186 Notices respecting New Books. 



to the manner in which ideas originated and grew in the fertile mind 

 of the author. His early investigations in the methods of elimination 

 and in the theories of determinants and invariants, and his 

 important contributions to the theory of equations and the pro- 

 perties of the Sturmian Functions, fall within this period ; but in 

 addition to the longer memoirs on these subjects there are a 

 number of shorter papers, sometimes amounting to mere notes, 

 which touch with a master's hand upon many other departments 

 of mathematics pure and applied. His poetic fancy and enthusiasm 

 combined at times to produce quaint turns of thought and expres- 

 sion, as when, in acknowledging a hint from Cayley, he speaks of 

 him as one "who habitually discourses pearls and rubies'"; or 

 when, in referring to an asymmetric proof by Salmon he remarks 

 that " Symmetry, like the grace of an eastern robe, has not un- 

 frequently to be purchased at the expense of some sacrifice of 

 freedom and rapidity of action" ; or when he begins his great 

 memoir on the Syzygetic Relations of Two Algebraic Functions 

 w T ith the quotation from Milton's Comus, "How charming is divine 

 philosophy, etc." The Editor has done his work with great care, 

 and has added a note presenting another view of Sylvester's main 

 theorems on determinants. 



Le'hrbuch Der PhysiJc. By O. D f Ohwolson. Band II. Translated 

 into German by H. Pflaum. Friedrich Vieweg und Sohn. 

 Braunschweig. 



We have already had occasion to notice the high merits of the 

 First Volume of this treatise. In the Second Volume we have 

 eleven chapters on Sound comprised within 140 pages ; and then 

 the remaining 880 pages are devoted to Radiant Energy. One 

 feature is the complete disuse of the customary phrases "strahlende 

 Warme," "Warmestrahlen," " Wiirinestrahlung," &c. The order 

 in which the various departments of this great section are taken 

 up differs considerably from what is usual. This is rendered 

 possible in part by the understanding that the student has already 

 been through a course of elementary physics. Thus, Kirchhoffs 

 Principle is taken up very early, practically at the beginning. 

 Then follow chapters on the speed of propagation of radiant 

 energy, on reflexion, refraction, dispersion, and transformation of 

 one type into another. Photometry, optical instruments, the 

 human eye and colour theories are taken up in succession ; and 

 after a discussion of the usual atmospheric phenomena connected 

 with light, the remaining chapters are devoted to interference, 

 diffraction, polarization, double refraction, all of which are treated 

 of in considerable detail and with a wealth of illustration. In 

 an interesting preface Professor Chwohlson says that his aim has 

 been to write a treatise, not for the expert or specialist in any 

 particular line, but for the student, so that he (the student) " may 

 find what he needs and need what he finds." 



