October 15, 1903] 



NATURE 



587 



has made great progress during the last thirty years. 

 Under the last head may be grouped periodic and asymp- 

 totic paths, the problem of the gaps in the asteroids and 

 the ring of Saturn, and the theory of the libration of the 

 moons of Jupiter and Saturn. .When these are carefully 

 considered, they appear to point to the stability of the 

 planetary system for all time. This conclusion is, indeed, 

 rendered less general by Poincard's proof of the divergence 

 of series in the theory of disturbances, but it can neverthe- 

 less be shown that, during a long period of time, for which 

 it is possible to give a lower limit, changes in the planetary 

 system are unimportant. The problems which still face the 

 astronomer who undertakes similar investigations were 

 exemplified by Lexell's comet and Darwin's periodic paths. 



Prof. Sommerfeld, in indicating the direction in which 

 mechanics comes into technical use, spoke of the confirm- 

 ation of experimental principles and the greater use of 

 theory. He gave an account of the teaching of mechanics 

 in the universities and Polytechnika of Germany, entering 

 somewhat into detail as regards the order of presentment of 

 various conceptions. Dr. Otto Fischer discussed the 

 necessity of determining the dimensions, the mass, the 

 centre of gravity, and the moment of inertia of various 

 portions of the living body, and the effects of external and 

 internal forces in altering these properties. 



On the morning of September 25 Sir William Ramsay 

 lectured on the periodic system of the elements. Prof. 

 Griesbach on school hygiene, and Prof, von Behring on 

 the fight against tuberculosis. Ramsay spoke of the 

 various attempts which have been made to ascertain whether 

 mass and inertia, on the one hand, are invariable, or, on 

 the other, whether the atomic weights show signs of vari- 

 ation. On the whole, the evidence is negative. He then 

 described the spontaneous change of the emanation from 

 radium bromide into helium, and concluded with some 

 speculations as to the possible formation and decomposition 

 of what are at present regarded as elementary bodies. The 

 subject of school hygiene, though a very important one, has 

 little scientific interest, but the lecture of von Behring was 

 listened to with the greatest attention. Prof, von Behring 

 has a large estate at Marburg where experiments on 

 tuberculosis are carried out on animals. For example, he 

 has rendered it very probable that vaccination of cows with 

 the tuberculosis antitoxin renders their milk immune, and 

 that the milk, in its turn, may render human beings 

 immune. He believes to have shown that infants acquire 

 tuberculosis through milk, and that even before birth the 

 skin of infants is penetrable by the tubercular bacillus. If 

 such infants are nourished on the milk of cows which have 

 been injected with tubercular bacillus, the milk contains an 

 antitoxin, and the tendency towards tuberculosis is obviated. 

 He advocated the view that adults seldom acquire tubercu- 

 lous diseases unless they are early predisposed to receive 

 them by infection as infants. But this tendency can be 

 combated by feeding infants with milk from cows which, 

 through vaccination with tubercular matter, have developed 

 the suitable antitoxin. 



Prof, van 't Hoff, the president of the Association, then 

 concluded by giving a short account of the most important 

 papers which had been communicated to the sections, after 

 which he thanked the town of Cassel, in the name of the 

 Society, for its hospitable reception. 



The German " Naturforscherversammlung," unlike the 

 British Association, includes many sections which treat of 

 medical subjects. Only those lectures which are of general 

 interest are delivered before the Association as a whole. 

 The proceedings of the medical sections will doubtless find 

 their way into the medical journals, and only the proceed- 

 ings of scientific interest will be treated of here. Through 

 the courtesy of the president and of Prof. Rassow, of 

 Leipzig, abstracts of the more noteworthy of the papers in 

 each section were furnished to the writer. 



Of the mathematical section, it was merely stated that 

 in all five meetings were held, in which twenty-eight papers 

 were read, three being of some length. It would appear 

 that mathematicians are too modest to thrust their views on 

 the scientific brethren, or perhaps they doubt if they would 

 be understood. 



