April 12, 1883] 
_ NATURE 
571 
EDINBURGH 
Royal Society, March 19.—Prof. Maclagan, vice-president, 
in the chair.—Mr. Sang read a paper on the impossibility of 
inverted images in the air, in which he discussed the conditions 
as to density necessary for such an effect, concluding that these 
atmospheric conditions were so unstable as to make it physically 
impossible for clear images to be formed. The famous observa- 
tion by Vince of the erect and inverted images high up in air 
was, he maintained, simply the case of a vessel and its reflection 
in the sea, which was so calm as to be indistinguishable from 
the sky—the apparent horizon being the margin of a ruffled por- 
tion of the surface between the true horizon and the observer. — 
Prof, Tait communicated a note on the thermoelectric positions 
of pure rhodium and iridium, specimens of which had been 
supplied him by Messrs. Johnson and Matthey. The lines of 
these metals on the thermoelectric diagram were found to be 
parallel to the lead line, that is, according to Le Roux, the 
Thomson effect is 77/inthem. Uv fortunately the lines are too close 
to be of any practical use as a thermoelectric thermometer.—Dr. 
Christison gave the results of the observations on the growth of 
wood in deciduous and evergreen trees, which had been begun 
by the Jate Sir Robert Christison in 1878, and continued by him- 
self since Sir Robert’s death. It appeared that the evergreen 
trees began their rapid growth much earlier in the year than the 
deciduous trees, and stopped sooner. Hence the reason why the 
variations in growth in successive years did not follow the same 
law in these two classes—an early winter affecting the deciduous 
trees, a late winter the evergreen. The effect of wet seasons 
was also indicated, the deciduous trees being apparently more 
influenced.—Mr. Buchan read a paper on the variation of tem- 
perature with sunspots. The comparison was nt a direct 
one, but was based upon the well-known phenomenon of 
the diurnal barometric oscillation viewed in relation to the 
amount of water vapour in the air. From the observa- 
tions of the Challenger Expedition, Mr. Buchan had con- 
cluded that this diurnal variation over the open sea was not 
the result of changes of surface temperature (for these were very 
small), but was to be referred to the direct heating effect of the 
sun upon the air, or more strictly upon the water vapour in the 
air. This view was supported by the fact that over the sea the 
diurnal variation of pressure was greatest where most vapour 
was ; whereas the contrary held over the land, the temperature 
of which varied greatly during the day, and the more so when 
the air above was drier, as more heat then reached the earth, In 
other words, the increase of moisture in the air increases the 
barometric oscillation over the sea and diminishes it over the 
land ; and hence it seemed probable that the discussion of these 
daily oscillations in sun-spot cycles might lead to some definite 
result. The long-continued observations at Calcutta, Madras, 
and Bombay were combined in this way, and yielded a remark- 
able result—there being a well-marked maximum of barometric 
diurnal oscillation half way between the minimum and maximum 
sun-spot years, and a minimum half way between the maximum 
and minimum years. The averages were taken for the five dry 
winter months, and the effects were explained as due to the accu- 
mulated water vapour in the upper southerly winds that exist 
over India during these months. When the rainfall on the 
southern slopes of the Himalayas was similarly treated—which 
rainfall is of course due to the arresting of these upper moist 
currents—the analogous fact was brought out, viz. minimum 
rainfall at times of maximum barometric oscillation and vice 
vers, 
DUBLIN 
Experimental Science Association, March 13.—On 
Ayrton and Perry’s voltmeter, by Prof. Fitzgerald.—On an 
experiment on the resonance of flames, by H. Maxwell. A 
vibrating tuning fork when held in a gas or candle flame, 
or in the heated current of air above, was shown to have its note 
greatly strengthened. A current of unignited gas produced no 
perceptible strengthening of the note.—A thermal galvanoscope, 
by C, D. Wray, A method of showing to an audience the 
expansion of a wire under the heating influence of a current of 
electricity.—On a thermometer that can be read by telegraph, by 
J. Joly. An arrangement whereby the level of the mercury in a 
thermometer can be read by reckoning the number of contacts 
made with a battery in the home station. Suitable mechanism 
on the thermometer causes a wire to advance down the open tube 
of the thermometer, by a known minute distance, at each 
passage of the current. On reaching the mercury, a current 
passes to a galyanometer in the home station. 
