374 



SCIENCE. 



[N. S. Vol. IX. No. 219. 



past history of a group by studying its species. 

 If the species are well defined and show elaborate 

 adaptations to the environment the group has 

 long existed under relatively uniform condi- 

 tions. If, on the other hand, the species are 

 defined with difficulty and connected by numer- 

 ous races it may be presumed that the environ- 

 ment of the group has changed in recent times, 

 and especially that it is undergoing expansion 

 and differentiation in new territory. In north- 

 ern regions the retreat of the ice has exposed 

 much such territory ; in the Antilles it has 

 been the elevation of the land ; in other cases 

 a type may have found new lands by migration, 

 and may thus exhibit incipient new species in 

 the midst of a stable ancient fauna. As an ex- 

 ample of the last-mentioned class may be men- 

 tioned Danais berenice jamaicensis in Jamaica, 

 as against the old Jamaican type Papilio homerus. 

 We have digressed from the immediate subject 

 of this useful catalogue, btit the interest of such 

 works lies largely in the suggestiveness of their 

 orderly and condensed array of facts. 



T. D. A. COCKERELL. 



Mesilla Park, N. M., February 12, 1899. 



Industrial Electricity. Translated and adapted 



from the French of Henry de Graffigny. 



Edited by A. G. Elliott, B.Sc. London and 



New York, The Macmillan Company. Pp. 



152. With 65 illustrations. Price, 75 cents. 



This little volume, according to the editor's 

 note, is the first of a series upon Electro- 

 mechanics, the other volumes of which will 

 treat the more important of the branches here 

 touched upon, separately and in detail. It is 

 divided into short chapters, and explains, in 

 very clear and non-mathematical language, the 

 various applications of electricity. 



Beginning with Nature of Electricity, a 

 resume of Hertz's work is given, showing the 

 identity of light and electrical vibrations. Then 

 follow, in order, chapters on Electric Units, 

 Magnetism and Induction, and Practical Meas- 

 urement of Electrical Quantities. 



Chapters V. and VI. are respectively on Chem- 

 ical Generators of Electricity and Accumulators, 

 covering the subjects of primary aud storage 

 batteries and containing much useful information 

 and explicit directions as to handling and care. 



Dynamo Electric Machinery is next touched 

 upon, including direct current dynamos, alter- 

 nators, two- and three-phase generators. The 

 remaining five chapters merely touch upon the 

 following subjects : Electric Light, Electricity 

 as a Motive Power, Electro-chemistry and 

 Electro-plating, Bells and Telephones, and 

 Telegraphs. 



The only criticisms that can be advanced are: 



1. On page 12 the table gives lO'^C.G.S. units 

 in one Henry instead of 10', while the table on 

 page 27 has many of the dimensions of the 

 mechanical, electro-magnetic and magnetic 

 unis given incorrectly. 



2. Besides these lapses the volume is, with 

 one or two exceptions, entirely devoid of allu- 

 sions to American apparatus and machinery. 



Taken as a whole, however, the volume is a 

 creditable piece of work, for the task of con- 

 densing 30 much in so small a space is, to say 

 the least, herculean. W. H. F. 



GENERAL. 



The Teachers' Professional Library, edited by 

 Professor Nicholas Murray Butler, of Columbia 

 University, is announced. by The Macmillan Co. 

 The books already published ou ' The Develop- 

 ment of the Child,' by Dr. Nathan Oppenheim ; 

 ' The Study of Children and their School Train- 

 ing,' by Dr. Francis Walker, and a ' Handbook 

 of Nature Study,' by O. Lange, are included in 

 the series and the following are announced for 

 early publication : 



'The Practical Lessons of History,' by William T. 

 Harris, LL.D., U. S. Commissioner of Education. 



' Social Phases of Education in the Home and in 

 the School,' by Samuel T. Dutton, Superintendent of 

 Schools, Brookline, Mass. 



'Educational Aims and Educational Values,' by 

 Dr. Paul H. Hanus, Harvard University. 



' The Hygiene of the School and of Instruction, ' 

 by Edward R, Shaw, Ph.D., New York University. 



'Method in Education,' by Walter L. Hervey, 

 Ph.D., Department of Education, New York City. 



'The Study and Teaching of History,' by Miss 

 Lucy M. Salmon, Vassar College. 



' The Study and Teaching of Geography, ' by Dr. 

 Jacques W. Eedway, of New Y'ork. 



'The Study and Teaching of English,' by Peroival 

 Chubb, of the Ethical Culture Schools, New York. 



'The Study and Teaching of Mathematics,' by 



