What disturb(s) the calm?

The Forst performs its secret ministry,    
Unhelped by any wind. The owlet's cry    
Came loud—and hark, again! loud as before.    
The inmates of my cottage, all at rest,    
Have left me to that solitude, which suits    
Abstruser musings : save that at my side    
My cradled infant slumbers peacefully.    
Tis calm indeed! so calm, that it disturbs    
And vexes meditation with its strange    
And extreme silentness ......    
— S.T. Coleridge