THE POPULAR SCIENCE MONTHLY. 



structive amusement of young people in the 

 country whose time hangs heavily on their 

 hands in the winter evenings. It consists of 

 a collection of simple experiments in mag- 

 netism and electricity, requiring only such 

 apparatus as the experimenters can construct 

 for themselves. The first class of experi- 

 ments described are with permanent mag- 

 nets. These are followed with a number of 

 experiments with electro-magnets. A chap- 

 ter is devoted to experiments with induction 

 coils, in which various forms of Geissler tubes 

 are shown and described. Most of the sim- 

 pler experiments with static electricity com- 

 monly described in the text-books are given 

 in the chapter devoted to this form of elec- 

 tricity, and the electrolysis of water and oth- 

 er liquids and the method of electro-plating 

 in that on electrolytic experiments. Some 

 miscellaneous experiments in thermo-electri- 

 city and with the electric light complete the 

 book. The experiments are, on the whole, 

 well selected to illustrate the characteristic 

 phenomena, and are clearly described in sim- 

 ple terms suitable to the audience to whom 

 the book is addressed. 



How TO MAKE INVENTIONS, OR INVENTING AS 

 A SCIENCE AND AN ART. By EDWARD P. 

 THOMPSON, M. E. Second edition, re- 

 vised and enlarged. New York: D. 

 Van Nostrand Co. Pp. 181. Price, $1. 



IN his preface Mr. Thompson says that 

 his object is " to establish inventing as a 

 science." In the first chapter he advances 

 excellent reasons for his claim that this may 

 be done, but he does not carry out his rea- 

 soning logically. For instance, in the four- 

 teenth chapter the author says that although 

 " Coster was the first to conceive the idea of 

 replacing handwriting by printing," his dis- 

 covery was " knowledge, not an invention." 

 Science is knowledge, and the application of 

 it to a hitherto unknown art surely might be 

 construed an invention. Nevertheless, Mr. 

 Thompson has given to the world in this 

 book a fund of useful and interesting infor- 

 mation which can not fail to be of benefit. 

 It contains some very excellent advice to 

 those who " have ideas," and if only his sug- 

 gestions were adopted many a tyro inventor 

 would be saved a good deal of both worry 

 and useless expense. 



The chapter entitled Suggestive Ideas is 



full of valuable promptings and advice. So 

 is Chapter VII. In the latter the author 

 lays down four rules which should be ob- 

 served by inventors. The first rule says, 

 " Do not begin with intricate problems." 

 The others warn inventors against confining 

 themselves to single devices, and exhorts 

 them to "practice medium problems," and 

 study the analysis of the methods by which 

 they desire to accomplish new results. 



In the chapters on Principles in Chem- 

 istry and Electricity " for making scientific 

 inventions " Mr. Thompson has treated the 

 probabilities of invention with the assistance 

 of these great factors, besides giving a large 

 fund of useful information regarding these 

 elements in the field of invention. The 

 major part of the volume treats of the possi- 

 bilities of invention in the field of electricity, 

 and consists for the most part of selections 

 from the author's writings upon this subject 

 in the Electrical Engineer and other scienti- 

 fic journals. 



MECHANICS AND HYDROSTATICS. By S. L. 

 LONEY. Cambridge: University Press. 

 1893. Pp. 304. Price, $1.25. 



PROF. LONEY has prepared this little 

 manual for the use of beginners, and pre- 

 sumes on only a limited mathematical knowl- 

 edge by the pupil. The subject-matter com- 

 prises statics, dynamics, and hydrostatics, 

 which are treated briefly and concisely, the 

 propositions being illustrated by appropriate 

 examples. A number of selected problems 

 are appended to each chapter for the student 

 to work out, the answers to which are given 

 at the end of the book. In an appendix a 

 sufficient exposition of elementary trigonome- 

 try is given to enable the student to follow 

 the text when the mathematical treatment 

 calls for more mathematical knowledge than 

 elementary geometry and algebra. 



THE MINERAL INDUSTRY: ITS STATISTICS, 

 TECHNOLOGY, AND TRADE, IN THE UNITED 

 STATES AND OTHER COUNTRIES, FROM THE 

 EARLIEST TIMES TO THE END OF 1892. 

 Vol. I. Edited by RICHARD P. ROTH- 

 WELL. Pp. 628. New York: Scientific 

 Publishing Co., 1893. 



THIS volume is a compilation of statistics, 

 essays, and general information concerning 

 the mineral industries of the United States 

 and of the world, which will be gladly wel- 



