May 26, 192 1] 



NATURE 



401 



secondary maximum follo\\ed at 8h. on May 

 16, It does not seem possible to associate 



the disturbance with one or other individual spot, 

 but rather with the group as a whole. In this 

 connection it is of interest to note that minor m-ag- 

 netic disturbances occurred on April 18 and March 

 21. Some years ago Mr. Maunder showed that 

 magnetic storms tend to recur at intervals of about 

 twenty-seven days, which corresponds to the time 

 taken for the sun to make one rotation relative to 

 the earth. If this sequence is continued we may 

 expect a further disturbance on June 9, when the 

 spot group, if still visible, will be in the same 

 relative position on the sun's disc as on May 13, 

 when the storm commenced. 



The general relation between the diurnal varia- 

 tion of the earth's magnetic elements and the 

 sun-spot cycle cannot be doubted. It is better 

 termed the soVrr cycle, for it is well known that 

 the solar prominences, the faculae and flocculi, and 

 the shape of the corona vary also with the sun- 

 spots in the same eleven-year period- The causes, 



however, of this terrestrial and solar relation are 

 still obscure, and the magnetic storms in par- 

 ticular offer other difficulties on account of their 

 anomalous occurrence, although on the whole they 

 follow the sun-spot curve. The theory which in 

 general seems best to fit the observed facts is that 

 which assumes a directive stream of charged par- 

 ticles ejected from a restricted area of the sun, 

 most probably in the region of a sun-spot. 

 Opinions differ as to the exact nature of the stream 

 and as to its action on meeting the earth. It 

 is, of course, admitted that such a stream, though 

 it may be a requirement, is not the sole factor in 

 the production of a magnetic storm, the energy of 

 which is to be traced to the earth's own mag- 

 netic system, and ultimately to the earth's 

 rotation. 



At Mount Wilson Observatory the magnetic 

 polarities of sun-spots are now investigated daily. 

 It will be interesting to see whether this group of 

 spots is associated with exceptionally strong or 

 otherwise abnormal magnetic fields. 



Obituary. 



Dr. G. B. Loxgstaff. 

 r\R. G. B. LONGSTAFF died on May 7, 

 ^-^ after a long period of failing health, at 

 his residence, Highlands, Putney Heath. Dr. 

 Longstaff was born on February 2, 1849, and 

 educated at Rugby and at New College, Oxford, 

 where he obtained a scholarship and a first class 

 in natural science. At a very early age his atten- 

 tion was attracted to the study of insects, mainly 

 through the influence of his uncle by marriage, 

 William Spence, of " Kirby and Spence's Intro- 

 duction to Entomology"; and he was already 

 recognised as one of the most energetic and 

 successful of the younger lepidopterists of his time, 

 when a regrettable accident in the second term 

 of his residence at Oxford, which resulted in the 

 loss of an eye, put an end to his activities in this 

 direction for many years. His later career 

 at St. Thomas's Hospital, where he \yas awarded 

 the Mead medal, was highly distinguished, and 

 in later life, besides taking an active part in 

 philanthropic and municipal work, he represented 

 Wandsworth on the London County Council for 

 fourteen successive years. 



Much attention also was devoted by Dr. 

 Longstaff to the scientific aspect of statistics, and 

 his well-known work on this subject (" Studies in 

 Statistics ") was published in 1891. His long- 

 dormant interest in entomology was revived by a 

 tour in India and Ceylon in the winter of 1903-4; 

 and in later years flying visits were made by him 

 to almost every accessible part of the world in 

 company with his accomplished second wife {nee 

 Mary Jane Donald, well known as an authority on 

 recent and fossil mollusca). The energy and 

 acumen with which insects were collected and 

 observed on these trips may be estimated by the 

 NO. 2691, VOL. 107] 



fact that Dr. Longstaff enriched the museum of 

 his old university by at least 14,000 specunens, 

 and the value of this generous contribution is 

 greatly enhanced by the full and accurate data 

 attached to every one of them. 



The gratitude of all entomologists is also due 

 to Dr. Longstaff for the finely illustrated and 

 most pleasantly written narrative of these collect- 

 ing trips which appeared in 191 2 under tne title 

 of "Butterfly Hunting in Many Lands." The 

 numerous and valuable observations on the bio- 

 nomics of the butterflies met with in the regions 

 visited — their flight, resting habits, seasonal forms, 

 mimicry, and sexual scents, to which last-named 

 subject Dr. Longstaff devoted special attention — 

 are embodied in the last chapter of this fine book, 

 which is supplemented by an equally valuable 

 series of papers on the same questions by the late 

 Fritz Miiller, here presented for the first time in 

 English. 



Dr. Longstaff was a highly appreciated member 

 of many learned bodies, and had been vice-presi- 

 dent of the Royal Statistical Society and of the 

 Entomological Society of London ; and the loss of 

 his commanding presence and genial address at 

 their meetings will long be regretted by his fellow- 

 members, as well as by his numerous friends in 

 private life. 



W^E notice with much regret the announcement 

 in the Times of the death of Dr. Edward B. 

 Rosa on Tuesday, May 17, at the age of fifty-nine 

 years. Dr. Rosa had been connected with the 

 L\S. Bureau of Standards since 1901, and from 

 1910 onward he held the position of chief 

 physicist at the bureau. 



