MO 



NA TURE 



[June i i, i! 



begun last year, were continued on nine nights, and the results 

 communicated to the Royal Astronomical Society in November. 

 The diameters of Jupiter were measured on nineteen nights with 

 the filar micrometer and, for comparison, wiih the double-image 

 micrometer ; the results were communicated to the Royal 

 Astronomical Society in May. The weather during the opposition 

 of Jupiter and Neptune made it impossible for any systematic 

 search to be made for Jupiter's fifth satellite, and the position of 

 Neptune's satellite was only observed on one night. 



The Photographic Chart and Catalogue. 

 With the Astrographic Equatorial 502 plates, with a total of 

 1224 exposures, have been taken on 123 nights in the year end- 

 ing May 10, 1S95. Of these, 135 have been rejected for 

 various reasons. 



The following statement shows the progress inade with the 

 photographic mapping of the heavens between May 11, 1895, 

 and May 10, iSg6 : — 



For the Chart For the Catalogue 



(Exposure (Exposures 6 m., 



40 m.). 3 m., and 20S.). 



Number of photographs taken iiS 353 



,, successful plates 89 247 



,, fields photo- 



graphed success- 



fidly ... ... 79 223 



Total number of fields photo- 

 graphed successfully since 

 the commencement of the 



work ... 490 732 



The question of the utilisation of the photographs taken for 

 the Astrographic Chart, and the formation of a catalogue of stars 

 down to the eleventh magnitude by means of photography, has 

 occupied much attention during the past year, and a satisfactory 

 working scheme for the measurement of the photographic plates 

 and determination of the positions of the stars on them has 

 been brought into operation. It is estimated that if no unfore- 

 seen difficulties arise the measures and calculations for the 

 Greenwich Astrographic Catalogue of Stars down to the 

 eleventh magnitude, from Dec. 64° N. to the Pole, will be 

 completed in about seven years, and that the positions of about 

 120,000 stars will be determined with a degree of accuracy at 

 least twice as great as that of the Astronomische Ge.sellschaft 

 Catalogues from meridian observations. When it is considered 

 that the Greenwich Astrographic Catalogue will contain about 

 ten times as many stars as the catalogues of the Astronomische 

 Gesellschaft for the corresponding zones, and that the Astro- 

 graphic Catalogue for the whole heavens will give the positions of 

 from two to three million stars with an accuracy hitherto un- 

 attained, and at a relatively small expenditure of labour, the 

 great advantage resulting from the application of photography 

 to the mapping of the heavens will be sufficiently evident. 



Spectroscopic and Heliographic Observations. 



Since the date of the last report, 189 measures have been 

 made of the displacement of the F line in the spectra of 17 

 stars, as well as 33 measures of the F line in the spectrum of 

 the moon for comparison. 



The spot activity of the sun has steadily declined from the 

 date of the last report. The mean daily spotted area of the sun 

 was decidedly smaller in 1895 than in 1S94, but a greater number 

 of small spots was observed. 



Magnetic Observations. 



The variations of magnetic declination, horizontal force and 

 vertical force, and of earth currents have been registered photo- 

 graphically, and accompanying eye observations of absolute 

 declination, horizontal force and dip, have been made as in 

 former years. 



The principal results for the magnetic elements for 1895 are 

 as follows : — 



Mean declination ... ... 16" 57''4 West. 



Mean horizontal force | 39739 (jn British units). 



\ I 8323 (in Metric units). 



Mean iliri [\ months, January to J^ ^,.;. ,1^ • u n i' 

 ^, 11 ' - 67 14 8 (by 6-inch needles). 



'^'^"'"' t67' l6'-6 (by 3.inch needles). 



-, ,. / .u c . 1 f 67" 10' 7 (by 9-inch needles). 



to December) '' ^'='"""''"- " ° i.'-8 lb • I-inch needles). 

 to December) y^.^.. j,,.^ j,,^ ^ ._^^,,^ needles). 



NO. 1389, VOL. 54] 



Uncertainty attaches to the results for mean horizontal force, 

 owing to the permanent effect of the iron in the new Altazimuth 

 Pavilion. 



