REESE LIBRARY 
 
 >F rrtr 
 
 UNIVERSITY OF CALIFORNIA. 
 
 ^ c cessions No. <3^- ^ Shelf No. 
 
APPLETONS' 
 SCIENCE TEXT-BOOKS 
 
 APPLIED GEOLOGY. 
 
APPLETONS' SCIENCE TEXT-BOOKS. 
 
 The following works of this new series will be im- 
 mediately issued ; others are to follow : 
 
 The Elements of Chemistry. 
 
 BY PROF. F. W. CLARKE, 
 Chemist of the United States Geological Survey. 
 
 The Essentials of 
 Anatomy, Physiology, and Hygiene. 
 
 BY ROGER S. TRACY, M. D., 
 
 Author of " Handbook of Sanitary Information for Householders," 
 Sanitary Inspector of the New York City Health Department. 
 
 A Compend of Geology. 
 
 BY JOSEPH LE CONTE, 
 
 Professor of Geology and Natural History in the University of 
 California ; author of " Elements of Geology," etc. 
 
 Elements of Zoology. 
 
 BY C. F. HOLDER, 
 
 Fellow of the New York Academy of Sciences, Corresponding 
 Member of the Linnaean Society, etc. ; 
 
 AND J. B. HOLDER, M. D., 
 
 Curator of Zoology of American Museum of Natural History, 
 Central Park, New York. 
 
 Descriptive Botany. 
 
 BY ELIZA A. YOUMANS. 
 
 Applied Geology. 
 
 BY SAMUEL G. WILLIAMS, 
 Professor of General and Economic Geology in Cornell University. 
 
jftcinite fat-0oks. 
 
 APPLIED GEOLOGY. 
 
 A TREA TISE 
 
 ON THE 
 
 INDUSTRIAL RELATIONS OF GEOLOGICAL STRUCTURE; 
 
 AND ON THE 
 
 NATURE, OCCURRENCE, AND USES OF SUBSTANCES 
 DERIVED FROM GEOLOGICAL SOURCES. 
 
 BY 
 
 SAMUEL G. WILLIAMS, 
 
 PROFESSOR OF GENERAL AND ECONOMIC GEOLOGY 
 IN CORNELL UNIVERSITY. 
 
 NEW YORK: 
 D. APPLETON AND COMPANY. 
 
 I, 3, AND 5 BOND STREET. 
 1886. 
 
'N/ 
 
 COPYRIGHT, 1885, 
 Bv D. APPLETON AND COMPANY. 
 
PREFACE. 
 
 So far as the author of this book has observed, 
 no work has yet been published in this country 
 which aims to give a connected and systematic 
 view of the applications of geology to the various 
 uses of mankind. A number of European and 
 American treatises have appeared which limit 
 themselves to special departments of applied geolo- 
 gy, some of them discussing the modes of occur- 
 rence and distribution of metallic ores or mineral 
 fuels ; others treating of agriculture in its geologi- 
 cal aspects, or dealing with the geological materials 
 of chemical industries, or devoting themselves to 
 building and ornamental stones, to mortars, or to 
 gems. The work of D'Orbigny and Gente on ge- 
 ology applied to the arts and to agriculture, pub- 
 lished more than a quarter of a century ago, is not 
 only in a foreign language, but is now obviously in- 
 complete ; and the excellent treatise of Dr. Page, 
 which reviews the entire field of applied geology, 
 is naturally too much devoted to English and Euro- 
 
vi PREFACE. 
 
 pean materials and sources of supply to be wholly 
 satisfactory to the American student. 
 
 Meanwhile an immense amount of work has 
 been done in revealing the geological structure of 
 the American Continent, and in making known its 
 rich and varied resources a work in which many 
 independent investigators and explorers have added 
 much of value to the information gained by the 
 various State and national surveys. The knowledge 
 thus acquired of the existence, the nature, the 
 abundance, and the distribution of substances of 
 practical utility, as well as of the important relations 
 which are sustained by geological structure to hu- 
 man well-being and to the successful pursuit of 
 many important callings, is scattered so widely in 
 geological reports, in scientific and technical jour- 
 nals, and in the transactions of learned associations, 
 as to be in a great measure inaccessible to the stu- 
 dent and the practical man, unless a large library 
 is at hand and abundant leisure to consult it. It 
 seems evident, therefore, that there is need of a 
 treatise such as this aims to be, which, avoiding 
 minute detail, shall give a systematic and compre- 
 hensive account of the most important relations 
 which geology sustains to human interests. 
 
 This book is written most largely from an 
 American stand-point, yet care has been taken, in 
 the case of all important substances, to give the 
 chief foreign as well as the domestic sources 
 
PREFACE. vii 
 
 whence they may be obtained, since those who 
 may, it is hoped, consult its pages for business pur- 
 poses, will naturally desire to know both where to 
 look for their supplies and whence their sharpest 
 competition is likely to come. With this view, 
 also, tables of the annual production of many lead- 
 ing minerals have been carefully compiled from the 
 most recent attainable data, and for these the excel- 
 lent tables published by the " Engineering and 
 Mining Journal " have furnished the largest part of 
 the materials. 
 
 A work of this kind is in its very nature a dis- 
 cussion and arrangement of materials derived from 
 various sources, and verified, so far as is practicable, 
 by personal observation and inquiry. The author 
 has endeavored to use the rich materials afforded 
 to him with proper discrimination. If somewhat 
 more space has been given to the chapters on " Agri- 
 culture," on " Materials of Construction,'' on " Min- 
 eral Fuels," and on "Ore Deposits" than to other 
 topics, it will probably be conceded that the wide- 
 reaching and important interests to which they relate 
 will fully warrant this greater fullness of treatment. 
 Where the works from which information has been 
 most largely obtained were likely to be within the 
 reach of those persons for whom this book is chiefly 
 intended, they have been mentioned in the lists of 
 works of reference appended to many of the chap- 
 ters. This has necessarily precluded any specific 
 
viii PREFACE. 
 
 mention of many valuable papers published in scien- 
 tific journals and in the " Transactions of the Ameri- 
 can Institute of Mining Engineers," to which this 
 book is indebted for many items of interest. For 
 the arrangement of the seemingly heterogeneous 
 materials of some of the later chapters, useful hints 
 were derived from the " Geology of Canada," 1863, 
 and from some features in the classification of the 
 economic collection of the Ecole des Mines in 
 Paris. The author wishes also to acknowledge his 
 indebtedness to the kindred works of D'Orbigny 
 and Gente, and of Dr. Page, for many important 
 suggestions, and to the first-named work especially 
 for valuable aid in the preparation of the chapter 
 on agriculture. 
 
 CORNELL UNIVERSITY, October i, 1885. 
 
ANALYSIS OF CONTENTS. 
 
 CHAPTER I. 
 
 PAGE 
 
 INTRODUCTION ROCK-FORMING MINERALS CLASSIFICATION . i 
 
 Quartz, feldspars, micas, hornblende, pyroxene, calcite, dolo- 
 mite, talc, chlorite, serpentine, clay Classification of rocks- 
 Sedimentary rocks and consolidation Crystalline rocks and their 
 structure Tables of classification and means of consolidation. 
 Structure and texture of rocks. 
 
 CHAPTER II. 
 
 DESCRIPTION OF ROCKS 15 
 
 Mechanical sediments Chemical sediments Organic sedi- 
 ments Metamorphic rocks Igneous rocks Key for proximate 
 determination of rocks. 
 
 CHAPTER III. 
 ARRANGEMENT OF ROCK-MASSES . . . . . .27 
 
 Stratified and definitions Unstratified Included or vein-like 
 Relative age of rocks Table of ages and periods. 
 
 CHAPTER IV. 
 ECONOMIC RELATIONS OF GEOLOGICAL STRUCTURE ... 44 
 
 Economic geology defined and illustrated Accessibility de- 
 pendent on dip, faults, uplifts Facility of extraction Expense 
 of excavation and tunneling Foundations of structures Water 
 supply Springs Wells Artesian wells Drainage. 
 
 CHAPTER V. 
 MATERIALS OF CONSTRUCTION ....... 66 
 
 Building-stonesProperties of Strength Table of strength 
 Durability Beauty Ease of working Selection of building- 
 
x ANALYSIS OF CONTENTS. 
 
 PAGE 
 
 stones North American building-stones Geological positions 
 and distribution Granitic Marble and slate Sandstones Lime- 
 stones Brick, terra-cotta, and drain-pipes Materials for mortar 
 and cement. 
 
 CHAPTER VI. 
 RELATIONS OF GEOLOGY TO AGRICULTURE . . . . 101 
 
 Soils, origin of Ingredients Nature and amelioration Table 
 of ash analyses Composition of soils Fertilization Geological 
 fertilizers Drainage and subsoils. 
 
 CHAPTER VII. 
 
 RELATIONS OF GEOLOGY TO HEALTH 129 
 
 Water supply of households and communities Drainage of 
 dwellings, cities, and districts. 
 
 CHAPTER VIII. 
 
 MINERAL FUELS 135 
 
 Coals, classification Analyses of twenty-two Geological as- 
 sociations Geological horizons American coal-fields Foreign 
 coal-fields Impurities in coals Fuel-value of coals Adaptation 
 to special uses Peat Coal product of 1881. 
 
 CHAPTER IX. 
 GEOLOGICAL MATERIALS FOR ILLUMINATION . . . .165 
 
 Petroleum Mode of occurrence Geological horizons Re- 
 gions Mode of exploitation Bituminous shales Natural gas 
 Ozocerite. 
 
 CHAPTER X. 
 MODE OF OCCURRENCE OF METALLIFEROUS DEPOSITS . . 183 
 
 Metallic ores Ore associations and gangues Structure of ore 
 deposits Beds and placers Impregnations Mass deposits 
 Veins of segregation Fissure veins Origin of fissures and con- 
 tents Arrangement of contents Positions relative to country 
 rock Disturbances of deposits Surface changes General distri- 
 butionProspectingValue, on what dependent Erroneous 
 ideas regarding ore deposits. 
 
 CHAPTER XI. 
 224 
 
 O res Mode of occurrence Geological horizons and localities 
 Production Uses. 
 
ANALYSIS OF CONTENTS. x i 
 
 CHAPTER XII. 
 
 PAGE 
 
 COPPER 231 
 
 Ores Mode of occurrence Distribution, geological and topo- 
 graphic Chief foreign localities Production in 1882 Uses. 
 
 CHAPTER XIII. 
 LEAD AND ZINC 241 
 
 Ores of lead Nature of deposits and geological horizons 
 American centers of production Foreign regions Production 
 Uses Zinc ores Mode of occurrence American localities For- 
 eign centers ProductionUses. 
 
 CHAPTER XIV. 
 
 TIN AND MERCURY . 254 
 
 Tin ore Mode of occurrence Localities Production and use 
 Ore of mercury Form of deposits Three regions of Produc- 
 tion of 1882 Uses. 
 
 CHAPTER XV. 
 SILVER 262 
 
 Ores Forms of deposit American silver regions Table of 
 production Foreign silver regions Table of world's product 
 Uses. 
 
 CHAPTER XVI. 
 GOLD . .- . . . . ' 273 
 
 Associations Mode of occurrence Regions of gold produc- 
 tion Tables of United States product, and of that of the world 
 Uses of gold Table of gold values Table of uses of gold and 
 silver Extraction of gold. 
 
 CHAPTER XVII. 
 
 PLATINUM AND OTHER METALS 284 
 
 Platinum Nickel Cobalt Antimony Bismuth Magnesium 
 Aluminium Chromium Manganese Arsenic Iridium 
 Tungsten. 
 
 CHAPTER XVIII. 
 SUBSTANCES ADAPTED TO CHEMICAL MANUFACTURES OR USE . 296 
 
 Pyrites Sulphur Salt Potash and soda Borax Alum- 
 Magnesia Strontia Titanium. 
 
xii ANALYSIS OF CONTENTS. 
 
 CHAPTER XIX. 
 
 PAGE 
 
 FICTILE MATERIALS 319 
 
 Potter's clay Table of analyses Properties Origin Locali- 
 ties Pottery mixtures and glazes Composition of glass Glass- 
 sand Granulite Coloring materials. 
 
 CHAPTER XX. 
 
 REFRACTORY SUBSTANCES . 334 
 
 Fire-clays Analyses Geological occurrence Dinas bricks 
 Canister Fire-stones Floating brick Graphite Lime and 
 Magnesia Soapstone Mica Asbestus. 
 
 CHAPTER XXI. 
 
 MATERIALS OF PHYSICAL APPLICATION 347 
 
 For roads and walks Abrasives: Grindstones, whetstones, 
 millstones, bort, corundum and emery, sand, pumice and tripoli 
 Graphic materials: Graphite, chalk, etc., lithographic lime- 
 stone Pigments : Whiting, ochre, umber, barytes Lubricators : ' 
 Graphite, petroleum, talc, felsite Molding-sand. 
 
 CHAPTER XXII. 
 
 ORNAMENTAL STONES AND GEMS 365 
 
 Quartz Amethyst Agates Moss-agate Onyx Jasper- 
 Feldspar Nephrite Lapis lazuli Malachite Fluorite Jet- 
 Amber Marbles Onyx marble Alabaster Verd-antique mar- 
 ble Porphyry. Gems : Diamond, corundum, spinel, topaz, beryl, 
 zircon, garnet, tourmaline, hiddenite, turquoise, opal. 
 
APPLIED GEOLOGY. 
 
 CHAPTER I. 
 
 INTRODUCTION ROCK-FORMING MINERALS CLASSIFICA- 
 TION. 
 
 THE science of geology has both a theoretical and 
 a practical side. Theoretically, it aims at an exhaustive 
 study of the phenomena presented by the earth's crust, 
 together with the order in time in which they originated, 
 and the forces to whose combined or successive action 
 they are due. It investigates the composition, the struct- 
 ure, the origin, and the arrangement of the earth's rocky 
 masses. It strives to refer the present phenomena of the 
 earth's crust to their appropriate causes. It reconstructs 
 the history of the earth and of its successive inhabitants, 
 using structure as its guide, and the present action of the 
 unchanging forces of nature as its interpreter. 
 
 On the practical side, geology uses the knowledge of 
 the earth's structure, and of the mode of occurrence and 
 properties of its various products, to subserve human 
 needs and promote human enjoyment. It guides the 
 architect and the builder in the selection of fitting mate- 
 rials for construction good building-stones, mortars, ce- 
 ments, and sands. It reveals to the agriculturist the ori- 
 gin of his soils, and points him to the cheapest and most 
 
2 APPLIED GEOLOGY. 
 
 effective means for correcting their defects. It teaches 
 the civil engineer that the feasibility and expense of most 
 of his important undertakings, the obstacles that he must 
 overcome, and the aids of which he may avail himself, 
 will depend in large measure on the geological structure 
 of the region in which he must operate ; and that he 
 needs to take this into careful consideration, if he would 
 guard against ruinous disasters, or almost equally ruinous 
 miscalculations as to expense. It furnishes to the mining 
 engineer the only available guide in his arduous calling, 
 teaching him the nature and the modes of occurrence of 
 those valuable substances for which he must seek, the 
 laws to which they are subjected, and the irregularities 
 and dislocations to which they are liable ; and supplying 
 him with those general principles, by applying which, he 
 may make the technical experience gained in any one lo- 
 cality available under other and widely different circum- 
 stances. It aids the sanitarian in securing the two most 
 subtile yet essential conditions of public health pure air 
 and wholesome water both of which depend largely on 
 circumstances purely geological. 
 
 Not only does practical geology hold such intimate 
 relations with these very important interests, but, more- 
 over, when we consider how large a proportion of the sub- 
 stances which civilized man utilizes for the supply of his 
 multifarious wants is drawn from the bosom of the earth, 
 we shall see how wide-reaching and vital are its connec- 
 tions with the very sources of human progress. Among 
 these substances are the fuels that we burn ; the materials 
 that we use for illumination ; the salt with which we pre- 
 serve or season our food, and which becomes the basis of 
 vast manufactures, some of whose products reach every 
 family ; the clays and sands that we fabricate into myriads 
 of useful and ornamental forms, a number of which are 
 found in every household, even the humblest ; the ores 
 that we smelt to provide ourselves with those implements 
 
/ 
 
 ROCK-FORMING MINERALS. 
 
 by whose ever-widening use we are daily exten< 
 mastery over the blind forces of nature ; and, finally, but' 
 by no means least, those substances by which a cultured 
 taste seeks for itself a refined pleasure brilliant pigments, 
 sparkling gems for jewelry, and handsome stones for do- 
 mestic and architectural adornment. The withdrawal of 
 any one of these classes of materials would seriously crip- 
 ple human resources, and the lack of some of them would 
 have made human advancement very difficult, if not im- 
 possible ; for the stages of man's progress are well marked 
 by the character of his pottery, and, better, by the nature 
 and material of his implements. 
 
 It is but natural that a science which touches so vitally 
 the interests of nearly all classes should attract the atten- 
 tion of enlightened governments ; and we accordingly 
 find that most civilized states have carried on to some 
 extent geological surveys, which, while primarily revealing 
 the geological structure of their domains, have also care- 
 fully sought out their various mineral resources. The pub- 
 lications of these surveys, giving an authoritative statement 
 of the localities where valuable substances might be found, 
 have naturally attracted capital to the development of 
 such means of wealth, and have, doubtless, repaid mani- 
 fold their cost by the increase in the taxable property of 
 the communities that have carried them on. The two 
 States of Ohio and Illinois published reports of their re- 
 sources, beginning the one in 1870 and the other in 1866. 
 The coal-trade alone of these two States increased from 
 two and a half million tons each in 1870 to more than 
 nine million tons each in 1882 ; and this industry in Illi- 
 nois gave employment to 19,400 men and $8,230,000 capi- 
 tal. There is no good reason to doubt that this great 
 increase in the coal-trade of those States was due in large 
 measure to the reliable information furnished by their 
 surveys. 
 
 Incidentally, also, such surveys have been of great 
 
4 APPLIED GEOLOGY. 
 
 service in discouraging misdirected and expensive explo- 
 rations after substances not likely to be found in certain 
 localities ; for, second only in importance to the knowl- 
 edge of what we may fairly expect to find in a given place 
 is the certainty of what we ought not to expect to find. 
 Large sums have been expended in New York by men 
 unacquainted with its geological structure, in a futile 
 search for coal in certain black, slaty rocks, holding geo- 
 logical positions such as have never yet furnished coal, 
 nor are ever likely to do so. Any man would show him- 
 self ignorant indeed who should now undertake a search 
 for coal in New York. 
 
 From what has already been said, it will be evident 
 that at least an elementary knowledge of the earth's geo- 
 logical structure is essential as a guide in the intelligent 
 prosecution of many great branches of industry. It will 
 be necessary for our purpose, therefore, first to examine 
 the most essential points of geological structure, and after- 
 ward to show their application to the various arts, draw- 
 ing our materials as largely as possible from American 
 sources. 
 
 Rocks : their Composition and Classification. 
 
 Geology deals with the rocks which form the earth's 
 framework ; and what is most essential to be known about 
 rocks for our present purpose is (i) their composition, i.e., 
 the mineral substances which enter into them and impart 
 to them most of their properties; (2) their texture and 
 structure, or the characteristics which distinguish them 
 both as rock-individuals and as rock-masses ; (3) their ori- 
 gin, or the agencies through which they assumed their 
 present form ; (4) their mode of arrangement ; and (5) the 
 order in which they occur. 
 
 Rock-Forming Minerals. Some careful examina- 
 tion of the rocks most commonly met with will prepare 
 the observer to admit that all rocks, whatever their origin, 
 
ROCK-FORMING MINERALS. 5 
 
 are composed of mineral species ; and, furthermore, that 
 the minerals which play the chief part in their composi- 
 tion, and which most largely condition their use and dura- 
 bility, are comparatively few in number. These minerals, 
 in particles varying greatly in size and regularity of form, 
 aggregated in the most variable proportions, and consoli- 
 dated by many different agencies to the most widely differ- 
 ing degrees of firmness, from mere incoherent masses of 
 sand, to the hardest quartzite and the toughest trap, make 
 up the chief bulk of the most important rocks of the 
 globe. Ready acquaintance with them in their smallest 
 discernible particles, and by their most obvious and easily- 
 tested properties, is highly essential to the practical geolo- 
 gist. Chief among such minerals is quartz, with its most 
 widely-disseminated compounds, viz. : the varieties of 
 feldspar, mica, hornblende, and pyroxene, to which may 
 be added talc, chlorite, and serpentine. Calcite and dolo- 
 mite are the essential components of the various kinds of 
 limestone and marble ; while pyrite, though not largely 
 present in rocks, should be known because of the injuri- 
 ous manner in which it affects their characters. The im- 
 portant ores and other minerals of economic use will be 
 considered in other connections. 
 
 For a complete knowledge of these minerals, and others 
 that will be mentioned in this treatise, the student should 
 study the minerals themselves all easy to be obtained 
 with the aid of some good treatise on mineralogy, Dana's 
 " Manual of Mineralogy " being the best. The properties 
 to which especial attention should be directed are, color 
 and luster, hardness, cleavage and fracture, behavior with 
 acids, and sometimes fusibility. 
 
 Quartz is readily distinguished by its glassy luster, its 
 hardness, so great as not to be scratched by a knife, and 
 by the fact that its fracture gives never flat but always 
 curved surfaces (conch oidal fracture). It will scratch all 
 the other minerals named above, being 7 on a scale of 
 
6 APPLIED GEOLOGY. 
 
 hardness beginning with talc, i, easily impressed with the 
 finger-nail, and ending with diamond, 10. 
 
 The hardest of the remaining minerals named as chief 
 components of rocks, the feldspars, can be scratched with 
 considerable difficulty by a knife, and their hardness is 
 counted 6. Besides this, the feldspars can be split with 
 flat, shining surfaces cleavage in two directions, making 
 a right angle with each other in orthoclase, the most com- 
 mon kind, and in the other two important varieties, oligo- 
 clase and labradorite, varying but a few degrees from a 
 right angle. The last two, in a good light, usually show 
 on the face of easiest cleavage fine parallel lines, while 
 orthoclase does not. The color of orthoclase and oligo- 
 clase varies from white to light red, while labradorite is 
 usually gray or brown, with a beautiful internal reflection 
 from smooth surfaces. Their luster differs somewhat from 
 that of quartz, inclining to pearly. Their slightly inferior 
 hardness and their flat cleavage surfaces usually make them 
 easily distinguishable from quartz ; but if any doubt still 
 remains, a thin, pointed splinter should be strongly heated 
 with the blow-pipe. Any of the feldspars can be fused 
 with more or less difficulty, while quartz can not. 
 
 The micas are readily distinguished by their very easy 
 cleavage into thin, elastic, shining leaves. Muscovite mica 
 is usually of light to brownish silvery colors, biotite black, 
 and phlogopite of bronze-color. All are easily scratched 
 with a knife. 
 
 Pyroxene, of which augite is the most abundant 
 variety, and hornblende, as they are commonly found in 
 rocks, are black, brown, or dark-green minerals, though 
 some varieties are lighter green and white, a little more 
 easily scratched than feldspar their hardness being about 
 5.5 and more easily fused. Both cleave in two directions, 
 making in pyroxene a little less than a right angle, and in 
 hornblende a very obtuse angle of 124 30'. Hence, when 
 the angle of cleavage can be seen, the two minerals can be 
 
ROCK-FORMING MINERALS. 7 
 
 easily distinguished, otherwise not. It is helpful, however, 
 to note that the cleavage of hornblende is easier than that 
 of pyroxene, hence gives usually more complete surfaces 
 and brighter luster ; also that hornblende is frequently 
 found associated in rocks with quartz and orthoclase, 
 while augite, the most common form of pyroxene, is rarely 
 so associated. Both are heavy minerals, and give more 
 than usual weight to rocks in which they occur abun- 
 dantly. 
 
 Calcite and dolomite are easily known by their ready 
 cleavage in three directions, when crystallized, giving rise 
 to a six - sided oblique - angled figure ; by being easily 
 cut with a knife hardness 3 to 4 ; and by effervescing 
 rapidly, from the escape of carbonic acid, with dilute hy- 
 drochloric acid. Their usual color is white. Dolomite 
 is a little harder and a little heavier than calcite, and 
 while calcite effervesces freely in cold acid, dolomite 
 effervesces but slightly, if at all, until the acid is heated. 
 Both are very important minerals, being, as has already 
 been said, the essential constituents of all limestones and 
 marbles. 
 
 Pyrite, or iron pyrites, is a mineral of metallic luster 
 and light-yellow or golden color, whence it is often mis- 
 taken for gold hence called " fool's gold " but is readily 
 distinguished from it by its great hardness, nearly equal 
 to that of quartz, and by its giving when heated the odor 
 of sulphur. It is little likely to be mistaken for any other 
 mineral save copper pyrites, from which it may be distin- 
 guished by the fact that copper pyrites is much softer 
 and its color is a deeper yellow. 
 
 Talc is a green, gray, or white mineral of pearly luster, 
 so soft as readily to be scratched by the finger-nail, greasy 
 to the touch, and usually of a scaly, foliated, or fibrous 
 texture. Its softness and its soapy feel render it easy to 
 be distinguished. 
 
 Chlorite, as it occurs forming a characteristic constit- 
 
8 APPLIED GEOLOGY. 
 
 uent of rocks, is usually a dark-green earthy mineral, but 
 little harder than talc, and of a pearly luster when cleav- 
 able. 
 
 Serpentine is usually a massive though sometimes 
 fibrous mineral, of an oily green color, sometimes red or 
 nearly black, of greasy luster and slightly greasy feel, easily 
 scratched with a knife, its hardness being about 3, and with 
 a conchoid or splintery fracture. 
 
 To these materials of rocks should be added clay, 
 an indefinite mixture of kaolin, which is a soft, unctuous 
 substance resulting from the decomposition of feldspar, 
 with varying amounts of quartz -sand often exceedingly 
 fine, powdered feldspar, iron oxide, and occasionally other 
 substances. It is plastic when wet, shrinks on drying or 
 when strongly heated, and emits an earthy odor when 
 breathed on. The rocks into which it enters are often 
 described as argillaceous rocks, from the Latin name for 
 clay : e. g., slate is an argillaceous rock, and a limestone 
 containing a considerable amount of clay would be termed 
 an argillaceous limestone. Also the following adjective 
 terms are of frequent occurrence, viz. : Quartzose or sili- 
 cious, applied to rocks containing quartz ; calcareous, to 
 those containing calcite ; ferruginous, to those colored by 
 iron oxide usually red, yellow, or brown ; and arenaceous, 
 to those containing sand. 
 
 Rocks. The minerals here described, with occasion- 
 ally quite subordinate amounts of some other minerals, 
 make up the rocks of chief economic importance. As 
 constituents of rocks they are found, sometimes as crys- 
 tals of usually imperfect outline, sometimes in the form of 
 broken and worn grains, of sizes varying from those so 
 minute as not to be perceptible to the unaided eye, to 
 masses of considerable size. Hence, according to the con- 
 dition of the composing substances, we may distinguish 
 crystalline rocks and fragmental, or, as they may with 
 equal propriety be termed, sedimentary rocks, because de- 
 
ROCK-FORMING MINERALS. g 
 
 posited from suspension or solution in water. The rocks 
 of the latter class are found always arranged in layers 
 or beds, and hence called stratified ; while the crystalline 
 rocks may occur either in beds more or less apparent, or 
 without any signs of a bedded structure, when they may 
 be termed massive. Stratified rocks, i. e., those having a 
 layered structure, are much the most common, and exam- 
 ples of them may be studied in most localities where the 
 rocks appear above the covering soil. 
 
 Sedimentary Rocks. The sedimentary rocks are of 
 three general kinds : (i) those formed from the worn frag- 
 ments of pre-existing rocks, which may be called mechani- 
 cal sediments, e. g., sandstones and shales ; (2) those de- 
 posited from solution in water, or chemical sediments, as 
 some limestones, many quartz rocks, and probably most 
 beds of iron-ore ; and (3) organic sediments, those formed 
 from the worn and subsequently consolidated results of 
 vegetable and animal growth, as most limestones and coal- 
 beds. Beds of the second class are formed of welded and 
 interlocked crystals, and have a degree of solidity equal to 
 that of the composing mineral. Beds of the two remain- 
 ing classes, though sometimes found as mere incoherent 
 or slightly cohering masses like sand, gravel, and chalk, 
 have more generally been consolidated by various means 
 to a greater or less degree of hardness. The following 
 are the chief means of consolidation : 
 
 Some rocks seem to be consolidated solely by the great 
 and long-continued pressure of the overlying beds, caus- 
 ing the particles to adhere to each other, as is the case 
 with many shales. When, as is often the case in sand- 
 stones, some finely-disseminated clay is present, making the 
 contact among the sand-particles more complete, pressure 
 gives the rock a greater degree of firmness. The presence 
 of this clay can be detected by subsiding the finely-pow- 
 dered rock in water, when the clay will remain long sus- 
 pended, making the water turbid. A common means of 
 
I0 APPLIED GEOLOGY. 
 
 consolidation is calcite, which has been introduced in solu- 
 tion, as in all sedimentary limestones and some sandstones. 
 Its presence as a consolidating ingredient in rocks other 
 than limestones can be readily detected by its efferves- 
 cence with dilute acids. Silica consolidates mjfciy sand- 
 stones and conglomerates to a very high degree of hard- 
 ness ; and iron oxide is also a frequent means of consoli- 
 dation, giving to rocks a red or yellow color. When red 
 or yellow sandstones are pulverized and heated for a little 
 time in strong hydrochloric acid, the cementing iron is 
 dissolved, giving a deep yellow solution, and colorless 
 grains of quartz remain. 
 
 Crystalline Rocks. The crystalline rocks, other 
 than the relatively small amounts of chemical sediments, 
 are made up usually of imperfect crystals, sometimes of 
 one mineral, but more commonly of two or more, welded, 
 interlocked, or felted together to a mass as firm at least as 
 the softest abundant constituent, unless a prevailing direc- 
 tion of some readily cleavable mineral like mica, talc, or 
 hornblende, may dispose the rock to split more easily in 
 certain directions. Some of these crystalline rocks have 
 a more or less observable bedded character, often with 
 foliation or schistose structure, and are generally believed 
 to have once been ordinary sedimentary rocks, which, hav- 
 ing been rendered somewhat plastic by heated water under 
 enormous pressure, have crystallized in their present form. 
 Hence they are termed metamorphic rocks, i. e., rocks 
 which have been changed from their original condition. 
 Other crystalline rocks show no signs of bedding what- 
 ever, their condition being probably due to a softening or 
 fusion so complete as to have obliterated all traces of bed- 
 ding, if they ever existed. In this condition they have 
 often been thrust in among or through other rocks, emerg- 
 ing frequently at the surface. Where the subsequent cool- 
 ing has proceeded at a very slow rate, and usually at very 
 considerable depths, the resulting texture is coarsely and 
 
ROCK-FORMING MINERALS. 
 
 II 
 
 obviously crystalline ; where the rate of cooling has been 
 relatively rapid, the crystalline texture may be so fine and 
 close as not to be apparent to the unaided eye, or the text- 
 ure may in some cases be partly or entirely glass-like, i. e., 
 vitreous. Rocks of this kind are termed igneous or erup- 
 tive, and those obviously crystalline are also frequently 
 called Plutonic rocks, a term which implies the opinion 
 that they were consolidated at great depths, and that our 
 present opportunities for becoming acquainted with them 
 are due to very great subsequent changes in the earth, in 
 consequence of which they have become surface-rocks. 
 
 To give a connected view of what has just been said, 
 a tabulated summary of rocks in general is here presented, 
 classified according to origin, with their structure as rock- 
 masses and the usual condition of their materials : 
 
 Classification on Origin. 
 
 Structure. 
 
 Condition of Materials. 
 
 C Mechanical, 
 Sedimentary \ Chemical, 
 I Organic. 
 Metamorphic. 
 Igneous. 
 
 Stratified. 
 
 Stratified. 
 Massive. 
 
 Fragmentary, sometimes 
 crystalline. 
 
 Crystalline. 
 Crystalline or vitreous. 
 
 Means of Consolidation : 
 
 1. Pressure. 
 
 2. Clay and pressure. 
 
 3. Silica. 
 
 4. Calcite. 
 
 5. Iron oxides. 
 
 6. Welding, interlocking, or felting of crystals. 
 
 Structure and Texture of Rocks. By the struct- 
 ure of rocks is meant those characters which distinguish 
 them as rock-masses, and which are usually best displayed 
 on the large scale. 
 
 Most important of structural characters is stratifica- 
 tion, which is the arrangement of rock-masses in tolerably 
 
12 APPLIED GEOLOGY. 
 
 parallel sheets or layers, varying in thickness from the 
 fraction of an inch to several feet, and separating readily 
 from each other. Layers of the same kind of rock lying 
 together form a stratum, and alternations of different kinds 
 of rock produce strata (plural of stratum). A stratum of 
 some valuable material, e. g., coal, is frequently termed a 
 seam or bed. Stratified rocks were undoubtedly formed 
 in all usual cases by deposition of their materials from 
 water, in precisely the same way that successive layers of 
 mud and sand are being deposited now in seas, lakes, and 
 rivers ; and it is altogether probable that the division into 
 layers is due to some considerable pause in the act of depo- 
 sition, whereby the lower layer became somewhat com- 
 pacted before the succeeding one was deposited ; while 
 the succession of strata marks changes in the conditions 
 of deposit by which materials of different kinds came to 
 be laid down. 
 
 The massive structure is contradistinguished from the 
 stratified, and belongs to igneous rocks, or to those which 
 have been so greatly changed from their original condi- 
 tion as to have lost all signs of bedding. The term mass- 
 ive is also used sometimes in contradistinction from lami- 
 nation. Lamination is where rocks reveal the thin succes- 
 sive layers of which they are made up, either by some 
 slight differences of color or texture in the several layers, 
 or by splitting more readily on certain planes, usually par- 
 allel to the bedding. This structural character is a com- 
 mon one in sandstones, especially where they are argilla- 
 ceous, and is occasionally seen in limestones. An excess 
 of lamination in highly argillaceous rocks, causing them 
 to split into thin, irregular, fragile slabs, constitutes the 
 shaly structure. 
 
 Foliation, or the schistose structure, is a character of 
 metamorphic crystalline rocks, analogous to lamination in 
 the sedimentary series, and is due to the arrangement of 
 the crystalline constituents in more or less definite planes, 
 
ROCK-FORMING MINERALS. 
 
 which often, no doubt, if not always, correspond 
 nal planes of lamination, since these are likely to be the 
 planes of easiest penetration and circulation for fluids. 
 The slaty structure is one which belongs to argillaceous 
 rocks that have been doubled up into folds, and so changed 
 by intense pressure as to develop a tendency to cleave 
 into hard, even slabs, in a direction at right angles to the 
 pressure, and corresponding with the direction of the 
 folds. The planes of cleavage rarely correspond with the 
 original planes of lamination, though they may occasion- 
 ally do so. 
 
 Joints are divisional planes in rocks, usually but not 
 always nearly vertical, which divide the rocks of many 
 regions into blocks that separate somewhat readily at these 
 planes. These blocks, in regions of jointed structure, 
 vary in width from an inch, or even less, to many feet, the 
 main joints forming the faces of the cliffs and the back 
 walls of the quarries ; and where, as is frequently the 
 case, there are two series of joints, cutting each other at 
 nearly right angles, the weathered faces of the cliffs pre- 
 sent a singular resemblance to regular piles of masonry. 
 This structure is not confined to any one of the great 
 classes of rocks that have been named, but may be found 
 in all of them, occasionally even giving to massive rocks 
 a false appearance of bedding. Practically considered, 
 while the jointed structure greatly facilitates the operation 
 of the quarryman, it also strictly limits the dimensions of 
 the blocks that can be obtained. 
 
 The columnar structure often seen in volcanic rocks, 
 especially the basalts, seems to be a variety of the jointed 
 structure, in which, by the intersection of several jointing 
 planes, the rock is divided into a series of rude pillars 
 which are at right angles to the original cooling surfaces 
 of the rock. 
 
 The concretionary structure is one which is displayed 
 in some rocks by the collection of some mineral, notably 
 
I 4 APPLIED GEOLOGY. 
 
 silica, calcite, pyrite, or iron carbonate, into spherical, 
 spheroidal, or irregular forms, e. g., the flinty nodules in 
 chalk and limestone, the silicious balls in some sandstones, 
 the calcareous and pyritous masses in some clay rocks, and 
 the kidney-shaped masses of clay iron-stone. 
 
 By the texture of rocks is meant the internal arrange- 
 ment of their constituents. The granular texture is dis- 
 played by rocks which are composed of worn grains or 
 irregular crystals. These grains or crystals may vary 
 from those of considerable size, giving a coarse-grained 
 texture, to very minute ones, giving rise to the compact 
 texture, as in many sedimentary limestones, and to the 
 aphanitic or crypto-crystallim texture, as in some igneous 
 rocks in which the really crystalline texture is revealed 
 only by the microscope. 
 
 The term granitoid is applied to thoroughly crystalline 
 rocks whose crystals are of approximately equal size, as 
 in granite ; while the term porphyritic describes those 
 which contain distinct crystals, notably of feldspar, im- 
 bedded usually in a very fine-grained base or ground-mass. 
 The vitreous or glassy texture resembles artificial glass, 
 and is found only in some eruptive rocks. The terms 
 porous, fibrous, earthy, and vesicular, as applied to text- 
 ure, hardly need explanation. Some eruptive rocks, origi- 
 nally vesicular, have had their rounded cavities subse- 
 quently filled by various minerals, giving rise to a vari- 
 ety of texture called the amygdaloidal, from the resem- 
 blance of many of the filled spaces to the almond, Latin 
 amygdala. 
 
CHAPTER II. 
 
 DESCRIPTION OF ROCKS. 
 
 Mechanical Sediments. Sand is an unconsoli- 
 dated mass of fine, worn grains of the harder minerals and 
 crystalline rocks, in which quartz usually plays by far the 
 largest and often the almost exclusive part, since it is the 
 hardest and most enduring of the ordinary rock-forming 
 minerals. Where the worn fragments range from the size 
 of a pea to that of an egg, it is called gravel, still coarser 
 gravel being sometimes termed shingle. Most sand con- 
 tains particles of magnetic iron- ore, which can be de- 
 tected by their clinging to a magnet. Sand, consolidated 
 in any way, forms sandstone. In some sandstones 
 pressure seems to be the sole consolidating agent, though 
 doubtless a minute amount of silica cements the points 
 of contact of the granules, producing a porous and 
 often friable rock. The presence of a small amount of 
 clay, forming a film which coats the grains of sand, or 
 of a larger amount partially imbedding them, makes a 
 firmer rock, often highly laminated an argillaceous sand- 
 stone. Iron oxide, usually mingled more or less with clay, 
 is a somewhat common cement, forming a red or yellow 
 sandstone. When silica is the cementing material filling 
 the spaces among the grains, it makes an exceedingly 
 hard rock called a silicious sandstone ; or where it oc- 
 curs, as it usually does, among metamorphic rocks, it is 
 called quartzite. Calcite is not often found as the chief 
 
l6 APPLIED GEOLOGY. 
 
 cementing material of sandstones ; but when it is present, 
 it is readily recognized by its effervescence with acids. 
 A sandstone which works equally well in all directions, 
 without a tendency to split, is often called freestone a 
 name which is also sometimes applied to other rocks of 
 like character. A thin-bedded laminated sandstone is a 
 flag-stone. Coarse, rough-textured sandstones are often 
 called grits a term, however, not very definitely used. 
 
 A conglomerate, sometimes called pudding-stone, is 
 formed of rounded pebbles, from the size of a pea to a 
 foot or more in diameter, consolidated in any way, and 
 with the spaces filled usually with cemented sand. Where 
 the pebbles, instead of being rounded, are angular, the 
 rock is called a breccia. 
 
 A shale is a highly laminated argillaceous rock, con- 
 solidated often by mere pressure, and so returning to mud 
 when exposed for some time to the weather. Where it 
 contains a considerable proportion of sand, it becomes an 
 arenaceous shale, and so may graduate into an argillaceous 
 sandstone. 
 
 Chemical Sediments. These rocks deposited from 
 solution in water by evaporation or cooling of the water, 
 or by dissipation of the chemical agent that held them 
 dissolved, although forming no great proportional amount 
 of the rocks of the earth, still furnish several substances of 
 great economical importance. 
 
 Calcareous deposits from water in which lime is held 
 in solution by carbonic acid, when porous and friable, 
 often incrusting twigs and leaves, are called calcareous 
 tufa ; when forming pendants from the roofs of caverns, 
 and incrustations on their floors, are called stalactites and 
 stalagmites ; when forming compact beds, are named trav- 
 ertine, which, when banded with various colors, becomes 
 onyx marble ; and when composed largely of rounded 
 concretionary grains, little larger than a mustard-seed, are 
 termed oolites. 
 
DESCRIPTION OF ROCKS. ij 
 
 Gypsum is a sulphate of lime, which, when crystalline, 
 is much softer than calcite, being easily scratched by the fin- 
 ger-nail, and cleaves easily in one direction, forming trans- 
 parent, inelastic plates which quickly whiten when held in 
 a flame. It forms considerable beds, or lenticular masses, 
 which in some cases have been deposited by evaporation 
 of the water that held the gypsum dissolved, and in 
 others have been formed by a change of ordinary lime- 
 stones through infiltration of sulphuric acid from sulphu- 
 retted springs. In the latter case, the gypsum forms a 
 soft, earthy rock, usually of a gray color. When ground 
 fine and heated, gypsum gives off much water, and leaves 
 a powder that will set with water. 
 
 Salt occurs in beds or masses, sometimes of enormous 
 thickness, which have doubtless been formed by the evapo- 
 ration of inclosed bodies of sea-water. It is usually asso- 
 ciated with beds of gypsum and of anhydrite a mineral 
 like gypsum, but containing no water. 
 
 The waters of some springs, especially in regions of 
 volcanic disturbance, deposit silica, sometimes on the sur- 
 face as hard, porous incrustations, called silicious sinter, as 
 about hot springs and geysers; sometimes filling fissures 
 in other rocks, forming common vein-stones that are con- 
 nected with many valuable ore-deposits. 
 
 Iron-ores, which occur usually as beds associated with 
 various other rocks, doubtless owe their origin to chemical 
 deposition. Siderite, i. e., iron carbonate or spathic iron, 
 occurs crystallized in the same form and with the same 
 cleavage as calcite, but is somewhat harder and of con- 
 siderably greater comparative weight specific gravity 
 besides being of a brownish color ; also, when heated in 
 a test-tube, it turns black and becomes magnetic. When 
 it occurs in kidney-shaped concretions, it is termed kid- 
 ney-ore or spherosiderite j when mixed with clay, it is clay 
 iron-stone ; and when forming a black, bituminous, shaly 
 mass, it is called black-band. 
 
1 8 APPLIED GEOLOGY. 
 
 Limonite is an iron oxide containing some water, and 
 forms masses of a fibrous or earthy texture, and of a color 
 varying from brown to black; but its powder and the 
 streak which it makes on an unglazed porcelain surface 
 are of a dull yellow color. When heated in a test-tube, 
 it yields steam which condenses in the upper part of the 
 tube, and becomes magnetic, though not so before heating. 
 
 Hematite has the composition of limonite, but without 
 water, and forms beds of a red, steel-gray, or black color, 
 and of a texture varying from earthy or compact, to those 
 mica-like, or to thin, tabular, very brilliant crystals. The 
 streak and powder are of a dark cherry-red. 
 
 Magnetite is black, has a black streak and powder, 
 and attracts the magnet strongly. It forms a crystalline, 
 granular, or sometimes compact rock, of great weight, and 
 is easily known by its magnetism and its black powder. 
 The last three iron-ores form very heavy rocks, and, when 
 crystalline or compact, are of about the hardness of feld- 
 spar, being scratched with some difficulty by a knife. 
 
 Organic Sediments. These rocks, formed of the 
 hard parts of very minute organisms, or of the remains of 
 any organic growth ground up or macerated, and after- 
 ward consolidated either by pressure or by partial solu- 
 tion of their own substance, embrace all the coal-beds of 
 the world, and all extensive deposits of limestone, besides 
 those peculiar silicious deposits called tripoli. 
 
 The limestones, usually composed mainly of calcite, 
 form beds of a drab, gray or blue color, sometimes red 
 or black, and of a texture varying from earthy to sub- 
 crystalline or compact, which last are the most common. 
 These rocks almost always contain a greater or less quan- 
 tity of some impurity iron, giving them a red color ; car- 
 bonaceous matter, making them dark ; or clay and silica, 
 which are often found in such amounts that when the rock 
 is burned for lime it will not slack with water, but when 
 ground and mixed into mortar will set under water to a 
 
DESCRIPTION OF ROCKS. ig 
 
 mass of great hardness, and is hence called hydraulic lime. 
 Many limestones, besides calcite, contain also a consider- 
 able proportion of dolomite, or are made up almost wholly 
 of dolomite. Such are called magnesian limestones or 
 dolomites. Chalk is a very soft, earthy limestone, usually 
 white, made up of the calcareous skeletons of very minute 
 organisms. The limestones, when burned properly, lose 
 their carbonic acid and become quicklime, which, on ap- 
 plication of water, falls into a powder, i. e., slakes, with the 
 evolution of considerable heat, which is greater in the 
 case of the calcitic than in that of the dolomitic limes. 
 Hence the former are called " hot limes," while the mag- 
 nesian are termed " cool limes." 
 
 The limestones that are found associated with crystal- 
 line rocks have been metamorphosed by the action of heat, 
 are of prevailing white or light colors, though often clouded 
 or tinted by impurities, and are of a crystalline granular 
 texture ; sometimes of very fine grain, as in the best stat- 
 uary and architectural marbles, sometimes coarse-grained. 
 Any limestone which is susceptible of a fine polish is usu- 
 ally called a marble^ the crystalline limestones furnishing 
 probably the largest proportion of these. The crystalline 
 limestones frequently contain certain disseminated miner- 
 als, forming mixtures, some of which are prized for orna- 
 mental purposes, like the verd-antique marble or ophiolite 
 formed by the intermingling of calcite and serpentine. 
 
 Mineral coals are formed of former vegetable growths 
 which have been more or less macerated, subjected to a 
 peculiar, partially smothered decomposition, and consoli- 
 dated by the pressure of the superincumbent rocks. A 
 rude but convenient commercial classification of them is 
 made according to the amount of volatile combustible mat- 
 ter that they contain. Those that contain little volatile 
 matter, and hence are hard and lustrous, kindling with dif- 
 ficulty, and burning with but slight blue flame, no smoke, 
 and intense heat, are called anthracites. Semi-bituminous 
 
20 APPLIED GEOLOGY. 
 
 coals are those that contain from ten to about eighteen or 
 twenty per cent of volatile matter, and bituminous coals 
 have a still higher percentage than this. Both these latter 
 kinds kindle easily, and burn with a yellow flame and 
 much smoke. Some of these coals soften while burning, 
 and the pieces fuse together into a mass, which needs to 
 be broken up to admit of ready burning these are called 
 caking coals ; others do not soften while burning such 
 are the non-caking coals, named, from various qualities, 
 splint or block coal, cherry coal, and cannel. The coals 
 will be more fully considered in another place, and are 
 mentioned here merely in their place as organic sedi- 
 ments. 
 
 Metamorphic or Stratified Crystalline Rocks. 
 A brief description only can here be given of the most 
 widely disseminated and important species of metamor- 
 phic as also of massive crystalline rocks. Many of the 
 varieties to which distinctive names are given by litholo- 
 gists are not frequently met with, and are of little practical 
 importance ; it will not be expedient, therefore, to burden 
 the attention of the student with them in a treatise like 
 this. 
 
 As has already been said, the metamorphic rocks are 
 those which are thought once to have been ordinary sedi- 
 mentary rocks, and to owe their present crystalline con- 
 dition to a more or less profound change caused by the 
 agency of heat and moisture. They still show their origi- 
 nal bedded structure with more or less distinctness, but 
 the beds are invariably much disturbed, thrown out of 
 their original nearly horizontal position, bent and folded, 
 testifying to the action of enormous mechanical forces. 
 
 The most widely-diffused and most profoundly changed 
 of these is gneiss, a foliated, crystalline compound of quartz, 
 feldspar usually orthoclase and mica, the foliated ar- 
 rangement of the minerals, sometimes very perfect, giving 
 the rock a highly schistose structure, sometimes so indis- 
 
DESCRIPTION OF ROCKS. 2 I 
 
 tinct as to make the mass difficult to distinguish from gran- 
 ite, which has the same composition, and which differs from 
 gneiss only in the absence of all traces of bedding. Indeed, 
 some masses of gneiss are believed by careful observers to 
 be of eiuptive origin, while it can hardly be doubted that 
 some granite is only the extreme stage of metamorphism 
 of rocks which once were stratified. Where hornblende 
 replaces the mica of gneiss in whole or in part, we have 
 hornblendic or syenitic gneiss. 
 
 Mica schist is a highly foliated rock composed of quartz 
 and mica, the mica often highly prominent and enveloping 
 the quartz, which is in irregular plates, knots, and seams ; 
 while in other cases the quartz predominates, the mica 
 being present in only sufficient amount to give the mass a 
 schistose structure. Where the mica almost wholly disap- 
 pears, the rock still retaining the schistose structure, it is 
 sometimes called quartz schist, which is therefore a rock 
 consisting almost wholly of quartz, and showing a tendency 
 to split into parallel layers. 
 
 A rock composed of grains of quartz, sometimes of 
 considerable size, bound together by a silicious cement 
 into a mass of flinty hardness, is called quartzite. It is a 
 sandstone, metamorphosed by the infiltration of a silicious 
 solution, or by the softening of the outlines of its grains, 
 into a rock breaking with the characteristic glassy fracture 
 of quartz, while its granular texture and bedded structure 
 testify to its original condition. 
 
 A variety of mica schist, in which the quartz is usually 
 in small amount, and the mica is a hydrous variety, i. e., 
 containing water, is called by Dana hydro - mica schist. 
 These schists have usually a grayish or greenish color, a 
 pearly luster, and a greasy feel like talc, whence they are 
 commonly called talcose schist. A true talcose schist is 
 not a common rock. It is a foliated aggregate of scaly 
 talc, with small amounts of quartz or feldspar, of whitish 
 to greenish colors, and unctuous to the touch. 
 
22 APPLIED GEOLOGY. 
 
 Chlorite schist is a foliated rock composed of chlorite 
 and some quartz, with occasionally small amounts of other 
 minerals. Its usual color is a dark green. It is commonly 
 a soft rock, but sometimes the quartz, which usually occurs 
 in scattered leaves or bunches, so interpenetrates and inter- 
 locks the entire mass as to give it a considerable degree of 
 hardness. 
 
 Hornblende schist is a black or dark-green foliated 
 rock, composed of dominant granular or fibrous horn- 
 blende, having a foliated arrangement, with minor quan- 
 tities of quartz or feldspar. When the foliated structure 
 is wanting, a rock of similar composition would be called 
 amphibolite or hornblende rock. 
 
 Serpentine is a dark-green or reddish-brown rock, of 
 compact texture and greasy feel. It is so soft as easily to 
 be scratched by a knife. The mineral serpentine of which 
 it is composed is probably, in all cases, a product of the 
 metamorphism of other minerals or rocks. It usually 
 occurs in irregular beds among metamorphic "schists. 
 
 The Igneous or Massive Crystalline Rocks. 
 Most important of these is granite, already alluded to un- 
 der gneiss. It is a compound of quartz, feldspar (mostly 
 orthoclase), and mica ; feldspar is usually the predominant 
 ingredient, of an impure white or reddish color, while 
 mica is the least prominent. The quartz varies from white 
 to smoky-brown in color, and may readily be distinguished 
 by its fracture, hardness, and luster. The texture of gran- 
 ite varies from very fine-grained to one made up of crys- 
 tals of considerable size, the crystals being interlocked, or 
 welded together at their surfaces, so as to form a mass of 
 great firmness. The mica in granite may be partially or 
 entirely replaced by hornblende, giving rise to a usually 
 darker-colored granite, called syenitic granite. Where the 
 quartz disappears from a granitic rock it is called minette 
 or mica trap ; where feldspar dies out we have greisen a 
 rock interesting only from its association with tin-ores ; 
 
DESCRIPTION OF ROCKS. 23 
 
 while the disappearance of mica gives rise to a rock called 
 aplite and pegmatite ; or, if of foliated structure, granulite. 
 
 Felsite is an intimate mixture of feldspar with some 
 quartz, of an exceedingly fine-grained i. e., aphanitic or 
 flinty texture, and of a variety of colors, from yellowish 
 to nearly black. It greatly resembles some quartz rocks, 
 from which it may be distinguished by its slightly inferior 
 hardness, its hardness being that of feldspar, and by the 
 fact that in thin splinters it can be fused like feldspar be- 
 fore the blow-pipe, while quartz can not. 
 
 Syenite is a granular crystalline rock, composed of 
 orthoclase and hornblende, the orthoclase predominating, 
 and, from its usually being of a reddish color, giving the 
 rock a prevailing red tint. Sometimes, however, feldspar 
 of a lighter color occurs, yielding grayish syenites. 
 
 Trachyte is a grayish, or sometimes reddish or brown- 
 ish, rough-textured compound, in which feldspar predomi- 
 nates, often showing glassy crystals, united with some 
 hornblende or augite and dark mica, while magnetite is 
 rarely absent. A trachytic rock of highly silicious charac- 
 ter, and often displaying quartz-granules, but rarely con- 
 taining hornblende, with a matrix usually very compact, 
 or even enamel-like, is called rhyolite or liparite. 
 
 Diorite is a granular, dark-green, tough rock, composed 
 of oligoclase feldspar and hornblende, with usually some 
 magnetite. It differs from syenite in its kind of feldspar, 
 in its usual range of color, and in being usually of finer 
 texture. 
 
 Dolerite is a granular rock of gray to black colors, 
 composed of labradorite feldspar and augite, with usually 
 some magnetite. When it is exceedingly fine-grained and 
 compact, it is called basalt. Basalt often contains grains 
 of a bottle-green mineral called chrysolite. When dolerite 
 contains chlorite, giving it a greenish color, it is often 
 called diabase. 
 
 The rocks described above are by far the most widely 
 
24 APPLIED GEOLOGY. 
 
 distributed, and therefore most commonly met with ; and 
 with them have been named a few of less frequent oc- 
 currence, as exhibiting interesting variations of composi- 
 tion or structure. 
 
 Key for Approximate Determination of Rocks.* 
 
 The following brief key for rock determination, based 
 on (i) texture, (2) hardness, and (3) structure and compo- 
 sition, may prove useful to the beginner : 
 
 1. Examine freshly broken, angular fragments with a lens. 
 
 A. Components not perceptible. See 2. 
 
 B. Components perceptible. See 4. 
 
 2. Test hardness of i A with a knife : 
 
 a. H i to 3^, easily scratched with a knife sedi- 
 
 mentary or decomposed : 
 
 a' Very soft, earthy aspect, plastic when wet, Clay, 
 
 b' Harder, in thin, irregular, fragile laminae, Shale. 
 
 c' Cleaving to thin firm plates, Slate. 
 
 d' H 3, effervescing strongly with cold acid, Limestone. 
 e' H 3 to 4, effervescing sluggishly with cold 
 
 acid, rapidly with hot, Magnesian Limestone. 
 
 f H 2.5 to 3.5, usually green, somewhat soapy 
 
 to the touch, not effervescing, Serpentine. 
 
 b. H 5 to 6, heavy, becomes black and magnetic by 
 
 heat: 
 
 g' Streak and powder yellowish brown, luster 
 
 earthy to silky, Limonite. 
 
 h' Streak and powder red, luster earthy to me- 
 tallic, may be perceptibly crystalline, Hematite. 
 
 c. i' Not scratched by knife, glassy luster, con- 
 
 choid fracture, Quartz Rock. 
 
 j' H 5 to 6, black or gray, often holds green 
 
 grains of olivine, Basalt. 
 
 k' H 6, fusible in thin splinters. See 3, or pos- 
 sibly, Felsite. 
 
 * The idea of this key was suggested by Geikie's excellent " Text- 
 Book of Geology." 
 
DESCRIPTION OF ROCKS. 2 $ 
 
 3. 2 k' may be glassy, when if 
 
 T Of uniform texture, dark color, translucent on 
 
 edges, of glassy aspect, Obsidian, 
 
 m' Of pitchy aspect, various colors, slighty trans- 
 lucent, Pitchstone. 
 n' Of rounded grains, of frequent concentric 
 
 structure, in enamel matrix, Perlite. 
 
 n" Of enamel-like matrix, often holding grains of 
 
 mineral, especially quartz, Rhyolite. 
 
 NOTE. The exact determination of hard, very fine-grained rocks 
 usually requires microscopic and chemical examination. 
 
 4. Test hardness of I B. 
 
 o' Soft, gray to white, crystalline to earthy, 
 
 heated yields vapor and whitens, Gypsum. 
 
 p' Easily scratched, effervesces readily with 
 
 acid, Limestone. 
 
 q' Slightly harder than p', effervesces sluggishly 
 
 with acid unless hot, Dolomite. 
 
 r' H about 4, brown, effervesces with hot HC1, 
 
 giving yellow solution, Siderite, etc. 
 
 s' Of hard, rounded grains, chiefly quartz, ce- 
 ment various, Sandstone. 
 
 t' Of hard, rounded, or angular pebbles, 
 
 Conglomerate or Breccia. 
 
 u' Of quartz-grains cemented by silica, fracture 
 
 usually glassy, Quartzite. 
 
 v' H 6, color and streak black, heavy, magnetic, Magnetite. 
 
 w' H variable, schistose, with glistening surface, 
 
 of mica and quartz, Mica Schist. 
 
 x' Soft, color white to light green, soapy feel, 
 
 schistose or massive, Talc. 
 
 y' Easily scratched, dark green, slightly soapy, 
 
 schistose, Chlorite Schist or Hydro-Mica Schist. 
 
 z' Hard, greenish black, rather heavy, schistose, 
 
 chiefly hornblende, Hornblende Schist. 
 
 a" Hard, chiefly quartz, but schistose from a lit- 
 tle mica, Quartz Schist. 
 
 b" Scratched with difficulty, of interlocked or 
 welded crystals. See 5. 
 
26 APPLIED GEOLOGY. 
 
 5. Rocks of 4 b" alternate with other crystalline rocks 
 
 or show some foliated arrangement of their 
 crystalline constituents metamorphic. See 6. 
 Rocks of 4 b" do not alternate, are massive, send 
 branches into other rocks igneous. See 7. 
 
 6. Composed of the following minerals, more or less 
 
 distinctly foliated : 
 
 c" Quartz, feldspar, and some mica, Gneiss, 
 
 d" Quartz, feldspar, and hornblende (mica), 
 
 Syenitic or Hornblenclic Gneiss. 
 
 e" Quartz, feldspar, and chlorite or talc, Protogine Gneiss, 
 f" Quartz and orthoclase, often garnets, Granulite. 
 
 7. Rocks eruptive or intrusive, composed of 
 
 g" Quartz, feldspar, and mica, Granite, 
 
 h" Quartz, feldspar, and hornblende (mica), 
 
 Syenitic Granite. 
 
 i" Orthoclase and hornblende, often red, Syenite, 
 
 j" Oligoclase and hornblende, dark green or 
 
 black, Diorite. 
 
 k" Labradorite and augite, gray to black, Dolerite. 
 
 1" Feldspar base and clear crystals of orthoclase, 
 
 rough to the feel, Trachyte. 
 
 m" Aphanitic base holding crystals of feldspar or 
 
 quartz, Porphyry or Quartz Porphyry. 
 
 This key is intended only as a convenient aid to the 
 student in finding the probable variety of rock with which 
 he has to deal. His specimens should with this aid be 
 carefully compared with descriptions in works on geology 
 or lithology, and much critical study and comparison will 
 be necessary to avoid the probability of error. It is well 
 to be slow and painstaking at first, that one may be rapid 
 later. 
 
 For a wider study of rocks, the student is referred to 
 the following works : Von Cotta, " Rocks Classified and 
 Described," translated by Lawrence ; Geikie, " Text-Book 
 of Geology," Book II ; Dana, " Manual of Mineralogy and 
 Lithology." 
 
CHAPTER III. 
 
 ARRANGEMENT OF ROCK-MASSES. 
 
 ROCK-MASSES may be built up into the structure of the 
 earth's crust in any one of three ways : First, and far the 
 most widely diffused, as stratified rocks, or those occurring 
 in nearly parallel beds of various thickness ; second, as great 
 unstratified masses like granite, exhibiting no signs of true 
 bedded structure ; and, third, as included or vein-form 
 sheets, or masses of rock-material, differing from the inclos- 
 ing rocks in composition or in structure, or in both respects, 
 and occupying what were once apparently open fissures or 
 cavities in these rocks. 
 
 Stratified Rocks. The most striking character that 
 marks the stratified rocks, and that from which they de- 
 rive their name, is their occurrence in parallel sheets or 
 strata piled one upon another to form masses often of vast 
 thickness. These beds, when not metamorphic, usually 
 contain indubitable evidences that they have been gradu- 
 ally and successively deposited in water, and mostly in the 
 waters of the sea, in a manner exactly analogous to that in 
 which beds of mud, sand, gravel, peat, and limestone are 
 being accumulated at the present day. Most convincing 
 of these evidences of formation in water is the frequent 
 occurrence in the bedded rocks, at the most various 
 depths, of the remains of animals, most commonly marine, 
 and occasionally of plants, which often retain their struct- 
 ural characters in a high degree of perfection. Such 
 
28 APPLIED GEOLOGY. 
 
 traces of the former plants and animals of the globe are 
 called fossils ; and they not only give us some glimpses of 
 the life-history of the usually remote periods during which 
 the rock-materials were accumulated, but they also furnish 
 valuable evidence of the conditions under which they 
 were formed, whether in marshes, or in water, marine, 
 brackish or fresh, clear or turbid, and at greater or less 
 depths. It is obvious that of the beds thus superimposed 
 on each other the lower will have been the earlier formed, 
 while the overlying beds will be successively younger. 
 Thus in stratified rocks whose normal position is obvious, 
 or can by any means be made out, superposition is re- 
 garded as a reliable evidence of relative age. The sev- 
 eral beds in any series of stratified rocks are usually sep- 
 arable from each other with little difficulty at their plane 
 of junction, probably indicating that the lower bed had 
 been somewhat consolidated before the materials of the 
 succeeding one were deposited. A character peculiar to 
 stratified rocks, because it results from successive depo- 
 sition, is lamination, as already defined. It belongs more 
 especially to the finer-grained sediments, like shales, fine- 
 grained and somewhat argillaceous sandstones, and to 
 some argillaceous limestones. Commonly the planes of 
 lamination are parallel, or nearly so, tc> those of bedding ; 
 but in some rocks, especially sandstones, they may be di- 
 agonal to the bedding, giving rise to what is called false 
 bedding or current bedding. Usually, but not invariably, 
 rocks split more easily on the lamination than in other di- 
 rections ; and such rocks, when used in structures, should 
 always be laid with their edges to the weather, as they 
 will be more durable in that position. 
 
 When a stratified rock becomes metamorphic, lamina- 
 tion gives place to foliation, the planes of mineral ar- 
 rangement, in most cases, probably following the original 
 planes of deposition ; or slaty cleavage takes the place of 
 the original tendency to split on lamination planes, while 
 
ARRANGEMENT OF ROCK-MASSES. 
 
 29 
 
 the laminae may still frequently be displayed in bands of 
 different shades of color. 
 
 Position of Strata and Definition of Terms. 
 The original position of the beds of stratified rocks must 
 have been nearly horizontal ; but, as the result of the 
 action of forces, for a discussion of which the student 
 should refer to general treatises on geology, the strata in 
 all metamorphic regions, and in many localities where the 
 rocks have undergone no noteworthy transformation, are 
 no longer horizontal, but are bent, doubled, and crumpled 
 on the large scale, and often broken, with the fractured 
 ends slipped past each other. The disturbances of strata, 
 and the changes to which they have been subjected, give 
 rise to the use of several terms, the meaning of which it is 
 important to understand. 
 
 The dip of strata is the amount of their departure from 
 a horizontal plane. 
 
 Where the dip is considerable, it is conveniently meas- 
 ured by means of an instrument called a clinometer, a 
 convenient form of which is that of a foot-rule, two inches 
 wide, folding to six inches, in one face of which is hung 
 a delicate pendulum, swinging on the center of a graduated 
 semicircle. (Fig. i.) 
 
 This instrument held before the eye, and its lower 
 
 FIG. i. 
 
 edge made to agree in direction with the slope of the in- 
 clined rocks or, better, set on its edge on a slip of board 
 laid upon the rocks and shifted carefully about until the 
 pendulum shows the greatest possible inclination will give 
 the dip of the strata with a good degree of accuracy. 
 
30 APPLIED GEOLOGY. 
 
 Where, however, the dip of the rocks is slight, as in much 
 of New York, in western Pennsylvania, and in several 
 Western States, it is found by ascertaining the height of 
 some persistent stratum above a fixed plane like the sea- 
 level, at several points where it appears in natural ex- 
 posures, or is revealed in borings or excavations. The 
 mutual distances of these points being found, the dip per 
 mile and the direction of the dip can be ascertained. The 
 amount and direction of dip are points of great practical 
 as well as scientific importance, and should be carefully 
 observed. 
 
 The strike of rocks is a direction at right angles with 
 their dip, so that when the second is given the first may 
 be known. For example : the dip of the rocks in a large 
 part of New York is south, inclining a little west. Hence, 
 the strike or the direction in which the rocks range across 
 the State is nearly west ; and it would be the same if the 
 dip were in an exactly opposite direction, or to the north. 
 
 A monoclinal fold is one in which the strata dip in 
 but a single direction. A common case in our Western 
 Territories is that which is sketched in the following dia- 
 gram, where horizontal strata are sharply folded up into a 
 somewhat steep ridge, and then resume their original nearly 
 horizontal position : 
 
 An anticlinal fold is one in which the strata dip away 
 from an axis, forming an arch, as in Fig. 3, where a repre- 
 sents the axis of the fold from which the strata dip each 
 way. A common occurrence with such folds is that the 
 strata are broken at the axis, when the agencies of wear 
 either plane down the fold to a level, its presence being 
 
ARRANGEMENT OF ROCK-MASSES. 31 
 
 indicated only by the opposite dip of the strata ; or, where 
 hard beds occupied the surface, the strata may be cut out 
 
 FIG. 3. Anticlinal. 
 
 along the axis, as indicated by the dotted line in Fig. 3, 
 leaving two more or less marked ridges. 
 
 A synclinal fold is where the strata dip from opposite 
 directions toward an axis, forming a trough, as in Fig. 4. 
 
 FIG. 4. Synclinal. 
 
 In greatly disturbed regions, these folds are often so 
 thickly set as to give the strata a crumpled appearance, 
 visible even in hand specimens. 
 
 Frequently, also, not only in folded regions, but also 
 in those in which the strata retain a nearly horizontal po- 
 sition, the strata are found to have been broken across, 
 and the beds on one side of the break to have been 
 dropped below those on the other, so that the two halves 
 of the same bed no longer occupy the same plane. Such 
 an occurrence is called a fault, and the faulted beds are 
 said to be thrown. Thus we speak of the downthrow and 
 the upthrow. The plane of fracture, though sometimes 
 
32 APPLIED GEOLOGY. 
 
 vertical, is usually inclined more or less from the vertical. 
 The amount of this inclination from the vertical is called 
 the hade of the fault. Vertical faults, therefore, have no 
 hade. In the great majority of cases, " faults hade in the 
 direction of the downthrow," so that the upper surface of 
 the beds that have slid down makes an acute angle with 
 the plane of fault. (See Fig. 5, in which a and b are 
 planes of fault, of which b has no hade, while a h hades at 
 
 FIG. 5. Faults. 
 
 an angle of 50 with the vertical.) The beds c d e f have 
 it may be seen, slid downward along the planes of fault 
 so that the upper surface of the downthrown beds g makes 
 an acute angle with the plane a h. Such a fault is called 
 a normal fault, while the much less frequent case in which 
 the downthrow side makes an obtuse angle with the plane 
 of fault is called a reverse fault. Hence, in mining faulted 
 beds, like those of coal or iron, in the absence of other 
 indications, the continuation of the bed is to be sought 
 down the fault-plane when it slopes from the workings, 
 and up it when it slopes toward the workings, as may be 
 seen from the left side of Fig. 5. The walls of fault-fis- 
 sures, when they consist of firm rocks, are often smoothed 
 or glazed, and striated in the direction of movement. Such 
 glazed surfaces are called slickensides. 
 
 Where strata are laid open to observation by the re- 
 moval of loose materials, the point of appearance is called 
 their outcrop or basset. Frequent places of outcrop 
 are along the shores of bodies of water, or in the banks 
 of deep-cut streams, or on the eroded sides and summits 
 of hills and mountains. 
 
ARRANGEMENT OF ROCK-MASSES. 
 
 33 
 
 Conformable strata are those which succeed each 
 other in the regular and parallel order of superposition. 
 
 Unconformable strata are those in which (i) the 
 overlying beds rest against the upturned and eroded sur- 
 face of the lower beds, not agreeing with them in dip, as 
 
 FIG. 6. Unconformity by Upthrow. 
 
 in Fig. 6 ; and (2) the overlying beds rest upon the much- 
 eroded surface of the underlying ones, agreeing with them 
 in dip, as in Fig. 7. 
 
 In either case, " the base of the one set of beds rests in 
 
 FIG. 7. Unconformity by Erosion. 
 
 different places on different parts of the other set of beds." 
 The first kind of unconformability is the more commonly 
 observed, and doubtless always includes what is essential 
 in the second, viz., the erosion or denudation of the lower 
 beds, before the deposition of the upper ones. Uncon- 
 formability testifies unmistakably to a considerable lapse of 
 time, during which important physical changes occurred, 
 including notable changes of level, as intervening between 
 the periods of deposition of the two sets of beds. 
 
 The term denudation is applied to the waste and 
 
34 
 
 APPLIED GEOLOGY. 
 
 wear df/#cks by weathering and by the agencies of water 
 atmosphere. (See Fig. 3 for illustration.) Denu- 
 dation is a phenomenon which is going on constantly be- 
 fore our eyes, not more obviously in the tremendous rend- 
 ing and grinding action of the waves than in the silent 
 activity of rivers, brooks, and rills, whose turbidity testifies 
 that they are tearing down and carrying away to valley or 
 ocean the materials of the uplands. The amount of denu- 
 dation in all elevated parts of the earth is enormous, and 
 to it is due almost wholly the present aspect of the land- 
 surface of the globe. 
 
 Unstratified Rocks. The structure of these rocks 
 is massive, and, as their name implies, they show no 
 signs of bedding or of successive accumulation, their only 
 divisional planes, where they occur, being of a jointed 
 character. Though it can hardly be doubted that unstrati- 
 fied rocks form the foundation on which all stratified 
 rocks rest, yet they are of far less frequent occurrence as 
 surface appearances than those of the stratified series ; 
 and it is probable that our opportunities for knowing them 
 are due in many cases to great uplifts and enormous denu- 
 dations. They owe their origin in all cases, perhaps, to 
 igneous agencies or to a metamorphism pushed to such an 
 extreme as to become essentially igneous. They occur, 
 sometimes as great bosses, like granite, surrounded by 
 other rocks into which they frequently send out arms ; 
 sometimes as the central portions of great mountain-chains, 
 as in parts of the Sierra Nevadas and the Alps ; some- 
 times as vast sheets of enormous thickness, as in portions 
 of our Western plains ; sometimes as great cake - like 
 masses, called laccolites, thrust into the midst of stratified 
 rocks and bulging them up into dome-like eminences, as 
 in the Henry Mountains of Utah ; and sometimes as great 
 interbedded sheets overlaid by beds deposited apparently 
 since they were poured out as lavas, as in the so-called 
 melaphyre rocks of northern Michigan, whose amygda- 
 
ARRANGEMENT OF ROCK-MASS, 
 
 loidal portions furnish in some cases rich 
 native copper. 
 
 Included or Vein-like Rocks. The masses here 
 called included fill what, in the great majority of cases if 
 not in all, appear once to have been open fissures or cavi- 
 ties in the inclosing rocks. In some cases the filling mate- 
 rials have evidently been introduced in a state of igneous 
 fusion, such included masses being called dikes. In 
 other cases the fissure or cavity has apparently been filled 
 from solution in water or by sublimation, such inclusions, 
 where they fill fissures of greater or less extent, being 
 called veins, and, where they fill irregular cavities, being 
 called by the German name Stbcke, or stocks. 
 
 Dikes are usually nearly vertical in position, and have 
 a more regular and wall-like form than veins, whence 
 the name dike, signifying a wall. Indeed, irregular and 
 branching fissures filled with material apparently injected 
 in a plastic state are usually called veins rather than dikes, 
 as in the case of granite veins. The fissures filled by 
 dikes not unfrequently follow pretty closely for consider- 
 able distances the bedding planes of stratified rocks, giv- 
 ing to such dikes the appearance of beds. The rocks 
 which form the walls of dikes have usually been metamor- 
 phosed to varying distances by the heat, common changes 
 being consolidation, baking, and crystallization. The ma- 
 terial of dikes is frequently fissured by joints, which pass 
 often into a columnar structure, the columns being per- 
 pendicular to the walls. Dolerite with its varieties, ba- 
 salt and diabase, is a common dike-forming rock, though 
 some other varieties of igneous rocks are occasionally 
 found forming dikes. 
 
 Some veins, usually in granite, gneiss, or the crystal- 
 line schists, are filled with material similar to that of the 
 surrounding rock, though in a somewhat different crystal- 
 line state, often coarser ; and their composing minerals 
 were apparently separated from the inclosing rock to fill 
 
36 APPLIED GEOLOGY. 
 
 rents of small extent during the process of consolidation. 
 Such are called veins of segregation. 
 
 True veins, called frequently mineral veins, fill what 
 have once been open fissures of variable extent, both ver- 
 tically and horizontally, some veins cutting the rocks to 
 unknown depths, while others are quite shallow ; some be- 
 ing traceable for miles, while others die out in a few rods. 
 The materials with which they are filled usually differ 
 notably from the inclosing or country rock. iThey are 
 usually of a crystalline granular texture, though often 
 earthy from decomposition or other causes, and have often 
 a banded structure of different minerals arranged parallel 
 to the walls. They are frequently the repositories of valu- 
 able metallic ores, and hence they, as also stocks, will be 
 more fully discussed in a subsequent chapter under the 
 head of ore deposits. 
 
 Relative Age of Rocks. Probably the most fre- 
 quent question asked about rocks by persons little versed 
 in geological science is with regard to the approximate age 
 of certain strata, the marks of whose great antiquity have 
 been so obvious as to impress even the casual observer. 
 To this question it is not probable that any very satisfac- 
 tory answer can ever be given. It can only be said, in a 
 vague and general way, that the time embraced in the 
 events to which geology testifies is very long even to those 
 computations which would make it briefest. The relative 
 age, however, of the stratified rocks can be made out 
 with a good degree of certainty, not only for limited 
 districts, but for all that portion of the globe which 
 has been geologically explored ; and the various strata 
 have been arranged in a series which expresses ap- 
 proximately the order of their appearance in time. This 
 series has also been separated into larger and smaller 
 subdivisions or groups, which, while based on certain 
 interesting facts in their life-history or lithological con- 
 stitution, are of vital importance as affording a means 
 
ARRANGEMENT OF ROCK-MASSES. 37 
 
 of ready reference for both scientific and economic pur- 
 poses. 
 
 These groups of strata, which, if piled upon one an- 
 other successively, would make a stupendous mountain- 
 mass more than a hundred thousand feet in height, are 
 nowhere found forming a complete and connected series ; 
 but rather, certain portions are found in one region, while 
 other parts of the series must be studied in other and per- 
 haps distant localities. The reasons for this fragmentary 
 distribution may be briefly stated. They are (i) that 
 during the vast periods of time embraced in geological 
 history, the regions where rock - materials might be de- 
 posited have been slowly but constantly changing, by rea- 
 son of fluctuations of level which have caused great and 
 often repeated changes in the distribution of land and 
 water. Thus, the areas where rocks were laid down have 
 been repeatedly shifted from age to age, regions which had 
 taken no part in rock-making, because they were dry land 
 while certain series of rocks were deposited, subsequently 
 changing places with former water areas, and becoming 
 themselves the theatres of deposition. 
 
 To this may be added (2) the probability that many 
 strata, once deposited in certain regions, have been en- 
 tirely or partially removed by denudation in the course of 
 subsequent changes. 
 
 The means by which an orderly arrangement of the 
 members of a series so essentially fragmentary into a con- 
 nected system has been effected are chiefly the following : 
 
 i. Superposition. From what has already been said 
 about the mode of formation of stratified rocks, it is ob- 
 vious that the lowermost strata will have been first formed, 
 while the overlying ones must be successively more recent. 
 Hence, in any region where the natural succession of the 
 strata has not been too much confused by uplifts and 
 faults with subsequent denudation, the observed order of 
 
 superposition of the strata, as studied in tolerably con- 
 8 
 
38 APPLIED GEOLOGY. 
 
 tinuous outcrops, will give their relative age ; and, if then 
 some well-marked bed or stratum of this region can be 
 positively recognized in some other locality where addi- 
 tional strata occur, the two series may be connected in 
 the order of time, and ultimately the same mode of obser- 
 vation may be extended to include other and far more 
 remote areas. Thus the observed order of superposition 
 is not only a very valuable but wholly indispensable 
 means of studying the relative age of strata. But it fre- 
 quently happens that over wide spaces the succession of 
 the strata can not be directly observed because they are 
 covered by surface accumulations, or separated by bodies 
 of water : how, then, shall we recognize strata already well 
 studied in certain localities, when we come upon them in 
 regions somewhat remote ? Or, again, from what is ap- 
 parently a completely continuous series of strata, whole 
 groups of beds may be wanting from the causes men- 
 tioned above, without leaving anything to mark their ab- 
 sence : how, then, shall we be able to detect this absence, 
 and to assign the strata that would make the series really 
 complete ? This recognition at distant localities of kin- 
 dred strata, that is, those having like positions in similar 
 series, this detection of groups missing from a seemingly 
 consistent series is accomplished by a second and highly 
 important means : 
 
 2. The Use of Fossils. Throughout a very large 
 portion of the time during which the stratified rocks have 
 been accumulating, it is certain that forms of life have ex- 
 isted on our globe ; and the fossil evidences of their exist- 
 ence have been preserved, to a very useful degree, in nearly 
 all stratified rocks which are not metamorphic. Now, the 
 various distinguishable stages in the great series of rocks, 
 arranged in the order of their relative age, are character- 
 ized by the prevalence of certain forms of life, species or 
 genera not found in other members of the series ; or by 
 certain groupings of forms which do not exist elsewhere 
 
ARRANGEMENT OF ROCK-MASSES. 
 
 39 
 
 in like relations ; so that by the careful comparative study 
 of the fossils of localities separated from each other more 
 or less widely, the rocks which contained them may be 
 placed in their proper relative place in the chronological 
 series. For figures and lists of the fossils which character- 
 ize the several members of the geological system, the stu- 
 dent will do well to refer to some one of the excellent 
 treatises on geology, like Dana's " Manual of Geology," 
 Geikie's " Text-Book of Geology," Lyell's " Elementary 
 Geology," or Le Conte's " Elements of Geology." Some 
 examples of their use may be profitable. A large and 
 peculiar family of crustaceans called Trilobites, because 
 the body is divided lengthwise by de- 
 pressions into three lobes (see Fig. 8), 
 while found somewhat abundantly in the 
 rocks below the coal-measures, has not 
 yet been seen in any higher rock ; and 
 some of its genera, and nearly all its 
 species, are limited in their range to 
 certain sets of rocks : hence the family 
 of Trilobites is characteristic of the 
 rocks from the coal-measures down- 
 ward ; and its species, and in some cases 
 genera, become distinguishing marks for 
 the groups of rocks to which they are confined. So the 
 Spirifer (see Fig. 9), an easily recognized genus of shells, 
 which is confined to the strata from 
 the Upper Silurian to the Lower 
 Jurassic (rock groups presently to 
 be mentioned), has well-marked 
 species which are confined to the 
 several groups of strata, and hence 
 are used as landmarks for these 
 
 groups, while the genus as a whole distinguishes all the 
 rocks within the limits named. 
 
 3. The lithological characters of strata, though in 
 
 FIG. 8. 
 
4 APPLIED GEOLOGY. 
 
 many cases they furnish very unreliable marks for recog- 
 nizing rocks, save within quite limited spaces, from the 
 fact that they do not remain constant, but frequently 
 change, so that within a comparatively short distance a 
 conglomerate may be seen to pass >into a sandstone and 
 then to shade off even into a shale, yet in some cases, 
 and especially among the older rocks, show such persist- 
 ency as to make them very convenient guides for the 
 rocks of certain districts. Thus, in central New York, a 
 band of limestone called the Tully, usually not more than 
 ten to fifteen feet thick, though occasionally rising to as 
 much as twenty-five or thirty, is persistent in character 
 over more than eighty miles from east to west, and fur- 
 nishes a most valuable guide to the relative age of the 
 rocks throughout its extent. So, likewise, in tracing coal- 
 beds from one valley to another, use is made of certain 
 somewhat persistent beds, usually of sandstone or lime- 
 stone, as &ry-rocks, within tolerably regular distances above 
 or below which the coal-beds are likely to be found. The 
 availability of these key-rocks is greatly increased if, in ad- 
 dition to pretty uniform lithological characters, they also 
 contain some well-marked distinguishing fossils ; but, in 
 any case, lithological characters, if carefully used within 
 limited areas, are of great use in giving guesses at truth, to 
 be afterward confirmed by other and more reliable evidence. 
 By the careful use of the three means just described, 
 the relative ages of the stratified rocks are made out. By 
 the use of characters derived from the last two sources, 
 but chiefly from the second, the entire series of strata is 
 also separated into greater and smaller groups, for con- 
 venience of reference, the larger divisions holding the 
 same relative position and bearing the same names over 
 the entire earth; while the smaller subdivisions, which 
 usually differ widely in details in regions very remote 
 from each other, are apt to receive in every country 
 special names of local significance, and are afterward 
 
ARRANGEMENT OF ROCK-MASSES. 41 
 
 paralleled with each other, as far as possible, by a careful 
 comparison of fossils. Thus the crystalline schists, which 
 underlie all the fossiliferous stratified rocks, are generally 
 termed Archaean ; the fossiliferous rocks which succeed 
 these, and which are characterized throughout by a pro- 
 fusion of invertebrate fossils, a few remains of fishes being 
 found only in the upper beds, are called Silurian, and 
 admit of a generally used division into Lower and Upper 
 Silurian ; the succeeding groups of strata, in which fishes 
 of strange aspect are the dominant though by no means 
 the most abundant forms of life, are called Devonian ; to 
 which succeeds the Carboniferous formation, characterized 
 by the abundance of its coal-beds, and by the prevalence 
 of land-plants belonging mostly to the highest cryptogams. 
 Overlying the Carboniferous are found in many places 
 great series of strata, which, with an abundance of other 
 fossils, are characterized by the remains of reptiles, often 
 of great size and uncouth forms. These rocks, termed 
 usually Mesozoic, are susceptible of a threefold divi- 
 sion, universally used, into Triassic, Jurassic, and Creta- 
 ceous periods. To the Mesozoic succeed the rocks called 
 Tertiary or Cainozoic, which are characterized by the 
 prevalence of mammals, forms of life which up to these 
 rocks are represented only by a few very rare fragments, 
 and in which the invertebrate remains have usually a 
 strong resemblance to, and often identity with, creatures 
 now living. Its widely recognized divisions are called 
 Eocene, Miocene, and Pliocene, Lying upon the Terti- 
 ary deposits, where these occur, are found the more recent 
 and usually unconsolidated surface materials, including 
 drift-clays and bowlders, beach and terrace deposits, and 
 other accumulations of kindred -character, containing in 
 some parts the remains of man or his works, and called 
 Post-Tertiary or Quaternary. 
 
 The whole series of formations, from the top of the 
 Archaean to the top of the Carboniferous, is usually called 
 
APPLIED GEOLOGY. 
 
 collectively the Palaeozoic i. e., the age of ancient life 
 because all the forms of life found in it resemble so re- 
 motely those now prevalent on the globe ; the term Meso- 
 zoic, applied to the succeeding rocks, signifying their 
 approximation in forms of life to the existing state of 
 things ; while the name Cainozoic (recent life), given to 
 the Tertiary strata, is significant of the resemblance of its 
 fossils to living species. 
 
 Subjoined is given, in tabulated form, the more com- 
 prehensive divisions just described, with the larger sub- 
 divisions, as recognized by American geologists : 
 
 Quaternary or Post-Tertiary, 
 
 Tertiary or Cainozoic, 
 
 Secondary or Mesozoic, 
 
 f Carboniferous, 
 
 Primary or 
 Palaeozoic, 
 
 Devonian, 
 
 Upper Silurian, 
 
 Lower Silurian, including 
 Cambrian or Primordial, 
 
 Archaean, 
 
 Recent or terrace, 
 
 Champlain, 
 
 Glacial. 
 
 Pliocene, 
 
 Miocene, 
 
 Eocene. 
 
 Cretaceous, 
 
 Jurassic, 
 
 Triassic. 
 
 Permian or Permo-car- 
 
 boniferous, 
 Coal-measures, 
 Sub - carboniferous or 
 
 Lower Carboniferous. 
 Catskill, 
 Chemung, 
 Hamilton, 
 Corniferous, 
 I Oriskany. 
 
 (Lower Helderberg, 
 Salina, 
 Niagara. 
 Hudson, 
 Trenton, 
 Canadian, 
 Primordial, Potsdam 
 
 most important. 
 Huron ian, 
 Lauren tian. 
 
ARRANGEMENT OF ROCK-MASSES. 
 
 43 
 
 Of a number of the divisions given, there are sub- 
 divisions of much local interest, for which, as well as for 
 the European subdivisions, the student can, if he desires, 
 consult the treatises mentioned on page 39. By the stu- 
 dent familiar with German, the elaborate tables of Euro- 
 pean strata given in Credner's " Elemente der Geologic " 
 can be consulted with advantage. 
 
CHAPTER IV. 
 
 ECONOMIC RELATIONS OF GEOLOGICAL STRUCTURE. 
 
 HAVING now briefly considered those portions of 
 structural geology which seem essential to the ready com- 
 prehension of what is to follow, let us consider how geo- 
 logical science may make men's practical endeavors more 
 effective. 
 
 Economic geology may be defined to be that de- 
 partment of science which treats of the earth's structure 
 and mineral products as they are related to the supply of 
 human wants. 
 
