----
Atomic weight 19.90
Number weight 360/18 20.00
META-NEON (Plate XX, 3 and 6) differs from its comrade by the insertion of
an additional atom in each of the groups included in the second body within
its arm, and substituting a seven-atomed group for one of the triplets in
neon.

META-NEON: Six arms of 47 atoms 282
Central tetrahedra 120
----
Total 402
----
Atomic weight ----
Number weight 402/18 22.33
ARGON (Plate XX, 4, 6 and 7) shows within its arms the _b_ 63 which we met
in nitrogen, yttrium, vanadium and niobium, but not the "balloon," which we
shall find with it in krypton and its congeners.

ARGON: Six arms of 99 atoms 594
Central tetrahedra 120
----
Total 714
----
Atomic weight 39.60
Number weight 714/18 39.66
METARGON (Plate XX, 5, 6 and 7) again shows only an additional seven atoms
in each arm.

METARGON: Six arms of 106 atoms 636
Central tetrahedra 120
----
Total 756
----
Atomic weight ----
Number weight 756/18 42
[Illustration: PLATE XXI.]

KRYPTON (Plate XXI, 1 and 4, and Plate XX, 6 and 7) contains the nitrogen
"balloon," elongated by its juxtaposition to _b_ 63. The central tetrahedra
appear as usual.

KRYPTON: Six arms of 224 atoms 1344
Central tetrahedra 120
-----
Total 1464
-----
Atomic weight 81.20
Number weight 1464/18 81.33
META-KRYPTON differs only from krypton by the substitution of _z_ for _y_
in each arm of the star.

META-KRYPTON: Six arms of 231 atoms 1386
Central tetrahedra 120
-----
Total 1506
-----
Atomic weight -----
Number weight 1506/18 83.66
XENON (Plate XXI, 2 and 4, and Plate XX, 6 and 7)