CONTENT S

Lesson One

Lesson Two

Lesson Three

Lesson Four

Lesson Five

Review One

Lesson Six

Lesson Seven

Lesson Eight

Lesson Nine

Lesson Ten

Review Two

Lesson Eleven

Lesson Twelve

Lesson Thirteen

Lesson Fourteen

Lesson Fifteen

Review Three

Lesson Sixteen

Lesson Seventeen

Lesson Eighteen

Lesson Nineteen

Lesson Twenty

Review Four

Lesson Twenty-One

Lesson Twenty-Two

Lesson Twenty-Three

Lesson Twenty-Four

Lesson Twenty-Five

Review Five

Ⅰ．The Story of Archimedes and the Bath

Supplementary Reading

Ⅱ．Sendirng Messages and Pictures by Satellites

Ⅲ．Living Under the Sea

Ⅳ．The World's First Completely Automatic Railway

Ⅴ．Helicopters—Aeroplanes of Many Uses

Ⅵ．The Wonderful Talking Machine

Ⅶ．Taming the Sun

Ⅷ．Plastics—Man's Most Useful Material

Ⅸ．Pollution

Reference Translations of Supplementary Reading

Appendixes