28 



NATURE 



[November 5, 1908 



need ; (3) generous provision of playgrounds, under skilful 

 supervision, with the view of encouraging a healthy cor- 

 porate life in all schools ; (4) the raising, at dates to be 

 fixed by Parliament, of the present age of exemption from 

 school attendance throughout the country (with a possible 

 reservation of the agricultural districts), first to thirteen 

 and then to fourteen years of age ; (5) the abolition by 

 statute of the half-time system in the textile districts ; 



(6) the provision of various forms of educational care for 

 young people during the critical years of adolescence ; 



(7) the laying upon all employers of a statutory obligation 

 to enable their younger workpeople, up to seventeen years 

 of age, to attend courses of suitable instruction, provided 

 or approved by the local authority of the district, and held 

 at a time of day which would prevent those attending the 

 classes from suffering from overstrain of body or of mind. 



A MEETING of the Child Study Society was held on 

 October 29, when a paper was read by Miss Alice Raven- 

 hill on the results of an investigation into hours of sleep 

 among elementary-school children. For nearly three years 

 Miss Ravenhill has been collecting information on the 

 question of the quantity of sleep secured by children in 

 English elementary schools. Of 10,000 forms issued, 6,180 

 were properly filled up, and gave particulars as to 3500 

 boys and 268(1 girls. A comparison between the standard 

 hours of sleep as defined by the best authorities and an 

 average struck from the whole of the material at com- 

 mand shows a deficiency of from 3:^ to 21 hours at each 

 age period, a loss equivalent to one night in four among 

 the youngest and eldest children, and to one night in five 

 among those of intermediate ages. For example, at ages 

 three to five years the average is 10-75 hours, against a 

 standard of fourteen hours, and, at thirteen years, eight 

 hours, against 1075 hours. The evil of insufficient sleep 

 is widespread. Parents must be roused to a sense of the 

 importance of the subject, and the enforcement of the 

 laws on the employment of children should be rendered 

 obligatory upon local authorities. Sir James Crichton- 

 Browne, who presided, emphasised the need of sufficient 

 sleep, and pointed out that sleep repairs waste in every 

 organ of the body, and stores oxygen in the tissues as a 

 reserve fund against the needs of the following day. 



The Board of Education has decided to introduce a new 

 system of organisation for the Victoria and Albert Museum. 

 Re-organisation of the administrative arrangements for 

 the museum has been rendered necessary by the transfer 

 of the technological branch of the Board of Education 

 from South Kensington to Whitehall. Hitherto the 

 administration of the museum has been supervised and 

 controlled by the principal assistant secretary in charge 

 of that branch of the fioard's office, and the removal of 

 that branch to Whitehall renders the continuance of that 

 arrangement impossible at so great a distance from South 

 Kensington. In consequence of this transfer the Board 

 decided to take the opportunity of placing the museum 

 on an independent basis, equipped with the necessary 

 administrative as well as technical machinery and staff. 

 .\ new post has therefore been established under the title 

 of " Director and Secretary of the Art Museum," the 

 holder of which will, in future, be directly responsible 

 to the Board, with assistance from the advisory council, 

 for the whole administration of the museum and for the 

 working of its staff. To this post the President of the 

 Board has appointed Mr. Cecil H. Smith, of the British 

 Museum. Mr. A. B. Skinner will take charge of a new 

 department of architecture and sculpture to be created in 

 the museum. It has been decided to classify the collec- 

 tions as far as possible by materials, and to constitute the 

 following eight departments : — (i) architecture (original 

 architectural objects and sculpture) ; (2) metahvork ; 

 (3) woodwork and leatherwork ; (4) textiles : (5) ceramics, 

 enamels, and glass ; (6) engraving, illustration, and design ; 

 (7) the library ; (8) pictures. Arrangements have further 

 been rnade in the new and old buildings of the museum 

 by which the staff attached to each of the eight depart- 

 ments will be provided with suitable offices in close 

 proximity to the collections respectively under their charge. 

