i66 



NATURE 



[JUNE l8, 1908 



of the secondary radiations in all directions from the ex- 

 posed plate for different angles of incidence of the primary 

 rays. A comparison of these results with those referring 

 to the plane of incidence only, shows that the reflected rays 

 are not strictly confined to the plane of incidence. Further 

 work on this subject is in progress. 



Mav 7. — " Helium and Radio-activity in Rare and 

 Common Minerals." By the Hon. R. J. 'strutt, F.R.S. 



(i) Helium can be detected in almost all the minerals 

 of the earth's crust. 



(2) The quantity is in most cases about what might be 

 anticipated from the traces of uranium and radium which 

 the minerals contain. This is illustrated by the following 

 selected results, which are given in round numbers only : — 



Helium ratio, 

 -.. . Helium present, /.c. ratio of 



^I'"=''='' c. mm. per kilo. heHum to 



uranium oxide 



Samarshile 1,500,000 14 



Htematite 700 9 



Galena ... ... 2 ... ■•. 17 



Quartz 2 10 



(3) Where much higher helium ratios than the above 

 have been observed, the excess of helium can always be 

 connected with the presence of thorium, except in one out- 

 standing case. Thus the experiments afford no evidence 

 in favour of helium production by radio-activity of ordinary 

 elements. 



(4) The outstanding case is beryl, which contains abund- 

 ance of helium, without anything approaching a sufficient 

 radio-activitv to explain its presence. This helium cannot 

 be connected with any known constituent of beryl. 



(5) Igneous rocks, and probably siliceous minerals 

 generally, contain small quantities of argon. In other 

 minerals its quantity is negligible, at all events in com- 

 parison with tlie lielium present. Nor is there any indica- 

 tion that it increases with the amount of radio-active 

 material. 



May 21. — " .\ Further Note on the Nutrition of the 

 Early Embryo: with .Special Reference to the Chicl-c." By 

 E. Emrys-Roberta. Communicated by Prof. C. S. 

 Sherrington, F.R.S. 



(i) The secretion of the resting mammalian uterus con- 

 tains protein, mucin, and salts ; during the pro-oestral 

 stage the proportion of mucin is decreased. 



(2) The profuse mucinous secretion of mammalia during 

 pro-oestrus is derived, not from the body of the uterus, but 

 from the cervix and vagina. 



(3'l The nutrition of the embryonic chick is not dependent 

 upon the volli alone, but also upon the egg-white. 



(4) Assimilation of the egg-white is divisible into three 

 heads — the water, the sails, and the proteid. 



(5) Of the three, the water is at first extracted at the 

 most rapid rate, i.e. the percentage of water decreases as 

 incubation proceeds. 



(6) The percentage of salts in the egg-white remains 

 more or less unchanged throughout incubation. 



(71 The proteid of the egg-w-hite is assimilated, not by a 

 process of osmosis, but by a process of digestion per- 

 formed by the chorionic cells. 



(8) During this process the egg-white is considerably 

 altered in composition and reaction, being converted, as 

 incubation proceeds, into a more and more vitreous mass 

 with a peculiar set of reactions, the outstanding reaction 

 being that demonstrating the presence of altumoses and 

 peptones. 



Physical Society, May 2'.— Dr. C. Chree. F.R.S., presi- 

 dent, in the chair. — The spectrum top : F. P. Sexton. 

 The coloured bands seen when a Benham top is rotated are 

 explained. The effect depends upon the position of the 

 sector lines and on a contrast. The rates of growth of the 

 colour sensations are assumed to be in the order red, green, 

 and blue, where red is the greatest, and the rates of decay 

 are assumed to be in the inverse order. The colour in 

 the inner ring with an anti-clockwise rotation, and also 

 the second ring, are explained. — The coefficient of 

 diffusion : B. W. Clack. The practicability of a new 

 method for the determination of the coefficient of diffusion 

 of salts through water, and to find how this coefficient 

 varies with the concentration of the solutions, is discussed. 



