THE MEASUREMENT OF CURRENT 07 



and the reading of the ammeter gives the strength of the stray 

 current. This method of measuring the current requires that 

 the observer remain continuously at his station. It is frequently 

 desirable to obtain records extending over a considerable time, 

 in which case the resistance of a section of pipe may be determined 

 as nbove and a registering millivoltmeter used. 



References 



1. "The Work of Lord Kelvin in Telegraphy and Navigation," J. A. 

 EWING, Journal Institution of Electrical Engineers, vol. 44, 1910, p. 538. 



2. "On the Magnetic Shielding. Effects of Tri-lamellar Spherical and Cylin- 

 drical Shells," A. P. WILLS, Physical Review, vol. 9, 1899, p. 193. "On 

 Magnetic Shielding," A. P. WILLS, Physical Review, vol. 24, 1907, p. 243. 



3. "On the Production, Properties and Some Suggested Uses of the Finest 

 Threads," C. VERNON BOYS, Phil. Mag., vol. 23, 1887, p. 489. "On the Elas- 

 tic Constants of Quartz Threads," RICHARD THRELFALL, Phil. Mag., vol. 

 30, 1890, p. 99. "The Attachment of Quartz Fibers," C. VERNON BOYS, 

 Phil. Mag., vol. 37, 1894, p. 463. "Quartz Fibers," C. VERNON BOYS, The 

 Electrician, vol. 38, 1896-97, p. 205. 



4. "Galvanometers," W.E. AYRTON,T. MATHER, and W. E. SUMPNER, Phil. 

 Mag., vol.30, 1890, p. 58; Phil. Mag., vol. 46, 1898, p. 359. " Instruments and 

 Methods of Radiometry,"W. W. COBLENTZ, Bulletin, Bureau of Standards,vol. 

 4, 1907, p. 424. "The Construction of a Sensitive Galvanometer for Spectro- 

 Bolometric Purposes," C. G. ABBOT, The Astrophysical Journal, vol. 18, 

 July, 1903, p. 1. See also Annals of the Astrophysical Observatory of the 

 Smithsonian Institution, vol. 1, 1900, p. 244, section on Galvanometers. 



5. "A Convenient Form of Galvanometer with Magnetic Shielding," 

 E. F. NICHOLS and S. R. WILLIAMS, Physical Review, vol. 27, 1908, p. 250. 



6. " Galvanometre Absolument Astatique et a Grande Sensibilite"," M. A. 

 BROCA, Journal de Physique, vol. 6, 3rd series, 1897, p. 67. 



7. "Some Properties of the Moving-coil Galvanometer," WALTER P. 

 WHITE, Physical Review, vol. 22, 1906, p. 371. "Everyday Problems of the 

 Moving-coil Galvanometer," WALTER P. WHITE, Physical Review, vol. 23, 

 1906, p. 382. "Sensitive Moving-coil Galvanometers," WALTER P. WHITE, 

 Physical Review, vol. 19, 1904, p. 304. "Das Drehspuelengalvanometer nach 

 Deprez-d'Arsonval im aperiodischen Grenzfall," W. JAEGER, Zeit. fur 

 Instrumentenkunde, vol. 23, 1903, p. 261. Die Empfindlichkeit des Dreh- 

 spuelengalvanometers im aperiodischen Grenzfall," W. JAEGER, Zeit. fur 

 Instrumentenkunde, vol. 23, 1903, p. 353. "General Design of Critically 

 Damped Galvanometers," FRANK WENNER. Bureau of Standards Scien- 

 tific Paper No. 273. 



8. "On the Use of Chilled Cast Iron for Permanent Magnets," A. CAMP- 

 BELL, Phil. Mag., vol. 12, 1906, p. 468. "On theTemperature Coefficient of 

 Magnets Made of Chilled Cast Iron," B. O. PEIRCE, Proc. American Academy 

 of Arts and Sciences, vol. 38, 1902-03, p. 551. 



7 



