336 



KENNELLY-NABESHIMA— ESTABLISHING A 



or 46.3 microseconds, so that, theoretically, i degree of arc in the 

 setting of the pointer P corresponds approximately to 2 micro- 

 seconds of time. 



Technique of Making Records. — The electrical connections of 

 the switch mechanism are indicated in outline by Fig. 6. The 

 alternating-current generator G, is supposed to be in regular opera- 

 tion at the correct frequency. The above mentioned synchronous 

 motor, shown in plan view in Fig. 7, is then started, and synchron- 



FiG. 7. Plan View of Synchronous Motor and Circuit-closing Switch. 



ized with the generator. The arc lamp for the oscillograph vibra- 

 tors is then lit. The brushes B^B^, Fig. 4, are next set in the correct 

 position to close the generator on the artificial line at an instant of 

 zero e.m.f. This adjustment is made by trial, substituting a simple 

 non-inductive resistance for the artificial line, and closing the gen- 

 erator through the brushes, and an oscillograph, so as to observe on 

 the translucent screen whether the beam of light starts into vibra- 

 tion without a splash. The setting of the brushes to effect this 

 result can usually be adjusted, with ordinary optical conditions, 

 within one electrical degree, or 46 microseconds for a 60.— ' gen- 

 erator. The artificial line is then reconnected to the apparatus, all 

 ready for the photographic record. A starting lever is moved by 

 hand, and this causes automatic switch S-^ to be closed, ahead of the 

 rotary switch D. The brushes B-^Bo then close the circuit finally, 