 NO. 2036, VOL. 79] 



SOCIETIES AND ACADEMIES. 

 London. 

 Royal Society, June 2?. — "The Emission and Trans- 

 mission of Rontgen Rays." By G. W. C. Kaye. 



The Rontgen rays produced by some twenty elements 

 used as anti-kathodes were investigated. 



(i) The relative intensities of the radiations, when un- 

 obstructed by any screen, do not follow the order of the 

 atomic weights of the anti-kathodes. 



(2) If the different radiations are cut down by screens 

 of increasing thickness, the intensities reach ultimate 

 relative values which are not altered by a further increase 

 in the thickness of the screen : thus at this stage all the 

 radiations have the same hardness. These intensities are 

 very approximately proportional to the atomic weights of 

 the radiators. The relative values of the heavy-atom 

 metals increase somewhat with a rise in potential on the 

 tube. 



(3) When screen and radiator are of the same metal, 

 selective transmission of the radiation is manifested, that 

 is, the radiation from the metal is augmented relative to 

 the radiations from other anti-kathodes. The effect is 

 also present to a less extent when radiator and screen have 

 closely adjoining atomic weights. 



(4) This augmentation, when radiator and screen are 

 alike, is most pronounced in the case of the metals of 

 the chromium-zinc group. It is least marked for a sub- 

 stance of low atomic weight. 



(5) When screen and radiator are alike, the absorption 

 per unit mass of unit area of the screen is relatively low. 

 Benoist's " transparency " curve is much straighler for a 

 radiator of aluminium than for one of platinum working 

 under the same conditions. With an anti-kathode belong- 

 ing to the chromium-zinc group the curve has to be 

 modified by the addition of a sharp maximum in the 

 neighbourhood of the radiator. 



(6) The question of the anomalous results obtained with 

 the secondary radiation from nickel is gone into. 



(7) The curve of transmission in which the thickness of 

 screen is plotted as abscissa against the logarithm of the 

 intensity consists of three parts when radiator and screen 

 are of the same metal. First, with thin screens, there is 

 a relatively steep portion, which for thicker screens is 

 followed by a straight-line region indicative of an ex- 

 ponential absorption ; this again is ultimately succeeded 

 by a region in which the slope gradually diminishes with 

 the thickness of the screen. The preliminary steepness 

 is attributed to secondary radiation ; the ultimate flatten- 

 ing of the curve is probably due to scattering of hard 

 primary rays. If the potential on the tube is not very 

 high the absorption curve indicates homogeneity through- 

 out its length. 



(8) When screen and radiator have very different atomic 

 weights, the region of exponential absorption does not 

 appear. 



Received .'\ugust 6. — " The Rate of Production of Helium 

 from Radium." By Sir James Devwar, F.R.S. 



Some time ago the author communicated a paper to the 

 society entitled " Note on the Use of the Radiometer in 

 observing Small Gas Pressures : Application to the Detec- 

 tion of the Gaseous Products produced by Radio-active 

 Bodies " (Roy. Soc. Proc, A, vol. Ixxix., p. 529, 1907). 

 In the course of the experiments recorded in that paper 

 it was shown that a pressure of the fifty-iriillionth of an 

 atmosphere could easily be detected by radiometer motion, 

 and that the helium produced by radio-active processes 

 from some 10 milligrams of bromide of radium could be 

 definitely detected after a few hours. This led the author 

 to desire some direct measurements of the amount of 

 helium produced by radium, and through the kindness of 

 the Royal Society in allowing him the use of some radium 

 chloride belonging to them, he Is able to give a condensed 

 abstract of the experimental results so far obtained. 



The salt employed was the 70 milligrams of radium 

 chloride prepared by Dr. T. E. Thorpe, F.R.S., for his 

 determination of the atomic weight of radium, the pre- 

 paration of which is fully described in Roy. Soc. Proc, 

 vol. Ixxx., p. 298. 



The apparatus used for the measurements was a McLeod 



