172 NOTICES OF BOOKS. 



are not always met by the instruction provided in a course of 

 lectures. To supply such a need, and to serve as a companion 

 in the practical work of such a course, is the aim of this little 

 book.. It has been found necessary to assume that the student 

 has "already acquired a knowledge of elementary physics and 

 crystallography. To the working microscopist who has devoted 

 his attention to the study of rock sections, the little book will 

 be very helpful indeed, and can be recommended. The book 

 is divided into two sections : the Optical Properties of Minerals, 

 and the description of the Common Rock-forming Minerals. The 

 latter part is illustrated by twelve plates which exhibit the 

 facies of the minerals as found in rock-sections. Many practical 

 hints given in the first part will prove very useful to the student 

 in working out the optical properties of the minerals under 

 examination. Pages 93-97 are devoted to the " shadow " 

 method of determining the refractive indices of isolated frag- 

 ments. This method has the advantage that only a very small 

 quantity of the mineral is required. The association of rock- 

 forming minerals is considered in the closing pages — " Hints on 

 Petrology." 



The publishers also issue a series of micro-slides representa- 

 tive of the various rocks, and such sections of minerals for the 

 polarising microscope as illustrate the methods of determination 

 described in the first part of the book. 



(1) The Mycetozoa : A Short History of their Study in Britain ; 

 an account of their habitats, generally ; and a list of species 



recorded from Essex. By Gulielma Lister, F.L.S. {Essex 

 Field Club Special Memoirs, vol. vi.) vi + 54 pages, 

 frontispiece. 8^ x 5| inches. (Stratford, Essex : The 

 Essex Field Club ; London : Simpkin, Marshall & Co., 

 Ltd., 1918. Price 3s. net.) 



(2) Guide to the British Mycetozoa exhibited in the Depart- 



ment of Botany. Fourth edition. 62 pages ; 51 figs, in 

 text. 8 J X 5| inches. (London : Brit. Mus. Nat. Hist., 

 1919. Price Is. net.) 



Our excuse for drawing attention to these two Httle books, 

 which are probably quite familiar to the worker in the study of 

 Mycetozoa, is the need of lending a helping hand to the junior 



