128 



NATURE 



[June 8, 189; 



preceding being ii'i, and the greatest in any of these 

 years 38 (in 1885), and that 24 groups of clock stars, 

 extending over more than twelve hours, were obtained, 

 the mean for ten years preceding in March and April 

 being 2"6. In the last case something must be attributed 

 to the special interest shown by the observers recently 

 in obtaining long groups of clock stars. 



The apparent correction for discordance between the 

 nadir observations and stars observed by reflexion for 

 1892 is o""25, and has been persistently negative for 

 some months. An investigation of the screws of the 

 microscopes used showed that several of them are the 

 worse for wear. 



From the observations of 1892 the west latitude of the 

 transit circle was found to be 38° 31' 22"'io, a value differ- 

 ing by + o"'2o from that adopted. Recent investigations 

 have made it probable that the co-latitude undergoes 

 fluctuations of short period : and in comparing the ob- 

 servations in the individual years 1877-86 with the final 

 results in the Ten Year Catalogue, confirmatory evidence 

 of these fluctuations was found. Mr. Thackeray was 

 thus led to undertake an examination of all the obser- 

 vations of N . P. D. of the four close circumpolar stars since 

 1851. The results were found to accord well with Mr. 

 S. C. Chandler's hypothesis {Astronomical Journal, No. 

 277), and have been communicated to the Royal Astro- 

 nomical Society (vide Monthly Notices, liii. p. 3). 



The correction to tabular obliquity of the ecliptic from 

 solar observations in 1892 is -|- o"-44, which is rather a 

 large quantity. The discordance between the results from 

 the summer and winter solstices is + o"'4o, indicating that 

 the mean of the observed distances from the pole to the 

 ecliptic is too small by -|- o"'2o, and thus confirming the 

 stellar observations for co-latitude. 



Computing the value from Hansen's lunar tables, the 

 mean error of the moon's tabular place was found to be 

 + 0083s. in R.A. and -)- i"'29 in longitude, as deduced 

 from ninety-five observations in 1892 ; this agrees well 

 with the results obtained in 1891. The mean value of 

 these quantities for the ten years 1883-92 are -|- o'044s. 

 and -|- o"'6i. The mean error of the moon in N.P.D. 

 for 1892 was — o"27. 



Owing to great pressure of longitude and other work, 

 the work with the altazimuth was suspended from May 

 to October 18, 1892, the number of observations falling 

 below that usually recorded. The total number in the 

 year ending May 10, 1892, is — 



Azimuth of the Moon and Stars 



,, ,, Mark I. 



,, ,, Mark II. 

 Zenith distances of the Moon... 

 „ „ Mark I. 



„ „ „ Mark II. 



167 

 62 

 64 

 62 

 60 

 62 



The provision of the new universal transit-circle to 

 replace the existing altazimuth, and to serve as a duplicate 

 meridian instrument for fundamental determinations, 

 with suitable building and dome, having been sanctioned 

 by the Government, its construction has been entrusted 

 to Messrs. Troughton and Simms, who are now preparing 

 the working drawings. This instrument will be erected 

 to the north of the Magnetic Observatory. Some difficulty 

 seems to have occurred with regard to the siderial 

 standard clock, which on June 26 was found to have 

 stopped. An examination soon showed that the oil on 

 the escape pivots had thickened. At the beginning of 

 this year the maintaining power was strengthened, and 

 the barometric inequality adjusted. 



Owing to the fact of the new dome only being 

 recently completed, the tube of the 28-inch refractor, 

 together with the declination axis cones, declination 

 circle, and clamping circle are not yet in place. The 

 object glass is at the Observatory, and ready for 

 mounting. 



NO. 1232, VOL. 48] 



Last May the Merz refractor (12 J inch) of the south- 

 east equatorial was mounted in place of the Lassell 2-feet 

 reflector, the same mounting carrying the Thompson 

 9-inch photographic telescope. 



Since February Mr. Lewis has used this instrument 

 for double-star work, and he has made 545 measures of 

 position angle, and 609 of distance of 85 pairs ; 32 pairs 

 being less than i" apart, 26 between i " and 2", 8 between 

 2" and 3", and 19 over 3". 



With regard to occultations, 26 disappearances and 7 

 reappearances of stars by the moon have been observed, 

 including 7 disappearances and 3 reappearances observed 

 during the lunar eclipse of May 11, 1892, and 10 dis- 

 appearances of stars below the Nautical Almanac limit 

 of brightness (6'5), approximately predicted by Mr. 

 Crommelin. Disappearance of Uranus behind the Moon 

 on July 3, an occultation of 73 Piscium by Jupiter on 

 May 23, and 62 phenomena of Jupiter's satellites were 

 also observed. All these observations are completely 

 reduced to February 26, 1893. 



Among other miscellaneous observations made may be 

 mentioned : — Observations of comets, differences of R. A. 

 and N.P.D. of Saturn and y Virginis, on the occasion of 

 their conjunction ; and of Mars and Ceres at the time of 

 their conjunction, &c. 



With the Astrographic equatorial 722 plates, with a 

 total of 1 81 2 exposures, have been taken on 161 nights 

 in the year ending May 10, and of these 1 16 have been 

 rejected, viz. 57 from photographic defects, 6 from me- 

 chanical injury, 12 from mistakes in setting, 6 from the 

 plate being wrongly placed in the carrier, 7 from failure 

 in clock driving, and 28 from interference by cloud. The 

 following statement shows the progress made with the 

 photographic mapping of the heavens in the year. May 

 II, 1892, to May 10, 1893 : — 



No. of 

 Photos 

 taken. 

 200 ... 183 



Successful 

 Plates. 



Astrographic Chart (exposure 40m.) 

 Plates for Catalogue (exposures 6m., 3111., 



and 20s.)... 367 ... 288 



Number of Fields photograped for the 



Chart — ... 172 



Number of Fields photographed for the 



Catalogue ... ... .. — ... 271 



Total number of Fields photographed since 



the commencement of the work for the 



Chart — ... 176 



Total Number of Fields photographed since 



the commencement of the work for the 



Catalogue — ... 299 



It has been made a practice to take a trail on each 

 night on a catalogue plate as a check on the orientation, 

 and during the past year 127 plates with trails have been 

 thus secured. 



With the same instrument, and included in the 722 

 mentioned above, were taken photographs of Nova AurigK 

 (49), for zero of scales and orientation (36), lunar eclipse. 

 May II (4), Comet Holmes (2), Saturn (5), conjunction of 

 Saturn and 7 Virginis (16), &c. 



Experimental plates of Jupiter, Saturn, double stars, 

 &c., have also been taken with the image enlarged about 

 fourteen times by a secondary magnifier, consisting of a 

 triple cemented concave lens of if inches diameter, and 

 3 inches focus, suppUed by Mr. T. R. Dallmeyer. The 

 results, as the report states, are very promising. 



No spectroscopic observations have been made during 

 the past year, the regular observations for stellar motion 

 in the line of sight having been interrupted by the dis- 

 mounting of the south-east equatorial, and there being 

 great pressure in the solar photographic work. The tele- 

 scope and camera of the Dallmeyer photoheliograph were 

 again removed on September 9, 1S92, from the wooden 

 dome, where the new buildings obscured the horizon, to 

 the first floor of the new museum, where they were re- 



