March ii, 1909I 



NA TURE 



57 



ill uhii li lie gives a helpful summary of tlic more important 

 educational experiments inaugurated in this and other 

 countries during 1908. Dr. Percy Nunn describes briefly 

 a pedagogical museum which is being arranged at the 

 London Day Training College ; the arts of reading and of 

 clear speech are discussed ably by Prof. Wyld and Principal 

 Burrell ; and .Mr. H. H. Hulbert' deals with the teaching of 

 hygiene in training colleges. The other contributions 

 similarly indicate that the age of empiricism and the blind 

 adherence to the obiter dicta of departed writers on educa- 

 tion is giving place to an attempt to understand by 

 observation and by suitable tests the working of the child 

 mind and the ways in which it is influenced by environ- 

 ment and other conditions. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, November 26, 1908. — "The Proportion of the 

 Se.\es produced by Whites and Coloured Peoples in Cuba." 

 By Walter Heape. 



This paper deals with data contained in publications 

 issued by the chief sanitary ot^icer of Cuba, 1904-5-6, in 

 which are recorded the sex of both legitimate and illegiti- 

 mate births and still-births for both classes of the popula- 

 tion. The totals dealt with amount to 177,704, viz. whites 

 135,881, and coloured peoples 41,823 births and still-births. 

 It is found : — 



(1) That there is a racial difTerence in the proportion of 

 the sexes produced ; for whites, 108-44 males, for coloured, 

 IOI-I2 males, per 100 females. This result is in close 

 agreement with other published statistics of both races, 

 and shows the influence of heredity. 



(2) That for both races, for both births and still-births, 

 there is a consistent variation in the proportion of the sexes 

 produced by legitimate as compared with illegitimate 

 union. For whites, legitimate 109, illegitimate 105-95 

 males per 100 females. For coloured, legitimate, 107-73, 

 illegitimate 97-91 males per 100 females. Illegitimate 

 unions result in a marked increase in the proportion of 

 females produced, and it is claimed that they are chiefly 

 induced by individual physiological conditions affecting the 

 metabolic activity of the woman. 



(3) That both whites and coloured experience two sharply 

 defined breeding seasons each year ; sudden, brief bursts 

 of reproductive activity, correlated with marked climatic 

 changes, which tend to increase individual metabolic 

 activity. Again, at these times of greatest fertility the 

 largest proportion of females is produced. 



(4) That a considerably higher proportion of females are 

 born in towns than in country districts, where life is 

 associated with greater hardships. 



(5) Conclusions : although heredity, in the main, governs 

 the proportion of the sexes produced by these two 

 races, conditions occur under which that proportion Is 

 varied, and although different in degree it is similar 



.in character for both races. These conditions are directly 

 associated with forces which affect the metabolic activity 

 :of the mother, and suggest the probability that the ripen- 

 ing and production of ovarian ova of different sexes is in- 

 fluenced thereby. Thus it is hold that a struggle for exist- 

 ence is always going on among the sexual ovarian ova, 

 and that these extraneous forces influence the result. 

 Speaking generally, this investig^ation indicates that the 

 greater the metabolic activity of The ovary the more females 

 are produced. 



January 14. — " On the Passage of Rontgen Rays 

 through Gases and ^'apours." By J. A. Crowther. 

 Communicated by Sir J. J. Thomson, F.R.S. 



A series of experiments has been made, under com- 

 parable conditions, on the behaviour of different gases and 

 vapours with respect to the passage of Rontgen rays 

 through them. The results obtained are thus sum- 

 marised : — 



(i) The amount of ionisation produced by the direct 

 action of the primary Rontgen rays on a gas is simply 

 proportional to the pressure of the gas. No evidence was 

 obtained of the emission of any appreciable amount of soft 

 secondary radiation by the gas, the ionisation being appar- 

 ently due to the direct action of the primary rays. 



