394 
Relation of series to melting points. 
ey go | 
Element Melting point | Peréentae cio 
Barium ... 1600° | fo) 
Gold 1200 4 
Copper ... 1050 6 
Silver =| 960 26 
Strontium... 700 20 
Caletump- ee 700 34 
Magnesium ... | 600 64 
Zin@ wae. saree 410 So 
Cadmium... | 320 50 
Lithium... ... 180 100 
Sodiumjy-., /-- feo) 100 
Gesium... ... 62 100 
Potassium... | 58 100 
Rubidium... | 38 100 
Mercury... | — 40 27 
These matters, of course, have been very carefully 
inquired into, and among them I will just point out that 
Meyer has shown that if the wave-lengths of all the lines 
for z=co be calculated and put as ordinates, and the 
atomic weights as abscissee, then all the points lie on a 
curve similar to that which gives the atomic volumes as 
functions of the atomic weights. He not only deals with 
the melting points, but he goes further and attempts to 
associate the melting points with the atomic weights. 
The next consideration is that in these investigations, 
in some cases, the series have reproduced the same 
chemical group, but in some instances the series group- 
ings, so to speak, are quite different from the chemical 
groupings. 
The facts so far ascertained are as follows :— 
Group I Lithium, Sodium, Potassium, Rubidium, 
Ceesium. 
33. 2 «| Copper, Silver, (Gold! ?). 
3» 3 + Magnesium, Calcium, Strontium. 
al Zinc, Cadmium, Mercury. 
eS Aluminium, Indium, Thallium. 
In the group of lithium, sodium, potassium, the series 
sequence follows absolutely the chemical sequence. 
But when we come to the chemical group—calcium, 
strontium, barium—you find it replaced by a group, 
magnesium, calcium, strontium, while barium is not used 
at all. That is avery remarkable departure, and it shows 
that we have to consider the various conditions which 
we observe in passing from group to group. 
From group to group with increasing atomic weights 
the series back towards the violet. Thus, as the limit of 
a series is represented by the first constant for the first 
subordinate of the four groups, the limit lies 
Between 2858'6 and 1974°3 for Lithium, Sodium, Potassium, 
Rubidium, Czsium, 
a 3159°I ,, 30782 ,, Copper, Silver, Gold. 
59 3979°6 ,, 3103°0 ,, Magnesium, Calcium, Stron- 
tium. 
A 4294°5 ,, 4015°9 ,, Zinc, Cadmium, Mercury. 
In each growp with the increasing atomic weight the 
spectrum advances continually towards the red end ; that 
is, in exactly the opposite direction we observed before. 
Having dealt with these details, there are several other 
general questions which I should like to say a word 
about, because it is evident that we are here in presence 
of the beginning of a new attack on the nature of the 
chemical elements. 
Let us attempt to compare these simplest results 
obtained by this newest form of spectrum analysis, in 
other words the simplest series, with the earliest stellar 
forms. 
NO. 1556, VOL. 60] 
INGA Re E 
[AucusT 24, 1899 
We found that the hottest stars contained hydrogen, 
helium, and asterium. Well, we have found that those 
substances have the simplest series ; that is to say, one 
set of three. I told you that it was more than probable, 
although it is not absolutely established, that the lithium 
group of metals is also represented in stars of very 
high temperature. There, again, we have the simple 
series of one set of three. About sulphur we do not yet 
know positively, but it is probable, I think, that sulphur 
may exist in the hot stars. There, again, we get another 
simple set of three; so that for three perfectly certain 
members of the hottest stars, together with one in all 
probability and one doubtful, we are dealing with the 
simplest series in the hottest stars. 
But now comes the remarkable fact that side by side 
with these simple substances we get in the hottest stars 
magnesium and calcium. We cannot suppose that the 
absence of the principal series there means a greater 
simplicity, because I have shown you that only about 
half the lines in the spectrum of each of these substances 
has yet been picked up in the series, and if the series. 
represent the vibrations of a single particle, of course 
the lines which are not represented in the series, by 
theory must represent the vibrations of some other 
particles. So that there we are face to face with the 
possibility of a much greater complexity. Coming a 
little further down in stellar temperatures we find oxygen, 
and here we deal with six series instead of three, or 
two, as in the case of magnesium and calcium ; and even 
then, as I have pointed out to you, we do not deal with 
above half the lines of the gas as we can see them at 
a higher temperature. This, then, seems to suggest that 
in the hottest stars there are very various stabilities of 
very various forms. In fact, there seems to be there as 
here distinctly the survival of the fittest ; otherwise how 
can we account for the fact that certainly in the hottest 
stars we get two metals, magnesium and calcium, before 
we have indication of any other metals, and that where 
we have those metals and bring our series touch-stone 
to them we find that instead of being very simple they 
are really very complex? However this may be, we are 
now assured that there is a much greater quantity of 
some apparently more complex forms in the hotter stars 
than of the more simple ones ; and that is a matter 
which the chemists, when they come to inquire into 
these questions which we are now considering, will 
certainly have to face. This fact suggests, too, another 
very interesting question which has some relation, per- 
haps, to some of those drawings that I have thrown on 
the screen from Lyell’s Elements, which showed that 
a great many simple organic forms appear in the strati- 
graphic series ata late period ; that some of the simplest 
forms died out, others remained. Now, it may be that 
some of the more simple forms in inorganic evolution, as 
in organic evolution, really represent later introductions ; 
but, however this may be, it is perfectly certain that we 
have not an absolute parallel between the results of the 
spectroscopic observations of series and the spectroscopic 
observations of stars. The accompanying table will show 
very generally how the matter stands. The chief points 
to refer to are the gaps in the table showing the prin- 
cipal series and the first and second subordinate series. 
We have the metals arranged in the order of Mendeleéjeff’s 
groups. You will observe that after the first metals we 
practically deal with no principal series at all until we 
come down at the bottom to oxygen, sulphur and sele- 
nium. The same thing happens with the subordinate 
series so far as the existence of single lines and double 
lines are concerned. Now, it is a curious point that in 
the case of several of those substances in which no prin- 
cipal series has been detected, certain lines in the ultra- 
violet of considerable strength have been observed which 
may ultimately turn out to represent principal series. Of 
course, if that should be so it will make the inquiry a 
