September 8, 1911] 



SCIENCE 



295 



in definite or multiple proportions, famili- 

 arized the world with the conception of 

 elements as the bricks of which the universe 

 is built. Yet the more daring spirits of 

 that day were not without hope that the 

 elements themselves might prove decompos- 

 able. Davy, indeed, went so far as to write 

 in 1811 : "It is the duty of the chemist to 

 be bold in pursuit; he must recollect how 

 ■contrary knowledge is to what appears to 

 be experience. ... To enquire whether the 

 elements be capable of being composed and 

 decomposed is a grand object of true phi- 

 losophy." And Faraday, his great pupil 

 and successor, at a later date, 1815, was 

 not behind Davy in his aspirations, when 

 he wrote : "To decompose the metals, to 

 re-form them, and to realize the once 

 absurd notion of transformation — these are 

 the problems now given to the chemist for 

 solution. ' ' 



Indeed, the ancient idea of the unitary 

 nature of matter was in those days held to 

 be highly probable. For attempts were 

 soon made to demonstrate that the atomic 

 weights were themselves multiples of that 

 of one of the elements. At first the sug- 

 gestion was that oxygen was the common 

 basis; and later, when this supposition 

 turned out to be untenable, the claims of 

 hydrogen were brought forward by Prout. 

 The hypothesis was revived in 1842 when 

 Liebig and Redtenbaeher, and subsequently 

 Dumas, carried out a revision of the atomic 

 weights of some of the commoner elements, 

 and showed that Berzelius was in error in 

 attributing to carbon the atomic weight 

 12.25, instead of 12.00. Of recent years a 

 great advance in the accuracy of the de- 

 terminations of atomic weights has been 

 made, chiefly owing to the work of Richards 

 and his pupils, of Gray, and of Guye and 

 his collaborators, and every year an inter- 

 national committee publishes a table in 

 which the most probable numbers are given 



on the basis of the atomic weight of oxygen 

 being taken as sixteen. In the table for 

 1911, of eighty-one elements no fewer than 

 forty-three have recorded atomic weights 

 within one-tenth of a unit above or below 

 an integral number. My mathematical col- 

 league, Karl Pearson, assures me that the 

 probability against such a condition being 

 fortuitous is 20,000 millions to one. 



The relation between the elements has, 

 however, been approached from another 

 point of view. After preliminary sugges- 

 tions by Dobereiner, Dumas and others, 

 John Newlands in 1862 and the follow- 

 ing years arranged the elements in the nu- 

 merical order of their atomic weights, and 

 published in the Chemical News of 1863 

 what he termed his law of octaves — that 

 every eighth element, like the octave of a 

 musical note, is in some measure a repeti- 

 tion of its forerunner. Thus, just as C on 

 the third space is the octave of C below the 

 line, so potassium, in 1863 the eighth 

 known element numerically above sodium, 

 repeats the characters of sodium, not only 

 in its physical properties — color, softness, 

 ductility, malleability, etc. — but also in the 

 properties of its compounds, which, indeed, 

 resemble each other very closely. The same 

 fundamental notion was reproduced at a 

 later date and independently by Lothar 

 Meyer and Dmitri Mendeleeff; and to ac- 

 centuate the recurrence of such similar 

 elements in periods, the expression "the 

 periodic system of arranging the elements" 

 was applied to Newlands 's arrangement in 

 octaves. As everyone knows, by help of 

 this arrangement Mendeleeff predicted the 

 existence of then unknown elements, under 

 the names of eka-boron, eka-aluminium and 

 eka-silicon, since named scandium, gallium 

 and germanium, by their discoverers, Cleve, 

 Lecoq de Boisbaudran, and Winckler. 



It might have been supposed that our 

 knowledge of the elements was practically 



