A study of the geological structure of continental margins makes it extremely difficult to accept geophysical deductions that there is an important difference in character between continents and the adjacent ocean floor. The continents are areas of great complexity and have been subjected to intense compression; their known structure shows no resemblance to the 'sialic' and 'simatic' layers postulated by the geophysicist. The continental structures frequently strike out into the ocean and it seems most improbable that they do not continue far out to sea. There is no positive geological evidence of the permanence of the ocean or that the ocean floors are structurally different from the continents. The seismic results may well be explained by extensive submarine lava floors or in some other way. A world-wide peridotite layer at such a depth seems most improbable.