,,principles ,,of ,,mining ---------------------------------------- ---------------------- ,published by the ,mc,graw-,hill ,book ,company ,new ,york ,successors to the ,book ,departments of the ,mc,graw ,publishing ,company ,hill ,publishing ,company ,publishers of ,books for ,electrical ,world ,the ,engineering and ,mining ,journal ,engineering ,record ,power and ,the ,engineer ,electric ,railway ,journal ,american ,machinist ,metallurgical and ,chemical ,engineering ---------------------------------------- ---------------------- ,,principles ,,of ,,mining ,,valuation1 ,,organization ,,and ,,administration ,,copper1 ,,gold1 ,,lead1 ,,silver1 ,,tin ,,and ,,zinc ,,by ,,herbert ,c4 ,,hoover ,member ,american ,institute of ,mining ,engineers1 ,mining and ,metallurgical ,society of ,america1 ,socit des ,ingnieurs ,civils de ,france1 ,fellow ,royal ,geographical ,society1 etc4 ,first ,edition ,,fourth ,,thousand ,mc,g,r,a,w-,,hill ,,book ,,company #bci ,,west #ci,,th ,,street1 ,,new ,,york ,,bouverie ,,street1 ,,london1 ,e4,c4 #aiji ,,preface4 ,this volume is a condensation of a series of lectures delivered in part at ,stanford and in part at ,columbia ,universities4 ,it is intended neither for those wholly ignorant of mining1 nor for those long experienced in the profession4 ,the bulk of the material presented is the common heritage of the profession1 and if any one may think there is insufficient reference to previous writers1 let him endeavor to find to whom the origin of our methods should be credited4 ,the science has grown by small contributions of experience since1 or before1 those unnamed ,egyptian engineers1 whose works prove their knowledge of many fundamentals of mine engineering six thousand eight hundred years ago4 ,if ,i have contributed one sentence to the accumulated knowledge of a thousand generations of engineers1 or have thrown one new ray of light on the work1 ,i shall have done my share4 ,i therefore must acknowledge my obligations to all those who have gone before1 to all that has been written that ,i have read1 to those engineers with whom ,i have been associated for many years1 and in particular to many friends for kindly reply to inquiry upon points herein discussed4 ,,contents4 ,,chapter #a4 ,valuation of ,copper1 ,gold1 ,lead1 ,silver1 ,tin1 and ,zinc ,lode ,mines ,determination of average metal content2 sampling1 assay plans1 calculations of averages1 percentage of errors in estimate from sampling4 ,,chapter ,,ii4 ,mine ,valuation 7,continued7 ,calculation of quantities of ore1 and classification of ore in sight4 ,,chapter ,,iii4 ,mine ,valuation 7,continued7 ,prospective value4 ,extension in depth2 origin and structural character of the deposit2 secondary enrichment2 development in neighboring mines2 depth of exhaustion4 ,,chapter ,,iv4 ,mine ,valuation 7,continued7 ,recoverable percentage of the gross assay value2 price of metals2 cost of production4 ,,chapter ,v4 ,mine ,valuation 7,continued7 ,redemption or amortization of capital and interest4 ,,chapter ,,vi4 ,mine ,valuation 7,concluded7 ,valuation of mines with little or no ore in sight2 valuations on second-hand data2 general conduct of examinations2 reports4 ,,chapter ,,vii4 ,development of ,mines ,entry to the mine2 tunnels2 vertical1 inclined1 and combined shafts2 location and number of shafts4 ,,chapter ,,viii4 ,development of ,mines 7,continued7 ,shape and size of shafts2 speed of sinking2 tunnels4 ,,chapter ,,ix4 ,development of ,mines 7,concluded7 ,subsidiary development3 stations2 crosscuts2 levels2 interval between levels2 protection of levels2 winzes and rises4 ,development in the prospecting stage2 drilling4 ,,chapter ,x4 ,stoping ,methods of ore-breaking2 underhand stopes2 overhand stopes2 combined stope4 ,valuing ore in course of breaking4 ,,chapter ,,xi4 ,methods of ,supporting ,excavation ,timbering2 filling with waste2 filling with broken ore2 pillars of ore2 artificial pillars2 caving system4 ,,chapter ,,xii4 ,mechanical ,equipment ,conditions bearing on mine equipment2 winding appliances2 haulage equipment in shafts2 lateral underground transport2 transport in stopes4 ,,chapter ,,xiii4 ,mechanical ,equipment 7,continued7 ,drainage3 controlling factors2 volume and head of water2 flexibility2 reliability2 power conditions2 mechanical efficiency2 capital outlay4 ,systems of drainage1--steam pumps1 compressed-air pumps1 electrical pumps1 rod-driven pumps1 bailing2 comparative value of various systems4 ,,chapter ,,xiv4 ,mechanical ,equipment 7,concluded7 ,machine drilling3 power transmission2 compressed air vs4 electricity2 air drills2 machine vs4 hand drilling4 ,workshops4 ,improvement in equipment4 ,,chapter ,,xv4 ,ratio of ,output to the ,mine ,determination of possible maximum2 limiting factors2 cost of equipment2 life of the mine2 mechanical inefficiency of patchwork plant2 overproduction of base metal2 security of investment4 ,,chapter ,,xvi4 ,administration ,labor efficiency2 skill2 intelligence2 application cordination2 contract work2 labor unions2 real basis of wages4 ,,chapter ,,xvii4 ,administration 7,continued7 ,accounts and technical data and reports2 working costs2 division of expenditure2 inherent limitations in accuracy of working costs2 working cost sheets4 ,general technical data2 labor1 supplies1 power1 surveys1 sampling1 and assaying4 ,,chapter ,,xviii4 ,administration 7,concluded7 ,administrative reports4 ,,chapter ,,xix4 ,the ,amount of ,risk in ,mining ,investments ,risk in valuation of mines2 in mines as compared with other commercial enterprises4 ,,chapter ,,xx4 ,the ,character1 ,training1 and ,obligations of the ,mining ,engineering ,profession ,index ,,principles ,,of ,,mining4 ,,chapter ,i4 ,valuation of ,copper1 ,gold1 ,lead1 ,silver1 ,tin1 and ,zinc ,lode ,mines4 ,,determination ,,of ,,average ,,metal ,,content2 ,,sampling1 ,,assay ,,plans1 ,,calculations ,,of ,,averages1 ,,percentage ,,of ,,errors ,,in ,,estimate ,,from ,,sampling4 ,the following discussion is limited to in situ deposits of copper1 gold1 lead1 silver1 tin1 and zinc4 ,the valuation of alluvial deposits1 iron1 coal1 and other mines is each a special science to itself and cannot be adequately discussed in common with the type of deposits mentioned above4 ,the value of a metal mine of the order under discussion depends upon3-- a4 ,the profit that may be won from ore exposed2 b4 ,the prospective profit to be derived from extension of the ore beyond exposures2 c4 ,the effect of a higher or lower price of metal 7except in gold mines72 d4 ,the efficiency of the management during realization4 ,the first may be termed the positive value1 and can be approximately determined by sampling or test-treatment runs4 ,the second and the third may be termed the speculative values1 and are largely a matter of judgment based on geological evidence and the industrial outlook4 ,the fourth is a question of development1 equipment1 and engineering method adapted to the prospects of the enterprise1 together with capable executive control of these works4 ,it should be stated at the outset that it is utterly impossible to accurately value any mine1 owing to the many speculative factors involved4 ,the best that can be done is to state that the value lies between certain limits1 and that various stages above the minimum given represent various degrees of risk4 ,further1 it would be but stating truisms to those engaged in valuing mines to repeat that1 because of the limited life of every mine1 valuation of such investments cannot be based upon the principle of simple interest2 nor that any investment is justified without a consideration of the management to ensue4 ,yet the ignorance of these essentials is so prevalent among the public that they warrant repetition on every available occasion4 ,to such an extent is the realization of profits indicated from the other factors dependent upon the subsequent management of the enterprise that the author considers a review of underground engineering and administration from an economic point of view an essential to any essay upon the subject4 ,while the metallurgical treatment of ores is an essential factor in mine economics1 it is considered that a detailed discussion of the myriad of processes under hypothetic conditions would lead too far afield4 ,therefore the discussion is largely limited to underground and administrative matters4 ,the valuation of mines arises not only from their change of ownership1 but from the necessity in sound administration for a knowledge of some of the fundamentals of valuation1 such as ore reserves and average values1 that managerial and financial policy may be guided aright4 ,also with the growth of corporate ownership there is a demand from owners and stockholders for periodic information as to the intrinsic condition of their properties4 ,the growth of a body of speculators and investors in mining stocks and securities who desire professional guidance which cannot be based upon first-hand data is creating further demand on the engineer4 ,opinions in these cases must be formed on casual visits or second-hand information1 and a knowledge of men and things generally4 ,despite the feeling of some engineers that the latter employment is not properly based professionally1 it is an expanding phase of engineers' work1 and must be taken seriously4 ,although it lacks satisfactory foundation for accurate judgment1 yet the engineer can1 and should1 give his experience to it when the call comes1 out of interest to the industry as a whole4 ,not only can he in a measure protect the lamb1 by insistence on no investment without the provision of properly organized data and sound administration for his client1 but he can do much to direct the industry from gambling into industrial lines4 ,an examination of the factors which arise on the valuation of mines involves a wide range of subjects4 ,for purposes of this discussion they may be divided into the following heads3-- #a4 ,determination of ,average ,metal ,contents of the ,ore4 #b4 ,determination of ,quantities of ,ore4 #c4 ,prospective ,value4 #d4 ,recoverable ,percentage of ,gross ,value4 #e4 ,price of ,metals4 #f4 ,cost of ,production4 #g4 ,redemption or ,amortization of ,capital and ,interest4 #h4 ,valuation of ,mines without ,ore in ,sight4 #i4 ,general ,conduct of ,examination and ,reports4 ,,determination ,,of ,,average ,,metal ,,contents ,,of ,,the ,,ore4 ,three means of determination of the average metal content of standing ore are in use--,previous ,yield1 ,test-treatment ,runs1 and ,sampling4 ,,previous ,,yield4--,there are certain types of ore where the previous yield from known space becomes the essential basis of determination of quantity and metal contents of ore standing and of the future probabilities4 ,where metals occur like plums in a pudding1 sampling becomes difficult and unreliable1 and where experience has proved a sort of regularity of recurrence of these plums1 dependence must necessarily be placed on past records1 for if their reliability is to be questioned1 resort must be had to extensive test-treatment runs4 ,the ,lake ,superior copper mines and the ,missouri lead and zinc mines are of this type of deposit4 ,on the other sorts of deposits the previous yield is often put forward as of important bearing on the value of the ore standing1 but such yield1 unless it can be authentically connected with blocks of ore remaining1 is not necessarily a criterion of their contents4 ,except in the cases mentioned1 and as a check on other methods of determination1 it has little place in final conclusions4 ,,test ,,parcels4--,treatment on a considerable scale of sufficiently regulated parcels1 although theoretically the ideal method1 is1 however1 not often within the realm of things practical4 ,in examination on behalf of intending purchasers1 the time1 expense1 or opportunity to fraud are usually prohibitive1 even where the plant and facilities for such work exist4 ,even in cases where the engineer in management of producing mines is desirous of determining the value of standing ore1 with the exception of deposits of the type mentioned above1 it is ordinarily done by actual sampling1 because separate mining and treatment of test lots is generally inconvenient and expensive4 ,as a result1 the determination of the value of standing ore is1 in the great majority of cases1 done by sampling and assaying4 ,,sampling4--,the whole theory of sampling is based on the distribution of metals through the ore-body with more or less regularity1 so that if small portions1 that is samples1 be taken from a sufficient number of points1 their average will represent fairly closely the unit value of the ore4 ,if the ore is of the extreme type of irregular metal distribution mentioned under previous yield1 then sampling has no place4 ,how frequently samples must be taken1 the manner of taking them1 and the quantity that constitutes a fair sample1 are matters that vary with each mine4 ,so much depends upon the proper performance of this task that it is in fact the most critical feature of mine examination4 ,ten samples properly taken are more valuable than five hundred slovenly ones1 like grab samples1 for such a number of bad ones would of a surety lead to wholly wrong conclusions4 ,given a good sampling and a proper assay plan1 the valuation of a mine is two-thirds accomplished4 ,it should be an inflexible principle in examinations for purchase that every sample must be taken under the personal supervision of the examining engineer or his trusted assistants4 ,aside from throwing open the doors to fraud1 the average workman will not carry out the work in a proper manner1 unless under constant supervision1 because of his lack of appreciation of the issues involved4 ,sampling is hard1 uncongenial1 manual labor4 ,it requires a deal of conscientiousness to take enough samples and to take them thoroughly4 ,the engineer does not exist who1 upon completion of this task1 considers that he has got too many1 and most wish that they had taken more4 ,the accuracy of sampling as a method of determining the value of standing ore is a factor of the number of samples taken4 ,the average1 for example1 of separate samples from each square inch would be more accurate than those from each alternate square inch4 ,however1 the accumulated knowledge and experience as to the distribution of metals through ore has determined approximately the manner of taking such samples1 and the least number which will still by the law of averages secure a degree of accuracy commensurate with the other factors of estimation4 ,as metals are distributed through ore-bodies of fissure origin with most regularity on lines parallel to the strike and dip1 an equal portion of ore from every point along cross-sections at right angles to the strike will represent fairly well the average values for a certain distance along the strike either side of these cross-sections4 ,in massive deposits1 sample sections are taken in all directions4 ,the intervals at which sample sections must be cut is obviously dependent upon the general character of the deposit4 ,if the values are well distributed1 a longer interval may be employed than in one subject to marked fluctuations4 ,as a general rule1 five feet is the distance most accepted4 ,this1 in cases of regular distribution of values1 may be stretched to ten feet1 or in reverse may be diminished to two or three feet4 ,the width of ore which may be included for one sample is dependent not only upon the width of the deposit1 but also upon its character4 ,where the ore is wider than the necessary stoping width1 the sample should be regulated so as to show the possible locus of values4 ,the metal contents may be1 and often are1 particularly in deposits of the impregnation or replacement type1 greater along some streak in the ore-body1 and this difference may be such as to make it desirable to stope only a portion of the total thickness4 ,for deposits narrower than the necessary stoping width the full breadth of ore should be included in one sample1 because usually the whole of the deposit will require to be broken4 ,in order that a payable section may not possibly be diluted with material unnecessary to mine1 if the deposit is over four feet and under eight feet1 the distance across the vein or lode is usually divided into two samples4 ,if still wider1 each is confined to a span of about four feet1 not only for the reason given above1 but because the more numerous the samples1 the greater the accuracy4 ,thus1 in a deposit twenty feet wide it may be taken as a good guide that a test section across the ore-body should be divided into five parts4 ,as to the physical details of sample taking1 every engineer has his own methods and safeguards against fraud and error4 ,in a large organization of which the writer had for some years the direction1 and where sampling of mines was constantly in progress on an extensive scale1 not only in contemplation of purchase1 but where it was also systematically conducted in operating mines for working data1 he adopted the above general lines and required the following details4 ,a fresh face of ore is first broken and then a trench cut about five inches wide and two inches deep4 ,this trench is cut with a hammer and moil1 or1 where compressed air is available and the rock hard1 a small air-drill of the hammer type is used4 ,the spoil from the trench forms the sample1 and it is broken down upon a large canvas cloth4 ,afterwards it is crushed so that all pieces will pass a half-inch screen1 mixed and quartered1 thus reducing the weight to half4 ,whether it is again crushed and quartered depends upon what the conditions are as to assaying4 ,if convenient to assay office1 as on a going mine1 the whole of the crushing and quartering work can be done at that office1 where there are usually suitable mechanical appliances4 ,if the samples must be taken a long distance1 the bulk for transport can be reduced by finer breaking and repeated quartering1 until there remain only a few ounces4 ,,precautions ,,against ,,fraud4--,much has been written about the precautions to be taken against fraud in cases of valuations for purchase4 ,the best safeguards are an alert eye and a strong right arm4 ,however1 certain small details help4 ,a large leather bag1 arranged to lock after the order of a mail sack1 into which samples can be put underground and which is never unfastened except by responsible men1 not only aids security but relieves the mind4 ,a few samples of country rock form a good check1 and notes as to the probable value of the ore1 from inspection when sampling1 are useful4 ,a great help in examination is to have the assays or analyses done coincidentally with the sampling4 ,a doubt can then always be settled by resampling at once1 and much knowledge can be gained which may relieve so exhaustive a program as might be necessary were results not known until after leaving the mine4 ,,assay ,,of ,,samples4--,two assays1 or as the case may be1 analyses1 are usually made of every sample and their average taken4 ,in the case of erratic differences a third determination is necessary4 ,,assay ,,plans4--,an assay plan is a plan of the workings1 with the location1 assay value1 and width of the sample entered upon it4 ,in a mine with a narrow vein or ore-body1 a longitudinal section is sufficient base for such entries1 but with a greater width than one sample span it is desirable to make preliminary plans of separate levels1 winzes1 etc41 and to average the value of the whole payable widths on such plans before entry upon a longitudinal section4 ,such a longitudinal section will1 through the indicated distribution of values1 show the shape of the ore-body--a step necessary in estimating quantities and of the most fundamental importance in estimating the probabilities of ore extension beyond the range of the openings4 ,the final assay plan should show the average value of the several blocks of ore1 and it is from these averages that estimates of quantities must be made up4 ,,calculations ,,of ,,averages4--,the first step in arriving at average values is to reduce erratic high assays to the general tenor of other adjacent samples4 ,this point has been disputed at some length1 more often by promoters than by engineers1 but the custom is very generally and rightly adopted4 ,erratically high samples may indicate presence of undue metal in the assay attributable to unconscious salting1 for if the value be confined to a few large particles they may find their way through all the quartering into the assay4 ,or the sample may actually indicate rich spots of ore2 but in any event experience teaches that no dependence can be put upon regular recurrence of such abnormally rich spots4 ,as will be discussed under percentage of error in sampling1 samples usually indicate higher than the true value1 even where erratic assays have been eliminated4 ,there are cases of profitable mines where the values were all in spots1 and an assay plan would show #hj of the assays nil1 yet these pockets were so rich as to give value to the whole4 ,pocket mines1 as stated before1 are beyond valuation by sampling1 and aside from the previous yield recourse must be had to actual treatment runs on every block of ore separately4 ,after reduction of erratic assays1 a preliminary study of the runs of value or shapes of the ore-bodies is necessary before any calculation of averages4 ,a preliminary delineation of the boundaries of the payable areas on the assay plan will indicate the sections of the mine which are unpayable1 and from which therefore samples can be rightly excluded in arriving at an average of the payable ore 7,fig4 #a74 ,in a general way1 only the ore which must be mined need be included in averaging4 ,the calculation of the average assay value of standing ore from samples is one which seems to require some statement of elementals4 ,although it may seem primitive1 it can do no harm to recall that if a dump of two tons of ore assaying twenty ounces per ton be added to a dump of five tons averaging one ounce per ton1 the result has not an average assay of twenty-one ounces divided by the number of dumps4 ,likewise one sample over a width of two feet1 assaying twenty ounces per ton1 if averaged with another sample over a width of five feet1 assaying one ounce1 is no more twenty-one ounces divided by two samples than in the case of the two dumps4 ,if common sense were not sufficient demonstration of this1 it can be shown algebraically4 ,were samples equidistant from each other1 and were they of equal width1 the average value would be the simple arithmetical mean of the assays4 ,but this is seldom the case4 ,the number of instances1 not only in practice but also in technical literature1 where the fundamental distinction between an arithmetical and a geometrical mean is lost sight of is amazing4 ,to arrive at the average value of samples1 it is necessary1 in effect1 to reduce them to the actual quantity of the metal and volume of ore represented by each4 ,the method of calculation therefore is one which gives every sample an importance depending upon the metal content of the volume of ore it represents4 ,the volume of ore appertaining to any given sample can be considered as a prismoid1 the dimensions of which may be stated as follows3-- ,w ,width in feet of ore sampled4 ,l ,length in feet of ore represented by the sample4 ,d ,depth into the block to which values are assumed to penetrate4 ,we may also let3-- ,c ,the number of cubic feet per ton of ore4 ,v ,assay value of the sample4 ,then ,,wld_/,c tonnage of the prismoid499 ,v ,,wld_/,c total metal contents4 ,footnote 993 ,strictly1 the prismoidal formula should be used1 but it complicates the study unduly1 and for practical purposes the above may be taken as the volume4 ,the average value of a number of samples is the total metal contents of their respective prismoids1 divided by the total tonnage of these prismoids4 ,if we let ,w1 ,w#a1 ,v1 ,v#a etc41 represent different samples1 we have3-- ,v7,,wld_/,c7 ,v#a 7,w#a ,l#a ,d#a_/;,c7 ,v#b 7,w#b ,l#b ,d#b_/;,c7 ---------------------------------------- ----------------------------- ,,wld_/,c ,w#a ,l#a ,d#a_/;,c ,w#b ,l#b ,d#b_/;,c average value4 ,this may be reduced to3-- 7,,vwld7 7,v#a ,w#a ,l#a ,d#a7 7,v#b ,w#b ,l#b ,d#b171 etc4 ---------------------------------------- ----------------------- 7,,wld7 7,w#a ,l#a ,d#a7 7,w#b ,l#b ,d#b71 etc4 ,as a matter of fact1 samples actually represent the value of the outer shell of the block of ore only1 and the continuity of the same values through the block is a geological assumption4 ,from the outer shell1 all the values can be taken to penetrate equal distances into the block1 and therefore ,d1 ,d#a1 ,d#b may be considered as equal and the equation becomes3-- 7,,vwl7 7,v#a ,w#a ,l#a7 7,v#b ,w#b ,l#b71 etc4 ---------------------------------------- ----------- 7,,wl7 7,w#a ,l#a7 7,w#b ,l#b71 etc4 ,the length of the prismoid base ,l for any given sample will be a distance equal to one-half the sum of the distances to the two adjacent samples4 ,as a matter of practice1 samples are usually taken at regular intervals1 and the lengths ,l1 ,l#a1 ,l#b becoming thus equal can in such case be eliminated1 and the equation becomes3-- 7,,vw7 7,v#a ,w#a7 7,v#b ,w#b71 etc4 ---------------------------------------- ,w ,w#a ,w#b 1 etc4 ,the name assay foot or foot value has been given to the relation ,,vw1 that is1 the assay value multiplied by the width sampled499 ,it is by this method that all samples must be averaged4 ,the same relation obviously can be evolved by using an inch instead of a foot1 and in narrow veins the assay inch is generally used4 ,footnote 993 ,an error will be found in this method unless the two end samples be halved1 but in a long run of samples this may be disregarded4 ,where the payable cross-section is divided into more than one sample1 the different samples in the section must be averaged by the above formula1 before being combined with the adjacent section4 ,where the width sampled is narrower than the necessary stoping width1 and where the waste cannot be broken separately1 the sample value must be diluted to a stoping width4 ,to dilute narrow samples to a stoping width1 a blank value over the extra width which it is necessary to include must be averaged with the sample from the ore on the above formula4 ,cases arise where1 although a certain width of waste must be broken with the ore1 it subsequently can be partially sorted out4 ,practically nothing but experience on the deposit itself will determine how far this will restore the value of the ore to the average of the payable seam4 ,in any event1 no sorting can eliminate all such waste2 and it is necessary to calculate the value on the breaking width1 and then deduct from the gross tonnage to be broken a percentage from sorting4 ,there is always an allowance to be made in sorting for a loss of good ore with the discards4 ,,percentage ,,of ,,error ,,in ,,estimates ,,from ,,sampling4--,it must be remembered that the whole theory of estimation by sampling is founded upon certain assumptions as to evenness of continuity and transition in value and volume4 ,it is but a basis for an estimate1 and an estimate is not a statement of fact4 ,it cannot therefore be too forcibly repeated that an estimate is inherently but an approximation1 take what care one may in its founding4 ,while it is possible to refine mathematical calculation of averages to almost any nicety1 beyond certain essentials it adds nothing to accuracy and is often misleading4 ,it is desirable to consider where errors are most likely to creep in1 assuming that all fundamental data are both accurately taken and considered4 ,sampling of ore in situ in general has a tendency to give higher average value than the actual reduction of the ore will show4 ,on three ,west ,australian gold mines1 in records covering a period of over two years1 where sampling was most exhaustive as a daily rgime of the mines1 the values indicated by sampling were #ab higher than the mill yield plus the contents of the residues4 ,on the ,witwatersrand gold mines1 the actual extractable value is generally considered to be about #gh to #hj of the average shown by sampling1 while the mill extractions are on average about #ij to #ib of the head value coming to the mill4 ,in other words1 there is a constant discrepancy of about #aj to #ab between the estimated value as indicated by mine samples1 and the actual value as shown by yield plus the residues4 ,at ,broken ,hill1 on three lead mines1 the yield is about #ab less than sampling would indicate4 ,this constancy of error in one direction has not been so generally acknowledged as would be desirable1 and it must be allowed for in calculating final results4 ,the causes of the exaggeration seem to be3-- ,first1 inability to stope a mine to such fine limitations of width1 or exclusion of unpayable patches1 as would appear practicable when sampling1 that is by the inclusion when mining of a certain amount of barren rock4 ,even in deposits of about normal stoping width1 it is impossible to prevent the breaking of a certain amount of waste1 even if the ore occurrence is regularly confined by walls4 ,if the mine be of the impregnation type1 such as those at ,goldfield1 or ,kalgoorlie1 with values like plums in a pudding1 and the stopes themselves directed more by assays than by any physical differences in the ore1 the discrepancy becomes very much increased4 ,in mines where the range of values is narrower than the normal stoping width1 some wall rock must be broken4 ,although it is customary to allow for this in calculating the average value from samples1 the allowance seldom seems enough4 ,in mines where the ore is broken on to the top of stopes filled with waste1 there is some loss underground through mixture with the filling4 ,second1 the metal content of ores1 especially when in the form of sulphides1 is usually more friable than the matrix1 and in actual breaking of samples an undue proportion of friable material usually creeps in4 ,this is true more in lead1 copper1 and zinc1 than in gold ores4 ,on several gold mines1 however1 tests on accumulated samples for their sulphide percentage showed a distinctly greater ratio than the tenor of the ore itself in the mill4 ,as the gold is usually associated with the sulphides1 the samples showed higher values than the mill4 ,in general1 some considerable factor of safety must be allowed after arriving at calculated average of samples1--how much it is difficult to say1 but1 in any event1 not less than #aj4 ,,chapter ,,ii4 ,mine ,valuation 7,continued74 ,,calculation ,,of ,,quantities ,,of ,,ore1 ,,and ,,classification ,,of ,,ore ,,in ,,sight4 ,as mines are opened by levels1 rises1 etc41 through the ore1 an extension of these workings has the effect of dividing it into blocks4 ,the obvious procedure in determining tonnages is to calculate the volume and value of each block separately4 ,under the law of averages1 the multiplicity of these blocks tends in proportion to their number to compensate the percentage of error which might arise in the sampling or estimating of any particular one4 ,the shapes of these blocks1 on longitudinal section1 are often not regular geometrical figures4 ,as a matter of practice1 however1 they can be subdivided into such figures that the total will approximate the whole with sufficient closeness for calculations of their areas4 ,the average width of the ore in any particular block is the arithmetical mean of the width of the sample sections in it199 if the samples be an equal distance apart4 ,if they are not equidistant1 the average width is the sum of the areas between samples1 divided by the total length sampled4 ,the cubic foot contents of a particular block is obviously the width multiplied by the area of its longitudinal section4 ,footnote 993 ,this is not strictly true unless the sum of the widths of the two end-sections be divided by two and the result incorporated in calculating the means4 ,in a long series that error is of little importance4 ,the ratio of cubic feet to tons depends on the specific gravity of the ore1 its porosity1 and moisture4 ,the variability of ores throughout the mine in all these particulars renders any method of calculation simply an approximation in the end4 ,the factors which must remain unknown necessarily lead the engineer to the provision of a margin of safety1 which makes mathematical refinement and algebraic formul ridiculous4 ,there are in general three methods of determination of the specific volume of ores3-- ,first1 by finding the true specific gravity of a sufficient number of representative specimens2 this1 however1 would not account for the larger voids in the ore-body and in any event1 to be anything like accurate1 would be as expensive as sampling and is therefore of little more than academic interest4 ,second1 by determining the weight of quantities broken from measured spaces4 ,this also would require several tests from different portions of the mine1 and1 in examinations1 is usually inconvenient and difficult4 ,yet it is necessary in cases of unusual materials1 such as leached gossans1 and it is desirable to have it done sooner or later in going mines1 as a check4 ,third1 by an approximation based upon a calculation from the specific gravities of the predominant minerals in the ore4 ,ores are a mixture of many minerals2 the proportions vary through the same ore-body4 ,despite this1 a few partial analyses1 which are usually available from assays of samples and metallurgical tests1 and a general inspection as to the compactness of the ore1 give a fairly reliable basis for approximation1 especially if a reasonable discount be allowed for safety4 ,in such discount must be reflected regard for the porosity of the ore1 and the margin of safety necessary may vary from #aj to #be4 ,if the ore is of unusual character1 as in leached deposits1 as said before1 resort must be had to the second method4 ,the following table of the weights per cubic foot and the number of cubic feet per ton of some of the principal ore-forming minerals and gangue rocks will be useful for approximating the weight of a cubic foot of ore by the third method4 ,weights are in pounds avoirdupois1 and two thousand pounds are reckoned to the ton4 ,number of ,weight per ,cubic ,feet ,cubic ,foot per ,ton of #bjjj lb4 ---------------------------------------- -- ,antimony #dag4ej #d4gi ,sulphide #bhe4jj #g4ja ,arsenical ,pyrites #cga4hg #e4cg ,barium ,sulphate #bgh4ab #g4ai ,calcium3 ,fluorite #aih4ge #aj4jf ,gypsum #ade4fb #ac4gc ,calcite #afi4cg #aa4hj ,copper #eeb4ej #c4fb ,calcopyrite #bfb4ej #g4fa ,bornite #cba4hg #f4ba ,malachite #bdg4ej #h4jd ,azurite #bcg4ej #h4db ,chrysocolla #acb4ej #ae4ji ,iron 7,cast7 #dej4jj #d4dd ,magnetite #cae4fb #f4cc ,hematite #cjf4be #f4ec ,limonite #bcg4ej #h4db ,pyrite #cab4ej #f4dj ,carbonate #bdj4fb #h4ca ,lead #gaj4fb #b4ha ,galena #dfh4ge #d4bg ,carbonate #djf4hg #d4ha ,manganese ,oxide #bfh4ge #f4ah ,rhodonite #bba4be #i4jd ,magnesite #ahg4ej #aj4ff ,dolomite #agh4ab #aa4bc ,quartz #afe4fb #ab4jg ,quicksilver #hdi4ge #b4ce ,cinnabar #eca4be #c4gf ,sulphur #abg4ab #ae4gd ,tin #dei4jj #d4ce ,oxide #dah4ge #d4gg ,zinc #dcg4ej #d4eg ,blende #bec4ab #g4ij ,carbonate #bgc4ab #g4cb ,silicate #bae4fb #i4bh ,andesite #afe4fb #ab4jg ,granite #afb4fb #ab4cj ,diabase #aha4be #aa4jc ,diorite #aga4hg #aa4fc ,slates #afe4fb #ab4jg ,sandstones #afb4ej #ab4cj ,rhyolite #aef4be #ab4hj ,the specific gravity of any particular mineral has a considerable range1 and a medium has been taken4 ,the possible error is inconsequential for the purpose of these calculations4 ,for example1 a representative gold ore may contain in the main #if quartz1 and #d iron pyrite1 and the weight of the ore may be deduced as follows3-- ,quartz1 #if x #ab4jg #aa4eh ,iron ,pyrite1 #d x #f4dj 4#be ----- #aa4hc cubic feet per ton4 ,most engineers1 to compensate porosity1 would allow twelve to thirteen cubic feet per ton4 ,,classification ,,of ,,ore ,,in ,,sight4 ,the risk in estimates of the average value of standing ore is dependent largely upon how far values disclosed by sampling are assumed to penetrate beyond the tested face1 and this depends upon the geological character of the deposit4 ,from theoretical grounds and experience1 it is known that such values will have some extension1 and the assumption of any given distance is a calculation of risk4 ,the multiplication of development openings results in an increase of sampling points available and lessens the hazards4 ,the frequency of such openings varies in different portions of every mine1 and thus there are inequalities of risk4 ,it is therefore customary in giving estimates of standing ore to classify the ore according to the degree of risk assumed1 either by stating the number of sides exposed or by other phrases4 ,much discussion and ink have been devoted to trying to define what risk may be taken in such matters1 that is in reality how far values may be assumed to penetrate into the unbroken ore4 ,still more has been consumed in attempts to coin terms and make classifications which will indicate what ratio of hazard has been taken in stating quantities and values4 ,the old terms ore in sight and profit in sight have been of late years subject to much malediction on the part of engineers because these expressions have been so badly abused by the charlatans of mining in attempts to cover the flights of their imaginations4 ,a large part of ,volume ,x of the ,institution of ,mining and ,metallurgy has been devoted to heaping infamy on these terms1 yet not only have they preserved their places in professional nomenclature1 but nothing has been found to supersede them4 ,some general term is required in daily practice to cover the whole field of visible ore1 and if the phrase ore in sight be defined1 it will be easier to teach the laymen