From April to August 1895, 'luring the progress of the build- 

 ing work on the new Altazimuth, the observations of magnetic 

 dip were subject to great uncertainty on account of the masses 

 of iron for the Iniilding being stored near the north end of the 

 New Library in immediate proximity to the dip instrument. 

 And after the completion of the building — that is to say, since 

 September 1S95 — the results of magnetic dip are affected to the 

 extent of about 3' or 4' by the permanent iron in the building 

 and instrument. An independent determination at a place 

 sufficiently removed from the Altazimuth building is urgently 

 required. The question, however, has necessarily been de- 

 ferred, pending the settlement of the site for the new Magnetic 

 Pavilion, which is to be built in Greenwich Park. 



The magnetic disturbances during the year 1895 have been com- 

 paratively trifling. There were no days of great magnetic dis- 

 turbance, and sixteen days of lesser disturbance. Tracings of the 

 photographic curves for these days, selected in concert with M. 

 Mascart, will be published in the annual volume as usual. The 

 calculation of diurnal inequalities from five typical quiet days in 

 each month has been continued. 



Meteorological Observations. 



The mean temperature of the year 1895 was 49°'3, being o'"l 

 below the average for the 50 years 1841-1S90. 



During the twelve months ending April 30, 1896, the highest 

 daily temperatuie recorded was 87'''3 on September 24. On 

 May 30 a temperature of 86°"2 was recorded. The temperature 

 rose above 80" on 26 days in 1895 as compared with seven days 

 in the preceding year. The monthly mean temperatures were 

 all in excess of the average values with the exception of the 

 month of October, which was in defect. The mean for Sep- 

 tember was in excess to the amount of 4" 7 ; that for November 

 in e.xcess by 4° '2, and that for March 1S96 by 4°. The mean 

 temperature for the twelve months May 1895 to April 1896 was 

 5i°'l, being l°7 above the 50 years' average. 



The characteristics of the fine and hot month of September 

 require to be examined in detail. It has been mentioned that 

 the highest temperature of the year (87' '3) occurred on Sep- 

 tember 24, a temperature greatly exceeding all temperatures 

 previously recorded at this advanced period of the year during 

 the 54 years 1841-1894. Only two instances of higher tem- 

 perature, both in the earlier part of the month, have been 

 experienced in .September, viz. 92°"! on September 7, 1868, 

 and 87^7 on September i, 1886. 



The winter of 1895-96 was very mild, and there were only 

 19 days on which the temperature of the air fell to or below the 

 freezing-point. The lowest winter temperature was 24°'3 on 

 February 25, 1896. 



The mean daily horizontal movement of the air in the twelve 

 months ending April 30, 1896, was 275 miles, which is 6 miles 

 below the average for the preceding 28 years. The greatest re- 

 corded movement was 1002 miles on December 5, and the least 

 70 miles on October 20. The greatest recorded jiressure of the 

 wind was 27 '5 lb. on the square foot on March 16, with an 

 extreme hourly velocity of 49 miles. 



The number of hours of bright sunshine recorded during the 

 twelve months ending April 30, 1896, by the Campbell-Stokes 

 instrument was 1176 out of the 4465 hours during which the .sun 

 was above the horizon, so that the mean proportion of sunshine 

 for the year was o'263, constant sunshine being represented by 

 I. In the corresponding period for 1894-95 'h<^ number of hours 

 of sunshine was 928, and the mean proportion 0'2o8. 



The rainfall lor the year ending April 30, 1896, was 1976 

 inches, being 478 below the 50 years' average. This is the 

 smallest rainfall since the year 1SS4-85, when the fall was !9'6l 

 inches. In 1864-65 the rainfall was 1771 inches, and in 1858- 

 59 it was I7'38 inches. The number of rainy days in the twelve 

 months was 151. 



Reorganisation of the Staff. 



The scheme for the re-organisation of the staff, referred to in 

 last two reports, has now been sanctioned. With a view to 

 strengthening the supervising power and increasing the permanent 

 subordinate staff, an additional chief assistant is appointed, and 

 the five second-class assistants of the old stafl' are to be replaced 

 by eight established computers, two of these to be of a higher 

 grade, the number of temporary computers being correspondingly 

 reduced; The future staff will be thus constituted : — 



