266 



NA TURE 



[January 22, 1903 



differences in spectra such as that indicated by a change 

 from a band to a line spectrum are due to changes in 

 molecular complexity, but one would like to see at least 

 one case worked out in detail. The change from the band 

 spectrum of sodium to the spectrum of lines probably 

 takes place simultaneously with the splitting up of the 

 molecule containing two atoms, but this has never been 

 clearly proved. A single example of this character 

 thoroughly investigated would set many conscientious 

 doubts at rest. When we further consider gases which 

 show much greater variability, such as oxygen, which has 

 seven undoubted different spectra, not counting sub- 

 divisions, justifiable speculation is obliged to go still 

 further ahead of experimental demonstration. All things 

 are possible in a vacuum tube, but all the same it would 

 be more satisfactory to know exactly what takes place. 



To explain the difference in spectra observed in 

 different circumstances, we have the choice between 

 molecular dissociations and molecular associations, and I 

 should like to suggest one further possible cause of 

 variability. We cannot doubt at present that it is pos- 

 sible to separate an electron from matter, and it is 

 possible to imagine that an atom may under electric 

 influence have on its surface one electron less or one 

 electron more than it possesses in its normal condition. 

 Such an increase or diminution would doubtless have a 

 very material effect on the radiations which the atom can 

 emit. Possibly the peculiar spectra which are seen in 

 the glow surrounding the negative pole of a vacuum 

 tube may be due to the association of an ordinary mole- 

 cule with the originally free electron projected from the 

 kathode. 



There is an interesting short chapter on the appearance 

 of spectrum lines, and Doppler's principle is discussed at 

 length (nearly one hundred pages) by Dr. H. Konen. 



We can only say a few words about the two last chap- 

 ters, yet they are perhaps the most important portions of 

 the book. In chapter viii. the relationships discovered 

 between the wave-lengths of lines belonging to the same 

 spectrum are discussed. Every reader of this notice 

 knows how much science owes to Prof. Kayser in this 

 portion of the subject and will give special weight to his 

 exposition of it. The structures of the so-called fluted 

 bands have not, perhaps, attracted the same amount of 

 attention as the regularities found in the component lines 

 of a "series" spectrum. The large number of lines 

 which make up a band may give larger possibility of 

 accidental coincidences, but the subject is one which 

 well deserves the attention of those who wish to advance 

 the mechanics of molecular structure. It is needless to 

 say that the series laws are fully discussed, as well as the 

 relationships so far found between, the spectra of 

 different elements. 



The last chapter, which deals with vibrations in the 

 magnetic field, is written by Prof. Runge. It is full of 

 interest, not only on account of the complete statement 

 of the facts so far as they are known at present, but also 

 on account of the clear exposition of the theoretical dis- 

 cussions by Lorentz and others, Prof. Runge himself 

 adding important contributions to it. Zeeman's dis- 

 covery has been remarkably fruitful in dividing spectral 

 lines into groups which seem intimately connected 

 with each other, and the subject is far from being ex- 

 NO. 1734, VOL. 67] 



hausted. The insensibility of band spectra to magnetic 

 influence is probably connected with their insensibility 

 to the effects of pressure, and seems to point to a mate- 

 rially different origin of the two classes of spectra. 



Prof. Kayser may congratulate himself on the successful 

 completion of this volume, which is full of suggestive 

 criticism. Its value is enhanced by the fact that it 

 brings the gaps in our knowledge prominently before us. 

 Anyone wishing to advance by original research a science 

 which is destined to clear up the secrets of molecular 

 and atomic constitution will find Prof. Kayser's work full 

 of promising starting points. ARTHUR Schu>ter. 



THE MAMMALS OF EGYPT. 

 The Zoology oj Egypt — Mammalia. By the late J. 

 Anderson. Revised and completed by W. E. de 

 Winton. Pp. xvii + 373 ; illustrated. (London : Hugh 

 Rees, Ltd., 1902.) Price 7 guineas net. 



FOR many years previous to his untimely death, the 

 late Dr. John Anderson devoted, with characteristic 

 energy and enthusiasm, a large amount of time, labour 

 and money to collecting the mammals of Egypt, with a 

 view of publishing a fully illustrated description and re- 

 vision of thit section of the fauna of the country. And 

 at his decease he left behind him the greater part of the 

 manuscript for the present work, in a state verging more 

 or less nearly on completion. It would have been a 

 thousand pities had this labour been lost to zoological 

 science ; and Mrs. Anderson, who has herself written the 

 preface, is entitled to the gratitude of all naturalists for 

 her resolve that the work should be completed and pub- 

 lished. No better memorial could indeed have been 

 devised to perpetuate the memory of her late husband, 

 of whom a life-like portrait is prefixed to the volume. 



In the selection of Mr. de Winton to undertake the task 

 of completion, and, where necessary, revision (for 

 zoology is not a science that stands still), Mrs. Anderson 

 has been thoroughly well advised, for that gentleman 

 has for some years made the mammals of Africa a 

 special study, in the course of which he has not only 

 added considerably to the list of species and races, but 

 has likewise made important contributions to our know- 

 ledge of the affinities and taxonomy of well-known forms. 

 Without in any wise detracting from the work of the 

 original author, it may be confidently stated that Mr. de 

 Winton's task has been by no means an easy one, and he 

 is to be congratulated on the manner in which he has 

 carried it through. Certain sections of the work— notably 

 those dealing with the shrews and the hares — are entirely 

 the work of the editor, who has also rewritten certain 

 other sections. Of many of the species and races re- 

 corded in the volume, he is also the first describer, al- 

 though all such forms have been previously named in other 

 publications ; and with the exception of that of one race 

 of striped polecat, no new names appear to be proposed 

 in the book. It is highly satisfactory to learn that Mr. 

 de Winton's labours have met with the thorough approval 

 of Mrs. Anderson, who observes in the preface that the 

 manner in which he has carried out his task will com- 

 mend itself to zoologists generally. 



A special feature of the book is formed by the fifty-five 



