February 8, 1906] 



NA TURE 



359 



of the distance. This derived solution is used in the two 

 following papers, for which it is found much more con- 

 venient than the solution used in §§ 5-31. — Illustrations 

 of the indefinite extension and multiplication of a group 

 of two-dimensional deep-sea waves, initially finite : Lord 

 Kelvin. The water is left at rest and free, after being 

 artificially displaced to a configuration of a finite number 

 of sinusoidal mountains and valleys — five mountains and 

 four valleys in the initiation of the diagrams placed before 

 the society. Immediately after the water is left free, the 

 disturbance begins analysing itself into two groups of 

 waves, seen travelling in contrary directions from the 

 middle line of the diagram. The perceptible fronts of 

 these two groups extend rightwards and leftwards from 

 the end of the initial single static group, far beyond the 

 " hypothetical fronts " supposed to travel at half the wave 

 velocity, which (according to the dynamics of Osborne 

 Reynolds and Rayleigh in their important and interesting 

 consideration of the work required to feed a uniform pro- 

 cession of water-waves) would be the actual fronts if the 

 free groups remained uniform. How far this is from being 

 the truth is illustrated by the diagrams. Besides the great 

 extension of the fronts outward from the middle, we see 

 that the two groups, after emergence from perceptible co- 

 existence in the middle, travel with their rears leaving a 

 widening space between them of water not perceptibly 

 disturbed, and with wavelets in ever augmenting number 

 following slower and slower in the rear of each group and 

 causing the extreme perceptible rear to travel at a much 

 smaller speed than half the " wave velocity." It is 

 obviously difficult to give any definition of an " effective 

 front," or of a " centre of group," or of a " virtual rear," 

 according to which we could regard the group as travelling 

 with half the wave velocity or with any single definite 

 velocity. — The initiation and continued growth of a train 

 of two-dimensional waves due to the sudden commencement 

 of a stationary periodically varying forcive : Lord Kelvin. 

 A forcive consisting of a finite sinusoidally varying pressure 

 is applied, and kept through all time applied, to the 

 surface of the water within a finite practically limited 

 space on each side of the middle line of the disturbance. 

 In the beginning the water was everywhere at rest and its 

 surface horizontal. The problem to be solved is, to find the 

 elevation or depression of the water at any distance from 

 the mid-line of the working forcive, and at any time after 

 the forcive began to act. The solution was illustrated by 

 two diagrams — time curves — one showing the motion of 

 the water at the mid-line of the working forcive, the other 

 showing the motion at a distance from this line equal to 

 the wave-length that would be in an endless uniform pro- 

 cession of waves having period equal to the period of the 

 disturbing forcive. Calculations are in progress to give the 

 motion of the water at eight wave-lengths from the source. 

 The detailed calculations were made and the curves drawn 

 for Lord Kelvin by Mr. George Green. 



Erratum. — In the report of the meeting of November 20, 

 1905 (Nature, December 28, 1905), the words " quite did 

 away with" on p. 216, line 23, should be "had no 

 appreciable effect on." 



Paris. 



Academy of Sciences, January 29.— M. H. Poincare in 

 the chair. — New researches on the insoluble alkaline com- 

 pounds contained in living plants : M. Berthelot.— The 

 capture of a whale (genus Kogia) near Roscoff, English 

 Channel : Yves Delagpe. The animal was captured at 

 Siec, about 6 kilometres from Roscoff. The species is 

 extremely rare, and has never been previously observed 

 in European waters. — Certain systems of circles and 

 spheres which occur in the deformation of quadrics : C. 

 Guichard. The perpetual secretary announced the death 

 of Sir John Burdon-Sanderson, correspondant for the sec- 

 tion of medicine and surgery.— Differential equations of 

 the second order of which the general integral is uniform : 

 -M. Gambier. — The flame spectrum of mercury : C. 

 de Watteville. Attempts to photograph a flame spectrum 

 of mercury have been hitherto unsuccessful. By the use 

 of solutions of the acetate and cyanide of mercury, sprayed 

 into a flame, the author has been successful in" obtaining 

 the flame spectrum of mercury, consisting of the single 

 line 2536-72. This line was measured bv Kavser and 



NO. I. 



VOL 



73] 



Runge in the arc spectrum of. mercury. — The duration of 

 the discharge in an X-ray tube : Andre Broca. With 

 equivalent sparking distances varying from 6 cm. to 10 cm., 

 the time was practically constant, o-ooob sec. — The diminu- 

 tion of the radio-activity of polonium with time : Mme. 

