THE PERIODIC LA^Y. 157 



is interesting to read the comments of Faraday: "Tliis circumstance 

 (the numerical relations between chlorin, bromin and iodin) has been 

 made the basis of some beautiful speculations by M. Dumas, specula- 

 tions which have scarcely yet assumed the consistence of a theory, 

 and which are at the present time to be ranged among the poetic day- 

 dreams of a philosopher; to be regarded as some of the poetic ilhimina- 

 tions of the mental horizon, which possibly may be the harbinger of a 

 new law. . . , We seem here to have the dawning of a new light, 

 indicative of the mutual convertibility of certain groups of elements, 

 although under conditions which as yet are hidden from our scrutiny." 

 In the succeeding decade we find many chemists speculating in a 

 similar way upon the connection which seemed to subsist between the 

 different elements. 



The two chemists whose names are associated with the dawn of the 

 Periodic Law are De Chancourtois and ISTewlands. De Chancourtois 

 arranged the elements in the order of their atomic weights in a helix 

 inscribed upon a vertical cylinder; this he called a 'telluric screw,' and 

 although there were many inaccuracies, as a whole it approached a 

 form in which the Periodic Law is to-day sometimes represented. The 

 ideas of De Chancourtois were by no means free from considerable haze, 

 as, for example, when he states that 'the properties of bodies are the 

 properties of numbers.' This may well be interpreted in the light of 

 the Periodic Law, which affirms that the properties of elements are 

 functions of their atomic weights. Even the important idea of perio- 

 dicity is not overlooked by De Chancourtois, but the speculations of 

 this ingenious French engineer and geologist had practically no effect 

 upon the chemical thought of that day; indeed, his articles were almost 

 unnoticed and were resurrected only after they had slumbered for 

 nearly tliirty years in obscurity. 



Somewhat otherwise was it with the work of Newlands, which be- 

 gan to appear in 1863, just a year later than that of his French con- 

 temporary. His work was, however, wholly independent of that of 

 De Chancourtois. His first paper was chiefly concerned with the de- 

 velopment of numerical relations between the atomic weights, follow- 

 ing out the ideas early expressed in Dobereiner's triads. He enlarged 

 this so as to include more than three elements in a group. For example, 

 not only was sodium the middle member, with mean properties, of the 

 triad, lithium, sodium, potassium; but rubidium also belonged to this 

 group, because two of potassium plus one of lithium gives the atomic 

 weight of rubidium. A year later he announced his law of octaves, 

 which is generally looked upon as a forerunner of the Periodic Law. 

 Here he arranged the elements in the order of their atomic weights 

 and showed that "elements having consecutive numbers frequently 

 either belong to the same group or occupy similar positions in different 



