NOTICES OF BOOKS. xlix 



As a supplement to these papers on the South African rock, Pro- 

 fessor Bonney has included in this little volume a chapter on the 

 " Kimberlites " from Syracuse, N.Y. and Elliot County, Ky., in the 

 United States. His account of these rocks is based on unpublished 

 notes by Professor Carvill Lewis himself, and on later memoirs by 

 Professor G. H. Williams and Mr. Diller. 



It is well known that Professor Carvill Lewis contemplated a com- 

 plete discussion of the relation of diamond-bearing deposits in different 

 parts of the world to olivine and serpentine rocks. But the notes left 

 on this subject were, m the judgment of Professors Bonney and 

 Rosenbusch, too incomplete for publication with advantage at the 

 present day. 



Electro-CIieiiiisfry. By Max Le Blanc. Translated by W. R. Whitney. 

 London : Macmillan & Co., iSg6. 



To those unacquainted with the chapters in Ostwald's Lehrbiich 

 dealing with the same subject this book will prove extremely interesting, 

 and even to those who are familiar with the views which Ostwald has 

 developed so plausibly the book will be very useful. 



Le Blanc's own researches, begun under Ostwald's direction, 

 occupy an important position in connection with the subject, and this 

 fact lends additional interest to the work. 



The first part of the book — containing chapters on the dissociation 

 theory, the migration of the ions and the conductivity of solutions — 

 deals very clearly with questions already familiar to the English reader. 

 The manner in which migration data are practically obtained is more 

 fully described than is usual. 



The second part -containing chapters on electromotive force and 

 polarisation — will, however, attract much more attention. 



It is unnecessary to refer to the contents of these chapters in de- 

 tail ; but one or two points are perhaps worth noticing. 



The conception of splution pressure is very useful when an attempt 

 is made to realise the nature of the equilibrium between a solution and 

 an electrode ; but the relation 



77 = k T log P/p 

 — where P is a constant depending on the nature of the electrode — can 

 be derived without the aid of this conception. For this reason the 

 method adopted by Le Blanc of first introducing the notion of solution 

 pressure and then deducing the relation above quoted is open to 

 criticism. The sentence which ends at the top of page 154 needs 

 qualification. 



While the author makes no attempt to discuss the nature of the 

 equilibrium between an electrode and a solution in the general case, 

 the view which he takes of the equilibrium in some particular cases 

 seems open to objection. For instance, in the case of an electrode of 

 zinc amalgam considered on p. 159, the zinc may determine the magni- 

 tude of the potential difference ; but no reason is given why the 

 "electrolytic solution pressure " of the mercury should not determine 



