Notices respecting New Books. 129 



incorrect, as the star never descends below magnitude 9|, and in 

 fact always remains visible in a telescope of 3 inches aperture, or 

 even 2 inches. The minimum of n Argus is given as 6 magnitude; 

 but the star has been seen as faint as 7 5 (in 1886), and is at present 

 about the 7th magnitude. Its period, if it has one, has not yet 

 been satisfactorily determined. These are trivial matters, however, 

 and do not detract from the value of a book which it is to be hoped 

 will meet with the success it deserves. All telescopists should 

 procure a copy of the work without delay. The book is well printed 

 and bound, and contains numerous excellent illustrations. 



J. E. GrOEE. 



A Treatise on Analytical Statics, with numerous examples. By E. 

 J. Kouth, Sc.D., F.R.S. Vol. I. (Cambridge : University 

 Press, 1891 ; pp. xii-f 407.) 



We approach this new work by Dr. Routh as if it were the work 

 of a " blessed Grlendoveer " (" 'tis mine to speak, and yours to hear "). 

 We never had the good fortune to sit at his feet and so have had 

 a more thorough enjoyment in reading it than any one of his 

 numerous " sons " who are familiar with his methods can have. 

 He himself opens his preface with the words : " During many 

 years it has been my duty and pleasure to give courses of lectures 

 on various mathematical subjects to successive generations of 

 students. The course on Statics has been made the groundwork 

 of the present treatise. It has, however, been necessary to make 

 mauy additions ; for in a treatise all parts of the subject must be 

 discussed in a connected form, while in a series of lectures a 

 suitable choice has to be made." We trust that Dr. Eouth will 

 not only complete his work on Statics, of which this is a first 

 instalment, but also, in due time, give students the results of his 

 many years' labours in other parts of the mathematical curriculum. 

 Our author's mode of procedure is to " examine first how the 

 elementary principles of statics are connected with the axioms 

 required for the more general problem of dynamics, and secondly 

 how they may be made to stand on a base of their own." J. 

 Walsh wrote to De Morgan : " In mechanics the parallelogram of 

 forces is quackery, and is dangerous ; for nothing is at rest, or in 

 uniform, or in rectilinear motion, in the universe. Laplace's 

 demonstration of the parallelogram of forces is a begging of the 

 question " *. Dr. E-outh gives both Newton's and Duchayla's 

 proofs. We do not intend, however, to go through the treatise in 

 detail. The matter and the manner happily call for no comments 

 of ours, we propose only to indicate what facts are taken up in 

 this first instalment. Chapters i. to iv. take us through the ele- 

 mentary portions, such as forces acting at a point, parallel forces 

 (theory of couples), forces in two dimensions, illustrated by a store 

 of carefully selected examples, many worked out and others with 

 pregnant hints for their solution. Chapter v. discusses friction ; 



* ' Budget of Paradoxes/ p. 155. 

 Phil Mag. S. 5. Vol. 32. No. 194. July 1891. K 



