I40 



jVA TURE 



\yune 6, 1889 



is being mounted on the Sheepshanks equatorial for trial. A 

 number of photographs of stars have been taken with the experi- 

 mental 6-inch object-glass, supplied as a preliminary to the con- 

 struction of the 13-inch, which is to take part in the construction 

 of the photographic map of the heavens. Only inconclusive 

 results have, however, as yet been obtained. The spectroscopic 

 work has mainly consisted of observations of motion of stars in 

 line of sight. We read : — 



" For determination of motions of approach or recession of 

 stars, 236 measures have been made of the displacement of the 

 F line in the spectra of 38 stars, and 18 of the b line in the 

 spectra of 8 stars, besides 5 of the b line in the spectrum of 

 Saturn's ring, and comparisons with the spectra of the mom, 

 Venus, the sun, or the sky, as a check on the general accuracy 

 of the results. Observations of Algol on three nights during the 

 past year confirm the previous results indicating orbital motion, 

 but further evidence is required to establish the fact. The spectra 

 of 7 Cassiopeia;, Ceti, ;8 Lyrse, P Cygni, R Cygni, and ;8 

 Pegasi, have been examined on several occasions, and Comet 

 e 1888 has been spectroscopically observed on one night, the 

 spectrum being chiefly continuous, The spectroscopic observations 

 of all kinds are completely reduced." 



Photographs of the sun have been taken 182 days in the year 

 ending on May 10, 1889. Indian and Mauritius sun photo- 

 graphs have been received from the Solar Physics Committee as 

 far as 1888 December 31 and December 9 respectively, and it is 

 noted that, by means of photographs from these two places sup- 

 plementing the Greenwich series, the daily photographic record 

 of the sun's surface is practically complete since the beginning 

 of 1882. For earlier years n8 photographs of the sun taken at 

 Harvard College, Cambridge, U.S.A., between 1874 December 

 9 and 1875 December 31, and ten photographs taken at Ely, 

 between January i and February 25, 1874, have been received 

 from the Solar Physics Committee. 



The photographs of the sun for 1888 show that it has been 

 free from spots on 155 days in the year 1888, the longest 

 spotless periods being February 4 to 17, May 24 to June 8, and 

 October 5 to 25. The mean spotted area in 1888 was half that 

 of the preceding year, and corresponded closely to that for 1877, 

 so that the minimum may be expected to occur during the pre- 

 sent year. The mean distance of spots from the equator has 

 also diminished to 7°'38 in 1888, being very little larger than it 

 was in 1878, just before the last minimum, and this is a further 

 indication that the sun-spot minimum is close at hand. The 

 faculse in 1888 show a diminution in correspondence with that 

 of sun-spots, their area for 1888 being intermediate between 

 those for 1876 and 1877. 



Continuous observation? of the changes in the three magnetic 

 elements of declination, horizontal force, and vertical force have 

 been photographically recorded. 



The following are the principal results for the magnetic 

 elements for 1888 : — 



Approximate mean declination 17'' 40' W. 



Mean horizontal force / 3 -9480 (in British units). 



/3-c 



Mean dip 



•8204 (in Metric units). 

 67° 24' 26" (by 9- inch needles). 

 67° 25' 33" (by 6-inch needles). 

 67° 26' 16" (by 3-inch needles). 



In the year 1888 there were only three days of great magnetic 

 •disturbance, but there were also about twenty other days of lesser 

 disturbance, for which tracings of the photographic curves will 

 be published, as well as tracings of the registers on four typical 

 •quiet days. 



The meteorological results are as follows : — 



"The mean temperature of the year 1888 was 47° 7, being 1° '6 

 below the average of the preceding forty-seven years. The 

 highest air temperature in the shade was 87"7 on August 10, 

 and the lowest 18° -4 on February 2. The mean monthly tempera- 

 ture in 1888 was below the average in all months excepting 

 May, November, and December. In March, April, July, and 

 October it was below the average by 3" 6, 3°-6,"4°-4, and 3°-9 

 respectively, and in November it was 4°-o above the average. 



''The mean daily motion of the air in 1888 was 296 miles, 

 being 12 miles above the average of the preceding twenty-one 

 years. The greatest daily motion was 790 miles on March 11, 

 ■and the least 57 miles on December 31. The only recorded 

 pressures exceeding 20 lbs. on the square foot were 31 lbs. on 

 -March 11, and 21 lbs. on August 28. 



