234 



KNOWLEDGE. 



[OCTOBEB, 1903. 



omit altoi!ether the question of calculating air-gap areas, as for 

 practical pur]ioses it is quite sufficient to ascertain the average 

 magnetic density over the pole-faces, and this quantity is far 

 more easily determined. The next chapter, on " copper calcu- 

 lations," as well as the following one on "insulating materials," 

 is extremely good, and both chapters contain valuable data. 

 We may note that on page ,5,3 the sign of equality is omitted 

 before the M in the first formula, which makes it unintelligible. 

 This opportunity may be taken of pointing out how very few 

 inaccuracies are to be found in the volume, especially con- 

 sidering that it is a first edition. Chapter V. deals at consider- 

 ,able length with Armature Winding Schemes, and Chapter VI. 

 with the estimation of the various losses ; both of these are 

 excellent. The rules for dynamo design are set forth in 

 Chapter VII. They should offer no difficulty to the reader 

 with practical experience. The reader without such experience 

 will be reminded from time to time of the necessity of the 

 warning given in the opening chapter. For example, on piige 

 147 he is told to assume a suitable value for the Steinmetz 

 CO efficient. Now this m,ay vary by about 300 per cent, in 

 different types of machine, and the reader who requires it will 

 receive a salutary warning of the fact that his progress will 

 necessarily be blocked from time to time unless he can fall 

 back upon the practical experience of himself or others. The 

 concluding chapter contains examples of dynamo design, 

 selected from the most recent machines of leading makers. A 

 series of useful tables and schedules, followed by a very 

 complete index, brings the work to a conclusion. 



"Electrical Engineering Measuring Instru.ments." 

 By G. D. Aspinall Parr. (Blackie & Son.) Price 9s. net.— This 

 is a useful volume on a branch of electrical engineering which has 

 hithertobeen comparatively neglected by the makers of text books. 

 The author very sensibly excludes any consideration of instru- 

 ments which are merely of historical interest, and confines his 

 attention to the description of those which are in general use at 

 the present time. After a chapter dealing with classification 

 and other general considerations, Chapters II. to V. are devoted 

 to the description of the various commercial types of ammeters, 

 voltmeters and wattmeters. Chapter VII. deals with Lord 

 Kelvin's standard balances, the potentiometer, and a few other 

 miscellaneous instruments. Chapter VIII. deals with electricity 

 supply meters, and the work concludes with an excellent index. 

 The volume is copiously illustrated, and a good feature is that 

 the illustrations, for the most part, really explain the con- 

 struction of the instruments, only a comparatively small 

 percentage being of the only too common trade catalogue type. 

 " A Treatise on Zoology." Edited by E. R. Lankester. 

 Part I., Introduction and Protozoa, '2nd fasc. By Messrs. 

 Farmer, Lister, Minchiu and Hickson. (London : A. & G. 

 Black. 1903.) Pp. vii-t-45L Illustrated. — Owing apparently 

 to the vast amount of additional matter which had to be in- 

 cluded as the result of recent discoveries, the editor has found 

 it necessary to sub-divide the fiist part of this most valuable 

 work into two sections, of which the second is now before us. 

 And before going further we may candidly say that it is an 

 utter impossibility to do anything approaching justice to a 

 volume so teeming with new and interesting facts within the 

 limits of space possible in this journal. As indicated by its 

 title, the volume is devoted entirely to the lowest forms of 

 animal life. It opens with an admirable dissertation by Dr. 

 Farmer on the nature of the organic cell, in the course of which 

 it is shown that, although this constituent of organised beings 

 was discoveied so long ago as 1665, yet that it was not till a 

 couple of centuries later that its prime importance was recog- 

 nised ; attention being at first concentrated on the cell-wall 

 rather than on the cell-contents. The Foraminifera fell to the 

 lot of Mr. J. J. Lister, whose name is a sufficient guarantee as 

 to the manner in which they are described ; and Dr. Hickson's 

 treatment of the Infusoria cannot but commend itself to all 

 those interested in the.se lowly oiganisms. 



The great interest of the volume is, however, undoubtedly 

 concentrated in Prof. Minchin's admirable .account of the 

 Sporozoa (a name probably unfamiliar to the majority of our 

 readers), not from its being in any way superior to the other 

 sections, but from its containing such a large portion of 

 entirely new matter. His account of the connection between 

 malaria and mosquitoes, and of the malaria parasite (for it is of 

 these and other parasitic organisms that the chapter treats), is, 



we believe, the first that has appeared in a general (we cannot 

 say a ])opular) natural history in this country, and therefore 

 gives to this volume a very special interest. Although we 

 cannot attempt any survey of the contents of this chapter, we 

 may direct attention to one or two of the most marvellous facts. 

 A malaria-breeding mosquito when it sucks the blood of an 

 infected human being, swallows the parasite in all stages of its 

 existence; but all stages, save the fertile " gametocytes," are 

 unable to resist the .action of the gastric juices, and continue 

 their development. Ou the other hand, if the biting insect be 

 a Culex instead of an Aimjihelcs, all stages of the parasite are 

 digested. But Culex is the intermediary for bird-malaria, and 

 when an infected bird's blood is sucked, the gametocytes survive 

 the digestive process ; the Culex, in fact, standing in the same 

 relation to the bird malarial parasite as does Aiiojilieles to that 

 of man. It may be added that there is an idea as to Auojiheles 

 becoming immune to the malaria-parasite, which, if well- 

 founded, may be the possible cause of the extinction of malaria 

 in the Fens. 



The volume, although of necessity extremely technical, is 

 teeming with interest, and fully maintains the high level of its 

 predecessors in appearance (although not in serial order) — and 

 this is saying a very great deal. 



"The Boiling Lake of Dominica." By F. Sterns-Fadelle, 

 B. es sc. (Dominica.) — If the writer's science is a little out of 

 date, and his language occasionally stilted, he has, nevertheless, 

 ](roduced a popular and interesting account of the discovery 

 and appearance of the extraordinary boiling lake of Dominica, 

 a phenomenon which remained unknown, even to the inhabitants 

 of the island, until so late as March, 1875. 



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Monthly Notices of the Royal Astronomical Society. Nos. 66, 

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On the Influence of Hrain-Power on History. By Sir Norman 

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