164 



SCIENCE. 



[Vol. XII. No. 296 



It had not been shown, until Hertz's experiments were made, 

 that the vibration of an electric current would set up disturbances 

 in the surrounding medium, — the assumption on which Maxwell's 

 theory was based. Hertz proved this in the following way : con- 

 ducting circuits have definite time-constants, just as stretched 

 strings have definite periods of vibration : and a disturbance 

 whose period is the same as the time-constant of the circuit 

 will produce a greater effect than any other, just as a piano-string 

 will vibrate if one sings the note to which it corresponds. Hertz 

 produced electric vibrations of a short and definite period, — one 

 hundred millionth of a second, of a wave-length of about two 

 metres, — and studied the effect on a receiving-circuit of the same 

 time-constant. The receiving-circuit had a short air-space in it, 

 and sparks were observed leaping across this space. By placing 

 the vibrator several wave-lengths from a reflector, and moving the 

 receiver,betvveen the two, he observed that at certain distances the 

 induced sparks were faint ; then, on moving the circuit, they be- 

 came brighter, then disappeared again, — phenomena e.xactly 

 resembling Lloyd's bands in optics, due to interference. To quote 

 Professor; Fitzgerald, " Henceforth I hope no learner will fail to be 

 impressed with the theory — hypothesis no longer — that electro- 

 magnetic actions are due to a medium pervading all known space, 

 and that it is the same medium as the one by which light is prop- 

 agated ; that non-conductors can, and probably do, as Professor 

 Poynting has taught us, transmit electro-magnetic energy. By 

 means of variable currents, energy is propagated into space with 

 the velocity of light." 



The experiments of Hertz have made Maxwell's theory of light 

 more than possibly true, and it seems as though light must be here- 

 after considered as an electro-magnetic phenomenon. 



A New System of Electrical Distribution by Storage- 

 Batteries. — Mr. Henry Edmunds has brought out a new system 

 of distribution by storage-batteries, that seems to have a good deal 

 of merit. The systems that have been used have objections which 

 Mr. Edmunds obviates. Mr. Crompton's plan for using batteries is 

 to have a number of groups in series on the main line, taking the 

 current for distribution from the ends of each group. The bat- 

 teries are connected with the charging and discharging circuits at the 

 same time. The obvious disadvantage of this plan is that a high po- 

 tential cannot be used, since the lamp-circuit is liable to have its poten- 

 tial raised to the maximum of the charging circuit ; and, with more 

 than four hundred volts difference of potential at the dynamo termi- 

 nals, this would be distinctly unsafe. The other system consists in 

 having two sets of cells, one of which is being charged while the other 

 is discharging. Mr. Edmunds's is a modification of the latter plan. 

 If he wishes forty-eight volts in the lamp-circuits, he uses thirty- 

 two cells, divided into four sets of eight cells each. Three sets in 

 series are constantly connected with the lamp-circuit, while the 

 fourth set is being charged. A device is provided by which the 

 various sets are put in rotation in the charging and discharging 

 circuits, remaining two minutes in the former, six in the latter. In 

 changing from one circuit to the other, a resistance is put in place 

 of the battery being charged, so the main circuit is never broken. 

 By putting two sets in parallel for an instant, a break in the lamp- 

 circuit is avoided. This plan has the advantage of allowing high 

 electro-motive forces to be used without necessitating a double out- 

 fit of batteries ; and the efficiency should be greater than when the 

 cells are charged for a considerable period and then discharged. 



BOOK-REVIEWS. 



The Aryan Race. By Charles MORRIS. Chicago, Griggs. 12". 

 $1.50. 



The present volume is a concise and pleasantly written review 

 of the results of recent investigations on the home and history of 

 the Aryan race. It is intended to be a popular book ; and its ob- 

 ject — to make clear to the general reader these interesting ques- 

 tions and their solutions, so far as reached to-day — has been well 

 accomplished. The author is careful to give the evidence favoring 

 the various theories as to the origin of the Aryans ; and, although 

 he states as his own view that they probably originated in south- 

 eastern Europe, he does not urge his opinion upon the reader, but 



allows him to draw his own conclusions from the evidence offered. 