" During the year 1888 Osier's anemometer showed an excess of 



about nineteen revolutions of the vane in the positive direction 

 north, east, south, west, north, excluding the turnings which are 

 evidently accidental. 



" The number of hours of bright sunshine recorded during 1888 

 by the Campbell-Stokes sunshine instrument was 1068, which is 

 about 250 hours below the average of the preceding eleven years, 

 after making allowance for difference of the indications with the 

 Campbell and Campbell-Stokes instruments respectively, and it 

 is 333 hours below that of 1887 recorded with the same instru- 

 meni , The aggregate number of hours during which the sun was 

 above the horizon wa> 4465, so that the mean proportion of sun- 

 shine for the year was 0*239, constant sunshine being represented 

 by I. A comparison has been made of the records of the 

 Campbell and Campbell-Stokes instruments forthetwelve months 

 from 1886 June i to 1887 May 31, with the result that the 

 former registered 1256 hours of bright sunshine, while the latter 

 registered 1364. It would appear, therefore, that the indica- 

 tions of the former instrument require to be multiplied by the 

 factor I -086 to make them comparable with those of the latter. 



"The rainfall in 1888 was 27*5 inches, being 2*9 inches above 

 the average of the preceding forty-seven years." 



The average daily number of chronometers and deck watches 

 being rated is 212, and the total number received up to May 10, 

 1889, was 668. The Astronomer-Royal notes that in future the 

 duration of the trial of deck watches will be increased from 

 twelve to sixteen weeks, viz. six weeks in the ordinary tempera- 

 ture of the room, four weeks in the oven (temperature 80' to 

 85"), and finally six weeks in the room. 



The Report concluded with a note on the re-determination of 

 the difference of longitude between Greenwich and Paris : — 



" Observations were made in four groups of three nights each 

 (or the equivalent in half nights). An English and a French 

 observer were stationed at each end, each with a separate in- 

 strument and chronograph, and the pairs of observers were 

 interchanged twice, to eliminate any change in the personal 

 equations during the progress of the work. The pairs of English 

 and French instruments were similar, and the signals as well as 

 the star transits were recorded on similar chronographs. On a full 

 night each observer recorded about forty star transits, reversing 

 his instrument three times, and exchanged signals twice (near 

 the beginning and end of the evening) with his compatriot at the 

 other end of the line, and once with the other observer. At 

 Greenwich the transits were referred to the sidereal standard 

 clock, and comparisons with the large Greenwich chronograph 

 enable the ordinary determinations of clock-error with the 

 transit-circle to be utilized as well as those specially made with 

 the portable transits. With this object transits of clock stars 

 with the transit-circle were usually taken by four observers on 

 each night during the longitude operations. The actual stations 

 were the Front Court of the Royal Observatory and the Observa- 

 tory of the Service Geographique de I'Armee at Paris, the 

 position of which reference to the Paris Observatory has been 

 accurately determined. Commandants Bassot and Defforges 

 were the French observers, and Mr. Turner and Mr. Lewis 

 the English. The observations lasted from September 23 to 

 November 15, and 18 nights of observation at both stations are 

 available, the two English observers having observed at Greenwich 

 653 transits of clock stars and 165 of azimuth stars, and at Paris 

 778 transits of clock stars and 165 of azimuth stars. All of 

 these, as well as the signals exchanged, have been read out from 

 the chronograph registers and the reductions are far advanced. 

 Subsidiary investigations of the value of a revolution of micro- 

 meter screw, of intervals of wires, of form of pivots, and of 

 errors of the axis-level have consumed much time, the last-named 

 having been a long and tedious discussion." 



The difference in longitude between Greenwich and Dunkerque 

 will be determined this month, and Commandant Defforges also 

 proposes to determine the latitude between these two places. 



THE EARTHQUAKE. 



C\^ the evening of Thursday, May 30, a considerable seismij 

 ^-^ disturbance was noticed over the English Channel and 

 the neighbouring districts. Its area cannot yet be preciseB 

 determined. It seems to have been felt most strongly in th 

 Channel Islands, but it was also very distinctly noticed over wic 

 districts in the south of England and the north of France, 

 bring together various facts relating to the earthquake, some 

 which have been communicated to us by correspondents. 