 The economic geologist considers structure as it con- 
 cerns the adaptability of rocks and strata for certain pur- 
 poses, or as it is related to the occurrence and accessibility 
 of valuable deposits. He regards rocks as in themselves 
 fitted for certain uses, or as the probable repositories of use- 
 ful materials. He is interested in the relative age of strata, 
 and the means by which it may be determined, because it 
 furnishes him an available guide to their possible desirable 
 contents. He aims at an accurate and extended knowl- 
 edge of those geological deposits which have practical 
 utility. Nay, more : these deposits bear to each other 
 practical and often very essential relations. Of these he 
 takes careful note for example, the proximity of metallic 
 ores to the fuels and fluxes necessary for their beneficia- 
 tion, or to the kindred ores with which they may profitably 
 be mixed. Moreover, useful materials are valuable or value- 
 
ECONOMIC ASPECTS OF STRUCTURE. 45 
 
 less, according to their relations to the currents of human 
 industry and to the means of profitable utilization. What 
 value has an excellent quarry-stone, remote from transpor- 
 tation and from the great centers of construction ? Of what 
 present worth is an ore of moderate richness, at a long dis- 
 tance from the means of smelting or of easy concentration ? 
 What avails a rich placer deposit, without an abundant 
 water-supply for its cheap separation ? To such consid- 
 erations, and others like these, little noted by the ordinary 
 geological observer, the economic geologist must be keenly 
 alive, for they are what constitute the relations of structure 
 and products to the supply of human wants. Nor are 
 these wants, as signified by demand, by any means con- 
 stant. The progress of discovery or invention may change 
 very greatly the economical estimate of a substance once 
 little regarded. The naphtha and Seneca oil of thirty 
 years ago are the petroleum of to-day. Iron pyrites has 
 become a substance of great commercial importance, since 
 its recent use as a source of sulphur in the manufacture 
 of sulphuric acid. The ores of molybdenum and tung- 
 sten, till lately regarded only as interesting minerals, are 
 now called to the attention of the United States geolo- 
 gists by their use as pigments ; while all deposits of nickel 
 have recently become of greatly increased interest since 
 the wide use of this metal in electro-plating. Hence it 
 is desirable that the economic geologist should always bear 
 in mind " that, much as may already have been utilized, 
 there are still many substances in the earth's crust which 
 can be turned to account in the increasing requirements 
 of modern civilization." (Page.) 
 
 Economic Relations of Geological Structure. 
 The economic bearings of geological structure are numer- 
 ous, and of the most obvious importance. Structure, for 
 example, conditions the relative accessibility of desirable 
 substances ; the facility with which they may be worked ; 
 the ease and consequent expense with which excavations 
 
46 APPLIED GEOLOGY. 
 
 and tunnels may be made, and their durability when fin- 
 ished ; the reliability of the foundations of important en- 
 gineering and architectural structures ; the accessibility, 
 the abundance, and the continued purity of deep-seated 
 water-supplies ; and not unfrequently the possibility of 
 effective drainage. 
 
 Accessibility. Among stratified rocks, it is obvious 
 that their dip must exert a paramount influence on the 
 accessibility of any particular bed from the surface. If 
 the dip is slight, the depth below the surface of a bed will 
 increase but slowly as we recede from the outcrop in the 
 direction of dip ; while, if the dip is considerable, the 
 depth, and consequently the difficulty of access, increases 
 rapidly. A dip of one degree carries the strata down 
 ninety-two feet in a mile. The following table shows the 
 descent for a surface-distance of one hundred rods for 
 dips of from one to twenty degrees, and for every five de- 
 grees thereafter up to forty. It will be obvious that when 
 we pass beyond the outcrop of a bed in the line of its as- 
 cent, this bed will disappear and give place to underlying 
 beds : 
 
 Dip i descent for 100 rods, 28.8 feet. 
 
 3 >> 86.5 
 
 4 II5-4 
 
 5 J 44-3 
 
 6 173 
 
 7 202.6 
 
 8 2 3 2 
 
 9 ,, 261.3 
 
 10 291 
 
 XI 3 2I -5 
 
 I2 35-7 
 
 13 38 1 
 
 14 
 
 44 2 
 
ECONOMIC ASPECTS OF STRUCTURE. 
 
 47 
 
 Dip 1 6 descent for 100 rods, 473 feet. 
 J 7 >, 54-5 
 
 18 536 
 
 J 9 ,, 568 
 
 20 600.5 
 
 2 5 769-4 >, 
 
 30 ,i 95 2 -7 
 
 35 ii55-4 
 
 40 ,, J 334-5 
 
 It may be seen from this table that even small dips 
 make an important difference in accessibility at some dis- 
 tance from the outcrop, while dips of 5 and upward make 
 necessary, before mining operations are begun, a careful es- 
 timate of the cost of sinking shafts, and the after perpetual 
 expense of hoisting to the surface the water and the min- 
 eral which is the object of search. In all cases, therefore, 
 where the dip of the rocks is known or can be ascertained, 
 it needs to be taken into careful consideration in judging 
 of the depth at which valuable deposits may be reached. 
 In making this estimate also it should be remembered that 
 the rate of deepening below a given plane is greatest di- 
 rectly down the dip, and diminishes each way from this 
 line. 
 
 Faults also affect the accessibility of deposits relatively 
 to our workings. They may bring the continuation of a 
 bed nearer to the surface or remove it farther from the 
 surface, or, bringing it within reach of denuding agencies, 
 they may have caused it to be entirely removed. In even 
 the most favorable cases, since they interrupt the continu- 
 ity *of beds, faults derange the underground approaches 
 and means of transportation and increase the expenses of 
 working. 
 
 Great uplifts with subsequent denudation have likewise 
 in many regions brought within easy reach deposits which 
 must otherwise have remained utterly inaccessible. In- 
 deed, it is reasonably certain that the great class of crys- 
 
48 APPLIED GEOLOGY. 
 
 talline rocks with their valuable stores of building and 
 ornamental stones, and the still more valuable veins of 
 metallic ores which many of them inclose, have by this 
 means alone been made accessible to man. In other cases 
 the agencies of denudation, by excavating deep valleys in 
 undisturbed and nearly horizontal strata, have, while sweep- 
 ing utterly away great masses of valuable deposits, made 
 the outcropping edges of the remainder easy of access 
 and of drainage by tunnels driven into the hill-sides where 
 they are found. Numerous examples of this kind may 
 be found in mining for coal and iron-ores. 
 
 Relations of Structure to Facility of Extrac- 
 tion. Useful substances, whether building-stones, min- 
 eral fuels, or ores, are extracted from their repositories 
 either by open workings called quarries or by underground 
 mining operations ; and the ease with which these pro- 
 cesses can be carried on, and the resulting materials re- 
 duced to merchantable dimensions, depends in an impor- 
 tant measure on structural characters. In many cases the 
 workings may be so arranged with reference to the dip of 
 the strata as to clear themselves of water or to collect it 
 where it can be most conveniently removed, while the 
 handling of the materials is facilitated by a descending 
 grade. The bedded and jointed structure of many rocks 
 greatly aids the operations of the quarryman, enabling 
 him, where there are two sets of joints at nearly right an- 
 gles, to extract, with little waste of material, tolerably regu- 
 lar blocks of a size limited by the distance apart of the 
 joints and the thickness of the beds. Where the bedding 
 or the jointed structure, one or both, is wanting, recourse 
 must be had to the laborious operations of channeling or 
 drilling, with subsequent wedging or blasting, in the last 
 case often with great waste of material. The jointed struct- 
 ure of coal, called the cleat or face, and the end, is of such 
 importance that the workings must agree with it in direc- 
 tion. Where the beds are very thin, or the joints very 
 
ECONOMIC ASPECTS OF STRUCTURE. 
 
 49 
 
 closely set, the rock may be unfitted for any useful pur- 
 pose, while the presence of a single system of joints at 
 suitable distances may adapt a thick-bedded or massive 
 rock for being extracted for large columns or for mono- 
 liths. The laminated or schistose structure of many rocks 
 is an important aid in reducing them to proper dimen- 
 sions. Availing himself of this, the workman, by repeated 
 blows along the edges, causes thick masses to split parallel 
 with the bedding, and thus with no great difficulty brings 
 them to the thickness desired. The presence of concre- 
 tions or of a concretionary tendency, as also of cross or 
 current bedding, should be carefully noted, as they meas- 
 urably or entirely unfit a rock for use. 
 
 Relations of Structure to Expense of Exca- 
 vation, Tunneling, etc. The ease and consequent ex- 
 pense with which excavations, tunnels, shafts, and other 
 engineering works of like character can be accomplished, 
 and their permanence when finished, will depend very 
 largely on the nature and structure of the rock formations 
 through which the works must be pushed ; and all esti- 
 mates of expense should be based on the best attainable 
 knowledge in these respects. The hardness of the rocks 
 that must probably be penetrated ; their firmness or ability 
 when cut through to sustain the pressure of the masses 
 above and around them without artificial support ; their 
 durability in sides and roof when exposed to the atmos- 
 phere and weather ; the position of beds, whether hori- 
 zontal or highly inclined ; and their succession* whether 
 tolerably uniform or in alternations of firm beds with 
 others that are friable or of ready disintegration; their 
 permeability^ whether close-grained and solid, or porous 
 and seamed with fissures and joints, so as to make them 
 ready water-ways these and other considerations of like 
 import are of vital interest in all undertakings of this 
 character, and they present questions which can be satis- 
 factorily answered only by a careful geological examina- 
 
50 APPLIED GEOLOGY. 
 
 tion. Beds of hard, firm rocks with few or no joints will 
 be difficult and expensive to penetrate ; but they will be 
 self-supporting throughout and durable when finished, 
 and in cuttings only a minimum of material needs to be 
 removed. The first cost, therefore, is likely to be the 
 only cost ; while incoherent strata of gravel and sand, 
 though easy of excavation, require support at every step 
 by expensive curbing or by arches of masonry, or, in cut- 
 tings, materials must be removed until the angle of rest is 
 attained, so that the cost in the two cases may eventually 
 prove not very unequal. Friable sandstones, fissile and 
 easily decomposed shales, and not unfrequently the cut 
 edges of highly inclined strata, will need proper support 
 in both sides and roof, while fissured and porous water- 
 bearing beds must have due provision made for carrying 
 away the superfluous water, or must be masked by imper- 
 vious walls. 
 
 The cutting of one of the most extensive tunnels in 
 this country passed through many vicissitudes, and was 
 ultimately completed only after years of delay, presum- 
 ably through insufficient knowledge on the part of its 
 projectors of the obstacles likely to be presented by the 
 region through which it had to be driven, and consequent 
 insufficient estimates of probable expense ; and the con- 
 tractors for driving a tunnel to supply one of our great 
 lake cities with water, meeting with an unsuspected water- 
 way in the tough clay through which they were cutting, 
 were forced to close the end of their workings by a strong 
 bulkhead, and make an expensive dttour to avoid the 
 obstacle thus unexpectedly presented, yet which careful 
 previous trials would probably have revealed. The his- 
 tory of many similar works would doubtless furnish addi- 
 tional illustrations of the importance of a knowledge of 
 geological structure to those engaged in engineering enter- 
 prises of the kind here considered. 
 
 Foundations of Engineering and Architectural 
 
ECONOMIC ASPECTS OF STRUCTURE. ^ 
 
 Works. It is evident that the stability of the founda- 
 tions of engineering and architectural structures must de- 
 pend entirely on their adaptation to the geological char- 
 acter of the underlying formations. If firm rock can be 
 reached at reasonable depths, the best possible foundation 
 is gained. Thick beds of tough and homogeneous clay 
 also afford good foundations. But, where a great depth of 
 loose, uncompacted materials is encountered, expensive 
 preparations must be made to insure the stability of heavy 
 structures. The great viaduct in Cleveland, constructed 
 at a cost of more than two million dollars, was built across 
 an alluvial flat, where immense sums had to be expended 
 in deep excavations, driving close-set piles, and building 
 up a substructure of grouting, before the piers of the 
 bridge could be commenced. Every considerable town 
 can furnish numerous examples, in the cracked and dis- 
 torted walls of buildings, not always large nor heavy, of 
 the need of using precautions proportioned to the native 
 instability of the substratum on which the structure must 
 rest. So, too, one occasionally sees important retaining 
 walls yielding to the easily foreseen thrust of alternating 
 beds of clay and quicksand, partly from insufficient at- 
 tention to the character of the beds to be sustained, and 
 partly from the lack of due provision for draining off the 
 water which, in heavy rains, heightens manifold the natu- 
 ral instability of such deposits. In structures intended to 
 hold or convey water, such as dams, reservoirs, and canals, 
 minute attention is needed to the character and structure 
 of the underlying beds. For such constructions, no sub- 
 stratum can be better than tough and compact clay, or 
 close-textured and massive rocks, nor could anything well 
 be worse than loose sands and gravel, or porous, fissured, 
 and jointed rocks. In the first case, little care is needed, 
 save to secure the requisite strength and thoroughness of 
 work ; while in the second no precaution can be too great 
 to remedy the innate defects of the foundation. Espe- 
 
52 APPLIED GEOLOGY. 
 
 cially is this true when high dams are to be built, in which 
 the pressure of a great column of water will heighten the 
 permeability of the substratum and exaggerate its every 
 defect, and where any defect unremedied is sure to lead 
 to terrible disasters. 
 
 Structure and Water-Supply. An abundant sup- 
 ply of wholesome water, free from risk of organic contami- 
 nation, is of vital importance to individuals and communi- 
 ties ; and it is a provision which the growth of population 
 and its concentration on limited areas render every day 
 more needful and more difficult. The usual sources of 
 supply for families and small communities, aside from cis- 
 terns filled from roofs, are wholly geological in their nature, 
 and depend for their character, their permanence, and their 
 safety, on the structure of the region in which they are found. 
 They are springs, wells dug or driven in drift or other sur- 
 face accumulations, and artesians bored through drift or 
 rock, often to very considerable depths, in which the water 
 either overflows at the surface, or rises within easy reach 
 of pumping apparatus. The term artesian is often con- 
 fined to wells of this class that overflow, though with no 
 very good reason ; for it will presently be seen that what 
 is really characteristic about wells of this kind is that they 
 derive their water from sources deeper seated than usual, 
 and that the origin of their supplies is not local, but more 
 or less remote. 
 
 Springs. These are sources of water arising from the 
 underground circulation of the water that penetrates the 
 earth from rain and snow. This water descends through 
 the loose and porous materials until it meets with an im- 
 pervious bed, usually of clay, along which it flows, until 
 it gushes forth in a valley, or on the eroded edge of some 
 hill. Such springs are liable to contamination from im- 
 purities on or near the surface into which their waters 
 first sink ; but, if the point of issuance is at a consider- 
 able distance, the impurities are likely to be removed, 
 
ECONOMIC ASPECTS OF STRUCTURE. 
 
 53 
 
 largely through the chemical agen- 
 cy of the air circulating in the per- 
 meable beds. 
 
 In Fig. 10, a and b are springs, 
 represented as issuing on the side 
 and at the base of the hill, at the 
 junction of the sand and gravel 
 beds i and 2 with the impenetra- 
 ble clay-beds 4 and 5. The por- 
 ous bed 3 is also a water-way, but 
 does not produce a spring because 
 the valley c is not eroded deep 
 enough to intersect it. The water 
 issuing at a is liable to contami- 
 nation from any sources of impur- 
 ities found between a and 4, and 
 that at b from the area between 4 
 and 5 ; but the latter, having a 
 greater distance to flow, would be 
 surer to be freed from organic con- 
 taminations by the action of the 
 air circulating in its bed. Both 
 will be likely to take into solution 
 portions of any soluble minerals, 
 like lime or gypsum, which they 
 may meet with in the beds through 
 which they percolate ; and, if such 
 minerals occur in any considerable 
 amount, the water of the springs 
 will be hard ; but, if little or no 
 soluble minerals are met with, it 
 will be soft the terms hard and 
 soft, applied to water, being used 
 to describe the extent to which they 
 are charged with or are free from 
 dissolved minerals, with certain 
 
54 APPLIED GEOLOGY. 
 
 other properties dependent on this. The abundance and 
 permanence of the flow of such springs will depend on (i) 
 the thickness of their porous beds, (2) the freedom of 
 percolation through these beds, dependent on their texture, 
 (3) the extent of the gathering ground from which their 
 supplies are derived, and (4) the amount of rainfall of the 
 district. 
 
 Springs are occasionally met with, like those at Union 
 Springs, New York, and the " Big Springs," so abundant in 
 northern Alabama, one of which supplies Huntsville with 
 water, which issue apparently from the mouths of caverns 
 in the solid rock. Such springs, because of the great 
 depth of their source and the extent of their gathering 
 ground, are apt to be of very considerable volume and of 
 great permanence. Also fissured rocks, such as jointed 
 limestones, resting on impermeable strata, cause lines of 
 springs or of wet ground on the sides of hills where they 
 outcrop in the direction of their dip. 
 
 Another class of springs is found in many regions, ris- 
 ing in strata of moderate dip, along lines of fault or on 
 open joints cutting down to porous, water-bearing strata. 
 They are often very copious, and are usually both durable 
 and of reliable purity. They are indeed a kind of natural 
 artesians. 
 
 In Fig. n, D represents a spring rising along the plane 
 of fault, D C, and deriving its waters from the porous sand- 
 stones 2 and 4, which are inclosed above and below by 
 the impervious strata i, 3, 5, while B represents a spring 
 rising along a jointing plane which penetrates to the porous 
 bed 2. The broken ends of the water-bearing beds, by 
 reason of the downthrow on the right of the faulting plane, 
 have been brought opposite to strata not easily penetrated 
 on the left, and hence the water with which they are satu- 
 rated rises along the fault or joint from hydrostatic press- 
 ure. The water at B having but little head would merely 
 well out of the ground, while that at D would be likely to 
 
ECONOMIC ASPECTS OF STRUCTURE. 55 
 
 gush out with considerable force, 
 since its sources at 2 and 4 are 
 elevated above the point of out- 
 flow. The force and abundance 
 of outflow and the quality of the 
 water will depend on the same 
 circumstances as in the case of 
 artesians presently to be de- 
 scribed. 
 
 Wells. The chief source of 
 water-supply for domestic uses, 
 for isolated dwellings, and small 
 towns, where springs are not at 
 hand, is found in wells, open ex- 
 cavations of varying depths, 
 reaching either to some water- 
 bearing stratum confined by im- 
 pervious beds of clay, or to a 
 common water-level of the dis- 
 trict, below which all the beds 
 are saturated with water. The 
 depth of the well in either case 
 will naturally depend on the 
 depth below the surface of the 
 general water-level, or of the 
 special water-bearing stratum. 
 In many localities the unconsoli- 
 dated materials are of little 
 depth, and do not carry water, 
 so that the well-excavation, if it 
 succeed at all, must be pushed 
 through rock to some porous or 
 open-jointed water-bearing stra- 
 tum, the probability of reaching 
 which within reasonable depth 
 through means so expensive 
 
5 6 APPLIED GEOLOGY. 
 
 should be carefully considered beforehand, in the light 
 of the geological structure of the district as revealed in 
 ravines and quarries. Otherwise, a costly excavation may 
 end in complete failure, or be forced to depend on the 
 scanty and uncertain supplies oozing from the joints and 
 bedding-planes of close-grained rocks. In still other locali- 
 ties the loose surface materials rest immediately on fissured 
 or even cavernous rocks, through which their water, de- 
 scending unchecked by any impervious bed, are drained 
 away beyond the reach of wells. Such are the so-called 
 dry lots found especially in some limestone regions. 
 
 In any case, this widely used and convenient, if not 
 essential, source of water-supply is liable to become a 
 source of extreme danger to health, and even life, unless 
 more than usual care is used as regards its location, its 
 surroundings, and its construction, and unless the nature 
 and extent of the precautions that are used are based 
 upon the structure of the locality in which the excavation 
 is made. Where the excavation has passed through a con- 
 siderable thickness of impervious clay before reaching the 
 water-bearing beds, this is highly favorable to security; 
 but even here there is danger that the water may be con- 
 taminated by organic impurities leaching into it through 
 porous beds nearer the surface. This should be guarded 
 against by laying the retaining wall in hydraulic cement, 
 at least from the middle of the clay-seam to a sufficient 
 height above the mouth of the well to be secure from any 
 possible surface inflow; special care being taken where 
 the cemented wall begins in the clay to fill the entire space 
 around the wall with puddled clay or cement. If such 
 precautions are needed to insure safety from vitiation, 
 even in situations favored by the underground structure, 
 what shall be said of those wells excavated wholly through 
 sand and gravel down to the water-level, located, as they 
 too often are, in close proximity to house-drains, cess- 
 pools, and yards where animals are kept ? In such cases 
 
ECONOMIC ASPECTS OF STRUCTURE. 
 
 57 
 
 an outbreak of certain too well-known types of disease, is 
 usually only a question of time and of the power of hu- 
 man beings to resist poisonous influences. In all such 
 localities it would be safer to obtain water for household 
 purposes from well-constructed cisterns, into which the 
 water should be admitted through a filter easily construct- 
 ed with washed gravel, sand, and coarsely powdered char- 
 coal ; but, if a well is to be dug, it should be carefully 
 located as remote as possible from every probable source 
 of contamination ; and, because of the extra hazard, spe- 
 cial precautions should be used in the way of water-tight 
 walls to secure filtration through as wide a space as possi- 
 ble. In a situation like that here described, and such are 
 frequently to be found, even the degree of care here recom- 
 mended may not secure perfect immunity ; less than this 
 is sure to expose health and life to needless hazard. Nor 
 should it be forgotten that the apparent purity and clear- 
 ness of water afford no reliable criterion to its freedom 
 from dangerous contamination. The germs of disease 
 lurk unsuspected in many a bright and sparkling draught ; 
 and it is to use very moderate language to say that a very 
 considerable proportion of the ailments with which human 
 beings are afflicted arise from the tainted waters which 
 they drink. Indeed, in most long-settled, highly culti- 
 vated, and densely peopled districts, the soil becomes so 
 saturated with organic substances that no comparatively 
 shallow and open surface-wells can be considered safe. 
 
 Driven Wells. These wells, made by driving down 
 to a water-bearing bed an iron pipe shod with an iron 
 point, and pierced with holes around the bottom to admit 
 the water when it is reached, are practicable in unconsoli- 
 dated beds of sand, gravel, and clay, where there are no 
 bowlders to obstruct the driving ; and present some great 
 advantages over the usual open excavations, not only in 
 the ease and rapidity with which they may be made, but 
 in their freedom from risk of contamination from above, 
 
5 8 APPLIED GEOLOGY. 
 
 by the access of those surface-supplies of water which are 
 liable to be loaded with organic impurities. If they reach 
 to considerable depths, and in their descent pierce through 
 beds of tough clay, the water that they furnish is likely 
 to be excellent and reliable. In some of the southward- 
 reaching valleys of the lakes of central New York, deeply 
 filled as they are with stratified beds of unconsolidated ma- 
 terials, wells of this kind are often sunk to depths of from 
 sixty to more than a hundred feet ; and, in many cases, 
 the structure of the containing beds causes them to over- 
 flow at the surface, sometimes with considerable force, 
 constituting them veritable artesians. The water of these 
 wells, though sometimes very slightly sulphurous, is ex- 
 cellent. 
 
 Driven wells are feasible only under the conditions 
 mentioned in the first sentence of this paragraph ; but 
 there are large areas in the United States where such con- 
 ditions are presented, and where the driven well would 
 doubtless yield more wholesome water-supplies than those 
 furnished by the common surface excavations. The 
 chances that the water will overflow in any given case 
 will depend on the conditions presently to be mentioned 
 as conditioning the outflow from artesian borings. 
 
 Artesian Wells. These wells are essentially borings, 
 often of very great depth, which penetrate porous water- 
 bearing strata of moderate dip, confined both above and 
 below by other strata that are practically water-tight, the 
 entire series of water-bearing and impervious beds out- 
 cropping at its elevated edge, often many miles distant 
 from, and at a considerable elevation above, the points 
 where borings are made. In some cases the series of 
 water-bearing beds with their impervious cover form great 
 basin -shaped depressions, around which their elevated 
 edges outcrop on all sides, covered only by loose surface 
 accumulations ; but this kind of structure is by no means 
 essential to success, provided only that the confined waters 
 
ECONOMIC ASPECTS OF STRUCK 
 
 do not find easy egress at some point 
 down the dip of the strata, or provided 
 that the porous strata gradually change 
 their character below the boring, as is 
 frequently the case, and become prac- 
 tically water-tight. 
 
 In Fig. 1 2, which represents an ideal 
 section across a basin-formed depres- 
 sion, i, 2 is a water-bearing sandstone 
 confined between impervious strata of 
 shale, 4, 5, and 6, 7 ; and 3 is also a stra- 
 tum of porous sandstone, which, near 
 the center of the basin, thins out and 
 becomes merged in the shale ; while 
 the dotted line C, D, marks the level 
 of the opposite edges of the strata. It 
 is evident that water entering at the 
 outcropping edges i, 2, and 3 of the 
 porous beds, and filling them to satu- 
 ration, will, at any points, as A and B, 
 be subjected to a pressure equal to 
 that of a column of water reaching from 
 the dotted line to the top of the bed at 
 that point ; and that, if borings be ex- 
 tended to the water-bearing strata at 
 these points, the water will overflow 
 through them with a force proportioned 
 to the height of the head above the 
 mouth of the well. Should a boring 
 be made at D through both water-bear- 
 ing beds, the water in it would barely 
 reach the surface, because its mouth 
 would be on a level with the upper 
 edges of the beds, while at A the water 
 would be under a great head, and 
 would issue with much force. At 
 
60 APPLIED GEOLOGY. 
 
 point's between A and D, water would issue with a force 
 varying from that at A to a mere quiet outflow. From this 
 it may be seen that the possibility of obtaining water-sup- 
 plies by artesian borings is entirely dependent on the larger 
 geological structure of the region ; and that this needs to 
 be studied by the aid of the best attainable means, to 
 make success in such necessarily expensive undertakings 
 anything but a mere lucky chance. A brief review of the 
 conditions which insure success will render this more obvi- 
 ous. These are : 
 
 1. The existence of porous strata to serve as collectors, 
 conductors, and reservoirs of the water supplied by the 
 rainfall of the region. The most reliable water-bearing 
 beds are usually porous sandstones and conglomerates; 
 or, where the water is derived from deep accumulations 
 of uncemented materials, the same substances as sand and 
 gravel, the materials of ancient beaches. Artesians may 
 occasionally derive their supplies from fissured and cav- 
 ernous limestones ; but the chances of striking such water- 
 pockets are usually too slight to encourage explorations. 
 The thicker such beds are known to be in the region, and 
 the more open their texture, the better will be the chances 
 of success so far as this condition is concerned. 
 
 2. An equally essential condition of success is that the 
 water-bearing strata should be covered and underlaid by 
 continuous, impervious strata, confining the waters, and pre- 
 venting their dissipation by percolation either above or 
 below. The most reliable strata for this purpose are thick 
 masses of clay or shale ; though compact rocks of other 
 kinds, when free from fissures, like some limestones, may, 
 in certain regions, prove useful auxiliaries. The continuity 
 of impervious cover throughout the entire extent of the 
 beds, while they retain their character as water-ways, is a 
 point of great importance. 
 
 3. A third essential condition is, that the series of 
 strata should have a moderate dip from their outcrop to- 
 
ECONOMIC ASPECTS OF STRUCTURE. 6l 
 
 ward the point where the boring is proposed. A dip of 
 one degree, as has been said on a former page, will carry 
 the strata down about ninety-two feet in a mile, and one of 
 two degrees one hundred and eighty-five feet per mile. 
 Hence, any very considerable dip would, in no great dis- 
 tance from the outcrop, carry the strata beyond the reach 
 of practical exploration. The table given on pages 46 and 
 47 will, where the dip is known, aid in estimating approxi- 
 mately the depth to which the boring must be carried. The 
 inclination of the beds, as it may carry the outcrop of the 
 water-bearing strata above the level of the well-mouth, will 
 cause the water to overflow, or bring it within the reach 
 of pumps. A deduction, however, of several feet for a 
 distance of a number of miles, needs always to be made 
 from the height to which the water might theoretically be 
 expected to rise, on account of friction, and the resistance 
 which even the most porous beds oppose to the free flow 
 of water. 
 
 4. A consideration of much importance as regards the 
 abundance of the water-supply that may be looked for 
 from any porous beds, and one also which depends on the 
 amount of dip, is the breadth of absorbing surface which 
 these beds expose at their outcrop. The breadth of ex- 
 posure on a level surface of beds one hundred feet thick, 
 with a dip of one degree, would be a trifle more than a 
 mile, and for two degrees dip, about half a mile, the breadth 
 of surface exposure varying inversely as the dip. Hence 
 a moderate degree of dip will give a greater extent of 
 gathering-ground, or area of catchment, as it is often termed. 
 
 5. A fifth essential condition is, that there shall be no 
 obstructions to a free flow between the site of the boring 
 and the outcrop of the water-bearing beds. Such obstruc- 
 tions may be presented either by faults interrupting the 
 continuity of the strata and rendering possible springs of 
 the kind described in a preceding paragraph, or by dikes 
 
 of volcanic origin cutting across the strata, and rendering 
 4 
 
62 APPLIED GEOLOGY. 
 
 hopeless any flow below the obstruction, although success 
 may be achieved above. Fig. 13, in which A represents a 
 volcanic dike intersecting the water-bearing stratum B, 
 
 FIG. 13. Illustrating effect of an Obstruction. (After Page.) 
 
 will illustrate the effect of this kind of obstruction. In 
 this case, a boring between A and B, as at the point i, 
 would be likely to succeed, while one below A, as at 2, 
 would be hopeless. Such obstructions, in regions where 
 they are likely to occur, are usually not difficult to dis- 
 cover, and should be sufficient to deter men from under- 
 takings that are sure to be futile. 
 
 6. The last consideration to be mentioned, which is 
 meteorological rather than geological, has reference to the 
 usual amount of rainfall which may be depended on to 
 supply with water the gathering-ground of the porous 
 strata. In large areas west of the Mississippi, the average 
 rainfall is but small, yet it may be sufficient, under condi- 
 tions otherwise favorable, to make artesian borings fairly 
 successful ; but in all the region east of the Mississippi 
 the usual annual amount of rainfall is so abundant as to 
 make the question of sufficient supply, under proper con- 
 ditions, a reasonable certainty. A rainfall of thirty inches 
 per annum, which is well within the average rainfall of the 
 Eastern United States, would supply to the gathering-area 
 of a hundred-foot stratum, dipping at an angle of one de- 
 gree, 3,400 barrels of water a year for every foot in width 
 across the outcrop ; of which, if but one third is taken up 
 by the stratum, upward of 1,100 barrels per year will be 
 stored in every foot of its width. Hence the enormous 
 
ECONOMIC ASPECTS OF STRUCTURE. 63 
 
 flow from some noted artesians need excite no surprise. 
 An artesian well in the city of Louisville is said to yield 
 330,000 gallons every twenty-four hours from a depth of 
 2,086 feet ; one in the city of Paris, the Crenelle well, dis- 
 charges over half a million gallons per day, from a depth 
 of i, 806 feet ; while one, bored by a French engineer in 
 the Sahara Desert, is said to have yielded at the outset 
 1,000 gallons per minute, or about 1,500,000 gallons per 
 day. 
 
 The quality of the water yielded by such borings will 
 naturally depend on the character of the strata which form 
 the water-ways. In many cases it is very good ; but in oth- 
 ers the water derived from certain strata is found to be too 
 heavily charged with mineral substances to be adapted for 
 domestic use. It is usually difficult to predict the quality 
 of the water that is likely to be obtained from a given set 
 of beds ; but a single test is commonly sufficient for a 
 large district, for these deep-seated water-ways are apt to 
 underlie extensive regions with strata of a tolerably uni- 
 form composition. 
 
 From what has been said of the structural characters 
 which are essential conditions of the success of artesian 
 wells, it may easily be understood that they should not be 
 undertaken without a careful consideration of the geologi- 
 cal character of the region. Much indispensable informa- 
 tion may be gained with regard to the nature, thickness, 
 order of succession, and dip of the strata, and the direc- 
 tion of their inclination, by consulting the geological re- 
 ports and maps published by many of the States, and now 
 being issued by the United States for the Western States 
 and Territories. This, supplemented by such local obser- 
 vations as may be possible, will enable a careful person to 
 form a judgment as to the probabilities of success in any 
 given case. To enter upon such undertakings without 
 such care would be to incur a great and needless hazard. 
 
 The student desiring larger information on the impor- 
 
64 APPLIED GEOLOGY. 
 
 tant subject of water-supply and artesian wells is referred 
 to the " Reports of the Geological Survey of New Jersey" 
 for 1876, 1882, and 1884, the last two of which are espe- 
 cially valuable ; and to the first volume of the " Geologi- 
 cal Survey of Wisconsin" (i873~'79), P- 689, from which 
 Fig. 12 was copied: the second volume of the same re- 
 port, pp. 149-171, has several interesting sections, show- 
 ing the conditions under which artesian borings have suc- 
 ceeded in that State. Also the second "Report of the 
 Geological Survey of Arkansas," pp. 52-67, has much of 
 interest on this same topic ; and notices of wells and bor- 
 ings may be found in many places in the " Final Reports 
 of the Ohio Geological Survey." 
 
 Structure and Drainage. The matter of effective 
 drainage, so important for both sanitary and agricultural 
 purposes, has also its geological aspects, though these may 
 not in the majority of cases be the chief ones. The neces- 
 sity for drainage, in not a few cases, arises from causes 
 purely geological, and in many of these the evil may be 
 remedied by means suggested by a knowledge of the geo- 
 logical structure. Fields rendered wet and cold by an 
 impervious hard-pan may be found capable of ameliora- 
 tion by the mere use of the subsoil-plow, breaking through 
 a thin crust to porous beds below. House-drainage on 
 clay sites may be found practicable by sinking cess-pools 
 to beds of sand and gravel beneath, in which case it is 
 well to remember that the water-supply derived from 
 neighboring wells will naturally be endangered. Districts 
 may be rendered swampy and malarious by impervious 
 strata at no great depth below the surface, where the to- 
 pography of the region is not such as to offer outlets for 
 drains. In some instances of this kind effectual relief has 
 been found in the existence of deeper-seated porous or fis- 
 sured strata, wells sunk to which have furnished the requi- 
 site outlets for drains. Still other districts have been made 
 pestilent marshes by the presence of outcrops of rock or 
 
ECONOMIC ASPECTS OF STRUCTURE. 65 
 
 tough clay obstructing the natural drainage by streams, 
 where the removal of such obstacles might reclaim to fer- 
 tility large tracts of land, with immediate improvement of 
 the health of the surrounding region. A work of this kind 
 has recently been completed in New Jersey, while others 
 are suggested all justly regarded as legitimately belong- 
 ing to the geological survey of the State. (See " Geologi- 
 cal Reports of New Jersey " for 1869, 1870, 1877, and 1884.) 
 From what has been said in the preceding pages, it 
 will be apparent that questions of geological structure are 
 of deep concern to many prominent branches of human 
 industry ; and that in some matters of paramount im- 
 portance they touch the interests of nearly every family. 
 Other highly interesting relations of geological structure 
 will be more appropriately treated of hereafter, when we 
 come to consider the mode of occurrence of ore deposits. 
 
CHAPTER V. 
 
 MATERIALS OF CONSTRUCTION. 
 
 AMONG the many useful substances which the earth's 
 crust yields for the supply of human wants, the materials 
 of construction may justly claim a leading place, both on 
 account of their wide diffusion and their very general and 
 highly important uses in both architectural and engineer- 
 ing structures. These, leaving out of view for the present 
 iron, so largely used in modern structures, as rather an in- 
 direct than a direct geological contribution to the arts of 
 construction, are the various kinds of building and or- 
 namental stones, the brick clays, the mortars, and the 
 cements. 
 
 Building-Stones. The qualities which fit a building- 
 stone for its various uses may be conveniently considered 
 as belonging to two classes : (i) the necessary qualities, 
 which are obviously strength and durability ; and (2) the 
 desirable ones, which are facility of working and beauty, 
 whether of color, texture, or susceptibility of finish. Un- 
 less a rock has strength sufficient to endure any strains to 
 which it may probably be subjected, and such powers of 
 resistance to the usual agencies of decay as to enable it to 
 withstand them for long periods under the conditions in 
 which it is to be placed, it is wholly unfit for use in any 
 important structure. When these essential qualities are 
 assured, any properties which it may possess that will fa- 
 cilitate the work of reducing it to desirable forms will 
 
MATERIALS OF CONSTRUCTION. 67 
 
 diminish largely the expenses of construction, while what- 
 ever may make it pleasing to the eye will greatly enhance 
 its value for architectural purposes and for many orna- 
 mental uses. 
 
 I. Strength. Let us first consider those properties 
 on which the strength of stones depends. These are (i) 
 Closeness and compactness of texture, in virtue of which all 
 the grains of the stone being closely approximated touch 
 each other at many points, and thus mutually sustain each 
 other. Where such grains are large and loosely arranged, 
 the tendency of strain is to press them more closely to- 
 gether, and so to tear them loose from their consolidating 
 means, and when this is done the stone crumbles. (2) 
 Degree and means of consolidation. The more completely 
 the consolidating medium enwraps the particles of the 
 stone and fills all the spaces among them, the stronger it 
 will be. Some of the porous sandstones and earthy lime- 
 stones have evidently but a small proportion of cementing 
 material ; a thin film of clay or of clay and iron oxide, a 
 minute amount of silica or calcite at the points where the 
 grains touch each other, seems to be all that holds them 
 together ; and, in the case of some friable rocks, it would 
 seem that the particles are consolidated merely by the ad- 
 hesion of their faces. Such rocks are not likely to have 
 any great amount of strength, though some of them may 
 be used for purposes where no considerable strength is 
 required. Again, among the several consolidating mate- 
 rials, some like silica have greater inherent firmness than 
 others, and this they are likely to impart to the stones 
 which they cement. (3) Hardness and deavability of 
 grains. It is natural to expect, especially in the case of 
 crystalline rocks whose grains are held in place by the 
 interlocking or felting of the crystals, or by the welding 
 together of their faces, that the intrinsic hardness of the 
 grains and their susceptibility to cleavage will determine 
 in a great degree the strength of the rocks. Moreover, 
 
68 APPLIED GEOLOGY. 
 
 where cleavable minerals are largely present, the smaller 
 the size of the grains the more varied will be the direction 
 which the planes of cleavage will be likely to have within 
 a given compass, and the less the liability to yield to 
 crushing from this cause. (4) Direction of strain. The 
 great majority of bedded rocks offer a decidedly greater 
 resistance to crushing when the strain is exerted in a di- 
 rection at right angles to their planes of bedding ; and the 
 difference in the power of resistance to transverse or par- 
 allel strains is the greater the more distinctly laminated or 
 foliated the rock is. This fact affords a good reason why 
 such stones should always be laid on their natural bed. 
 (5) Elasticity. The results of experiments recently pub- 
 lished in the Geological Report of Indiana for 1881, indi- 
 cate that where weight is to be sustained by stones with 
 only the ends supported, as in the case of lintels and 
 beams, elasticity is an important consideration, and that 
 the elasticity of limestones is probably greater than that of 
 sandstones or even of granite. 
 
 The strength of building-stones is determined by crush- 
 ing cubes of a given size, usually of two inches edge, in a 
 press which indicates the amount of force applied, and 
 then reducing the result to terms of the force exerted on 
 a square inch of surface. A table of the strength of sev- 
 eral well-known building-stones, derived chiefly from the 
 determinations of General Gillmore, is given below, with 
 the percentage of water absorbed by each. Where the 
 absorption is given as " very little," as in the marbles and 
 granites, it is far below one per cent. The extremes of 
 strength in the stones tested by General Gillmore are : for 
 granites, from 9,500 pounds to 24,040 pounds ; for mar- 
 bles, from 7,612 pounds to 20,025 pounds ; for limestones, 
 from 3,450 pounds in a Caen freestone to 25,000 pounds ; 
 and for sandstones, from 4,250 pounds in a stone which 
 absorbed nearly seven per cent of water to 17,250 pounds 
 in No. ii of the following table. It will be seen from 
 
MATERIALS OF CONSTRUCTION. 
 
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; APPLIED GEOLOGY. 
 
 this table that, in the uncrystalline rocks, the limestones 
 and sandstones, there is an obvious relation between the 
 ultimate strength and the porosity as shown by amount of 
 water absorbed, the more porous being generally the weak- 
 est, and where deviations from this occur they are prob- 
 ably due to differences in degree and means of consolida- 
 tion. 
 
 2. Durability. The durability of building-stones de- 
 pends chiefly on certain assignable properties inherent in 
 the rock ; but it is affected also in a very considerable 
 degree by the conditions to which the stone is subjected. 
 These are now to be considered. The inherent qualities 
 which condition the durability of building-stones are the 
 following: (i) Sufficient consolidation. This quality of a 
 proper degree of firmness is a condition as well of dura- 
 bility as of strength. A slightly cemented stone, though 
 sometimes a favorite for certain uses, because of the ease 
 with which it may be worked, is peculiarly liable to mis- 
 haps in the somewhat rough usage to which stones in 
 structures are likely to be subjected in the course of years. 
 Accidental blows mar it or break fragments from its an- 
 gles and edges ; slight inequalities of pressure cause it to 
 crack and crumble ; and mere attrition, in places exposed 
 to the contact of men and animals, or even to the force 
 of wind-blown sand and dust, may slowly remove particles 
 from its surface. All this, too, even though its lack of 
 firm consolidation should not be correlated, as it is quite 
 sure to be, with the lack of a second requisite of durability 
 now to be mentioned. (2) Density \ or closeness of texture. 
 In a dense or compact stone, the cementing material, what- 
 ever it may be, is present in sufficient quantity to fill en- 
 tirely the space between its grains ; or, if it is of crystal- 
 line character, its crystals are so interlocked as to leave 
 no vacant spaces. Density is shown by the relative im- 
 perviousness of a stone to water, and from this arises its 
 importance as a condition of durability. Water is the 
 
MATERIALS OF CONSTRUCTION. ^ 
 
 chief medium through which the chemical agencies of de- 
 cay in rocks gain access to their pores ; and though proba- 
 bly no mineral substance is wholly impermeable to water, 
 still, if the texture of a building-stone is close, the change 
 from this cause will be very slow. The exclusion of water 
 from the interior of a rock is even more important where 
 the climate is liable to extreme cold, because of the violent 
 rending effects due to the expansion of water in freezing. 
 Water, in freezing, expands about nine per cent, with a 
 force sufficient to tear asunder the grains of a stone with- 
 in which it finds lodgment, and so causes its surface to 
 crumble, or its laminae to separate. Were it not that a 
 marked degree of porosity in a stone promotes also rapid 
 drying, and permits a considerable portion of the expan- 
 sive force to be expended otherwise than in pushing apart 
 the grains of the stone, the disaggregating effects arising 
 from this cause would doubtless be greater and more rapid 
 than they are ; but, in any case, a very porous stone 
 should have given undoubted proofs of durability before 
 being used in important structures, where it must be ex- 
 posed to the vicissitudes of a highly variable climate, like 
 that of the Northern United States. (3) Fineness and 
 uniformity in size of grains. It is undoubted that this 
 quality exerts a decided influence upon the durability of 
 building-stones ; due, probably, in a considerable degree, 
 to the weakening effect of large and irregular-sized grains 
 which offer unequal resistance to pressure at different 
 points ; but it can hardly be doubted that, in a rock com- 
 posed of two or more minerals, and exposed to great and 
 sudden changes of temperature, the inequalities in the ra- 
 tio of expansion of the constituent minerals must cause a 
 tendency to disaggregation, which will be heightened by an 
 increase in the size or in the inequality of the grains, and 
 which will be likely to be reduced to a minimum when the 
 grains are small and of uniform size. (4) Freedom from in- 
 jurious minerals. It is obvious that the presence in a build- 
 
72 APPLIED GEOLOGY. 
 
 ing-stone of any substance which is subject to decomposition 
 when exposed to the weather, will seriously affect its dura- 
 bility. Of such substances pyrites is one of the most dan- 
 gerous and yet widely diffused. Where it occurs lining 
 seams, or in nodules and crystals of some size, its decompo- 
 sition leaves unseemly holes and crevices, and gives the stone 
 a disagreeable stain. Where it is disseminated in minute, 
 almost imperceptible grains, it is often even more dele- 
 terious, since its ultimate decomposition produces a wide- 
 spread disaggregation of the stone. So, too, iron carbon- 
 ates and other protoxide compounds of iron are injurious 
 to the rocks, chiefly bluish or greenish gray sandstones, in 
 which they occur, through their tendency to pass to a higher 
 state of oxidation. Many reddish and brown sandstones 
 show little durability, and this is commonly attributed to 
 the iron oxide, which acts as a coloring agent and also as 
 a cement ; though it is quite possible that the lack of dura- 
 bility may be due quite as much to the superabundant 
 clayey matter which is apt to be also present in such 
 rocks. Clay, which when present uniformly disseminated 
 through a stone, to the amount of but a few hundredths 
 of the mass, as in many limestones and sandstones, is 
 rather beneficial than injurious, where it occurs in too 
 great abundance, forming seams in sandstones or knots and 
 irregular crevice-fillings in limestones, becomes a source 
 of serious injury, not only by its own ready disintegra- 
 tion under atmospheric agencies, but also, through the 
 tenacity with which it retains any water that it may take 
 up, offering occasion for the destructive action of frost on 
 the surrounding stone. Especially when a rock is some- 
 what porous, clayey matter, by its retentiveness for moist- 
 ure, may become very destructive in severe climates, as 
 has been suggested above in the case of brown sandstones. 
 But, besides those conditions affecting the durability 
 of building-stones which are inherent in them, there are 
 others which arise from the circumstances under which 
 
MATERIALS OF CONSTRUCTION. 73 
 
 they are used in structures : (i) The great majority of the 
 bedded rocks are most durable when laid upon their natu- 
 ral beds, that is, with their edges exposed. This is due, 
 not merely to the fact that most such stones are thus laid 
 in the position in which they are strongest, as has been 
 stated in a preceding paragraph, but also to this, that the 
 planes of bedding in rocks which are in any degree po- 
 rous are naturally also the planes of easiest penetration for 
 water. Hence, when they are set with the planes of bed- 
 ding vertical, water soaks into them most freely, and the 
 exposed surface is apt to show a disposition to crumble off 
 in grains, or even, where they are distinctly laminated, to 
 peel off in flakes, mostly from the effects of freezing ; 
 whereas, when laid with the edges exposed, they admit 
 water much less readily. (2) Stones, when used in con- 
 structions, are doubtless much less affected by the solvent 
 action of water than when they are in their native beds, 
 for they are then no longer exposed to its constant perme- 
 ation, and to the attacks of those chemical agents with 
 which water is apt to become charged in passing through 
 the soil. Yet it is believed, and apparently with good rea- 
 son, that in great cities, the rains and fogs, charged with the 
 sulphurous gases which the consumption of coal furnishes 
 to the atmosphere, become active agents of destruction to 
 some classes of building-stones, especially magnesian lime- 
 stones. To this is attributed the rapid deterioration of the 
 magnesian limestone used in constructing the new Houses 
 of Parliament in London, a material which had endured for 
 centuries in ancient structures, very little affected by the 
 pure air of the country. (3) Again, building-stones, while 
 conducting heat very slowly, are yet subject to expansion 
 and contraction from variations of temperature. Experi- 
 ments on the linear expansion of granite, limestone, and 
 sandstone, conducted in 1832, under the direction of Gen- 
 eral Totten, the results of which were published in vol. 
 xxii of "American Journal of Science," showed that a fine- 
 
74 APPLIED GEOLOGY. 
 
 grained granite varied .000004825 of its length for a change 
 of i Fahr., that white, fine-grained, crystalline limestone 
 from Sing Sing, N. Y., varied .000005668, and that a some- 
 what coarse-grained red sandstone from Chatham, Conn., 
 varied .00000944, or nearly twice as much as granite. Eng- 
 lish experiments, quoted by Geikie in his " Text-Book of 
 Geology," show that gray Aberdeen granite has nearly the 
 same rate of variation (.00000438) as the above, and white 
 Sicilian marble a somewhat greater rate (.00000613) than 
 the above stone of the same class ; while a Welsh slate va- 
 ried .00000576 for i Fahr. Hence, in a climate of great 
 and sudden variations of temperature, the difference of 
 temperature and of consequent tension between the inter- 
 nal and external portions of a building-stone, and between 
 its surfaces differently exposed to heat and cold, must sub- 
 ject it to a severe and often-recurring strain, to which it 
 must eventually yield. Livingstone says, in his " Travels 
 in South Africa," that the rocks in those tropical regions 
 are exposed to so great variations of temperature between 
 day and night, that fragments, varying in weight from a 
 few ounces to upward of a hundred pounds, split and fly 
 off. It can hardly be doubted that, in a climate like that 
 of the Northern United States, this cause of dilapidation 
 must seriously affect the ultimate durability of building- 
 stones ; and that, if the sandstone tested by General Tot- 
 ten shows even approximately the relative variation of 
 sandstones under temperature changes, they may be ex- 
 pected to be most affected by this agency. Doubtless, 
 also, those stones which possess the highest degree of elas- 
 ticity, which has been referred to on a preceding page, 
 may be expected to resist most successfully great extremes 
 of heat and cold. The expansion and contraction of 
 stones in structures naturally has an unfavorable effect on 
 the tightness of joints and the adhesion of mortars and ce- 
 ments. Besides what has just been said, investigations 
 prosecuted chiefly by German physicists on the ratios of 
 
MATERIALS OF CONSTRUCTION. 75 
 
 expansion of several of the most important rock-forming 
 minerals, like quartz, orthoclase, hornblende, and calcite,* 
 have revealed in them marked differences in expansibility 
 by heat, a fact which shows that the movements which 
 must take place among the constituents of a rock com- 
 posed of two or more minerals, when exposed to consider- 
 able variations of temperature, may be expected ultimately 
 to lead to its gradual disaggregation. This fact will also 
 explain the well-known tendency of granite, one of these 
 composite rocks, to burst in pieces when exposed to the 
 heat of conflagrations, though, in this case, something is 
 probably due also to differences of temperature in differ- 
 ent parts of the stone. (4) Prof. James Hall, in his excel- 
 lent " Report on Building-Stones," calls attention also to 
 the effects produced on stones by the growth of lichens 
 in the small surface inequalities, thus affording a lodg- 
 ment for dust, and detaining moisture to act slowly on the 
 surface. 
 
 Beauty of Building and Ornamental Stones. 
 In the choice of stones designed for architectural uses, 
 those qualities that please the eye naturally exert a great 
 influence on the estimate in which they are held. Much 
 depends, of course, on individual tastes, and something 
 on the currents of fashion ; but in the matter of color, 
 the neutral tints, the grays, the buffs, and drabs, usually 
 please longest ; the reddish browns are also pleasing tints 
 and largely sought after ; but great care is needed in the 
 selection of stone of this color, since experience has shown 
 that it is liable to disintegrate from the influence of its ce- 
 menting material. Dark colors give a heavy and somber 
 appearance to buildings, which may be judiciously relieved 
 by the use of light trimmings. White is glaring and painful 
 to the eye in the blazing sunshine of American climates, 
 and is besides apt to become soiled and dingy in the at- 
 
 * " Constants of Nature," Part III, " Smithsonian Miscellaneous 
 Publications." 
 
76 APPLIED GEOLOGY. 
 
 mosphere of cities, especially if the stone is somewhat 
 porous. This remark is also true of many neutral-tinted 
 porous sandstones. In the selection of colors, it is also a 
 matter of much interest, by the observation of long-exposed 
 outcrops, to note the tint which the stone may be expect- 
 ed to acquire by weathering, since some stones which are 
 pleasing when recently quarried, become, when long ex- 
 posed, of a dead and disagreeable hue. Besides mere 
 color, certain qualities of texture which adapt a stone to 
 receive a fine finish, like some sandstones and earthy 
 limestones, or to develop by polishing a beautiful surface 
 or a pleasing variety of figures and colors, like some fos- 
 siliferous limestones, marbles, granites, and porphyries, 
 place the stones which possess them in the category of 
 ornamental materials ; and some stones, like the highly 
 esteemed Caen stone, may be judiciously chosen for pur- 
 poses of interior decoration which would be perishable if 
 exposed to the weather. 
 
 Facility of Working. This is a quality of very 
 considerable importance in a building-stone when it can 
 be secured without a sacrifice of the essentials of sufficient 
 strength and durability, for on this depends in a large de- 
 gree the expense of construction. Indeed, the ultimate 
 durability of important structures is not unfrequently over- 
 looked in the effort to diminish present expense, and fa- 
 cility of working becomes a controlling rather than a sub- 
 ordinate consideration in determining the choice of a 
 stone. The ease with which a stone may be wrought into 
 desired forms depends : (i) On the hardness of its con- 
 stituent minerals and the means by which they are ce- 
 mented. Thus the granites and the silicious sandstones 
 and limestones are, as a class, more difficult to dress than 
 the nearly pure granular limestones and the sandstones of 
 somewhat open texture, or those whose chief cementing 
 material is a small amount of thoroughly disseminated 
 clay. (2) A second condition, adapting a stone to the 
 
MATERIALS OF CONSTRUCTION. 77 
 
 mode in which it is desirable that it should be worked, is 
 often presented by its structure and mode of fracture. 
 Thus, a laminated or foliated structure is a very important 
 aid in reducing a stone to the desired thickness, to which 
 if a tendency to a somewhat even cross-fracture be added, 
 a hard stone may be dressed at reasonable expense. So, 
 too, a conchoidal fracture facilitates the labor of the work- 
 man in dressing a stone for a rough-faced wall ; while, 
 where fine carving and delicate tracery are intended, the 
 stone should be without brittleness, and should possess 
 that complete homogeneity of both structure and texture 
 which will adapt it to being cut with equal ease in any di- 
 rection, and which is an essential character of the class 
 called freestones, whether silicious or calcareous. 
 
 As is well known, all stones are more easily dressed 
 when but recently removed from the quarry, as the surface 
 hardens somewhat on exposure to the air, and in some 
 cases in a very marked degree. 
 
 The manner in which a building - stone should be 
 dressed is a matter chiefly technical, belonging to the archi- 
 tect and stone-cutter ; but from one point of view it has 
 a geological bearing, since upon it depend in a considerable 
 degree the strength and durability of the stone. A mode 
 of dressing which attacks the stone by blows directed 
 against its face affects injuriously both its strength and 
 durability. General Gillmore's experiments on the strength 
 of granites showed that polished cubes were on an average 
 twenty-five per cent stronger than cubes of the same stone 
 that had been reduced to size by dressing ; and experi- 
 ments instituted in Indiana, on the oolitic limestone se- 
 lected for the State Capitol, showed a difference of more than 
 one third in strength and nearly one half in elasticity be- 
 tween sawed and tool-dressed stone. Nor should this seem 
 surprising when we consider that any stone may be broken 
 by repeated blows along a definite line. The effect of the 
 blows directed against the stone is to weaken or destroy 
 
78 APPLIED GEOLOGY. 
 
 the cohesion of all the grains to which the jar is communi- 
 cated. In like manner such blows crush the surface and 
 measurably loosen the cementation of the stone for some 
 distance inward, giving easier admission to water, and thus 
 lessening its durability. 
 
 Selection of Building-Stones. In the selection of 
 a stone for construction, attention should be paid first of 
 all to its durability^ for, when this is made sure, sufficient 
 strength will rarely be wanting. In the examination need- 
 ful for this, while careful heed should be given to the quali- 
 ties and conditions which have been enumerated as those 
 on which durability depends, the most helpful and reli- 
 able indications may be obtained by observing the manner 
 in which the stone has endured the weather in old struct- 
 ures, and especially its condition in its natural outcrops. 
 If in these exposures the edges and angles of the stone re- 
 main sharp if its surface shows no signs of flaking or 
 crumbling, no cracks nor holes where pyrites or clay has 
 lurked, nor dark stains from the change of iron compounds 
 it may be relied upon for structures if proper care is 
 used to reject suspicious blocks ; but if a contrary state 
 of things be revealed by such an examination, and if in 
 old natural exposures the edges of the stone are furrowed 
 by unequal weathering, while heaps of crumbled material 
 are piled at the base of the cliff, the stone should be re- 
 jected. It is well to remember, however, in examining 
 natural exposures, that some argillaceous sandstones, which 
 are very durable if properly dried before being exposed to 
 freezing, split up on their planes of lamination from the 
 action of frost on their quarry-water in exposed cliffs, and 
 that in their case the examination should be extended to 
 determining whether the splitting reveals any gathering of 
 the clay in seams. 
 
 As regards strength, a very large margin for safety is 
 always allowed over the force needed to crush the stone, 
 and it is probably very rare that a building-stone is sub- 
 
MATERIALS OF CONSTRUCTION. 79 
 
 jected to even one twentieth of the load under which it 
 would be likely to yield. The extreme pressure on stone 
 in a wall fifty feet high is from fifty to sixty-five pounds 
 per square inch. In a tower of stone two hundred feet in 
 height, the strain at the base would be from two hundred 
 to two hundred and fifty pounds per square inch, about 
 one fourteenth the strength of the weakest stone given in 
 the table on a preceding page. 
 
 Attention has already been directed to the error of se- 
 lecting a stone for its beauty rather than for its durability. 
 It should also be borne in mind that pleasing effects may 
 be produced with a stone of a somber color by the judicious 
 use of light-colored materials for trimmings, while even 
 the more agreeable tints lose much of their effect if unre- 
 lieved by contrasting colors. 
 
 By attention to the suggestions already given, stone of 
 a reasonable degree of facility in dressing may be secured 
 in many localities ; and it is well to bear in mind that the 
 harder kinds of rocks commonly produce their best effects 
 in buildings when rough dressed, and so with a minimum 
 of expense in working. When elaborate ornamentation is 
 proposed, the question is usually one of fitness of materials 
 rather than of expense. 
 
 After all, in the majority of cases where stone is used 
 in constructions, local supplies must be the chief depend- 
 ence, on account of the great expense of transportation ; 
 and the suggestions here made are intended mainly to aid 
 in the selection of the best materials from the supplies 
 afforded by the rocks which may exist in the vicinity. 
 Many stones also may do fairly well for cellars and foun- 
 dations, where they are not exposed, which, from various 
 causes, would not be durable if exposed to the weather ; 
 and others may serve a useful purpose in rough construc- 
 tions, like bridge-abutments, retaining walls, and under- 
 pinnings of farm-buildings, which from their coarseness 
 of texture, their faults of color, or their hardness and ir- 
 
8o APPLIED GEOLOGY. 
 
 regular fracture, would be unsuited for a better class of 
 structures. Indeed, many regions may furnish materials 
 for these wide-reaching and very essential uses, which 
 would yield none suitable for higher purposes. 
 
 North American Building-Stones. A general 
 idea of the relative amounts of the several classes of build- 
 ing-stones that are used in the United States from impor- 
 tant quarries may be gained by observing the production 
 reported in the census returns for 1880. The number of 
 cubic feet of marketable stone reported was over 115,000,- 
 ooo. Of this, considerably more than a half, or 65,500,- 
 ooo cubic feet, was limestone and marble ; a little less 
 than 25,000,000, sandstone ; about 20,500,000, granite and 
 other crystalline rocks of the same class ; while the slate 
 product was somewhat more than 4,500,000 cubic feet. 
 These amounts would be largely increased, could the local 
 supplies derived from numerous small quarries be known ; 
 but it is not likely that the relative amounts of the sev- 
 eral stones would be materially changed. Hence it would 
 seem that limestones and marbles are much more largely 
 used than any other class of building-stone a fact which 
 is due, partly to their wide distribution, and partly to the 
 comparative ease with which they may be dressed. 
 
 A general view may also be obtained of the distribution 
 of building-stones of special value, by observing the States 
 reporting the largest production of the several classes. 
 Thus, in the production of limestones, Illinois leads in 
 amount, followed by Ohio, Iowa, Indiana, Missouri, and 
 Wisconsin, in the order named ; while Vermont, which 
 stands twelfth in amount of product, leads the list in point 
 of value, her product of about 1,200,000 cubic feet, chiefly 
 marble, being worth somewhat more than the 13,000,000 
 cubic feet of Illinois limestone. In sandstone, Ohio ranks 
 first in both amount and value, Pennsylvania second in 
 amount, New York third, New Jersey fourth, and Con- 
 necticut fifth. In stones of the granite class, Massachu- 
 
MATERIALS OF CONSTRUCTION. 8 1 
 
 setts ranks first in amount and value of product, followed 
 in order of value by Maine, Rhode Island, Connecticut, 
 Virginia, and New Hampshire ; while in the production 
 of slate, Pennsylvania is foremost, yielding, with Vermont, 
 over 83 per cent of the total product, minor amounts 
 being supplied by Maine, New York, Maryland, and Vir- 
 ginia. 
 
 It will be seen from this that the production of gran- 
 ite, slate, and marble is chiefly confined to the Appalachian 
 belt from Maine to Georgia Colorado and California also 
 producing small amounts ; that the greatest limestone pro- 
 duction is from the north central group of States ; while 
 the chief supplies of merchantable sandstones are, at pres- 
 ent, derived from the region between these areas. A brief 
 review of the geological distribution of the various classes 
 of building-stones will not only reveal the reason for this 
 grouping of productive areas, but will also be likely to 
 suggest additional areas whence valuable building mate- 
 rials for both local use and commercial distribution may 
 be derived, as the progress of settlement and the supply 
 of easy means of transportation encourage their develop- 
 ment. 
 
 Geological Position of Granitic Rocks. The 
 oldest rocks on this continent are found occupying much 
 of British America, in a great V-shaped area with the 
 point near the eastern end of Lake Ontario, extending 
 into Labrador with its shorter branch, which covers most 
 of the explored region north of the St. Lawrence, and 
 with its longer branch skirting the north sides of Lakes 
 Huron and Superior, and stretching away northward 
 to the Arctic Ocean. From the point of the V, these 
 rocks extend across the St. Lawrence at the Thousand 
 Islands, and occupy a large area in northeastern New 
 York the well-known Adirondack wilderness. Rocks of 
 similar character, but a portion of which are probably of 
 somewhat later age, occupy parts of Nova Scotia and 
 
82 APPLIED GEOLOGY. 
 
 New Brunswick, most of New England, the southeast cor- 
 ner of New York and northwestern New Jersey, and 
 extend along the Appalachian range through Virginia, 
 North and South Carolina, and Georgia, into eastern Ala- 
 bama. These most ancient rocks also occupy a large part 
 of northern Michigan, cover much of northern Wisconsin 
 'and Minnesota, and are extensively developed in the 
 Rocky Mountains, the Wahsatch, the Sierra Nevada, and 
 in many parts of the ranges of the Great Basin. This 
 very ancient series of deposits, called the Archaean or 
 Azoic, consists wholly of crystalline rocks of various kinds, 
 arranged in rude beds, showing that they were once or- 
 dinary sediments which owe their present condition to 
 metamorphism ; and they have been penetrated in many 
 places by vast masses of granite which have been thrust 
 through them in a plastic state. Granitic rocks of several 
 kinds form some of the series of beds also, as well as oc- 
 casional crystalline limestones that furnish marbles. In 
 the areas, chiefly Archaean, then, which have been de- 
 scribed above, and in a few other limited exposures that 
 have not been mentioned, but which lift themselves like 
 islands from the midst of the newer rocks that surround 
 them, and in these only, may we expect to find building- 
 stones of the granitic class the granites, the syenites, the 
 gneisses, and the highly silicious schists. In several parts 
 of these areas, rock of this class is now quarried in large 
 amounts ; in many others stone of fine quality and great 
 beauty is known to exist, though not yet worked ; and 
 doubtless building-stone of equal merit will be found in 
 many other localities not yet explored. Considerable 
 amounts are already quarried in Colorado, and in Cali- 
 fornia on the line of the Central Pacific Railroad. Be- 
 sides our domestic supplies, considerable amounts are 
 imported for monumental and ornamental uses, especial- 
 ly from Aberdeen and Peterhead in eastern Scotland. 
 These rocks, composed of two or more of the minerals 
 
MATERIALS OF CONSTRUCTION. 83 
 
 quartz, feldspar, hornblende, and mica, are as a class very 
 durable, though some of them, in which feldspar is largely 
 present and has microscopic pores, giving easier admission 
 to water, weather somewhat rapidly. Pyrites should also 
 be guarded against, in these as in other rocks, for it is 
 sure to impair their durability. Where the constituents 
 are very coarsely crystalline also, the rock is unfit for 
 building purposes. Those granitic rocks which are com- 
 posed of quartz and feldspar, or quartz, feldspar, and horn- 
 blende, with mica in small proportion, if present at all, and 
 with the ingredients in small or moderate-sized grains, are 
 the best. These rocks are harder than the other classes of 
 building-stones ; but most, and perhaps all of them, split 
 with comparative readiness in one direction, called by the 
 workmen the rift, and break most easily at right angles to 
 the rift, thus making the dressing easier. They vary much 
 in color, according to the color and proportions of their 
 constituents, those composed chiefly of quartz and light- 
 colored feldspars, with but little black mica, being of a gray 
 or grayish-white color ; those containing much reddish 
 feldspar are reddish, and often very ornamental ; while 
 hornblende imparts to granites and syenite its own dark 
 hue, as in some of the Quincy granites. Many of the gran- 
 ites are susceptible of a high polish, and are on this account 
 considerably used for internal ornamentation in expensive 
 buildings, as also for monumental purposes. Where the 
 feldspar in a granite occurs in well-formed crystals of 
 pleasing color, as in the so-called shap of Cumberland in 
 England, it increases its value for ornamental purposes. 
 Granites of this character can doubtless be obtained also 
 at some localities in this country. Besides the silicious 
 building-stones here described, trachyte, a volcanic rock 
 composed chiefly of feldspar, is said to be used as a build- 
 ing-stone at Virginia City, in Nevada ; and porphyry, an- 
 other volcanic rock containing crystals of feldspar imbed- 
 ded in a fine-grained matrix, chiefly of feldspar, with some 
 
84 APPLIED GEOLOGY. 
 
 hornblende or augite, though little suited for building, has 
 long been used for ornamental purposes, for which some 
 kinds have an ancient and deserved celebrity. Handsome 
 porphyry is reported to be found in Grenville, Province 
 of Ontario. 
 
 Geological Position and Localities of Marble 
 and Slate. Although the crystalline marbles and slates 
 are chiefly derived from Silurian rocks, later in age than 
 those from which the granitic building-stones are obtained, 
 still their local distribution, and in some cases their geo- 
 logical position, is so closely related to these that they 
 may conveniently be considered in this place. Excellent 
 roofing-slates are quarried near Huron Bay, in northern 
 Michigan, from rocks of the later Archaean, and others, it 
 is said, in Minnesota, probably from rocks of the same 
 age. Likewise the first " Annual Report on Mineral Sta- 
 tistics of Michigan, 187 7-^ 8," states that desirable mar- 
 bles may be obtained from the Archaean, not far from 
 Marquette. So also the Archaean limestones of eastern 
 Canada, at a number of localities, yield marbles suited 
 for building and ornament, though these limestones are 
 apt to be too much contaminated with various minerals, 
 or too coarsely crystalline, to be desirable for such pur- 
 poses. But the metamorphic rocks of the Lower Silurian, 
 stretching along the east side of the Archaean in eastern 
 Canada, Vermont, and southeastern New York, and along 
 the same range in west Massachusetts and Connecticut, 
 furnish the chief present supplies of handsome marbles 
 for building and for ornamental uses ; and in some locali- 
 ties the marble is veined with serpentine, making an es- 
 teemed ornamental stone called verd-antique marble. The 
 serpentinous limestones of the Canadian Archaean can also 
 yield supplies of this stone at some localities ; while beau- 
 tiful serpentines occur in Wake County, North Carolina, 
 and in some of the western counties of that State. The 
 Lower Silurian rocks of East Tennessee likewise yield 
 
MATERIALS OF CONSTRUCTION. 85 
 
 highly esteemed marbles of various colors, which are ex- 
 ported chiefly from Hawkins and Knox Counties, though 
 several other counties near the western base of the Appa- 
 lachians can, it is said, furnish stone of equal beauty. The 
 colored marbles for the interior decoration of the Capitol 
 extension in Washington were obtained from Hawkins 
 County, while that which was used in the construction of 
 the building was dolomitic marble from Lee, Mass. Beau- 
 tiful marbles are also reported from the western part of 
 North Carolina, and a recent display (1883) of some of 
 these in Boston attracted much attention. 
 
 Cleavable slates are obtained from argillaceous rocks 
 that have been folded and subjected to great pressure, 
 thus rendering them very compact, and developing in 
 them a tendency to cleave at various angles with the origi- 
 nal bedding-planes. The largest supplies are derived, as 
 has already been stated, from Pennsylvania and Vermont. 
 The slate region of eastern Pennsylvania is along the 
 southeast base of the Appalachians, the chief quarries 
 being in Lehigh and Northampton Counties, the adjacent 
 part of New Jersey also furnishing some, and in Lancaster 
 and York Counties. The remaining States mentioned be- 
 fore as furnishing slates yield them under similar geo- 
 logical conditions in regions where the rocks have been 
 much disturbed and folded. It is quite probable that 
 other localities of good roofing-slates will be found in the 
 disturbed regions along the Appalachians, the Rocky 
 Mountains, and the Sierra Nevadas. Indeed, slates are 
 said to be already obtained in California near the base of 
 the last-named range. The best British supplies of slate 
 are obtained from the folded rocks of the Lower Silurian 
 in northern Wales. 
 
 Slate should be susceptible of being split easily into 
 thin, even plates ; should be free from seams and strings 
 of quartz, which interrupt the cleavage, and from crystals 
 of pyrites, which would be likely to weather out, leaving 
 
86 APPLIED GEOLOGY. 
 
 holes, and should be so firmly compacted as to endure 
 weathering without change. The softer cleavable beds, 
 which, though sound, would not endure exposure to the 
 weather, are wrought into school-slates and tablets. 
 
 Among the crystalline marbles, the very fine-grained 
 and homogeneous kinds are the best, and have a high de- 
 gree of durability, save possibly in moist climates. Those 
 of coarse grain and friable texture, or those contaminated 
 with foreign minerals, or containing soft spots of " talc-like 
 mineral," are not only difficult to polish, but are apt to 
 endure exposure to the weather badly. The older stones 
 in cemeteries long occupied afford convenient opportu- 
 nities for observing the behavior of marbles under ex- 
 posure. 
 
 Besides the true marbles of crystalline texture, some 
 compact limestones of pleasing and varied colors, fre- 
 quently owing much of their beauty to sections of fossils 
 contained in them, are polished and used for ornamental 
 marbles. Of this kind is the marble from East Tennessee, 
 mentioned above (Safford). 
 
 Besides our domestic supplies, considerable amounts 
 of very fine marble are imported from Italy, chiefly from 
 Carrara in, the Apennines. Greece is also famous for fine 
 statuary marble from the island of Paros, and from Mounts 
 Pentelicus and Hymettus. 
 
 Sandstones and Limestones. In studying the 
 geological relations and topographical distribution of the 
 two remaining and very important classes of building- 
 stones, the sandstones and limestones, it will be helpful to 
 remember that in the vicinity of the great Archaean re- 
 gions, described in a preceding paragraph, which consti- 
 tuted the land areas of succeeding geological ages, and 
 which directly or indirectly furnished the ground-up or 
 dissolved materials of all later rocks, the chief strata are 
 mechanical sediments sandstones and shales the lime- 
 stone bands, important though they are, forming but sub- 
 
MATERIALS OF CONSTRUCTION. 87 
 
 ordinate parts of the great thickness of strata. On the 
 other hand, the area now occupied by the great central 
 group of States, from central Ohio westward into Kansas, 
 seems to have been a vast interior sea of no great depth, in 
 which chiefly limestones were formed through the agency 
 of corals and other sea creatures ; sandstones and shales 
 being here but subordinate members in the series of strata. 
 While, therefore, limestones furnish the chief building ma- 
 terials of the latter region, sandstones are the chief ma- 
 terials of the former Ohio, which lies between the two, 
 furnishing excellent varieties of both kinds of stone from 
 her eastern and western sections, being the foremost pro- 
 ducer of desirable sandstones, and second to but one State 
 in amount of limestone quarried. In the first-named 
 area, sandstone is furnished from several geological hori- 
 zons, and at very numerous localities. The lowest un- 
 changed formation, the Potsdam, affords much good stone 
 of red and light gray colors, across the northern parts of New 
 York and the adjacent portions of Canada ; and it borders 
 nearly the entire south shore of Lake Superior with sand- 
 stone of a brown color, which at Marquette, Mich., and 
 Fond du Lac, Minn., is quarried, yielding an admired 
 building-stone, and which will doubtless afford stone of 
 equal quality at many other points along this shore. South 
 of the Archaean, in central Wisconsin and Minnesota, this 
 formation covers large areas, but furnishes little good 
 building-stone, being usually too friable. The two suc- 
 ceeding periods offer, in parts of the Quebec and Hudson 
 River groups, sandstones usually argillaceous, and suitable 
 for flagging and for foundation-walls ; the former chiefly in 
 eastern Canada, the latter across New York from Oswego 
 eastward. Next in ascending order, the Medina sand- 
 stone, along the south shore of Lake Ontario, yields, in 
 one of its members, a usually hard but excellent sandstone 
 of light gray and reddish-brown colors, which is largely 
 quarried west of Rochester at Albion, Medina, Lockport, 
 
88 APPLIED GEOLOGY. 
 
 and'Other places, and is widely used both for buildings 
 and for paving, promising great durability where carefully 
 selected. The same geological formation in Canada, 
 where it is called the "Gray Band," stretches across the 
 Province of Ontario from Queenstown to Collingwood, and 
 yields an excellent building-stone wherever it has been 
 quarried. In the southern counties of New York, and in 
 northern Pennsylvania, the Portage and Chemung groups 
 yield, in many places and at various horizons, beds of 
 dark gray,~olive, and dark brown argillaceous sandstones, 
 suitable for all ordinary building purposes, though of some- 
 what somber colors unless properly relieved by trimmings. 
 Like all argillaceous sandstones, they need careful selec- 
 tion to avoid blocks containing seams of clay which soon 
 disintegrate ; but when properly selected, and seasoned be- 
 fore being exposed to frost, they give promise of great du- 
 rability. The Sub-carboniferous yields, in parts of Pennsyl- 
 vania and in eastern Ohio, beds of good sandstone, which 
 in Ohio is the fine silicious freestone so largely quarried 
 in the vicinity of Cleveland for ornamental building-stone, 
 for grindstones, and for sawed flagging. It is easy to work, 
 takes a fine surface, and is susceptible of delicate carving ; 
 and though very porous, seems, from its purely silicious 
 character, to promise a good degree of durability. Along 
 the Atlantic slope of the Appalachians, apparently filling 
 long, narrow valleys formed by their folding, and running 
 parallel with them, are found thick deposits of sandstone 
 and shale of earlier Mesozoic age, in the Connecticut River 
 Valley, and stretching across New Jersey, Pennsylvania, 
 Virginia, and North Carolina. These deposits furnish, at 
 many places, beds of a handsome brown freestone, easily 
 worked, but not usually very durable. This freestone is 
 largely quarried in Connecticut and New Jersey for use 
 in New York and other cities. Deposits of similar and 
 somewhat later age are extensively developed along the 
 eastward side of the Rocky Mountains, in the so-called 
 
MATERIALS OF CONSTRUCTIO. 
 
 " hog-backs " of Colorado and Wyoming, where t 
 capable of furnishing excellent freestones of various agree- 
 able shades of color. These freestones are already quar- 
 ried at two or three points, notably at Morrison in the 
 vicinity of Denver, for use in the public buildings of that 
 city. California is also said to have, at several points, 
 useful sandstones in the later geological formations, as well 
 as an abundance of handsome marbles and limestones. 
 
 The precautions that should be observed in selecting 
 sandstones for exposed parts of constructions 'are chiefly 
 these : to choose the more purely silicious, and those of 
 finer and closer texture ; to avoid those containing pyrites, 
 a large proportion of clayey matter, or seams of clay ; to 
 be suspicious of those in which a dark reddish coloring- 
 matter is a principal means of consolidation ; and, among 
 porous sandstones, to select only those of proved dura- 
 bility, since, though some porous sandstones of purely sili- 
 cious character are very durable, the durability of stone in 
 general is inversely proportioned to its porosity. 
 
 Like the sandstones, the limestones, in the region bor- 
 dering the Archaean, occur at certain geological horizons 
 only, and even in the great central limestone area the 
 stone which has been found to be adapted to the higher 
 class of uses in construction is found mainly in a few geo- 
 logical formations. The lowest geological period which 
 affords good limestones is the Canadian, which in its low- 
 est group, called the Calciferous, furnishes in Minnesota 
 the desirable stone quarried chiefly at Frontenac, Kasota, 
 and Mankato, and in southeastern Missouri forms the 
 magnesian limestone beds. The uppermost group of the 
 same period, called the Chazy, furnishes a limestone which 
 is quarried at many points in the northeast corner of New 
 York and the adjacent parts of Canada, yielding an es- 
 teemed building-stone. The Trenton limestone, which 
 extends across New York just north of the Mohawk River, 
 and passes northwestward through Herkimer County into 
 
9 o 
 
 APPLIED GEOLOGY. 
 
 St. Lawrence, is quarried at many places, yielding a gray 
 and a dark-blue stone, and in eastern Canada it furnishes 
 most of the building-stone used in Montreal and much of 
 that which is used in Quebec. The limestones of the 
 same formation, which occupy a large part of southern 
 Wisconsin, are too much interlaminated with clay to yield 
 much good building-stone ; but in Minnesota the upper 
 beds are said to be free from clay-seams, and to be capable 
 of furnishing reliable stone. The best limestones of Wis- 
 consin are obtained from rocks of the Niagara period, 
 which stretch along Lake Michigan in the eastern part of 
 the State, and furnish an excellent building-stone at many 
 points. Limestone of the same age is largely quarried in 
 several parts of Illinois, furnishing the Joliet stone and 
 Athens marble, in southeastern Indiana and in southwest- 
 ern Ohio, yielding in the latter State the highly valued 
 Dayton stone, as well as that obtained at Springfield and 
 other places. The higher strata of this formation are also 
 quarried in the western part of New York, at Lockport 
 and other places ; and, in the Province of Ontario, these 
 beds, extending northwestward from Niagara Falls to 
 Lake Huron, are capable of furnishing an excellent mag- 
 nesian limestone at many points. In ascending order, 
 the Lower Helderberg period is composed of limestones 
 which have their chief development in eastern New York, 
 where the lower members are quarried for local use from 
 Schoharie County westward to Oneida County. The Cor- 
 niferous limestone which succeeds this is of great extent 
 and importance, stretching across New York from near 
 Albany to Buffalo and thence across the Province of On- 
 tario, and sending a branch down through the Lake Erie 
 islands and central Ohio to a considerable distance south 
 of Columbus, a second branch being found farther west in 
 the same State. Throughout this wide extent it is quar- 
 ried at many points for both building-stone and for lime, 
 yielding, where free from quartz-nodules, with which some 
 
MATERIALS OF CONSTRUCTION. 91 
 
 of its beds are thickly set, a strong and durable stone. 
 This is the last of the limestones of the eastern division of 
 States which is much used for building purposes. The 
 Tully limestone of the upper part of the Hamilton period 
 is confined to central New York, and can be used only for 
 rough work, while the beds of limestone that occur in the 
 coal-measures of Pennsylvania seem to be little used for 
 construction. In the Western States it is different, for 
 there the Sub-carboniferous limestones afford excellent 
 building materials in Indiana, Illinois, Missouri, and Iowa, 
 though in the last-named State the best supplies of build- 
 ing-stone are obtained from rocks of the Niagara period. 
 In the Sub-carboniferous of Indiana, beds of highly es- 
 teemed oolitic limestone are largely quarried in several 
 counties, extending from Montgomery County southward 
 to Harrison, and this stone has been used in many im- 
 portant buildings, among which is the new State Capitol of 
 Indiana. The same formation yields good building-stone 
 at three different horizons in Illinois and at two in Mis- 
 souri, 
 
 Although the limestones most highly esteemed and 
 most widely used for construction in England, France, 
 and southern Europe are obtained largely from forma- 
 tions younger than those named above, viz., the Permian, 
 the Jurassic, and the earlier Tertiary, it is not known that 
 any younger than the Carboniferous have yet been consid- 
 erably used in this country. 
 
 In the ranges that have been described, limestones 
 suitable for buildings can by no means be found in all 
 places where the formations are exposed, for limestones, 
 like other formations, are apt to present important differ- 
 ences at different exposures. In some places their bed- 
 ding may be such as to unfit them for use ; in others their 
 texture may expose them too much to the attacks of frost 
 or to the solvent action of carbonated waters. Some are 
 contaminated with pyrites, or contain so considerable a 
 
92 APPLIED GEOLOGY. 
 
 proportion of argillaceous matter as to impair their dura- 
 bility, while others contain clay in thin seams or irregular 
 crevices, which, if it does not lead to their early decay, 
 soon gives them a cracked and unsightly appearance. This 
 seems to be more largely true of the gray sub-crystalline 
 limestones. In other cases the strata may contain crystals 
 and nodules of quartz, unfitting them for regular working ; 
 yet some silicious limestones in which the silica in fine 
 particles is uniformly disseminated throughout the mass, 
 though somewhat harder to dress, will doubtless be found 
 possessed of desirable qualities in point of durability and 
 strength. The points here mentioned are those that need 
 to be carefully observed in choosing places for opening 
 large quarries, and in selecting those seams that it is pro- 
 posed to use for building purposes, while careful attention 
 should always be given to the condition of all seams that 
 have long been exposed to the elements. Of the lime- 
 stone formations of North America, the Niagara and Cor- 
 niferous appear to be the most generally useful over wide 
 extents of country, the others being either limited in their 
 range to certain regions, or presenting great differences of 
 condition in sections remote from each other. Thus the 
 more valuable Sub-carboniferous limestones are limited to 
 the Western States, while the Trenton, which furnishes 
 good building-stones in northern New York, in Canada, 
 and in East Tennessee, is worthless in Ohio and Indiana, 
 and of doubtful repute in Wisconsin, Minnesota, and 
 Iowa. 
 
 Brick, Terra-Cotta, and Drain-Pipes. These 
 articles, so widely used for house construction, ornamen- 
 tation, and drainage, are fabricated, as is well known, from 
 clays possessing sufficient plasticity to permit of their be- 
 ing shaped in molds, and then burned in kilns to the requi- 
 site degree of hardness. Coarse clays, suited for bricks 
 and drain-pipes, are widely distributed over our country. 
 In the regions covered with drift deposits north of the 
 
MATERIALS OF CONSTRUCTION. 93 
 
 parallel of 39, they are found as large parts of these de- 
 posits, which, when free from stones, and from pebbles of 
 limestone, can be used for brick-making. They are also 
 found as a result of the weathering of shales, or of the 
 disintegration of gneissose and other rocks, in the recent 
 deposits of rivers and smaller streams, and in some lacus- 
 trine deposits formed when the lakes occupied a consider- 
 ably higher level than at present as, for example, along 
 the shores of Lake Michigan. Besides these wide-spread 
 deposits, clays, some of which are adapted for much 
 choicer uses, and which will be described in another con- 
 nection, but the coarser of which make superior bricks, 
 terra-cotta, and drain-pipes, are found in the Cretaceous 
 deposits of New Jersey, Minnesota, and doubtless of some 
 Western States and Territories ; others may be found in 
 the Tertiary deposits along the Atlantic coast and the 
 Gulf of Mexico ; while clays of great excellence may be 
 obtained by the proper weathering of some of the under- 
 clays of coal-beds, both of the coal-measures and of the 
 Cretaceous deposits of Colorado, Wyoming, New Mexico, 
 Montana, and some of the Pacific States and Territories. 
 As may readily be inferred from the wide differences in 
 origin of clays, they present also wide differences in com- 
 position and character. Essential ingredients in all of 
 them are a sufficient proportion of kaolin, or true clay, to 
 give them the requisite adhesiveness and plasticity, and of 
 quartz sand to correct the tendency of clay when burned 
 to excessive shrinking, warping, and cracking. The relative 
 proportion of these ingredients may vary, however, within 
 wide limits, and they are mingled besides with variable 
 amounts of iron oxide, of the alkalies potash and soda, 
 and of the alkaline earths lime and magnesia. The iron 
 usually gives to bricks, as they are commonly burned, 
 their well-known red color, by becoming the red oxide ; 
 but when a considerable proportion of lime and magnesia, 
 or of these with potash, is present, these substances at a 
 
94 
 
 APPLIED GEOLOGY. 
 
 high temperature form with the iron and silica a com- 
 pound which partially fuses, giving to the bricks a greater 
 degree of solidity, and imparting to them the agreeable 
 cream-color which is so favorably known in the so-called 
 Milwaukee brick. As examples, both of the essential in- 
 gredients of clays and of their differences of composition, 
 it may be said that the common brick-clays from the New 
 Jersey Cretaceous contain about 45 per cent of kaolin, 30 
 per cent or more of sand, and 8 to 10 per cent of iron and 
 the alkaline ingredients ; that the ordinary clays of Wis- 
 consin contain usually less than 25 per cent of kaolin, 60 
 per cent and upward of sand, and about 9 per cent of 
 iron and alkaline substances, both these kinds of clay 
 yielding red bricks; while the clay from which is fab- 
 ricated the cream-colored Milwaukee brick has only 
 about 20 per cent of kaolin, 4 per cent of iron oxide, and 
 more than 40 per cent of lime, magnesia, and potash ; this 
 last clay being the more noteworthy because of the preva- 
 lent opinion that any considerable proportion of lime and 
 potash is fatal to the excellence of a clay, whereas, in 
 the use of this clay, the presence of these substances is 
 counted a great advantage, not only as giving the bricks a 
 greater solidity and an agreeable color, but as furnishing 
 a reliable test of the thoroughness with which they have 
 been burned ; since, with insufficient burning, they have a 
 red color, while the creamy tint appears only with a tem- 
 perature that produces an incipient fusion. Brick clays 
 are much improved by weathering. They are then tem- 
 pered with a sufficient amount of clean, sharp sand, if the 
 clay is deficient in this ingredient, ground in a pug-mill 
 to secure uniformity of composition, and molded for burn- 
 ing either by hand or by a machine which is capable of 
 shaping many thousands in a day. In the common mode 
 of burning, a considerable portion of the product is apt to 
 be unfit for use, partly from being overburned, and so glazed 
 and cracked, and partly from being underburned, with the 
 
MATERIALS OF CONSTRUCTION. 
 
 95 
 
 result of being weak and crumbling. In the Geological Re- 
 port of New Jersey, for 1870, a perpetual kiln is figured 
 and described, which appears to be ingeniously devised 
 for securing uniformity of product with great economy of 
 fuel. It is said to be capable of turning out from three 
 to five millions of brick per year, at an expense for fuel of 
 less than forty cents per thousand, waste coal being used 
 for this purpose. 
 
 In the year 1880 over four thousand millions of com- 
 mon and pressed brick are reported to have been manu- 
 factured in the United States, the States which were fore- 
 most in that industry being New York, Pennsylvania, 
 Ohio, Illinois, Indiana, New Jersey, Missouri, and Massa- 
 chusetts. In the manufacture of drain-pipes Ohio leads, 
 while New Jersey produces fully eighty per cent of all the 
 terra-cotta. The manufacture of this last article requires 
 the superior kind of refractory clay fitted for fire-brick, 
 and a variety of colors is produced by the judicious admix- 
 ture of clays having slightly different ingredients. Sewer- 
 pipes are also made from the same kind of clay, both arti- 
 cles requiring to be burned at a high temperature. 
 
