Final answer:
The unusual syntax in these lines from "The Negro Speaks of Rivers" by Langston Hughes lends a sense of antiquity and intimacy to the speaker's connection to rivers.
Step-by-step explanation:
The effect of the unusual syntax in these lines from "The Negro Speaks of Rivers" by Langston Hughes is that it lends a sense of antiquity and timelessness to the speaker's connection to rivers. By saying, "I've known rivers" instead of "I have known rivers," Hughes uses a colloquial and informal tone that suggests a personal and intimate relationship with the rivers. This syntax choice emphasizes the speaker's deep understanding and experience with rivers, highlighting their significance in the speaker's life and the history of the world.