Only a man harrowing clods
In a slow silent walk
With an old horse that stumbles and nods
Half asleep as they stalk.
Only thin smoke without flame
From the heaps of couch-grass;
Yet this will go onward the same
Though Dynasties pass.
Yonder a maid and her wight
The object of contemplation is a pile of grass-like weeds smouldering. 
 This stanza, like the first, begins with the word “Only.” There are no verbs in these two lines; in face, the only words here are modifiers of the noun “smoke.” All these modifiers are absolutely necessary to make the point (or produce the impression) that man’s involvement here is not evil, destructive, or intrusive. “Couch-grass” is also known as  quack grass , a creeping, invasive weed that strangles out other plant life. 
 The humans who make this smoldering pile are acting constructively, and the “thin smoke” contrasts with battle scenes from the Great War, where the smoke is usually thick and poisonous. 
 These lines anticipate lines in a later poem by T.S. Eliot, The Hollow Men: 
 Shape without form, shade without colour, Paralysed force, gesture without motion
In Time of The Breaking of Nations