Properties of Pure Substances : Nitrogen. 31 



down the tube to the mercury, and was much increased by 

 touching the outside of the tube near the mercury. This dis- 

 charge, of course, was small compared with the discharge in 

 the main tube. There was no effect on the gauge. 



Sept. io. Sparked with rather large sparks 6^ hours. No 

 effect. 



Sept. 24. Sparked strongly, so as to make the tube warm, 

 for 6 -J- hours. No effect. 



Sept. 25. The mercury boiled up into tube. This led to 

 the gauge showing a real increase of pressure of a little less 

 than "1 millim.; I attribute this to gas from the sides of the 

 tube between it and the mercury. Sparked strongly for 

 5 j- hours ; when all w r as cold the pressure excess had grown 

 to about '2 millim., i. e. in a direction contrary to the one 

 expected. 



Sept. 26. Discharge on for 6-^ hours fairly strong, so as 

 to warm tube perceptibly. The gauge then showed the same 

 pressure on each side. 



Sept. 27. A wet paper band round thafc part of the tube 

 where the mercury was most thickly condensed. Sparked 

 four hours (?) . No effect. 



Sept. 28. Ditto 3 hours. No effect. 



Sept. 29. Faint sparks for 5 hours ; wet paper band, as 

 before. No effect. 



Oct. 1. Temperature being more rigorously equal, and 

 gauge carefully tapped, there is a shrinkage of about '1 millim. 

 Sparked six hours with faint sparks and wet paper round 

 tube. No effect 



Oct. 2. Strong current on 6 hours. Looking the next 

 day (October 3rd), a faint yellow tinge was observed round 

 the mercury drops, and the gauge showed "8 millim. difference 

 of pressure. Sparked hard 6 hours; the mercury was now 



» obviously attacked, and when examined on October 3rd it was 

 found that the pressure difference amounted to 3*2 millim. 

 Sparked 3 hours with full discharge ; this increased the effect 

 to 6 millim., and in another 4-^ hours the discharge had become 

 splendidly golden, the resistance in the tube small, and the tube 

 was fluorescing strongly (a sign of mercury vapour) . Effect 

 increased to about 7 millim. The experiment was then inter- 

 rupted by the cracking of the tube. 



No opportunity for examining the deposit occurred till 

 November lo'th, i.e. for more than a month. The tube was 

 then cut into bits, and it was observed that the deposit had 

 become partly incrusted with some whitish incrustation. On 

 trying to produce an explosion the experiment failed, and it 

 was obvious that the film had quite decomposed. It is to be 

 noted that the mercury was only attacked with difficulty. 



