The low values found for this transformation coefficient, together with the results of other related experiments, find an explanation in the hypothesis that in some cases (conditions as yet undetermined) the excited K radiation does not escape the atom, but is "internally absorbed " in the outer electron shells, giving rise to highspeed proto-electrons. It is found experimentally that the probability of K-series emission as opposed to its internal absorption is independent of the frequency of the exciting radiation, indicating that the "internal conversion process is a mechanism

to be associated with the ionised atom itself, and is quite independent of the radiation field responsible for the initial ionisation of the atom.

The K-quantum transformation coefficient is a function of atomic number, and such that it seems probable that similar laws, relating probability of absorption to atomic number and wave-length, hold in cases of "normal" and "internal" absorption.

ELECTRONIC STATES AND BAND SPECTRUM STRUCTURE IN DIATOMIC MOLECULES. IV. HUND'S THEORY; SECOND POSITIVE NITROGEN AND SWAN BANDS; ALTERNATING

INTENSITIES.

By ROBERT S. MULLIKEN.

ABSTRACT.

After a brief review of Hund's theory of molecular electronic states and band spectra, and a discussion of intensity relations and selection principles in terms of the correspondence principle, it is shown that practically all the available evidence, as embodied in previous papers of this series and elsewhere, is in agreement with the theory. The occurrence of p-type S terms and σ-type P and D terms is explained by the theory,as also the existence of p-type and σ-type doubling. Selection rules and other relations in 2P-S and S-2P transitions (including, in agreement with Mecke and Hulthen, the CH, OH, MgH, and CaH bands) are discussed. Hund's interpretation of the second positive nitrogen bands as a 3P-3P transition is further developed, and extended to the Swan bands; the apparent absence of Q branches, and other intensity relations in these bands, are explained; the rotational doubling in these bands (accompanied by alternating intensities )is interpreted as o-type doubling. It is shown that the alternating intensities or alternate missing lines in the He,, N2, Swan,

29

=

;

and N, bands can all be accounted for formally by the postulate that they are due to alternate (partially or completely) suppressed levels such that the suppressed values of (j ) are always as follows: Brotational sub-states, (j – å σk) 0, 2, 4, . . .; A sub-states, 1, 3, 5, here σ is the part of σ which is due to the orbital angular momentum of the electron, and j is the resultant of σ and the quantity in which measures the nuclear angular momentum in quantum units. Finally, the questions of term-notation and -formulation, j values for odd and even molecules, eac., are considered. The NH ẞ bands (PS) are briefly discussed.

-Physical Review, U.S.A.

SCIENCE AS A CAREER.

Science men engaged in the teaching profession are not infrequently called upon to advise concerning the future prospects of their individual students. In the case of promising pupils it may be presumed that the vast majority would recommend some branch of pure or applied science according to the type of student.

The anxious parent may well ask: "What has Science to offer?"

Major A. Church, who is well qualified to answer, contributes a valuable article on this subject in an important volume* compiled by J. A. R. Cairns, in which 36 eminent men offer their own practical solutions of the Problem of a Career.

The profession of Science presents great scope for transcendent originality and creative genius and constitutes a field of activity which has wide and beneficial influences upon mankind. The scientific aspirant who revels in study for its own sake, provided he is otherwise fitted, will find scope for such a career in one of many and various kinds of educational institu- | tions, either at home or in the Colonies. Mr. Frank Roscoe, M.A., addresses these and others, contemplating entering the Teaching profession, in a chapter of the same volume. Mr. Roscoe explains the procedure to follow and gives sound advice which will enable those who bear it in mind to make the best out of themselves and acquire the greatest proficiency, at the same time obtaining pleasure from their results. He emphasises that not all who know their subject well are able to impart their know

ledge to others. It is necessary to cultivate the ability of presenting the subject in a manner which renders easy its assimilation by the students.

The monetary rewards in the Teaching profession are never great, and even a successful professor seldom receives a stipend of more than £1,500. This position, too, is only attained by a few of the many members of university staffs. The salary of a Science Master in a secondary or technical school is very modest. This is only partly compensated by an enthusiasm for the subject and eagerness to enjoy the satisfaction of imparting it to fresh minds. Many, it is true, carry on research work on possibly some simple problem which interests them without the prospect of any financial gain.

As Major Church points out (p. 173) only a small proportion of the yearly number of graduates take up appointments in Statemaintained institutions. Most are concerned with the application of science in which there is equal scope for enterprise and research. He mentions in how many directions a student with a science degree can look for a suitable post with the prospects of a promising career. For almost all these, however, a long and arduous apprenticeship is essential to success. The period of study is as long as for medical practitioners and members of the legal profession. The same may be said, indeed, for almost every calling dealt with in The Problem of a Career in which each man, eminent in his own field, reiterates the necessity for hard work, keenness and adaptability on the part of the prospective entrant. He is repeatedly warned, especially, for example, as concerns

the Stage, that fame and success are not easily achieved. Science is also not free from disillusionment.

