The Metallurgy of Gold ... Fourth edition, enlarged, etc

Front matter

THE METALLURGY OF GOLD BY THE SAME AUTHOR, Crown 8vo, 360 pp., with 150 Illustrations, price ios. 6d. cloth. THE METALLURGY OF SILVER: A Practical Treatise on the Amalgamation, Roasting, and Lixiviation of Silver Ores; including the Assaying, Melting, and Refining of Silver Bullion. Second Edition, Enlarged. " A practical book for practical men ... A convenient and useful work, containing a good deal of original matter." — Athenæum. Crown 8vo, 336 pp., with about 100 Illustrations, price ios. 6d. cloth. A HANDBOOK ON MODERN EXPLOSIVES: a Practical Treatise on the Manufacture and Application of Dyna mite, Gun-cotton, Nitro-glycerine, aud other Explosive Com pounds ; including the Manufacture of Collodion Cotton. " A book which should be acquired by every one who has to deal with either the use or the manufacture of the powerful explosives of modern days.'1 — Board of Trade Journal.

Crown Svo, 400 pp., with 183 Illustrations, price 12s. 6d. cloth. THE METALLURGY OF ARGENTIFEROUS LEAD : A Practical Treatise on the Smelting of Silver-Lead Ores and the Refining of Lead Bullion. (The Illustrations include Plans and Sections of Smelting Furnaces and Plant in Europe and America.) "Those who wish to obtain a thorough insight into the present state of this industry cannot do better than read this volume." — Industries. last Published. Large Crown Svo, with Diagrams and Working Drawings, 7s. 6d. cloth. (Being tubstantially a reprint i f Chapters XI.— XV. of the present volume) THE CYANIDE PROCESS OF GOLD EXTRACTION; and its Practical Application on the Witwatersrand Gold Fields in South Africa. " This book is j*st what was needed to acquaint mining men with the actual working of a process which is not only the most popular, but Is, as a general -rule, the most successful for the extraction of gold from tailings." — Mining Journal.

London : CROSBY LOCKWOOD & SON, 7, Stationers' Hall Court, E.C. 160-stamp Battery Langlaagte Estate. [FrontitpUce. THE Metallurgy of Gold A PRACTICAL TREATISE ON Œfje iŒUtallurgical treatment of C5oIti--3iJeaung ©res INCLUDING THE PROCESSES OF CONCENTRATION, CHLORINATION, AND EXTRACTION BY CYANIDE, AND THE ASSAYING, MELTING, AND REFINING OF GOLD BY M. EISSLER MINING ENGINEER; A.I.M.E.; MEMBER OF THE INSTIK^E OF MINING AND METALLURGY AUTHOR OF "MODERN HIGH EXPLOSIVES," " THE METALLURGY OF SILVER," ETC, ETC. FOURTH EDITION, ENLARGED fflSIitf) afcout Œfoa--f)uu&re&'an&=Jift2 Sllutftratian? an& jhimermuf JFnRrtnfl $Hatnf LONDON CROSBY LOCKWOOD AND SON 7, STATIONERS* HALL COURT, LUDGATE HILL

Preface

. In this volume my aim has been to present in a condensed form such an account of the several pro cesses which are generally used for the Extraction of Gold from the Ore as shall be sufficient for the full information of investors, and others interested in gold mining operations, who may wish to gain an intelli gent insight into the modus operandi at the gold mines. At the same time I have given full descriptions, with illustrations, of the machinery employed in those processes, in sufficient detail to make the book of substantial value to professional men and manufacturers concerned in the gold-mining industry. The treatment of gold-bearing ores, although at one time so uncertain in its results as to be, not only a hazardous, but almost a purely speculative business, has now, through continued improvements in appliances and the adoption of more economical methods, developed into a settled industry, in which more or less profitable results may be obtained even from comparatively low grade ores.

When, forty years ago, the news was circulated throughout the world from California, that gold had been found in that territory by Mr. Marshall, in a mill- VI

PREFACE.

