438 THE WORLD MACHINE 



charged particles so small as to be repelled by the negatively 

 charged earth with greater force than the pull of gravitation. 

 Arrhenius computes that a particle one-seventh a micron in 

 diameter, possessing a unit charge, might be driven off and out 

 of the earth's atmosphere by this means. 



A seventh of a micron is about the size of the smallest 

 bacterium known. We have life particles, therefore, of the 

 requisite minuteness. But how could they acquire an electrical 

 " charge " ? Arrhenius answers : from the sun. The particles 

 shot off from candescent bodies bear always a negative electrical 

 charge. The sun, we know, is raining these cathode particles or 

 corpuscles into space in every direction. The earth is rushing 

 through a continuous if imperceptible hail of them. It is the 

 beating in and union of these solar corpuscles with the particles 

 of air in the upper strata of the atmosphere which probably 

 explains the appearance of the polar light. 



These corpuscles could just as well unite with a germ or a 

 spore as with a particle of water or of air. They are of ultra- 

 atomic mass. They would add practically nothing, therefore, 

 to the weight of the germ or spore, while they would impart to 

 the latter their electrical charges. In the outermost strata of 

 the atmosphere the free-path motion of the air molecules may 

 be rods or even miles wide ; the germs would encounter no 

 retaining force to hold them in leash ; they would go travelling 

 out into the void, where they would come under the impulsion 

 of the pressure of light. Arrhenius' calculates that a germ of 

 this size would be driven at a speed sufficient to carry it to the 

 nearest of the fixed stars in three thousand years. 



We may conceive of yet another rate of transport than that 

 suggested by Arrhenius. We have seen that space is swarming 

 with meteorites ; the spores might readily be caught up in a 

 meteoritic stream and be carried onward to far realms of stars. 

 The germs might easily become embedded in the growing bodies 

 of the meteors, and thus they might penetrate the atmosphere 

 of another planet with the latter. We should have then a 

 realisation of precisely the conditions imagined by Kelvin and 

 von Helmholtz. 



It might readily be objected that no germ or spore is known 

 capable of retaining its vital energies for so long a period. But 

 a germ or spore in its travels would be subjected to the tempera- 

 ture of space, and this we estimate at but a few degrees above 



