Read it through once

When I had learned the name and position of every visible feature of the river; when I had so mastered its shape that I could shut my eyes and trace it from St. Louis to New Orleans; when I had learned to read the face of the water as one would cull the news from the morning paper; and finally, when I had trained my dull memory to treasure up an endless array of soundings and crossing-marks, and keep fast hold of them, I judged that my education was complete: so I got to tilting my cap to the side of my head, and wearing a tooth-pick in my mouth at the wheel. Mr. Bixby had his eye on these airs. One day he said--