218 



DE. W. GEOFFREY DUFFIELU ON THE 



(3) The Spectrum of the Nickel Arc under Pressures of + 155 and + 200 

 Atmospheres. The range of spectrum which has been explored at higher pressures 

 of +155 and +200 atmospheres extends from X = 4050 to X = 4600. The 

 investigation, which involved a certain amount of risk, showed that there is no 

 discontinuity in the nature of the pressure-effect between 1 and +200 atmospheres. 

 As special interest attaches to the effect of such high pressures, and as measurements 

 of the lines are extremely difficult, a qualitative account of the behaviour of the 

 nickel lines at these pressures is given in the following table ; when readings have 

 been attempted they are included, bxit they cannot be regarded as more than 

 approximate : 



TABLE IV. 



Line. Wave-length. 



126 

 133 

 135 

 137 



141 



100 



161 



163 



165 

 167 



4064-55 

 4104-37 

 4116-14 

 4121-48 



4142-4 



4288-16 



4296-06 



4307 40 



4331-0 

 4359 73 



155 atmospheres. 



Vanished. 

 Faint indication only. 



Vanished. 



Considerably broadened, fairly sym- 

 metrical. Remains fairly compact 

 throughout. Resembles 136, which 

 is due to iron. Displacement 

 0-170 A.U. to red. Displacement 

 per atmosphere = O'OOll A.U. 

 No sign of line, but background is 



of increased intensity here. 



Faint indication of very broad line. 



Vanished. 



Merged. 



Vanished. 



Broadened, but not unduly, remains 

 fairly compact. 



)) )) !> 



Greatly broadened and displacement. 



Merged into 160. 

 Same as 200 atmospheres. 



Immense broadening and displace- 

 ment. Unsymmetrically broad- 

 ened to red. 



Considerably broadened. 



Vanished. 



Greatly broadened and displaced to 

 red. Broadening unsymmetrical. 

 Displacement between 0'57 to 

 0-83 A.U. 



200 atmospheres. 



Vanished. 

 Invisible. 

 Vanished. 



Considerably broadened, as at 

 155 atmospheres. Displacement 

 0-250 A.U. Displacement per 

 atmosphere = 0'0013 A.U. 



Invisible. 



Invisible. 



Vanished, though strong at 1 atmo- 

 sphere. 

 Merged into very faint hazy band. 



Vanished. 

 Very faint. 



Greatly broadened and displaced. 



Merged into 160. 



Immense broadening and displace- 

 ment. Unsymmetrical to red, but 

 curve too flat topped for accurate 

 measurement. 



Very faint. 



Broadening rather greater, but now 



very faint. 



Vanished. 



Very broad and diffuse. 



