106 
NATURE 
[JuNE 1, 1899 
the substances which we find in the table, we must 
certainly add sodium, and also aluminium, and chlorine 
possibly, but about sulphur at present I have no 
certain knowledge; you will see the reason for these 
references later on. At all events, we can with the 
greatest confidence point out the remarkable absence 
of substances of high atomic weights, and the extra- 
ordinary thing that the metals magnesium and calcium 
undoubtedly began their existence in the hottest stars 
long before, apparently, there is any obvious trace of many 
of the other metals which a chemist would certainly have 
been looking out for. 
In relation to this new work, the first point to make is 
that the chemical forms we see in the hottest stars are 
amongst the simplest. What is the justification for this 
statement? Well, there are two reasons. The chemist 
will acknowledge that if there be such a thing as chemical 
evolution, an element of low atomic weight is simpler, that 
is, less massive, than an element of high atomic weight. 
If we rely upon spectrum analysis we can say, when dealing 
with the question of “series,” about which I hope to say 
something in my next lecture, that the elements which 
have the smallest number of “series” are in all probability 
simpler than those which have a large number, and this is 
still truer when we find that all the lines in the spectrum 
of a substance can be included in those rhythmical series, 
as happens in the case of the cleveite gases. So that the 
first stage of inorganic evolution, if there has been such 
an evolution, is certainly a stage of simplest forms as 
in organic evolution. 
The next point is that the astronomical record, studied 
from the evolution point of view, is in other ways on all- 
fours with the geological record. We get the same 
changes of forms, I may say that we get the sudden 
breaks in forms, disappearances of old accompanied by 
appearances of new forms, and with this we get, whether 
we consider the atomic weight point of view or the series 
point of view, a growth of complexity. 
The geological story is exactly reproduced. Now, 
here it is obvious that a very important point comes 
in. In inorganic evolution we are dealing with a great 
running down of temperature ; how tremendous, no man 
can say. We know the temperature of our earth, but we 
do not know, and we cannot define, the temperatures of 
the hottest stars. So that how great the temperature of 
the earth may once have been, supposing it to be repre- 
sented by the present temperature of the hottest star, no 
man knows anything with certainty. 
With regard to organic evolution, however, which has 
to do with the plant world and the animal world, there 
can have been no such running down of temperature at 
all. The temperature must have been practically constant. 
Please bear that in mind, because I shall have to refer 
to it later on. 
It is proper that I should say that just as the work of 
Darwin in the nineteenth century was foreshadowed by 
seventeenth century suggestions, so the stellar demon- 
stration which I have brought before you to-night has 
been preceded by hypotheses distinctly in the same 
direction. The first stage of chemistry, as you know, 
was alchemy. Alchemy concerned itself with trans- 
mutations, but it was found very early that the real 
function of the later science of chemistry was to study 
simplifications, and, of course, to do this to the utmost 
we want precisely those enormous differences in tem- 
perature which it appears the stars alone place at our 
disposal. 
With regard to the general question of inorganic 
evolution, the first idea was thrown out in the year 1815 
by Prout, who, in consequence of the low atomic weight 
of hydrogen, suggested that that gas was really the 
primary element, and that all the others, defined by 
their different atomic weights, were really aggregations 
of hydrogen, the complexity of the aggregation being 
NO. 1544, VOL. 60] 
determined by the atomic weight; that is to say, the 
element with an atomic weight of twenty contained 
twenty hydrogen units ; with an atomic weight of forty 
it contained forty, and so on. The reply to that was 
that very minute work showed that the chemical elements, 
when they were properly purified and examined with the 
greatest care, did not give exactly whole numbers re- 
presenting their atomic weights. They were so and so 
plus a decimal, which might be very near the zero point, 
or half-way between, and that was supposed to be a 
crushing answer to Prout’s view. The next view, which 
included the same idea—that is to say, a physical con- 
nection between these different things as opposed to the 
view that they were manufactured articles, special 
creations, each without any relation whatever to the 
other, was suggested by Débereiner in 1817, and the 
idea was expanded by Pettenkoferin 1850. Both pointed 
out that there were groups of three elements, such as 
lithium, sodium, and potassium, numerically connected ; 
that is, their atomic weights being 7, 23, and 39, the 
central atomic weight was exactly the mean of the other 
two, 7 + 39 = 46, divided by 2, we get 23. Another 
way, however, of showing that is that 7 + 16 = 23, and 
23 + 16 = 39; the latter method suggests a possible 
addition of something with an atomic weight of 16, 
In 1862 de Chancourtois came to the conclusion that the 
relations between the properties of the various chemical 
elements were really simple geometrical relations. That, 
you see, is a much broader view. It is not till 1864 that 
we come to the so-called “ periodic law,” which was first 
suggested by Newlands, and elaborated by Mendeléeff in 
1869. According to this law, the chemical and physical 
properties of the elements are periodic functions of their 
atomic weights. Lothar Meyer afterwards went into 
this matter, and obtained some very interesting results 
from the point of view of atomic volumes. He showed 
that if we plot the atomic volumes of the different ele- 
ments, arranged according to their atomic weights from 
left to right, there is a certain periodicity in the apices of 
the curve indicating the highest atomic volumes. 
So far there was no reference to the action of tem- 
perature in relation to this, but in 1873 I suggested that 
we must have a fall of temperature in stars, and that 
the greater complexity in the spectra of certain stars 
was probably due to this fall of temperature. This idea 
was ultimately utilised by Sir William Crookes in an 
interesting variation of the periodic law, in which he 
assumes that temperature plays a part in bringing about 
the changes in the characters of the elements. Brodie, 
in 1880, came to the conclusion that the elements were 
certainly not elementary, because in what he called a 
“chemical calculus” he had to assume that certain sub- 
stances, supposed to be elements, were really not so ; and 
he then threw out the very pregnant idea that possibly in 
some of the hotter stars some of these elements which he 
predicted might be found. Nine years afterwards, Ryd- 
berg, one of the most industrious investigators of the 
question of “series” to which I have referred, stated that 
most of the phenomena of series could be explained by 
supposing that hydrogen was really the initial element, 
and that the other substances were really compounds of 
hydrogen ; so that you observe he came back to Prout’s 
first view in 1815. 
All these ideas imply a continuous action, and suggest 
that there was some original stuff which was continuously 
formed into something more complex as time went on. 
That is to say, that the existence of our chemical elements 
as we know them does not depend upon their having 
been separately manufactured, but that they are the result 
of the working of a general law, as in the case of plants 
and animals. 
You see at once that the stellar facts which have 
already been brought before you are entirely in harmony 
with the highest chemical thought, and indeed establish 
