M'Clelland and Powkr — Electrification by Friction. 47 



against the metal was in these experiments usually linen, but silk was some- 

 times used. 



There is thus a marked difference in the form of the curves showing the 

 variation of the rate of production of electrification with amount of moisture 



F I G. 3. 



lron(+) on Linen 



Humidity=l-e 



where 4- = IOOO(approx) 



present according as the metal surface is charging positively or negatively. 

 There is one factor which we must remember in considering these curves,[and 

 which explains some of their features, but is not sufficient to account forjthe 



/oo 





FIG 



4. 



Nicke 



(-) or 



Ljnen. 



Humid 



ty= 1 



vt 



-e N 



where -£■ = 



848 



Time of F/ow of Air in mins 



20 



SO 



50 



60 



SO 100 



difference between the two types. As the amount of moisture increases, the 

 conductivity of the silk or linen also increases. The initial small rate - I 



R.I. A. PROC, VOL. XXXIV, SECT. A. [8] 



