under the Influence of the Electric Discharge. 365 



I desire to express my best thanks to Mr. Koth for the 

 assistance he has rendered me in the measurements. 



3. General Measurements. 



Three groups of observations were made, in order to obtain 

 a general idea of the way in which the thermic phenomena of 

 the tube depended on the pressure. 



1. The heating in the whole of a discharge- tube was 

 determined. 



2. The heating in a capillary tube was investigated, and 

 experiments made on the influence of the width of the tube 

 and of the shape of the electrodes. 



3. The heating at an electrode was determined when the 

 electrode was positive and when it was negative, and also 

 both when it was connected with the source of electricity and 

 when it was put to earth. 



In particular cases the number of discharges was deter- 

 mined, and the measurements made with hydrogen-vacua, 

 and then repeated with air- vacua. Further, air-sparks were 

 introduced into the circuit, always between the machine and 

 the discharge-tube. 



Further experiments were made on the influence of the 

 condensation of electricity on the walls of the discharge- 

 tube, using mercury instead of turpentine as calorimetric 

 fluid. 



The arrangement of the tables is always the same. The 

 first column, headed p, gives the pressure. At very low 

 pressures which could not be read on the manometer the 

 degree of the exhaustion is denoted by x or xx. 



The following columns give the corrected amounts of heat- 

 ing of the calorimeter in one minute, calculated for an inten- 

 sity of current corresponding to a galvanometer-deflection of 

 100 millims. 



+ or — in the heading of a column indicates that the posi- 

 tive or negative electrode was connected with the machine, the 

 other pole being put to earth. 



• The number of discharges given corresponds to a current 

 giving a deflection of 10 millims. 



I. The heating in the luhole tube was determined by means 

 of three different forms of apparatus. 



The first consisted of a glass vessel, I, of the form shown 

 in Plate IX. fig. 7. The distance of the electrodes was 

 16 millims., the water-equivalent of the whole apparatus 

 27*5 grammes. 



Phil. Mag. S. 5. Vol. 10. No. 63. Nov. 1880. 2D 



