224 



DR. W. GEOFFREY DUFFlELD ON THE 



TABLE VIII. 



Displacements are in Angstrom units. 



200 



DIAGRAM 4 . 



Pressures in atmospheres (excess above one atmosphere). 



Changes in Relative Intensity. The series lines, all of which were obliterated 

 below 100 atmospheres, do not reappear between 100 and 203 atmospheres, and the 

 strengthened and weakened lines do not differ from those given in Table VI. (p. 219). 



The Colour of the Arc. As has already beeii stated, the arc is green at normal 

 pressure, and this colour characterises the arc up to 100 atmospheres, when it appeared 

 bluer ; this colour became less pronounced as the pressure was increased until at 

 203 atmospheres it appeared blue-white, like a carbon arc. 



The Brightness of the Arc. The increase in brilliance with pressure, though 

 noticeable between 100 and 200 atmospheres, was not so striking as between 1 and 

 100 atmospheres. 



