Electric Discharge in Gases. 53 



a brighter luminosity of the gas. To the same cause I should 

 be disposed to refer the great heating, otherwise so remark- 

 able, in a calorimeter surrounding the discharge-tube, when a 

 powerful discharge is sent through, and a good conducting 

 fluid in connexion with the earth is employed in the calori- 

 meter. The quantities of electricity, which become bound, 

 become greater, especially where air-sparks are included, and 

 consequently the formation of the dark space is much facili- 

 tated, so that the resistance offered to the passage of the 

 discharge must increase in a high degree. 



5. Influence of a powerful Magnet upon the Discharge. — The 

 results which we have obtained also explain the phenomena 

 which take place when the discharge is subjected to the action 

 of a powerful magnet. The best form of magnet to employ 

 is a cylindrical magnet, magnetized by a spiral of wire. It 

 is known that under the influence of such a magnet the 

 positive light is thrown into curves, which correspond nearly 

 to those assumed by a solid flexible conductor fixed at both 

 ends, whilst the glow-rays behave like a conductor fixed at 

 one end. In a wide, strongly exhausted tube the stratified 

 discharge was obtained, and then one pole of the electro- 

 magnet described was moved along gradually from the 

 positive pole-plate a. The well-known forms appeared in 

 the positive light ; the discharge appeared continuous in the 

 revolving mirror. If we bring the magnet nearer to the 

 negative pole, the glow-rays become compressed at the side, 

 as may be seen from the green light which appears along the 

 wall, and the positive light with its stratifications is seen to 

 move, somewhat deformed it is true, in the space vacated by 

 the glow-rays. The form of the discharge is represented in 

 fig. 8. The bend at b corresponds to the magnet beneath. 



If the magnet is brought still nearer to the kathode, and so 

 far that the tongue a reaches to the limit of the dark kathode- 

 space, it suddenly falls down and unites with glow-rays at the 

 point where they strike the wall, and the discharges become 

 discontinuous ; so that in this case a much higher potential is 

 necessary for the discharge than in the first case, or a con- 

 siderable resistance is produced. 



These experiments appear to me to show that the formation 

 and position of the positive light does not depend so much on 

 the position of the positive and negative polis, but rather 

 upon the formation of the glow-rays issuing from the negative 

 pole, and that generally, in accordance with their formation 

 and position, the discharge shows a greater or less degree of 

 discontinuity. 



The above observation of the transformation of the con- 