its proper use than to abolish it4 ,in fact1 the substitutes are becoming abused as much as the originals ever were4 ,all convincing expressions will be misused by somebody4 ,the legitimate direction of reform has been to divide the general term of ore in sight into classes1 and give them names which will indicate the variable amount of risk of continuity in different parts of the mine4 ,as the frequency of sample points1 and consequently the risk of continuity1 will depend upon the detail with which the mine is cut into blocks by the development openings1 and upon the number of sides of such blocks which are accessible1 most classifications of the degree of risk of continuity have been defined in terms of the number of sides exposed in the blocks4 ,many phrases have been coined to express such classifications2 those most currently used are the following3-- ,positive ,ore ,ore exposed on four sides in blocks of a size ,ore ,developed _/ variously prescribed4 ,ore ,blocked ,out ,ore exposed on three sides within reasonable distance of each other4 ,probable ,ore ,ore ,developing _/ ,ore exposed on two sides4 ,possible ,ore ,the whole or a part of the ore below the ,ore ,expectant _/ lowest level or beyond the range of vision4 ,no two of these parallel expressions mean quite the same thing2 each more or less overlies into another class1 and in fact none of them is based upon a logical footing for such a classification4 ,for example1 values can be assumed to penetrate some distance from every sampled face1 even if it be only ten feet1 so that ore exposed on one side will show some positive or developed ore which1 on the lines laid down above1 might be probable or even possible ore4 ,likewise1 ore may be fully developed or blocked out so far as it is necessary for stoping purposes with modern wide intervals between levels1 and still be in blocks too large to warrant an assumption of continuity of values to their centers 7,fig4 #a74 ,as to the third class of possible ore1 it conveys an impression of tangibility to a nebulous hazard1 and should never be used in connection with positive tonnages4 ,this part of the mine's value comes under extension of the deposit a long distance beyond openings1 which is a speculation and cannot be defined in absolute tons without exhaustive explanation of the risks attached1 in which case any phrase intended to shorten description is likely to be misleading4 ,illustration3 ,fig4 #a4--,longitudinal section of a mine1 showing classification of the exposed ore4 ,scale1 #djj feet #a inch4 ,therefore empirical expressions in terms of development openings cannot be made to cover a geologic factor such as the distribution of metals through a rock mass4 ,the only logical basis of ore classification for estimation purposes is one which is founded on the chances of the values penetrating from the surface of the exposures for each particular mine4 ,ore that may be calculated upon to a certainty is that which1 taking into consideration the character of the deposit1 can be said to be so sufficiently surrounded by sampled faces that the distance into the mass to which values are assumed to extend is reduced to a minimum risk4 ,ore so far removed from the sampled face as to leave some doubt1 yet affording great reason for expectation of continuity1 is probable ore4 ,the third class of ore mentioned1 which is that depending upon extension of the deposit and in which1 as said above1 there is great risk1 should be treated separately as the speculative value of the mine4 ,some expressions are desirable for these classifications1 and the writer's own preference is for the following1 with a definition based upon the controlling factor itself4 ,they are3-- ,proved ,ore ,ore where there is practically no risk of failure of continuity4 ,probable ,ore ,ore where there is some risk1 yet warrantable justification for assumption of continuity4 ,prospective ,ore ,ore which cannot be included in the above classes1 nor definitely known or stated in any terms of tonnage4 ,what extent of openings1 and therefore of sample faces1 is required for the ore to be called proved varies naturally with the type of deposit1--in fact with each mine4 ,in a general way1 a fair rule in gold quartz veins below influence of secondary alteration is that no point in the block shall be over fifty feet from the points sampled4 ,in limestone or andesite replacements1 as by gold or lead or copper1 the radius must be less4 ,in defined lead and copper lodes1 or in large lenticular bodies such as the ,tennessee copper mines1 the radius may often be considerably greater1--say one hundred feet4 ,in gold deposits of such extraordinary regularity of values as the ,witwatersrand bankets1 it can well be two hundred or two hundred and fifty feet4 ,probable ore should be ore which entails continuity of values through a greater distance than the above1 and such distance must depend upon the collateral evidence from the character of the deposit1 the position of openings1 etc4 ,ore beyond the range of the probable zone is dependent upon the extension of the deposit beyond the realm of development and will be discussed separately4 ,although the expression ore in sight may be deprecated1 owing to its abuse1 some general term to cover both positive and probable ore is desirable2 and where a general term is required1 it is the intention herein to hold to the phrase ore in sight under the limitations specified4 ,,chapter ,,iii4 ,mine ,valuation 7,continued74 ,,prospective ,,value499 ,,extension ,,in ,,depth2 ,,origin ,,and ,,structural ,,character ,,of ,,the ,,deposit2 ,,secondary ,,enrichment2 ,,development ,,in ,,neighboring ,,mines2 ,,depth ,,of ,,exhaustion4 ,footnote 993 ,the term extension in depth is preferred by many to the phrase prospective value4 ,the former is not entirely satisfactory1 as it has a more specific than general application4 ,it is1 however1 a current miner's phrase1 and is more expressive4 ,in this discussion extension in depth is used synonymously1 and it may be taken to include not alone the downward prolongation of the ore below workings1 but also the occasional cases of lateral extension beyond the range of development work4 ,the commonest instance is continuance below the bottom level4 ,in any event1 to the majority of cases of different extension the same reasoning applies4 ,it is a knotty problem to value the extension of a deposit beyond a short distance from the last opening4 ,a short distance beyond it is proved ore1 and for a further short distance is probable ore4 ,mines are very seldom priced at a sum so moderate as that represented by the profit to be won from the ore in sight1 and what value should be assigned to this unknown portion of the deposit admits of no certainty4 ,no engineer can approach the prospective value of a mine with optimism1 yet the mining industry would be non-existent to-day were it approached with pessimism4 ,any value assessed must be a matter of judgment1 and this judgment based on geological evidence4 ,geology is not a mathematical science1 and to attach a money equivalence to forecasts based on such evidence is the most difficult task set for the mining engineer4 ,it is here that his view of geology must differ from that of his financially more irresponsible brother in the science4 ,the geologist1 contributing to human knowledge in general1 finds his most valuable field in the examination of mines largely exhausted4 ,the engineer's most valuable work arises from his ability to anticipate in the youth of the mine the symptoms of its old age4 ,the work of our geologic friends is1 however1 the very foundation on which we lay our forecasts4 ,geologists have1 as the result of long observation1 propounded for us certain hypotheses which1 while still hypotheses1 have proved to account so widely for our underground experience that no engineer can afford to lose sight of them4 ,although there is a lack of safety in fixed theories as to ore deposition1 and although such conclusions cannot be translated into feet and metal value1 they are nevertheless useful weights on the scale where probabilities are to be weighed4 ,a method in vogue with many engineers is1 where the bottom level is good1 to assume the value of the extension in depth as a sum proportioned to the profit in sight1 and thus evade the use of geological evidence4 ,the addition of various percentages to the profit in sight has been used by engineers1 and proposed in technical publications1 as varying from #be to #ej4 ,that is1 they roughly assess the extension in depth to be worth one-fifth to one-third of the whole value of an equipped mine4 ,while experience may have sometimes demonstrated this to be a practical method1 it certainly has little foundation in either science or logic1 and the writer's experience is that such estimates are untrue in practice4 ,the quantity of ore which may be in sight is largely the result of managerial policy4 ,a small mill on a large mine1 under rapid development1 will result in extensive ore-reserves1 while a large mill eating away rapidly on the same mine under the same scale of development would leave small reserves4 ,on the above scheme of valuation the extension in depth would be worth very different sums1 even when the deepest level might be at the same horizon in both cases4 ,moreover1 no mine starts at the surface with a large amount of ore in sight4 ,yet as a general rule this is the period when its extension is most valuable1 for when the deposit is exhausted to #bjjj feet1 it is not likely to have such extension in depth as when opened one hundred feet1 no matter what the ore-reserves may be4 ,further1 such bases of valuation fail to take into account the widely varying geologic character of different mines1 and they disregard any collateral evidence either of continuity from neighboring development1 or from experience in the district4 ,logically1 the prospective value can be simply a factor of how far the ore in the individual mine may be expected to extend1 and not a factor of the remnant of ore that may still be unworked above the lowest level4 ,an estimation of the chances of this extension should be based solely on the local factors which bear on such extension1 and these are almost wholly dependent upon the character of the deposit4 ,these various geological factors from a mining engineer's point of view are3-- #a4 ,the origin and structural character of the ore-deposit4 #b4 ,the position of openings in relation to secondary alteration4 #c4 ,the size of the deposit4 #d4 ,the depth to which the mine has already been exhausted4 #e4 ,the general experience of the district for continuity and the development of adjoining mines4 ,,the ,,origin ,,and ,,structural ,,character ,,of ,,the ,,deposit4--,in a general way1 the ore-deposits of the order under discussion originate primarily through the deposition of metals from gases or solutions circulating along avenues in the earth's crust499 ,the original source of metals is a matter of great disagreement1 and does not much concern the miner4 ,to him1 however1 the origin and character of the avenue of circulation1 the enclosing rock1 the influence of the rocks on the solution1 and of the solutions on the rocks1 have a great bearing on the probable continuity of the volume and value of the ore4 ,footnote 993 ,the class of magmatic segregations is omitted1 as not being of sufficiently frequent occurrence in payable mines to warrant troubling with it here4 ,all ore-deposits vary in value and1 in the miner's view1 only those portions above the pay limit are ore-bodies1 or ore-shoots4 ,the localization of values into such pay areas in an ore-deposit are apparently influenced by3 #a4 ,the distribution of the open spaces created by structural movement1 fissuring1 or folding as at ,bendigo4 #b4 ,the intersection of other fractures which1 by mingling of solutions from different sources1 provided precipitating conditions1 as shown by enrichments at cross-veins4 #c4 ,the influence of the enclosing rocks by3-- 7a7 ,their solubility1 and therefore susceptibility to replacement4 7b7 ,their influence as a precipitating agent on solutions4 7c7 ,their influence as a source of metal itself4 7d7 ,their texture1 in its influence on the character of the fracture4 ,in homogeneous rocks the tendency is to open clean-cut fissures2 in friable rocks1 zones of brecciation2 in slates or schistose rocks1 linked lenticular open spaces2--these influences exhibiting themselves in miner's terms respectively in well-defined fissure veins1 lodes1 and lenses4 7e7 ,the physical character of the rock mass and the dynamic forces brought to bear upon it4 ,this is a difficult study into the physics of stress in cases of fracturing1 but its local application has not been without results of an important order4 #d4 ,secondary alteration near the surface1 more fully discussed later4 ,it is evident enough that the whole structure of the deposit is a necessary study1 and even a digest of the subject is not to be compressed into a few paragraphs4 ,from the point of view of continuity of values1 ore-deposits may be roughly divided into three classes4 ,they are3-- #a4 ,deposits of the infiltration type in porous beds1 such as ,lake ,superior copper conglomerates and ,african gold bankets4 #b4 ,deposits of the fissure vein type1 such as ,california quartz veins4 #c4 ,replacement or impregnation deposits on the lines of fissuring or otherwise4 ,in a general way1 the uniformity of conditions of deposition in the first class has resulted in the most satisfactory continuity of ore and of its metal contents4 ,in the second1 depending much upon the profundity of the earth movements involved1 there is laterally and vertically a reasonable basis for expectation of continuity but through much less distance than in the first class4 ,the third class of deposits exhibits widely different phenomena as to continuity and no generalization is of any value4 ,in gold deposits of this type in ,west ,australia1 ,colorado1 and ,nevada1 continuity far beyond a sampled face must be received with the greatest skepticism4 ,much the same may be said of most copper replacements in limestone4 ,on the other hand the most phenomenal regularity of values have been shown in certain ,utah and ,arizona copper mines1 the result of secondary infiltration in porphyritic gangues4 ,the ,mississippi ,valley lead and zinc deposits1 while irregular in detail1 show remarkable continuity by way of reoccurrence over wide areas4 ,the estimation of the prospective value of mines where continuity of production is dependent on reoccurrence of ore-bodies somewhat proportional to the area1 such as these ,mississippi deposits or to some extent as in ,cobalt silver veins1 is an interesting study1 but one that offers little field for generalization4 ,,the ,,position ,,of ,,the ,,openings ,,in ,,relation ,,to ,,secondary ,,alteration4--,the profound alteration of the upper section of ore-deposits by oxidation due to the action of descending surface waters1 and their associated chemical agencies1 has been generally recognized for a great many years4 ,only recently1 however1 has it been appreciated that this secondary alteration extends into the sulphide zone as well4 ,the bearing of the secondary alteration1 both in the oxidized and upper sulphide zones1 is of the most sweeping economic character4 ,in considering extension of values in depth1 it demands the most rigorous investigation4 ,not only does the metallurgical character of the ores change with oxidation1 but the complex reactions due to descending surface waters cause leaching and a migration of metals from one horizon to another lower down1 and also in many cases a redistribution of their sequence in the upper zones of the deposit4 ,the effect of these agencies has been so great in many cases as to entirely alter the character of the mine and extension in depth has necessitated a complete requipment4 ,for instance1 the ,mt4 ,morgan gold mine1 ,queensland1 has now become a copper mine2 the copper mines at ,butte were formerly silver mines2 ,leadville has become largely a zinc producer instead of lead4 ,from this alteration aspect ore-deposits may be considered to have four horizons3-- #a4 ,the zone near the outcrop1 where the dominating feature is oxidation and leaching of the soluble minerals4 #b4 ,a lower horizon1 still in the zone of oxidation1 where the predominant feature is the deposition of metals as native1 oxides1 and carbonates4 #c4 ,the upper horizon of the sulphide zone1 where the special feature is the enrichment due to secondary deposition as sulphides4 #d4 ,the region below these zones of secondary alteration1 where the deposit is in its primary state4 ,these zones are seldom sharply defined1 nor are they always all in evidence4 ,how far they are in evidence will depend1 among other things1 upon the amount and rapidity of erosion1 the structure and mineralogical character of the deposit1 and upon the enclosing rock4 ,if erosion is extremely rapid1 as in cold1 wet climates1 and rough topography1 or as in the case of glaciation of the ,lake copper deposits1 denudation follows close on the heels of alteration1 and the surface is so rapidly removed that we may have the primary ore practically at the surface4 ,flat1 arid regions present the other extreme1 for denudation is much slower1 and conditions are most perfect for deep penetration of oxidizing agencies1 and the consequent alteration and concentration of the metals4 ,the migration of metals from the top of the oxidized zone leaves but a barren cap for erosion4 ,the consequent effect of denudation that lags behind alteration is to raise slowly the concentrated metals toward the surface1 and thus subject them to renewed attack and repeated migration4 ,in this manner we can account for the enormous concentration of values in the lower oxidized and upper sulphide zones overlying very lean sulphides in depth4 ,some minerals are more freely soluble and more readily precipitated than others4 ,from this cause there is in complex metal deposits a rearrangement of horizontal sequence1 in addition to enrichment at certain horizons and impoverishment at others4 ,the whole subject is one of too great complexity for adequate consideration in this discussion4 ,no engineer is properly equipped to give judgment on extension in depth without a thorough grasp of the great principles laid down by ,van ,hise1 ,emmons1 ,lindgren1 ,weed1 and others4 ,we may1 however1 briefly examine some of the theoretical effects of such alteration4 ,zinc1 iron1 and lead sulphides are a common primary combination4 ,these metals are rendered soluble from their usual primary forms by oxidizing agencies1 in the order given4 ,they reprecipitate as sulphides in the reverse sequence4 ,the result is the leaching of zinc and iron readily in the oxidized zone1 thus differentially enriching the lead which lags behind1 and a further extension of the lead horizon is provided by the early precipitation of such lead as does migrate4 ,therefore1 the lead often predominates in the second and the upper portion of the third zone1 with the zinc and iron below4 ,although the action of all surface waters is toward oxidation and carbonation of these metals1 the carbonate development of oxidized zones is more marked when the enclosing rocks are calcareous4 ,in copper-iron deposits1 the comparatively easy decomposition and solubility and precipitation of the copper and some iron salts generally result in more extensive impoverishment of these metals near the surface1 and more predominant enrichment at a lower horizon than is the case with any other metals4 ,the barren iron hat at the first zone1 the carbonates and oxides at the second1 the enrichment with secondary copper sulphides at the top of the third1 and the occurrence of secondary copper-iron sulphides below1 are often most clearly defined4 ,in the easy recognition of the secondary copper sulphides1 chalcocite1 bornite1 etc41 the engineer finds a finger-post on the road to extension in depth2 and the directions upon this post are not to be disregarded4 ,the number of copper deposits enriched from unpayability in the first zone to a profitable character in the next two1 and unpayability again in the fourth1 is legion4 ,silver occurs most abundantly in combination with either lead1 copper1 iron1 or gold4 ,as it resists oxidation and solution more strenuously than copper and iron1 its tendency when in combination with them is to lag behind in migration4 ,there is thus a differential enrichment of silver in the upper two zones1 due to the reduction in specific gravity of the ore by the removal of associated metals4 ,silver does migrate somewhat1 however1 and as it precipitates more readily than copper1 lead1 zinc1 or iron1 its tendency when in combination with them is towards enrichment above the horizons of enrichment of these metals4 ,when it is in combination with lead and zinc1 its very ready precipitation from solution by the galena leaves it in combination more predominantly with the lead4 ,the secondary enrichment of silver deposits at the top of the sulphide zone is sometimes a most pronounced feature1 and it seems to be the explanation of the origin of many bonanzas4 ,in gold deposits1 the greater resistance to solubility of this metal than most of the others1 renders the phenomena of migration to depth less marked4 ,further than this1 migration is often interfered with by the more impervious quartz matrix of many gold deposits4 ,where gold is associated with large quantities of base metals1 however1 the leaching of the latter in the oxidized zone leaves the ore differentially richer1 and as gold is also slightly soluble1 in such cases the migration of the base metals does carry some of the gold4 ,in the instance especially of impregnation or replacement deposits1 where the matrix is easily permeable1 the upper sulphide zone is distinctly richer than lower down1 and this enrichment is accompanied by a considerable increase in sulphides and tellurides4 ,the predominant characteristic of alteration in gold deposits is1 however1 enrichment in the oxidized zone with the maximum values near the surface4 ,the reasons for this appear to be that gold in its resistance to oxidation and wholesale migration gives opportunities to a sort of combined mechanical and chemical enrichment4 ,in dry climates1 especially1 the gentleness of erosion allows of more thorough decomposition of the outcroppings1 and a mechanical separation of the gold from the detritus4 ,it remains on or near the deposit1 ready to be carried below1 mechanically or otherwise4 ,in wet climates this is less pronounced1 for erosion bears away the croppings before such an extensive decomposition and freeing of the gold particles4 ,the ,west ,australian gold fields present an especially prominent example of this type of superficial enrichment4 ,during the last fifteen years nearly eight hundred companies have been formed for working mines in this region4 ,although from four hundred of these high-grade ore has been produced1 some thirty-three only have ever paid dividends4 ,the great majority have been unpayable below oxidation1--a distance of one or two hundred feet4 ,the writer's unvarying experience with gold is that it is richer in the oxidized zone than at any point below4 ,while cases do occur of gold deposits richer in the upper sulphide zone than below1 even the upper sulphides are usually poorer than the oxidized region4 ,in quartz veins preminently1 evidence of enrichment in the third zone is likely to be practically absent4 ,tin ores present an anomaly among the base metals under discussion1 in that the primary form of this metal in most workable deposits is an oxide4 ,tin in this form is most difficult of solution from ground agencies1 as witness the great alluvial deposits1 often of considerable geologic age4 ,in consequence the phenomena of migration and enrichment are almost wholly absent1 except such as are due to mechanical penetration of tin from surface decomposition of the matrix akin to that described in gold deposits4 ,in general1 three or four essential facts from secondary alteration must be kept in view when prognosticating extensions4 ,oxidation usually alters treatment problems1 and oxidized ore of the same grade as sulphides can often be treated more cheaply4 ,this is not universal4 ,low-grade ores of lead1 copper1 and zinc may be treatable by concentration when in the form of sulphides1 and may be valueless when oxidized1 even though of the same grade4 ,copper ores generally show violent enrichment at the base of the oxidized1 and at the top of the sulphide zone4 ,lead-zinc ores show lead enrichment and zinc impoverishment in the oxidized zone but have usually less pronounced enrichment below water level than copper4 ,the rearrangement of the metals by the deeper migration of the zinc1 also renders them metallurgically of less value with depth4 ,silver deposits are often differentially enriched in the oxidized zone1 and at times tend to concentrate in the upper sulphide zone4 ,gold deposits usually decrease in value from the surface through the whole of the three alteration zones4 ,,size ,,of ,,deposits4--,the proverb of a relation between extension in depth and size of ore-bodies expresses one of the oldest of miners' beliefs4 ,it has some basis in experience1 especially in fissure veins1 but has little foundation in theory and is applicable over but limited areas and under limited conditions4 ,from a structural view1 the depth of fissuring is likely to be more or less in proportion to its length and breadth and therefore the volume of vein filling with depth is likely to be proportional to length and width of the fissure4 ,as to the distribution of values1 if we eliminate the influence of changing wall rocks1 or other precipitating agencies which often cause the values to arrange themselves in floors1 and of secondary alteration1 there may be some reason to assume distribution of values of an extent equal vertically to that displayed horizontally4 ,there is1 as said1 more reason in experience for this assumption than in theory4 ,a study of the shape of a great many ore-shoots in mines of fissure type indicates that when the ore-shoots or ore-bodies are approaching vertical exhaustion they do not end abruptly1 but gradually shorten and decrease in value1 their bottom boundaries being more often wedge-shaped than even lenticular4 ,if this could be taken as the usual occurrence1 it would be possible 7eliminating the evident exceptions mentioned above7 to state roughly that the minimum extension of an ore-body or ore-shoot in depth below any given horizon would be a distance represented by a radius equal to one-half its length4 ,by length is not meant necessarily the length of a horizontal section1 but of one at right angles to the downward axis4 ,on these grounds1 which have been renforced by much experience among miners1 the probabilities of extension are somewhat in proportion to the length and width of each ore-body4 ,for instance1 in the ,a mine1 with an ore-shoot #ajjj feet long and #aj feet wide1 on its bottom level1 the minimum extension under this hypothesis would be a wedge-shaped ore-body with its deepest point #ejj feet below the lowest level1 or a minimum of say #bjj1jjj tons4 ,similarly1 the ,b mine with five ore-bodies1 each #cjj hundred feet long and #aj feet wide1 exposed on its lowest level1 would have a minimum of five wedges #ajj feet deep at their deepest points1 or say #ej1jjj tons4 ,this is not proposed as a formula giving the total amount of extension in depth1 but as a sort of yardstick which has experience behind it4 ,this experience applies in a much less degree to deposits originating from impregnation along lines of fissuring and not at all to replacements4 ,,development ,,in ,,neighboring ,,mines4--,mines of a district are usually found under the same geological conditions1 and show somewhat the same habits as to extension in depth or laterally1 and especially similar conduct of ore-bodies and ore-shoots4 ,as a practical criterion1 one of the most intimate guides is the actual development in adjoining mines4 ,for instance1 in ,kalgoorlie1 the ,great ,boulder mine is 7,march1 #aijh7 working the extension of ,ivanhoe lodes at points #ejj feet below the lowest level in the ,ivanhoe2 likewise1 the ,block #aj lead mine at ,broken ,hill is working the ,central ore-body on the ,central boundary some #cej feet below the ,central workings4 ,such facts as these must have a bearing on assessing the downward extension4 ,,depth ,,of ,,exhaustion4--,all mines become completely exhausted at some point in depth4 ,therefore the actual distance to which ore can be expected to extend below the lowest level grows less with every deeper working horizon4 ,the really superficial character of ore-deposits1 even outside of the region of secondary enrichment is becoming every year better recognized4 ,the prospector's idea that she gets richer deeper down1 may have some basis near the surface in some metals1 but it is not an idea which prevails in the minds of engineers who have to work in depth4 ,the writer1 with some others1 prepared a list of several hundred dividend-paying metal mines of all sorts1 extending over ,north and ,south ,america1 ,australasia1 ,england1 and ,africa4 ,notes were made as far as possible of the depths at which values gave out1 and also at which dividends ceased4 ,although by no means a complete census1 the list indicated that not #f of mines 7outside banket7 that have yielded profits1 ever made them from ore won below #bjjj feet4 ,of mines that paid dividends1 #hj did not show profitable value below #aejj feet1 and a sad majority died above #ejj4 ,failures at short depths may be blamed upon secondary enrichment1 but the majority that reached below this influence also gave out4 ,the geological reason for such general unseemly conduct is not so evident4 ,,conclusion4--,as a practical problem1 the assessment of prospective value is usually a case of cut and try4 ,the portion of the capital to be invested1 which depends upon extension1 will require so many tons of ore of the same value as that indicated by the standing ore1 in order to justify the price4 ,to produce this tonnage at the continued average size of the ore-bodies will require their extension in depth so many feet--or the discovery of new ore-bodies of a certain size4 ,the five geological weights mentioned above may then be put into the scale and a basis of judgment reached4 ,,chapter ,,iv4 ,mine ,valuation 7,continued74 ,,recoverable ,,percentage ,,of ,,the ,,gross ,,assay ,,value2 ,,price ,,of ,,metals2 ,,cost ,,of ,,production4 ,the method of treatment for the ore must be known before a mine can be valued1 because a knowledge of the recoverable percentage is as important as that of the gross value of the ore itself4 ,the recoverable percentage is usually a factor of working costs4 ,practically every ore can be treated and all the metal contents recovered1 but the real problem is to know the method and percentage of recovery which will yield the most remunerative result1 if any4 ,this limit to profitable recovery regulates the amount of metal which should be lost1 and the amount of metal which consequently must be deducted from the gross value before the real net value of the ore can be calculated4 ,here1 as everywhere else in mining1 a compromise has to be made with nature1 and we take what we can get--profitably4 ,for instance1 a copper ore may be smelted and a #ii recovery obtained4 ,under certain conditions this might be done at a loss1 while the same ore might be concentrated before smelting and yield a profit with a #gj recovery4 ,an additional #bj might be obtained by roasting and leaching the residues from concentration1 but this would probably result in an expenditure far greater than the value of the #bj recovered4 ,if the ore is not already under treatment on the mine1 or exactly similar ore is not under treatment elsewhere1 with known results1 the method must be determined experimentally1 either by the examining engineer or by a special metallurgist4 ,where partially treated products1 such as concentrates1 are to be sold1 not only will there be further losses1 but deductions will be made by the smelter for deleterious metals and other charges4 ,all of these factors must be found out1--and a few sample smelting returns from a similar ore are useful4 ,to cover the whole field of metallurgy and discuss what might apply1 and how it might apply1 under a hundred supposititious conditions would be too great a digression from the subject in hand4 ,it is enough to call attention here to the fact that the residues from every treatment carry some metal1 and that this loss has to be deducted from the gross value of the ore in any calculations of net values4 ,,price ,,of ,,metals4 ,unfortunately for the mining engineer1 not only has he to weigh the amount of risk inherent in calculations involved in the mine itself1 but also that due to fluctuations in the value of metals4 ,if the ore is shipped to custom works1 he has to contemplate also variations in freights and smelting charges4 ,gold from the mine valuer's point of view has no fluctuations4 ,it alone among the earth's products gives no concern as to the market price4 ,the price to be taken for all other metals has to be decided before the mine can be valued4 ,this introduces a further speculation and1 as in all calculations of probabilities1 amounts to an estimate of the amount of risk4 ,in a free market the law of supply and demand governs the value of metals as it does that of all other commodities4 ,so far1 except for tariff walls and smelting rings1 there is a free market in the metals under discussion4 ,the demand for metals varies with the unequal fluctuations of the industrial tides4 ,the sea of commercial activity is subject to heavy storms1 and the mine valuer is compelled to serve as weather prophet on this ocean of trouble4 ,high prices1 which are the result of industrial booms1 bring about overproduction1 and the collapse of these begets a shrinkage of demand1 wherein consequently the tide of price turns back4 ,in mining for metals each pound is produced actually at a different cost4 ,in case of an oversupply of base metals the price will fall until it has reached a point where a portion of the production is no longer profitable1 and the equilibrium is established through decline in output4 ,however1 in the backward swing1 due to lingering overproduction1 prices usually fall lower than the cost of producing even a much-diminished supply4 ,there is at this point what we may call the basic price1 that at which production is insufficient and the price rises again4 ,the basic price which is due to this undue backward swing is no more the real price of the metal to be contemplated over so long a term of years than is the highest price4 ,at how much above the basic price of depressed times the product can be safely expected to find a market is the real question4 ,few mines can be bought or valued at this basic price4 ,an indication of what this is can be gained from a study of fluctuations over a long term of years4 ,it is common to hear the average price over an extended period considered the normal price1 but this basis for value is one which must be used with discretion1 for it is not the whole question when mining4 ,the normal price is the average price over a long term4 ,the lives of mines1 and especially ore in sight1 may not necessarily enjoy the period of this normal price4 ,the engineer must balance his judgments by the immediate outlook of the industrial weather4 ,when lead was falling steadily in ,december1 #aijg1 no engineer would accept the price of that date1 although it was then below normal2 his product might go to market even lower yet4 ,it is desirable to ascertain what the basic and normal prices are1 for between them lies safety4 ,since #ahhd there have been three cycles of commercial expansion and contraction4 ,if the average prices are taken for these three cycles separately 7#ahhe-ie71 #ahie-aijb1 #aijb-jh7 it will be seen that there has been a steady advance in prices4 ,for the succeeding cycles lead on the ,london ,exchange199 the freest of the world's markets was #ab #abs4 #d;d41 #ac #cs4 #g;d41 and #ag #gs4 #j;d4 respectively2 zinc1 #ag #ads4 #aj;d41 #ai #cs4 #h;d41 and #bc #cs4 #j;d42 and standard copper1 #dh #afs4 #j;d41 #ei #ajs4 #j;d41 and #fe #gs4 #j;d4 ,it seems1 therefore1 that a higher standard of prices can be assumed as the basic and normal than would be indicated if the general average of1 say1 twenty years were taken4 ,during this period1 the world's gold output has nearly quadrupled1 and1 whether the quantitative theory of gold be accepted or not1 it cannot be denied that there has been a steady increase in the price of commodities4 ,in all base-metal mining it is well to remember that the production of these metals is liable to great stimulus at times from the discovery of new deposits or new processes of recovery from hitherto unprofitable ores4 ,it is therefore for this reason hazardous in the extreme to prophesy what prices will be far in the future1 even when the industrial weather is clear4 ,but some basis must be arrived at1 and from the available outlook it would seem that the following metal prices are justifiable for some time to come1 provided the present tariff schedules are maintained in the ,united ,states3 ,footnote 993 ,all ,london prices are based on the long ton of #b1bdj lbs4 ,much confusion exists in the copper trade as to the classification of the metal4 ,new ,york prices are quoted in electrolytic and ,lake2 ,london's in ,standard4 ,standard has now become practically an arbitrary term peculiar to ,london1 for the great bulk of copper dealt in is electrolytic valued considerably over ,standard4 ,lead ,spelter ,copper ,tin ,silver ---------------------------------------- ----------------- ,london ,n4,y4,lon4 ,n4,y4,lon4 ,n4,y4,lon4 ,n4,y4 ,lon4 ,n4,y4 ,ton ,pound,ton ,pound,ton ,pound,ton ,pound,per oz4,per oz4 ---------------------------------------- ------------------------ ,basic ,price #aa4 4#jceag 4#jdjeb 4#aaeajj4bbj #bb;d44#dd ,normal ,price #ac4e 4#jdc #ba 4#jej #fe 4#adj #acj 4#bij #bf 4#eb ,in these figures the writer has not followed strict averages1 but has taken the general outlook combined with the previous records4 ,the likelihood of higher prices for lead is more encouraging than for any other metal1 as no new deposits of importance have come forward for years1 and the old mines are reaching considerable depths4 ,nor does the frenzied prospecting of the world's surface during the past ten years appear to forecast any very disturbing developments4 ,the zinc future is not so bright1 for metallurgy has done wonders in providing methods of saving the zinc formerly discarded from lead ores1 and enormous supplies will come forward when required4 ,the tin outlook is encouraging1 for the supply from a mining point of view seems unlikely to more than keep pace with the world's needs4 ,in copper the demand is growing prodigiously1 but the supplies of copper ores and the number of copper mines that are ready to produce whenever normal prices recur was never so great as to-day4 ,one very hopeful fact can be deduced for the comfort of the base metal mining industry as a whole4 ,if the growth of demand continues through the next thirty years in the ratio of the past three decades1 the annual demand for copper will be over #c1jjj1jjj tons1 of lead over #a1hjj1jjj tons1 of spelter #b1hjj1jjj tons1 of tin #bej1jjj tons4 ,where such stupendous amounts of these metals are to come from at the present range of prices1 and even with reduced costs of production1 is far beyond any apparent source of supply4 ,the outlook for silver prices is in the long run not bright4 ,as the major portion of the silver produced is a bye product from base metals1 any increase in the latter will increase the silver production despite very much lower prices for the precious metal4 ,in the meantime the gradual conversion of all nations to the gold standard seems a matter of certainty4 ,further1 silver may yet be abandoned as a subsidiary coinage inasmuch as it has now but a token value in gold standard countries if denuded of sentiment4 ,,cost ,,of ,,production4 ,it is hardly necessary to argue the relative importance of the determination of the cost of production and the determination of the recoverable contents of the ore4 ,obviously1 the aim of mine valuation is to know the profits to be won1 and the profit is the value of the metal won1 less the cost of production4 ,the cost of production embraces development1 mining1 treatment1 management4 ,further than this1 it is often contended that1 as the capital expended in purchase and equipment must be redeemed within the life of the mine1 this item should also be included in production costs4 ,it is true that mills1 smelters1 shafts1 and all the paraphernalia of a mine are of virtually negligible value when it is exhausted2 and that all mines are exhausted sometime and every ton taken out contributes to that exhaustion2 and that every ton of ore must bear its contribution to the return of the investment1 as well as profit upon it4 ,therefore it may well be said that the redemption of the capital and its interest should be considered in costs per ton4 ,the difficulty in dealing with the subject from the point of view of production cost arises from the fact that1 except possibly in the case of banket gold and some conglomerate copper mines1 the life of a metal mine is unknown beyond the time required to exhaust the ore reserves4 ,the visible life at the time of purchase or equipment may be only three or four years1 yet the average equipment has a longer life than this1 and the anticipation for every mine is also for longer duration than the bare ore in sight4 ,for clarity of conclusions in mine valuation the most advisable course is to determine the profit in sight irrespective of capital redemption in the first instance4 ,the questions of capital redemption1 purchase price1 or equipment cost can then be weighed against the margin of profit4 ,one phase of redemption will be further discussed under ,amortization of ,capital and ,ratio of ,output to the ,mine4 ,the cost of production depends upon many things1 such as the cost of labor1 supplies1 the size of the ore-body1 the treatment necessary1 the volume of output1 etc42 and to discuss them all would lead into a wilderness of supposititious cases4 ,if the mine is a going concern1 from which reliable data can be obtained1 the problem is much simplified4 ,if it is virgin1 the experience of other mines in the same region is the next resource2 where no such data can be had1 the engineer must fall back upon the experience with mines still farther afield4 ,use is sometimes made of the comparison ton in calculating costs upon mines where data of actual experience are not available4 ,as costs will depend in the main upon items mentioned above1 if the known costs of a going mine elsewhere be taken as a basis1 and subtractions and additions made for more unfavorable or favorable effect of the differences in the above items1 a fairly close result can be approximated4 ,mine examinations are very often inspired by the belief that extended operations or new metallurgical applications to the mine will expand the profits4 ,in such cases the paramount questions are the reduction of costs by better plant1 larger outputs1 new processes1 or alteration of metallurgical basis and better methods4 ,if every item of previous expenditure be gone over and considered1 together with the equipment1 and method by which it was obtained1 the possible savings can be fairly well deduced1 and justification for any particular line of action determined4 ,one view of this subject will be further discussed under ,ratio of ,output to the ,mine4 ,the conditions which govern the working costs are on every mine so special to itself1 that no amount of advice is very useful4 ,volumes of advice have been published on the subject1 but in the main their burden is not to underestimate4 ,in considering the working costs of base-metal mines1 much depends upon the opportunity for treatment in customs works1 smelters1 etc4 ,such treatment means a saving of a large portion of equipment cost1 and therefore of the capital to be invested and subsequently recovered4 ,the economics of home treatment must be weighed against the sum which would need to be set aside for redemption of the plant1 and unless there is a very distinct advantage to be had by the former1 no risks should be taken4 ,more engineers go wrong by the erection of treatment works where other treatment facilities are available1 than do so by continued shipping4 ,there are many mines where the cost of equipment could never be returned1 and which would be valueless unless the ore could be shipped4 ,another phase of foreign treatment arises from the necessity or advantage of a mixture of ores1--the opportunity of such mixtures often gives the public smelter an advantage in treatment with which treatment on the mine could never compete4 ,fluctuation in the price of base metals is a factor so much to be taken into consideration1 that it is desirable in estimating mine values to reduce the working costs to a basis of a per unit of finished metal4 ,this method has the great advantage of indicating so simply the involved risks of changing prices that whoso runs may read4 ,where one metal predominates over the other to such an extent as to form the backbone of the value of the mine1 the value of the subsidiary metals is often deducted from the cost of the principal metal1 in order to indicate more plainly the varying value of the mine with the fluctuating prices of the predominant metal4 ,for example1 it is usual to state that the cost of copper production from a given ore will be so many cents per pound1 or so many pounds sterling per ton4 ,knowing the total metal extractable from the ore in sight1 the profits at given prices of metal can be readily deduced4 ,the point at which such calculation departs from the per-ton-of-ore unto the per-unit-cost-of-metal basis1 usually lies at the point in ore dressing where it is ready for the smelter4 ,to take a simple case of a lead ore averaging #bj3 this is to be first concentrated and the lead reduced to a concentrate averaging #gj and showing a recovery of #ge of the total metal content4 ,the cost per ton of development1 mining1 concentration1 management1 is to this point say #d per ton of original crude ore4 ,the smelter buys the concentrate for #ie of the value of the metal1 less the smelting charge of #ae per ton1 or there is a working cost of a similar sum by home equipment4 ,in this case #d4ff tons of ore are required to produce one ton of concentrates1 and therefore each ton of concentrates costs #ah4fd4 ,this amount1 added to the smelting charge1 gives a total of #cc4fd for the creation of #gj of one ton of finished lead1 or equal to #b4dj cents per pound which can be compared with the market price less #e4 ,if the ore were to contain #bj ounces of silver per ton1 of which #ae ounces were recovered into the leady concentrates1 and the smelter price for the silver were #ej cents per ounce1 then the #g4ej thus recovered would be subtracted from #cc4fd1 making the apparent cost of the lead #a4hf cents per pound4 ,,chapter ,v4 ,mine ,valuation 7,continued74 ,,redemption ,,or ,,amortization ,,of ,,capital ,,and ,,interest4 ,it is desirable to state in some detail the theory of amortization before consideration of its application in mine valuation4 ,as every mine has a limited life1 the capital invested in it must be redeemed during the life of the mine4 ,it is not sufficient that there be a bare profit over working costs4 ,in this particular1 mines differ wholly from many other types of investment1 such as railways4 ,in the latter1 if proper appropriation is made for maintenance1 the total income to the investor can be considered as interest or profit2 but in mines1 a portion of the annual income must be considered as a return of capital4 ,therefore1 before the yield on a mine investment can be determined1 a portion of the annual earnings must be set aside in such a manner that when the mine is exhausted the original investment will have been restored4 ,if we consider the date due for the return of the capital as the time when the mine is exhausted1 we may consider the annual instalments as payments before the due date1 and they can be put out at compound interest until the time for restoration arrives4 ,if they be invested in safe securities at the usual rate of about #d1 the addition of this amount of compound interest will assist in the repayment of the capital at the due date1 so that the annual contributions to a sinking fund need not themselves aggregate the total capital to be restored1 but may be smaller by the deficiency which will be made up by their interest earnings4 ,such a system of redemption of capital is called ,amortization4 ,obviously it is not sufficient for the mine investor that his capital shall have been restored1 but there is required an excess earning over and above the necessities of this annual funding of capital4 ,what rate of excess return the mine must yield is a matter of the risks in the venture and the demands of the investor4 ,mining business is one where #g above provision for capital return is an absolute minimum demanded by the risks inherent in mines1 even where the profit in sight gives warranty to the return of capital4 ,where the profit in sight 7which is the only real guarantee in mine investment7 is below the price of the investment1 the annual return should increase in proportion4 ,there are thus two distinct directions in which interest must be computed1--first1 the internal influence of interest in the amortization of the capital1 and second1 the percentage return upon the whole investment after providing for capital return4 ,there are many limitations to the introduction of such refinements as interest calculations in mine valuation4 ,it is a subject not easy to discuss with finality1 for not only is the term of years unknown1 but1 of more importance1 there are many factors of a highly speculative order to be considered in valuing4 ,it may be said that a certain life is known in any case from the profit in sight1 and that in calculating this profit a deduction should be made from the gross profit for loss of interest on it pending recovery4 ,this is true1 but as mines are seldom dealt with on the basis of profit in sight alone1 and as the purchase price includes usually some proportion for extension in depth1 an unknown factor is introduced which outweighs the known quantities4 ,therefore the application of the culminative effect of interest accumulations is much dependent upon the sort of mine under consideration4 ,in most cases of uncertain continuity in depth it introduces a mathematical refinement not warranted by the speculative elements4 ,for instance1 in a mine where the whole value is dependent upon extension of the deposit beyond openings1 and where an expected return of at least #ej per annum is required to warrant the risk1 such refinement would be absurd4 ,on the other hand1 in a ,witwatersrand gold mine1 in gold and tin gravels1 or in massive copper mines such as ,bingham and ,lake ,superior1 where at least some sort of life can be approximated1 it becomes a most vital element in valuation4 ,in general it may be said that the lower the total annual return expected upon the capital invested1 the greater does the amount demanded for amortization become in proportion to this total income1 and therefore the greater need of its introduction in calculations4 ,especially is this so where the cost of equipment is large proportionately to the annual return4 ,further1 it may be said that such calculations are of decreasing use with increasing proportion of speculative elements in the price of the mine4 ,the risk of extension in depth1 of the price of metal1 etc41 may so outweigh the comparatively minor factors here introduced as to render them useless of attention4 ,in the practical conduct of mines or mining companies1 sinking funds for amortization of capital are never established4 ,in the vast majority of mines of the class under discussion1 the ultimate duration of life is unknown1 and therefore there is no basis upon which to formulate such a definite financial policy even were it desired4 ,were it possible to arrive at the annual sum to be set aside1 the stockholders of the mining type would prefer to do their own reinvestment4 ,the purpose of these calculations does not lie in the application of amortization to administrative finance4 ,it is nevertheless one of the touchstones in the valuation of certain mines or mining investments4 ,that is1 by a sort of inversion such calculations can be made to serve as a means to expose the amount of risk1--to furnish a yardstick for measuring the amount of risk in the very speculations of extension in depth and price of metals which attach to a mine4 ,given the annual income being received1 or expected1 the problem can be formulated into the determination of how many years it must be continued in order to amortize the investment and pay a given rate of profit4 ,a certain length of life is evident from the ore in sight1 which may be called the life in sight4 ,if the term of years required to redeem the capital and pay an interest upon it is greater than the life in sight1 then this extended life must come from extension in depth1 or ore from other direction1 or increased price of metals4 ,if we then take the volume and profit on the ore as disclosed we can calculate the number of feet the deposit must extend in depth1 or additional tonnage that must be obtained of the same grade1 or the different prices of metal that must be secured1 in order to satisfy the demanded term of years4 ,these demands in actual measure of ore or feet or higher price can then be weighed against the geological and industrial probabilities4 ,the following tables and examples may be of assistance in these calculations4 ,table #a4 ,to apply this table1 the amount of annual income or dividend and the term of years it will last must be known or estimated factors4 ,it is then possible to determine the present value of this annual income after providing for amortization and interest on the investment at various rates given1 by multiplying the annual income by the factor set out4 ,a simple illustration would be that of a mine earning a profit of #bjj1jjj annually1 and having a total of #a1jjj1jjj tons in sight1 yielding a profit of #b a ton1 or a total profit in sight of #b1jjj1jjj1 thus recoverable in ten years4 ,on a basis of a #g return on the investment and amortization of capital 7,table ,i71 the factor is #f4eb x #bjj1jjj #a1cjd1jjj as the present value of the gross profits exposed4 ,that is1 this sum of #a1cjd1jjj1 if paid for the mine1 would be repaid out of the profit in sight1 together with #g interest if the annual payments into sinking fund earn #d4 ,,table ,i4 ,present ,value of an ,annual ,dividend ,over -- ,years at -- and ,replacing ,capital by ,reinvestment of an ,annual ,sum at #d4 ,years #e #f #g #h #i #aj ---------------------------------------- --------- #a 4#ie 4#id 4#ic 4#ib 4#ib 4#ia #b #a4he #a4hb #a4gh #a4ge #a4gb #a4fi #c #b4gj #b4fc #b4ef #b4ej #b4dd #b4ch #d #c4ej #c4ch #c4bg #c4ag #c4jg #b4ih #e #d4bf #d4ji #c4ic #c4gh #c4fd #c4ea #f #d4ih #d4gd #d4ec #d4cc #d4ae #c4ii #g #e4ff #e4cf #e4ji #d4hd #d4fb #d4da #h #f4ca #e4ic #e4fj #e4cj #e4jd #d4gi #i #f4ib #f4dg #f4jh #e4gc #e4db #e4ad #aj #g4ej #f4ih #f4eb #f4ab #e4gg #e4de #aa #h4je #g4de #f4id #f4di #f4ji #e4gd #ab #h4eh #g4ij #g4cb #f4hb #f4ci #f4jj #ac #i4jh #h4cb #g4fh #g4ac #f4ff #f4bd #ad #i4ee #h4gb #h4jb #g4db #f4ia #f4df #ae #aj4jj #i4ji #h4cd #g4gi #g4ad #f4fg #af #aj4dc #i4de #h4fc #g4ie #g4cf #f4hf #ag #aj4he #i4gh #h4ia #h4ah #g4ef #g4jc #ah #aa4bd #aj4aj #i4ag #h4dj #g4ge #g4ai #ai #aa4fa #aj4dj #i4db #h4fa #g4ic #g4cd #bj #aa4if #aj4fh #i4fe #h4hj #h4ji #g4di #ba #ab4cj #aj4ie #i4hg #h4ii #h4bd #g4fb #bb #ab4fb #aa4ba #aj4jh #i4af #h4ci #g4gd #bc #ab4ic #aa4de #aj4bh #i4cb #h4eb #g4he #bd #ac4bc #aa4fh #aj4df #i4dg #h4fe #g4if #be #ac4ea #aa4ij #aj4fd #i4fa #h4gg #h4jf #bf #ac4gh #ab4aa #aj4hj #i4ge #h4hh #h4af #bg #ad4jd #ab4ca #aj4if #i4hh #h4ii #h4be #bh #ad4bh #ab4ej #aa4aa #aj4jj #i4ji #h4cc #bi #ad4eb #ab4fh #aa4be #aj4aa #i4ah #h4da #cj #ad4gd #ab4he #aa4ch #aj4bb #i4bg #h4di #ca #ad4if #ac4ja #aa4ea #aj4cb #i4cf #h4ef #cb #ae4af #ac4ag #aa4fc #aj4db #i4dd #h4fb #cc #ae4cf #ac4ca #aa4ge #aj4ea #i4ea #h4fi #cd #ae4ee #ac4df #aa4hf #aj4fj #i4ei #h4ge #ce #ae4gc #ac4ei #aa4if #aj4fg #i4fe #h4hj #cf #ae4ij #ac4gb #ab4jf #aj4gf #i4gb #h4hf #cg #af4jg #ac4hd #ab4af #aj4hd #i4gh #h4ia #ch #af4bb #ac4if #ab4be #aj4ia #i4hd #h4if #ci #af4ch #ad4jg #ab4cd #aj4ih #i4hi #i4jj #dj #af4eb #ad4ah #ab4db #aa4je #i4ie #i4je ,condensed from ,inwood's ,tables4 ,table ,,ii is practically a compound discount table4 ,that is1 by it can be determined the present value of a fixed sum payable at the end of a given term of years1 interest being discounted at various given rates4 ,its use may be illustrated by continuing the example preceding4 ,,table ,,ii4 ,present ,value of #a1 or #a1 payable in -- ,years1 ,interest taken at --4 ,years #d #e #f #g ------------------------------- #a 4#ifa 4#ieb 4#idc 4#icd #b 4#ibd 4#ijg 4#hij 4#hgc #c 4#hhi 4#hfd 4#hdj 4#haf #d 4#hed 4#hbc 4#gib 4#gfc #e 4#hba 4#ghc 4#gdg 4#gac #f 4#gij 4#gdf 4#gje 4#fff #g 4#gfj 4#gaa 4#ffe 4#fbc #h 4#gca 4#fgg 4#fbg 4#ehb #i 4#gjb 4#fde 4#eib 4#edd #aj 4#fge 4#fad 4#eeh 4#ejh #aa 4#fdi 4#ehe 4#ebg 4#dge #ab 4#fbe 4#eeg 4#dig 4#ddd #ac 4#fjj 4#ecj 4#dfi 4#dae #ad 4#egg 4#eje 4#ddb 4#chh #ae 4#eee 4#dha 4#dag 4#cfb #af 4#ecd 4#deh 4#cid 4#cci #ag 4#eac 4#dcf 4#cga 4#caf #ah 4#did 4#dae 4#cej 4#bif #ai 4#dge 4#cif 4#ccj 4#bgf #bj 4#def 4#cgg 4#caa 4#beh #ba 4#dci 4#cei 4#bid 4#bda #bb 4#dbb 4#cdb 4#bgg 4#bff #bc 4#djf 4#cbe 4#bfb 4#baa #bd 4#cij 4#caj 4#bdg 4#aig #be 4#cge 4#bie 4#bcc 4#ahd #bf 4#cfa 4#bha 4#bbj 4#agb #bg 4#cdg 4#bfh 4#bjg 4#afa #bh 4#ccc 4#bee 4#aif 4#aej #bi 4#cba 4#bdc 4#ahd 4#adj #cj 4#cjh 4#bca 4#agd 4#aca #ca 4#bif 4#bbj 4#afd 4#abc #cb 4#bhe 4#baj 4#aee 4#aae #cc 4#bgd 4#bjj 4#adf 4#ajg #cd 4#bfc 4#aij 4#ach 4#ajj #ce 4#bec 4#aha 4#acj 4#jid #cf 4#bdd 4#agb 4#abc 4#jhg #cg 4#bcd 4#afd 4#aaf 4#jhb #ch 4#bbe 4#aef 4#aji 4#jgf #ci 4#baf 4#adi 4#ajc 4#jga #dj 4#bjh 4#adb 4#jig 4#jfg ,condensed from ,inwood's ,tables4 ,if such a mine is not equipped1 and it is assumed that #bjj1jjj are required to equip the mine1 and that two years are required for this equipment1 the value of the ore in sight is still less1 because of the further loss of interest in delay and the cost of equipment4 ,in this case the present value of #a1cjd1jjj in two years1 interest at #g1 the factor is 4#hg ,x #a1cjd1jjj #a1acd1dhj4 ,from this comes off the cost of equipment1 or #bjj1jjj1 leaving #icd1dhj as the present value of the profit in sight4 ,a further refinement could be added by calculating the interest chargeable against the #bjj1jjj equipment cost up to the time of production4 ,,table ,,iii4 ,annual ,number of years of life required to yield-- interest1 and in ,rate of addition to furnish annual instalments which1 if reinvested at ,dividend4 #d will return the original investment at the end of the period4 ---------------------------------------- ---------------------------------- #e #f #g #h #i #aj #f #da4j #g #bh4j #da4j #h #ba4f #bh4j #da4j #i #ag4g #ba4f #bh4j #da4j #aj #ae4j #ag4g #ba4f #bh4j #da4j #aa #ac4j #ae4j #ag4g #ba4f #bh4j #da4j #ab #aa4e #ac4j #ae4j #ag4g #ba4f #bh4j #ac #aj4c #aa4e #ac4j #ae4j #ag4g #ba4f #ad #i4d #aj4c #aa4e #ac4j #ae4j #ag4g #ae #h4f #i4d #aj4c #aa4e #ac4j #ae4j #af #g4i #h4f #i4d #aj4c #aa4e #ac4j #ag #g4c #g4i #h4f #i4d #aj4c #aa4e #ah #f4h #g4c #g4i #h4f #i4d #aj4c #ai #f4d #f4h #g4c #g4i #h4f #i4d #bj #f4j #f4d #f4h #g4c #g4i #h4f #ba #e4g #f4j #f4d #f4h #g4c #g4i #bb #e4d #e4g #f4j #f4d #f4h #g4c #bc #e4a #e4d #e4g #f4j #f4d #f4h #bd #d4i #e4a #e4d #e4g #f4j #f4d #be #d4g #d4i #e4a #e4d #e4g #f4j #bf #d4e #d4g #d4i #e4a #e4d #e4g #bg #d4c #d4e #d4g #d4i #e4a #e4d #bh #d4a #d4c #d4e #d4g #d4i #e4a #bi #c4i #d4a #d4c #d4e #d4g #d4i #cj #c4h #c4i #d4a #d4c #d4e #d4g ,table ,,iii4 ,this table is calculated by inversion of the factors in ,table ,i1 and is the most useful of all such tables1 as it is a direct calculation of the number of years that a given rate of income on the investment must continue in order to amortize the capital 7the annual sinking fund being placed at compound interest at #d7 and to repay various rates of interest on the investment4 ,the application of this method in testing the value of dividend-paying shares is very helpful1 especially in weighing the risks involved in the portion of the purchase or investment unsecured by the profit in sight4 ,given the annual percentage income on the investment from the dividends of the mine 7or on a non-producing mine assuming a given rate of production and profit from the factors exposed71 by reference to the table the number of years can be seen in which this percentage must continue in order to amortize the investment and pay various rates of interest on it4 ,as said before1 the ore in sight at a given rate of exhaustion can be reduced to terms of life in sight4 ,this certain period deducted from the total term of years required gives the life which must be provided by further discovery of ore1 and this can be reduced to tons or feet of extension of given ore-bodies and a tangible position arrived at4 ,the test can be applied in this manner to the various prices which must be realized from the base metal in sight to warrant the price4 ,taking the last example and assuming that the mine is equipped1 and that the price is #b1jjj1jjj1 the yearly return on the price is #aj4 ,if it is desired besides amortizing or redeeming the capital to secure a return of #g on the investment1 it will be seen by reference to the table that there will be required a life of #ba4f years4 ,as the life visible in the ore in sight is ten years1 then the extensions in depth must produce ore for #aa4f years longer--#a1afj1jjj tons4 ,if the ore-body is #a1jjj feet long and #ac feet wide1 it will furnish of gold ore #a1jjj tons per foot of depth2 hence the ore-body must extend #a1afj feet deeper to justify the price4 ,mines are seldom so simple a proposition as this example4 ,there are usually probabilities of other ore2 and in the case of base metal1 then variability of price and other elements must be counted4 ,however1 once the extension in depth which is necessary is determined for various assumptions of metal value1 there is something tangible to consider and to weigh with the five geological weights set out in ,chapter ,,iii4 ,the example given can be expanded to indicate not only the importance of interest and redemption in the long extension in depth required1 but a matter discussed from another point of view under ,ratio of ,output4 ,if the plant on this mine were doubled and the earnings increased to #bj 7#djj1jjj per annum7 7disregarding the reduction in working expenses that must follow expansion of equipment71 it will be found that the life required to repay the purchase money1--#b1jjj1jjj1--;and #g interest upon it1 is about #f4h years4 ,as at this increased rate of production there is in the ore in sight a life of five years1 the extension in depth must be depended upon for #a4h years1 or only #cfj1jjj tons1--that is1 #cfj feet of extension4 ,similarly1 the present value of the ore in sight is #bfh1jjj greater if the mine be given double the equipment1 for thus the idle money locked in the ore is brought into the interest market at an earlier date4 ,against this increased profit must be weighed the increased cost of equipment4 ,the value of low grade mines1 especially1 is very much a factor of the volume of output contemplated4 ,,chapter ,,vi4 ,mine ,valuation 7,concluded74 ,,valuation ,,of ,,mines ,,with ,,little ,,or ,,no ,,ore ,,in ,,sight2 ,,valuations ,,on ,,second-,,hand ,,data2 ,,general ,,conduct ,,of ,,examinations2 ,,reports4 ,a large number of examinations arise upon prospecting ventures or partially developed mines where the value is almost wholly prospective4 ,the risks in such enterprises amount to the possible loss of the whole investment1 and the possible returns must consequently be commensurate4 ,such business is therefore necessarily highly speculative1 but not unjustifiable1 as the whole history of the industry attests2 but this makes the matter no easier for the mine valuer4 ,many devices of financial procedure assist in the limitation of the sum risked1 and offer a middle course to the investor between purchase of a wholly prospective value and the loss of a possible opportunity to profit by it4 ,the usual form is an option to buy the property after a period which permits a certain amount of development work by the purchaser before final decision as to purchase4 ,aside from young mines such enterprises often arise from the possibility of lateral extension of the ore-deposit outside the boundaries of the property of original discovery 7,fig4 #c71 in which cases there is often no visible ore within the property under consideration upon which to found opinion4 ,in regions where vertical side lines obtain1 there is always the possibility of a deep level in inclined deposits4 ,therefore the ground surrounding known deposits has a certain speculative value1 upon which engineers are often called to pass judgment4 ,except in such unusual occurrences as ,south ,african bankets1 or ,lake ,superior coppers1 prospecting for deep level of extension is also a highly speculative phase of mining4 ,the whole basis of opinion in both classes of ventures must be the few geological weights1--the geology of the property and the district1 the development of surrounding mines1 etc4 ,in any event1 there is a very great percentage of risk1 and the profit to be gained by success must be1 proportionally to the expenditure involved1 very large4 ,it is no case for calculating amortization and other refinements4 ,it is one where several hundreds or thousands of per cent hoped for on the investment is the only justification4 ,,opinions ,,and ,,valuations ,,upon ,,second-,,hand ,,data4 ,some one may come forward and deprecate the bare suggestion of an engineer's offering an opinion when he cannot have proper first-hand data4 ,but in these days we have to deal with conditions as well as theories of professional ethics4 ,the growing ownership of mines by companies1 that is by corporations composed of many individuals1 and with their stocks often dealt in on the public exchanges1 has resulted in holders whose interest is not large enough to warrant their undertaking the cost of exhaustive examinations4 ,the system has produced an increasing class of mining speculators and investors who are finding and supplying the enormous sums required to work our mines1--sums beyond the reach of the old-class single-handed mining men4 ,every year the mining investors of the new order are coming more and more to the engineer for advice1 and they should be encouraged1 because such counsel can be given within limits1 and these limits tend to place the industry upon a sounder footing of ownership4 ,as was said before1 the lamb can be in a measure protected4 ,the engineer's interest is to protect him1 so that the industry which concerns his own life-work may be in honorable repute1 and that capital may be readily forthcoming for its expansion4 ,moreover1 by constant advice to the investor as to what constitutes a properly presented and managed project1 the arrangement of such proper presentation and management will tend to become an a priori function of the promoter4 ,sometimes the engineer can make a short visit to the mine for data purposes1--more often he cannot4 ,in the former case1 he can resolve for himself an approximation upon all the factors bearing on value1 except the quality of the ore4 ,for this1 aside from inspection of the ore itself1 a look at the plans is usually enlightening4 ,a longitudinal section of the mine showing a continuous shortening of the stopes with each succeeding level carries its own interpretation4 ,in the main1 the current record of past production and estimates of the management as to ore-reserves1 etc41 can be accepted in ratio to the confidence that can be placed in the men who present them4 ,it then becomes a case of judgment of men and things1 and here no rule applies4 ,advice must often be given upon data alone1 without inspection of the mine4 ,most mining data present internal evidence as to credibility4 ,the untrustworthy and inexperienced betray themselves in their every written production4 ,assuming the reliability of data1 the methods already discussed for weighing the ultimate value of the property can be applied4 ,it would be possible to cite hundreds of examples of valuation based upon second-hand data4 ,three will1 however1 sufficiently illustrate4 ,first1 the ,r mine at ,johannesburg4 ,with the regularity of this deposit1 the development done1 and a study of the workings on the neighboring mines and in deeper ground1 it is a not unfair assumption that the reefs will maintain size and value throughout the area4 ,the management is sound1 and all the data are given in the best manner4 ,the life of the mine is estimated at six years1 with some probabilities of further ore from low-grade sections4 ,the annual earnings available for dividends are at the rate of about #dej1jjj per annum4 ,the capital is #ddj1jjj in #a shares4 ,by reference to the table on page #df it will be seen that the present value of #dej1jjj spread over six years to return capital at the end of that period1 and give #g dividends in the meantime1 is #d4ec x #dej1jjj #b1jcf1ejj #ddj1jjj #d #abs4 #g;d4 per share4 ,so that this mine1 on the assumption of continuity of values1 will pay about #g and return the price4 ,seven per cent is1 however1 not deemed an adequate return for the risks of labor troubles1 faults1 dykes1 or poor patches4 ,on a #i basis1 the mine is worth about #d #ds4 per share4 ,second1 the ,g mine in ,nevada4 ,it has a capital of #aj1jjj1jjj in #a shares1 standing in the market at #ej cents each4 ,the reserves are #bej1jjj tons1 yielding a profit for yearly division of #g per ton4 ,it has an annual capacity of about #ajj1jjj tons1 or #gjj1jjj net profit1 equal to #ad on the market value4 ,in order to repay the capital value of #e1jjj1jjj and #h per annum1 it will need a life of 7,table ,,iii7 #ac years1 of which #b-a_/b are visible4 ,the size of the ore-bodies indicates a yield of about #a1ajj tons per foot of depth4 ,at an exhaustion rate of #ajj1jjj tons per annum1 the mine would need to extend to a depth of over a thousand feet below the present bottom4 ,there is always a possibility of finding parallel bodies or larger volumes in depth1 but it would be a sanguine engineer indeed who would recommend the stock1 even though it pays an apparent #ad4 ,third1 the ,b mine1 with a capital of #aj1jjj1jjj in #b1jjj1jjj shares of #e each4 ,the promoters state that the mine is in the slopes of the ,andes in ,peru2 that there are #f1jjj1jjj tons of ore blocked out2 that two assays by the assayers of the ,bank of ,england average #i copper2 that the copper can be produced at five cents per pound2 that there is thus a profit of #aj1jjj1jjj in sight4 ,the evidences are wholly incompetent4 ,it is a gamble on statements of persons who have not the remotest idea of sound mining4 ,,general ,,conduct ,,of ,,examination4 ,complete and exhaustive examination1 entailing extensive sampling1 assaying1 and metallurgical tests1 is very expensive and requires time4 ,an unfavorable report usually means to the employer absolute loss of the engineer's fee and expenses4 ,it becomes then the initial duty of the latter to determine at once1 by the general conditions surrounding the property1 how far the expenditure for exhaustive examination is warranted4 ,there is usually named a money valuation for the property1 and thus a peg is afforded upon which to hang conclusions4 ,very often collateral factors with a preliminary sampling1 or indeed no sampling at all1 will determine the whole business4 ,in fact1 it is becoming very common to send younger engineers to report as to whether exhaustive examination by more expensive men is justified4 ,in the course of such preliminary inspection1 the ore-bodies may prove to be too small to insure adequate yield on the price1 even assuming continuity in depth and represented value4 ,they may be so difficult to mine as to make costs prohibitive1 or they may show strong signs of petering out4 ,the ore may present visible metallurgical difficulties which make it unprofitable in any event4 ,a gold ore may contain copper or arsenic1 so as to debar cyanidation1 where this process is the only hope of sufficiently moderate costs4 ,a lead ore may be an amorphous compound with zinc1 and successful concentration or smelting without great penalties may be precluded4 ,a copper ore may carry a great excess of silica and be at the same time unconcentratable1 and there may be no base mineral supply available for smelting mixture4 ,the mine may be so small or so isolated that the cost of equipment will never be justified4 ,some of these conditions may be determined as unsurmountable1 assuming a given value for the ore1 and may warrant the rejection of the mine at the price set4 ,it is a disagreeable thing to have a disappointed promoter heap vituperation on an engineer's head because he did not make an exhaustive examination4 ,although it is generally desirable to do some sampling to give assurance to both purchaser and vendor of conscientiousness1 a little courage of conviction1 when this is rightly and adequately grounded1 usually brings its own reward4 ,supposing1 however1 that conditions are right and that the mine is worth the price1 subject to confirmation of values1 the determination of these cannot be undertaken unless time and money are available for the work4 ,as was said1 a sampling campaign is expensive1 and takes time1 and no engineer has the moral right to undertake an examination unless both facilities are afforded4 ,curtailment is unjust1 both to himself and to his employer4 ,how much time and outlay are required to properly sample a mine is obviously a question of its size1 and the character of its ore4 ,an engineer and one principal assistant can conduct two sampling parties4 ,in hard rock it may be impossible to take more than five samples a day for each party4 ,but1 in average ore1 ten samples for each is reasonable work4 ,as the number of samples is dependent upon the footage of openings on the deposit1 a rough approximation can be made in advance1 and a general idea obtained as to the time required4 ,this period must be insisted upon4 ,,reports4 ,reports are to be read by the layman1 and their first qualities should be simplicity of terms and definiteness of conclusions4 ,reports are usually too long1 rather than too short4 ,the essential facts governing the value of a mine can be expressed on one sheet of paper4 ,it is always desirable1 however1 that the groundwork data and the manner of their determination should be set out with such detail that any other engineer could come to the same conclusion if he accepted the facts as accurately determined4 ,in regard to the detailed form of reports1 the writer's own preference is for a single page summarizing the main factors1 and an assay plan1 reduced to a longitudinal section where