7IO NATURAL SCTENCE. >,„,,. 



and enumerated by him in preliminary accounts, and will be found 

 recorded in the Zoological Record for 1890. Hence, they are not all 

 of them, strictly speaking, new species, though here described for the 

 first time. The nomenclature of spicules published in the 

 "Challenger" Reports is adopted, with the addition of a few 

 names for some new forms of spicules. In classification, the following 

 modifications are proposed : — The order Carnosa, of Carter, is revived, 

 to include the suborders Microsclerophora (Sollas), Oligosilicina 

 (VosmsLer pars,CJiondyina),a.nd Myxospongida (Chondrosia RVid Oscnrella). 

 The Monaxonida are classified into Spintharophora (Sollas emend.) 

 and Halichondrina. The latter name is used in the same sense as 

 by Ridley and Dendy in the "Challenger" Reports (vol. xx.). The 

 Spintharophora are divided into Aciculida, with diactinal spicules 

 (Epallacidae, Stylocordyla, and Tethyadse), and Clavulida with 

 monactinal spicules (Spirastrellidae, Suberitidse, and Clionidae). The 

 monograph is got up in splendid style, and well printed, and the 

 illustrations are excellent. We may specially draw attention to 

 plate i., containing beautiful coloured pictures of living sponges 

 depicted on board the yacht. M. Topsent must certainly be con- 

 gratulated on having given us a valuable contribution to the study of 

 an interesting group. E. A. M. 



The Future of Silver. [Die Zukunft des Silbers.] By Professor Edward Suess, 

 8vo. Pp. iv. and 227. Vienna and Leipzig: 1892. 



The Silver Question in general, and the theory of Bimetallism in 

 particular, in the main lie outside the scope of Natural Science ; 

 both, however, ultimately depend on the relative abundance of the 

 supply of gold and silver, and this is a purely geological question. 

 We cannot, therefore, follow Professor Suess into the interesting 

 questions of economics and currency raised in his latest work, but as 

 the main part of the volume is devoted to a sketch of the present 

 condition and future prospects of the gold and silver mining fields, of the 

 mode of occurrence of the ores, and of the factors which govern the 

 possibility of their profitable exploitation, the book cannot be allowed 

 to pass unnoticed. Professor Suess, the Professor of Geology in the 

 University of Vienna, is one of the foremost of living geologists, and 

 his " Antlitz der Erde " inspired two of the Presidential Addresses at 

 the last meeting of the British Association ; he has special qualifica- 

 tions for the treatment of this subject, being equally eminent as an 

 economist, and his work " Die Zukunft des Goldes," which appeared 

 in 1877, has taken high rank in the literature of the Silver Question. 

 To this, the present volume is a sequel, written to trace the history 

 of the production of gold and silver during the past fifteen years, and to 

 show that the predictions then made have been verified by subsequent 

 events. The book is divided into ten chapters, of which the first five 

 deal with the questions of the occurrence and supply of gold and 

 silver, and the last five with the economic consequences that result 

 therefrom. 



In the introductory chapter Professor Suess deals briefly with the 

 Californian and Australian gold discoveries of 1849, and with the 

 visions that these encouraged of a universal international gold currency. 

 These hopes were, however, strongly discouraged by the geologists of 

 the time, and quotations are made from a paper by Murchison in 1854 

 warning politicians that the enormous gold supply of that period was 

 quite temporary. In the second chapter the author summarises the 

 history of the variations in thegold supply since 1877, and points out that 



