Analysis of Comparison

THE sky of brightest gray seems dark
To one whose sky was ever white.
To one who never knew a spark,
Thro' all his life, of love or light,
The grayest cloud seems over-bright.
The robin sounds a beggar's note
Where one the nightingale has heard,
But he for whom no silver throat
Its liquid music ever stirred,
Deems robin still the sweetest bird.