A Route of Evanescence
With a revolving Wheel--
A Resonance of Emerald--
A Rush of Cochineal--
And every Blossom on the Bush
Adjusts its tumbled Head--
The mail from Tunis, probably,
Just like  the Emerald from the previous line , another descriptive and detailed image appears. 
 Cochineal is both an insect, a dye, and a shade of colour: 
 

A Route of Evanescence