THERE are very few recorded observations on the temperature coefficient of contact angles1. These suggest that the coefficient is very small, if not zero, which is at first sight surprising. Adam2 has pointed out that, as a consequence, “it appears that temperature affects the surface tension and the adhesion to the solid to very nearly the same proportionate extent”. He has discussed this in terms of the thermal motions of the liquid, and has suggested that “the decrease in the adhesive field of force with rising temperature is much less in solids than in liquids and is due principally or wholly to translatory motion”. The implication, however, that the temperature coefficient of the free surface energy of solids is negligible because translatory motions are absent seems to require further justification.