A few years ago, while inspecting some iron ore deposits at Smallacombe, near Bovey Tracey, in Devon, I noticed the occurrence of certain brightly colored green, red and brown clays in considerable quantity. I took several specimens of the green clay at the time, and on my return home laid them aside in a lumber closet, where they became buried with other specimens, from which they have only lately been disinterred. After so long a stay in a tolerably dry situation I thought they might be regarded as in a normally hygrometric condition, and it was in this state that I subjected then to examination and analysis, with the following results.