A CENTURY OF CHEMISTRY. 109 



confirming the doctrine of the regularity of chemical 

 proportions in all combinations. 



Others again, without accepting any protyle-hy- 

 pothesis, pointed out the existence of serial regular- 

 ities in the atomic weights of the elements, (Lens- 

 sen 1857, Pettenkofer 1850, Dobereiner 1817, and 

 even before the atomic theory, J. B. Kichter 1798). 

 Dobereiner pointed out that a number of elements 

 could be arranged in groups of three, or triads; e.g., 

 calcium, strontium, and barium, the members of each 

 triad having analogous properties and displaying a 

 certain regularity in the relations of their atomic 

 weights. This idea of family characteristics was 

 afterwards extended by Dumas. 



Most noteworthy, however, was the work of New- 

 lands (1863-4), who showed that when the elements 

 were arranged according to the magnitude of their 

 atomic weights, " similar elements were found at 

 approximately equal distances in the series; count- 

 ing from any one element, every eighth was in gen- 

 eral more similar to the first than the other ele- 

 ments." * 



As the eighth element, starting from a given one 

 is a kind of repetition of the first, like the eighth note 

 of an octave in music, he called the regularity " The 

 Law of Octaves." He did not succeed, however, in 

 fully carrying out his idea. In the same year 

 (1864), Dr. Odling also published a suggestive pa- 

 per on " The Proportional Numbers of the Elements 

 and their Serial Relations." 



Independent Discovery ly Meyer and Mendelejeff. 

 We accept the conclusion of expert authorities 

 that in 1869 Lothar Meyer and D. Mendelejeff inde- 



* Ostwald, General Chemistry, trans, by Walker, 1890, 

 p. 35. 



