194 



NATURE 



[April 15, 1920 



tage of having- such information is sufficiently 

 obvious. 



(i) The volume on zinc is an excellent example 

 of what such books ought to be ; it gives, first, 

 a brief history of the metal, then a description of 

 the various ores from which it is extracted, and 

 of the processes employed in dressing these ores 

 or rendering them marketable, including, it may 

 be noted, a very fair summary of the modern 

 flotation processes. The next chapters give a 

 good and quite up-to-date account of the methods 

 employed in smelting the metal or extracting it 

 from the ores, and a final chapter is devoted to 

 the alloys of which it forms an important con- 

 stituent. It is a pity that the author did not keep 

 clear altogether of chemical equations, which he 

 might easily have done in a purely popular 

 treatise, as he has been somewhat unfortunate in 

 their use ; it is difficult to understand how he ever 

 came to write such an equation as 



2ZnS + 20o = Zn2+ 2SO2, 



for the context shows that he knows well enough 

 that no such reaction ever takes place. Again, 

 he would have done better to omit the 

 equation 2ZnO + 2CO = Zng + 2CO2, because 

 although oxide of zinc can be reduced by carbonic 

 oxide, the reaction can take place normally only 

 in the presence of excess of carbon, which at once 

 again reduces the carbonic anhydride to carbonic 

 oxide. The author's equation would suggest that 

 carbonic anhydride is evolved in the process of 

 zinc smelting, whereas, in fact, the evolved gases 

 consist almost entirely of carbonic oxide. In a 

 future edition the author might with advantage 

 devote a little space to the galvanising of iron, 

 seeing that about half the world's production of 

 zinc is used for this process. 



(2) The volume on "Asbestos " decidedly suffers 

 by comparison with its companion volume, as the 

 author does not take care to avoid a number of 

 errors, which, though common enough in the 

 trade, ought not to find their way into a book of 

 this description. He does not by any means make 

 it clear, as he should have done at the outset, 

 that the trade name " asbestos " is applied to 

 several different minerals ; the name was appar- 

 ently given originally to tremolite, actinolite, and 

 other varieties of amphibole, but it is also applied 

 to fibrous forms of pyroxene, to the very different 

 mineral crocidolite, distinguished by the large 

 proportion of ferrous iron that it contains, and, 

 ■lastly, to chrysolite, a fibrous variety of serpen- 

 tine, which differs from all the foregoing in that 

 it is a hydrated silicate, whereas all the others are 

 anhydrous. Again, no serious work should con- 

 tain such statements as ; " Next to coal, asbestos 

 NO. 2633, VOL. 105] 



is now undoubtedly the most important of the non- 

 metallic mineral products of the world," or "older 

 than anything in the animal or vegetable king- 

 dom " ; surely the author cannot suppose that 

 asbestos is of more importance than salt, for 

 example, and surely he would not question the 

 inclusion of, say, Silurian trilobites in the animal 

 kingdom. His statement that the works of the 

 United Asbestos Co., Ltd., at Harefield, Middle- 

 sex, are alongside a coal-pit is unintelligible ; 

 there are certainly no collieries in that part of 

 England. When he deals with the manufacture 

 of asbestos into cloth, yarn, packing, boiler cover- 

 ings, and the numerous patented materials of 

 which it forms an essential constituent, he is on 

 safer ground, and supplies much useful informa- 

 tion in a convenient form. 



(3) and (4) The Imperial Institute is doing ex- 

 cellent service in issuing the handy monographs 

 on the mineral resources of the British Empire, 

 two of which have recently appeared. There is, 

 of course, nothing new in either of these works, 

 they being careful compilations of well-known in- 

 formation and statistics ; this does not imply that 

 the production of such compilations is at all an 

 easy task, or that the compiler has not done good 

 service in carrying it out. On the contrary, the 

 collection of the large mass of material which has 

 here been brought together requires a laborious 

 and painstaking search through many and various 

 sources of information, not all of which are 

 readily accessible to the general reader, as a glance 

 at the very useful bibliographies appended to both 

 volumes will at once show. In one respect the 

 two mineral substances discussed in the respective 

 volumes show a marked contrast : workable tin 

 ores occur in relatively few localities, whilst ores 

 of manganese are very widely distributed, and 

 to be found In most parts of the world, although 

 It is true that large deposits of manganese 

 orgs are far from plentiful; but in other re- 

 spects the tasks of the authors have been very 

 similar. 



The general scheme of both books is identical. 

 The first chapter is devoted to the uses and appli- 

 cations of the metal and Its compounds, and to the 

 nature and general characters of the ores ; the 

 second deals in some detail with the occur- 

 rences of the ores within the British Empire ; 

 and the third reviews briefly the main sources 

 of supply in other parts of the world. In 

 both cases the work has been carefully and 

 thoroughly done, and the handbooks may be 

 looked upon as giving trustworthy information 

 upon the subjects treated In a compact and con- 

 venient form. 