 Materials for Mortar. The materials for the mortar 
 to be used in various kinds of construction are sand, quick- 
 lime, and hydraulic cements, both natural and artificial. 
 The type of a good sand for mortar-making is an aggre- 
 gation of clean, sharply angular granules of quartz, of 
 somewhat coarse texture ; and the more closely a sand 
 approximates to this type the better it is. In many sec- 
 tions an impure mixture of quartz sand with rounded 
 grains of other substances and some clay is used, pro- 
 ducing great annoyance by the crumbling of the mortar 
 and the frequent fall of portions of the plastering of 
 houses. It would be better, and in the end cheaper, to 
 bring good sand from a considerable distance, rather than 
 to use such inferior materials. Sands for mortar are found 
 widely distributed in various superficial deposits along 
 
96 APPLIED GEOLOGY. 
 
 stream-courses, and on the shores of the ocean and other 
 bodies of water, in the modified drift, in unconsolidated 
 beds of Tertiary and Cretaceous age, and occasionally in 
 the incoherent sandstones of much greater geological age. 
 Quicklime for use in mortar is obtained by properly cal- 
 cining in kilns any of the limestones and dolomites, whose 
 general distribution has been given on a preceding page, 
 and which are of a reasonable degree of purity ; i. e., which 
 contain no more than six to eight per cent of silicious and 
 earthy impurities. Doubtless, limestones less pure than 
 this are frequently burned when nothing better can be ob- 
 tained ; but it is obvious that the nearer a limestone is to 
 absolute purity, the better it is for lime-making. A rough 
 test of the purity of a limestone may be made by dissolv- 
 ing small fragments, chipped from various parts of the 
 stone, in hydrochloric acid, applying a little heat if mag- 
 nesian, and noting the nature and amount of the residue. 
 This test can of course be made much more accurate if 
 means can be had for weighing the stone fragments, and 
 then weighing the filtered and dried residue. Quicklime 
 obtained from ordinary limestone differs in some marked 
 respects from that obtained from dolomites or highly mag- 
 nesian limestones. The former, called hot limes, on the 
 application of one third their volume of water, slack, i. e., 
 fall rapidly into a fine, whitish powder, with great evolu- 
 tion of heat ; and when made into a paste with water, with 
 which paste is thoroughly incorporated from three to five 
 times its volume of clean, sharp sand, form a mortar which 
 sets or hardens very quickly in the air. The latter, called 
 cool limes, require less heat for their thorough calcination, 
 slack less rapidly and with smaller evolution of heat, and 
 form a mortar which sets more slowly, and so admits of more 
 deliberate work on the part of the mason. While equally 
 good with the other for all common uses of mortar, the 
 dolomitic limes have evidently a special adaptation to the 
 operations of the plasterer. Lime would undoubtedly 
 
MATERIALS OF CONSTRUCTION. 
 
 97 
 
 make better mortar could it, after being slacked, be thor- 
 oughly covered from the air, and left for some months to 
 ripen before being mixed. In this way, and with very 
 coarse, angular sand, is said to have been made the mortar 
 found in many ancient European structures, which rivals 
 the firmness of the stones which it cements. A vast frag- 
 ment of the old castle of Heidelberg, comprising nearly 
 one half of one of the enormously thick towers, blown up 
 by the French in 1688, still lies in the moat into which it 
 slid, the entire mass firmly welded by the adhesion of its 
 mortar, whose stony hardness seems unimpaired by an 
 exposure of nearly two centuries. Our modern mortars, 
 quickly made, can bear no comparison with such endur- 
 ance as this. Indeed, in the removal or alteration of 
 somewhat recent structures, the adhesion of the mortar 
 too often opposes little resistance to the operations of the 
 workmen, and not unfrequently, after the lapse of a few 
 years, it crumbles spontaneously from between the stones 
 which it was intended to cement. 
 
 In the selection of a limestone for calcination, after a 
 sufficient degree of purity is assured, it is better to choose 
 such beds as, without being friable, possess a somewhat 
 granular and porous texture, since they burn to lime most 
 easily and uniformly. The magnesian limestones have this 
 constitution more generally than others, furnishing another 
 reason for their selection where they are attainable. The 
 Census Reports of 1880 show that lime suitable for mortar 
 is found in greater or less abundance in every State and 
 Territory of our Union, though it would appear that Ore- 
 gon and Washington are least abundantly supplied. 
 
 While the mortars made from the kinds of lime just de- 
 scribed, when immersed in water, remain soft and without 
 cohesion, and gradually part with their lime by solution, 
 that made from hydraulic limes and cements, either with 
 or without admixture with sand, possesses the singular and 
 valuable property of setting more or less quickly under 
 
98 APPLIED GEOLOGY. 
 
 water to a mass of stony hardness and great strength. 
 Hence, in all constructions where moisture is to be with- 
 stood, as in damp foundations or submerged structures, 
 the mortar should contain the latter kind of lime to the 
 extent of at least half that which is used in the mixture, 
 and in many cases the whole of it. This difference in be- 
 havior between common and hydraulic limes is due to an 
 important difference in their composition. Common lime 
 is burned from carbonate of lime or carbonate of lime and 
 magnesia as nearly pure as can be obtained ; and the hard- 
 ening of the mortar made from it is due in part to the re- 
 formation of lime carbonate, in part to the crystallization 
 of hydrate of lime upon the grains of sand, and probably 
 in part to the slow formation, during ages, of lime silicate, 
 in virtue of which a good mortar grows harder with age. 
 Hydraulic lime, on the other hand, is burned from lime- 
 stones notably impure, containing, as analyses show, from 
 twenty to about fifty per cent of silica, alumina, and iron 
 oxide ; it either does not slack at all with water, or slacks 
 very slowly, and with great difficulty, needing, therefore, to 
 be ground to a fine powder before being used ; and its hard- 
 ening in mortar is due to a chemical combination of lime, 
 or lime and magnesia, with silica and alumina, partially 
 effected during the burning, and partially by the agency 
 of water, forming hydrated silicates and aluminates of 
 lime and magnesia, which are insoluble in water. The im- 
 pure limestones suitable to yield hydraulic lime by proper 
 burning naturally constitute, as General Gillmore remarks, 
 transition beds between mechanical sediments like sand- 
 stones and shales, and the purer limestones ; and in such 
 geological positions they are usually found. From their 
 nature as transition beds, also, and dependent as their 
 properties are upon a due intermingling of substances 
 from two very distinct sources, they possess, as might be 
 supposed, but " little uniformity of composition over any 
 wide areas, or through any considerable thickness of 
 
MATERIALS OF CONSTRUCTION. 
 
 99 
 
 strata," and consequently need great care in selection, to 
 secure stone which, when burned, will yield a good hy- 
 draulic lime. Indeed, some of the most reliable and 
 highly esteemed materials of this class, like the celebrated 
 Portland cement, are made artificially by burning a care- 
 fully proportioned and thoroughly incorporated mixture 
 of clay and chalk. Where, however, natural stone can be 
 found which, by proper care in selection and burning, 
 will yield hydraulic limes and cements of good quality, it 
 can be more cheaply obtained, and is good enough for all 
 practical purposes. The United States, fortunately, has 
 such limestones occurring at several different horizons, 
 and of somewhat extensive distribution. The lowest of 
 these horizons is in the Calciferous group, which at Utica 
 in La Salle County, 111., and at several points in Ma- 
 ryland and Virginia, furnishes hydraulic limes of satis- 
 factory quality, and may be expected to do the same at 
 points on the same range in eastern Pennsylvania. The 
 Water- Lime group, at the base of the Lower Helderberg, 
 with some kindred limestones belonging just beneath it in 
 the geological series, furnishes nearly ninety per cent of all 
 the hydraulic lime and cement produced in the United 
 States, being largely burned in Ulster County, N. Y., fur- 
 nishing the esteemed Rosendale cement, also in Oneida, 
 Madison, Onondaga, and Erie Counties, and near San- 
 dusky, in Ohio; while the well-known Louisville cement 
 is obtained, according to Prof. James Hall, from beds 
 of the Corniferous period belonging just above this in 
 the geological series. A limited outcrop of rocks of the 
 Hamilton period at Milwaukee, Wis., furnishes the Mil- 
 waukee cement. The St. Louis limestone, of the Sub-car- 
 boniferous, is said to give promise of possessing hydraulic 
 properties at several points in Illinois ; while impure lime- 
 stones of the coal-measures furnish "Parker's cement" 
 in Belmont County, O., and the " Johnstown cement " in 
 Cambria County, Pa. A volume on " Mineral Resources 
 
100 APPLIED GEOLOGY. 
 
 of the United States," published by the United States 
 Geological Survey in 1883, states that limestone suitable 
 for hydraulic cements is found also in California, Oregon, 
 and Washington Territory. The same work gives the 
 United States production of cement for 1882 as about 
 3,250,000 barrels, of about 300 pounds each, of which 
 New York is credited with 2,000,000 barrels, Ulster Coun- 
 ty alone furnishing over 1,500,000 barrels; the vicinity of 
 Louisville, Ky., ranking second as a great producing center. 
 
 Works on building materials which students are recommended to consult. 
 
 " Tenth Census of the United States," Vol. X. 
 
 Prof. James Hall's " Report on Building-Stones." 
 
 Hull, " Building 4fcd Ornamental Stones of Great Britain," etc. 
 
 " Geology of Wisconsin, i873-'79," Vol. I, Part III, chap. iv. 
 
 " Mineral Resources of the United States, 1883," p. 450, et seq. 
 
 Gillmore on " Limes, Hydraulic Cements, and Mortars." 
 
 Totten on " Mortars." 
 
 " Report on Clays of New Jersey," 1878. 
 
 " Geological Report of Minnesota," N. H. Winchell. 
 
 The student should also carefully consult the geologi- 
 cal reports of his own State, by the aid of the index with 
 which they are usually furnished. 
 
CHAPTER VI. 
 
 RELATIONS OF GEOLOGY TO AGRICULTURE. 
 
 IN the organization of the geological surveys of the va- 
 rious States, the advancement of agriculture has in nearly 
 all cases been made one of the leading objects to be at- 
 tained ; yet it is doubtful whether the importance of the 
 relations of geology to the tillage and improvement of the 
 soil is fully realized, especially by those most immediately 
 concerned. Questions as to the origin and distribution of 
 soils ; their character, and how it originated, and by what 
 means it may be most cheaply improved ; the means by 
 which the reproduction of a proper arable surface may be 
 made to keep pace with the natural processes of waste 
 through tillage and other agencies; and the sources of 
 supply and the proper use of mineral fertilizers to make 
 good the necessary losses incurred in cropping all involve 
 considerations of a geological character, and it may easily 
 be seen that they are of no secondary importance. 
 
 Those superficial portions of the unconsolidated sur- 
 face-materials of the earth's crust, usually of but little 
 depth, which are termed soils, with the subsoils extending 
 to variable depths beneath them, are composed chiefly of 
 exceedingly variable mixtures of sand and clay, with con- 
 siderable proportions of vegetable mold and iron oxide, 
 and usually smaller but very important amounts of lime, 
 magnesia, the alkalies potash and soda, and phosphoric 
 acid. 
 
102 APPLIED GEOLOGY. 
 
 These soils and subsoils, like all other unconsolidated 
 earthy materials, have originated from the decay, the dis- 
 aggregation, and the wear of rocks once solid. Rocks de- 
 cay through the chemical action on some of their con- 
 stituents of water holding in solution carbonic acid and 
 other chemical agents, which, penetrating deeply into their 
 pores and crevices, unites with some of their components, 
 and carries them away in solution, leaving the residue in 
 an incoherent state. They are disaggregated, to some 
 extent, by the roots of trees and vegetables, which insinu- 
 ate themselves into their crannies and larger pores, and 
 split them in pieces by progressive growth ; but much 
 more rapidly, in frosty latitudes, by the expansion in freez- 
 ing of water, which is present in some amount in the sub- 
 stance of nearly all rocks. This agency of destruction, 
 which has already been mentioned as a chief cause of 
 dilapidation in building-stones, is a very efficient instru- 
 mentality in the formation and comminution of soils. 
 Rocks are worn away and ground to powder by the fric- 
 tion of sand and of loose fragments of other rocks, dragged 
 over them by moving water, or by blocks and sheets of ice, 
 or which are swept along and dashed against them by the 
 wind. These fragments of rock-materials, set in motion by 
 any of the agencies that have been named, not only wear 
 away the solid rocks, but also, by their mutual rubbing, 
 grind each other down to an ever-increasing degree of 
 fineness, until what were once large angular fragments 
 become rounded pebbles, and ultimately fine mud or sand. 
 Abundant examples of this mode of formation of the ma- 
 terials for soils may be seen, not only in the deep valleys 
 and ravines that have thus been produced, but in the gul- 
 lies filled with worn stones which every rain-storm is 
 likely to make on cultivated slopes ; and also in the rocks 
 of some regions, which are worn and rounded, and even 
 under-cut, by the agency of wind-swept sand. 
 
 The materials of soils and subsoils, originating in the 
 
RELATIONS OF GEOLOGY TO AGRICULTURE. 103 
 
 ways described above, may in some cases occupy very 
 nearly their original position, when their character will 
 naturally be dependent largely on that of the underlying 
 rocks ; while in other cases they have been removed to 
 greater or less distances from their place of origin, and so 
 bear no relation whatever, in character or composition, to 
 the rocks on which they rest. Considered, therefore, with 
 reference to this circumstance only, we have soils of disin- 
 tegration, or those owing their existence to the waste of 
 rocks in place ; and soils of transportation, whose materials 
 have been brought to their present position by agencies 
 such as ice and water from regions often quite remote. The 
 soils of those portions of the eastern and central United 
 States which lie south of the thirty-ninth parallel of lati- 
 tude belong largely to the first class ; while north of this 
 parallel the soils are chiefly soils of transportation. 
 
 Soils of Disintegration. Soils derived from the 
 disintegration of sandstones are, as might be supposed, 
 sandy, containing only those proportions of clay which 
 were present in the original rock. These are frequently 
 sufficient, in the argillaceous sandstones, to form a light 
 sandy loam, lending itself easily to tillage, but apt to be 
 less retentive than could be desired. Shales and soft slates 
 form by weathering clay soils, which, where the rocks 
 are pretty purely argillaceous, are heavy and undesirably 
 compact, difficult to work, but highly retentive both of 
 water and fertilizers. Where, however, shales contain a 
 large proportion of sand, their disintegration produces 
 either clay loams, or those very desirable soils called 
 loams, in which the proportions of sand and clay are so 
 happily adjusted as mutually to correct the defects arising 
 from an excess of either ; and which, while sufficiently 
 easy of cultivation, are also properly retentive of all ele- 
 ments of fertility. The disintegration of limestones is 
 due usually to the gradual solution and removal of the 
 lime which forms their characteristic ingredient. Hence, 
 
104 APPLIED GEOLOGY. 
 
 the soil which arises from their destruction contains no very 
 marked amount of lime, but is composed mostly of the 
 original impurities of the rock, chiefly clay and iron, with 
 sometimes silica, forming usually a reddish clay with rarely 
 more than from one to five per cent of lime. Indeed, 
 some shale soils contain a larger percentage of lime than 
 those derived from the decomposition of limestones, prob- 
 ably because from their retentiveness they have not readily 
 permitted it to be carried away in solution. Soils derived 
 from the wear rather than the disintegration of limestones 
 contain a larger proportion of lime in fine or coarse grains 
 and pebbles ; but these, from the manner of their forma- 
 tion, have been borne to some distance from their place of 
 origin, and have usually been mingled with materials from 
 other sources, to which they impart a useful modification. 
 Soils derived from the disintegration of rocks of the gra- 
 nitic class owe whatever mineral elements of fertility they 
 may possess to the decomposition of the feldspathic, mica- 
 ceous, and hornblendic constituents of these rocks, which 
 furnish a clayey matter retaining some of the alkaline, cal- 
 careous, and ferruginous ingredients of the original miner- 
 als ; and this, mingled with the silica of the rock, may fur- 
 nish, where the decomposition is unusually rapid, a soil of 
 a good degree of fertility. More commonly, the native soil 
 of granitic areas is thin and poor. On the contrary, the 
 soils derived from the decomposition of the traps and other 
 volcanic rocks are usually excellent, having a good texture 
 and color, and being abundantly charged with the alkalies, 
 lime, magnesia, and iron of the minerals entering into such 
 rocks, with almost always favorable amounts of phosphoric 
 acid. 
 
 Soils of Transportation. Soils such as have just 
 been described, which owe their leading characteristics to 
 the nature of the underlying rocks and to the agencies to 
 which these have been subjected, and which often at but 
 little depth beneath the surface exhibit the same essential 
 
RELATIONS OF GEOLOGY TO AGRICULTURE. 105 
 
 structural characters as the parent rock, into which they 
 gradually merge by a diminution in the degree of disin- 
 tegration, differ widely in origin, topographical position, 
 and in some marked features of constitution, from the 
 second kind of soils which have been called soils of trans- 
 portation. The former, with some general exceptions 
 presently to be noted, constitute the fundamental soils of 
 our Southern and central range of States south of a line 
 coinciding rudely with the thirty-ninth parallel of latitude. 
 The latter cover, with few exceptions, those parts of the 
 United States lying north of this limit and all of British 
 America. 
 
 It will be obvious to any one who attentively considers 
 the surface appearance's presented by this latter region, 
 that some widely operative and exceedingly powerful 
 agency has, within a comparatively recent geological pe- 
 riod, been active in shaping its surface features and in ac- 
 cumulating, mingling, and distributing the great irregular 
 sheets of unconsolidated materials with which its rocks are 
 more or less thickly covered. The thoughtful observer 
 will note that the upper surface of the harder rocks ex- 
 posed in quarrying or by the wash of rains is curiously 
 smoothed and scored with fine parallel scratches, or some- 
 times with wider grooves usually running in a nearly north 
 and south direction. His attention will be attracted by 
 the great rudely rounded blocks of stone, sometimes of 
 several tons weight, scattered here and there in the fields, 
 which he can readily see are strangers to his vicinity, and 
 which, if his geological knowledge permits, he may often 
 recognize as similar to the rocky formations of regions far 
 northward of that where they are now found. He will ob- 
 serve that thick sheets of blue and yellow clay, often thick- 
 ly studded with blocks of stone, or irregularly alternating 
 beds of sand and gravel and loam, or sometimes ridges of 
 confusedly intermingled earth and stones, now rest on rocks 
 of widely different character and of much simpler constitu- 
 
106 APPLIED GEOLOGY. 
 
 tion than the materials which cover them. He may even 
 learn from well-excavations, and deep borings in the val- 
 leys of rivers and streams, that many of these now flow 
 scores of feet above their original rocky beds in channels 
 cut in the unconsolidated materials with which they have 
 by some agency been filled. These facts, and some others 
 of similar import which he would probably observe, would 
 be likely to suggest to him that the agent which produced 
 them, whatever it may have been, proceeded from the 
 north ; and that the loose superficial materials which now 
 veil the rocks and fill deep the valleys, and whose fertile 
 upper surface constitutes the soils, probably had their ori- 
 gin to the northward of their present locality. The only 
 known agent that could have produced effects so great and 
 so enormously wide-spread, planing and scoring rocks over 
 areas hundreds of thousands of miles in extent, and trans- 
 porting far from their birthplace great blocks of stone, is 
 the power of a great, slowly-moving sheet of ice, such as 
 that which now envelops a large part of Greenland ; and 
 to such an agent these phenomena are now very generally 
 ascribed. This vast ice-sheet, whose thickness, as judged 
 by the heights which it overtopped, must have been many 
 hundreds or even thousands of feet, enveloped and bore 
 along with it all loose or projecting materials which it en- 
 countered or which dropped upon its surface ; and, armed 
 with these, its under surface became a grinding instrument 
 of enormous power, like a gigantic rasp, by which in its 
 slow progress southward the surfaces of all underlying 
 rocks were worn away and reduced to a fine rock paste, 
 while the pre-existing valleys either were obliterated or 
 were widened and deepened, according as their courses 
 opposed or coincided with the direction of movement of 
 the vast abrading mass. By this means were formed, dur- 
 ing the unknown ages of duration of unusual cold called 
 the glacial period, enormous amounts of what has not in- 
 aptly been called " rock-flour," which, when a warmer cli- 
 
RELATIONS OF GEOLOGY TO AGRICULTURE. 107 
 
 mate again prevailed and the ice-sheet slowly melted, was 
 intermingled more or less completely with the other sub- 
 stances previously frozen into the glacial mass, and cov- 
 ered the surface with the raw materials of a soil of highly 
 complex and varied constitution. With regard to these 
 materials thus brought together it is obvious, first, that, 
 being the result not of disintegration but of wear, they 
 must at the outset have contained the constituents of the 
 parent rocks unchanged ; second, that, from the manner 
 in which they were formed, substances from widely differ- 
 ent sources were likely in most cases to be commingled, so 
 that their composition might be expected usually to be 
 more complex and variable than that of soils derived from 
 rocks in place ; and, third, that they have no relationship 
 to the rocks on which they at present repose other than 
 that of mere accidental juxtaposition. The surface por- 
 tions of these crude materials of soils have since their depo- 
 sition been subjected to the usual atmospheric agencies 
 of disintegration, which have broken up and comminuted 
 in various degrees their coarser portions, have made solu- 
 ble and subjected to the processes of plant-growth parts 
 of their alkaline, calcareous, and phosphatic ingredients, 
 and have mingled the whole with the organic residues de- 
 rived from the decay of successive generations of plants, 
 forming soils such as we now find them in areas not yet 
 subjected to tillage. The subsoils have been subjected in 
 a less degree to these atmospheric agencies, and retain 
 more nearly their original constitution. They are likely, 
 therefore, to be charged with a number of ingredients 
 necessary to plant-growth, in greater abundance than the 
 surface soils, and may, by proper mechanical treatment 
 and by the action of certain natural agencies, restore to 
 them elements of fertility of which they constantly tend 
 to become exhausted, not only by the growth of crops, 
 but also by that slow but incessant removal of the surface 
 to which cultivated fields are subjected by the wash of 
 
108 APPLIED GEOLOGY. 
 
 rains. The most obvious mechanical means by which the 
 proper renewal of the surface soil may be secured is deep 
 tillage and subsoiling. By this means materials hitherto 
 untouched are brought within reach of atmospheric influ- 
 ences which compel them to yield to agriculture any fer- 
 tilizing principles they may possess. Among the natural 
 agencies through which the subsoil appears to react bene- 
 ficially upon the soil may be mentioned the capillary ac- 
 tion of well-conditioned soils and earth-worms. The fine 
 pores of a soil of proper texture not only furnish channels 
 through which the rains sink into the earth, but also, when 
 the surface has become dry, the deeper seated supplies of 
 moisture ascend through their minute tubes by an action 
 termed capillary to supply the losses occasioned by evap- 
 oration, bringing up with them in solution small but im- 
 portant amounts of fertilizing elements obtained from the 
 subsoil which their evaporation leaves in the surface soil. 
 Hence, after periods of drought, when this capillary action 
 is more than usually active, the farmer frequently observes 
 that his fields show more than usual fertility, due without 
 doubt to this cause, which yet in ordinary seasons is con- 
 stantly operating to augment the fertility of well-tilled 
 lands. The humble earth-worms will, doubtless, seem to 
 many a very insignificant agent in promoting the fertility 
 and renewal of soils ; yet the careful observations of the 
 distinguished naturalist, Charles Darwin, have left no room 
 for doubt, not only that the active burrowing of their in- 
 numerable myriads plays a very important part in loosen- 
 ing the soil and making it readily accessible to atmos- 
 pheric agencies of change, but also that their digestive 
 action on the finer soil particles is a highly influential 
 agency in the formation of vegetable mold, and in bringing 
 to the surface sorne deeper seated elements of fertility 
 contained in the subsoil. 
 
 Another kind of soils of transport, by no means con- 
 fined to the region of glacial action that has just been de- 
 
RELATIONS OF GEOLOGY TO AGRICULTURE. 109 
 
 scribed, but found covering areas of considerable extent 
 in all regions, is that which finds its type and exemplar 
 in " bottom-lands." These soils are due to the carrying 
 power of flowing water, which in times of rain collects the 
 wash of the uplands into rivulets, streams, and rivers, all 
 rushing downward, turbid with the earthy matters with 
 which their waters are loaded, until they reach the low- 
 lands, where, when their flow is checked, they deposit first 
 the coarser and then the finer materials that they have 
 transported, gradually filling the hollows and coating the 
 flood-plains of streams and rivers with a soil of exuberant 
 fertility, and whose mass is augmented with every period 
 of flood. Soils originating in this way are not confined 
 wholly to lowlands and to the valleys of rivers and streams ; 
 but, especially in the glacial region, they may be found oc- 
 cupying apparently the ancient sites of vanished pools and 
 lake-like expanses, which were probably formed by the 
 waters of the great melting glacier. 
 
 It may thus be seen that our present arable soils owe 
 their origin, their renovation, and much of their present 
 condition, to the disintegration and wear of rocks ; and 
 that the means by which this work has been done are the 
 chemical action of the atmosphere, and the mechanical 
 force exerted by freezing water, and by moving water and 
 ice. It is needful also to bear distinctly in mind that the 
 mechanical agents, by their own unaided action, can not 
 produce a fertile soil. Their efficiency is limited to their 
 aid in reducing rock materials to a suitable degree of fine- 
 ness, and there it ceases. But the plant-food, locked up 
 in even the finest particles of rock, must be offered to 
 plants in a soluble form before it can be used ; to accom- 
 plish this solution, the co-operation of those native chemi- 
 cal agents contained in the atmosphere must be invoked. 
 The mechanical agencies merely prepare the materials for 
 the freer and more effective action of the real soil-makers, 
 the chemical ones. Now, the agency of man, aided by 
 
HO APPLIED GEOLOGY. 
 
 such natural helpers as capillarity, the roots of deep-grow- 
 ing plants, and burrowing animals, is a mechanical one, 
 and consists in putting the soils which he tills into the 
 best possible condition for the action of the needed chemi- 
 cal agents. The more truly, then, he copies nature, and the 
 more thoroughly he learns to accelerate the slow-moving 
 operations which geological agencies effect, the more suc- 
 cessful his labor is likely to prove. Deferring, then, for the 
 present, any consideration of the fertilizing ingredients of 
 soils, it may be profitable to direct our attention first to 
 their nature and physical condition, and to consider how 
 this may best be improved. 
 
 Nature and Amelioration of Soils. The physical 
 properties, in virtue of which a soil lends itself kindly to 
 culture, are (i) easy penetrability to roots, to moisture, to 
 air, and to fertilizers ; (2) a sufficient retentiveness to pre- 
 vent the ready escape of moisture and of fertilizing ingre- 
 dients ; and (3) readiness to absorb and utilize the solar 
 warmth, for which last property color and texture are essen- 
 tial conditions, dark-colored and permeable soils and light- 
 colored tenacious ones being the opposite extremes in this 
 respect. These physical characters depend essentially on 
 the relative proportions of three substances, viz., silicious 
 sand, day, accompanied usually with a notable amount of iron 
 oxide, and those residues of organic decay which are termed 
 humus. An undue preponderance of sand gives rise to a 
 light soil easy of cultivation, and readily dried and warmed 
 by the heat of the sun, but tending constantly to sterility 
 from the ease .with which it permits all soluble substances 
 to be leached from it by the rains. A like excess of clay 
 forms what is called a heavy soil, very tenacious, retentive 
 in a high degree of moisture and fertilizers, and capable 
 of giving a firm foothold to plants, but cold, impermeable, 
 and difficult to till. Where humus preponderates, we have 
 a peaty or turfy soil, which, when properly drained, is 
 warmed and dried with wonderful rapidity, but which 
 
RELATIONS OF GEOLOGY TO AGRICULTURE, m 
 
 gives little support to plants, is apt to be sour from car- 
 bonic and other acids, and is usually deficient in some 
 highly essential mineral elements of plant-food. So far 
 as physical constitution is concerned, therefore, that soil 
 is best " whose condition, equally removed from too great 
 compactness and too great permeability, fits it to absorb 
 and retain the due amount of moisture while giving easy 
 exit to any overplus, to permit the ready access of air, and 
 to absorb and utilize the warmth proper to its location." 
 To judge from a comparison of many analyses, such a soil 
 would contain from sixty to eighty-five per cent of sand, 
 from ten to thirty per cent of clay and iron oxide, and 
 from five to ten per cent of humus. Where a soil, from an 
 excess of any component, does not naturally possess a 
 proper texture, it stands in need of amelioration ; and the 
 means by which this may be best and most cheaply effected 
 will naturally depend on the nature of its defect : it is also 
 well to observe that amendments of the soil, i. e., bene- 
 ficial changes in its condition and texture, should precede 
 the application of manures, inasmuch as they prepare it in 
 some cases to retain the fertilizing principles, and in all 
 cases to derive the fullest benefits from their use. 
 
 An obvious means for improving sandy soils is mixture 
 with clay to increase their retentiveness, and where this is 
 found, as is sometimes the case, at no great depth in the 
 subsoil, this improvement may be effected at no undue 
 expense. Very great benefit may also be derived by treat- 
 ing such a soil with either variety of quicklime, or with 
 clayey marls, either of which, while improving its texture, 
 adds to it an important element of plant nutrition, in which 
 such soils are apt to be deficient. The tillage of sandy 
 soils should also be shallow, three inches in depth being 
 probably quite sufficient, and every means should be used 
 both to retain and increase any original solidity they may 
 possess. 
 
 Turfy or peaty soils and swamp mucks contain a su- 
 
112 APPLIED GEOLOGY. 
 
 perabundance of humus, in virtue of which their materials 
 may be profitably composted with manures, and used to 
 improve other soils which are deficient in this ingredient. 
 Mucky soils need first of all as careful drainage as is prac- 
 ticable, and then thorough treatment with quicklime and 
 mixture with coarse, gravelly sand and animal manures. 
 
 Heavy clay soils need first of all thorough under-drain- 
 ing to remove the superfluous water with which they are 
 apt to be clogged, and by which they are rendered both 
 adhesive and difficult to be warmed. By the removal of 
 this superabundant moisture, the texture of such soils is 
 at once very materially improved. Their texture may then 
 be further loosened and made more pulverulent by treat- 
 ment with quicklime, by admixture with coal-ashes, or by 
 burning portions of the surface in ridges or heaps with 
 dried leaves and weeds or brush, and then mingling the 
 burned portions with the remaining soil. Deep and rough 
 plowing of heavy soils in the late autumn permits advan- 
 tage to be taken of the powerful pulverizing action of 
 winter frosts. It has also been suggested that, in the vi- 
 cinity of iron - furnaces, their slags, previously rendered 
 pulverulent by being run from the furnace into shallow 
 pools of water, could be utilized advantageously for light- 
 ening the texture of heavy soils, adding to them also 
 some elements of value in the compounds of lime and 
 iron, and the small amounts of phosphorus which they 
 contain. Doubtless the slags from the basic process, re- 
 cently devised for the elimination of phosphorus from 
 iron, containing as they do a considerable percentage of 
 this element, will be found especially useful for this pur- 
 pose, because of their unusual content of this valuable 
 fertilizer. 
 
 Besides that proper physical condition which has just 
 been described, with some of the means for its promotion, 
 and which fits a soil to give suitable support to growing 
 plants, to permit the easy spread of their roots in search 
 
RELATIONS OF GEOLOGY TO AGRICULTURE. 113 
 
 Chlorine. 
 
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114 APPLIED GEOLOGY. 
 
 of nourishment, to favor a proper circulation of air, and 
 to retain the moisture needed for plant-growth while yield- 
 ing ready outflow to all excess, every fertile soil must pos- 
 sess also sufficient amounts of the inorganic substances 
 and nitrogen which enter into the tissues of plants. What 
 are the inorganic substances appropriated from the soil 
 by the various cultivated plants can be learned from the 
 analyses of their ashes, and a table of such analyses for a 
 number of common plants, derived from French authori- 
 ties, is given on the preceding page. 
 
 Tables of the mineral components of the above plants, 
 derived from the ash analyses of Emil Wolff, may also be 
 found in the Geological Report of Ohio for 1870, pages 
 366 and 367, which, while differing somewhat from the 
 above in the relative proportions of some constituents, 
 present no material differences in the substances them- 
 selves, and these, as they are present in some proportion, 
 doubtless subject to considerable variations, in the tissues 
 of all cultivated plants, are obviously essential to their 
 growth and health. These substances must, with slight 
 exceptions, be supplied by the soil ; and a very impor- 
 tant part of scientific agriculture consists in knowing by 
 what means to keep up in the soil a due amount of these 
 important constituents, which would otherwise tend to ex- 
 haustion by successive cropping. Some of these, like silica 
 and iron, need little attention, being present in sufficient 
 amounts in nearly every soil, and being rendered readily 
 available for plant- growth by natural causes. In many 
 soils, lime and magnesia also are found in proportions 
 sufficient to supply the needs of a long series of crops, 
 while in others there is a deficiency of these substances. 
 An average soil will give about two million pounds per 
 acre, for a depth of eight inches. If, then, it contains one 
 per cent of lime, this will make available with ordinary 
 cultivation at least 20,000 pounds per acre. It will be 
 seen, by reference to the table, that tobacco is the most 
 
RELATIONS OF GEOLOGY TO AGRICULTURE. 115 
 
 exhaustive of lime among the common crops, containing 
 about 9^ pounds per hundred of dried leaves, or 190 
 pounds per ton. It would require, therefore, one hun- 
 dred crops of a ton per acre much more than the usual 
 crop to exhaust this element from a soil containing one 
 per cent. It is obvious that this is an extreme case for 
 any soil ingredient. For an ordinary rotation of crops, 
 one per cent of lime or magnesia in a soil would suffice 
 for a long succession of crops. It may be observed that, 
 among the cereals, lime predominates in the straw and 
 magnesia in the grain. Hence the latter is likely to tend 
 to more rapid exhaustion than the former, since, in good 
 farming, the straw is mostly returned to the soil in the 
 form of manure. 
 
 Of the mineral ingredients of soils, those that need 
 most attention are phosphoric acid and the alkalies potash 
 and soda, especially potash, which, as may be seen by the 
 table, enters largely into most cultivated plants. It is 
 justly thought, therefore, that phosphates, potash, and ni- 
 trogen are vital points in the art of fertilization ; and a 
 high authority says, " A fertilizer may be considered com- 
 plete when it contains lime, potash, lime phosphate, and 
 a nitrogenous substance." Before considering the geo- 
 logical means which may be made available for keeping 
 up the fertility of the soil, it will be well to examine a few 
 analyses of soils of various kinds ; for, although questions 
 are often raised as to their practical value, based on the 
 local variability of soils, yet there can be no reasonable 
 doubt that, when properly made after careful sampling, 
 they may be of the greatest service to the agriculturist 
 in revealing to him the capabilities of his soils and their 
 needs. 
 
 The soil No. 3 of the Barrens is striking, from its de- 
 ficiency in phosphoric acid, the alkalies, and organic mat- 
 ter ; and its very small proportion of alumina, the basis of 
 clay, shows it to be excessively leachy, whence, doubtless, 
 
u6 
 
 APPLIED GEOLOGY. 
 
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RELATIONS OF GEOLOGY TO AGRICULTURE. 117 
 
 its deficiencies originate. Soil No. 5 probably owes its 
 exhaustion to its low proportion of organic matter and of 
 lime. Nos. 7, 8, and 9 abound in fertilizing elements, but 
 would be likely to need attention to their physical condi- 
 tion. No. 4, which is considered still good after a cent- 
 ury of culture, though evidently not abounding in organic 
 matter, has in eight inches of depth, on the moderate 
 estimate of two million pounds to the acre 
 
 Phosphoric acid, 3,000 pounds per acre. 
 Potash, 14,800 
 
 Lime, 19,400 
 
 Magnesia, 15,000 
 
 Using now the table of ash analyses and per cent of 
 ash given on a preceding page, it may be seen that a 
 crop of twenty-five bushels of wheat = 1,500 pounds, if 
 the straw, etc., equals fifty-six per cent of the crop, will 
 take from the soil 
 
 Phosphoric acid, 11.175 pounds in grain and 4.1 pounds in straw. 
 Potash, 5^ 18.1 
 
 Lime, -j% 4j 
 
 Magnesia, 2j 
 
 Several other crops draw much more of these ingredi- 
 ents from the soil. An estimate made in the " Geological 
 Report of New Jersey," 1879, at page 116, of the amounts 
 of important minerals withdrawn from the soil by a five 
 years' rotation, of clover two years, and Indian corn, pota- 
 toes, and wheat, each one year, gives 581 pounds potash, 
 259 pounds lime, and 179 pounds phosphoric acid, of which, 
 however, nearly all the lime, and considerably more than 
 one half of the potash and phosphoric acid found in the 
 clover, straw, corn-stalks, and potato-tops would, in care- 
 ful farming, be retained on the estate and returned to the 
 soil in the form of manure. The tables that have been 
 given, and the specimen of computations that may be 
 based on them, will serve to indicate the proportions of 
 
Il8 APPLIED GEOLOGY. 
 
 essential mineral elements that are found in various fertile 
 soils, the approximate amounts that are certain to be with- 
 drawn from them by various crops, and the importance of 
 restoring to them in some form the fertilizing principles 
 that have been withdrawn, to prevent a progressive ex- 
 haustion. An examination of Table I will show that, 
 while lime preponderates over magnesia in the straw of 
 the various cereals, the reverse is true for the grain ; and 
 when to this is added the fact that magnesia, from its great 
 power of absorbing and retaining moisture, tends to give 
 freshness to soils, it will suggest the expediency of testing 
 magnesian quicklime on soils in which lime is deficient, 
 despite the prejudice against it. 
 
 Geological Fertilizers. Recalling now to mind the 
 native composition of fertile soils, and that the constant 
 tendency of the most judicious cultivation is to withdraw 
 from them certain substances of capital importance, espe- 
 cially nitrogenous compounds, the phosphates, the alkalies 
 potash and soda, as also lime and magnesia, it becomes a 
 question of much importance what materials the earth's 
 crust can supply to enhance the fertility of the soil without 
 undue expense. Among these substances, one of the most 
 widely distributed and cheaply available is peat, or swamp- 
 muck. There are few localities in the Northern United 
 States or Canada where it does not occur, and often in de- 
 posits of very considerable extent, in marshy spots, or at 
 small depths beneath the surface, occupying the sites of for- 
 mer swamps and ponds. It not only improves the color of 
 soils, making them more readily warmed, and their texture, 
 rendering them more pulverulent and more retentive of 
 moisture, but it also adds to them small but important 
 amounts of alkalies, and often phosphoric acid, while by 
 its decomposition it furnishes to growing plants supplies of 
 nitrogen and carbonic acid ; and it is claimed that it also 
 absorbs ammonia from the air. It should be weathered in 
 heaps for some months before being used ; or, better, it 
 
RELATIONS OF GEOLOGY TO AGRICULTURE. 119 
 
 may be composted in various ways. It may be composted 
 with barn-yard manures, to which it not only adds its own 
 fertilizing principles, but aids very materially in retaining 
 the nitrogenous substances which might otherwise be dis- 
 sipated in the process of fermentation. It is also com- 
 posted with quicklime, or with lime and a small amount 
 of salt, a good mixture being, it is said, a bushel of freshly 
 slaked quicklime, or of lime slaked by brine, to twenty 
 bushels of peat. " Experience has fully sustained its 
 claims as a useful fertilizer, and chemical analysis shows 
 that it contains the elements needed to stimulate the growth 
 of farm-crops." (" Geology of New Jersey," 1868, p. 486.) 
 
 Another widely diffused mineral fertilizer, previously 
 mentioned in another connection, is lime, which is already 
 much used in agriculture, and is destined, doubtless, to a 
 much wider application, with the spread of better methods 
 of tillage. Not only those wide-reaching formations of cal- 
 citic and magnesian limestones, mentioned in the section 
 on building materials, but also thinner and more locally 
 developed seams, little regarded as building-stones, and 
 somewhat too largely charged with impurities to be favor- 
 ites for mortars, may furnish cheap local supplies for agri- 
 cultural uses, benefiting the soil as well by the silicates 
 and sulphates of lime developed in the burning, as by the 
 caustic lime and magnesia which they furnish in their most 
 finely divided and active form. These, as has already 
 been remarked, make clay soils lighter and silicious ones 
 more firm, lighten and sweeten damp and turfy soils, and 
 contribute to the destruction of weeds and insects, while 
 furnishing elements which analysis shows to be essential 
 to the growth of most cultivated plants. Their efficiency 
 in promoting the solution of other constituents of the soil 
 is also, doubtless, very considerable. To derive the fullest 
 benefits from their use, their application should usually be 
 followed by that of organic manures. 
 
 Besides the use of quicklime as a fertilizer, a stimulant, 
 
120 APPLIED GEOLOGY. 
 
 and a solvent, benefit would doubtless be derived by many 
 soils from the application of calcareous marls, where they 
 may be obtained in the immediate neighborhood. Such 
 marls may be found, usually in small ponds, in some por- 
 tions of the Northern and Eastern States, where they are 
 occasionally burned for lime ; but their original pulveru- 
 lent condition permits their application to the soil in their 
 raw or unburned state, where their action as a source of 
 lime is more gradual and prolonged than that of caustic 
 lime. Also, under many peat-beds is found a calcareous 
 marl, formed of fresh-water shells, which may be advan- 
 tageously used for the same purpose. Beds of calcareous 
 marls of marine origin are extensively developed in the 
 Cretaceous and Tertiary formations of the States bordering 
 the Atlantic and the Gulf of Mexico, from New Jersey 
 southward, which, besides their carbonate of lime, contain 
 often important amounts of potash and phosphoric acid, 
 and which are destined to be largely used in the regions 
 where they occur. 
 
 Of greater importance, however, than these last-named 
 marls are the greensand or glauconitic marls, which are 
 found in similar geological formations and in the same re- 
 gions, and which derive their chief value from the very im- 
 portant proportions of potash and phosphoric acid with 
 which they are charged. These marls have been very largely 
 used in New Jersey, where they abound in three beds of 
 somewhat different properties ; and the effects that have 
 followed from their use are thus strongly stated by Prof. 
 Cook, "Geology of New Jersey," 1868, page 442 : " The 
 marl which has been described in the preceding pages has 
 been of incalculable value to the country in which it is 
 found. It has raised it from the lowest stage of agricult- 
 ural exhaustion to a high state of improvement. . . . Lands 
 which in the old style of cultivation had to lie fallow, by 
 the use of marl produce heavy crops of clover and grow 
 rich while resting. Thousands of acres of land which had 
 
RELATIONS OF GEOLOGY TO AGRICULTURE. 121 
 
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122 APPLIED GEOLOGY. 
 
 been worn out and left in commons are now, by the use 
 of this fertilizer, yielding crops of the finest quality. In- 
 stances are pointed out everywhere in the marl district, of 
 farms which in former times would not support a family, 
 but are now making their owners rich from their produc- 
 tiveness. Bare sands, by the application of marl, are made 
 to grow clover, and then crops of corn, potatoes, and 
 wheat." The work from which this is quoted gives, in the 
 succeeding pages, an account of the mode of using this 
 fertilizer and its results, which the student can profitably 
 consult ; as also Prof. Kerr's " Report on North Carolina 
 Geology," 1875, in which will be found an account of the 
 Tertiary calcareous marls of that State and their great value 
 in agriculture. On page 121 are given a few analyses of 
 greensand marls from New Jersey which may be found use- 
 ful, those being selected which have been approved in use. 
 It will be observed that in all these marls phosphoric 
 acid is present in considerable proportion, and to this sub- 
 stance much of their efficiency is ascribed. In many of 
 them, -also, potash is found in very considerable amounts, 
 and there is no good reason to doubt that its liberation in 
 the soluble form, in the course of the decompositions that 
 go on in the soil, gradually furnishes to plants this impor- 
 tant element in their nutrition. Of the silicic acid, a very 
 considerable proportion exists in an easily soluble condi- 
 tion ; and when it is considered how large a proportion of 
 this substance is found in the stems of plants, the prob- 
 able significance of this fact will be apparent. Doubt- 
 less, some other elements in these fertilizers, especially 
 lime, aid in enhancing their value. The use of these marls 
 in New Jersey is fully 100,000 tons per year, 1,080,000 
 tons having been dug in that State in 1882 for use and ex- 
 port ; and it is certain that with the advancement of agri- 
 culture in the Southern seaboard and Gulf States, in which 
 these and other marls are known to occur, they will be 
 sought out and used with great benefit to agricultural in- 
 
RELATIONS OF GEOLOGY TO AGRICULTURE. 123 
 
 terests ; though, from the few analyses at present attain- 
 able, it would seem that the greensand marls are not there 
 so rich in phosphoric acid and potash as those of the more 
 northern localities. 
 
 A rich supply of the phosphates needed in agriculture 
 is obtained from the region in the vicinity of Charles- 
 ton, S. C, where it is estimated that nearly eight hundred 
 square miles are underlaid more or less abundantly 
 with phosphatic masses, of which twenty thousand acres 
 are counted worth working with the present appliances for 
 obtaining it. In this region, the phosphatic nodules are 
 found along the courses and in the beds of streams, from 
 which they are dredged, or underlying the surface at vary- 
 ing depths in a stratum which, according to Prof. Holmes, 
 averages about fifteen inches in thickness. It is reported 
 that, in 1883, 332,079 gross tons were produced, the rock 
 being sold on a guarantee of containing not less than 
 55 per cent of lime phosphate, or about 25 per cent of 
 phosphoric acid ; and in the same year the shipments 
 of manufactured fertilizers from Charleston are reported 
 as amounting to 130,000 tons. These figures will give an 
 idea of the vast extent to which the supply of this valu- 
 able fertilizer has already attained, from a source whose 
 importance had not come to be understood so recently as 
 1868. 
 
 Another source of phosphoric acid which is rapidly 
 attaining importance in this country is found in the mineral 
 apatite, which occurs as beds and veins in rocks, chiefly of 
 Archaean age. Deposits which may prove of economic 
 importance occur at Bolton, Mass., and at Crown Point, 
 N. Y., the latter of which is said to be extensive and has 
 been mined to a limited extent. The deposits of greatest 
 present importance are those found in Canada, in a region 
 extending northeastwardly from near Kingston in Ontario, 
 into Ottawa County, Province of Quebec. The deposits 
 here occur in both beds and veins, of which the former 
 
124 APPLIED GEOLOGY. 
 
 afford the largest and purest supplies. The amount mined 
 in 1883 reached, it is said, 23,000 tons of rock, containing 
 from 75 to 85 per cent of lime phosphate. A small por- 
 tion of this comes to the United States, but most of it is 
 sent to England, where it is made available for agriculture 
 by treatment with sulphuric acid. 
 
 Guano, also, which attains to the rank of a kind of 
 geological deposit on certain islands off the coast of Peru, 
 and to some extent of Africa, may pioperly be mentioned 
 here. These deposits, formed from the droppings and 
 remains of sea-fowls, during countless generations, in re- 
 gions nearly rainless, are very rich in compounds of am- 
 monia and phosphorus, and have for forty years been 
 largely imported into Europe, and to some extent into this 
 country, for use in agriculture. According to estimates 
 made in 1873 of the amounts then remaining available, the 
 supply is destined to speedy exhaustion, as at that time 
 less than twenty years' supply could apparently be count- 
 ed on. 
 
 A geological source of the nitrogen so needful for plant- 
 growth may be found in the waste from the distillation of 
 bituminous coal in gas-making and coking. Nearly all 
 the bituminous coals of Ohio and Indiana which have 
 been fully analyzed show a content of nitrogen amounting 
 to an average of about one and a half per cent, and the 
 same is doubtless true of other coals of this class. In 
 the process of distillation this nitrogen is driven off in the 
 form of ammonia, which may be converted into the sul- 
 phate or used to increase the ammonia in the compost- 
 heap. 
 
 A mineral fertilizer very largely used as a top-dressing 
 for various crops, especially clover and Indian corn, is 
 ground gypsum, commonly known as land-plaster. This 
 substance is a sulphate of lime, and there is a wide diversity 
 of opinion as to the cause of the surprising results attending 
 its use in many cases. The Atlantic seaboard States are 
 
RELATIONS OF GEOLOGY TO AGRICULTURE. 
 
 12$ 
 
 supplied with it from Nova Scotia, where it is found in 
 enormous beds in rocks of Lower Carboniferous age. 
 New York has large deposits in rocks of the Salina period, 
 ranging from Oneida County westward, near the line of 
 the Erie Canal ; and it is quarried at many places and 
 shipped to considerable distances, both ground and un- 
 ground. Near Sandusky, O., it is obtained from rocks of 
 the same age, and prepared both for agricultural use and 
 for plaster of Paris. The great deposits in Michigan, 
 along Saginaw Bay and near Grand Rapids, are found in 
 rocks of the Lower Carboniferous ; and those at Fort 
 Dodge, Io., are associated with rocks of the same age, 
 these last deposits being of especial interest, because fur- 
 nishing this fertilizer to an extensive region otherwise 
 nearly destitute of it. Important beds of gypsum occur 
 in two sections of Kansas, in the western part of Virginia 
 on a branch of the Holston River, and in Pike County, 
 Ark., while vast supplies of it are known to exist in the 
 Triassic rocks of Texas. Great beds and lenticular masses 
 of this substance, often of wonderful purity, are known to 
 exist in nearly all the States and Territories of the far 
 West, partly, as in Arizona, in rocks of the Carboniferous 
 period, but chiefly in beds of the Triassic or of still later 
 geological age. It will thus be seen that most sections of 
 the United States and of the British Provinces are abun- 
 dantly supplied with this mineral fertilizer, and that it 
 occurs chiefly in rocks of the Salina, the Lower and Upper 
 Carboniferous, and Triassic periods. The European de- 
 posits are found chiefly in the Permian and Triassic, some 
 also occurring in the Eocene Tertiary. Besides their use 
 as fertilizers, many of these gypsum deposits are of suffi- 
 cient purity to be available for use in the arts as plaster of 
 Paris, more particular mention of which will be made in 
 another connection. 
 
 Common salt, also largely used as a fertilizer to supply 
 to plants soda and chlorine, is very widely distributed 
 
126 APPLIED GEOLOGY. 
 
 over the United States and Canada, being obtained chiefly 
 from brine-wells sunk in rocks of the Salina period, in 
 western New York, largely at Syracuse and Warsaw, and 
 at Goderich in the Province of Ontario ; and in rocks of 
 the Lower Carboniferous and Carboniferous periods in 
 eastern Michigan, West Virginia, and the adjacent part of 
 Ohio. Great deposits of rock-salt are found at Petit Anse 
 in Louisiana, in materials of somewhat recent geological 
 formation, and throughout the far Western and Pacific 
 States and Territories abundant supplies await the devel- 
 opment of those regions. In these latter regions are also 
 found at several points mixtures of salt with sulphates and 
 nitrates of potash and soda, affording substances which 
 must ultimately become of great importance in agriculture 
 as sources of nitrogen and potash. Similar crude salts 
 are obtained for use in agriculture and for other purposes 
 from South America in the rainless western regions ; and 
 crude salts of potash used in European and American ag- 
 riculture are obtained from beds occurring in the Permian 
 salt deposits of Stassfurt in Germany. 
 
 What have here been briefly enumerated and described 
 are the chief fertilizers supplied to agriculture from geo- 
 logical sources, and the judicious use of which may be ex- 
 pected to increase largely the productive capacity of the 
 soil. The beneficial effects of some of these are produced 
 at once, and are quite limited in their duration, while 
 others, acting more gradually, constitute a permanent im- 
 provement of the soil. Both of these classes of fertilizers 
 may be used with advantage; but questions of expense 
 incurred, as compared with benefits received and returns 
 obtained, depend on many circumstances which belong 
 rather to the science and art of agriculture than to applied 
 geology. 
 
 Drainage and Subsoils. The geological considera- 
 tions which influence drainage, whether undertaken in the 
 interests of agriculture, or for the promotion of healthful 
 
RELATIONS OF GEOLOGY TO 
 
 surroundings, or for the reclamation of waste lan< 
 already been suggested on page 64. They consist in the 
 presence of a sufficient declivity to insure the easy passage 
 of water through under-drains, and ultimately the free 
 outflow of the collected waters of drainage, or, in the case 
 of flat-lying districts, in the possible existence in the sub- 
 soil or underlying rocks of porous beds or fissured and 
 jointed strata, which may serve as water-ways and afford 
 an underground outlet to drains and cess-pools ; or, on a 
 larger scale, in the removal of geological barriers and ob- 
 structions caused by geological agencies, such as have con- 
 verted tens of thousands of acres in central New York 
 into the pestilent fen called the Montezuma Marsh. An 
 example of the reclamation of a similar district by the re- 
 moval of a barrier has recently been presented by the suc- 
 cessful draining of the " Great Meadows " in Warren 
 County, N. J., where an area of five thousand five hun- 
 dred acres has been opened to cultivation, while the sur- 
 rounding region has been freed from a fruitful breeding- 
 place of malarial diseases. In all cases of difficult drainage 
 examination should be made of the structure of what lies 
 beneath the soil. Not unfrequently it may be found that 
 the need of drainage arises from the presence of a com- 
 paratively thin crust of hard-pan, and that if this be broken 
 up the difficulty will disappear. In a much greater pro- 
 portion of cases than would be supposed, also, porous or 
 fissured strata at no very considerable depths will furnish 
 an easy outlet for both farm and house drains, promoting 
 at the same time agricultural fertility and personal health 
 and comfort. Prof. Emmons, in his report on New York 
 agriculture, vol. i, calls marked attention to this too often 
 neglected means of drainage. Such an examination can 
 be easily and cheaply made, and, though it may not be 
 needed for the purpose of facilitating drainage, it will re- 
 veal to the agriculturist the nature and resources of his 
 subsoils, giving him information which is second in im- 
 
128 APPLIED GEOLOGY. 
 
 portance only to a knowledge of the capabilities and needs 
 of the soil ; for the subsoil may aggravate the defects of 
 the arable surface by its tenacity or its permeability, or, 
 on the other hand, it may furnish a ready means of reme- 
 dying these defects by beneficial mixtures. Very fre- 
 quently it will be found capable of restoring to the soil 
 elements of fertility of which it may be measurably ex- 
 hausted, or it may even be found to contain at no great 
 depth unsuspected deposits of valuable fertilizers, as has 
 been found true already in many sections of our country. 
 Expedient as such careful examinations clearly are in all 
 ordinary cases, their importance becomes especially great 
 in regions where valuable fertilizers are known sometimes 
 to occur, as well as in those where it may reasonably be 
 suspected that deposits of valuable minerals like iron and 
 coal may exist. It has frequently happened that estates 
 have been sold merely for their value as farming-lands, 
 from the mineral resources of which well-instructed in- 
 vestors have derived great wealth wealth, too, which the 
 former owners might have shared had they taken the pains 
 to make or procure a proper examination of their lands. 
 Scientific surveys made by governments can afford little 
 benefit to those who permit themselves to be ignorant of 
 their results, or who neglect to apply their teachings by 
 such careful local examinations as they ought obviously to 
 
 suggest. 
 
 Works which may profitably be consulted. 
 
 In general, the Geological and Agricultural Reports of one's own 
 State. " Natural History of New York, Agriculture," vol i ; " New 
 Jersey Geological Report," 1868, pp. 378-500; and 1879, pp. 103- 
 120; "Ohio Geological Report," 1870, pp 320-381 and pp. 452- 
 459; "Second Geological Report of Arkansas," p. 42-54 and pp. 
 171-179, etc. ; " Geological Report of North Carolina," 1875, pp. 
 162-217. The " Annual Report of New Jersey for 1870 " also con- 
 tains an account of the drainage of marshes. I have also been greatly 
 indebted in the preparation of this chapter to the following French 
 works : Meugy, " Geologic Applique"e a 1'Agriculture," and D'Orbigny 
 et Gente, " Geologic Applique"e aux Arts et a 1'Agriculture." 
 
CHAPTER VII. 
 
 RELATIONS OF GEOLOGY TO HEALTH. 
 
 Two highly essential conditions of health for both in- 
 dividuals and communities are supplied by wholesome 
 water and pure air. Indeed, it can not be doubted that a 
 large part of the diseases to which human beings are liable 
 is due to the lack of one or both of these essentials. Both 
 are very largely dependent on geological agencies, or on 
 geological structure ; and hence it is proper that the im- 
 portant subject of sanitation should be considered here in 
 its geological aspects. 
 
 The purely geological sources of water-supply have al- 
 ready been discussed in the chapter on springs, wells, and 
 artesians, in which also were pointed out the dangers of 
 contamination, and the precautions needed in some cases 
 to secure a tolerable degree of purity. The importance 
 of the subject is so great, however, that there is little dan- 
 ger of its being pressed too strongly upon public attention ; 
 since, even with the wide diffusion of information with 
 regard to it, large numbers of people thoughtlessly persist 
 in exposing both health and life to imminent risk by the 
 use of readily obtainable water-supplies from sources pe- 
 culiarly liable to contamination, while quite generally also 
 showing a disposition to attribute the disorders resulting 
 from this carelessness to some other than the real cause. 
 Doubtless, a considerable portion of diseases incident to 
 the settlement of some of our new territories could be 
 
130 APPLIED GEOLOGY. 
 
 avoided by the use of filtered rain-water ; while in thick- 
 ly settled villages and cities, the water of all wells, save 
 those most favored by the underground structure, and 
 most carefully guarded, can be used only at great risk 
 to health. Even in the case of deep driven wells passing 
 through thick beds of clay, a source of danger has re- 
 'cently been revealed, in the occasional corrosion of the 
 iron tubing by foul superficial waters, which may thus 
 gain unsuspected access to the domestic supply, suggest- 
 ing the expediency of a frequent examination of these 
 tubes, possibly by drawing up to view the portion that is 
 exposed to risk of corrosion. In any use of the water 
 from wells and from springs, save those from exception- 
 ally deep-seated and remote sources, safety can be assured 
 only by the exercise of intelligent care at the outset, and of 
 constant vigilance afterward. So limited, however, is the 
 supply from most of the geological sources, and so great 
 is the risk of dangerous contamination in those most 
 widely used, that nearly all large cities seek their water 
 from other sources. Many, like Philadelphia and St. 
 Louis, draw their supplies from the higher reaches of riv- 
 ers on which they are situated, trusting to the purifying 
 effects of atmospheric exposure to so far free the waters 
 from the organic impurities with which they are more or 
 less largely charged as to bring them within reasonable 
 limits of safety ; this source of supply being open to the 
 obvious objection that, whatever may be the present con- 
 dition of the water, it is sure to undergo a progressive de- 
 terioration from the growth of cities, villages, and manu- 
 factories on the upper course of the river, all of which will 
 discharge their waste into it ; not to speak of the impor- 
 tant increase in amount of organic matter that must find 
 its way into it from fields coming more widely into a high 
 state of cultivation. Other cities, like Chicago and Cleve- 
 land, drive expensive tunnels far out beneath great bodies 
 of fresh water, where the geological nature of the bottom 
 
RELATIONS OF GEOLOGY TO HEALTH. 131 
 
 makes this feasible, deriving thereby abundant and unob- 
 jectionable supplies. Still others, like New York, construct 
 costly dams and reservoirs and aqueducts, to gather and 
 bring water from distant, sparsely settled, and elevated dis- 
 tricts ; in which case many important circumstances need 
 to be carefully weighed, some of which, and those of no 
 minor importance, involve questions of geological structure. 
 For not only is it necessary to consider the average amount 
 of rainfall and the extent of gathering-ground, but also the 
 geological character of the entire area becomes a matter 
 of serious importance, since it is sure to influence the 
 character of the water derived from it, and to condition 
 both the feasibility and the expense of the dams that are 
 to be constructed, and the ability of reservoirs to retain 
 the water that may be collected into them. The water 
 derived from a granitic area of catchment will differ 
 greatly from that drawn from a limestone region, or from 
 one underlaid with ferruginous sandstones and shales, and 
 containing, it may be, considerable tracts of swampy 
 ground. It is worthy of observation, also, that those dis- 
 tricts which are likely to yield the most unobjectionable 
 supplies of water are those least likely in the course of 
 time to attract a numerous population, and thus to furnish 
 an ultimate source of defilement. So, too, " the rocks of 
 one glen may be retentive and eminently suited for a 
 reservoir, while those of another may be so porous as to 
 cause perpetual leakage ; the rocks and springs of one 
 tunneled aqueduct might be innocuous to the supply, 
 while those of another might contaminate it with sa- 
 line and metallic impurities." (Page's "Economic Geolo- 
 gy.") It is evident, then, that the problem of wholesome 
 water-supply is by no means a very simple one, requiring, 
 in the case of small communities, the intelligent applica- 
 tion of geological principles and precautions ; while, 
 where great numbers are to be provided for within small 
 areas, it may tax the resources of the highest engineer- 
 
132 
 
 APPLIED GEOLOGY. 
 
 ing ability, aided by no slight knowledge of structural 
 geology. 
 
 The securing of pure and healthful atmospheric condi- 
 tions is, in a very large degree, a matter of proper drain- 
 age. Malarious localities are usually wet or at least damp 
 ones, those in which certain forms of vegetation flourish 
 and decay, giving rise to unhealthful exhalations, to which 
 any organic waste from neighboring dwellings adds a deep- 
 er taint. When the damp spot is dried, the wet or marshy 
 tract drained of its superfluous water, the peculiar prod- 
 ucts of organic decomposition which cause disease cease 
 after a time to be supplied, and the region becomes more 
 salubrious. Drainage for sanitary purposes, as well as for 
 agricultural improvement, depends in numerous cases on 
 expedients suggested by facts of geological structure. Ac- 
 cording to the testimony of the Geological Survey of New 
 Jersey ("Report" of 1880), the drainage of the Great 
 Meadows in that State by the removal of a geological ob- 
 struction has been quite as marked a success for sanita- 
 tion as for agriculture, as is shown in the striking decrease 
 of malarial diseases in the surrounding region. This is 
 but one of many instances that could be given, where the 
 sanitary improvement of considerable tracts of *' drowned 
 lands " could be effected by the removal of geologically 
 formed barriers to drainage. The reports of engineers 
 show that the vast malarial region previously mentioned 
 as the Montezuma Marshes, in central New York, owes 
 its existence to such a barrier, and that its restoration to 
 healthfulness can be effected only by the removal of this 
 barrier. Of similar import is the necessity for sanitation, 
 in grading portions of cities where great hollows occur 
 surrounded by impervious barriers, of making sufficient 
 provision for the under-drainage of these hollows before 
 filling them up for building. Otherwise, even if unobjec- 
 tionable materials are used in the filling, they are destined, 
 through percolation from the streets and leakage from im- 
 
RELATIONS OF GEOLOGY TO HEALTH. 
 
 133 
 
 perfect sewers, to become ultimately subterranean reser- 
 voirs of filth, the emanations from which can not but affect 
 unfavorably the health of such localities. The sewerage 
 systems of cities will always present some questions of 
 geological significance. The course of the main sewers is 
 naturally dictated by the slope of the ground, the oppor- 
 tunities for safe outlet, and, not unfrequently also, by the 
 relative expense of excavation. Besides this, in some lo- 
 calities, the only desirable object may be the safe convey- 
 ance of sewage, while in others it may be highly desirable 
 to provide also for the drainage of wet tracts ; such con- 
 siderations, in either case, controlling the choice of the 
 materials with which the sewer should be constructed. In 
 villages and small cities, where no general sewerage sys- 
 tem is provided, the needful sanitary arrangements for 
 dwellings must depend mainly upon supplying subterra- 
 nean outlets through porous beds for superfluous or con- 
 taminated fluids. Where, from the nature of the under- 
 ground structure, such drainage is not practicable, careful 
 provision should be made for the frequent disinfection and 
 proper discharge of impervious receptacles. When porous 
 beds are made the outlets for house-drainage, it should 
 always be borne in mind that any water-supplies derived 
 from them will inevitably be contaminated. Sewage, how- 
 ever filtered and diluted, is not a fit beverage for human 
 use. Numerous cases of severe and often fatal illness can, 
 with a little care, be traced to this cause. 
 
 Should any one think that such careful provision for 
 pure water and untainted air as has here been suggested is 
 unnecessary, or too troublesome, it will be well to reflect 
 that it accords with the uniform experience of civilized 
 mankind ; and that matters of such vital consequence as 
 the health and happiness of human beings are too serious 
 to be trusted to chance. All experience has shown that 
 regions well drained and supplied with wholesome water 
 are healthful ones ; that cities kept properly clean and 
 
134 APPLIED GEOLOGY. 
 
 abundantly supplied with pure water show a diminished 
 death-rate ; that great epidemics, like cholera and yellow 
 fever, either leave such cities and regions unscathed, or 
 visit them with greatly mitigated violence, having their 
 breeding-places in regions of filth, and confining their 
 ravages chiefly to uncleanly and badly watered localities ; 
 and that diseases like diphtheria and typhoid fever can 
 usually be traced to defective drainage and impure water. 
 
CHAPTER VIII. 
 
 MINERAL FUELS. 
 
 AMONG all the mineral substances procured from the 
 earth, the mineral fuels doubtless hold a foremost rank in 
 importance, contesting even with iron for the supremacy 
 in supplying the wants of civilized man. Indeed, the in- 
 dustrial rank of nations may be very accurately judged 
 from the extent to which they utilize their fuel supplies. 
 Great Britain, the United States, and Germany, the three 
 foremost manufacturing nations, produce four fifths of the 
 mineral fuels of the entire globe. 
 
 These highly important substances, whether anthra- 
 cites, bituminous coals, lignites, or peat, are generally con- 
 ceded to have resulted from a peculiar decomposition of 
 vegetable tissues. There are a number of questions as to 
 the particular mode in which these deposits originated, 
 and the special forms and portions of vegetation that fur- 
 nished their chief materials, which, although they are of 
 much theoretical interest, are yet not of such practical im- 
 portance to the student of economical geology as to claim 
 our consideration here. It is sufficient for our present 
 purpose to observe that the chief constituents of all vege- 
 table tissue are carbon, oxygen, and hydrogen, with small 
 proportions of nitrogen and some earthy substances. 
 When these tissues decay or are burned with free access of 
 air, their elements are dissipated in the form of carbonic 
 acid and watery vapor, and ultimately nothing remains 
 
136 APPLIED GEOLOGY. 
 
 but an inorganic residue constituting the ash of the 
 plants. When, however, vegetable substances undergo 
 decay out of contact with the air, whether covered with 
 earth or heaped together in wet places, and partly or 
 wholly covered with water, the changes that take place in 
 them are due mainly to chemical rearrangements that 
 occur among their own elements. Of these, the oxygen 
 unites with somewhat more than one third its own weight 
 of carbon and with one eighth its weight of hydrogen to 
 form carbonic acid and water. A portion of the hydrogen 
 also unites with one third its weight of carbon to form 
 marsh-gas, the fire-damp of coal-mines. The result of 
 these several changes is that the relative amount of oxygen 
 in the mass is diminished, while that of carbon, originally 
 about one half of the whole, is increased ; the color be- 
 comes darker, first brown, then nearly or quite black, 
 from the increasing preponderance of coaly carbon, while 
 the relative proportion of hydrogen is but slightly changed. 
 The resulting substance, in the slow process of ages of this 
 kind of change, passes through the condition of peat or 
 brown coal, to become what is known as bituminous coal, 
 or ultimately to be converted into anthracite, in some 
 much-disturbed regions where probably heat accelerated 
 the dissipation of most of the oxygen and hydrogen still 
 remaining in the coal. That this process of chemical 
 change is a gradual and protracted one, continuing even 
 to the present day, is shown by the fact that marsh-gas 
 and carbonic acid, or " choke-damp," are still eliminated 
 from most coal-beds, and present some of the most 
 dreaded dangers of coal-mining, against which careful 
 provisions for ventilation, and the use of safety-lamps, do 
 not always avail to prevent frightful casualties. Thus 
 oxygen, useless as a fuel, is progressively eliminated, while 
 the combustible elements, carbon and hydrogen, become 
 ever more dominant, during the process by which coal is 
 formed. By reference to the table of analyses given on a 
 
MINERAL FUELS. 137 
 
 subsequent page, it may be seen that, in the course of this 
 series of changes, the carbon, from being originally a little 
 less than 50 per cent of the whole, becomes 60 per cent in 
 well-formed peat, more than 66 per cent in brown coal 
 from 70 to more than 80 per cent in ordinary bituminous 
 coal, and finally 90 per cent or more in anthracite ; that 
 the hydrogen, originally 6^ per cent, remains tolerably 
 uniform in relative amount till the anthracites are reached, 
 when it becomes, together with other volatile ingredients, 
 not more than from 3 to 10 per cent, while oxygen dimin- 
 ishes from 43 per cent to an average of about 10 per cent 
 in bituminous coals (a considerable portion of this being 
 due to the presence of water), and to a much smaller 
 amount in anthracite. 
 
 Now, these progressive changes in the relative propor- 
 tions of the constituent elements are attended with con- 
 siderable differences in the physical character of the suc- 
 cessive products, and in their behavior when used as fuels. 
 On these differences has been based a convenient prac- 
 tical classification of those variable substances called 
 collectively mineral coals. This classification is primarily 
 into anthracite and bituminous coal, the first of which 
 neither softens nor swells in burning, yielding no smoke 
 and little or no yellow flame, while the second softens and 
 often swells in the fire, emitting much smoke and abun- 
 dant yellow flame. These two great classes admit of a 
 somewhat convenient subdivision, not always observed in 
 practice, into hard and semi-anthracites, semi-bituminous 
 and bituminous coals a subdivision which is based on the 
 relative proportion of volatile combustible substances con- 
 tained in them, together with certain tolerably well-marked 
 differences in their physical characters. 
 
 The hard anthracites, which usually contain less than 
 5 per cent of combustible gases, kindle with difficulty, and 
 burn with an intense heat and little blue flame, have a 
 more or less marked conchoidal fracture, a brilliant luster, 
 
138 APPLIED GEOLOGY. 
 
 and a specific gravity of from 1.5 to 1.8, being the heaviest 
 and hardest of all coals. 
 
 The semi-anthracites, containing from 5 to 1 1 per cent 
 of volatile combustible materials, kindle and burn more 
 readily than the former class, giving a strong heat, often 
 accompanied at first with a little yellow flame. They 
 have a specific gravity of from 1.4 to 1.5 and sometimes 
 more, are softer and less lustrous than the hard anthra- 
 cites, and have usually an angular fracture with a tend- 
 ency to break up while burning. 
 
 The semi-bituminous coals have from 12 to 20 per cent 
 of volatile constituents and a specific gravity between 1.3 
 and 1.45, while the bituminous coals have more than 20 per 
 cent of volatile matter, and their specific gravity is from 
 1.2 to 1.35, that of some of the Ohio coals being even 
 more than 1.4, though the average gravity of this class of 
 coals is less than 1.3. Both these kinds of coal liberate a 
 part of their volatile matter, when heated, in the state of a 
 dense oily liquid resembling bitumen, whence their name ; 
 they also emit a bituminous odor when burning. A further 
 subdivision of the bituminous coals is made on physical 
 characters of much economical importance, into caking, 
 cherry, splint or block, and cannel coals. 
 
 The caking coals, when heated, soften greatly, and the 
 fragments fuse together, or agglutinate into an adhesive 
 mass, which is puffed up, by the gases liberated by the 
 heat, into a hard and highly cellular substance called 
 coke, consisting of the fixed carbon and mineral matters 
 originally present in the coal. This property fits them to 
 be used for the manufacture of coke, and for purposes 
 where a " hollow fire " is desirable, as in blacksmithing, 
 while rendering them much less convenient for domestic 
 use. 
 
 The cherry coals, which owe their name to the beauty 
 of their appearance, are usually highly lustrous but very 
 brittle coals, which do not agglutinate when heated. 
 
MINERAL FUELS. 
 
 139 
 
 Their brittleness gives rise to a great amount of waste in 
 mining and transportation, while their lack of adhesive- 
 ness when heated fits them for use as a domestic fuel. 
 
 The splint or block coals are hard, highly laminated, 
 and difficult to be broken across, have a dull luster, and 
 do not agglutinate when heated. Their properties adapt 
 them especially for use in iron-smelting, for which they 
 are largely utilized. They are often called dry-burning or 
 open-burning coals, a name equally applicable to any of 
 the non-agglutinating coals. 
 
 The cannels, of which Prof. H. D. Rogers proposed to 
 make a distinct primary class under the name of hydro- 
 genous coals, are characterized by their large proportion 
 of volatile matter and their small amount of coke-like 
 residue, their dull luster, their conchoidal or slaty fracture, 
 and their tendency to split when burning with a crackling 
 noise, somewhat like the chatter of a parrot, whence they 
 are often called parrot-coals. They derive the name can- 
 nel (i. e., candle) coals from the readiness with which they 
 take fire, and the cheerful flame with which they burn. 
 This makes them favorites for use in open grates ; they 
 are also largely used in making illuminating gas. 
 
 The lignites or brown coals are of much more recent 
 geological origin, and usually much less completely car- 
 bonized, than those which have just been described. 
 They are called lignites, because they frequently exhibit 
 the woody structure of the plants from which they are de- 
 rived, from the Latin word for wood, and brown coals, 
 from their color or that of their powder. They burn read- 
 ily without fusing, and emit a sooty smoke and a disagree- 
 able smell. The lignites, as a class, contain a much larger 
 proportion of water than other coals a circumstance 
 which greatly diminishes their value as fuel, since so large 
 a portion of their heating power is wasted in converting 
 into steam the water which they contain. The lignitic 
 coals, which occupy vast areas in the western part of this 
 
140 
 
 APPLIED GEOLOGY. 
 
 continent, differ widely in quality. Some are hardly dis- 
 tinguishable in appearance or character from the true bi- 
 tuminous coals, having but a small per cent of water, and 
 being sometimes capable of yielding a good coke ; while 
 others have a high per cent of water, often from 12 to 20 
 per cent, and crumble to a coarse powder when exposed 
 to the air, being on both accounts very indifferent fuel. 
 
 It will be convenient, for purposes of reference, to re- 
 sume in tabular form the classification of the mineral 
 fuels, with the characters on which chiefly it is based, omit- 
 ting for the present any consideration of peat : 
 
 Anthracites do not soft- 
 en ; no smoke ; little 
 
 flame. 
 
 Hard anthracite volatile to 5 per cent ; 
 sp. gr. 1.5 to 1.8; hard; lustrous; 
 conchoidal fracture. 
 
 Semi-anthracite volatile 6 to n per 
 cent ; sp. gr. 1.4 to 1.5 ; less hard ; 
 luster dull ; fracture angular. 
 Semi-bituminous volatile 12 to 20 per 
 
 cent ; sp. gr. 1.3 to I 45. 
 Bituminous volatile above 20 per cent ; 
 
 sp. gr. 1.2 to 1.4. 
 Caking agglutinates. 
 Cherry non-agglutinating ; lustrous ; 
 
 brittle. 
 Splint or block non - agglutinating ; 
 
 dull ; tough ; laminated. 
 Cannel largely volatile ; dull luster ; 
 I conchoidal or slaty fracture. 
 
 Lignite brown powder ; usually contains much water ; no fusion ; 
 sooty smoke ; bad smell. 
 
 Bituminous soften ; yield 
 oily fluid ; much smoke 
 and flame. . . . 
 
 The following table of analyses, derived from various 
 sources, is given to illustrate the composition of the vari- 
 ous classes and kinds of mineral fuel ; to which is added 
 an average analysis of woody tissue derived from several 
 different kinds of tissue. About one half of these are what 
 are called proximate analyses, i. e., those giving only the per- 
 centages of fixed carbon, volatile constituents, and ash, 
 with sometimes those also of water and sulphur. The re- 
 
MINERAL FUELS. 
 
 141 
 
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 f^-t^OCO MCOO ON 
 
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 \O CO M t^ ON rt* O vO 
 
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 r^o^MOcovo rfo 
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 mo ONf^coO inw 
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 CO M Q 
 
 w co q 
 r^ \o Tt* 
 
 W o A 
 
 SWMOMininr^OOcoQ OcoO 
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 cotNint^t>ONCOinONMCO ONO 
 MWCOCOCOM ^-inm 
 
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 coomONOi-iinininin *f O 
 OWOcocMONMMinONMco OmQ 
 
 R 
 
 CO 
 
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 &$ '&'8 5c?^ 
 
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 t^ CNJ in rj- ON O 
 
 d t>. co' ci d w 
 
 8 
 
 w 
 
 8coOOMONHf^ininininiNvNOOcoOrj-t->.O 
 MOmMvOMt^MCOTj-CONinTj-MvOOCOMO 
 
 ovd TJ-cdvdvd M d inci M coco>ne4 cot>-coT}-ci ci 
 
 oyibadg 
 
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 b/> . . 
 
 
 -"rt . >^ : 
 
 
 j" 8 V j S a ^ . j d 05 !^ 1 : : i i 
 
 
 *. g s c^ ^=f 0-^ -a : ; 
 
 ^1^-rts^^bJD ^^i^y ) e :>. 
 
 iIi;ilfll!iKii4f 
 
 S ^ J* S limits 111 | 
 
 lllll 1 Ititlllll! 
 
 r ^ s - s ^ S je 
 .-a 6 f 5 , ^ fc 
 I 'J3 -g Tf 
 
 ig. Wigan, Lancashire.. . 
 20. Brown coal, Bovey, England. 
 21. Lignitic coal, Bellemonte, Col.. 
 22. Woody tissue, average 
 
 5 ~ s s 'S 'S 1 ' ~ g = = 
 
 a g = | = .-a 
 <J c/3 $ M U 
 
 w cJ corfinvd l^-od O>O w c cOTfinvo' t^-cd 
 
I 4 2 APPLIED GEOLOGY. 
 
 mainder are ultimate analyses, giving the percentage of all 
 the elements ; while five of them, taken from the " Geo- 
 logical Report of Ohio," 1870, combine both forms of 
 analysis : 
 
 Geological Associations of Mineral Fuels. The 
 coals and lignites occur as beds of varying thickness, in- 
 terstratified with other beds of sandstones, shales, fire- 
 clays, and occasionally limestones. The coal-beds, or 
 seams, as they are frequently called, vary in thickness 
 from the fraction of an inch to many feet. The Mammoth 
 bed, in the Pennsylvania anthracite region, measures, at 
 two points mentioned by Ashburner, one hundred and one 
 hundred and fourteen feet, ranging between sixty and ninety 
 feet over a large area in the Black Creek basin ; while at St. 
 Etienne, near Lyons, France, the main coal, according to 
 Geikie, averages forty feet in thickness, and swells out oc- 
 casionally to as much as one hundred and thirty feet. The 
 main seam at Pictou, Nova Scotia, is about forty feet in 
 thickness, and the Xaveri seam in Upper Silesia is, ac- 
 cording to Credner, sixteen metres or over fifty-two feet 
 thick. On the other hand, in every coal-region there are 
 large numbers of very thin seams which are economically 
 worthless, a thickness of three feet being usually consid- 
 ered as small as can be profitably worked by underground 
 operations. Of the eighty or more seams found along the 
 head of the Bay of Fundy, not more than four or five are 
 workable. Southern Wales has twenty-three workable 
 seams out of more than eighty. Southern Russia is said 
 to have, on the river Donetz, as many as two hundred and 
 twenty-five coal-seams, of which but forty-four are consid- 
 ered worth working ; while of the one hundred and thirty- 
 two seams in the Westphalian coal-field, near the Rhine, 
 seventy-four are workable. These few examples, which 
 could be greatly multiplied, will serve to show both the 
 wide variations in thickness which coal-beds, like other 
 strata, may assume, and also the extent to which they may 
 
MINERAL FUELS. 
 
 143 
 
 alternate with other rocks in the series of strata or meas- 
 ures in which they occur. Very thick coal-seams, like 
 some of those mentioned above, are by no means made up 
 entirely of coal. They are nearly always separated, by 
 seams of shaly matter or of very impure coal, into several 
 subordinate layers or benches, which often differ consider- 
 ably in character. Thus the Mammoth seam, where it is 
 one hundred and fourteen feet thick, has eight feet of 
 rock other than coal interlaminated with it ; and the Pictou 
 main seam, where nearly forty feet thick, affords but about 
 twenty-four feet of good coal, being interstratified with six 
 bands of shale and ironstone or coarse impure coals. 
 
 Besides the seams of coal, the rock series, constituting 
 coal-measures, is made up of various alternations of sand- 
 stones, fire-clays, shales containing not unfrequently valu- 
 able deposits of clay ironstone, and, less frequently, strata 
 of limestone. Occasionally, also, there occur in some re- 
 gions seams of highly bituminous iron carbonate called 
 black-band iron-ore, highly esteemed as a source of iron. 
 The coal-seams are almost invariably found to be under- 
 laid by a bed of fire-clay, or of clayey sandstone, varying 
 from a few inches to several feet in thickness, and contain- 
 ing usually great numbers of fossil roots and curiously 
 pitted stumps, called stigmarice, which are evidently the 
 remnants of a former vegetation that grew on them as 
 soils. These under-days are therefore generally believed 
 to be the ancient dirt-beds from which sprang the vegeta- 
 tion that was transformed into coal. The under-clays are 
 often found to be clays of such purity as to be capable, 
 after being properly disintegrated by weathering, of being 
 wrought into pottery, or molded into highly refractory 
 fire-brick, whence their name of fire-clays. Their refrac- 
 tory character is, in all probability, due to the circumstance 
 that the vegetation of the coal-beds withdrew from them 
 those ingredients, like potash and lime, which cause clays 
 to fuse at very high temperatures. (Newberry.) 
 
144 APPLIED GEOLOGY. 
 
 Aside from the usual position of the under-clays, there 
 is no fixed order of sequence of the strata which make up 
 coal-measures ; though it is very common to find a layer, 
 sometimes quite thin, of bituminous shale, or very shaly 
 coal filled with leaves and fragments of plants, resting im- 
 mediately on the coal-seam. The nature of the strata 
 which immediately overlie the coal is a matter of great 
 practical importance, since upon it depend very much the 
 ease and safety with which the coal may be mined. A 
 roof of firm, thick-bedded sandstone greatly facilitates 
 mining operations; while one of slippery and shivery 
 shales is sure to cause difficulty and danger. Sandstones? 
 however, sometimes present a curious danger of their own, 
 in the form of what are called coal-pipes, the skeletons of 
 ancient trunks of trees extending in a nearly vertical di- 
 rection through the strata, the place of the bark being 
 occupied by a tender film of coal, while that of the wood 
 is filled with a solid column of sandstone. These, enlarg- 
 ing downward and generally destitute of branches, are 
 easily dislodged, and in their fall crush whatever may be 
 underneath, a peculiar example, as Lyell remarks, of the 
 long-deferred action of gravity. 
 
 But though the various kinds of rocks which make up 
 coal-measures in general present no settled order of rela- 
 tive arrangement, yet in any particular coal-field the lead- 
 ing strata, though often varying considerably in thickness, 
 commonly show a surprising and very helpful degree of 
 persistency in character and relative position. This is 
 true, within limited areas, of some of the more important 
 sandstone strata, but is more widely true of the leading 
 seams of coal and limestone. For instance, Prof. H. D. 
 Rogers estimates .that the great Pittsburg seam of the Ap- 
 palachian coal-field underlies an area of not less than 
 fourteen thousand square miles, in a continuous sheet of 
 varying thickness, some other coal-seams showing a simi- 
 lar constancy of position, though probably more limited in 
 
MINERAL FUELS. 145 
 
 extent. In like manner, some of the limestones of the 
 Pennsylvania coal series are recognized in similar posi- 
 tions in Ohio, where they are found persistent over large 
 areas. Thus these persistent strata, whether of coal, of 
 limestone, or sometimes of sandstone, become valuable 
 standards of reference, or key-rocks, for determining the 
 existence and the position of the useful rocks, which have 
 been observed at some points to lie at a certain distance 
 below or above them, due allowance being made for possi- 
 ble local changes in character and thickness of strata. 
 
 To illustrate what has been said as to the mode of oc- 
 currence and associates of coal-seams, and as to persistent 
 strata, the following general section of the lower coal- 
 measures of Ohio has been taken from the second volume 
 of the Ohio Geological Report : 
 
 Thickness in feet. 
 
 36. Red and gray shales of barren measures 
 
 35. Stillwater sandstone, often conglomerate o to 50 
 
 34. Gray shale alternating with No. 35 o 50 
 
 33. Buff limestone, ferruginous " mountain ore ".... o 10 
 
 32. Blackband iron-ore, often replacing No. 33. ... o 14 
 
 31. Coal No. 7, " Cambridge," etc., seam 2 7 
 
 30. Fire-clay 3 5 
 
 29. Limestone in eastern and southern counties. ... o TO 
 
 28. Shale and sandstone 40 50 
 
 27. Coal No. 6 a, or " Norris" coal, sometimes with 
 
 limestone over it o 6 
 
 26. Fire-clay 3 5 
 
 25. Mahoning sandstone, often conglomerate o 50 
 
 24. Gray or black shale, alternating with No. 25... . 5 50 
 23. Coal No. 6, " Straitsville " or "Big Vein" 
 
 Upper Freeport of Pennsylvania 3 12 
 
 22. Fire-clay 3 5 
 
 21. Limestone in eastern counties = Freeport of 
 
 Pennsylvania 2 8 
 
 21. Gray or black shale, nodular ii-on-ore at base ... 25 50 
 20. Coal No. 5, " Mineral Point," " Newberry " 
 
 = " Lower Freeport " of Pennsylvania 2 5 
 
 19. Fire-clay, often non-plastic and excellent 3 6 
 
 18. Shale and sandstone 20 ,,4 
 
I4 6 APPLIED GEOLOGY. 
 
 Thickness in feet. 
 
 17. Limestone, " Putnam Hill " or " Gray " 2 to 8 
 
 16. Coal No. 4, often double, " Flint Ridge cannel " 
 
 = " Kittanning " of Pennsylvania i 7 
 
 15. Fire-clay 2 12 
 
 14. Shale and sandstone, sometimes with coal 3 a. . 20 90 
 13. Blue limestone with iron-ore = Ferriferous of 
 
 Pennsylvania 2 6 
 
 12. Coal No. 3, " Creek vein " i 3 
 
 II. Fire-clay, extensively used for pottery 5 15 
 
 10. Shale and sandstone, " Tionesta " sandstone.. . 30 50 
 
 9. Coal No. 2, generally thin, " Strawbridge " coal I 5 
 
 " 8. Fire-clay I 3 
 
 7. Shale 20 50 
 
 6. Massillon sandstone 20 80 
 
 5. Gray shale 5 ,,40 
 
 4. Coal No. i, " Brier Hill," " Massillon " 3 6 
 
 3. Fire-clay 3 5 
 
 2. Sandstone and shale 10 ,, 50 
 
 I. Conglomerate 
 
 The average thickness of the rocks in this section is 
 about four hundred feet, and a considerable number of 
 the strata included in it are recognized as identical with 
 those holding corresponding positions in the lower coal 
 series of Pennsylvania. In this series of four hundred 
 feet of strata there is a maximum thickness of fifty-one 
 feet of coal, with a probable average of about twenty-five 
 feet or one foot of coal to sixteen feet of the measures. 
 This is doubtless considerably above the average ratio of 
 coal to rock. In the Pictou coal-field there is one foot 
 of good coal to about twenty-six feet of poor coal and 
 rock ; in that of Illinois, one to twenty-five or thirty feet ; 
 in the Saarbriick area, the ratio is one to twenty-six ; in 
 that of Westphalia, one foot of workable coal to thirty- 
 two feet of rock ; and in the Southern Wales coal-basin, 
 if the entire thickness of the Carboniferous rocks be con- 
 sidered, which is said to be twelve thousand feet, the ratio 
 is about one to one hundred. 
 
