338 



SCIENCE. 



[X. S. Vol. XVIII. No. 4.54. 



ment or moment, wliicli movement continues 

 until sucli particle meets an obstacle and the 

 energy is again reconverted to heat, light and 

 to those forms of obscure radiation, more or 

 less penetrating to ordinary matter. 



It is doubtful whether radio-active sub- 

 stances like radium are the fluorescent detect- 

 ors of such rays as reach us from space, and 

 which are not absorbed by our atmosphere. The 

 simpler hypothesis is that of atomic insta- 

 bility. But the hypotheses which have been 

 outlined above — and they are, of course, only 

 scientific speculations or hypotheses as yet — 

 naturally suggest lines of investigation which 

 are desirable to be carried out. In that way 

 only can any truth, if it exists in these ideas, 

 be determined; or the ideas disproved, as the 

 case may be. 



Eliho Thomson. 



a possible use foe radium. 



On the authority of M. Curie radium is 

 worth about one million dollars a pound. 

 This estimate is based on the cost of isolating 

 this rarest, newest and most wonderful of the 

 metals, rather than upon its uses to practical 

 people. 



Utilitarians may demand : ' Of what use is 

 radium ? ' Sir Oliver Lodge has said this is 

 difficult to answer for people who wish to 

 make money out of it, but although at pres-- 

 ent radium grinds no axes, it is held in great 

 estimation by physicists who see in its amaz- 

 ing energy possible solutions for old problems 

 and materials for new ones. A British writer 

 in the Daily Graphic of July 13 points out 

 one direction in which a study of the prop- 

 erties of radium may prove of the greatest 

 benefit to mankind, and that is the analogy 

 between its rays and those of luminous insects. 

 As Sir Oliver Lodge remarks, if we could dis- 

 cover the secret of the fire-fly's power to con- 

 vert some unknown source of energy into light, 

 we could produce light without heat. 



Hope is expressed that the study of radium 

 may lead us to a method of obtaining light in 

 a cheaper and more convenient manner than 

 any now known. 



SHORTER ARTICLES. 



THE FISHES OF THE AFRICAN FAMILY KNERUD.-E. 



In 1866 Dr. Steindachner introduced into 

 the iclithyological system a peculiar western 

 African fresh-water fish which he called 

 Kneria angolensis and referred to the family 

 Acanthopsidas or Cobitidse. Two years later 

 (1868) Dr. Giinther added another species from 

 central Africa (Kneria speJcii) and ranked 

 the genus as the representative of a pecu- 

 liar family — ^Kneriidee. He placed it as an 

 'Appendix to the Cyprinidas,' and there it has 

 ever since been allowed to remain, but I have 

 always felt convinced that it was not at all 

 related to the Cyprinids or Plecto^iliJitlil^ even. Sf" 

 Very recently data have been acquired which 

 may help us to a solution of the taxonomic 

 problem. 



In 1901 Dr. Boulenger made known a re- 

 markable pigmy fish (30 mm. long) from the 

 upper Nile (Fashoda) which he named 

 Cromeria nilotica and referred to the family 

 Galaxiidse, thinking that it ' appears to be 

 most nearly related to Galaxias.' 



It is very unlikely that the tropical fish 

 should be a member of a family all of whose 

 certain representatives are characteristic of 

 the cool and cold waters of the southern hemis- 

 phere and I was inclined to believe that it 

 was really related to the Kneriidse. An im- 

 portant paper just published by Dr. Swin- 

 nerton appears to confirm this view. 



In the Zoologisclier Jahrhiicher (Anatomie) 

 published in Jime, 1903 (pp. 58-70), Dr. 

 Swinnerton has given an article on ' The 

 Osteology of Cromeria nilotica and Galaxias 

 attenuatus ' and made known some extremely 

 interesting results. It appears that there 

 is no relationship between Cromeria and the 

 Galaxiids, and that Cromeria belongs to a 

 peculiar family remarkably distinct from any 

 other known unless it be that of the kneriids. 

 To that, indeed, it seems to belong. It has 

 the same general form, the same arrangement 

 of the fins, the projecting snout or upper jaw, 

 the toothless trenchant jaws, the absence of 

 pharyngeal teeth, the three branchiostegal 

 rays, the very narrow branchial apertures, and 

 the simple air-bladder. Indeed, in all essential 