possible4 ,then there should be added1 for purposes of record and for submission to other engineers1 a set of appendices going into some details as to the history of the mine1 its geology1 development1 equipment1 metallurgy1 and management4 ,a list of samples should be given with their location1 and the tonnages and values of each separate block4 ,a presentation should be made of the probabilities of extension in depth1 together with recommendations for working the mine4 ,,general ,,summary4 ,the bed-rock value which attaches to a mine is the profit to be won from proved ore and in which the price of metal is calculated at some figure between basic and normal4 ,this we may call the ,a value4 ,beyond this there is the speculative value of the mine4 ,if the value of the probable ore be represented by ,x1 the value of extension of the ore by ,y1 and a higher price for metal than the price above assumed represented by ,z1 then if the mine be efficiently managed the value of the mine is ,a ,x ,y ,z4 ,what actual amounts should be attached to ,x1 ,y1 ,z is a matter of judgment4 ,there is no prescription for good judgment4 ,good judgment rests upon a proper balancing of evidence4 ,the amount of risk in ,x1 ,y1 ,z is purely a question of how much these factors are required to represent in money1--in effect1 how much more ore must be found1 or how many feet the ore must extend in depth2 or in convertible terms1 what life in years the mine must have1 or how high the price of metal must be4 ,in forming an opinion whether these requirements will be realized1 ,x1 ,y1 ,z must be balanced in a scale whose measuring standards are the five geological weights and the general industrial outlook4 ,the wise engineer will put before his clients the scale1 the weights1 and the conclusion arrived at4 ,the shrewd investor will require to know these of his adviser4 ,,chapter ,,vii4 ,development of ,mines4 ,,entry ,,to ,,the ,,mine2 ,,tunnels2 ,,vertical1 ,,inclined1 ,,and ,,combined ,,shafts2 ,,location ,,and ,,number ,,of ,,shafts4 ,development is conducted for two purposes3 first1 to search for ore2 and second1 to open avenues for its extraction4 ,although both objects are always more or less in view1 the first predominates in the early life of mines1 the prospecting stage1 and the second in its later life1 the producing stage4 ,it is proposed to discuss development designed to embrace extended production purposes first1 because development during the prospecting stage is governed by the same principles1 but is tempered by the greater degree of uncertainty as to the future of the mine1 and is1 therefore1 of a more temporary character4 ,,entry ,,to ,,the ,,mine4 ,there are four methods of entry3 by tunnel1 vertical shaft1 inclined shaft1 or by a combination of the last two1 that is1 by a shaft initially vertical then turned to an incline4 ,combined shafts are largely a development of the past few years to meet deep level conditions1 and have been rendered possible only by skip-winding4 ,the angle in such shafts 7,fig4 #b7 is now generally made on a parabolic curve1 and the speed of winding is then less diminished by the bend4 ,the engineering problems which present themselves under entry may be divided into those of3-- #a4 ,method4 #b4 ,location4 #c4 ,shape and size4 ,the resolution of these questions depends upon the3-- a4 ,degree of dip of the deposit4 b4 ,output of ore to be provided for4 c4 ,depth at which the deposit is to be attacked4 d4 ,boundaries of the property4 e4 ,surface topography4 f4 ,cost4 g4 ,operating efficiency4 h4 ,prospects of the mine4 ,illustration3 ,fig4 #b4--,showing arrangement of the bend in combined shafts4 ,from the point of view of entrance1 the coperation of a majority of these factors permits the division of mines into certain broad classes4 ,the type of works demanded for moderate depths 7say vertically #b1ejj to #c1jjj feet7 is very different from that required for great depths4 ,to reach great depths1 the size of shafts must greatly expand1 to provide for extended ventilation1 pumping1 and winding necessities4 ,moreover inclined shafts of a degree of flatness possible for moderate depths become too long to be used economically from the surface4 ,the vast majority of metal-mining shafts fall into the first class1 those of moderate depths4 ,yet1 as time goes on and ore-deposits are exhausted to lower planes1 problems of depth will become more common4 ,one thing1 however1 cannot be too much emphasized1 especially on mines to be worked from the outcrop1 and that is1 that no engineer is warranted1 owing to the speculation incidental to extension in depth1 in initiating early in the mine's career shafts of such size or equipment as would be available for great depths4 ,moreover1 the proper location of a shaft so as to work economically extension of the ore-bodies is a matter of no certainty1 and therefore shafts of speculative mines are tentative in any event4 ,another line of division from an engineering view is brought about by a combination of three of the factors mentioned4 ,this is the classification into outcrop and deep-level mines4 ,the former are those founded upon ore-deposits to be worked from or close to the surface4 ,the latter are mines based upon the extension in depth of ore-bodies from outcrop mines4 ,such projects are not so common in ,america1 where the law in most districts gives the outcrop owner the right to follow ore beyond his side-lines1 as in countries where the boundaries are vertical on all sides4 ,they do1 however1 arise not alone in the few ,american sections where the side-lines are vertical boundaries1 but in other parts owing to the pitch of ore-bodies through the end lines 7,fig4 #c74 ,more especially do such problems arise in ,america in effect1 where the ingress questions have to be revised for mines worked out in the upper levels 7,fig4 #g74 ,illustration3 ,fig4 #c4--,longitudinal section showing deep level project arising from dip of ore-body through end-line4 ,if from a standpoint of entrance questions1 mines are first classified into those whose works are contemplated for moderate depths1 and those in which work is contemplated for great depth1 further clarity in discussion can be gained by subdivision into the possible cases arising out of the factors of location1 dip1 topography1 and boundaries4 ,,mines ,,of ,,moderate ,,depths4 ,case ,i4 ,deposits where topographic conditions permit the alternatives of shaft or tunnel4 ,case ,,ii4 ,vertical or horizontal deposits1 the only practical means of attaining which is by a vertical shaft4 ,case ,,iii4 ,inclined deposits to be worked from near the surface4 ,there are in such instances the alternatives of either a vertical or an inclined shaft4 ,case ,,iv4 ,inclined deposits which must be attacked in depth1 that is1 deep-level projects4 ,there are the alternatives of a compound shaft or of a vertical shaft1 and in some cases of an incline from the surface4 ,,mines ,,to ,,great ,,depths4 ,case ,v4 ,vertical or horizontal deposits1 the only way of reaching which is by a vertical shaft4 ,case ,,vi4 ,inclined deposits4 ,in such cases the alternatives are a vertical or a compound shaft4 ,,case ,i4--,although for logical arrangement tunnel entry has been given first place1 to save repetition it is proposed to consider it later4 ,with few exceptions1 tunnels are a temporary expedient in the mine1 which must sooner or later be opened by a shaft4 ,,case ,,ii4 ,,vertical ,,or ,,horizontal ,,deposits4--,these require no discussion as to manner of entry4 ,there is no justifiable alternative to a vertical shaft 7,fig4 #d74 ,illustration3 ,fig4 #d4--;,cross-sections showing entry to vertical or horizontal deposits4 ,case ,,ii4 ,illustration3 ,fig4 #e4--;,cross-section showing alternative shafts to inclined deposit to be worked from surface4 ,case ,,iii4 ,,case ,,iii4 ,,inclined ,,deposits ,,which ,,are ,,intended ,,to ,,be ,,worked ,,from ,,the ,,outcrop1 ,,or ,,from ,,near ,,it 7,fig4 #e74--,the choice of inclined or vertical shaft is dependent upon relative cost of construction1 subsequent operation1 and the useful life of the shaft1 and these matters are largely governed by the degree of dip4 ,assuming a shaft of the same size in either alternative1 the comparative cost per foot of sinking is dependent largely on the breaking facilities of the rock under the different directions of attack4 ,in this1 the angles of the bedding or joint planes to the direction of the shaft outweigh other factors4 ,the shaft which takes the greatest advantage of such lines of breaking weakness will be the cheapest per foot to sink4 ,in ,south ,african experience1 where inclined shafts are sunk parallel to the bedding planes of hard quartzites1 the cost per foot appears to be in favor of the incline4 ,on the other hand1 sinking shafts across tight schists seems to be more advantageous than parallel to the bedding planes1 and inclines following the dip cost more per foot than vertical shafts4 ,an inclined shaft requires more footage to reach a given point of depth1 and therefore it would entail a greater total expense than a vertical shaft1 assuming they cost the same per foot4 ,the excess amount will be represented by the extra length1 and this will depend upon the flatness of the dip4 ,with vertical shafts1 however1 crosscuts to the deposit are necessary4 ,in a comparative view1 therefore1 the cost of the crosscuts must be included with that of the vertical shaft1 as they would be almost wholly saved in an incline following near the ore4 ,the factor of useful life for the shaft enters in deciding as to the advisability of vertical shafts on inclined deposits1 from the fact that at some depth one of two alternatives has to be chosen4 ,the vertical shaft1 when it reaches a point below the deposit where the crosscuts are too long 7,c1 ,fig4 #e71 either becomes useless1 or must be turned on an incline at the intersection with the ore 7,b74 ,the first alternative means ultimately a complete loss of the shaft for working purposes4 ,the latter has the disadvantage that the bend interferes slightly with haulage4 ,the following table will indicate an hypothetical extreme case1--not infrequently met4 ,in it a vertical shaft #a1ejj feet in depth is taken as cutting the deposit at the depth of #gej feet1 the most favored position so far as aggregate length of crosscuts is concerned4 ,the cost of crosscutting is taken at #bj per foot and that of sinking the vertical shaft at #ge per foot4 ,the incline is assumed for two cases at #ge and #ajj per foot respectively4 ,the stoping height upon the ore between levels is counted at #abe feet4 ,dip of ,depth of ,length of ,no4 of ,crosscuts ,total ,length ,deposit from ,vertical ,incline ,required from of ,crosscuts1 ,horizontal ,shaft ,required ,v ,shaft ,feet ---------------------------------------- ------------------------------ #hj #a1ejj #a1ebb #aa #hei #gj #a1ejj #a1eie #ab #a1iaa #fj #a1ejj #a1gcb #ac #c1bdg #ej #a1ejj #a1jeh #ae #e1chi #dj #a1ejj #b1ccd #ah #h1jch #cj #a1ejj #c1jjj #bc #af1bcg ,cost of ,cost ,vertical ,total ,cost ,cost of ,incline,cost of ,incline ,crosscuts #bj ,shaft #ge of ,vertical #ge per ,foot #ajj per ,foot per ,foot per ,foot and ,crosscuts ---------------------------------------- ------------------------------ #ag1ahj #aab1ejj #abi1fhj #aad1aej #aeb1bjj #ch1bbj #aab1ejj #aej1gbj #aah1fbe #aei1ejj #fd1idj #aab1ejj #agg1ddj #abi1ijj #agb1bcj #ajg1ghj #aab1ejj #bbj1bhj #aad1hej #aie1hjj #agh1gfj #aab1ejj #bia1bfj #age1jej #bcc1djj #cbd1gdj #aab1ejj #dcg1bdj #bbe1jjj #cjj1jjj ,from the above examples it will be seen that the cost of crosscuts put at ordinary level intervals rapidly outruns the extra expense of increased length of inclines4 ,if1 however1 the conditions are such that crosscuts from a vertical shaft are not necessary at so frequent intervals1 then in proportion to the decrease the advantages sway to the vertical shaft4 ,most situations wherein the crosscuts can be avoided arise in mines worked out in the upper levels and fall under ,case ,,iv1 that of deep-level projects4 ,there can be no doubt that vertical shafts are cheaper to operate than inclines3 the length of haul from a given depth is less2 much higher rope speed is possible1 and thus the haulage hours are less for the same output2 the wear and tear on ropes1 tracks1 or guides is not so great1 and pumping is more economical where the ,cornish order of pump is used4 ,on the other hand1 with a vertical shaft must be included the cost of operating crosscuts4 ,on mines where the volume of ore does not warrant mechanical haulage1 the cost of tramming through the extra distance involved is an expense which outweighs any extra operating outlay in the inclined shaft itself4 ,even with mechanical haulage in crosscuts1 it is doubtful if there is anything in favor of the vertical shaft on this score4 ,illustration3 ,fig4 #f4--;,cross-section showing auxiliary vertical outlet4 ,in deposits of very flat dips1 under #cj1 the case arises where the length of incline is so great that the saving on haulage through direct lift warrants a vertical shaft as an auxiliary outlet in addition to the incline 7,fig4 #f74 ,in such a combination the crosscut question is eliminated4 ,the mine is worked above and below the intersection by incline1 and the vertical shaft becomes simply a more economical exit and an alternative to secure increased output4 ,the ,north ,star mine at ,grass ,valley is an illustration in point4 ,such a positive instance borders again on ,case ,,iv1 deep-level projects4 ,in conclusion1 it is the writer's belief that where mines are to be worked from near the surface1 coincidentally with sinking1 and where1 therefore1 crosscuts from a vertical shaft would need to be installed frequently1 inclines are warranted in all dips under #ge and over #cj4 ,beyond #ge the best alternative is often undeterminable4 ,in the range under #cj and over #ae1 although inclines are primarily necessary for actual delivery of ore from levels1 they can often be justifiably supplemented by a vertical shaft as a relief to a long haul4 ,in dips of less than #ae1 as in those over #ge1 the advantages again trend strongly in favor of the vertical shaft4 ,there arise1 however1 in mountainous countries1 topographic conditions such as the dip of deposits into the mountain1 which preclude any alternative on an incline at any angled dip4 ,,case ,,iv4 ,,inclined ,,deposits ,,which ,,must ,,be ,,attacked ,,in ,,depth 7,fig4 #g74--,there are two principal conditions in which such properties exist3 first1 mines being operated1 or having been previously worked1 whose method of entry must be revised2 second1 those whose ore-bodies to be attacked do not outcrop within the property4 ,the first situation may occur in mines of inadequate shaft capacity or wrong location2 in mines abandoned and resurrected2 in mines where a vertical shaft has reached its limit of useful extensions1 having passed the place of economical crosscutting2 or in mines in flat deposits with inclines whose haul has become too long to be economical4 ,three alternatives present themselves in such cases3 a new incline from the surface 7,a ,b ,f1 ,fig4 #g71 or a vertical shaft combined with incline extension 7,c ,d ,f71 or a simple vertical shaft 7,h ,g74 ,a comparison can be first made between the simple incline and the combined shaft4 ,the construction of an incline from the surface to the ore-body will be more costly than a combined shaft1 for until the horizon of the ore is reached 7at ,d7 no crosscuts are required in the vertical section1 while the incline must be of greater length to reach the same horizon4 ,the case arises1 however1 where inclines can be sunk through old stopes1 and thus more cheaply constructed than vertical shafts through solid rock2 and also the case of mountainous topographic conditions mentioned above4 ,illustration3 ,fig4 #g4--;,cross-section of inclined deposit which must be attacked in depth4 ,from an operating point of view1 the bend in combined shafts 7at ,d7 gives rise to a good deal of wear and tear on ropes and gear4 ,the possible speed of winding through a combined shaft is1 however1 greater than a simple incline1 for although haulage speed through the incline section 7,d ,f7 and around the bend of the combined shaft is about the same as throughout a simple incline 7,a ,f71 the speed can be accelerated in the vertical portion 7,d ,c7 above that feasible did the incline extend to the surface4 ,there is therefore an advantage in this regard in the combined shaft4 ,the net advantages of the combined over the inclined shaft depend on the comparative length of the two alternative routes from the intersection 7,d7 to the surface4 ,certainly it is not advisable to sink a combined shaft to cut a deposit at #cjj feet in depth if a simple incline can be had to the surface4 ,on the other hand1 a combined shaft cutting the deposit at #a1jjj feet will be more advisable than a simple incline #b1jjj feet long to reach the same point4 ,the matter is one for direct calculation in each special case4 ,in general1 there are few instances of really deep-level projects where a complete incline from the surface is warranted4 ,in most situations of this sort1 and in all of the second type 7where the outcrop is outside the property71 actual choice usually lies between combined shafts 7,c ,d ,f7 and entire vertical shafts 7,h ,g74 ,the difference between a combined shaft and a direct vertical shaft can be reduced to a comparison of the combined shaft below the point of intersection 7,d7 with that portion of a vertical shaft which would cover the same horizon4 ,the question then becomes identical with that of inclined versus verticals1 as stated in ,case ,,iii1 with the offsetting disadvantage of the bend in the combined shaft4 ,if it is desired to reach production at the earliest date1 the lower section of a simple vertical shaft must have crosscuts to reach the ore lying above the horizon of its intersection 7,e74 ,if production does not press1 the ore above the intersection 7,,eb7 can be worked by rises from the horizon of intersection 7,e74 ,in the use of rises1 however1 there follow the difficulties of ventilation and lowering the ore down to the shaft1 which brings expenses to much the same thing as operating through crosscuts4 ,the advantages of combined over simple vertical shafts are earlier production1 saving of either rises or crosscuts1 and the ultimate utility of the shaft to any depth4 ,the disadvantages are the cost of the extra length of the inclined section1 slower winding1 and greater wear and tear within the inclined section and especially around the bend4 ,all these factors are of variable import1 depending upon the dip4 ,on very steep dips1--over #gj1--the net result is in favor of the simple vertical shaft4 ,on other dips it is in favor of the combined shaft4 ,,cases ,v ,,and ,,vi4 ,,mines ,,to ,,be ,,worked ,,to ,,great ,,depths1--,,over #c1jjj ,,feet4--,in ,case ,v1 with vertical or horizontal deposits1 there is obviously no desirable alternative to vertical shafts4 ,in ,case ,,vi1 with inclined deposits1 there are the alternatives of a combined or of a simple vertical shaft4 ,a vertical shaft in locations 7,h1 ,fig4 #g7 such as would not necessitate extension in depth by an incline1 would1 as in ,case ,,iv1 compel either crosscuts to the ore or inclines up from the horizon of intersection 7,e74 ,apart from delay in coming to production and the consequent loss of interest on capital1 the ventilation problems with this arrangement would be appalling4 ,moreover1 the combined shaft1 entering the deposit near its shallowest point1 offers the possibility of a separate haulage system on the inclined and on the vertical sections1 and such separate haulage is usually advisable at great depths4 ,in such instances1 the output to be handled is large1 for no mine of small output is likely to be contemplated at such depth4 ,several moderate-sized inclines from the horizon of intersection have been suggested 7,,ef1 ,,dg1 ,,ch1 ,fig4 #h7 to feed a large primary shaft 7,,ab71 which thus becomes the trunk road4 ,this program would cheapen lateral haulage underground1 as mechanical traction can be used in the main level1 7,,ec71 and horizontal haulage costs can be reduced on the lower levels4 ,moreover1 separate winding engines on the two sections increase the capacity1 for the effect is that of two trains instead of one running on a single track4 ,,shaft ,,location4--,although the prime purpose in locating a shaft is obviously to gain access to the largest volume of ore within the shortest haulage distance1 other conditions also enter1 such as the character of the surface and the rock to be intersected1 the time involved before reaching production1 and capital cost4 ,as shafts must bear two relations to a deposit1--one as to the dip and the other as to the strike1--they may be considered from these aspects4 ,vertical shafts must be on the hanging-wall side of the outcrop if the deposit dips at all4 ,in any event1 the shaft should be far enough away to be out of the reach of creeps4 ,an inclined shaft may be sunk either on the vein1 in which case a pillar of ore must be left to support the shaft2 or1 instead1 it may be sunk a short distance in the footwall1 and where necessary the excavation above can be supported by filling4 ,following the ore has the advantage of prospecting in sinking1 and in many cases the softness of the ground in the region of the vein warrants this procedure4 ,it has1 however1 the disadvantage that a pillar of ore is locked up until the shaft is ready for abandonment4 ,moreover1 as veins or lodes are seldom of even dip1 an inclined shaft1 to have value as a prospecting opening1 or to take advantage of breaking possibilities in the lode1 will usually be crooked1 and an incline irregular in detail adds greatly to the cost of winding and maintenance4 ,these twin disadvantages usually warrant a straight incline in the footwall4 ,inclines are not necessarily of the same dip throughout1 but for reasonably economical haulage change of angle must take place gradually4 ,illustration3 ,fig4 #h4--,longitudinal section showing shaft arrangement proposed for very deep inclined deposits4 ,in the case of deep-level projects on inclined deposits1 demanding combined or vertical shafts1 the first desideratum is to locate the vertical section as far from the outcrop as possible1 and thus secure the most ore above the horizon of intersection4 ,this1 however1 as stated before1 would involve the cost of crosscuts or rises and would cause delay in production1 together with the accumulation of capital charges4 ,how important the increment of interest on capital may become during the period of opening the mine may be demonstrated by a concrete case4 ,for instance1 the capital of a company or the cost of the property is1 say1 #a1jjj1jjj1 and where opening the mine for production requires four years1 the aggregate sum of accumulated compound interest at #e 7and most operators want more from a mining investment7 would be #baf1jjj4 ,under such circumstances1 if a year or two can be saved in getting to production by entering the property at a higher horizon1 the difference in accumulated interest will more than repay the infinitesimal extra cost of winding through a combined shaft of somewhat increased length in the inclined section4 ,the unknown character of the ore in depth is always a sound reason for reaching it as quickly and as cheaply as possible4 ,in result1 such shafts are usually best located when the vertical section enters the upper portion of the deposit4 ,the objective in location with regard to the strike of the ore-bodies is obviously to have an equal length of lateral ore-haul in every direction from the shaft4 ,it is easier to specify than to achieve this1 for in all speculative deposits ore-shoots are found to pursue curious vagaries as they go down4 ,ore-bodies do not reoccur with the same locus as in the upper levels1 and generally the chances to go wrong are more numerous than those to go right4 ,,number ,,of ,,shafts4--,the problem of whether the mine is to be opened by one or by two shafts of course influences location4 ,in metal mines under ,cases ,,ii and ,,iii 7outcrop properties7 the ore output requirements are seldom beyond the capacity of one shaft4 ,ventilation and escape-ways are usually easily managed through the old stopes4 ,under such circumstances1 the conditions warranting a second shaft are the length of underground haul and isolation of ore-bodies or veins4 ,lateral haulage underground is necessarily disintegrated by the various levels1 and usually has to be done by hand4 ,by shortening this distance of tramming and by consolidation of the material from all levels at the surface1 where mechanical haulage can be installed1 a second shaft is often justified4 ,there is therefore an economic limitation to the radius of a single shaft1 regardless of the ability of the shaft to handle the total output4 ,other questions also often arise which are of equal importance to haulage costs4 ,separate ore-shoots or ore-bodies or parallel deposits necessitate1 if worked from one shaft1 constant levels through unpayable ground and extra haul as well1 or ore-bodies may dip away from the original shaft along the strike of the deposit and a long haulage through dead levels must follow4 ,for instance1 levels and crosscuts cost roughly one-quarter as much per foot as shafts4 ,therefore four levels in barren ground1 to reach a parallel vein or isolated ore-body #a1jjj feet away1 would pay for a shaft #a1jjj feet deep4 ,at a depth of #a1jjj feet1 at least six levels might be necessary4 ,the tramming of ore by hand through such a distance would cost about double the amount to hoist it through a shaft and transport it mechanically to the dressing plant at surface4 ,the aggregate cost and operation of barren levels therefore soon pays for a second shaft4 ,if two or more shafts are in question1 they must obviously be set so as to best divide the work4 ,under ,cases ,,iv1 ,v1 and ,,vi1--that is1 deep-level projects1--ventilation and escape become most important considerations4 ,even where the volume of ore is within the capacity of a single shaft1 another usually becomes a necessity for these reasons4 ,their location is affected not only by the locus of the ore1 but1 as said1 by the time required to reach it4 ,where two shafts are to be sunk to inclined deposits1 it is usual to set one so as to intersect the deposit at a lower point than the other4 ,production can be started from the shallower1 before the second is entirely ready4 ,the ore above the horizon of intersection of the deeper shaft is thus accessible from the shallower shaft1 and the difficulty of long rises or crosscuts from that deepest shaft does not arise4 ,,chapter ,,viii4 ,development of ,mines 7,continued74 ,,shape ,,and ,,size ,,of ,,shafts2 ,,speed ,,of ,,sinking2 ,,tunnels4 ,,shape ,,of ,,shafts4--,shafts may be round or rectangular499 ,round vertical shafts are largely applied to coal-mines1 and some engineers have advocated their usefulness to the mining of the metals under discussion4 ,their great advantages lie in their structural strength1 in the large amount of free space for ventilation1 and in the fact that if walled with stone1 brick1 concrete1 or steel1 they can be made water-tight so as to prevent inflow from water-bearing strata1 even when under great pressure4 ,the round walled shafts have a longer life than timbered shafts4 ,all these advantages pertain much more to mining coal or iron than metals1 for unsound1 wet ground is often the accompaniment of coal-measures1 and seldom troubles metal-mines4 ,ventilation requirements are also much greater in coal-mines4 ,from a metal-miner's standpoint1 round shafts are comparatively much more expensive than the rectangular timbered type49999 ,for a larger area must be excavated for the same useful space1 and if support is needed1 satisfactory walling1 which of necessity must be brick1 stone1 concrete1 or steel1 cannot be cheaply accomplished under the conditions prevailing in most metal regions4 ,although such shafts would have a longer life1 the duration of timbered shafts is sufficient for most metal mines4 ,it follows that1 as timber is the cheapest and all things considered the most advantageous means of shaft support for the comparatively temporary character of metal mines1 to get the strains applied to the timbers in the best manner1 and to use the minimum amount of it consistent with security1 and to lose the least working space1 the shaft must be constructed on rectangular lines4 ,footnote 993 ,octagonal shafts were sunk in ,mexico in former times4 ,at each face of the octagon was a whim run by mules1 and hauling leather buckets4 ,footnote 99993 ,the economic situation is rapidly arising in a number of localities that steel beams can be usefully used instead of timber4 ,the same arguments apply to this type of support that apply to timber4 ,the variations in timbered shaft design arise from the possible arrangement of compartments4 ,many combinations can be imagined1 of which ,figures #i1 #aj1 #aa1 #ab1 #ac1 and #ad are examples4 ,illustration3 ,,fig4 #i4 ,,fig4 #aj4 ,,fig4 #aa4 ,,fig4 #ab4 ,,fig4 #ac4 ,,fig4 #ad4 ,the arrangement of compartments shown in ,figures #i1 #aj1 #aa1 and #ac gives the greatest strength4 ,it permits timbering to the best advantage1 and avoids the danger underground involved in crossing one compartment to reach another4 ,it is therefore generally adopted4 ,any other arrangement would obviously be impossible in inclined or combined shafts4 ,,size ,,of ,,shafts4--,in considering the size of shafts to be installed1 many factors are involved4 ,they are in the main3-- a4 ,amount of ore to be handled4 b4 ,winding plant4 c4 ,vehicle of transport4 d4 ,depth4 e4 ,number of men to be worked underground4 f4 ,amount of water4 g4 ,ventilation4 h4 ,character of the ground4 i4 ,capital outlay4 j4 ,operating expense4 ,it is not to be assumed that these factors have been stated in the order of relative importance4 ,more or less emphasis will be attached to particular factors by different engineers1 and under different circumstances4 ,it is not possible to suggest any arbitrary standard for calculating their relative weight1 and they are so interdependent as to preclude separate discussion4 ,the usual result is a compromise between the demands of all4 ,certain factors1 however1 dictate a minimum position1 which may be considered as a datum from which to start consideration4 ,first1 a winding engine1 in order to work with any economy1 must be balanced1 that is1 a descending empty skip or cage must assist in pulling up a loaded one4 ,therefore1 except in mines of very small output1 at least two compartments must be made for hoisting purposes4 ,water has to be pumped from most mines1 escape-ways are necessary1 together with room for wires and air-pipes1 so that at least one more compartment must be provided for these objects4 ,we have thus three compartments as a sound minimum for any shaft where more than trivial output is required4 ,second1 there is a certain minimum size of shaft excavation below which there is very little economy in actual rock-breaking499 ,in too confined a space1 holes cannot be placed to advantage for the blast1 men cannot get round expeditiously1 and spoil cannot be handled readily4 ,the writer's own experience leads him to believe that1 in so far as rock-breaking is concerned1 to sink a shaft fourteen to sixteen feet long by six to seven feet wide outside the timbers1 is as cheap as to drive any smaller size within the realm of consideration1 and is more rapid4 ,this size of excavation permits of three compartments1 each about four to five feet inside the timbers4 ,footnote 993 ,notes on the cost of shafts in various regions which have been personally collected show a remarkable decrease in the cost per cubic foot of material excavated with increased size of shaft4 ,variations in skill1 in economic conditions1 and in method of accounting make data regarding different shafts of doubtful value1 but the following are of interest3-- ,in ,australia1 eight shafts between #aj and #aa feet long by #d to #e feet wide cost an average of #a4bj per cubic foot of material excavated4 ,six shafts #ac to #ad feet long by #d to #e feet wide cost an average of #j4ie per cubic foot2 seven shafts #ad to #af feet long and #e to #g feet wide cost an average of #j4hb per cubic foot4 ,in ,south ,africa1 eleven shafts #ah to #ai feet long by #g to #h feet wide cost an average of #j4hb per cubic foot2 five shafts #ba to #be feet long by #h feet wide1 cost #j4gd2 and seven shafts #bh feet by #h feet cost #j4fj per cubic foot4 ,the cost of timber1 it is true1 is a factor of the size of shaft1 but the labor of timbering does not increase in the same ratio4 ,in any event1 the cost of timber is only about #ae of the actual shaft cost1 even in localities of extremely high prices4 ,third1 three reasons are rapidly making the self-dumping skip the almost universal shaft-vehicle1 instead of the old cage for cars4 ,first1 there is a great economy in labor for loading into and discharging from a shaft2 second1 there is more rapid despatch and discharge and therefore a larger number of possible trips2 third1 shaft-haulage is then independent of delays in arrival of cars at stations1 while tramming can be done at any time and shaft-haulage can be concentrated into certain hours4 ,cages to carry mine cars and handle the same load as a skip must either be big enough to take two cars1 which compels a much larger shaft than is necessary with skips1 or they must be double-decked1 which renders loading arrangements underground costly to install and expensive to work4 ,for all these reasons1 cages can be justified only on metal mines of such small tonnage that time is no consideration and where the saving of men is not to be effected4 ,in compartments of the minimum size mentioned above 7four to five feet either way7 a skip with a capacity of from two to five tons can be installed1 although from two to three tons is the present rule4 ,lighter loads than this involve more trips1 and thus less hourly capacity1 and1 on the other hand1 heavier loads require more costly engines4 ,this matter is further discussed under ,haulage ,appliances4 ,we have therefore as the economic minimum a shaft of three compartments 7,fig4 #i71 each four to five feet square4 ,when the maximum tonnage is wanted from such a shaft at the least operating cost1 it should be equipped with loading bins and skips4 ,the output capacity of shafts of this size and equipment will depend in a major degree upon the engine employed1 and in a less degree upon the hauling depth4 ,the reason why depth is a subsidiary factor is that the rapidity with which a load can be drawn is not wholly a factor of depth4 ,the time consumed in hoisting is partially expended in loading1 in acceleration and retardation of the engine1 and in discharge of the load4 ,these factors are constant for any depth1 and extra distance is therefore accomplished at full speed of the engine4 ,vertical shafts will1 other things being equal1 have greater capacity than inclines1 as winding will be much faster and length of haul less for same depth4 ,since engines have1 however1 a great tractive ability on inclines1 by an increase in the size of skip it is usually possible partially to equalize matters4 ,therefore the size of inclines for the same output need not differ materially from vertical shafts4 ,the maximum capacity of a shaft whose equipment is of the character and size given above1 will1 as stated1 decrease somewhat with extension in depth of the haulage horizon4 ,at #ejj feet1 such a shaft if vertical could produce #gj to #hj tons per hour comfortably with an engine whose winding speed was #gjj feet per minute4 ,as men and material other than ore have to be handled in and out of the mine1 and shaft-sinking has to be attended to1 the winding engine cannot be employed all the time on ore4 ,twelve hours of actual daily ore-winding are all that can be expected without auxiliary help4 ,this represents a capacity from such a depth of #hjj to #a1jjj tons per day4 ,a similar shaft1 under ordinary working conditions1 with an engine speed of #b1jjj feet per minute1 should from1 say1 #c1jjj feet have a capacity of about #djj to #fjj tons daily4 ,it is desirable to inquire at what stages the size of shaft should logically be enlarged in order to attain greater capacity4 ,a considerable measure of increase can be obtained by relieving the main hoisting engine of all or part of its collateral duties4 ,where the pumping machinery is not elaborate1 it is often possible to get a small single winding compartment into the gangway without materially increasing the size of the shaft if the haulage compartments be made somewhat narrower 7,fig4 #aj74 ,such a compartment would be operated by an auxiliary engine for sinking1 handling tools and material1 and assisting in handling men4 ,if this arrangement can be effected1 the productive time of the main engine can be expanded to about twenty hours with an addition of about two-thirds to the output4 ,where the exigencies of pump and gangway require more than two and one-half feet of shaft length1 the next stage of expansion becomes four full-sized compartments 7,fig4 #aa74 ,by thus enlarging the auxiliary winding space1 some assistance may be given to ore-haulage in case of necessity4 ,the mine whose output demands such haulage provisions can usually stand another foot of width to the shaft1 so that the dimensions come to about #ba feet to #bb feet by #g feet to #h feet outside the timbers4 ,such a shaft1 with three- to four-ton skips and an appropriate engine1 will handle up to #bej tons per hour from a depth of #a1jjj feet4 ,the next logical step