December 31, 1891] 



NATURE 



215 



free periods of molecular vibration, associated with the rotational 

 property, — On the theory of elastic wires, by A. B. Basset, F, R. S. 

 The stresses which act across any section of a thin elastic wire 

 consist of a tension along the tangent, two shearing stresses 

 along the principal normal and binormal respectively, and three 

 couples about these directions. By resolving parallel to these 

 directions, and taking moments about them, six equations can 

 be obtained, which determine the stresses, when the unstrained 

 form of the wire is given. The values of the three couples can 

 be obtained by a method similar to that employed in my papers on 

 thin elastic plates and shells ; and when the wire is inextensible, 

 these values lead to four equations connecting the displacements 

 of any point on the axis, together with a quantity &, such that 

 d^jcls measures the twist per unit of length. The torsional 

 vibrations of a complete circular wire are afterwards investi- 

 gated ; and it is shown that they consist of a long period and a 

 short period ; that the gravest note is due to the torsional 

 vibrations, and its frequency is proportional to the square root 

 of \%nqc'-lfa\%n + q), where a and c are the radii of the axis 

 and cross-section respectively, p the density, n the rigidity, and 

 q is Young's modulus. — Researches in the calculus of variations ; 

 ii., discrimination of maxima and minima solutions when the 

 variables are connected by algebraical equations, the limits being 

 supposed fixed, by \L. P. Culvervvell. — Note on the algebraic 

 theory of elliptic transformation, by J. Griffiths. — Messrs. A. B. 

 Kempe and J. Hammond made short impromptu communica- 

 tions, and also took part with Messrs. Larmor, Basset, Forsyth, 

 Love, S. Roberts, and the President, in the discussions on the 

 papers. 



Royal Meteorological Society, December i6. — Mr. 

 Baldwin Latham, President, in the chair. — Mr. W. Marriott 

 gave the results of the investigation undertaken by the Society 

 into the thunderstorms of i88S and 1889, which he illustrated 

 by a number of lantern slides. The investigation was originally 

 confined to the south-east of England, but as this district was 

 found to be too circumscribed, it became necessary to include 

 the whole of England and Wales. After describing the arrange- 

 ments for collecting the observations, and the methods adopted 

 for their discussion, Mr. Marriott gave statistics showing the 

 number of days on which thunderstorms occurred at each station ; 

 the number of days of thunderstorms in each month for the 

 whole country ; the number of days on which it was reported 

 that damage or accidents from lightning occurred ; and also the 

 number of days on which hail accompanied the thunderstorms. 

 In 1888 there were 113 days, and in 1889 123 days on which 

 thunderstorms occurred in .some part of the country. The 

 number of days with damage by lightning was 33 in 1888, and 

 38 in 1889 ; and there were 56 days in each year on which hail 

 accompanied the thunderstorms. The tables of hourly frequency 

 show that thunderstorms are most frequent between noon and 

 4 p.m., and least frequent between I a.m. and 7 a.m. Thunder- 

 storms appear to travel at an average rate of about 18 miles per 

 hour in ill-defined low barometric pressure systems, but at a 

 higher rate in squally conditions. The author is of opinion 

 that individual thunderstorms do not travel more than about 20 

 miles ; and that they take the path of least resistance, and are 

 consequently most frequent on flat and low ground. Detailed 

 isobanc charts, with isobars for iwo-hundredths of an inch, were 

 prepared for 9 a.m. and 9 p.m. each day for the month of June 

 1888. An examination of these charts showed that, instead of 

 the pressure being so very ill-defined as appeared on the daily 

 weather charts, there are frequently a number of small but 

 distinct areas of low pressure, or cyclones, with regular wind 

 circulation ;• and that these small cyclones passed over the 

 districts from which thunderstorms were reported. Sometimes 

 it is not possible to make out well-formed areas of low pressure 

 from two-hundredths of an inch isobars, but there is a deflection 

 of the wind which shows that there is some disturbing cause ; 

 and thunderstorms have usually occurred in that immediate 

 neighbourhood. The author believes that the thunderstorm 

 formations are small atmospheric whirls — in all respects like 

 ordinary cyclones ; and that the whirl may vary from I mile to 10 

 miles or more in diameter. There are frequently several whirls 

 near together, or following one another along the same track. 

 The numerous oscillations in the barometric curve are evidently 

 due to the passage of a succession of atmospheric whirls ; and it 

 appears that lightning strokes are most frequent when these 

 oscillations are numerous. — Mr. F. J. Brodie read a paper on 

 the prevalence of fog in London during the twenty years 1871 

 to 1890. The popular notion that November is p3,r excellence a 



NO. 1 157, VOL. 45] 



month of fog is not confirmed by the figures given by the 

 author. The number of fogs in that month is, if anything, 

 slightly less than in October or January, and decidedly less than 

 in December, the last-mentioned month being certainly the 

 worst of the whole year. The latter part of the winter is not 

 only less foggy than the earlier part, but is clearer than the 

 autumn months. In February the average number of days with 

 fog is only 6'6, as against 89 in January, iO'2 in December, 

 9 '2 in October, and 8 "8 in November, 



Linnean Society, December 17. — Prof. Stewart, President, 

 in the chair. — Mr. G. C. Druce exhibited specimens of Sagina 

 maritima, Don MS., var, alpitia, Syme, gathered on steep 

 rocky places on the Cairngorms, a.ndoi /lleccbruniverticillatuni, 

 Linn,, found near Wellington College, Berks. — Dr. R, C. A. 

