24 TWO NEW WORLDS 



and that our imagination recoils helplessly from any 

 attempt to picture an electron as it really is. That 

 this attitude is quite mistaken I hope to show in 

 what follows. 



2. We have found that the electric forces " make 

 the world go round " in the infra-world. But before 

 we can prove the complete analogy between an atom 

 with its electrons and our solar system, several 

 objections remain to be dealt with. These are 



(1) An electron, having such a prodigious charge 

 in comparison with its mass and size, could not be 

 held together by any known force. 



(2) If there are several electrons revolving about 

 an atom, they would seriously perturb each other by 

 their mutual repulsions. 



As regards the h'rst objection, it is best answered 

 by a comparison with the earth. Who would 

 suspect that the earth is negatively charged to a 

 potential of a billion volts ? Yet so it is, as can be 

 easily proved from the data of atmospheric elec- 

 tricity. The earth's charge is certainly not less than 

 10 18 electrostatic units. It surface density of elec- 

 trification is just about one electrostatic unit per 

 square centimetre, meaning that 2930 million free 

 electrons are distributed over every square centi- 

 metre of its surface. And yet we find no electric 

 phenomena in ordinary objects around us. The 

 charges are there all the same. But they pass into 

 the atmosphere and back into the earth, and all we 