N'O. 2054, "^'OL. 80] 



(2) The relative ionisation in the different gases, com- 

 pared with aTr as the standard, varies considerably with 

 the hardness of the rays. Hydrogen and ethyl bromide 

 show an increase as the hardness of the rays increases. 

 Other gases remain constant or give a diminution. There 

 is no indication of any approximation to a " density law ' 

 as the hardness of the rays is increased. 



(3) The relative ionisation in a gas follows appro.ximately 

 an additive law. It does depend somewhat, however, on 

 the state of combination, especially for soft rays. 



(4) The absorption varies with the pressure according to 

 an exponential law. 



(5) The amount of secondary radiation emitted by 

 different gases relative to air is, generally, approximately 

 independent of the hardness of the primary rays. For 

 very hard rays ethyl bromide shows a slight decrease. On 

 the other hand, the values for methyl iodide increase fairly 

 rapidiv as the hardness of the rays is increased. 



(6) The coefficient of absorption of the secondary rays 

 emitted by a gas, in the gas itself, is not abnormal. 



(7) The' total ionisation in different gases is not a 

 constant, and the relative values obtained differ with the 

 hardness of the rays. 



(8) The amount of energy required to produce an ion in 

 different gases is different, and also varies with the hard- 

 ness of the ravs. 



No relationship has been found between the relative 

 ionisation and the secondary radiation, or between either, 

 and anv other known property of the gases and vapours, 

 and the explanation of the relatively large amounts of 

 secondary radiation emitted by ethyl bromide and its class 

 compared with air, and of the large relative ionisations in 

 methyl iodide, ethyl bromide, &c., still remains to be 

 sought. 



It appears that on the whole less energy is required to 

 produce an ion in the more ionisable gases, but the valiies 

 obtained do not differ very largely, and are totally in- 

 adequate to explain the very large amounts of ionisation 

 in these gases and vapours. 



Both the ionisation and the secondary Rontgen radiation 

 follow, at any rate approximately, an additive law. It 

 appears, therefore, that these properties are properties of 

 the atoms themselves, and that an explanation must be 

 sought in their atomic structure. 



February 25.— Sir Archibald Geikie, K.C.B., president, 

 in the chair. — The statistical theory of the form of the curve 

 of oscillation for the radiation emitted by a black body : 

 Prof. H. A. Wilson. The view adopted in this paper is 

 that the radiation from a black body is an irregular dis- 

 turbance subject to statistical laws. It is shown that 

 these laws can be deduced from the distribution of energy 

 in the spectrum, and that they enable the character of the 

 disturbance to be described. The disturbance at any 

 instant is taken to be the sum of the displacements in the 

 infinite number of simple harmonic vibrations of arbitrary 

 phases which are obtained when the radiation is dispersed 

 into a spectrum. Expressions are found for the chances 

 that the displacement and its derivatives lie between given 

 limits. These expressions enable the average number of 

 zero values per cm. of the displacement and its derivatives 

 to be calculated. The distribution of maxima and minima 

 is estiinatcd, and a curve has been drawn having 

 approximately the statistical properties deduced. The 

 mean wave-length (\') of the radiation is defined as_ 2/n„, 

 where n„ is the average number of zeros per cm. in the 

 displacement curve. If A,„ denotes the wave-length in the 

 spectrum at which the energy is a maximum, it is shown 

 that \7a„=2-5. It is shown that the number of maxima 

 and minima is about double the number of zero values 

 and about half the number of points of inflection in the 

 curve.— The flight of a rifled projectile in air : Dr. J. B. 

 Henderson. The problem is attacked from first principles 

 simply as a case of a moving rotating body meeting with 

 certain resistances due to the air. and it is found that all 

 the known phenomena are accounted for by the precessional 

 motions of the shot, due to the tilting and friction couples 

 which arise from the obliquity of the axis of the projectile 

 to the direction of motion, the complete trajectory m all 

 its details can be thus constructed from the initial condi- 

 tions and the laws of resistance so soon as these are 