 In nearly all cases, areas of coal-measures are basin- 
 
MINERAL FUELS. 147 
 
 shaped that is, they thin out on all sides as they approach 
 their limits, and are surrounded by older rocks, somewhat 
 like a picture set in a frame. They owe this form occasion- 
 ally, it is probable, to the original form of the area in 
 which they were deposited. This appears to be true of the 
 great Appalachian coal-field as a whole, which seems to 
 have been deposited in a long and shallow trough, inclosed 
 on one side by land which now forms the crests of the 
 Appalachians, and on the other by a low anticlinal ridge, 
 extending through western Ohio and central Kentucky, 
 the bottom of this trough having evidently been lowered 
 by gradual subsidence to permit the deposition of the suc- 
 cessive strata. In a case like this, the chief upper coal- 
 seams would be likely to be more extended than those 
 lower in the series, as is true of the Pittsburg seam. In 
 much the greater number of instances, however, the basin- 
 form is due to disturbances of position that have taken 
 place since the rocks were deposited ; the strata, by move- 
 ments of the earth's crust, having been thrown into folds, 
 sometimes wide and gentle, sometimes very abrupt; and 
 when the crests of these folds have been removed by subse- 
 quent denudation, areas once continuous have been left 
 as isolated, basin-shaped remnants. A striking illustra- 
 tion of this is presented in the sharply folded and denuded 
 anthracite basins of Pennsylvania ; while it is probable 
 that the present separation of the coal areas of Illinois 
 and Missouri is due to the denudation of a wide and 
 gentle fold, cutting away the strata down to the rocks that 
 underlie the coal. In these latter cases, the chief lower 
 coal-beds would be likely to be most extended and contin- 
 uous, the upper ones being largely swept away. 
 
 Geological Horizons of Mineral Fuels. Al- 
 though thin layers of carbonaceous matter are occasion- 
 ally met with in rocks of Silurian and Devonian age, and 
 even, as stated by Murchison, a small deposit of anthra- 
 cite, from one to twelve feet thick, occurs in the Lower Si- 
 
1 48 APPLIED GEOLOGY. 
 
 lurian of Ireland, the material for which has apparently 
 been derived from masses of sea-weeds, yet no beds of 
 mineral fuel, of any considerable economic importance or 
 reliability, have yet been found below that series of rocks 
 which is called the Carboniferous, from the great preva- 
 lence in it of land-plants and beds of coal. The strata 
 of the middle portion of this series are frequently called 
 the coal-measures par excellence, because they furnish very 
 much the largest part of the mineral fuel of the world, 
 although coal-measures of great importance occur at sev- 
 eral other geological horizons presently to be mentioned. 
 The carboniferous rocks, omitting the upper or Permian 
 portion, which is not coal-bearing and has little develop- 
 ment on this continent, admit of the following subdivisions, 
 recognizable in a general way in most American localities 
 of these rocks, and nearly all of which, under various 
 names, are found also in the European Carboniferous : 
 
 7. Upper barren measures with thin coals ; Washing- 
 ton seam workable in West Virginia. 
 
 6. Upper productive measures Pittsburg seam the 
 chief, in Appalachian area. 
 
 5. Lower barren measures Mahoning sandstone at 
 base, with thin coals. 
 
 4. Lower productive coal-measures. 
 
 3. Millstone grit, or conglomerate. 
 
 2. Sub-conglomerate measures coals of Arkansas; 
 Sharon coal of Pennsylvania ; lower or " edge coals " of 
 Scotland ; coal horizon of Russia and northern Spain. 
 
 i. Sub-carboniferous limestone, etc. 
 
 The uppermost of these subdivisions is thought by 
 Messrs. White and Fontaine to show Permian characters 
 in West Virginia, where it contains a three-foot seam of 
 coal, besides several thin seams. 
 
 The upper productive coal-measures (6) have their 
 greatest economic importance in the Appalachian coal 
 area, and in western Kentucky. The lower productive 
 
MINERAL FUELS. 
 
 149 
 
 coal series is the most widely reliable of all, in both 
 America and Europe ; while the millstone grit, usually 
 considered the base of the coal-bearing series, and hence 
 sometimes called the Farewell rock, because when it is 
 reached in mining the miners consider that they bid fare- 
 well to further hopes of coal, still has beneath it the coal- 
 bearing rocks of Arkansas and northern Spain, most if 
 not all those of Russia, and the lower or " edge coals " of 
 Scotland. 
 
 Above the geological horizon of the Carboniferous, val- 
 uable measures of coal of the usual character are found in 
 rocks of probable Triassic age, in central Virginia and 
 North Carolina, and also in the Lower Oolite, a subdivision 
 of the Jurassic, of Great Britain. Next in importance to 
 the Carboniferous, on this continent, as a horizon of min- 
 eral fuel, is the rock series of probable Upper Cretaceous 
 age, whose vast and wide-spread measures of lignitic coal 
 are of so great importance to the development of the re- 
 gion lying west of the Missouri River. 
 
 Valuable deposits of brown coal are found in Europe 
 in the Middle Tertiary, and are extensively utilized in 
 Germany and Austria, but none of importance have yet 
 been found in the Tertiary of North America. Thus the 
 geological horizons of mineral fuels are : 
 
 7. Middle Tertiary brown coals. 
 
 6. Upper Cretaceous lignitic coals. 
 
 5. Lower Oolite in Great Britain bituminous. 
 
 4. Triassic bituminous chiefly. 
 
 3. Upper productive measures of Carboniferous. 
 
 2. Lower productive measures of Carboniferous. 
 
 i. Sub-conglomerate coal of Carboniferous. 
 
 Regions of Mineral Fuel. The easternmost coal 
 area of North America is that of northern Nova Scotia, 
 east New Brunswick, and Cape Breton Island. It covers 
 about eighteen thousand square miles, much of which 
 seems likely to be of little value. There is a small area in 
 
150 APPLIED GEOLOGY. 
 
 Rhode Island, extending a little way into Massachusetts, 
 and containing about five hundred square miles, the coal 
 of which is a very hard variety of anthracite. It is not 
 largely worked, the product reported in 1882 being only 
 ten thousand tons. 
 
 In Jhe extent, variety, and excellence of its coal-beds, 
 the Appalachian area surpasses any other on this conti- 
 nent, or indeed in the world. This vast coal-field, covering 
 nearly fifty-nine thousand square miles, occupies a large 
 part of western Pennsylvania and West Virginia, the western 
 extremity of Maryland and Virginia, southeastern Ohio, 
 the eastern part of Kentucky and Tennessee, and northern 
 Alabama, with a corner of Georgia. The northeast ex- 
 tremity of this area furnishes the anthracite of Pennsyl- 
 vania, the best in the world, in several detached basins 
 carved out of the folds of the Alleghanies, and contain- 
 ing in all about four hundred and seventy square miles. 
 In the Appalachian area, workable coal is obtained from 
 all the coal-bearing horizons of the Carboniferous that 
 have been enumerated, stretching from the Sharon sub- 
 conglomerate seam in No. 2 of our section, p. 148, to the 
 Washington seam in the upper barren measures, No. 7. 
 The Pittsburg seam, so celebrated for its vast extent, its 
 considerable thickness, and the superiority of its coal for 
 coking purposes, is at the base of the upper productive 
 measures, No. 6 ; while most of the coal of Ohio is ob- 
 tained from the lower productive measures, No. 4. 
 
 The Illinois coal-field covers a large part of central 
 and southern Illinois, the southwestern part of Indiana, 
 and the western portion of Kentucky, occupying somewhat 
 more than forty-seven thousand square miles. This area 
 is producing large and rapidly increasing amounts of bitu- 
 minous coals, chiefly from the lower productive measures, 
 with some in Kentucky from the upper productive. 
 
 The largest in superficial extent of the Carboniferous 
 coal areas is the Western one, occupying, it is estimated, 
 
MINERAL FUELS. 151 
 
 seventy-nine thousand square miles, in southwestern Iowa, 
 northern and western Missouri, eastern Kansas and In- 
 dian Territory, northern Texas, and western Arkansas. 
 Over much of this area the coal-seams are thin, and the 
 coal not of the best quality. The producing horizons are 
 chiefly the sub-conglomerate measures in Arkansas, some 
 of -whose coals are semi-anthracites, and the lower pro- 
 ductive measures in Missouri and Iowa. The largest pro- 
 duction is from Iowa and Missouri, Kansas also furnish- 
 ing nearly a million tons annually. 
 
 Besides these there is a rudely circular area in central 
 Michigan, covering about six thousand seven hundred 
 square miles with Carboniferous coal-measure rocks, about 
 three hundred feet in maximum thickness, which contain, 
 at several points, one seam three to four feet thick of bi- 
 tuminous coal, somewhat sulphurous, but considered a 
 good fuel for steam purposes. The area seems not to be 
 very promising for a large coal production. 
 
 The Triassic coal-fields of Virginia and North Caroli- 
 na occupy four narrow, elongated basins running parallel 
 with the Blue Ridge Mountains in the east central part 
 of those States. These areas, although some of them have 
 been long known, have been as yet but little developed. 
 The one best known and most largely worked is in the 
 near vicinity of Richmond, where one of its seams attains 
 sometimes a thickness of forty feet. The coal is highly 
 bituminous, as is also that of the other basins, save that 
 of the Dan River in North Carolina, stretching into Vir- 
 ginia, which is shown by analyses to be semi-bituminous. 
 The productive area of the several basins does not proba- 
 bly reach five hundred square miles. 
 
 The lignitic coal-fields of probable Upper Cretaceous 
 age, in the far Western States and Territories, have not yet 
 been sufficiently explored to give more than a vague ap- 
 proximation to their extent ; but they are known to cover 
 vast areas, especially in Colorado, Wyoming, Dakota, and 
 
152 APPLIED GEOLOGY. 
 
 Montana. Those best known and most largely worked at 
 present are those along the eastern base of the Rocky 
 Mountains, through much of Colorado, and extending 
 some distance into New Mexico ; those along the Union 
 Pacific Railway in southern Wyoming ; those on the Weber 
 River, and at other points, at no great distance from Salt 
 Lake City in Utah ; on Bellingham Bay and Puget Sound, 
 in Washington Territory ; and at Mount Diablo, near San 
 Francisco, California. Several seams of superior anthra- 
 cite and bituminous coal occur twenty-five miles south- 
 west of Santa Fe, New Mexico. 
 
 Valuable deposits of anthracite and coking bituminous 
 coal are found at Crested Butte, on the upper branches 
 of the Gunnison River in Colorado, and are coming into 
 extensive use ; while near Durango, in the same State, 
 and extending south into New Mexico, are enormous de- 
 posits of lignitic coal of excellent quality, some of the 
 seams being said to range from twelve to near ninety feet 
 in thickness. Valuable deposits occur also at Coos Bay 
 in Oregon, and in Vancouver's Island. Rough estimates 
 assign to the lignitic measures of Colorado about thirty 
 thousand square miles of area, and to those of Wyoming 
 twenty thousand square miles ; but those which claim for 
 Montana sixty thousand square miles, and for Dakota one 
 hundred thousand square miles of coal-bearing territory, 
 appear likely to be great overestimates. 
 
 As has already been remarked, the lignitic coals pre- 
 sent very wide variations in character and value. Some, 
 like parts of the seams of Crested Butte and Santa Fe, are 
 anthracites, apparently equal in quality to those of Penn- 
 sylvania ; others, like those of southern Colorado and ad- 
 jacent parts of New Mexico, and part of those at Crested 
 Butte, are coking coals which furnish a superior coke. 
 Some, like those of Cafion City, Colorado, and part of 
 those in Wyoming, are firm and open-burning, with a low 
 per cent of water, much resembling " block-coal " ; while 
 
MINERAL FUELS. 153 
 
 many others have much water, and crumble readily on ex- 
 posure, hence furnishing an inferior fuel. All kinds, with 
 the increase of population and the growth of mining and 
 other industries, are destined to be eagerly sought out, 
 and to furnish supplies of inestimable value to a vast re- 
 gion otherwise scantily supplied with fuel. Six of the 
 Western States and Territories had already, in 1882, a re- 
 ported production of two million three hundred and fifty 
 thousand gross tons, ranging from about one hundred and 
 fifty thousand tons each in California and New Mexico, 
 to nearly a million tons in Colorado, and two thirds as 
 much in Wyoming. 
 
 Foreign Coal-Fields. The chief coal areas of Eu- 
 rope are those of Great Britain, Belgium and France, 
 Germany and Austria, southern Russia, and Spain. The 
 coal-fields which have long given England its industrial 
 supremacy occupy an area of less than twelve thousand 
 square miles, and extend, in many separate basins, from 
 South Wales, northeasterly through western England to 
 the great Newcastle coal-field on the North Sea, with 
 areas of sub-conglomerate coals in southern Scotland. 
 All these areas of any considerable importance belong to 
 the Carboniferous age, and the coal is mostly bituminous, 
 with some valuable anthracite in South Wales. 
 
 The Belgian coal-field, of five hundred and eighteen 
 square miles area, extends in a lengthened belt eastward 
 from near Valenciennes, in France, to Aix-la-Chapelle ; 
 and its apparent eastern continuation across the Rhine 
 forms the great Westphalian coal-field northeast of Diis- 
 seldorf. 
 
 The coal-fields of Germany, with an area of about 
 eighteen hundred square miles, consist of several basins, 
 mostly small in extent, the chief of which are those of West- 
 phalia and Saarbruck, near the Rhine, Upper and Lower 
 Silesia, and some small basins in Saxony. There are also 
 important deposits of lignite in the Tertiary of North 
 
154 APPLIED GEOLOGY. 
 
 Germany, some of them of great thickness. Austria has 
 coal-fields and deposits of lignite of considerable extent in 
 Bohemia. 
 
 Russia, which is credited with about thirty thousand 
 square miles of coal territory, has a large portion of this in 
 the more central provinces, supplied with but a few thin 
 seams of inferior coal ; its most valuable coal area being 
 about eleven thousand square miles on the river Donetz, 
 with one hundred and fourteen feet of workable coal, at 
 the geological horizon of the millstone grit. (Credner and 
 Murchison.) 
 
 The coal-fields of France aggregate two thousand and 
 eighty-six square miles, in many isolated basins, scattered 
 widely over its territory, some of which contain anthracite 
 coal. Some of the more noteworthy are those of Valen- 
 ciennes near the borders of Belgium, of Autun, and of 
 St. Etienne, previously mentioned, in the southern part. 
 In some of these basins the coal series occurs in the sub- 
 conglomerate, but in most, at the usual horizon of the 
 Carboniferous coal-measures. 
 
 The Spanish Peninsula has three thousand five hun- 
 dred and one square miles of 'coal area, chiefly in the 
 province of the Asturias, in the north part of the king- 
 dom, and on the southern declivity of the Sierra More- 
 na, both in rocks subordinate to the Carboniferous con- 
 glomerate. 
 
 India is reported to have about two thousand square 
 miles of coal-fields, chiefly of Triassic age, and Japan five 
 thousand square miles in the Tertiary. China is known 
 to be exceptionally rich in coal, of Triassic or Lower Ju- 
 rassic age, with some Carboniferous coal in the province 
 of Hunan ; but our knowledge of that country is too im- 
 perfect to permit any estimate of the area which bears 
 coal-seams. The map published by Prof. Pumpelly, in 
 the " Smithsonian Contributions," indicates the possibility 
 that a very large portion of China proper is covered by 
 
MINERAL FUELS. 
 
 155 
 
 rocks pf the same age with those that bear valuable coal- 
 seams at many known points. Further than this our 
 knowledge does not extend. It is also reported that coal- 
 beds, of Carboniferous, Jurassic, and Tertiary age, occur 
 in Siberia. 
 
 True Carboniferous rocks with coal-seams are found 
 in the eastern colonies of Australia, and especially in New 
 South Wales, where there are said to be a number of beds 
 of coal ranging from three to thirty feet in thickness. 
 The following table, the materials for which are taken 
 with slight change from the report on mineral resources 
 of the United States, will give in compact form the prob- 
 able areas of fossil fuels in the various countries, with 
 their reported or estimated production in 1881 : 
 
 
 AREAS. 
 
 Square miles. 
 
 PRODUCTION. 
 
 Gross tons. 
 
 Great Britain 
 
 II,QOO 
 
 I 4 184 7QO 
 
 United States . ... .... 
 
 IQI QQ4 
 
 76 67Q 4QI 
 
 
 I.77O 
 
 6l ^4O 47^ 
 
 France . 
 
 2 086 
 
 IQ QOO O^7 
 
 Austria .. 
 
 I 8OO 
 
 19 ooo ooo 
 
 
 5 l8 
 
 1 7, c OO.OOO 
 
 India . . 
 
 2 OO4 
 
 4 ooo ooo 
 
 Russia 
 
 3O,OOO' 
 
 a 2<CR OOO 
 
 
 24,840 
 
 1,771:, 224 
 
 Nova Scotia, etc .... . . 
 
 18 oco 
 
 I 124 27O 
 
 Spain . ... 
 
 i CQI 
 
 800 ooo 
 
 Japan 
 
 5,ooo 
 
 8OO,OOO 
 
 Vancouver's Island 
 
 2QO 
 
 390 
 
 q2C OOO 
 
 China 
 
 
 ? 
 
 
 
 
 
 293,803 * 
 
 360,892,817 f 
 
 The coal area of the United States, given above, does 
 not include the lignitic coal-fields; but their product is 
 included in the second column. The areas of United 
 States coal-fields, known and estimated, are as follow : 
 
 * Exclusive of China and Western America, f Exclusive of China. 
 
1 56 APPLIED GEOLOGY. 
 
 New England area 500 square miles. 
 
 Appalachian 58,731 
 
 Michigan 6,700 
 
 Illinois, etc. ,, 47,138 
 
 Missouri, etc. 78,430 ,, 
 
 Virginia and N. Carolina area 495 = 191,994 sq. miles. 
 
 Colorado 30,000? 
 
 1 Wyoming 20,000? 
 
 Montana 60,000? ,, 
 
 Dakota 100,000? = 2 10,000 sq. miles. 
 
 No guesses seem yet to have been hazarded as to the 
 extent of coal lands in Washington, Oregon, California, 
 Arizona, Utah, and New Mexico. It will probably be no 
 exaggeration to concede to the entire lignitic coal area an 
 extent of one hundred and seventy-five thousand square 
 miles. 
 
 Impurities in Coal. Besides their fuel constituents, 
 carbon and hydrogen, all coals contain variable propor- 
 tions of other substances. Some of these, like nitrogen 
 and the mineral ingredients which constitute the ash, are 
 inert, acting merely to diminish by so much the fuel value 
 of the coal ; some, like moisture and oxygen, which in 
 combustion is removed as water, carry away a portion of 
 the heat evolved, as the latent heat of steam ; still others, 
 like sulphur and phosphorus, are directly injurious to the 
 fuel, both from evolving offensive gases in combustion, 
 and from acting injuriously upon iron. 
 
 Ash. The ash in good coals may range from not 
 more than i per cent to 5 or 6 per cent, or somewhat more 
 in anthracite. The ash of one hundred and fifty-two 
 bituminous coals, examined in Ohio, averaged somewhat 
 less than 5 per cent, ranging from .77 per cent to 17 per 
 cent, ten of the samples yielding more than 10 per cent ; 
 while that of eighty-three bituminous coals, analyzed by 
 the present Geological Survey of Pennsylvania, gave an 
 average of 5.45 per cent, ranging from i-j- per cent to 19 
 per cent. It is probable that, in bituminous coals, ash 
 
MINERAL FUELS. 157 
 
 not exceeding 5 per cent may be due almost wholly to 
 the mineral constituents of the original woody tissue, but 
 that much more than 5 per cent of ash would indicate the 
 probable presence of foreign earthy matter, either dissem- 
 inated, or occurring as thin laminae of shale. 
 
 Anthracite coals, from their greater loss of the original 
 constituents of woody tissue, in which loss the mineral 
 constituents could obviously take no part, will naturally 
 have a larger average of ash than the bituminous coals. 
 Analyses of twenty-seven anthracites and semi-anthra- 
 cites, recorded by the first Geological Survey of Penn- 
 sylvania, show an average of 6.13 per cent of ash ; analy- 
 ses of six, given in vol. M a of the second survey, show 
 a 9 per cent average, ranging from 4^- to 14 per cent. 
 Probably about 7 per cent would be a fair average for 
 the ash in an anthracite free from foreign admixture. 
 
 Ash which contains any considerable proportion of iron, 
 lime, and alkalies, is apt to cause serious difficulty, where 
 high temperatures are required, from its tendency to fuse 
 and form clinkers, which clog the grates and adhere to 
 the fire-proof linings of stoves and furnaces. Coals which 
 yield a white ash are less likely to give trouble of this 
 kind, being nearly free from iron ; while red-ash coals 
 owe the color of their ash to a considerable amount of 
 iron, and are liable to clinker. 
 
 Water and Oxygen. The amount of water in vari- 
 ous coals shows great variations, corresponding, doubtless, 
 to the porosity of their texture. The average amount of 
 water, shown by ninety-seven Pennsylvania bituminous 
 coals, is about i per cent ; by one hundred and twelve 
 Missouri coals, is 3.4 per cent ; by one hundred and fifty- 
 nine Ohio coals, is 4.65 per cent ; and by sixty-four Iowa 
 coals, is 8.57 per cent. In combustion, both this water and 
 the oxygen which is present to some extent in all coals 
 must be driven off in the form of steam, diminishing pro- 
 portionally the effective heat of the fuel. 
 8 
 
158 APPLIED GEOLOGY. 
 
 Sulphur and Phosphorus. These two directly in- 
 jurious substances are present in variable proportions in 
 almost every coal phosphorus, the more deleterious of 
 the two, in much the smaller proportion. Both generate 
 offensive gases in combustion, and both act injuriously on 
 iron, one tenth of one per cent of phosphorus present in 
 iron causing it to be brittle when cold, or cold short ; 
 while the presence of sulphur in iron makes it brittle when 
 hot, red short, and any marked amount of it in coal cor- 
 rodes the iron-work of stoves, furnaces, and smoke-pipes, 
 causing serious inconvenience and expense. Phosphorus 
 is rarely present in the coals that have been examined 
 with reference to it in Ohio and Pennsylvania, to the ex- 
 tent of .001 of the coal ; usually its amount is much less 
 than this, and it is quite probable that the recently de- 
 vised basic process for eliminating it from iron will make 
 its presence in coal a matter of small moment to iron- 
 smelters ; although for domestic use, where its products 
 are liable to escape into inhabited rooms, even small 
 amounts of it are objectionable. The amount of sulphur 
 in coal rarely falls below a half of one per cent, an 
 amount which is not seriously injurious ; while it some- 
 times reaches as much as 6 or even 8 per cent, making 
 the coal worthless for most ordinary uses. Analyses of 
 eighty-two Pennsylvania bituminous coals show an aver- 
 age of 1.41 per cent of sulphur, ranging from .425 to 8.43 
 per cent ; and of fifty-six Ohio coals a range from . n to 
 6.19 per cent, giving an average of 1.9 per cent. The 
 sulphur in coal exists in at least two different states, a con- 
 siderable portion being combined with iron to form py- 
 rites, or with lime as gypsum, while the remainder is in 
 some obscure form of combination, as yet little under- 
 stood. A portion of the sulphur can be eliminated by 
 coking, but the proportion that can be so removed varies 
 greatly in different coals, adapting them to different uses, 
 as will be shown in a subsequent paragraph. 
 
MINERAL FUELS. 
 
 159 
 
 Fuel Value of Coals. Although some valuable ex- 
 perimental investigations of the heating power of a con- 
 siderable number of coals of different kinds, based on the 
 number of pounds of water evaporated from the boiling- 
 point by one pound each of the various coals, have been 
 made for the United States Government by Prof. W. R. 
 Johnson in 1842, and by General Meigs quite recently, 
 yet the lack of any general series of experimental tests 
 will make it convenient for the student to have at hand a 
 theoretical method of reaching a tolerable approximation 
 to the heating values of various fuels. Such a method is 
 based on finding the sum of the heating powers of the 
 two combustible constituents, carbon and hydrogen, of 
 any coal, shown by its ultimate analysis, and subtracting 
 from this sum the amount of heat wasted in driving off its 
 oxygen in the form of steam. Experiments have shown 
 that the complete combustion of one pound of carbon 
 will heat 8,080 pounds of water i centigrade, and of one 
 pound of hydrogen will produce a like effect on 34,462 
 pounds of water. The oxygen in the coal, during com- 
 bustion, unites with one eighth its own weight of the hy- 
 drogen of the coal to form water, and the expulsion of 
 this water requires 537 C. of heat per pound. Hence 
 the formula for the theoretical heating power of any coal 
 will be C X 8,080 + (H - \ O) X 34,462 -40X537 = 
 heating power, in which C, H, and O stand for the re- 
 spective percentages of the carbon, hydrogen, and oxygen. 
 
 For example, coal 9 of the table on p. 141 contains in 
 one pound .7145 of a pound of carbon and .0547 of a 
 pound of hydrogen, of which .0201 will form with the 
 .1607 of oxygen .1808 of a pound of water, leaving 
 .0346 of hydrogen available as fuel. Hence .7145 X 8080 
 + .0346 X 34,462 .1808 X 537 = 6868.45 C. for the 
 theoretical heating power of this coal ; and, since 537 C. 
 of heat are required to convert one pound of water at the 
 boiling-point to steam, this would theoretically evaporate 
 
160 APPLIED GEOLOGY. 
 
 12.79 pounds of water. Similar computations may be 
 made on any other coal of the table whose ultimate analy- 
 sis is given. For example, No. 12 has a heating power of 
 8171.15, sufficient to convert 15.21 pounds of boiling 
 water to steam ; and woody tissue, No. 22, has a heating 
 power of 4077.3, or an evaporative power of 7.56 pounds 
 of water. The theoretical heating power of fuels can, 
 however, by no means ever be attained in their practical 
 use. Indeed, the loss of heat by conduction, by imper- 
 fect combustion, and by excess of air in the draft, is so 
 great that it is rare that so much as two thirds of the abso- 
 lute heating power is realized in practice, with even the 
 best of appliances. The best results attained by Prof. 
 Johnson were from five semi-bituminous coals, which 
 evaporated each from n to 11.62 pounds of water per 
 pound of fuel, equaling within a trifle the theoretical heat- 
 ing power of the fixed carbon alone. The highest result 
 obtained by General Meigs was the evaporation of about 
 ten pounds of water with one pound of fuel. Prof. John- 
 son was inclined to think, from the results of six closely 
 agreeing tests, that the practical heating power of coals 
 is no greater than that which is due to their carbon, an 
 opinion in which Prof. H. D. Rogers concurs. Others 
 think that the heating power of the fixed carbon, given by 
 proximate analyses of coals, may afford a useful approxi- 
 mation : an examination, on this basis, of the table of 
 forty-four coals given by Prof. Johnson, shows certainly 
 some striking agreements, and some equally striking dis- 
 crepancies. On the basis of the heating power of the 
 fixed carbon only, the two coals, already used as exam- 
 ples, would have an evaporative power respectively of 
 8.66 and 10 pounds of water, or about two thirds of 
 their theoretical heating power. It seems probable that 
 two thirds of the theoretical result obtained by the formula 
 given above will prove to be as convenient an approxima- 
 tion as can be gained. 
 
MINERAL FUELS. 161 
 
 Adaptation to Uses. In selecting a coal for any of 
 the multifarious purposes which fuel subserves, due regard 
 being always had to relative cost and accessibility, it will 
 usually be found that the combination of qualities pos- 
 sessed by the several classes of coals gives them special 
 adaptations to certain uses for which they can be most 
 economically employed. For all uses, except perhaps the 
 coarsest, like the burning of lime and brick, it is essential 
 that a coal shall be as free as possible from sulphur and 
 phosphorus, as also from an undue amount of ash, espe- 
 cially of that kind which is liable to clinker at the temper- 
 ature that must be maintained. For most purposes, also, 
 it is highly desirable that coal should possess sufficient 
 strength to bear handling and transportation without un- 
 due breakage and consequent waste, the caking coals being 
 those in which breakage is of least consequence. 
 
 For domestic and kindred uses a coal should be non- 
 agglutinating, free from sooty smoke and light ash, and of 
 a high degree of heating power ; and it should be capable 
 of maintaining a steady combustion without too frequent 
 attention. This combination of qualities is found in a 
 high degree in the anthracites, and, for burning in close 
 stoves and furnaces, no coal could be better. With proper 
 appliances they are used also in open grates, the semi-an- 
 thracites being somewhat the better for this use, on account 
 of their freer combustion. Cannel and open-burning bi- 
 tuminous coals are also adapted to open fires, the cannels 
 being favorites for this use on account of their cheerful 
 flame, despite their usual abundance of ash, and their 
 somewhat low degree of heating power. These last- 
 named species of coal, also, do not produce the unpleasant 
 dryness in the atmosphere of rooms which is observable 
 where anthracite is used in open grates. 
 
 For the generation of steam a coal should combine, 
 with a high degree of evaporative power, the qualities of 
 easy kindling and a free combustion. There should be no 
 
1 62 APPLIED GEOLOGY. 
 
 tendency to agglutinate, but rather to split up moderately 
 in burning, thus exposing a larger surface to the fire ; where 
 the coal is to be used on long voyages, it is highly essen- 
 tial also that it should be susceptible of compact stowage 
 much steam-making power in little bulk a property in 
 which coals differ as much as 15 or 20 per cent. The 
 semi-bituminous and free-burning anthracite coals are 
 well adapted for steam purposes, the former class, accord- 
 ing to the investigations of Prof. Johnson, excelling both 
 in evaporative power and in capability of compact stow- 
 age ; while Prof. H. D. Rogers inclines to give the prefer- 
 ence to the latter class. Hard anthracite, and especially 
 anthracite waste and slack, is also largely used for steam 
 purposes where it is favored by cheap transportation. 
 
 For the use of blacksmiths, where a hollow fire is de- 
 sirable, a pure agglutinating coal is employed ; and this 
 kind of coal is essential also for the manufacture of coke. 
 For the last purpose the coal should have a high percent- 
 age of fixed carbon ; and whatever sulphur it may contain 
 should be, as far as possible, in that condition which 
 renders it easy of elimination by heat. The operation of 
 coking drives off the water, the volatile combustible mat- 
 ter, and the separable sulphur, leaving the fixed carbon 
 and the ash as coke, which, in its best condition, is a 
 hard, strong, and highly cellular substance of a silvery 
 color. 
 
 Anthracite and open-burning bituminous coals are also 
 largely used for iron-smelting, it being essential for this 
 purpose that the coal should have sufficient strength 
 to bear the weight of the charge without crushing, and 
 that it should be free from injurious amounts of sulphur 
 and phosphorus. Where dry-burning bituminous coal is 
 used for smelting, it is freed from its volatile matter in the 
 upper part of the furnace, the gases being drawn off by 
 proper arrangements near the top of the stack, and used 
 for heating the blast and for other fuel purposes. 
 
MINERAL FUELS. 163 
 
 For the manufacture of illuminating gas, a coal should 
 have a high percentage of volatile combustible constitu- 
 ents, and any sulphur which it may contain should be, as 
 far as possible, in that state in which it is not volatilized 
 during distillation. A residue of good coke is also highly 
 desirable. For this purpose, therefore, the fat, caking, 
 bituminous coals are selected, with which cannel coal is 
 sometimes mixed ; this latter kind of coal, although very 
 rich in volatile matter, yielding a residue of too inferior a 
 character to be used profitably alone. 
 
 Although what has here been said may serve as useful 
 suggestions to the student, in the selection of fuels best 
 adapted to certain purposes, where such a selection is pos- 
 sible within reasonable limits of cost, yet it must always 
 hold true that local supplies of mineral fuels, whatever 
 their quality, must be the chief dependence of communities, 
 because of their proximity to the consumer. Lignites, 
 often of very inferior quality, are coming into increasing 
 use in the western part of our continent ; and the statistics 
 of Germany and Austria show that more than 22,000,000 
 tons of this fuel are annually used in those countries for 
 domestic and other purposes. Although peat is widely dis- 
 tributed in marshy places over the Northern United States 
 and Canada, it has not yet been much used as fuel in 
 this country, because of its high percentage of water and 
 its objectionable odor, as well as because of the abundance 
 and cheapness of coal. It is, however, largely used in Ire- 
 land, Scotland, and some parts of Germany ; and it is said 
 that more than 40,000,000 tons of this fuel are burned 
 annually in Holland. It is prepared for use by cutting 
 and drying, or by compressing it into bricks of convenient 
 size. It has been suggested that its efficacy as fuel may 
 be increased, and its disagreeable odor removed, by char- 
 ring it like wood before burning. (Page.) 
 
 For the natural gas, which is coming into so large 
 use very recently as a fuel, the student is referred to the 
 
1 64 APPLIED GEOLOGY. 
 
 succeeding chapter, where it is spoken of as the usual at- 
 tendant of petroleum, although frequently found without 
 this substance. 
 
 The student will do well to consult the geological manuals of Dana, 
 Geikie, and Credner, Dawson's "Acadian Geology," the geological 
 reports of the coal-producing States, and especially the second volume 
 of Rogers's report on Pennsylvania, the volume on mineral resources 
 of the United States, published by the Geological Survey in 1883, and 
 Johnson's report on American coals. 
 
CHAPTER IX. 
 
 GEOLOGICAL MATERIALS FOR ILLUMINATION. 
 
 CHIEF of the geologically furnished light-producers, at 
 present, is petroleum, which, within the last quarter of a 
 century, has attained a foremost place in point of cheap- 
 ness and efficiency, to which must be added the bitumi- 
 nous shales and cannels, which yield illuminating oil by 
 distillation, and ozocerite, or mineral wax, besides illumi- 
 nating gas, which has already been mentioned as derived 
 from bituminous coals. 
 
 What is known under the general name of petroleum, 
 includes a series of hydrocarbon oils, varying widely in 
 physical properties. Some are limpid fluids and may be 
 burned for light without refining, while, with many inter- 
 mediate grades, others are found viscid and even tar-like, 
 having sufficient body to make excellent lubricators for 
 machinery. Their color, by transmitted light, ranges 
 from a light yellow, through orange and red, to a reddish 
 brown so dense as to be translucent only in thin films, 
 while, by reflected light, it passes from a light dusky to a 
 dark green and to a black. Their gravity ranges from 
 about 26 to 52 Beaume". They differ as markedly in 
 odor, also, as in other properties, some having a very dis- 
 agreeable smell, while that of others is considered even 
 pleasant. 
 
 Mode of Occurrence of Petroleum. Petroleum 
 is found at many points, issuing in small quantities from 
 
1 66 APPLIED GEOLOGY. 
 
 the earth in the form of springs; but, as a substance of 
 economic importance, it is almost invariably found stored 
 in deposits of porous rock, usually sandstones or con- 
 glomerates, which are incased above and below in prac- 
 tically impervious strata of shale or other clayey materials. 
 The porous rock plays the part, in truth, of a vast sponge 
 saturated in all its pores with petroleum and its usual 
 accompaniment, combustible gases. It is obvious, then, 
 that the storage capacity of such a bed will depend on its 
 extent, its thickness, and its porosity. An oil-bearing 
 sand-rock of considerable thickness, and of tolerably 
 uniform and loose texture, is likely to yield largely, and 
 to afford a good degree of certainty of success to the 
 operator, while one of little thickness, or whose texture 
 varies greatly in a vertical and horizontal direction, will 
 be not only uncertain to reach at favorable points, but 
 less likely to yield supplies of much durability. For ex- 
 ample, the unusually thick and uniform sand-rock of 
 Bradford, Pa., has given but a small percentage of unsuc- 
 cessful ventures over a considerable area, and is still pro- 
 ducing largely after a number of years of vigorous ex- 
 ploitation ; while the territory along Oil Creek and the 
 Alleghany River in western Pennsylvania, where the oil- 
 bearing rocks occur in long and narrow belts, and are 
 made up of irregular alternations of materials of highly 
 variable texture, and often of no great thickness of porous 
 rock, has afforded a large percentage of unproductive 
 wells, and, while often producing largely, has in many 
 localities been subject to early exhaustion. The imper- 
 vious incasement is also highly essential, to retain within 
 the sponge-like rock a substance so volatile as petroleum, 
 and to prevent its dissipation. Where the oil-bearing 
 rock is intersected by fissures which reach the surface, or 
 is tilted so as to outcrop, much of its valuable contents is 
 sure to have been lost. The idea, once somewhat preva- 
 lent, that the oil is stored in fissures, has been shown by 
 
GEOLOGICAL LIGHT-PRODUCERS. 167 
 
 developments to have little foundation in fact ; and the 
 oil-producer looks for success rather to a properly con- 
 ditioned rock than to any fissures which may casually be 
 encountered in boring. Where fissures occur locally in 
 the rock they are helpful, not so much by increasing its 
 storage capacity as by promoting a ready flow of its con- 
 tents ; and, in all cases, the operator produces them arti- 
 ficially, by shattering the oil-rock with explosives, to in- 
 crease the extent of surface from which percolation may 
 take place. Where favorable conditions are met with, of 
 a porous storage-rock and an impervious incasement, the 
 petroleum and its accompanying gas are usually found, at 
 the outset, existing under enormous pressure, so that, 
 when a fresh territory is first pierced with the drill, the oil 
 frequently rises to the surface with great force, even from 
 the depth of many hundred feet, producing flowing wells. 
 A number of such wells in Pennsylvania have poured 
 forth at first from two thousand to more than three thou- 
 sand barrels of oil per day. As the pressure is relieved 
 by the flow and by the sinking of additional wells, the 
 rate of flow invariably diminishes, until ultimately the oil 
 no longer reaches the surface, and resort must then be 
 had to pumping. The question of the origin of. this in- 
 teresting substance is one which can by no means be con- 
 sidered to have been definitely settled as yet. It seems 
 probable, however, that it has originated from accumula- 
 tions of marine vegetation, and possibly, in some cases, 
 also from animal substances, which, subjected during vast 
 ages to a process of gradual change and distillation, have 
 evolved fluids and gases that have slowly permeated the 
 minute crevices of the overlying strata, until they have 
 found final lodgment in the porous strata where they now 
 occur. 
 
 The chief geological horizons from which petroleum is 
 procured in paying quantities, leaving out of view those 
 in which it has not yet proved of economic importance, 
 
X 68 APPLIED GEOLOGY. 
 
 are, first, the Corniferous, from which it is obtained in the 
 western part of the Province of Ontario near Lake St. 
 Clair ; second, several different geological levels in the 
 Upper Devonian of Pennsylvania and New York, of which 
 that of Bradford and its vicinity is lowest, succeeded by 
 that of the Warren and Forest County region, and this by 
 that of Oil Creek and the Alleghany River ; third, the Car- 
 boniferous, in which are found the usually heavy oils of 
 West Virginia and the adjacent part of Ohio, with two 
 other limited areas in northern and eastern Ohio ; and, 
 fourth, the Tertiary and possibly more recent deposits, in 
 which occurs the petroleum of California, that east of the 
 Carpathians in Galicia and Moldavia, that near Baku, 
 on the Caspian Sea, and that on the Irrawaddy River, in 
 Burmah, and on some of the coast islands of Burmah. 
 
 At the first of these horizons, near Lake St. Clair, some 
 petroleum has been obtained from surface-wells, sunk in 
 the drift materials overlying the limestones ; but the chief 
 supplies have been drawn from the Corniferous limestones 
 themselves, which here vary from a close to an open text- 
 ure, and are overlaid by about three hundred feet of 
 shales. The oil is black, of an unpleasant odor, and of 
 somewhat higher gravity than that of Pennsylvania, in 
 comparison with which last region its production has 
 always been small. Oil is also known to occur, near this 
 horizon, in southern Kentucky and adjacent parts of Ten- 
 nessee, but it has not yet been considerably produced in 
 this section. 
 
 The Upper Devonian rocks of the Chemung and possi- 
 bly of the Catskill period have, for many years, in west- 
 ern Pennsylvania and the adjacent part of New York, 
 furnished by far the greatest supplies of petroleum known 
 to exist, about five sixths of the world's supply being de- 
 rived from this region. The petroleum is here obtained 
 from a porous sand-rock, underlaid and covered by im- 
 pervious shales. The oil territory which was first discov- 
 
GEOLOGICAL LIGHT-PRODUCERS. 169 
 
 ered and developed, occupying parts of several counties 
 in western Pennsylvania, along Oil Creek and the Alle- 
 ghany River, has given rise to the prevailing nomenclature 
 of the oil-producers. Petroleum is here found in a triple 
 group of white or gray, often loosely cemented, and porous 
 sandstones and conglomerates, called respectively the 
 first, second, and third sands, which are separated from 
 each other by considerable beds of shaly rocks. This oil- 
 bearing series has an average thickness of about three 
 hundred and fifty feet, and is overlaid by about four hun- 
 dred feet of soft, impervious shales. Still above these, in 
 many places, are found beds of sandstones or conglomer- 
 ates belonging to the Lower Carboniferous, and termed the 
 first and second mountain sands, because they usually cap 
 the highest hills. The oil-bearing sand-rocks are very 
 variable in thickness, composition, and texture, and are 
 sometimes split into benches by intercalations of shale, 
 thus locally giving rise to more than three sand-rocks, 
 while the series as a whole retains its usual thickness. 
 The portions which produce oil are usually of but little 
 width, often no great number of rods, though sometimes 
 extending, with occasional interruptions, for some miles 
 in the same general direction, bearing thus the character 
 of deposits along an ancient shore-line. These lines of 
 productiveness are the oil-belts. The lowermost, or third 
 sand, is, in much the greater number of cases, the storage- 
 rock ; and hence an oil-bearing rock is apt to be called 
 the third sand by operators, even in regions of quite dif- 
 ferent structure. Where the third sand is wanting, as, for 
 example, where the others overlap it, or where it is not 
 porous, the second or the first sands may produce oil, but 
 often of a different character from that usually found in 
 the third sand. The usual third sand oil has a gravity of 
 about 46 Beaume", and is of a dark-green color by re- 
 flected light, while some of those from the higher sands 
 are black, or have a reddish tint, or are of so high gravity 
 
1 70 APPLIED GEOLOGY. 
 
 as to fit them for lubricators rather than for illumination. 
 The depth of the wells in this region varies from a few 
 hundred feet to 1,600 or 1,800 feet, the deepest wells 
 occurring in the southern part of the territory, toward 
 which the strata have a gentle dip. 
 
 The celebrated Bradford region, in McKean County, 
 Pennsylvania, with its continuation in New York, which 
 has for a number of years produced so vast an amount of 
 petroleum, has its storage-rock at a geological level fully a 
 thousand feet below that which has just been described, 
 and differs widely from it in general structure. The oil- 
 bearing sand-rock is of a fine texture, tolerably compact, 
 yet loosely cemented, and ranging in color from brown to 
 a light gray, forming a storage-rock of an average thick- 
 ness of perhaps forty-five feet, and varying so little in 
 texture that over a producing territory of about one hun- 
 dred and ten square miles not more than four per cent of 
 the wells have proved unproductive. Above this stratum, 
 which is called the third sand, lies a very thick mass of 
 shaly rock with occasional sandy strata, among which the 
 well-drillers number a first and second sand, following the 
 traditions of the region first explored, to which this bears 
 no structural resemblance. The average depth of the wells 
 in this district ranges from 1,200 to about 2,000 feet, the 
 deepest wells being found in its southwestern part. The 
 cost of drilling and equipping a well 1,500 feet deep, in 
 1880, was estimated to be about $3,250. 
 
 The oil-producing horizon in Warren and Forest 
 Counties, intermediate between that of Bradford and that 
 of Oil Creek, has yielded productive wells in porous rocks, 
 varying t greatly in character and at different levels, the 
 physical characters of the product being as variable as 
 those of the conditions under which it occurs. Some of 
 these oils are transparent, and of various reddish or amber 
 tints, with .a gravity of about 47 or 48, while others are 
 greenish and nearly opaque, with a gravity of 40. A 
 
GEOLOGICAL LIGHT-PRODUCERS. 171 
 
 number of remarkable wells have been found in this 
 region, several of which have started out with the aston- 
 ishing daily production of from 2,000 to 3,000 barrels ; 
 but their activity has invariably been very short-lived, and 
 as a class the wells of this district have shown little dura- 
 bility. 
 
 The oil district of West Virginia, extending into Wash- 
 ington County, Ohio, obtains its supplies from sandstones 
 of Carboniferous age. The oil is said to occur in fissures 
 on the site of gentle anticlinal axes. Its actual mode of 
 occurrence probably does not differ materially from that 
 which has been found to hold true on so extensive a scale 
 in Pennsylvania. The oil is of greater gravity than that 
 of Pennsylvania, ranging from 28 to 40 B., and the 
 production has not been large, amounting in 1880 to 
 about 220,000 barrels of 42 gallons, or about 600 barrels 
 daily. The oil-producing territory of California occurs 
 in two of its southwestern counties near the coast. In 
 this region, large natural springs of petroleum with exten- 
 sive sheets of asphaltum arising from its evaporation, 
 have for many years been known to exist ; the oil issuing 
 from the outcropping edges of highly inclined bituminous 
 strata of probable Tertiary age. The amount of oil ob- 
 tained from borings in these strata has not hitherto met 
 the sanguine expectations of the earlier explorers, appar- 
 ently so well justified by the surface exudations. The 
 estimated production of 1882 was about 70,000 barrels, or 
 less than 200 barrels per day ; though for a portion of 
 that year a daily production of 500 barrels was claimed. 
 From what are now known to be the usual conditions on 
 which large supplies of petroleum seemingly depend, a 
 great production can hardly be looked for from this dis- 
 trict. 
 
 Of all the regions at present producing petroleum from 
 the Tertiary or later deposits, that of Baku, on the Cas- 
 pian Sea, is by far the most promising. Here, for many 
 
1/2 APPLIED GEOLOGY. 
 
 ages, a tract twenty-five miles long and a half-mile in width 
 has yielded petroleum (naphtha) from a porous argilla- 
 ceous sandstone of Tertiary age, the wells being usually not 
 more than twenty-five feet deep. Recent careful explora- 
 tions show, it is said, that the possible productive area 
 may amount to as much as 1,260 square miles ; and the 
 active development now in progress resulted in a produc- 
 tion, in 1882, of nearly 5,000,000 barrels, and in 1884 of 
 about 6,700,000 barrels; from which it seems likely that 
 this is destined to be a formidable competitor to the oil- 
 regions of Pennsylvania. The petroleum of Baku is said 
 to vary from a clear naphtha-like fluid to one of a yellow- 
 ish-green and reddish-brown, with a gravity of from 26 to 
 36 B. It yields only about 33 per cent of illuminating oil, 
 the residuum being burned for fuel. 
 
 The long-known petroleum of Burmah is obtained 
 chiefly from wells of no considerable depth, in a soft 
 greenish sandstone of late geological age, inclosed in im- 
 pervious beds of sandy clay, near the Irrawaddy River. 
 The productive territory is said to be less than a square 
 mile in area, and the amount produced annually does not 
 reach 1,000,000 barrels. Petroleum is also found in 
 small quantities in springs on several islands off the west 
 coast of Burmah. The Burmese product is of two kinds : 
 one, which seems to resemble our u amber oil," is of light 
 gravity and reddish color, and yields a high per cent of 
 illuminating oil with little parafnne ; the other is thick, of 
 a greenish color and agreeable smell, and holds a large per 
 cent of paraffine. The petroleum which is reported to ex- 
 ist in considerable quantities in deposits of Tertiary age 
 north of the Carpathians does not seem as yet to have 
 made any figure in the markets of the world. Of that 
 which is said to have been long produced in China, little 
 is known wkh certainty. Small quantities are also ob- 
 tained in Japan, according to Prof. Lyman, from wells 
 dug to no considerable depth. 
 
The amount of petroleum produced in 
 and adjacent parts of New York, in 1882, was reported to 
 be 30,053,500 barrels of forty-two gallons ; and in June, 
 1883, the daily production was nearly 66,000 barrels, or at 
 the rate of about 24,000,000 barrels yearly, a rate which 
 was continued in 1884. It may thus be seen that the 
 production of Pennsylvania is by far the greatest factor in 
 the world's supply of this very useful commodity, that of 
 the Caspian region ranking second. 
 
 How Oil-Weils are bored and operated. In 
 few branches of business have there been more remark- 
 able improvements made, both in simplicity and effective- 
 ness of work and in diminution of expense, than those 
 which have been suggested by experience in drilling and 
 operating oil-wells. This might naturally be expected, 
 when we consider the great number of active and highly 
 intelligent men who are engaged in a business involving 
 more than usual risks, and in which the tendency to a 
 constant diminution in the price of the product demands 
 a corresponding diminution in the cost of production. 
 Then, too, the number of these usually very deep borings 
 has been enormous, being counted by the tens of thou- 
 sands. The number of oil-wells producing simultaneously 
 in the Pennsylvania region has sometimes been more than 
 nineteen thousand ; and the number of new wells in prog- 
 ress has not for many years fallen so low as a hundred, 
 and has, not unfrequently, been more than four hundred. 
 Hence, undertakings which thirty years ago would have 
 been considered remarkable, have come to be matters of 
 ordinary every-day business, and the means by which they 
 could most easily be accomplished have demanded the 
 attention of many clear-sighted men. At the outset, bor- 
 ings at first four inches and later five and a half inches in 
 diameter were sunk to the oil-producing rock, no effort 
 being made to shut off the water which entered the boring 
 from porous rocks encountered in the strata that were 
 
174 
 
 APPLIED GEOLOGY. 
 
 penetrated. Hence the well, however deep, was always 
 nearly full of water while the boring was in progress, caus- 
 ing serious inconveniences, not only by lessening the force 
 of the drilling-tools, and by converting into fluid mud 
 some of the softer shales to embarrass the drillers, but 
 also by making it uncertain when an oil-bearing rock had 
 really been reached, until the water-veins had been shut 
 off and the well cleared of water by pumping. These and 
 other difficulties eventually led to the adoption of the pres- 
 ent form of boring, which seems admirably adapted to its 
 purpose. 
 
 Where the loose surface materials are of considerable 
 depth, a wrought-iron drive-pipe, of eight inches interior 
 diameter, is forced down vertically to the bed-rock, in suc- 
 cessive lengths of nine feet each ; and an eight- inch hole 
 is drilled through this pipe till it reaches the bottom of the 
 lowest water-bearing stratum, when it is tapered gradually 
 down to five and a half inches. Into this hole, an iron pipe 
 of five and a half inches inside diameter, called the casing, 
 screwed together in lengths, and surrounded at the bottom 
 by a properly constructed collar, is lowered and firmly seat- 
 ed on the tapering shoulder prepared for it, thus shutting 
 off all water from above. From this point downward the 
 drilling, five and a half inches in diameter, is prosecuted 
 dry, water being poured in from the top through the casing 
 to moisten the powder produced by the drill, so that it may 
 be removed as mud by an instrument called a sand-pump, 
 which consists usually of a cylinder six to ten feet long of 
 thin iron, provided at the bottom with a spindle-valve 
 opening upward, and at the top with a bail by which it is 
 attached to a stout rope of proper length. The usual 
 drilling-tools are sixty-two feet long and weigh twenty- 
 one hundred pounds. They consist of several parts 
 screwed firmly together, and called, commencing from be- 
 low, the bi^ the auger-stem, the jars, the sinker-bar, and the 
 rope-socket. The first named is the steel-edged chisel which 
 
GEOLOGICAL LIGHT-PRODUCERS. 175 
 
 cuts the rock, and is screwed above to the auger-stem, a 
 bar of iron thirty feet in length. The jars, a highly im- 
 portant device, are two elongated steel-faced links with a 
 play of thirteen inches, the lower link of which is screwed 
 to the auger-stem, and aids in giving the downward or cut- 
 ting blow, while the upper link attached to the sinker-bar 
 aids the two upper members to give a sharp upward stroke 
 to the tools on their ascent, by which the bit is loosened 
 from the rock. The rope-socket is the upper member of 
 the series, and is securely attached to the great rope-cable 
 by which the string of tools is to be raised and lowered, 
 and given motion in drilling. For the purpose of raising 
 and lowering the drilling-tools, and of operating the well 
 after it is completed, a stout, pyramidal framework about 
 seventy-five feet in height, called a derrick, is erected over 
 the site of the proposed well. At one side of this is set 
 the steam-engine that furnishes the power, with the band- 
 wheel and walking-beam by which the drilling-tools and 
 other parts of the machinery are driven. At the top of 
 the derrick is a stout pulley over which the drill-cable 
 passes, and a little below a second pulley for the sand- 
 pump rope. The end of the drill-cable opposite to that 
 to which the tools are attached is coiled around a large 
 cylindrical drum, called a bull-wheel, to which motion is 
 given by the engine in raising the tools from the well : 
 they will naturally descend by their own weight when per- 
 mitted, the rate of their descent being controlled by a 
 powerful brake applied to the bull-wheel. When the tools 
 are lowered ready for drilling, they are connected with the 
 end of the walking-beam by an arrangement called a tem- 
 per-screw, the lower end of which is firmly clamped to the 
 cable at the proper point. By this means, as the bit cuts 
 deeper into the rock, the tools can be gradually lowered 
 until the screw, about four feet long, is run out, when the 
 tools must be raised and the well cleaned out with the 
 sand-pump. When the oil-sand is reached, specimens of 
 
176 APPLIED GEOLOGY. 
 
 the drillings are taken for every run, and carefully pre- 
 served to serve as a guide in operating the well. In order 
 to secure a perfectly cylindrical hole, the tools are rotated 
 when in action, by means of a lever inserted in rings of 
 the temper-screw. 
 
 A full description of the mode of drilling oil-wells, with 
 working drawings, may be found by the student in Vol. 
 I 8 of the " Second Geological Survey of Pennsylvania." It 
 seemed fitting, however, to include, in a work of this char- 
 acter, this brief account of an operation so interesting 
 even aside from oil-production, the improvements in which 
 have reduced the cost of deep borings to about one fourth 
 of what they were less than twenty years ago, while di- 
 minishing the time consumed in fully as great a ratio. 
 
 In the present mode of drilling a well dry, it can be 
 ascertained, soon after the oil-rock has been penetrated, 
 whether the well is likely to be successful. In case the 
 show of oil and gas is satisfactory, the drilling-tools are 
 removed, and the well is tubed with iron tubing of two 
 inches diameter inside, screwed together in lengths until 
 the bottom of the well is reached. The lower end of the 
 tubing is provided with an anchor, made of a piece of per- 
 forated casing a few feet in length, to the top of which 
 the working barrel is attached. The pump-rods, with a 
 suitable valve at bottom, are next inserted into the tubing, 
 being screwed together in lengths ; the upper end of the 
 pump-rod is attached to the walking-beam, and the opera- 
 tion of pumping oil begins. The oil passes to a tank by a 
 side-pipe near the top of the tubing, while the gas, which 
 is usually present, rises in the annular space between the 
 tubing and casing, and is carried by another side-pipe to 
 be burned as fuel under the boiler. In many cases, espe- 
 cially in the Bradford district, the oil is of such quality 
 that the operation of pumping can be dispensed with, and 
 the well compelled to flow by heads. This is effected by 
 encircling the tubing, at a proper point above the oil-rock,, 
 
GEOLOGICAL LIGHT-PRODUCERS. 177 
 
 with an annular valve called a. packer, by which the space 
 between the tubing and the walls of the well is closed 
 gas-tight. The accumulating force of the oil and gas thus 
 imprisoned below will then cause the well to flow periodi- 
 cally, or by heads. 
 
 Almost universally, before the well is tubed, the oil- 
 producing rock is shattered by means of torpedoes charged 
 with nitro-glycerine to facilitate the influx of oil. These 
 torpedoes are simply tin shells, sometimes twenty to thirty 
 feet long, and containing not unfrequently from thirty 
 to sixty quarts of nitro-glycerine. These are lowered to 
 their place by means of a wire, which is then unhooked 
 and withdrawn, and the torpedo exploded by dropping a 
 weight from above upon a detonating cap in its top. "The 
 commotion caused by so large an amount of this violent 
 explosive can be more easily imagined than described. 
 This operation is also frequently resorted to when the 
 production of a well becomes greatly diminished, the tub- 
 ing being withdrawn before the torpedo is used. 
 
 Refining. The method of refining crude petroleum, 
 to fit it for being burned in lamps, is based on the fact 
 that the various ingredients of this highly complex sub- 
 stance have different boiling-points. Hence, by a process 
 of fractional distillation at regulated temperatures, the 
 more volatile ingredients, such as gasolene, naphtha, and 
 benzine, which would render the oil dangerous to be 
 burned in lamps, are first driven off, succeeded next by 
 illuminating oil, and leaving behind in the still a tarry 
 residue which may be further separated by distillation, 
 leaving a final residue of coke. The illuminating oil is 
 then further purified by agitation with sulphuric acid, by 
 which a tarry substance is separated from it, and finally 
 by agitation with water and an alkali to remove all traces 
 of the acid. The average results obtained at a refinery in 
 Titusville, Pa., treating petroleum of about 46 Beaume, 
 were given as the following : 
 
178 APPLIED GEOLOGY. 
 
 Naphtha, etc '. 10 per cent. 
 
 Illuminating oil 75 
 
 Tarry residue 7 
 
 Gas and loss 8 
 
 Total 100 
 
 In a different mode of refining, a smaller proportion of 
 illuminating oil is made, and the heavier products are 
 separated as lubricators for machinery. 
 
 Uses. Besides the well-known extensive use of petro- 
 leum for lighting purposes, the crude heavy oils are very 
 valuable as lubricators for machinery. Several of its by- 
 products are also largely used ; as, for example, paraffine, 
 which, besides entering into the manufacture of candles, 
 has several other valuable applications ; the so-called 
 naphtha, which is used for mixing paints and varnishes, 
 and as a solvent for resins and grease ; while gasolene is 
 employed as a carburetting agent in automatic gas-ma- 
 chines. Both crude petroleum and the residue from re- 
 fining are also largely used as fuel in Russia. 
 
 For additional information with respect to petroleum, the student 
 will do well to consult the " Second Geological Survey Reports of 
 Pennsylvania," Vols. I, I 3 , I 4 , J, and R ; the section on petroleum in 
 " Mineral Resources of the United States," published by the United 
 States Geological Survey in 1883 ; " Tenth Census of the United 
 States," Vol. X ; and the article " Petroleum " in Appletons' " Amer- 
 ican Cyclopaedia." Valuable information may also be obtained from 
 " Geology of Canada," 1863, and Vols. I, II, III of Ohio " Geological 
 Reports," as well as from papers of Drs. Newberry and T. S. Hunt, 
 on this and allied subjects. 
 
 To illustrate what has been said of the mode of occur- 
 rence of petroleum, the present mode of drilling and 
 operating oil-wells, and the tools that are used in drilling, 
 the following figures are appended. 
 
 Other Mineral Light-Producers. Before the dis- 
 covery and development of the great sources of natural 
 rock oils, illuminating oils were produced to a consider- 
 
OIL 
 
 3'6" [f] Rope-socket. 
 
 Sinker-bar. 
 
 CASINt 
 HEAD 
 
 Drift with 8" drive 
 
 Shale.! 
 
 PIPE 
 
 First mountain sand,. 
 water-bearing. 
 
 30' Au i er - stem - 
 
 Shale.! 
 
 Second mountain^ 
 sand, lowest wa-~ 
 ter-bearing. Cased; 
 here, 5$" casing. = 
 
 Shale.! 
 
 ILL-H(. 
 
 Bit. 
 
 Oil series. First: 
 sand. 
 
 Shale.^ 
 
 Second sand.] 
 
 Shale.] 
 
 Third sand.} 
 
 Bottom shale j 
 
 FIG. 14. Drilling-tools. To- 
 tal length, 61' i* ; weight, 
 2,100 Ibs. ; down stroke, 
 1,320 Ibs. ; upward stroke, 
 780 Ibs. 
 
 F IG 15. Ideal Section of Oil- Well, Oil 
 Creek, Pa. 
 
180 APPLIED GEOLOGY. 
 
 able extent by the distillation, at a dull-red heat, of cannel 
 and fat bituminous coals, and also by the distillation of 
 black bituminous shales called oil-shales or pyroschists. 
 The use of oil obtained from these substances has been 
 wholly superseded in this country by the abundant and 
 cheap mineral oil ; but the manufacture of oils from these 
 sources continues to be a considerable one in some parts 
 of Europe, both cannels and oil-shales being used for this 
 purpose. Of the latter, more than a million tons were 
 raised for distillation in Great Britain in the year 1882.* 
 Should the production of petroleum seriously diminish in 
 this country, as it seems quite likely to do at an early day, 
 unless sources of supply now unknown are discovered, re- 
 course must be had, at no distant time, to our cannels, 
 like the Breckenridge of Kentucky, and to our bituminous 
 shales, now useless, which are found abundantly at many 
 geological horizons. The bituminous shales at the base 
 of strata of the Hudson period in the Lower Silurian, 
 called the Utica slates, extend widely over the north- 
 ern part of New York and Canada, containing important 
 amounts of carbonaceous matter, amounting sometimes to 
 as much as 20 per cent, and are thought by Dr. Newberry 
 to be the ultimate source of the oils of western Canada. 
 At the base and summit of rocks of the Hamilton period, 
 in central New York, are found the Marcellus and Gene- 
 see black shales, which are often marked along their out- 
 crops by springs of oil and gas, and the latter of which, 
 in its western extension, becomes the Huron shale of 
 central Ohio, being there about three hundred and fifty 
 feet thick, and stretching southward into Tennessee. It 
 is estimated by Dr. Newberry to be capable of yielding 
 by distillation from ten to twenty gallons of oil per ton. 
 From the horizon of the Genesee and Huron shales, 
 abundant gas-wells have also been obtained along the 
 shores of Lake Erie, from Fredonia, in New York, to near 
 * This amount was increased to 1,518,871 tons in 1884. 
 
GEOLOGICAL LIGHT-PRODUCERS. 181 
 
 Cleveland, and also in Knox County, Ohio. The gas is 
 utilized for heat and light, and, in Knox County, for mak- 
 ing what is called " carbon-black," a substance nearly 
 equal in value to ivory-black. Bituminous shales are 
 found abundantly in the Carboniferous, as might be ex- 
 pected, since the source of the bituminous matter is doubt- 
 less largely vegetable; in the Triassic of Virginia and 
 North Carolina, some of the strata of which are so highly 
 bituminous as to be classed by O. J. Heinrich as the 
 Oleiferous group ; in the Cretaceous of Colorado and ad- 
 joining regions ; and in the Tertiary rocks of western Cal- 
 ifornia, especially in Venturas and Santa Barbara Counties, 
 from whose interbedded sandstones is derived the oil men- 
 tioned on a previous page. Most pyroschists contain also 
 a considerable amount of nitrogen, which, by proper mani- 
 pulation during distillation, can be obtained as ammonia. 
 
 In some of the earlier reports of the Geological Sur- 
 vey of Canada, Dr. T. Sterry Hunt has drawn attention 
 also to our abundant beds of peat as a possible future 
 source of oil, paraffine, gas, and other products, by distilla- 
 tion. 
 
 In 1877 an important deposit of ozocerite, or mineral 
 wax, was discovered in southern Utah, this substance hav- 
 ing previously been known chiefly from Moldavia, east of 
 the Carpathians. It is of a wax-like appearance, and 
 ranges in color from whitish to black. It is said to yield 
 by fractional distillation from 8 to 10 per cent of illumi- 
 nating oil, and 60 per cent of paraffine. Such are the 
 chief light-producers of mineral origin. To recapitulate 
 briefly, they are : 
 
 1. Gas and oil, obtained by the distillation of bitumi- 
 nous and cannel coals, bituminous shales, peat, and, to a 
 small extent, from ozocerite. 
 
 2. Petroleum, occurring at present in porous or some- 
 times fissured storage-rocks, but having its probable deep- 
 seated source in bituminous shales. 
 
 9 
 
1 82 APPLIED GEOLOGY. 
 
 3. Natural gas, derived from oil-bearing rocks, and 
 from wells sunk in bituminous shales. 
 
 4. Paraffine, obtained from ozocerite, and as a by- 
 product in the refining of various bituminous sub- 
 stances. 
 
CHAPTER X. 
 
 MODE OF OCCURRENCE OF METALLIFEROUS DEPOSITS. 
 
 ON account of the very great importance of many of 
 the metals in the arts and industries of civilized man, as 
 well as of the difficulties and uncertainty that attend their 
 discovery and exploitation, much attention has naturally 
 been directed to the various combinations in which they 
 occur, to the minerals with which they are found associ- 
 ated, and to the geological nature, structure, and origin of 
 the deposits in which they are found. 
 
 As is pretty generally known, very few of the metals 
 occur in nature in the metallic or uncombined state. In 
 the vast majority of cases, they are found in chemical 
 combination with some other element or elements, form- 
 ing that class of mineral substances known as ores. These 
 ores usually differ widely in appearance and properties 
 from the metals which give them their value, and require 
 to be subjected to some chemical process before the metal 
 which they contain can be separated and utilized. Nor 
 are the ores themselves usually found simple and unmixed. 
 Almost universally they occur associated and intermingled 
 with other mineral substances, which frequently make up 
 the chief bulk of the metalliferous deposit, and from 
 which they must be separated by processes sometimes 
 mechanical, sometimes chemical. These associated min- 
 erals are known by the name of gangues or vein-stones. 
 Again, although several of the metallic ores occur widely 
 
1 84 APPLIED GEOLOGY. 
 
 diffused in minute quantities in many rocks as, for ex- 
 ample, iron, traces of which may be found in nearly all 
 rocks still, to be of any economic importance, they must 
 by some means have been concentrated in certain places 
 into deposits of such richness as to admit of their profit- 
 able extraction. Such concentrations are called ore de- 
 posits, and to these various names are given, according to 
 their structure and the geological conditions under which 
 they occur. 
 
 Metallic Ores. Of the metals possessing economic 
 importance, gold and platinum are almost always found in 
 the metallic state ; bismuth also most largely so ; and cop- 
 per, which usually occurs in the state of ores, in one fa- 
 mous region is found in vast quantities as a native metal. 
 Besides these, silver and mercury occasionally occur in 
 the metallic state. Much the most widely diffused miner- 
 alizing agents of ores are sulphur, oxygen, and carbonic acid, 
 to which are added in much smaller measure silica, arsenic, 
 and chlorine. Most of the leading metals have compounds 
 with sulphur, and in the case of several of the metals 
 these sulphides form their chief ores. Pyrites, the iron 
 sulphide, common as it is, and great as is its economic 
 importance, can hardly be called a source of iron ; but the 
 sulphides of silver, both alone and combined or associ- 
 ated with sulphides of lead, antimony, and arsenic, con- 
 stitute a chief source of silver. So the sulphide of mer- 
 cury (cinnabar), stibnite (the sulphide of antimony), and 
 galena (the lead sulphide), are the main sources of these 
 three metals ; while blende (the zinc sulphide) and the 
 various sulphides of copper, or of copper combined with 
 iron, are leading ores of their respective metals. Millerite, 
 a nickel sulphide, is also a valuable ore ; and bismuthinite, 
 the sulphide of bismuth, is said to be the source whence 
 the United States are likely to derive their future supplies 
 of this metal. 
 
 Among the oxide ores, those of iron have a foremost 
 
METALLIFEROUS DEPOSITS. 185 
 
 place, being, though not the sole, yet a leading source 
 whence are derived the supplies of this most important 
 metal. Tin is obtained almost wholly from its oxide, cas- 
 siterite. The most valuable ores of manganese are its 
 oxides ; and the brilliant compounds of chromium are 
 wholly derived from chromite, an oxygen compound of 
 chromium and iron. Zincite, the red oxide of zinc, found 
 in New Jersey, is a valuable ore. Oxides_of copper and 
 of cobalt also occur, and are used wherever found as 
 sources, the one of copper, and the other of smalt. 
 
 The important carbonate ores are those of iron, cop- 
 per, lead, and zinc. The iron carbonate, called siderite, 
 or spathic iron, whether pure or mingled with varying 
 amounts of earthy or bituminous matters, as clay iron- 
 stone and black-band ore, are highly important ores of iron 
 and largely utilized. Malachite (the copper carbonate), 
 the lead carbonate (cerusite), and smithsonite (the carbon- 
 ate of zinc), occur usually associated with other ores of 
 their respective metals, notably the sulphides, have evi- 
 dently been derived from them, and are valuable ores. 
 
 The silicate ores are those of zinc called calamine, of 
 copper called chrysocolla, and several of nickel, all of 
 which are employed as sources of their metals. Rho- 
 donite, a manganese silicate, is also utilized somewhat in 
 coloring glass and porcelain. 
 
 The only chloride ore of any importance is cerargyrite 
 or horn-silver, which is a considerable source of silver. 
 Arsenic forms several ores with nickel and cobalt which 
 are important as sources of nickel and of the compounds 
 of cobalt. 
 
 Besides these, ores, notably those of gold and silver, 
 are sparingly met with in which tellurium is the mineral- 
 izing agent. These tellurides, variously combined, consti- 
 tuting the minerals sylvanite, hessite, petzite, nagyagite, 
 and calaverite, are valuable ores of the precious metals in 
 the few localities where they occur. 
 
!86 APPLIED GEOLOGY. 
 
 Ore Associations and Gangues. Besides the com- 
 paratively simple ores that have been mentioned above, 
 others of a much more complex character are frequently 
 met with, formed by the union of two or more metals with 
 the same mineralizing agent, or by the partial replacement 
 of one element by another. Thus the most common ore 
 of copper, chalcopyrite, is a double sulphide of iron and 
 copper. Common ores of silver are sulphides of silver 
 and antimony, or of silver and arsenic ; and in the first, 
 portions of the silver and antimony may be replaced by 
 copper and arsenic. Cobalt and nickel also have arsen- 
 ides and sulphides in which one metal may partially re- 
 place the other, forming double compounds ; or antimony 
 may partly replace arsenic in the nickel arsenides, giving 
 rise to another form of complication. So in the mineral 
 tetrahedrite, often called gray copper, which is a sulphide of 
 copper and antimony, the copper may be partially replaced 
 by iron and zinc, or by silver, forming a valuable ore of 
 silver ; while arsenic may take the place of a part of the 
 antimony, giving rise to a highly complicated ore. Be- 
 sides the complications of composition of which these few 
 examples have been given, others arise from frequent 
 associations of ores. Thus ores of silver are so frequently 
 associated with those of lead that argentiferous lead-ores 
 are a large source of silver, as in some of our great West- 
 ern mining regions. Silver sulphide is found also with 
 zinc sulphide, forming another often rich but somewhat 
 troublesome ore, as in some of the mines about George- 
 town, Colorado. So, too, the ores of lead and zinc are 
 very often closely associated ; iron pyrites is intermingled 
 usually with more or less of copper pyrites, and vice versa ; 
 and manganese-ores occur with those of iron. Tin-ore is 
 almost always associated with a mineral called wolfram ; 
 platinum, always native, is invariably alloyed with one or 
 more of the rare metals iridium, palladium, rhodium, 
 and osmium ; and gold, likewise native, though alloyed 
 
METALLIFEROUS DEPOSITS. 187 
 
 with silver, is commonly associated with iron or copper 
 pyrites, making its extraction difficult save where its asso- 
 ciates have been removed by weathering. Only a few 
 of the more common associations and combinations have 
 here been mentioned by way of illustration. The student 
 who desires to go more fully into this subject will find 
 many more in special treatises on ore deposits like those 
 of Grimm, Von Cotta, and J. A. Phillips. 
 
 Ores of metals thus composed and associated are in 
 most cases arranged and disseminated in a considerable 
 bulk of other minerals having no value as ores, and which 
 are called gangues, or vein-stones. The most common of the 
 gangues are quartz, calcite, baryte, often called heavy-spar, 
 and fluor-spar. Sometimes the ore has little gangue, as 
 is the case with some deposits of iron-ore ; more common- 
 ly the gangue greatly surpasses- the ore in amount. This 
 is especially true in the case of ores of the precious metals, 
 as can be readily understood when we reflect that an ore 
 containing three hundred dollars' worth of silver per ton, 
 which would be considered very rich, would have no 
 more than one per cent of the metal, and that a gold -ore 
 of the same value would contain only about one twentieth 
 of one per cent, or about a pound in a ton. We call such 
 deposits gold or silver deposits, because they contain 
 enough of these metals or their ores to be worked with 
 profit ; when they might more justly be considered depos- 
 its of the gangue minerals slightly contaminated with gold 
 or with silver ores. Proportions of these ores such as 
 have been named, when viewed in the light of human en- 
 terprise, would be counted very rich and enormously 
 profitable ; but considered with reference to the relation 
 that they bear to the mass of the rock, they are evidently 
 but very minor accessories. The ratio which the ores of 
 the base metals bear to their gangues must naturally be 
 much greater than this, to bring them within the limits of 
 profitable working ; yet with these the question of profit 
 
1 88 APPLIED GEOLOGY. 
 
 is often dependent on some cheap and effective means of 
 separating a large amount of worthless rock from a com- 
 paratively small amount of valuable material. For exam- 
 ple, in the great Lake Superior copper-mines the native 
 copper is mingled with from 85 to 99 per cent of worth- 
 less vein-stone, which, however, can be mostly separated 
 by pulverizing the rock and washing it in suitable appa- 
 ratus. Such a process of separation of ore from gangue 
 is called concentration, and many very ingenious devices 
 have been contrived for this purpose, descriptions of which 
 may be found in technical works. They mostly depend 
 upon the use of currents of water, but sometimes of air, 
 whose velocity is so regulated as to sweep away the lighter 
 materials, leaving the heavier behind. The greater the 
 difference in weight of particles made nearly equal in size, 
 the easier and more complete the separation can be made. 
 Geological Mode of Occurrence and Structure 
 of Ore Deposits. Ore deposits are unquestionably due 
 to some process of concentration of substances, once wide- 
 ly and sparsely disseminated, or too deep-seated to be 
 available for human use. In some cases the concentra- 
 tion has been due to mechanical agencies, by which rocks 
 have been ground up, and their heavier and more un- 
 changeable portions collected in favorable places ; in 
 some others it has been effected possibly by the agency 
 of heat, which may have volatilized certain substances 
 and forced them up from considerable depths in the form 
 of vapor, to 'be condensed on cooling; but in the vast 
 majority of cases the accumulation of ore deposits has 
 been due to chemical solution, in which water has played 
 a prominent and essential part. By this last means, par- 
 ticles widely diffused have been removed by solution from 
 their parent rock, and have been carried away to be rede- 
 posited in fissures and cavities, or to fill the pores and 
 cellules in rocks ; or to react chemically with favorable 
 portions of some rocks, chiefly limestones, and thus to re- 
 
METALLIFEROUS DEPOSITS. 189 
 
 place them ; or, through change or dissipation of their 
 solvent, to be deposited in beds at the existing surface, 
 either alone or mingled with other substances. The most 
 important forms in which metalliferous deposits, thus 
 originating, are found to occur, though variously grouped 
 by different authors, may be conveniently tabulated as 
 follows : 
 
 a. Placers and other superficial deposits. 
 
 b. Deposits forming entire strata. 
 
 c. Deposits disseminated in strata. 
 
 d. Ores segregated from strata. 
 
 e. Infiltrations into beds. 
 
 2. Impregnations -j f. Contact zones enriched from neighboring 
 
 deposits. 
 g. Gash-veins and caverns in limestone. 
 
 h. Quasi-veins or chambers. 
 
 3. Mass deposits J . 
 
 1 t. Contact deposits. 
 
 j. Stockworks. 
 f k. Segregated veins. 
 
 4. Veins I f ( r ) Bedded veins. 
 
 1 /. Fissure-veins -| (2) Cross-cutting veins. 
 I I (3) Contact veins. 
 
 I. Stratified Deposits. Many valuable metallifer- 
 ous deposits are found occurring in the form of beds, 
 evidently deposited in most instances as sediments, but in 
 at least one case, that will be mentioned, in sheets of vol- 
 canic rock interbedded with mechanical sediments. The 
 bedded form of deposits is especially common with the 
 ores of iron, though it is by no means confined to them. 
 Usually the origin of the ores has been contemporaneous 
 with that of the accompanying and inclosing rocks ; where, 
 however, it seems evident that it has been subsequent to 
 that of the beds in which they are contained, they would 
 properly be classed as impregnations. Bedded deposits 
 have pretty definite limits above and below ; their arrange- 
 ment is parallel with that of other beds of the same series, 
 whether the position of the series is horizontal or inclined; 
 they have no special connection with other similar parallel 
 
APPLIED GEOLOGY. 
 
 beds ; and their valuable contents are in general more 
 evenly distributed than is the case with other forms of ore 
 deposits. 
 
 (a) Placers. This important form of metalliferous 
 deposits may, it would seem, be classed with beds, owing 
 their origin as they do to the same kind of agencies by 
 which mechanical sediments are formed, and when they 
 come to be covered, as they sometimes are, by deposits 
 of other materials, being considered and treated as beds. 
 Placers originate from the disaggregation of other forms of 
 ore deposits, and from the sorting of their materials by the 
 action of running water. The substances which give them 
 their value are of much greater specific gravity than the 
 minerals with which they were originally associated, and 
 are not affected by the usual agencies of change. Hence 
 they retain their integrity, and are separated by the action 
 of water from the lighter substances and from those 
 which yield to disintegrating influences. Sometimes the 
 valuable minerals remain nearly in their original position, 
 and are merely separated in a greater or less degree from 
 their accompanying rock. In much the more numerous 
 and important cases, all the material of the disaggregated 
 deposit is transported to some distance from its place of 
 origin ; the desirable substance, by reason of its greater 
 gravity, is washed free from the lighter and finer rock, and 
 is ultimately accumulated in the lower portions of a rude 
 mass of the coarser rubbish, mingled usually with sand 
 and in some places with " occasional beds of tenacious 
 clay." The usual places of accumulation of placers are 
 naturally at the base of declivities, in valleys, and in wa- 
 ter-courses ; and in the last case, the ancient water-course, 
 now entirely filled with transported material, may long 
 since have been abandoned by the stream to which its 
 origin was due. These accumulations have in not a few 
 cases been cemented to a solid mass, especially in their 
 lower portions, by the infiltration of mineral waters, and 
 
METALLIFEROUS DEPOSITS. 191 
 
 some of the placers of the Pacific coast and of Australia 
 have subsequently been covered by sheets of lava of great 
 thickness. Placer deposits are sometimes hundreds of 
 feet in thickness, and have a rudely stratified structure, 
 marking undoubtedly periods of rapid and tumultuary dep- 
 osition, alternating with others of more quiet action. The 
 distribution of the valuable substance in such masses is 
 by no means uniform. Being of high specific gravity, as 
 has before been remarked, it naturally tends to the lowest 
 point in the deposit, and is found most abundant on and 
 near the bed-rock, the richest accumulations being found in 
 holes, splits, and depressions of this rock, and at points 
 where the current of the depositing stream had been ar- 
 rested or suddenly changed by any cause. When several 
 periods of deposition are superposed, several richer hori- 
 zons or pay-streaks may occur, occupying each the lowest 
 place in its own bed. The substances commonly found 
 in placers are, besides precious stones, gold, platinum, tin 
 oxide, and magnetite, all of them highly insensible to the 
 usual agencies of change. 
 
 Although Von Cotta, in his excellent treatise on ore de- 
 posits, expresses a doubt whether placer deposits occur of 
 earlier date than the Post-Tertiary, yet Dawson, in his " Aca- 
 dian Geology," shows that gold-bearing placers are found 
 in Nova Scotia at the base of the Lower Carboniferous as 
 conglomerates deriving their materials from Silurian au- 
 riferous rocks ; and in the vicinity of Deadwood, in the 
 Black Hills, auriferous conglomerates of probable Primor- 
 dial age occur, having all the characteristics of modern 
 placers, both in the nature of the materials constituting 
 the deposits, and in the distribution of the gold. (" En- 
 gineering and Mining Journal," 1882, p. 335.) 
 
 Besides placers, deposits of metallic ores of bedded 
 structure occur, (b) forming the entire mass, or at least the 
 greatly preponderating material of beds of considerable 
 extent and thickness ; such is the case with many very im- 
 
192 APPLIED GEOLOGY. 
 
 portant deposits of iron-ore. Or (c) the metallic substance 
 may be found disseminated more or less richly throughout 
 certain beds ; examples of which may be seen in the copper- 
 bearing conglomerates of Lake Superior, and in the bitumi- 
 nous shale of Mansfeld, containing profitable amounts of 
 ores of copper and silver. Lastly, ores may occur (d) as 
 concretionary masses of variable size, in beds from whose 
 remaining materials they have segregated themselves by 
 virtue of the mutual attraction exerted by particles of a 
 like kind ; e. g., the kidney-shaped masses of clay iron- 
 stone occurring abundantly in some strata of the coal- 
 measures. 
 
 The principal ores occurring in beds, besides gold, 
 platinum, and cassiterite, mentioned as found in placers, 
 are those of copper, lead, zinc, and iron, the last named of 
 which, as a workable substance, occurs in this country al- 
 most exclusively in beds. 
 
 2. Impregnations. Impregnations are deposits of 
 ores found disseminated more or less richly in certain re- 
 gions of rock, into which they have apparently been in- 
 troduced subsequently to the origin of the containing rock. 
 Their determining characters are their subsequent origin, 
 and their usual lack of any definite limits other than the 
 extent to which the rock containing them can be profitably 
 extracted. They may occur (e) as infiltrations into pre- 
 existing zones of rock, usually having the bedded structure, 
 which from their porous or cellular texture, or from their 
 fissured condition, have afforded access to metalliferous 
 solutions or sublimations by which they have been en- 
 riched. -Examples of this kind of impregnation are 
 afforded by the deposits of Silver Reef, Utah, where sev- 
 eral beds of Triassic sandstone inclosed in clay-slates 
 contain profitable amounts of silver chloride and sulphides ; 
 by the deposits of copper glance in the Oscuras Mount- 
 ains, in New Mexico, which occur impregnating con- 
 glomerates and decomposed argillaceous slates, and in some 
 
METALLIFEROUS DEPOSITS. 193 
 
 cases incrusting or replacing fossil plants and shells ; by 
 the Triassic sandstone of Cornmern in the Rhenish Province 
 of Prussia, whose loose, fine-grained sandstone, according 
 to Credner, sometimes nearly two hundred and fifty feet 
 thick, is thickly strewed with grains of galena, constituting 
 one of the most valuable lead deposits in Germany ; and 
 by the deposits of native copper in the Lake Superior re- 
 gion, which occur disseminated in sandstones and con- 
 glomerates, or filling the amygdaloidal cavities in great 
 sheets of bedded volcanic rock. Impregnations of the 
 kind here described are often by no means easy to be dis- 
 tinguished from true bedded deposits. The distinction, 
 where it can clearly be made out, will depend upon ob- 
 serving how far all the attending circumstances point 
 to contemporaneous deposition, or to subsequent introduction. 
 The usually vague limits of such impregnations may either 
 coincide in a general way with those of the beds in which 
 they are found, or they may be confined chiefly to such 
 portions of them as were most easily permeable to the en- 
 riching agency. 
 
 Besides these independently occurring impregnations, 
 having no obvious connection with other accumulations 
 of similar ores from which their materials may have been 
 derived, others are found (./) closely dependent on other 
 forms of ore deposit, to which they form a more or less 
 enriched incasement or zone of contact. They may oc- 
 cur in the rock inclosing any of the other forms of de- 
 posit, whether beds, mass deposits, or veins. Their ores 
 have in some cases, it is probable, been derived merely 
 from the same source as those of the main deposit, with 
 which in such case they would be contemporaneous ; and, 
 since the agency which formed the chief mass permeated 
 also to some extent the surrounding rock, the ores of both 
 would be quite likely to have a similar mineralogical 
 character. In other cases, the enrichment of the sur- 
 rounding rock has evidently been subsequent to the ac- 
 
1 94 APPLIED GEOLOGY. 
 
 cumulation of the main deposit, and has been derived 
 from it by decomposition and solution of some of its con- 
 tents. Hence the impregnation in this case would be 
 likely to hold its ores in mineral combinations somewhat 
 differing from those of the parent mass. 
 
 3. Mass Deposits. These deposits, called also by 
 the German name Stocke, are accumulations of ore of 
 irregular form, but with somewhat clearly marked bound- 
 aries. The defmiteness of their limits will usually serve 
 to distinguish them from impregnations ; their great irreg- 
 ularity of form, and the limitation of their boundaries in 
 all directions, separate them sufficiently from most veins ; 
 while they are distinguished from bedded deposits, both 
 by their irregularity of form and position and by the fact 
 that their ores are usually subsequent in origin to the in- 
 casing rocks, in which they either fill pre-existing cavities, 
 or occupy tracts by virtue of a chemical replacement. In 
 position these accumulations may coincide in their greater 
 dimensions with the bedding of the inclosing rocks, or 
 may be transverse to their bedding planes. In extent, 
 they vary greatly, many of the lead-bearing crevices and 
 flats of Illinois and Wisconsin being of no very consider- 
 able dimensions, while some of the mass deposits of 
 argentiferous galena, etc. , in our Western Territories, have 
 yielded hundreds of thousands of dollars' worth of ore ; 
 and one of the great deposits of cupriferous pyrites on the 
 Rio Tinto, in southern Spain, was reported in 1883 to be 
 in places more than thirteen hundred feet wide and six 
 thousand feet in length. Indeed, their frequent great 
 dimensions, their comparatively small distance from the 
 surface, and the consequent ease with which they may be 
 worked, afford some compensation for the uncertainty 
 attending their exploration, and the certainty that, when 
 their boundaries are reached, these isolated deposits will 
 afford no reliable guide to anything beyond. Similar ore 
 bodies may be likely to occur in the neighboring rocks, 
 
METALLIFEROUS DEPOSITS. 195 
 
 either at the same or at a different geological level, but 
 their lack of dependence on each other renders each an 
 object of independent and often costly search. 
 
 These accumulations are often found filling partly or 
 entirely cavernous spaces in limestones (g) which, when 
 they have been formed by the widening of joints, are 
 called often gash-veins, or, if by the partial or entire re- 
 moval of beds, flats. Such are the lead deposits of Illi- 
 nois and Wisconsin. The ores found in these cavernous 
 spaces seem either to have been introduced from above, 
 or to have been acquired by infiltration from the sur- 
 rounding rocks. (h) Deposits of somewhat similar form, 
 filling fissures and cavernous spaces in limestones that 
 have been disturbed and thrown into inclined positions, 
 and whose ores have, it seems highly probable, been 
 brought in solution from below through fissures in the 
 lower rock, may conveniently be called quasi veins, from 
 the similarity of their position and of their probable mode 
 of filling to that of fissure-veins. They are also called 
 chambers by the distinguished geologist Dr. Newberry. 
 The deposits of gold- and silver-bearing lead-ores of 
 Eureka, Nev., are examples of this kind of mass depos- 
 it. (/') Ore accumulations frequently occur occupying 
 spaces at the plane of contact between rocks of dissimilar 
 character, and from this circumstance are called contact 
 deposits. The celebrated deposits of rich argentiferous 
 lead-ores of Leadville are of this character, occurring at 
 the contact of porphyry with an underlying limestone. 
 According to Emmons, these ore-masses are not fillings 
 of pre-existing cavities, but have been formed by the 
 replacement of the limestones by ore-bearing solutions 
 penetrating them from the overlying porphyry. Accumu- 
 lations thus originating are sometimes called metamorphic 
 or transformation deposits. Contact deposits and flats 
 which occupy a nearly horizontal position are frequently 
 called blanket-lodes. (J) Stockworks are regions of rock 
 
196 APPLIED GEOLOGY. 
 
 so cut by a network of irregular, vein-like, ore-bearing fis- 
 sures or sheets, that the entire mass must be mined out. 
 An example of this kind of deposit is furnished by the 
 Fresnillo mines, at Zacatecas, Mexico, which work an 
 interlaced mass of fissures carrying ores of silver, with 
 which also the inclosing rock is impregnated to varying 
 distances from the stockwork. 
 
 It is well for the student to bear in mind that the dis- 
 tinction of these three classes of mineral deposits, viz., 
 beds, impregnations, and mass deposits, is not always 
 sharply drawn nor easily made. The extreme and well- 
 marked forms will present no great difficulties ; but not 
 unfrequently they so approximate in characters that they 
 are classed differently by different observers, and that the 
 distinction among them, if it can be decisively made, will 
 depend upon a careful study, not only of the circum- 
 stances under which they occur, but of the conditions in 
 which they originated. 
 
