CONTEMPORARY ADVANCES IN PHYSICS, XXVIII 



587 



elements, apart from what is known about the correlated gamma-rays 

 (see footnote 21). 



Fine-structure was discovered, as I said before, with the great 

 magnet of Bellevue. This has soHd pole-pieces (75 cm. in diameter!) 

 instead of rings; it is not necessary to adjust the field-strength step by 

 step so as to bring group after group to a narrow detector,; all the groups 



3.3 3.4 



3.7 3.8 

 RANGE IN 



3.9 4.0 4.1 4.2 



AIR IN CENTIMETERS 



Fig. 8 — Alpha-ray spectrum of RaC; peak observed with differential ionization- 

 chamber, never before detected because of immensely greater number of particles in 

 RaC peak just off the diagram to the right; asymmetry indicating fine-structure. 

 (Rutherford, Ward & Wynn- Williams; Proc. Roy. Soc). 



-1 



UJ o 



I- 3 



tr O 



< a 



Q. o 



ct z 



UJ < 



25 



8490 8470 8450 8430 8410 8390 8370 8350 8330 8310 8290 



MAGNETIC FIELD IN GAUSS 



Fig. 9 — Fine-structure of alpha-ray spectrum of RaC; as asymmetric peak of Fig. 8 

 resolved into two nearly equal peaks by annular magnet. (Rutherford, Wynn- 

 Williams, Lewis & Bowden; Proc. Roy. Soc). 



of various speeds are deviated simultaneously in circular arcs each of 

 its own particular radius, and simultaneously fall upon a photographic 

 plate, producing what looks precisely like a line-spectrum in optics 

 (Figs. 10, 11). The example in Fig. 10 relates to ThC, the earliest to 



