Changes in the relative level of sea and land along the oceanic borders of the globe seem to have been in continual progress during the entire historic period. Too slow and gradual for direct observation, they can only be detected through comparison of ancient with modern maps, records, or statements. This comparison has now, in hundreds of cases, been made, and it is well established that stability of coastline is the exception, movement of elevation or depression the rule. In one region, it has been observed, the sea for long periods of time has been in continual retreat; at another location it has been long advancing over the land, while at some third point it seems to have remained fixed in position.