element between silver and gold would
form a link between them.

[Illustration: PLATE VI.]

SODIUM (Plate VI, 2) has been already described (p. 349, January), as a
type of the group, so we need only refer to its internal arrangement in
order to note that it is the simplest of the dumb-bell group. Its twelve
funnels show only four enclosed bodies, the same as we see in chlorine,
bromine, iodine, copper and silver, and which is very little modified in
gold. Its central globe is the simplest of all, as is its connecting rod.
We may therefore take it that sodium is the ground-plan of the whole group.

SODIUM: Upper part
{ 12 funnels of 16 each 192
{ Central globe 10
Lower part same 202
Connecting rod 14
----
Total 418
----
Atomic weight 23.88
Number weight 418/19 23.22
COPPER (Plate VI, 3) introduces an addition in the funnel, that we shall
find elsewhere, _e.g._, in silver, gold, iron, platinum, zinc, tin, the
triangular arrangement near the mouth of the funnel and adds to the ten
atoms in this nineteen more in three additional enclosed bodies, thus
raising the number of atoms in a funnel from the sixteen of sodium to
forty-five. The number in the central globe is doubled, and we meet for the
first time the peculiar cigar or prism-shaped six-atomed arrangement, that
is one of the most common of atomic groups. It ought to imply some definite
quality, with its continual recurrence. The central column is the three,
four, five, four, three, arrangement already noted.

COPPER: Upper part {12 funnels of 45 atoms 540
{Central globe 20
Lower part same 560
Connecting rod 19
----
Total 1139
----
Atomic weight 63.12
Number weight 1139/18 63.277
SILVER (Plate VI, 4) follows copper in the constitution of five of the
bodies enclosed in the funnels. But the triangular group contains
twenty-one atoms as against ten, and three ovoids, each containing three
bodies with eleven atoms, raise the number of atoms