Feb. 13, 1890] 



NATURE 



359 



distributed in the head of this comet. There exist peveral centres 

 of condensation with apparent diameters of i" or 2", their mutual 

 distances changing from time to time, but their position remaining 

 constant in the same straight line, which revolves progressively 

 round the principal nucleus. These conditions are specially 

 favourable for the development of secondary nuclei, which the 

 author regards as so many minor comets submitted to the attrac- 

 tion of the sun alone, moving in very elongated elliptical orbits 

 with a common perihelion and different long axes, disposed, 

 however, according to the same straight line. Hence the comet 

 contained within itself the germs of disrupture, its elements in 

 this respect resembling those of the 1843 and 1880 comets. — On 

 the roots of an algebraic equation, by Prof. A. Cayley. Resum- 

 ing the theory of the roots of the equation /{«) = o, instead of 

 the surface c - z — 2"- ■\- Q'\ the author now studies the surface 

 (c _ z)- = P- -f- Q-, taking into consideration the positive values 

 only of z that are not greater than c. He hopes to apply this 

 theory to the case of a cubic equation, where the calculations, 

 however, are much more difficult. — Determination of regulated 

 harmonic surfaces, by M. L. Raffy. Very few surfaces are 

 known whose linear element is reducible to the harmonic form 

 (Liouville's form). To find others, the author employs two dis- 

 tinct processes. The first consists in taking the analytical form 

 of the co-ordinates of the surface in function of two parameters, 

 and determining the unknown functions, so that the linear ele- 

 ment may be harmonic ; the second, in seeking for harmonic 

 surfaces amongst those which may be generated by taking their 

 linear element alone. — Solar observations for the last six months 

 of 1889, by M. Tacchini. Excluding the month of August, the 

 observations here tabulated for the spots and faculas show that 

 the period of calm has continued to the end of the year, and 

 the observations already made for January 1890 show that this 

 period still continues. The same result is shown in the case of 

 the protuberances, so that we appear to have entered the period 

 of absolute minimum. — On the propagation of sound, by MM. 

 Violle and Vaulier. These experiments, made with a cylindical 

 tube, lead to the inference that, whatever be the nature of the 

 initial impulse, the sound-wave tends towards a simple, deter- 

 mined form, and this form once acquired, the various parts of the 

 wave are propagated with a uniform velocity which must be re- 

 garded as the normal velocity of the sound. The velocity in the 

 open air is greater than in a tube, where the influence of the walls 

 causes a retardation in inverse ratio to the diameter, and ex- 

 ceeding 046 m. in a tube with diameter of i meter. The nor- 

 mal velocity of sound in a dry atmosphere at zero is 331 'lO m., 

 with probable error less than o"io m. — On the state of the mag- 

 netic field in conductors of three dimensions, by M. P. Joubin. 

 The results of these researches, which agree with experience, show 

 that the magnetic field produced by a current exists in the medium 

 traversed by the electric flux as well as in the exterior medium. — 

 On the mechanical actions of variable currents, by M. J. Berg- 

 man. In reproducing, with the limited resources of a laboratory, 

 the interesting experiments exhibited by Prof. E. Thomson at 

 last year's Exhibition, the author has obtained some fresh results, 

 which are here described. — Results of the actinometric observa- 

 tions made at Kiev in 1888-89, by M. R. Savelief. These 

 observations lead to the general conclusion that 63*5 per cent, of 

 the annual solar heat reaching the earth is absorbed by the ter- 

 restrial atmosphere, only 36-5 arriving on the surface of the 

 ground ; in October the proportion is 41, in January and 

 February 28 per cent. The maximum received on a fine day in 

 the beginning of July is 610, and in December 87 calories on a 

 given space. — On the compounds of the metals of the alkalies with 

 ammonia, by M. Joannis. In continuation of his previous com- 

 munication {Com/>/es rendus, cix. p. 900) the author describes 

 some further experiments, which are totally at variance with the 

 theory advanced by M. Bakhuis Roozeboom {Comptes retiihis, 

 ex. p. 134) to explain the phenomena already observed by M. 

 Joannis. — On the combinations of ammonia and phosphuretted 

 hydrogen with dichloride and dibromide of silicon, by M. Besson. 

 Withrammonia a solid, white, amorphous substance of the for- 

 mula SioBr4, 7NH3, is obtained, in all respects resembling the 

 corresponding compound of the chloride. Phosphuretted hy- 

 drogen has no action on silicon dichloride at the ordinary tem- 

 perature, but is absorbed at low temperatures. At - 60 C. 

 the composition is approximately Si2Cl4, 2PH3. — On the part 

 played by certain foreign substances in iron and steel, by M. F. 

