The story of the first attempt to reach the North Pole. Houghton Mifflin Vocabulary Readers, Book 6.1.4. Key Vocabulary: ascent, endeavored, entangled, ratlines, rigging, seasoned, and treacherous. Number of Words: 611.The story of the first attempt to reach the North Pole. Houghton Mifflin Vocabulary Readers, Book 6.1.4. Key Vocabulary: ascent, endeavored, entangled, ratlines, rigging, seasoned, and treacherous. Number of Words: 611.