AucusT 24, 1899] 
NATURE 
407 
physical theory, The necessary physical theory may be regarded 
as afforded by the mechanism which thus forms an essential part 
of Lord Kelvin’s mode of accounting for magneto-optic effects. 
Lord Kelvin, in his Baltimore Lectures, has suggested for 
magneto-optic rotation a form of gyrostatic molecule consisting, 
as shown in the figure, of a spherical sheath enclosing two equal 
gyrostats. These are connected with each other and with the 
case by ball-and-socket joints at the extremities of their axes, as 
shown in Fig. 15. If the spherical case were turned round any 
axis through the centre no disalignment of the gyrostats con- 
tuined in it would take place, and it would act just like a simple 
gyrostat. If, however, the case were to undergo translation in 
any direction except along the axis, the gyrostats would lag 
behind, and the two-link 
chain which they form would 
bend at the centre. This 
bending would be resisted 
by the quasi-rigidity of the 
chain produced by the rota- 
tion, and the gyrostats would 
react on the sheath at the 
joints with forces as before 
at right angles to the plane 
in which the change of direc- 
tion of the axis takes place. 
The general result is, that 
if the centre of this molecule 
be carried with uniform 
velocity ina circle in a plane 
at right angles to the line of 
axes, the force required for 
the acceleration towards the centre, and which is applied to it 
Fic. 15. 
by the medium, is greater or less according as-the direction in | 
which the molecule is carried round is with or against the | 
direction of rotation of the gyrostats. That is, the effect of the 
rotation is to virtually increase the inertia of the molecule in the 
one case and diminish it in the other. 
These molecules embedded in the medium are supposed to be 
exceedingly small, and to be so distributed that the medium 
may, in the consideration of light propagation, be regarded as 
of uniform quality. 
Lord Kelvin’s last 
form of molecule, it 
may be pointed out, 
if the surface of its 
sheath adheres to the 
medium, will have 
efficiency as an ord- 
inary single gyrostc: 
es regards rotations 
of the molecule, and 
efficiency likewise as 
regards translational 
motion of the centre 
of the molecule. The 
former efficiency can 
be made as small as 
may be desired by 
making the molecule 
sufficiently small ; the 
latter may be main- 
tained at the same 
value under certain 
conditions, however 
small the molecule 
* be made. 
The lately discovered effect of a magnetic field in giving one 
period of circular oscillation of a particle or another according 
as the particle is revolving in one direction or the other about 
the direction of the magnetic force, is connected with magneto- 
optic rotation. There is a connection between velocity of 
propagation and frequency of vibration, which is exemplified by 
the phenomena of dispersion. In the Faraday effect, the two 
modes of vibration, if of the same period, have different velocities 
of vibration, consequently these two modes of vibration must 
have different frequencies for the same velocity of propagation. 
The vibrations of the molecules of a gas in which the Zeeman 
effect is produced by a magnetic field may be represented by 
the motion of a pendulum the bob of which contains a rapidly 
1G. 1€.—Path of the Bob of a Gyrostatic Pen- 
dulum. As the pendulum moves, it passes 
:rom cne ray to another on the opposite side, 
and the direction of motion at each swing 
alters through the angle between two rays. 
The central parts of the rays are left out. 
The marking point does not pass exactly 
through the centre. 
rotating gyrostat with its axis in the direction of the supporting | 
NO. 1556, VOL. 60] 
wire of the pendulum. The period of revolution of the bob 
when moving asa conical pendulum is greater or less than the 
period when the gyrostat is not spinning according as the 
direction of revolution is against or with the direction of 
rotation. 
The bob when deflected and let go moves in a path which 
constantly changes its direction, so that if a point attached to 
the bob writes the path on a piece of paper, a star-shaped figure 
is obtained. I cause the gyrostatic pendulum here suspended 
to draw its path by a stream of white sand on the black board 
placed below it, and you see the result. 