in advance is the shaft of five compartments with four full-sized haulage ways 7,fig4 #ac71 each of greater size than in the above instance4 ,in this case1 the auxiliary engine becomes a balanced one1 and can be employed part of the time upon ore-haulage4 ,such a shaft will be about #bf feet to #bh feet long by #h feet wide outside the timbers1 when provision is made for one gangway4 ,the capacity of such shafts can be up to #d1jjj tons a day1 depending on the depth and engine4 ,when very large quantities of water are to be dealt with and rod-driven pumps to be used1 two pumping compartments are sometimes necessary1 but other forms of pumps do not require more than one compartment1--an additional reason for their use4 ,for depths greater than #c1jjj feet1 other factors come into play4 ,ventilation questions become of more import4 ,the mechanical problems on engines and ropes become involved1 and their sum-effect is to demand much increased size and a greater number of compartments4 ,the shafts at ,johannesburg intended as outlets for workings #e1jjj feet deep are as much as #df feet by #i feet outside timbers4 ,it is not purposed to go into details as to sinking methods or timbering4 ,while important matters1 they would unduly prolong this discussion4 ,besides1 a multitude of treatises exist on these subjects and cover all the minuti of such work4 ,,speed ,,of ,,sinking4--,mines may be divided into two cases1--those being developed only1 and those being operated as well as developed4 ,in the former1 the entrance into production is usually dependent upon the speed at which the shaft is sunk4 ,until the mine is earning profits1 there is a loss of interest on the capital involved1 which1 in ninety-nine instances out of a hundred1 warrants any reasonable extra expenditure to induce more rapid progress4 ,in the case of mines in operation1 the volume of ore available to treatment or valuation is generally dependent to a great degree upon the rapidity of the extension of workings in depth4 ,it will be demonstrated later that1 both from a financial and a technical standpoint1 the maximum development is the right one and that unremitting extension in depth is not only justifiable but necessary4 ,speed under special conditions or over short periods has a more romantic than practical interest1 outside of its value as a stimulant to emulation4 ,the thing that counts is the speed which can be maintained over the year4 ,rapidity of sinking depends mainly on3-- a4 ,whether the shaft is or is not in use for operating the mine4 b4 ,the breaking character of the rock4 c4 ,the amount of water4 ,the delays incident to general carrying of ore and men are such that the use of the main haulage engine for shaft-sinking is practically impossible1 except on mines with small tonnage output4 ,even with a separate winch or auxiliary winding-engine1 delays are unavoidable in a working shaft1 especially as it usually has more water to contend with than one not in use for operating the mine4 ,the writer's own impression is that an average of #dj feet per month is the maximum possibility for year in and out sinking under such conditions4 ,in fact1 few going mines manage more than #djj feet a year4 ,in cases of clean shaft-sinking1 where every energy is bent to speed1 #aej feet per month have been averaged for many months4 ,special cases have occurred where as much as #bac feet have been achieved in a single month4 ,with ordinary conditions1 #a1bjj feet in a year is very good work4 ,rock awkward to break1 and water especially1 lowers the rate of progress very materially4 ,further reference to speed will be found in the chapter on ,drilling ,methods4 ,,tunnel ,,entry4--,the alternative of entry to a mine by tunnel is usually not a question of topography altogether1 but1 like everything else in mining science1 has to be tempered to meet the capital available and the expenditure warranted by the value showing4 ,in the initial prospecting of a mine1 tunnels are occasionally overdone by prospectors4 ,often more would be proved by a few inclines4 ,as the pioneer has to rely upon his right arm for hoisting and drainage1 the tunnel offers great temptations1 even when it is long and gains but little depth4 ,at a more advanced stage of development1 the saving of capital outlay on hoisting and pumping equipment1 at a time when capital is costly to secure1 is often sufficient justification for a tunnel entry4 ,but at the stage where the future working of ore below a tunnel-level must be contemplated1 other factors enter4 ,for ore below tunnel-level a shaft becomes necessary1 and in cases where a tunnel enters a few hundred feet below the outcrop the shaft should very often extend to the surface1 because internal shafts1 winding from tunnel-level1 require large excavations to make room for the transfer of ore and for winding gear4 ,the latter must be operated by transmitted power1 either that of steam1 water1 electricity1 or air4 ,where power has to be generated on the mine1 the saving by the use of direct steam1 generated at the winding gear1 is very considerable4 ,moreover1 the cost of haulage through a shaft for the extra distance from tunnel-level to the surface is often less than the cost of transferring the ore and removing it through the tunnel4 ,the load once on the winding-engine1 the consumption of power is small for the extra distance1 and the saving of labor is of consequence4 ,on the other hand1 where drainage problems arise1 they usually outweigh all other considerations1 for whatever the horizon entered by tunnel1 the distance from that level to the surface means a saving of water-pumpage against so much head4 ,the accumulation of such constant expense justifies a proportioned capital outlay4 ,in other words1 the saving of this extra pumping will annually redeem the cost of a certain amount of tunnel1 even though it be used for drainage only4 ,in order to emphasize the rapidity with which such a saving of constant expense will justify capital outlay1 one may tabulate the result of calculations showing the length of tunnel warranted with various hypothetical factors of quantity of water and height of lift eliminated from pumping4 ,in these computations1 power is taken at the low rate of #fj per horsepower-year1 the cost of tunneling at an average figure of #bj per foot1 and the time on the basis of a ten-year life for the mine4 ,feet of ,tunnel ,paid for in #aj ,years with ,under-mentioned ,conditions4 ,feet of #ajj1jjj #bjj1jjj #cjj1jjj #ejj1jjj #a1jjj1jjj ,water ,lift ,gallons ,gallons ,gallons ,gallons ,gallons ,avoided per ,diem per ,diem per ,diem per ,diem per ,diem ---------------------------------------- ---------------- #ajj #fjj #a1bjj #a1hjj #c1jjj #f1jjj #bjj #a1bjj #b1djj #c1fjj #f1jjj #ab1jjj #cjj #a1hjj #c1fjj #e1djj #i1jjj #ah1jjj #ejj #c1jjj #f1jjj #i1jjj #ae1jjj #cj1jjj #a1jjj #f1jjj #ab1jjj #ah1jjj #cj1jjj #fj1jjj ,the size of tunnels where ore-extraction is involved depends upon the daily tonnage output required1 and the length of haul4 ,the smallest size that can be economically driven and managed is about #f-a_/b feet by #f feet inside the timbers4 ,such a tunnel1 with single track for a length of #a1jjj feet1 with one turn-out1 permits handling up to #ejj tons a day with men and animals4 ,if the distance be longer or the tonnage greater1 a double track is required1 which necessitates a tunnel at least #h feet wide by #f-a_/b feet to #g feet high1 inside the timbers4 ,there are tunnel projects of a much more impressive order than those designed to operate upper levels of mines2 that is1 long crosscut tunnels designed to drain and operate mines at very considerable depths1 such as the ,sutro tunnel at ,virginia ,city4 ,the advantage of these tunnels is very great1 especially for drainage1 and they must be constructed of large size and equipped with appliances for mechanical haulage4 ,,chapter ,,ix4 ,development of ,mines 7,concluded74 ,,subsidiary ,,development2--,,stations2 ,,crosscuts2 ,,levels2 ,,interval ,,between ,,levels2 ,,protection ,,of ,,levels2 ,,winzes ,,and ,,rises4 ,,development ,,in ,,the ,,prospecting ,,stage2 ,,drilling4 ,,subsidiary ,,development4 ,stations1 crosscuts1 levels1 winzes1 and rises follow after the initial entry4 ,they are all expensive1 and the least number that will answer is the main desideratum4 ,,stations4--,as stations are the outlets of the levels to the shaft1 their size and construction is a factor of the volume and character of the work at the levels which they are to serve4 ,if no timber is to be handled1 and little ore1 and this on cages1 the stations need be no larger than a good sized crosscut4 ,where timber is to be let down1 they must be ten to fifteen feet higher than the floor of the crosscut4 ,where loading into skips is to be provided for1 bins must be cut underneath and sufficient room be provided to shift the mine cars comfortably4 ,such bins are built of from #ej to #ejj tons' capacity in order to contain some reserve for hoisting purposes1 and in many cases separate bins must be provided on opposite sides of the shaft for ore and waste4 ,it is a strong argument in favor of skips1 that with this means of haulage storage capacity at the stations is possible1 and the hoisting may then go on independently of trucking and1 as said before1 there are no idle men at the stations4 ,illustration3 ,fig4 #ae4--;,cross-section of station arrangement for skip-haulage in vertical shaft4 ,illustration3 ,fig4 #af4--;,cross-section of station arrangement for skip-haulage in vertical shaft4 ,it is always desirable to concentrate the haulage to the least number of levels1 for many reasons4 ,among them is that1 where haulage is confined to few levels1 storage-bins are not required at every station4 ,figures #ae1 #af1 #ag1 and #ah illustrate various arrangements of loading bins4 ,,crosscuts4--,crosscuts are for two purposes1 for roadway connection of levels to the shaft or to other levels1 and for prospecting purposes4 ,the number of crosscuts for roadways can sometimes be decreased by making the connections with the shaft at every second or even every third level1 thus not only saving in the construction cost of crosscuts and stations1 but also in the expenses of scattered tramming4 ,the matter becomes especially worth considering where the quantity of ore that can thus be accumulated warrants mule or mechanical haulage4 ,this subject will be referred to later on4 ,illustration3 ,fig4 #ag4--;,arrangement of loading chutes in vertical shaft4 ,on the second purpose of crosscuts1--that of prospecting1--one observation merits emphasis4 ,this is1 that the tendency of ore-fissures to be formed in parallels warrants more systematic crosscutting into the country rock than is done in many mines4 ,illustration3 ,fig4 #ah4--;,cross-section of station arrangement for skip-haulage in inclined shaft4 ,,levels4 ,the word level is another example of miners' adaptations in nomenclature4 ,its use in the sense of tunnels driven in the direction of the strike of the deposit has better1 but less used1 synonyms in the words drifts or drives4 ,the term level is used by miners in two senses1 in that it is sometimes applied to all openings on one horizon1 crosscuts included4 ,levels are for three purposes1--for a stoping base2 for prospecting the deposit2 and for roadways4 ,as a prospecting and a stoping base it is desirable that the level should be driven on the deposit2 as a roadway1 that it should constitute the shortest distance between two points and be in the soundest ground4 ,on narrow1 erratic deposits the levels usually must serve all three purposes at once2 but in wider and more regular deposits levels are often driven separately for roadways from the level which forms the stoping base and prospecting datum4 ,there was a time when mines were worked by driving the level on ore and enlarging it top and bottom as far as the ground would stand1 then driving the next level #ae to #bj feet below1 and repeating the operation4 ,this interval gradually expanded1 but for some reason #ajj feet was for years assumed to be the proper distance between levels4 ,scattered over every mining camp on earth are thousands of mines opened on this empirical figure1 without consideration of the reasons for it or for any other distance4 ,the governing factors in determining the vertical interval between levels are the following3-- a4 ,the regularity of the deposit4 b4 ,the effect of the method of excavation of winzes and rises4 c4 ,the dip and the method of stoping4 ,,regularity ,,of ,,the ,,deposit4--,from a prospecting point of view the more levels the better1 and the interval therefore must be determined somewhat by the character of the deposit4 ,in erratic deposits there is less risk of missing ore with frequent levels1 but it does not follow that every level need be a through roadway to the shaft or even a stoping base4 ,in such deposits1 intermediate levels for prospecting alone are better than complete levels1 each a roadway4 ,nor is it essential1 even where frequent levels are required for a stoping base1 that each should be a main haulage outlet to the shaft4 ,in some mines every third level is used as a main roadway1 the ore being poured from the intermediate ones down to the haulage line4 ,thus tramming and shaft work1 as stated before1 can be concentrated4 ,,effect ,,of ,,method ,,of ,,excavating ,,winzes ,,and ,,rises4--,with hand drilling and hoisting1 winzes beyond a limited depth become very costly to pull spoil out of1 and rises too high become difficult to ventilate1 so that there is in such cases a limit to the interval desirable between levels1 but these difficulties largely disappear where air-winches and air-drills are used4 ,,the ,,dip ,,and ,,method ,,of ,,stoping4--,the method of stoping is largely dependent upon the dip1 and indirectly thus affects level intervals4 ,in dips under that at which material will flow in the stopes--about #de to #ej--the interval is greatly dependent on the method of stope-transport4 ,where ore is to be shoveled from stopes to the roadway1 the levels must be comparatively close together4 ,where deposits are very flat1 under #bj1 and walls fairly sound1 it is often possible to use a sort of long wall system of stoping and to lay tracks in the stopes with self-acting inclines to the levels4 ,in such instances1 the interval can be expanded to #bej or even #djj feet4 ,in dips between #bj and #de1 tracks are not often possible1 and either shoveling or bumping troughs99 are the only help to transport4 ,with shoveling1 intervals of #ajj feet9999 are most common1 and with troughs the distance can be expanded up to #aej or #age feet4 ,footnote 993 ,page #acf4 ,footnote 99993 ,intervals given are measured on the dip4 ,in dips of over #dj to #ej1 depending on the smoothness of the foot wall1 the distance can again be increased1 as stope-transport is greatly simplified1 since the stope materials fall out by gravity4 ,in timbered stopes1 in dips over about #de1 intervals of #aej to #bjj feet are possible4 ,in filled stopes intervals of over #aej feet present difficulties in the maintenance of ore-passes1 for the wear and tear of longer use often breaks the timbers4 ,in shrinkage-stopes1 where no passes are to be maintained and few winzes put through1 the interval is sometimes raised to #bej feet4 ,the subject is further discussed under ,stoping4 ,another factor bearing on level intervals is the needed insurance of sufficient points of stoping attack to keep up a certain output4 ,this must particularly influence the manager whose mine has but little ore in reserve4 ,illustration3 ,fig4 #ai4 ,,protection ,,of ,,levels4--,until recent years1 timbering and occasional walling was the only method for the support of the roof1 and for forming a platform for a stoping base4 ,where the rock requires no support sublevels can be used as a stoping base1 and timbering for such purpose avoided altogether 7,figs4 #ch1 #ci1 #db74 ,in such cases the main roadway can then be driven on straight lines1 either in the walls or in the ore1 and used entirely for haulage4 ,the subheading for a stoping base is driven far enough above or below the roadway 7depending on whether overhand or underhand stoping is to be used7 to leave a supporting pillar which is penetrated by short passes for ore4 ,in overhand stopes1 the ore is broken directly on the floor of an upper sublevel2 and in underhand stopes1 broken directly from the bottom of the sublevel4 ,the method entails leaving a pillar of ore which can be recovered only with difficulty in mines where stope-support is necessary4 ,the question of its adoption is then largely one of the comparative cost of timbering1 the extra cost of the sublevel1 and the net value of the ore left4 ,in bad swelling veins1 or badly crushing walls1 where constant repair to timbers would be necessary1 the use of a sublevel is a most useful alternative4 ,it is especially useful with stopes to be left open or worked by shrinkage-stoping methods4 ,if the haulage level1 however1 is to be the stoping base1 some protection to the roadway must be provided4 ,there are three systems in use1--by wood stulls or sets 7,figs4 #ai1 #cj1 #dc71 by dry-walling with timber caps 7,fig4 #ce71 and in some localities by steel sets4 ,stulls are put up in various ways1 and1 as their use entails the least difficulty in taking the ore out from beneath the level1 they are much favored1 but are applicable only in comparatively narrow deposits4 ,,winzes ,,and ,,rises4 ,these two kinds of openings for connecting two horizons in a mine differ only in their manner of construction4 ,a winze is sunk underhand1 while a rise is put up overhand4 ,when the connection between levels is completed1 a miner standing at the bottom usually refers to the opening as a rise1 and when he goes to the top he calls it a winze4 ,this confusion in terms makes it advisable to refer to all such completed openings as winzes1 regardless of how they are constructed4 ,in actual work1 even disregarding water1 it costs on the average about #cj less to raise than to sink such openings1 for obviously the spoil runs out or is assisted by gravity in one case1 and in the other has to be shoveled and hauled up4 ,moreover1 it is easier to follow the ore in a rise than in a winze4 ,it usually happens1 however1 that in order to gain time both things are done1 and for prospecting purposes sinking is necessary4 ,the number of winzes required depends upon the method of stoping adopted1 and is mentioned under ,stoping4 ,after stoping1 the number necessary to be maintained open depends upon the necessities of ventilation1 of escape1 and of passageways for material to be used below4 ,where stopes are to be filled with waste1 more winzes must be kept open than when other methods are used1 and these winzes must be in sufficient alignment to permit the continuous flow of material down past the various levels4 ,in order that the winzes should deliver timber and filling to the most advantageous points1 they should1 in dipping ore-bodies1 be as far as possible on the hanging wall side4 ,,development ,,in ,,the ,,early ,,prospecting ,,stage4 ,the prime objects in the prospecting stage are to expose the ore and to learn regarding the ore-bodies something of their size1 their value1 metallurgical character1 location1 dip1 strike1 etc41--so much at least as may be necessary to determine the works most suitable for their extraction or values warranting purchase4 ,in outcrop mines there is one rule1 and that is follow the ore4 ,small temporary inclines following the deposit1 even though they are eventually useless2 are nine times out of ten justified4 ,in prospecting deep-level projects1 it is usually necessary to layout work which can be subsequently used in operating the mine1 because the depth involves works of such considerable scale1 even for prospecting1 that the initial outlay does not warrant any anticipation of revision4 ,such works have to be located and designed after a study of the general geology as disclosed in adjoining mines4 ,practically the only method of supplementing such information is by the use of churn- and diamond-drills4 ,,drilling4--,churn-drills are applicable only to comparatively shallow deposits of large volume4 ,they have an advantage over the diamond drill in exposing a larger section and in their application to loose material2 but inability to determine the exact horizon of the spoil does not lend them to narrow deposits1 and in any event results are likely to be misleading from the finely ground state of the spoil4 ,they are1 however1 of very great value for preliminary prospecting to shallow horizons4 ,two facts in diamond-drilling have to be borne in mind3 the indication of values is liable to be misleading1 and the deflection of the drill is likely to carry it far away from its anticipated destination4 ,a diamond-drill secures a small section which is sufficiently large to reveal the geology1 but the values disclosed in metal mines must be accepted with reservations4 ,the core amounts to but a little sample out of possibly large amounts of ore1 which is always of variable character1 and the core is most unlikely to represent the average of the deposit4 ,two diamond-drill holes on the ,oroya ,brownhill mine both passed through the ore-body4 ,one apparently disclosed unpayable values1 the other seemingly showed ore forty feet in width assaying #hj per ton4 ,neither was right4 ,on the other hand1 the predetermination of the location of the ore-body justified expenditure4 ,a recent experiment at ,johannesburg of placing a copper wedge in the hole at a point above the ore-body and deflecting the drill on reintroducing it1 was successful in giving a second section of the ore at small expense4 ,the deflection of diamond-drill holes from the starting angle is almost universal4 ,it often amounts to a considerable wandering from the intended course4 ,the amount of such deflection varies with no seeming rule1 but it is probable that it is especially affected by the angle at which stratification or lamination planes are inclined to the direction of the hole4 ,a hole has been known to wander in a depth of #a1ejj feet more than #ejj feet from the point intended4 ,various instruments have been devised for surveying deep holes1 and they should be brought into use before works are laid out on the basis of diamond-drill results1 although none of the inventions are entirely satisfactory4 ,,chapter ,x4 ,stoping4 ,,methods ,,of ,,ore-,,breaking2 ,,underhand ,,stopes2 ,,overhand ,,stopes2 ,,combined ,,stope4 ,,valuing ,,ore ,,in ,,course ,,of ,,breaking4 ,there is a great deal of confusion in the application of the word stoping4 ,it is used not only specifically to mean the actual ore-breaking1 but also in a general sense to indicate all the operations of ore-breaking1 support of excavations1 and transportation between levels4 ,it is used further as a noun to designate the hole left when the ore is taken out4 ,worse still1 it is impossible to adhere to miners' terms without employing it in every sense1 trusting to luck and the context to make the meaning clear4 ,the conditions which govern the method of stoping are in the main3-- a4 ,the dip4 b4 ,the width of the deposit4 c4 ,the character of the walls4 d4 ,the cost of materials4 e4 ,the character of the ore4 ,every mine1 and sometimes every stope in a mine1 is a problem special to itself4 ,any general consideration must therefore be simply an inquiry into the broad principles which govern the adaptability of special methods4 ,a logical arrangement of discussion is difficult1 if not wholly impossible1 because the factors are partially interdependent and of varying importance4 ,for discussion the subject may be divided into3 #a4 ,methods of ore-breaking4 #b4 ,methods of supporting excavation4 #c4 ,methods of transport in stopes4 ,,methods ,,of ,,ore-,,breaking4 ,the manner of actual ore-breaking is to drill and blast off slices from the block of ground under attack4 ,as rock obviously breaks easiest when two sides are free1 that is1 when corners can be broken off1 the detail of management for blasts is therefore to set the holes so as to preserve a corner for the next cut2 and as a consequence the face of the stope shapes into a series of benches 7,fig4 #bb71--;inverted benches in the case of overhand stopes 7,figs4 #bj1 #ba74 ,the size of these benches will in a large measure depend on the depth of the holes4 ,in wide stopes with machine-drills they vary from #g to #aj feet2 in narrow stopes with hand-holes1 from two to three feet4 ,illustration3 ,fig4 #bj4 ,the position of the men in relation to the working face gives rise to the usual primary classification of the methods of stoping4 ,they are3-- #a4 ,underhand stopes1 #b4 ,overhand stopes1 #c4 ,combined stopes4 ,these terms originated from the direction of the drill-holes1 but this is no longer a logical basis of distinction1 for underhand holes in overhand stopes1--as in rill-stoping1--are used entirely in some mines 7,fig4 #ba74 ,illustration3 ,fig4 #ba4 ,,underhand ,,stopes4--,underhand stopes are those in which the ore is broken downward from the levels4 ,inasmuch as this method has the advantage of allowing the miner to strike his blows downward and to stand upon the ore when at work1 it was almost universal before the invention of powder2 and was applied more generally before the invention of machine-drills than since4 ,it is never rightly introduced unless the stope is worked back from winzes through which the ore broken can be let down to the level below1 as shown in ,figures #bb and #bc4 ,illustration3 ,fig4 #bb4 ,this system can be advantageously applied only in the rare cases in which the walls require little or no support1 and where very little or no waste requiring separation is broken with the ore in the stopes4 ,to support the walls in bad ground in underhand stopes would be far more costly than with overhand stopes1 for square-set timbering would be most difficult to introduce1 and to support the walls with waste and stulls would be even more troublesome4 ,any waste broken must needs be thrown up to the level above or be stored upon specially built stages--again a costly proceeding4 ,a further drawback lies in the fact that the broken ore follows down the face of the stope1 and must be shoveled off each bench4 ,it thus all arrives at a single point1--the winze1--and must be drawn from a single ore-pass into the level4 ,this usually results not only in more shoveling but in a congestion at the passes not present in overhand stoping1 for with that method several chutes are available for discharging ore into the levels4 ,where the walls require no support and no selection is desired in the stopes1 the advantage of the men standing on the solid ore to work1 and of having all down holes and therefore drilled wet1 gives this method a distinct place4 ,in using this system1 in order to protect the men1 a pillar is often left under the level by driving a sublevel1 the pillar being easily recoverable later4 ,the method of sublevels is of advantage largely in avoiding the timbering of levels4 ,illustration3 ,fig4 #bc4--,longitudinal section of an underhand stope4 ,,overhand ,,stopes4--,by far the greatest bulk of ore is broken overhand1 that is broken upward from one level to the next above4 ,there are two general forms which such stopes are given1--horizontal and rill4 ,illustration3 ,fig4 #bd4--;,horizontal-cut overhand stope--longitudinal section4 ,the horizontal flat-back or long-wall stope1 as it is variously called1 shown in ,figure #bd1 is operated by breaking the ore in slices parallel with the levels4 ,in rill-stoping the ore is cut back from the winzes in such a way that a pyramid-shaped room is created1 with its apex in the winze and its base at the level 7,figs4 #be and #bf74 ,horizontal or flat-backed stopes can be applied to almost any dip1 while rill-stoping finds its most advantageous application where the dip is such that the ore will run1 or where it can be made to run with a little help4 ,the particular application of the two systems is dependent not only on the dip but on the method of supporting the excavation and the ore4 ,with rill-stoping1 it is possible to cut the breaking benches back horizontally from the winzes 7,fig4 #be71 or to stagger the cuts in such a manner as to take the slices in a descending angle 7,figs4 #ba and #bf74 ,illustration3 ,fig4 #be4--,rill-cut overhand stope--longitudinal section4 ,in the rill method of incline cuts1 all the drill-holes are down holes 7,fig4 #ba71 and can be drilled wet1 while in horizontal cuts or flat-backed stopes1 at least part of the holes must be uppers 7,fig4 #bj74 ,aside from the easier and cheaper drilling and setting up of machines with this kind of cut1 there is no drill dust1--a great desideratum in these days of miners' phthisis4 ,a further advantage in the rill cut arises in cases where horizontal jointing planes run through the ore of a sort from which unduly large masses break away in flat-back stopes4 ,by the descending cut of the rill method these calamities can be in a measure avoided4 ,in cases of dips over #dj the greatest advantage in rill stoping arises from the possibility of pouring filling or timber into the stope from above with less handling1 because the ore and material will run down the sides of the pyramid 7,figs4 #cb and #cd74 ,thus not only is there less shoveling required1 but fewer ore-passes and a less number of preliminary winzes are necessary1 and a wider level interval is possible4 ,this matter will be gone into more fully later4 ,illustration3 ,fig4 #bf4--,rill-cut overhand stope-longitudinal section4 ,,combined ,,stopes4--,a combined stope is made by the coincident working of the underhand and rill method 7,fig4 #bg74 ,this order of stope has the same limitations in general as the underhand kind4 ,for flat veins with strong walls1 it has a great superiority in that the stope is carried back more or less parallel with the winzes1 and thus broken ore after blasting lies in a line on the gradient of the stope4 ,it is1 therefore1 conveniently placed for mechanical stope haulage4 ,a further advantage is gained in that winzes may be placed long distances apart1 and that men are not required1 either when at work or passing to and from it1 to be ever far from the face1 and they are thus in the safest ground1 so that timber and filling protection which may be otherwise necessary is not required4 ,this method is largely used in ,south ,africa4 ,illustration3 ,fig4 #bg4--,longitudinal section of a combined stope4 ,,minimum ,,width ,,of ,,stopes4--,the minimum stoping width which can be consistently broken with hand-holes is about #cj inches1 and this only where there is considerable dip to the ore4 ,this space is so narrow that it is of doubtful advantage in any case1 and #dj inches is more common in narrow mines1 especially where worked with white men4 ,where machine-drills are used about #d feet is the minimum width feasible4 ,,resuing4--,in very narrow veins where a certain amount of wall-rock must be broken to give working space1 it pays under some circumstances to advance the stope into the wall-rock ahead of the ore1 thus stripping the ore and enabling it to be broken separately4 ,this permits of cleaner selection of the ore2 but it is a problem to be worked out in each case1 as to whether rough sorting of some waste in the stopes1 or further sorting at surface with inevitable treatment of some waste rock1 is more economical than separate stoping cuts and inevitably wider stopes4 ,,valuing ,,ore ,,in ,,course ,,of ,,breaking4--,there are many ores whose payability can be determined by inspection1 but there are many of which it cannot4 ,continuous assaying is in the latter cases absolutely necessary to avoid the treatment of valueless material4 ,in such instances1 sampling after each stoping-cut is essential1 the unprofitable ore being broken down and used as waste4 ,where values fade into the walls1 as in impregnation deposits1 the width of stopes depends upon the limit of payability4 ,in these cases1 drill-holes are put into the walls and the drillings assayed4 ,if the ore is found profitable1 the holes are blasted out4 ,the gauge of what is profitable in such situations is not dependent simply upon the average total working costs of the mine1 for ore in that position can be said to cost nothing for development work and administration2 moreover1 it is usually more cheaply broken than the average breaking cost1 men and machines being already on the spot4 ,,chapter ,,xi4 ,methods of ,supporting ,excavation4 ,,timbering2 ,,filling ,,with ,,waste2 ,,filling ,,with ,,broken ,,ore2 ,,pillars ,,of ,,ore2 ,,artificial ,,pillars2 ,,caving ,,system4 ,most stopes require support to be given to the walls and often to the ore itself4 ,where they do require support there are five principal methods of accomplishing it4 ,the application of any particular method depends upon the dip1 width of ore-body1 character of the ore and walls1 and cost of materials4 ,the various systems are by3-- #a4 ,timbering4 #b4 ,filling with waste4 #c4 ,filling with broken ore subsequently withdrawn4 #d4 ,pillars of ore4 #e4 ,artificial pillars built of timbers and waste4 #f4 ,caving4 ,,timbering4--,at one time timbering was the almost universal means of support in such excavations1 but gradually various methods for the economical application of waste and ore itself have come forward1 until timbering is fast becoming a secondary device4 ,aside from economy in working without it1 the dangers of creeps1 or crushing1 and of fires are sufficient incentives to do away with wood as far as possible4 ,there are three principal systems of timber support to excavations1--by stulls1 square-sets1 and cribs4 ,stulls are serviceable only where the deposit is so narrow that the opening can be bridged by single timbers between wall and wall 7,figs4 #bh and #dc74 ,this system can be applied to any dip and is most useful in narrow deposits where the walls are not too heavy4 ,stulls in inclined deposits are usually set at a slightly higher angle than that perpendicular to the walls1 in order that the vertical pressure of the hanging wall will serve to tighten them in position4 ,the stull system can1 in inclined deposits1 be further strengthened by building waste pillars against them1 in which case the arrangement merges into the system of artificial pillars4 ,illustration3 ,fig4 #bh4--,longitudinal section of stull-supported stope4 ,illustration3 ,fig4 #bi4--,longitudinal section showing square-set timbering4 ,illustration3 ,fig4 #cj4--,square-set timbering on inclined ore-body4 ,showing ultimate strain on timbers4 ,square-sets 7,figs4 #bi and #cj71 that is1 trusses built in the opening as the ore is removed1 are applicable to almost any dip or width of ore1 but generally are applied only in deposits too wide1 or to rock too heavy1 for stulls4 ,such trusses are usually constructed on vertical and horizontal lines1 and while during actual ore-breaking the strains are partially vertical1 ultimately1 however1 when the weight of the walls begins to be felt1 these strains1 except in vertical deposits1 come at an angle to lines of strength in the trusses1 and therefore timber constructions of this type present little ultimate resistance 7,fig4 #cj74 ,square-set timbers are sometimes set to present the maximum resistance to the direction of strain1 but the difficulties of placing them in position and variations in the direction of strain on various parts of the stope do not often commend the method4 ,as a general rule square-sets on horizontal lines answer well enough for the period of actual ore-breaking4 ,the crushing or creeps is usually some time later2 and if the crushing may damage the whole mine1 their use is fraught with danger4 ,renforcement by building in waste is often resorted to4 ,when done fully1 it is difficult to see the utility of the enclosed timber1 for entire waste-filling would in most cases be cheaper and equally efficient4 ,illustration3 ,fig4 #ca4--;,cribs4 ,there is always1 with wood constructions1 as said before1 the very pertinent danger of subsequent crushing and of subsidence in after years1 and the great risk of fires4 ,both these disasters have cost ,comstock and ,broken ,hill mines1 directly or indirectly1 millions of dollars1 and the outlay on timber and repairs one way or another would have paid for the filling system ten times over4 ,there are cases where1 by virtue of the cheapness of timber1 square-setting is the most economical method4 ,again1 there are instances where the ore lies in such a manner--particularly in limestone replacements--as to preclude other means of support4 ,these cases are being yearly more and more evaded by the ingenuity of engineers in charge4 ,the author believes it soon will be recognized that the situation is rare indeed where complete square-setting is necessarily without an economical alternative4 ,an objection is sometimes raised to filling in favor of timber1 in that if it become desirable to restope the walls for low-grade ore left behind1 such stopes could only be entered by drawing the filling1 with consequent danger of total collapse4 ,such a contingency can be provided for in large ore-bodies by installing an outer shell of sets of timber around the periphery of the stope and filling the inside with waste4 ,if the crushing possibilities are too great for this method then1 the subsequent recovery of ore is hopeless in any event4 ,in narrow ore-bodies with crushing walls recovery of ore once left behind is not often possible4 ,the third sort of timber constructions are cribs1 a log-house sort of structure usually filled with waste1 and more fully discussed under artificial pillars 7,fig4 #ca74 ,the further comparative merits of timbering with other methods will be analyzed as the