818 



SCIENCE. 



[N. S. Vol. XV. No. 386. 



engineering. But college laboratories in this 

 country are not well supplied with, funds and 

 they cannot afford (nor do they need) the 

 elaborate ultimate standards for the recovery 

 of the several electrical units which are here 

 adverted to as desirable or even essential por- 

 tions of a laboratory equipment. Neither do 

 our manufacturers usually find it warrantable 

 to carry their measurements to the refinement 

 that this chapter implies is essential to reason- 

 able laboratory practice. Such refinement is 

 necessary and warrantable in only a few stan- 

 dardizing laboratories, or the laboratories 

 maintained by the equally few manufacturers 

 of fine electrical measuring instruments; and 

 we therefore believe that the book in its present 

 form is seriously misleading to students unless 

 accompanied by extended oral explanatory 

 lectures. 



The second chapter of the book partakes of 

 the character of the first. It contains much of 

 interesting and valuable suggestion to the 

 laboratory administrator and laboratory 

 teacher, but little which commends it for use 

 as a text-book with the average undergraduate 

 laboratory classes. Neither can a large pro- 

 portion of the methods, discussed in this chap- 

 ter, serve a useful purpose in the daily work 

 of a manufacturer's laboratory, unless he is a 

 manufacturer of standard electrical measuring 

 instruments. 



The third and fourth chapters, which treat 

 of the measurement of electrical currents and 

 pressures, make closer contact with daily work 

 in the electrical laboratory, whether it be of 

 the college or the manufacturer. But even 

 here are to be found various recommendations 

 which are of doubtful value in commercial 

 testing. For instance, the author, in harmony 

 with methods of testing used by him some 

 years ago, recommends the adoption of a small 

 synchronous motor as a means for driving a 

 contact maker when it is desired to delineate 

 the current or pressure curves of an alternat- 

 ing current circuit. The author fails, however, 

 to caution the reader that inevitable error is 

 introduced into the forms of the delineated 

 curves by the 'hunting' of the synchronous 

 motor, unless the curves of motor counter- 

 pressure and impressed pressure (line pres- 



sure) are nearly alike, or the motor construc- 

 tion contains special expedients to prevent 

 appreciable hunting. 



The author wisely gives much attention to 

 the potentiometer as an instrument to be used 

 for' setting the pressure when calibrating 

 voltmeters and for general use as an accurate, 

 convenient and reasonably rapid device for 

 measurement of electrical pressure. He 

 curiously fails to note the universal sluggish- 

 ness of hot wire voltmeters and amperemeters 

 which often causes their readings to be mis- 

 leading when the quantity under measurement 

 is Bubject to fluctuations— as, for instance, the 

 current feeding a constant pressure arc lamp. 

 The author wholly omits from consideration 

 the ordinary two-coil frequency indicator for 

 alternating current circuits. While this in- 

 strument does not read in absolute values, it 

 is admirable as an indicator of the constancy 

 with which frequency is maintained during a 

 series of tests, and is far more useful in the 

 average laboratory than either of the 'fre- 

 quency tellers ' described in the text. 



The final chapter of the book, chapter 5, on 

 the measurement of electrical power, is par- 

 ticularly disappointing. It fails to throw any 

 light upon the diflicult problem of measuring 

 the power absorbed, in an alternating current 

 circuit, by devices of low power-factor. The 

 only expedient proposed by the author is one of 

 little utility, if not of impracticability, under 

 ordinary conditions. It also fails to deal ade- 

 quately with power measurements, in alter- 

 nating current circuits, when the currents and 

 pressures are great. Wattmeters and their 

 use are dealt with and described, but the 

 admirable portable wattmeters made in this 

 country by the Weston, General Electric and 

 Whitney companies are not described or re- 

 ferred to. This indeed is characteristic of the 

 book, and such excellent secondary standards 

 as the so-called 'laboratory standard' ampere- 

 meters and voltmeters of the Weston Company 

 are given no attention. A noteworthy feature 

 of the book, but one of doubtful merit, is the 

 enthusiastic recommendation of instruments 

 using mirror and scale. This recommendation 

 extends to electrostatic voltmeters. 



It may seem ungracious to farther criticize 



