170 Dr. C. Sheard on the Positive 



The coefficient of cos 30 is in like manner 



*£ + £+* U53) 



r 2 T 4a 2 2r v y 



These coefficients are annulled and ap /T is rendered con- 

 stant so far as the second order of r /a inclusive, when we 

 take r 4 , r 5 , &c. equal to zero and 



r 2 /r = r 2 /4a 2 , rjr = -3r 3 /64a 3 . . . (34) 



We may also suppose that ^ = 0. 



The solution of the problem is accordingly that 



r=r A i+ i cos2d -M gcosS0 } ■ • (35) 



gives the figure of equilibrium, provided w be such that 



=£&=!+.§•£ (36) 



The form of a thin ring of equilibrium is thus determined ; 

 but it seems probable that the equilibrium would be unstable 

 for disturbances involving a departure from symmetry round 

 the axis of revolution. 



XXIII. The Positive Ionization from Heated Platinum. 

 By Charles Sheard, Ph.D., Ohio State University *. 



I. Introduction. 



THIS paper will present the results of some investigations 

 made as to the dependence of the positive ionization 

 from heated platinum wires upon (1) temporary heatings of 

 the wire when earthed and at temperatures higher than 

 a chosen lower temperature at which the positive ther- 

 mionic current was subsequently measured ; (2) temporary 

 heatings of the wire under negative potential and at 

 such temperatures as to give small negative currents, the 

 positive emission being investigated at an arbitrary, chosen 

 temperature ; and (3) heating the wire in a Bunsen flame 

 and in carbon dioxide, and also re-washing in nitric acid. 

 Some experiments carried out some time ago with a form of 

 apparatus somewhat different from that used in this work 

 and exhausted to a pressure of about 0*0001 mm., showed 

 that the positive currents at any given temperature could 

 be enhanced, by either heating the wire at a higher tempe- 

 rature, the wire being connected to earth, or by discharging 



* Communicated by the Author. 



