Further Evidence of the Complexity of the Atoms.
§ 83. There are also certain other facts which appear to demand such a modification of Dalton’s Atomic Theory as is found in the Electronic Theory. One of the characteristics of the chemical elements is that each one gives a spectrum peculiar to itself. The spectrum of an element must, therefore, be due to its atoms, which in some way are able, at a sufficiently high temperature, to act upon the ether so as to produce vibrations of definite and characteristic wave-length. Now, in many cases the number of lines of definite wave-length observed in such a spectrum is considerable, for example, hundreds of different lines have been observed in the arc-spectrum of iron. But it is incredible that an atom, if it were a simple unit, would give rise to such a number of different and definite vibrations, and the only reasonable conclusion is that the atoms must be complex in structure. We may here mention that spectroscopic examination of various heavenly bodies leads to the conclusion that there is some process of evolution at work building up complex elements from simpler ones, since the hottest nebulæ appear to consist of but a few simple elements, whilst cooler bodies exhibit a greater complexity.