426 
carbonate and sulphate, sodium as chloride, silver and lead as 
sulphides ; but why do we find certain groups of elements with 
little affinity for each other yet existing in juxtaposition or com- 
mixture? The members of some of these groups are far from 
plentiful, not generally or widely diffused, and certainly they are 
not easy to separate. 
As instances of such grouping we may mention :— 
(1) Nickel and cobalt, of which it may be said that had their 
compounds been colourless, they would have been long regarded 
as identical, and possibly even yet would not have been 
separated, 
(2) The two groups of platinum metals. 
(3) The so-called ‘‘rare earths,” occurring in gadolinite, 
samarskite, &c., and evidently becoming more numerous the 
more closely they are examined. 
Certain questions here suggest themselves :—-Is the series of 
these elements like a staircase or like an inclined plane? Will 
they, the more closely they are scrutinised, be found to fade 
away the more gradually the one into the other? Further, will 
a mixture hitherto held to be simple, like (e.g. didymium, be 
capable of being split up in one direction only, or in several ? 
Thave been led to ask this last question because I have separated 
from didymium bodies which seem to agree neither with the 
praseodymium and neodymium of Dr. Auer von Welsbach, nor 
with the components detected by M. de Boisbaudran and 
M. Demarcay. 
Why, then, are these respective elements so closely associated ? 
What agency has brought them together ? 
An eminent physicist evades the difficulty by suggesting that 
their joint occurrence is simply an instance of the working of the 
familiar principle, ‘‘ Birds of a feather flock together.” In 
their chemical and physical attributes these rare earths are so 
closely similar, that they may be regarded as substantially 
identical in all the circumstances of solution and precipitation 
to which they may have been exposed during geological 
ages. 
But do we, in point of fact, recognise any such agency at work 
in Nature? Is there any power which regularlyand systematic- 
ally sorts out the different kinds of matter from promiscuous 
heaps, conveying like to like and separating unlike from unlike ? 
I must confess that I fail to trace any such distributive agency, 
nor, indeed, do I feel able to form any distinct conception of its 
nature. : 
I must here remark that coral worms in some cases do effect 
a separation of certain kinds of matter. Thus a Gorgonia of 
the species of Melithea, and Mussa sinuosa, undoubtedly elimin- 
ate from sea-water not merely lime, but even yttria ; and other 
recent corals, Pocillopora damicornis, and a Symphyllia close to 
the yttria-secreting AZussa, separate samaria from sea-water. 
Sea-weeds and aquatic mollusks contain a larger proportion of 
iodide and bromine than the waters which they inhabit, and may 
thus be said to separate out these elements from the chlorine 
with which they are mingled. 
But if we examine these cases of elimination we see that they 
are limited in theirscope. They extend only to substances exist- 
ing in solution of which there is a fresh supply always at hand. 
and which are capable of entering into the animal or vegetable 
economy. Again, the elimination of iodine and bromine, 
effected as just described, is of a very imperfect character, and, 
when such water-plants and animals die and decay, their con- 
stituents will be again distributed in the water. 
We cann it well consider that nickel and cobalt have been 
deposited in admixture by organic agency, nor yet the groups 
iridium, osmium, and platinum—ruthenium, rhodium, and 
palladium. 
Since the earthy metals to which I have referred—such as 
yttrium, samarium, holmium, erbium, thulium, ytterbium, &c.— 
are very rare, the probability of their ever having been brought 
together in some few uncommon minerals discovered only in a 
few localities must be regarded as trifling indeed, if we suppose 
that these metals had at any time been widely diffused in a state 
of great dilution with other matter. The features which we have 
just recognised in these earths seem to point to their formation 
severally from some common material placed in conditions in 
each case nearly identical. The case is strengthened by a con- 
sideration of the other groups of elements, also similar in pro- 
perties, having little affinity for each other and occurring in 
admixture ; either all or at least some of the elements concerned 
being moreover decidedly rare. Thus we have nickel and cobalt 
not plentiful or widely distributed ; cobalt, perhaps, never found 
| NATURE 
ne MG Se ee 
[Sepz. 2, 1886 
absolutely free from nickel, and wice versé. We have also the 
two platinum groups, where very similar features prevail. 