NO. 2016, VOL. 78] 



The apparatus consists of a special kind of flask of about 

 450 c.c. capacity fitted with a vertical glass tube of known 

 dimensions. The flask, filled with the salt solution* was 

 suspended in cooled distilled water. The apparatus was 

 so designed that one end of the vertical tube was main- 

 tained in contact with a salt solution of constant concentra- 

 tion, while the other end was kept in contact with dis- 

 tilled water. .As the salt diffuses through the tube the 

 weight of the flask varies, and an expression was deduced 

 by which it is possible to find the value of the coefllcient 

 of diffusion from this rate of change in weight, which 

 was automatically recorded. The salts experimented upon 

 were NaCl, KCi, and KNO,. The coefficient for NaCI 

 and KCI decreases as the concentration of the solution 

 decreases. For KNO, the opposite phenomenon is ex- 

 hibited. — The production of small variable frequency 

 alternating currents suitable for telephonic and other 

 measurements : B. S. Cohen. A new method for pro- 

 ducing these currents is described ; this consists of a form 

 of vibrating wire interrupter which operates a make-and- 

 break contact. This is used to put a source of potential 

 on and off a resonating circuit tuned to any desired fre- 

 quency. The alternating current is taken from a small 

 transformer in the resonating circuit. .\ series of damped 

 wave-trains of any frequency can be produced by this 

 means, the trains following each other with the frequency 

 of the wire vibrations. The theory of action of the various 

 circuits, and some applications of the waves to both tele- 

 phonic and general electrical measurements, are given. 



Mathematical Society, June 11. — Prof. W. Burnside, 

 president, in the chair. — Relations between the divisors of 

 the first n natural numbers: Dr. J. \\". L. Glaisher. — 

 ■ Electrical resonance : Prof. H. M. Macdonald. — .\ form 

 of the eliminant of two binary quantics : A. 1.. Dixon. — 

 Perpetuant syzygies of the nth kind : H. Piaggio. 



Royal Astronomical Society, June 12. — Mr. H. F. 



Newall, F.R.S., president, in the chair. — .\n example of 

 Prof. Karl Pearson's calculation of correlation in the case 

 of the periodic inequalities of long-period variables: 

 H. H. Turner. After tabulating Chandler's periodic in- 

 equalities, the author worked out the correlation according 

 to Prof. Pearson's method, and then made an examina- 

 tion of eight stars in detail for which special information 

 was available. — Report of the expedition to Flint Island 

 for the observation of the total solar eclipse of 1908 

 January 3 : F. K. McClean. The author gave an account 

 of his expedition, to undertake which he chartered a 

 steamer to start from Auckland for Tahiti and Flint 

 Island, being joined by a small party of astronomers from 

 Australia and New Zealand. The difficulties of landing 

 were overcome, and all preparations made, in spite of 

 almost continual rains. Heavy rain came on upon the 

 morning of the eclipse, and only ceased just as totality 

 commenced. Very successful photographs of the corona 

 and prominences were taken, which were shown to the 

 meeting. Mr. McClean recommended the observation of 

 the eclipse of iqio in Tasmania, and Mr. Crommelin re- 

 marked that Halley's comet would come to perihelion 

 about the time of the eclipse, and could be much better 

 observed in the southern than in the northern hemisphere. 

 — Observations of the sixth, seventh, and eighth satellites 

 of Jupiter from photographs taken at the Royal Observa- 

 torv, Greenwich : Astronomer Royal. — The orbit of 

 Jupiter's eighth satellite : P. H. Cowell and .A. C. D. 

 Crommelin. Two hypotheses were considered, the one 

 of direct and the -other of retrograde motion ; the ques- 

 tion was not finally decided, but retrograde motion seemed 

 much more probable. The orbit had 31° inclination from 

 the ecliptic, and a period of about tw-o years, but no 

 definitive orbit could be obtained until the satellite had 

 been again observed at the next opposition of the planet. 

 — The mathematical theory of two star drifts, and on the 

 svsteniatic motions of zodiacal stars : A. S. Eddington. 

 —The lunar bright rays : H. G. Tomkins. The author 

 showed the different characteristics of the bright rays on 

 the moon, and explained his theory that they are caused 

 by salt efflorescence. Photographs were shown of saline 

 regions in India and other countries, as well as speci- 

 mens of saline deposits. He considered that there was 

 evidence of a radial arrangement of terrestrial salt districts. 



