"These moribund shapes were free as air--and nearly as thin. I began to distinguish the gleam of eyes under the trees. Then,
glancing down, I saw a face near my hand. The black bones reclined at
full length with one shoulder against the tree, and slowly the eyelids
rose and the sunken eyes looked up at me, enormous and vacant, a kind of
blind, white flicker in the depths of the orbs, which died out slowly.
The man seemed young--almost a boy--but you know with them it's hard to
tell. I found nothing else to do but to offer him one of my good Swede's
ship's biscuits I had in my pocket. The fingers closed slowly on it and
held--there was no other movement and no other glance."

Identify the theme of this excerpt from The Heart of Darkness, by Joseph Conrad, and explain the author's interpretation of the British Empire.