. race near Sutter Creek, thousands of enterprising ad venturers nocked to the new Eldorado. So abundant were the glittering scales of metal which appeared in the gravel washes and in the rivers and tributary streams of the western slopes of the Sierra Nevada mountain ranges, that little or no metallurgical know ledge was required for the successful extraction of the precious gold dust. No machinery was then needed beyond a pair of stout arms, a pick, a shovel and pan — with perhaps a rocker and a few boards nailed together in a trough-like sluice; and it was with rude appliances such as these that many millions' worth of gold was taken from the Placer mines, thus laying the founda tions for the Pacific empire. The gold discoveries in Australia — which came a few years later — nearly outrivalled the rich Californian deposits, and gave a new lease of life to the Austra lian colonies ; and to-day Great Britain looks with pride at those magnificent domains at the Antipodes, teeming with a large population and many flourishing cities, all of them owing their prosperity, in no small measure, to the discovery of gold and other metals.

From present indications the South African gold fields have also a brilliant future in store, but the discoveries in that region are too recent to afford means for the full appreciation of the possible results. When gold was first discovered in California, the knowledge of metallurgy and mining in their several branches, among the people of the United States, was very rudimentary. But with that discovery a new era began over the vast expanse of territory extend-

PREFACE.

. VII ing from the Atlantic to the Pacific. The citizens of the great Republic awoke to the fact that in their mountain ranges were minerals of all kinds, representing enormous wealth, which could not be secured without extended knowledge of the requisite appliances. These were rapidly introduced in all branches of metallurgy, and in the advances thus made the treatment of gold-bearing ores has kept pace with the improvements effected in other branches of the science. Brilliant results have been achieved in the last twenty years, and I shall rejoice if the present work assists in extending knowledge of the subject, and in further stimulating progress in invention and the development of gold mining. London, August, 1888.

PREFACE.

TO THE SECOND EDITION. In preparing a new edition — which I am glad to find so soon required — I have been at some pains to supply additional matter on those subjects a fuller treatment of which has seemed desirable in the light of my experience with the first edition. The result is the enlargement of the work by about one hundred and fifty pages and forty additional illustrations. My best thanks are due to the public press and private correspondents for valuable suggestions for a

PREFACE.

. new edition ; and of these I have availed myself wherever practicable. There has been no interference in the present edition with the main plan of the original work, although five new chapters have been added. In these (amongst other matter) will be found much additional information as to machinery employed in crushing and amalgamation, and as to mills in actual operation. Later developments of the process of Chlorination are also described, and a chapter has been added on the Smelting of gold ores and the refining and parting of gold bullion. I have also given some account of the physical features of the gold-producing districts of North- Western America, which I hope will be none the less interesting because of the element of personal experience which is there introduced. In the first chapter of the work I have inserted an account of the interesting operations of Hydraulic Mining, with which the history of many gold-producing districts is so largely concerned.

In its enlarged form I trust the work may prove increasingly acceptable and useful to those for whom it is designed. 17, Belsize Crescent, South Hampstead, London, N.W. Afril, 1889.

PREFACE.

TO THE FOURTH EDITION. In the Third edition of this work (which was called for early in 1891), although considerable additions had been made to the Second edition, the volume was further enlarged by the addition of four new chapters and about fifty new illustrations. I was thus enabled to give particulars of various improvements in gold milling appliances which had then been recently introduced with the view of cheapening the treatment of the ore. The attention of inventors having been largely directed to Chlorination, and the roasting of the ores being a necessary preliminary to that process, a large part of two of the new chapters was devoted to that subject. In the preface to the Third edition, however, I pointed out that the question still arose what should be done with the free gold ores, carrying, say, from five to seven pennyweights of very fine gold — so fine that it is impracticable to save it by amalgamation ; while in distant localities such ores would not bear the cost X

PREFACE.

. of treatment by chlorination ; and I added that, besides the large bodies of such ores which are known to exist, there were at many mines vast accumulations of tailings, awaiting the discovery of a suitable method of utilising their hidden wealth of gold. Since those remarks were written, the use of po tassium cyanide solutions for the recovery of gold from tailings has been adopted with great success in the Witwatersrand gold-fields under the patents of Messrs. MacArthur and Forrest, notwithstanding that patents had been (since 1867) previously brought out, and the process tried in various ways in the United States, without successful results, at all events from the commercial point of view. Further steps in advance have been accomplished by the in troduction — also in the Witwatersrand — of the Cyan ide process as developed by Messrs. Siemens and Halske, under whose patents electricity is utilised for the precipitation of the gold from the cyanide solu tions.

