Apkil 13, 1900.] 



SCIENCE. 



585 



the equations deduced. In a following paper 

 discussing Young and Forbes' experiments in 

 wliioli the velocity of violet light apparently 

 exceeds the velocity of red light by 1.8 per 

 cent., Rayleigh again accentuates the difference 

 between the group velocity and the individual 

 velocity of waves. The last optical paper in 

 the volume reopens the question relative to the 

 production of a truly compound yellow made 

 of red and green, and treats other questions of 

 similar psychological interest. The concluding 

 paper of the book is an investigation in pure 

 elastics, dealing with the infinitesimal bending 

 of surfaces of revolution, with particular refer- 

 ence to the theory of bells. 



I am of course well aware that the account 

 which I have endeavored to give of this great 

 book is altogether inadequate ; but with such 

 an exuberance of material, and so much of it 

 expressed either in untractable equations or in 

 a style admitting of. expansion only, all at- 

 tempts are foredoomed. Besides the larger 

 papers which I have mentioned, there is a be- 

 wildering array of smaller articles, sententious 

 criticisms or suggestions mathematical or not, 

 theorems, special solutions, computations, etc. 

 Some of Lord Rayleigh's most helpful services 

 to science are to be found in these current notes 

 and as a rule they are hard to find. For this 

 reason the present complete republication of 

 his works is additionally to be welcomed. 



Ra5'leigh's style is exquisitely terse. Even 

 those papers which are free from mathemat- 

 ics are not easy reading. The endeavor to 

 make a clear statement more intelligible is 

 rarely thought worth while. The greater num- 

 ber of papers are short. The average 7 pages 

 each (78 papers in the 562 pages of this first 

 volume). Withal it is a book to which one 

 may come for fundamental originality, but one 

 must expect to pay for the privilege. It is 

 pleasant to note that Eayleigh cheerfully gives 

 credit to the labors of others and not only to 

 those of his own nation. But however genial 

 his criticism it is none the less keen. Errors 

 are virtually dismembered with a few deft 

 strokes, and the incident passes before there is 

 time to cry for mercy. On the whole a wise 

 man will think twice before he disagrees with 

 the author of these ' Scientific Papers.' 



Lord Rayleigh is not quite as radical as some 

 of the other English mathematicians in eschew- 

 ing formulated mathematics as far as possible, 

 a method which those of us who do not aspire 

 to become too mathematical for mathematics, 

 cannot but regret — at least when we have 

 practical occasions for following the argument. 

 There is moreover something amusing about 

 this fashion of verbally treating abstruse mathe- 

 matical doctrine. Our host, as it were, re- 

 ceives us at his ease, quite unarmed, and dis- 

 cusses the most delicate matters with complete 

 nonchalance. But nobody is deceived. One 

 may be quite sure that a strong man, armed 

 cap-i-pie, is hidden away somewhere in. the 

 closet. When mathematics becomes verbal 6ne 

 feels that she is speaking a foreign tongue and 

 that something is actually being translated. 

 The original would be far preferable. 



On closing the book one can not but wonder 

 how much talk could be made out of a single 

 page of it ; or perhaps more graciously, how 

 immensely science would be benefited if the 

 bulk of what is now rampant were to shrink to 

 the standard of Lord Rayleigh's text. 



Carl Baeus. 

 Beown" Univeesity, 

 providk^-ce, r. i. 



System der Bakterien. By Professor W. Mi- 

 GXJLA. Handbuch der Morphologic, Ent- 

 wickelungsgeschichte und Systematik der 

 Bakterien. Bd. II. Specielle Systematik 

 der Bakterien. Jena, Gustav Fischer. 1900. 

 Pp. 1068, pi. 18, figs. 35. 



The working bacteriologist has long been in 

 need of some treatise that would enable him to 

 trace to the original description at least a fair 

 proportion of the ' species' and ' varieties' that 

 he finds referred to in the literature of the day. 

 It is one of the great stumbling-blocks in bac- 

 teriology that a bewildering multiplication of 

 names and synonyms has taken place during 

 the last decade and has had its natural result 

 in an almost hopeless confusion of bacteriolog- 

 ical classification and nomenclature. 



The great task essayed by Professor Migula 

 may well command respect and admiration. 

 Not only is enormous mechanical labor in- 

 volved in the extracting and collecting of 1200 



