Argon, and Krypton in the Scheme of Elements. 409 



supposed to follow one another at equal distances along the figure- 

 of-eight spiral, a gap of one division being left at the point of 

 crossing. The vertical height is divided into 240 equal parts on 

 which the atomic weights are plotted, from H = 1 to Ur = 239'59. 

 Each black disc represents an element, and is accurately on a level 

 with its atomic weight on the vertical scale. 



The accompanying figure, photographed from the solid model, 

 illustrates the proposed arrangement. The elements falling one 

 under the other along each of the vertical ordinates, are 



The bracketed spaces between cerium and tantalum are probably 

 occupied by elements of the didymium and erbium groups. Their 

 chemical properties are not known with sufficient accuracy to enable 

 their positions to be well defined. They all give coloured absorption 

 spectra and have atomic weights between these limits. Positions 

 marked by a dash ( ) are waiting for future discoverers to fill up. 



Let me suppose that at the' birth of the elements, as we now know 

 them, the action of the vis generatrix might be diagrammatically 

 represented by a journey to and fro in cycles along a figure-of-eight 



