Lubrication of Resistance-Box Plugs. 213 



from the results obtained another final mean value was 

 calculated. 



Thirdly, the oil was entirely removed, the plugs lubricated 

 with medicinal paraffin oil, and a further series of observations 

 proceeded with. For a fourth series the lubricant was "pure " 

 vaseline. 



Finally, the plugs, their seats and the ebonite top of 

 the resistance-box were, with the aid of purified benzene, 

 thoroughly freed from the lubricant, and a last series of 

 determinations of the total plug-resistance carried out. The 

 results of the several groups of measurements are set forth in 

 Table A in the order in which they were obtained. 



Table A. 



Expf 



1 



3 ........ 



4 



5 



6 



7 ........ 



8 



9 



10 



Means 



Max. value. 

 Min. „ 

 Variation = 



Box No. I. Fitted with 9 plugs. 



Resistance. 



Plugs in batli 



of Geryk 



pump^oil. 



(1) 

 •00170 

 144 

 116 

 127 

 131 

 131 

 131 

 153 

 122 

 122 



•00135 

 •00170 

 •00116 



±•00027 

 ±20 per cent. 



Plugs smeared 

 with Greryk 

 pump oil. 



(2) 

 •00112 

 137 

 137 

 095 

 117 

 112 



•00118 

 •00137 

 •00095 



± -00022 

 ±186 per cent. 



Plugs 

 smeared with 

 medicinal 

 in oil. 



(3) 

 •00094 

 122 

 131 

 127 

 142 

 130 



•00124 

 •00142 

 ■00094 

 •00024 



Plugs 



smeared with 



vaseline. 



(4) 

 •00109 

 124 

 109 

 129 

 109 

 116 

 124 

 110 

 124 

 109 



•00116 



•00129 



•00109 



+ -00010 



±19-3 per cent. ±8-6 percent. 



Plugs 

 unlubricated. 



(5) 

 •00101 c 

 123 

 188 

 176 

 194 

 124 

 127 

 177 

 166 

 113 



00119 

 •00194 

 •00023 



±•00086 

 ±722 per cent. 



Experiments were also tried with the plugs in a bath of 

 medicinal paraffin ; but as the results were practically 

 identical with those given in the above series (3), it is not 

 necessary to tabulate them here. 



The data contained in Table A show that in every instance 

 a distinct advantage is gained by lubricating the plugs. For 

 two series, (1) and (3), the mean resistance of the oiled 

 plugs is greater than the normal value (series (5)). In 



