June 4, 1891] 



NATURE 



119 



taking for his subjefet "The Secondary Sexual Characters of 

 Animals and Plants," of which he gave several interesting ex- 

 amples, illustrating his remarks with graphic sketches in coloured 

 chalks. On the motion of Mr. H. Druce, seconded by Mr. C. 

 Tyler, a vote of thanks was accorded to the President for his able 

 address, with a request that he would allow it to be printed. — 

 The Linnean Society's Gold Medal for the year 1891 was then 

 formally awarded to Dr. Edouard Bornet, of Paris, for his 

 researches in botany, and on his behalf was presented to M. 

 Raymond Lecomte, Secretary to the French Embassy. The 

 proceedings then terminated. 



Institution of Civil Engineers, May 26. —Annual General 

 Meeting. — Sir John Coode, K.C.M.G., President, in the chair. 

 — In the Report of the Council for the session 1890-91, it was 

 remarked that the salient feature of the session, now termi- 

 nated, had been the realization of a proposal made more than 

 forty years ago — namely, the formal reception by the President \ 

 and Council on stated evenings after the ordinary meetings of , 

 the members and visitors then present. A series of receptions j 

 was held after the ordinary meetings in the months of January, | 

 February, March, April, and May, of this year. An endeavour j 

 has also been made to identify, in some degree, each gathering 

 with a particular branch of engineering, both in respect to those I 

 invited to be present and to the models and other objects of i 

 interest exhibited. These receptions were believed to have ' 

 been most successful, and experience would doubtless suggest 

 directions in which they might be rendered still more , 

 useful and attractive in the future. The effective increase in | 

 the roll of the Institution during the past year was 247. The 

 number of members of all classes, students excepted, on March 

 31 last, was 5150, as against 4903 on the same day last 

 year, representing an increase at the rate of 5 per cent. — The 

 adoption of the Report was moved, seconded, and carried, and 

 it was ordered, to be printed in the Minutes of Proceedings. 

 Cordial votes of thanks were then passed to the President, to 

 the Vice-Presidents and other Members of the Council, to the 

 Auditors, to the Secretaries and Staff, and to the Scrutineers. — 

 The ballot for Council resulted in the election of Mr. George 

 Berkley as President ; of Mr. H. Hayter, Mr. A. Giles, M. P., Sir 

 Robert Rawlinson, K.C.B., and Sir Benjamin Baker, K.C.M.G., 

 as Vice-Pre.-idents ; and of Mr. W. Anderson, D.C.L., Mr. J. 

 Wolfe Barry, Mr. E. A. Cowper, Sirjas. N. Dougla'^s, F.R.S., 

 Sir Douglas Fox, Mr. J. Clarke Hawkshaw, M.A., Mr. Charles 

 Hawksley, Sir Bradford Leslie, K.C.I.E., Mr. George Fosbery 

 Lyster, Mr. J. Mansergh, Sir Guilford Molesworth, K.C.I.E., 

 Mr. W. H. Preece, F.R.S., Sir E. J. Reed, K.C.B., F.R.S., 

 M.P., Mr. W. Shelford, and Mr. F. W. Webb as other Mem- 

 bers of Ihe Council. — The session was adjourned until the second 

 Tuesday in November, at 8 p m. [At the first meeting of the 

 newly-elected Council, the following officers were re-appointed : 

 Mr. H. L. Antrobus, as Treasurer; Dr. Wm. Pole, F.R.S., 

 Honorary Secretary; and Mr. James Forrest, the Secretary.] 

 Edinburgh. 



Royal Society, May 4. — Sir Douglas Maclagan, President, 

 in the chair. — A preliminary note by Mr. John Aitken, on a 

 method of observing and counting the number of water particles 

 in a fog, was communicated. The phenomena which are 

 denoted by the names fog, mist, and rain, diiTer merely in 

 degree, and not in kind. In a haze dry dust particles are present 

 in the air to a greater or less extent. The haze turns into a fog 

 when water vapour is condensed upon the particles, and the fog 

 will develop into mist upon the condensation of a sufficient 

 amount of moisture. So that we may regard an ordinary fog 

 and a mist as a dry fog and a wet fog respectively. The water 

 drops in a fog will gradually settle upon the exposed surfaces of 

 bodies. Hence it might seem that, in order to determine the 

 extent to which moisture is present in a fog, it would be 

 sufficient to allow the drops to fall upon a piece of mirror, 

 which they would soon wet. But Mr. Aitken has found that 

 when exposed surfaces are quite dry, a great quantity of water 

 drops are often present in the air. The drops are exceedingly 

 small and evaporate with great rapidity from the surfaces (heated 

 by radiation) upon which they fall. The instrument which Mr. 

