318 WALL STREET AND THE WILDS 



the insulation might conceal, if not repaired be- 

 fore another layer went on, would spell ruin to 

 the coil. It was my method of testing for these 

 breaks which provided perennial excitement in 

 the shop. I interposed a small battery in the 

 primary coil and attached a coarse file to one of 

 the poles. Then when I drew the wire of the 

 other pole lengthwise of that file I caused a 

 rapid making and breaking of the circuit. The 

 average boy of the present day would smile at 

 the thought of getting a shock through a pri- 

 mary coil of two hundred feet of big wire at- 

 tached to a small battery, but that same boy 

 would shake his sophisticated head if you sug- 

 gested his touching the tiny wires of the second- 

 ary coil, even though he knew no battery was in 

 the circuit. 



When I had wound the first layer I attached 

 the terminals of the coil to pieces of metal which 

 I asked the workman nearest me to hold. As 

 I drew the wire across the file I asked if he felt 

 anything and he remarked that he did. As an- 

 other layer was wound I tried him again until 



