NA TURE 



[November 7, 1901 



of Mauritius, and soon thereafter turned his attention 

 to meteorology, of which he continued to the end one of 

 its most ardent students. It was chiefly by his influence 

 and exertions that the Meteorological Society of Mau- 

 ritius was founded in 1S31, he being its first secretary. 

 He was appointed (Government Meteorological Observer 

 in i86i and Director of the Royal Alfred Observatory in 

 1875 ; and in recognition of the great public services he 

 had rendered to the colony he was made a member of 

 the Government Council of Mauritius. For his services 

 to science, more particularly to meteorology, his own 

 University of ."Aberdeen conferred on him the honour of 

 LL.D. ; in 1874 he was elected a F.R.S. ; and in 1886 

 he was honoured with a C.M.G. 



Meldrum was a man of untiring energy and perse- 

 verance, and to this was added the keenest perception of 

 the absolute necessity there was to replace theoretical 

 speculation by accurate observations in all attempted 

 solutions of the problems of meteorology. In carrying 

 on this large and irksome work he soon displayed a 

 genius in devising the methods for obtaining the physical 

 ■data required for the investigations he took in hand. 

 His self-devotion to the work was unsparing and un- 

 remitting to the end. 



His first notable contribution to science was in the 

 attractive field of practical meteorology, by which signal 

 service was rendered to the forecasting of storms within 

 the tropics. The data collected for the purpose was of a 

 twofold nature. First, he clearly saw the paramount 

 importance of a statement of the hourly variations 

 through the months of the year of the pressure, tempera- 

 ture, wind and cloud, and to arrive at which he early insti- 

 tuted " Term Day Observations " as part of the systematic 

 work of the Observatory. In a year or two, approxi- 

 mate hourly averages were thus obtained, and, from 

 these averages, deviations were at once apparent from 

 the regular normal hourly march of the pressure, 

 temperature, wind and cloud. 



In the second place, a unique and rich collection of 

 maps of the cyclones of the Indian Ocean began to be 



from the normal values of pressure, wind, &c., observed 

 at the Observatory. The inquiry resulted in showing 

 unmistakably (i) that the direction in which the cyclone 

 was from Mauritius could be readily known from the 

 wind ; (2) that its distance from Mauritius could be 

 known from the amount of fall of the barometer and the 

 rate of the fall, taken in connection with the x ariations in 

 humidity, wind and cloud ; and (},) that its progressive 

 motion could be known chiefly from the veerings of the 

 wind. These novel conclusions were soon put to practical 

 use in sending to the daily Press prognostics of cyclones 

 which were attended with complete success. This great 

 result was all the greater inasmuch as it showed that 

 what was done at an isolated station in the ocean might 

 equally be done with success at sea. 



In 1874 he submitted another important paper to the 

 British Association at Belfast, "The Cyclone and Rain- 

 fall Periodicities in connection with the Sun-spot 

 Periodicity," and in several subsequent years he re- 

 turned to the same subject. He was one of the earliest 

 workers in this attractive department of science, and his 

 contributions, more particularly as regards the rainfall 

 drawn from all climates, were alike remarkable for the 

 enormous labour involved in their preparation and the 

 lucid clearness with which they established and presented 

 the intimate connection subsisting between the sun-spots 

 and the cyclone and rainfall periodicities. 



The Observatory of Mauritius stands second to no 

 other Observatory in the world for the excellence of the 

 physical data it has supplied towards the investigation of 

 these periodicities. As regards the prime elements of 

 climate its records aftbrd the requisite data for the last 

 four complete sun-spot periods from 1S55 to 1888, and 

 also the annual number of cyclones in the Indian Ocean 

 from 1847 to 1900, or fifty-four years in all. The follow- 

 ing table gives a comparison of the periodicities of the 

 rainfall, pressure, temperature and cyclones. The figures 

 for the rainfall, pressure and temperature are given as 

 differences from their annual averages, the differences 

 being " blo.xammed " in the usual way. 



prepared from the Mauritius observations, combined with 

 ■observations obtained from ships' logs, on which isobars, 

 isotherms, winds and clouds were entered, thus depict- 

 ing from strict observations 'the outstanding features of 

 the cyclones and gales of the Indian Ocean. In a 

 valuable paper read to the British Association at 

 Dundee, it was shown that the gales and hurricanes of 

 the Indian Ocean south of the equator were conveniently 

 grouped into three distinct types : (l) trade-wind gales, 

 in which the wind veers little, these occurring chiefly in 

 the winter months of June, July and' August, when the 

 S.W. monsoon prevails north of the equator ; (2) the 

 extratropical gales, occurring south of lat. 30^ in which 

 the wind veers or shifts, these storms being somewhat 

 analogous to the storms of north-western Europe and 

 are most frequent and violent from May to August ; and 

 (3) the tropical hurricanes, or true cyclones, in which the 

 wind always veers. It was to this last class that Meldrum 

 mainly directed his attention. 



A strict and extended inquiry was carried on respect- 

 ing the relations between the course pursued by individual 

 cyclones and their changing intensity, and the deviations 



NO. 167 I, VOL. 65] 



The result shows an intimate connection between the 

 prime elements of meteorology and the sun-spot varia- 

 tion. 



In 1866 Dr. Meldrum visited England, one of the chief 

 objects in view being to obtain a complete set of mag- 

 netical and meteorological registering instruments suit- 

 able for a first-class observatory. These were received in 

 course, and by the end of 1 874 were installed, and at work, 

 in the new Royal Alfred Observatory, of which he was 

 appointed the first director. The results have been pub- 

 lished in the .Annual Reports since, and in the Report 

 for 1899 Mr. Claxton has begun to give the larger re- 

 sults of the work of this (Observatory, beginning with the 

 diurnal variation of the atmospheric pressure deduced 

 from twenty-five years' observations (1875 99)i and of 

 some of the other chief elements of climate for shorter 

 terms of years. These results are simply of inestimable 

 value, not only to men of science, but also to navigators. 



Sometime ago there was added to the regular routine 

 of the Observatory the taking of photographs of the 

 sun when the weather permitted. The number of 

 photographs taken in 1900 was 377 ; they have been 



