',n_n_n-_ I REESE LIBRARY UNIVERSITY OF CALIFORNIA. XT* J e .. \ ,.-... :"/ S3 1 A TEXT-BOOK OF ORE AND STONE MINING. Morfes FOE THE USE OV MANAGERS OF MINES & COLLIERIES, MINING ENGINEERS, SURVEYORS, AND METALLURGISTS. PRACTICAL GEOLOGY (AIDS IN). By G. A. J. COLE, F.G.S., Prof, of Geology, Royal College of Science, Dublin. With numerous Illustrations.. SECOND EDITION. 10s. 6d. COAL MINING. By H. W. HUGHES, F.G.S., Assoc. R.S.M. With 490 Illustrations. SECOND EDITION. 18s. MINE SURVEYING. By B. H. BROUGH, F.G.S., formerly Instructor of Mine Surveying, Royal School of Mines. FOURTH EDITION, Illustrated, 7s. 6d. TRAVERSE TABLES ; computed to Four Places Decimals for every Minute of Angle up to 100 of Distance. By RICHARD LLOYD GUEDEN, Author- ised Surveyor for the Government of New South Wales and Victoria. THIRD- EDITION. 21s. BLASTING AND THE USE OF EXPLOSIVES. By 0. GUTTMANN, A.M.lnst. C.E. With Folding Plates and Illustrations. 10s. 6d. ASSAYING. By J. J. BERINGER, F.C.S., F.I.C., and C. BERINGER,. F.C.S. SECOND EDITION. 10s. 6d. ELEMENTS OF METALLURGY ; The Art of Extracting Metals from their Ores. By J. ARTHUR PHILLIPS, C.E., F.C.S., F.G.S., and H. BAUEBMAN,. F.G.S. With numerous illustrations. THIRD EDITION. 36s. NEW METALLURGICAL SERIES RDITED BY W. C. ROBERTS-AUSTEN, C.B., F.R.S., Chemist and Assay er of the Royal Mint ; Prof, of Metallurgy , Royal College of Science. 1. INTRODUCTION TO THE STUDY OF METALLURGY. By the EDITOR. THIRD EDITION. 12s. 6d. 2. GOLD. By T. K. ROSE, Assoc. R.S.M., B.Sc., Assistant-Assayer of the Royal Mint. 21s. 3. COPPER. By THOS. GIBB, Assoc. R.S.M., F.I.C. 4. IRON AND STEEL. By THOS. TURNER, Assoc. R.S.M., F.I.C. 5. METALLURGICAL MACHINERY. By H. JENKINS, Wh.Sc., Assoc.. E.S.M., Assoc.M.lnst.C.E., of the Koyal Mint. 6. ALLOYS. By the EDITOR. \* Other Volumes in Preparation. LONDON : CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND.. OF THE * >t CVERSITT) A TEXT-BOOK OF OEE AND STONE MINING. BY C. LE NEVE FOSTER, B.A., D.Sc., F.B.S., /' - ASSOCIATE OF THE ROYAL SCHOOL OF MINES, ONE OF HER MAJESTY'S INSPECTORS OF MINES, AND PROFESSOR OF MINING AT THE ROYAL COLLEGE OF SCIENCE, LONDON, WITH WHICH IS INCORPORATED THE ROYAL SCHOOL OF MINES. WITH FRONTISPIECE AND 716 ILLUSTRATIONS. A??\ OF THE ' \ UNIVERSITY) - f ? LONDON: CHAELES GRIFFIN & COMPANY, LIMITED, EXETER STREET, STRAND. 1894. \_All rights resewed.] wr j nt ~ tJNIVERsiTT PEEFACE. THE object of my text-book is to assist students in acquiring a knowledge of the art of mining. Books and lectures are not intended to take the place of practical teaching at mines ; but they render the training more thorough and complete in many ways : they serve to explain the principles of the art, to solve difficulties which ^perplex the beginner, to suggest matters which he should observe, to tell him of things beyond his ken, and to supply him with a system for arranging his ideas methodically. It will be seen by my numerous references that I have not hesitated to avail myself of very varied sources of informa- tion, and that I have taken care to avoid dwelling too much upon English examples. As far as possible I have set my face against the indis- criminate use of the local slang of any particular district. Mining is quite difficult enough without introducing unneces- sary technical terms, and if words which are generally under- stood by English-speaking nations will express our ideas clearly, it is far better to employ them than to fall back upon provincialisms which vary from one district to another ; on the other hand, certain expressions may sometimes recommend themselves by reason of their pithiness, for adoption into our tongue. Within the limits of this preface it is impossible to name vi PREFACE. all the persons to whom I am indebted for matter contained in this volume. Many useful facts have been picked up while visiting mines at home and abroad, and in the course of conversation with my colleagues. I therefore gladly record my obligations to mining men generally, whom I have invariably found ready to give me the benefit of their experience. I have to thank the Council of the Institution of Civil Engineers, the Council of the Institution of Mechanical Engineers, the Editors of Engineering and of the Engineering and Mining Journal, M. Paulin Arrault, Mr. Augustus Bowie, Mr. William Galloway, Messrs. Letcher and Michell, and others, for permission to reproduce some of their figures. A few of the blocks have been borrowed from Mr. Hughes' " Text-book of Coal Mining." Mr. J. G. Lawn and Mr. L. H. Cooke have given me valuable assistance in correcting proofs, and the former espe- cially has saved me from some of the pitfalls which beset the path of an author who is passing a book through the press. The very full index prepared for me by Mr. S. W. Price will facilitate reference to my pages. LLANDUDNO, NORTH WALES, May, 1894. UNIVERSITT GENERAL CONTENTS. INTRODUCTION. CHAPTER I. MODE OF OCCURRENCE OF MINERALS. Classification . PAGE 3 Gold ore . PAGE 41 Tabular Deposits 5 Graphite . 50 i. Beds 5 Gypsum 5 2. Veins or Lod es Ice . 51 Masses . 18 Iron ore 51 Examples 20 Lead ore . 55 Alum . 20 Manganese ore 57 Amber 21 Mica . 58 Antimony . 21 Natural Gas 59 Arsenic 21 Nitrate of Soda 62 Asbestos . 21 Ozokerite . 63 Asphalt . 22 Petroleum . 65 Barytes 2 3 Phosphate of Li me 67 Borax 2 3 Potassium Salts 69 Boric Acid 25 Quicksilver ore 7i Carbonic Acid 2 5 Salt . 75 Clay . 26 Silver ore 77 Cobalt ore . 2 7 Slate . 79 Copper ore 28 Sulphur 81 Diamonds . 37 Tin ore 83 Flint . 39 Zinc ore 85 Freestone . 41 j Faults 87 CHAPTER II. PROSPECTING. Chance Discoveries . . -93 Adventitious Finds . . -95 Geology as a Guide to Minerals 97 Associated Minerals . . -97 Surface Indications . . -97 Form of the ground . . 98 Sheading Hushing Piercing Lode Lights . Altered Vegetatior Old Workings Names of Places Divining Rod Dipping Needle i Gozzan .... Indicative Plants . Animals as Indicators . . 99 . 103 . 105 106 107 107 108 no III III Vlll CONTENTS. CHAPTER III. BORING. Uses of Bore-holes . Methods of Boring Holes I. Boring by Rotation Auger . Diamond Drills II. Boring by with Rods Percussion PAGE 113 "3 "3 "3 118 124 Iron Rods . Wooden Rods . III. Boring by Percussion with Rope . American System PAGE I2 4 Mather and System Platt's 137 137 142 CHAPTER IY. BREAKING GROUND. Hand tools . . % . .151 Shovel 151 Crowbar . . . .151 Pick 152 Wedge . . . .154 Saws 154 Tools for Boring and Blast- ing 154 Machinery for Breaking Ground 162 Transmission of Power . .163 By Air 164 Water . . -171 Electricity . . .172 Excavating Machinery . .173 I. Steam Diggers . . 173 II. Dredges . . .175 III. Rock Drills . . .177 i. Rotary Drills . 177 2. Percussive Drills . 180 IV. Machines for Cutting Grooves . . -199 i. Mechanical Picks 2. Rock 199 Travelling Drills . 3. Circular Saws 4. Endless Chains with Cutters 5. Wire Saw 6. Revolving Bar with Cutters V. Machines for tunnelling 206 Modes of using Holes for Breaking Ground . . . 207 Driving and Sinking . .221 Fire-setting .... 225 Excavating by Water . . 226 20 1 202 204 204 206 CHAPTER V. SUPPORTING EXCAVATIONS. Timbering .... 227 Kinds of Timber used . . 227 Preservation of Timber . 229 Levels 232 Shafts 236 Working-places . . . 244 Masonry ..... 249 Levels 250 Shafts ..... 252 Working Places . . . 254 Metallic Supports . . . 255 Levels . . . . - 255 Shafts 263 Working Places . . . 265 Watertight Linings for Shafts 266 Special Processes . . .271 Boring Method . . .271 Compressed Air Method . 277 Freezing Method . . .279 Haase Process . . . 283 CHAPTER VI. EXPLOITATION. Open Works . . . .285 Hydraulic Mining . . . 292 Excavation of Minerals under Water .... 302 Extraction of Minerals by Wells and Bore-holes . . . 304 Underground Workings . Beds A. Pillar Workings B. Longwall Workings . Veins .... 308 309 309 322 325 340 CONTENTS. IX CHAPTER VII. HAULAGE OR TRANSPORT. PAGE Underground . . . 348 PAGE Machinery. . . 363 By Shoots . . . 348 a. Locomotives 363 Pipes . . 349 &. Stationary En- Persons . . . 349 gines 364 Sledges . . . 350 Conveyance by Boats . 372 Vehicles . . . . 350 Above Ground .... 373 Wheelbarrow . . 350 Shoots 373 Carts and Waggons . 350 Pipes 373 Railways . . .351 Persons ..... 375 Power Used . . 361 Sledges 375 Human Labour . .361 Vehicles .... JJ J 375 Animal Labour . .361 380 Gravity . . . 362 Aerial Ropeways . O 380 CHAPTER VIII. HOISTING OR WINDING. Motors, Drums and Pulley Keps 419 Frames .... 387 Signals . 420 Ropes, Chains, and Attach- Safety Appliances 422 ments .... 398 Overwinding. 422 Receptacles .... 404 Stopping Gear 424 (a) Buckets . . . 404 Safety Catches 426 (b) Guided Buckets . . 408 (c) Cage . . . .417 Springs . Testing Ropes 427 427 Other Appliances . . .418 Pneumatic Hoisting 427 CHAPTER IX. DRAINAGE. Surface Water .... 429 Accessories 457 Dams 430 Pumping Engines below ground 466 Drainage Tunnels . . . 433 Worked by Steam . 466 Siphons . . . . 437 Water . 469 Winding Machinery. . . 437 Compressed Pumping Engines above ground 441 Air 470 Motors .... 442 Electricity 470 Rods . . . .445 Co-operative Pumping 473 Pumps .... 447 CHAPTER X. VENTILATION. Atmosphere of Mines . . 475 Fire Damp .... 498 Causes of Pollution of Air in Carbonic Acid . Mines . . . .480 Oxygen .... 505 Natural Ventilation . . . 482 Measuring the Quantity and Artificial Ventilation . . 490 Pressure of the Air . 506 I. Furnace Ventilation . 490 Anemometers 507 II. Mechanical Ventilation . 491 Water Gauge . 508 Water Blast . .491 Efficiency of Ventilating Appli- Steam Jet . . . 492 ances 509 Air Pumps (Fans) . 492 Resistance caused by Friction . 510 Testing the Quality of Air . 498 CONTENTS. CHAPTER XI. LIGHTING. Keflected Daylight Candles . Torches . Lamps 513 513 515 515 Wells Light Safety Lamps Gas . Electric Light 516 518 523 523 CHAPTER XII. DESCENT AND ASCENT. Steps and Slides Ladders . . 526 I Backets and Cages . . 527 | Man Engine 534 CHAPTER XIII. DRESSING. I. Mechanical Processes . 538 Washing . . .538 Hand Picking . .541 Breaking Up . -542 Agglomeration of Con- solidation . . . 565 Screening . . . 566 II. Processes depending upon Physical Properties . 568 Motion in Water . . 568 Simple Fall in Water . 570 Upward Current Sepa- rators . . . 574 Separation by Water Flowing down Planes . . .579 Plane Tables . 579 Percussion Tables 584 Travelling Belts . 585 Buddies . . 587 Motion in Air . . 589 Desiccation .... 592 Liquefaction and Distillation . 597 Magnetic Attraction . . 600 III. Processes depending upon Chemical Properties . 607 Solution, Evaporation, and Crystallisation . 607 Atmospheric Weather- ing .... 610 Calcination or Roasting 611 Cementation . Amalgamation Application of Processes Loss in Dressing Sampling Hand Sampling Machine Sampling 616 616 620 630 632 632 634 CHAPTER XIV. PRINCIPLES OF EMPLOYMENT OF MINING LABOUR. Payment by Time . . . 637 Measure or Weight 638 Payment by Combination of these 64 1 Value of Product . 641 CHAPTER XV. LEGISLATION AFFECTING MINES AND QUARRIES. Ownership .... 653 Taxation 655 Working Regulations . . 655 Metalliferous Mines Regula- tion Acts .... 656 Coal Mines Regulation Act . 662 Other Statutes affecting Mines 662 Alkali Acts . . . .665 Boiler Explosions Acts . . 666 Brine Pumping Act . . 666 Elementary Education Acts . 666 Employers' Liability Act . 666 Explosives Act . . .666 Factory and Workshop Acts 667 Quarry Fencing Act . . 667 Rivers Pollution Prevention Act ..... 667 Stannaries Act . . . 668 Truck Acts . . . .668 CONTENTS. XI CHAPTER XYI. CONDITION OF THE MINER. Clothing . Hat Boots . Jacket . Housing . Barracks PAGE 669 6 7 I 6 7 2 673 673 674 Cottages Education Sickness . Thrift Recreation PAGE 677 682 683 690 696 CHAPTER XVII. ACCIDENTS. Death Rate of Miners from Ac- cidents .... 698 Relative Accident Mortality Un- derground and Aboveground 699 Classification of Accidents . 702 Underground . . . 704 Explosions of Fire Damp or Coal Dust . . . 704 Falls of Ground . 704 Shaft Accidents . 705 Miscellaneous . . 706 On the Surface . . 711 By Machinery . 711 Boiler Explosions . 711 Miscellaneous . 711 Ambulance Training . 712 EEEATA ET CORRIGENDA. Page 36, line 10 from bottom, for " Kearsage " read " Kearsarge." 36, 18 "33,359,ooo" "33,350,000." 124, 17 ,, "Healey" "BeaL" 182, 10 "Githen" "Githens." 209, 17 "Nobel" "Noble." 311, 4 from top "detachod" "detached." ,,607, 16 "Buttengenbach" " Biittgenbach.'' 675, owing to an error in the original, the scale is incorrect, and the readings should be multiplied by i^. LIST OF ILLUSTRATIONS. Frontispiece : Overhand Stoping, Carn Brea Tin Mine, Cornwall. OCCURRENCE. FIG. PAGE 1. Stratified deposits, section ........ 5 2. Lead lode in slate, Wheal Mary Ann, Menheniot, Cornwall . 6 3. Tin lode in granite, West Wheal Basset, Cornwall ... 7 4. Section of lode, Canton mine, Otago, New Zealand ... 8 5. Diagram to show underlie . . . . . . . .10 6. Measurement of underlie . . . . . . . .10 7. General section of a lode 10 8. Longitudinal section of a lode showing ore-bodies . . .11 9. Intersection of veins . . . 12 10. Section of vein with feeders 12 11. Plan showing fahlbands, Kongsberg silver mines, Norway . . 12 12. Change of strike affecting richness of a lode . . . -13 13. Richness or poverty of parallel parts of lodes : " Ore against ore " 17 14. Haematite deposit, Ulverston ....... 19 15. Calamine deposit, Altenberg, Moresnet 19 16. Stockwork, Mulberry mine, near Bodmin, Cornwall ... 19 17. Borax Lake, California, plan 24 1 8. Cobalt ore, Skutterud, Norway ....... 27 19. ,, New Caledonia 28 20. Section across Mansfeld district . . . . . .28 21. of Eduard II. Shaft, Mansfeld . . . . .30 22. Geological map of Rio Tinto, Huelva, Spain . . . .31 23 3 27) 28} 29. 30. 3i- 32. 33- -34 Cross-sections of San Dionisio Lode, Rio Tinto . . Map of Lake Superior copper district .... De Beers mine, Kimberley, vertical section Plan of diamond-bearing deposits, Kimberley Section of strata at the flint mines, Brandon, Suffolk Salisbury mine, Johannesburg 33 : H - 38 . 40 . 42 |: auriferous alluvium, Caratal District, Venezuela showing auriferous " rainwash," Caratal Saddle-reefs, Bendigo ........ 44 . 45 46,47 xiv LIST OF ILLUSTRATIONS. 39. Mount Morgan mine, Queensland, section to illustrate geyser theory .... 40. view of deposit ... 41. sections based on late developments . 42. Gypsum mine, Nottinghamshire ..... 43. Sections of ironstone bed, Cleveland .... 44. Chapin Iron mine, Lake Superior, section ... 45. Lead-bearing sandstone, Mechernich, general section 46. Evening Star mine, Leadville, Colorado, section . . 47. Manganese ore bed, near Barmouth, North Wales . 48. Natural gas ; section through Findlay, Ohio . . 49. Nickel deposit, New Caledonia ..... bearing veins, New Caledonia 48 49 50 51 52 54 55 56 58 60 60 61 deposit, Sudbury, Canada ..... 61,62 Nitrate of soda, Chili ..... . .62 Ozokerite at Boryslaw, Galicia, plan . . . -63 ,, ,, section . . .64 filling fissures, Boryslaw . . .64 Baku oil region, section .... . -65 Spouting oil well, Baku .... . .66 Deposit of phosphate of lime, Beauval, France . . 68 Bed of phosphatic nodules, South Carolina. . . 68 Potassium salts and rock salt, Stassfurt . . 70 Quicksilver-bearing sandstone, section, Ekaterinoslav, Southern Eussia ........... 72 Cross section of quicksilver deposit, Great Western mine, California 73 Longitudinal section ,, -74 Cross section of Eureka mine, Nevada ..... 77 ... 80 slate beds, Festiniog, N. Wales the Oakeley Quarries, Festiniog Sulphur bank, Iceland seam, near Caltagirone, Sicily Cross sections of tin veins, St. Agnes, Cornwall 81 82 82 84 Map of part of Vegetable Creek, New South Wales ... 85 Cross section showing "deep-leads" of tin ore, Vegetable Creek 86 Wash-out fault ........ . . 87 Ordinary fault ........ 88 Step fault ........... 88 Fault with zone of broken rock . ...... 88 Measurement of throw of a fault . ..... 89 Section of fault indicating amount of throw .... 89 Variation of throw along the strike of a fault Reversed fault showing bending of strata Plan showing heave of vein sideways ...... Illustration of heave sideways produced by a sliding along dip of fault ........... Schmidt and Zirnmermann's rule ..... - 90 90 90 91 91 92 Succession of faults, Penhalls mine ...... 92 PROSPECTING. 89. Section of mineral vein showing projecting outcrop of a hard vein 98 LIST OF ILLUSTRATIONS. xv FIG. PAGE 90. Cross-section of lode with gozzan ..... . 101 91. Longitudinal section showing relation of the gozzan to natural drainage level . . . . . . . . . 101 92. Use of the divining rod . . . . . . . 1 1 1 93. Dipping needle used in searching for iron ore . . . .112 BORING. 94. Earth auger or gouge . . . . . . . . .114 95. Derrick for lifting rods . . . . . . .114 96. ,, &c., for boring by rotation ...... 115 97. Screwed coupling for hollow boring rods . . . . .116 98. Rotating and guiding arrangements and loose connection . . 117 99. Boring bit with two sets of cutters . . . . . . 1 1 7 100. Cutting out a core with diamond drill . . . .118 101. Plan of large crown for diamond drill . . . . .118 102. Arrangement of core tube and sediment tube . . . .119 103. Core-extractor . . . . . . . . . .119 104. Dauntless diamond drill ........ 120 105. Little Champion diamond drill . . . . . . .123 106. Small diamond drill for prospecting ...... 123 107. Chisel bit ........... 125 108. Screw-joint for boring-rods ....... 125 109. ,, . ,, with connecting socket . . . 125 no. Lifting hook or dog . . . . . . . . 125 in. Retaining key .......... 125 112. Cap, or lifting ring and socket . . . . . . .125 113. Portable plant for boring with rods ...... 126 114. Set of tools for use with above ....... 127 115. Shell-pump or sludger . . . . . . . . .128 11 I Oeynhausen's sliding joint ........ 129 Free-falling tool .......... 129 1 20. Arrault's free-falling tool used with bumping piece . . .130 121. Enlarged view of catch for free-falling tool . . . .130 122. Kind's free-falling tool . . . . . . . .130 123. Crow's-foot ........... 131 124. Bell-screw ........... 131 125. Riveted lining tube with screwed joints . . . . -131 126. Lining tube with flush screwed joint . . . . -131 12 A I Rotating tool for cutting out a core . . . . . .132 129. Core extractor .......... 132 1 3 j- Compass-case for marking core ...... 133 131. Wooden boring rod used in Galicia . . . . . 134 132. Rig for boring by the Canadian system . . . . 135 133. American rig for boring a well ....... 138 134. Rope-socket .......... 139 135. Sinker-bar ........... 139 136. Jars ........... 139 137. Auger-stem ........... 139 * ........... '39 140. Temper screw ... ....... 140 141. Sand-pump ........... 140 142. Method of working maul for drive-pipe ..... 140 cr THE XTNIVERSITY xvi LIST OF ILLUSTKATIONS. FIG. PAGE 143. Boring plant, Mather and Platt's system 143 144. Enlarged view of Mather and Platt's cylinder and pulley . -144 145. Mather and Platt, boring head and turning device . . .146 146. Recording phial for Macgeorge's clinograph . . . .147 g L Survey of bore-hole, Scotchman's United mine, Victoria . 149 BREAKING GROUND. 149. Poll-pick 152 150. Double-pointed pick . -152 151. Pick used for cutting jad, Bath stone quarries . . . -152 152. ,, with movable blade, Mansfeld . . . . . -152 153. Acme pick . . . . . . . . . . 153 154. Universal pick .......... 153 155. Cornish gad .......... 154 156. Saw for cutting freestone . . . . . . . 154 157. Elliott drill 155 158. Ratchet drill 155 1 59. Jumper used at Mechernich 156 160. in Northamptonshire . . . . . .156 161. in Festiniog slate mines 156 162. in Cleveland iron mines . ..... 156 163. Borer or drill 156 J g 4 1 Cutting edge of drill, Minera, North Wales . . . .158 1 66. Bore-hole with triangular section . . . . . 159 167. Hammer for single-handed boring, Festiniog . . . 159 168. Cornish mallet, or double-handed boring hammer . . . 160 169. Tamping bar 160 170. Needle, or pricker . . 161 171. Charging spoon and scraper ....... 161 172. Claying bar 161 1 73 JKnox system of boring rending holes 162 175. Reamer, or broach for enlarging holes by the Knox system . 162 176. Hanarte air- compressor ........ 165 177. Dubois and Frangois air-compressor 166 178. Ingersoll- Sergeant air-compressor ...... 167 179. Valve of Ingersoll-Sergeant air-compressor . .' . . 168 180. Arrangement of steam and air cylinders . . ... 168 181. Underground reservoir for compressed air, Mansfeld . .169 182. Joint for compressed air main, Blanzy . . . .170 1 3 I Mode of fixing air main in shaft . 170 184, 185. Eadie and Sons' joint for lap- welded pipe . ... .170 1 86. Dunbar and Ruston's steam navvy . . ~. . . . 174 187. Kincaid and McQueen's bucket dredge . ... . 176 1 88. Priestman's grab dredger . . . . . . 177 189. Steavenson's twist drill on carriage, worked by electric motor . 179 190. ,, ,, petroleum engine ib'o I9O J 92 L Bits used with machine drills . . . y . . .181 194) 195. Shaped bars of steel for cross-bits . . . . ; .182 196. Barrow drill . . 183 197. Drill mounted on stretcher bar 184 LIST OF ILLUSTRATIONS. xvii FIG. PAGE 198. Climax drill 185 1 9" -Bosseyeuse, or boring ram of Dabois and Francois . . . 186 201. Ingersoll-Sergeant Eclipse drill . . . . . . .188 2^ j Socket for holding the tool 189 204. Franke drill 190 205. Use of Franke drill and undercutting chisel, Mansfeld copper mines 191 206. Hirnant drill 192 207. Sergeant drill 208. turning mechanism 209. Adelaide drill 210. Darlington drill, longitudinal section . 211. side elevation 212. ,, mounted on stretcher-bar 213. Marvin electric drill, working parts . 214. Franke's mechanical chisel .... 215. Gillott and Copley's undercutting machine . 216. Walker's circular saw . 193 194 '95 196 196 197 198 200 203 204 217- Wire saw ........... 205 218. Stanley's tunnelling machine, side elevation .... 207 219. Elliott multiple wedge, longitudinal and cross sections . . 208 220^ 221 , -Strength of explosives as shown by Trauzl's lead block test . 216 224' 225^ 226. Detonator, Nobel's, treble strength 218 227. quintuple strength 218 228. Firing a charged hole 219 229. Kifting hole with air-space above charge, Knox system . .219 230. Simultaneous fuse of Bickford, Smith & Co 219 231. Brain's high-tension electric fuse 220 232. Nobel's 221 233. low-tension 221 234. Planning holes for driving a level by hand ..... 222 235. Section of lode with youge or selvaye 222 236. Arrangement of holes for driving a level with a machine drill (elevation) 223 237. Arrangement of holes for driving a level with a machine drill (longitudinal section) ........ 223 238. Halkyn drainage tunnel, arrangement of holes for driving . 223 239. Driving level with Ferroux drill and bosseyeuse, Bex, Switzerland 224 240. Arrangement of holes for sinking a shaft, Foxdale, plan . . 225 241- ,, ,, section . 225 SUPPORTING EXCAVATIONS. 242. Level with cap or bar supporting roof 232 243- and leg 232 44 [ Joints between cap and leg 232 246. Timber frame and lagging for level 232 247. Horned set for level in loose ground ...... 233 248. Timber frame and lagging for heavy ground, Comstock lode . 233 249. Timbering for level, Rio Tinto mines 233 b xviii LIST OF ILLUSTRATIONS. FIG. PAGE 250. Pigsty timbering for wide level, cross-section .... 234 251. ,, section along line of strike . 235 252. Spilling in loose ground, longitudinal section .... 236 253. ,, ,, cross section ..... 236 254. Plank lining for shaft, plan 237 255. Shaft frame or set 237 256. ,, enlarged view of joint 237 257. Plan of timbering for shaft, Comstock lode .... 238 258. Section through dividing .... 238 259. End view of timbering for shaft ,, ,, .... 238 260. Plan of timbering for shaft, Calumet and Hecla mine . . 239 261. Shaft timbering, Clausthal, plan 240 262. ,, end view 241 263. Timbering chamber for water-wheel, Clausthal . . . .241 264. Plan of shaft frame for spilling 242 265. Sinking shaft by spilling, vertical section ..... 243 266. Prop supporting roof of bed ....... 244 267. Chocks supporting roof 245 268. Large chocks, Wieliczka salt mines 245 269. Pigsty timbering in stopes, Day Dawn mine, Queensland . . 245 270. Square set, Comstock lode, Nevada, elevation .... 246 271. plan 246 272. application in overhand stopes 246 273. Kichmond mine, Nevada ...... 247 274. timbering in overhand stopes, Broken Hill mines, sectional elevation 248 275. timbering in overhand stopes, Broken Hill mines, horizontal section . ... 248 276. Joint for square set, Broken Hill mines 277. Square sets supporting hanging wall . 278. Strengthening square sets . 279. Dry walling for level, Forest of Dean . 280. Level lined with masonry, Clausthal . 281. Level with arch of masonry 282. ,, at side 283. Lining shaft with brickwork 284. Shaft lined with concrete, Foxdale mine 285. Stone pillar supporting roof 249 249 249 250 250 251 25i 252 253 254 286. Halkyn drainage tunnel, section showing iron supports ". .255 287. cast-iron prop and chair . . . 255 288. section of iron rail used . . . 256 289. Section of steel beam, Nunnery Colliery, Sheffield . . . 256 290. Steel beam on timber legs 257 291. Rolled steel caps and legs forming frame for level . . . 258 ^ i Section and plan of steel plate used .258 294. Level lined with curved iron rails, Hartz . . . * ' 258 295. Bent steel bar for supporting roof of level . . . . . 259 296. Steel frame in two parts for lining level, Anzin .... 259 297. Cross section showing joint . . . . . . . 260 298. Steel frame in three pieces, Anzin . . . . . . 260 299. Circular frame for level, channel steel 261 300. Section through joint of the frame . . . . . . 261 301. Circular frame for level, bulb-tee steel . . ... . 262 302. Section through joint of the frame . . . . . 262 303. Iron ring in two parts for supporting shaft lining . . . 263 304. Shaft lining, ozokerite mines, Boryslaw ..... 264 305. King of channel iron for shaft . 264 306. Section through joint of ring 265 LIST OF ILLUSTKATIONS. xix FIG. PAGE 307. Prop of I-steel, and plan of end 266 308. Solid wooden tubbing for shaft, plan 266 309. Sections of cast-iron wedging cribs 267 310. Section through coffering ........ 268 311. Segment of cast-iron tubbing 269 3 12 1 Cast-iron tubbing resting on curb 270 314. Small composite borer or trepan, Kind-Chaudron system . . 272 315. Large composite borer ,, ,, 273 316. Section of tubbing with moss-box ,, 274 317. ., ,, compressed, and false tubbing 274 318. Enlarged section of the three wedging curbs .... 274 319. Section of tubbing at Lievin ....... 276 320. Sinking by freezing process in watery strata, Siberia . . . 279 321. . 280 322. Poetsch's freezing process, section of freezing tube . . . 282 323. ,, vertical section of shaft . . . 282 EXPLOITATION. 324. Open workings for iron ore, Northamptonshire .... 287 325. plan showing arrangement of workings . . 288 326. Section of terraces, Penrhyn slate quarry ..... 288 327. View of opencast, Kio Tinto mines ...... 289 328. Section of Mulberry mine near Bodmin, Cornwall . . . 289 329. Section showing effect of a large blast, Messina . . . 290 33 I Details of the tunnel for large blast ,, . . . .291 332. China clay workings, Hensbarrow, Cornwall .... 292 333. End view of flume and trestle ....... 294 334. View of flume carried across a valley ...... 294 335. ,, by iron brackets on side of cafton . . 295 336. Kiveted wrought-iron water pipe . . . . . . 295 338 I Pressure box or "bulkhead" 296 339J 340. Monitor ...... ..... 296 341. Hydraulic mining, attacking the gravel bauk . . . . 297 342) 343 I Sluice box .298 344J 345 34 I Hydraulic elevator 300 w 348J 349. ., at the Blue Spur, Otago, New Zealand . 350. Working salt by bore-hole, Middlesbrough .... 351. Plan of bore-holes, Middlesbrough ..... 352. Section of underground gypsum quarries, Paris . 353. Plan . 354. Underground workings for stone, near Bath, plan 355. ,, vertical section 35 6 - .1 it P lan 357. Plan showing pillars, Marston Hall salt mine, Northwich . 358. Vertical section ,, 359. Underground workings for slate, Festiniog, plan ^60. cross- section . 301 305 306 309 309 3io 310 310 3ii 3" 313 313 361. French Ardennes, cross-section 313 xx LIST OF ILLUSTRATIONS. FIG. PAGE 362. Working ironstone, Cleveland, plan . . . . . .316 363. Eestronguet tin stream works, plan . . . . . .317 364. section 317 365. Cross-section of the Ked Point and Darnrn channels, California . 319 366. Plan of longwall workings, Mansfeld copper mine . . . 324 367. Transverse section of an ore mine, lode worked by vertical shaft 326 368. Longitudinal ,, 326 39 I Underhand stoping, original method 327 371. on sides of winze ..... 327 372. Longitudinal section of Dolcoath mine, Cornwall . . . 328 373. Transverse section ,, ... 329 374. Overhand stoping, with rubbish stowed on stulls . . . 329 375. cross-section 330 376. excavation left open . . . . 330 377. ,, on a narrow lode, cross-section . . . 330 378. Working a wide lode with filling up, Van mine . . . .331 379. Wide lode worked by cross-cutting, transverse section . . 334 380. plan . ^ . . . -334 381. worked in slices, parallel to the dip .... 335 382. worked in horizontal slices, with filling up, Fox dale Mine 336 ?8 I Working a wide lode having a hard and a soft part . . 337 385. Bio Tinto, pillar and chamber workings, vertical section . . 339 386. plan of preliminary drivages . . 339 387. plan of completed chambers . -339 388. Working " churns," Forest of Dean ... . . 340 389. Plan of De Beers Mine, new system of working . 390. of drivages and chambers 391. Vertical section of drivages and chambers . 392. HEematite deposit, North Lancashire, cross-section 393. plan of main levels and crosscuts 394. ,, plan of workings . 395. section of working 396. Working zinc ore, Diepenlinchen mine HAULAGE. 342 342 342 343 344 345 346 39 Sections of rails 351 399. Steel sleeper, Legrand's 352 400. ,, Howard's ........ 352 401. made from bridge rail . . . . . . 353 401 a] 402 I Clip used with above . 353 4020] 403. Sleeper made of channel-iron 353 404. ,, flat bar-iron 353 405. Cast-iron turnplate ......... 354 406. Turnplate with iron bar guides ....... 354 407. Mine waggon, Van mine ........ 355 4 L Mine waggon, with sheet-iron body and bent sides . . .356 410 j ,, oval body and automatic lubrication, 411) Saint-Etienne ......... 359 LIST OF ILLUSTRATIONS. xxi FIG. PACK 4 12 | Steel waggon, Llanbradach colliery ...... 359 414. Self -oiling pedestal ......... 361 415. Diagram, main and tail rope system . . . . 366 4 Rice ' s c i utc h .......... 369 418) 419 /-Endless rope system, plans of sidings ...... 370 420] 421. double track . ..... 371 422. Drums and air-brake of self-acting incline, Bilbao . . . 377 423. Aerial ropeway, Otto's system, view of tub ..... 382 424 j. ?j 5j ?j M iron standard . . . . 383 426. clip, side view . . . .384 427. ,, cross-section of clip . . . 384 428. ,, plan of clip .... 384 429. ,, Sheba Gold Mining Company, Barberton ....... 384 430. Gottessegen Colliery, Upper Silesia . . . 385 HOISTING. 431. Turbine and connections for winding, Great West Van mine . 390 43 2 1 Compound winding engine, Llanbradach Colliery . . .391 434. Drum with reserve length of rope ...... 392 435. section . . . 392 436. Keel for flat rope, elevation 437- >, P lan 438. Wooden pulley-frame, side elevation 394 394 395 395 439. ., front 440- > P lan 395 441. Wrought-iron head-gear, " Kock Shaft," De Beers mine . . 396 442. " Incline Shaft " ,, ,, . 397 443. Winding pulley 398 443a. Wire rope with hemp core 399 444 1 ordinary, new and when worn ..... 400 4451 446| |f n Lang's lay 400 44 8 1 Latch and Batchelor's " flattened strand " . . 400 449 J 450. ,, outside view . . . 400 451. Elliot's " locked coil " 401 452. Spring hook for attaching rope to bucket, &c. .... 402 453. Capping wire ropes, eye spliced on ...... 402 454. eye made with screwed clamps . . . 402 455- ,, .,- >. section . 402 456. ,, socket riveted on . . . . 4 02 457) 458^ for locked coil rope, outside view and sections 403 459 J improved form of clamped capping . . 403 462. Wrought-iron kibble ,, . 404 463. Aerial incline, <; Blondin," used at granite quarries, near Aber- deen 407 cr THE Y ^S. IVERSITY) OP / xxii LIST OF ILLUSTRATIONS. FIG. PAGE 464. Galloway's improved wire rope guides for bucket . . . 408 465. walling stage, elevation ...... 409 466. ,. plan of lower floor .... 409 467. Filling skip in shaft ......... 4" 468. Self -discharging skip, De Beers mine, plan . . . .412 469. side elevation . . .412 470. Improved shoot with double doors, De Beers mine . . . 413 471. Automatic dumping arrangement for inclines, side elevation . 413 472. plan . 4T3 473. perpendicular "Rock" shaft, De Beers mine, side eleva- tion ..... 414 474- , front eleva- tion of a part . . . 415 475. Ormerod's detaching link ........ 4 l & 476 Self-discharging skip, Frongoch mine 47* 479 480 481. Cage, Comstock lode, front elevation . . . . . .418 482. side elevation ...... 4 l8 483) 484 \ Haniel & Lueg's keps for cage ....... 4 2 485] Detaching hooks, King & Rumble's ...... 422 Walker's 423 490. open 424 DRAINAGE. 491. Wooden dam in level, plan . . . . . . 430 49 ^ I Spherical wooden dam 431 496. Brick dam in shaft, vertical section ...... 433 497 I Galloway's pneumatic water tank, vertical section . . . 438 499. automatic water tank, side view .... 439 500. front view . . . * . 440 5*l Bowden's automatic tanks for use on slopes . . . .441 503. dumping at head of slope . .441 504. Compound double-acting pumping engine, Mansfeld . . . 444 505. Strapping-plates for wooden pump rod . . . . ' . 445 506. V-bob, side elevation 446 507. plan '. - . .446 508. Fend-off bob, side elevation 446 509. Running loop, side view ........ 447 510. front view 447 511. West & Darlington's hydraulic plungers for working inclined rods 447 512. Drawing lift in shaft, vertical section . . . . . . 449 5*3 j. Pump bucket for single valve 449 LIST OF ILLUSTRATIONS. xxiii FIG. PAGE 515. Half -moon 449 516. Form for two valves attached at circumference .... 449 517. in the middle .... 449 518. Shape of leather band for packing pump bucket . . . 449 519. Lifting pump used on the Comstock lode. . . . . . 451 520 ) Bising main, joint and mode of supporting column in shaft, Com- 521)" stock lode 451 522. Plunger pump in shaft, vertical section . . . . .451 5^3 1 Hake's mouth valve . . 453 5*| 1 Butterfly valve 453 5^7 jTrelease's valve . 453 5 2 9) 530 \- Teague's noiseless valve, vertical section, side view and plan . 454 530 532. Double-beat valve fixed in place, vertical section . . . 454 533- ,, open 454 534. ,, ,, elevation of valve and lower seat . . 454 535. Kittinger pump, elevation 456 536. ,, vertical section 45 6 537. Balance bob 457 538. West and Darlington's hydraulic counterbalance . . . 458 539- v ,1 for inclined rods 458 540. Bochkoltz regenerator . 459 541. Eossigneux's system of counterbalancing ..... 460 542. ,, plan . . . .460 543. Catches 461 544. Pumping engine, Shakemantle Mine, side view .... 462 545. ,, front view . . .463 546. Pumps fixed in shaf t ,, ,, side view . . . . 464 547. front view . . .464 548. Pumps in shaft, bottom lift, Shakemantle Mine, side view . 465 549. Plan of shaft ' .... 465 550. Pumps in shaft, bottom lift front view . 465 551. Underground pumping engine, Mansfield 468 552. plan . . . ' ' . 468 553. Pulsometer, vertical section . 409 554. Moore's hydraulic pump . . . . . . 470 555. Pohlepump -~ . . 47 1 556. Pump worked by compressed air, Evans and Veitch . . . 472 557. ,, cylinders for working valves . 472 VENTILATION. 558. Natural ventilation by two shafts joined by a level . . . 483 559. by adit and shaft ...... 483 560. 56i. 562. 563. 564- 565. 566. 567. by two shafts joined by an incline . . 483 of end of level 485 bad 485 of a single vertical shaft .... 486 of an incline ...... 486 of a rise 486 of end of level by an air-sollar . . . 487 longitudinal ^^^ section . 487 568. 487 xxiv LIST OF ILLUSTRATIONS. FIG. PAGE 569. Natural ventilation of shaft by an air pipe .... 488 570. Method of ventilating a rise . .... 488 571. lower levels . .... 489 572. by winzes . .... 489 573. Ventilating furnace, vertical section . .... 491 574. plan ... .... 491 575. ,, front elevation . . 491 576. Williams' water-jet apparatus . . .... 492 577. Teague's aspirator .... .... 493 578. Hartz blower, elevation ... . 494 579. section .... .... 494 580. Roots' blower, cross section . .... 494 581. Capell fan, vertical section . .... 495 582. ,, cross section ... ~ . . . . 495 583. Guibal fan, vertical section . .... 496 584. Schiele fan .... 497 585. Waddle fan 497 586. Lunge's apparatus for testing the air of mines .... 504 587. valve-tube, vertical section .... 504 588. Water-gauge, model to illustrate action of .... 508 589. Murgue's graphic representation of the influence of the sides of airways upon the amount of friction . . . . . 5 1 1 LIGHTING. 590. Candle holder, United States 514 591. . (" Spider "), Au&tralia . . . . . . 5:5 592. Lamp for burning oil, Scotland . . . . . . .516 593. Wells light 517 594. Davy lamp 519 595. Clannylamp 519 596. Mueseler lamp 520 597. Marsaut lamp .......... 521 598. Ashworth's Hepplewhite-Gray lamp 522 599. Sussmann electric lamp ........ 523 DESCENT AND ASCENT. 600. Iron ladder 529 601. Section showing manner of joining two ladders .... 529 602. Arrangement of ladders in shaft ...... 530 - Double-rod man-engine ........ 534 605. Single-rod man-engine ........ 534 DRESSING. 606. Rotary diamond washing machine 540 607. Revolving drum for washing smalls before picking . ,. . 541 608. Scraper 542 609. Ragging 543 610. Spalling . 544 611. Cobbing , . . "" 544 612. Bucking 545 613. Thin wedge for splitting slate, North Wales .... 545 614. Blake's rock-breaker, section ....... 547 LIST OF ILLUSTRATIONS. xxv FIG. PAGE 615. Dodge crusher .......... 548 616. lo-stamp battery with wooden frame ...... 549 617. Single discharge mortar ........ 549 618. Tappet 549 619. Cam ............ 549 620. Stamp head, shoe, and die ........ 549 621. Steel shoe and die before and after wear ..... 550 622. Ball's steam-hammer stamp . . . . . . '552 623. Leavitt's differential steam-cylinder ...... 553 624. Cornish crushing rolls . . . . . . . '554 625. Kolls, cross section ......... 554 626. Krom's roll, section 555 627. Krom's crushing rolls, side elevation ...... 555 628. Edge-runner 557 629. Ball pulveriser, Krupp-Grusonwerk, cross-section . . 558 630. ,, ,, longitudinal section . . 558 631. Carr's disintegrator, section ....... 559 632. Gates crusher .......... 560 633. Huntington mill, plan 561 634. ,, sectional elevation ...... 562 635. Paxman's improved roller and yoke, section .... 562 636. ,, plan 562 637. 563 638. Sawing machine for slate ........ 564 639. Greaves' circular slate-dressing machine ..... 565 640. Perforated sheet-metal, with round holes, imm. . . . 567 641. 2mm. . . .567 642. 5mm. . . .567 6420. Trommel for making four classes ...... 567 643. Experiment to show separation of minerals by free fall in water 569 6 4 ^ I Tossing and packing in keeve 571 646. Experimental jigging-sieve . 571 647- jigger 572 648. Two-compartment jigger, front sectional elevation . . . 573 649. ,, cross-section 573 650. Experimental jigger with fixed sieve ...... 573 651. Jigger with piston moving horizontally, Frongoch mine, cross- section 574 652. Jigger with piston moving horizontally, longitudinal cross- section 574 653. Pyramidal separator, Jacomety and Lenicque, section . . 575 654. plan . . .575 655. Upward current separator, Frongoch mine, section . . . 576 656. plan . . -576 657. Osterspey's siphon separator, vertical section .... 578 658. ., longitudinal section of front chamber 578 659. plan 578 660. Cornish self-acting double frame, plan 580 fa 1 r , , sectional elevation . . .580 663. Linkenbach table, sectional elevation 582 664. plan . . r 582 665. Kevolving round table, Jacomety andJtenicque .... 584 666. W,, ' plan . . .584 667. Rittinger's side-blow percussion table, plan .... 585 668. Frue vanner, diagrammatic longitudinal section . . . 585 669. Stein's endless belt, side elevation 587 xxvi LIST OF ILLUSTRATIONS. FIG. 670. Stein's endless belt, plan ....... 587 671. ,, ,, end elevation ..... 672. Convex round buddle, sectional elevation .... 673. plan 674. Experimental pneumatic jigger 675. Clarkson-Stanfield concentrator 676. Tanks and drying floors for china clay, plan and a cross-section 677. Kiln for drying fuller's earth, section .... 678. Euelle's revolving drier, longitudinal section 679. Large kiln, Sicilian sulphur mines, vertical section . 680. plan .... 68 1. Chase magnetic separator, longitudinal section (diagrammatic) 682. Conkling magnetic separator 683. Hoffmann magnetic separator 684. Kessler magnetic separator . 685. Lovett-Finney magnetic separator 686. Ball-Norton magnetic separator . 687. Buchanan magnetic separator . . 688. Friederichssegen magnetic separator, longitudinal section . 689. ,, plan .... 690. Wenstrom magnetic separator 691. Edison's magnetic separator ...... 692. Brunton's calciner, sectional elevation .... 693. Hockin's calciner, longitudinal section .... 694- ft plan 695. Sampling quartering . 696. ,, shovel . . . . . ... 697. Clarkson's rapid sampler 698. Bridgman's ore-sampler, first apportioner 587 588 588 590 591 593 595 596 599 599 60 1 60 1 602 603 603 603 604 605 605 605 606 614 615 633 635 635 699. second 635 CONDITION OF WORKMEN. 700. Barracks for workmen, Eisleben, front elevation . . . 675 701. ,, ,, ,, ground plan .... 675 702. Cottage, Bolsover Collieries, front elevation .... 678 703- ,, >, back 678 704. first floor plan . . . " . 678 70S- i. ground plan 678 706. Dry or changing house, Levant Mine, Cornwall, side elevation . 680 707- plan . . 680 708. Shower-baths, Anzin Collieries, France 68 1 ACCIDENTS. 709. Lowmoor jacket and Furley pattern stretcher . . . .712 710. Placing stretcher on Ashford litter . . . . . .713 711. Ashford litter ; . 713 LIST OF ABBREVIATIONS. Ann. Mines. Annales des Mines. Ann. Hep. B. Cornwall Pol. Soc. Annual Report of the Royal Cornwall Polytechnic Society. B. u. h. Z. Berg- und hUttenmannische Zeitung. Bull. Hoc. Lid. Hin. Bulletin de la Societe de 1' Industrie Minerale. Coll. Guard. The Colliery Guardian. Comptes Rendus Mensuels, Soc. Ind. Min. Comptes rendus mensuels de la Societe de 1'Industrie Minerale. Eng. Min. Jour, or E. M. J. The New York Engineering and Mining Journal. Jahrb. f. d. Berg- und Hiittenwesen im K. Sachsen. Jahrbuch fiir das Berg- und Hiittenwesen im Konigreiche Sachsen. Jahrb. f. Geol. Min. Palaont. Jahrbuch fiir Geologic, Mineralogie und Palaontologie. Jour. Eoy. Inst. Cornwall. Journal of the Royal Institution of Cornwall. Jour. Soc. Arts. Journal of the Society of Arts. Jour. Soc. Chem. Ind. Journal of the Society of Chemical Industry. Mem. Geol. Survey. Memoirs of the Geological Survey of Great Britain. Min. Jour. Mining Journal. Min. Stat. Mineral Statistics of the United Kingdom. Neues Jahrb. f. Miner. Geol. u. Palaontologie. Neues Jahrbuch fiir Mineralogie, Geologic und Palaontologie. Oest. Zeitsckr. f. B.-u. H.- Wesen. Oesterreichische Zeitschrift fur Berg - und Hiittenwesen. Phil. Trans. Philosophical Transactions. Proc. Fed. Inst. M. E. Proceedings of the Federated Institute of Mining Engineers. Proc. Inst. Civil Eng. or Proc. Inst. C. E. Proceedings of the Institution of Civil Engineers. Proc. Inst. Mech. Eng. or Proc. Inst. M. ^.Proceedings of the Institution of Mechanical Engineers. Proc. Min. Inst. Cornwall. Proceedings of the Mining Institute of Corn- wall. Proc. South Wales Inst. Eng. Proceedings of the South Wales Institute of Engineers. Quart. Jour. Geol. Soc. Quarterly Journal of the Geological Society. xxviii LIST OF ABBREVIATIONS. Rec. GeoL Survey, India. Eecords of the Geological Survey of India. Eep. Miners' Assoc. Cornwall. Eeport of the Miners' Association of Corn- wall and Devon. Stat. Min. France. Statistique de 1' Industrie minerale en France. Trans. Amer. List. M. E. Transactions of the American Institute of Mining Engineers. Trans, Inst. Eng. and Shipbuilders in Scotland. Transactions of the Insti- tute of Engineers and Shipbuilders in Scotland. Trans. Inst. Marine Eny. Transactions of the Institute of Marine En- gineers. Trans. Mancli. GeoL Soc. Transactions of the Manchester Geological Society. Trans. Min. Assoc. and Inst. Cornwall. Transactions of the Miners' Asso- ciation and Institute of Cornwall. Trans. Min. Inst. Scotland. Transactions of the Mining Institute of Scotland. Trans. N. of Eny. List. Min. Eny. Transactions of the North of England Institute of Mining and Mechanical Engineers. Trans. E. GeoL Soc. Cornwall. Transactions of the Koyal Geological Society of Cornwall. Trans. Technical Soc. Pac. Coast. Transactions of the Technical Society of the Pacific Coast. Zeitschr. d. d. geol. Gesellsch. Zeitschrift der deutschen geologischen Gesellschaft. Zeitschr. f. B.-H.-u. S.-Wesen. Zeitschrift fur das Berg- Hiitten- und Salinenwesen im preussischen Staate. A TEXT-BOOK OP ORE AND STONE-MINING. INTRODUCTION. THE art of mining, in the broadest sense of the word, consists of the processes by which the useful minerals are obtained from the earth's crust. This definition is wide, for it includes under the term " mine " both open and underground excavations ; but it excludes subterranean workings which are simply used as passages, such as railway tunnels, sewers, and galleries for military purposes. The word " mine " is derived from a low-Latin verb meaning to lead, and equivalent to " ducere ; " we have the French word " mener," from the same source. No doubt originally the mineral deposit itself was called the "mine" or " lead," and this signifi- cation has not been entirely lost, for we still find the word " mine " used as a synonym for " seam " in the case of coal and ironstone. I must remark that the word " mine," or its equivalent in other languages, varies in signification in different countries on account of legal enactments or decisions which define it. In the United Kingdom it is the nature of the excavation, and not the nature of the mineral, which decides whether the workings are a mine or not. For legislative purposes the term "mine" is restricted to workings which are carried on below ground by artificial light ; but in common parlance this rule is not observed, and the word used depends upon the mineral itself. Thus the underground workings for building stone near Bath, and for slate at Festiniog, are usually spoken of as quarries, but are treated legally as mines. In Belgium, France, and Italy, on the other hand, the work- ings for mineral are classified according to the mineralogical nature of the substance wrought. The French law of 1810 makes three classes of workings : mines, minieres, and carrieres. Deposits of gold, silver, lead, copper, sulphur, coal, and beds or veins of iron ore form mines. Under the head of minieres, for which we have no equivalent word in English, are included bog iron ore, pyritous earths fit for working, sulphate of iron, aluminous earths and peat, whilst the carrieres, or quarries, comprise workings for 2 ORE AND STONE-MINING. stone, clay, sand, etc., whether above or below ground. The statute of 1866 has assimilated the minieres to the quarries, and the law now becomes very like that of Italy (1859), which distin- guishes simply mines (miniere) and quarries (cave). Deposits con- taining metallic ores (excepting metal-bearing sand or earth), sulphur, bitumen, coal, or lignite are worked as " mines," whilst pits from which sand and gravel are obtained become legally "quarries.'' The consequence is that what is merely an underground stone quarry in France would be a mine in England ; whilst open workings for iron ore, such as those of Northamptonshire, would be true mines under the French or Italian laws. In a general text-book upon mining, it is therefore necessary to go beyond the British definition of a mine and to include the methods of working minerals in excavations open to the daylight, as well as in those which are purely subterranean. The mining of coal is a subject of so much importance, especially in this country, that it requires a special treatise ; this has been prepared by my friend, Mr. H. W. Hughes,* and my task consists in describing the methods of winning and work- ing all other useful minerals, whether solid, liquid, or gaseous. Furthermore, as it is customary for the miner to cleanse or pre- pare his ore or stone for sale, I shall explain the processes which are usually carried on at the mine, and can be fairly included under the convenient term "dressing." Finally, a few remarks will be made concerning legislation affecting mines in the United Kingdom, the condition of workmen, and the accidents to which they are exposed. The subject has been divided into the following chapters: (i) Occurrence, or manner in which the useful minerals are found in the earth's crust. Prospecting, or search for minerals. Boring. (4) Excavation. (5) Supporting excavations. (6) Exploitation, or working away of minerals. (7) Haulage, or transport along roads. (8) Winding, or hoisting in shafts. (9) Drainage, or removal of water. (10) Ventilation. (n) Lighting. (12) Descent and ascent. (13) Dressing. (14) Principles of employment. Legislation. (16 (17 Condition of workmen. Accidents. * A Text-Book of Coal Mining, London, 1892. ( 3 ) CHAPTER I. MODE OF OCCURRENCE OF MINERALS. Classification of mineral repositories. Beds. Veins. Masses. Causes affecting the productiveness of veins. Theories concerning the formation of veins. Examples of mineral deposits arranged alpha- betically. Faults or dislocations. CLASSIFICATION. Various conditions may be taken as the bases of classification of the rocks which form the crust of the earth. One striking characteristic is the presence or absence of beds or layers. A rock made up of parallel beds, or layers, or strata, is said to be stratified ; a rock in which no such structure exists is called iw stratified. When we examine the stratified rocks closely, we find that, as a rule, they have been formed at the bottom of seas, lakes, or rivers by the gradual deposition of sediment, by precipitation from solutions, and by the growth or accumulation of animal or vegetable organisms. As instances may be cited beds of sandstone or clay, formed by particles of sand or mud settling down in water ; beds of rock salt, resulting from the gradual drying-up of inland seas ; beds of limestone, formed out of old coral reefs ; beds of coal, due sometimes to plants growing upon the spot and sometimes to plants washed into lakes or estuaries. The unstratified rocks are frequently crystalline. In the case of recent volcanoes we see molten rocks issuing forth from the earth, spreading over it, and consolidating into a crystalline mass, and we may fairly assume that many of the crystalline rocks now met with at the surface were at one time in a soft fused condition. Internal evidence leads to the belief that the process of consolidation often took place at a very great depth, and on this account geologists have subdivided the crystalline unstratified rocks into volcanic, which hardened like recent lavas near the surface, and^tfomc, which became solid under the heavy pressure of thick masses of superincumbent strata. One class of crystalline rocks has given rise to much contro- versy, viz., the rocks in which the crystals of the constituent minerals are arranged in roughly parallel layers. The rock has a flaky structure, and is known as a crystalline schist. Some crystalline schists have all the appearance of being altered sedi- 4 ORE AND STONE-MINING. mentary strata ; in others the foliated structure is considered to be the result of pressure upon pre-existing crystalline rocks. We therefore may classify the principal rocks as follows : (Sedimentary origin. Chemical origin. Organic origin. TT ,-r. ! ( Volcanic. 2. Unstratified . The crystalline schists must be placed in one or other of these two great divisions, according as they are looked upon as an altered form of stratified or of unstratified rocks. This classification is not entirely satisfactory. For instance it separates two of the products of a volcano. Volcanic ash falling into the sea will settle down and form a stratified rock, whilst the lava issuing from the same vent is unstratified. Again it does not include sea- water, an important source of salt. How- ever, for the purpose of the miner a simple classification is advisable, and it will be found sufficient for his purpose so long as it is recollected that occasional anomalies must be expected. Any one of the five classes of rocks just mentioned may be extracted from the crust of the earth for commercial purposes. Among the bedded or stratified rocks coal is the most im- portant, but in addition we have beds which are commercially valuable on account of the metals they contain, such as copper, gold, iron, lead, manganese, silver, and tin, or precious stones such as diamonds, garnets, rubies and sapphires ; other valuable beds are native sulphur, rock-salt, and innumerable kinds of stone for building, decoration, paving and road-making, clays for making pottery and cement, oil-shale and alum-shale. From the unstratified rocks we obtain supplies of stone for a great variety of purposes. In addition to mineral deposits, which consist mainly of original constituent members of stratified or unstratified rocks, we have a third important class in which the repository of the valuable mineral has come into existence subsequently to the consolidation of the rocks which surround it. If the repository is, roughly speaking, tabular or sheet-like, it is called a mineral vein or lode, and if in any other form it is a mass. Hence the series of mineral repositories might be classed according to their origin as follows : Primary origin . | T , ( Unstratified. Secondary origin MODE OF OCCURRENCE OF MINERALS. 5 But even here we encounter difficulties, for unstratified rocks sometimes cccur in the form of veins ; besides which primary origin is not a term which is strictly applicable to beds formed from sediment which consists of fragments of other rocks. It is not unnatural, therefore, that outward form should have been chosen as a convenient basis of classification, and accordingly mineral repositories have been separated into : Tabular or sheet-like . If ( 2. Veins. Non- tabular . . 3. Masses. TABULAR DEPOSITS. These are repositories which have a more or less flattened or sheet-like form. They may be divided according to their origin into (i) beds or strata; (2) mineral veins. (1) Beds. The characteristic feature of a bed or seam is that it is a member of a series of stratified rocks ; the layer above it is called the roof, the one below it is the floor. Its thickness is the distance from the roof to the floor measured at right angles to the planes of stratification ; its dip is the inclination downward measured from the horizontal; its strike is the direction of a horizontal line drawn in the plane of stratification. The thickness of workable beds varies within very wide limits. The productive part of the copper-shale at Mansfeld is only 3 inches to 7 inches thick ; and one of the beds of gold- bearing conglomerate at Johannesburg is only 6 inches to 2 feet across ; we find, on the other hand, the lead-bearing sandstone of Mechernich, in Rhenish Prussia, is 100 feet (30 m.), and a bed of brown coal at Briihl in the same neighbourhood no less than 131 feet (40 m.) thick. The principal bed of slate at the Oakeley Quarry, Festiniog, is 120 feet thick (36-5 m.). It must not be supposed that the thickness of a bed necessarily remains uniform. Occasionally this is the case over a very large area; but FlG * * frequently the thickness varies, and the bed may dwindle away gradually, or increase in size, or become divided into two, owing to the intercalation of a parting of valueless rock; but, in spite of such variations, a bed is much more uniform in thickness and com- position than a vein. Fig. i shows beds of shale, limestone, iron ore and sandstone, any one of which may be the object of a mining undertaking. (2) Veins or Lodes. Veins or lodes are more or less tabular or sheet-like mineral deposits, formed more or less entirely since the enclosing rocks (country], and either occupy ing cavities formed ORE AND STONE-MINING. FIG. 2. originally by fissures, or consisting of rock altered in the vicinity of fissures. A simple and typical example of a vein is shown in Fig. 2, representing a lead lode in slate at Wheal Mary Ann in Cornwall.* It is evident that a fissure in the slate has been filled up by the successive deposition of bands of mineral on both sides. The unfilled cavities are called lochs (Wales and Isle of Man), or vugsft (Cornwall). The definition given above differs some- what from that of some standard authors, whose opinions I will quote. Werner says :J "Veins are special tabular mineral repositories which nearly always cut across the strati- fication of rocks and so far have a different lie to them, and are filled with a mineral mass differing more or less from the surrounding rocks ; " and further, " Mineral veins may be more exactly defined by saying that they are fissures in the rocks which have been subsequently filled up with various minerals differing more or less from the surrounding rock." Carne's definition is this : || "By a true vein, I understand the mineral contents of a vertical or inclined fissure, nearly straight, and of indefinite length and depth." Von--!otta!s~-is shorter :^[ " Mineral veins are the contents of fissures," whilst Grimm says :** " Veins are fissures in rocks which have been wholly or partly filled with minerals." Von Groddeck's explana- tion runs thus :tt " Veins are fissures which have been filled up." In Geikie's text-book we find :%% "A mineral vein consists of one or more minerals deposited within a fissure of the earth's crust." Professor von Sandberger's idea of a vein is the same : "True veins, that is to say, fissures filled with ores." In France |||| and similar definitions prevail. * C. Le Neve Foster, " Kemarks on the Lode at Wheal Mary Ann, Men- heniot," Trans. R. Geol. Soc. Cornwall, vol. ix. p. 153. t Probably taken from the Cornish word " fogou/ a cave. J A. G. Werner, Neue Theorie von der Entstehung der Gdnae. Freiberg, I79i, P- 3- Ibid. || J. Carne, "On the Kelative Age of the Veins of Cornwall," Trans. It. Geol. Koc. Cornwall. Penzance, 1822, vol. ii. p. 51. T Die Lehre von den Erzlagerstdtten. Freiberg. 1859, p. 102. ** Die Lagerstatten der nutzbaren Miner alien. Prague, 1869, p. 97. ft Die Lehre von den Lagerstatten der Erze. Leipsic, 1879, p. 31. +J Text Booh of Geology . London, 1882, p. 591. Vatersuchangen iiber Erzgdnge. Wiesbaden, 1882, p. 4. I! || Haton de la Goupilliere, Cours d 1 Exploit at ion des Mines. Paris, 1883, P- 33- HIT V. Zoppetti, Arte Mineraria. Milan, 1882, p. 16. MODE OF OCCURRENCE OF MINERALS. 7 As long ago as the year 1 864,* Mr. Richard Pearce brought forward the theory that many of the tin lodes of Cornwall have been formed by the alteration of granite, and my own f investi- gations have convinced me that he is right. The lodes appear to be bands of stanniferous rock formed by the alteration of granite in the vicinity of fissures. The tabular mass of tin-bearing rock 10 or 15 feet thick, called the lode, is traversed by sundry fissures and passes without any distinct walls or boundaries into non-stanniferous granite; sometimes the main fissure is a few inches wide filled with crystallised quartz and other minerals. This filled-up crack answers to the common definition of a vein, but the rest of the stanniferous mass does not. It has no definite bounding planes, it contains no fragments of the surrounding rocks, and presents no appear- ance of having been formed by the deposition of minerals upon the sides of an open rent (Fig. 3). As much of the stan- niferous rock as will pay for working is known as the lode. i f 3 | I think the geologist must give way and suit his definition to the wants of the miner. It is too much to expect the miner to give up a term consecrated by universal usage, simply because geologists have made the mistake of supposing that all lodes have been formed on the same plan. If Cornwall furnished the only exceptions to the time-honoured definition of a mineral vein, one would perhaps hesitate in pro- posing any alteration ; but when similar or somewhat similar cases are met with in other parts of the globe, the necessity for some change becomes apparent. Mr. Kendall 1 says that the haematite veins of the Lake District (England) are not filled fissures, but are substitutioiial deposits, the result of a gradual replacement of the original rock by other minerals. Mr. S. F. Emmons takes a similar view : "I consider it reasonably certain that a very large proportion of the so-called fissure-veins in the Rocky Mountain region, notably those in * R. Pearce, " The Influence of Lodes on Rocks," Rep. Miners" Assoc. Cornwall. Truro, 1864, p. 18. t C. Le Neve Foster, " On the Great Flat Lode South of Redruth and Camborne and on some other Tin-deposits formed by the alteration of Granite," Quart. Jour. Geol. 8oc., London, 1878, vol. xxxiv. pp. 640-653. J. D. Kendall, "On the Mineral Veins of the Lake District," Trans. Manch. Geol. Soc. Manchester, 1884, vol. xviii. p. 292. R. C. Hills, " Ore Deposits of Summit District, Rio Grande County, Colorado." Condensed for the Engineering and Mining Journal, by S. F. Emmons. Eng. Mln. Jour. 1883, vol. xxxv. p. 334. s ORE AND STONE-MINING. Colorado and Montana, are simply the alteration, silicification, and mineralisation of the country rock along certain planes which for some reason or other offered exceptionally easy access to per- colating mineral solutions, and are not the filling up of pre- existing cavities in the rock, as is generally supposed to be the characteristic of a true fissure-vein." Some of the lodes of Otago, New Zealand,* may be described as belts or zones of auri- Fic. 4. ferous mica-schist with- out any definite bound- aries ; Fig. 4 shows one of them, which is worked at Canton mine. AA is A a vein of quartz, BB a channel or zone of dis- turbed and distorted schist, CC a false wall or plane, along which there has been a shift- ing of the strata. The vein AA, which has been formed along one of the lines of fracture and dislocation, is called the " indicator," as it acts the part of a guide to the miner in his en- deavours to follow the auriferous channel ; but the precious metal is not confined to the space between A and C. The question as to what constitutes a vein or lode has been more thoroughly threshed out in the United States than elsewhere, because in some parts of that country the miner's title .to his property depends upon the definition of the word. The consequence is that the term "lode" has been defined by judicial decisions. In the year 1877, Mr. Justice Field, in the celebrated Richmond v. Eureka case, ga,ve the following interpretation : f " We are of * Rickard, "The Gold-fields of Otago," Trans. Amcr. List. M. E. Meeting of June 1892. t Transcript of Record. Supreme Court of the United States, Nos. 1038 CANTON MINE MODE OF OCCURRENCE OF MINERALS. 9 opinion, therefore, that the term lode, as used in the Acts of Congress, is applicable to any zone or belt of mineralized rock lying within boundaries clearly separating it from the neighbour- ing rock." This definition, which has been framed for the practical work- ing of an Act of Congress, is not a satisfactory one for the scientific miner, because it would include a bed or seam, whilst it would exclude some of the Cornish tin lodes which have no distinct boundaries. Some subsequent decisions cover more ground, for they ignore the question of shape. Judge Hallett * gave the following charge in the case of Hymanv. The Aspen Mining and Smelting Company : " It may be said that with ore in mass and in position in the body of a mountain, no other fact is required to prove the existence of a lode of the dimensions of the ore. As far as it prevails, the ore is a lode whatever its form or structure may be, and it is not at all necessary to decide any question of fissures, contacts, selvage, slickensides, or other marks of distinction, in order to establish its character. As was said in another case f in this court : ' A body of mineral or mineral-bearing rock in the general mass of the mountain, so far as it may continue unbroken and without interruption, may be regarded as a lode, whatever the boundaries may be. In the existence of such body, and to the extent of it, boundaries are implied.' " While quoting these decisions on account of their importance to prospectors and to holders of mining property in the United States, I think it wise to adhere, for the purposes of the student, to the definition I have proposed, and to consider tabular shape and origin subsequent to that of the enclosing rocks as the chief characteristics of mineral veins or lodes. No doubt a very large number of mineral veins are simply the contents of fissures ; others are bands of rock impregnated with ore adjacent to fissures ; others, again, have been formed by the more or less complete replacement of the constituents of the original rock by new minerals. Veins may occur in stratified or unstratified rocks, and in the former they usually cut across the planes of bedding. Like a bed, a vein has its dip and strike ; but as the dip of veins is generally great, it is often measured from the vertical, and is then spoken of as the underlie, underlay, or hade. Instead of being expressed in degrees, the underlie is sometimes measured by the amount a lode plunges under cover, or away from the vertical, in a distance of i fathom (6 feet) measured along the dip. Thus and 1039. The Richmond Mining Company of Nevada v. The Eureka Con- solidated Mining Company. Appeal from the Circuit Court of the United States for the district of Nevada, p. 604. Filed January 17, 1878. * "The Aspen Case," Eng. Mln. Jour. New York, vol. xliii. 1887, p. 21. t " The Smuggler Case," op. cit. p. 20. 10 ORE AND STONE-MINING. if AB (Fig. 5) represents a lode, and AC = 6 feet, AD being verti- cal, draw the line CE at right angles to AD, the inclination is measured by the relation of EC to AC. If EC = 2 feet the underlie is said to be 2 feet in a fathom. This approaches very closely to a dip of 70, or FIG. 5. underlie of 20, whilst i foot in a fathom, for most practical purposes, corresponds to a dip of 80, or underlie of 10. This method of expressing the dip enables it to be determined with a rule or tape. If AB (Fig. 6) is a lode at the end of a mining tunnel (level), the miner has simply to measure the distance EC = 6 feet, drop a stone from C and ascertain the distance from D, where it falls, to E. However, there is the disadvantage that some miners take the standard fathom vertically and not along the dip ; therefore, to avoid any chance of confusion it is wiser to express the inclination of veins in degrees, and not by " feet in a fathom." The bounding planes of a vein, VY (Fig. 7), are called the walls or cheeks, and they are frequently smooth and striated, showing that one side must have slid against the other. These striated surfaces are called slickensides. At the Halkyn mine, Flintshire, the whole side of one of the levels, for a distance of ten yards, is a smooth flat polished surface, with small striae, precisely like the scratchings produced upon rocks by the action of glaciers. In this particular case the striations are horizontal ; more frequently they are inclined. The wall above a lode is called the hanging wall, AB, the one underneath, the foot ivall, CD. The rock surrounding or enclosing the lode is called the country, EE. I give this term, not because I wish to perpetuate a mere Cornish provincialism, but because it has crept into use elsewhere. To use the words country rock, as is done very frequently, is to be guilty of tautology. I may here remark, once for all, that, as a general rule, it is best to avoid local technical terms, and as far as possible employ words which are understood by every one ; but MODE OF OCCURRENCE OF MINERALS. n some expressions are so convenient on account of their brevity that they may fairly be adopted into our language. It is not un- common to find a layer of clay, FG, between the lode and the enclosing rocks ; such a layer is called a selvage, dig (Cornwall), gouge (U.S.), or alta (California). A large mass of the adjacent rock found enclosed in the lode is called a horse, HH. The valueless components of a lode which surround the ore are often spoken of as forming the gangue. I mention the word in order to enter a protest against its use, because, in its passage to us from the German through the French, it has lost part of its original meaning. We already have the words veinstone, lode- sty ff, and matrix, which are more strictly correct and more easily understood than gangue, which, by Englishmen, should be con- signed to oblivion. Veins often continue for a great distance along their strike. The Van lode in Montgomeryshire is known for a length of nine miles, whilst the Great Quartz Vein in California has been traced for a distance of no less than eighty miles. Veins are of less uniform productiveness than beds, and are rarely worth working through- out. Rich portions alternate FIG. 8. with poor or worthless portions. SU*C.J^N, . . . 3? The rich parts have received A ' T * ty ' L ^-. : .f$$> ../ + various names according to the - ' ""^^^ff!^-^ c ,.*f '%&?" forms they assume : Fig. 8 re- a ^^''^f^^ff .^' jft\ ^tfj? presents a longitudinal section along the strike of a lode, and the stippled parts are ore-bodies. ' tor.... L^. o^' ~*^B BBB are bunches ; A is a large bunch or course of ore ; when an ore-body forms a sort of con- tinuous column we have a shoot (chute, ~U.$.}. Ore-bodies which upon being excavated leave chimney -like openings are called pipes (C). In the United States the Spanish word bonanza, literally meaning " fair weather " or " prosperity," is frequently used for a rich body of ore. The inclination of a shoot in the direction of the strike is called its pitch and sometimes its dip, though it is better to restrict this word to the meaning it receives among geologists. It is of the utmost importance to the miner to know where he may expect to find a rich ore-body in a mineral vein. Experience shows that many conditions affect its productiveness,* viz. : 1. Intersections with other veins. 2. Nature of the adjacent rock. 3. Change of dip. 4. Change of strike. * See also, L. Moissenet, Observations on the Rich Part* of the Lodes of Cornwall. Translated from the French by J. H. Collins. London and Truro, 1877. 12 ORE AND STONE-MIXING. (1) Intersections of veins. AB (Fig. 9) is a vein intersecting another CD at an acute angle AEG ; it is frequently the case that there is an enrichment about the junction E. If the lines A'B', C'D' represent the lodes at a lower FIG. 9. level, then EE' indicates the line of intersection, which may be the axis of a shoot of ore upon one of them ; but ; - ^^^^ ~ when the angle AEG approaches a right i "^ o angle a favourable result is not ex- c'. . ^ i pected. r.V--^. .. . g- If AB (Fig. i o) represents a section of a lode along the dip, and CD, EF. and GH are small veins (feeders, drop- pers) falling into it, an increase in the productiveness of the lode often occurs near the intersection. (2) Nature of the adjacent rock. Few facts are more generally recognised than the influence of the enclosing rock upon the productiveness of a lode. I will cite some well-known examples. In the Alston Moor district the veins cross alternating beds of limestone, sandstone, and shale; they are generally more pro- ductive in the limestone than in the sandstone or the shale. At Kongsberg, in Norway, the silver veins are productive in the -D* FIG. 10. FIG. ii. fahlbands, that is to say, quartz schist, mica schist, hornblende schist, and chlorite schist impregnated with iron pyrites and other metallic sulphides, but are poor where they cross the gneiss. The lines ABand CD in Fig. n represent two such veins in plan; the portions ab and cd are worth working, but the other parts are not. MODE OF OCCURRENCE OF MINERALS. 13 In the Gympie* gold field, Queensland, the veins are richest in certain bands of black shale. Four principal belts of black shale have been recognised, and their influence is so thoroughly known that " the fact has determined the system of mining on the field." Turning to another part of Australia, we may notice the " indicators " at Ballarat.f These are narrow beds, some only inch thick, parallel to the planes of stratification of the enclosing slate, and full of small cubical crystals of iron pyrites. Their dip is nearly vertical, and they can be traced for miles. When a quartz vein crosses an " indicator " there is usually rich gold along the line of intersection. Mr. Charles King says: " About ten of these ' indicators ' are known within a width east and west of 1,400 feet, and in the case of six out of these, the quartz crossing them contains, at the line of intersection, exceed- ingly rich patches of gold, frequently in nuggets many ounces in weight." Why only six out of the ten indicators should have the enriching effect is not stated. A third instance of the enriching effect of a pyritiferous rock is afforded in the Thamesf gold-field of New Zealand, where, instead of a narrow " indicator," there is a marked belt of rock, 60 to 80 feet thick, in which the veins prove remunerative. This " congenial " bed is a felspathic sandstone containing pyrites, and is probably a volcanic ash. The veins are poor, or die out altogether 011 entering the harder diorite or underlying slate. Even in the case of earthy minerals the same phenomenon occurs. At Wotherton mine, in Shropshire, the barytes vein is wide and worth working when the adjacent rock is volcanic ash, but narrow and valueless in shale. Lead veins in Derbyshire, which are productive in limestone, rarely yield much ore in the loadstone, an interbedded lava. (3) Change of dip. In a, given vein the parts approaching verticality are often noticed to be richer than those which are comparatively flat. (4) Change of strike. The veins of a mining district are com- monly found to have the same prevailing strike. FIG. 12. Thus the tin and copper lodes of the Camborne and Redruth districts, Cornwall, usually run from S.S.W. to N.N.E., and are spoken of * K. L. Jack, Annual Report of the Department of Mines, Queensland, for the year 1885. Brisbane, 1886, p. 58. t C. Le Neve Foster, " Mining Industries," Reports on the Colonial Sec- tions of the Exhibition. London, 1887, p. 18. $ OP. at. P . 35 . Kenwood, " On the Metalliferous Deposits of Cornwall and Devon," Trans. 11. Geol. Soc. Com. Penzance, 1843, vo1 - v - P- 250. 14 ORE AND STONE-MINING. as east and west lodes. Slight changes in the direction of the strike are sometimes followed by variations in the productive- ness ; in the case of a lode with an average strike repre- sented by the dotted line a b, it may happen that the parallel parts a b, c d, ef, are poor, and the parallel parts b c and d e rich* (Fig. 12). Too much stress must not be laid upon this question of strike, because there are so many exceptions to the rule that a certain strike is favourable. For instance, the two principal mines in the Isle of Man, Laxey and Foxdale, are wrought, one upon a north and south vein, the other upon an east and west vein, only a few miles apart ; and at St. Just, in the extreme west of Corn- wall, the mean direction of the lodes is 35 N. of W., and there- fore quite different from what it is in the chief metalliferous region ; but with individual lodes changes of strike should not pass unnoticed. Formation of Mineral Veins. Though this book is intended to deal mainly with the working of mines, a few remarks con- cerning the origin of veins are necessary first, because the posteriority of their formation is one of their chief characteristics ; and, secondly, because a knowledge of the manner in which useful minerals came to be concentrated along certain lines may enable us some day to predict the precise spots where subterranean riches are accumulated. The principal theories are ; 1 . Fracture and motion with mechanical filling. 2. Fracture and injection of molten matter. C (a) from above. 3. Fracture and deposition from solutions -j (b) from below. ( (c) from the sides. 4. Fracture and sublimation, or deposition from gases. (1) Mechanical Filling. If a rock is fractured, and one side of the crack slides against the other, a vein of crushed material is formed. If the rock is shale or slate, the vein is a band of clay more or less mixed with uncrushed fragments, and in Cornwall is known as a,jlookan. (2) Injection. Veins formed by the injection of a molten or plastic rock into fissures are usually known as dykes. (3) Deposition from Solution. The lode at Wheal Mary Ann, Cornwall (Fig. 2), is an instance of a vein formed apparently by deposition from solution. Many of the common constituents of mineral veins, such as silica, carbonate of calcium, sulphate of barium, are known to be slightly soluble in water, whilst the metallic sulphides can be formed by the reduction of a soluble sulphate, or by the reaction of a soluble sulphide or sulphuretted * Charles Thomas, Remarks on tJie Geology of Cornwall and Devon. Red- ruth, 1859, p. 5. MODE OF OCCURRENCE OF MINERALS. 15 hydrogen upon metallic compounds. Some metallic sulphides are soluble in alkaline solutions. Much discussion has arisen concerning the place whence the mineral-bearing solutions came. The theory that they came from above finds few upholders nowadays, and the battle rages principally between the advocates of the ascensional theory, or supposition that the minerals came up in solution from very great depths, and the upholders of the lateral secretion theory, in which it is assumed that they were leached out of the adjacent rocks and re- deposited in the vein cavity. This latter theory has been powerfully espoused of late years by Professor Fridolin von Sandberger,* who has pursued his investigations with great ardour. He shows that small quantities of antimony, arsenic, bismuth, cobalt, copper, lead, silver, and tin are contained in silicates such as augite, hornblende, mica, and olivine, which are essential constituents of plutonic and volcanic rocks ; and he concludes that these rocks are the sources from which the lodes have derived their riches. Prof, von Sandberger's views have not been allowed to pass unchallenged, for Prof. Alfred Stelznerf combats his methods of analysis. It is naturally impossible to affirm with certainty that a given mineral, such as mica, contains lead for instance, so long as there is a possibility that particles of galena were mixed with it. The absolute freedom of the rocks submitted to analysis, from any mechanical admixture with pyrites or other sulphides is a neces- sary foundation-stone of von Sandberger's theory. It is against this point that Professor Stelzner directs his attack, and he shows, by the results of numerous carefully conducted experiments, that the metals found on analysis by Professor von Sandberger did not necessarily come from the silicates, but may have been derived from mechanically mixed sulphides which had resisted his attempts to remove them. Stelzner points out that the occurrence in the country of sulphides, similar to those existing in the lodes, may be explained quite as well by their having travelled from the fissure into the adjacent rock, as in the reverse direction. With reference to the silver found in the rocks, Stelzner re- marks that the mica of granite at Sulzbachle in the Black Forest, stated by von Sandberger and others to contain o'ooi to 0*006 per cent, of silver, was found to be absolutely free from any traces of the metal when assayed with special precautions at the Mining College of Freiberg. Under these circumstances von Sandberger's theories must for the present be looked upon as not entirely proven, much as one * Untersuckungen iiber Erzyange. Wiesbaden, 1882 and 1885. t " Die Lateralsecretions-Theorie und ihre Bedeutung fiir daa Pribramer Ganggebiet," Jahrbuch der k.k. Bergakademieu zu Leoben und Pribram und der kgl. ung. JBergalcademie zu /Schemnitz, vol. xxxvii. 1 6 ORE AND STONE-MINING. would like to be able to account in so direct a manner for the in- fluence of the country upon the contents of the lodes. The views of Mr. Becker,* with reference to the quicksilver mines of California and Nevada, deserve special mention, because the adherents of both parties will probably claim them as support- ing their theories. To avoid any chance of mistake, I quote ver- batim : " The evidence is overwhelmingly in favour of the supposi- tion that the cinnabar, pyrites, and gold of the quicksilver mines of the Pacific slope reached their present positions in hot solutions of double sulphides, which were leached out from masses under- lying the granite or from the granite itself." Mr. Becker supposes that the hot alkaline solutions were the products of volcanic agencies, and he decidedly leans to the view that they took up the heavy metals in their passage through the granite itself, and not from rocks underlying it. Even if the ore was not leached out of the immediately adjacent rocks, these may have influenced its deposition either chemically or mechanically. It is possible that a certain bed may act as a reducing agent upon a solution which touches it, and so cause precipitation ; this may be the reason why rich gold has been deposited where the pyritiferous "indicators" intersect the Ballarat lodes. The mechanical effect is also very simple. A fissure formed in a soft rock is likely to be filled up by pieces of the sides dropping in, especially if there is any sliding of the hanging wall upon the foot wall ; on the other hand, if the rock is hard, the chasm will remain open and leave a space for the reception of ores. This fact gives a reason for the steep parts of lodes being sometimes richer than the flatter parts. If a wavy cut is made in a piece of card or paper to represent the fissure, and the " hanging wall " slid down a little, we have open spaces where the fissure is steep, whilst the " walls " touch where the fissure is flatter, leaving no room for any deposition of ore to take place. A wavy crack of this kind may be caused by variations of hard- ness and fissility, such as happen when shale is interbedded with limestone ; here the crack will be propagated more readily along the planes of stratification of the shale than across them. After a slight shift of the " hanging wall " downwards, the cavities in the limestone become receptacles for mineral deposits, whilst the crack contains little but crushed rock in the shale. In a like manner the variation in productiveness noticed upon a slight alteration of strike may be due to change in the nature of the " country," which not only caused a deviation from the general direction of the fissure, but also affected its ore-bearing qualities. Here, too, we find an explanation of the phenomenon called "ore against ore." In Fig. 13 let ABCD, and EFGH * "Geology of the Quicksilver Mines of the Pacific Slope," Monographs of the U.S. Geol. tiurvey, vol. xiii. p. 449. Washington, 1888. MODE OF OCCURRENCE OF MINERALS. 17 represent a plan of two parallel lodes, BC and FG being rich parts ; the miner notices that an improvement in the productiveness takes place in both lodes when the strike changes from E. and W. to E. 25 N., and that the rich part, BC, is opposite the rich part FG. This is not surprising if the parts BC and FG are in a special belt or zone, included between the lines FIG. 13. HK, LM, capable > of exerting either a , \ mechanical effect H \ \ upon the size of the vein-cavity by its hardness, or a chemical effect by its composition. The adjacent rock may likewise have affected the lode by its porosity or by its impermeability, in the former case by affording an easy channel for the solutions which brought in the minerals, and in the latter by interposing a dam which prevented or delayed their escape. (4) Sublimation. The sublimation theory meets with little favour nowadays, though certain minerals known as constituents of lodes are formed in furnaces, or can be produced artificially from gases. Nearly half a century ago, Daubree * produced crystals of oxide of tin by passing a current of stannic chloride together with steam through a red-hot porcelain tube. One great objection to the universal acceptance of the sublimation theory is that many of the minerals found in lodes would be decomposed at high temperatures. Formations. The lodes in some districts are grouped into different classes according to their mineralogical characters, and careful observations have shown that those which are similar in mineral contents usually agree in strike and in age. Distinctions of this kind have been skilfully worked out at Freiberg f in Saxony, where six of these classes or " formations " are recognised. Anomalies. It must be understood that we cannot expect Nature to make distinct lines of demarcation between the different kinds of mineral repositories. Though we may be able to see clearly that * " Kecherches sur la production artificielle de quelques especes minerales cristallines, particulierement de 1'oxyde d'etain, de 1'oxyde de titane et da quartz. Observations sur 1'origine des filons titaniferes des Alpes," Ann. Mines, 46 serie, vol. xvi, 1849, p. 129. Compt. Rend., vol. xxix. 1849, p. 227, and vol. xxx. 1850, p. 383. t Freibergs Berg- und Hiittenwesen. Freiberg i. S., 1893, p. 32. B i8 ORE AND STONE-MINING. a seam of coal is contemporaneous with the enclosing rocks, and that a vein, intersecting successively beds of limestone, shale, and sandstone, is evidently of later formation, cases frequently occur in which the origin of the mineral is uncertain. For example we have the lead-bearing sandstone of Mechernich, the silver -bearing sandstone of Utah, the gold-bearing conglomerate of the Transvaal. The grains of sand and the pebbles of quartz are unquestionably of sedimentary origin ; but opinions differ as to whether the lead, silver, and gold were deposited originally with the sand and gravel, or were introduced subsequently by metal-bearing solutions, which found a passage through the beds. It has been shown by Mr. Becker* that ample space exists in an ordinary sandstone for the deposition of ores. Supposing that all the grains were true spheres of the same size, and as closely packed together as possible, there would be 26 per cent, of inter- stitial space. If this space is even partly occupied by an ore, the percentage of metal may very easily be sufficient to render the stratum worth working. For example, a sandstone with a specific gravity of 2*25 requires only 3-7 per cent, of its interstitial space to be filled by cinnabar with a specific gravity of 8, in order to furnish an ore with 10 per cent, of mercury, about the average contents of the rock worked at Almaden. This 3*7 per cent, is " less than half the interstitial space in some indurated sandstones employed for paving streets." In the case of sandstones worked for mercury, it seems to be quite certain that the cinnabar was brought in by aqueous solutions long after the deposition of the sediment indeed, long after the solidification and upheaval of the rocks. According to Dr. Sorby, the iron of the well-known Cleveland bed was " derived partly from mechanical deposition and partly from subsequent replacement of the originally deposited car- bonate of lime."f Other cases of more or less complete replacement may be cited. We find chalk changed into flint, limestone into chert; and if " subsequent origin " were the only characteristic distinguishing a vein from a bed, we should be landed in a difficulty. It will be found convenient to consider as seams any stratified deposits in which the impregnated, altered, or pseudomorphous mass occupies the position of an original bed, and to call the sheets veins when they cross the bedding-planes, or occupy a fissure, or have been formed by the alteration of a rock at the side of a fissure. MASSES. These are deposits of mineral, often irregular in shape, which cannot be distinctly recognised as beds or veins. Such, for instance, are certain of the red haematite deposits of * " Geology of the Quicksilver Deposits of the Pacific Slope," Monographs of the U.S. Geol. Survey, vol. xiii. p. 399. Washington, 1888. t Quart. Jour. Geol. Soc., vol. xxxv., 1879, p. 85. Anniversary Address of the President. MODE OF OCCURRENCE OF MINERALS. 19 the Ulverston district (Fig. 14),* which occupy irregular cavities in the Carboniferous Limestone. They may have been formed FIG. 14. A, the enclosing limestone ; B, red haematite ; C, sand and clay : D, a thick capping of glacial drift. by the percolation of water Bringing down iron in solution from overlying rocks, which by gradual replacement changed part of the limestone into a mass of haematite. Other examples of masses are the calamine deposits of Altenberg (Fig, 15),! Sardinia, and FIG. 15. FIG. 1 6. B, the enclosing slate, d, dolomite, C, calamine, L, clay. Scale *i. Tin=iff =i 2 Sleet Mulberry Mine, near Bodmin. Lombardy, the huge upright " necks " or " pipes " of diamond- bearing rock in South Africa, and the granite decomposed in situ worked for china clay in Cornwall. Under this head also are included by most authors the so-called " stockworks," " reticulated masses " or " network deposits," names applied to masses of rock intersected by so many little veins as to make the whole worth excavating. Fig. 1 6 shows a number of steeply dipping strings of cassi-. terite, generally only two or three inches apart, intersecting beds * "Beschreibung der Rotheisenerzlagerstiitten von West Cumberland und North Lancashire," Stahl und Eisen, 2 Jahrgang, No. 12, Plate VI. t M. Braun, Zeitschr. d. d. geol. GesellscJi., vol. ix. (1857) ; and A. von Groddeck, Die Lelire von den Lagerstcitten der Erze. Leipsic, 1879, p. 242. 20 ORE AND STONE-MINING. of slate. The mass of rock penetrated by this network of little tin veins is 300 yards long by more than 30 yards wide, and the whole of the stanniferous stone is quarried and stamped.* EXAMPLES. These abstract definitions are not sufficient ; the student should see how they can be applied to particular cases ; and I now propose to give a series of examples of the modes of occurrence of the most important minerals. As the same mineral may be found in a bed, a vein, or a mass, it is simplest, for the purposes of the miner, to classify these examples alphabetically. I therefore arrange the information about tin, for instance, under one head, instead of separating the tin veins from the stockworks, and these from the alluvia. The minerals to which I propose to refer are : Alum, amber, antimony ore, arsenic, asbestos, asphalt, barytes, borax, boric acid, carbonic acid, clay (including china clay, fire clay, fuller's earth, potter's clay), cobalt ore, copper ore, diamonds, flint, freestone, gold, graphite, gypsum, ice, iron ore, iron pyrites, lead ore, manganese ore, nitrate of soda, ochre, oil shale, ozokerite, petroleum, phosphate of lime, potassium salts, quicksilver ore, salt, silver ore, slate, stone, strontium sulphate, sulphur, tin ore, zinc ore. Alum. The alum-stonet obtained at Allumiere and Tolfa, near Civita Vecchia, occurs in very irregular veins, which are supposed to be due to the action of heated water and sulphurous gases upon the felspar contained in trachyte. An important deposit of alunite has lately been discovered^: in New South Wales, at the Bullahdelah Mountain, which rises up from the bank of the Myall River, a tributary of Port Stephens. Marked cliffs, overlooking the river, consist of alunite in varying quality, ranging from pure alunite to a mineral in which there is as much as 40 per cent, of silica. The deposit is traced for over a mile in length and nearly three-quarters of a mile in breadth, the thickest band of stone being from 60 to 70 yards in width. The average composition of the rock now being worked is as follows : Per cent. Water , 7-80 Alumina , 34'7o Oxide of iron ...... i 'oo Potash 6-10 Sulphuric acid 32-30 Silica . . . 18-10 lOO'OO * C. Le Neve Foster, " On some Tin Stockworks in Cornwall," Quart. Jour. Geol. Soc., vol. xxxiv., 1878, p. 655. t A. K, de la Grange, Le Tracliiti ddla Tolfa e le formazioni attuminifere. Rome, 1 88 1. t MS. information from Mr. S. Herbert Cox, A.R.S.M,, the discoverer of the alunite. MODE OF OCCURRENCE OF MINERALS. 21 The surrounding rocks belong to the Carboniferous system of New South Wales, and it is supposed that the alunite has been formed by solfataric action upon dykes of a felsitic rock. Amber. This fossil resin is found in a bed of Tertiary age, which extends along the shores of the Baltic from Western Russia to Denmark. The principal workings are about halfway between Memel and Dantzig, and the amber is obtained by diving and dredging in the sea and by ordinary mining inland. After a storm pieces are cast up on the shore. The stratum containing the amber is known from its colour as the " blue earth." Antimony. Antimony ore usually occurs in veins. In York County, New Brunswick,* the veins are from a few inches to 6 feet wide in Lower Silurian slate. The veinstone is white quartz, calcite, and iron pyrites in small crystals. The ore raised from the mine contains about 10 per cent, of stibnite. Arsenic. The white arsenic of commerce is mainly obtained from mispickel, which is either mined by itself or more commonly in connection with the ores of copper, tin, or gold. It is there- fore in most cases a by-product in the preparation of these ores for the market. Asbestos. The asbestos of commerce is in part chrysotile and in part the fibrous variety of hornblende. Italy and Canada are the chief sources of supply, and in both countries the mineral is found in veins in serpentine. The principal Italian mines are in the Susa and Aosta valleys and the Yaltellina.f In one of the mines in a tributary of the latter valley the rock is " cut in every direction by thin seams of asbestos, which seem to start as from a centre and spread out in every direction, and these again are traversed by thin seams both horizontally and diagonally. Entering into the rock, these seams generally converge to a centre, where the various thin seams unite themselves, and here a pocket of a ton or a ton and a half of asbestos may be found, and then all appearance of its presence ceases. Continuing to work inwards, the seams generally re-appear and spread themselves out as before." The most important of the Canadian quarries are situated in the townships of Thetford and Coleraine, in the province of Quebec. A belt of serpentine runs through the district, and it is intersected by innumerable small veins of chrysotile, varying in width from a mere knife-edge to about 6 inches at the most, the fibres of the mineral running almost at right angles to the walls. The common width of the veins is from i to 2 inches, and as they "cross and recross each other in every direction and at * E. M. J., vol. xvi., 1873, P- 7 J an d B. u. h. Z. 1874, p. 237. t James Boyd, "Asbestos and its Applications," Jour. Soc. Arts, vol. xxxiv. (1886), p, 583. J. A. Fisher, "Mining, Manufacture and Uses of Asbestos," Trans. List. Marine Eng., vol. iv., 1892. 22 ORE AND STONE-MINING. every angle," * the whole of the enclosing rock has to be quarried in order to get out the asbestos. Asphalt. The various modes of occurrence of asphalt or bitumen have been described by Malof and Greene,^ and the following table is made up from their works : State. Localities. (viscous . . Pitch springs in Alabama, France, Venezuela, solid . . Dead Sea, Cuba, Texas, Utah. 2. Mixed with earthy matter . Pitch Lake, Trinidad. 3. Mixed with sand . . . California, France, Utah. (bituminous sandstone) 4. Impregnating limestone , Colorado, Cuba, France, Mexico, (bituminous limestone) Sicily, Spain, Switzerland. The nearly pure asphalt does not occur in sufficiently large quantities to be worked on a commercial scale, and the Pitch Lake of Trinidad. long known as a natural wonder, has not been utilised to any great extent until of late years. The lake occupies an area of 99 acres, and is on an average from 20 to 30 feet deep. Its surface is not one continuous sheet, but is broken up by pools and channels of rain water ; the asphalt is nearly everywhere solid enough to walk on. The crude asphalt has the following composition :|| Per cent. Bitumen ....... 34 Water 30 Clay 36 100 "The bituminous sandstone of California is found in large quantities at various points between San Francisco -and Los Angeles. It contains about 1 2 to 18 per cent, of bitumen, and the rest is quartz sand, in grains about one-tenth of an inch in We now come to the bituminous limestone. Val-de-Travers, in Switzerland, and Seyssel, in France, are the most important sources of this rock for paving purposes. At Seyssel there are no less than seven beds of bituminous limestone, varying from 10 to 20 feet (3 to 6 m.) in thickness. One analysis of the rock** was as follows : * Boyd, op. cit. p. 586, t Leon Malo, L' Asphalts, Paris, 1888, p. 20, F. V. Greene, " Asphalt and its Uses," Tram. Am. List. M.E., vol. xvii. 1888, p. 355. Wall, Report on the Geology of Trinidad. London, 1860, pp. 94, 140. !l Malo, op. cit., p. 75. 1T Greene, op. cit. ** Notice sur la Societe civile de bitume et d'asphalte du Centre. Paris, 1889, p. 7. MODE OF OCCURRENCE OF MINERALS. 23 Per cent. Bitumen 670 Clay ... . 3'oo Peroxide of iron Lime Magnesia Sulphuric acid Phosphoric acid Carbonic acid, water and loss 2-60 45-00 S'SO O'2O 0'20 38-60 99-60 Barytes. This mineral frequently accompanies lead ore, but veins are sometimes worked for it alone, as at Wotherton in Shropshire. Borax. The American borax deposits* now being worked are situated in a vast depression known as the Great Basin, which exists between the Sierra Nevada on the West and the Rocky Mountains on the East. Much of the region is a desert with rivers and lakes which have no visible communication with the ocean. The rivers lessen in volume gradually from absorption and evaporation, and end in lakes. During the rainy season soda is dissolved out of felspars contained in the lava which covers much of the country, and in the dry season the salts of soda crystallise out at the surface in the form of efflorescent crusts, 12 to 18 inches in thickness. The rain dissolves tho crust, which is carried away in solution into the rivers, and eventually into depressions which form saline lakes. The two principal deposits, known as Borax Lake and Teel's Marsh, were discovered in 1873 ; the former lies in the Mojave desert in California, 450 miles S.E. of San Francisco, and the latter is in Nevada. The Borax Lake is oval in shape, its greatest length and greatest breadth being 1 2 miles and 8 miles respectively (Fig. 1 7). The greater part of the lake is covered with a hard crust from a few inches to several feet in thickness, consisting of various salts. On the top of this crust there is usually white efflorescent matter mixed with sand, whilst under it is black mud containing much iron sulphide, saline matter, and sulphuretted hydrogen. The lake may be divided into three sections, containing respec- tively: (i) borax, (2) bicarbonate of soda, (3) common salt. Near the centre of the borax section, an area of about 300 acres is covered with water, i inch to i foot deep, and the mud under- neath is full of large crystals consisting of carbonate of soda and common salt, with a large proportion of borax. The ground around this " crystal bed " is a dry hard crust containing car- bonate and sulphate of soda and i per cent, of borax. Upon this hard crust there is efflorescent matter containing on an average : * C. Napier Hake, " An Account of a Borax Lake in California," Journ. Soc. Chem. 2nd., vol. viii. (1889), p. 854. 2 4 ORE AND STONE-MINING. Sand , Sulphate of soda Common salt Carbonate of soda Borax . Per cent. 50 . 16 , 12 . 10 12 This surface efflorescence, which is about an inch thick, is scraped off with shovels and swept into windrows, leaving space FIG. 17. Borax Deposit Bi-carbonate of Soda mmm Chloride of Sodium ** l\\\\\\VM enough between them for a cart to pass. When the surface has been cleared, the moisture finds its way up again by capillary action and is evaporated by the sun. The formation of the MODE OF OCCURRENCE OF MINERALS. 25 efflorescence is allowed to go on for three or four years, and then the new crop is scraped off. The sand is blown on by high periodical westerly winds. The question naturally arises : Why is the borax mainly con- fined to one part of the lake ? It appears necessary in order to produce the efflorescence that the crust should touch the water, so as to get a supply of the saline matter. The borax section is the lowest part of the lake, and the hard crust dips into the water. When the level of the water is low during a very dry season, the formation of the efflorescence goes on slowly or ceases altogether. In addition to borax there are sundry deposits of borate of lime in the same region. Boric Acid. Boric acid is obtained in considerable quantities from gaseous emanations which come to the surface through in- numerable fissures, probably dislocations, in the Eocene and Cretaceous rocks of Central Italy.* The best known localities are the four contiguous parishes of Pomarance, Castelnuovo di Val di Cecina, Massa Marittima, and Montieri, in the province of Pisa. A pit is dug around any natural " steam-puff," or " blower " (soffione), water is run in, and the steam and other gases, which boil up through it, leave a little boric acid in solution. The gases that escape are steam, a good deal of carbonic acid and nitrogen, some oxygen, and a little sulphuretted hydrogen. The very weak boracic solution is concentrated by heat derived from some of the steam -puffs. The total production of the provinces of Pisa and Grosseto in 1891 was 1775 metric tons of boric acid, worth ^35,500, and 2056 tons of borax worth ^5 3, 45 6. Carbonic Acid. Liquefied carbonic acid is now a regular article of commerce, and Germany has taken the lead in utilising the natural supplies of the gas. In 1883 a bore-hole was put down for carbonic acid at Burgbrohl,f near Andernach on the Rhine, and since then others have been made at Obermendig, Tonnistein, Honningen, and Gerolstein. All have been successful ; they show that the subterranean supplies of carbonic acid are very plentiful, and that in places where the gas is already known to issue, nothing but a comparatively shallow hole is needed to increase the quantity very considerably. At Honningen, about five-eighths of a mile (i kilometre) from the Rhine, an emanation of carbonic acid gas had long been known, and was piped off to compression works before any boring had been made. The rocks in which the carbonic acid occurs at Honningen consist of grey wacke and clay-slate, with vein-like masses of quartz ; they belong to the Lower Devonian or so-called * Jervis, Guida alle Acque Miner ali cT Italia, Turin, 1868, p. 121 ; and 1 Tesori sotterranei dell' Italia, Turin, 1874, p. 427. t Heusler, Sitzungsberichte der niederrheinischen GeseUschaft filr Natur- vnd Heilkunde in Bonn. Meeting .of July 9, 1888. 26 ORE AND STONE-MINING. Coblentz beds, and the bore-holes at Burgbrohl, Obermendig, and Tonnistein have been put down in strata of the same age. The Honningen hole was bored with a diameter of 13 inches (33 cm.) to a depth of 230 feet (70 m.) from the surface. The first water containing carbonic acid was met with at a depth of 92 feet (28 m.), and it still remains at this level. The quantity of gas is greater than was given off by the old emanation at the surface, and is reckoned to be 500 litres (nearly 18 cubic feet) per minute, corresponding to 720 cubic metres (25,428 cubic feet) of gas, or i kilog. (2*2 Ibs.) of liquid carbonic acid in twenty-four hours. The Honningen spring differs from some others by the fact that at a depth of 230 feet (70 m.) the water is already at a tempera- ture of 72 F. (22 C.), and probably a higher temperature would be reached if the hole were deepened. A second hole has been bored to a like depth by another company at a distance of 50 feet (15 m.) from the first, and a good supply of gas has been obtained. At Gerolstein the bore-hole passed through alluvial gravel into solid dolomite, and was stopped at a depth of 156 feet (47 J m.). It seems probable that the hole has penetrated into a wide fissure filled with loose fragments of dolomite. The water which flows out contains such an excess of carbonic acid that it froths up at the surface. The quantity of water coming up is 8476 cubic feet (240 cb. m.) in twenty- four hours, with an estimated minimum of 1060 cubic feet (30 cb. m.) of carbonic acid gas per hour. Though natural outflows of this gas are common, especially in volcanic regions, the number of places where they are utilised commercially is small. In addition to the German localities, I may mention two places in Italy.* There are springs of water impregnated with carbonic acid and emanations of the gas at Cinciano, in the Yalle d'Elsa, province of Siena, which are used for making pure bicarbonates of potash and soda from the crude carbonates, and also for making white-lead from the acetate, the gas being perfectly free from any sulphuretted hydrogen. Similar blowers (soffioni) at Montione, near Arezzo, are em- ployed for the latter purpose. Clay (including common clays, china-clay, fire-clay, fuller's earth, pipe-clay, potter's clay). As a rule, clay occurs in the form of stratified deposits, and this is the case with an important British clay, the fire-clay of the Coal Measures, which is found in beds sometimes several feet in thick- ness and usually under a seam of coal. The coal is often too thin to be worked and may be only i inch thick, but both coal and the underlying fire-clay may be worth working together. Various beds of clay of Secondary and Tertiary age are dug in England * Jervis, Guida alle Acque Minerali d 1 Italia. Turin, 1868, pp. 54, 63. MODE OF OCCURRENCE OF MINERALS. 27 for making pottery, drain pipes, and Portland cement. The beds of fuller's earth near Bath are of Oolitic age, whilst those which are mined in Surrey belong to the Lower Greensand. The china clay* of Cornwall and Devon exists in irregular deposits of a totally different nature ; they consist of granite decomposed in situ, not by atmospheric agencies as is often stated, but far more probably *by hydrofluoric acid brought up by deep-seated fissures. That the decomposition was due to the veins or fissures seems evident from the fact that the altered rock occurs in bands adjacent and parallel to them. Where the veins are numerous a very large mass of china clay may be found, extending for a width of a hundred or more yards, and a length of a quarter of a mile or half a mile along their strike ; the depth to which the alteration of the granite continues is quite unknown. The veins are often tin-bearing, and workings for tin have led to the discovery of china clay; indeed the two minerals may be worked together. The altered granite consists of quartz, white mica, sometimes a little gilbertite, and felspar which has been more or less completely converted into kaolin. This last mineral is easily separated when the soft rock is washed down by a current of water, for it is so finely divided that it is the last to settle when the milky stream is led into depositing pits. Cobalt. The cobalt ore worked at Skutterud in Norway is found in certain bands of quartz schist and mica schist which contain small particles of cobalt glance, skutterudite, cobalti- ferous mispickel, ordinary mis- pickel, iron pyrites, and other metallic sulphides. The accompanying figure (18) illustrates what I saw at Skut- terud some years ago ; a, a, a, are bands of mica schist with little or no cobalt ore ; b, b, are bands of quartz schist containing the cobaltic minerals dissemi- nated through them, and c, a cobaltiferous band of mixed quartz schist and mica schist. The rocks appear to be altered sedimentary strata, and the deposits must be spoken of as beds. The strike is N. and S., and the beds dip at a very high angle to the east. Quartz schist is the rock most likely to be cobaltiferous, the mica schist may be also worth working, but hornblende schist is poor. The cobaltic beds are commonly two or three fathoms wide, but a number of * J. H. Collins, The Hensbarrow Granite District. Truro, 1878. And*, " On the Nature and Origin of Clays : the Composition of Kaolinite," JUin. Mag. London, vol. vii. (1887), p. 205. as 28 ORE AND STONE-MINING. adjacent beds may produce a much greater thickness of cobalt- iferous rock. In New Caledonia* the mode of occurrence is totally different. FIG. 19. a a irs-w-Ki fain of Chromic Iron of fragm en U of Chromic Iron ited from Uit Veins of ColcUl it 'trout Afanyontse ore The cobalt is found as a hydrated oxide, without a trace of sulphur or arsenic, intimately associated with hydrated oxide of manganese, in irregular " pockets " of red clay in serpentine. In Fig. 1 9 S is the serpentine and A the red clay ; a a represent veins of chromic iron in the serpentine ; a' a' is a little stratum of fragments of chromic iron derived from these veins, whilst b b are beds of cobaltiferous manganese ore in the clay. The ore lying about on the surface or obtained from these pockets has from 2 J to 3 per cent, of cobalt. At Rhyl, in Flintshire,t there is a curious irregular cavity in FIG. 20. HORIZONTAL SCALE MOO 1000 2000 3000 4000 5000 6000 7000 8000 SpOQ IQOttOnv VERTICAL SCALE THREE TIMES THAT OF THE HORIZONTAL SCALE the Mountain Limestone filled up with red clay which encloses small lumps of asbolane. This deposit was worked on a small scale for several years. Copper. The most important copper mines of the world * Levat, " Memoire sur les progr^s de la metallurgie du nickel." Ann. Mines, ge serie, vol. i. p. 147. f Irans. R. Cornwall Geol. Soc., vol. x. p. 107. MODE OF OCCURRENCE OF MINERALS. 29 nowadays are those of Mansfeld in Germany, Rio Tinto and Tharsis in Spain, San Domingos in Portugal, Lake Superior, Arizona and Montana in the United States. Germany. Copper mining has been carried on near Mansfeld, in the Prussian province of Saxony, since the commencement of the twelfth century, and the district is specially interesting from the fact that the ore is found in a bed or seam, which can be worked with profit in spite of its thinness and comparative poverty in metal. The Mansfeld district (Figs. 20 and 21) is mainly occupied by the rocks of the following formations : Trias . . , . . 3. Bunter Sandstone. -p (2. Zechstein. Permian . . . . \ -^ ,, ,. , I i. Rothliegendes. (1) "Das Rothliegende," or the red floor, is the old miners' name for the sandstone and breccias lying almost immediately below the bed of cupriferous shale. In contradistinction to the ore-bed, it is also called " das Todtliegende " (the dead floor). It can always be distinguished by its characteristic red colour. One of its most constant beds is the so-called " porphyry con- glomerate," consisting of pebbles of milk-white quartz, hard siliceous slate, and grey and reddish porphyry, (2) The Zechstein formation consists of three divisions. The lowest division comprises the " Weissliegendes," the bed of copper shale and the Zechstein. The middle division consists of the anhydrite or older gypsum, or of its equivalent the " Rauchwacke," " Asche," " Rauhstein " and Stinkstone ; the upper division is made up of variegated clays with intercalations of gypsum, the residues left when some of it is dissolved away (Asche), and cal- careous or dolomitic concretions.* The " Weissliegendes " is petrographically like the " Rothlie- gendes" below it, and is looked upon by many as merely an uppermost bed deprived of colour. Above it with great regularity comes the ore bed, a blackish, bituminous, marly shale, about 15 to 1 8 inches thick. The ore of the shale bed is usually disseminated through it in the form of fine particles (/Speise), which impart a metallic glitter to the surface of cross-fractures. A golden yellow col our indicates chalcopyrite, a bluish and reddish variegated look, bornite, and a steel grey, seen more rarely, is due to copper glance ; whilst a greyish yellow denotes a predominance of iron pyrites, and a leaden grey, galena. The following minerals also occur : cinnabar, blende, kupfernickel, speiskobalt, and compounds of manganese, molybdenum and selenium. Oxidised ores are found at the outcrop. * The figures and some of the details concerning the Mansfeld mines are borrowed from a pamphlet entitled. " Der Kupferschieferbergbau und der Hiittenbetrieb zur Verarbeitung der gewonnenen Minern in den beiden Mansf elder Kreisen der Preussischen Provinz Sachsen." Eisleben, 1889. ORE AND STONE-MINING. and are naturally of secondary origin. In addition to the finely disseminated grains, there are often small strings of bornite and copper glance, generally parallel to the bedding, and thin coatings of copper glance, bornite, chalcopyrite, and native silver along the FIG. 21. SECTION OP EDUARD II. SHAFT. Soil Bunter Sandstone Gypsum . Stinks tone and " Asche ' Blue Shale Stinkstone and " Asche ' Gypsum . Zechstein . Copper Shale R othliegendes Conglomerate Rothliegendes Rothliegendes 'with Melaphyre Rothliegendes . M planes of bedding or in cross joints. Finally there may be small nodules of copper ore lying singly. The whole of the bed of copper shale is ore-bearing ; but, as a rule, only the bottom 3 or 4 inches are rich enough to be worked with profit. Occasionally 6 or 7 inches can be taken, and in ex- ceptional cases the whole of the bed goes to the smelting works. Although there are minor variations, the shale is fairly regular MODE OF OCCURRENCE OF MINERALS. 3 1 as regards ore-bearing when dealt with on a large scale. On an average, in the true Mansfeld district, between Gerbstedt and Eisleben, it contains 2 to 3 per cent, of copper and 163 oz. of silver to the ton of copper (5 kil. per metric ton). The importance of the copper shale will be appreciated from the fact that in the year 1888, 14,178 persons were employed at the mines, or more than all the miners of Cornwall and Devon. The output of ore was 469,716 metric tons, which produced 13,600 metric tons of refined copper, and 77,950 kilogrammes (208,845 Troy pounds) of silver. Spain and Portugal. The famous mines of Rio Tinto,* FIG. 22. Tharsis, and San Domingos are contained in a great metalliferous belt of country, 140 miles long by 30 miles wide, stretching across the province of Huelva in Spain and into Portugal. The rocks consist of slate of Upper Devonian age, often altered locally into jasper, talc schist, chiastolite schist, etc., with great intrusions of quartz and felspar-porphyries, diabase, quartz- syenite, and granite. The geological horizon of the slate has been determined by finding Posidonomya Becheri, P. acuticosta, a goniatite allied to G. subsulcatus and other fossils. The strike of the slates is about 15 to 25 north of west, and the dip either * Collins, " On the Geology of the Rio Tinto Mines, with some General Kemarks on the Pyritic Kegion of the Sierra Morena," Quart. Journ. Geol. &>c., vol. xli. (1885), p. 245. ORE AND STONE-MINING. vertical or at a high angle to the north. Through having the same general strike as the slate, the masses of porphyry may appear to be interstratified, but a close examination of the junction proves them to be intrusive. As shown by the map (Fig. 22), there are four principal deposits of pyrites at Eio ' IG ' 2 3- Tinto, viz., the North Lode, the South Lode, the San Dionisio Lode, and the Valley Lode. They all occur at or near the junction of the porphyry and the slate ; and they are supposed by Mr. Collins to occupy cavities produced by fis- sures. On the other hand, the somewhat similar deposit of the Rammels- berg mine in the Hartz is now unanimously con- sidered by geologists to be of sedimentary origin, and to be strictly con- formable to the surround- ing beds of slate. The South Lode, the one most largely wrought hitherto, is sometimes as much as 450 feet (140 m.) wide, and is known along the strike for a -distance of about a mile, or, in- deed, for two miles if the San Dionisio lode is con- sidered to be an extension of it to the west. Fig. 23 is a cross-section of the South Lode at San Inocente shaft, and Figs. 24, 25, and 26 are taken at points a little to the east. INDEX FOR FIGS. 23 TO 26. Porphyry. Porphyry worked away. Slate worked away. Pyrites. Pyrites -worked away. \ Ferruginous breccia and gozzan. MODE OF OCCURRENCE OF MINERALS. 33 Figures* 27 and 28 show the curious manner in which the San Dionisio lode swells out suddenly at a depth of about 150 metres from the surface, and actually attains the enormous width of 200 metres. A, is slate ; B, porphyry ; C, cupreous pyrites ; D, iron ore, the " gozzan " or iron cap of the lode. The slate is dipping steeply towards the lode, as indicated by the lines denoting planes of bedding. The hatching of C itself does not represent any structure. It will be interesting geologically and important commercially to watch the further development of the workings upon this remarkable lode. The character of the ore varies a good deal. Mr. Collins names fourteen different kinds. The principal are : (i) Ore treated for copper on the spot, and (2) that which is exported. The former consists of fine-grained and compact iron pyrites with i to 2\ per cent, of copper, existing as copper-pyrites minutely disseminated throughout the mass, and the latter only differs by being richer in copper, and containing up to 3! per cent. Little veins of copper-pyrites, erubescite, and occasionally copper-glance, more or less mixed with iron - pyrites, FIG. 27. quartz, blende, and other minerals, traverse the mass, and there is sometimes a compact mixture of galena, blende, chalcopyrite, and iron-pyrites resembling the " bluestone " of Anglesey. Few mines in the world are of more importance than Rio Tinto. The quan- tity of ore extracted in I 9 * * i892f was 1,402,063 tons of ^ mmm - 21 cwt., of which 995,151 ^ ^ tons were for local treat- ment and 406,912 for shipment to Great Britain, Germany, and the United States. The average percentage of copper was 2-819. The deposits of iron ore marked on the map are horizontal beds, probably formed at the bottom of lakes in Miocene times. The ore is brown haematite, with varying proportions of silica. The sections show that the upper part of the pyrites has been converted into a gozzan ; much of this is a good iron ore, and is being stocked for disposal at some future time. * From drawings kindly supplied by Mr. James Osborne, the general manager of the Rio Tinto Mines. f Rio Tinto Co. Ltd., Twentieth Annual Report, April 1893. C 34 ORE AND STONE-MINING. The Tharsis and San Domingos mines are likewise vast under- takings, and the total imports of cupreous iron-pyrites into this country alone from Spain and Portugal in 1891 amounted to 608,000 tons, worth over one million sterling.* FIG. 28. SCALE United States. Crossing the Atlantic, we will now turn our attention to the mines on the southern shore of Lake Superior, which are remarkable for their productiveness, and which are equally attractive to the geologist and to the miner. The copper-bearing districtf lies on a long peninsula, 15 to 20 miles wide, with a north-easterly trend, which projects into Lake Superior (Fig. 29 J:) some 60 miles beyond the general run of its southern shore, and terminates in Keweenaw Point. The western half of the peninsula is formed by rocks belonging to the Keweenaw Series, considered by many to be younger than the Huronian and older than the Cambrian. They consist of sand- stones and conglomerates, interstratified with flows of eruptive rocks of various kinds. The beds dip to the north-west, at an angle of 22 in the northern part of the mineral district, and in going south the dip increases to 56. The outcrop of the actual copper-bearing part of the series occupies a belt of country from 4 to 5 miles wide. * Mm. Stat.for i8gi. London, 1892, p. 59. f B. D. Irving, " The Copper-bearing Eocks of Lake Superior," United States Geol. Survey. Washington, 1883. Douglas, " The Copper Resources of the United States," Trans. Amer. Inst. M.E., vol. xix. 1890, p. 679 ; and Jour. JSoc. Arts, vol. xli. 1892, p. 39. J Engineering, vol. 1. 1890, p. 553; and Guide-book prepared for the members of the Iron and, Steel Institute, 1890. MODE OF OCCURRENCE OF MINERALS. 35 The modes of occurrence of the copper may be classified as follows : A BEDS I T * ^PP er ~b ear i n g conglomerate and sandstone. I 2 - B. VEINS. Copper-bearing amygdaloid. A. (i) The deposits of the first class are beds of conglomerate and sandstone impregnated with native copper. In most cases the cupriferous beds are interstratified with diabase flows ; but FIG. 29. this connection between the proximity of diabase and the presence of copper is not universal. The copper occurs as the cementing material of the pebbles and grains of sand, and also replaces the pebbles themselves, large stones several inches or even a foot in diameter being converted into the native metal. The copper has evidently been deposited from aqueous solutions. By far the greatest proportion of the Lake Superior copper is obtained from these conglomerates. A. (2) The cupriferous amygdaloids are portions of the old lava flows, and are not strictly speaking beds as defined, though it is convenient to call them by that name. Often they are highly altered and have lost all sign of having 36 ORE AND STONE-MINING. once been vesicular ; the native copper which they contain must have found its way in long after their eruption.* It is usually very irregularly distributed, and the parts rich enough to be worked may be surrounded by much poor or barren rock. The presence of epidote and calcite is regarded as a good indication for the proximity of copper. B. As the cupriferous lava beds and conglomerates are locally called "veins," it is necessary to say that the real veins run in a direction at right angles to the general trend of the beds, and are almost vertical. Their usual width is from one to three feet, but it may become as much as 10, 20, and even 30 feet. They are largest and richest when they have amygdaloid or loose- textured diabase for their walls, and they become pinched up and worthless in the compact greenstone or sandstone. To a great extent they consist of altered rock, and are an instance of lodes formed by replacement of the " country." According to Irving these veins were formed by copper-bearing solutions which found a path through zones of fissured rock, instead of following certain easily permeable beds. The copper is in the native state, and generally in masses -of considerable size, the largest found weigh- ing nearly 600 tons. The following statistics relating to the Lake Superior mines are taken from a guide-book prepared for the members of the Iron and Steel Institute in 1890. Name of Mine. Nature of deposit. Depth in feet. Tons rock hoisted 1889. Tons Refined Copper 1889. Tons Copper to date. Per cent, copper in rock stamped. Dividends to date. Dollars. Alloucz . . Conglo- 1700 126,125 881 11,427 076 merate Calumet and Hecla . . I 3750 807,918 24-334 301,538 3-01 33,359,000 Peninsula . 600 368 Tamarack . 2818 196,707 5.Si8 16,624 3-26 1,200,000 Atlantic . . Amyg-da- , 1660 288,040 1,849 23,786 0-66 560,000 loid Copper Falls H 1500 435 10,789 070 100,000 Franklin . fj 2620 186,740 2,i73 3L96i 1-87 960,000 Huron . . 1800 159.333 1,109 10,652 0-98 Kearsage- . 5 , 1000 76,54i 960 1,384 171 80,000 Osceola . . n 2162 208,299 2,631 25,312 1-29 1,222,500 Quincy . . 3070 123,998 3-203 53.250 272 5,250,000 Central . . Veins 2900 Mostly 635 20,355 1,930,000 mass. 1 As will be seen from these figures, the Calumet and Hecla mine is the most important on Lake Superior. The bed of copper-bearing conglomerate is from 8 to 25 feet thick, and Irving, Op. cit. p. 421. MODE OF OCCURRENCE OF MINERALS. 37 about 12 feet on an average. The dip is 37^ to the north-west. The depth of the mine which is given in the table is measured on the dip, and would be about 2,280 feet if measured vertically ; but these figures are now greatly exceeded, and shafts are being sunk which will enable the Calumet and Hecla and the Tamarack mines to be worked to the enormous depth of 5000 feet. The very low percentage of copper in the Atlantic amygdaloid, which nevertheless is worked at a profit, is remarkable ; but, unlike the amygdaloids generally, the Atlantic rock is very regular in its yield. This makes up for its poverty. Arizona* produces large quantities of oxidised ores of copper, especially the oxide and carbonates, which occur in or adjacent to the Carboniferous limestone. Sometimes there are irregular ore- bodies at the contact of the limestone with granite or with sand- stone. Masses of sulphuretted ores which have escaped decay show whence the oxidised ores have been derived. The Butte district, Montana,f has surprised the world of late years by the enormous quantities of copper ore which it has sent into the market. The deposits are east and west lodes in granite, usually dipping steeply to the south. The main lode, which supports the celebrated Anaconda and Parrott mines, has proved productive for a distance of three miles along the strike. The principal ores are erubescite, copper glance, and chalcopyrite. Everywhere near the lodes the granite is soft and friable, and often contains ore-bodies. Though the granite has been greatly fissured, it seems likely that much of the ore does not fill up cracks, but has gradually taken the place of the rock by a process of substitution. The width of the lodes varies considerably ; however, on an average it may be taken at ten feet. The copper ore is silver-bearing, the proportion varying from J oz. per unit of copper to 2 oz. per unit. The upper parts of the veins consisted of oxidised minerals, from which the copper had been leached out almost entirely, but in which the silver was retained and formed the original object of the mining. At the Anaconda mine there was no copper worth speaking of for the first 400 feet in depth; then came a rich zone of oxisulphides and erubescite, considered to contain some of the copper which had been dissolved out of the vein at a higher level, and after lasting for zoo feet it was succeeded by the unaltered sulphides. Diamonds. By far the most important diamond district in the world is Kimberley, in Cape Colony, 648 miles by rail from Cape Town. Strange to say, most of the precious gems are * Douglas, Op. cit. t Douglas, Op. cit. Vogelsang, " Mittheilungen iiber den Kupferberg- bau in Nord-America," Zeitschr. B.- H.- u. S.- Wesen, vol. xxxix. 1891, p. 231. G. vom Kath, " Ueber das Gangrevier von Butte, Montana," N. Jahrb.f. Miner. Geol u. Paldont., vol. i. (1885), p. 158. ORE AND STONE-MINING. obtained from four deposits situated in close proximity to each other ; indeed, all four are included in a circle three miles in diameter. The masses of diamond- bearing rock may be described as huge vertical columns, of round, oval, or kidney-shaped section, as shown by Figs. 30 and 31.* The un weathered diamond-bearing FIG. 30. _fiOC/f SHAFT FIG. 31. D BEERS MINE KIMBERLEY MINE rock, locally known as " blue ground," or " blue," is a breccia, consisting of fragments of shale, basalt, diorite, and a little sandstone, cemented together by olivine rock containing diamonds and various other minerals, such as bronzite, biotite, talc, garnet, graphite, magnetite, and iron pyrites. The surrounding rocks, locally called " reef," are beds of carbonaceous and pyritiferous shale lying horizontally, and sheets of basalt and melaphyre, under which comes quartzite. The mela- phyre is a hard amygdaloidal rock, which has also been called olivine dia- base.f Large detached masses of the surrounding rocks are sometimes in- cluded in the " blue," and are then known as " floating reef." The upper parts of the deposits have been decom- posed by atmospheric agencies, and changed into a soft friable earth to a depth varying from 45 to 60 feet, and the colour is yellow, instead of the slaty blue of the unweathered rock. The surrounding rocks have naturally shared in this weathering. * De Beers Consolidated Mines, Limited, Second Annual Report, 1890, including a technical report with plates, f Ibid. p. 13. DUTOITSPAM BULTFONTeiN^Q MODE OF OCCURRENCE OF MINERALS. 39 The diamond-bearing rock appears to be the filling-up of the necks or throats of old volcanoes by a mud from below. From the frequent occurrence of broken diamonds it is fairly inferred that the gems were not formed in situ, but were carried up with the " blue." Not only does the yield in 'diamonds vary in the different mines, but the diamonds themselves have their peculiar characteristics, which enable the expert to say at once from which mine a stone has been obtained. The average yield of the "blue ground" per load of 16 cubic feet * is as follows : - Value per carat Area. Carats per load. in 1889. Bultfontein . . i to . .177 De Beers . . . . itoi$ . . .176 Du Toil's Pan . . | to | . I 19 io Kimberley . . . l| to 1$ . ' . . i 7 9i In addition to these four mines there are some other workings in the neighbourhood, such as Wesselton and St. Augustine ; whilst at Jagersfontein, 80 miles to the south in the Orange Free State, there is a similar deposit, producing stones of the finest water. The commercial importance of the diamond deposits cannot be overestimated, for the value of the diamonds produced annually at Kimberley is between three and four millions sterling, or more than the value of the gold produced by any one of the British colonies.f Until lately, the largest diamond found weighed 42 8 J carats in the rough state, and 228^ carats after cutting ; it came from De Beers mine. This large stone has been eclipsed by one of 96 9 J- carats discovered at Jagersfontein in the month of June last. In addition to diamonds found in a solid matrix, there are those from the river diggings. It was in the recent alluvium of the Yaal River that diamonds were first discovered in 1867, and though thrown into the shade by the output of the mines, the gravel is still washed by parties of men scattered along the banks of the river for a distance of 70 miles. Diamonds are found in alluvial gravel and in conglomerate in Brazil, India, and other localities. Flint. It may be thought strange by some that I give flint a * Sixteen cubic feet of broken ground correspond to about 9 cubic feet of solid ground. t Further information about the Kimberley diamond mines will be found in the following publications : T. Reunert, " Diamond Mining at the Cape," History, Production*, and Resources of the Cape of Good Hope. Cape Town, 1886. C. Le Neve Foster, "Mining Industries," Reports on the Colonial and Indian Exhibition. London, 1887. E. Boutan, "Sur 1'etat actuel des mines de diamants du Cap," Genie Civil. Paris, January 26, 1889. 40 ORE AND STONE-MINING. place among the important minerals which deserve special de- scription. My reasons for mentioning it are twofold. First, the FIG. 32. Sand and Gravel Dead Lime Soft White Chalk Horns Flint Soft White Chalk . Toppings Flint . Soft White Chalk First Pipeclay . Hard White Chalk . Upper Crust Flint . Soft White Chalk Second Pipeclay . Hard Chalk . Soft White Chalk Wall Stone Soft Chalk with_Horns Soft White Chalk Third Pipeclay . Hard Chalk . Floor Stone . Soft White Chalk Hard Chalk . K. Rough and Smooth Blacks, ss. Soft White Chalk . a*. ; si M' E*. ~^r*c.". -, r^fe? -OftLi^ I iy* _-v] earliest underground workings in this country were probably for flint ; and secondly, flint affords a good instance of the replace- ment of an original bed by another mineral. MODE OF OCCURRENCE OF MINERALS. 41 Pits in the chalk known as " Grime's graves,"* were at one time a puzzle to the antiquary, but it is now generally conceded that they are the mine shafts by which beds of flints were worked for the manufacture of stone implements in Neolithic times. This old trade of flint mining still survives at Brandon in Suffolk, for though stone hatchets and arrow-heads are no longer wanted, there is still a market for gun-flints in parts of Africa. The mode of mining the stone, splitting off flakes and knapping them into gun-flints has been admirably described and illustrated by Mr. Skertchlyf in one of the " Memoirs of the Geological Survey of England and Wales." Fig. 32 represents a section of the beds in which the flint occurs. It shows that the layers of flint are sometimes continuous, and sometimes consist merely of a succession of nodules which do not touch each other. Some of the flint has knobs and even horn-like projections, the transformation from chalk into silica not being confined strictly to one particular layer of the original sea-bottom. The principal bed is the " floor-stone," No. 20, about 8 inches thick, but other layers are mined from time to time for building stone or gun-flints.* Freestone. Freestone is largely quarried in England from beds of Jurassic age, and the so-called " Bath stone " is not only quarried but also mined at Corsham in Somersetshire, and at Weldon in Northamptonshire. The bed worked in the Corsham underground quarries varies from 8 to 24 feet in thickness, lying almost flat ; it is a typical oolitic limestone which can be sawn freely in any direction. Gold. This metal is so widely distributed over the earth that it will be impossible to compress into the space at my disposal anything more than a very summary description of the principal modes of occurrence in beds, veins, and masses. Beds. During the last few years the attention of cap- italists, miners, and geologists has been often directed to the marvellous resources of the Witwatersrand|| or simply " Rand " goldfield, in the Transvaal or South African Republic, and situated about 35 miles south of Pretoria, the capital. The gold is obtained entirely from beds of conglomerate or puddingstone called banket, which is the Dutch name for almond rock, the hardbake of the British schoolboy, because the pebbles look like * The word " grave " no doubt corresponds here to the German Graben, a ditch or trench, and has no reference to burial. t On tlie Manufacture of Gun-Flints, &c. London, 1879. + A more or less regular and continuous layer of flints is locally called a sase or sese, which recalls the French word " assise." C. Le Neve Foster, " Some Mining Notes in 1887," Trans. Min. Assoc. and Inst. Cornwall, vol. ii. p. 136. Camborne, 1888. || A very complete summary of papers upon South African Geology is given by Mr. Gibson in his memoir, " The Geology of the Gold-bearing and Associated Rocks of the Southern Transvaal," Quart. Jour. Geol. Soc., vol. xlviii. (1892), p. 406. ORE AND STONE-MINING. the almonds in the sugar. The layers of auriferous conglomerate lie conformably among beds of sandstone, shale, clay, and quartzite. At Johannesburg the beds strike east and west and dip to the south. The conglomerate consists mainly of pebbles of white quartz, and in the upper parts of the workings they are cemented together by oxide of iron, sand, and clay. Below the influence of atmospheric agencies, the cementing material is found to consist largely of silvery-grey mi- caceous matter with cubical crystals of iron pyrites, and the colour of the banket changes from red and brown to blue and bluish grey. It is quite evident from the examina- tion of specimens that much of the ferruginous matter in the upper parts of the conglomerate is derived from the decomposition of iron pyrites, and visible gold is seen in the cavities formerly occupied by crystals of that mineral. The bulk of the gold is said to exist in the cement and not in the pebbles ; but some assays made by the late Mr. Richard Smith show that this is not invariably the case. Fig. 33,* a section across the Salisbury Mine at Johannesburg, shows four beds of auriferous con- glomerate, known respectively as the North Reef, the Main Reef, the Main Reef Leader, and the South Reef. As would naturally be expected in the case of beds which must have been deposited in shallow water, there are frequent variations of character and thickness in a short distance. Whilst certain beds of conglome- rate are auriferous, others are not, * Gibson, Ibid. p. 411. MODE OF OCCURRENCE OF MINERALS. 43 or contain merely traces of gold. The sandstone, as a rule, is not auriferous, but layers within the banket may be worth working. The richest beds are the Main aijd South Reef with some of the thin " leaders." The gold is not distributed uniformly through the bed of banket ; but upon the whole there ib far greater regularity of yield than can be expected in a vein, and as a rule the whole of the bed is worked away like a seain of coal, without poor portions being left. The fact of being able to form a rough approximate estimate of the probable yield of a given area of banket is of the utmost commercial importance. The Rand output in 1892* was 1,210,865 ounces of bar gold ; the average total yield of the conglomerate stamped was 12 J dwt. of gold per ton, of which about four-fifths were obtained at once by amalgamation at the mills, and one-fifth by subsequent treat- ment of the tailings and concentrates. The gold-bearing strata are supposed to be of Devonian age. Whether the gold was deposited at the same time as the pebbles of quartz, or whether it was brought by the subsequent FIG. 34. a, hard grey siliceous shale : 6, massive qtiartzite, becoming talcose and highly auriferous in zones ; c, schistose quartzite, becoming argillaceous in places ; d, impure sandstone quartzite, e, quartzose breccia with fragments of felsite and clay shale ; /, hard grey siliceous shale ; -r:g| SLATE SADDLE. fcvX. -;' : QUARTZ iron pyrites ; when it decomposes a cellular honeycombed quartz is left behind, and the gold is unmasked and rendered visible in the little rusty cavities. Other heavy metallic sulphides are common here as elsewhere. The peculiarities of the so-called "saddle-reefs" of the Sand- * " Notes on the Great Mother Lode of California," Jour. Roy. Inst. Cornwall. Truro. Vol. ix. (1886), p. 64. MODE OF OCCURRENCE OF MINERALS. 47 hurst or Bendigo gold-field, Victoria, which differ considerably from typical veins, have been very clearly explained by Mr. T. A. Rickard,* from whose useful memoir the following account is borrowed. These reefs are arch-like masses of quartz conform- able to the bedding of the surrounding Lower Silurian slate and sandstone, as shown by the letters BACin Fig. 37. The part A is called the " cap " or " apex " ; B is the " west leg " and C the " east leg," because the main anticlinal axes strike N.N.W. and S.S.E. The part D is known as the " centre country," the rocks to the east of C form the " east country," and those to the west of B the " west country." The inclination of the line of the ridge, northwards or southwards, is spoken of as the " pitch," in order to FIG. 38. distinguish it from the dip of the strata. There may be more than one such saddle, or a long succession of them, one below the other (Fig. 38), but they are not all equally auriferous. Trms, out of five which have been discovered and explored at " 180" mine, only three have proved to be worth working for gold. Similar masses of auriferous quartz have been found at some of the synclines ("inverted saddles"), and worked to a slight extent. Very large dividends have been paid by many of the companies working the " saddle-reefs." Masses. Having given examples of auriferous beds and veins, I come to masses. Tread well mine,f situated SADDLES on Douglas island, Alaska, owes its existence to a mass of auriferous altered granite, 400 feet wide and of considerable length. The rock, which appears to have been a hornblende granite originally, now consists principally of quartz and felspar, with a little calcite and specks of iron pyrites, and it is traversed by strings of quartz, iron pyrites, and calcite. The original rock was probably crushed and fissured, and then brought under the action of solutions which penetrated into it in all directions, and so produced the alteration. The yield is considerably less than J oz. per ton, but as the deposit can be * "The Bendigo Gold-Field," Trans. Amer. Inst. M.E., vol. xx. (1891), p. 463. t G. M. Dawson, " Notes on the Ore-deposit of the Treadwell Mine, Alaska,'' American Geologist, 1889, p. 84; and Frank D. Adams, "On the Microscopical Character of the Ore of the Treadwell Mine, Alaska," Ibid. p. 88. 4 8 ORE AND STONE-MINING. worked opencast, the cost of getting is low. Much of the gold is free, and can be extracted by amalgamation in spite of its being enveloped by pyrites. This mass may be called a stock work or net- work deposit. The productive Mount Morgan mine,* near Rockhampton, in Queensland, while astonishing the world by its richness, affords a puzzle to geologists which has not yet been satisfactorily solved. The auriferous deposit, which is worked as an open quarry, is a mass of brown haematite, sometimes stalactitic and containing a little silica, which passes gradually into a ferruginous siliceous sinter. Some of it is spongy and frothy in appearance, and so full of cavities that it will float upon water like pumice. The precise nature of the gold-bearing mass is well illustrated by twenty views which accompany the " Third Report " of Mr. R. L. Jack, the Government geologist. Both the sinter and the brown iron ore contain gold, and yield on assay several ounces to the ton. The auriferous stone FIG. 39. , pipe of geyser (theoretical) ; b, cup-deposit of geyser ; c, over- flow deposit of geyser ; s, metamorphic rocks ; d, rhyolite dykes. caps a hill rising about 500 feet above the neighbouring table- land, and the most important part of it is the actual top or crown, an oval mass 300 yards long by 170 yards wide. Mr. Jack considers that the deposit is the product of a geyser, and he explains his views by the section (Fig. 39). This naturally represents the present condition of the hill, much of the original geyser deposit being supposed to have been removed by denu- dation. The gold exists in a state of great fineness, and the metal extracted is of extreme purity, for it contains 99-7 of gold, the rest being copper, a trace of iron, and a minute trace of silver. Dr. Leibius, of the Sydney Mint, speaks of it as the richest native gold hitherto found. Without having examined the deposit upon the spot, one scarcely likes to criticise the conclusions of so able an observer as Mr. Jack; but looking at his section of the No. i tunnel, we find that the auriferous mass must repose upon highly pyritous rocks, such as quartzite full of fine pyrites, in which the latter constituent may sometimes predominate. The suspicion * R. L. Jack, " Mount Morgan Gold Deposits." Brisbane, 1884. Second Report, 1889 ; and Third Report, 1892. MODE OF OCCURRENCE OF MINERALS. 49 naturally crosses one's mind that the gold-bearing cap may simply be due to the decomposition and weathering of the pyritiferous rock. Mr. Jack combats this theory, and says that it is dis- proved by three facts : ist. A dyke of dolerite in the quartzite does not reach up into the overlying sinter. 2nd. The pyri- tiferous quartzite is poor in gold. 3rd. The silica of the sinter is hyd rated. He therefore still maintains his original opinion that the sinter and ironstone were deposited by a thermal spring on the pyritous quartzite, and are not altered portions of it.* Mr. Rickard,f while disagreeing with the geyser theory, concurs in Mr. Jack's opinion that the deposit is not an altered portion of the pyritous quartzite, though he remarks that the FIG. 40. Mount Morgan rock bears a strong outward resemblance to the decomposed outcrop of the Broken Hill lode in New South Wales. This can be easily imagined from an inspection of the views given in Mr. Jack's third report, from which the outlines of Fig. 40 have been copied. The theory propounded by Mr. Rickard (Fig. 41) is that the auriferous stone of Mount Morgan is rock shattered by the intrusion of dykes, and then altered by the per- colation of underground mineral solutions, which found an easy passage through the cracked and fissured mass. He points out that the gold may have been derived from the poor pyrites disseminated through the quartzite, or from the sandstone of the district, which has been shown to be auriferous. The quantity of stone treated by chlorination at Mount Morgan * Second Report, p. 4. t " Mount Morgan Mine, Queensland," Trans. Amer. Inst. M.E. vol. xx. (1891), p. 133. D 50 ORE AND STONE-MINING. in the twelve months ended ^oth November, 1889, was 75,415 tons, from which 323,542 oz. of gold were obtained, equal to FIG. 41. MOUNT MORGAN SECTIONS. based on late developments !:-... .-., '.:'.| ORE DEPOSIT. INTERSECTED BY SMALL DYXES NOT SHOWN R^^-M pyRfTIOUS OUARTZITE P"V"'y;-''J CYR33 4 oz. 6 dwt. per ton. The gold was sold for ^1,33 1,484, and ji, 1 00,000 was paid in dividends. Graphite. The great graphite mines of the world are those of Ceylon, where the mineral is found in layers from a few inches to several feet in width, in gneiss and mica schist. The graphite is associated with quartz and a little iron pyrites. There are various graphite deposits in Austria and Bavaria.* At Kaiserberg, in Styria, the mineral is found in graphitic schist ; the beds vary in thickness very rapidly from a few inches to 20 feet. In Lower Austria, Moravia, Bohemia, and Bavaria graphite occurs in gneiss usually accompanied by granular limestone. The Passau graphite is in the form of small black scales, and appears to take the place of some of the mica in a highly felspathic gneiss ; the thickness of the beds varies greatly, but may be as much as 1 6 feet (5 m). The Bavarian mines produced 3352 tons of graphite in 1888. Gypsum. As one of the principal uses of gypsum is for making plasber-of-paris, we naturally turn to the French metropolis for an example of the mode of occurrence of this mineral. The gypsum is found in beds from 50 to 60 feet thick, which are of Upper Eocene age (Fig. 352). In England and elsewhere, the Triassic rocks have long been remarkable for containing valuable beds of gypsum, and they are largely worked in Derbyshire and Nottinghamshire. Fig. 42 re- presents the layers of nodules in a gypsum mine at Kingston-on- Soar, Nottinghamshire. There are three beds a few feet apart in the New Red Marl. The bottom bed consists of large spheroidal masses, varying from 5 to 8 feet in thickness, and 5 to 10 feet in diameter ; above it are two layers of " balls " and nodules, more or less continuous. The highly gypsiferous marl, locally called * Th. Andree, "Der osterreichische und bayerische Graphitbergbau," B. u. h. Z. 1890, p. 269. MODE OF OCCURRENCE OF MINERALS. FIG. 42. " fault," B, between the big balls, A A, is left, so as to form pillars, which support the roof of the workings. White translucent alabaster for statuary purposes is mined at Castellina Marittima,* in the province of Pisa. Its mode of occurrence resembles that just de- scribed, for it is found in irregular spheroidal or kidney-shaped masses called "ovuli" by the workmen, from a few inches to several feet in dia- meter, and occasionally weighing more than a ton each. The grey marl surrounding the nodules is of Pliocene age. The alabaster is sac- charoidal and very fine grained. Ice. By some per sons this mineral maybe considered beneath notice, but the trade in ice is so large that it deserves at least a passing mention. The United States f are the largest METRt Trf" '*. ',' '^ f IMC* producers of natural ice in the world, arid in some years 12,000,000 tons are gathered from the lakes and rivers, and especially from the Hudson. The gathering in of the ice crop affords employment to " 12,000 men and boys, 1,000 horses, and 100 steam engines." Much ice is exported from Boston, and Norway also is a country with a large ice trade. Iron. This metal is very widely distributed over the globe, and affords examples of many modes of occurrence, though veins of iron ore are quite driven into the background by the yield of beds, and especially those of the Jurassic age. The most productive European deposits at the present time are : the bed of iron ore in the Cleveland district, the masses of red haematite in Cumberland and North Lancashire, the bed of brown haematite in German and French Lorraine, and Luxem- burg, and the beds of red and brown haematite near Bilbao, in Northern Spain. The bed of ironstone worked in the Cleveland district of North Yorkshire is found in the Middle Lias. Mr. Kendall J gives the following general section of the rocks : * Jervis, Itesori sotterranei deW Italia, vol. ii. p. 419, and vol. iv. p. 318. t "The Trade in Ice," Jour. Soc. Arts. London, 1890, vol. xxxviii. p. 765. J " The Iron Ores of the English Secondary Kocks," Trans. N. of Eng. Inst. Min. Eng., vol. xxxv. (1886), p. 113. Barrow, "The Geology of North Cleveland," Mem. Geol. Survey, 1888. ORE AND STONE-MINING. Description. Thick- ness. Characteristic Ammonite. /Shale with cement stone ft. in. TT nodules (alum shale series) 115 o A. communis upper j ghale with doggers * Q et rock Llas series) .... 48 o A. serpentinus ^Grey shale with doggers 30 o A. annulatus r Ironstone (Main seam) . Shale with doggers ii 6 10 6 .A. spinatus Ironstone (bottom seam) 2 9 s Shale with nodules of clay Middle . ironstone .... 20 Lias Ironstone in thin bands Shale with ferruginous i 9 -A. margaritatus doggers .... 30 o Sandstone, sometimes flaggy, * calcareous, and ferruginous 40 o "\ A. capricornus, Ja- T [Shale with numerous thin ijower j limestones in the lowest Lias I 300 feet .... 700 o mesoni, armatns, - oxynotus, Buck- landi, angulatus, and planorbis Fig. 43! illustrates sections of the bed at Eston and Upleatham. FIG. 43- Grey shale and ferruginous nodules Ironstone (top block) in alternate hard and] ^2, soft layers, not worked ... j Ironstone (main block], -workable part of bed \ ^oVf at present ) ^^ Ironstone (bottom block) not worked . . i JO Shale The Main Seam practically furnishes all the Cleveland ore. It probably extends over an area of 350 square miles, though it * Doggers are nodules of ironstone, t Kendall, Op. cit. Fig. 5, Plate XIII. MODE OF OCCURRENCE OF MINERALS. 53 cannot be profitably worked over anything like the whole of this district. The average thickness where worked is about 10 feet. The beds dip very gently about i in 15, to the south-east. The seam is thickest and best at Normanby, Eston, and Upleatham ; in proceeding to the south-east, partings of shale appear, and split up the main seam into numerous comparatively thin layers of ironstone, with a smaller percentage of metal. Some of the ironstone is oolitic and of a greenish grey colour, but much of it is not oolitic, and is bluish grey in colour, resembling a mudstone. The iron exists chiefly as carbonate, some of which, according to Dr. Sorby, was deposited mechanically, whilst the rest was formed chemically by replacement of carbonate of lime. As a general average, it may be said that the ore contains 30 per cent, of iron. The district produced 5,128,303 tons of ore in 1891. The masses of red haematite worked in Cumberland and North Lancashire have already been noticed (Fig. 14). The great iron-field of Lorraine,* much of which became the property of Germany in 1871 after the Franco-Prussian war, stretches out from Nancy past Metz and Diedenhofen into Luxemburg. It may be called 60 miles long by 10 to 12 miles wide (100 km. by 15 to 20 km.). The iron-bearing strata belong to the Lower Dogger or Brown Jura (Inferior Oolite), and consist of marly sandstone, marl and sandy clay, interstratified with beds of limestone and iron ore. In places there is no iron, and in others, especially in the south and on the eastern edge, the beds of ore are thin. On the other hand, at Esch, in Luxemburg, four beds of iron ore and their partings of limestone and sandstone make up a total thickness of 65 feet (20 m.), and at Deutsch-Och and Oettingen three beds and the partings are 32 feet (10 m.) thick; then at Hayingen the total thickness sinks to 20 feet (6 m.), and at Ars there is only one bed 5 to 6 feet thick. The strata are slightly undulating, but the general dip is i to 2\ in a hundred to the south-west. The iron exists in the state of hydrated oxide, probably for the most part as 2Fe 2 3 3H 2 0, which constitutes the roe-like grains which are so characteristic of the ore. The oolitic particles are enclosed in a calcareous matrix, which may contain quartz. The matrix is always more or less ferru- ginous, and sometimes consists of a greenish mineral, which is probably a silicate of iron. The ore has usually from 32 to 38 per cent, of iron and from J to 2 per cent, of phosphorus ; there is also a little sulphur, due to occasional small strings of iron pyrites. The name " minette," or " little, unimportant ore," was given many years ago to this bed in contradistinction to the * Wandesleben, " Das Vorkommen der oolithischen Eisenerze (Minette) in Lotbringen, Luxemburg und dem Sstlichen Frankreich." Der IV. All- gemeine Deutsche Bergmannstag in Halle (Saale}. Fesiberkltt und Ver- handlungen, Halle, 1890, p. 297. TT TvT T \r T-. - 54 ORE AND STONE-MINING. " mine" or " mineral de fer fort," a much richer ore found in the neighbourhood, which is now no longer worked. Nearly a hundred blast furnaces are dependent upon the " minette " for their supplies of ore, and in 1888 they produced 2,500,000 tons of pig iron, .or 40 per cent, of the total production of Germany, Luxemburg, and France. More than four-fifths of all the iron ore raised in this last country is obtained from this bed. The amount of ore still available in German Lorraine is estimated at 2,100 million tons, or enough to maintain the pre- sent rate of production for 750 years. Sweden is justly famous for its great deposits of magnetite. These are generally lenticular masses, often similar in shape to the Rio Tinto copper veins, and enclosed by highly metamorphosed rocks, such as gneiss, mica schist, and the hard compact hcilleflinta of the Swedish geologists. It would not be right to quit the subject of iron ore without mentioning at least one of the mines situated in the neighbour- hood of Lake Superior, where the Menominee, Gogebic, Vermilion and Mesabi districts are producing large quantities of mineral. At Chapin Mine* near the town of Iron Mountain (Mich.) there are huge lenticular masses of haematite, which lie parallel to the enclosing Huronian strata (Fig. 44).t One large lens is FIG. 44. half a mile long, 130 feet wide in the middle, and gradually tapering out to a point at each end ; it strikes 15 N. of W., and dips from 70 to 80 N., and the axis of the lens pitches 30 W. The ore contains about 63 per cent, of metallic iron, and only o'07 per cent, of phosphorus. * Larsson, "The Chapin Iron-mine, Lake Superior," Trans. Amer. Inst. M.E., vol. xvi. (1887), p. 119. t Engineering, vol. 1. (1890), p. 552. MODE OF OCCURRENCE OF MINERALS. 55 Lead. Though lead ore is largely wrought from veins, one of the great mines in the world obtains its supplies from a bed. The lead-bearing sandstone at Mechernich, in Rhenish Prussia,* is of Triassic age (Bunter) and is on an average nearly 100 feet thick. It rests upon and is covered by conglomerate, and is often split up into two or more beds by thick partings of conglomerate. The ore exists in the form of little concretions of galena and grains of quartz, but these are not uniformly distributed through the sand- stone. The concretions are from ^ inch (i mm.) to J inch (3 mm.) FIG. 45. Jt.lOO A, greywacke ; B, conglomerate ; C, lead-bearing sandstone ; D, conglomerate; E, so-called "red rocks," consisting of red, yellow, and white sandstone, with variegated shales and clay. in diameter, and are harder than the surrounding sandstone, which is generally very friable. When the rock is pulverised the little shot-like masses remain, and are called "knots" (Knotten), whence the name " Knottensandstein " given to the bed. The amount of metallic lead in the sandstone is between 2 and 3 per cent. ; but the concretions themselves contain from 20 to 24 per cent. According to the statement of accounts presented to the shareholders,t the average percentage of lead contained in the whole of the sandstone treated in 1890 was 2*318; 347,706 cubic metres (454,806 cubic yards) of sandstone, were raised from the mine and open work, and yielded 36,245 tons of lead ore for smelting and 733 tons of potter's ore. This would be at the rate of io4kil. of dressed ore per cubic metre, or i j cwt. per cubic yard, but it must not be forgotten that the bulk of the ore i.e., that which goes to the furnaces is not highly concentrated and con- tains only 54 per cent, of metal. The proportion of silver in it is 5! ounces (180 grammes) per metric ton. The history of Leadville, in Colorado, seems like a romance when we read of the rapid development of the mines, the creation of a large and important town, the erection of smelting works and the building of railways, under very adverse conditions, in * Der Bergbau und Hutteiibetrieb cles Jfechernichtr Bergwerlcs-Actieii- Vereins. Cologne, 1886. t Mining Journal, vol. Ixi. (1891), p. 499. ORE AND STONE-MINING. MODE OF OCCURRENCE OF MINERALS. 57 the heart of the Rocky Mountains, all within the space of four or five years. It affords additional proof that the miner is the true pioneer of civilisation. The Leadville deposits have been ad- mirably described by Mr. S. F. Emmons,* from whose exhaustive report I borrow, not only the following facts, but also a section across one of the mines (Fig. 46). The principal deposits of the region are found at or near the junction of white porphyry with the underlying Blue Limestone, which is the lowest member of the Carboniferous formation. This bed is about 150 or 200 feet thick, and consists of dark-blue dolomitic limestone. At the top there are concretions of black chert. The porphyry occurs in intrusive sheets, which generally follow the bedding, and almost invariably a white porphyry is found overlying the Blue Limestone. This porphyry is of Secondary age. It is a white homogeneous-looking rock, com- posed of quartz and felspar of even granular texture, in which the porphyritic ingredients, which are accidental rather than essen- tial, are small rectangular crystals of white felspar, occasional double pyramids of quartz, and hexagonal plates of biotite or black mica. Along the plane of contact with the porphyry the limestone has been transformed, by a process of gradual replace- ment, into a so-called " vein " consisting of argentiferous galena, cerussite, and kerargyrite, mixed with the hydrous oxides of iron and manganese, chert, granular cavernous quartz, clay, heavy spar, and " Chinese talc," a silicate and sulphate of alumina. The vein seems to have been formed by aqueous solutions, which took up their mineral contents from the neighbouring eruptive rocks, and brought about the alteration of the limestone as they percolated downwards through it. In Carbonate Hill a gradual passage may be observed from dolomite into earthy oxides of iron and manga- nese. The masses of workable ore are extremely irregular in shape, size, and distribution. They are often from 30 tor 40 feet, thick vertically, and occasionally 80 feet, but only over a small area. The rich ore bodies are commonest in the upper part of the ore-bearing stratum. At Fryer Hill the Blue Limestone is almost entirely replaced by vein material. The metallic ores appear to have been deposited originally as sulphides ; the oxidised or chloridised ores found near the surface are the products formed by the percolation of surface water like any ordinary gozzan. Manganese. The great manganese-producing countries of the present day are Russia f and Chili, and in both the ore is derived from beds, and not from veins or masses. At Tschiatoura in the Caucasus, about thirty miles from Kwirilly station on the Poti- Tiflis Railway, there are beds of manganese ore of Miocene age. The beds worked are from 5 to 6 feet thick (1*5 m. to 2 m.), and * Geology and Mining Industry of Leadville, Colorado. Washington, 1886. f B. u. h. Z. 1890, pp. 32, 215. 58 ORE AND STONE-MINING. are made up of several small seams of clean manganese ore, separated by partings of soft sandstone and clay. The manganese exists principally in the form of Mn0 2 , and the ore contains 50 to 55 per cent, of metal. The mines are at present heavily handicapped by the long and expensive carriage to Kwirilly station, but this will be reduced when a railway is made. Both in Wales and Belgium there are beds of manganese ore in the Cambrian rocks. The Welsh beds are about a foot thick (Fig. 47), sometimes running up to FIG. 47- 1 8 inches or 2 feet. The man- ganese is principally in the form of carbonate, though there is a little silicate, and near the surface these have been converted into hydrous oxides. The ore is inter- bedded with fine - grained sandstone, hard mudstone, and shale, also manganifer- ous, and often containing chlorite, iron pyrites, and magnetite; the whole man- ganiferous series is enclosed in the regular Cambrian grits and conglomerates. The ore contains from 20 to 32 per H A, fine-grained sandstone with mag- cent " n^ganese. netite, chlorite, and iron pyrites ; 13, Marble. The famous manganese ore ; C, fine-grained shaly white statuary marble of sandstone. Italy is found in the Apuan Alps from Carrara to Staz- zema, on the S.W. slope of the mountains, and from Frvizzanoto Vagli Sotto on the N.E. slope.* It occurs in very thick beds, with the stratification sometimes well denned, but generally completely obliterated, and it rests upon compact limestone, which in its turn lies upon pre-palseozoic mica-schist and talc-schist. The age of the marble beds has not been ascertained without doubt ; some geologists say they are Triassic, whilst Jervis calls them pre-palseozoic. Mica. This mineral is obtained in North Carolina at the present time, just as it was in the days of the prehistoric mound builders, from veins of giant granite, or granite in which the con- stituent minerals have crystallised on a huge scale. According to Phillips,! a single block of mica has weighed nearly a ton, and * Jervis, / Tesori soiterranei dtW Italia, vol. iv. p. 261. t "Mica Mining in North Carolina," Eng. Min. Jour., vol. xlv. (1888), p. 286. MODE OF OCCURRENCE OF MINERALS. 59 pieces 6 feet long and 3 feet wide are sometimes met with ; a single crystal of felspar weighing 800 Ib. is preserved in the State Museum at Raleigh. The veins are from 30 to 40 feet wide, and are enclosed in mica schist, of which they follow the strike and dip ; but they occupy fissures which took place along planes of easy fracture, and being of subsequent origin to the surrounding rocks, are veins and not beds. Natural Gas.* Though the Chinese were before the Ameri- cans in their use of natural gas, it is to the United States that we must look for examples of gas springs, which have been so largely turned to account during the last ten years, more especially in Pennsylvania, but also in Ohio and New York. According to the late Mr. Ashburner,f the gas in these States comes from beds of Palaeozoic sandstone and limestone. He considers, with many others, that both gas and petroleum have been formed by the decomposition of animal and vegetable remains in the rocks, and that in order to have a productive gas region, it is necessary that there should be a porous or cavernous rock to contain the gas, and an impermeable covering, such as shale, to prevent its escape, conditions resembling those required for artesian wells. A further condition is that the strata should be bent into a dome, anticlinal or arch, at the crown of which the gas will be found ; but if the rocks have been much disturbed, contorted, and fissured, natural vents have been formed, through which the gas will have escaped. The rocks now containing the gas are often those in which it was generated. There are several gas-producing beds of sandstone in Pennsyl- vania, in the Carboniferous rocks ; but the most important supplies are obtained from sands of the Venango- Butler oil-group, belong- ing to the Catskill Rocks of the Devonian period. There are other gas-sands in the Chemung and Portage rocks, also of the Devonian Period, but lower down. Some of them produce both gas and oil. The most productive gas-bearing rocks in Ohio are the Berea grit in the Sub-carboniferous period, and the Trenton Limestone in the Lower Silurian period. The section (Fig. 48)4 shows the Silurian and Devonian strata bent into an arch or dome at Findlay, Ohio, where gas and petro- leum are obtained by boring into the Trenton Limestone, the reservoir in which they are confined by the Utica Shale. The gas varies in composition, not only from well to well, but also from time to time in the same well. Some analyses given by Prof. Lesley show that the gas of a certain well contained upon * Topley, " The Sources of Petroleum and Natural Gas," Jour. Soc. Arts, vol. xxxix. (1891), p. 421. t " The Geologic Distribution of Natural Gas in the United States," Trawt. Amer. lust. M.E., vol. xv. (1886-87), P- 505. Topley, Op. cit. p. 413. 