 Osmond. The author here gives results for boron, nickel, 

 copper, silicium, arsenic, and tungsten, reserving for a future 

 paper full treatment of the subject. — On lussalite, anew crystal- 



lized variety of silica, by M. Kr. Mallard. To the substance 

 here described as nearly pure silica, the author gives the name 

 of lussatite, from the deposits of bitumen at Lussat, near Pont- 

 du-Chateau, where its properties may best be studied. — On the 

 oxides of manganese, by M. Alex. Gorgeu. In this paper, the 

 author studies the psilomelanes and wads, reserving for a future 

 note the manganites, properly so called : hausmannite, acerdese, 

 and braunite. — Papers were read by M. Paul Marchal, on the 

 structure of the excreting organ in the prav\n ; by M. P. A. 

 Dangeard, on the junction of stem and root in the gymno- 

 sperms ; by M. Stanislas Meunier, on a new method of arti- 

 ficially producing ferriferous platinum with magnetic poles ; and' 

 by M. Alexis de Tillo, on the hypsometric chart of European 

 Russia.— M. Gilbert was nominated Corresponding Member of 

 the Section for Mechanics in place of the late M. Broch. 



Berlin. 



Physiological Society, January 17. — Prof, du Bois-Rey- 

 mond. President, in the chair. — Dr. Weyl gave an account of 

 experiments which he had made in conjunction with Dr. Kitasato 

 on the biology of anaerobic Bacteria. Koch had only imperfectly 

 overcome the difficulty in the way of a pure culture of these 

 Bacteria, viz. the exclusion of atmospheric oxygen, by covering 

 the plates on which they were being grown with films of mica. 

 Livonius was more successful by means of a deep layer of Agar- 

 Agar, and by replacing the air by an atmosphere of hydrogen. 

 The speaker had endeavoured to arrive at the same result by 

 mixing the material on which the cultivation was carried on witb 

 some substance which has an affinity for oxygen, and obtained 

 good results with dioxyphenols and aldehydes, but more par- 

 ticularly with formate of soda. The members of the first class 

 of substances, of which a large number were tried, had for the 

 most part to be abandoned, for they exerted a toxic action on the 

 Bacteria when they were employed in quantities sufficient to in- 

 sure the complete absorption of oxygen. Very fine pure 

 cultures of the anaerobic Bacteria of "quarter-evil" {Raiisch- 

 brand), of tetanus, and of malignant oedema, were obtained on. 

 Agar- Agar by the use of eikonogen and of formate of soda, and! 

 were exhibited to the meeting. By means of these pure cultures 

 it was possible to demonstrate that the anaerobic Bacteria exert a 

 powerful reducing influence ; this was shown on preparations in 

 which the culiure-material was deeply coloured with indigo-blue, 

 the latter being then reduced by the organisms to indigo-white. 

 These simple methods of cultivation facilitate greatly the further 

 investigation of these Bacteria. — Prof. Liebreich spoke on the 

 function of the bladder in fishes. During his investigations of 

 the inert layer on the upper surface of fluids, he had allowed a 

 float whose specific gravity was slightly less than that of the fluid 

 to ascend through the fluid, and observed that it came to rest a 

 short distance below the surface and remained there. During 

 these experiments the slight changes of temperature which are 

 unavoidable in large masses of fluid produced irregularities 

 which led him to study the phenomena exhibited by a " Carte- 

 sian diver." These are not correctly described in either the 

 older original works on the subject or in the more recent text- 

 books of physics. The equilibrium of the diver is unstable for any 

 given pressure exerted upon the elastic membrane which covers 

 the upper end of the vessel in which he is contained. This the 

 speaker proved, not only by developing the formulae which hold 

 good for a system composed partly of solids and partly of air when- 

 immersed in a liquid, but also by means of a series of striking 

 experiments. When the attention is directed to the experiment, 

 it may readily be noticed that it is impossible to keep the diver 

 in a condition of rest at any given level by exerting a unifarm 

 pressure with the finger on the elastic membrane, but that in 

 order to produce this result the pressure must be continuously 

 varied. If the pressure is applied by a screw instead of the 

 finger, the diver does not remain at rest. When the air is com- 

 pressed until the specific gravity of the diver is slightly greater 

 than that of the liquid, he sinks to the bottom and remains 

 there, however great the air-pressure may be. If now he is 

 drawn to the top of the liquid by means of a magnet attracting 

 a small slip of iron attached to the diver, he similarly remains at 

 rest at the surface. If, again, he is now drawn slightly down, 

 he rises towards the surface again, when left to himself, until he 

 reaches a level above which he no longer rises but now sinks to the 

 bottom. This layer of fluid— such that when drawn above it he 

 rises and when drawn down below it he sinks — may be called his 

 "hydrosphere," or, in other words, it is a layer of liquid within 

 the limits of which his specific gravity is unity. A fish possessed 



