The Concrete Devices of Structural

In the teaching of science it is common practice to use models and devices which make it possible for the pupils to see with their own eyes all those usually “invisible” objects which they want to study. A model of the solar system, for instance, allows the pupils to discover the relative movements of earth, sun, and moon in a simple set-up which shows the structure of the system. Even abstract principles and formulas become clear when they arc illustrated by experiments which the pupils carry out with structura lly correct concrete devices.