In responding to the kind invitation of the Clay Minerals Group, may I say that my notes are intended to express appreciation by a geologist of the illuminating work of the Group, as well as a plea for many favours to come?

History repeats itself. Forty years ago, when the coarser detrital and authigenic constituents of sediments were first being systematically examined, it became evident that their significance could not be assessed until we knew, in broad outline at least, the characters of the assemblages in all the major stratigraphical divisions. The more finely-grained materials were at that time in the main intractable: their investigation has had to await the development of the now familiar techniques utilized by the Group.