In the present edition, full attention has been given to these important developments ; and in the five new chapters devoted to the subject those metallurgists who desire to avail themselves of the Cyanide pro cess will (I believe) find the methods of procedure described with sufficient fulness and completeness for practical purposes. Not only the working details, but full particulars of the results actually obtained, are given, while a chapter is devoted to the Chemistry of the Cyanide Process..

PREFACE.

. XI That I am in a position to deal with the matter so fully is owing to the lact of my having made a lengthened stay in the Witwatersrand gold-fields — whence I have just returned — and to my having enjoyed there unique opportunities of studying the process in actual operation. As becomes the importance of this branch of the Metallurgy of Gold, special care has been taken to secure full and sufficient diagrams in illustration of the Cyanide process and the necessary plant. Some further additions have also been made to the present edition, including — besides a chapter on Recent Milling Operations in the Transvaal — par ticulars of various appliances which the energy and ingenuity of manufacturers and inventors have pro duced for the assistance of the gold-mining community since this work was first prepared ; as well as the results of recent researches upon various questions touching the treatment of the gold and its ores ; with details of working operations and results which have been collected by me at various mines which I have had occasion to visit.

Some Statistical Notes which were supplied to me on those occasions, and some remarks on the Future Outlook in the South African Gold Fields, will be found in an Appendix. I have taken the opportunity of inserting also in the present edition some additional diagrams, illustrating the construction and arrangement of Plants for Gold mining. These illustrations — being given on a full

PREFACE.

. scale, and in some cases in much detail — cannot fail to be of material service to those who have the responsibility of providing similar plants for new or existing mines. With these several enlargements and additions, I trust the work may prove as acceptable in the future as in the past ; and I shall hope, indeed, that it may prove increasingly useful to all who avail themselves of its pages. London, 1895. P.S. — It should be noted that the present Edition has been passed through the press during the Author's absence in Australia. CONTENTS.

Chapter I. Zn Tr Od Uctor

Y. PAGB Section I. — Gold Mining in California. — Quartz-mining Operations — Free Milling — Failure to " Catch the Gold " — Quartz Mines at Grass Valley — Progress in Milling Appliances — Loss in Working Gold Ores — Yield in California, in Australia, in Colorado — Professor Egleston on Loss in Extraction — Total Produce of Gold in California since 1848 ....... 1 Section II. — Gold as a Metal.— Its Valuable Properties — Gold in the Pure State — Distribution — Composition — Properties of Pure Gold — Gold-bearing Ores ........ "J Section III. — Gold Washing by the Hydraulic Process. — Applied to Deposits of Gravel — How the Gold lies in such Deposits — Laying out an Hydraulic Mine — Working the Mine — Results 11

Chapter II. Treatment Of Gold-bearing Ores

: CRUSHING AND AMALGAMATION. Section I. — Mechanical Preparation of Gold Ores. — Rock-breaking Machines — Blake's Patent — Reduction of the Ore by Stamps — Arrangement of a Battery described — Feeding the Battery with Ore — Tulloch's Ore Feeder — Recent Battery Frames ,.,,,,,,.,. 18 Frames ,.,,,., CONTENTS. FAGl Section H.— Amalgamation of the Free Gold— Attwood Amalgamator— Hydrogen Amalgam Process— Grinding Pans— Knox Pan— Wheeler Pan— SoderUng Pan— Settlers and Rubbers —Eureka Rubber— Gauthier's Shaking Table— Bazin's Amalgamator—Treatment of Amalgamated Copper Plates— Silver-plated Copper Plates 45 Section III.— The Process of Amalgamation.— Operation of the Mill— Capacity and Regulation of a Stamp Mill— Professor Raymond on Crushing— Aprons, Sluices, and Blankets— Water required for Milling— Process of Amalgamation— Commencing Operations at a Mill— Amalgamation in the Battery— Treatment of Tailings— The Edison Process— Conditions of Good Result- Bad Condition of the Plates— Condition of Mercury— Cleaning Gold off Plates 74

