EFFECT OF PRESSURE UPON ARC SPECTRA. 
139 
11. Mean Values of Displacements. 
Table TIL—Set A. 
o 
Displacements in thousandths of an Angstrdm unit. 
Atmospheres .... 
5. 
10. 15. 
20. 
25. 
30. 
40. 
60. 
80. 
95. 
100. 
Group I., unreversed. 
24 
23 52 
54 
102 
80 
72 
101 
161 
183 
164 
Group I., reversed. 
21 
23 45 
67 
101 
74 
86 
136 
203 
227 
191 
Grouj) II. 
41 
63 94 
194 
245 
187 
185 
252 
371 
359 
366 
Group IIP, unreversed .... 
82 
118 310 
490 
— 
452 
475 
510 
620 
680 
730 
Group III., reversed. 
31 
54 71 
109 
203 
157 
193 
323 
— 
— 
- - 
Table IV.-—Set B. 
Atmospheres.... 
t 
Displacements in thousandths of an 
o 
Angstrom unit. 
3. 
4. 
10. 
15. 
20. 
25. 
40. 
50. 
70. 
80. 
100. 
Group I., unreversed. 
20 
23 
27 
43 
52 
45 
62 
59 
102 
122 
153 
Group I., reversed .'. 
18 
20 
26 
51 
59 
55 
81 
124 
129 
186 
194 
Group II. 
45 
47 
74 
95 
116 
120 
168 
181 
256 
283 
338 
Group III., unreversed .... 
100 
84 
166 
171 
280 
212 
374 
426 
539 
510 
655 
Group III., reversed. 
29 
34 
64 
95 
137 
90 
177 
263 
388 
293 
* 
12. Discussion of the Displacement Tables and Curves. 
Tables I. and II., Diagrams /., II., III., and IV. 
The values for the shifts given in Tables I. and II. have been plotted in Diagrams 
I. and II., in which the abscissae represent the excess of pressure over one atmosphere, 
and the ordinates the increase in wave-lengths of the lines in thousandths of an 
o 
Angstrom unit. 
Each line on the diagram depicts the behaviour under pressure of one spectral line, 
which may be identified by the letter attached to it. The reversal of a spectral line 
is indicated by the dotting of the line on the diagram near the pressure at which 
reversal takes place. Small arrows indicate those pressures at which measurements 
have been made. 
The Curves and Tables show that— 
(1) No lines remain undisplaced. 
(2) The displacement is always towards the red end of the spectrum, indicating a 
decrease in the frequency of the vibrating particle. 
t 2 