 Aitken has adopted for the purpose of determining whether or 

 not witer drops are present is essentially identical with his 

 pocket-dust counter. It consists of a glass micrometer divided 

 into squares of a known size, a spot mirror for illuminating the 

 stage, and a strong lens or a microscope for observing the drops 

 on the stage. It is found convenient to observe an area of the 

 stage equal to about i/i6th or i/20th square centimetre when 



NO. II 2 7, VOL. 44] 



working with a magnifying lens. In one fog which was ob- 

 served, objects at a greater distance than loo yards were quite 

 invisible, and the surfaces of exposed objects were quite dry. 

 The number of drops which fell per minute varied greatly, 

 sometimes reaching 3000 per square centimetre, sometimes only 

 300 per square centimetre. Two days later the same apparent 

 external conditions regarding fog again obtained, and the 

 number was found to be 1300 per square centimetre per minute 

 — which remained fairly constant until the fog began to clear off 

 when it slowly diminished. In both cases the observation was 

 made at 10 a.m. If the stage be slightly heated, the drops 

 never reach the surface but evaporate in the layer of heated air 

 over it. Mr. Aitken has also modified this apparatus in order 

 to admit of the counting of the number of drops which fall from 

 a column of air of known height. A low power microscope is- 

 used, and So a column of air 5 centimetres long can be obtained 

 over the stage. Underneath, and concentric with the micro- 

 scope, a tube 5 centimetres long and 4 centimetres in diameter 

 is mounted. The top and bottom of this tube can be simulta- 

 neously closed by covers which turn on an axis parallel to the 

 axis of the tube. A micrometer, illuminated by a spot mirror, 

 is fixed in the centre of the bottom, and, in the centre of the 

 upper cover, a small opening which corresponds to the lens of 

 the microscope is made. The former instrument may be used 

 to observe the larger particles of dust in the atmosphere. — Dr. 

 J. M. Macfarlane read a paper, illustrated by lantern demon- 

 strations, on a comparison of the minute structure of plant 

 hybrids with that of their parents. He finds that the minute 

 structure of the hybrid, like the larger features, is always 

 intermediate in character between the corresponding structures 

 of the parents. 



Paris. 

 Academy of Sciences, May 25. — M. Duchartre in the 

 chair. — Researches on the camphene series, by MM. Berthelot 

 and Matignon. — Researches on the vapour-tension of saturated 

 water- vapour at the critical point, and on the determination of 

 this critical point, by MM. Cailletet and Colardeau. In a recent 

 note {Compies rendus, vol. cxii. p. 563, 1891) the authors com- 

 municated to the Academy a new method for determining 

 critical temperatures and presiures. They now give the results 

 obtained in the case of water. Six series of experiments with 

 different weights of water indicate that the critical temperature 

 is 365° C, the critical pressure which corresponds to this being 

 200-5 atmospheres.— On the analysis of the sunlight diffused by 

 the sky, by M. A. Crova. If B be the intensity of the blue 

 light diffused by the sky, and S the intensity of incident sun- 

 light, it may be shown that - , = loof ^-^ ) , where 565 repre- 

 sents 'the wave-length of the maximum light intensity of the 

 spectrum, and n is an empirical coefficient. M. Crova calcu- 

 lates values with « = 4 and « = 4*5, and finds that, although 

 Lord Rayleigh's observations (Phil. Mag., 1871, p. 107) are 

 best in accord in the former case, his own observations at Monl- 

 pellier give results which are better represented when the latter 

 value of n is used.— On the relative age of the Quaternary 

 stratum of Mont Dol (Ille-et-Vilaine), by M. Sirodot. The 

 author's observations lead him to believe that the d^ris on 

 Mont Dol belongs to an epoch anterior to the movement which 

 in Quaternary times elevated the coasts of certain regions of the 

 Baltic Sea. — On the exact determinatian of the glycolitic power 

 of the blood, by M. R. Lepine and Barral. — Observation of the 

 passage of Mercury across the sun's disk on May 9, 1891, made 

 with the Ploessl equatorial at the National Observatory of 

 Athens, by M. D. Eginitis. The internal contact of egress 

 occurred at i8h. 17m. 20s., and external contact at i8h. 2211. os. 

 (Athens mean time). The irradiation phenomenon known 

 as the "black drop" was not observed.— The atmospheric 

 conditions of Greenwich with regard to the universal hour ques- 

 tion, by M. Tondini. The cloudy state of the Greenwich sky,^ 

 and the many rainy days recorded st the Observatory, are 

 adduced as arguments against the adoption of Greenwich as the 

 prime meridian. The meridian of Jerusalem-Nyanza is said 

 to possess numerous atmospheric and other advantages. — On the 

 algebraic integration of differential equations of the first order, 

 by M, Painleve.— On the determination of the integrals of 

 equations from derived partials of the first order, by M. J. 

 Collet.— On Abelian equations, by M. A. Pellet.— Researches 

 in thermoelectricity, by MM. Chassagny and Abrahain. — De- 

 termination of the solar constant, by M. R. Savelief. From an 

 actinometric curve obtained on December 26, 1890, the author 



