5 io SCIENCE PROGRESS 



graphical methods of treating the rise of current in a circuit possessing self- 

 induction when connected to a D.C. supply, for the mathematical solution of the 

 problem now given. Next follow chapters on Alternating Current Power and its 

 measurement, and on the effect of capacity in Alternating Current Circuits. A 

 chapter on Circle Diagrams is a useful introduction to the study of these diagrams 

 in connection with Induction Motors. There is also a chapter on the Magnetisa- 

 tion of Iron when subjected to alternating magnetisation. 



The chapter dealing with wave forms and the analysis of wave form is very 

 complete and elaborate, and will be of great value to engineers who have to deal 

 with the problem. Luckily for the student and the engineer the number of wave 

 forms met with in practice that depart very much from the sine wave shape is 

 rapidly decreasing, and this process will undoubtedly continue, as it becomes 

 more universally recognised how many of the difficulties that arise in A.C. 

 supply systems are caused by wave forms that differ from the pure sine shape. 

 Polyphase currents are next dealt with, and then follow two valuable chapters on 

 alternating current instruments. These include, besides the descriptions of 

 commercial ammeters and voltmeters, wattmeter and power factor indicators, 

 such instruments as the oscillograph, both of the bifilar pattern and of the form 

 in which cathode rays are used to delineate the wave shapes. There are also 

 descriptions of frequency meters and leakage indicators. The chapter on trans- 

 formers is clear and good, but it is to be regretted that in dealing with performance 

 and testing, the author has made no mention of the triangle diagram developed 

 by Morris for determining regulation from a short-circuit test. This diagram is 

 much the most useful for practical work that has been devised. There is a long 

 chapter on alternators, which includes not only testing but design schedules. 



There are chapters on power transmission, synchronous motors, phase 

 advancers, rotary converters, and, finally, induction motors and single phase 

 motors. The author is to be congratulated on his book ; it is very complete in its 

 treatment up to the standard whick it proposes to reach ; the chief criticism that 

 can be urged (and that is not really a drawback) is that it includes a good deal of 

 matter which is beyond the practical requirements of the student for whom it is 

 primarily intended. 



E. W. M. 



MISCELLANEOUS 



Life and Letters of Sir Joseph Dalton Hooker, O.M.. G-.C.SL Based on 

 materials collected and arranged by Lady Hooker. By Leonard Huxley. 

 [Vol. I., pp. x + 546, with 4 plates and 1 map ; Vol. II., pp. vi + 569, with 

 5 plates.] (London : John Murray, 1918. Price 36^. net.) 



It is no easy task, even in the 1 100-odd pages of these two volumes, to compass 

 an account of a life that extended over a period of nearly a century ; a life replete 

 with experiences, and one which embraced some seventy-three years of active 

 scientific work. 



The story of Sir J. D. Hooker's life could not fail to be of interest from his 

 eminence as a botanist, but added to this his most active years marked the 

 renaissance period of modern scientific thought, and were enriched by the friend- 

 ship of those biologists whose names stand foremost as pioneers of the doctrine of 

 Evolution. The friend and confidant of Darwin, he was one of the earliest 

 converts to the new view-point for which he was mainly instrumental in supplying 

 the botanical data. 