 4. Veins. Referring to what has already been said at 
 page 35 for an account of vein-formed rocks in general, 
 what follows here will be confined to a description of veins 
 which carry metallic ores as an important portion of their 
 contents. Such veins are frequently called lodes, although 
 this term is sometimes loosely applied to ore deposits 
 which are not, strictly speaking, veins. Metalliferous 
 veins are sheets of mineral matter, differing usually some- 
 what markedly in mineralogical character from the in- 
 closing or country rock, and filling pretty clearly defined 
 fissures, or occupying definite structural planes therein. 
 They tend to a vertical or highly inclined rather than to 
 a horizontal position ; differing in this respect, as well as 
 in the subsequent origin of their contents, from bedded 
 deposits, which originally, at least, must have been nearly 
 horizontal, and whose ores were deposited as part of the 
 continuous series of operations that formed the beds. 
 
 Segregated veins (k) are lenticular masses, chiefly of 
 
METALLIFEROUS DEPOSITS. 
 
 197 
 
 quartz, and sometimes of great dimensions, formed appar- 
 ently by elimination of their materials from the surround- 
 ing metamorphic rocks, and by the concentration of these 
 materials along certain planes of the bedding during the 
 process of metamorphism. Gold is the chief valuable 
 substance found in such veins, associated always with iron 
 pyrites and sometimes with chalcopyrite, both of which 
 may occur in sufficient abundance to be worth working, 
 even if unaccompanied by gold. Of this kind are the 
 quartz veins and lenticular masses of chalcopyrite with 
 pyrites, which occur in the metamorphic schists of the 
 Alleghany range from Georgia to Canada, and which in 
 some places contain valuable amounts of gold and copper. 
 On account of their conformity with the bedding of the 
 accompanying rocks, they are often spoken of as beds, 
 though apparently differing in mode of origination from 
 true beds. Where they swell out to considerable dimen- 
 sions also, they are indistinguishable from mass deposits, 
 to which they are closely allied, and with which, doubtless, 
 they might not inappropriately be classed. 
 
 Fissure-veins, or metalliferous lodes (/), are fissures of 
 the earth's crust which have, subsequent to their forma- 
 tion, been filled with mineral substances of which metallic 
 ores constitute a part. Such veins are often of very con- 
 siderable length, being sometimes traceable for several 
 thousand feet, or even for miles, in the same general direc- 
 tion, and it is highly probable that in many cases their ex- 
 tent is greater than can conveniently be traced. As to 
 the depth to which they reach, it can only be said that it 
 is greater than that to which the deepest human workings 
 have yet been prosecuted, or indeed are likely, for prac- 
 tical reasons, ever to be prosecuted. Work on metallic 
 lodes has been suspended, temporarily or finally, at vari- 
 ous depths and for various reasons, but never, so far as 
 known, from any real cessation of the vein in depth. The 
 fissures occupied by the deposits now under consideration 
 
I9 8 APPLIED GEOLOGY. 
 
 are doubtless fractures of the earth's crust, resulting from 
 deep-seated causes, such as produce uplifts and other 
 changes of level in rocks, earthquakes, and volcanic out- 
 bursts. Hence, veins are found chiefly in regions which 
 have been subjected to powerful agencies of disturbance, 
 regions rent by the throes of volcanic activity, regions of 
 metamorphic rocks, mountain-regions, to whose larger 
 structural lines they conform in direction. Also, the sys- 
 tem of veins of any special region, made up of a number 
 of separate veins, presents usually a rude but striking 
 parallelism among its several members, as might be ex- 
 pected with fractures produced by the same disturbing 
 cause, acting with a certain constancy of direction. Ex- 
 amples of this parallelism are presented by many vein- 
 mining districts, as in the northwest coursing veins of 
 Reese River, Nev., and the nearly east and west coursing 
 veins of Gilpin County, Col. Sometimes a tendency to a 
 radiate arrangement is observable in a system of veins. 
 
 It is obvious, however, that for the formation of a 
 mineral vein mere fracture of the rocks is not sufficient. 
 Doubtless many fractures have been made by movements 
 in the earth's crust, the opposite sides of which have re- 
 turned so nearly to their original position that no observ- 
 able space has been left for future deposits. But ex- 
 tensive rock-fractures inevitably present a very uneven 
 surface, as can easily be understood by observing, on a 
 small scale, the irregular surface of a broken block of 
 stone. If, then, the force which causes fracture causes 
 also, as is very likely, some movement of the broken parts 
 upon each other in any direction, it is easy to see that the 
 fracture will present irregular open spaces, with the oppo- 
 site walls resting upon each other at some points. The 
 student can illustrate this clearly to himself by cutting a 
 sheet of cardboard across irregularly, as was done for 
 Fig. 1 6 ; or, better, by breaking a block of stone, and then 
 moving the parts upon each other in any direction. Fig. 
 
METALLIFEROUS DEPOSITS. 
 
 199 
 
 1 6 presents a section of 
 such a fissure, which, by 
 the movement of the upper 
 part from a to b, presents 
 the appearance d, while a 
 movement from a to b' 
 gives the form c. 
 
 To such movements in 
 their walls is doubtless at- 
 tributable the striking irreg- 
 ularity in width which most 
 fissure-veins present, vary- 
 ing from bulges of consid- 
 erable width to a pinch-out, 
 where the walls are sepa- 
 rated from each other only 
 by a seam of clay. In these 
 faulting movements, the 
 overhanging portion of the 
 country rock y significantly 
 called by miners the hang- 
 ing wall of the vein, has 
 usually slid downward on 
 the underlying or foot-wall 
 side. 
 
 Another means by 
 which the walls of veins are 
 held asunder, to be after- 
 ward filled with minerals 
 and ores, is by the break- 
 ing off of fragments of the 
 hanging wall, either by the 
 shock that formed the fis- 
 sure, or by gravity, and 
 their sliding downward un- 
 til they become wedged be- 
 
200 APPLIED GEOLOGY. 
 
 tween the walls. Such fragments of the country rock en- 
 countered in mining are called horses or riders, and are 
 characteristic of many veins. Some of the horses met 
 with in the famous Comstock vein were of such vast 
 dimensions as to give it, in places, the delusive appear- 
 ance of being divided into two veins. 
 
 The open fissures thus formed, as also those occupied 
 by many mass deposits, have doubtless been filled with 
 their mineral contents, both ores and gangues, by a slow 
 and long-continued process of deposition from solutions 
 or vapors circulating through them. In some cases it is 
 possible that the process has been in part one of sublima- 
 tion, the ores being introduced into the fissure at great 
 depths in the state of vapor, and being deposited as a re- 
 sult of the progressive diminution of heat. In the great 
 majority of instances, however, all the observed facts point 
 to water, everywhere present in rocks, as the medium 
 through whose agency the various vein-forming minerals 
 have been appropriated, transported, and finally deposited 
 in fissures which furnished convenient channels for its cir- 
 culation. Its solvent power has doubtless in most cases 
 been vastly enhanced by great elevation of temperature 
 under pressure, and by the presence of various chemical 
 agents, such as carbonic acid and alkaline sulphides and 
 carbonates, taken up in its passage through the rocks. It 
 has permeated the rocks often to vast depths ; has ab- 
 stracted from them their sparsely disseminated ores and 
 other minerals which, under the circumstances, it was 
 capable of dissolving ; and has finally made its way into 
 open fissures, along whose sides in its upward course it 
 has deposited its contents in consequence of a decrease of 
 temperature and pressure, or of some change in the chem- 
 ical condition of the solution. The source of the miner- 
 als which fill the veins, therefore, is believed to be usually 
 the country rock itself, considered in the wide rather than 
 the merely local sense. Sometimes, indeed, the rocks im- 
 
METALLIFEROUS DEPOSITS. 20 1 
 
 mediately adjoining the present position of the ore depos- 
 its appear to have furnished the ores and gangues by lat- 
 eral secretion, as is probably true of many vein-like mass 
 deposits. But, in the case of true fissure-veins, all the 
 circumstances point to the ascent of the solutions from 
 great depths, and consequently to the derivation of their 
 contents from the leaching of areas of the country rock 
 of considerable extent in both width and depth. These 
 deposits, therefore, are, as has already been said, concen- 
 trations, within a limited and available compass, of ores 
 originally valueless from their wide dissemination. Much 
 undoubtedly still remains to be done in investigating the 
 chemistry of the process by which these seemingly insol- 
 uble substances have been brought into solution ; but 
 enough has already been done to render no longer doubt- 
 ful the possibility of the translocation and concentration 
 through aqueous solution of all the minerals found in veins 
 and other ore deposits. It should also be borne in mind, 
 in considering how ore deposits have been accumulated, 
 that the present condition in which ores occur in veins is 
 by no means always the same as that in which they were 
 originally deposited. On the contrary, it is often apparent 
 that important changes, not only of condition but also of 
 location within the deposit itself, have taken place since 
 their deposition. Thus the question that not unfrequently 
 arises is, not how a given substance could have been dis- 
 solved, but what was the original form under which it was 
 rendered soluble and brought to its present place, and by 
 what means has it been made to assume its present state ? 
 Some examples of these transformations will be given 
 hereafter, when we come to consider the surface appear- 
 ances of ore deposits. 
 
 Arrangement of Vein Contents. The mode of 
 arrangement of the minerals with which veins are filled 
 is quite variable. In some, especially those filled mostly 
 with a single mineral, e. g., quartz, the structure is mas- 
 
2O2 
 
 APPLIED GEOLOGY. 
 
 sive, any ores that are present being disseminated in gran- 
 ules often very fine, or in irregular lumps and threads. A 
 common mode of arrangement, where the veins contain 
 several minerals, is the banded, in which the different min- 
 erals, or sometimes different states of the same mineral, 
 are arranged in more or less regular sheets parallel to the 
 walls, and often showing duplicated or corresponding 
 sheets on the opposite walls, as in Fig. 17, which exhibits 
 a section of a copper-mine in Cornwall, from De La 
 Beche's " Geological Observer," p. 659. 
 
 FIG. 17. i, i, Country Rock ; 2, Massive Quartz ; 3, 3, Agate-like Quartz ; 
 4, 4, Quartz-Crystals or Combings ; 5, Chalcopyrite. 
 
 Such a structure indicates that different conditions of 
 deposition prevailed in the fissure at different times, or 
 that solutions of a different character succeeded each 
 other during the period in which it received its contents. 
 In this mode of arrangement the valuable ore usually 
 forms one or more of the successive bands of the vein 
 commonly known by miners as pay-streaks. Where vacant 
 spaces have been left in veins, usually along the plane of 
 final closure, such spaces are called vugs ; or, where lined 
 with crystals, as is apt to be the case, they are called druses 
 or drusy cavities. Ores are often found lining such drusy 
 cavities. Occasionally the vein structure is brecciated, i. e., 
 the fissure has been filled with rounded or angular frag- 
 ments of the country rock coated and cemented with the 
 ore and gangue. This type of structure is presented by a 
 few celebrated mines in our Western Territories. Besides 
 the modes of occurrence mentioned above, it is common 
 
METALLIFEROUS DEPOSITS. 203 
 
 to find ores lining cracks and fissures of the vein-stone in 
 the form of irregular strings, sheets, and incrustations. 
 
 The distribution of the ores in veins is apt to be very 
 irregular, considerable portions of the vein being practi- 
 cally barren, or carrying ores of but low grade, while oth- 
 ers present tracts of unusual richness. Such rich zones 
 of ore are called bonanzas, or ore-chimneys. They are apt 
 to occur in the wide portions of veins ; either because 
 width of fissure and consequent slower movement of ore- 
 bearing solutions afforded unusually favorable conditions 
 for deposition ; or because, in the case of subsequent 
 movement of the vein, crushing and fissuring its original 
 contents, the wider parts offered favorable places for an 
 after-concentration of ores within the vein itself. The 
 Comstock vein of Nevada has afforded many remark- 
 able examples of the alternation of wide tracts of barren 
 rocks with ore-bearing zones, sometimes of great extent 
 and astonishing productiveness, these bonanzas occurring 
 in the wider parts of the vein. Also, there can be no 
 doubt that the unequal distribution of ores in many veins 
 is due in a great measure to the influence of the country 
 rock ; for where this differs in character in different parts 
 of the fissure, some portions rather than others promote 
 the deposition of ores, apparently from their greater 
 roughness of surface, their readier conduction of heat, or 
 their presenting conditions for a chemical reaction with the 
 solutions circulating in the fissure. From these and other 
 causes, veins usually present an irregularity in the distri- 
 bution of their ores, as well as a heterogeneity of mineral 
 composition, in somewhat marked contrast with any 
 bedded deposits to which they may sometimes bear a close 
 superficial resemblance. 
 
 Characteristic for deposits filling fissures are branch- 
 veins or leaders, horses, and selvages or fluccan. Branch- 
 veins, called also leaders and stringers, are small subsidi- 
 ary veins diverging from the main vein, and leading some 
 
204 APPLIED GEOLOGY. 
 
 little distance into the country rock, where they may 
 gradually die out. They have evidently been formed and 
 filled by the same agencies as the main veins. Some- 
 thing akin to branches may occasionally occur in mass de- 
 posits which fill pre-existing cavities, but they can evident- 
 ly not occur with beds, since these were deposited upon 
 the underlying beds, and were subsequently covered by 
 the accumulation of the overlying ones. Horses have 
 already been mentioned as portions of the country rock, 
 usually fragments of the hanging wall of inclined veins, 
 which have broken off and slid down into the fissure, 
 where they have subsequently been enveloped by the re- 
 maining contents. They occur in fissure-veins, and may 
 occur in some mass deposits, but, not in beds or impreg- 
 nations. What is called fluccan or selvage is a sheet of 
 earthy matter frequently found lining one or both walls 
 of fissure-veins. It is caused sometimes by movements of 
 the vein, which have ground up the materials along the 
 walls ; more frequently, doubtless, by the percolation of 
 water along the walls, and the consequent decomposition 
 of the adjacent rocks. Such decomposed sheets of rock 
 are called by the miners gouge, because their softened 
 condition renders them easy to be penetrated and gouged 
 out by tools in mining operations. Where the selvage has 
 been caused by movement, the adjacent rock usually pre- 
 sents a polished, glazed, and striated surface, termed slick- 
 ensides, the striations bearing evidence of the direction of 
 the movement. Appearances of this kind between the 
 bands of a vein, and others presented by the structure of 
 the vein contents, not unfrequently testify to the reopen- 
 ing of a vein after it has been filled, and the formation of 
 a secondary fissure, which has subsequently been filled 
 within the vein itself. Thus, in the section presented by 
 Fig. 17 on a preceding page, the want of correspondence 
 between the exterior bands 2 and 5 may possibly have 
 resulted from reopenings of the vein-fissure. An un- 
 
METALLIFEROUS DEPOSITS. 
 
 205 
 
 doubted illustration of a 
 vein presenting several re- 
 openings may be found by 
 the student in Fig. 292, at 
 page 658 of De La Beche's 
 " Geological Observer," 
 and another on page 48 of 
 Phillips's " Treatise on Ore 
 Deposits." 
 
 Veins occupy various 
 positions with reference to 
 the structural planes of the 
 inclosing rock. Most fre- 
 quently they are found cut- 
 ting at various angles across 
 the bedding of the country 
 rock, where this is percep- 
 tible : e. g., a, Fig. 18, which 
 incloses a horse (e). 
 
 Sometimes the vein-fis- 
 sure has followed the con- 
 tact-plane of unconf ormable 
 rocks differing in charac- 
 ter : e. g., b, Fig. 18. Such 
 veins are called contact- 
 veins. The Comstock is a 
 contact-vein through a por- 
 tion of its course. Final- 
 ly, where the country rock 
 is much inclined, the vein 
 may be mainly parallel to 
 the bedding, often making 
 it difficult to determine 
 whether it is really a fis- 
 sure-vein or a bedded de- 
 posit : e. g., c, Fig. 18. In 
 10 
 
206 APPLIED GEOLOGY. 
 
 this case, a decision may often be reached by observing 
 the presence or absence of horses, stringers, and selvage, 
 as well as the composition and mode of arrangement of 
 the contents of the deposit ; by noting whether at all 
 points of its course it holds the same position among the 
 inclosing beds, or, rather, breaks across in places so as to 
 occupy somewhat different planes at different points, as a 
 vein is likely to do, but never a bed ; and, finally, should 
 it be crossed by other deposits, by observing whether it is 
 continuous across these, and whether it causes any change 
 in the relative position of their opposite parts, neither of 
 which circumstances could be true of beds. The bedded 
 vein, c, Fig. 18, is shown to be really a vein : (i) by hav- 
 ing branches, ff; (2) by crossing the inclosing beds 
 > at V (3) by faulting the vein, a; while the deposit, d, 
 which is everywhere conformable to the bedding, and is 
 faulted by a, is, so far as these circumstances show, prob- 
 ably a bed contemporaneous in origin with the country 
 rock. 
 
 Disturbances of Metalliferous Deposits Faults. 
 All the forms of metalliferous deposits are liable to have 
 their continuity interrupted, either in depth or in hori- 
 zontal extension, by faults caused by fissures formed since 
 their deposition by disturbances of the earth's crust. 
 These faulting fissures may themselves have subsequently 
 been filled with minerals from solution, constituting veins ; 
 or they may have remained merely crevices, filled only 
 with materials formed by the attrition or decomposition of 
 their walls. 
 
 As has already been remarked in a preceding chapter, 
 the displacement has been caused in the great majority of 
 cases by the sliding downward of the hanging wall of the 
 faulting fissure. Such faults are therefore called normal 
 faults, or simply slides. In cases, however, where the fault- 
 ing is an attendant result of powerful disturbances and 
 considerable folding of the strata, examples may occur 
 
METALLIFEROUS DEPOSITS. 
 
 207 
 
 where the hanging- wall side of the faulting fissure has been 
 thrust upward, producing a reverse fault, or heave. 
 
 In Fig. 19, representing 
 faults of veins produced by 
 fissures whose course is ap- 
 proximately parallel to that 
 of the veins, i, 2, and 3 illus- 
 trate normal faults, or slides, 
 and 4, 5, and 6, heaves ; i 
 and 4 being caused by fis- 
 sures dipping toward the 
 veins, 2 and 5 by fissures 
 dipping in the same direction 
 as the vein at a lower angle, 
 and 3 and 6 by fissures dip- 
 ping with the vein at a steeper 
 angle. A simple inspection 
 of the figures will make it 
 obvious that, in i and 6, the 
 continuation of the vein may 
 be found by a cross-cut from 
 the interrupted end into the 
 hanging wall of the vein in 
 the direction of the arrows ; 
 that in 2 the cross-cut should 
 be into the foot-wall of the 
 vein ; that in 3 and 5 a verti- 
 cal shaft or winze should be 
 sunk, and cross-cuts made in 
 the direction of the hanging 
 wall of the vein ; while in 4 
 the vein would be found by 
 a winze. The cases i, 2, and 
 3 will be those most frequent- 
 ly met with. In the absence 
 of any other means of infor- 
 
208 APPLIED GEOLOGY. 
 
 mation as to the direction of the faults of a new region, it 
 is safest to assume at the outset that the faults, if any occur, 
 are normal, and to act accordingly. When, however, defi- 
 nite information as to the direction of faulting has been ob- 
 tained in some cases by exploration, then it is well to re- 
 member that the faults produced by the same system of fis- 
 sures are likely to agree in direction, i. e., to be all slides or 
 all heaves. The examples given above represent cases where 
 the continuity of the vein is interrupted in depth. But cases 
 may occur where a vein is faulted by a fissure striking across 
 it at a wide angle, in which case, unless the vein be vertical, 
 or even then if the direction of movement be oblique, the 
 continuity of the vein in length will be interrupted. Such 
 cases are not easily represented by diagrams ; but the 
 thoughtful student, by an attentive consideration of the 
 respective dips of the vein and of the faulting fissure, will 
 be able to solve for himself the problem of the relative 
 positions of the parts of the vein with any given direction 
 of movement. For example, suppose a vein, in a line with 
 the observer and dipping to the right, to be cut by a fis- 
 sure at right angles to its course, and dipping toward him ; 
 then it is obvious that a slide would throw the portion 
 nearest to the observer out of line with the rest of the vein 
 to the left, while a heave would displace it to the right. 
 Indications of the direction of movement will be likely to 
 be obtained in practice from striations of the walls of the 
 faulting fissure, or from the relative positions on its oppo- 
 site sides of peculiar zones or beds of rock. 
 
 Displacements occurring in beds, mass deposits, and 
 impregnations are not likely to present cases more compli- 
 cated in character than those of veins, or differing from 
 them in principle. 
 
 Surface Appearance of Ore Deposits. The char- 
 acter of those portions of veins and other ore deposits which 
 are near the surface is commonly very different from that 
 which the same deposits present at considerable depths. 
 
METALLIFEROUS DEPOSITS. 
 
 209 
 
 This change of character, which is due to the action of 
 the air, and of water charged with various chemical agents, 
 is usually confined chiefly to the uppermost fifty or sixty 
 feet ; but not unfrequently, in the case of permeable and 
 fissured deposits, it extends to much greater depths. 
 " The general character of these altered outcrops consists 
 in a disintegration and softening of the adjacent country 
 rock, in the lack of sulphur compounds, and the preva- 
 lence of metallic oxides, salts of the metals, hydrates, car- 
 bonates, phosphates, arseniates, chlorides, etc., which often 
 produce very striking colors ; these change-products are 
 also, mayhap, accompanied by the development of metallic 
 copper and silver. In depth, these products of decompo- 
 sition pass often very gradually into everywhere preva- 
 lent sulphides of the metals or into iron carbonate." 
 (Von Cotta.) The superficial materials resulting from this 
 change have received various names in different regions. 
 In this country they are usually called gossan, a name de- 
 rived from the mining districts of Cornwall ; the Germans 
 apply to them the significant name of the iron hat, and 
 have an ancient rhyming rule which signifies that however 
 good a vein may be, it will have an iron hat ; while in 
 Mexico and South America they are called pacos, colorados 
 and negrillos. The nature of the change that occurs, and 
 the special character which the altered outcrop is thus 
 caused to assume, will naturally depend in every case on 
 the original character of the contents of the deposit, both 
 ores and gangues. Probably the most widely diffused and 
 obvious change is the one which is signalized in the Ger- 
 man and French name iron hat^ applied to weathered de- 
 posits, and which originates in the conversion of the wide- 
 ly disseminated compounds of iron, notably pyrites, into 
 the hydrated peroxide, giving to the mass a reddish or 
 yellowish-brown color, and in some cases making it to a 
 certain depth an available source of iron. Thus the out- 
 crops of copper deposits present usually a mass of spongy 
 
210 APPLIED GEOLOGY. 
 
 iron oxide mingled with the original veinstone, and show- 
 ing few if any traces of copper, which has been changed 
 from the original sulphide to the soluble sulphate (blue 
 vitriol) and washed away. This may be succeeded below 
 by a rich zone of copper oxides and carbonate with 
 metallic copper, and finally by the unchanged sulphides 
 of copper and iron. The copper veins of Ducktown, 
 Tenn., illustrated by Safford in his " Geology of Tennes- 
 see," and also by Le Conte in his " Elements of Geology," 
 will afford a good example of this kind of transformation. 
 
 Deposits of lead and zinc are in like manner found 
 changed to the carbonates of those metals, cerusite and 
 smithsonite, sometimes inclosing cores of the original 
 galena or blende but partially transformed; and where 
 pyrites was originally mingled with the ores, the carbonates 
 are reddened or intimately mixed with spongy oxide of 
 iron, as is the case with the argentiferous carbonates of 
 Leadville and Eureka. The superficial portions of silver 
 deposits are apt to contain the precious metal in the form 
 of native silver or of the chloride, mingled sometimes 
 with the bromide and iodide, succeeded at greater depths 
 by the usual compounds of silver with sulphur, antimony, 
 and arsenic. 
 
 Auriferous quartz veins, containing, as they usually do, 
 disseminated iron pyrites or chalcopyrite, present at the 
 surface masses of rusty cellular quartz from which the py- 
 rites has been removed, leaving the rock stained with iron 
 oxide, and containing the threads and grains of gold in a 
 state such that it may easily be obtained by crushing and 
 amalgamation. At no great depth, the unaltered form of 
 the vein is met with, in which the gold is so associated 
 with the metallic sulphides as to be by no means so easily 
 and completely secured. 
 
 It is obvious that a knowledge of the surface appearances 
 usually presented by the ore deposits of any region is of 
 very great importance to those engaged in searching for 
 
METALLIFEROUS DEPOSITS. 211 
 
 such deposits in that region j yet it would be a great error 
 to suppose that inferences derived from the examination 
 of the deposits in any one district can be safely treated 
 as unerring guides in the exploration of all others. For 
 example, however true it may usually be that the outcrops 
 of gold-veins are indicated by iron-stained and cellular 
 quartz, and however expedient it may be to follow up and 
 test carefully any such indications in a district that is 
 known to be gold-bearing, yet the converse of the propo- 
 sition is by no means true, that every outcrop of rusty 
 cellular quartz is probable evidence of the existence of 
 gold ; for such appearances occur in many places where 
 no gold has ever been found. To an important extent, 
 every mineral region is likely to present distinctive char- 
 acters of its own ; and general statements as to the effects 
 of atmospheric and aqueous agencies upon ore deposits 
 need to be supplemented by a careful study of the special 
 modifications that are liable to be met with in any particu- 
 lar district, from differences, it may be, in the nature of 
 the minerals with which the ores may be associated, or in 
 that of the substances with which the permeating water 
 may be charged. 
 
 General Distribution of Ore Deposits. Since, as 
 has already been remarked, ore deposits seem in all cases 
 to be concentrations, under favorable conditions, of sub- 
 stances once widely disseminated in rocks, it is obvious 
 that they are most likely to be found in localities where 
 the conditions for such a concentration have been pre- 
 sented. Such favorable conditions are most likely to be 
 found in regions cut by ancient eruptive rocks, since they 
 bespeak the former activity of forces that would produce 
 fractures and fissures, and would furnish the heat essen- 
 tial for the solution of many substances found in ore de- 
 posits ; in regions of fractured, folded, and altered rocks, 
 mountainous regions, because in them also fissures would 
 be likely to be opened, the circulation of fluids facilitated, 
 
212 APPLIED GEOLOGY. 
 
 and heat generated by the intense exertions of mechanical 
 force ; in regions of rocks of great geological antiquity, 
 rather than in those of more modern date, because the 
 more ancient rocks, by reason of their age, have been 
 longer exposed to occasions for the action of those slow- 
 working and protracted agencies by which ore deposits 
 have doubtless been most largely produced, and because, 
 to effect the solution and deposition of many highly re- 
 fractory substances frequently found in veins, masses, and 
 impregnations, the action of water at a very elevated tem- 
 perature must be requisite, needing the concurrence of 
 heat with the pressure of a great thickness of covering 
 rock, a circumstance which implies not only relative an- 
 tiquity in the rocks which were the deep-seated theatre of 
 such action and deposition, but also the lapse of vast pe- 
 riods of time during which these deeply placed rocks 
 were elevated and laid open to human search by an enor- 
 mous denudation ; whence also mountain-regions, whose 
 rounded forms and comparatively slight elevation above 
 the general surface show that their very roots have been 
 exposed by wear, are likely to be more favorable than 
 those whose rugged and elevated peaks testify to a briefer 
 exposure to elemental waste. 
 
 It will thus be seen that conditions favoring the ac- 
 cumulation of ore deposits are presented (i) by great 
 disturbances of the earth's crust by which fissures may be 
 produced, heat generated, and circulation promoted; (2) 
 by heat, such as initiates, accompanies, and succeeds out- 
 bursts of volcanic activity ; (3) by original depth of action 
 and consequent pressure, through which the solvent possi- 
 bilities of heated waters are enormously increased ; and 
 (4) by great lapse of time during which the repeated and 
 protracted action of agencies seemingly feeble may pro- 
 duce important accumulations, which may subsequently 
 be brought within reach of human explorations by great 
 uplifts and denudation. 
 
METALLIFEROUS DEPOSITS. 213 
 
 The regions, therefore, in which the great majority of 
 valuable ore deposits are found are (i) those which are in 
 close proximity to eruptive rocks, especially those of some- 
 what ancient date ; (2) mountainous regions, more par- 
 ticularly those whose low and rounded outlines show that 
 large portions of their original bulk have been removed 
 by denudation ; and (3) regions of rocks geologically 
 ancient, the more recent formations containing usually 
 little of value besides iron-ore. It has been observed also 
 that regions where rocks of very dissimilar character are 
 found in contact are favorable to the accumulation of ore 
 deposits, hence contact deposits, whether from their lia- 
 bility to separate and form fissures as the result of disturb- 
 ances, or from their presenting planes of easy percolation 
 to metallic solutions, or from some favoring circumstances 
 of the wall-rocks. 
 
 It should by no means be inferred that regions like 
 those here enumerated are likely in every case to furnish 
 valuable ores in some portion of their extent ; but only 
 that ore deposits occur mainly in such connections and 
 much more rarely elsewhere. It is well also to bear in 
 mind that the conditions which have produced one dis- 
 covered ore deposit in a region are quite likely to have 
 produced others also which are apt to bear to this some 
 definite relation of kind, position, or direction. 
 
 Prospecting. What has been said as to the general 
 distribution of ore deposits may be useful to the observer 
 at the outset in directing him to the kind of localities 
 which are likely to reward his search. Its proper appli- 
 cation will depend, as may be seen, upon some knowledge 
 of the geological structure of the region, and a prelimi- 
 nary acquaintance with the general character of its rocks. 
 Without these, any first discovery of valuable minerals 
 would be due merely to a lucky accident, as indeed most 
 first discoveries have probably been. In the absence of 
 other sources of information, traces of ancient workings 
 
214 APPLIED GEOLOGY. 
 
 may prove useful guides to the explorer, indications such 
 as would be given by old pits not yet wholly obliterated, 
 and heaps of debris whose weathered contents may afford 
 some hints of what explorations would be likely to reveal. 
 Such ancient workings of the aboriginal inhabitants of the 
 country have led, it is said, to the discovery of some of 
 the copper-mines of Lake Superior, and of the best mica 
 deposits of North Carolina. Mere local traditions of the 
 occurrence of minerals, however, when unsupported by 
 perceptible traces of former workings, are notoriously 
 unreliable. 
 
 In districts where there is a strong probability of the 
 existence of ores, useful indications to aid in their search 
 may be gained in several ways : from peculiarities of vege- 
 tation, since many ore deposits exert a special influence 
 on the vegetation along their course ; from the contents or 
 the depositions of springs issuing from the hidden courses 
 of veins, etc. ; or from some marked features of the topog- 
 raphy, such as sharp, narrow ridges marking the outcrop 
 of veins harder than the country rock, or linear hollows 
 suggesting the presence of those made up of materials 
 softer and more easily decomposed than the inclosing 
 walls. The best and most helpful aid is furnished, how- 
 ever, by the debris arising from the disintegration and 
 wear of ore deposits, which is likely to be found strewed 
 along stream-courses and slopes below the outcrop of the 
 parent formation. Such transported materials, called 
 usually shode-stones, or in our Western mining regions more 
 commonly float, will naturally present the surface appear- 
 ances of the deposits from which they were derived, such 
 as cellular iron-stained quartz and the like. These float 
 minerals, indicating the possible proximity of an ore de- 
 posit, are traced carefully upward along stream-beds or 
 slopes, to the point beyond which they are no longer 
 found; and at this point further search is made for the 
 originating deposit by trenches or pits excavated to the 
 
METALLIFEROUS DEPOSITS. 
 
 215 
 
 underlying rock. Should this examination reveal the 
 probable presence of a vein or some other form of mineral 
 deposit, more extended explorations are made by means 
 of pits and shafts, to determine its direction, extent, and 
 character ; and these explorations are accompanied by 
 assays, which, if made upon samples fairly taken, may in- 
 dicate the possible value of the deposit, and whether it is 
 likely to justify extended working. 
 
 Circumstances which condition the Value of 
 Ore Deposits. Sound business discretion will naturally 
 dictate that the work of exploration should be pushed far 
 enough to reveal the real nature and probable abundance 
 of the valuable mineral, in both depth and extent, and 
 that the conditions on which the present and prospective 
 value of such a deposit must depend should be carefully 
 considered, before the necessarily costly preparations for 
 extensive mining and for the beneficiation of the product 
 should be undertaken. 
 
 A primary consideration in determining the value of 
 an ore deposit will, of course, be the relative amount of 
 the valuable metallic substance which the ore mass con- 
 tains. Where the ore is intimately mingled with the 
 gangue, the value should be estimated on the basis of the 
 entire mass that must be subjected to the processes of 
 concentration and reduction. When, however, the ore is 
 found concentrated into a somewhat definite pay-streak, or 
 in a narrow vein, while the value of the ore may be esti- 
 mated on this same basis, careful consideration should be 
 given to the fact that with the ore a sufficient amount of 
 barren rock must be taken down to give room for con- 
 venient mining operations, usually three feet or more in 
 width, increasing by so much the cost of getting the 
 really valuable ore. The value of ores of the precious 
 metals is usually stated as so many dollars or so many 
 ounces per ton ; thus, an eighty-dollar ore is one contain- 
 ing that value of gold or silver in a ton. Sometimes the 
 
2i6 APPLIED GEOLOGY. 
 
 value of low-grade gold-rock is given as so much per 
 cord, the cord being approximately eight tons. In the 
 case of the less valuable metals, like mercury, copper, lead, 
 and iron, the percentage which the metal bears to the ore 
 mass is given. It is obvious that to attain even an ap- 
 proximately reliable estimate of the average value of a 
 deposit, the samples that are subjected to assay should 
 fairly represent what must be treated as ores ; otherwise, 
 all further calculations must be mere wild guess-work, as 
 indeed too many estimates of the prospects of new mines 
 are apt to be. Reasonably fair samples can be obtained 
 only by some systematic operation which will exclude en- 
 tirely the chance for even an unintentional selection, such 
 as by taking shovelfuls indiscriminately from many parts 
 of a well-mixed ore-pile, breaking this material into small 
 fragments, heaping it up, and subjecting it to successive 
 quarterings, until a specimen of convenient bulk is ob- 
 tained for the assayer. Before, however, a final decision 
 is reached, a mill test should be made, by hauling several 
 tons of what is to be considered ore to the most con- 
 venient reduction-works, and finding what it will yield to 
 this practical test. 
 
 Second only in importance to the relative amount of 
 metal in the ore mass is the state in which it occurs : 
 whether native, and obtainable by a process merely of 
 crushing and washing, like the copper-rock of Lake Su- 
 perior ; or free milling, like some ores of gold and silver, 
 which after crushing yield their metallic contents mostly to 
 amalgamation, with little accessory treatment ; or in some 
 simple form of combination from which the metal may be 
 liberated by a process involving few operations, like galena 
 and iron oxide ; or involved in such complications with 
 other substances as to require an intricate and costly se- 
 ries of operations for its beneficiation ; whether also, in 
 case the ore is intimately mingled with so much gangue as 
 to reduce it below the limits of profit, it is in such physi- 
 
METALLIFEROUS DEPOSITS. 217 
 
 cal condition, and bears such relations of gravity to the 
 gangue, as to admit of easy concentration, and whether in 
 such case there is a sufficient supply of water for the pur- 
 pose. It is easy to see that, if one ore costs ten dollars 
 per ton more for reduction than another, it needs to be 
 ten dollars richer to pay ; and that if fifty dollars' worth of 
 ore disseminated through ten tons of vein-stone can, with 
 but little loss, be concentrated into one ton worth nearly 
 fifty dollars, it may, if the process of concentration is made 
 cheap enough by abundant water, become valuable when 
 it would otherwise be valueless. 
 
 The question of ready and cheap transportation is 
 also one of vital importance. Remote regions, difficult of 
 access, can utilize at first only their richest ores, those 
 whose value is so concentrated as to bear heavy transpor- 
 tation charges and still leave a margin for profit. Every 
 improvement in the means of communication, every re- 
 duction in the charges for carriage, will render available 
 ores of lower and still lower grade, and will bring the 
 products of such regions nearer in value to more favored 
 localities. Many districts in our own country of well- 
 known promise have their mining industries still hampered 
 by the difficulties and cost of transportation. For what 
 avail mines capable of producing an abundance of ores of 
 fair nominal value, all of which and even more may be 
 consumed by the charges for mining, reduction, and ex- 
 cessively dear transportation ? 
 
 The probable expense of working the deposit also 
 needs the most attentive consideration, depending as it 
 does on several circumstances, such as the cost of labor; 
 the hardness of the rock that is to be dealt with; the 
 structure of the deposit, whether likely to need much or 
 little support for roof or walls, and whether the timber for 
 this purpose is at hand ; the cost of food, tools, and mining 
 appliances in general ; and the cost of the power that 
 must be used for hoisting ores, and for handling the water 
 
2l8 APPLIED GEOLOGY. 
 
 that is likely to be encountered. All these elements of 
 inevitable expense must vary greatly, as may readily be 
 seen, with the circumstances of different localities, and 
 must be carefully estimated in view of such circumstances, 
 if one would avoid the risk of unprofitable undertakings. 
 
 Finally, the relation which the particular metal that is 
 to be produced is likely to bear to the supply of human 
 wants, as indicated by the state of the market for that 
 metal, needs to be taken into account. For example, a 
 deposit of copper which, in view of all the considerations 
 above enumerated, would seem likely to yield a good 
 profit when the metal is selling at sixteen cents per pound, 
 might be found to promise no margin of profit with copper 
 selling at fourteen cents or less. 
 
 The practical importance of the considerations given 
 above, and the frequency with which some of them are 
 overlooked, sometimes intentionally, by promoters of 
 mining enterprises, will justify a brief abstract of the chief 
 conditions on which depends the value of ore deposits : 
 
 1. On the relative amount of metal in what must be 
 treated as ore, needing 
 
 a. Fair sampling to secure a reliable estimate of the 
 
 average value. 
 
 b. Due consideration of the amount of dead rock to 
 
 be handled in securing the ore. 
 
 2. On the nature of the combination in which the 
 metal occurs ; often also on susceptibility to concentration. 
 
 3. On situation with respect to cheap transportation. 
 
 4. On the cost of exploitation, which includes a con- 
 sideration of 
 
 a. The cost of labor. 
 
 b. The hardness of the rock to be mined. 
 
 c. The structure of the deposit as regards the need 
 
 of costly support. 
 
 d. The cost of food, tools, mining supplies, etc. 
 
 e. The cost of power for hoisting and pumping. 
 
METALLIFEROUS DEPOSITS. 219 
 
 5. On the relations to the supply of human wants, in- 
 dicated by current price. 
 
 Erroneous Ideas regarding Ore Deposits. 
 There are prevalent among persons engaged in mining a 
 number of false or only partially justified notions, arising 
 partly from an imperfect knowledge of the true character 
 of ore deposits, partly from a tendency to too wide gener- 
 alization in formulating as general laws applicable to all 
 mining regions the results of an experience gained in 
 some limited district whose conditions were possibly 
 largely peculiar to itself. As these ideas in many cases 
 tend to foster too sanguine expectations, and to encourage 
 too hazardous ventures without proper examination, while 
 in others they may unduly discourage careful investigation, 
 they deserve to be briefly stated and discussed in a work 
 of practical character, as this aims to be. 
 
 1. A somewhat prevalent idea of this kind is, that fis- 
 sure-veins are likely to increase in width as they descend. 
 From what has already been said as to the manner in 
 which open fissures are formed, partly by a faulting move- 
 ment of walls of irregular contour, partly by the aid of 
 detached masses of the country rock, it may be seen that 
 this idea is likely to be baseless. Veins may be expected 
 to vary greatly in width, passing from a mere narrow clay 
 seam in one place, to a bulge of considerable width in 
 another. If now at the present surface, resulting always 
 from denudation, the vein happens to be encountered at a 
 narrow point, it will naturally widen for a time, sometimes 
 to a considerable depth, before again contracting ; if, 
 however, it should be struck at a wider portion, the con- 
 trary may be true. The idea has probably sprung from 
 men's disposition to believe easily what they strongly de- 
 sire, coupled with the well-known tendency to permit a 
 single success to blot out the remembrance of many fail- 
 ures. 
 
 2. Somewhat closely akin to this error is the notion that 
 
220 APPLIED GEOLOGY. 
 
 fissure-veins grow richer in depth. This may have arisen 
 from the fact that where the products of the decomposi- 
 tion of the ores are soluble, as in the case of copper and 
 silver, the outcropping portions of the veins are impover- 
 ished, and their true character does not appear until the 
 weathered portions are passed. When, however, the me- 
 tallic substance is itself unchangeable, e. g., gold, the out- 
 cropping portion may be not only relatively richer, but 
 also much more easily reduced than the unweathered part 
 of the vein ; so that it may very well happen that a mine 
 which " pays from the grass-roots " may pay nowhere else, 
 for the reason that the sparsely distributed metal may be 
 so involved with other substances in the unchanged vein 
 as not to yield itself to any cheap method of beneficiation. 
 Veins, where found in their natural condition in depth, 
 are likely, as has been stated on a former page, to have 
 their chief value collected in richer zones alternating with 
 tracts of ground practically barren, the richer zones being 
 met with more commonly in the wider parts of the vein. 
 It will therefore be a mere accident dependent upon de- 
 nudation, whether the vein shall be struck in a richer or 
 poorer portion of its extent. The opinion, once current 
 on high geological authority, that gold has been accumu- 
 lated in paying quantities only in the superficial portions 
 of veins, is probably entertained by very few persons at 
 present, since mining investigations have shown that it 
 was based on incomplete data. 
 
 3. Another current opinion, viz., that certain directions 
 of strike in veins are decisive indications of their possible 
 value, and its modification ascribing certain specialties of 
 course and form to veins of certain metals, may furnish 
 good illustrations of too sweeping generalizations. It is 
 undoubtedly true that, within given regions, the courses 
 of veins, and also of other forms of deposit that have been 
 greatly disturbed, are likely to have a tolerably definite 
 direction, conforming themselves, indeed, in a general way, 
 
METALLIFEROUS DEPOSITS. 2 2I 
 
 to the prevailing structural lines of the region due to up- 
 lifts, as if related to them in origin, as they doubtless are. 
 The error, then, is not in expecting certain prevailing di- 
 rections in the courses of deposits in a given region, but 
 in looking to find the same in all regions, without regard 
 to that which conditions their direction, viz., the structural 
 characters produced by upheaval. Still more, it is to be 
 considered that it is merely the existence of the fissure that 
 is due to the causes which control its direction, and not 
 the nature of its contents, whether or not they shall be met- 
 alliferous, or what ores they shall contain. The filling of 
 the fissure is a subsequent process, and is due to a quite 
 different agency. For the forces which produced all the 
 fissures of any region of fissure-veins, and which hence con- 
 trolled their direction, were mechanical, and thus totally 
 different from the chemical agencies which filled them, and 
 so conditioned the nature of their contents. The same 
 kind of mechanical forces, exerted in the same region at a 
 subsequent period and in a somewhat different direction, 
 may produce a second set of fissures varying in direction 
 from the first, and which, if filled by solutions of a different 
 kind, may form veins containing the ores of a different 
 metal. To this cause is due the fact that veins of the same 
 region which course differently are apt to have unlike me- 
 tallic contents. Yet veins of similar ores in distinct min- 
 ing regions which have different structural features may 
 have widely different courses, because their courses, and 
 not their contents, are conditioned by such structural 
 causes. 
 
 4. The sentiment in favor of some kinds of country 
 rock, as likely to be favorable to richness in deposits, and 
 against others as likely to be unfavorable, is not without 
 justification so long as it is restricted to districts in which 
 such influences have been observed. There is no reason 
 to doubt that from several causes, some of which have 
 been briefly mentioned on a preceding page, the country 
 
222 , APPLIED GEOLOGY. 
 
 rock does exert an influence on the deposition of the con- 
 tents of veins. What influence, however, is a matter which 
 needs to be carefully studied in each region for itself, and 
 not to be hastily inferred of any region because of observa- 
 tions made in a different one. For it is to be borne in 
 mind that the nature of the solutions circulating in fissures 
 must have been an influential factor in determining the 
 deposition of ores upon one kind of wall-rock rather than 
 upon another, the interaction between the two varying 
 with the nature of the solution ; also, that the relative com- 
 position of rock species is to a great extent variable and 
 indefinite, so that one is liable, while using the same rock 
 name, to be dealing with rocks that, from the difference in 
 the relative amounts of their constituents, might be likely 
 to exert notably different influences on ore deposition.* 
 
 5. Finally, it may be well. to mention in this connection 
 the prejudice, common among men engaged in mining, in 
 favor of fissure-veins, and against some other forms of ore 
 deposits. It is true that a fissure-vein whose average rich- 
 ness gives evidence of being satisfactory, has the great 
 advantage of affording such promise of continuance as to 
 justify large expenditures for its proper development, but 
 coupled with the certainty that the cost of both explora- 
 tion and extraction must increase greatly as depth is at- 
 tained. Other forms of deposit are, however, not without 
 their compensating advantages. Mass deposits, for exam- 
 ple, though of very uncertain extent and duration, are 
 frequently of vast dimensions, and their uncertainty is 
 fortunately counterbalanced, as Rossiter W. Raymond re- 
 marks, not only by this circumstance, but also by " their 
 comparative small depth and the consequent ease and 
 cheapness of extraction and of exploration." As a matter 
 of fact, very large portions of our mineral wealth are de- 
 rived from deposits other than fissure-veins. Not to men- 
 tion the vast stores of iron-ore obtained from beds, it is 
 * Von Cotta, " Erzlagerstatten." 
 
METALLIFEROUS DEPOSITS. 
 
 enough to allude, for a few examples out of many, to the 
 gold derived from placers ; the copper from the deposits 
 of Lake Superior, whether they be called beds or impreg- 
 nations ; and the silver and lead from the mass deposits 
 and quasi veins of Leadville and Eureka. Hence, it is 
 well for men interested in mining enterprises to cherish 
 no prejudices for or against particular forms of deposit, 
 but to endeavor, by the wise adaptation of methods to the 
 special deposits in hand, to extract from them the greatest 
 attainable profit, which is the true purpose of all intelligent 
 mining. 
 
 The student will do well to consult, for further information with 
 regard to ore deposits, " A Treatise on Ore Deposits," J. A. Phillips ; 
 De La Beche, " Geological Observer " ; R. W. Raymond, chapter on 
 ore deposits in " United States Report on Mineral Resources," 1870 ; 
 Burat, " Geologic Applique " ; and Von Cotta, "Erzlagerstatten," Part I ; 
 also papers on ore deposits by Dr. J. S. Newberry. 
 
CHAPTER XI. 
 
 IRON. 
 
 IRON may justly claim the foremost place among the 
 metals, from the indispensable relations which it bears to 
 most forms of human industry. The sources from which 
 it is obtained commercially are the oxide ores and the 
 carbonates, viz., magnetite, hematite, limonite, spathic ore 
 or siderite, clay iron-stone, and black-band. Richest 
 among these is magnetite, which when pure contains a little 
 more than 72 per cent of metallic iron. It is highly mag- 
 netic, yields a black powder and a black streak on un- 
 glazed porcelain,and is so hard as to be scratched with diffi- 
 culty by a knife. It is often crystalline granular, the faces 
 of the crystals being triangular when perfect. Hematite 
 when pure contains 70 per cent of iron. It is not usually 
 magnetic, though sometimes it slightly affects the mag- 
 netic needle, and its powder and streak are of a dark red. 
 It varies much in appearance, being sometimes hard and 
 of a steely metallic luster, when it is called specular ore ; 
 often constituting a reddish ochreous mass of an earthy 
 texture ; occasionally composed of black, shining, mica- 
 like scales, and hence called micaceous ore ; and some- 
 times made up of red, oolitic grains. Limonite differs 
 from hematite in being hydrated (combined with water), 
 and so containing a smaller percentage of metallic iron 
 about 60 per cent and in yielding a brown powder and 
 streak. It is often found in stalactitic and semi-concre- 
 
IRON. 22$ 
 
 tionary forms, with a smooth and shining surface, and a 
 fibrous, often radiated, internal structure. The pure iron 
 carbonate called siderite or spathic iron-ore, which con- 
 tains about 48 per cent of metallic iron, is a sparry mineral 
 of brownish color, and of an easy, threefold rhombohedral 
 cleavage, in which it closely resembles calcite and dolo- 
 mite, from which its cleavage angles differ but little. 
 When strongly heated, it decrepitates, turns black, and be- 
 comes magnetic ; and when heated in hydrochloric acid, 
 it dissolves with effervescence, yielding a yellow solution. 
 In its impure forms it occurs abundantly in certain shaly 
 strata of coal-regions, mingled with a considerable propor- 
 tion of earthy matter, forming beds of clay iron-stone, or 
 collected into kidney-shaped concretions disseminated 
 through the beds, when it is called kidney-ore ; or some- 
 times it is found mingled with much bituminous matter 
 forming black, shaly-looking seams called black-band. 
 These impure carbonates, though not so rich in iron as 
 several other ores, by reason of their close proximity to 
 fuels and fluxes, and of the ease with which they are re- 
 duced, are a large and valuable source of iron. 
 
 Mode of Occurrence. Although iron- ores are some- 
 times found filling fissures and irregular cavities, their 
 usual mode of occurrence in this country is in bedded 
 deposits, whether disseminated in the beds like the kidney- 
 ores, or forming nearly the entire bulk of strata which are 
 not unfrequently of great dimensions. Where the strata 
 with which they are associated have been greatly altered 
 and thrown into highly inclined positions, the ore-beds 
 have much the appearance of veins and are often so called ; 
 but there is little reason to doubt that they are really beds, 
 often of lenticular shape, formed as part of the regular 
 series of events by which the strata in which they are in- 
 closed were accumulated. Many of the limonites seem to 
 have arisen from the transformation or disintegration of 
 other kinds of iron-bearing strata, and occupy somewhat 
 
226 APPLIED GEOLOGY. 
 
 ill-defined positions, yet related to those of the probable 
 parent deposits. 
 
 Geological and Topographical Distribution. 
 Though small amounts of iron-ores may be found in near- 
 ly every geological position, still their occurrence in work- 
 able quantities is chiefly confined to a comparatively few 
 geological horizons. Of these horizons in this country, 
 the Archaean is much the most prolific in excellent ores, 
 magnetite and hematite. From this horizon come the ores, 
 so largely worked, and furnishing more than half the iron 
 of the United States, of the Lake Superior region, of 
 northeast New York and adjacent Canada, of northwest 
 New Jersey, and of the celebrated Iron Mountain region 
 of southeast Missouri. Enormous beds of iron-ore occur 
 also in this horizon in southern Utah, and along the Ap- 
 palachian range south of New Jersey, especially in North 
 Carolina. 
 
 From the horizon of the Lower Silurian Potsdam and 
 Calciferous are derived most of the valuable deposits of 
 limonite which occur along the Appalachain range from 
 New York and Connecticut to Alabama, and which are 
 largely worked for local use at many points along this 
 range, in New York, Pennsylvania, western Virginia, East 
 Tennessee, and Alabama. 
 
 The horizon of the Clinton Group of the Upper Silu- 
 rian affords a singularly persistent seam of oolitic hema- 
 tite, which extends with some interruptions from central 
 New York through Pennsylvania, etc., into Alabama, and 
 ranges in thickness from one foot to a maximum of twelve 
 or more feet. Above this horizon little of value is found 
 until the Carboniferous is reached, where beds of clay 
 iron-stone, kidney-ore, and black-band, are met with in 
 most coal- regions, furnishing large local supplies of ores 
 which are destined to become of increasing value with the 
 rapid growth of the iron industry on this continent. Ores 
 of this same character are also found associated with the 
 
IRON. 227 
 
 coal-beds of Triassic and Cretaceous age in the United 
 States, and much of the iron-ore of France, according to 
 Lebour, is derived from the Jurassic and Lower Creta- 
 ceous. A famous iron horizon occurs in the Middle Lias 
 (Jurassic period) of Great Britain, where a clay carbonate 
 in the so-called Cleveland District, Yorkshire, yields near- 
 ly one tenth of the iron of the world from an ore averag- 
 ing 30 to 35 per cent of iron. 
 
 Besides the iron regions mentioned above, the United 
 States is known to possess rich deposits in the Rocky 
 Mountain region and on the Pacific slope, though they 
 are still undeveloped save to a limited extent in Colorado 
 and Oregon. The magnetite deposits of southern Utah 
 are said to be very extensive. Besides our native supplies 
 of ore, considerable amounts are yearly imported, chiefly 
 from the island of Elba, from Algiers, and from Spain, 
 which last country is reported to mine annually for export 
 about four million tons of iron-ore. 
 
 Other highly important foreign regions of iron produc- 
 tion, besides those that have been named, are those of the 
 coal districts of Great Britain ; those of Germany, which 
 raise her to the third place as an iron-producer ; those in 
 the ancient crystalline rocks of Sweden and Norway ; and 
 that of Luxembourg, which supplies much of the iron-ore 
 smelted in Belgium. It is also recently reported that 
 southeast Cuba, through American enterprise and capi- 
 tal, is likely soon to become a considerable producer of 
 iron-ores. 
 
 In the case of a substance so abundant and widely dif- 
 fused as iron-ore, its economic importance must largely 
 depend on (i) its proximity to the fuels and fluxes needed 
 for its reduction to the metallic state, (2) its freedom from 
 injurious ingredients not readily removed in smelting, and 
 (3) the percentage of iron which it is capable of yielding. 
 The fuels used for its reduction are anthracite and dry-burn- 
 ing bituminous coals, coke, and charcoal ; while limestone is 
 
228 APPLIED GEOLOGY. 
 
 the flux most largely employed for removing in the form 
 of slag the usual silicious and clayey impurities. Near- 
 ness to the prime necessaries may bring into early use 
 comparatively lean ore deposits ; while even richer ones, 
 less favorably located, may wait long for development. 
 Where, therefore, abundant iron-ores of reasonable rich- 
 ness are found in convenient proximity to good fuels and 
 limestone, there prosperous centers of iron production are 
 likely to arise, and transportation facilities to be furnished. 
 To such fortunate concurrences is largely due the suprem- 
 acy in iron production of Great Britain, where the ores 
 most largely utilized are only moderately rich. Many lo- 
 calities in our own country afford examples of a similar 
 character, which are likely to be considerably multiplied 
 in the near future. 
 
 Where abundant and cheap fuel and limestone are not 
 at hand, an iron-ore needs usually to be both pure and rich 
 to warrant distant transportation. The most troublesome 
 impurities in iron-ores are sulphur and phosphorus, neither 
 of which is easily eliminated from the iron in the process 
 of smelting, and both of which necessitate increased ex- 
 pense for even their partial removal. A small amount of 
 sulphur in iron causes it to be " red-short," i. e., brittle 
 and difficult to work at a red heat ; while more than a 
 tenth of one per cent of phosphorus makes it "cold- 
 short," or brittle when cold, thus unfitting it for many uses 
 where great strength is required, and rendering it wholly 
 unsuitable for the manufacture of steel. Where ores are 
 sufficiently free from these injurious accessories, and are 
 capable of yielding 60 per cent or more of pig-iron, they 
 may be profitably transported to smelting centers at con- 
 siderable distances. Hence the Archaean ores of New York, 
 Missouri, and of the Lake Superior region, are largely car- 
 ried for reduction to Pennsylvania, Ohio, and Illinois ; 
 while the rich and pure ores of Spain and Elba are 
 brought by cheap ocean-carriage to be mixed with other 
 
IRON. 
 
 229 
 
 ores in iron for various steel-making processes. A re- 
 cently devised modification of the Bessemer process, 
 which, by the use of a basic lining for the converter, con- 
 sisting essentially of some mineral rich in magnesia, frees 
 iron from phosphorus, promises to make available for the 
 highest uses ores otherwise unobjectionable, but held in 
 bad repute because of their large amount of phosphorus. 
 
 According to a somewhat careful estimate of the iron 
 production of 1882 
 
 The production of the world was 20,656,184 tons gross or metric ; 
 Great Britain, 8,493,287 gross tons ; 
 
 United States, 4,623,323 ,, 
 
 Germany, 2,945,007 metric tons 
 
 these three leading producers having, therefore, furnished 
 somewhat more than sixteen million tons, or nearly four 
 fifths of the product of the world. The steel product for 
 the same year was given as 6,307,756 tons, of which Great 
 Britain produced 2,259,649 tons and the United States 
 1,736,692 tons, these two nations together producing nearly 
 two thirds of the steel of the world. 
 
 These figures will serve to give some idea, not only of 
 the vast proportions of the industries for which iron-ores 
 furnish the basis, but also of the countries which, by a 
 fortunate combination of circumstances, seem to be best 
 adapted to be leaders in those industries. 
 
 The rapid growth of the iron industry in the United 
 States may be seen when it is considered that in 1854 the 
 entire product was 656,445 gross tons, and that it rose in 
 twenty-six years to 3,835,191 gross tons in 1880. Among 
 the States of the Union, Pennsylvania is foremost in pro- 
 duction, from causes that may easily be inferred, yielding 
 in 1882 more than 47 per cent of the entire product of 
 the United States, with Ohio, New York, and Illinois hold- 
 ing second, third, and fourth rank ; while Michigan, New 
 Jersey, Tennessee, Missouri, and Alabama each produced 
 100,000 or more gross tons. 
 11 
 
230 
 
 APPLIED GEOLOGY. 
 
 The uses of iron and steel may justly be said to be 
 coextensive with civilized industry. Some of its leading 
 uses only can here be indicated, viz., in constructing and 
 operating railways, for rails, bridges, and rolling-stock ; in 
 ship-building ; in architecture, for pillars, girders, and mul- 
 tifarious other purposes ; in tools and machinery for both 
 agricultural and manufacturing uses ; in pipes for the con- 
 veyance of water and petroleum, and in tanks for storage ; 
 in stoves, furnaces, and boilers ; and in wire for fencing 
 and for lines of telegraph. 
 
 The works to which the diligent student might refer for more 
 complete information with regard to the ores of this important metal 
 are very numerous. He will do well to consult the Geological Re- 
 ports of Missouri, Michigan, and Wisconsin, and those of the States 
 along the great Appalachian range, from Canada and New York to 
 Alabama, some or all of which may be within his reach. Many valu- 
 able papers on this subject may also be found in the volumes of 
 " Transactions of the American Institute of Mining Engineers." The 
 " Statistics and History of Iron and Steel," in the "Report of the 
 Tenth Census of the United States," and the article " Iron," in the 
 " Mineral Resources of the United States," published by the Geologi- 
 cal Survey, 1883, should be consulted ; also Wright's " Reports on 
 Mineral Statistics of Michigan," for iSyy-'yS, i88o-'82 ; and Phillips's 
 " Treatise on Ore Deposits." 
 
CHAPTER XII. 
 
 COPPER. 
 
 THE chief sources whence are derived the supplies 
 of this metal of great and growing importance in the 
 arts, are the native metal, and the sulphides, chalcopyrite, 
 bornite, and chalcocite. These yield more than seven 
 eighths of the world's supply of copper, the sulphides 
 furnishing fully three fourths, while native copper affords 
 somewhat more than a seventh, mostly from the Lake 
 Superior region. The remainder is supplied by the car- 
 bonates, malachite and azurite, and by the red and black 
 oxides formed by the transformation of other ores, with 
 minor amounts from the silicate, chrysocolla, and tetra- 
 hedrite or gray copper. Metallic copper and all its com- 
 mon ores yield with no great difficulty to the knife, having 
 a hardness varying from about three to four ; they are 
 also soluble with more or less ease in nitric acid, giving 
 green or blue solutions, into which, if a clean knife-blade 
 be dipped, it will soon be covered with a red coating of 
 copper. 
 
 The native metal is easily distinguished by its well- 
 known red color, its bright metallic luster, and the flexi- 
 bility of a thin shaving cut off with a knife. 
 
 Chalcopyrite, its most common ore, somewhat resembles 
 iron pyrites, with which it is often associated, but is easily 
 distinguished by its greatly inferior hardness, and by its 
 deeper shade of yellow, with a tint verging on green. It 
 
232 APPLIED GEOLOGY, 
 
 is a double sulphide of copper and iron, and yields, when 
 pure, about 34 per cent of copper. 
 
 Bornite, called usually variegated copper pyrites and 
 erubescite, is also a sulphide of iron and copper of some- 
 what variable composition, carrying from 55 per cent to 
 more than 60 per cent of copper. Its color varies from 
 red to brown, and it easily tarnishes on exposure, taking 
 the variegated colors from which it derives its common 
 name. 
 
 Chalcocite, or copper glance, is of a dark, lead-gray color, 
 with usually a blue or green tarnish, and is somewhat 
 softer than the two preceding ores, with which it is often 
 associated. It is a simple sulphide of copper, and con- 
 tains nearly 80 per cent of the metal. These three sul- 
 phides of copper give fumes of sulphur when heated on 
 charcoal, and when dissolved in nitric acid, with heat if 
 necessary, leave a residue of sulphur. 
 
 Malachite is a light-green carbonate of copper, holding 
 nearly 57 per cent of the metal ; and azurite is a blue car- 
 bonate, with about 55 per cent of copper. Their hardness 
 is about four, and when dissolved in nitric acid they effer- 
 vesce from the escape of carbonic acid. They are easily 
 distinguished by these characters and that of their solu- 
 tion. When malachite occurs in thick, compact incrusta- 
 tions, showing delicate bands of color, as in some of the 
 Siberian mines, it is considerably used as an ornamental 
 material in inlaid work. 
 
 The black oxide of copper, called tenorite, and the deep 
 red oxide, called cuprite and tile ore, or, when it occurs in 
 crystals, ruby copper, are both minerals of high specific 
 gravity, and contain respectively, when pure, 80 and 88 
 per cent of the metal. Both dissolve in nitric acid, and, 
 when heated with the blow-pipe on charcoal, yield a 
 malleable globule of copper. These oxides are often 
 found in some abundance in the middle and lower zones 
 of the decomposed parts of copper veins, and are valuable 
 
COPPER. 233 
 
 sources of the metal. Large, rounded masses of tenorite, 
 streaked with green, were found, at an early day, in con- 
 siderable abundance in the Lake Superior copper regions. 
 
 Chrysocolla, a bright bluish-green silicate of copper, 
 which contains, when pure, about 36 per cent of copper, 
 is found in sufficient amount in some of our Western cop- 
 per regions to be a valued source of copper. It has 
 nearly the same hardness as malachite, for which it* is 
 often mistaken ; but its shade of color is noticeably differ- 
 ent, and it does not, like malachite, effervesce with nitric 
 acid. 
 
 Tetrahedrite, called usually gray copper , from its pre- 
 vailing color, is a complex sulphide of copper and anti- 
 mony, with commonly some other metals, notably sil- 
 ver. It occurs somewhat abundantly in some of the 
 mines of the Rocky Mountain region, where it is valued 
 rather as a source of silver than of copper. 
 
 Mode of Occurrence. Copper or its ores occurs in 
 all the great classes of metalliferous deposits that have 
 been described in a preceding section : (i) It is found in 
 veins intersecting the older rocks, or forming lenticular 
 deposits in certain planes of their highly inclined bedding, 
 as at many points along the Appalachian Mountains, at the 
 Bruce and other mines on the north shore of Lake Huron, 
 at the mines like the Cliff on Keweenaw Point, which have 
 become famous from the enormous masses of native cop- 
 per which they have yielded, and in the very rich district 
 around Butte City in Montana. (2) It occurs in mass 
 deposits, as along the base of the Sierra Nevada in Cali- 
 fornia, in the Harz Mountains at Goslar, and in the enor- 
 mous deposits in southwest Spain on the Rio Tinto, in all 
 of which localities the copper ore is mingled with large 
 proportions of pyrites. The very rich copper deposits of 
 Globe, Arizona, and of the Copper Queen, seem also to be 
 of this character, though the ores are widely different. 
 (3) It occurs disseminated in beds, as in the deposits of 
 
234 
 
 APPLIED GEOLOGY. 
 
 Ste. Genevieve County, Mo., which are in two beds of 
 Lower Silurian limestone, at several points in the Lower 
 Silurian beds of Canada, which have not yet risen to great 
 commercial importance, and in the famous copper slate of 
 the Harz Mountains, which, in the vicinity of Mansfeld, 
 yields so large a portion of the copper of Germany from a 
 seam of but inconsiderable thickness. (4) It is found in 
 impregnations, as in the rich deposits of native copper, 
 disseminated in amygdaloids and conglomerates, on Ke- 
 weenaw Point, in northern Michigan ; in the oxide and 
 carbonate ores which enrich enormous zones in beds of 
 felsitic rock, on the boundaries of Arizona and New 
 Mexico, near the Gila River ; and in the beds of con- 
 glomerate and underlying slate, impregnated with copper 
 sulphides and oxide, in the Oscuras Mountains of central 
 New Mexico. Thus far, in this country, the deposits 
 which have here been classed as veins and impregnations 
 have been much the most largely worked, and with the 
 greatest profit, though important amounts are also pro- 
 duced from the other two classes of deposit. 
 
 Geological and Topographical Distribution. 
 Although workable deposits of copper are sometimes found 
 in formations as late as the Permian, as at Mansfeld, and 
 in the possibly younger beds of the Oscuras Mountains, 
 yet they are most largely accumulated in the ancient crys- 
 talline or eruptive rocks of the Archaean and in the often 
 much-disturbed and altered beds of the earlier Silurian. 
 
 The most notable copper region in North America is 
 that of the southern shore of Lake Superior, in the north- 
 ern peninsula of Michigan. The copper here occurs in 
 the native state, in a very thick series of interbedded vol- 
 canic rocks, sandstones, and conglomerates, of probably 
 later Archaean age, though they are thought by some ex- 
 cellent geologists to belong to the Cambrian. The metal 
 is found partly in fissure-veins, in which the copper has 
 been met with largely in masses, sometimes of enormous 
 
COPPER. 235 
 
 size, several having been discovered which weighed from 
 two hundred to nearly five hundred tons ; partly as one of 
 the minerals filling amygdaloidal cavities in the volcanic 
 rocks, some of the irregularly shaped masses here also at- 
 taining considerable dimensions ; and partly disseminated 
 in conglomerates, in which it constitutes a portion of the 
 cementing material. The fissure-veins are no longer so 
 productive as they once were, the great masses being now 
 unfrequently found, so that the product depends chiefly 
 on the copper disseminated in lumps, strings, and grains 
 in the vein-rock. The largest part of the product is de- 
 rived from the amygdaloids, in which, besides the fine 
 grains and strings of metal with lumps of a few pounds in 
 weight, irregular masses weighing more than a ton are 
 sometimes encountered, filling large scoriaceous cavities in 
 the ancient lava-beds ; and from the cupriferous conglom- 
 erates, in which one great mine, the Calumet and Hecla, 
 produces considerably more than half the copper of the 
 region from a conglomerate impregnated with about five 
 per cent of the metal. The amygdaloids are more easily 
 worked than the conglomerates, and their average of metal 
 varies from about three per cent in the Quincy mine to 
 0.72 per cent in the Atlantic. The process of extraction 
 consists in freeing the lumps and masses, as far as possible, 
 from the accompanying minerals, by steam-hammers, rock- 
 breakers, and stamps, stamping the finer copper and gangue 
 to a coarse powder, and washing away the waste rock in 
 jigs and buddies, and then smelting the lumps, masses, and 
 washed grains to rid them of the remaining gangue in the 
 form of slag. 
 
 Second in the list of copper-producers is the region im- 
 mediately around Butte City, Montana, which in 1882 
 produced over four thousand gross tons of metal from rich 
 sulphide-ores, yielding also usually valuable amounts of 
 silver, and in 1884 reached a production of over eighteen 
 thousand gross tons. 
 
236 APPLIED GEOLOGY. 
 
 Ranking third in amount of metal produced since 1883 
 are the copper-producing districts of Arizona, at present 
 three in number. The Clifton district is in the southeast 
 part of the Territory, on the Gila River, near the boundary- 
 line of New Mexico. The ores, mostly carbonates and 
 oxides, are said to occur in enormous zones in vertical 
 beds of felsite rock, and to average fifteen per cent of cop- 
 per in a gangue of manganese and iron oxides. The Cop- 
 per Queen mine at Bisbee is the largest producer in Ari- 
 zona, having a very rich body of carbonates and oxides in 
 limestone with, it is said, some native copper, and copper 
 glance in the deeper workings. A block of this ore, weigh- 
 ing three tons, recently sent to the Museum of Cornell 
 University by Prof. W. P. Blake, is made up chiefly of 
 malachite intermingled with black oxide of manganese and 
 calcite. The Globe District, in Gila County, though situ- 
 ated badly in regard to transportation, is yet producing 
 largely in several mines, the ores of all which are carbon- 
 ates and oxides, containing also small amounts of the pre- 
 cious metals. The Old Dominion mine, in this district, is 
 said to yield annually more than two thousand net tons of 
 copper. Besides these chief producing centers there are 
 some other promising mines in this remote Territory, of 
 which the Peabody, in Cochise County, a little north of 
 the famous Tombstone region, is stated (" Report of the 
 Director of the Mint for 1882 ") to be producing at the 
 rate of eighteen hundred tons per year, from an ore carry- 
 ing a high percentage of gold and some silver. In 1884 
 the estimated yield of Arizona was 11,920 gross tons of 
 copper. 
 
 Colorado produces considerable amounts of copper, 
 solely as a secondary product from ores worked chiefly 
 for their gold and silver. Most of this is from the mines 
 of Gilpin County, west of Denver, with smaller amounts 
 from the San Juan region, and from a locality near Canon 
 City. New Mexico, though not yet producing more than 
 
COPPER. 237 
 
 four or five hundred tons per year, is known to have very 
 rich deposits in not less than six counties, many of the 
 mines carrying also important amounts of the precious 
 metals. Wyoming, in 1883, increased its copper product 
 about twelve-fold, producing nearly six hundred tons from 
 mines on the Platte River, ninety miles north of Cheyenne. 
 The ores are rich carbonates and cuprite. Vermont has 
 long had a steady production from low-grade pyritiferous 
 ores, chiefly in Orange County. Besides these main pro- 
 ducing regions, promising deposits are known to exist and 
 have been considerably worked in many places along the 
 Appalachian range, chiefly in western Virginia, the north- 
 west part of North Carolina at Ore Knob, and at Duck- 
 town in southeast Tennessee ; as well as in California, 
 Nevada, Utah, Ste. Genevieve County, Missouri, and in 
 Maine. 
 
 Other North American deposits of copper are found 
 in the southeast part of Cuba, near Santiago de Cuba, 
 which formerly yielded annually as high as thirty thousand 
 tons of eighteen-per-cent ore ; and in the British domin- 
 ions, on the north shores of Lakes Superior and Huron, 
 in southern Quebec, and in Newfoundland. Judging from 
 the statistics of production, these are rather regions of 
 promise than of present vigorous working, with the ex- 
 ception of Newfoundland, which in 1883 is credited with 
 a product of ten hundred and fifty-three tons from two 
 localities, and of Capelton, in the southern part of Que- 
 bec, which annually sends to the United States a large 
 amount of cupriferous pyrites to be used in the manufact- 
 ure of sulphuric acid, from which is extracted about four 
 hundred and fifty tons of copper. 
 
 Under the existing conditions of production, arising 
 from large output and low prices of copper, the chief North 
 American centers of growth for this industry for the im- 
 mediate future seem likely to be those of Lake Superior, 
 Arizona, Butte, with probably Wyoming, New Mexico, and 
 
238 APPLIED GEOLOGY. 
 
 Newfoundland, and those sections in which, like Colorado, 
 the production of copper is made an accessory to the ex- 
 traction of the precious metals, or to the manufacture of 
 sulphuric acid. 
 
 Of the foreign producers of copper on a large scale, 
 Chili, with Bolivia, still ranks foremost, although the pro- 
 duction of Chili has greatly diminished in recent years, 
 while Spain and Portugal have risen to almost equal rank. 
 The product of Spain is obtained from enormous mass 
 deposits of copper-bearing pyrites near the Rio Tinto, in 
 the extreme southern part of the peninsula, and extending 
 into adjacent Portugal. These great deposits, called mass 
 deposits (Stocke) by Von Cotta, are pronounced fissure- 
 veins in a recent account by a French engineer (" Engi- 
 neering and Mining Journal," November 17, 1883), and 
 yield an average of about three per cent of copper. 
 
 Next to Spain, as a producer of copper, is Germany, 
 whose largest product by far is derived from the beds of 
 Mansfeld, before mentioned, the residue coming from cu- 
 priferous pyrites, mainly from great mass deposits in the 
 Harz Mountains. Australia also furnishes large amounts, 
 chiefly from the divisions of South Australia and New 
 South Wales. 
 
 England, once a large producer of copper-ores, has 
 maintained her supremacy in the copper industry mainly 
 by large importations of ores, cupriferous pyrites, and par- 
 tially reduced copper, from Spain, South America, the 
 Cape of Good Hope, Australia, and some other countries, 
 her own once famous mines in Cornwall, Devon, Anglesea, 
 etc., yielding little more than three thousand tons an- 
 nually. 
 
 The following table of the product for 1883, recently 
 compiled in London, partly from estimates, will give an 
 idea of the most important sources of supply. In this the 
 German product has been corrected from more recent 
 statistics, as also that of the Cape of Good Hope. France, 
 
COPPER. 
 
 239 
 
 which in 1882 produced 3,627 tons, is for some reason 
 omitted from this table : 
 
 Tons. 
 
 United States 52,080 
 
 Chili and Bolivia 44,349 
 
 Spain and Portugal 43,655 
 
 Germany 18,205 * 
 
 Australia. 12,000 
 
 Cape of Good Hope 5,175 
 
 Venezuela 4,018 
 
 Norway and Sweden 3,43O 
 
 England 3,000 
 
 Russia 3,000 
 
 Japan 2,800 
 
 Italy 1,600 
 
 Newfoundland 1,053 
 
 Hungary 1,000 
 
 Algiers 600 
 
 Austria 500 
 
 Mexico 489 
 
 Peru 395 
 
 Canada 329 
 
 Argentine Republic. . . 293 
 
 Total 197,971 
 
 A table of production of the various parts of the 
 United States in 1882, prepared by the United States Geo- 
 logical Survey, will show the distribution of our own prod- 
 uct. It is reduced to gross tons of 2,240 pounds : 
 
 Tons. 
 
 Lake Superior region 25,439 1 
 
 Arizona 8,025 
 
 Montana, Butte 4,44 
 
 Colorado 667 
 
 Vermont 564 
 
 New Mexico 3^9 
 
 California 369 
 
 Utah 271 
 
 Southern States 180 
 
 Nevada 156 
 
 * Of which 17,501 was from Mansfeld. 
 f Calumet and Hecla mine, 14,309 tons. 
 
2 4 APPLIED GEOLOGY. 
 
 Tons. 
 
 Missouri o ...... 132 
 
 Maine 130 
 
 Wyoming 45 
 
 Pyrites, mostly Canadian 446 
 
 From desilverizers 56 
 
 Total 40,913 
 
 The increase in 1883 was due mostly to the first three 
 regions in the list and to Wyoming, and in 1884 the esti- 
 mated product of the United States was 64,831 gross tons. 
 
 Uses of Copper. The uses of copper are numerous 
 and important. Among these is its employment for 
 sheathing the hulls of wooden ships ; in wire, in the vari- 
 ous appliances connected with the widely and rapidly de- 
 veloping applications of electricity ; in the fashioning of 
 many articles for domestic uses, and also for manufactur- 
 ing purposes, such as boilers and evaporating-pans for 
 sugar-works and stills for distilleries ; as one of the ele- 
 ments in some forms of galvanic battery ; and as a chief 
 component in several alloys very largely used in the arts, 
 such as brass for many parts of machinery and for numer- 
 ous other uses, and bronze for cannon, bells, and statuary. 
 It has also a considerable use as an essential or subsidiary in- 
 gredient in alloys for coins, and for the manufacture of vari- 
 ous ornaments. Besides this, several of its salts are largely 
 used in the arts, such as the sulphate, called blue vitriol or 
 blue-stone, the acetate, known as verdigris, and the brilliant 
 though dangerous green pigments formed by its combina- 
 tions with arsenic. 
 
 Works to be consulted. 
 
 "Mineral Resources of the United States," 1882, article "Cop- 
 per " ; Von Cotta, " Erzlagerstatten," Part II, for Europe ; Geological 
 Reports of Michigan, Missouri, Tennessee, and North Carolina ; 
 Geological Report of Canada, 1863 ; " Third Annual Report of the 
 United States Geological Survey" I rving's Report ; Wright's "Re- 
 ports on Mineral Statistics of Michigan," iSj'j-'jS, 1880, 1882; Phil- 
 lips, u Treatise on Ore Deposits." 
 
CHAPTER XIII. 
 
 LEAD AND ZINC. 
 
 Lead. Lead was smelted in the United States as 
 early at least as 1825, but during nearly half a century 
 from that date, down to the close of 1872, with wide fluc- 
 tuations in the amount of production, the annual out- 
 put had never exceeded 27,000 gross tons. Since that 
 date, the discovery of rich stores of argentiferous lead- 
 ores in Colorado, Nevada, Utah, and some other Western 
 regions, has swelled our production of lead, mainly as an 
 accessory to the extraction of silver, to five-fold its for- 
 mer amount, and we now rank foremost among producers 
 of this metal. 
 
 The sources from which lead is derived are the sul- 
 phide (galena) and the carbonate, with minor amounts 
 from the sulphate, which is often associated with galena as 
 a product of its transformation by atmospheric agencies, 
 as is also the carbonate. 
 
 All these ores yield easily to the knife, their hardness 
 not exceeding 3 ; they are of high specific gravity, and 
 are easily fused by the blow-pipe, being reduced to a mal- 
 leable bead of lead, with the exception of the sulphate, 
 which requires the addition of soda for its reduction. 
 
 Galena, the fundamental and most common ore, occurs 
 in granular or in cubical crystals, has an easy cubical 
 cleavage, a lead-gray color, and a brilliant metallic luster, 
 and contains 86 per cent of lead. The carbonate, cerus- 
 
242 
 
 APPLIED GEOLOGY. 
 
 site, which contains 77 per cent of lead, is usually white 
 or gray in color, occurs massive or in right rhombic prisms, 
 its crystals have a brilliant luster, and it dissolves with 
 effervescence in nitric acid. Anglesite, the lead sulphate, 
 holding about 68 per cent of lead, occurs massive or gran- 
 ular, and is of white or gray color, and bright, resinous 
 luster. It melts very easily, but yields a bead of lead only 
 by the addition of soda carbonate ; and it does not effer- 
 vesce with acids, by which characters it may be distin- 
 guished from the carbonate. 
 
 Nature of Deposits and Chief Geological Hori- 
 zons. Ores of lead occur (i) most largely in mass de- 
 posits in limestone formations, filling irregular cavities 
 formed by the enlargement of joints, or extending between 
 beds, or occurring at the plane of contact of limestone 
 with some rock of dissimilar character. Of this kind are 
 the deposits of Eureka district, Nevada, of southeast 
 Missouri, of the Galena district of Illinois and Wiscon- 
 sin, and of Wythe County, Virginia, occurring in limestone 
 of Lower Silurian age ; and those of Leadville, and of 
 southwest Missouri and adjacent Kansas, in limestone of 
 the Carboniferous. 
 
 (2) They are found disseminated in beds, as, e. g., in 
 beds of Lower Silurian limestone in East Tennessee (Saf- 
 ford) ; and near Commern, in the Rhenish Province of 
 Prussia, where they impregnate abundantly thick beds of 
 loose white sandstone of Triassic age, constituting the 
 richest lead deposits of Germany. 
 
 (3) They occur in veins cutting strata of different 
 kinds, but productive chiefly in limestone, between whose 
 beds, or at their contact planes, they not unfrequently 
 form also flat deposits connected with the fissures, as in 
 northern England, in Derbyshire, and in the two northern 
 counties of Wales. 
 
 (4) They are also met with in veins, usually more or 
 less argentiferous, cutting ancient crystalline formations, 
 
LEAD AND ZINC. 
 
 243 
 
 as at Georgetown and in the San Juan region, Colorado, 
 at Freiberg in Saxony, and in Cornwall. 
 
 The chief lead-bearing geological horizons of this 
 country and of England are the Lower Silurian and the 
 Carboniferous, with some in crystalline formations; the 
 same appears to be true also for Spain ; while in Germany, 
 lead is derived mostly from Triassic rocks. Limestone 
 appears to be a rock which is especially favorable to the 
 deposition of ores of lead. These ores are usually associ- 
 ated with more or less of silver, sometimes in proportions 
 too minute to be separated with profit, but not unfre- 
 quently the silver contents equal or surpass in value the 
 lead with which they are blended. 
 
 Chief American Centers of Production. Of the 
 lead production of the United States more than 43 per 
 cent is credited to Colorado, in which State its extraction 
 is wholly accessory to that of silver ; and the larger portion 
 of the product is derived from the famous region about 
 Leadville. The ore masses are found here chiefly at the 
 contact of a limestone of Lower Carboniferous age with 
 overlying masses of porphyry, and, according to Emmons, 
 they owe their origin to a replacement of the substance of 
 the magnesian limestones by silver-lead solutions which 
 were derived from the overlying eruptive rocks. The ores 
 are argentiferous lead sulphide and carbonate in a gangue 
 of ferruginous silica and clay. Besides the Leadville re- 
 gion, the silver-lead veins around Georgetown and in the 
 San Juan region, cutting Archaean rocks, afford consider- 
 able amounts of lead. 
 
 Next in production to Colorado is Utah, 60 per cent 
 of whose product in 1882 was derived from the Horn Sil- 
 ver mine in Beaver County, most of the residue coming 
 from the region around Salt Lake City. Here, also, as in 
 all the Rocky Mountain region, the extraction of lead is 
 an accessory to that of the precious metals, the value of 
 which usually equals or surpasses that of the lead. 
 
244 APPLIED GEOLOGY. 
 
 The mines of Eureka district, in Eureka County, yield 
 nearly all the lead of Nevada, the reported product varying 
 from about 8,000 to 28,000 gross tons per annum. The 
 ores here, which are chiefly carbonate of lead in a highly 
 ferruginous gangue, carrying 20 to 30 per cent of lead with 
 a high value in gold and silver, occupy great chambers in 
 a magnesian limestone of Lower Silurian age. The inclos- 
 ing limestone is tilted up at a considerable angle, and bears 
 evidence of great compression, in consequence of which 
 it -is much fractured and crushed, so that the ore masses, 
 in their mode of introduction and after -concentration, 
 seem to have a considerable resemblance to fissure-veins. 
 They therefore belong to that variety of mass deposits 
 which in a preceding chapter has been described as " quasi 
 veins," i. e., those which, while mass deposits in mode of 
 occurrence, are allied to true veins in having derived their 
 ores from some deep-seated source rather than from local 
 concentrations. 
 
 The State of Missouri, which is an important producer 
 of lead, has two geological horizons of lead-bearing strata. 
 A very considerable area in the southeast portion of the 
 State, with some of the central counties, has deposits of 
 lead-ores in Lower Silurian limestones, partly occurring 
 in mass deposits, partly disseminated in certain of the 
 beds, according to Prof. Brodhead. The deposits, how- 
 ever, which are at present most largely worked, are those 
 occurring in crevices and flats, true mass deposits, in the 
 Lower Carboniferous limestones of the southwest part of 
 the State, about Joplin and Granby, and extending into 
 adjacent Kansas. The ores here are associated with im- 
 portant amounts of zinc ores, but contain only insignificant 
 proportions of silver. 
 
 In the Galena district of Illinois, Wisconsin, and Iowa, 
 lead-ores, associated with zinc but poor in silver, are found 
 in vertical crevices formed by the widening of the joints 
 of the Lower Silurian limestone in which they occur, or 
 
LEAD AND ZINC. 245 
 
 sometimes in flats between the beds of the limestone. This 
 region does not appear to be a large producer at present. 
 
 Besides these well-known and most largely productive 
 districts, most of the States and Territories of the Rocky 
 Mountain division are reported to have promising deposits 
 of lead-ores, though little worked as yet, unless where they 
 contain paying amounts of the precious metals. This is 
 especially true of Montana and of the Wood River region 
 in Idaho, from both of which a considerable production of 
 argentiferous lead was reported in 1882. In Wythe Coun- 
 ty, Va., also, large bodies of sulphide and carbonate of 
 lead, associated with ores of zinc, are known to exist and 
 have been somewhat worked, in limestone of Lower Silu- 
 rian age ; and they need only good facilities for transporta- 
 tion to build up a prosperous center of metallic production. 
 
 The lead product of the United States for 1882, which 
 was considerably increased in 1883, was reported to be 
 120,832 gross toris, distributed as follows : 
 
 Tons. 
 
 Colorado 52,360 
 
 Utah 26,786 
 
 Missouri, Kansas, Illinois, etc 25,906 * 
 
 Nevada 7,670 
 
 Idaho 4,45O 
 
 Montana .... 3,660 
 
 Total 120,832 
 
 The foremost foreign producers of lead are Spain, Ger- 
 many, and England, with minor amounts from Austria, 
 Greece, Italy, and France. Of these, Spain is much the 
 largest producer. 
 
 The lead-producing regions of this kingdom are in 
 the provinces of Murcia and Almeria on the southeast coast 
 near Cartagena, and about Linares, in the province of 
 Jaen, a little farther inland, on the head-waters of the 
 Guadalquiver. The district about Linares is said to yield 
 
 * Less than one tenth from Illinois and Wisconsin. 
 
246 APPLIED GEOLOGY. 
 
 nearly two thirds of the lead, but it is poor in silver ; while 
 the coast deposits about Cartagena, which, according to 
 Von Cotta, are veins of galena and blende, cutting Silurian 
 limestones and slates, contain profitable amounts of the 
 precious metals. 
 
 The large lead product of Germany is derived from 
 Commern, in the Rhine Province ; from Upper Silesia, 
 where it is subordinate to a very large output of zinc ; from 
 the Harz Mountains, Nassau, and Freiberg. At Com- 
 mern, according to Credner, the galena is found richly im- 
 pregnating a friable white sandstone of Triassic age, which 
 attains sometimes a thickness of eighty metres, or more 
 than two hundred and sixty feet. In Upper Silesia, ac- 
 cording to the same author, the associated ores of lead and 
 zinc occur in mass deposits in a dolomitic limestone of 
 the Muschelkalk (Triassic). 
 
 England has also a large but somewhat decreasing pro- 
 duction, chiefly from Alston Moor, from Derbyshire, and 
 from Flintshire and Denbighshire in North Wales, with 
 some from other localities. 
 
 The following table of the lead production of the world, 
 from the latest attainable statistics, will afford a good idea 
 of the most important lead-producing countries. The 
 amounts are given in gross tons for England and the 
 United States ; for the Continental states of Europe they 
 are supposed to be metric tons of 2,204^ pounds : 
 
 Tons. 
 
 United States, 1883 129,722 
 
 Spain, ,, 123,000 
 
 Germany, . 89,767 
 
 England, 1882 50,328 
 
 Austria, ,, 11,899* 
 
 Greece, 1881 njoof 
 
 Italy, 1873 15, 500 J 
 
 France, 1882 8,067 
 
 Total 439,983 
 
 * Partly litharge. f Amount exported. \ Sardinia. 
 