6o ORE AND STONE-MINING. FIG. 48. SECTION THKOUGH FINDLAY, OHIO. (Orton.) X-X Sea Laud ^ (7- Ohio shale. 1 Silurian 1 6. Upper Helderberg limestone. 5. Lower Helderberg limestone. ( Niagara limestone. ' 4. \ Niagara shale. (Clinton limestone. j Hudson Kiver shale. 3> I Medina shale. Utica shale. Trenton limestone. different occasions from 50 to 75 per cent, of marsh gas, 9 to 35 per cent, of hydrogen, 4 to 1 2 per cent, of ethylic hydride with small quantities of olefiant gas, oxygen, carbonic oxide and carbonic acid, and in one instance as much as 23 per cent, of nitrogen, though usually this gas was absent. The pressure of the escaping gas is often very great, and in one case reached 450 Ib. per square inch. Nickel. Until recently our supplies of this metal were obtained from sulphides or sulpharsenides, and espe- cially from nickel-bearing pyrrhotine. The discovery by Gamier of hydrated sili- cate of nickel and magnesium in New Caledonia revealed the existence of an unsuspected source of wealth. The nickel is found in serpentine,* either at the contact of this rock with " pockets" of red clay, or near such a contact, but never in the clay itself. * Levat, "Memoire sur les progres de la metallurgie du Nickel," A nn. Mines, 96 fcerie, vol. i. (1892) p. 141. | Nickel ore. [-?;ffl:*ff| Oolitic broicn iron ore. S Serpentine. A Red Clay. MODE OF OCCURRENCE OF MINERALS. 61 FIG. 50. Figs. 49, 50, and 51 are examples of various types of such deposits. In all three cases A is the pocket of red clay, and S is the serpentine. In Fig. 49 the nickel ore lies between the rock and the clay. In Fig. 50 there are a number of interlacing veins in the serpentine forming a net- work deposit which is quar- ried, whilst in the case re- presented by the Fig. 51, the original fissures were bigger, but less numerous, and are now filled up with nickel ores forming veins 20 to 26 feet in width. The ferruginous red clay often contains the hydrated oxides of manganese and cobalt, besides chromic iron (Fig. 19). Large lumps of limonite are frequently FIG. 51. found lying upon the clay, Fig. 49. The ore which is exported has from 7 to 1 8 per cent, of nickel. Of still later date are the discoveries of nickel ore at Sudbury* on the Canadian Pacific Railway, about 40 miles north of Georgian Bay. Here the ore is a nickel -bearing pyrrhotine associated with FIG. 52. a, Huronian strata ; 6, diorite ; c, ore-body ; s, shaft ; x x, boreholes. chalcopyrite. These two minerals form large ore bodies (Figs. 52 and 53) in or near a belt of diorite in a district occupied * Collins, "On the Sudbury Copper Deposits," Q. J. G. S., vol. xliv. (1888), p. 834, from which paper the two figures are borrowed. Snelus .and Colquhoun in the special volume of Proceedings, The Iron and Steel Institute in America in 1890, pp. 213, 359. 62 ORE AND STONE-MINING. by rocks belonging to the Huronian and Laurentian systems. The shape of the ore bodies is very irregular, but their size is great ; some are hundreds of feet long, by a hundred or more feet in breadth. The two minerals are worked and treated FIG. 53- FIG. 54. a, Huronian rocks ; b, diorite ; c, ore-mass ; s, shaft on diagonal vein. together, for picking by hand has been found to be impracticable on a commercial scale, and separation by the ordinary washing process is impossible, owing to the small difference between their specific gravities. Ore of good average quality contains 4 per cent, of nickel. Nitrate of Soda. The existence of beds of nitrate of soda, cubic nitre, in the rainless regions on the West Coast of South America had been noticed in books on mineralogy for many years ; but it was not till this mineral was found to be a valu- able fertiliser that steps were taken to work it on a large scale. The raw nitrate of soda (caliche) is found in beds from 6 inches to 12 feet thick, be- neath a covering of hard con- glomerate (costra) from i to 10 feet thick, as shown in Fig. 54.* It is supposed that it been formed by the action a, soft earth ; &, " caliche " ; c, con- glomerate ; d, sand ; e, charge of gun- powder ; /, tamping ; g, safety-fuse. of animal and vegetable matter upon salt left by the evaporation of sea- water, and this theory is supported by the fact that guano and the remains of * Harvey, " Machinery for the Manufacture of Nitrate of Soda at the Ramirez Factory, Northern Chili," Proc. Inst. C.E., vol. Ixxxii. (Session 1884-85), P- 337- MODE OF OCCURRENCE OF MINERALS. 63 birds and fish are found close to the caliche, and also by the presence of iodine, an element pertaining to the sea, in the form of iodides and iodates. Another theory, that of Dr. Carl Ochsenius,* is that salt lakes were formed by the elevation of a barrier which shut out the sea, that these gradually evaporated, that carbonic acid due to volcanic agencies converted some of the chloride of sodium into carbonate, and that finally guano dust, wafted by the prevailing breeze from guano islands near the coast, brought nitrogenous matter, which eventually became oxidised and converted the carbonate into nitrate. An analysis of caliche given by Mr. Harvey is as follows : Nitrate of soda . Common salt Sulphate of soda . Sulphate of magnesia Insoluble matter . Per cent. This sample was richer than the average ; for the best caliche contains about 40 to 50 per cent., middle 30 to 40, and poor caliche 17 to 30 per cent, of nitrate. Ozokerite. The most productive ozokerite mines are found at FIG. 55- SCALE. 1400 MCTRCS Boryslaw, near Drohobycz, in Galicia. The mineral occurs in an oval area some 1,500 yards long and a quarter of a mile wide at the broadest part, with the long axis, AB, running in a N.W. and * Eng. Min. Journ., vol. xlvi. (1888), p. 152. 6 4 ORE AND STONE-MINING. S.E. direction, or parallel to the trend of the Carpathians* (Fig. 55). The surrounding rocks are beds of sandstone arid shale of Miocene age, bent into a dome like a dish-cover, whilst the productive area itself consists of the same strata traversed by a main set of FIG. 56. fractures in the direction AB (Fig. 55), and numerous cross- fractures. In this mass of shattered, crushed, and faulted rock the ozokerite has been deposited ; it fills every crack and crevice into which it could penetrate, sometimes crossing the stratification Inches 12 6 o 2 feet o 20 40 60 So too centimetres. and sometimes following the planes of bedding for some distance, and then breaking across in an irregular manner (AB, Fig. 57). The veins vary in thickness from a mere knife-edge to several feet. Fig. 56 is a diagrammatic section along the line CD (Fig 55), and is intended to convey some idea of the jumble of rocks between E and F, the centre part from G to H being specially cracked, squeezed, and faulted. The richest mines are those sunk in the deeply-shaded part of the plan, corresponding to GH of the section. Petroleum is found in the rocks within the ozokerite area and also in those surrounding it for a certain distance, but there is less on the north side than on the south. * For much of the information concerning Boryslaw, I am indebted to explanations given to me on the spot by Mr. A. Platz, manager of the largest mine. MODE OF OCCURRENCE OF MINERALS. 65 Petroleum. The conditions under which rock-oil is found in the earth's crust are precisely the same as those described in speaking of natural gas, viz., a porous bed for storing the mineral, an impermeable bed for preventing its escape, and very often an anticlinal arrangement of the strata, though this is of less importance than in the case of gas. The three great oil regions of the world at present are Baku, Burmah, and Pennsylvania. I put Baku first, because the existence of the eternal fires of the Apsheron Peninsula on the Caspian Sea has been known for about 2,500 years, and because some of its wells have surpassed in productiveness anything met with elsewhere. The principal wells are in the FIG. 58. Balakhani-Saboontshi district, some eight miles North of Baku, and at Bibi-Eibet, a little to the south. The rocks are of Lower Miocene age,* and consist of sand, calcareous clays, marls, and in places compact sandstone. The sectionf (Fig. 58, after Abich) shows the wells on the crown of a low anticlinal. The petroleum is found in three well-defined beds of sand ; these sands are in a semi-fluid condition and contain salt water in addition to petroleum and carburetted hydrogen gas. Sometimes the pressure of the gas amounts to 300 Ibs. per square inch. At some of the wells it is necessary to pump up the petroleum, but at others it rises naturally and occasionally with great force and in immense quantities. In fact, Tagieff's spouterj in 1886 actually threw up, on the eighth day after oil had been struck, the immense quantity of n,ooo tons or 2J millions of gallons in twenty-four hours. The flow then diminished and was got under control by the engineers, and reduced to a quarter of a million gallons a day. Fig. 59, copied from a photograph, represents a spouting well at Baku. The principal oil-fields of Burmah || are situated near the villages of Twingoung and Berne, about a mile and a half east of Yenangyaung on the Irrawaddy, and 130 miles south of Mandalay. The rocks belong to the Tertiary period and are probably of Miocene age, the prevailing strata being clayey sands * Vasilieff, "The Oil Wells of Baku," Proc. Inst. C.E., vol. Ixxxiii. (1885-6), p. 406. t Topley, Op. tit., p. 429. i Marvin, The Coming Deluge of Russian Petroleum. London, 1886, p. 9. Lent to me by Mr. Boverton Redwood. || F. Noetling, " Keport on the Oil Fields of Twingoung and Berne, Burma," Records of Geol. Survey of India, vol. xxii. (1889), p. 75. 66 ORE AND STONE-MINING. and soft sandstone. The petroleum is found in beds of soft sand- stone, which, together with partings of blue clay, have been proved to be 200 feet thick, and are probably very much more. The sand- stone is soaked with petroleum, which oozes gradually into the wells, but certain layers are richer in petroleum than others. The lower strata of the formation are more productive than the upper- ones. The oil-bearing rocks are overlain by thick beds of blue FIG. 59. clay which prevent the petroleum from rising. The greatest depth reached by a Burmese well is 310 feet. Noetling thinks that the oil was produced in the sandstone formation in which it is now found, though perhaps not in the uppermost beds. At present there are no flowing wells, but these might be obtained if the oil-bearing strata were tapped at a greater depth, for then the gas which accompanies the petroleum would be under greater pressure. Where beds lie as shallow as they do at the existing workings, the gas has already drained off to a great extent through cracks in the strata. The highest daily yield of a single well was 500 viss,* but many of what can be called fairly rich wells pro- duced upwards of 100 viss a day. The yield decreases rapidly during the first two years to the extent of at least 25 per cent., and after ten or fifteen years a well does not produce more than 5 per cent, of what it did at first. The total daily production of the two fields ranges from 15,000 to 20,000 viss per day. * i ^$ = 3-0857 Ibs. MODE OF OCCURRENCE OF MINERALS. 67 The year 1859 marks the first discovery of petroleum on a commercial scale in the United States, though the oil had been known as long ago as 1627. The strata which yield oil in Pennsylvania and New York belong to the Devonian and Carboniferous periods. They are beds of sand and sandstone, sometimes coarse-grained, and are the same as those producing gas ; in fact a well may often produce both gas and petroleum, or first gas and then a little oil. In Ohio the two chief sources of oil are the Trenton Limestone [Lower Silurian] and the Berea Grit near the base of the Carboniferous rocks.* Phosphate of Lime. The trade in this fertiliser is very large, and fortunately the sources of supply are numerous. Deposits of phosphate of lime are found in rocks of all ages, from the Laurentian to the recent period. I may mention specially apatite from Canada, and various kinds of phosphate from the Cretaceous rocks in Europe, from South Carolina, Florida, and the West Indies. The Laurentian rocks are the home of the apatite in Canada. The principal mines are in the county of Ottawa (Q.), and the mineral occurs mainly in pyroxenite, sometimes as a contem- poraneous bed and sometimes as a vein of posterior origin. The beds are from i foot to 3 or 4 feet thick, and the veins from a few inches to 8 or 10 feet wide. Though worked to some extent in Bedfordshire, Buckingham- shire, and Cambridgeshire, the Cretaceous rocks have of late years yielded far more abundant supplies of phosphate in France than in England. In the mining district of Arrasf deposits of phosphate of lime are worked in three horizons : (i) At the base of the Gault, in the form of a bed of nodules, generally about 2 inches thick, and sometimes as much as 6 inches thick ; (2) above the Gault, in the form of beds of nodules, 6 inches (15 cm.) to 3 feet 3 inches (i m.) thick ; (3) in the state of sand, in more or less regular pockets, in the upper beds of the Chalk. This sandy phosphate is covered by a bed of clay with flints, above which comes brick-earth (Fig. 60). The sides of the pockets are formed by the chalk with Micraster cor-anguinum, or " Santonien " ; whilst the fossils in the pockets belong to the base of the " Senonien," or chalk with Belemnites quadratus. The pockets are generally contiguous to each other, but vary a good deal in depth up to 65 feet (20 m.) The phosphatic deposit is a * Ashburner, Op. cit. Topley, Op. cit. Weeks, " Petroleum," Mineral Resources of the United States, Calendar Year 1886. Washington, 1887, p. 458 ; and Calendar Years 1889 and 1890, p. 287. f Statist ique de V Industrie Miner ale et des appareils a vapeur en France .et en Alf/erie pour Pannee 1886. Paris, 1888, p. 243. Figure 60 is taken from my own notes, and differs slightly from the one given in the official volume. 68 ORE AND STONE-MINING. very fine yellowish and occasionally white sand, which under the microscope is found to consist of transparent concretionary grains, FIG. 60. FIG. 61. A, chalk ; B, phosphatic chalk ; C, sandy phosphate of lime ; D, clay with flints ; E, brick-earth ; F, soil. made up of concentric layers ; its average thickness may be taken at 3 feet 4 inches (r m.) The chalk adjacent to the pockets is often phosphatic. M. Merle and other geologists think that the phosphate is derived from the lixiviation in situ of the chalk with belemnites by rain water containing carbonic acid. The famous beds of South A Carolina,* besides satisfying to a _ ____ great extent the wants of the SCALES United States, are able to supply 7 ? ? 1 . v '.* FEET large quantities of the fertiliser ' ? METRES to other countries. They were ^J^ in . I $ 6 7, ' and, owing to * h e facility with which they can be worked and their proximity to a seaport, the trade has in- creased very rapidly. The mineral occurs in the form of nodules, from the size of a pea to that of a man's head, in a bed from a few inches to 2<| feet thick, the average thickness being 7 to 9 inches (Fig. 61). With the nodules are found bones of fish and especially teeth of great sharks, together with teeth of the A, Ashley marl (Eocene) ; B, bed of phosphatic nodules ; C, ferru- ginous sand ; D, clayey sand. * E. A. F. Penrose, " Nature and Origin of Deposits of Phosphate of Lime," Bulletin of the U.S. Geol. Survey, No. 46. Washington, 1888, p. 63. MODE OF OCCURRENCE OF MINERALS. 69 horse and other land animals. The deposit is considered to be of Post-Pliocene age. The existence of valuable deposits of phosphate in Florida* was not known till 1887. There are four different kinds of the fertiliser (i) "hard rock" phosphate, (2) "soft" phosphate, (3) "land pebble" phosphate, (4) "river pebble" phosphate. The "hard rock" is a hard, massive, light grey phosphate of lime, with cavities lined with secondary mammillary incrustations of the mineral. It has been produced by the alteration of Eocene and Miocene limestone, and yields about 36 or 37 per cent, of phosphoric anhydride (P 2 5 ). The "soft" phosphate includes material resulting from the disintegration of the hard phosphate, and also highly phosphatic sands and clays, rarely averaging more than 22 per cent, of phos- phoric anhydride. The " land pebble '' phosphate is made up of pebbles of various sizes, up to that of a walnut. They consist of an earthy material carrying pisolitic grains of phosphate of lime, or of a substance resembling the hard rock phosphate. The percentage of phos- phoric anhydride is about 32. The "river pebble" phosphate is found in the beds of the present rivers, and also in their ancient channels. The pebbles are blue, black, and grey in colour, and contain the bones and teeth of various animals. They yield from 20 to 28 per cent, of phosphoric anhydride. The phosphate of lime worked at Aruba and Sombrero, in the West Indies, was originally a coral limestone ; its conversion into phosphate has been effected by the percolation of water containing phosphoric acid derived from the dung of sea-fowl. This interesting fact is made very plain by finding corals themselves changed into phosphate of lime. In the island of Redonda, owing to a difference in the rocks acted on by the drainage from the excrement, the mineral produced is phosphate of alumina. Potassium Salts. The deposits of various potassium salts at Stassfurt belong to the Bunter Sandstone formation of the Magdeburg-Halberstadt basin, and workings have now shown that they attain a thickness of very nearly 3000 feet (900 metres). The beds may be divided according to their chemical com- position into four regions,f which in descending order are : * Eldridge, "A Preliminary Sketch of the Phosphates of Florida," Trans. Amer. Inst. M.E., vol. xxi. (1892), p. 196. Wyatt, The Phosphates of America. New York, 1891. t Fiihrer zum vierten Bergmannstag, 1889. Halle a. d. Saale, 1889, p. xxxiv. 7 ORE AND STONE-MINING. APPROXIMATE THICKNESS. Feet. Metres. 4. Carnallite region. Carnallite is the double chloride of potassium and magnesium (KC1, MgCl, + 6H 2 O) 82 3. Kieserite region. Kock salt with beds of kieserite (MgSO 4 + H 2 O) . . . .183 2. Polyhalite region. Rock salt with strings of polyhalite (KjSO,, MgS0 4 , 2CaS0 4 , + 2H 2 O) 197 i. Rocksalt. An exceedingly thick bed. 2 5 56 60 As is shown by the section (Fig. 62), the edge of the carnallite region consists of kainite (K 2 S0 4 , MgS0 4 , MgCl, + 6H 9 O) ; this w.s.w. I FIG. 62. Xudwiy ff Skaff_ a, Older rock salt ; &, polyhalite region ; c, kieserite region ; fZ, carnallite ; e, saliferous clay ; /, kainite ; g, sylvinite ; h, gyp- sum and anhydrite ; i, younger rock salt ; j, gypsum ; 7j, /,; varie- gated marls with thin beds of limestone and of oolite ; I, diluvium and alluvium. The depths marked are in metres. is considered to be of secondary origin, and so also is regarded the sylvinite, a mixture of potassium and sodium chlorides with their sulphates, which occurs in workable quantities. Above the potassium salts is a bed of saliferous clay 26 feet (8 m.) thick, and then 290 feet (90 m.) of anhydrite, which forms the floor of the Bunter beds. At several places there is a younger bed of rock-salt from 130 to 400 feet (40 to 120 m.) thick. Rock-salt is worked to a small extent, but the potassium salts, MODE OF OCCURRENCE OF MINERALS. especially carnallite and kainite. are the main objects of the mining.* Quicksilver. The principal quicksilver producing mines at the present time are Almaden, in Spain, Idria, in Carniola, and New Almaden, in California. There are also several other mines in California, and workings of some importance in Russia and Italy. Peru was at one time remarkable for its quicksilver deposits at Huancavelica, but these are no longer worked. China possesses some little-known mines in the province of Kwei-Chau. The relative importance to the world of the principal deposits is shown by the following table, taken from Mr. Becker's mono- graph, t PRODUCT OF THE PRINCIPAL DISTRICTS, IN SPANISH FLASKS OP 75 SPANISH POUNDS, OR 34*507 KILOGRAMMES. || Up to 1700. 1700 to 1800. 1800 to 1850. 1850 to 1886. Total to Jan. 1886. Aliiiadcu . . Idria. . . . Huancarelica . California . . Year 1564 1525 i57i 1850 517,684 399,861 881,867 1,221,477 608,743 543.642 1,091,075 242,226 75.604 1.135.576 3!. 549 1,429,346 3,965,812 1.552,379 1,501,113 1,429,346 1,799,412 2,373. 8 62 1,408,905 2,866,471 8,448,650 Mr. Becker has brought together a vast array of useful facts concerning the occurrence of quicksilver in his valuable mono- graph, which may be very briefly summed up as follows : J Cinnabar is found in rocks of all ages and of all descriptions, viz., conglomerate, sandstone, quartzite, limestone, shale, slate, serpentine, crystalline schist, and basic and acidic volcanic rocks, but it exhibits a preference for sand- stone. The quicksilver deposits are found along lines of country marked by past or present volcanic disturbances. This fact is made very plain by a map of the world on which are indicated all important occurrences of the metal. Some cinnabar has certainly been precipitated from hot solutions brought up by volcanic springs, and it seems likely that many of the quicksilver deposits have been formed in this manner.|| The cinnabar is often found filling up interstitial spaces of the rock, and if the rock is sedimentary it sometimes cuts across the planes of stratification, and sometimes runs parallel to them. * Precht, Die Safe-Industrie von Stassfurt und Umgeyend. 4th edition, Stassfurt, 1889. t Becker, " Geology of the Quicksilver Deposits of the Pacific Slope," Monographs of U. 8. Geol. Survey, vol. xiii. Washington, 1888, p. 7. $ Ibid. p. 50. Ibid. p. 15. || Ibid. p. 55. 72 ORE AND STONE-MINING. Spain. The famous and productive Almaden mine is situated on the northern slope of the Sierra Morena, where the rocks coming up to the surface are of Silurian and Devonian age. These rocks are beds of sandstone and quartzite interstratified with slate and a little limestone. The cinnabar occurs impregnat- ing the sandstone ; the slate is rarely, if ever, quicksilver-bearing. There are three principal deposits extending for a distance of 200 to 220 yards (180 to 200 m.) along the strike, the dip is almost vertical. The total useful thickness of the three beds is reckoned to be 40 feet (12 m.), and the mercurial rock yields on an average 10 per cent, of metal. It seems probable that these sandstone beds were impregnated by aqueous solutions which came up from below. They may be called veins or beds according to the defini- tions one chooses to adopt for a vein. No doubt the cinnabar is of subsequent origin to the main part of the stratum ; but the same may be said for the copper in the conglomerate beds of Lake Superior, and possibly for the gold in the " banket " of South Africa. The quicksilver solutions deposited their metal in cavities existing between the particles composing the sand- stone, and I think in a case of this kind, where more than 90 per cent, of the deposit is matter of detrital origin, it is most convenient to speak of the deposits as beds. However, in two of the mercurial strata there are little strings arid seams, either parallel to the bedding or crossing the planes of stratification in all directions. Looked at on a small scale, these strings could be called veins, but when one has to deal with the workable stratum as a whole it may be called a bed. Austria. At Idria, in Carniola,* cinnabar occurs in theTriassic FIG. 63. A, compact sandstone ; B, less compact sandstone impregnated with cinnabar 13 to 16 feet (4 to 5 m.) thick ; C, shale ; D, thinly- bedded sandstone. rocks in three ways : (i) impregnating beds of shale, conglomerate and dolomitic breccia ; (2) filling up of cracks like ordinary fissure veins ; (3) in irregular veins across the mass, making a stock- work. Lipold supposes that it was introduced by watery solu- tions in late Tertiary times. * Das k. 7b. Quecksilberiverk zu Idria in Krain. Vienna, 1881. MODE OF OCCURRENCE OF MINERALS. 73 Russia. An interesting and important deposit is being worked at Ekaterinoslav in Southern Russia, a section of which is given in Fig. 63. The cinnabar is disseminated through a sandstone, which lies between another bed of sandstone of a more compact nature and a bed of shale. Once more we have a case in which the mercurial solutions made their way upwards along the easiest channels they could find. California. The quicksilver deposits of California* are found in various parts of the State, from the extreme north to Los Angeles. The most important mine is New Almaden, situated about fifty miles to the S.E. of San Francisco. In California, as in Austria, the deposits of cinnabar are of several types, even at one and the same mine. Thus, at New FIG. 64. Almaden the commonest kind of ore-body is a network of veins and veinlets through the rock, in fact a stockwork. If the disturbance pro- duced a clean fissure instead of a multitude of irregular cracks, then the single rent was filled up and produced what some would call a typical vein. Lastly, if the mercu- rial solutions traversed beds of sand- stone, they deposited some of their contents in the interstitial spaces between the grains, and so formed an ore-bearing stratum. All three kinds of ore-bodies were formed by the same process of deposition, the difference, if I may use the simile, depending upon the lodgings that happened to be vacant, and not upon the lodger who came to take up his abode there, nor upon the vehicle that brought him to his new home. The ore- bodies at New Almaden occur close to faults filled with clay and fragments of rock, more or less rounded by the attrition produced by movements of the " country." The name given to these faults by the miner is " altas," a Spanish term referring to their usual position on the hanging side of the deposit. It seems as if the impermeable clay had arrested and directed the course of the ore-bearing solu- tion as it ascended ; this is highly probable, and it is an explana- tion which has been offered in many cases when the ores of other metals have been found to " make up against a slide." The surrounding rocks at New Almaden are metamorphosed Becker, op. eit. p. 317. 74 ORE AND STONE-MINING. sediments of Neocomiau age, pseud odiorite, pseudodiabase, phthanites, sandstone, shale, and serpentine. The minerals accompanying the cinnabar are iron pyrites, marcasite, quartz, calcite, dolomite, magnesite, and rarely chalcopyrite. The deposit worked at Great Western mine, 70 miles north of San Francisco, is a tabular reticulated mass of rock (Fig. 64),* impregnated with cinnabar and a little native quicksilver. It lies between serpentine and a very slightly altered Neocomian sandstone. The serpentine is accompanied by a belt of black opaline rock, called the " quicksilver rock " by the miners. The FIG. 65 SCALE OF FEET. longitudinal section (Fig. 65) explains that the ore-bodies are separated by spaces of barren ground, just as they are in an ordinary lode. The Sulphur Bank mine is of interest because the solfataric action, which no doubt caused the deposition of the cinnabar, is still going on. At first the surface was worked for sulphur, which had been formed by deposition from sulphuretted hydrogen escaping through basalt, just as it does in so many places in the other volcanic areas. A few yards below the surface, the sulphur proved to be cinnabar- bearing, and lower down cinnabar was found in large quantities. Cinnabar has since been worked from the strata underlying the basalt. There are beds of shale and sandstone of Neocomian age, in which the quicksilver ore is found as impregnations and irregular seams. The ore is accompanied by quartz, opal, iron pyrites, calcite, bitumen, and marcasite. This last mineral con- tains small quantities of gold and copper. Hot springs are common * Becker, op. cit. p. 36 MODE OF OCCURRENCE OF MINERALS. 75 in the mine, and many of them give off gases, viz., carbon dioxide, sulphuretted hydrogen, marsh gas, nitrogen and ammonia. Nevada, From a scientific point of view, one of the most in- teresting mineral deposits in the United States is that of Steam- boat Springs in Nevada, only six miles from the Comstock lode. A number of hot springs exist along a series of fissures about a mile in length ; siliceous sinter is being deposited by them, and there are also mounds of sinter formed by springs that are no longer flowing, or whose only sign of activity consists in emana- tions of steam, sulphuretted hydrogen, carbonic anhydride, and sulphurous anhydride. These solfataric gases also escape with the water at some of the living springs. The sinter is found on analysis to contain many of the heavy metals, viz., antimony, arsenic, cobalt, copper, gold, iron, lead, manganese, mercury, silver, and zinc, some of them certainly existing in the form of sulphides. A sample of the water taken from a spring with a temperature varying from 167 to 184 Fahr. (75 to 84.5 C.) was analysed; it showed weighable quantities of arsenic and antimony, and a trace of mercury ; as it cooled it could be seen to deposit the sulphides of antimony and arsenic together with silica. In one part of the district, instead of sinter, a deposit like that at Sulphur Bank, consisting of sulphur and cinnabar, has been formed ; and it has been worked for the commercial extraction of mercury. Salt. Sea water, salt lakes, brine springs and wells, sali- ferous marls and rock salt are the sources of this very important mineral. The extraction of salt from sea-water is carried on in Southern Europe and other countries, where the heat of the sun is sufficient to evaporate the water which has been led into shallow ponds ; and the industry is fostered in many cases by the traffic in salt being a Government monopoly. In South Africa and elsewhere salt is obtained from " pans" or shallow inland lakes, which become partially dried up in the hot season. Natural springs yielding brine are not uncommon, and brine wells are dug or bored so as to reach a salt-bearing stratum. At Northwich,* in Cheshire, there are two main beds of rock- salt, each from 84 to 90 feet thick, separated by a bed of hard marl 30 to 33 feet thick. All these beds belong to the Keuper division of the Triassic rocks. The amount of rock-salt mined in England is small, only about one-tenth of that obtained from brine, which is pumped from flooded mines, and from wells or boreholes penetrating saliferous strata. * Dickinson, " Report on the Salt Districts," Reports of the Inspectors of Mines for the Year 1881, p. 55. 76 ORE AND STONE-MINIXG. Silver. All galena carries some silver, and in very many cases there is enough to make the extraction profitable. Copper ores also are frequently argentiferous : the silver in the Mansfeld cupriferous shale has already been mentioned, and the ores of the Butte district, Montana, are often rich in the precious metal ; it is needless, however, to dwell upon this and similar sources of silver, though they are of great commercial importance. Among well-known silver mines may be mentioned those of the great Comstock Lode in Nevada, the Eureka and Richmond mines in the same State, Huanchaca in Bolivia, and Broken Hill in New South Wales. Comstock Lode. This remarkable lode strikes about north and south and dips about 43 to the east. The vein, which is usually from 20 to 60 feet thick and as much as several hundred feet thick in some places, consists in the main of crushed and decomposed portions of the " country " together with clay and quartz. The sur- rounding rocks are syenite and propylite, according to King,* or cliorite and diabase, according to Becker.f The latter says that the so-called propylite is only a decomposed form of other rocks. The silver is found native and in the form of silver glance, polybasite, stephanite, and occasionally pyrargyrite ; other minerals in the vein are quartz, iron pyrites, copper pyrites, besides oxides of iron and manganese, sulphates of calcium and magnesium and car- bonates of magnesium, calcium, lead and copper. The ore -bodies are soft and irregular. The heat of the Comstock lode is noteworthy. In the 2700 feet level of the Yellow Jacket mine, Mr. Becker found the temper- ature of the water to be 153 Fahr. and that of the air 126 Fahr., whilst the water of the Yellow Jacket shaft at a depth of 3065 feet had a temperature of 170 Fahr. Eureka-Richmond. The nature of the curious lode worked at the Eureka-Richmond .t mines will be best understood by reference to Fig. 66 ; much of it is a mass of crushed limestone of Cambrian age lying between two faults, a main one dipping N.E. at an angle of 70, and a secondary one which is much natter. The main fault is a fissure filled with clay or with decomposed rhyolite and clay, varying from a few inches to 15 feet in width. It shifts the rocks many hundreds of feet, and at Eureka the throw exceeds 1400 feet. The valuable parts of the lode are ore- bodies of every possible shape and size, some measuring upwards of 100 feet in all directions. Above the water level, or horizon of decomposition by atmospheric agencies, the minerals constitut- * King and Hague, " Mining Industry," U. S. Geol. Exploration of the Fortieth Parallel. Washington, 1870. t " Geology of the Comstock Lode and Washoe District," Monograph 111. of U. 8. Geol. Survey. Washington, 1882. Curtis, "The Silver-lead Deposits of Eureka, Nevada," Monogranh VIII. of U. S. Geol. Survey. Washington, 1884. MODE OF OCCURRENCE OF MINERALS. 77 ing the ore-bodies, are galena, cerussite, mimetite, wulfenite, with very little quartz and calcite, the remainder of the veinstuff being mainly hydrated oxide of iron carrying silver and gold, with some carbonate and silicate of zinc. Below the water level the minerals are pyrites, arsenical pyrites, galena, blende and a few other sulphides, besides silver and gold. One of the char- FIG. 66. F T ioo o SCALE OF FEET 200 400 600 800 1000 100 METRIC SCALE 100 200 M. H. Ore. G. Hamburg Limestone. F. Secret Canon Shale. E. Stratified Limestone. D. Limestone. C. Shale. (Prospect Mountain Limestone. ^ A. Prospect Mountain Quartzite. acteristics of the ore is the presence in it of gold in paying quantities. It is considered by Mr. Curtis that an eruption of rhyolite caused the upheaval which made the main fault in Ruby Hill ; this eruption occurred in the Tertiary period. It is sup- posed that solfataric action decomposed some massive rock and so formed metalliferous solutions, which ascended and, penetrating into the limestone, deposited the ore. Some of the ore is pro- bably pseudomorphous after limestone. The average contents of all the Richmond ore worked in 1879 were : Lead . . -33 per cent. Silver . . . 274 oz. per ton (2000 Ib.) Gold . . i -59 oz. Iron . . .24 per cent, corresponding to 34 per cent, of Fe 2 O,. 78 ORE AND STONE-MINING. Huanchaca. The mines of Huanchaca are situated near the town of that name in the department of Potosi in Bolivia, at a great altitude, for the entrance of the San Leon adit is 13, 500 feet above the level of the sea. The silver lodes occur in a soft de- composed trachyte ; the actual silver-bearing mineral is fahlerz, containing about 10 per cent, of the precious metal. Fortunately for the shareholders the percentage of silver increases with the depth of the mine. The accompanying minerals are galena, blende, iron pyrites, copper pyrites, with heavy spar arid quartz, and rarely a little stibnite and pyrargyrite. The main lode runs about east and west, and is from 3 to 10 feet in width (i to 3 metres) ; it has three particularly rich shoots which incline from west to east. The total output of silver in 1887 was 4,214,510 oz. (131,086 kil.). At the famous Potosi mines also, the silver occurs in a fahlerz. Broken Hill. The mines at Broken Hill are remarkable for their enormous output of silver and lead during the last few years. They are situated in the Silverton or Barrier Ranges district of New South Wales, near the western boundary of the colony. The deposit is generally spoken of as a vein or lode, but there seems some doubt whether this appellation is correct ; further develop- ments of the workings may prove that it is a bed. The vein, if it may be so called, runs, roughly speaking, N.E. and S.W. ; the dip varies, being sometimes to the S.E. and sometimes to N.W., and is always steep. At and near the surface, the vein * consisted of dark-brown haematite, often blackened by psilomelane, together with ferruginous carbonate of lead, kaolin, and the chloride, chloro- bromide and iodide of silver; besides these there were pyromorphite, atacarnite, cuprite, malachite, and chrysocolla, with quartz, quartzite, and garnet rock. Below this upper weathered zone, containing minerals usually met with in gozzans, come the sulphides, especially galena and zinc blende, together with pyrites, chalcopyrite, and mispickel. Some of the galena is so intimately mixed with the blende as to render its separation by any ordinary dressing process very difficult, if not commercially impossible. Ores of this class f contain 15 to 40 per cent, of lead, 15 to 30 per cent, of zinc, and 8 to 24 ounces of silver to the ton, and at present the owners of the mines have not settled what method of treatment will prove the most efficacious and economical. The width of the lode is from 15 to 316 feet. The enclosing rocks are gneiss and garnetiferous mica and talcose schists, and the vein lies * John Provis, " Report on the Broken Hill Proprietary Co.'s Mines," contained in the Company's Reports and Statements of Accounts for the Half Year ended Nov. yotli, 1886. Melbourne, Victoria. Jamieson and Howell, "Mining and Ore-treatment at Broken Hill, N.S.W.," Proc. List. C.E., vol. cxiv. (1892-93), Part IV. t Schnabel, " Vorschlage zur Verarbeitung australischer silberhaltiger Blende-Bleiglanzerze," B. u. h. Z., 1882, p. 429. MODE OF OCCURRENCE OF MINERALS. 79 parallel to the planes of foliation. In the seven years ending 3ist May, 1892,* the principal mine, owned by the Broken Hill Proprietary Company, produced 984,349 tons of ore, which yielded 36,512,445 ounces of silver and 151,945 tons of lead, worth altogether ^8, 252,138, of which ^3, 896,000 has been paid in dividends and bonus. Silver-bearing Sandstone. Silver is found in workable quantities in certain beds of sandstone, interstratified with shale, considered to be of Triassic age, at Stormont in Southern Utah.f All the strata contain at least some traces of silver, but three or four special horizons were rich enough to be worked ; even here the precious metal was distributed irregularly, and mining was confined to rich " shoots " or chimneys, which some- times followed one particular stratum of the general ore-bearing bed, and sometimes cut across it. It is supposed that silver- bearing solutions came up through the rock, and flowed along the portions which they found most porous. The precipitation of the silver was, perhaps, caused by the presence of organic matter. The metal exists in the form of sulphide and chloride, though there is a little native silver. These minerals are dissemi- nated through the sandstone, and occur especially along the planes of bedding and of fracture. The ore-beds were mined for a thickness of six, eight, or even ten feet, though the whole of the rock was not always worth milling. Much of the ore milled about 1879 contained from 20 to 30 oz. of silver per ton, and yielded by amalgamation 15 to 24 oz4 Garfield Mine, near Calico, California, owes its existence to a network deposit or stockwork. The surrounding rock is liparite or rhyolite, which is traversed near by a number of irregular fissures. The cracks contain kerargyrite and embolite, with chry- socolla and heavy spar, and the stockwork may be described as a breccia of liparite cemented by the argentiferous and other minerals. Slate. Wales is so renowned for its slate that the example of a deposit of this mineral may fairly be taken from the Principality. About two-thirds of the Welsh slate are got from beds of Cambrian age in Carnarvonshire, and one-third from beds in the Lower Silurian (Ordovician) rocks in Merionethshire. The quarries in the former county are mostly open, whilst in the latter the local conditions have led to the adoption of true mining, especially at Festiniog, which can boast of the most extensive underground * Company's Half -Yearly Report, dated July 27, 1892, p. 86. t R. P. Rothwell, "Report on the Stormont Silver Mining Company's Property, Silver Reef." Utah, 1879. + Jackson, " Silver in Sedimentary Rocks," fieport of the Directors of the U.S. Mint. Washington, 1881, p. 384. W. Lindgren, " The Silver Mines of Calico, California," Trans. Amer. Inst. M.K, vol. xv. (1886-87) p. 725. 8o ORE AND STONE-MINING. workings for slate in the world. The northern part of the parish of Festiniog is occupied by the outcrop of a thick series of slaty rocks (K, Fig. 67*), resting upon coarse volcanic agglomerate, H, and interstratified with thinner beds of volcanic ash, and inter- sected from time to time by intrusive dykes of diabase, locally called whinstone. The beds have a general northerly or north- westerly dip of 20 to 35, whilst the cleavage planes throughout the district dip at a greater angle than the bedding by about 1 5, and very nearly in the same direction. Owing to peculiarities of texture, due apparently to the fineness of the sediment deposited upon the old sea-bottom, certain beds or sets of beds furnish a slate which can be split into very smooth sheets, as thin as T \ inch and even less. Any set of beds worked as a whole is known locally as a " vein," but it does not necessarily furnish saleable roofing material for its entire thickness. Some- Dolwen. Foel Rydd. A, granite ; B, Tremadoc rocks ; C, Garth Grit ; D, Lower Slate ; E, Arenig rocks above the grit ; F, Lower Agglomerate; F', Middle Agglomerate ; G', Middle Slate; G, Upper Slate ; H, Upper Agglomer- ate ; K, Llandeilo slates. times unprofitable rock is taken away above the good slate in order to reach a firm layer, such as a bed of volcanic ash, or a " whinstone " dyke, which can be trusted to stand as the roof of the underground chambers, and at others the fine-grained slate has beds of coarser sediment interstratified with it, which cause irregularities in the planes of cleavage, and so give rise to inferior products. The " Old Vein," famous for the quality of its slates, is 120 feet (36.5 m.) thick at the Oakeley quarries, where other " veins " of less importance are also being worked (Fig. 68). At some of the other quarries of the district, beds of slate in the underlying rocks of the Arenig series are found to be profitable, such as G' in Fig. 67, and i in Fig. 68. The property possessed by the slate of rending along planes, cutting across both dip and cleavage, must not be forgotten, for upon it depend both the getting of the rock and the direction given to the supporting pillars. At the Oakeley quarries the "line * Jennings and Williams, " Manod and the Moelwyns," Q. J. Geol. Soc. vol. xlvii. (1891), p. 368. MODE OF OCCURRENCE OF MINERALS, 81 of pillaring," that is to say, the direction along which the cross- rending or rifting takes place most readily, runs about N. 7 W., whereas the dip is N. 40 W. The planes along which the slate rends or " pillars " best are at right angles to the cleavage planes, not quite vertical, but dipping at a high angle to the east; the consequence is that the eastern side of an underground chamber at these quarries overhangs slightly. The value of a slate bed, or " vein," depends greatly upon the number and nature of the natural joints by which it is intersected. If they are very numerous, the workings will yield blocks too small for making the larger and higher priced sizes of slates ; if they are rare, more expense will be incurred in severing the material from its bed. Disturbances of the strata resulting in FIG. 68. SECTION OF THE OAKELEY QUARRIES, FESTINIOG.* Ag 1 , Ag 2 , Ag, volcanic agglomerates ; i, slate vein worked at Wrysgan and New Quarry, Diphwys ; 2, new or south vein ; 3, old'vein ; 4, 2A vein ; 5, back vein ; 6, north vein ; WD, " whin- stone " dykes (diabase) ; P, porphyrite ; As, volcanic ash. fissures filled either mechanically with clay and broken slate, or chemically by the deposition of quartz, may render the " vein " utterly worthless in places ; but, as in the case of other bedded deposits, changes in productiveness are far less frequent than with lodes. Sulphur. The industrial sources of sulphur are : (i) deposits of native sulphur, and (2) iron pyrites. Native sulphur occurs as a product of volcanic emanations, and in sedimentary deposits. The amount of sulphur obtained from deposits of volcanic origin is small ; but this mode of occurrence is of geological interest, because we can observe the processes of accumulation in actual operation, whereas usually the secrets of Nature's laboratory are hidden from us. * Made by Mr. G. J. Williams, F.G.S. 82 ORE AND STONE-MINING. Deposits of this kind are generally found at or near spent vol- canic craters, the emanation of sulphurous gases being one of their last signs of activity. Sulphur has been worked on a small scale at the famous Solfatara of FIG. 69. Pozzuoli, near Naples, at Yulcano, one of the Lipari Islands, and in volcanic re- (. 3&-S? which denotes basalt ; this flowed down an old valley and filled it up entirely, as shown by the section (Fig. 74). The hard cover of lava has preserved the stanniferous alluvium and the white clay from denudation. Old alluvia of this description are known as "deep leads." Zinc. Zinc ore is found in veins, beds, and irregular masses. Liiderich mine, situated near Bensberg, on the right bank of the Rhine, not very far from Cologne, derives large quantities of blende from a huge vein in the Devonian rocks. The actual horizon is that of the " Lenneschiefer," which is classed as Middle 86 ORE AND STONE.MINING. Devonian. The rocks are slate, interstratified with sandstone and slaty sandstone. The lodes of the district, as a rule, run E. and W., or a little north of west ; the Liiderich mine, however, is an exception, for the lode strikes, roughly speaking, north and south. It may be best de- scribed as a zone or belt of broken and disturbed rock, 40 to 50 metres wide, containing ore in irregular veins and masses. The ore-bodies are usually lenticular in shape, dying out gradually in every direction ; they sometimes consist of solid blende for a width of several yards. The minerals found in the lode are : blende, galena, copper pyrites, iron pyrites, fahlerz, quartz and, rarely, chalybite. The fahlerz is silver-bearing, and the blende always contains cadmium, and occasionally gallium. The total production of the mine in 1890 was 8304 tons of blende ready for the smelter, and 423 tons of lead ore. It is therefore of more importance as a zinc mine than any in this country. The largest zinc mine in the British Isles at the present time is Minera, near Wrexham. It may be safely inferred from its name that it was worked during the Roman occupation of the country ; but the object of the mining in those days, and, indeed, until quite a recent date, was lead and not zinc ore. The surrounding rocks are Carboniferous Limestone and Millstone grit, and as the lode is a well-marked fault, the Coal Measures are met with on the downthrow side. There are two principal veins running parallel to one another in a general N.W. and S.E. direction, and dipping steeply to the N.E. ; and where pro- ductive they are nearly perpendicular. They vary in size from a mere cleft in the rock to a width of 1 8 feet ; a fair average size is 6 feet. Besides these two main veins there are numerous branches and ramifications. The valuable mine- rals are zinc blende and galena, and, as would be expected, the matrix consists mainly of calc- spar. In the upper parts of the mine to a depth of 220 yards, galena was met with in large quan- tities, and the mine made considerable profits upon its sales of lead ore ; but during the last twelve years blende has greatly predominated. At the present time it may be reckoned that the " stuff " MODE OF OCCURRENCE OF MINERALS. 87 brought up from the mine yields yj percent, of blende and i^ per cent, of galena. The total production of the mine in 1891 was 5433 tons of zinc ore and 906 tons of lead ore ready for the market. o At *Ammeberg, near the northern extremity of the Wetter Lake, in Sweden, zinc blende occurs in beds. The surround- ing rock is a schist consisting of felspar and quartz, with a little mica, which may be regarded as a variety of gneiss. The blende is accompanied by iron pyrites, pyrrhotine, hornblende, chlorite, garnet, tourmaline and other minerals, and in places it may be plainly seen to replace the mica of the gneiss. The Ammeberg beds are worked on a large scale by the Vieille Montagne Company. Diepenlinchen mine, near Stolberg, in Prussia, is interesting not only on account of being a large producer of zinc ore, but also because some of it is derived from a great stockwork, a form of deposit less common with zinc than tin. The stockwork consists of an oval mass of limestone, about 120 metres long from east to west, and 50 metres across from north to south. In this region the limestone is full of cracks, which have been filled up with zinc blende, and this mineral is also seen lining small irregu- lar cavities in the rock; judging by its structure it has been deposited layer after layer, and probably from an aqueous solution. The rock is so intermingled with blende that the whole of it has to be worked away, and the separation of the valuable con- stituent from the waste is effected by dressing. Fig. 15 is a section across one of the irregular masses of calamine at Altenberg, in the neutral territory of Moresnet, be- tween Belgium and Prussia. FAULTS. All kinds of deposits are subject not only to irregularities dependent upon their mode of formation, such as a gradual thinning out or thickening, but to others which have taken place FIG. 75. subsequently. Sometimes a bed, _ T _ 1 such as AB, has had a portion de- -\ V- * -v '--+*! K ~ w ~i~~ v nuded by a current during the . . -. ' ; 0..- -..-'. -. -' ;'..- .; . general period of deposition. Such an occurrence is called a "wash ^ _ out " fault, or " dumb fault " ^~-^^- ^ r-^vq-fr (Fig. 75)-. In addition to irregularities of this kind, deposits suffer from the disturbances which have taken place in the rock masses which contain them. Slight undulations of the strata are common, and when the disturbance has been greater, the beds are bent into arches and troughs, or anticlinals and synclinals. Further, a * A. von Groddeck, Die Lelire von den Lagerstdtten der Erze. Leipsic 1879, p. in. 88 ORE AND STONE-MINING. FIG. 76. lateral pressure may have been sufficient to cause great crumplings and contortions, and in places to invert the order of succession, in other words to make the newer beds lie under, instead of above, the older ones. When beds are much bent there is often a thickening in the anticlinals and synclinals, and a corresponding thinning in the connecting limbs. A bed may be so folded and crumpled as to lose its original sheet-like form in places, and assume the shape of an irregular mass. This may happen even with a coal seam.* The disturbances of the rocks may finally produce rents, accompanied by displacement, which are called faidts, heaves, throws, or slides. We will take the case of a bed (Fig. 76). AB is a seam which ends suddenly at B, whilst the continua- tion is found at a lower level, CD. The two parts of the bed must have originally been on the same horizon, but subsequently a fracture took place along the line XY, followed by a movement of one side or both sides. As a rule the portion of rock on the upper or hanging wall side appears to have slid downwards, or the under portion to have been thrust upwards. The rent may be clean, sharp, and narrow, with the shifted portions of rock touching each other ; or there may be a suc- FIG. 77. FIG. 78. cession of fissures producing a step-like arrangement of the seam (Fig. 77) ; frequently the cracks are filled up with clay, or there is a zone several yards in width composed of broken fragments and clay, produced by the attrition of the sides of the two rock masses (Fig. 78). Signs of rubbing may be seen upon the walls * J. Gallon, Lectures on Mining, vol. i. p. 63, and Atlas, Plate VIII., Fig. 44- MODE OF OCCURRENCE OF MINERALS, 89 FIG. 79. in the form of grooves and scratches, or polished surfaces known as " slickensides." A fault is of the same origin as a mineral vein ; the filling is due either to mechanical or chemical agencies, or to both combined, but does not happen to be worth working com- mercially. The prolongation of a valuable mineral vein may be unproductive on entering certain rocks, and will then be looked upon as a fault. Thus, some of the mineral veins of the Carboniferous Limestone in Flintshire appear to be continued as faults in the Coal Measures. The throw of a fault is measured by the amount of vertical displacement. If XY is a fault shifting a bed AB (Fig. 79), draw BE vertical and CF at right angles to BE. Then BF is the vertical dov, r nthrow, CF represents the horizontal displacement, and BC the shift along the line of dip. The study of faults is important be- cause the miner working the bed AB (Fig. 78), wants to know after reaching the fault XY where to find the continuation of the de- posit. The rule is to follow the greater angle. The angle ABY is greater than the angle ABX, and the missing part may be expected somewhere along the line BY. If the miner were work- ing from D to C, the same rule would apply, for the angle DCX is greater than DCY. This rule gives the direction of the throw, but affords no indi- cation as to its amount, which may vary considerably. If the beds are distinctly marked by lithological pe- culiarities or by fossils, the miner can obtain useful information by driving through the fault into the rocks upon the other side. Suppose, for instance, that a valuable bed of shale AB (Fig. 80) ended off suddenly ao-ainst a fault FG. A continuation of the workings in the direction AB comes upon a bed of conglomerate, which the miner recognises as one that is usually 40 feet above him. He can fairly conclude that the distance BE at right angles to the prolongation of DC will be 40 feet. As the respective dips of the bed and of the fault are known, the angle EBC can at once be ascertained and the distance BC calculated. The throw of a fault is not always the same ; it varies along the strike, and finally dies away altogether. This will be understood by making a slit with a penknife through a sheet of cardboard FIG. 80. 90 ORE AND STONE-MINING. or india-rubber, and pressing down one side ; the throw dimin- ishes from a maximum at C to nothing at A and B (Fig. 81). Change in the direction of throw may be due to the beds on FIG. 8 1. FIG. 82. one side of a fault being puckered or bent, whilst they are flat or dip evenly on the other (Fig. 82). The distance to which some faults may be traced is very great. The Gorze-Ars-Metz fault* extends from St. Julien in France, right across Lorraine to beyond the Saar, near Wacheren, a total distance of 53 miles (85 kilometres), and another fault in the same district is known for 28 miles (45 kilometres). The throw of a fault varies from a few inches to hundreds and even thousands of feet. Near a fault a bed is often found to dip more steeply, as if it had been bent before it broke. This is the case with the great iron ore bed of Lorraine.f The usual dip is very slight, only i to 2 1 in a hundred, but near faults it is decidedly more, and reaches 4 in a hundred. The rule that the portion of the hanging wall side has shifted downwards along the dip of the fault is not without exceptions, FIG. 83. FIG. 84. especially in localities where rocks are much bent and folded. Heim shows by a series of figures the various stages in the pro- duction of a displacement of this kind, which is known as a reversed or overlap fault (Fig. 83). Fig. 84 also shows a reversed fault. As mineral veins have been formed in regions where rocks have been broken and dislocated, it is only natural to expect that * Wandesleben, " Das Vorkommen der oolitischen Eisenerze (Minette) in Lothringen, Luxemburg und dem ostlichen Frankreiche." Festschrift tmd Verhandlungen Der IV. Allyemeine Deutsche Bcrgmannstay in Halle (Sadie.} Halle, 1890, p. 301. f Ibid. p. 301. MODE OF OCCURRENCE OF MINERALS. PLAN. they also should be affected by movements and shif tings of the earth's crust. Owing to the fact that veins are usually highly inclined, and that there is often much difficulty in deciding how the dislocated rocks fitted together before they were shifted, the vein miner speaks of faults in different terms to the bed miner. Instead of talking of doivntkrows and upthroifs, he looks at the shift produced sideways and calls it a heave. The miner driving a horizontal tunnel AB (Fig. 85) in a vein, comes into the fault XY at the point B, and finds that his vein ends off suddenly ; in order to regain it he is obliged to drive sideways in barren ground from B to C, where he meets with the con- tinuation along the line CD. The miner says that there has been a left- hand heave, because whether driving in the direction A to B or D to C, he finds the faulted portion to the left hand. It is evident in many cases from the striations upon the walls of the faults, that the displacement of the two adjacent rock masses took place, not along the line of greatest dip, but in a diagonal direction, causing a shifting sideways as well as downwards. Nevertheless, where beds or veins are not horizontal, a mere shift along the line of dip is suffi- cient to cause a heave sideways. This will be understood from Fig. 86. Let AB and CD represent two portions of the lode dislocated by the fault EF. The point B' corresponded originally with B, and the dislocation was caused by the simple sliding of B' along the line of dip of the fault. Here again the mincer would speak of the heave as taking place to the left. The subject of the heaves of lodes and beds has been elucidated by Schmidt,* Zinimermann t and others. Zimmermann's rule for finding the lost part of a vein on the other side of a fault is as follows : Lay down upon paper the line of strike of the lode and the line of strike of the fault (cross-course), and by construction ascertain the horizontal projection of the line of their intersection ; from the point where the cross-course was struck by the lode, draw a line at right angles to the strike of the former and directed to its opposite wall. Notice on which side of the line of * Theorie der Verschiebung alter er Gdnpe. Frankfort, 1810. t Die Wiederausrichtung venvorfener Gange, Lager und Flbtze. Darm- stadt and Leipsic, 1828. FIG. 86. 92 ORE AND STONE-MINING. intersection this perpendicular falls, and, after cutting through the cross-course, seek the heaved part of the lode on that side. Thus let AB (Fig. 87) represent, at some given depth, the line of strike of a fault or cross- FIG. 87. course dipping east, and CD the line of strike of a lode dip- ping south, and we will sup- pose that in driving from C to D, in a westerly direction, the fault has been met with at D. Knowing the dip of the lode and that of the fault, it is easy to lay down, on any given scale, A'B' and C'D', the lines of strike of the fault and lode respectively at a certain depth, say ten fathoms, below AB. The point D", where A'B' and C'D' meet, is one point of the line of intersection. Join D and D" and prolong on both sides. The line MN represents the horizontal projection of the line of intersection of the two planes. At D erect DE at right angles to AB, and directed towards the opposite wall of the fault. As FIG. DE falls south of MN, the miner, after cutting through the fault would drive in a southerly direction, and eventually strike the lode again at F. It will be at once understood that if the miner were following the lode from G to F, the perpendicular would lie to the north of the line of intersection, and following the rule he would drive in that direction, after cutting through the fault. When several faults dislocate lodes one after the other very great complications may arise. Fig. 88* is, fortunately for the miner, an unusual instance of a succession of faults. * J. W. Pike, " OQ some remarkable He ft res or Throws in Penhalls Mine," Quart. Jour. Geol tioc., vol. xxii. (1866), p. 537. ( 93 ) CHAPTER II. PROSPECTING. Chance discoveries. Adventitious finds. Uses of geology. Associated minerals. Surface indications : form, colour, gozzans, springs, indica- tive plants, burrows of animals. Shoading. Hushing. Piercing. Lode-lights. Altered vegetation and other indications. Old workings, slag heaps, ruins. Names of places. Divining-rod. Dipping needle. Qualifications of the prospector. Chance Discoveries. The number of discoveries of valuable mineral deposits by pure chance is very great. I will mention a few cases, mostly recent, taking the minerals in alphabetical order. Amber. Pieces of amber cast up on the shores of the Baltic after storms, no doubt were the first sources of supply of the mineral, and eventually led to a search for the parent beds. Cobalt. The cobalt ore recently worked in Flintshire was dis- covered in 1870, by Mr. Gage, who happened to test with the blowpipe some black matter which formed strings in the Carboni- ferous Limestone. Copper. The owner of a sheep run on Yorke's Peninsula, South Australia,* picked up some atacamite on the coast in 1859, and became convinced that there were deposits of copper ore inland. In 1860 he came across the workings of a wombat which had thrown out a quantity of this green ore in making its burrow. Pits were put down, and the great Wallaroo lode was thus dis- covered. Other lodes in the district were afterwards hit upon in the same way, or from green ore thrown up by some burrowing insect. Diamonds. The fate of South Africa has been wholly changed by the finding of diamonds. Mr. O'Reilly, a trader, describes his discovery in these words : "In March 1867, I was on my way to Colesberg, from the junction of the Vaal and Orange Rivers ; I outspanned at Mr. Niekerk's farm, where I saw a beautiful lot of Orange River stones on his table, which I examined. I told Niekerk they were very pretty. He showed me another lot, out of which I at once picked the ' first diamond.' I asked him for it, and he told me I could have it, as it belonged to a Bushman boy of Daniel * S. Higgs, " Some Remarks on the Mining District of Yorke's Peninsula. South Australia," Trans. It. Geol. 8oc. Cornwall, vol. ix. p. 127. 94 ORE AND STONE-MINING. Jacobs." Mr. O'Reilly then sent the stone to Cape Town for examination, when it turned out to be a true diamond, worth 509." The value of the diamonds produced annually far exceeds that of the gold of any one of our colonies. Gold. The story told of the finding of gold in California, in 1848, is that Marshall, who was superintending a sawmill, hap- pened to see something glittering in the mill leat. It turned out to be gold. He found more nuggets, and soon the discovery was noised abroad. In Australia the first discoveries of gold were by chance. The attention of Dr. Plassard was directed to the existence of gold in Venezuela from seeing some specimens in the possession of a native. Iron. Traces of soft haematite, noticed among the roots of an overturned tree, led to the discovery, in 1891, of the important Biwabikf iron mines of the Mesabi range, Minnesota. Nickel. The Sudbury nickel deposits were discovered in making a cutting for the Canadian and Pacific Railway, and even then it was the copper which first attracted notice. Phosphate of Lime. In May 1886, a geologist, M. Merle, took it into his head to analyse the sand of an apparently abandoned pit, which had been worked for centuries in order to give bricks a violet tint much esteemed in the neighbourhood. He found it contained 77^85 per cent, of phosphate of lime. This was the origin of the workings in the Upper Chalk at Beau val, in the department of the Somme.t The discovery of the phosphate beds of Florida was made in the autumn of 1889 by an orange-grower, who out of curiosity sent to a chemist a sample of the white subsoil of his grove; this turned out to contain 80 per cent, of phosphate. Quicksilver. The Redington Quicksilver Mine,|| in California, was discovered in making a cutting for a road. Silver. A man made a fire to cook his food and protect himself from the cold, near the site of Catorce,fl in Mexico, and in the morning found silver shining in the ashes. This was in 1775^ * T. Keunert, " Diamond Mining at the Cape," Official Handbook to the Colonial Exhibition. History, Productions, and Resources of the Cape of Good Hope. Cape Town, 1886, p. 178. t Winchell, Twentieth Annual Report of the GeoL and Nat. Hist. Survey of Minnesota, p. 157. Minneapolis, 1893. $ Statisque de V Industrie Miner ale en France pour I'annee 1886. Paris, 1888, p. 252. Ledoux, " The Phosphate Beds of Florida," Eng. Min. Jour., vol. xlix. (1890), p. 176. || Becker, " Geology of the Quicksilver Deposits of the Pacific Slope," Monographs of the U.S. GeoL /Survey, vol. xiii. p. 10. Washington, 1888. ^f Chism, " The Catorce Mining District," Eng. Min. Jour. , vol. xlviii (1889), p. 340. PROSPECTING. 95 and three years later another man pulled up a bush to throw upon his fire, and found native silver in the roots. Mining soon began, and between 1779 and 1812 the district yielded ore worth from thirty to forty million pounds sterling. Tradition relates that the famous silver mines of Potosi, in Bolivia, were dis- covered in a similar manner in 1538, by the accidental displace- ment of a bush which had small lumps of native silver among the roots. The existence of silver in the Province of Famatina, in the Argentine Republic,* was made known by a pure accident. Leita and Echavarria were making a journey, in 181 1, across the Andes, and during a terrible storm, took refuge in a cave, and there passed the night. In the morning they found that the stones they had put round the fire at night were white, and on further examination silver was plainly to be seen in them. Adventitious Finds. Search for one mineral often leads to the discovery of another. The working of veins for tin ore has revealed the presence of the decomposed granite which furnishes china clay. The finders of the Comstockt lode worked it at first for gold, being quite ignorant of the presence of rich silver ore. In the winter of 1858-59, some prospectors washed a panful of earth from a broad-topped mound which one of them had noticed previously. This gave gold to the value of fifteen cents, a high average return. They then noticed a gopher hole in the mound, and took up the earth which had been thrown up. This they washed, with satisfactory results, and at once staked out claims. Another part of the lode was discovered by some other prospectors, who had dug a hole in order to make a little reservoir for water. They chanced to wash some of the earth, and to their surprise found it rich in gold. The upper part (back) of the lode was then worked for this metal. They threw away bits of a black rock which they found mixed with the earth and yellow sand, and when, at a depth of 3 or 4 feet, they came upon a vein of the black mineral, they had not the least idea that it was valuable. Pieces, however, were carried away by curious visitors, and one was given to Mr. Melville Attwood for assay. He discovered that it was worth $3,000 per ton for silver and $876 for gold. The black mineral was sulphide of silver, and the yellow sand proved to be the chloride. The working of the Comstock lode for silver dates from this discovery, which was in June 1859. There are reasons for supposing that the original discoverers of the Comstock lode were two brothers named Grosh who had found a rich vein of silver in 1856. But one brother died from * Hoskold, La Republique Argentine, p. 19. f Lord, " Comstock Mining and Miners," Monographs of the U.S. Geol. Survey, vol. iv. pp. 34-55- J Op. cit. pp. 27-31. 96 ORE AND STONE-MINING. the effects of a slight accident, and the other soon after succumbed under the hardships he had undergone in crossing the snows of the Sierras in December 1857. The knowledge of this vein was then lost for a time. In 1885* some natives or Spaniards took to M. Bastide speci- mens of what they thought was calarnine from the top of Djebel Toumai'-Kebir, Department of Oran, Algeria. It turned out to be phosphate of lime. "When boring for rock salt in 1839 near Stassfurt,t the Prussian Government found brine with chloride of magnesium and chloride of potassium. Later, in 1852, they sank two shafts through the beds containing these minerals, without in any way recognising their value, in order to work the rock-salt underneath. However, it was not long before this mistake was corrected, and the potassium salts soon became the main object of the mining. The sub-wealden bore-hole near Battle, which was put down for general information concerning the underlying strata, met unexpectedly with a bed of gypsum, which is now regularly mined. The bed of salt in the Cleveland district was discovered in 1863 by a boring made for the purpose of getting water. The total area now proved is 20 square miles ; and if the approximate average thickness of the bed is taken at only 90 feet, it may be estimated to contain 115,200,000 tons of salt per square mile.+ A bore-hole was put down in Louisiana near Lake Charles on the New Orleans-Texas Railway in search of petroleum, and a rich bed of sulphur-bearing rock, 100 feet (30 m.) thick, was pierced unexpectedly. Owing to the watery .nature of some of the strata by which it is overlain, it has not yet been worked. According to a statement issued by the Broken Hill Proprietary Company, Limited, || the original claims of this productive silver mine were pegged off under the impression that the outcrop was that of a tin lode. The Sulphur Bank^f in California was originally worked for sulphur, and the fact of there being quicksilver was long unsuspected. Instances of valuable minerals passing unrecognised are common. It is related that the original proprietor of the site of Mount * Statistique de VIndustrie minerale en France, pour I'anme 1886. Paris, 1888, p. 285. t Filhrer zum vierten allgemeinen Deutschen, Bergmannstag.iSSg. Halle a.d. Saale, 1889, p. xxxiii. Marley, " On the Cleveland and South Durham Salt Industry," Trans. Fed. Inst. Af.E., vol. i. (1889-90), p. 342. Hivista del Servizio Miner ario, 1888, p. clxxxiii. || Report and Statement of Accounts for Half-year ending November 30, 1886. Melbourne, Victoria, 1886, p. 57. 1" Becker, op. cit. p. 10. PROSPECTING. 97 Morgan gold* mine used to sell some of the auriferous stone, which resembles pumice, as hearthstone for cleaning doorsteps. Geology as a Guide to Minerals. A knowledge of geology will often serve to guide the miner. Coal has been discovered in the south-east of England by very careful reasoning, based upon the geological structure of South Wales and Somer- setshire on the west and that of Northern France and Belgium on the east. M. Meugy,f Inspector-General of Mines, hearing of the dis- covery of phosphate of lime in the Lower Greensand of England, concluded that similar deposits might occur in the Cretaceous rocks of France. Search was made, and valuable deposits were found in 1852. Geology also affords the miner aid by enabling him to identify certain horizons in stratified rocks by their fossils. The valuable bed itself may not always be fossiliferous, but definite horizons above or below it may be recognisable, and so guide the miner in his explorations. Associated. Minerals. The existence of valuable minerals may be suspected from meeting with some of their common associates, and, even for the sake of its importance to the prospector, the subject of the paragenesis of minerals deserves careful study. The facts are specially marked in the case of tin ore. Cassit- erite is usually associated with minerals containing boron and fluorine, such as tourmaline, topaz, fluor-spar and lithia mica, and also with wolfram, chlorite, and arsenical pyrites ; masses of magnetic iron ore are frequently accompanied by rocks containing garnets, hornblende, and epidote. Zinc blende is a common hanger-on of galena, which likewise often has barytes in its train. Galena invariably contains silver, and frequently enough to enhance its value. The associates of gold in quartz veins are various metallic sulphides, such as iron pyrites, magnetic pyrites, copper pyrites, mispickel, galena, zinc blende, stibnite, tetradymite, and bis- muthine. Salt is accompanied by gypsum and anhydrite, and frequently has its habitat in red rocks. Mottura explains this by pointing out that when sea water is evaporated, the first precipitate is oxide of iron, that gypsum crystallises out next, and later the sodic chloride. S HBP ACE INDICATIONS. The indications which guide the prospector are precisely those upon which the geological sur- veyor depends in making his maps, viz., form of the ground, colour, nature of the decomposed outcrop, ordinary springs, mineral springs, indicative plants, altered vegetation, burrows of animals, old workings, slag heaps, ruins, names of places and old records. * W. H. Dick, A Mountain of Gold. Brisbane, 1889, p. 11. f Stat. Min. France, 1886. Paris, 1888, p. 280. G 98 ORE AND STONE-MINING. Form of the Ground. If the valuable mineral is harder or softer than the surrounding rocks, it will affect the manner in which the surface is sculptured by atmospheric agencies. Hard rocks will project in some way, soft ones will be cut into hollows, especially if they are impermeable. The outcrop of a hard bed will be denoted by a steep face or escarpment, and unyielding mineral veins project above the surface in the form of huge crags (Fig. 89). In parts of our country, these out- FIG. 89. crops have been worked away and are no longer apparent ; but lode- quartz blanched by weathering may often be seen standing up several feet above the surface on the Welsh hills, and the run of some lodes can be traced for a long distance by a succession of such outcrops. In the United States and in Australia this phenomenon is common. At the Great Western Quicksilver Mine* in California, the outcrop of the vein appears as a dike over 100 feet wide, and having precipitous sides in places 75 feet high. Some of the silver veins of Butte, Montana, crop out, according to vom Rath,f as great wall-like ridges of brown and black rock, which is quartz containing the oxides of iron and manganese ; the Rainbow lode stood up 20 feet above the surface. The Broken Hill lode at Silverton, New South Wales, was traceable for fourteen miles by the outcrop of huge black crags consisting of ferruginous quartz, brown ironstone, pyrolusite and other minerals, which in places rose to a height of 50 feet above the ground, and were 10 to 120 feet wide. Speaking of the outcrops of gold veins of the Hodgkinson gold- field of Queensland, Mr. R. L. Jack,J the government geologist, says, " they can be followed from hill top to hill top, forming at times insurmountable walls a hundred feet high ; as, for example, in the peaks west of Mount Tenison Woods. In other places denudation has left their remains on hill sides or hill tops in the form of huge cubes of quartzite, from which the surrounding soft rocks have crumbled away. These cubes stand up weird and solitary, like the * perched blocks ' of Alpine and Arctic lands." The tin lodes of San Jacinto in California are found in a country destitute of all vegetation except grass, and their black outcrops are said to be unusually distinct. * Luther Wagoner, " The Geology of the Quicksilver Mines of California," Eng. Min. Jour., vol. xxxiv. (1882), p. 334. f Neues Jahrb. f. Miner., Geol, u. Palaontologie, 1885, p. 162. J Handbook of Queensland Geology. London, 1886, p. 27. Benedict, "The San Jacinto Tin Mines," Eng. Min. Jour., vol. 1. (1890), p. 452. PROSPECTING. 99 The Great Quartz Vein of California has "a very conspicuous outcrop, forming the crest of the hills, so that it can be readily seen from a distance of several miles."* The " main reef " of auriferous conglomerate at Johannesburg, in the Transvaal, could be traced in places by the pebbles on the surface. Soft minerals like clay offer less resistance to rain, flood, and frost, are more deeply cut into, and give rise to hollows. Thus the bed of clay known as the Gault, occupies a depression between the hard and pervious beds of the Chalk and the Lower Greensand. The presence of the masses of decomposed granite which fur- nish china clay t is almost always indicated by a slight depression of the surface. The ore bodies in the Sierra Mojada, Mexico, are softer than the enclosing rocks, which often stand out when the ore has been worn away by weathering.* Colour. Colour is an important factor in the discovery of mineral deposits. Sometimes the ore itself has a distinct hue. When Gamier was exploring New Caledonia in 1863, he was struck by the special green colour of the rocks, and he found that it was due to coatings, veins, and lumps of a hydrous silicate of nickel and magnesium, which is now largely worked. Copper minerals will produce green, blue, and red stains, which catch the attention very quickly. Iron gives a red or brown colour, manganese a black ; lead may furnish a green, a yellow, or a white coating, cobalt a pink one, whilst cinnabar is the natural vermilion. Coloured minerals are often used as pig- ments by savages, and in this way may be brought to the know- ledge of the explorer. Gozzan. A mineral deposit near the surface is frequently so altered by atmospheric agencies that it bears little resemblance to the undecomposed bed or vein which will eventually be met with at a greater depth. A bed of hard shale will crop out at the surface as a soft clay ; but the most common cases of change are furnished by the conversion of sulphides into oxides or oxidised compounds, and the removal of some of the mineral in the form of a soluble sulphate. Thus iron pyrites, which is such a frequent constituent of mineral veins, is converted into hydrated oxide of iron, and a vein, originally consisting of iron pyrites and quartz, becomes a honeycombed brown and yellow rock, the removal of the iron pyrites in the form of a soluble sulphate leaving cavities which are only partly filled up by oxide. The ferruginous solutions which flow away stain and discolour the adjacent rock. * Whitney, The Auriferous Gravels of the Sierra Nevada of California. Cambridge, U.S., 1880, p. 46. t J. H. Collins, "The Hensbarrow Granite District." Truro, 1878, p. 7. Chism, " Ore Deposits of Sierra Mojada," Trans. Am. Inst. M.E., vol. xv. (1886-87), P- 549- ioo ORE AND STONE-MINING. The ferruginous outcrop of mineral veins has been noticed in all mining countries. In Cornwall it is called gozzan, and this term has been carried by the ubiquitous Cornish miner to other English-speaking countries, though in Australia we hear of iron- stone blows. In Germany the iron hat gives the proverb Es ist kein Bergwerk nie so gut, Es hat denn einen eisern Hut ; translated by the late Sir Warington Smyth as follows " A lode will ne'er cut rich and fat, Unless it have an " iron hat." In France the chapeau en far is the equivalent of the German expression, whilst the Italian miner, ascribing the cindery, burnt- up appearance to the action of fire, calls such outcrops bruccioni.* The Spanish term colorados has reference to the red tint due to iron oxides. In some parts of South America, such as the Argentine Republic and Bolivia, the word pacos is used for the oxidised ores. The nature of a gozzan varies naturally very greatly, not only in different districts, but also in different parts of the same lode. If the vein originally consisted very largely of iron pyrites, the gozzan will be mainly ochre and brown iron ore, often in botry- oidal and stalactitic forms. If quartz was present also, a cellular, cindery, cavernous, ferruginous rock is the result of the atmos- pheric weathering. Other metallic minerals will leave their traces. Galena be- comes changed into anglesite, cerussite, pyromorphite, and mime- tite. The sulphides of copper yield native copper, melaconite, cuprite, malachite, chessylite, together with phosphates, arseniates, and silicate of the metal, and sometimes the oxychloride or oxy- sulphide. Carbonate of manganese gives rise to black oxides, whilst argentiferous minerals furnish native silver, kerargyrite and embolite. Gold is unlocked from enveloping sulphides, and specimens of quartz may be seen from nearly every gold-field in which cubical cavities, left by the removal of iron pyrites, are partly filled up with ochre and delicate skeletons of the precious metal. Gold may exist in combination with other elements and be liberated by the weathering process. The depth to which the oxidising and leaching action proceeds is often considerable. In the Comstock lode f " the quartz is reddened and the iron minerals more or less oxidised to a depth of 500 feet, but it is probable that the lower ioo feet are chiefly * Zoppetti, Arte Mineraria. Milan, 1882, p. 85. t Hague, Mining Industry of the Fortieth Parallel. Washington, 1870, P- 75- PROSPECTING. 101 coloured by the percolation of the surface waters." Sometimes there is a sharp line of demarcation, sometimes a gradual passage, between the gozzan and the sulphides. In the sections of a mineral vein, Figs. 90 and 91, A, is the gozzan, showing itself occasionally by rough crags at the surface ; C, represents the undecomposed sulphides, and B is an interme- diate zone where the process of alteration is incomplete. At Huanchaca silver mine, Bolivia, the oxidised ores near the sur- face are called pacos, the transition oxysulphides mulatos, whilst the unchanged sulphides are known as metales frios. In the longitudinal section, Fig. 91, the alteration is shown as ceasing FIG. 90. FIG. 91. soon after the level of the bottom of the valley is reached, that is to say when the water no longer has an easy exit ; but cir- cumstances may bring about a system of circulation causing the rainwater to penetrate below this level, and then the gozzan will naturally extend to a greater depth. Gozzan is important to the miner not only because it is an indication of a lode, but also because the ore is sometimes more valuable from the decomposition of the sulphides. This is specially the case with gold and silver. Gold, as already explained, is set free from a tight covering of pyrites, or possibly from a state of combination with some other element, and can now be easily caught by quicksilver. The miner speaks of the ore as " free- milling " on this account. Silver, when brought into the native state, or converted into chloride, is likewise readily extracted by amalgamation. In the case of argentiferous lead veins, chloride of silver mixed with carbonate of lead and oxide of iron is. more acceptable to the smelter than a complex mass of metallic sulphides. The removal of zinc blende by atmospheric agencies, no doubt through its conversion into a soluble sulphate, is of much importance; for the ore is thus freed from an ingredient which gives trouble in the lead furnaces, and which cannot be satisfactorily separated mechanically when very intimately mixed with galena, iron pyrites and other sulphides. Furthermore the removal of some io2 ORE AND STONE-MINING. of the heavy worthless ingredients, whilst the silver remains fixed as insoluble chloride, raises the tenour of the ore in the precious metal. Lastly, the upper parts of the vein are more cheaply worked from their softness, and the small cost of pumping and winding. Under these circumstances the fact of a mine sometimes becoming less profitable, or wholly un- profitable, when the zone of sulphides is reached will easily be understood. These points must not fail to be considered by the miner ; he must recollect that the zone of the oxidised ores will be succeeded by sulphides, more costly to work, and sometimes requiring totally different treatment. Gozzans should be carefully assayed, especially for silver. Instances could be given of gozzans having been stamped and worked for gold, to the utter neglect of the silver which was by far the more valuable ingredient. In Cornwall gozzans of copper lodes have been worked for tin ore, which was originally enclosed in or mixed with copper and iron pyrites. Owing to its insolubility it resisted the weathering which carried away the copper and some of the iron in solution. The Anaconda mine* at Butte, Montana, now famous for its enormous output of copper, was originally bought as a silver mine. For a depth of 400 feet the ores contained no notable quantity of copper ; this metal had been carried off in solution, whilst the silver, converted into an insoluble chloride, was rendered proof against any further action of rainwater. Deposits of cupreous iron pyrites may have the copper and sulphur so completely removed that the remaining oxide of iron is worked as an ore of this metal.f The iron ores of Bilbao are the decomposed portions of deposits of the carbonate. The weathering has had two useful effects ; it has raised the percentage of iron, and it has lowered the amount of sulphur by decomposing the iron pyrites, which occurs in small quantities in the unaltered ore. The seams containing native sulphur in Sicily often show no trace of that element at the surface, as the sulphur-bearing limestone weathers into a soft, white, grey, or yellowish white, granular or pulverulent variety of gypsum, called briscale$ by the miners, and considered by them to afford important indications concerning the bed itself. In this case the sulphur has gradually become oxidised and has combined with some of * Douglas, "The Copper Eesources of the United States," Trans. Amer. Inst. M.K., vol. xix. (1890-91), p. 679. t Moxham, "The 'Great Gossan Lead' of Virginia/' Trans. Amer. Inst. 31.fi., vol. xxi. (1892), p. 134. Lorenzo Parodi, Suit' estrazione detto Solfo in Sicilia. Florence, 1873, pp. 7, 24 : and L. Baldacci, Descrizione geoloyica dclV Isoki di Sicilia. Home. 1886 p. 106. PROSPECTING. 103 the lime to form a sulphate ; and it is only natural to suppose that the thicker and the richer the original bed was, the greater will be the amount of briscale produced, and the more apparent its signs on the surface. Each mineral therefore has to be considered separately, and I may mention a few other special cases. Veins of asbestos have been discovered by noticing a white powdery substance in cracks in the rocks, which led to fibrous asbestos when worked. Steam-puffs are indications of the small superficial deposits of sulphur in volcanic districts ; and here sight is aided by the sense of smell, for I recollect remarking the odour of sulphuretted hydrogen long before I rode up to some sulphur banks in Iceland. In Tuscany the natural steam-puffs which yield boracic acid are plainly visible, and bore-holes * are also put down to produce them artificially where the rocks are hot at the surface, and so give hopes of tapping vapour at a shallow depth. Some of the successful bore-holes for carbonic acid gas in the Eifel, Germany, were planned on account of natural emanations of the gas in the immediate vicinity. Attention has been directed to petroleum by a layer or an iridescent film of the oil upon pools of water, and the odour is sometimes perceptible for a long distance. Off Baku, on the Caspian, even the sea is sometimes covered with an oily film of petroleum. Brine springs point to salt, chalybeate springs to iron, but not necessarily to deposits of any commercial value ; the same may be said of water impregnated with sulphuretted hydrogen as an indication of native sulphur. Springs of ordinary water may be expected to appear where a pervious bed rests upon an imper- vious one, so that the outcrop of a bed of clay under sandstone is often denoted by a succession of springs, in addition to the change in the form of the ground. Even when the valuable deposit presents no striking outcrop, it may be followed by observing some more marked attendant. Thus the " red bar "f of the Johannesburg district, is a bed of dark red slate which is seen protruding above the surface, a little to the north of the gold-bearing conglomerate, for a distance of 20 miles along the strike. In California a dark opaline or chalcedonic rock, known to the miners as " quicksilver rock," is associated with the deposits of cinnabar, and owing to its comparative hardness stands out sometimes as a projecting outcrop. Indicative Plants. As plants derive part of their nourish- * Jervis, 1 tesori sotterranei dell' Italia, vol. ii. p. 428. t Quart. Jour. Geol. /S'oc., vol. xlvi. (1890), Proceedings, p. 4. J Becker, ' Geology of the Quicksilver Deposits of the Pacific Slope, Monograph of the U.S. Geol. /Survey, vol. xiii. p. 360. Washington, 1888. io 4 ORE AND STONE-MINING. ment from their roots, and as different plants require different foods, it is only natural to suppose that a change of soil causes a change in the vegetation. Beds of porous limestone let the rain soak down at once, the soil is shallow, and the foothold for trees is not so good as in the case of clays. Thus the chalk hills are bare, and the Weald clay is the home of the oak from a mechanical reason, in addition to the chemical one of nourishment. Clays will retain water and naturally be the habitat of rushes and other moisture-loving plants. The effect of salt in the rocks is especially marked, and Gatzschmann* gives a long list of plants which either flourish best when getting salt, or cannot exist without it. The flora of Monte Catini,f in the province of Lucca, well known for its brine baths, resembles that of the coast, although 24 miles away from the sea, and separated from it by the Pisan Hills. My friend, Mr. S. Herbert Cox, tells me that the run of the deposit of alunite which he is working in New South Wales, is marked by a lighter green in the colour of the leaves of the eucalyptus trees which cover the district. He has also noticed in New Zealand that the Karacca trees growing upon limestone have darker leaves than those growing upon slate. A band of limestone can be traced in this way. The subject of indicative plants is dealt with in an interesting paper by Raymond,! who gives some additional details concerning the calamine pansyof Rhenish Prussia, mentioned by Gatzschmann. This pansy, called by botanists Viola calaminaria, is peculiar to the calamine-bearing hills near Aix-la-Chapelle, and in West- phalia. The blossoms are almost always yellow ; but on the borders of the zinc regions some are light violet, or bluish, or mixed yellow and blue, and are supposed to be hybrids between V. calaminaria and the ordinary wild pansy, V. tricolor. Analysis has revealed the presence of zinc in the plant and in the sap. This plant is said to have been recognised at Horn Silver Mine in Utah, the ore of which contains zinc blende. The lead plant, Amorpha canescens, Nutt., is a low shrub, i ft. to 3 ft. high, whitened with hoary down. The plant is most abundant in Michigan, Wisconsin, and Illinois, and miners believe that it flourishes best where lead ore exists in the soil. Dr. F. Stapff found that prospectors for phosphorite, in Estremadura were guided by a creeping plant with bell-shaped flowers, Convolvulus althceoides ; in Montana the Erigonum * Die Aufsuchung und Untersuchung von Lagerstatten nutzbarer Miner alien. Leipsic, 1866, p. 321. t Jervis, Guida (die deque minerali d'ltalia. Turin, 1868, p. 12. I Trans. Am. Inst. M.E., vol. xv. (1886-87), p. 647. PROSPECTING. 105 ovali/olium, Nutt., is looked upon as an indication of silver ore in the vicinity. Animal's as Indicators. Animals also may occasionally render services to the prospector. I have already mentioned the case of the wombat, by whose burrows copper was discovered in South Australia. Prospectors seeking for tin lodes in Victoria* have also been guided to success by the ore thrown out from decomposed dykes by this animal. Ledouxf says that a useful indication of phosphate of lime in Florida was furnished by ant- hills and gopher holes, which showed small whitish grains of the mineral in the earth. GatzschmannJ mentions cases of the discovery of valuable ores by the scratchings of the beaver, the bear, and the marmot, as well as by the wallowing of pigs ; he also brings forward in- stances in which the first indications of mineral wealth were afforded by stones kicked up by a horse, or tossed out by a bull, or lying in the nest of a vulture, or found in the crop of a grouse. At the Caratal diggings in Venezuela, a bird called the minero was thought to mark the site of gold-bearing gravel. I often heard its notes when passing pits where gold was being obtained, and it is possible that it preferred certain trees which grew upon the old alluvia. In fact, as so many animals obtain their food from special plants, it is evident that the fauna dependent upon the flora must be affected indirectly by the minerals of the soil. The special case of there being more genera and species of snails in a limestone country is a case in point. Lastly, the tracks of animals may lead to salt springs which they frequent. Sheading. The prospector seeks * for natural sections of the rocks such as occur in cliffs, or in river valleys and their tributary gullies and gorges. He examines the materials constituting the river beds, especially when the water is low in the dry season, often digging up and washing portions in a pan or in a batea, in order to ascertain whether they contain traces of the heavy ores or metals. If, while prospecting in a valley, he discovers stones that have the appearance of having once belonged to veins or other valuable deposits, he endeavours to trace them to their source, and is, perhaps, rewarded by finding similar fragments, but less water- worn, as he goes up the stream. Further on he may come upon large blocks of veinstuff lying about, and finally find the veins laid bare in a gorge, or at the bottom of a brook, or possibly pro- jecting above the soil in the form of huge crags of quartz in the manner already described. * Victoria, Reports and Statistics of the Mining Department for tlie Quarter ended March 31, 1890, p. 15. Melbourne, 1890. t A. K. Ledoux, " The Phosphate Beds of Florida," Etuj. Miii. Jour., vol. xlix. Feb. 1890, p. 176. Op. cit. p. 311. io6 ORE AND STONE-MINING. Loqse pieces of veinstuff found lying about on the surface are known in Cornwall as shoad-stones ; and sheading is the term given to the process of tracking them to the parent lode. If the prospector has ascertained the existence of a lode by shoad-stones, and has some idea of the position of the outcrop which lies concealed under the soil, he proceeds to dig trenches across the presumed line of strike, until he hits upon the back of the lode. When the covering of soil is too deep for trenching, a little shaft is sunk, and a tunnel is driven out at right angles to the supposed course of the vein. Loaminy in Australia corresponds to sheading. The prospector washes earth from the base and slope of a hill till the specks of gold are pretty frequent, and then endeavours to trace the gold uphill to the reef that furnished it. When he can no longer get gold by washing he concludes he has gone past the outcrop of the reef, and he proceeds to search for it by trenching. Reefs have been discovered in this way which showed no surface indication whatever.* Hushing.t Hushing consists in causing a stream of water to rush down a hillside, and cut a ditch through the soil, which will lay bare the outcrops of veins, if any exist. A reservoir is made at some suitable spot on the high ground, and a shallow gutter is dug down the slope along the line which it is pro- posed the stream should take. The water is allowed to run down gently at first, and then as a torrent, which scours out a trench to the solid rock. An examination of the trench and of the stones washed out of it may result in the discovery of a vein. Piercing. In some special cases when the mineral lies very near the surface, and is either harder or softer than the surround- ing rock, the searcher makes use of a sharp pointed steel rod, which he thrusts into the ground. The well-known French J burr-stones, lying in soft sand and clay at a depth of 10 to 18 feet, are found in this way ; whilst in the Isle of Man superficial pockets of umber in the Carboniferous Limestone are detected by the ease with which the rod runs down. Kauri gum, a semi-fossil resin of New Zealand, which occurs in lumps of about the size of a hen's egg a few inches below the sur- face in the high ground, and a few feet in the swamps, is sought for by a similar tool. Mr. Lawn informs me that in the Furness district a pointed iron rod is occasionally used in searching for shallow deposits of haematite, lying within 6 or 8 feet of the surface. The miner examines the point of the rod after thrusting it through the thin * "The Gold-fields of Victoria," Reports of the Mining Registrars for the Quarter ended March 31, 1888. Melbourne, 1888, p. 68. t Williams, Natural History of the Mineral Kingdom. Edinburgh, 1789, vol. i. p. 370. + Gallon, Lectures on Mininy. London, 1881, vol. ii. p. 41. PROSPECTING. 107 covering of soil, and if he finds it to be red, he concludes that there is iron ore underneath. If the indications are sufficient, he sinks a little pit and begins to work the ore. The valuable bed of phosphatic nodules in South Carolina * is much harder than the overlying sand and clay ; the prospector carrying a steel rod works it down, until he meets with the resist- ing stratum. He notes the depth, which is under 15 feet, as no phosphate is at present worked deeper than that, and after walking on 100 feet further forces the rod down again. By thrusting down the rod at regular intervals in this way, and noting the results, he obtains a general idea of the lie of the phos- phate bed, and proceeds to make a more minute examination by sinking exploratory pits, 10 feet by 5 feet, at intervals of 500 feet. The phosphate rock laid bare is taken out, carefully sampled and analysed, and in this way a very fair estimate can be made of the yield of a given area. The process of testing a bed of mineral by pits is sometimes carried out on a very extensive scale. According to Winchell $60,000 have been spent in mere explorations at the Biwabik Iron Mine,f in the Mesabi Range, Minnesota ; but in this case the pits were practically small shafts, many of which exceeded 100 feet in depth. Lode-lights. Appearances of flame above mineral veins are said to have been seen, and at all events are sufficiently well estab- lished to have received a special name, " lode-lights," in Cornwall. It is possible that a will-of-the-wisp (phosphoretted hydrogen) may have been produced occasionally by the action of organic matter and water upon phosphates, which are so common in the upper parts of mineral veins. Marsh-gas is known in the workings of some lead lodes, and may have occasionally issued in sufficient quantity to produce flame when ignited accidentally. Altered Vegetation and other indications. One hears of differences in the appearance of the vegetation along the line of mineral deposits, of places where the snow will not lie in the winter, and of vapours hanging over the ground. Though some writers refuse to put any value on these indications, they should not be entirely overlooked, because the outcrop of a lode, of different nature and texture to the surrounding rocks, may readily cause the phenomena just mentioned. One need only look at the rubbish-heaps of some mines, especially those yielding pyrites, which remain year after year bare and barren, to understand the blighting and withering action of the products of decomposition of some minerals upon vegetation, It is only natural to suppose that * Wyatt, The Phosphates of America. New York, 1891, p. 49. t "The Biwabik Mine," Trans. Amer. lust. M.E., vol. xxi., 1892-3, p. 951 ; and Geol. and Nat. Hist. Survey of Minnesota. Twentieth Ann. Hep. for the year 1891. Minneapolis, 1893, p. 156. io8 ORE AND STONE-MINING. grass would grow less luxuriantly upon a wide pyritous vein than upon adjacent slate, and that a decided streak of altered colour and growth would be visible upon the turf. A very simple experiment will convince the student more readily than the mere statement. Spread a thin layer of earth upon a tray, and imitate the outcrop of a lode by scraping away some of the earth and re-placing it by powdered iron pyrites or marcasite. Now scatter mustard seed over the surface, and water frequently. In the course of a few days there will be a crop of mustard on the earth, but the track of the pyrites will be marked by a bare streak on which the seeds have been killed by sulphate of iron formed by its decomposition. The rapid disappearance of snow on the outcrop of a lode has been noticed at Ducktown Mine, Tennessee,* among other places. The oxidation going on in a pyritous lode near the surface must produce a certain amount cf heat, which would make the outcrop of a lode warmer than the adjacent rock ; but one need not have recourse to this hypothesis in order to account for phenomena of this kind. Mineral veins are often channels along which under- ground waters circulate ; this water may come near to the surface in places, or even issue forth as a spring, and the proximity of the comparatively warm water may keep the outcrop warm enough not to freeze. In a porous cavernous gozzan it is easy to imagine the existence of slow currents of the air which would have the same effect. The fact of a vein often being a channel of water will also explain the rising of vapours from lodes under certain favourable conditions of the atmosphere. Where the surface is cultivated and the natural springs are tapped by adit levels or other mine workings, these appearances cannot be looked for to any great extent ; and it is not unlikely that the old miners, who have handed us down traditions con- cerning the signs of mineral veins, were keener observers of nature than some of their successors, just as the savage may be guided by marks which do not catch the eye of the civilised traveller. Old Workings, Slag Heaps, Ruins. Signs of old workings, such as pits and rubbish-heaps, often tell useful tales. When workings were shallow, miners put down shafts in close proximity, and the line of a series of shafts and rubbish-heaps will give a fairly correct idea of the strike of a lode. The rubbish-heaps will show what was the ore worked, and with what it was asso- ciated. It even happens that mining refuse, thrown away as worthless in the days when dressing appliances were crude and rough, will pay for being worked over again. On the other hand it is not safe * Wendt, " The Pyrites Deposits of the Alleghanies," Encj. Min. Journ., vol. xli. (1886), p. 408. PROSPECTING. 109 to conclude that, because it paid to work a mine some centuries ago, the same ore will yield a greater profit or even be worth working nowadays. The change in the value of the precious metals, and the change in the remuneration of the labourer, must be duly weighed before a decision can be arrived at. It is important to ascertain why the old mines were abandoned. If no good reason, such as a sudden inrush of water, or the break- ing out of a great war, for instance, can be assigned for the stop- page, it is usually safe to assume that no great riches have been left in sight ; statements to the contrary must be very carefully sifted. Minerals that were at one time worthless or even regarded as obnoxious, such as nickel and cobalt ores, or zinc blende, become valuable by the discovery of new or improved processes of manu- facture or smelting. An instance of this kind has occurred quite lately. Some forty years ago the outcrops of beds of impure car- bonate of manganese in North Wales were worked for the black oxides, the gozzans, in fact, which had been produced by the weathering of the deposit near the surface. The undecomposed carbonate was at that time of no value and was carefully separated by cobbing and rejected ; and the workings had to be abandoned when the black oxide diminished in quantity at a shallow depth, and was replaced by unweathered ore. Owing to the use of ferro- manganese in making steel, the carbonate can now be utilised, and the ore is regularly mined and sent to the blast furnaces to be smelted with iron ore. On the other hand the discovery of a new process may be the means of causing a mine to be unprofitable. The discovery by Weldon of a method of regenerating the oxide of manganese used in making bleaching powder, seriously affected manganese mining by lessening the demand for the ore. Old mine. plans, reports, and deeds should be consulted when available ; and information should be sought from official geological surveys and mining records when they exist, as they do in this country. A prospector told me a few years ago that he missed securing some manganese properties in North Wales, from not being aware that a government geological map of the district had been published, showing some of the outcrops of the manganiferous bed. Slag heaps afford indirect evidence of mining, and like old rubbish-heaps may occasionally be worth smelting. The most notable instance of late years has been the profitable treatment of such heaps at Laurium, in Greece. Ruined cities, or other indications of a country having been more thickly populated, are sometimes adduced as proofs of its mineral wealth. Where it is possible to show, from remains found in the towns or encampments, that the inhabitants were engaged in mining or smelting operations, the prospector may fairly lay stress no ORE AND STONE-MINING. upon evidence of this kind. It has often been supposed that some of the old entrenchments in Cornwall were made for the protec- tion of diggers or smelters of alluvial tin ore ; and after the careful explorations of Mr. Theodore Bent at Zimbabwe, in Mashonaland, most persons will be disposed to agree with him that this old city and its fellows owed their existence to gold mining. Names of Places. Local names may sometimes supply in- formation, either by denoting some natural feature connected with the deposit, or by recording in some way the existence of mine work- ings. They will be found in all languages, and I need only give a few instances. " Cae Coch," near Trefriw, in Carnarvonshire, means the " red field," from the chalybeate springs, which are due to the existence of a bed of iron pyrites now being worked. " Graig Goch " or " red rock," a name which is not uncommon for mines in Wales, denotes no doubt that the vein was discovered by a red ferruginous outcrop, and so does the name " Fron Goch " or " red breast." Red Mountain, near Birmingham, Alabama, owes its name to the outcrop of an important bed of iron ore. " Glasdir," meaning " blue ground," is the name of a copper mine in North Wales. I cannot help suspecting that the locality was so called in consequence of the blue colour given to rocks or stones by coppery minerals derived from chalcopyrite near the surface. " Balmy nhir " or the " diggings at the long stone," denotes work- ings for tin in the neighbourhood of a " menhir " or erect stone in Cornwall. Sometimes the substance is named, as in the words Tincroft, Stahlberg (steel mountain), Porto Ferraio (iron port) in Elba, Gebel Zeit (oil mountain) on the shores of the Red Sea, Yenang-yaung (Creek of oil), the site of the petroleum wells in Burmah. The names Leadhills (Scotland), Bleiberg (Germany), and Gebel-el-Kohol (Tunis), all have the same signification, and have been given from the existence of workings for lead ore. " Al maden " means *' the mine," and turning from Spain to our own country, we find " Minera," near Wrexham, with a similar signification given in this case by the Romans, instead of the Moors. The Smoky Mountains,* in North Carolina, were called by the Indians " Unaka," from their word " Unakeh," meaning " white," because they obtained white kaolin from them. Salt is indicated by the prefix " Sal," " Salz," or its equivalent " Hall," in numerous names of places. The German word for miner, "Bergmann" i.e., mountain man or highlander reminds us that the old ore-seekers were hillmen, and found their treasures among the mountains, and we constantly find the word " Berg " (mountain), or its equivalent in other languages, forming part of the names of mines or mining towns. Schneeberg, Marienberg, Freiberg, in Saxony, are instances, and of recent date we have Mount Morgan in Queens- * W. B. Phillips, "Mica Mining in North Carolina," Encj. Min. Journ., vol. xlv. (1888), p. 398. PROSPECTING. in land, and Broken Hill in New South Wales. In the list of copper mines of South Australia* I find no less than twenty-six names of mines beginning with " Mount," in addition to others containing the word " hill " or " knob." Other names refer to mining or smelting operations. The village of Pestarena, near Monte Rosa, was evidently so called from the crushing of gold ore in the days of the Romans. " Cinderford," in the Forest of Dean, points to old heaps of iron slag, and such a name as " hammer pond," in the Weald of Kent and Sussex, likewise tells us of iron working in days gone by. But no stress should belaid upon names ; they afford at most an indica- tion of the existence of a mineral, without any evidence of its value at the present day. Divining Bod. Belief in the divining rod, or dowsing rod, has not died out completely even in Cornwall, where one still FIG. 92. meets with educated persons who profess to be able to discover mineral veins by the dipping down of the forked twig when they walk across them. Fig. 92, reduced from Agricola,f shows old German miners searching for veins with the rod. Dipping Needle. In the special case of magnetic iron we have a safer guide. In Sweden a magnet, suspended so that it can dip * H. Y. L. Brown, "A Record of the Mines of South Australia." Adelaide, 1890. t De re Metallicd, Basle, 1556, p. 28 ; and Brough, " Cantor Lectures on Mine Surveying," Jour. Soc. Arts, vol. xl. (1892), p. 803. 112 ORE AND STONE-MINING. FIG. 93. in any direction, is regularly used for tracing masses of magnetic iron ore, even when concealed by some thickness of drift or some depth of water; when the lakes are frozen over in winter, this kind of pro- specting is easy. The miner carries his compass care- fully over the ground, and on approach- ing magnetic ore the needle dips towards it ; the amount of dip increases, until at last, when standing directly over the deposit, the needle becomes vertical, and remains so as long as there is a strong mass of ore underneath it. The boun- dary of the deposit can thus be laid down on a map with some degree of accuracy. The modification of the Swedish dipping needle shown in Fig. 93, borrowed from Brough,* has been adopted in the United States. Improved methods devised by Brooks, Thalen, and Tiberg are described by the same author. Qualifications of the Prospector. From the above observations it will be seen that the miner is greatly aided in his search by a variety of natural indications ; but in a new and unsettled country the physical difficulties of travel are often so great, that strength of body and the capability of supporting fatigue and hardships become some of the most important qualifications of the prospector. He should have a general knowledge of geology, and understand mineralogy sufficiently to recognise all the common and valuable minerals and their ordinary associates, and to confirm his opinion by simple tests. The pick, shovel, and pan should be handled with ease, as well as the rifle and the gun. Keen and good eyesight is a sine qua non ; a myopic prospector would fail to recognise natural features, and a colour-blind person would not be struck by important differences of tint. * The mode of discovering minerals by boring is a subject of so much importance that it requires a separate chapter. * A Treatise on Mine Surveying. London, 1891, p. 261. CHAPTER III. BOEING. Uses of bore-holes. Methods of boring holes: I. Boring by rotation ;. Auger ; Diamond drills. II. Boring by percussion with rods ; Iron rods, wooden rods ; Driven wells. III. Boring by percussion with rope; American system; Mather and Platt's system. Surveying bore-holes. The uses of bore-holes are numerous : ' i. To reach a mineral deposit by a small hole and ascertain its nature,, depth from the surface, thickness, dip, and strike, with the object of working it if possible. 2. To ascertain the nature of the subjacent rocks for engineering pur- poses, such as their suitability for railways, canals, locks, sewers,, or foundations of bridges and buildings. 3. To obtain liquids, such as ordinary water, mineral water, brine or petroleum, which either rise to the surface, or have to be pumped up from a certain depth. 4. To make absorbent wells in dry and porous strata. 5. To obtain gases, such as natural inflammable gas, carbonic acid gas, or vapours containing boric acid. 6. To drain off gas from rocks, and water or gas from mine workings. 7. To make passages for conveying power into underground workings by steam, water, wire-ropes, or electricity. 8. To put signal wires or speaking tubes into underground workings. 9. To introduce cement into unsound foundations in order to strengthen, them, and also into mine-workings in order to dam back water. 10. To sink holes for lightning conductors, house-lifts, or piles. u. To sink mine shafts. The methods of boring holes for these purposes are : I. By rotation. II. By percussion, with rods. III. By percussion, with ropes. I. BORING BY ROTATION. Auger. Soft rocks, such as clay, soft shale, sandy clay, and sand can be bored by an open auger (Fig. 94), like the well-known carpenter's tool. The mode of working consists* in twisting the tool round by means of a cross-head or spanner, and lengthening it as the hole is deepened. The lengthening rods are made of wood or iron, the iron ones being ij inch gas-pipe, with screwed pin * Darley, " Artesian Wells," Engineering, vol. xxxix. (1885), p. 683. u OKE AND STONE-MINING. and box ends welded on. Even when iron rods are used, some made of pine, 4 inches by 4 inches, are added in order to take off part of the heavy weight by their buoyancy in water. For raising the rods an iron or wooden derrick is employed, such as is FIG. 94. FIG. 95. shown in the figure 95. It is 30 feet high, so as to give room for pulling up a rod of the usual length of 25 feet, which is drawn up by means of a crab-winch with a i J inch iron or steel wire rope. The winch is worked by hand or horse-power as required. The top rod is made of square iron, and the cross-head or capstan spanner can be fixed to it at the height most convenient for handling. or THE UNIVERSITT n6 OEE AND STONE-MINING. FIG. 97. The process of boring consists in turning the rod by two men at the capstan until the working tool has filled itself ; it has then to be drawn up and emptied. In drawing up, each rod has to be unscrewed and taken off, and the process is reversed when the tool, after having been cleaned out, is again lowered. In favourable strata holes are bored 400 feet deep at the rate of 25 feet a day by this method ; it is obvious that, owing to the time occupied in raising and lowering the rods, the first part of the boring is performed at a much greater speed than the last. In order to obviate the loss of time which ensues in raising and lowering the rod, for the purpose of extracting the contents of the auger, a current of water may be sent down through the hollow rod, and made to ascend in the annular space be- tween it and the side of the hole with sufficient velocity to carry up the debris. Fig. 96, again borrowed from Barley,* shows the derrick and general arrangement of the plant : a is the boring rod made of 2^- inch (in- ternal diameter) gas-pipe or lap-welded iron pipe, in lengths of 25 feet. The separate rods are joined, as shown in Fig. 97, by screwed spigot and socket connections which are riveted on. The short topmost piece of rod b (Fig. 98), carries the chamber c, at the base of which the head of b can revolve freely. On the same rod b is keyed the spur-wheel d. This is actuated by the pinion e upon the vertical shaft f, which re- ceives its motion from the horizontal shaft h (Fig. 96), through a belt and the mitre wheels g. The boring rod is driven at a speed of 80 to 100 revolutions per minute. It is easy to under- stand from the figure how the rope drums j are worked from the same shaft h at slow or high speed by using one or other of the two clutches upon this shaft. Water is pumped into c by a hose, descends the rod, and passing through the bit ascends with the sludge and chips of rocks. As the bit and rods descend, the carrier under the spur-wheel d follows them, and also the pinion e, which is loose upon the square shaft f. Fig. 99 represents a favourite form of cutting tool or boring bit, which begins by making a small hole and then speedily enlarges it to the full diameter. As the lining tubes are usually 7 inches in diameter, the annular space between the tube and the boring rod is large, Op. tit. p. 684. BORING. 117 and this is diminished by adding a lagging of wood (shown in Fig. 97) for the purpose of increasing the velocity of the upward current and so promoting the discharge of the debris. The rapidity with which some holes are bored by this machinery is considerable. Mr. Darley mentions that a hole had been bored FIG. FIG. to the depth of 500 feet, and cased all the way in n^ days, including the time occupied in putting up the derrick. Another rotatory method for sinking wells or exploring in soft or moderately hard ground consists in revolving the casing or lining tube, which is shod with hard steel teeth,* whilst a stream of water is forced down through it ; the water ascends in the narrow annular space between the tube and the sides of the hole. The core is gradually washed away by the descending current, and the inventors claim that any clay carried up by the water forms in time a protecting shell to the sides of the bore-hole, if composed of very loose strata. They even send down clay, chaff, bran, or cement by the tube for the express purpose of its making a resisting lining shell. In the alluvium of the Mississippi at New Orleans a 7 -inch well was bored in this manner 500 feet deep in 48 hours. For boring holes not exceeding 40 or 50 feet ( 1 2 to 1 5 in.) in depth, which may be required for geological surveys or for investigating shallow-lying deposits, a convenient portable set of tools has been arranged by Messrs. Van den Broeck and Kutot.f It consists of the following parts : (i) a series of rods 4 feet i inch (1*25 m.) long, which can be put together by screw joints; (2) either a chisel cutter or a twisted auger, for doing the actual boring ; and (3) a handle which is attached to the topmost rod. As accessory .* Encyclopedia of Well-Sinking Appliances. The American Well Works, Aurora, Illinois, U.S.A., 1886, p. 183. t " Un nouvel appareil, portatif de sondage pour reconnaissance rapide du terrain," Bulletin Soc. Beige de Geologic, tome ii. (Annee 1888), 29 Mai. n8 ORE AND STONE-MINING. FIG. ioo. parts, there are spanners for unscrewing the rods, a key for support- ing the rods during this operation, and a second handle which can be fixed on any part of the line of rods if more force is required for the work. By a very ingenious clip, each joint can be so fixed that it cannot become unscrewed during the process of boring. The diameter of the large auger is if inch (45 mm.) and the cutting part has two wings which are of service in penetrat- ing the ground. The chisel is used for hard seams, such as ironstone, grit, and beds containing fossils or pebbles ; like the auger, it is if inch across. The apparatus is very portable, for no part is more than 4 feet i inch long ; each rod weighs 4*4 Ibs. (2 kil.), and the total weight of all the plant required for making a boring 40 feet deep is only 64 Ibs. (29 kil.). Diamond Drills. The most important kind of boring by rotation is done with the diamond drill. The working part of the drill consists of the so-called crown, which is a short piece of tube made of cast steel, at one end of which a number of black dia- monds are fastened into small cavities. The crown is screwed on to wrought-iron pipes, which constitute the boring rod. This is made to rotate, and the result is that an annular groove is cut at the bottom of the hole, leaving a core which often breaks off of itself, is caught by a little shoulder, and brought out with the rod (Fig. ioo).* In places where it is not necessary to make any verification of the rocks traversed, the crown may be arranged with diamonds in the centre also, so that the whole of the bottom of the hole is ground away. The debris in either case are washed away by a stream of water, which is forced down the tube and flows up the sides of the hole. In order to prevent capital from being locked up in a stock of large crowns, Messrs. Docwra sometimes fix the diamonds in steel plugs, which will fit. holes in any ring. The diamonds can then easily be taken out of one crown and placed in another without re- setting. The crown represented in Fig. 101 was the largest employed at the deep boring at Northampton. It was screwed to a tube 30 feet long (Fig. 102), which enabled cores of almost that length to be cut without withdrawing the tool. The object of the open sediment-tube above the core-tube was to catch FIG. 101. * Eunson, " On a Deep Boring at Northampton," Min. Proc. Inst. C.E., vol. Ixxiv. (1883), p. 270. BORING. 119 FIG. 102. FIG. 103. any coarse particles too heavy to be carried up by the water, as well as any fragments falling from the sides of the hole. Though pieces of the core often broke off of themselves and came up in the tube, it was necessary to use the extractor (Fig. 103) ; it consisted of a ring A, which was screwed by a few threads to the core-tube in the place of the crown. On reaching the bottom of the hole the screw- ing-up was continued, and the descent of the portion C gradually forced down six teeth, such as B, into the position shown by B', gripping the core tightly. If not broken off completely by this action, it gave way when the tube was pulled, and came up inside it. The " Dauntless" (Fig. 104) is one of the diamond drills made by the Bullock Manu- facturing Company, of Chicago, for boring prospecting holes, and is capable of drilling a 2 -inch hole to a depth of more than 2000 feet, and furnishing cores of i T Vjh inch in diameter. Cores show- ing visible gold have lately been brought up from a hole 2500 feet deep, bored by one of these drills near Johan- nesburg. The machine is con- structed as follows : A is one of a pair of cylin- ders, driven by steam or compressed air, which work the bevel wheel B by gearing. The feed-screw CC can slide readily up and down through B ; but as B carries a feather lying in a slot in C, the latter is driven round when the former rotates. D is the crown set with diamonds, screwed on to the first piece of boring tube C", attached to C by the chuck C'. The hose, E, coming from a special pump, brings in a continuous supply of water which passes down C and comes out through D. F', F", F'", and G', G", G"', constitute the differential feed-gear for causing the feed-screw C, and consequently the bit D, to descend as the hole is deepened. F 7 , F", and F" 7 are connected with B so that they revolve when it does ; G', G", and G"' are loose upon the counter-shaft, but any one of them can be made fast to it by operating the clutch H. K is a toothed wheel attached solidly to the bottom of a feed-nut through which C passes ; when K rotates it causes C to ascend or 15 120 ORE AND STONE-MINING. descend. L is a wheel equal in size to K, which it drives when its shaft is rotated by G', G", or G'". If F' and G' had the same number of teeth each, one revolution FIG. 104. of B would make one revolution of G', one revolution of L, and one revolution of K ; consequently the feed-nut attached to K would be revolving at the same rate as C, and C would not descend. In reality G', G", and G'" have a slightly smaller number of teeth than E', F", and F'"; therefore one revolution of F' causes slightly BORING. 121 more than one revolution of G', K moves rather faster than C, and descends slowly. As arranged in this particular case, the gear F 7 G 7 causes C to descend i inch for every 300 revolutions, the gear F" G' 7 gives a feed of i inch for every 450 revolutions, and F'" G'" a similar feed for 750 revolutions. The driller is thus enabled to regulate his feed to the hardness of the rock bored. In practice these three speeds of advance have been found sufficient. M is a drum which is used for hoisting the rod out of the hole ; N is the hinge upon which the whole of the boring head can be turned, so as to leave the mouth of the hole perfectly free while raising or lowering rods. O is the thrust register, upon which is indicated by a dial the resistance exerted by the rock against the bit. This is an addition of great importance, for by watching the indicator the driller can detect changes in the hardness of the strata passed through, and can measure the exact thickness of the hard and soft beds before he has seen either the cuttings or the cores. The thrust register prevents the possibility of drilling through a bed of coal or other mineral without its being noticed, as has happened when the seam was so soft that it failed to furnish a core, The rod is lengthened as the drilling proceeds by screwing on piece after piece between C' and the topmost rod projecting above the hole. Mr. Bullock has recently brought out a contrivance by which the core can be drawn up through the hollow boring rods without removing them from the hole. The immense saying of time effected in this manner is of supreme importance when boring at great depths. The large rock drill used by the American Diamond Rock Boring Company,* for putting down holes to a depth of 2000 feet, consists of a 20 horse-power boiler with two oscillating 6-inch cylinders and the necessary gearing for working the drill, .all mounted on a carriage, so that the whole machine is readily moved from place to place. The feed is effected hv Bearing, or VL^by hydraulic pressure, a 2 f -inch crown is employed, leaving a .2 -inch core. Each separate drill rod is 10 feet long. The total weight of the machine is about four tons. The newt Victorian Giant Drill, said to be the largest and most powerful drill in Australia, contains some improvements suggested by experience. The cylinders are 7^ inches in diameter, and are made stationary, because the heavy vibrations of oscillating cylinders are imparted to the boring rods and diamond bit, and do harm to the machinery. The winding drum has a friction pulley and a brake, which enable the rods to be lowered without working the engine, and so prevent unnecessary wear and tear. * Eng. Min. Jour., vol. xlviii. (1889), p. 569. t Victoria, Annual Report of the Secretary for Mines for the Year 1889. Melbourne, 1890, p. 35. 122 ORE AND STONE-MINING. Various parts are strengthened, and there is an arrangement for working the steam expansively. This method of boring is expensive. During the year 1889, the cost of prospecting for gold by diamond drills in Victoria* was i os. 3jjjd. per foot bored, exclusive of the wear and tear of diamonds, taking the average of a total 18,454 feet bored. The cost for the wear and tear of diamonds for 30,294 feet bored in search of coal and gold is put down at ^6000, or nearly 43. per foot. In the borings executed by the Government of New South Wales,f the cost for diamonds is very much less, varying as a rule from is. to 2S. per foot. This may probably be accounted for by the fact that most of the New South Wales bore-holes were made in the comparatively soft Carboniferous strata, whilst some of the bore-holes for deep leads in Victoria had to traverse hard basalt. The cost at Broken Hill, where a boring 3 inches in diameter was carried from 1122 feet to a depth of 1880 feet in 1889, was i 95. iojd., or, roughly speaking, 303. per foot, exclusive of office salaries, store wages, rent, and the Superintendent of Drills' travelling expenses. The rocks traversed were gneiss, mica schist and quartzite, sometimes garnetiferous. The average rate of boring was only 571 inches per hour, whilst in the sandstone and shale of the Carboniferous strata there was a progress of 9 to 31 inches per hour, at a cost (exclusive of the items mentioned above) of 6s. 2d. to i8s. 4d. per foot. The average working cost of 7854 feet bored by the Department of Mines, New South Wales, in 1889, including all expenses, was 143. 3^-d. per foot. Of the total 7854 feet, no less than 7096 were in strata of Car- boniferous age, and only 758 in metamorphic schists; the holes were from 2\ inches to 4 inches in diameter. With reference to the rate of boring, it must be remembered that the figures given refer to the speed obtained while the machine was at work, but the average amount of deepening of the hole at Broken Hill during the year was little over 2 feet per day. Omitting Sundays, there were 313 working days. Only 199, or less than two-thirds, were employed in boring; of the remainder, 86 were occupied in repairing, 15 in reaming, 4 by delays, 9 by holidays ; the working day was eight hours. The amount of core obtained at Broken Hill compared with the total depth bored was as much as 97 -J per cent., and the average for the total 7854 feet referred to above was 89-33 per cent., a very excellent result. Small diamond drills, which will bore in any direction, and which are driven by hand, compressed air, or electricity, are largely used underground for prospecting. The hand drill of a * Op.cit.,p. 63. t Annual Report for the Department of Mines, New /South Wales, for the Tear 1889. Sydney, 1890, p. 139. BORING. 123 Swedish boring company* gives cores J inch in diameter. Ex- ploration by these little machines is very decidedly cheaper than by driving or sinking by hand in hard rocks, and fully ten times as quick. On the other hand, the ground is not opened out as it would be by a shaft or drift, and the sample furnished is but small. Several good veins have been discovered by the aid of the little hand-machine in Scandinavia for instance, a copper lode 1 5 feet (4*5 m.) wide at Roraas, and iron lodes from 32 to 65 feet (10 m. to 20 m.) wide at Dannemora and Persberg. The hand-power drill of the Bullock Manufacturing Company, Chicago, is a somewhat similar little machine, and it is said to be FIG. 105. FIG. 1 06. capable of boring a hole of if inch diameter, with a i j s inch core, to a depth of 400 feet. Machines driven by compressed air are often employed at ore mines in the United States for exploratory purposes. Fig. 105 shows the Little Champion prospecting drill. Two inclined cylinders drive a horizontal crank-shaft, which works bevel gear, causing the drill to revolve. At the same time a counter-shaft is likewise set in motion, and this effects the advance of the drill by driving the feed-screw, in the manner already explained in the description of the " Dauntless " machine * Nordenstrom, " Die Diamantbohrmaschine mit Handbetrieb," B. u. h. Z. 1889, pp. 389 and 449 ; and Petiton, Bull. Soc. 2nd. Min., 36 Serie, vol. lii. (1559), P- 1395- t Eng. Min. Jour., vol. xxxiii. (1882), p. 119. 124 ORE AND STONE-MINIHG. (p. 120). The feed-screw and its connections are carried by a swivel-head, and this can be turned so as to drill holes at an angle. The drum shown above the cylinders is used for hoisting out the drill-rods by a rope. The rods are lap-welded iron tubes 1 1 inch in diameter, fitted with a bayonet joint. Another light portable prospecting drill for underground work is represented in Fig. 106.* It is intended for drilling holes ij inch in diameter to a depth of 150 feet. The cores which it yields are J inch in diameter. It has double oscillating cylinders 3^ inches in diameter, with 3 \ inches stroke, which are run up to a speed of 800 revolutions a minute. The drill can be set to bore in any direction by turning the swivel-head on which it is carried. The Sullivan prospecting drill is a diamond borer driven by an electric motor on the same frame as the drill. The motor also works the force-pump. The feed is not by toothed wheels as shown in the figures, but by friction gearing. It will bore at any angle to a depth of 300 feet. Georgi's t electric diamond drill, primarily intended for boring holes for blasting, can also be employed for prospecting under- ground. Substitutes for Diamonds. Olaf TerpJ uses emery instead of diamonds. In some cases he puts in the fragments of emery loose at the bottom of the hole and allows them to wedge them- selves into grooves in the boring crown, which is made of soft metal. Another plan is to make the boring crown entirely of emery. The speed of rotation is three or four times as great as with diamonds, and holes can be bored from f inch (20 mm.) to 3 feet 4 inches (i m.) in diameter. Healey bores with small chilled cast-iron shot, which are dropped into the hole while a wrought-iron tube is revolving in it. The debris are carried up by water, and the cores are extracted in the ordinary way. II. BORING BY PERCUSSION WITH RODS. Iron Rods. The rods are either of iron or wood. In France preference is given to iron, and the following details relate to modes of construction now employed by M. Paulin Arrault, the well-known boring engineer of Paris. The actual boring apparatus consists of the cutting tool, the rods, and the driving machine ; but in addition it is necessary to * Eng. Mln. Jour., vol. xxxiii. (1882), p. 273. t Jahrb.f. d. Berg- und Hiittenwesen im K. SacJisen, 1890, p. 95. I Olaf Terp's " Bohrmaschine mit Schmirgelbohrkrone," B. u. h. Z., 1890, P- 4i5- The figures are copied by permission from M. Arrault's work, Outils et proctdts de Bondage. Paris, 1890. BORING. 125 have clearing tools, and appliances for remedying accidents, lining the bore-holes, and obtaining samples of the rocks traversed. Cutting Tools. The actual cutting tool is usually a chisel (Fig. 107) of some kind ; for soft rocks the edge is straight ; for hard rocks there are wings to guide the tool and keep the hole vertical, or even special guides above FIG. 107. it. For diameters not exceeding 40 inches (i m.), there is usually only one chisel; but the actual cutting blade is sometimes made in a separate piece fastened by gibs and cotters to the tool carrier (Fig. 1 1 8). In boring larger holes the chisel is made of two, three, or four separate blades. Boring Rods. The boring rods are made of iron of square section. The usual mode of connection is by a screw- joint such as is shown in Fig. 108, care being taken to have all the bars alike, so that any two bars can be screwed together. M. Arrault prefers to have a connecting socket (Fig. 109). The ordinary rods have a thread at each end, to one of which is screwed a socket or sleeve which is fixed by a pin. This socket then receives the end of another rod, which is screwed up until both ends meet. When the thread of a socket becomes worn, it is taken off and put on to the other end of the rod ; in a FIGS. 108 & 109. similar manner, if the thread of a rod is worn, the socket may be screwed on to it and the un- worn end used in the process of jointing and unjointing. The rods are generally screwed up to the right and are turned in that direction ; but in special cases it may be necessary to have the sockets fixed by two pins, or to have a special joint or a left-handed thread. The height of the tower, derrick, or shears erected above the bore-hole should be some multiple of the length of the rods, so as to be able to detach or attach two or three lengths at a time, instead of having to make and unmake every joint. FIG. no. FIG. in. FIG. 112. Arrault's rods vary in length from i foot 8 inches (0*50 m.) to 20 feet (6 m.), being usually an exact number of metres, and in size from J inch (22 mm.) to 3! inches (90 mm.) on the side. 126 ORE AND STONE-MINING. They have two shoulders at each extremity, so that the upper one can be used with the lifting hook, Fig. no, when the lower is resting upon the key, Fig. in. A cap such as Fig. 112, maybe screwed on and used instead of the lifting hook for raising the rods by the rope. Working the Rod. The up-and-down movement of the rods may be obtained in various ways. For depths not exceeding 60 to 80 FIG. 113. feet, nothing can be simpler than the device shown in Fig. 113. The man at the windlass raises the rods by turning the handle, and the master borer detaches them and causes them to fall by simply pressing down the end of the hook, which he holds in his right hand. The chain is lowered, the hook put in, the rods are raised by the winch, and then again allowed to fall, the master borer taking care to turn them a little each time. BORING. 127 Fig. 114 shows the principal tools supplied by Arrault f or a small boring. For greater depths a lever has to be employed, the rods being suspended at one end, while the other can be pressed down by men using their hands or feet. The spring pole is another arrangement ; the pole is pulled down to make the stroke, and its elasticity lifts the rod again. The length of the stroke can be FIG. 114. B i, guide tube; 2, bit or chisel with wings; 3, straight bit or chisel : 4, ordinary open scoop or wimble ; 5, scoop or wimble with auger ; 6, closed scoop ; 7, sludger with ball valve ; 8, bell- screw or screw grab ; 9, auger ; 10, combination bit and sludger with ball valve; n, combination auger and sludger with ball valve; 12, boring rod; 13, matching piece; 14, wrench for un- screwing rods ; 15, matching or lengthening piece ; 16, clamp ; 17, clamp with eye ; 18, wrench ; 19, retaining or supporting key ; 20, cap ; 21, tiller ; 22, double wrench ; 23, scraper; 24, picker. rendered uniform during the boring by means of a screw in a swivel-head at the top of the rod. With deep holes, and especially those of large diameter, steam machinery has to be employed for working the rod. Arrault frequently uses a winch driven by steam. The chain to which the rods are attached passes over a pulley hung from a derrick and is coiled on a drum, which is loose upon the main axle of the winch ; it can be thrown in and out of gear by a clutch moved by a lever. It is easy therefore to raise the rods by working the winch, and then let them drop by simply releasing the clutch. 128 ORE AND STONE-MINING. Occasionally a direct-acting engine is placed immediately above the bore-hole, but a commoner arrangement is to employ a single-acting cylinder with its piston acting at one end of a beam, while the rods are attached to the other end. A favourite plan also is to actuate the beam by a connecting rod worked by a crank. Process of Boring. The actual machinery has now been described, and the mere boring appears to be a very simple matter, consisting only in lifting the rod a little and allowing it to drop, after turning it slightly before each stroke. Never- theless the process of putting down a bore-hole is far more com- plicated than it might seem, for there are numerous operations which take up much time. In the first place the debris must be removed by a clearing tool, and before this can be lowered the cutting tool must be taken off. The swivel-head is disconnected, and a cap screwed on ; a length of rod is now drawn up by a hand or a steam windlass, the retaining key is put under a shoulder, and the joint unscrewed by another key. It is well to have as many c/ips as there are lengths to be drawn up, and then each length can be suspended in the boring house or derrick. As soon as the hole is free the clearing tool is lowered, either by the rods in precisely the same way as the boring chisel, or by means of a rope and windlass. The clearing tool FIG. 115. is usually a hollow cylinder with an ordinary clack or a ball valve (shell pump or sludger) (Fig. 115). It is worked up and down a little till it is filled, and it is then drawn up to the surface and emptied. The opera- tion is repeated if necessary, and the boring is resumed with the rod. Sometimes a cutting blade is added to the sludger so that it bores a little and picks up the debris at the same time. In certain rocks such as marls, it is convenient to have a shell-pump with a lip. It is fixed to the rods, and when it is turned a little as well as moved up and down, it soon fills itself. Oeynhauseris Joint and free-falling tools. When a hole of large diameter is being bored, the weight of the rods is so great that much vibration ensues when they are suddenly arrested by the chisel striking against the bottom. Yarious devices have been contrived for overcoming this difficulty, among which may be mentioned Oeynhausen's sliding joint and three methods of making the tool fall independently of the rod. Oeynhausen's contrivance (Figs. 116 and 117) consists of an upper piece a pro- vided with a slot in which the lower piece b can slide ; b is pre- vented from dropping out by a crosshead and carries the boring chisel, whilst a is attached to the line of rods. When a down-stroke is made and the chisel strikes the bottom, the piece a slides over b and is therefore but little affected by any jar produced by the blow of the tool. The length BORING. 129 FIGS. 116, 117 & 118. ft. C of the stroke is arranged so that the top of the slot will not descend far enough to touch the crosshead ; a is then raised once more and again catches the crosshead. One of the simplest arrangements for making the tool fall independently is the sliding joint shown in Fig. 118. The piece supporting the boring tool has two wings (-Fig. 119) which rest upon shoulders, at the top of a long slot in a cylinder attached to the lowest rod ; by giving the rods a sharp turn to the left, the wings lose their support and the tool drops. The actual process of boring is carried on in the following manner : The line of rods suspended to a chain is raised by a steam winch. FIG. 119. Steam is then shut off, and the master borer by a sudden twist of the tiller causes the bayonet joint to act ; the tool drops and makes its cut. The rods are then lowered, and the slot comes down over the wings which are pressed by the inclined sur- faces at the end on to the shoulders; the steam is turned on again, and the operations of winding up, stopping, twisting, letting the tool fall and lowering are repeated. The contrivance acts so easily that it is sometimes used even for comparatively v~v shallow bore-holes. LJ The free fall is obtained by Arrault in a different manner when the boring is done by a beam (Fig. 120). The tool is suspended from the catch h (Fig. 121). The part a b has a pin i t which lies in an oval hole. While the rods are being lifted the beam strikes a bumping- piece, and their upward movement is suddenly checked ; inertia carries the catch a b up a little, the end a strikes an inclined surface and causes the end b to move outwards and detach the tool. When the rods are lowered the part h hooks itself on without difficulty, and the chisel is raised and dropped. This tool requires the boring rod to be guided, for otherwise the hole might not be bored straight. 130 ORE AND STONE-MINING. Fig. 122 explains a well-known free-falling tool invented many years ago by Kind.* The head of the actual boring rod is held FIG. 121. FIG. 122. FIG. 120. by a click or grapple. When the main rod descends, the resist- ance of the water in the hole checks the sliding disk D ; the jaws J J are opened by the little rod which connects them to D, and the boring part falls and strikes the bottom without any injurious vibrations being communicated to the main rod. When the disc descends further, the head is caught again by the click. Accidents. Tools for putting things right in case of accident are numerous, and many of the contrivances which have been invented by engineers are extremely ingenious. Among the accidents is a breakage of the rod. If the rods are not caught in any way, a claw called the crow's-foot (Fig. 123) is lowered and turned round till it catches a rod below one of the shoulders ; it is then drawn up. Sometimes it is found that a hole has suddenly deviated from the vertical, owing to a difference in hardness in the rock, which causes the chisel to work more easily on one side than the other. One method of remedying this evil is to fill the bad part with cement, and rebore it very carefully. Broken ropes can be caught hold of by tools resembling a cork- screw. The tool shown in Fig. 124 serves to cut a thread upon the end of a broken rod. The position of the broken end is first * J. Gallon, Lectures on Mining, vol. i., Atlas, Plate IX., Fig. 52. BORING. ascertained by taking an impression upon tallow or wax, and the cone is then lowered on to it ; by turning it round a thread is cut on the broken end, which can now be raised with the rods and tools attached to it. If the cutting chisel is broken, some kind of grasping nippers must be used, and there are contrivances for making them act when they have reached the bottom of the hole. Linings. Where the strata are soft and would fall in, or where it is necessary to shut off the inflow of certain water-bearing beds in order to confine the well to one particular source of FIGS. i?3 & 124. FIG. 125. FIG. 126. supply, the hole has to be lined with a tube. Tubes are made of iron, copper, or wood. This last material is seldom employed nowadays, because it occupies so much space, and because it is not easy to make good wooden tubes. Fig. 125 is a tube of riveted sheet iron with sockets fixed on, which enable the joints to be made by screwing. Fig. 126 is a tube with a screwed joint perfectly smooth outside and inside. Copper tubes are advisable when the water, such as that coming from pyritiferous beds, would attack iron and in time eat it away; but this difficulty is also overcome by putting earthenware pipes inside, and filling up the interspace with cement. Cores. Though the fragments brought up in the sand-pump will indicate the nature of the rocks which are being traversed, it is often desirable to obtain a core of the actual stratum itself, which will show the direction and amount of the dip of the rocks, and possibly contain fossils and so afford valuable knowledge concerning their precise age. A core is cut out either by rota- tion or percussion. In the former case the tool consists of a sheet-iron cylinder (Figs. 127 and 128) armed at the bottom with I 3 2 ORE AND STONE-MINING. steel sawing teeth ; in the latter the cylinder is surrounded by four cutting chisels, which chip out a ring and leave a solid cylinder standing. The core now has to be detached, and for this purpose various contrivances may be adopted. One of Arrault's tools is shown in Fig. 129. It is a hollow cylinder a attached to the fork b c, with a longitudinal slot containing a sliding bar d, armed with a toothed wedge e, which is prevented from dropping out by the shoulder./. The bar d is further kept in position by the spring g h, fixed at FIGS. 127 & 128. FIG. 129. l Section at A B. the top of the tube, which presses it against the two outer plates ij and the ring k ; I is a little slot in the spring, and m a small stud upon the bar d. When this tool is lowered over the core and the wedge e touches the bottom of the annular groove around it, the tube slides down and forces the wedge inwards ; the weight of the rods causes sufficient pressure to drive the teeth of the wedge into the core and break it off. In the meantime the slot I has passed over the stud m ; the wedge is thus prevented from slipping down, and the core is held till it is drawn up to the surface. In order that the direction of the dip may be ascertained from the core, it is necessary to know exactly how it stood when it was BORING. 133 in situ. In Victoria* the rods and the core-breaker are put together at the surface, and all the joints are marked in a straight line with a chisel. The rods are then taken apart, and are care- fully screwed together in precisely the same manner when thej T are lowered into the bore-hole. If the position of the marks at the surface is noted while the core is being detached, the direction of the dip can at once be determined. To prevent the possibility of error from a movement of the core after it has been detached, it is marked while at the bottom of the hole with a vertical scratch or groove. This is made by a sharp steel point on the gripper as it slides down over the core. A method lately invented by Arrault consists in lowering a compass, enclosed in a case made of phosphor bronze, on to the FIG. 130. FIG. I30A. top of the core (Figs. 130 and I30A). The case has an india- rubber base, with two grooves filled with felt impregnated with a thick ink. The compass case also contains clockwork, arranged like an alarum, which can be made to liberate a catch and so clamp the compass. The compass is lowered by a rope, and suffi- cient time is given to enable it to assume its proper position before * ^Reports and Statistics of the Mining Department, Victoria, for ilie Quarter ended March j/, 1891, p. 28, with Plate. ORE AND STONE-MINING. t it is fixed by the clockwork. It is drawn up, the core is then extracted, and by means of the ink marks the compass can be put upon the core in precisely the same position as it originally occupied in the hole. Instead of using ink marks, some plastic material* such as clay may be lowered on to the top of the core and allowed to remain long enough to take an impres- sion. A clockwork arrangement in a watertight box above the plastic lump sets a magnet fast after the lapse of a given time as before, and when the core is brought up it is placed so as to fit the impressions, the orientation of which is known by the magnet.t Wooden Rods. In some districts wooden rods are found more suitable than iron ones. They have been used in Canada, and they are preferred in Galicia. Fig. 131 represents the manner in which the rods are made for boring oil wells in that country. The rods employed in Galicia are of ash, 32 feet 10 inches (10 m.) long, and 2 inches in diameter ; at each end a forked iron coupling is riveted on, terminating by a conical male or female screw, and in the middle are two strapping plates of iron to give more strength and stiffness. To the end of the lowest rod is attached an Oeynhausen sliding joint which carries a sinker bar with the cutting chisel attached to it. The sinker bar is from 20 to 30 feet (6 to 9 m.) long, and weighs from 12 to 15 cwt. (600 to 750 kil.). The top of the line of rods is fastened to a chain (Fig. 132) ; this makes three turns round one end of the boring beam, capped for this purpose by a casting with a spiral groove, and is then wound on to a little windlass placed on the beam. The beam receives its up-and-down movement from a connecting rod attached to a crank upon the axle of a wheel driven by a belt from a small steam-engine. J After boring, the chain is unfastened, and the rods are drawn up by means of a hemp or manilla rope if inch (45 mm.) in diameter, which is also used for working the sand-pump. The master borer can per- form all the necessary operations while sitting in front of the hole. By means of the rope a he can work the windlass upon which the chain is coiled, and by pulling the lever b he can throw in or out of gear the * B. u. h. Z., 1890, p. 205, f lleports and Statistics of the Mining Department, Victoria, Quarter ended March 31, 1891, Dip contrivance, p. 28. J Syroczynski, "Note sur le forage canadien," Bull. Soc. Ind. Min., tome iii., 3 Serie. Saint-Etienne, 1889, p. 1417. BORING. 135 pulley which drives the drum with the winding rope, and so raise or lower the rods or the sand-pump. The lever c actuates a brake which enables him to stop the machinery, if necessary, and with his left foot he can press upon a pedal e, and so regulate the steam valve, and alter at pleasure the speed of the engine. FIG. 132, The cord d works a second steam valve. Two other workmen, one at the bore-hole, and the other on a platform 33 feet (10 m.) above him, are shown in the act of unscrewing and putting away the rods. During the actual boring, the two assistants stand at the hole and turn the rods, whilst the master borer regulates the blow by 136 ORE AND STONE-MINING. the cord a which commands the windlass, and the cord d which controls the admission of steam. The tower or derrick is about 50 feet (15 to 16 m.) high, and 1 6 feet (5 m.) square at the base. It is closed in with planks. The adjacent space required for the steam-engine, belts, wheels, the tool is used close to the - roof (Fig. 156). Tools used, for Boring and Blasting. We now come to hard ground ; and in this class we have a large.propor- tion of the rocks met with by the miner, such as slate of various kinds, hard grit and sandstone, limestone, the metamorphic schists, granite, and the contents of many mineral veins. Hocks of this kind are attacked by boring and blasting. The tools employed are the auger, jumper, or borer (drill), hammer or sledge (mallet, Cornwall), scraper and charger, tamping bar or stemmer, pricker or needle, claying bar and crowbar. Augers. At English gypsum mines a tool resembling the car- penter's shell-auger is regularly used for boring holes for blasting. It is worked by a cross handle, and makes a hole ij inch in diameter. Boring is done in the bituminous limestone of Seyssel by screw-augers in a similar manner. Elliott Drill. Screw-augers mounted upon stands are common. Fig. 157 represents the Elliott drill, which consists of an auger inserted into a socket upon a feed-screw c, which works upon a worm-wheel a, held fast in a ring, when the screw clamp b is tightened. On moving a ratchet brace backwards and forwards, BREAKING GROUND. 155 c is turned round, carrying the auger with it, and when the worm- wheel is tight, it advances slowly at the same time. If a very hard piece of rock prevents the penetration of the auger, the worm-wheel slips in the ring, and, by suitably arranging the tightness of the clamp 6, the machine can be made to accommo- date its advance to the nature of the rock. The drill itself is made of a bar of twisted steel, which clears itself of the debris to a certain extent ; when it has penetrated as far as it will go, the clamp is loosened, enabling the feed- screw to be drawn back rapidly without rotating at all. A longer drill is put in, and work continued. The light frame or standard is made in two halves, and by shifting a pin its length can be altered to suit the height of the FIG. 157. FIG. 158. working place, whilst the final tightening is done by a screw at the bottom. Ratchet Drill. Where even more simplicity is required, a self- feeding ratchet drill can be employed, with a piece of timber set up in the working place as an abutment. An auger is inserted into a socket upon a feed-screw a (Fig. 158), working in the nut b, attached to a long sheath. When the ratchet handle c is worked, a revolves and at the same time advances from the feed-nut, carrying the auger with it. The sheath is prevented from turning by putting the eye of a pin over one of the projecting pegs at the rear end, and allowing the pin to be brought up by the first twists against the piece of timber. For enabling the feed-screw, after it has advanced to its full length, to be quickly returned into the sheath, the Hardy Patent Pick Company sometimes use Stayner's Patent '56 ORE AND STONE-MININC4. 7/6 all Efficiency. 03 '/2 03 |*ti OH fe" ^ ^ ^ Electric . I5-4 IO ! 2OOO A in - 2IO I 9 2 95 497 65% Compressed air 33'3 10 2000 4 ins. 130 700 63 893 30% Compared with compressed air, the plant is less expensive, and there is the immense advantage of a smaller loss of power in transmission. t According to experiments made with the electric plant at St. John's Colliery, Normanton, and Llanerch Colliery, Monmouthshire, the efficiency of the plant i.e., the ratio between * Proc. Inst. Civ. JEng., vol. civ. Session 1890-91, p. 89. t Snell, "Electrical Transmission of Power in Mining Operations."' Paper read before the Lancashire Branch of the National Association of Colliery Managers, Wigan, September 28, 1889. BREAKING GROUND. 173 the work done in pumping and hauling by the electric motor, and the work given out by the steam engine at the surface is as much as from 43 to 48 % . Making every allowance for the fact that these figures are given by avowed advocates of electricity, it undoubtedly seems that compressed air is at a disadvantage as regards cost and efficiency when compared with its youngest rival. A combination of electricity and compressed air has been found advisable in some cases. The power is transmitted under- ground by electricity to motors which drive small air-compressors placed in the vicinity of the working places where percussive drills are required. Hitherto the principal applications of electrical transmitting plant have been for pumping, winding, and hauling, and little has been done in the way of machines for breaking ground ; but rotary and percussive drills driven by electricity are already beginning to be employed. EXCAVATING MACHINERY. The machines used for excavating may be classified as follows : (1) Diggers. (2) Dredges. (3) Drills for boring holes for blasting or wedging. (4) Machines for cutting grooves. (5) Machines for excavating complete tunnels. I. Steam Digger. The steam navvy, though specially the machine of the railway or canal engineer, must not be forgotten by the miner, who has to excavate large quantities of com- paratively soft deposits near the surface, or to remove overburden such as sand, gravel, stiff clay, or chalk. After a preliminary shattering by blasting, even hard rock may be shovelled up by these machines. Among them we may mention Dunbar & Rmtoris Steam Navvy * (Fig. 1 86), largely used in making the Manchester Ship Canal. It is a steam crane which brings a bucket, armed with teeth and a sharp edge, against the side of the excavation, draws it up and drops its contents into a railway waggon. The figure needs but little explanation. A is the vertical boiler giving steam to two cylinders, one of which is shown at B. These &re made to work drums for raising and lowering the bucket C, by the chain D, or for turning the jib G. In order to work the navvy the bucket is lowered till the handle E is vertical ; it is then brought against the bottom of the working face, and drawn up by the chain D; the teeth enter the earth and open the way for the cutting edge. The bucket fills itself, is swung over the waggon by the jib, and * Mining Journal, vol. Iviii. (1888), p. 1242. I 74 ORE AND STONE-MINING. emptied by pulling tlie cord H. It closes automatically when lowered. The depth of the cut depends upon the length of the radius given to the circular arc described by the cutting tool. The radius, -and therefore the cut, can be altered by a man, standing at the foot of the jib-post, who works the chain F ; this actuates a pinion gearing into a rack upon the bucket handle E. The navvy requires three men, one attending to the raising and lowering of the bucket and swinging of the jib ; a second regulating the depth of the cut and the discharge, and lastly a FIG. 1 86. fireman. Each bucket contains i to ij cubic yards, and three buckets will fill a contractor's waggon. In ten hours this machine will excavate and load from 700 to 1000 cubic yards of earth. When all the earth within reach has been excavated, the jack screws are loosened and the machine made to propel itself forward on the rails a few feet. A somewhat similar machine is Wilson's Steam Crane Excavator. It is a 10 ton steam crane to which a digging bucket can speedily be attached. The machine can therefore be used as a crane or as a digger, as occasion requires. This is also possible with the Wkittaker Excavator, which, like the two previous steam navvies, has been used for making the Manchester Ship Canal. Steam diggers are much used by miners and quarriers in the United States, and especially the machines made by the Marion and the Bucyrus Steam Shovel Companies, which in principle resemble the Dunbar and Huston Navvy. The Earnhardt Steam Shovel of the former company is employed in the Mesabi Range, BREAKING GROUND. 175 Minn., and in other places, for stripping off overburden and for excavating iron ore, and the Bucyrus Company applies its digger with success to auriferous gravel, instead of washing it down by the hydraulic process. Besides serving as true excavating machines, these steam shovels are found economical for loading ore from stock piles into railway waggons. Another kind of digger may be spoken of as a dry dredye ; a machine of this class, made by a Liibeck Company,* is in use, among other places, at a large openwork where brown coal is being worked near Briihl, between Bonn and Cologne. The excavating part of this steam digger consists of a long arm with a chain of buckets, like those of a dredge, which are brought successively against the face of the overburden and then carry the gravel into a hopper ; side-tipping waggons are run under this hopper and quickly filled by opening a door. The pulley which makes the endless belt of buckets revolve is set in motion by friction gear, so that there is no fear of a break- age, even when a bucket comes against some very hard place in the overburden which it cannot penetrate. The arm carrying the buckets can be raised and lowered as required. Theoretically this machine will excavate 1000 cubic metres (1300 cubic yards) in ten hours; the actual work is stated to be about 700 cubic metres (915 cubic yards) in that time. The Bucyrus Steam Shovel Company likewise makes a machine of this type. II. Dredges. The beds of rivers and lagoons, and even sea beaches and bottoms, sometimes contain minerals which can be excavated by dredges like those used for improving harbours. There are three types : (1) Bucket dredges. (2) Grab dredges. (3) Suction dredges. i. Bucket Dredges. Kincaid & McQueen's machine (Fig. 187), used with success upon the Molyneux river,f New Zealand, is a big barge, 66 feet long, with an endless chain of buckets and a pontoon on each side. The total width of the barge and two pontoons is 26 feet. The buckets are worked by a steam-engine upon the barge, which also drives a cylindrical screen for separating any large stones. The engine is a vertical inverted compound steam-engine, with cylinders of 1 2 inches and 2 2 inches diameter respectively, and 1 8 inches stroke, working at a pressure of 60 Ibs. per square inch. * " Liibecker Maschinenbau Gesellschaft." * f Mines Statement. By the Minister of Mines, the Hon. W. J. M. Larnach, C.M.G. Delivered July 6, 1886, p. 17. i 7 6 ORE AND STONE-MINING. The buckets can be made to raise as much as 150 tons of stuff per hour, and to excavate to a depth of 25 feet below the level of the water. A steam winch serves for raising and lowering each FIG. 187. of the dredging ladders, or frames, carrying the endless chains of buckets, and also for working the mooring chains. A dredge of a similar kind has been used on the river Oreo, in Piedmont,* for the purpose of excavating an auriferous alluvium in order to extract gold from it, and with the further object of preventing floods by straightening the course of the river and embanking it. The dredge has an engine of 50 h.-p., and is said to be capable of raising 3200 cubic yards of alluvium (2500 cubic metres) in 22 hours. It can excavate to a depth of 26 feet (8 m.). 2. A yrab dredge consists of a single hemispherical or semi- cylindrical vessel, which is made so that it opens when lowered, fills itself on touching the earth and closes as soon as it is raised. The raising and lowering are done by a crane. The semi-cylindrical bucket may be armed with teeth ; it descends with the teeth open and is drawn up with them closed. Bruce & Batho make some of their grabs with three or four sharp blades, like very pointed spades, which close upon being lifted, and form a hemispherical bucket. A somewhat similar grab dredge has been employed for stripping off the overburden from a bed of auriferous gravel in Calif ornia.f The Priestman Grab dredger has been used for excavating the * Gazzettadi Torino. May u, 1886. t Eighth Annual Report of ilie State Mineralogist, for the year 1888. .Sacramento, 1888, p. 100. BREAKING GROUND. 