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He compared the appearances also of the anode and cathode brushes in different gases at different pressures. He noticed that in air, the superiority of the anode brush was not very marked (ssss1 at end.) In nitrogen, this superiority was greater yet. A line of theory ran through Faraday’s mind in connection with all these experiments, whereby he held that there is “A direct relation of the electric forces with the molecules of the matter concerned in the action.” ssss1. He made a practical application of the principles in the explanation of lightning, because nitrogen gas forms 4/5 of the atmosphere, and as the discharge takes place therein so easily.

From Magnetographs by Prof. McKay. p. ssss1. 1. Platinum wire. 2. Copper gauze. 3. Iron gauze. 4. Tinfoil. 5. Gold-foil. 6. Brass protractor. 7. Silver coin. 8. Platinum-foil. 9. Brass. 10. Lead-foil. 11. Aluminum. 12. Magnesium ribbon. 13. Copper objects.

From Sciagraph of Various Objects. p. 130. By Prof. Terry, U. S. Naval Academy.

11. Glow by Discharge. Glow Changed to Spark. Motion of Air. Continuous Discharge During Glow. The glow was most easily obtained in rarefied air. The electrodes were of metal rods about .2 of an inch in diameter. He also obtained a glow in the open air by means of one or both of the small rods. He noticed some peculiarities of the glow. In the first place, it occurred in all gases and slightly in oil of turpentine. It was accompanied by a motion of the gas, either directly from the light or towards it. He was unable to analyze the glow into visible elementary intermittent discharges, nor could he obtain any evidence of such an intermittent action, ssss1. No sound was produced even in open air. ssss1. He was able to change the brush into a glow by aiding the formation of a current of air at the extremity of the rod. He also changed the glow into a brush by a current of air, or by influencing the inductive action near the glow. The presentation of a sharp point assisted in sustaining or sometimes even in producing the glow; so also did rarefaction of the air. The condensation of the air, or the approach of a large surface tended to change the glow into a brush, and sometimes into a spark. Greasing the end of the wire caused the glow to change into a brush.