282 THE ORIGIN OF LIFE 



charge, act as highly electrified particles. The 

 corpuscles or electrons will be attracted towards 

 them and towards the walls of the tube with great 

 acceleration and attain great velocity if the free- 

 path be suflS.ciently long ; the free-path affects 

 the nature of the collisions, if the approach with 

 the molecules be sufficiently near, and then produces 

 light. Those luminous molecules should be very 

 large aggregates like clouds which are produced 

 by ultra-violet light. 



The phenomenon of the spontaneous discharge in 

 high vacua illustrates this fact ; for if the ionisa- 

 tion is first produced, phosphorescence is manifested 

 when the free path reaches a certain amount. Thus 

 when a discharge is sent through oxygen at pressures 

 of about 2 or 3 cm., and this pressure is reduced, 

 no effect is observed until the pressure is below 

 0"7 mm. The spectrum of this glow, observed by 

 Schuster, which is the same as that of the negative 

 glow in oxygen at the boundary of the dark 

 space and beyond it, results doubtless from the 

 collisions of the corpuscles with the molecules 

 of the gas in moving through the dark space 

 when the former have acquired a sufficient 

 velocity under the electromotive force. The 

 gas then begins to phosphoresce. There does not 

 seem to be any reason to suppose that the 

 diminution of pressure gives rise to any change in 

 the gas, other than that of increasing the free-path 

 of the molecules ; unless an electric discharge is sent 

 through it, so that when the free-path is of suffi- 



