The Groundwork of the Universe, Sec. 43 



element, lithium, shows an analogy with the tenth element, 

 sodium ; whilst the third and eleventh elements, beryllium and 

 magnesium, also show a close resemblance in properties. (The 

 similar elements are indicated by one, two and three asterisks). 

 Thus we can say that every eighth element in the series will have 

 similar chemical properties, and that by such an arrangement we 

 obtain a regular periodicity. The same type of element recurs 

 at regular intervals in the series as in the notes of the musical 

 scale, from which analogy Newlands called his system the " Law 

 of Octaves." 



A further periodicity is seen in the number of hydrogen 

 atoms which one atom of an element will displace from combination, 

 the figures rising regularly from zero to four and thence falling 

 as regularly again to begin a new series with another zero. The 

 following Table shows the system of classification now adopted : — 



