APEIL28, 1899.] 



SCIENCE. 



609 



of repetitioa of the first, like the eighth 

 note of an octave in music' This discovery 

 of Newlands of a fact which later developed 

 into the Periodic Law does not, however, 

 mark tlie beginning of a new direction in 

 chemical thought. It marks rather that 

 point in a long series of speculations at 

 which chemists were beginning to grasp an 

 idea after which thej^ had been groping 

 blindly for many years, the conception that 

 the elements are not wholly unrelated 

 bodies, but that there is some definite law 

 connecting their properties with tlieir 

 atomic weights. Beginning in 1815, with 

 the claim of Prout that the atomic weights 

 of the elements are multiples of that of 

 hydrogen, which led him to suggest that 

 hydrogen is the primitive element from 

 which the others are built up, we find nu- 

 merous speculations, some devoted merely 

 to finding arithmetical relations among tlie 

 atomic weights, such as the law of triads, 

 others attempting to show how the elements 

 could be built up from one or more primi- 

 tive constituents. Most of these did not 

 lead to any marked advance of chemical 

 theory, but Front's hypothesis found very 

 able defenders and greatlj^ encouraged ac- 

 curate atomic-weiglit determinations. The 

 labors of Dumas, Marignac and especially 

 of Stas, in this field, are directly due to the 

 desire to test the validity of Prout's sug- 

 gestion. Up to 1860 not only were the 

 atomic weights uncertain to within a few 

 decimals, but, for other reasons, even the 

 relative position of the elements in an as- 

 cending series was often uncertain ; our 

 present empirical formulas had not been 

 fully established ; it was uncertain, for in- 

 stance, whether water was HO with = 8 

 or H^O with = 16, or whether silica was 

 SiO, with Si = 28 or SiOj with Si = 21. So 

 when Gladstone, in 1853, arranged the ele- 

 ments in the order of ascending atomic 

 weights he failed to perceive any note- 

 worthy relation; Nine years later the 



French engineer and geologist de Chan- 

 courtois, using the newer and now adopted 

 atomic weights, arranged the elements in a. 

 spiral or helical form around a cjdinder, ia 

 ascending order, and was led to the conclu- 

 sion that the ' properities of bodies are 

 properties of the numbers,' a vague state- 

 ment of the now familiar phase that the 

 properties of the elements are functions of 

 their atomic weights. As already men- 

 tioned, he was followed closely b^^ New- 

 lands, whose work, however, met with but 

 slight recognition. Time is wanting to 

 show how in the period 1864-1869 the 

 Periodic Law was developed by the labors 

 of Newlands, and more especially of Lothar 

 Meyer and Mendelejeff, working independ- 

 ent!}'. It affords an interesting example 

 of how a great idea is developed about 

 the same time in the minds of several 

 men working independently and unknown 

 to each other. In 1871 Mendelejeff pub- 

 lished a table which shows the periodic law 

 essentially as we find it todaj^, the only 

 changes consisting in the addition of a few 

 newly discovered elements and in placing a 

 few of the older elements in their proper 

 positions, as a result of more accurate 

 atomic- weight determinations. 



The period 1863-1870 was, therefore, of 

 the greatest importance for inorganic chem- 

 istry, as it saw the development of the 

 idea that the properties of the elements are 

 periodic functions of their atomic weights. 

 The time which has since elapsed has been 

 even more fruitful than any previous period 

 in speculations, having for their object the 

 finding of mathematical relations between 

 the atomic weights and in theories of the 

 evolution of matter from one or two primal 

 constituents. Many modifications of the 

 periodic scheme have been devised, but 

 they present but few or no advantages over 

 the simple arrangement of Mendelejeff and 

 Lothar Meyer. The great fact still remains, 

 unmodified and unimproved, that if the ele- 



