The orientation of graves is the result of many factors, and explanations for this custom are diverse. West—east orientation is frequent, and is explained by astronomical or theological considerations, which are difficult to separate in practice; the adoption of this custom by the Christian Church reflects earlier practice, rather than a new dogma. Some post-Roman cemeteries seem to be orientated by reference to the position of sunrise. This allows possibilities of determining season of burial, and even perhaps the incidence of plague. More scientific observation and analysis are needed to resolve these problems, as well as the use of well-dated evidence from modern graveyards.