of view of the Kinetic Theory of Matter. 25 



( P, = P u 2 + p£_ + puv +pjr] + pnw + piC 



1- < P y = pVU + p£-q + pV*+prf + pVW + p£ > y] 

 ( P z == pwu + p££ + piov + prj£ + put* + pC 



Where — above quantities signifies mean values. If we con- 

 sider the gaseous medium to move parallel to the axis of X, 

 then v = w = 0, and the above equations for pressure take the 

 simplified form : 



2 - i P y = piy +py 2 +p£y 



(p a = piz+ptf+pc 



If p%r), pty, etc., be small in comparison with p%% etc., and we 

 put 



Sp = pF + prf + pC, equation 2 becomes, 



3 - \P„ = P t =p 



This last equation plainly shows that when gaseous matter 

 moves in a stream in any definite direction, say that of X, the 

 pressure of the gas in that direction is increased by an amount 

 proportional to the square of the velocity of translation. 



§ 4. If, in electrical discharge through a gas, the discharge 

 stream be a stream of gaseous matter, it should be found, ac- 

 cording to the above consideration, that the pressure in the 

 direction of discharge is greater than in either of the directions 

 at right angles, by an amount depending upon the velocity of 

 the discharge stream. 



In order to determine whether or not this inequality of pres- 

 sure actually exists in a gas transmitting electrical discharge, 

 an experimental tube, as described below and illustrated in 

 figs. 1 and 2, was made. 



As shown in fig. 1 (p. 26), the tube is of cylindrical form, about 

 33 cm long, and 3 # 6 cm internal diameter. It is provided with 

 three electrodes, but in the experiments to be described, only 

 the electrodes (a) and (b) are used, (a) is an aluminum electrode 

 of spherical form, 2*8 cm in diameter, having a radius of curva- 

 ture of 2*5 cm . (b) is a plane platinum electrode. (D) is a 

 funnel-shaped glass diaphragm sealed to the walls of the tube 

 around its base and having an opening of about *5 cm at its apex. 

 (R, R) are two similar radiometers, communicating with spaces 

 (A) and (B) of the tube respectively ; the connecting tubes 

 from the radiometers are provided with stopcocks (C, C). One 



