Wane 
TRANSACTIONS OF SECTION B. 453 
we shall see that they arrange themselves in a series of curves similar to but not at 
all coincident with his. The observations are not so complete or accurate as those of 
the molecular volumes, but they seem sufficient to establish the fact, while the 
points of the curves would appear to be, not the alkaline metals, as in Meyer's 
diagram, but hydrogen, phosphorus and sulphur, titanium and vanadium, selenium, 
antimony. Now, if we were to insert the specific refractions of cyanogen, ammo- 
nium, and methyl into this table, we should again show that it was an intrusion 
of strangers not in harmony with the family of elements. 
But there is another argument to be derived from the action of light. The 
refraction equivalent of a compound body is the sum of the refraction equivalents 
of its compounds; and, if there is anything known for certain in the whole 
subject, it is that the refraction equivalent of an organic compound advances by 
the same quantity (7°6) for every increment of CH,. If, therefore, the increment 
between the different members of a group of analogous elements, such as the 
alkaline metals, be of the same character, we may expect to find that there isa 
regular increase of the refraction equivalent for each addition of 16. But this is 
utterly at variance with fact : thus, in the instance above quoted, the refraction 
equivalent of lithium being 3:8, that of sodium is 4:8, of potassium 8:1, of rubidium 
14:0, and of cesium about 13°7. Neither does the law obtain in those series in 
which the increment is not a multiple of 8, as in the ease of the halogens, where 
the increment of atomic weight is 45, and the refraction equivalents are chlorine 9°9, 
bromine 15°3, and iodine 24:5. 
The refraction equivalents of isomeric bodies are generally identical; and the 
refraction equivalents of polymeric bodies arein proportion to their atomic weights. 
Among the groups of analogous elements of the same, or nearly the same, atomic 
weight we do find certain analogies: thus cobalt and nickel are respectively 
10:8 and 10°4, while iron and manganese are respectively 12°0 and 12:2. But, as 
far as observation has gone at present, we have reason to conclude that, if metals 
stand to one another in the ratio of 2: 1 in atomic weight, their refraction equiva- 
lents are much nearer together than that; while, on the other hand, the equivalent 
of sulphur, instead of being the double of that of oxygen, is at least five times as 
great. 
The general tendency of these arguments is evidently to show that the elementary 
radicals are essentially different from the compound radicals, though their chemical 
functions are similar. 
There remains still the hypothesis that there is a ‘ primordial element, from 
which the others are derived by transmutation. With the sages of Asia it was the 
‘blue ether,’ with Thales water, with Dr. Prout hydrogen. The earlier views 
have passed away, and the claims of hydrogen are being fought out by some of 
our ablest analysts on the battlefield of atomic weights and their rigorous deter- 
mination. 
There does not appear to be any argument which is fatal to the idea that two 
or more of our supposed elements may differ from one another rather in form than 
in substance, or even that the whole seventy are only modifications of a prime 
element ; but chemical analogies seem wanting. The closest analogy would be if 
we could prepare two allotropic conditions of some body, such as phosphorus or 
cyanogen, which should carry their allotropism into all their respective compounds, 
no compound of the one form being capable of change into a compound of the other. 
Our present knowledge of allotropism, and of variations in atomicity, affords little, 
if any, promise of this. 
The remarkable relations between the atomic weights of the elements, and 
many peculiarities of their grouping, force upon us the conviction that they are not 
separate bodies created without reference to one another, but that they have been 
originally fashioned, or have been built up from one another, according to some 
general plan. This plan we may hope gradually to understand better; but if we 
are ever to transform one of these supposed elements into another, or to split up 
one of them into two or three dissimilar forms of matter, it will probably be by 
the application of some method of analysis hitherto unknown. 
Nothing can be of greater promise than the discovery of new methods of 
