Oceanography, as is well known, is considered a young science, lacking in old traditions. Nevertheless, the interest in oceans and seas may in some special cases be traced back as far as the centuries before the beginning of the Christian era. Reference may be made, for instance, to the Roman poet Lucretius, who in his work De rerum natura expressed astonishment that the amount of water in the seas does not augment in spite of the fact that the discharge of all the rivers in the world gathers there. Lucretius considered the effect of evaporation a possible explanation for this fact, thus mentioning one of the principal factors which determine the water cycle in nature, at least during periods in which average climatological conditions prevail. During periods characterised by more pronounced climatological deviations the equilibrium of the water cycle may be greatly disturbed. As an interesting example it may be mentioned that during the last glacial period considerable quantities of sea water were transformed into inland ice. It has been estimated that the water level in the oceans and seas at that epoch was approximately 100 metres lower than at the present time.