THE BALLISTIC GALVANOMETER 127 



That is, the deflection is proportional to the change in the flux 

 threading the exploring coil. In the actual instrument the scale 

 is calibrated experimentally. The advantages of the flux meter 

 over the ballistic galvanometer are portability, ease of reading, 

 and independence of the time required for the flux changes and of 

 the manner in which they take place. It is therefore a con- 

 venient workshop instrument. As ordinarily constructed, its 

 accuracy is inferior to that of the ballistic galvanometer. 7 



References 



1. "On Precision Measurements with the Moving Coil Ballistic Galva- 

 nometer," ANTHONY ZELENY, Physical Review, vol. 23, 1906, p. 399. 



2. "The Damped Ballistic Galvanometer," O. M. STEWART, Physical 

 Review, vol. 16, 1903, p. 158. 



3. "The Theory of Ballistic Galvanometers of Long Period," B. OSGOOD 

 PEIRCE. Proc. American Academy of Arts and Sciences, vol. 44, 1909, p. 283. 



4. "The Ballistic Use of a Moving Coil Galvanometer in Measuring 

 Discharges Obeying the Exponential Decay Law," A. G. WORTHING, Physical 

 Review, vol. 6, 1915, p. 165. 



5. "The Effect of the Time of Passage of a Quantity of Electricity on 

 the Throw of a Ballistic Galvanometer," F. WENNER, Physical Review, 

 vol. 25, 1907, p. 139. 



6. "An Electric Quantometer," R. BEATTIE, The Electrician, vol. 50, 

 1903, p. 383. "Fluxmetre," M. E. GRASSOT, Journal de Physique, 4th 

 series, vol. 3, 1904, p. 696. 



7. "On the Determination of the Magnetic Behaviour of the Finely 

 Divided Core of an Electromagnet while a Steady Current is being Estab- 

 lished in the Exciting Circuit," B. OSGOOD PEIRCE, Proc. American Academy 

 of Arts and Sciences, vol. 43, 1907, p. 99. 