A young investigator may do something original, perhaps, and will probably find his seniors at best polite, but cold. He will hope to gain recognition by publication. His account may not conform with editorial requirements and it will be rejected without explanation and the young man may be discouraged perhaps for ever.

Even publication will not always bring recognition. This is partly due to professional indifference and to public lack of interest in science generally. This latter, however, is a diminishing factor and it is often said by the public Press that it welcomes scientific matter. Yet how many scientific writers have had rejected their attempts to give lay readers important scientific information. Much science that is so published, fortunately, anonymously, is intended to be sensational, but is more often stupid or inaccurate, and at best, trivial, compared with what might have been said in the same space.

The volume under review contains many excellent accounts of other callings which cannot even be mentioned here. In almost all, the monetary reward is rightly given a very secondary consideration when the question of a life's work is being discussed. Few rich men are able to employ their leisure with pleasure and (mental) profit, but most men of science have such wide interests that seldom does a dull moment step into their life.

Curiously enough, the only slip in Mr. Cairn's compilation is by a successful business man, who is referring to an incident in his capacity as a member of a hospital board. An ingredient in a medicine was quince, which came from the cinchona trees."

66

Of Science, to quote Major Church's concluding paragraphs,

66

Enough has been said to show that blessing and honour and glory and power' are not the usual rewards even of the greatest men of science. The glittering prizes of worldlings rarely fall to their lot. There is no profession which makes greater demands upon the altruism of its coteries. At the end of a stern and arduous apprenticeship there must be a period of further work before it can become in the least degree distinctive.

Then there is the struggle for recognition by the masters. This attained, there can be no resting upon the oars or basking in the sun of established reputation. There is a

We have received a copy of the above Journal (Vol. xv, No. 77) and have pleasure in stating that it contains amongst other matter a summary of the work on the inert gases relative to their chemical combining properties. This article is by DR. H. DAMIANOVICH. It will be of interest to note the references here which are:- Rayleigh and Ramsay, Roy. Soc. Proc., 1895, LVII, 265, 296; H. Moissan, ibid, 1895, pp. 120, 121; Ramsay and Collie, ibid, 1896, LX, 53; T. Cooke, Zeit. für Physik. chem., LV, 537, 46. Strutt, Roy. Soc. Proc., 1912, pp. 381, 384; Boomer, ibid, July 7, 1925; H. Damianovich, this journal under notice, XIII, No. 67, p. 63; Berthelot, C.R., 1895, Cxx, 581; Berthelot, ibid, Jan, 1897, CXXIV, 113; Ramsay, "The Gases of the Atmosphere," 1898; Strutt, Roy. Soc. Proc., 1912, LXXXVII, 381; Soddy and Mackenzie, Proc. Roy. Soc., 1907, LXXX, 381; Villiard, C.R., 1896, CXXIII, Forcrand, C.R., 1923, CLXXVI, 355; W. T. Cooke, Roy. Soc. Proc., 1906, LXXVII, 128; W. Ostwald, Zeit. für Phys. Chem., 1906, LV, 537; Stead, Phil. Mag., Nov. 1924; Manley, Nature, Dec. 13, 1924, March 7, 1925, April 24, 1926; Troost and Ouvrard, C.R., 1895, p. 395; Kayser and Friedlander, Chem. Zeit. Ung., v, 9, p. 524; M. W. Travers, Roy. Soc. Proc., 1897, LX; Runge and Paschen, Phil. Mag, 1895, Vol. 1, pp. 297, 302; Ramsay and Travers, Roy. Soc. Proc., 1897, LXI, A, 267; A. Campbell Swinton, ibid, 1907 LXXXIX, A,

377;

