March 3, 1892J 



NATURE 



419 



5 a.m., north-easterly at noon, easterly at 2 p.m., and 

 south-easterly at 7 p.m., and this occurs winter and 

 summer, and is independent of the sea breeze. 



This points plainly to a cause in daily operation, which 

 the unique position and work of the Blue Hill Obser- 

 vatory enable us to deduce from a comparatively few 

 years' observations. This cause is the diurnal barometric 

 tide, with its two maxima and minima, which, as regards 

 the Blue Hill, are more pronounced over the land to 

 westward than over the ocean to eastward, and become 

 still more pronounced on advancing southward into lower 

 latitudes and westward into more inland situations. Thus, 

 at 9 a.m., the time of the morning maximum, pressure at 

 the Blue Hill is o"023 inch above the daily mean ; at 

 New York, 0028 inch ; at Philadelphia, 0-031 inch ; and 

 at Washington, o'035 inch. Now at this physical instant, 

 9 a.m. local time, this atmospheric tide becomes relatively 

 less and less on advancing eastward across the Atlantic, 

 and at Kew (about 2 p.m. G.M.T.) pressure is o"oi2 inch 

 below its average. From its position with respect to this 

 wide-spread shallow diminution of pressure, northerly and 

 north-easterly winds attain their diurnal maximum fre- 

 quency at this hour. Again, at the Blue Hill, pressure falls 

 to the daily minimum at 3 p.m. (local time), after which 

 it continues slowly to rise ; and, while rising, pressure is 

 relatively lower to the westward. From its position in 

 the north-easterly segment of this wide-spread area of 

 lower pressure, the south-easterly winds at the Blue Hill 

 attain their daily maximum frequency at 3 p.m. 



The mean maximum velocity of the wind, about the rate 

 of twenty-two miles an hour, occurs from November to 

 March, and the minimum, nearly fifteen miles an hour, 

 from June to August. As regards the hourly velocity of 

 the wind, the records show the occurrence of the daily 

 maximum at 3 p.m., being the hour of occurrence gener- 

 ally, except at high-level Observatories ; but the time of 

 the minimum, 8 a.m., is markedly different. This pecu- 

 liarity arises from the curious but highly interesting fact 

 that the Blue Hill shows a secondary maximum imme- 

 diately after midnight, or the time when the daily maxi- 

 mum velocity occurs at high-level Observatories, thus 

 linking the Blue Hill Observatory with both high and 

 low level Obseivatories. 



There are also published valuable results of humidity, 

 cloud, sunshine, rain, gales, thunderstorms, and visibility 

 of distant objects, for which we must refer to the Report 

 itself. As the Meteorological Service of the United 

 States has recently taken a new departure, it is to be 

 hoped that Mr. Rotch, who has generously established 

 this Observatory, and has its admirable work well in 

 hand, will yet see his way to the continuance of the 

 tabulation and publication of the hourly values of the 

 elements, which cannot but prove to be of essential 

 service to the Department in carrying out certain de- 

 velopments of American meteorology which, it is 

 understood, are under consideration. 



GUST A V PLARR. 

 /^NE of the older generation of mathematicians has 

 ^^ lately passed away in the person of Dr. Gustav 

 Plarr, who died atTonbridge on January 11, of bronchitis 

 following influenza. He was born on August 27, 18 19, 

 at Kupferhammer, a country house near Strasburg. He 

 was educated at the Gymnase and at the University in 

 that city, whence he proceeded to Paris University, where 

 he obtained his diplomas as Licentiate of Sciences and as 

 " Docteur cs Sciences Mathcmatiques." Among his 

 close friends at school and at the University was M. 

 Wurtz, while M. Gerhardt, another great chemist, was 

 among his Strasburg contemporaries. Dr. Plarr for 

 some time meditated a life of chemical research, but 

 found that his health would not permit of prolonged 

 NO. I 166, VOL. 45] 



laboratory work. After taking his doctorial degree, he 

 was for some time mathematical master at a College at 

 Colmar, and, on the Chair of Mathematics becoming 

 vacant in the University of Strasburg, was one of the 

 candidates for the post. He was strongly supported by 

 the Strasburg academic party, especially by M. Sarrus, 

 the outgoing Professor, but clerical influences were at 

 work against him, and a Parisian was finally imposed on 

 the little Germanizing University. 



In 1857, Dr. Plarr married an English lady, and 

 during his honeymoon in Dublin was introduced to Sir 

 William Rowan Hamilton, the originator of the Qua- 

 ternion method, and became thenceforth a devoted 

 student and exponent of the work of that great genius. 



The British Association met at Dublin in the autumn 

 of 1857, and Dr. Plarr was one of the eight foreign men 

 of science who were that year elected " Corresponding 

 Members." Whewell, Hamilton, Vignoles, and Brewster 

 were, we believe, his sponsors on this occasion. The 

 paper then communicated by him to the Mathematical 

 Section of the Association will be found at p. loi of the 

 Report. 



The other seven men of science elected at this meeting 

 were Barth, Bolzani, d'Abbadie, Loomis, Pisani, and the 

 I two Schlagintweits. Of these, only Herman Schlagint- 

 j weit survives. Indeed, at the time of his death, Dr. 

 [ Plarr was one of the half-dozen oldest living " Corre- 

 sponding Members " of the British Association. 

 j In the Franco- German war of 1870, Kupferhammer 

 \ was burnt by the French, in order to dislodge Prussians 

 who had been able thence to command the sluices of the 

 moat round Strasburg. Dr. Plarr accordingly came to 

 reside among his wife's relatives, first at St. Andrews, 

 and then at Tonbridge. 



Since 1870, Dr. Plarr's time was almost exclusively 

 devoted to the study of Quaternions. In 1882-84 his 

 French translation of Prof. Tait's Treatise was published 

 by Gauthier-Villars. Several papers by him, on abstruse 

 points connected with the Quaternion method, were com- 

 municated to the Royal Society of Edinburgh. Beside 

 these there is a very interesting piece of ordinary analysis 

 connected with Spherical Harmonics. 



Modest, unambitious, studious, simple in his habits to 

 the verge of asceticism, Dr. Plarr was of a type rare in 

 these days and in this country. Although a man of wide 

 scientific culture, and of many literary interests, he was 

 content to be a pioneer in a realm of thought for which 

 there is necessarily no popular sympathy at present. 

 Quaternions, indeed, were to him the mathematics of the 

 future, and he was to the last happy in the thought that 

 he had assisted, however obscurely, in their development. 



NOTES. 

 Two international scientific Congresses are to be held at 

 Moscow in August. One will relate to anthropology and 

 archaeology, the other to zoology. There will be exhibitions 

 in connection with both Congresses, and appeals have been 

 issued for the loan of objects which are likely to be useful and 

 interesting. Among the things wanted for the Anthropological 

 Congress are phonograms of the language and songs of different 

 races. French will be the official language of the two meetings. 

 The more important papers will be printed before members 

 come together, so that discussion may be facilitated. 



The death, on February 20, of Prof. Hermann Kopp is 

 announced. He died at Heidelberg, after a long and painful 

 illness, in the seventy-fifih year of his age. 



The well-known botanist and philologist Stephan End- 

 licher was buried in 1849 in a churchyard near Vienna. This 

 churchyard is about to be closed, and it is proposed that End- 

 licher's remains shall be removed to the new central cemetery 