 In an introductory chapter the author discusses the division of 

 mankind into races, and claims that the Caucasians are a branch 

 of the Mongols. He even goes so far as to divide mankind into- 

 two races, — the Mongoloid and Negroid. Anthropologists will 

 hardly concur with the author's views expressed in this chapter. 

 He next sets forth very candidly the arguments advanced by vari- 

 ous writers as to the early home of the Aryans, and continues to- 

 trace their migrations as compared to those of other races. From 

 linguistic evidence he describes their early stage of culture, their 

 ancestral and nature worship, and their political development. 

 When the author, in the chapter on the development of language,, 

 turns to consider languages other than Aryan, he is somewhat too 

 sweeping in his statements regarding them, and we find throughout 

 the book that the author's desire to eulogize the Aryan race has led 

 him to underestimate the merits of the rest of mankind. The his- 

 tory of the Aryans is followed in general outlines up to the present 

 time ; and the book concludes with a glowing prospect of the 

 future, the author assuming that even the fastnesses of Central 

 Africa will become the home of the conquerors of the world. 



On the Study of Words. By R. C. Trench. New York, Macmil- 

 lan. 16°. Si. 



This is the twentieth edition of Archbishop Trench's charming 

 book, revised by A. L. Mayhew. The editor has not made any 

 change in the arrangement of the book, but he has purged it of all 

 erroneous etymologies, and corrected in the text small matters of 

 detail, according to the recent advances of the science of philology. 

 He has done well in altering as little as possible of the author's 

 work, for it would be hardly possible to increase the attractiveness 

 of Trench's style, and of his method of treating his subject. He bas- 

 set forth the charms of the study of etymologies in a way that can 

 hardly be improved, and that will make every reader a friend of 

 this science. It will also induce the reader to a thoughtful use of 

 words; to considering their "poetry and morality," to use the- 

 author's words. It is hardly necessary to recommend the interest- 

 ing little volume, for the fact that it was necessary to publish a 

 twentieth edition is sufficient proof of its great merits. 



The Essentials of Geography. By G. C. FiSHER. Boston, N. E. 

 Publ. Co. 8". 

 This is one of the old-style geographies, which are of no educa- 

 tional value, and only adapted for rote work. It is the briefest 

 possible compilation of geographical facts, arranged without any 

 geographical or educational method. The statements are e.\- 

 tremely meagre, and the author has not been sufficiently critical in 

 selecting them to make his book an 'authority,' as he expresses 

 himself in the preface. The book is accompanied by sketch-maps,, 

 by the use of which the author hopes to enliven the teaching of 

 geography ; which, however, are also only useful for a teacher who- 

 is satisfied with routine work, and with cramming the minds of his- 

 pupils with facts. 



Ho'iv the Peasant Owner Liiies. By Lady Verney. London and- 

 New York, Macmillan. 12°. $1. 

 Lady Verney has collected some descriptions of the life of 

 peasant-owners in France, Germany, Italy, and Russia, with the 

 object of defending the large English and more particularly Irish, 

 estates. She dwells on the fact that small estates cannot be worked 

 economically, especially where they consist of small detached sec- 

 tions. She shows more particularly the evil results of this system 

 in France. The authoress sees the only remedy against these 

 effects in the consolidation of these small estates in the hands of 

 great land-owners and the abolishment of small farms. Her ideal 

 is that the small farmer should not try to make his living out of the 

 produce of his little patch of land, but that he should become a 

 laborer on a large estate. She deems the attempts to consolidate 

 farms, that have been made on the European continent, unimpor- 

 tant, and also hardly touches the state of the workingman-peasants, 

 who earn money as workers in factories, but at the same time own 

 small patches of land on which they raise some of the necessaries- 

 of life. From this point of view, she condemns the efforts to create 

 a peasantry in Ireland, and concludes her book with a touching ro- 

 mance, ' A Yeoman's Home in the Dales Sixty Years since.' 



