The Brain, within its Groove
Runs evenly—and true—
But let a Splinter swerve—
'Twere easier for You—
To put a Current back—
When Floods have slit the Hills—
And scooped a Turnpike for Themselves—
And trodden out the Mills—
Water, it is said, is the most destructive force on earth. With time, a simple trick of water can hollow out a cave, or create a grand canyon. Here Emily Dickinson is showing the awesome force of the mind’s discursiveness, saying that it is easier to prevent water from destroying what it does — think of a Hurricane for instance — than to keep the mind in its groove 
 (Source:   Corsera – Modern Poetry.  )
The Brain within its Groove