T wanted to repeat the magnetism experiments of several months ago, so on his own he and W looked at how magnetic force can pull through glass and water and how magnets only attract iron, not glass (glass marbles were not drawn to magnet). T then described his experiment to me.
A month ago ben also made a game with boys demonstrating how magnetic force works through cardboard. They drew a racing track on strong cardboard and made paper cars with paperclips stuck to the bottom. A magnet applied to the paperclip from underneath the cardboard pulls the paper car around the track.