July 19, 1917] 



NATURE 



403 



("Electrical Papers," vol. i., p. 42 and p. loi, or 

 Russell, "Alternating: Currents," vol. i., p. 199). 

 The collection of methods of measuring- 

 inductance and capacity given in chaps, iii. and 

 iv. will be found useful. The discussion in chap, 

 vi. of Duddell, Campbell, and Drysdale vibration 

 g-alvanometers is good so far as it goes, but the 

 reader would be grateful for more information. 

 The author seems to have written the book rather 

 hurriedly. The wireless electrician and the 

 physicist, however, will find it useful. 



(3) Prof. Smith's book consists partly of lec- 

 tures and partly of laboratory exercises on electric 

 and magnetic measurements. The arrangement 

 of the subject is good, and the lengthy definitions 

 and explanations of units will be helpful to 

 students. The definitions of self and mutual 

 inductance are very properly given in terms of 

 the linkages of flux and current, but the author 

 has not made it quite clear what a linkage is. 

 In order to explain what is meant by a linkage, 

 it is necessary to show how the linkages of the 

 magnetic flux inside the wire itself with fractional 

 parts of the current can be calculated. As an 

 elementary knowledge of the calculus is pre- 

 supposed, this can easily be done. 



The definitions of electrostatic capacity are not 

 quite happy. No clear distinction is made 

 between the capacity of a conductor and the 

 capacity between two conductors. For example, 

 the author says that a condenser is "a device by 

 means of which the capacity of an isolated con- 

 ductor can be very greatly increased " by the 

 presence near it of another charged conductor. 

 Unless, however, the conductors have equal and 

 opposite charges, the equations given later do 

 not apply. The book is clearly printed and the 

 methods are up to date. 



(4) These leaflets form a laboratory course for 

 boys and apprentices in vocational schools and 

 shop classes. Gaps are left in the printing of the 

 leaflet where the boy has to write down what he 

 has observed, and spaces are provided for a 

 sketch of the apparatus used and for a g:raph of 

 his results. Rough sketches are ^iven in the 

 appendix of the apparatus used, and these will be 

 a great help to beginners. Numerous easy 

 examples are given. The leaflets are excellently 

 adapted for the class of student for whom they 

 have been written. The Brown and Sharp Wire 

 Table and the "circular mil" are much in 

 evidence. The "circular mil " is a quaint unit, 

 being the area of a circle i mil (0001 of an inch) 

 in diameter. \\'e hope that it will soon become 

 obsolete. 



(5) Mr. Chester Dawes is instructor in electri- 

 cal engineering at Harvard University. This 

 "loose-leaf." laboratory manual is intended to be 

 used in conjunction with Timbie's "Electrical 

 Measurements" and Karapetoff's "Elementary 

 Electrical Testing." The leaflets are thoroughly 

 practical, and the arrangement of the experiments 

 Is excellent. After doing-, for instance, the 

 experiment on "conduit-wiring," the student 

 would have acquired excellent ideas about the 

 best methods of installing electric-light wires in 



NO. 2490, VOL. 99] 



conduits. He would also know how to make 

 joints in cables and how to test their insulation 

 resistance. Given an elaborate electrical labora- 

 tory, this manual is admirably adapted to train 

 students to become really useful electricians in the 

 minimum possible time. Some of the questions 

 asked on the leaflets will give them plenty of food 

 for thought. 



(6) This book gives a well-arranged series of 

 experiments suitable for a junior course in an 

 electrical engineering laboratory. They are all 

 thoroughly utilitarian and will be a g-reat help to 

 the student when he goes to an electrical works 

 or a power station. Prof. Maclean asks the 

 student to obtain the "efficiency " of an arc lamp 

 in watts per mean hemispherical candle-power. 

 He very properly puts the word "efficiency" 

 between quotation marks. The efficiency is really 

 the mean hemispherical candle-power per watt, 

 and it is high time that this definition were 

 adopted by engineers. We are doubtful whether 

 the use of Rousseau's diagram to measure the 

 mean hemispherical candle-power of arc lamps is 

 justified, considering how uncertain some of the 

 measurements are owing to the continual fluctua- 

 tion in the intensity and the colour of the light. 

 One of the simpler methods of approximating to 

 the mean hemispherical candle-power would be 

 more suitable. A. Russell. 



OVR BOOKSHELF. 



Lessons in Pharmaceutical Latin and Prescript 

 Hon Writing and Interpretation. By Hugh C. 

 Muldoon. Pp. vii + 173. (New York: John 

 Wiley and Sons, Inc. ; London : Chapman and 

 Hall, Ltd., 1916.) Price 65. net. 

 For the past quarter of a century the Latin used 

 by medical practitioners in writing their prescrip- 

 tions has become more and more simple, and the 

 use of the vernacular has correspondingly 

 increased. Nevertheless, so many prescriptions 

 are still written in that language that the 

 pharmacist must be sufficiently well acquainted 

 with it to interpret them correctly. The author 

 assumes no knowledge of Latin on the part of 

 the student and endeavours to teach him what 

 is essentiar in the limited time at his dis- 

 posal. To accomplish this, much of the con- 

 jugation of the verbs and of the declension of the 

 nouns, and so on, has been omitted, and the 

 student's attention concentrated on those parts 

 which are of constant recurrence. 



The work is divided into twenty-five chapters. 

 From the commencement the exercises are based 

 on such words and expressions as occur in 

 prescriptions, passing from the simplest to the 

 more complex. While it is not, and does not 

 profess to be, a complete Latin grammar of phar- 

 macy, it certainly embodies a rational method of 

 teaching a student the Latin essential to his 

 calling without burdening his memory with a 

 host of conjugations and tenses with which he 

 will never meet. The necessary rules are clearly 

 and concisely stated. Though written for .A^meri- 

 can students, it can equally well be used by British, 

 and undoubtedlv deserves to meet with success. 



