March, 1918] 



.1 Lecher System — Experimental 



147 



A sample of such curves is shown in Figure 2. For the 

 bridge at 150 the lower of the two curves of Figure 2 was taken, 

 then a bridge curve was taken and the reading of the maximum, 

 viz., 100, was so far above the maximum of Figure 2 (lower 

 curve) viz., 6G, that another spark-gap curve was taken, the 

 upper curve of Figure 2. These two curves illustrate very 

 clearly and forcibly the meaning of oscillator deterioration. 

 Evidently with so narrow a gap, viz., O.OOOK) inch, it is easy for 

 carbon soot from the decomposed oil to bridge, partially or 

 wholly, the gap and thus decrease the intensity materially. 



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Length o^ S/f^^f^-g^f "t 7>t distorts 



Figure 2. 



The matter would be easy to handle if the gap were occasionally 

 wholly bridged in this way, for observations under such con- 

 ditions could easily be detected, and hence eliminated. If, 

 however, in spite of the fact that we used only filtered oil the 

 gap was only partially bridged by the carbon soot there does 

 not appear any easy way to correct for this. When for the 

 sake of inspection the oscillator rods were removed, the ends 

 that constituted the spark-gap would be covered in places with 

 dark spots, due to extremely fine soot being deposited in an 

 extremely thin layer. This matter of oscillator deterioration 

 would not be serious provided one could always employ a 

 check receiver to advantage. This was indeed done in a con- 

 siderable part of the work here reported. But we shall show 

 later on in this paper that the profitable use of a check receiver 

 is very limited. 



