June 5, 1902] ' 
grounds, that the imaginal limb is a distinct structure from the 
larval limb during the instar preceding pupation.—On the unit 
of classification for systematic biology, a reply to Mr. Bernard, 
by Mr, J. Stanley Gardiner.—Remarks on Marconi’s system of 
telegraphy, by Mr. H. M. Macdonald.—On trinodal quartics, 
by Mr. A. B. Basset.—On a definite integral, by Mr. T. J. I'A. 
Broimwich.—Reflection and transmission of light by a charged 
metal surface, by Mr. P. V. Bevan.—Note on a_ general 
numerical connection between the atomic weights, by Mr. C. A. 
Vincent. Ifa list of all the atomic weights in ascending order 
of magnitude be taken and the order in this list be called 7, 
then the wth atomic weight, from #=3 to 2=60, is given by 
the equation 
W=(2+2)P21, 
If the atomic weights are from Clarke’s 1gor list with hydrogen 
as unit, then the greatest difference between the computed and 
determined value will not exceed 4 units, nor will the error ever 
be greater than 5 per cent. ; in thirty-six cases the result will 
not be a unit wrong and in twenty cases will not be 1 per cent. 
wrong ; the mean error for the whole fifty-eight elements con- 
sidered is about 1°005, the mean percentage error about 1°6. 
By replacing +2 of the above formula by N, and taking N as 
indicating the order in an augmented list of the elements, the 
formula may be made to embrace the whole of the seventy-seven 
elements now definitely known. This necessitates predicting 
an element between hydrogen and helium and one between 
helium and lithium. No other gaps are left until after samarium, 
when in order to complete the list it is necessary to assume 
elements in various places, making fifteen gaps in all. The 
thirteen gaps introduced after samarium are in general accord 
with those predicted by the periodic table.—On radioactive 
rain, by Mr. C. T. R. Wilson. As the experiments of Elster 
and Geitel and of Rutherford have shown, a negatively charged 
body exposed in the atmosphere becomes radioactive, apparently 
showing the presence of some radioactive substance in the 
atmosphere ; it occurred to the author to test whether any of 
this radioactive substance is carried down in rain. Freshly 
fallen rain-water (less than 50 c.c. was generally used) was 
found when evaporated to dryness’ to leave behind a radioactive 
residue. The radioactivity was detected by means of the 
increase in the ionisation of the air within a small vessel, of 
which the top, or, in other experiments, the bottom, was of thin 
aluminium or of gold-leaf, the other walls being of brass. The 
metal surface on which the rain had been evaporated was placed 
close up to the aluminium or gold-leaf, and the rate of move- 
ment of a small gold-leaf which served to measure the ionisation 
was observed (v. Roy. Soc. Proc., vol. Ixviii. p. 151). In many 
cases the radioactivity obtained from the rain was sufficient to 
increase the ionisation five- or six-fold. From the evaporation 
of distilled water, of tap-water or of rain-water which had 
stood for many hours no radioactivity was obtained. Like the 
induced radioactivity obtained on a negatively charged body, 
that derived from rain gradually dies away, falling to about half 
its initial value in the course of an hour.—On the increase in 
the electrical conductivity of air produced by its passage through 
water, by Prof. J. J. Thomson. In continuation of the experi- 
ments brought before the Society last term, the author investigated 
the effect produced on the conductivity of air by bubbling it 
through water. The air from a large gas-holder of about 350 
litres capacity was bubbled vigorously through water by making 
the air in the vessel circulate through a water-pump; this 
treatment increased the conductivity of the air, and when the 
bubbling had been going on for some time the conductivity of 
the air was ten or twelve times the initial conductivity. When 
once the air has been put in this highly conducting state it stays 
in it for a very considerable time; a large part of the con- 
ductivity produced by the bubbling remains in the air forty-eight 
hours after the bubbling has ceased, nor does it disappear when 
an intense electric force is kept applied to the gas. The 
effect produced by the passage of the air through water is 
similar to that which would be produced if the bubbling pro- 
duced a radioactive ‘‘emanation”’ similar in properties to those 
emitted by thorium and radium. The conducting gas can be 
passed from one vessel to another; it retains its conductivity 
after passing through a porous plug; passage through a long 
tube heated to redness destroys the conductivity ; it takes, how- 
ever, a very high temperature to do this, temperatures less than 
300° or 400° C. seem to produce comparatively little effect ; if 
the gas is passed very slowly through a long tube filled with 
beads moistened with sulphuric acid, the conductivity is 
NO. 1701, VOL. 66] 
NATURE 
143 
destroyed ; unless, however, the stream of gas is very slow, the 
air retains a good part of its conductivity in spite of the sul- 
phuric acid. Another point of resemblance between the 
“emanation” from radioactive substances and a gas in this 
state is that if astrongly negatively electrified conductor be kept 
in the gas for some time, the conductor becomes radioactive. 
