June i, 191 i] 



NATURE 



469 



exert forces on electric charges in their neighbourhood 

 vastly greater than those exerted by molecules. 



We may compare the forces exerted by a neutral atom 

 on the 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 rearrange 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 freedom, though not so great as in a metal, the attrac- 

 tion, though still appreciable, is very much less than it 

 was with the metal. A very simple experiment will illus- 

 trate this point. I have on this cardboard disc, 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, however, I take the magnets off their 

 pivots, so that they are no longer free to turn, the magnet 

 exerts very little attraction upon them. 



Fig. 6. 



A view of chemical combination which I gave some 

 time ago in T/ie 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 produce 

 the difference between the behaviour of atoms and mole- 

 cules. 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 con- 

 figuration 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 cor- 

 puscles 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 constitution 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 

 W more stable form. We may roughly picture to ourselves 

 the atom with one extra corpuscle as consisting of a 

 number of fixed corpuscles plus one which is free to move 

 about ; the freedom of this corpuscle would enable the 

 electricity in the atom to move about, and would endow 

 the atom with the property of attracting any electrical 

 charges which might be near it. If there were two cor- 



NO. 2170, VOL. 86] 



puscles in the atom more than the number required for 

 the most stable form, we can picture the atom as having 

 two corpuscles free and the rest fixed. Similarly, if we 

 had more than two extra corpuscles. Thus we may regard 

 the atom as possessing o, i, 2, 3 corpuscles which are 

 able to move about with more or less facility, and the 

 free corpuscles will give to the atom the power of exerting 

 attractions on electrical charges to an extent which depends 

 on both the number of corpuscles and the freedom with 

 which they can move about. On the theory to which I 

 have alluded, the number of these " free " corpuscles 

 determines the valency of the atom. 



Now let us suppose that two such atoms come into such 

 close connection that the corpuscles in the one exert con- 

 siderable forces on those in the other. The system con- 

 sisting of the two atoms will rearrange itself so as to get 

 into a more stable form, if necessary, corpuscles passing 

 from one atom to the other to enable it to do so. The 

 greater stability, however, implies a loss of mobility ; the 

 free corpuscles have become parts of a more stable system, 

 and have therefore lost to a greater or less extent their 

 mobility. But with the mobility of the corpuscles goes 

 their power of exerting forces on electrical charges, and 

 thus the combination of the atoms diminishes to a great 

 extent the attractions they exert outside them. Speaking 

 generally, we may say that on this view the combination 

 of atoms to form molecules, either of compounds or 

 elements, fixes corpuscles which were previously mobile 

 and converts the atoms from conductors of electricity into 

 insulators with a small specific induction capacity. 



Fig. 7. 



I have brought these illustrations before you with the 

 object of showing that we have now methods which are 

 capable of dealing with much smaller quantities of matter 

 than the methods now used by chemists, methods which 

 are capable of detecting transient phases in the processes 

 of chemical combination, and I am hopeful rnay be of 

 service in throwing light on one of the most interesting 

 and mysterious problems in either physics or chemistry — 

 the nature of chemical combination. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 

 Edinburgh. — Mr. A. D. Darbishire has been appointed 

 to the newly instituted lectureship in genetics, and will 

 deliver a course of six lectures on heredity during the 

 summer session, the course to be free to all matriculated 

 students. Dr. W. G. Smith has been reappointed Combe 

 lecturer in psychology. The executive committee of the 

 Chiene portrait fund has resolved to hand to the University 

 the balance of the fund (a sum of from 310/. to 320^.) for 

 the foundation of a bronze medal, to be called the " Chiene 

 medal in surgery." 



M. TissoT, an assistant in the Paris Museum of Natural 

 History, has been appointed professor of physiology in the 

 museum. 



Dr. D. Fraser Harris, lecturer on physiology in the 

 University of Birmingham, has been appointed the 

 Thompson lecturer in natural science for 1911-12 at the 

 United Free Church College, Aberdeen. 



Sir J. Cameron Lamb, C.B., C.M.G., has been appointed 

 to represent the Royal Society of Arts at the forthcoming 



