Unit Three 1
47．The American Scene 1
48．The Voices of Time 10
49．A World Without Oil 17
50．The Tornado 22
51．Venus—the Burning Question 30
52．My Uncle 35
53．Running for Governor 41
54．Factory Life—a Student's Experience 46
55．The Open Boat 52
56．Electric Fish 60
57．The Vanishing Lady 65
58．The Cable That Crossed the Atlantic 76
59．The Mistake 84
60．Dr.Einstein's Marvelous Flying Machine 90
Unit Four 96
61．Shipwreck 96
62．Black Holes 113
63．Time Zones and the Date Line 119
64．A New Kind of Whale 124
65．School and Life 140
66．A Warmer or a Colder Earth? 145
67．Smoking and Cancer 150
68．A Robot About the House 155
69．The Olympic Games 163
70．Plague and Fire 168
71．Symptoms 177
72．After Twenty Years 184
Key to Exercises 192