The long ovoids within each bar revolve round the central axis of the bar, remaining parallel with it, while each spins on its own axis; the iron cone spins round as though impaled on the axis. 14 bars of 72 atoms 1008 Atomic weight 55.47 Number weight 1008/18 56.00 IRON (Plate IV, 1, and XVII, 3): 14 bars of 74 atoms 1036 Atomic weight 57.70 Number weight 1036/18 57.55 COBALT (Plate XVII, 4): 14 bars of 76 atoms 1064 Atomic weight 58.30 Number weight 1064/18 59.11 NICKEL (Plate XVII, 4): (The weight of cobalt, as given in Erdmann's _Lehrbuch_, is 58.55, but Messrs. Parker and Sexton, in _Nature_, August 1, 1907, give the weight, as the result of their experiments, as 57.7.) [Illustration: PLATE XVIII.] The next sub-group, ruthenium, rhodium, and palladium, has nothing to detain us. It will be observed that each bar contains eight segments, instead of the six of cobalt and nickel; that ruthenium and palladium have the same number of atoms in their upper ovoids, although in ruthenium a triplet and quartet represent the septet of palladium; and that in ruthenium and rhodium the lower ovoids are identical, though one has the order: sixteen, fourteen, sixteen, fourteen; and the other: fourteen, sixteen, fourteen, sixteen. One constantly asks oneself: What is the significance of these minute changes? Further investigators will probably discover the answer. 14 bars of 132 atoms 1848 Atomic weight 100.91 Number weight 1848/18 102.66 RUTHENIUM (Plate XVIII, 1): 14 bars of 134 atoms 1876 Atomic weight 102.23 Number weight 1876/18 104.22 RHODIUM (Plate XVII, 2): 14 bars of 136 atoms 1904 Atomic weight 105.74 Number weight 1904/18 105.77 PALLADIUM (XVIII, 3):