ning members are (see
Crookes' table, p. 28), manganese, iron, cobalt, nickel; ruthenium,
rhodium, palladium; osmium, iridium, platinum. If we take all these as
group V, we find that fluorine and manganese are violently forced into
company with which they have hardly any points of relationship, and that
they intrude into an otherwise very harmonious group of closely similar
composition. Moreover, manganese reproduces the characteristic lithium
"spike" and not the bars of those into whose company it is thrust, and it
is thus allied with lithium, with which indeed it is almost identical. But
lithium is placed by Crookes at the head of a group, the other members of
which are potassium, rubidium and caesium (the last not examined). Following
these identities of composition, I think it is better to remove manganese
and fluorine from their incongruous companions and place them with lithium
and its allies as V _a_, the Spike Groups, marking, by the identity of
number, similarities of arrangement which exist, and by the separation the
differences of composition. It is worth while noting what Sir William
Crookes, in his "Genesis of the Elements," remarks on the relations of the
interperiodic group with its neighbours. He says: "These bodies are
interperiodic because their atomic weights exclude them from the small
periods into which the other elements fall, and because their chemical
relations with some members of the neighbouring groups show that they are
probably interperiodic in the sense of being in transition stages."

Group V in every case shows fourteen bars radiating from a centre as shown
in iron, Plate IV, 1. While the form remains unchanged throughout, the
increase of weight is gained by adding to the number of atoms contained in
a bar. The group is made up, not of single chemical elements, as in all
other cases, but of sub-groups, each containing three elements, and the
relations within each sub-group are very close; moreover the weights only
differ by two atoms per bar, making a weight difference of twenty-eight in
the whole. Thus we have per bar:--

Iron 72 Palladium 136
Nickel 74 Osmium 245
Cobalt 76 Iridium 247
Ruthenium 132 Platinum A 249
Rhodium 134 Platinum B 257
It will be noticed (Plate XVII, 3, 4, 5,) that each bar has two sections,
and that the three lower sections in iron, cobalt and nickel a