DUBLIN. 
Royal Irish Academy, May 26.—Dr. R. Atkinson, 
president, in the chair.—Prof. Grenville A. J. Cole read a 
paper on Composite Gneisses in Boylagh, West Donegal, 
in which he urged that the essential features of the foliation in 
the gneissoid granite from Ardara to Finntown were due to 
conditions of original flow, and not to subsequent dynamo- 
metamorphism. He attributed the darkened types of granite, 
with a specific gravity of about 2°74, to admixture of the pure 
aplitic intrusive rock (specific gravity about 2°59) and the 
already foliated schists. The foliation in the granite is com- 
monly accompanied by numerous residual flecks of schist, and 
larger elongated inclusions occur which have retained the strike 
of the masses of which they once formed a part. Subsequent 
shearing has here and there produced mylonitic structures, but 
the granite was converted into a gneiss by its mode of intrusion, 
under mountain-building pressures, along the planes of separ- 
ation of an altered sedimentary series, The gneisses of Boylagh 
are thus almost all of composite origin, and the foliated masses 
and limestone bands lying in the central granite of Donegal, 
and running with so persistent a N.E. and S.W. strike, repre- 
sent the undissolved residue of an anticlinal mass composed 
originally of numerous parallel folds. The trend of these folds 
and of the granite axis points to their establishment in the 
Caledonian epoch of mountain-building. The later pegmatitic 
veins which cut them, and which are not affected by the folding, 
may, then, be of Devonian age. 
PARIS, 
Academy of Sciences, May 26.—M. Bouquet de la Grye 
in the chair.—The motor muscle employed in the production of 
positive work. The comparison with inanimate motors, from 
the point of view of the dissociation of the several constitutive 
elements of the energy expenditure, by M. A. Chauveau.—On 
the ethology of the larva of Sciara medullaris, by M. Alfred 
Giard. The biological history of the larvae of Sciara is 
dominated and directed by the conditions of the humidity of the 
medium in which the organism is placed.—The synthesis of 
petroleum: contribution to the theory of formation of natural 
petroleum, by MM. Paul Sabatier and J. B. Senderens (p. 138). 
—On the rays of convergence of a double series, by M. Eugene 
Fabry.—On the general exponential representation and some of 
its applications, by M. L. Desaint.—On functions of complex 
variables, by M., D. Pompéiu.—The receiver in wireless tele- 
graphy, by M. Edouard Branley. The receiver in common 
use in wireless telegraphy has a radioconductor containing a fine 
metallic powder. Owing to the numerous contacts, these tubes 
are sometimes a little variable in their behaviour, and in 
attempting to increase the regularity of working the author has 
recognised that a radioconductor of the type oxidised metal- 
polished metal is the best, as it not only possesses the required 
regularity of working, but is more sensitive than the ordinary 
type. A description and figure of the instrument that has been 
found to give the best results is given.—On the electric dis- 
charge in flames, by M. Jules Semenov. In electric discharge 
in flames it was found that the negative pole heats much more 
than the positive pole, the negative pole being the seat of a 
phenomenon of a reflux of material particles the direction of 
which appears to be independent of the relative position of the 
two poles.—On the temperature of the electric arc, by M. Ch. 
Féry. The optical pyrometer of Chatelier was modified by the 
introduction of a thin prism of absorbent glass for the production 
of the photometric equilibrium. The temperatures thus observed 
with prisms of red and green glass were compared directly with the 
readings of a platinum-rhodium platinum couple, the results 
being in very close agreement up to 1500’ C., the highest tem- 
perature attainable with the couple. Within these limits the 
law of Wien was found to be verified, and these results were 
then extended to the case of the temperature of the electric 
arc. The value found, 3882° C., differs considerably from the 
value found by Chatelier, 4100° C., from which the conclusion 
is drawn that carbon does not behave at its boiling point as a 
perfectly black substance.—Fields of force of bipolar diffusion, 
by M. S. Leduc.—On the modifications brought about by self- 