different systems are described4 ,,filling ,,with ,,waste4--,the system of filling stope-excavations completely with waste in alternating progress with ore-breaking is of wide and increasingly general application 7,figs4 #cb1 #cc1 #cd1 #ce74 ,although a certain amount of waste is ordinarily available in the stopes themselves1 or from development work in the mine1 such a supply must usually be supplemented from other directions4 ,treatment residues afford the easiest and cheapest handled material4 ,quarried rock ranks next1 and in default of any other easy supply1 materials from crosscuts driven into the stope-walls are sometimes resorted to4 ,in working the system to the best advantage1 the winzes through the block of ore under attack are kept in alignment with similar openings above1 in order that filling may be poured through the mine from the surface or any intermediate point4 ,winzes to be used for filling should be put on the hanging-wall side of the area to be filled1 for the filling poured down will then reach the foot-wall side of the stopes with a minimum of handling4 ,in some instances1 one special winze is arranged for passing all filling from the surface to a level above the principal stoping operations2 and it is then distributed along the levels into the winzes1 and thus to the operating stopes1 by belt-conveyors4 ,illustration3 ,fig4 #cb4--,longitudinal section4 ,rill stope filled with waste4 ,illustration3 ,fig4 #cc4--,longitudinal section4 ,horizontal stope filled with waste4 ,illustration3 ,fig4 #cd4--,longitudinal section4 ,waste-filled stope with dry-walling of levels and passes4 ,in this system of stope support the ore is broken at intervals alternating with filling4 ,if there is danger of much loss from mixing broken ore and filling1 sollars of boards or poles are laid on the waste4 ,if the ore is very rich1 old canvas or cowhides are sometimes put under the boards4 ,before the filling interval1 the ore passes are built close to the face above previous filling and their tops covered temporarily to prevent their being filled with running waste4 ,if the walls are bad1 the filling is kept close to the face4 ,if the unbroken ore requires support1 short stulls set on the waste 7as in ,fig4 #ci7 are usually sufficient until the next cut is taken off1 when the timber can be recovered4 ,if stulls are insufficient1 cribs or bulkheads 7,fig4 #ca7 are also used and often buried in the filling4 ,illustration3 ,fig4 #ce4--;,cross-section of ,fig4 #cd on line ,a-,b4 ,both flat-backed and rill-stope methods of breaking are employed in conjunction with filled stopes4 ,the advantages of the rill-stopes are so patent as to make it difficult to understand why they are not universally adopted when the dip permits their use at all4 ,in rill-stopes 7,figs4 #cb and #cd7 the waste flows to its destination with a minimum of handling4 ,winzes and ore-passes are not required with the same frequency as in horizontal breaking1 and the broken ore always lies on the slope towards the passes and is therefore also easier to shovel4 ,in flat-backed stopes 7,fig4 #cc7 winzes must be put in every #ej feet or so1 while in rill-stopes they can be double this distance apart4 ,the system is applicable by modification to almost any width of ore4 ,it finds its most economical field where the dip of the stope floor is over #de1 when waste and ore1 with the help of the rill1 will flow to their destination4 ,for dips from under about #de to about #cj or #ce1 where the waste and ore will not flow easily1 shoveling can be helped by the use of the rill system and often evaded altogether1 if flow be assisted by a sheet-iron trough described in the discussion of stope transport4 ,further saving in shoveling can be gained in this method1 by giving a steeper pitch to the filling winzes and to the ore-passes1 by starting them from crosscuts in the wall1 and by carrying them at greater angles than the pitch of the ore 7,fig4 #cf74 ,these artifices combined have worked out most economically on several mines within the writer's experience1 with the dip as flat as #cj4 ,for very flat dips1 where filling is to be employed1 rill-stoping has no advantage over flat-backed cuts1 and in such cases it is often advisable to assist stope transport by temporary tracks and cars which obviously could not be worked on the tortuous contour of a rill-stope1 so that for dips under #cj advantage lies with flat-backed ore-breaking4 ,illustration3 ,fig4 #cf4--;,cross-section showing method of steepening winzes and ore passes4 ,on very wide ore-bodies where the support of the standing ore itself becomes a great problem1 the filling system can be applied by combining it with square-setting4 ,in this case the stopes are carried in panels laid out transversally to the strike as wide as the standing strength of the ore permits4 ,on both sides of each panel a fence of lagged square-sets is carried up and the area between is filled with waste4 ,the panels are stoped out alternately4 ,the application of this method at ,broken ,hill will be described later4 7,see pages #abj and ,figs4 #da and #db47 ,the same type of wide ore-body can be managed also on the filling system by the use of frequent bulkheads to support the ore 7,fig4 #ca74 ,compared with timbering methods1 filling has the great advantage of more effective support to the mine1 less danger of creeps1 and absolute freedom from the peril of fire4 ,the relative expense of the two systems is determined by the cost of materials and labor4 ,two extreme cases illustrate the result of these economic factors with sufficient clearness4 ,it is stated that the cost of timbering stopes on the ,le ,roi ,mine by square-sets is about #ba cents per ton of ore excavated4 ,in the ,ivanhoe mine of ,west ,australia the cost of filling stopes with tailings is about #bb cents per ton of ore excavated4 ,at the former mine the average cost of timber is under #aj per ,m board-measure1 while at the latter its price would be #ej per ,m board-measure2 although labor is about of the same efficiency and wage1 the cost in the ,ivanhoe by square-setting would be about #fe cents per ton of ore broken4 ,in the ,le ,roi1 on the other hand1 no residues are available for filling4 ,to quarry rock or drive crosscuts into the walls might make this system cost #fe cents per ton of ore broken if applied to that mine4 ,the comparative value of the filling method with other systems will be discussed later4 ,,filling ,,with ,,broken ,,ore ,,subsequently ,,withdrawn4--,this order of support is called by various names1 the favorite being shrinkage-stoping4 ,the method is to break the ore on to the roof of the level1 and by thus filling the stope with broken ore1 provide temporary support to the walls and furnish standing floor upon which to work in making the next cut 7,figs4 #cg1 #ch1 and #ci47 ,as broken material occupies #cj to #dj more space than rock in situ1 in order to provide working space at the face1 the broken ore must be drawn from along the level after each cut4 ,when the area attacked is completely broken through from level to level1 the stope will be full of loose broken ore1 which is then entirely drawn off4 ,a block to be attacked by this method requires preliminary winzes only at the extremities of the stope1--for entry and for ventilation4 ,where it is desired to maintain the winzes after stoping1 they must either be strongly timbered and lagged on the stope side1 be driven in the walls1 or be protected by a pillar of ore 7,fig4 #cg74 ,the settling ore and the crushing after the stope is empty make it difficult to maintain timbered winzes4 ,illustration3 ,fig4 #cg4--,longitudinal section of stope filled with broken ore4 ,where it can be done without danger to the mine1 the empty stopes are allowed to cave4 ,if such crushing would be dangerous1 either the walls must be held up by pillars of unbroken ore1 as in the ,alaska ,treadwell1 where large rib pillars are left1 or the open spaces must be filled with waste4 ,filling the empty stope is usually done by opening frequent passes along the base of the filled stope above1 and allowing the material of the upper stope to flood the lower one4 ,this program continued upwards through the mine allows the whole filling of the mine to descend gradually and thus requires replenishment only into the top4 ,the old stopes in the less critical and usually exhausted territory nearer the surface are sometimes left without replenishing their filling4 ,the weight of broken ore standing at such a high angle as to settle rapidly is very considerable upon the level2 moreover1 at the moment when the stope is entirely drawn off1 the pressure of the walls as well is likely to be very great4 ,the roadways in this system therefore require more than usual protection4 ,three methods are used3 7a7 timbering2 7b7 driving a sublevel in the ore above the main roadway as a stoping-base1 thus leaving a pillar of ore over the roadway 7,fig4 #ci72 7c7 by dry-walling the levels1 as in the ,baltic mine1 ,michigan 7,figs4 #cd and #ce74 ,by the use of sublevels the main roadways are sometimes driven in the walls 7,fig4 #ch7 and in many cases all timbering is saved4 ,to recover pillars left below sublevels is a rather difficult task1 especially if the old stope above is caved or filled4 ,the use of pillars in substitution for timber1 if the pillars are to be lost1 is simply a matter of economics as to whether the lost ore would repay the cost of other devices4 ,illustration3 ,fig4 #ch4--;,cross-section of shrinkage stope4 ,frequent ore-chutes through the level timbers1 or from the sublevels1 are necessary to prevent lodgment of broken ore between such passes1 because it is usually too dangerous for men to enter the emptying stope to shovel out the lodged remnants4 ,where the ore-body is wide1 and in order that there may be no lodgment of ore1 the timbers over the level are set so as to form a trough along the level2 or where pillars are left1 they are made ,a-shaped between the chutes1 as indicated in ,figure #cg4 ,illustration3 ,fig4 #ci4--;,cross-section of shrinkage stope4 ,the method of breaking the ore in conjunction with this means of support in comparatively narrow deposits can be on the rill1 in order to have the advantage of down holes4 ,usually1 however1 flat-back or horizontal cuts are desirable1 as in such an arrangement it is less troublesome to regulate the drawing of the ore so as to provide proper head room4 ,where stopes are wide1 ore is sometimes cut arch-shaped from wall to wall to assure its standing4 ,where this method of support is not of avail1 short1 sharply tapering stulls are put in from the broken ore to the face 7,fig4 #ci74 ,when the cut above these stulls is taken out1 they are pulled up and are used again4 ,this method of stoping is only applicable when3-- #a4 ,the deposit dips over #fj1 and thus broken material will freely settle downward to be drawn off from the bottom4 #b4 ,the ore is consistently payable in character4 ,no selection can be done in breaking1 as all material broken must be drawn off together4 #c4 ,the hanging wall is strong1 and will not crush or spall off waste into the ore4 #d4 ,the ore-body is regular in size1 else loose ore will lodge on the foot wall4 ,stopes opened in this manner when partially empty are too dangerous for men to enter for shoveling out remnants4 ,the advantages of this system over others1 where it is applicable1 are3-- 7a7 ,a greater distance between levels can be operated and few winzes and rises are necessary1 thus a great saving of development work can be effected4 ,a stope #hjj to #ajjj feet long can be operated with a winze at either end and with levels #bjj or #bbj feet apart4 7b7 ,there is no shoveling in the stopes at all4 7c7 ,no timber is required4 ,as compared with timbering by stulling1 it will apply to stopes too wide and walls too heavy for this method4 ,moreover1 little staging is required for working the face1 since ore can be drawn from below in such a manner as to allow just the right head room4 7d7 ,compared to the system of filling with waste1 coincidentally with breaking 7second method71 it saves altogether in some cases the cost of filling4 ,in any event1 it saves the cost of ore-passes1 of shoveling into them1 and of the detailed distribution of the filling4 ,compared with other methods1 the system has the following disadvantages1 that3 ,a4 ,the ore requires to be broken in the stopes to a degree of fineness which will prevent blocking of the chutes at the level4 ,when pieces too large reach the chutes1 nothing will open them but blasting1--to the damage of timbers and chutes4 ,some large rocks are always liable to be buried in the course of ore-breaking4 ,b4 ,practically no such perfection of walls exists1 but some spalling of waste into the ore will take place4 ,a crushing of the walls would soon mean the loss of large amounts of ore4 ,c4 ,there is no possibility of regulating the mixture of grade of ore by varying the working points4 ,it is months after the ore is broken before it can reach the levels4 ,d4 ,the breaking of #fj more ore than immediate treatment demands results in the investment of a considerable sum of money4 ,an equilibrium is ultimately established in a mine worked on this system when a certain number of stopes full of completely broken ore are available for entire withdrawal1 and there is no further accumulation4 ,but1 in any event1 a considerable amount of broken ore must be held in reserve4 ,in one mine worked on this plan1 with which the writer has had experience1 the annual production is about #bej1jjj tons and the broken ore represents an investment which1 at #e1 means an annual loss of interest amounting to #g cents per ton of ore treated4 ,e4 ,a mine once started on the system is most difficult to alter1 owing to the lack of frequent winzes or passes4 ,especially is this so if the only alternative is filling1 for an alteration to the system of filling coincident with breaking finds the mine short of filling winzes4 ,as the conditions of walls and ore often alter with depth1 change of system may be necessary and the situation may become very embarrassing4 ,f4 ,the restoping of the walls for lower-grade ore at a later period is impossible1 for the walls of the stope will be crushed1 or1 if filled with waste1 will usually crush when it is drawn off to send to a lower stope4 ,the system has much to recommend it where conditions are favorable4 ,like all other alternative methods of mining1 it requires the most careful study in the light of the special conditions involved4 ,in many mines it can be used for some stopes where not adaptable generally4 ,it often solves the problem of blind ore-bodies1 for they can by this means be frequently worked with an opening underneath only4 ,thus the cost of driving a roadway overhead is avoided1 which would be required if timber or coincident filling were the alternatives4 ,in such cases ventilation can be managed without an opening above1 by so directing the current of air that it will rise through a winze from the level below1 flow along the stope and into the level again at the further end of the stope through another winze4 ,illustration3 ,fig4 #dj4--,longitudinal section4 ,ore-pillar support in narrow stopes4 ,,support ,,by ,,pillars ,,of ,,ore4--,as a method of mining metals of the sort under discussion1 the use of ore-pillars except in conjunction with some other means of support has no general application4 ,to use them without assistance implies walls sufficiently strong to hold between pillars2 to leave them permanently anywhere implies that the ore abandoned would not repay the labor and the material of a substitute4 ,there are cases of large1 very low-grade mines where to abandon one-half the ore as pillars is more profitable than total extraction1 but the margin of payability in such ore must be very1 very narrow4 ,unpayable spots are always left as pillars1 for obvious reasons4 ,permanent ore-pillars as an adjunct to other methods of support are in use4 ,such are the rib-pillars in the ,alaska ,treadwell1 the form of which is indicated by the upward extension of the pillars adjacent to the winzes1 shown in ,figure #cg4 ,always a careful balance must be cast as to the value of the ore left1 and as to the cost of a substitute1 because every ore-pillar can be removed at some outlay4 ,temporary pillars are not unusual1 particularly to protect roadways and shafts4 ,they are1 when left for these purposes1 removed ultimately1 usually by beginning at the farther end and working back to the final exit4 ,illustration3 ,fig4 #da4--;,horizontal plan at levels of ,broken ,hill4 ,method of alternate stopes and ore-pillars4 ,illustration3 ,fig4 #db4--,longitudinal section of ,figure #da4 ,a form of temporary ore-pillars in very wide deposits is made use of in conjunction with both filling and timbering 7,figs4 #cg1 #ci1 #dj74 ,in the use of temporary pillars for ore-bodies #ajj to #bej feet wide at ,broken ,hill1 stopes are carried up at right angles to the strike1 each fifty feet wide and clear across the ore-body 7,figs4 #da and #db74 ,a solid pillar of the same width is left in the first instance between adjacent stopes1 and the initial series of stopes are walled with one square-set on the sides as the stope is broken upward4 ,the room between these two lines of sets is filled with waste alternating with ore-breaking in the usual filling method4 ,when the ore from the first group of alternate stopes 7,,abc1 ,fig4 #db7 is completely removed1 the pillars are stoped out and replaced with waste4 ,the square-sets of the first set of stopes thus become the boundaries of the second set4 ,entry and ventilation are obtained through these lines of square-sets1 and the ore is passed out of the stopes through them4 ,illustration3 ,fig4 #dc4--;,cross-section of stull support with waste renforcement4 ,,artificial ,,pillars4--,this system also implies a roof so strong as not to demand continuous support4 ,artificial pillars are built in many different ways4 ,the method most current in fairly narrow deposits is to renforce stulls by packing waste above them 7,figs4 #dc and #dd74 ,not only is it thus possible to economize in stulls by using the waste which accumulates underground1 but the principle applies also to cases where the stulls alone are not sufficient support1 and yet where complete filling or square-setting is unnecessary4 ,when the conditions are propitious for this method1 it has the comparative advantage over timber systems of saving timber1 and over filling systems of saving imported filling4 ,moreover1 these constructions being pillar-shaped 7,fig4 #dd71 the intervals between them provide outlets for broken ore1 and specially built passes are unnecessary4 ,the method has two disadvantages as against the square-set or filling process1 in that more staging must be provided from which to work1 and in stopes over six feet the erection of machine-drill columns is tedious and costly in time and wages4 ,illustration3 ,fig4 #dd4--,longitudinal section of stull and waste pillars4 ,in wide deposits of markedly flat1 irregular ore-bodies1 where a definite system is difficult and where timber is expensive1 cribs of cord-wood or logs filled with waste after the order shown in ,figure #ca1 often make fairly sound pillars4 ,they will not last indefinitely and are best adapted to the temporary support of the ore-roof pending filling4 ,the increased difficulty in setting up machine drills in such stopes adds to the breaking costs1--often enough to warrant another method of support4 ,illustration3 ,fig4 #de4--,sublevel caving system4 ,,caving ,,systems4--,this method1 with variations1 has been applied to large iron deposits1 to the ,kimberley diamond mines1 to some copper mines1 but in general it has little application to the metal mines under consideration1 as few ore-bodies are of sufficiently large horizontal area4 ,the system is dependent upon a large area of loose or heavy ground pressing directly on the ore with weight1 such that if the ore be cut into pillars1 these will crush4 ,the details of the system vary1 but in general the modus operandi is to prepare roadways through the ore1 and from the roadways to put rises1 from which sublevels are driven close under the floating mass of waste and ore1--sometimes called the matte 7,fig4 #de74 ,the pillars between these sublevels are then cut away until the weight above crushes them down4 ,when all the crushed ore which can be safely reached is extracted1 retreat is made and another series of subopenings is then driven close under the matte4 ,the pillar is reduced until it crushes and the operation is repeated4 ,eventually the bottom strata of the matte become largely ore1 and a sort of equilibrium is reached when there is not much loss in this direction4 ,top slicing is a variation of the above method by carrying a horizontal stope from the rises immediately under the matte1 supporting the floating material with timber4 ,at ,kimberley the system is varied in that galleries are run out to the edge of the diamond-iferous area and enlarged until the pillar between crushes4 ,in the caving methods1 between #dj and #ej of the ore is removed by the preliminary openings1 and as they are all headings of some sort1 the average cost per ton of this particular ore is higher than by ordinary stoping methods4 ,on the other hand1 the remaining #ej to #fj of the ore costs nothing to break1 and the average cost is often remarkably low4 ,as said1 the system implies bodies of large horizontal area4 ,they must start near enough to the surface that the whole superincumbent mass may cave and give crushing weight1 or the immediately overhanging roof must easily cave4 ,all of these are conditions not often met with in mines of the character under review4 ,,chapter ,,xii4 ,mechanical ,equipment4 ,,conditions ,,bearing ,,on ,,mine ,,equipment2 ,,winding ,,appliances2 ,,haulage ,,equipment ,,in ,,shafts2 ,,lateral ,,underground ,,transport2 ,,transport ,,in ,,stopes4 ,there is no type of mechanical engineering which presents such complexities in determination of the best equipment as does that of mining4 ,not only does the economic side dominate over pure mechanics1 but machines must be installed and operated under difficulties which arise from the most exceptional and conflicting conditions1 none of which can be entirely satisfied4 ,compromise between capital outlay1 operating efficiency1 and conflicting demands is the key-note of the work4 ,these compromises are brought about by influences which lie outside the questions of mechanics of individual machines1 and are mainly as follows3-- #a4 ,continuous change in horizon of operations4 #b4 ,uncertain life of the enterprise4 #c4 ,care and preservation of human life4 #d4 ,unequal adaptability of power transmission mediums4 #e4 ,origin of power4 ,first4--,the depth to be served and the volume of ore and water to be handled1 are not only unknown at the initial equipment1 but they are bound to change continuously in quantity1 location1 and horizon with the extension of the workings4 ,second4--,from the mine manager's point of view1 which must embrace that of the mechanical engineer1 further difficulty presents itself because the life of the enterprise is usually unknown1 and therefore a manifest necessity arises for an economic balance of capital outlay and of operating efficiency commensurate with the prospects of the mine4 ,moreover1 the initial capital is often limited1 and makeshifts for this reason alone must be provided4 ,in net result1 no mineral deposit of speculative ultimate volume of ore warrants an initial equipment of the sort that will meet every eventuality1 or of the kind that will give even the maximum efficiency which a free choice of mining machinery could obtain4 ,third4--,in the design and selection of mining machines1 the safety of human life1 the preservation of the health of workmen under conditions of limited space and ventilation1 together with reliability and convenience in installing and working large mechanical tools1 all dominate mechanical efficiency4 ,for example1 compressed-air transmission of power best meets the requirements of drilling1 yet the mechanical losses in the generation1 the transmission1 and the application of compressed air probably total1 from first to last1 #gj to #he4 ,fourth4--,all machines1 except those for shaft haulage1 must be operated by power transmitted from the surface1 as obviously power generation underground is impossible4 ,the conversion of power into a transmission medium and its transmission are1 at the outset1 bound to be the occasions of loss4 ,not only are the various forms of transmission by steam1 electricity1 compressed air1 or rods1 of different efficiency1 but no one system lends itself to universal or economical application to all kinds of mining machines4 ,therefore it is not uncommon to find three or four different media of power transmission employed on the same mine4 ,to illustrate3 from the point of view of safety1 reliability1 control1 and in most cases economy as well1 we may say that direct steam is the best motive force for winding-engines2 that for mechanical efficiency and reliability1 rods constitute the best media of power transmission to pumps2 that1 considering ventilation and convenience1 compressed air affords the best medium for drills4 ,yet there are other conditions as to character of the work1 volume of water or ore1 and the origin of power which must in special instances modify each and every one of these generalizations4 ,for example1 although pumping water with compressed air is mechanically the most inefficient of devices1 it often becomes the most advantageous1 because compressed air may be of necessity laid on for other purposes1 and the extra power required to operate a small pump may be thus most cheaply provided4 ,fifth4--,further limitations and modifications arise out of the origin of power1 for the sources of power have an intimate bearing on the type of machine and media of transmission4 ,this very circumstance often compels giving away efficiency and convenience in some machines to gain more in others4 ,this is evident enough if the principal origins of power generation be examined4 ,they are in the main as follows3-- a4 ,water-power available at the mine4 b4 ,water-power available at a less distance than three or four miles4 c4 ,water-power available some miles away1 thus necessitating electrical transmission 7or purchased electrical power74 d4 ,steam-power to be generated at the mine4 e4 ,gas-power to be generated at the mine4 a4 ,with water-power at the mine1 winding engines can be operated by direct hydraulic application with a gain in economy over direct steam1 although with the sacrifice of control and reliability4 ,rods for pumps can be driven directly with water1 but this superiority in working economy means1 as discussed later1 a loss of flexibility and increased total outlay over other forms of transmission to pumps4 ,as compressed air must be transmitted for drills1 the compressor would be operated direct from water-wheels1 but with less control in regularity of pressure delivery4 b4 ,with water-power a short distance from the mine1 it would normally be transmitted either by compressed air or by electricity4 ,compressed-air transmission would better satisfy winding and drilling requirements1 but would show a great comparative loss in efficiency over electricity when applied to pumping4 ,despite the latter drawback1 air transmission is a method growing in favor1 especially in view of the advance made in effecting compression by falling water4 c4 ,in the situation of transmission too far for using compressed air1 there is no alternative but electricity4 ,in these cases1 direct electric winding is done1 but under such disadvantages that it requires a comparatively very cheap power to take precedence over a subsidiary steam plant for this purpose4 ,electric air-compressors work under the material disadvantage of constant speed on a variable load1 but this installation is also a question of economics4 ,the pumping service is well performed by direct electrical pumps4 d4 ,in this instance1 winding and air-compression are well accomplished by direct steam applications2 but pumping is beset with wholly undesirable alternatives1 among which it is difficult to choose4 e4 ,with internal combustion engines1 gasoline 7petrol7 motors have more of a position in experimental than in systematic mining1 for their application to winding and pumping and drilling is fraught with many losses4 ,the engine must be under constant motion1 and that1 too1 with variable loads4 ,where power from producer gas is used1 there is a greater possibility of installing large equipments1 and it is generally applied to the winding and lesser units by conversion into compressed air or electricity as an intermediate stage4 ,one thing becomes certain from these examples cited1 that the right installation for any particular portion of the mine's equipment cannot be determined without reference to all the others4 ,the whole system of power generation for surface work1 as well as the transmission underground1 must be formulated with regard to furnishing the best total result from all the complicated primary and secondary motors1 even at the sacrifice of some members4 ,each mine is a unique problem1 and while it would be easy to sketch an ideal plant1 there is no mine within the writer's knowledge upon which the ideal would1 under the many variable conditions1 be the most economical of installation or the most efficient of operation4 ,the dominant feature of the task is an endeavor to find a compromise between efficiency and capital outlay4 ,the result is a series of choices between unsatisfying alternatives1 a number of which are usually found to have been wrong upon further extension of the mine in depth4 ,in a general way1 it may be stated that where power is generated on the mine1 economy in labor of handling fuel1 driving engines1 generation and condensing steam where steam is used1 demand a consolidated power plant for the whole mine equipment4 ,the principal motors should be driven direct by steam or gas1 with power distribution by electricity to all outlying surface motors and sometimes to underground motors1 and also to some underground motors by compressed air4 ,much progress has been made in the past few years in the perfection of larger mining tools4 ,inherently many of our devices are of a wasteful character1 not only on account of the need of special forms of transmission1 but because they are required to operate under greatly varying loads4 ,as an outcome of transmission losses and of providing capacity to cope with heavy peak loads1 their efficiency on the basis of actual foot-pounds of work accomplished is very low4 ,the adoption of electric transmission in mine work1 while in certain phases beneficial1 has not decreased the perplexity which arises from many added alternatives1 none of which are as yet a complete or desirable answer to any mine problem4 ,when a satisfactory electric drill is invented1 and a method is evolved of applying electricity to winding-engines that will not involve such abnormal losses due to high peak load then we will have a solution to our most difficult mechanical problems1 and electricity will deserve the universal blessing which it has received in other branches of mechanical engineering4 ,it is not intended to discuss mine equipment problems from the machinery standpoint1--there are thousands of different devices1--but from the point of view of the mine administrator who finds in the manufactory the various machines which are applicable1 and whose work then becomes that of choosing1 arranging1 and operating these tools4 ,the principal mechanical questions of a mine may be examined under the following heads3-- #a4 ,shaft haulage4 #b4 ,lateral underground transport4 #c4 ,drainage4 #d4 ,rock drilling4 #e4 ,workshops4 #f4 ,improvements in equipment4 ,,shaft ,,haulage4 ,,winding ,,appliances4--,no device has yet been found to displace the single load pulled up the shaft by winding a rope on a drum4 ,of driving mechanisms for drum motors the alternatives are the steam-engine1 the electrical motor1 and infrequently water-power or gas engines4 ,all these have to cope with one condition which1 on the basis of work accomplished1 gives them a very low mechanical efficiency4 ,this difficulty is that the load is intermittent1 and it must be started and accelerated at the point of maximum weight1 and from that moment the power required diminishes to less than nothing at the end of the haul4 ,a large number of devices are in use to equalize partially the inequalities of the load at different stages of the lift4 ,the main lines of progress in this direction have been3-- a4 ,the handling of two cages or skips with one engine or motor1 the descending skip partially balancing the ascending one4 b4 ,the use of tail-ropes or balance weights to compensate the increasing weight of the descending rope4 c4 ,the use of skips instead of cages1 thus permitting of a greater percentage of paying load4 d4 ,the direct coupling of the motor to the drum shaft4 e4 ,the cone-shaped construction of drums1--this latter being now largely displaced by the use of the tail-rope4 ,the first and third of these are absolutely essential for anything like economy and speed2 the others are refinements depending on the work to be accomplished and the capital available4 ,steam winding-engines require large cylinders to start the load1 but when once started the requisite power is much reduced and the load is too small for steam economy4 ,the throttling of the engine for controlling speed and reversing the engine at periodic stoppages militates against the maximum expansion and condensation of the steam and further increases the steam consumption4 ,in result1 the best of direct compound condensing engines consume from #fj to #ajj pounds of steam per horse-power hour1 against a possible efficiency of such an engine working under constant load of less than #af pounds of steam per horse-power hour4 ,it is only within very recent years that electrical motors have been applied to winding4 ,even yet1 all things considered1 this application is of doubtful value except in localities of extremely cheap electrical power4 ,the constant speed of alternating current motors at once places them at a disadvantage for this work of high peak and intermittent loads4 ,while continuous-current motors can be made to partially overcome this drawback1 such a current1 where power is purchased or transmitted a long distance1 is available only by conversion1 which further increases the losses4 ,however1 schemes of electrical winding are in course of development which bid fair1 by a sort of storage of power in heavy fly-wheels or storage batteries after the peak load1 to reduce the total power consumption2 but the very high first cost so far prevents their very general adoption for metal mining4 ,winding-engines driven by direct water- or gas-power are of too rare application to warrant much discussion4 ,gasoline driven hoists have a distinct place in prospecting and early-stage mining1 especially in desert countries where transport and fuel conditions are onerous1 for both the machines and their fuel are easy of transport4 ,as direct gas-engines entail constant motion of the engine at the power demand of the peak load1 they are hopeless in mechanical efficiency4 ,like all other motors in mining1 the size and arrangement of the motor and drum are dependent upon the duty which they will be called upon to perform4 ,this is primarily dependent upon the depth to be hoisted from1 the volume of the ore1 and the size of the load4 ,for shallow depths and tonnages up to1 say1 #bjj tons daily1 geared engines have a place on account of their low capital cost4 ,where great rope speed is not essential they are fully as economical as direct-coupled engines4 ,with great depths and greater capacities1 speed becomes a momentous factor1 and direct-coupled engines are necessary4 ,where the depth exceeds #c1jjj feet1 another element enters which has given rise to much debate and experiment2 that is1 the great increase of starting load due to the increased length and size of ropes and the drum space required to hold it4 ,so far the most advantageous device seems to be the ,whiting hoist1 a combination of double drums and tail rope4 ,on mines worked from near the surface1 where depth is gained by the gradual exhaustion of the ore1 the only prudent course is to put in a new hoist periodically1 when the demand for increased winding speed and power warrants4 ,the lack of economy in winding machines is greatly augmented if they are much over-sized for the duty4 ,an engine installed to handle a given tonnage to a depth of #c1jjj feet will have operated with more loss during the years the mine is progressing from the surface to that depth than several intermediate-sized engines would have cost4 ,on most mines the uncertainty of extension in depth would hardly warrant such a preliminary equipment4 ,more mines are equipped with over-sized than with under-sized engines4 ,for shafts on going metal mines where the future is speculative1 an engine will suffice whose size provides for an extension in depth of #a1jjj feet beyond that reached at the time of its installation4 ,the cost of the engine will depend more largely upon the winding speed desired than upon any other one factor4 ,the proper speed to be arranged is obviously dependent upon the depth of the haulage1 for it is useless to have an engine able to wind #c1jjj feet a minute on a shaft #ejj feet deep1 since it could never even get under way2 and besides1 the relative operating loss1 as said1 would be enormous4 ,,haulage ,,equipment ,,in ,,the ,,shaft4--,originally1 material was hoisted through shafts in