February 13, 1902] 



NA TURE 



359 



extended. The paper is illustrated by some ninety figures. 

 Three desmids, Mkraslerias ftircata, Ag. , Stauraslritm Arciiscon 

 (Khrenb.), Lund., and Slaiirasliiim longhpinum {ViA\\.), Arch., 

 are of particular interest in that they appear to be confined to 

 the western shores of the British Isles — being known only as 

 occurring in the small lakes in the hilly districts of Connemara 

 and Donegal in Ireland, the lakes of the Snowdon range in 

 North Wales, and from similar situations in the extreme north- 

 west of Scotland. No species of Vaucheria were found, and 

 Botrydium granulatum is recorded for the first time in Ireland. 



Royal Dublin Society, December iS, 1901.— Dr. W. E. 

 Adeney in the chair. — Sir Howard Grubb, F.R.S., on some 

 new forms of geodetical instruments. The author applies the 

 principle he recently described [Scientific Transactions^ Royal 

 Dublin Society, vol. vii. p. 321) for gun sights for large and 

 small ordance to various forms of geodetical instruments. — 

 Prof. J. Joly, F.R.S., on sedimentation experiments and theories. 

 T he rales of settlement of suspensions consisting of 5 grammes 

 of finely powdered solid in 12 c.c. of water containing ions in 

 various degrees of concentration, indicate that above a certain 

 concentration the rate of fall of the surface of the suspension is 

 fairly independent of the degree of concentration. Below 

 certain concentrations (about five times greater for monad 

 positive ions than for diad) a distinct surface to the descending 

 suspension fails, and the sediment is only seen to collect from 

 the bottom of the vessel upwards. A suspension precipitated 

 at a concentration so low as to be near the point of failure to 

 show surface will, if reshaken, not again precipitate with a 

 distinct surface. On removing the electrolyte from such an 

 " exhausted " suspension after it has stood sufficiently long to 

 settle, it is found that the liquid is as efTective as at first in pro- 

 ducing surface if a fresh sample of the powder is used. On 

 the other hand, the original powder will not again show surface 

 when treated with fresh electrolyte of the same strength, but it 

 will require a much more concentrated electrolyte to do so. 

 The failure is therefore to be traced to some alteration in the 

 solid particles. On testing the fresh powder it is found that 

 this is negative towards distilled water ; the used powder is 

 apparently quite neutral towards its salt solution. An explana- 

 tion of sedimentation is advanced, based on the low specific 

 inductive capacity of the solid particle compared with the 

 specific inductive capacity of the water, the charges on the 

 ions being assumed to exert an expulsive action consequent on 

 the increased energy required to establish the electric field in 

 the medium of low specific inductive capacity. In other words, 

 the solid particles have a de-ionising influence, and experience 

 a reaction in consequence, which will tend to retain in juxta- 

 position particles which from any cause are once approximated. 

 A principal cause of aggregation upon first precipitation is to be 

 ascribed to the negative sign of the particles leading to motions, 

 all in the end favourable to aggregation, seeing that the state of 

 aggregation is alone stable in the medium. On second disturb- 

 ance the particles are neutral, and aggregates are not formed 

 with sufficient rapidity to lead to a general and simultaneous 

 descent of the suspension. — Lord Rosse, K.P., F.R.S., ex- 

 hibited working models of apparatus for turning aside leaves in 

 the water supply of a turbine. — Sir Howard Grubb exhibited 

 the coelostat constructed for the Royal Dublin Society and 

 used at the solar eclipse of 1900. 



January 22. — Prof. W. F. Barrett, F. R.S., in the chair. — 

 Mr. W. E. Wilson, F.R.S., on the nebula; surrounding Nova 

 Persei.— Prof. Barrett, Mr. W. Brown and Mr. R. A. Hadfield, 

 on researches on the electric properties of an extensive series of 

 alloys of iron. — Mr.RichardJ. Moss, on an improved volumetric 

 method for the determination of sugar. In Pavy's modification 

 of Fehling's method, cupric oxide is reduced in presence of a 

 a lar^e excess of ammonia, which prevents the precipitation of 

 cuprous oxide. The temperature of the boiling liquid varies 

 from about 70° C. to 90° C. , and the rate of reduction varies to 

 a corresponding extent. The author overcomes this objection 

 to the method by using a much smaller quantity of ammonia, 

 and conducting the titration under pressure, at the temperature 

 of boiling water. The reduction of the cupric oxide is 

 apparently instantaneous, and the results are very sharp and 

 constant. 



P.^Ris. 

