Meta-krypton; Xenon, Meta-xenon; Kalon, Meta-kalon; the last pair and the
meta forms are not yet discovered by chemists. These all show the presence
of a periodic law; taking an arm of the star in each of the five pairs, we
find the number of atoms to be as follows :--

40 99 224 363 489
47 106 231 370 496
It will be observed that the meta form in each case shows seven more atoms
than its fellow.

[Illustration: PLATE XX.]

HELIUM (Plate III, 5, and Plate XX, 1) shows two "cigar"-bearing
tetrahedra, and two hydrogen triangles, the tetrahedra revolving round an
egg-shaped central body, and the triangles spinning on their own axes while
performing a similar revolution. The whole has an attractively airy
appearance, as of a fairy element.

HELIUM: Two tetrahedra of 24 atoms 48
Two triangles of 9 atoms 18
Central egg 6
----
Total 72
----
Atomic weight 3.94
Number weight 72/18 4.00
NEON (Plate XX, 2 and 6) has six arms of the pattern shown in 2, radiating
from the central globe.

NEON: Six arms of 40 atoms 240