177 auriferous gravel of the river Nechi and its tributaries in the United States of Colombia (Fig. 188), and it likewise serves as a digging machine on land, and even for sinking shafts. FIG. 1 88. 3. The Suction dredge may be described very shortly as a cen- trifugal pump arranged to draw up sand and gravel with the water. It is placed upon a barge, and the suction pipe can be lowered, raised, or moved from one side to the other, so as to attack any part of the sea or river-bottom. A Welman dredge of this type,* used for excavating the ocean beach at the mouth of the Waipapa Creek, has suction and delivery pipes 12 inches in diameter. It appears to be doing excellent work where the bulk of the material to be treated consists of sand and fine shingle. The beach is reckoned to yield about 3 grains of gold per ton, whilst the working expenses are only 2 grains per ton. III. Rock Drills. Most of the machine drills have a per- cussive action, but a few are rotary ; for Stapff pointed out some years ago that if a rock may be chipped off by power communi- cated by a blow, it may also be chipped off by a similar amount of power communicated by pressure. i. Rotary Drills. Following the order I have adopted in * J\tr/itni/t 1/ttii-t/ /,'< f,/>rlH on the Min'nuj Industry of New Zealand. Wel- lington, 1890, p. 87 ; and 1891, p. 75. i 7 8 OKE AND STONE-MINING. the case of the hand tools, I will first speak of the rotary machines. Brandt's rotary drill consists of a hollow borer which has a steel crown, with cutting edges, screwed on. The tool is kept tight against the rock by the pressure of a column of water, and is at the same time made to rotate by two Jittle water-pressure engines, whilst a stream of water passing down through the borer washes away the chips and sand, and keeps the cutting edges cool. In principle, therefore, this drill resembles the original diamond boring machine of De la Roche Tolay and Perret, save that the crown is made of steel and not of diamonds. It has been used with success in railway tunnels and mines. Brandt's machine was worked at one of the mines at Freiberg* in Saxony, with water at a pressure of 83*5 atmospheres, of which 56*6 atmospheres were obtained by pressure pumps provided with an accumulator, and 26*9 atmospheres by natural fall, owing to the level in which the machine was used being 277 metres below the pump. The water was conveyed to the pump in iron pipes ij- inches in diameter inside. The diameter of the holes was 2 1 inches, and they could be bored in gneiss at the rate of i J inches per minute. The stretcher bar on which the machine is carried is hollow, and has a piston which can be forced out by hydraulic pressure so as to fix it firmly. A similar bar is some- times used with percussive drills.f Comparative experiments were made at Freiberg between this drill, hand-labour, and a percussion drill, and the results given below are of much interest and importance. In the case of the two machine drills, the cost includes interest on and depreciation of plant, repairs, and the estimated expense of providing steam power, which would have been necessary if water power had not been available : Hand boring. Schram's drill. Brandt's drill. Distance driven per week in metres ..... '95 4 '5 5' Cost in marks per metre driven Wages realised by the miners in 120-134 77-4-85-25 74-34 marks, per eight-hours shift , 1-85-2-05 3-48-3-66 376 The benefits of machine work are very marked indeed, both as regards rate and cost of driving, and wages earned by the men. Brandt's rotary drill did its work cheaper and faster than Schram's machine ; but nothing is said in the original notice of * JaJirbuch fur das Berg- und Huttenwesen im Konigreiche Saclisen auf das Jahr 1882, p. 18. t Ann. Mines. Ser. 8, vol. ii. 1882, PI. I., Fig. 6. BREAKING GROUND. 179 the advantage of a machine driven by compressed air for venti- lating workings, such as advanced headings in which these drills are employed. In Jarolwiotis* drill the borer is likewise a rotating tube armed with steel teeth, but it is fed towards and pressed against the rock by a differential screw arrangement. Water passing through the hollow borer keeps the teeth cool and carries away the debris. The machine can be worked by hand, but a little water-pressure or compressed-air engine, or an electric motor will be preferable. Experiments have been made lately at Zauckerode,t in Saxony, with a diamond drill for boring holes for blasting. The machine is a steel tube with a steel crown screwed on, con- taining four black diamonds ; it is driven by a small electric motor upon a carriage on wheels in the level, by means of a shaft with two universal joints. This arrangement allows holes to be bored in any direction required for driving the tunnel. The holes are from IT inch to 1*3 inches (28 to 34 mm.) in diameter. The result of the experiments is that in hard clay-slate with numerous veins of quartz, or in gneiss, granite, or rocks of similar FIG. 189. hardness, a level can be driven nearly twice as fast as by hand, and at about the same cost. It is also possible to attach a motor of some kind to a twist * Oest. Zeitsclir.f. B.- u. H.- Wesen, vol. xxix. (1881), p. 184; and vol. xxx. (1882), p. 103. t Georgi, " Die Diamant-Bohrmaschine mit elektrischem Antriebe am koniglichen Steinkohlenwerke zu Zauckerode," Jahrb. f. d. Berg- und Hiit- tenwesen im Konigreiche Sachsen auf das Jahr 1890, p. 95. i8o ORE AND STONE-MINING. drill similar to Elliott's hand tool already described. The Jeffrey Manufacturing Company, Columbus, O., have well-designed drills of this class driven by air or elec- tricity. For working the Cleveland iron- stone, Mr. Steavenson* is employing twist drills driven by water-power, petroleum engines or electricity. His latest drill is shown by Fig. 189 : A, electric motor ; B, hollow arm with a shaft inside driven by A, and work- ing the bevel wheel C by suitable gearing ; D, twist drill ; E, socket for drill; F, universal joint connecting the feed-screw G, to the drill-socket ; H, feed-nut. Fig. 190 is a similar drill worked by a Priestman petro- leum engine.f The cost per ton of getting the Cleveland ironstone has been greatly reduced by the adoption of these machines in the place of hand-labour ;. but, as is usually the case, the cost of explosives per ton of stone broken has increased, because holes are bored so easily and quickly that less care is taken in planning them. The extra cost of powder is more than repaid by the saving in labour. The Sprague Electric Railway and Motor Company of New York J have a small electric rotary diamond drill for boring holes for blasting. The motor is light and carefully cased in to preserve it from dust and dirt ; it is mounted upon an adjustable stretcher bar, and it drives the drill direct. 2. Percussive Drills. Machine drills are usually designed with a view of carrying out the three opera- tions of hand-work viz., the blow, * Steavenson, " On the System of Work- ing Ironstone at Lumpsey Mines by Hy- draulic Drills," Proc. N.E. Inst. M. and M. Evg.. vol. xxxvi. (1886-87), p. 67. t Unwin, " Petroleum Engines," Proc. Inst. C.E., vol. cix. (1891-92), part iii. Eng. Min. Jour., vol. xlix. (1890), p. in. BREAKING GROUND, 181 the rotation, and the advance. As a rule a percussive drill consists of a cylinder with a piston, which is moved backwards and forwards by compressed air ; the cutting tool or chisel is firmly attached to the piston rod, made specially strong to stand the great amount of shock to which it is subjected. The rotation is almost always effected by a twisted or rifled bar and a ratchet wheel ; and, in order to keep the machine constantly in the proper position for work, it is fed forwards upon a cradle by the workman behind, who has merely to turn a handle, and so cause a screw to revolve inside a big nut attached to the machine. Drills which will advance automatically have been invented and used in some cases, but as a rule nowadays the automatic feed has been given up ; indeed, it seems quite unnecessary to increase the number of the working parts and make the machine more com- plicated, simply to save the attendant the trouble of turning a handle. Though the plain chisel-shaped edge is the commonest form given to the bits used with machine drills, it is by no means uni- versal ; other forms shown in the figures are the cross-bit, the FIG. 191. FIG. 193. FIG. 194. X-bit, the Z-bit, and the horse-shoe bit (Figs. 191, 192, 193, and 194). The object in all cases is to secure a perfectly round hole and so prevent jamming. If a band of hard rock crosses a hole in a slanting direction, the single- edged bit is apt to be diverted by it slightly, and become fast. At the outset also, when the drill is striking an uneven surface, it is not always easy to bore the hole properly ; for this reason the first drill is sometimes made with the cross-bit, whilst the remainder of the hole is bored with the single chisel-edge, which will work properly when the hole is deep enough to act in some way as a guide for the tool. Bits with two or three edges are not so easily sharpened as those which have but one ; however, the work of the smith may be lightened by using a swage (dolly, U.S.A.), which is, practically, a steel mould, into which one end of the steel bar is placed when soft, whilst blows are struck upon the other end. This gives the proper shape, and the smith can finish up the bit upon the anvil. 1 82 ORE AND STONE-MINING. The adoption of the ingenious-shaped bars of the Crescent Steel Company of Chicago (Fig. 195) will likewise relieve the smith, but the saving of labour at the forge is FIG. 195. not the only advantage claimed for the invention. The shaped steel will discharge the debris more freely than round steel, a matter of no slight importance, for the cleaner the hole the more effective the blow ; the little chips should be got rid of as soon as possible, and any means of facili- tating the discharge should be welcomed. A represents the pattern made originally for the iron mines of Lake Superior, and B the section preferred in the Rocky Mountains. Less sharpening is required when boring by a machine than when boring the same depth by hand, and for two reasons : first, the bit suffers less, because the blow given by the machine is straighter and fairer ; and secondly, owing to the greater force of the blow work can be done by the tools when they have become very much blunter than those which would be put aside in hand- drilling. For machine-drilling in soft sandstone in Ohio, the borer is made with a narrow but perfectly flat bit, instead of being chisel-shaped. A flat-ended borer is likewise used by the Inger- soll-Sergeant Rock Drill Company for boring elongated holes by the Githen system. The tool does not rotate, and acts by pound- ing the bottom of the hole to dust. The object of the elongated hole is to make the rock rend along a pre-arranged line, a matter of importance in quarrying certain kinds of stone. Percussive drills may be classified according to the power used for driving them, and those worked by air may be further sub- divided according to the kind of valve employed for reversing the direction of the stroke. The following table contains a list of several well-known drills, arranged according to their mode of action and alphabetically : BREAKING GROUND. PERCUSSIVE DRILLS. 183 Power. Kind of distributing valve. Name of the drill. / Barrow ( Climax / (1) Valve worked by mechanical ; Dubois and connections . . . J Franois Holman Rand Rio Tinto ( Bickle \ (2) Air-driven valve . Coles Eclipse Optimus Compressed air I (3) Valve worked by mechanical ) connections and air pressure . j Franke Him ant (4) Two valves, a main one air- "j driven, and an auxiliary one 1 worked by mechanical connec- i Sergeant tions . . . . . ) f Adelaide , (5) No valve . . . . - Darlington ( Minera Electricity . . Marvin For the purposes of this work it will be quite sufficient to de- scribe only a few of these machines, especially as in many instances there is a great similarity between them. (i) The Barrow drill* (Fig. 196) consists essentially of a gun- Fro. 196. metal cylinder C, about 2 feet in length and 4 inches in diameter, in which works a cast-steel piston-rod D, fitted with two pistons G, about 1 2 inches apart, midway between which is the * George Seymour, " On the Barrow Rock Drill," Proc. Min. Inst. Corn- wall, vol. i. (1876-83), p. 12. 1 84 OKE AND STONE-MINING. tappet or boss G'. In a valve-box at the top of the cylinder is placed the oscillating slide-valve H (shown separately), pivoted at M ; it is worked by the reciprocation of the tappet G' coming in contact with its lower edges, which, for this purpose, are sloped at each end, as shown. There are ports, corresponding with openings in the slide-valve face, for admitting the fresh steam or compressed air from the inlet pipe I (Fig. 197) to the ports j (Fig. 196) at each end of the cylinder, and for letting the spent or exhaust air or steam escape by the exhaust pipe J (Fig. 197). This simple arrangement con- stitutes the whole valve gear of the machine. " The borer is inserted into a hole formed in the fore-end of the piston-rod, and is fixed therein by means of a screw. Its rotation is effected by hand by means of the handle D" turning a spindle D', FIG. 197. which is so fitted by means of the cotter d, made fast in the piston DG, and fitting in a slot in the spindle D', that the latter can slide in the piston DG, but when turned by the handle causes the piston to turn with it. The spindle D' has a pinion E, gear- ing into a pinion on the adjusting and feeding screw C', so that when the piston D is turned by means of the handle D", the cylinder C is simultaneously pushed along the bed-plate A. These pinions can be easily disconnected by loosening the nut jf, and thus the piston and the adjusting screw can be turned inde- pendently of one another when required. " The borers used are respectively i J, i J, and i inch in. diameter, the length of the stroke 4 inches, and the maximum number of blows about 300 per minute. " The gross weight of the machine, including the bed-plate and gudgeon, is about 115 Ibs. " The bed-plate, A, of the machine is formed with a gudgeon A", which fits into and can be adjusted to any position in a socket formed in or on a clamp B', which can be fixed on any part of the wrought-iron box or column B, thus forming a universal joint. This bar or column can be placed in position either horizontally or vertically, as may be most convenient, but is BREAKING GROUND. 185 generally placed across the level, against the sides of which it is secured by means of the clamp L, adjusting screw M, and claws N and N'." Pieces of wood O O', are placed against the wall, and the claw is jammed against them by screwing out the bar. The Climax Drill* (Fig. 198) recalls the Barrow; A is the cylinder, B B are the two pistons, and C the boss or swelling which strikes the valve D and rocks it up and down on the centre pin E. The valve has two admission ports, F and F', which, when passing corresponding ports in the valve-chest face, allow the compressed air to pass into G or G'. On the inner face of the valve, above F and F', there are two recesses, precisely similar to H and H', which control the two ports on each side of the valve-chest face. In the position shown in the figure, the compressed air could pass from the valve-chest through F' into G' and drive the piston FIG. 198. forward, whilst the air in the front part of the cylinder would escape by G, which is now put into communication with the exhaust port by the recess above F. The object of the two recesses, H and H', is to enable the valve to be reversed when one face is worn. The rotation is effected by a rifled bar I at the back end of the cylinder, which projects into a long cavity K in the rear piston and piston rod. It can be turned easily in one direction, but is prevented from moving in the opposite direction by the teeth of a crown ratchet clutch L, a device which is thought by the maker to offer a better guarantee against injury than the ratchet wheel with one or two pawls common in most other drills. When the * Figures and descriptions of the Bickle, Climax, Coles, Daw, Eclipse, Ingersoll, and Kio Tinto drills will be found in a paper by Carbutt and Davey, " On Recent Trials of Rock Drills," Min. Proc. List. Meek. Eng., London, March 1891. 1 86 OKE AND STONE-MINING. piston moves forward, the nut in the rear piston passes over the rifled bar, and causes it to turn round, but when the motion of the piston is reversed the rifled bar is prevented from turning by the ratchet clutch, the piston is forced to rotate, and with it the borer. M is the feed-screw worked by a handle not shown in the figure, and N the feed-nut. The Dubois and Francois Boring Earn (Bosseyeuse)* is a machine of a totally different type (Figs. 199 and 200) ; it bores large holes for the insertion of a wedge, and it is fitted with a ram for driving in the wedge, and so breaking the rock. The machine has been specially designed for driving levels in mines where there is so much fire-damp as to render blasting FIGS. 199 & 200. >. Elevation A SCALE Of FEET dangerous, and it therefore more especially concerns collieries than ore and stone mines ; but it should be mentioned in connec- tion with the latter, because it will also bore holes for blasting, and because it is sometimes used for cutting a series of holes, and so creating a first opening, which enables blasting to be conducted with greater advantage (Fig. 239). The boring cylinder, A, has a long piston B, with spiral grooves which produce the rotation by means of a ratchet wheel C, whilst the slide-valve, which effects the distribution, lies in the valve- chest F, and is brought into action when a swelling, D, on the piston-rod touches a bent lever E. The borer, G, is fixed in the end of the piston-rod, and makes a hole 3 or 4 inches in diameter. As the hole is deepened, the * Mathet, L'air comprimt aux mines de Blanzy, Saint-Etienne, 1889, p. 66. BREAKING GROUND. 187 cylinder is made to travel along the frame, H, by means of a screw, and at the same time the counterpoise, I, is also moved by a screw so as to balance it. The machine can be made to turn round the central column, and can also be moved in a vertical plane, so that holes may be bored in any direction ; and the special carriage in use at the Blanzy mines permits the machine to be moved laterally, and take a position near the side of the tunnel. The whole machine is very heavy, weighing no less than 2 tons 13 cwt. (2700 kil.); but it is found that the greater power and stability so obtained fully compensate for any inconvenience caused by its weight. At Blanzy one boring ram has taken the place of four small drills mounted upon one stand ; and this diminution in the number of machines requiring attention is no inconsiderable advantage. An ingenious contrivance used with the Blanzy boring ram must on no account be passed over viz., the special pipe for con- veying water to the bottom of the bore-hole. A small copper tube (L, enlarged cross-section, Fig. 200) lies in a groove in the borer, and carries in a jet of water which keeps the bit or boring edge quite cool, and washes out all the chippings as soon as they are produced. The tool is thus enabled to work fairly and freely the whole time, and the result at Blanzy has been a great increase both in the speed of boring and in the duration of the bits. The water is supplied to the drill by the india-rubber pipe J, which leads to the hollow collar K. The collar is fixed with a water-tight joint upon the drill socket, so that the latter can revolve freely. The water finds its way through a hole in the drill-socket to the outside, when a short piece of india-rubber tube takes it to the copper pipe. The collar is kept in one posi- tion either by a weight hanging down from it, or by a rod which moves forwards with the machine. Care is taken to pass the supply of injection water through wire gauze, to remove any matter which might choke the small copper tube. When the necessary holes have been bored, the drill is taken off and replaced by a strong ram or hammer-head, which is made to strike powerful blows upon a wedge between two feathers fitting into the hole. Large masses of rock are broken off in this way, and the level is driven with any required dimensions. (2) The American Ingersoll Sergeant Eclipse Drill (Fig. 201) may be taken as an example of the machines having the valve worked by differences of air-pressure, which are caused by the opening and closing of certain passages by the piston in its course. It consists of the following main parts : the cylinder A, the piston M, the piston-rod B, and the valve chest C. The valve is like a D-slide- valve, but its face is turned so as to fit the cylindrical interior of the valve-chest, and it is provided at each end with a piston. It J mi 1 88 OEE AND STONE-MINING. therefore has the form of a spool or reel enclosing a D-slide- valve, and it moves backwards and forwards on a guide-pin. The air enters the valve-chest at 0, and, when the piston has reached the position shown in the figure, it finds its way round the valve to N', enters the port P', and finally reaches the rear end of the cylinder ; when the valve is reversed, it goes past N into P, and to the front end of the cylinder. The port P is shown in the figure communicating by the slide-valve with the exhaust E. The letters S S' represent a shallow recess cut round the piston, in reality making one piston into two ; F F' are two ports leading to the exhaust, and lastly D D' are two small ports which FIG. 201. communicate crosswise with the ends of the valve-chest; that is to say, D is connected with the end II', and D' with the end E-. Bearing these details of construction in mind, the action of the drill can be followed. The drawing shows the machine ready to begin its forward stroke. The rear end of the valve-chest is con- nected with D, which is closed by the piston, whilst the front E, is open through D' and the annular recess S to the port F' and the atmosphere. The compressed air from leaking past the rear valve-piston presses upon it and keeps it in the position shown, for any air leaking past the other valve piston at the end K can escape vid D', S, F' and E into the atmosphere. We will now suppose that the main piston M is being driven forward by the pressure behind it ; the annular space S gradually approaches the port D, but the length of the groove is so arranged that D' becomes closed just before D is opened to the exhaust. When the new state of things has arisen that is to say, when D is open to the exhaust and D' closed the pressure in the space II' at once drops to that of the atmosphere, and the valve is driven across by the pressure upon the piston at the end R. At both ends of the cylinder there is a strong india-rubber washer, protected by a steel washer, which is represented by a black line. If the miner fails to feed his machine forward pro- perly, the elasticity of the washer prevents the end of the cylinder from being broken. The rotation is performed by the usual rined bar and ratchet wheel, and the machine is advanced by BREAKING GROUND. 189 FIGS. 202 INCHES turning the handle and so causing the carrying nut to move along the feed screw. The Optimus drill, invented by Ogle, has two pistons, a large one in front and a small one behind. The compressed air, after- acting at the rear end and making the tool strike its blow, is led to the front end of the cylinder, and pressing upon the large piston drives it back. The inventor claims considerable economy for his drill, because the backward stroke is made with air which usually goes direct to the exhaust. Figs. 202 and 203 show one method of attaching the drills to the piston-rod. A is the piston- rod with an enlarged head, H ; S is the shank of the tool which is gripped in the socket by a chucking block fj, tightened by a U-shaped clamping-bolt 0. (3) Franke drill* This drill (Fig. 204) is especially interesting from being the smallest and lightest boring machine in actual use. Including the borer, it weighs only 16 Ibs. (yj kil.), and it may, therefore, be placed at one end of the scale whilst the ponderous " bosseyeuse " of Dubois and Frangois occupies the other. Both in his drill and in his mechanical chisel, Franke adopts the prin- ciple of doing the work by a light blow repeated very rapidly indeed, instead of a heavy blow at less frequent intervals. The principal parts of the machine are : A, outer case or shell ; J.', cylinder proper ; JB, piston ; (7, ring-shaped slide-valve, which can slide backwards and forwards in a short recess in the piston ; 1}, tool-holder ; JS, pipe bringing air ; f t rear end of cylinder proper with admission ports ; G, spiral spring ; N, exhaust port ; V, piston-rod ; J, striking head of piston-rod ; P, pin passing through the piston-rod a, passage bringing air from F ; 6, port admitting air to slide-valve ; c, one of three longitudinal passages connecting the front end of the piston with the annular recess in which the slide-valve works ; e, one of three similar passages connecting the same recess with the rear end of the piston; f, hollow centre of piston and piston-rod communicating by g with the exhaust port H h h, two of the three radial passages which put the slide-valve into connection withy"; i, part of tool-holder ; j, collar preventing the tool-holder from being driven back too far ; ll v straight slots in the shell A o o v oblique slots in the * Schrader, " Die neueren Fortschritte bei derAnwendung von Gesteins- Bohrmaschinen und die Versuche mib kleinen Schrammaschinen beim Mansf elder Kupferschieferbergbau," Zeitschr. f. B.- H.- u. - Wesen, vol. xli., 1893, p. 1 10. 190 ORE AND STONE-MINING. hollow cylinder q ; q v end of the cylinder q ; r r v ends of the pin P ; tt, pawls attached to q l ; u, hexagonal end of the tool- j! <0 3 i -: o 5 z ^ g ? 224 ORE AND STONE-MINING. FIG. 239. Koughly speaking, it takes five hours to bore the fourteen holes, and five hours more to charge and blast them, and clear away the rubbish. Some engineers direct the four centre holes so that they meet at the apex of an acute pyramid, and, after all have been charged with dynamite, only one receives a primer and cap, because the shock of the explosion of this charge is sufficient to fire the other three adjacent charges simultaneously. The preliminary opening is not necessarily made in the centre of a level. Sometimes it is blasted out in the bottom or on one side where there are natural joints to favour one of these methods ; but when the rock is uniform it is best made in the centre, for there the blasts can have the freest play. At Bex, in Switzerland, where water power is abundant, a con- siderable saving in cost has been effected by cutting a preliminary groove in the centre line of the level by a bosseyeuse. Seven holes, each 3^ inches (8 cm.) in diameter, are bored 2 inches (5 cm.) apart in a straight line, and the borer is then replaced by a tool which breaks down the partitions. A groove 2 feet 10 inches (86 cm.) long and 3 J inch (8 cm.) wide is thus formed, and after the bosseyeuse has been removed, holes 1-2 inches (3 cm.) in diameter are bored around by a Ferroux drill as shown in the diagram, Fig. 239. The holes A, B, C, D, E, F, G, are blasted at one time, but the fuses of A and B are cut shorter than the others, so that they go off first. The result of this volley is the produc- tion of a large opening, and then the firing of hole H, and subsequently of the outside holes, completes the level for a length of 4 feet (1-20 m.).* In driving with the Ferroux drill in the ordinary way, blasting out a central core, with dynamite, the cost per metre of level driven was . . Fr. By using the bosseyeuse to make a central groove, and then the Ferroux drill for the remaining holes, the cost per metre was only . . . Fr. 39 73 40 40 Saving effected by the use of the bosseyeuse . Fr. 34 oo The saving therefore is as much as 46 per cent. ; but in this case the extra water power required is costing nothiog. * Eosset, Notice sur les salines de Bex, Bex, 1888, p. 21. BREAKING GROUND. 225 In sinking shafts by boring machines, operations are con- ducted much in the same way as in levels, save of course that the holes are directed downwards. Figs. 240 and 241 are a plan and a section of a shaft which was sunk at the Foxdale mines in the Isle of Man. About forty-five holes were bored in the bottom of the shaft before the drills were removed. Two of the holes (A and B), and occasionally four, were FIG. 240. FIG. 241. .-- - 13 rr 6 i; --___ bored only 4 feet deep, and were blasted with ordinary fuse. They served simply to smash up and weaken the core ; then the six holes nearest the centre, which were 8 feet deep, were blasted all together with Bickford's instantaneous fuse, and the result was the removal of a large core, leaving a deep sink. The re- maining holes were fired in volleys of four at a time in the ordinary way. In this manner the shaft, which was in hard granite, was deepened at the rate of 3^ or 4 fathoms a month. Tonite w r as the explosive used. FIRE-SETTING. Though hard ground is almost invariably nowadays attacked by boring and blasting, the very ancient pro- cess of fire-setting is not quite obsolete. The effect of a fire is to make a rock split and crack, and render it easily removable by the pick or by wedges. In 1876 I saw a level in course of being driven in the Kongsberg silver mine, Norway, through crystalline schists, by this method. A fire of logs of fir was made in the end, and the smoke was conducted away to one of the shafts by an oval sheet-iron pipe, 2 feet by i foot. It took eight cords of wood to drive i fathom of level, and the rate of advance was 9 fathoms in 7 months. The fire was usually made up twice in every 24 hours. In another part of the mine an adit level was being driven at the rate of 2 fathoms a month, with a consumption of 15 to 18 cords of wood. In this case an arch was built in the roof of the level to form a passage for the smoke, and the iron pipe was used near the end. In driving in hard rock in the gold mines of Korea,* a pile of * W. J. Pierce, "Gold Mining and Milling in Korea," Trans. Am. /wrf. M. E., vol. xviii., 1890, p. 363. P 226 ORE AND STONE-MINING. wood is set on fire near the face of the tunnel, and allowed to burn for 24 hours. The place is then allowed to cool for three or four days, when the miners return and break down the loosened rock with hammer and gad. Fire-setting is also employed in mining jade in Burmah,* and in quarrying stone in India, f Lastly, the Siberian prospector avails himself of the softening action of fire for sinking small trial shafts through ice and frozen ground in search of auriferous gravel. EXCAVATING BY WATER. We turn naturally from fire, one of the four elements of the ancients, to another, water, as a means of breaking ground. Water can be applied either for dissolving the rock or mineral, or for loosening it and then carrying it away. There are two cases in which water may act as a solvent viz., common salt and copper. It is used, as we shall see in speaking of the methods of working, to dissolve out salt from saliferous rocks, and it can also be employed for excavating upwards or downwards in rock-salt. For excavating upwards (" putting up a rise"), a jet of water is made to play upon the roof of a level, and means are taken to carry off the brine in troughs (launders) without dissolving away the floor. For sinking from one level to another, a bore-hole is first put down, and this is gradually widened by the solvent action of water. When old workings containing the sulphides of copper are left exposed to the action of air and the percolation of rain water, part of the copper becomes converted into a soluble sulphate, and water pumped up from the mine may become a profitable source of the metal. This is the case at Parys mine in Anglesey. There are also two cases in which water is made to act as a loosener and conveyer viz., for working clay and gold. A stream of water is turned on to the deposits of china clay, and, aided by work with a pick, it carries everything to settling pits. The most important application of water is the process of washing away thick beds of auriferous gravel, known as hydraulic mining. A huge jet of water under pressure is made to play against the bank of gravel, undermine it, cause it to fall, and so thoroughly disintegrate it that everything save the largest boulders is carried away in the stream. Full details of these pro- cesses will be given in Chapter VI. (Exploitation). * Eng. Min. Journ., vol. xlviii., 1889, p. 359. f Ibid., p. 547. CHAPTER Y. SUPPORTING EXCAVATIONS. Yarious kinds of timber used for supports. Preservation of timber from dry rot. Tools. Timbering levels, shafts, and working places. Masonry, brickwork and concrete for levels and shafts. Iron and steel supports for levels, shafts, and working places. Special pro- cesses for sinking through watery strata : boring, compressed air and freezing methods. EXCAVATIONS made in hard ground will frequently stand with- out any props whatever for an unlimited time, but the miner has generally to deal with rocks which sooner or later give way unless supported. Consequently it becomes necessary to adopt means of securing the underground passages and working places, either during the process of excavation, or at all events very soon afterwards. The methods of securing mining excavations may be classified according to the materials used for the protective lining, viz., timber, masonry, iron, or steel. TIMBER. In Europe, varieties of the following kinds of trees are those most frequently employed underground : Oak, larch, pine, fir, and acacia. The oak is especially adapted for mining purposes on account of its strength and its durability. It will resist alternate exposure to wet and dryness, and under water it is almost im- perishable. In England we have two principal varieties, Quercus robur pedunculata and Quercus robur sessiliflora. The conifers, larch, pine, and fir, have the advantage of furnishing straight timber, of even grain, comparatively light, easily worked, having few branches, and less expensive than oak. The larch (Abies larix or Larix Europcea, D. C.) is an excellent mining timber. The large amount of resin it contains seems to act as a preventive against decay. It is tough and strong, and lasts a long time, even when alternately wet and dry. The American pitch pine (Pinus rigida) is a timber largely imported into this country for mining purposes, and it is used not only for securing shafts and levels, bufc also for pump-rods, bridges, sides of ladders, &c. It is remarkable for its perfectly straight growth ; it is hard, highly resinous, and very durable. 228 ORE AND STONE-MINING. The Scotch fir (Pinus sylvestris) is a tree that furnishes a great deal of mining timber. The British-grown timber is largely used for props, whilst balks imported from Norway and Sweden serve for heavy work in many mining districts. The spruce fir (Abies excelsa) is not a timber to be recom- mended for mine supports where durability is required. The acacia has the property of resisting the effects of bad air and high temperatures very much better even than oak. Mr. Fernow* gives the following list of the various kinds of mining timber which are available in the United States, each series being arranged in order of durability, beginning with the trees most adapted to resist decay. EASTERN RANGE. Conifers. Eed cedar (Juniperus Virginiana, L.) ; White cedar ( Chamcecy- paris sphceroidea, Spach.) ; Arbor vitas (Thuya occidentalis, L.) ; Bald cypress (Taxodium distichum, Rich); Long-leaved pine ( Pinus palustris, Miller) ; Red pine (Pinus resinosa, Ait.) ; Cuban pine (Pinus Ciibensis, Griseb.) ; Short-leaved pine (Pinus mitis, Michx.). Broad-leaved trees. White oak (Quercus alba, L.) ; Post oak (Quercus obtusiloba, Michx.) ; Chestnut oak (Quercus prinus, L.) ; Live oak (Quercus virens, Ait.); Basket oak (Quercus Michauxii, Nutt.) ; Burr oak (Quercus macrocarpa, Michx.) ; Osage orange (Madura aurantica, Nutt. ) ; Hardy catalpa (Catalpa speciosa, Warder); Black locust (Rdbinia pseudacacia, L.) ; Honey locust (Gleditschia triacanthos, L.); Red mulberry (Morusrubra, L.); Chestnut (Castanea vulgaris, var. Americana, A.D.C.) ROCKY MOUNTAIN REGION. Red cedar (Juniperus Virginiana, L.) ; Pinyon pine (Pinus edulis, Engelm.) : Foxtail pine (Pinus Balfouriana, Murray) ; Douglas spruce (Pseudotsuga Douglasii, Carr.); Western larch (Larix occidentalis, Nutt.); Burr oak ( Quercus macrocarpa, Michx.) PACIFIC SLOPE. Yew (Taxus brevifolia, Nutt.); Redwood (/Sequoia sempervirens, End- licher); Lawson's cypress (Chamcecyparis Lawsoniana, Parl.) ; Canoe cedar (Thuya gigantea, Nutt.); Douglas spruce (Pseudotsuga Douglasii, Carr.) ; Western larch (Larix occidentalis, Nutt.) ; Live oak (Quercus chrysolepis, Liebm.) ; Post oak (Quercus Garryana, Dougl.). The Douglas spruce, or Oregon fir or pine, is not only used in America, but also exported to Australia. It is a very straight wood, of even grain ; it has the disadvantage of easily taking fire. In Australia, the native woods are commonly used for mining purposes, and among them different species of Eucalyptus are specially prominent. The Jarrah (Eucalyptus marginata) is a native of Western * " The Mining Industry in its Relations to Forestry," Trans. Am. Inst. M.E., vol. xvii., 1888, p. 264. SUPPORTING EXCAVATIONS. 229 Australia. It gives a red, heavy, intensely hard wood, which is difficult to work with ordinary tools. It resists decay in a re- markable manner, in fact it is practically indestructible ; the white ant and the " teredo navalis " will not attack it. Up to the present time there has been little need of mining timber in the colony of which it is a native ; but it is exported to South Australia and New South Wales, and used for shaft-frames and other special purposes. The grey or white iron-bark (Eucalyptus crebra, F. v. M.), and the red or black iron-bark (Eucalyptus leucoxylon, F. v. M.), both give hard, heavy, strong, and durable timber, and are among the most useful of the forest trees in Australia. Grey box (Eucalyptus largiflorens) is a hard, tough, durable wood which lasts well underground. The young trees supply much prop timber in certain localities. Stringy bark (Eucalyptus obliqua), possesses similar good qualities ; and it is imported into Australia from Tasmania if the supply of the native-grown timber is insufficient or less easily obtainable. It is employed as sawn timber, or split, and the small trees make excellent props. Among other species of Eucalyptus may be mentioned the slaty gum (E. bicolor, A. Cunn.), and bloodwood, (E. corymbosa, ,Sm.), both strong and durable and used for railway sleepers. The prickly leaved tea-tree (Melaleuca armillaris) gives a hard, strong, heavy timber, lasting well underground. New Zealand can boast of the magnificent Kauri pine (Dammara Australis), a slow-growing tree, some living examples being estimated to be 2000 years old.* It contains a fluid resin which oozes out from every part, and hardens into large masses of opaque gum. It is light, elastic, even-grained and strong. ."Besides being used for timbering mines in New Zealand, it is exported to Australia for the same purpose. Matai (Podocarpus ferruginea), a reddish-brown, moderately hard wood, Miro (Podocarpus spicata), and Rewarewa (Knightia excelsa) may also be mentioned among the New Zealand mining timbers. In Japan the levels are sometimes timbered with bamboo. Preservation of Timber. Most authorities consider that the best time for felling timber is winter,, when the wood has the least amount of sap in it, because fermentation of the sap is one great cause of decay. For this reason also, timber should be seasoned before it is used ; that is to say, it should be allowed to dry gradually and so lose the sap by evaporation. Fernowf says that proper seasoning is more important than the time of felling. As regards * Laslett, Timber and Timber Trees, London, 1875, P- 2 9^- t Op. cit. and " Eelation of Kailroads to Forest Supplies and Forestry." Bulletin No. I, Forestry Division, Department of Agriculture, U.S.A. Wash- ington, 1887, pp. 37 and 67. 2 3 o ORE AND STONE-MINING. the removal of the bark or not, there is a difference of opinion, but it certainly facilitates the seasoning ; and in the case of oak the bark may be taken off for sale by the owner of the plantations, before he disposes of the timber to the miner. On the whole it seems advisable to remove the bark, and for two reasons ( i ) less liability to rot, and (2) earlier indications of incipient crushing, When stored at the mine, timber is best preserved under cover, protected from wind and weather, but with ample access of air ; and it is important to remove all decaying wood, whether logs, chips, or sawdust, and destroy it by fire, so as to prevent the spread of the contagion. The timber should lie upon supports and not directly on the ground, and the pieces should not be placed too close together. According to Laslett,* "the approximate time required for seasoning timber under cover, and protected from wind and weather, is as follows : Oak. Fir. Pieces 16 to 12 inches square 14 months. 7 months. 12 to 8 10 ,, 5 8 to 4 6 3 Planks, from one-half to two-thirds the above time according to thickness." Timber is often found to decay very rapidly in some mines, or in certain parts of a mine, owing to the spread of what is called dry rot. This is a white fungus which grows over the timber, and causes the woody fibre to decompose and become so soft and rotten that a knife or pick can be run in with the greatest ease. Various methods of preventing dry rot have been tried with more or less success. Good ventilation is all-important, for timber is found to become affected most rapidly in places where the air is foul or stagnant. Water has a decided preservative effect, so much so that arrangements are sometimes made for causing it to trickle down continuously over the timber in a shaft, or to form a spray in timbered levels. Probably the water acts by washing oif the spores of the fungus as fast as they are deposited upon the timber, and also by cleansing the atmosphere and keeping it cool. Mine timber is also occasionally treated with antiseptics, such as brine (with or without chloride of magnesium), borax, creosote, carbolineum, coal-tar, corrosive sublimate, chloride of zinc, sul- phate of zinc, sulphate of copper and sulphate of iron ; but far less attention has been given to this subject by mining than by civil engineers, to whom the duration of railway sleepers (ties, U.S.A.) is a matter of much importance. Treatment with a metallic salt is preferred to creosoting, if the timber is at all exposed to the risk of catching fire. * Op. dt. p. 316. SUPPORTING EXCAVATIONS. 231 The timber is treated in one of the following ways : (1) Steeping. The timber is simply placed in the preservation solution, and allowed to absorb what it can. (2) Hydrostatic Process. The preservative solution is forced in by hydrostatic pressure. (3) Vacuum Process. The timber is placed in boilers, and steam is admitted ; the air and vapours are then exhausted, and a preservative turned in under pressure. (4) Painting, i.e., application with a brush. It was found by experiments carried on at Commentry during a long series of years, that one of the best methods was soaking the timber for twenty-four hours in a strong solution of sulphate of iron (green vitriol). The total cost was only Jd. per yard of prop, whilst the timber lasted eleven times as long as when this simple treatment was omitted. " Carbolineum " is a patent preparation laid on with a brush like paint, which is well spoken of by the mining officials at Saarbriicken.* The cost of two coats of the preservative material on a prop 8 feet long by 10 inches in diameter (2*5 m. by 25 cm.) is about 7^d. The duration of a prop, or other piece of timber, is not the only point to be considered in deciding whether it is worth while paying the cost of some preservative treatment. The expense of the labour in the renewal of unsound timber, such as the cutting of fresh hitches, must not be overlooked. Tools. Timber is used in various forms either whole and merely sawn into lengths, or hewn or sawn into square balks, or sawn in half, or sawn or split into planks of different thicknesses. The tools used by the miner for shaping the timber are the saw and axe ; in addition he requires a measuring staff, a sledge or a wooden mallet for driving the timber into its place, a hammer and " moil " for chipping out recesses or niches (hitches), plumb line and level. The saws vary in different countries. In Great Britain the timberman's saw is the ordinary hand-saw of the carpenter, though a cross-cut saw worked by two men is used for cutting large props or balks. In the Hartz the timberman uses a saw somewhat resembling our cross-cut saw in shape, but smaller in size, and having the toothed edge curved, whilst in Saxony a frame saw is preferred. All large mines have a circular saw, and some are provided with special machines for cutting the joints of supporting frames. The axe varies in shape more according to the fancy of the user than any special difference in the purpose for which it is used. The moil is merely a pointed steel bar. In order to ascertain the length required for a piece of timber to fit a given place, the timberman uses a measuring staff, consisting of two bars of wood * Zeitschr.f. B.- H t - u. S.-Wesen t vol. xxxviii., 1890, p. 265. 232 ORE AND STONE-MINING. which are made to slide upon each other, and then fixed in any position by a thumb-screw. One end is often rounded so that it may reach to the bottom of the niche (hitch) which has been cut in the rock. The plumb line and level need no description. The principal kinds of excavations in mines are levels, shafts, and ordinary working places. These will be taken in order, and the methods of securing them dealt with briefly. Levels. Though a level is an excavation of a very simple nature, the methods of timbering it vary considerably, because the parts requiring support may either be the roof alone, or the roof and one or two sides, or the roof, sides, and bottom. If the roof only is weak, as is the case with a soft lode between two hard walls, a cap with a few boards resting on it (Fig. 242) FIG. 242. is sufficient to prevent falls. If one side is weak the cap must be supported by a side prop or leg (Fig. 243), and very often by two legs. The form of joint between cap and leg are numerous (Fig. 244), depending to a great extent on the nature of the FIG. 244. FIG. 245. A B FIG. 246. u pressure, whether coming upon the top or sides, and also on the shape of the timber, whether round or square. With round timber the top of the leg may be hollowed out as shown in Fig. 245 A ; but occasionally the joint is flat, and a thick nail or nog is put (Fig. 245 B) to prevent the effects of side pressure, SUPPORTING EXCAVATIONS. 233 or, better, a piece of thick plank is nailed under the cap (Fig. 246). Where the floor of a level is soft and .weak, a sole-piece or sill becomes necessary, and if the sides or roof are likely to fall in, a FIG. 247. CAP FIG. 248. SOLE PIECE. Horned sets FIG. 249. lining of planks or poles is used (Fig. 246). (Fig. 247)* are useful in loose ground. Fig. 248 shows the special system adopted on the Comstock lodef for some very heavy ground. The outer planks (lagging} are put close together, and the method of jointing has been carefully de- signed so as to prevent any yield- ing under the enormous pressure to which it is subjected. These levels are 6 feet high inside the timber. As an instance of timbering on a much larger scale, I give a re- presentation of the supports at Rio Tinto, Spain (Fig. 249 ); the height of the level from the groundsill (a) to the cap (c) is 1 2 feet 7 inches (3*85 m.), so as to allow the passage of locomotives. In driving levels for the deep gold-bearing gravels in the Cari- boo district, B.C.,| spruce fir i to 2 feet in diameter, simply barked, is used for making the sets. The lagging is in pieces * Rep. Insp. Mines, Victoria, for 1873, p. 7. Melbourne, 1876. t Hague, ''Mining Industry," United States Geological Exploration of the Fortieth Parallel, vol. iii., plate iv., p. 113. Washington, 1870. t Dawson, "General Note on the Mines and Minerals of Economic Value GO > 234 ORE AND STONE-MINING. 4 feet long, 5 inches wide, and 2 inches thick, and is split out of logs. The ground is so heavy that the frames (sets) are only a few inches apart in some places. Where the ground is very wet, spruce brush- wood is placed behind the lagging. In the Day Dawn mines in Queensland,* the gold vein some- times attains a width of 60 feet ; the hanging wall is not strong, and large portions of the lode itself are apt to slip away. ^ SCALE 10 5 10 15 20 25 FEET 'IMETKE 1 0123 A 5 6 7 METRES Though the levels could be driven without difficulty, it was found impossible, with the ordinary methods of timbering, to keep them open permanently after the vein had been worked away, and the whole pressure of the heavy ground on the hanging wall had to be supported. At last the so-called " pigsty " method was tried, and it has been found very successful. It consists in piling up logs 4 to 8 feet long, two by two, crosswise, and so building a support which covers a comparatively large area. Figs. 250 and 251 represent the pigsty timbering; the former is of British Columbia," Geol. Survey, Canada. Reprinted from Canadian Pacific Railway Report, 1877, p. 8. * This description and the figures have been kindly supplied by Mr. Joseph Shakespear, one of the Government Inspectors of Mines in Queens- land. SUPPORTING EXCAVATIONS. 235 a section along the line of dip, the latter along the line of strike. As the drivage progresses, strong sills, 10 to 12 inches in diameter, are laid along the floor of the level. These sills may be as much as 25 feet in length, and two of them are laid under each row of sties, which are placed about 6 or 8 ft. apart in the direction of the level. The number across the level depends upon the width of the lode, and the spaces between the rows of pigsties form the roads for the waggons. The cap-pieces are made of FIG. 251. SCALE i o 25 FEET (METRE 7 METRES timber 15 inches in diameter, and they rest upon the pigsties. Upon the cap-pieces comes a row of poles, which support the deads when the lode is worked away above. Where the width of the lode is not too great, the sills are dis pensed with ; the ground at the bottom of the level behind the end is excavated, and the pigsties are built up from the foot- wall. Consequently, when the lode is removed by the workings below, the level is not affected because the timbering is supported from the undisturbed footwall. When sills are used in a very wide lode, pigsties resting upon the footwall are built up whilst the ore is being excavated, and they are arranged so as to come exactly under the sills and carry their weight. This method of support requires a great deal of timber, but it has the advantage that the small logs used for the pigsties are inexpensive and easily handled, compared with huge balks required with the other systems. 236 ORE AND STONE-MINING. If the ground is loose so that the roof or sides, or both, will run in unless supported, the method of working called spilling, spiling, or poling is pursued. It consists in supporting the weak parts by boards or poles in advance of the last frame set up. The process may be described as pushing out a protecting shield in very narrow sections, one at a time. The poles or boards (laths) are driven forward by blows from a sledge, and the ground is then worked away with the pick ; this removal of ground enables the laths to be driven in further ; the pick is now once more called into requisition, and by successive small advances the shield of poles or boards is extended a distance of 3 or 4 feet. Fig. 252 shows one of the advance poles partly driven, with the front end FIG. 252. FIG. 253. resting upon a set of timber ; the pole behind it is in its final position. The section, Fig. 253, explains that the lower set of poles, those which are in the course of being driven, have room enough to slide on top of the cap, owing to the blocks placed upon it being slightly thicker than their diameter. In running ground it is necessary to have the laths- fitting closely together, and the working face must also be supported by breast-boards, kept in place by little struts resting against the nearest frame. These are removed and advanced one by one, after the laths in the roof, sides and bottom have been driven beyond them. In a few instances the end of a level in running ground has been kept up by covering the entire working face with wooden wedges ; an advance was gradually effected by driving them in with a heavy sledge. The sides and top of the level were pro- tected by laths in the ordinary way. Shafts. The timbering required for shafts varies according to the nature of the ground and the size of the excavation. A mere lining of planks set on their edges (Fig. 254) suffices for small shafts, corner-pieces being nailed on so as to keep the successive frames together. The usual method of securing shafts is by sets or frames. Each set consists of four pieces two longer ones called wall 'plates, and SUPPORTING EXCAVATIONS. 237 two shorter ones called end-pieces. They are joined by simply halving the timber at each end, as shown in Fig. 255, the wall- plate being made to rest upon the end-piece, though this arrange- ment is sometimes reversed. A more complicated joint (Fig. 256) is often preferred. The separate frames are kept apart by distance FIG. 254. FIG. 255. FIG. 256. pieces (studdles, Cornwall; jogs, Flintshire; posts, U.S.), and loose ground is prevented from falling in by boards or poles outside. The length of the distance pieces must depend upon the solidity of the ground. If the ground is very weak they are not used at all, and the successive frames are put in touching each other ; in loose ground near the surface the distance between the frames may be 18 inches, for instance, and then increased gradually to 4 or 5 feet when the shaft has penetrated into harder strata, The end-pieces are sometimes made long enough to project a foot or eighteen inches beyond the wall-plates, and rest in niches in the rock. Another plan is to insert bearers at regular intervals say every 30 feet under the end-pieces. The bearers are generally of oak, and in a shaft of medium size pieces 1 2 inches by 1 2 inches are taken, and cut four or five feet longer than the end- pieces. They therefore project 2 to 2 feet 6 inches at each end into solid ground, and decidedly add to the security of the timber lining. The sides of the shaft are further prevented from falling in by planks which rest against the wall-plates and the end-pieces. During the process of sinking, the last frames are kept in position by strong iron clamps, and when a length of 10 or 12 feet has been completed, planks (lashings or listings) are nailed on inside, stretch- ing over several frames and so binding them all together. This lining of a shaft may be regarded as a very long box, with strengthening ribs at short intervals. As shafts are frequently used for the several purposes of pumping, hoisting, and affording means of ingress and egress by ladders, it becomes necessary to divide them into compartments. Pieces of timber parallel to the end-pieces (bunions or dividings) are fixed across the shaft, and serve to stay the wall-plates, to hold the guides or 238 ORE AND STONE-MINING. conductors, to support planks (casing boards}, which are nailed to them so as to form a continuous partition or brattice, and to assist in carrying the ladder platforms. The magnificent timbering of some of the shafts on the Comstock lode is described by Mr. James D. Hague* as follows : " The timbering consists of framed sets or cribs of square timber, placed horizontally 4 feet apart, and separated by uprights or posts introduced between them. Cross-timbers for the par- titions between the compartments form a part of every set. The whole is covered on the outside by a lagging of 3 -inch plank placed vertically." Figs. 257, 258, and 259, copied from Mr. Hague's plates, illustrate this method of timbering. Fig. 257 is a plan of the shaft. " S S FIG. 257. .are the longitudinal or sill-timbers; T T, the transverse end timbers ; r, guide-rods between which the cage moves ; if* i ? in' i)" : 6 d rf j tf <5 I g fel u diameter; 66, the end-pieces; e e, the studdles, which are 18 inches long. The end-pieces are not halved as in Fig. 255, but are slightly wedge-shaped, so as to preserve their whole strength for prevent- ing the wall-plates from being squeezed together. However, reli- ance is mainly placed upon frameworks of round timber, 1 5 inches in diameter, placed at the ends and near the middle of the shaft, and shown in elevation in Fig. 262. Each framework consists of two pieces, 1 8 to 20 feet long (wall-posts, c c), kept apart by dia- gonal struts (stempels or spur-timbers, d, d', /"). The foot of the lowest stempel fits into a hitch cut in the long wall-post, whilst the head is merely hollowed out to suit the curvature of the opposite wall-post. All the other stempels are cut out in this way at both ends, and when the bottom stempel has been put in, the others are very speedily fixed one above the other. If necessary, a strong bearer, h, is put in from time to time under the wall-posts, and projects a foot or 18 inches into the ground on each side of the shaft ; thin poles placed vertically and horizontally,/ and g, pre- vent loose stones from falling in. * Engineering, vol. 1., 1890, p. 553. SUPPORTING EXCAVATIONS. 241 Special excavations have to be timbered according to circum- stances ; thus a chamber for a water-wheel at Clausthal in the FIG. 262. FIG. 263. Hartz was made decagonal (Fig. 263). The main horizontal pieces at the side were of lo-inch round' timber cut at the ends to the 242 ORE AND STONE-MINING. proper angle; behind them came half-round timber, trees 12 or 14 inches in diameter sawn in half, arranged vertically, and finally a backing of common planks; the successive horizontal frames were kept apart by studdles, one at each end of each side of the polygon. Spilling. When ground is loose, recourse is had to a spilling process like that described for levels. Strong balks of timber are FIG. 264. A > * A PLAN c C * SCALE o < 2 3 4. 5 FEET METRE fixed at the surface or in solid ground in the shaft, and the first frame is supported upon these bearers ; the next frame is hung from the first, the third from the second, and so on until the loose ground is passed. In Fig. 265 a a are the " bearers," which are made to project a couple of feet into solid ground : upon them rest the end-pieces b b '(Figs. 264 and 265), halved at the ends so as to support the two wall-plates c c ; e e are two rods of 2 -inch round iron, which hold up the end-piece d of the second frame or " set of timber." They are fixed tightly by means of cotters. The wall-plates // of the second frame rest upon the end-pieces in the usual way, and when it becomes necessary to put in a third set or frame, the end- pieces g are hung by cottered bolts from the frame above, d ; h h are the wall-plates. The fourth frame with its end-piece i and wall-plates j follows in the same manner ; therefore, until the pressure of the ground comes into play, the bearers a a are carry- ing the whole weight of the timber. The pieces k k, known as SUPPOKTING EXCAVATIONS. 243 " laths," are made of 2 -inch plank, 9 or 10 inches wide, sharpened at the ends ; they serve to keep the loose ground from falling into the shaft; II are the so-called " tailings " which keep the laths in position. The lath k' is one which is being put in ; it has to be struck with a heavy sledge until it makes its way into FIG. 265. Sectional elevation along line A A of Fig. 264. the loose ground. If very heavy blows are required, the head of the lath is protected by an iron shoe. The piece m is a stay put in for the purpose of keeping the set or frame in its place until the laths have been driven. The frames are kept at the proper distance apart, and the timber structure is stiffened by the usual corner posts n n (sttcddlee). 244 ORE AND STONE-MINING. The loose ground is excavated gradually, while each protecting sheath of planks is in process of being driven down, and in due course another frame is FIG. 266. hung on, and the opera- tions of driving laths and excavating are repeated. At mines on the Corn- stock lode, the bolts for keeping the frames to- gether are made in two parts, with a tightening screw in the middle ; great firmness is secured in this manner. Working Places. The timbering of working places varies very greatly. The simplest case is that of a horizontal bed. Here, props put in vertically of ten suffice to support the weight of the roof. The addition of a lid, a flat or slightly wedge-shaped piece of board at the top, extends the bearing surface, and, by presenting a smooth face to the top of the prop, enables this to be forced in more firmly into position than it could be against a rough roof. It also yields a little to the pres- sure of the roof, and lengthens the life of the prop in this way. When the bed is inclined, the props are not set quite at right angles to the plane of bedding ; one reason for this is that if so set they might be easily knocked out by an accidental blow from a falling stone. Mr. Sawyer* has made out a table showing the deviation from the normal which should be given : Set or Underset of Posts. Dip of Seam. Minimum. Maximum. 6 O 1 12 2 18 1 3 24 1 4 3 2 5 36 2 6 42 2 7 48 3 8 54 3 9 and upwards Accidents in Mines from Falls of Hoof and Sides, London, 1886, p. 50. SUPPORTING EXCAVATIONS. 245 Fig. 266, copied by permission from Mr. Sawyer, is an instance of a prop and lid for working in a bed of clay ironstone. Logs laid two by two crosswise (chocks or cribs), the pigsties of the Australian miner, form efficient supports. Fig. 267 repre- sents the manner of using them in a bed of potter's clay ; Fig. 268, FIG. 268. FIG. 267. 20fr one of the huge structures which may be seen in the Wieliczka salt mines ; and lastly, Fig. 269,* the method adopted at Day Dawn FIG. 269. gold mine, Queensland, in the case of a vein. The pigsties for supporting the hanging wall are built up at intervals in the work- * Kindly furnished by Mr. Joseph Shakespear, Government Inspector of Mines, Queensland. 246 ORE AND STONE-MINING. ing places (stopes), and then filled up with rubbish (deads, mullock). The pigsties on the foot -wall serve to keep up a portion of the vein until it is time to break it down. Square timber is used for chocks as well as round.* According to Heathcote, the " square set " system of timbering, so largely used in the United States, is not an invention of American origin, as is usually supposed. It appears to have been FIG. 270. FIG. known in Australia as long ago as 1854. The manner in which it is employed in Nevada for working away the soft " bonanzas," or ore-bodies of the great Comstock lode (Figs. 270, 271, and 272) is well described by Hague.f It consists in framing timbers together in rectangular sets, each set being composed of a square base placed horizontally, formed FIG. 272. of four timbers, sills, and cross- pieces, 4 to 6 feet long, framed together, surmounted by four posts 6 to 7 feet high, at each corner, and capped by a frame- work similar to that of the base. These cap-pieces, forming the top of any set, are at the same time the sills, or base, of the next set above, the posts, as the sets rise one above the other in the stope, being generally placed in position directly over those below. "The timbers are usually of 1 2-inch stuff, square hewn or sawn." Each post has a tenon 9 inches long at the upper end, and a tenon of 2 inches at the other end, which fit into mortices in the cap and sill respectively ; and " the sills and caps have short tenons on each end, and shoulders cut to receive the ends of the post and the horizontal cross-pieces." The walls of the excavation are sustained by a lagging of 3-inch or 4-inch plank. * Discussion upon Messrs. Jamieson and Ho well's paper, " Mining and Ore-treatment at Broken Hill, N.S.W." Min. Proc. Inst. C.E., vol. cxiv., Session 1892-93. Part IV. t Op. cit., p. 112. SUPPORTING EXCAVATIONS. 247 The whole width of the ore-body is stoped away at once, and its place supplied by timbering, and finally the vacant space is filled with waste rock derived from dead work in the mine or from special excavations underground quarries in fact in barren ground. The stoping is carried on overhand, starting from an intermediate shaft or winze, and Fig. 272 will explain how the different frames are built up one above the other. In the Eureka district, Nevada,* the system employed for securing the chambers left by the excavations of the ore-bodies is FIG. 273. by similar square sets, but the mode of joining the pieces of timber presents some peculiarities. Fig. 273 is a general view of a square set employed at the Richmond mine, which explains the manner in which the tenons and shoulders are cut. This complicated method of framing is admitted to be expensive, but its adherents claim that it possesses great strength. At Eureka mine the joint is simpler. The Eureka timbering is designed for resisting pressure in all directions, the Richmond method for offering the greatest resist- ance in the direction of the caps, the ties being placed parallel to the walls. * Curtis, " Silver-lead Deposits of Eureka, Nevada," Mon. U.S. Geol. Survey, vol. vii., p. 154. Washington. 1884. 248 ORE AND STONE-MINING. The dimensions of the pieces between the shoulders are : posts 6 feet, caps 5 feet, ties 4 feet, and the timber employed is pine FIG. 274. CJU_E or rceT from the Sierra Nevada, hewn into balks 12 by 12, 10 by 12, or 10 by 10 inches. SUPPORTING EXCAVATIONS. 249 Square sets are likewise adopted at the Broken Hill mines* where a wide and soft lode has to be stoped away (Figs. 274 and 275), and they are being tried in Hodbarrow mine in Cumberland. The joint used at Broken Hill t is represented in plan by Fig. 2 7 6, in which A A are the caps, B B the struts, and C the tenon 4 inches FIG. FIG. 277. FIG. 278. n n square on the end of the upright post or leg. Fig. 277 explains the manner of packing the hanging wall with timber, so that the load may be distributed evenly upon the supporting framework. It also shows how a weak spot at A is further secured by horizontal stays. When additional strength is required, a lining A (Fig. 278), or an angle-stay, B, is put in ; and should these precautions appear insufficient to prevent a movement of the ground, the framework may be reinforced in various ways, as illustrated by C, D, E and F (Fig. 278); F is a solid lo-inch wall of timber. MASONRY. Masonry has long been used for supporting the roof and sides of mining excavations. The materials necessary are stone, ordinary bricks or slag-bricks, and they may be built * Victoria, Annual Report of the Secretary of Mi 1 ) p. 36. t Heathcote, op. cit. for the Year 1889, 250 ORE AND STONE-MINING. up alone (dry walling), or with the aid of mortar or hydraulic cement. Concrete, a mixture of hydraulic cement and small FIG. 279. Scale* of Feet stones, is occasionally employed, and probably could be more so with advantage. Once more I will take the three cases of a level, a shaft, and a working place. Levels. In levels dry walling and timber are sometimes FIG. 280. Scede. combined. Thus, after the excavation of a wide lode, the rubbish is piled up on the sides, walls are built up of the large SUPPORTING EXCAVATIONS. stones, and caps of timber are laid across, which support the " deads " when the higher portions of the lode are taken away. Fig. 279 represents a level in an iron mine in the Forest of Dean, where sandstone is available. The pieces are hewn and trimmed roughly, and a semi-circular arch is made to rest upon walls at each side. Fig. 280 is a level in one of the mines at Clausthal in the Hartz ; the sides are constructed of slag-bricks, and at the bottom of the tunnel there is a channel, made of concrete, for carrying water and preventing its percolation into lower workings, which would other- wise necessitate unprofitable pumping. If both sides (walls) of a vein (Fig. 281) are firm, an arch affords ample protection when the ore has been removed, and provides a resting place for the rubbish (deads, attle Corn.) A vein is very often a fault, and soft beds may be found FIG. 281. FIG. 282. opposite a hard wall of solid rock. In this case the arch is made to reach from the roof to the floor (Fig. 282). One of the main crosscuts at Mansf eld * was lined with concrete for a length of 1000 m. (f mile) ; 12 metres (40 feet) a day were put in, and for this purpose 50 metres (164 feet) of centering were required. The laths were covered with thin sheet-iron, so as to prevent the concrete from sticking. The concrete was made of Portland cement, broken stone, and gravel, in the proportion of i to 7, viz., i part of cement, 2\ of broken stone, and 4jof gravel. Up to a height of 16 inches (^cTcm.) from the ground, the layer of concrete was made thick enough to join on to the sides of the level, in order to assure a firm foundation. Above that height it was made only 6 inches thick, the sides of the level having been previously built up with dry walling. The centering could be removed at the end of three days, but it was usually kept in four or five. It was found that five men could * Pamphlet describing the exhibits of the Mansfeld Company at the Berlin Exhibition for the Prevention of Accidents, 1889, p. 20. 2 5 2 ORE AND STONE-MINING. FIG. 283. put in 6 m. (20 feet) of concrete lining in a shift of twelve hours. The cost per running metre was 31 marks 70 pf. (i 8s. ^d. per yard). Shafts. Like levels, shafts are lined with masonry, brick- work, or concrete, and these have the advantage of being far more permanent than timber, and of requiring fewer repairs. When due weight is given to the fact that the shafts are usually the main thoroughfares of a mine, the necessity of having a lasting lining becomes very evident. This kind of shaft-lining is especially desirable in loose ground near the surface, because if the working is discontinued tem- porarily, the shaft still remains secure and available for use at any future time ; whereas if timber is put in, it soon decays, the top of the shaft collapses, and much expense is incurred in the process of reopening it. Another immense advantage of a shaft without timber is its immunity from fire. The section of walled shafts is generally circular, as affording the best resistance to pressure. Elliptical walling is also met with, and sometimes the two long sides are made with a flat curve, and the two ends with a curve of much shorter radius. The wall- ing may be dry or with mortar, according to circumstances. The masonry lining is put in either in one length, or in successive rings or sections in descending order, and this is the usual plan. The shaft is sunk to a certain depth with a temporary lining of timber, and when firm ground has been reached, a bed is cut out on which is placed a crib or curb, A B, Fig. 283,* consisting of seg- ments of timber forming a ring. This serves as a foundation for the brickwork, which is built up to the surface ; the tem- porary timbering is sometimes left in and sometimes removed as the work progresses, and any vacant space is filled up with earth or concrete. Sinking is then resumed, and of a smaller diameter for a certain distance, so as to leave a bracket or ledge to support the curb. On arriving, after a certain depth of sinking, at another firm bed, a second curb, C D, is put in, and a second ring of brickwork built up. When the intervening ledge of rock is reached, it is carefully removed in small sections, and the brickwork brought up to the first curb. This process is repeated until the shaft is completed, or reaches rock in which no masonry is requisite. If, * J. Gallon, Lectures on Mining, vol. i. atlas, plate xxviii. SUPPORTING EXCAVATIONS. 253 owing to the nature of the ground, it is impossible at first to find firm seats for the curbs, it becomes necessary to hang them by iron bolts from a strong bearing frame at the surface, or to support them on iron bars fixed in the sides. Fig. 284 shows a concrete lining put in at the top of the main shaft at Foxdale mine, in the Isle of Man. The shaft is rect- angular, 1 3 feet 6 inches by i o feet 6 inches. The concrete serves not only to support the sides in the loose, weak ground near th& FIG. 284. HO* .6' 5- 4.'- -> f^ i3$3 *$$$ iSS >-;, VRD ROCK 7 -^'x *' '*"* top, but also to keep out much of the surface water. The concrete was made of 4 parts by volume of stones 2 J inches to 3 inches across, 2 parts of sharp sand and i of Portland cement, and the total cost for materials and labour was 135. 6d. per cubic yard. Some shafts in Germany have lately been lined with concrete blocks shaped so as to fit the curvature of the sides.* Each block is fluted at the top and at the ends, whilst the bottom has a bead- ing, which lies in the channel of the block below it. As the blocks may weigh as much as one-third of a ton each, it is con- venient to have some easy means of handling them. A vertical hole is therefore left in each block which receives a ring bolt, fixed by a cotter inserted through a horizontal hole. The block can then be easily slung to a rope and lowered into position, and on knocking out the cotter the bolt can be withdrawn. The spaces between the blocks, and also the bolt-holes, are filled with cement ; the shaft thus receives what is practically a solid lining of concrete, which, besides supporting the ground, keeps back water and acts the part of tubbing. As pointed out by Mr. * Zeitachr.f. B.- H.- u. S.-Wesen, vol. xxxix. 1891, p. 98. 254 ORE AND STONE-MINING. Brough,* a lining of this kind has the advantage over cast-iron and timber of not corroding or decaying, besides which its strength increases with age, and any expansion or contraction from changes of temperature are inappreciable. Finally, it is far cheaper than a lining of brickwork or iron. The Monier system consists in strengthening the concrete by a coarse net-work or skeleton of iron wire embedded in it. Re- inforced in this way, the fabric has greater tensile strength. Working Places. In temporary excavations, like working places, rough pillars,, built up of lumps of waste stone or of the FIG. 285. useful mineral itself, will take the place of timber in supporting the roof, or may be used as an adjunct to it, as is the case in Fig. 285, borrowed from Mr. Sawyer, t The timber at the top serves to make the pressure come gradually upon the stone.' The post is eventually drawn out and the stone recovered. Walls are also built up with waste stone enclosing spaces which are filled up with any available rubbish ; and in some instances excavations are entirely packed with rubbish after the removal of the useful mineral. It is only in exceptional cases that it is possible to incur the expense of building pillars with cement or mortar to support the roof and sides of working places ; but masonry or concrete * " Notes on the Use of Cement in Shaft-SiDking," Proc. N. E. Inst. M. E., 1893. t Op. cit., Fig. 4. SUPPORTING EXCAVATIONS. 2 55 arches may be constructed for carrying the rubbish used for filling the vacant places left by workings upon mineral veins. METALLIC SUPPORTS. There are various ways of using iron and steel as supports for levels, shafts and working places, Levels. In one part of the Halkyn Drainage tunnel, Flint- shire, a combination of cast-iron and wrought-iron has been em- ployed. Much of the level is in hard, solid limestone, and requires no lining of any kind ; but where small beds of shale were inter- mixed with the harder rock, timber supports were put in. As the timber originally used was showing signs of decay, it was decided in 1887 to replace it by a more lasting material iron. The nature of the Halkyn supports will be easily understood by Fig. 286. There are two vertical props ov legs, which are hollow cylinders of cast-iron, 6 feet 6 inches long, 5 inches in diameter FIG. 286. FIG. 287. -5 ins-- <_ g i ns . ^ n externally, and 4 inches internally, with a flange 8 inches diameter at the top, and 9 inches in diameter at the bottom. A chair, shown in section by Fig. 287, drops into the top of the iron column, and receives a reversed iron rail, 7 feet long, weigh- ing 117 Ib. (50 Ib. to the yard), the precise shape of which is shown on a larger scale by Fig. 288. The iron frames are placed about 3 feet apart, planks or rails are laid from one to the other, and the space between them and the roof tightly packed with stones. A dry stone wall is built up on each side, with an occa- sional plank or rail to make it firmer. Fig. 286 also shows a timber X*^ E f (UNIV V OF THE UNIVERSITY 2 5 6 ORE AND STONE-MINING. " spreader " above the water level, carrying longitudinal sleepers with bridge rails forming a waggon-way with a 26-inch gauge. This method of support is designed for a case where the roof is weak, and where no great pressure is expected from the sides. It FIG. 288. FIG. 289. would evidently be unsuitable for the Cornish County adit in Gwennap, because the water would speedily eat away the iron. In the Halkyn adit, however, no corrosion need be feared ; for iron rails which were laid near the mouth of the tunnel very many years ago have not been injured by the water. Its cheapness, as compared with the cost of the walling, was the reason why iron was adopted in Flintshire. It was estimated that to secure this part of the adit with the best Buckley brick and hydraulic lime, would cost over ^4 per yard, whereas the present method has cost only 2 45. per lineal yard of tunnel, It cannot be denied that a brick lining would be more permanent, as the planks in the roof of the level will have to be replaced from time to time ; but the cost of repairs is likely to be slight. In more recent work iron rails and old fire-bars are used instead of wooden lagging. Steel beams have been used with success for some years at the Nunnery Colliery, Sheffield, in the place of timber. They are of I-section, 4 inches wide, 5 inches deep, with the web f inch thick (Fig. 289), and they are considered by Mr. Bainbridge, the manag- ing director of the colliery, to be of the same strength as 1 2-inch Norway balk. The beams are supplied in lengths of 6, 7, 8, 9, and 10 feet, so as to suit drivages of various widths. There are two ways of using them (i) as " bars," or caps, resting upon the timber legs; (2) as legs and caps. Fig. 290 shows the former method a horizontal cap, 10 feet long, rests upon two legs of round Norway timber, 8 to 10 inches in diameter, and a lug or band of wrought iron, i inch by J inch, shrunk on, prevents the leg from coming in sideways. The frames or sets are generally placed 3 feet apart, and old timber laid across from cap to cap forms the so-called lofting supporting the roof. The steel beams are tarred over with unboiled gas tar, and some have been in use several years without showing any signs of deterioration, whereas the average life of English larch or Norway timber, at this colliery, is only two years. SUPPORTING EXCAVATIONS. 257 The beams cost about ^5 105. per ton, delivered at the colliery ; in other words, a ro-foot beam costs 8s. A beam of Norway timber 10 feet by 12 inches by 12 inches would contain 10 cubic feet, and at 8^d. per cubic foot, would cost 75. id. The difference in original cost is therefore not very great. FIG. 290. Scale Inches 12 6 1 2 ~8 9 '- 10 Feet The advantages of the steel over timber beams are numerous : 1. Greater durability, which means a great reduction in the cost of repairs. 2. Possibility of using the beams elsewhere when taken out. If bent slightly, they can be reversed ; if badly knocked about, they can be sent to the steel works and worked up again. In any case, they are of some value, 3. Lightness and handiness. A ic-feet steel beam weighs 166 Ibs. ; a lo-feet beam, 12 inches square, of Norway timber, weighs 3 cwt. The steel beams are not only lighter, but also less bulky, and consequently more easily handled. Therefore men can do more work in a given time. 4. Increased space for ventilation. The free space in a level will be from 5 to 7 inches higher with steel than with timber in lining an excavation of a given size. Six inches added to a height of 6 feet means an increase of i-i2th, or 8| per cent., in the area of the airway. 5. Less deterioration of the air of the mine by decaying timber. 6. No danger from fire. When girders are used as legs as well as caps (Fig. 291), a plate B 258 ORE AND STONE-MINING. of rolled steel, of the shape shown in Figs. 292 and 293, is placed at each extremity of the leg. The plate is J inch thick, 6^ inches FIG. 291. FIG. 292. FIG. 293. FIG. 294. long, by 6 inches wide, with a slot J- inch wide and 2 ^ inches long. The web of the leg passes into this slot and is thus prevented from slipping sideways, while the turned-up rim prevents slipping out- wards or inwards. Lugs of wrought iron are shrunk on to the cap as in the previous case. In making the comparison of cost, it is necessary to recollect that I have chosen a case extremely favourable to steel, because the beams are made at Sheffield, and any waste material can be worked up again on the spot with- out having to pay a heavy cost of carriage back to the steelworks. One kind of joint used in Bel- gium* for I -iron is a flanged bonnet of cast-iron, which receives the top of the leg and one end of the cap. A wooden wedge is placed in the bonnet under the cap, so as to give a certain amount of elas- ticity to the frame. In doing work with a new ma- terial, a servile imitation of the old forms is often remarked. The fact of timber being most readily obtainable in straight pieces naturally led to the adoption of rectangular, trapezoidal or polygonal forms for supporting linings ; but there is no necessity with iron or steel for copying the shapes which are most suitable with wood. This was recognised by the Germans in the early days of iron supports. A method in use in the Hartzin 1872 consisted in bending an iron * Habets, "Le materiel et les precedes de 1'Exploitation des Mines," Extraits des Rapports du Jury International des ^Recompenses de V Exposition Unwerselle d'Anvers, 1885. Paris and Liege, 1887, p. 61. SUPPORTING EXCAVATIONS. 259 rail as shown by Fig. 294, and making it support other rails laid longitudinally, against which flattish stones were placed ; the vacant place between these and the rock was filled with rubbish. The ends of the rails were footed in holes cut in large stones. FIG. 295. Some neat and effective forms of steel supports are made in France, where more attention has been paid to the subject than in this country. ." Three kinds made of I-steel by the " Societe anonyme des FIG. 296. Hauts-Fourneaux, Forges et Acieries de Denain et d'Anzin," will serve as good examples of steel supports for levels. Fig. 295 is a slightly bent bar, the ends of which are made to 260 ORE AND STONE-MINING. FIG. 297. rest upon dry walls at the sides of a level. It, therefore, takes the place of an arch. Fig. 296 represents a favourite form of lining for levels ; it is composed of two side-pieces suitably bent at the top, and united by a couple of fish-plates (Fig. 297) and four bolts , in some cases a cast-iron sleeve is used instead of the fish-plates. When the floor is soft and liable to " creep," the frame may be made of three pieces (Fig. 298). Some mines utilise old rails, weigh- ing 36 to 40 Ibs. per yard (18 to 20 kil. per metre) for frames. The rails are bent into semicircles, and two of these are united by sleeves of riveted sheet- iron, in which they are kept tight by wooden wedges. Elliptical frames are used in the Freiberg district, made of two pieces of rail held together by a "- - - - SQmnt - couple of fish-plates at the top and bottom. FIG. 298. SCALE. OF FEET 1234- SCALE. OF METRES O.5* SUPPORTING EXCAVATIONS. 261 The frames made by the " Compagnie des Fonderies et Forges de 1'Horme " (Loire) are almost invariably composed of two semi- circles of mild steel. Two kinds of sections are employed FIG. 299. FIG. 300. namely, channel steel and bulb tee steel. Bars of channel steel, 70 mm. x 40 mm., weighing 16 Ibs. to the yard, are sawn into proper lengths on leaving the rolls, and while still hot are bent into semicircles. The ends are carefully planed square, so that the top semicircle may rest accurately upon the lower one (Fig. 299). They are joined by sleeves made of sheet-steel, fixed by a couple of small iron wedges (Fig. 300). It is claimed by the Horme Company that these frames never give at the joint. Steel of bulb tee section, weighing 26 Ibs. per yard, is employed for heavier ground (Fig. 301). The sleeves are made of riveted sheet-steel, and are fixed by two wooden wedges, one on each side of the web (Fig. 302). Bars of U -steel of a hollow semicircular section are used as the lagging ; the steel is J inch thick and about i J inch in diameter, weighing scarcely 2 Ibs. per yard (i kilo, per metre), and it is usually cut in lengths just sufficient to go from one frame to the next. Small bars of steel of square section are employed for the same purpose. 262 ORE AND STONE-MINING. Iron and steel may be used with advantage instead of timber for the construction of supporting platforms (stulls) in vein- mining. At Freiberg* full-sized rails are employed as cross- beams (stull-pieces) ; they are covered with small mine rails, FIG. 301. FIG. 302. and these with flat stones. Where the pressure is not very great, wire rope is used for the covering. The rope is cut into pieces about 2 metres long, and the ends are welded up and bent into hooks. These pieces are laid across the iron stull-pieces and covered with stones and rubbish. In places where the two walls of a lode are likely to come together a little after a time, the stull-pieces are cut about i or ij inch shorter than required, and a wooden wedge is put in at each end. The pressure of the ground squeezes up the wedges gradually, and finally the rock comes against the iron. The rails used as stull- pieces are often slightly arched so as better to support the weight of the rubbish, and the flange of the rail is placed underneath, as its long straight edge gives a better hold in the rock than its head. The rails are not cut across at right angles to their length, but are made somewhat longer above than below, * freibergs Berg- und JHuttenwesen, Freiberg i. S., 1893, P- I 7^- SUPPORTING EXCAVATIONS. 263 in order that they may not drop through if small pieces of rock break off under them. In addition to all sorts of small rails, old fire-bars and old boiler-plates are occasionally utilised for " lagging." A new departure in driving tunnels in soft ground is furnished by the Greathead* shield, by the aid of which two long parallel tunnels have been driven through clay and gravel, in London, for passenger traffic by an electric railway. As cases may arise in mines where this method would be available, it is desirable to explain briefly the mode of working adopted, and to indicate the sources where full details will be found. The tunnels of the City and South London Railway may most easily be described as long tubes of cast iron, built up ring after ring as the excavation pro- gressed. The rings are i foot 7 inches long, made in seven seg- ments bolted together by f -inch bolts passing through the internal flanges. They therefore closely resemble the watertight lining of shafts known as " tubbing," to which reference will be made later. The ground in the centre part of the end of the tunnel was dug out, and a cylindrical shield was forced forward by hydraulic jacks. The shield had a cutting edge and penetrated into the clay under the pressure. The clay was removed as the shield went forward, and at last, when the advance amounted to 20 inches, a new ring was formed by bolting together the segments, which then exactly fitted the inside of the shield. The progress of the shield left an annular empty space 1 1 inches deep between the last ring and the surrounding clay, equal to the thickness of the shield. This was filled by injecting Lias lime grout through a hole in each segment, and so encasing the tunnel in concrete. The average progress per day was 13 feet 6 inches. When the tunnel came to water- bearing gravel and sand, it was necessary to have an air-lock and keep the water back by compressed air. In order to prevent the escape of air into the porous gravel, the face was cut away in sections, and as each portion was exposed, a jet of grout was played upon it to close the interstices. Shaft Linings of Iron. Fig. 303 shows a method of temporary support for sinking little shafts 30 or 40 feet deep. Iron rings, 4 feet 6 inches to 8 feet in diameter are employed to keep lining planks in position. The rings are made in two or three segments, bolted together inside. The iron used is from ij to 2\ inches wide by \ inch thick.' * Engineering, vol. 1., 1890, p. 551. FIG. 303. OFTHF 264 ORE AND STONE-MINING. FIG. 304. FIG. 305. SUPPORTING EXCAVATIONS. 265 FIG. The rings may be hung one from the other by iron hooks, and channel iron may take the place of the flat iron in the circles around the shaft. Steel and iron rings are also used in the case of permanent supports for shafts. The accompanying figure (304) shows the lining of a shaft at Boryslaw, adopted by Herr Platz, the director of the ozokerite mines be- longing to the " Compagnie Cem- merciale Frangaise." The shaft is kept open in very heavy ground by rings of channel iron placed 1 metre apart from centre to cen- tre. Each ring is made in two halves arid these are connected by two special castings, with holes for bolts ; they act the part of fish- plates, two bolts being on one side of the joint, and two on the other. Around the rings come oak planks, 2 inches thick, and there are four distance pieces (studdles or posts) between every two rings. At intervals of 2 or 3 metres, two oak bearers are placed across the shaft, which serve to take up the weight of the rings if necessary, though, as a rule, the pressure of the ground holds the rings very firmly. The bearers are also ,_ utilised for carrying the guides or conductors for the cage. Fig. 305 represents a ring simi- o ' * ' * ' ' ' .0 ' ,* ',*',' , B ao lar to those used at Boryslaw, made by the Witkowitz Ironworks for a shaft 8 feet 6 inches in diameter, and Fig. 306 gives the details of the connecting piece and bolts. Working Places. We may start with simple cast-iron props used instead of timber in places where they can be withdrawn. They are rather heavy, but they will serve over and over again. At some collieries a large number of these props, from 3 feet 6 inches to 5 feet 6 inches long, are employed, and they appear to give satisfaction. Naturally they have to be made of the same height as the particular seam which is worked, but any minor irregularities in the roof are suited by the thickness of the lid, or by making the lid of two pieces of board. They are set with the small end downwards. Cast-iron props are not suited for resisting cross pressures, and they are liable to break occasionally when they happen to fall. SCAL.E OF INCHES SCALE OF MILLIMETRES 266 ORE AND STONE-MINING. Howell's prop is a hollow lap-welded steel tube or pipe, 4 inches in diameter outside, with the ends expanded till they are slightly conical, in order that the top may receive a wooden plug which projects about f inch above the steel. These props are used alone in working places, or in conjunction with bars of I-steel, to support the roadways. The foot of the prop in this case is set out about 6 inches in the bottom so as to pre- vent it from coming in sideways. The object of the plug is to obtain a certain amount of elasticity. A third kind of prop is made of I-iron or steel, either cut off square or with the web cut out for a few inches, and the two flanges turned over so as to make ends with a larger bearing FIG. 307. FIG. 308. surface (Fig. 307). The holes a a enable the props to be with- drawn by a hook. WATERTIGHT LININGS FOR SHAFTS. We must now turn to the special case of shafts which have to pass through watery strata. Here it is often advisable to put in a watertight lining, in order to prevent the inflow of water, and so save the expense of pumping it out day after day, and year after year. The lining may be made of wood, brick, and hydraulic lime or cement, or, lastly, iron. There are two kinds of wooden tubbing: (i) Plank tubbing, whence this kind of lining originally received its name; and (2) solid timber tubbing. Plank tubbing is made of boards from 2 to 3 inches thick, arranged vertically round the shaft and cut with a bevel like the staves of a cylindrical barrel. The planks are nailed on to rings of wood placed at suitable intervals. SUPPORTING EXCAVATIONS. 267 Solid wooden tubbing (Fig. 308) consists of carefully shaped blocks of oak or elm, with thin sheets of deal placed between the joints. The joints are wedged up as tightly as possible, and a lining of this kind can be made so as to resist a very considerable pressure of water, even 200 to 300 Ibs. per square inch.* The method known as " coffering " consists in lining the shaft with a wall made of brick and cement, or brick and hydraulic lime, and backing this up with puddled clay. It is specially used for keeping back the surface-water. Full details concerning this method will be found in the paper t quoted below, and my description may be very brief. In one particular instance the shaft received first of all a temporary lining of g-inch brickwork put in dry during the course of sinking, the successive sections being held up by wooden cribs or curbs that is to say, rings of oak placed 4 to 5 feet apart. Each ring was hung from the one above it by vertical pieces of i J-inch plank FIG. 309. spiked on to both rings. When firm ground below the watery strata had been reached, a level bed was cut for putting in the wedging-crib a ring made of segments of cast-iron, either like A or B in section (Fig. 309). By means of wedges driven in behind, it was made perfectly tight and stanch. Three courses of brickwork made with Roman cement were built up on the crib and the wedges behind it ; they formed the foundation for the "coffering " proper, which consisted of three rings of brickwork in hydraulic mortar EE (Fig. 310), separated by the two rings of hydraulic mortar F F, and the puddled clay D. B represents the original lining of nine inches of dry brickwork put in against the watery strata. As water running down the sides of the shaft would render it impossible to carry out this kind of work satis- factorily, means had to be adopted for getting rid of it. A garland or circular launder was fixed around the shaft so as to intercept it before it could interfere with the work of coffer- ing, whilst water coming in behind the coffering was drawn off during the progress of the work by placing a vertical launder against the preliminary lining of bricks. This launder was pierced with holes every three inches, and communicated at the bottom * E. Bainbridge, " On the Kind-Chaudron System of Sinking Shafts through Water-bearing Strata," Proc. List. C.E., vol. xxxiv., 1871-1872, Plate 12. t N. K. Griffith, " On the Coffering of Shafts to keep back Water," Trans. N. Eny. Inst. Min. Mech. Eny., vol. xxvi., 1876-77, p. 3. 268 ORE AND STONE-MINING. with a block of wood which had a 3-inch hole bored through it, opening into the shaft just above the wedging-crib. As it became FIG. 310. Scale of Feel I" 6"?* o I 2 gradually buried by putting in the clay D, the holes were plugged up, and finally the launder was filled with pieces of stone, and cement was run in. The walling was done with hydraulic mortar, ma'de of one of blue lias lime to two of sand, and the middle course was grouted in, either with a similar mixture or with pure Roman cement. The advantage of coffering over the ordinary metallic lining known as tubbing is its cheapness. Mr. Griffith puts the cost of coffering a shaft he sank at 10 55. per yard, and he estimates that a suitable cast-iron tubbing would have cost ,23 per yard. The pit was 20 feet in diameter clear within the original lining of dry bricks, and as the coffering was 2 feet thick, the final diameter of the pit was reduced to 16 feet. Where the ground is soft, a cast-iron lining may be made to sink down by its own weight and by pressure applied to it. This process was adopted at Restronguet Creek,* a branch of Falmouth Harbour, in order to work a bed of stream-tin. The creek had 10 or 12 feet of water at high tide, and was nothing but a mud- bank at low tide. A staging was constructed upon piles in the creek, in order to have room for working, and a first cylinder, with * Taylor, " Description of the Tin Stream Works in Restronguet Creek, near Truro," Proc. Inst. M.E., 1873, p. 155. SUPPORTING EXCAVATIONS. 269 a cutting edge, was placed upon the mud, two more cylinders were then bolted on, and their weight caused the whole to sink down. The cylinders, made of cast-iron, were 6 feet high by 6 feet in diameter and i| inch thick, and they were joined by internal flanges faced in the lathe. Each ring weighed about 2^ tons, and was lowered by a crane through an opening in the stage, between guides in order to keep it vertical. When the first three rings had ceased to sink, the mud inside was cleared out, and further cylinders were added and forced down by pressure from the chain of a crab-winch. Afterwards an ingenious method of taking advantage of the rise and fall of the tide was resorted to. A huge girder was laid across the top ring, and a barge laden with stone was attached to each end. The fastening was made complete at high water, and when the tide fell the full weight of the barges came npon the girder, and so upon the shaft. The cylinder was thus sunk to the full depth without difficulty. During the sinking the core was always cleared out a little below the bottom of the cylinder before the barges were attached, and, if left for a day, the mud was found to swell up 3 or 4 feet into it. A total weight of about 250 tons was required to sink the cylinder FIG. 311. &J&T. \ as it neared the bed of tin ore. Altogether, thirteen of the 6-feet rings were sunk, making a total depth of 78 feet. The ordinary method of tubbing is that in which the rings are made up of segments, and as a rule the cylinder of cast-iron plates is built up within some temporary lining ; this is carried down until it reaches some solid and impervious stratum below the 270 OEJE AND STONE-MINING. water-bearing measures, fit to serve as a foundation. When such a stratum has been found, the sinking is continued for a few feet, and a bed is cut out very carefully, and trimmed perfectly even and horizontal, so as to receive the first crib or curb similar to those just described in the case of coffering. The curb is a hollow ring of cast-iron made in segments about 4 feet long. Strips of deal about J-inch thick are placed between every joint, and the seg- ments are brought tightly together by wedging up the space be- tween the outside of the curb and the rock. The joints are finally rendered perfectly stanch by driving in wedges into the deal strips. A second curb is laid upon the first, with intervening strips of deal, and the wedging process repeated ; sometimes a third curb comes upon the second. The top curb is the foundation for the tubbing proper, which is built up segment after segment. The segments are usually i to 3 feet high and 4 feet long (Fig. 311); their thick- ness depends upon the pressure of water they have to withstand and varies between \ inch and 3 J inches. They are smooth inside, but are strengthened with flanges and ribs on the side turned towards the ground. The segments a,re kept in place by wedging them against the sides of the pit, and filling up the interspace with earth or con- crete ; thorough stanchness is secured by interposing a half -inch strip of deal or pitch pine at every joint, and finally driving in wedges when all the tubbing is fixed. Water coming in from the surrounding strata is al- lowed to escape through the central hole of each segment. A cast-iron lining cylinder (Figs. 312 and 313) is thus built up inside the shaft until an impervious stratum above the water-bearing ground is reached ; another wedging curb then completes the tubbing. The joints are wedged up as tightly as possible, and finally plugs are driven into the cen- tral holes of the segments. If the work has been properly performed, the lining will be water- tight. The tubbing is sometimes put in by a succession of com- paratively short sections, each resting upon its own wedging curb, and shutting off a portion of the water-bearing beds. If this method is pursued, each separate section is continued upwards to the next wedging curb above, resting upon a bracket of rock ; this is cut away very carefully in small sections, and the last ring of segments made to join it exactly. When the amount of FIGS. 312 & 313. I SUPPORTING EXCAVATIONS. 271 water is not excessive, it is usual to sink through the whole of these strata before setting a wedging curb and fixing the seg- ments.* In a few cases no temporary lining is used, and the segments are at once inserted in descending order, each ring hanging from the one above it. After several rings have been so fixed, a bearing-ring is put in and the wedging of the joints proceeded with. This process is repeated until strata are reached which require no such lining. SPECIAL PROCESSES. The amount of water met with has been sometimes so great as to render sinking by the ordinary methods quite impossible, on account of there not being room enough in the shafts for fixing pumps sufficiently large to cope with the enormous feeders of water, and even where pumping is possible the expense may render it out of the question. A few figures quoted by Mr. Bainbridge t will give some idea of the enormous cost due to water-bearing beds. In Germany the sink- ing of a pit, only 239 feet deep, cost ^96,000, and occupied 40 months, although the quantity of water pumped was only 606 gallons per minute. For another pit the corresponding figures were 570 feet, ^140,000, 91 months, 2200 gallons. Taking eleven cases, it appears that the cost varied between ^36 and ^245 per foot of sinking, and that the average rate at which the sinking progressed varied from 3-9 to 17-2 feet per month. For dealing with cases of this kind, there are three principal methods of sinking which deserve special mention: (i) Kind- Chaudron or boring method; (2) Triger or compressed air method; (3) Poetsch or freezing method. Boring Method. Kind's process as improved by Chaudron consists briefly in boring out the shaft by means similar to those employed for searching for mineral, and then lowering into the pit so formed a watertight lining of cast-iron, which can be made stanch at the bottom even under water. The great advantage of this process is that there is no pumping at all until the operations of sinking and lining are complete ; and then, indeed, it is only the contents of the shaft itself that have to be drawn up. The various stages of the process are as follows : (1) Alternately boring a small pit in advance, and enlarging it by a bigger tool to the full size of the shaft. (2) Preparing a seat for the moss-box. (3) Lowering the water-tight lining (tubbing) with its moss-box at the bottom. (4) Putting in the outside lining of concrete. (5) Pumping out. This process has been frequently described at great length, and persons who require more details than can be given in a general * Bainbridge, ibidem. t Ibidem. 272 ORE AND STONE-MINING. FIG. 314. text-book will do well to consult the original papers mentioned below.* The preliminary pit is bored 4 or 5 feet in diameter, and is always kept well in advance of the full-sized shaft, generally from 30 to 100 feet. The tool used is a compositejjorer with fourteen cutting chisels a fixed in round sockets (Fig. 314). Above the chisels there is the cross-piece 6, with two cutters, which serve to trim off any slight irregularities ; at the same time it acts as a guide, and so tends to ensure the verticality of the hole. There is also a second guide c above it, without teeth. The total weight of this tool is from 7 to 8 tons. It is suspended from a series of pitch-pine rods, each 58 to 59 feet in length. Some used in Belgium were 7 j inches square. Those used at Marsdeii were only 5 inches square. At each end of the rod an iron fork is clamped and bolted on, terminating in a taper male or female screw. The top rod is connected to a strong chain hanging from one end of a huge hori- zontal wooden beam. The other end of the beam is attached by a chain to the piston of a vertical steam cylinder. When steam is admitted on the top of the piston, the rods and tool are raised, but as soon as the engine-man opens the valve which lets the steam escape, the rods and tool fall by their own weight, and the rock is chipped at the bottom of the hole. Two methods have been employed for avoiding the injurious vibrations of the rods which would occur if there were a rigid connection be- tween them and the tool. One is a sliding joint similar in principle to that of Oeynhausen; the other is some free-falling arrangement, such as the catch actuated by a disc, which has already been described (Fig. 122). The rods are turned in the usual way by a tiller, and they can be lowered, as the hole is deepened, by a screw similar to that used in small borings. The mud and fragments produced in boring are cleared out by a sludger ; that is to say, a hollow sheet-iron cylinder provided with "semicircular flap-valves at the bottom. The sludger is sometimes worked by the rods and sometimes by a rope, which * Chaudron, " Precede Kind. Travaux executes en Belgique," Annales des Mines, c; e Serie, tome xviii. pp. 435 et seq. ; Smyth, " On the Sinking of Pit Shafts by Boring under Water, as practised by Messrs. Kind & Chau- dron," Trans. N. E. Inst. M. Eng., vol. xx., 1871, p. 187 ; Bainbridge, "On the Kind-Chaudron System of Sinking Shafts through Water-bearing Strata, without the Aid of Pumping Machinery," Proc. Inst. C.E., vol. xxxiv., 1871-72, p. 43; Daglish, " On^the Sinking of Two Shafts for the Whitburn Coal Company," Proc. Inst: C.E., voL Ixxi., 1882-83, p. 178. SUPPORTING EXCAVATIONS. 273 FIG. passes over a pulley at the top of the boring tower, and is coiled on a drum set in motion by a special steam-engine. When a small shaft has been cut out in this way, either for part or the whole of its depth, the work of enlarging may com- mence. The enlarging tool is a huge composite borer (Fig. 315), with twenty-eight cutting chisels, weighing i6j tons; in he centre it has a projecting loop of iron a, which fits loosely into the small shaft, and serves as a guide. The chisels are arranged so as to make a sloping cut, in order that the sludge and chips may pass down easily into the inner pit. In some cases the ordinary sludger is em- ployed for clearing out this hole, but arrange- ments may be made for catching the debris in a special bucket, which is either placed at the bottom of the hole, or is hung from a little ledge cut for the purpose. When it is supposed that it is full, the boring rods are lowered and the bottom one screwed on to it. This operation might appear somewhat diffi- cult, but by providing the female screw at the end of the bottom rod with a funnel- shaped bonnet, it is guided into its proper course over the male screw on the sludger bucket, and the necessary connection is easily made. The shaft is thus sunk to the required depth, which must previously have been ascertained by a small borehole. When therefore it is known that a bed suitable for a foundation below the water-logged strata has been reached, a seat is prepared by boring very carefully with the chisels arranged horizontally. The seat is scraped with a special tool, so as to clear off any stones, and the tubbing can now be lowered. The scraping claws can also be used just before the tubbing touches the bottom, as they will pass through the central equilibrium pipe which will be de- scribed immediately. The tubbing is made of rings of cast-iron joined by bolts through theiF internal flanges. A thin strip of sheet lead is put in the joint so as to make it stanch. The flanges are sail faced in a lathe in order to secure not only a watertight joint, but also the perfect verticality of the whole column. At the very bottom there are two rings with flanges turned outwards, and the upper is capable of sliding down over the lower. The space between the two outer flanges is filled with moss, which is further kept in place by a net. Lastly, just above this moss-box, as it is called, a dish-like bottom is bolted on, carrying a central 8 274 ORE AND STONE-MINING. pipe which can be lengthened as the tubbing descends. The pipe is called the equilibrium tube. The whole arrangement is best understood from Fig. 316.* B is the bottom ring carrying the moss outside it ; A is the ring which can slide down over it telescopically ; G is the close bottom of the column of tubbing, H the equilibrium tube, I the space between FIGS. 316, 317 & 318. the tubbing and the sides of the shaft. The column is lowered into the shaft by means of six iron rods, to which lengthening- pieces are added as required. The top part of each suspend- ing rod is a strong screw, 13, feet long, working in a big nut on a frame above the shaft. The screwed rod, attached by a swivel to the rod below, can be turned round by a little winch. After a new ring has been put on, men at these six little winches lower the column slowly ; but the whole weight of the column * Daglish, op. cit. SUPPORTING EXCAVATIONS. 275 does not come upon the screws. The watertight bottom Gr causes the tubbing to displace so much water in the shaft, that the whole column could be made to float if necessary. Such buoyancy would be inconvenient ; and it is desirable that the column should be made heavy enough to sink down of itself when the screws are worked. The necessary excess of weight is obtained by tapping the equilibrium pipe, and allowing a certain amount of water to flow into the annular space around it. The column weighted in this way finally arrives at the bottom of the pit, and the broad flange of the ring B rests on D as shown. When the lowering is continued, the ring A slides down over B, which is stationary, and the flange C compresses the moss lying in the moss-box, squeezes it outwards against the sides of the shaft and makes a watertight joint (Fig. 317). The next operation is filling up the annular space outside the tubbing with cement or concrete. The cement used in cer- tain cases was a mixture of hydraulic lime with sand and trass. It is lowered in special boxes so constructed that their contents can be discharged when they have reached any required position. After ample time for hardening has been given, the water is drawn out of the shaft by a bucket ; the dish-like bottom is now taken off, and the joint made by the moss-box can be examined. Even when this joint seems perfectly good, it is thought desirable by some to take the additional precaution of putting in a wedging curb in the ordinary way a little below the moss-box (Figs. 317 and 318) ; a few rings of ordinary segmental tubbing are then built up in the interval. A careful joint is made, and the shaft is looked upon as permanently secure. The advantages of >the Kind-Chaudron process, which are enumerated at length in Sir Warington Smyth's paper, may be briefly summed up as follows : safety, economy and speed. During the last few years several modifications of the original Kind-Chaudron process have been introduced with success. At Gneisenau near Dortmund all tubbing above the level of the water-bearing measures was discarded. A column of tubbing, closed at the top as well as at the bottom, and somewhat longer than the height of the watery strata, was lowered into the shaft ; and in order to overcome its buoyancy a sufficient amount of water was let into it by a valve, worked by a rod reaching to the surface. When the moss-box had been compressed by the descent of the column, cement was lowered, into the annular space, along special guide-ropes extending from the bottom ring but one of the tubbing to the top of the pit. This plan enabled the boxes to be sent down and drawn up more speedily than would have been the case if they had been loose. After allowing sufficient time for the complete hardening of the cement, the water was drawn out of the pit, and a regular wedging curb was put in above the column >of tubbing and its protecting jacket of cement. 2 7 6 ORE AND STONE-MINING. This method of doing the work saved 190 yards (174 m.) of tubbing at the top of the pit, and the gain in money was estimated . At the present time the moss-box seems to be losing much of the prestige which it formerly possessed, and French engineers a,re content to rely solely upon careful cementing for a water-tight joint at the bottom of the tubbing. A shaft was successfully sunk a few years ago by the " Compagnie de TEscarpelle " in the North of France without using either moss-box, equilibrium Cm. tOO SO / 2 3 ^ o -+ -j --r !<. <'<> j ^% a ^^AW'fy^ A rock. Exploratory pits are sunk in Eastern Siberia to a depth of 85 feet (26 m.) by this method. Shafts are even put down in shallow rivers to see whether their beds are gold-bearing. In autumn, when the water is shallow, a set of frames, like shaft frames, 6 or 7 feet square, is lowered till it touches the bottom, whilst the top is above the level of the stream. It is filled up with stones, and loose stones are placed around it. When winter sets in, the river freezes, and the con- tents of the box gradually become hard. A first layer of stones is then worked out with the pick, and the frost allowed to pene- trate downwards. Another layer of stones is taken out, and again there is an interval for freezing. By repeating this pro- cess the contents of the box are removed little by little, and at last the river bed is reached and allowed to become hard and solid from the cold, whilst at the same time the water in the interstices between the outer stones has been congealed, and has SUPPORTING EXCAVATIONS. 281 formed strong protecting walls of icy conglomerate. Further sinking is now carried on as in Western Siberia. In some cases the wooden box is dispensed with, and when the river is covered with a thick coat of ice, the prospector cuts out a space a few inches deep of the size of the shaft. The removal of a part of the ice at the top allows the cold to be felt further down, and the ice becomes thicker underneath. Another slice is taken off the top and again the cold penetrates further, arid in proportion as the top is removed the bottom re- ceives coat after coat of new ice. By successive thickenings the ice finally reaches the river bed, and the prospector can then pro- ceed by the West Siberian method. Poetsch's artificial freezing process consists in causing a very cold liquid to circulate in pipes through the ground, and so con- vert it into a solid mass, in which an excavation can be made without timber or other supports. While the ground is kept frozen some form of watertight lining is put in, sufficiently stanch to keep out the water when the cold-producing appliances are removed. Poetsch employs a Carre machine for generating cold. Anhy- drous ammonia gas is liquefied by compression in suitable pumps, and the liquid which leaves at a temperature of 102 F. (38 C.) is cooled by passing it through pipes surrounded by cold water. The cold liquid ammonia is then made to flow into a long series of pipes, placed in a large wooden tank containing a solution of chloride of calcium. The liquid ammonia expands into gas in these pipes, and extracts heat from the solution surrounding them to such an extent that the temperature of the contents of the tank is brought down to 8 or 9 F. ( - 13 C.) The ammonia gas is returned to the compressor to be again liquefied and utilised for the production of cold. The refrigerating solution of chloride of calcium is pumped from the tanks into a main, which leads it to a series of pipes, placed in boreholes arranged in a circle around the top of the proposed shaft. The pipes are double, that is to say, there is an inner small pipe i J or 2 inches in diameter for the down- ward journey of the cold solution, and an outer one 4^ to 7 inches in diameter, carefully closed at the bottom, by which the solution ascends and does its cooling work on the way. When it- reaches the surface it returns to the cooling tank, and is again refrigerated. The process is, therefore, continuous, the ammonia and the chloride being used over and over again. The nature of the freezing-tube will be evident from Fig. 322 * ; a is the large outer pipe connected to another, m, by the piece,/; n is a small * Poetsch, "Ueber die verbesserte Ausfuhrung des Gefrierverfahrens beim Schachtabteuf en und Streckenbetrieb," Der iv. allyemeine Bergmanns- tag in Halle [Saale]. Fesibcriclit und Verliandlungen. Halle, 1890, p. 119, and Plate x. 282 ORE AND STONE-MINING. inner pipe, and the arrows show the course of the solution. The supply of chloride is taken from a circular pipe at the top, fed FIG. 323. from the main, and in like manner the solution ascending the various pipes is collected by another ring and led back to the cooler. The particular pipe shown in the figure is destined for the case of a sinking, in which the upper part, m, is in strata that SUPPORTING EXCAVATIONS. 283 do not need to be frozen. The letter p represents a jacket made of some bad conductor, to prevent the solution from becoming warmed unnecessarily in its ascent. In sinking through ground consisting of watery strata alternat- ing with dry measures, Poetsch advises the following method of procedure. A (Fig, 323) represents dry ground through which the shaft has been sunk and timbered in the ordinary way; B indicates watery beds where tubbing is necessary. Poetsch puts in first of all a circle of holes, a a, round the outside of the shaft, and a smaller circle b b, around the inside. When these latter have frozen the ground adjacent to them, the still smaller circle of holes b b, are bored and fitted with refrigerating tubes ; as soon as the ground about them has become converted into a solid pro- tecting wall, the shaft is sunk with a reduced diameter, until the dry strata, C, are pierced. On reaching ground suitable for the wedging curb, the tubbing is built up in the ordinary way; the parts b b are cut away, and by this time the freezing has become so complete at a that there is no danger of the walls falling in. In this process there is a risk of failure, or at all events of trouble, if there is any escape of the freezing solution from the pipes, because the ground impregnated with it would be uncon- gealable. Gobert proposes to overcome this difficulty, and at the same time to make the method more economical, by sending down anhydrous, or all but anhydrous, ammonia, and allowing it to vaporise in the tubes, instead of circulating a refrigerating solution, Intense cold is thus produced at the very point where it is required, and the ground is frozen. The ammonia gas is drawn out by a pump, and after having been reliquefied by pressure is used over again. Gobert claims for this process that both the original outlay for plant, and the subsequent running expenses, are considerably reduced. He has also been led by his experience to introduce improvements in the joints of the freezing pipes, with the object of ensuring absolute freedom from leakage, and of making the line of pipes quite flush outside, so as to facilitate their withdrawal at the end of the sinking. II has been proposed* to inject powdered cement, by means of compressed air or steam, into watery strata, and so consolidate them sufficiently to render the sinking of a shaft a matter of no great difficulty. The Haase Process,! for sinking through quicksands, consists in forcing down a set of wrought-iron tubes around a circular or rectangular area destined for the shaft. The narrow inter- spaces between the tubes are closed by angle-iron and T-iron riveted on longitudinally, which form a joint permitting vertical motion and stanch enough for the work in question. Water forced * Colliery Guardian, vol. Ixi. 1891, p. 1089. t Zeitschr. f. B.- H.- u, /SI- Wesen, vol. xxxvii. 1889, p. 204. 284 ORE AND STONE-MINING. down a hollow boring rod in the middle of each tube loosens the sand and carries it up to the surface. The tube can then be driven down by a screw-jack or an hydraulic press. The tubes are carefully guided in order to ensure a strictly vertical path ; and as soon as they have been forced down into hard or compara- tively hard rock, the quicksand can be excavated, for the iron lining prevents any influx from the outside. Instead of iron tubes, Haeuser* employs sheets of corrugated iron, with tongues riveted on so that the bottom of each sheet is held by the top of the one below. Like the Haase tubes, the sheets are forced down with a strong screw-jack. Another plan adopted by Haeuser consists in making the protecting shield of pieces of flat iron 6 inches wide ; each " lath," if it may be so called, is connected to its neighbour by a longitudinal groove formed by riveting -on two strips of iron. * Herold, " Das Schacht-Abteufen im schwimmenden Gebirge mit Haase' schem und Haeuser' schem Verfahren beim Braunkohlenwerk ' Zwenkau ' in Zwenkau," Jahrb.f. d. B.- und If.- Wesen i. K. Sacksen, 1891, p. 27. CHAPTER VI. EXPLOITATION. Classification of methods of working (i) Open works of all kinds, including hydraulic mining. (2) Excavation of minerals under water. (3) Extraction of minerals by wells or bore-holes. (4) Underground workings. THE methods of working mineral deposits may be naturally arranged into two great classes viz., open works, in which the ex- cavation is open to the sky ; and underground works, in which the miners perform their labour in chambers or passages under a cover of rock or earth, and in which they usually need artificial light. But there are in addition two other classes of workings, used in comparatively exceptional cases, which require a place in any com- plete classification. Gold-bearing gravel and phosphates are occa- sionally dredged up from river-bottoms ; and liquid, gaseous, or soluble minerals can be got by wells or bore- holes. Consequently it is necessary to subdivide the subject into four heads : 1. Open works of all kinds, including hydraulic mining. 2. Excavation of minerals under water. 3. Extraction of minerals by wells or boreholes, 4. Underground workings. OPEN WORKS. Some minerals are always obtained in this way ; others are worked open before regular underground mining begins ; and, thirdly, it often happens that underground and surface workings are both being carried on simultaneously in adja- cent parts of the same mine. Among the minerals worked open- cast are the ores of copper, gold, iron, lead and tin, to say nothing of all sorts of stone. The advantages of open works may be summed up as follows : (a) Complete removal of the mineral without any loss in the form of pillars. (&) No expense or trouble as regards ventilation, men always working in good air ; no danger of explosions. (c) No expense for lighting, unless work is carried on at night. (d) No expense for timbering. (e) Possibility of laying out the work in larger steps or stopes than can usually be done in underground working places. (/) Easier supervision. 286 ORE AND STONE-MINING. On the other hand, there is usually the immense disadvantage of it being necessary to remove a great deal of waste rock covering the deposit, technically known as overburden. Work too may be stopped by bad weather, such as heavy rain or snow ; open quarrying may spoil land or interfere with roads or canals, so that the benefits do not all lie with the open works. The cryolite of Greenland* is worked opencast from April to December, and dur- ing the rest of the year the miners are employed below-ground. One of the simplest cases of working away a mineral is that of borax in California. The efflorescence has merely to be swept into wind-rows and carted away to the refining works. The beds of nitrate of soda in Chili are worked by large blasts as shown in Fig. 54.! A small shaft is sunk a little below the bottom of the " caliche " and enlarged in order to receive a charge of slow burning powder made on the works. The explosion loosens and breaks up the ground over an area about twenty yards in diameter. The hard overlying stratum of " costra " is then easily removed, and the " caliche " is broken up into lumps, which are taken to the lixiviating and crystallising works. Generally the first process in an open working is the removal of the overburden, and the manner in which this is done depends upon the nature of the ground. A first example may be taken from Northamptonshire, where very large quantities of iron ore are obtained from beds of Jurassic age. .Similar beds are also worked in the counties of Lincoln and Oxford. The actual bed of ore at Cranford in Northamptonshire is from 8 to 12 feet thick, and the amount of overburden taken off is sometimes as much as 20 feet ; when this thickness is exceeded the ore can no longer be worked with profit. The soil or " meat earth," which is from 8 inches to 2 feet deep, is put aside carefully, for it has to be restored to make the surface good and available for tillage. The remainder of the overburden is cut away in one or more steps or " stopes," for the convenience and safety of the workmen, the base of any step being usually about equal to its height. The accompanying figure (324) represents a pit at Kettering in Northamptonshire, in 1889, where 15 feet of overburden were being removed from a 12 -feet bed of ironstone. The soil having been cleared off with the shovel, the men undercut the first stratum with a double-pointed pick at a and then drive down a crowbar at b and another at a little distance from it. By working the bars backwards and forwards they cause a big block to break off along the dotted line. This crumbles in its fall, is shovelled into barrows, wheeled across the planks, and tipped on to * " Die Kryolitverarbeitung in der Eresundschen Fabrik in Kopenhagen," B. u. h. Z., 1893, p. 69. f Robert Harvey, "Machinery for the Manufacture of Nitrate of Soda at the 'Ramirez' factory, Northern Chili," Proc. Inst. Civ. Eny., vol. Ixxxii, 1884-85, p. 341. EXPLOITATION. 287 the bank. After the top has been cleared away for a few feet, the next bed is treated in the same way, and then the third, until the ironstone is reached, and laid quite bare. The ore can usually be easily broken with the pick and at once loaded into small waggons, holding about a ton each. Occasionally a shot is fired, in order 2 88 ORE AND STONE-MINING. to loosen parts that are hard. The loading is done with an eight- proiiged fork, so as to separate the fine ore which the smelters refuse to take. If there is much fine, the ore is sifted ; one man stands over a wheel-barrow holding a round sieve, with a half- inch mesh, and another shovels the ore to him. The fine drops into the barrow and can be wheeled away, while the coarse is thrown into the waggon. The men working on the overburden are paid per cubic yard, and those excavating ore are paid per ton of ore placed in the trucks. The working faces are long, in order that a large number of men may be employed at one time. As surface rent must be paid whilst the ground is useless, the soil is put back with the least possible delay, and tillage then goes on once more upon fields which have been lowered several feet. In the figure a small waggon is FIG. 325. FIG. 326. shown, but in some of the pits a full-sized railway waggon is brought into the cutting and loaded directly with 8 or 10 tons of ironstone. When a slice 10 or 12 feet wide has been removed all along the face, the rails are shifted and a fresh cut taken. The workings start; for instance, from some convenient point, C (Fig. 325), connected to a main railway or wharf at X, and the first line of workings is supposed to be shown by CD, reaching to the boundary of the property AB. The successive positions of the working faces take such lines as CE, CF, &c., radiating out from C as a centre, and all the ground CDK may have been given back to the farmer, before the working face has assumed the position OP. In hard rocks the steps may be made very much higher. Thus, at the great Penrhyn slate quarry, near Bangor, in North Wales, the valuable slate and the valueless overburden are both taken away by a series of terraces on an average 60 feet high by 30 feet wide, as shown in Fig. 326. The great opencast at Rio Tinto (Fig. 327) is a huge open pit EXPLOITATION. 289 from which the ore is got by a succession of stopes, benches or terraces, 33 feet to 50 feet high. The pit is oval in shape, and 650 yards (600 m.) in length on the top of the ore. FIG. 327. A, cupreous pyrites ; B, slate ; C, porphyry. The opencast at the Mechernich lead mine is also worked in a similar manner. The Government regulations make it necessary that the base of each step shall be at least 10 feet wide, so that. FIG. 328. stuff may not roll down from one floor on to the men working below. The actual width is very much more, being usually 26 feet (8 m.), whilst the height is 33 feet (10 m.) When the rock is firm enough to stand for a great height, it is sometimes found convenient to take it down in one vertical slice T 290 ORE AND STONE-MINING. without making a series of steps. The general appearance of Mulberry mine,* near Bodmin in Cornwall, which is worked in this manner, will be understood by a reference to Fig. 328. Men standing at A bore and blast holes, which throw the rock to B, under which a level has been driven with an opening C, usually closed by a covering of timber. A waggon is run in under this opening and is easily filled. Another method is that of firing a very large blast, which brings down thousands of tons of rock at a time. It is prepared by FIG. 329. Xte^y i it ' ,-si ir" / . SCALE. ' pT 10 '80 200 FEET ME.TRES 10 o w 20 30 AO so &o 70 80 MEITRE.S ABC, Outline of the face of the quarry before the blast ; AB'C', Outline after the blast. driving in a tunnel at right angles to the face of the quarry and making one or more chambers, which are charged with gunpowder or some other explosive ; the tunnel is tamped up like a gigantic shothole, and the charge is fired by a fuse or by electricity. As an example of a blast of this kind, I take some workings for building stone near Messina (Fig. 329)^ A tunnel was driven into the face of the limestone quarry for a distance of 56 feet (i7m.), and then turned off at a right angle. The chamber * C. LeNeve Foster, "On Some Tin Stockworks in Cornwall," Quart. Jour. Geol. 8oc., vol. xxxiv. 1878, p. 655. t Falangola, " Sulle grandi mine nella roccia calcarea della catena Peloritana (Sicilia) e nella roccia granitica di Baveno (Lago Maggiore)/' Sivista di Artiglieria e Genio, vol. iv. 1887, p. 343. EXPLOITATION. 291 60 formed was lined with a quick-setting cement in order to keep out any moisture, and a cubical wooden box was built up inside and charged with 64. bags of gunpowder, or in all 31 cwt. (1600 kil.) Four ordinary fuses, placed in a long box with sawdust, furnished the means of firing the charge. The tunnel was then filled up in the manner shown in Figs. 330 and 331. The object of the slightly sinuous form of the tunnel was to increase the resistance of the tamping. The effect of the large blast was to break up and move more rthan 100,000 cubic yards (80,000 c.m.) of rock, with the advantage FIGS. 330 & 331. DETAILS OF THE TUNNEL. PLAN. .i,so^ C \ SECTION ALONG THE LINES AB. BC. 1.50 , damp earth beaten in ; &, brick wall built with common mortar ; c, dry stone wall ; d, wall built with a quick-setting cement ; e, wall built with hydraulic lime ; dimensions in metres. of producing less small stone than would have been the case if the ordinary method of quarrying had been employed. The dotted line A B' C' shows the outline of the face after the explosion. We now come to an important class of workings, namely, recent alluvial beds, such as river gravel containing diamonds, gold or tin ore. The banks may be left high and dry when the river is low, or the stream may be diverted and any pools drained by some simple pump. The whole process of working often consists merely in dig- ging up the earth with pick and shovel, and washing it on the spot with a pan or batea. If there is not enough fall for discharging the refuse, in places where the operations are on a large scale, it becomes necessary to raise the earth by some appliance, such as the hydraulic elevator (Fig. 345).* * Kickard, "Alluvial Mining in Otago," Trans. Amer. Inst. M. E.. vol. xxi. 1892, p. 445. 2 9 2 ORE AND STONE-MINING. Dams for diverting rivers are sometimes of considerable size. For instance, on the Feather river, in California, there is a darn 80 feet wide and 50 feet high. The water is carried off in a " flume" or launder, 50 feet wide and 6 feet high. The sand of beaches is occasionally scraped up at low tide and washed for gold or tin ore. Hydraulic Mining. Under this head it is convenient to include all methods of working in which water is used for breaking away the ground, and not to restrict the term, as is most commonly done, to the process of working auriferous gravel by a jet of water under considerable pressure. I will take some examples : i. China Clay Workings in Cornwall* The first operation is the removal of the overburden, and a small shaft is then sunk in FIG. 332, A, undecomposed granite ; B, decomposed granite ; C, overburden ; D, engine-house ; EE, EE, successive outlines of the open pit ; aa, shaft ; bb, level ; d, top of upright launder placed in the small shaft sunk in the middle of the decomposed granite ; ee, column of pumps through which the milky stream of china clay and mica is lifted to the launder, /. the middle of the area to be worked ; the bottom is put into com- munication with the surface either by an adit level, if the contour of the ground is favourable, or by a tunnel and shaft (Fig. 332), if the contour of the surface does not permit the driving of an adit save at a prohibitory cost, or if it is more convenient to have the settling pits close by. The shaft has to be fitted with pumps. A stream of water is led on to the decomposed granite, which the workman loosens with a heavy pick; the disintegrated particles are carried away in suspension to a first settling pit. where the coarse grains of quartz are deposited, and * Collins, The Hensbarrow Granite District, Truro, 1878, p. 17. EXPLOITATION. 293 the milky stream then falls down the launder d, into the level and either runs out naturally or is pumped up to the surface. It passes on to other settling pits, and deposits first the mica and then the very finely divided kaolin. 2. Auriferous Gravel The process known as "booming,"* practised in California, Colorado, Idaho and Montana, consists in discharging the contents of a reservoir all at once on to beds of auriferous gravel. The powerful stream carries away the stones and dirt into wooden troughs or launders, called " sluices," and leaves behind the gold on the bed-rock, or in the upper part of the run of sluices. In Peru f a similar process is adopted. By a natural transition from "booming," we come to 41 hydraulicking," | a process in which a jet of water under pressure is made to play against a bank of auriferous gravel, break it down, disintegrate it, and wash it into wooden troughs, arranged so as to catch the gold by means of mercury on special floors, and at the same time to discharge the stones, sand and mud. For the purpose of storing a proper supply of water, large reservoirs have to be constructed, sufficiently high above the gravel bank to secure the necessary amount of pressure. They are formed by erecting dams across the valleys, and they are made either of earth, cribs of timber, or dry rubble masonry. One of the largest in California is the Bowman reservoir, with a high water area of 500 acres and a dam 100 feet high, which cost $151,521, or speaking roughly ^30,000. The water is taken to the place where it is required by (i) ditches (" leats," Eng.) ; (2) flumes; or (3) pipes, (i) The ditches are cut out on the sides of the hills, and the earth thrown out serves to strengthen the lower bank. The shape most commonly .adopted for the ditches is a half -hexagon, or the upbank may be made with an angle of 60 and the lower with 65. The gradient or " grade " varies according to circumstances from 7 to 20 feet per mile. (2) Flumes are merely wooden troughs, or "launders," as we should call them in England. Figs. 3334! and 334 show the manner in which they are usually made and supported. In valleys or canons with very precipitous sides, the flume is sometimes car- ried by iron brackets let into holes bored in the rock and hung by * California State Mining Bureau, Ninth Annual Report of the State Mineralogist for the year ending December i, 1889, p. 122, Sacramento 1890. Bowie, A Practical Treatise on Hydraulic Mininq in California, New York. 1885, p. 81. t Kohlmorgen, "Die Goldgruben von Carabaya in Peru," B. u. h. Zeitung, 1890, p. 303. This account of " hydraulicking" is in the main based, by permission, on Bowie's Practical Treatise on Hydraulic Mining in California, New York, 1885. Taliesin Evans, "Hydraulic Mining in California," The Century Magazine, vol. xxv. 1883, p. 332. 294 ORE AND STONE-MINING. FIG. 333. iron rods (Fig. 335).* Where it is- possible, ditches should be put in instead of flumes, because the latter cost more for maintenance. They also suffer more from wind, snow and storms, and lastly they are liable to destruction from fire. On the other hand, it may be impossible in some cases to put in ditches, or the ground may be too hard and too porous to make a ditch advisable. When water is scarce, the loss by soakage- and evaporation is a matter of im- portance. (3) The third method of conveying water is by iron or steel pipes. They are useful in crossing a deep, valley, for they save the expense of con- FIG. 334- structing a very long ditch round its head, or a very high trestle bridge across it. Pipes crossing deep valleys are called " inverted * Bowie, op. cit. EXPLOITATION. 295 siphons," although the principle of the siphon in no way comes into play. The pipes are made of riveted iron or steel, and one form of FIG. 335- joint is shown in Fig. 336,* made tight by running in lead and caulking it. The riveting may be straight or spiral. To prevent rusting, the pipes are coated externally and internally with a mixture of coal-tar and bitumen. Some of the pipes used for conveying water in this way are 20 or even 30 inches in diameter, and in such cases the thick- ness of the iron is from No. FIG. 336. 1 6 to No. i 4 B.W.G. Whether brought by ditch, flume or pipe, the water is led to the so-called "pressure-box" or "bulk- head" (Figs. 337,338, and 339!), a cistern situated at a sufficient elevation to give the jet the force it requires. The cistern is strongly made, and has a grating A to catch floating sticks which might otherwise choke the pipe. At the bottom there is a recep- tacle B to receive gravel and sand, which are discharged from time to time by opening a hatch at C. The pipe leading away from the pressure-box is similar to that used for crossing valleys, and it is brought down into the workings ; if it is advisable to attack the bank in two places at once, the pipe is forked, each branch having its valve. The pipe terminates in a nozzle from 5 to 9 inches in diameter known as a is a wrought-iron collar ; &, the lead 5 c, a nipple of sheet-iron riveted to one end of the pipe d, each length having a similar nipple. Bowie, op. cit. t Bowie, op. cit. 296 OKE AND STONE-MINING. " monitor." The monitor shown in Fig. 340 * is provided with an arrangement by means of which one man can deflect it with great ease. If the nozzle B is in a straight line with A, the stream passes through it unimpeded ; when it becomes necessary FIG. 337. FIG. 339. FIG. 340. to turn the water on to another part of the gravel bank, the lever C is held to the side to which the jet has to be deflected. The pressure of the water in B then moves the monitor as desired. The manner of using the powerful jet of water to wash down banks of gravel is well depicted in Fig. 341, borrowed from Mr. Evans' interesting article. If the gravel is cemented into a hard conglomerate, drifts * Bowie, op. cit. EXPLOITATION. 297 are run into the bank ; they are charged with a number of 25lb. kegs of powder, tamped up, and fired by electricity. The jets of water will then do the rest. The gravel washed down by the jets of water is led first into ditches cut in the "bed-rock," and then into " sluices." Sluices are large troughs or launders lying upon the ground, and paved with loose blocks of wood or with stones, in order to form a FIG. 341. surface fit for catching the gold and the amalgam. Figs. 342, 343, and 344,* show a section, elevation and plan of a sluice-box with two kinds of lining ordinarily adopted. It will be seen that the sluice in this case is a trough 5 feet 3 inches wide, made of ij inch plank at the sides and 2-inch plank at the bottom, upon which are placed blocks of wood 20^ inches square, and 13 inches deep, set with the grain on end. They are separated at the bottom by cross strips of wood i J inches thick, and the sides are protected by blocks 3 inches thick. At one end the paving is of large stones. The sluice is generally made in twelve-foot llngths, and the inclination is commonly defined by the fall given to such a length. * Bowie, op. cit., p. 222. 298 ORE AND STONE-MINING. FIG. 342 w 4x6x4" FIG. 343. FIG. 344. IP LH1 LONGITUDINAL SECTION A B, EXPLOITATION. 299 Thus it is said that the grade is 6 inches, meaning 6 inches to 1 2 feet or J inch to the foot. The run of sluices may be several hundred or several thousand feet long. The false-bottoms for sluices are called "riffles." The wood preferred for the block-riffles is that of the " digger " pine (Pinus sabiniana). Longitudinal riffles are made of poles, wooden rails covered with strips of iron, or iron rails, In New Zealand* the riffles are sometimes made of transverse bars of angle-iron, riveted to angle-iron or placed in a wooden frame, which enables them to be reversed when worn. The sluice-boxes are lined with thin sheet iron, and sacking or cocoa-nut matting is placed under the riffles to assist in retaining the gold. In order to catch its gold more effectually, the finer material is taken out and treated separately in broad sluices called " under- currents," at the side of the main one. A grating of bars of iron, i inch apart, called a "grizzly," is fixed across the main sluice, and the fine gravel and sand which drop through are led to a broad, shallow, sloping box, eight or ten times as wide as the sluice itself, and paved like it with stones, wooden blocks, or longitudinal riffles. The finer portions of the gravel, after passing over the "undercurrent" and depositing much of their gold, are once more turned into the main sluice lower down. The big boulders rushing down the sluice are of service at first by breaking up gravel which is much cemented together, but at the same time they naturally wear out the sides and the pavement. It is therefore advisable to get rid of them, as soon as they have done all the useful work they are capable of performing. This is effected by arranging a " grizzly " or grating which will deliver the boulders into a ravine or gully, and so dispose of them without any further cost. Mercury is added several times a day at the head of the sluice ; and the upper part, say, the first 1000 feet, is cleaned up every two or three weeks. At the time of the clean-up the washing down of the gravel bank is stopped, or the current is diverted into a parallel line of sluices. A small quantity of water is turned into the sluice which is to be cleaned up, the blocks are then taken out, washed, and put on one side. All the amalgam is picked up with iron scoops, washed, and squeezed through canvas or leather, and the amalgam is retorted. The spongy gold remaining behind in the retorts is then finally melted into bars. The mercury recovered by condensation is used over again. When the bed-rock is below the drainage level, the hydraulic elevator * may be employed. A jet of water under heavy pressure * Eickard, " The Gold-fields of Otago and Alluvial Mining in Otago," Trans. Amer. Inst. M. E., vol. xxi. 1892, p. 443 and 455 ; Parliamentary Reports on the Mining Industry of New Zealand, Wellington, 1891, p. 67, with plates. 300 ORE AND STONE-MINING. is brought by a pipe A (Figs. 345 to 348) to the nozzle B, and rushes up the pipe D, producing a powerful suction in the " hopper " C. The water and gravel are carried up against the cast-iron striking plate S, and then run down the sluice-boxes. FIG. 345. Fig. 349 explains the method of using the elevator for treating an immense accumulation of tailings at the Blue Spur, Otago, N.Z. On the left hand side is a huge nozzle playing upon the face of the tailings, 59 feet high, and washing clown the gravel and sand of which they are composed. To the right is the first elevator, which raises the stuff 15 J feet into a set of sluice-boxes, and further to the right is a second elevator lifting it 56 feet vertically into another run of sluice-boxes. EXPLOITATION. 301 The quantity of water used is measured by a unit called the " miner's inch,"* which unfortunately is not invariably the same.. The term means the quantity of water discharged per square inch of sectional area of an orifice cut through a vertical board, forming one side of a box. The discharge will necessarily vary with the height of the surface of the water above the orifice, the thickness of the board, and the shape and nature of the orifice ; as these factors of the problem are not the same in all localities, it is impossible to give one definite value for the miner's inch of water. The orifice is usually rectangular, but it may differ in height and width. However, the quantity represented by the miner's- inch may be taken as varying from 2000 to 2600 cubic feet per FIG. 349. THE BLUE- SPUN OtBtfO. X X. 24 hours; in some cases the outflow is reckoned for 10 hours only, and is spoken of as the " ten hours miner's inch." Under these circumstances it is evident that great care must be taken to ascertain precisely what inch is meant, before making any estimates based upon this uncertain unit, the miner's inch. The "duty" of the miner's inch is "the quantity of material washed by an inch of water in 24 hours." As might be expected, the duty varies very considerably, indeed from i to 4 cubic yards. The duty necessarily depends upon the pressure o: the jet of water, and upon other causes, such as " character of the material washed, height of banks, use of explosives, size and grade of sluices, and class of riffles. The sluice affects the duty of the inch in so far as its capacity regulates the quantity washed." f Under favourable conditions at Cherokee Flat, viz., fine * " The Auriferous Gravels of California," Ninth Annual Report of the State Mineralogist for the year ending December i, 1889 ; Sacramento, 1890, p. 122 ; and Bowie, op. cit. p. 124. f Bowie, op. cit. p. 268. + Bowie, op. cit. pp. 268, 269. 3 02 ORE AND STONE-MINING. material, high banks, head of 300 to 350 feet, and grade ^, 5*5 cubic yards are said to be the duty of the miner's inch. At Osceola,* in Nevada, the average washing in 1890 was 1-62 cubic yards to the inch of water and it was expected that the duty would be raised eventually to 2 cubic yards. It is hardly necessary to say that the yield of the gravel varies between very wide limits, and it is consequently impossible to lay down any average for the hydraulic mines of California or any other country. But the accompanying table gives the results of actual work, and will at all events show that poor gravel, con- taining gold worth only 10 or 15 cents, say, $d. to j^d. per cubic yard, can sometimes be made to pay good profits. With the exception of Osceola, the works were all in California the figures are borrowed from Mr. Bowie, and many other ex- amples of the yield of auriferous gravel will be found in his work and in Mr. Hammond's report. A cubic yard of gravel is estimated by Mr. Hammond to weigh from i J to if tons. One of the great difficulties with which the hydraulic miner has to contend is getting rid of the enormous quantities of refuse produced by his washings. Some idea of these quantities will be gathered from the statement that one working alone, the Gold Bun Ditch and Mining Company, was for a period of eight years discharging 4000 to 5000 cubic yards of sand, gravel and boulders daily into a tributary of the Sacramento. As a natural con- sequence banks were formed in the river, obstructing the navigable channels, rendering overflows more frequent and destructive, and causing valuable land to be destroyed by de- posits of sand. Litigation ensued, and some years ago the Superior Court of Sacramento decided that the hydraulic mining companies must build dams to impound the coarse and" heavy debris, or take other means to prevent their being washed down the rivers. The consequence of this decision was a great diminution of the amount of hydraulic mining carried on in the State ; but quite lately an Act of Congress has been passed which will allow work to be resumed at many of the mines. (2) EXCAVATION OF MINERALS UNDER WATER. In Chapter IY. mention was made of dredges of various types, which are employed for the purpose of extracting gold-bearing sand and gravel from the beds of rivers. Gold is not the only mineral worked in this fashion ; in South Carolina phosphate of lime is dredged up from river-bottoms, and in Prince Edward Island a shell-marl obtained in a similar manner is sold as a fertiliser. Lastly, on the coast of Germany, between Dantzig and Memel, two forms of subaqueous work are applied to the getting * Eng. Min. Jour., vol. li., 1891, p. 630. EXPLOITATION. 33 oto.8 CO ^ or ON sJ'I'H | | | | * 5 s "o 00 c? S" 1 o* <2 2,^ 1 i 4 4 4 vo c> #* & SSLS-p CO VO to vo CO CO o o 1 g vg VO N H-C 5||1 4 & & i i i A & & 1 A i J^BAV J ^ CO vo 00 N oo r^. VO N ON qoui jad paAOra 1 CO \ p Tf op p OO VO OO spaB.C oiqno " ** 1-1 *-* -' "* "* CO w M f- O O N vo Tj- 8 8 CO" ^ c3 > ^ M *H ON Q vo ON Q ON co r* ^ > ^ od j* S V0~ 10 OO c 0% CO CO~ lO ^ ^-t T^- hH C^ vo^ vo M N vo CXD o\ M I-H HH 5 cT 10 CO N" " N~ ?i -2 i i 1 1 i O O G 1 3 ! 1 1 'a O 10 "3 ^ M N oo ^ 4n IM d vO <* O s-a SJ H 0? O M i ( 2| fc Tf O 1 O i 1 5 1 1 ^ HH > o T^- ^--^ -^ M N w 0^ vo vo in ^ t2* 4H vo M VO N 2 M VO 25 1 1 1-1 U S 1 o O o 5 | 5 002 d fl .S s r ~ = r r-l r-l '.-w' -JO* hi HM H51 CO Tj- Tj- CO * vo vd VO CO ^ s J d O * * J | w - O H 1 ^ -0* o> - ^O c3 c/2 d jo O d rS O cS *" * 1 1 3d f Temperanc ( Yuba Co Nevada Co. f Patricksvil { Stanislaus Forest Hill, P go f Patricksvil ( Stanislaus Stanislaus C f Patricksvil { Stanislaus cu >. Anhydrite Marl the underlying anhydrite. It now has to be lined with a steel tube bb (Fig. 350, in which the size of the tubes is greatly exaggerated), 6f inches in diameter internally; for the first 150 feet from the bottom the steel is J inch thick, then T 5 ^ inch for 300 feet, and the remainder is | inch thick. With the sleeve u 306 OKE AND STONE-MINING. couplings over them, the tubes just pass down the drive-pipe. In the rock-salt and in the 600 feet of water-bearing sandstone, the lining pipe is perforated with holes i inch in diameter, and 1 2 inches apart vertically. Lastly, a steel suction pipe (Fig 350, c), 3 inches in diameter internally, and J inch thick, made in 2o-feet lengths, united by sleeve couplings, is lowered into the borehole; about 240 feet from the surface is fixed a brass working barrel (Fig. 350, d), 6 feet long, 4! inches in diameter and ^ inch thick, and above it steel tubes, 4 1 inches in diameter, which reach to the surface. The working barrel has a ball valve at the bottom. When the pump bucket, also fitted with a ball valve, has been let down by a series of rods, and the last one has been connected to the end of the walking beam, the extraction of brine can commence. It is evident from the figure that when a pump is set in motion at d, water will ascend the suction pipe, and its place will be taken by water from the sandstone. This descends the outer tube to the rock-salt, brings it into solution, and is pumped up as brine. As the pumping proceeds, the rock-salt is gradually eaten away all round the borehole ; in time the marl roof must fall in, and eventually the pipes will get more or less choked, and the brine will be too weak to be worth pumping. The rate of pumping is regulated so that the brine is delivered with 25 per cent, of salt. As it comes FIG. 351. up it is full of gas, which is mainly nitrogen with a small proportion of hydrocarbons. The boreholes are arranged in fours at the corners of a square, with a -400ft > diagonal of 200 feet (Fig. 351). The brine is delivered into a large storage and settling-pond, whence it flows into sheet-iron evaporating pans. If there is no natural supply avail- able, as is the case in the Middles- brough district, fresh water from the surface is run down the outer pipe, and the dissolving proceeds as before. Natural sheets of saline water or brine can be tapped by wells or boreholes in some districts ; indeed salt was worked in this way in Cheshire long before the discovery of the rock-salt. Some of the Cheshire salt is derived from brine pumped up from inundated mines worked originally for rock-salt, which are now full of water and cannot be entered. This therefore is practically a combination of underground work with extraction by solution, and the process which in these cases has been finally adopted, through force of circumstanceSj is some- times found advisable from the commencement. EXPLOITATION. 307 Gallon* describes and figures the method of working the salt marls of the Salzkammergut by huge elliptical chambers. A network of drivages is first of all made at the floor of the proposed chamber, and then fresh water is brought in, until it fills the excavations and gradually eats away the pillars and roof. The brine is pumped up and the clayey matter falls on the floor of the chamber and is left there. At Bex in Switzerland the process is similar, only it has to be adapted to the nature of the deposit worked. The salt occurs in the form of large lenticular masses of saliferous anhydrite surrounded by anhydrite free from salt. The lenses are from 10 to 50 metres wide, and are known to extend to a depth of 300 or 400 metres, dipping almost vertically. A main shaft is sunk and the saliferous rock is reached by cross- cuts and dissolved away in slices 100 metres thick at a time. An intermediate shaft, or winze, is sunk from the crosscut, .and when it has reached a depth of 100 metres a second crosscut is put out, from which two long drivages, 2 metres high and i '5oni. wicfe, are made in the direction of the major axis of the deposit. By a series of drivages at right angles to each other, the lowest part of the slice is cut up into a set of square pillars about 5 or 6 metres on the side. Water is let into the winze, and is allowed to rise to the level of the upper crosscut. It dissolves the salt from the rock, is pumped up, piped out to the surface through a long adit, and evaporated. As the strongest brine sinks to the bottom, the pumps are made to take their supply from the lowest part of the workings. The saliferous anhydrite contains from 25 to 30 per cent, of salt, and when this has been dis- solved out, the rock does not fall to pieces as might have been expected. Gypsum is soluble in water containing 10 to 14 per cent, of salt, so the first action of the water is to dissolve some of the anhydrite ; but when the brine becomes more concentrated, gypsum is deposited in the form of small crystals, which bind the anhydrite into a firm mass. Consequently the leached rock stands perfectly well by itself, and there is no fear of the sides falling in. One of these large workings, when once properly laid out, will go on furnishing brine for thirty or forty years. The rate of pumping is regulated so as to supply brine with 25 to 26 per cent, of salt. A last instance of a combination of underground workings and extraction by watery solution may be taken from Parys Mountain in the island of Anglesey. During the active working of the Parys mine many years ago, poor copper ore which had been broken, but which would not pay for the expense of winding and dressing, was left underground. Under the action of air and * Lectures on Mining, vol. ii. p. 23 ; Atlas, plate xliii. Figs. 251, 252. 308 ORE AND STONE-MINING. moisture, the chalcopyrite in the refuse and in the pillars is gradually decomposed, producing a certain quantity of soluble sulphate of copper. Rain finding its way down the mine dissolves the sulphate, and the pumps draw up a strongly coloured water, which in contact with scrap iron yields merchantable copper precipitate. The mine is now worked solely in this way. In a like manner a little copper has been got from the water flowing out of the County adit in Cornwall. (4) UNDERGROUND WORKINGS. The methods em- ployed for excavating minerals underground are almost as various as the different forms in which the minerals themselves occur. The deposit must first be reached by a shaft, or, where the contour of the country permits it, by an adit. The choice between these two methods of attack must be entirely governed by the circumstances of the case. In a comparatively level country, it would be impossible to bring in an adit capable of rendering any real service without going to a distance which would make the cost of driving prohibitory; but among the mountains an adit may be the quickest and cheapest means of entering productive ground. It has the advantage of enabling all pumping to be dispensed with for a time, of reducing subsequent water-charges, of affording an opportunity of easily utilising water supplies in the neighbourhood, and often of bringing out the mineral to a more suitable locality for treatment than could be obtained by raising it perpendicularly to the surface. Instances often occur in which the adit can be driven along the course of the deposit itself, and so furnish valuable data concerning it. A shaft sunk upon the dip of a deposit has this same advantage ; but here it is necessary to remark that the term " shaft " does not always convey the same meaning. The ore-miner uses the word to denote not only a vertical pit, but also one sunk upon a vein, even if the inclination is but slight. There are portions of shafts in Cornwall which do not dip more than 1 5 degrees from the horizontal. Shafts with an inclination of 60 or 70 from the horizontal are common in vein-mining, and no ore-miner would think of calling them by any other name. On the other hand, the coal-miner seems to confine the word shaft to vertical pits. If a pit is sunk vertically till it meets a seam of coal, and is then continued along the dip of the bed, the latter sloping part of the excavation, even if it has a dip of 50 or 60. is called an " in- cline," and not a shaft. The term " slope " is used in places to denote an inclined pit along the dip of the strata. We will suppose that the deposit has been struck by a shaft, incline, or level. The problem is how to remove it to the best advantage. As the conditions are so various, it is advisable to classify the methods according to the nature of the deposit, and treat separately the modes of working (i) beds ; (2) veins; and (3) masses. EXPLOITATION. 309 FIGS. 352 & 353. BEDS. - - Two great divisions stand out prominently : {A) Methods in which the bed is cut out into pillars; and {B) methods in which the bed is removed at once without this preliminary treatment. In the former the pillars may either be left as permanent supports, or they may be removed in a second sta.ge of the process of exploitation. We have thus three prin- cipal processes of working to consider 7 as shown in the following table : [Ai. Pillars left as permanent supports. (A. Pillar workings, -j Beds J (A2. Pillars worked away. (B. Longwall workings. Ai. Pillars Left as Permanent Supports. This system is adopted with minerals of no great intrinsic value, as it is often better to lose much of the mineral in the form of pillars, than to go to the expense of putting in artificial supports during the period of exploitation. The method can be best understood by giving a few charac- teristic examples taken from minerals of various kinds viz., gypsum, iron pyrites, limestone, salt, and slate. Gypsum. Figs. 352 and 353 repre- sent in section and in plan the cham- bers and pillars of the underground gypsum quarries at Paris, which supply the stone from which the well-known plaster is made.* The principal bed is from 50 to 60 feet in thickness. Pillars are left 10 feet square at the m pn pa k base, and the stalls between them are 1 6 feet wide. The workings are slightly H 111 11 arched, and are not carried up to the true roof, for the purpose of better maintaining the security of the chambers, because heavy damages would have to be paid if they " caved in " arid rendered the surface useless. A similar layer of gypsum left for the floor prevents "creep" that is to say, arising of the floor owing to the thrust of the pillars, and enables the underground roads to be kept in order with little expense. In Nottinghamshire the poor parts of the bed of gypsum are left as pillars, and they are sufliciently frequent to prevent any waste of good rock for supports. Iron Pyrites. At Cae Coch Mine, near Llanrwst in North Wales, there is a bed of iron pyrites, about 8 feet thick, which is worked by leaving pillars from 2 to 3 yards in diameter, at intervals of 8 or 10 yards. The pillars are somewhat irregular, because where the roof is firm and strong more space can be * Gallon, Lectures on Mining, vol. ii. plate xli. 3io ORE AND STONE-MINING. left without support. If the roof appears at all weak, the- pillars are made closer together. The excavations are slightly arched at the top, so as to obtain a little more strength. Limestone. A considerable quantity of limestone is wrought in this country by underground mining, especially in Wiltshire, Worcestershire, South Staffordshire, and Scotland. The beds of freestone which are worked near Bath occur in the Great Oolite, and vary from 8 or 9 to 1 8 or 24 feet in thickness - r the dip is slight, being only i in 33. FIG. 355- Section FIG. 354. < -2 \side hole \ Wjisidehole * Main heading j ,-J I side hole The bed of stone, which it is proposed to work, is reached by an inclined plane, and a main heading is driven out 15 to i6< feet wide, with " side holes " at right angles, as wide as the roof or ceiling will admit with safety, say 20 feet to 24 feet, leaving pillars 10 feet square and upwards (Fig. 354). If any rock is unsound, it is left as a pillar, and this may cause som& irregularity in the plan of the mine. The first process in removing the stone consists in excavating the " jad," a horizontal groove at the top of the bed, which is cut in for a depth of 5 feet FIG. 356. and a width of 20 to 25, A p/ v feet (Figs. 355 and 356). After the jad has been, excavated with the pick (Fig. 355), a vertical cut is made with a saw along the line BA (Fig. 356), and another along the line DC, and a piece ABDC, called the " wrist," is wedged up from the bottom or off from the side ; it breaks along the line AC. When the " wrist " has been removed, the blocks are simply cut out with saws. These saws are 6 or 8 feet long by 10 inches to 12 inches wide. The first saw used in the jad has to be narrower, and is called the " razor saw." The heaviest saw weighs 56 Ibs., and the handle ca,n be fixed -20to25ft.- EXPLOITATION. 