LEAD AND ZINC. 247 
 
 Chief Uses of Lead. The very great increase in 
 the production of lead within the past ten years has doubt- 
 less been attended by a corresponding increase in its use. 
 It is employed in the arts, in the form of metal, in a num- 
 ber of important alloys, and in several chemical combina- 
 tions. As metal, it is used in sheets for covering roofs, for 
 lining sulphuric-acid chambers in chemical works, and for 
 conden sing-pans and cisterns, and for lining tea-chests. 
 It has a large use in pipes for the conveyance of water and 
 gas. Coated with a thin film of tin, as tin-foil, it has a 
 large and increasing use for linings and wrappers of many 
 articles for culinary and other purposes. Its alloys with 
 tin, bismuth, and antimony are used as soft solder and 
 pewter, and for type and stereotype metal. Either alone, 
 or slightly alloyed with arsenic, it is used for bullets and 
 shot. White lead, an artificial carbonate, the chromate, 
 or chrome-yellow, and red lead, are largely used as pig- 
 ments ; both litharge and red lead enter into the composi- 
 tion of the most brilliant kinds of glass ; and the acetate, 
 called also sugar of lead, is largely used in the arts and in 
 medicine. 
 
 Books of reference. 
 
 " Geological Reports of Missouri " ; " Geological Reports of Illi- 
 nois," Vol. I ; " Geological Report of Wisconsin," Vols. II and IV ; 
 " First Geological Report of Iowa," Vol. I, Part I ; " Second Geological 
 Report of the United States" Emmons on Leadville ; "Mineral 
 Resources of the United States," 1882 ; Wallace, "Laws which Reg- 
 ulate the Deposition of Lead-Ores in Veins " ; Phillips, " Treatise on 
 Ore Deposits." 
 
 Zinc. The ores from which zinc is extracted are the 
 sulphide, called blende, smithsonite, the carbonate, and cala- 
 mine, a silicate of zinc ; besides which, in a New Jersey 
 locality, three minerals, which are rare elsewhere, occur 
 abundantly and constitute valuable ores of the metal, 
 viz., the red oxide zincite, ivillemite another silicate, and 
 franklinite. 
 
248 APPLIED GEOLOGY. 
 
 The most widely diffused ore is that popularly known 
 as blende, or black-jack, but whose scientific name is spha- 
 lerite, and which contains 67 per cent of zinc. It occurs 
 commonly massive, but sometimes in crystals ; has an 
 easy cleavage, is of a variety of colors, the more com- 
 mon ones being yellow, brown, and black, with a resin- 
 ous luster; and its hardness is that of dolomite, yielding 
 with no great difficulty to the knife. It is infusible before 
 the blow-pipe on charcoal ; but, when strongly heated, it 
 yields fumes of zinc oxide which coat the coal with a 
 yellow film that becomes white when cold ; and in nitric 
 acid it dissolves, giving the disagreeable odor of sulphu- 
 retted hydrogen. 
 
 The carbonate, smithsonite, which results from the 
 weathering of the sulphide, contains about 52 per cent 
 of zinc, and occurs usually in dirty-white or brownish 
 masses, crusts, or stalactites, which when crystalline have a 
 pearly luster. It is harder than blende, being somewhat 
 difficult to scratch ; it dissolves in nitric acid with effer- 
 vescence, and before the blow-pipe behaves like blende. 
 This ore is the " dry bone " of Western miners. 
 
 Calamine, the common zinc silicate, called Galmei by 
 the Germans, contains about 54 per cent of the metal, and 
 occurs usually in whitish masses or crusts, but sometimes 
 in rhombic prisms with a pearly luster. Its hardness is in- 
 termediate between that of blende and smithsonite ; and 
 it dissolves in hot sulphuric acid, the solution becoming 
 jelly-like when cold. 
 
 Zincite, the native oxide of zinc, containing 80 per cent 
 of the metal, is of a deep-red color, very easy cleavage, 
 and brilliant luster, and is found usually in cleavable, foli- 
 ated masses. It is infusible before the blow-pipe, but gives 
 a zinc film like blende on coal, and, when heated with 
 borax, yields a yellow glass. It dissolves in nitric acid, 
 and its hardness is a little greater than that of blende. 
 
 Willemite, a second zinc silicate containing 58 per cent 
 
LEAD AND ZINC. 249 
 
 of zinc, occurs usually massive, but sometimes in rhom- 
 bohedral crystals. It has various colors, as yellow, green, 
 red, and yellowish brown, and, with soda on charcoal, it 
 gives a zinc film before the blow-pipe. It dissolves in 
 hydrochloric acid, yielding a jelly of silica, like calamine. 
 
 Franklinite, a complex compound of oxides of iron, 
 manganese, and about 17 per cent of zinc, greatly resembles 
 magnetite in form, color, magnetism, and hardness ; but 
 its streak is reddish brown, and before the blow-pipe on 
 charcoal with soda it yields a film of zinc. 
 
 Mode of Occurrence. In their mode of occurrence 
 and geological horizons, the ores of zinc present no 
 marked differences from those of lead, with which, in the 
 majority of cases, they are intimately associated. Thus, 
 in the lead regions of Missouri, and of the Galena dis- 
 trict, forming mass deposits occupying flats or irregular 
 fissures discontinuous in depth, in limestones of the Lower 
 Silurian and Lower Carboniferous, the two sets of ores are 
 found associated ; and in the Galena district, as shown 
 by Chamberlin, in tolerably equal amounts, though with 
 a tendency to occupy somewhat different levels ; while in 
 deposits of similar character in Lower Silurian limestone 
 near Bethlehem, Pa., the zinc-ores are remarkably free 
 from lead. In the veins, often following faulting fissures, 
 productive chiefly in Lower Carboniferous limestones, of 
 North Wales, Derbyshire, and northern England, the two 
 ores are also frequently found associated. In the silver- 
 bearing veins cutting Archaean rocks about Georgetown, 
 Col., zinc blende is a frequent large constituent of the ore, 
 making a mixture from which it is difficult to extract the 
 silver without great loss by volatilization ; and the remark- 
 able deposits of franklinite, zincite, and willemite, near 
 Franklin, N. J., in Archaean limestones, form part of the 
 series of highly metamorphosed and greatly disturbed beds 
 of that region. These few examples will serve to show 
 that, although the ores of zinc and lead are not always 
 
250 APPLIED GEOLOGY. 
 
 found together, their modes of occurrence are yet striking- 
 ly similar, even when they form distinct and separate 
 deposits. 
 
 American Centers of Production of Zinc Ores. 
 The Lower Carboniferous lead region of southwestern 
 Missouri and adjacent Kansas, mentioned in the previous 
 'section, is at present the foremost producer of rich zinc- 
 ores in the United States, it being estimated to yield fully 
 two thirds of the zinc which we produce. The ores are 
 blende, with considerable amounts of calamine. The zinc 
 deposits of eastern Missouri, covering, in connection with 
 lead, copper, and nickel, a considerable area in portions of 
 ten counties, and once yielding a considerable supply of 
 ores, are said to be doing little at present. 
 
 The zinc-ores of the Galena district, blende and 
 smithsonite, according to Chamberlin are proving fully 
 equal in amount to those of lead, and show a marked 
 tendency to accumulation in the limestone crevices at 
 lower levels than the galena with which they mingle in the 
 middle zones of deposit. Here, as in Missouri, in the 
 earlier periods of mining, they were thrown on the waste- 
 heaps as worthless " black-jack " and " dry bone," but have 
 later been collected as the basis of a prosperous industry. 
 
 The ores of zinc with lead occurring in eastern Ten- 
 nessee, in the Lower Silurian (Knox dolomite), are re- 
 ported to be worked for zinc near Knoxville. Passing 
 northeastward from this point, we meet with the zinc 
 deposits of Wythe County, Va., and of Lehigh County, 
 Pa., both in strata of the same geological age as the 
 Knoxville deposits. According to C. R. Boyd (Institute 
 of Mining Engineers, June, 1883), the ores of Wythe 
 County are carbonate and sulphide of zinc, remarkably 
 free from lead, occurring in great mass deposits in dolo- 
 mite, and yield a zinc of exceptional purity. The deposits 
 in Lehigh County, near Bethlehem, are not worked at 
 present. The ores, blende with the results of its transfer- 
 
LEAD AND ZINC. 
 
 mation, smithsonite and calamine, occur in crevices, some- 
 times parallel, sometimes perpendicular, to the bedding 
 of greatly disturbed and fractured magnesian limestones, 
 and seem to belong to the variety of mass deposits which 
 have been described as " quasi-veins." 
 
 The unique deposits of franklinite, zincite, and wil- 
 lemite, in Essex County, N. J., in the vicinity of Franklin, 
 are found in Archaean limestone, in beds conformable to 
 the highly inclined and crystalline strata of the region. 
 They are of great dimensions, and furnish important sup- 
 plies of ore for the manufacture of a high grade of metal, 
 and also of white zinc oxide and spiegeleisen. The re- 
 gions above described are at present the only important 
 producers of zinc-ores in North America. 
 
 Foreign Zinc-producing Regions. Among for- 
 eign producers of zinc, Prussia ranks easily foremost, her 
 mines in Upper Silesia, in the Rhenish Province, and 
 Westphalia, yielding more than two fifths of the zinc of 
 the entire world. The famous zinc district of Upper 
 Silesia, which yields annually about seventy thousand met- 
 ric tons of the metal, obtains its ores, chiefly calamine 
 with minor amounts of blende, from mass deposits in a 
 dolomitic limestone of Triassic age ; while in the Rhenish 
 district and Westphalia the ore is blende with but a small 
 proportion of calamine, in irregular deposits in the De- 
 vonian or Lower Carboniferous limestone, which is chiefly 
 dolomitic. The very large product of Belgium is derived 
 in but small measure from its native ores. According to 
 the latest returns available, less than 12 per cent of the 
 zinc- ores smelted in that country came from Belgian 
 mines, which resemble in character and horizon those of 
 the Rhine Province ; the residue being imported from 
 Greece, Sardinia, Spain, Sweden, Germany, and France, 
 most largely from the two regions first named. England is 
 a considerable producer of zinc from her lead regions in 
 Wales, northern England, Cornwall, and Devonshire. 
 
252 APPLIED GEOLOGY. 
 
 Besides these countries, France, Spain, Austria and 
 Poland, Greece and Italy, yield important amounts; 
 France, as appears from Von Cotta's description, chiefly 
 from veins in crystalline and eruptive rocks ; and Spain 
 partly from the lead district near Cartagena, mentioned in 
 the preceding section, and partly from the province of 
 Santander, on the northern coast, where large mass de- 
 posits and impregnations (?) occur in Cretaceous strata 
 between dolomite and clay slate, which yield nearly two 
 thirds of the zinc of Spain. 
 
 The zinc product of the world, according to the latest 
 available data, approximates 290,000 gross or metric tons, 
 distributed as follows : 
 
 Tons. 
 
 Prussia, 1883 116,644 
 
 Belgium, ,, 78,220 
 
 United States, ,, 29,747* 
 
 England, ,, 27,661 f 
 
 France, 1882 18,325 
 
 Spain, 1881 7>O32 
 
 Austria, 1882 4>79* 
 
 Poland, 1883 3,783 
 
 Total 286,203 
 
 Zinc is used in sheets as a covering for roofs, as a lin- 
 ing for various receptacles, and as a protection for floors 
 and walls against the heat of stoves. It has a very im- 
 portant use in most forms of galvanic battery. It is very 
 largely used for coating sheet-iron and wire for fencing to 
 protect them from rust, a process which is called galvaniz- 
 ing. A single manufactory in this country is said to use 
 more than three thousand tons annually for galvanizing 
 fence-wire. Several of its alloys, like brass, Mosaic gold, 
 German silver, hard solder, and Babbitt's metal, are largely 
 used in the arts. Among its compounds, zinc-white is a 
 highly valued paint, zinc sulphate is used in medicine and 
 
 * And 9,000 gross tons zinc oxide. f Estimated. 
 
LEAD AND ZINC. 253 
 
 in the arts, and zinc chloride is employed in the process 
 called Burnettizing, for the preservation of timber, as also 
 for a disinfectant. 
 
 As works of reference, most of those mentioned under lead may be 
 consulted with profit, to which should be added " Geology of New 
 Jersey," published in 1868. 
 
 12 
 
CHAPTER XIV. 
 
 TIN AND MERCURY. 
 
 Tin. Although a sulphide of tin is occasionally met 
 with, the only ore that seems to be relied upon as a source 
 of the metal is cassiterite^ an oxide which contains y8f per 
 cent of tin. It is a brown or black mineral of brilliant 
 luster when in crystals, and is of nearly the hardness of 
 quartz. It is infusible by the blow-pipe on charcoal, but, 
 if soda be added, it yields a white, malleable bead of tin. 
 It is found sometimes crystallized in modified square 
 prisms and octahedrons, but more commonly massive, in 
 grains, lumps, and kidney-shaped masses, which, when 
 they have a concentric and radiated structure, are called 
 wood tin, or toad's-eye tin. 
 
 Mode of Occurrence and American Localities. 
 Tin-ore occurs (a) disseminated in bunches and grains in 
 veins cutting ancient crystalline rocks like granite, gneiss, 
 micaceous and hydro-micaceous schists, and is often as- 
 sociated with a peculiar kind of granitic rock called 
 greisen, composed of quartz and mica without feldspar. 
 It is accompanied by a great number of minerals, like 
 pyrite, chalcopyrite, albite feldspar, tourmaline, and wol- 
 fram. (<) From its hardness and unalterability by atmos- 
 pheric agencies, cassiterite is one of the ores which is 
 found largely accumulated \nplacer deposits, in the neigh- 
 borhood of tin-veins, from whose denudation it has been 
 accumulated in favorable localities ; and it is said that a 
 
TIN AND MERCURY. 255 
 
 large proportion of the tin product is still obtained from 
 this source. Hence the name stream-tin, since these tin 
 placers are often called streams. 
 
 Tin-ore has not been found hitherto in quantities of 
 economic importance in North America, although a num- 
 ber of localities, apparently of great promise, have been 
 discovered within the last few years which seem likely 
 soon to give both the United States and Mexico a rank 
 among producers of tin. Quite recently, Prof. W. P. 
 Blake has reported the occurrence of tin-stone in the 
 Black Hills of Dakota. It is there found both in placers 
 and in irregular bunches and seams in veins of coarse 
 granite, associated in some places with greisen, and in 
 others in a greisen-like rock of albite and mica. 
 
 Tin is reported as occurring in very promising deposits 
 in two of the southern counties of California, ores from 
 San Bernardino County giving an analysis of about 60 per 
 cent of the metal. In Clay County, Ala., deposits of tin- 
 stone have been opened and worked to some extent since 
 1 88 1. The ore here occurs disseminated in grains in 
 vertical beds of gneiss, interstratified with micaceous and 
 chloritic schists. Six beds of the tin-bearing gneiss are 
 said to occur, some of them yielding an average of i\ per 
 cent of the oxide. Tin-ores are said also to have been 
 discovered at King's Mountain in North Carolina, and at 
 several other points in the United States, but whether in 
 quantities sufficient to justify mining, is still to be shown. 
 
 Mexico is reported to have deposits of cassiterite of 
 great extent and high promise in the States of Durango 
 and Chihuahua, but they are as yet very little worked, 
 and have not apparently added anything to the supply of 
 the world. From South America, Bolivia yields annually 
 about one thousand metric tons, and the States of Colom- 
 bia are said also to produce small amounts. 
 
 Foreign Producers. The chief supplies of tin are 
 from three regions, viz., from Cornwall, England ; from 
 
256 APPLIED GEOLOGY. 
 
 Banca and Billiton, in the Straits of Malacca, hence called 
 Banca tin and Straits tin ; and from the eastern part of Aus- 
 tralia, chiefly from New South Wales, with some from adja- 
 cent Queensland and Victoria. The tin deposits of Corn- 
 wall have been worked for many ages, the earliest workings 
 extending back, it is supposed, some centuries before the 
 Christian era. The ore is still obtained to some extent 
 from placers, but chiefly from veins in ancient crystalline 
 rocks. The Australian deposits, which in New South 
 Wales are found over an area of 8,500 square miles, oc- 
 cur in narrow veins, irregularly disseminated in bunches, 
 grains, and seams, and associated with quartz, feldspar, 
 greisen, and chlorite, the country rock being, like that of 
 Cornwall, granite and crystalline schists. The largest 
 supplies are obtained, however, from extensive placer 
 deposits derived from the disintegration and wash of the 
 veins. The latest government report gives the product of 
 New South Wales for 1883 as 9,125 gross tons of tin and 
 its equivalent in ore, and the chief hindrance to making 
 the output much greater evidently arises from the fre- 
 quent defective supply of water to wash the ore-bearing 
 gravels. Some of these placer deposits are of very con- 
 siderable depth, occupying the sites of ancient water- 
 courses, and are covered with masses of basalt, presenting 
 a striking resemblance to the deep gold placers of Califor- 
 nia. The large supplies of Banca and Billiton are said to 
 be derived chiefly from placers, which yield annually 
 about eight thousand tons. Besides these, small amounts 
 of tin are produced in Germany and Bohemia, from de- 
 posits similar to those of Cornwall, the product of the two 
 regions amounting together to one hundred and thirty-six 
 tons in 1882. 
 
 The entire product of the world for 1881 is said to 
 have been 38,123 gross tons. 
 
 The statistics of production, so far as they could be 
 obtained, are as follow : 
 
TIN AND MERCURY. 257 
 
 Tons. 
 
 England, 1882 9,158 
 
 New South Wales, 1883 9,125^ 
 
 Banca and Billiton about 8,000 
 
 Bolivia, 1881 1,000 
 
 Germany, 1882 (from Saxony) IO2 
 
 Austria (from Bohemia) 34 
 
 Tin, used somewhat in castings, is much more exten- 
 sively employed as a coating for other metals, as, for ex- 
 ample, iron in the widely used tin-plate, copper in many 
 vessels for culinary purposes, and lead in the so-called 
 tin-foil. Its alloys, chiefly with copper, but somewhat 
 with lead and bismuth, are numerous and important. 
 Among them are bronze, bell-metal, gun-metal, britannia, 
 pewter, soft solder, Babbitt's metal, and the amalgam with 
 mercury for coating mirrors, besides several others. 
 
 Several of its compounds also have important uses in 
 the arts. Tin oxide is used for enamels, as a coating for 
 razor-strops, and for giving a fine polish to some orna- 
 mental stones ; the chlorides have valuable applications in 
 dyeing and calico-printing ; and the bisulphide, under the 
 name of bronze-powder, is considerably used for ornamental 
 purposes. 
 
 Mercury. Although mercury or quicksilver is not 
 unfrequently found native in small quantities, the only 
 source of it which is of economic importance is cinnabar, 
 the sulphide, which contains when pure about 87 per cent 
 of the metal. This ore is of a bright red or brownish 
 red color and scarlet streak ; is of high gravity, about 
 9, and is easily scratched, its hardness being less than 
 that of calcite. Before the blow-pipe it is easily dissipated 
 in vapor, leaving no residue save the substances with 
 which it may be mingled. 
 
 Mode of Occurrence and Localities. Its mode 
 of occurrence in all the great producing regions, three in 
 number, is the same, viz., as an impregnation, either 
 from solution or from vapor, in certain porous or fissured 
 
258 APPLIED GEOLOGY. 
 
 beds of tilted and sometimes metamorphosed stratified 
 rocks. The three regions, however, while agreeing in the 
 character of the deposits, contain them in rocks of widely 
 different geological age ; the Spanish deposits being in- 
 closed in Silurian strata, the Austrian in rocks of the 
 Lower Triassic, and the Californian in strata not older 
 than the Cretaceous. 
 
 The production of mercury in the United States, 
 which is now nearly one half the entire product of the 
 world, is confined wholly to the vicinity of the Coast 
 Range in California. In this region, at least eight coun- 
 ties, ranging from Fresno on the south to Trinity County on 
 the north, are known to contain workable deposits of cin- 
 nabar. The richest deposits that have been opened hith- 
 erto are those of New Almaden, in Santa Clara County, 
 while important supplies are also derived from Napa, 
 Lake, Sonoma, and Fresno Counties, the mines in other 
 sections seeming to depend for their working upon favor- 
 able prices for quicksilver. The inclosing strata in the 
 entire region are usually serpentine, and sandstones and 
 shales, the last-named rocks being sometimes much 
 metamorphosed, in other cases wholly unchanged, and in 
 some localities containing fossils of probable Tertiary age. 
 The cinnabar occurs in irregular deposits, impregnating in 
 some cases talcose, argillaceous, and jaspery slates ; in 
 others, sandstone ; while in others, quartzites and opaline 
 quartz form the gangue. The average contents of metal 
 in the New Almaden mine are said to be about 3^ per 
 cent, and the average cost of production in well-conducted 
 mines is said by Wagoner to be 27 -J- cents per pound. 
 Throughout the region, irregular deposits of chromic iron 
 are said to be as constant as cinnabar. As an indication 
 of the location of the mines whose product is at present 
 the most important, the following table is given for the fis- 
 cal year ending June 30, 1883 5 it is stated in flasks of 76 \ 
 pounds : 
 
TIN AND MERCURY. 
 
 259 
 
 Flasks. 
 
 New Almaden (Santa Clara County) 28,753 
 
 Napa Consolidated (Napa County) 6,351 
 
 Great Western (Lake County) 4,514 
 
 Sulphur Bank ,, 4,053 
 
 Reddington 2,555 
 
 Great Eastern (Sonoma County) 2,673 
 
 New Idria (Fresno County) 1,720 
 
 Other mines 671 
 
 Total 5 1,290 
 
 The famous Spanish quicksilver mines of Almaden, 
 northeast of the city of Cordova, have been wrought for 
 many centuries, having been known, it is said, to the an- 
 cient inhabitants of the peninsula before the time of the 
 Roman occupation. The ore deposits here occur in ver- 
 tical Silurian strata of sandstone, quartzite, and bitumin- 
 ous schist, with hard sandstone and limestone which do 
 not contain ores. The cinnabar, in a compact or earthy 
 condition, is found, in the largest mine, impregnating a 
 gray sandstone to such a degree that the mass may yield 
 as much as 25 per cent of mercury, and leave as a residue 
 when distilled only loose sand. In other cases the impreg- 
 nated beds are of quartzite, creviced with fissures running 
 in all directions, into which the cinnabar has penetrated, 
 forming sometimes also great masses, with occasional cavi- 
 ties containing metallic mercury. That these deposits are 
 really impregnations, and not bedded veins, as they have 
 sometimes been considered from the presence of a selvage, 
 seems to be conclusively shown by the fact that the origi- 
 nal planes of stratification of the beds are often percep- 
 tible in the midst of the deposits. The chief mine in 1851 
 was already 1,050 feet in depth, and the width which had 
 been mined out at the 8oo-foot level was said to be 67 
 feet. No ores are treated here which carry less than two 
 per cent of mercury, and the cost of production is not 
 more than twenty cents per pound. 
 
 The quicksilver-mines of Idria are in Carniola, in the 
 
260 
 
 APPLIED GEOLOGY. 
 
 southern part of Austria, not far from the Adriatic Sea, 
 and have been worked since the latter part of the fifteenth 
 century. They occur in greatly inclined strata of Triassic 
 age, impregnating black bituminous schists, or forming 
 contact deposits between dolomites and slates, or filling 
 transverse fissures in dolomite and limestone. The work- 
 ings have now reached the depth of 950 feet, and the ore- 
 bearing rock is found to grow richer as greater depth is 
 gained, confirming the opinion that the cinnabar has been 
 derived from a deep-lying source by infiltration or subli- 
 mation. The ores of the Idrian mines are reported to 
 average about 1.6 per cent of mercury, and the annual 
 production is much smaller than in the other two regions. 
 Besides these three chief sources of supply, compara- 
 tively insignificant amounts of mercury are obtained from 
 Italy and other parts of Europe ; but the total supply es- 
 timated to be received from these scattered localities is of 
 little importance, as may be seen from the following statis- 
 tics of the world's production in the year 1882. In this 
 table the product is given in flasks, of which those of the 
 United States, as has already been said, contain 76.5 
 pounds of mercury, while those of Spain and Austria 
 hold 76.07 pounds. The amounts are also given in a sec- 
 ond column in metric tons of 2,204.6 pounds : 
 
 PRODUCTION OF MERCURY IN 1882. 
 
 
 Flasks. 
 
 Metric tons. 
 
 United States 
 
 52,372 
 
 1, 8^O 
 
 Spain . . 
 
 AC Q2I 
 
 I 6lO 
 
 Austria . 
 
 ii, 8^ 
 
 4OQ 
 
 Italy etc., estimated 
 
 2,000 
 
 <*^y 
 60 
 
 
 
 
 Total 
 
 112,506 
 
 7 q-;8 
 
 
 
 
 California, therefore, furnished about 46^ per cent of 
 the mercury of the world, and the New Almaden mine 
 alone fully 25 per cent. 
 
TIN AND MERCURY. 2 6l 
 
 Uses of Mercury. The largest uses to which mer- 
 cury is applied are in the extraction of gold and silver, and 
 in the preparation of the brilliant pigment vermilion. From 
 the valuable property which this fluid metal possesses, of 
 readily forming alloys, called amalgams, with the precious 
 metals at ordinary temperatures, it has become indispensa- 
 ble in the processes by which these metals are cheaply 
 extracted from ores of too low grade to be smelted with 
 profit ; and about 45 per cent of all mercury is used for 
 amalgamation. A still larger proportion of the product is 
 employed in the manufacture of vermilion, the artificial 
 sulphide of mercury, used as a pigment. 
 
 Other important applications of mercury are found in 
 the making of mirrors and philosophical and meteorologi- 
 cal instruments, such as barometers and thermometers, in 
 the manufacture of fulminates for percussion caps, and of 
 various preparations for medical use, as well as in a pro- 
 cess for preserving timber from decay, called kyanizing. 
 
 Works of reference. 
 
 "Geological Report of California," Whitney, Vol. I; J. Ross 
 Browne, " Report on Mineral Resources of the United States," 1867, 
 p. 170 ; R. W. Raymond, " Report on Mineral Resources of the 
 United States," 1873, p. 18 ; Williams, " Report on Mineral Resources 
 of the United States," 1883 ; " Engineering and Mining Journal," Nos. 
 for December 24, 1881, and October 7 and December 23, 1882 ; Von 
 Cotta, " Ore Deposits," Part II, pp. 248 and 455 of German edition ; 
 Phillips, " Treatise on Ore Deposits." 
 
CHAPTER XV. 
 
 SILVER. 
 
 THIS, which is counted one of the two precious metals, 
 and which in all ages of the world has been held in high 
 estimation and largely used for coinage and for articles 
 of luxury and ornamentation, is found native in small 
 amounts in most great regions where it is mined, when it 
 is easily distinguished by its pure white color, often with 
 a dark superficial tarnish, by the ease with which it may 
 be cut and its brilliant luster on a cut surface, and by its 
 solution in nitric acid, from which it may readily be pre- 
 cipitated by a clean slip of copper, yielding a coating of 
 silver, or by a solution of common salt, yielding a white 
 chloride of silver which soon becomes discolored on ex- 
 posure to light. More commonly it is found in various 
 combinations with other substances, forming ores of silver. 
 Those most largely met with are its combination with sul- 
 phur, called argentite j with sulphur and antimony, forming 
 stephanite and pyrargyrite ; with sulphur and arsenic, called 
 proustite ; with chlorine, called cerargyrite, or horn-silver; 
 and with sulphur, antimony, and lead, called freieslebenite, 
 a mineral found as an ore in the mines of Guadalajara in 
 Spain. It also frequently replaces a part of the copper in 
 tetrahcdrite, or gray copper, thus making it a valuable ore 
 of silver, as has been mentioned in the chapter on copper. 
 In many of our Western mines, also, it is largely obtained 
 from its associations with ores of lead and with zinc blende. 
 
SILVER. 263 
 
 All these ores of silver are so soft as to be easily cut with 
 a knife, and have a specific gravity varying from 5^ to 7^ ; 
 all melt with little difficulty before the blow-pipe, emitting 
 fumes of sulphur, antimony, arsenic, or chlorine, and yield- 
 ing a bead of silver, either alone or by addition of soda 
 carbonate ; and all, save cerargyrite, dissolve in nitric acid 
 with precipitation of any sulphur, antimony, and arsenic 
 that may be present, and the silver may be deposited from 
 this solution on a clean slip of copper, or may be precipi- 
 tated as chloride by salt water. These ores may be dis- 
 tinguished from each other argentite, or silver glance, by 
 its dark lead-color and lustrous streak, its malleability and 
 sectility, and its yielding a silver bead by heat on charcoal 
 without soda ; stephanite, or brittle silver, by its black color 
 and streak ; pyrargyrite, by its usual dark-red though some- 
 times black color, and its red streak, from which it takes 
 its common name of ruby silver ; proustite, also called ruby, 
 or light-red silver-ore, by its light-red color and the odor 
 of garlic which it emits when heated ; freieslebenite, by its 
 steel-like color, and its yielding when heated on coal a 
 globule of silver-lead, from which the lead may be burned 
 off by heating with the blow-pipe on a little cup of boae- 
 ash, leaving a bead of silver, an operation which is termed 
 cupellation ; and cerargyrite, called usually horn-silver, by 
 its looking and cutting somewhat like horn, and by its 
 emitting peculiar pungent fumes when heated on charcoal, 
 and yielding a bead of silver without soda. When pure, 
 argentite contains 87 per cent of silver, stephanite 69 per 
 cent, pyrargyrite 59 per cent, proustite 65 per cent, frei- 
 eslebenite about 24 per cent, and cerargyrite 75 per cent. 
 Argentiferous galena requires no special description. Its 
 silver contents may be ascertained by cupelling the silver- 
 lead globules obtained by heating on charcoal. 
 
 When it is considered that an ore-mass containing one 
 thousand dollars' worth of silver per ton would hold no 
 more than a thousand ounces avoirdupois per gross ton 
 
264 APPLIED GEOLOGY. 
 
 of rock, or about three per cent of silver, and that such an 
 ore-mass would be counted very rich, while one yielding 
 one half of one per cent, if abundant, would be worked 
 with enormous profit, it will be obvious to the student that 
 the ores of silver, described above, can not usually be ex- 
 pected to occur in pure and easily determinable masses of 
 considerable size, but rather as strings, thin seams, and 
 stains disseminated in a comparatively large bulk of gangue 
 rock, most commonly quartz or calcite, where its determin- 
 ation as a silver-ore, and as to the amount which it may yield 
 per ton, will often be easier and of greater economic impor- 
 tance than any exact answer to the question of precisely 
 what silver-ores are present in the mass. For this reason 
 the description of the most common silver-ores has here 
 been made chiefly as general as possible, embracing those 
 characters which are common to them all, as in this form 
 it will be more likely to be generally useful to the practical 
 man. For more complete descriptions, and for desirable 
 additions to the few specific characters here given, the stu- 
 dent can refer to any good manual of mineralogy like Dana's. 
 
 Mode of Occurrence of Silver Deposits. The 
 forms of deposit in which workable silver-ores are found 
 are various, including most, if not all, the chief classes of 
 deposit described in a preceding chapter. They occur in 
 veins, cutting granitoid rocks, and crystalline schists of the 
 Archaean, as in the Reese River region of Nevada, in the 
 Atlanta and associated lodes of Salmon River, Idaho, in 
 the mines about Georgetown, Col., and in those of Kongs- 
 berg, Norway, and Freiberg, Saxony. Some of the great- 
 est silver-veins of the world are incased in or associated 
 with volcanic rocks of Tertiary age, called variously an- 
 desite, propylite, and sometimes diorite, e. g., the celebrated 
 Comstock vein of Nevada, the Veta Grande of Zacatecas, 
 and some others in Mexico, and those of Felsobanya and 
 Schemnitz in Hungary. 
 
 It occurs in impregnations, as in the Triassic sand- 
 
SIL VER. 265 
 
 stones of Silver Reef, in southwestern Utah, and in the 
 joints and bedding planes of Devonian limestones of the 
 White Pine region, Nevada. Associated with ores of lead, 
 it is found in mass deposits and ^zfcWf-veins, as at Lead- 
 ville, in many mining districts of New Mexico, and at 
 Eureka, Nev. It forms flat deposits, connected in origin 
 with mineralized dikes of eruptive nature, of which char- 
 acter, according to W. P. Blake, are the silver deposits of 
 Tombstone in southern Arizona. Finally, as an example 
 of silver in beds, may be cited the copper schists of Mans- 
 feld, which, besides affording much of the copper of Ger- 
 many, yield also important amounts of silver. An inter- 
 esting occurrence of silver may also be noted here, viz., 
 that in the regions of native copper on Lake Superior, 
 where the two native metals are not unfrequently found 
 forming parts of the same lump, and thoroughly welded 
 together without being alloyed. 
 
 Regions producing Silver. Of the vast silver pro- 
 duction of North America, derived almost entirely from 
 the United States and Mexico, it may be said in a general 
 way that, with comparatively trivial exceptions, it is ob- 
 tained from the great mountainous region of the western 
 part of the continent, comprised between the Front range 
 of the Rocky Mountains on the east, and the Cascade and 
 Sierra Nevada ranges on the west, with their southern ex- 
 tension into Mexico. The only exceptions worthy of note 
 are the product of Dakota, which might without great vio- 
 lence be included in the first, and that of the Appalachian 
 range mostly from North Carolina, and of Canada, the three 
 together amounting to little more than three hundred thou- 
 sand dollars in value in a product of more than seventy- 
 five million dollars. A similar statement may also be 
 made with regard to the silver production of South Amer- 
 ica, second only to that of the United States and Mexico, 
 which is derived from the Andes and their western slope. 
 
 Within the great mountain-region indicated above, the 
 
266 APPLIED GEOLOGY. 
 
 United States has much the largest silver production of any 
 country in the world. Of the eleven States and Territo- 
 ries included within its limits, all save Wyoming, Oregon, 
 and Washington, in 1882 yielded amounts of silver valued 
 at eight hundred thousand dollars or more. The State 
 ranking highest in silver production in that year was Colo- 
 rado, whose sixteen and a half million dollars' worth of sil- 
 ver was derived most largely from three chief districts : 
 that of which Leadville may be considered the center, in- 
 cluding Lake County and small portions of Summit, Gun- 
 nison, Eagle, and Chaffee ; Clear Creek County, of which 
 Georgetown is the center ; and the San Juan region, in- 
 cluding portions of about six very rugged and mountain- 
 ous counties, whose chief centers seem to be Silverton 
 and Ouray. Besides these chief regions, Boulder, Custer, 
 Gilpin, and Park Counties yield important amounts. The 
 mines of these four counties are chiefly in veins, and the 
 vein system in all of them yields' gold as well as silver; 
 that of Gilpin County, in particular, affording six times as 
 much gold as silver. The two great mines of Custer 
 County, the Bassick and the Bull Domingo, present features 
 worthy of mention, since their gangue is a kind of breccia 
 of the country rock, carrying the ores of gold and silver 
 of the first, and of silver of the second named mine, as a 
 cementing incrustation of the blocks of stone ; while the 
 ore-bearing fissure of the Bassick has the character of a 
 chimney of unknown depth but limited extent, giving rise 
 to the theory that it is the pipe of an ancient hot spring. 
 
 Next in value of silver output to Colorado is Arizona, 
 in which the noted Tombstone region, in the southernmost 
 county of the Territory, yields fully two thirds of its sil- 
 ver ; while Final County, chiefly through the Silver King 
 mine ; Gila County, so rich in copper ; Yavapai, Yuma, and 
 Final Counties are also important producers. The large 
 silver product of Utah may conveniently be said to be de- 
 rived from three chief districts, of which what may be 
 
SILVER. \ V J 267 
 
 called the Salt Lake district, since its mines use 
 City as a center or are in convenient proximity to it, in- 
 cludes Salt Lake and Tooele Counties and the Tintic dis- 
 trict of Juab County, the ores of which are mostly treated 
 near Salt Lake ; as also Summit County, in which the very 
 rich Ontario mine produces yearly about two million four 
 hundred thousand dollars in silver. In the Frisco dis- 
 trict of Beaver County, the Horn Silver mine is much the 
 largest producer ; and the Harrisburg or Silver Reef dis- 
 trict, in the very southernmost part of the territory, yields 
 about nine hundred thousand dollars a year from its 
 unique reefs of sandstone permeated with ores of silver. 
 
 Nevada, so short a time ago the foremost State in sil- 
 ver production, mainly from the Comstock mines, the Eu- 
 reka and Reese River districts, and from Esmeralda and 
 White Pine Counties, has during the past few years sunk 
 to the fourth place, the great diminution in the yield of the 
 Comstock mines not having been compensated by a corre- 
 sponding increase elsewhere. Besides the regions named 
 above, Elko, Lincoln, and Nye Counties are important 
 producers of silver. 
 
 Of the silver produced in Montana, about five sixths 
 are reported to come from the near vicinity of Butte City, 
 the remaining sixth being made up mostly by three coun- 
 ties, Beaver Head, Deer Lodge, and Jefferson, which sur- 
 round it, in the western portion of the Territory. 
 
 The silver of Idaho, amounting to about two million 
 dollars per year, is derived almost wholly from the three 
 counties of Custer, Alturas, and Owyhee: in the first, 
 from the region on the head-waters of the Salmon River ; 
 in Alturas, from the Atlanta vein and the Wood River re- 
 gion, these districts being in near proximity to each other ; 
 while the mining districts of Owyhee County are in the 
 southwest corner of the Territory, in the vicinity of Silver 
 City. Most of the silver of New Mexico so far has been 
 derived from mines along the Mimbres, or Black range, 
 
268 APPLIED GEOLOGY. 
 
 and the Socorro Mountains, in portions of Grant, Dona 
 Ana, and Socorro Counties, in the southwest part of the 
 Territory ; and that of California from the Sierra Nevada 
 Mountains, chiefly on their eastern declivity. The an- 
 nexed table of the silver product of the United States in 
 1882 will aid the student to gain a clearer idea of its rela- 
 tive distribution from the preceding brief description. 
 The values are reckoned on the coinage estimate of silver, 
 viz., $i.29 1 2 o 9 o- P er ounce, troy. As the selling price of un- 
 coined silver during that year was not more on the aver- 
 age than $1.11 per ounce, troy, the real value of the 
 total is given also at that rate. 
 
 Colorado $16,500,000 
 
 Arizona 7,500,000 
 
 Utah 6,800,000 
 
 Nevada 6,750,000 
 
 Montana 4,370,000 
 
 Idaho 2,000,000 
 
 New Mexico 1,800,000 
 
 California 845,000 
 
 Oregon 35,ooo 
 
 Dakota 175,000 
 
 North Carolina 25,000 
 
 Total $46,800,000, or 
 
 $40,179,440 value at $i.n per ounce troy. 
 
 Foreign Silver Regions. In amount of silver pro- 
 duced, Mexico is second only to her neighboring republic, 
 the United States. Some of the mines, like those of Gua- 
 najuato and Zacatecas, have been long known, having been 
 opened even before the time of the Spanish conquest, 
 and, though worked fitfully and without system, have 
 yielded enormous quantities of the precious metal. In 
 more recent times many of them have fallen into the 
 hands of English and American capitalists, and with im- 
 proved methods are yielding regularly and largely. 
 These silver deposits, chiefly veins, or, as at Fresnillo, 
 stockworks accompanied by impregnations, follow the line 
 
SIL VER. 269 
 
 of the Cordilleras from Tasco, south of the city of Mexi- 
 co, as far northward at least as Batopilas in the southwest 
 corner of Chihuahua. The foremost silver-producing 
 States are Guanajuato and Zacatecas, both of which have 
 famous mines, as the Valencian in Guanajuato and those 
 of Zacatecas, Sombrerete, Fresnillo, Pachuco, and Real del 
 Monte in Zacatecas. Besides these States, silver in im- 
 portant amounts is obtained from Queretaro, and from 
 parts of Jalisco, Durango, and Chihuahua. The Mexi- 
 can yield of silver in 1883 is reported to have been more 
 than twenty-nine million five hundred thousand dollars. 
 The deposit of Silver Islet, on the north shore of Lake Su- 
 perior, which has yielded three million dollars' worth of 
 the metal, mostly from native silver in a vein cutting Ar- 
 chaean schists and dikes, is no longer a considerable pro- 
 ducer; and its companion veins, if any exist, have not 
 yet been discovered on the mainland. 
 
 The silver of South America is derived mainly from 
 Bolivia and Chili, with much smaller amounts from Colom- 
 bia and the Argentine Republic, Peru not being named in a 
 recent list of silver-producing countries published by the 
 Director of the United States Mint, although in 1880 its 
 average annual product was given as 79,365 kilogrammes 
 =$3,298,410, mostly from Cerro de Pasco. These silver 
 deposits, as has already been said, are in the Andes 
 Mountains, and on their Pacific slope. The mines of Po- 
 tosi in Bolivia have been long celebrated, but are now 
 greatly surpassed by those of Huanchaca and Colque- 
 chacq, west and north from it. The most important mines 
 of Chili are in the regions near Copiapo and Iquique, a 
 port belonging until recently to Peru. 
 
 The large silver product of Germany is derived 
 mostly, it is said, from the vicinity of Freiberg, from the 
 Harz, and from Mansfeld where it is an accessory to the 
 production of copper. The silver mines of the Austrian 
 Empire are in the Tyrol, and on the slopes of the Carpa- 
 
2/0 
 
 APPLIED GEOLOGY. 
 
 thians at Schemnitz, Kremnitz, and Felsobanya in Hun- 
 gary, and in Transylvania. Spain produces a consider- 
 able amount of silver from the mines of Hiendelencia in 
 the province of Guadalajara, northeast of Madrid, as also 
 from the argentiferous lead deposits on the southeast coast 
 in the vicinity of Cartagena and in the northeast part of 
 the province of Almeria. The product of Norway from 
 Kongsberg, of Russia from its Siberian provinces, and of 
 Japan, are none of them so much as four hundred thou- 
 sand dollars per annum. The silver of Japan, according 
 to Prof. Lyman, of the University of Tokio, is derived 
 from argentite, antimonial sulphides, and native silver, 
 which occur mostly in veins, though sometimes in irregular 
 mass deposits in volcanic rocks. The production of Japan 
 was formerly much more considerable than at present. 
 
 A table of the production of the precious metals 
 throughout the world for the year 1883, prepared by the 
 Director of the United States Mint, has recently been pub- 
 lished, and the table below is a copy of that portion of 
 this which relates to silver : 
 
 
 Weight in 
 kilogrammes. 
 
 Mint value. 
 
 United States 
 
 I III 4^7 
 
 
 Mexico. . . 
 
 711 "347 
 
 2o 568 ^76 
 
 Colombia 
 
 18 28^ 
 
 
 Bolivia 
 
 284 021 
 
 16 ooo ooo 
 
 Chili 
 
 128 106 
 
 
 Argentine Republic 
 
 IO IOO 
 
 ,j^5,uoo 
 
 Canada 
 
 
 AQ one 
 
 Russia 
 
 7 78l 
 
 
 Austro- Hungary. . 
 
 48 708 
 
 J^J4^7 
 
 Germany 
 
 27O 6oA 
 
 
 Norway 
 
 e f\A 
 
 >D 9)3 
 
 
 I ^82 
 
 ^J4.<J4D 
 
 Turkey 
 
 2 164 
 
 
 Italy 
 
 
 
 17 
 bpain 
 
 4J^ 
 
 J 7949 
 
 Japan 
 
 8 488 
 
 
 Australia 
 
 I Q24 
 
 JDJ.^5 
 
 80 ooo 
 
 
 
 
 Total.., 
 
 2.747.78J. 
 
 ifcl 14.2 1 7.717 
 
SILVER. 2/1 
 
 The silver product of the world, therefore, was 2,747^0% metric tons. 
 The mint value given in the table is $1.29 ^ per ounce troy, which 
 equals $41.56 per kilogramme. As the average market rate of silver 
 during 1883 was $1.10 per ounce troy, a deduction of 14.92 per cent 
 should be applied to the above, making the real value $97,176,447. 
 
 The enormous increase in the production of silver since 
 1860, resulting from the discovery of our Western deposits 
 and from the more thorough working of the Mexican 
 mines, and which has, since the year 1872, increased the 
 annual output fully 80 per cent, has produced the effect 
 that might naturally be anticipated for silver, as for any 
 other metal, of diminishing its value in comparison with 
 gold and with all salable commodities. It already inter- 
 feres seriously with its availability for its largest use, viz., 
 in coinage, rendering necessary a resort to artificial and 
 arbitrary expedients for the continuance of its use at a 
 rate of estimation which was fixed in times when the metal 
 was much less abundant ; and it threatens, unless a great 
 falling off in production soon occurs, or unless new and 
 wider avenues for its employment are soon opened, to 
 force a fundamental revision in the ideas of coinage, with 
 the abandonment of any serious attempt to fix its relative 
 estimate with the less abundant metal, gold, which is so 
 generally made the standard of value by commercial na- 
 tions. 
 
 Uses of Silver. The uses of silver have always been 
 determined by the beauty of the metal, by its rarity in 
 comparison with other metals save gold, and by its un- 
 alterability by the ordinary agencies of change which so 
 soon affect most other metals. From these circumstances 
 it has for ages been dedicated to coinage, and to the fab- 
 rication of articles of luxury and ornament, articles which 
 in a measure bespeak the wealth and importance of their 
 possessors. For these uses, it is always alloyed with a 
 certain proportion of copper, usually from 7^ to 25 per 
 cent, to increase its hardness and durability. Besides 
 
272 
 
 APPLIED GEOLOGY. 
 
 these chief uses, silver is also largely employed in plating 
 other metals and alloys, either by applying to them a thin 
 sheet of silver, or more commonly by depositing the metal 
 from solution upon the objects to be plated by the gal- 
 vanic current. Some of the compounds of silver also have 
 a very considerable use in photography, in surgery, and 
 in the plating of mirrors. 
 
 A table of the uses of silver in the arts, for other pur- 
 poses than coinage, will be given in connection with gold 
 in the chapter on gold. 
 
 Works of reference. 
 
 Clarence King, " Geological, etc., Survey of the Fortieth Parallel," 
 Vol. Ill ; " Sutro Tunnel Report " Von Richthofen's description of the 
 Cqmstock lode ; " Geology of the Comstock Lode and Washoe Dis- 
 trict," G. F. Becker, United States Geological Survey; " Second An- 
 nual Report of the Director of the United States Geological Survey " ; 
 Raymond's " Reports on the Mineral Resources of the United States," 
 from 1869 to 1876 ; " Reports of the Directors of the United States 
 Mint" ; Von Cotta, " Erzlagerstatten," Part II, for Europe; Phillips, 
 " Treatise on Ore Deposits." 
 
CHAPTER XVI. 
 
 GOLD. 
 
 THIS, the more highly valued of the two precious met- 
 als, is found very widely distributed over the earth, but 
 usually in traces so minute as to be economically valueless. 
 It is only when it has been accumulated in rock deposits, 
 in proportions varying from a considerable fraction of an 
 ounce to a number of ounces per ton of rock, or when, by 
 the disaggregation of the containing rocks, it has under- 
 gone a process of concentration in the channels of ancient 
 or modern stream-courses, that it becomes an object of 
 other than theoretical interest. Gold is rarely found form- 
 ing ores, properly so called, although its common associa- 
 tions with iron and copper pyrites, and with some other 
 minerals, are often conveniently called ores. It usually 
 occurs in the metallic state, almost always alloyed with 
 more or less of silver and occasionally with other metals. 
 When it is in visible particles it is readily distinguished by 
 its yellow color, its luster, its malleability, and by the ease 
 with which it may be cut with a knife. The only minerals 
 which are liable to be mistaken for it are iron and copper 
 pyrites, which somewhat resemble it in color, but in no 
 other respect, since both are harder, pyrites very much so ; 
 both crumble instead of flatten under the hammer, and, 
 though copper pyrites can be cut with no great difficulty, 
 it yields a greenish powder instead of a flexible metallic 
 shaving like gold. When heated strongly with the blow- 
 
274 APPLIED GEOLOGY. 
 
 pipe, also, gold melts to a brilliant globule on coal, while 
 both of the minerals in question yield fumes of sulphur. 
 Besides its usual occurrence as native metal, true ores of 
 gold are sometimes met with which are compounds of tel- 
 lurium with gold, either alone, as in calaverite, or with sil- 
 ver, as in sylvanite and petzite, or with lead, as in nagyagite. 
 These minerals, which are usually mineralogical rarities 
 rather than sources of the precious metals, have been found 
 in sufficient abundance to become valuable ores at a few lo- 
 calities in our Western mining regions, notably in the region 
 around Gold Hill in Boulder County, Col., where mines, like 
 the Red Cloud, Cold Spring, Keystone, and Smuggler, have 
 yielded considerable amounts ; and in the Bassick mine, 
 Custer County, Col., where the tellurides occur in some of 
 the incrustations which cement the breccia-like gangue. 
 
 Mode of Occurrence of Gold. Gold is found in 
 both original and secondary deposits, the original deposits 
 being the veins and beds, or impregnations in which it was 
 originally accumulated by various agencies ; and the sec- 
 ondary those which have resulted from the disintegration of 
 the first, and the concentration of their heavy auriferous con- 
 tents by running water, in the channels and accumulations 
 of streams, usually in their lowest parts and in their hollows 
 and eddies, and which are called alluvial deposits, or placers. 
 
 Gold-bearing veins occur cutting granite and other 
 crystalline or eruptive rocks, as in the veins of Gilpin 
 County, Col., and some of those of California ; or follow- 
 ing mostly the planes of bedding of highly inclined schists, 
 of which kind are the veins of Nova Scotia and many of 
 those of the Appalachian range and of the Sierra Nevada. 
 In these veins quartz is the usual gangue, in which the 
 gold is disseminated in minute grains, films, and strings, 
 usually associated with pyrites, arsenical pyrites, and chal- 
 copyrite, and not unfrequently with some galena and 
 blende. In the upper and exposed portions of such veins, 
 these sulphides have been weathered out, leaving the quartz 
 
GOLD. 
 
 275 
 
 cellular and rusty and the gold free, so that it is easily ob- 
 tained by crushing the rock and amalgamating with mer- 
 cury ; but where the sulphides are not decomposed, the 
 gold is so incased in them that but little of it can be ob- 
 tained by such simple methods, and the ores are called 
 rebellious. In some veins, as in the Comstock, the Atlanta 
 lode in Idaho, the ^#0j/-veins of the Eureka district, Nev., 
 and in the veins of Kremnitz in Hungary, gold is found 
 associated with silver, forming a considerable part of the 
 value of the ore body. This is notably the case in those 
 unfrequent instances where the ores are tellurides, as in 
 the regions named in a preceding paragraph, and in the 
 veins of Nagyag, in Transylvania. Besides its occurrence 
 in veins, gold is also found disseminated in beds of talcose, 
 chloritic, and micaceous schists, or in lenticular segrega- 
 tions parallel with their bedding planes. Deposits of this 
 kind have yielded important amounts of gold, for example, 
 at King's Mountain and Gold Hill in North Carolina. 
 (Kerr.) Workable amounts of gold are also sometimes 
 found as impregnated zones of the country rock of veins. 
 The greenstone walls of the vein of Kremnitz are impreg- 
 nated for some distance with valuable amounts of gold ; 
 and the schists which incase some of the quartz-veins of 
 California contain gold, possibly derived from the veins. 
 
 But, important as are these original and primary de- 
 posits of gold, and destined as they doubtless are to be- 
 come in the future even more important, yet the secondary 
 deposits, or placers, have in all time been the source of 
 much the largest part of the gold, and continue to be a 
 very large source, although the output from veins is in- 
 creasing. Of the enormous gold product of our Pacific 
 coast fully nine tenths, it is said, has been derived from 
 placers ; most of the gold of South America is from the 
 same kind of deposits, as is also two fifths of the product 
 of Victoria, in Australia, and a much larger proportion of 
 that from the more northern provinces of the east coast 
 
276 APPLIED GEOLOGY. 
 
 of that island ; the large product of New Zealand is mostly 
 from placers ; and nearly all of that from Russia, from the 
 Siberian side of the Ural Mountains, is likewise from a 
 similar source. In Australia, as well as in California, many 
 of the older and deeper placer deposits have been covered 
 by thick sheets of volcanic rocks, forming what are called 
 "deep placers," from which the auriferous gravel is ex- 
 tracted by subterranean workings, similar to those by 
 which coal-beds are worked. Gold, as it occurs in placers, 
 offers some signal advantages to those engaged in obtain- 
 ing it. By the agencies of disintegration and transporta- 
 tion, through which the placers have originated, the metal 
 has been freed from entangling alliances with the sulphides 
 with which it is so commonly associated, and is presented 
 in the state most favorable for being seized upon by the 
 mercury which is used for its collection. Again, the gold, 
 which in many of its original deposits was in amounts too 
 minute and insignificant to justify even the least expensive 
 efforts at extraction, has been mostly separated from its 
 containing rocks and concentrated into deposits where it 
 may be profitably worked. A third and very important 
 advantage is the facility with which enormous amounts of 
 these superficial accumulations can be handled, and their 
 valuable contents extracted, by modern hydraulic methods, 
 where the requisite conditions can be obtained, of sufficient 
 slope of surface and an abundant supply of water under 
 great head. Streams of water of from four to nine inches 
 diameter, and under a head due to a descent of from one 
 hundred to more than four hundred feet, directed against 
 a bank of auriferous gravel, unless its parts are very firmly 
 cemented, tear down and disaggregate the materials with 
 great rapidity, and send them rushing tumultuously through 
 long sluices, where the gold is caught by mercury distrib- 
 uted in the stone or iron riffles with which the bottoms 
 are paved. In this way gravels which contain but ten to 
 twenty cents' worth of gold per cubic yard can be profita- 
 
GOLD. 277 
 
 bly worked. In placer deposits only are occasionally found 
 those exceptionally large masses of gold, called nuggets, 
 which weigh from a few ounces or pounds to one hundred 
 and fifty pounds and even more. Nuggets of considerable 
 size have been met with in our Southern Atlantic States 
 and in California, but the greatest masses of this kind have 
 been found in Australia, one of which weighed over one 
 hundred and forty-six pounds, another nearly one hundred 
 and eighty-three pounds, and two others weighed respect- 
 ively one hundred and thirty-five and ninety-two pounds. 
 The largest reported from the United States was from 
 North Carolina, and weighed twenty-eight pounds avoirdu- 
 pois, or a trifle more than thirty-four pounds troy. Since 
 bunches of this size have, it is claimed, not yet been met 
 with in undecomposed veins, and since the gold of nuggets 
 is usually considerably purer than that in veins, it seems 
 possible that the nuggets may be due to some process of 
 gradual solution and subsequent precipitation of the gold 
 within the placers, as has been maintained by Prof. T. 
 Eggleston ; an opinion which has, however, been strongly 
 opposed by Dr. Newberry, in an article on the " Genesis 
 and Distribution of Gold," in which an explanation of the 
 origin of nuggets is given, wholly consonant with the gen- 
 erally accepted theory of the formation of placers. 
 
 Regions of Gold Production. About 93 per cent 
 of the gold of the world is derived from four great regions 
 of production, viz., the mountainous western section of 
 the United States from the meridian of the Black Hills 
 westward ; the Australian region, consisting of the eastern 
 part of Australia, with Tasmania and New Zealand ; the 
 Russian gold region of Siberia ; and the two northern 
 divisions of South America, Colombia and Venezuela. If 
 to these be added the product of Africa, the Austrian 
 Empire, Mexico, Canada, and Brazil, little more than 
 $1,000,000 worth per year remains to be credited to the 
 
 rest of the world. 
 13 
 
278 APPLIED GEOLOGY. 
 
 The following table of the gold product of the United 
 States for 1882, from the report of the Director of the 
 Mint, will afford a fair idea of our gold-yielding regions, 
 and of their relative importance : 
 
 GOLD PRODUCTION OF THE UNITED STATES IN 1882. 
 
 1. California $16,800,000 
 
 2. Colorado 3,360,000 
 
 3. Dakota 3,300,000 
 
 4. Montana 2,550,000 
 
 5. Nevada 2,000,000 
 
 6. Idaho 1,500,000 
 
 7. Arizona 1,065,000 
 
 8. Oregon 830,000 
 
 9. Georgia 250,000 
 
 10. Utah 193,000 
 
 11. North Carolina 190,000 
 
 12. New Mexico 150,000 
 
 13. Alaska 150,000 
 
 14. Washington 120,000 
 
 15. South Carolina 25,000 
 
 16. Virginia 15,000 
 
 17. Wyoming 5,coo 
 
 Total . . $32,500,000 
 
 From this table it may be seen that the Southern Ap- 
 palachian States, which, up to the time of the discovery of 
 gold in California in 1848, were our sole producers of gold, 
 but which after that time came to be little regarded, are 
 again showing much activity and are yielding a creditable 
 output, aggregating in 1882 $480,000 in value, mostly from 
 Georgia and North Carolina. The large product of Cali- 
 fornia, more than one half that of the entire United States, 
 is credited to no less than thirty-two counties, but is ob- 
 tained chiefly from the Sierras and their Pacific slope, 
 Nevada and Mono Counties taking the lead, while Ama- 
 dor, Plumas, and Sierra Counties have each a product of 
 more than $1,000,000. Nearly one half the product of 
 
GOLD. 279 
 
 Colorado is from Gilpin County, with large amounts also 
 from Lake, Boulder, Clear Creek, Custer, and Rio Grande 
 Counties, eight others of the mountain counties aiding to 
 swell the total. The gold of Dakota is derived from the 
 Black Hills region in the southwest part of the Territory, 
 most largely from mines working the enormous belt of low- 
 grade rock in Lawrence County, but with considerable 
 amounts also from placers, and from the peculiar fossil 
 placer of Lower Silurian age which was mentioned in the 
 chapter on ore deposits, and which is here called cement. 
 The gold of Nevada is derived mostly from the Comstock 
 and Eureka district mines, the first group of mines yield- 
 ing gold and silver in tolerably equal proportions, and the 
 second producing gold, silver, and lead. The localization 
 of the gold product of the remaining gold-producing sec- 
 tions can not be profitably attempted, since the produc- 
 tion in those new regions is subject to great fluctuations, 
 from the discovery of new mines and the partial aban- 
 donment of older locations by a population intent on rapid 
 gain. Placers of small extent become exhausted and the 
 course of production drifts elsewhere ; or the weathered 
 portions of the veins in a newly-discovered territory are 
 hastily worked out by simple appliances, and then the lo- 
 cality is measurably abandoned, awaiting the advent of 
 capital for its more complete and systematic development ; 
 or rumors of a rich strike elsewhere may cause an almost 
 total exodus of that adventurous class who are the pio- 
 neers of all new mining regions. From these various 
 causes the production of gold in several promising sections 
 has not yet sufficiently settled about great centers to make 
 it safe to note them definitely. 
 
 An estimate of the gold production of the world for the 
 year 1883 has recently been published by the Director of 
 the Mint, which, with a slight rearrangement, to bring to- 
 gether regions which are contiguous, is given below, with 
 weight and values : 
 
280 
 
 APPLIED GEOLOGY. 
 
 
 Kilo- 
 grammes. 
 
 Value. 
 
 
 United States 
 Mexico . ... 
 
 45,140 
 i 438 
 
 $30,000,000 
 Q<;5,63Q 
 
 
 Canada 
 
 I 4.35 
 
 954,OOO 
 
 
 Colombia 
 
 5 802 
 
 3 856 ooo 
 
 
 Venezuela 
 Argentine Republic 
 Brazil. 
 
 5,022 
 
 118 
 
 QC2 
 
 3,333,058 
 78,546 
 
 632, ^ 2O 
 
 $8,140,499 for South 
 
 
 IOQ 
 
 72, 375 
 
 America. 
 
 Chili . . 
 
 2AZ 
 
 163 ooo 
 
 
 Africa 
 
 3 ooo 
 
 I,QQ3,8OO 
 
 $28 613 880 for South- 
 
 Australia, etc 
 
 OQ 87-7 
 
 26,5OO,OOO 
 
 ern Hemisphere and 
 
 Japan 
 
 181 
 
 1 2O O8O 
 
 TaDan 
 
 Russia 
 
 <ie Qja 
 
 23,867,Q35 
 
 
 Austro-Hungary . . . 
 Germany . 
 
 1,638 
 A 7 
 
 1,088,615 
 2Q3 722 
 
 
 Italy. 
 
 IOQ 
 
 72,375 
 
 $25,363,883 for Eu- 
 
 Sweden 
 
 27 
 
 24,590 
 
 rope. 
 
 Turkey .. 
 
 IO 
 
 6.646 
 
 
 
 
 
 
 Total 
 
 141 47Q 
 
 $Q4 O2 7 QOI 
 
 
 
 
 
 
 From this table it appears that the total annual product 
 of gold is about 141^ metric tons, worth, at $664.62 per 
 kilogramme, $94,027,901 ; and that North America pro- 
 duces over a third of this, chiefly from the Rocky Mount- 
 ain division of the United States, with nearly a million 
 dollars' worth each from the Pacific slope of Mexico and 
 from Canada. The gold of Canada is derived from the 
 quartz-veins on the Atlantic side of Nova Scotia, and from 
 veins and placers in Quebec, not far from the United 
 States boundary ; promising veins of gold-bearing pyrites 
 also occur in the township of Marmora, Hastings County, 
 Ontario, and gold is obtained from placers in British Co- 
 lumbia. Next to the gold product of North America 
 ranks that of the Australian provinces, from the quartz- 
 veins and placers of the four eastern divisions of Aus- 
 tralia, of which Victoria is the largest producer, from 
 Tasmania and from New Zealand, whose placers yield 
 several million dollars' worth annually. The Orange 
 Free State of South Africa exhibited at Philadelphia in 
 
GOLD. 28l 
 
 1876 a rich collection of gold nuggets gathered from its 
 " golden sands " ; and more recently rich placers have 
 been opened in the Transvaal, from which, and from the 
 longer known placers of the east and west coast, the gold 
 of Africa is derived. The best known sources of the large 
 gold product of Russia are the placers and occasional veins 
 of the Urals, chiefly on the eastern slope ; and the gold 
 of the Austrian Empire is derived almost wholly from 
 Hungary, from veins on the lower declivities of the Car- 
 pathians and their outliers, ranging from Schemnitz and 
 Kremnitz in the north, around to the region called the 
 Banat in the south. The gold of Colombia and Venezu- 
 ela is derived mostly from placers, the attempts at work- 
 ing veins having, it is said, not been satisfactory ; and the 
 production of Brazil, according to recent reports, is ob- 
 tained mostly from five mines, one of which, the St. John 
 del Rey, yields fully seven eighths of the entire amount. 
 
 Uses Of Gold. The uses of gold, like those of silver, 
 have from the earliest periods been based on its intrinsic 
 beauty, rarity, and unchangeability by chemical agencies, 
 and have been for coinage and articles of luxury. In 
 recent years it has had also a considerable use for pens 
 and dental supplies, as well as for coating less valuable 
 metals. For coinage and most other purposes it is alloyed 
 with copper or silver to increase its hardness, the standard 
 of fineness for coin in this country being nine tenths gold, 
 and in England eleven twelfths. For other purposes the 
 amount of alloy varies widely. The report of the Director 
 of the Mint for the year ending June 30, 1884, gives a 
 table of the uses of gold and silver for purposes other than 
 coinage during the fiscal year, based on a wide correspond- 
 ence with manufacturers ; from which it appears that in 
 the United States alone nearly fourteen and a half million 
 dollars' worth of gold, and more than five and a half 
 million dollars' worth of silver, was so used. This table 
 is here given : 
 
282 
 
 APPLIED GEOLOGY. 
 
 Gold. 
 
 Silver. 
 
 Watch-cases $3,598,308 $1,845,599 
 
 Watch-chains 827,000 23,544 
 
 Jewelry and watches 7,905,163 1,098,220 
 
 Plate 528,868 2,066,294 
 
 Leaf 1,084,824 46,883 
 
 Pens 145,924 6,730 
 
 Spectacles 215,428 23,782 
 
 Instruments 5, I 99 I 3,99 
 
 Dental supplies 37,912 6,738 
 
 Supplies for watchmakers, etc 79,227 8,331 
 
 Chemicals 31,611 416,419 
 
 Total "... $14,459,464 $5,556,530 
 
 TABLE OF VALUE OF FINE GOLD. 
 
 Per ounce, troy $20.6718. 
 
 Per pound, troy 248.06. 
 
 Per ounce, avoirdupois 18.84^. 
 
 Per pound, avoirdupois 301.46. 
 
 Per kilogramme 664.628. 
 
 Modes of Extraction of Gold. Although the ex- 
 traction of gold from the gold-bearing rock is an operation 
 which belongs rather to the metallurgist than to the geolo- 
 gist, yet the great general interest which attaches to this, 
 the most highly valued of the precious metals, will render 
 not inappropriate a brief sketch of the two most common 
 modes of extraction. The mode of getting gold in the 
 large way from placers by hydraulic methods has already 
 been outlined, and needs no repetition. Where gold oc- 
 curs in rock material not intimately associated with sul- 
 phides, as in some quartz-veins and talcoid schists, or in 
 the decomposed outcroppings of deposits, it is reduced to 
 a fine powder or pulp with water in stamp-mills, and the 
 gold caught on copper plates coated with mercury, and ar- 
 ranged partly inside the stamp-boxes, partly on an inclined 
 platform over which the pulp flows after leaving the bat- 
 tery. At proper intervals of time the amalgam of gold is 
 scraped from the plates, and, after being cleaned, the vola- 
 tile mercury is distilled off from the gold by heating in 
 
GOLD. 283 
 
 iron retorts. When, however, the gold is involved in sul- 
 phides like pyrites and arsenical pyrite, and so becomes 
 what is called rebellious instead of free-milling, it is first 
 crushed to powder in a stamp-mill or otherwise, in which 
 operation any free gold may be caught as in free-milling if 
 thought desirable ; second, concentrated, i. e., freed from 
 gangue by washing in gigs, buddies, or vanners ; third, 
 roasted, to free the sulphides from sulphur and reduce 
 them to oxides, thus liberating the gold from its entangle- 
 ments ; and, fourth, the gold is amalgamated, or, better, re- 
 duced to the form of the soluble chloride of gold, by 
 treating the moistened pulp with chlorine gas in a suitable 
 vessel, an operation which can be greatly hastened by 
 keeping the pulp in motion, and introducing the chlorine 
 under considerable pressure (Mears's process) ; when, fifth, 
 the chloride is leached from the pulp with water, and the 
 gold precipitated as a powder by adding a solution of iron 
 sulphate. When the gold is associated with valuable 
 amounts of copper, a much more complicated process of 
 smelting and separation of the metals is resorted to, for 
 which any one interested in such matters will need to refer 
 to treatises on metallurgy. 
 
 Works of reference, 
 
 Besides the works mentioned under silver, most of which are ap- 
 plicable also to gold, the student will do well to consult Whitney's 
 "Treatise on the Auriferous Gravels of California" ; Dawson's " Aca- 
 dian Geology " ; the Geological Reports of Canada for 1863 and 1870- 
 '71 ; " Geological Reports of North Carolina," Emmons, 1856, and 
 Kerr, 1875 ; and also numerous papers in " Transactions of American 
 Institute of Mining Engineers." Many other works might easily be 
 named, but some of the above are most likely to be accessible to the 
 diligent student. 
 
CHAPTER XVII. 
 
 PLATINUM AND OTHER METALS. 
 
 Platinum. This metal, whose singular infusibility 
 and indifference to nearly all chemical reagents, com- 
 bined with its remarkable ductility and its malleability, 
 make it an object of great importance in the arts, is 
 always found in the metallic state, and usually alloyed 
 with iron and certain rare metals, of which the most com- 
 mon are iridium and osmium. It has never yet been 
 found in any other than placer deposits, in which it 
 usually occurs in flattened grains, readily distinguished by 
 their infusibility and malleability, and their great specific 
 gravity. Nuggets of considerable size are also occasion- 
 ally met with, the largest of which, according to Phillips, 
 weighed twenty-two pounds troy. Although the original 
 deposits from whose destruction the platinum has been 
 supplied to placers have never yet been discovered, still, 
 according to Von Cotta, its occasional occurrence with 
 chromic iron in bits of serpentine, point to veins of that 
 mineral as the source of the metal. Although platina was 
 first discovered in Colombia in 1735, an( ^ ^ as smce been 
 found at several points in Brazil, it does not appear that 
 South America adds any important amount to the small 
 product of the world. Nearly the whole supply is derived 
 from placers on the east slope of the Urals in Russia, the 
 product of 1881 amounting to 6,798 pounds avoirdupois. 
 Besides this, Borneo is said to furnish about five hundred 
 
PLATINUM AND OTHER METALS. 285 
 
 pounds a year, and in 1882 the United States yielded 
 about thirteen and three fourths pounds avoirdupois. The 
 entire product of the world does not probably exceed 
 four net tons per year. Discoveries of small quantities of 
 platinum have repeatedly been announced from various 
 localities of the United States, especially in the gold 
 placers of California, and recently in the Wood River 
 region of Idaho ; but nothing of economic importance 
 has yet come to light, although the demand for the metal 
 to be used in the arts constantly exceeds the meager sup- 
 ply. It is quite possible that a careful examination of the 
 placer deposits of California might reveal a much greater 
 abundance of this metal than has been suspected hitherto. 
 Indeed, operations directed to securing gold from aurifer- 
 ous sands, by washing and amalgamation, would be very 
 little likely to detect platinum, which does not amalga- 
 mate. If the idea of Von Cotta and also of Prof. W. P. 
 Blake is well founded, that the mother rock of platinum is 
 serpentine, the most promising localities in which to search 
 in California will be those alluvial deposits which have 
 been formed from the cttbris of the serpentinous rocks of 
 the Coast Range. 
 
 The uses of platinum are based on its infusibility, its 
 resistance to most chemical agents, and its ductility. It 
 is used in chemical manufactories for the large stills in 
 which the ultimate concentration of sulphuric acid is 
 effected ; in numerous forms of chemical apparatus, as 
 crucibles and evaporating dishes, and as foil, wire, and 
 the tips of forceps to support objects in blow-pipe opera- 
 tions ; as one of the elements in the most powerful form of 
 galvanic battery ; in fine wire for incandescent lighting by 
 electricity, and for forming the cutting edge of a number 
 of surgical instruments the wire, when in use, being 
 heated to whiteness by a galvanic current, and searing as 
 it cuts so as to prevent the effusion of blood. Platinum is 
 used somewhat for medals and ornaments, for dentists' 
 
286 APPLIED GEOLOGY. 
 
 supplies, and in porcelain-painting, to give a steel-like 
 color to objects, and it was once used in Russia for coin- 
 age. Its uses would doubtless be much extended did the 
 supply of the metal permit. 
 
 Nickel and Cobalt. Nickel, which, from its wider 
 applications and its valuable properties, has within a 
 comparatively recent period come to be a metal of in- 
 creasing economic interest, is derived from ore compounds 
 with sulphur, arsenic, and silica, in which it is very com- 
 monly associated with cobalt, forming a considerable group 
 of minerals, of which the most common are millerite, a yel- 
 low sulphide in needle-like crystals or wool-like bunches ; 
 siegenite, a steel-gray sulphide of nickel and cobalt ; nicco- 
 lite, or copper nickel, a copper-colored arsenide ; and sili- 
 cates of an apple-green color, which have recently been 
 found in so considerable quantities and of such excep- 
 tional purity on the island of New Caledonia as seriously 
 to affect the price of the metal. The ore from which the 
 largest supplies have always been obtained is magnetic 
 iron pyrites, containing nickel, with which some of the 
 other nickel compounds are often associated. Although 
 ores of nickel occur at numerous localities in the United 
 States and Canada, mostly in ancient crystalline rock, and 
 often associated with serpentine, as on the north shore of 
 Lakes Superior and Huron, at Oxford in Quebec, and 
 Chatham, Conn., its extraction has been attended with 
 success only at the Lancaster Gap mines in Pennsylvania, 
 which have yielded in some years fully one fifth the nickel 
 of the world from arsenical pyrites and millerite aver- 
 aging not more than two per cent of the metal ; and at 
 Mine La Motte, in southeastern Missouri, where its extrac- 
 tion was subsidiary to the production of lead. Besides 
 these localities, deposits said to be of great promise occur 
 in Churchill County, Nev., and in Douglas County, Ore., in 
 which last region the ores are green silicates, resembling 
 in grade and purity those of New Caledonia. Near Schnee- 
 
PLATINUM AND OTHER METALS. 287 
 
 berg, in Saxony, are mines which have been wrought for 
 more than two centuries, yielding nickel, cobalt, bis- 
 muth, and arsenic, and which still furnish most of the im- 
 portant production of Germany. The silicate ores of 
 New Caledonia, which yield a nearly pure metal more 
 easily than any others known, are mostly shipped to 
 France, of which the island is a penal colony. Although 
 the ores of nickel occur usually in veins, in Mine La 
 Motte, mentioned above, they are found in a thin seam 
 of slate associated with the lead-bearing Lower Siluri- 
 an limestones of that region, or coating the seams of 
 galena. 
 
 The entire amount of nickel produced in 1877 was 
 estimated at 550 metric tons. No complete statistics of 
 nickel production are attainable ; but that of the United 
 States in 1882 was 125 metric tons, and that of Germany 
 for the same year was 121 metric tons, France yielding 30 
 metric tons. The chief uses of nickel are for the alloy 
 called German silver, for minor coinage, and for electro- 
 plating, for each of which uses the demand is very con- 
 siderable. German silver, which is an alloy of copper and 
 zinc with one third or less of nickel, is largely used for 
 fabricating many domestic implements and wares, which 
 are then electro-plated with silver. An alloy of 25 per 
 cent of nickel with 75 per cent of copper is used in the 
 United States coinage for three and five cent pieces, and 
 one containing 12 per cent of nickel for pieces of one 
 cent. Nickel alloys are used also in Germany and Bel- 
 gium for minor coinage. For the electro-plating of many 
 instruments, articles of domestic use, portions of stoves 
 and machinery, nickel is peculiarly adapted by reason of 
 its hardness, its difficulty of fusion, its resistance to rust, 
 and its susceptibility to a high polish ; and its use for 
 this purpose is very large and rapidly increasing. By a 
 recently devised process, it is possible to make nickel- 
 coated iron-plate, which, for the manufacture of cooking 
 
288 APPLIED GEOLOGY. 
 
 utensils that are to be subjected to heat, has several strik- 
 ing advantages over tin-plate. 
 
 Of cobalt, whose ores occur very commonly associated 
 with those of nickel, it is sufficient to say that it is pro- 
 duced in small amounts in the United States at the two 
 nickel-producing localities ; that it has at present no use 
 as a metal ; and that it is employed to give a blue color 
 to glass, porcelain, and earthenware, in the form of the 
 black oxide, and of smalt, which is a silicated oxide made 
 by fusing cobalt oxide with glass, or with quartz sand 
 and potash. The production of cobalt oxide at the works 
 of Lancaster Gap mine in 1882 was 11,653 pounds. 
 
 Besides the metals already described, there are several 
 others which are of considerable economic interest, 
 whether from the valuable properties that they impart to 
 certain alloys, like antimony and bismuth ; or from their 
 adaptation to certain special uses, like magnesium and alu- 
 minium, which last metal awaits only cheaper processes 
 of extraction to be largely used ; or from the large use of 
 some of their compounds in the arts, like manganese, 
 chromium, and arsenic. 
 
 Antimony has already been mentioned as a common 
 mineralizing agent in ores of silver ; but the usual source 
 of the metal is the sulphide stibnite, a soft, lead-gray, and 
 easily fusible mineral, occurring in rhombic prisms of easy 
 cleavage, or in radiating needles, as also massive ; and 
 readily distinguished by these characters as well as by be- 
 ing dissipated into a white vapor with an odor of sulphur 
 before the blow-pipe on charcoal. It occurs most com- 
 monly in veins in crystalline rocks, and the largest depos- 
 its yet found in the United States are those near Battle 
 Mountain in the Humboldt region of Nevada, and in 
 Kern County, Cal. These deposits are said to be of 
 great importance, and have been worked to some extent, 
 though difficulties arising from distance from markets 
 and from easy transportation have not hitherto made 
 
PLATINUM AND OTHER METALS. 289 
 
 their exploitation profitable. Besides these, promising de- 
 posits are reported to exist in Sevier County, Ark. Valu- 
 able foreign sources of supply occur in Germany, Hun- 
 gary, France, Spain, Borneo, and in New South Wales. 
 From its ready fusibility, the ore is easily separated from 
 its gangue by heat. It is used in alloys, as type and stereo- 
 type metal, and in britannia ; and some of its compounds 
 are used in medicine, in orange and yellow pigments, and 
 in pyrotechny for Bengal fire. 
 
 Bismuth occurs native, associated often with ores of 
 cobalt and silver in veins inclosed in crystalline rocks, as 
 also in the form of a sulphide called bismuthinite, and as an 
 impure oxide called bismuth ochre. The chief supplies are 
 derived from Schneeberg, Saxony, the German product of 
 1 88 1 being reported as fifty-six metric tons; from Bolivia, 
 the value of whose product for the same year is reported 
 at $61,189; and from South Australia. Deposits of some 
 importance are said also to exist in Utah, in Boulder and 
 La Plata Counties, Col., and near Golden, in the same 
 State. Its uses are somewhat limited, being chiefly in 
 compounding fusible alloys, soft solder, and britannia; 
 in the preparation of pearl-powder, and of mordants for 
 calico-printing, and in coloring glass and porcelain. 
 
 Magnesium is very widely diffused as a constituent 
 of several common rock-forming minerals ; but the sources 
 whence the metal is obtained are the mineral carnallite, a 
 double chloride of magnesium and potassium occurring 
 associated with the salt deposits of Stassfurt in Germany, 
 and magnesite, a magnesian carbonate which is associated 
 with serpentine, and which to obtain the metal is con- 
 verted to a double chloride of magnesium and sodium by 
 dissolving in hydrochloric acid and adding a solution of 
 common salt. The metal is obtained from either of these 
 double chlorides by fusing with metallic sodium and fluor- 
 spar. It is rolled into thin ribbons or made into wire, and 
 in this form burned in a proper lamp, giving a light of ex- 
 
290 APPLIED GEOLOGY. 
 
 ceeding brilliancy for use in signaling. It is also used in 
 filings for pyrotechny. 
 
 Aluminium is a recent addition to the list of metals, 
 but its remarkable characters promise to render it highly 
 useful in the arts as soon as processes shall be devised by 
 which it may be liberated from its combinations within 
 reasonable limits of cost. It is a white metal of singular 
 lightness, its specific gravity being only about one third 
 that of iron ; it is malleable and very tenacious, and unal- 
 terable by atmospheric agencies ; and its alloy with copper, 
 called aluminium bronze, is of a golden yellow color, very 
 hard and malleable, and of a tensile strength which is said 
 to be greater than that of Bessemer steel. The compounds 
 of this metal with silica are some of the most widely dis- 
 tributed constituents of rocks, and kaolin, the essential 
 constituent of clays, is a hydrous silicate of alumina ; but 
 it has not yet been found practicable to obtain the metal 
 from its silicated compounds. The sources from which it 
 is obtained are bauxite, a hydrous oxide of aluminium 
 and iron containing but a trifling amount of silica, found 
 abundantly in France, and cryolite, a double fluoride of 
 aluminium and sodium, which is brought from Greenland. 
 Bauxite is first converted into a chloride of sodium and 
 aluminium, and then the latter compound is fused with 
 metallic sodium and a flux, thus liberating the metal ; 
 while cryolite can be fused direct with sodium. A process 
 is said recently to have been devised in Philadelphia by 
 which the reduction of the metal will be very greatly 
 cheapened by dispensing with the use of sodium, and re- 
 ducing the cost of preparing the aluminium compound ; 
 and, if it proves successful, this interesting metal will soon 
 be largely used in the fabrication of engineering and other 
 instruments, and for various other purposes where strength 
 combined with lightness is desirable. The French pro- 
 duction of aluminium in 1882 was 2,349 kilogrammes.* 
 * While this work is going through the press, it is announced that 
 
PLATINUM AND OTHER METALS. 291 
 
 Chromium. This metal is of little economic impor- 
 tance as a metal, having merely a limited application in the 
 manufacture of what is called chrome-steel ; but its brill- 
 iant colored compounds are largely used in the arts as pig- 
 ments and in calico-printing ; and they have also a limited 
 use in galvanic batteries. The source whence it is derived 
 is the mineral chromite, or chromic iron, a hard, black, 
 feebly magnetic compound of chromium and iron oxides, 
 which contains when pure about 68 per cent of chromic 
 sesquioxide, but rarely has more than 60 per cent. This 
 mineral occurs usually in beds or veins of serpentine in 
 crystalline rocks, as along the eastern base of the Appa- 
 lachians, and in the Coast Range of California, at favor- 
 able localities in which it is found in great abundance. 
 It was formerly derived wholly from Wood's Mine, Lan- 
 caster County, Pa., and the adjacent parts of Maryland 
 not far from Baltimore. Lancaster County is said to 
 have yielded ninety-five thousand tons of the ore, aver- 
 aging 48 per cent of the oxide. The supplies from these 
 localities are said to be now mostly superseded by the 
 richer ores of California, which are drawn most largely 
 from mines in San Luis Obispo County, and from Placer 
 County near Auburn, rich deposits being also known to 
 exist in several other counties. By appropriate treatment, 
 this ore is converted into bichromate of potash, the basis 
 of all chrome pigments. 
 
 Manganese. The direct uses of this metal are in 
 alloys with iron, called spiegeleisen, or ferro-manganese, 
 according to the percentage of manganese which they 
 contain, and which are largely used in the manufacture of 
 steel ; and in an alloy with copper called manganese 
 bronze, which from its hardness is well fitted for bearings 
 in heavy machinery. The iron alloys are obtained by 
 smelting manganiferous ores of iron, procured mostly 
 
 Messrs. E. H. and A. H.Cowles, of Cleveland, O., have perfected a process 
 by which the manufacture of aluminium bronze will be much cheapened. 
 
2 9 2 APPLIED GEOLOGY. 
 
 from Germany and southern Spain, the American ores be- 
 ing too commonly contaminated with phosphorus to be 
 used for this purpose. Several native compounds occur in 
 considerable abundance, chiefly oxides, which are black, 
 a rose-red carbonate, and a lighter red silicate; but that 
 which is most used in the arts is pyrolusite, a tolerably soft 
 black dioxide of manganese (MnO 2 ), whose impure mix- 
 ture with iron oxide, called wad, is also employed for some 
 of its uses. These oxides are found in the Atlantic 
 States from Maryland to Georgia, the purest being ob- 
 tained from Bartow County, Ga., and the Virginia de- 
 posits being next in value, Augusta County yielding fully 
 one half of the product of Virginia, from a single mine. 
 Promising deposits occur also on the Pacific coast, the one 
 best known being on an island in the Bay of San Fran- 
 cisco. Deposits of this mineral should contain at least 60 
 per cent of the oxide to justify their exploitation. Pyro- 
 lusite is largely employed in the arts for the liberation of 
 chlorine and the manufacture of bleaching-powder, in the 
 preparation of varnish and " boiled oil," and in glass- 
 making to discharge the green tints which iron imparts. 
 It is also used in glazing and painting pottery, and in glass- 
 staining, and to some extent with potassium chlorate in 
 making oxygen. The permanganate of potash has like- 
 wise a large use as a disinfectant. 
 
 Arsenic. This metal, so widely known by reason of 
 the deadly nature of all its compounds, is but little used in 
 the metallic state. It enters into a few alloys, the chief of 
 which is with lead to give it greater hardness in the manu- 
 facture of shot. Its compounds are, however, considerably 
 used for various purposes. The yellow sulphide, called 
 orpiment, or king's yellow, the red sulphide realgar, and 
 the arsenite of copper, called Scheele's green, are used as 
 pigments, realgar being also used in pyrotechny and for 
 signaling purposes as an ingredient in "white Indian 
 fire " ; the oxide is used in glass-making and for the pres- 
 
PLATINUM AND OTHER METALS. 293 
 
 ervation of natural history specimens ; and some of the 
 compounds enter into pharmaceutical preparations. Ar- 
 senic occurs in the crystalline rocks, forming important 
 ores with silver, nickel, and cobalt ; and its compound 
 with sulphur and iron called mispickel, or arsenical iron 
 pyrites, a hard, silver-white, and brittle mineral which 
 yields an odor like garlic when heated, is found abun- 
 dantly in many places associated with ores of silver, cop- 
 per, and other metals, as at Freiberg, and with ores of tin, 
 as in Cornwall. From this last mineral chiefly, and from 
 the ores of nickel and cobalt, it is obtained for commer- 
 cial purposes in the form of the well-known white arsenic, 
 by roasting the ores and condensing the arsenic in cham- 
 bers and flues. It is made mostly in Germany, and in 
 Cornwall and Devon. The ores from which it is obtained 
 exist also in sufficient abundance at various points in re- 
 gions of crystalline rocks in the United States. 
 
 Iridium, which is found sparingly associated with plat- 
 inum, has a limited but important use, based on its ex- 
 treme hardness, in wire draw-plates and knife-edges for 
 balances, in the nibs of gold and stylographic pens, and in 
 the contact-points of telegraph instruments. It is said, 
 also, to be used somewhat in porcelain-painting to give a 
 black color. Its chief source is iridosmine^ an alloy of 
 iridium with osmium and one or more other rare metals 
 of the same class, which is found not only in the Urals, 
 but also in the gold placers of California and Oregon, 
 where its weight, which equals that of gold, renders it easy 
 to be recovered, so that this region now yields important 
 supplies. The value of pure iridium is nearly that of gold, 
 the iridosmine selling at from twenty-five to sixty dollars 
 per pound troy, according to the percentage of the metal 
 which it contains. 
 
 Besides these metals, a few others, whose ores are of 
 somewhat unfrequent occurrence, but which are utilized 
 in the arts for special purposes, deserve brief mention here. 
 
294 APPLIED GEOLOGY. 
 
 Molybdenum, in the form of molybdenite, a mineral which 
 resembles graphite, but is easily distinguished from it by 
 yielding sulphur by heat, has been found at several locali- 
 ties in the Eastern States, and is said to occur in some 
 abundance in Gunnison County, Col., and in Utah. It is 
 used to give a blue color to pottery. Uranium, also used 
 in porcelain-painting for yellow and black colors, has been 
 found as the mineral pitchblende at the Wood mine near 
 Central City, Col., and also near Denver. Its chief sup- 
 plies are, however, derived from Bohemia. Tungsten is 
 obtained from wolfram, a compound of tungsten, iron, and 
 manganese, found as a somewhat frequent associate of the 
 tin-ores of Cornwall and of Saxony. It has been found 
 in small quantities in Maine, Connecticut, North Carolina, 
 Missouri, and Nevada, and is quite likely to be met with 
 in the tin region of the Black Hills. Tungsten has in re- 
 cent years come into use for making a special grade of 
 steel, which is of extreme hardness without being very 
 brittle, and which is therefore adapted to the manufacture 
 of tools for turning and planing iron. Some of its soluble 
 compounds are used to a small extent in calico-printing, 
 and other compounds are of excellent promise as valuable 
 pigments. 
 
 In this necessarily condensed treatment of the metals, 
 their mineralogical and geological mode of occurrence, the 
 regions where they are most largely obtained, and their 
 leading uses, no attempt has been made to do more than 
 to give the student such information as may serve as a 
 guide to his active efforts or to his more extended re- 
 searches in special directions. It is hoped that it may 
 also prove helpful to the practical man, not only by indi- 
 cating the most promising sources of materials for his 
 technical pursuits, but also by pointing him to regions 
 whence he may look for the most effective competition in 
 his business. To these ends the leading foreign deposits 
 have been noted, as well as those which are found in our 
 
PLATINUM AND OTHER METALS. 295 
 
 own country; and the extent and importance of both 
 sources of supply and competition have been suggested by 
 the tables of production, which have been compiled from 
 the latest statistics and estimates that have come to hand 
 in Government reports and technical journals. A number 
 of rare metals have been entirely omitted, while the metals 
 of the alkalies and alkaline earths, which, with a single 
 exception, have no technical use as metals, will be treated 
 in their appropriate place under their most important 
 native compounds. 
 
