"A Cub Pilot" was written by Mark Twain. It's an autobiographical chapter where Twain tells about the day he had an experience as a steamboat pilot. The whole piece talks about Twain's life from childhood to adulthood and how his passion for steamboats began. Twain's adult narrative has a wise humor that does not detract from the reader and makes reading very enjoyable, fluid and pleasurable, proving how talented and intelligent the writer was.
There are several things that might be symbolized by the word bridge in this line from the poem, but perhaps one thing would be the connections that you form in life.