COLOR AND CHEMICAL CONSTITUTION 121 



doubtedly to be accounted for by the vibrations within the atoms, 

 we may well have recourse to the modern conception of the atom 

 as advanced by J. J. Thomson. Here the atom is considered as 

 made up of a central mass carrying a positive charge. Surrounding it 

 are numerous electrons of a negative charge, the number of which 

 increases directly with the atomic weights of the elements concerned. 

 The electrons are undoubtedly arranged in some systematic order and 

 may, as Nagaoki imagines, follow parallel courses closely analogous 

 to the rings of Saturn. A disturbance of any one group or belt of 

 electrons will undoubtedly produce a disturbance in yet other groups 

 and, according to the amount of disturbance, the definite vibratory mo- 

 tions established will set up vibratory motions in the ether, later to be 

 detected in the spectrum. From this hypothesis the spectrum of an 

 element of high atomic weight might be expected to contain more lines 

 than one of low atomic weight. Such, however, need not necessarily 

 follow. If we take the case of radium, uranium, etc., we may imagine 

 the electrons in its atom to be grouped closely together in only a few 

 courses or belts. In fact this very hypothesis may well account for the 

 discharge of electrons from such highly condensed arrangements and 

 give rise to radioactivity. 



From this modern standpoint the molecule is regarded as a com- 

 bination between atoms as effected by the loss or gain of one or more 

 electrons from one to the other, developing what is commonly termed 

 " bonds of affinity " and corresponding in number to the valence of the 

 particular atoms concerned. These may be more correctly construed 

 as Faraday tubes of force. 1 



With these ideas in mind the banded spectra of compounds may be 

 accounted for by disturbances induced between the atoms, as well as 

 by small electronic vibrations set up in the atoms themselves and due 

 to the perturbances of the Faraday tubes of force. The vibrations 

 resulting from this composite arrangement of vibratory centers may 

 be sufficient to extend over a considerable area of wave-lengths and thus 

 produce a band. As the temperature increases these band spectra, 

 always obtained with compounds, pass over gradually into the line 

 spectra of the constituent elements concerned. There follows, then, 

 with increase of temperature or electric stress, as has already been noted, 



1 The lines of force binding two atoms and constituting an electrical field 

 between these charged atoms is conveniently regarded as made up of tubes of 

 force, each with its positive electrical charge at one end, the beginning of this 

 tube, and its negative and equal electrical charge at the other end or termina- 

 tion of the tube. Each Faraday tube, therefore, encloses a charge of electricity 

 of unit value or that denoted by one single electron and consequently an atom 

 that is univalent must enter into combination by means of one Faraday tube of 

 force, one that is bivalent by two such tubes, etc. The positive atoms are those 

 formed by the loss of electrons and the negative atoms are those which can take 

 up these same electrons. 



