45^ 



NATURE 



[August 29, 1907 



lion to ihe discussion took up a very definite line; "The 

 (Electrical theory explains both inertia and radiation ; and 

 when a satisfactory explanation is given it ought to be 

 supposed to be the right explanation, inasmuch as it is 

 unlikely that two dilferent systems will both tit the 

 facts." One difiiculty that has to be faced is that dis- 

 persion, absorption, and radiation (which are all con- 

 nected) appear to indicate that the electronic constituents 

 of an atom are few, but the electrons so tested may be 

 only those which are comparatively free, and are' not 

 completely encased or submerged in an opposite charge. 

 Such deep-seated or constitutional electrons would be in- 

 accessible to light vibrations, and would take no part in 

 dispersion unless violently shaken bv chemical clash. 

 Ihe real diiriculty is our present ignorance of the nature 

 of positive electricity. .Sir Win. Ramsay urged that the 

 chemist is at present more interested in the detachable 

 electrons, and leaves the nature of the constitution of the 

 atom as non-essential from the point of view of chemistry 

 Ihesc detachable electrons are the cause of valency and 

 chemical elements of the metallic class must be regarded 

 as compounds ; for example, HE niav represent an atom 

 of hydrogen the E of which is an electron; for hydrogen 

 chloride, dissolved in water, gives as one of its products 

 11 while the E is transferred to the chlorine atom. He 

 referred to Prof. Rutherford's statement that no profound 

 change had been discovered to take place in matter bv 

 the loss of electrons, and he pointed out that nickel under 

 combined bombardment bv electrons is partially trans- 

 formed into a radio-active body belonging to thit •;erip<; 

 of metals which yield insoluble sulphates. .\ fain of 

 electrons, therefore, produces a permanent chance in 

 matter. " 



To Mr. F. Soddy, the philosophic unification for which 

 ■ \ ,7 Se had pleaded seemed " unphilosophic and 

 strained. _ ^ It was possible to retain the idea of the inertia 

 of electricity as being due to the magnetic field around 

 the moving charge without taking the further step of 

 supposing that matter was ultimately electrical in 

 character. The subject is being approached from both 

 the speculative and experimental sides, and the hypotheses 

 of the former side often failed when subjected to the 

 supreme test of prediction, and were sometimes little more 

 than an ingenious mimicry of known facts. Mr G \ 

 Schott considered that it w^as too soon to expect' the 

 mathematical physicist to predict new phenomena since it 

 IS only within the last few years th.al he has been sup- 

 plied with the materials necessary for his method eg. 

 he eectron He adduced one positive result which may 

 help to decide between the static and the kinetic view of 

 the atom. A uniform magnetic force acting on a rotaiine 

 ring gives a periodic mechanical force capable of pro- 

 ducing resonance. In consequence, a rotating ring is 

 capable of yielding a magnetic moment very much larger 

 than it would do if at rest relatively in the field Prof 

 Larmor claimed the right of physicists to make hypotheses 

 even with regard to the atom'. He considered that our 

 views about the electron would have been just the same 

 as they now are if radio-activity had not been discovered 

 and he gave a short historical account of the develop- 

 ment of electronic theory from Faraday through Maxwell 

 to modern times. Lord Kelvin preferred to regard the 

 .-itom as a big gun loaded with an explosive shell. The 

 firing of a shell does not cause the destruction of the 

 gun ; the electron, however, changes its nature in a way 

 analogous to the bursting of the shell after explosion. 



The discussion throughout was very stimulating, even if 

 few decisive statements could be made. It was note- 

 worthy that no allusion was made to the late.st optical 

 papers of Drude, in which he allocated the parts played 

 by bodies the mass of which is that of an electron, and 

 bodies the mass of which is comparable with the mass of 

 an atom, in determining the optical dispersion of solids 

 e.g. fluorspar. 



A paper was next read by Sir Wm. Ramsav detailing 

 the remarkable discoveries announced in a' letter to 

 Natuke, July 18. Briefly stated, it appears that helium, 

 neon, or .argon is formed from radium emanation 

 according as it is dry. dissolved in water, or dissolved 

 in a strong solution of a copper salt. Simultaneously, 

 lithium and perh.nps sodium are formed, the presumption 



NO. T974 vor,. 76] 



being that they are formed at the expense of the copper. 

