June 24, 1915] 
NATURE 
473 


systems, as these can readily be arranged in a form 
suitable for logarithmic calculation. When a calculat- 
ing machine is available such computations can be 
carried out more expeditiously by using algebraic 
formula; in form these correspond with the expres- 
sions for paraxial rays, and a comparison of the 
numerical result is likely to suggest what alterations 
should be made when a general ray does not behave 
as desired. If the two points in which a general ray 
meets an axial plane are defined as conjugate points, 
all pairs of conjugate points on a ray are connected 
by the same relations as hold for object and image 
points for paraxial rays, and the theory for paraxial 
rays can be extended to rays in general by placing a 
suitable interpretation on magnification, etc. The 
definition of conjugate points can be extended to 
include rays lying in axial planes, in which case the 
one point marks the intersection of the ray with the 
radial focal line formed by rays passing through its 
conjugate.—H. R. Nettleton: The accuracy of the lens 
and drop method of measuring refractive index. A 
simple arrangement for comparing on an optical bench 
the refractive indices of liquids for monochromatic 
light by the lens and drop method is described. The 
accuracy and sensibility of the method are discussed. 
Attention is directed to the accuracy obtainable in 
measuring a small radius of curvature of a lens face 
in terms of the well-known refractive index of water, 
and in measuring the refractive index of the glass of a 
lens. 
Royal Meteorological Society, June 16.—Prof. H. H. 
Turner: Discontinuities in meteorological phenomena. 
Meteorological history is divided into ‘‘chapters”’ 
averaging 63} years long, with abrupt changes (or 
‘discontinuities,’ as the author calls them) between. 
The dates of change are apparently settled by the 
movement of the earth’s axis. They oscillate about 
mean positions in a cycle of 40:5 years, which appears 
in Briickner’s collected ‘‘cold winters’’ for 800 years; 
in Nile flood records for tooo years; and in measures 
of Californian tree rings for 520 years. The chapters 
are alternately hot: and cold, wet and dry, as shown 
by rainfall and temperature records at Greenwich, 
Padua, and Adelaide.—C. Harding : Battle weather in 
western Europe, nine months, August, 1914, to April, 
1915. The author briefly described the weather con- 
ditions bordering on the battle area of the western 
front. At the commencement of the war generally 
bright and dry weather prevailed, with occasional 
short spells of rain, but from mid-October to the end 
of February rainy and rough weather continued with 
but little cessation. Taking widely distributed stations 
over the British Isles, it was shown that the rainfall 
for the nine months in the north and west was below 
the average, but in the south and south-east it greatly 
exceeded the normal. With the western Continental 
stations the rainfall for the same period was every- 
where excessive. The author says :—‘‘It is not sug- 
gested that in the recent wet weather the rainy con- 
ditions have been generated by gun-firing, but it seems 
quite possible that at times, when the conditions are 
favourable to rain, the rains have been augmented 
or accelerated by the concussion initiated over the 
battle-grounds.” 
DUBLIN. 
Royal Irish Academy, June 
of Bladensburg, vice-president, in the chair.— 
H. Ryan and Miss P. O'Neill: Studies‘ in 
the diflavone group. II.—Derivatives of diflavan- 
one. By the action of benzaldehyde on _ diaceto- 
resorcinol four isomeric substances were obtained. 
Three of these were cis-trans stereoisomeric dihydroxy- 
dichalkones, and the fourth was a structural isomeride 
of the others. o-Dihydroxydichalkone in the presence 
NO. 2382, VOL. 95] 
14.—Sir John Ross 

of alcoholic hydrochloric acid condensed with benz- 
aldehyde, anisaldehyde, and piperonal, to yield di- 
benzylidene, dianisylidene, and  dipiperonylidene 
derivatives of diflavanone. It was also found that 
dibenzylidenediflavanone can be obtained directly from 
diacetoresorcinol by condensation with excess of benz- 
aldehyde in the presence of alcoholic hydrochloric acid, 
and in the same way the authors obtained dipiperonyl- 
idenedimethylenedioxydiflavanone. The latter method 
was also found well suited for the preparation of 
analogous monoflavanone derivatives, and was applied 
to the preparation of the flavindogenides derived trom 
gallacetophenonedimethylether on the one hand, and 
benzaldehyde, anisaldehyde and piperonal on the other, 
Paris. 
Academy of Sciences, June 7.—M,. Ed. Perrier in the 
chair.—A. Lacroix: Some remarkable contact meta- 
morphic phenomena of Madagascar granite. A de- 
scription of a new type of amphibole, termed imerinite, 
intermediate between the richterites and glaucophanes ; 
petrographic examination proved the presence of mon- 
azite as well as other minerals. As the presence of the 
monazite appeared singular, several grams were 
isolated and analysed and proved to contain 1-05 per 
cent. of thoria, ceria, 39:51 per cent. oxides of 
lanthanum and didymium, 27-8o per cent. The thorium 
is unusually low.—G. Bigourdan ; Equatorial observa- 
tions of comets, minor planets, etc., made between 
1880 and 1904.—Jules Amar; Functional re-education. 
A description of a new arthrodynamometer for measur- 
ing the values of the angular displacements of the 
limbs and absolute forces exerted by groups of muscles 
in the case of invalids recovering from wounds.—M. 
Agnus ; The echo of the ball and shell. An explanation 
of the double detonation heard on the discharge of a 
rifle or gun.—Stanislas Meunier: The structure of the 
Kodai Canal meteorite (India); an example of cata- 
clasis in meteoric irons.—P. Maze: The réle of chloro- 
phyll. The author regards the pigments in the higher 
plants as possessing a purely physical function, and 
considers the direct controlling action of chlorophyll 
on the assimilation of carbon dioxide as doubtful. 
Em. Bourquelot and A, Aubry: A comparative study 
of the influence of acetic acid on the synthetising and 
hydrolysing properties of a-glucosidase (glucosidase 
from low yeast, air dried). This ferment is very 
sensitive to the poisonous action of acids. It is 
destroyed in liquids containing very small proportions 
of acetic acid, and the fact that the two properties 
of synthesis and hydrolysis disappear simultaneously 
under the influence of these quantities demonstrates 
that both properties belong to one and the same 
enzyme. 
June 14 —M.. Ed. Perrier in the chair.—].- 
Boussinesq : The approximate calculation of the effect 
of climate on the velocity of increase of temperature 
with depth in the soil.—C. Guichard ; The W congruences 
which belong to a complex of the second order, Case 
where the equation in S has a triple root.—Pierre 
Delbet : Pyoculture. Pus from a wound is suggested 
as the culture medium in vitro. It is concluded that 
if the general and local conditions are such that the 
patient cannot make headway against the micro- 
organisms, then the latter will multiply rapidly in the 
pus secreted. If, on the contrary, the conditions are 
favourable, then the pus will be a less suitable medium 
of growth than the ordinary media. These hypotheses 
have been confirmed experimentally, and details of the 
method of applying them in practice are given.— 
Ernest Lebon: A new table of divisors of nuimbers.— 
E. Bompiani: The linear element of hyper-surfaces.— 
Arnaud Denjoy : Derived numbers.—Thadée Peczalski : 
Researches on thermal conductivity. A description of 
a new arrangement for the determination of the 

