Read it through once

By the time we had gone seven or eight hundred miles up the river, I had learned to be a tolerably plucky up-stream steersman, in daylight, and before we reached St. Louis I had made a trifle of progress in night-work, but only a trifle. I had a note-book that fairly bristled with the names of towns, 'points,' bars, islands, bends, reaches, etc.; but the information was to be found only in the notebook--none of it was in my head. It made my heart ache to think I had only got half of the river set down; for as our watch was four hours off and four hours on, day and night, there was a long four-hour gap in my book for every time I had slept since the voyage began.