v.] EARLY CHEMICAL VIEWS. 59 



opens up a road much too wide to be completely filled by it in its 

 original form, and a more comprehensive one must take its place. 



The great chemist was careful whilst tabulating the irresolv- 

 able substances in his time into elements, to state that it is 

 probable we do not know the elements themselves, but rather should 

 understand that by analysis we have arrived at a limit at terminal 

 constituents and that for our purpose all such bodies may be 

 looked upon as simple. 



But this idea of " elements " as the basis of matter took very 

 firm root, and while it has contributed immensely to the growth of 

 chemistry it cannot, latterly at least, be considered as all-sufficient. 



At the time, however, of Kirchhoff's earlier work the notion of 

 the elements being absolutely elemental appears to have been held 

 very firmly, and no doubt seems to have been felt that the numerous 

 lines forming the spectrum of any one so-called element were other 

 than peculiar to that element alone. In other words, no hesitation 

 was felt at ascribing a most complex spectral appearance to a 

 simple element, regarded as such from its chemical irresolvability 

 under ordinary circumstances. 



The idea that the " elements " were final substances or forms of 

 matter was first shaken by the discovery and isolation of groups of 

 substances whose chemical behaviour was exactly analogous to that 

 of other substances regarded as elemental. The full meaning and 

 importance of this idea of compound radicals or groups has perhaps 

 only been fully recognised during the past decade, it certainly was not 

 at the time of Kirchhoff's first investigations on spectra. On the con- 

 trary, the " finality of elementary matter" notion was much strength- 

 ened by the coincidence of solar with terrestrial spectral results. 



With our present knowledge of the behaviour, chemical and 

 physical, of the groups we call radicals, especially those classed as 

 organic ; and our extended notions of allotropism, and isomeric and 

 polymeric forms of bodies ; it is very unlikely, were spectrum analysis 

 to be discovered now, that the notion of an elemental form of matter 

 would be ascribed to substances giving complex spectra, but rather 

 having regard to the analogies above referred to, the phenomena 

 would be ascribed to groups of elements the peculiarity of which is 

 that they act, within certain ranges of condition, as individuals 

 as complexes of atoms of wider range of existence to the limits 

 of which we have not as yet attained. 



