Langmuir circulations in a wind wave tank have been observed and measured by a variety of methods including dye patterns and floating surface tracers. On the basis of measurements of cellular wavelength λc as a function of surface wavelength λω and depth H a tentative functional relation for the dependence of λc/H upon λω/H is proposed. The experiements clearly imply that the waves play an important role in the mechanism of formation of the Langmuir circulations but that the depth of the layer has a significant modifying influence. On the basis of certain 'rake' experiments and other indirect observations it is proposed that when λω/H<1, the primary scale of Langmuir circulations, related to λω, transfers energy to a larger scale that is commensurate with the depth such that λc/H?2. Under these circumstances, two distinct scales of Langmuir circulations may exist simul