Rain, 44, 85, 86 Rational analysis, 141 Reading clays, 63 Recent clays, 67 Rectorite, 158 Re-deposited clays, 98 Red bricks, 12 Red burning clays, 141, 142, 166 Red iron oxide, 12 Red ware, 113 Reduction in volume, 30 Refractoriness, 34, 119, 120, 123, 155 Refractory articles, 5, 119 Refractory clays, 9, 32, 33, 35, 38, 52, 65, 82, 104, 116, 165, 166 Residual clays, 70, 84, 166 Resistance to abrasion, 119 Resistance to corrosion, 119 Resistance to crushing, 46 Resistance to cutting, 119 Resistance to temperature, see _Refractoriness_ Resistance to weathering, 76 Ringing sound, 110 River-deposited clays, 88 Rivers, 85, 87 Rock binds, 53 Rockingham, 113 Rock-like clays, 2 Rocks associated with clay, 48 Roman cements, 133 Roofing tiles, 57, 63, 126, 128 Sagger marls, 54 Sand, 7, 31, 41, 62, 82, 89, 100, 101, 117, 133, 138, 144 Sandstones, 53 Sandy clays, 68 Sandy loams, 88 Sandy marls, 88 Sanitary articles, 5, 113 Sawdust, 40 Scum, 10 Sea, action of, 85, 89, 99 Sea-deposited clays, 93 Secondary clays, 70, 82, 83, 166 Sedimentary rocks, 48 Sedimentation of clay, 43, 88, 90, 104 Seger cones, 33, 34 Selection of clay, 122 Selenite, 10 Separation of clays, 90, 145 Settling, 43 Sewerage pipes, 113 Shale oil, 15, 61 Shale tar, 123 Shales, 2, 5, 51, 52, 53, 57, 61, 96, 104, 122, 130, 132, 138, 151, 162, 166 Shrinkage, 11, 29, 58, 68, 102, 110, 117, 119, 121, 127, 131, 153 Sifting, 7, 138 Silica, 6, 7, 80, 154, 155, 161 Silica rock, 118 Silicates, 8, 82 Siliceous clays, 117 Sillimanite, 46, 154 Silt, 90, 91, 99, 139, 144 Silurian clays and shales, 51, 124 Sintering, 38 Size of particles, 18, 21, 31, 106, 107, 150 'Skeleton,' 115 'Skin' on ware, 131 Slag in bricks, etc., 11, 13, 119, 155 Slates, 51 Slurry, 39, 43, 152 Snow, 85 Soda compounds, 7, 10, 113, 115, 116, 121, 157, see _Alkalies_ Softening point, 33 Soil, see _Agriculture_ Solubility of clay, 151, 159 Soluble salts, 10 Sorting, 90 Sources of clays, 85 Specification of fire clays, 120 Specific gravity, 18, 106, 151 Staffordshire bricks, 13, 56 Standard clay, 4 Stone, Cornish, 110, 116 Stoneware clays, 104, 112, 113, 156, 165, 166 Stones, 7, 65, 100, 102, 128, 138, 144 Streams, 85, 86 Strength, 23, 45, 113 Sub-surface clays, 5 Sulphates in clay, 10, 12, 82 Sulphides in clay, 10, 82 Sulphuric acid, 124 Sunlight, 45 Surface clays, 2, 5, 52, 112 Suspension of clay, 43, 90, 140, 152 Swelling, 15, 102