February i, 19 12] 



NATURE 



469 



that the late Mr. VV. M. Rice, who was for many years 

 a resident in Houston, left a large sum of money, which 

 after reduction by litigation still reached 2,ooo,oooZ., to 

 endow and equip the institute. President Lovett, who is 

 in charge of the new institution, came from Princeton 

 University, and spent a year visiting seats of learning 

 throughout the world, so as to enable him to advise the 

 trustees as to the character the buildings and work of the 

 new institute might with advantage take. The result is 

 that the first of the palatial buildings are now almost com- 

 plete, and will form the nucleus of what will eventually be 

 a much more extensive suite of halls and residences. For 

 the present no upper limit will be assigned to the work 

 of the institute, and the lower limit will be that of the 

 more conservative of American universities. The initial 

 teaching staff is to be organised for university work in 

 science and letters, and it is intended to build up a school 

 of pure and applied science of the highest grade. Men 

 and women will be admitted, and there wmH be no charge 

 for tuition. Rooms in the residential hall and board will 

 be provided at actual cost price. It is interesting to record 

 that the corner-stone of the administration building was 

 laid last year on the seventy-fifth anniversary of the date 

 when Texas declared its independence of Mexico. For the 

 first few years this building will be used to meet some of 

 the needs of instruction. The first building in the students' 

 I esidential group for men has been begun, and the 

 mechanical laboratory, machine shop, and power house are 

 being erected north of the administration building. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, January 2S. — Sir Archibald Geikie, K.C.B. 

 president, in the chair. — Prof. J. S. ToMrnsend : Deter- 

 mination of the coefficient of interdiffusion of gases and the 

 velocity of ions under an electric force, in terms of the 

 mean free paths. A method is described by which an ex- 

 pression for the rate of interdiffusion of gases may be 

 easily found, either on the ordinary supposition that the 

 effect of a collision makes all subsequent directions of 

 motion of the mo'ecules equally probable, or without 

 specifying in any way the effect of a collision. Similar 

 expressions are found for the velocity of ions under electric 

 forces. In all cases the rate of diffusion of the ions is of 

 the form K = JLV, and the velocity under the electric force 



X^ L 

 M= — . ^j.. L does not, in general, represent the mean 

 m V 



free path, but it has the same meaning in both expressions, 



so that when an ion is moving under the action of a force 



and also by the process of diffusion its velocity is given 



bv the equation 



-Kdn Xe L 



n dx 



V 



\»in\-u mV" dn , v- 



•' = - — + Ken, 



K z dx 



or 



K dx 



which is the well-known form to which Maxwell's equation 

 reduces when external electric forces are acting. The 

 general equations for the motion of ions may thus be easily 

 found from the rate of diffusion and the velocity under an 

 electric force when these quantities are correctly deter- 

 mined. — Dr. H. Qeigrer : Note on the scattering of a 

 particles. In a previous paper experiments were described 

 on the scattering of the a particles by foils of various 

 materials and thicknesses. The present note deals with a 

 theoretical examination of the question. The scattering is 

 considered as the result of a multitude of small deflections 

 of the a. particle by the individual atoms of the matter 

 traversed. The experimental curve of distribution with 

 angle for a scattered pencil of a particles is found to be 

 in good agreement with that derived from simple 

 probability theory. The deductions also explain the experi- 

 mental result that for thin foils, which do not appreciably 

 alter the velocity of the a particles, the most probable 

 angle of scattering varies as the square root of the thick- 



NO. 2205, VOL. 88] 



ness. To find the variation of the most probable scatter- 

 ing angle for large thicknesses of matter traversed, the 

 . change in velocity of the a particles has to be taken into 

 account. Assuming, as found by experiment, that the most 

 probable angle of scattering is inversely proportional to the 

 third power of the speed, the theoretical curve is found to 

 give a satisfactory explanation of the experimental results 

 obtained with thick foils. — \. S. Russell : The effect of 

 temperature upon radio-active disintegration. The effect of 

 temperature upon the rate of decay, and the amount of 

 ^ and 7-ray activity, of radium emanation, of active 

 deposit, and of radium C has been investigated. The 

 results are entirely negative. .AH abnormalities of activity 

 of fi rays obtained by previous authors, and by the author 

 in this research, may be completely explained on two 

 simple grounds. The first of these is a change of distribu- 

 tion of radium C caused by its partial volatilisation inside 

 the quartz tube at temperatures greater than 320°. The 

 second is a change in the partition of radium C between 

 the walls of the quartz envelope and the space enclosed. 

 At room temperature the greater part of the radium C is 

 usually on the walls. At room temperature, after the tube 

 has been cooled suddenly from high temperatures, it is 

 entirely on the walls. Above 650° the radium C is dis- 

 tributed homogeneously throughout the volume of the tube. 

 Each of these partitions gives a different )3-ray ionisation 

 in an electroscope, because the average path of the rays 

 through the walls of the quartz envelope depends upon the 

 partition. Under the conditions of experiment, radium B 

 and radium C, and very probably radium \, may be com- 

 pletely volatilised inside sealed quartz tubes at a tempera- 

 ture of 650°. Radium B commences to volatilise at room 

 temperature. — F. W. Aston and H. E. Watson : The 

 relation between current, voltage, pressure, and the length 

 of the dark space in different gases. In a previous paper 

 one of the authors has shown that in the discharge between 

 large plane aluminium electrodes in gases at various 

 pressures the following empirical equations are approxi- 

 mately true : — 



-^^•--¥ 



where D is the length of the dark space, V the voltage 

 between the negative glow and the kathode, c the curren 

 density, P the pressure, and A, B, E, F constants depend- 

 ing on the nature of the gas. The first part of the present 

 communication gives the results of the continuation of this 

 work, with the values of the constants for hydrogen, 

 nitrogen, air oxygen, carbon monoxide, helium, and argon. 

 The second part deals with a systematic investigation into 

 the behaviour of the inactive gases when in a pure state. 

 It was found that these gases behaved in an anomalous 

 manner, and by no means satisfied the above equations in 

 general, but gave values in better agreement with a third 

 equation obtained by eliminating P from the two above. 

 The results are described for helium, neon, argon, krypton, 

 and .xenon. Peculiar interest attaches to these gases in 

 that all of them exhibit to a more or less striking degree 

 the primary dark space recently discovered by one of the 

 authors in hydrogen and helium. The behaviour of helium 

 was exceedingly erratic, and seemed to indicate that this 

 gas could support the discharge in two entirely different 

 ways. — Dr. A. O. Rank! no : The viscosities of gaseous 

 chlorine and bromine. By means of a method resembling 

 in some respects that described by the author in earlier 

 communications, the viscosities of chlorine and bromine 

 have been compared with that of air. From these ratios 

 the absolute values are deduced. The viscosities of 

 chlorine having been obtained at two temperatures, it has 

 been possible to calculate Sutherland's constant. The 

 various values are as follows : — 



Gat. TemperaiH!. \ ,s<:o»ity in C.G.S. 



Chlorine 127" ( 1297 xio"* 



Chlorine Q9>' <^ I'dSSxio-* 



Bromine 987* <-• 1 869 x 10 * 



The value of Suihi 1 1.uui's constant for chlorine is 



C = 3aS. 

 The ratio of the critical temperature of chlorine (416° abs.) 

 to this constant is 1-28, which is somewhat higher than 

 the constant value (114) of the corresponding ratio for 



