TRANSACnOXS OF SECTION B. 655 



of isolation, and properties of this gas have been described in the papers recently- 

 published by Professor Ramsay and his colleagues. Not the least interesting fact 

 is the occurrence of helium and argon in meteoric iron from Virginia, as announced 

 by Professor Ramsay in July.' Like argon, helium is monatomic and chemically 

 inert so far as the present evidence goes. The conditions under which this element 

 exists in cleveite, uraninite, and the other minerals have yet to be determined. 



Taking a general survey of the results thus far obtained, it seems that two 

 representatives of a new group of monatomic elements characterised by chemical 

 inertness have been brought to light. Their inertness obviously interposes great 

 difficulties in the way of their further study from the chemical side; the future 

 development of our knowledge of these elements may be looked for from the 

 physicist and spectroscopist. Professor Ramsay has not yet succeeded in eff'ectino' 

 a combination between argon or helium and any of the other chemical elements. 

 M. Moissan finds that fluorine is without action on argon. M. Berthelot claims 

 to have brought about a combination of argon with carbon disulphide and mercury, 

 and with ' the elements of benzene, . . , with the help of mercury,' under the 

 influence of the silent electric discharge. Some experiments which I made last 

 spring with Mr. R. J. Strutt with argon and moist acetylene submitted to the electric 

 discharge, both silent and disruptive, gave very little hope of a combination between 

 argon and carbon being possible by this means. The coincidence of the helium 

 yellow line with the Dj line of the solar chromosphere has been challenged, but the 

 recent accurate measurements of the wave-length of the chromospheric line by Prof. 

 G. E. Hale, and of the line of terrestrial helium by Profs. Runge and Paschen, leave 

 no doubt as to their identity. Both the solar and terrestrial lines have now been 

 shown to be double. The isolation of helium has not only furnished another link 

 proving community of matter, and, by inference, of origin between the earth and sun, 

 but an extension of the work by Professor Norman Lockyer, M. Deslandres, and 

 Mr. Crookes, has resulted in the most interesting discovery that a large number of 

 the lines in the chromo.«pheric spectrum, as well as in certain stellar spectra, which 

 had up to the present time found no counterparts in the spectra of terrestrial elements 

 can now be accounted for by the spectra of gases contained with helium in these 

 rare minerals. The question now confronts us. Are these gases members of the same 

 monatomic inert group as argon and helium ? Whether, and by what mechanism, a 

 monatomic gas can give a complicated spectrum is a physical question of supreme 

 interest to chemists, and I hope that a discussion of this subject with our colleagues 

 of Section A will be held during the present meeting. That mercury is capable under 

 diflijrent conditions of giving a series of highlj' complex spectra can be seen from 

 the memoir by J. M. Eder and E. Valenta, presented to the Imperial Academy of 

 Sciences of Vienna in July 1894. With respect to the position of argon and 

 helium in the periodic system of chemical elements, it is, as Professor Ramsay 

 points out, premature to speculate until we are quite sure that these gases are homo- 

 geneous. It is possible that they may be mixtures of monatomic gase.s, and in fact 

 the spectroscope has already given an indication that they contain some constituent 

 in common. The question whether these gases are mixtures or not presses for an 

 immediate answer. I will venture to suggest that an attack should be made by 

 the method of diff'usion. If argon or helium were allowed to diffuse fractionally 

 through a long porous plug into an exhausted vessel there might be some separation 

 into gases of different den.sities, and showing modifications in their spectra, on the 

 assumption that we are dealing with mixtures composed of molecules of different 

 weights. - 



' Nature, vol. Hi. p. 224. 



^ The above was written before the interesting work of Profs. Runge and Paschen 

 had become known in this country. These authors communicated papers to the 

 Prussian Academy of Sciences on June 20 and July 11, in which they showed by the 

 method advocated that lielium from cleveite consists of two different gases (Sitzunrfs- 

 hericMe d. k. Prcuss. Ahad. d. Wisscnsch. z. Berlin, 1895, xxx. and xxxiv. ; also 

 Nature, vol. Hi. p. 520). The results were also made known by Prof. Runge at the 

 joint meeting of Sections A and B on September 13. 



