ABSTRACT
The actual way in which a demonstration is introduced and performed can have a profound influence on its effectiveness. Barlex and Carré58 have some wise things to say about making lessons visually appealing; they are discussing teach ing in school., but the same principles apply at any level. They show two photographs of alternative layouts for a demonstration lecture on the preparation of chlorine. In the first there is a jumble of reagent bottles behind the lecturer 3 leftovers from the last lesson still piled on the bench, yesterday’s homework still written on the blackboard and the apparatus set out in a rather confusing way so that it is not immediately obvious which tube is going where. In the second photograph there is nothing visible except the appar atus itself and this is arranged very clearly so that students can see exactly what is connected to what. Obviously it is not necessary to elaborate on the important principles illus trated by the two pictures.
