522 
NATURE 
[| March 29, 1883 
Hartley, M. de Chardonnet, and other investigators, For these 
observations the spark of an induction coil, with Leyden jar, 
between iron electrodes, was generally used as the source of 
light. The lines of iron are so multitudinous, and so closely set 
ina large part of the ultra-violet region of the spectrum, that 
they form almost a continuous spectrum, at the same time there 
are amongst them a sufficient number of breaks and conspicuous 
lines to serve as points of reference. The optical train used was 
wholly of quartz, and the spectra were all photographed. 
Chlorine in small quantity shows a single absorption band 
extending from about N (3580) to T (3020). As the quantity of 
chlorine is increased this band widens, expanding on both sides, 
but rather more rapidly on the less refrangible side. Different 
quantities of chlorine produced absorption from about H (3968) 
to wave-length 2755, from wave-length 4415 to 2665, and from 
wave-length 4650 to 2630. With the greatest quantity of 
chlorine tried, the absorption did not extend above wave-length 
2550. 
Bromine vapour in small quantity absorbs light up to about L 
(3820), and is quite transparent above that. With larger quan- 
tity the absorption increases, gradually extending with increase 
of bromine vapour from L to P (3360); and at the same time 
there is a gradually increasing general absorption at the most 
refrangible end of the spectrum beginning at about wave-length 
2500; so that the denser bromine vapour is transparent for a 
band between wave-length 2500 and 3350. 
Liquid bromine in very thin film between two quartz plates is 
transparent for a band between wave-length about 3650 and 
3400, shading away on both sides, so that below M on one side 
and above P on the other the absorption seems complete. The 
transparency of the liquid film ends on the more refrangible side 
just where that of the vapour begins. 
Iodine vapour tolerably dense cuts off all within the range of 
our photographs below wave-length 4300, and its absorption 
gradually diminishes from that point up to about wave-length 
4080; from that point it is transparent. Denser vapour pro- 
duces complete absorption up to 4080 and partial absorption 
above that point. 
Comparing the absorptions of the three haloid elements, the 
principal band shifts towards the less refrangible side with 
increasing atomic weight, as Lecoq de Boisbaudran has noticed 
in the case of lines corresponding to one another in the spectra 
of groups of similar metals. 
Iodine dissolved in carbon disulphide is transparent for a band 
between G and H, cutting off all above and below. It is not 
possible to tell how much of the light above M (3727) is absorbed 
by iodine in such a solution, inasmuch as carbon disulphide is 
opaque for rays more refrangible than M, 
Iodine dissolved in carbon tetrachloride when the solution is 
weak shows only the absorption due to the solvent, described 
below. More iodine increases the absorption until it is complete 
above P (3360), with shading edge as far down as about wave- 
length 3400. 
Sulphurous acid gas produces an absorption band which is 
very marked between R (3179) and wave-length 2630, and a ! 
fainter absorption extending on the less refrangible side to O 
(3440), and on the other side to the end of the range photo- 
graphed, wave-length 2300. 
Sulphuretted hydrogen produces complete absorption above 
wave-length 2580. Below that a partial general absorption. 
Vapour of carbon disulphide in very small quantity produces 
an absorption band extending from P to T, shading away at 
each end; no absorption in the higher region. With more 
vapour the absorption band widens, extending from about wave- 
length 3400 to 3000, and a second absorption occurs beginning 
at about wave-length 2580, and extending to the end of the 
range photographed. 
Carbon tetrachloride liquid produces an absorption band with 
a maximum about R, extending, but with decreasing intensity, 
up to Q (3285) on one side, and to s (3045) on the other. In 
the higher region there is a second absorption sensible about 
wave-length 2600, and increasing in intensity up to about wave- 
length 2580, beyond which point it is complete. 
Chlorine peroxide gives a succession of nine shaded bands, at 
nearly equal intervals, between M and S, with faint indications 
of others beyond. In the highest region this gas seems quite 
transparent. 
A slice of chrome-alum a quarter of an inch thick is trans- 
parent between wave-lengths 3270 and 2830; its absorption 
rapidly on the more refrangible side than on the other, and be- 
comes complete below about wave-length 3360 and above wave- 
length 2730. 
A very thin plate of mica shows absorption beginning about 
S (3100), rapidly increasing above U (2947), and complete above 
wave-length 2840. 
