December 4, 1902] 



NA JURE 



lot 



to be congratulated on having been the immediate causes 

 of the publication of three such works as the Gifford 

 lectures of Profs. Ward, Royce and James. There have 

 been few equally important additions to English philo- 

 sophical speculation in recent years. A. E. Taylor. 



THE PARALLEL RUNNING OF 

 ALTERNATORS. 

 Der Parallelbetrieb von Wechselstrommaschinen. By Dr. 

 Gustav Benischke. Pp. 55. (Brunswick : Friedrich 

 Yieweg und Sohn, 1902 ; Price M. 1.20. 



THE second volume of " Elektrotechnik in Einzel- 

 Darstellungen," of which the first was mentioned 

 in these columns some time ago, appears in the above 

 form and fully sustains, if it does not surpass, the 

 excellent character of the first volume. Besides the 

 general normal parallel running of alternators, including, 

 of course, polyphase machines, the disturbing influences 

 which make parallel running difficult or impossible 

 are discussed. To the mathematically inclined, the 

 theoretical explanation of the phenomena met with in 

 the parallel running of alternating-current machinery 

 offers exceptional opportunity for a fine display of 

 mathematical calculations and formula?. Fortunately, 

 Dr. Benischke is not so inclined, and in his preface 

 declares that the physical explanation of the phenomena 

 appeals more direcHy to one's intelligence than the 

 mathematical, and that, in the cases under consideration, 

 the swinging and falling out of step of alternators, the 

 mathematical method is not much good, as it is not 

 possible thereby to prophesy whether two machines will 

 run in parallel or not. This is, of course, what has been 

 found in practice, and it is now usual in the construction 

 of alternators to so design them that means for the 

 prevention of swinging (Le Blanc's damping rings) can be 

 placed in position should it prove necessary. The author 

 is to be particularly congratulated on chapters x. and xi., 

 in which these matters are discussed, for the very clear 

 and logical manner in which he has put them. 



As an introduction, the first three chapters of the book 

 deal with the parallel running of continuous-current 

 machinery, and the question of motor current and division 

 of the load between the parallel sets. With continuous- 

 current generators, the division of the load between the 

 machines is a question for the switchboard attendant, 

 who simply has to regulate the exciting currents, the 

 steam-engine governors doing the rest. With alternators, 

 the task becomes more difficult, for not only have we the 

 additional necessity of the machines being in synchronism 

 one with the other, but also the proper division of the 

 load between the generators can only be attained by con- 

 current adjustment of both the exciting current and the 

 steam admission. This is due to the fact that increase 

 of the excitation of the unloaded machine is not followed 

 by a diminution in speed due to current flowing, followed 

 by a greater admission of steam, as in a direct-current 

 machine, as the alternator is kept at the same speed 

 always, being in synchronism. The proper division of 

 the load between the alternators becomes, therefore, 

 largely the work of the engine-driver, acting under the 

 instructions received from the switchboard attendant, 



NO. 1727, VOL. 67] 



while the latter has to see that the wattless current 

 given by the machines is kept at a minimum by the 

 proper regulation of the exciting currents. In accordance 

 with German practice, the author recommends the use of 

 an indicating wattmeter or power-factor indicator on 

 each machine to control the power factor. This has 

 not been the usual practice in England, as the matter 

 can just as well be done by regulating to minimum 

 current on the machine ammeters. To-day, recording 

 power-factor indicators are being demanded in England; 

 this is presumably to enable the engineer to have a check 

 on his assistants. They are also, so far as we are aware, 

 only for use on circuits off" which synchronous substation 

 machinery is running, where the question of power 

 factor is of greater importance than in the case now 

 considered. 



We can now only refer to the other chapters in the 

 book, which treat of the influence of the shape of the 

 current and electromotive-force curves, the electrical 

 connections for parallel running with diagrams, synchron- 

 isers, under which we did not find a description of the 

 Lincoln synchroniser, which we think is an omission, 

 parallel running of machines situated on the same axil, 

 and of alternators driven by gas engines. We can 

 warmly recommend the book to all who seek trust- 

 worthy and detailed information on this important 

 engineering subject. C. C. G. 



OUR BOOK SHELF. 



Hand- und Hiilfsbuch zur Ausfiihrung physiko- 



themischer Messungen. By W. Ostwald und R. 



Luther. Zweite Auflage. Pp. xii + 492. (Leipzig : 



W. Engelmann.) Price l$s. net. 

 The second edition of this well-known work will un- 

 doubtedly be welcomed by a large circle of students and 

 teachers, the more so since for some time the first edition 

 has been out of print. The cooperation of the original 

 author with Dr. Luther in the production of the second 

 edition has resulted in a considerable number of changes 

 being made in the book ; a new work is, in fact, the 

 result. Dr. Luther's long experience as demonstrator and 

 later as subdirector of the Physico-chemical Institute at 

 Leipzig has made him specially fitted for this collabor- 

 ation, and the value of the book is greatly enhanced by 

 the results of his daily contact with the practical diffi- 

 culties of students engaged in physico-chemical work. 



In the new edition, the headings of the first fifteen 

 chapters agree with those of the first issue. Considerable 

 changes have, however, been made in detail by the intro- 

 duction of new matter. The sixteenth chapter of the 

 original edition is represented by five chapters in the 

 present one, the headings of which are respectively 

 electrical measurements, electromotive force, conductivity 

 of electrolytes (dielectric constant), quantity of electricitv 

 and transport number and finally electrical measurement 

 of temperature. In this portion of the book, the chief work 

 of reconstruction has been performed. The twentieth 

 chapter deals with chemical dynamics, and a new chapter 

 has been added on the application of physico-chemical 

 methods to chemical questions. 



Noteworthy alterations in detail are the introduction of 

 a number of new tables of useful data, the use of the new 

 unit for the expression of conductivity values and the 

 inclusion of copious references to original papers dealing 

 with the subject-matter in hand. Special forms of ap- 

 paratus and details of manipulation which cannot be 

 included in a practical text-book of anything like modest 



