in preserving the
bar form, gaining the necessary increase by a multiplication of contained
spheres within the ovoids. Osmium has one peculiarity: the ovoid marked _a_
(XVIII, 4) takes the place of axis in the upper half of the bar, and the
three ovoids, marked _b_, revolve round it. In the lower half, the four
ovoids, _c_, revolve round the central axis. In platinum, we have marked
two forms as platinum A and platinum B, the latter having two four-atomed
spheres (XVIII, 6 _b_) in the place of the two triplets marked a. It may
well be that what we have called platinum B is not a variety of platinum,
but a new element, the addition of two atoms in a bar being exactly that
which separates the other elements within each of the sub-groups. It will
be noticed that the four lower sections of the bars are identical in all
the members of this sub-group, each ovoid containing thirty atoms. The
upper ring of ovoids in iridium and platinum A are also identical, but for
the substitution, in platinum A, of a quartet for a triplet in the second
and third ovoids; their cones are identical, containing twenty-one atoms,
like those of silver and tin.

14 bars of 245 atoms 3430
Atomic weight 189.55
Number weight 3430/18 190.55
OSMIUM (Plate XVIII, 4):

14 bars of 247 atoms 3458
Atomic weight 191.11
Number weight 3458/18 192.11
IRIDIUM (Plate XVIII, 5):

14 bars of 249 atoms 3486
Atomic weight 193.66
Number weight 3486/18 193.34
PLATINUM A (Plate XVIII, 6 _a_):

14 bars of 251 atoms 3514
Atomic weight ------
Number weight 3514/18 195.22
PLATINUM B (Plate XVIII, 6 _b_):

V a.--THE SPIKE GROUPS.

I place within this group lithium, potassium, rubidium, fluorine, and
manganese, because of their similarity in internal composition. Manganese
has fourteen spikes, arranged as in the iron group, but radiating from a
central globe. Potassium has nine, rubidium has sixteen, in both cases
radiating from a central globe. Lithium (Plate IV, 2) and fluorine (Plate
IV, 3) are the two types which dominate the group, lithium supplying the
spike which is reproduced in all of them, and fluorine the "nitrogen
balloon" which appears in all save lithium. It will be seen that the
natural affinities are strongly marked. They are all