'768 



NA TURE 



[June 17, 1922 



author might justly complain that a similar diagram 

 has been allowed to pass for several years without 

 comment in the Admiralty Tide Tables ! 



For the calculation of approximate predictions Van 

 der Stoic's scheme of calculation is explained and used 

 in the book, and the calculations are facilitated by 

 appropriate tables. Some little confusion is caused, 

 however, by using the same symbol (k) for the phase- 

 lag (in degrees) and time-lag (in hours) when the tidal 

 constituent is referred to a fictitious satellite; it is 

 customary to use k for the phase-lag. It is doubtful 

 whether it was wise to depart from the usual rule of 

 stating the astronomical argument ; it is customary 

 to make the speeds positive and the arguments 

 therefore increase with time. Except to those using 

 the harmonic method for the first time there is a 

 liability of confusion between theory and practice, a 

 positive speed and a decreasing argument being 

 difficult to reconcile. If, however, the instructions 

 are carefully followed the required predictions can be 

 readily obtained, whether there is much or little diurnal 

 tide. 



It ought to be added that a criterion given for the 

 relation between semi-diurnal and diurnal tides so 

 that one maximum per day only can occur, has a very 

 limited application. 



The manual gives authoritative explanations of the 

 non-harmonic methods of collecting and using tidal 

 information. In spite of the blemishes mentioned 

 above, the book should serve a useful purpose in making 

 seamen acquainted with the reasons why such methods 

 are often futile. At the same time, it provides an 

 alternative and more exact method, and in doing this 

 Commander Warburg has initiated a movement which, 

 we hope, will lead to much-needed reforms in the 

 everyday applications of tidal science. 



A. T. DooDSON. 



Electrothermic Processes in Steel 

 Manufacture. 



The Electro-Metallurgy of Steel. By C. C. Gow. (A 

 Treatise of Electro-Chemistry. Edited by Bertram 

 Blount.) Pp. xvi-F35i. (London: Constable and 

 Co., Ltd., 1921,) 275. 6d. 



WHAT are usually called electro-metallurgical 

 processes of steel manufacture now consti- 

 tute an applied science of considerable industrial im- 

 portance. Strictly speaking, however, the processes 

 are not electfo-metallurgical since electrolysis is not 

 an essential feature. Electrical energy is transformed 

 into heat energy which is applied to the making and 

 refining of steel of many types. The possibility 

 of applying electrical energy in this way was first 

 NO. 2746, VOL. 109] 



demonstrated by the late Sir William Siemens almost 

 twenty years before its commercial possibilities were 

 recognised by later investigators. Prior to the out- 

 break of the late war the electric furnace had only a 

 very Hmited apphcation in steel metallurgy. Since 

 then it has had a rapid and vast development, due partly 

 to the shortage of high-grade raw materials, partly to 

 the enormous demand for alloy steels, and partly to 

 the need for utilising in some way the vast accumulation 

 of heavy steel turnings. These conditions presented 

 an exceptional opportunity for the electric furnace, and 

 it was only then that its economic advantages in certain 

 branches of steel-making were actually demonstrated. 

 According to Mr. D. F. Campbell, who has written a 

 preface to Mr. Gow's book, the electric furnace is now 

 absorbing millions of electrical horse-power for various 

 purposes and has produced more than a million tons 

 of steels of various types. 



Mr. Gow is well fitted to write a book on electro- 

 thermic processes of steel manufacture, both on account 

 of his scientific training and his wide experience of 

 steel works practice. These qualifications have stood 

 him in good stead in producing a book which should 

 attract the attention both of students of metallurgy - 

 and practical steel-makers. Following an introductory I 

 chapter on the historical development of electric steel 

 furnaces, the early chapters deal with the general 

 principles and application of alternating currents. In 

 writing these the author expresses his great indebted- 

 ness to Mr. R. P. Abel. Then come chapters on electro- 

 thermal methods of melting and refining cold charges, 

 and refining liquid steel, and these in their turn ar( 

 followed by a chapter on ingot casting. Later chapters 

 deal with characteristic principles and features o 

 electric furnace design and modern types of furnaces 

 suitable refractory materials, and the properties anc 

 manufacture of carbon electrodes. Finally, there is ai 

 appendix detailing rapid methods of analysis of batli 

 samples. 



The melting of steel on a large scale in a strictly 

 reducing atmosphere is possible only in the electric 

 furnace. New phenomena are observed and striking 

 results have been obtained. It is therefore correct to 

 say that the electric furnace gives the steel-maker and 

 refiner a new atmosphere in which to conduct his 

 operations. Owing primarily to the much higher tera^ 

 peratures which can be reached, steels of inferior grade 

 can be melted and their deleterious constituents to a 

 great extent removed, because it is possible to intro- 

 duce refining slags which can be fused and operated only 

 at temperatures reached in the electric furnace. This 

 type of furnace has now rendered available new alloys 

 of special value, such as low carbon ferro-chromiumj 

 and high-grade ferro-silicon, which in their turn hav6 



