BABBITT. — THE VON WALTENHOFEN PHENOMENON. 237 



paper, and the second layer of the primary, followed in the order given. 

 Care was taken to make the winding as uniform as possible. The data 

 for the toroid are as follows: 



Average diameter of the iron wire of the core 0.0254 cm. 



Number of turns of iron wire in the core 600 



Weight of iron in the core 98.23 gm. 



Area of cross-section of the iron in the core 0.303 sq. cm. 



Average radius of the iron ring 5.6 cm. 



Secondary, 4 coils, No. 26, double silk insulation. 



Coil A 50 turns. 



Coil B 75 turns. 



Coil C 100 turns. 



CoilD 340 turns. 



Primary, 2 layers 



First layer 164 turns 



Second layer 157 turns 



The core II consisted of iron wire not so well annealed as that of I. 

 Insulation was obtained by dipping the wound core into hot paraffine. 

 The primary and secondary were put on with the same precautions as 

 to paper insulation and the uniformity of winding as in the case of 

 toroid I. The data for II are: 



Average diameter of the iron wire of the core 0.0285 cm. 



Number of turns of iron wire in the core 500 



Weight of iron in the ring 88.1 gm. 



Area of cross-section of the iron ring 0.318 sq. cm. 



Average radius of the iron ring 5.55 cm. 



Secondary, 4 coils, No. 26, double silk insulation, 



Coil A 157 turns. 



CoilB 146 turns. 



Coil C 154 turns. 



CoilD .•* . 131 turns. 



Primary, 2 layers. 



First layer 160 turns. 



Second layer 160 turns. 



The core of III ^^ weighing 55 lbs. consisted of wire approximately 

 one third of a millimeter in diameter. Insulation ' of the iron was 

 effected by means of paraffine. The larger wire used for both primary 

 and secondary afforded by its double insulation complete freedom from 

 any appreciable leakage. 



^^ The same core was used by B. 0. Peirce: These Proceedings, 43, 5 

 (1907). 



