Decembee 25, 1914] 



SCIENCE 



937 



Institute, BeKast. Longmans, Green & Co. 



Pp. 344. 201 illustrations. $2.25 net. 



It is seldom that a reviewer has the privilege 

 of examining a book which so well accomplishes 

 its purposes as does this elementary text on 

 radio telegraphy. The author states in the 

 preface that his book is designed to fill the 

 needs of those students who, with practically 

 no previous knowledge of electric circuits, de- 

 sire to become acquainted with the simple 

 theory of wireless telegraphy and with the 

 various pieces of apparatus at present used in 

 radio work. There is surely no text on the 

 market to-day which fiUs the needs of such 

 students as well as does Professor Stanley's 

 book. 



The subject-matter is all useful, live mate- 

 rial and is strictly up to date. The historical 

 development of the subject is given only suffi- 

 cient space to make the student realize the se- 

 quence in which the different pieces of appa- 

 ratus and circuits appeared in the art. Many 

 texts devote a deal of space to detailed de- 

 scriptions of the early experiments, but this 

 text is fortunately entirely free from such 

 irrelevant material. 



The first five chapters deal with general con- 

 cepts of magnetism and electricity and intro- 

 duce the reader to the modem idea of the elec- 

 tric current being motion of electrons. Next 

 follows a chapter on measurements and cal- 

 culations of series and parallel circuits, volt- 

 age, current, power, etc. The material of this 

 chapter is well illustrated by problems worked 

 out in the text. Three chapters are devoted 

 to inductance, capacity and oscillatory dis- 

 charges, with methods of producing them. 



Chapter X., on " How Ether Waves are 

 Propagated and Received," deals with a very 

 difficult subject but the author has treated it 

 exceptionally well, bringing into his discus- 

 sion, day and night effects, effect of water and 

 dry land, etc., and illustrating his explanations 

 by experimental data. 



There are six chapters devoted to the vari- 

 ous circuits and pieces of apparatus used in 

 sending and receiving stations where the so- 

 called " damped wave system " or spark system 

 is used and one chapter on the generating and 



receiving apparatus used in systems using 

 continuous waves. A short discussion on mis- 

 cellaneous apparatus, such as direction finders, 

 amplifiers, galvanometers, hot-wire meters, 

 etc., is followed by the last chapter of the book 

 in which various measurements of radio cir- 

 cuits and apparatus are described. 



Four short appendices are devoted to the 

 standard code, call letters of British stations, 

 extracts from international radio regulations 

 and the system of time signals and weather 

 reports sent out from Eiffel Tower. Questions 

 added at the end of each chapter increase the 

 value of the book as a text. 



The paper on which the book is printed is 

 not suitable for fine half tones and these are 

 rather disappointing, but to offset this defect 

 the diagrams of circuits and connections are 

 exceptionally well executed. They show 

 thought and skill on the part of the one who 

 designed them. There are minor errors, such 

 as appear in Pigs. 38, 43 and 45, but for a 

 first edition the number of errors is very small. 

 The author and publishers deserve much praise 

 from those interested in radio work for putting 

 out this commendable text. 



J. H. M. 



BOTANICAL NOTES 



SOME CORRECTIONS EST REGAED TO TROPICAL LEAVES 



Dr. Shreve's paper on " The Direct Effects 

 of Eainfall on Hygrophilous Vegetation"^ 

 will serve as a corrective for some " casual ob- 

 servation and vivid imagination " in regard to 

 certain adaptational features, in tropical vege- 

 tation, especially those pertaining to leaf 

 shapes and structures. His studies were made 

 in the Jamaican forests where the rainfall 

 ranges from 266.Y cm. (100 inches) to 426.7 

 cm. (170 inches), insuring, with the aid of a 

 generally prevalent fog blanket, an almost 

 continual wetness of the foliage. In these 

 conditions it has generally been assumed that 

 the leaves should have dripping points, velvet 

 surfaces, epiphyllse and hydathodes. And yet 

 Dr. Shreve found " a very weak representa- 

 tion of such features as the hydathode, the 



1 Journal of Ecology, June, 1914. 