 Academy of Sciences, February 3. — M. Bouquet de la 

 Grye in the chair. — On a new synthesis of formic acid, by 

 M. Henri Moissan. Potassium hydride absorbs carbonic 



NO. 1685, VOL. 65] 



acid at the ordinary temperatures producing potassium form- 

 ate. The formation of formic acid was confirmed by the 

 production of the free acid, which showed the ordinary re- 

 ducing properties, and by the preparation and analysis of the 

 crystallised lead salt. Carbon monoxide also reacts with potass- 

 ium hydride at 150° C, potassium formate being formed and 

 carbon set free. — On certain cases of adherence of a viscous 

 liquid to the solid with which it is in contact, by M. P. Duhem. 

 — New observations on the folds of the phosphatic chalk in the 

 Somme, by M. J. Gosselet. The strongly inclined layers of 

 phosphatic chalk discovered at Etaves in 1S96 might have been 

 looked upon as a local accident, but the same facts have now 

 been noticed at Hargicourt, and at two places at a much greater 

 distance, Eclusier, between Peronne and Albert, arid at Crecy 

 in Ponthieu. These layers are small, but are too widely ex- 

 tended to be the result of a purely local accident. The facts 

 observed confirm the views of M. Marcel Bertrand on the slow 

 and progressive formation of the folds of a geological basin. — • 

 Remarks by M. Albert Gaudry on presenting to the Academy 

 a work on the comparison of the teeth of man and the anthropo- 

 morphic apes. — M. Alfred Picard was elected a free member in 

 the place of the late M. de Jonquieres. — Observations of the 

 sun made at the Observatory of Lyons with the Brunner 16 cm. 

 equatorial during the second quarter of 1901, by M. J. Guil- 

 laume. Tables are given showing the number of spots, their 

 distribution in latitude and the distribution of the faculce in 

 latitude. — Researches on the Hertzian waves emanating from the 

 sun, by M. Charles Nordmann. The experiments described 

 were carried out at the Grand-Mulets on Mt. Blanc, the 

 weather conditions being too unfavourable to utilise the ob- 

 servatory at the summit. The conclusions drawn from the 

 experiments are that the sun does not emit electric radiations 

 capable of affecting radioconductors, or that, if they 

 are given off, they are completely absorbed by its 

 atmosphere or by the upper portions of the terrestrial 

 atmospheie. — Some remarks on entire functions, by M. Edmond 

 Maillet. — The variation of the electromotive force and the tem- 

 perature coefficient of the Daniell cell with the concentration of 

 the zinc sulphate solution, by M. J. Chaudier. Starting with a 

 saturated .solution, the electromotive force of a Daniell cell 

 increases when the concentration of the zinc sulphate diminishes, 

 passes through a maximum for a \ per cent, solution, and then 

 again decreases for smaller concentrations. The temperature co- 

 efficient, which at first is negative, increases and becomes zero 

 at a concentration of between 7 and S per cent. ; but, after 

 having attained a positive maximum,' it falls off and vanishes a 

 second time for a i per cent, solution. From this it follows that 

 the Daniell cell furnishes a standard cf electromotive force which 

 is independent of the temperature when it is made up with a 

 saturated solution of copper sulphate and a 7 '5 per cent, or i per 

 cent, solution of zinc sulphate. — On the galvanometric observ- 

 ation of distant storms, by M. J. J. Landerer. With the 

 arrangement described the electrical disturbances due to distant 

 storms have been observed up to a distance of 240 kilometres. — 

 Comparison between the properties of hydrogen selenide and 

 those of hydrogen sulphide, by MM. de Forcrand and Fonzes- 

 Diacon. Data for hydrogen sulphide are given in the present 

 paper. The boiling-point at a pressure of 773 mm. was found 

 to be -6i°C.,and the melting-point -S6^C. The density of 

 liquid sulphuretted hydrogen at its boiling-point is o'86. A 

 comparison with the data previously given for hydrogen selenide 

 shows great analogies between the two compounds. They have 

 practically identical molecular volumes, their boiling-points 

 expressed as fractions of their critical temperatures are the same, 

 and the ratio of latent heat of vaporisation to the boiling-point 

 is also nearly the same for the two gases. — On the action of 

 lithium-ammonium on antimony, and on the properties 

 of the antimonide of lithium, by M. P. Lebeau. Lithium- 

 ammonium reacts upon antimony, giving a compound of 

 the formula ShLi.,, identical with that previously obtained by 

 electrolysis. This substance dissolves in liquid ammonia, uniting 

 with it to form the compound SbLijNHj. Lithium antimonide 

 is less fusible than either of its constituents, and possesses very 

 energetic reducing properties. — On oxy-isopropyl-hypophos- 

 phorous acid, by M. C. Marie. — On the hydrolysis of pyro- 

 mucic urethane, by M. R. Marquis. — The action of nitric acid 

 upon trichloro- and tribromo-veratrol, by M. H. Cousin. The 

 action of nitric acid upon these substituted veratrols gives rise 

 to mono-nitro-derivatives, the reaction being altogether different 

 from the action of nitric acid upon the tetra-chloro- and tetra- 



