The sample of Gault, of which the analysis is given below, was obtained from the Clay Pits at Dunton Green, which I visited with the “London Geological Field Class” during June last. At this place the Gault rests upon a bed of reddish yellow sand (Lower Greensand), which is mixed in certain proportions with the Gault clay to form bricks. This sand, of which I also give an analysis, is very moist when first taken from the bed, but very rapidly becomes dry, upon exposure to the air, so that it afterwards loses very little more water at 100°C. The Gault, as taken from the pit, contained 26·68 per cent of moisture, but upon ignition of the dried substance, in a muffle furnace, it becomes so hard that it will scratch glass easily.