1911] on a New Method of ChemicaJ Analysis. 147 



corpuscles with those exerted by an unelectrified piece of metal on a 

 charged body in its neighbourhood. In consequence of electrostatic 

 induction, the charge and the metal will attract each other. This 

 attraction is dependent on the electricity in the metal being able to 

 move under the electric forces exerted by the charge, and to re- 

 arrange itself in such a way that if the charge is positive, the 

 negative electricity in the metal moves to the part of the metal 

 nearest to the charge, while the positive electricity moves to the part 

 remote from the charge. The force between the metal and the 

 charge depends on the freedom of the electricity to move about in 

 the metal under the action of the electric field. If the metal is 

 replaced by a substance of high specific inductive capacity, like 

 sulphur, in which the electricity has an appreciable amount of free- 

 dom, though not so great as in a metal, the attraction, though still 

 appreciable, is very much less than it was with the metal. A very 

 simple experiment will illustrate this point. I have on this card- 

 board disk, which is suspended from a long string, a number of 

 magnets, such as are used for compasses ; if I mount the magnets on 

 pivots, so that they are free to turn round, the system of magnets is 

 strongly attracted when another magnet is brought near it ; if, how- 

 ever, I take the magnets off their pivots so that they are no longer 

 free to turn, the magnet exerts very little attraction upon them. 



A view of chemical combination which I gave some time ago in 

 the ' Philosophical Magazine,' and also in my Corpuscular Theory of 

 Matter, suggests that there is a very close analogy between the causes 

 at work in the experiment we have just made and those which pro- 

 duce the difference between the behaviour of atoms and molecules. 

 On that theory the atom was supposed to consist of a large number 

 of corpuscles arranged inside a sphere of positive electricity ; the 

 corpuscles arranging themselves so as to be in equilibrium under 

 their mutual repulsion and the attraction of the positive electricity. 

 The configuration depends on the number of corpuscles, and the 

 stiffness and stability of the system also change as the number changes. 

 For some particular numbers of corpuscles the system is very rigid, 

 and any movement of the corpuscles would be strongly resisted ; 

 since the movement of electricity inside the atom is brought about 

 by the movement of the corpuscles, the electricity could only 

 move with great difficulty inside these atoms, and they would 

 therefore not be able to exert more than feeble forces on electrical 

 charges outside the atom : they would therefore not enter readily 

 into combination with other atoms. We may ascribe such a constitu- 

 tion as this to the atoms of the inert gases, helium, argon, and neon. 

 A system with one, two, or three more corpuscles than the system 

 we have just described would not be nearly so stable, and there 

 would be a tendency to discard the extra corpuscles from the atom 

 so that it might return to the more stable form. We may roughly 

 picture to ourselves the atom with one extra corpuscle as consisting 



L 2 



