Observations at the Poles of the Electric Arc. 



963 



with different sizes of hole and current afford additional 

 support for this view. 



Readings were obtained for holes 



Curves III. 



ISO 



- 











IkO 



• 





* X 







V>a 







* 







no 













tio 













'Ts&ssu^t, 















loo 















S>0 







• 







T° 







a 



__ 





to 





& 









•So 



• Pi 



NOBS-. JRe.SiSVJFVt. AHD f\RC t-*£MC'fH . 







kO 





c 



ft.5Se.ot! - • Q cr-i ' x> i <f,r; - 









1 



iOLL _ - • 15 o-j- 







AO 





* 



s Oj.RRej*f or 15 t«ps 







2.0 









- ioq 







10 

 





A 



- 1-o - 







10 %0 ->a US SO Go "jo SO qc 10-Q ll-O 12-0 

 U'&Wc-tM Of AfK ».h t^ris. 



up to 5 mm. in diameter, and it was found that the pressure 

 decreased as the hole was made larger. Now there are 

 three possible causes for this effect, namely : — 



(1) If the pressure is set up by evolved gas, its effect will 

 be reduced by the reduction in constriction. 



(2) If (he pressure reaches a maximum at the centre of 

 the incandescent patch and falls off towards its circum- 

 ference, the average pressure over a large hole will be less 

 than over a small one when properly centred. 



(3) If the origin of the pressure lies in a layer quite close 

 to the electrode, as the pressure-arc length curves suggest. 