311 as shown by the dotted lines (Fig. 156), or entirely below the eye for working immediately below the roof. When set free by sawing on all four sides, the block is easily detached by wedges driven in along a plane of bedding. The blocks are lifted off by cranes, and either loaded at once on to trucks or stacked inside the quarry, after having been roughly dressed with an axe or with a saw. A workman can saw 1 5 square feet of the softest beds in an hour. In the neighbourhood of Dudley there are two beds of Upper Silurian limestone worked by true mining. The top bed is from 1 6 to 1 8 feet thick, and it is got by a system of pillars and chambers. The pillars are 8 yards square, and the stalls between them 13 to 17 yards. Near the outcrop both the pillars and the stalls are rather smaller than this. The top 2 feet of stone are left to support the roof. Salt. The salt mines of Cheshire * are an excellent example of pillar and chamber workings. The bed is 84 feet thick, but only FIG. 357. FIG. 358. the bottom part, 15 to 18 feet thick, is mined. Pillars 10 yards square are left promiscuously, about 25 yards apart, or closer if thought desirable in any special places. Fig. 357 represents part of Marston Hall Mine near Northwich. The bed is almost horizontal, and is reached by two perpendicular shafts ; wide stalls are then driven out on all sides. The workings are advanced by making an excavation in the upper part called the " roofing " (a, Fig. 358) ; and the lower two-thirds of the thickness worked are got by blasting slanting holes. This part is called the " benching." The roofing is made by holing or under-cutting by hand, or better by a Walker circular saw driven by compressed air (Fig. 216), and bringing away the salt by horizontal holes bored with a jumper and charged with gunpowder. The old method of working salt in Koumania f was by bell- shaped pits, which were widened out gradually till their diameter * Dickinson, "Keports on the Salt Districts," Reports of tlie Inspectors of Mines for the Year 1881, p. 66. t Notice sur la JRoumanie. Exposition Vniversalle de Paris en 1889, pp. 1 16 to 119. 312 ORE AND STONE-MINING. reached 160 to 200 feet (50 to 60 m.), after which the sides were carried down vertically. Nowadays long chambers are excavated with intervening pillars, A chamber is begun by driving a level 10 to 50 feet wide (3 to 1 6 m.), and this is deepened and widened at the same time, so that the sides make an angle of 30 to 45, until the full width of 1 64 feet (50 m.), is attained; the excavation is then continued with vertical sides. The section therefore resembles that of an ordinary house. A gangway is carried round the roof for the purpose of inspecting it regularly. At Turgu-Ocna Mine there are four of these chambers which will eventually vary from 100 to 160 feet in width (30 to 49 m.) and 450 to 560 feet (138 to 170 in.) in length, and afford a total working area of 22,000 square yards (18,550 square metres). As regular blocks of almost uniform weight are preferred for exportation, great pains are taken to get out the rock-salt in the form which meets with the readiest sale, and to reduce the quantity of " smalls " to a minimum. The blocks are cut by hand or by machine. Three cutting machines are used : one makes horizontal cuts in the direction of the long axis of the chamber, the second vertical cuts, and the third transverse cuts, so as to divide the rock-salt into regular cubes, about one foot on the side, weighing 132 Ibs. each (60 kil.). Slate. In the Festiniog district in North Wales the principal bed is 120 feet (36 \ metres) thick in places, and there are others from 30 to 70 feet thick; these beds are spoken of as "veins," though they are true sedimentary deposits. The dip of the beds is from 20 to 30 or 35, whilst the dip of the planes of cleavage is about 45; the strike of the planes of cleavage is very nearly the same as the strike of the planes of bedding. The method of working consists in making a series of- parallel chambers (openings) separated by pillars (walls). These do not follow the dip, but run somewhat askew, because it is found that the slate rends well at right angles to the cleavage planes in a direction which does not coincide with the dip exactly. The width of the chambers along the line of strike varies accord- ing to the firmness of the bed selected as roof of the chamber, and is commonly from 35 to 50 feet. The width of the inter- vening pillars is usually somewhat less. The workings are divided into a succession of floors about 50 feet one below the other vertically. The first operation consists in reach- ing the bed by means of an adit or an incline sunk along the dip of the bed and then levels are driven out along the strike, A B C D (Fig. 359, plan ; Fig. 360, cross section), under some bed which offers the necessary guarantee of solidity, very often an altered volcanic ash. When a new level, such as D (Fig. 360), has been driven a certain distance it is connected with the level above by an inclined drift called a " roof." The " roof," or " rise " as it would be called by EXPLOITATION. 313 an ore-miner, is a passage about 4 feet high, and 4 feet wide, generally excavated from below upwards, on account of its being more economical to let the broken rockfall into the level underneath than to draw it up by hand, which becomes necessary if the passage is made by "sinking" i.e., excavating from above downwards. The "roof" is usually carried up on one side of the proposed new chamber. The third step in the process is the " widening," or excavation of the rock 011 one side of the " roof," until the slate is uncovered for a width of 40 or 50 feet. The result of this work is the formation of an inclined open space 40 feet long, for instance, along the strike, and stretching up from one level to the next one 50 feet above it vertically. While this work is going on, the level is being prolonged ; a distance of 30, 40 or 50 feet is left for the pillar, and eventually a new " roof " is put up for a second chamber. In most cases the excavation of the FIG. 359. FIG. 360. roof" and the process FIG. 361. of widening go on at the same time, because it is found that the atmosphere of a small passage like a " roof " naturally becomes bad during work, unless it is provided with some special venti- lating appliance, whereas if the amount of space is increased, the impurities introduced into the atmosphere are spread over a greater volume of air, and the evil is lessened. This preliminary work of driving levels, " roofing up," and " widening," is all done by a special set of men, known as " miners," to distinguish them from the slate-getters, who are called " rockmen," for slate is par excellence " the rock " in the district. The productive period of the life of a chamber now begins. The first duty of the rockmen is to examine very carefully the roof of the chamber, which ought to have been left perfectly secure by the miners ; but as the rockmen have to work under it possibly for ten years or more, they naturally are anxious to feel that every chance of a fall has been prevented as far as possible. In the early part of the working of a chamber, when the roof is within reach, the examination can be made with ease ; 314 ORE AND STONE-MINING. later on when the slate has been excavated, or partly excavated, long ladders are required, and the task becomes much more difficult. Having satisfied themselves and the agents that all is safe, the rockmen proceed to remove, bit by bit, the huge mass of slate lying between their floor and the one above it. Such a mass will sometimes be sufficient to produce merchantable slate worth ;io,ooo or even ^15,000, and to give work to a small gang of men for fifteen years. In the plan (Fig. 359), the lines PP' are the sides of the chambers and also indicate the direction of the " pillaring." When the slate is taken away a large chamber is left, and the series of chambers one above the other forms a huge continuous inclined opening stretching down from the surface, it may be, for a distance of several hundred yards. Between each two of such openings, there is the supporting pillar, nearly if not quite equal in size to that of the excavation. The consequence is that very nearly one- half of the available slate is lost in the form of pillars ; much again is entirely wasted in making the preliminary drivage, the " roof," the " widening," and the " free side." There is a further loss in getting the blocks arid, as we shall see later on, in making these into marketable roofing slates or slabs. Jndeed it is reckoned that even a good " vein " will yield only about 40 per cent, in the form of blocks, and that two-thirds of this are wasted in the subsequent dressing. Therefore, the slate miner does not sell more than one-tenth to one-sixth of the slate rock which he lays bare in a chamber, to say nothing whatever of the loss in the form of pillars, which have to be left in the mine as perma- nent supports. There are varieties of this method of working. For instance, at Aberllefenny in Merionethshire,* a bed 60 feet thick, dipping at an angle of 70, is worked by alternate pillars and chambers with a much smaller loss in supporting rock. The pillars are from 24 to 30 feet long, and the chambers 100 to 187 feet along the line of strike. Indeed even at Festiniog, there are chambers at Wrysgan Mine, where the roof is very strong, more than 130 feet in length, whilst the pillars are only 50 feet. At Angers, in France, the beds dip at a high angle, and the underground workings are carried on like an open quarry under a strong roof of slate ; the floor is being continually worked away in steps, and an immense open chamber is left with perpendicular sides. In the French Ardennes the beds of slate are inclined at lower angles, and in this respect more resemble those at Festiniog; but the pillars run indefinitely along the strike, instead of approaching the line of dip. The cross-section (Fig. 361) shows * C. Le Neve Foster, "Notes on Aberllefenny Slate Mine," Trans. R. Geol. /S'oc. Cornwall, vol. x. p. 169. EXPLOITATION. 315 these pillars A A, and the chambers between them. The attack of the bed is made from below, and not from above as in Wales, and the slate is removed slice after slice parallel to the bedding. The men stand upon the rubbish, which finally fills up the chambers completely. In the figure the upper chamber is exhausted, the next one is half worked out, and in the lowest only one slice has been taken off. This method of mining is favoured by the presence of natural joints, which can be utilised for forming the roofs of the chambers without any cutting. In this case the walls of the excavation are supported eventually, not only by the pillars, but also by the rubbish, and other instances may be found where a filling up with waste rock constitutes a feature of the method of working. For instance, the thick seam of carnallite or kainite at Stassfurt is worked by huge chambers, between which pillars are left. The Prussian Govern- ment, fearing that, in spite of wide pillars, a " caving-in " may possibly occur, has ordered all the excavations to be filled up. The cheapest method of doing this is by working out chambers in the bed of rock-salt, lying geologically below the potash salts, and using the salt as stowing. The chambers in the rock-salt stand well without fear of the roof giving way. At the Wieliczka salt mines it has been found that the natural pillars, originally supposed to afford ample support, are not always capable of preventing the roof from falling, and in some places they are supplemented by huge timber frames (Fig. 268), which are nothing more than " cogs " or " pigsties," on a gigantic scale. A 2. Pillar Workings with Temporary Pillars. It is naturally far more satisfactory from an economic point of view to leave as little of a deposit as possible : a larger output can be got from a given working area if everything is removed, and it seems a pity after a bed of mineral has been discovered, and after all the dead work of sinking shafts and driving levels has been accomplished, to allow any of the valuable material, the very object of the mining, to be left behind. We therefore now come to the cases in which driving galleries and cutting up the bed into pillars form only a first stage in the actual exploitation. The most important example in this country, after coal, is the mining of ironstone in the Cleveland district. The bed has an average thickness of about 12 feet (Fig. 43) where worked. If the contour of the country is not suitable for bringing in adit levels, two vertical shafts are sunk, one of which is shown in Fig. 362. An almost level road, the main way, is driven out with a width of 5 yards ; drivages are put out, at right angles to it, at intervals of 20 yards, called bords, also 5 yards wide, and at distances of 30 yards apart cross-drivages are made, called walls. These are only 4 yards wide. By this system of galleries, FIG. 362. jUULJL rar~ 316 ORE AND STONE-MINING. the bed is cut up into a series of pillars, 30 yards long by 20 yards wide, and owing to the size of the tunnels the quantity of ore got out in this preliminary stage is by no means small. When the bed has been divided up in this way, the work of removing the pillars begins. As a rule, the attack begins on pillars situated near the boundary, so that whilst the first carving out proceeded towards the boundary, the removal goes on in the opposite direction viz., towards the shaft. A place or drift a b is worked across the pillar for a width of 2 to 4 yards, and then, starting from the drift a b, the rect- angle beyond it is removed by drivages, called lifts, sometimes two in number, sometimes three, as shown in the figure and marked i, 2 and 3. It may be _ necessary in some cases to leave a little of the pillar, in order to keep out the fallen rubbish beyond and to prevent a too sudden fall of roof. According to circum- stances, it may be a corner of the pillar that is left, or a narrow strip on one side. The working place is timbered during the removal of the ironstone, and when all has been taken out the timber is withdrawn and the roof allowed to fall. While the lifts i, 2, 3. are being worked away, another place c d is being driven across the pillar, which is a preparation for another set of lifts 4, 5, 6 ; lastly, lifts 7, 8, 9 are worked away, and with the exception of occasional small corners or strips, the removal of the pillar is complete, and its place is taken by fallen rubbish. The ironstone is got by boring and blasting ; the holes are bored by hand or by machine, and gunpowder is the explosive mostly used. The jumper employed and the three forms of mechanical augers have already been described. Varieties of this method of pillar working naturally occur, but they all come back to this main principle, when the bed is of a thickness which enables it to be dealt with in one operation. As another example I will take a bed of alluvial tin ore, to which I have already alluded in speaking of thje sinking of a shaft through mud near Falmouth (p. 268). The bed of stanniferous gravel varied in thickness from 3 inches to 7 feet, but as a rule it was not thick enough for men to stand upright when at work ; the maximum width was 100 yards. It was reached by a shaft D sunk through the mud of the tidal creek, and also by a shaft C and level AA in the hard slate (Figs. 363 and 364). Main levels EE were driven in the gravel EXPLOITATION 318 ORE AND STONE-MINING. bed 20 fathoms apart, and air levels GG, all strongly timbered. Cross or stripping levels HH, 14 feet apart, were pushed out from one air level to the other, and the gravel was removed for a distance of 7 feet on each side, as shown by the shading J. The mud forming the roof was allowed to fall, and fill up the empty spaces. The gravel was wheeled in barrows to the main levels EE, and conveyed by a railway to one of the passes FF, which led to large bins, whence it could be drawn off into waggons in the main rock-level A A, and sent to the shaft. Drift mining, or the working of auriferous alluvial gravel, is carried on in a similar manner. Old river beds which carry gold are common in California, and especially in Sierra and Placer Counties. These beds once occupied the lowest ground of the district, and became covered over by true lava flows, volcanic ash and mud, sometimes also by the deposition of pipeclay and infusorial earth. The streams were diverted and cut themselves new channels, which in process of time were so much deepened as to lie many hundred feet below the level of the old buried auriferous beds. The width and thickness of the old gold-bearing alluvia vary greatly, as might be expected from observing the bed of a river at the present day, and the gold is not uniformly distributed in the gravel. The total thickness of the gold- bearing gravel may amount to as much as 600 feet. In drift- mining the workings are confined to the "pay-lead," usually the very bottom of the channel, varying from 100 to 150 feet in width on an average.* Where there is a rich gravel with $5 to $8 per cubic yard, the leads may be only 50 to 75 feet wide ; where gravel with $2 to $4 is being mined, they are often 300 feet to 400 feet wide. By tracing the junction of the underlying slate and the volcanic capping (Fig. 365!), an idea is obtained of the run of the ancient valley, and arrangements are made for reaching the old river-bed, either by an adit driven into the hillside, or by a shaft sunk from the top. Working by shafts entails the expense of winding and pumping, and adits are therefore preferred. In fixing a position for the adit, care is taken to start it so that it will come in a little below the level of the gold-bearing gravel, and so that it will afford sufficient tip-room for the waste material. The adit of the Forest Hill Divide Company, Placer County, is 600 yards long, some others are nearly a mile in length before getting underneath the old channel. When the goal has thus been attained, a level is driven in the general direction of the " lead," or, roughly speaking, at right angles to the first part of the adit ; the whole of this work is carried on in the slate or " bed-rock," in order * Hammond, "The Auriferous Gravels of California," California State Mining Bureau, Ninth Annual Report of the State Mineralogist, Sacramento, 1890. p. in. t EXPLOITATION. 319 to save the cost of timbering and repairs, which would be considerable in the gravel itself. Rises (upraises, U.S.A.) are put up into the gravel bed, and, after a preliminary division into HO t> It's, sv P 3". a ;-? " frR o fo li g o H - II blocks by a series of cross drivages, the bed is worked away. The gravel is wheeled to the rises (passes, chutes, U.S.A.) leading to the main tunnel, and thence drops into waggons which are drawn out by horses to the surface. 320 OEE AND STONE MINING. It is reckoned in Placer County, California,* that, in the case of a mine producing 250 tons (or carloads) of gravel a day, the total cost of getting, tramming, washing and agency is about $1.10, or 45. 6d., per ton. The yield in this region varies from $ i to $10 per ton (carload,) and may be taken at $2.50 or los. per ton on an average. The method of working by temporary pillars is not confined to beds of small or medium thickness. The lead-bearing sandstone at Mechernich furnishes a good example of what can be done in a rock which, though far from being hard, will nevertheless allow large excavations to be made without any timber. As has been already mentioned, the bed of sandstone is sometimes as much as 100 feet thick. Drivages are made in the bottom part of the bed, about 2 m. high by 2 in. wide, and these are followed by a series of cross drivages, dividing the bed up into a number of square pillars, 6 m. by 6 m., or 8m. by 8 m., resembling the squares of a chess-board. Then, beginning at the outer part of the boun- dary of the sett, the miners proceed to remove the whole of the sandstone from the floor to the roof, and at last let the roof of conglomerate fall in. As a rule they convert the space covered by four adjacent pillars into one chamber. This is done by cutting round each of the four pillars and gradually reducing it in size, until at last there is an open space where the four pillars stood, say a square 22 to 24 yards (20 to 22 m.) on the side, the height still being the same as that of the original drivages i.e., 2 metres. Standing upon the broken rock, the men now attack the roof, which they can often get away in layers of about 5 feet in thickness, by cutting a big groove round the periphery of the chamber and often putting in a suitable blast. The central part will then fall in one mass breaking up as it strikes the ground. A second layer is taken off and the chamber again heightened 5 feet. While this work is going on the roof is sounded by being struck with a long pole. The miners learn by the sound given out whether the rock is firm or not, and regulate their work accordingly. They work upwards till they reach the conglomer- ate, and having cleared out all the ore allow the roof to fall in. It is important that the roof should fall in, because, as long as it remains, it throws its weight upon the other adjacent pillars ; but when it has come down, the pillars have only to support the weight of the strata immediately above them. In the direction of the dip, the chambers are sometimes made larger, and six pillars are taken instead of four. With a very strong roof the chambers may even cover an area of 109 yards by 43 yards (100 m. by 40 m.). At Mechernich the workings are arranged so that the chamber remains open until the last moment, the roof not falling in till * " Bergmannische Mittheilungen von derPariserWeltaustellung," 1889, B. u. h. Zeitung, 1890, p. 314. EXPLOITATION. 321 the completion of the process of excavation. The sulphur seams of Sicily are wrought differently.* The thick beds are pierced by networks of tunnels superposed one above the other, and the workings are allowed to fall in. After a time, when the collapse is complete, the miners make drivages in the mass of crushed and broken pillars, and so reap a second harvest. The details of the mode of procedure are as follows : When the clip of the beds is less than 30, one set of tunnels is driven along the strike and another set along the line of dip. The tunnels are made 8 to 13 feet (2.5 to 4m.) wide. Those along the strike are 8 to 13 feet apart, and those along the dip 10 to 16 feet apart, leaving rectangular pillars between them. If the dip exceeds 45, tunnels as before are driven along the strike, and these are intersected by horizontal cross tunnels running from the roof to the floor of the deposit. The height and width of these tunnels do not as a rule exceed 10 feet (3111.). If the bed is thick the tunnels are traced out in superposed planes, leaving a solid slice of ground 8 to 10 feet (2.5 to 3 m.) thick between any two successive -networks of drivages. The first part of the process is now complete, and it is followed by the thinning of the pillars. Beginning near the boundary of the mine, a tunnel is driven through a pillar, or two tunnels are driven if it is a big one. The sides of the tunnels are cut away gradually, until at last the weight of the superincumbent rock breaks down what remains of the pillar; sometimes shots are put in to effect or hasten the fall. As much sulphur rock as possible is taken out, and the next pillar is treated in the same way, and so on, always proceeding from the boundary towards the shaft. This method of working has been the cause of the worst accidents and of the majority of the fires, especially when the stratum is thick, and several sets of tunnels have been driven one above the other. In some parts of the Colle Croce mines, Lercara, there have been as many as ten working horizons one above the other, each horizon, or slice, being 16 feet (5 m.) thick, and the bed itself 164 feet (50 m.). Sometimes mines of this kind have " caved in" of themselves ; in other cases the general breaking up and crushing together has been produced intentionally by bringing down some of the lowest pillars by a few shots. During this crush the heat produced by the friction of great masses of rock falling against one another is sufficient to make the sulphur take fire. The mine is then closed, and the fire eventually dies out for want of oxygen, though there are instances of fires going on burning for more than sixty years. When the fire is supposed to be completely * " Sui sistemi di lavorazione impiegati nelle solfare del gruppo di Colle Croce in Lercara, e sui provvedimenti da adottarsi per migliorarne le condizioni di sicurezza," Rivista del servizio minerario nel 1888, Florence, 1890, pp. 67 to 99. 322 ORE AND STONE-MINING. extinguished, work is begun in the broken mass, by driving a series of tunnels, along much the same lines as those made originally in the virgin bed. The tunnels are supported by walling and timber. A similar network is then made at a level 18 feet (5.50111.) above, and in some instances there are three such sets of levels in " the broken " one above the other. The tunnels of the lowest horizon are widened out, and by means of suitable shots the whole mass of broken rock is made to fall again, and of course the tunnels disappear. This process of making a network of levels at two or three horizons is repeated, and the "caving-in" is brought about again until the sulphur-bearing rock is exhausted, or so much barren stuff from the roof is mixed with it as to make the work unprofitable. The crushes themselves have not generally been accompanied by accidents, but work in the broken ground has been very fatal. For working these deposits, and especially the thick ones, a filling-up method is preferable, and the " ginesi," or residues from the treatment of the sulphur-rock in kilns, are ready at hand as the most convenient material for the purpose. The filling-up method enables the sulphur bed to be worked away completely, whereas with the method of networks of drivages followed by falls, fully one-fifth or even one-fourth of the mineral is lost. Besides, there are fires and subsidences of the ground causing fissures which let water in, and therefore producing more danger to the men and also to the adjoining mines. The Italian Inspectors of Mines are of opinion that poor beds, which could not be wrought profitably by the filling-up pro- cess, may in certain exceptional cases be worked by the old method, because the firmness of the rock increases as the percentage of sulphur diminishes. However, they limit the number of super- posed working floors to three, and stipulate that an upper floor shall be entirely worked out before a lower one is taken away. It is estimated that in the year 1889* only 43 per cent, of the sulphur produced in Sicily came from virgin ground, and that all the rest was obtained from drivings among broken pillars and workings that had " caved in." B. Longwall. Having discussed the various ways of work- ing a bed by permanent or temporary pillars, we now come to the so-called longwall method. In this case there is no pre- liminary carving out into pillars, but the mineral is worked away in long faces, whence the name applied to the system. A typical case is found in the workings for copper shale in the Mansfeld district, Germany.t * Bivista del servizio minerario nel 1889, p. 76. f This account of the workings of the copper shale is based upon the description in the pamphlet, ' ' Der Kupf erschief erbergbau und der Hiitten- betrieb zur Verarbeitung der gewonnenen Minern in den beiden Mansfelder Kreisen der Preuss. Provinz Sachsen,i889," and upon personal observations. EXPLOITATION. 323 The bed, as already mentioned, is usually from 3 to 5 inches thick, but it makes up for its thinness and poverty by its uniformity of yield, at all events compared with a mineral vein. It is worked for a distance of n miles (18 kil.) along the strike, and the present plan of operations consists in having a set of shafts for every 2\ miles (4 kil.), that is to say a set of shafts serves for the workings ij mile (2 kil.) on each side of it. The great difficulties encountered in sinking shafts through the watery measures above the copper shale have led to the adoption of the system of driving out long crosscuts to intersect the bed on the floor side. These crosscuts can be driven with speed by machine-drills, and various mechanical means are available for haulage. On the other hand, in spite of the considerable im- provements which have been introduced into shaft sinking by the Kind-Chaudron process, much time is required and a very heavy expenditure of capital. There is also the consideration that if the shafts were on the roof side, crosscuts would have to be driven at the level of the adit in order to get rid of the water. These crosscuts would sometimes traverse the troublesome gypseous measures, full of unknown pools, and they would be above the worked-out bed of copper shale and therefore be subject to slight sinkings of the ground. Crosscuts in the measures below the copper shale do not present these difficulties. Of course it would be possible to lift the water to the surface and not discharge it into the adit. This would entail extra expense for pumping, and in this particular instance there is the further objection that the water is so salt that it cannot be discharged without damage into any small brook. It therefore becomes necessary to conduct it into a river like the Saale, too big to be seriously affected by the briny stream from the mines. The workings are arranged in a succession of floors taken exactly 62.7 m. apart. This distance is the equivalent of 30 German fathoms, and is 68J yards. To save expense, crosscuts are put out from the shaft at every second floor, that is to say, they are vertically 125.4 metres one below the other. Drivages along the strike are pushed out on each side of the crosscut, and by putting up " rises " each level is brought into com- munication with the one above. Intermediate tunnels are then driven along the shale from a point midway between the two crosscuts, and the bed is now traversed by levels along the strike, at intervals of 62.7 metres vertically, which constitute the main working roadways. As the dip is about 5 or 6, the distance from one main roadway to the next is as much as 600 to 800 yards, and constitutes a long working face or "longwall." In Fig. 366, A B represents a main level, and C D the next one below it. E F is the working face, which is cut away gradually till it becomes E' F', and then E" F", and so on. This working face is occupied by a string of miners, in fact as 324 ORE AND STONE MINING. many are employed as the space will accommodate. The workman lies upon his left side, reposing upon a shoulder-board and a leg- board. The latter is strapped to the thigh, but the former is free, and is shifted as required. The work comprises the following suc- cessive operations (i) Holing with the pick ; (2) wedging down the copper shale ; (3) blasting down the roof ; (4) stowing the deads. The holing is done in the lowest part of the bed of copper ore, along the hard and smooth floor. Enough of the roof is taken down to give the miner just room enough to do his work. It is best to have as much as 23 inches (58 cm.), but if there is a convenient smooth plane of bedding for forming the roof at a height of i8J inches (47 cm.) no more is taken down ; indeed, in some exceptional cases the height is only 15! inches (40 cm.). FIG. 366. PLAN g^ggg| )^>^r i^^^jjji^v^ff^p^^ The barren rock serves as material for stowing or filling up, and as the quantity is more than sufficient for this purpose, some of it has to be drawn up to the surface. It is necessary to have roads for taking away the ore from the face, and they are formed by reserving passages in the stowing and by blasting down the roof, so as to give suffi- cient height. These divisional roads are shown by the letters a b, c d. e f, &c. The interval between them varies from 50 to 1 20 yards; and in all cases there are diagonal branch roads leading from the railroad towards the face, which is finally reached by the so-called " Fahrten." They are low passages in the stowing, along which the ore is dragged by boys in little carts. The diagonal roads, however, are made 5 feet high by blasting down the roof. Owing to the small scale of the diagram it is impossible to show all the branch roads connecting the working- face with the levels running along the strike. The direction given to the working face is a matter of importance, for it EXPLOITATION. 325 enables the amount of pressure coming upon the rock to be varied. The pressure is felt most when the face is parallel to the strike and the working carried up to the rise ; it is felt least when the face is parallel to the strike and the work is proceeding down- wards. If the face runs in a direction parallel to the line of dip, the pressure is intermediate in amount. Therefore by regulating the line of the face, the mining authorities have it in their power to cause what amount of pressure they think most desirable for the work. As a rule the line chosen for the working face lies somewhere between the line of strike and the line of greatest dip. In new ground in the deeper workings, holing with the pick is a very laborious operation, and has on that account been given up in such places the shale is got by blasting. After the lapse of three-quarters of a year or a year and a half, when a large area has been worked away and the roof begins to subside upon the stowing, pressure is felt on the working face and the holing be- comes much easier. In order to bring about this state of affairs as soon as possible, Jager drills worked by compressed air have been employed in getting the ore. The Mansfeld longwall has the peculiarity that more deads are produced than can be stowed away in the excavations ; these are therefore packed very full and the amount of subsidence is not great. In some other varieties of the longwall method there is no stowing at all and the roof is allowed to fall in, or the amount of rubbish produced by the seam is insufficient to fill up the empty spaces. There is also a diversity of practice with regard to the direction in which the longwall face is carried, sometimes the seam is worked by longwall outwards that is to say, the face is carried from the neighbourhood of the shaft towards the boundary of the property, in others it is carried " homewards " from the boundary towards the shaft. 2. VEINS. In the case of a vein, an exploratory pit is often sunk upon it for 20 or 30 fathoms, and, if the indica- tions found in driving out levels warrant further prosecu- tion of the mine, a first working shaft is put down to intersect the lode at a depth of 100 fathoms or more from the surface. Crosscuts are then driven out at intervals of 10, 15, or 20 fathoms to reach the lode as shown in Fig. 367, which represents a section at right angles to the line of strike. Sometimes the main shafts are carried down all the way along the dip of the vein, though perpendicular shafts have the advantage of being better suited for quick winding and cheap pumping, to say nothing of the rapid ascent and descent of the miners in cages. If an inclined shaft appears to be advisable, great care should be taken to sink it in a straight line. The worst shafts are the crooked ones so common in 326 ORE AND STONE-MINING. Cornwall, vertical perhaps for the first hundred fathoms until the lode is struck, and then carried downwards along its varying dip. Whatever kind of shaft is adopted, levels are driven out along the strike of the lode, as shown in the longitudinal section (Fig. 368), in the hope of meeting with valuable ore-bodies such as are represented by the stippled portions of the figure. For the purpose of affording ventilation, and still further exploring the ground and working it, intermediate shafts, called winzes (Cornwall), or sumps (North Wales), are sunk in the lode from one level to the other. In some cases the communicating passage is excavated upwards, or, in other words, the miner " puts up a FIG. 367. FIG. 368. SOUTH. WEST. rise." When the communication is complete, there is no differ- ence whatever between a rise and a winze. On looking at the longitudinal section (Fig. 368), which may be regarded as representing a common state of things, it will at once be remarked that only certain parts of the vein are valuable. When dealing with a bed or seam, we constantly find that the whole area covered by it can be worked away profitably. With a lode this is the exception, and therefore the problem of exploit- ation is not the same in the two cases. The vein-miner has to remove portions of a sheet-like deposit usually dipping at a high angle, and the bed-miner to excavate the whole of a sheet-like deposit lying frequently nearly horizontal. The un worked por- tions of the lode serve to support the hanging wall, and form in this way the equivalent of irregular pillars. The actual mode of removing the valuable part of the lode itself depends a great deal upon circumstances viz., its width,, the nature of its contents, and that of the walls or enclosing rock ; but the methods of working may generally be brought EXPLOITATION. 327 under one of two heads viz., underhand stoping or overhand stoping. The word " stope " is equivalent to step, and the term " stoping " means working away any deposit in a series of steps. Underhand or bottom stopes are workings arranged like the steps of a staircase seen from above, whilst overhand or back stopes are like similar steps seen from underneath. Both methods have their advantages and disadvantages, and both are largely used. We will first take underhand stoping, as this is the older FIG. 369. W//////MMW/////// FIG. 371. method. In the old days the miner began in the floor of the level (Fig. 369), and sank down a few feet, removing the part i ; he followed with 2, 3, 4, &c., until the excavation finally presented the appearance shown in Fig. 370. Any valueless rock or mineral was deposited upon platforms of timber (stidls), and the ore was drawn up into the level by a windlass. One great disadvantage of this method was the cost of winding up the ore and water by hand labour. At the present day the disadvantage would not be so great, because power is so easily conveyed to underground winches by compressed air or elec- tricity. There always remains, however, the necessity of pro- viding much timber for the stulls, if there is a large quantity of worthless stuff in the vein, or if the sides are weak. The advan- tages are that ore can be worked away as soon as a level is driven, that the men are always boring downwards, and, lastly, that the ore can be carefully picked after it is broken, without fear of any valuable particles being lost. A more economical method of working by underhand stopes, and one largely employed in Cornwall at the present day, consists in reserving any attack upon the ore-ground until a lower level has been driven. A connection is then made between the two levels by sinking a winze from the upper one, or by putting up a rise from the lower one. The work of stoping is commenced from the two upper ends of 328 ORE AND STONE-MINING. FIG. 372. EAST EH N B OU NDA RY GREAT CROSS COURSE EXPLOITATION. 329 373- this intermediate shaft, and the lode is removed in a succession of steps, the workings assuming the appearance exhibited in Fig. 371. The steps are gener- ally made steep, so that the ore may readily roll down into the winze, and so that the boreholes may do better execution : but these steep stopes are dangerous if a man hap- pens to slip and fall. The huge open chasms left by the removal of a wide lode in this way are also a source of danger, for there is always a risk of falls of rock, and from places which cannot easily be examined. Figs. 372 and 373 ex- plain the general arrange- ments for working Dol- coath, the largest tin mine in Cornwall. The lode, after producing copper ores for a considerable depth, changed its char- acter and became rich in tin. The workings for tin are confined almost en- tirely to the granite. The section (Fig. 373) shows that the main shaft of the mine is at first vertical and then carried down on the dip of the lode. The mine is now consider- ably deeper than indicated in the figures, but the method of work- ing remains the same. The process of overhand stoping is precisely the reverse of that which has been des- cribed : the work is commenced from a rise (Fig. 374, A), or better, from the two ends of a winze (Fig. 374, B). As soon as the men have excavated a sufficient height of the level, they put in strong pieces of timber from wall to wall (stempels, stull-pieces), and cover these cr OSS- FIG. 374. 330 CUE AND STONE-MINING. pieces with boards or poles, and throw down the rubbish upon the platform (stull, bunning) thus formed. In the midst of the rubbish, chimney-like openings (mills, passes) are reserved, lined with boards or dry walling, and closed at the bottom with shoots provided with doors. The ore is thrown into these passes, which FIG. 375. FIG. 376. \\X\\\\x\\\\\\\\\\\ \ FIG. 377- are tapped when necessary. The ore falls into the tram-waggon placed ready to receive it. Fig. 375 is a transverse section, showing the rubbish resting on the stulls. This may be called the typical mode of stoping, when the lode affords enough rubbish for the men to stand on, and to keep them close to the rock they are attacking. Very often such is not the case, and the whole of the lode has to be sent up to the surface for treatment. If the walls are firm, a stull is put in, and a sufficient heap of broken ore is left upon it to give the men good standing ground ; the excess is thrown over the ends of the stull, or the great heap is tapped by cutting a hole in the supporting platform and letting a quantity of ore run down into the level. Another method consists in putting in temporary stages or platforms upon which the men stand to do their work, whilst the excavation is left as an open space (Fig. 376). This mode of working is incompatible with weak walls. If a lode does not afford rubbish enough for completely filling up the excavated space, or if it is too narrow for the men to do their work comfortably, one of the walls may be cut into and blasted down (Fig. 377), in order to give the men a firm bed of rubbish to stand on while at work, and to prevent any chance of a collapse of the mine. In certain special cases rubbish is sent down from the surface to fill up the excavations. EXPLOITATION. 331 The advantages of overhand stoping are that the miner is assisted by gravity in his work, that no ore or rock has to be drawn up by hand labour, and that less timber is required. On the other hand, the miner is always menaced by falls of the roof of his working place ; but as he is close by, he can constantly test the solidity of the roof and sides by sounding them with his sledge. If the rock rings clearly he feels safe, but if it emits a dull hollow sound he knows that it must be taken down at once, or be supported in some way. A last disadvantage of overhand compared with underhand stopes, is the chance of valuable particles of ore being lost in the rubbish ; but this loss can be prevented by laying down planks or sheets of iron while the lode is being broken down. When very wide lodes have to be worked, recourse is often had to a filling-up method, and, indeed, such a method becomes imperative if the sides are weak. The great lode at the famous Van Mine, in Montgomeryshire, once the premier lead mine of the United Kingdom, had to be worked in this fashion, ^ FlG - 37&- and as the work was carried out very carefully and sys- tematically, no better example of the method can be chosen. The lode is evidently a fis- sure vein as it cuts across the planes of bedding and of cleavage of the adjacent slate rock. It is composed of three parts : the flucan or soft lode B (Fig. 378), the bastard lode C, and the regular lode E. The flucan consists of clay and soft broken slate. The bastard lode is a mass of slate rock, 4 or 5 fathoms wide, between the flucan and the regular lode ; it is much softer than the true country, and, though intersected by numerous small strings of galena, is rarely rich enough to be worked. The regular lode consists of masses of slate traversed by veins of galena, or it is a breccia of fragments of slate cemented together by quartz, galena and blende. The regular lode was at times as much as 48 feet (14.60 m.) wide, and if the excavation formed by the removal of such a quantity of rock had been left open, the hanging wall would speedily have fallen in, and indeed even during the progress of the work the men would have been exposed to very great danger. A filling-up method was therefore adopted, and as soon as the ore had been removed the open spaces were packed with rubbish. Crosscuts were driven out at vertical intervals of about 1 5 fathoms to reach theflucan B, which was chosen for driving a preliminary 332 ORE AND STONE-MINING. east and west level on account of its softness. This preliminary level enabled the regular lode to be reached very quickly in several places by short crosscuts, from which the first level in the lode was pushed out east and west. The next process consisted in stripping away both sides of the level, as far as the footwall on the north and the bastard lode on the south, unless the latter happened to be productive, in which case it likewise was excavated. This left a space about 7 feet high, which was at once filled with deads, save a working level reserved in the middle, which was properly secured with timber. Endeavours were always made to keep this level as straight as possible, so as to facilitate the tramming. The letter H in Fig. 378 represents this working level. Upon its com- pletion the preliminary level became superfluous ; the timber was drawn out and allowed to crush together, as shown in the lower part of the figure. In the meantime, starting from the level above, winzes were sunk, 20 or 30 fathoms apart, in the flucan or in the lode itself, if the flucan happened to be too far away from the produc- tive part. The winzes served not only for ventilation, but also as shoots for the rubbish used in filling up ; they were called passes, I (Fig. 378). They were carefully timbered and divided into two compartments : one was used as a passage for the rub- bish, the other was provided with ladders, and formed a foot- way, besides affording access to the other compartment, in case it became choked with the waste rock shot clown it. As soon as arrangements for supplying the deads were complete, stoping was begun. The height taken off in each stope varied, according to the firmness of the lode, from 2 to 6 feet, and when the ore was removed the excavation w r as packed with rubbish (D) drawn down from the nearest pass, such as I (Fig. 378), and wheeled in a barrow to the place where it was wanted. As the passes were made at close intervals, the amount of wheeling was very little. The broken ore was thrown down into a pass or mill, K, whence it could be drawn off at pleasure into a waggon. The ore-passes were of the same size as the winzes sunk for letting down the rubbish, and were timbered and divided into two compartments in the same way. The lode itself furnished enough rubbish to fill up about one- third of the excavation ; waste rock was likewise obtainable from workings in dead ground, such as crosscuts, and the preliminary or permanent levels ; and finally slate was quarried at the surface, shot down special shafts, and trammed through a level such as P, and a crosscut N and level H, to any special pass where it was required. To prevent any loss of ore among the loose stones used for filling up (stowing), it was usual to spread over the top of the rubbish a layer of soft flucan for a depth of a few inches, and when the lode had been stoped away to the required height, this floor EXPLOITATION. 333 was shovelled into the ore-passes and went to the dressing floor with the rest of the stuff. It was found cheaper and better to dress a few extra tons of stuff than to pay for laying down boards or sheets of iron to catch the fine ore. Slice after slice was taken off in this way, and the long working face formed by the roof of the stopes corresponded in some measure to a lorigwall face in bed mining. On arriving within 12 feet of the old workings above, packed with rubbish, it w^as unadvisable to make openings of the full width of the lode, and the ore was got by crosscuts. A level was driven along the strike in the middle of the lode, or on one side if more convenient ; crosscuts, from 5 to 8 feet wide, were started from each side of it, and driven north and south to the footwall and hanging wall respectively, the ground being supported by strong props of timber. The lode standing on the sides of the crosscut was then removed by a series of cross drivages similar to the original crosscut, only, as one side was free, the work was much less expensive, costing abont ^4 per fathom instead of 10. The empty spaces were packed with waste to the top, and as much of the timber was drawn away as could be removed with safety. When the lower half of the 1 2 -feet slice had been taken away in this fashion by a series of short contiguous cross drivages, another level was driven along the strike above the old one which had been filled with rubbish. Crosscuts similar to the ones below were driven, save that spilling had to be resorted to, as the roof was formed of the deads of the earlier workings. Whilst this work was going on, the miners could recover any pieces of timber which had been left in the midst of the rubbish used for stowing the lower half of the slice. The legs or forks were always put in with the large end uppermost, and could be drawn up by putting a chain round the top and applying a lever. As soon as the upper half of the i2-feet slice had been taken off by these cross drivages, the working level H above it was filled up and abandoned. The block of lode 1 5 fathoms high was thus removed entirely, and its place filled by rubbish ; consequently there was no danger of the walls falling in and of the mine collapsing. No high openings were made during the progress of the work, so the roof and sides could be sounded and examined without scaffolding ; any loose pieces could be taken down at once, and there was little fear of their falling unawares upon the miners. Before a block was completely stoped away, the so-called perma- nent level at the bottom had to be prepared, in order to furnish a road for conveying deads to the block beneath. Crosscuts, N, were pushed out from the level H, at intervals of 20 or 30 fathoms, to a distance of 10 fathoms beyond the flucan, and " ends " were driven east and west till they met and formed a continuous gallery, P. Rails were laid and the road was ready for use. Several men were kept constantly employed at a quarry 334 ORE AND STONE-MINING. .adjoining the mine for obtaining slate, which was trammed to and shot down one of the two special rubbish shafts. These could be tapped at the adit, and the supplies were conveyed by tram- roads and other special shafts, used as shoots, to the places where they were required. Excepting the first two rubbish shafts from the surface, no shoots were made more than 15 fathoms deep, because it was found by experience that the timber was broken up very quickly by the fall of the stuff when they were deeper. The bottom of one shoot was always near the mouth of the next, so that the rubbish never had to be trammed far; and in some instances the shoots were so near that, by fixing a few planks in a sloping direction, the waste rock ran directly from one to the other. I have entered somewhat into detail in this case, because wide lodes with weak w r alls have often given much trouble, when the .attempt has been made to work them with the use of timber FIG. 379. FIG. 380. supports. The amount of timber required at the Van Mine was small, and many of the pieces were used over and over again. Another advantage in this particular case was the certainty that no ore was lost or left behind ; for although money was sometimes spent in breaking down poor parts of the lode to make sure of not missing any lead ore, the barren rock could be utilised for filling, instead of drawing supplies from quarries at the surface. At the Van Mine the lode was firm enough to allow the whole width to stand without supports during the time a stope was carried along, except in the case of the two last slices at the top of a block. These, as we have seen, were taken off by a succession of conti- guous crosscuts. When a lode is wide and too weak to stand open with safety for its whole width, the crosscut method may be applied from the beginning, instead of confining it to the last slices. The method is illustrated by Figs. 379 and 380. The lode is removed in successive horizontal slices, A B C D E, beginning at the bottom, and for each slice a level, L, is driven, either wholly in the lode, or partly or entirely in the country ; from this level, EXPLOITATION. 335 FIG. 381. crosscuts are put out 6 or 8 feet wide, as shown in the plan (Fig. 380). These are regularly timbered, according to the necessi- ties of the case, and when No. i is completed, No. 2 is begun, and the rubbish from No. 2 thrown into the empty space of No. i cross- cut. If the quantity is insufficient, deads are brought in from the surface or from exploratory workings in worthless rock in the neighbourhood. Sometimes the crosscuts are not driven side by side, but i and 5 may be driven first, leaving 2, 3, and 4 as a solid pillar ; then 3 is worked away, and finally 2 and 4 between the timber and rubbish on each side. The greater part of the timber can be recovered when the next slice above is taken off, as the props are put in with their small ends downwards, and can be drawn up with a lever. M (Fig. 379) is a level reserved in the deads for traffic and ventilation. This method of working is applicable not only to lodes, but also to irregular masses. The mode of working the soft ore-bodies such as are met with in the Comstock lode, in the Eureka-Bichmond mines, Nevada, and at Broken Hill in New South Wales, has been already described in the chapter upon timbering. The excavations are supported by huge frames of timber, made by adding one " square set " to another as required, and are finally filled up entirely with rubbish. Another method of working a wide lode is to attack it in slices parallel to the dip, removing each slice separately, as if it were a lode of ordinary dimensions, and filling up with rubbish (Fig. 381). We have here been supposing that the whole of the lode is taken away from wall to wall. Other cases may arise. Thus at Foxdale mine, in the Isle of Man, we have to deal with a vein of lead-bearing rock which is not ore-bearing for its entire width. The vein runs east and west, and in places is 140 feet wide. Levels are driven along the northern and southern boundaries, and show whether or no there is any payable ground on these walls ; crosscuts put through from time to time further prove the lode, and sometimes there may be three parallel workable portions with barren rock between them. Each of these portions, which will rarely exceed 1 2 feet in width, is then treated as a separate lode. The rule at Foxdale (Fig. 382) is to drive the levels 15 fathoms apart, and to effect a communication between two adjacent levels at intervals of 30 fathoms, either by a rise or a winze. The lode thus becomes cut up into blocks 1 5 fathoms deep by 30 fathoms long, in the direction of the strike. These blocks are worked away from below upwards in separate "pitches," each 10 fathoms long, arranged like three steps. The block therefore affords 336 ORE AND STONE-MINING. three pitches, or subordinate blocks. Thus if ABDC represents a block contained between an upper level AB and a level CD, 15 fathoms below it, and bounded on the two ends by the winzes AC and BD, we must first divide it in imagination into the three parts AEGC, EFHG, and FBDH. The removal of each pitch, or third of a block, is confided to a separate set of men. The first set begin at the bottom of AEGC, and take off a slice 6 feet thick, filling up the vacant space with rubbish ; then they begin a second slice, and go on taking off slice after slice until they reach the level above. Work upon the second division viz., EFGH, is not begun until the first slice of the adjacent "pitch" has been filled up, FIG. 382. SCALE 2 4-6 8 10 12 14. 16 18 20 22 FATHOMS 05 10 15 20 25 30 35 4-0 4-5 METRES and in the same way block FBDH is not attacked until at least one slice of EFHG has been worked away. At -some given time the workings will have assumed the form shown in the figure. If, as is often the case, there is a hard and a soft part in the lode, the work in the overhand stopes goes on as follows : Start- ing from a winze, the miners push on a drivage in the soft part, and timber it up with a cap resting upon the hard side and upon one leg (Fig. 383). This renders the working of the hard part very much less expensive, for it can be got by shots which take full effect in such large openings. Before blasting out the side, the caps are supported by a longitudinal carrier resting upon a few upright props in the manner shown in figure 384. All the rock is picked in the mine, and any waste is used for filling up. At last the whole excavation that has been made is packed, with the exception of a passage, 18 inches high, below the caps, along which the men can creep if necessary. A floor of planks is laid down, and serves to make a bed to prevent the FIG. 383. 4 v /. Scale, o-f Me&r&t FIG. 384. A. Granite, or barren part of the lode ; B. Soft part of the lode ^ C. Hard part of the lode ; D. Leg ; E. Cap ; F. Floor of planks ; G. Longitudinal cap or carrier ; H. Prop ; I. Prop ; K. Filling of waste rock. 338 ORE AND STONE-MINING. loss of small ore when the next stope or slice is taken off. Shoots or " passes " lined with timber are reserved in the rubbish ; there is generally one at the end of each pitch and one in the middle. In this way the miner always has one close at hand, and never need wheel the ore very far. The shoots are furnished with doors at the bottom, and the ore is drawn off directly into waggons underneath without any shovelling. Care is taken to drive a crosscut from time to time, to prevent any chance of possible bunches of ore in the sides being missed. Waste rock obtained in this way is always useful for filling up. The Foxdale lode furnishes about enough barren rock to fill up the excavation, without its being necessary to draw supplies from the surface. The timber buried in the rubbish is not lost, for it can be withdrawn when the next slice is taken off. A piece of J-inch iron chain is made fast round the top of the leg, which always has the small end at the bottom, and the hook of a special lever is put into a suitable link. The fulcrum of the lever is carried by an upright bar attached to a square base, and by applying pressure to the lever the leg is gradually pulled up. Wide Lodes worked with Pillars and Chambers. The present method of working the wide veins at the Rio Tinto mines may be briefly described as pillar and chamberwork, with a solid roof and floor between the working horizons. For the present the pillars must be looked upon as permanent. The details of the system are as follows : A vertical shaft is sunk in the adjacent rock, and crosscuts are driven out to the lode at intervals of 25 metres (82 feet); these form the main working floors or horizons. A main level is carried along the strike of the lode at each horizon, and, by sinking from one level and rising from the one below, a vertical intermediate shaft is formed, effecting a communication between them. All this preliminary work is done by the aid of rock drills. An inter- mediate level is next pushed out along the strike by hand labour midway between the two main levels ; the vein may then be regarded in imagination as divided into a series of horizontal slices, each 12 J metres in thickness, as shown by the dotted lines, AB, CD, EF, &c. in the section (Fig. 385). The formation of pillars now begins : the lower part of each slice is cut up by a network of drivages 3 to 3 J metres wide, and 3 to 3 J metres high, at right angles to one another, leaving pillars 6J to 7 metres square (Fig. 386). A very large amount of ore is produced in this way. The next stage in the process of mining is heightening and widening the chambers ; in ordinary hard pyrites the pillars can be thinned down until they measure only 3 metres by 3 metres, and the chambers can be carried to a height of 9 to i o metres. Where the ground is weak more has to be left for support. The two plans (Figs. 386 and 387) show the EXPLOITATION. 339 initial size and the final size of the pillars, whilst the section (Fig. 385) further explains the progress of the work. At the 225- metres horizon there are preliminary levels 3 metres wide and pillars of 7 metres ; at the 2i2j-metres horizon the enlargement of the chambers has begun; at the 2oo-metres level the process has been carried further, and at the two upper horizons it has been completed, the pillars being reduced to 3 metres. The solid slice of ore, 2 J to 3^ metres thick between two storeys, remains for the present untouched, and forms with the small pillars a reserve stock which can be removed at some future time. Great care is taken to arrange the pillars vertically one under the other with FI0 . 3 86. FIG. 387. SCALE ME.TRE.SI their centre lines coinciding exactly. When operations have been finished, the workings have the appearance of very high columns supporting huge arches. It must not be supposed that the honeycombed part of the vein formed by the deserted chambers is entirely unproductive; a very large surface of ore is left exposed to the action of air and moisture, oxidation goes on, copper and iron sulphates are produced, and during the rainy season water trickling down" the sides of the caverns carries them in solution to the bottom of the mine. The coppery water pumped up from underground is led into precipitation pits, similar to those employed for treating the cupreous solutions obtained more rapidly from the ore burnt at the surface. At the present time the quantity of ore in sight is so great that it is not necessary to devise schemes for removing the reserves; but the work might be accomplished by a filling-up process, beginning at the bottom. The pillars and the intervening 340 ORE AND STONE-MINING. solid floors of ore could be removed as horizontal slices, fol- lowed by a filling up with rubbish let down from the surface. In this manner the workmen would always be standing on firm ground within easy reach of the ore. 3. MASSES. The methods of working masses may be classified thus: (a) Method by chambers without filling up. (6) Method by horizontal slices, taken in descending order, allowing the surface to sink down, (c) Method by horizontal slices, taken in ascending order, with complete filling up. (a) The first of the three methods is applicable when the enclosing rock is strong enough to allow chambers to be worked out without FIG. 388. SCALE J 2 4. 68 10 YARDS A. " Grey limestone " ; B. Limestone, the so-called " Crease measures "; C. Chambers or caverns left by the excavation of the ore; D. Brown haematite ; E. Top or Whitehead limestone ; F. Sand- stone (Millstone Grit) ; G, Main level ; H. Supporting pillar built up of stones and timber. danger from the roof and sides falling in. As an instance I may take the so-called " churns " of the Forest of Dean, which are worked for iron ore. Brown haematite occurs in irregular pockets in a certain bed of the Mountain Limestone (Fig. 388), which is from 14 to 1 6 yards thick, and usually dips at a considerable angle. At the particular mine chosen as an example the dip is 52. Perpen- dicular shafts are sunk, and the ore-bearing limestone is reached by crosscuts at vertical intervals of 100 to 150 feet. A good main level is driven along the strike of this bed, and small crosscuts are put out in order to search for the churns, which have often been EXPLOITATION. 34* followed down from the surface to a depth of 200 yards. The exploitation consists in removing the soft ore with the pick, and supporting the roof with occasional props or rough walls built with pieces of ^barren rock; timber and stone may be used together^ as shown in the figure. If the pocket is very steep it is worked like a mineral vein ; the men stope the ore away overhand, standing upon platforms of timber erected across the chasm left by workings below. (b) An excellent example of the second method of working is furnished by De Beers diamond mine, where a mass of diamond- FIG. 389. PLAN OF DE BEERS MINE. 800 FT LEVEL ORIENTAL SHAFT "bearing rock occurs as a huge vertical column, with an irregular oval section (Figs. 30 and 31). It was worked for many years as an open quarry, but falls of the surrounding rocks (reef] caused so much trouble, as the huge pit increased in depth, that under- ground mining had to be adopted. The system consists in excavating chambers, and then letting rubbish from the open pit above run in and fill them up. The details of the method will be plain from consulting Figs. 389, 390, and 391, which are copied from the second and third annual reports of the De Beers Company. The deposit is reached by an inclined shaft sunk in the surrounding rocks, and main levels are driven at successive horizons which are from 90 to 120 feet .apart vertically. Fig 389 shows these main drivages at_the 800- 342 ORE AND STONE-MINING. SCALES 10 19 30 40 60 70 80 M 100 FttT FIG. 391. FIG. 390. feet level; there are two* principal drivages parallel to each other and follow- ing the direction of the axis of the rough oval, and from them cross tunnels are put out at intervals of 36 feet, and extended to the limits of the " blue," or, when directed to- wards each other, till they meet. Another set of levels is driven at a depth of 30 feet below the main tunnels, and a third set at a further depth of 30 feet. The block of ground between two main horizons thus becomes divided up into a series of horizontal slices, 30 feet thick, each of which is cut up by a net- work of tunnels 36 feet apart extending to the surrounding rock. When this rock is reached, the tunnels are widened out till two adja- cent working-places meet as shown in the plan (Fig. 390). The next process is to rise, or work upwards, until the "blue" is traversed and the waste fallen rock FIG. 392. Original s A. Enclosing limestone ; B. Eed haematite ; C. Sand and clay ;, D. Glacial drift. EXPLOITATION. 343 above it is met with. This is allowed to run in and form a upon which the workmen stand, in order to blast down the re- maining part of the slice of " blue." As this is taken away the waste rock (reef] follows. Fig. 391 also shows that the workings in an upper slice are always further advanced than those in a lower one. Only the main levels are provided with regular tramways. The blue got in the intermediate levels is thrown FIG. 393. Shaft Shaft Sand &c. Jron On down shoots, and so finds its way to the main level, whence it can be hoisted to the surface. A somewhat similar mode of working is customary in the iron mines of North Lancashire, which have to deal with irregular masses of hematite in the Mountain Limestone (Fig. 392).* Shafts are sunk at a distance from the deposit, which is reached by crosscuts at intervals of 10 fathoms vertically. Levels and cross levels are then driven which bring all parts within easy reach (Fig. 393). Rises, E, R, are put up from the main floor * I am indebted to Mr. J. G. Lawn, A.K.S.M. and De la Beche Medallist, for his notes on the method of working ; from these, and from my own recollections, this description has been written. 344 ORE AND STONE-MINING. or horizon to the next one above, and the deposit is now taken away in slices or " heights," 9 or 10 feet thick. A and B of Fig. 394 represent two adjacent rises. The men starting from -4, push out the drift z, and those from E the drift /, until they meet, for the sake of ventilation. This air-road il has to be kept open while work is proceeding in the slice or height in this district. Branch drifts, 2 and //, are carried forward to the boundary of the deposit or of the area the men have to work, and lastly comes the robbing of the ore by a series of drifts, such as Si 4> 5i 6"> or HI, IV) V, in the order of the numbers. The work is thus carried on towards a rise and not from it. After the ore is robbed, the roof crushes in, smashing the timber and forming a safe ceiling for the workings in the FIG. 394. next slice underneath. The surface sinks down in proportion as the ore is removed, so that in some parts of the district immense holes exist, giving evidence of the working out of vast bodies of haematite underneath (Fig. 392). As the overlying drift often contains clay, rain water collects in these holes, and it has to be pumped out lest it should break through and drown the miners. The rises are usually made 6 feet by 4 feet 6 inches within the timbering, which consists of sets of Norway or Swedish timber 6 or 7 inches square, simply halved at the joints and placed directly one above the other. Most of the rises are divided into two compartments by pieces of 3 -inch plank cut to the right length and wedged in; these are made firm by nailing on to the rise-timber "listing pieces," strips of wood 3 inches by J inch, on each side. One of the compartments serves for a ladder- way, for pulling up timber and for an airway ; the other as a receptacle for the ore. The latter is called a "hurry," and is provided at the bottom with an inclined shoot through which the ore can be let into waggons or " bogies " at pleasure. Sometimes EXPLOITATION, 345 the rise is made 9 feet by 4 feet 6 inches, and divided into three compartments viz., two hurries, and a ladderway between them. One hurry then serves for ore, and the other for rubbish. When the men have all but removed one slice or "height," they take out the timber of the rise on one side, in order to start a new drift ; it is about 7 feet wide, and is supported by frames, each made of a cap or head -tree resting upon two legs or " forks." To protect the men while working in the forebreast, small planks (spiles) are driven under one head-tree and over the next, and, if necessary, along the sides behind the props. The men are not allowed to advance more than 4 feet beyond their timber. As soon as the slice above is quite exhausted, they open out at the other side of their rise, and after putting in a strong covering of FIG. 395. timber, they clear all the rise of its lining down to the level at which they are working. In driving below the old timber and rubbish, it is necessary to be careful that the supporting frames are properly put in and kept well forward ; they are often held in place by nailing spiles to them, but this is only necessary before they get the weight from above. It is possible in many cases to save much of the timber used in lining the drifts which are made for robbing the ore, but in all cases the roof comes down very quickly, whether the timber is left in or not. (c) The last method namely, working away the mass by hori- zontal slices, in ascending order, with complete filling up exactly resembles that which is adopted for certain wide veins, such as the lode at the Van mine, Montgomeryshire. However, it may be well to mention, as an example, the great zinc ore stockwork at Diepenlinchen, near Stolberg. The Mountain Limestone is full of cracks and cavities containing blende, which cannot be worked to advantage without breaking down the whole 346 ORE AND STONE-MINING. of the rock. The limestone is ore-bearing over an oval area, 120 metres long from east to west and 50 from north to south (130 yards by 54 yards). This great mass of zinc-bearing rock is subdivided for the pur- pose of working into a series of storeys or floors, each 16 metres. (52^ feet) thick vertically, and a main level is driven along the major axis of the oval at the bottom of each storey, as shown in Fig. 396. Cross-cuts, 14 metres apart, are driven out north and south from each main level, and are connected with similar cross- cuts below by winzes. The block of ground between two main levels is then taken away in slices, 2 metres thick, in ascending order. However, with the view of saving the expense of putting FIG. 396. 2OO METRES LLVCL ^ 2/6 METRES LEVEL ^%%^^ in timber to support the deads, which would be necessary if the main roads had to be kept up in a part of the mine stowed with rubbish, the first two slices that is to say, the one in which the levels are driven and the one immediately above it are left intact at the outset. Work is started from a winze at a point 2 metres above the top of the level, and the whole area of the deposit cleared out for a height of 2 metres ; the excavation is then filled up with deads. The deads are obtained by picking the rock broken down in the stopes, or from any drivings or sinkings in barren ground, and also by sending down supplies from the surface. Shoots are reserved in the stowing for throwing down the ore, which is drawn off at the bottom when required. Fig. 396 shows the stoping going on between the 200 and the 2i6-metres levels. When the stopes come up to the sole of the 2oo-metres level, the ore surrounding the network of levels and that of the overlying slice can be attacked. By this time this double slice, 4 metres thick, is somewhat crushed and broken. EXPLOITATION. 347 It would be dangerous to have the wide working-places, which can be excavated without fear in virgin ground; therefore, just as happened in the Van Mine, the two last slices are got by a series of small drivings, in which the miners resort to a process of spilling. By applying this process the remainder of the ore is obtained in safety, and the final result is that the great mass of zinc-bearing rock is replaced by barren material with the expenditure of very little money for timber. ( 348 ) CHAPTER VII. HAULAGE OE TKANSPOBT. Underground transport Shoots Pipes Carriage by persons Sledges Wheeled vehicles Mechanical haulage Boats Transport above ground by similar means and by aerial ropeways. AFTER having been excavated, the mineral must be conveyed to the surface. In very many cases the journey is performed in two stages first, along a more or less horizontal road to the shaft- bottom ; and thence by a vertical or inclined road which leads up to the daylight. The first process is often spoken of as haulage and the second as winding : but there is no distinct line of de- marcation between the two, for certain sloping passages, called shafts by the ore-miner, would be denied that name by the collier. It will be convenient to say a few words here about transport above ground, although, strictly speaking, this subject should not be dealt with until after the chapter on winding. The transit of the mineral from the working-place to the shaft may be carried on in part or wholly by one of the following processes : I. Fall down a shoot (mill or pass}. II. Flow along pipes or troughs (launders). III. Carriage by persons. IV. Conveyance by sledges. V. ,, ,, vehicles with wheels. VI. boats. I. TALL DOWN A SHOOT. This first method is one to which reference has already been made more than once in describing the modes of working. When a deposit is inclined at a steep angle, or when a mass has to be dealt with, the mineral will readily drop from the working-place to the level below. The passages provided for this purpose are called " shoots," " passes," or " mills." If the excavation is filled up with rubbish, a space like a small shaft is reserved in the stowing by building a wall with some of the large stones. This kind of "pass" may be described as a large chimney, about 3 feet in diameter, lined with coarse rubble masonry. To prevent choking, it is advisable to make the pass slightly conical, the large end at the bottom. It may HAULAGE OR TRANSPORT. 349 be constructed in the middle of the rubbish, or if there is a convenient smooth face on the footwall of a lode, a semicircular wall built against it encloses a space very suitable for the purpose required. The pass may serve also as a climbing way for the men, especially if it is provided with a chain ; but it should be used in this manner only for short distances. It is far better to keep the ore-pass distinct from the climbing way, in case any stones should lodge on the sides and fall during the ascent or descent of the men. A pass is often lined with timber instead of stone, and some- times it is merely an intermediate shaft or winze set apart as a shoot. At the Van Mine the passes, whether they are small shafts sunk on purpose, or passages reserved in the rubbish used as filling, are 6 feet by 3 feet, within the timber ; each pass is divided into two unequal compartments by a partition made of ij-inch plank nailed to cross-timbers called dividings, and the larger one is closely lined with similar planks. This forms the " shoot " proper. The small compart- ment is provided with ladders and serves as a climbing way, and is also useful in case the larger one should become choked ; a board can be taken out from the side at any time, and large stones obstructing the passage can be dislodged with safety. Vertical passes lined with timber sometimes have pieces of steel rail put across at intervals, to break the fall of the " stuff." The pass is provided at the bottom with a mouth closed by a door of some kind, and when this is opened, the mineral falls out into the waggon which has been brought underneath, II. FLOW ALONG PIPES. This method of transport becomes available when one has to deal with liquid or gaseous minerals, or with solutions, but these cases occur more frequently above than below ground. However, brine is led along wooden launders and pipes in some salt mines. Natural inflammable gas in a few exceptional cases is piped off from a blower and burnt for illuminating purposes ; this is done at a salt mine at Bex in Switzerland. III. CARRIAGE BY PERSONS. The simplest and no doubt the oldest method of transport along underground roads is carriage by persons. It still survives in some places for short distances. In the Forest of Dean, boys carry iron ore on the back in oval trays, called "billies," from the actual working-place to the nearest barrow-road or waggon-road. The tray is made of wood, with a rim of sheet iron, and is about 6 inches deep, 22 inches in length in the direction of the long axis, and 12 to 15 in the direction of the short one. The load carried in a " billy " varies, according to the nature of the ore and the strength of the lad, from 90 to 112 Ibs. or even more. The lad goes on all-fours, using his hands to support himself as he makes his way through 350 OKE AND STONE-MINING. low and tortuous passages. This method of transport is rendered necessary by the nature of the excavations, which are very irreg- ular ; but the distances along which the ore is carried are small, generally from 30 or 40 to 50 yards, and rarely as much as 100 yards. The German miner commonly makes use of a tray into which he scrapes his mineral or rubbish with a tool like a hoe, and he then carries his load to the nearest " pass " or to a waggon-road in the immediate neighbourhood. In the little slate mines near Cochem on the Moselle, men and lads carry up the blocks of slate upon their backs, walking upon steps cut in the rock. They come up with their hands upon the ground, bent almost double under the weight of the block, which rests upon a thick pad. Again, blocks of slate are still carried on the back from the working-place to the waggon-roads in the slate mines of the Ardennes. In the Sicilian sulphur mines the same method is common, and it is also found in some parts of Spain and China, where baskets are used, whilst bags are employed in Mexico and Japan. Indeed, in these cases, as at Cochem, the mineral is not only carried along comparatively level roads but is also brought to the surface. IV. CONVEYANCE BY SLEDGES. Sledges, or sleds, enable greater loads to be transported ; but they are not available unless the conveyance takes place along roads sloping downwards. They are little employed underground. V. CONVEYANCE BY VEHICLES WITH WHEELS. We now come to the methods by which minerals and rubbish are usually transported both above and below ground viz., by some kind of wheeled vehicle. Here we may at once make two classes. A. Vehicles running upon the ground or on boards ; B. vehicles running upon rails. A. Vehicles Running on the Ground or on Boards. Wheelbarrow : The simplest wheeled carriage is the barrow. It consists of a body with two handles and one wheel. The barrow used in Cornwall at the present day is not unlike that figured more than three centuries ago by Agricola. It has no legs, but in many ore-mines a barrow with legs is em- ployed, somewhat resembling a navvy's barrow. Mine-barrows are usually made of wood, and have either a wooden or a steel wheel. The Cornish barrow is tipped sideways, whilst the barrow with legs is tipped either sideways or over the end. This latter form of barrow requires a higher and better level ; it is a more advantageous appliance, as it throws a greater part of the load on to the wheel and relieves the miner's arms to a certain extent. The barrow often runs along the natural floor of the working- place or level, but less labour is required if it is provided with a road made of planks or strips of iron. Carts and Waggons. In the low passages, only 18 inches to HAULAGE OR TRANSPORT. 351 20 inches high (Fahrten), leading from the working face of the copper-shale mines at Mansfeld to the main roads, tiny waggons on four wheels are employed. Carts drawn by horses are used in some large underground quarries. A mine waggon largely employed in Germany at one time, and still seen occasionally, is the so-called Hungarian " Hund." It has a rectangular body resting upon four wheels, two small in front and two large near the middle ; the workman presses down a little handle at the back to make the load rest upon the two big wheels only, and pushes the waggon along a board at the bottom of the level. The Germans have also used four-wheeled waggons running upon two boards ; and they were sometimes provided with a projecting pin underneath which kept them upon the track. B. Vehicles Running upon Rails. The points to be con- siderd are (a) the road ; (b) the waggons ; (c) the power employed for traction. (a) Railways. Cast-iron tram-plates were introduced in the last century, and were succeeded by wrought-iron rails ; these in their turn are being superseded by rails made of steel. Various forms of rails are in use. The simplest is a bar of iron set on its edge, or a strip of flat iron nailed to longitudinal sleepers. Rails of the former kind are made, for instance, of bars J by^ 2 \ inches, or f by 2j inches, fixed by wooden wedges in slits cut in the sleepers. This rail has the disadvantage of wearing a groove in the flange of the wheel, but it is easily and quickly laid and readily bent into curves. Rails made of bars of round iron are used in some Welsh slate quarries. The bridge-rail was in great favour at one time, either laid upon longitudinal or cross sleepers ; but nowadays flanged T-headed rails made of steel are preferred. Care should be taken to have strong and well-laid lines, especially where there is likely to be much traffic. In this, as in many other depart- ments of mining, it is very bad economy to cut down the ori- FlG - 397- FIG. 398. ginal expenses too much. What is saved on the first cost will be spent over and over again in repairs, to say nothing of the loss of time and money caused by delays in the traffic. The gauge varies from 14 inches to 3 feet or more ; 20 inches to 22 inches is a common gauge in vein mining. The weight of the rails for such roads is from 10 to 30 Ibs. per yard. Fig 8 - 397 an d 398 show the sections adopted respectively by Legrand of Mons and Howard of Bedford, for rails weighing 352 ORE AND STONE-MINING. 1 8 Ibs. per yard. The rails may be simply spiked to wooden sleepers, or they may be laid in chairs. In important roads fish- plates should be used. There is a tendency at the present day to adopt steel sleepers, which are supplied by the makers to suit roads of various gauges. They have proved to be very convenient and efficient, and in this country they are cheaper in the end than wood. Among their advantages are exact uniformity of gauge, easy and rapid FIG. 399. laying, fewer repairs. They are usually made of rolled steel, and the rails are fixed either by clips, or by clips and keys. One form of road supplied by Legrand of Mons (Fig. 399), has the clips of one sleeper on the outside of the rail and those of the next on the inside of the rail. The clips are firmly riveted to the sleepers. In constructing the road, the sleepers B are laid at suitable distances apart, exactly parallel to one another ; the alternate sleepers A are then put in obliquely, as shown by the dotted lines, and knocked into position with a hammer ; the rails are joined by fish-plates. Howard's sleeper (Fig. 400) is made from a plate of steel rolled with a corrugation ; the lips which constitute the chairs for the rails are formed by pressing FIG. 400. down this corrugation with- out cutting away any of the metal . The jointing sleepers have a double corrugation, and the rails are fastened with a simple key which is serrated on one side. Some of Howard's sleepers for under- ground work can be used without any keys. Bagnall's sleeper is also distinguished by longitudinal corru- gations which stiffen it and prevent its buckling. The Widnes Chair and Sleeper Company prefer a section like that of a V-shaped trough ; they claim that the penetration of this sleeper into the ground ensures great stability. Where a mine has a stock of old rails or old iron, it is often more economical to convert it into sleepers than to sell it as scrap. HAULAGE OR TRANSPORT. 353 There are several methods in use. White * of Widnes utilises old bridge rails (Figs. 401 and 401 a) by inserting two clips (Figs. 402 and 40 2 a) into a piece of rail cut to the required length ; the clip is held in place by a pin which passes into a hole punched FIG. 401. FIG. 40 1 a. FIG. 402. FIG. 4020. in the sleeper. At the Llechwedd slate mine in North Wales, two other methods have been devised by Mr. 0. Warren Roberts (Figs. 403 and 404) for utilising old channel iron and flat iron. Stamped iron clips are riveted on so as to take the outer side of FIG. 403. _^=>7=aA&<&, mis* FIG. 404. the flange of the rail, and similar clips are bolted on against the inner flange. In order to allow for any small irregularity in the width of the flange, the hole for the bolt is made oval, and this enables the clip to be adjusted to the flange exactly. * Engineering, vol. lv., 1893, P- H 6 - z 354 ORE AND STONE-MINING. Points and crossings must be provided. The points may be like those of an ordinary railway, with tongues moved by levers. Another plan is to leave gaps between the rails where the lines diverge or cross,, and interpose plates of cast-iron upon which the flanges of the wheels run without any difficulty. This arrange- ment is suitable for cases where a man is pushing the waggon, for he can turn it on to whichever road he chooses, but it will not answer in the case of haulage by engine power. Each plate has a rim or edge on the outer side, which prevents the wheels from running off. Flat plates are commonly used where there is a very sharp bend in the road, such as when a cross-cut joins a level almost, if not quite, at right angles. The plate is made of cast-iron with ridges forming prolongations of the rails as shown in Fig. 405. FIG. 405. FIG. 406. The waggon leaves the metals and the flanges of the wheels run upon the plate ; as its surface is perfectly smooth, the waggon is easily turned into the required direction, and the curved ridges guide the wheels into the track which they have to follow. In places where there is a difficulty in procuring a casting, the plate may be made of sheet iron, and the necessary guiding ridges are formed by the overlapping ends of the rails. The flange of the rail is cut away for a length of 8 or 9 inches and also part of the web ; the projecting piece of the head is then hammered out so that the top of the rail slopes down sufficiently to touch the plate. Another device for guiding a waggon from a plate on to a line of rails is a curved piece of round iron, i inch in diameter (Fig. 406). The two ends are bent at right angles and sharpened so that they can be driven into a sleeper at the edge of the flat plate. The ridge formed by this piece of iron, guides the inner side of tho flange of the wheel. HAULAGE OR TRANSPORT. 355 The inclination of the road is not without importance, because there are usually waggons travelling in both directions, full ones going towards the shaft or other outlet from the mine, and empty ones returning to the working-places. The inclination down- wards towards the shaft assists the work, but if it is too great the return journey causes a useless expenditure of labour. The rule in many ore-mines is to drive the levels as flat as possible, with only just slope enough to make the water flow away; the tendency of the workmen is always to rise too much, and one sometimes meets with old levels where, through careless- ness or inattention of the agent, the loss of level is very consider- able. An inclination of - to J inch per yard, or i in 216 to i in 288 is common. The condition of the road between the metals deserves more attention than is usually bestowed upon it. There is unneces- sary labour on the part of the man or the horse employed in traction, if the road upon which he walks presents obstacles through great unevenness. I have seen roads which were simply a succession of deep puddles between the sleepers, a striking con- trast to the well-kept main levels at the Mansfeld copper mines. These levels are carefully paved with artificial stones, made from slag afc the Company's smelting works. The paving-stones are about 5 inches square at the top and 6 inches deep ; they are also sold to the public, at prices varying from fc. to id. each. (b) Waggons. Mine -waggons are made of wood, iron or steel. They consist of a body or box resting on a frame carried by four wheels. They vary greatly in shape and size according to the nature of the excavation and the kind of material transported. FIG. 407. Figure 407 represents the plain but strong waggon of the Van Mine, Montgomeryshire, with a rectangular body of sheet iron, an oak frame and cast steel wheels. The top is strength- ened by a band of flat iron. The wheels are n finches in diameter and are just low enough to go under the body ; they are therefore protected from blows, to which they would otherwise be liable from stones dropping during the process of filling. The waggon is emptied by being run in to a " tippler," that is to say, a cage turning on pivots, which enables it to be completely overturned. At the Mansfeld copper mines the general shape is similar. Formerly waggons of various shapes and sizes were in use, but now one uniform model has been adopted. The body is made of sheet-iron l inch thick, and the upper edge is strengthened by an iron band |~| inch thick and 2j inches wide, whilst the corners are stiffened with angle iron. The body is 3 feet 5^ inches long, 2 feet 2 inches broad, and i foot lof inches deep inside. The 356 ORE AND STONE-MINING. capacity of the waggon is 13^ cubic feet, and it carries 10 cwt. The body rests upon two pieces of iron placed lengthwise, across which are fixed the two axles. The wheels are of chilled cast-iron with special grease-boxes. The gauge of the road is 19 J inches, and the wheels are nj inches in diameter, so that they can be placed under the waggon. The total height of the waggon is 3 feet i inch, and it weighs 716 Ibs. When made of sheet-iron or steel the sides can be bent, as shown in Figs. 408 and 409, and larger wheels can be employed without unduly raising the body. In order to suit the small levels of some vein mines, the waggons are made long and narrow. In the Isle of Man, one meets with waggons 6 feet long and only 19 to 21 inches wide at the top ; the depth being 2 feet. The sides slope inwards so that the bottom is only 13 inches wide by 4 feet 9 inches, or 5 feet long. The waggons are made of sheet steel about y\ inch thick, or of i| inch FIG. 408. FIG. 409. plank. The discharge is by a door at one end, kept in its place by a bolt. When the waggon has to be emptied, the miner knocks up this bolt and lifts the waggon up behind till it slopes enough for the " stuff " to run out. The top of the steel waggons is stiffened by a band of J-inch iron 2 inches wide firmly riveted on, and pieces of angle- iron, where the plates come together, give a further amount of strength. Wooden waggons have the bottom lined with sheet-iron ^ inch thick. The diameter and nature of the wheels vary. At one mine in the Isle of Man the wheels are loj inches in diameter, and run loose upon the axles, which are bolted to the frame under the body ; they are 1 5 inches apart, from centre to centre. The wheels are brought close together with a view of making the waggons pass round curves without trouble. In order to render the tipping easy, the centre of the front axle is placed 6 inches in front of the middle of the waggon ; the miner, therefore, has the greater part of his load balanced when he pivots his waggon on the axle of the front wheels in the act of discharging it. At a neighbouring mine under very similar conditions cast- iron brackets are bolted under the body to receive the two axles to which the wheels are firmly keyed, but the hinder axle is not HAULAGE OR TRANSPORT. 357 in any way attached to the bracket ; when it is desired to empty the waggon, the hind end is lifted up and both sets of wheels remain on the ground. The hind axle is made fast to the front one by a couple of straps, for otherwise the hind wheels might run away when the waggon was emptied. A disadvantage of this kind of waggon is that it may require two men to replace it on the road if it comes off; one may be wanted to see that the wheels will drop properly on to the rails, while the other is managing the body. In both these waggons the wheels project outside the body, instead of being underneath it out of harm's way, but they are protected to a certain extent by the overhanging sides, and they can be further screened by riveting on little shields of sheet-iron. The lateral position of the wheels reduces the height of the waggon required for any given capacity, a decided advantage when it has to be filled with the shovel ; but in ordinary vein mining the ore ought to be drawn down from shoots, and therefore the benefit of easier shovelling comes into play only when loading rubbish or ore in such places as the " ends." In some mines the mineral is loaded in the level into an iron bucket (kibble) standing upon a trolley, which is merely a small platform upon four wheels. This trolley is pushed (trammed) to the shaft ; the full kibble is hooked on to the winding rope and drawn up, whilst an empty kibble is placed upon the trolley and trammed along the level to the spot where it is again loaded from a shoot or by the shovel. Wheels for mine-waggons generally have a single flange, and are made of ordinary cast-iron, chilled cast-iron, cast-steel, or forged steel. Steel and chilled cast-iron are the materials most in favour; both have advantages. The wheels made of chilled cast-iron are rather heavier than those of steel, and are brittle ; the flange, for instance, will break under a blow which will not damage a steel wheel; but a pair of chilled wheels will often outwear several pairs of steel wheels if they happen to escape the hard raps to which mine-waggons are liable. Under Eyre's patent, wheels are made by forging a steel bloom under a steam-hammer into dies; they are reported to give great satisfaction and to be capable of standing much knock- ing about. Wheels with two flanges are used in the Festiniog slate mines, and are considered best fitted for the work on account of the sharp turns in the roads. Much difference of opinion and practice exists concerning the attachment of the wheels. Four systems are in vogue : axles fixed and wheels running loose on them; wheels fixed to the axles, which run loose in pedestals attached to the frame or to the body of the waggon; thirdly, a combination of these two systems viz., wheels running loose on the axles and axles run- 358 ORE AND STONE-MINING. ning loose in the pedestals ; fourthly, one wheel fast on the axle, and the other loose. At a first glance it might be thought that it would undoubtedly be best to follow the lead of the great railways, and have the wheels fixed to the axles, because experience has shown that this system answers so well above ground. Nevertheless, it must be remem- bered that the conditions of underground roads are often very different, the curves are frequently of very small radius, and there is usually more difficulty in keeping the roads in perfect order. By allowing the wheels and axles both to be loose, the Festiniog miner, for instance, who may be tramming out a block of slate 18 feet long, can slew his load on the truck and so pass round sharp curves which would oppose an insur- mountable obstacle if the wheels or axles were fixed. Loose wheels with loose axles look clumsy and unnatural, aiid in spite of all that may be said in their defence, it is probable that it would in many cases pay the mine owner to improve the condition of his roads and so render a more stable form of waggon available. Lubrication of the bearing parts is too often performed in a perfunctory and wasteful manner, especially in mines where the waggon never comes to the surface except for repairs. A little grease or oil applied at the beginning and in the middle of the shift is all that is considered necessary. Such a procedure must be defective ; either there is too much of the lubricant at first, or there is too little after the waggon has been in use for a time. An automatic lubricating apparatus is sometimes fixed in the road and every waggon is greased in going over it. The appa- ratus consists of a wheel placed in a trough containing the grease, and as each axle touches this wheel it receives a little lubricant. A defect of these lubricators is that when a waggon is going at great speed, as is the case with some systems of underground haulage, the grease is flung about and wasted ; besides, where a bearing can be greased in this manner it is necessarily exposed to the dust or mud of the mine, which must cause wear and friction. It is better to provide constant lubrication and to protect the bearing parts as much as possible from dirt. One method by which this object is attained is shown in Figs. 410 and 411, which represent a waggon used at some collieries at Saint Etienne, in France, and embodying the results of long experience. The wheel, which is made of steel, is placed under the waggon, and the journal is encased in a chamber kept full of oil. The chamber has two holes which serve for passing in the linch-pin and putting in the oil. They are afterwards closed with plugs. Other points which may be noticed about this waggon are its shape and mode of construction. The body is oval and made up of wooden staves like a barrel. HAULAGE OK, TRANSPORT. 359 As an example of a waggon constructed entirely of steel, I take a "tram" designed for the Llanbradach colliery by Mr. Galloway (Figs. 412 and 413). The body has the form FIG. 410. FIG. 411. SCALE OF FEET SCALE OF DECIMETRES of a very blunt oval; it is made of sheet steel -^ inch thick, stiffened round the top by channel steel. The wheels are fixed to the axles, which are kept constantly lubricated by Stauffer's lubricators placed immediately above them in the hollow axle- 360 ORE AND STONE-MINING. boxes. The empty waggon weighs 1 2 cwt. and will carry 2 tons of coal, when the load is built up higher than the sides. When dealing with a tender mineral like coal, which decreases in value if knocked about, it is important to reduce the effects of bumping to a minimum; and with this object in view the waggon rests upon springs and the bufiers are elastic. The conse- quence is that the waggon runs very smoothly, and is likely to require less expenditure for repairs than one constructed in the ordinary fashion without these appliances. There will likewise be a diminution in the quantity of dust dropped on the road, a matter of moment in collieries. HAULAGE OR TRANSPORT. 361 The Hardy Patent Pick Company makes self-oiling pedestals for waggons with the wheels fast upon the axles (Fig. 414) ; a is the upper part of the pedestal, and b the lower part, containing felt or wool saturated with oil. This presses lightly against the axle and keeps it oiled for several weeks, without re- FIG. 414. quiring any attention. It will be seen from these remarks that a number of points have to be considered in design- ing a mine-waggon. They may be summed up as follows : Smallest weight compatible with strength. Small height, if the waggon is to be filled with the shovel. Protection of the wheels from injury. Constant lubrication. Adoption of a uniform type of waggon for the mine. Material which causes the least expenditure for repairs. Easy handling and easy replacement upon the rails. In a few exceptional cases the mineral raised in the mine does not require a box or chest. This happens with slate, for the blocks are brought up on trucks to which they are made fast by chains. (c) Power used for Underground Transport. The sources of power are as follows : 1. Men, boys, women, and girls. 2. Horses, ponies, donkeys, and mules. 3. Gravity acting upon the material moved. 4. Machines driven by steam, water, compressed air, and elec- tricity. 1 . Human Labour. Female labour underground is prohibited by law in the United Kingdom, and no doubt it is destined to disappear in other countries. We need only deal with men and boys. Where the passages are high enough to take waggons standing 3 feet above the ground, men are usually employed for drawing or pushing them. It is convenient to have waggons small enough to be handled by one man, and also to be put back on to the road by one man, if by chance they leave the rails. The large waggons and loads at Festiniog require two men, for the load of rubbish commonly amounts to i f or 2 tons. The waggon and load together may weigh as much as 2j tons. The men who push out these waggons usually do the loading also, shovelling in the small pieces and lifting on the large ones. 2. Animal Labour. Traction by horses or ponies is cheaper than using human power, but it is not always practicable to 362 ORE AND STONE-MINING. employ it. There are many ore mines in which it would be impossible to lower a horse down the shaft ; and even where the descent could take place, there would often be the further draw- back, that as the work proceeds with comparative slowness, owing to the hardness of the rock, there would not be " stuff" enough broken in a given time to keep a horse constantly employed at any particular level, whilst shifting it from one level to another would entail much difficulty. The load drawn by a horse at the Festiniog slate mines is as much as eight waggons, a gross weight of 20 tons, or net weight of 1 6 tons, along a road with an inclination of J inch per yard. Where a mine is entered by a shaft, the horses are stabled below ground, and much care is taken in many instances to provide proper accommodation for them. The stables are paved with bricks or concrete, sloping towards a gutter ; each horse has its stall, or a loose board is hung between every horse and its neighbour. Clean water is at hand for drinking. At a French colliery I found the daily allowance of food to be as follows : Oats ' .... 10 kil. (22 Ibs.) Chopped hay from lentil and rye grass . 5 kil. (n Ibs.) Bran 2 kil. (4-4 Ibs.) In addition each horse had 5 kil. (n Ibs.) of straw per day as litter. The horses do not always belong to the mining company ; at Festiniog, where the workings can be entered by adits, horses are hired from persons in the district, who supply a horse and man for eight shillings per day, and pay all the cost of food and stabling. 3. Gravity. In working stratified deposits, it is often necessary or convenient to lower a waggon down an inclined plane made along the dip. At Mansfeld, for instance, instead of maintaining a number of levels at short intervals apart, it is more economical to reserve only a few for traffic, and abandon certain portions, as already pointed out in Chapter YI. The waggons then have to be lowered from the working level to one which is kept up as a main roadway. Inclines for this purpose have two lines of rails, one for the descending and the other for the ascending waggon. A wire rope or a chain passes round a pulley or drum at the top, the axis of which may be horizontal or at right angles to the plane of the deposit. Each end of the rope can be hooked on to a waggon, and the weight of the full waggon going down suffices to raise the empty one. The speed is regulated by a brake on the pulley or drum. Another method of working inclines is to make the full waggon draw up a weight, running on a special line of rails, which is heavy enough to bring up the empty when it de- HAULAGE OR TRANSPORT. 363 scends. In order to economise space, the line of rails for the weight may be made narrower than the one used for the waggon, and may be laid between the two main rails. If the incline is steep, a carriage with a horizontal platform is provided. The mine-waggon is pushed on to this travelling platform and ascends or descends in its ordinary position. 4. Machinery. Underground haulage may be carried on either by travelling engines or stationary engines. Locomotives fired with coal have the great disadvantage of polluting the air by the products of combustion, consequently they are not available unless the ventilation is very good, nor unless there is absence of inflammable gases and freedom from the risk of setting fire to the timbering or to the mineral itself. A small locomotive of two horse-power nominal is used on an i8 inch track in the long adit of the Great Laxey lead and zinc mine in the Isle of Man ; and at Rio Tin to in Spain a much larger engine plies in the adit on a line with a gauge of 3 feet 6 inches. Locomotives driven by compressed air, carried in a reservoir upon a tender, improve the ventilation instead of injuring it, and are not a possible source of danger from fire ; but, except in special cases, they cannot be worked so cheaply as engines fired with coal. However, the advantages they afford have led to their adoption in some mines ; Lishman and Young's air locomotive is employed in several collieries in the North of England. To overcome the inconveniences and dangers of engines of the ordinary type, fireless locomotives have been proposed and con- structed. That of Lamm and Franck has a cylindrical reservoir, instead of the boiler, filled three-quarters full of water. The reservoir is heated by steam from the surface, until it is capable of giving off vapour with a pressure of 235 to 294 Ibs. per square inch (16 to 20 atmospheres). As the temperature and conse- quently the pressure of the steam supplied by the reservoir are constantly falling, a regulator is interposed between the reservoir and the steam cylinder, which enables both the pres- sure of the steam and the amount of expansion to be changed at will. This arrangement renders extra power available if a steep gradient has to be mounted. Rolland's fireless locomotive is similar.* His reservoir has a capacity of 19^ cubic feet (0.550 cb.m.), and contains water at a temperature of 205 C., or with a pressure of 235 Ibs. per square inch (16 atmospheres). M. Rolland states that his locomotive, charged in this fashion, will run for 2 to 2 J miles (3 to 4 kms.). When going at a speed of 2 m. (6 feet 6f inches) per second, the locomotive exerts 6 h.p. ; the speed of a horse may be taken as 0.9 to i m. (3 to 3^ feet). The locomotive ready for work weighs three tons. * B. und h. Zeitung, 1890, p. 375. 364 ORE AND STONE-MINING. As pointed out by Holland, the fireless locomotives have the following advantages in addition to being more economical : No danger of fire and no inconvenience from smoke. Improvement in the atmosphere of the mine, owing to absence of the horses and their droppings. The Honiginann * locomotive depends upon the fact that a solution of caustic soda, of a certain strength, will absorb steam and give out heat. This heat is utilised to convert hot water into steam, which works an engine and then passes into the soda solution, causing a further development of heat. The process of steam-making goes on thus of itself, until the soda solution reaches a certain stage of dilution. The locomotive is re- stored to a state of activity by bringing back the solution to the proper degree of saturation. This is done by passing steam from a stationary boiler through coils of tubes in the reservoir containing the soda, a process occupying little time. Experiments have been made, and will be continued, with the Honigmann soda locomotive, and also with Krauss' tunnel locomotive, at the Mansfeld copper mines. Stationary Engines. An enormous amount of underground traffic is carried on by some system in which the power for haulage is derived from an engine placed above or below ground ; but the practice is far more developed in collieries than in vein mines, where the quantities of mineral to be handled are as a rule very much smaller. With reference to the application of the power itself, the various systems of underground haulage might be classified thus : Steam or water power at the surface,] I. Ropes. transmitted to machinery under- I 2. Compressed air. ground by ' . . . . . j 3. Electricity. Water power below ground driving the machinery Steam power below ground driving th^ (2. Boilers below ground; Petroleum engine below ground driving the machinery. The subject of the transmission of power has already been sufficiently discussed in Chapter IV., and need not be dealt with here, save that it is necessary to point out that the conditions of the problem are not the same when power has to be applied to haulage, as when it is required in a constantly changing working face. As the mineral has to be brought to the shaft, the engine and its boiler, if necessary, can be placed in the immediate vicinity of the pit-bottom and the exhaust steam can be got rid of without interfering with the comfort of the men or injuring the condition of the workings. Proper rooms can be made for the * Official Catalogue of Royal Mining^, Engineering, and Industrial Exhi- bition, Nervcastle-on-Tyne, 1887, p. xxxvi. HAULAGE OR TRANSPORT. 365 engine and the boiler, coal can be brought down and the ashes removed without difficulty. Everything can be arranged in a permanent and substantial fashion, so that steam power may be generated for haulage purposes below ground when it would not be practicable to employ it for breaking down the mineral. Again, when power has merely to be transmitted down a vertical shaft in order to work a drum near the bottom, endless ropes may be used, although they would be quite out of place if they had to be carried along narrow, low, and crooked levels. For subsidiary haulage purposes that is to say, for bringing trams from the immediate vicinity of the workings to a main line Galloway employs a small engine with two drums placed upon a waggon, which is small enough to go into the cage and which will run upon its own wheels along the underground railways. It can therefore be moved about as required, and when coupled up to the compressed air main can be set to work immediately to haul out trams, instead of employing horses for this work. We will suppose that the question of the most suitable driving machinery has been settled according to the circumstances of the case, and that the miner has~to consider how he will apply it to the transport of mineral. Five systems are in use : i. Single rope- ii. Main and tail ropes, iii. Endless rope, iv. Endless chain. v. Electric railways. i. Single Rope. This system is available with a road sufficiently inclined for the empty waggon to run down of itself, after the load has been brought up, and draw back the rope with it. One road will suffice, and the machinery required will be some kind of drum, around which the rope is coiled, and an engine for driving it. The drum is usually placed horizontally ; it is provided with a brake, and there is a disengaging clutch by which it can be thrown in or out of gear with the engine. A pair of horizontal engines, which have their cranks upon the drum-shaft, or which drive it by means of a pinion and spur wheel, form the common method of applying the power. The wire rope has one end fixed to the drum and the other is provided with a hook of some kind ; this is attached to a link of the coupling chain of the truck and the load is drawn up. On reaching the top of the incline or engine-plane, the waggon is unhooked, and either pushed or allowed to travel of itself, under the action of gravity, to the pit-bottom, where the onsetter runs it on to the cage in which it is raised to the surface. An empty waggon is then hooked on and run on to the incline, and the engine-man, with his brake under proper control, dis- 366 ORE AND STONE-MINING. engages the drum by means of the clutch and lowers the load without using any steam. When worked in this way, the incline requires only one line of rails. A series of rollers have to be put in for the purpose of keeping the rope from trailing on the ground and of thus preventing much unnecessary wear and friction. These rollers are small wooden, cast-iron, or steel cylinders, often with a low flange at each end to keep the rope in its place ; they are laid horizontally and are capable of revolving around a horizontal spindle. Care is, or ought to be, taken to see that they are ver}' correctly set and that they are well lubricated, so that they may revolve freely when the rope is drawn over them ; otherwise the strands are sure to be worn down rapidly from rubbing against them. The incline may also be worked with two lines of rails, after the fashion of the self-acting inclines ; and this system has the advantage of being more economical, for the deadweight of the loaded waggon coming up is balanced by the weight of the empty one going down. It is not even necessary to have two lines all the way ; provided there is a sufficient length of double line where FIG. 415. the waggons meet, the incline can be worked with a length of single line at the top and a similar length of single line at the bottom. To prevent a waggon from running down in case a coupling link or the rope should break, a safety appliance, called a backstay, may be attached to it. It is a sort of fork which hangs behind the waggon, and just touches the ground ; - if the rope breaks, it digs itself into the road and prevents the waggon from going down. Of course it can only be used while the waggons are being raised, bub it is during the journey of the loaded waggon that the rope is most likely to break, ii. Main and Tail Ropes. On the engine planes just described, the empty waggon goes back under the action of gravity ; but with very slightly inclined, flat, or undulating roads this is impossible. One method of getting over this difficulty is to add a rope, called the " tail rope," which will draw the empties back ; the rope which draws the full waggons is known as the " main rope." The system is perhaps best explained by a diagram (Fig. 415) : a is a drum upon which is coiled the strong main rope ; b is another drum upon which is coiled the tail rope, passing round the pulley c. The waggons are coupled together and form the train or " set," which may in reality consist of as many as 100 waggons. Suitable clutches enable either drum to be worked at pleasure by the HAULAGE OR TRANSPORT. 367 engine, while the other is allowed to run loose upon the shaft. Each drum has a brake, by means of which the rope can be prevented from becoming too slack while uncoiling itself. When the drum a is made to revolve by the engine, the main rope is wound up, the drum b running loose, and the train or "set" is drawn from c to a. Here the waggons are uncoupled and pushed to the shaft, or, better, the station at a is arranged so that it is sufficiently high for the waggons to run down of them- selves under the action of gravity. A new train of empties is then made up, the tail and main ropes are attached to it and the drum b is set in motion so as to wind up the tail rope and draw the waggons into the terminus at c. It will be evident from a glance at the figure that the tail rope must be twice as long as the main rope. As the tail rope has simply a train of empties to haul out, it may be made smaller than the main rope, except in cases where the road has a downward inclination towards the shaft sufficient to cause the loaded train to run down of itself and draw the tail rope after it. A single line suffices for this system of haulage ; the main rope lies in the middle of the road, resting upon a series of horizontal rollers similar to those used upon ordinary inclined planes. Where there are curves, however, the rope must be guided by small vertical rollers. The tail rope is brought along the side of the road, or if more convenient, along a separate road, also resting upon rollers or pulleys and suitably guided at the curves. The system is applicable to roads of varying gradients, and arrangements can easily be made for working branches, by having a special piece of tail rope in each branch going round a pulley at the end of it. When mineral has to be drawn away from the branch, the piece of tail rope on the main road beyond the junction is disconnected, and the piece belonging to the branch is attached. Traffic then goes on as before, save that the train is made up in the branch. Another plan is to disconnect the tail rope at the end of the train, and couple one end of the branch rope to the train and the other to the free end of the ordinary tail rope. During the running of a train the tail rope then goes round the pulley at the end of the main road, passes round another at the junction of the two roads, proceeds along the branch round its terminal pulley, and back to a pulley which again puts it into the direction of the main road. The trains are in a large number of cases made to run at a great speed, even as much as 10 or 15 miles or more an hour, and if by some mischance an accident does happen from one of the waggons getting off the road, a good deal of damage may be done to the train and roadway. iii. Endless Rope. A favourite method of underground haulage is by an endless rope passing round a pulley at each terminus, and generally travelling continuously in the same 368 ORE AND STONE-MINING. direction. The rope is kept in a state of tension by passing it round a tightening sheave, which in some instances is one of the terminal pulleys. The tightening sheave or pulley is carried by a frame running upon wheels, and is constantly drawn back by a heavy weight. The necessary grip of the rope is obtained by coiling it several times round the driving drum, or around a driving pulley with grooves and a second grooved pulley close by ; the rope wraps itself, for instance, upon three half circumferences of one pulley and tw T o of the other. The speed of an endless rope is usually from two to three miles an hour, though instances might be cited of as low a speed as one mile an hour. The endless rope system admits of so many modi- fications that it is necessary at once to classify them before entering into any details. We may begin by making two broad divisions : * Waggons attached singly at intervals along the rope. Waggons attached in groups or trains (sets). Waggons Attached /Singly. Two distinct lines of rails are required, because there is a constant stream of full waggons coming out to the shaft and a constant stream of empties going into the workings. This class has two subdivisions : Hope above the waggons. Hope below the waggons. "When the rope is above the waggons, no rollers are necessary except at the curves. Several modes of attaching the waggon to the rope are in use. If the gradient is all up hill a very simple clip is sufficient. The rope is made to rest in a fork on the waggon, and as it is bent slightly out of the line of pull when in motion, it is held tightly enough by friction to draw along the load. If the gradient varies, a fork is put on each end of the waggon, or a screw clip is employed ; this resembles a pair of tongs, the jaws of which are brought tightly together by a screw worked by a handle, and hold the rope with a firm grip. Another common attachment is by a piece of chain 6 or 8 feet long with a hook at each end. A boy puts one hook into an eye on the drawbar of the waggon, and giving the other end of the chain four turns round the rope makes it fast in the hook. To detach a waggon the boy presses down the chain near the waggon, takes out the hook from the drawbar, and then unwinds the other end from the rope. After a little practice the boys become very dexterous in this hooking on and off, and perform * The classification and some of the information is taken from the Catalogue of the Eoyal Mining, Engineering, and Industrial Exhibition, Newcastle-on-Tyne, 1887, p. xxxiv. HAULAGE OR TRANSPORT. 3 6 9 FIG. 416. FIG. 417. these operations with great rapidity. If there is a downward gradient the waggon would outrun the rope, and it is necessary to put a chain at the rear end as well as in front. When the rope is below the waggons, rollers are required on the road, similar to those already described for engine-planes and main and tail ropes. The attachment to the rope is made by some form of clip. At the Hodbarrow iron mine in Cumber- land, Rice's clutch (Figs. 416 and 417) has been used for many years with good results. The rope can be put in or taken out sideways after raising the sliding piece A as far as the projecting pin. The clip is hung by its hook on to the waggon and the rope is lifted in ; the motion of the rope draws the clip a little away from the vertical, and this slight devia- tion of the groove from the line of pull gives sufficient grip for haulage. The number of clips or clutches is very great, and it would be useless to attempt to describe them all within the limits of this work. An advantage of this system is the smooth and regular manner in which it works. The waggons are attached at intervals of about 20 yards or even less, and they arrive without the bustle of a long train. The men and boys are kept constantly employed, but have ample time for doing all that is required of them. If a waggon goes off the line, it is true that a large number of the succeeding ones may be thrown off too, before the damage becomes known ; but the absence of a high speed tends to render the consequences less perilous than with the fast-running trains of the main and tail rope system. Waggons Attached in Groups or Trains (Sets). As in the previous case there are two subdivisions : Eope above the waggons. Hope below the waggons. The former of these two methods is very easily understood. For instance, several waggons may be coupled together and the train thus formed is connected to the moving rope by a short piece of chain with two hooks, in the manner described for a single waggon. Other attachments are of course available. The second subdivision admits of a great many varieties : (a) Single road, with a siding or sidings for the full train to pass the empty one. (ai) Single central siding. The rope is arranged in the form of a double loop, represented diagramma- tically by the dotted line (Fig. 418) ; S denotes the shaft end of the 2 A 370 ORE AND STONE-MINING. haulage system, W the end near the workings, and C the central siding. The full lines indicate the railroads. When moving in the manner shown by the arrows, the rope brings out a train of full waggons from the workings, and takes in a train of empties from the shaft. On arriving at the central siding the rope is stopped, the empties are shunted on to the siding, and the FIG. 418. train of full waggons is attached to the part of the rope which has just brought in these empties. The empties are shunted back on to the main line and attached to the part of the rope just used for bringing out the full waggons. On reversing the motion of the engine, the empties proceed to the workings and the full train travels to the shaft. (02) One or more sidings. The two ropes (Fig. 419) lie within the road, except at the sidings, each of which has one of them. There are points at the ends of the sidings, for diverting the trains on to the proper roads. Each train has a special truck, or FIG. 419. bogie, in front, upon which rides a conductor. It is his business to pick up with a hook the rope he requires, and grip it with his clutch ; his train then moves along on to the main line till he comes to a pass-by. A boy attending to the points makes the train take the proper line, and if one train arrives a little too early for the passing, the conductor loosens his clutch and brings his train to a standstill until the other train has gone by. He can then proceed along the main road till it becomes necessary to cross a second train. (/3) Two roads formed by three rails with one or more sidings for the passing of trains. One-half of the endless rope (Fig. 420) FIG. 420. lies in the middle of one track, and the other in the middle of the other track. The trains pass as they did in the previous system ; but there is the advantage that no points are required. (y) Two entirely separate lines of rails. In this case (Fig. 421) no intermediate sidings or points are necessary, for each train has its own line, and the services of the conductor can be dispensed with. HAULAGE OK TRANSPORT. 371 In making a choice between these various methods, much depends on the nature of the roads. At some mines it may be difficult to keep a road open of the width necessary for two separate lines of rails, or indeed for one; so that a system which can be worked by a single line with occasional sidings will be preferred. Besides, it may be necessary to introduce mechanical haulage into a mine laid out originally for horse traffic, and the expense of making a second road might be fatal to a double-line system, in spite of its manifest advantages". ' FIG. 421. iv. Endless Chain. This may be looked upon as a variety of the previous system, a chain being substituted for the rope. The chain is usually made to ride upon the waggons, and as each link lies in a plane at right angles to that of its neigh- bour, it is easy to devise a simple catch or clip. A common one is a bar with a fork at the top, which is attached to one end of the waggon. The waggon is pushed under the chain, which is sagging down a little, so that a link lying vertically drops into the fork; the next link will catch against the clip and set the waggon in motion. On arriving at the terminus the chain is raised by a pulley, and so lifted out of the fork. The waggons are attached singly. v. Electric Railways. In the previous four cases we have been dealing with the transmission of power by a moving rope or chain, we now come to a totally different solution of the problem viz., the transmission of power by a wire or wires to a motor which runs on a track and draws a train of cars after it. As an example * of an electric railway, I may take one which has been running for some years at the Neu-Stassfurt mine, where potassium salts and rock salt are the object of the workings. The underground railway runs for a distance of nearly 1000 yards ^(900 m.), along the strike of the deposit ; a cable is brought down the shaft, and there are two insulated conductors hung from the roof of the level ; one conveys the current to the electric locomotive by means of a slide, dragged along by a small rope, and the other has a similar slide for the return. The road in this case is perfectly horizontal, and the locomotive draws a train made up of 20 waggons. An empty waggon weighs 400 kil., and takes a load of 750 kil.; 20 full waggons make up therefore a total weight of 23 tons. The locomotive weighs 2*1 tons, consequently the total weight of the train is about 25 tons. The steam engine for driving the dynamo at the surface is of about 20 "* MS. notes and B. und h. Zeitung, 1888, p. 300. 372 ORE AND STONE-MINING. horse-power. The locomotive is 3 feet J inch wide by 4 feet 1 1 inches high, and 8 feet 9 inches long between the buffers (930 mm. by 1500 mm. by 2670 mm.) and the centres of the axles are i8f inches (480 mm.) apart. The gauge of the road is 24! inches (628 mm.), and the diameter of the driving wheels 13! inches (350 mm.). The locomotive is made alike at both ends, with a seat for the driver, so that he can travel in either direction, with- out having to turn it round. It takes a train five minutes to run the 900 metres. The cost compares favourably with that required for tramming by men or horses, and in 1888 the figures given were as follows : Electric Eailway. Horses. Men. Cost of haulage per ton ) per kilometre . j Pfennige. 12-9 Pfennige. l6'00 Pfennige. 34*20 Speaking roughly these figures are i^d. per ton per kilometre for the electric railway, i^d. for horses, and ^d. for men. Comparing the electric railway with horse traffic, there are other advantages besides that of cost. The mine is kept much sweeter and cleaner, from the absence of the droppings of the horses, and in this particular case, the animals would suffer in their hoofs, from constantly walking in the damp salt. The Neu-Stassfurt line is not working under the most favour- able conditions for economy, because it cannot be kept fully employed ; and considering the rapid strides which have been made during the last few years in electric transmission, it is certain that a line put up nowadays would furnish more favourable results. The line shown by Messrs. Siemens and Halske, at the late Frankfort Exhibition, had a single wire hung from the roof of the level, and the current was brought down to the motor on the locomotive by a running pulley held by a balanced arm, which ensured contact, although the distance between the wire and the locomotive was not always exactly the same. The return current travelled along the rails. At Greenside mine in Westmoreland, there are two wires along the roof of the level, one for bringing the current to the electric locomotive and the other for the return. VI. CONVEYANCE BY BOATS. This is a very excep- tional method of conveying mineral underground at mines ; but it needs mention to make the subject complete. In this country there is an adit level at the Tankerville and Bog mines in Shropshire, known as the " Boat level,'* because the ore was carried in boats to its mouth, a distance in some places of if miles. As the adit had been driven with too great a fall originally, it was necessary to have small locks under- HAULAGE OR TRANSPORT. 373 ground, and so subdivide the whole length into several parts, one slightly above the other. This level now serves simply as a drainage tunnel. At the Dorothea Mine, near Clausthal in the Hartz, there is a level more than 400 yards below the surface, along which there was at one time a large amount of traffic by boats. The level is 10 feet high, by 7 feet wide, with 5 feet of water in the bottom. The boats used on this underground canal were about 31 feet long, 4^ feet wide outside, and 3 feet deep. The part used for holding the ore had a capacity of about 220 cubic feet ; the load was 5 or 6 tons of ore, and a full load would bring the edge of the boat within 6 inches of the water. The boat was propelled by the men, who pushed with their feet against the roof of the level. TRANSPORT ABOVE GROUND. In commencing this chapter I said that it would be convenient in this place to take the subject of conveyance of mineral above ground, though, strictly speaking, it would not come until after the consideration of methods of raising ore and rubbish to the surface. This part of the subject must be treated in a somewhat summary manner for want of space, and also for the reason that much that has been said about underground traffic will apply in the case of conveyance above ground, indeed the same heads may be taken, with the addition of a seventh transport by aerial ropeways. 1. Shoots made of timber, with the wearing parts protected by iron, can be applied in places where there is a sufficient amount of fall. In a hilly country it may sometimes be worth while sinking a shaft solely for the purpose of using it as a means of dropping ore to a lower level. 2. Flow along Pipes is made use of on a very extensive scale for the transport of natural gas, petroleum and brine. The Annual Report of the Philadelphia Company, one of the six companies supplying Pittsburg, shows that in the year 1885 it had 331 miles of mains and distributing pipes, which brought in the natural gas from distances of 22 to 24 miles; at that time it was estimated that there were at least 500 miles of pipes coming into the city. The mains vary in diameter from 3 inches to 30 inches, the largest sizes being made of cast-iron and the others of wrought-iron. There are more pipes of 8 inches in diameter than of any other size, and the mains are made to increase in diameter as they approach the city, in order to reduce the pressure of the gas. Many of the wells when shut would have a pressure of 500* Ibs. per square inch, and even when the pressure is far lower than this, it is necessary to reduce it in order to prevent leakage, which means not only diminished profits to the * C. A. Ashburner, " The Geologic Distribution of Natural Gas in the United States." Trans. Amer. Inst. M.E., vol. xiv. 1886, p. 428. 374 OEE AND STONE-MINING. company, but also danger to the consumer. In the town the- pressure nowhere exceeds 13 Ibs., and in many of the mains it is not more than 6 or 8 Ibs., whilst in the low pressure mains it is only 4 or 5 ozs. per square inch. Another case of conveyance of gas by pipes is seen at the bore- holes furnishing carbonic acid gas in Germany ; under its natural pressure the gas flows through wrought-iron pipes, either to the works where it is compressed into the liquid state, or to those where it is utilised for the manufacture of white lead. Crude petroleum, which either rises naturally to the surface or is pumped up, has to be refined before it can be utilised com- mercially, and it has been found convenient in many districts to- send the oil to the refineries by pipe-lines.* Pumps are employed for forcing the oil through the long lines of pipes, as there is no natural pressure in this case. The United Pipe-lines Company in America had, in 1886, "over 4000 miles of piping and 500 reservoirs, each holding from 20,000 to 30,000 barrels," f and probably now there are more than 5000 miles of pipe-lines in the United States. The pipe-line from the Lima! il district of Ohio to Chicago is 210 miles long; the pipes are 8 inches in diameter, and each piece 22 feet long. The cost of the pipes alone was estimated to be $7000 per mile, and the total cost of the undertaking, in- cluding the pumps and reservoirs, $2,250,000. Another of the great American pipe lines connects Olean in the Bradford oil-field with New York City. It consists of two lines of 6-inch pipes, more than 300 miles in length, and it is divided into 1 1 separate sections. At each station there are two tanks and a pump ; when one tank is receiving oil, the other is supplying it to the pump for transmission to the next station further east, a week being required to complete' the journey. As the lines of pipes follow the irregularities of the surface, ample pumping power has to be provided. One of the Worthington pumps || on this line exerts a pressure of 900 Ibs. per square inch, and is capable of delivering 1,^00,000 gallons in 24 hours. Mr. Marvin also mentions a pipe-line at the Burmese oil-fields made of lacquered bamboos, for taking the oil from the wells to- the river. Modest as this line appears compared with the great undertakings just described, it is nevertheless an advance upon the old plan of putting the petroleum into earthen jars, and carting it. In this country, brine is sent by pipe-lines from the wells * Kedwood, "Petroleum and its Products." Journ. Soc. Arts, xxxiv. 1886, p. 832; and " Cantor Lectures," published separately, p. 30. f The Times, 29th September, 1886. \ Engineering, vol. xlv. 1888, p. 439. C. Marvin, " England as a Petroleum Power," London, 1887, p. 19. || Eng. Min. Jour., vol. li. 1891, p. 745. HAULAGE OR TRANSPORT. 375 to convenient places for evaporation or to alkali works, where it is used in making carbonate of soda by the Solvay process. Lastly, it has been suggested that the solution of the " caliche," or raw nitrate of soda, should be sent down in pipes to the coast for evaporation, instead of performing this process in the arid desert in the neighbourhood of the diggings. The flow of mineral in suspension in water along troughs (lauiiders), or channels made in the ground, or pipes, is a process which may be seen on the dressing-floors at metalliferous and other mines, as well as at china clay works. At the Mechernich lead mines the waste from the preliminary dressing-floors is forced by plunger-pumps through a large pipe to pyramidal boxes, in which the water is separated from the sand, so that it may be used over again. Though not a true flow, I may here mention the conveyance of a mineral for short distances by revolving screws in troughs (" screw conveyors "), which serve to transport a mineral from one part of a factory or dressing-floors to another. 3. Human Labour. In mountainous districts where the inhabitants are accustomed to carry their provisions, their hay or other agricultural produce upon their backs, it is not unnatural to find ore transported in the same way from the mine to the dressing-works. Not many years ago, gold ore was regularly carried to the little amalgamating mills in the Italian Alps on women's backs. The ordinary load for a woman down hill was 100 Ibs. (45 kil.). If the woman took tools or materials up hill, the load was naturally less, and amounted to about 75 Ibs. (34 kil.). The ore was carried in a basket or creel (scivera), an appliance to which every peasant-girl had been accustomed from early youth. Ore may be moved from one part of the dressing-floors to another by hand-barrows. These are merely rectangular trays or boxes, with a pair of handles in front and a pair behind. The hand- barrow requires two persons to carry it (.Fig. 61 1). Carriage on the head is met with in some countries. 4. Conveyance by Sledges. Sledges drawn by men or horses still survive in some hilly districts. Even in Wales at the present day, manganese ore is sometimes brought down from the mine to the nearest cart-road in this primitive fashion. But it is a toil- some and unsatisfactory method of transport, and justifiable only in the case of trials, which have not yet proved a sufficient amount of ore to warrant the construction of a tramway or a ropeway. 5. It is by wheeled conveyances that minerals are most commonly transferred from one part of a mine to another, or from the mine to a railway or port of shipment. Wheelbarrows are applicable for distances measured by yards, such as one may have on dressing-floors, and carts are sometimes the only available means of transport for one or two. hundred miles ; but the traflic 376 ORE AND STONE-MINING. should be conducted in some cheaper fashion, by railways for instance, as soon as possible. It is not necessary to go over all the old ground with regard to rails, sleepers, points and crossings ; suffice it to say that though the surface railway resembles the underground one, it is generally better kept ; first, because its defects are more palpable to every one by daylight than when seen by the glimmer of a candle, and secondly, because there are fewer difficulties in laying it properly and keeping it in order. At the surface as well as underground we have self-acting inclines, and traction by locomotives and ropes. Self-acting inclines stand the miner in good stead in hilly countries. There are either two entirely separate roads, one for the full waggon going down and the other for the empty which is being brought up, or there are three rails with a pass-by in the middle, or even a single road, except at the pass-by. The incline is worked by a drum at the top, placed most commonly on a horizontal axis, and of course provided with a brake. As examples of large inclines, I may refer to those erected by the " Societe Franco-beige des Mines de Somorrostro," * for bringing down iron ore to their railway, which then conveys it to the port of Bilbao. The lower of the two planes is 737 yards (674 m.) long, with an average inclination of 30, the maximum inclination being 36 near the top. It is worked by steel wire ropes i J inch (38 mm.) in diameter, which are coiled around two conical drums, united by their bases and having a mean diameter of i6J feet (5 in.). In order to regulate the descent of the trains, the drums are connected by gearing with an air-brake, identical in principle with the fly of a clock (Fig. 422). It is composed of four straight vanes made of wood and iron, about 6J feet (2 m.) wide, and 16 J feet (5 m.) in diameter outside. Twelve waggons coming from the mine are coupled together so as to form a train, and when it starts down the incline, the air-brake begins to revolve and soon develops a considerable amount of resistance as the speed increases ; the consequence is that the train descends with an almost uniform velocity. The strap-brake on the drum simply serves to moderate the speed if necessary and to stop the train ; but in no case is much power required to work it. The train makes a journey in three minutes, and it takes three minutes to make up and couple on a train ; therefore there is one train every six minutes, and as each waggon contains two tons, the quantity delivered by each train is 24 tons, or with ten trains an hour the quantity per day of ten hours will be 2400 tons. By increasing the number of waggons in each train, the day's work * Exposition Universelle de 1889. Note sur ^Exposition de la Societe Franco-beige des Mines de Somorrostro en 1889. Paris, 1889, p. II. Les Orandes usines de Turgan. August, 1889, p. 50. Forges et Ateliers de Con- struction de Mme. Vve. Taza- Villain. HAULAGE OR TRANSPORT. FIG. 422. 377 3/8 ORE AND STONE-MINING. may be run up to 2600 tons. The fan-regulator has the advan- tage of saving the wear of the ordinary strap-brakes and of rendering the speed uniform. If nothing but a strap-brake was used, there would be a very great amount of friction, which might cause the wooden shoes to take fire ; in any case it would throw a great strain upon the machinery, and involve the risk of a serious accident if it happened to break. The fan- regulators avoid all these difficulties ; but they must be made very strong, as they have to counteract a considerable amount of vis viva at the particular incline mentioned no less than 42 & horse-power. I have dwelt somewhat upon this fan-regulator, as it has been found extremely serviceable at Somorrostro, though little known elsewhere. Locomotives burning coal can be used without inconvenience, and effect a great saving in most places, when compared with horse traffic. At the Festiniog slate mines, small locomotives running on a track with a 23^-inch gauge are employed for drawing trains of rubbish to the tips ; the total weight of a train may be as much as 80 tons. As the men who are removing rubbish from the underground or surface workings are paid by the ton, the loads have to be weighed. When the trains are drawn by a horse, it is necessary to stop each time a waggon is brought on to the weigh-bridge ; but when the locomotive is used, the train runs so smoothly that the waggons can be weighed during their passage, without any halts being made. This is a small advantage it is true, but it saves time and consequently money, and should therefore be noticed. The endless rope and the endless chain conveying single waggons at stated intervals are both in favour, either for trans- porting the valuable mineral to any required spot, or for taking the waste to the tip or " dump." An example of the former system may be seen at the De Beers * diamond mine, South Africa, where the gem -bearing rock has to be exposed to the action of the atmosphere for some months in order to make it crumble away and become ready for the pro- cess of washing. Large areas have to be covered with the " blue," and cheap haulage is a matter of importance. The depositing floors commence at a point a mile from the mine and extend for three miles to the east and one mile to the west. The main line is three miles in length and it has two branches, one a mile long, and the other three-quarters of a mile long. The rope is driven by a horizontal engine, with two cylinders, each 14 inches in diameter, and having a stroke of 3 feet. It is | inch in diameter and, as is very commonly the case elsewhere, it has an iron instead of a hempen core, in order to prevent a reduction of * De Beers Consolidated Mines, Limited. Second Annual Eeportfor the Year ending ^ist March, 1890, p. 17. HAULAGE OR TRANSPORT. 379 section when it is subjected to continued tension. It is carried on the steel trucks, which can be tipped on either side, as the body is supported on two trunnions (H, Fig. 442). The device for attaching the rope to the waggon is very simple ; the rope lies in a fork or " jockey," which is slightly out of the direct line of traction. The jockey is free to turn in a socket on the truck, and the slight bend given to the rope is sufficient to afford the necessary grip, even in going up an incline of i in 20. If the " blue " has to be deposited at a point nearer the mine than the terminus, the part of the rope beyond the place where the waggons are taken off is supported by pulleys. Horses are employed to draw the trucks from the main rope haulage lines to the places on the floors where they have to be tipped. The endless chain has been chosen for bringing down the ore from some of the mines of the Somorrostro Company,* in a part where self-acting inclines cannot be used because there is not a descent all the way. A second reason for adopting this system was the fact that it admits of considerable changes in the amount of traffic, by altering the speed of the chain and the distance between two successive trucks. It further allows branch lines to be taken off from the main one. At Somorrostro there are in all very nearly two miles (3000 m.) of endless chain haulage. The greatest difference of level between the highest point at the Sol mine and the terminus at the station of Cadegal is 802 feet (244-60 m.), and on one part of the line the gradient is as high as 29*5 per 100 or i in 3-4. The fall is so great that the chain requires no power but gravity to work it ; in fact, it is necessary to use brakes to oppose the vis viva. Strap-brakes are employed in the same manner as they are on the inclines just described, solely for the purpose of stopping the chain. The danger of depending entirely upon such brakes for working inclines has already been pointed out, and a uniform speed is maintained by affixing fan-regulators working in water. They are chosen in this case in preference to the fans working in air, because the latter must revolve at a great velocity in order to be efficient, and there- fore could not be applied to the slow chain haulage without gearing, which would introduce complications. These hydraulic governors are like the air-regulators in principle, except that the blades are immersed in water ; the speed of the chain can be adjusted with the greatest nicety by altering the quantity of water in the tank in which the blades work, and so introducing the amount of resistance required. The usual speed at which the chain is run is 5 feet (1*5 m.) per second, but it can be raised to 6 feet 6 inches. The chain is made of J-inch (22 mm.) iron, which corresponds to about 19^ Ibs. per * Exposition Universelle de 1889. Op. cit., p. 15. 380 OEE AND STONE-MINING. yard (yS26 kil. per metre). The last section, however, has harder work, and the chain is of i-inch iron (26 mm.) and weighs 28 Ibs. per yard (14 kil. per metre). Each waggon holds iyf cwt. (900 kil.) of ore, and when the waggons are arranged 2 7 yards (25^2 m.) apart, the chain haulage is capable of transporting 2500 to 2600 tons of ore a day, in addition to a certain amount of rubbish which is tipped before arriving at the port. 6. Conveyance of Mineral by Boats from one part of a mine to another is exceptional ; but transport by canal or sea to the consumer is common, and is chosen whenever available on account of its comparative cheapness. It is of the utmost importance when dealing with large quantities of mineral to have cheap and rapid methods of shipping it. At Huelva, the shipping- port of the Rio Tinto mines, the trains of ore are drawn on to a part of the pier which has just enough inclination to make a truck run down of itself. A workman then uncouples a truck and allows it to run opposite a shoot, which leads to the hold of the vessel lying alongside the pier. The truck is emptied by opening the bottom and letting the contents drop into the mouth of the shoot. The bottom is then closed and the truck is allowed to run on a little further, when it is shunted back on to a side line, and made to join the train of empties ready to be drawn back to the mine. After the locomotive has once hauled a train on to the proper part of the pier, the discharge of its contents into the ship proceeds very rapidly and requires the attendance of only one man. The arrangements are so perfect that 500 tons can easily be loaded in an hour, but naturally a good deal of time is lost in shifting the steamers and berthing them. The greatest amount of work in loading at Huelva pier has been a little over 3000 tons in a single day. A steamer has been known to come into Huelva harbour by one tide, and leave by the next with a cargo of 1500 tons of ore. The Somorrostro Company loads its iron ore at Bilbao in a similar manner. The Company has three wharves, at each of which 2000 tons can be shipped in a day ; indeed a ship of 1490 tons has been loaded in six hours. 7. Aerial Ropeways. These ropeways may be divided into five classes : a. Single supporting rope, with or without a hauling rope. b. Endless rope, which is the supporting rope and hauling rope at the same time. c. Two supporting ropes and an endless rope for hauling the load. d. Double endless travelling rope or chain. e. Telpherage line. a. Lines erected on the first of these principles may be seen in hilly countries. An iron or steel wire rope is stretched across a valley, and forms the rail .supporting the load, which is put into HAULAGE OR TRANSPORT. 381 a sack and hung on by a grooved pulley. If the heights of the departure and receiving stations are properly arranged, the load on going down the slope acquires enough momentum to bring it up to the station on the other side, without rushing in too violently. The objection to this system is that the sacks and the pulleys have to be carried back by men or women, but it has the merit of simplicity and cheapness. By the addition of a small hauling rope on a drum, the method is available for steep moun- tain sides ; the load is lowered with use of the brake, and the drum is worked to draw up the empties along the supporting rope. b. In this system there is an endless rope, supported by pulleys on strong wooden or iron posts placed at suitable intervals, which is set in motion by any available source of power. Suspended from the rope are the buckets or other vessels in which the mineral is carried. The buckets maybe detachable at pleasure or they may be fixed. The former plan is the one brought out by Hodgson in 1869, The bucket or other receptacle is suspended by an iron hanger from a grooved block of wood which rests upon the rope. The carrying block has a spindle with a small grooved pulley, which can be made to run upon a rail at each terminus and so let the rope move on without the load. The bucket is filled from a shoot or hopper while hanging on the rail at the loading terminus. A workman then pushes it along the rail until the carrying block is taken up by the rope, which is always in motion ; the load now travels along suspended from the rope, the carriers being con- structed so as to pass over the pulleys. On reaching the unload- ing terminus, the carrying block is again shunted on to a rail, and the bucket is tipped by lifting up the catch which had kept it from turning about pivots ; after having been put into position, it is brought round to the point where the rope, after passing round a terminal pulley, is about to begin its journey back to the loading station. Here it is shunted on to the rope and travels along with it. One great disadvantage of this system, in the case of steep in- clines, is that the carriers may slip upon the rope, and that the loads either fall off or do damage in some other way. To over- come this difficulty, some of the constructors of aerial ropeways attach the loads to a clip which is tightly fixed to the rope. The clip must be of such a nature that it will pass the supporting sheaves or pulleys. When the inclination is sufficient, an aerial line of this description will work automatically, the weight of the full loads being enough to draw up the empties. c. The third system has two fixed ropes, which serve as aerial rails and act solely as supports, and an endless travelling rope, to which the loads are made fast at pleasure. It resembles, therefore, the endless rope haulage, of which mention has been made for underground work, save that the rails are above the load instead of being below it. 382 ORE AND STONE-MINING. FIG. 423. Ropeways working upon this plan have been perfected of late years by Otto and by Bleichert in Germany, where they are commoner than in this country. They are constructed for distances of from 2 to 8 or even 10 miles, with a carrying capacity of 600 to 800 tons per day of 10 hours. The separate loads may vary from J cwt. to i ton each. The points to be considered are : Carrying rope and vessel. Posts or standards. Hauling rope and attachments. Terminals and their shunting arrangements. The kind of cable used on the most recent lines erected on the Otto system * is that known as " locked coil wire rope," the con- struction of which is explained in the next chapter (Fig. 451). It has the advantage of presenting a perfectly smooth surface, ad- mirably adapted for the running of the grooved pulleys by which the load is suspended. The vessel in which the mineral is conveyed may be any convenient form of bucket or box, supported by pivots around which it can be easily tipped, or the actual mine-waggons may be slung up and the ore carried in them. Each box, bucket, or waggon, is at- tached to a hanger suspended from a spindle placed midway between two grooved pulleys or wheels, which rest on the rope (Fig. 423). The posts or standards are constructed of wood or iron, sometimes with two, and sometimes with four legs, suitably stiffened by braces and held in position by guy ropes or rods (Figs. 424 and 425). The four-legged standards are used for heavy loads or long spans. The distance between the standards varies according to the nature of the country, and is often about 30 to 60 yards ; but where the country is much broken by ravines, these short spans are unat- tainable without standards of an impracticable height, and the cable is then made to stretch across very long intervals without intermediate supports. Spans of 550 yards (500 m.) are not unknown. The hauling rope must be very flexible, and is made of fine steel wire with a hempen core. The mode of attachment of the load varies with the gradient of the line. If the gradient is less than * J. Pohlig, " Aerial Kopeways, Otto System." Tram. Amer.Inst. M.E., vol. xix. 1891, p. 760. HAULAGE OR TRANSPORT. 383 i in 6, the amount of friction necessary for gripping the rope tightly can be obtained by bringing it between two flat iron discs and clamping them together with a screw. One of these discs is rigidly attached to the hanger, and the tightening screw of the other can be loosened automatically by providing it with a projecting lever, which comes in contact with a stop at the terminus. If the gradient is between i in 6 and i in 3, the discs are made FIG. 424. FIG. 425. VOODEN STAN with corrugated instead of smooth surfaces. When the gradient exceeds i in 3, another device has to be employed ; projecting knobs are inserted into the rope at regular intervals, and on meeting with properly arranged stops upon the loads they cause them to travel along. Figs. 426, 427 and 428 show the details of the arrangement. Each terminus is provided with an iron rail which is fixed so as to meet the rope where the v buckets have to be loaded or unloaded ; by suitably arranging the end of the rail, the load passes quite smoothly from it to the rope and vice versd. 384 ORE AND STONE-MINING. An example of one of the Otto ropeways is given in Fig. 429, which is a section of the line put up for the Sheba Gold Mining FIG. 426, FIG. 427. Company, Limited, Barberton ; it is 2\ (4-4 kil.) miles long, and will carry 150 tons per day of 10 hours. The maximum incline is i in i '6, and the greatest span 1480 feet (451 m.). FIG. 429. Tntermtdialf '/cnsim drur Intermediate \7ension Clear VERTICAL SCALE IOO M. O 100 2OO 3OO 4OO 50O METRES HORIZONTAL SCALE. A line erected in Southern Spain for carrying iron ore is 9*69 miles (15*6 kil.), long, divided into four independent sections. The greatest span is 918 feet (280 m.), but on an average the sup- HAULAGE OR TRANSPORT. 385 porting posts are only 44 yards (40 m.) apart. The hauling rope is made to travel at the rate of 100 yards (90 m.) a minute, and deliver two buckets, each containing 7 cwt. (350 kil.) in that time. This means a carrying capacity of 1200 buckets or 420 tons per day of 10 hours. The line has also been worked with two shifts of 8 hours each, and has transported 900 tons in that time. The total cost of this line, which was surveyed, erected in a very difficult country, and ready to start in ten months, was ,26,000 ; and it has been worked at a cost of is. $d. per ton, which includes all that is spent for labour, maintenance and repairs. At the Menzel colliery in Upper Silesia, 500 to 700 tons of coal are carried in ten hours a distance of r6 miles, for i \d. per 2 B 386 ORE AND STONE-MINING. ton per mile, including wages, repairs, interest on capital and depreciation of plant. Fig. 430 shows part of the line at Gottes- segen colliery, Upper Silesia.* A line carrying iron ore in Luxembourg is 3 miles long, and transports 300 tons of iron ore in 10 hours at a cost, again in- cluding all expenses viz., wages, repairs, interest on capital, and depreciation of plant, of ^\d. per ton, or i^d. per ton per mile. d and e. Ropeways worked by these systems are rare. * "Otto Patent Kopeway." The Engineer, vol. Ixvii. 1889, p. 115. ( 387 ) CHAPTER VIII. HOISTING OB WINDING. Motors, drums, and pulley-frames. Kopes, chains, and attachments. Kibbles, skips, and cages. Keps, guides, signals. Safety appliances, detaching-hooks, safety-catches, automatic stopping gear Pneumatic hoisting. BY hoisting is meant raising the minerals from the underground workings to the surface. In speaking of the subject generally, it is more correct to say hoisting than winding, because this latter term implies the use of the rope, which is not quite universal. As already explained in the last chapter, there is no clear line of demarcation between haulage and winding. In the typical case of a vertical shaft and a nearly horizontal level, it is easy to make the distinction ; but when the mineral is drawn up through inclines, the name given to the process depends upon local custom. Thus, part of the shaft at a Cornish tin mine is inclined at an angle of only 15^ from the horizontal, and nevertheless the work of drawing up the ore is always called winding. In a few districts carriage on the back still survives; in Sicily, for instance, much of the sulphur rock is brought to the surface by boys on their backs up rough paths, or steps cut in the ground. As lately as ten years ago, I found slate being brought up on the back in the Moselle district. In Mexico and in China, too, the same method is pursued in some silver and other mines. However, this barbarous mode of raising mineral is simply mentioned for the purpose of con- demning it. The regular method of bringing a mineral to the surface is to draw it up a shaft or an incline by means of a rope. The subject is such a wide one that it must be treated under different headings as follows: (i) Motors, drums and pulley-frames; (2) Hope, or chain ; attachments of the rope; (3) Receptacle for the mineral or waste rock ; (4) Other indispensable appliances, guides, signals, keps ; (5) Safety appliances. i. MOTORS, DRUMS, AND PULLEY-FRAMES. Motors As in other departments of mining, the motor employed may be worked by animal power, or by an engine driven by water, steam, compressed air, petroleum or electricity. 388 ORE AND STONE-MINING. (a) Animal Power. The simplest contrivance for winding is a pulley supported by some suitable frame above the shaft ; a bucket is attached to the end of a rope hanging down the shaft, whilst the other end, passing over the pulley, is drawn by men or women : they simply walk away from the shaft and haul up the bucket. Oil wells are sunk in Burmah by this primitive method of hoisting. The usual method of applying human power is by a windlass. This well-known appliance consists of a wooden cylinder, about eight inches in diameter, provided with two iron handles and supported by two upright posts which are suitably stayed. A sliding bar, which can be drawn out either above or below the cylinder, serves to hold one of the handles, when required. In this country, the ordinary windlass is used for shallow sinkings of twenty, thirty, or forty yards in depth, such as are made in commencing work at a mine, or in effecting a communi- cation between two levels ; but in countries where mining is less advanced, and where labour is cheaper, the windlass may form the sole means for hoisting from depths of a hundred and even two hundred yards. Thus, for instance, at Boryslaw, in Galicia, it is reckoned that six or seven thousand shafts have been sunk during the last thirty years, for the purpose of working- ozokerite, to an average depth of one hundred yards, by human labour ; four, five, and even six men and women may be seen working the Boryslaw windlass. In the neighbouring country of Roumania, oil wells are sunk in like manner. The windlass is used either with one or two buckets ; in the latter case the labour is lightened, for the weight of the empty bucket going down balances the dead weight of the bucket coming up with a load of rock. As a rule too little attention is paid to the state "of the axles and bearings. Windlasses, like other machines, cannot be worked with economy unless means are taken to prevent unnecessary friction, which is sure to arise unless the axles and bearings are kept perfectly true ; this fact should be specially borne in mind when the mine-owner is employing expensive human power. The capstan is an unusual form of winding machine at mines ; it differs from the windlass by having its cylinder vertical. As an instance of its use, I may mention the little underground quarries at Swanage in Dorsetshire, where blocks of stone are drawn up inclines by means of capstans turned with bars, after the manner of those used on board ship. When a horse is employed in the place of men, the bucket, attached to a rope passing over a pulley, is sometimes drawn up by making the animal walk away from the shaft. The framework and pulley constitute what is called a whipsiderry. Animal power is usually applied by means of a machine called HOISTING OR WINDING. 