of an observa- 

 tion, when the special phase correction and probable variations 

 due to rotation have been allowed for, appears to be less for an 

 asteroid than for the fixed stars, the mean error of an observa- 

 tion of the solar illumination in the inquiry referred to above 

 being given as o - n6m. 



New Catalogue of Variable Stars. — Nos. 179 and 180 

 of Gould's Astronomical Journal contain a new catalogue of 

 variable stars by Mr. S. C. Chandler. Mr. Chandler is not 

 only a diligent observer of variable stars, the discoverer of 

 several, and a zealous computer of the elements of their varia- 

 tions, but several years ago undertook an important and much- 

 needed work, viz. the complete study of the bibliography of 

 known and suspected variables. This cttalogue coming from 

 his hand, therefore, will be especially valuable, and the more 

 welcome since it is thirteen years since Schonfeld published his 

 second catalogue. Mr. Chandler puts it forward as merely a 

 preliminary publication, a second more definitive being designed 

 to follow as soon as the investigations now in hand shall have 

 been completed. The present catalogue is no mere compilation. 

 Almost every star in it visible from the latitude of Boston has been 

 observed by Mr. Chandler, who has also gathered together and 

 discussed every available published observation. The calalogue 

 embraces 225 stars, and of these the variations of 160 are dis- 

 tinctly periodic ; for 12 the periodic character is ill-defined, 14 

 are irregular, 12 are Novae, and the remainder have been too 

 little observed for the character of the variation to be properly 

 known. Of the 160 periodic stars, the elements of 124 are the 

 results of Mr. Chandler's own work, 22 are Schonfeld's, and 14 

 those of other computers after Mr. Chandler had carefully con- 

 firmed them. A point sure to lead eventually to an important 

 advance in our knowledge of the cause of variation has received 

 much attention from Mr. Chandler, viz. the systematic perturba- 

 tions shown by so many of the periods, and a table is given of 

 these inequalities for 26 stars. A useful novelty is introduced in 

 the numeration of the stars of the catalogue, for, in-tead of giving 

 them consecutive numbers, each is distinguished by a number 

 equivalent to one-tenth of its R.A. for the mean equinox of 

 1900*0, expressed in seconds of time, thus securing that the 

 numeration need not be disturbed by fresh discoveries. 



Minor Planet No. 275. — This object has been named 

 Sapientia. 



ASTRONOMICAL PHENOMENA FOR THE 

 WEEK 1888 OCTOBER 7-13. 



/"pOR the reckoning of time the civil day, commencing at 

 ' Greenwich mean midnight, counting the hours on to 24, 



is here employed.) 



• At Greenwich on October 7 

 Sun rises, 6h. 13m. ; souths, nh. 47m. 40 # 2s. ; sets, I7h. 22m. : 



right asc. on meridian, I2h. 53"9jx ; decl. 5 46' S. 



Sidereal Time at Sunset, i8h. 29m. 

 Moon (at First Quarter October 12, 5h.) rises, 8h. 18m. : 



souths, I3h. 38m. ; sets, i8h. 46m. 



nh. 44 - 6m. ; decl. 10° 51' S. 



Planet. Rises. Souths. Sets, 



h. m. h. m. h. m. 



Mercury.. 8 47 ... 13 19 ... 17 51 ... 14 257 ... 17 24 S. 



Venus ... 8 27 ... 13 17 ... 18 7 ... 14 23-4 ... 14 7 S. 



Mars ... 12 18 ... 16 3 ... 19 48 ... 17 9-5 ... 24 33 S. 



Jupiter ... 10 50 ... 15 2 ... 19 14 ... 16 9 - 2 ... 20 28 S. 



Saturn ... 46 ... b 16 ... 15 46 ... 9 21 8 ... 16 17 N. 



Uranus... 6 27 ... 11 59 ... 17 31 ... 13 5-2 ... 6 17 S. 



Neptune.. 19 10*... 2 56 ... 10 42 ... 4 1*3 ... 18 54 N. 



* Indicates that the rising is that of the preceding evening. 



Occultations of Stars by the Moon (visible at Greenwich). 



Corresponding 



right asc. on meridian, 



Right asc. and declination 

 on meridian, 

 h. m. „ . 



Oct. 



11 . 



12 , 



13 • 



Oct 



7 



Star. 



B.A.C. 6524 ... 

 B.A.C. 6889 ... 

 20 Capricorni ... 

 h. 



Mag. 



6i 



6 



6 



Disap. 

 h. m. 



20 35 

 19 53 

 19 5 



Reap. 



h. m. 

 21 17 

 21 6 

 19 55 



angles from ver- 

 tex to right for 

 inverted image. 



... 72 O 

 ... IIO 3II 

 ••■ 153 24O 



4 ... Venus in conjunction with and 5 6' south 

 of the Moon. 



7 ... 5 ... Mercury in conjunction with and 8° 8' •' juth 



of the Moon. 



8 ... 6 ... Mercury at greatest elongation from the 



Sun 25 west. 



9 ... 1 ... Jupiter in conjunction with and 3 33' south 



of the Moon. 

 9 ... 22 ... Mercury in conjunction with and 3 9' south 



of Venus. 

 10 ... 3 ... Mars in conjunction with and 4° 38' south 



of the Moon. 

 10 ... 13 ... Uranus in conjunction with the Sun. 



Saturn, October 7. — Outer major axis of outer ring = 38" "9 : 

 outer minor axis of outer ring = 9"'8 : southern surface visible. 

 Variable Stars. 