Chapter III. Treatment Of Gold-bearing Ores

: CRUSHING AND AMALGAMATION— continued. Cleaning the Mill — Cleaning the Quicksilver — Sodium Amalgam — Retorting the Amalgamated Metals — Value of the Amalgam — Workmen in the Mill and their Duties — Wear and Tear of a Mill — Cost of a Complete Mill — Cost of Milling — Working of Gold Ores in Californian Gold Mills — Statistics of Queensland Gold Mines — Mining of Gold Ores in California — Results of the Mill Process — Loss in Milling — Mr. Paul on Waste of Gold in Amalgamation — Checking the Mill Returns — Mr. Skey on the Absorption of Sulphur by Gold — Conditions of Successful Working of a Gold Mine — Amalgamation of Concentrated Sulphurets after Roasting — Iron Battery Frames — Illustrations and Specifications of Batteries — Power Required for Wet Crushing Gold Mills — Chemicals in Use — Battery Arrangements . . . . . 95

Chapter IV. Mills In Operation

: NEW MILLING MACHINES. Zeile Mine and Mill— Providence Mill, near Nevada City— Father de Smet Mill— Largest Stamp Mill in the World— When Dry Crushing is Required — Huntington Milling Machine — Gates Rock Breaker— Crushing Rollers— Gates Cornish Roller— Globe Mill— Krupp Grusonwerk Dry Grinding Mill — Krom Roll . . .125 FAOH CONTENTS.

Chapter V. Treatment Of Gold-bearing Ores

: CONCENTRA TION. Concentration Explained— When Concentration precedes Amalgamation — Operations in Concentration — Spitzkasten : Rittenger's Pointed Box — The Trichter Apparatus — Concentration in Sluices — Further Concentration in Rockers and Buddies— Green's Jigger —The Dolly Tub— The Round Buddie— Collom's Buddie— The Concave Buddie — The Tossing Tub— Hendy's Concentrator — The Frue Concentrator — Its Operation described — Concentration of the Sulphurets — Results of Concentration — Colonel Taylor's Experience 149

Chapter VI. The Metallurgical Treatment Of Rebellious Gold And Auriferous Silver Ores

What is understood by a Rebellious or Refractory Ore — The Roasting of Ores — Oxidizing Roast — Dead Roast or Sweet Roast — Reverberatory Furnaces — Chemical Reactions during an Oxidizing Roast — Rebellious Ores and their Comportment when Roasted — Iron Sulphides — Copper Sulphides — Lead Sulphide— Sulphuret of Bismuth — Zinc Blende or Sulphuret of Zinc — Molybdic Sulphide — Silver Glance — Arsenical Pyrites — Sulphide of Antimony — Roasting Reactions in Reverberatory Furnaces — Influence of Gangue Rocks — Loss of Gold by Volatilization in Chloridizing Roasting — Loss of Gold at Las Minas — Professor Christy's Investigations — Proposed Condensation of Fumes by Electricity — Loss of Gold in Muffle Roasting — Mr. Wilson's Experiments — Mr. Falkenau's Experiments — Reduction of Loss of Gold in Roasting to a Minimum 1 99

Chapter VII. The Roasting Of Pyritic Ores

The Roasting of Iron Pyrites— Heap Roasting — Kiln Roasting —Kilns with Grates — The Freiberg Pyrite Burner — English Pyrite Burner — Perret and Olivier's Shelf Furnace — Hansenclever and Helbig's Burner — Hansenclever's Improved Burner — Gersten- CONTENTS. XVI MM hofer's Furnace— The Boussield K_ln— Roasting Furnaces— Single Roasting Furnace-Double Furnaces— Pontgibaud Furnace— Kustel's Furnace— Mechanical Roasting Furnaces— Bruckner's Cylinder-The Ottokar-Hoffman Furnace-The Spence Furnace —The McDougall Furnace 2z8

