Compact and safe heat source for school heat radiation experiments. It comprises a base and cage containing a custom made infra-red heating lamp of the dull emitter type. This means that it is impossible for a pupil to get an electric shock by prodding it with a paper clip etc. In normal use, four thermometers, one with a blackened bulb, one with a silvered bulb, one with a white bulb and one with a €œnude