What thing is this that, built of salt and lime

What thing is this that, built of salt and lime
And such dry motes as in the sunbeam show,
Has power upon me that do daily climb
The dustless air?—for whom those peaks of snow
Whereup the lungs of man with borrowed breath
Go labouring to a doom I may not feel,
Are but a pearled and roseate plain beneath
My winged helmet and my winged heel.
What sweet emotions neither foe nor friend
Are these that clog my flight? what thing is this
That hastening headlong to a dusty end
Dare turn upon me these proud eyes of bliss?
Up, up, my feathers!—ere I lay you by
To journey barefoot with a mortal joy.