When they are complète, descending genealogies constitute remarkable sources for the analysis of past demographic behaviour. However, few of them possess all the required qualities. Besides the risks of biases arising from the small numbers involved, they almost always present representativeness problems at the social level. Furthermore, the compilers of such genealogies often fall to include death certificates of adults, date of birth of the wives and most of ail information relating to children dying at an early age. On the other hand, the use of reconstituted lineages favours differential analysis and overcomes most problems associated with family reconstitution at the parish level. The study of adult mortality and of migrations are thus...