88 Prof. J. Dewar. Studies on the Electric Arc. [Jan. 15, 



occult power located in the arc, or was simply the result of the high 

 temperature attained by the carbons, a series of experiments was made 

 in carbon tubes, the arc being merely used as a means of heating. The 

 following is the method of arranging the arc for this experiment. 



A block of limestone about five inches long by three inches thick 

 was drilled horizontally as shown in the drawing, another hole being 

 drilled so as to meet it in the centre of the mass. 



A. drilled purified carbon was placed in the horizontal channel and 

 made the positive pole, the negative pole being a solid rod of carbon 

 passing through the vertical aperture. Gases were passed through 

 the positive carbon, and were thus subjected to the intense heat of the 

 walls of the tube, the arc passing outside. 



The walls of the positive carbon burnt through with great rapidity, 

 not lasting as a rule more than fifteen minutes. This action could 

 only be prevented by using much thicker carbons, and consequently 

 reducing considerably the intensity of the heat. 



The porosity of the carbons, which allowed a constant diffusion of 

 gases through their walls, was another source of difficulty, which has 

 now been overcome. 



On passing a mixture of three volumes hydrogen and one volume 

 nitrogen thoroughly dried through the positive pole, a large yield of 

 hydrocyanic acid was always obtained, and on using equal volumes of 

 hydrogen and nitrogen the quantity was if anything increased. 



Pure dry hydrogen by itself gave a trace of hydrocyanic acid, and 

 a considerable quantity of acetylene. 



Pure dry air gave no hydrocyanic acid or acetylene ; moist air, on 

 the contrary, giving abundance of the former, but only a trace of the 

 latter. 



The yield in all these experiments altered considerably with the rate 

 at which the gases were passed, a quick stream always producing 

 more than a slow one, unless when oxygen was present. 



Formation of Nitrites in the Arc. 

 In these experiments the annular vessel was made use of, in which 