Chapter VIII. The Hydro-metallurgy Of Auriferous Ores

: CHLORINATION. The Plattner Process of Chlorination, according to Prof. Kiistel— Conditions for Successful Chlorination— Assay of Gold Sulphurets— Chlorination Process for Sulphurets and Arseniurets —Roasting of the Sulphurets— Roasting Arsenical Pyrites — Operation of Roasting — Apparatus for Chlorination — Treatment of the Ore with Chlorine Gas — Lixiviation — Precipitation — Cost of Treatment by Planner's Method — Arrangement of Chlorination Works — The Plattner Process at Plymouth Mine— At the Merrifield Mine — Gold and Silver Lixiviation Works . . . .268

Chapter IX. Later Processes Of Chlorination

The Mears Chlorination Process — Treatment of Arsenical Ores at the Deloro Mine— The Adolph Thies Process— Working Pyrites at the Phœnix and Haile Gold Mines — Barrel Chlorination at the Bunker Hill Mine — The Newbury- Vautin Process — The Pollok Hydraulic Chlorine Process — The Swedish (or Munktell) Process — The Rottermund Process — The Ottokar-Hoflman Process — The Von Pateras and Roeszner Process — Kiss's Method : how Distinguished — Hauch's Treatment of Telluride Gold Ores . 304

Chapter X. The Electro-metallurgy Of Precious Metals

Electrolysis as applied to Gold and Silver— The Electro- Chlorination of Gold Ores: Cassel's Process — Greenwood's Electrolytic Chlorination Process — Electrolytic Precipitation of the Gold — Apparatus for Continuous Lixiviation — Julian Process — Dr. Kiliani on Electrolytic Refining of Copper CONTENTS. XVII PACE

Chapter XI. The Cyanide Process For The Extraction Of Gold

Synopsis of the Process — Conditions which influence Precipitation — Smelting of the Slimes — Treatment of Acid Ores or Tailings — Concentrates — Adverse Conditions which affect the Cyanide Treatment — Practical Results 378

Chapter XII. The Siemens-halske Cyanide Process

How the Process was Discovered — Action of the Electric Current — Why Mercury cannot be used as a Cathode — Conditions which the Metal Cathode must fulfil — The Avode — Electric Current required for Precipitation — Advantages of Electrical Precipitation — Practical Working Results — Scheme of Working . . . 395

Chapter XIII. Erection Of

A CYANIDE PLANT. Planning the Works — Slimes — Effect of Stamping on the Ore — Plant — Intermediate Filling — Direct Filling — The Filter or Leeching Tanks — Stock Solution Tanks — Zinc Precipitation Boxes . 412

Chapter XIV. The Cyanide Process In Operation At Various Works

Crown Reef Works— Simmer and Jack Works — Langlaagte Estate— Rand Central Ore Reduction Company— Dry Crushing . 435

Chapter XV. The Chemistry Of The Cyanide Process

Solution OF the Gold — Solubility of other Metals — Louis Janin's Experiment on Silver Ores— Results of Experiment made •with Potassium Cyanide on Gold and Silver Ores— Treatment of Pyritic Ore previous to Lixivation with Cyanide— Treatment of Pyritic Ores by Cyanide of Potassium— Precipitation of the Gold —Decomposition of the Cyanide— Testing the Strength of Solutions—Determination of Gold in Cyanide Solutions— Extraction Tests CONTENTS. PACK

Chapter XVI. Smelting Of Pyritic Ores

The Hungarian Method of Smelting with Iron Pyrites— Matting Dry Auriferous Silver Ores at Toston, Montana— Treatment of Argentiferous and Auriferous Matte— Spur-ofen for Matte Fusion— The Herresshoff Furnace for Pyritic Smelting— Smelting of Pyritic Ores in Reverberatory Furnaces — Fusion for Matte of Auriferous Pyrites at the Boston and Colorado Smelting Works- Economic Advantages of Smelting Pyrites by "Utilising their Fuel Qualities 47°

Chapter XVII. The Cupelling, Parting, And Refining Of Gold Bullion

Cupellation — The English Method — Cupelling Furnaces on the Continent — The Parting Process — At the Refineries of the United States — At the San Francisco Assaying and Refining Company's Works — Gold and Silver Parting at Oker in the Unterharz — Mint Parting with Nitric Acid — Refining of Brittle Gold with Chlorine Gas: Miller's Process — Separating Iridium from Gold in Mint Deposits 501

