104 



SCIENCE. 



[Vol.. II., No. 25. 



results of the nadir-observations to make them agree 

 in the mean with the results of the refleclion-obser- 

 vaticms of stars. This discordance was in-ignificant 

 in 1S7S, and is on the increase: its source has not 

 yet been traced. Three determinations of fle.Kure 

 have been made during the year. The correction for 

 jfj— O, the error of assumed co-latitude, and the posi- 

 tion of the ecliptic, have been investigated for 1882. 

 The value for the co-latitude, from the observations of 

 1S82, is 38° 31' 21".98. The correction to the tabular 

 obliquity of the ecliptic is -I- 0".44. The mean error 

 of the tabular right ascension of the moon, from 

 observations with the transit-circle, is -f 0".82. 



The (ibservalious of the moon with the altazimuth 

 have been restricted to the seini-lunatiou between 

 last quarter and first quarter ; ami some limitations 

 have been adopted in the computations wliich 

 render the reduction of observatiims with this in- 

 strument comparatively light. The moon's diameter 

 has been measured thirty-three times, counting meas- 

 ures in both co-ordinates with the transit-circle and 

 the altazimuth. 



A very valuable addition has been made to the 

 instruments of the Royal observatory by the gift of 

 the Lassell two-feet reflecting equatorial, generously 

 presented by the Misses Lassell. This is tlae instru- 

 ment with which the Saturnian satellite Hyperion was 

 discovered in 1848. It was removed from Maiden- 

 head early in March, and has been suitably mounted 

 in the grounds of the Royal observatory. The tele- 

 scope has two large mirrors available for use; and 

 the astronomer royal contemplates attaching one of 

 them to the tube of the ' south-east equatorial,' which 

 has a firm mounting and a perfect clock-work, and 

 employing it for spectroscopic and photographic 

 work. The Lassell telescope itself is well suited for 

 the observation of faint satellites and comets which 

 are beyond the present instrumental means of the 

 observatory. 



The observations of the solar eclipse of 1882, May 

 17, with the south-east equatorial, have been com- 

 pletely reduced, and the final equations solved. 



Spectroscopic observations during twelve months 

 have been somewhat restricted through the pressure 

 of photographic reductions at the time of a maxi- 

 mum of sun-spot frequency. The solar prominences 

 were observed on eight days, and four sun-spots 

 were examined on eight days with reference to 

 broadening of lines in their spectra. The spectrum 

 of the great spot of 1882, Nov. 12-25, showed some 

 remarkable reversals of the lines of hydrogen and 

 sodium, and extraordinary displacement of the F line. 



As regards determinations of motion of stars in the 

 line of sight, a hundred and forty-two measures have 

 been made of the displacement of the F line in the 

 spectra of twenty-three stars, and twenty-six meas- 

 ures of the line bi in nine stars. The observations 

 of Sirius during the past winter tend, on the whole, 

 to confirm tlie impression that the rate of recession 

 of this star had diminished progressively since 1877, 

 and that its motion is now on the point of being 

 converted into one of approach. 



The spectrum of comet a 1882 was examined on 

 three nights; that of the great comet 6 1882, also on 

 three nights; and that of comet a 1883, on one night. 

 The spectrum of the first-named object showed the 

 yellow sodium-lines with great brilliancy just before 

 perihelion passage. The spectrum of the aurora 

 was also examined in 1882, Nov. 17. The spectro- 

 scopic observations of all kinds are completely re- 

 duced to 1883, May 20. 



During the year ending at this time, photographs 

 of the sun were taken on two hundred days, and 

 three hundred and thirty-nine plates have been 

 selected for preservation. The sun's disk was free 

 from spots on seven days; and, since the extraordi- 

 nary outburst of last November, the sun has been 

 comparatively quiescent. The astronomer royal pro- 

 poses soon to employ a modififd photoheliograph for 

 this work, so as to obtain photographs of the sun 

 eight inches in diameter instead of four. The meas- 

 urement of a large number of Indian and other 

 photographs of the sun, required to fill gaps in the 

 Greenwich series, has been completed, these photo- 

 graphs having been received from the Solar physics 

 comniiltee. 



The course of the magnetic observations has 

 remained the same as in former years. Improve- 

 ments have been made in the methods of photo- 

 graphic registration. There has been considerable 

 magnetic activity during the year. The disturbances 

 of November last are to be detailed graphically in the 

 ' Greenwich magnetic results for 1882.' Particulars 

 of magnetic disturbances are regularly communicated 

 to the Colliery guardian newspaper, for the infor- 

 mation of raining surveyors. 



The mean temperature of 1882 was 49°.6, or 0°.l 

 lower than the average. The highest air-tempera- 

 ture was 81°.0, on Aug. 6; and the lowest, 22°.2, on 

 Dec. 11. The mean monthly temperature was above 

 the average from January to May, then below until 

 September, and differed little from the average dur- 

 ing the remainder of the year. The mean daily 

 motion of the air was 306 miles, 27 miles greater 

 than the average. The greatest daily motion was 758 

 miles, on Nov. 4; and the least, 3U miles, on Dec. 11. 

 The greatest hourly velocity was 64 miles, Oct. 24. 

 The number of hours of bright sunshine, as recorded 

 by Campbell's sunshine instrument, was 1,245; that 

 is, 40 hours above the average of the five preceding 

 years. The rainfall of 1882 was 25.2 inches, slightly 

 above the average. 



In c<mclusiou, the restriction in the observations 

 of the moon with the altazimuth enables more 

 attention to be given to observations with the equa- 

 torials. Two observers are now available for spectro- 

 scopic observations during the coming year. Mr. 

 Christie characterizes the past year as, in some 

 slight degree, one of transition, and preparation for 

 future work. Some administrative changes have 

 been made; but the regular course of observation 

 and reduction has not been disturbed, and the stand- 

 ard meridian observations have been maintained in 

 full vigor. 



