February 13, 1896] 



NATURE 



359 



of expansion, a base line can be measured at the rate of 2500 

 metres per diem, as against 400 metres when bars are used as 

 the standards of length. — Solar observations made at the obser- 

 vatory of the Roman College during the second half of 1895, 

 by M. P. Tacchini.— On the complete solutions of the equation 



x^ tan "'- + Xj tan -' L + ... j^x tan ~^\=i k .Z , 



tiy M. C. Stormer. A continuation of a note presented to the 

 preceding meeting of the Academy.— On the energy dissipated 

 in magnetisation, by M. Maurain. An attempt to measure the 

 energy dissipated by iron and steel wires in a closed magnetic 

 cycle when the variations in the strength of the field are very 

 rapid (see p. 350).— Resistance'of thin metallic sheets, by M. Ed. 

 Branly.— Observations on a recent note, by M. G. Le Bon, on the 

 " dark light," by M. G. H. Niewenglowski. A repetition of M. 

 Le Bon's experiment, carried out in complete darkness, still gave 

 a similar result, showing that the image is due to stored-up 

 luminous energy. — Photography with dark light, by M. Gustave 

 Le Bon. In further experiments made on this subject especial 

 care has been taken to eliminate the possible influence of heat, and 

 of light stored up in the plates.— New properties of the X-rays, 

 bv MM. L. Benoist and D. Hurmuzescu. The X-rays discharge 

 a gold-leaf electroscope, and this offers a ready method for 

 examining the permeability of various substances to these rays. 

 — Experiments on the Rontgen rays, by M. A. Nodon. These 

 rays are clearly distinguishable from the ultra-violet rays by the 

 feet that the latter, obtained from a powerful arc lamp, fail 

 entirely to affect a sensitive plate protected with several thick- 

 nesses of blackened paper. The Rontgen rays readily affect the 

 plate under these conditions.— Transparency of metals for the 

 X-rays, note by M. V. Chabaud. In sheets of 0-2 mm. thick- 

 ness, platinum and mercury alone are perfectly opaque,- while 

 lead, zinc, copper, tin, steel, gold, silver, and aluminium are 

 more or less transparent. In sheets of -oi mm. thickness, 

 platinum also ceases to be perfectly opaque.— The photography 

 of metallic objects through opaque bodies, by means of the 

 brush of an induction coil, without a Crookes' tube, by M. G. 

 Moreau.— On the acid fluorides, by MM. Meslans and F. 

 Girardet. The method employed is to act on the corre- 

 sponding chloride with the fluoride of either arsenic, 

 antimony, silver, or zinc. The fluorides of propionyl and 

 of benzoyl were prepared and their properties examined. — 

 Method of preparation of acid fluorides, by M. A. Colson. 

 The acid anhydrides, treated with hydrofluoric acid, give the 

 corresponding acid fluoride and acid. The chlorides of acetyl 

 and propionyl are very easily obtained in this way.— On a hydride 

 of lithium, by M. Guntz. Lithium, at a low red heat, absorbs 

 about seventeen times its volume of hydrogen without any 

 change of appearance ; at about a red heat further absorption 

 commences, and on cooling the lithium is seen to be covered 

 with a layer of hydride. This was prepared in a pure state, and 

 proved to be LiH.— The negative reaction and the centre of the 

 retina, by M. Aug. Charpentier.— Researches on the embryonic 

 nervous system of the Nauplius and of some larvae of marine 

 animals, by M. N. de Zograf.— Onan Ophidian of the cretaceous 

 earths of Portugal, by M. H. E. Sauvage.— Physiological re- 

 searches on the respiration of fishes (Atnmodytes tobianus), by 

 M. J. B. Fieri. This fish was able to completely extract the 

 oxygen from a solution of air in water, although it could not 

 take out all the oxygen from a solution rich in the gas. As- 

 phyxia is never instantaneous, even when the Ammodyies is 

 mtroduced into water completely freed from dissolved oxygen. 

 This fish can exist without inconvenience in water con- 

 taining a considerable quantity of dissolved carbon dioxide. 

 — Observations on the cephalic vesicle of insects of the 

 family Muscides, by M. A. Laboulbene.— i^/wtor and Tricho- 

 dertna, by M. Paul Vuillemin. Some remarks on a paper of 

 M. J. Ray on the parasitism of a Trichoderma on a supposed 

 new species of Mucor.—Oxx the geological characters of the 

 auriferous conglomerates of the Transvaal, by M. L. de Launay. 

 —On the bed of eruptive and metamorphic rocks of the basin'of 

 Lavol, by M. D. P. CEhlert. — Petrographic study of the Albi- 

 tophyres of the Laval basin, by M. Michel L^vy.— The effects 

 of the solar displacements, considered by themselves, on the 

 barometric pressures of the zone io° to 30° N., by M. A. 

