478 FB.INCIPLES OP CHEMISTRY 



relations existing between the atomic volumes of all alkali metals; 

 can be expressed, according to his views, by the formula 



A(2^- 0-00535 Aw), 



where A is the atomic weight, and n is equal to 8 for lithium and sodium, to 

 4 for potassium, to 3 for rubidium, and to 2 for caesium. If n remained equal 

 to 8 during the increase of A, the volume would become zero at A = 40$, 

 and it would reach its maximum at A - 23. The close approximation of 

 the number 46 to the differences between the atomic weights of analogous 

 elements (such as Cs Bb, I Br, and so on) ; the close correspondence of 

 the number 23 to the atomic weight of sodium ; the fact of n being neces* 

 earily a whole number, and several other aspects of the question, induce 

 Tchitcherin to believe that they afford a clue to the understanding of the 

 nature cf the elements ; we must, however, await the full develcpment of 

 his theory before pronouncing judgment on it. What we can at present only 

 be certain of is this : that attempts like the two above named must be re- 

 peated and multiplied, because the periodic law has clearly shown that the 

 masses of the atoms increase abruptly, by steps, which are clearly connected 

 in some way with Dalton's law of multiple proportions ; and because the 

 periodicity of the elements finds expression in the transition from BX to 

 BX 2 , EX 3 , BX 4 , and so on till RX d , at which point, the energy of the com- 

 bining forces being exhausted, the series begins anew from BX o BX.,, and 

 so on. 



While connecting by new bonds the theory of the chemical elements with 

 Dalton's theory of multiple proportions, or atomic structure of bodies, the 

 periodic law opened for natural philosophy a new and wide field for specula* 

 tion. Kant said that there are in the world ' two things which never cease 

 to call for the admiration and reverence of man : the" moral law within 

 ourselves, and the stellar sky above us.' But when we turn our thoughts 

 towards the nature of the elements and the periodic law, we must add a third 

 subject, namely, ' the nature of the elementary individuals which we discover 

 everywhere around us.* Without them the stellar sky itself is inconceiv- 

 able ; and in tho atoms we see at once then* peculiar individualities, the in- 

 finite multiplicity of the individuals, and the submission of their seeming 

 freedom to the general harmony of Nature. 



Having thus indicated a new mystery of Nature, which does not yet yield 

 to rational conception, the periodic law, together with the revelations of 

 spectrum analysis, have contributed to again revive an old but remarkably 

 long-lived hope that of discovering, if not by experiment, at least by a 

 mental effort, the primary matter -which had its genesis in the minds of 

 the Grecian philosophers, and has been transmitted, together with many 

 other ideas of the classic period, to the heirs of their civilisation. Having 

 grown, during the times of the alchemists up to the period when experimental 

 proof was required, the idea has rendered good service; it induced those 

 careful observations and experiments which later on called into being the 

 works of Scheele, Lavoisier, Priestley, and Cavendish. It then slumbered 

 awhile, but was soon awakened by the attempts either to confirm or to refute 

 the ideas of Prout as to the multiple proportion relationship of the atomic 



