xviii Journal of the Asiatic Society of Bengal. {N.S.. XIV. 
conductivity metal (silver or copper) cooled by a liquid—no 
iron being employed at all. They hope to produce a field of 
100, gauss. Professor Kammerlingh Onnes has suggested 
the use of liquid air or liquid hydrogen for cooling the coil and 
hopes to obtain still higher fields. There is no doubt that the 
employment of very high fields would unravel some of the 
perplexing mysteries and allow us to understand the magnetic 
phenomena much better. : 
Direct Effect. 
Since Zeeman’s paper on the doublets and triplets in the 
spectrum produced by external magnetic fields, scores of im- 
portant papers have appeared embodying the results of more or 
less systematic work on the magnetic resolution of spectrum 
lines. Almost all the elements have been investigated, and 
though many lines have baffled investigation, a large number 
have yielded results which are highly interesting. 
_ The accumulated data indicate that spectrum lines split 
up into types which are fairly well classified and which, independ- 
ent of any spectrum formula, prove that the lines of a series 
are grouped together. Hence the use of the magnetic resolu- 
tions in the study of spectral series. However, the study of 
the Zeeman effect has not resulted in the discovery of the laws 
of distribution in the spectra of non-series lines. 
ost. of the investigators of the Zeeman effect have con- 
. 
fined themselves to the study of lines in the visible region of 
of interference, are usually made of glass and are obviousl; 
not suitable for observation in the ultra-violet or infra-red 
regions 
Quite recently Nagaoka and Takamine have taken up the 
study : of the Zeeman effect in the ultra-violet region and have 
investigated a few lines. Croze, on the other hand, has ¢¥ 
tended his examination of the lines and bands of hydroge}: 
oxygen and nitrogen, into the infra-red as faras the photo 
graphic methods allow—up to <=9000 A.U. The need for 
further research in these directions is evident. 
There is yet another direction in which the need of further 
observation is great. Up to the present, different investigators 
have employed fields of different strengths and very fe 
ave deen systematically studied in a field of gradually increas” 
power of the spectroscope for the detection of the § 
magnetic resolutions. 
Satellites : 
t is a well-known fact, that some of the spectrum ie 
are very complex in structure (cf. mercury green line, _ 