389 a horse-whim. It may be looked upon as a gigantic capstan, worked by horses, mules, or donkeys. It consists of an upright axle, usually of timber, supported at the bottom by an iron pin or pivot, which works in a hole in a large stone, forming a primi- tive foot-block. A horizontal beam, known as the driving beam, is attached to the axle, and above it comes a hollow wooden cylinder or drum, around which the rope is coiled, proper project- ing horns or flanges being provided to prevent it from slipping off. The other end of the axle works in an iron socket, carried by a great horizontal beam, known as the span-beam, which is supported by two legs. In this country the horse-whim is not roofed over, and it forms a prominent feature in many mining districts; where the weather is more severe, a house becomes necessary. The winding rope is coiled several times around the drum, and both ends, after passing over pulleys, hang down the shaft ; when the horse walks round, one bucket is raised and the other lowered. Before the introduction of steam, the horse- whim was a very important means of winding ; and in countries where water- power is lacking, coal dear, and fodder cheap, it still performs very useful services. As many as six to eight horses may be harnessed to a horse-whim for the purpose of working it. (6) Water. I will now pass on to the engines worked by water, steam, compressed air, petroleum, or electricity. When the water-wheel is used for hoisting, it is necessary to have means of reversing the motion, in order to raise or lower the rope at pleasure. Two methods may be employed : A double wheel with the buckets fixed in opposite directions ; a single wheel provided with suitable gearing or belts. The double wheel is frequently seen underground in Germany ; it has sluices (hatches) which will turn the water on to either side, and there is a brake for controlling the motion. The winding-drum is placed on the shaft of the water-wheel, and according as the water is turned on to the right-hand or to the left-hand side, the wheel revolves one way or the other. When gearing is employed, a bevel-wheel upon the shaft of the water-wheel drives a pair of bevel-wheels, facing each other, which run loose upon the shaft of the drum. By means of a suitable clutch either of them can be brought into firm connection with the drum-shaft, and so made to drive it in the required direc- tion. Fig. 43 1 shows the method adopted at Great West Van Mine in Cardiganshire by Messrs. Urquhardt and Small. A, Girard turbine ; B, belt driving the shaft of two pulleys C D ; E and F, pulleys loose upon the shaft ; G, clutch ; H, handle working clutch ; I, pinion driving spur-wheel on drum J J ; K, brake strap ; L, pin connected, when required, to "bob " of pumps. The belt from C 390 ORE AND STONE-MINING. FIG. 431. to E is straight, and that from D to F is crossed ; therefore the two pulleys E and F are always revolving in opposite directions. According as E or F is made fast to the shaft by the clutch G, the pinion I turns the drum one way or the other. (c) Steam. Steam-engines em- ployed for winding have usually two cylinders, either vertical or horizontal; the latter are preferred. In some mining districts, notably in Cornwall, one finds a single vertical cylinder working a beam by which motion is communicated to a fly-wheel; but for rapid work it is necessary to have more com- mand of the engine than can be furnished by a machine of this kind. It was the fashion at one time to put a pinion upon the crank- shaft and a spur-wheel upon the drum shaft ; nowadays for quick winding the drum is placed upon the same shaft as the cranks. This is called working on the first motion, whereas if gearing is used the method is said to be on the second motion. In any case the engine must be provided with an adequate brake, and where the drum is worked by gearing, it is necessary to have a brake upon the drum shaft, because otherwise there would be no means of arresting the descent of the load in case of fracture of some of the cogs. Although many winding engines work without expansion, automatic expansion gear is common, and some of the engines are arranged so that the commencement and end of the run shall be worked with the full power of the steam, and the middle of the run expan- sively. Compound engines, and indeed triple expansion engines, have been erected for winding purposes, though the advisability of employing them is questioned by some mining engineers ; while fully admitting the value of this principle in the case of engines which are working constantly, such as those used for pumping, they contend that it is not advisable to complicate HOISTING OR WINDING. FIG. 433. machinery which is performing very irregular work, and is being continually stopped and started. Compound engines have, however, been adopted recently for winding at Llanbradach Colliery, near Cardiff, by Mr. Galloway. The two cylinders on each side are arranged tandem fashion (Figs. 432 and 433). A, high pressure cylinder; B, low pressure cylinder; C, drum. (d) Compressed Air. Compressed air is largely employed when the hoisting engine has to be placed underground, and it is especially suitable for sinking intermediate FlG> 43 2 - shafts (winzes). Com- pact and handy forms of engines are supplied by various makers ; many of them are similar to the steam winches used on board ship, and consist of two cylinders driving a pinion which works a spur - wheel placed upon the same shaft as the drum. Occasionally, as for instance at the Long Tunnel, Walhalla, in Victoria, all the hoist- ing of a mine is done by a compressed air engine. The reason for this choice at the Long Tunnel was the fact that lode was reached by a long adit, in which compressed air appeared to be the most convenient method of transmitting power from a motor at the surface. (e) Electricity. Winding by electricity is as yet in its in- fancy; but, no doubt, in the course of a few years, we shall hear more of this convenient method of conveying power to the place where it is to be used. It is easy to understand that an electrical motor can be applied to the drum used for winding, its rapid motion being reduced to a suitable speed by means of gearing. Drums. A winding drum is usually a mere revolving cylinder, around which the rope coils itself. It is formed of two centre- pieces keyed to the shaft, each carrying arms, to which are attached rings. Supported by these rings are pieces of plank or plates of iron or steel, which build up a hollow cylinder, the length and diameter of which depend upon the importance of the plant. In large mines one may see drums 20 and even 30 feet in 392 ORE AND STONE-MINING. diameter ; with a drum of 20 feet, 10 revolutions mean coiling or uncoiling 209 yards of rope. A drum constructed for Llanbradach Colliery is a hollow cylinder 17 feet in diameter, and 8 feet wide. In Figs. 434 and 435, A is a cast-iron centre-piece; B B are arms made of H -steel, to which are riveted the crossbars of channel-iron C. The skeleton formed in this way is covered with plates of steel D, f inch thick, which are fixed with countersunk rivets to J-iron E, where they meet. F is the flange to prevent the rope from slipping off the drum, and G the wrought-iron ring upon which the brake acts. A novelty introduced by Mr. Galloway is the arrange- ment for keeping a reserve length of rope to supply the loss FIG. 434. FIG. 435. caused by successive re-cappings. Inside the main drum is the hollow cast-iron cylinder H, capable of turning independently. When a new rope is put on, 50 yards of it are coiled upon H, the bolts of the clip I are fastened, and the remainder is wound round the main drum. After re-capping the rope at the end of two months, it is easy to unloose the clip and draw out what is required. The drum is constructed as light as possible, in order to prevent power from being wasted in starting and stopping an unnecessarily heavy mass. The shaft is 20 feet in diameter and 550 yards deep to the first seam of coal intended to be worked ; but it will be probably made 600 to 630 yards deep in time. The engine (Fig. 432) is expected to raise 200 tons of coal per hour with two mine waggons in each cage, each waggon carrying 2 tons. An objection urged against the plain cylindrical drum is that it in no way compensates for the change of work required of the HOISTING OR WINDING. 393 engine during the different phases of the act of winding. To make this plain, suppose one end of the rope to be at the bottom of the shaft with the full load attached to it, whilst the other end is at the top with nothing but an empty cage. On starting, the engine has to raise not only the weight of the load of mineral, but also the entire weight of the rope hanging down the shaft, and in deep mines with large cages, this weight is by no means inconsiderable. In proportion as the full cage is raised, the amount of dead weight of rope to be lifted becomes less and less. Eventually the full and empty cages meet ; the two portions of the rope then balance each other, and the engine has simply to overcome the action of gravity upon the mineral; later on the rope of the empty cage is longer than that of the full one, and assists the engine in doing its work. At last when the load is Hearing the top, the drum is feeling the full weight of the rope of the empty cage. Constancy of load is easily obtainable with the cylindrical drum by the simple expedient of adding a balance rope that is to say, a rope hanging down the shaft with one end attached to the bottom of each cage. Provided that this rope agrees in weight with the winding rope, the counterpoising is perfect, for on each side, in every phase of the ascent or descent, there is always the same dead weight acting upon the drum. This method is adopted at Llanbradach and also at De Beers Mine. The balance rope often, but not invariably, passes round a pulley at the bottom of the shaft. With the same object in view the drum is made spiral or conical, or rather of a combination of two such drums united by their larger bases. The rope is so arranged that the diameter of the coil increases as the act of winding up proceeds. The load at the bottom of the pit acts upon the drum shaft with a small amount of leverage, and its leverage increases as the weight due to the rope diminishes. The reverse condition of affairs exists with the descending load : it has a large leverage while there is only a short length of rope hanging down the shaft, but as the weight thrown upon the drum increases, so the leverage diminishes. Intermediate between the conical and the cylindrical drum is one which combines the two systems ; the conical end is used for starting the load from the bottom and the main part of the operation is performed with the cylindrical surface. When a flat rope is used instead of a round one, it is convenient, for the sake of distinction, to speak of the winding cylinder as a reel or bobbin (Figs. 436 and 437).* It is provided on both sides with long radial arms, which serve the same purpose -as the horns or flanges in the case of the drum ; that is to say, they prevent the rope from slipping off sideways. * Gallon, Lectures on Mining, vol. ii. plate Ixi. 394 ORE AND STONE-MINING. The flat rope coils upon itself, and as the winding proceeds the diameter of the coil increases, if the cage is being raised, or decreases if the cage is being let down. In this way there is a certain compensating action similar to that which is obtained with a spiral drum in other words, at the moment of starting, when the load is at the bottom, the smallest amount of leverage is exerted upon the driving shaft of the reel ; whereas at the end of the wind, when the load is least, it is exerting the greatest leverage. FIG. 436. FIG. 437. SCALE 3 METRES 13 14 FT. Pulley- Frames. The framework at the top of the shaft for supporting the pulley or pulleys is known by different names. It is sometimes called the head-gear, the pit-head frame, or poppet heads (Cornwall). It may be constructed of timber, iron or steel, and metal pulley-frames are usually seen nowadays at large mines, where winding is conducted upon an extensive scale ; at small mines and also during sinking operations a timber head-gear is common. A kind of frame often used is shown by Figs. 438, 439, 440, from which it will be seen that four large upright posts support cross-beams A, B, C, D, upon which the pulleys rest. The frame is suitably stiffened by struts. Its principal duty is to resist two forces, HOISTING OR WINDING. 395 one exerted by the load and rope hanging down the shaft, and the other by the rope which is being hauled in by the drum. At a FIG. 439. FIG. 438. moment just before the load begins to move the two forces will be equal, and the direction of their resultant will be a line bisecting the angle between the two parts of the rope, and passing through FIG. 440. the centre of the pulley. Provision therefore should be made for resisting this pull, and this is effected by stays, such as are shown in Figs. 438 and 440, which represent a pulley-frame used fo 396 ORE AND STONE-MINING. sinking a shaft some 200 yards deep at Halkyn Mine in Flint- shire. The backstay may be placed in any position between FIG. 441. the bisectrix and a line parallel to the rope going to the drum. During the sinking at Halkyn only one bucket was used, and HOISTING OR WINDING. 397 as this had to hang in the middle of the shaft the pulley was placed between the two beams B and C. Now, the shaft is used for winding with two small cages and there are two pulleys, one between A and B, the other between C and D. Fig. 441 shows the head-gear erected at the perpendicular " Rock shaft" of De Beers Mine,* whilst Fig. 442 represents the arrange- ments at the Incline shaft of the same mine. The head-gear at both shafts is made of wrought-iron trellis work. At the Rock shaft the legs and stays are of 3 J-inch angle- iron, | inch thick. The lattice bars are 3 J by f inch ; the total height from the ground to the centre of the pulleys is 6 1 feet. FIG. 442. Pulleys. Winding pulleys have to be placed on the pit-head frame in order to change the direction of the rope. Nowadays, in all important windings, the pulleys are made from 10 to 15, and even 20 feet in diameter, in order to subject the rope as little as possible to sharp bendings, which would reduce its life. The cast-iron boss, or centre, is joined by wrought-iron arms to a grooved rim also made of cast iron (Fig. 443). In course of time steel ropes wear away the rim, and to lessen this source of trouble, the part in which the rope lies may be chilled. The groove should fit the rope; for if it is too wide, the rope will rest upon a small part of its circumference and be liable to be squeezed. At some mines pulleys are made with a light rim, which will not last for more than a year. The object in view is the preven- tion of wear from rubbing. When the speed of the engine is * Second Annual Report of De Beers Consolidated Mines, Limited, for the Year ending March 31, i$go, p. 16 and plates 10 and 7. 398 ORE AND STONE-MINING. slackening, the pulley, in virtue of its momentum, tends to travel faster than the rope, and thereby to grind its surface. A dimi- nution in the weight of the rim lessens the momentum, and therefore reduces the rubbing action. The advantage gained in this way, is considered sufficient to compensate for the more frequent changing of the pulleys. 2. HOPES, CHAINS, AND ATTACHMENTS. Ropes. Ropes are made of vegetable fibre of some kind, or of iron or FIG. 443- steel wire. The vegetable fibres used are hemp and manilla, which are twisted into yarn ; the yarns are laid together so as to form strands, and finally the strands are laid together to form the rope. For winding by hand, in sinking small intermediate shafts (winzes), a hemp-rope, about | inch in diameter and made up of three strands, is commonly employed. For heavier work, either a round rope of larger section is necessary, or a flat rope formed by sewing together several round ropes, Iron is very little employed nowadays for making wire ropes its place has been taken by steel. HOISTING OR WINDING. 399 The advantage of using steel as compared with iron, is evident from the following figures : * Us* , 3 lls gas S.S8 . Kind of Wire. Tensile str per sq. m kilogram Kind of Rope. Total useful effect in kilogrammetres. V -w.2 Eemarks. Iron . 60 Cylindrical 5,387,124,051 5*5 Kreuzer. 0-817 Crucible ) Cast Steel J 1 2O ,, 26,519,326,190 22-3 0-354 j ? 35 120 1 80 Tapering 56,797,296,369 69,898,974,017 26-1 20-8 0-198 0-238 Kope still in use. FIG. 4430. It must be remarked that the data concerning the last rope are incomplete, as it was still in use when the paper was written. At Pribram,f where winding is carried on in perpendicular shafts, one of which has attained the enormous depth of 3642 feet, the ordinary crucible cast-steel, with a tensile strength of 120 kilos per sq. mm., was used up to the year 1885 ; since then they have employed wire of " patent crucible cast steel " or " extra " or " special crucible cast steel," with a tensile strength of 1 80 to 190 kilos per sq. mm. ; the results are most satisfactory, and the ropes, after having been in use for two and a half years, showed very little sign of wear, and not a single broken wire. The former ropes, made of ordinary cast steel, lasted on an average only 26 months. Winding-ropes are usually made with six strands and a central core of hemp, each strand being made up of seven wires (Fig. 443^). The core is sometimes made of wire ; for instance, if the rope has to work in a very hot shaft, or if it is used for haulage purposes with clips which require that the diameter should remain constant. In or- dinary ropes the "lay" of the strand is like that of hemp ropes ; that is to say, the reverse of the lay of the rope (Figs. 444 and 445). Lang has improved the method of manufacture by making the lay of the strand the same as the lay of the rope ; the wires are less sharply bent, and present a longer wearing surface. * Habermann, " Ueber die Drahtseilfabrikation in PHbram mit besonderer Riicksicht auf die Drahtseile fiir die Verticalf orderung. " Beilage z. Oest- Zeitschr. f. B.- u. H.- Wesen, 1891, p. 8. t Habermann "Anwendung verjiingter Forderseile aus gewohnlichem und aus Patent- oder Extra-Tiegelgussstahldraht bei den grossen Schacht- tiefen des Pfibramer Bergbaues." Oest. Zeitschr. f. . u. If.- Wesen, vol. xxxviii. 1890, pp. 403, 415, 432. 400 ORE AND STONE-MINING. FIGS. 444 and 445. FIGS. 446 and 447. The result is, that whilst the wires of an ordinary rope wear quickly on the crown of the bend and break (Fig. 445), Lang's rope, with its greater wearing surface, has a much longer life. Figs. 446 and 447 are taken from actual examples of Lang's rope before and after use. Haggle's patent Protector rope has a special covering destined to take the wear. Each strand has a wire wound round it spir- ally, which protects it from rubbing, and therefore a more flex- ible wire can be used than would be advis- able with an unpro- tected rope, Whilst an ordinary rope is weak- ened by the wear of its wires, the strength of the protected rope does not suffer from the gradual thinning of the covering. Messrs. Latch and Batchelor have lately introduced a "flattened strand "rope (Figs. 448, 449, and 450). The object of the new method of construction is to obtain an outer surface more nearly cylindrical than that of the ordinary rope (Fig. 443<0- The strands are oval in section, and this form is produced by " lay- ing " ordinary wires round a flat wire or a combination of wires. It is evident from the figures that the bearing surface of the rope is thus increased, or, in other words, that the liability of any individual wire to wear is lessened. It is asserted by the inventors that their rope has 150 per cent, greater wearing surface than Lang's or ordinary ropes. In designing the " locked coil wire rope," now made by Messrs. George Elliot & Co., the inventors departed entirely from the old traditions of manufacture. They considered, and very properly, FIG. 450. HOISTING OR WINDING. 401 FIG. 451. that when one is dealing with a material like steel- wire, which can be obtained of very great length, it is quite unnecessary to copy the methods suitable for the short fibres of hemp. These ropes are made of wires of different sections ; some of the wires are V-shaped, others more like the letter S, and the adjacent wires fit into one another like a set of spoons, the concave part of one wire receiving the convex part of the next. The rope is not composed of a series of strands, but of a series of concentric rings of shaped wires, and the separate wires form long spirals. By consulting Fig. 451, which represents one variety, it is evident that nearly the whole of the section of the rope is made up of useful material. There are scarcely any spaces such as exist between the wires and the strands of an ordinary rope, and consequently for any given section the locked coil variety of rope is stronger than a strand rope. It is very flexible and has a smooth uniform surface, which makes it look at a little distance like a solid bar of iron. No one wire of the outer ring is more exposed to wear than the other ; consequently there is not the danger of having broken wires, arising from the top of the crown being rubbed off by continued use (Fig. 445). Another advantage is the absence of any tendency to turn, whereas the ordinary rope with the spiral strands twists somewhat when passing over a pulley. In sinking a shaft with such a rope, the kibble spins round during its descent and ascent, involving a risk of accident, which is best avoided. However, strand ropes that will not twist are supplied by some makers. The disadvantage of the locked coil rope is that it cannot be spliced, but sockets can be used for connecting one length to another. Intermediate in character between the ordinary rope and the locked coil rope is the variety known as Laidler's patent " Sector wire rope." Each strand is cylindrical, and is composed of several wires in the form of sectors of a circle, and the strands are laid together to make the rope. Fathom for fathom, it is a little heavier than Lang's rope, but it is said to give a great deal of wear. Chains. Chains were largely used in ore-mining at one time. They have the advantage that they will coil round a small drum, and the further advantage that they will stand much rough usage, such as fell to their lot formerly in some {of the crooked shafts in Cornwall. But there 1 is the overwhelming dis- advantage that a chain is no stronger than its weakest link ; a-nd now that wire ropes have come into use in mines, winding with the chain is practically a thing of the past. 2 C 4O2 ORE AND STONE-MINING. Attachments. It is important to study the modes of connect- ing the rope to the receptacle by which the mineral is drawn up. In sinking by hand in Cornwall, FIG. 452. the hemp rope is attached to the bucket by a knot known as the " gooseneck," which is said never to slip, and which is easily and quickly made; but where the bucket is emptied without being de- tached, this latter point is of little importance. In Wales and the Isle of Man a spring hook (clevis) is preferred, such as shown in Fig. 452, the rope being put through an eye and made secure by a large knot. This method is convenient when it is necessary to detach the bucket, and move it away from the shaft before it is emptied. A third device is a spiral hook which will not allow the bucket to fall off in the operations FIG. 453. FIG. 455- FIG. 456. of raising and lower _ ing, whereas it can be readily taken off by the workman. With a wire rope it is necessary to form a loop of some kind, which can be attached to the load by a D- shaped link with a screw pin. There are several means of ef- fecting this purpose. The ropes sent from the makers are often supplied with an eye spliced in (Fig. 453*), that is to say, the end of the rope is turned round an eye and then spliced back so as to hold it firm. As there is not always a competent splicer at mines, methods of attachment have to be employed which are within the capa- FlG ' 454- city of an ordinary smith. Thus the end of the rope may be bent back over an eye * Copied, by permission, from Messrs. George Cradock & Co.'s figures. HOISTING OR WINDING. 403 and held in position by three clamps (Figs. 454 and 455),* or a socket may be riveted on (Fig. 456).* Figs. 457, 458 and 459 represent a socket made by Messrs. George Elliot & Co. for the locked coil rope and for ordinary round wire ropes. A, locked coil wire rope ; B, socket ; C, hollow conical plug ; I), wire bound or " served " round the rope ; E, ends of the wires of the rope turned back over the cone ; F, wire bound round them. After the end of the rope has been prepared in FIG. 460. FIG. 461. FIG. 457. FIG. 458. FIG. 459. SCALE 2 FEET i METRE this way and drawn into the socket, the rings G G G are driven down, and the fastening is complete. Figs. 460 and 46 1 explain the " capping," which has been adopted at some collieries near Bristol, since the failure of a riveted socket. A A, clamps for holding the rope, each with four bolts; B, cast-iron plate with a groove all round it in which the rope lies ; C, a large shackle attached to the iron plate by a pin E. A description of the method of splicing ropes will be found * Copied, by permission, from Messrs. George Craddock & Co. 's figures. 404 ORE AND STONE-MINING. in the catalogues of some of the well-known rope-makers, and need not be repeated here. Splicing is not always adopted for joining two parts of a wire rope; sometimes a socket is attached to each end, and the two sockets are then connected by a D-link with a screw pin. It should be remarked that it is often at or near the socket that the rope wears, and consequently it is advisable to remove the sockets at regular intervals, cut off a piece of the rope, and replace the socket where the rope is good and sound. I have hitherto been speaking of winding ropes of uniform section, but tapering ropes have advantages. Let us take the case of a wire rope which is hanging down a deep pit. The part of the rope at the bottom of the shaft has simply to support the cage or bucket and the load contained therein, whilst the part at the top must be strong enough to support not only the weight of the receptacle and its load, but also the weight of the rope below it. In other words, greater strength is required at one end of the rope than at the other, and on this account tapering ropes are sometimes employed. The advantage of employing such ropes is especially felt in the case of very deep shafts, such as those of the famous lead and silver mines of Pribram already alluded to. Three of the principal shafts have the following depths : Kaiser Franz Josef shaft Adalbert shaft . * Maria looo metres or 3281 feet. 1070 3510 1 1 10 3642 FIG. 462. The taper is produced by using successively wires of smaller section, and not by reducing their number. 3. RECEPTACLES. There are three kinds of .receptacles in which the load is raised in the shaft : (a) Buckets (kibbles), baskets or bags which are swinging loose in the shaft ; (b) buckets or boxes (skips, Cornwall) working between guides ; (c) cages carrying one or more waggons. (a) The buckets are made of wood, sheet iron, or sheet steel. Wooden kibbles are made of staves in the same way as a barrel, and are suitably strength- ened with bands of iron in order to resist the wear. A petroleum barrel cut down at one end may be easily converted into a kibble. Various forms are seen viz., round, elliptical, or square, and the sides are straight, or bulging in the middle. Fig. 462 represents a common form of sheet-iron kibble, made of hammered plates riveted together and closed at the bottom by a circular plate provided with a ring. 4-t the top is the so-called bow, HOISTING OR WINDING. 405 either a bar of round iron with a hook at each end and bent so as to form a loop in the middle, or else made thicker and provided with a hole, to which the rope or chain is attached. In perpendicular shafts, a lining of planks is often put in around the winding compartment, so that the kibble may glide up and down smoothly, without risk of catching against the sides. In inclined shafts the " foot wall " side is lined with boards (bed-planks) resting upon cross sleepers. Hard wood, such as oak or beech, will naturally last longer, and require fewer repairs than deal. In the Hartz, poles fixed lengthwise take the place of boards, which are customary in this country. Other receptacles used in winding are baskets, whence comes the name corf(Korb, German), bags made of hides used in Mexico, small wooden platforms suspended by chains from the four corners, and, lastly, nets, which are employed in Roumania. A word must be said about the actual loading and emptying of the kibble ; sometimes, as already mentioned, the kibble is filled at the working- place or from a shoot (pass, Cornwall), and is then conveyed on a trolley to the shaft, where it is hooked on to the rope and drawn up. More frequently the filler, standing in an enlarged part of the level (plat) where it joins the shaft, loads the kibble with a shovel ; in order to save time, two kibbles are often provided, one being filled while the other is making the journey to and from the surface. In this case it is necessary to have some kind of clevis, which will enable the kibble to be readily detached from the winding rope and quickly and securely fastened on again. On the arrival of the kibble at the surface, the lander seizes an eye or ring at the bottom (Fig 462) by a pair of tongs sus- pended to a chain, and then gives the signal for the rope to be lowered slightly. The kibble turns over because it is suspended from the bottom, and its contents are shot out into a tram- waggon placed ready to receive them. During the operation of discharg- ing the kibble, the mouth of the shaft should be covered by a hinged door, so as to prevent stones from falling down and injuring the filler in the plat. The inconveniences of this method of winding are considerable, especially in inclined and crooked shafts. Rapid hoisting is out of the question. Power is wasted in overcoming friction, and there is great wear and tear of the bed-planks and casing boards ; and, unless constant attention is paid to repairs, holes are worn in which the kibble catches, causing the rope to break. The fall of a kibble and its contents not only does much damage to the shaft, but is also a source of danger to the men. In some old shafts the friction must have been enormous, for deep grooves have been worn in hard rock by the constant rubbing of the chain. The aerial incline, known in Scotland as the " Blondin," is a 406 OEE AND STONE-MINING. convenient method of raising stone from open quarries, when it is necessary from time to time to alter the point at which load- ing takes place. A B (Fig. 463 *) is a strong upright post, held firmly in posi- tion by guy ropes, of which only one, C A, is shown. A D is a stout wire rope, fixed to the top of the post, and anchored at D on the opposite side of the quarry. It constitutes an aerial rail for two grooved pulleys contained in the travelling cradle E. The rope F, attached to the cradle, passes over the large pulley G, and thence to a horizontal winding-drum, not shown in the figure. The engine-house is at the very edge of the quany, and is so placed that the engine-man can look down to the bottom. The cradle E will run down from A to D by its own weight, and can be drawn up by winding the rope F upon its drum. A loop attached to E supports the large pulley H, and the hoisting rope I. This rope passes under the pulley K, over the pulley H, over a pulley immediately by the side of G, and thence to a drum precisely like that of F, and running upon the same shaft. L is a rectangular box, like the body of a waggon, which is loaded with stone at the bottom of the quarry, and hooked on to the four chains hanging from K ; it is then drawn up arid landed on to the truck M. I will suppose that the load has been hooked at the point N in the bottom of the quarry, vertically below L in its present position. The drum of I is thrown into gear by a clutch and the rope wound up. K is gradually raised, and when it ap- proaches H, the drum belonging to F is thrown into gear; the ropes F and I are now wound up at the same speed, until E is drawn close up to A, with its load hanging directly over M. Winding is stopped, brakes are put on, and the drum of I is disengaged by its clutch. By slackening the brake of I, while that of F is kept tight, the load can be lowered on to M, which is trammed away as required. An empty box is hooked on, K is wound up a little, till it approaches H, and then, throwing the drum of I out of gear, the engine-man lets both ropes run out under the control of their brakes. When E has reached its proper position, it is stopped by tightening the brake of the F drum ; K then descends vertically till L has reached the bottom of the quarry. It is evident that by properly arresting the descent of E, the box can be lowered so as to pick up a load at any point along the line O P, which is vertically below A D. If after a time it becomes more convenient to load elsewhere, the anchorage at D is shifted accordingly. At slate quarries in North Wales and Cornwall, the rope F is not used, and E is stopped by a clamp fastened at any desired point of the rope A D. The arrangement shown in Fig.. 463 introduced many years ago by Mr. Fyfe at granite quarries near * For the sake of making a clear diagram on a small page, Fig. 463 is not drawn to scale. HOISTING OR WINDING. FIG. 463. 407 4o8 ORE AND STONE-MINING. Aberbeen, is better, for it does away with the necessity of sending a man down the rope to adjust the clamp. A slightly different plan is in use at Easdale slate quarry in Argyllshire. The travelling cradle carries the usual hauling rope I, but in place of F there is attached to it an endless rope, which stretches across the quarry, and passes over suitable pulleys. So long as the endless rope is free to move, the cradle will run from A to D, but when the banksman stops its travel by a screw clamp, the load ascends or descends vertically. If the slope of the carrying rope fixed across the quarry is too small to allow the cradle E to run of itself, an endless rope, worked by a drum, is used for hauling it backwards or forwards as required. (b) Guided Buckets or Boxes. When winding in shafts it is best to employ guides, in order to keep the receptacle in one proper course, and prevent it from touching the sides. The guides may be chains, wire ropes, bars of wood or round iron, or, lastly, iron or steel rails. Chains are rarely met with ; the commonest method of guiding in perpendicular shafts is to hang two stout wire ropes from the top to the bottom of the pit, and to provide the winding receptacle with eyes which pass over them. They are kept taut by weights or screws. Wire-rope guides may be used even in the case of a kibble ; a cross-bar with two eyes is attached near the end of the winding rope ; though the kibble remains loose, it is so close to the cross- bar that it can swing but little. By fitting wire-rope guides of this kind to perpendicular shafts originally worked with the ordinary loose kibble, winding can be carried on with greater speed and safety, whilst the cost of making the alteration is com- paratively small. There is the further advantage that the shaft when provided with guides becomes available for raising and lowering the men. Some years ago Mr. William Galloway* introduced an ingenious method of apply- ing these wire-rope guides to a shaft in the course of sinking. He provides two wire-rope guides coiled upon two drums which are worked by a steam crane, either separately or together. The guide ropes (a a, Fig. 464) pass over two pulleys at the top of the shaft, parallel to the winding pulley, and are attached to a platform, which serves as a walling stage, and is raised and lowered as required. A hole in the middle affords a for the bucket (kibble, bowk, tioppef). * " Sinking Appliances at Llanbradach," Trans. /South Wales Inst. of ., vol. xvi., 1888, p. 113. FIG. 464. HOISTING OR WINDING. 409 FlG ' 465. As the shaft is deepened, the guide ropes are paid out from time to time, and in this manner it is only at the very bottom that the bucket is swinging loose. The guiding apparatus consists of a cross-bar having a round hole in the centre c, through which the winding rope passes. It has two legs with holes, b b, at top and bottom which receive the guides. This rider descends as the bucket is lowered, but when the legs meet with the walling stage their motion is arrested ; the kibble, however, can proceed further because the winding rope passes down through the central hole c. After passing below the stage the kibble is unguided, but the distance it has to travel is rarely more than 15 or 20 yards. Before starting on its upward journey, the kibble is brought properly into line with the rope and steadied, and on arriving at the stage, an india-rubber buffer, carried by an iron plate at the bottom of the rope, lifts up the rider ; the remainder of the ascent is per- formed without fear of the kibble swinging or catching. Mr. Galloway's latest walling stage has two floors, 10 feet 6 inches apart ; the lower one is a circular platform of timber fixed to a frame of angle-iron d 1 d? (Figs. 465 and 466), and made to fit the inside of the shaft as closely as possible. The part h is hinged, and can be raised by means of the chain, when passing the cross- beams (bunions) which support a ventilating pipe. The upper floor of the stage is similar to the lower one, except that it is somewhat smaller in diameter, and is not made to cover the hinged segment below. The two floors are held apart by four corner pieces of angle-iron, to which are attached four plates of sheet iron, forming together a frustrum of a pyramid, 5 feet 6 inches square at the top, and 6 feet 6 inches square at the bottom. The object of these plates is to prevent men who are standing upon the lower stage from falling into the central opening, and at the same time the upper floor constitutes a protecting roof over their heads. Men can climb from the lower to the upper platform by means of the ladder m which passes through a small man-hole in the iron covering plates. The two guide ropes which carry the stage are shown by letters n n'. This double stage is decidedly safer than the single platform originally employed by Mr. Galloway. -p IG 410 ORE AND STONE-MINING. Although primarily designed for sinking coal-pits, and most frequently applied for this purpose, this method of guiding was used with marked success in sinking a shaft at New Minera lead and zinc mine near Wrexham ; it was found that the great advantage of being able to wind with safety at a higher speed, fully repaid the expense of putting in the guides. In the Northwich mines, rock-salt is brought up in wooden buckets guided much in the same way, except that round iron bars are employed instead of ropes. Each length of rod has a socket at one end and a projecting pin at the other ; the pin of one rod fits into the socket of the next and is fastened by a, key driven through a slot. These guides are chosen in the special case of salt because they suffer less from rusting than those made of wire ropes, owing to the absence of interstices in which saline water would collect and corrode the iron. We next come to the box of rectangular or circular section (skip), made of sheet iron or sheet steel. It usually has a sloping bottom, and is provided with a hinged door for discharging its contents ; in some instances it is emptied by being turned over automatically on reaching the top of the shaft. The skip may be used in perpendicular, inclined, or crooked shafts. The guides or conductors are most commonly rectangular bars of wood, bolted to the end-pieces of the shaft and to the " dividings " in the manner shown by Fig. 257. If the shaft is perpendicular the skip may be guided by two U-shaped shoes of iron, which clasp the three sides of the con- ductor. If it is inclined the skip runs upon four wheels, as shown by Fig. 467. In an inclined shaft the conductors sometimes have rails, upon which the wheels of the skip run, in others the timber is not protected in any way. Some of the skips in Cornwall are made to hold as much as a ton and a half of tin-bearing rock. When winding is going on from any particular level, a stop, such as a strong bar of iron, is put across the shaft to arrest the skip ; the miner, standing in the plat, shovels the mineral into it, and gives the signal to have it drawn up as soon as it is filled. A better plan is to adopt the arrangement explained in Fig, 467, which will easily be understood. B is a strong plate working on a pivot which is put down to stop the skip ; C is a pivoted hood turned over the mouth of the skip so as to prevent stones from falling into the shaft, and when this is in its place the workman raises the door of a large bin or hopper, and allows part of its contents to run out. The hopper has been filled by tipping waggons from the line of rails in the level above. On reaching the surface a hinged sloping door is turned over the shaft, and the skip is lowered a little until it rests upon it ; the workman (lander) then knocks up the bolt retaining the door of the skip, and the contents fall out into the tram-waggon placed to receive them. The lander replaces the bolt, the skip is raised HOISTING OR WINDING. 411 slightly, the door pulled back, and the skip lowered once more into the shaft. The skip is sometimes tilted completely over instead of being emptied through a hinged door ; this arrangement is in use in some German mines, where the skip is made of wood and is guided on each side by^two pins or rollers running between two con- FIG. 467. ductors. On reaching the surface, the two lower pins are sup- ported and act as pivots, while the upper ones pass through openings in the front guides ; the skip turns upon the lower pins, is tipped over, and so emptied. Some very rapid work is done at De Beers mine* with a self- discharging skip, which shows that this method of hoisting must not be despised, even by those who are accustomed to the wind- ing of large quantities of coal from well equipped pits. * Second Annual Report of De Beers Consolidated Mines, Limited, for the year ended jsst March 1890, p. 14, plate 8. 412 ORE AND STONE-MINING. The skip (Figs. 468 and 469) runs upon four flanged wheels, and the two upper or front wheels are half the width or tread of the two back or lower ones. The winding rope is attached to two chains, which are fixed to the cross-bar of a loop or stirrup which can turn upon pins fixed to the sides. The skip runs upon steel FIG. 468. SCALE 2 METRES rails (46-!- Ibs. to the yard) laid upon what may be called con- ductors or longitudinal sleepers. At the bottom of the shaft there is an iron shoot, without any door, leading to the skip. During the descent of the skip, four end-tipping waggons are brought into position round the shoot, the catches of the flap-doors are loosened, and the doors held closed by two labourers. As soon as it is seen to pass, the trucks are tipped, and the signal is given FIG. 469. to wind up. The skips are filled so quickly at the bottom, that the man at the top sometimes receives this signal before he has completely stopped his engine. When the skip B (Fig. 442), ascending the incline shaft A, reaches the point C, its rear wheels are caught up by a special broad road D, the gauge of which is wide enough to let the front wheels pass through. Whilst the front wheels are travelling on the rails E, the rear wheels continue to mount, and consequently the skip turns over and discharges its contents into the bin F. HOISTING OR WINDING. H is a waggon waiting to be filled, and G a counterpoise to the discharge door. On lowering the rope, the skip falls back into its original position and descends the shaft. The inclination of the shaft is 56 20' from the horizontal. The skip-ways are 5 feet wide and 4^ feet high, and the gauge of the railway is 3 feet 1 1 inches. There are two tracks, which converge at the bottom into one, so that both skips can be filled from the same shoot. A skip holds 64 cubic feet, or 4 loads, weighing in all 2 tons 17 cwt., or 2903 kilos. The best single day's work, in two shifts of 10 to icj hours each, was 6222 loads, or 4444 statute tons. The depth of the FIG. 470. FIG. 471, FIG. 472. 6 Fee.* shaft is 840 feet along the incline, or 700 vertical; the speed in the shaft is 840 feet in 30 seconds, and the time occupied in tipping and reversing about 6 seconds. This rate of working has been carried on for an hour at a time, 5 skips being discharged every three minutes that is to say, 285 statute tons per hour. Fig. 470 shows the details of double-lipped mouth of the shoot at the bottom of the great bin (F, Fig. 442), which receives the blue ground brought up from underground. The door A is con- trolled by the cam worked by the lever B, and the door C is upon the same axis as the lever D. The discharge is thus easily regulated, and waggons can be filled with great rapidity. The arrangement for inclines shown in Figs. 471 and 472 differs slightly from that adopted at De Beers. A waggon A, TT "NT T T- v-, J 414 ORE AND STONE-MINING. running upon four wheels B, is drawn up by the bow F, and the rope J. The bow is attached to the axles of the hind wheels, FIG. 473. and in front it carries the door I of the waggon. K repre- sents the railway at the top of the incline, and P an additional HOISTING OR WINDING. FIG. 474. outer line of rails at a steeper angle. When the waggon in its upward course reaches the point L, the rails P pick up the small outer wheels C on the rear axle. These travel up at the steeper angle whilst the front wheels follow the rails K. Conse- quently, the waggon is tilted, and, as the front end or door is attached to the bow, the contents are shot out. The stud G keeps the waggon in position if it is drawn up too far. On lowering the rope, the waggon rights itself and descends properly. Automatic tipping, or dump- ing, is also possible in per- pendicular shafts. The "Kock" shaft at De Beers is 20 feet by 6 feet, divided into four com- partments which are each 4 feet 4 inches by 6 feet within the timber : one for the pumps and ladder-way, another for a cage, and two for the skips. Figs. 441, 473 and 474* repre- sent the arrangements adopted. A is the skip, a box of rect- angular section, 5 feet by 3 feet at the top and 6 feet deep; B, frame which clasps the wooden guide on three sides ; C, hinge by which the skip is attached to the frame ; D, hooked bar which catches upon the pin E ; F, guide which presses the little roller D 1 and so unhooks the catch ; G, roller which travels along the guide- rails H for causing the tipping ; I, nose upon the skip, which is temporarily caught upon the roller J during the tipping ; K, inclined guide for the roller G; L, crosspiece attached firmly to the side-frames B, with a hole M, through which slides the strong square bar N; 0, toothed segments forming the safety catches ; P, plate attached by chains to the axles of the catches ; Q, Ormerod's detaching link ; R, shackle which is released ; S, rope-socket ; T, wire-rope ; U (Figs. 441 and 475), bell-mouthed cylinder for causing the * From drawings kindly supplied by the makers, The Grange Iron Co., Limited, of Durham. 416 ORE AND STONE-MINING. detaching link to come into action; V, chain-pulley of safety catch ; W, strong spring, like a huge watch-spring. After this explanation of the parts, the manner in which the tipping or dumping is performed will be easily understood. As long as the hook D is horizontal, the skip is prevented from falling forwards, but on arriving at the top of the shaft, its roller D 1 is drawn up against the guide F and the catch is released. By this time the roller G has reached the guide-rails H, and whilst the frame B follows a vertical path upwards, the box itself, held back by G, turns upon the hinge C until it assumes the position shown by the dotted lines, with the nose I resting upon the roller J. As the frame ascends still further, the roller G is drawn up along the inclined guide K, the bottom of the box is tilted up, and its contents are discharged into the bin or hopper. On lowering the rope the frame descends, the skip drops back into its original normal position and is clamped automatically by the bar D. Whilst the plate P is held up against the cross-bar L, the chains of the safety catches O are drawn tight, and the teeth are held clear of the wooden guides in the position shown. The moment the rope breaks, the chains become slack, the springs are then free to uncoil slightly and they force FIG. 475. the teeth into the wooden guides. If, instead of a breakage of the rope, there is an overwind, the detaching link Q is drawn into the bell-mouthed cylinder U (Fig. 475), the lower part of the link is squeezed, as it is too wide to pass through, and is thereby caused to throw out projecting shoulders which rest upon the top of U and hold up the skip. By the same action the shackle K is set free and goes with the rope over ^^^^^__ M , the pulley. A self -discharging skip, suitable for vertical, inclined, or crooked shafts, is that of Messrs Kitto, Paul and Nancarrow, used at Frongoch mine in Cardiganshire.* (Figs. 476 to 480). The skip is the usual box A, made of sheet iron or sheet steel, with four wheels B B, running on the vertical wooden conductors, H H, and prevented from leaving them by the back guide D (Figs. 477 and 479) at or near the bottom. The bow or loop E, instead of being attached to the top of the skip, reaches down, and takes hold of the axles of the bottom wheels ; in its usual position (Fig. 478) it rests against the axles of the upper wheels, and holds the skip upright. * C. Le Neve Foster, " Some Mining Notes in 1887," Trans. Min. Assoc. and Inst. of Cornwall, vol. ii. p. 140. HOISTING OR WINDING. At the surface, each of the two ordinary conductors bends round and terminates in a horizontal piece, as shown in Fig. 480, whilst a front guide H' is added on each side. When the skip comes up, these front guides press upon the top wheels, and turn them on to the flat ends of the ordinary conductors. Deep grooves cut in the conductors at I enable the back guide D to pass through, and as the rope continues to be drawn up the bottom end of the skip is raised and its contents are tipped or " dumped " into a large bin or pass, from which the ore can be drawn away at pleasure. If the engine-man does not stop quite soon enough, the skip is simply drawn up a little way, resting upon the front guide, and the stop or stud F prevents it from assuming a wrong position. FIG. 476. FIG. 478. FIG. 480. FIG. 477. FIG. 479- Scale ^ In..l2 P ? ? 3 * 5 Fee* As soon as the engine-man begins to lower, the top wheels fall upon the flat ends of the conductors, and, turning upon them, the tail end of the skip drops, the back guide passes through the slot I, and the skip, resuming its upright position, descends the shaft. The great advantage of this and other self -tipping arrange- ments is the saving of time and labour. The time occupied in lowering an ordinary skip on to the shaft-door, in knocking up a bolt so as to discharge its contents, in closing it again, and in raising the skip so that the shaft-door may be thrown back, is all saved, and the services of the lander are dispensed with. (c) Cage. The system of winding adopted almost universally at collieries is that of using cages ; this method is likewise very general in mining seams of ore, and is not uncommon in the case of veins and masses. 2 D 418 ORE AND STONE-MINING. The cage, as its name implies, is a more or less open receptacle, which receives the waggon used for underground transport, and conveys it to the surface. Figs. 481 and 482 represent the light and simple cage used in the mines on the Comstock lode : * it is a mere timber platform 5 feet by 4 feet, resting on iron bars p and supported by iron rods on each side. It is provided with a sheet-iron bonnet to protect the men inside from anything falling down the shaft, and also with safety catches, which come into play if the rope breaks. FIG. 482. The hand levers k k at the ends of the cage, raise up blocks which keep the tram-waggon in its place during the ascent or descent ; g g are the guides for the ends of the cross-bar b c, the bar working the teeth t t by levers ; / shoe or ear embracing the guide- rod, or conductor, in the shaft ; r, the lifting bar ; s, a strong spring which comes into operation if the rope breaks. This kind of cage looks somewhat bare to European eyes, and it is usual, on this side of the Atlantic, to make the sides less open than shown in Fig. 482. The dimensions of the cage are limited by the size Sf the shaft; but where it is desired to raise a larger quantity of mineral than * J. H. Hague, " Mining Industry," Eep. U. S. Geol. Expl. o/ 4 oth Parallel, vol. iii., plate vii., p. 119. HOISTING OK WINDING. 419 can be contained in one waggon, or in two placed side by side, the carrying capacity may be increased by constructing the cage with two or more platforms, technically called decks. As a rule, the full waggon is drawn out of the cage at the top of the shaft, and is trammed to some convenient place where it is tipped ; of late years the ingenuity of American inventors has led them to introduce methods of tipping the waggon automatically on reaching the surface, without its leaving the cage, in order to save time in winding. Russell and Parson's automatic dump- ing cage, said to be doing good work in the United States, has its platform movable upon an axle underneath, which allows it to be tilted on one side or the other. The cage has the usual shoes at the top and bottom, which cover 5^ inches of the wooden guides or conductors ; the tilting platform has its own two separate shoes, which clasp only 2\ inches of the guides. Whilst the cage is in the shaft, the platform is held in a horizontal position by its shoes running upon the guides. At the surface the wooden con- ductors are cut away for a depth of 2|- inches, so that, although the cage itself is guided, the small shoes are free to move side- ways and permit the tilting, when the platform touches a properly arranged stop. The flap-door of the waggon is released automati- cally at the same time, and the mineral is shot out into a large bin at the pit-top. 4. OTHER APPLIANCES Keps. On arriving at the surface the cage is usually lifted a little higher than the landing platform, and supports of some kind (heps) are brought under- neath it, so as to hold it up while the full waggon is drawn off and an empty waggon pushed on. The cage is then slightly raised, the supports (heps) are drawn back by a lever, and the descent begins. Several methods of simplifying the work have been devised, and among them is that of Messrs. Haniel and Lueg,* which has been found to act satisfactorily at the well-known Mansfeld copper mines. The kep a, which is made of steel (Figs. 483 to 485), has an in- clined face 5, and is provided with two slots, one horizontal and the other d inclined. The former acts as a guide to the block e, which is loose upon the axle f\ f is supported by the bearing g. The pin i, surrounded by a steel roller h, can slide in the slot d ; it connects the two levers k, one on each side of the kep , which are keyed to the axley*. These are kept in a horizontal position by a lever m provided with a spring catch. The steel shoes 1 1, attached to the bottom of the frame of the cage, will, if desired, rest upon the inclined faces b b of the keps. As long as the lever m is held in the position shown in Fig. 483, the keps cannot open under the pressure of the load, because the pin i prevents any motion in a horizontal direction. * The explanation and figures are borrowed from their description. 420 ORE AND STONE-MINING. When the lever m is being drawn back, as shown by Fig. 484, the pin i with its roller h is forced up the slot and the keps slide back on the bed-plate of the bearing g, until the cage has room enough to pass ; when it has gone down, the keps are returned to their original position FIG. 483. (Fig. 483) by moving the lever m forwards. The ascending cage opens the keps by itself, for the shoes 1 1 turn them upwards (Fig. 485), the lower part of the slot d being concentric to the spindle /. As soon as the cage has passed, they fall back into their normal posi- tion (Fig. 483), and the cage is lowered so as to rest upon them. The advantage claimed for keps of this kind are : Eco- nomy of steam and saving of time, besides the increased duration of the rope, which no longer has to under- go the strain of start- ing the cage upwards before it begins its downward journey. Signals. It is ne- cessary to have some means of communi- cation between the various on-setting places and the top of the shaft, so that the man at the bottom (on-setter, hooker-on) may be able to inform the man at the top (banksman, lander, or engine-man), when he is ready for the cage, skip, or kibble to be drawn up. In shallow workings shouting is sufficient ; when the pit becomes deeper a speaking-tube is sometimes put in, but the commonest method of signalling is by a cord made of seven galvanised wires, and varying in diameter from J to f inch. The object of the zinc coating on the wire is of course to prevent or delay rusting, which would otherwise go on rapidly in the damp atmosphere of many shafts. HOISTING OR WINDING. 421 The cord is carried round curves and corners by means of cranks similar to those used for house-bells, only larger and stronger, and when it is pulled by a lever at the bottom, it moves a hammer which strikes a bell at the surface. Instead of a bell,. a loose plate of iron is sometimes used, which makes a very audible signal ; the number of strokes indicates what is required. The usual code is as follows : 1 stroke means " Stop." 2 strokes mean "Wind up." 3 "Lower." Yarious signals can be arranged to indicate when men are to be drawn up in place of the ordinary load of mineral ; and sometimes a visible signal is combined with an audible one, a hand upon a dial recording the number of times the bell has been sounded. When persons are raised and lowered, there must also be means of signalling from the surface to the on-setting places ; the object is to assure the men at the bottom that their signal has been correctly received and understood. Electricity can also be called to the aid of the miner, and electric bells are common. Telephones * of various descriptions are some- times used, but for the ordinary purposes of winding, the simple signal given by a bell is quite sufficient. In addition to the signal for starting and stopping, there is an indicator which shows the engine-man the exact position of the load in the shaft. The indicator may be a dial with a hand, worked by gearing connected with the crank-shaft of the winding-engine \ the various stopping places are denoted in the same way as the hours on the face of a clock, the gearing being arranged so that the hand does not travel more than the entire circumference during the longest journey of the load. Another form of indicator is an upright standard, 6 or 8 feet in height, with a slot, in which a pointer moves up and down. It is worked by a cord, or a steel band connected to the crank-shaft. The standard has horizontal lines, numbered according to the depths of the different stopping-places ; the gearing is contrived &o that when the finger points to one of these lines, the cage is at the corresponding stopping-place. The arrival of the load near the surface may be brought to the engine-man's notice in several ways : by a mark on the rope, by the pointer on the indicator, and by some audible signal, worked automatically by the winding-engine. A travelling hammer may be carried along by a screw, connected by gearing * The first time the telephone was used for 1 ransmitting speech from underground workings of a mine was in September 1877, when Mr. Arthur Le Neve Foster made some experiments at West Wheal Eliza, in Corn- wall. 422 ORE AND STONE-MINING. with the crank-shaft, and eventually brought up against a bell ';. it works in the same manner as the device upon typewriters which warns the operator that he is coming to the end of a line. Instead of striking a bell, the traveller may open a cock and start a steam whistle. 5. SAFETY APPLIANCES Overwinding, In rapid winding with large drums, a slight inadvertence on the part of the engine-man may cause the load to be drawn up against the pulley, and this is what is commonly known as over-winding. In the case of a drum 18 feet in diameter, a single revolution raises the rope 56^ feet; therefore, if even half a revolution is allowed beyond the proper number, an accident will ensue, unless the pulley frame gives a margin of nearly 30 feet. There are various contrivances for preventing disasters of this FIG. 486. FIG. 487. kind ; one method consists in interposing between the rope and the cage a special appliance, called a detaching hook, which will- sever the connection between them, allow the former to be wound up, and at the same time hold up the latter safely without damage to the load or persons inside. Some well-known detaching hooks are those of King and Humble, Walker, and Ormerod (Fig. 475). King and Humble's consists of an outer framework of two cheeks or sides, containing two inner plates which can move about a central bolt b (Fig. 486). Each plate has a wing a, projecting, beyond the framework. When in use the two plates are pre- vented from coming apart by a small pin or rivet, c. If the cage attached to e is wound beyond a certain height, the detaching hook is drawn into a round hole in a strong iron plate (Fig. 487), and when the projecting wings, a a, strike against this plate, they are forced to move inwards, the HOISTING OR WINDING. 423 rivet is cut, the shackle d at the end of the rope is set free, and two catches ff are thrown out; these drop upon the plate and hold the cage firmly suspended. Walker's detaching and suspending hook is like a pair of tongs, which hold the shackle at the end of the rope ; the legs of the tongs are bent out, and if they are brought together the tongs open. FIG. 489. FIG. 488. In Figs. 488, 489 and 490, L is the end of the winding rope, and A the shackle attached to it by the pin P. D D are the two jaws of the tongs, and F F are projecting hooks. E is the centre pin about which the jaws can move, and H an annular clamp which prevents the jaws from opening, as long as it is kept up by the two supporting pins I I. The cage or skip is hung on to the link B, and the weight of the load acting upon the two legs of the tongs tends to bring them together and open the jaws D D, When winding is going on properly, the jaws are kept together 424 ORE AND STONE-MINING. FIG. 490. by the clamp, and the load remains firmly attached to the rope ; but if it is raised too high the detaching hook enters the strong ring C, through which it can pass freely until the flanges K K of the clamp H strike against it. The pins I I are sheared off and the clamp drops ; but as soon as the hooks F F have passed through the ring, the jaws D D are drawn open by the weight of the load, the shackle is thus released and the hooks catch on the top of the ring C. As an 'addi- tional precaution there is a projecting rim at O, to catch the hooks if by some chance they should fail to act at the top. Stopping Gear. The dis- engaging appliances just de- scribed are designed with a view of correcting the effects of an overwind, by preventing the ascending cage from being dashed against the pulley, arid then possibly falling down the shaft. But they in no way protect the descend- ing cage from bumping on the bottom ; even if they did, the old motto still holds good that " prevention is better than cure," especially as detaching hooks have been known to fail. Engineers have therefore been anxious to obtain some means of automatically stop- ping the cage before it is raised too far, and many appliances for this purpose have been invented. Three which were exhibited at the Paris Exhibition of 1889 deserve special mention, as they are in regular use at large and important mines viz., the automatic speed-checkers and stopping- gears of Reumaux, Yilliers, and Wery.* M. Reumaux lays down * Pamphlets issued by the Mining Companies at the Exhibition, and Bevue Universelle des Mines et de la Mttallurgie. 3 Serie, vol. xix., 1892 pp. 949-956, and plates. HOISTING OR WINDING. 425 the principle that too much confidence must not be placed in an appliance which is only occasionally called into action ; and his self- acting speed-checker conies into play at every wind. When the cage in its ascent passes a point 30 m. below the surface, a tappet upon the revolving indicator lifts a valve, and so puts one end of a piston valve into communication with the atmosphere ; as steam or compressed air is pressing upon the other end, the valve moves and shuts off steam from the engine almost completely. The same release of pressure causes another valve to rise and let steam into the cylinder working the brake. If the engine-man, after turning on steam again, is again inattentive and allows the cage to be drawn up 2 feet above the landing, a second tappet upon the indicator once more causes the steam to be shut off; and a third tappet, by opening an exhaust passage, makes another valve drop and turn steam on to the cylinder controlling the brake. M. Reuinaux's appliance is attached to all the winding machines used at the extensive Lens collieries, whether they are worked by steam or compressed air. Villiers' apparatus is somewhat complicated, and cannot be properly understood without a figure. Suffice it to say that a nut travelling upon a screw sets gearing in motion and so actuates a friction clutch ; this brings into play a regulator which opens a valve and lets out the compressed air from under a piston holding up a weight. The weight in dropping shuts off steam and puts on the brake. A second part of the apparatus, working in a different manner, produces like effects ; and, lastly, if the cage is wound up a certain distance above the landing, it strikes a catch which releases another counterpoise, the descent of which also causes the brake to act. With Wery's contrivance the connection between the winding drum and the checking apparatus is again effected by gearing and levers instead of fluid pressure. When the cage has reached a certain point near the surface, a nut travelling upon a screw lifts a rod carrying a pawl, which rests upon the teeth of a wheel turning round by clockwork. If the pawl rises more quickly than the wheel revolves, it lifts it, and by means of levers brings the steam-brake into action ; the speed of winding is thus diminished. The clockwork is so regulated that the brake is not made to act unless the speed is excessive. To prevent danger from a slow overwind, a second rod acts in any case and turns steam on to the brake cylinder if the cage is drawn up too high. Bertram* and Cobboldf have invented automatic stopping appliances which depend upon the action of a ball governor, * " On Overwinding and its Prevention," Trans. Fed. Inst. M.E., vol. i., 1890, p. 55. f "A Patent Apparatus, Indicator and Valves for the Prevention of Overwinding at Mines." Ibid., p. 61. 426 ORE AND STONE-MINING. connected by gearing with the main driving shaft of the winding drum. Paschke and Kastner's apparatus, used at many mines in the Freiberg district, is spoken of favourably. It automatically shuts off steam and puts on the brake, not only when the cage is being drawn up too high, but also when the speed is excessive. Safety Catches. Much ingenuity has been displayed by various inventors during the last fifty years, with the object of providing some form of catch which will come into play if the rope breaks, grip the guides or conductors, and prevent the cage or skip from falling down the shaft. Many of them are actuated by a spring, and one form has already been figured in describing the cage used on the Comstock lode (Figs. 481 and 482). While the load is hanging from the rope, the spring s s is drawn into the position shown by the dotted lines by the lifting bar r, the eye of which is figured in its two positions. The bar c is drawn up at the same time, and the teeth t t are held apart and kept clear of the guide. If the rope breaks, the spring forces down the bar b and with it c ; the teeth jam into the wooden conductor, and the cage is arrested and held firmly. The safety catch used for the De Beers skip (Fig. 473) likewise depends upon the action of springs. An objection often urged against safety catches is that they occasionally come into play when not wanted, and that owing to rust and disuse they get out of order, and sometimes fail to act at the proper moment ; for these reasons they are less popular on this side of the Channel than on the Continent. Many engineers, rather than trust to contrivances which may possibly fail under the conditions met with in mines, are more inclined to put their faith in the following precautions : 1. Insuring an excellent quality of rope, by going to a maker of good repute and paying a fair price. 2. Frequent minute examination of the rope. 3. Testing p;eces of the rope at regular intervals. 4. Protection of the rope from the action of the atmosphere or acidulous water in the mine by a suitable grease. 5. Cutting off the end of the rope where it is attached to the cage and re-making the attachment at regular intervals. 6. Discarding the rope after it has been in use a certain fixed time, even if it is apparently sound as far as outward exam- ination can show. The same feeling seems to have existed among the members of the Royal Commission upon Accidents in Mines,* for they say, " We have, however, examined several varieties of the safety cages in * Final Report of Her Majesty's Commissioners appointed to inquire into Accidents in Mines, p. 109. London, 1886. HOISTING OR WINDING 427 use, as well as those exhibited at successive Internationa] Exhibi- tions, and we have considered a large number recently described and figured in an elaborate paper by Herr Selbach,* and we are unable to come to the conclusion that any one of them is a trust- worthy safeguard against accidents." This opinion does not settle the question ; for, on the other hand, I may refer to the con- clusions which Menzel f draws from the study of carefully pre- pared official statistics. Though far from asserting that existing safety catches are perfect, he shows that on the whole they did useful work during the seven years 1884-1890 in the coal and ore mines of Saxony, and he considers that they should be applied to all cages used for winding men. Springs. The rope suffers the greatest strain at the com- mencement of the ascent of the cage. There is always a little slack rope, which is taken up as the winding begins, and this leads to the danger of a sudden strain being put upon the rope every time that it begins to lift the cage, especially in cases where winding is being carried on rapidly. In order to spare the rope from a shock of this kind and cause it to take the weight gradually, a steel or india-rubber spring may be interposed between the cage and the rope, arranged in such a fashion that the first action of the pull is merely to compress it; finally, when the compression has reached a certain stage the cage will be lifted. The bearings of winding pulleys are sometimes supported by springs with a similar object in view. Testing Ropes. The Commentry Fourchambault Mining Company keep a useful record of the state of their winding ropes by testing them at regular intervals. Once in every six months a piece of rope about 9 feet long is cut off and sent to a powerful testing machine, called the antheximeter, capable of breaking a new wire rope more than 2 inches in diameter. The machine registers upon paper not only the force required to break the rope, but also its elongation previous to rupture. By comparing the results obtained in this way, the gradual deterioration of the rope from wear can be followed with great precision.:}: In the mines of the Dortmund district, no winding-rope can be used for raising and lowering men until it has been carefully tested in a manner prescribed by the Government authorities. A piece of the rope one metre in length is cut off, and the tensile strength and the flexibility of each wire are determined, with the exception of wires forming cores. Pneumatic Hoisting. The most novel hoisting apparatus * Zeitschr. fur das B.- H.- und /&- Wesen, vol. xxviii. 1880. B. Abhartd- lungen, p. I. t "Die in den Jahren 1884-1890, beim sachsischen Bergbau vorge- kommenen Briiche von Forderseilen, Schurzketten und dergleichen." Jalirb.f. d. B.- u. H.- Wesen i.K. Sachsen, 1891, p. 39. Comptes Bendus Mensuels, Soc. Ind. Min. 1891, p. 257. OF THE UNIVERSITY 428 ORE AND STONE-MINING. is that of M. Blanchet, which was regularly at work in the Hottinguer shaft at Epinac in France for some years. M. Blanchet fixed in the shaft a large pipe with a piston, from which was suspended a cage carrying waggons. By exhausting the air above the piston the load was gradually forced up by the atmo- spheric pressure below it. The Hottinguer shaft is 660 yards deep, and the pipe was 5 feet 3 inches in diameter, made up of a succession of cylinders of sheet-iron about T \ inch thick and 4 feet 4 inches high, joined by flanges and bolts. The 485 rings composing the long pipe weighed altogether 418 statue tons. The cage had nine decks, and arrangements were made for unloading three at a time ; each waggon held half a ton, so that the total useful load was 4^ tons. The speed of hoisting was 20 feet per second. If two hoisting pipes are connected, the dead weights may be made to balance each other, and the power required is simply that which is necessary to overcome the weight of the useful load. All the men preferred the pneumatic hoist to the ordinary cage for descending and ascending the mine, and were regularly lowered and raised by it. The advantages claimed by M. Blanchet for this system are (i) the possibility of hoisting from depths at which rope- winding would no longer be practicable ; (2) getting rid of the costly ropes and dangers connected with rope-winding; (3) better utilisation of the engine power; (4) improvement of the ventilation and diminution of the amount of fire-damp. At the present time Blanchet 's apparatus is no longer employed, but the disuse of the pneumatic method is in no way due to any difficulty in making it work satisfactorily.* * Nougarede, "Etude historique sur le puits Hottinguer des Mines d'Epinac," Bull. Soc. 2nd. Min. 3 e Serie, vol. vii., 1893, p. 563. ( 429 ) CHAPTER IX. DRAINAGE. Surface drainage Dams Drainage tunnels Siphons Raising water by winding machinery Pumps worked by engines at the surface Rittinger pump Counterbalances Bochkoltz's regenerator Rossig- neux's contrivance Catches Pumps worked by engines placed below ground " Duty " " Slip " Co-operative pumping. THE mineral having been raised to the surface, the task of the miner might appear to be at an end ; but this is not the case, for it is further necessary that he should keep his mine free from water and foul air. These two indispensable operations of drain- ing and ventilating require special appliances, which often add considerably to the general cost of mining. Surface Water. As far as possible the miner should endeavour to prevent the entry of water both at the surface and under- ground, and so escape the unnecessary expense of pumping it up. In some instances a good deal can be done in this direction ; for it has been abundantly proved, in many cases, that the bulk of the water with which the miner is burdened is merely the result of the percolation of the rain falling in the district. The effect even of a prolonged rainfall is not usually felt at once, for it takes time for the water to find its way through minute cracks and crevices in the ground and reach the workings. In lime- stone districts, however, the rain may find large channels eaten out by atmospheric agencies, and affect mines at a depth of a couple of hundred yards within twenty-four hours after it has fallen. It often happens that the mineral was quarried near the surface before underground mining was resorted to, and in that case there is always the danger of the old open pits forming a sink, so to say, which will collect water from the neighbourhood and let a considerable quantity percolate into the workings. To avoid such an objectionable state of things, the surface must be drained ; special care is imperative where the ground is cracked by sub- sidences, and the neighbouring streams should be examined and the water carried along in launders or other safer channels, if their beds cannot be made stanch by filling the fissures with concrete. 43 ORE AND STONE-MINING. When working under the sea or a river, a rich lode must not tempt the miner to carry on his work too far. At Wheal Cock, near St. Just in Cornwall, the miners working in some overhand stopes actually bored more than one hole through to the sea- bottom. They were well aware of the proximity of the ocean, for they could hear the boulders crashing against each other in stormy weather, and they had wooden plugs ready, which they drove into the holes when they actually tapped sea water. But it was a dangerous experiment, and though in this case the rocks are so hard and compact that the amount of percolation is small, a narrow wall only four feet thick between the sea and the workings cannot be left without fear of trouble and danger from water above. Dams. In addition to preventing the access of water from the surface, it is advisable to cut off underground inflows as far as practicable. In the chapter upon supporting ground, imperme- able linings of shafts and levels have been described, and where water can be shut out by tubbing or by coffering, the mine-owner is saved the constant expense of pumping; indeed, he is sometimes thus enabled to work deposits which he would not be able to reach if he had to fight against the enormous streams issuing from certain strata. Water from adjacent abandoned workings is shut out by dams that is to say, artificial stoppings placed in levels or shafts. They may be made of timber, brickwork, masonry or concrete, and, when intended for temporary purposes, of iron. In erecting a dam the first consideration is the choice of a suitable place, for it is useless to take the trouble to put in a stanch stopping unless the ground is firm enough to support it, and free enough from cracks to prevent the water behind it from finding its way round to the front. If the ground is thoroughly strong, a dam may be put in by cutting a recess in the sides of the level, as represented by Fig. 491,* and stopping the water back by a wall made of horizontal balks of timber. Oak is usually chosen for the purpose. Before the timber is put in, the rock is very carefully dressed until the surface is perfectly smooth, and ready to receive a similar surface of wood. Each balk is wedged up against the side just in the same way as a wedging curb, and the joints between the separate balks are caulked. * Gallon, Lectures on Mining, vol. ii., plate Ixxvi. DRAINAGE. 43 1 For heavier pressures the spherical dam is available; it is constructed of wooden logs placed longitudinally and wedged up very tightly. A wooden dam of this kind has the advantage that it will yield a little if there are movements of the ground, whereas a dam constructed of bricks might become cracked and leak so badly as to be almost useless; the wooden dam is also more easily repaired. Oak, pine, and fir are all employed for making dams ; the two latter are sometimes preferred to the former, because they are more easily wedged. The following account of a spherical dam is based upon a description written by Gatzschmann * (Figs. 492 to 495). FIG. 492. FIG. 493. A nail is fixed upon a cross-piece in the middle of the level, about 23 feet (7 m.) from the proposed outer face of the dam, and the sides of the level are trimmed smooth with the greatest care along planes which would intersect in this point as a centre. Pieces of timber are cut in the form of truncated pyramids, the four faces of which converge to a centre agreeing with that chosen underground; they are fitted together at the surface, with the horizontal joints arranged along the lines of the same great circles of the sphere and the vertical joints alternating. When the logs have been duly fitted, the work of putting them in is begun. Tarred canvas is placed upon the floor of the level and the first row of * Jahrbuchfur den Berg- und Hutten- Mann auf das Jalir 1841^ Freiberg. Combes, Traite del 'Exploitation des Mines. Paris, 1884, vol. ii., page 721, and plates. 432 ORE AND STONE-MINING. pieces laid down ; the last piece acts as a keystone and is driven in with a sledge. One of the pieces of the second layer has a hole bored through it so as to let off any water during the progress of the work. When the middle of the dam is reached, a flanged cast- iron pipe is put in as a man-hole, and the other rows are built up to the roof, which has been covered with tarred canvas : a hole is bored through one of the pieces of the uppermost row but one and fur- nished with a bent pipe, which serves to carry off the air at the top when the dam is finally closed. The joints between the logs are made watertight by driving in wedges around them obliquely ; the first wedges are of pine, the next are of hard wood, and the final set are of iron. A coating of cement, made of cart-grease, tar FIG. 494. 495. FIG. and slacked lime, completes the outer face of the dam. The miners then close the water-hole with a plug made of beech, and after retiring through the man-hole, draw into it a huge wooden stopper. The water is allowed to rise, and in due course some passes out by the air pipe ; the air-hole is then plugged, and the inside face of the dam is wedged up in the same manner as the outside. When exposed to considerable pressure a spherical dam of this kind is found to slide inwards a little. One which was put in at Churprinz Mine, Freiberg, shifted 19 J inches (0.50 m.) in the first fourteen hours after it had been closed, and 23! inches altogether in the first ten days; after that the motion was exceedingly slow, in fact, almost imperceptible ; but it did not absolutely cease for several years. Fig. 496* is a dam in an abandoned shaft, intended to shut * Gallon, Lectures on Mining, vol. ii., plate Ixxvi., fig. 409. DRAINAGE. 433 FIG. 496. off any possible influx of water into the adjacent workings in case the tubbing should fail. It consists of a strong arch of masonry, covered by a thick layer of clay and a pavement of stones. The clay will keep the dam stanch even if the masonry becomes slightly cracked from movements of the ground, and the object of the stone pavement is to prevent the clay from being washed away suddenly in the event of a large crack being formed. The vertical pipe serves to carry down the water during the erection of the dam. A temporary dam is some- times required close to a shaft, in order to keep back the water of the mine, and pre- vent it from drowning the pumps while they are being repaired. A strong and tightly-fitting hinged door may suffice for the purpose; in the Furness district the door-frame is set in a very massive structure of concrete, brickwork and steel rails. A large pipe is put in at the bottom and fitted with a good valve, which enables the water to be let out gradually when the pumps are once more ready for work. In spite of all precautions o the miner generally has to contend with water which percolates into the workings. Four methods of getting rid of it are available viz., drainage tunnels, siphons, winding machinery and pumps. DRAINAGE TUNNELS. An adit, day-level, or sough, is a nearly horizontal tunnel with one end opening at the surface, allowing the water to drain away naturally. In hilly countries mines are often worked entirely by adits, and even for the deeper workings the adit presents several advantages: it lessens the quantity of water percolating into them ; it diminishes the height to which the water has to be pumped ; if the contour of the sur- face permits it, its outflow may be utilised for producing water power; and lastly, it affords a natural discharge for water used in driving hydraulic engines underground. On account of these 2 E SCALE 234.56789 2 3 METRES 10 II 12 13 FEET 434 ORE AND STONE-MINING. very important advantages, some long and costly adits have been driven in certain metalliferous districts. Thus in the Hartz, the Ernest Augustus adit or drainage tunnel, (" Ernst August Stolln ") has been driven a distance of nearly 6 J miles into the Clausthal district. The total length of the adit, including its branches, is no less than 14 miles. It intersects many of the lodes at a depth of 400 yards from the surface. The total cost of this adit is estimated at 85,500.* Another long adit is the celebrated " Rothschonberger Stolln," which unwaters some of the most important mines at Freiberg in Saxony, The length of the main or trunk adit is more than 8J miles; the gradient of the greater part of it is only ri8 inch in 100 yards. Branches of this adit among the mines are more than 1 6 miles in length, so that the total length of the main tunnel with its ramifications amounts to about 25 miles. Most of the mines are now drained by it to a depth of 250 to 300 yards. The cost of the main tunnel was .359,334, or nearly 24 per yard, but this includes the cost of eight shafts, heavy expenses for pumping from these shafts, the walling of the adit for f mile, and all general expenses. The length of time occupied in driving this adit was thirty- three years. The " Kaiser Josef Erbstolln," in Hungary, is another remark- able mining tunnel, which was commenced in 1782 and com- pleted in 1878, at a total cost of 4,599,000 florins. It is loj miles in length, extending from the river Gran to the town of Schemnitz, where it intersects the lodes at depths vary- ing from 300 to 600 yards according to the contour of the surface. In Bohemia I may mention the " Kaiser Josef II." adit which drains the Pribram mines. The length from the mouth to the Stefan shaft is 4j miles, and the side branches bring up the total length to 13! miles. The great adit of the Mansfeld copper mines was begun in 1 809, and was seventy years in course of construction. It reaches from Friedeburg on the Saale to Eisleben. The first part was driven across the measures, and is, in fact, a crosscut, and it was then continued along the strike of the cupriferous seam. The total length is now 21 miles (33,900 m.). All the workings below its level, extending for a distance of more than TI miles (i 8 km.), have their water pumped into it. The adit was driven with a rise of i in 7200 (J inch in 100 yards). It is 9 feet 10 inches high (3 m.), and 6 feet across (1*85 m.), in the middle where it i& widest. The bottom part, 5 feet 8 inches in height, was carefully kept in the Rothliegendes so as to prevent percolation into the work- ings. Cross-timbers (spreaders) were put in about 5 feet above the * Bauerman, " Note on the new deep adit in the Upper Hartz Mines, " Irans. Min. Assoc. Cornwall and Devon, 1868, p. n. DRAINAGE. 435 floor and serve to support a single line of rails and a gangway of planks,* The adit at Monteponi,f in Sardinia, recently finished, is 3f miles (6 kil.) in length, and relieves the mine of its water for an additional depth of about 160 feet (50 m.). The great County adit in Cornwall was driven for the purpose of draining the Gwennap copper mines, and it was pushed on to Redruth. This adit differs from those just mentioned by the fact that it commences in the mining district itself, and though the length of all the drivages amounts to more than 30 miles, the water from the most distant mine does not run more than 6 miles before reaching daylight. The average depth is only 70 or 80 yards from the surface. In fact this great adit, though a work of great utility when the Gwennap district was in a flourishing condition, is merely a network of shallow tunnels, often driven along the lodes themselves, and therefore for bold- ness of execution cannot for one moment be compared to the great adits in Germany and Hungary. The Blackett level in Northumberland is an adit which has been driven a distance of about 4} miles, and which will have to be extended about 2 miles further before arriving at Allen- heads. Its depth from the surface at that place will be about 200 yards. The main part of the Halkyn tunnel in Flintshire has now reached a total length of 4 miles. The branch which goes out to Rhosesmor Mine is nearly half a mile long and a second branch has been commenced. The greatest depth from the surface is 230 yards, and the average depth under Halkyn Mountain about 215 yards. The length and depth of the adit are not remarkable ; but the quantity of water discharged is a matter of interest and impor- tance. It is estimated that this adit is now discharging 15 million gallons or 66,000 tons of water in 24 hours, although the outflow is purely natural, for no mines are pumping water into it, It is easy to understand that the Rhosesmor Mine, though provided with powerful pumping machinery, was unable to cope with the springs it encountered. In the "United Kingdom, where the land and the minerals are parcelled out among various owners, an undertaking of this kind requires a special Act of Parliament, for otherwise one obstinate proprietor might bar the way altogether, or mines drained by the adit might refuse to pay for the advantages they received. Before the Halkyn tunnel was driven, the area which appeared likely to be benefited was duly determined, and the * Der Kupfersctiieferlerglau und der Hilttenletrieb zur Verarleitung der gewonnenen Minern in den beiden Kreisen der Preuss. Prov. /Sacksen. Halle an der Saale, 1889, page 48. t Pellati, "I Progress! nelle Industrie Minerarie e Mineralurgiche Italiane," Jndustria, vol. v., 1891, p. 637. 436 ORE AND STONE-MINING. mines now worked within it have to pay a royalty to the tunnel company for every ton of ore they raise. Fired by the success of the Halkyn adit, which has proved a lucky investment for the shareholders, a company has lately commenced driving a similar tunnel in the Llanarmon district. The United States may fairly boast of the Sutro Tunnel, which enters the workings on the Comstock lode at a depth of 1700 feet from the surface. Work was begun on a small scale in October 1869, and the tunnel was "holed" into the workings of the Savage Mine in July 1878. The length of the main tunnel is 3 1 miles, and the cost of excavating it and timbering it up to the date of its completion, September i, 1878, was $1,367,577. To this must be added $296,724 for enlarging the heading, $384,824 for cutting a drainage channel at the bottom, of the tunnel and lining it with wooden launders or drain boxes, and the cost of repairs $43,441, making the total cost of the main tunnel up to October 1881, $2,096,566. This sum does not include the expenses of management of the company.* The size of the adit at first was 10 feet high clear and 15 \ feet wide ; but after 366 yards had been driven the dimensions were reduced to 6 feet high clear by 5 feet wide. In the original scheme it was proposed to sink four shafts and ex- pedite the work by having nine points of attack ; however, this plan could not be carried out. The first two shafts were sunk down to the level of the tunnel, but the quantity of water met with proved such an obstacle that the tunnel was practically driven entirely from one end. Work with machine drills was begun in April 1874, and the height of the heading was raised to 9^ feet, and the width to 13 feet, both outside the timber. In 1875 and 1876 the monthly progress was on an average 308^ feet. Much of the tunnel, indeed 45*5 per cent, of the total length, had to be timbered. In addition to the main tunnel there are branches along the course of the lode. In October 1880, the length of the north branch was 4403 feet, and that of the south branch 4114 feet. Both branches are 8 feet in width by 7 in height clear. The quantity of water running out daily in 1879 was 12,000 tons, at a temperature of 123 F. (50*5 C.) when leaving the mouth of the tunnel. All this water would otherwise have been pumped to the surface, at a cost estimated at $3000 a-day. The obstacles to the progress of the work were very great ; not only was the heat extreme, but swelling ground was encountered which snapped the strongest timber. Thanks, however, to the untiring energy of Mr. Adolph Sutro, the difficulties were at * Eliot Lord, "Comstock Mining and Miners." Monographs of the U. S. Geol. Survey, vol. iv., p. 342. Washington, 1883. There is an error of $4000 either in one of the items or in the total ; but I give the figures as they stand in the Keport. C. L. N. F. DRAINAGE. 437 last successfully overcome, and this great work will long remain as a monument to his foresight, skill, and patient pertinacity. The Atlantic- Pacific tunnel, which was commenced in 1880 and then stopped for a time, is intended to pierce the heart of the Rocky Mountains, under Grey's Peak, Colorado. It will be driven from both sides of the watershed, and will have a total length of 4} miles from end to end. SIPHONS. Siphons are used for draining mines in a few special cases in which the barrier over which the water has to be raised is very decidedly less than 33 feet. The workings of a shallow mine in North Wales are kept clear of water by a siphon made of ij-inch gas-pipe. At the crown there is an iron tank full of water, the contents of which can be run into the siphon by a 3 -inch pipe in order to start it. At Mountfield gypsum mine, in Sussex, the water is brought to the shaft from the neighbourhood of the working-face, a distance of 300 yards, by a siphon also made of i J-inch gas-pipe. It has two branches, but only one is working at a time. The water is lifted a height of 2 2 feet. When the water in the workings sinks, so that there is a danger of the siphon running dry, the foreman moves a lever which brings a pad of india-rubber against the outlet of the pipe, and so keeps it full and ready to act the next time it is wanted. A force pump is set up at the far end of the workings for filling the siphon if b}~ any chance the water has run out. WINDING MACHINERY. When a mine cannot be drained by tunnels or siphons, it is necessary to raise the waiter mechanically, either to the surface, or at all events to an adit through which it can flow out naturally. If the quantity is not excessive, it is often convenient to use the winding machinery, and draw up the water in special buckets (water-barrels) or tanks. The bucket may be tilted over on reaching the surface, or it may be emptied by opening a valve at the bottom. This means of raising water is commonly adopted in sinking shafts, when it may be desirable to wait till the whole or a portion of the pit is completed, before putting in the final pump- ing machinery. The water is usually lifted by hand into the bucket or tank, an operation involving a good deal of labour. Some of the baling may be avoided by collecting as much as possible of the inflow in a cistern above the bottom, and drawing off its contents by a hose into the bucket. This device is of no use for the water actually at the bottom, but baling may be dis- pensed with even in this case by the adoption of an ingenious arrangement invented by Mr. Galloway, and applied very success- fully by him in sinking a shaft near Cardiff* (Figs. 497 and 498). * "Sinking Appliances at Llanbradacb," Trans. South Wales lust. Eng, vol. xvi., 1888, p. 117. 438 ORE AND STONE-MINING. By means of a pump at the surface, the air is constantly being exhausted from a pipe, which descends the shaft and terminates in a long piece of flexible hose provided with a stopcock. When the cylindrical water-barrel has been lowered to the bottom of the shaft and is standing with its base in the FIGS. 497, 498. , door for entering barrel if required; b, flat cast- iron valve attached to the spindle h; c d, bottom plate of the barrel ; e, sec- tion of the valve showing universal joint attach- ment ; I, water-pipe, pro- vided at the end Jc with a coupling to which the suction hose is attached ; m, water-gauge. water, the flexible hose is quickly attached to it at the point k by an instantaneous coupling, and the cock is turned. Water is at once sucked up through the valve 6, and as soon as the gauge-glass m shows that it has reached the desired height, the stopcock is closed and the hose uncoupled. On arriving at the top of the pit, the water- barrel is lowered on to a trolley carry- ing a projecting conical block of wood, which knocks up the valve and allows the contents to run out. It was possible with the aid of this contrivance, while sinking a shaft in hard sandstone at the rate of 5 to 5^ yards per week, to cope with an influx of 5000 gallons (22*7 cubic metres) of water per hour at the bottom. A water-barrel can be filled auto- matically, when it can be made to plunge into a deep cistern or collect- ing pit (sump). Mr. Galloway's arrangement is shown by Figs. 499 and 500. The former represents. ais auto- matic water-tank with one side partly removed : a is the winding-rope, b the tank, which is guided in its descent and ascent by the studs c (Fig. 500) run- ning upon the guide ropes e. At the surface the tank is further steadied by side grooves, made of angle-iron d, which clasp the studs. When the tank is lowered into the cistern, the valve k opens of itself and lets the water rush in. It is then wound up to the top, where the short lever at o comes in contact with the piece of timber p ; the rod attached to the valve is lifted, and the water rushes out by the sloping mouth / into the wooden trough or launder m. The bar p is movable about the point Geol. Soc. Cornwall, vol. vii. p. 345. VENTILATION. 479 Fire-damp is frequently encountered in the old workings of alluvial mines in the goldfields of Victoria ; * in some instances it is doubtless due to the decomposition of prop timber, as at Ding Dong, and in others to the gradual alteration of driftwood or organic matter in the alluvial beds themselves. A serious accident, caused by a fire-damp explosion, is recorded as having injured two men at the Try-again Company's mine, El Dorado, in the Beech- worth Mining district.! Nitrogen, if given off in small quantities, is likely to pass un- noticed by the miner ; but it makes its presence felt occasionally. Miners in Strinesdale tunnel, near Stockport, have been troubled by the escape of nitrogen from fissures in the rock. It has been ascertained by analysis that the gas consists of 92 volumes of nitrogen, 8 volumes of oxygen, and a trace of carbonic acid. It came from openings in the roof, sides and floor, and was strong enough, in one case, to put out a candle 18 inches away from the fissure. The men became sick and dizzy, and their limbs were semi-paralysed. On some occasions the fissures drew the candle- flame in, instead of blowing gas out, suggesting a communication with old workings in the neighbourhood. The highly poisonous sulphuretted hydrogen is of frequent occurrence in the Sicilian sulphur mines, where the water is often saturated with it. At the 3ooo-foot level of the Corn- stock J lode, the water is charged with carbonic acid and sulphuretted hydrogen, and has a temperature of i7oF. (76*7 C.). A blower of the gas, met with in a copper mine at Ducktown, Tennessee, was strong enough to drive the men away from their work for a time. Two bad accidents took place in sink- ing a shaft at Stassf urt, through rock-salt, from sudden irruptions of the gas : on one occasion eight persons, and on the other seven persons, were stifled. Various fatalities are ascribed to sul- phuretted hydrogen at the ozokerite mines of Boryslaw, but here it is thought that the gas was generated by some process of de- composition in old workings, which were " holed into " by the miners. Sulphuretted hydrogen produced in a somewhat similar way is supposed to have been the cause of a death at a mine on the Gympie goldfield, Queensland.)) As a natural emanation in mines, sulphurous acid is very rare, but Becker has noticed a pungent gas near the i5o-foot level at the Bedington quicksilver mine in California, which he considers must contain both it and sulphuretted hydrogen.^" * Report o/ the Chief Inspector of Mines, Victoria, for the Year 1874, Mel- bourne, 1875, P- 9- t Reports of the Mining Registrars for the Quarter ended ^oth September, 1885, Melbourne, p. 15. J Becker, op. cit., p. 339. Phillips, Ore Deposits, 1884, London, p. 574. || Fryar, Gases in Mines, Brisbane, 1890, p. 8. IT Op. cit., p. 287. . /-_ OF 480 ORE AND STONE-MINING. Sulphurous acid is generated in the underground fires of sulphur mines in Sicily, and some will be formed in other cases of under- ground fires, if the rock contains iron pyrites. Small quantities of mercurial vapour are stated to be found in quicksilver mines, and to be the reason of their unhealthiness ; but one may also suggest that constant contact with cinnabar, inhaling the dust of the mineral, and allowing some to enter the stomach from eating with dirty hands, may possibly account for all the symptoms observed, without having recourse to the theory that the vapour is present in the atmosphere of the mine. Artificial Pollution of the Air in Mines. The pollution of the air is not due solely to gases introduced naturally from the surrounding rocks ; various other causes combine to render the atmosphere of the mine unfit for life, and among them may be mentioned the following : 1 . Kespiration of the persons and animals in the pit ; exhalations from their skin, and emanations from excrement left underground. 2. Combustion of the lamps and candles used for lighting the working places. 3. Absorption of oxygen by pyrites and other minerals. 4. Putrefaction of timber. 5. Explosion of gunpowder, dynamite, &c. 6. Stone dust from boring. 1,2. Dr. Angus Smith* reckons that two men working eight hours, and using J- Ib. of candles and 12 ozs. of gunpowder, produce 25*392 cubic feet of carbonic acid at 70 F. viz., 10*32 by breathing, 12*276 by candles, and 2*796 by gunpowder. It is considered by some medical authorities that the injurious effects of breathing an atmosphere polluted by the products of respiration, are due more to organic matter than to the small proportion of carbonic acid it contains. The quantity of carbonic acid serves, however, as an index of the amount of organic pollution, and when the air of a room is found to contain 0*06 per cent, by volume of the gas, the atmosphere is said to be unhealthy. Care should be taken to prevent the men from habitually using the workings as latrines, and to apply suitable disinfectants if the rule has been disobeyed. 3. Where the ventilation is sluggish, the absorption of oxygen by pyrites, or by ferruginous minerals passing to a higher state of oxidation, is sometimes very marked. 4. More important is the foulness of the underground atmo- sphere produced by the decay of the timber supports. The rapidity with which timber rots underground in certain circumstances has already been mentioned ; the practice of leaving the useless decaying timber to infect the new pieces that are put in, turns a * Report of the Commissioners appointed to inquire into the Condition of all Mines in Great Britain to which the Provisions of the Act 23 & 24 Viet. c. 151 do not apply, Appendix B., London, 1864, p. 224. VENTILATION 481 level in some instances into a hotbed of putrescent matter, offensive to the smell, and injurious to the health of the men. Steel supports should be welcomed, if only for ridding mines of one source of pollution of the atmosphere. One of the recommenda- tions of the Ventilation Board in Victoria is that all the bark should be removed from the timber before it is sent down under- ground.* 5. The nature of the gases and solid residues produced in blasting has been already explained in Chapter IV., and the statement made by some manufacturers that their explosives produce "no noxious fumes" is evidently misleading. In the case of gunpowder, we have the smoke made up of fine particles of carbonate and sulphide of potassium with some sulphur, whilst the explosive force has been due to the formation of a number of invisible gases, especially carbonic acid, carbonic oxide and nitrogen, with sulphuretted hydrogen, marsh-gas and hydrogen. Nitro-cotton should produce nothing by its explosion but carbonic acid, carbonic oxide, hydrogen and nitrogen ; and nitro- glycerine only carbonic acid, nitrogen, and oxygen. But when imperfectly detonated the resultant gases are more noxious ; both explosives generate a large proportion of nitric oxide, and carbonic oxide is liberated in considerable quantity. Dynamite produces the same gases as nitro-glycerine, but, in addition, it sends into the atmosphere, in a very finely divided state, the 25 per cent, of infusorial earth which it contains. Tonite, made from gun- cotton and nitrate of barium, produces solid carbonate of barium, and the quantity is estimated to be 55 per cent, of its weight.f More has been written of late years about the fumes of roburite than about those of any other explosive, and many useful observa- tions have been made concerning it. After a close examination and an analysis of the fumes produced by tonite and roburite, Prof. Bedson and two medical menj have come to the conclusion that these two explosives are no worse for the health of the miner than gunpowder. With all three explosives they found traces of carbonic oxide in the air, and they recommend in consequence that an interval of five minutes be allowed to elapse before the men return to their working places after firing. The ore-miner, in studying these conclusions, must not forget that the recommend- ation is made in the case of working-places which were being swept out by air-currents of noo to 5000 cubic feet per minute in other words, the moral is, that if no such currents exist, a longer interval should be given. No nitrobenzene was detected * Report of the Ventilation of Mines Board, Melbourne, 1888, p. x. *f " An Investigation as to whether the Fumes produced from the Use of Roburite and Tonite in Coal Mines are injurious to Health," Trans, Fed. Inst. Min. Eng., vol. ii., 1891, p. 380. J Ibidem, p. 388. 2 H 482 ORE AND STONE-MINING. in. analysing the air after firing roburite, though its odour was noticed on some occasions. 6. We now, lastly, come to stone dust, which is certainly not the least noxious of the impurities of the atmosphere breathed by the miner. It is formed in the process of boring holes for blasting, by the shots themselves and by the attrition of pieces of rock tumbling about during the ordinary processes of mining. However, it is probable that tbe first cause is the one from which the miner is most likely to suffer injury : when he is boring a hole downwards he puts in water, which serves the double purpose of facilitating his work and of preventing any dust from being formed; but when he bores an "upper" by hand, water is not used, and even where machine drills are employed, it is not always that one sees a jet of water under pressure applied to the bore- hole. The result is that the atmosphere of an "end " or other working place may contain a quantity of fine particles of stone in suspension, which are inhaled into the lungs, and irritate the air-passages ; very probably they are the principal cause of the complaint known as " miner's asthma " or " miner's con- sumption." Having pointed out the manner in which the atmosphere of mines is constantly being deteriorated, it is necessary to explain how it can be renewed, and so kept in a fit state for the workmen employed underground. NATURAL VENTILATION. Two systems of ventilation are employed in mines natural and artificial, either separately or .combined. Under the former, currents set up by natural differences of temperature change the air of the workings ; under the latter, artificial means are employed to bring about the same result. The principle upon which natural ventilation depends is very easily understood. The temperature of the earth increases at the rate of i F. for about every 60 feet of depth, and this natural heat is the mainspring in creating air-currents. Suppose a very simple case, two shafts AB, CD (Fig. 558), connected by a horizontal level B D. The air in the shafts and level, warmed by its contact with the sides of these underground passages, gradually assumes their temperature, which will be usually higher or lower than that of the external atmosphere ; the problem is simply that of two communicating vases. At the point D we have the pressure due to the weight of the column of air CD + the weight of the atmosphere at C. At B the pressure is due to the weight of the smaller column AB + the weight of the atmosphere at A. Draw the horizontal lines CF and AE and prolong the line of the shaft AB upwards by the dotted lines. The pressure of the atmosphere at F and C is the same, and therefore any difference of pressure at B and D depends upon the relative weights of the columns FB and CD ; but AB is equal to ED, so VENTILATION. 483 that the real difference depends upon the weights of the two columns of air FA outside the mine and CE inside the mine. In this country the external atmosphere in summer is often hotter than that of the mine ; therefore the column CE will be heavier than the column FA. The column CD will overcome the resistance presented to it by the column AB, and create a natural current going in the direction CDBA. In winter the conditions are FIG. 558. FIG. 559. reversed. The cold external column FA is heavier than the comparatively warm internal column CE, and the weight of the entire column FB will be greater than that of the column CD. The result is that the weight of the column FB will cause motion in the direction ABDC. A still simpler case is one of common occurrence in vein mining (Fig. 559). Let AB be an adit driven into a hill-side. Draw CD horizontal, and by the dotted lines AD indicate a column of air. The pressure of the atmosphere at C and D is the same ; the pressure at A is that of the column of air AD + the weight of the atmosphere above the line CD, whereas at B one has the same constant FIG. 560. weight above the line DC together with N. the column CB. If AD is warmer than BC, there will be a greater pressure at B than at A, and the current will move in the direction CBA ; if AD is colder than BC, a condition of things happen- ing in winter, the current moves in pre- cisely the opposite way. Another state of things is shown in Fig. 560, in which there are two shafts of unequal depth connected by an in- clined passage or drift. If AE is drawn horizontal, as before, at the level of the higher opening to the mine, and CF parallel to it at the level of the lower opening, the air in the bent tube, so to say, CDB, will exactly balance that contained in the vertical shaft FB, and for motive power we have to depend upon the difference in weight of the two columns AF and EC, a difference depending upon their relative tempera- 484 ORE AND STONE-MINING. tures. Therefore in summer we get a current travelling in the direction ABDC, whilst in winter it is reversed. In any one of these cases, the greater* the difference in tempera- ture, the greater will be the velocity of the ventilating current. In winter the ventilation will be more active than in summer, because there will be more difference between the outside and inside tem- peratures ; and, furthermore, though there are differences between the day temperature and the night temperature, still the tendency is always to produce a current in the same direction. In summer the nights may be cold though the days are hot, and therefore the difference in temperature between the air of the mine and that of the surface may be acting in two opposite ways according to the period of the day or night. A shaft which is drawing up, or is an "upcast," during the heat of the day may have a descending current, or be a " downcast," in the cool hours of the night, and practically have no current at all while the outside and inside temperatures are alike. There is not only this objection to natural ventilation that it may vary in direction during the course of the twenty-four hours, but the still greater objection that at certain seasons of the year it may be nil, because there is no difference in temperature between the outside and inside air to make one column heavier than the other. The creation of a natural air-current is not due solely to the difference of temperature caused by the natural warmth of the rocks. The heat engendered by the respiration of the men and animals, by the combustion of the candles or lamps, and, lastly, by the explosives is also a factor in making the air of the mine warmer than that of the surface and so setting up a current. The character of the sides of the shaft itself may also play its part. A shaft which has water dropping down it, either from natural springs that find their way in, or from slight leaks in the pumping plant, will naturally become the downcast, if the other orifice is dry. The strength of the current may be improved, or a natural draught created where none existed before, by building a chimney above one of the shafts, and so producing artificially a difference of level between the two outlets. The direction of the wind may also- turn the scale, and it is often found that a mine is better ventilated with some prevailing winds than with others. As an illustration of an effect of this kind, I need only refer to smoky chimneys, commonly caused by the wind striking some natural or artificial obstruction, which directs it downwards and makes it overcome the upward draught of the fire. The result is sometimes so- marked that the householder can tell the direction of the wind, before looking out of doors, by noticing which of his chimneys is giving trouble. With some mines in which the natural current has less force than that of a chimney, it is not to be wondered that similar occurrences take place. VENTILATION. 485 When speaking of natural ventilation, the property of diffusion requires a word of comment. This property is one by which two bodies of gas placed in juxtaposition with one another gradually become mixed, even if the lighter occupies the higher position. The process is slow compared with the mixing that is brought about by convection, but still it has some effect in causing the dis- persion of noxious fumes. In the examples of natural ventilation just given, it has been assumed that the mine has two orifices ; but many workings, at all events at the beginning, have only one. Let us take the three typical cases of a level, a shaft, and a " rise." Let Fig. 561 represent a level driven a short way into the FIG. 561. side of a hill. How is the atmosphere of the " end " renewed without artificial appliances? On entering such a level after blasting, the explanation becomes apparent : a current of powder smoke is seen hugging the roof, whilst the lower half of the level is clear. If a candle is set up on the floor, its flame is deflected inwards or towards the " end." The heated gases from the ex- plosive, accompanied by air warmed by breathing and the combus- tion of the candles, rise as much as they can, and make their way out by the upper part of the level, while their place is taken by cold air from the outside. The course of the gentle current is shown by the dotted lines. The same phenomenon may be observed in FIG. 562. a cross cut driven out from a shaft. This explains the import- ance, or indeed the necessity, of keeping a level as horizontal as possible if it is being ventilated naturally. Take an exaggerated case, in which the men have allowed their " end " to rise consider- ably, as shown in Fig. 562, so that the floor of the working place is three feet above a horizontal line drawn through the top of the mouth of the tunnel. Smoke and warm gases produced in the " end " will rise, and, finding no means of exit, will remain in the highest part until they cool down and diffusion has had time to play its part. It might seem at first sight that a current could not be formed in a shaft which does not communicate with other workings ; but 486 ORE AND STONE-MINING. even when no partition of any kind has been put in, the sides of the pit kept cool by trickling water may cause the air to form descending currents, whilst in the centre there is an ascending current, as shown in the diagram (Fig. 563). In an incline (Fig. 564) the ascent of the warm smoke along the dry roof and the influx of cold air along the floor are sometimes very noticeable. When the working place is a "rise," it is evident theoretically, and still plainer practically, that the warmth of the foul gases at the top tends to keep them in that position, and that the evil must increase as the place gets hotter (Fig. 565), The nature of the excavation prevents things from improving, and the necessity for artificial ventilation is nowhere more apparent than in a working place of this kind, especially if the space is confined. The common statement that carbonic acid collects in the lowest part of the workings is correct only in cases where the gas is FIG. 563. FIG. 564. FIG. 565. LEVEL issuing forth from the rocks and sinks down like water. "Where it is produced by respiration, candles, lamps, or explosives, it is diffused through a warmed atmosphere, ascends with it and does not separate from the other gases. The consequence is that a " rise " may be found badly ventilated although the air in the level below is fresh and pure. We will suppose that by reason of the difference in level of the two main orifices of the mine, a trunk ventilating current has been established. The air will then take the easiest road from one shaft to the other, and will not penetrate into any other parts of the workings unless compelled to do so. The turning of the current into any required direction is effected by putting in partitions and doors. In a few cases, the partition serves to make a clean and sharp line of division between two currents which would to a certain extent exist naturally. Thus, we have seen that when the length of a level is not great, an outward current travels along its roof, and an inward current along its floor (Fig. 561) ; between the two there is a dead space more or less interfering with both currents by making their boundaries ill-defined. If a horizontal partition of planks (air-sollar) is put in (Figs. 566 and VENTILATION. 487 567), the two currents are kept perfectly distinct, and the natural ventilation, aided in this way, proceeds in a much more effective manner; the level can therefore be driven further without having recourse to machinery for creating an artificial current. A common problem is the ventilation of the far end of a drivage, AB (Fig. 568), provided with a little shaft, CD, which, in winter, naturally creates a current proceeding from A to D, and ascending at once to C. The desired effect may be attained by putting in an air-sollar DE, which compels the air to travel to the far end before it can begin its ascent ; another plan consists in covering the bottom of the shaft by a platform (sottar), and carrying a pipe from it all the way along the roof of the level to the " end." This has, of course, the same effect as the air-sollar, but, unless the pipe is large, it does not give FIG. 566. FIG. 567. FIG. 568. so much area for the current. Pipes have the advantage that they are very easily put in and that they can be used again and again. These methods of conducting an air current are so self-evident, that I should not have mentioned them, were it not for the fact that some mine agents appear to be ignorant of these simple expedients for improving the ventilation of their drivages. Where the level is wide enough, the partition may be placed vertically ; it is then called a brattice. If required for temporary purposes it may be made of canvas, tarred to prevent its rotting (brattice cloth). More lasting and effective partitions are con- structed of plank or of brick. Any close vertical partition in a shaft dividing it into two separate compartments invariably improves matters, when the ventilation of a sinking is becoming sluggish ; some trifling differ- ence in the condition of the two compartments decides which is to be the upcast and which the downcast. Where it is not con- venient to put in a partition, a separate air compartment may be formed by fixing a large pipe against one side of the shaft and taking it up 30 or 40 feet above the level of the ground 488 ORE AND STONE-MINING. (Fig. 569); in this manner two columns of unequal height are produced with the desired effect. If a rise is being put up, or if stoping is being carried on without any winze, there is no difficulty in diverting a natural current existing in the level below and making it serve the work- ing place. All that is required is to block the passage of the current along the level, and so force it to take the only road that lies open to it. In Fig. 570, AB is a level, and C the top of a rise, which has an open compartment at each end ; one is fitted with ladders, and the other serves as a shoot, down which ore or rubbish can be thrown into the level below. They are separated by the thick partition of rubbish piled upon a platform in the roof of the level and confined by timber at both ends. By putting a FIG. 569. FIG. 570. -? partition in the level, the air is made to pass up one end of the rise, sweep out the foul air produced by the men, candles and explosives at C, and then descend into the level once more. The partition may be a wooden door closing tightly against its frame, or a piece of brattice cloth hung from the roof, which is readily lifted when a tram waggon has to pass underneath. In the case of stopes the mode of procedure is identical, but the air current has not to make such sharp turns. The case represented in Fig. 568 is that of workings at one level. In vein mining the ore is generally being excavated, or at all events preliminary drivages are being made, at more than one horizon. In Fig. 571 two shafts have been sunk, and two drivages have been made, one below the other. It is easy to understand that at an earlier stage of the working, before the shafts had been sunk to E and F, and the level EF driven, VENTILATION. 489 B C a current was set up from A to C via B and D, or from C to A, according to the season of the year ; but when the level EF has been driven, what is to bring the current down to E, for instance, when it has the shorter and easier road direct from B to D ? It often happens that special condi- FIG. 571. tions in the shafts themselves, to which allusion has already been made, would in any case cause a movement in the air from B to E, F and D, even if the two columns of different height did not exist above them, and in that case some air would find its way down to E and F; but by putting a door at G, somewhere between B and D, the main current can be forced to proceed by the longer road and ventilate the lower workings. If air is required for men working in the level BD, the partition, or door G, is not made close ; then part of the main current takes the shorter road from B to D, and part the longer road from B to E, F and D. Owing to the number of shafts which are usually sunk in working veins, and differences in the level of their mouths, natural currents are set up to a much greater extent than is the case in working beds, where a FIG. 572. couple of pits situated close to one another and at the same level have to serve as the sole inlet and outlet orifices. For this reason natural ven- tilation is often found to provide a fairly suffi- cient supply of air along the main course of the current, and the miner has merely to provide for the ventilation of workings in the form of a cul-de-sac, such as ends, rises, and winzes, which are at a distance from this current. A common method of procedure is to sink winzes at frequent intervals ; if AB and CD (Fig. 572) represent two levels, 10 to 15 fathoms apart, which are being driven from A to B and C to D respectively, we will suppose that a ventilating current exists as J21 490 ORE AND STONE-MINING. shown by the arrows. B and D are blind alleys, so to say, but so long as their ends B and D are not far from the main draught, they may be sufficiently ventilated by convection currents, set up in the manner explained in Fig. 561. Soon, however, this mode of supplying air becomes inadequate, and the miner estab- lishes another communication between the two levels by a fresh winze or rise JK; the current is made to take the road shown by the dotted arrow, if a stopping of some kind is put into the winze FE. The name " winze," sometimes written " winds," suggests that the original purpose of the intermediate shaft was to furnish air. In some mines winzes are sunk at fairly regular intervals of 30 fathoms ; of course, in selecting a place for a winze, preference is given to ore-bearing parts of the vein, because the cost of sinking will then be partly or wholly repaid by the mineral excavated. Even when the indications at the top may not warrant the assumption that ore is present in paying quantities, the winze serves to prove the ground and sometimes to reveal unsuspected sources of profit. Winzes may be said, then, to have five useful purposes : ventilation, exploration, starting-points for stoping, shoots for ore or rubbish, ladder-roads for the miners. I have thought it advisable to devote more space to natural ventilation than the coal-miner would think it deserves, because it is the method by which the trunk ventilation of most vein- mines is carried on at the present day, and has been carried on for centuries. Nevertheless, I am fully alive to its two weak points viz., want of constancy and want of strength. The miner- is therefore often driven to seek artificial aid in order to make up for these defects. ARTIFICIAL VENTILATION. Artificial ventilation is produced either by (I.) furnaces, or (II.) machines. I. FURNACE VENTILATION. By employing a furnace, the miner can effect an artificial difference of temperature between two columns of air in the mine, and so produce a current similar to the natural draughts just described. In small undertakings a fire lit at or near the bottom of the upcast shaft, or contained in an iron vessel suspended in the pit, suffices to create a current, when the natural ventilation is no longer adequate, owing to the state of the external atmosphere. From small beginnings of this kind has developed the large underground furnace, which is, however, in the vast majority of cases, confined to the domain of the coal-miner, and even there is being gradually replaced by fans. My description may, therefore, be extremely brief. The ventilating furnace (Figs. 573, 574, 575) * is a huge fireplace at or near the bottom of the upcast shaft, over which is led either all the air of the mine, or a part of it. The air heated in this way is rendered specifically lighter, and the * Callon, Lectures on Mining, vol. ii., plate Ixxxvi. VENTILATION. 491 weight of the column of cold air in the downcast shaft overcomes that of the air in the upcast and causes it to ascend. It is pre- cisely the same action as that which takes place with the usual domestic fireplace in this country, the chimney playing the same part as the upcast shaft. Cold air is drawn in from crevices around the doors and windows, is heated by the fire, and ascends the chimney. If the air of the workings is charged with a dangerous proportion of inflammable gas, it is led into the upcast shaft by a special drift the dumb drift at u point where there is no danger of its FIG. 573- FIG. 574. taking fire. In this case the air in the shaft becomes warmed in its upward passage, not only from mixing with the current coming from the furnace, but also by absorbing caloric from the heated sides of the pit. II. MECHANICAL VENTILATION. The methods of mechanical ventilation may be classified as follows : (1) Water blast. (2) Steam jet. {(i) Reciprocating, fa. Acting by displacement, (ii) Rotary. \ [6. ,, centrifugal force. (i) The ordinary water blast is a very simple appliance : it is the well-known tromp, used in some countries for blowing smiths' 492 ORE AND STONE-MINING. forges. A stream of water falls down a pipe, entangling air drawn in by lateral holes, and drops into a box or barrel with two orifices ; these are so arranged that the air shall escape by one, under a slight pressure, and the water from the other. The current of air is carried by square pipes made of boards, or, better, by cylindrical pipes made of sheet zinc, to the place where ventilation is required. The fall of water is also applied by Williams's water-jet apparatus (Fig. 576). The water brought down in a pipe from a reservoir, or from the FIG. 576. rising main of the column of pumps, issues in the form of a jet from a nozzle, and, driving out the air in front of it, draws in air behind. The water is let off by a box with a discharge designed, like that of the tromp, to give a little pressure, whilst the air-current proceeds through a series of pipes to the " end " or other working-place. The water-blast has the merit of supply- ing a stream of cool moist air which is very acceptable where the working-place is dry and dusty. By reversing the apparatus the current may be made to flow in the opposite direction, and the " end " is then ventilated by having its foul air drawn out and replaced by an inward draught along the level, instead of being supplied directly with fresh air from the outside or from the main ventilating current. (2) A steam jet may be applied, like a jet of water, to create an exhaust and to draw out the foul air. For instance, we will suppose that during the sinking of a shaft the air-pipe in Fig. 569 fails to act in an adequate manner, owing to a change in the atmospheric conditions. The agent desires to remedy this state of affairs by some cheap and temporary expedient. If he brings a pipe from the boiler of the winding engine to the upright ventilating pipe, and provides it with a nozzle pointing upwards, he can speedily and at small expense produce an upward current by turning on steam. The steam jet drives air in front of it up the pipe, and at the same time warms it slightly. The exhausting effect produced in this way at the bottom of the pipe is sufficient, in small sinkings, to draw out all the foul air. A draught may be produced in an upcast shaft by a ring at the bottom, from which issue a number of jets of steam. Such a mode of ventilation may be useful in cases of emergency. (3) Air Pumps. Mechanical ventilation on a large scale is always effected by some kind of air pump, and generally by one which has a rotary action. (i) Among the pumps which have a reciprocating action, the ordinary air compressor must be named first, as its utility VENTILATION. 493 as a ventilating agent is great. The air escaping from boring or other machines renders good service in driving out foul gases generated in the workings, and there is the advantage that, after blasting, a powerful stream of air can be turned on for a short time so as to sweep out the noxious fumes completely. Even where the ground is soft and no machine drill required, it is easy to bring in air from the main by a line of smaller pipes, and turn on a fresh current when needed. In one sense it is very uneconomical to bring air to a pressure of 60 or yolbs. to the square inch for ventilating purposes only; but where compressing machinery is always at hand for working underground engines, it is better to be a little wasteful of a cheap power at the surface than to go to the greater expense of having a boy or a man to work a fan. In a long level driven by boring machinery, with its " end " far removed from the main ventilating current, the smoke produced by blasting, though driven away from the actual working face, still hangs about for a time, and pollutes the atmosphere which the miner has to breathe in going backwards and forwards. In such cases it is best to draw away the foul gases as soon as they have been produced, and prevent their mixing with the air of the level. With compressed air at his command, the miner can easily work an aspirator of FIG. 577. some kind, such as Korting's, or the somewhat similar con- trivance of Mr. Teague (Fig. 577). The ordinary air-main for bringing in the compressed air working the boring mn- _-_; chinery is shown at the bottom of the level, with the piece of flexible hose at the end. The boring machine has been removed and the air shut off from the hose; by turning another cock, it passes up the upright piece of pipe and rushes out of the nozzle in a direction opposed to that of the drivage. This has a powerful exhausting effect,, and the " end " can be cleared of smoke in a few minutes. The Hartz blower (duck machine, Cornwall) (Figs. 578 and 579) is an air pump of simple construction which can be made up by any mine carpenter. It consists of two round or rectangular boxes, one fitting inside the other, and moved up and down by being connected to the main rod of the pumps ; the upper box has a valve at the top, and the lower box is provided with a pipe also having its valve. The lower box is partly filled with water so as to make an airtight connection. With the valves arranged as shown in Fig. 579, the machine will act as an exhausting pump and draw out the foul air ; if the play of the valves is reversed it acts as a blower. 494 ORE AND STONE-MINING. Struve's ventilator is a gigantic double-acting machine of this class, so constructed that it draws air from the mine during the down stroke as well as during the up stroke. (ii) a. Among the rotary air pumps acting by displacement may be mentioned Boots's ventilator, of which various sizes are made, suitable to the requirements of the whole of a large mine or merely to those of a single " end." This air machine (Fig. 580) consists essentially of two similar pistons upon parallel shafts, revolving in a casing, but without actually touching each other or the casing. The clearance in a large ventilator is under \ inch. The pistons are of such a shape FIG. 578. FIG. 579. FIG. 580. that a definite volume of air is drawn in or forced out by each half-revolution. As the pistons are always kept in position by gearing, there is no fear of one coming in contact with the other. (ii) b. Centrifugal Ventilators or Fans. This class includes all the most important ventilators in use at the present day. They are characterised by the fact that the current is produced by blades or vanes fixed to a shaft, revolving at a high speed. The air lying between them is whirled round and flies off tangen- tially at the tips, like a stone from a sling. The space occupied by this air is at once filled by supplies coming in at the centre, and the process goes on continuously. The centrifugal ventilators or fans are generally used as exhausters that is to say, they are arranged so as to suck air out of the mine, instead of forcing it in. They can claim the merit of great simplicity, and of being capable of withdrawing very large volumes of air. VENTILATION. 495 Four types of fans very largely used in this country at the present day are the following : Oapell, Guibal, Schiele and Waddle. The Capell fan (Figs. 581 and 582) consists of two concentric cylindrical chambers, each provided with six curved vanes or blades, the convex sides of which are turned in the direction of the rotation. The cylindrical shell or drum, 6, between the two sets of vanes contains openings, or portholes, d d, allowing the air to pass from the inner to the outer chambers. There is one such opening between every two vanes. The air contained between any two of the inner vanes, c, is thrown out by centri- fugal force when the fan revolves, and passes at a high velocity into the corresponding outer chamber. Here it is supposed to strike against the concave vane, and give back to it the greater part of the impulse received from the inner chamber. The object of the inventor of this and of other fans is to discharge FIG. 581. FIG. 582. the air with the least possible velocity, for velocity imparted to the outgoing air means work done to no purpose, or, in other words, a diminution of the useful effect of the power employed in driving. The advantage claimed for the fan is that it succeeds in effect- ing this object even when driven at a high speed, and that, therefore, it can do a large amount of work in spite of its com- paratively small diameter. The smallness of the fan of course reduces its first cost. It is not only capable of withdrawing large quantities of air, but also of effecting a considerable diminution of pressure. The fan may be made with an inlet on one side only or with an inlet on both sides. It runs in a spiral casing, not fitting closely, which gradually gives a larger and larger outlet for the air and then finally discharges it into an expanding chimney. Figs. 581 and 582 show a double inlet fan, a being the close vertical diaphragm separating it into two parts. A special passage (fan drift) brings the air from the upcast shaft to the ventilator, which is set in motion by a belt driven by the fly-wheel of a pair of horizontal engines. These fans are made of diameters varying from 8 to 15 feet; 496 ORE AND STONE-MINING. the width of the small ones is 7 feet, that of the largest 1 1 J feet ; they are driven at speeds varying from 180 revolutions per minute in the case of the largest fans, to 300 in the case of the smallest. Under these conditions the smallest fan is said to be capable of passing a volume of 100,000 cubic feet of air per minute, with a diminution of pressure (water-gauge) of 2\ inches, whilst the large fan moves the enormous quantity of 300,000 cubic feet per minute. The power required is estimated at 60 I.H.P. in one case and 180 in the other. The Guibal fan, brought to us from Belgium (Fig. 583), has deservedly been a favourite for many years. It is a fan with eight or ten straight FIG. 583. blades, which are not set radially. An important peculia- rity, introduced by Guibal and since copied by others, is the expanding stack or chimney, which gradually lessens the velocity of the air as it travels towards the point of discharge into the outer atmo- sphere, and the slid- ing shutter, a. The shutter enables the opening of the fan- casing into the ex- panding chimney to be regulated at pleasure : if this opening is too big, eddies are formed and air re-enters the fan ; if, on the other hand, the opening is too restricted, an unnecessary amount of force is required to- work the fan, and the air escapes with too great velocity. By careful regulation the best possible effect is attained. The regulating shutter has been greatly improved by Messrs. "Walker Brothers of Wigan, who make the opening in the form of an inverted V, with the object of producing a gradual instead of a sudden change as each blade passes into the enclosed part of the casing. The consequence is that the amount of vibration is. greatly reduced and the fan rendered nearly noiseless. They build their fans entirely of iron or steel. Guibal fans are made of diameters varying from 20 to 46 feet,. and widths varying from 6 to 13 feet. Fans 30 feet in diameter are usually driven at a speed of about sixty revolutions per minute, and the large fans of 40 to 46 feet at fifty revolutions. VENTILATION. 497 The Schiele fan is somewhat like the Guibal. It has the same expanding chimney, but the blades are curved and the casing is not close (Fig. 5 84) ; besides, the width of the blades is FIG. 584. not the same throughout. The blade is widest in the middle, and then it de- creases both towards the centre of the fan and to- wards the tips. It is a small fan compared with the Guibal, the diameter varying from 5 to 20 feet, width from i to 3 feet. The speed of driving is 500 revolutions per minute for the smallest fans and no per minute for the largest. The air is always taken in on both sides. We come lastly to the Waddle fan, which differs from those just described by running open that is to say, it is not enclosed in any external casing (Fig. 585). It is a very flat hollow truncated cone, with the base closed and a central opening on the other FIG. 585. side. Originally the blades a b were curved, as shown in the figure, but latterly they have been made radial ; c c are some of the outer plates. The air passes in at the centre and is discharged at the circumference. These fans are made with a diameter of 30 to 45 feet. A recent improvement is the addition of a 2 I 4 g8 ORE AND STONE-MINING. divergent outlet in other words, the two rims projecting beyond the blades are inclined outwards. The velocity of the air leaving the fan is thus lowered, and less power is required for driving. A Waddle fan, described by Mr. Walton Brown,* had the following dimensions : Ft. in. Diameter to periphery of divergent outlet 36 4 ,, of the extremities of the blades 35 o ,, ,, inlet ring ... 136 Width at outlet i i ,, ,, periphery of fan ... 2 2j The Waddle, like the Guibal, is a slow-running fan, which can be driven directly from the engine without the aid of belts or gearing. Professor Luptonf has designed a fan, which he calls the Medium fan, in which he considers that he has brought together the good points both of the large fans, such as th& Guibal and the Waddle, and of the small fans, such as the Schiele and the Capell. It is from 15 to 25 feet in diameter. TESTING THE QUALITY OF THE AIR. In a well- regulated mine the manager should be able to determine the quality and quantity of the air circulating in the workings, and the efficiency, from a mechanical point of view, of the machinery employed for ventilation. A knowledge of the quality of the air is necessary for two reasons : it may contain gases capable of causing accidents by explosion or suffocation, or it may be polluted by gaseous and other impurities likely to injure the health of the men who have to breathe it. Fire-damp. Though ore and stone miners are rarely exposed to any danger from fire-damp, exceptional cases arise in' which car- buretted hydrogen is emitted naturally or formed artificially in mines, as mentioned in the beginning of this chapter. It is therefore- essential that the miner should have some knowledge of the means employed in testing for fire-damp, even if he is not going to manage a colliery. However, the subject must be treated briefly, and the student desirous of further information may be referred to treatises on coal -mining. Indications of fire-damp are afforded by the singing noise made by the gas if it is issuing forth in large quantities from moist coal,, by its bubbling up in water, and by the cracking noise of bubbles as they burst ; but its presence is commonly detected by its effect upon the flame of a lamp burning oil, benzine, alcohol, or hydrogen. The additional brilliancy which it imparts to a platinum wire made incandescent by the passage of an electric current may also be employed as a test, or the diminution in the volume of a measured * " Waddle Patent (1890) Fan," Trans. Fed. Inst. M. E., vol. ii., 1890- 91, p. 173. t Notes on the Medium Fan, Proc. Fed. Inst. M. E., vol. i., 1890, p. 65. VENTILATION. 499 quantity of air, exposed to the action of a red-hot palladium or platinum wire, causing combustion. The lamp employed should be a safety lamp, for fear that an accidental ignition of the gas should cause an explosion. A few safety lamps will be described in the next chapter. They are fed with vegetable or mineral oil, or with a mixture of them. In test- ing for "gas," the wick is drawn down until the yellow flame almost disappears, and the lamp is held in the place where the fire-damp is supposed to be present ; on account of its specific lightness it lodges against the roof, and it is there, if anywhere, that it is most likely to be found. If fire-damp is present in sum- cient quantity, its combustion produces a pale blue "cap" (halo, or aureola) around the little flame, and the greater the proportion of fire-damp, the higher the cap. According to Professor Galloway * 2 per cent, of fire-damp in the air will give an exceed- ingly faint cap J inch high, whilst 4 per cent, gives a conical cap J to | inch high. If a lamp fed with benzine is used, the phe- nomena are plainer. The appearances of the flame burning in mixtures of air and marsh-gas of different proportions are well represented by coloured plates in a report made by Professors Kreischer and Winkler,f and in the Proceedings of the Austrian Fire-damp Commission. { With i per cent, of fire-damp there is a faint aureola, and with 2 per cent, it is plain, conical at the top and inch (10 mm.) high ; when the proportion is increased to 3 per cent., there is a well-defined cap f inch (20 mm.) high. By using a dead-black background, it is claimed that Ashworth's modified benzoline safety -lamp will give a distinct cap J inch high with J per cent, of fire-damp. The blue non-luminous flame of alcohol enables still smaller quantities of fire-damp to be made known, and the Pieler lamp || * "On the Fire-damp Cap," Proc. South Wales Inst. JEng., vol. x., 1876-7, p. 290. " Untersuchungen itber Sicherheitslampen," Jahrb. f. d. Berg- und Huttenwesen im K. Saclisen, 1884, p. 54, and plates ii. to vi. J Verhandlungen der Centralcomit6s der osterreichischen Commission zun Ermittlung der zweckmdssigsten Sicherheitsmaassregeln gegen die Explosion, scUagender Wetter in Hergwerken. 3 Heft. Vienna, 1890, plates ii. and iii., p. 225. Clowes, " On the Application of the Hydrogen Flame in an ordinary Safety-lamp to the Detection and Measurement of Fire-damp," Proc. Boy. Soc., vol. Ii. 1892, p. 90. || Pieler, Veber einfache Methoden zur Untersuchung der Grubenwetter, Aix-la-Chapelle, 1883. Kreischer and Winkler, op. cit., p. 77. C. Le Neve Foster, " On the Pieler Lamp for indicating small quantities of Fire- damp," Trans. Geol. Soc. Manchester, vol. xvii., 1884, p. 252. Broockmann, " Untersuchung der durch Sumpfgas hervorgebrachten Erscheinungen der Pieler- Lampe," Anlagen zum Haupt-Bericlde der Preussischen /Schlag- wetter Commission, vol. i.,p. 129, vol. iii., p. 167, and plates. Walton Brown, " The Pieler Spirit-lamp as a Fire-damp Indicator," Trans. N. E. Inst. M. E., vol. xxxviii., 1890, p. 177 and plates. Austrian Fire-damp Com- mission, op. cit., plate iv. 500 ORE AND STONE-MINING. is based upon this fact. It begins to indicate with J per cent, of fire-damp, and even with ^ per cent, the cap or aureola is 2 to 2 J inches high, and clearly recognisable ; with i per cent. it is nearly 4 inches high. Chesneau * obtains a plainer and more brilliant cap by adding a little nitrate of copper and an organic chloride to the alcohol, and Stokes has introduced the improvement of combining a detachable alcohol-reservoir with an ordinary safety-lamp, and so enabling the official to test with the oil or the spirit flame at pleasure. Mallard and Le Chatelier pointed out the value of the hydrogen flame as a fire-damp indicator in a report to the French Fire-damp Commission, and Pieler made use of it for testing samples of mine air which were brought to a laboratory at the surface. Quite recently Prof. Clo west has constructed a hydrogen lamp sufficiently portable for use underground in the working places themselves. The lamp is so constructed that it will burn either an illuminat- ing oil or hydrogen as required. A little tube is brought up through the oil reservoir, and, on turning a cock, a jet of hydrogen issues forth close to the ordinary oil flame. It ignites at once, and the wick of the oil flame is pulled down till it goes out ; the non-luminous hydrogen flame now serves as a delicate indicator. The oil flame is relighted from the hydrogen flame when the testing is concluded, and the gas is then turned off. The cap with J per cent, of fire-damp is f inch (17 mm.) high, and with i per cent, it is | inch (22 mm.) high. The hydrogen is contained in a small steel cylinder which can be attached to the lamp in the form of a handle. The combination of a very delicate testing apparatus with the ordinary lamp has the advantage of enabling the official to do his work with one lamp instead of two. Liveing'sJ patent gas indicator depends upon the fact that fine platinum wire, made red-hot by the passage of an electric current, will glow with greater brilliancy when there is fire- damp present in the atmosphere than when there is none. This phenomenon is due to the heat given off by the com- bustion of the fire-damp in immediate contact with the wire; and the greater the heat, the more the wire will glow. The increase in brilliancy corresponding to a given percentage of fire- * " Notes sur un nouvel indicateur de grisou ; " " Essais effectues dans les mines avec 1'indicateur de grisou de G. Chesneau ; " " Instruction pour 1'emploi de 1'indicateur de grisou de G. Chesneau," Ann. des Mines, Paris, 1892 and 1893. Comptes-rendus Soc. Ind. Min., 1894, p. 25. t " On the Application of the Hydrogen Flame in an ordinary Safety- lamp to the Detection and Measurement of Fire-damp," Proc. Boy. Soc., vol. li., 1892, p. 90. Liveing, On an Instrument for the Detection and Measurement of Inflam- mable Gas in the Atmosphere of Mines. L. Clark, Muirhead and Co., West- minster, London, 1881. VENTILATION. 501 damp is measured by a small photometer, which cannot be understood without a figure. Shaw's apparatus is based upon the principle of determining the limits of inflammability of gaseous mixtures, or, in other words, of ascertaining the precise degree of dilation which renders the mixture just capable of being ignited. It consists of two main parts, an ingenious mixing apparatus and an exploding chamber. By the aid of the first, a mixture of pure air with inflammable gas, or with mine air, can be prepared in any desired proportions, and then driven into a cylinder, where it meets with a naked flame, If the mixture contains a sufficient proportion of inflammable gas to explode, a loose stopper is blown out and strikes a bell, giving an audible signal. By making a succession of experiments, the exact volume of mine air required to bring a known mixture of gas and air to the ignition point can be ascertained, and from this the percentage of fire-damp is determined. Samples of mine air can thus be tested at the surface with a considerable amount of accuracy by any intelligent foreman. Carbonic Acid. Two evils are feared from the presence of this gas in the atmosphere of mines either suffocation when the pro- portion is large, or injury to health when the proportion is smaller. If the gas is issuing from the rocks, it settles down at the bottom of the excavation in virtue of its specific gravity, and men have been asphyxiated by descending into shafts or wells in which the gas had accumulated without their knowledge. Where danger of this kind may be apprehended for instance, in mines known to be liable to emissions of carbonic acid, or in the case of old work- ings that have not been recently entered, the usual test is lowering a lighted candle. If the candle is found to burn brightly, it is concluded that there will be no danger in making the descent ; if it goes out, it is evident that the air is unfit to support combustion and human life ; if it burns dimly, there is need for the greatest caution. The ore and stone miner also relies upon the candle for testing the air of his working place, in cases where the proportion of carbonic acid falls very far short of that required to produce suffo- cation. He is apt to consider that if the candle burns freely when held upright, and does not go out when moved quickly from side to side, the ventilation must be good. Dr. Angus Smith states in his report to Lord Kinnaird's Commission * that this is a fallacy, and he considers that the candle test affords no distinct sign that the air is bad, until the impurities have reached an amount beyond the maximum which is consistent with good ventilation. Thus, the candle affords no indication of the presence of J per cent, of carbonic acid ; if the percentage is greater than this he says that men should not be allowed to work, and, to use his own words, "it follows therefore that the candle, as used, is only valuable * Op. cit. Appendix B, p. 254. 502 ORE AND STONE-MINING. when the air is so bad that no one should be allowed to remain in it." He is of opinion that the carbonic acid of dwelling rooms should not be allowed to exceed 0-06 or o'oy per cent., and agrees with Pettenkofer,* who lays down o'i per cent, of the gas as the beginning of decidedly bad ventilation. The latter says : " A series of examinations have resulted in the conviction that one volume of carbonic acid in 1000 volumes of room air indicates the limits which divide good from bad air. This is now generally adopted and practically proved, always provided that man is the only source of carbonic acid in the space in question." Other good authorities f write to the same effect. Such small percentages of carbonic acid, which are wholly unrecognisable by the candle test, can be readily detected and easily measured by methods which are quite within the powers of an ordinary mine agent. Angus Smith 's Process. The first process is one proposed by Dr. Angus Smith J in 1864 v i z -> shaking a known quantity of lime-water with a known volume of air, and observing whether there is sufficient carbonic acid in the air to neutralise the lime. The only alteration I propose is the use of phenolphthalein as an indicator, instead of turmeric paper or rosolic acid. The necessary apparatus consists simply of : 1. One 8-oz. bottle and cork. 2. One 5-oz. bottle and cork. 3. One bottle of lime-water with excess of lime. 4. One pipette or measure holding \ oz. 5. Four 3-oz. bottles corked. 6. One -oz. bottle containing an alcoholic solution of phenol- phthalein. 7. One piece of india-rubber tube, about a foot long. According to Dr. Angus Smith, lime-water is fairly constant in strength, and sufficiently so for his process of air-testing. After the bottle (No. 3) has been well shaken up several times with the excess of lime, the solution is allowed to stand till it is quite clear. \ ounce of it is measured exactly, and poured into the 5 -ounce bottle, which is then filled up with distilled water or boiled rain-water. This gives a solution of one-tenth the strength of the original lime-water. Add a drop or two of the solution of phenolphthalein, and the lime-water at once assumes * The Relations of the Air to the Clothes we Wear, the House we Live in, and the Soil we Dwell on. Abridged and translated by Augustus Hess. London, 1873- f Parkes and de Chaumont, " A Manual of Practical Hygiene,'" 6th edition, London, 1883, p. 153. Meymott Tidy, " Handbook of Modern Chemistry,' 1 ' London, 1878, p. 102. Op. cit. Appendix B, p. 239. C. Le Neve Foster, " On One of Dr. Angus Smith's Methods of Testing Air," Trans. Min. Assoc. and Inst. Corn., vol. ii., part 2, p. 40. VENTILATION. 503 a beautiful pink colour, which remains so long as there is any lime un-neutralised. This dilute lime-water is now of a strength that J ounce of it will neutralise the carbonic acid in an 8-ounce bottle,* if the air in it contains -} per cent, of this gas by volume. This percentage has been proposed as a standard which should not be exceeded. In order to make a test, fill the 8-ounce bottle with the air of the place, by sucking out its contents with a piece of india- rubber tube, of course taking special care not to breathe into it afterwards ; then add |- ounce of dilute lime-water, cork the bottle and shake it. If the pink colour disappears, the air contains more than per cent, of carbonic acid ; if the colour is not discharged, the air contains less than that amount. If the colour fades slowly, and does not finally vanish until after a great deal of shaking, it may be assumed that the percentage of carbonic acid does not greatly exceed J, whereas if the disappear- ance is rapid after a few shakes, the contrary of course is the case. It need hardly be said that the accuracy of the process depends upon the precision with which the solution is measured, and for this purpose a pipette, or a burette, will do better than a graduated glass cup. I think it best to carry each separate J- ounce of lime-water in its own bottle, and it is well to see by actual measurements that ^ ounce can be poured from the little bottle, for a few drops always remain behind. However, even if all precautions are taken, the observations cannot pretend to vie with Dr. Hesse's method (p. 505) in accuracy, because changes of temperature and pressure alter the weight of the air contained in the 8-ounce bottle. Luckily in the case of mines, the two sources of error act in opposite directions, and sometimes may neutralise each other, the tendency to expand, owing to increased temperature, being counteracted by a greater barometric pressure due to the depth of the mine. A leather case containing an 8-ounce bottle and four half- ounces of lime-water, by means of which four tests can be made, measures only 7^ inches by 3^ inches by 2 inches, and is sufficiently portable to be easily carried, even when climbing up "rises" or "stopes.". Lunge's Apparatus. Instead of simply deciding whether or no the carbonic acid exceeds the proposed standard of 0*25 per cent, by volume, it may be sometimes desirable to ascertain the precise amount of the impurity. This can be done by Dr. Lunge's t little apparatus which I described some years ago. I The method was * The exact size should be 8^5- oz., the volume of air being 7f & oz., because the lime-water occupies ^ oz. ; but an ordinary 8-oz. bottle is near enough for the purpose. t Zur Fraye tier Ventilation, Zurich, 1877. C. Le Neve Foster, " On Dr. Angus Smith's Method of Testing the Air of Mines and Dwelling-houses," Ann. Rep. Hin. Assoc. Corn, and Devon for 1882, p. 7. 54 ORE AND STONE-MINING. originally suggested by Dr. Angus Smith,* and his process consisted in pumping the air of the working place through lime-water until a known standard of milkiness or opacity of the solution was attained. Bad air would cause the standard amount of opacity with very few strokes of the pump, whilst good air required many. I now find it convenient to use lime-water of known strength, and to go on with the pumpings until the pink colour given by phenol - phthalein is discharged. This method is, I consider, more accurate than endeavouring to reach the proposed standard of milkiness. Dr. Lunge's apparatus consists (Fig. 586) of a No. i, or i -ounce, flexible ball-syringe A, connected by a piece of india- rubber tube B, with the bent glass tube D; at the point C a slit about f inch long is cut in the tube with a very sharp knife. FIG. 586. FIG. 587. This acts as a valve. The tube D passes very little beyond the cork of the bottle E, which holds about two ounces. F is a tube extending nearly to the bottom, connected by a small piece of india-rubber pipe with the valve-tube G, shown on a larger scale in Fig. 587. It is simply a piece of glass tube, with a ring made of india-rubber tube, supporting a glass valve. The top part of the valve is flat, not spherical, and it allows free' passage of the air when in the position shown in the figure. If you squeeze the ball A, supposing the bottle partly full of water, the valve in G rises and prevents any escape of liquid, and the air rushes out at C. On allowing the ball A to expand again, the slit C closes, air enters through G, and bubbles up from the bottom of F into the bottle. In order to make the bottle as portable as possible, I prefer to use one piece of tube containing the valve instead of having a- separate valve-tube as shown ; however, this is a mere detail of minor importance. * Op. cit., p. 238. VENTILATION. 505 Half an ounce of lime-water or baryta-water of known strength, and coloured pink by phenolphthalein, is put into the bottle ; the ball is squeezed and allowed to expand, and a definite volume of air is drawn into the apparatus. A good shaking is given, and continued long enough to cause the absorption of all the carbonic acid by the solution. This process of squeezing the ball and shakiDg the bottle is repeated until the pink colour is discharged, and knowing the strength of the solution and the volume of air passed through, it is easy to calculate the percentage of carbonic acid contained in the air. Lunge reckons that each squeeze of a No. i ball causes the entry of 23 cubic centimetres of air. The " No. i " means a one-ounce size ; it really contains about 28 cubic centimetres, but the whole of this cannot be expelled by squeezing. To save the trouble of making calculations each time, a table should be drawn out once for all with two columns, the first giving the number of squeezes, and the second the corresponding percentages of carbonic acid. Further details are given by Winkler,* but the form of bottle shown by him, with a long projecting valve tube, is not so portable as the one which I use with the valve contained in the piece of tube inside the bottle. My case is not larger than a field-glass, and holds all that is necessary for making six determinations underground ; it is most convenient to wear it upon the belt, in the same manner as the " Tscherpe-Tasche," or pouch of the Saxon miner. Where greater accuracy is required, I recommend Hesse's apparatus,f with which I have made a very large number of carbonic acid determinations in the working places of mines. The leather case, which contains the necessary bottles, burettes, barometer and thermometer, measures 15 inches by 9^- by 5. Oxygen. The unfitness of air for breathing is indicated not only by an excess of carbonic acid, but also by a deficiency of oxygen. When there is both a lack of oxygen and an undue proportion of carbonic acid, it is evident that some process of oxidation has been going on, such as the respiration of the miners, the burning of candles or lamps, the slow combustion of coal or pyrites, or, lastly, the putrefaction of timber or other organic matter in the mine. All four causes may combine to render the atmosphere unhealthy. Dr. Angus Smith considers that when the proportion of oxygen * Lehrbuch der teckniscken Gasanalyse, Freiberg, 1885. f Hesse, " Anleitung zur Bestimmung der Kohlensaure in der Luff, nebst einer Beschreibung des hierzu nothigen Apparates." JEulenbery's Vierteljahrsschrift fur gericlttliclie Medicin und offentliches Sanitatswesen , Neue Folge, vol. xxxi., Berlin, 1879, p. 357. Hesse, " Zur Bestimmung der Kohlensaure in der Luft," Hid., vol. xxxiv., I88i, p. 361. Winkler, Anleitung zur chemise/ten Untersuchung der Industrie- Gase, Freiberg, 1877, p. 375. Winkler, Lehrbuch der technisc/ien Gasanalyse, Freiberg, 1885, P 67. 506 ORE AND STONE-MINING. by volume has been reduced below 20*9 per cent., the atmosphere is impure, and when the percentage descends below 20*6, he calls it exceedingly bad. Lindemann's Apparatus. For determining the percentage of oxygen in the air of mines, the simplest apparatus is that of Lindemann, which is figured and described by Winkler.* It is based upon the property possessed by moist phosphorus of combining with the oxygen of the air at ordinary temperatures ; if a large surface of phosphorus is presented to the air, the absorption takes place comparatively rapidly at temperatures between 60 and 70 F. (15 to 20 C.). This apparatus, and instruments of a similar class in which an alkaline solution of pyrogallic acid is used as an absorbent of oxygen, are better suited for use in the laboratory than for making determinations in the mine itself, unless it is desired to confine the observations to one spot. The box containing Lindemann's apparatus is 17^ inches high by i of inches wide, and 5^ inches deep, and the weight when ready for use is 8 Ibs. The dimensions and weight are not prohibitive, but it would not be safe to carry such a box with its glass vessel of phosphorus when climbing up stopes by a chain ; and there are two other important objections to its use underground : (i) it is difficult to manipulate such instruments with the dirty hands inevitable in mines ; and (2) in each working place it would be necessary to wait until the whole of the apparatus had assumed the temperature of the surrounding atmosphere, because unless this were done the results would be erroneous from changes of volume. However, it is easy to bring up samples in suitable glass bottles, and then submit them to analysis in a laboratory above ground. The manipulations are not difficult, and any mine agent capable of doing the delicate work required for an. accurate mine survey or the assay of an ore, would find no difficulty in making determinations, sufficiently exact for his purpose, of carbonic acid and oxygen in underground air. When the task consists in determining the proportion of such gases as sulphuretted hydrogen or the quantity of organic matter, he must call in the services of the chemist. MEASURING THE QUANTITY AND PRESSURE OF THE AIR. More attention is paid by miners to measure- ments of quantity than to determinations of quality. The quantity of air passing through any given passage can be calcu- lated by measuring its sectional area and ascertaining the speed of the current. In the old days there were two rough methods of estimating the velocity of an air-current: (i) by carrying a candle in the hand and regulating the pace so that the flame was not deflected either backwards or forwards, the rate of walking was therefore precisely that of the current; (2) by * Lehrbuch der technischen Gasanatyse, Freiberg, 1885, p. 58. VENTILATION. 