Magnesium compounds, 7, 10, 11, 41, 47, 113, 115, 116, 121, 133, 155 Malm-bricks, 11 Malms, 10, 68 Marcasite, 10, 13 Marine clays, 61, 93 Marls, 10, 51, 54, 55, 57, 67, 68, 88, 130, 132, 166 Mechanical analysis, 137 Medway mud, 132 Melting point, 31, 32 Mica, 7, 8, 76, 104, 105, 116, 140, 141, 144, 160 Microscopical examination, 18, 105, 143, 158 Millstone grit, 54, 55, 117 Mineral nature of clay, 3 Minerals resembling clay, 158 Mining ball clay, 111 Modelling clays, 130 Moisture, 15, 144 Molecular attraction, 22 Molecular constitution of clay, 21, 156 Montmorillonite, 134 Mundic, 13 Muscovite, 105 Newtonite, 158 Nodules, 121, 127 Non-plastic material, 43, 121, 151 Non-refractory clays, 166 Occurrence of clays, 48, 116 Ocean currents, action of, 89 Odour of clay, 19 Oil, bleaching, 134 Oil shales, 61, 122, 123 Oolite clays, 59, 134 Ooze, 95, 99 Organic matter, 19, 119 Origins of clays, 48, 71, 160, 165 Oxford clay, 59, 95, 164 Oxides in clay, 10, 82 Paint, clays for, 109 Paper, clays for, 109 Particles, nature of, 18, 31, 106, 107, 150 Paving brick clays, 166 Pelagic ooze, 95, 99 Pelinite, 83, 148, 149 Permian clays and shales, 57, 112, 124 Pholerite, 117 Physical characters of clays, 17 Picking clay, 121 Pipe clays, 64, 65, 82, 109, 166 Plant-extracts in clays, 26 Plastic clays, 2, 43, 65, 67, 82, 88, 102, 112, 123, 147, 148, 160 Plasticity, 20-27, 41, 46, 97, 98, 99, 108, 109, 112, 117, 123, 125, 127, 151, 160 Pleistocene clays, 67 Pockets, 65, 85, 101, 116, 166 Porcelain, 37, 46, 73, 109, 110, 125, 129 Pores in clay, 30, 114 Porosity, 30, 39, 121, 131, 155 Portland cement, 131 Potash compounds, 7, 10, 113, 115, 116, 121, 157, see _Alkalies_ Pottery clays, 1, 5, 31, 46, 66, 100, 101, 104, 110, 112, 114, 125, 129, 162, 166 Precambrian clays, 51 Precipitated clays, 97, 152 Primary clays, 70, 71, 84, 165 Proximate analysis, 16, 144 Purbeck clays, 59 Pure clays, 5, 6, 7, 142, 155, 156 Purification of clay, 7, 66, 78, 104, 113, 128, 140 Pyrites, 10, 13, 44, 56, 57, 119, 124, 128 Quartz, 8, 104, 110, 118, 140, 141, 143