 Prior exhibited some fruits of the baobab {Adattsonia), and an 

 undetermined species of palm, which had been sent from Mata- 

 bele Land as good to eat, under the misleading names of 

 "cream of tartar fruit" and "wild orange." He read an 

 extract from Oates's " Matabele Land," describing the natural 

 growth and appearance of the baobab as observed in that 

 country. — The Hon. W. B, Espeut exhibited some nests of 

 humming-birds from Jamaica, and pointed out the variety of 

 materials used by the same species, though placed in the same 

 tree (a mangrove), the coloration in some cases being protective, 

 in others not, — A paper was then read on the occurrence of two 

 species of Crustacea belonging to the sub-order Cumacea in New 

 Zealand, whence none had been previously described. The 

 author gave the result of his dredging in the Bay of Islands 

 in the north, and in the inlets of Stewart Island in the south, 

 and furnished drawings and descriptions of the species referred 

 to. — A paper on the development of the head of the imago of 

 Chironomus, by Prof. L. C. Miall and A. R. Hammond, was 

 read by Mr. Hammond, accompanied by a series of illustra- 

 tions with the o.xyhydrogen lantern. The subject was intro- 

 duced by a brief sketch of the life-history of the insect in its 

 three stages, followed by detailed descriptions of the head both 

 of the larva and of the imago. The history of the epidermic 

 invaginations, by which the imaginal head is formed within the 

 larval head and prothorax, was then followed out to its consum- 

 mation in the development of the fly. The lantern arrange- 

 ments were successfully carried out by Mr, Frederick Enock. 



Paris. 

 Academy of Sciences, December 21. — M. Duchartre in the 

 chair, — List of prizes awarded to successful competitors in 

 1891 : — Geometry. — Prix Francoeur, M. Mouchot ; Prix Ponce- 

 let, M. Humbert. Mechanics. — Extraordinary Prize of 6000 

 francs : this was divided into four, two principal prizes of equal 

 amount to MM. Pollard and Dudebout, one to M. Guyon, and 

 the fourth to M. Chabaud-Arnaud. Prix Montyon, M. Camere. 

 Prix Plumey, M. de Maupeou. Prix Dalmont, M. Considere ; 

 MM. Autonne and Ocagne being given honourable mention. 

 Astronomy. — Prix Lalande, M. G. Bigourdan, Prix Damoiseau 

 (not awarded). Prix Valz, Prof. Vogel. Prix Janssen, M. G. 

 Rayet, Physics. — Prix La Caze, M. J, Violle, Statistics. — 

 Prix Montyon, MM, Cheysson and Toque, Chemistry. — Prix 

 Jecker, MM. Behal and Meunier. Prix La Caze, M, A, Joiy, 

 Geology. — Prix Delesse, M. Barrois. Botany. — ^x'w. Bordin, 

 M. Leon Guignard. Prix Desmazieres, M. Auguste-Napoleon 

 Berlese. Prix Montagne, M. Henri Jumelle. Prix Thore, 

 MM. J. Costantin and L. Dufour. Anatomy and Zoology. — 

 Grand Prix des Sciences Physiques, M. Jourdan. Prix Bordin, 

 M. Beauregard, Prix Savigny, Dr. Lionel Faurot. Prix Da 

 Gama Ma-chado (not awarded). Medicine and Surgery. — Prix 

 Montyon, divided between MM. Dastre, Duroziez, and Lanne- 

 longue ; mentions were accorded to MM. Sanchez-Toledo and 

 Veillon, to M. Soulier, and M. Zambaco ; and citations to MM. 

 Arthaud and Butte, M. Batemann, MM. Bloch and Londe, .VI. 

 Catsaras, M. Debierre, M. Gamier, M. Gautrelet, and M. Netter. 

 Prix Barbier, M. Tscherning ; mentions were accorded to MM. 

 Delthil and Dupuy, Prix Breant (not awarded). PrixGodard, 

 M. Porier ; honourable mention to Dr. Wallich, Prix Chaus- 

 sier, Dr, ISrouardel ; honourable mention to the late M. E, 

 Duponchel, Prix Bellion, divided between MM, Carlier and 

 Mireur, Prix Mege, M, Frederic Courmont. Prix Lallemand, 

 divided between MM. Gilles de la Tourette, H. Cathelineau, 

 and F. Raymond ; honourable mentions were accorded to MM, 

 Legrain, Debierre, and Le Fort, Bruhl, Sollier, and Colin. 

 Physiology. — Prix Montyon, MM. Bloch and Carpentier ; men- 

 tions were accorded to MM, Hedon and Lesage, Prix La Caze, 



