WHAT IS SOUND?

Do you know that hearing is just feeling with the ear? That in reality,

the thing we call sound, which we think of as a noise or as a musical

note, is just an impression on the brain? Very few boys know this, and

if you would like to be one of the few that do, you surely want an

outfit of

Gilbert Weather Bureau (Meteorology) for Boys · 第 120 / 128 题