I must here leave the subject, and may venture to express the 
hope that on some other occasion some one more specially 
acquainted with the electromagnetic aspects of the phenomenon 
may be induced to place the latest results of that theory before 
you. 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE. 
Mr. JAMES Brown THomson, of Kinning Park, Glasgow, 
who died ten months ago, left $0,000/. to Glasgow institutions 
—mostly educational and benevolent. The Glasgow University 
will receive 10,000/. 
THE recent discussion in NATURE on ‘‘The Duties of 
Provincial Professors” forms the subject of a short critique in 
the August number of the Aducational Review. While fully 
endorsing the general views expressed in our columns, the 
Review remarks: ‘‘ There is only one flaw in the indictment 
—the insinuation, namely, that university professors should take 
no part in the social life and physical activities, the general 
discipline, the corporate existence of the university or university 
college.” But where does this flaw exist ? No such insinuation 
is made in the article in NATURE. 
THE Department of Science and Art has issued the following 
list of successful candidates for Royal Exhibitions, National 
Scholarships, and Free Studentships (Science) awarded this 
year :—Royal Exhibitions: William M. Selvey, Edward C. 
Moyle, Archibald D. Alexander, Charles W. Price, George 
F. A. Cowley, Edgar Sutcliffe, Sydney A. Edmonds. National 
Scholarships for Mechanics: Francis P. Johns, George F. 
Turner, Walter A. Scoble, Arthur J. Spencer, William H. 
Adams. Free Studentships for Mechanics: R. Borlase 
Matthews, William H. Outfin. National Scholarships for 
Physics: William R. Daniel, William J. Lyons, James Lord, 
William M. Varley, Wilfred H. Clarke. Free Studentships 
for Physics: John H. Shaxby, Gerald Henniker. National 
Scholarships for Chemistry: William D. Rogers, John H. 
Crabtree, Howard E. Goodson, Arthur H. Higgins, Montague 
W. Stevens. Free Studentships for Chemistry: John R. 
Horsley, Arthur C. Nicholson. National Scholarships for 
Biology : Eric Drabble, Louis E. Robinson, Ernest A. Wraight, 
Reginald F. G. Bayley, Harold B. Fantham. National 
Scholarships for Geology: William H. Goodchild, Thomas 
Thornton. 
THE iollowing list of candidates, successtul in this year’s com- 
petition for the Whitworth Scholarships and Exhibitions, has 
been received from the Department of Science and Art :— 
Schoiarships, tenable for three years, 125/. a year each: 
Alec W. Quennell, London ; Hanson Topham, Great Horton, 
Bradford ; William V. Shearer, Langside, Glasgow; George 
Wall, Oldham. Exhibitions, tenable for one year, value 50/. 
each: Arthur J. Spencer, Portsmouth; George F. Turner, 
Sheffield ; Harold P. Philpot, London; William H. Adams, 
Devonport; Edward C. Moyle, Devonport ; Walter A. Scoble, 
E. Stonehouse, Devon ; Archibald D. Alexander, Portsmouth ; 
Sydney A. Edmonds, Devonport; George F. A. Cowley, 
Portsmouth ; Albert Wilson, Leeds; Edwin J. Britton, Ports- 
mouth ; Harry Duncan, Plumstead; Samuel C. Rhodes, Mor- 
ley, Leeds; Harry M. Andrew, Manchester; Alexander P. 
Traill, North Shields; Leonard Bairstow, Halifax ; William T. 
S. Butlin, Bristol; Albert E. Dodridge, Devonport ; James 
Lowe, Alloa; William J. Rodd, Plumstead ; Francis C. Rendle, 
| Plymouth ; Thomas E. Heywood, Cardiff; James Paul, Wool- 
wich; Charles P. Raitt, Portsmouth; Charles H. Booth, 
Bolton ; Edward Howarth, Oldham; Percy Down, London ; 
Marshall H. Straw, Sneinton, Nottingham; R. Borlase 
Matthews, Swansea ; Samuel Crossley, Oldham. 
