
Particles illustrating the Line and Band Spectrum. 455 
which contribute to the instability of the system are those 
associated with the higher harmonics. This evidently lies 
in the region of small wave-length, and the destruction of the 
system will be easier for ultra-violet light to bring into effect, 
if the system will resonate to these oscillations. The actino- 
electric action may be the result of the destruction of atoms 
under the combined action of electric force, which places the 
electrons in a constrained state, and the resonance to ultra- 
violet rays of the period participated in by the rings. The 
dismemberment of the rings will result in the ionization ot 
gas in the neighbourhood of the illuminated surface. 
The same course of reasoning with regard to resonance 
seems to apply to the change of resistance often observed in 
semi-insulators. Apply electromotive force to a semi-insulator 
and pass the electromagnetic wave whose period coincides 
with that of the constituent atoms, then it will set the electrons 
in resonating vibration, break them from the revolving system, 
and thereby cause the flow of electrons and reduce the 
resistance of the circuit. This perhaps explains in a simple 
manner the change of resistance in selenium by exposure to 
light : that the green light is less effective than red or violet 
seems to give strong evidence to the resonating action. 
The metals have usually a large number of spectral lines, 
extending from ultra-violet to the infra-red region. The 
exposure of metallic filings to electric waves has the same 
action as that of light in the case of selenium. Perhaps 
the same reasoning as above applies to this case, as the Hertz 
Waves are more penetrating , and there will be a greater 
number of resonating atoms than when illuminated with 
visible light. The theory of the coherer is probably to be 
based on the footing that electric current consists in the stream 
of electrons set free by the incident electromagnetic wave. 
As another example of forced oscillation ‘i may mention 
the fluorescence or phosphorescence of certain substances, 
the vibrations of particles being excited either by light or 
by electromagnetic pulses. In the former phenomenon the 
action is apparently temporary, but remanent in the latter. 
In fact, the theory of luminiscence will be capable of further 
development on the line of reasoning here expounded. 
There are various problems which will possibly be capable 
of being attacked on the hypothesis of a Saturnian system, 
such as chemical affinity and valency, electrolysis and many 
other subjects connected with atoms and molecules. The 
rough calculation and rather unpolished exposition of various 
phenomena above sketched may serve as a hint to a more 
complete solution of atomic structure. 