Chapter XVIII. The Melting And Assaying Of Gold

Melting and Assaying — Fusion with Borax — Melting Furnaces — Assaying of the Gold Ingot — Several Processes of an Assay — Weighing the Assay Piece — Valuation of Gold Alloys — Preparation of the Assay Piece — Cupellation — Parting of the Assay — Professor Roberts-Austen on the Parting Process — Parting Assays —Gold containing Oxidizable Metals — Assaying Gold Quartz — Assaying by Scorification — Forms of Cupels — Weighing the Button of Precious Metal 533

Chapter XIX. Chemical Examination Of Gold Ores

Tests for Presence of Gold — Reagents employed— Preparation for Testing — Action of Sulphate of Iron ; of Protochloride of Tin ; of Oxalic Acid— Tests for Metals associated with Gold : Copper ; Silver ; Platinum— Application of Reagents — Quantitative Determination of Gold by the Wet Process— Determination of Metals CONTENTS. XIX PAGB other than Gold, in Ores — Quantitative Estimation by Specific Gravity ........... 571

Chapter XX. Physical And Geological Features Of Gold-producing Countries

The Sierra Nevadas — The "Mother Lode" of California — Hot Springs of California and Nevada — Other Features of those Countries — Death Valley — Hot Mud Springs — Telluride Ore Veins of Colorado — Origin and Position of Gold Deposits — Characteristics of Gold Deposits — Placer Mines of California — Formation of Gold Deposits — Gold in Australia — Chemical Geology of Gold — The Conglomerate Beds of the Witwatersrand . 589

Chapter XXI. Milling Operations In The Transvaal

Gold Mills in the Transvaal — Mode of Treatment — The Deep Level — Crown Deep Mine — Results of Concentration — Treatment of Slimes — Crushing the Ore — Grizzlies — Crown Deep Mine — Ore Sorting Floors — Langlaagte 160-Stamp Battery — City and Suburban Battery — Paarl Central Battery — Champ d'Or Deep Level Battery — Water Power — Inside Amalgamation — Duty of Stamps . 610

Chapter XXII. Mill Site And

BATTERY— RECENT APPLIANCES. Mill Site and Battery — Framing of the Battery — Homestake Mortar — Shoes and Dies — Cams, Cam-Shasts, Stems, Stamp- Heads — Blanton's Cam — Tappets — Automatic Tailing Sampler — Mercury Troughs — The Batea 629

Appendix

. A. Causes of Failure in Gold-Mining — Mr. William Topley (1887) on the Future Production of Gold— The Outlook (Dec. 1894) in the South African Gold Fields 645 B. Recent Developments in the Witwatersrand. By Mr. Hamilton Smith 654 C. — Statistical Notes and Memoranda 665 INDEX .671 b BO. PAGE 160-stamp Battery, Langlaagte Estate . . FRONTISPIECE I. Hydraulic Mining in California M 2. Blake's Rock-breaker 2I 3. Section of same ......... 22 4. Front Elevation of Battery 24 5. Transverse Section of same 25 6. Elevation of Battery Frame 26 7. Section of same ......... 27 8. Stone Foundation for Battery 28 9. Arrangement of Stamp Stems 29 10. Complete Battery Frame 29 1 1 . Mortar for Front Lining 3° 12. Mortar for Front and Back Lining 30 13. Mortar with Sieve Frame 3° 14. Sieve Frame .......... 31 15.

The Die 31 16. The Head 3-2 17. The Stem and Tappet 32 18. The Shoe 33 19. The Journal Boxes 34 20. The Cam Shaft 36 21. Double Cam .......... 37 22. Cams and Cam Curve ........ 37 23. The Screen Frame ......... 39 24. The Screen .......... 39 25. The Splash Box 41 26. The Self-Feeder 42 27. Tulloch's Ore-Feeder 43 Plate I. Framework of Battery erected by Messrs. Fried. Krupp Grusonwerk for the Queen Mine, near Johannesburg facing 44 Plate II. Wooden-frame Stamp Battery, erected by the Sandycroft Foundry facing FIG. PAGE Plate III. Ten-head Gravitation Stamp Battery, erected by the Sandycroft Foundry facing 44 28. Attwood Amalgamator 45 29. Riffle Sluices 46 30. Molloy' s Hydrogen Amalgamator 48 31. Knox Pan 5° 32. Wheeler Pan - - - • 52 33. Section of Wheeler Pan 53 34. Ground View of Wheeler Pan 54 35.

