440 Prof. Challis on a Theory of Galvanic Force, 



is flowing in a closed circuit, it must be supposed that very 

 minute and rapid electric discharges arc taking place at the 

 same time. 



16. The light and heat accompanying electric and galvanic 

 discharges may, according to the Undulatory Theories of Light 

 and Heat which I have proposed, be ascribed to vibrations of the 

 atoms of aeriform or solid bodies, excited by the dynamic action 

 of aetherial currents. When the electrodes terminate in charcoal 

 points, the dynamic action is increased both by the condensation 

 of the streams due to the pointed form, and, on approaching the 

 points, by the impulse given to the streams in consequence of 

 the opposite states of electricity of the terminals. 



It seems to be a sufficient explanation of the voltaic arc, to 

 say that the air between the poles, being heated by the galvanic 

 discharge, continually rises, and that consequently the path of 

 least resistance, which depends only on the density of the air, is 

 not the straight line joining the poles, but a course above this. 



17. The coloured light in the tubes with which Mr. Gassiot 

 experimented seems to be caused by vibrations of some gaseous 

 substance enclosed within them, the atoms of which, it being of 

 extreme rarity, may be made to perform large excursions by the 

 dynamic action of the current, and reciprocally may produce 

 agitations of the aether rendered sensible in the form of light. 

 If the gas were of considerable density, its elastic force would 

 resist the action of the stream, and the excursions of its atoms 

 might consequently be too small to produce a sensible amount 

 of light. The stratification may be due to the nodes and loops, 

 that is, positions of minimum and maximum vibration, which 

 are always consequent upon exciting vibrations of elastic gases 

 in tubes. The colour is probably to be ascribed to the particular 

 quality of the gas. The glow at the terminals appears to have 

 a different origin from that of the stratification, and may possibly 

 be due to the agitations of the aether, caused by the sudden 

 changes of the stream on its passing out of, or entering into, a 

 terminal. 



18. Different dynamic effects of the motions of the aether 

 may co-exist without mutual disturbance, if the motions be 

 vibratory ; but the dynamic effects of steady currents interfere 

 with each other. This known result from hydrodynamical prin- 

 ciples at once explains the disturbance of a galvanic current by a 

 magnet, supposing the magnetic influence to be due to steady 

 aetherial currents. 



19. If two electrodes be placed near each other and parallel, 

 and galvanic currents pass along them in the same direction, 

 they are attracted towards each other. The explanation of this 

 fact by the theory is, that the contiguity of the electrodes de- 



