April 



D' 



1917] 



NATURE 



115 



""^vision for the education and instruction of children 

 i young persons after the war, regard being had 

 iticularlv to the interests of those (i) who have 



been abnormally employed during the war; (ii) who 



cannot immediately find advantageous employment; 



(iii) who require special training for employment. 



Among the twenty-three recommendations made by 



the committee are the following : — 



(1) That a uniform elementary school leaving age 

 ot fourteen be established by statute for all districts, 

 urban and rural, and that all exemptions, total or 

 partial, from compulsory attendance below that age 

 be abolished. 



(2) That steps be taken, by better staffing and other 

 improvements in the upper classes of elementary 

 schools, to ensure the maximum benefit from the 

 last vears of school life. 



(3)' That it be an obligation on the local education 

 authority in each area to provide suitable continua- 

 r on classes for young persons between the ages of 



urteen and eighteen, and to submit to the Board 

 Education a plan for the organisation of such a 

 >vstem, together with proposals for putting it into 

 effect. 



(4) That it be an obligation upon all young persons 

 between fourteen and eighteen years of age to attend 



:ch dav continuation classes as may be prescribed 



: thern by the local education authority, during a 



number of hours to be fixed by statute, which should 



be not less than eight hours a week, for forty weeks 



the year, with the exception of: (a) Those who 



re under efficient full-time instruction in some other 

 manner; (fe) those who have completed a satisfactory 

 course in a secondary school recognised as efficient 

 ' V the Board of Education and are not less than 

 -xteen; (c) those who have passed the matriculation 



xtmiination of a British university, or an equivalent 



xamination, and are not less than sixteen; (d) those 



ho are under part-time instruction of a kind rot 

 garded as unsuitable by the Board of Education 



nd entailing a substantially greater amount of s'udy 

 the daytime than the amount to be required by 

 - atute. 



(5) That all classes at which attendance is com- 

 pulsory- be held between the hours of 8 a.m. and 



(6) That it be an obligation on all employers of 

 \oung persons under eighteen to give them the 

 necessary facilities for attendance at the statutory 

 continuation classes prescribed for them by the local 

 education authority-. 



(7) That where there is already a statutory' limita- 

 tion upon the hours of labour, the permitted hours 

 of labour be reduced by the number of those required 

 for the continuation classes 



(8) That the curriculum of the continuation classes 

 include general, practical, and technical instruction, 

 and that provision be made for continuous physical 

 training and for medical inspection, and for clinical 

 treatment where necessary, up to the age of eighteen, 



(9) That suitable courses of training be estab- 

 lished and adequate salaries be provided for teachers 

 of continuation classes. 



(10) That the system of continuation classes come 

 normallv into operation on an aj^>ointed day as early 

 as possible after the end of the war, and that the 

 Board of Education have power to make deferni^ 

 orders fixing later appointed days within a limited 

 period, where necessary, for the whole or part of 

 the area of any local education authority. 



(11) That the State grants in aid of Present f^ 

 well as future expenditure on education be simplified 

 and verv' substantially increased. 



RECENT PROGRESS IN SPECTROSCOPY.' 

 ^rEN years ago the subject of Prof. Crew's vice- 

 A presidential address was •'Facts and Theories 

 in Spectroscopy." Since that time some notable dis- 

 coveries have been made and some remarkable theories 

 have challenged attention. It is my purpose to review 

 a few of the more important experimental results and 

 to discuss the relations of some of them to theories 

 brought before you in two recent vice-presidential 

 addresses on "Atomic Theories of Radiation " and 

 "The Theory of the Nucleus Atom." Inasmuch as 

 it will be necessary to refer to them, I will restate 

 the salient features of the theories which have 

 attracted the most attention. 



Planck derived an expression for the spectral energy 

 distribution of black-body radiation from the assump- 

 tion that the radiation was emitted and absorbed by 

 electric oscillators in definite quanta, each equal to 

 the frequency of the oscillator multiplied by a uni- 

 versal constant, h, the wirkungsquantum. Later he 

 modified this theory- so far as absorption is concerned. 

 Einstein and others went farther in assuming that 

 these quanta preser\-e their identity in their propaga- 

 tion through space, thus reviving a form of corpus- 

 cular theory. This extreme view has been generally 

 abandoned, but it has been found impossible to explain 

 away the wirkungsquantum h. It appears in too 

 many relations to be the result of chance. The work 

 of Millikan in particular proves the exact validity of 

 Einstein's relation Fe = h(i^o) »" t^e photoelectric 

 effect, in which Ve is the measure of the emission 

 energy of the electrons, v the frequency of the inci- 

 dent light, and v, the minimum frequency which will 

 cause emission of electrons. A similar relation appears 

 to hold good in many cases of X-ray and light spectra. 

 It seems probable that this constant depends upon 

 atomic structure only, and affects radiation through 

 space only in so far as emission and absorption are 

 determined bv atomic structure. _ 



The theory of the nucleus atom is hkewise ot 

 fundamental' importance in spectroscopy. The work 

 of Rutherford and others leaves no escape from the 

 conclusion that the nucleus of the atom is a concen- 

 trated group of positive charges and electrons, with 

 an excess of positive elementary charges approxi- 

 mately equal to half the atomic weight, while the 

 same number of electrons circulate about the nucleus 

 in rings. The spectroscopist must try to fit his 

 theories to these probable facts, but he is met at the 

 outset with apparently insuperable difficulties in 

 accounting for the stabilitv of such atoms and for the 

 manifold complexity of spectra according to accepted 

 electrodvnamical laws. Bohr cut the Gordian knot 

 bv supposing that the classic laws apply only to con- 

 ditions of stabiUty, when no energy is radiated, and 

 that radiation attends the transition of an electron 

 from one state of stability to another, the frequencv 

 being determined bv the relation that h multiplied 

 bv the frequency is equal to the difference between 

 the energies of the system in the two stable states. 

 In the case of hvdrogen, to which he assigns one 

 radiating electron and one nucleus charge, it is diffi- 

 cult to account for the existence of so many stable 

 states for the failure to radiate while subject to 

 uniform radial acceleration, and for monochromatic 

 radiation while passing between two positions of 

 stabilitv-. Nevertheless, Bohr derived an expression 

 like that of Rvdberg which kxrates accurately not only 

 the Balmer series, but also an infra-red and an ultra- 

 violet series predicted by Ritz and found by Paschen 



1 Addrr« delivered t- Section B-Physic^-of the America -'^aodatkm 

 for the Advancement of Science «t the New \ork meeting. December, 1916 

 by the chairman of the Section, Prof. E. P. Lewis. 



NO. 2475, VOL. 99] 



