June 26, 1903.] 



SCIENCE. 



1003 



ground of general phosphorescence which 

 renders the eye less able to see the scintil- 

 lations. 



It is probable that in these phenomena 

 we actually Mdtness the bombardment of 

 the screen by the positive ions hurled off 

 by radium with a velocity of the order of 

 that of light. Each particle is rendered 

 apparent only by the enormous extent of 

 lateral disturbance produced by its impact 

 on the sensitive surface, just as individual 

 drops of i*ain falling on a still pool are 

 not seen as such, but by reason of the 

 splash they make on impact, and the rip- 

 ples and waves they produce in ever-widen- 

 ing circles. 



Indulging in a 'scientific use of the im- 

 agination,' and pushing the hypothesis of 

 the electronic constitution of matter to 

 what I consider its logical limit, we may 

 be, in fact, witnessing a spontaneous dis- 

 sociation of radium — and we begin to 

 doubt the permanent stability of matter. 

 The chemical atom may be actually suffer- 

 ing a katabolie transformation; but at so 

 slow a rate that supposing a million atoms 

 fly off every second, it would take a cen- 

 tury for weight to- diminish by one milli- 

 gram. 



It must never be forgotten that theories 

 are only useful so long as they admit of 

 the harmonious correlation of facts into a 

 reasonable system. Directly a fact refuses 

 to be pigeon-holed and will not be explained 

 on theoretic grounds, the theory must go, 

 or it must be revised to admit the new 

 fact. The nineteenth century saw the 

 birth of new views of atoms, electricity 

 and ether. Our views to-day of the con- 

 stitution of matter may appear satisfactory 

 to us, but how will it be at the close of 

 the twentieth century? Are we not inces- 

 santly learning the lesson that our re- 

 searches have only a provisional value? 

 A hundred years hence shall we acquiesce 



in the resolution of the material universe 

 into a swarm of rushing electrons-? 



This fatal quality of atomic dissociation 

 appears to be universal and operates when- 

 ever we brush a piece of glass with silk; 

 it works in the sunshine and raindrops, 

 and in the lightnings and flame; it pre- 

 vails in the waterfall and the stormy sea, 

 and although the whole range of human 

 experience is all too short to afford a par- 

 allax whereby the date of the extinction 

 of matter can be calculated, protyle, the 

 'formless mist,' once again may reign su- 

 preme, and the hour hand of eternity will 

 have completed one revolution. 



William Crookes. 



SOlENTrFW BOOKS. 

 Index Animalium, sive index nominum quw 

 ah A. D. MDGCLVIII, generibus et spe- 

 ciehus animalium imposita sunt. By C. 

 Davies Sherborn. Part I., January, 1758, 

 to December, 1800. Cambridge (England), 

 University Press. (New York, Macmillan 

 Co.) 1902. 8vo. Pp. lix+1195. 

 All zoologists have been aware of the stu- 

 pendous undertaking upon which Mr. Sher- 

 born has been at work for the last twelve 

 years, except for an interval during which 

 his health was so impaired as to necessitate 

 a temporary interruption. 



The aim of the undertaking was ' to pro- 

 vide zoologists with a list of all the generic 

 and specific names which have been applied 

 by authors to animals since January 1, 1758,' 

 together with an exact date for each page 

 cited, and a reference ' sufficiently exact to 

 be intelligible alike to the specialist and to 

 the layman.' Special groups of animals have 

 been so treated before, but this is the first 

 work planned to include the entire animal 

 kingdom in its scope. 



Work was begun in July, 1890 ; in 1892 the 

 British Association extended its support, and 

 two years later appointed a committee to 

 watch and advise the undertaking. Financial 

 support has also been extended by the Eoyal 

 Society and the Zoological Society of London. 



