THE ATOMIC VIEW OF NATURE. 



423 



which the gap in the series which gives the distances 

 of the planets from the sun indicated the existence of a 



planet," a chercher une aiguille dans 

 une botte de foin." About the 

 same time that this search was 

 contemplated Piazzi found the first 

 of the small planets, which like 

 the other subsequently discovered 

 asteroids corresponds very nearly 

 with the expected position in the 

 system. The periodic system of 

 the elements, according to which 

 the physical and chemical pro- 

 perties of all the elements show 

 a periodic dependence upon the 

 atomic weights, was first system- 

 atically stated by Newlands (in 

 1864) and by Lothar Meyer and 

 Mendeleeff on the Continent. The 

 latest edition of Meyer's treatise on 

 " Modern Theories of Chemistry," of 

 which only the first part, with the 

 title 'Die Atome und ihre Eigen- 

 schaften " has been published (post- 

 humously by the author's brother, 

 Breslau, 1896), gives a good idea of 

 how from small beginnings these 

 statistics of the atomic theory of 

 matter have grown into a great 

 accumulation of interesting facts, 

 upon which a system of inorganic 

 chemistry can now be based which 

 compares with the system of or- 

 ganic chemistry founded upon the 

 types of Gerhardt in their orig- 

 inal or in some modified form, 

 and upon the " homologous " series 

 of hydrocarbon compounds. As 

 the typical arrangement of organic 

 compounds, or rather of carbon 

 compounds (for many real organic 

 compounds are not easily classed 

 by these methods), led to the sug- 

 gestion of the existence of many 

 compounds which were not known 

 at the time, and have since been 

 prepared, so the periodic arrange- 

 ment enabled Mendeleeff to predict 

 the properties of missing numbers 

 of the periodic series. And al- 

 though this mapping out of the 



elements according to their atomic 

 weights does not indicate how and 

 where the missing numbers are to 

 be found, as is the case with the 

 law of Titius and Bode, and still 

 more so with the homologous series 

 of carbon compounds, still it is 

 interesting to be able to state that 

 in several instances notably on 

 the discovery of the new elements, 

 gallium (by Lecoq de Boisbaudran 

 in 1878), scandium (by Nilson in 

 1880), and germanium (by Winkler 

 in 1886) the properties of these 

 substances confirmed to a very 

 great extent the predictions of 

 Mendele"eff. And when in 1894 

 Lord Rayleigh and Professor Ram- 

 say announced their discovery of a 

 new element in atmospheric air, 

 which, from its inertness, was 

 called argon, interesting sugges- 

 tions as to its properties were 

 drawn from speculations regarding 

 its probable position in the periodic 

 curve (see Lothar Meyer, loc. cit., 

 p. 165). It is true that these 

 numerical regularities, which for 

 some minds possess a great fascina- 

 tion, are, so far, purely statistical. 

 It is possible to arrive by inter- 

 polation or extrapolation at valu- 

 able suggestions in statistics, in 

 meteorology, and in mining opera- 

 tions ; but so long as the actual 

 cause or intrinsic connection is not 

 known, which explains the neces- 

 sity of these regularities, they are 

 apt to be misleading, and have to 

 be used with great caution. Still, 

 the fact alone that they bring some 

 order into a bewildering mass of 

 figures and data makes them al- 

 most indispensable. For similar 

 reasons many chemists adopted 

 Gerhardt's types and homologous 

 series as affording a ready method 

 of classification, though not a 

 rational explanation of phenomena. 



