III. The Effect of Pressure upon Arc Spectra. — No. 1. Iron. 
By W. Geoffrey Duffield, B.Sc. [Adelaide], B.A. (Cantab.), Honorary Research 
Fellow in Physics at the Manchester University, Mackinnon Student 
of the Royal Society. 
Communicated by Professor A. Schuster, F.R.S. 
Received July 4,—Read November 7, 1907. 
[Plates 3-8.] 
Contexts. 
t 
Part I. 
The mounting and adjustment of the Rowland grating. 
Part II. 
The effect of pressure upon the spectrum of the iron arc . . . . 
1. Preliminary. 
2. Description of the apparatus. . 
3. The illumination of the slit.. . . 
4. The system of mirrors. 
5. The general arrangement of the apparatus. 
6. The precautions necessary in taking the photographs. 
7. The behaviour of the iron arc under high pressures. 
8. General features of the results. 
9. The measurement of the photographs . . . 
10. Tables of the displacements. 
11. Tables of mean values of the displacements. 
12. Discussion of the displacement tables and curves. 
13. The relation between the pressure and the displacement. 
14. Phenomena relating to. the departure from a linear relation. 
15. The displacement and the tendency to reverse. 
16. The anomalous displacement of unsymmetrically reversed lines . . . . 
17. The reversal of lines under pressure. 
18. The order of reversal. 
19. Lines enhanced and weakened under pressure. 
20. Series of lines in the iron spectrum. 
21. Summary of results. 
VOL. CCVIII.—A 429. 
Page 
112-122 
123-162 
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