FEBRuARY II, 1897 | 
metals, still 7 cms. apart. We then found the difference 
of zeros to be — 89 sc. divs., or — 0°64 of a volt; but 
instead of seven minutes, scarcely a quarter of a minute 
was taken to reach the rays-zero after the metallic con- 
nection was broken. These results are substantially in 
accordance with Erskine Murray’s §§ 9 of his paper 
already referred to. 
KELVIN. 
J. C. BEATTIE. 
SMOLUCHOWSKI DE SMOLAN. 
THE EFFECT OF 
THE NATURE OF LIGHT EMITTED BY A 
SUBSTANCE. 
1 consequence of my measurements of Kerr's mag- 
neto-optical phenomena, the thought occurred to 
me whether the period of the light emitted by a flame 
might be altered when the flame was acted upon by 
magnetic force. It has turned out that such an action 
really occurs. I introduced into an oxyhydrogen flame, 
placed between the poles of a Ruhmkorff’s electro- 
magnet, a filament of asbestos soaked in common salt. 
‘The light of the flame was examined with a Rowland’s 
grating. Whenever the circuit was closed both D lines 
were seen to widen. 
Since one might attribute the widening to the known 
effects of the magnetic field upon the flame, which would 
cause an alteration in the density and temperature of the 
sodium vapour, I had resort to a method of experimen- 
tation which is much more free from objection. 
Sodium was strongly heated in a tube of biscuit porce- 
lain, such as Pringsheim used in his interesting inves- 
tigations upon the radiations of gases. The tube was 
closed at both ends by plane parallel glass plates, whose 
effective area was 1cm, The tube was placed horizontally 
between the poles, at right angles to the lines of force. The 
light of an arc lamp was sent through. The absorption 
spectrum showed both D lines. The tube was continuously 
rotated round its axis to avoid temperature variations. 
Excitation of the magnet caused immediate widening of 
the lines. It thus appears very probable that the period 
of sodium light is altered in the magnetic field. It is 
remarkable that Faraday, as early as 1862, had made 
the first recorded experiment in this direction, with the 
incomplete resources of that period, but with a negative 
result (Maxwell, “ Collected Works,” vol. ii. p. 790). 
It has been already stated what, in general, was the 
origin of my own research on the magnetisation of the 
lines in the spectrum. The possibility of an alteration 
of period was first suggested to me by the consideration 
of the accelerating and retarding forces between the atoms 
and Maxwell's molecular vortices ; later came an example 
suggested by Lord Kelvin, of the combination of a quickly 
rotating system and a double pendulum. However, a 
true explanation appears to me to be afforded by the 
theory of electric phenomena propounded by Prof. 
Lorentz. 
In this theory, it is considered that, in all bodies, there 
occur small molecular elements charged with electricity, 
and that all electrical processes are to be referred to the 
equilibrium or motion of these “ions.” It seems to me 
that in the magnetic field the forces directly acting on 
the ions suffice for the explanation of the phenomena. 
Prof. Lorentz, to whom I communicated my idea, was 
good enough to show me how the motion of the ions 
might be calculated, and further suggested that if my 
application of the theory be correct there would follow 
these further consequences : that the light from the edges 
of the widened lines should be circularly polarised when 
the directioniof vision lay along the lines of force ; further, 
that the magnitude of the effect would lead to the deter- 
1 Translated by Arthur Stanton from the Proceedings of the Physical 
Society of Berlin, 
NO. 1424, VOL. 55 | 
NATURE 
MAGNETISATION ON | 
347 
mination of the ratio of the electric charge the ion bears. 
to its mass. We may designate the ratio e/7. I have 
since found by means of a quarter-wave length plate and 
an analyser, that the edges of the magnetically-widened 
lines are really circularly polarised when the line of sight 
coincides in direction with the lines of force. An alto- 
gether rough measurement gives 10’ as the order of 
magnitude of the ratio e/#z when e¢ is expressed in electro- 
magnetic units. 
On the contrary, if one looks at the flame ina direction 
at right angles to the lines or force, then the edges of the 
broadened sodium lines appear plane polarised, in accord- 
ance with theory. Thus there is here direct evidence 
of the existence of ions. 
This investigation was conducted in the Physical In- 
stitute of Leyden University, and will shortly appear in 
the “ Communications of the Leyden University.” 
I return my best thanks to Prof. K. Onnes for the in- 
terest he has shown in my work. P. ZEEMAN. 
Amsterdam. 
NOTES. 
THE Council of the Royal Society have invited Prof. C. S. 
Sherrington, F.R.S., Professor of Physiology in University 
College, Liverpool, to deliver the Croonian Lecture on April 1, 
the subject being ‘* The Spinal Cord and Reflex Actions.” 
TuESDAY’s Gazette contains the formal intimation that the 
dignity of a Baron of the United Kingdom has been granted to 
Sir Joseph Lister, Baronet, President of the Royal Society, by 
the title of Baron Lister, of Lyme Regis, in the county of 
Dorset. 
Pror. Dr. RuDOLF VIRCHOW has been elected president of 
the German Anthropological Society for the year 1897. 
Ir is expected that Prof. Barnard will attend the meeting of 
the Royal Astronomical Society to-morrow, February 12, to 
receive the gold medal which has been awarded him for his 
numerous contributions to astronomy. Sir Robert Ball has 
been nominated as the new president of the Society. 
THE Council of the Royal Meteorological Society have 
arranged to hold, from March 16 to 19, in commemoration: 
of the diamond jubilee of H.M. the Queen, an exhibition of 
meteorological instruments in use in 1837 and in £897, and 
of diagrams, drawings, and photographs illustrative of the 
advances which have been made. 
Tue Government of the Colony of the Cape of Good Hope 
has undertaken an investigation of the marine fauna of the 
South African coast, with reference both to economic value and 
scientific interest. A small marine station will probably be 
erected on False Bay, and a suitable steam vessel of about 150 
tons is now being built for this purpose. It is confidently hoped 
that results of some scientific value may be obtained from the 
exploration of this little-known coast, and more especially of 
the Agulhas Bank. We are requested to state that the services 
of specialists are invited to work up the material that may be 
procured, under the following arrangements. Specimens will 
be forwarded as procured, and, on receipt of manuscript and 
drawings, each piece of work will be published without delay in 
a uniform style, so as to form ultimately a complete record of 
the Cape marine fauna. Authors’ copies will be forwarded as 
soon as published, and a certain circulation will be guaranteed. 
No money remuneration is offered, but duplicate specimens may 
be retained by the authors. Unique specimens it is intended) 
to be handed over to the South African Museum in Cape Town. 
Further information will be supplied to those interested in th 
work, on application to J. D. F. Gilchrist, Marine Biologist to. 
Cape Government Agricultural Department, Cape Town. 
