How does Joseph Conrad use imagery in Nostromo?

Imagery:

"These, then, are the legendary inhabitants of Azuera guarding its forbidden wealth; and the shadow on the sky on one side with the round patch of blue haze blurring the bright skirt of the horizon on the other, mark the two outermost points of the bend which bears the name of Golfo Placido, because never a strong wind had been known to blow upon its waters."

"Born in the country, as his father before him, spare and tall, with a flaming moustache, a neat chin, clear blue eyes, auburn hair, and a thin, fresh, red face, Charles Gould looked like a new arrival from over the sea."

"Worked in the early days mostly by means of lashes on the backs of slaves, its yield had been paid for in its own weight of human bones."