Shoe for the same 55 36. Soderling's Improved Pan 56 37. Do. Stirling Apparatus 56 38. Soldering Pan 59 39. Settler 6° 40. Eureka Rubber : Plan 61 41. Section of same 61 42. False Bottom for same 62 43 . Eccentric for same . . . . . • ■ • .62 44. Movable Frame for same 63 45. Gauthier's Shaking Table : Plan 64 46. ,, ,, ,, Section 64 47. Bazin's Amalgamator 67 Plate IV. Pit-Head and Ore-Bin, erected by Messrs. Fried. Krupp Grusonwerk, at the Incline Shaft of the Main Reef Gold Mining Company, Johannesburg . . . facing i)\d 48. Retort for Large Mills 99 49. Retort for Small Mills 100 50. Iron Frame Battery "9 51. Ten Stamp Battery 120 Plate V. Iron Frame Battery', as erected by the Sandycroft Foundry facing 124 Plate VI. Ore Bin and Battery lIou=e, erected by Messrs. Fried. Krupp Grusonwerk facing 124 52.

Father de Smet Mill lj1 53. Huntington Mill ij6 54. „ ,, Plan 137 55. „ „ Scraper 138 56. „ ,, Perspective View 139 57. Gates Rock-Breaker 141 58. „ „ '42 59. ,, Cornish Rollers . . . ■ . • • • '45 Plate VII. The Globe Wet Crushing Mill . . facing 148 •60. Krupp Grusonwerk Dry Grinding Mill . . - . .148a 61. „ „ „„„..■-■ '48* 62. Krom Rolls ....'-.- ' }8<* PACK PLATE VIII. Krupp Grusonwerk Dry Grinding Mill facing 148* Plate IX. Krom RoU Crushing Plant . . • facing 148,2 63. Spitzkasten : Longitudinal Section 153 64. ,, Vertical Section JS3 65. Spitz Lute IS+ 66. ,, Plan 1^ 67. Trichter Apparatus 1-57 68. The Rocker 1iS 69. Green's Jigger : Plan • IS9 70 „ Section l6° 71. „ „ , l6t 72. Dolly Tub: Plan l63 73. n ,, Section l64 74. Round Buddie : Perspective View 165 •75. n „ Section 166 76.

CoUom's Buddie : Plan 167 -7-7. ,, ,, Section 168 78. Concave Buddie 17' 79. Tossing Tub I73 80 173 81. „ „ Gearing 174 82. Hendy's Concentrator '75 83. Mill with Hendy's Concentrators 177 84. Frue Vanner l7& 85. „ , l8° 86. „ , l82 87. „ , ,84 88. Freiburg Pyrite Burner : Elevation 232 89. „ „ „ Section 233 90. EngUsh Pyrite Burner 234 91. „ „ * „ Section 234 92. Hansenclever's Improved Furnace 236 93. „ „ „ Plan of Tower . . .237 94. Bousfield Kiln : Plan 239 95. „ ,, Section 240 96. Single Roasting Furnace : Plan 243 97. „ „ „ Section 243 98. Grappling Irons 244 99- 245 100. Double Roasting Furnace 245 101. ,, ,, „ 246 102. Pontgibaud Furnace : Section 246 103. „ „ Plan 247 104. Kiistel's Furnace : Plan 248 105. „ „ Section . 249 ,> >- FIG. PAGE 106. Bruckner's Roasting Cylinder 251 107. ,, ,, ,, Section ..... 252 108. „ „ „ Section 253 109.

