430 
NATURE 
[| Sept. 2, 1886 
vary in intensity among themselves, and continued fractionation 
increased the differences first observed. Whilst I was in this 
state of doubt and uncertainty, and only beginning to see my way 
towards arranging into a consistent whole the facts daily coming 
to light, help came from an unexpected quarter. M. de Marignac, 
with whom I had been for some tine in correspondence, kindly 
sent me a small specimen of the earth which he had discovered 
and provisionally named Ya. In the radiant-matter tube this 
earth gave a bright spectrum like the one in the diagram before 
you (Fig. 3). The spectrum above it (Fig. 2) is that ascribed to 
yttria. Look atthe two. Omitting minor details, Ya is yttria with 
the chief characteristic band—the citron band—left out, and 
with the double green band of samaria added to it. Now look 
at Fig. 4, which represents the spectrum of a mixture of 61 parts 
of yttria and 39 parts of samaria. It is identical almost to its 
minutest detail with the spectrum of Ya, with this not unim- 
portant differeace—the citron band is as prominent as any other 
line. Ya consists, therefore, of samaria with the greenish blue 
of yttria and some of the other yttria bands added to it. 
I may aptly call the Ya spectrum my Rosetta stone. It threw 
a flood of light on all the obscurities and contradictions I had 
found so plentiful, and showed me that a much wider law than 
the one I had been working upon was the true law governing 
the occurrence of these obscure phenomena. For what does the 
spectrum of Ya show? It proves that what I had hitherto 
thought was one of the chief bands in the yttria spectrum—the 
citron band—could be entirely removed, whilst another character- 
istic group—the double green of yttria—could also be separated 
from the citron. 
It would exceed legitimate limits were I to enter into details 
respecting the chemical and physical reasons which led me to 
these definite conclusions. To settle one single point more than 
2000 fractionations have been performed. 
The meaning of the strongly marked symbolic lines had first 
to be ascertained. For a long time I had to be content with 
roughly translating one group of coloured symbols as “‘ yttrium ” 
and another groupas ‘‘samarium,” disregarding the fainter lines, 
shadows, and wings frequently common to both. Constant 
practice in the decipherment has now given me fuller insight 
into what I may call the grammar of these hieroglyphic inscrip- 
tions. Every line and shadow of a line, each faint wing 
attached to a strong band, and every variation in intensity of | 
the shadows and wings among themselves, now has a definite 
meaning which can be translated into the common symbolism of 
chemistry. 
In a mineral containing the rarer earths, those most widely 
separated in chemical properties are most easily obtained in a 
state of comparative purity by simple chemical means, For 
instance, in separating didymium from lanthanum, or samarium 
from yttrium, a few simple chemical reactions and a little 
waste will give these bodies in a state of purity ; but when it 
comes to splitting up yttrium into its components ordinary 
chemical separation is useless, and fractionation must be pushed 
to the utmost limit, many thousand operations and enormous 
waste of material being necessary to effect even a partial 
separation. 
Returning therefore, after this explanatory digression, to the 
idea of heavy and light atoms, we see how well this hypothesis 
accords with the new facts here brought to light. From every 
chemical point of view the stable molecular group, yttrium, 
behaves as an element. Excessive and systematic fractionation 
has acted the part of a chemical ‘‘ sorting Demon,” distributing 
the atoms of ytrrium into several groups, with certainly different 
phosphorescent spectra, and presumably different atomic weights, 
though all these groups behave alike from the usual chemical 
point of view. Here, then, is one of the elements the spectrum 
of which does not emanate equally from all its atoms, but some 
atoms furnish some, other atoms others, of the lines and bands 
of the compound spectrum of the element. And as this is the 
case with one element, it is probably so in a greater or less degree 
with all. Hence the atoms of this element differ probably in 
weight, certainly in the internal motions they undergo. 
Another important inference which may be drawn from the 
facts is, that the atoms of which yttrium consists, though differ- 
ing, do not differ continuously, but fer saltum. We have 
evidence of this in the fact that the spectroscopic bands charac- 
teristic of each group are distinct from those of the other groups, 
and do not pass gradually into them. We must accordingly 
expect, in the present state of science, that this is probably the 
case with the other elements. And the atoms of a chemical 
element being known to differ in one respect may differ in other 
| respects, and presumably do somewhat differ in mass. 
