SCIENCE. 
2 7 
held together by the forceps, and slightly warmed, 
just sufficient to soften thegutta percha ; the forceps 
may now be laid aside, or used simply to press the 
cover home, warming the slide gently, also the 
cover; the perfect contact of the softened “ tissue” 
with the cover and slide is easily recognized, and 
with a little care this can be effected very quickly, 
and nothing further is necessary. A finishing ring 
of colored cement makes a very neat mount, but it 
is not necessary. 
ON MULTIPLE SPECTRA. 
"Nunc age, quo motu genitalia materiai 
Corpora res varias gignant, genitasque resolvant 
Et qua vi facere id cogantur.” 
Lucretius ii. , 61-2. 
“ Prima moventur enim per se primordia rerum : 
Inde ea, quae parvo sunt corpora conciliatu, 
Et quasi proxima sunt ad vireis principiorum, 
Ictibus illorum caecis impulsa cientur 
Ipsaque, quae porro paulo maiora, lacessunt.” 
Lucretius, ii., 132-6. 
" It is conceivable that the various kinds of matters, now rec- 
ognized in different elementary substances, may possess one and 
he same ultimate or atomic molecule existing in different con- 
ditions of movement. 
"The essential unity of matter is an hypothesis in harmony 
with the equal action of gravity upon all bodies ." — Graham s Re- 
searches, p. 299. 
In a recent paper* I showed that a study of the minute 
anatomy of spectra, both terrestrial and celestial, forces 
upon us the conclusion that both in the electric arc and in 
the hottest region of the sun the so-called chemical ele- 
ments behave after the manner of compound bodies. 
I then dealt more especially with the question of the 
basic lines in the various spectra, and it is clear that if at 
any one temperature, there be some lines only truly basic 
in the spectrum of any element, we at once divide the lines 
visible at that temperature into two groups, those which 
are basic and those which are not. This would give a 
compound origin to the lines, and this is the real point. 
It is now years ago since the view was first held that the 
elementary bodies had double spectra, that is, that each, of 
at all events several, under changed conditions of temper- 
ature or electric tension, gave us now a fluted spectrum 
and now one composed of lines. 
I glimpsed the idea some time afterward that the line 
spectrum was in its turn in all probability a complex 
whole, in other words that it was the summation of the 
spectra of various molecular groupings. 
Recent work has to my mind not only shown that this is 
true, but that in the case of many bodies the complexity, 
and therefore the number, of the molecular groupings 
which give rise to that compound whole called a line spec- 
trum, is considerable. 
It is therefore important from my point of view to recon- 
sider the evidence on which the assertion that the fluted 
bands and the line spectrum (taken as a whole) of a sub- 
stance really belong to that substance, because if we find 
that this must be accepted and that it can easily be ex- 
plained on the view that the two kinds of spectra are pro- 
duced by different molecular groupings, the fact of other 
molecular groupings, giving rise to a complex line spec- 
trum can be more readily accepted, contrary though it be 
to modern “ chemical philosophy,” as taught at all events 
in the text-books. 
Pliicker and Hittorf were, I believe, the first to point out 
that the same chemical substance, when in a state of gas 
or vapor, gave out different spectra under different con- 
ditions. On this point they wrote fifteen years ago; 
“ The first fact which we discovered in operating with our 
tubes . . was the following one : 
“ There is a certain number of elementary substances ■which, 
when differently heated, furnish two kinds of spectra of quite 
a different character, not having any line or any band in com- 
mon. 
“ The fact is important, as well with regard to theoretical 
conceptions as to practical applications — the more so as 
the passage from one kind of spectrum to the other is by 
no means a continuous one, but takes place abruply. By 
regulating the temperature you may repeat the two spectra 
in any succession ad libitum .” (Pliicker and Hittorf on 
the Spectra of Ignited Gases and Vapors; Phil. Trans, 
Royal Society, 1865, part i. p. 6.) 
Angstrom, whose name must ever be mentioned with 
the highest respect by any worker in spectrum analysis, 
was distinctly opposed to this view, and in the text which 
accompanies his Spectre Normal we find the following 
statement ; 
“ Dans un Memoire sur les spectres ‘ doubles’ des corps 
elementaires que nous publierons prochainement, M. Thaldn 
et moi, dans les Actes de la Society des Sciences d’Upsal, 
nous traiterons d’une manibre suffisamment complete les 
questions importantes qu’on peut se proposer sur cet 
interessant sujet. Pour le present, je me borne a dire 
que res rdsultats auxquels nous sommes arrives, ne con- 
firmed aucunement l’opinion dmise par Pliicker, qu’un 
corps dlementaire pourrait donner, suivant sa temperature 
plus ou moins elevee, des spectres tout-a-fait differents. 
C’est le contraire qui est exact. En effet en augmentant 
successivement la temperature, on trouve que les raies 
varient en intensite d’une maniere trescompliquee, et que, 
par suite, de nouvelles raies peuvent meme se presenter, 
si la temperature s’eleve suffisamment. Mais, independ- 
amment de toutes ces mutations, le spectre d’un certain 
corps conservera toujours son caracteire individuel.” * 
Angstrom did not object merely on theoretical grounds. 
He saw, or thought he saw, room to ascribe all these fluted 
spectra to impurities. 
He was strengthened in this view by observing how, in 
the case of the spectra of known compounds, there were 
always flutings in one part of the spectrum or another ; a 
rapid induction naturally, therefore, ascribed all flutings 
to compounds. The continuity of the gaseous and liquid 
states of matter, let alone the continuity of Nature’s pro- 
cesses generally, never entered into the question. For 
Angstrom, as for the modern chemist, there was no such 
thing as evolution, no possibility of a close physical rela- 
tionship between elements, so called, driven to incand- 
escence from the solid state, and binary compounds of 
those elements. 
In a memoir, however, which appeared after Angstrom’s 
death, and which, though under a different title, was in all 
probability the one referred to, this opinion was to a large 
extent recalled, and in favor of Pliicker’s view, in the fol- 
lowing words ; — 
*• . . . Nous ne nions certainement pas qu’un corps 
simple ne puisse dans certains cas donner differents spectres, 
Citons, par exemple, le spectre d’absorption d’iode que ne 
ressemble en aucune faqon au systeme des raies brillantes 
du m£me corps, obtenues au moyen de l’ 61 ectricit 6 ; et 
remarquons de plus qu’en general tout corps simple, pre- 
sentant la propriete d’allotropie, doit donner a l’etat d’in- 
candescence des spectres differents, pourvu que la dite prop- 
riete de la substance subsiste non seulement a l’etat gazeux 
du corps, mais encore a la temperature meme de l’incand- 
escence. . . 
“ Le soufre solid poss&de, somme on-sait, plusieurs 6tats 
allotropiques, et, d’apres certaines observations, ce corps, 
meme a son that gazeux, prendrait des formes diffbrentes. 
Par consequent, en supposant que cela soit vrai, le soufre 
gazeux doit donner plusieurs spectres d’absorptio, tandis 
que la possibility d’un seul on de plusieurs spectres brillants 
dfependra de la circonstance suivante, savoir si les 6tats 
allotropiques plus complexes de cette substance supporter- 
ont la temperature de l'incandescence, avant de se decom- 
poser. 
*“On the Necessity for a New Departure in Spectrum Analysis” 
(Nature, vol. xxi. p. 8.) 
Angstrom sur “ Le Spectre normal du Solcil,” page 39, 
