Periodical

Earth, air,

fire and water: just the four—

but the chemists need many more.

The top of the table is sparse, but every second period or layer,

like the bard from Japan whose verses never would scan, adds an extra list.

As we* reach the sixth and seventh periods, short of horizontal space,

we must** resort to footnotes just to keep a healthy handle on the case.

            * following the example of the chemists and their sort

            ** because the margin is too narrow for a full report

Turns out† that the seventh layer consists mostly of ones that do not exist

but need‡ to be synthesised.  Some of them do not even have proper names.

The eighth layer has not been started yet, so the only thing to do about

it is to turn back and traverse the table from the bottom to the top

so that the same period games

allow the lines to peter out

and stop.

            † as we step through the double-starred list of the actinoids

            ‡ by means of reactors or colliders or other toys