14 Prof. E. Edlund's Researches on the Passage 



from the other at pleasure by means of a micrometer-screw, 

 the distance separating them being read on a graduated scale. 

 The spark micrometer and the glass tube with aluminium 

 electrodes used in the previous experiment were connected 

 with the electrophorus in the way indicated by fig. 3; but the 

 distance between the electrodes 

 was now 30 millim., and not 5 as Fig. 3. 



in the foregoing experiments. d h " v ^~ -^ 



Two electrodes, connected with ^^^-^^ \ * 



one of the receiving combs of the ^X^ 



electrophorus, proceed from the ^^^^ \m 



point g to the metal ball / (the /? v ^^~- 



same as that denoted by this 

 letter in fig. 1). The glass tube 



containing the rarefied air is inserted at a in one of the elec- 

 trodes, and the spark micrometer at m in the other. When 

 the distance between the balls of the micrometer was great, 

 the discharge passed exclusively through the rarefied-air 

 space ; but if they were brought sufficiently nearer, the dis- 

 charge passed only at m, through the spark micrometer. The 

 distance was now regulated so that the successive discharges 

 passed alternately through a and through m. For this case 

 the sum mentioned, e + rl, was regarded as equal in the two 

 tubes ; and the distance between the balls, which constituted 

 a measure of that sum, was read on the scale. The following 

 results were obtained:— 

 Experiment 3. 



Pressure of -p.. , , , 



the air. Distance between 



millini the baUs ' 



46-5 1-31 



25-1 1*31 



17-5 1*36 



13-0 1-25 



6-4 1-14 



4-0 1-10 



2-3 1-10 



0-8 1-15 



0-007. .... 2-33 



Experiment 4. In this experiment the aluminium electrodes 

 were replaced by electrodes of platinum, and the distance 

 between them was 30 millim. The fo lowing distances be- 

 tween the balls of the micrometer were obtained, according to 

 the modification of the air-pressure in the rarefied-air space: — 