 Poincar^.— On a meteor seen at Baleine on January 6, 1896, by 

 M. Doumet-Adanson. This meteor, the appearance of which 

 was noted to the Academy on January 13, was seen at Baleine 

 at 5.7 p.m. (Paris time), passing horizontally, about 25° above 

 the horizon. 



NO. 1372, VOL. 53] 



Berlin. 

 Meteorological Society, January 7.— Prof. Bornstein, 

 President, in the chair.— Prof. Kremser spoke on the duration 

 of sunshine over Europe, basing his remarks on the data avail- 

 able from the various stations. The mean duration increases 

 from the north towards the south, being least in Scotland and 

 greatest in Spain. There is also a distinct increase from the 

 west eastwards. It is less on mountains than over open plains, 

 except at very high stations which are frequently above the level 

 of the clouds and mist. All stations show a yearly minimum in 

 the winter solstice, and a maximum in the summer ; the latter 

 occurs as early as May in Scotland, in June over Germany, and 

 in July over Spain. There is no such annual variation observ- 

 able at the highest stations. The amplitude of the annual curve 

 is less when based on the percentage of observed to possible 

 duration of sunshine. The curve of daily variation rises sharply 

 in the morning, is then steady for some time, and falls again 

 sharply towards the evening. At high stations the daily maxi- 

 mum occurs in the afternoon. 



Amsterdam. 

 Royal Academy of Sciences, November 30, 1895.— Prof. 

 Van de Sande Bakhuyzen in the chair. — Prof. Engelmann 

 treated the following subjects, (i) The influence of the pulse 

 frequency upon the physiological conductive power of the ventri- 

 cular muscle. (2) A means of rendering extra-polar electric im- 

 pressions upon muscles and nerves impossible. — Prof. Lorentz 

 read a paper on Poynting's theorem concerning the transfer of 

 energy in the electromagnetic field, and on two general pro- 

 positions in the theory of light. After showing how Poynting's 

 theorem may serve to calculate the energy of a magnetised body 

 and the development of heat due to magnetic hysteresis, the 

 author discussed a more general formula, already used by 

 Volterra. The application of this equation to the propagation 

 light (homogeneous and of constant intensity) leads in the first 

 place to a well-known law of reciprocity (viz. a relation between 

 the vibrations at a point A, caused by a source of light at B, 

 and the vibrations at B, produced by a source at A) and in the 

 second place to a generalisation of " Huygens' principle." If, 

 in a system of conducting or dielectric, isotropic, or anisotropic 

 bodies, surrounded on all sides by the ether, a closed surface be 

 arbitrarily chosen, so, however, .that all sources of light are 

 external to it, then a definitive distribution of sources of light 

 over this surface may be indicated, which would give rise at all 

 internal points to the same vibrations as are produced by the 

 external sources.— Prof. Kamerlingh Onnes communicated Dr. 

 Zeeman's further measurements on the absorption of electrical 

 waves in different electrolytes. The results are : (i) the intensity 

 of electrical vibrations (wave-length 6"5 m. ) decreases to one-third 

 of its original value when the vibrations pass a layer of a solution 

 of sulphate of copper, 5 per cent. cm. in thickness, the resistance 

 being 3340-io-i<' jj^^^j ^f mercury. (2) Different aqueous solutions 

 of the same conductivity absorb vibrations of the same frequency 

 in the same degree. — Dr. W. van Bemmelen has drawn the lines 

 of equal secular variation of the magnetic declination for the 

 period 1540- 1880. The values of the yearly variations have 

 been determined by measuring the inclination of the curves on 

 his map, which shows the curves of the secular variation for 

 8 X 18 intersections of meridians and parallels (meeting of 

 September 28). — The maps for 1780 and 1880 show that Bauer's 

 isoclinal poles lie in the immediate vicinity of the lines of 

 maximum variation ; whilst the whole system of maps points out 

 the fact that in the tropical zone these lines and the agonic lines 

 accompany each other. The mean yearly rates of shifting of 

 the poles, the agonic lines and the maximum lines, viz. o'''l94, 

 o°'J84 and o°'2i, agree very closely. 



December 28, 1895.— Prof, van de Sande Bakhuyzen in the 

 chair. — Prof. W. Kapteyn gave a new treatment of a problem 

 on Analysis situs. 



GOTTINGEN. 



Royal Society of Sciences.— The third part of the Nach- 

 richten (physico-mathematical series) for 1895 contains the fol- 

 lowing papers communicated to the Society : — 



May 25. — On the development of Dadocrinus gracilis (von 

 Buch) and Holocrinus IVag/u-ri (Ben.), and their relation to 

 other crinoids, by A. von Koenen. 



June 15. — On the integration of the partial differential equa- 

 tion Am + k-u = o on Riemann's surfaces, by A. Sommerfeld. — 

 The hypsographic curve of the earth's crust and the relations of 

 Romieux .by Hermann Wagner. 



