March 17, 1398 J 



NA TURE 



459 



new and very powerful agents, by which it became 

 possible to isolate from their compounds several elements 

 the existence of which was well recognised, but which 

 had previously resisted all attempts to obtain them in a 

 separate state. Among these was aluminium, which was 

 seen for the first time in 1828 by Wuhler, who succeeded 

 in decomposing the chloride by potassium. With the 

 substitution of the cheaper sodium for potassium, and 

 the occasional replacement of the chloride by the fluoride 

 of aluminium, this was practically the method adopted 

 by the experimentalist and manufacturer alike down to 

 quite recent years. The Aluminium Company, already 

 referred to, was formed for the purpose of working such a 

 process with the use of sodium obtained more abundantly 

 and cheaply than before by Castner's process. All this 

 is now changed. So long ago as 1854 aluminium was 

 deposited in the metallic state by the electrolysis of the 

 fused chloride of aluminium and sodium according to 

 the method introduced by Bunsen. It was also stated 

 to have been obtained by the electrolysis of aqueous 

 solutions of certain aluminium compounds, but this 

 appears to have been a mistake. The method now 

 adopted consists in subjecting to the electric current 

 pure alumina in a fluid state, that is fused alone or 

 dissolved in melted cryolite. 



Now that the ehergy of falling water is being turned 

 to account on a large scale, works have been established 

 at Neuhausen near the falls of the Rhine, at Niagara, 

 and at Foyers in Scotland, for the production of the 

 current by means of vast dynamo machines, and its 

 application, among other chemical manufactures, to the 

 reduction of aluminium. 



Little else remains to be said of the book except by 

 way of commendation. A few minor matters have been 

 passed over rather slightly. Thus the solubility of cal- 

 cium sulphate in water containing chlorides is a matter 

 of some importance from a technical point of view ; and 

 the simple statement of the text fp. 437), that "according 

 to Anton i part of gypsum dissolves in 122 parts of a 

 saturated solution of sodium chloride," is neither very 

 precise, nor is it of much practical use. A long series 

 of determinations of the solubility of calcium sulphate 

 in chlorides is provided by the work of Lunge {J. Soc. 

 Chem. Ind., 4, 31), and by that of Tilden and Shenstone 

 \Proc. R. S., 38, 331). As regards the temperatures 

 supposed to be indicated by the colours developed upon 

 the surface of steel in the process of tempering, it has 

 been shown, more especially by Turner, that these colours 

 can be successively developed by protracted heating to 

 the same temperature, and under any circumstances are 

 not to be interpreted to within a considerable range of 

 degrees. As the interesting lead tetrachloride has been 

 properly mentioned, the more stable tetracetate (Hutchin- 

 son and Pollard) should have been noticed at the same 

 place. 



The whole of such a volume as this should be read 

 attentively by every serious student of chemistry ; and if 

 this treatise does not displace all other English text- 

 books devoted to mere description, it will be solely on 

 account of the unfortunate but unavoidable high price, 

 a consideration which necessarily influences so many 

 students in their choice. W. A. T. 



NO. 1 48 1, VOL. 57] 



SUBMARINE CABLE TESTING. 



Student's Guide to Submarine Cable-Testing. By 

 H. K. C. Fisher and J. C. H. Darby. Pp. 165. 

 (London: The Electrician Printing and Publishing 

 Co., 1897.) 



THIS practical and useful little book is designed as 

 its title indicates, and, as its authors state in their 

 preface, to meet the requirements of young students in 

 this particular branch of submarine cable engineering, 

 and to endeavour to place before them in as concise 

 and lucid a manner as possible, not only the practical 

 problems involved in the study of cable-testing, but also 

 the simple algebraical formulae necessary for their 

 solution. 



Many of the large submarine cable companies now 

 demand that their employes shall qualify themselves in 

 electrical subjects, and shall pass certain examinations 

 before being considered eligible for promotion from the 

 lower to the higher grades of the service. 



This very proper requirement on the part of the corri- 

 panies has resulted in stimulating their staffs to greatet 

 exertions ; but it has been found that the ordinary text- 

 books in circulation are either too theoretical and ad- 

 vanced for beginners, or fail to deal with and thoroughly 

 explain just those particular points upon which they seek 

 instruction. 



The authors of the little work under review — practical 

 electricians and cable engineers themselves — were con- 

 stantly being asked for information upon these points, 

 and their first effort to meet this demand upon their 

 time and patience took the form of a small pamphlet 

 entitled " Notes on Practical Cable-Testing," of which a 

 small numbfer was printed and issued privately. 



This first effort was so far appreciated, as to encourage 

 them to hope that a more ambitious work, carried out 

 on the same lines, might be found still more useful ; 

 and although, as the authors modestly remark in their 

 preface, " the scope of the present work is bounded by 

 the requirements of the electrical examinations for super- 

 visors, and the ordinary electrical outfit of all the com- 

 pany's stations," we venture to think they have so far 

 succeeded in their purpose, that this book will be found 

 of practical value, not only to those for whom it was 

 originally written, but to all desirous of studying and 

 understanding this most interesting subject. 



As we have already observed, too many of the existing 

 text-books are the works of theorists who do not concern 

 themselves with the practical features of the matters 

 upon which they write ; in fact, who do not possess the 

 necessary practical experience themselves, which would 

 enable them to do so satisfactorily ; and we think, 

 therefore, that this little book will be accepted, and 

 rightly so, as a useful contribution not only to our 

 knowledge, but also to submarine cable bibliography. 



The work is divided into two parts : the first dealing 

 with simple testing, such as the measurements of re- 

 sistances and of electrostatic capacity, together with the 

 testing of batteries for electromotive force and interna 

 resistance ; and the second, with the various known 

 methods which are adopted for the localisation of faults 

 in submarine cables. 



