FEBRUARY 4, 1904] 
NATURE 335 
Titherley and J. F. Spencer.—The action of heat on 
d-hydroxycarboxylic acids: H. R. Le Sueur. A descrip- 
tion of the aldehyde produced by heating a-hydroxystearic 
acid.—The fusicn of iso-pilocarpine with caustic potash : 
H. A. D. Jowett. It is shown that the acid produced in 
this reaction is n-butyric acid, and not the iso acid as. was 
formerly supposed.—Organic derivatives of silicon: F. S. 
Kipping. A description of the products obtained by the 
interaction of magnesium alkyl haloids with silicon and 
alkyl silicon chlorides.—Derivatives of highly substituted 
D. Chattaway and J. M. Wadmore. 
Physical Society, January 22.—Dr, R. T. Glazebrook, 
F.R.S., president, in the chair.—Notes on non-homocentric 
pencils, and the shadows produced by them. (1) An 
elementary treatment of the standard astigmatic pencil : 
W. Bennett. It is shown that several of the properties 
of the standard astigmatic pencil, and the variations in the 
form of its cross section, can be simply deduced from a con- 
sideration of the projections of its rays upon two planes, 
each of which is at right angles to one of the two focal lines. 
The projections of the rays are in each case concurrent. The 
shadow of a straight wire at right angles to the axis is also 
dealt with, and it is shown that the rays intercepted by the 
wire are one set of generators of a hyperbolic paraboloid. 
The section of this surface by any other plane is a hyperbola 
or a parabola. The rays are seen to be all parallel to a 
plane through the axis. If the object wire is not at right 
angles to the axis the shadow surface is a hyperboloid of 
one sheet. The section by any plane is, in general, a hyper- 
bola, which is rectangular when the plane is at right angles 
to the axis and reduces to two straight lines when the plane 
passes through either of the focal lines. The asymptotes 
of the rectangular hyperbolas lie in two planes which 
pass respectively through the two focal lines. The author 
showed string models of the various pencils and shadow 
surfaces and of pencils produced by lenses or mirrors. 
The paper concludes with a simple method for obtaining, by 
the method of sagittze, the positions of the approximate 
lines produced in a small pencil refracted obliquely through 
a lens.—Some new cases of interference and diffraction : 
Prof. R. W. Weed. In this paper Prof. Wood discusses 
certain types of the interference of light which have been 
known for many years, as well as some cases which he 
thinks are quite new. The colours of mixed plates and the 
phenomena of interference in transparent films deposited on 
metallic reflectors are the cases chiefly considered. The 
facts which have been brought out may be summed up as 
follows. The colours of mixed plates are due to diffraction, 
and should not be classed with interferences in their films. 
The explanation originally given by Young, and the treat- 
ment given by Verdet and others, are unsatisfactory, and 
do not indicate what becomes of the energy. In the cases 
of films deposited on perfectly reflecting surfaces, which, 
according to the elementary theory, should exhibit no inter- 
ference colours, we may, under certain conditions, have 
colours far more brilliant and quite as saturated as any 
shown by the soap bubble. In other cases, where at first 
sight no interference appears to have taken place, we may, 
by employing polarised monochromatic light, obtain fringes 
of a very curious nature, which are the result of the inter- 
ference between the elliptical vibration comin& from the 
metal surface and the plane-polarised vibration reflected 
from the surface of the transparent film.—On the photo- 
graphic action of radium rays: S. Skinner. It is well 
known that a photographic plate by exposure to radium 
rays is affected in such a way that the plate develops 
similarly to its development after exposure to light. The 
experiments described in the paper are an attempt to answer 
the question: Are the actions the same? So far as can be 
seen, the final results of the actions and developments are 
the same, and the experiments appear to indicate that only 
slight differences occur in the early stages. 
anilines: F. 
Entomological Society, January 20.—The 7oth annual 
meeting, Prof. E. B. Poulton, F.R.S., president, in the 
chair.—It was announced that the following had been 
elected officers for the session 1904-5 :—President, Prof. 
Edward B. Poulton, F.R.S.; treasurer, Mr. 