A thin film of silver precipitated chemically on a plate of 
quartz transmits well a band of light between wave-length about 
3350 and 3070, but is quite opaque beyond those limits on both 
sides. 
A thin film of gold similarly precipitated merely produces a- 
slight general absorption all along the spectrum. 
The difference between the limits of transparency of Iceland 
spar for the ordinary and extraordinary rays, inferred from 
theory, was found to be very small, and hardly to be detected 
without using a considerable thickness, three inches or more, of 
the spar. 
The authors had expected to be able to apply the well-known 
photometric method by means of polarised light to the compari- 
son of intensities of ultra violet rays. Ordinary Nicol’s prisms 
are not applicable to ultra-violet rays on account of the opacity 
of the Canada balsam, with which they are cemented, so Fou- 
cault’s prisms were used. Upon taking photographs of the 
spectrum of the iron spark through this pair of prisms at various 
inclinations between the planes of polarisation of the two prisms, 
it was found that for the whole range between the position of 
parallelism and the inclination of 80° there was no sensible dif- 
ference of effect upon the photographic plate, though the length 
of exposure was in all cases the same. For inclinations between 
80° and go° there was a sensible and increasing diminution in the 
photographic effect as the planes of polarisation of the polariser 
and analyser were more nearly at right angles to one another. 
It seems to follow from this that the full photographic effect on 
the dry gelatine plates used ensues when the intensity of the 
light reaches a certain limit, but that for intensities of light 
beyond that limit there is no sensible increase in the effect until 
the stage of solarisation is reached, 
Chemical Society, March 15.—Dr. Gilbert, president, in 
the-chair.—Dr. Gilbert will resign the presidential chair at 
the end of the session.—The Council have proposed Dr. W. 
H. Perkin to fill the vacancy, and Mr. J. Millar Thomson 
to be Secretary.—The following papers were read :—On some 
condensation-products of aldehydes with aceto-acetic ether 
and with substituted aceto-acetic ethers, by F. E. Matthews. 
The author has studied the following reactions : condensations 
of aceto-acetic ether with isobutylic aldehyde, valeric aldehyde, 
chloral furfurol, acrolein; of benzoic aldehyde with aceto- 
diethylacetic ether, aceto-dichloracetic ether, and aceto-benzili- 
dene-acetic ether, and of benzoic aldehyde with aceto-mono- 
ethylacetic either.—Contribution to the chemistry of ‘‘ Fairy 
Rings,” by Sir J. B. Lawes, Dr. Gilbert, and Mr. Warington. 
The authors have analysed samples of the soil inside the ring, 
on the ring, and outside the ring. The soil inside is much poorer 
in organic carbon and nitrogen than the soil outside the ring ; 
the soil at the ring itself is intermediate in character as to car- 
bon and nitrogen, but contains a larger quantity of nitrates. 
The fairy ring fungi seem to derive and assimilate nitrogen from 
the soil; this nitrogen is eventually deposited as manure at the 
ring, and becomes available to the associated herbage, which 
thereby acquires the characteristic dark-green colour.—On lines 
of no chemical change, by Dr. Mills and Mr. D. Mackey. The 
authors have investigated the strength at which sulphuric acid 
ceases to attack zine at certain temperatures.—On homologous 
spectra, by W. N. Hartley. The author has photographed and 
mapped the spectra of various elements belonging to the same 
homologous series, e.g. magnesium, zinc and cadmium, calcium, 
strontium and barium, &c., especially with a view to finding out 
whether the striking similarity in such spectra was due to har- 
monic vibrations of a common fundamental vibration. The 
author concludes that -the data contained in the paper support 
the view that elements whose atomic weights differ by a constant 
quantity, and whose chemical character is similar, are truly 
homologous, or in other words, are the same kind of matter in 
different states of condensation, 
® Cornu (‘Spectre Normal du Soleil,” p. 23, #o¢e) mentions that such 
films of silver are transparent for rays about A= 270, which is a good deal 
too high. Chardonnet (Comptes Rendus, February, 1883) states that the 
band extends from Oto S. W. A. Miller (PA??. Trans. 1863) noticed that 
gradually increases on both sides of those limits, but rather more | a silver reflector failed to reflect a band in the ultra-violet. 
| 
