296 



NATURE 



[June 7, 1917 



the proper motions of about 12,000 stars. These have 

 been obtained by comparison of the Greenwich posi- 

 tions with those given in the catalogues of the Astro- 

 nomische Gesellschaft and the earlier catalogues of 

 Bessel and Lalande. For the latter catalogues 

 systematic corrections were determined for each 

 separate. night's observations. 



A determination of the mean parallax of stars of 

 different magnitudes has been made from these proper 

 motions and published in the Monthly Notices of the 

 Royal Astronomical Society. The results confirm very 

 closely the formula given by Kapteyn. It is hoped to 

 communicate to the society a short discussion of the 

 proper motions with reference to star streaming. The 

 publication of these summaries of results by the Royal 

 Astronomical Society is specially valuable because of 

 the delay in the printing and publication of the cata- 

 logue itself. 



During the year 222 photographs were taken with 

 the Cookson floating zenith-telescope, 216 for latitude 

 groups and six for scale determination. The measure- 

 ment of the photographs to the end of 1916 is com- 

 pleted, and the results for the variation of latitude for 

 19 16 were communicated to the Royal Astronomical 

 Society, and published in the Monthly Notices for 

 March, IQ17. 



Throughout the year the 28-in. refractor was at the 

 disposition of M. Jonckheere. Fifty-nine new close 

 double stars were detected, making 259 since October, 

 1914. Up to November 22, 1916, the observations 

 mainly consisted of the measurement and verification 

 of stars discovered to be double since 1905, the date 

 to which Mr. Burnham's catalogue extends. Since 

 November 22 the programme of work has comprised 

 (i) the measurement of stars from Burnham's General 

 Catalogue which had been previously observed at the 

 Lille Observatory, and (2) the re-measurement of 

 double stars in vol, Ixi. of the Royal Astronomical 

 Society's Memoirs. Altogether 604 double stars have 

 been measured during the year. Of these stars — 

 213 have a separation under 2". 

 1 56 „ „ between 2" and 3". 



132 „ „ „ 3^' » 4'; 



62 „ „ „ 4" »^ 5"- 



41 „ ,, greater than 5". 



The catalogue of double stars discovered since 1905 

 has been published by the Royal Astronomical Society 

 in vol. Ixi. of the Memoirs. 



With the Thompson equatorial, in accordance with 

 the programme of previous years for the determination 

 of stellar parallax, a first exposure has been made on 

 eighty-six plates, and a second one on 154 plates. At 

 the request of Dr. de Sitter the series of photographs 

 commenced at the Cape Observatory for the deter- 

 mination of the constants of the four Galilean satellites 

 of Jupiter has been continued at Greenwich. 



With the astrographic equatorial during the year 

 109 plates have been taken on thirty-five nights for 

 the determination of proper motion by comparison with 

 earlier plates. Of these nine have been rejected; 

 eighty-five plates, of which fifty-two have two fields 

 on them, have two short exposures, usually of 4m. 

 and 2m. ; fourteen have a single exposure of 12m. ; 

 one is for focus of the instrument. 



The plates with short exposures are being compared 

 In the duplex micrometer, but only for the stars con- 

 tained in the Bonn Durchmusterung. The plates with 

 longer exposures are being compared with earlier 

 olates — usually chart plates — ^by Mr. Innes at 

 Johannesburg, using a blink microscope. With the duplex 

 micrometer 177 pairs of plates have been measured 

 during the year. From the results obtained all proper 

 motions greater than 10* a century and many smaller 

 ones are being determined. Simultaneously the proper 

 NO. 2484, VOL. 99] 



motions of the brighter stars are being determined by 

 comparison with earlier meridian observations. 



In the year ended May 10, 1917, photographs of the 

 sun were obtained on 208 days. Photographs have 

 been received from the Royal Observatory, Cape of 

 Good Hope, and supplementary photographs have 

 been received through the Solar Physics Committee, 

 from Dehra DQn," India, In both cases to the close of 

 the year 1916. Two days in 19 16 still remain un- 

 represented, viz. June 19 and September 29. 

 From 1910 to 1916 inclusive there are only 

 two other days unrepresented in the combined 

 series of photographs for measurement, one in 19 11 

 and one in 1912. 



The mean daily spotted area of the .sun continued 

 to increase during the past twelve months, and there 

 is no Indication as yet that the maximum has been 

 reached. 



The mean values of the magnetic elements for 1916 

 and five previous years are as follows : — 



Year Declination W. Horizontal Dip 



force (C.G.S) . , „ 



'9II J5 33'o . 0-I8549 66 52 6 (3-in, needles) 



1912 24*3 018548 51 46 „ „ 



1913 15-2 0-18534 50 27 „ „ 



1914 15 6-3 0-18518 ( 4927 „ ,, 

 ^ ^ •' -^ ^ i 5113 (inductor) 



1915 14 56-5 0-18508 51 50 „ 



1916 46-9 •0-18494 52 45 „ 



It will be noticed that the annual diminution of 

 declination increased considerably about 19 10, its 

 average value from 1900 to 19 10 being 4-9'. The hori- 

 zontal force, which had been Increasing since measure- 

 ments at Greenwich were begun in 1846, reached a 

 maximum about 1910, and is now diminishing. The 

 dip, which has been diminishing since measurements 

 were begun in 1843, appears also to have recently 

 reached a turning point. There were no days of great 

 magnetic disturbance in 19 16, but three were classified 

 as of lesser disturbance. 



The principal features of Interest In the meteoro- 

 logical conditions at Greenwich during the year ended 

 April 30, 19 17, are : — (I) The continued cold weather 

 from December to April — the latter month had a mean 

 temperature 1° lower than any other April since 1841 ; 

 and (11) the general deficiency of sunshine. 



The scientific work of the observatory has necessarily 

 been somewhat curtailed, but it has been found pos- 

 sible to keep up all observations of the sun, moon, and 

 planets ; sun-spots ; latitude ; magnetic and meteoro- 

 logical registers — observations which would otherwise 

 have been permanently lost. 



One special piece of work to which a good deal of 

 attention was devoted this year was the preparation of 

 magnetic charts. In 1912 It was arranged that the 

 compilation of the Admiralty charts of magnetic varia- 

 tion, hitherto undertaken by the Compass Department, 

 should be transferred to the Royal Observatory. A 

 card catalogue of magnetic declination data from all 

 parts of the world was formed. From this and pub- 

 lished data of various surveys the charts for 19 17 have 

 been prepared during the past vear. They are now In 

 courSfe of publication by the Hydrographic Office. 



RESEARCHES ON KALA-AZARA 



I HAVE chosen the subject pf twenty years' research 

 on kala-azar for the main portion of my address 

 to-night, both because of the great importance of this 

 disease in a large area of India, and also of the 

 ignorance of the general public regarding It. ^ Most 

 p>eople have fairly definite Ideas about malaria and 



1 From the presidential address delivered to the Asiatic Society of Bengal 

 on February 8 by Sir Leonard Rogers, F.R.S. 



