A loaded barge is easier to move than a loaded cart, and early engineers knew i long bef they co explain w. Water car the wei, so a sin horse o a tow could pu a load that twenty horses could not drag along a road. The difficulty was never the boat but the hill, and the lock, a chamber that raises a vessel one step at a time, is what finally let canals cross uneven country.

Type only the missing letters. Each box is one letter, and the number of boxes matches the letters that are missing.