 The importance of the former discovery is that this is the 

 first time the nature of the products of radio-active dis- 

 integration has been found to be controllable. 



In a paper by .Mr. F. Soddy and T. D. Mackenzie 

 (Carnegie research scholar) on pseudo-high vacua, it was 

 shown that the electrical characteristics of a high vacuum 

 occur in helium (purified by calcium and subjected to 

 further purification by the passage of the discharge) at 

 pressures between J mm. and ij mm. of mercury, whereas 

 in hydrogen the s.ime holds at i 25 mm. These pressures 

 are far higher than is commonly supposed. The absorp- 

 tion of helium, argon, and neon in spectrum tubes after 

 continuous running occurs mainly in the volatilised film 

 of aluminium deposited from the electrodes. The gas can 

 be mainly recovered by dissolving the film in mercury or 

 heating the tube. 



Prof. Larmor gave a very brief summary of a paper 

 on the range of freedom of electrons in metals. It was 

 remarked that a hopeful plan for elucidating the 

 mechanism of the transfer of electricity (electrons) from 

 molecule to molecule is to study the time relations. The 

 optical phenomena of metals introduce times, viz. the 

 periodic times of ihe vibrations which are small enough 

 for this purpose. Ilagen and Rubens's experiments on the 

 connection between infra-red radiation and electric con- 

 ductivity show that the time required to establish con- 

 duction completely is a small fraction of the period of such 

 waves. If the semi-free electrons to which conduction is 

 due have a velocity of mean square determined by the 

 gas laws, this restricts their range of freedom almost to 

 ihe interspaces between the molecules. On the other 

 hand, the fact that the square of the quasi-index of re- 

 fraction of light for the nobler metals is not far removed 

 from being a real negative quantity, indicates that the 

 number of such free electrons is of about the same order 

 of magnitude as the number of molecules. 



The proceedings on Monday, .'\ugust 5, opened with a 

 paper by Dr. L. Holborn on optical pyrometry, in which 

 he outlined the various radiation methods of measuring 

 temperature. The most recent optical experiments give 

 for the melting point of platinum the value lyqo" C. if 

 the melting point of gold (1064° C.) is taken as the funda- 

 mental point. Prof. C. Fery followed with a discussion 

 of the various difficulties which are met with in connec- 

 tion with the subject. He mentioned that an apparatus 

 had recently been devised in which there is nothing elec- 

 trical. In this the thermometric receiver, instead of being 

 a Ihermo-element, is a bimetallic spiral which deflects a 

 pointer over a scale attached to the instrument. 



Dr. Harker, who had in recent years obtained a con- 

 siderably lower value for the melting point of platinum, 

 pointed out some of the defects to which the optical 

 method was liable. In particular, there is an uncertainly 

 arising from the absorption of the light by the vapour 

 given off the walls of the furnace. 



After the end of this discussion the section divided into 

 two departments. In the department of mathematics 

 Prof. Forsyth led the way with a brief review of the 

 progress of the calculus of variations during the last 

 century, and in particular of the work of Weierstrass. 

 .\fter referring lo later developments of the subject, he 

 gave an outline of the set of four conditions to be satisfied 

 by an integral involving a derivative of the first order of 

 a single dependent variable, and discussed the necessity 

 and sufficiency of these conditions. 



Dr. W. H. Young gave an outline of some new results 

 reached by himself in the theory of functions of a real 

 variable. He proved that there could be no difference 

 between the right- and left-hand discontinuities of a func- 

 tion except at a countable number of points, and that a 

 similar result held good for non-uniform convergence. Dr. 

 \\\ de Sitter, in ,1 paper on a remarkable periodic solution 

 of the restricted problem of three bodies, showed that one 

 of the orbits worked out by Sir G. Darwin is very nearly 

 of the type called by Poincar^ a periodic solution dc 

 scconde espice. 



Mr. H. Bateman followed with a paper on essentially 

 double integrals, and the part which they play in the 

 theory of integral equations. Starling with the integral 



