238 



NA TURE 



[December 23, 1909 



specific heat of the molecule. By the aid of the kinetic 

 theory, Q may readily be approximately calculated from 

 the mean molecular velocity and the molecular heat at 

 constant volume. In the table the gases have been arranged 

 in ascending order of K. In the second column, which 

 gives the relative conductivity of the gas at ordinary pres- 

 sures, the figures refer to the watts dissipated by the s>;i 

 in the apparatus at pressures such that conductivity was 

 independent of pressure. In the last three columns the 

 values of K, Q, and of the ratio of K to Q, are given. 



For argon and neon the agreement between the observed 

 and calculated conductivity is as good as can be expected, 

 whereas for all the other gases the ratio is less than unity, 

 and in the case of hydrogen and helium the divergence is 

 especially marked. The results appear to afford the means 

 of obtaining information concerning the nature of the 

 single impact of the gas molecule with a surface. Whereas 

 for the denser monatomic gases the interchange of energy 

 appears perfect, for the more rapidly moving molecules of 

 helium and hydrogen this is not the case. The results are 

 preliminary, and the conclusions now tentatively suggested 

 are being tested further with improved apparatus. — T. 

 Wright : Harmonic tidal constants for certain Chinese and 

 New Zealand ports. — S. Kinoshita : The photographic 

 action of the a particles emitted from radio-active sub- 

 stances. The photographic action of a rays is quite dis- 

 tinct from that of light. There is no diminution in the 

 action when the rays are screened by an absorbing sub- 

 stance, so long as they are capable of passing through 

 the photographic film. In the case of light, the action 

 varies with the intensity of the light, which decreases on 

 passage through an absorbing screen. The photographic 

 action of a rays is thus independent of the velocity of the 

 rays and depends on the number of a particles, N, which 

 passes through the film and can be expressed, when 

 measured by the density, D, as 



D = D//r/7-t-\ I — <? ), where C is a constant. 



This formula can be theoretically deduced on the assump- 

 tion that each halide grain is rendered capable of develop- 

 ment when struck by a certain number of a particles. By 

 counting the number of silver grains in the film exposed 

 to a known number of a particles, it was found that each 

 halide grain was rendered capable of development when 

 struck by a single a particle. The mass of silver per unit 

 area of a developed film, calculated from the number of 

 grains and their average size (deduced from the constant, 

 C, in the above equation) by a consideration of the theory 

 of probability, agrees well with the value determined from 

 the density and the photometric constant. The sensitive- 

 ness of a photographic film to o rays cannot be charac- 

 terised by its inertia. A rapid plate is more sensitive to 

 a rays than a slow plate, if density be taken as a criterion. 

 The reverse holds, however, when the number of grains 

 is considered, provided that the total amount of silver halide 

 per unit area is the same in both cases. The authors have 

 now this new method of counting single a particles, in 

 addition to the electrical and scintillation methods. The 

 photographic method should prove very valuable for count- 

 ing very small numbers of a particles, since it is applicable 

 to very weak sources by using very long exposures, and 

 also to a particles having a very short range. — Hon. R. J. 

 Strutt : The accumulation of helium in geological time, 

 III. The present experiments refer to the amount of 

 helium in zircon. This mineral is found in igneous rocks 

 of all ages, and the experiments show clearly that the 

 quantity of helium generated closely follows the geological 

 age. This must not be taken to prove that they retain the 

 NO. 2095, VOL. 82] 



whole of the helium generated within them by radio-active 

 change, but rather that, as they all crystallise from fusion, 

 they are all of similar structure, and retain a not very 

 different fraction of the full quantity of gas in each case. 

 The following table summarises the results. The last 

 column shows the ratio of helium to radio-active matter 

 (c.c. per gram of uranium oxide), thoria being reckoned as 

 equivalent, in helium production, to 0203 times its weight 

 of U,0. :— 



Campbell I.', "New 



Zealand 



Mayen, Eifel 



Expailly, Auvergne ... 



N.E.Tasmania 



Brevig, Norway 



Cheyenne Canon, 

 Colorado 



Green River, Hender- 

 son Co., N. Carolina 



Ural Mts 



Kimberley Diamond 

 Mines 



Ceylon 



Ceylon 



Ceylon 



Sebastopol, Renfrew 

 Co. .Ontario , Canada 



Geological 

 Ago. 



Tertiary ... 



Tertiary ... 

 Tertia.y .. 

 Tertiary .. 



Post Devon 



Per Gram of Zir 



U3OB ThOa 





56-6 



Royal Anthropological Institute, December 14. — Mr. H. 

 Balfour, past-president, in the chair. — E. Torday : Results 

 of a recent ethnographical expedition to the Congo Free 

 State. The expedition left England in October, 1907, and 

 travelled by the Kasai and the Sankuru to the Ba-Songe 

 country. The Ba-Songe are a tribe of the Ba-Luba people, 

 whose affinities lie rather to the south. The next tribe 

 visited was the Ba-Tetela, a cannibal people who occupy 

 a large extent of country between the second and fifth 

 degrees of southern latitude. These people seem to have 

 been extending, gradually but steadily, south and west 

 from the Lower Lomami. Their culture is interesting as 

 exhibiting a transition between that of the forest and of 

 the plains. Other tribes visited were the Bu-Shongo, the 

 .\kela, and the cannibal Ba-Nkutu, who seem to have 

 cultural affinities with the northern Ba-Tetela. The 

 Ba-Songo Meno, a term given to a large number of tribes 

 on both banks of the Kasai between the Sankuru and 

 the Mfini, were also visited. These tribes have never been 

 investigated, and show great hostility to the white man. 

 The western Bu-Shongo tribes were also visited. These 

 people, originally migrants from the north, gained most of 

 their culture from the tribes to the west, and it was with 

 these people that the paper chiefly dealt, including the 

 Ba-Kongo and the Bashi Leie, who represent the first 

 waves of Bu-Shongo immigration into the country. With 

 regard to history, it is a remarkable fact that the Bu- 

 Shongo people have preserved their records. The name 

 means people of the Shongo, the shongo being a weapon, 

 now obsolete, which was the principal arm of offence in 

 the early days. The chief drew a picture of this weapon 

 in the sand, and it was unmistakably a throwing knife. 

 Now the throwing knife as a weapon does not occur 

 south of the great bend of the Congo. The argument, 

 therefore, that the people originally came from the north 

 is strengthened by this fact, as the north was the original 

 home of the weapon. From evidence of language, tribal 

 history, and culture, the original home of the people 

 seems to have been the west central Sudan. The remainder 

 of the paper dealt with the institutions, government, and 

 religion of the people. The tribal organisation is extremely 

 elaborate. At the head is the chief, but in certain points 

 his mother appears to take precedence. There are also 

 six great officers and a host of other officials. Although 

 nominally absolute, the chief has little real power. The 

 right to the throne descends in the female line, but a 

 woman can only come to the throne if the male stock fails. 



