Analysis of Unity

Space is ample, east and west,
But two cannot go abreast,
Cannot travel in it two:
Yonder masterful cuckoo
Crowds every egg out of the nest,
Quick or dead, except its own;
A spell is laid on sod and stone,
Night and day were tampered with,
Every quality and pith
Surcharged and sultry with a power
That works its will on age and hour.