507 exploding a little gunpowder and observing how long the smoke took to travel along a measured distance in a level. These methods have been abandoned in favour of speed-measuring instruments known as anemometers. Anemometers. Two kinds may be mentioned : fan-plate type and windmill type. Dickinson's * is one of the former class ; it consists of a plate of mica, hung from two fine bearings, and counterpoised so that a very light breeze will deflect it from its normal vertical position. The deflection is measured by a quadrant attached to the frame of the fan-plate, and, instead of marking the angles, it is usual to show by the graduations the velocity of the air in feet per minute. The instrument is graduated by actual experiments upon a test- ing machine. In anemometers of the second type, the speed of the air- current is determined by the number of revolutions of an instrument provided with vanes like those of a windmill. Biram's anemometer, one very commonly used, has eight or ten vanes made of mica or vulcanite or aluminium, attached to arms radiating from a small central wheel. The instrument is held up at arm's length in the current, and by the aid of suitable gearing and dials and pointers, like those of a gas-meter, it registers either the number of its revolutions, or the rate in feet or metres at which the air is travelling, during a short period of time, measured by a watch. As a slow current of air will not make the vanes move round, from its being unable to overcome the friction of the parts, the makers usually supply a certificate with each instrument showing what correction must be made on this account. The correction is determined by a testing machine, on which the anemometer can be whirled round at various rates of speed ; it can then be seen how far the readings of the anemometer agree with the known velocity at which the whirling has been carried on. Messrs. Davis and Son, of Derby, make a self -timing anemo- meter which dispenses with the use of a watch ; it is held up in the current and when the vanes are considered to be revolving at a constant speed, a catch is pressed ; this allows the vanes to act on a pointer which indicates on a dial the velocity in feet or in metres per second. In making observations with the anemometer, it is essential that an airway of uniform section be taken ; levels which are lined with brick arching are well adapted for the purpose. If the airway is not regular, eddies will be set up interfering with the accuracy of the results. A further necessary precaution is taking observations in various parts of the area chosen for the experiment, because the velocity is not uniform through- * Dickinson, "On Measuring Air in Mines," Trans. Manchester Geol. Soc., vol. xiv., 1878, p. 31. ORE AND STONE-MINING. out this area. The mean of the readings gives the mean velocity of the current. In the instructions laid down by a committee appointed by three of the British Mining Institutes,* the area at which the observations are made has to be divided up by horizontal and vertical strings into sixteen equal parts, and a reading of the anemometer taken in each. Water- Gauge. For calculating the efficiency of the venti- lating machinery, a mere knowledge of the volume of air passed through the workings does not suffice ; in addition, its pressure has to be determined, or rather the difference between its pressure and that of the external atmosphere. The instrument employed for this purpose is the manometer, or water-gauge. It is a glass tube bent in the form of a U, partly filled with water; one leg is in communication with the outer atmosphere and the other with that of the mine. Usually it is placed in the engine-house of the fan, and a pipe is carried from it into the fan drift. The suction of the fan causes the pressure of the air in the mine to be less than that of the external atmosphere, and the diminution of pressure is indicated by the difference in the heights of the two columns of water in the U-tube, The manner in which a water-gauge acts can easily be explained to students by construct- ing a model from a Woulff's bottle (Fig. 588), or any other bottle or jar which will take three pieces of glass tube. If the mouth is applied to the piece of india-rubber tube A, air can be drawn through the bottle in the direction indicated by the arrows. With a certain degree of suction, the resistance caused by the passage through the tube B becomes plain, and a strong air current is not produced until the external pressure is decidedly greater than that inside the bottle, which is indicated by the rise of the coloured water in the gauge C, as shown in the figure. In the instruments employed in mines, the difference in pressure is measured by a scale which can be moved up and down by a screw, so as to make the zero correspond with the level of the water in the free limb. It usually varies from i to 4 inches. In order to prevent the water in the gauge from oscillating rapidly up and down, which would happen if the current were irregular, the tube connecting the two upright limbs is contracted, or, what comes to the same thing, the gauge is * Joint Committee of the North of England Institute of Mining and Mechanical Engineers, Midland Institute of Mining, Civil, and Mechanical Engineers, and the South Wales Institute of Engineers, " On Mechanical Ventilators, 1888," " Observations to be Made, and Instructions to the Engineers." Trans. N. E. Inst. H. M. Eny., vol. xxxvii., 1887-8, p. 190. VENTILATION. 509 made in the form of two chambers with a glass front and a connect- ing aperture, the size of which can be regulated by a tap. This is Dickinson's water-gauge,* which is a brass box 6 inches high, 4 inches wide, and 3 inches deep, with a partition in the middle, making two chambers each 2 inches by 3 inches. A glass front shows the two columns of water, and a scale, graduated into inches and tenths, enables the difference in their heights to be measured. Efficiency of Ventilating Appliances. The efficiency of a fan or other ventilator is calculated by comparing the work which it does in drawing air through the mine, with the work done by the steam in moving the piston of the engine that drives it. The work done in moving air is reckoned from the volume displaced and the pressure ; the former is ascertained by the anemometer and the latter by the water-gauge. As a cubic foot of water weighs 62*425 -pounds, each inch indicated by the water- gauge will represent pressure of one-twelfth of this amount, or 5-2 pounds per square foot. A depression of the water-gauge of 2 inches will mean 2 x 5*2 or 10*4 pounds pressure per square foot. In common parlance the word " depression " is understood, and the miner speaks of a " water-gauge " of 2 inches, for instance, meaning thereby a depression of the water-gauge. The work done is looked upon as that of pushing a volume of air through a pipe under the pressure indicated by the water- gauge. Let A represent the area of the airway in square feet, Y the velocity of the air current in feet per minute, as measured by the anemometer, Wthe water-gauge in inches, 5*2 pounds being the weight of a column of water one inch high with an area of i square foot, E the useful effect of the ventilator. Then E = (A V W x 5*2) foot-pounds per minute. To ascertain the horse-power it is only necessary to divide by 33,000, and we may state : E = AVWx 5-2 H . p 33,ooo Thus to take an example : If the quantity of air in circulation, A V, is 100,000 cubic feet per minute, the water-gauge 1*5 inches, the useful effect of the ventilation will be : 100,000 x i -5 x 5-2 = 6 H p 33,ooo The efficiency of the ventilating plant is the ratio of the horse- power of the ventilation so calculated to the indicated horse- power of the driving engine. * Dickinson, op. cit., p. 12. 510 ORE AND STONE-MINING. Supposing that the indicated horse-power was found to be 45 T we should have the ratio of 23*63 to 45 as denoting the efficiency. In other words : Efficiency = 2 -3_J*= -5251 or 52-51 per cent, 45 Resistance caused by Friction. The amount of power required to overcome the friction of the air current in passing through the passages of the mine must be studied, because it is an important factor in the problem of ventilation ; and unless its effects are appreciated the best method of arranging the ventila- tion will not be understood. The amount of friction depends upon five conditions : 1. The length of the airway, which we may call L. 2. The perimeter of the airway, P. 3. The sectional area of the airway, A. 4. The velocity of the current, V. 5. The nature of the rubbing surface, the effect of which may be expressed by a co-efficient C. The friction is directly proportional to the length of the airway and its perimeter; in other words, if there is twice as much rubbing surface, there is twice as much friction. It is inversely proportional to the sectional area of the airway that is to say, a level 7 feet high and 10 feet wide will cause only one-half of the friction produced in a level of the same height, but 5 feet wide. Lastly, the friction increases as the square of the velocity. These relations may be expressed by the general formula : Eesistance due to friction = C L F ^ It is evident from this formula that it is desirable to shorten the path of the air as far as possible; much is done in this direction nowadays by " splitting" the air current that is to say, dividing it into separate branches instead of causing the whole of the current of the downcast shaft to travel through the entire length of the workings, With regard to the second factor, the perimeter, it may be well to notice that a circular section is the one with which a given length of perimeter affords the largest area. Take, for instance, the case just cited of a rectangular airway, 7 feet high by 5 feet wide, with a perimeter of 24 feet and an area of 35 square feet. A circle having a circumference of 24 feet would have an area of 45 '8 square feet, or 30 per cent, more than the rectangle. Splitting has also the effect of reducing the velocity required for the passage of a given quantity of air through the mine. Suppose that 90,000 cubic feet are wanted per minute in order to ventilate the mine ; if the mine is divided into three equal and similar districts and each is ventilated separately by one- VENTILATION. 511 third of the main current, the velocity of the minor currents need be only one- third of what would have been necessary if all the air had had to travel by one road. Reducing the velocity to one-third means, according to the formula, a diminution of the resistance caused by friction to one-ninth. The co-efficient, C, varies according to the nature of the rubbing surface ; in smooth passages, such as those of levels lined by an arching of brick, it will naturally be less than in the irregular airways along the working face, or in an airway with frames of timber, forming a succession of projecting obstacles at short intervals. FIG. 589. 0-5 If the resistance due to friction, or, in other words, the pressure required to overcome it, is measured in pounds per square foot, then taking L and P in feet, Y in thousands of feet per minute, and A in square feet, the co-efficient C varies from 0*002 to 0*014* according to the nature of the airway. Mining engineers owe a debt of gratitude to M. Murgue t for his graphic representation (Fig. 589), which illustrates the influ- * Elwen, " An Account of Experiments on the Resistance to Air Currents in Mines," and Walton Brown in the discussion. Trans. N. E. Inst. M. E. t vol. xxxviii., 1888-9, P- 205-218. f " Recherches Experimentales sur la Perte de Charges dans les Parcours Souterrains," Bull. Soc. Ind. Min., vol. vii., 1893, p. 5 ; and translation in Trans. Amer. Inst. M. E. t vol. xxii., 1893-1894. 512 ORE AND STONE-MINING. ence of the sides of an airway in a most striking fashion. He compares three kinds of airways : one arched, ABC; a second, D E F G, in bare rock ; and a third, H I J K, lined with timber ; and he shows that, with the dimensions given in the figure, all three airways produce the same amount of friction, or cause the same loss of " head." In other words, the arched passage ABC, in spite of its small dimensions, offers no greater resistance to the air current than the large timbered tunnel H I J K ; whilst you may put the brick lining ABC inside a level D E F G without in any way requiring additional ventilating power. He concludes that it is more important to diminish the friction in the air- passages than to seek for .better ventilators, and that the miner can lessen the resistance to air-currents not only by increasing the size of his levels, but also by lining them with brick or stone in place 'of timber, and by keeping them as straight as possible. CHAPTER XI. LIGHTING. Keflected daylight Candles, candle-holders Lamps and lamp oil Wells light Magnesium wire Safety lamps : Davy, Clanny, Mueseler, Marsaut, Hepple white- Gray Locks: lead rivet, magnetic bolt, Cuvelier's lock Coal gas Electricity. MIXES are usually lighted by candles, torches, lamps, gas, or electricity. In a few cases the miner does his work without artificial light. In sinking oil-wells in Burma,* the quantity of explosive gas is so great that no naked light can be used, and even if the work- man had a safety lamp, he would be unable to stay below ground long without being affected by the noxious atmosphere. He therefore carries no light at all, and has his eyes bandaged up before he goes down, because otherwise it would take longer for his eyes to become accustomed to the semi-darkness of the bottom of the pit, than the whole time he can stay below ground. Reflected Daylight. For sinking oil-wells in Japan t reflected daylight is used. A piece of yellowish translucent oil- paper, about 5 feet by 3 J feet, is suspended over the well at an angle of 45 and throws fight down the pit. The wells are about 3! feet square, and are dug to a depth of 600 to 900 feet. In driving the Bell tunnel at the New Idria quicksilver mine,J in California, there was a disastrous explosion from the igni- tion of some inflammable gas, and after this occurrence the tunnel was lighted by the reflection of the sun's rays. A mirror was kept at the mouth of the drift at the proper angle to effect this, and with a straight tunnel and in a sunny country like California the device answered perfectly. Candles. The candles used by miners are very frequently the so-called " dips " that is to say, they are made by dipping a wick into molten tallow and allowing it to take up grease; the process is repeated several times, until the thickness of tallow is sufficient. The wick is made of cotton, or of cotton and linen. * Noetling, liec. Geol. Surrey India, vol. xxii., 1889, P- 97- t Redwood, "Petroleum and its Products," Jour. Soc. Arts, voL xxxiv., 1886, p. 832. J Becker, " Geology of the Quicksilver Deposits of the Pacific Slope," Mon. U.S. Geol Survey, vol- xiii., 1888, p. 308. 2 K 514 ORE AND STONE-MINING. At Snailbeach Mine, in Shropshire, the manager stipulates that the wick shall be made of three threads of cotton and three of linen ; this is folded, and the candle therefore has a wick of six threads of cotton and six of linen. The size of the candles is reckoned by the number that go to a pound, which varies from 20 to 6. Candles of six- teen to the pound are very commonly used by the miners, while the agents, who want an extra amount of light for their exam- inations, find it convenient to have "eights" and occasionally " sixes." These candles require snuffing from time to time, though I have seen snuffless dips employed in exceptional cases. In hot mines special dips are necessary, for those made of ordinary tallow become soft and bend down. As a rule the British ore-miner holds his candle in a lump of clay, which forms a very convenient support. It has the advan- tage that the candle can be stuck up at any point where it is wanted, without a moment's delay in seeking for a place to fix it ; it is also readily stuck upon the hat when the miner wants to climb a ladder or a chain. But the clay must be soft, well kneaded, and free from stones or lumps ; from time to time it has to be moistened, and care and practice are required in order to work it down properly as the candle is consumed. In the Forest of Dean many years ago, the candle was stuck into a cleft stick, which was carried in the mouth. Nowadays metal candle-holders are used instead, with a point which can be stuck into the timber or a crevice in the rock. The tallow candle has the disadvantage of guttering in a draught and of causing a good deal of smoke, which is bad if the working place is at all close. The Festiniog men guard their candles against draughts, when walking to and from their work, by shades made out of old meat-tins with a handle of wire. If there is much water dropping down a shaft the miner can protect his. candle by a shield of tin-plate nailed to a piece of wood. Grease is bad for amalgamation, and sperm candles are adopted in some gold mines, as they are less objectionable than those made of tallow. Paraffin, stearine FIG. 590. and "composite" candles may be and are used in place of the common dip; they do not stand a strong draught or drops of water so well as the latter, but they give less smoke _ and do not gutter so much. JJZ) Moulded candles are conve- niently carried by a holder,. such as is seen in the United States, made of a small rod of iron with one end bent into a handle and the other pointed (Fig. 590). In the middle there is a cylinder of thin sheet iron which has LIGHTING. spring enough to clip the candle firmly ; a sharp hook, sticking up at right angles to the horizontal rod, enables the holder to be hung on to the slightest little projection, if there is no convenient crevice or piece of timber into which its point can be thrust. The Australian has a somewhat similar holder made of wire, known as the " spider."* The wire is about one-sixteenth of an inch thick, twisted as shown (Fig. 591); the spiral portion holds the FIG. 591. candle, and the little hook will hang on to the face of the rock. A candle-holder of some kind is more convenient to an official who has to make notes underground, than the usual lump of clay ; with the latter it is difficult to keep the note- book clean. Torches. Torches are em- ployed in a few exceptional instances. The foremen at Falun, in Sweden, carry torches consisting of bundles of pine sticks held together by an iron ring, and some gold mines in Japan f were lighted a few years ago by torches made of dried bamboo twigs ; fires of pitch- wood have been used at night when washing down gravel by the hydraulic process. Large underground chambers may be lit up for a short time, in order to examine the roof, by burning a bundle of wood shavings soaked with naphtha and petroleum. Lamps. Lamps vary much in shape and size. The Sicilian miner has a lamp of the simplest construction imaginable ; it is a mere open cup of unglazed pottery, about 2 inches in diameter and i inch deep, with a little lip for holding a cotton wick, which lies loosely in the olive oil used as an illuminant. It is ruder than the old Roman lamps found at Pompeii, which somewhat resemble those still employed in the Hartz. The latter are provided with a hook, by which they can be held between the thumb and forefinger when climbing ladders; the hook has a sharp point which the miner can stick into a timber prop or a crevice in the rock while at work. The body of the lamp is closed ; it has a tube for the cotton wick and a hole with a screw-plug through which the supply of oil can be replenished. * Annual Eeport of the Secretary for Mines, Victoria, for the year 1 888, Melbourne, 1889, p. 36. t Frecheville, " The Mining and Treatment of Gold Ores in the North . of Japan," Min. Proc. Inst. C.E., vol. Ixxv., 1883-84, p. 169. J Bowie, Hydraulic Mining in California, New York, 1885, p. 246. 516 ORE AND STONE-MINING. A pricker for trimming the wick is attached by a light chain. A smaller but similar lamp is met with in France, northern Italy, and parts of Spain ; the body is lenticular, and is suspended by a long hook. The foremen in the Hartz mines prefer a somewhat similar lamp in which they can burn tallow ; it is an open tray with a rim around it and a lip for the cotton wick ; a large lump of tallow lies in the lamp at the opposite side to the wick, and if the agent wishes to make a flare-up, to illuminate a working place more thoroughly, he need only push a good supply of tallow towards the wick holder, and soon obtains the desired effect. In the Mansfeld copper district the miner has a small tin lamp which can be hung by a wire loop to a hook on the hat, if he is climbing, or be placed upon the ground in the working place. It has a double case, the outer one serving to catch any oil which may run over from the spout-like wick-tube. The Saxon miner still adheres to the " Blende," a wooden case lined with tin-plate or brass, in which he carries a small globular oil lamp. The case is useful in walking or climbing in very draughty parts of the mine, and can be hung from the neck by a leather strap. In Scotland and in some parts of the United States, a small but serviceable tin lamp, of the shape shown in Fig. 592,13 very common. It can be hooked on to the hat when climbing FIG. 592. ladders, or on to the rock. Olive oil or rape oil is burnt in the lamps just described, and the miner carries with him a supply in a little flask. Lamps have the advantage of being cheaper and cleaner than tallow candles, but the latter do not seem likely to be displaced in English and Welsh ore mines, though the Scotch lead miner prefers the former. Mineral oils are occasionally used instead of vegetable oils for ordinary miners' lamps. At the underground stone quarries near Bath the men employ small lamps fed by ben- zoline, which is held by a sponge in the reservoir. Petroleum "Hurricane" lamps for lighting up pit-bottoms and landings (plats) are not uncommon, and even levels are lit up in this way by hanging a lamp at each bend in the road. This saves the miner the trouble of carrying a lamp, and the light is quite sufficient for the purpose of tramming, even if the stretches are somewhat long. Flare lamps, similar to those used by " Cheap Jacks," which generate gas from naphtha, or a mixture of naphtha and petroleum, flowing into a hot burner, may occasionally be seen in parts of underground slate quarries, where a good deal of light is required for hooking-on and unhooking waggons. Wells Light. Among recent inventions for illuminating, I LIGHTING. must specially mention the Wells light, which, after being largely used for surface works, is now finding applications underground. The Wells light is a contrivance for burning tar oils converted into gas, when forced through a heated burner by pressure pro- duced by a hand air-pump. Fig. 593 shows the principal parts of the lamp, A is a closed cylinder made of steel boiler plate, B is a pump worked by the handle C, which can be used for pumping in either air or oil ; whilst the light is run- ning, the oil is drawn from a bucket by the piece of hose D. E is the oil which has been pumped in, thereby compressing the air above it to about 20 Ibs. per square inch. On turning the tap G, the oil is forced up the pipe H to the generating tubes I I, which have been pre- viously heated by lighting some cotton waste and oil in the tray K. The prelimi- nary heating may also be effected by burning a spray of the oil, produced by a special starting appliance forming part of the lamp. The oil in its passage through the hot burner I is converted into vapour, which issues forth from the nozzle L and produces a flame of 1 2 to 30 inches in length, with a con- sumption of half a gallon to J 2" g a ll oris f il per hour, giving a light of 500 to 4000 candles. O is a plug con- nected to a rod which serves the double purpose of letting off the air quickly at any time, and also of gauging the depth of the oil in the cylinder. The lamp is easily carried about from place to place. The smallest size and the larger one, No. 3, have both been employed of late in the large chambers of the Festiniog slate mines for examining the roof and sides, and also for plate-laying. The pressure of the air in the reservoir is kept up by a few strokes of the pump from time to time. ; : The brilliant light emitted by burning magnesium is utilised at 518 ORE AND STONE-MINING. Festiniog, in addition to the "Wells light, for examining the underground chambers. The agents of some of the mines carry a little stock of magnesium ribbon in their pocket-books, and set fire to a piece if they wish to throw a powerful light upon any particular spot which may require special attention. At two of the mines the metal is burnt in a special lamp. It consists of a coil of magnesium ribbon about J inch wide wound upon a reel, which is fed by clock-work, so that it issues from a tube at the focus of a silvered mirror about 8 inches in diameter. The lamp is held by a convenient handle, and the light can be directed on to any given point without dazzling the eyes. The ribbon is consumed at the rate of about i o inches per minute ; the lamp can be started and stopped by touching a catch which controls the clock-work, and there are means of altering the speed at which the ribbon is fed forwards. Safety Lamps. The subject of safety lamps that is to say, lamps which can be used in an atmosphere containing a certain amount of inflammable gas without fear of causing an explosion may seem out of place to some who suppose that their use is confined to coal pits : but when we recollect that fire- damp has been met with in mines worked for diamonds, gold, iron, lead, quicksilver, salt, silver, sulphur, and tin, and further that a lead mine in this country is lighted entirely with such lamps, and that they are indispensable in the case of ozokerite, it is evident that miners generally should have some knowledge of the principles upon which they are constructed, and the manner in which they are used. However, in the mines with which we are dealing, safety lamps are the exception, and, therefore, the subject can be dealt with in a summary manner. The construction of the safety lamp is based upon the fact that gauze of a certain mesh, made with wire of a certain gauge, is capable of cooling burning gases to a point below that at which combustion will take place in other words, it will pre- vent the passage of flame. Therefore, when a lamp enclosed in a suitable cylinder of this gauze is placed in an atmosphere con- taining fire-damp, the inflammable gas inside the envelope will burn without igniting that which is outside. I will now describe briefly the lamps most commonly in use in mines containing inflammable gas ; they are named after their inventors, viz., the Davy, Clanny, Mueseler, Marsaut, and Hepple- white-Gray lamps. The ordinary Davy lamp (Fig. 594)* consists of a brass oil vessel b, on to which is screwed a cylinder of wire gauze a, about i^ inches in diameter and 4^ to 5^ inches high. The * The materials used in constructing the lamps are indicated thus : J3rvtss W Thtn STicctMetctl/ LIGHTING. FIG. 595. cylinder is further closed at the top by a cap of wire gauze e, which overlaps the main gauze for a distance of i inch to ij inches. In the centre of the oil-vessel is a round tube containing a cotton wick, which can be trimmed from the outside by a piece of wire f passing up through the bottom. The gauze used has 28 holes or meshes per linear inch, or, in other words, 784 per square inch. The wire varies slightly in size; some which I very carefully measured was "016 inch in diameter, and was probably intended for No. 27 S.W.G. A maker of repute informs me that he usually employs No. 30 of the old B.W.G. Speaking roughly, the holes are -^ i ncn (k mm -) square. Three rods c, attached oelow to a ring screwed on to the oil-vessel and above to n plate, protect the gauze to a certain extent. The lamp is carried by a strong wire ring fastened to the top plate d. Rape, colza, or seal oil, alone or with the addition of petroleum, are used as il- luminants. The Davy lamp has several grave defects : in the first place it gives very little light ; and secondly, as pointed out by the Royal Commission on Accidents in Mines,* it will fire an explosive mixture if the velocity of the current exceeds 6 feet a second. According to the photometric tests made for the Royal Commission by Professor Clifton,t the light of the Davy lamp varied 1'rom 7 to 22 percent, of that of a standard candle ; these were laboratory experiments, in which the light was not further diminished by the accumula- tion of dirt, grease, soot, and coal dust upon the gauze, as may often happen underground, and nothing is said about the absence of illumination immediately above the lamp. With the powerful ventilating currents in use nowadays, the second defect is a very real one ; it is sometimes overcome by placing the Davy lamp in a cylindrical tin case with a glass window. It was very natural to attempt to remedy the first defect of the Davy lamp by using glass instead of gauze, for the lower part of the enclosing cylinder. In the Clanny lamp (Fig. 595), constructed upon this principle, * Preliminary Report, 1881, p. xiii. t Final Report, 1886, Appendix xxiv., p. 87. 5 2 OKE AND STONE-MINING. FIG. 596. the air which feeds the flame comes in through the gauze just above the glass a, descends along its inner face and goes to the wick ; the products of combustion then pass up the centre. Nothing separates the descending current of air from the ascending current, and consequently the oil, from want of a direct supply of fresh air, does not always burn so brightly as it does in a lamp fed from under the gauze ; but the light is far better than that of a Davy lamp. The letter b represents one of the metal rods for protecting the glass. Professor Clifton's experiments usually gave 26 to 50 per cent, of the light of a standard candle, or, on an average, more than twice as much light as the Davy. In a current having a velocity of more than 6 feet a second it behaves like the Davy, and ignites an explosive mixture. Mueseler's lamp (Fig. 596) may be conveniently described as a Clanny lamp, with a chimney a fixed above the flame, and attached at the level of the top of the glass to a dia- phragm or horizontal partition of wire gauze 6. The path taken by the air is shown by the arrows. The fact of the inward current of fresh air being kept separate from the outward current of foul air assists the illuminating power of the lamp. The wick is sometimes flat. The Mueseler lamp, which is the only one allowed in fiery pits in Belgium, is a favour- ite in many countries, and leaving aside its use in collieries, I may mention that it is the only lamp employed at the very dangerous ozokerite mines of Boryslaw and at the Mill Close lead mine in Derbyshire. It has the merit of going out in an explosive atmosphere, and of so removing a cause of danger. The lamp is extinguished because the chimney is unable to carry off the products of combustion quickly enough; they spread out under the bottom edge of the chimney, and pollute the fresh current to such an extent that it becomes incapable of supporting the combustion of the oil. The lamp will not stand being jerked or inclined, for any- thing which will turn the currents out of their proper course causes the bottom part of the gauze to be filled with the products of combustion and puts the flame out. It is evident that when the lamp is held in an inclined position, all the foul gas will not go up the chimney, and that some will become mixed with the inward current; a jerk downwards checks the supply of air passing in through the gauze, and again the lamp is extinguished. On the other hand, it resists a horizontal current better than the two lamps mentioned previously. If the lamp is struck LIGHTING. 5 21 obliquely by the current an explosion may sometimes take place inside it. Before concluding this very short account of the Mueseler lamp, it is important to point out that a mere diaphragm with a chimney does not necessarily constitute a lamp of the original Belgian pattern. The dimensions of the parts are carefully prescribed by law in Belgium, for it has been found that a slight departure from them may affect the properties of the lamp very materially. A lamp which has come largely into use of late years, and especially in this country after the favourable report of our Hoyal Commission, is that of M. Marsaut, of Besseges. to whom miners FIG. 597. FIG. 598. are indebted for many useful investigations (Fig. 597). It is of the Clanny type that is to say, it has a glass cylinder with the air entering above it, and no chimney ; but it has the extra safety afforded by a second or even a third gauze, and a bonnet or shield of sheet iron. These additions enable it to resist currents of 2000 feet per minute ; other advantages are an illuminating power of about two-thirds of a standard candle, simplicity and strength, for the gauze is protected by the shield from accidental blows of the pick or other sources of injury. The outer shield adds somewhat to the weight of the lamp, but the slight diminution of portability is amply repaid by the increased security which it affords. The Hepplewhite-Gray lamp, with some modifications intro- duced by Ashworth (Fig. 598), is of a totally different type; the wick is fed with air coming in below the glass, through a ring 522 ORE AND STONE-MINING. of wire gauze cZ, on the inside of an annular chamber. When testing for " gas," the openings at the bottom of three brass tubes, through which the air passes into the annular chamber, are closed, and the lamp draws its supply of air from the top of tubes. The path taken by the air is shown by the arrows ; b b are the holes by which the products of combustion escape. The glass is no longer cylindrical, but is made in the form of a truncated cone, with the object of illuminating the roof ; the smallness of the top of the shield a conduces to the same desirable object. If the inside of the glass is blackened at the back, the efficiency for testing is decidedly increased, as images of the flame, such as are reflected from both sides of the ordinary glass, no longer trouble the observer. This lamp has the further advantage for testing that it takes in its supply of air from the top, and will therefore test a layer of air close to the roof which could not be examined by an ordinary lamp, except by tilting it so much that there would be danger of its going out. Locks. In order to prevent careless and imprudent men from risking their lives and those of their comrades by opening their lamps, it is necessary to lock them securely before they are taken into the workings. Various devices have been proposed and adopted. A little bolt screwed in by a key like a large watch-key, through the ring holding the glass or the gauze, was thought at first to offer sufficient guarantee of security ; but it was soon found that ingenious miners could pick a lock of this kind without difficulty, and other plans had to be devised to baffle their skill. The most common systems employed are the lead rivet, the magnetic bolt, and the C livelier fastening. The lead rivet is placed through two holes, one in the brass ring holding the glass and the other in the oil-vessel j it is then firmly squeezed with a pair of nippers, and thus impressed with a mark, which can be changed from day to day if necessary. When this has been done, the lamp cannot be opened without cutting the rivet, which would at once be noticed when the miner handed it in at the end of the shift. The lamp-man easily cuts the rivet before proceeding to clean the lamp; the pieces of lead are collected, melted up again, and once more cast into rivets. The cost of this very effective method of locking is but slight. Several inventors have resorted to magnetism in order to obtain an unpickable form of lock, and Wolf's fastening is one of this description. It consists of a bolt held in its place by a spring, which can only be drawn back when the lamp is placed against a very powerful magnet. This form of lock is largely used. Cuvelier's ingenious fastening, \vhich gives great satisfaction at some French collieries, may be described as a vertical bolt which keeps the lamp locked until it is set free by hydraulic pressure. LIGHTING. 5 2 3 FIG. 599. The two ends of a piece of metal tube, bent into the form of a circle, come close together under the bolt, whilst on the opposite side there is a projecting tube with a very small hole. If hydraulic pressure is exerted on the inside of the tube by means of an accumulator acting through the little hole, the two arms tend to straighten out, and the ends move a little away from one another ; in so doing they allow the bolt to fall from its own weight and the pressure of a spiral spring. The operation of opening is very quickly performed, and the hole in the projecting tube is so small only i to i of a millimetre in diameter that the quantity of water used is insignificant. The hole is on the under side of the tube and has not been found to become choked up by dirt, as might have been expected. Gas. Gas is employed for lighting pit-bottoms, hanging-on places, or sidings, where there is a large amount of traffic. Electric Light. Up to the present time, owing to its want of portability, the electric light has not displaced candles and ordinary lamps in the work of "getting" minerals, save in a few special cases. It is true that various small portable incandescent lamps have been in- vented and tried, but until lately they have failed to satisfy all the conditions which are necessary for commercial success. More promising than its predecessors is the Sussmann lamp, which is now coming into the market. A (Fig. 599) is a steel case enclosing a dry storage battery ; B is an outer protecting cylin- der of glass, held between four upright rods, C ; 1) is the vacuum bulb with the filament which becomes incandescent ; E and F are conical whitened reflectors destined to make the best possible use of the light. The back half of the glass cylinder is whitened for a similar reason. The lamp is 2f inches square at the base and 8 inches high ; it weighs 3 Ibs. 10 oz. (1*64 kil.). One pattern is said to give a light of one candle- power for fourteen or fifteen hours, and another three candle-power for nine and a half hours. The advantage of this lamp over those previously brought forward is the absence of any liquid. The interior of the battery is solid, and consequently the lamp can be held or laid in any position. The company owning the patents is ready to make contracts with mine-owners to supply lamps, charge them daily, and keep them in repair for 4cZ. per lamp per week, or about what oil alone is costing at the present time. As regards its safety, it is stated, as the result of numerous experiments, that the smallness of the filament prevents any chance of its igniting explosive mixtures, in the event of both the 524 ORE AND STONE-MINING. outer cylinder and the bulb being broken. Like all other electric lamps, it has the defect of affording no indication of fire-damp or carbonic acid. Where a fixed light can be used in other words, where the nature of the excavation to be lighted is not rapidly changing the electric light is rendering incalculable services. Thus, in sinking shafts, a few incandescent lamps hung from an electric cable enable the miner to do his work under unaccustomed con- ditions of brilliancy. He not only gets better illlumination, but he is relieved from all trouble about candles or lamps, and can set about his work as a navvy would at the surface. This means a saving of time which is often well worth paying for. While blasting is going on, the lamps are drawn up out of the way of stones which might be hurled up and break the glasses. Fixed glow lamps form a convenient and desirable means of lighting up pit-bottoms, on-setting places, levels and sidings where the trafiic is large, and ladder-ways and man-engines which are much frequented. When the area to be illuminated is large, an arc-lamp may be employed with advantage. Among the first successful applications of electric lighting to underground excavations may be mentioned that of M. Blavier at the Angers slate quarries.* In the year 1879 he fixed two Serrin lamps in one of the large underground chambers with an area of 2400 square yards, and he found that they gave light enough for all the men at work. The total cost, reckoning everything viz., coal, carbons, repairs, labour, deprecia- tion of plant, and interest on capital was 50 francs a day; the gas formerly in use cost 54 francs a day and gave much less light. The large chambers in the salt-mine of Maros-Ujvar in Hungary t have been lighted up by electricity since 1880. The cost is some- what greater than that of the tallow, oil, or petroleum formerly in use ; but, per contra, the illumination is better, the men can do more work and are more easily supervised, whilst the air of the mine is not deteriorated by the products of combustion of the lamps. Slanic salt-mine in Roumania has been lit with the electric light in a similar manner since 1883. In a previous chapter I described the working of the thick bed of lead-bearing sandstone at Mechernich by large underground chambers, which eventually are allowed to collapse. Of late years arc lights have been largely used for illumination, although the number of men in one chamber is never more than six and often not more than two. The great advantage derived from the use of the powerful light has been the possibility of removing with safety thousands of tons of ore, which otherwise would have been left undergound for fear of accidents in taking it down. * Blavier, " L'Eclairage electrique aux Ardoisieres d'Angers," Annales des Mines, ser. 7, vol. xvii., 1880, p. 5. t Oest. Zeitschr. B. u. H. W., 1882, p. 296. LIGHTING. 525 It is proposed to use arc lights with reflectors, similar to the naval search lights, for examining the roofs and sides of the large underground chambers in the Welsh slate mines. Arc lights stand in good stead when work has to be done at night above ground. Thus, at Rio Tinto, the great open-cast is lit up by two arc lights, one at each end of the major axis of the elliptical pit. In the same way two arc lights of 2000 candle power are used for night-work in washing down auriferous gravel at the works of the Osceola Company in Nevada.* As the use of electricity spreads for the purpose of transmitting power, we may naturally expect further development of the lighting of parts of mines from the same source. * Eny. Min. Jour., vol. li., 1891, p. 630. ( 5*6 ) CHAPTER XII. DESCENT AND ASCENT. Steps and slides Ladders Bucket or cage Man-engine, single and double. AT first sight this subject might seem scarcely to deserve a separate chapter ; but if one considers the time occupied by the miner in going to and from his work, and recollects that his hours are reckoned " from bank to bank" i.e., from the moment he leaves the surface till he reaches it again and if one further dwells upon the terrible waste of energy involved by climbing up and down deep shafts by ladders, it will be admitted that the question of descent and ascent requires to be discussed. Where mines are worked by adit levels, the men naturally walk in along the ordinary roadways. Such mines, however, are exceptional, and the workmen generally have to climb down and up by ladders, or are lowered and raised by the winding machinery. The means of access to and from the workings may be classified as follows : 1. Steps and slides. 2. Ladders. 3. Bucket or cage. 4. Man-engine. Steps and Slides. If the dip of a seam or vein is small, an inclined pathway, leading down through the old workings, forms a safe and pleasant travelling road into the mine, and it has the further advantage that the ponies or horses can be brought out at the end of each shift. When the inclination reaches 20 it is well to have regular steps, instead of making the men scramble down an irregular path ; it is true that the miner, accustomed to the road, does not lose so much time as a stranger in picking his way along a rough or slippery track, but still a bad path causes a little unnecessary delay which is best avoided. Steps are much less fatiguing than ladders placed so flat that part of the weight of the body has to rest upon the arms. Steps may be cut in the rock itself, if it is hard enough, and if not, wooden or stone stairs can be put in, with a handrail. When the dip is too high for making the stairs straight, they may be DESCENT AND ASCENT. 527 arranged in a zigzag line, provided that the excavation affords sufficient space. The height of the steps should not exceed 8 inches, so as to avoid a fatiguing lift of the foot. In parts of the Sicilian sulphur-mines,* where the dip does not exceed 30 to 35, the steps are from 8 to 10 inches high and 12 to 14 inches broad, and occupy the whole width of the travelling road ; if the dip is from 40 to 50, two sets of steps are made, so that the level of the tread on one side corresponds with the middle of the height on the other. This system is known as that of the scaloni rotti, and greatly facilitates the ascent up such steep roads. In some of the Austrian salt-mines the men descend by wooden slides inclined at angles varying from 30 to 50, flattening at the bottom so as to reduce the velocity gradually ; the miner can increase his speed by leaning forwards or lesse'n it by leaning back. The ascent is by steps. Ladders. Ladders are very largely used in ore-mines all over the world, but they vary a good deal in different countries. In Mexico and in Chili, the common ladder is merely a pole with notches at the sides for receiving the feet. These ladders, especially when worn, are better fitted for barefooted or sandaled miners than for those wearing a heavy and unyielding boot. The so-called " centipede ladder," met with in out-of-the-way parts of Australia, and even sometimes seen in Europe, is very properly condemned by the inspectors of mines in Queensland.f It is made of a single pole, often a sapling with the branches cut off, with auger holes through which wooden pegs are inserted at regular intervals. The projecting pegs form the rungs of the ladder. If such a ladder is new, with the pegs set evenly and firmly, and placed at a proper angle, it will serve for shallow depths ; but ladders of this description are usually put in by men who are not good at carpentry, they are hung vertically, the pegs are uneven originally or are allowed to get rotten, and the suc- cessive ladders are not securely joined ; the task of climbing then becomes a dangerous one. The ordinary ladder consists of two sides and a series of rungs (staves, Cornwall). The principal points that have to be considered are the material, the size, and the mode of fixing. In this country the mine ladder is most commonly made with wooden sides and iron rungs. The sides are easily formed by putting a sawcut through a plank as supplied by the timber- merchant. 2 inches thick by 8 inches wide, giving two pieces 4 by 2 inches ; pitch-pine is largely used on account of its durability. The two sides are fastened together temporarily, and auger holes bored through them both, so that they match exactly. The rungs * Parodi, Sutt* Estrazione dello Solfo in Sirilia. Florence, 1873, p. 24. t Ann. Bep. Dep. Mines, Queensland, for the Year i8$9, p. 122; 1890, p. 130. 528 ORE AND STONE-MINING. are made of pieces of round iron, f to J inches in diameter. It is true that one may see inch iron employed for the rungs ; but, leaving aside the question of safety, this is false economy. The thin rung wears quickly, if there is much traffic, and soon has to be replaced, entailing an expense which would have repaid the extra cost of the thicker iron in the first instance. On the Continent wooden rungs are common, and oak is preferred on account of its durability ; the wooden stave is often made flat, instead of round, so that it may last longer, and iron sides may be seen where dry rot is very bad. A ladder made entirely of wood is lighter than one with iron staves, and this is an advantage if it has to be moved about much. In places where an ordinary ladder would be knocked to pieces by blast- ing, such as the bottom of a shaft in course of sinking, a short length of chain ladder is put in ; the sides are made of pieces of chain, and iron rungs are attached at suitable intervals. Wire rope is also used for the sides of ladders, and Rochebeau uses steel tube for the rungs. He supplies the ladders of this description, which can be rolled up into a coil and kept in readi- ness in case of an emergency. A very important point is the distance between the rungs : it should be chosen so as not to cause too great a lift of the foot at each step, whilst at the same time the number of steps must not be increased out of reason. Experience shows that a distance of 10 inches from centre to centre is very suitable ; ladders with a step of 1 1 inches or 1 2 inches are far more fatiguing to climb. The two end rungs often have collars, and, like them, the middle rung is screwed at the ends for nuts ; these add to the general strength of the ladder; the sides are thus kept permanently about n inches apart. If not secured in some fashion the ends may come together a little and the middle bulge out. It is advisable to have a uniform pattern for all the ladders in a mine, such as 14 feet, for instance, and when an old ladder has tobe replaced, a suit- able new one is ready in stock, without any delay for taking measurements or making it. Two such ladders joined together form a very convenient length for a " footway " in a shaft ; they make a ladder 28 feet long, and allowing 4 feet to project above the platform, for safety and comfort in getting on and off, there remains a length of 24 feet for actual climbing between the plat- forms or sollars. The two ladders can be fastened together by an iron strapping-plate on each side, held in position by the nuts of the two terminal rungs. Where the ladders have plain rungs at the ends a strong wooden cleat nailed on to both ladders makes the connection. In making the joint between two ladders, care should be taken to maintain the proper distance between the staves and the regular inclination ; for when once a man has got into the rhythm, so to say, of climbing, he is liable to miss his step and fall if a rung fails to come just where he expects it. DESCENT AND ASCENT. 5 2 9 FIG. 600. Fig. 600 represents a ladder * made entirely of iron, such as is largely used in mines in the north of France. The sides are of flat iron, 7 x 70 mm. (about \ x 2\ ins.) and the rungs are of round iron, 22 mm. (f inch) in diameter; they are 252 mm. (9-9 inches) from centre to centre. Three of the rungs are bolts with nuts, and the others are riveted ; the manner of joining two ladders by a cotter bolt with a square end is evident from Fig. 60 1. The iron may be galvanised to prevent rusting. Ladders of this descrip- tion weigh 10 kil. per metre (20 Ibs.) per yard. Platforms (sollars, Cornwall) should be fixed at short intervals; though our British law allows them to be placed 60 feet apart, the distance can be reduced with great advantage FIG. 601. -ire.. 295-M IZ-I6.NS -30M U to 1 8, 20, or 24 feet in perpendicular or highly inclined shafts. A much shorter interval would mean too many changes, and a longer one would render falls more danger- ous, besides curtailing the number of enforced short rests, which are a relief in climbing up from great depths. One side of the ladder may be fastened to timber in the shaft by strong staples ; and if not, it should be kept rigid by stays, so as to prevent any swaying. Lastly comes the question of the angle at which the ladder should be inclined. The mine-owner should spare no pains to render the " travelling " as safe and as easy as possible, and should recollect that the miner climbs with the least amount of fatigue, when the greater part of the work of raising the body is thrown upon the muscles of the legs and not upon those of the * One of the patterns supplied by Komain Sartiaux, of Henin-Lietard, Pas-de-Calais. 2 L 530 ORE AND STONE-MINING. arms; the part played by the arms should be keeping the body in a proper position and preventing falls. It may here be noted that the miner does not climb a ladder like a bricklayer or a house-painter. The latter place their hands upon the sides of the ladder ; the miner grasps the rungs, and even if his foot slips, or if a faulty rung gives way under him, he has a chance of saving himself. In climbing down he frequently misses every alternate stave with his hands, or, in other words, he makes two steps with his feet for one grasp with the hand. The most convenient angle for ladders is about 20 from the vertical ; if they are much natter than this, the arms have to be used in order to prevent the body from falling forwards ; if they are steeper, the arms have to lift part of the weight of the body. In either case there is fatigue for the arms, and in the latter the danger of falls is increased; these dis- advantages become very marked when the ladders are placed in a vertical or overhanging position. Ladders so fixed are prohibited by law in this country, for it is not only the life of the man who falls which is endangered, but he may sweep off several men beneath him. Unfortunately, our present law does not go quite far enough ; it forbids a vertical ladder, but permits a ladder inclined at an angle of i or 2 from the vertical, provided the shaft is not large enough to admit of any better arrangement. In other words, it does not compel the mine-owner to sink a shaft large enough for a proper ladder- road. The Belgian law,* enacted twenty- one years before ours, is more wisely worded ; it decrees that no ladder shall be inclined at an angle of less than 10 from the vertical. Furthermore, of the two arrangements shown in Fig. 602, A is better than B, because it not only affords a greater in- clination for the ladders, but also renders it less likely that a man will drop through the opening (manhole) in the platform (sollar) if he loses his hold and falls. In planning the regular permanent ladder-road for the miners, it is well to avoid shafts in which other operations, such as winding or pumping, are going on. By law, in this country, the ladder compartment has to be partitioned off from the winding compart- ment ; a better plan, if possible, is to provide an entirely separate shaft for a footway. In vein mines, a number of the winzes can conveniently be set apart for " travelling " purposes. Occasionally the ladderway is made double in the upper part of the mine, so FIG. 602. * ArrSte royal du Janvier 1851, Article 2. DESCENT AND ASCENT. 531 as to prevent loss of time at the change of the shifts, when an ascending stream of men meets a similar descending stream. Some of the matters just mentioned may seem trifling, but, leaving aside the question of safety, the economy derived from fixing the ladders at the best possible inclination is by no means small. To make this apparent, we must recollect the depths to and from which men have to climb viz., 300, 400, and even 500 yards or more. It is, therefore, important to save every unnecessary expenditure of energy, which, though trifling for one ladder, becomes considerable if very frequently repeated. When a mine has reached a depth of 100 yards, and a fortiori when it has exceeded it, mechanical appliances should certainly be intro- duced for raising and lowering the men, because time and strength are wasted by climbing ; besides which, medical men are agreed that excessive ladder-climbing is injurious to the health of the miner. Therefore upon hygienic and upon financial grounds, one of the first thoughts in working a mine should be the conveyance of the men down and up the shaft with the least possible fatigue, by means of machinery. Buckets and Cages. This method of going down and com- ing up from mines recommends itself by its simplicity, and when carried out with modern appliances it is remarkably safe. If the machinery is being worked by hand, the miner usually stands with one foot in the kibble and uses the other to guide himself, while he holds the rope in his hands ; this guiding is specially necessary when going down an inclined winze with Tough and rugged sides. Some men prefer to have one foot in a loop at the end of the rope, whilst others like a special stirrup. At the ozokerite mines of Boryslaw, and also in sinking oil- wells in Burma, special precautions are taken in case the men should become unconscious from breathing an atmosphere highly charged with noxious gases. In every case the man is secured by a second rope, so that he can be drawn up even if he falls from the bucket. The Boryslaw safety-gear is a strong leathern waist-belt to which is attached a broad strap divided into two at each end. One thong passes over each shoulder and is buckled to the belt, and one under each leg is attached in a similar manner. An iron ring between the shoulders completes the gear. It serves for attaching the second rope, or life-line, coiled upon a separate windlass, and paid out as fast as the main rope with the bucket in which the man stands with one leg. Many of the shafts worked in this way are more than 150 yards deep, and one has attained a depth of 262 yards (240 metres). Guides are compulsory in this country after a depth of 50 yards is exceeded, unless the owner of the mine has obtained an exemp- tion from the inspector of the district. I explained in the chapter upon winding how they can be applied to the kibble or bucket even in a sinking shaft ; but the usual method of ascent and 532 ORE AND STONE-MINING. descent is by the cage, or some form of guided box. Little need be said about the process of lowering and raising, for it is practically the same as winding mineral. Rules are made defining the number of men allowed to ride at one time, and generally there is a bar near the top of the cage which the men can hold, in case there should be a little jerk. In some countries it is necessary that the cage should be so enclosed that there is no possibility of a man falling out during his rapid ride. As sending the men down and up in this fashion interferes with the winding of minerals, access to the cage should be easy ; even stooping causes a little loss of time, and the despatch of the men into the mine will be expedited if the cage is high enough for them to walk in upright without any thought for their heads. If the space is too low for standing up conveniently, the men may be made to crouch down in mine-waggons, which are pushed on to the cage as- if they contained mineral. The extent of the interference with the regular winding opera- tions will be best understood by examples. The Government regulations at Mansfeld* do not allow a greater speed than 328 yards per minute (5 metres per second) when men are being wound. At Ernst I. shaft, which is 411 yards (376 metres) deep, it was reckoned, a few years ago, that seven hours out of the twenty-four were occupied with the descent and ascent of 1069 persons, thus : Persons. Morning from 4.30 A.M. to 6. 30 A.M., 2 hours ... 450 Afternoon,, 12.30 P.M. 3.45 P.M., 3$ ... 415 Evening 9.15 P.M. n.o P.M., if ,, 204 Total 7 ... 1069 At Ernst III. shaft, which is 273 yards (250 m.) deep, the figures were as follows : Persons. Morning from 5.0 A.M. to 6. 15 A.M., labours ... 260 Afternoon,. 1.15 P.M. ,, 2.30 P.M., ij .. 234 Evening ,', 9.30 P.M. 10.30 P.M., i 149 Total 31 ... 643 The cage at the former shaft took seven men at a time, and that of the latter, sixteen men, as it was double-decked. With the object of relieving the ordinary winding-plant from this task in one part of the district, a new shaft was sunk solely for raising and lowering the men. The British law demands that, in addition to the guides already mentioned, there should be a cover overhead, so as to protect the men from things accidentally falling down the shaft. The use of * Der Kupfersehieferbergbau und der Jfiittenbetrieb zur Verarbeitung der gewonnenen Minern in den beiden Mans/elder Kreisen der Preuss. Provinz Saclisen. Halle an der Saale, 1889, p. 72. DESCENT AND ASCENT. 533 .a single-linked chain is forbidden, except for the short coupling piece connecting the cage to the rope. There must be flanges to prevent the rope from slipping off the drum ; the winding machine has to be provided with an adequate brake and a proper indicator ; and, lastly, there must be means of signalling up and down from every landing-place in the shaft. In some countries safety catches are compulsory. An ingenious and useful method of signalling is that of Mr. Armstrong, who inserts an electrically insulated wire into the centre of the winding rope for the purpose of communicating from the cage itself to the engineman, no matter whether the cage is in motion or not. The electric wire is brought into contact with an insulated metal ring placed upon the crank shaft of the engine, and a copper lever pressing upon this ring places the wire in communi- cation with a small battery. The wire rope itself serves as a return. The circuit can be completed by pushing a button inside the cage, or another placed upon the roof, and the ringing of a bell at the surface gives the necessary signals to the engineman. This rope, which is made by Messrs. Haggie & Co., of Sunder- land, is being used with success at collieries in the north of England, and at one of them a separate shaft is set apart for the men, so as not to interfere at all with the winding of coal ; the cage carries twenty men at once, and is always in charge of a con- ductor, whose duties resemble those of the attendant at an hotel lift or elevator. By merely pressing a button he signals direct to the engineman to start or to stop as required. At mines under the Coal Mines Act in this country, the rate of winding men must not exceed three miles an hour after the cage has reached a point in the shaft which is fixed by Special Rules. However, this regulation applies only in cases where the hoisting apparatus is not provided with some automatic contriv- ance to prevent overwinding. In Germany a speed indicator has to be applied when men are being raised or lowered ; among instruments of this class may be mentioned the tachometer of Messrs. Schaffer and Budenberg, which indicates the rate of winding by a pointer on a dial in full view of the engineman. Winding by the cage is not confined to perpendicular shafts. At Carn Brea Mine in Cornwall a two-decked cage, holding six- teen persons, runs in a shaft which is perpendicular for the first 120 fathoms and then follows the changing dip of the lode for 170 fathoms more. The inclination varies from about 10 to 30 from the vertical. In a shaft of this kind it is impossible to wind with safety at speeds which are common at collieries ; nevertheless the cage does very useful work, and as the rope is renewed every four months, there is little chance of a breakage. The cage at Junge hohe Birke* Mine, near Freiberg, consists of * Freibergs Berg- und Huttemcesen, 1893, p. 156. 534 OEE AND STONE-MINING. FIGS. 603, 604. A .1 five small compartments one above the other, each forming, as it were, a separate link of a chain ; the cage can thus accommodate itself to bends in the shaft. Each compartment takes two men. Man-engine. The first man-engine was put up in the Hartz in 1833, and nine years later a similar machine was fixed in Tresavean Mine in Cornwall. Since that time this useful means of conveying men up and down shafts has been resorted to in other mining districts, such as Belgium, Westphalia, and Saxony. Two kinds of man-engine are in use the double-rod and the single-rod machines. The double-rod, or original man-engine, consists of two reciprocating rods, like the main rods of pumps, carrying small platforms upon which the men stand. The stroke is from 4 to 16 feet, and the little platforms are arranged so that they are always opposite each other at the beginning and end of each stroke. Figs. 603 and 604 represent the rods in the two final positions. A man who wishes to go down, steps upon platform b (Fig. 603), the rod B goes down and A goes up, so that b is brought oppo- site c (Fig. 604). The man steps across from b to c, the rod A makes a down stroke, and B an up-stroke. Platform c is now opposite d (Fig. 603), and the man again steps across ; and thus, by constantly stepping FIG. 605. from the rod as it completes its down-stroke, the man is gradually conveyed to the bottom of the shaft. By reversing the process, or, in other words, by stepping off on to the opposite platform as soon as the rod has completed its up-stroke, the man is raised to the surface without any fatigue beyond the very slight effort of stepping side- ways. If each rod makes four up and down strokes of 10 feet each per minute, the rate of ascent or descent will be 80 feet per minute. The single-rod man- engine has one rod carrying steps, while fixed platforms are arranged in the shaft so as to correspond exactly with them (Fig. 605). If a man wants to go down, he steps on to A when the up-stroke is completed ; the rod goes down and the step A is brought opposite the fixed platform 5, on to which he steps off. He then waits on b until the rod has finished its up-stroke. B is brought opposite b, he steps on to B, the rod goes down and he is brought opposite c, where he again steps off and waits. By reversing the operation he is gradually lifted up to the top of the shaft. The- single-rod engine may be used by men going up while others are- DESCENT AND ASCENT. 535 going down, provided that there is sufficient room upon the fixed platforms (sollars, Cornwall). It is best to have platforms right and left, as shown in the figure, and then the ascending men step off always to the left, for instance, while the descending men take the right hand sollars. The ascending man steps on to the man- engine as soon as the descending man steps off, and so the rod may be always carrying men up or down. The usual stroke in Cornwall is 12 feet, and there are from 3 to 6 double strokes per minute. With 5 strokes the men descend 10 fathoms a minute, or, in other words, a descent or ascent of 300 fathoms occupies half-an-hour. However, after the first man has reached the bottom, the rest will be coming down at the rate of five a minute. The reciprocating motion is best obtained from a crank (Fig. 706), because in this case the speed is gradually diminished at the dead points, and the danger of an accident in stepping off and on is thereby lessened ; man-engines, however, are sometimes driven by direct-acting engines, and, at Laxey Mine, in the Isle of Man, a water-pressure engine furnishes the motive power for one of these machines. Man-engine rods are constructed of wood or iron ; and at St. Andreasberg, in the Hartz, each rod was replaced by two wire ropes. Like a pump rod the man-engine rod requires proper balance-bobs and catches, and for the safety of the men a handle is provided at a convenient height above each step. Sloping boards should be fixed under each platform, so as to make a funnel-shaped passage guiding the man's head into the proper channel, in case he is not standing upright when "riding" up. A useful addition is a small wire rope passing down from sollar to sollar, and placed within easy reach of a man when standing on a step ; he grasps this with one hand as he steps off on going down, and steadies himself by it if necessary. When riding up, he passes through the sollar and sees where he is going to step before he gets off, so it is not required on both sides of the fixed platform. There should be a signal line, with means of working it, at every sollar, for enabling any miner to ring and stop the man-engine in case of an accident. It is well, too, to have a ladder-road at the side of the man-engine, in order to afford a means of going up or down in the event of some unexpected breakdown of the machinery ; but the plan of fixing this ladder- way between the two rods of a double engine is not to be com- mended, for the wider the space between the rods the greater the chance of an accident. The man-engine has the advantage that it can be safely applied in inclined and crooked shafts, and it is convenient in vein-mining where the men have to work at very many different levels. The cost of raising and lowering men by the machine is not great. At Dolcoath, a tin mine in Cornwall, more than 400 fathoms deep, it was reckoned a few years ago that \\d. per man 536 OKE AND STONE-MINING. per day covered all expenses, including interest upon the capital expended and depreciation of plant. Judging by what has taken place during the last ten years, it seems likely that the man-engine will eventually die a natural death. It has all but disappeared at Mansfeld, being replaced by the safer and more convenient cage, and there seems little probability of new machines being erected in Cornwall. ( 537 ) CHAPTER XIII. DRESSING. I. Mechanical processes: (i) Washing in order to separate clay, mud and sand (2) Hand-picking (3) Breaking up, subdivision, or shaping (4) Agglomeration or consolidation (5) Screening or sifting. II. Pro- cesses depending upon physical properties : (i) Motion in water (2) Motion in air (3) Desiccation (4) Liquefaction and distillation (5) Magnetic attraction (6) Separation according to degree of friability. III. Processes depending upon chemical properties : ( i ) Solution, eva- poration, and crystallisation (2) Atmospheric weathering (3) Calci- nation (4) Cementation or precipitation by iron (5) Amalgamation. Examples Loss in dressing Sampling. UNDER the convenient term of "dressing" are included the processes by which the miner prepares his mineral for sale, or by which he extracts a marketable product from it. These processes are very various, and cannot all be properly comprised under the French heading "Preparation mecanique," because, in addition to using mechanical means, the miner often invokes the aid of heat, magnetism, or chemical affinity, in order to separate the valuable material, from the worthless rock with which it is associated in the earth. It must also be recollected that there is a borderland between mining and metallurgy, on which both miner and smelter may fairly claim a footing, because the former does not always send away his ore in the same state of elaboration. Some may be inclined to cut the knot by saying that the business of the miner is at an end when the mineral is landed at the surface ; but in actual practice this is the exception, and the person in charge of the mine has usually to superintend certain processes which are carried on in order to obtain a readily saleable article. I propose in this chapter first to describe the various dressing processes, and then to explain how they are applied to the most important minerals with which the miner has to deal. In order to have a clear idea of the principles which guide the miner, it is requisite that we should classify the processes which he employs; and we may at once make three main divisions, according as the process is effected solely by mechanical means, or is based upon the physical or chemical properties of the minerals treated. This classification is somewhat arbitrary : differences of opinion may exist, for instance, concerning solution, some persons considering it as a chemical process, others, as a mere 538 ORE AND STONE-MINING. change of state without any chemical action ; again the process by which a physical property is brought into play is usually effected with the aid of mechanical appliances ; and lastly, chemical and physical actions may both be involved in the method of treatment. It must, therefore, be understood that the classification is estab- lished rather for the convenience of the student, than with the idea that the subdivisions of the subject are strictly denned in reality. It will be seen also as we proceed, that many of the sub-classes refer to exceptional processes applicable only to special minerals. The following table gives an outline of the operations employed in dressing : I. MECHANICAL PROCESSES. 1. Washing in order to separate clay, mud and sand. 2. Hand-picking. 3. Breaking up, subdivision, or shaping. 4. Agglomeration or consolidation. 5. Screening or sifting i.e., classification according to size. II. PROCESSES DEPENDING UPON PHYSICAL PROPERTIES. 1. Motion in water. 2. Motion in air. 3. Desiccation. 4. Liquefaction and distillation. 5. Magnetic attraction. 6. Separation according to degree of friability. III. PROCESSES DEPENDING UPON CHEMICAL PROPERTIES. 1. Solution, evaporation and crystallisation. 2. Atmospheric weathering. 3. Calcination. 4. Cementation or precipitation by iron. 5. Amalgamation. i. MECHANICAL PROCESSES. (i) WASHING. The object of washing is twofold: removal of earthy impurities, and preliminary cleansing previous to hand- picking, for the valuable mineral, as it comes from the mine, is often completely masked by a coating of dirt. The process is carried out by hand or by machinery. The simplest appliances are the pan and the batea, which are specially used in the case of gold and tin. The pan is a circular dish made of tin-plate or stamped iron or steel, about 15 or 16 inches in diameter at the top and 10 or u at the bottom, with a depth of 3 or 4 inches. After having been partly filled with the mineral to be washed, it is held in a pool of water, or a vat, in which it can be moved so as to impart a circular motion to its contents. By suitably inclining the edge, the muddy stream is made to flow off, more clean water is taken on, and the process is repeated until there DRESSING. 539 remains nothing but well-washed sand and gravel in the bottom. The big stones are taken out and examined, and thrown away if worth- less ; large nuggets, if present, are now visible and can be picked out, whilst the small stones and sand are again mixed with water and washed, so that the lighter particles flow over the edge and the heavy ones remain in the pan. By careful manipulation the water is made to run repeatedly over the residue, and separate the various ingredients according to their specific gravities, as will be explained later. The pan, therefore, acts not only as a washer, but also as a concentrator. Though the main use of the pan is for prospecting, it must be remembered that very large quantities of alluvial gold have been extracted by its aid. The batea fulfils the same purpose as the pan. It is usually a shallow conical bowl made of wood, stamped sheet iron, hammered copper, or spun aluminium or copper. Convenient dimensions are: diameter 18 to 20 inches and depth 2.\ to 3 inches. In some parts of India the wooden gold-washing dish is rectangular. The mineral is treated much in the same way as in the pan, but the batea has the great advantage of bringing all the heaviest particles to a point, instead of an edge. Much gold has been obtained with this primitive appliance, especially in South America and Central America, whilst in the Malay Peninsula it is used for extracting tin ore from gravel, and in Brazil for washing out diamonds. In prospecting the batea is in- valuable. If large quantities of mineral have to be handled, it is necessary to separate the adherent dirt in some cheaper fashion. Occupying an intermediate position between the hand-bowls and the rotary machines are simple washing pits of different descriptions. Some of the lead ore of North Wales occurs in the form of solid lumps of galena enveloped in clay. The ore coming from the mine is thrown into a stone-lined pit about 18 inches deep, partly filled with water, in which it is pushed backwards and forwards until the galena is separated from its clayey matrix. This kind of washing pit is known as a ''jobbing buddle." Phosphatic nodules are cleansed from sand in a similar manner, by being raked or shovelled backwards and forwards in long wooden troughs full of water. The Australian puddling machine is an example of an appliance for doing similar work by the aid of a horse or other available power. It is a circular pit in which gold-bearing gravel is stirred up with water by knives attached to radial arms, which are carried round by a vertical axis. The rotary washing machine employed at the diamond mines (Fig. 606) is identical in principle. The object is to free the weathered " blue ground " from the finest sand and mud and leave a clean gravel in which the diamonds shall be distinctly visible. The 540 ORE AND STONE-MINING. rotary washer is an annular iron pan A (Fig. 606) 8 to 15 feet in diameter and 16 inches to 2 feet deep externally, whilst the inner rim, B, 4 feet in diameter, is only 6 inches deep. In the centre is a revolving vertical shaft, C, carrying 8 or 10 radial arms, D, each provided with 6 or 7 vertical blades which dip into the mud and gravel, and stir it up as they revolve. At De Beers mine the washers are usually 14 feet in diameter. The stuff is fed in at the outer circumference by a shoot coming from a screen, and the muddy water escapes over the low inner rim of the pan. The teeth or stirring knives are arranged so as to bring FIG. 606. SCAUE: DECIMETRES 10 8 a FE.ET 2 METRES the heavy gravel towards the outer circumference. As a pre- caution, the muddy water flowing out of the washer is run into a similar machine, and is again stirred up so as to catch any diamonds which may by chance have escaped in the first operation. When the pan has been at work for twelve hours, a sliding door is pulled out at the bottom, through which the gravel falls into a truck underneath, as it is drawn round by scrapers attached to the arms. Another form of mechanical washer* (Fig. 607) is a revolving sheet iron drum, made in the form of a truncated cone revolving upon a horizontal axis, and provided with internal stirring blades. The " stuff " to be washed is fed in at the centre of the small end * Linkenbach, Die Aufbereitung der Erse, Berlin, 1887, plate II. DRESSING. 54i with a stream of water. In Fig. 607, a is the drum, b the conical mouth, CG the arms which attach the drum to the central shaft d ; ee are teeth, f the shoot from a hopper, g a pipe bringing water, the amount of which can be regulated by a cock. The greater part of this particular drum is perforated, and it acts as a sizing machine after having done the washing ; m is the driving pulley, h an iron trough catching the discharge of the sieve, and i a small trough which takes the stones discarded by the sieve. This machine is intended for washing small stuff (" smalls ") previous to picking. The washing of the larger lumps is often effected by turning a stream of water upon them over a coarse iron grating. FIG. 607. (2) HAND-PICKING-. No process is simpler in principle, it is merely the separation by hand into classes of varying quality and richness ; the difficulty in practice is to know how far it should be carried, before the mineral is treated by machinery. In many cases hand-picking may begin underground, and where worthless rock can be so separated without difficulty, it should be removed with care, so as to avoid useless ex- penditure for tramming, hoisting and dressing. If a mineral is specially valuable, it is often worth while picking it out and sending it up by itself, with a view to preventing loss or theft in transit, or loss in dressing due to the admixture of a large pro- portion of refuse. Picking of this kind is resorted to in working rich pockets of gold or silver ore under the superintendence of a foreman. Pieces of pure ozokerite are picked out by the Boryslaw miners and sent to the surface in sacks, and the men are stimulated to do the work as thoroughly as possible by a premium paid for the clean lumps. By the dim light of a candle the picking process cannot, as a rule, be carried further than the separation of worthless rock, and, 542 ORE AND STONE-MINING. occasionally, the selection of some very rich pieces of mineral ; nor, if the light were better, would it be advisable to do more, for the underground traffic would be complicated if a number of classes of mineral were made, and the work of picking can be better per- formed by keen-eyed boys and girls at the surface than by the miners underground, especially after they have passed middle age. Picking is generally carried on after the mineral has been subjected to a washing process of some kind. The washed mineral is spread out on a table, and boys and girls, standing by the side, separate the stones that lie before them according to their richness and the subsequent processes they will have to undergo. A scraper made of a piece of iron, bent as shown by FIG. 608. Fig. 608, assists them in drawing the lumps towards them or into a box, waggon, or barrow by the side of the table. In a lead-mine we may have () clean galena ; (b) mixed ore, i.e., pieces consisting partly of galena and partly of barren veinstone ; (c) barren veinstone and pieces of the surrounding rocks (country). This is a most simple case ; but very frequently one has to deal with a deposit producing the ores of two or three metals, especially in the case of lead and zinc, and then the classification into various qualities becomes O more complicated. Where the amount of mineral to be picked is con- siderable, labour may be economised by self -discharging tables, of which there are two kinds revolving round tables and tra- velling-belts. With the former the mineral is fed on at some point of the circumference and the picking is done by boys or girls- standing around. They select pieces of certain qualities and richness as the table revolves in front of them, and finally, when a revolu- tion is all but completed, nothing remains on the table but mineral of one quality, which is swept into a box or waggon by a fixed projecting scraper. Endless belts are made of hemp, wire-gauze, or steel plates attached to endless chains, and they are sometimes as much as 4 feet wide. The refuse is picked off as the mineral travels by, and the clean product can at once be delivered into railway waggons, ready for despatch to smelting works or to some further process of dressing. (3) BREAKING UP, SUBDIVISION, OB SHAPING. Reduction in size is necessary for various reasons. Even when an ore is clean enough for the smelter, the large lumps are often crushed by the miner for the sake of obtaining a fair sample of the whole, or of supplying a product which is at once fit for the furnace. Fertilisers, cements and pigments have to be finely ground before they can be used, and the grinding may or may DRESSING. 543 not take place at the mine. The chief object of breaking up, however, is to set free the particles of ore, which are generally found enclosed in or adhering to particles of barren veinstone. Few processes in dressing are of more importance than the proper breaking up of the ore or other mineral. A very large number of machines are employed suitable for the different substances which have to be treated, and it will be impossible FIG. 609. RAGG/N G. within the limits of this chapter to do more than pass the most important in review in a somewhat summary manner. The breaking may be done by hand or by machinery. The processes of breaking by hand may be divided, according to the precise object in view, into : a. Breaking with the sledge hammer [ragging and spatting]. b. Cobbing. c. Bucking. d. Splitting. e. Trimming into shape with the saw, axe, hammer, or knife. 544 ORE AND STONE-MINING. a. Breaking with the Sledge Hammer. The term "ragging" is applied, in Cornwall (Fig. 609)*, to the process of breaking up the very big lumps (rocks) as they come from the mine by a large sledge hammer weighing about 10 or 12 Ibs. The FIG. 6 10. SPELLING . work is done by men, who, in addition to breaking the lumps, may separate the broken pieces into various categories according to quality. Spatting is work of a similar nature, but performed with a smaller sledge, weighing 4 or 5 Ibs., which in Cornwall can be wielded by a woman (Fig. 610). Sometimes there is a little FIG. 6n. COBBING. picking at the same time. The process of spalling is often a preliminary to crushing by stamps or rolls. b. Cobbing. Cobbing is a special kind of breaking with a small hammer, in which the blow is directed with the object of knocking off a piece of poor rock from a lump of mixed ore and refuse. The work is usually performed by women (Fig. 611), * Henderson, " On the Dressing of Tin and Copper Ores in Cornwall," Proc. Inst. G.E., vol. xvii., 1857-58, plate 7. DRESSING. 545 girls, or boys, who commonly sit down and strike the lumps upon an anvil of some kind, often an old stamp-head. As the lumps are held in position by the left hand, a badly directed blow may FIG. 612. FIG. 613. BUCKING MILLS. cause a nasty wound ; to prevent injuries of this kind, the girls formerly employed in cobbing copper ore, at the Mona and Parys mines in Anglesey, wore pieces of iron around their fingers, and short pieces of india-rubber tube are used for the same purpose. c. Bucking. Bucking is breaking with a very broad flat hammer in order to reduce an ore to coarse powder. The hammer, called a "bucking-iron," is about 4 inches square with a steel face ; the handle is from 18 inches to 2 feet long. The ore is struck upon a thick flat plate of iron (Fig. 612). d. Splitting. Splitting is required with slate, and also with stone which will rend along certain directions other than cleavage planes, such as planes of bedding. It is done with a wedge of some kind, increasing in sharpness with the thinness of the slice re- quired. Blocks of slate are split by the Welsh quarrymen with a stout wedge into slabs about 3 inches thick, and the process is then repeated with a thin one (" cyn maen hollti") (Fig. 613) until they obtain a roofing more than y or ^ inch thick. material often not 2 M 546 OKE AND STONE-MINING. e. Trimming. Trimming into shape is necessary with many kinds of stone. Thus the Bath freestone is resawn by hand at the surface (Fig. 156), if the blocks are not quite suitable for the market as they come from the mine. The hearthstone raised at Godstone in Surrey is hewn into neat blocks by a peculiar double- headed axe, whilst paving- stones, chert, and gun-flints are fashioned with the hammer ; roofing-slate is chopped into rect- angular pieces with a large knife. Many of these hand-processes are gradually disappearing, owing to the introduction of machinery which will perform the work with a saving of time and labour. Machines for breaking up, subdividing, or shaping ores and stone may be classed as follows : a. Breakers with reciprocating jaws. b. Stamps. c. Kolls. d. Mills. e. Edge-runners. /. Ball-grinders. g. .Disintegrators. h. Conical grinders and breakers. i. Centrifugal grinders. j. Pneumatic pulverisers. k. Miscellaneous pulverisers. I. Sawing machines. m. Planing machines. n. Slatemaking machines. a. Jaw-breakers. These machines, often called rock-breakers and stone-breakers, crack stones by the near approach to one another of two powerful iron or steel jaws. The best known stone-breaker is the machine invented by Blake, which has rendered inestimable services to the miner for the last thirty years, and the introduction of which constituted a most important step in advance in the art of ore-dressing. Its mode of action is very simple. When the shaft A (Fig. 614) revolves, an eccentric raises the pitman B, and by means of the toggle-plates C C causes the movable jaw D to approach the fixed jaw E, and so crack any stones lying between them. During the descent of the pitman the jaw D is drawn back by an india-rubber spring. The jaws are usually toothed, the ridges of one jaw being opposite the grooves of the other when the machine is employed for breaking stones at mines ; if the object is to make road-metal, the two sets of ridges are brought opposite each other. The wearing parts of the two jaws E E and D D are replaceable, and if these castings cannot be immediately obtained in a distant country, it is possible to do good work with flat plates of steel. The stone-breaker used at mines commonly has the renewable part of each jaw made of one casting instead of two as represented in the figure. The distance between the two jaws, and conse- DRESSING. 547 quently the fineness of the product, can be regulated by raising or lowering the wedge-piece on the right-hand side of the figure, or by inserting other toggle-plates. The Blake rock-breaker, with the improvements introduced by Marsden, is made in various sizes, so as to take stones as large as 34 inches by 18 inches; the smallest machine is 10 inches by 8 inches in the mouth. Various similar machines are in the market. Baxter claims that he produces fewer small chips and less dust matters of import- ance in making road-metal by his so-called " knapping-motion." Marsden has a breaker with what he calls a " lever motion," in which the toggle-plate moving the jaw forwards is impelled by a FIG. 614. bent lever worked by crank. Hall has two movable jaws placed side by side which act alternately ; as all the parts are balanced, less power is said to be required to drive it. Lester's machine is- very simple, as the moving jaw is driven directly by the pitman without the intervention of any toggle-plates. For crushing to finer sizes, Marsden has an ingenious pulveriser. It resembles his stone-breaker by having two jaws, one fixed and the other movable, but the moving jaw has a rubbing as well as a squeezing action. The machine is supplied with a sieve, so that any part of the product not fine enough for use is returned automatically so as to be recrushed. The Dodge crusher (Fig. 615*) differs from those just described * Copied by permission from a paper by Mr. A. H. Curtis, which may be consulted with advantage by those who desire information on the subject of crushing : " Gold-quartz Keduction," Proc. Inst. C. E., vol. cviii., 1891-92, p. 108. Further details are given by Professor Egleston in his useful paper, "California Stamp Mills, "Engineering, vol. xli., 1880, pp. 19, 85, 163, 256 548 ORE AND STONE-MINING. in having the moving jaw pivoted below, instead of above. Consequently the effect of the stroke is felt most at the top. One object of this arrangement is to obtain a more uniform product than is possible with a constantly varying discharge orifice, like that of the Blake breaker. FIG. 615. THE DODGE CRUSHER. b. Stamps. Though used at mines for several centuries, stamps still hold their own in spite of many competing forms of crushing machinery. The simplest mode of describing stamps is to say that they are pestles worked by machinery in large mortars. In most instances the blow of the pestle is caused by its mere weight, sometimes a spring is added, and occasionally the action of gravity is aided by compressed air, or by steam pressure. We thus have four kinds of stamps : a. Gravitation stamps. /3, Stamps with spring. 7. Compressed air stamps. 5. Steam-hammer stamps. A little study of the accompanying figures (616-620*) will explain the most important characteristics of a modern stamp- battery. a. A A (Fig. 6 1 6) are blocks of timber forming the solid founda- tion, which is required on account of the heavy pounding action of the machinery ; B B, the transverse sills, with the battery-posts C C, the braces E and the tie- timbers D D form the framework holding the mortar or battery-box (kofer, Cornwall) F, in which the mineral is pounded by any one of the five stamps moving up and down in it. G is a perforated plate or screen which pre- vents the mineral from leaving the mortar until it has been brought down to the required degree of fineness. H is the shaft carrying cams, which lift the stems by tappets ; K K are the ends of the stems or lifters of the stamps proper; L is the pulley through which motion is transmitted to the cam shaft by * Curtis, Op. cit. DRESSING. 549 the belt upon the driving pulley M. N is the gear by means of which the driving belt can be tightened. FIG. 616. 10 STAMP BATTERY, WOO Each stamp proper, K K, consists of a turned rod of iron with tapering ends, either of which will fit into a corresponding hole in a cast-iron cylinder known as the " head" (Figs. "617 and 620). FIG. 620. FIG. 617. FIG. 618. FIG. 619. SINGLE DISCHARGE MORTAR. The conical hole or socket in the bottom of the head receives the shank of the "shoe," which is made of cast-iron, cast-steel, or forged steel. When worn the shoe can be removed from the head OEE AND STONE-MINING. by driving a steel key into a slot above it (Fig. 620), and the stem or lifter is extracted in a similar manner by means of a second . slot at right angles to the first. The mortar is shown on a larger scale in Fig. 617. It is a cast-iron box with an opening E at the back for feeding, and one in front, into which is wedged the frame F of the screen. Some- times there is a screen behind as well as one in front, or screens at both ends as well as at the two sides. Fig. 618 represents the tappet, a hollow cylinder of cast-iron, which is fastened to the lifter by steel keys and a gib. The gib is a piece of wrought-iron fitting the FIG. 621. curved surface of the lifter and capable of being jammed against it tightly when steel keys are driven into three holes in the tappet. As the shaft H revolves, the cams (Fig. 619) lift the tappets, and at the same time cause a slight rotation of the stamp, which conduces to regular and even wear. The head B, with its shoe C (Fig. 617), drops upon a cylinder of similar metal known as the die, and it is be- tween C and D that the mineral is pulverised. Both shoe and die wear away and have to be changed from time to time. The worn shoe and die represented in Fig. 621 were reckoned to have stamped 150 tons of gold quartz at the Morgan mine, North Wales, before they were given up ; they were made of Fraser and Chal- mers' forged steel. The order in which the heads drop is not invariable; the object of any arrangement is to make each head do its fair share of work. Egleston mentions six different orders of dropping which are in use, and this shows how much opinions are divided on the subject. Among them may be mentioned 3, 4, 5, 2, i, and i, 5> 2 4, 3- The screens through which the pulverised mineral has to pass are made of punched iron, steel, or copper plates, and occasionally of wire gauze. The holes are round, or in the form of long narrow slots. The size of the holes is better expressed by their actual dimension than by their number per linear inch or centimetre. The total weight of each stamp when new, that is to say stem, head and shoe, varies from 500 to 950 Ibs. ; weights of 700 to 800 Ibs. are common. The precise height and number of the drops are further points requiring consideration ; the height varies DRESSING. 551 generally from 8 to n inches, and there are 70 to 100 drops per minute. Ore may be stamped dry or wet ; in the latter case, water constantly flowing into the mortar-box carries oft' the mineral through the screens in the form of a muddy stream known as " pulp." Egleston reckons that the quantity of water used in wet stamping is from | to ^ cubic foot per stamp per minute, or 200 to 300 cubic feet per ton of rock stamped. The quantity stamped per head per day must necessarily vary within very wide limits, according to the weight of the stamps, the nature of the stone treated, and the degree of fineness desired. Speaking roughly, it may be said that each head will stamp 2 tons per 24 hours and require 2 h.-p. Regular feeding is of much importance, and several automatic arrangements can be applied to the battery for securing the desired result. Most frequently a tappet upon one of the stems comes into play when the stamp has a longer drop than usual, owing to want of ore under it, and strikes a lever which brings the ore-feeding contrivance into action. j3. Spring stamps are but little used. Patterson's " Elephant " stamps belong to this class : the object of the inventor was to secure a stronger and quicker blow than would be given by a mere fall, and so enable a small machine to do more work than would be possible if gravitation were acting alone. The stamp is worked by a crank, and interposed between the striking head and the connecting rod there is a strong spring, which assists by its recoil and allows for the varying height of the ore in the battery-box. y. Husband's pneumatic stamps were designed with the same intention viz., a quicker and a harder blow. The stem or lifter of the stamp is attached to a piston working in a cylinder which is lifted rapidly up and down by a crank. There are holes in the cylinder which allow the air to escape during the middle of the stroke, but after it has been raised beyond a certain point, the air below the piston becomes compressed and the stamp is lifted. The cylinder in its downward course travels quicker than the stamp would fall, and compressing the air above the piston helps to drive it down and with it the stamp ; it thus increases the force of the blows, which can be given at the rate of 140 per minute. Though good results have been obtained in some cases, these stamps have not made their way into general use, for mining engineers seem to consider that the simplicity of the ordinary stamps, and the ease with which any slight defects can be repaired, make up for the disadvantages which Husband tried to remedy. 8. We now, lastly, come to the steam-hammer stamp, which has proved a most efficient machine at the Lake Superior mines for the treatment of rock containing native copper. The first stamps of this kind were constructed by Ball in 1856 ; since then great improvements have been made, and the present Leavitt stamp will crush 250 tons of copper-bearing rock in 24 hours. 552 ORE AND STONE-MINING. The Ball* stamp (Fig. 622) consists of a vertical steam-cylinder, C, with the stamping head attached to the piston-rod. The various parts are designated as follows : D, cast-iron die ; E, cast-iron shoe ; F, frame of mortar ; G G, grates of punched sheet steel; H H, cast-iron head posts; L, cast-iron sills or girders; M, cast-iron mortar; P, pulley by which the valve is FIG. 622. SCALE. FT 1 IS FEET M.I 0* 4 MET RES driven ; R R, cross sills ; S, shoot supplying the ore ; T T, spring timbers ; U, " urn " or cistern supplying water ; Y V, cast-iron lining plates, resting upon a cast-iron ring surrounding the die ; Y, pulley by which the stamp is rotated. The slide-valve is worked from the pulley P by the elliptical spur-wheels indicated by the dotted lines ; the valve is opened fully for making the down-stroke, and the pressure of the steam * Ruthbone, "On Copper Mining in the Lake Superior District," Proc. Inst. Mech. Eng., 1887, p. 9(3. DRESSING. 553 FIG. 62?. greatly increases the blow due to gravity, but for making the up-stroke the steam is admitted sharply, and in just sufficient quantity to lift the head. The peculiarity of the Leavitt * stamp lies in the differential steam-cylinder (Fig. 623). There are two cylinders, one above the other : a large one A with a piston B, above a small one C with a piston D. Steam is admitted on to the top of piston B through the valve at E, and is exhausted through a valve at F into the condenser. The space under the piston D in the cylinder C as well as the annular space G is filled with steam admitted through the opening H, and kept by a regulator at a uniform pressure sufficient to raise the stamp. The stamp is thus lifted by the lower piston, and is forced down by the large upper one against the constant pressure exerted by the lower. The valves regu- lating the admission of the steam and the exhaust valves are worked by cams upon a shaft driven by a belt from some independ- ent source of power. The cams which open the steam and close the exhaust valves are fixed, but the cams which close the admission of steam and open the exhaust can be adjusted at pleasure. The moving parts of each Leavitt stamp at the Calumet and Hecla mine weigh about 5000 Ibs., and the blow is struck with a velocity of 20 to 22 feet per second. The number of blows is 98 per minute ; the screens are made of the best steel -^ inch thick, punched with round holes ~ 3 g- inch in diameter, and speaking roughly about 10 tons of rock an hour are stamped fine enough to pass through them, and are carried away by water to the concentrating machinery. c. Rolls. Rolls were introduced into the West of England in the early part of the present century to replace bucking by hand. They are a pair of smooth, fluted, or toothed cylinders, made of cast-iron or steel, which revolve in opposite directions, and crush any stone which is allowed to fall between them. The cylinders or rolls are generally from i foot to 3 feet in diameter, and i foot to 3 feet wide ; they are kept pressed together by levers or springs. For crushing metallic ores, the diameter of the roll is generally from two to three times its width. The original form of crushing rolls, and one still largely used * F. G. Cogging, "Notes on the Steam Stamp,'' Engineering, vol. xli., 1886, pp. 119, 130, 200. 554 ORE STONE-MINING. in this country, is represented in Fig. 624, in which the letters have the following meanings : G, hopper, into which the ore is shovelled from the floor, H H ; A B, the two cylinders or rolls shown on a larger scale in Fig. 625. The roll B has plummer- blocks which can slide along a bed-plate, and so allow the opening between it and the roll A to be increased or diminished ; C is a bent lever, to one end of which is attached a weighted box, whilst the other constantly presses a pin against the plummer-block of B; the crushed rock after leaving the rolls falls into a revolving cylindrical sieve. All that fails to pass through the sieve drops into the " raff- wheel " E, which has buckets on the FIG. 624. face turned towards the crusher ; these carry up the coarse fragments as the wheel revolves and tip them on to a sloping apron F, whence they fall again into the hopper G to undergo a further crushing.* One end of the shaft of the roll A is coupled to the main driving shaft of the machine, which carries the raff- wheel ; the other end has a cog-wheel which gears into a similar one on the shaft of B, and so drives it. The inclined sieve is driven from the shaft of A by means of bevel gearing. An improved form of the Cornish rolls has been introduced by Krom,f and is meeting with approval. His improvements are: * Ferguson, " On the Mechanical Appliances used for Dressing Tin and Copper Ores in Cornwall," Proc. Inst. Mech. Eng., 1873, plate liv., and p. 133. t Krom, " Improvements in Ore-crushing Machinery," Trans. Amer* Inst. M. E., vol. xiv., 1885, p. 497. FIG. 626. DRESSING. 555 Steel tires, pulley gearing, housing to enclose the rollers, swinging pillow-blocks, tie-bolts to take the crushing strain, hopper for auto- matically ensuring a regular feed. The tires (Fig. 626) are made of mild forged steel,* and are held by two cores in the form of truncated cones. One of the cores is shrunk firmly on to the main shaft, the other is split on one side, but when drawn in towards its fellow by bolts, it grips the shaft very tightly, and at the same time fastens the tire securely. The main shaft (Fig. 62 7) f is driven by a pulley, indi- cated by the dotted line, revolving at the rate of 80 to 100 times FIG. 627. lNS.12 CLCIMC.TRE.SIO SCALE.S 3 7 FEET. i METRE. * Messrs Bowes Scott and Western use a special steel of their own which is said to be exceedingly durable. t Curtis, op. ctt. 556 ORE AND STONE-MINING, a minute ; the other shaft is driven at the same speed, but in the opposite direction, by crossing the driving belt of the smaller pulley. The bearing of the shaft of the movable roll is carried by a swinging pillow-block pivoted underneath, and constantly drawn towards the other roll by the strong spiral springs. The upper part of the figure represents the bottom of the hopper which supplies the rolls, and the oscillating feed-tray, set in motion by an excentric. Actual experience extended over a considerable time has proved that a pair of Krom rolls at the Bertrand Mill, in Nevada, will crush 150 tons of quartzose silver ore in 24 hours, so as to pass through a screen with 16 holes to the linear inch. It is claimed that less fine dust is produced with these rolls than with stamps, a matter of importance, owing to the losses in dress- ing or lixiviation when there is a large proportion of slime. Fluted rolls are used in crushing rock-salt, and toothed rolls are used for breaking comparatively soft minerals such as rock- salt or gypsum, and even hard stone for road-metal. Some of the rolls for rock-salt are made of toothed rings threaded upon a shaft, and the two rolls are arranged so that the teeth of one lie between those of the other. d. Mills. The term " mill " has a very vague signification among miners ; all sorts of machines employed in crushing arid grinding are commonly known as mills. I propose to restrict the term to grinders, in which the working parts consist of flat or approximately flat surfaces, one of which revolves. They are called into requisition for reducing a mineral to a fine state of division. The typical mill of this class is the well-known fl.our mill, made of two horizontal cylindrical stones, one fixed, the other revolving ; sometimes it is the lower stone that is fixed, sometimes the upper. Mills of this kind serve to grind barytes and fertilisers. The stones are generally the French burr, and have to be dressed from time to time as they wear. The mineral is fed in at the centre, and is discharged at the circumference. Instead of one top stone, there may be several separate pieces; this combina- tion forms the " arrastra " employed for grinding and amalgama- tion. When the mill is made of iron, with iron or steel replaceable wearing parts, it is generally called a " pan " ; like the arrastra, it serves for fine grinding and amalgamating. Millstones need not necessarily be arranged horizontally ; the first grinding of phosphate of lime is sometimes done by stones set vertically, the moving stone being fixed upon a horizontal axis. e. Edge-runners. The edge-runner is a cylinder turning upon a horizontal axis which is made to revolve around a vertical axis, In its simplest form, it is a large stone wheel, the horizontal axis DRESSING. 557 of which is drawn round an upright post by a mule. The stone crushes by its weight, and as it has to slide a little in order to keep its circular path upon the bed, there is also a rubbing action. This primitive form of edge-runner, known as the Chilian mill, is employed in crushing and amalgamating gold and silver ores. It is better to have two of the upright wheels at opposite ends of the horizontal axis, as then the machine will work more smoothly (Fig. 628). Each wheel is made of a strong tire of chilled cast-iron wedged to a centre-piece of ordinary cast-iron, and the bed is composed of sectors of chilled cast-iron, which can FIG. 628. be changed when they are worn. The driving gear may be above or below. /. Ball-grinders. In machines of this class the mineral is pulverised by its contact with a number of cast-iron balls, which are constantly rolling against each other when the case containing them revolves. Jordan's Centrifugal Grinder and Amalgamator is a circular pan set upon an inclined axis with a few large iron balls like cannon-balls which lie in the lowest part ; the machine is supplied with crushed ore, which is soon ground fine and escapes through a sieve placed around the outside of the pan. The ingenious " Grusonwerk " ball-grinder (Figs. 629 and 630), now made by Krupp, has a continuous feed and discharge. It con- sists of a horizontal iron cylinder provided with several curved plates 558 ORE AND STONE-MINING. a a, which carry a number of steel balls. The stuff which is fed in by the hopper h falls among the balls and is ground by their rubbing. During each revolution of the drum, they drop five times as they come to the edges of the plates. The ground mineral passes through holes in the curved plates a a, and in the cylindrical sieve- c made of punched steel plate ; it now meets with the fine wire gauze sieve d, which lets through all that is sufficiently pulverised into the hopper s, whence it can be drawn off at pleasure. The object of the punched steel sieve c is to prevent the unnecessary wear of the fine wire gauze, which would naturally suffer if it- DRESSING. 559 were exposed to the rubbing of coarse particles. The stuff which is too coarse to pass through the fine outer sieve d is collected by plates f and led back into the inside of the drum, where it is again exposed to the grinding action of the balls ; b b are lining plates to prevent the wear of the ends of the cylinder ; 1 1 and i denote bars closing a manhole which can be opened after the removal of the sheet-iron casing surrounding the whole machine. g. Disintegrators. Though any reduction of a mineral into fragments or powder may be spoken of as " disintegration," th& word disintegrator has been appropriated by the grinders which do their work with revolving bars or beaters. The best-known machine of this class is Carr's disintegrator (Fig. 631). It may be described as consisting of two cylindrical cages, revolving one inside the other in opposite directions. Each cage is made up of two concentric sets of bars, attached to a disc on one side and to a ring on the other. The stuff which is fed into the centre is thrown by the bars a a of the cage X, against the bars b b of the cage Y ; thence it flies against the outer circle of bars c c of X, and finally against the outer circle of bars d of the cage Y. It then enters the circumferential space e, whence it can be allowed to- escape by a suitable opening in the outer casing/. It is claimed for this machine that some of the pulverising is done by the impact of the particles one against the other, and that consequently the wear of the steel bars is less than might be expected. However, the disintegrator is found most fitted for comparatively soft materials, such as coal, gypsum, phosphates, and rock-salt. Instead of being arranged in the form of concentric circles in ORE AND STONE-MINING. this cage-like manner, the beaters are sometimes radial, and, when revolving at a very high speed, quickly reduce soft minerals to powder. h. Conical Grinders. In these grinders the crushing action is usually produced by the revolution of a toothed cone, inside a toothed cup; they thus resemble in principle the old- fashioiied coffee-mill. The Gates crusher (Fig. 632) acts differently. It consists of an outer conical shell Q (Fig. 632), lined with removable plates E, around which travels the conical breaking head F carried by the upright spindle G ; both E and F are made of chilled cast-iron. The lower end of the spindle G fits loosely in the excentric box D, and is a little out of the centre ; it is supported by the step P, which can be raised or lowered by the screw S, in order to regulate the distance between the breaking head and the shell, and consequently the fineness of the crushed product. The upper end of the spindle G lies loosely in a socket in the top framing C. The belt-pulley T U is loose upon the shaft X, and it drives it by means of the clutch V, firmly keyed to X, and the pin W. In case of any undue strain, the pin W breaks and prevents damage, for the machine at once stops until the obstruction is removed and a new pin has been inserted. DRESSING. 561 The bevel pinion upon X drives the bevel wheel L with its excentric box ; when L revolves, the lower end of G is carried round excentrically, whilst the top moves in its socket. The breaking head is thus made to approach and recede from each part of the shell in succession, producing practically the same effect as the reciprocating jaw of the Blake machine. The loose collar I serves to keep out dust, and it has a hole J, through which the machine is oiled ; N N are holes for conveying oil to the space Y. The material to be crushed is fed in through three large openings in the top frame ; it falls between E and F, is FIG. 633. INS 12 SCALE 3 OEClMtTRLJIO crushed by the movement of the breaking head and drops through at Q Q on to an inclined apron, whence it slides into any con- venient bin or receptacle. i. Centrifugal Grinders. There are several grinding machines in which a roller is whirled round upon the inside of a cylinder against which it presses by centrifugal force. The machine of this class most largely employed is the Huntington mill (Figs. 633 and 634). A vertical shaft G, driven by bevel gearing from below, carries a horizontal frame, which supports four grinding rollers by the yokes Y Y lying in the pockets P. The yoke allows a radial swing of the crushing roller against the steel ling (Fig. 634) lining the pan in which the grinding takes place. The construction of Paxman's improved roller is shown by 2 N 562 ORE AND STONE-MINING, Figures 635 to 637. E. is a steel ring which does the actual grinding and is renewable when worn ; it is fixed by wooden FIG. 634. ROLLER HUMTINGTOK MILL.B FT DIAMETER, SECTIONAL ELEVATION. SCALE: INS, 12 I 2 3 4. 56 7 FLtT DECIMLTRLi'O JETRL wedges W to the core G, and a sleeve bolted on to the core receives the spindle S. From this explanation it will be seen that FIG. 635. FIG. 636. FIG. 637. PLAN. PLAN At A.B. SCALE INS.12 2 FEE 10 DECIMETRES I i i ' . i I I SECTIONAL ELEVATION. the roller can revolve round the spindle S, but that the latter does not turn upon its own axis when it is carried round by the revolving frame supporting the yokes. A, B, C, D (Fig. 633) are DRESSING. 563 wooden scrapers which force the ore from the centre to the circumference and so bring it under the action of the rollers. It is easy to understand, therefore, that when the shaft G revolves the rollers are thrown out by centrifugal force against the annular lining, and crush and amalgamate the ore. The stuff which is pulverised sufficiently fine escapes through a wire-gauze sieve placed on the side of the pan, just above the lining ring. As this sieve has not to resist the violent blows to which the screens of stamps are liable, it may be made of much finer material. j. Pneumatic or Air-current Pulverisers. In one of these pulverisers, it is proposed to crush the mineral by driving the particles violently against each other by means of two power- ful opposite jets of air or superheated steam. To use a familiar illustration, it may be said that stone bullets are fired from air-guns against each other with such force that they break into powder upon meeting.* The Cyclone Pulveriser, which excited a good deal of interest .at the Paris Exhibition of 1889, is based upon the same idea. It consists of two beaters, something like screw-propellers, driven at a speed of 1000 to 3000 revolutions per minute in opposite directions in a small cast-iron chamber or case, in the form of two truncated cones joined together at their larger bases. The material to be crushed is delivered regularly into this case by mechanical feeders, and the whirlwind created by the beaters hurls the particles against each other with such violence that they are almost instantly reduced to the state of impalpable powder. The fine dust produced in this way is constantly being sucked off by a fan, arid allowed to settle in , chambers whence it is conveyed mechanically into hoppers. It can then be drawn off into sacks as required. As the aspirating force of the fans can be regulated at pleasure, the mineral can be brought to any desired degree of fineness without any screening. Before treatment in this machine, the material must be crushed small enough to be set in motion by the hurricane-like blast of the beaters; in the case of a mineral like quartz the fragments must not be larger than walnuts. k. Miscellaneous Pulverisers. These are so numerous 'that it is out of the question even to think of giving their names. The Sturtevant mill bears some resemblance in its mode of action to the Cyclone pulverisers, inasmuch as the particles are flung against each other with great force and break up in mid-air, so to say. The stones are projected, however, by centri- fugal force and not by air-currents. The Sturtevant mill is made of two horizontal hollow cups which revolve at great speed in * Industrial Review, vol. i., 1886, p. 56. 564 CUE AND STONE-MINING. opposite directions. The mineral is fed into the interval between the two caps, and as fast as it makes its way into one of them r it is hurled out again by centrifugal force and strikes other fragments which are thrown across by the opposite cup. The- powdered mineral is drawn off through a screen by a fan. Though the hurling cups are cylindrical, the crushed rock packs itself into the ends and forms a conical stone lining which prevents wear upon the iron surfaces. The Sturtevant mill is- said to be largely used in the United States for grinding phosphate of lime. The crushing machines in these descriptions have been arranged according to their modes of construction ; it will be well to point out in conclusion the uses to which they are applied, viz. : 1. Preliminary breaking : jaw-breakers, and Gates rock breaker. 2. Coarse crushing : rolls. 3. Fine crushing : stamps, rolls, mills of various descriptions, and disintegrators. 1. Sawing Machines. These are necessary in the case of stone and slate. The simplest machine is merely a plain blade held in a frame, moved backwards and forwards by a crank or excentric, whilst sand or chilled cast-iron shot and water are sup- plied to aid the saw in its cutting work. The wire saw, already described in a previous chapter, is employed for the same purpose. FIG. 638. In the case of slate, the work is usually done with circular saws. The blocks, which have been split into slabs about 4 inches thick, are fastened by wedges upon a sawing table, such as is represented in Fig. 638. It is a cast-iron bed, A B, moving upon rollers, with holes into which wedges can be placed for fixing the slabs of slate. The pulley C drives the circular saw D, and at the same time gives motion to a chain which draws the table along from one end of its frame to the other. When the table has gone as far as possible, the workman turns a hand-wheel which reverses the motion, it is drawn back, and another set of slabs are arranged so that they may be cut when it again moves forward. The saw sometimes lies in a semicircular trough full of water, which serves to keep it cool. m. Planing. Machines. Planing machines, somewhat similar DRESSING. 565 to those used in engineering shops, are employed for making the smooth slate-slabs required for cisterns or billiard- tables. The tool is held in one direction only and is not reversed after each stroke. n. Slate-making Machines. Greaves' circular slate-dressing machine (Fig. 639) does precisely the same work as the quarry- man's knife. It is a frame carrying two knives, C, which are made to revolve by the pulley A upon the same shaft as the little flywheel B. D is a fixed knife and E a cast-iron arm with a number of notches on the inside, which are gauges for enabling the quarryman to cut the slates to exact sizes. The belt pulley A is thrown in and out of gear by a clutch. Another machine for doing the same kind of work acts like a FIG. 639. guillotine, and has a knife which slides up and down vertically between guides. In both machines the action of the hand -knife is imitated that is to say, the cut is made gradually along the desired line. . (4) AGGLOMERATION OB CONSOLIDATION. Pro- cesses of this kind are more particularly used in the case of coal or brown coal, small particles of which can be pressed, either with or without the addition of some cementing material, into blocks of fuel of convenient shapes and sizes. At the same time agglomeration is nob confined to coal : some of the poor clayey phosphate of lime of the department of the Somme is made into bricks, so that it may be readily burnt in kilns and deprived of its moisture before being ground or sent away; the so-called " purple ore," the residue after the treatment of cupreous iron pyrites by the wet process, and other kinds of fine iron ore, are also sometimes made into bricks for the purpose of obtaining a product suitable for smelting in the blast-furnace. 566 OKE AND STONE-MINING. In order to get rid of water, washed graphite is pressed into- cakes, which are then ready for the drying stove. (5) SCREENING OR SIFTING. This is an important branch of dressing. Sometimes it is a preliminary process which is necessary or advisable previous to concentration by specific gravity, or to picking by hand. Sometimes it is a final process- previous to sale, and for several reasons : the purchaser usually requires cements, pigments, and fertilisers in a state of fine sub- division and free from any coarse particles, or, contrariwise, he may object to ores in the form of " smalls " or dust, which would choke his smelting furnaces. Lastly, in a case of coal, which is beyond the province of this treatise, the consumer prefers lumps, because they burn more readily than dust and afford a rough guarantee of purity ; whilst with anthracite the sifting process is carried out on a very elaborate scale, in order to obtain suitable kinds of fuel. Minerals are classified according to size by means of sieves worked by hand or by machinery. Hand-sieves are often employed underground for taking out " smalls " which are not acceptable to the purchaser. Thus at the Merionethshire manganese mines, the workmen shovel the fine stuff on to circular hand-sieves with holes | inch square, and use all that goes through as material for filling up. In speaking of the iron ore worked opencast in Northamptonshire a similar separation of the fine was mentioned (Chap. VI., p. 288). Sifting by hand is shown in Fig. 612 following bucking, so as to ensure a proper degree of hand-crushing. It is more econo- mical to employ a rectangular sieve fixed in a steeply sloping position, and throw the mineral against it with the shovel. In- clined gratings (grizzlies, U.S.) formed of bars of flat iron or steel, on to which the waggons of mineral are tipped as they come from the mine, are another form of sifting apparatus. Machine-sieves. Most of the sizing at mines is performed by sieves set in motion by machinery ; there are two principal kinds of machine-sieves : flat oscillating sieves and revolving cylindrical, conical, pyramidal, or spiral sieves. The most common in ore mines are revolving sieves, either cylin- drical or in the form of truncated cones. A sieve of this kind is often known as a " trommel." The word is expressive enough to the German ; but it fails to tell the Englishman that the machine is drum-shaped, and it can be tolerated in our language simply on the score that it has so long been in use that it is practically naturalised. The sifting is done by wire web or by perforated sheets of metal, either iron, steel, copper, brass, or bronze. Figs. 640, 641 and 642 represent sieves with round holes 1,2, and 5 millimetres respec- tively. The holes are sometimes square or oblong. The trommel consists of the perforated plate or the wire cloth bent into the required conical or cylindrical form, and supported by DKESSING. 567 rings attached by arms to a central axis. The conical trommel has the advantage that its axle can be placed horizontal, for the slight inclination of the sieve causes the mineral to make its way from the feed or smaller end to the discharge or larger end, provided of course that the machine is in motion. If the trommel is cylindrical, its axis must be inclined in order to secure the same result. FIG. 640. FIG. 641. FIG. 642. When it is necessary to separate a crushed mineral into a number of different sizes, the trommels are commonly arranged so as to discharge one into the other. This plan has the dis- advantage of requiring much gearing or many belts, for the sieves have to be arranged step-fashion, each one a little below its predecessor. If, on the other hand, only one long trommel is used, with the holes increasing in size from the feed to the discharge end, there is the evil of letting the very coarse stuff FIG. 64205. SCALE 2 METRO IZIN. 9 FEET wear away the fine sieve, and cause more frequent repairs. A good form, made by Jacomety and Lenicque of Paris, is that shown in Fig. 64 2 a. The feed-end A is free from cross-arms, having a large cast-iron ring B as support, and there are in all three sieves C, E and F. Suppose, for instance, that the trommel is supplied with stuff which has left a crusher sieve with no particles bigger than 8 millimetres ( J inch) across ; this passes 011 to the inner sieve C with holes of 6 mm. (J inch). The next ring, D, is of sheet iron. In this way the coarsest stuff never touches the fine sieve. 5 68 ORE AND STONE-MINING. The two sieves, E and F, on the outside have holes of 2 mm. and 4 mm. Consequently this trommel makes four classes : smaller than 2 mm., i.e., that which drops through the finest sieve, E ; size 2 to 4 mm., dropping through sieve F; size 4 to 6 mm., discharged at G ; and, lastly, size 6 to 8 mm., which passes out at H. An objection to trommels with concentric sieves is the difficulty of effecting repairs inside, if the plates become worn. This defect is remedied in the trommel figured by fixing on the perforated plates with screw bolts ; they can then be taken off quickly and easily. II. PBOCESSES DEPENDING UPON PHYSICAL PROPERTIES. (i) MOTION IN WATER. Many of the more important dressing processes depend upon the rate at which particles of mine- rals fall in water. The velocity of fall depends upon the specific gra- vity and the volume. A piece of galena with a specific gravity of 7*5 sinks to the bottom more quickly than a piece of quartz of equal bulk, which has a specific gravity of only 2 '6. Nevertheless, if the piece of quartz is large enough, it will fall to the bottom as fast as the smaller piece of galena Particles which have equal velocities of fall, though differing in size and specific gravity, are said to be like-falling or equivalent. P. von Rittinger * gives the following table to show the rates of fall of spheres of three, minerals differing considerably in specific gravity : jj* ti Velocity in Metres after the Lapse of SUBSTANCE. 11 1 coo Q isec. isec. sec. i sec. 2 sec. Galena . 7*5 mm. 16 0-903 1*411 1-630 I '650 I '650 Iron pyrites . 5' 16 0-825 1*174 1-287 1*293 1-293 Quartz . . . . 2-6 16 0-570 0*767 O'Soi 0*817 0-817 Galena .... 7;s 4 0-704 0*814 0-823 0*824 0*824 Iron pyrites . 4 0-586 0*643 0-646 0-646 0-646 Quartz .... 2-6 4 0-383 0*409 0*409 0-409 0-409 Galena .... 7'5 i 0-409 0-413 0*414 0-414 0-414 Iron pyrites . 5'o i 0-321 0-323 0*323 0-323 0*323 Quartz .... 2-6 1 0*203 0-204 0*204 0-204 0*204 This table shows that the particles at the very outset have an accelerated velocity, and that the velocity speedily becomes uniform. It also shows that a small sphere of quartz 4 * Lehrluch der Aufbereitungskundc, Berlin, 1867, p. 178. DRESSING. 569 FIG. 643. millimetres in diameter sinks down at almost precisely the same rate as a sphere of galena only i millimetre in diameter. These two particles are therefore like-falling or equivalent. It is evident that if the sphere of galena has a greater diameter than i millimetre it will fall faster than the grain of quartz which is 4 millimetres across. Consequently, if a mixture of minerals differing decidedly in densit} T is separated by sifting into lots consisting of particles nearly alike in size, there is no difficulty in effecting a separation by their mere descent through still water. This fact may be rendered very plain by a simple experiment. Prepare a mixture of like- sized grains of coal, calc-spar, and galena by sifting the pounded minerals and retaining, for instance, the portion which has no particles more than | inch in diameter or less than y 1 ^. Put the mixture into a glass tube 4 or 5 feet long and j inch or i inch in diameter, corked at one end (Fig. 643). Fill completely with water and cork the other end ; reverse the tube briskly and hold it upright. The galena will fall to the bottom first, then the calc-spar, and lastly the coal, and the three minerals will form separate layers distinctly marked by their differences of colour. A shorter and narrower tube may be used, but the greater the depth of the water the more accurately can the descent of the particles be watched. The experiment may be repeated by reversing the tube, for the galena will soon make up by its high specific gravity for the slightly longer path which it has to travel. Though the final velocity attained by a par- ticle of a mineral falling through water depends both upon its volume and its specific gravity, it is nevertheless true that in the early part of the fall the influence of the specific gravity preponderates, and the denser particles take the lead. This appears from the table. Take, for instance, a particle of quartz 16 millimetres in diameter and one of galena of 4 millimetres, which are practically like- falling after the lapse of a second ; at the end of | second, on the other hand, the galena is falling with a velocity 2 5 per cent, greater than that of the quartz. This fact is utilised in practice, for instead of simply letting the mixture of minerals fall through a certain depth of still water, it is made to undergo a rapid succession of very small falls. In this manner, particles vary- ing in specific gravity can be separated into distinct layers, although they have not been so closely sized as would have 570 ORE AND STONE-MINING. been requisite if the separation had depended upon equivalence alone. In a few exceptional cases the valuable mineral rises, as it is lighter than water ; when a mixture of ozokerite and clay is thrown into water, the waste falls to the bottom whilst the useful substance floats and may be skimmed off at the top. Bitumen, too, comes to the surface when bituminous sandstone is thrown into boiling water and stirred. Croll's process for extracting sulphur from rock containing the element in the native state, now abandoned on account of practical difficulties, is another instance of a separation by buoy- ancy. A solution of chloride of calcium was prepared strong enough to have a specific gravity decidedly above 2 ; when the rock was plunged into a hot solution of this kind, the sulphur gradually liquefied, oozed out and rose to the top, leaving the heavier matrix at the bottom. A second method of utilising the fall in water consists in subjecting the particles to a current flowing upwards ; by suitably regulating its force, light particles can be carried away and only the heavier allowed to sink. Lastly, a third kind of motion is that of small particles car- ried down inclined planes by a thin sheet of water. We have now to consider the various machines by which the fall in water is made to effect a separation on a commercial scale. 1. Simple Fall in Water, Keeve or Dolly-tub. This appliance is merely a vat or tub in which the finely divided ore is stirred and then allowed to settle ; it is specially used for the final treatment of fine lead ore and tin ore. The stirring may be done with a shovel whilst the ore is thrown into the water, but more commonly blades, attached to a vertical axle driven by gearing (Figures 644 and 645),* are made to keep the mixture of ore and water in a thorough state of agitation. When enough ore has been added, the stirring process (tossing) is stopped and the agitator removed ; the contents of the vat are allowed to settle, while the water is kept in a state of vibration by taps upon the outside from the iron hammer 6, lifted by the cams c, upon the driving shaft. This process of settling is locally called packing; as soon as it is complete, the water is baled out or drawn off by removing plugs in the side, and the deposit is scraped off layer after layer, increasing in richness as the bottom is approached. Jigger or Jig. The principal machine for concentrating particles varying in size from i inch to -fa inch is the jigger. The hand-jigger is merely a round sieve which is charged with the crushed ore and then moved up and down in a tub full of * Teague, " On Dressing Tin Ore," Proc. Min. Inst. Cornwall, vol. i. DRESSING. 571 water. Each time that the sieve is lowered sharply into the water, the particles are free to drop a short distance, and they gradually arrange themselves in layers, the heaviest at the bottom FIG. 644. FIG. 645. FIG. 646. and the lightest at the top. On lifting out the sieve the light waste can be skimmed off with a scraper, leaving a well-defined layer of the heavy rich mineral at the bottom, which is removed separately. This process of separation can be watched by the aid of a very simple piece of apparatus which the stu- dent can construct for himself (Fig. 646). A model jigging-sieve can be made with a cylindrical lamp-glass by fixing on a piece of wire gauze by means of sealing- wax, or by tying on a piece of any net-like fabric. A mixture of crushed coal, calc- spar, and galena, prepared as in the pre- vious case, is placed upon the sieve, and the glass cylinder is now moved down and up in a large tumbler partly filled with water. A distinct separation is soon effected. Instead of moving the sieve in still water, it is more common nowadays to make the sieve stationary and to force water up through it with a pulsating action. The particles are thus subjected to a series of repeated lifts and falls, and after the lapse of a little time the charge of crushed ore placed upon the sieve becomes separated into a layer of rich mineral at the bottom, and a layer of light waste at the top ; in the middle there may be a 572 ORE AND STONE-MINING. layer consisting of rich particles with more or less waste material attached to them. An illustrative model is again easily constructed (Fig. 647) by fixing a piece of wire gauze in a lamp-glass, between two rings cut from india-rubber hose of suitable diameter, whilst a flexible ball syringe supplies the means of pumping water up and down. However, this is not the form in which the jigger FIG. 647. i g made in actual practice. It usually consists of a box (hutch) divided by a partial partition into two compartments ; in one is fixed a flat sieve s (Figs. 648 and 649), which carries the ore, and in the other a piston, p, is made to work up and down by an ex- centric. The mode in which the separation is effected can be watched in a model made out of a U-tube, with a round stick or a test-tube as the piston (Fig. 650). The great advantage of these jiggers is that they readily allow a continuous feed of the ore and dis- charge of the products without any stoppages. The ore is fed on by a hopper placed at one end of the machine, or is delivered already mixed with water. Several methods of discharge can be adopted : viz., (a) at the end ; (b) in the centre ; and (c) through the meshes of the sieve. (a) With the first kind of discharge, the enriched product lying on the sieve passes out through open- ings at the end of the jigger, and the amount escaping is regulated by an adjustable shutter which enables the size of the outlets to be increased or diminished at pleasure ; the middle product can be drawn off by open- ings placed at a slightly higher level, whilst the waste is washed over a sill at the end of the sieve at each pulsation. Very often a first sieve simply separates a concentrated product and discharges a poorer product on to a second sieve where a similar separation is effected. (b) With the central discharge method, a pipe is brought up through the middle of the sieve, and the size of the opening for the escape of the concentrated ore is governed by a cylindrical cap, which can be raised or lowered by a screw. (c) The discharge through the sieve is specially adapted for the finer products from the crusher, though it is also used for grains up to and even above \ in. in diameter. The mesh of the sieve is chosen so that the particles under treatment will just pass through, but above the sieve is a layer (bed) of clean ore, or of some substance of about the same density, in fragments too large to drop through. The pulsations of the water cause the usual separation into layers, and the heavy rich particles find their way down through the bed of mineral of like specific gravity and DRESSING. 573 drop into the hutch, whence they can be drawn off through a hole as required. The poorer part passes over a sill at the end FIG. 649. FIG. 650. of the sieve, as a worthless product, or on to a second sieve, so that more valuable mineral may be taken out of it. Three or four sieves are often arranged in a row in one machine, and, by proper arrangement in dressing mixed lead and zinc ores, the first compartment may be made to yield clean galena, the second a mixture of galena and blende, the third clean blende, the fourth mixed blende and rock, whilst the greater part of the waste material passes over the sill at the end. These jiggers, with the discharge through the sieve, are commonly known as Hartz jigs. The number of strokes per minute, the length of stroke and the thickness of bed depend upon the fineness of the particles under treatment ; the former gradually in- creases, while the two latter decrease as the particles diminish in size. The piston of the jigger need not neces- sarily be horizontal. Messrs. Kitto and Paul place it vertically in the jiggers employed at Frongoch mine, Cardiganshire, for treating blende and galena. A and B (Fig. 651) are the two hutches, and C is a partition in the middle. D is the piston working between two plates of 574 ORE AND STONE-MINING. iron V V. The piston occupies the whole length of the jig, shown by T (Fig. 652) ; it is worked by the rod E, guided at F, and passing through a stuffing-box, G. The reciprocating motion is given by a crank M through the connecting-rod L and FIG. 651. Scale Ifcfe, wM ~6 feet lever H, which traverses the head of the piston-rod I. The crank has a long loop, which enables the stroke to be varied. The same end can be attained by an excentric with a slot, which allows the excentricity to be altered at pleasure. N shows where the ore is fed on, and is the place of discharge of the waste or impoverished FIG. 652. ore. S is the sieve, and P P are holes with plugs manipulated by handles not shown in the figures, by which the concentrates which pass through the sieve are drawn off. It is the pipe bring- ing in clean water. 2. Upward-current Separators. We must now pass on to the second method of utilising the motion of minerals in water, viz., by subjecting them to an upward current; and here it may be remarked that the con- DRESSING. 575 tinuous jig to a certain extent produces an action of this kind, for the light waste, brought to the top by the pulsating movement, is finally carried away by the outflow of the fresh water. Upward-current separators are usually inverted pyramidal or conical boxes with water under pressure brought in near the bottom. A stream of ore and water is fed in at the top, some of the heavier particles sink and make their escape with a portion of the water, at or near the bottom, whilst the lighter grains are carried over the edge of the box. A separator of this FIGS. 653 and 654. SCALE M.I 0-5 I2INS 0123456703 FEET kind simply extracts a number of like-falling particles, and the product may require further treatment before a sufficient degree of concentration is obtained. Jacome'ty and Lenicque's Separators. Figures 653 and 654 represent Jacomety and Lenicque's pyramidal separator with six compartments, A, B, C, D, E, F, which make seven cate- gories from pulp with all its particles under i mm. in diameter. Each compartment is merely a box in the form of an inverted pyramid, and for convenience of transport, the machine is made in three separate castings, which can be easily bolted together, as shown at R and S. Pipes bring down water from the main G H, and the amount supplied to each division can be regulated by a cock ; the water strikes a little plate attached to the end of the pipe and rises up. o 576 ORE AND STONE-MINING. The pulp is fed on at J and escapes at K. Particles which can overcome the upward current are discharged continuously through a nozzle at the apex of each pyramid. These nozzles are shown at L, M, N, 0, P, Q ; they are easily detachable, and can be taken FIG. 655. twith handle 4 Feat off during the progress of the work, if by any chance they become choked. Though separators of this kind are usually employed for the treatment of fine sand and slime, they are occasionally applied to comparatively coarse stuff. The separator shown in Figures 655 and 656 is used at Frongoch mine, Cardiganshire, for treating an ore consisting of blende and galena, mixed with slate, just as it leaves the rolls, after having been crushed fine enough to pass DRESSING. 577 through a sieve with 12 holes per square inch (3 holes by 4 holes). The coarse goes to the jigs, the fine to the buddies. It is an inverted wooden cone A, which can be more or less com- pletely closed at the bottom by a plug B, controlled by a handle C. The cone stands upon a wooden box D, which receives water under pressure from a pipe E, and is provided with a discharge valve F, a mere flat plate of iron, working on a pin, which can be pushed sideways so as to close the orifice partially or entirely. Inside the wooden cone there is a sheet- iron funnel G, which receives the stream of ore and water from a launder H, and causes it to descend to the level I. There it meets with the upward current of clean water, and a separation is effected. The coarse and heavy particles which can overcome the stream pass into the box below, and flow out con- tinuously at F, while the fine and light particles are mastered by the current and carried over the top edge of the wooden cone, which is surrounded by a circular launder. By regulating the upward current of clean water and the size of the discharge orifice, the separator can be adjusted to the requirements of any particular case. Lockhart's Automatic Gem Separator. In this machine the particles of minerals fall into a current of water ascending in an annular space, purposely made narrow in order to prevent eddies, which would interfere with the desired results. The velocity of the current can be regulated by stop-cocks, and arranged so that only the denser of any like-sized particles shall be able to overcome it and sink. Its primary object is to treat clean-washed concentrates from gem-bearing gravel after a careful preliminary sizing by screens. Siphon Separator. A most successful application of an upward current of water is in the machine known as the siphon separator, though its action is not based upon the principle of the appliance from which it takes its name. It consists of a rectangular box (Figs. 657, 658, and 659),* made of sheet iron or wood with a partition, dividing it into two chambers B and E. The front one B resembles a pyramidal separator, receiving an upward current of fresh water from the adjacent compartment E and an orey stream from the launder Gj the continuation of which carries away the light waste. The compartment E has a partition z, dividing it into two parts : A, which receives a supply of fresh water by means of the pipe a, and C, which has the regulating float s. To prevent shocks and eddies, the water does not fall directly into E, but first passes through holes in the partition u. The precise position of the float s can be altered at pleasure by the rod /, which connects it to the lever h, movable about the fulcrum i attached to the * Heberwasche des Mechernicher Bergwerks-Actien-Vereins, B. . h. Z. , 1886, p. 476. 2 O 578 ORE AND STONE-MINING. upright bar t. The travel of the lever is controlled by means of the rod g. A light rod e carrying the outlet valve is attached to the lever at d ; this valve is set in the middle of a pyramidal sieve bottom b, and governs the discharge into the pipe q, which FIG. 657 FIG. 658. leads to the outlet orifice r. The object of these arrangements is to obtain a self-regulating discharge, the action of which is very simple. As the ore-bearing stream passes along over the box , the heaviest particles overcome the upward pressure of the ascending current and drop ; if the valve is shut, they DRESSING. 579 accumulate upon the sieve, and prevent the passage of some of the water through it. The obstruction causes the water in the chamber C to rise, the float ascends at the same time, and in so doing lifts up the valve and allows the discharge of the grains of ore into the pipe q. The float then sinks, the valve goes down, another little deposit of ore causes an obstruction and the process is repeated. These separators are some of the principal machines employed at Mechernich for the treatment of the friable lead-bearing sandstone ; in fact, there are no less than 124 of them in use. They are remarkable for their simplicity and for the large amount of stuff that they will treat. The quantity of broken sandstone which can be successfully passed through one machine per hour is from 270 to 300 cubic feet (8 to 9 cubic metres). Sometimes two or three of these machines are placed one after the other, the second receiving the overflow of the first, and the third the overflow of the second. The quantity of water required is somewhat large viz., 9900' gallons (45 cubic metres) per hour ; but at Mechernich it is used over and over again, after the fine matter in suspension has been, allowed to settle. 3. Separation by Water flowing down Planes. We lastly have to deal with the third manner of utilising the motion of mineral particles in water, that is to say, allowing them to be carried down inclined surfaces by a stream of water. Two classes of appliances are used : those in which the deposit is cleaned off as soon as a thin layer has settled down, and those in which the deposit is allowed to go on forming until it has attained a thickness of at least several inches or a foot. (i) The first class includes various kinds of plane and conical tables, certain percussion tables, and the travelling belts. Plane Tables. Plane tables, often called "frames," and sometimes, but incorrectly, called " buddies," are slightly inclined rectangular surfaces of wood down which the pulp flows in a regular stream. An even flow over the whole width of the table is secured by first passing the stream over a head-board, which divides it into a number of little rills. The strength of the current depends upon the quantity of water, and upon the inclination given to the table. These are arranged so that some of the mineral under treatment will settle down and resist the action of the water, which is always tending to carry it on further. After a deposit of this kind is formed, clean water is often allowed to run down over the table to carry off any light particles intermixed with the heavy ore, and its action is aided by brushing lightly with a broom. The deposit is then washed, off and collected in a tank for further treatment. S 8 ORE AND STONE-MINING. Where the mineral to be treated is poor, the tables have to be worked with as small an expenditure of labour as possible ; and FIG. 660. INS. 12 to FE:E:T DE.CIME.TRE.S 10 2 METRE.S FIG. 66 1. SCALE. DtCIMETRLS the device adopted in Cornwall is explained by Figs. 660 to 662.* A is a launder bringing the pulp, which flows down over the head- * Ferguson, " On the Mechanical Appliances usod for Dressing Tin and Copper Ores in Cornwall," Proc. Inst. 31. E., 1873, p. 130. DRESSING. 581 board B on to the inclined surface of the table, leaving upon it, in virtue of their high specific gravity, some of the heavy particles of tin ore, and carrying the lighter refuse into the launder C. While this action is proceeding, the clean water launder E is filling the two V-like troughs D and D'. When these are full, they tilt over (Fig. 662) and discharge their contents suddenly on to the table, washing off the deposit. The troughs D and D', on turning over, carry the bar H H forwards, and thus lift the flaps at F and F', so that the upper and richer part of the deposit is washed into the launder F, the lower and poorer part into F'. As soon as the troughs have discharged their water, they are brought back into their original position by the simple cataract G, and the process is repeated. Round tables are bluntly conical, convex or concave surfaces ; with the former the pulp is fed on at the centre and runs down to the circumference ; with the latter, the direction of flow is reversed. The tables are made of wood, planed cast-iron, or cement ; the wooden tables may be plain or covered with india-rubber. They are stationary or revolving. An excellent stationary table is that of Linkenbach* (Figs. 663 and 664). The table itself, a, is made of masonry with a smooth surface of cement ; b is an upright shaft, which carries the pulp-dis- tributor and the pipes supplying water for cleaning and for wash- ing off the deposit ; it is set in motion by the worm d and wheel c. Two of eight radial arms, borne by a centre-piece, are indicated by e e ; they carry the apron g, the clean water pipes, h, h, h, the position of which can be regulated at pleasure, and the washing- off pipe i. The clean water is brought in by the circular box &, rotating with the arms e, and supplied from the pipe I ; the pulp is delivered through the pipe m, which passes along the conduit n under the table into the inner ring o of the adjustable dis- tributor o. The distributor is constructed so as to deliver pulp at o" and clean water at o'" ; p p are pipes bringing down clean water from the rotating launder k, and q', q", q" are three concentric gutters, by which the various products are led away. The innermost gutter takes the waste " tailings," the middle one the mixed product, and the outer gutter the clean concentrate. The two latter products are conducted each into its proper channel by the apron g, which is made of sheet zinc. The mode of action of this table is easily understood. The distributor is constantly feeding on slime by the part of its circum- ference r o s (Fig. 664) ; a deposit forms on the table, whilst the lighter tailings run off into the gutter q', which is freely open to them in the absence of the apron. As soon as the feeding part of the distributor has passed, clean water begins to flow down over the de- posit from the trough o'", carrying oft the middlings into the gutter * Linkenbach, Die Auflereitung der Erze, Berlin, 1887, p. 101, and plate xvi. 5 8 2 ORE AND STONE-MINING. FIG. 664. FiG,664. GROUND PLAN SCALES FttT ID 1 L. DtCIMtTRL-o DRESSING. 583 q", and having its action aided by the washing-off jets h. There now remains on the table nothing but a clean concentrate, and this is washed off into the gutter q" f by the jets i ; r' is a launder carry- ing away the waste ; r" conducts the middlings to a settling pit A, and the concentrate escapes by a similar launder r'" into B ; z is a wire rope for driving a second table. An easy way of realising the mode of action of this table is to divide it mentally into three portions viz., the sector from t to r, which is receiving the slime ; the sector from t to w, from which the middlings are being washed off; and lastly, the sector from v to w with the clean concentrate, which yields to the jets issuing from i, and passes over the apron into the outer gutter q'". Where the amount of space is limited, Linkenbach places three tables on the same central shaft ; but the economy of space and of original first cost is accompanied by less easy supervision. The mode of action of round tables is very often just the reverse of what has been described ; that is to say, the table revolves and the distributor is stationary. Linkenbach points out that a revolving table is necessarily subject to vibrations, which must interfere with the evenness of the flow down the inclined surface, whilst the fixed table with a travelling distributor is free from influences of this kind and is likely to work more regularly. Nevertheless, in spite of this objection, revolving round tables may be seen doing good work. The table represented in Figs. 665 and 666 is one designed by MM. Jacomety and Lenicque. A is the head-board or distributor which feeds the table B with a stream of the fine slime ; the table is made of arms of T-iroii, radiating out from a cast-iron centre-piece C, which support a light covering of planks. Over this is stretched sheet india-rubber, which forms a smooth surface, free from any liability to warp and get out of shape. The table is set in motion by the vertical shaft D, driven by the wheel G and worm H. L L are various pipes bringing clean water, supported by rods N N, and capable of being placed in any suitable position. M M are pipes which wash off the deposit from the table; they are held up by standards N' N', which can be shifted about at pleasure. K is a circular launder round the table, with discharge holes t t, and movable wooden partitions *, s', ", '", s"" ; lastly, the pipe O sends out jets of water which clean off everything remaining upon the table. If the table is supposed to be moving in the direction of the arrow, it is evident that products of different kinds will be washed off at different periods of the revolution, and that towards the end nothing will remain on the table but the heaviest particles. By suitably arranging the amount of feed and the position of the different washing-pipes, the table can be made to give clean ore, waste, and intermediate products ; the latter are passed over the same or a similar machine once more. 584 ORE AND STONE-MINING. The table is 16 feet 5 inches (5 m.) in diameter, with a useful working surface 4 feet n inches (1*50 m.) long; it makes one revolution in 3^ minutes, requiring less than ^ h.-p. to work it. The quantity of water used is about 26 gallons (120 litres) per minute, and the table will treat from 5 to 8 tons of slime in ten hours. As it is made of eight segments bolted together, it is easily transported and erected. FIGS. 665 and 666. Percussion Tables. Rittinger's side-blow percussion table (Fig. 667) is an inclined rectangular platform suspended by the four corners A B C D, receiving blows and bumps on the side. A stream of orey water S is fed on to the corner A, and clean water W runs down from other head-boards H H H. By means of cams upon a revolving shaft, the table is pushed out in the direction of the arrow, and it is then driven back by a spring, so that the cross-piece E strikes against the bumping-block L. The light particles travel down the table much faster than the heavy ones, and taking a comparatively straight course, leave the table at K; whereas DRESSING. 585 the heavy and richer particles remain on the table, subject to the influence of the side-blows, for a much longer time, and travelling along a curved path reach the bottom at F. An intermediate product is discharged at G. The exact degree of richness or poorness can be regulated by pointers, strips of wood which can be turned so as to divide the stream of ore and waste where thought most desirable. The great advantage of this machine over the old percussion frame is its continuous action. Travelling Belts. We now come to the travelling belts, of which there are many varieties. An early form was that of Brunton,* an endless belt of canvas acting in the same way as FIG. 667. s w FIG. 668. the now favourite Frue-vanner, save that there was no shake sideways. In fact, the latter machine is regarded by some as an improved form of the Brunt on cloth. The Frue-vanner (Fig. 668) is an endless band of india-rubber cloth, 4 feet wide and 27 feet long, with an upper working surface of about 1 2 feet in length. The belt is supported by a frame with a number of small rollers on which it travels easily, and it is driven slowly in the direction of the arrows by the upper end roller shown in the figure. The small roller by the side of the large one, which dips into the tank, serves for tightening up the belt when required. The whole frame carrying the belt receives a motion sideways from three little cranks upon a small shaft running parallel to its length. The pulp is fed on by the head-board A, and clean water by another B. The natural path of the particles is down the inclined belt, but those which can resist the action of the * Sopwith, " The Dressing of Lead Ores," Proc. List. C. E., vol. xxx., 1870, p. 112. 586 ORE AND STONE-MINING. stream of clean water at B, go over the top end, and are washed off as the belt passes through the tank. The poor stuff is discharged into the waste launder at the other end. The degree of concentration can be regulated by the slope and speed of the belt and the strength of the streams of ore and water. The Frue-vanner has the disadvantage that it makes only two classes, rich and poor, without any intermediate product. The success of the Frue-vanner has naturally brought a number of somewhat similar contrivances into the market. The Embrey concentrator may be likened to a Frue-vanner, with a longitudinal instead of a lateral shake. The Woodbury ore concentrator is made up of several narrow belts each with its own flanges, instead of there being one broad band. The object of this arrangement is to prevent uneven- ness of flow, for if strong, irregular currents are formed in the centre of the belt, they may carry away good ore into the waste launder. Stein's endless belt, which has been improved by Bilharz, has a totally different mode of action. It resembles the Rittinger percussion table in its manner of effecting a separation,, but the work is done on a travelling belt instead of an unchanging sur- face. Stein's machine * (Figs. 669, 670, and 671) is a rectangular frame a, suspended between two posts p, by rods i, at the four corners, so that it can swing in the direction of its long side. The inclination of the frame can be altered at pleasure, by the handle attached to the cross-beam I, which works upon the screw e, but the long side always remains horizontal. The frame is drawn slightly out of position by cams r, acting upon the lever m, and as soon as it is released it is pulled back against a bumping-piece , by a spring n. The frame has two large rollers c c, and three mall ones underneath, which carry an endless belt of india-rubber/, the upper part of which is further supported by the flat bed of boards b. The belt slides over this bed, and is prevented from sticking to it by a constant flow of water, supplied by the pipe g, along narrow diagonal grooves. One of the end rollers is made to revolve and carries the belt with it. The pulp is fed on by a head-board k, and clean water is turned on through holes in the pipe o. The direction of travel of the belt is indicated by the arrow. The concentrating action is like that of a Rittinger table. The lightest particles run down at once, and leaving the belt at the right-hand end of the table, fall into the first compartment of the launder g, whilst the heaviest remain on the table much longer, and are finally discharged at the left-hand end. Intermediate products run off in the middle. (2) The second set of appliances includes the buddies and ordinary percussion tables. * Blomeke, " Ueber den Stein'.schen Plaimen-Stossherd," B. u. h. Z., 1891, p. 69. DRESSING. 587 Buddies. The hand -bud die is a rectangular wooden box with a sloping bottom. A stream of pulp is fed in by a head-board at FIGS. 669 and 670. nfl I FIG. 671 the upper end and gradually forms a deposit on the floor of the bud die. A boy with a broom keeps the surface of the sediment even, so as^to ensure regularity of action. After a thick deposit 5 88 ORE AND STONE-MINING. has accumulated, it is dug out in sections, which decrease in rich- ness from the upper end (head} to the lower end (tail). Round buddies bear the same relation to hand buddies that round tables do to hand frames. They may be concave or convex, but the latter are the more common. The convex round buddle (Figs. 672 and 673) is a circular pit * with a truncated cone, or head, of varying size in the centre, and a bottom sloping towards the circumference. The orey stream, A, FIG. 672. FIG. 673. falling over this head runs down gently, depositing the heaviest particles near the top, the lighter ones further down, while the lightest of all flow away at C. The surface of the sediment is kept even by the revolving brushes D. This machine may be compared to a number of hand-buddies arranged radially round a centre. The deposit which is formed is dug out in rings of varying richness. The concave buddle is a circular pit with the bottom sloping * Henry T. Ferguson, " On the Mechanical Appliances used for Dressing Tin and Copper Ores in Cornwall/' Proc. Inst. Mecli. Eng., 1873, plate xli., and p. 124. DRESSING. 589 towards the centre. The stream of ore is fed all round the cir- cumference, and runs inwards towards the middle, where the lightest particles escape. The rich head is, of course, near the circumference. Ordinary Percussion Table. The ordinary percussion table, though rarely if ever seen in this country, is still employed in Germany and regarded with favour. Those familiar with the hand-buddle will understand what it is like, if it is described as a swinging hand-buddle which is continually being bumped at the upper end. It is a shallow rectangular sloping wooden or iron tray suspended from the four corners, so that it can move back- wards and forwards in the direction of its length, and as soon as it has been pushed out of position by a cam, it is at once forced back by a spring against a fixed wooden bumping-block at the upper end. The pulp is fed on at the upper end by a head-board, and the lightest particles run off at the lower end, which has no rim, whilst the heavier and richer ones form a gradually thickening layer upon the bed. When sufficiently thick, the deposit is shovelled off in sections varying in richness as they do in a buddle. The bump assists in making the particles settle, just as it does in the " keeve," and at the same time, in virtue of the vis viva acquired during the backward stroke of the table, grains of ore are constantly being thrown up a little, as they are with the German hand- washing dish. Machines of this class have two grave defects : careful watching is necessary, in order to keep the surface of the deposit perfectly even ; otherwise gutters are formed, down which the water runs with too great a velocity, carrying away rich ore or depositing it near the tail end when it ought to have subsided at the head. Secondly, the deposit has to be shovelled off, and the parts requiring further treatment have again to be mixed with water and brought into a proper consistency, before they can flow on to other machines. In spite of these drawbacks, buddies and percussion tables are still largely employed. (2) MOTION IN AIR. In countries where water is scarce, or where the valuable mineral is specially liable to be affected or carried off by water, engineers have long desired to employ air as the medium in which the concentration should be effected. Three kinds of machines are used : the pneumatic jig, the fan, and the centrifugal concentrator. l(heiimatic Jig. The pneumatic jig resembles the hydraulic jig in principle ; that is to say, particles of minerals varying in specific gravity can be separated if they are lifted and then allowed to fall again, provided that the sizes of the grains do not differ too widely, and that the specific gravities do not approach too closely. The principle will be most easily grasped if the student constructs a very simple model (Fig. 674). A piece of glass tube with the upper end covered by net or muslin is 590 ORE AND STONE MINING. inserted into a slightly larger tube. The lower end is then connected to an india-rubber pump, such as is used with scent diffusers. Pour a mixture of like-sized grains of galena and sand on to the sieve, and give the pump a succession of gentle squeezes. Puffs of air are sent up through the sieve, and the two FIG. 674. minerals arrange themselves as shown, the galena below, and the sand above. By using a bed of fine shot, jigging through the sieve may be carried out, the action resembling that of the Hartz sand-jigs. Krom's* pneumatic jig, which is in actual use for treating silver ore, is a wooden chest in which a flat vane moving backwards and forwards sends a number of rapid puffs of air through a bed of fine ore, resting upon a sieve made of short upright tubes of wire cloth, with small spaces between them. The fine ore is fed in from a hopper on one side of the long narrow sieve. The repeated falls bring about a separation, and the light waste passes over the edge of the sieve opposite to the feed-hopper, whilst the concentrate sinks down through the interspaces between the sieve tubes into a reservoir, from which it is drawn off gradually by a fluted roller. As this reservoir is always kept full, the rate of discharge and degree of concentration can be varied by altering the speed of the roller. Fans. A fan is used in connec- tion with some grinding machines in order to draw off the powdered mineral, and, in dealing with a homogeneous substance, the amount of suction can be regulated so as not to draw the mineral out of the machine until it has been sufficiently pulverised. If the dust-laden air is then discharged into a large chamber, the coarsest particles will settle down first, whilst the finest will be wafted to the far end. As an instance of fan-action, the dressing of phosphate of lime may be mentioned. Some of the phosphate of lime which is. ground between millstones in France is not passed through any sieve at all ; a fan is adjusted so as to draw it away from the mill sufficiently fine to be put into sacks at once. Tests are made from time to time to see that the product is properly ground, for it is sold with the guarantee that not more than a certain percentage shall be too coarse to pass through a given sieve. Another example may be taken from some of the fuller 's- earth dressing establishments. The earth is ground in an * Gallon, " Lectures on Mining," Paris and London, 1886, vol. iii., p. 104 and Atlas, plate civ. DRESSING. 