56 Notices respecting New Books. 



The resumption of magnetic power by iron after being raised 

 to bright incandescence is thus described by Mr. Faraday : — 

 " The intensity of the force did not appear to increase until the 

 temperature arrived near a certain point ; and then, as the heat 

 continued to diminish, the iron rapidly, but not instantaneously, 

 acquired its high magnetic power, at which time it could not be 

 kept from the magnet, but flew to it, bending the suspending 

 wire and trembling as it were with magnetic energy as it adhered 

 by one end to the core " (Exp. Res. § 2345). 



Approximately at that temperature wherein a cooling iron 

 wire resumes its magnetic state, a profound change occurs in 

 the physical condition of the metal*. A momentary dilatation 

 of the iron takes place ; its thermoelectric position is reversed ; a 

 sound is emitted ; and a sudden reheating, or " after-glow," is 

 seen to diffuse itself throughout the metal just before it ceases 

 to be incandescent; and its electric and thermal resistance at 

 this point appears to undergo a change, though this has yet to 

 be strictly determined. 



IX. Notices respecting New Books. 



Elementary Geometry. Books I., II., III., containing the subjects of 

 Euclid's first four Books : following the Syllabus of Geometry pre- 

 pared by the Geometrical Association. By J. M. Wilson, M.A., 

 late Fellow of St. John's College, - Cambridge, and Mathematical 

 Master of Rugby School. Third Edition. London : Maemillan 

 and Co. 1873. 12mo. pp. 188. 



n^HE first two books only of the present work have been published 

 "*- before ; they have been revised and in several respects im- 

 proved. In the composition of the third book Mr. Wilson has 

 been assisted by Mr. Moulton. Both these gentlemen, we believe, 

 took part in drawing up the Syllabus of the Association for the Im- 

 provement of G-eometrical Teaching, in conformity with which the 

 present work has been written. It is needless to add that great 

 care has been bestowed on the book. Its contents, so far as the 

 text is concerned, are substantially those of Euclid's first four books. 

 Many exercises and deductions are given in illustration of the text. 

 In many cases the diagrams are so drawn as to show the data of 

 the proposition. Playfair's treatment of parallel straight lines is 

 given in place of the method used in former editions. Geometrical 

 Loci are admitted into the text; and their use is illustrated by several 

 examples. On the whole, the book, though by no means free from 

 faults, is well executed ; and a student who makes himself master 

 of the text and is able to solve the problems and exercises will have 

 a very good knowledge of the subject. 



* The series of phenomena associated with this molecular change are 

 detailed in my preliminary note on the subject in last month's Philoso- 

 phical Magazine. 