A weighty argument in favour of the compound nature of t 
elements is that drawn from a consideration of the compound 
radicals, or, as they might be called, pseudo-elements. Their 
similarity with the accepted elements is perfectly familiar to all 
chemists. If, for example, we suppose that in some age or in 
some country men of science were cognisant of the existence 
and of the behaviour of cyanogen, but had not succeeded 
resolving it into its constituents, nothing, surely, would prevent 
their viewing it as an element, and assigning it a place with t 
halogens. It may fairly be held that if a body which we know 
to be compound can be found playing the part of an element, 
this fact lends a certain plausibility to the supposition that t 
elements also are not absolutely simple. This line of thought, 
or at least one closely approximating to it, was worked out by 
Dr. Carnelley in a paper read before this Association at its las 
meeting. From a comparison of the physical properties of 
inorganic with those of organic compounds, Dr. Carnelley 
concludes that ‘‘ the elements, as a whole, are analogous to th 
hydrocarbon radicals.” This conclusion, if true, he adds, shoul 
lead to the futher inference that the so-called elements are no 
truly elementary, being made up of at least two absolute 
elements, named provisionally A and B. Hence, he argues, it 
should be possible to build up a series of compounds of these 
two primary elements which would correspond to what we now 
call elements. Such an arrangement, to be admissible, would 
have to fulfil certain conditions :—The secondary elements thus 
generated from A and B must exhibit the phenomena o} 
periodicity, and the series would have to form octaves: the 
entire system is bound to display some feature corresponding to 
the ‘‘odd and even series” of Mendeléeft’s classification ; the 
atomic weights must increase across the system from the first to the 
seventh group—that is, from the positive to the negative end of 
each series ; the atomicity would have to increase from the first 
to the middle group, and then either increase or decrease to the 
seventh group; some feature should appear corresponding to 
the eighth group; and, lastly, the atomic weights in such a 
system ought to agree with the atomic weights as experimentally 
determined. 
This last condition Dr. Carnelley rightly regards as the most 
crucial, and he finds his arrangement gives atomic weights which 
in a majority of instances coincide approximately with the actual 
atomic weights. Thus out of a total of sixty-one elements whose 
atomic weights have been determined with at least approximate | 
accuracy, and whose places in the periodic system is not dis- 
puted, twenty-seven agree almost exactly with the actual 
numbers, whilst nineteen others are not more than one unit 
astray. 
For a detailed consideration of the conclusions which follow 
from Dr. Carnelley’s views I must refer to his paper as read at 
our last meeting. Two points bear more especially upon the 
subject now under consideration—that is, if this speculation on 
the genesis of the elements is well-founded. First, the existence 
of elements of identical atomic weights, isomeric with each other, 
would be possible ; as such, Dr. Carnelley mentions respectively 
nickel and cobalt (now found to have slightly different atomic 
weights), rhodium and ruthenium, osmium and iridium, and the 
metals of some of the rare earths. Secondly, in Dr, Carnelley’s 
scheme all the chemical elements save hydrogen are supposed to” 
be composed of two simpler elements, A = 12 and B= —2. 
Of these he regards A as a tetrad identical with carbon, and 
B as a monad of negative weight—perhaps the ethereal fluid of 
space. p 
Dr. Carnelley’s three prinary elements therefore are carbon, 
hydrogen, and the ether. 
Starting from the supposition that pristine matter was once i 
an intensely heated condition, and that it has reached its pres =n 
state by a process of free cooling, Dr. E. J. Mills suggests tha 
the elements, as we now have them, are the result of successive 
polymerisations. Dr. Mills reminds us that chemical substan 
in the process of cooling naturally increase in density, and, 
such increase be measured as a function of time or of tempera 
ture, we sometimes observe that there are critical points corre 
sponding to the formation of new and well-defined substances. 
In this manner ordinary phosphorus is converted into the red 
variety, I is transformed into I,, Sy becomes Ss, and NO, N,Oy. 
Among organic bodies styrol, in like manner, according to Dr. 
