In his paper Mr Wilson finds that at very light loads the deformations of the contacting summits of the surface irregularities are of an essentially elastic nature, thus confirming some earlier work by Holm (1929). At the other extreme, there is the finding by Moore (1948) that under loads so high that they cause even the metal-in-bulk to deform plastically, the irregularities are nevertheless not necessarily permanently (i.e. plastically) deformed to such an extent as to become completely levelled.