The periodic sentence is a long sentence which doesn’t complete until the end.
A classic example is Rudyard Kipling’s poem If, which is one long sentence and has been voted several times the most popular poem of the English.
If you can keep your head when all about you
Are losing theirs and blaming it on you…
If you can dream – and not make dreams your master;
If you can think – and not make thoughts your aim;
If you can meet with Triumph and Disaster
And treat those two impostors just the same….
If you can talk with crowds and keep your virtue,
‘ Or walk with Kings – nor lose the common touch…
If If you can fill the unforgiving minute
With sixty seconds’ worth of distance run,
Yours is the Earth and everything that’s in it,
And – which is more – you’ll be a Man, my son!
Of course, Shakespeare did it too:
And, like the baseless fabric of this vision,
The cloud-capp’d towers, the gorgeous palaces,
The solemn temples, the great globe itself,
Yea, all which it inherit, shall dissolve …
And so did Sting:
Every breath you take,
Every move you make,
Every bond you break,
Every step you take,
I’ll be watching you.
It can be done in other ways, as Milton showed:
Of man’s first disobedience and the fruit
Of that forbidden tree, whose mortal taste
Brought death into the world, and all our woe,
With loss of Eden, till one greater
Man Restore us, and regain the blissful seat,
Sing Heav’nly Muse …