134; Pohl, Ver. der Deutschen Phys. Ges, 1907, 9306, Le Radium, April, 1908; Chrisler, Phys Zeit., 1909, x, 745, Le Radium, Dec. 1909, p. 382; Gmelin-Kraut, v, III, p. 263; Friedlander, Zeit. Phys. Chem., 1896, XIX, 665; Kayser, Math. Naturew. Mith., 1896, 221; Winchester, Phys. Rev., 1914, (I.), p. 287; Ramsay, Collie and Patterson, Nature, 1913, xc, 650; Merton, Roy. Soc. Proc., 1914, xc, 549; Strutt, ibid, LXXXIX, 499; Piutti and Cardoso, Journ, de Chem. Physique, 1920, xvIII, 81; Thomson, La Structure de l'Atome, Institut International de Physique Solvay . . Bruxelles 27 and 31 October, 1913. Published 1921: Discussion du rapport de Thomson; S. E. Lind, "The Chemical Effects of alpha particles and electrons," 1921, p. 127; Collie, Roy. Soc. Proc., 1920, XCVII, A, pp. 349-54; Rutherford, "Radioactive Substances," 1913, p. 482; Campbell, Phil Mag., 1920, XL, pp. 585-611, ibid, 1921, XLI, 681-706, ibid, 1921, XLII, 227-246, ibid, 1922, XLIII, 914-937; Dunoyer, La technique du vide : recueils des conferences, rapports des documentations sur la Physique ,1924, pp. 206215; Claude, C.R., 1911, CLII, 1377; Miss H. F. Homfry, Roy. Soc. Proc., 1911, v, LXXXIV, 99; Dejardin, Ann. de Phys., 1924, 10 serie, Vol. 1, p. 275; E. Goldstein, Tables annulles de constants et données numeriques (Spectroscopie : Bruninghaus) Vol. 4, 1913 and 1916 (Pub. 1923); Phys. Z., 1913-1914, p. 624; W. E. Curtis, Tables, etc., Roy. Soc. Proc., 1913, LXXXIX, 148; Sommerfeld, La constitution de l'atom et les raies spectrales, Traus 3rd Edition, by Bellenot, 1923, p. 528; Frank and Knipping, Phys. Zeit, 1919, xx, 481; Curtis, The structure of the bands spectrum of helium," Roy. Soc. Proc., 1922, CL, 38, 64, ibid, 1925, CVIII, 513; T. R. Merton and J. W. Nicholson, Roy. Soc. Proc., 1919, A, 96, 112; Merton and Barrett, Phil. Trans. Roy. Soc. Lond., 1922, A, 232, 269, and Tables annueles de constants, etc., 1925, pp. 448, 458; Rayleigh, Roy. Soc. Proc., 1923, A. CII, 453; Johnson and Cameron, ibid, 1924, CVI, 195, Dejardin, Annales de Phys., Sept.-Oct., 1924, p. 275; G. Claude, C.R., 1925, CLXXX, 890; C. R. Johnson, Phil. Mag., 1924, XLVIII, 1069, 1074, Journ. de Phy. et Radium, 1925, vi; W. Steunlin and M. Toussaint, Zeits. f. Phys., 1924, pp. 128, 137; J. C. McLennan and Shrum, Roy. Soc. Proc., 1925, cvш, A; H. B. Lemon, Phys, Rev., 1925, p. 109; J. J. Thomson, Conferencia dada en la Royal Institution. 17 Jan. 1913: F. W. Aston, les Isotopes, tr. par Mlle. S. Veil,1923, p. 37; Thomson, Roy. Soc, Proc., 1922, CI, 290; Aston, Roy.

66

Soc. Proc., 1923, сIII, 462; Leon Bloch, Ionisation et resonances des gas et des vapeurs. Recueils des conferences rapports sur la Physique, 1925; J. Franck and R. W. Wood, Phil. Mag., 1911, p. 314 and Le Radium, Sept. 1911, p. 343; Wood, Roy. Soc. Proc., 1924, cvi, A, 679, and Journ. Phy. et Radium, July, 1925; O. W. Richardson, Phil. Trans. 1906, CCVII, A, 413; Franz and Kaupy, Z. Physik, 1920, 1, 49, 50; W. A. Bone, D. M. Newitt and D. T. A. Townud, Roy. Soc. Proc., 1926, cx, 645; Ramsay and J. N. Collie, Roy. Soc. Proc., 1896, LX, 206; Ettore Cardoso and Gabriele Battista, Anales de la Sociedad Espanola de Fisica y Quimica, Oct. 1922, p. 421; Dolezalek, Zeit. Phys. Chem., 1919, XCV, 585; J. Duclaux, L'adsorption en relation avec la catalyse et les actions enzymiques Institut International de chimie Solvay, 2 Conseil de chemie tenue a Bruxuelles du 16 au 24 Avril,1925. Publié en 1926; H. E. Armstrong "Graham Lecture," Trans. Roy. Phil. Soc. Glasgow, 1912, XCIII, 77; Mendelejeff, Rev. de Chemie pure et appliquee, 1906, IV, 533, cit por Enciclop di chimica, 1906, Iv, p. 278; Soddy," La chemie des elements radio-actif," tr. par E. Phillippe, 1915, p. 166.

We might add to the above full bibliography the experiments of F. Fischer and F. Schröter, Berichte, 1910, XLIII, 1442.

REPORT OF H.M. INSPECTORS ON THE PROVISION OF INSTRUCTION IN PURE CHEMISTRY IN TECHNICAL COLLEGES AND SCHOOLS IN ENGLAND.

(Copyright vested in H.M. Stationery Of ice.)

(Continued from p.39.)

CHARACTER OF THE INSTRUCTION. As a rule the quality of the teaching is good. The high educational qualifications of many of the teachers ensure accuracy and fullness, and the matter is generally well arranged and sound. In many cases the method, also, is excellent. But all teachers are not endowed with equal judgement, nor with a natural aptitude for teaching, and all have not had the same experience. It will, therefore, be useful to indicate the more important defects which have been observed. Thus, while in the majority of cases the lectures are adequately illustrated by experiment, there are a few centres in which more experimental illustration is desirable. Even if an experiment cannot be perforemd it is often useful to set up the necessary apparatus, because