Lesson 25-2 Non-auditory effects of noise On turning eagerly to the text...

Lesson 25-1 Non-auditory effects of noise Many people in industry and th...

Lesson 24-2 Beauty There is no sky in June so blue that it does not poin...

Lesson 24-1 Beauty A young man sees a sunset and, unable to understand o...

Lesson 23-2 Bird flight Duck, and like them the pigeons, are endowed wit...

Lesson 23-1 Bird flight No two sorts of birds practise quite the same so...

Lesson22-2 Knowledge and progress 知识和进步 Then knowledge began to be accum...

Lesson22-1 Knowledge and progress 知识和进步 Why does the idea of progress lo...

Lesson 21-2 William S. Hart and the early 'Western' film And although no...