591 Askhara mill and forced by a fan into a chamber some 50 feet long by 10 feet wide, where it drops upon the ground ; the deposit is shovelled away afterwards in sections, which are finer and finer as one goes away from the orifice through which the dust enters. The requirements of different customers can thus be satisfied. When a fan is employed for drawing off the fine product from a mill or crusher, it likewise serves the useful purpose of pre- venting the atmosphere of the works from being polluted by noxious dust. Centrifugal Concentrator. These concentrators are based upon the fact that when bodies of equal volume are whirled round, the centrifugal force developed is proportional to their densities. Therefore, if the like-sized particles are projected by centrifugal force from a machine, the denser ones, with their larger store of energy, will be better able to overcome the resistance of the air than those which are specifically lighter, and will consequently travel further. The truth of this can be made manifest with a child's top. Spin the top in a saucer or dish raised a little above the table, previously covered with a sheet of paper or cardboard, and feed on to its flat upper surface a thin stream of finely powdered galena and sand, which has passed through a sieve with 100 holes to the linear inch and refused to pass the 120 mesh. The particles will be whirled off, light sand will drop close to the saucer or even into it, whilst the heavy galena picks up a larger amount of energy from the spinning-top and flies further away before settling. By brushing up the dust concentrically, the FlG> effect will be apparent. The Clarkson-Stanfield concen- trator (Fig. 675) works precisely in this way. B is a distributor, which is made to revolve rapidly by its spindle 0. The hopper A supplies it with finely powdered and carefully sized ore, which escapes by a number of radial holes. The dotted lines show the paths taken by the particles of mineral, which drop into a series of concentric troughs from which they can be swept by revolving brushes into discharge-spouts. In order to work successfully, the ore must be very carefully separated by screening into particles of approximately the same volume. The machine is new, and has yet to bear the test of actual practice on a large scale at mines, but it is worth noting that a similar appliance is used at mills * for freeing semolina from bran and dust. The Pape-Henneberg f ore concentrator is identical in principle with that of Clarkson and Stanfield. A disadvantage of all pneumatic dressing is that the ore has to * Spon's Dictionary of Engineering, London, 1873, vol. vii., p. 2499. t B. u. h. Z., 1893, p. IQI. 592 ORE AND STONE-MINING. be very thoroughly dried, for otherwise the particles stick together slightly and counteract the action of the forces which should effect the desired separation. (3) DESICCATION. Various reasons call for the drying of minerals. Sometimes the mineral cannot be ground until it is freed from moisture ; in other cases drying is advisable in order to save the payment of carriage upon a useless ingredient ; it is like- wise necessary before a mineral is roasted in furnaces, or passed through certain magnetic separators, and, as has just been remarked, it is indispensable when the subsequent treatment is effected by a pneumatic process. Drying may be carried on in one of the following ways : a. By exposure to the air. 6. By open fires. c. On open floors or pans. d. In enclosed stoves or kilns. e. By filter presses. a. Air Drying. Simple exposure to the action of the atmosphere, under a light roof as a protection from occasional showers, is quite sufficient for the purpose of drying many minerals, provided that the weather is fine. China clay and ochre are sometimes dried in this way. The roughly cubical clods are piled up one above the other, allowing free access of air, and. if the weather is favourable, a sufficient amount of moisture evaporates naturally to render the mineral fit for the market ; but a wet season sadly interferes with the work, frost will cause the clods to crumble, and artificial drying often becomes necessary in order to satisfy the demands of customers. In Chili the crystals of nitrate of soda are soon dried perfectly by exposure to the atmosphere. 6. Open - fire Drying. The phosphate of lime dug or dredged in South Carolina is sometimes dried by heaping it upon piles of wood which are set alight. c. Drying on Heated Open Floors. Heated floors are em- ployed in drying barytes, fuller's earth, and phosphates previous to grinding, other minerals previous to roasting, and china clay previous to sale. Fig. 676 shows a Cornish " dry" for china clay.* The letters I I represent the " settling tanks" or stone-lined pits into which the clay is run, in the form of a thin mud, after the coarsest particles of the decomposed granite have been separated. Here it forms a sediment of the consistency of thick cream, which is trammed to the " dry," after the water has been drawn off. The drying- house is composed of the dry proper m m, and the storing sheds or " linhays," o o. The floor of the dry is made of large fire-clay tiles, which cover a number of flues, each about 14 inches wide, * Collins, " The Hensbarrow Granite District," Truro, 1878, p. 20. DRESSING. 593 leading away from the fireplaces, s 8. The tiles are 5 or 6 inches thick over the fires, where the heat is greatest, and the thickness is reduced to 2 J or 2 inches at the other end of the building. The clay is trammed in along the road 1 1, and tipped on to the floor or " pan " m m, until it forms a layer 9 inches thick at the fire-end and 6 inches thick at the stack-end. The clay at the fire-end is dried in 24 hours ; it is cleared off and stored in the linhay o o, and another charge of wet clay trammed in ; the further the clay is from the fire, the longer it takes to dry, and at the stack-end, the " pan " can be cleared and re-loaded only twice or three times a week. It appears that much more of the FIG. 676. moisture soaks down through the tiles and is carried away as steam by the flues, than evaporates from the surface of the pan, and for this reason the tiles are made as porous as possible. The open floors used for drying phosphate of lime in the North of France previous to grinding have the bed made of sheets of iron. The plates are about one metre square and are laid upon a series of parallel flues formed of little walls one brick thick. The floors are often about 20 metres long and 4 metres wide. In order to accelerate the process of drying the sandy phosphate is shovelled over from time to time by men, but the cost of labour can be reduced by using Arnett's mechanical hoe which performs the same office. It is a frame stretch- ing across the whole width of the floor, carrying a single row of broad blades or spades, which can be inclined at any 2 P 594 ORE AND STONE-MINING. desired angle to the bed; it is drawn backwards and for- wards by machinery. The blades pass into the layer of phosphate on the floor, heap up the stuff in front of them, and cause the particles to mount up, and then fall over on to the bed again. Each time the hoe passes along, the stuff is shifted forwards a little, so that when the frame arrives at the end of its course, it pushes off a portion of the charge, which is now dry enough for milling, as it has travelled along the full length of the bed. As the inclination of the blades can be altered, the rate at which the stuff is carried forwards can be regulated so as to prolong or shorten the drying process, as required. The machine is made to reverse its direction of travel automatically, but it does no stirring on the return stroke. Thelen's drier is an open semi-cylindrical iron pan heated by a fire below, in which the charge is stirred by knives moved me- chanically. d. Stoves and Kilns. The number of kinds of enclosed stoves and kilns employed for drying minerals is very great ; and it is especially in the case of brown coal* that the ingenuity of in- ventors has been exercised to devise means of getting rid of moisture. However, as the subject of brown coal does not belong to this work, the special stoves made use of cannot be dealt with at length ; still it is right that they should be mentioned, as some of them could be used for other minerals. With such a large number of drying stoves, it is absolutely necessary that there should be a classification of some kind, for otherwise the student runs the risk of being confused. It is perhaps most convenient to classify them first of all accord- ing to the mode of heating, and then make a further subdivision according as kiln or furnace is stationary or revolving. Enclosed Kilns and Stoves. Mode of Heating. Kind of Drying Surface. Name of Drying Stove. {American Phosphate kiln. Fullers' earth kiln Krom's stove. Riebeck's stove. (Revolving . Brunton's furnace. Direct fire and hot air ... Hot air ... Stationary , f Stationary Steam - (Revolving Hot air and steam ... Stationary American Phosphate Kiln. The kilns employed for drying phosphate of lime in South Carolina f after washing are simply * Vollert, Der Braunkohleriberglau im Oberbergamts-BezirJc Halle und in den angrenzenden Staaten, Halle a. d. S. 1889, p. 249. t Benedict, "Mining, Washing, and Calcining South Carolina Land Phosphate," Eng. Min. Jour., vol. liii., 1892, p. 349, Ruelle's stove. Rowoldt's stove. Steam stove. Schulz's stove. Jacobi's stove. DRESSING. 595 rectangular chambers, built of brick and roofed with wood. The whole of the bottom is covered with a pile of wood, on to which the wet phosphate is tipped from barrows. The wood is set alight and flues supply it with air for combustion. Each kiln holds from 1000 to 1200 tons of phosphate ; the fire burns out in from two to five days, and the phosphate is then ready for export. Fullers' Earth Kiln. The fullers' earth kiln may be taken as another example of the first class. It is a brick or stone build- ing about 36 feet long and 15 feet wide, with an arched roof of brick (Fig. 677) or a sloping roof of slate. About 9 feet above the bottom is a floor a, made of cast- iron plates full of holes about J inch in diameter, underneath which are two sets of sloping shelves, made of sheets of iron, b 6, c c, which can be taken out at pleasure ; d is a deep flue bringing in air from the outside, and having two openings into the kiln, covered with fire-bars, upon each of which a coke fire, e, is maintained. A sheet of corrugated iron,/, is hung up over each fire, in order to pre- vent the clay immediately above it from being too strongly heated. Both the upper and lower floors of the kiln can be entered by large doors. The charging is all done from the floor a; a few of the plates are taken up on each side, the sheets b b removed, and clay is wheeled in barrows along a and tipped on to c. The plates b are replaced and similarly covered with a charge of clay, and finally a receives a layer of damp clay 6 or 8 inches thick. The doors are shut and the fires lighted ; though the heat is con- siderable, it is not enough to prevent men going in from time to time to put on more fuel, if required. The moisture-laden air ascends and escapes through the roof at g. Krom's Stove. Krom's stove has a series of inclined shelves, something like those of the Hasenclever furnace, down which the mineral gradually makes its way under the action of gravity, while exposed to the direct action of the hot gases coming from a fire.* Riebeck's Stove. Riebeck's "Tellerofen" consists, as its Ger- man name denotes, of a number of superposed circular plate- like shelves ; a central revolving shaft carries arms with * Sahlin, " Magnetic Separation of Iron Ore," Eng. Min. Jour., vol. liii,, 1892, p. 638. SCALE OF FEET 505 SCALE. OF METRES I OS 59 6 ORE AND STONE-MINING. teeth or knives which alternately cause the mineral to travel out- wards and inwards. Thus the mineral fed on to the top shelf, for instance, will be made to travel outwards to the circumfer- ence, where it drops through holes on to shelf No. 2 ; here the revolving teeth, arranged in the reverse fashion, draw it in gradu- ally to the centre, where it falls upon shelf No. 3, and it goes on travelling backwards and for- wards in this fashion until it reaches the bottom of the kiln. During all this time it is sub- jected to the action of the hot gases coming from a fire below. Brunton's Furnace. Though Brunton's calciner (Fig. 692) was invented for the purpose of roast- ing ores, driers have been con- structed upon the same principle ; the stove is a circular revolving horizontal bed, with teeth fixed above it which cause the mineral, fed in at the centre, to travel gradually to the circumference. A fireplace on one side sends the products of combustion directly upon the mineral. This stove is used for phosphate of lime, be- sides being employed in the . manufacture of patent fuel. Ruelle's Stove. Ruelle's re- volving drier (Fig. 678), on the other hand, recalls the Hockin and Oxland calciner. It is made of two long truncated cones of boiler-plate, one inside the other ; the inner one is destined for the drying proper, and the outer one allows the very hot mineral to cool down a little before it is discharged and sent to be ground. The outer shell runs upon fric- tion rollers, and both it and the DRESSING. 597 inner case have internal projecting spiral blades, which lift the mineral a little and cause it to travel along. At one end there is a fireplace ; at the other a charging hopper and a dust -chamber. The mineral fed by the hopper into the inner cone is gradually brought along by the spiral blades towards the fire-end, whilst it is being exposed to the hot gases of the fire, as well as to a current of hot air blown in by a fan, and heated by its passage through pipes at the side of the fireplace. On reaching the fire-end of the inner cone, the mineral falls through one of four holes into the outer shell, and is now conveyed back by spiral blades to the other end, where it drops into the pit of an elevator, which lifts it high enough for the hopper of the mills. Any dust carried off by the draught is deposited in a chamber built for that purpose. This drier does good work at phosphate mills. Rowoldt's Stove. This stove, which is specially designed for brown coal, is made up of a number of small lattice-like shelves down which the mineral gradually drops, while surrounded by air warmed to 75 C. (167^.) by its passage through small pipes heated by steam. Steam Stove. The steam stove, also designed for brown coal, is somewhat like the ordinary " Tellerofen." A number of circular drying plates are superposed one above the other in a cylindrical casing, and are heated by steam passing under them. Schulzs Stove. Schulz's steam stove is a large revolving iron cylinder like a tubular boiler, 19 feet to 20 feet long, and 7 to 8 feet in diameter, traversed by 180 or 200 small pipes 4 inches in diameter and a large central one. The cylinder is inclined to the horizon at an angle of 5 to 6. The exhaust steam from an engine is passed into the large central tube and finds its way through holes into the space outside it, heating the small tubes and their contents. The mineral is carefully fed from a hopper into the small tubes at the upper end, so as to prevent any choking, for otherwise the free passage of the air would be impeded, and the drying would be very imperfect. Jacobi's Stove. In the Jacobi stove the mineral falls down over a series of pentagonal cast-iron pipes heated by the passage of steam, instead of the plain lattice-like shelves of the Rowoldt apparatus, in addition to being exposed to an atmosphere of hot air. Many of the brown-coal driers are specially designed so that the products of combustion of the fire do not come into contact with the mineral, for fear the charge might be ignited accidentally. This difficulty does not crop up with many of the other minerals which have to be dried, though it is important with some that the degree of heat to which they are exposed should not be too great. (4) LIQUEFACTION AND DISTILLATION. The miner resorts to melting as a purifying or preparatory process in 598 ORE AND STONE-MINING. treating amber, antimony ore, asphalt, ozokerite, and sulphur; and in the very exceptional case of carbonic acid, a gas is com- pressed to the liquid state. Small lumps of amber, after having had the dark outer rind dissolved away, are melted together before being sold to the varnish merchants.* The liquation of antimony ore is usually regarded as a metal- lurgical process ; but if a mere melting is carried on at the mine in order to rid an ore of earthy matters, there is no more reason for refusing this operation a place among " dressing " processes, than there would be for excluding the similar purification of asphalt, ozokerite, or sulphur. This is an instance of the difficulty of defining the boundaries between the province of the miner and that of the smelter. The domain of the former is already so large that it does not require to be extended unnecessarily, and as the liquation of antimony ore is fully described in many metallurgical text-books the process may be dismissed here in a very few words. It is based upon the easy fusibility of stibnite. The impure ore coming from the mine is subjected to the action of heat in pots or tubes ; the stibnite melts, trickles away from the earthy matters with which it is mixed, runs into moulds and is allowed to cool gradually, furnishing the crude antimony of comm'erce. Trinidad pitch is purified or refined in the island by being melted in iron pans ; much of the intermingled earthy matter sinks, and the supernatant comparatively pure product is ladled out into moulds. The asphalt rock of Seyssel t is prepared for the market by melting it up with Trinidad pitch, or pitch obtained from bitu- minous sandstone, in the proportion of i of pitch to 14 of the finely crushed rock. When the mixture has become pasty, it is cast into blocks weighing about J cwt. each. These are now ready for sale for making pavements. The sponge-like masses of gold obtained by the distillation of amalgam are melted in crucibles and cast into ingots for The comparatively clean pieces of ozokerite, which have been picked out, below and above ground, and scraped clean, are more fully purified by melting; the heavy refuse sinks to the bottom, whilst the pure wax is decanted off and poured into cylindrical moulds. By far the greater portion of the native sulphur of Sicily is extracted from the limestone, or other rock by which it is accom- panied, by a simple process of liquation in kilns ; the necessary heat is produced by the combustion of part of the sulphur in the rock, it being cheaper in Sicily to do this than to import * B. u. li. Z., 1887, p. 24. f Malo, UAsphalte, Paris, 1888, p. 52. DRESSING. 599 fuel. The " calcarone," * or large kiln (Figs. 679 and 680), as distinguished from the " calcarella " or small one, is a circular pit surrounded by a wall, having a sloping bed leading to a rectangular aperture in front. The bed is covered with a layer of burnt refuse (ginese) from a previous operation, which is stamped down hard. The charging proper then begins, the large lumps are placed on the bottom, and various small vertical chimneys are left as passages for the air; when the " calcarone " is full up to the level b e, the mineral is heaped up so as to form a conical pile b c d e, which is covered over with a FIG. 679. PLAN layer of fine " ginese." The thickness of the outer covering of refuse varies according to the season. The total charge of a large "calcarone" may be as much as 700 tons. The aperture / in front is closed with a thin wall, built with plaster of Paris, and the charge is lit at the little chimneys. The heat produced by the combustion of part of the sulphur liquefies the remainder, which gradually runs down the bed to the front wall, and is either tapped from time to time or is allowed to escape continuously into moulds. Some of the large " calcaroni " take three months before they are burnt out completely. It is reckoned that one-third or even two-fifths of the sulphur * Parodi, SuWestrazione dello solfo in Sicilia, Florence, 1873, p. 49. The word " calcherone " is also used. 6oo OEE AND STONE-MINING. in the rock are consumed in liquefying the part that is obtained. This immense loss of such a valuable material has very naturally caused inventors to turn their attention to cheaper methods of extraction; but even as late as the year 1889, nearly seven-eighths of the total quantity of sulphur obtained in Sicily were extracted by the " calcarone " process. A little was got by a steam extractor and about 10 per cent, of the total pro- duction by Gill's regenerative furnace ; * the former is an iron vessel into which steam is conducted after it has been filled with mineral ; the sulphur melts under the action of heat and runs out at the bottom. Rich sulphur rock is sometimes subjected to distillation in iron retorts in order to extract the valuable element with less loss than that of the kilns, and the process is also employed in expelling mercury from amalgam. In order to produce a commercial article suitable for despatch to a distance, the natural carbonic acid of Germany is compressed into the liquid state. The gas coming from the bore-hole is led to a double pump. The first pump compresses the gas to a certain extent, and forces it through a worm in a cooling tank ; a second pump then takes up the process, and compressing the gas still further sends it through a second cooling worm into strong bottles, made of wrought-iron or steel, in which the actual lique- faction takes place at a pressure of 31 atmospheres. The bottles are of four sizes, for holding 4, 8, 10, or 20 kilos, of liquid acid. An 8-kilo. bottle weighs 37 kilos, when empty, or 45 when full ; the dead weight which has to be transported is therefore very great. (5) MAGNETIC ATTRACTION. Magnetism is applied in dressing either for treating poor iron ores, in order to produce a concentrate richer in metal and freer from noxious elements than the crude material, or for extracting magnetic particles from ores of bismuth, copper, gold, lead, or zinc, in which iron minerals play the part of troublesome refuse. The machines for treating ores magnetically may be classified as follows : Kind of Machine. Name of Inventor or Machine. Mode of Working. ( a. Chase .. Wet or dry. Endless belt b. Conkling .. Wet. c. Edison .. Dry. d. Hoffman e. Kessler \ /. Lovett-Finney . Wet. (g. Ball-Norton ("Monarch") . D -y. h. Buchanan i. Friederichssegen j- King k. Wenstrom Deflection ... /. Edison * Rivista del servizio minerario nel 1889, Florence, 1890, p. 83. DRESSING. 601 Endless Belts. (a) The Chase separator* (Fig. 681) has two endless belts with magnets underneath. A, B are two revolving iron rollers 4 inches in diameter and 3 feet long, converted into magnets by electric currents, and the space between them is occupied by a stationary electro-magnet ; C is a driving pulley, and D a tightening pulley. A cotton belt is made to travel round these four pulleys in the direction shown by the arrow. F is another magnetic roller, and G a driving pulley for the second belt, travelling as shown. The ore is fed on to the belt at the point E, and on arriving at A the non-magnetic waste is thrown off by centrifugal force, whilst the magnetic particles are attracted and held against the belt. All the time they are passing from A to B they are subject to the in- fluence of the electro-magnet, and owing to its construction they come under the influence of a succession of poles alternating in polarity. This causes the particles to turn over constantly and so free themselves from the non-magnetic or slightly magnetic FIG. 68 1. FIG. 682. grains, which fall into the compartment immediately below the belt, destined for the middlings. The thoroughly magnetic par- ticles travel with the belt to B, and as it moves up and the influence of B becomes less sensible, they are attracted by the third magnetic roller F, and at last leaping across the small inter- vening space, they are carried up the belt to G, where they drop off into the box containing the " heads." In making the little jump from B to F they still further free themselves from incom- pletely magnetic middlings. (6) The Conkling machine (Fig. 682) is an inclined endless belt travelling upon a roller at each end, with stationary electro- magnets E E under the upper half. The ore is fed on from a hopper, and is subjected to the action of a stream of water; this washes down the non-magnetic particles, whilst the magnetite adhering to the belt is carried over the top end. The Conkling machine may therefore be looked upon as a Brunton separator * Sahlin, " Magnetic Separation of Iron Ore," Eng. Min. Jour., vol. liii., 1892, p. 663. This article gives recent information on the subject of magnetic separation, and has furnished not only the account of the Chase machine, but also many of the details concerning some of the others. See also Trans. Amer. List. M.E., vol. xvii., 1890, p. 728. 602 ORE AND STONE-MINING. in which the rich grains are held against the belt by magnetic attraction, and thus enabled to resist the force of the stream of water. (c) Edison's second separator, which is used for the final treatment of re-crushed concentrates, furnished by the deflection machine (p. 606), is an endless belt placed vertically, with electro- magnets behind one side; they attract the fine particles of magnetite and cause them to adhere sufficiently to be carried upwards, whilst the non-magnetic grains drop. The electro-magnets are arranged so that the particles travel over magnets alternating in opposite polarity ; this causes, as in the Chase machine, a succession of tumbles or somersaults, which set free the non-magnetic particles and allow them to fall. The magnetite is carried up over the top roller by buckets attached to one side of the belt. (d) The Hoffman separator * (Fig. 683) is an endless belt arranged horizontally upon the two FIG. 683. drums A and B, provided with two sets of magnets. The I magnets C and also those inside the drum B have their poles arranged alternately. "W 11611 the ore is fed on to the belt from the hopper, it travels along over the magnets 0, and is subject to magnetic attrac- tion varying in amount, ac- cording to the distance from the pole, and also in polarity. This action tends to make the magnetic particles group themselves into a layer resting imme- diately upon the belt, whilst the non-magnetic particles lie upon the top. On arriving at B these latter are easily thrown off by centrifugal force, and fall into the compartment E, whilst the magnetic grains still cling to the belt. Those which are in- completely magnetic drop at F ; a better product is collected at G, and a clean concentrate at H. . The partitions, which separate the waste and divide the orey shower into classes of varying rich- ness, can be set so as to obtain any kind of classification which is most suitable to the ore under treatment. A blast of air is drawn along the face of the belt in the opposite direction to that of its travel, and helps to set free any non- magnetic grains caught up between the others. (e) Kessler,f of Oberlahnstein, is the inventor of a machine acting in a totally different manner (Fig. 684). It is a broad, endless belt or chain, armed with a number of iron points, travel- ling over the two rollers A and B ; the former is an electro- * " The Hoffman Magnetic Separator," Eng. Min. Jour., vol. lii., 1891, p. 680, t B. u. h. Z., 1891, p. 382. DKESSING. 603 magnet, the latter is made of wood. The stuff* falls from the hopper F into the conveyor C, which feeds it across the whole width of the cylinder A, and then drops into the curved gutter G, where the iron points are drawn through it as the belt revolves. The points, while under the influence of the electro-magnet A, pick up the magnetic particles, and let them drop into the compartment E on losing their power, while the non-magnetic particles fall at D. The partition between can be placed FIG. 684. FIG. 685. FIG. 686. in any suitable position. This machine has been used in Spain for separating iron ore from calamine, after the former has been made magnetic by a reducing calcination. (/) Lovett-Finney machine (Fig. 685 ) in some respects resembles the Conkling separator. It is a wet machine, consisting of an end- less canvas belt travelling upon two drums, A and B, one of which, A, has its outer surface made of bars of iron ; these become magnets of alternate polarity, as they are connected alternately with the iron discs forming the ends of the drum, which form the poles of an electro-magnet. The ore is fed against the belt about half-way up the magnetic drum A, and as the belt revolves with the drum, the magnetic particles are carried up, whilst the non-adherent waste is washed off by a stream of water. The concentrate is conveyed over the pulley B into a tank, and drops off, as it is no longer subject to the attractive force. (g) Rolls. In the Ball-Norton machine (Fig. 686) the magnetic particles are drawn against re- volving drums made of paper pulp, instead of being attracted to the surface of a canvas belt. There are two drums, A and B,revolvinginthesame direction, in each of which are arranged electro-magnets capable of holding magnetic particles against a certain portion of the under surface. As usual, the magnets are alternate in polarity. The ore is fed from a hopper C against the roll A, the tails drop at once into D, and the adherent magnetite travels along with the roll till it begins to leave the 604 ORE AND STONE-MINING. FIG. 687. magnetic field; the centrifugal force now overpowers the magnetic attraction, throwing the grains against the roll B. Those which are completely magnetic attach themselves to B, while ore mixed with waste falls into the compartment E ; lastly, the clean magnetite, on escaping from the influence of the magnets, yields once more to the centrifugal force and is deposited at F. A strong current of air is being constantly drawn through the machine in the opposite direction to the travel of the ore and assists in the cleaning. (h) The Buchanan separator* (Fig. 687) is 'made of two cast- iron rolls, revolving in opposite directions, supported on the ends of an electro-magnet ; the two rolls thus become the poles of a huge horse-shoe magnet, and the magnetism is most strongly developed where they most closely approach each other. As the ore drops down between the rolls, the mag- netic particles fly to them, and are carried along until they fall off at the JS sides, when the centrifugal force over- powers the now diminishing magnetic attraction. The poor non-magnetic par- ticles fall vertically. (i) Zinc blende found mixed with chalybite at Friederichssegen is roasted, so as to convert the latter mineral into magnetite, and then treated in the machine shown in Figures 688 and 689. It is composed of a brass cylinder A, with a number of little ridges S, parallel to the axis, and four sets of stationary electro-magnets B. T is the ore-hopper which supplies the feeder D : this is a sheet-iron tray, which is made to oscillate by cams upon a little shaft driven by the pulley Q. P is the main belt pulley upon H, the shaft of the brass drum, and R is a pulley which drives Q by a belt.f A regular stream of fine ore is fed against the brass cylinder by the feeder D, and the grains of blende at once fall into the com- partment Z ; the magnetic oxide of iron is held against the cylinder by the attraction of the electro-magnets, and is carried over by the little longitudinal ridges until it falls into the com- partment F. (j) King's I magnetic dressing machine works by the aid of permanent magnets fixed upon a revolving drum. Like other inventors he arranges his magnets so that their poles alternate, * Eng. Min. Jour., vol. xxxv., 1883, p. 133 ; vol. xlvii., 1889, p. 542. t Bellom, " Etat actuel de la preparation mecanique dans la Saxe, le Hartz et la Prusse Rhenane," Annales des Mines, ser. 8, vol. xx., 1891, p. 5 ; B. u. h. Z., 1892, p. 37. J Fifty-third Ann. Hep. B. Corn. Pol. Soc. Falmouth, 1885, P- 44- DRESSING. 605 and he thus makes the grains tumble over and shake off any loosely intermingled non-magnetic particles. (k) The Wenstrom * is a Swedish machine, which has been in use at Dannemora and other mines for some years (Fig. 690). It has a stationary electro-magnet A, and a revolving armature barrel B,. consisting of a number of soft iron bars separated by strips of FIG. 688. Scale'/ wood. The electro-magnet lies on one side of the centre of the barrel, so that the iron bars of the armature become magnetised only during part of the revolution. C is a tray feeding the ore on to the top of the barrel, D a shoot for the non-magnetic particles, and E the shoot for the concentrate. The magnetic grains adhere to the soft iron bars when these are close to the electro-magnet, and are carried past D as the barrel revolves; * E. M. /., vol. xlvi., 1888, p. 437. B. u. h. Z., 1891, p. 178. 606 ORE AND STONE-MINING. as the bars recede from the electro-magnet, they lose their power and let the iron ore drop into E. (1) Deflection. The simplest of all magnetic separators is one devised by Edison (Fig. 691).* It is based upon the fact that if a thin sheet of finely crushed ore drops past a powerful electro- magnet, the magnetic particles will be drawn towards it and deflected from their direct downward path, whereas the non- magnetic particles will fall vertically. If a partition is fixed in a suitable manner, the concentrate falls on one side and the waste on the other. Diagrammatically the machine may be shown thus : A A represent the electro-magnets, B a hopper delivering the fine ore through a long narrow slit; C is a thin partition. The waste falls vertically into the compartment D, and the iron ore into E. Magnetic separators are chiefly used for concentrating the FIG. 690. FIG. 691. magnetite from ores that are too poor to go to the furnace in the orude state ; and it has been proposed to make brown haematite magnetic by partial reduction at a low red-heat, but other uses have been mentioned in describing the various machines. For instance, by the ordinary washing processes it is impossible to separate chalybite with a density 3-7 to 3*9 from blende with a density of 3*9 to 4*2. The aid of magnetism is here invoked with success as already explained. The Namaqua Copper Company use King's magnetic separator for extracting the magnetite which is mixed with bornite and chalcopyrite, in order to obtain a product richer in copper. In a similar manner a magnetic concentrator of the Ball-Norton type has been employed in Queensland for treating a mixed con- centrate of magnetite and bismuth ore, obtained by a wet-dressing process. The percentage of bismuth is raised in this way from 10 or 12 to 20 per cent. On a small scale, the magnet is of service for extracting magnetic * E. M. J., vol. lix. 1889, p. 479, and vol. liii. 1892, p. 662. DRESSING. 607 particles when washing samples of tin ore on the vanning shovel, or gold in the batea. (6) FRIABILITY. Some minerals are more easily crumbled and reduced to powder than others, and if the difference in friability is great, it is possible after crushing to effect a separation by a mere process of sifting. An instance of this rare method of concentration occurs at the graphite mines near Passau, in Bavaria.* The softer kinds of mineral obtained from the mine are ground in mills, when the thin greasy elastic plates of graphite arrange themselves parallelly to the surface of the stones, and preserve their flat shape, while pieces of more brittle minerals are reduced to the state of fine powder. The ground product is sifted upon fine silk cloth, the dust poor in graphite passes through the fine holes, but the scales of graphite are left behind. As might be supposed, the separation is not very thorough. Biittengenbachf has separated blende from iron pyrites in a somewhat similar way, the former mineral being much more easily pulverised than the latter. He used a Vapart disintegrator to treat a mixture of blende and pyrites, in grains J inch to inch across, and by suitably regulating the speed, he was able to reduce the blende to the state of fine sand without affecting the pyrites to any appreciable extent. The blende extracted by sifting con- tained 50 to 55 per cent, of zinc, whilst the pyrites was almost free from this metal. The dressing of the plumbiferous sandstone of Mechernich is probably the most important instance of a difference in friability affecting the method of treatment. The little concretions of galena and quartz are comparatively hard and the sandstone very friable. The greater part of the stuff coming from the mine has crumbled to the state of loose sand before it reaches the works, so that the first comminution, which sets free the rich knots, is sufficiently effected by the mere handling, without the powerful crushing machinery usually required for the preliminary treatment of a lead ore. III. PROCESSES DEPENDING UPON CHEMICAL PROPERTIES. (i) SOLUTION, EVAPORATION, AND CRYSTALLI- SATION. Processes of this kind are employed by the miner in some of the few cases where the mineral is soluble in water ; aid is derived from certain other solvents, such as benzine and hydro- chloric acid. The principal minerals soluble in water are borax, nitrate of soda, potassium salts, and common salt. * Andree, "Der osterreichische und bayerische Graphitbergbau," B. u. h. Z., 1890, p. 270. t " Auf bereitung von Blende und Schwefelkies," B. u. h. Z., 1881, p. 294. 608 ORE AND STONE-MINING. The crude borax of California* is ground and thrown into a pan containing a boiling saline solution, frequently the mother- liquor from the second crystallisation. The salts dissolve and the sand sinks to the bottom. The hot solution is allowed to stand so as to clarify, and is then run off into pans and left to cool for five to nine days, during which time the borax crystallises out. The crystals obtained in this way are somewhat impure. They are refined by being dissolved and allowed to crystallise a .second time. Nitrate of soda is treated on a larger scale. f The caliche, crushed into lumps about 2 inches across, is tipped into large rectangular boiling tanks full of water, which are heated by a spiral 3 -inch steel pipe with steam at a pressure of 60 Ibs. to the square inch. The boiling is carried on by Shanks' lixiviating system, which causes a continual circulation of the lighter liquid to the other boiling tanks by following the denser and heavier solution. As soon as the solution is concentrated to no by Twaddell's hydrometer, it is allowed to settle for a short time, and is then drawn off to the crystallising tanks. The refuse in the boiling tanks is again treated with water in order to extract a little nitrate which it still contains. The crystals are shovelled out on to drying floors and put up in sacks for export. The mother-liquor, which contains a little sodium iodate, is added to the water used for dissolving a fresh stock of " caliche," and by repetitions of the process it becomes rich enough for the extraction of the iodine ; this is precipitated by sodium bisulphite, washed and pressed into cakes. The crude iodine so obtained is purified by sublimation. The principal potassium salt of Stassf urt is carnallite, a hydrated double chloride of potassium and magnesium. Some of it is treated on the spot in order to produce commercial chloride of potassium. The crude mineral, after being coarsely ground, is treated with hot water, and the strength of the solution is so arranged that only the chlorides of potassium and magnesium are dissolved out. The residues are treated with cold water which dissolves out some sodium chloride and leaves behind kieserite (hydrated magnesium sulphate). This is passed through a fine sieve, moulded into blocks, and sold. The solution of the chlorides of potassium and magnesium is allowed to settle and cool, and three products are obtained from it : (a) crystals of potassium chloride ; (b) mother-liquor ; (c) slimes. The crystals (a) still contain a little sodium chloride. They are lowered into water in iron vessels and much of the sodium chloride * C. Napier Hake, "An Account of a Borax Lake in California," Jour. Soc. Cliem. 2nd., vol. viii., 1889, p. 854. t Harvey, " Machinery for the Manufacture of Nitrate of Soda at the Kamirez Factory, Northern Chili," Proc. Inst. C. E., vol. Ixxxii., 1884-85, P- 337- DRESSING. 609 is dissolved out ; they now contain 80 per cent, of potassium chloride, and after being freed from moisture in Thelen's drier, they are packed in bags and sold. The mother-liquor (6) is heated and gives crystals of artificial carnallite, which are treated again in the same way as the native mineral. On evaporation the final mother-liquor yields hydrated magnesium chloride. The slimes (c) are put into a filter press, and the solid cakes so obtained are calcined and sold as manure after being ground. They owe their fertilising value to some potassium chloride which they still contain. The evaporation of brine may be carried out naturally or artificially. In Southern Europe, and in other countries where the sun has sufficient power, sea-water led into shallow ponds gradually becomes concentrated enough to deposit salt. In Germany, weak brine is strengthened by allowing it to trickle down through brush-wood contained in huge frameworks of timber. A great surface is thus exposed to the atmosphere with much evaporative effect if the weather is dry. In this country common salt is mostly obtained from brine pumped up out of bore-holes or out of inundated salt mines. After being allowed to settle, the brine is evaporated in large sheet-iron pans heated by the flame of a coal fire passing under- neath along flues. Some of the pans in the Middlesbrough district are 70 feet long and 24 feet wide, with a depth of 20 inches at the fire-end, and gradually lessening to 16 inches at the other. In Cheshire, even larger pans may be seen, some, in fact, as much as TOO feet long by 45 feet wide. The heat of the fire gradually drives off the water, and crusts of salt form on the surface ; they fall to the bottom and are shovelled out ; after being allowed to drain, the salt is ready for despatch to the alkali works. At Bex, in Switzerland, where fuel is dear and water-power abundant, the brine is evaporated in a closed boiler, like a large egg-ended steam boiler, heated from below; the process of evaporation goes on continuously, brine being constantly pumped in and salt being drawn off as it is deposited. Benzine is employed in the exceptional case of ozokerite for dis- solving out remnants of the mineral left in some of the residues. Heavy spar stained by oxide of iron is " bleached " by sulphuric acid ; the mineral, after being crushed to the state of coarse powder, is put into lead-lined vats with dilute sulphuric acid, which is brought to the boiling-point by the injection of steam. The acid dissolves the oxide and leaves white barytes ready for grinding after it has been dried. Tin ore contaminated with copper ore may be freed from the latter metal by hydrochloric acid ; the so-called " burnt leavings," that is to say the tailings produced in washing the roasted concentrates of tin ore, originally enveloped or accompanied by 2 Q 6 jo ORE AND STONE-MINING. sulphides, are treated with hydrochloric acid ; the coppery solution is led into pits, where the metal is precipitated by iron. (2) ATMOSPHERIC WEATHERING. I must point out that though weathering often results from mere loss of water, it may in other cases be caused by the chemical decomposition of one of the minerals contained in the stuff under treatment. As already stated, the boundaries between the various dressing pro- cesses are not distinctly defined. The crumbling-up of the diamond-bearing rock under atmospheric agencies plays an important part in the extraction of the gems, and with no other mineral is a weathering action of this kind carried out on so large a scale or in such a systematic manner. The floors devoted to this process at De Beers* mine occupy some thousands of acres. They are merely fairly level ground from which the bush and grass have been removed, and which has been rolled to make it hard. The ground is laid out in rectangular sections, 600 yards long and 200 wide, and is enclosed by high wire fences. Main lines of rails on each side of the floors and subsidiary portable lines serve to bring the trucks of "blue," which is tipped and spread out so that a load, i.e., 16 cubic feet or 1600 Ibs., will occupy an area of 21 square feet. After being left for some time, the " blue " is broken up by means of picks into pieces not larger than 4 inches cube, and is again left to dry for a farther period, until most of the natural water has evaporated. The artificial " diamond field " is then watered, to aid the disintegration, and lastly harrowed and rolled ; in fact, the miner endeavours to bring about the pulverisation somewhat in the same way that the farmer prepares his land for tillage. The stuff is known at first as "coarse blue ground,", then as " broken blue ground," and finally, after the rolling, as " pulverised blue ground." The length of time required for this disintegration depends not only upon the atmospheric conditions that is to say, the season of the year and the amount of rain but also upon the mine from which the blue is obtained. The blue from Kimberley mine becomes sufficiently disintegrated in three months in summer, whilst the De Beers blue requires double that time. It is evident, therefore, that a very large stock of blue has to be kept on the floors, if the washing machines are to be supplied regularly. The diamond is not the only gem which may be released from its matrix by disintegration under atmospheric agencies. The garnetiferous gravel of Bohemia f was at one time allowed * De Beers Consolidated Mine?, Limited, Second Annual Report for the Year ended $ist March, 1890, p. 18. f Kaymond, Discussion upon Kunz's paper on " Bohemian Garnets," Irans. Amer. Inst. M. E. t vol. xxi., 1892, p. 249. DRESSING. 611 to weather for three months on the surface, in order to fit it for the subsequent washing process. Phosphate of lime occurring in the form of nodules in clay is treated in a like manner. The phosphate dug from open pits in the Lias in the department of the Haute-Saone * is left exposed to the air often all the winter ; a part of the earthy matter falls off, and the nodules have simply to be screened dry, in order to separate a large portion of the clay with which they were only originally mixed. Again, in the Yosges there is a phos- phatic bed of the same geological age, consisting of soft nodules forming only -^ or ^ of the bed of brown clay by which they are enveloped. The stuff is spread out on the fields and raked over occasionally. The clay crumbles off, and at the same time the nodules harden from losing their moisture ; they are then picked out by hand. Nodules of clay ironstone are freed from shale in a similar way ; and ores of iron more or less contaminated with iron or copper pyrites gradually have a portion of their sulphur washed out in the form of soluble sulphates, if exposed for a sufficient time to the action of air and rain. Fire-clay is found to be better suited for making bricks after weathering for some months, than when first raised from under- ground. (3) CALCINATION OB ROASTING. The object of calcination or roasting may be : a. To effect a change in the chemical composition of a valuable mineral, and so produce either an ordinary article of commerce or one that is more readily saleable than the raw material. b. To effect a change in the chemical composition of some of the substances accompanying a valuable mineral, and so get rid of them partially or render them more easily separable by other processes. The commonest example which can be cited is burning limestone ; the action of heat is made use of to drive off the carbonic acid and leave quicklime. Another instance is furnished by clay ironstone, or any ore in which the iron occurs mainly in the form of carbonate. Simple exposure to heat con- verts ferrous carbonate into magnetic oxide ; the former contains 48 per cent, of iron, the latter 7 2 per cent. ; consequently, if the ore has to be sent to a distance there is a saving in freight, besides which the ore is more acceptable to the ironmaster for his furnaces. Gypsum is calcined in order to expel the water chemically combined with it, and convert it into plaster of Paris. With the ores of arsenic, it is the valuable ingredient which is driven off. Mispickel and other arsenical ores are roasted at * titatistique del 'Industrie mintrale en France et en Algtrie en 1 886, Paris, 1888, p. 268 and p. 282. 612 ORE AND STONE-MINING. mines in order to produce arsenious acid, which is collected in special flues. Ores of copper are sometimes calcined at mines, with the object of extracting the arsenic before sale to the smelters, who would pay nothing for this latter metal and prefer its absence. Calcination is resorted to in the case of some iron ores in order to get rid of the sulphur, due to intermixed iron pyrites or pyrrho- tine, and so free the ore from an element which the smelter dislikes. Thus in Northamptonshire the undecomposed greenish lumps in the bed are picked out on account of the sulphur they contain, and put aside. When a sufficient quantity has accumulated, a heap is made with a little coal and fired ; the ore loses nearly all its sulphur in the burning and is thus fitted for the blast- furnace. Auriferous ores are roasted in some instances for the purpose of liberating the gold which is so enveloped in sulphides and sulpharsenides, such as iron pyrites and mispickel, as to be caught with difficulty by mercury. Partially concentrated tin ore (whits) is roasted in order to convert iron pyrites and mispickel into pulverulent oxides which can easily be separated by washing. Again, tin ore is occasionally associated with a considerable amount of wolfram, which approaches it so closely in density that separation by washing is impossible. The mixed concentrate obtained by the ordinary dressing processes, consisting of cassiterite mixed with wolfram, is roasted with carbonate or sulphate of soda; soluble tungstate of soda is produced, which is dissolved out by water, leaving behind the insoluble cassiterite fit for the smelter. Lastly, we may take the case of zinc ore. Blake * renders the separation of blende from marcasite commercially possible, by roasting the mixed minerals at a temperature sufficient to convert the latter into oxide, while the former remains unchanged. The difference in specific gravity is then sufficient to allow the ordi- nary washing processes to take effect. Smithsonite mixed with limonite f is roasted with coal in order to reduce the ferric oxide to the state of magnetic oxide, and thus render it separable by a magnetic process. It now remains to be seen how calcination is carried out. Minerals may be burnt in heaps, in kilns and in furnaces. Clay ironstone is usually burnt in heaps with the addition of a little coal ; but one variety, black band ironstone, contains a sufficient amount of carbonaceous matter to burn of itself. The spat hose ore underlying the limonite (" rubio ") at Bilbao is now being successfully calcined on a very large scale previous to shipment. According to Mr. Windsor Kichards,J the raw ore * " The Separation of Zinc Blende from Iron Pyrites. " Trans. Amer. Imt. M. H., vol. xxii., 1893-4 ; and (t) Payne in the Discussion. J "Pres. Address to I. and S. Inst.," Coll Guard., vol. lxv. } 1893, p. 955. DRESSING. 613 contains 43 per cent, of iron and 25 per cent, of carbonic acid, whilst the calcined ore gives 58 per cent, of iron and only 2 per cent, of moisture. One of the large kilns gets through 1500 tons of raw ore weekly. The commonest example of calcination in kilns is making lime. At large works the time-honoured semi -spheroidal kiln with intermittent action is often supplanted by the Hofmann kiln, in which the processes of charging, burning, arid discharging go on continuously. Some of the baking ovens used for converting gypsum into plaster of Paris, by the simple expulsion of the water of combi- nation, are cylindrical brick kilns so arranged that the flame nowhere comes in contact with the mineral. The fireplace is in the centre, and the hot gases are drawn down flues into an annular arched passage all round the bottom of the kiln, and then ascend through the charge by means of a number of cast-iron pipes. The kiln is covered by a brick dome over which comes a conical hood or chimney. In making Parian cement from gypsum a different oven is employed, in which a central coke fire sends out its hot gases directly on to the charge itself. The furnaces used by the miner are usually of the reverberatory type, in which the flame plays into the space containing the charge ; the bed may be stationary or revolving. The two most frequently employed in Cornwall and Devon, for roasting the ores of arsenic, copper and tin, are Brunton's calciner and Hockin and Oxland's calciner. The former (Fig. 692) * has a revolving circular bed about 10 feet in diameter, supported by a vertical shaft, which is made to revolve slowly by any convenient source of power, whilst the flames of two fireplaces at the sides play upon it and produce the requisite amount of heat. Depend- ing from, cast-iron frames fixed in the roof of the furnace, are three sets of knives or teeth, inclined in such a manner as to shift the ore gradually from the centre, where it is fed on, towards the circumference, where it is discharged. The action of heat in the presence of atmospheric oxygen converts the sulphur and arsenic into sulphurous and arsenious acids, which escape with the other hot gases, and are led into long condensing flues. These are brick or stone passages high enough for a man to stand upright, with partial partitions so arranged as to make the hot gases take a tortuous path. There are large openings on one side for drawing out the arsenical soot at intervals. During the actual calcination these doors or manholes are closed by sheets of iron carefully luted with clay. The Hockin and Oxland calciner is not unlike the Bruckner furnace used in the United States, as it is a revolving cylinder * Hendersofi. Op. cit. TTN1 614 OKE AND STONE-MINING. lined with fire-brick. Figures 693 and 694* show the construction of such a furnace. A is the cylinder lined with fire-brick, set at a slight inclination and supported on rollers. It is made to revolve at the rate of six to eight revolutions per hour ; B is a screw which FIG. 692. brings down a regular supply of ore from a hopper. The ore travels along very gradually in the direction of the arrow and finally drops into the chamber C. D is the fireplace opening into the lower end of the cylinder, and E is the beginning of the flues, * Ferguson, " On the Appliances used for Dressing Tin and Copper Ores in Cornwall," Proc. Inst. Mech. Eng., 1873, p. 128. DRESSING. 6'S in which the arsenious acid is condensed and through which the sulphurous acid passes on its way to the chimney. The longi- tudinal ribs of fire-brick, extending two-thirds of the length of the furnace from the lower end, serve to lift up the charge and let it fall, so as to expose new surfaces to the action of the air. One of these calciners used some years ago at Devon Great Consols mine was simply an old boiler tube, 30 feet long by 3 feet -6 inches in diameter, lined with 4^-inch fire-brick, so that the clear diameter inside was 2 feet 9 inches. Another was made of an old boiler 5 feet in diameter. The inclination was i in 24. FIG. 693. SCALE 20 FEET 7 METRES Some of the calamine at Monteponi, which has been concen- trated by the ordinary wet methods until it contains 20 per cent, of zinc, is still much mixed with oxide of iron and dolomite. Two per cent, of coal are added, and the ore is passed through the rotary furnace, 42 feet (13 m.) long, working continuously like the Hockin and Oxland calciner ; the iron is thus brought to the state of magnetic oxide. On leaving the furnace the ore is moistened with water, which causes the calcined dolomite to fall to powder. It is next treated on screens, and the various cate- gories produced are sent separately to a magnetic concentrator.* * Oest. Zeitschr.f. B. u. IF., vol. xxxvii., 1889, p. 36; and Eng. Min. Jour., vol.liv., 1892, p. 77. 616 ORE AND STONE-MINING. (4) CEMENTATION. The precipitation of copper by iron may fairly be regarded as coming within the province of the miner, when the solution flows naturally out of an adit level or is pumped up from underground, or when it is obtained artificially as a by-product in tin-dressing. On the other hand, the metallurgist may fairly claim such operations as those conducted on a huge scale at Rio Tinto, where the cupreous solution is mainly produced by leaching the ore which has been burnt in heaps, or a mixture of burnt ore and raw ore. However, as in other cases, the line of demarcation between the two do- mains is an arbitrary one, and on this account it is advisable that the mining student should be well grounded in metallurgy. The famous old Parys mine in Anglesey, now shorn of its glory owing to the low price of copper, affords the most important example of cementation carried on at a mine in this country. Coppery water is pumped out of the mine, and is led into brick-lined pits containing scrap-iron. The iron is raked over from time to time, and eventually the old pots, kettles, shovels, meat-tins, &c., pass into solution, while the copper is precipi- tated. As might be imagined, when one looks at the heterogeneous mixture of articles constituting the scrap-iron thrown into the pits, the precipitate is very impure and contains only some 20 to 30 per cent, of metallic copper. The iron used is not lost ; the ferruginous solution running away from the precipitating pits is led into large pools, and there exposed to the action of air and rain. The dissolved iron gradually passes to a higher state of oxidation, producing in- soluble ochre, and little by little a deposit of this substance forms upon the bottom of the big ponds. According to the strength of the irony solution supplied, the ponds are run dry and cleared out once in every two or three months. Wind and rain aid the process of oxidation. (5) AMALGAMATION. Two metals, gold and silver, are extracted from their ores by amalgamation, that is to say, by processes based upon their affinity for mercury ; and here we are once more on the borderland between mining and metallurgical practice. In the case of silver ores, the processes are often complex and require the precious metal to be brought into the state of chloride before amalgamation is possible ; besides which they are frequently carried on at works which do not belong to the mining company. I therefore consider that the miner would be encroaching upon the territory of his neighbour by interfering in this instance, whilst, on the other hand, with gold the process is generally simple, and the ore goes straight from the shaft or adit to crushing and amalgamating works owned by the same company as the mine. The amalgamation of gold takes place by mere contact, either when the particles touch the mercury as they slide or roll along. DRESSING. 617 in a current of water, or when they are in some way mechanically rubbed against it. An instance of the first kind of action has already been given in the description of hydraulic mining in Chapter VI., and another may be taken from the ordinary stamping mill of most gold mines in which auriferous quartz is being treated. The pulp discharged through the grates of the mortar-box is allowed to flow over an inclined table, covered with a sheet of copper which has been amalgamated. The surface of the copper plate is first very carefully scoured, then cleaned with a solution of cyanide of potassium, and finally rubbed with mercury arid a little sal- ammoniac. The bright silvery surface is then capable of picking up the little particles of gold in the pulp and retaining them in the form of a coating of amalgam, which is naturally thickest where the pulp first comes upon the table. When a sufficient thickness has accumulated, the amalgam is scraped off, washed, mixed with a little fresh quicksilver, washed with water, and finally squeezed through canvas or chamois leather. The hard amalgam so obtained is retorted. Various devices are in use for making the little particles of gold turn over from time to time and so expose fresh surfaces to the quicksilver, in order to increase the chances of such intimate contact as will ensure amalgamation. Sometimes steps are made in the tables, giving the thin stream of pulp a little drop, some- times the tables are shaken, whilst in the Hungarian mill the pulp flows over the surface of a bath of mercury, the surface of which is lightly skimmed by revolving iron knives. Amalgamation will not take place unless the two metals are bright and clean ; any slight film upon the mercury, such as is produced by grease or tarnish, prevents contact, and the little particle of gold rolls or slides down over the plate, just as it would do on a plain sheet of copper, and is liable to escape. The greatest care has therefore to be taken to keep the amalgamated plates clean, and from time to time any tarnish may be removed by brushing them with a solution of cyanide of potassium. Other means of keeping quicksilver bright are the addition of a little sodium amalgam, or the production of nascent hydrogen upon the surface of a mercury bath by the passage of a current of electricity. This is the principle of Molloy's amalgamator, and that invented by Chaster and Beck. It is evident from experiments, when the mercury covered with water is connected to the negative pole of a dynamo, and lead plates forming the anode are connected to the positive pole, that the disengagement of hydrogen does keep the bath constantly bright and lively, and fully entitles the metal to its familiar name " quicksilver." Under these circumstances it takes hold of the gold more readily, but the process does not appear to have gone beyond the experimental stage at present. 618 ORE AND STONE-MINING. Considering the ease with which amalgamation is impeded or prevented by a flimsy coating upon the mercury or upon the gold, it is not surprising that rubbing of some kind should have been tried in order to brighten the surfaces of the two metals and so secure perfect contact. It seems probable that when gold was worked by the Romans in the Alps, the precious metal was extracted by rubbing the ore to powder with water and mercury upon slabs of gneiss by stone mullers. {Subsequently, no doubt, the quern was pressed into the service of the gold-miner, and by adding a rude horizontal water-wheel to the quern, the hardy Piedmontese miners developed their molinello, or small mill, by means of which large quantities of gold have been obtained. Proceeding one step further, we have the arrastra, the most perfect form of which can probably be seen in Italy, and substituting iron and steel for stone we have the various pans. All these mills perform a double service ; they not only break up the ore and set free the minute particles of gold, but they at the same time scour the gold, make it bright and rub it against the quicksilver. Probably in many cases the gold makes a streak upon the bed, just as it would do if rubbed upon a jeweller's touchstone, and so gives a clean bright surface with which the mercury at once amalgamates. The mills may also be worked as concentrators, for if a stream of water is run through them while they are being driven slowly, the light particles are carried off, and the heavy metallic sulphides lie at the bottom in contact with the mercury, ready to give up the gold they contain as soon as they are crushed fine enough to liberate it. The heat developed by the friction of the muller is consider- able and may assist the process of amalgamation, and indeed it may explain how it is possible to extract 80 percent, of the gold from ores containing 10 to 20 per cent, of iron pyrites by simple amal- gamation in arrastras. The arrastra is a more suitable amalgamator for such ores than the copper plate, but it is a slow grinder and it causes a large loss in quicksilver when raw ore is treated by it. Various other mills are used for the same purpose. APPLICATION OF PROCESSES. Having now passed in review the various mechanical, physical, and chemical processes which are employed by the miner in preparing his minerals for sale, it remains to say a few words upon the manner in which they are applied in different cases. Space will not admit more than an outline, nor is it necessary in a general text-book to enter deeply into details. For the sake of convenience the various minerals will be taken in alphabetical order. Amber. The lumps are separated by washing from the enclos- ing sand, and are sorted according to colour and size. The small pieces are treated in a steam bath at a temperature of 150 with certain re-agents in order to remove the dark rind, and the clear DRESSING. 619 kernels which remain are melted up together and sold to the varnish merchants. Arsenic. Arsenious acid is obtained by roasting and sublima- tion. The crude arsenic resulting from the treatment of tin " whits" is usually of a dirty grey colour owing to the ad- mixture of solid carbonaceous particles deposited by the smoke ; it is spoken of as " arsenical soot," and is sold by the miner to works where it can be purified by being re-sublimed. At some mines, however, which yield large quantities of mis- pickel, the final purification is performed on the spot, and white sublimed arsenic and arsenical glass are prepared by re-sublima- tion, put into barrels and sent out into commerce. Asbestos. The dressing of the asbestos (chrysolite) of Canada is simply a process of cobbing i.e., the separation of the valuable mineral from the enclosing serpentine by well-directed blows of the hammer. Asphalt. The crude Trinidad pitch is purified or refined on the island by melting it in iron pans and allowing the earthy matter to fall to the bottom. In France the process is some- what different : the crude pitch is boiled with a heavy tar oil obtained from the distillation of shale, in the proportion of 9 of pitch to 4 of tar oil. The 30 per cent, of water in the pitch is driven off and a small amount of earthy matter is deposited, but the refined pitch, consisting of the two ingredients which were mixed, still contains a large percentage of clay. Bituminous sandstone * is made to yield up its pitch by melting with water. The sandstone is broken up into lumps about 3 inches across, thrown into cauldrons of boiling water, and stirred for an hour. The bitumen melts and rises to the top, whilst the sand falls to the bottom. The bitumen is skimmed off, though it is by no means free from sand, if the original sandstone was fine- grained. It is then re-melted and the sand allowed to sink; the liquid bitumen is drawn off and allowed to cool in moulds, but the sandy deposit at the bottom still contains a good deal of pitch which cannot profitably be separated. The treatment of the bituminous limestone of Seyssel has already been described in the general part of this chapter. Barytes. The principal processes in preparing barytes for the market are drying and grinding. The barytes coming from the mine is washed and picked, and pieces intermixed with rock are cleaned by cobbing. The lumps are dried upon a tiled floor heated by flues underneath, and are then crushed, either by rolls or an edge-runner, to a coarse powder, which is twice ground in mills like flour- mills. French burr stones are preferred. The second grinding yields a powder as fine as flour, which is put up into barrels ready for sale. * Malo, UAsplialte, Paris, 1888, p. 68. 6 2 o ORE AND STONE-MINING. Iron-stained barytes is " bleached " by acid, as already ex- plained. Borax. The earth obtained at the borax la.ke, California, is ground, and then dissolved in water brought to the boiling point in large iron vats by injecting steam. The contents are allowed to settle, and the clear solution, containing the carbonate, sulphate, chloride, and borate of sodium, is drawn off into pans and allowed to cool. The borax is the first to crystallise out, and the crystals are collected and sold, or are re-dissolved ; this second solution furnishes, on crystallising, the refined borax of com- merce.* Boric Acid. The solution of boric acid, obtained in Tus- cany by passing natural steam-puffs (soffioni) through water, is evaporated either by the heat of some of these soffioni, or artificially, until the gypsum and other impurities separate; the liquid is drawn off and the acid is allowed to crystallise out. Carbonic Acid. If not at once piped off to white lead or soda works, carbonic acid is compressed and sold in the liquid state. Clay. Common clays are used on the spot, and made into bricks, tiles, or drain-pipes. The potter's clay of Devonshire is sent away in cubical lumps just as they come from the pit, but the china clay is obtained by a true dressing process. The stream of water running down the side of the openwork, and carrying with it all the ingredients of the decomposed granite, is led into a pit where the coarse particles of quartz settle,t whilst the clayey water is conducted into long channels in which fine sand and mica are deposited gradually. Lastly, the milky stream reaches circular pits, 20 to 40 feet in diameter, and 6 to 20 feet deep, drops its kaolin, and passes off as almost clean water. The creamy deposit is dried in the manner already described (Fig. 676), and the china clay of commerce is the result. Fuller's earth is also a clay which has to be dressed before being sent into the market. The processes to which it is usually sub- jected are drying, sifting, and grinding. The clay coming from the pits is dried in kilns (Fig. 677) and sifted by hand to take out the fine, if the customer insists upon having nothing but lumps. The dry lumps are put up into sacks, and the small is sifted again. The very fine, below J inch, is thrown away, and the coarser part is ground to fine flour in an Askham mill, and so sold. In addition to this dry dressing, some of the clay is ground in an edge-runner, run into settling tanks, and dried much in the same way as china clay. * Napier Hake, " An Account of a Borax Lake in California," Jour. Soc. Chem. Jnd., vol. viii., 1889, p. 856; E. L. Fleming, "Borax," Chem. Neics, vol. Ixiii., 1891, p. 74. f Collins, Ihe Hensbqrrow Granite District, Truro, 1878, p. 18. DRESSING. 621 Copper Ore.* The ores of copper are so different that no general scheme of treatment suitable to all of them can be pre- scribed. Thus, for instance, the copper shale of Mansfeld is merely picked at the mine before going to the smelting works, which receive an ore containing only 2 to 3 per cent, of metal. At the Lake Superior mines concentration by water can be carried to such a pitch that the " barrel copper " leaving the dressing establishments often has more than 70 per cent, of metal. Hand-picking is generally an important part of the dressing when the ore consists largely of a mineral like chalcopyrite, because it is easily crushed to powder liable to be carried away by water in washing. At the Rio Tinto mines t the following are the principal varieties separated by picking : a. Rich ore with 5 cr 6 per cent, of copper, which is smelted on the spot. b. Lump ore with 2 to 3 per cent of copper, which is exported. c. Lump ore with 2 per cent, of copper, which is burnt in heaps on the spot. d. Fine ore, which is added to the burnt ore, so that its copper may be gradually rendered soluble. e. Quartzose ore, which is retained for the furnaces. When copper pyrites occurs coarsely intermixed with quartz and other earthy minerals, the dressing usually begins with hand-picking and crushing by rolls ; the coarser grains are jigged, and the finest particles are cleaned and rendered rich enough for sale, by buddies, frames, revolving tables, or endless belts. Intermediate products made up of ore and waste have to be re-crushed before a complete separation is possible. At the Lake Superior mines, where the mineral is native copper, the treatment is different. The rock from the mine is stamped by huge Ball or Leavitt stamps until it will pass through holes of T 3 F - inch, and the copper-bearing stream is delivered into upward current separators, which make five classes; the four coarsest sizes are treated on Collom jigs, and the fifth upon revolving tables. Diamonds. The dressing of the diamond-bearing rock of South Africa J may be divided into the following separate operations : a. Natural disintegration, under atmospheric agencies, aided by watering, rolling and harrowing. * Egleston, " Copper Dressing in Lake Superior," Metallurgical JReview, New York, vol. ii., 1878. Henderson, " On the Methods generally adopted in Cornwall in Dressing Tin and Copper Ores," Proc. Inst. C. E., vol. xvii., 1857-58, p. 106. Rathbone, " On Copper Mining in the Lake Superior District," Proc. Inst. Meek, fing., 1887, p. 86. t Collins, " On the Geology of the Rio Tinto Mines," Q. J. Geol. Soc. t vol. xli., 1883, p. 256. De Beers Consolidated Mines, Limited, Second Annual Report, for the Year ending %ist March 1890, p. 19. 622 ORE AND STONE-MINING. b. Screening in a revolving screen, with holes i inch by i inch, or i inch by T J, which take out coarse lumps ; these are returned to the depositing floors to undergo the weathering process a little longer. c. Washing the fine in rotary pans, which separate clean gravel from the fine sand and mud; the latter flow into another similar washer, where the process is repeated in case any diamonds should have escaped in the overflow from the first. d. Screening the clean gravel through a cylindrical sieve, with round holes varying from J inch to f inch in diameter, making in all five sizes. The largest grains discarded by the sieve are picked at once. e. Treatment in a " pulsator," which is simply a jig with con- tinuous feed and discharge like the Hartz jigs. The bed is formed of leaden bullets. A concentrate, containing the diamonds, passes through the bed, and refuse goes over the edge of the jig- f. Picking out the diamonds by hand, first by white men when the gravel is wet, and then by native convicts when it is dry. The operation of picking is repeated as often as enough diamonds are found to repay the cost of the labour. Flint and Chert. Flints are trimmed into square-faced lumps for building purposes, or are split and trimmed into gun-flints. Chert is trimmed by hammering into blocks for use in the potteries. Gold. The precious metal may be extracted from simple sand and gravel by mere washing, or by washing combined with amal- gamation. Hydraulic mining affords an example of the latter method. When the gold is enclosed in hard rock such as quartz, or occurs in a hard tightly cemented conglomerate, the auriferous stone has to be crushed in order to set the metal free. The crushing is most often effected by a stonebreaker, followed by stamps, and the pulp is run over amalgamated copper plates. Mercury is often added in the battery so as to catch the coarse gold at once. The amalgam scraped off the plates and taken out of the battery-box is cleaned and retorted, giving spongy gold, which is melted in crucibles and cast into bars. If the ore contains much pyrites or other heavy metallic sulphides, the stuff leaving the amalgamated plates is taken to a dressing machine of some kind, such as a Frue-vanner, which furnishes a concentrate consisting largely of metallic sulphides, more commonly known to miners by their older name of " sulphurets." These are sure to contain gold, and they are further treated in various ways : by direct amalgamation in pans, which means a still finer grinding, to liberate more of the fine particles of gold, by smelting, by chlorination, or by the cyanide process. Gold is also extracted by grinding up the ore in mills or arras- tras with water and a little mercury. Excellent results have DRESSING. 623 been obtained in Italy by this method, even with highly pyritic ores. It is very necessary that the miner should recollect that gold does not always exist in the same state in the ore, and that the value of the ore depends not only upon the amount of metal in it, but also upon the ease with which it is extracted. A mere assay gives information upon the first point only. It tells how much gold there is per ton, but it does not say whether the metal is in the native state, or whether it is combined with some other element which may render extraction by amalgamation quite impossible. Even when the gold is all native, the size of the particles varies considerably, and they may or may not be wrapped up in iron pyrites or other metallic sulphides. Con- sequently it is futile to suppose that all gold ores can be treated by one and the same method. Graphite. The graphite of Ceylon is first picked at the mine, and then despatched to Colombo to undergo the processes of cobbing, picking, and screening. Men and women, using a tool like a little axe, chip off the waste material from the lumps, and sift the small fragments upon slightly inclined screens made of sheet-iron. They also clean the lumps with brushes made of cocoa-nut husks. In this manner four different kinds of graphite are produced viz., " large lumps," pieces about as big as the fist or larger ; " ordinary lumps," about the size of walnuts ; " chips," about the size of grains of wheat ; and " dust," which includes everything smaller. The graphite is now ready to be barrelled for export. One mode of concentrating certain kinds of graphite has been mentioned as an instance of a method depending upon differences of friability ; but in addition to these dry processes, graphite is also dressed by the aid of water. In Moravia and Bohemia graphite is found in gneiss, and may be intermixed with lime- stone, quartz, iron pyrites, garnets and hornblende. Rock of this kind is pulverised by grinding in mills, or by stamping, and the pulp is made to flow into rectangular wooden boxes in which the coarser particles and part of the rock and pyrites are deposited. The graphite-bearing water passes on into a number of long rectangular wooden troughs (tyes, strips, or strakes, Cornwall), in which the graphite deposits itself gradually, whilst clean water flows out of the last trough. The first trough has the worst graphite, and the last the best quality of the mineral. The deposit is dug out, pressed in filter presses, and the resulting cakes are dried in stoves.* Gypsum. The preparation of gypsum for the market resolves * Andree, " Der osterreichische und bayerische Graphitbergbau," B. u. li. Z.< 1890, p. 269. Schauenstein, DenHuch des osterreicliischen Berg- und Hiittenwesens, Vienna, 1873, p. 116. 624 ORE A^D STONE-MINING. itself into picking, breaking, burning and grinding ; or where the gypsum is required for other purposes than cement making, the burning or baking is omitted. In Sussex the waggons coming from the mine are tipped on to a floor, the large lumps are broken up with a sledge hammer, and any pieces much mixed with worthless rock are picked out as useless. The remainder is sent to a stonebreaker, and the broken lumps go either to a baking oven to be made into plaster, to a burning oven if Parian cement is required, or to a grinding apparatus if the gypsum is sold to manure merchants. After burning or baking, the product is ground, first by toothed rolls and then under edge-runners. It is now taken up by an elevator, put through a tine revolving screen, and is drawn off into sacks. Iron. With a substance of small intrinsic value like iron ore, the methods of dressing must be inexpensive if they are to be commercially profitable ; and at the present time it may be said that most of the iron of commerce is obtained from ores which go direct to the smelter without any preparation beyond picking out refuse underground. A few instances of calcination have already been noted, and also the separation of fine ore by a sieve. Iron ore is sometimes washed in order to get rid of adherent clay, and at the mines of North Lancashire some of the haematite, mixed with clay and siliceous matter, is made fit for the blast furnace by crushing and jigging.* The same line of treatment is pursued in the dressing works of the Chateaugay Ore and Iron Company, at Lyon Mountain, N.Y. The mine produces magnetic iron ore, the richer parts of which are picked out, whilst the leaner parts, consisting of grains of magnetite disseminated through gneiss, go to the mills .for con- centration. This mixed ore is crushed by Blake breakers, and after screening is treated in Conkling jigs.f Haematite for fettling puddling furnaces is ground under edge- runners, and that which is used for making castings malleable is carefully screened. Special qualities are picked out for these purposes. In this country the supply of magnetic iron ore is insignificant, and consequently we cannot show examples of concentrating by the aid of magnetism, such as may be found in Sweden and the United States, where this method is occupying much attention, as may be inferred from the descriptions of magnetic separators just given. Lead.J A few mines produce lumps of galena so pure that * J. G. Lawn. t Euttmann, " Concentrating Magnetite with the Conkling Jig at Lyon Mountain, N.Y.," Trans. Amer. Inst. M.E., vol. xvi., 1888, p. 609 ; and E. M. J., vol xlvi., 1888, p. 870. J For details consult Bellom, " Etat actuel de la preparation mecanique DRESSING. 625 they merely require washing in order to be ready for sale to the smelter or the potter. Much of the lead ore from veins is dressed by crushing, sizing and jigging ; the particles under i mm., or at all events under \ mm., are treated by revolving tables, percussion tables, endless belts, or buddies. The crushing is done first by a stonebreaker and then by rolls. Blende is often associated with galena, but owing to the difference in their specific gravities, a separation can be made by the appliances just mentioned. Products obtained from the jigs consisting of mixed minerals have to be re-crushed, and then treated once more by machinery similar to that used for the original ore.* The soft lead -bearing sandstone of Mechernich f crumbles to pieces so easily, that by the time it reaches the dressing establish- ment, after having fallen down in the underground chambers and dropped through shoots into the waggons, most of it is in a fit state for the concentrating machinery. The works are specially designed for treating very large quantities of poor ore consisting almost entirely of galena and quartz sand ; their main feature is the use of the siphon separator (p. 578), by which a very large pro- portion of the stuff is at once concentrated into clean concretions (Knotten) containing about 22 per cent, of lead. This concentrate goes to another establishment, where it is stamped and passed through siphon separators, jigs, revolving tables and round buddies, in order to separate lead ore fib for the furnaces. Manganese. The only preparation of the Welsh manganese ore is separating the fine ore under J inch, by sifting in the mine, and picking out of any pieces of waste or very poor rock. The Devonshire ore, which consisted largely of psilomelane, was washed and picked, and the " smalls " were jigged. Some of the large ore was crushed ; the coarse part was jigged, and the fine cleaned in buddies. Mica. | The rough blocks obtained from the mine are cleaved by means of steel wedges into sheets | inch or less in thickness, and these are cut by the " scriber " into the shapes required for stove windows. There are a very large number of patterns, ranging in size from ixitoSxio inches. The cutting is done des minerals dans la Saxe, le Hartz et la Prusse Rhenane,'' Annales des Mines, ser. 8, vol. xx., 1891, p. 5. Munroe, " The New Dressing Works of St. Joseph Lead Company, at Bonne Terre, Missouri," Trans. Amer. Inst. M.E., vol. xvii., 1888, p. 659. * Sopwith, " The Dressing of Lead Ores," Proc. Inst. C. E., vol. xxx., 1869-70, p. 1 06. f Der Bergbau und Hiitteribetrieb des Jlechernicher Bergwerks-Actien- Vereins, Cologne, 1886, p. 10, and Tables II. and III. ; and B. u. h. Z., 1886, p. 476. Phillips, " Mica Mining in North Carolina," Eng, Min. Jour.,vc]. xlvi., 1888, p. 418. 2 R 626 ORE AND STONE-MINING. with a knife along the edges of a template made of iron or tin- plate. The blocks of crude mica yield from ^ to J of cut mica fit for the market. The refuse scraps are now ground up into fine powder and used in the manufacture of wall-paper, tinsel, hair-powder, and lubricants.* Nitrate of Soda. The process of extracting the commercial nitrate from the crude caliche has already been sufficiently described, in speaking of the preparation of minerals by solution and crystallisation. Ochre. Native ochre is ground under an edge-runner with water, and the product is run into settling pits. Coarse sand settles first, and further away the sediment consists of fine ochre, which is dug out and dried. The ochre deposited by the water coming from cementation pits has simply to be dug up and dried. The native umber of Devonshire is stamped and ground under edge-runners ; the umber suspended in water is pumped up and allowed to settle in tanks until it can be dug out. It is then dried in the same way as china clay.t Ozokerite. Some of the mineral is brought up in the form of fairly clean lumps which have been picked out underground and put into sacks. These, together with similar pieces picked out above ground and scraped free from dirt, are melted in large semi-spherical open cast-iron pans and boiled. When allowed to settle, the earthy matter falls to the bottom and clean ozokerite floats on the top. This is ladled out into cylindrical moulds, and on cooling furnishes the large loaves of commercial ozokerite. Water is added to the earthy residues at the bottom of the pans, and the whole brought to the boiling-point. Ozokerite rises to the top and is skimmed off, whilst the residues remaining at the bottom, which still contain some 10 per cent, of wax, are sold to dealers who extract it by means of benzine. The small stuff coming from the mine which will go through a grating with bars 2 inches apart is put into a tub of water ; the wax rises, is skimmed off with a sieve and purified by melting, and the earthy residues are sold, or are stocked until the miner puts up plant for extraction by benzine. Phosphate of Lime. The varieties of this mineral are so numerous, from the hard compact apatite of Canada to the pulveru- lent mineral of the Somme district, that the modes of treatment must necessarily be extremely different ; sometimes also the mineral is sold finely ground and put up in sacks ready for the farmer, in other cases the miner satisfies himself with removing all waste, and leaves to other persons such processes as milling or manu- facture into superphosphate. * Nitze, " Ground Mica Industry in North Carolina," Eng. Min. Jour., vol. liv., 1892, p. 292. t Frecheville, " The Umber Deposits at Ashburton," Ivans. JR. Geol. Soc., Cornwall,'' vol. ix. p. 219. DRESSING. 627 As a rule, the treatment may be summed up as drying and grinding, often preceded by a preliminary washing. For instance, the phosphate of the Somme is dried first upon iron-plated floors, and then in a Ruelle stove or a revolving calciner. This prepares it for grinding. The first grinding is done between two vertical stones, and all that is fine enough is drawn out by an exhaust fan j the portion which is too coarse to be sucked up by the current of air passes into a mill with horizontal stones and is re- ground. After being put into sacks it is ready for the manure merchant, or for the farmer if he applies it to his land direct. The nodules of the South Carolina phosphate are freed from the sand and clay by a mechanical washer, in the form of a helix revolving i n a trough. The material is fed in at the lower end and is gradually screwed up to the other against a strong stream of water. The water carries away the waste, and clean lumps are delivered at the other end. The washed nodules are dried in. kilns and are then ready for export.* Potassium Salts. The two principal potassium salts obtained by mining are carnallite and kainite. Simple grinding is often the only preparation before sale, but in some cases, as explained on page 608, the carnallite undergoes a complicated treatment by solution and crystallisation, for the purpose of extracting chloride of potassium and utilising the by-products obtained in these processes. Quicksilver. The great intrinsic value of quicksilver ore enables hand-picking to be carried further than would be compatible with a mineral of little worth. At Idriaf the loss of mercury was so great under the old system of wet dressing, in spite of the high specific gravity of cinnabar, that this, method was given up some fifty years ago. Nowadays, the preparation for the smelting is done solely by crushing, sizing, and hand-picking. The stuff broken in the mine is separated under- ground into waste, poor ore and rich ore. The first is left in the workings, and the two kinds of ore are tipped separately on to a grating with holes of 4 inches (100 mm.) across. The coarse lumps are crushed by Blake's stonebreakers, and the broken ore which is too big to pass through holes of inch (20 mm.) is hand-picked ; the portions so separated are made ready for the smelting works by further crushing. When poor ore is being treated, waste can be picked out and thrown away at once. The stuff passing through the 20 mm. mesh is crushed by rolls and sent to the smelting works. The "smalls" which passed the 100 mm. grating are screened on a 2-inch (50 mm.) sieve; the coarse goes to the stonebreaker and the fine to screens of different sizes. All that is over inch * Benedict, " Mining, Washing, and Calcining South Carolina Phosphate,'" Eng. Min. Jour., vol. liii., 1892, p. 349. t Das k. k. Quecksilberwerk zu Idria in Krain, Vienna, 1881, p. 19. 628 ORE AND STONE-MINING. (20 mm.) is picked, and some waste taken out ; what is under this size is passed through the rolls and so made fit for the furnaces. Salt. The mode of making a saleable product from brine has already been described ; but it must not be forgotten that brine itself is sold as such to works which make alkali by the Solvay process. Some rock-salt is prepared for the market by crushing. At one of the Cheshire mines there are three pairs of crushing rolls one above the other, the first pair coarsely fluted, the second pair fluted, but less coarsely, and the third or lowest pair smooth. The rolls are from 18 inches to 2 feet in diameter and 2j feet long. The rolls of another crusher are made up of toothed rings threaded upon shafts, and so arranged that the teeth of one roll fit between two of the rings of the opposite roll. Some of the salt is also ground by a disintegrator. Silver. The ores of silver may be divided into two classes : silver ores proper and argentiferous lead and copper ores. Many of the silver minerals are very friable, and are liable to be carried off with the refuse, if subjected to the ordinary wet dress- ing processes ; the preparation of such ores at the mine is gene- rally limited to crushing, picking, and cobbing. The miner then relegates to others the task of extracting the precious metal by methods based upon its affinity for quicksilver or molten lead, or upon the leaching properties of hyposulphite of soda. Argentiferous lead and copper ores are concentrated by the processes in vogue for the baser metals ; but if the proportion of silver is large, a greater amount of labour may be expended upon hand-picking and cobbing than would be permissible with ores of lead and copper alone. Slate. Two articles of commerce are made at the quarries : roofing slates and thick slabs used for cisterns, billiard-tables, and tombstones. The slate arrives at the surface in the form of large blocks, often weighing two tons or more. These are divided by splitting into slabs about 3 inches thick, which go to the sawing tables. The circular saws cut up the slabs into pieces suitable for the operation of fine splitting ; by the careful and dexterous use of his wedge and mallet, the quarryman is able to split the slab into thin sheets, which at Festiniog often do not exceed ^ inch in thickness. These have to be trimmed, generally into a rectangular form. Though this operation can be and often is performed by hand, it is more common to use some kind of knife worked by machinery (Fig. 639). The slates are then sorted by hand according to their quality. The slabs are first split out of blocks, and are finished by being sawn into shape and planed smooth by machinery. Stone. It is impossible in a general treatise to enter into any details concerning the preparation of stone at mines and open- DRESSING. 629 works. Some stone is shaped by hammering, into paving blocks or " setts " ; much is crushed by stonebreakers and sold as road- metal after removal of the fine by screening ; freestone is sawn so as to suit the builder ; flags are obtained by splitting micaceous sandstone along the planes of bedding and trimming the edges, and, lastly, gunflints are made from the well-known nodules by the dexterous chipping of the " knapper." Sulphur. This element is obtained from the rock, which contains it in the native state, by simple liquation in a kiln of some kind, intermittent (calcarone) (Fig. 677) or continuous (Gill's furnace), by liquation in steam-heated cylinders, or by distillation in iron retorts ; this last process, which was at one time practised with rich ore in the Romagna. is now almost entirely abandoned. Tin.* The tin ore obtained from veins usually contains the cassiterite so finely disseminated through the stone, that a considerable amount of comminution is required before the valu- able grains are thoroughly liberated, and so rendered capable of being separated by washing. In Cornwall the first process is a preliminary crushing by a Blake's stonebreaker, followed by stamping until the pulp will pass through a fine grate. The pulp is led into round buddies in order to produce a first concentrate, containing not only all the cassiterite, but also the iron pyrites, mispickel and other metallic sulphides with which it is so often associated. By repeating the operation of huddling, a concentrate is obtained, which is subjected to " tossing and packing ; ' in order finally to prepare it for the furnace. This first concentrate, known in Cornwall by the name of whits, is dried upon the top of the calciner and then roasted in the manner already described. After roasting, the buddling is repeated, and, lastly, the tossing and packing, with the result that clean tin ore with 65 to 70 per cent, of metal can be put away in bins, ready to be done up in sacks and despatched to the smelting works. In some cases the ore is not contaminated with sulphides, and no roasting is required. The tin-bearing sand and gravel, which have furnished and are still furnishing such a large proportion of the world's supply of the metal, can be treated in a speedier fashion. The wash-dirt is simply shovelled or hoed against a stream of water in a ditch or trough -, the light waste is washed away, and the heavy pebbles and clean grains of cassiterite are left at the head. This is the method usually employed in the East. The tin-gravel worked at Restronguet Creek,t near Truro, was washed with water in order to separate adherent clay, and then * Ferguson, " On the Mechanical Appliances used for dressing Tin and Copper Ores in Cornwall," Proc. Imt. Mech. Eng., 1873, P- I1 9 > Henderson, "On the Methods generally adopted in Cornwall in dressing Tin and Copper Ores," Proc. Inst. C.E., vol. xvii., 1857-58, p. 106. f Taylor, " Description of the Tin Stream Works in Restronguet Creek, near Truro," Proc. Imt. Mech. Eng., 1873, p. 161. 630 OEE AND STONE-MINING. passed to a revolving sieve. The fine stuff was jigged, and finally cleaned by a propeller-knife huddle ; the large pebbles were picked over, and those containing tin were stamped and treated like vein rock. At Mount Bischoff,* in Tasmania, the process of dressing may be briefly summed up as follows : Comminution by stamps, and extraction of the tin ore from the pulp by jigs and revolving tables. Zinc. Calamine has sometimes to be washed, in order to rid it of clay, before it is crushed and jigged like lead ore. Blende is dressed in the same way as lead ore, and is often ob- tained from one compartment or portion of a dressing machine, whilst galena is being discharged from another. LOSS IN DRESSING. The loss in dressing is frequently very great, and proofs of this fact constantly come under one's notice. Old heaps of mining refuse left by former workers may be seen yielding an abundant harvest to a later generation, and even with the machinery of to-day the extraction is far from perfect. For instance, in the year 1891 no less than 879 tons of dressed tin ore, worth ,33,704, were ex- tracted from the muddy water discharged into the " Red River " and its tributaries by some of the large tin mines near Camborne and Redruth. The loss is due to several causes. First comes imperfect severance of the valuable mineral from the worthless constituents of the ore during the crushing process r } this is unavoidable if the mineral occurs in the state of very minute particles. Secondly, the thickness of the dirty water escaping from the machines, which impedes the subsidence of the fine grains ; thirdly, want of care on the part of the persons placed in charge of the machinery. In addition to these causes, which are general, special reasons ac- counting for loss will be found with certain minerals : the amalgamation of gold is prevented by grease, by any coating or film upon it which impedes close contact with the mercury, by the presence in the ore of substances which have an injurious effect upon the mercury, " sickening " it, or in other words depriving it of its natural activity. Again, if the mineral is flaky, it will not fall so easily in water as if the particles more nearly approached a spherical shape. The actual loss has been very carefully ascertained in some cases, though less attention is paid to exact determinations than the subject deserves. M. Bellomf cites three cases of loss at mines producing argentiferous galena and blende. The ore delivered to the Himmelfahrt Works, near Freiberg, * Kayser, " Advantages of Ore-dressing by Automatic Machinery/' Trans. Min. Assoc. and Inst. Cornwall, vol. ii., 1888, p. 51. f Op. cit., p. 624. DRESSING. 631 contains 2 per cent, of lead, 0*275 percent, of zinc, and 7*3 ozs. of silver per metric ton (23 grammes per 100 kil.), besides a little copper, J per cent, of arsenic, and 5 per cent, of sulphur. The galena is dressed to 85 per cent, of lead and 96 ozs. of silver (3 grammes per 100 kil.), the blende to 40 per cent, of zinc and 9-6 ozs. of silver (30 grammes per 100 kil.), the pyritic minerals to 40 per cent, of sulphur and 16 ozs. of silver (50 grammes of silver per 100 kil.). The losses are found to be 21 per cent, of the silver, 38 per cent, of the lead, and 60 per cent, of the sulphur. At the Churprinz Works, also near Freiberg, the raw ore con- tains 3 per cent, of lead, and 3 ozs. of silver per metric ton (9^ grammes per 100 kil.), and a dressed product is prepared with 70 per cent, of lead and 16 ozs. of silver per ton (50 grammes of silver per 100 kil.). The loss in dressing is 2 2 '8 per cent, of the silver and 14*9 per cent, of the lead. The ore treated at Ems contains 4 per cent, of lead, 2 J per cent, of zinc, and i"j ozs. of silver per metric ton (5*4 grammes per 100 kil.), but the enrichment by washing is not carried so far as at the other works. The galena is dressed to 36 per cent, of lead and 9- 6 ozs. of silver per metric ton (30 grammes per 100 kil.), and the blende, which is not argentiferous, to 44 \ per cent, of zinc. The losses are 8 per cent, of the silver, 6 per cent, of the lead, and 34 per cent, of the zinc. It is to be regretted that so many dressing establishments in this country are working entirely in the dark, and are, therefore, utterly ignorant of the losses that are going on. At few places in the world is the loss more carefully studied than at the mines of the Pestarena Company in Northern Italy, for a sample is taken from every waggon of crushed ore before it goes to the mills. The quantity of gold in the ore treated can, therefore, be ascertained with great accuracy, and by comparing this amount with the quantity extracted, it is found that about one-fifth escapes amalgamation and is lost ; the ores sometimes contain 10 to 20 per cent, of pyrites. Another kind of loss which requires to be ascertained is the purely mechanical waste in preparing stone for the market. In the case of slate it is very large, for the blocks brought from the workings into the mills frequently yield only 25 per cent, of roofing material. As the amount of rubbish produced in getting out the blocks is also considerable, the quantity of saleable slate is often only one-twelfth of the actual rock excavated. Seeing that the proportion of waste material, whether in ore mines or stone mines, is usually large, it behoves the miner in laying out his dressing establishment, to make provision for the disposal of great quantities of refuse. 632 ORE AND STONE-MINING. SAMPLING. The miner may have to sample the produce of his mine tor a variety of reasons. Sometimes sampling is necessary in order to ascertain the amount of money due to the workmen ; it is indis- pensable when the loss in dressing has to be ascertained, and, lastly, the miner, after preparing his various products for sale, requires samples for possible purchasers. Sampling may be done by hand or by machinery. Four methods of hand-sampling may be mentioned : HAND-SAMPLING. i. Sampling by taking out small lots. If the mineral is in coarse lumps and the valuable ingredient irregularly distributed, picking up a few stones here and there is not likely to yield a very correct sample ; but, on the other hand, if the mineral is already crushed, and if the small lot is taken regularly, say for instance every tenth shovelful, it is possible to obtain great accuracy. Thus at the Pestarena mines the gold ore before being milled is crushed by rolls until it will pass a sieve with three holes to the inch ; and from each waggon of crushed ore about 2 kilos, are taken by a tin measure. The load is spread out horizontally with the hand and a tin measure is filled from this flat surface and thrown into a tub. Each waggon is weighed, and the 2 kil. represent about o^th ^ ^he load. At the end of the day the tubful is taken as the sample of the stuff sent to the mills. From this large sample a small one is prepared by the process of quartering, which will be described immediately. This method of sampling will also suffice in the case of an ore of small intrinsic value, such as an iron ore, consisting in the main of one mineral. 2. Trenching. In order that this method of sampling may be accurate, it is necessary that the mineral be well mixed, and where a valuable ore is concerned, great care is expended upon the operation. It may happen that there are a number of small heaps of dressed ore, each produced by a different gang of men, which have to be mixed before being sold in one lot. The stuff from the first heap is spread out evenly on a smooth flat floor. Layer after layer is added from the other small heaps until a large square or rectangular pile is obtained made up of horizontal strata. The mixing is now carried out by taking off a slice from the side of the heap with a shovel, so as to cut through all the layers ; the stuff is tossed on to the floor and spread over a large area, and the thorough intermingling is aided by a boy who stirs it as it falls. The original heap is cut away slice after slice, and gradually, at the side of it, another heap is formed with the particles thoroughly mixed, which is ready for the operation of trenching ; it may be, for instance, 10 ft. wide by 15 ft. long, and 18 inches high. If the operation of turning DRESSING. 633 over and mixing was carried on along the long side of the rectangle, a couple of trenches are dug across the heap at right angles to this direction, or in other words parallel to the short sides. The trenches are cut down to the bottom, and after they have been carefully swept out, the sampler slices off small portions of the sides with his shovel. All that he cuts down in this way is shovelled into hand-barrows, and constitutes the large sample, which has simply to be reduced in bulk by quartering. With coarsely broken mineral the part shovelled out in making the trench is often taken as a first sample and not the thin slices from the sides, as is done with fine material. The two trenches are sometimes cut at right angles to one another, forming an ordinary cross, or along the diagonals, forming a St. Andrew's cross, and the heaps are often round instead of being rectangular. (3) Quartering. Quartering is a process of dividing a given lot of mineral again and again until a sufficiently small sample remains. The mineral is made into a conical heap by letting each FIG. 695. FIG. 696. shovelful which is emptied fall down evenly over the apex of the cone. The apex is pressed down, and the heap is spread out till it forms a low truncated cone, a cross is marked upon it with the point of the shovel, and the two opposite quarters, say 1 and 3 (Fig. 695), are scraped aside and discarded, leaving 2 and 4, or one-half of the original sample. These two quarters, 2 and 4, are mixed by hand, a new conical heap made and the quartering repeated. The next time the sampler will retain the quarters i and 3, and put aside 2 and 4. If the mineral is not fine, it should be crushed once or twice and put through a finer sieve during the process. In this manner a large sample is reduced sufficiently in bulk, to give the miner a small lot which is a fair average of the whole. (4) Sampling Shovel.* This implement is designed for the purpose of obtaining an average sample of a heap of mineral by merely shovelling it over. It consists of a flat rectangular plate with vertical sides (Fig. 696), and two vertical partitions which enclose a central compartment occupying one fourth of its area. This compartment is closed at the back or handle end, whilst the rest of the plate is open. After the * Eng. Hin. Jour., vol. li., 1891, p. 718. 634 ORE AND STONE-MINING. shovel has been filled by a thrust into the heap of finely crushed mineral, it is easy to discharge the outer three-fourths of its con- tents over the back end, and then, turning it over, to deposit the central quarter in a separate place as the sample. MACHINE SAMPLING. While we have generally been content on this side of the Atlantic to go on with the old- fashioned methods of hand-sampling, much ingenuity has been displayed in the United States with the object of producing machinery for doing the work, and thereby saving time and labour, to say nothing of furnishing more accurate results. According to the principle upon which they work, sampling machines may at once be divided into two great classes : * (1) Machines which take part of the stream of material for the whole of the time. (2) Machines which take the whole of the stream of material for part of the time. (i) In the former class a spout or opening of some kind is arranged so as to divert part of the stream of ore, coming from a crusher for instance, into a separate receptacle. Two samplers used some years ago in Colorado belong to the first class. One of them is a hollow cone with four large holes ; the stream of crushed ore falls upon the apex, and the particles spreading themselves out slide down over the steep surface. The path of some of the particles leads them to the holes, where they drop through, forming a sample of the whole. The size of the holes can be arranged so as to extract a given percentage of the total quantity, and this first sample can be reduced in bulk by a second passage over the cone. In the other the desired result is obtained by letting the ore fall on to three inclined shelves one above the other, f Each shelf has openings which allow a 'portion of the ore to drop through. The ore dropping through the first shelf falls upon the second, which in its turn eliminates part and lets the remainder drop on to the third shelf, where the process is repeated. The portion which has passed through the three shelves constitutes the sample. Clarkson's Rapid Sampler, an English machine (Fig. 697), consists of a revolving conical hopper, supplied with the mineral, which runs through a hole in the bottom, and drops on to the apex of a cone. In the path of the falling stream of mineral, now converted into a hollow rotating cylinder, there are two segmental spouts, which intercept any desired proportion of it, and so furnish two independent samples. The size of the spout determines the percentage which is diverted as a sample. * Bridgman, "A new System of Ore-sampling," Trans. Amer. Inst.M.E., vol. xx., 1891, p. 416. t Egleston, " Sampling Ores in Colorado," Engineering, vol. xxii., 1876, P. 495- DRESSING. 635 (2) In the second class the whole stream is deflected at regular intervals, and this method has the advantage of ensuring the proper proportion between the fine and the coarse, which cannot always be attained by the fixed spout ; where the constituent minerals vary in friability the accuracy of the result must de- pend upon this proportion being strictly maintained. In Brunton's * sampler the stream of ore falling down a vertical trough is diverted to one side or the other by a partition which is moved backwards and forwards by very simple machinery. There are means of regulating the proportion of the time during which the stream is being turned into the side for receiving the sample. Bridgman's ore-sampler f has the advantage of supplying two FIG. 697. FIG. 698. FIG. 699. absolutely independent samples, and it divides them as often as desirable previous to a recrushing. The work is begun by a horizontal revolving wheel formed of two concentric rings, with vertical partitions dividing it into eight segments (Fig. 698). Underneath this first " apportioner," as it is called by the inventor, comes a second one (Fig. 699) ; it is a funnel with openings, a, b, c, d, on the side, and is made to revolve in the opposite direction to the first. It is succeeded by a third of similar construction. The ore is fed from a pipe on to some point of the first apportioner, and each segment necessarily receives one-eighth of the stream ; segment No. i has a spout which travels round the outer circumference of the apportioner below it, passing over the holes a and 6, whilst the spout of No. * "A new System of Ore-sampling," Trans. Amer. lust. M.E., vol. xiii., 1885, p. 639. t Op. tit. 636 GEE AND STONE-MINING. 5 takes an inner path, including the holes c and d ; the spouts of 2, 3, 4, 6, 7, and 8, deliver their ore into the centre C. One- eighth of the stream from the spout of No. i drops through a and another eighth through b ; the rest falls on to the parts A and B of the funnel and is discharged into the centre. Likewise the original one-eighth from spout 5 drops in part through c and d, and in part on to A and B. The portion passing down through a and 5, or through c and d, is therefore one- quarter of one-eighth, or one-thirty-second, of the original bulk. The third apportioner again collects one-quarter and discards three-quarters of each of the two samples coming to it, so that the final samples furnished by the machine are both T ^g- of the total. These first samples are then recrushed and passed through another machine of similar construction but giving only one sample. Mr. Bridgman has likewise devised a small sampler for use in the laboratory. 637 CHAPTER XIV. PRINCIPLES OF EMPLOYMENT OF MINING LABOUK. Modes of payment, according to time, measure or weight ; tribute systems. PERSONS employed at mines may have their wages reckoned in one of four different ways : 1. By time. 2. ,, measure or weight. 3. a combination of Nos. i and 2 systems. 4. ., value of the mineral obtained. (i) The first system is largely adopted for surface labour, such as is required on the dressing floors. Enginemen, stokers, millmen, smiths and carpenters are likewise paid so much a day of a stated number of hours. A time-book is kept, and the wages are reckoned up at the end of the week, fortnight, or month by a simple multiplication sum. For true mining or quarrying that is to say, for excavating valuable mineral and removing worthless rock this system is far less common than the other three. There are objections to it both on the part of mine-owners and on the part of many of the men. The owner has to employ more foremen to look after the work, and an amount of supervision which would be sufficient at the surface is utterly inadequate below ground, because the working places are not within sight from any one point, and can only be reached by traversing low and tortuous passages, or by climbing down and up ladders. The men, too, in many cases prefer to be paid on some system which gives the skilled and steady miner the advantage of deriving some profit from his exertions, over and above the average daily wage he would receive if time were the only standard for good and bad workers alike. In rare cases persons are hired for the day only ; this is done sometimes at the ozokerite mines at Boryslaw, where the agent picks out in the morning as many men as he wants from those assembled at the top of the pit. In new countries or districts, payment of miners by the day may be necessary at first, because the work is so strange that the men are afraid to enter into contracts, which would appear perfectly reasonable and satisfactory to them if they had been 6 3 8 ORE AND STONE-MINING. used from boyhood to this system of arranging earnings. After the more enterprising men have learnt by actual practice what they are capable of doing, they drop into the contract system, and in due course of time the others follow them. (2) Much of the work at mines is regulated by a system of piecework of some kind, calculated by measure or by weight. In Cornwall and some other districts, work done in this fashion is known as "tutwork." No doubt the original meaning of the word was " dead work," from the German word " todt," because preliminary and unremunerative work was paid for in this manner ; nowadays the meaning of the term is extended, and it includes the excavation of ore. In driving a level, for instance, the man- ager specifies that the height shall be 7 feet and the width 5 feet, and agrees to pay so many pounds for every yard or fathom of advance. As a rule the mine-owner provides all the necessary materials, and deducts their value at the end of the contract. An example or two will make the system plain. THE ADVENTUKE MINING COMPANY, LIMITED. Tutwork pay for the Month of May 1886. JOHN SMITH AND PAETNERS. 6 Men. Amount. Fms. Ft. In. Price. s. d. Sinking . , . . .42 o I40/- 30 6 8 Stoping .....20 6o/- 6 Putting in 9 stulls 10 1- 4 10 40 ,6 8 . d. DEDUCTIONS. Cash on account .... 21 O Candles, 72 Ibs. at 4^. . ^ I 4 O Powder, 100 Ibs. at 40?. I 13 4 Dynamite, 20 Ibs. at is. 8d. I *3 4 Fuse, 34 coils, at $d. . . H 2 Hilts, at 6d. . ... Shovels, at 25. . . . Smith's cost . .... Powder cans, at is. Doctor and club ... 18 27 2 10 Balance . . , . 13 13 TO PRINCIPLES OF EMPLOYMENT. 639 The meaning of this pay-bill is that John Smith and five other men took a contract to sink a certain shaft at ^7 per fathom, and to stope part of the lode at ^3 per fathom. They sank the shaft 4 fathoms 2 feet, and stoped away 2 fathoms ; in addition to this they put in some timber, a matter not included in the original contract, and for which they are credited with 4. IQS. extra. The gross balance due to them is therefore 40 i6s. Sd., against which they are debited with the cost of the candles and explosives supplied to them, and with their subscriptions for medical attendance and accident club. While the contract was running they received 2 1 on account, so that on the pay- day they took up a balance of ^13 13$. iod. In a contract of this kind the leading man, John Smith, is known as the " taker." In stoping a vein, the price is calculated per square fathom of advance for its whole width ; thus if a lode is 4 feet wide, stoping i fathom of ground means the removal of a block 6 ft. high 6 ft. long and 4 feet wide ; in other words, 144 cubic feet. In wide lodes the men are sometimes paid per cubic fathom excavated. At one British lead mine, where the lode sometimes measures several fathoms from wall to wall, a standard price is arranged for a width of 6 feet, and where the stopes are wider than this the men are paid extra. In order to prevent loss of ore through carelessness, the men are paid a premium of 155. a ton for all the lead ore they save. Another example (p. 640) gives an instance of " tutwork " wages calculated by weight. It is copied from the figures on the back of the little envelope in which the money is handed to the "taker " on the pay-day. The account shows that Richard Williams and his six partners excavated 120 tons 9 cwt. of tin ore ("tinstuff") at 6s. per ton, and were credited with ^36 2s. Sd. Against this they had to pay ^5 43. ^d. for materials (candles, explosives, &c.), 75. for doctor, 55. $d. for club and is. gd. for barber,* leaving a balance of ,30 45. ^d. to be divided among them, that is to say j is. yd. per man per week. A third basis of payment is the number of inches bored in the shift. This plan was in vogue in stoping the wide lead-lodes in the Upper Hartz some years ago ; it necessitated careful supervision, for otherwise the men bored their holes in the softest places they could find, or in positions enabling them to wield their hammers with the greatest ease, without any thought for the work required from the shots. A foreman came round at the beginning of the shift, and pointed out how the holes were to be placed ; in the middle of the shift he returned, measured the depths bored, and then charged and fired the holes while the men rested. The positions for fresh holes were then indicated, and at the end of * The item "barber," a charge of yL per man per month, still remains in a few of the oldest mines in Cornwall. The barber attends at the mines on Saturdays. 640 ORE AND STONE-MINING. the shift the depths were measured and booked, previous to the charging and blasting. The price paid was i M. 38 Pf. per metre of hole bored upwards, and i M. 13 Pf. per metre of hole bored downwards ; in the latter case the men could put water in the holes, which keeps the finely powdered rock in suspension and allows the cutting edge of the tool to do better execution. The men working away the great pyrites deposit at Rammels- berg in the Lower Hartz by means of boring machinery are paid WHEAL CHANCE. EICHAED WILLIAMS AND PAETNERS. Pay for 4 weeks ending 27th May. Paid loth June 1893. TUTWORK. Fms. Ft. Ins. Price. 8. rf. Driving Sinking Kising Tons. Cwts. Stoping Stems . . 1 2O 9 61- 36 2 8 Subsist .... s. d. Materials .... 5 4 4 Doctor, Club, and Barber . i 14 5 18 4 I Balance ' j6 30 ' 4 4 per metre of hole bored, as this method is more convenient than measuring up the amount of "ground" removed in wide work- ings and paying per cubic metre. The latter system, however, is adopted in driving levels and sinking shafts where the dimensions of the excavation are regular. In removing overburden, where everything has to be sent away indiscriminately, payment per cubic yard excavated is common, just as it is in making railway cuttings ; this system is adopted with the men who uncover the iron ore in Northamptonshire (Fig. 324), whilst those employed in getting the ore are paid so much per ton put into the waggons. PRINCIPLES OF EMPLOYMENT. 641 (3) The combination of the two methods, payment by time and payment by measure or weight of some kind, may be adopted when men are too inexperienced or too timid to take contracts depending solely upon results. This plan has been found to answer at a pyrites mine in North Wales, where the mineral is got by the aid of rock drills worked by compressed air. The miners receive a fixed wage of a pound per week and a premium of a penny per foot for every foot bored over 12 feet per day of eight hours. The company finds the machines and all tools The mine is worked in three shifts of eight hours each ; in two of them the men are merely boring, and in the third shift a set of blasters come round to charge and fire the holes. Of course, as in the Hartz, the position of the holes is planned by the foreman. By working in this way the men generally make from 3$. to 45. a week extra pay, for they are able to bore 40 or 50 feet a week more than the standard task. The ore is fairly uniform in hard- ness, for otherwise it would be impossible to maintain a single tariff for the whole of the mine. This system has been advan- tageous both to the men and to the company. Previous to its introduction the men were all on one dead level, and had no interest in exerting themselves ; they each got their i a week by doing the minimum amount which enabled them to escape a scolding from the foreman, whilst now the man who works hard feels that he will get some recompense for his extra exertions. The company benefits by having an increased output at a smaller cost per ton, without any extra plant. (4) We now come to the fourth or last system viz., payment by value of the product. This system has had its home in the south-west of England for many years, and has been transplanted by the ubiquitous Cornishman to many other ore-mining districts. In Cornwall it is known as working on " tribute." Under the tribute system a gang of men agree to hand over to the mining company all the ore they raise, on condition that they receive a certain proportion of its value. Thus, supposing that the tribute is ^, or 55. in the^i, and that a couple of men produce marketable copper ore worth ^50, their share will be j>S * i r j 12 i os., less the cost of the materials they have been supplied with, and all the expenses for winding, dressing, sampling, &c. In other words, the tributer may be said to take a sublease of part of the mine and pay a royalty, in this case of J or 75 per cent, for the permission to work accorded to him. But it must be recollected that the mining company renders the place accessible to him, keeps it drained and ventilated, and supplies him with machinery for raising his ore to the surface and dressing it, which he could not provide. The tributer is therefore a person who can speculate upon the value of the ore in a certain small working area, without having any capital beyond his brain and his muscle. 2 S 642 ORE AND STONE-MINING. The precise nature of this mode of payment will be best under- stood by an actual example. John Jones and Partners, WHEAL CHANCE. Pay for 4 weeks ending 27th May. Paid loth June, 1893. TBIBTTTB Tribute. Amount. T. C. Q. LBS. . d. Tin i : 6 : 3 : 23 Price $2 per ton Value 70 is. Sd. 13/4 46 14 5 Keturning charges Subsist and dressing 8. d. 10 10 3 13 6 I Materials and drawing . 4 4 9 Doctor, club, and barber ii 25 12 4 Balance 21 2 i The pay-ticket shows that John Jones and his partners, a gang of three men, raised a certain quantity of crude tin ore (tinstuff) which, according to assays, contained i ton 6 cwt. 3 qrs. 23 Ibs. of clean tin ore (black tin). The value of this quantity, at $2 per ton, is *]Q is. Sd. The pay -ticket also states that the tribute was 13$. ^d. in the pound, or, in other words, two-thirds of the value. The gross total credited to the gang was therefore ^46 145. $d. Against this come the returning charges, subsist, dressing, drawing, and sampling, as follows : s. d. Eeturning charges . . . 10 3 6 Subsist 8 10 o Dressing 231 Materials 2 10 8 Drawing and sampling: . . . . i 14 i Doctor, 55., Club, 4.9. 6d., Barber, is. 6d. on o 25 12 4 These deductions require a word of explanation. The return- ing charges represent the cost of treating the "stuff "from the time it goes to the stamps until the dressed tin . ore (black tin) PKINCIPLES OF EMPLOYMENT. 643 is fit for the smelter. The amount charged varies slightly in different mines.* " Subsist " is another name for an advance, or money paid on account, during the running of the contract, which in this case lasted eight weeks. The term " dressing" as used in these accounts is not very happily chosen, because the returning charges represent all the cost of stamping and washing. The " dressing " referred to in the pay-bill is the preparation of the "tinstuff" for the stamps by "ragging," "spalling," &c. The charge varies from 4^. to 6d. per ton, according to the hardness of the veinstuff. In this case the books of the company showed that 96 tons 6 cwt. i qr. of tinstuff had been dressed. The " materials" included candles, powder, fuse, dynamite, pick hilts, detonators, a shovel, clay for the candles, and the smith's cost for sharpening drills and picks. " Drawing " is the Cornish term for winding, and is charged at the rate of $d. per ton. The "sampling" refers to the assays of the tin ore made upon the vanning shovel by the mine agent ; they are charged at the rate of is. each, and it is upon the results of these assays that the mine-owner ascertained that the 96 tons 6 cwt. i qr. of " tinstuff" contained i ton 6 cwt. 3 qr. 23 Ib. of " black tin." One of the three men being a bachelor, paid only 6d. per month for the doctor, instead of the usual is. of the married man, whose wife and family are likewise entitled to receive medical attendance. In former days the " tribute," or proportion of the value re- tained by the workmen, was publicly fixed by Dutch auction on the "setting" day. The miners assembled outside the mine office (counting-house), and the manager, after reading out the nature of the " pitch," or working place, asked for bids ; the lowest bidder received the contract. If a certain place seemed likely to be profitable, there was frequently much competition among the men in order to get the " pitch." Nowadays the agreements are often made privately. It is evident that the richer the lode, the smaller will be the proportion of the value necessary for giving the men a fair return for their labour ; in other words, the tribute will decrease as the lode improves. This system of working has many advantages, which have rendered it popular with men and masters in Cornwall and else- where. The man's pay does not depend solely upon his muscular exertion, but also upon his judgment. He exercises his wits, he * Common rates are : . d. On tinstuff producing i^ % (or less) of " black tin," 2 o per ton. i4% to 24% 3 o 24% 3f% 3 6 3i% 5 % 40 5 % 6i% 50 6i% 74% 7 o 10 % or above 10 o 644 OEE AND STONE-MINING. observes the nature of the ground, and notices what conditions are most favourable for ore-bearing, such as colour and texture of the surrounding rock ; what signs are the forerunners of richness or poverty of the lode, such as intersections with " droppers " or " feeders," joints in certain directions, "the appearance of asso- ciated minerals. Guided by slight indications of this kind, which would pass unnoticed by the inexperienced, he is ready to back his favourable opinion of a certain working place (pitch) by agreeing to work it at a price (tribute), which would seem quite inadequate if one judged by the actual ore in sight at the time of making the agreement. If he is correct in his inference, he may make a large sum of money, and receive, for instance, one fourth of ^200, instead of one-fourth of ^50, which seemed probable from the original appearance of the ground. This constant study of the geological features of the working- places and the calculations concerning the probable expenditure for explosives and other materials, educate the miner, make him brighter, shrewder, and more self-reliant, and so raise him mentally. The advantages of this training are also felt by the mining company; they have in the mine a body of expert detectives constantly on the watch for clues to lead them to hidden ore- bodies which might otherwise go undiscovered, and while the tributer is at work in any given " pitch," the mine-owner feels little fear of ore being thrown away in the rubbish, or of " waste " being unnecessarily sent to the surface. As the interests of the employer and the employed are in these respects identical, the former knows that little or no supervision is required on his part to prevent loss from either of the two causes just mentioned. The tributer is therefore left much more to himself than the man employed upon tutwork. Lastly, it may be pointed out that so long as the profit made out of each bargain is sufficient to pay its proportion of the general expenses of pumping, ventilating, and management, the mining company cannot lose by employing tributers. It is not to be wondered that with these advantages the tribute system should be vaunted to the skies by many mining engineers. The other side of the picture must not be forgotten. In the first place, the system is apt to promote duplicity among the men. They are constantly endeavouring to outwit the agent by fair means or foul, and will candidly confess that " the whole art of mining is fooling the captain." The latter has often been a tributer himself, and is fully alive to all the tricks which the men are likely to practise upon him, such as concealing any indication of an approaching improvement, in order to get better terms at the next " setting." This is not all ; it may happen that two "pitches" not very far from one another are being worked at very different tributes, one bargain being rich and the other PRINCIPLES OF EMPLOYMENT. 645 poor. One gang may be getting two-thirds of the value of the ore they raise, the others only one-tenth ; the men with the low tribute, that is to say, the men in whose working place the ore is abundant, are often ready enough for a consideration to part- with some of their stock to their neighbours, who transfer it secretly to the " pile " which they are sending up to the surface, carrying it perhaps from one working place to the other in an improvised sack made out of a pair of trousers. The result is that the squad with the high tribute are paid at a far better rate for some of their ore, than the trouble of getting it warranted. When the rates of tribute vary between narrow limits the case is different. For instance, the manager of a zinc mine was lately paying 405. per ton for blende as the highest tribute and 305. as the lowest, which, with the ore selling at ^5 per ton, corresponded to 8s. and 6s. in the pound respectively ; there was therefore little or no temptation to transfer ore from one " pitch " to another, and so defraud the company. The training in trickery which is inherent to this system may have its effect later on, when the tributer is promoted to a higher position ; from having been taught to consider that cheating the captain is perfectly fair and legitimate, he may be ready to conclude that " the whole art of mining is fooling the public." And blunting of the moral sense of the men is an undoubted evil. Payment by tribute involves the necessity of ascertaining the value of each gang's raisings separately. In the case of tin ore the percentage of cassiterite is learnt by washing a sample upon the vanning shovel, and from the result of this assay the total amount is easily reckoned ; but with lead and zinc each parcel is dressed by itself, and the final lots of clean galena or clean blende are weighed separately, before being mixed and made into heaps for sale to the smelter. This multiplication of small operations, cleanings-up, and weighings, naturally makes the cost of dressing higher than it would be if all the ore were treated alike, without regard to the persons who had raised it. Another objection to the tribute system is that the lessened amount of supervision for commercial purposes may tend to a lessened amount of supervision for purposes of security; the working place is not visited so often by the agent, and he has fewer opportunities of pointing out to the men possible dangers from want of timbering or other sources. The men sometimes court this lack of supervision by making access to their " pitch " difficult, or, at all events, troublesome. Lastly, there is an element of gambling involved in the tribute system, which it is scarcely advisable to cultivate. The tributer is a speculator, who hopes by a lucky hit, as comrades have done before, to make a lot of money in a short time. Where one succeeds in so doing, how many fail ? According to the report of Lord Kinnaird's Commission in 646 ORE AND STONE-MINING. 1864,* the tutworker at that time was better housed than the- tributer ; the moral of this is that, on the whole, it is better for the working miner to be in receipt of fairly constant regular wages than to trust to the chance of occasional runs of luck. The advantages accruing to a mine from the tribute system are far less marked when there is a lode of pretty even character, than when the deposit is fitful and uncertain in its nature. This explains, to some extent, why the tribute system occupies a less important place in Cornwall now than it did in the first half of this century. Cornish mines at the present day are mainly dependent upon tin lodes, in which the cassiterite is finely dis- seminated through a hard close-grained rock. The consequence is that it is impossible to do much picking underground, or indeed at the surface ; the whole of the stuff raised from the stopes has to be sent to the stamps. For deposits of this kind it is more advantageous to employ the tutworker, who excavates the ground at so much per fathom, than the tributer. Fifty years ago things were different ; copper was then the mainstay of Cornwall, and the chief ore was chalcopyrite. While cassiterite is a mineral well adapted for dressing by water, chalcopyrite is not ; it crumbles to dust very easily, and the fine particles are liable to be washed away with the refuse. A large amount of hand-picking was required, in order to save as much of the ore as possible from treatment in water. The care of the tributer in the stopes of copper mines was a matter of vital importance in the old days, and his services were really valuable. Where an old mine is re-worked after a period of abandonment, the tribute system often does good service, especially if the object is to recover some mineral considered worthless in former times, or when branches of ore exist in the sides, after the main part of the vein has been removed. In a like manner it proved a valuable remedy f in the Eureka district for evils which had resulted from the plan of working the ore by day labourers. The ore occurs in bodies of irregular shape and size ; men working by the day had not been careful to get out as much ore as they might have done, and others were induced by the tribute system to extract the portions remaining behind, which would otherwise have been lost altogether. Besides which it was known that small ore-bodies had been passed over as too poor or too insignificant to be worth removing in the ordinary way, but which were quite good enough to afford a scope for the talents of a man who had a direct interest in the ore he got out. In 1881 the men received $2-50 for all ore assaying * Report of the Commissioners appointed to Inquire into the Condition of all Mines in Great Britain to which the Provisions of the Act 23 & 24 Viet, c. 151 do not apply. t Curtis, " The Silver-lead Deposits of Eureka, Nevada," Hon. U.S. Geol. Purvey, vol. vii., Washington, 1884, p. 151. PRINCIPLES OF EMPLOYMENT. 647 per ton, and 50 per cent, of all that it assayed above $30. Thus an ore worth $65 per ton brought to the tributer $2*50 + $17*50, or $20. In cases of this kind the services of the tributer are often requisitioned with good results to the mine ; that is to say, when the greater part of the ore has been extracted by some other method of payment, and when more judgment and care are required to ferret out and take away partly hidden treasures distributed here and there in the workings. Under the old Cornish system of tribute, the partners are all working men, who are all employed in the particular " pitch " assigned to them ; but in Colorado one meets with a modification of the method, in which the actual miner avails himself of outside aid, and may or may not employ labourers who have no interest in the adventure. A party of miners who have confidence in the future resources of some part of a mine, take it upon lease and obtain the assistance of shopkeepers or others in the neighbour- hood, in order to buy tools, explosives, and materials, and to have means of living during the unproductive stage of the under- taking. If the hopes of the miners are realised, the sleeping partners receive a share of the profits ; if the speculation turns out badly, the miners have had a bare subsistence, and the petty capitalists lose their money. This system has the advantage that it enables a certain amount of dead work to be combined with the extraction of ore. Under the Cornish system working men will not drive levels and sink shafts in unproductive ground ; because, however high the tribute may be, they receive nothing so long as they raise no ore, and they cannot afford, on their own resources, to spend weeks and months in making the preliminary openings, which may be required before some given block of ground is made ready to yield up its supposed riches. A little outside capital tides the workers over their difficulty, and gives them a chance of making money by the exercise of their brains as well as by the expenditure of their muscular strength. The question will be asked : How does the small capitalist guard himself against the risk of having to provide for the living of some lazy miners, who, hidden below ground, are merely making a pretence of working ? In the first place, he may take a pre- caution, often omitted by the large capitalist, of associating himself only with men whom he knows and can trust, and secondly, as he is frequently a bit of a miner himself, he visits the mine from time to time, and watches the progress of the work. The mine-owner favours this system, and even becomes a partner himself, because he gets some of his dead work done without any risk to his pocket. In the case of mines drained by adit-levels and swept through by natural draughts, as is commonly the case in Colorado, the mine-owner is put to no cost whatever for pumping or ventilation, and therefore he loses no money even if ORE AND STONE-MINING. the " lease " turns out a failure, whereas he is bound to be a gainer if any ore is met with. The following are two actual examples which explain the system very clearly : COLOEADO LEASE. Profitable Lease to both Company and Lessee. Company or Owner having ^ interest) and Lessee ^ interest. LEASE ACCOUNT. Dr. Or. $ c. $ c. Nov. 30. To Lessee's wages . . . '. 72.00 ,, Other wages . . . . . 407.00 Supplies, powder, &c. . .- . 19.25 ,, 151 ore sacks . . . . -, 30.20 Hoisting, training, &c. . . . 99-55 Blacksmithing . . . . 12.40 ,, Hauling ore to mill . , , 26,70 By Proceeds of ore . * . . . 2238.95 To Koyalty . . . ... . 1119.40 Dec. 30. ,, Lessee's wages . ..'' . . 78.00 Other wages . \ . , 573. 10 Powder, fuse, &c. . , . . 27.05 100 ore sacks . . . . . 20.00 Hoisting, training, &c. . , <. .. 131.45 Blacksmithing . . . , 17.25 Hauling ore to mill . . . 36.00 By Proceeds of ores .... 3471-75 To Koyalty 1735.85 4405-20 5710.70 Net profit on lease .... 1305.50 $5710.70 $5710.70 Lessee received : Wages for his labour . . . . 150.00 of profits . . . . '. . 326.40 476.40 Company or owner received : Royalty 2855.25 | of profits 979. 10 3834.35 Cost of work exclusive of lessee's labour . 1399-95 Total . . $57io.7o PRINCIPLES OF EMPLOYMENT. 649 COLORADO LEASE. Unprofitable Lease to Lessee. Owner \ Interest^ and Lessee Interest. LEASE ACCOUNT. Sept. 30. To Lessee's wages Other wages , Powder, fuse, &c. . Hoisting and training Hauling ore to mill By Proceeds of ore To Royalty . Oct. 31. , Lessee's wages Other wages . Powder, fuse, &c. . Hoisting and training Hauling ore to mill loo ore sacks . By Proceeds of ore To Royalty . Nov. 30. Lessee's wages - . ,, Other wages . , ,, Powder, fuse, &c. . Hoisting and training ,, Hauling ore to mill By Proceeds of ore To Royalty . Loss on lease Thus the lessee received : His wages for working amounting to Less half loss on lease Leaving him for his work The Company received : Koyalty amounting to . . ' . Less half loss on lease Net profit by the Company Dr. $ c. 117.00 442.30 50-30 07.85 26.95 660.80 117.00 483.90 25.15 66.95 16.65 17-35 3846.60 Cr. $ c. 1321.60 1070.20 1322.60 3714.40 132.20 3846.60 356.20 66.10 290.10 1857.20 66..IO $1791.10 The men who are excavating slate rock (rock-men), and those who are subdividing it into merchantable slates (quarry- men) , in the Festiniog district, are paid by a method which in principle resembles the tribute system. The earnings of the men depend upon the value of the stock of merchantable slate which they obtain from their working place or " bargain." At the end of the month the stock of each partnership is counted, 650 ORE AND STONE-MINING. and the men are credited with the value of their make according to a fixed tariff. Thus, for instance, we may suppose that the men had made fourteen hundred slates of the size 24" x 14", at 27$. 6d. per thousand ; for this their account would be credited with i 1 8s. 6d., and so on with each size. On looking down an account, it will often be found that the men have made " best " slates of twenty different merchantable sizes, to say nothing of several kinds of " seconds." The total of these various items is a first basis of the amount due to the partnership ; but as the " rock " varies in quality in the different working places, owing to the presence or absence of joints, the interference of quartz veins, or alterations of texture, the result of a given amount of labour must necessarily vary also. In good rock the men will make a large quantity of " best " slates of large sizes ; elsewhere, though working equally hard and excavating quite as many cubic feet, they will be able to make only slates of small sizes, or " seconds " in the place of " bests." The companies find the simplest method of adjusting these differences is to pay a premium or allowance, varying with the quality of the rock in each " bargain," and determined at the " letting," i.e., at the time of making the contract. A " bargain " may be let for a month or for several months. The premium is called " poundage." Thus to take an actual case : s. d. Value of the slate produced, at tariff prices . . 16 19 i Poundage io. ....... 896 Total . . 25 8 7 The " poundage " of 105. means a premium of IDS. in the pound ; for every pound's worth of slate at tariff prices, the workmen receive an additional half-sovereign; in other words, the value of the total make is reckoned at 50 per cent, more than the tariff" prices. If the bargain is a good one, the poundage will be low ; if the rock deteriorates in quality, the poundage will have to be raised at the next letting. Another example will make this plainer : s. d. Value of the slates produced, at tariff prices . . 9 19 i Poundage 325. 6d. ....... 16 3 6 Total . . 26 2 7 These two amounts, ,25 85. yd. and 26 28. yd., are the gross earnings, in each case, of four men for a month, and are subject to deductions for materials supplied. In the former case the deductions were : explosives, 6s. 6d., fuse, is., candles, 45., smith, 55. ii<#., or 175. $d. in all, leaving a balance of 24 us. 2d. which was handed to the men. In this PRINCIPLES OF EMPLOYMENT. 651 bargain there were three partners, who employed a labourer, and worked twenty-four days. The company leaves the division of the money to the men themselves, but keeps an account so as to know precisely what the earnings are. The recognised wages of a labourer at Festiniog were 45. 2d. a day, so the labourer was paid ^"5, i.e., twenty-four times 45. 2d. There remained, there- fore, a net balance of ;i9 us. 2d. to be divided among three men. According to the time-book, these men worked 70 J days between them, and therefore their average wages were 55. 6d. per man per day. In the other case the account stood thus : . d. Gross earnings - 26 2 7 DEDUCTIONS. s. d. Powder 14 IO Blasting gelatine 6 6 Detonators . i 6 Fuse . 2 o Candles 4 4 Smith . . 4 6 i 13 8 Net balance . . . 24 8 ii Here there were four partners and no labourer; they made 94 days between them, or at the rate of 55. 2d. per man per day. In spite, therefore, of the very great difference in the rock, the poundage was so fixed beforehand as to enable each set of men to earn very nearly the same wage per day. At Festiniog the partnership commonly consists of four per- sons : two working below ground, and engaged in getting the slate- rock, and two working above ground in the mills, engaged in making the blocks into merchantable slates. The reason for this arrangement is the fact that the yield of slate from any given block depends very largely on the skill of the dressers, and if the splitting and making of the slates were confided to men paid by the day, these would have no interest in doing their best with the material delivered to them. Now the men working below ground can rely upon their own partners to work up the blocks into slates with the least possible loss ; the case is a totally different one from dressing a metallic ore. Owing to the nature of the substance which is being quarried, the payment by a varying " poundage " is free from some of the objections which 652 OHE AND STONE-MINING. are inseparable from the " tribute " system at ore mines. At the latter the change in the value of a lode may be so sudden, that a single blast will convert a " pitch " originally " set " at a tribute of two-thirds, into one which could be worked profitably by the men at one-twentieth. If such a change takes place some time before the end of the contract, the men raise far more ore than was thought possible when the bargain was arranged, and make what is known to Cornishmen as a " start "or " sturt," in other words "a big haul." Cases are known in which a party of tributers have earned as much as ^100 each in a month, instead of the expected ^4 or ^5. The possibility of such good fortune naturally encourages the miner to take the risks incident to work- ing upon tribute, and at the same time prompts him to deceive his superiors if he can. With slate, the " rockman " may be favoured by unexpected joints, and he may be able to earn twice as much as was expected when he entered into his contract, but he does not get twenty times as much, nor is he liable to find his " bargain" so suddenly become poor or absolutely worthless as may happen with a copper lode in Cornwall. There are also fewer opportunities of hiding coming improvements from the eyes of the agents. The result is that there are fewer attempts at concealment, and consequently there is less chance of the moral feeling being blunted ; sudden great variations in the earnings are rare, and the solution of the problem of payment by results seems very satisfactory. As a final instance of the payment of wages, may be mentioned that of piecework combined with premiums for good conduct. This system was introduced at the large stone quarries of Quenast in Belgium * in order to make the men stick to their work during the regular hours, and not absent themselves, on the pretext that, as they were paid by results, they could do as they pleased. The company instituted a higher rate of wages and prices applicable only to men who did not leave the quarry during working hours without permission. The men soon dis- covered that it was to their advantage to get the higher tariff, the public-houses were less frequented, the average earnings increased, and the company had more work done. * " Continental Notes," reporting communication by Urban to Brussels Section of the Liege Engineers. Coll. Guard., vol. Ixiii. 1892, p. 844. CHAPTER XV. LEGISLATION AFFECTING MINES AND QUAEEIES. Ownership Taxation Working regulations ; Metalliferous Mines Regula- tions Acts, 1872, 1875, and ^91 ; Coal Mines Regulation Act, 1887 ; Alkali Acts Boiler Explosions Acts Brine Pumping (Compensation for Subsidence) Act Elementary Education Acts Employers' Liability Act Explosives Act ; Factory and Workshop Acts Quarry Fencing Act .Rivers Pollution Prevention Act Stannaries Act, 1887 Truck Acts. THE object of this chapter is to call the student's attention to the principal laws affecting the working of mines and quarries in the British Isles. The subject may be taken under the following heads : 1. Ownership. 2. Taxation. 3. Working regulations. 4. Sundry special statutes. i . Ownership. In the United Kingdom the person owning the surface is primd facie entitled to all the minerals under- neath, excepting in the case of mines of gold and silver, which belong to the Crown. The Crown, however, does not claim gold and silver extracted from the ores of the baser metals. Thus we find that the Crown receives a royalty for the gold extracted from auriferous quartz raised upon private property in Wales, but gets nothing whatever for the silver contained in argenti- ferous galena. The ownership of the minerals can be, and often is, severed from that of the surface, the latter being sold whilst the mineral rights are reserved by the original owner. Minerals lying under the surface between high and low water mark are claimed by the lord of the manor, while everything under the sea and beyond low water mark is the property of the Crown. In the majority of cases in the British Isles,* the proprietor of the minerals does not work them himself, but concedes the right * Final Report of the Royal Commission appointed to Inquire into the subject of Mining Royalties. London, 1893. This Report contains much information also about the Mining systems of the Colonies and foreign countries. 654 ORE AND STONE-MINING. to another person in return for an annual rent and a royalty. Usually a certain minimum rent is fixed, which has to be paid even if no mineral is being raised, but this rent merges in the royalties ; that is to say, the amount paid as royalty is put to the credit of the rent, or, if sufficient, covers it entirely. The royalty may be : (a) A fixed sum per acre worked. (&) A fixed siim per ton raised. (c) A fixed proportion of the value of the mineral raised. (d) A varying proportion of the value of the mineral sold, regulated by a sliding scale. The first principle is more especially adopted in the case of coal ; on the other hand, a fixed rate per ton is common in the case of stratified ironstone. In the Cleveland district, the royalty is 6d. per ton on an average, and the leases extend for 42 years. Mineral veins are generally worked upon the third system ; royalties vary from one-tenth downwards, though this amount is quite exceptional. It is not uncommon for the lessee to pay one- eighteenth or one-twenty-fourth as royalty, and if a mine is struggling against low prices of metal, the "lord" is often induced to abate his legal claims very considerably, or even to agree to forego all payments until trade revives. The royalty is calculated upon the ore made ready for the market. Thus, for instance, in one of the reports of Dolcoath mine in Cornwall we read : By tin ore, 257 tons igcwt. I qr. ?lbs . ^19,596 13 6 Deduct G-. L. Basset, Esq., dues i-2oth. . 979 16 8 ,18,616 16-10 Leases in Cornwall are usually granted for 21 years. The lessor stipulates that a certain number of men shall be kept con- stantly at work. Ground for tipping rubbish has to be paid for, and sometimes at extravagant rates. When a lease is drawing to a close, a new one is usually granted upon terms at least as favourable as those of the old ones; but cases have arisen in which the " lord " has required a heavy premium before he would grant a new lease. The haematite of the Carboniferous Limestone of Cumberland and North Lancashire is usually leased upon a sliding scale, which increases the proportion paid as royalty when the price of ore goes up. Thus if iron ore is selling under 93. per ton the lessor receives lod. per ton as royalty, i.e., exactly one-tenth if the price is 8s. 4d. Supposing the value of the ore to rise to 143. per ton, the lessee would have to pay 2S. or one-seventh. With intermediate prices the fraction might be one-eighth or one-ninth. The leases are for 2 1 years. LEGISLATION AFFECTING MINES, ETC. 655 Many centuries ago the Crown claimed the right to all minerals, and, in order to promote mining, privileges were granted to persons who would endeavour to discover and work mines ; from these privileges and from old usages have resulted special mining rights peculiar to certain districts. Those per- taining to Derbyshire have now been definitely fixed by two special Acts of Parliament, the High Peak Mining Customs and Mineral Courts Act, 1851 (14 & 15 Viet. c. 94) and the Derby- shire Mining Customs and Mineral Courts Act, 1852 (15 & 16 Viet. c. 43). Again, there are two special statutes (i & 2 Viet. c. 43 and 24 & 25 Viet. c. 40) which regulate the opening and working of mines and quarries in the Forest of Dean, where the " free miners " have certain peculiar rights. These Acts are merely of local importance, but they are of interest as preserving old customs. 2. Taxation. Mining companies have to bear their share of Imperial taxes and local rates.* By " The Rating Act, 1874" (37 & 38 Viet. c. 54) tin, lead, and copper mines are assessed on the amount of dues payable, and in some districts a large pro- portion of the rates may be paid by the mines, an arrangement which is not unfair, if they are the cause of heavy burdens being thrown upon the community. 3. Working Regulations. We now come to the third division of this chapter, viz., the statutory regulations which are in force for the safe working of mines. Special legislation for promoting the safety and well-being of the miner is a growth of the last half-century. I do not mean by this that there were absolutely no regulations in days gone by ; there were rules which had grown up in some places, from customs and privileges so carefully preserved that they had become laws, but these related mainly to the acquisition and preservation of mining property, and only incidentally to the prevention of accidents. In order to make the state of our laws clear, and especially to those who may be accustomed to Continental regulations, it is necessary to point out once more that the sources from which we obtain minerals are of three kinds : a. Open works, that is to say workings open to the sky. b. Mines, that is to say workings carried on underground by artificial light. c. Boreholes, or old flooded mines, from which brine is pumped. As was said in Chapter I., it is the nature of the excavation and not the nature of the mineral, which settles, in this country, whether a given working is a mine or not. Consequently it must * Coal, Ironstone, and other Mines (Eating). Parliamentary Paper No. 405, Session 1890. Price 2\d. 656 ORE AND STONE-MINING. be understood that the purely mining Acts in no way affect open workings, save such as may form part and parcel of a true mine. The actual mining statutes now in force are as follows, in chronological order : The Metalliferous Mines Regulation Act, 1872 (35 36 Viet. c. 77). The Metalliferous Mines Regulation Act, 1875 (38 & 39 Yict. c. 39)- The Slate Mines (Gunpowder Act), 1882 (45 Viet. c. 3). The Coal Mines Regulation Act, 1887 (50 & 51 Viet. c. 58). The Metalliferous Mines (Isle of Man) Act, 1891 (54 & 55 Viet. c. 47). The first of these Acts was passed after the report of the Royal Commission appointed in 1860 to inquire into the condition of mines which were then not under inspection, and it was made to embrace every mine to which the sister Act, the Coal Mines Act of 1872, did not apply. Therefore every mine in the kingdom is under inspection : either it is subject to the provisions of the Coal Mines Act, 1887, which has taken the place of the 1872 statute, or it is under the Metalliferous Act of 1872. The former Act applies to mines of coal, stratified ironstone, shale, and fire-clay, and therefore the latter takes cognizance of everything else. The titles of the two Acts are misleading. Three times as much iron ore is obtained from mines under the Coal Act as from mines under the Metalliferous Act, and the largest mine under the latter does not produce metallic ores. Soon after the passing of the Metalliferous Act, the owners of an underground slate quarry in North Wales refused to have their workings treated as mine?. They asserted with some plausibility that the Statute was the " Metalliferous Mines Act," and that their workings had invariably been known as " quarries," and never as " mines." The matter had to be brought before the Court of Queen's Bench, and there it was speedily decided that, in spite of popular phraseology, the Festiniog underground quarries were legally "mines," and, as such, subject to inspection, quite as much as the Cornish tin mine, the Cumberland iron mine, or the Derbyshire lead mine. I will now proceed very briefly to pass in review the most salient points of these two Acts of Parliament, beginning with the simpler, and incidentally point out the slight modifications intro- duced by the other three statutes mentioned in my list. The Metalliferous Act is divided into three parts. Part I. deals with employment of women, girls, and boys. No females can work below ground, nor can any boy under 1 2 years of age. Boys under 16 cannot be employed more than 54 hours in any one week, or more than 10 hours in any one day. The person in charge of machinery for raising and lowering men must be a male of at least 18 years of age. LEGISLATION AFFECTING MINES, ETC. 657 Wages must not be paid in public-houses. An Annual Return has to be sent every year to the Inspector of Mines of the district, specifying the number of persons em- ployed, and the output of mineral. Under the 1872 Act, the mine-owner was not obliged to furnish this return for any given year until ist August following. This delay in the despatch of the return was manifestly absurd, for the statistics based upon them could not be published until they had lost much of their interest; the fault in the 1872 Act was corrected by the short amending Act of 1875, which changed the date from the ist August to the ist February every year. The owner * or agent has to send to the Inspector of Mines of the district notice of every fatal accident, of every accident causing serious personal injury, and of every accident, no matter how trifling, causing personal injury by reason of any explosion of gas, powder, or of any steam-boiler. The word " serious " gave a little trouble at first. Some agents were inclined to interpret it as meaning " likely to prove fatal," and did not report broken arms and legs, because there was every reason to suppose that the man would recover. Nowadays, when the period of disablement is likely to exceed a week or ten days, the accident is usually notified. Notice of opening, discontinuance, recommencement or aban- donment, has to be sent within two months. The section which follows (sec. 13) is one which was very much wanted, and which is still often called into requisition. It is the portion of the Act which provides for the secure fencing of shafts and side entrances of mines which are no longer at work. In working mineral veins, the " old men " sank their shafts as close to one another as they still do in mining ozokerite at Boryslaw, and the surface of open and uninclosed land was often riddled with holes like a sieve. If the tops of these shafts were in hard rock or were lined with stone, they remained open, and were a source of danger by day and by night, for many were close to roads or foot-paths, and, when partly or entirely concealed by brambles or bushes, they formed veritable man-traps. In other cases the timber lining at the top had decayed and the ground had run in, leaving a huge yawning crater, 10 or 20 yards across, leading to a pit hundreds of feet deep. It is true that a visible danger of this kind was known to the inhabitants of the district and could be avoided by daylight, but strangers were exposed to a considerable amount of peril. Five and twenty years ago the state of some of the open commons in Cornwall and Flintshire was simply scandalous ; and even now there are often good grounds for complaint on the part of the public, as fences become defective from having been constructed originally in too flimsy a manner, or * The word "owner "has a special interpretation under the statute and refers to the lessee or company working the mine, and not to the pro- prietor of the soil or mineral rights. 