McLachlan, F.R.S.; secretaries, Mr. Herbert Goss and 
Mr. H. Rowland-Brown.—The President delivered an 
No. 1788, VOL. 69] 
Robert | 
| there to fill the vacancy 
| breeding 
| definitions, 
address on the subject of ‘* What is a Species?’’ What is 
left by the disappearance of the 
Linnean conception, founded on “‘ special creation’’? In 
many respects it would be advantageous to abandon the 
word, or to use it solely with its original logical meaning 
of ‘‘ kind,’’ or, as zoologists would say, ‘‘ form.’’ This 
view was, however, regarded as a “‘ counsel of perfection,’’ 
impossible of attainment; and the attempt was made to 
show that the conception of a naturally and freely inter- 
(or syngamic) community lies behind the usuak 
and that the barrier between species not 
but simply cessation of interbreeding or asyngamy- 
is 
sterility, 
Paris. 
Academy of Sciences, January 25.—M. Mascart in the 
chair.—On certain doubly periodic solutions of some partial 
differential equations : Emile Picard.—On the light emitted 
spontaneously by certain salts of uranium: Henri 
Becquerel. Some salts of uranium emit light continuously 
and with an intensity which is greater than would be ex- 
pected from their radio-activity. The effects are best shown 
by the double sulphate of uranyl and potassium, and there 
is a relation between the luminosity and the phosphor- 
escence, since different preparations of this double salt un- 
equally phosphorescent to light are also unequally luminous 
in the dark. The effects observed are so small that it is 
necessary for the observer to be in the dark for some time 
before attempting an experiment. Crystals of the double 
sulphate exposed to the intense radiation of an electric arc 
or of a radium salt, and then examined some seconds later 
in the dark, were no more luminous than specimens of the 
same salt which had been kept continuously in the dark. 
The light was too feeble to permit of the examination of 
the spectrum.—Some new observations on Piroplasma 
Donovani: A, Laveran and M. Mesnil. This parasite, 
first found by Dr. Donovan in cases of a fever common near 
Madras, would also appear to be the cause of a disease 
known as Kala-Azar, or the black fever of the valley of 
Brahmapootra.—M. Calmette was nominated a_ corre~ 
spondant for the section of medicine and surgery in the place 
of M. Laveran, elected a member in the same section.—The, 
examination of the gases given off or occluded by radium 
bromide: MM. Dewar and Curie. <A specimen of pure 
radium bromide was placed in a vacuum in connection with 
a manometer; gas was found to be evolved at the rate of 
about 1 c.c. per month, which on spectroscopic examination 
proved to be hydrogen, most probably produced by the 
action of the radium compound upon a small quantity of 
water present. The same specimen, placed in a quartz tube, 
was heated to redness, any gases given off being removed 
by the mercury pump. These gases were drawn through 
tubes cooled down to the temperature of liquid air. The 
gas which passed through the tube cooled in liquid air 
was radio-active and strongly luminous, spectroscopic ex- 
amination of the light emitted showing the three principal 
bands of nitrogen. The quartz tube containing the radium 
bromide was then sealed off with the oxyhydrogen blow- 
pipe. Twenty days later M. Deslandres found that the tube 
gave the complete spectrum of helium, and no other rays 
could be detected.—On an electrical law of the electricat 
transportation of dissolved salts: A. Ponsot. From the 
experimental results of M. Chassy, laws are deduced which 
are in opposition to the hypotheses on which M. Kohlrausch 
has relied in deducing the molecular conductivity of solu- 
tions from the migration numbers.—On certain phenomena: 
arising from physiological sources capable of being trans- 
mitted along wires formed of different substances : Augustin 
Charpentier. The physiological radiations, probably 
identical with the n-rays, can be transmitted through a 
metallic wire as well as through the air. This allows of 
a much more precise study of these rays from a physio- 
logical point of view, one great advantage of the method 
being that the observer may be placed so far from the 
sensitive screen as to reduce to a minimum muscular or 
mental effects foreign to the experiment.—The emission of 
the Blondlot rays during the action of soluble ferments - 
M. Lambert. The n-rays are produced during the action 
of ferments, the effect being particularly marked for the 
digestive ferments of albumenoid materials.—On the fluo- 
chlorides, the fluobromides and the fluoiodides of the metals 