The most noteworthy papers in the physical section 

 were, first, a confirmation by Prof. Rubens of Maxwell's 

 theory by experiments on the optics of metals — their re- 

 fractivity, and behaviour to electric currents; and, second, 



NO. 1772, VOL. 68] 



a paper by Prof. Nernst, in which he described and showed 

 his iridium apparatus, by means of which a temperature 

 of 2000° C. has been attained, and determinations of vapour 

 density carried out. Nernst 's " furnace " consists of an 

 iridium tube about 10 inches long and \\ inches diameter. 

 By means of a powerful current which passes through the 

 walls of the tube the temperature can be raised to any 

 desired degree, short of the melting point of iridium. A 

 small " bulb " of iridium, similar to that used for Victor 

 Meyer's density apparatus, hangs inside the tube, and 

 attains the temperature of the iridium tube. Nernst's 

 balance, by means of which a couple of milligrams of sub- 

 stance can be correctly weighed to within a half per cent., 

 consists of a glass fibre suspended by a quartz fibre at right 

 angles to it ; from one end hangs a small iridium capsule 

 counterpoised by a small weight ; the other end of the glass 

 fibre projects over a mirror-scale ; the balance acts partly 

 by torsion of the quartz fibre, partly like a steelyard. The 

 density of vapours of " non-volatile " substances is deter- 

 mined exactly as with a Victor Meyer apparatus, and while 

 that of sulphur was found to correspond to S,, that of 

 phosphorus gave negative results in an atmosphere of 

 nitrogen, due, no doubt, to the formation of a compound 

 of phosphorus with nitrogen, stable only at a high tempera- 

 ture. Nernst also described his method of measuring high 

 temperatures by noting the intensity of the radiation from 

 the interior of the tube. 



In the section of applied mathematics. Dr. Otto Thilo 

 spoke of the necessity of a knowledge of mechanics for the 

 investigator. By help of preparations and models he demon- 

 strated the relation of sinews to bones, especially those 

 which confine the motion to one plane, the mechanism for 

 getting over the " dead-point," and those for restraint, so 

 that muscular power is saved, for example, when a man is 

 standing erect. He further went on to demonstrate the 

 mechanism by which the pressure of air in the swimming- 

 bladder of fishes is communicated to the brain. His con- 

 tention was that even biologists must be instructed in 

 mechanics if they wish to study the movements of living 

 organisms. 



In the chemical section. Prof. Biltz spoke about the pre- 

 cipitation of colloids by salts. He advanced the theory that 

 a colloidal solution consists of a colloid suspended in an 

 electrolyte ; when a precipitant is added a new form of com- 

 bination occurs, for instance : — 

 Electrolyte — colloid -f- colloid-precipitant = 



colloid — colloid-precipitant + electrolyte. 



The precipitation of the iodine-starch substance by means 

 of alumina was illustrated, and also of the meta-phosphoric 

 acid-albumen couple. Prof. Ostwald suggested that the 

 precipitation depends on the relative velocity of the two re- 

 actions, and that that reaction which takes place most 

 rapidly gives rise to the formation of stable substances. 

 Prof. Wedekind showed isomeric organic ammonium salts 

 containing radicals of high molecular weight, and Prof. 

 Ladenburg also read a paper on asymmetric nitrogen. Prof. 

 Wallach mentioned a new instance of optical isomerism, in 

 which, if the molecular weight of the substituting group is 

 low, no isomerism is noticeable, but if high, isomerism exists. 

 CH, OH 



For example, the compound -^ {^ gives us iso- 



H ri 



merides (the benzene nucleus is here seen in perspective), 

 while the similar compounds 



CO . CgHj r-Tj H 



CH, 



1< 



H 



N. 



> 



H 



CH3 

 and <^~ 



H 



-N. 



> 



CO . CgHs 



are isomeric. 



Prof. Nernst read a paper on the theory of ozone form- 

 ation. The potential difference between the system 

 O3, OjlelectrolytejOj is 057 volt, and this corresponds with 

 the heat of formation of ozone, for the couple has practically 

 no temperature-coefficient. He calculated that if oxygen is 

 heated to 6400° it should contain 10 per cent, of ozone, at 

 3230° I per cent., and at 2183° 01 per cent. In the sun 

 the oxygen must be wholly in the state of ozone, owing to 

 th'i high temperature and the enormous gravitational 

 pressure. Prof. Abegg spoke of two cases of heterogeneous 



