Aime estimated this depth at 150-200 fathoms, while the observations of the Austrian expedition in the eastern Mediterranean found it to be from 200 to nearly 400 fathoms. In the Red Sea, where a similar seasonal change occurs, the depth to which the surface layer warms up is about 275 fathoms. The great difference in salinity between the surface and the deep water excludes the possibility of effective convection in the seas of northern Europe, and in the open ocean the currents which are felt everywhere, and especially those with a vertical component, must exercise a very disturbing influence on convection.