JUNE 17, 1915] 
NATURE 
445 

photometric observations extend the observations of 
Z Draconis over nearly 7000 periods and of RT Persei 
over nearly 11,000 periods. Visual and photographic 
light-curves were compared. 
R. J. McDiarmid: ‘‘The Variable Stars TV, TW, 
and TX Cassiopeiz.”’ 
A brief discussion of the light-curves of the variable 
stars TV, TW, TX Cassiopeiz and T Leonis Minoris 
Was given, pointing out interesting features in con- 
nection with each system. In the system TV Cass. 
we have two stars of nearly the same size but of 
different surface brightness, the ratio being 5-5 to 
ro. In this system other points of interest are 
brought out, such as the reflection and _ ellipticity 
effects. The system TW Cass. represents two stars 
of almost equal brightness and of nearly the same 
size, moving in an eccentric orbit. In the third system 
TX Cass. the two stars are very unequal in size with 
a ratio of surface brightness of 1-0 to 1-5. The stars 
are ellipsoidal in shape, giving rise to an ellipticity 
effect shown by the light-curve. The system is of 
special interest, as there seems to be little doubt of 
its being similar to the sun, bright at the centre, 
decreasing in brightness towards the limb. T Leonis 
Minoris is an eclipsing variable. The ratio of the 
surface of the two stars in the eclipsing system 
T. Leonis Minoris is 1 to 25. 
Dr. Edwin B. Frost: ‘Radial Velocities in 
Orion Nebula.” 
The investigations of the nebula in Orion by Messrs. 
Bourget, Fabry, and Buisson, of Marseilles, pub- 
lished in the Astrophysical Journal for October, 1914, 
show that the photographic interferometer method can 
be applied successfully to the study of the radial velo- 
cities of the nebula, both as a whole ‘and in its 
separate parts. Their conclusion that there are appre- 
ciable motions in closely adjacent portions of the 
nebula have been confirmed by observations made 
the 
recently with the Bruce spectrograph. Differences 
of more than to km. per second in the _ velo- 
city in the line of. sight have been found, and 
the general effect of rotation of the nebula inferred 
by the French observers is confirmed by the spectro- 
graph. 

UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE. 
BrrMINGHAM.—The council has decided that in the 
existing circumstances of national stress the ordinary 
annual degree congregation with its attendant cere- 
monial and festivity would be inappropriate. All 
degrees this year will therefore be granted in absentia. 
Dr. T. Sydney Short has been appointed Ingleby 
lecturer for 1916, and Dr. Douglas Stanley has been 
appointed honorary examiner for the Russell Memo- 
rial Prize for the current year. 

Tue Board of Trinity College, Dublin, has appointed 
Miss E. M. Maxwell, of the Royal Victoria Eye and 
Ear Hospital, Dublin, to the Montgomery lectureship 
in ophthalmology, the establishment of which was 
announced in Nature of February 25 last. 
We have received from Washington a copy of the 
report of the librarian of Congress and of the super- 
intendent of the library building and grounds for the 
financial year ending June 30, 1914. It is interesting 
to note that in 1897 the library comprised about 
850,000 printed volumes and pamphlets and about 
500,000 other articles—manuscripts, maps, and prints; 
and_a staff of forty-two persons. The grants for the 
purchase of books was 6oool. a year, and for printing 
and binding 5oool. At the date of the report the 
NO. 2381, VOL. 95] 

grant for the purchase of books had increased to 
20,000l., the statf in the library proper was 385, and 
the number of books had reached two millions, and 
the other articles another million. In other words, 
the collection is now in size third among those of the 
world. We have also received from the Library of 
Congress a catalogue of the publications issued by the 
library since 1897. 

SOCIETIES AND ACADEMIES. 
LONDON. 
Royal Society, June 3.—Sir William Crookes, presi- 
dent, in the chair.—Prof, C. H. Lees: The shapes of 
the equipotential surfaces in the air near long build- 
ings or walls, and their effect on the measurement 
of atmospheric potential gradients. The shapes of the 
equipotential surfaces are determined, and the equi- 
potential lines drawn to scale in the following cases ;— 
(1) A thin vertical wall; (2) a retaining wall separating 
a lower from a higher horizontal plane; (3) a series 
of equidistant parallel vertical walls. In each case the 
normal vertical potential gradient may be calculated 
from observations of the potential at any point. A 
point on each wall is indicated at which the horizontal 
potential gradient is identical with the normal vertical 
gradient.—Prof. O. W. Richardson: The influence of 
gases on the emission of electrons and ions from hot 
metals. As is well known, the thermionic saturation 
current 7 is expressed accurately and quite generally 
over wide ranges of temperature by the equation 
i=ATze—>/T, In the case of metals, in particular, the 
equation is satisfied when the metals are contaminated 
by the presence of a gaseous atmosphere, as well as 
when the surfaces of the pure metals are tested. In 
general, however, the effect of the contaminating gas 
is to cause large changes in the values of the constants 
A and b. The changes which are thus brought about 
in these constants are considered in the present paper. 
So far as it may be considered trustworthy, the avail- 
able evidence shows that A and b for a given metal 
always change together in such a way that the change 
in logA is proportional to the change in b. This 
linear relation is very closely satisfied by the results of 
all Langmuir’s observations with tungsten, for which 
substance different gases change A by as large a factor 
as 10%. A similar relation, with an almost equal 
coefficient of proportionality, is required by the best 
observations on the negative emission from platinum, 
In the case of tungsten, contaminants cause an in- 
crease in A and b, whereas with platinum a diminu- 
tion occurs. All the known data point to the existence 
of a similar law governing the steady emission of. 
positive ions from platinum. By applying thermo- 
dynamic considerations to the emission of electrons 
from contaminated surfaces, it is shown to follow 
from the linear relation between log A and b, that the 
contact potential difference between the pure and the 
contaminated metal is of the form a,(1—aT), where 
the constant a, has opposite signs for tungsten and 
platinum, and a has approximately the same value for 
both metals. T is the absolute temperature.—Prof. 
J. W. Nicholson: The band spectrum associated with 
helium. Fowler has concluded recently that the heads 
of the bands in the new spectrum associated with, and 
perhaps due to, helium follow laws of the type hitherto 
peculiar to line-series. A further examination of some 
points which were in doubt has been made with the 
following results:—(1) The paper supports the con- 
clusion that the heads of the bands in the spectrum 
of Goldstein and Curtis follow ordinary series laws by 
showing that the doublet separations actually tend to 
zero at the limits of the series; (2) both the doublet 
