I am the ghost of Shadwell Stair.
Along the wharves by the water-house,
And through the cavernous slaughter-house,
I am the shadow that walks there.
Yet I have flesh both firm and cool,
And eyes tumultuous as the gems
Of moons and lamps in the full Thames
When dusk sails wavering down the pool.
Owen is asserting his physical presence, the reality of his flesh. The description ‘firm and cool’ suggests awareness and strong purpose in what he is doing.