Title: Up, down, or open-moving machines
Description: Discusses how simple machines work using drawbridges, escalators, and retractable roofs as examples.
Subjects: Simple machines, Juvenile literature, Machine design, History, Readers (Elementary), Readers (Primary), Machines simples, Ouvrages pour la jeunesse, Machines, Conception et construction, Histoire, Anglais (Langue), Lectures et morceaux choisis (Enseignement primaire)