内容简介：
From the "Wrigley Books" series - little science books arranged by topic for the youngest reader. Clear, straightforward words and illustrations introduce children to the things around them and the practical uses to which they are put. Other titles by Denis Wrigley published by the Lutterworth Press: "Ideas: Wrigley Book No. 10", "Magnet: Wrigley Book No. 17", "Oil: Wrigley Book No. 12", "Reflection: Wrigley Book No. 18", "Springs: Wrigley Book No. 13", "Strength: Wrigley Book No. 15", "Time: Wrigley Book No.16", and "Wood: Wrigley Book No. 14".