502 



STATE BOARD OF AGRICULTURE. 



2. CONSIDIOKATION OF TIIK SOI KCIOS OF lOKKOU. 



SOURCIO OF CURRENT. 



All (hose who lia\c had any expt'iiciuc with (lie usual method of de- 

 termining' the conductance of electrolytes will agree that of all the parts 

 of the apparatus the induction coil gives the most trouble. It is continu- 

 ally getting out of adjustment. Somelimes this lia]ii)ens while a measure- 

 ment is being made. Ferhaps one of the larger more expensive coils is 

 less apt to get out of order. These, however, are not as efficient as the 

 small cheap ones because in the latter the current that passes at each 

 pulse is small, and consequently, error from ]»olarization is negligible. 

 Again, in the small cheaj) induction coils (he vibration of the "hammer" 

 is rapid and the tone, therefore, is high-pitched and more readily audible 

 in the telephone. A tone similar to (he hum of a gnat is the most desir- 

 able. 



There is a more serious trouble in the use of the induction coil than 

 that mentioned above and for this reason it should be abandoned. The 



Fig. 3. 

 Curve from au oscillogi'ain of an induction coil current. After E. W. Wasliburn. From 

 page 10, catalogue 48, 1915, Leeds & Northrup Cu. 



K 



k 



KSKK 



Fig. 4. 

 Curve from an oscillogram of an induction coil current when operating well. After E. W. 

 Wasliburn. From page 10, catalog 48, 1915, Leeds & Nortbrup Co. 



