348 



SCIENCE. 



[Vol. XV. No. 383 



Electrical Influence Machines. By John Gkat. London, Whit- 

 taker; New York, Van Nostrand. 12°. $1.75. 



In this volume Professor Gray, who is an associate of the In- 

 stitute of Electrical Engineers of London, gives a very full ac- 

 count of the historical development and modern forms of electri- 

 cal influence-machines, together with instructions for making 

 them. The branch of electrical science covered by this treatise 

 has been apparently somewhat neglected of late years ; and for 

 that reason alone the volume would be welcome, aside from the 

 fact that it contains in compact form all that is really useful and 

 interesting about influence-machines. It shows, also, that the 

 neglect of investigators in this direction has been more apparent 

 than real, for great progress has been made, but the greater 

 progress made in the development and commercial utilization of 

 dynamical electricity has made it seem that the static form had 

 almost been forgotten. But, as the author shows, the influence- 

 machine has an important field of its own, and, in some of its 

 latest and most improved foruis, is a simple and convenient gen- 

 erator of high-tension electricity, nearly as reliable as the induc- 

 tion-coil, and less expensive. 



The work is divided into three parts. The first is devoted to a 

 general sketch of the phenomena and leading principles of static 

 electricity, a chapter each being given to experimental data, to a 

 working hypothesis of the electrical field, and to electrometers. 

 This part is sufiiciently complete to serve instead of a text-book 

 for beginners, and will enable those with little mathematical 



knowledge to understand the nature of electrical quantities, The 

 second part is devoted to the historical development of the ma- 

 chines, and also contains descriptions of modern ones, such as 

 Varley and Topler's, Holtz's, Wimshurst's, Sir W. Thomson's, Max- 

 well's, and ' 'addition" machines such as Bertsch's and Carry's. The 

 third part contains all the information needed by instrument- 

 makers and amateurs to guide them in making the influence-ma- 

 chines most commonly used. The book is illustrated by two hun- 

 dred and twenty-eight engravings, and has a very complete index. 



AMONG THE PUBLISHERS. 



It is proposed to publish the results of the research of the 

 special students in the Department of American History at the 

 University of Pennsylvania in a regular series of pamphlets. 



— D. C. Heath & Co. will publish June 10, " A Compendious 

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— The New York Home Journal just now is of especial interest 

 to people who contemplate spending the summer, or part of it, in 

 the country. It is issuing several editions of a "Summer Resort 

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— The Political Science Quarterly for June opens with a de- 

 fence of national sovereignty in the United States, by John A. 

 Jameson, against the theories of the "analytical jurists;" E. I. 

 Renick of the Treasury Department discusses the relations of the 



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 LOWELL, J. R. 

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