460 



NATURE 



[March 17, 1892 



OUR BOOK SHELF. 

 UElectricitd dans la Nature. Par Georges Dary. 

 " Biblioth^que Internationale de I'filectricitd et de ses 

 Applications." (Paris: Georges Carrd, 1892.) 



A POPULAR and accurate account of the various forms 

 and ways in which electricity appears in Nature is sure 

 to find a great many readers, for the subject is most in- 

 teresting. Everyone should become acquainted with at 

 any rate some of the most ordinary electrical pheno- 

 mena of every-day life, even if he should learn no more 

 than the cause of a flash of lightning and the sub- 

 sequent peal of thunder. In this volume the author has 

 brought together accounts of many interesting phenomena 

 that have been observed from time to time, with the 

 hypotheses that have been put forward to explain them. 

 The subject is divided into seven parts or chapters. The 

 first relates to the origin, presence, and distribution of 

 electricity in our atmosphere, and also to cosmical elec- 

 tricity, in which the influence of solar spots on atmo- 

 spheric electricity and the electrical nature of comets 

 and nebulas are mentioned. There are also descriptions 

 of various conductors and electrometers, the principles 

 of each being brought out clearly. Chapter ii. deals with 

 storms. The author in this part has collected many 

 typical examples which represent various classes of 

 storms. After reference to the formation, height, and 

 constitution of storm-clouds, and the variation and dis- 

 tribution of the storms themselves on the earth's surface, 

 he describes the various forms in which lightning has 

 been observed. Very curious effects, both on men and 

 trees, are recorded to have taken place. An interest- 

 ing instance here given relates to a flash of lightning 

 that, having struck one tree and travelled down its trunk 

 spiral fashion, suddenly leapt across to another one close 

 by, and went to earth, the spiral curve being continued 

 on this second tree. Chapter iii. contains some useful 

 information relating to lightning-conductors, in which a 

 brief historical summary is given : many kinds that have 

 been or are now in use are described, with accounts 

 of their action, verification, and efficiency. In the next 

 two chapters, hail-storms, waterspouts, tornadoes, and 

 cyclones are dealt with, while earthquakes and aurorae 

 form the subjects of the concluding chapters. 



In the above summary of the contents of this volume 

 there is much to which we should have liked to refer, 

 but the reader at any rate will be able to form a general 

 idea of the range of subjects treated of in these four 

 hundred pages. 



Besides being interesting, the book will form a useful 

 volume to many readers, for its value is very much in- 

 creased by the great number of references inserted. 



The First Book of Euclid's Eletnents. By the Rev. 

 J. B. Lock, M.A. (London: Macmillan and Co., 



1892.) 



Now that the concession has been made by the Uni- 

 versity of Cambridge of allowing in all her public 

 examinations any sound proof of the propositions of 

 Euclid provided that their logical sequence remains 

 unaltered, teachers of geometry will have a far freer 

 scope ; since they are no longer bound by any hard 

 and fast rule. The present work, by a writer familiar 

 to our readers, will be read with interest, for the arrange- 

 ment of the text has undergone somewhat of a change 

 from the sequence usually followed. With regard 

 to the order of the propositions, it will be noticed 

 that the theorems are separated from the problems. 

 This seems to be advantageous, for after all there 

 is a fundamental difference between theorems and 

 problems : as the author says, a theorem is a geo- 



NO. I 168, VOL. 45] 



metrical truth based on fundamental ideas and defini- 

 tions of geometry, while problems entirely depend on 

 postulates which are practically impossible. 



The definitions have also received great attention, 

 and are here thoroughly and clearly explained ; in two 

 cases, that of the " straight line " and " angle," the author 

 has thought fit to make a slight divergence from the 

 customary definitions. Accompanying the propositions 

 are numerous exercises, while interpolated occasionally 

 are many worked out examples. 



Altogether, the book is one that should be in the 

 hands of teachers, and is worthy of being well tested by 

 them in their classes. W. 



The J If or d Manual of Photography. By C. H. 

 Bothamley. (London : The Britannia Works Co., 

 Ltd., 1892.) 



This manual, which has been compiled at the request 

 of the Britannia Works Company, will be found by our 

 photographic readers to be both well written and useful, 

 containing as it does all information generally needed by 

 amateurs. It is not a complete treatise on the subject, 

 but is intended to aid those who are indulging in the 

 various applications of this art at the present day from a 

 thoroughly practical point of view. The first few chapters 

 are devoted to the description of the apparatus, deve- 

 loping manipulations, faults in negatives, and various 

 printing processes, all of which are well treated ; we 

 then come to the method of making enlargements, 

 mounting and framing, lantern sHdes and transpar- 

 encies. The concluding chapters are of special interest, 

 consisting of portraiture, copying, photographing of 

 objects in motion, orthochromatic photography, and 

 photography by artificial light. 



Preceding the appendix are tables of English and 

 French weights and measures, while the appendix itself 

 contains some formulae and reprints from one or two 

 photographic journals. Besides an account of the Ilford 

 universal hydroquinone developer, there are papers by 

 Mr. John Howson, on the " Printing Paper of the Future," 

 " Lantern Plates," together with the best methods of 

 cutting up printing-out paper. 



A most useful table presents a list of dealers and 

 dark rooms situated all over the world, ranging from 

 modest dealers in Bettws-y-Coed and Leighton-Buzzard 

 to those in South Africa, New Zealand, and Japan. 

 From this table, it can be at once ascertained whether, 

 at a certain place, Ilford plates or paper, chemicals 

 or apparatus, are kept in stock ; whether amateurs 

 can receive help or get work done for them, such as 

 printing, mounting, &c. ; or whether a dark room is 

 obtainable or not. This list, when thoroughly completed, 

 and other first-class firms included, will be invaluable 

 for tourists on the Continent, while at present it should 

 be used very largely by those travelling in this country. 



W. 



The Advanced Class-Book of Modern Geography. By 

 William Hughes and J. Francon Williams. (London : 

 George Philip and Son, 1892.) 



It is impossible not to have some pity for the unfortu- 

 nate boys and girls who will have to learn geography 

 from this gigantic " class-book." It consists of more 

 than 800 closely-printed pages, the very appearance of 

 which would suffice to discourage most young students. 

 Geography is one of those subjects in the learning of 

 which very much more depends on the teacher than on 

 the text-book ; and a good teacher would have no desire 

 to see so elaborate a work as this in the hands even of 

 "advanced" pupils. The information, so far as we have 

 been able to examine it, is accurate ; but it is not, as a 

 rule, presented in a way that would be likely to excite 

 interest or curiosity. 