Ottokar Hoffman Furnace 257 1 10. Spenee Furnace : Longitudinal Section 259 m. ,, „ Side View 260 112. „ ,, Plan 260 113. ,, „ Cross Section of Double Furnace . . . 261 114. ,, ,, Stirring and Raking Instruments . . . 262 115* .. » » » „ . . . 262 116. McDougaU Furnace 265 117. Chlorination Test Apparatus 270 118. Chlorination Vessel 273 119. The Hoe 277 120. Chlorination Vat 282 121. „ Apparatus 283 122. Chlorine Generator Set in Furnace 284 123. Chlorine Generator 285 124. Wash Bottle 287 125. Plan of Chlorination Works 295 126. Section of same 296 127. Gold and Silver Lixiviation Works 302 128. Newbury- Vautin Process : Elevation of Plant .... 324 129. ,, „ ,, Chlorinating Barrel .... 325 130. „ „ „ Down Filter 325 131. „ „ „ Up Filter 325 132. Section of Chlorination Works .* MunkteH's Plant . . . 330 133.

Longitudinal Section of same 331 134. Plan of same 332 135. Rottermund Plant : Section 334 136. „ „ „ 334 137. „ „ Plan 335 138. Greenwood's Process: Chlorine Generator .... 353 139. „ ,, Elevation of Plant .... 354 140. „ „ Vertical Section of Electrolytic CeU . 355 141. ,, „ Horizontal Section of Electrolytic Cell . 355 142. „ „ Electric CeU 361 143. Apparatus for Continuous Lixiviation 3***7 144. The JuUan Process Plant : Side Elevation .... 370 145. ,, ,, Front Elevation .... 370, 146. „ „ Plan • 37' Plate X. The Worcester Cyanide Plant . . . . 39<-> Plate XI. „ „ >> 39<> Plate XII. Depositing Box 398 Plate XIII. Cyanide Plant at Princess Works in Section . PAGB F'3' Plate XIV. Messrs. Butters and Mein's Automatic Distributor . ■ • ■ " . ' ./ . . ,n i46<z. Messrs. Butters and Mein's Automatic . ' 42° Plate XV.

TaUing Wheel, Vanner Room, and C5 amde Vats -. r- ... 420 at the Jumpers Mine 146J. Staves cut to Circle ..---■ 4 146c. Construction of FU ter Vats . ,s 146-*/. Stone Foundation for Fflter Vats 4 146*. Solution Pipes .-■•-• ""4*21 146/, 1465*. Butters' Discharge Lid 43 146/z. Zinc Precipitation Box * * " 133 Plate XVI. General View of the Simmer and Jack Cyanide Plant 44° Plate XVII. Simmer and Jack Filter Vats . . . - 44° Plate XVIII. Simmer and Jack Extractor House ... 440 Plate XIX. Central Works of the Rand Central Ore Reduction Company 44° 147 Spur-Ofen for Matte Fusion : Section 47° 148.' „ „ >. Flan 477 149. Herresshoff Furnace: Vertical Section 479 , cn „ Well or Receiver 48° '5°- " . . 480 151. „ » » " \ ,„_ n ,, Plan showing the Tuyeres . . .401 ,„' „ DetaUs 4gI \H[ " " „ 481 155.

Reverberatory Furnace for Matte Smelting: Plan . . .486 156.I „ .. •> •• Section . . 487 157. Cupel: Plan S°3 158. „ Section 5°3 159. Plan of CupeUation Furnace 5°4 160. Section of same -505 161. Parting StiU at Oker 5'° 162. „ „ 163. Chlorine Refining Apparatus S'9 164. Plumbago Crucible . . 533 165. Melting Furnace 534 166. Portable Wind Furnace 535 167. Ingot Mould 535 168. Crucible Tongs 53& 169. Assay Scales 54° 170. Stirrups of Assay Scales 54° 171. RoUers 544 172. Shears ........... 544 173. Cupel Tray 545 174. Parting Flasks FIG. PAGB 175. Button and Comets ... .... 551 176. Mortar 558 177. Pulp Scales 558 178. Clay Crucible .......... 559 179. Button Mould 559 180. Roasting Dishes .......... 560 181. Muffle Furnace 562 182. Battersea Muffle Furnace ....... 563 183. Scorifier ........... 564 184.