Conservation in Physics Teaching,History of Science and in Child Development

The current work is an exploratory study on the ideas thatstudents in their fourth semester of engineering have about ``conservation'. Wereview the Piagetian position on the importance of conservations in logical operational structures inchild development and we comment upon other current trends in cognitive psychology. We discussbriefly the development of conservations in science during the 17th, 18th and 19th centuries and we pointout the contrast between this and how most textbooks introduce this subject. We have also carried out afirst, tentative analysis of the answers given by a sample of these students to a brief questionnaire about``conservation' and ``non-conservation'.