Dorking, well at, 171 Drainage area, definition, 25 Drift, 5-7, 21, 22 ---- outcrop covered by, 21 Driving tubes, 67, 73, 74 ---- tube well, 81-83 Drum curb, 42 Dru's first trepan, 113 ---- system, 113 ---- ----, summary, 126 Dudlow Lane well, 160 Dulwich, well at, 193 Durham, sinkings in, 93 ---- wells in, 155 Dyke, effect of, 4 Dynamite, 44 Earth-fast, definition, 44 East Barnet, well at, 190 East Ham Level, well at, 193 Edgware, well at, 193 Edgware Road, well at, 193 Edlesborough, well at, 193 Eltham, wells at, 193 Enfield Lock, well at, 193 Enlarging hole below tubes, 67, 68 ---- shot-holes, 48 Epping, well at, 193 Erith, well at, 193 Europe, rainfall in, 28, 29 Euyenhausen joint, 85, 88 Excavation in wells, table of, 204 Explosive agents, use of, 45 Fan, for ventilation, 52 Farnham, well at, 193 Fault, effect of, 4 Fauvelle's system, 79 Fissures, 2, 12 ---- in blasting, 46 ---- in chalk, 8 Flat chisels, 62 Fleet Street, well at, 193 Formation, mineral character of, 11 Foul air in wells, 52, 209 Four and a half inch steining, 59 Free-falling tools, Dru's, 117-123 Freshwater, well at, 187, 188 Fulmer, well at, 193 Fuse for blasting, 50 Gases in wells, 52, 209 Gault, 5 General conditions of outcrop, 18 Geological conditions, epitome of, 10 ---- ---- primary, 4 Gneiss, rainfall on, 27 Golden Lane, well at, 193 Granite, rainfall on, 27 Grapin, or clutch, 107 Grapnels, 107, 139-141 Gravesend, well at, 193 Green Lane wells, 160 Greensands, 5, 8 Greenwich, wells at, 193 Grenelle, well at, 85, 179 Guides, bore-head, 132 ----, Dru's, for rods, 121 Guncotton, 44 Gunpowder, 44 ---- weight of, 49 Hackney Road, well at, 193 Haggerstone, well at, 194 Hainault Forest, well at, 194 Half-brick steining, 59 Halstead, well at, 194 Hammersmith, well at, 194 Hampstead, wells at, 194 ---- Road, wells at, 194 Hand-dog, 65 Hand-jumpers, 47 Hanwell, well at, 194 Hard rock, Dru's system, 125 ---- ---- sinking in, 44, 53 Harrow, well at, 171, 194 Hastings sand, 5 Haverstock Hill, well at, 194 Hayes, well at, 194 Headings or tunnels, 53, 54 Hedgerley, sands and clays at, 17 Height of strata above surface, 23 Hendon, well at, 194 Herne Bay, section at, 12 Highbury, wells at, 172, 194 Hills or mountains, 5 ---- drift on, 6 ---- flat-topped, 20 ---- outcrop on, 19 Hoddesdon, well at, 194 Holloway, wells at, 194 Hollow rods, 80 Hoop-iron, boring with, 60, 61 Horizontal strata, 9 Hornsey, wells at, 194 Horselydown, well at, 194 Hoxton, well at, 195 Hungerford, section near, 14 Hyde Park Corner, well at, 195 Hydraulic tube-forcers, 146-148 Ickenham, well at, 195 Instruments used in blasting, 46 Iron cylinders for lining, 56 ---- drum curb, 42