CHAPTER XVIII. 
 
 SUBSTANCES ADAPTED TO CHEMICAL MANUFACTURES OR 
 
 USE. 
 
 THE earth's crust affords a considerable number of 
 substances whose applications are chiefly of a chemical 
 character, or which form the basis of extensive chemical 
 manufactures before they attain the varied forms in which 
 they may most completely supply human wants. Some 
 few of the substances which may most conveniently be dis- 
 cussed under this head, besides their chemical applications, 
 have also direct uses in their native condition, like salt 
 and sulphur ; some, like the fluxes, are used either to re- 
 move unwelcome ingredients in the form of a liquid slag 
 in metallurgical operations, or to give a fine exterior finish 
 to pottery ; while some, like pyrites and niter, may furnish 
 the initiative to series of chemical operations resulting in 
 a number of useful products. It may also with propriety 
 be stated here, once for all, that some mineral substances 
 are of varied utility, and might with equal fitness be con- 
 sidered under any one of two or more different classes of 
 applications. Such substances will receive whatever gen- 
 eral discussion may seem desirable in the first class in 
 which they may occur ; and any subsequent mention of 
 them will imply an acquaintance with their previous treat- 
 ment. 
 
 Pyrites. Pyrites, so called from the Greek word for 
 fire y because its hardness is such as to enable it to strike 
 
SUBSTANCES FOR CHEMICAL PURPOSES. 297 
 
 fire with steel, is a sulphide of iron, FeS 2 , containing, when 
 pure, 53.3 per cent of sulphur. It is found frequently in 
 cubic crystals of a light yellow color and brilliant metallic 
 luster, gives a black streak on porcelain, is very hard 
 though brittle, and emits when heated the odor of sulphur, 
 yielding finally a black magnetic globule. Although a 
 compound of iron, it was not described among the ores of 
 iron, because it is not directly used as a source of that 
 metal, though the residues from its treatment for chemical 
 purposes are in recent years coming into use for making 
 certain grades of iron and steel. Pyrites, in small quanti- 
 ties, is very widely disseminated in rocks of all ages, and, 
 by the readiness with which it oxidizes when exposed to 
 the weather, it constitutes one of the most active agents 
 in their decay ; but, to be of any economic importance, it 
 needs to occur in deposits of great dimensions, and rea- 
 sonably free from admixture with other minerals save 
 chalcopyrite, with which it is usually associated. 
 
 The workable deposits of pyrites occur in great beds, 
 swelling out often to dimensions so vast as to be consid- 
 ered mass deposits, and intercalated mostly in crystalline 
 schists, which in this country at least seem to be of Ar- 
 chaean age. Deposits of this kind are found along the 
 eastern slope of the Appalachians from eastern Alabama 
 to New Hampshire and Maine. Along this range mines 
 have been opened at Capelton in the Eastern Townships 
 of Quebec, at Milan in New Hampshire, Stafford in Ver- 
 mont, Rowe in Massachusetts, and at Tolersville in Lou- 
 isa County, Va. From the Canadian locality about forty 
 thousand tons are sent yearly to the United States. The 
 deposits at Milan, which have been proved for more than 
 nine hundred feet in length, are from eight to more than 
 forty feet thick ; and those of Tolersville, according to a 
 recent account, are capable of yielding easily one thousand 
 tons daily. The pyrites from all these localities contains 
 valuable amounts of copper, and all are claimed to be re- 
 
298 APPLIED GEOLOGY. 
 
 markably free from arsenic, a deleterious ingredient which 
 is rarely entirely absent from pyrites deposits, and whose 
 presence in any considerable proportions seriously im- 
 pairs the value of the mineral for some of its foremost uses. 
 Besides these deposits, which are favorably situated with 
 regard to transportation, others of the greatest promise 
 are known to exist within the Appalachian region which 
 are still untouched from lack of a market. The State geolo- 
 gist of Alabama reports extensive deposits of cupriferous 
 pyrites in Clay County ; and, according to C. R. Boyd, in 
 the western part of Carroll County, Va., occurs a body of 
 pyrites in talcose schists, which has an average length of 
 ten miles with an average width of thirty-three feet, and 
 which contains an average of two and a half per cent of 
 copper and 45 per cent of sulphur. 
 
 Large as are our American deposits of pyrites, they 
 sink into comparative insignificance in comparison with 
 some of the enormous masses which are found in Sweden, 
 Spain, and Germany. The greatest of these are the de- 
 posits of Rio Tinto in southwestern Spain, extending west 
 into Portugal. Here are worked two vast beds or veins in 
 highly disturbed and metamorphosed schists, associated 
 with quartz porphyry, which are thought to be of Per- 
 mian age. The southern vein, which is from three hun- 
 dred to four hundred feet in width, is opened for sixteen 
 hundred feet of its length, and is known to be at least 
 twenty-five hundred feet in length, while the northern 
 vein is much more enormous, being fully six thousand 
 feet long, and swelling in places to a width of from thir- 
 teen hundred to sixteen hundred feet. The pyrites from 
 these immense deposits contains highly important amounts 
 of copper, a recent analysis of the export material showing 
 3.69 per cent of copper, with 47.76 per cent of sulphur, 
 but contaminated by nearly one per cent of arsenic. The 
 Spanish output of pyrites in 1881 was nearly a million and 
 a half tons, and it has greatly increased since that date ; 
 
SUBSTANCES FOR CHEMICAL PURPOSES. 299 
 
 and the large amount of copper directly and incidentally 
 derived from these deposits is a highly important factor in 
 determining the present low prices of that metal. 
 
 At Goslar, in the Harz Mountains, in a region of De- 
 vonian limestone and slate, occurs an enormous mass de- 
 posit of cupriferous pyrites, which, as described by Von 
 Cotta, has a known length of eighteen hundred feet, with 
 a width of three hundred and fifty feet, and sends a con- 
 siderable branch into the hanging wall, showing that it 
 can not be considered a bed, although in other respects its 
 position is conformable with the stratification of the in- 
 closing rocks. The pyrites of this deposit contains 
 arsenic and lead, with small amounts of several other 
 metals. The German output of pyrites in 1883 was 
 148,700 metric tons. 
 
 At Fahlun, in Sweden, a great irregular mass deposit 
 of copper-bearing pyrites, with numerous outliers, is met 
 with in schists and gneiss of Archaean age. Portions of 
 this deposit contain also lead and zinc. Also at Agordo, 
 in the Tyrolese Alps, occurs a considerable mass deposit 
 of pyrites, varying in width from twelve to two hundred 
 and fifty feet, in a country rock of talcose and clay slate, 
 with the bedding of which it conforms. 
 
 Uses of Pyrites. The foremost use of pyrites is as 
 a cheap source of sulphur in the manufacture of sulphuric 
 acid, and it has within the past twenty-five years rapidly 
 replaced native sulphur in this very important industry. 
 For this purpose, the pyrites is burned in properly con- 
 structed combustion-chambers, the sulphur being elimi- 
 nated in the form of sulphurous acid ; and it is said that 
 some of the arrangements for this purpose are so effective 
 as to leave less than one per cent of sulphur in the iron of 
 the residue. After burning, the copper in the pyrites is 
 extracted by a leaching process, and the residual some- 
 what sulphurous iron oxide can then be used as a source 
 of certain grades of iron, and for some other purposes. 
 
3 oo APPLIED GEOLOGY. 
 
 The characters which best adapt pyrites for the use of 
 acid manufacturers are the following: (i) A high per- 
 centage of sulphur. As has already been stated, absolute- 
 ly pure pyrites contains about 53 per cent of sulphur ; 
 but most of the mineral in commercial quantities holds 
 varying amounts of quartz and other substances, which 
 diminish the percentage of sulphur by so much. The 
 Spanish pyrites contains, according to the analysis al- 
 luded to above, about 2^ per cent of silica and lime, and 
 a little less than 48 per cent of sulphur. It has recently 
 been stated that pyrites capable of yielding 45 per cent of 
 sulphur is worth about seven dollars per ton for acid- 
 making. (2) Freedom from arsenic, antimony, and lead, 
 the first of which substances unfits the acid containing it 
 for many of its uses, while the second and third promote 
 the fusion of the pyrites while burning, and so hinder the 
 complete elimination of its sulphur. Arsenic, while es- 
 pecially common in pyrites, is also especially objection- 
 able, and, in the foregoing account of the great deposits, 
 its presence or absence where known has been mentioned 
 for this reason. (3) Readiness to part with the contained 
 sulphur, in which different lots of pyrites show consider- 
 able differences ; partly in consequence of the physical 
 condition of the mineral, that which is more granular and 
 porous presenting a larger surface for the combustion of 
 the sulphur ; partly from differences of fusibility, arising 
 from the presence or absence of minerals that are liable 
 to act as fluxes at the temperature which is employed ; 
 partly, also, from the presence of sulphur compounds 
 which retain their sulphur with considerable tenacity, like 
 copper, the presence of which, while adding to the selling 
 value of the pyrites in one direction, diminishes, to a 
 certain extent, its value to the acid-maker as a source of 
 sulphur, since it prevents its complete elimination. (4) It 
 is desirable that pyrites for acid-making should not have 
 a tendency to crumble readily in mining and handling, 
 
SUBSTANCES FOR CHEMICAL PURPOSES. 301 
 
 since this produces a great amount of " fines," rendering 
 necessary special arrangements for its burning. (5) Py- 
 rites sometimes contains water mechanically inclosed, ren- 
 dering it liable to decrepitate violently while burning 
 a troublesome character, which detracts from its value. 
 (6) As was suggested above, the presence of a consider- 
 able proportion of copper adds much to the value of py- 
 rites, since it becomes a source of copper as well as of 
 sulphur. The copper is paid for, on analysis, in addition 
 to the obtainable sulphur ; or else, in some cases, the resi- 
 dues, after burning, are returned to the seller. It can 
 hardly be expected that all these desirable characters will 
 concur in every lot of pyrites that is worth extracting. 
 That will be the best which has the greatest number of 
 excellences, and those most essential. With a careful ex- 
 amination of fair average samples of pyrites as regards 
 these requisites, the probable value of any great body of 
 pyrites well located for cheap transportation to markets 
 can be closely approximated. The extent and impor- 
 tance of the chemical industries to which pyrites furnishes 
 the initiative can not be better stated than by quoting 
 from the "Geology of Canada," 1863, p. 746 : "In order 
 to give some idea of the great importance of iron pyrites 
 and of its products in a manufacturing point of view, it 
 must be said that sulphuric acid, which is now for the 
 most part manufactured from pyrites, is the agent used 
 for decomposing common salt for the manufacture of 
 soda in its various forms of soda-ash, carbonate of soda, 
 and caustic soda. From this decomposition is also ob- 
 tained hydrochloric acid ; this is used in the manufacture 
 of chlorine, and of bleaching-powder or chloride of lime, 
 which are indispensable in the bleaching of cotton, linen, 
 and of the materials for paper. Besides this, the manu- 
 factures of soap and glass, and many other chemical prod- 
 ucts, are dependent upon the soda thus obtained. The 
 
 sulphuric acid is also used for the manufacture of nitric 
 14 
 
302 APPLIED GEOLOGY. 
 
 acid, of superphosphate of lime, of alum, and many other 
 products, all of which are generally manufactured in the 
 vicinity of sulphuric acid and alkali works." 
 
 Besides its use in the manufacture of sulphuric acid, 
 pyrites is largely utilized in making iron sulphate or cop- 
 peras, to be employed in dyeing fabrics black and as a 
 disinfectant. Incidental to this process, sulphur is some- 
 times extracted for the market from the pyrites, by heat- 
 ing the mineral in retorts to drive off about one third of 
 the sulphur, which is condensed. The pyrites, partially 
 roasted in this way or merely in heaps, or quite as fre- 
 quently without preliminary roasting, is piled on tight 
 floors under a shed-cover, moistened with water, and left 
 to the action of the atmosphere, by the agency of which it 
 is oxidized to iron sulphate ; this is then leached out with 
 water, and the solution, properly concentrated by boiling, 
 is left to deposit the copperas in crystals. 
 
 Sulphur. As will already have been observed in the 
 preceding chapters, the compounds of sulphur with the 
 metals constitute a highly important and widely diffused 
 class of metallic ores called sulphides or sulphurets, and 
 from some of these a part of the sulphur can be obtained 
 by a process of distillation, as in the case of iron pyrites. 
 As a commercial article, however, it is more largely ob- 
 tained from deposits in gypsum, bituminous marl, and 
 limestone, or from volcanic regions, where it is found un- 
 combined, filling fissures and cavities, and mingled usually 
 with varying amounts of earthy substances, from which it 
 is easily separated by melting in large kettles ; the sulphur 
 melts at a temperature a little above that of boiling water, 
 the impurities settle to the bottom or are skimmed out, 
 and the sulphur, in a tolerably pure condition, is then 
 ladled out into molds. A simpler mode of separation is by 
 setting fire to the sulphurous earth in heaps or kilns, when 
 the heat generated by the combustion of a portion of the 
 sulphur melts the rest, which flows off and is caught ; or it 
 
SUBSTANCES FOR CHEMICAL PURPOSES. 303 
 
 can be obtained much purer by distilling off the sulphur 
 from the earthy mass in iron or earthenware retorts. The 
 source of the sulphur in these deposits is doubtless from 
 the decomposition of earthy or metallic sulphides and 
 sulphates, in some cases possibly by heat, but in most by 
 the agency of water and oxygen or organic matter, giving 
 rise to sulphur springs which deposit their sulphur by 
 the action of atmospheric oxygen. The largest supplies 
 of sulphur, for both Europe and the United States, are 
 derived from Sicily, where the deposits are found in foli- 
 ated gypsum, bituminous marls, and limestones of Tertiary 
 age. These deposits contain from 20 to 40 per cent of 
 sulphur, of which they yield somewhat more than half to 
 the usual processes of extraction. The United States 
 imported in 1880 more than 100,000 tons of sulphur, nearly 
 all from Sicily, and it is said that Europe derives nearly 
 nine tenths of its sulphur from the same region. Impor- 
 tant deposits also occur in Italy and Poland. Iceland 
 contains rich but undeveloped deposits of sulphur, and it 
 is found in most volcanic regions. In the United States, 
 sulphur has hitherto been obtained from native deposits 
 only in California and Nevada, though deposits of great 
 promise are known to exist at Cove Creek in western 
 Utah, in New Mexico, in the Yellowstone region, and 
 near Evanston, in Wyoming. The deposits of Cove 
 Creek, and those of Rabbit Hole in northwestern Nevada, 
 are said to be in regions of comparatively recent volcanic 
 activity, occupying in the first case the sites of not yet 
 extinct solfataras, and either filling fissures in the rocks 
 or impregnating and cementing tufas. 
 
 Sulphur has several important and extensive uses, fore- 
 most among which is its employment in the manufacture 
 of sulphuric acid. Until within a very few years, all the 
 acid made in this country was manufactured from sulphur, 
 chiefly Sicilian ; and although it is now being slowly su- 
 perseded for this purpose by pyrites, on account of the 
 
304 APPLIED GEOLOGY. 
 
 greater cheapness of the latter substance, still, for many 
 uses where perfect freedom from arsenic is required, acid 
 made from sulphur is sure to be preferred. Some of our 
 Western sulphur deposits, however, are said not to be 
 wholly free from arsenic, a fact which indicates that such 
 deposits were derived from sublimation in which case 
 arsenic from its volatility would accompany sulphur, rather 
 than from elimination from the water of sulphur springs. 
 Other large uses of sulphur are in the making of gun- 
 powder, in the manufacture of matches, for which its ready 
 inflammability adapts it, in the vulcanizing of rubber and 
 gutta-percha, in bleaching straw and woolen goods, and 
 as a cementing material between iron and stone. It is 
 used in the manufacture of vermilion, an artificial sul- 
 phide of mercury ; of mosaic gold or bronze powder, a 
 bisulphide of tin, and of several other useful compounds ; 
 has some important pharmaceutical applications, and the 
 sulphurous-acid gas generated by its combustion is a very 
 valuable disinfectant. 
 
 Salt. This useful and indeed indispensable substance 
 occurs in nature in two states either (i) in solution, as 
 in the waters of the ocean, and of salt lakes and ponds, or 
 in those of salt springs and wells, the waters of which de- 
 rive their salt from subterraneous masses, or from perco- 
 lating through clays and marls in which salt is dissemi- 
 nated ; or (2) in irregular beds and masses of rock-salt, 
 which are sometimes of enormous dimensions, and from 
 which the salt is obtained by regular mining operations. 
 From whichever source derived, salt, which, as is generally 
 known, is a chloride of sodium, is never absolutely pure, 
 but holds variable amounts of sulphates of lime, magnesia, 
 and soda, chlorides of calcium and magnesium and some- 
 times of potassium, with usually a little iron carbonate, 
 and often, in the case of rock-salt, some finely disseminated 
 clay. The salt of this country has hitherto been derived 
 almost entirely from the evaporation of natural brines, 
 
SUBSTANCES FOR CHEMICAL PURPOSES. 305 
 
 like those of Syracuse, N. Y., and of the region around 
 Saginaw Bay, Mich., by solar or artificial heat ; or from 
 the solar evaporation of sea-water in salt-pits at favor- 
 able points, as in California ; while a very considerable 
 portion of the European supply has for ages been drawn 
 from beds of rock-salt, the famous mines of Wieliczka, 
 near Cracow, in Polish Austria, having, it is said, been 
 worked since the eleventh century. 
 
 A pure saturated brine contains at ordinary tempera- 
 tures about 25.7 per cent of salt, and the strength of 
 brines is usually tested by an instrument called a salome- 
 ter, an areometer graduated from o, the point to which it 
 sinks in pure water, to 100 for the point at which it stands 
 in a pure saturated brine. A degree of the salometer 
 answers, therefore, to about one fourth per cent of salt in a 
 pure solution ; while a degree of the ordinary hydrometer 
 of Beaume corresponds very nearly to i per cent of salt, 
 if the brine is pure. Sea-water contains 2.6 per cent of 
 salt, and nearly i per cent more of other saline ingredi- 
 ents ; the brines of Syracuse hold from 14 to about 18 per 
 cent of salt ; those of Michigan, from 15 to nearly 20 per 
 cent ; those of Goderich, Ontario, from 20 to 24 per cent ; 
 and the weaker brines of West Virginia and Ohio, about 
 10 per cent. 
 
 Beds or deposits of rock-salt occur associated with 
 beds of gypsum, marls, and clays, and sometimes, as at 
 Goderich, of porous dolomites. They have in all proba- 
 bility originated from the desiccation of salt lakes, or of 
 sea-borders cut off from the main body of water by bar- 
 riers which were occasionally overleaped by the outside 
 waters, thus adding new supplies to be concentrated by 
 evaporation. In the process of concentration such waters 
 would naturally first deposit their least soluble ingredient, 
 gypsum or anhydrite, which is always present in sea-water, 
 and afterward, with increasing concentration, their salt ; 
 while earthy substances, washed from the adjacent lands, 
 
3 o6 APPLIED GEOLOGY. 
 
 furnished the solid impurities and the materials for the 
 interstratified beds of marls and clays. Every fresh influx 
 of sea-water will give occasion for a new deposition of gyp- 
 sum to be interlaminated with the salt ; while the more 
 soluble sulphates and chlorides of magnesium and potash 
 become greater in amount in closed basins, like that of 
 the Dead Sea at present, and may ultimately, under fa- 
 vorable circumstances, on the final drying up of the area, 
 form deposits of carnallite, sylvite, kainite, etc., like those 
 of Stassfurt in Germany, and in the eastern Carpathians, 
 which will be mentioned in subsequent sections. Some of 
 the deposits of salt thus formed are of vast dimensions. 
 Probably the most amazing yet known is that at Speren- 
 berg, south of the city of Berlin, which, according to Roth 
 and Credner, has been explored by boring nearly four 
 thousand feet without penetrating to its base. That of 
 Wieliczka is said to be in places not less than fourteen 
 hundred metres thick. 
 
 Salt deposits are by no means limited to any special 
 members of the geological series. On the contrary, they 
 are found in rocks of various geological ages, from the 
 Upper Silurian to the present time. Yet, aside from the 
 deposits which are now accumulating in closed basins and 
 lagoons, there are recognized on both continents geological 
 horizons which are especially rich in salt. Thus, in North 
 America, a group of Upper Silurian rocks has been appro- 
 priately called the Salina, because of its salt-bearing char- 
 acter ; along it are ranged the great salt-works of Syracuse, 
 the two recently discovered salt-beds of Wyoming County, 
 thirty and seventy-five feet thick, from which a nearly 
 saturated brine is drawn, and the deposits around Go- 
 derich, on Lake Huron, consisting of six salt-beds of an 
 aggregate thickness of one hundred and twenty-six feet, 
 some of which are of unusual purity, besides salt-wells at 
 many other points, the brine of which is not strong enough 
 to be worked with profit under the existing conditions of 
 
SUBSTANCES FOR CHEMICAL PURPOSES. 307 
 
 production. A second profitable salt horizon is that of 
 the Lower Carboniferous up to the base of the coal-meas- 
 ures, which yields the brines of the Saginaw region in 
 Michigan, and those of Ohio and West Virginia near the 
 Ohio River. The great mass of extraordinarily pure salt 
 at Petit Anse in Vermilion Bay, southern Louisiana, which 
 has been explored to the depth of one hundred and sixty- 
 five feet without reaching the bottom, is said by Hilgard 
 to be of probable Cretaceous age. In Europe the Triassic 
 is often called the Saliferous system, on account of the rich 
 deposits of rock-salt that occur in it at several different 
 horizons ; in England, at Northwich in Cheshire, and in 
 Germany at Vic and Dieuze in Lorraine, on the upper 
 Neckar in Wiirtemberg, and at a number of other points. 
 Yet the rocks of the Permian period might with nearly 
 equal propriety be counted a saliferous system, since in 
 them occur the enormous deposits of Stassfurt and Speren- 
 berg, which have already been mentioned, as well as those 
 of the government of Perm in eastern Russia, and those of 
 the Kirghiz Steppe near the Caspian Sea ; while in the 
 Tertiary are found the celebrated deposits of Wieliczka, 
 and those occurring along both sides of the Carpathians 
 to Wallachia and Transylvania ; as also, quite probably, 
 those of Cardona, in the Pyrenees of northeast Spain, 
 which are thought by some to belong to the Cretaceous 
 period. 
 
 Besides the chief salt-producing centers in the United 
 States that have been mentioned above, the great Western 
 region, extending from the Rocky Mountains to the Pacific 
 coast, is abundantly supplied with salt at many points, 
 from salt lakes, pools, and marshes, and surface incrusta- 
 tions overlaying beds of salt of unknown depth, and which 
 occupy apparently the sites of ancient salt lakes long since 
 dried up. Nevada, in particular, abounds in salt deposits 
 of these various kinds. Near Columbus, Esmeralda Coun- 
 ty, a salt-field of nearly fifty square miles is found ; on the 
 
3 o8 APPLIED GEOLOGY. 
 
 Rio Virgen, in Lincoln County, are said to occur enormous 
 masses of rock-salt with an outcrop of not less than twenty- 
 five miles ; and several other counties have supplies almost 
 equally abundant, while every State and Territory in this 
 region may draw sufficient supplies of this needful sub- 
 stance from sources existing within its own limits. 
 
 In 1882 the United States produced 801,547 gross tons 
 of salt, of which 71 per cent was furnished by the Saginaw 
 region and Syracuse; about 18 per cent more by West 
 Virginia and Ohio, in nearly equal proportions, while most 
 of the residue was derived from California, Pennsylvania, 
 Utah, Virginia, Louisiana, and Nevada. In the same year 
 the reported product of Great Britain was 2,135,499 gross 
 tons, and that of Germany 322,422 metric tons of rock-salt, 
 her production from salt-works in 1881 having also been 
 456,958 tons. The product of Russia in 1874 was 769,000 
 tons, 54,630 tons of which was rock-salt ; and that of Aus- 
 tria, for the same year, was 249,521 tons, of which 81,081 
 tons was rock-salt. 
 
 The largest use to which salt is applied is doubtless for 
 household purposes, in the seasoning of food and the pres- 
 ervation of provisions. This use among civilized nations 
 is everywhere large, varying with the habits of the people 
 from about ten to more than thirty pounds per capita. It 
 is estimated that the people of the United States consume 
 in this way about thirty-two pounds per person ; and, if this 
 estimate is correct, our production, large as it is, is mostly 
 consumed for this single use. Another large use of salt 
 is in chemical manufactures, as a source of soda by the 
 Leblanc process, or by the recently devised ammonia pro- 
 cess ; as a source of hydrochloric acid incidental to the 
 Leblanc process ; and, directly or indirectly, for the lib- 
 eration of chlorine in the manufacture of chloride of lime, 
 to be used for bleaching purposes and as a disinfectant. 
 Large amounts are used, also, in the metallurgy of silver, 
 as a chloridizing agent preparatory to amalgamation ; in 
 
SUBSTANCES FOR CHEMICAL PURPOSES. 
 
 309 
 
 the manufacture of pottery as a glaze ; and as a fertilizer 
 in agriculture. 
 
 For additional information on the occurrence of salt, and the mode 
 of extraction from brines, the student is referred to " Natural History 
 of New York," Beck's " Mineralogy " ; " Geological Report of Michi- 
 gan," Vol. Ill ; T. Sterry Hunt's articles on salt in the " Geological 
 Survey Reports of Canada " for 1866, 1866-1869, and i876-'77 ; " Min- 
 eral Resources of the United States," 1883 ; Credner, " Geologic," pp. 
 45 and 291 ; Hoffman, "Chemische Industrie," and Ure's "Diction- 
 ary of Arts," etc. 
 
 Alkalies from Geological Sources. The ultimate 
 source of the alkalies potash and soda, save such portions as 
 may always have been present in oceanic waters, is doubt- 
 less to be found in the decomposition of the rock-forming 
 minerals which contain them, chiefly feldspars and micas. 
 From these they have passed partly into soils, from which 
 they are withdrawn by plants in the processes of growth ; 
 and a very important portion of the potash of commerce 
 is still obtained from leaching the ashes of plants and 
 evaporating the solution. Still larger portions of these 
 soluble substances have been carried into great bodies of 
 water, like the ocean and inland seas and lakes ; and, on 
 the final desiccation of isolated bodies of such waters, have 
 formed deposits of salts of potash, soda, and magnesia 
 overlying salt-beds, as at Stassfurt, Kaluscz in eastern 
 Hungary, and Maman in Persia ; or, in arid regions, like 
 those of northern Chili and adjacent Peru, and portions of 
 our great Western basin region, have formed extensive 
 alkali flats impregnated with carbonates, sulphates, and 
 sometimes nitrates of soda, occupying the sites of former 
 inland seas, portions of which in some cases still remain, 
 forming lakelets of intensely alkaline water. 
 
 Of the potash salts, the nitrate, called niter or salt- 
 peter, is spontaneously generated in the soil of a number 
 of hot regions like India, Persia, Arabia, and Egypt, doubt- 
 less by the action of organic matter on the debris of feld- 
 
310 APPLIED GEOLOGY. 
 
 spathic rocks ; as also on the earth floors of some caves in 
 our Western States. India formerly yielded the largest 
 supplies ; but, during recent years, a chief source of the 
 salts of potash has been the vast deposits overlying the 
 beds of rock-salt near Stassfurt in Germany. Here a 
 series of beds, several hundred feet in thickness, is made 
 up of alternating layers of rock-salt and hydrous sulphates 
 and chlorides of potash, soda, magnesia, and lime, called 
 kainite, carnallite, sylvite, kieserite, and polyhalite. These 
 are largely extracted and sent into commerce. Sylvite, 
 which is the chloride of potassium, is readily converted 
 into saltpeter by the agency of soda nitrate, yielding ni- 
 trate of potash and common salt. In 1882 Germany 
 produced 141,272 metric tons of kainite, which is a com- 
 plex compound of potassium and magnesium sulphate, 
 magnesium chloride, and water, and 1,063,592 metric tons 
 of other potash compounds. These are utilized as ferti- 
 lizers, and in the manufacture of the various valuable com- 
 pounds of potash. The occurrence of these desirable de- 
 posits of potash minerals, in connection with the upper 
 beds of salt deposits in several foreign localities, suggests 
 the expediency of a careful examination of what overlies 
 any beds of rock-salt that may be found in our own coun- 
 try, to see whether similar sources of potash and magnesia 
 may not possibly be discovered here. The numerous uses 
 of potash compounds, in the manufacture of gunpowder, 
 matches, soap, glass, saleratus, alum, and nitric acid, in 
 photography and dyeing, in galvanic gilding and silvering, 
 and in medicine, are familiar to most persons. The Unit- 
 ed States imported in 1882 5,225 net tons of saltpeter, 
 which is said to have been obtained mostly from India. 
 
 As has already been said, in treating of pyrites and of 
 salt, the compounds of soda are very largely manufactured 
 from common salt. But, besides this, the nitrate, carbon- 
 ate, and sulphate of soda occur native in very important 
 deposits in several arid regions, where they occupy usu- 
 
SUBSTANCES FOR CHEMICAL PURPOSES. 311 
 
 ally the dry basins of former bodies of saline waters, the 
 shrunken remnants of which sometimes remain as alkaline 
 pools and lakelets. Probably the most noteworthy of 
 these deposits are those of Chili and Peru, of Central 
 Asia, and of several portions of the great basin region in 
 the Western United States. The salinas of Chili and 
 Peru extend over several degrees of latitude in that rain- 
 less region, and in many places the soil is richly impreg- 
 nated to the depth of several feet with various salts of 
 soda, magnesia, and lime, of which the nitrate of soda, 
 often called Chili saltpeter, is a considerable constituent. 
 The nitrate, with some of the other more soluble sub- 
 stances, is leached from the soil, the solution evaporated, 
 and the crude salt exported, to be used as a fertilizer, 
 and in the manufacture of nitric and sulphuric acids and 
 nitrate of potash. Among the most notable of the nu- 
 merous saline deposits and lakes of the Great Basin, im- 
 pregnated more or less richly with the carbonate and sul- 
 phate of soda, and in some places with the nitrate, together 
 with common salt and compounds of magnesia, are, first 
 those of Humboldt County and Churchill County, Nev., 
 in what is called the Forty-Mile Desert, the first of which 
 has valuable amounts of nitrate of soda, and the second, 
 in a depressed basin of several acres in area, is said to be 
 filled to the depth of ten feet or more with nearly pure 
 carbonate of soda divided into layers by thin seams of 
 clay ; second, those reported from San Bernardino County, 
 Cal., and the southern border of New Mexico, containing 
 nitrate of soda ; third, those of Carbon County, Wyo., where, 
 sixty-five miles north of Rawlins, a lake of three hundred 
 acres area is said to hold in solution about 10 per cent of 
 soda sulphate and carbonate, while a lakelet three and a 
 half acres in extent which receives its overflow is filled 
 with solid carbonate to more than six feet in depth, a 
 number of other soda lakes being also found about Inde- 
 pendence Rock in the same region ; and, fourth, the 
 
312 
 
 APPLIED GEOLOGY. 
 
 soda lake at Morrison, near Denver, Col., the sulphate of 
 soda from which is said to be coming into use in Denver 
 for glass-making. It is highly probable that the thorough 
 examination of this vast region will reveal the presence of 
 many valuable deposits of the alkalies not at present 
 known. A recent geological reconnaissance of southern 
 central Oregon, made by Mr. J. C. Russell, the results of 
 which are published in the recently issued Fourth Report 
 of the Director of the United States Geological Survey, 
 has shown that the waters of two considerable lakes in 
 that region, Lakes Sumner and Abert, are " strong solu- 
 tions of potash and soda salts," an analysis of the water 
 of the last-named lake revealing the presence of two per 
 cent of potash compounds and a little salt, the origin of 
 which Mr. Russell attributes to the decomposition of the 
 feldspars in the surrounding volcanic rocks. 
 
 Besides the uses of soda compounds that have already 
 been incidentally mentioned, they are largely employed as 
 detergents in households and in bleaching establishments, 
 in the manufacture of hard soaps and of glass, in cookery 
 for raising bread and cake, in medicine and photography, 
 and in some metallurgical operations as a solvent of silver 
 salts. 
 
 Borax. This substance, which is largely used in the 
 arts for several important purposes, is a biborate of soda, 
 which occurs native in several localities, and is also ob- 
 tained by treatment of native boracic acid, and of ulexite 
 or boronatrocalcite, a double borate of lime and soda, 
 found in rounded masses made up of white, silky radiating 
 fibers. These compounds, with some others of little com- 
 mercial importance, are found dissolved in the waters or 
 crystallized in the mud of the margins and bottoms of 
 closed and greatly shrunken saline lakes, or forming in- 
 crustations, mingled with other salts and earthy matters, in 
 marshes which are dry during a portion of the year ; or 
 issuing in the water of hot springs in a few volcanic dis- 
 
SUBSTANCES FOR CHEMICAL PURPOSES. 313 
 
 tricts. For a long time it was brought to Europe in an 
 impure form called tincal> from Thibet, where it was found 
 in the borders of a saline lake, and the process of refining 
 was long kept secret by the Dutch and Venetians. Sup- 
 plies of tincal were also obtained from Nepaul, in India, 
 and from Ceylon. Later, it was made largely from the 
 boracic acid which issues with steam from the hot springs 
 of the lagoons of Tuscany. To these sources are now 
 added the rainless region of Chili, in the vicinity of 
 Iquique, where boronatrocalcite is found in large quanti- 
 ties, and the borax lakes and marshes of Nevada and Cali- 
 fornia. Large deposits of berates have also recently been 
 discovered near the Sea of Marmora in Asiatic Turkey. 
 The first locality in the United States where borax was 
 discovered was in a small saline lakelet,, very near Clear 
 Lake, in Lake County, Cal., where it occurred in crystals 
 enveloped in the gelatinous mud and underlying clay of 
 the bottom. Hot springs in the vicinity were also found 
 to contain boracic acid. For a number of years, a con- 
 siderable amount of borax was derived from this lake, but 
 it seems now to be superseded by richer or more acces- 
 sible localities. The largest amount of borax produced in 
 this country at present is derived from the borax marshes 
 near Columbus, in the southeast part of Esmeralda 
 County, Nev. It occurs here in extensive salines or 
 marshes, called Teel's Marsh, and Fish Lake, Columbus, 
 and Rhodes Marshes. These are all in oval alkaline flats, 
 occupying closed basins, which are dry during a portion 
 of the year, but in the wet season have shallow pools in 
 their lowest parts. The borax occurs forming incrusta- 
 tions mingled with salt, soda, and earthy substances, from 
 which it is freed by dissolving it with the aid of steam, 
 and then crystallizing it. A considerable amount of the 
 double borate of lime and soda is also found in these 
 marshes in the usual white fibrous balls. In 1882 nearly 
 half the borax produced in the United States was derived 
 
APPLIED GEOLOGY. 
 
 from Teel's Marsh, a considerable quantity being also ob- 
 tained from Fish Lake Marsh. Similar borax deposits 
 occur in Slate Range Marsh, San Bernardino County, 
 Cal., from which a large amount of borax is obtained ; 
 and very promising deposits are reported also to occur in 
 Inyo County, about one hundred miles northward from 
 the last. The output of borax in the United States for 
 1884 was 3,500 tons of 2,000 pounds. The result of the 
 late discoveries of borax has been to reduce the wholesale 
 price to about thirteen cents per pound, which is not more 
 than two fifths of the price that formerly prevailed. 
 
 The largest uses of borax are based upon its property 
 of dissolving the oxides of many of the metals at a high 
 temperature, and forming with them a kind of glass, 
 which, in a number of cases, has characteristic colors. 
 Hence it is used as a flux in refining metals ; by iron and 
 steel workers in welding, to preserve the surfaces of the 
 metal clean from oxide during the operation ; by braziers 
 and jewelers in soldering ; by enamelers ; and by chem- 
 ists, as a most valuable reagent in blow-pipe operations. 
 It is an essential ingredient in all artificial gems ; is a 
 component of some varnishes and fine toilet soaps ; and 
 is said to enter into some kinds of glass. Considerable 
 amounts are also used as a detergent for household pur- 
 poses, by packers in preserving meats, and in some me- 
 dicinal applications. 
 
 The student will gain some additional information about borax 
 from " Mineral Resources of the United States " for 1867, p. 178, 
 which contains an account of the first discovery of borax in the Unit- 
 ed States, by the discoverer ; " Mineral Resources of the United 
 States," 1883 ; Ure's " Dictionary of Arts," etc. ; and Watt's " Dic- 
 tionary of Chemistry." 
 
 Alum. This well-known substance is a hydrous dou- 
 ble sulphate of potash, soda, or ammonia, with alumina, 
 the base of clay. It is sparingly found native as an efflo- 
 rescence on rocks, where it originates from the weathering 
 
SUBSTANCES FOR CHEMICAL PURPOSES. 
 
 315 
 
 of pyritous clays containing potash, but is more commonly 
 manufactured from pyritous shales, called alum-shales, or 
 from alunife, an insoluble sulphate of potash and alumina, 
 called commonly alum-stone. The latter occurs in rocks 
 of volcanic regions, where it probably originates from the 
 action of sulphurous vapors on feldspars containing pot- 
 ash. It is a somewhat rare substance, but is found in 
 quantities of commercial importance at Tolfa near Rome, 
 and at two or three localities in Hungary, where it forms 
 considerable beds. The mineral is carefully calcined to 
 avoid fusion and loss of sulphur, then kept moist in 
 heaps, and left to the action of the weather, by which it 
 is disintegrated, with the development of soluble alum. 
 This is leached out and crystallized, forming opaque 
 cubes ; and, under the name of Roman alum, derived 
 from the chief locality whence it is obtained, it is pre- 
 ferred to other alums for some uses. By far the most 
 abundant material for the manufacture of alum is afforded 
 by the alum-shales. Those best adapted to the purpose of 
 alum-making are pyritous clay rocks, in which coaly mat- 
 ter is disseminated, thus affording readier access to the 
 air, by which the decomposition of the pyrites is effected. 
 The decomposition of the pyrites, accelerated usually by 
 the long-continued application of a low degree of heat in 
 extensive piles, converts the alumina of the clay into sul- 
 phate of alumina, which is leached out, concentrated, and 
 converted into alum by the addition of a proper amount 
 of sulphate or chloride of potash or ammonia. The sul- 
 phate of alumina for this purpose is also largely made by 
 treating with sulphuric acid calcined clays which are as 
 free as possible from lime and iron oxide. For this use, 
 the excellent clays which abound in the Cretaceous beds 
 of New Jersey are admirably adapted ; and there can be 
 no doubt that pyritous shales, adapted to alum-making, 
 can be found in many portions of our own country, es- 
 pecially in the coal and lignite regions, from which they 
 
3 i6 APPLIED GEOLOGY. 
 
 are mostly extracted in Europe, though it has recently 
 been stated that most of the clays used in the United 
 States for alum-making are imported. It has also been 
 proposed to manufacture alum from the greensand which 
 abounds in the Cretaceous of New Jersey, by treating the 
 gently ignited greensand with sulphuric acid, the green- 
 sand furnishing the requisite potash and alumina. 
 
 On account of the strong affinity of its aluminous base 
 for organic coloring-matters, alum is largely used as a 
 mordant in dyeing, and by manufacturers of what are 
 called lakes, which are compounds of organic coloring 
 principles with alumina, of which madder lake, and the 
 brilliant cochineal lake called carmine, are familiar ex- 
 amples. It is also used in clarifying liquors, in some pro- 
 cesses of tanning skins, in medicine as an astringent, in 
 pastes for paper, and in small amounts by bakers for 
 whitening and raising bread. 
 
 Besides the substances applicable to chemical manu- 
 facture or use that have already been described, some 
 mention should also be made in this connection of mag- 
 nesia, strontia, and titanium. Magnesia will require some 
 mention in the chapter on refractory materials ; but, be- 
 sides the use based on its resistance to heat, are others of 
 a chemical nature. The sulphate, which is much used in 
 medicine under the name of Epsom salt, is found native 
 at Stassfurt as the mineral kieserite, and is also ob- 
 tained from the residues after extraction of potash from 
 some other Stassfurt salts. It is said to be used as a 
 cheap substitute for sulphuric acid in the preparation of 
 blanc fixe, a white pigment obtained by the precipitation 
 of chloride of barium, and also in the manufacture of 
 pearl-white, to be used in paper-making. Epsom salt and 
 magnesia alba can also be manufactured from magnesite, a 
 carbonate of magnesia, much resembling calcite and dolo- 
 mite in color and cleavage, but containing no lime, be- 
 sides being somewhat harder and more sluggish in its 
 
SUBSTANCES FOR CHEMICAL PURPOSES. 317 
 
 effervescence with acids. It occurs in considerable beds 
 in the Lower Silurian rocks of Bolton and Sutton in Que- 
 bec, near the boundary-line of Vermont, where it is as- 
 sociated with beds of dolomite, steatite, and serpentine, 
 and in one locality with argillite ; and it will doubtless be 
 discovered in similar associations elsewhere, whenever an 
 active demand for it shall arise. 
 
 Strontia, the almost sole use of which has been here- 
 tofore in pyrotechny in the form of the nitrate for making 
 red fire, is recently coming into a greatly increased de- 
 mand, since it has been found that it can be utilized in 
 recovering sugar from the " melasse" which has hitherto 
 occasioned great loss in making beet-sugar. The two 
 minerals in which it occurs in economically important 
 amounts are strontianite, the carbonate, and a sulphate 
 called celestite (Latin ccdum), from its frequent sky-blue 
 tint. They are both heavy minerals, their specific gravity 
 being from 3.6 to 4 ; both are quite brittle, and both give 
 a bright-red colored flame when heated before the blow- 
 pipe. Like other carbonates, strontianite effervesces with 
 acids, and by this it may readily be distinguished from 
 celestite. These two minerals are sparingly distributed, 
 being found in nests and crevices, most commonly in lime- 
 stones, in the United States and Canada, but sometimes 
 also in sandstone and clay, or associated with gypsum. 
 They have been foun4 in the Lower Silurian limestones 
 of Manitoulin Islands, somewhat abundantly at Kingston, 
 and on the Ottawa River in Canada, as also in Jefferson 
 County, N. Y. ; and in Upper Silurian limestone near Scho- 
 harie and Lockport, N. Y., in Blair and Mifflin Counties, 
 Pa., and on Strontian and Put-in Bay Islands, Ohio, where 
 celestite is more than usually abundant. Strontianite is 
 obtained from Argyleshire in Scotland, where it was first 
 discovered, and somewhat abundantly in Westphalia, where 
 it occurs in veins or shrinkage cracks in Cretaceous clays; 
 while Sicily is much the most considerable producer of 
 
3 i8 APPLIED GEOLOGY. 
 
 celestite, exporting, it is said, about four thousand tons 
 annually. For its new use, in the manufacture of beet- 
 sugar, caustic strontia is obtained from strontianite by 
 heating it to redness to expel the carbonic acid. This, 
 when boiled with " melasse," forms a compound with the 
 sugar from which the strontia is separated by carbonic 
 acid, leaving the sugar to be dissolved and crystallized. 
 On account of its infusibility, caustic strontia is also 
 utilized in making tuyeres for blast-furnaces. The nitrate 
 of strontia, for use in pyrotechny, is obtained by treating 
 strontianite with nitric acid, or by heating celestite, mixed 
 with charcoal, to a high temperature, and then treating 
 with nitric acid the sulphide of strontia thus formed. 
 
 The compounds of titanium, which are now consider- 
 ably used in the manufacture of artificial teeth and in 
 porcelain-painting, are probably destined to a greatly in- 
 creased use in the manufacture by various chemical means 
 of a number of brilliant and permanent pigments. It is 
 found abundantly, in the form of ilmenite, or titanic iron, 
 in the Archaean rocks of Canada and Norway, where it 
 bears a great resemblance to magnetite, being, however, 
 very little magnetic It occurs also in crystalline rocks as 
 titanic acid, forming the minerals rutile and brookite. 
 
CHAPTER XIX. 
 
 FICTILE MATERIALS. 
 
 THE arts of the potter and the glass-maker afford a 
 striking exemplification of what human skill can accom- 
 plish by a dexterous use of the properties of substances 
 which in their original condition are among the most com- 
 mon and least valued objects. What could be more dis- 
 similar to the magnificent creations of porcelain and of 
 glass which, in varied forms, deck the tables and adorn 
 the mansions of the rich, and which are objects of eager 
 desire to princes, or even to the humbler wares which 
 spread the board and minister to the modest wants of the 
 poor laborer, than heaps of clay and sand, of lime and 
 feldspar, with bins of soda, potash, salt, and borax, and a 
 few metallic oxides ? Yet the former are but the latter, 
 mingled by knowledge bought by generations of experi- 
 ence, fashioned by skill and taste, and subjected to a treat- 
 ment adapted to develop to the utmost their latent capa- 
 bilities. The art of shaping rude vessels from clay and 
 hardening them by fire is one which has been practiced 
 in the infancy of civilization ; but the highest and most 
 refined developments of this art tax to the utmost the sci- 
 entific resources and the cultivated taste of the most en- 
 lightened nations. 
 
 A number of the substances used as materials for the 
 manufacture of porcelain, earthenwares, and glass, have 
 already been described, as regards their geological occur- 
 
3 20 APPLIED GEOLOGY. 
 
 rence, in the preceding pages. Such are potash, soda, and 
 lime, used as fluxes in glass-making and in glazes for pot- 
 tery ; such is oxide of lead, used as a flux for flint-glass 
 and in many glazes ; such are the oxides and a few other 
 compounds of the metals employed in glass- staining and 
 porcelain-painting ; such is salt, used as a glaze for stone- 
 ware, and borax, used also in some glazes, and as a partial 
 substitute for silica in some fine sorts of glass and artifi- 
 cial gems. Of the remaining substances, including clay, 
 silica, feldspar, granulite, steatite, and baryta, all of which 
 are used more or less largely in one or both of these arts, 
 clay is of the greatest interest, since it forms the basis of 
 all pottery- wares, and has also some other highly important 
 applications. This substance is a highly variable mixture 
 of kaolin, the mineral on which its valuable properties 
 depend, with silica, iron, lime, magnesia, the alkalies pot- 
 ash and soda, and often a small amount of mica and par- 
 tially decomposed feldspar. In blue and black clays, or- 
 ganic matter is also present, and disappears on burning, 
 leaving the clay white. Kaolin is a usually white and 
 unctuous 'hydrous silicate of alumina, which contains in 
 round numbers 46 per cent of silica, 40 per cent of alu- 
 mina, and 14 per cent of water. From this it will be seen 
 that two and a half times the alumina given in the analysis 
 of a clay will show the amount of kaolin that enters into 
 its composition. In some of the best clays this mineral is 
 much the largest ingredient, but small proportions of other 
 substances being mingled with it ; while in others it may 
 constitute considerably less than half of the aggregate, to 
 which, nevertheless, it gives its essential characters. Kao- 
 lin, then, is the essential ingredient of every true clay, and 
 by itself constitutes a clay of the finest quality ; all other 
 ingredients are non-essential accessories, and in some cases 
 injurious ones, rendering the clay unfit for its highest uses. 
 The most invariable accompaniment of kaolin in clay is 
 free silica, occurring in the form of sand intimately min- 
 
FICTILE MATERIALS. 321 
 
 gled with the mass, and varying in amount from a mere 
 fraction of one per cent to more than fifty per cent of the 
 whole. This silica, though sometimes in grains of moder- 
 ate size, frequently exists in the state of an almost im- 
 palpable powder or dust, yet showing itself under the 
 microscope as minute angular particles of white, transpar- 
 ent quartz. The quartz in clay to be used for pottery 
 can hardly be considered as anything but a diluent of the 
 clay. Indeed, for the purposes of the potter, rich or fat 
 clays need to be mingled with finely comminuted silica, 
 in preparation for their use. By itself in a clay, it is inert, 
 acting, however, physically to counteract the tendency to 
 shrinkage and the production of checks and cracks which 
 kaolin alone exhibits when subjected to great heat. When, 
 however, verifiable bases, like potash, soda, and lime, are 
 present in the clay, the readiness of finely divided silica 
 to form with them fusible compounds at a high tempera- 
 ture causes that slight incipient fusion which gives rise to 
 the hardness and strength of the productions of the pot- 
 ter. Some one or all of the three bases that have just 
 been named, but potash much the most generally, are 
 found in nearly all clays, but usually in small quantities 
 in the best. It seems quite probable that these alkaline 
 substances which analysis reveals, and which produce 
 their effect on the fusibility of the clayey mass, are due, in 
 some cases at least, to partially decomposed feldspar, and 
 sometimes to mica present in the clay. Both of these 
 minerals contain potash, and feldspar usually contains 
 some soda and lime also. Feldspar in clays occurs in 
 small, sandy particles. Mica, from the ready flotation of 
 its minute laminae, is little likely to be found in clays 
 which are somewhat remote from their place of origin, and 
 which have possibly been worked over more than once by 
 transporting agencies before resting in their present beds. 
 The most undesirable contamination of clays for potter's 
 use is iron, which in some of its forms, as oxide, carbon- 
 
322 APPLIED GEOLOGY. 
 
 ate, or sulphide, seems never to be wholly absent from any 
 clay. Sometimes its proportions sink to not more than a 
 fifth of one per cent ; more frequently, however, it is pres- 
 ent to the extent of two or three per cent or even more, 
 unfitting the clay for any save the coarsest and most com- 
 mon wares, since it imparts to them yellow, red, or brown 
 colors, according to its amount and the degree of heat to 
 which the articles are subjected. The following table of 
 analyses of a few approved pottery clays will give a fair 
 idea of their composition, and of the extent to which the 
 various ingredients other than kaolin may be present 
 without proving seriously detrimental. The titanic acid, 
 which will be observed to be present in several of the 
 clays, especially those from New Jersey, seems to be 
 wholly inert, producing no appreciable effect on their 
 properties. Following the excellent arrangement of analy- 
 ses given in the New Jersey Report on Clay Deposits, and 
 in the Ohio Report on Economic Geology, the kaolin- 
 forming compounds, the inert substances, and the com- 
 pounds which promote fusibility, with their respective 
 amounts, are placed in separate groups. It may here be 
 said that, for their finest uses, clays are washed by mixing 
 them thoroughly with water, and then allowing the creamy 
 liquid in which the clay will remain long suspended to 
 flow off into settling-vats where the clay is deposited. By 
 this means the coarser and heavier impurities are easily 
 separated. 
 
 The properties of clays which are of chief interest to 
 the potter are plasticity, and a tendency to shrink at a high 
 temperature. Most clays which are used by potters when 
 properly moistened are tenacious and pasty, and are sus- 
 ceptible of being easily shaped into any desirable form in 
 molds or on the potter's wheel. The forms thus made 
 harden considerably on drying, and when heated to a high 
 temperature assume the stony consistency which is famil- 
 iar to every one in earthenware and porcelain. This 
 
FICTILE MATERIALS. 
 
 323 
 
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324 APPLIED GEOLOGY. 
 
 valuable property of plasticity belongs solely to the kaolin 
 of the clay ; and plastic clays, rich in alumina, admit the 
 addition of a considerable amount of fine sand without 
 any material diminution of their plasticity. The plas- 
 ticity of clays is doubtless dependent in part on the water 
 held in chemical combination by the kaolin, since, when 
 this water is driven off by a red heat, plasticity is perma- 
 nently lost, and can not be restored by any treatment of 
 the stony product with water. That it is by no means 
 due wholly to the combined water, however, is shown by 
 the fact that some highly valued porcelain clays or kaolins 
 are but slightly plastic. An example of this is presented 
 by the clay of which the beautiful Sevres porcelain is 
 made, which, when prepared for use, is so little tenacious 
 as to require a quite special and expensive mode of hand- 
 ling in shaping the articles which are fashioned from it, a 
 fact to which the high price of this porcelain is in a great 
 measure due. Prof. George H. Cook, in his report on the 
 clay deposits of New Jersey, has shown that very probably 
 the plasticity of kaolin is largely due to a minute sub- 
 division of the crystalline plates and bundles of which the 
 mineral is originally composed, since recognizable crystals 
 of kaolin are found, by microscopic examination, to abound 
 in clays which are deficient in this property, while they are 
 absent, or nearly so, from highly plastic clays. 
 
 The shrinkage of clays, when subjected to great heat, 
 is a character quite as remarkable as their plasticity. 
 This arises partly, no doubt, from the expulsion of water ; 
 but that this is not the only cause, is shown by the fact 
 that the clay continues to contract with an increase of 
 temperature, even after the water has been entirely ex- 
 pelled. On this fact was based the pyrometer of Wedg- 
 wood, which attempted to measure very elevated tempera- 
 tures by the degree of contraction which they produced 
 in rods of clay ; an attempt which was not entirely suc- 
 cessful, on account of irregularities in the contraction 
 
FICTILE MATERIALS. 325 
 
 of clays when exposed to long-continued heat. Highly 
 aluminous or fat clays shrink the most by heat, while very 
 sandy or lean clays shrink less or not at all. Hence, to 
 counteract the excessive shrinkage of fat clays, which is 
 apt to cause irregularities and cracks in the wares when 
 burned, they are tempered by mixing them intimately, be- 
 fore molding, with a proper amount of finely divided 
 silica, or with thoroughly burned and pulverized clay. 
 
 Clays originate doubtless from the decomposition of 
 feldspathic rocks, such as granites, gneisses, and porphy- 
 ries. The feldspars, from whose decomposition kaolin is 
 derived, are orthoclase, albite, and oligoclase, albite being 
 the most readily attacked by the agencies of decay, but 
 orthoclase, from its greater abundance, being the most 
 important source. These minerals, which are silicates of 
 alumina, with potash, soda, and lime, when exposed to the 
 action of carbonic acid and water, slowly lose their alka- 
 line constituents and some of their silica, take in water, 
 and so are ultimately converted to kaolin. When kaolin 
 is found on the place of its origin, it is naturally associ- 
 ated with the quartz and mica, which are the remaining 
 constituents of granite and gneiss ; or, with quartz alone, 
 when it is derived from the variety of granite called aplite 
 or graphic granite, which contains little or no mica. Such 
 clays are usually deficient in plasticity, probably from the 
 undisturbed crystalline condition of their kaolin. Of this 
 kind are apparently the porcelain clays of China, from 
 which the names kaolin and china clay have been de- 
 rived ; that of Saint Yrieix-la-Perche, not far from Li- 
 moges, which is the basis of the French manufacture of 
 porcelain ; that of Saxony, from which Dresden porcelain 
 is made ; and the china clay cf the granite district of 
 Cornwall. The Chinese kaolin and that of Cornwall, ac- 
 cording to Ure, have more plasticity than that of France 
 and Germany. On account of the slowness with which 
 kaolin subsides in water, with which it readily forms a 
 15 
 
326 APPLIED GEOLOGY. 
 
 milky mixture, and of the consequent ease with which it 
 may be transported to long distances from the place of its 
 origin, much the largest portion which is formed is washed 
 away from its parent rock, and deposited in low grounds 
 or in bodies of water, forming often considerable beds, 
 like those found so abundantly in parts of New Jersey, 
 and those which constitute the under-clays of many coal- 
 beds. These translocated clays, as a result of their trans- 
 portation by moving water, have usually been freed from 
 most of their mica, and from their free silica, save that 
 which existed in a state of fine subdivision. They are 
 also commonly highly plastic, although those which have 
 been much solidified by pressure need to be softened by 
 weathering before they exhibit this character. These 
 clays are occasionally of such purity as to be adapted to 
 the finest uses in the manufacture of porcelain ; such, 
 however, are found in but few localities. Clays, adapted 
 to the manufacture of the more common articles of white 
 and ornamented stoneware, are more abundantly dis- 
 tributed, while others, which are too much contaminated 
 with iron for this purpose, are used for making jars, jugs, 
 and many other articles of a coarser kind. 
 
 Pottery clays are known to occur at many points in 
 the Archaean districts along the Appalachian range, from 
 New England to Georgia, and they are dug to a limited 
 extent in several localities. These are all surface deposits 
 of geologically recent origin, and some of them may be 
 found suitable for porcelain-making. Clay deposits, suit- 
 able for common wares, are reported at a number of 
 points in the far West, and are said to be utilized to some 
 extent ; but none of the very best quality, apparently, 
 have yet been found, unless the clay of Golden, Col., 
 given in analysis No. 10, on a preceding page, should 
 prove to be one. The clay deposits most largely wrought 
 in this country hitherto are of Cretaceous and Carbonifer- 
 ous age. The Cretaceous clays of New Jersey, chiefly in 
 
FICTILE MATERIALS. 327 
 
 Middlesex County, are abundant, and of qualities fitting 
 them for various uses. The excellent pottery clays are 
 not only largely sent to other States, but are the basis of a 
 very important manufacture of wares of various kinds at 
 Trenton, Jersey City, and Elizabeth, New Jersey produc- 
 ing nearly three fifths of the pottery wares that are made 
 in the United States. It can hardly be doubted that 
 some of the New Jersey clays may be used for the manu- 
 facture of the best porcelain. Some of the under-clays of 
 the lower coal-measures, in several of the coal-producing 
 States, are suited to the manufacture of pottery. They 
 have been most largely utilized for this purpose at Liver- 
 pool, O., on the Ohio River, and at two or three other 
 localities in the same State, where they are mixed with 
 clays from other regions, Ohio ranking next to New 
 Jersey in the amount of wares produced. At Huron, 
 Ind., and at other points in Lawrence County and also in 
 Owen County, noted deposits of kaolin called indianaite 
 occur, an analysis of which, showing an unusual propor- 
 tion of water, has been given on a preceding page. This 
 clay is used at Indianapolis for making encaustic tiles of 
 the highest grade of excellence, and at various points in 
 the United States in the manufacture of fine qualities of 
 white ware ; and it seems to be suitable for the very high- 
 est uses of the potter. No attempt has here been made 
 to enumerate the many promising localities of pottery 
 clays which are known to exist in the United States, but 
 which have not as yet been much developed. It is 
 certain, however, that clays adapted to the more common 
 uses are widely distributed, while it is probable that here, 
 as in all other countries, kaolins suitable for the manu- 
 facture of fine porcelain will be found to be rare. Any 
 mention of fire-clays has been purposely deferred to a 
 succeeding chapter ; and those coarser clays, which are so 
 widely used for brick-making and similar purposes, have 
 already been described in treating of building materials. 
 
328 APPLIED GEOLOGY. 
 
 The materials on which is based the vast English 
 manufacture of pottery and porcelain in Staffordshire are 
 derived from the southwest counties of Cornwall, Devon, 
 and Dorset, in which are found extensive deposits of ex- 
 cellent clays and kaolin. 
 
 Although clay is the basis of pottery, several other 
 minerals are mingled with it to form the pastes that are 
 employed for the various kinds of ware. Of these, silica 
 has the most universal use, being mingled with the clays 
 in proper proportions to correct their tendency to too 
 great and irregular shrinkage in burning. This may be 
 obtained in the state of clean silicious sand, or of flint, 
 found disseminated in chalk and other limestone rocks ; 
 or of massive quartz, from veins of this mineral occurring 
 in regions of granitic rocks and silicious schists, such as 
 the Archaean areas described in treating of building- 
 stones. From whatever source derived, the silica is 
 ground to a very fine powder before it is used, and the 
 massive forms are frequently calcined before grinding, to 
 render them more brittle. This finely divided silex is not 
 only mingled intimately with the clay which forms the 
 body of the ware, but also enters into most of those vitri- 
 fiable mixtures which are used as glazes. Both silex and 
 pure clay or kaolin, however, are wholly infusible at the 
 temperature attained in porcelain-kilns. Hence, to im- 
 part to the clay mixture a tendency to that incipient vitri- 
 faction which increases the strength of the more common 
 wares, and gives to fine porcelain the translucency which 
 is so much admired, minerals like feldspar, lime, and crys- 
 tallized gypsum, are added, which at high temperatures 
 form with silica fusible compounds. The Chinese use for 
 their porcelain a mixture of kaolin with a silicious feld- 
 spar called petuntse, which mixture requires an exceed- 
 ingly high temperature for its vitrifaction. The standard 
 mixture for Sevres porcelain is, according to Ure, 59 per 
 cent of silica, 35.2 per cent of alumina, 2.2 per cent of 
 
FICTILE MATERIALS. 
 
 329 
 
 potash, and 3.3 per cent of lime, which may be formed by 
 mingling kaolin with proper proportions of feldspar, flint, 
 and chalk. The English " tender porcelain" is composed 
 of clay and flint, with bone-dust, and sometimes potash, 
 as a vitrifying agent ; and in Wedgwood-ware, baryta is 
 used as a flux for the clay. The feldspar which is used 
 in these mixtures, to add the needful alkalies, is to be 
 sought, as might be expected, in regions of coarsely crys- 
 talline granitic rocks. That which is used in this country 
 seems to be obtained mostly from near Middletown and 
 Portland, Conn., and from middle Virginia; but numer- 
 ous other localities are known in the New England and 
 Atlantic seaboard States, where it can be found abun- 
 dantly. 
 
 The glazes which give to wares their impermeability, 
 and their smooth and often brilliant finish, are various 
 mixtures of flint, feldspar, ground glass, lead oxide, borax, 
 potash, soda, and lime. From among these substances, 
 various manufacturers compound for their wares glazes 
 which experience teaches them to be most suitable for 
 their purposes, the glazes being artificial glasses, some- 
 times transparent, sometimes opaque, which coat the 
 wares to heighten their beauty, or sometimes to conceal 
 their defects. Some porcelain has a glaze of feldspar 
 only. Many coarser articles of pottery are glazed by 
 merely throwing salt into the kiln among them at the 
 proper stage of the baking ; the salt is decomposed by the 
 heat, and its soda forms a fusible glaze with the silica and 
 alumina of the surface of the wares. 
 
 The colors which are used for the ornamentation of 
 pottery are mostly oxides of the metals, with a few chlo- 
 rides and chromates. These are mingled or fused with 
 proper fluxes, ground fine, and applied to the wares before 
 their final burning in a medium of gum-water, or of some 
 volatile oil. The colors are in some cases fused into the 
 glaze of the wares, and in others they are laid on under the 
 
330 APPLIED GEOLOGY. 
 
 glaze and show through its transparent substance. The 
 oxides, which are chiefly used for painting porcelain and 
 other wares, are those of cobalt, iron, copper, antimony, 
 uranium, nickel, manganese, chromium, tin, and titanium, 
 with chlorides of gold, silver, and platinum, and a few chro- 
 mates. By a proper treatment of these substances and 
 their fluxes, the skillful porcelain-painter attains as com- 
 plete a mastery over the effects that he desires to produce 
 with these coloring materials that must pass through the 
 fire before showing their real nature, as the artist who 
 paints on canvas with ordinary pigments. 
 
 Glass. It may be stated in a general way that this 
 beautiful, transparent, and impervious substance, which 
 plays so large a part in the comforts, conveniences, and 
 elegancies of civilized life, is a double silicate of potash or 
 soda and lime or lead. Its foremost materials are there- 
 fore silica, the alkaline substances, and lead oxide. In 
 some of the finer kinds of glass, boracic acid takes the 
 place of a portion of the silica. To correct the effects of 
 impurities in these materials, a little niter is commonly 
 used, as also small amounts of arsenic, and of black oxide 
 of manganese, which, from its purifying effects, is often 
 called glass soap. The geological occurrence of most of 
 these substances has already been described elsewhere. 
 The silica, which constitutes the largest ingredient in all 
 varieties of glass, was formerly prepared for the finer kinds 
 by calcining and grinding flint, from which is derived the 
 name of flint or crystal glass, applied to the very dense, 
 lustrous, and highly refracting double silicate of potash and 
 lead. It has, however, been found that, in somewhat nu- 
 merous localities, sand may be obtained of sufficient pu- 
 rity to be used for all the purposes of glass-making. For 
 all except the coarser varieties of glass a tolerably fine, 
 angular, white sand is needed, free from earthy impurities, 
 and especially from iron, which gives to glass a green tint. 
 In some localities, sea-sands are found of sufficient purity 
 
FICTILE MATERIALS. 
 
 331 
 
 for any purpose. Thus the English manufacturers obtain 
 much of their sand from the Isle of Wight, and from 
 points on the coast of Norfolk and of Holland. In south- 
 ern New Jersey a large number of glass-houses obtain an 
 inexhaustible supply from a bed of Tertiary sand more 
 than ninety feet thick, and of very considerable extent, 
 much of which is so pure as to require no washing before 
 being made into window-glass. The glass-works in cen- 
 tral New York obtain a good sand for window-glass from 
 the modified drift around Oneida Lake.- In four counties 
 of central and southern Indiana great deposits of pure 
 white sand and slightly indurated sandstone occur, from 
 which an approved quality of plate-glass is manufactured. 
 Besides such deposits of incoherent sands of Tertiary age 
 and of recent origin, which are pure enough for glass- 
 making, white silicious sandstones are occasionally met 
 with in much more ancient rocks, which are so friable as 
 to be readily reduced to sand, and are then used for the 
 manufacture of glass. Notable among these is the St. 
 Peter's sandstone of the Lower Silurian, which occupies 
 considerable areas in Missouri, Minnesota, and Wisconsin, 
 and in La Salle County, 111. At many of its exposures, it 
 occurs as a clean white sandstone, remarkably free from 
 impurities, and so friable as to be readily extracted from 
 its beds by pick and shovel. A considerable manufacture 
 of glass is already based upon this sand, and its use seems 
 destined to be greatly increased. The Potsdam sand- 
 stone, which occupies the lowest horizon of the Lower 
 Silurian, also occurs of sufficient purity to afford a good 
 material for glass, in portions of northern New York, 
 Canada, and Wisconsin. A few only of the more note- 
 worthy exposures of sands which have been proved by 
 use to be sufficiently pure for the manufacture of the bet- 
 ter grades of glass have here been mentioned. Many 
 others will doubtless be eventually brought into use with- 
 in our broad domains ; but it will easily be conceived 
 
332 APPLIED GEOLOGY. 
 
 that, though sand is a very widely and abundantly dis- 
 tributed substance, yet that which is of the high degree 
 of purity needed for the manufacture of fine white glass 
 is by no means common. For the making of bottle-glass, 
 in which purity of color is not required, inferior sands are 
 largely utilized. For this last purpose a rock called 
 granulite has recently come into quite extensive use in 
 Saxony and in southern England. Granulite, though 
 sometimes granular, is usually a schistose rock composed 
 of alternating layers of quartz and feldspar, with little or 
 no mica, and is usually of a white color, so that it is called 
 by the Germans weiss-stein, or white stone. The Saxon 
 granulite contains from 70 to 80 per cent of silica, with 
 a considerable per cent of potash in its feldspar, and less 
 than one per cent of iron; and, when melted with the 
 addition of sufficient lime to secure perfect fusion, makes 
 a pale- green bottle-glass, at about two fifths of the usual 
 cost for this article. Rock of this character, or that which 
 will serve the same purpose, viz., granite free from mica 
 and containing but a minimum amount of iron, may doubt- 
 less be found in the Archaean areas of Canada and New 
 England, as well as elsewhere, and where met with it will 
 afford excellent opportunities for the profitable invest- 
 ment of capital. The Saxon production from this source 
 is said to have reached twenty-two million bottles in 1880, 
 and to have increased rapidly since that time. It has 
 recently been proposed to use this glass for gas and water 
 pipes and other large castings, and, should this idea be 
 carried out successfully, deposits of granulite and graphic 
 granite, favorably located with respect to transportation, 
 will naturally assume great economic importance. 
 
 The substances which are used for coloring glass, like 
 those employed in porcelain-painting, are metallic oxides 
 and a few other compounds of the metals, all of which, it 
 need hardly be said, are obtained from geological sources. 
 Thus the white opaque glass called enamel derives its 
 
FICTILE MATERIALS. 333 
 
 color and opacity from the oxide of tin ; a blue color is 
 given by the oxide of cobalt, green by oxide of copper, 
 yellow by chromate of lead and by silver chloride, and 
 other colors by similar means. Without at all entering 
 into the technicalities of glass-making, it may appropri- 
 ately be said here, in illustration of the geological origin 
 of its materials, that the chief varieties of glass are com- 
 pounded of the following ingredients : 
 
 Common bottle-glass, of silica, alumina, soda, and 
 lime ; Bohemian glass, of silica, potash, and lime ; crown- 
 glass, of silica, potash or soda, and lime ; window-glass 
 and mirror-plate, of silica, soda, and lime ; crystal and 
 flint glass, of silica, potash, and lead oxide ; strass for arti- 
 ficial gems, of silica and boracic acid, potash, and lead 
 oxide. 
 
 The differences of quality are due to the relative 
 purity of the ingredients, the proportions in which they 
 are compounded, and the skill and care with which they 
 are treated. 
 
 For additional information with regard to materials for the manu- 
 facture of pottery and glass, the student is referred to the following 
 works : Ure's " Dictionary of Arts," etc., articles on clays, glass, and 
 pottery ; " Geology of New Jersey," 1868 ; the " New Jersey Report 
 on Clay Deposits," 1878 ; and " Ohio Geological Report," Vol. V, 
 chap. ix. 
 
CHAPTER XX. . 
 
 REFRACTORY SUBSTANCES. 
 
 FOR numerous and highly important purposes among 
 civilized nations, materials are required which will endure 
 very high degrees of heat without injury; and every im- 
 provement whereby more elevated temperatures are se- 
 cured by the skillful use of fuel, renders the need of such 
 refractory substances more imperative. It is necessary 
 only to direct attention to the furnaces used for various 
 metallurgical operations, and especially those in which 
 iron and steel are to be treated ; the kilns in which 
 pottery is baked and the materials of glass are fused ; the 
 seggars, or fire-proof boxes, in which earthenware and 
 porcelain are exposed to the heat of the kiln ; the large 
 pots or crucibles in which the ingredients of glass, and 
 metals like copper, silver, and steel, are melted ; and the 
 linings of Bessemer converters, in which molten iron is to 
 be subjected to ebullition by the action of a current of air 
 to burn out its impurities to indicate the variety and im- 
 portance of the uses for which refractory substances are 
 required, and the fierce heats which they are called upon 
 to endure without softening. All these substances are 
 minerals which enter into the composition of rocks, and 
 are therefore derived from geological sources. 
 
 Foremost in importance among these is fire-clay, both 
 from its great infusibility, and from the readiness with 
 which it may be fashioned into convenient forms. This 
 
REFRACTORY SUBSTANCES. 335 
 
 clay does not differ from the pottery clays described in 
 the preceding chapter in any respect save in its greater 
 necessary freedom from the fluxing ingredients, potash, 
 soda, lime, magnesia, and iron oxide. The presence of 
 any considerable proportion of these fluxes in a clay, to 
 the extent, for example, of two or three per cent, in- 
 juriously affects its heat-resisting properties ; and the 
 combination of two or more of them proves more detri- 
 mental than a like amount of any one, because the com- 
 pound silicates are more fusible than the simple ones. 
 The more completely a clay is composed of kaolin, or of 
 kaolin and silicious sand, the more refractory it is likely 
 to show itself, since both these substances are wholly in- 
 fusible at the temperatures attained in industrial opera- 
 tions. This may be seen by examining the following 
 analyses of several of the most celebrated fire-clays of 
 this country and of Europe. They are arranged in the 
 order of their resistance to an extreme fire-test, made by 
 exposing small triangular prisms of each with sharp edges, 
 for a half-hour, to a heat in which platinum was melted. 
 Exposed to this heat, some of the clays retained their 
 sharp edges ; others, while retaining the sharpness of their 
 edges, were more or less blistered or distorted ; in others, 
 the edges were rounded and fused, and a number melted. 
 This series of tests was undertaken by the Geological Sur- 
 vey of New Jersey, and its results and methods are pub- 
 lished in the annual report of that State for 1880. On 
 this was founded a tentative division of the clays into 
 seven classes, according to their relative refractoriness ; 
 and to this classification the numbers in the first column 
 refer. The analyses of the same clays have been selected 
 from those given in the New Jersey report on clay de- 
 posits, to which reference has been made before. Neither 
 soda nor lime appears in any of these analyses. 
 
 As all these clays are well esteemed for their resistance 
 to heat, it may be assumed that the amount of the flux- 
 
336 
 
 APPLIED GEOLOGY. 
 
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REFRACTORY SUBSTANCES. 337 
 
 ing ingredients in a fire-clay can not safely exceed what is 
 found in these, especially as one of the clays which occu- 
 pies the lowest class contains the most of the fluxes. 
 When it is considered, also, that in these tests pure rock- 
 crystal was melted, a reason will be found why the four 
 clays that contained the most free silica rank lowest in 
 this list. It would be difficult to assign reasons for some 
 other differences in refractoriness shown by the clays in 
 the table, as, for example, why clay No. 7 should not have 
 been as refractory as Nos. 2 and 3, unless it is to be found 
 in the texture and density of the clays. 
 
 Aside from the very superior fire-clays obtained from 
 the Cretaceous clay deposits of New Jersey, the great 
 bulk of the refractory clays of Europe and the United 
 States are derived from the under-clays of coal-beds not 
 only those of the coal-measures proper, but also, as in 
 several of our Western Territories, those bearing similar 
 relations to the lignitic coals of the Upper Cretaceous. 
 These under-clays doubtless owe their freedom from alka- 
 line constituents to the fact that, having once been soils 
 which sustained a luxuriant vegetation, these substances 
 have largely been withdrawn from them by the processes 
 of plant-growth. When first dug, they are hard and 
 stony, but can be softened and rendered somewhat plastic 
 by sufficient weathering. Frequently, however, they are 
 merely ground fine with water, mixed with a proper 
 amount of previously burned and pulverized fire-clay 
 called calcine, and sufficient sandy, plastic clay to serve 
 as a bond, and then molded and burned for fire-brick, 
 glass-pots, retorts for gas and zinc works, terra-cotta 
 wares, chimney-tops, and many other articles which are 
 either to be exposed to high temperatures, or which need 
 to be fired strongly to secure the characters desired. 
 
 Dinas or silicious bricks, which are employed where an 
 excessive temperature is attained, as in the melting-cham- 
 ber of regenerative furnaces, in which ordinary fire-brick 
 
338 APPLIED GEOLOGY. 
 
 does not endure well, were originally made from a sili- 
 cious rock locally called clay, though containing about 97 
 per cent of silica, occurring in the Carboniferous strata of 
 South Wales. This rock was disaggregated and mixed 
 with a small portion of lime to serve as a cement, then 
 molded and burned at a high heat for several days. At 
 the high temperature employed, the lime combines with 
 an equivalent amount of silica to form a refractory silicate 
 which binds the whole together. Similar bricks are now 
 made from any pure silicious rock, which is ground and 
 mixed with about one per cent of milk of lime to form a 
 bond for the mass when burned. The silicious rock em- 
 ployed for this purpose should be free from iron and 
 mica. Silicious bricks expand somewhat when heated, 
 and so keep the parts of the furnace tight. 
 
 The substance called ganister, used as a refractory lin- 
 ing for Bessemer converters, is a very fine-grained and 
 tough sandstone, or quartzite, containing a certain amount 
 of finely disseminated aluminous matter. When this is 
 ground fine and mixed with water, the contained alumina 
 acts as a sufficient bond. Rock for this purpose is ob- 
 tained in England from a silicious under-clay of the coal- 
 measures at several points, the best being found in the 
 vicinity of Sheffield. A rock of a similar character is 
 found in the Archaean strata in the immediate vicinity of 
 Marquette, Mich., where a thin-bedded and ripple-marked 
 quartzite is quarried to a considerable extent for this use. 
 Any pure silicious rock, ground to a fine powder and 
 mixed with a proper amount of good fire-clay, is said to 
 answer well in place of ganister. 
 
 What are called fire-stones are usually silicious sand- 
 stones, which should be free especially from iron, and 
 from mica the potash in which renders it a fluxing in- 
 gredient. Fire-stones may be found by careful exam- 
 ination and trial in many localities, where their cheap- 
 ness makes them a reasonably good material for many 
 
REFRACTORY SUBSTANCES. 339 
 
 purposes, as for the hearths of furnaces and fireplaces, 
 and for the construction of kilns, though their use is now 
 largely superseded by that of fire-brick. Where used, it 
 is hardly necessary to say that they should be thoroughly 
 dried before being subjected to heat. 
 
 For a number of purposes bricks are very desirable 
 which shall combine with the ability to endure unchanged 
 all ordinary degrees of temperature, very feeble conduc- 
 tivity for heat, and much less specific weight than common 
 fire-brick. Such materials, called floating bricks, because 
 they are lighter than water, are made from an infusorial 
 earth called "fossil meal," composed of the microscopic 
 skeletons of silicious organisms, and forming a whitish 
 earthy mass, very light, and resembling chalk in appear- 
 ance, but yielding no effervescence with acids. This sub- 
 stance, mingled with a small amount of clay, may be made 
 into bricks which weigh less than one fifth as much as or- 
 dinary bricks, which resist heat well, and which when red- 
 hot at one end are not perceptibly warm at the other. An 
 earth of this kind is abundant in Tuscany ; and it is prob- 
 able that the Tertiary infusorial earth which occurs in a 
 bed thirty feet thick near Richmond, Va., and in a still 
 thicker deposit at Monterey, Cal., is adapted to this use. 
 
 Graphite or plumbago, under the name of black-lead, is 
 familiar to every one from its wide use in lead-pencils. It 
 is a soft, black mineral, of a greasy feel and metallic luster, 
 and easily gives a lead-gray mark on paper, on which ac- 
 count it is used in the manufacture of pencil-leads. Aside 
 from the impurities with which it is often contaminated, it 
 is pure carbon, having the same composition as the dia- 
 mond, to which in other respects it is so unlike ; and it is 
 in all probability the ultimate stage in the series of changes 
 which vegetable matter undergoes, passing through the 
 conditions of peat, lignite, and mineral coal, to end in 
 graphite, which is not only infusible, but also incombusti- 
 ble under the conditions which are presented in the in- 
 
340 APPLIED GEOLOGY. 
 
 dustrial use of heat. It is usually found in quantities of 
 economic importance only in the most ancient crystalline 
 rocks, associated frequently with limestones, and also with 
 gneiss and schistose rocks. In these it occurs, either dis- 
 seminated more or less abundantly in certain horizons of 
 the rock, or forming pockets and nests, or filling vein-like 
 fissures with mineral of a high degree of purity. It is met 
 with at many points in the Archaean region, extending from 
 the Province of Quebec, in Canada, through New York, 
 New Jersey, etc., to North Carolina and Alabama ; but in 
 most of the localities it is either too sparingly dissemi- 
 nated to pay for its extraction, or is of such physical char- 
 acter as not to admit of cheap separation from its impuri- 
 ties. It has been mined to some extent at Bloomingdale, 
 N. J., Bucks County, Pa., and Sturbridge, Mass., being 
 found in graphitic gneiss ; but the chief place in the 
 United States where it is mined at present is near Ticon- 
 deroga, N. Y., where it is obtained from a graphitic 
 schist, about fifteen feet thick, and containing from 8 to 
 15 per cent of disseminated graphite. This locality 
 yielded two hundred net tons of graphite in 1882, the 
 remainder of the United States producing only twelve 
 tons. In Ottawa County, Quebec, extensive deposits 
 occur in the Laurentian limestones, containing in some 
 localities 20 to 30 per cent of disseminated graphite. Fis- 
 sure-veins are also found here, which yield a very pure 
 mineral, but it is said to be usually in quite limited 
 amounts. Graphite deposits have also been worked at 
 intervals in the Archaean rocks near St. John, New Bruns- 
 wick, and it is reported to occur in graphitic schists in the 
 Archaean area of northern Michigan, as also in some of 
 the Western Territories. The Island of Ceylon furnishes it 
 in immense vein deposits of singular purity at Travancore, 
 and from these the largest supplies of the world are de- 
 rived, although Austria and Bavaria produce annually 
 from 15,000 to 18,000 metric tons. The rocks in which 
 
REFRACTORY SUBSTANCES. 341 
 
 available graphite is most likely to be found are, there- 
 fore, those of Archaean age, though small amounts occur 
 in strata as late as the coal-measures. The famous de- 
 posit of Borrowdale in England, which is now no longer 
 worked, occurs in veins in interbedded trap ; and its 
 product was once sold at from $8 to $12 per pound, for 
 the manufacture of pencils, extraordinary precautions be- 
 ing taken to prevent theft. The present price of graphite 
 is from $25 to $200 per ton, according to its purity and 
 fineness. 
 
 The properties on which depend the important uses of 
 graphite in the arts are its infusibility, its unchangeable- 
 ness in the air, even when exposed to high heat, its soft, 
 unctuous texture, its ready conduction of electricity, and 
 its graphic quality, from which is derived its name graph- 
 ite, from the Greek grapho, I write. Of these, its in- 
 fusibility properly concerns us in this place ; but, for the 
 sake of completeness, its leading uses may be briefly 
 enumerated here, although some of them belong properly 
 in the succeeding chapter, where they will be referred to. 
 Fully one third of all the graphite that is produced is 
 used for refractory articles, such as small furnaces, nozzles 
 and stoppers for the Bessemer process, and crucibles for 
 melting steel, silver, copper, and brass. For these pur- 
 poses it should be free from lime and iron oxide, with 
 which it is liable to be contaminated ; since, for such 
 uses, it must be intimately mingled with a proper propor- 
 tion of fire-clay to give it strength, and the silica of the 
 clay would form fusible compounds with iron and lime. 
 Other large uses of graphite are for stove-polish, to pro- 
 tect iron articles from rust, and for foundry-facings, two 
 fifths of the product being employed for these purposes, 
 an additional amount being also used for glazing powder 
 and shot. A fourth highly important and increasing use 
 is for the lubrication of heavy machinery, in which it is 
 employed in the state of a fine powder, and in various 
 
342 APPLIED GEOLOGY. 
 
 patent greases. Its use in pencil-leads is familiar to every 
 one, besides which it is considerably employed in electro- 
 typing and for several minor purposes. 
 
 Although caustic lime is one of the most infusible as 
 well as most easily obtained of known substances, it is not 
 capable of being used in the large way as a refractory 
 material, because of the readiness with which it absorbs 
 water from the air and then crumbles to powder. It is, 
 however, used for constructing the small furnaces and 
 crucibles in which platinum is melted and refined by the 
 heat of the oxyhydrogen blow-pipe flame, a small but 
 quite important use. Caustic magnesia is also highly in- 
 fusible, and in Germany is converted into a very refrac- 
 tory brick, being cheaply obtained from the waste liquors 
 of the Stassfurt salts described in a preceding chapter, by 
 precipitation from its chloride by milk of lime, or by sub- 
 jecting the chloride to the action of an oxidizing flame 
 and superheated steam. A cheap and effective mode of 
 utilizing in the large way the refractory properties of a 
 combination of these two alkaline earths has recently 
 been devised, whereby the lime produced by calcining 
 strongly a somewhat silicious dolomite is made into a 
 paste with pitch, and then molded into bricks, or used 
 directly as a refractory lining for Bessemer converters. 
 By gradual heating, the pitch is burned out, and the re- 
 fractory earths are left in the shape required. This is the 
 so-called " basic lining," by the agency of which a consid- 
 erable percentage of phosphorus may be eliminated from 
 iron, rendering available, for steel-making purposes, iron 
 hitherto wholly unfit for this use. Magnesian limestones, 
 suitable for this purpose, are widely distributed among the 
 geological formations, and need no special mention in 
 this connection. It is said by Bloxam, on the authority of 
 Gilchrist, that the best composition of a magnesian lime 
 for the basic process is, lime, 52 per cent ; magnesia, 36 
 per cent ; silica, 8 per cent ; alumina and iron, 4 per cent. 
 
REFRACTORY SUBSTANCES. 343 
 
 Steatite, called commonly soapstone or potstone, is a soft, 
 compact, gray or greenish form of talc, and derives its 
 name soapstone from its soapy feel. In composition, it is 
 a hydrous silicate of magnesia, and is highly infusible, on 
 which account it is considerably used as a fire-stone in 
 hearths, stoves, and furnaces, and for register borders and 
 pipe-holes, as also in gas-jets and in several articles for 
 household purposes. It is found in the ancient crystal- 
 line rocks of the Atlantic border States, and is quarried 
 chiefly in Vermont and New Hampshire, though similar 
 deposits are known to occur in several other States. 
 
 Mica and Asbestus. The leading uses of these two 
 minerals are based upon their infusibility, coupled in the 
 one case with toughness and great transparency, and in 
 the other with a highly fibrous texture and a very slight 
 conductivity for heat. The only desirable variety of mica 
 is muscovite, in large transparent crystals, free from irreg- 
 ularities and accessory minerals. Such crystals occur 
 chiefly in veins of exceedingly coarse-grained granite, and, 
 as might naturally be expected, they are to be sought for 
 chiefly in regions of Archaean rocks, as along the Appala- 
 chian range, and in the vicinity of the Rocky Mountains 
 and the Sierra Nevadas. The chief production of mica 
 has hitherto been from western North Carolina, and from 
 the Black Hills, near Deadwood. In North Carolina, ac- 
 cording to the Geological Report of that State in 1875, the 
 mica occurs in veins of coarse granite with walls of gneiss, 
 in which are found rude crystals of mica weighing from 
 thirty to fifty pounds, and in a few instances even as 
 much as a thousand pounds, affording, occasionally, sheets 
 three feet across. The most profitable workings here are 
 on the sites of pits and galleries of some ancient race of 
 men. Similar ancient workings are reported by Prof. 
 Smith to exist at various points of eastern Alabama, giving 
 promise of merchantable mica in that State. The mica 
 from the Black Hills is reported to be of very fine quality, 
 
344 APPLIED GEOLOGY. 
 
 and plates of large size are sometimes produced. " The 
 main ledge is said to be fourteen feet wide, and to consist 
 of a central mass of feldspar and 'porphyry,' with a casing 
 of mica which varies in width from three to four feet on 
 each side. The country rock is granite." Mica is pro- 
 duced also in Maine and New Hampshire ; and a com- 
 pany with large capital is reported to have been lately 
 formed in Marquette to develop a promising mica prop- 
 erty in northern Michigan, and another in Chaffee County, 
 Col., for a like purpose. It is well to bear in mind that it 
 has been observed in North Carolina that, wherever horn- 
 blendic rocks or chloritic schists form the walls of the 
 mica-bearing veins, the mica is apt to be badly specked 
 with magnetite. The chief use of mica is for the trans- 
 parent plates of stoves and furnaces, and for lanterns, 
 some of the larger plates being also occasionally utilized 
 in surveyors' instruments in the place of glass. Finely 
 pulverized mica is also used as an absorbent of nitro- 
 glycerine in one variety of high explosives, and likewise 
 as a finish for wall-papers, and for some other ornamental 
 purposes. The price of sheet-mica varies at present from 
 twenty-five cents to five dollars per pound, according to 
 size and quality, exceptionally large and fine sheets bring- 
 ing even a higher price. 
 
