Very old times

“I was thinking of very old times, when the Romans first came here, nineteen hundred years ago—the other day…Light came out of this river since.” (Conrad 5).

This is one of Marlow’s first statements displaying his opinion that colonization and imperialism are evil, and associating them with evil. The Romans came to England, conquering it and its people, in 43 AD. By saying that the “light came out” of the river since then, he means that the river used to be beautiful and pure, but is now used only for conquering and colonizing.
(http://www.historic-uk.com/HistoryUK/England-History/RomanEngland.htm)