 Curie. The intensity of the radiation diminishes with the 

 time according to a simple exponential law, I = l„e-"'. 

 If / is expressed in days, 11=0-00495, or the intensity falls 

 to half its value in 140 days. A diagram is given showing 

 the linear relation between log I and the time, the devi- 

 ations between the values obtained from the above law 

 and from experiment not exceeding 3 per cent. The agree- 

 ment of the constant (0-00495) with that found by 

 Marckwald for radiotellurium (0-00497) shows that the 

 latter substance is identical with polonium. — The sulphates 

 of some rare metals : Camille Matignon. Thermo- 

 chemical measurements on the sulphates of lanthanum, 

 praseodymium, neodymium, and samarium. — The rapid 

 preparation^ of solutions of hydriodic acid : F. Bodroux. 

 A given weight of iodine is divided into two equal portions. 

 By the interaction of barium peroxide and the first por- 

 tion, barium iodide is produced; the remainder of the 

 iodine is dissolved in the solution of barium iodide, and 

 the liquid treated with sulphur dioxide until decolorised 

 filtered from the barium sulphate, and redistilled.— Aii 

 alloy of thorium and aluminium : O. Honigschmid. 

 This alloy, the composition of which corresponds to the 

 formula ThAl a , can be obtained in the form of long 

 hexagonal prismatic needles possessing the colour and 

 metallic lustre of aluminium, by the reduction of thorium 

 oxide by aluminium in the electric furnace. It can also 

 be obtained by the interaction of aluminium and the double 

 fluoride of aluminium and thorium at a high temperature. 

 — Researches on the halogen compounds of the borates of 

 barium and strontium : L. Ouvrard. The borates of 

 barium and strontium appear to enter into combination 

 with chlorine and bromine less easily than the correspond- 

 ing salts of calcium, only one halogen compound of each 

 being obtainable.— a- and jB-eampholytic alcohols : G. 

 Blanc. Details of preparation and physical properties. 

 The pyruvic ester of each is described, and the correspond- 

 ing semicarbazones.— The influence of the reaction of the 

 medium upon the activity of the diastases : A. Fernbach. 

 Remarks on a recent note on the same subject by L. 

 Maquenne and E. Roux.— The nutrition of green plants 

 by amides in the absence of carbon dioxide : Jules Lefevre. 

 Experiments made on the dwarf nasturtium led to the 

 following conclusions :— Plants deprived of carbon dioxide 

 and amides lose a notable proportion of their initial weight 

 this loss being due to respiration. Plants kept in the 

 light, with amides present in the soil, in spite of the 

 absence of carbon dioxide, developed and increased their 

 dry weight. Light is essential for the utilisation of the 

 amides by the plant.— A new parasitic fungus, Tremato- 

 valsa Matruchoti, causing the disease of the silver lime 

 tree : Nicolas Jacobesco. This fungus is the cause of a 

 disease which has ravaged the lime 'forests of Wallachia. 

 It .qipears to belong to a new family.— The classification 

 into genera of the family of the 'BradvpodidEe (genus 

 Hemibradvpus) : R. Anthony.— Contribution to the general 

 morphology of the higher Protozoa: J. Kunstler and Ch. 

 Gineste. — The anatomy and histology of the Ixodida? : A. 

 Bonnet. — The effect of the injection of extract of the 

 interstitial gland of the testicle on the growth : P. Ancel 

 and P. Bouin — Tables of growth drawn up in 1905 from 

 the measurements of 4400 Parisian children between the 

 ages of one and fifteen years : MM. Variot and Chaumet. 

 The results are given both in graphical and tabular form, 

 comparison being made with similar measurements of 

 Bowditch (Massachusetts) and Rotch (Boston).— The 

 physiological conditions of oral teaching : Pierre Bonnier. 

 The effects of a want of knowledge uf the principles of 

 voice production are throat troubles with the teachers and 

 increased mental effort on the part of the pupils. Measure- 

 ments are given showing the importance of the latter effect. 

 — Chloroform anaesthesia. The estimation of the chloro- 

 form before, during, and after anaesthesia is set up, and 

 the quantity in the blood at the moment of death : Maurice 

 Nicloux. — The Neocretacean ammonites collected by the 

 Swedish Antarctic Expedition : W. Kilian.— The geology 

 of the Peloponnesus : Ph. Nesrris. 



