ii8 



NATURE 



[April 5, 1917 



number of weaker components of both kinds — truly a 

 formidably complicated system. In general, the longi- 

 tudinal components appear to be unpolarised, although 

 Miss Howell has found some anomalies with lithium 

 and calcium. In some cases the components are un- 

 symmetrical both in position and in intensity. Of all 

 the other elements investigated, mercury alone shows 

 a slight broadening. It mie^ht be expected that the 

 great nuclear charges of heavy atoms would diminish 

 the effect of an external field. The inverse absorption 

 effect has so far not been observed. 



Long before the Stark effect was observed Voigt 

 showed that such results might be expected from quasi- 

 elastic forces in the atom and the stresses produced 

 by the field. Schwarzschild has attempted to explain 

 it by the ordinary laws of electrodynamics, and War- 

 burg, Gehrcke, Garbasso and Bohr by Bohr's theory. 

 Each attempt was successful in some respects, but 

 each failed to account fully for all the components, 

 their displacements and their state of polarisation, and 

 all the theories assign the same number of components 

 to each line of a series, whereas one of the most 

 significant features is the progressive difference in 

 number of components, displacements and relative in- 

 tensities in passing from one line to another. Stark 

 not only rejects them all, but is led by his study of 

 the phenomenon to abandon finally the quantum and 

 light-cell theories, because he considers that he has 

 proved that the greatest possible energy which an 

 electron can acquire in its orbit falls far short of one 

 energy quantum. Moreover, he argues that it seems 

 impossible to explain the phenomenon in terms of 

 Bohr's one electron. He concludes that a number of 

 electrons must take part in the emission of a single 

 line, each having the same frequency under ordinary 

 conditions or in a magnetic field, but different fre- 

 quencies when displaced unsymmetrically in an electric 

 field. It is difficult, however, to understand why 

 hydrogen has only one detachable electron if Stark's 

 view is correct. 



It has already been mentioned that at low pres- 

 sures the width of lines may be ascribed entirely to 

 the Doppler effect. The great broadening at higher 

 pressures has never been explained, but it has been 

 assumed that damping, collisions and rotations all 

 play a part. Stark suggests that it may be largely 

 due to atomic electric fields, which may exercise a 

 large influence when the atoms are crowded together. 

 It seems significant that the broadening increases with 

 the ordinal number of a line in a series, is often un- 

 symmetrical, and diminishes with increasing atomic 

 weight in most cases, quite in harmony with the 

 effects of an electric field. Nicholson and Merton have 

 found^ that the broadening of hydrogen lines is in 

 quantitative agreement with Stark's suggestion. 



With changes in vapour density, pressure, tempera- 

 ture or the mode of excitation lines belonging to one 

 series may weaken or disappear, other lines may be 

 strengthened, and new lines may appear. W^e must 

 assume that different groups of lines are due to different 

 emission centres. These differences must depend upon 

 the size of the particles, or upon the number and 

 arrangement of electrons. Any theory must take 

 account of the molecular or atomic state or the elec- 

 trical charge of the emission centres. In some cases 

 we have rather definite information on these points. 



A number of elements emit band spectra under some 

 conditions, line spectra under others. One conclusion 

 which seems to be well established is that band spectra 

 a.re^ emitted by molecules, line spectra by atoms. 

 Universally, we find that compounds give band spectra, 

 never_ line spectra. If a compound is dissociated by 

 the discharge the line spectrum of one or both con- 

 stituents appears. Elements give band spectra with 

 feeble excitation, line spectra when the discharge is 

 NO. 2475, VOL. OqI 



so intense as to cause dissociation. It seems reason- 

 able to infer that the band sp>ectra of elements is like- 

 wise associated with the molecular condition. In the 

 case of monatomic elements which give both band and 

 line spectra electrical conditions must determine the 

 nature of the radiation. 



(7"o he continued.) 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



The war has brought women students into pro- 

 minence in Germany. They form a third of the 

 actual number of students in residence at the twenty- 

 two universities of the Empire, and one-tenth of the 

 total number of registered students. During the 

 winter of 1916-17 there were more women than men 

 at several German universities, e.g. Marburg and 

 Miinster; in Bonn, Frankfurt, Munich, Heidelberg, 

 and Jena the women formed half the students, 

 while they were in a fninority at Strassburg, 

 Leipzig, Breslau, and Giessen. Altogether, there 

 were 5757 women undergraduates at the German uni- 

 versities during the last term, distributed as follows : — 

 Literature and history, 2789 ; mathematics and 

 science, 1036; medicine, 1479; dentistry, 64; economics 

 and agriculture, 225; law, n6 ; Protestant theology, 

 18; and pharmacy, 30. 



The committee appointed to consider arrangements 

 for post-graduate teaching in the Calcutta University 

 has, we learn from the Pioneer Mail, presented a 

 report dealing exhaustively with that subject. In 

 summing up the recommendations the committee 

 states that the proposals, in the main, amount to 

 the acceptance of two fundamental principles : (a) an 

 intimate association and co-operation between the 

 college and the university staffs is imperative in the 

 interest of all concerned and of the development of 

 higher teaching; (b) it is necessary to constitute a 

 suitable organisation within which the teachers will 

 be enabled by discussion among themselves efficiently 

 to conduct the teaching and examination of graduates. 

 Beyond this, says the report, the committee has been 

 unable to go and has refrained from commenting on 

 the wider problems which confront the University. 



SOCIETIES AND ACADEMIES. 

 London. 

 Royal Society. March 22. — Sir J. J. Thomson, presi- 

 dent, in the chair. — J. C. Mottram and Dr. S. Rnss : 

 Observations and experiments on the susceptibility 

 and immunity of rats towards Jensen's rat sarcoma. 

 Observations have been made upon the modes of 

 growth of Jensen's rat sarcoma following inoculation. 

 There is a gradual transition from those cases in 

 which the tumours spontaneously disappear to those 

 in which they grow in a uniformly progressive manner. 

 The experimental production of the immune condition 

 can be brought about in several ways. Animals made 

 refractory to the growth of the tumour have been 

 given various doses of X-rays; the effect of such 

 irradiation upon the blood was to cause a marked 

 reduction in the number of lymphocytes. Over suit- 

 able conditions of exposure it has been possible to 

 destroy the immune condition and thus convert refrac- 

 tory into tumour-bearing animals. There is a tendency 

 for the immune condition to be restored. Histological 

 and other evidence is brought forward which indicates 

 that the failure of sarcoma cells to grow in an immune 

 animal is due to an active resistance thereto on the 

 part of the host. — S. Pickering : Problems bearing on 

 residual affinity. It has been ascertained that the 



