209 
ence of 4 between the atomic weights of the halogens and 
their positive homologues of position Na, K, Rb, and Cs. 
Now if the groups of oxygen elements O, S, Se, Te, be 
considered as negative forms of H2 n, homologous in 
character and position with the negative forms of H n, it 
will be seen that besides the triad of atomic weight formed 
by S, Se, and Te, there is a common difference of 8 between 
them and their positive homologues Mg, Ca, Sr, and Ba ; 
or double the common difference between the positive and 
negative members of the series H n. The oxygen elements 
are multiples of 2, 4, 8, and 16, and may accordingly be 
considered as products of the first, second, third or fourth 
power of H2 n. Whichever view be taken of the formation 
of the first negative member of the series H2^, it is probable 
that both fluorine and oxygen were not formed direct from 
Hn, and H2^, but from members homologous in ^position 
with Li, and Gl, but which have become extinct by absorp- 
tion into F and 0. 
Another numerical relation subsisting among the halo- 
gens which it may be of interest to point out is, that the 
difference of a unit in their atomic weights will make them 
multiples of 3 and 9, and these numbers, commencing with 
Cl = 36, are all respectively three times the atomic weights 
of the first three members of the series ITS ft. These rela- 
tions would indicate that the halogens, usually regarded as 
monatomic, are also built up in multiple proportions, and 
may also throw some light on the variable quantivalence 
which Wanklyn and other chemists have shown the alka- 
line metals and halogens to possess. 
The recent researches of chemists leave no doubt that all 
the elements which I have classified as forms of H 5n, except 
boron, belong to the same group. Now, boron bears a 
greater resemblance to phosphorus in its combinations and 
occurrence in nature than it does to other elements, and 
whether the first three members of the series be considered 