Restricted by limited time and means, even a partial separa- 
tion of these atomic groupings is possible to me only with 
enormous difficulty. Have we any evidence that Nature has. 
effected such a separation? The following facts, I think, 
supply this evidence. 
The earth yttria occurs in several minerals, all extremely rare. 
These minerals are of very diverse chemical composition, and 
occur in localities widely separated geographically. Does the 
pure yttria (we in respect to every other known element) from 
these different sources behave differently to the radiant-matter 
test? To the chemist hitherto the earth yttria has been the 
sane thing, and has possessed the same properties whatever its 
source ; but armed with this new power of seeing into the atomic 
groupings which go to make up yttrium, we find evidence of 
differentiation between one yttrium and another. 
Thus when the samarskite yttrium was formed, all the con- 
stituent atoms—deep red, red, orange, citron, greenish blue, and 
blue 1—condensed together in fair proportion, the deep red being 
faintest. In gadolinite yttrium the citron and greenish blue 
constituents are plentiful, the red is very deficient, the orange is 
absent, and the others occur in moderate quantities. In the 
yttrium from xenotime the citron is most plentiful, the greenish 
blue occurs in smaller proportion, the red is all but absent, and 
the orange is quite absent. Yttrium from monazite contains the 
greenish blue and citron, with a fair proportion of the other 
constituents ; the greenish blue is plentiful, and the red is good. 
Yttrium from fluocerite is very similar to that from monazite, but 
the blue is weaker. Yttrium from hielmite is very rich in citron, 
has a fair quantity of blue and greenish blue, less of red, no 
orange, and only a very faint trace of deep red. Yttria from 
euxenite is almost identical with that from hielmite. 
This is unlikely to be an isolated case. The principle is very 
probably of general application to all the elements. In some, 
| possibly in all elements, the whole spectrum does not emanate 
from all its atoms, but different spectral rays may come from 
different atoms, and in the spectrum as we see it all these partial 
spectra are present together. This being interpreted means that 
there are definite differences in the internal motions which go on 
in the several groups of which the atoms of a chemical element 
consist. For example, we must now be prepared for some such 
events as that the seven series of bands in the absorption-spec- 
trum of iodine may prove not all to emanate from every molecule, 
but that some of these molecules emit some of these series, others 
others, and in the jumble of all these kinds of molecules, to 
which is given the name ‘‘iodine vapour,” the whole seven 
series are contributors. 
To me it appears the theory I have here ventured to formulate, 
taken in conjunction with the diagram in Fig. 1, may aid the 
scientific imagination to proceed a step or two further in the 
order of elemental evolution. In the undulating curve may be 
seen the action of two forces, one acting in the direction of the 
vertical line, and the other pulsating backwards and forwards 
like a pendulum. Assume the vertical line to represent tempera- 
ture slowly sinking through an unknown number of degrees, 
from the dissociation point of the first-formed element down to 
the dissociation point of those last shown on the scale. But 
what form of energy is represented by the oscillating line? 
Swinging to and fro like a mighty pendulum to points equi- 
distant from a neutral centre ; the divergence from neutrality 
conferring atomicity of one, two, three, and four degrees as the — 
distance from the centre is one, two, three, or four divisions ; 
and the approach to, or retreat from, the neutral line deciding 
the electro-negative or electro-positive character of the element 
—all on the retreating half of the swing being positive and all 
on the approaching half negative—this oscillating force must be 
intimately connected with the imponderable matter, essence, or 
source of energy we call electricity. 
Let us examine this a little more closely. Let us start at the 
moment when the-first element came into existence. Before this 
time matter, as we know it, was not. It is equally impossible 
to conceive of matter without energy, as of energy without 
matter ; from one point of view the two are convertible terms. 
Before the birth of atoms all those forms of energy which 
become evident when matter acts upon matter, could not have 
| existed—they were locked up in the froty/e as latent potentialities 
x For brevity I call them by their domiaant spectrum band, 
1 