2 T 658 ORE AND STONE-MINING. from the mischievous pranks of passers-by. Occasionally, too, an un- known shaft comes to light from the decay of the platform of planks which had been put over it and covered with earth when the mine was abandoned. If treated in this way the top soon becomes grown over with grass, and recollection of the shaft gradually fades away. These timber " sollars," as they are called, should never be put in unless there is also a secure fence. Many narrow escapes have occurred in Cornwall from the giving way of such coverings, where the presence of a shaft was quite un- suspected. Abandoned mines are not only a source of danger to the general public by creating pitfalls, but they may also threaten the workers in the vicinity by holding accumulations of water or gas, liable to be tapped unexpectedly if the boundaries of the old workings are not known. To guard against such possibilities, the owner, who is bound to keep an accurate plan and section of his mine during the progress of the workings, is further obliged to deliver up a copy when he abandons them ; these plans are filed at the Home Omce, and can be consulted if necessity arises. They serve also to show new-comers, who pro- pose to reopen an old mine, what work has been done by their predecessors. The next section of the Act relates to the Inspectors of Mines, who are appointed by the Secretary of State for the Home Department. The Inspector may not practise as a mining engineer, manager, agent or valuer of mines. In addition to enforcing the provisions of the Act, the Inspector has the right to complain of any thing or practice in the mine which is- dangerous, or defective, or, in his opinion, threatens or tends to the bodily injury of the persons employed. In order to prevent an unreasonable Inspector from pushing matters too far, the owner and agent are duly safeguarded. They can object to the Inspector's notice about these alleged defects and have the matter referred to arbitration. Each Inspector has to make an Annual Report, which is laid before Parliament and afterwards published as a Blue-book. This is a convenient place for explaining that the United Kingdom is divided, for the purposes of inspection, into thirteen districts, each under a Chief Inspector, who, as a rule, has from one to three assistants. The following separate publications are issued annually by the Home Office : Report by each Inspector for his district. Statistical Summaries showing the number of persons em- ployed, the deaths from accidents, and the quantity of mineral raised, together with the corresponding figures for previous years. List of all the Mines in the United Kingdom. LEGISLATION AFFECTING MINES, ETC. 659 List of Record Plans deposited at the Home Office. Mineral Statistics of the United Kingdom. The last section of Part I. of the Act refers to the duties of the coroner, who cannot conclude an inquest upon the body of a person killed by a mine accident, unless due notice has been given to the Inspector of the district. As a rule the Inspector attends the inquest, and can be of much assistance to the coroner in eliciting evidence, for he will have seen the place where the accident took place, and will know whether it is likely that it has been caused by pure ill-luck or through neglect of proper precautions. Part II. of the Act contains the General Rules, and sets forth the mode of establishing Special Rules. The General Rules are a series of nineteen regulations which have to be observed in every mine. Ventilation. Rule i relates to ventilation. It prescribes that an adequate amount of ventilation shall be constantly produced, so that the various parts of the mine shall be in a fit state for working and passing therein. No standard of ventilation is laid down, nothing is said about the number of cubic feet per minute that have to be supplied, nor as to any given percentage of noxious gas rendering the ventilation " inadequate." Explosives and blasting. Rule 2 defines how explosives are to be taken into the mine, and lays down the precautions which have to be observed while they are being used. Storage under- ground is forbidden ; the mine should have a proper magazine above ground, from which explosives should be dealt out daily to the miners in small lots as required. In order to save trouble in keeping the account of the small daily doles, a subsidiary magazine is sometimes kept up, in which each gang of men has a locker. A proper attendant then serves out explosives every day from the lockers, without weighing the quantities. The explosives must be taken into the mine in a case or canister which must not contain more than four pounds. Iron and steel needles or prickers are prohibited, but the Secretary of State has power to exempt mines from this restriction if he thinks fit. Exemptions of this kind have been granted in the case of the salt mines of Cheshire. Iron and steel tamping bars may not be used for ramming in the wadding or the first part of the tamping. It is lastly illegal to pick out or bore out the tamping of a charge of powder which has missed fire. By the Slate Mines (Gunpowder) Act, 1882, the Secretary of State has power to relax the restrictions concerning explosives. This Act was passed for the convenience of workers in slate mines, who occasionally have to fire large blasts of 8, 10 or 12 pounds of powder, in order to sever a large block of slate which has not been completely released by the original shot. The powder is 660 ORE AND STONE-MINING. sometimes required on the spur of the moment, as water might fill up the crack by the time the man had made the journey to and from the surface for a supply. Many agents of slate mines are of opinion that it is safer to carry powder into the mine in the 25-pound kegs coming direct from the manufacturer than in the ordinary 4-pound canisters. Where exemptions have been granted under this Act, the dangers incident to storing these kegs of powder and opening them by candle-light are reduced as far as possible by stringent special rules. Inclined Planes and Horse Roads. Rules 3, 4, and 5 relate to signals and refuge places on inclined planes or horse roads. Shafts. In Rules 6, 7, and 8 are very important regulations concerning shafts. The sides have to be made secure, and the top of the shaft and all entrances to it have to be fenced. Descent and Ascent. The next seven rules relate to the descent into mines and ascent therefrom, whether by ladders or machinery. If ladders are used, the ladderway must be partitioned off from the winding compartment. The object of such a partition is not only to prevent men from falling into the winding compartment, but also to protect them from stones, which might drop from the bucket or skip during hoisting operations. Vertical and overhanging ladders are forbidden, and substantial platforms are required at intervals not exceeding 20 yards. The rule also says that " a ladder shall be inclined at the most convenient angle which the space in which the ladder is fixed admits." The wording is unfortunate, because it sometimes fails to secure a proper inclination for ladders; there is nothing to prevent a person from sinking too small a shaft, and then alleging want of space as an excuse, when a complaint is made to him about the great steepness of his ladders. The Belgian law is worded better, for it says that no ladder shall be inclined at an angle of less than 10 from the vertical. The only statutory enactment about man-engines is that they shall be partitioned off from the winding compartment of the shaft. We now come to ascent and descent by winding machinery. Guides and signalling apparatus are required as soon as a shaft exceeds 50 yards in depth, and a cover overhead is obligatory unless an exemption has been granted by the inspector. A single linked chain is forbidden ; the winding drum must be provided with flanges to prevent the rope from slipping off; there must be an adequate brake, and an indicator to show the position of the load in the shaft. Dressing-room. It was quite right on the part of the Legislature to make provision by Rule 16 for a changing house, or " dry," enabling the men to change their clothes in comfort, and have easy means of drying their wet underground suits ready for the next day ; but the wording might have been a little more elastic. LEGISLATION AFFECTING MINES, ETC. 661 As the law stands, a mine need not have a " dry " if fewer than thirteen persons are employed below ground ; and yet one meets with wet sinking shafts employing only ten or a dozen men, where some accommodation is desirable, and with large mines which are so dry that a changing house, as generally understood, is superfluous. Fencing Machinery. Rule 17 prescribes that all dangerous machinery must be fenced. Steam Boilers. The only statutory regulations concerning steam boilers are found in Rule 1 8, which says that every such boiler must be provided with three fittings, viz., a steam gauge, a water gauge, and a safety valve. Wilful Damage. The last Rule, No. 19, forbids the wilful damage of, or removal of fences or appliances provided for the safety of the men. In order to make the owner and agent responsible for the proper carrying out of these essential regulations, this section of the Act concludes with a very strict clause. As a rule, in this country, a man is. assumed to be innocent until he is proved guilty. In mining, it is different ; if a contravention of the Act by any person whomsoever, for instance, a workman, is proved, the owner and the agent are each made guilty of an offence and are liable to punishment, unless they can prove that they had taken all reasonable means to prevent the contravention by publishing, and to the best of their power, enforcing the rules. The Legislature has therefore taken strong means in order to render the miner's calh'ng safe. On the other hand, the owner and agent are thoroughly safeguarded by a clause, which governs the whole of the section, and says that the rules are to be observed " so far as may be reasonably practicable." Special Rules may be regarded as by-laws framed to suit the conditions of any particular district or mineral deposit; when once established with the formalities prescribed by law, they have all the power of the statute itself. They are a very useful institution, and as there are simple means of modifying them, changes can be introduced from time to time, without having to set in motion the ponderous machinery required to alter an Act of Parliament. At mines under the Metalliferous Act, special rules are not compulsory as they are under the Coal Mines Act ; but the Secretary of State can propose any rules he thinks fit to the owner of the mine, who may object and have the matter decided by arbitration. An Abstract of the Act, and a copy of the Special Rules (if any) have to be posted up in a conspicuous place at the mine, where they can be conveniently read by the workpeople. The name and address of the Inspector of the district have to be appended, so that every one may know to whom to apply in case of need. Part III. deals with penalties for offences and the technicalities 662 ORE AND STONE-MINING. relating to legal proceedings. The penalties to which a person, is liable for a breach of the Act are a maximum of 20 if he is an owner or agent, and a maximum of 2 if he is any other person ; the fine may be increased by i a day so long as the offence continues, if the offender has received notice in writing from the Inspector. For wilful neglect, endangering life and limb, a person may be sentenced to imprisonment, with or without hard labour, for a period not exceeding three months. The owner and agent cannot be prosecuted except by an Inspector, or with the consent in writing of the Secretary of State. The workman can be prosecuted by his master ; and proceedings against the men become necessary when the master finds that mere words fail to secure strict obedience to regula- tions, which is imperative in a dangerous occupation like mining. Strange to say, the clause which prevents interested magis- trates from sitting in cases under the Coal Mines Act, is omitted altogether in the Metalliferous Act. Where a penalty amounts to or exceeds half the maximum, the person convicted may appeal to a higher court. The last Mining Act, that of 1891. was passed in order to correct a curious omission in the old statute of 1872, which failed to define the Court of Summary Jurisdiction in the Isle of Man before which proceedings could be taken. Having thus briefly explained the statute by which the working of many ore and stone mines is regulated, we must now pass on to the Coal Mines Regulation Act, 1887, which governs mines of stratified ironstone, shale and fireclay, as well as collieries. Com- pared with coal, it is true that these minerals are of minor import- ance; but as their total output amounts to more than 12,000,000 tons annually, of which 7,000,000 tons are ironstone, it is evident that even the ore miner should be acquainted with the requirements of this statute. It presents many points of resemblance with the Metalliferous Mines Regulation Act, but it is far more elaborate in its details ; to save repetition it will be best to dwell more especially upon the points in which it differs from the Act which we have just been discussing. In Part I. the principal new features are : Hours of Labour. Regulation of the hours of labour of boys and females employed above ground. Check Weigher. If the majority of the men wish it, they may appoint a check weigher to see that the weighing is done correctly, and that deductions are made fairly. Prohibition of Single Shafts. The object is to provide two means of egress in case of accident ; certain mines may be exempted from this provision. Division of Mine into Parts. Under certain circumstances each part must be treated as a separate mine. LEGISLATION AFFECTING MINES, ETC. 663 Certificated Managers. This is one striking difference between the Metalliferous Act and the Coal Act. Under the former a per- son without any pretensions to professional qualifications may be placed in charge of a mine ; under the latter every mine employ- ing more than thirty persons below ground must have a certificated manager. In order to obtain a certificate the candidate must have had practical experience in a mine for at least five years, and must then pass an examination. For the purpose of granting certificates, boards for examination have been appointed in each of the twelve districts into which the kingdom is divided for the purposes of the Coal Mines Act. Unfortunately the statute makes no provision for securing uniformity in the examinations. Even the limits of age are not the same ; but, nevertheless, a certifi- cate when once obtained, is good for any part of the kingdom. Returns. The Annual Return which has to be furnished under the Coal Mines Act not only gives the output of the mine and the number of persons employed, but also supplies details con- cerning the mode of ventilation ; the part relating to the quantity of mineral wrought cannot be published, save by consent of the person making it, or of the owner of the mine. This restriction prevents the publication of such details as appear in the " Mineral Statistics " in the case of mines under the Metalliferous Act. Inquests. At coroners' inquests, a relative of the person killed, the owner, agent, or manager of the mine in which the accident happened, and any person appointed by the order in writing of the majority of the workmen employed in the mine may attend -and examine witnesses. No such power is conceded under the Metalliferous Act. Part II., as in the other Act, contains the General Rules, and regulates the establishment of Special Rules, which are compul- sory instead of being voluntary. The General Rules are 38 in number, or twice as numerous as those in the sister Act. They may be passed in review very briefly .as follows : Ventilation (i, 2, 3). Amount of ventilation to be adequate; quantity of air to be measured monthly ; special airway to carry the return current clear of the ventilating furnace ; ventilating machines to be placed where they will not be injured by explo- sions. Inspections by Officials (4, 5). The working place has to be inspected before men begin their work, and during the progress of their work. Machinery must be inspected daily and shafts weekly. Fencing (6). Dangerous places must be fenced off. Withdrawal of Men (7). Men must be withdrawn from dangerous places. Safety-Lamps (8, 9, 10, n). Use, construction, and examina- tion of safety-lamps. Situation of lamp stations. 664 OEE AND STONE-MINING. Explosives (12). Prohibition of iron and steel tools for charging holes, and special precautions for blasting in mines where fire- damp has been noticed, or which are dry and dusty. Advance Boreholes (13). These are made compulsory when approaching water. Signalling and Man- Holes for Travelling Roads (14, 15, 16). Very like the rules in the Metalliferous Act. Dimensions of Travelling Roads (17). Here we find that the comfort of animals is not forgotten, for roads must be big enough to allow the horses or ponies to pass along without rubbing. Fencing of Shafts (18, 19). Very like the rules in the Metalli- ferous Act. Securing of Shafts (20). Identical with the rule in the Metalli- ferous Act. Securing of Travelling Roads (21). This very useful rule, though contained in the Coal Mines Act of 1872, was not incor- porated with the Metalliferous Act. Timber (22). Props have to be provided at a convenient place in the mine. Descent and Ascent (23 to 30). In addition to the regulations found in the Metalliferous Act, there is a rule preventing a speed of more than three miles an hour after the cage has reached a certain point in the shaft, when the winding apparatus is not pro- vided with some automatic contrivance for preventing overwind- ing. Men may use the downcast shaft for descent and ascent if they wish to do so. No mention is made of ladders or man- engines, which are not in use at mines under the Coal Mines Act. Fencing Machinery (31). Identical with the Rule in the Metalliferous Act. Fittings for Steam Boilers (32). Very like the Rule " in the Metalliferous Act. Barometer and Thermometer (33). These have to be placed in a conspicuous position at the mine. Ambulances (34). As suffering may be mitigated or life saved by having proper appliances at hand for relieving and moving injured men, the statute requires that stretchers, splints, and bandages shall be kept ready for immediate use. Wilful Damage to Fences, or Appliances for Safety (35). Very like the rule in the Metalliferous Act. Observance of Directions (36). Men are bound to obey direc- tions with respect to working, given with a view to comply with the Act or Special Rules. Books recording Results of Inspections (37). These have to be kept at the office of the mine. Periodical Inspection on Behalf of Workmen (38). The men may appoint two practical working miners to inspect the mine, at their own cost, once a month. The result of the inspection has to be recorded in a book, and if the report states the existence or LEGISLATION AFFECTING MINES, ETC. 665 apprehended existence of any danger, the inspector has to be informed of it. Experienced Workmen (39). Men are not allowed to work alone in getting coal or ironstone at the face of the workings unless they have had two years' experience in or about the face of the workings of a mine. Part III. relates mainly to legal proceedings, and the only special point to which attention need be called is the section which prohibits persons interested in mines, or their near relations, from sitting on the Bench and adjudicating upon breaches of the Act. 4. Sundry Special Statutes. It might be thought that statutes framed for regulating mines would contain all that the law requires for their safe and proper working ; but such is not the case in this country. Miners and workers of open pits are often affected by one or more of the following Acts of Parliament, which are arranged in alphabetical order : Alkali, &c., Works Regulation Acts, 1881 and 1892 (44 & 45 Viet. c. 37, and 55 and 56 Viet. c. 30). Boiler Explosions Acts, 1882 and 1890 (45 and 46 Viet. c. 22, and 53 and 54 Viet. c. 35). Brine Pumping (Compensation for Subsidence) Act, 1891 (54 and 55 Viet. c. 40). Elementary Education Acts, 1870 to 1891 (33 and 34 Viet. c. 75 ; 38 and 39 Viet. c. 79, and 43 and 44 Viet. c. 23 ; 53 and 54 Viet. c. 22 ; 54 and 55 Viet. c. 56). Employers' Liability Act, 1880 (43 and 44 Viet. c. 42). Explosives Act, 1875 (38 Viet. c. 17). Factory and Workshops Acts, 1878 and 1891 (41 and 42 Viet. c. 1 6, and 54 and 55 Viet. c. 75). Quarry Fencing Act, 1887 (50 and 51 Viet. c. 19). Rivers Pollution Prevention Act, 1876 (39 and 40 Viet. c. 75). Stannaries Act, 1887 (50 and 51 Viet. c. 43). Truck Acts, 1831 and 1887 (i and 2 William IV. c. 37, and 50 and 51 Viet. c. 46). The Alkali Acts were passed with a view to prevent noxious and offensive gases produced in manufacturing processes from being discharged into the atmosphere, or at all events to reduce their escape to a minimum. These Acts apply to a few mineral workings viz : (1) Salt works in which brine is being evaporated for the manufac- ture of salt. (2) Cement works in which clays are made into cement. (3) Tin and copper mines where ores containing arsenic are being roasted. (4) Collieries where tar and ammoniacal liquor, obtained from the waste gases of coke ovens, are being treated ; the former is dis- tilled for the production of paraffin and burning oils, the latter is made into sulphate of ammonia. 666 ORE AND STONE-MINING. The Acts are administered by Inspectors under the Local Government Board. The Boiler Explosions Acts compel the owner of a mine to report to the Board of Trade any explosion of a steam boiler, which may happen at his works whether above or below ground. The Board of Trade officials can then make a preliminary investigation into the cause of the explosion, and afterwards hold a formal inquiry if they think fit. The Court holding this formal inquiry is usually composed of two Commissioners specially appointed by the Board of Trade, who are endowed by the Acts with ample power for punishing the owners and agents of mines, if an explosion has in any way been caused by their neglect. The Commissioners cannot inflict a " fine " in a criminal sense, such as is imposed by a Court of Summary Jurisdiction at proceedings taken under the Mines Regulation Acts ; but, where neglect has been proved, the responsible persons have been ordered to pay as much as ^100 or ;i2o to the solicitor of the Board of Trade "towards the costs and expenses of the investigation," which practically comes to the same thing. Under the Mines Regulation Acts the mine- owner can appeal to a superior court and have the matter re-heard ; but the decision of the Commissioners under the Boiler Explosions Act is final and not subject to review. The Brine Pumping Act provides compensation for owners of property who suffer through the subsidence of the ground caused by the pumping of brine. The working of the Act is controlled by the Local Government Board. The Elementary Education Acts make provision for the educa- tion of children : they prohibit absolutely the employment of children below the age of 10, and do not permit the employment of children below the age of 13 unless they have reached the standard of education fixed by the by-laws in force in the district. Children between 13 and 14 are allowed to work if they can produce a certificate of proficiency or of previous due attend - ance at school. After they have attained the age of 14, they are no longer " children " within the meaning of the Education Acts. The Employers' Liability Act extends and regulates the liability of employers to make compensation for personal injuries suffered by workmen in their service. Until this Act was passed a work- man could not claim compensation for injuries due to the neglect of a fellow-servant. The statute of 1880 has broken down this doctrine of " common employment " to a certain extent, and has made the master liable if the injury was caused by the negligence of a foreman or person entrusted with superintendence ; but it does not make the master liable for the negligence of all the fellow-servants. The Explosives Act regulates the manner in which licences for storing explosives are obtained, the construction and maintenance of the magazines at mines, the subdivision of the trade packages, LEGISLATION AFFECTING MINES, ETC. 667 ;and the delivery to the men. The Act is enforced by Inspectors under the Home Department, and also by the Police on behalf of the Local Authorities. The two Factory and Workshop Acts, which are enforced by Inspectors serving under the Home Department, apply to certain quarries, and to surface works at mines under the Metalliferous Act, such as the dressing sheds. They contain provisions for promoting the health and safety of the workpeople, and regulate the hours of employment of women, young persons, and children. It is probable that all quarries will eventually be placed under the supervision of the Inspectors of Mines. The object of the Quarry Fencing Act is evident from its title, ,nd it is the business of the Local Authorities to see it enforced. By section 5 of the Rivers Pollution Prevention Act, the mine- owner is prohibited from discharging into streams any solid matter in such quantity as to prejudicially interfere with its flow, or any poisonous, noxious or polluting solid or liquid matter, unless he proves that he is using the best practicable and reason- ably available means to render such matter harmless. The administration of this law rests with the Sanitary Authority of the district, and in this, as in other matters, the work of the .Sanitary Authorities is supervised by Inspectors acting under the Local Government Board. The large amount of refuse which is produced in extracting some minerals from their ores, makes the task of getting rid of it, without polluting the rivers, far from easy; and the miner often incurs the wrath of the fisherman, who stirs up the Sanitary Authorities or River Conservancy Boards into action. Coarse waste, such as comes from jigging the larger sizes of the crushed rock, can always be made into heaps upon the land ; but the fine slimes, whether coming from stamping or other dressing processes, are carried away in suspension, and turn a bright trout stream into a muddy drain, or are spread over the meadows in flood time, to the annoyance of the farmer. These evils may be greatly lessened by providing large pits into which the water from the mine is allowed to settle, and so deposit much of the solid matter which it contains in suspension. Effective filtering pools have been made in Germany from the coarse refuse (skimpings) from the jigs. It is tipped so as to form high banks enclosing a rectangular area, into which the muddy water from the " floors" is led, and allowed to form a large pool. Some of the solid matter settles down on the bed of the pool, as it would do in any ordinary pond, and the rest is deposited in the bank itself, as it permeates through the tortuous passages left between the little fragments of stone. In time, the inner .sides of the banks become somewhat choked with slime and the percolation no longer proceeds so rapidly; this state of things is remedied by letting out the water during a holiday, and scraping 668 ORE AND STONE-MINING. down the sides, so as to expose a fresh unchoked surface to the slimy water. Old heaps of mine refuse can be utilised in a similar manner ; the stream of dirty water led into the top will escape fairly clear at the bottom. As soon as one part of the heap becomes choked with slime, the out-fall of the " floors " must be shifted to another part of the bank. The Stannaries Act, 1887, was passed to remedy certain evils of which miners and shareholders complained at mines in Cornwall and Devon. The Act extends only to metalliferous mines and tin streaming works i.e., works where tin ore is extracted from the dirty water flowing away from mines, within the Stannaries. The miner now has a first charge upon the property of a mining company, and is less likely to lose his earnings when a mine is stopped for want of funds, than he was some years ago. Surface hands have to be paid once a fortnight; miners employed by contract below ground are entitled to claim " subsist " once a fortnight that is to say, a payment on account equal to the esti- mated amount of their earnings. Money deducted for sick and accident funds has to be accounted for, and a copy of the balance- sheet must be posted up in the " dry " or changing house. The miners have the power to appoint a check-weigher. Meetings of the shareholders of every " cost book " mine must be held at least once in every sixteen weeks. Tools and materials supplied to the miners have to be charged as nearly as possible at the market prices. Other regulations relate to the settlement of disputes,, mortgages, relinquishment of shares, and registration of companies, A copy of the Act has to be kept posted up in the smith's shop and in the changing house of every mine. The object of the Truck Acts is to prevent the mine owner from making a profit out of the tools and materials which he supplies to his men ; but he has a right to make deductions from the men's- wages for medicine, medical attendance, materials and tools, pro- vided that they agree in writing to this system. As a rule the- men would sooner obtain the necessaries for their work in this way, than purchase them at the shops in the district. The Truck Acts have to be enforced at mines by the Inspectors under the Mining Acts. From the foregoing pages it is very evident that the manager of a mine in this country may have to make himself well acquainted with a considerable number of legal enactments, mostly of recent date, if he desires, as he should do, to carry on his work in strict accordance with the law. 669 CHAPTER XYI. CONDITION OF THE MINER. Clothing : hat, boots, jacket Housing : barracks, cottages, changing houses Education Sickness Thrifc Recreation. IT is perfectly impossible to do justice to the importance of this subject in the few pages that can be devoted to it in a general text-book; but the following remarks will serve to call the attention of the student to matters with which he may have to deal when he enters into the active duties of his profession, and becomes either an employer of labour himself, or the agent of a mining company. I propose to treat the subject under the following heads : 1. Clothing. 2. Housing. 3. Education. 4. Sickness, Thrift. Recreation. I i. CLOTHING. At the surface we clothe ourselves in order to keep our bodies warm, and to protect ourselves from the sun and rain ; in the mine the conditions are totally different, and the clothing may be altered accordingly. On the whole the tem- perature is more uniform than it is above ground ; the miner in most cases finds his working-place warmer in winter and cooler in summer than it would be if he were working in the fields in the neighbourhood. It is the exception to have the temperature below 32 F. in mines even in winter. Occasionally in this country a freezing wind rushing down the shaft will coat the ladders with ice and make climbing unpleasant and risky, and where the climate is cold and the openings to the surface large, the effects of frost are felt far deeper than they are here. The sinkings through alluvial deposits in Siberia are instances of great cold in mines; and even where the operations are more truly underground the temperature is sometimes below freezing point. This is the case at the Algachi silver mine.* The other extreme was found in the workings on the Comstock * Kennan, " In East-Siberian Silver Mines," The Century Magazine, vol. xxxviii., 1889, p. 803. 670 ORE AND STONE-MINING. lode.* In the year 1868, when a depth of 1000 to 1200 feet had been reached, the heat in some drifts was becoming unbearable. In August 1868 at a depth of 1 100 feet in the Chollar-Potosi Mine, the temperature was 100 F. (37*7 C.),and in the lower level of the Hale and Norcross 1 10 F. (43*3 C.) In June 1870 at the goo-foot level of the Yellow Jacket Mine the temperature was 97F. (36-1 C.) at a point only 300 feet from the shaft, although blowers were at work. The highest temperatures were observed when long levels were driven without any ventilating shafts or winzes. As soon as a proper air-current was established the temperature usually sank rapidly. Thus the thermometer stood at 130 to 140 F. (54 to 60 C.) in a drift at the i85o-foot level of the Bullion Mine, but when connection was made with another shaft the thermometer went down to 100 F. (37*7 C.) The miners working in the hot levels were supplied with ice, which was sent down by the ton. Their average daily consumption in the hottest parts of the California and Consolidated mines during the summer of 1878 was 95 pounds of ice per man, and they would commonly drink as much as three gallons of water in the shift of eight hours. It was not only the air of the mine which was hot, the water was even hotter. The spring in the Savage mine had a tempera- ture of no less than 157 F. (69*4 C.), and the incline was filled with scalding vapour. Up to the end of 1877 * ne highest recorded temperature of the water was 154 F. (67*7 C.) ; but since then an increase in the water temperature to i7oF. (76*6 C.) has been noted. The Comstock mines are the hottest in the world. At Dolcoath,t the largest and deepest tin mine in Cornwall, the temperature of the water issuing from the rock in the lowest workings is nearly 100 F. (37'7 C.) and that of the air 96 F. (35-5 C.) The bottom level is now 2424 feet vertically below the surface. In the adjacent Cook's Kitchen mine, which approaches its neighbour in depth, the air in the end of the 394-fathom level, at no great distance from a winze, will raise the thermometer to 95 F. (35 C.), whilst in the ends of the 420-fathom level, driven out but a very short distance from the bottom of the shaft, the temperature of the air is 100 F. (37*7 C.) and that of the water slightly higher. Some workings for copper at St. Day, Cornwall, were even hotter, but the mine has long been abandoned. The submarine mines near the Land's End are also warm, and air- temperatures above 90 F. (32 C.) are often recorded. In Corn- wall, as in Nevada, the hottest places are " ends " or " rises ''" before they are " holed " to other workings. When once a com- munication has been effected and a through draught established, the rock-faces cool down quickly. * Lord, " Comstock Mining and Miners," Monographs U.S. Geol. Survey,. Washington, 1883, p. 391 et seq. t MS. information from Mr. W. Thomas, F.G.S., 1893. CONDITION OF THE MINER. 671 With the temperatures just mentioned, it is evident that the miner requires very little clothing, but even when the air is comfortably cool, he often strips himself to the waist, in order to secure that freedom of limb which so much conduces to the efficiency of muscular labour. In some cases, such as in the salt mines of this country, the working-places are very comfortable ; indeed the miner is better off than the labourer at the surface. He is not exposed to the burning sun, cutting winds or torrents of rain ; but he works in a cool and pleasant atmosphere, varying little in temperature, and he has not to assume a cramped posture. On the other hand, the miner's working- pi ace may be moist and steaming, or hot, dry and dusty, or cold, wet and draughty ; and on reaching the surface in a cage, he may have to face an icy blast after leaving a tropical atmosphere only a minute or two before. Where circumstances are so unlike, the clothing worn in the mine must necessarily vary, to say nothing of differences in attire due to the habits of the people. The South African native, content with a waist-cloth above ground, requires nothing more when he descends into the diamond mines, whilst the white man, true to his bringing up, needs, or thinks he needs, more abundant vestments. Hat. Some of the clothing used below ground has to serve a different purpose to that required of it at the surface. One object of the miner's hat is to preserve his head from blows, as he walks along low and rugged tunnels, and from falls of stones while work- ing in shafts. The Cornishman wears a hat made of felt and rosin, shaped like an ordinary " pot hat " of everyday life. It is cheap and durable, and affords admirable protection against hard raps ; but it is not ventilated, and it is heavy, weighing about one pound, or four times as much as an ordinary felt hat. Under it the Cornishman wears a cap of calico or linen, which often con- stitutes the headgear in the working place itself, whilst 'the hard hat is donned in going to and from the surface. A few gimlet holes improve the Cornish hat, by affording a little vent for the perspiration given off so freely when climbing ladders in warm shafts. The Cornish hat is serviceable as the brim keeps the neck dry, and in sinking very wet shafts a waterproof flap can be added, so as to increase the amount of protection. Lastly, the lump of clay used as a candle-holder can be easily and safely stuck upon the hat, leaving the miner both hands free when he is climbing about the workings by rope, chain or ladder. The British miner, working upon seams of stratified ironstone, affects a leathern cap, which he wears with the small peak turned towards the back. It is far lighter than the Cornish hat, but it is not capable of resisting so hard a blow. In France a leathern hat, in shape like the Cornishman's, 672 ORE AND STONE-MINING. is common. It is made of thick solid leather, and is therefore very strong and durable, but it is heavy and expensive. In some parts of Germany the miner wears a brimless hat, something like a busby, made of loose-textured felt, thick enough to prevent a tolerably hard knock from doing any harm, and yet porous enough to admit the passage of perspiration. In sunless workings a brim is not required for guarding the eyes, and in dry mines the German hat with an undercap of linen forms a very suit- able head covering. It is light, weighing only about half a pound, and it can be folded, which is an advantage if one is travelling. On the other hand, its porosity and its want of a brim render it unfitted for very wet places, and it cannot be used for carrying the candle in the same way as the Cornish hat. The hat of the Mansfeld copper miner is made of thick black felt and weighs half a pound ; it has a broad brim which is turned up in front and covered with leather. A piece of wire sewn on under the leather serves as a hook for carrying the lamp on the head, though, now that the shafts are mostly provided with cages, there is little ladder work to make this necessary. The felt is thick enough to save the head if struck, and the brim protects the neck from drops of water. It is a light, comfortable and cheap hat. In sinking oil wells in Roumania, the mirier adopts a conical hat, shaped like that of the Chinaman, but made of tinplate, which serves to keep off the drops of water and petroleum. Looking at the number of accidents from falls of roof, to say nothing of accidents from things falling down shafts, the nature of the head-gear adopted by the miner is not without importance. It is especially necessary that shaft-sinkers should be careful to have suitable hats. An ideal hat would be light, but strong, welJ- ventilated, and with brim enough to prevent water from running down the neck. Boots. Turning to the other extremity of the body, it is fre- quently noticed that the Cornishman, though careful about his head, pays very little attention to his feet. He often has to walk through wet levels, and knowing that he cannot reach his working-place dry-shod, he is quite content with any dilapidated foot-gear. Unfortunately this carelessness is sometimes the cause of accidents, for men have been known to slip from ladders from wearing shoes which did not give them a proper foothold. In some of the Welsh ore mines the clog is very commonly worn ; it is a boot with wooden soles and leather " uppers." The sole is protected from too rapid wear by irons at the bottom and sides. Many miners like clogs, as the wooden sole is warmer than leather, and consider that they are less likely to slip than ordinary boots or shoes in climbing up and down ladders or steep "stopes." I can well imagine that the stiff wooden sole gave a better foothold on the vertical ladders of the Flint- shire mines years ago than yielding leather. The clog has tht CONDITION OF THE MINER. 673 further merit of cheapness, but the unbending sole renders it therefore less comfortable than the ordinary foot-gear for much walking. Men who use clogs below ground often walk to and from the mines in leathern boots or shoes. The Festiniog " rockman," whose working-place lies among smooth surfaces of slate, trusts to a strong laced boot well shod with nails to prevent his slipping, while he climbs about chain in hand. Another reason for the strong foot-covering is the fact that the fragments of rock are often sharp and cutting. Many miners in France still wear the clumsy but cheap wooden shoe or "sabot," whilst in Spain they have sandals made of esparto grass. These cost only $d. or 3^. per pair, and last from three weeks to a month. Lastly, when we travel further afield, we find the hardy miner going barefoot, provided by nature alone with a tongh outer tegument, which gives him a better hold on rock or ladder than any which art can furnish. Jacket. Little need be said about the clothing of the worker at the surface, save that where he is engaged near machinery it is advisable that the jacket should fit closely. Accidents have happened from loose clothing being blown on to revolving gearing or shafting, which could not be stopped until the unfortunate workman had been drawn in and mangled. As has been already explained,, it is necessary from time to time to clean out the flues in which arsenic has collected from the calcination of ores containing mispickel. Under the Special Rules in force at some of the Cornish mines, the owner has to provide suitable clothing for this work ; probably the best is a combination suit consisting of jacket and trousers in one garment, such as is used for going into boilers. The legs of the trousers should be tied round the ankles, and the sleeves round the wrists, in order to prevent any particles of arsenic from finding their way to the skin and so doing mischief. 2. HOUSING. It may or may not fall to the lot of the mine-owner to provide dwellings for some or all of his workmen, but in any case it is his duty to interest himself in the question of the living accommodation for them and their families. Even if he is not moved by considerations of a humanitarian nature, as he certainly ought to be, the mine-owner must recognise the fact that it does not answer commercially to let his men fall sick, become prematurely unfit for work or die at an early age j nor does it pay to have the working staff constantly changing. A valuable horse is put into a good stable, is well tended and not overworked, if the master wishes to derive as much profit as possible from it ; and it cannot be expected that the best results will be got from the miner's labour, unless he is treated with at least as much con- sideration as the lower animal. Therefore on the score of profit as well as upon the score of humanity, the mine-owner should insist upon proper dwellings being available for his men. 2 u 674 ORE AND STONE-MINING. When mining is carried on in the midst of a fairly populous district, private enterprise may often be relied on for providing suitable cottages, nevertheless even here the mine-owner may do good by calling the attention of the local authorities to insanitary dwellings or cases of overcrowding. It frequently happens, however, that mines are worked in out-of-the-way places, where, at all events in the early days of the enterprise, there is a total absence or utter inadequacy of accommodation for the workpeople. The mine-owner is then obliged to take upon his own shoulders the burden of providing dwellings. Two classes may be erected : (1) Barracks, which serve for unmarried men, or for married men whose homes are not within the reach of a daily walk ; (2) Cottages for married couples and their children. Barracks. Excellent examples of barracks are found, for instance, at the Mechernich lead and the Mansfeld copper mines, owned by two enlightened and prosperous companies. The large workmen's hotel at Mechernich is capable of accommodating about 400 men. The workmen are perfectly free to do as they like, as regards living in the barracks or not ; but if they do live there, they must conform to the regulations. The cost of lodging is yd. per week ; for this a man gets a comfortable bed with a spring mattress, and clean sheets and blankets. The beds are such as I would sleep in without hesi- tation. The space allowed in the bedrooms is 400 cubic feet per man, and in winter the rooms are warmed by hot air. They are kept scrupulously clean, and the men are obliged to change their working clothes as soon as they come in, and put on other suits. The men can be supplied with their meals at stated hours in the large dining hall at low prices, and boiling water is always ready for them gratis, so they can make coffee from their own store if they like. The dining hall has a tiled floor, and the tables are scrubbed until they are exquisitely clean. The sanitary conveniences are ample and well kept, and the men can have warm shower-baths free of cost. The mental comforts are not forgotten. There is a reading- room, with newspapers, which is open after working hours, and a library, from which the men can borrow books. At the Mansfeld copper mines the company have provided no less than nine barracks, capable of accommodating 2268 men and 48 females. The barracks at Eisleben, which will house 350 men, are represented in Figs. 700 and 701, taken from the long and careful report of Oberbergrath Taeglichsbeck.* The house is a three-storey brick building, with bedrooms for nine, ten, or eleven men each. In accordance with official regulations, there is an air * " Die Wohnungsverhaltnisse der Berg- und Salinenarbeiter im Ober- bergamtsbezirke Halle, einschliesslich der Mansf elder Hiittenarbeiter," Zeitsckr.f. B.- H.- u. S.-Wesen im Preuss. Staate, vol. xl. 1892, p. 44. CONDITION OF THE MINER, FIG. 700. 675 Front Elevation. FIG. 701. 5METRES Ground Plan. SCALE 10 20 METRES 25 10 FEET 20 30 40 50 60 70 FEET80 676 ORE AND STONE-MINING. space of 350 to 400 cubic feet (10 to n cubic metres) per man, The rooms are heated with hot air in winter, and there is a large dining-hall adjoining the kitchen, in a separate building, connected with the dormitories by a covered way. This building cost ^9370, including a house for the steward, who superintends everything, and laying on water. The barracks are built in airy situations, and are mostly surrounded by gardens. They are provided with all sorts of conveniences, baths, reading-rooms, libraries, skittle-alleys, &c. The men lodging at the barracks pay the fixed tariff of gd. per day for their board ; for breakfast each man gets J litre of coffee and milk ; for dinner ri litre (2 pints) of thick soup or vege- tables, with I kil. (4! ozs.) of beef or pork, weighed after cooking and without bone ; and for supper if litres (3 pints) of thick soup, made with suet, or coffee and milk. In addition to this, he receives weekly two loaves of bread, each weighing 3 kil. (6 '6 Ibs.), 5 kil. (^ Ib.) of butter, and the same amount of fat. Those who prefer it can take ham, sausage, or bacon instead of the butter and fat. For lodgings, lights, and firing, each boarder has to pay o'6d. ($pf.) per day in summer and o'gd. (8 pf.) per day in winter. Order and cleanliness are enforced by a code of regulations, which have to be strictly observed by all the boarders. The rules prescribed for the barracks at Mansfeld, Stassfurt, &c., are given at length by Taeglichsbeck.* The barrack system is also found in this country, especially in North Wales, but not on so large or so sumptuous a scale as in Germany. In Wales the men often sleep two in a bed, upon straw mattresses; and, as a rule, there is not a separate eating-room, nor are there any arrangements for supplying meals. One sees the men arrive on a Monday morning, carrying their provisions for the week on their backs ; and they cook their food themselves by the common fire of the eating and sleeping apartment. Often there is no person provided for keeping the rooms clean, and the disorder and discomfort are consequently great. Sheer ignorance is sometimes the cause of some of the evils. I have seen bunks prepared for 2 1 men in a room without a window or a chimney, and containing only 2200 cubic feet of space i.e., about one-third of the smallest amount which sanitarians would consider requisite. If mining companies build barracks, they should employ some one acquainted with the rudiments of sanitary science to design them ; the eating-room should be separate from the dormitories, and the house should be kept clean and tidy. The most extensive development of the barrack system in any British possessions is at the Kimberley diamond mines, where the particular exigencies of the case have led to a modification which is not found elsewhere. One great diificulty of diamond * Op. cit. p. 170. CONDITION OF THE MINER. 677 mining in the early days was the prevention of thefts of valuable stones. Gems of great value can be so easily secreted about the person, or indeed swallowed, that the mine owner could be, and was, robbed with little fear of detection. It is true that since the passing of the Illicit Diamond Act, the disposal of stolen diamonds has become more difficult, but the protection afforded by this statute does not entirely suffice. The plan now adopted with the native miners is to confine them for the length of their contract, often three months, and not allow them on any pretext to leave the company's premises. They go straight from their barracks to the mine by a securely enclosed way, and return to them as soon as work is over. The barracks consist of one-storey buildings, made of corrugated iron, arranged so as to form the four sides of a large square, and divided into rooms holding about twenty natives each. The " compound," * as it is called, often covers several acres ; and it is surrounded by a high iron fence 10 feet from the building. The natives can procure all the necessaries of life from a store within the compound, whilst food and water are supplied free. A large swimming bath enables them to enjoy a dip when- ever they like. If perchance a man falls ill, he is taken to a hospital, also belonging to the company. Of course, this system would not find favour with European miners, who would resent the enforced confinement and regard it as an irksome imprisonment ; but the native, with fewer wants, is quite content to put up with the temporary loss of liberty for the sake of getting good wages. Cottages. Enough has been said about barracks, and we may now pass on to cottages for families. At many of the collieries of this and other countries, great attention has been paid to the erection of workmen's villages, and a large amoum; of capital has been sunk in providing comfortable and convenient dwellings. It is an advantage to the mine-owner to have his men on the spot, coming to their work without the fatigue of a long walk ; and it is a benefit to the man to have his home within easy reach. When, therefore, the preliminary explorations and workings have revealed the existence of enough mineral to supply a mine for a number of years, a company is thoroughly justified in spending money upon houses. Figures 702 to 705 represent the type of miner's cottage lately erected by Mr. Emerson Bainbridge for the Bolsover Collieries in Nottinghamshire. It will be seen that each cottage has a good living-room and scullery on the ground floor, two good bedrooms on the first floor, and an attic above. Many a workman, however, would rather be his own landlord, and not feel the restraint of living in a cottage belonging to the company, because he may have to quit it if he goes to work at * Second Annual Report of the De Beers Consolidated Mines, Limited, for the year ended March 1890, p. 23. 678 ORE AND STONE-MINING. another mine, or because he feels the natural ambition of wishing- to own a house himself. In order to encourage this very laudable- object, mining companies often make it easy for the workman to buy his cottage by small instalments, and they thus gather around their mines a number of small householders, who are less likely to encourage disturbances than men who have no special interest in the preservation of order. To the workman there are advantages- FIG. 702. FIG. 703. CROUrtD PLM as well as disadvantages ; if the cottage belongs to him, he has a feeling of independence, and he does not mind spending money to embellish or improve it, which he would not do if it were the pro- perty of somebody else. The purchase may be a wise and profitable one, if he feels pretty sure that he is going to spend all his days in one place ; but this fixedness to one district cannot always be assured or advised. Wages may be better in an adjoining county or in some foreign land, mining may decline at home or entirely cease, and a move may become a necessity, with no chance of selling the cottage property. Under such circumstances the earnings spent in buying a cottage will have been badly invested. CONDITION OF THE MINER. 679 It also happens that during a period of high wages, a man is tempted to arrange for the purchase of his house with one of the numerous building societies, and he agrees, for instance, to pay i per month for ten years, at the end of that time becoming the owner of a house worth ,120. If his wages are ^7 a month he can manage the monthly instalments without difficulty; but let wages drop to ^5, and he will find it far less easy to keep up his payments. As an example of the manner in which workpeople are housed, I will again extract some figures from Taeglichsbeck's report.* For the Halle district he gives the following numbers and pro- portions : - Kind of Dwelling-house and Percentage of the Total Number of Persons. Rent free, but Eent reckoned as part of Wages. Living in their own Houses. Living in hired Houses. Living in Barracks, &c. Workmen. Private works (40,372 persons) Government works (3274 persons) . Officials. Private works (1196 persons) Government works (122 persons) . o-53% 0-36% 45-82% 7377% 2r85% 27-92% 17-23% 9-84% 70" II % 71-14% 36-95% I6'39% 7-51% 0-58% He further shows that 25 per cent, of the persons employed at the Mansf eld copper mines are living in their own houses, of which nearly one quarter have been purchased with the assistance of the Company. Before concluding this subject of housing, a word may be said about the " dries," or changing houses, which have to be provided at mines under the Metalliferous Act, when more than twelve persons are employed below ground. Such a house is very necessary when the men come up wet and dirty, and often soaked with perspiration from working in hot places or from climbing long runs of ladders. They then change all their clothes, and leave them to be dried ready for use on the following day. One of the best modes of heating a " dry " is by steam ; the shell of an old boiler is placed along the centre of the house and is supplied with steam from any convenient source. Owing to the large surface of the shell the room is speedily heated, and the clothes hung about it are quickly dried. The water condensing from the steam may be drawn off by a cock and used for washing purposes. Figs. 706 and 707 represent the changing house erected at Levant Mine in Cornwall by Mr. Eustice, which has the advantage of being put into communication with the man-engine shaft by a passage and staircase, so that the men stand no risk of * Op. cit. p. 7. 68o ORE AND STONE-MINING. CONDITION OF THE MINER. 681 exposure to the fierce breezes coming straight off the Atlantic, which might sometimes be trying after the underground warmth. It is heated by rows of hot-water pipes. The floor of the " dry " should be made of cement and not of boards, to permit the application of the hose for washing it. Benches and lockers should be removable in order to facilitate the cleaning, which is frequently necessary, considering the amount of dirt which cannot fail to accumulate in such a place. A wooden floor has the disadvantage that the boards are sure to shrink under the constant warmth, and when once full of FIG. 708. gaping chinks it can never be effectually cleaned ; besides, there is the danger from fire, either from matches left carelessly about or from the men smoking in a place where the wood gets as dry as tinder. The walls should be whitewashed at regular and frequent intervals, in order to keep the place thoroughly sweet. It is not difficult to give the miner the luxury of a shower- bath at a small cost, and it seems to me far better that the miner should change and perform all necessary ablutions at the mine, than go home in his underground clothes, and depend upon the resources of his cottage for washing himself and drying his working apparel. At the Anzin collieries, in the North of France, a large number of shower-baths (Fig. 708), are provided at the different shafts, so 682 ORE AND STONE-MINING. that the men have not to wait for their turn. The Anzin arrange- ments are excellent, and might be copied with advantage at some of our mines. 3. EDUCATION. The school education may be of two kinds, general and technical. In this and other countries, where the primary education is free, the mine-owner need not concern himself with providing schools and teachers ; but where the State does not take this paternal care of the rising generation, a certain responsibility for the young is often felt by the shareholders of the mining companies, and they endeavour to equip the children of their workmen, at all events, with the three R/s. For carrying on mining, it is not sufficient merely to provide strong bones and well-developed muscles; there must also be brains, or, in other words, no matter how good the miners are, their work must be directed by trained engineers and competent foremen. The latter may well be recruited from among the actual working men, who should have some general knowledge of science and some special training in the various branches of their pro- fession. This scientific and technical training is frequently provided by the large foreign mining companies at their own expense. The best of the young men attend classes out of working hours, and thus manage to carry on their lecture-room teaching hand in hand with the practical instruction which they are acquiring in the mine itself. In this country the education of the young miner is largely aided by classes held in the evenings, under the auspices of the Science and Art Department, the City and Guilds of London Institute, and some of the County Councils. The energetic and ambitious workman can nowadays obtain instruction in mathe- matics, mechanics, chemistry, physics, geology, the principles of mining, ore-dressing, assaying and mine-surveying in any large town and often in outlying villages. To those preparing to pass the examination for a certificate under the Coal Mines Act, these classes are very valuable. The success of local schools and classes depends a good deal upon the attitude assumed by the managers of mines in the neighbourhood. If educational work is pooh-poohed by the masters, the men follow suit and the teaching languishes. On the other hand, if the head-piece of the school is one of the chief mining engineers of the district, pupils flock to the lecture-rooms and laboratories, and success is almost a certainty. By forming and encouraging these local schools or classes, owners and managers of mines are not only promoting the welfare of the rising generation around them, but they are at the same time doing good to mining generally, and are contributing to the intro- duction of the most improved methods of extracting minerals. Just as the success of an army depends largely upon its trained CONDITION OF THE MINER. 683 non-commissioned officers, so the prosperity of a mining enter- prise is largely influenced by the competency of the foremen ; many of them by virtue of their talent and industry rise from the ranks and become excellent managers of mines. The training of foremen must not be carried on to the exclusion of all thought for their sisters, who will make better wives and mothers if they receive some instruction in the arts which belong more particularly to the domain of women, such as housekeeping, cookery and nursing. Teaching of this kind becomes more than ever necessary in localities where females are largely employed on the dressing floors, for then the girls fail to receive that practical training in household work, which would otherwise fall to their lot, if they entered domestic service, or assisted their mothers in their own homes. 4. SICKNESS. At first sight it might be supposed that milling is necessarily an unhealthy occupation, that confined for hours in dark and gloomy passages a man cannot keep well and strong. Stubborn facts and figures show that a general asser- tion of this kind is not well-founded ; but nevertheless the miner does suffer in some cases from diseases inherent to his calling, and these can be best combated if their causes are thoroughly understood by all who are connected with mining operations. The diseases to which miners are most liable have been care- fully studied by Dr. Ogle,* who with infinite pains has worked out the death-rates for mining, as well as for other occupations, from the figures contained in the national register of deaths. Of course it is very difficult, if not impossible, in comparing the death-rate of the miner with that of some other working man, to say precisely how much of the difference is due to the effect of the calling. The miner is to a certain extent a picked man ; the weaklings of a family do not go to work underground, conse- quently in the race of life the miner has, so to say, a start, which ought ceteris paribus to make him a winner. The actual death- rates of some occupations are given in the table on p. 684, extracted from Dr. Ogle's much more complete list. The com- parative mortality figure affords the easiest means of contrasting the differences between the various callings as regards healthiness. The figure 1000 represents the total number of deaths among a certain number of male persons between the ages of 25 and 6 for the whole of England ; then taking the same number o persons in any particular calling at the same ages, Dr. Ogle has calculated the corresponding number of deaths. The lower the figure, the healthier the occupation. In very healthy dis- tricts the mortality figure is as low as 804, that of the agricul- tural labourers is only 701. If we take miners, we do not find a high mortality figure for the collier, nor for the ironstone * Supplement to the Forty-ffth Annual Report of the Registrar of Births] Deaths and Marriages in England. London, 1885, pp. xxv., et seq. 68 4 ORE AND STONE-MINING. miner ; but the figure for Cornwall is appalling. Mining coal and ironstone appears to be less fatal to life than baking bread or making boots and shoes. Mean Annual Death-rates per 03 3 > 6C . looo living. |B? 1860-1-1871. 1880-1-2. If OCCUPATION. Years of Age. Years of Age. Years of Age. 25-45- 45-65- 25-45- 45-65. 25-65- All males .... II'27 23-98 10-16 25-27 IOOO Males in selected healthy ] districts f ' 8-47 1974 804 Baker .... 1072 26-39 870 26-12 958 Blacksmith . 10-07 23-88 9-29 25-67 973 Boilermaker . . 9-27 26-65 994 Builder, mason, bricklayer II"43 27-16 9-25 25-59 969 Butcher 13-19 28-37 I2"l6 29-08 1170 Carpenter 9 '44 21-36 777 21-74 820 Fisherman ... 11-26 '5 '84 8-32 1974 797 Miner, coal . 7-64 25-11 891 ,, ironstone . 8-05 21-85 834 Cornwall . 11-94 41-73 14-77 53*69 1839 Labourer, agricultural . 17-68 701 Plumber, painter, glazier 12-48 34-66 11-07 3 2 '49 1 202 Quarrier, stone and slate 10-88 28-67 9'95 31-04- 1 122 Tailor . . . . " Shoemaker . 12-92 10-39 22-30 10-73 26-47 23-36 1051 921 The diseases inherent to the miner's calling are due to the following causes : Breathing a polluted atmosphere. Excessive ladder climbing. Working in constrained positions. Exposure to heat and cold. Working in compressed air. Of these various causes the first is undoubtedly by far the worst : it brings on phthisis and other diseases of the respiratory organs. There is nearly six times as great a mortality from these diseases among Cornish miners as there is among fishermen. The manner in which the air of mines is polluted has been explained in the chapter upon Ventilation viz., by the breathing of the men and animals in the pit, the combustion of lamps or candles, exhala- tions of decaying timber, smoke of explosives, natural emanations CONDITION OF THE MINER. 685 of gases, and dust. It is the opinion of the best qualified judges that dust is largely responsible for the respiratory ailments from which the miner so often suffers. The difference between the atmosphere of a mine and that of the external atmosphere is often made very plain by the state of the nostrils after a few hours spent in underground workings; it is found that they have strained off a part of the solid particles floating about in the air of the mine, and the amount so arrested will serve as some gauge of the quantity inhaled. Besides, men commonly breathe a great deal through the mouth, and lose the benefit of their natural air- filter. The dust acts mainly mechanically, but in a few exceptional cases its evil effects are due also to poisonous chemical properties. The mechanical action is at first an irritation of the delicate lining membrane, and then the particles make their way into the tissues, choke them and harden them, and so render them unfit for allowing the chemical action of the air upon the impure venous blood which is necessary to life. The diseases caused by the inhalation of dust in this way are bronchitis, shortness of breath, asthma and consumption. A large proportion of the dust is produced in the process of boring holes for blasting in an upward direction. If the hole has a downward inclination the miner puts water in, which not only prevents any dust, but also renders his work easier by allowing the edge of the tool to act more fairly against the rock. When, on the other hand, the miner is boring upwards, the dust is scraped out or falls out, and though the coarsest particles may at once drop to the ground, the very fine and light ones float about, and produce a cloudy and noxious atmosphere. If machine drills are employed, the amount of dust produced in a given time is. of ten considerable, as will be instantly recognised by any one dressed in a dark suit who stands by one of these machines while it is working in dry ground. Prevention is better than cure, and the evil consequences can be averted by forcing a jet of water into the hole during the boring operations. The jet may be produced either by allowing the com- pressed air to act upon the surface of a tank containing water, or by bringing down a supply in a pipe from a tank situated at a higher level ; keeping the sides of the level moist is another precaution, the particles of dust wafted against the wet sur- face are caught, like flies upon sticky paper, and so rendered harmless. Some of the dust arises from the rock being broken up in the process of blasting, and some comes from the explosive itself, if it consists, for instance, of infusorial earth mixed with nitro- glycerine. A fine spray is very effective in laying the dust and fumes pro- duced by blasting, and an easy method of producing it is to 686 ORE AND STONE-MINING. turn a jet of compressed air into a pipe supplied with water.* An appliance of this kind is specially desirable when the blast- ing in an "end" is done by volleys, when the miner has to walk into the smoke of one blast in order to charge another set of holes. Some men make use of a sponge as a respirator while exposed to the dust and fumes, and no doubt with good effects ; but it is well to delay the return as long as possible, unless the " end " is provided with such an apparatus as Teague's ventilator, which speedily withdraws all noxious fumes from the working place. If it is necessary in some particular case to go into an "end" full of smoke, the harmful effects may be reduced by making use of Nature's respirator, namely, the nose, and not breathing at all through the mouth. Dusts which have a poisonous effect are those of certain minerals containing arsenic, lead and mercury. According to Dr. Harting and Dr. Hesse,f cancer in the lungs is not uncommon among the men working in the cobalt mines of Schneeberg in Saxony, and they ascribe the disease to dust containing arsenic in combination with cobalt, which produces a permanent chemical irritation in the delicate air-passages. It seems to be mainly the mineral speiscobalt or smaltite (CoAs 2 ) which is the source of the disease , the cobalt minerals containing sulphur in addition to the arsenic are far less poisonous, as they are less readily decomposed. When one reflects how soon cobalt bloom, the hydrated arseniate of the metal, is formed upon the ores in a damp atmosphere, it is not surprising that a similar action should go on with minute particles of smaltite imbedded in the lung tissue, and eventually set up a considerable amount of irritation. Far more dangerous than the dust of arsenical minerals under- ground, are the fumes produced in roasting ores containing mis- pickel, a process which goes on in many tin mines and some gold and copper mines. Particles of arsenious acid attach themselves to the skin, in places where it is moist from perspiration, and produce nasty sores, whilst those which enter the body give rise to various disturbances of the digestive organs. The best means of avoiding the ills due to arsenic have been pointed out by Hirt J at some length. Only thoroughly healthy men should be allowed to work in places where there is danger from arsenic, and they should be relieved at regular intervals. Bottles of hydrated oxide of iron, in the form of an emulsion should be kept in readiness, both as a preventative and an antidote. The men must be compelled to exercise the greatest cleanliness, and when exposed to the dust and vapours should cover the mouth with a dry cloth. Arsenical sores * Reports of H. M. Inspectors of Mines for the Year 1879, p. 527. t "Der Lungenkrebs, die Bergkrankheit in den Schneeberger Gruben." Etdenberg's Vierteljahrsschrift fur gerichtliche Medicin. Neue Folge, xxx. Band, p. 296, Berlin, 1879. Arbeiter-Schutz,, Leipsic, 1879, P- I 3 I CONDITION OF THE MINER. 687 should be plastered over with fuller's earth moistened with water and hydrated oxide of iron ; strong drinks, especially brandy, must be avoided, but milk and greasy soups help to resist the poison. In an ordinary lead mine, where the ore consists entirely or almost entirely of galena, plumbism is rarely heard of ; but when the ore is cerussite, a different state of things arises and the disease may be rife. It is well known that the arti- ficial carbonate, the white lead of commerce, produces poisoning among painters, so much so indeed that one of the ailments due to lead is known as " painters' colic ; " it cannot therefore surprise us, when mere handling is injurious, that breathing a lead-laden atmosphere should likewise be pernicious. Plumbism among miners has probably never been so prevalent as in the Broken Hill district in New South Wales, where some of the ore in the shallow levels is a pulverulent earthy carbonate of lead. According to published accounts,* the state of things must have been very bad in- deed comparatively lately. Miners suffered more than the smelters, but even the ore-pickers were not exempt from the malady. From this fact we may conclude that lead may have entered the system in some cases by eating food with dirty fingers, or, as suggested by the writer of the article alluded to, from smoking a pipe filled with tobacco rubbed in a leady hand. The baneful effects have been reduced by not allowing the men to work very long at one time in the parts of the mine where the soft carbonate occurs. The managers arrange, for instance, that a man shall take one fort- night at mining the earthy cerussite ; the next fortnight he is put to work at the surface and made to quarry the ironstone i.e., the ferruginous outcrop of gossan, which is used as a flux at the smelting works ; and then he takes a fortnight underground in mining the kaolin ore, which consists largely of kaolin and chloride of silver, and has no deleterious effect upon the men, or at all events does not cause lead-poisoning. The precautions to be adopted against plumbism at mines of this description are : ample ventilation, laying the dust as far as possible by a spray of water, and the strictest cleanliness. The mine-owner should do his share by giving the men every possible convenience for washing themselves and changing their working clothes, but no amount of forethought on his part will suffice to prevent the evil entirely, if the men fail to avoid every chance of defiling their food or tobacco by lead ore. Working in the quicksilver mines is found to be unhealthy, and the men suffer from mercurial poisoning unless special precautions are taken. Thus, at Almaden, even if the ventilation is good, the miner cannot work more than four to four and a half hours a day, nor can he work more than seven or eight days in a * " Lead Poisoning," The Australian Mining /Standard, vol. vi., 1891, p. 13, and Report of Board of Inquiry at Broken Hill, Sydney, 1898. 688 ORE AND STONE-MINING. month without injuring his health very rapidly.* Ifc is true that the miners suffer less than the smelters, which is the reverse of what happens at Broken Hill, and the explanation of this is that mercurial poisoning is mainly due to the vapour of the metal. At Almaden some of the mercury exists in the native state and is supposed to sublime slowly ; t but even at Idria, where there is no native mercury, where the ore is less rich than at Almaden, and the ventilation excellent, the men work only four hours at a stretch i.e., four hours in the morning and four in the afternoon, with an interval of rest of four hours. The symptoms of mercurial poisoning noticed at Almaden are : inflammation of the mouth, salivation and loss of teeth, shiver- ings, gradual and general wasting away. Excessive ladder-climbing has long been pointed out by medical men as a cause of disease.^ If the heart is over-stretched day after day and year after year, it becomes dilated, loses some of its contractile power, and is therefore less capable of performing its pumping action properly. The miner who for years has had to descend and ascend by ladders in deep mines, will generally be found to have a feeble heart and weak pulse on this account. Young miners should be careful to avoid the over-exertion caused by climbing with unnecessary haste. In these days of excellent steel wire ropes for winding men up in cages, it is perfectly absurd that a miner should be condemned to the treadmill toil of ladder- climbing, which has nothing to be urged in its favour. The shareholder has to pay for an unprofitable form of labour, his mine is conducted with less supervision than there would be if access to the workings were easier, whilst the unfortunate miner suffers in health and strength. When a mine reaches a depth of i oo yards the owner should introduce means of raising and lower- ing the men mechanically without fatigue. It is easy to conceive, when a man is working continuously for years in -a constrained position, that certain muscles will be stunted in their growth from want of use, and that others will be abnormally enlarged from over-use, and so cause a distortion of the body. This happens to a slight extent with the men working on the thin bed of copper shale of Mansfeld. The disease of the eye known as nystagmus has been noticed among colliers. A person suffering from nystagmus sees objects apparently moving in a circle ; gas lights in a room, for instance, seem to dance ; the man also suffers from headache and giddiness, * Kuss, " Note sur 1'etat actuel de la mine et de 1'usine d' Almaden," Annales des Mines, 8me. serie, tome xi., p. 138. t Eng. Min. Jour., vol. xlvi., 1888, p. 435. I Dr Peacock, " Medical Keport on the Condition of Miners " ; Bankart, "Medical Report on the Condition of Miners in Cornwall and Devon" ; Appendix B. to the Eeport of the Commissioners appointed to Inquire into the Condition of all Mines in Great Britain to which the Provisions of the Act 23 & 24 Viet. cap. 151 do not apply. P. 7 and p. 95, London, 1864. CONDITION OF THE MINER. 689 and the eyeballs are noticed to oscillate or rotate. According to Snell * the men most afflicted with nystagmus are those who have to work lying on their side; owing to this unnatural position the muscles of the eyes are unduly strained and suffer from overwork. Mere work upon the side is in some districts insufficient to set up the disease, for during a period of six years only two cases were noticed among the 14,000 Mansfeld copper miners. As these men use open lights, it is not unnatural that nystagmus should have been ascribed by some doctors to the insufficient illumination afforded by the safety lamp. Snell combats this hypothesis, and cites cases of the disease in persons who have never used a safety lamp ; therefore the want of a better light cannot be the only cause. To a layman it seems quite possible that both views may be correct; the two sets of doctors agree that the disease is produced by over-strain of the ocular muscles, and as either of the two causes appears capable of occasioning such a strain, why should there be a difficulty in admitting both explanations ? The great heat of the workings on the Comstock t lode has been mentioned in the early part of this chapter, and many men are said to have lost their lives from it, being picked up dead in the mine. New-comers suffered more than the old hands. There was also the danger of falling into scalding water; men fell accidentally into pools of water at a temperature of 157 or 158 and perished in great suffering from their skin peeling off. In some cases the effect of the hot air on the men is said to have been beneficial, acting like a succession of Turkish baths. When the heat on the Comstock lode first became intense, the miners suffered from pneumonia and rheumatism, because they went out at once into the cold and freezing atmosphere at the top of the shaft, although only a few minutes before they had been in the heated atmosphere of the lower levels. Such sudden changes of temperature were naturally injurious ; and experience soon taught the men and the managers that risks of this kind could not be run with impunity. Good rooms were erected at the tops of the shafts, in which the men could change their clothes, and some were provided with baths. These precautions soon brought about an improvement in the general health of the men. In ordinary mining operations, men are rarely subjected to a pressure considerably above that of the surrounding atmosphere ; but as work in compressed air is occasionally necessary, it is well that the student should be reminded of its danger to health. Men who are employed in making foundations for bridges or in driving tunnels, where compressed air is used as a means of * Miners" Nystagmus, Bristol, 1892. t Lord, " Comstock Mining and Miners." MonograpJis U.S. Geol. Survey, vol. iv., Washington, 1883, pp. 374 to 399. 2 X 690 ORE AND STONE-MINING. keeping out water, suffer at times from paralysis and intense pain in the back. These effects of the confinement seem to be mainly felt on coming out into a less dense atmosphere, and may be lessened by prolonging the stay in the air-lock, and so causing the diminution of pressure to be felt gradually. 5. THRIFT. Remarks upon the condition of the miner would be incomplete without some mention of the following subjects: (i) Provision against loss of pay from sickness acci- dents, strikes, and old age ; (2) Obtaining medical attendance at a small cost ; (3) Procuring supplies of food and clothing upon the most reasonable terms. Provident societies are no new thing for the miner ; it has been pointed out by Dr. Wahle, the Director of the Mining Depart- ment at Freiberg, that they date back in Saxony to the fifteenth century, and are as old as mining itself. In this country at the present day three systems are in vogue : clubs for individual mines, general relief societies for large districts, and, lastly, the ordinary friendly societies, not confined to miners, which are resorted to by all classes of workmen. In Cornwall and Devon, and in many parts of Wales, there is a club for each mine, and the men agree to a deduction being made from their wages every month for " doctor and club." At many mines the monthly deduction for the doctor is either six- pence, or one shilling, according as he attends the miner only, or his family also.* Under the provisions of the Stannaries Act, 1887, some of the old grievances of the Cornishmen have been made to disappear. Each man has a right to choose his own doctor, to whom the amount deducted from his wages is paid. If a surgeon renders himself unpopular by not attending to a case with sufficient care, the men do not select him another time, and his pay and reputation suffer. This check upon the doctors seems to be a sufficient guarantee of the system working smoothly, and to the satisfaction of those most interested in the matter viz., the men themselves. The usual deduction for " club " is 6d., and in a few cases gd. per man per month ; the usual " hurt pay " for disablement is is. per day. In the event of a fatal accident the funeral expenses are borne by the mine, and sometimes the sum of ^"10 is given to the widow or dependent relatives, or a levy of is. per man is made for their benefit. The great faults of this system are : First, the want of some provision for widows, orphans, or dependent relatives of persons killed by accidents ; secondly, the fact that a man loses his " hurt pay" and is probably thrown on the parish if the mine in which he had been working is stopped ; thirdly, the want of any * Foster and Pike, " Suggestions for the Formation of a Miners' Per- manent Club and Relief Society for Cornwall and Devon," Proc. Min. Inst. Cornwall, vol. i., p. I. CONDITION OF THE MINER. 691 provision for ordinary sickness. Of course the first and third objections might be removed by increasing the monthly subscrip- tions, but the second would still remain viz., the uncertainty of the benefits being kept up permanently. Far better than the clubs of individual mines are the perma- nent relief societies, of which British miners have reason to be proud. There are now nine of these societies in different parts of England and Wales, and there is also a central society for promoting and watching over their interests and extending their work to new districts.* Though started for colliers, these societies include many iron- stone miners and some lead miners and slate quarriers among their members. According to the annual report of the Asso- ciation for 1891, there were 268,971 persons members of these relief societies in the year 1890, whilst the total number employed in and about the mines of the United Kingdom was 674,434, inclusive of those employed on private branch railways and tramways, and in washing and coking coal on premises adja- cent to or belonging to the mine. The exact nature of one of these societies will be best appre- ciated by examining the rules of the largest, which has done, and is still doing, much excellent work in the North of England, t As it includes the Cleveland ironstone district, although this does not appear from the title, it is specially adapted for my purpose. Its objects are very clearly defined thus : " The objects of this Society are the raising of funds by volun- tary subscriptions amongst the members thereof, and by donations' from others to make provision in case of fatal and non-fatal accidents as follows : " (a) A sum at the death of a member. " (6) A weekly allowance to the widow and children of married members. " (c) A weekly allowance to members who suffer from non-fatal accidents. " (d) An allowance to the parent, or sister, or brother of a deceased member during sickness or other infirmity. " (e) Also to make a provision for miners over 60 years of age who are permanently unfit to work, the allowance to be paid to be in accordance with the contributions received. ' ' The weekly contribution of each member is 4d., and of a half- member i.e., a boy under i8J only 2d. Three-eighths of these sums are devoted to the superannuation fund. * Central Association for Dealing with Distress caused by Mining Accidents, 31 A, King Street, Wigan ; George L. Campbell, Secretary. + Eules of the Northumberland and Durham Miners' Permanent Belief Fund Friendly Society. Established June 7, 1862. Chief Office 5, Queen's Square, Newcastle-upon-Tyne. 1892. J A boy under 18 but over 16 may be a whole member if he likes ; a boy under 16 can only be a half member. 692 OKE AND STONE MINING. The benefits are in the case of 1. Non-fatal accidents. 2. Fatal accidents. 3. Old age. If a member is disabled by an accident for more than a week y but not less, he receives the sum of 55. a week or lod. per work- ing day, and a half-member 2s. 6d. per week or $d. per day. The payments go on in this way for twenty-six weeks, when, if the person is still disabled, he becomes entitled to the higher relief of 8s. per week, or 45. if he is a half -member, so long as he is unable to work from the effects of the accident. In the case of a death by accident, the widow of a married member receives a legacy of ^5, the relatives of an unmarried member receive ^23, and those of a half -member 12. The widow also draws 5$. a week from the funds for the rest of her life, so long as she remains unmarried, and 2s. a week for each child, until the boys are thirteen and the girls fourteen years of age. Aged and infirm members over sixty years of age who are certified medically to be unfit to follow their employment receive 45. per week ; but the amount of the pension may be reduced if the funds at any time are insufficient to keep up the present allowance. During the year 1891 this Society had 113,124 members; the contributions of the members amounted to ^90,169, those of the owners of collieries to ^4860, in addition to which there was an income of ^5208 from invested funds. The following claims were made upon the Society : Minor Accidents. 16,500 claims for relief were made; the average length of the period of disablement was about 3^- weeks each. Permanent Disablement. 195 claims for accidents that have caused disablement lasting more than 26 weeks; the average duration of each is estimated to be 3^ years. Fatal Accidents. 93 widows came on to the funds. Children. 185 children came on to the funds. Old Age. 442 new claims for superannuation were made. According to the report of the Central Association * the nine societies gave relief for 754 deaths by accidents, and for 39,411 cases of disablement during the year 1890. We learn from the Reports of Inspectors of Mines that there were 1206 deaths from accidents at all the mines of the United Kingdom in that year, consequently it is evident that a large pro- portion of the victims of these fatalities were insured, and that * Central Association for Dealing with Distress Caused by Mining Acci- dents. Report of the Proceedings at the Twelfth Annual Conference, London, 1891, Tables VI. and VII., pp. 36-7. CONDITION OF THE MINER. 693 their families or dependent relatives received some form of relief. Altogether there were 2 39 5 widows and 3496 children receiving benefits from the funds of the nine societies in the year 1890. The percentage proportion of the contributions of the colliery owners to those of the ordinary members is less in the Northumber- land and Durham Society than in the others. In 1890 it repre- sented only 5- 7 per cent.,* whilst in the Lancashire and Cheshire Society it was 24*1 per cent., in the North Wales Society 25*2 per cent., and in the Monmouthshire and South Wales Society 24 per cent. If we turn to Table IX. of the report, the reason of this difference becomes apparent ; it will be seen that all, or a very large number, of the members of these three societies have entered into an agreement with the owners not to bring any claim against them under the Employers' Liability Act of 1880, or, to use the common expression, they have " contracted them- selves out of the Act." They consider that the employer's con- tribution is worth more to them than the chance of occasionally obtaining compensation by proving negligence against him in a court of law. Enough has been said to show the present state of the volun- tary system of relief as it now exists in England and Wales ; much of the distress caused by mining accidents is relieved by the nine principal societies, and, in addition, there are numerous smaller societies established for individual mines, having in the main the same objects as the larger ones. Something more is needed viz., relief in sickness, and old .age pensions for all. Some of the existing clubs of individual mines give sick pay to their members, and there are the ordinary Friendly Societies established on a far firmer basis, which can be resorted to by the miner like any other workman. As far there- fore as sickness is concerned there is machinery available by which the miner in any part of the kingdom can make the neces- ,sary provision for himself and his family. If he requires a pension, he can get one upon the very best security by going to the nearest Post Office. A young man of twenty can obtain a deferred annuity of 55. a week, commencing .at the age of sixty, by paying 2 35. ^d. a year, or lod. a week. If the person wishes to discontinue his insurance, he can do so, and all the money he has paid will be returned to him, provided that an instalment of the annuity has not become due. However, as the facilities afforded by the Post Office have not been utilised to any great extent, compared with the numbers of the working classes, and as a large number of persons spend the last years of their lives and end their days as paupers in the workhouse, it is thought by most people that something more should be done. Great * Op. tit. Tables IV. and V., pp. 34-5. 694 ORE AND STONE-MINING. difference of opinion exists upon the subject; much has been written, and still more said during the last few years, and the controversy has raged mainly upon the question of State aid. The proposals may be summed * up as involving one of the three following principles : 1. State endowment. 2. State assistance. 3. State compulsion. 1. The first, that of Mr. Charles Booth, means the free gift by the State of a pension of 55. a week to every citizen on attaining the age of sixty-five years. 2. The best known scheme coming under the second head is that proposed by a Parliamentary Committee,t presided over by Mr. Joseph Chamberlain, M.P. Its main features are as follows : If a young man pays ^5 to the Post Office Savings Bank before the age of twenty-five, he is to be at once credited with ^15 more from a State pension fund ; he will then have to pay i a year to the Post Office for forty years, and at sixty-five he will become entitled to a pension of 55. a week. If he dies before the age of sixty-five, there are arrangements for granting a pension to his widow and children. It is also proposed that a male shall be able to purchase a pension of 55. a week on payment of one- half of the sums just mentioned ; but in this case there is no provision for a family. 3. The last plan of providing old age pensions is that which has been advocated for so many years and with so much skill by the Rev. Canon Blackley. He would compel every one to de- posit with the State, before the age of twenty-one, a sum of about ;io, which would suffice to provide him with a pension of 55. a week on attaining his sixty-fifth year. Canon Blackley points out that in his youth, before marriage, a man would be able to make the proposed saving, and that after this he would no longer be troubled by the thought of not being able to keep up his payments. Many arguments may be adduced in favour of each of the three principles of old age pensions, but opinions concerning them must largely depend upon the " personal equation " of the individual that is to say, upon his general views regarding the interference of the State in such matters. The Gordian knot of this difficult question has been cut in Germany by the Law of Insurance against Old Age and Infirmity J passed in 1889. Under this law the means for providing the allowances to infirm and aged persons are made up of contribu- * Reports of the Chief Registrar of Friendly Societies for the Year 1891, London, 1892, p. 26. f The Times, London, May 21, 1892. J Translated in Parliamentary Paper (C. 5827), 1889, price ^d. CONDITION OF THE MINER. 695 tions from the State, the employers and the persons insured, the two latter paying like amounts. The method of insurance may be briefly described as that of State compulsion with State aid, together with obligatory contri- butions from the employer. This bold experiment will be watched with interest. This subject of thrift must not be concluded without a few words about one requisite for the treatment of diseases viz., hospitals. In this country the provision of such institutions is frequently left to private benevolence; in the great tin mining centre of Redruth, for instance, the burden of ensuring accom- modation for the sick and injured has been taken by a charitable owner of mineral property. According to the balance sheets of the institution from 1885 to 1892, he has paid on an average more than 40 per cent, of the total cost, which exceeds ^1300 yearly ; the remainder is met by contributions from private per- sons, companies working mines in the neighbourhood and their workmen. The Oakeley Hospital at Blaenau Festiniog, which ministers to the ills of some of the quarry men, was built by the landowner, and is now supported by the largest slate mine. Many of the large Continental mines keep up establishments of this kind, and throw them open gratis to their employes. The same plan is adopted by some of the large British companies working mines abroad, and even at Boryslaw, where much of the mining is being carried on in the most primitive manner, a Gali- cian company supports a small hospital, and admits not only its own servants, but also any urgent cases requiring surgical or medical attendance. Fortunately, it often happens that a mine has not accidents enough to require the constant use of a hospital and the entire services of a surgeon. This is the case, for instance, at some large mines near Ems ; the company has built a hospital and keeps it in readiness, in case of accidents or sickness, with a doctor on the premises ; but, in consideration of his small stipend, he is allowed to have three rooms at his disposal in which he can treat private patients. In the United States sick and injured miners sometimes go to private hospitals, which are managed by medical men. Before complete recovery from an illness or the effects of an accident, a man passes through a period of convalescence, during which he requires little medical aid, but depends for his final restoration to health mainly upon good food, quiet and regular living, and plenty of fresh air. It is a question in some mining districts whether it is better to support a convalescent home in the locality itself, or to subscribe to one at a distance. The latter plan is in many cases cheaper, owing to the smaller cost for general expenses ; and at the same time it is better for the patient, wLo profits by the change of air and scene, which in 696 ORE AND STONE-MINING. themselves are powerful remedial agents. In a small island like ours, it is not difficult as a rule for the patient to get to the sea coast without a ruinous expenditure of money in railway fares. At some of the sea-side convalescent homes a miner may be boarded and lodged for three weeks at a total cost of 1. i6s. ; therefore if a mine is employing 500 men, and each man sub- scribes ^d. per month of four weeks, more than ^13 can be raised annually, or sufficient to give seven invalids a stay of three weeks each at the sea. In writing upon the question of thrift, mention must be made of co-operative societies, which give the workman the opportunity of buying his food and clothing at the most reasonable rates. They are so well known nowadays that no description of their advantages is required ; but it is well to point out that their success does not necessarily depend upon their having a very large number of customers, such as could only be expected in a very populous district. Two instances of co-operative societies in the Isle of Man prove this fact, and show that such an institution may prosper commercially, and do good and useful work in a mere village depending upon a mine employing only 200 or 300 persons underground. 6. RECREATION. I am well aware that many will say that in the matter of recreation the mine manager had better not interfere at all ; I do not take this view. Men and boys require diversions of some kind in order to refresh their bodies after toil, and the manager of a large mine often has the oppor- tunity of directing their amusements into the best channels. Tastes differ: some men will find relaxation in reading, and will be glad to be able to borrow books from a library ; others are musical, and will prefer to join a band ; boys, in spite, of hard bodily work at the mine, will delight in active games as soon as they are free. As an example of what may be done I will cite the names of the clubs established at the collieries of the Douchy Com- pany in the north of France as recreative institutions : Archers, crossbowmen, gymnasts, philharmonic, and pigeon fanciers. It will be seen from this list that a great many different tastes have been studied in order to encourage the men to employ their spare time in a wholesome manner instead of going to pot-houses, to the injury of their purses, if not to the detriment of their health. An example on this side of the Channel may be taken from the extensive collieries in Derbyshire and Nottinghamshire, owned by Colonel Seely, M.P., who has established workmen's clubs, cricket club, football club, pig club, a band, and an annual Hower show for the benefit of his men. The cricket ground is one of the best in Derbyshire, and the club-house is a large build- ing containing three billiard-tables, reading and smoking rooms, and a lending library ; the members can obtain any sort of CONDITION OF THE MINER. 697 refreshment they like at reasonable prices. The band plays three times a week in the club grounds. In addition, each sepa- rate colliery has its club with a billiard-table, and other appli- ances for recreation. All these institutions are under the control of committees of the workmen, presided over by the General JManager. 698 CHAPTER XVII. ACCIDENTS. Death-rate of miners from accidents Relative accident mortality under ground and above ground Fatalities : underground, from falls of roof, from accidents in shafts, from blasting accidents, from under- ground fires, from irruptions of water and sundry other causes Accidents above ground Boiler explosions Non-fatal accidents Ambulance training. FEW persons will deny the dangers of the miner's calling ; some, how- ever, consider that the public form an exaggerated idea of these perils from dwelling too much upon occasional colliery explosions. Death-rate of Miners from Accidents. In the first place comes the question : What is a dangerous trade ? If we look at the vital statistics quoted from Dr. Ogle in the last chapter, it appears that the majority of miners, thanks, partly, to their starting originally with a more than average good constitution, lead a longer life than many tradesmen in towns. In spite of the diseases and accidents to which he is liable, the average miner is better off than most people would have supposed, before they became acquainted with the figures. On the other hand, if w r e limit our attention to accidents, we find that the miner- gets far more than his share. It may be asserted without fear of contradiction that a calling with an annual mortality of i per 1000 from accidents, is hazardous. The statistics concerning accidents in this country are given annually in the statistical summaries prepared by Her Majesty's Inspectors of Mines; and it will be seen from the published figures that, taking all the mines in the United Kingdom and including casualties above and below ground, there was an average annual mortality from accidents of 2-18 per 1000 persons employed during the ten years 1873 * x ^^ 2 inclu- sive, and that in the next decade the mortality dropped to 178 per 1000. In this country an accident is classed as fatal if it causes the death of the injured person within a year and a day of the date of the occurrence ; it is therefore possible that in certain very rare cases, when more than a year elapses before a man succumbs to his hurts, an accident may be registered as non-fatal, although it finally turns out to be fatal. Cases of ACCIDENTS. 699 this kind are so few that the correctness of the British statistics cannot be appreciably affected by them. In an interesting report upon the Exhibition held in Berlin in 1889 of appliances for the prevention of accidents, M. Paul Habets gives a careful summary of the progress realised in Belgium, France, Great Britain, and Prussia.* He divides his results into periods of ten years : TABLE I. Annual Death-rate from Accidents per 1000 Persons Employed, Period. Belgium. France. Great Britain. Prussia. 1851 to i860 1861 to 1870 1871 to 1880 1880 to 1888 2'97 260 2'45 2-13 3-40* 2- 9 6 2'2I i'57 4-07 3-32 2'35 1-94 4'9lt 6-33 4-90 2-96 1853 to 1860. t 1852 to 1860. These figures show a steady diminution in the number of accidents excepting in Germany, for in the decade 1861 to 1870 the mortality was terrible ; but even the most favourable averages are far above the standard of i per TOOO, which has been assumed as the mortality ratio of a dangerous occupation. Relative Accident Mortality amongst Underground and Above-ground Workers. Descending into details, let us examine how the two classes of mines viz., those under the Coal and those under the Metalliferous Act compare with one another. The figures will be made most plain by putting them in a tabular form. TABLE II. Decennial Period. Average Number of Persons Employed Underground and Above-ground Annually. Total Number of Lives lost by Accidents in the D eennial Period. Average Annual Death- rate from Accidents per 1000 Persons Employed. Mine 1873 to l8 82 1883 to 1892 3 classed under the ( 503,428 571,719 3oal Mines Regula 11,294 10,327 tion Act. 2-243 I -806 Mines cla 1873 to 1882 1883 to 1892 ssed under the Mete 55,388 42,481 illiferous Mines R< 909 612 'gulation Act. 1-641 1-440 According to these figures, work at mines under the Coal Mines * "Les Accidents dans les Mines et 1'Exposition Generate Allemande pour la Protection centre les Accidents (Berlin, 1889)." Revue Universellc. des Mines, 3 strie, t. ix. et xi., 34 annee, 1890. 700 ORE AND STONE-MINING. Act presents decidedly more perils than work at mines under the Metalliferous Act. Speaking roughly, the relative degrees of danger were as i i]to 8 in the first period and 9 to 7 in the second. In order to make the comparison of any real value, it is neces- sary to go somewhat further. Owing to the amount of labour required for " dressing," the proportion of surface hands is much larger at a tin, copper, lead, or slate mine, than at a colliery. In round numbers about one-fifth of the persons employed at mines under the Coal Mines Regulation Act work above ground, and four- fifths underground ; at mines under the Metalliferous Mines Act the proportions are two-fifths above ground, and three-fifths under- ground. Consequently, as the proportion of the surface hands with a small risk is twice as great in one case as in the other, it is impossible properly to compare the risks of the underground workers until this source of error has been eliminated. The death-rates calculated separately are as follows : TABLE III. Average Annual Death-rate from Accidents per 1000 Persons employed in and about the Mines of the United Kingdom of Great Britain and Ireland. Decennial Period. Below Ground. Above Ground. Coal Mines Act. Metalliferous Mines Act. Coal Mines Act. Metalliferous Mines Act. 1873 to 1882 . 1883 to 1892 . 2-572 2 'OO9 2-348 2-145 0-919 Q'959 0-578 0-392 In the first period the relative amounts of danger to under- ground workers were as 51 to 47, a very different proportion from 1 1 to 8 as appeared from the other table ; in the second period the mines under the Coal Mines Act have the advantage, whereas by the original table "they seem to be more dangerous than those under the Metalliferous Act. The necessity for considering the underground death-rate separately, when inquiring into the relative amounts of danger at different classes of mines is well illustrated in the case of the underground slate quarries of North Wales. These appear to be less dangerous than collieries, or more dangerous according as the surface hands are included or not in the calculations. Taking the ten years 1875 to 1884, the annual death-rate from accidents at the underground slate quarries was 2*07 per 1000 among all the workers as a whole, and 3-2 per 1000 among the under- ground workers taken separately. The former rate is better than the corresponding 2-243 (Table II.) of mines under the Coal Mines ACCIDENTS. 70I Act, and the latter is worse than 2^572 (Table III.). Conse- quently the average underground slate-quarrier has a more perilous calling than the average collier. While correcting one misapprehension I must guard against another, and point out that the Coal Mines Kegulation Act applies to mines of coal, stratified ironstone, shale, and fireclay. Therefore the figures given do not refer solely to coal-mines, and do not re- present precisely the risks of the collier, and it becomes necessary to examine whether the introduction of certain disturbing elements affects the average risk to any great extent or not. Compared with coal, the amounts of fireclay, ironstone, and shale are small, and the total quantity of these minerals raised in 1893 was less than 6 per cent, of the weight of the coal ; any error caused by the introduction of ironstone and other mines, is likely therefore to be inconsiderable. After coal, the most important mineral wrought under the Coal Mines Act is ironstone, and more than half the total quantity raised is obtained in the Cleveland district. From the figures given in the reports of the inspectors of mines, I find that from 1873 to 1882 there were 183. deaths from accidents underground in the Cleveland district, with an average annual underground staff of 6863 persons, con- sequently the average death-rate was 2'66 per 1000; in the following decennial period it was 2-21 per 1000.* Both these proportions are higher than the corresponding ratios calculated for the whole of the mines under the Coal Mines Act ; therefore if all disturbing factors were eliminated, we may fairly assume that the average underground death-rate at the coal-mines proper did not exceed the figures given in Table III. On the other hand, I must remark that the Metalliferous Mines- Regulation Act applies to all mines not included under the Coal Mines Act, and the statistics under the former Act refer not only to mines worked for ores, but also to salt-mines and underground slate and stone quarries. The figures quoted cannot be taken as- relating solely to true metalliferous mines. For the sake of comparison I have extracted from the annual reports of the inspectors of mines, the figures for the metalliferous mining district of Cornwall and Devon, including also a few mines in Somersetshire and Dorsetshire. During the ten years 1873 to 1882 there were 280 deaths from accidents under- ground, with an average underground staff of 10,629 persons. This means an average annual death-rate among the underground workers of 2-63 per 1000. The corresponding figure for the ten years 1883 to 1892 was found to have been 2-54 per 1000. The conclusions arrived at from these statistics are, first, that * From 1873 to 1883 the published statistics refer to the whole of the North Biding of Yorkshire, where a little coal is worked, but not in suffi- cient quantity to affect the ratios perceptibly ; since 1883 the Cleveland figures have been kept entirely separate. 702 ORE AND STONE-MINING. the mines under the Coal Mines Regulation Act are not always more destructive of life than the mines under the Metalliferous Mines Regulation Act ; and secondly, that certain mines worked for metallic ores, such as the iron mines of Yorkshire, and the tin and copper mines of Cornwall and Devon, present more dangers to the underground worker than an average colliery, in spite of the almost complete absence of explosions of gas. In other words, as has been pointed out repeatedly, fire-damp is not the worst enemy the miner has to contend with. It is very evident also that if different classes of mines are to be compared as regards dangers, the figures must be restricted to those working below ground ; and it is to be regretted that some of the official reports concerning mines in other countries afford no means of making the proper compa- rison. On the other hand, foreigners sometimes complain that our British statistics do not give them the true coal-mining accidents separately ; but when the two minerals, coal and ironstone, are being worked in the same pit, and when the preliminary and exploratory work is common to both minerals, it is impossible to draw any strict line of division. Classification of Accidents. In order to obtain some general ideas concerning the kinds of accidents which occur at mines we must begin by classifying them. The basis of such a classification may be either the place where the accident happened, or the cause of the occurrence. Usually the classification is founded upon both. Following the plan which was adopted in the early days of mine inspection in this country, the British classification begins by separating the accidents which happened underground from those which took place at the surface, and then the underground accidents are arranged under the four main heads : Explosions of fire-damp or coal-dust. Falls of ground. In shafts. Miscellaneous. The classification is not strictly logical, because it to a certain extent mixes up cause and place ; there may be explosions of fire- damp or falls of ground in shafts, but these would naturally be placed under the headings which most particularly describe them, so that the heading " in shafts " does not always include every accident which has happened there. However, the classification has been used so long, and is so well understood, that it would be absurd to make any great alteration now. The relative importance of each of these classes is brought out by the following table, which has been calculated for the same periods as the preceding one : ACCIDENTS. TABLE IV. 703 Kinrl nf Annidpnt All the Mines in the United King- dom under the Coal Mines Regu- lation Act. All the Mines in the United King- dom under the Metal- liferous Mines Regulation Act. Stratified Ironstone Mines of the Cleveland District. Tin, Copper, &c., Mines of Cornwall, Devon, Dor- set, and part of Somerset. 3 * ! % * (-1 "o f-i O GO % ||| -5 o 111 |1 111 || 1|| / differential feed gear, 119 Diamond drill continued. for boring holes for blasting, 179, 1 80 Georgi's electric, 124 Little Champion, 123 prospecting, 123 sediment tube for, 119 Sullivan's prospecting, 124 Swedish for hand-power, 123 thrust register, 121 Victorian " Giant Drill," 121 Dickinson's anemometer, 507 water-gauge, 509 Diepenlinchen, pumping engine at, 445 working zinc ore at, 345 zinc ore stockwork, 87 Diffusion of gases, 485 Dig, definition of, 1 1 Ding Dong mine, fire-damp in level at, 477 Dip, definition, 5 influence of change of on veins, 13 Dipping needle, 1 1 1 Discovery of minerals, 93 Diseases caused by arsenical mine- rals, 687 inhalation of dust, 685 ladder climbing, 688 lead ores, 687 quicksilver ores, 687 Disintegrators, 559 Distillation, of rich sulphur rock, 600 use in dressing, 600 Dividings, 237 Divining rod, 1 1 1 Doctor, deduction for, 639 Docwra, diamond setting for boring crown, 118 Dodge Crusher, 547 Dolcoath Mine, Cornwall, 328, 329. man- engine, cost of working, 535 heat at, 670 Dolly, or swage, 181 Dolly tub, or keeve, 5-70 Dorothea mine, Clausthal, under- ground traffic by boats, 373 Double-beat valve, 454 Douglas spruce, 228 Downcast shaft, 484 Downthrow, 91 Dowsing rod, 1 1 1 Drainage, 429 by adit, 433 by pumps, 441 by siphon, 437 by winding machinery, 437 724 INDEX. Drawing lift, 448 Dredges, 175 grab, 176 Kincaid & McQueen's, 175 Priestman's grab, 176 suction, 177 Dressing, definition of, 537 amber, 618 arsenic ore, 619 asbestos, 619 asphalt, 619 barytes, 619 bituminous rock, 598, 619 blende, 625, 630 borax, 620 boric acid, 620 carbonic acid, 620 chert, 622 china clay, 620 clays, 620 copper ore, 621 diamond -bearing rock, 621 flint, 622, 629 fuller's earth, 620 galena, 624, 625 gold ore, 622 graphite, 623 gypsum, 624 haematite, 624 iron ore, 624 lead ore, 624 loss in, 630 magnetite (see magnetic sepa- rators), 624 manganese ore, 625 mica, 625 mispickel, 611, 612, 613, 619 ochre, 626 ozokerite, 626 phosphate of lime, 626, 627 potassium salts, 627 quicksilver ore, 627 salt, 628 silver ore, 628 slate, 628 stone, 628 sulphur rock, 629 Trinidad pitch, 619 tin ore, 629 umber, 626 zinc ore, 625, 630 Drill, ratchet, 155 Drilling rig,- 138 tools, 139 Drills, Adelaide, 195 automatic rotation of, 194 Barrow, 183 Brandt's, 178 classification of, 183 Drills continued. Climax, 185 Darlington, 195 diamond, 179 Eclipse, 187, 1 88 electric percussion, 198 Elliott, 154, 155 for boring by hand, 157 Franke, 189 Hirnant, 192 Ingersoll-Sergeant, 193 Jarolimek, 179 Marvin, 198 Optimus, 189 percussive, 181 rotary, 177 Sergeant, 193 sharpening, 158, 182 Steavenson, 180 steel for, 182 Drive-pipe, 140 Driving levels, 221 tunnels in soft ground, 263 Drums for winding, 391 with reserve of rope, 392 Dry compressors, 166 for China clay, 592 or changing house, 679 rot, prevention of, 230 Drying of minerals, 592 Dubois and Francois air-compressor, 166 boring-ram, 186 Duck machine, 493 Ducktown mine, Tennessee, 108 blower of sulphuretted hydro- gen, 479 Dudley, workings for limestone, 311 Dumb fault, 87 Dunbar and Euston's steam navvy, 173 Dust in mines, evil effects on health, 685 in air of mines, 482 Duty of the miner's inch, 301 of pumping-engines, 472 Dykes, definition of, 14 Dynamite, 213 danger from exudation, 213 pan for thawing when frozen, 213 E EADIE & SONS', joint for lap-welded pipes, 171 Eclipse drill, 188 INDEX. 725 Edge-runners, 556 Edison's deflection magnetic sepa- rator, 606 second magnetic separator, 602 Education Acts', Elementary, 666 general and technical, 682 Efficiency of ventilating appliances, .509 Eisdeben, barracks for workmen, 674 Electric drill, Marvin, 198 Steavenson, 180 lamp, Sussmann, 523 light, 524 percussion drill, 198 railways, 371 Electricity, firing by, 220 pumps worked by, 470 transmission of power by, 172 Elementary Education Acts, 666 Elephant stamps, 551 Elliot's locked coil wire rope, 400 Elliott drill, 155 multiple wedge, 208 Elwen on the resistance to air- currents, 511 Embrey concentrator, 586 Emmons, S. T., on the geology of the Leadville district, 57 on the veins in the Kocky Mountain region, 7 Employers' Liability Act, 666 Ems, loss in dressing at, 631 End, ventilation of an, 485, 487, 492, 493 going into, after blasting, 686 Endless chain system of haulage, 37i rope system of haulage, 367 advantages of, 369 attachment of waggons to, 368, 379 De Beers mine, 378 End-piece, 237 Equilibrium pipe, 274 Erigonum ovalifolium, 104 Ernst August Stolln, 434 Eucalyptus, species used for mining purposes, 229 Eureka, Nevada, silver-lead deposits of, 77 square-set timbering, 247 Europe, trees used for mining pur- poses, 227 Eustice, changing house at Levant Mine, Cornwall, 679 Evans and Veitch, pump for raising water by compressed air, 471 Evaporation of brine, 609 Excavating by water, 226 machinery, 173 Excavation of minerals underground, 308 under water, 302 Excavations, supporting. 227 Exploitation, 285 Explosions of fire-damp, 476, 477 Explosives, accidents from, 707 strength of, 216 used in mining, 209 Explosives Act, 666 Extraction of minerals by wells and boreholes, 304 F FACTORY and Workshop Acts, 667 Fahlbands at Kongsberg, Norway, 12 Falls of ground, accidents from, 704 Falun, torches used at, 515 Fans, Capell, 495 efficiency of, 509 Guibal, 496 Schiele, 497 use of, in dressing, 590 Waddle, 497 Faults, 87 length of, 90 measurement of throw of, 89 recovery of lost part of bed, 89 recovery of lost part of lode or vein, 91 reversed, 90 variations of throw along the strike, 90 Feeders or droppers, definition of, 12 Fencing Act, Quarry, 667 Fend-oft' bob, 446 Fernow on the trees available for mining purposes in the United States, 228 Festiniog, boot worn by rockman, 673 method of working slate at, 312 preparation of slate at, 628 slate mines, charging spoon used at, 161 drivages at, 222 jumper used at, 157 tribute system at, 649, 651 Field, Mr. Justice, on the Kichmond v. Eureka case, 8 Filling up, working with complete, 322, 331, 335, 341, 343, 346 Fir, Scotch, 228 726 INDEX. Fire-clay, 26 weathering of, 611 Fire-damp found in ore mines, 476 testing for, 498-501 Fireless locomotives, 363 Fires, accidents from underground, 708,709 in sulphur mines, Sicily, 321 Fire-setting, 225 Firing by electricity, 220 explosives, 218 Firth's pick machine, 199 Flare lamp, 516 Flat-rope, winding with the, 393 Flattened strand wire rope, 400 Flint, dressing of, 622 mining at Brandon, Suffolk, 41 Flints, shaping of, 629 Floating reef in Kimberley dia- mond mines, 38 Flooded workings, breaking into, 707 Flookan, explanation of term, 14 Floor of a bed, definition of, 5 of changing house, 68 1 Florida, phosphates of, 69 Flume, 294 Fluted rolls, 556 Foot-wall, definition of, 10 Forest of Dean, method of working haematite masses, 340 Mining Acts relating to, 655 Form for pump bucket, 448 Form of the ground indicating de- posits, 98 Formation of mineral veins, 14 Formations or classes of lodes, 17 Foxdale lead mine, carbonic acid at, 475 mode of working lode, 335 strike of lode, 14 Frames, 579 for levels, steel, 260 wood, 233 for shafts, 236 France, underground workings for slate, 314 Franke drill, 189 Franke's mechanical chisel, 199 Free-falling tools, Arrault, 129 Kind, 130 Free-milling ores, 101 Freestone, 41 mode of working, 310 Freezing method of sinking shafts, 278 Freiberg, formations of lodes at, 17 French miner's hat, 671 Friability, use of in dressing, 607 Friction due to sides of airway, 510 Frongoch jigger, 573 self-discharging skip, 416 separator, 576 Frozen dynamite, 213 Frue vanner, 585 for gold ores, 622 Fuller's earth, 27 dressing of, 620 kiln, 595 Furnace, Brunton's, 596, 613 roasting, 611 ventilation, 490 Furness district, temporary dam used in, 433 Fuse, electric, 220 for blasting purposes, 217 for simultaneous blasting, 220 GAD, 154 Galena, dressing of, 624, 625 Galicia, Canadian system of boring in, 134 ozokerite mines of, 63 Galloway on the fire-damp cap, 499 Galloway's automatic water tank, 438 double walling stage, 409 method of guiding kibble, 408 pneumatic water-barrel, 438 steel tram, 359 winding drum, 392 Garfield Mine, California, 79 Garland, 267 Gamier, discovery of nickel ore in New Caledonia, 99 Gas for underground lighting, 522 Gases produced by decomposition of gun-cotton, 215 of nitro-compounds, 212 explosion of gunpowder, 210 blasting, 481 Gates crusher, 560 Gatzschmann, on animals as indica- tors, 105 Gearing pump-buckets, 448 Geikie, Sir A., definition of a mineral vein, 6 Gelatine dynamite, 214 Gelignite, 214 Geology as a guide to minerals, 97 German miner's hat, 672 Germany, amber dredging, 304 carbonic acid gas in, 25 copper deposits of, 29 death-rate from accidents, 699 Law of Insurance, 694 occurrence of zinc ore in, 87 INDEX. 727 Gerolstein, borings for carbonic acid gas at, 25 Giant granite, 58 mines, 290 powder, 214 Gillott and Copley's machine, 203 Gill's furnace for sulphur extraction, 600 Githens system of boring, 162 Gobert's modification of Poetsch's freezing process, 283 Gold, amalgamation of, 616 associated minerals, 97 in gozzan, 100 modes of occurrence, 4 1 ores, treatment of, 622 Run Ditch and Mining Co. , 302 worked in Alps by Romans, 618 Gold-bearing gravel, method of mining in California, 318 prospecting for in Siberia, 278 working, 293 yield of, 302 Good conduct, premiums for, 652 Gooseneck, 402 Gouge, definition of, n Gozzan, 99 at the Anaconda mine, 37 at Rio Tinto, 33 influence of, on value of ore, 101 Graphite, 50 dressing of, 623 in Bavaria, 607 Gravitation stamps, 548 Great Basin, borax deposits of the, 2 3 Greathead shield, 263 Great Laxey Mine, locomotive, 363 overshot wheel, 442 Great Quartz Vein of California, length of, 1 1 outcrop of, 99 Great Western quicksilver mine, California, 74 outcrop of lode, 98 Greaves' circular slate-dressing machine, 565 Grey box, 229 Griffith, on coffering, 268 Grime's graves or ancient workings for flint, 41 Grimm, definition of a mineral vein, 6 Grinders, Grusonwerk ball, 557 ball, 557 centrifugal, 561 conical, 560 Jordan's, 557 /See also tinder CEUSHEES Grizzly, 299 Groove-cutters, 201 Groove-cutting machines, 199 Grooves cut by circular saw, 202 travelling rock drill or jumper, 20 1 made by endless chain with cutters, 204 revolving bar with cutters, 206 wire saw, 204 Grusonwerk ball grinder, 557 Gudgeon, 457 Guibal fan, 496 Guides for shafts, 408 Guillotine slate-dressing machine, 5.65 Guinotte, pumping-engines with fly- wheel, 444 Gun for clearing bore-holes, 160 Gun-cotton, 215 products of decomposition, 212, 215 Gunpowder, 209 charging holes with, 217 products of explosion of, 210 Gunpowder Act, Slate Mines, 659 Gutta-percha packing for pump, 448 Gympie gold-field, lodes of, 13 Gypsum, 50 calcination of, 611, 613 discovery of, by sub-wealden boring, near Battle, 96 dressing of, 624 occurrence of, 50 quarries, Paris, 309 H HAASE process of sinking shafts, 283 Habets on annual death-rate from accidents, 699 Hade, definition of, 9 Haematite at Iron Mountain, Mich- igan, 54 deposits of the Ulverston dis- trict, 19 dressing of, 624 method of working, 340, 343 searching for by piercing, 106 veins of the Lake District, Kendall on, 7 Haeuser process for sinking in quicksand, 284 Haggle's patent Protector rope, 400 Hake's mouth valve, 453 Hale and Norcross mine, heat at, 670 728 INDEX. Half-moons, 448 Halkyn Drainage Tunnel, 223, 435 iron supports, 255 Halkyn Mine, Flintshire, slickenside at, 10 wooden pulley-frame, 395 Hallett, Judge, on the Aspen Case, 9 Hall's stone-breaker, 547 Hammer, of Mansfeld, on lifting beam of pumping engine, 461 on the friction of guides for pump rods in shaft, 473 Hammers for boring by hand, 159 Hanarte's air-compressor, 165 Hand-barrows, 375 Hand- drilling, 157, 160 Hand-picking, 541 Hand-power diamond drill, 123 rotary drills, 155 Hand-sampling, 632 Hand-sieves, 566 Hand-tools, 151 Hang- fire, 217 Hanging wall, definition of, 10 Haniel and Lueg's keps, 419 Hurting and Hesse, on cancer of lungs caused by dust, 686 Hartz blower, 493 Ernest Augustus adit, 434 foreman's lamp, 516 iron rails used as supports, .. 2 5 8 Jig. 570 miner's lamp, 515 timbering chamber for water- wheel, 241 timbering for shaft, 240 use of water power, 442 Harvey on the occurrence of ni- trate of soda in Chili, 62 Hat, Cornish miner's, 671 French miner's, 671 German miner's, 672 ideal miner's, 672 ironstone miner's, 671 Mansfeld miner's, 672 Koumanian miner's, 672 Hatches, 389 Haulage, 348 electric railways, 371 endless chain, 371, 379 endless rope, 367 horses, 362 locomotive, 363 main and tail rope, 366 single-rope system, 365 Head-gear, 394 Heat at mines, 670 of mines on Comstock Lode, 76 of workings, influence on health, 689 Heated floors, drying on, 592 Heave, 88 of vein sideways caused by slip along line of dip, 91 Heavy spar, bleaching of, 609 occurrence, 23 Heights (N. Lancashire), 344 Hepplewhite-Gray lamp, 521 Hercules powder, 214 Hesse's method of testing the air, 503 505 Himmelfahrt works, loss at, 630 Hirnant drill, 192 Hirt, on prevention of illness from arsenic, 686 Hitches, 154, 231 Hockin and Oxland calciner, 613, 6i5 Hoffman magnetic separator, 602 Hofmann kiln, 613 Hoisting, 387 Holes, arrangement of, for driving and sinking, 222, 225 Holway Consols mine, explosion of fire-damp, 476 Honigmann, soda locomotive, 364 Honningen, carbonic acid gas at, 25 Hopper of hydraulic elevator, 300 Hoppet, 408 Horned sets, 233 Horse in lode, definition of, 1 1 -whim, 389 Horses, underground hau-lage by, 362 Hospitals, 695 Hot springs, 476 Hottinguer shaft, Blanchet's pneu- matic hoist at, 428 House, changing, 679 Housing of workmen, 673 Howard's steel sleeper, 352 Ho well's steel tube prop, 266 H-piece, 451 Huanchaca silver mines, 78 Huelva, port of, 380 Hund, 351 Huntington mill, 561 Hurricane lamp, 516 Hurry, 344 Husband's stamps, 551 Hushing, 106 Hydraulic cartridge, 208 drill, 1 80 elevator, 300 lock for safety lamps, 522 INDEX. 729 Hydraulic continued. mining, 226, 292 power, 171 for breaking ground, 163 transmission of power, 469 Hydrogen flame used in testing for fire-damp, 500 I ICE, 51 Iceland, mode of occurrence of sul- phur in, 82 Idria, occurrence of quicksilver ore at, 72 treatment of quicksilver ores, 627 Illicit Diamond Act, 677 Incandescent lamps in shaft sinking, 524 portable, 523 Inclination of a level, effect of, on ventilation, 485 of underground road, 355 Incline, natural ventilation of, 486 Inclined planes, accidents on, 708 underground, 362 shafts sunk on lode, 225 Inclines, 308 self-acting, 376 Indications of tire-damp, 498 Indicative plants, 103 Indicator for winding engines, 421 Indicators at Ballarat, 13, 1 6 Inflammable gas, 59, 476 Ingersoll bar-channeller, 201 -Sergeant air-compressor, 167 Injection compressors, 166 of veins, 14 Intersection of veins, 1 1 Inversion of strata, 88 Inverted saddle-reefs of Victoria, 47 Iron and steel supports for levels, 255 shafts, 263 working places, 265 Iron-bark, 229 Iron hat, or gozzan, 100 Iron ladders, 529 Iron mines, Forest of Dean, method of working, 340 N. Lancashire, method of work- ing, 343 Iron ores, dressing of, 624 occurrence of, 51 Northamptonshire open work- ings, 286 Iron pump-rods, Shakemantle mine, 461 Iron pyrites, Carnarvonshire, 83 Iron rails used for supporting roof of level, 256, 259 Iron rings for supporting shaft linings, 263 Iron rods for boring, 124 Ironstone blows (Australia), 100 Ironstone, method of working in Cleveland district, 315 miner's cap, 671 Irruptions of water into mines, 707 Irving on the copper veins of Lake Superior, 36 Itabirite, 40 Italy, alabaster in, 51 asbestos mines of, 21 boric acid in, 25 carbonic acid gas in, 26 marble in, 58 mining law in, i, 2 mode of occurrence of sulphur in, 82, 83 JACK, on the Mount Morgan gold deposits, 48 on the outcrop of gold veins in Queensland, 98 Jacobi's stove, 597 Jacomety and Lenicque's separa- tors, 575 table, 583 trommel, 567 Jacotinga, 44 Jad, 310 Jagersfontein diamond mines, 39 Jan Ham's clack, 453 Japan, torches used in, 515 working by reflected daylight in. 53 Jarolimek's drill, 179 Jarrah, 228 Jars, 140 Jaw-breakers, 546 Jigger, 570 pneumatic, 589 Jiggers, discharge of, 572 Jog, 237 Johannesburg, deep boring at, 119 gold-bearing rocks of, 42 thickness of beds of auriferous conglomerate, 5 Joint for wooden rods, 445 Jordan's grinder, 557 730 INDEX. Jumper, 157 Jtmge hohe Birke mine, cage at, 533 KAINITE, occurrence of, 70 Kaiser Josef Erbstolln, Hungary, 434 Kaiser Josef II. adit, Pribram, 434 Kauri gum, searching for by piercing, 106 pine, 229 Keeve, or dolly-tub, 570 Kendall on the geology of the Cleve- land district, 41 on the hasmatite veins of the Lake District, 7 Kennedy on the efficiency of com- pressed air, 164 Keps, 419 Kessler, magnetic separator, 602 Kibble, 404 Kieselguhr, 213 Kiln, American phosphate, 594 fuller's earth, 595 Hofmann, 613 Kilns for drying, 594 Kimberley diamond district, 37 mines, compound for native workmen, 677 method of working at De Beers, Kincaid and McQueen's bucket dredger, 175 Kind, free-falling tool for boring, 130 -Chaudron process of sinking shafts, 271 recent modifications, 276 King and Humble's detaching hook, 422 King,ori the "indicators " at Ballarat, 13 on the Comstock Lode, 76 King-post, 457 King's magnetic separator, 604, 606 Kitto, Paul and Nancarrow, self- discharging skip, 416 Knots in the lead-bearing sand- stone at Mechernich, 55 Knox system of boring holes for rending stone, 162 of charging holes, 220 Kongsberg silver mine, fire-setting, 225 silver veins of, 12 Korea, fire-setting in, 225 Kreischer and Winkler on the ap- pearance of the fire-damp cap, 499 Krom rolls, 554 Krom's stove, 595 LABOUR, principles of employment of mining, 637 Ladder-climbing, diseases caused by excessive, 688 Ladders, 527 iron, 529 Lagging, 233 Laidler's sector wire rope, 401 Lake Superior, copper-bearing dis- trict of, 34 iron ores of, 54 mines, stamps used at, 551, 553 treatment of copper ore at, 621 La Louvifcre mine, Belgium, 467 Lamm and Franck's fireless locomo- tive, 363 Lamp, electric, 523 flare, 516 Hartz foreman's, 516 Hartz miner's, 515 Hurricane, 516 magnesium ribbon, 517 Mansfeld, 516 safety, 518 Saxon miner's, 516 Scotch, 516 Sicilian, 515 United States, 516 Lander, 410 Lang's wire rope, 400 Larch for timbering excavations, 227 Lashings, 237 Latch and Batchelor's flattened strand wire rope, 400 Lateral secretion theory of forma- tion of mineral veins, 15 Laths, 243 Lawn, on searching for haematite in the Furness district, 106 on working haematite in North Lancashire, 343 Laxey mine, locomotive at, 363 man-engine at, 535 strike of lode at, 14 Lead lode at Wheal Mary Ann, 6 ores, dressing of, 624 modes of occurrence, 55 state of in gozzan, 101 plant, 104 poisoning, 687 prevention of, 687 rivet for safety lamps, 522 INDEX. Lead-bearing sandstone, Mecher- nich, 1 8 Lead, mode of working, 320 Leadville, Colorado, mode of occur- rence of lead ores at, 55, 57 Lease system in Colorado, 647 Leather packing for pumps, 448 Leats, 293 Leavitt stamp, 553 Legal definition of the term lode, 8 Legislation affecting mines and quarries, 653 Leg, or side-prop, 232 Legrand's steel sleeper, 352 Lenneschiefer, Liiderich mine, 85 Lesley on the composition of natural gas, 59 Lester's stone-breaker, 547 Levant Mine, changing house at, 679 Level, natural ventilation of end of, 485 use of air-sollar in ventilating end, 487 Levels, driving, 222 iron and steel supports for, 255- 263 lined with masonry, 250 methods of timbering, 232 ventilating lower, 489 Liability Act, Employers', 666 Lid, 244 Lievin Company, shaft sunk by, 277 Lifts (Cleveland), 316 Lighting workings, 513 Lime cartridge, 208 Limestone, bituminous, Val de Travers, 22 burning of, 611, 613 Lime-water test for the air of mines, 502, 503 Lindemann's apparatus, 506 Lining boards, 445 bore-holes, 131 tube, boring by revolving the, 117 tube for brine well, 305 Linkenbach, stationary table of, 581 Liquefaction of carbonic acid, 600 use of, in dressing, 597 Listings, 237 Lithofracteur, 214 Liveing's indicator for fire-damp, 500 Llanbradach Colliery, automatic water-tank at, 437 sinking arrangements at, 408 steel trams at, 359 Loading kibble, 405 skip in shaft, 410, 412 Learning (Australia), 106 Lochs, definition of, 6 Locked coil wire rope, 382, 400 socket for, 403 Lockhart's gem separator, 577 Locks for safety lamps, 522 Locomotives for underground use, 363 for use at the surface, 378 Lode at Wheal Mary Ann, 6 definitions of, 5, 6 legal definition of, 9 modes of working, 325, 340 narrow, mode of working, 330 wide, with weak sides, mode of working, 331 worked away in slices parallel to dip, 335 Lode-lights, 107 Lodes, conditions affecting produc- tiveness of, 1 1 length of, along strike, 1 1 formed by alteration of the en- closing rock, 7 wide, worked with pillars and chambers, 338 Lofting, 256 Longwall workings for copper-shale at Mansfeld, 322 Loose ground, supporting excava- tions in, 242 timbering levels in, 236 Lorraine, iron ores of, 53 Loss in dressing at Churprinz works, 631 at Ems, 631 at Himmelfahrt works, 630 at Pestarena, 631 cause of, 630 slate, 631 Lovett-Finney magnetic separator, 603 Lowmoor jacket, 713 Lubrication of mine waggons, 358 Luderich zinc mine, 85 Lunge's apparatus for testing the air of mines, 503, 505 M MACGEOKGE on deviation of bore- holes, 148 Machine drills, 181 sieves, 566 Machinery, accidents from, 711 clothing for men engaged near, 673 Magnesium ribbon lamp, 517 732 INDEX. Magnetic lock for safety lamps, 522 separation, 600 bismuth ore with magnet- ite, 606 Namaqua Copper Co., 606 objects of, 600 Queensland, 606 separators, 600 Ball-Norton, 603, 606 Buchanan, 604 Chase, 60 1 Conkling, 601 Edison, deflection, 606 second, 602 Hoffman, 602 Kessler, 602 King, 604, 606 Lovett-Finney, 603 Wenstrom, 605 Magnetite, dressing of, 600 jigging, 624 Main and tail rope system of haul- age, 366 Majendie, Colonel, on the effect of oil on safety fuse, 217 Malay Peninsula, tin-bearing alluvia of, 85 Mallard and Le Chatelier on testing for fire-damp, 500 Mallet, or sledge, 154, 159 Man-engine, 534 accidents on, 705 Manganese ore, dressing of, 625 occurrence of, 57 Mansfeld copper-mines, 29 adit at, 434 barracks for workmen, 674 compound pumping engine, Ernst IV. shaft, 443 compound pumping engine, Otto IV. shaft, 444 cross-cut lined with concrete, 251 descent and ascent of men, 532 employes living in own houses, 679 hydraulic counterpoise to pump rods, 458 lamp used at, 516 man-engine at, 536 method of working copper- shale, 322, 325 miner's hat, 672 pick used at, 153 Kittinger pump at, 456 thickness of bed of copper- shale, 5 treatment of copper ore at, 621 Mansfeld copper-mines continued. underground air reservoirs at, 169 underground pumping engines at, 467 Marble, 58 Maros-Ujvar, arc-lamp at, 524 Marsaut lamp, 521 Marsden's pulveriser, 547 stone-breaker, 547 Marshall, discovery of gold in California by, 94 Marsh-gas, found in mines, 476 Marston Hall mine, 311 Marvin drill, 198 Masonry, for lining levels, 249 shafts, 252 dam in shafts, 433 Masses, or non-tabular deposits of minerals, 18 methods of working, 340 Matai wood, 229 Mather and Platt's system of boring, 142 Mathet, joint for air-mains, 170 Matrix, definition or', 1 1 Maul, 141 Measure, payment by, 638, 639, 640 and time, payment by, 641 Measuring the quantity and press- ure of air in mines, 506, 512 staff, 231 Meat earth, 286 Mechanical picks. 199 processes of dressing, 538 ventilation, 491 Mechernich, arc-lamp at, 524 barracks for miners, 674 dressing lead ore at, 625 friability of ore, 607 jumper used at, 157 lead-bearing sandstone of, 5, method of working lead-bearing sandstone, 320 opencast, 289 pumping engines at, 467 siphon separator used at, 579 Medical attendance, deduction for, 639 Medium fan, 498 Mercurial poisoning, symptoms of, 688 vapour in quicksilver mines, 480 Metales frios, or unchanged sul- phides, 1 01 Metallic supports for excavations, 255 INDEX. 733 Metalliferous Mines Regulation Acts, 656 accident statistics, 700, 701 Mica, dressing of, 625 mode of occurrence of, 58 Middlesbrough, extraction of salt by bore-holes, 305 marsh-gas with brine, 476 Mill, Chilian, 557 Huntington, 561 Sturtevant, 563 Close lead mine, Derbyshire, explosion of fire-damp, 476 Mills for grinding, 556 or passes, 330 Mine, atmosphere of, 475 definition of, i derivation of word, i Miner, clothing of, 669 condition of, 669 regulations for benefit of, 655 Minera zinc mine, Wrexham, 86 Mineral deposits, classification of, 3 repositories, anomalies in, 17 veins, connection of, with faults, 89 formation of, 14 Minerals, ownership of, 653 Minero bird at Caratal, 105 Miners' cottages, 677 housing, 673 inch, definition of, 301 Minette, 53 Minieres, definition of, i Mining, comparative healthiness of, 683 definition of, i labour, principles of employ- ment of, 637 law, in France, i in Italy, i, 2 in the United Kingdom, i in the United States, 8, 9 statutes, 656 relating to Derbyshire, 655 to Forest of Dean, 655 subdivision of the subject, 2 Miscellaneous pulverisers, 563 Mispickel, treatment of, 611, 612, 613, 619 Miss-fire, 217 danger from, 213 Moil, 231 Molinello, 618 Mona and Parys mines, cobbing at, 545 Monier system of using concrete, 254 Monitor, 296 Montana, copper deposits of, 37 Monte Catini, flora of, 104 Monteponi, Sardinia, adit at, 435 roasting calamine at, 615 Moore, pumps worked underground by hydraulic power, 469 Moravia, dressing of graphite in, 623 Mortality, comparative figures, 683, 684 Moss-box, 273 Mother Lode or " Great Quartz Vein," California, 45 Motion of particles in water, 568 Mount Bischoff, dressing tin ore at, 630 Morgan gold mine, 48, 97 Mountfield gypsum mine, Sussex, 437 Mueseler's lamp, 520 Mulberry mine, near Bodmin, 19 mode of working, 290 Murgue, on the resistance to air- current due to sides of airway, NAMAQUA COPPEE Co., magnetic separator used by, 606 Names of places, information afforded by, no Natural gas, conveyance by pipes, 373 occurrence of, 59 Natural ventilation, 482 Needle, 161 Neu-Stassfurt mine, electric rail- way, 371 Nevada, Comstock lode, 76 mineral deposits at Steamboat Springs, 75 New Almaden, California, 73 Brunswick, antimony ore in, 21 Caledonia, cobalt ore in, 28 nickel ore in, 60 Idria, working by reflected day- light at, 513 South Wales, alunite in, 20 tin-bearing alluvia of, 85 Zealand, trees used for mining purposes, 229 Nickel ore, discovery of, in New Caledonia, 99 ores, mode of occurrence of, 60 Nitrate of soda, mode of occurrence of, 62 mode of working, 286 preparation of, 608 or THE 734 INDEX. Nitrate mixtures (explosives), 210 Nitro-cellulose, 215 Nitrogen in mines, 479 Nitro-glycerine, 211 products of explosion of, 212 Noble and Abel, on fired gunpowder, 209 Noetling, on the oil-fields of Bur- mah, 66 Nog, 232 Nolten, on finding deviation of bore- holes, 148 Northampton, deep boring at, 118 Northamptonshire, mode of working iron ore, 286 North Lancashire, dressing haema- tite in, 624 working hsematite deposits, 343 royalties in, 654 North Wales, iron pyrites, 83 slate mines, 312 washing pit used in, 539 North wich, salt beds of, 75 Nunnery Colliery, steel beams, 256 Nystagmus, 688, 689 OAK for timbering excavations, 227 Ochre at Parys mine, 616 dressing of, 626 Ochsenius, on the origin of the nitrate deposits of South America, 63 Oeynhausen's sliding joint, 128 Ogle, Dr., on annual death-rates in various trades, 683, 684 Ohio, mode of occurrence of natural gas in, 59 Oil, effect of on safety fuse, 217 fields of Baku, 65 of Burmah, 65 of the United States, 67 Oil-wells, gases met with in sinking, 477 Oils used in lamps, 515, 516, 519 Olaf Terp, use of emery for boring, 124 Open-fire drying, 592 Open works, 285 Optimus drill, 189 Ormerod's detaching link, 416 Osceola Co.'s mine, arc-lamp at, 525 Otago, New Zealand, lodes of, 8 Otto's system of aerial ropeway, 382 Outcrop of lodes, 98 Overburden, 286 Overhand stoping, 329 advantages of, 331 Overlap fault, 90 Overwinding, 422 Ovuli, 51 Ownership of minerals, 653 Oxygen, absorption of, 480 determination of, in the air, 506 necessity for a large proportion of, 505 Ozokerite, dressing of. 626 extraction of, by benzine, 609 mines, Boryslaw, inflammable gases at, 477 mode of occurrence of, 63 purification of, 598 PACKING plunger pump, 452 pump bucket, 448 Pacos (S. America), 100 Pan, for amalgamating gold ores, 622 for grinding and amalgamating, 556 for prospecting, 538 Paragenesis of minerals, 97 Parian cement, 613 preparation of, 624 Parodi on the Sicilian sulphur beds, 83 Parys mine, extraction of copper by solution, 307 precipitation at, 616 Pass, 332 best form of, 348, 349 Patterson's stamps, 551 Paxman's roller for Huntington mill, 561 Pay-bill for payment by measure, 638 value of product, 642 weight, 640 Pay-lead, 318 Payment by measure, 638, 639. 640 time, 637 time and measure, 641 value of product, 641 weight, 639 Pearce, on the tin-lodes of Corn- wall, 7 Peeker, 222 Penhall's mine, Cornwall, succes- sion of faults at, 92 Penrhyn slate quarry, 288 Pensions, 693 INDEX. 735 Percolation of surface water into workings, 429 Percussion tables, 584, 589 Perpendicular shafts, advantages of, 325 Pestarena, loss of gold at, 631 Petroleum, 65, 66 conveyance by pipes, 374 extraction by wells, 304 Petroleum engine, 163 for pumping, 445 for working drill, 180 Pettenkof er, on the limit of carbonic acid in air, 502 Phenolphtbalein, use of, in lime- water test, 502 Phillips, on the mica of North Carolina, 58 Phosphate kiln, American, 594 Phosphate of lime, 67, 69 discovery of, at Beauval, France, 94 in South Carolina and Florida, 68, 69 search for, by piercing, 107 treatment of, 626 weathering of, 611 Photometric tests of light given by safety lamps, 519, 520 Physical properties, dressing pro- cesses depending on, 568 Pick and gad work, 154 handles, 153 Picking by hand, 541 Picks, 152 mechanical, 199 sharpening, 153 with separate blades, 153 Picric acid, explosives containing, 215 Pieler lamp, 499 testing for fire - damp with hydrogen flame, 500 Piercing, 106 Pigsty timbering, 245 for levels, 234 for shafts, 239 Pilar, on Franke's mechanical chisel, 199 Pillaring of slate, 81 plane, 314 Pillars and chambers, working wide lodes with, 338 left as permanent supports, 309 worked away, 315 Pine, varieties used for mining purposes, 227, 228 Pipe- lines, 374 Pipes, conveyance of minerals by, 349 Pipes continued. for compressed air, 170 for conveying water, 295 for pump column, 450 wooden, 450 Pitch lake of Trinidad, 22 of a shoot of ore, definition of, ii purification of, 598 pine, 227 Pit-head frame, 394 Plane tables, 579 Planing machines, 565 Plank tubbing for shafts, 266 Plants, indications of minerals afforded by, 103 Plaster of Paris, 613 preparation of, 624 Plat, 405 Plug and feathers, 208 Plumbism, 687 Plunger pump, 451 Plutonic rocks, 3 Pneumatic hoisting, 427 jig, 589 Poetsch's freezing process, 281 Pohle pump, 470 Points and crossings, underground, 354 Poling, 236 Pollution Prevention Act, Eivers, 667 Pontgibaud lead mines, carbonic acid at, 475 Poppet heads, 394 Post, 237 Potassium salts, deposits at Stass- furt, 70 discovery of, at Stassfurt, 96 method of mining, 315 treatment of, 627 Potosi, 78 Precipitation, 616 Premiums for good conduct, 652 Preparation of ores. See DRESSING, Preservation of timber, 229 Pressure of air, influence on health, 689 box, 295 Pricker, 161 Piibram, deep shafts at, 404 underground fire at, 708 Priestman's grab dredger, 176 Principles of employment of mining labour, 637 Prop, 244 Props, iron and steel, 265 736 INDEX. Prospecting, or search for minerals, 93 by the diamond drill, 119, 123 by the diamond drill, cost of, 122 Prospector, qualifications of, 112 Provident societies, 690 Prussia, accidents from man-engines, 705 Puddling machine, Australia, 539 Pulley-frame, 394 Pulleys, 397 Pulsator, 622 Pulsometer, 468 Pulveriser, Cyclone, 563 Marsden's, 547 Pulverisers, miscellaneous, 563 pneumatic, 563 Pump column, 450 for extracting brine from bore- hole, 306 lifting, 448 plunger, 451 plunger, advantages of, 452 Pohle, 470 pulsometer, 468 Biedler, 467 Rittinger, 454 rods, 445 counterbalancing, 457 iron, 461 valves, 453 Pumping engines, compound, 443- 445 duty of, 472 placed underground, 466 single acting, 443 machinery, moving heavy parts of, 461 plant, Shakemantle mine, 461 Pumps, drainage by, 441 driven compressed air or elec- tricity, 470 drowning of, 450, 446, 467 wooden, 450 worked by hydraulic power, 469 Purifying water from dressing works, 667 Pyrites, Carnarvonshire, 83 mode of working in North Wales, 309 worked opencast, Rio Tinto, 289 Q QUAEEIES, definition of, I raising stone from open, 406 Quarries continued. slate, North Wales, 312 underground sJate, Ardennes, 3H stone, Bath, 310 Quarry Fencing Act, 667 Quartering, sampling by, 633 Quenast quarries, premiums for good conduct, 652 Quicksand, Haase process of sinking in, 283 Poetsch process of sinking in, 283 Triger's process of sinking in, 277 Quicksilver, chance discovery of, in California, 94 mines of California and Nevada, Becker on, 16 mines, unhealthiness of, 687 ore, occurrence of, 71 ore, treatment of, 627 rock, 74, 103 II RACK-A-EOCK, 211 Ragging, 544 Rails, 351 Railways, electric, 371 surface, 376 underground, 351 Rammelsberg Mine, Hartz, pyrites deposit, 32 Rand, gold output, 43 Ratchet drill, 155 Rating Act, 655 Raymond, on indicative plants, 104 Recreation, 696 Red clay of New Caledonia, 28, 60 Red bar (Johannesburg), 103 Redonda, phosphate of alumina at, 69 Red River, tin ore got from, 630 Reflected daylight, working by, 5 J 3 Regulations for mines, working, 655 Regulations. See ACTS, 656 Reservoirs for compressed air, 168 for hydraulic mining purposes, 293 Resistance to air-current, 510-512 Restronguet creek, dressing of tin ore at, 629 method of working tin-bearing gravel, 316 occurrence of tin- ore in alluvium of, 85 shaft- sinking at, 268 INDEX. 737 Reticulated masses, 19 Retorting amalgam, 600 sulphur ores, 600 Returning charges, 642 Reumaux's automatic speed checker, 425 Revolving round table, 583 Reversed fault, 90 Rewarewa, 229 Rhosesmor mine, Flintshire, 435 Rice's clutch, 369 Richness of lodes, conditions affect- ing, ii Richmond v. Eureka case, 8 Rickard, on Mount Morgan mine, Queensland, 49 on the saddle-reefs of the Ben- digo gold-field, 47 Riebeck's stove, 595 Riedler pumps, 467 Riffles, 299 Rigg and Meiklejohn's machine, 203 Rinchiusu, 475 Rio Tinto, arc-lamp at, 525 character of ore at, 33 geology of the district, 31 gozzan, 33 lodes at, 32 mines, shipping arrangements at Huelva, 380 opencast, 289 pillar and chamber workings, 338 precipitation at, 616 timbering for levels, 233 treatment of copper ore at, 621 Rise, difficulty of ventilating, 486 mode of ventilating, 488 Rises, method of timbering, 344 Rittinger, fall of spheres in water, 568 Rittinger pump, 445, 454 Rittinger's percussion table, 584 Rivers Pollution Prevention Act, 667 Rivers, sinking shafts in, by freezing, 280 Roasting, 611, 613 Roberts, C. Warren, sleeper, 353 Roburite, 215 fumes from explosion of, 481 Rock-boring competition, 159 Rock-drills, 177 Rock-salt at Stassfurt, 70 Rods for man-engines, 535 for pumps, 445 Rolland's tireless locomotive, 363 Rolls, Cornish, 553, 554 Krom, 554 Roof of a bed, definition of, 5 slate mining, 312, 313 Root's blower, 494 Rope haulage, 365 preventing shock to, in winding, 427 socket, 139, 140 Ropes for winding, steel, 399 modes of capping, 402 testing, 427 Rossigneux system of counterbalanc- ing, 459 Rotary machine drills, 178 washing machine for diamonds, 540 Rothliegendes in Mansfeld district, 29 Rothschonberger Stalin, 434 Rou mania, salt mines, 312 Roumanian miner's hat, 672 Round tables for picking, 542 for sluices, 581 Rowoldt's stove, 597 Royalties, 654 sliding scale for, 654 Ruelle's stove, 596 Ruins, indications afforded by, 109 Running loop, 447, Russia, manganese ores of, 57 occurrence of quicksilver in, 73 Ry land's glass-lined pipe, 171 S SABOT, 673 Saddle reefs, Victoria, 47 Safety catches, 426 on cage, 418 fuse, 217 gear for hauling men at Bory- slaw, 531 lamp, used for testing for fire- damp, 499 lamps, 518 St. Agnes, Cornwall, tin lodes of, 84 St. Day mines, heat at, 670 Saint-Etienne, mine-waggon used at, 358 St. Just, strike of lodes at, 14 Salisbury Mine, Johannesburg, 42 Salt, discovery of in Cleveland district, 96 excavating by water, 226 extraction by wells and bore- holes, 304 3 A INDEX.' Salt continued. minerals associated with, 97 mines, Cheshire, 311 Roumania, 312 occurrence of, 75 preparation of, 628 workings for at Bex, 307 works affected by Alkali Acts, 665 Salzkammergut, mode of working salt-marl, 307 Sampling by hand, 632 quartering, 633 taking out small lots, 632 trenching, 632 object of, 632 machine, Bridgman's, 635 Brunton's, 635 Clarkson's, 634 Colorado, used in, 634 shovel, 633 Sandals, 673 San Domingos, 34 Sand-pump, 140 Sand-reel, 139 Sandstone, bituminous, California, 22 interstitial space in, 18 lead-bearing, Mechernich, 5, 18 silver-bearing of Utah, 18 Sarrau and Vieille, on the decompo- sition of certain explosives, 212 Savage mine, heat at, 670 Sawing machines for stone, 564 Saws, circular, use for undercutting, 202 for cutting stone, 154 timbermen's, 231 used in getting freestone, 310 wire, 204 Sawyer on underset of props in in- clined beds, 244 Saxon gad, 154 miner's lamp, 516 Schaffer and Budenberg's speed indicator, 533 Schiele fan, 497 Schools, 682 Schrader on Franke's mechanical chisel, 199 Schulz's stove, 597 Scotch fir, 228 lamp, 516 Scotchman's United mine, bore- hole at, 148 Scraper, 160 Screening, 566 Screw-conveyors, 375 Seams, 18 Seasoning of timber, 230 Sector wire rope, 401 Securite, 215 Sediment-tube for diamond drill, 119 Self -discharging skips, 412 advantages of, 417 Self -oiling pedestals, 361 Selvage, definition of, 1 1 Separator, Frongoch, 576 Jacomety and Lenicque's, 575 Lockhart's gem, 577 siphon, 577, 579 Separators, upward current, 574 Sergeant drill, 193 groove-cutter, 199 Serpentine, occurrence of asbestos in, 21 occurrence of nickel in, 61 Sets or frames, 234, 236 Seyssel, France, bituminous lime- stone of, 22 treatment of asphalt rock of. 598 Shaft accidents, 705 arrangement of pumps in, 451, 461, 464, 465 linings of iron, 263 natural ventilation of, 486 rolls, 446 use of air-pipe for ventilating, 488 Shafts, cost of sinking in watery strata, 271 crooked, arrangement of pump rods in, 446 deep, at Pfibram, 404 freezing process of sinking, 278 for working mineral deposits,3o8 for working veins, 325 Kind-Chaudron process of sinking, 271 lined with concrete, 253 lined with masonry, 252 natural ventilation by two, 483 Poetsch's freezing process for sinking, 281 sunk by boring process, time required, 277 timbering of, 236 Shaft-sinking, 225 by incandescent lamps, 524 through bed of river, 268 Shakemantle Mine, pumping plant at, 461 Shanks' system of treating caliche, 608 Shaw's apparatus for testing for fire-damp, 501 INDEX. 739 Sheba Mine, Barber ton, 44 Gold Mine, aerial ropeway at, 384 Shell pump, 128 Shipping ores, arrangements for, 380 Sheading, 105 Shoad-stones, 106 Shoe of stamps, 549 wooden, 673 Shoot of ore, definition of, 1 1 Shoots, 348, 373 mouth for regulating dis- charge of, 413 Shovel, 151 Shower-bath for miners, Anzin, 68 1 Siberia, freezing method of sinking pits, 278 Sicilian miner's lamp, 515 Sicilian mines, steps for descent or ascent, 527 Sicily, modes of working sulphur- bearing limestone, 321 occurrence of sulphur in, 82 Sickness, 683 Side holes, 310 Sidings, endless rope system, 370 Sieves, 566 Signalling, 420 from cage, 533 Sill, 233 Silver, chance discoveries of, 95 Silver ores, occurrence of, 76 Broken Hill, N.S.W., 78 Calico, California, 79 Comstock Lode, Nevada, 76 Eureka Richmond, Nevada, 76 Huanchaca, Bolivia, 78 Kongsberg, Norway, 12 Stormont, Utah, 79 treatment of, 628 Silver-bearing sandstone, Utah, 18 Simultaneous fuse, 220 Single-rope haulage, 365 Sink, 222 Sinker-bar, 139 Sinking by compressed air method, influence on health, 689 Kind-Chaudron method, 271 Poetsch, or freezing method, 281 shafts, 225 through watery strata, cost of, 271 Triger's method, 277 Siphon, draining mines by, 437 Siphon separator, 577 Skertchly on the mining and knap- ping of flint, 41 Skip, 404, 410 loading in shaft, 410, 412 self -discharging, De Beers in- clined shaft, 412 for perpendicular shaft, 415 Skutterud, cobalt ore, 27 Slag-heaps, indications afforded by, 1 08 Slate, charging holes forrending, 219 circular saws used for, 564 dressing machines, 565 loss in dressing, 631 loss in mining, 314 methods of working, 312-315 Mines (Gunpowder) Act, 659 occurrence of, 79 planing machines for, 565 preparation of, 628 splitting of, 545 Sledges, 350, 375 Sleepers, steel, 352 Slickensides, 10, 89 Slide, 88 Slides for descent, 527 Sliding joint, Oeynhausen's, 128 Sliding scale for royalties, 654 Slip, 473 Slopes, 308 Sludger, 128 Sluices, 297 Smith, Dr. Augus, on the candle- test, 501 on the pollution of the air in mines, 480 on the proportion of oxygen in respirable air, 506 process of testing air, 502 Richard, on the gold-bearing conglomerate of the Trans- vaal, 42 Snell, on miners' nystagmus, 689 Snore-piece, 448 Snow, disappearance of, from out- crop of lode, 1 08 Societies, provident, 690 Sockets, joining two ropes by, 494 Solepiece, 233 Solfatara of Pozzuoli, sulphur from, 82 Solution, extraction of minerals by, 305 preparation of borax by, 608 nitrate of soda by, 608 potassium chloride by, 608 Somme department, occurrence of phosphate of lime in, 68 treatment in, 627 Somorrostro, endless chain haulage, 379 self-acting incline, 376 740 INDEX. Sorby, on the origin of the Cleve- land ironstone, 18, 53 Sores produced by arsenious acid, 686 Sough, 433 Sounding, testing ground by, 705 Sources of mineral supply in British Isles, 655 South Africa, discovery of diamonds in, 93 dressing of diamonds, 621 gold ore deposits, 41 South Carolina, phosphate beds, 68 treatment of phosphate of lime in, 627 South Staffordshire Mines Drainage Commission, 474 Space required per head, in rooms, 676 Spain, cupreous pyrites deposits of, 3 J -34 occurrence of quicksilver in, 72 Spalling, 544 Spathose ore, calcination of, 612 Spear-rod, 445 Speed indicator for winding engine, 533 Spider (candle-holder), 515 Spiles, 345 Spilling, or spiling, 236, 242 Spiral drum, 393 Splitting air- current, 510 slate, 545 Sprague electric diamond drill, 180 Sprengel type of explosives, 215 Spring stamps, 551 Spruce fir, 228 Square-set system of timbering, 246 Squib, 218 Stalls, 309 Stamps, gravitation, 548 pneumatic, 551 spring, 551 steam-hammer, 551 Standards for wire ropeways, 382 Stanley's tunneller, 207 Stannaries Act, 668 Stapff, on prospecting for phos- phorite, 104 Stassfurt, discovery of potassium salts at, 96 occurrence of potassium salts at, 70 preparation of salts at, 608 salt mines, sulphuretted hydro- gen at, 479 treatment of potassium salts,627 workings for carnallite, 315 Stationary engines for haulage, 364 table of Linkenbach, 581 Statutes affecting mines or quarries, 656, 659, 662, 665 Mining, 656 See ACTS OP PABLIAMBNT, 655 Steamboat springs, Nevada, 75 Steam digger, 173 engines for winding, 390 hammer stamps, 551 jet for ventilating, 492 process for sulphur, 600 shovel, 173 stove, 597 Steavenson twist drill driven by power, 1 80 Steel beams used for supporting levels, 256, 258 car wheels, 357 frames for levels, 259 shafts, 263 mine-waggons, 356, 360 props for working places, 266 pump rods, 445 sleepers, 352 wire-ropes, 399 Stein's endless belt, 586 Stelzner, on the lateral secretion theory, 15 Stempels, 240, 329 Step-fault, 88 Steps for descent and ascent, 526 or stopes in open works, width of, 286, 288, 289 Stockworks, 19 quicksilver ore, 73 silver ore, 79 tin ore, 19, 84 zinc ore, 87 Stokes' alcohol-reservoir for safety lamp, 500 Stone, preparation of, 628 breakers, 546 Stoping, overhaud, 329 underhand, 327 Stoves, for drying, 594 Jacobi's, 597 Krom's, 595 Eiebeck's, 595 Rowoldt's, 597 Ruelle's, 596 Schulz's, 597 steam, 597 Strapping plates, 445 Stratified deposits, 4 Straw for firing shots, 218 Stream works, tin ore, 85 Strength of explosives, 216 Stretcher-bar, 197 Stretchers, 713 Strike, definition of, 5 influence of change of, on veins, 1 3 INDEX. 741 Stringy bark, 229 Struve's ventilator, 494 Studdles, 237, 243 Stull, 327 Sturgeon on the efficiency of com- pressed air, 164 Sturtevant Mill, 563 Styria, graphite in, 50 Sublimation, formation of veins by, Sub-Wealden boring near Battle, 96 Suction dredge, 177 pipe for brine well, 306 pumps, 448 Sudbury, discovery of nickel ore at, 94 nickel ores of, 61 Suffocation by gases, 707, 710 Sulphate of iron used for preserving timber, 231 Sulphur, distillation of, 600 liquation of, 598 mode of occurrence of, 81 preparation of, 629 rock, Sicily, fire-damp emitted by, 478 Bank Mine, California, 74 discovery of quicksilver at, 96 gas from hot springs, 476 bearing limestone in Sicily, 82 mode of working, 321 seams, outcrop of, 102 Sulphuretted hydrogen in mines, 479 Sulphurous acid in mines, 479 Sump, 326 Supporting excavations, 227 Surface accidents, 711 drainage, 429 indications guiding the pros- pector, 97 Surveying bore-holes, 147 Surveys, danger from inaccurate, 707 Sussex, preparation of gypsum, 624 Sussmann electric lamp, 523 Sutro Tunnel, Nevada, 436 Swab-stick, 160 Swage, 181 Sweden, iron ores of, 54 occurrence of zinc ore in, 87 searching for iron ore with the magnetic needle, 112 Switzerland, workings for salt, 307 Sword, 448 Synclinals, 47, 87 TABLES, Jacomety and Lenicque's, 583 Linkenbach's, 581 percussion, 584, 589 picking, 542 plane, 579 revolving round, 583 Kittinger's percussion, 584 round, 581 Tabular deposits, 5 Tachometer, 533 Taeglichsbeck's report on housing of miners, 674, 679 Tagieff' s spouting oil-well, Baku, 65 Tailings, 243, 588 Tamarack copper mine, Lake Supe- rior, 36, 37 Tamping bar, 160 charge, 217 Tapering ropes, 404 Taxation of mines, 625 Tasmania, dressing tin ore in, 630 Teague's aspirator, 493 noiseless valve, 453 Teel's Marsh, borax deposit, 23 Telephones used for signalling in mines, 421 Temper screw, 140 Temporary dam, 433 Testing air of mines, 498-510 ropes, 427 Thames gold-field, New Zealand, 13 Tharsis, pyrites mines, 34 Thawing dynamite, 213 Thickness of bed, measurement of, 5 Thrift, 690 Throw, or heave, 88 Throw of a fault, definition of, 89 mode of determining amount of, 89 Timber, decaying, affects air of mine, 480 kinds used underground, 227 preservation of, 229 seasoning, 230 supports compared with steel, 257 used in Australia, 228 in England, 227 in United States, 228 withdrawing, from rubbish, Foxdale, 338 Timbering in loose ground, 242 levels, 232 pigsty system, 234, 239, 245 shafts, 236 special excavations, Hartz, 241 square-set, 246 working places, 244 742 INDEX. Time occupied in descent and ascent at Mansfeld, 532 payment by, 637 and measure, payment by, 641 Tin ore, alluvial deposit at Re- st ronguet Creek, 316 calcination of, 612, 613 dressing of, 629 lodes in granite, 7 mines affected by Alkali Acts, 665 mode of occurrence of, 83 separation from copper ore, 609 stockwork, Mulberry mine, near Bodmin, 19 Toadstone, influence on lead veins in Derbyshire, 13 Tonite, 215 fumes from explosion of, 481 Tools used for working timber, 231 Toothed rolls, 556 Torches, 515 Torpedo, 304 Transmission of power, 163 Transport above ground, 373 underground, 348 Trays, 349 Treadwell Mine, Alaska, 47 Treatment of ores. See DRESSING, Trelease's valve, 453 Trenching, sampling by, 632 Tribute, 641 advantages of working on, 643, 646 disadvantages of working on, 644, 645 system in Colorado, 647 at Festiniog, 649, 651 Triger's method of sinking, 277 Trimming stone by hand, 546 Trinidad, Pitch Lake of, 22 dressing of, 619 purification of, 598 Tripoli, occurrence of beds of, in Sicily, 82 Trommels, 566, 567 Trouve", apparatus for examining bore-holes, 150 Trubi, 82 Truck Acts, 668 Tubbing for shafts, cast -iron, 268 wood, 266 Tunnelling machines, 206 Turbine, used for hoisting. 389 Turgu-Ocna mine, 312 Turn plates, 354 Tuscany, occurrence of boric acid, 25 preparation of boric acid, 620 Tutwork, 638, 639 r ULVERSTON, haematite deposits of, 19 Umber, dressing of, 626 searching for by piercing, 106 Undercurrents, 299 Undercutting machines, 199, 202 Underground pumping engines, 466 workings, 308 Underhand stoping, 327 Underlie or underlay, definition of, 9 United Kingdom, death-rate from accidents, 700 United States, candle-holder used in, 514 gathering of natural ice, 5 1 lamp used in, 516 legal definition of lode in, 9 occurrence of copper in, 34 gold ore, 45 iron ore, 54 lead ore, 55 natural gas, 59 petroleum, 67 phosphate of lime, 68 quicksilver ore, 7 r silver ore, 76 trees used for rnmine; purposes. 228 Universal pick, 153 Unstratified deposits, 4 Upcast shaft, 484 Uppers, dust from boring, 685 Upthrow, 91 Upward-current separators, 574 Utah, silver-bearing sandstone, 79 VAL-DE-TRAVERS, Switzerland, bi- tuminous limestone of, 22 Value of product, payment by, 641 Valve, butterfly, 453' double-beat, 454 Jan Ham's, 453 Hake's mouth, 453 ordinary leather, 448 Teague's noiseless, 454 Trelease's, 453 Van den Broeck and Rutot, portable boring outfit, 117 Van lode, length of, 1 1 Van mine, fire-damp at, 476 method of working the wide lode, 331 Vanner, Frue, 585 V-bob, 446 Vegetation on outcrop of lodes, 107 INDEX. 743 Veins, definition of term, 5 heave sideways caused by slip along line of dip, 91 influence of change of strike on, 13 of enclosing rock on, 12, 13 intersections of, 12 mechanical filling of, 14 modes of working, 325-340 name applied to slate beds in North Wales, 81 origin of, 14 varying width of, 16 Zimmermann's rule for finding faulted portion of, 91 Veinstone, definition of, 1 1 Velocity of air-current, measure- ment of, 506, 507 Venezuela, discovery of gold in by Plassard, 94 occurrence of gold in, 44 Ventilating appliances, efficiency of, 509 Ventilation, 475 compressed air, 492 fans, 494 furnace, 490 steam jet, 492 water blast, 492 falling down shaft, 486 effect of, on timber, 230 measurement of amount of air passing, 506 natural, 482 Victoria, gold-fields of, 46 Villiers' stopping gear, 425 Viola calaminaria, 104 Volcanic emanations,sulphurfrom,8 1 rocks, 3 Vom Kath on the outcrop of the silver veins of Butte, Montana, 98 Von Cotta, definition of a mineral vein, 6 on the Zwitter of Altenberg, 84 Von Groddeck, definition of a mineral vein, 6 Von Sandberger, definition of a mineral vein, 6 on the lateral secretion theory, 15 Vugs, definition of, 6 Vulcano, sulphur from, 82 W WADDLE fan, 497 Waggons for underground use, 350, 35S-36o points to be considered in de- signing, 361 Wales, barracks for workmen, 676 manganese ore in, 58 lead ore in, 331 slate in, 79 underground workings for slate, 312 Walker's circular saw, 203, 204 detaching hook, 423 shutter for Guibal fan, 496 Wallace on emanations of carbonic acid at Alston Moor, 475 Wallaroo lode, discovery of, 93 Walling, 249 Walling stage, Galloway's, 409 Wall-plate, 236 Wall-posts, 240 Walls, Cleveland, 315 Festiniog, 312 of a lode, definition of, 10 Walton Brown on the resistance to air-currents, 511 Wardwell stone-channelling ma- chine, 202 Warming pan for dynamite, 213 Warocquere, 706 Washer, Australian, 539 De Beers, 540 revolving drum, 541 Washing ores, &c., 538 Wash-out fault, 87 Washing-pit used in North Wales, 539 Water, amount used by siphon separator, 579 amount used in stamping, 551 barrel for winding, 437 column compressors, 165 excavating by, 226, 292 from dressing works, purifica- tion of, 667 gauge, 508 irruptions of, into mines, 707 jet ventilating apparatus, 492 motion of particles in, 568 power used for working pumps, 442 spray for laying dust, 685 tanks, automatic, 438 used for rending rocks, 208 wheel used for hoisting, 389 Watertight linings for shafts, 266 Weathering of diamond-bearing rock, 610 fire-clay, 611 ironstone, 611 phosphate of lime, 61 1 Wedge, 154, 208 Elliott multiple, 208 Wedging-crib, 267, 270 Weight, payment by, 639 744 INDEX. Wells, 304 boring by rotation, 117 driven, 137 Wells light, 516 Welsh barracks, 676 manganese ore, occurrence of, 58 dressing of, 625 lead ore, 331 miner's clogs, 672 slate mines, 79, 312 Wenstrom magnetic separator, 605 Werner, definition of a mineral vein, 6 Wery's stopping gear, 425 West and Darlington, hydraulic counterpoise, 458 hydraulic plungers for working inclined rods, 447 Wheal Mary Ann, section of lode at, 6 Wheelbarrow, 350 Wheels for mine-waggons, 357 Whipsiderry, 388 White's sleeper, 353 Whitney, on the " Great Quartz Vein " of California, 45 Wicks, candle, 513 Wide veins, method of working, 33 1 Wieliczka salt mines, 315 timber chocks, 245 Wind-bore, 448 Winding, 387 drum, 391 engines, 390 men at Cam Brea mine, 533 pulleys, 397 removing water by, 437 Windlass, 388 Windmills used for working pumps, 442 Winstanley's machine, 204 Winze, 326 Winzes, use of for ventilating, 489, 490 Wire saw, 204 Witwatersrand, 41 Wolf's magnetic lock for safety lamps, 522 Woodbury ore concentrator, 586 Wooden pipes, 450 plugs used for rending rocks, 208 pulley frame, 395 Working barrel of pump, 448 in constrained position, effect on men, 688 masses by horizontal slices, ascending, 345 descending, 341 mineral deposits, methods of, 285 places, iron and steel supports. 265 supported by masonry, 254 timbering, 244 regulations for mines, 655 Workings, carbonic acid in old, 501 laying out open, 288 Workmen, housing, 673 Wotherton mine, Shropshire, 13 Wrist, 310 Wrysgan mine, 314 YELLOW Jacket mine, heat at, 670 ZIMMEKMAN'S rule fo'r finding lost part of a vein, 91 Zinc blende, minerals associated with, 97 Diepenlinchen, method of working, 346 ores, calcination of, 612, 615 dressing of, 625, 630 occurrence of, 85, 86 Z witter, or tin-bearing rock at Alten- berg, 84 Printed by BALLANTYNE, HANSON