1-48 A Neiv Method of Chemical Analysis. [April 7, 



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 corpuscles in the atom more than the number required for 

 the most stable form, we can picture the atom as having two cor- 

 puscles free and the rest fixed. Similarly, if we had more than two 

 extra corpuscles. Thus we may regard the atom as possessing 0, 1, 

 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 

 connexion that the corpuscles in the one exert considerable forces 

 on those in the other. The system consisting 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 there- 

 fore lost to a greater or less extent their mobility. But with the 

 mobility of the corpuscles goes their power of exerting forces on elec- 

 trical 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 conduc- 

 tors of electricity into insulators with a small specific induction 

 capacity. 



I have brought these illustrations before you with the object of 

 showing that Ave 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 which I am hopeful may 

 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. 



[J. J. T.] 