SYDNEY 
Linnean Society of New South Wales, January 31.— 
C. S. Wilkinson, F.G.S., president, in the chair.—The follow- 
ing papers were read:—On a new form of mullet from New 
Guinea, by William Macleay, F.L.S., &c. This is a descrip- 
tion of a very remarkable freshwater fish from the interior of 
New Guinea, allied to Mugil, but constituting a new genus to 
which the author gives the name of Zschrichthys.—By J. J. 
Fletcher, M.A., B.Sc. The second part of his paper upon the 
anatomy of the urogenital organs in females of certain species of 
Kangaroos.—On remains of an extinct Marsupial, by Chas. W. 
De Vis, B.A, This is a very careful description of a number of 
bones found together and evidently of the same individual, by 
Mr. Henry Tryon, in Gowrie Creek, Darling Downs. The 
bones and teeth point to some bilophodont form, showing affinity 
with A/acropus and Palorchestes on the one hand, and with WVo‘o- 
therium and Diprotodon on the other.—Contributions to the 
ornithology of New Guinea, by E. P. Ramsay, F.L.S., &c. 
This contained a complete list of the birds recently brouzht by 
Mr, Goldie and others from the <outh-east part of the island.— 
On a new species of Tree Kanyaroo from New Guinea, by the 
sameauthor. This differs from Dendrolagus venustus in some 
particulars, and is named after the Marquis Doria. A new Rat 
(Hafpalotis Papuanus) was also described.—On some habits of 
Pelopeus letus and a species of Larrada, by Mr. H. R. 
Whittell.—Mr. Whittell also read a short paper on the voracity 
of a species of /eterostoma. He had observed one of these 
centipedes in the act of eatirg a live lizard. The aggressor, 
evidently finding his victim too powerful for his unassisted 
strength, had ingeniously taken a double turn with the posterior 
portion of his body around a small stem which was found con- 
veniently at hand, and so was enabled to continue his meal with- 
out interrurtion. 
BERLIN 
Physical Society, March 2.—Prof. Kirchhoff in the chair, 
—Dr. Konig reported on two optico-physiological researches, 
which he had carried out in consequence of his optical studies 
with the leucoscope. In the first he has, with the aid of a 
special apparatus, examined a number of colour-blind per-ons as 
to the position in the spectrum of their so-called ‘‘neutral’’ point. 
According to the Young-Helmboltz theory, it is known, there are 
three primary colours (red, green, and violet), each of which 
produces its special colour-sensation, while all combined give 
the impression of white. The sen-ibility for the three primary 
colours is so distributed over the spectrum that their curves in 
great part coincide on the abscissa of wave-lengths, and there- 
fore mixed colour-sensations occur everywhere, while the maxima 
of the separate curves occur at the places of brightest red, green, 
and violet respectively. In the case of the colour-blina one 
curve is wanting, and the two remaining ones have therefore a 
point of section where their ordinates are the same. Hence the 
eye must at this part have the impression of white or grey. For 
finding this neutral point in the spectrum, an apparatus served, 
in which the telescope of a spectroscope was so arranged with 
regard to the non-refringent angle of the prism that the spectrum 
took up only half of the field of vision, while the other half was 
occupied with the image of the white-painted ground-surface of 
the prism. Instead of the eyepiece there was another slit in the 
telescope, in which one saw only a small section of the spectrum ; 
by micrometric displacement of the collimator of the spectral 
apparatus any part of the spectrum could be brought on the 
sht. Now ata particular part of the spectrum the coJour-blind 
person saw both halves of the field of vision white, while the 
person with normal vision saw the part of the spectrum in 
question in its normal colour, and so could determine the wave- 
length at which the neutral point of the colour-blind person 
occurred. Changes of light-intensity displaced the neutral 
p int; hence in comparative measurements care must be taken 
to have the same intensityin the source of light. Such mea- 
surements were made by Dr. Kénig with great precision on 
nine colour-blind persons, and it appeared that the neutral points 
are situated between about 491 aid 500 millionths of a milli- 
metre, and (what is of special interest theoretically) that the 
mean values of the separate observations with different colour- 
blind persons were not equal, but varied in a pretty regular 
series between the two terminal values. According to the 
common view that colour-blindness depends on the disappear- 
ance of one of the normal three curves of colour-percep- 
tion, the position of the neutral point as point of section of 
the two curves present must be always the same, and for the 
