Companion volume, but the same criticism maintains here- the presentations are good, but there seems no central thought, no core to the idea, and the result seems a hodgepodge.... Where does a spring come from? What happens when a ship comes to a drawbridge? What goes on in a bulb between flowerings? What can prevent the sun's rays from falling on the earth? Why does fire make the engine go? The text is again expanded captions accompanying diagram type pictures.