52 3Ir. William CrooJces [Feb. 18, 



matter, rushing suddenly together from every point of space, we thus 

 get Sir William Thomson's incandescent mass which is presently to 

 cool down into a solar system. We cannot tell if electricity existed 

 prior to the origin of the atomic condition of matter, but with the 

 formation of atomic matter the other forms of energy which require 

 matter in order to manifest themselves, begin to act, amongst others 

 that form of energy which has for one of its factors that which we 

 now speak of as atomic weight. 



We have now to seek how protyle was converted not into one only 

 kind of matter but into many. If we recognise that it contained 

 within itself the potentiality of all atomic weights, how did these 

 potentialities become actual ? We may here call to mind the sug- 

 gestion of Dr. E. J. Mills, that our elements are the result of suc- 

 cessive polymerisations during the cooling process. We shall also 

 derive much assistance from a method of illustrating the periodic law 

 proposed by my friend Professor Emerson Keynolds, of the University 

 of Dublin. 



I must call your attention to a diagram (Fig. 5) in which I have 

 slightly modified the original design of Professor Reynolds. I have 

 represented the pendulum swing as gradually declining in amplitude 

 according to a mathematical law. I have further interposed between 

 cerium and lead another half-swing of the pendulum. This renders 

 the oscillations more symmetrical and brings gold, mercury, thallium, 

 lead, and bismuth to the side where they are fully in harmony with 

 members of previous groups. 



The chemical elements are arranged in order, according to their 

 atomic weights, on the centre vertical line which is divided into equal 

 parts. 



Following the curve from hydrogen downwards, we see that the 

 elements forming the eighth group of Mendeleeff's arrangement are 

 situate near three of the ten nodal points. This eighth group is 

 divided into the three triplets — iron, nickel, and cobalt ; rhodium, 

 ruthenium, and palladium ; iridium, osmium, and platinum. 



These bodies are interperiodic because their atomic weights 

 exclude them from the small periods into which the other elements 

 fall, and because their chemical relations with some members of the 

 neighbouring groups show that they are probably interperiodic in the 

 sense of being in transition stages. 



Notice how accurately the series of like bodies fits into this 

 scheme. Beginning at the top, run the eye down analogous positions 

 in each oscillation, taking either the electro-positive or electro-negative 

 swings. (See Table, p. 51.) 



Notice, also, how orderly the metals discovered by spectrum 

 analysis fit in their places — gallium, indium, and thallium ; rubidium 

 and caesium. 



The symmetry of nearly all this series proclaims at once that we 

 are working in the right direction. Much also may be learned from 

 the anomalies here visible. A few bodies, such as didymium, erbium, 