 Asbestus affords a curious example of a mineral whose 
 leading properties have been known for many centuries, 
 and have caused it to be somewhat used by the ancients 
 for incombustible fabrics, which were objects of curiosity 
 rather than of practical utility ; yet whose important in- 
 dustrial capabilities have been neglected until very recent 
 years. It is a fibrous form of several minerals, like horn- 
 blende, pyroxene, and serpentine, is of a white, light 
 green, or brownish color, and is practically infusible by 
 the heat of ordinary fires. The most valuable kinds 
 occur in long, silky, parallel fibers, which are strong and 
 flexible, and capable of being spun like flax by proper 
 
REFRACTORY SUBSTANCES. 345 
 
 machinery, and woven into fabrics that are incombustible. 
 Hence its name, which is a Greek word applied to the 
 mineral with reference to this property. Other varieties, 
 in which the fibers interlace so as to form a kind of 
 natural felt, are called mountain leather and mountain 
 cork, while the fine, silky, fibrous variety is sometimes 
 called amianthus, from a Greek word meaning unpolluted, 
 because the fabrics woven from it, when soiled, may be 
 readily cleansed by passing them through fire. To be of 
 any considerable economic importance, asbestus needs to 
 have length and fineness of fiber, combined with tough- 
 ness and flexibility. These qualities are often lacking in 
 mineral which has a promising appearance, the fiber being 
 short, or brittle and harsh to the touch, making a sub- 
 stance of little or no value. Hence the expediency, when 
 a new deposit is discovered, of having the mineral care- 
 fully tested in respect to these qualities, before incurring 
 any considerable expense in working it. Asbestus is 
 found in regions of crystalline rocks, most commonly 
 associated with serpentine, occupying vein-like crevices 
 which are of uncertain and usually quite limited extent, 
 causing great difficulty in mining it with profit. The 
 finest is produced in the Italian Alps and in Corsica ; but 
 a considerable amount of asbestus of good quality is ob- 
 tained from the Province of Quebec, from several of our 
 Atlantic seaboard States, ranging from New York to 
 Georgia, and from some of the far Western States, es- 
 pecially California. Doubtless more diligent search with- 
 in our great areas of crystalline rocks, stimulated by the 
 rapidly growing demand for this mineral, will result in 
 many new discoveries, some of which may yield an article 
 equal in quality to the best Italian. 
 
 The uses of asbestus are based upon its fibrous text- 
 ure, its resistance to fire, and its very feeble conduction of 
 heat and electricity. It is most largely used for packing 
 the joints and working parts of steam-machinery ; for 
 
346 APPLIED GEOLOGY. 
 
 covering boilers and steam-pipes to prevent loss of heat 
 by radiation ; and as a fire-proof lining for floors and 
 ceilings, and for the walls of wooden buildings. For 
 some of these purposes it is spun into yarn by the aid of 
 special machinery, or woven into sheets and tape, with 
 the addition, for some uses, of India-rubber ; for others, it 
 is felted and pressed into sheets of a kind of paper called 
 mill-board, of any required thickness. In this latter form 
 it is used also as an insulator in dynamos. It is woven 
 into fire-proof cloth for the drop-curtains of theatres, for 
 furnace-men's aprons and leggings, and for other similar 
 purposes ; and it has been proposed to construct from 
 such cloth light fire-proof shields to protect firemen from 
 the heat of conflagrations. Twisted into cord and rope it 
 may be used for fire-escapes, since it has great tensile 
 strength. It has long had a limited use in incombustible 
 wicks for lamps, for which it is admirably adapted. It 
 is also used for making fire-proof cements and paints. 
 There is no reason to doubt that, with the probable in- 
 crease in the production and diminution in cost of this 
 useful mineral, there will be a large increase in its indus- 
 trial applications in the immediate future. 
 
 The United States production of asbestus in 1882 was 
 reported to be twelve hundred tons, and its average value 
 at the mines about thirty dollars per ton, varying from 
 fifteen to sixty dollars, according to quality, exceptionally 
 fine mineral commanding much higher prices than these. 
 
 With reference to the substances treated of in this chapter, the stu- 
 dent can profitably consult the following works, to which many others 
 might easily be added : Bloxam on Metals the chapter on " Refrac- 
 tory Materials " ; " New Jersey Report on Clay Deposits," 1878, and 
 Annual Report for 1880 ; " Ohio Geological Report," Vol. V ; " Geo- 
 logical Report of North Carolina," 1875 ; " Geology of Canada," 1863, 
 section vi of chapter xxi ; " Mineral Resources of the United States," 
 1883 ; also any good encyclopaedia ; and the files of the " Engineering 
 and Mining Journal," by the aid of its excellent indexes. 
 
CHAPTER XXI. 
 
 MATERIALS OF PHYSICAL APPLICATION. 
 
 A VERY considerable number of purposes, some of 
 which are sufficiently common and consequently of a high 
 degree of importance, are subserved by substances of geo- 
 logical origin by reason of their possession of certain 
 physical properties, as texture, hardness, and color ; little 
 previous preparation, and that of a purely mechanical 
 nature, being necessary to adapt them for their uses. 
 Such are the substances which are used for mending 
 roads and improving streets and walks ; for grinding vari- 
 ous kinds of grain as well as many minerals ; for giving a 
 keen edge to cutting instruments, and for imparting a fine 
 polish to wood, stone, and metals ; for drawing purposes, 
 and for the cheap and rapid reproduction of pictures ; for 
 diminishing friction ; for making molds for castings in 
 metal ; and for some other uses of analogous character. 
 The mere enumeration of these utilities is sufficient to 
 show how nearly some of them touch the comforts and 
 conveniences of civilized man ; how much others affect 
 the efficiency of his efforts ; and how intimately still 
 others concern his opportunities for refinement. 
 
 Materials for Roads and Walks. The commer- 
 cial rank and the industrial advancement of any commu- 
 nity are pretty fairly expressed in the excellence of its 
 means of communication, not merely by lines of railway, 
 but also by those more numerous and highly important 
 
348 APPLIED GEOLOGY. 
 
 avenues of travel and intercommunication which afford 
 ready access to every hamlet and every home. The im- 
 provement of country roads is usually effected by the 
 judicious use of those materials which are most easily 
 accessible in any given locality. In very many regions, 
 deposits of gravel, the accumulations of streams, and 
 sometimes of the ocean, or the relics of the glacial age, 
 afford a convenient means of improvement, which, from 
 the usual hard and silicious nature of the pebbles, is both 
 cheap and durable, making, with due preparation of the 
 foundations, and by proper arrangement of the coarser 
 and finer portions, excellent and enduring roadways. In 
 some few localities where gravel is not found, ledges of 
 conglomerate, not too closely cemented, may be acces- 
 sible, which, at some slight cost for crushing, may afford 
 excellent material for roads. In other cases, silicious 
 limestones of the vicinity, crushed by rock-breakers, or 
 broken to proper sizes with hammers, are used for road 
 purposes, needing occasional renewal on account of the 
 comparative softness of the stone. Harder and more en- 
 during material is afforded by the hornstone and chert 
 which occur at most of the exposures of the largely 
 quarried Corniferous limestone across the State of New 
 York and westward, and which are found accompanying 
 some of the limestones of the Lower Carboniferous age in 
 the Western States. In regions of crystalline formations, 
 rocks of the granite class quartzites, felstones, tough 
 porphyries, and still tougher traps may be made avail- 
 able for road-metal. All these rocks, of hard and tough 
 character, can be most cheaply reduced to sizes proper 
 for macadamizing roads by means of rock-crushers driven 
 by steam or water power ; and though the first cost of the 
 roads constructed from such materials may be somewhat 
 large, yet their convenience and durability, when once 
 properly made, will more than compensate for the original 
 outlay. In European countries, permanent roadways are 
 
MATERIALS OF PHYSICAL APPLICATION. 349 
 
 constructed from all the substances that have here been 
 enumerated ; their use is increasing in the more thickly 
 settled portions of our own country ; and there can be no 
 doubt that, ere long, a people so progressive and so prac- 
 tical as ours will become impatient at the too often 
 wretched condition of our roads, and will seek, in durable 
 rock materials, for a permanent means of improvement. 
 The need of previous careful drainage, and the prepara- 
 tion of a suitable foundation for a road, before using any 
 of these materials, has not been insisted on here, because 
 it is a matter which belongs rather to the road-engineer 
 than to the geologist. 
 
 For those streets of cities and large towns which are 
 devoted chiefly to residences, and which are little used 
 for transportation, macadamized roadways, properly con- 
 structed of materials such as have already been mentioned, 
 present the advantage of being comparatively noiseless 
 an advantage which may compensate in a good degree 
 for their liability to dust in dry weather. .But for streets 
 which are much used as thoroughfares for heavy traffic, 
 the road materials need to be employed in larger and 
 more solid forms, to secure stability under stress. For 
 this purpose, rectangular blocks of hard and tough varie- 
 ties of stone are used, arranged in courses, such width of 
 the blocks being best as affords the most convenient hold 
 for the feet of horses. A number of kinds of rock are 
 well adapted to this use, such as granites, hard sandstones, 
 quartz schist, felstone, trap, and porphyry. The granites 
 most suitable for pavements are those of medium fineness 
 of grain, in which quartz rather than feldspar is a domi- 
 nant ingredient, or those into which hornblende enters in 
 a considerable amount, those being naturally selected in 
 which a somewhat easy rift in certain directions facilitates 
 their reduction to proper shapes. Quartz schists, or those 
 highly silicious mica schists in which the mica is barely 
 
 in sufficient amount to impart a schistose structure, may 
 16 
 
350 APPLIED GEOLOGY. 
 
 be wrought with ease into good paving-blocks. Felstone 
 is also sometimes used for pavements where its structure 
 admits of easy working. These three kinds of paving ma- 
 terials may be obtained in those regions of Archaean rocks 
 which were described in the chapter on building-stones, 
 and which have since been several times mentioned. In a 
 number of our Northern cities, of which Rochester, Buffalo, 
 and Cleveland are examples, a silicious sandstone obtained 
 from the lower member of the Niagara period in western 
 New York, and called the Medina sandstone, from one of 
 the villages where it is largely quarried, is extensively used 
 for pavements, and is found excellent for this purpose. 
 In the region about Medina and Albion it is a hard, well- 
 cemented sandstone of extraordinary strength, susceptible 
 of being wrought without much difficulty into convenient 
 blocks, and of sharp grit, so that it shows little tendency 
 to become smooth by wear. In the northeast part of New 
 York, also, very hard silicious sandstones occur in strata 
 of the Potsdam period, which are admirably suited for use 
 in paving. In the immediate neighborhood of New York 
 city, at many points in Connecticut and New Jersey, and 
 in elongated belts of strata which stretch parallel to the 
 Atlantic border even to the boundary of South Carolina, 
 occur dikes of basaltic trap-rock which has a very exten- 
 sive use for paving-blocks. It is a hard, heavy, and very 
 tough rock, and makes pavements of unsurpassed dura- 
 bility ; but its tendency to become smooth and slippery 
 by wear renders it expedient to shape it into narrower 
 blocks than those which are commonly used. It is per- 
 haps needless to say that only those portions of the trap- 
 rock are fitted for this use whose structure admits of their 
 being easily split into the required forms. 
 
 It will be seen, therefore, that for all purposes of road 
 construction, a rock needs to be hard, that it may endure 
 wear ; tough, that it may not easily yield to blows ; of such 
 structure as to admit of being wrought without too great 
 
MATERIALS OF PHYSICAL APPLICATION. 351 
 
 expense ; and, if possible, of such texture as to remain some- 
 what rough in use. 
 
 The qualities which are desired in a material for the 
 construction of sidewalks, and for some other kindred 
 uses, are evenness of surface, closeness of texture to resist 
 the penetration of moisture, and a sufficient degree of 
 hardness to withstand the kind of wear to which it is to 
 be subjected. The ability to secure slabs of different di- 
 mensions and thickness, to adapt them to use under a 
 variety of circumstances, is also very desirable. These 
 qualities are well combined in what are called flag-stones, 
 which are even-bedded and somewhat argillaceous sand- 
 stones, occurring in sheets of from two to eight inches in 
 thickness, associated with shales and thicker bedded sand- 
 stones. Such flagging is largely quarried in beds of the 
 upper part of the Hamilton period and of the Lower Che- 
 mung (Portage group), near the Hudson River, in Ulster 
 and Greene Counties ; at the south end of Cayuga Lake 
 near Ithaca, in strata of the Chemung period ; in the 
 northern part of Wyoming County, Pa., in strata which are 
 referred by the Pennsylvania geologists to the lower part of 
 the Catskill period ; and near Warren, Ohio, in beds of the 
 Lower Carboniferous (Waverly group). Where such flag- 
 stones can not be obtained without too great expense, re- 
 sort is often had to thin-bedded or easily divided rocks of 
 other kinds. Thus, thin-bedded limestones are sometimes 
 applied to this purpose, though the surface is liable to be 
 somewhat uneven, and to become dangerously smooth by 
 use. In northern Ohio, soft sandstones, of Lower Car- 
 boniferous age, are split or sawed into slabs of proper 
 thickness, which, although somewhat porous and liable to 
 wear, make very handsome walks. In many localities, 
 sidewalks and sometimes roadways are constructed from 
 a concrete of fine gravel, pulverized limestone, and asphal- 
 tum, or of sand and hydraulic cement, which, when prop- 
 erly made, are very good. 
 
352 APPLIED GEOLOGY. 
 
 Asphaltum, for this purpose, is obtained chiefly from 
 the Island of Trinidad, and some also from Santa Barbara 
 County, Cal., which is used on the Pacific coast. The tar 
 from gas-works serves as a fair substitute for asphaltum 
 for this use. Many of the streets of Paris are paved with 
 a calcareous asphalt, obtained from Val de Travers and 
 elsewhere in Switzerland ; and this substance is also im- 
 ported into the United States to a considerable extent, to 
 be used in sidewalks and for coating roofs. The Geo- 
 logical Report of Canada for i88o-'82 announces the dis- 
 covery, on the Athabasca River, of a bituminous sand-rock, 
 which is probably suitable for walks and water-proofing. 
 It is worthy of consideration whether a valuable applica- 
 tion of such water-proof concretes could not be made in 
 the pavements of cities, especially on streets devoted to 
 residences, by using them as an impervious cement be- 
 tween the paving-blocks, thus preventing, at least in a 
 measure, the unhealthful emanations which arise in warm 
 weather from the putrefaction of organic matters, while at 
 the same time guarding against displacements by the 
 action of frost. 
 
 This enumeration of some of the leading geological 
 substances which are utilized for roads and walks may 
 serve as an indication of those physical properties of 
 rocks and minerals which best adapt them to such uses, 
 and may guide the inquirer to still other substances in his 
 own neighborhood that may be employed for a like pur- 
 pose. 
 
 Abrasives. What are here classed as abrasives are 
 those rocks and minerals which, by reason of their in- 
 trinsic hardness, or of certain grades of hardness and 
 texture, are used for sharpening all kinds of edge-tools, 
 for triturating grain and minerals, for polishing wood, 
 stone, and metals, and for rock-drills. These are, with a 
 single exception, wide-reaching as well as important uses, 
 affecting the convenience and efficiency of many arts and 
 
MATERIALS OF PHYSICAL APPLICATION. 353 
 
 trades, and some of them concerning every household. 
 And foremost among these in treatment as in importance 
 may justly be placed those substances used to give a keen 
 edge to cutting instruments, the grindstones and whet- 
 stones; for, not to speak of the many occupations which 
 owe much of their efficiency to the excellence and variety 
 of their edge-tools, there are few individuals who do not 
 find daily occasion to use such articles as knives and 
 scissors. 
 
 A better description could not well be given of the 
 conditions which must combine to make a good grind- 
 stone-rock than that of Dr. Dawson, in his "Acadian 
 Geology," p. 154: " These grindstones have been formed 
 from beds of sand, deposited in such a manner that the 
 grains are of nearly uniform fineness, and they have been 
 cemented together with just sufficient firmness to give 
 'cohesion to the stone, and yet to permit its particles to 
 be gradually rubbed off by the contact of steel. A piece 
 of grindstone may appear to be a very simple matter, but 
 it is very rarely that rocks are so constituted as perfectly 
 to fulfill these conditions." The infrequency of occur- 
 rence here spoken of is well exemplified in this country 
 and Canada, which, in all their vast area, have as yet de- 
 veloped but three or possibly four regions in which occur 
 strata of the proper quality to yield first-rate grindstones : 
 one, near the head of the Bay of Fundy in Nova Scotia ; a 
 second, in northern Ohio, near and west of Cleveland ; 
 and a third, at Point au Barques in Michigan. These are 
 all in strata of the Carboniferous age, and mostly in its 
 lower portion ; though one of the two geological horizons 
 which yield grindstones in Nova Scotia lies above the 
 productive coal-seams. Besides these localities, what is 
 called the "Gray Band," in the lower portion of strata of 
 the Niagara period (Medina group), in the Province of 
 Ontario, Canada, is said at some points to present the 
 characters requisite to make grindstones of good quality. 
 
354 APPLIED GEOLOGY. 
 
 It is interesting to observe that in England, also, most of 
 the rock which is used for grindstones is derived from the 
 grits of the Carboniferous age. Of this age are the grind- 
 stones quarried near Newcastle and Sheffield, as also in 
 Yorkshire and Staffordshire, and at a few other localities. 
 It would seem that in this age, more frequently than in 
 the others,' conditions were presented favorable for the 
 formation of an even-grained, homogeneous sand-rock, not 
 too closely cemented. 
 
 Rock suitable for the manufacture of whetstones and 
 hone3 is composed of some very hard mineral, like quartz, 
 and occasionally garnet, in the condition of fine, even 
 grains, cemented to a firm mass. If the grains are some- 
 what coarse, the stone cuts down instruments rapidly, but 
 gives a coarse edge. In the best honestones for delicate 
 instruments, the grain is almost imperceptibly fine. The 
 finer-grained and stronger portions of grindstone-rock are 
 wrought into a coarser kind of whetstones for sharpening 
 farm implements and other tools, in which a fine, smooth 
 edge is not required. Stones of similar character but 
 tougher fiber are made from mica schists or slates which 
 contain, thoroughly disseminated, a large proportion of 
 fine-grained silica. Such is the rock which is manu- 
 factured into whetstones in the southern part of Quebec 
 on Lake Memphremagog, at Bridgewater, Vt., and doubt- 
 less at other points in regions of mica slates. Whetstones 
 for finer uses are made from varieties of very fine-grained 
 silicious slates called nov acuities, some of the most valued 
 among which are nearly pure quartz in an excessively 
 minute state of division, and cemented by silica. Such is 
 the Arkansas or Ouachita oilstone obtained at the Hot 
 Springs of Arkansas, which, according to two different 
 analyses, contains from 98 to 99^- per cent of silica. This 
 rock is of the age of the Lower Carboniferous, and, ac- 
 cording to Dr. Owen, it owes its snowy whiteness and its 
 impalpably fine grain to the long-continued action of hot 
 
MATERIALS OF PHYSICAL APPLICATION. 355 
 
 silicious waters. The finest of these stones are known to 
 the trade as Arkansas oilstones, while those of somewhat 
 coarser grain are sold at much cheaper rates as Ouachita 
 stones. The Turkish oilstones are also highly esteemed, 
 their grain being slightly less fine than that of the best 
 Arkansas stone. The very superior yellow Belgian hone- 
 stones owe their fine quality to microscopic garnets set in 
 a garnet paste. 
 
 For the grinding of grain, almost any hard, tough, 
 sharp-grained rock will serve fairly well, and several kinds 
 of rock of this character have been and still are employed 
 locally for this purpose, some of which have even more 
 than a local use. Thus, tough, coarse-grained gneisses, 
 and some firmly cemented conglomerates, are so em- 
 ployed. A white, hard, sharp-grained sandstone, of sub- 
 Carboniferous age, found at Peninsula, O., is used near 
 where it is found, and also sent elsewhere, for preparing 
 oatmeal and for pearling barley, for which purposes it ap- 
 pears to be specially fitted. A basaltic lava, found in 
 Germany, is used for millstones, especially for grinding 
 minerals, because of its peculiarities of texture. The 
 rock, however, which is most suitable for millstones of 
 any yet known, is a highly cellular quartz-rock called 
 buhrstone. That which has the highest reputation, and is 
 most largely used, is obtained from the vicinity of Paris, 
 France, from rocks of earlier Tertiary age. It is of fresh- 
 water origin indeed, often contains great numbers of si- 
 licified fresh-water shells, and in the best portions the 
 cellular spaces occupy more than one third the bulk of 
 the stone. Its superiority is due to its cellular structure 
 and its hardness. The stone is cut into blocks of proper 
 form, which are fitted together and held to their place by 
 iron bands to form millstones. Rock of similar charac- 
 ter, and in strata of about the same geological age, is 
 found also in South Carolina, Georgia, and Alabama. 
 The use of millstones in making flour has been, to a con- 
 
356 APPLIED GEOLOGY. 
 
 siderable extent, superseded in large flouring establish- 
 ments by that of iron rollers ; but for other purposes, and 
 in most small mills, there is likely to be always a wide de- 
 mand for stones to be used in grinding. There will be 
 needed here no more than an allusion to the use of stone 
 in heavy wheels for pulverizing clays, quartz, and other 
 minerals as well as ores, and for some pulping purposes ; 
 and the much ruder use of heavy stone blocks, dragged 
 round and round on a pavement of stone, for grinding 
 ores in the arrastra. 
 
 For the rapid grinding, cutting, drilling, and polishing 
 of the harder rocks and minerals and of steel, resort is 
 had to the hardest of known minerals, the diamond and 
 corundum, or to the impure and somewhat less hard but 
 tougher variety of the latter mineral called emery. The 
 diamond, because of its rarity and great cost, is confined 
 to special uses. Small crystals and angular fragments are 
 firmly cemented into handles to be used in cutting and 
 ruling glass, in drilling and cutting rubies, sapphires, and 
 some other gems, and for the fine dressing of millstones. 
 Diamond drills, used for prospecting mineral deposits and 
 veins at considerable depths, are made by cementing 
 small diamonds around the edge of a hollow cylinder of 
 steel. This, being swiftly revolved by machinery, not 
 only cuts rapidly through rocks, but also enables the 
 miner to bring up from various depths a solid cylindrical 
 core of rock for examination. For this purpose, black 
 diamonds, not suited for jewelry, are used, called borts, 
 carbons, or carbonados. They are procured, it is said, 
 chiefly from the Brazilian diamond regions. Other dia- 
 monds of inferior quality are used for the other purposes 
 that have been named, or crushed to fine powder to be 
 used for cutting and polishing the harder gems and the 
 diamond itself. 
 
 The mineral corundum, which is inferior only to the 
 diamond in hardness, in the condition of transparent crys- 
 
MATERIALS OF PHYSICAL APPLICATION. 357 
 
 tals of various colors furnishes the gems sapphire, ruby, 
 emerald, etc. That which is used as an abrasive is most 
 commonly gray and imperfectly transparent, and is of no 
 value as a gem. It has been found in the Appalachian 
 region of the United States at many localities, the most 
 important of which are in Clay and Macon Counties, N. C., 
 and Chester County, Pa. Masses of corundum are said 
 to have been found in Clay County, N. C., weighing from 
 three to six hundred pounds, associated with the olivine 
 rock of that region. It is estimated that about five hun- 
 dred tons are produced annually by the United States. 
 Emery, which is an impure form of corundum contaminated 
 with varying amounts of iron oxide, whence it derives its 
 dark color, is obtained chiefly from near Smyrna, in Asia 
 Minor, where it occurs in considerable masses, and from 
 the island of Naxos. It has also been mined at Chester, 
 Mass. Both corundum and emery are pulverized to a 
 powder of different degrees of fineness for different pur- 
 poses, and sold, under the name of emery, for polishing 
 glass and the harder kinds of stone and metals, a large 
 part of the price at which it is sold being due to the labor 
 of reducing to fine powder minerals of such hardness. 
 The powder of emery, though not so hard as that of pure 
 corundum, and hence not abrading so rapidly, is said to 
 be less brittle and so more durable. What are called em- 
 ery-wheels, so largely used in machine-shops for grinding 
 and polishing iron and steel, are made by mixing powdered 
 emery into a paste with water-glass, fire-clay, or some other 
 cementing material, then molding into the proper shape 
 and baking. Emery-paper is made by cementing emery- 
 powder to stout paper with glue. Sand-paper, to be used 
 for polishing wood, is made in like manner from sharp* 
 quartz sand. 
 
 Sand is also largely used -as an abrasive in sawing and 
 rubbing to a smooth surface marble and sandstone. Other 
 mineral substances, which are utilized for polishing wood 
 
358 APPLIED GEOLOGY. 
 
 and stone, bone and ivory, as also metallic articles, are 
 pumice and tripoli. Pumice is a light, porous, felspathic 
 lava which is brought chiefly from the neighborhood of 
 Mount Vesuvius and the Lipari Islands, but is said to 
 occur abundantly also in San Francisco County, Cal. 
 Tripoli is a silicious, infusorial earth of very fine grain 
 which is found near Richmond, Va., and Monterey, Cal., 
 as also in Nevada and at a number of foreign localities. 
 Tripoli has also been somewhat used as an absorbent of 
 nitro-glycerine in making dynamite. 
 
 Graphic Materials. What have been thus grouped 
 in this place are those geological substances which, by 
 reason of their texture, softness, color, and some other 
 properties, are used with no other than a mechanical prepa- 
 ration for making, or for receiving and transferring, draw- 
 ings and writings. As is well known, great improvements 
 have been made within the present century in the adapta- 
 tion of means for these purposes, whereby the multiplica- 
 tion of writings and of works of art has been greatly facili- 
 tated and cheapened, to the great advantage of business, 
 while bringing within the reach of all classes of people 
 better means for cultivating a refined taste, and for the 
 illustration of subjects otherwise difficult of comprehen- 
 sion. Some portion of this improvement has been due to 
 the discovery, or adaptation and preparation, of geological 
 substances, such as graphite, chalk, steatite, and litho- 
 graphic limestone. Graphite, the mode of occurrence and 
 localities of which have been given in the preceding chap- 
 ter, has long been used in pencils for drawing and writing, 
 being sawed into slender prisms from blocks of granular 
 graphite ; and for this use that of Borrowdale, England, 
 had a special value, being pure and of granular texture. 
 Now, however, purified graphite, in a fine state of divis- 
 ion, is either compressed intp solid masses by hydrostatic 
 pressure, to be afterward sawed into pencil " leads," or else 
 mingled into a paste with certain proportions of the finest 
 
MATERIALS OF PHYSICAL APPLICATION. 359 
 
 clay, run into molds, dried, and heated to such tempera- 
 tures as are needful to secure the degrees of hardness 
 which are requisite for different purposes. Chalk, so 
 largely used in crayons for school and other purposes, is 
 a soft, white, earthy limestone, composed of the calcareous 
 skeletons of microscopic organisms. This forms nearly 
 the uppermost deposit of rocks of the Cretaceous period 
 in southern England and northern France, where it covers 
 considerable areas. Because of its peculiar soft and fria- 
 ble condition it is easily pulverized and molded into proper 
 shapes, either alone or mingled with various coloring in- 
 gredients. Its physical condition fits it also to be used in 
 some porcelain mixtures, and to be mingled with a proper 
 proportion of clay for burning into hydraulic cements. 
 The so-called red chalk, used for graphic purposes, is an 
 argillaceous ochre, i. e., a soft, earthy form of red iron 
 oxide mingled intimately with clay, which occurs in re- 
 gions of iron-ores. The massive granular form of talc, 
 called steatite and soapstone (see preceding chapter), is 
 used, under the name of French chalk, for marking on 
 cloth, and in crayons for drawing in fine white lines on a 
 dark ground ; and pyrophyllite, a soft, aluminous silicate, 
 closely resembling talc in its light colors, its softness, and 
 its greasy feel, is much used for slate-pencils. The latter 
 occurs in the Archaean slates of Georgia and both Caro- 
 linas, and near Little Rock, Ark. 
 
 The very important graphic material known as litho- 
 graphic limestone is a very fine-grained, compact, and per- 
 fectly homogeneous limestone, of conchoid fracture, and 
 usually of a pale-gray or yellowish tint, and having a suf- 
 ficient degree of porosity to slightly absorb water and oil. 
 On the smoothed or finely granulated surface of such a 
 stone, drawings are executed with a properly prepared 
 greasy pigment, called lithographic chalk and lithographic 
 ink, or such drawings may be transferred to it from spe- 
 cially prepared paper. The stone absorbs the greasy draw- 
 
360 APPLIED GEOLOGY. 
 
 ing material sufficiently to retain it firmly, and, if it now 
 be moistened with water, all except the greasy portions 
 absorb the water and become wet. A roller charged with 
 the oily printer's ink, passed over the moistened stone, will 
 now wet only the greasy lines of the drawing, which may 
 then be printed from as from an engraving. Limestones 
 possessed of this peculiar combination of characters are 
 very rarely met with. Hitherto they have been obtained 
 wholly from certain thin-bedded limestones of the upper 
 part of the Jurassic period at Solenhofen, Bavaria, a local- 
 ity famous also for the remarkably preserved fossils which 
 it affords. Limestone of the required quality is, however, 
 reported to occur in strata of the Trenton period in Mar- 
 mora, Hastings County, Ontario, and in a yellowish dolo- 
 mite of the Salina period on the Saugeen River in Bruce 
 County, of the same province. It is said, also, that litho- 
 graphic limestones in small slabs may be obtained at some 
 localities in the Lower Carboniferous limestone of Mis- 
 souri, portions of which, however, are apt to show spots of 
 different texture, and so to be worthless. 
 
 Pigments. A great majority of the pigments that 
 are in common use are derived from the metals by chemi- 
 cal processes, and hence have already been mentioned in 
 their proper places among the useful applications of the 
 metals from which they are derived. Such, for example, 
 are the various pigments manufactured from lead, zinc, 
 chromium, mercury, arsenic, antimony, copper, and cobalt. 
 Besides these, however, there are some other substances 
 which, with no other than a mechanical preparation, are 
 used as cheap pigments. Thus, graphite, so largely utilized 
 for other purposes that have been mentioned before, is also 
 somewhat used as a black paint. Finely pulverized chalk, 
 under the name of whiting and Spanish white, is used as a 
 white or tinted wash for walls ; and caustic lime is also 
 widely employed for the same purpose. Besides these 
 substances, which have already been described in other 
 
MATERIALS OF PHYSICAL .APPLICATION. 361 
 
 connections, ochre, umber, and barytes have a large use as 
 pigments. Ochre is a soft, pulverulent form of hydrated 
 peroxide of iron, mingled usually with more or less con- 
 siderable proportions of clay, silica, and organic matter, 
 and affording various shades of yellow, red, and brown. 
 It occurs in deposits of various geological ages, and often 
 as superficial accumulations of recent periods. Thus, the 
 softer earthy portions of some hematite beds are ground 
 and used as pigments, called iron paints. The ochre de- 
 posits of Great Britain are found chiefly at the base of the 
 Cretaceous system, while the extensive beds of ochre along 
 the St. Lawrence in Canada are superficial deposits which, 
 in some cases, are interstratified with peat, and have been 
 accumulated by the solvent action on iron compounds of 
 organic acids resulting from vegetable decomposition, and 
 the subsequent deposition of the iron oxide by atmospheric 
 oxidation. Ochre is procured also from the muddy fer- 
 ruginous waters pumped from mines. Its color may be 
 greatly modified by calcination, thus driving off its water 
 of hydration. Beds of red and reddish-brown clay-rocks, 
 colored by iron oxide, are also ground and used as a cheap 
 paint. Umber is a soft, earthy variety of ochre, which is 
 colored brown by oxide of manganese, and becomes red- 
 dish brown by calcination. It occurs usually in crystalline 
 rocks, and is brought mostly from the island of Cyprus. 
 It is found, also, at a few localities in Great Britain, and 
 is said to be produced to some extent in this country. 
 
 The mineral barytes, called also heavy spar, because of 
 its great specific gravity, is a white crystalline or massive 
 sulphate of baryta, of about the same hardness as calcite, 
 and is fusible by the blow-pipe, giving a green color to the 
 flame. On account of its great weight, it is little liable to 
 be mistaken for any other white mineral save celestite, 
 which has nearly the same weight and hardness ; and from 
 this, the color imparted to the blow-pipe flame readily dis- 
 tinguishes it, that of celestite being a bright red. It oc- 
 
362 APPLIED GEOLOGY. 
 
 curs commonly as a vein-stone, especially in veins of lead 
 and copper. It is found in workable quantities at quite a 
 number of localities in North America ; as in the copper 
 veins on the north shore of Lake Superior ; in the central 
 Missouri lead region, especially in Miller and Morgan 
 Counties; in several counties of East Tennessee, being 
 worked in some; and in Wythe, Smyth, and Campbell 
 Counties, Va., a single mine in the county last named be- 
 ing reported to be able to produce a hundred tons per 
 day. Considerable amounts are produced also in Penn- 
 sylvania and Maine. The largest production is from 
 Missouri and Virginia ; Connecticut grinds also a large 
 amount of barytes imported from Germany. About 
 twenty-five thousand tons a year are mined in the United 
 States, of which much the largest part is used for mixing 
 with white lead and zinc white, in the preparation of 
 white paint. This employment of barytes is commonly 
 considered an adulteration, and manufacturers do not 
 seem eager to publish the fact of its use ; yet, when 
 properly prepared, it produces a good opaque white color, 
 which is not, like lead, liable to discoloration from sul- 
 phuretted hydrogen. 
 
 Lubricators. The mineral substances which are 
 most largely employed for diminishing friction in ma- 
 chinery, viz., graphite and the heavy varieties of petroleum, 
 have already been mentioned in other connections as fitted 
 for this use. The foliated varieties of talc, when free from 
 needles and grains of the harder minerals, are also used to 
 a considerable extent in lubricating compositions. This 
 last-named mineral, which, like soapstone, its massive form 
 from which it is distinguished commercially, occurs in 
 crystalline schists, is found in several of the States of the 
 Atlantic border most largely in Georgia, Pennsylvania, 
 New York, and Vermont. The fibrous form of this miner- 
 al, which is found in considerable quantities near Gouver- 
 neur, N. Y., is quite largely mined and ground for pulp to 
 
tSE- 
 
 -^ 
 
 MATERIALS OF PHYSICAL APPLICA%$^ \^' 
 
 ' 
 
 be used in paper-making. It may readily be judged that 
 only the fibrous variety could be used for this purpose, 
 since only this has any staple to form a felt ; and the St. 
 Lawrence mineral may, it is said, enter into printing paper 
 to the extent of twenty per cent, or even more. Talc has 
 also a quite extensive use in soap-making, and in dressing 
 skins and leather, these various applications rendering it a 
 mineral of considerable economic importance. In the 
 " Geological Report on the Midland Counties of North 
 Carolina," 1856, Prof. Emmons speaks of a valuable anti- 
 friction hornstone as abounding in several counties of 
 that State. This rock, probably a felstone, since it gradu- 
 ated into porphyry, was of flinty aspect and very fine and 
 compact texture, and was highly valued locally as a bear- 
 ing for the axles of heavy wheels. From its fine texture 
 and great hardness, this distinguished geologist pro- 
 nounced it to be fitted to take the same part in diminish- 
 ing the friction of heavy machinery that rubies play in the 
 works of watches. 
 
 Molding-Sand. This substance, which is of so 
 much importance for foundry use, is an intimate mixture 
 of quartz sand with just sufficient proportions of clay and 
 ochre to enable it to retain the form given by the pattern, 
 and to withstand in founding the current of molten metal 
 without displacement. If the proportions of the cohesive 
 substance are too small, even if the mold retains its form 
 before it is used, it is apt to wash, i. e., to be swept away 
 in places by the flowing metal, and so to cause irregulari- 
 ties in the casting, or to ruin it wholly. If, on the other 
 hand, there is more clay than is needed, it is burned in the 
 founding, and forms a crust on the casting which is some- 
 what troublesome to remove. A good sand for molder's 
 use should contain about 92 per cent of fine quartz sand, 
 6 per cent of clay, and 2 per cent of iron oxide. The 
 fineness and delicacy of the impression that can be given 
 will depend on the fineness of the sand that is present in 
 
364 APPLIED GEOLOGY. 
 
 the molding mixture. For some very fine castings, an 
 artificial mixture is prepared by calcining loamy sand, 
 grinding it very fine, and adding some substance to impart 
 the necessary adhesiveness. Good molding-sand is of a 
 yellow color, soils the fingers when dry, and when damp, 
 if grasped in the hand, it retains a delicate impression of 
 the fingers. It occurs in superficial deposits, usually of 
 no great thickness, and is liable to great variations in 
 quality at points little removed from each other. Mold- 
 ing-sand is by no means of common occurrence, and the 
 foundries of very considerable sections of country are 
 often obliged to depend for their supplies on material 
 brought from a distance. Saratoga County, N. Y., fur- 
 nishes a molding-sand of fine reputation and of various 
 qualities fitted for special purposes, which is transported 
 to long distances. Good sand for this purpose is found 
 at some localities in New Jersey, from which supplies are 
 sent to the Southern seaboard States. Tompkins County, 
 N. Y., has a fair quality of sand which supplies the local 
 demand for ordinary foundry uses. For some purposes, 
 as for large castings in bronze, molding-sand is even im- 
 ported from Europe. For the facing of molds, called 
 foundry facings, graphite is largely used, as has already 
 been said. A cheaper facing, and one which, for some 
 purposes at least, is less liable to wash, is afforded by 
 hydraulic lime. 
 
CHAPTER XXII. 
 
 ORNAMENTAL STONES AND GEMS. 
 
 A TREATISE which is intended to present any just view 
 of the contributions which geology makes to the supply of 
 the multifarious wants of mankind, can not omit some ac- 
 count of those substances which, while not ministering to 
 man's necessities, nor promoting his comfort, nor increas- 
 ing the efficiency of his efforts, are nevertheless strongly 
 desired by him as a gratification to his tastes, as the ex- 
 pression of his wealth and social consequence, or as fitted 
 to be fashioned into the most permanent monuments of 
 his culture and refinement ; objects which, though not 
 necessary, are yet essential, because without them some- 
 thing would be lacking for the complete satisfaction of his 
 many-sided nature. Man loves beauty and craves orna- 
 ment, and all that ministers to this sentiment and craving 
 is more elevating in its tendency than what satisfies merely 
 his bodily wants. Many of the substances which are 
 drawn from geological sources lend themselves to these 
 higher wants of mankind by their durability, combined 
 with their beauty, their brilliancy of color or of luster, and 
 often their rarity. Several of them are found in consider- 
 able abundance, and a great part of the estimation in 
 which they are held is due to their adaptation to the pur- 
 poses of refined and artistic workmanship. Such are the 
 ornamental stones, the objects wrought from which usually 
 far surpass the raw material in value. Others add to 
 
366 APPLIED GEOLOGY. 
 
 beauty of color and brilliancy of luster a greater or less 
 degree of hardness and of rarity, and, while gratifying the 
 taste of their possessor, become in a certain degree badges 
 of his wealth and importance. Such are the gems, a large 
 part of whose value is usually intrinsic, i. e., dependent in 
 but a minor degree on excellence of workmanship. 
 
 Ornamental Stones. On account of the hardness 
 and unalterability of the mineral, the various forms of 
 quartz have, for many centuries, been used for ornamental 
 purposes. The transparent varieties were fashioned by the 
 ancients into crystal cups and vases, and set in jewelry. 
 Its use for most such purposes is now largely superseded 
 by that of the finer kinds of glass, which are more brilliant 
 and cheaply formed, but more liable to be marred in use 
 because of their inferior hardness. Clear white quartz has 
 a considerable use in lenses and for spectacles ; and un- 
 der such names as Rhine-stone and California diamond, 
 quartz is still quite largely cut and polished for cheap 
 jewelry, that which is of a clear yellow color figuring as 
 false topaz, and that of a smoky tint as Cairngorm-stone. 
 The purple variety of quartz called amethyst, when trans- 
 parent crystals of sufficient size and proper depth of color 
 are met with, is cut for valuable jewelry. Much, however, 
 that is sold under these various names is artificial, being 
 made from strass. Handsome crystals and clusters of 
 crystals of quartz are held in some estimation as house- 
 hold ornaments. Fine specimens for this purpose are 
 found at the Hot Springs of Arkansas, and in Herkimer 
 County, N. Y. ; as also frequently in regions of Archaean 
 rocks. The most valued amethysts are brought from 
 India, Ceylon, Siberia, and Brazil ; and they are found 
 also on Keweenaw Point, and in some of the Eastern 
 States, but seldom good enough for jewelry. The massive 
 translucent varieties of quartz with waxy luster, and es- 
 pecially those which present alternating bands and spots 
 of different colors and shades of color, due to impurities 
 
ORNAMENTAL STONES AND GEMS. 367 
 
 introduced during the successive deposition of the layers 
 from silicated waters, make very handsome ornamental 
 stones, and are wrought into a variety of beautiful objects, 
 such as vases, cups, boxes, necklaces, seals, buttons, knife- 
 handles, and small columns for cabinets ; or they are 
 merely cut and polished to display their spots and bands 
 of color, and used for mantel and cabinet ornaments. 
 Varieties of milky and bluish tints are called chalcedony, 
 abundant in geodes in Iowa and Illinois ; of bright, rich 
 red, carnelian, brought from the East Indies ; of concen- 
 tric and often zigzag bands of color, agates, found on Lake 
 Superior ; of smoky tints, containing moss-like figures in 
 metallic oxides, moss-agates, occurring in the Rocky 
 Mountain region ; and of flat, parallel layers of white and 
 black or brownish shades, onyx and sardonyx. These last 
 are the materials in which are cut miniature articles of 
 sculpture called cameos, in which the alternation of layers 
 of different colors is dexterously made to heighten the 
 effect, and in the art of cutting which the ancients had 
 attained as great skill as is displayed by modern artists. 
 The opaque red, yellow, and green variety of quartz, called 
 jasper, when it occurs in bands of different colors, is val- 
 ued for ornaments like vases, handles, boxes, and small 
 cabinets, and especially for mosaics and inlaid work. 
 Handsome varieties are found in Calaveras County, Cal. ; 
 Graham County, Kan. ; near Troy, N. Y. ; and at Chester, 
 Mass. 
 
 Some of the varieties of feldspar also afford orna- 
 mental material. Thus sunstone, a yellowish or grayish 
 feldspar, containing minute scales of mica, and moonstone, 
 a milky opalescent feldspar with pearly reflections, are cut 
 for jewelry ; and labradorite, a dark-gray or brown feld- 
 spar, which when polished often presents a beautiful play 
 of bright bluish and greenish colors from internal reflec- 
 tions, is a handsome material for ornamental uses. The 
 last-named mineral is obtained of good quality from Lab- 
 
368 APPLIED GEOLOGY. 
 
 rador, whence its name, being also found in northern 
 New York ; while the first two occur in Amelia County, 
 Va., and Delaware County, Pa. Moonstone is brought 
 also from Ceylon, and sunstone from Norway. The feld- 
 spars used for ornament occur in regions of .crystalline 
 rocks. The tough, heavy, compact, and translucent stone, 
 called nephrite and jade, of green and blue colors, obtained 
 from China, India, Siberia, Alaska, and New Zealand, is 
 used for making carved ornaments, for which purpose it 
 has long been held in high estimation by the Chinese. 
 Lapis lazuli, a mineral usually compact and of rich blue 
 color, occurring in the ancient crystalline rocks of Persia, 
 China, Siberia, and Thibet, furnishes a valued material for 
 objects of luxury, like vases, rich mosaics, and the inlaid 
 work of costly furniture, besides being used in jewelry. 
 When powdered, it becomes the costly blue pigment, 
 ultramarine, which is now, however, prepared artificially 
 at much smaller expense than that from the native min- 
 eral. 
 
 The use of malachite, the green banded carbonate of 
 copper, in magnificent inlaid furniture, has already been 
 mentioned in the chapter on copper. It is a common ore 
 of copper in our Southwest Territories ; but large concre- 
 tionary masses, fit to be cut for ornamental uses, are not 
 often met with, the Ural Mountains being still the chief 
 source of supply for such purposes. 
 
 The fluoride of calcium, called fluor-spar and Derby- 
 shire spar, which occurs both massive and crystalline as a 
 vein-stone in many veins, especially those of lead, when 
 transparent, and of fine colors, such as green, purple, and 
 red, is sometimes wrought into ornamental articles, like 
 vases, snuff-boxes, and candlesticks. Derbyshire, England, 
 affords a handsome blue fluorite, whence the mineral has 
 derived one of its common names. Fluorite fit for orna- 
 mental uses is said to be found in Hardin County, 111., 
 and in Colorado. The chief use of the mineral, however, 
 
ORNAMENTAL STONES AND GEMS. 369 
 
 is for a flux in metallurgical operations, and as a glaze for 
 pottery. A hard, compact, and lustrous variety of brown 
 coal, which admits of a high polish, is used on this ac- 
 count, and because of its black color, for personal orna- 
 ments, especially mourning jewelry, under the name oijet. 
 It occurs abundantly in El Paso County, Col., and at 
 some localities in Texas ; also in England (Whitby be- 
 ing a celebrated locality), in France, and in Spain. Like 
 the lignites and brown coals, jet occurs in the later geo- 
 logical deposits, the Tertiary and Upper Cretaceous ; and 
 like these, also, it is very light when compared with other 
 minerals, by which character it may easily be distinguished 
 from its imitations made of glass. 
 
 Another very light mineral substance, largely used for 
 small ornamental objects, is amber, a transparent fossil 
 resin of yellow and orange colors, frequently inclosing in- 
 sects. It occurs in irregular lumps in the Tertiary beds 
 of several European and Asiatic localities, and on the 
 Atlantic borders of Massachusetts and New Jersey ; but 
 much the most important source of supply is the Baltic 
 coast, chiefly of Prussia, where it is washed out of its con- 
 .taining strata and thrown on the shore by the action of 
 the waves. It is manufactured into ornaments for the 
 person, such as ear-pendants, bracelets, necklaces, and 
 brooches, and into boxes, mouth-pieces for pipes, and han- 
 dles for canes and paper-knives. As its weight is less 
 than half that of an equal bulk of glass, this character, as 
 well as its softness, affords an easy means of distinguishing 
 it from imitations. 
 
 The ornamental employment of marbles in the interior 
 decoration of houses has already been mentioned under 
 building-stones ; but, aside from this, a large use of mar- 
 bles of fine texture and pleasing and varied colors is made 
 in the ornamentation of articles of furniture and in sculpt- 
 ure, one of the noblest of the fine arts. For the latter 
 purpose marble is required which is of fine and even text- 
 
370 APPLIED GEOLOGY. 
 
 lire, free from any foreign minerals, and of a pure and 
 uniform white color. Such marble is of rare occurrence, 
 and hence the celebrity of some of the marbles of Italy 
 and Greece, those of Carrara and Paros. What is called 
 onyx marble is a translucent stalagmite, prettily banded 
 with different light shades, and obtainable in masses of 
 considerable size. It is a beautiful material for ornamental 
 purposes, and may be wrought into many pleasing objects. 
 Attention has recently been called to it by large specimens 
 from Algiers and Mexico, exhibited at some of the World's 
 Expositions. Alabaster, a compact, translucent variety of 
 gypsum, and verd-antique marble, a rock composed of green 
 serpentine and white calcite, are also used in ornamental 
 work. 
 
 Mention should also be made here of the porphyries, 
 hard and tough varieties of rock, made up of a very fine- 
 textured felspathic base inclosing well-defined crystals* 
 usually of feldspar. Where the base and inclosed crystals 
 are of pleasing and finely contrasted colors, as dark red, 
 green, and white, this rock, from its susceptibility to high 
 polish, has in all ages been an admired material for orna- 
 mental objects, such as vases, caskets, columns, parts of 
 furniture, and handles of knives. The antique red and 
 green porphyries have an ancient celebrity. As porphyry 
 is of volcanic origin, its geological position is naturally in 
 dikes ; and material suitable for ornamental uses is more 
 likely to occur in those which cut rocks of great geological 
 antiquity. 
 
 Gems. The minerals which, from their transparent 
 brilliancy, their beauty of color, and their hardness, coup- 
 led with their rarity, are held in esteem as gems are but 
 few in number, not more than a dozen in all. They are 
 the diamond, corundum, spinel, topaz, beryl, zircon, gar- 
 net, tourmaline, spodumene, turquoise, and opal, some even 
 of these holding but a doubtful place in a list of gems, 
 although occasional examples of uncommon size and beau- 
 
ORNAMENTAL STONES AND GEMS. 371 
 
 ty sell at a considerable price. Of these, only the trans- 
 parent varieties, and those of pleasing and uniform colors, 
 have any considerable value as gems, some others being 
 utilized on account of their hardness, like the black dia- 
 mond and bort, and the gray and black corundum, or 
 being valued merely as mineralogical specimens. With 
 the exception of the opal, which occurs in nests and veins 
 in volcanic rocks like the rhyolites, all the gems have their 
 birthplace in the ancient crystalline rocks, although several 
 are most commonly met with in alluvial deposits formed 
 from the ground-up and assorted debris of such rocks. 
 Where used as gems, all are transparent save turquoise, 
 which is opaque, and opal, which is usually merely trans- 
 lucent. They range in hardness from the diamond and 
 corundum, which scratch all other minerals, to opal and 
 turquoise, which may be scratched by quartz ; all but the 
 last two can therefore be easily distinguished from their 
 glass imitations by their superior hardness, since that of 
 the brilliant variety of glass called strass or paste, from 
 which imitation gems are made, is not more than 5 on 
 the scale of hardness, while that of the softest gems is 6, 
 and of quartz 7. Hardness is essential in gems, since, 
 though entailing greater expense in cutting, it preserves 
 their colors and polish undimmed for ages. A few of the 
 gems are colorless, like the diamond, and occasionally the 
 topaz and zircon ; but most of them present various clear 
 shades of red, green, blue, and yellow ; and some of them, 
 like corundum and beryl, afford gems of several different 
 colors which bear different names. The carat, in which 
 the weight of many precious stones is reckoned, is a con- 
 ventional weight, equal, according to Ure, to about 3.88 
 grains troy, although sometimes used as no more than 3.1 
 grains. Gems are cut, according to their nature and shape, 
 in four different styles, of which the brilliant consists of a 
 truncated double pyramid, the truncated ends being octa- 
 gons, and the sides made up of a combination of triangular 
 
372 APPLIED GEOLOGY. 
 
 and rhomboid or pentagonal facets ; the rose cut has a 
 flat base surmounted by a pyramidal dome, made up usu- 
 ally of twenty-four triangular facets ; the table has a rect- 
 angular face and beveled edges ; and the en cabochon cut 
 has a flat base and smooth, rounded dome. 
 
 As is well known, the diamond is the most highly val- 
 ued of the gems. This mineral, which is pure crystallized 
 carbon, the same element which in other conditions con- 
 stitutes charcoal and graphite, is the hardest of all known 
 substances, readily scratching every other mineral and 
 being scratched by none. The peculiar charm of the dia- 
 mond lies in its singular brilliancy of luster, in which it as 
 far surpasses all other gems as it does in hardness, and 
 which depends on the great refractive and dispersive 
 power that it exerts on the rays of light. The diamond 
 is usually colorless, but has not unfrequently a slight tinge 
 of color, of which yellow is the most common and least 
 esteemed. A diamond of the first water is perfectly trans- 
 parent and colorless, and free from spots or flaws, those 
 of clear green and rose tints being also very highly prized. 
 Diamonds are occasionally found of considerable size : 
 the largest from South Africa weighed 308 carats, the 
 largest from Brazil 254!- carats, and one is mentioned from 
 India which is said to have weighed originally 900 carats. 
 Those weighing more than twenty carats are rarely met 
 with, the vast majority of those found being much smaller 
 than this ; and they lose, on the average, about one half 
 their weight in cutting and polishing operations which 
 can be performed only by the aid of the powder of the 
 diamond itself. The diamond has very rarely been found 
 in any other than alluvial deposits made up probably of 
 the debris of its original rocky matrix ; so that there has 
 been much conjecture as to the nature of the formations 
 in which it originated. In Brazil it is found in a peculiar 
 rounded gravel of milky quartz, associated with coarse 
 ferruginous sand, called by the miners cascalho. This may 
 
ORNAMENTAL STONES AND GEMS. 373 
 
 have been derived from a ferruginous conglomerate, or, 
 more probably, it is thought, from a laminated and some- 
 times slightly flexible quartzite called itacolumite, which 
 belongs to the ancient crystalline series of that country. 
 In India, where its mode of occurrence is said to be simi- 
 lar to that in Brazil, a French geologist, M. Chaper, has 
 recently found the diamond in situ, associated with corun- 
 dum, in a matrix of rose-colored pegmatite, a variety of 
 granite, the granitic rocks in the vicinity of the gems being 
 traversed by veins of feldspar and epidotiferous quartz ; 
 thus we have reliable information of one mode of original 
 occurrence of this gem, if not the only one. The great 
 diamond-producing regions of the world are three in num- 
 ber, viz., the southern part of Hindostan, Brazil, and South 
 Africa. The diamond region of the Indian Peninsula has 
 been known from a remote antiquity, and from it have 
 been derived most of the famous diamonds which are 
 among the crown jewels of European sovereigns. The 
 Brazilian diamond-fields are chiefly in the provinces of 
 Minas-Geraes and Bahia, north of Rio Janeiro, though 
 gems are found also in Parana, Goyaz, and Matto-Grosso. 
 The black diamonds, or carbonados, mentioned in the pre- 
 ceding chapter, are found in Bahia. The Brazilian prod- 
 uct is said to amount to from forty to fifty pounds troy 
 per annum. The latest discovered and most prolific re- 
 gion is that of Griqualand and the Orange Free State in 
 South Africa, of which Kimberley is the center, and which 
 has been known only since 1867. The workings here ex- 
 tend to the depth of some hundreds of feet, and the value 
 of the product for 1881 is said to have been about $22,- 
 000,000. Besides these chief regions, diamonds are found 
 in the Ural Mountains and in Borneo, and a few isolated 
 occurrences have been noted in the United States in 
 Georgia, North Carolina, Virginia, and California. 
 
 Corundum, which ranks next to the diamond in hard- 
 ness, is pure crystallized alumina, and, when occurring in 
 IT 
 
374 APPLIED GEOLOGY. 
 
 transparent crystals of pure colors, yields gems which rank 
 next to the diamond in value, and which receive different 
 names in jewelry according to the colors that they present. 
 Thus, the transparent blue corundum is called sapphire j 
 the red, oriental ruby ; the green, oriental emerald; the 
 violet, oriental amethyst j and the yellow, oriental topaz 
 white stones also occurring which have passed for dia- 
 monds. While the original matrix of these gems, like 
 that of ordinary corundum, is in crystalline rocks, they are 
 most frequently found in alluvial deposits. The finest 
 stones are obtained mostly from the East Indies, some be- 
 ing found also in Saxony, Bohemia, and France. Gems of 
 the corundum species are found occasionally in North 
 Carolina ;' also in southern Colorado, New Mexico, and 
 Arizona, in sand with garnets. 
 
 The spinel is a mineral composed of alumina and mag- 
 nesia, with usually a little iron, is in hardness next below 
 corundum, by which it may be scratched, and when used 
 as a gem is of a fine rosy red color, though green and violet 
 tints also occur. This gem, which is called by jewelers 
 spinel ruby and balas ruby, is obtained chiefly from Siam 
 and Ceylon, where it occurs in crystalline rocks, but most- 
 ly in alluvial deposits derived from their wear. Spinel is 
 also found in Sussex County, N. J., and Orange County, 
 N. Y., sometimes in crystals of large size, but rarely if ever 
 fit for jewelry. 
 
 The topaz, which is a silicate of alumina containing 
 a considerable proportion of fluorine, occurs in rhombic 
 prisms with perfect cleavage across the prism, has a hard- 
 ness about equal to that of spinel, and its color is most 
 commonly yellow, but sometimes green, blue, and white. 
 Like the other gems, it occurs in crystalline rocks, or in 
 their cttbris. Those used in jewelry are mostly brought 
 from Siberia, Kamchatka, and Brazil ; it is found also in 
 Saxony and Bohemia, in Arizona and New Mexico, and 
 on Pike's Peak ; the last-named locality, which has recent- 
 
ORNAMENTAL STONES AND GEMS. 375 
 
 ly been discovered, gives promise, it is said, of yielding 
 a light-blue topaz which will be valuable for gems color- 
 less and pellucid crystals being also found. 
 
 Beryl, a silicate of alumina and glucina, which occurs 
 in six-sided prisms, sometimes of great size, in the crystal- 
 line rocks of some of the Eastern States, when transparent 
 and of fine colors affords the valuable green gem, emerald, 
 the sea-green or bluish aqua marine, and the yellow or 
 light-green beryl. Its hardness is somewhat less than 
 that of the spinel and topaz, by which it may be scratched. 
 Crystals fit for jewelry are sometimes found in New 
 England and in Alexander County, N. C., but the emerald 
 and aqua marine are mostly obtained from New Granada, 
 Brazil, Hindostan, and Siberia. 
 
 Zircon, the silicate of zirconia, transparent red crystals 
 of which constitute the gem called hyacinth, and colorless 
 or smoky ones, the jargoon, although found in crystalline 
 rocks at several localities in North Carolina, New York, 
 and New England, has not yet afforded any valuable gems 
 in the United States. These are derived from Ceylon, 
 which furnishes so many other gems, from Siberia, Green- 
 land, and some European localities. The hardness of zir- 
 con is about the same as that of beryl, and exceeds that 
 of quartz. 
 
 The garnet, which is a silicate of quite variable com- 
 position, is of about the same hardness as quartz ; and 
 though of quite common occurrence in mica schist, horn- 
 blende schist, and some other crystalline rocks, still, clear 
 red crystals of proper size are held in some estimation 
 as gems. Stones of the finest quality are found in south- 
 ern Colorado, New Mexico, and Arizona, excellent ones 
 being also obtained from Greenland and Ceylon. It is 
 usually cut in thin tables, or low, rounded forms. 
 
 The tourmaline is a variable compound of silica, alumi- 
 na, and boracic acid, with several other substances. It oc- 
 curs in prisms, usually black, of three, six, nine, or twelve 
 
376 APPLIED GEOLOGY. 
 
 sides, with a low, three-sided pyramidal end, has about the 
 same hardness as quartz, and is found as a common acces- 
 sory of various ancient crystalline rocks. It is occasion- 
 ally met with in transparent crystals of clear yellow, green, 
 blue, and pink colors, when it becomes a gem of consider- 
 able value. Fine yellow gems of this mineral are obtained 
 from Ceylon, and sold often as topaz. Paris, in Oxford 
 County, Me., is a celebrated locality for tourmaline gems 
 of various colors, yielding, it is said, more than two thou- 
 sand dollars' worth per year ; and two or three other lo- 
 calities in the vicinity of Paris give promise of yielding 
 similar gem-stones. 
 
 Hiddenite, or lithia emerald, a variety of spodumene, 
 and composed of silica, alumina, and lithia, is a gem re- 
 cently discovered at Stony Point, Alexander County, N. C., 
 where it occurs in small open pockets in gneiss-rock, asso- 
 ciated with emeralds and several other crystallized min- 
 erals. The most valued gems are of a brilliant grass-green 
 color, those of light-green and yellow colors as well as 
 colorless being also found, but held in less esteem. Ac- 
 cording to its discoverer, the gem has a brilliant cleav- 
 age, and is somewhat harder than the emerald. The lo- 
 cality is being diligently explored for the mineral, which 
 is in good demand for cabinet specimens as well as for 
 gems. 
 
 Turquoise is a hydrous phosphate of alumina, opaque, 
 of a delicate blue or bluish-green color, due to copper, and 
 of a hardness inferior to that of quartz. Despite its in- 
 ferior hardness and opacity, it has long been held in esteem 
 as a gem, because of its pleasing color and the beautiful 
 combinations that it makes when cut with a smooth, 
 rounded surface and set with diamonds or pearls. It 
 occurs in small, rounded masses, or in thin veinlets trav- 
 ersing eruptive or crystalline rocks. The best has for 
 ages been obtained from Khorassan, a province of Persia. 
 Attention has recently been called to two localities of this 
 
ORNAMENTAL STONES AND GEMS. 377 
 
 mineral that were largely worked by the ancient Mexicans, 
 among whom, at the time of the Spanish conquest, it was 
 highly prized as a gem under the name of chalchihuitl, or 
 chalchuite. One of these localities, showing old workings 
 of vast extent, is in the Los Cerillos Mountains, twenty 
 miles southeast of Santa Fe, and the other in Cochise 
 County, Arizona. The mineral at both these localities is 
 bluish green. It has also been found at a locality in south- 
 ern Nevada of a rich blue color, disseminated in grains in 
 a hard sandstone, which is polished and makes a beautiful 
 mottled stone for jewelry. 
 
 Opal is a peculiar, massive, uncrystalline form of quartz, 
 containing a variable proportion of water, somewhat softer 
 than crystalline quartz, by which it may be scratched, and 
 also of a lower specific gravity, its weight rarely exceeding 
 2.2 that of water, while that of quartz is about 2.65. When 
 used as a gem it is translucent, and usually of a milky 
 color, and presents a vivid, iridescent play of colors, due 
 to internal reflections with decomposition of the luminous 
 rays, by microscopic laminae. (Zirkel, " Die mikrosko- 
 pische Beschaffenheit der Mineralien," etc., p. 116.) To 
 this charming opalescence, which is best displayed when 
 the gem is cut with a smooth convex surface, it owes the 
 high estimation in which it was held by the ancients not 
 less than by modern nations. It occurs in small nests and 
 thin veins traversing certain volcanic rocks. The precious 
 opal, and the girasol, or fire opal, have not yet been found 
 fit for jewelry in the United States. They are obtained 
 from Hungary, Honduras, and Mexico, and to some ex- 
 tent from the Faroe Islands. 
 
 Besides the minerals here briefly described as precious 
 stones, some others are occasionally used in jewelry, for 
 example, chrysoberyl, kyanite, idocrase, and chrysolite ; 
 of which it will be sufficient to say that the first named, 
 which nearly equals corundum in hardness, is a valuable 
 gem in the rare cases when it is transparent and free from 
 
378 
 
 APPLIED GEOLOGY. 
 
 flaws ; and that chrysolite is in some demand because of 
 its olive-green tint. 
 
 Although most of the gems are by nature singularly 
 indestructible, still, from the comparative unfrequency of 
 the occurrence of stones suitable for gems of the first qual- 
 ity, it may be doubted whether the increase in the supply 
 more than keeps pace with the increase in wealth and lux- 
 ury, and with the consequent disposition to acquire precious 
 stones. Even the recent large increase in the supply of 
 diamonds, resulting from the discoveries in South Africa, 
 does not appear yet to have produced any perceptible 
 effect in diminishing their price as gems. The demand for 
 several of the precious stones is indeed subject to the ca- 
 prices of fashion, like that for most things which are objects 
 of taste and preference rather than of necessity. Hence 
 occur temporary fluctuations in their price, which bear 
 little or no relation to variations of supply. Yet, on the 
 whole, these minor fluctuations serve but to accentuate 
 more sharply the fixedness and constancy of the passion 
 for the more indestructible gems, showing how unchange- 
 able is the principle of human nature in which it has its 
 roots. 
 
INDEX. 
 
 Abrasive substances, 352. 
 Accessibility of deposits, 46. 
 Agate, 367. 
 
 Age of rocks, 36, 40, 42. 
 Agordo, pyrites, 299. 
 Agriculture, geologic relations, 
 
 101. 
 
 Alabaster, 370. 
 
 Alkalies, geological sources, 309. 
 Almaden, mercury, 259. 
 Alston Moor, 246. 
 Aluminium, 290. 
 Alum shales, 315. 
 
 sources, 315. 
 
 uses, 316. 
 Alunite, 315. 
 Amber, 369. 
 Amethyst, 366. 
 
 Oriental, 374. 
 Amphibolite, 22. 
 Amygdaloidal texture, 14. 
 Analyses of soils, 116. 
 Ancient workings of deposits, 214. 
 Anglesite, 242. 
 Anthracite coal, 19, 137. 
 Anticlinal, 30. 
 
 Anti-friction hornstone, 363. 
 Antimony, 288. 
 Aphanitic, 14. 
 Aplite, 23, 325. 
 Aqua marine, 375. 
 Archaean rocks, where found, 81. 
 Arenaceous, 8. 
 Argillaceous, 8. 
 
 sandstone, 15. 
 Arrangement of rocks, 27. 
 
 vein contents, 201. 
 Arsenic, 292. 
 
 Arsenical ores, 185. 
 
 Artesian wells, 58, 60. 
 
 Asbestus, needful qualities, 344, 
 
 345. 
 
 uses, 346. 
 Ash in coals, 156. 
 Ashes of plants, analyses, 113. 
 Asphalt, 352. 
 Associations of ores, 186. 
 Atlanta vein, Idaho, 267. 
 Augite, 6. 
 Australia, 238, 256, 276, 280. 
 
 Banca, tin, 256. 
 
 Banded structure of veins, 202. 
 
 Barytes, 361. 
 
 Basalt, 23, 350. 
 
 Basic lining of converters, 229. 
 
 Basins of coal, 147. 
 
 Bassick mine, Col, 202, 266, 274. 
 
 Bauxite, 290. 
 
 Beauty of building-stones, 75. 
 
 Bedded deposits of ores, 189, 191. 
 
 structure, 48. 
 Belgium, zinc, 251. 
 Beryl, 375. 
 Billiton, tin, 256. 
 Bismuth, 289. 
 
 Bituminous coal, 21, 138, 140. 
 Black-band ore, 17, 143, 225. 
 Black Hills, 255, 279. 
 Blanket lodes, 195. 
 Blende, 248. 
 Block coal, 139. 
 Bonanzas, 203. 
 Borax, occurrence and uses, 312, 
 
 314. 
 Bornite, 232. 
 
INDEX. 
 
 Bort, 356. 
 
 Breccia, 16. 
 
 Brecciated vein structure, 202. 
 
 Brick clays, 92, 93. 
 
 kiln, perpetual, 95. 
 Brown coal, 139. 
 Bruce mine, 233. 
 
 Building -stones, desirable quali- 
 ties, 66. 
 
 choice of, 78. 
 
 distribution of, 80. 
 
 essential qualities, 66, 67. 
 
 of America, 80. 
 Bull Domingo mine, 266. 
 Butte City, 233, 235. 
 
 Calamine, 248. 
 Calaverite, 274. 
 Calcareous, 8. 
 
 tuff, 16. 
 Calciferous period, hydraulic lime, 
 
 99. 
 
 Calcite, 5, 7. 
 California, 258, 278, 313. 
 Caking coal, 138, 140. 
 Cameos, 367. 
 
 Canadian period, limestone, 89. 
 Cannel coal, 20, 139, 140. 
 Capelton, Quebec, 237. 
 Carat, 371. 
 Carbonate ores, 185. 
 Carbons, 356, 373. 
 Carboniferous, subdivisions, 148. 
 Carnallite, 289. 
 Carnelian, 367. 
 Cassiterite, 254. 
 Cement, hydraulic, 19, 97, 359. 
 Cerussite, 242. 
 Chalcedony, 367. 
 Chalchuite, 377. 
 Chalcocite, 232. 
 Chalcopyrite, 231. 
 Chalk, 19, 359. 
 Chamber deposits, 189, 195. 
 Characteristics of fissure veins, 
 
 203. 
 Chemical manufacture, geological 
 
 materials of, 296. 
 Chemical sediments, 16. 
 Chemung period, sandstone, 88. 
 Cherry coal, 20, 138, 140. 
 Chili, copper, 238. 
 Chimneys of ore, 203. 
 
 Chloride ore, 185. 
 Chlorite, 7. 
 
 schist, 22. 
 Chromium, 290. 
 Chrysocolla, 233. 
 Classes of rocks, table, II. 
 Clay, 8, 92, 320. 
 
 ironstone, 17, 225. 
 Clay County, Ala., tin, 255. 
 Clays, origin, 325. 
 
 pottery, 321, 326. 
 
 properties, 322. 
 Cliff mine, 233. 
 Clifton District, Arizona, 236. 
 Clinometer, 29. 
 Coal, adaptation to uses, i5i. 
 
 analyses, 141. 
 
 American regions, 149, 156. 
 
 foreign regions, 153. 
 
 fuel value, 159. 
 
 geologic associations, 142. 
 
 geologic horizons, 148, 149. 
 
 impurities, 156. 
 
 kinds, 19, 137. 
 
 origin, 19, 135. 
 
 pipes, 144. 
 
 product of 1881, 155. 
 
 relative thickness, 146. 
 Cobalt, 288. 
 Coke, 162. 
 
 Cold-shortness of iron, 158, 228. 
 Colorados, 209. 
 Coloring for glass and pottery, 
 
 329, 332. 
 
 Columbus Marsh, borax, 313. 
 Columnar structure, 13. 
 Commern, 193, 242, 246. 
 Compact texture, 14. 
 Complications of ores, 186. 
 Comstock vein, 200, 203, 205, 
 
 267. 
 
 Concentration of ores, 188. 
 Concrete for paths, 351. 
 Concretionary structure, 13. 
 Conditions of ore deposits, 211, 
 
 212. 
 
 Conformability of strata, 33. 
 Conglomerate, 16, 348. 
 Consolidation, means of, n, 67, 
 
 70. 
 Contact deposits, 195. 
 
 veins, 205. 
 Cool limes, 19, 96. 
 
INDEX. 
 
 381 
 
 Copper, forms of deposit, 233. 
 
 glance, 232. 
 
 ores, 231. 
 
 production, 239. 
 
 uses, 240. 
 
 Copper Queen mine, 233, 236. 
 Corniferous period, limestone, 90. 
 Cornwall, tin, 255, 256. 
 Corundum, 356, 373. 
 Country rock, 36, 196, 199. 
 Cretaceous coals, 149, 151. 
 Cryolite, 290. 
 Cuba, copper, 237. 
 Cuprite, 232. 
 
 Denudation, 33. 
 
 Derbyshire, lead, 246. 
 
 Derbyshire spar. See Fluorite, 368. 
 
 Diamond, 356, 372. 
 
 Diabase, 23. 
 
 Dikes, 35. 
 
 Dip of rocks, 29. 
 
 effect on accessibility, 46. 
 
 on ease of extraction, 48. 
 Diorite, 23. 
 
 Dinas brick (silicious brick), 337. 
 Distribution of ore deposits, 211. 
 
 of ores in deposits, 203. 
 Dolerite, 23. 
 Dolomite, 7, 19. 
 Drainage, agricultural, 127. 
 
 dependence on structure, 64. 
 
 sanitary, 132. 
 
 Dressing of stone, effects, 77. 
 Driven wells, 57. 
 Druses, 202. 
 Ducktown copper, 237. 
 Durability of building-stones, 70. 
 
 Earth-worms, agency in soils, 
 
 108. 
 
 Economic geology defined, 44. 
 Elasticity in building-stones, 68. 
 Emerald, beryl, 375. 
 
 Oriental, 374. 
 Emery, 356, 357. 
 
 wheels, 357. 
 England, 153, 238, 246, 251, 
 
 255- 
 
 Erroneous ideas regarding ore de- 
 posits, 219. 
 
 Eureka District, Nev., 210, 244. 
 
 Excavations, 49. 
 
 Facility of dressing building- 
 stones, 76. 
 
 Fahlun, Sweden, pyrites, 299. 
 False or current bedding, 28. 
 Faults, 31, 206, 297. 
 
 effect on accessibility, 47. 
 Feldspar, 6, 328, 367. 
 Felsite, 23. 
 Ferruginous, 8. 
 Fertilizers, geological, 118. 
 Fertilizing ingredients of soils, 
 
 114, 116. 
 
 Fictile materials, 319. 
 Filling of veins, etc., 200. 
 Fire-clay under coal-seams, 143. 
 Fire-clays, composition, 335, 336. 
 
 tests of, 335. 
 
 uses, 337. 
 Fire opal, 377. 
 Fire-stones, 338. 
 Fissures, how formed, 197, 199. 
 Fissure-veins, 189, 197. 
 Flagging-stones, 16, 351. 
 Flats, 195. 
 Floating brick, 339. 
 Flucan, 204. 
 Fluor-spar, fluorite, 368. 
 Foliation, 12. 
 Foot-wall, 199. 
 Forms of ore deposits, 189. 
 Fossils, 28. 
 
 use of, 38. 
 Foundations, dependence on 
 
 structure, 51. 
 Foundry facings, 364. 
 Franklin, N. J., 249, 251. 
 Franklinite, 249. 
 Freestone, 16. 
 French chalk, 359. 
 Fuels, mineral, 135. 
 
 Galena, 241. 
 
 Galena District, 242, 244, 250. 
 
 Gangues, 183, 187. 
 
 Canister, 338. 
 
 Garnet, 375. 
 
 Gas, natural, 166, 180. 
 
 Gems, 365, 366, 370. 
 
 forms in which cut, 371. 
 Genesee and Huron shale, 180. 
 Geology, practical purposes, I. 
 
 theoretic objects, I. 
 Georgetown, Col., 243, 249, 266. 
 
382 
 
 INDEX. 
 
 Germany, Commern, lead, 246. 
 Gilpin County, Col., gold, 274, 279. 
 Girasol, 377. 
 Glacial agencies in soils, 105. 
 
 materials, nature, etc., 107. 
 Glass, 330, 333. 
 Glazes of pottery, 329. 
 Globe, Arizona, 233, 236. 
 Gneiss, 20. 
 
 Gold Hill, Col., tellurides, 274. 
 Gold, extraction of, 282. 
 
 modes of occurrence, 274. 
 
 production, tables, 277, 278. 
 
 regions, 277. 
 
 surface appearance of deposits, 
 210. . 
 
 uses of, table, 281, 282. 
 
 value, table, 282. 
 Goslar, pyrites, 233, 299. 
 Gossan, 209. 
 Gouge, 204. 
 Granite, 22, 26, 82. 
 Granitic building-stones, distribu- 
 tion, 8 1. 
 
 Granitoid texture, 14. 
 Granular texture, 14. 
 Granulite, 23, 332. 
 Graphic materials, 358. 
 Graphite, plumbago, 339, 358, 360, 
 
 362. 
 
 Gravel, 15, 348. 
 Gray-band, sandstone, 88, 353. 
 Gray copper, tetrahedrite, 186, 233. 
 Great Meadows, N. J., drained, 
 
 127, 132. 
 Greisen, 22. 
 Grindstones, 353, 
 Grit, 16. 
 Guano, 124. 
 Gypsum, 17, 124. 
 
 Hade of veins, 32. 
 Hanging-wall, 199. 
 Health, geological conditions of, 
 
 129. 
 
 Heavy spar, 361. 
 Hematite, 18, 224. 
 Hiddenite, 376. 
 Honestone, 354. 
 Hornblende, 6. 
 Hornblendic gneiss, 21. 
 Hornblende schist, 22. 
 Horn Silver mine, 243, 267. 
 
 Hornstone, anti-friction, 363. 
 Horses or riders of veins, 200, 
 
 204, 206. 
 
 Hot limes, 19, 96. 
 Huron shale, 180. 
 Hyacinth, 375. 
 Hydraulic lime, 19, 97. 
 
 geologic occurrence, 98. 
 Hydro-mica schist, 21. 
 
 Idria, mercury, 259. 
 Igneous rocks, II, 22. 
 Illuminating substances, 165. 
 Impregnations, 189, 192, 257, 275. 
 Iridium, 293. 
 Iron ores, 17, 224. 
 
 chief geologic horizons, 226. 
 
 forms of deposit, 225. 
 
 paints, 361. 
 
 production, 1882, 229. 
 Irregularities in width of veins, 
 
 199, 219. 
 Itacolumite, 373. 
 
 Jade, 368. 
 Japan, 270, 280. 
 Jargoon, 375. 
 Jasper, 367. 
 Jet, 369. 
 
 Johnstown cement, 99. 
 Jointed structure, 48. 
 Joints, 13. 
 
 Joplin and Granby lead and zinc, 
 244, 250. 
 
 Kainite, 310. 
 Kaluscz, 309. 
 
 Keweenaw Point, 233, 234. 
 Key for determining rocks, 24. 
 Key rocks, 145. 
 Kidney ore, 17, 225. 
 Kieserite, 310, 316. 
 Kimberley, S. Africa, 373. 
 
 Labradorite, 367. 
 
 Laccolites, 34. 
 
 Lake Superior copper, 234. 
 
 Lamination, 12, 49. 
 
 Lancaster Gap mine, 286. 
 
 Lapis lazuli, 368. 
 
 Lead, chief uses, 247. 
 
 forms of deposit, 242. 
 
 ores, 241. 
 
 product, 1882, 245, 246. 
 
INDEX. 
 
 383 
 
 Leaders or stringers of veins, 
 
 203. 
 
 Leadville, 195, 210, 243, 266. 
 Lignite, 139, 140. 
 Lime, 96, 119, 342. 
 Limestone, 18, 19, 89, 92. 
 Limonite, 18, 224, 225. 
 Liparite, 23. 
 
 Lithographic limestone, 359. 
 Lode, 196, 197. 
 Los Cerillos Mountains, 377. 
 Louisville cement, 99. 
 Lower Helderberg limestone, 90, 
 
 99. 
 Lubricators, mineral, 362. 
 
 Magnesia, 316, 342. 
 Magnesian limestone, 19. 
 Magnesite, 289, 316. 
 Magnesium, 289. 
 Magnetite, 18, 224. 
 Malachite, 232, 368. 
 Manganese, 291. 
 Mansfeld, copper, 234, 238. 
 Marble, 19, 84, 369. 
 Marls, calcareous, 120. 
 
 greensand and analyses, 120, 
 121. 
 
 Mass deposits, stocks, 189, 194. 
 Massive rocks, 9. 
 
 structure, 12. 
 Materials of physical application, 
 
 347- 
 
 Medina sandstone, 87, 350. 
 Mercury, three regions of, 257. 
 Mesozoic sandstone, 88. 
 Metamorphic ore deposits, 195. 
 
 rocks, 10, 20. 
 Mexico, 255, 268. 
 Mica, 6, 343. 
 
 schist, 21. 
 Millstones, 355. 
 Milwaukee cement, 99. 
 Mine la Motte, 286. 
 Mineral lubricators, 362. 
 Minette, 22. 
 Mispickel, 293. 
 Missouri, 244, 250, 360. 
 Molding sand, 363. 
 Molybdenite, 293. 
 Monoclinal, 30. 
 
 Montezuma Marsh, N. Y., 127, 
 132. 
 
 Moonstone, 367. 
 Mortar, 95. 
 Moss agate, 367. 
 Muck, 118. 
 
 Nagyagite, 274. 
 
 Nephrite or jade, 368. 
 
 New Almaden, 258. 
 
 New Mexico, 234, 236, 267. 
 
 Niagara limestone, 90, 92. 
 
 Nickel, 286. 
 
 Nitre, 309. 
 
 Nitrogen from coal and shale, 124, 
 
 181. 
 
 Normal faults, 206. 
 Nuggets of gold and platinum, 
 
 277, 284. 
 
 Ochre, iron paint, 361. 
 
 Ohio lower coal measures, 145. 
 
 Oil sands of Bradford, 166, 170. 
 
 Oil Creek, Pa., 168. 
 
 Warren, etc., Counties, Pa., 170. 
 
 West Va. and Ohio, 171. 
 Oil territory of Baku, 171. 
 
 Burmah, 172. 
 
 California, 171. 
 Oil wells, how bored, 173. 
 
 how operated, 176. 
 Oil shales, 180. 
 Old Dominion mine, 236. 
 Ontario mine, 267. 
 Onyx, 367. 
 
 marble, 16, 370. 
 Oolite, 16. 
 Opal, 371, 377. 
 Ophiolite, 19. 
 Ores, defined, 183. 
 
 agents of mineralization, 184. 
 Ore chimneys, 203. 
 
 deposits, 184. 
 Ore Knob, N. C., 237. 
 Organic sediments, 18. 
 Origin of ore deposits, 188. 
 Ornamental stones, 365, 366. 
 Oscuras Mountains, 234. 
 Outcrop, 32. 
 Oxide ores, 184. 
 
 Parker's cement, 99. 
 Paving-stones, 349. 
 Pay streaks, 202. 
 Peabody mine, Arizona, 236. 
 
INDEX. 
 
 Pegmatite, 23. 
 
 Periods of rocks, table, 42. 
 
 Petroleum, nature, etc., 165. 
 
 refining and use, 177. 
 Petzite, 274. 
 
 Phosphates, mineral, 123. 
 Phosphorus in coal, 158. 
 Pigments, mineral, 360. 
 Pike's Peak, topaz, 374. 
 Pittsburg coal seam, 144. 
 Placers, 190, 275. 
 Platinum, 284. 
 Plumbago. See Graphite. 
 Plutonic rocks, n. 
 Porphyries, ornamental, 370. 
 Porphyritic texture, 14. 
 Portland cement, 99. 
 Positions of strata, 29. 
 Potash, 126, 309. 
 Potsdam sandstone, 87, 331, 350. 
 Pottery clays, 320, 323. 
 Proportions of precious metals in 
 
 ores, 187. 
 Prospecting, 213. 
 Pumice, 358. 
 Pyrite, 7, 296. 
 
 qualities needed, 300. 
 
 uses, 299. 
 Pyrolusite, 292. 
 Pyrophyllite, 359. 
 Pyroschists, 180. 
 Pyroxene, 6. 
 
 Quartz, 5, 21, 328, 366. 
 Quartzite, 15, 21. 
 
 Quasi-veins, chambers, 189, 195, 
 251, 275. 
 
 Red chalk, 359. 
 
 Red-shortness of iron, 158, 228. 
 Regions of vein-fissures, 198. 
 
 of ore deposits, 211, 213. 
 Reopening of veins, 204. 
 Reverse faults, 207. 
 Rhyolite, 23, 25. 
 Rift of granites, 83, 349. 
 Rio Tinto, Spain, 233, 238, 298. 
 Road materials, 347. 
 Rocks, condition of components, 
 8. 
 
 crystalline, 8, 10. 
 
 mineral components, 4. 
 
 sedimentary, 9, 15. 
 
 Rocks, stratified, 9. 
 Rock masses, arrangement, 27. 
 Rosendale cement, 99. 
 Ruby, balas, and spinel, 374. 
 Ruby, Oriental, 374. 
 
 Salometer, 305. 
 
 Salt and uses, 17, 125, 304, 308. 
 
 Salt, forms of deposit, 304. 
 
 geological horizons, 306. 
 Sampling ores, 216. 
 Sand, 15, 95, 330, 357. 
 Sand-paper, 357. 
 Sandstone, 15, 86, 357. 
 Sanitation, geologic considerations, 
 
 129. 
 
 San Juan region, 236, 243, 266. 
 Sapphire, 374. 
 Sardonyx, 367. 
 Schistose structure, 12. 
 Seam, 12. 
 
 Sedimentary rocks, 9, 15. 
 Segregated veins, 36, 196. 
 Selvage, 204. 
 
 Semi-anthracite coal, 138, 140. 
 Semi-bituminous coal, 138, 140. 
 Serpentine, 8, 22. 
 Shale, 13, 16. 
 Shingle, 15. 
 Sicily, 303. 
 Siderite, 17, 225. 
 Silesia, 246, 251. 
 Silicate ores, 185. 
 Silicious, 8. 
 Silver, American regions, 265. 
 
 foreign regions, 268. 
 
 forms of deposit, 264. 
 
 ores, 260. 
 
 production, 268, 270. 
 
 uses, 271, 282. 
 Silver Islet, 269. 
 Silver King mine, 266. 
 Silver Reef, 265, 267. 
 Sinter, silicious, 17. 
 Slate, 85. 
 
 Slate Range Marsh, borax, 314. 
 Slaty structure, 13. 
 Slickensides, 32, 204. 
 Smithsonite, 248. 
 Soapstone, 343, 359. 
 Socorro Mountains, N. M., 268. 
 Soda, 310. 
 Soils, amendments, in. 
 
INDEX. 
 
 385 
 
 Soils, composition, 101. 
 
 from various rocks, 103. 
 
 of disintegration, 103. 
 
 of transport, 104, 109. 
 
 origin, 102. 
 
 physical characters, no. 
 Solenhofen, 360. 
 Spain, 238, 245, 259, 270. 
 Spathic iron, 17, 225. 
 Sperenberg, 306, 307. 
 Sphalerite, 248. 
 Spinel, 374. 
 Spirifer, 39. 
 Splint coal, 138, 140. 
 Springs, 52. 
 
 Stalactite and stalagmite, 16. 
 Stassfurt, 126, 306, 310. 
 Steatite, 359. 
 Ste. Genevieve County, Mo., 234, 
 
 237- 
 
 Stocke, 35, 194. 
 Stockworks, 189, "95. 
 St. Peter's sandstone, 331. 
 Strass, 371. 
 Stratification, n. 
 Stratified rocks, 27. 
 Stream tin, 255. 
 Strength of building-stones, 67. 
 
 of stones, table, 69. 
 Strike of rocks, 30. 
 Strontium, 317. 
 
 Structure, economic relations, 45, 
 48, 49. 
 
 of rocks, n. 
 Sub-carboniferous limestones, 91. 
 
 sandstones, 88. 
 Subsoils, 107, 127. 
 Sulphide ores, 184. 
 Sulphur in coal, 158. 
 Sulphur, origin and uses, 302, 
 
 303. 
 
 Sunstone, 367. 
 Superposition, test of relative age, 
 
 37- 
 
 Surface appearance of ores, 208. 
 Syenite, 23, 26. 
 Syenitic granite, 22, 26. 
 Synclinal, 31. 
 Sylvanite, 274. 
 Sylvite, 310. 
 
 Talc, 7, 362. 
 Talcose schist, 21. 
 
 I Tell's Marsh, borax, 313. 
 1 Telluride ores, 185. 
 
 Temperature changes, effects on 
 building-stones, 73, 74. 
 
 Tenorite, 232. 
 
 Tetrahedrite, 186, 233. 
 
 Texture of rocks, 14. 
 
 Tin, 254. 
 
 Titanium, 318. 
 
 Tombstone District, 266. 
 
 Topaz, 374. 
 
 Torpedoes in oil-wells, 177. 
 
 Tourmaline, 375' 
 
 Trachyte, 23, 26. 
 
 Transportation, importance of, 
 217. 
 
 Travertine, 16. 
 
 Trenton limestone, 89. 
 
 Triassic, coal-fields, 149. 
 
 Trilobites, 39. 
 
 Tripoli, 358. 
 
 Tungsten, 294. 
 
 Turquoise, 371, 376. 
 
 Ultramarine, 368. 
 
 Umber, 361. 
 
 Unconformability of rocks, 33. 
 
 Under-clays of coals, 143. 
 
 Unstratified rocks, 34. 
 
 Uplifts, effect on accessibility, 
 
 47- 
 
 Uranium, 294. 
 Utica slate, oil shale, 180. 
 
 Value of ore deposits, 215, 218. 
 
 Veins, 35, 196. 
 
 Vein-stone, 183, 187. 
 
 Verd - antique marble, 19, 84, 
 
 370. 
 
 Vermont, 237, 354. 
 Vitreous texture, 14. 
 Vugs, i.e., druses, 202. 
 
 Water in coals, 157. 
 Water-lime group, 99. 
 Water supply, 52, 129. 
 Wells, 55. 
 Whetstones, 354. 
 Whiting, 360. 
 Wieliczka, 306, 307. 
 Willemite, 248. 
 Wolfram, 254, 294. 
 
386 
 
 INDEX. 
 
 Wood's Mine, Pa., 291. 
 Wood River region, 245. 
 Working ore deposits, costs, 
 
 217. 
 
 Wyoming, 237, 311. 
 Wythe County, Va., 245, 250. 
 
 Zinc, American localities, 250. 
 
 foreign centers, 251. 
 
 ores, 247. 
 
 product and uses, 252. 
 Zincite, 248. 
 Zircon, 375. 
 
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APPLETONS' ARITHMETICAL SERIES. 
 
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APPLETONS' 
 
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 The series comprises two books for graded schools. 
 
 I. Appletons' Elementary Geography. Small 4to. 108 pages. 
 
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