buckets4 ,then came the cage for transporting mine cars1 and in more recent years the skip has been developed4 ,the aggrandized bucket or kibble of the ,cornishman has practically disappeared1 but the cage still remains in many mines4 ,the advantages of the skip over the cage are many4 ,some of them are3-- a4 ,it permits #be to #dj greater load of material in proportion to the dead weight of the vehicle4 b4 ,the load can be confined within a smaller horizontal space1 thus the area of the shaft need not be so great for large tonnages4 c4 ,loading and discharging are more rapid1 and the latter is automatic1 thus permitting more trips per hour and requiring less labor4 d4 ,skips must be loaded from bins underground1 and by providing in the bins storage capacity1 shaft haulage is rendered independent of the lateral transport in the mine1 and there are no delays to the engine awaiting loads4 ,the result is that ore-winding can be concentrated into fewer hours1 and indirect economies in labor and power are thus effected4 e4 ,skips save the time of the men engaged in the lateral haulage1 as they have no delay waiting for the winding engine4 ,loads equivalent to those from skips are obtained in some mines by double-decked cages2 but1 aside from waste weight of the cage1 this arrangement necessitates either stopping the engine to load the lower deck1 or a double-deck loading station4 ,double-deck loading stations are as costly to install and more expensive to work than skip-loading station ore-bins4 ,cages are also constructed large enough to take as many as four trucks on one deck4 ,this entails a shaft compartment double the size required for skips of the same capacity1 and thus enormously increases shaft cost without gaining anything4 ,altogether the advantages of the skip are so certain and so important that it is difficult to see the justification for the cage under but a few conditions4 ,these conditions are those which surround mines of small output where rapidity of haulage is no object1 where the cost of station-bins can thus be evaded1 and the convenience of the cage for the men can still be preserved4 ,the easy change of the skip to the cage for hauling men removes the last objection on larger mines4 ,there occurs also the situation in which ore is broken under contract at so much per truck1 and where it is desirable to inspect the contents of the truck when discharging it1 but even this objection to the skip can be obviated by contracting on a cubic-foot basis4 ,skips are constructed to carry loads of from two to seven tons1 the general tendency being toward larger loads every year4 ,one of the most feasible lines of improvement in winding is in the direction of larger loads and less speed1 for in this way the sum total of dead weight of the vehicle and rope to the tonnage of ore hauled will be decreased1 and the efficiency of the engine will be increased by a less high peak demand1 because of this less proportion of dead weight and the less need of high acceleration4 ,,lateral ,,underground ,,transport4 ,inasmuch as the majority of metal mines dip at considerable angles1 the useful life of a roadway in a metal mine is very short because particular horizons of ore are soon exhausted4 ,therefore any method of transport has to be calculated upon a very quick redemption of the capital laid out4 ,furthermore1 a roadway is limited in its daily traffic to the product of the stopes which it serves4 ,,men ,,and ,,animals4--,some means of transport must be provided1 and the basic equipment is light tracks with push-cars1 in capacity from half a ton to a ton4 ,the latter load is1 however1 too heavy to be pushed by one man4 ,as but one car can be pushed at a time1 hand-trucking is both slow and expensive4 ,at average ,american or ,australian wages1 the cost works out between #be and #ce cents a ton per mile4 ,an improvement of growing import where hand-trucking is necessary is the overhead mono-rail instead of the track4 ,if the supply to any particular roadway is such as to fully employ horses or mules1 the number of cars per trip can be increased up to seven or eight4 ,in this case the expense1 including wages of the men and wear1 tear1 and care of mules1 will work out roughly at from #g to #aj cents per ton mile4 ,manifestly1 if the ore-supply to a particular roadway is insufficient to keep a mule busy1 the economy soon runs off4 ,,mechanical ,,haulage4--,mechanical haulage is seldom applicable to metal mines1 for most metal deposits dip at considerable angles1 and therefore1 unlike most coal-mines1 the horizon of haulage must frequently change1 and there are no main arteries along which haulage continues through the life of the mine4 ,any mechanical system entails a good deal of expense for installation1 and the useful life of any particular roadway1 as above said1 is very short4 ,moreover1 the crooked roadways of most metal mines present difficulties of negotiation not to be overlooked4 ,in order to use such systems it is necessary to condense the haulage to as few roadways as possible4 ,where the tonnage on one level is not sufficient to warrant other than men or animals1 it sometimes pays 7if the dip is steep enough7 to dump everything through winzes from one to two levels to a main road below where mechanical equipment can be advantageously provided4 ,the cost of shaft-winding the extra depth is inconsiderable compared to other factors1 for the extra vertical distance of haulage can be done at a cost of one or two cents per ton mile4 ,moreover1 from such an arrangement follows the concentration of shaft-bins1 and of shaft labor1 and winding is accomplished without so much shifting as to horizon1 all of which economies equalize the extra distance of the lift4 ,there are three principal methods of mechanical transport in use3-- #a4 ,cable-ways4 #b4 ,compressed-air locomotives4 #c4 ,electrical haulage4 ,cable-ways or endless ropes are expensive to install1 and to work to the best advantage require double tracks and fairly straight roads4 ,while they are economical in operation and work with little danger to operatives1 the limitations mentioned preclude them from adoption in metal mines1 except in very special circumstances such as main crosscuts or adit tunnels1 where the haulage is straight and concentrated from many sources of supply4 ,compressed-air locomotives are somewhat heavy and cumbersome1 and therefore require well-built tracks with heavy rails1 but they have very great advantages for metal mine work4 ,they need but a single track and are of low initial cost where compressed air is already a requirement of the mine4 ,no subsidiary line equipment is needed1 and thus they are free to traverse any road in the mine and can be readily shifted from one level to another4 ,their mechanical efficiency is not so low in the long run as might appear from the low efficiency of pneumatic machines generally1 for by storage of compressed air at the charging station a more even rate of energy consumption is possible than in the constant cable and electrical power supply which must be equal to the maximum demand1 while the air-plant consumes but the average demand4 ,electrical haulage has the advantage of a much more compact locomotive and the drawback of more expensive track equipment1 due to the necessity of transmission wire1 etc4 ,it has the further disadvantages of uselessness outside the equipped haulage way and of the dangers of the live wire in low and often wet tunnels4 ,in general1 compressed-air locomotives possess many attractions for metal mine work1 where air is in use in any event and where any mechanical system is at all justified4 ,any of the mechanical systems where tonnage is sufficient in quantity to justify their employment will handle material for from #a4e to #d cents per ton mile4 ,,tracks4--,tracks for hand1 mule1 or rope haulage are usually built with from #ab- to #af-pound rails1 but when compressed-air or electrical locomotives are to be used1 less than #bd-pound rails are impossible4 ,as to tracks in general1 it may be said that careful laying out with even grades and gentle curves repays itself many times over in their subsequent operation4 ,further care in repair and lubrication of cars will often make a difference of #ge in the track resistance4 ,,transport ,,in ,,stopes4--,owing to the even shorter life of individual stopes than levels1 the actual transport of ore or waste in them is often a function of the aboriginal shovel plus gravity4 ,as shoveling is the most costly system of transport known1 any means of stoping that decreases the need for it has merit4 ,shrinkage-stoping eliminates it altogether4 ,in the other methods1 gravity helps in proportion to the steepness of the dip4 ,when the underlie becomes too flat for the ore to run1 transport can sometimes be helped by pitching the ore-passes at a steeper angle than the dip 7,fig4 #cf74 ,in some cases of flat deposits1 crosscuts into the walls1 or even levels under the ore-body1 are justifiable4 ,the more numerous the ore-passes1 the less the lateral shoveling1 but as passes cost money for construction and for repair1 there is a nice economic balance in their frequency4 ,mechanical haulage in stopes has been tried and finds a field under some conditions4 ,in dips under #be and possessing fairly sound hanging-wall1 where long-wall or flat-back cuts are employed1 temporary tracks can often be laid in the stopes and the ore run in cars to the main passes4 ,in such cases1 the tracks are pushed up close to the face after each cut4 ,further self-acting inclines to lower cars to the levels can sometimes be installed to advantage4 ,this arrangement also permits greater intervals between levels and less number of ore-passes4 ,for dips between #be and #ej where the mine is worked without stope support or with occasional pillars1 a very useful contrivance is the sheet-iron trough--about eighteen inches wide and six inches deep--made in sections ten or twelve feet long and readily bolted together4 ,in dips #ce to #ej this trough1 laid on the foot-wall1 gives a sufficiently smooth surface for the ore to run upon4 ,when the dip is flat1 the trough1 if hung from plugs in the hanging-wall1 may be swung backward and forward4 ,the use of this bumping-trough saves much shoveling4 ,for handling filling or ore in flat runs it deserves wider adoption4 ,it is1 of course1 inapplicable in passes as a bumping-trough1 but can be fixed to give smooth surface4 ,in flat mines it permits a wider interval between levels and therefore saves development work4 ,the life of this contrivance is short when used in open stopes1 owing to the dangers of bombardment from blasting4 ,in dips steeper than #ej much of the shoveling into passes can be saved by rill-stoping1 as described on page #ajj4 ,where flat-backed stopes are used in wide ore-bodies with filling1 temporary tracks laid on the filling to the ore-passes are useful1 for they permit wider intervals between passes4 ,in that underground engineer's paradise1 the ,witwatersrand1 where the stopes require neither timber nor filling1 the long1 moderately pitched openings lend themselves particularly to the swinging iron troughs1 and even endless wire ropes have been found advantageous in certain cases4 ,where the roof is heavy and close support is required1 and where the deposits are very irregular in shape and dip1 there is little hope of mechanical assistance in stope transport4 ,,chapter ,,xiii4 ,mechanical ,equipment4 7,continued74 ,,drainage3 ,,controlling ,,factors2 ,,volume ,,and ,,head ,,of ,,water2 ,,flexibility2 ,,reliability2 ,,power ,,conditions2 ,,mechanical ,,efficiency2 ,,capital ,,outlay4 ,,systems ,,of ,,drainage1--,,steam ,,pumps1 ,,compressed-,,air ,,pumps1 ,,electrical ,,pumps1 ,,rod-,,driven ,,pumps1 ,,bailing2 ,,comparative ,,value ,,of ,,various ,,systems4 ,with the exception of drainage tunnels--more fully described in ,chapter ,,viii--all drainage must be mechanical4 ,as the bulk of mine water usually lies near the surface1 saving in pumping can sometimes be effected by leaving a complete pillar of ore under some of the upper levels4 ,in many deposits1 however1 the ore has too many channels to render this of much avail4 ,there are six factors which enter into a determination of mechanical drainage systems for metal mines3-- #a4 ,volume and head of water4 #b4 ,flexibility to fluctuation in volume and head4 #c4 ,reliability4 #d4 ,capital cost4 #e4 ,the general power conditions4 #f4 ,mechanical efficiency4 ,in the drainage appliances1 more than in any other feature of the equipment1 must mechanical efficiency be subordinated to the other issues4 ,,flexibility4--,flexibility in plant is necessary because volume and head of water are fluctuating factors4 ,in wet regions the volume of water usually increases for a certain distance with the extension of openings in depth4 ,in dry climates it generally decreases with the downward extension of the workings after a certain depth4 ,moreover1 as depth progresses1 the water follows the openings more or less and must be pumped against an ever greater head4 ,in most cases the volume varies with the seasons4 ,what increase will occur1 from what horizon it must be lifted1 and what the fluctuations in volume are likely to be1 are all unknown at the time of installation4 ,if a pumping system were to be laid out for a new mine1 which would peradventure meet every possible contingency1 the capital outlay would be enormous1 and the operating efficiency would be very low during the long period in which it would be working below its capacity4 ,the question of flexibility does not arise so prominently in coal-mines1 for the more or less flat deposits give a fixed factor of depth4 ,the flow is also more steady1 and the volume can be in a measure approximated from general experience4 ,,reliability4--,the factor of reliability was at one time of more importance than in these days of high-class manufacture of many different pumping systems4 ,practically speaking1 the only insurance from flooding in any event lies in the provision of a relief system of some sort1--duplicate pumps1 or the simplest and most usual thing1 bailing tanks4 ,only ,cornish and compressed-air pumps will work with any security when drowned1 and electrical pumps are easily ruined4 ,,general ,,power ,,conditions4--,the question of pumping installation is much dependent upon the power installation and other power requirements of the mine4 ,for instance1 where electrical power is purchased or generated by water-power1 then electrical pumps have every advantage4 ,or where a large number of subsidiary motors can be economically driven from one central steam- or gas-driven electrical generation plant1 they again have a strong call1--especially if the amount of water to be handled is moderate4 ,where the water is of limited volume and compressed-air plant a necessity for the mine1 then air-driven pumps may be the most advantageous1 etc4 ,,mechanical ,,efficiency4--,the mechanical efficiency of drainage machinery is very largely a question of method of power application4 ,the actual pump can be built to almost the same efficiency for any power application1 and with the exception of the limited field of bailing with tanks1 mechanical drainage is a matter of pumps4 ,all pumps must be set below their load1 barring a few possible feet of suction lift1 and they are therefore perforce underground1 and in consequence all power must be transmitted from the surface4 ,transmission itself means loss of power varying from #aj to #fj1 depending upon the medium used4 ,it is therefore the choice of transmission medium that largely governs the mechanical efficiency4 ,,systems ,,of ,,drainage4--,the ideal pumping system for metal mines would be one which could be built in units and could be expanded or contracted unit by unit with the fluctuation in volume2 which could also be easily moved to meet the differences of lifts2 and in which each independent unit could be of the highest mechanical efficiency and would require but little space for erection4 ,such an ideal is unobtainable among any of the appliances with which the writer is familiar4 ,the wide variations in the origin of power1 in the form of transmission1 and in the method of final application1 and the many combinations of these factors1 meet the demands for flexibility1 efficiency1 capital cost1 and reliability in various degrees depending upon the environment of the mine4 ,power nowadays is generated primarily with steam1 water1 and gas4 ,these origins admit the transmission of power to the pumps by direct steam1 compressed air1 electricity1 rods1 or hydraulic columns4 ,,direct ,,steam-,,pumps4--,direct steam has the disadvantage of radiated heat in the workings1 of loss by the radiation1 and1 worse still1 of the impracticability of placing and operating a highly efficient steam-engine underground4 ,it is all but impossible to derive benefit from the vacuum1 as any form of surface condenser here is impossible1 and there can be no return of the hot soft water to the boilers4 ,steam-pumps fall into two classes1 rotary and direct-acting2 the former have the great advantage of permitting the use of steam expansively and affording some field for effective use of condensation1 but they are more costly1 require much room1 and are not fool-proof4 ,the direct-acting pumps have all the advantage of compactness and the disadvantage of being the most inefficient of pumping machines used in mining4 ,taking the steam consumption of a good surface steam plant at #ae pounds per horse-power hour1 the efficiency of rotary pumps with well-insulated pipes is probably not over #ej1 and of direct-acting pumps from #dj down to #aj4 ,the advantage of all steam-pumps lies in the low capital outlay1--hence their convenient application to experimental mining and temporary pumping requirements4 ,for final equipment they afford a great deal of flexibility1 for if properly constructed they can be1 with slight alteration1 moved from one horizon to another without loss of relative efficiency4 ,thus the system can be rearranged for an increased volume of water1 by decreasing the lift and increasing the number of pumps from different horizons4 ,,compressed-,,air ,,pumps4--,compressed-air transmission has an application similar to direct steam1 but it is of still lower mechanical efficiency1 because of the great loss in compression4 ,it has the superiority of not heating the workings1 and there is no difficulty as to the disposal of the exhaust1 as with steam4 ,moreover1 such pumps will work when drowned4 ,compressed air has a distinct place for minor pumping units1 especially those removed from the shaft1 for they can be run as an adjunct to the air-drill system of the mine1 and by this arrangement much capital outlay may be saved4 ,the cost of the extra power consumed by such an arrangement is less than the average cost of compressed-air power1 because many of the compressor charges have to be paid anyway4 ,when compressed air is water-generated1 they have a field for permanent installations4 ,the efficiency of even rotary air-driven pumps1 based on power delivered into a good compressor1 is probably not over #be4 ,,electrical ,,pumps4--,electrical pumps have somewhat less flexibility than steam- or air-driven apparatus1 in that the speed of the pumps can be varied only within small limits4 ,they have the same great advantage in the easy reorganization of the system to altered conditions of water-flow4 ,electricity1 when steam-generated1 has the handicap of the losses of two conversions1 the actual pump efficiency being about #fj in well-constructed plants2 the efficiency is therefore greater than direct steam or compressed air4 ,where the mine is operated with water-power1 purchased electric current1 or where there is an installation of electrical generating plant by steam or gas for other purposes1 electrically driven pumps take precedence over all others on account of their combined moderate capital outlay1 great flexibility1 and reasonable efficiency4 ,in late years1 direct-coupled1 electric-driven centrifugal pumps have entered the mining field1 but their efficiency1 despite makers' claims1 is low4 ,while they show comparatively good results on low lifts the slip increases with the lift4 ,in heads over #bjj feet their efficiency is probably not #cj of the power delivered to the electrical generator4 ,their chief attractions are small capital cost and the compact size which admits of easy installation4 ,,rod-,,driven ,,pumps4--,pumps of the ,cornish type in vertical shafts1 if operated to full load and if driven by modern engines1 have an efficiency much higher than any other sort of installation1 and records of #he to #ij are not unusual4 ,the highest efficiency in these pumps yet obtained has been by driving the pump with rope transmission from a high-speed triple expansion engine1 and in this plant an actual consumption of only #ag pounds of steam per horse-power hour for actual water lifted has been accomplished4 ,to provide1 however1 for increase of flow and change of horizon1 rod-driven pumps must be so overpowered at the earlier stage of the mine that they operate with great loss4 ,of all pumping systems they are the most expensive to provide4 ,they have no place in crooked openings and only work in inclines with many disadvantages4 ,in general their lack of flexibility is fast putting them out of the metal miner's purview4 ,where the pumping depth and volume of water are approximately known1 as is often the case in coal mines1 this1 the father of all pumps1 still holds its own4 ,,hydraulic ,,pumps4--,hydraulic pumps1 in which a column of water is used as the transmission fluid from a surface pump to a corresponding pump underground has had some adoption in coal mines1 but little in metal mines4 ,they have a certain amount of flexibility but low efficiency1 and are not likely to have much field against electrical pumps4 ,,bailing4--,bailing deserves to be mentioned among drainage methods1 for under certain conditions it is a most useful system1 and at all times a mine should be equipped with tanks against accident to the pumps4 ,where the amount of water is limited1--up to1 say1 #ej1jjj gallons daily1--and where the ore output of the mine permits the use of the winding-engine for part of the time on water haulage1 there is in the method an almost total saving of capital outlay4 ,inasmuch as the winding-engine1 even when the ore haulage is finished for the day1 must be under steam for handling men in emergencies1 and as the labor of stokers1 engine-drivers1 shaft-men1 etc41 is therefore necessary1 the cost of power consumed by bailing is not great1 despite the low efficiency of winding-engines4 ,,comparison ,,of ,,various ,,systems4--,if it is assumed that flexibility1 reliability1 mechanical efficiency1 and capital cost can each be divided into four figures of relative importance1--,a1 ,b1 ,c1 and ,d1 with ,a representing the most desirable result1--it is possible to indicate roughly the comparative values of various pumping systems4 ,it is not pretended that the four degrees are of equal import4 ,in all cases the factor of general power conditions on the mine may alter the relative positions4 ,direct,compressed ,steam- ,steam ,air ,electricity,driven,hydraulic,bailing ,pumps ,rods ,columns ,tanks ---------------------------------------- ---------------------- ,flexibility4 ,a ,a ,b ,d ,b ,a ,reliability4 ,b ,b ,b ,a ,d ,a ,mechanical ,efficiency4 ,c ,d ,b ,a ,c ,d ,capital ,cost ,a ,b ,b ,d ,d -- ,as each mine has its special environment1 it is impossible to formulate any final conclusion on a subject so involved4 ,the attempt would lead to a discussion of a thousand supposititious cases and hypothetical remedies4 ,further1 the description alone of pumping machines would fill volumes1 and the subject will never be exhausted4 ,the engineer confronted with pumping problems must marshal all the alternatives1 count his money1 and apply the tests of flexibility1 reliability1 efficiency1 and cost1 choose the system of least disadvantages1 and finally deprecate the whole affair1 for it is but a parasite growth on the mine4 ,,chapter ,,xiv4 ,mechanical ,equipment 7,concluded74 ,,machine ,,drilling3 ,,power ,,transmission2 ,,compressed ,,air ,,vs4 ,,electricity2 ,,air ,,drills2 ,,machine ,,vs4 ,,hand ,,drilling4 ,,work-,,shops4 ,,improvement ,,in ,,equipment4 ,for over two hundred years from the introduction of drill-holes for blasting by ,caspar ,weindel in ,hungary1 to the invention of the first practicable steam percussion drill by ,j4 ,j4 ,crouch of ,philadelphia1 in #ahdi1 all drilling was done by hand4 ,since ,crouch's time a host of mechanical drills to be actuated by all sorts of power have come forward1 and even yet the machine-drill has not reached a stage of development where it can displace hand-work under all conditions4 ,steam-power was never adapted to underground work1 and a serviceable drill for this purpose was not found until compressed air for transmission was demonstrated by ,dommeiller on the ,mt4 ,cenis tunnel in #ahfa4 ,the ideal requirements for a drill combine3-- a4 ,power transmission adapted to underground conditions4 b4 ,lightness4 c4 ,simplicity of construction4 d4 ,strength4 e4 ,rapidity and strength of blow4 f4 ,ease of erection4 g4 ,reliability4 h4 ,mechanical efficiency4 i4 ,low capital cost4 ,no drill invented yet fills all these requirements1 and all are a compromise on some point4 ,,power ,,transmission2 ,,compressed ,,air vs4 ,,electricity4--,the only transmissions adapted to underground drill-work are compressed air and electricity1 and as yet an electric-driven drill has not been produced which meets as many of the requirements of the metal miner as do compressed-air drills4 ,the latter1 up to date1 have superiority in simplicity1 lightness1 ease of erection1 reliability1 and strength over electric machines4 ,air has another advantage in that it affords some assistance to ventilation1 but it has the disadvantage of remarkably low mechanical efficiency4 ,the actual work performed by the standard #c-c_/d-;inch air-drill probably does not amount to over two or three horse-power against from fifteen to eighteen horse-power delivered into the compressor1 or mechanical efficiency of less than #be4 ,as electrical power can be delivered to the drill with much less loss than compressed air1 the field for a more economical drill on this line is wide enough to create eventually the proper tool to apply it4 ,the most satisfactory electric drill produced has been the ,temple drill1 which is really an air-drill driven by a small electrically-driven compressor placed near the drill itself4 ,but even this has considerable deficiencies in mining work2 the difficulties of setting up1 especially for stoping work1 and the more cumbersome apparatus to remove before blasting are serious drawbacks4 ,it has deficiencies in reliability and greater complication of machinery than direct air4 ,,air-,,compression4--,the method of air-compression so long accomplished only by power-driven pistons has now an alternative in some situations by the use of falling water4 ,this latter system is a development of the last twelve years1 and1 due to the low initial outlay and extremely low operating costs1 bids fair in those regions where water head is available not only to displace the machine compressor1 but also to extend the application of compressed air to mine motors generally1 and to stay in some environments the encroachment of electricity into the compressed-air field4 ,installations of this sort in the ,west ,kootenay1 ,b4,c41 and at the ,victoria copper mine1 ,michigan1 are giving results worthy of careful attention4 ,mechanical air-compressors are steam-1 water-1 electrical-1 and gas-driven1 the alternative obviously depending on the source and cost of power4 ,electrical- and gas- and water-driven compressors work under the disadvantage of constant speed motors and respond little to the variation in load1 a partial remedy for which lies in enlarged air-storage capacity4 ,inasmuch as compressed air1 so far as our knowledge goes at present1 must be provided for drills1 it forms a convenient transmission of power to various motors underground1 such as small pumps1 winches1 or locomotives4 ,as stated in discussing those machines1 it is not primarily a transmission of even moderate mechanical efficiency for such purposes2 but as against the installation and operation of independent transmission1 such as steam or electricity1 the economic advantage often compensates the technical losses4 ,where such motors are fixed1 as in pumps and winches1 a considerable gain in efficiency can be obtained by reheating4 ,it is not proposed to enter a discussion of mechanical details of air-compression1 more than to call attention to the most common delinquency in the installation of such plants4 ,this deficiency lies in insufficient compression capacity for the needs of the mine and consequent effective operation of drills1 for with under #ge pounds pressure the drills decrease remarkably in rapidity of stroke and force of the blow4 ,the consequent decrease in actual accomplishment is far beyond the ratio that might be expected on the basis of mere difference of pressure4 ,another form of the same chronic ill lies in insufficient air-storage capacity to provide for maintenance of pressure against moments when all drills or motors in the mine synchronize in heavy demand for air1 and thus lower the pressure at certain periods4 ,,air-,,drills4--,air-drills are from a mechanical point of view broadly of two types1--the first1 in which the drill is the piston extension2 and the second1 a more recent development for mining work1 in which the piston acts as a hammer striking the head of the drill4 ,from an economic point of view drills may be divided into three classes4 ,first1 heavy drills1 weighing from #aej to #djj pounds1 which require two men for their operation2 second1 baby drills of the piston type1 weighing from #aaj to #aej pounds1 requiring one man with occasional assistance in setting up2 and third1 very light drills almost wholly of the hammer type4 ,this type is built in two forms3 a heavier type for mounting on columns1 weighing about #hj pounds2 and a type after the order of the pneumatic riveter1 weighing as low as #bj pounds and worked without mounting4 ,the weight and consequent mobility of a drill1 aside from labor questions1 have a marked effect on costs1 for the lighter the drill the less difficulty and delay in erection1 and consequent less loss of time and less tendency to drill holes from one radius1 regardless of pointing to take best advantage of breaking planes4 ,moreover1 smaller diameter and shorter holes consume less explosives per foot advanced or per ton broken4 ,the best results in tonnage broken and explosive consumed1 if measured by the foot of drill-hole necessary1 can be accomplished from hand-drilling and the lighter the machine drill1 assuming equal reliability1 the nearer it approximates these advantages4 ,the blow1 and therefore size and depth of hole and rapidity of drilling1 are somewhat dependent upon the size of cylinders and length of stroke1 and therefore the heavier types are better adapted to hard ground and to the deep holes of some development points4 ,their advantages over the other classes lie chiefly in this ability to bore exceedingly hard material and in the greater speed of advance possible in development work2 but except for these two special purposes they are not as economical per foot advanced or per ton of ore broken as the lighter drills4 ,the second class1 where men can be induced to work them one man per drill1 saves in labor and gains in mobility4 ,many tests show great economy of the baby type of piston drills in average ground over the heavier machines for stoping and for most lateral development4 ,all piston types are somewhat cumbersome and the heavier types require at least four feet of head room4 ,the baby type can be operated in less space than this1 but for narrow stopes they do not lend themselves with the same facility as the third class4 ,the third class of drills is still in process of development1 but it bids fair to displace much of the occupation of the piston types of drill4 ,aside from being a one-man drill1 by its mobility it will apparently largely reproduce the advantage of hand-drilling in ability to place short holes from the most advantageous angles and for use in narrow places4 ,as compared with other drills it bids fair to require less time for setting up and removal and for change of bits2 to destroy less steel by breakages2 to dull the bits less rapidly per foot of hole2 to be more economical of power2 to require much less skill in operation1 for judgment is less called upon in delivering speed2 and to evade difficulties of fissured ground1 etc4 ,and finally the cost is only one-half1 initially and for spares4 ,its disadvantage so far is a lack of reliability due to lightness of construction1 but this is very rapidly being overcome4 ,this type1 however1 is limited in depth of hole possible1 for1 from lack of positive reverse movement1 there is a tendency for the spoil to pack around the bit1 and as a result about four feet seems the limit4 ,the performance of a machine-drill under show conditions may be anything up to ten or twelve feet of hole per hour on rock such as compact granite2 but in underground work a large proportion of the time is lost in picking down loose ore1 setting up machines1 removal for blasting1 clearing away spoil1 making adjustments1 etc4 ,the amount of lost time is often dependent upon the width of stope or shaft and the method of stoping4 ,situations which require long drill columns or special scaffolds greatly accentuate the loss of time4 ,further1 the difficulties in setting up reflect indirectly on efficiency to a greater extent in that a larger proportion of holes are drilled from one radius and thus less adapted to the best breaking results than where the drill can easily be reset from various angles4 ,the usual duty of a heavy drill per eight-hour shift using two men is from #bj to #dj feet of hole1 depending upon the rock1 facilities for setting up1 etc41 etc499 ,the lighter drills have a less average duty1 averaging from #ae to #be feet per shift4 ,footnote 993 ,over the year #aijg in twenty-eight mines compiled from ,alaska to ,australia1 an average of #bc4e feet was drilled per eight-hour shift by machines larger than three-inch cylinder4 ,,machine vs4 ,,hand-,,drilling4--,the advantages of hand-drilling over machine-drilling lie1 first1 in the total saving of power1 the absence of capital cost1 repairs1 depreciation1 etc41 on power1 compresser and drill plant2 second1 the time required for setting up machine-drills does not warrant frequent blasts1 so that a number of holes on one radius are a necessity1 and therefore machine-holes generally cannot be pointed to such advantage as hand-holes4 ,hand-holes can be set to any angle1 and by thus frequent blasting yield greater tonnage per foot of hole4 ,third1 a large number of comparative statistics from ,american1 ,south ,african1 and ,australian mines show a saving of about #be in explosives for the same tonnage or foot of advance by hand-holes over medium and heavy drill-holes4 ,the duty of a skilled white man1 single-handed1 in rock such as is usually met below the zone of oxidation1 is from #e to #g feet per shift1 depending on the rock and the man4 ,two men hand-drilling will therefore do from #a_/d to #b_/c of the same footage of holes that can be done by two men with a heavy machine-drill1 and two men hand-drilling will do from #a_/e to #a_/b the footage of two men with two light drills4 ,the saving in labor of from #ge to #cc by machine-drilling may or may not be made up by the other costs involved in machine-work4 ,the comparative value of machine- and hand-drilling is not subject to sweeping generalization4 ,a large amount of data from various parts of the world1 with skilled white men1 shows machine-work to cost from half as much per ton or foot advanced as hand-work to #be more than handwork1 depending on the situation1 type of drill1 etc4 ,in a general way hand-work can more nearly compete with heavy machines than light ones4 ,the situations where hand-work can compete with even light machines are in very narrow stopes where drills cannot be pointed to advantage1 and where the increased working space necessary for machine drills results in breaking more waste4 ,further1 hand-drilling can often compete with machine-work in wide stopes where long columns or platforms must be used and therefore there is much delay in taking down1 rerection1 etc4 ,many other factors enter into a comparison1 however1 for machine-drilling produces a greater number of deeper holes and permits larger blasts and therefore more rapid progress4 ,in driving levels under average conditions monthly footage is from two to three times as great with heavy machines as by hand-drilling1 and by lighter machines a somewhat less proportion of greater speed4 ,the greater speed obtained in development work1 the greater tonnage obtained per man in stoping1 with consequent reduction in the number of men employed1 and in reduction of superintendence and general charges are indirect advantages for machine-drilling not to be overlooked4 ,the results obtained in ,south ,africa by hand-drilling in shafts1 and its very general adoption there1 seem to indicate that better speed and more economical work can be obtained in that way in very large shafts than by machine-drilling4 ,how far special reasons there apply to smaller shafts or labor conditions elsewhere have yet to be demonstrated4 ,in large-dimension shafts demanding a large number of machines1 the handling of long machine bars and machines generally results in a great loss of time4 ,the large charges in deep holes break the walls very irregularly2 misfires cause more delay2 timbering is more difficult in the face of heavy blasting charges2 and the larger amount of spoil broken at one time delays renewed drilling1 and altogether the advantages seem to lie with hand-drilling in shafts of large horizontal section4 ,the rapid development of special drills for particular conditions has eliminated the advantage of hand-work in many situations during the past ten years1 and the invention of the hammer type of drill bids fair to render hand-drilling a thing of the past4 ,one generalization is possible1 and that is1 if drills are run on #dj-ej pounds' pressure they are no economy over hand-drilling4 ,,workshops4 ,in addition to the ordinary blacksmithy1 which is a necessity1 the modern tendency has been to elaborate the shops on mines to cover machine-work1 pattern-making and foundry-work1 in order that delays may be minimized by quick repairs4 ,to provide1 however1 for such contingencies a staff of men must be kept larger than the demand of average requirements4 ,the result is an effort to provide jobs or to do work extravagantly or unnecessarily well4 ,in general1 it is an easy spot for fungi to start growing on the administration1 and if custom repair shops are available at all1 mine shops can be easily overdone4 ,a number of machines are now in use for sharpening drills4 ,machine-sharpening is much cheaper than hand-work1 although the drills thus sharpened are rather less efficient owing to the difficulty of tempering them to the same nicety2 however1 the net results are in favor of the machines4 ,,improvement ,,in ,,equipment4 ,not only is every mine a progressive industry until the bottom gives out1 but the technology of the industry is always progressing1 so that the manager is almost daily confronted with improvements which could be made in his equipment that would result in decreasing expenses or increasing metal recovery4 ,there is one test to the advisability of such alterations3 ,how long will it take to recover the capital outlay from the savings effected8 and over and above this recovery of capital there must be some very considerable gain4 ,the life of mines is at least secured over the period exposed in the ore-reserves1 and if the proposed alteration will show its recovery and profit in that period1 then it is certainly justified4 ,if it takes longer than this on the average speculative ore-deposit1 it is a gamble on finding further ore4 ,as a matter of practical policy it will be found that an improvement in equipment which requires more than three or four years to redeem itself out of saving1 is usually a mechanical or metallurgical refinement the indulgence in which is very doubtful4 ,,chapter ,,xv4 ,ratio of ,output to the ,mine4 ,,determination ,,of ,,the ,,possible ,,maximum2 ,,limiting ,,factors2 ,,cost ,,of ,,equipment2 ,,life ,,of ,,the ,,mine2 ,,mechanical ,,inefficiency ,,of ,,patchwork ,,plant2 ,,overproduction ,,of ,,base ,,metal2 ,,security ,,of ,,investment4 ,the output obtainable from a given mine is obviously dependent not only on the size of the deposit1 but also on the equipment provided1--in which equipment means the whole working appliances1 surface and underground4 ,a rough and ready idea of output possibilities of inclined deposits can be secured by calculating the tonnage available per foot of depth from the horizontal cross-section of the ore-bodies exposed and assuming an annual depth of exhaustion1 or in horizontal deposits from an assumption of a given area of exhaustion4 ,few mines1 at the time of initial equipment1 are developed to an extent from which their possibilities in production are evident1 for wise finance usually leads to the erection of some equipment and production before development has been advanced to a point that warrants a large or final installation4 ,moreover1 even were the full possibilities of the mine known1 the limitations of finance usually necessitate a less plant to start with than is finally contemplated4 ,therefore output and equipment are usually growing possibilities during the early life of a mine4 ,there is no better instance in mine engineering where pure theory must give way to practical necessities of finance than in the determination of the size of equipment and therefore output4 ,moreover1 where finance even is no obstruction1 there are other limitations of a very practical order which must dominate the question of the size of plant giving the greatest technical economy4 ,it is1 however1 useful to state the theoretical considerations in determining the ultimate volume of output and therefore the size of equipments1 for the theory will serve to illuminate the practical limitations4 ,the discussion will also again demonstrate that all engineering is a series of compromises with natural and economic forces4 ,,output ,,giving ,,least ,,production ,,cost4--,as one of the most important objectives is to work the ore at the least cost per ton1 it is not difficult to demonstrate that the minimum working costs can be obtained only by the most intensive production4 ,to prove this1 it need only be remembered that the working expenses of a mine are of two sorts3 one is a factor of the tonnage handled1 such as stoping and ore-dressing2 the other is wholly or partially dependent upon time4 ,a large number of items are of this last order4 ,pumping and head-office expenses are almost entirely charges independent of the tonnage handled4 ,superintendence and staff salaries and the like are in a large proportion dependent upon time4 ,many other elements of expense1 such as the number of engine-drivers1 etc41 do not increase proportionately to increase in tonnage4 ,these charges1 or the part of them dependent upon time apart from tonnage1 may be termed the fixed charges4 ,there is another fixed charge more obscure yet no less certain4 ,ore standing in a mine is like money in a bank drawing no interest1 and this item of interest may be considered a fixed charge1 for if the ore were realized earlier1 this loss could be partially saved4 ,this subject is further referred to under ,amortization4 ,if1 therefore1 the time required to exhaust the mine be prolonged by the failure to maintain the maximum output1 the total cost of working it will be greater by the fixed charges over such an increased period4 ,conversely1 by equipping on a larger scale1 the mine will be exhausted more quickly1 a saving in total cost can be made1 and the ultimate profit can be increased by an amount corresponding to the time saved from the ravages of fixed charges4 ,in fine1 the working costs may be reduced by larger operations1 and therefore the value of the mine increased4 ,the problem in practice usually takes the form of the relative superiority of more or of fewer units of plant1 and it can be considered in more detail if the production be supposed to consist of units averaging say #ajj tons per day each4 ,the advantage of more units over less will be that the extra ones can be produced free of fixed charges1 for these are an expense already involved in the lesser units4 ,this extra production will also enjoy the interest which can be earned over the period of its earlier production4 ,moreover1 operations on a larger scale result in various minor economies throughout the whole production1 not entirely included in the type of expenditure mentioned as fixed charges4 ,we may call these various advantages the saving of fixed charges due to larger-scale operations4 ,the saving of fixed charges amounts to very considerable sums4 ,in general the items of working cost alone1 mentioned above1 which do not increase proportionately to the tonnage1 aggregate from #aj to #be of the total costs4 ,where much pumping is involved1 the percentage will become even greater4 ,the question of the value of the mine as affected by the volume of output becomes very prominent in low-grade mines1 where1 if equipped for output on too small a scale1 no profits at all could be earned1 and a sufficient production is absolutely imperative for any gain4 ,there are many mines in every country which with one-third of their present rate of production would lose money4 ,that is1 the fixed charges1 if spread over small output1 would be so great per ton that the profit would be extinguished by them4 ,in the theoretical view1 therefore1 it would appear clear that the greatest ultimate profit from a mine can be secured only by ore extraction under the highest pressure4 ,as a corollary to this it follows that development must proceed with the maximum speed4 ,further1 it follows that the present value of a mine is at least partially a factor of the volume of output contemplated4 ,,factors ,,limiting ,,the ,,output4 ,although the above argument can be academically defended1 there are1 as said at the start1 practical limitations to the maximum intensity of production1 arising out of many other considerations to which weight must be given4 ,in the main1 there are five principal limitations3-- #a4 ,cost of equipment4 #b4 ,life of the mine4 #c4 ,mechanical inefficiency of patchwork plant4 #d4 ,overproduction of base metal4 #e4 ,security of investment4 ,,cost ,,of ,,equipment4--,the saving of fixed charges can only be obtained by larger equipment1 which represents an investment4 ,mining works1 shafts1 machinery1 treatment plants1 and all the paraphernalia cost large sums of money4 ,they become either worn out or practically valueless through the exhaustion of the mines4 ,even surface machinery when in good condition will seldom realize more than one-tenth of its expense if useless at its original site4 ,all mines are ephemeral2 therefore virtually the entire capital outlay of such works must be redeemed during the life of the mine1 and the interest on it must also be recovered4 ,the certain life1 with the exception of banket and a few other types of deposit1 is that shown by the ore in sight1 plus something for extension of the deposit beyond exposures4 ,so1 against the savings to be made1 must be set the cost of obtaining them1 for obviously it is of no use investing a dollar to save a total of ninety cents4 ,the economies by increased production are1 however1 of such an important character that the cost of almost any number of added units 7within the ability of the mine to supply them7 can be redeemed from these savings in a few years4 ,for instance1 in a ,californian gold mine where the working expenses are #c and the fixed charges are at the low rate of #cj cents per ton1 one unit of increased production would show a saving of over #aj1jjj per annum from the saving of fixed charges4 ,in about three years this sum would repay the cost of the additional treatment equipment4 ,if further shaft capacity were required1 the period would be much extended4 ,on a ,western copper mine1 where the costs are #h and the fixed charges are #hj cents per ton1 one unit of increased production would effect a saving of the fixed charges equal to the cost of the extra unit in about three years4 ,that is1 the total sum would amount to #hj1jjj1 or enough to provide almost any type of mechanical equipment for such additional tonnage4 ,the first result of vigorous development is to increase the ore in sight1--the visible life of the mine4 ,when such visible life has been so lengthened that the period in which the saving of fixed charges will equal the amount involved in expansion of equipment1 then from the standpoint of this limitation only is the added installation justified4 ,the equipment if expanded on this practice will grow upon the heels of rapid development until the maximum production from the mine is reached1 and a kind of equilibrium establishes itself4 ,conversely1 this argument leads to the conclusion that1 regardless of other considerations1 an equipment1 and therefore output1 should not be expanded beyond the redemption by way of saving from fixed charges of the visible or certain life of the mine4 ,in those mines1 such as at the ,witwatersrand1 where there is a fairly sound assurance of definite life1 it is possible to calculate at once the size of plant which by saving of fixed charges will be eventually the most economical1 but even here the other limitations step in to vitiate such policy of management1--chiefly the limitation through security of investment4 ,,life ,,of ,,the ,,mine4--,if carried to its logical extreme1 the above program means a most rapid exhaustion of the mine4 ,the maximum output will depend eventually upon the rapidity with which development work may be extended4 ,as levels and other subsidiary development openings can be prepared in inclined deposits much more quickly than the shaft can be sunk1 the critical point is the shaft-sinking4 ,as a shaft may by exertion be deepened at least #djj feet a year on a going mine1 the provision of an equipment to eat up the ore-body at this rate of sinking means very early exhaustion indeed4 ,in fact1 had such a theory of production been put into practice by our forefathers1 the mining profession might find difficulty in obtaining employment to-day4 ,such rapid exhaustion would mean a depletion of the mineral resources of the state at a pace which would be alarming4 ,,mechanical ,,inefficiency ,,of ,,patchwork ,,plant4--,mine equipments on speculative mines 7the vast majority7 are often enough patchwork1 for they usually grow from small beginnings2 but any scheme of expansion based upon the above doctrine would need to be modified to the extent that additions could be in units large in ratio to previous installations1 or their patchwork character would be still further accentuated4 ,it would be impossible to maintain mechanical efficiency under detail expansion4 ,,overproduction ,,of ,,base ,,metal4--,were this intensity of production of general application to base metal mines it would flood the markets1 and1 by an overproduction of metal depress prices to a point where the advantages of such large-scale operations would quickly vanish4 ,the theoretical solution in this situation would be1 if metals fell below normal prices1 let the output be reduced1 or let the products be stored until the price recovers4 ,from a practical point of view either alternative is a policy difficult to face4 ,in the first case1 reduction of output means an increase of working expenses by the spread of fixed charges over less tonnage1 and this in the face of reduced metal prices4 ,it may be contended1 however1 that a falling metal market is usually the accompaniment of a drop in all commodities1 wherefore working costs can be reduced somewhat in such times of depression1 thereby partially compensating the other elements making for increased costs4 ,falls in commodities are also the accompaniment of hard times4 ,consideration of one's workpeople and the wholesale slaughter of dividends to the then needy stockholders1 resulting from a policy of reduced production1 are usually sufficient deterrents to diminished output4 ,the second alternative1 that of storing metal1 means equally a loss of dividends by the investment of a large sum in unrealized products1 and the interest on this sum4 ,the detriment to the market of large amounts of unsold metal renders such a course not without further disadvantages4 ,,security ,,of ,,investment4--,another point of view antagonistic to such wholesale intensity of production1 and one worthy of careful consideration1 is that of the investor in mines4 ,the root-value of mining stocks is1 or should be1 the profit in sight4 ,if the policy of greatest economy in production costs be followed as outlined above1 the economic limit of ore-reserves gives an apparently very short life1 for the ore in sight will never represent a life beyond the time required to justify more plant4 ,thus the economic limit of ore in reserve will be a store equivalencing a period during which additional equipment can be redeemed from the saving of fixed charges1 or three or four years1 usually4 ,the investor has the right to say that he wants the guarantee of longer life to his investment1--he will in effect pay insurance for it by a loss of some ultimate profit4 ,that this view1 contradictory to the economics of the case1 is not simply academic1 can be observed by any one who studies what mines are in best repute on any stock exchange4 ,all engineers must wish to have the industry under them in high repute4 ,the writer knows of several mines paying #bj on their stocks which yet stand lower in price on account of short ore-reserves than mines paying less annual returns4 ,the speculator1 who is an element not to be wholly disregarded1 wishes a rise in his mining stock1 and if development proceeds at a pace in advance of production1 he will gain a legitimate rise through the increase in ore-reserves4 ,the investor's and speculator's idea of the desirability of a proved long life readily supports the technical policy of high-pressure development work1 but not of expansion of production1 for they desire an increasing ore-reserve4 ,even the metal operator who is afraid of overproduction does not object to increased ore-reserves4 ,on the point of maximum intensity of development work in a mine all views coincide4 ,the mining engineer1 if he takes a ,machiavellian view1 must agree with the investor and the metal dealer1 for the engineer is a fixed charge the continuance of which is important to his daily needs4 ,the net result of all these limitations is therefore an invariable compromise upon some output below the possible maximum4 ,the initial output to be contemplated is obviously one upon which the working costs will be low enough to show a margin of profit4 ,the medium between these two extremes is determinable by a consideration of the limitations set out1--and the cash available4 ,when the volume of output is once determined1 it must be considered as a factor in valuation1 as discussed under ,amortization4 ,,chapter ,,xvi4 ,administration4 ,,labor ,,efficiency2 ,,skill2 ,,intelligence2 ,,application ,,coordination2 ,,contract ,,work2 ,,labor ,,unions2 ,,real ,,basis ,,of ,,wages4 ,the realization from a mine of the profits estimated from the other factors in the case is in the end dependent upon the management4 ,good mine management is based upon three elementals3 first1 sound engineering2 second1 proper cordination and efficiency of every human unit2 third1 economy in the purchase and consumption of supplies4 ,the previous chapters have been devoted to a more or less extended exposition of economic engineering4 ,while the second and third requirements are equally important1 they range in many ways out of the engineering and into the human field4 ,for this latter reason no complete manual will ever be published upon ,how to become a ,good ,mine ,manager4 ,it is purposed1 however1 to analyze some features of these second and third fundamentals1 especially in their interdependent phases1 and next to consider the subject of mine statistics1 for the latter are truly the microscopes through which the competence of the administration must be examined4 ,the human units in mine organization can be divided into officers and men4 ,the choice of mine officers is the assembling of specialized brains4 ,their control1 stimulation1 and inspiration is the main work of the administrative head4 ,success in the selection and control of staff is the index of executive ability4 ,there are no mathematical1 mechanical1 or chemical formulas for dealing with the human mind or human energies4 ,,labor4--,the whole question of handling labor can be reduced to the one term efficiency4 ,not only does the actual labor outlay represent from #fj to #gj of the total underground expenses1 but the capacity or incapacity of its units is responsible for wider fluctuations in production costs than the bare predominance in expenditure might indicate4 ,the remaining expense is for supplies1 such as dynamite1 timber1 steel1 power1 etc41 and the economical application of these materials by the workman has the widest bearing upon their consumption4 ,efficiency of the mass is the resultant of that of each individual under a direction which cordinates effectively all units4 ,the lack of effectiveness in one individual diminishes the returns not simply from that man alone2 it lowers the results from numbers of men associated with the weak member through the delaying and clogging of their work1 and of the machines operated by them4 ,cordination of work is a necessary factor of final efficiency4 ,this is a matter of organization and administration4 ,the most zealous stoping-gang in the world if associated with half the proper number of truckers must fail to get the desired result4 ,efficiency in the single man is the product of three factors1--skill1 intelligence1 and application4 ,a great proportion of underground work in a mine is of a type which can be performed after a fashion by absolutely unskilled and even unintelligent men1 as witness the breaking-in of savages of low average mentality1 like the ,south ,african ,kaffirs4 ,although most duties can be performed by this crudest order of labor1 skill and intelligence can be applied to it with such economic results as to compensate for the difference in wage4 ,the reason for this is that the last fifty years have seen a substitution of labor-saving machines for muscle4 ,such machines displace hundreds of raw laborers4 ,not only do they initially cost large sums1 but they require large expenditure for power and up-keep4 ,these fixed charges against the machine demand that it shall be worked at its maximum4 ,for interest1 power1 and up-keep go on in any event1 and the saving on crude labor displaced is not so great but that it quickly disappears if the machine is run under its capacity4 ,to get its greatest efficiency1 a high degree of skill and intelligence is required4 ,nor are skill and intelligence alone applicable to labor-saving devices themselves1 because drilling and blasting rock and executing other works underground are matters in which experience and judgment in the individual workman count to the highest degree4 ,how far skill affects production costs has had a thorough demonstration in ,west ,australia4 ,for a time after the opening of those mines only a small proportion of experienced men were obtainable4 ,during this period the rock broken per man employed underground did not exceed the rate of #cjj tons a year4 ,in the large mines it has now1 after some eight years1 attained #fjj to #gjj tons4 ,how far intelligence is a factor indispensable to skill can be well illustrated by a comparison of the results obtained from working labor of a low mental order1 such as ,asiatics and negroes1 with those achieved by ,american or ,australian miners4 ,in a general way1 it may be stated with confidence that the white miners above mentioned can1 under the same physical conditions1 and with from five to ten times the wage1 produce the same economic result1--that is1 an equal or lower cost per unit of production4 ,much observation and experience in working ,asiatics and negroes as well as ,americans and ,australians in mines1 leads the writer to the conclusion that1 averaging actual results1 one white man equals from two to three of the colored races1 even in the simplest forms of mine work such as shoveling or tramming4 ,in the most highly skilled branches1 such as mechanics1 the average ratio is as one to seven1 or in extreme cases even eleven4 ,the question is not entirely a comparison of bare efficiency individually2 it is one of the sum total of results4 ,in mining work the lower races require a greatly increased amount of direction1 and this excess of supervisors consists of men not in themselves directly productive4 ,there is always1 too1 a waste of supplies1 more accidents1 and more ground to be kept open for accommodating increased staff1 and the maintenance of these openings must be paid for4 ,there is an added expense for handling larger numbers in and out of the mine1 and the lower intelligence reacts in many ways in lack of cordination and inability to take initiative4 ,taking all divisions of labor together1 the ratio of efficiency as measured in amount of output works out from four to five colored men as the equivalent of one white man of the class stated4 ,the ratio of costs1 for reasons already mentioned1 and in other than quantity relation1 figures still more in favor of the higher intelligence4 ,the following comparisons1 which like all mine statistics must necessarily be accepted with reservation because of some dissimilarity of economic surroundings1 are yet on sufficiently common ground to demonstrate the main issue1--that is1 the bearing of inherent intelligence in the workmen and their consequent skill4 ,four groups of gold mines have been taken1 from ,india1 ,west ,australia1 ,south ,africa1 and ,western ,america4 ,all of those chosen are of the same stoping width1 #d to #e feet4 ,all are working in depth and with every labor-saving device available4 ,all dip at about the same angle and are therefore in much the same position as to handling rock4 ,the other conditions are against the white-manned mines and in favor of the colored4 ,that is1 the ,indian mines have water-generated electric power and ,south ,africa has cheaper fuel than either the ,american or ,australian examples4 ,in both the white-manned groups1 the stopes are supported1 while in the others no support is required4 ,tons of ,average ,tons ,material ,number of ,men per ,cost per ,group of ,mines ,excavated ,employed ,man ,ton of over ,period--------------- per ,material ,compiled#e;,colored ,white ,annum ,broken ---------------------------------------- -------------------------- ,four ,kolar mines#a #ifc1iej #ac1faa #cjb #fi4c #c4he ,six ,australian mines#b #a1jbg1gah -- #a1ecd #ffi4i #b4dg ,three ,witwatersrand mines#c #b1ifb1fdj #ac1efj #a1eie #aie4e #b4fh ,five ,american mines#d #a1jhi1ejj -- #a1ebd #gac4c #a4ib ,footnote #a3 ,indian wages average about #bj cents per day4 ,footnote #b3 ,white men's wages average about #c per day4 ,footnote #c3 ,about two-fifths of the colored workers were negroes1 and three-fifths ,chinamen4 ,negroes average about #fj cents1 and ,chinamen about #de cents per day1 including keep4 ,footnote #d3 ,wages about #c4ej4 ,tunnel entry in two mines4 ,footnote #e3 ,includes rock broken in development work4 ,in the case of the specified ,african mines1 the white labor is employed almost wholly in positions of actual or semi-superintendence1 such as one white man in charge of two or three drills4 ,in the ,indian case1 in addition to the white men who are wholly in superintendence1 there were of the natives enumerated some #ajjj in positions of semi-superintendence1 as contractors or headmen1 working-gangers1 etc4 ,one issue arises out of these facts1 and that is that no engineer or investor in valuing mines is justified in anticipating lower costs in regions where cheap labor exists4 ,in supplement to sheer skill and intelligence1 efficiency can be gained only by the application of the man himself4 ,a few months ago a mine in ,california changed managers4 ,the new head reduced the number employed one-third without impairing the amount of work accomplished4 ,this was not the result of higher skill or intelligence in the men1 but in the manager4 ,better application and cordination were secured from the working force4 ,inspiration to increase of exertion is created less by driving than by recognition of individual effort1 in larger pay1 and by extending justifiable hope of promotion4 ,a great factor in the proficiency of the mine manager is his ability to create an esprit-de-corps through the whole staff1 down to the last tool boy4 ,friendly interest in the welfare of the men and stimulation by competitions between various works and groups all contribute to this end4 ,,contract ,,work4--,the advantage both to employer and employed of piece work over wage needs no argument4 ,in a general way1 contract work honorably carried out puts a premium upon individual effort1 and thus makes for efficiency4 ,there are some portions of mine work which cannot be contracted1 but the development1 stoping1 and trucking can be largely managed in this way1 and these items cover #fe to #ge of the total labor expenditure underground4 ,in development there are two ways of basing contracts1--the first on the footage of holes drilled1 and the second on the footage of heading advanced4 ,in contract-stoping there are four methods depending on the feet of hole drilled1 on tonnage1 on cubic space1 and on square area broken4 ,all these systems have their rightful application1 conditioned upon the class of labor and character of the deposit4 ,in the hole system1 the holes are pointed by some mine official and are blasted by a special crew4 ,the miner therefore has little interest in the result of the breaking4 ,if he is a skilled white man1 the hours which he has wherein to contemplate the face usually enable him to place holes to better advantage than the occasional visiting foreman4 ,with colored labor1 the lack of intelligence in placing holes and blasting usually justifies contracts per foot drilled4 ,then the holes are pointed and blasted by superintending men4 ,on development work with the foot-hole system1 unless two working faces can be provided for each contracting party1 they are likely to lose time through having finished their round of holes before the end of the shift4 ,as blasting must be done outside the contractor's shifts1 it means that one shift per day must be set aside for the purpose4 ,therefore not nearly such progress can be made as where working the face with three shifts4 ,for these reasons1 the hole system is not so advantageous in development as the foot of advance basis4 ,in stoping1 the hole system has not only a wider1 but a sounder application4 ,in large ore-bodies where there are waste inclusions1 it has one superiority over any system of excavation measurement1 namely1 that the miner has no interest in breaking waste into the ore4 ,the plan of contracting stopes by the ton has the disadvantage that either the ore produced by each contractor must be weighed separately1 or truckers must be trusted to count correctly1 and to see that the cars are full4 ,moreover1 trucks must be inspected for waste1--a thing hard to do underground4 ,so great are these detailed difficulties that many mines are sending cars to the surface in cages when they should be equipped for bin-loading and self-dumping skips4 ,the method of contracting by the cubic foot of excavation saves all necessity for determining the weight of the output of each contractor4 ,moreover1 he has no object in mixing waste with the ore1 barring the breaking of the walls4 ,this system therefore requires the least superintendence1 permits the modern type of hoisting1 and therefore leaves little justification for the survival of the tonnage basis4 ,where veins are narrow1 stoping under contract by the square foot or fathom measured parallel to the walls has an advantage4 ,the miner has no object then in breaking wall-rock1 and the thoroughness of the ore-extraction is easily determined by inspection4 ,,bonus ,,systems4--,by giving cash bonuses for special accomplishment1 much the same results can be obtained in some departments as by contracting4 ,a bonus per foot of heading gained above a minimum1 or an excess of trucks trammed beyond a minimum1 or prizes for the largest amount done during the week or month in special works or in different shifts1--all these have a useful application in creating efficiency4 ,a high level of results once established is easily maintained4 ,,labor ,,unions4--,there is another phase of the labor question which must be considered and that is the general relations of employer and employed4 ,in these days of largely corporate proprietorship1 the owners of mines are guided in their relations with labor by engineers occupying executive positions4 ,on them falls the responsibility in such matters1 and the engineer becomes thus a buffer between labor and capital4 ,as corporations have grown1 so likewise have the labor unions4 ,in general1 they are normal and proper antidotes for unlimited capitalistic organization4 ,labor unions usually pass through two phases4 ,first1 the inertia of the unorganized labor is too often stirred only by demagogic means4 ,after organization through these and other agencies1 the lack of balance in the leaders often makes for injustice in demands1 and for violence to obtain them and disregard of agreements entered upon4 ,as time goes on1 men become educated in regard to the rights of their employers1 and to the reflection of these rights in ultimate benefit to labor itself4 ,then the men1 as well as the intelligent employer1 endeavor to safeguard both interests4 ,when this stage arrives1 violence disappears in favor of negotiation on economic principles1 and the unions achieve their greatest real gains4 ,given a union with leaders who can control the members1 and who are disposed to approach differences in a business spirit1 there are few sounder positions for the employer1 for agreements honorably carried out dismiss the constant harassments of possible strikes4 ,such unions exist in dozens of trades in this country1 and they are entitled to greater recognition4 ,the time when the employer could ride roughshod over his labor is disappearing with the doctrine of laissez faire1 on which it was founded4 ,the sooner the fact is recognized1 the better for the employer4 ,the sooner some miners' unions develop from the first into the second stage1 the more speedily will their organizations secure general respect and influence499 ,footnote 993 ,some years of experience with compulsory arbitration in ,australia and ,new ,zealand are convincing that although the law there has many defects1 still it is a step in the right direction1 and the result has been of almost unmixed good to both sides4 ,one of its minor1 yet really great1 benefits has been a considerable extinction of the parasite who lives by creating violence4 ,the crying need of labor unions1 and of some employers as well1 is education on a fundamental of economics too long disregarded by all classes and especially by the academic economist4 ,when the latter abandon the theory that wages are the result of supply and demand1 and recognize that in these days of international flow of labor1 commodities and capital1 the real controlling factor in wages is efficiency1 then such an educational campaign may become possible4 ,then will the employer and employee find a common ground on which each can benefit4 ,there lives no engineer who has not seen insensate dispute as to wages where the real difficulty was inefficiency4 ,no administrator begrudges a division with his men of the increased profit arising from increased efficiency4 ,but every administrator begrudges the wage level demanded by labor unions whose policy is decreased efficiency in the false belief that they are providing for more labor4 ,,chapter ,,xvii4 ,administration 7,continued74 ,,accounts ,,and ,,technical ,,data ,,and ,,reports2 ,,working ,,costs2 ,,division ,,of ,,expenditure2 ,,inherent ,,limitations ,,in ,,accuracy ,,of ,,working ,,costs2 ,,working ,,cost ,,sheets4 ,,general ,,technical ,,data2 ,,labor1 ,,supplies1 ,,power1 ,,surveys1 ,,sampling1 ,,and ,,assaying4 ,first and foremost1 mine accounts are for guidance in the distribution of expenditure and in the collection of revenue2 secondly1 they are to determine the financial progress of the enterprise1 its profit or loss2 and thirdly1 they are to furnish statistical data to assist the management in its interminable battle to reduce expenses and increase revenue1 and to enable the owner to determine the efficiency of his administrators4 ,bookkeeping per se is no part of this discussion4 ,the fundamental purpose of that art is to cover the first two objects1 and1 as such1 does not differ from its application to other commercial concerns4 ,in addition to these accounting matters there is a further type of administrative report of equal importance--that is the periodic statements as to the physical condition of the property1 the results of exploration in the mine1 and the condition of the equipment4 ,,accounts4 ,the special features of mine accounting reports which are a development to meet the needs of this particular business are the determination of working costs1 and the final presentation of these data in a form available for comparative purposes4 ,the subject may be discussed under3-- #a4 ,classes of mine expenditure4 #b4 ,working costs4 #c4 ,the dissection of expenditures departmentally4 #d4 ,inherent limitations in the accuracy of working costs4 #e4 ,working cost sheets4 ,in a wide view1 mine expenditures fall into three classes1 which maybe termed the fixed charges1 proportional charges1 and suspense charges or capital expenditure4 ,fixed charges are those which1 like pumping and superintendence1 depend upon time rather than tonnage and material handled4 ,they are expenditures that would not decrease relatively to output4 ,proportional charges are those which1 like ore-breaking1 stoping1 supporting stopes1 and tramming1 are a direct coefficient of the ore extracted4 ,suspense charges are those which are an indirect factor of the cost of the ore produced1 such as equipment and development4 ,these expenditures are preliminary to output1 and they thus represent a storage of expense to be charged off when the ore is won4 ,this outlay is often called capital expenditure4 ,such a term1 though in common use1 is not strictly correct1 for the capital value vanishes when the ore is extracted1 but in conformity with current usage the term capital expenditure will be adopted4 ,except for the purpose of special inquiry1 such as outlined under the chapter on ,ratio of ,output1 fixed charges are not customarily a special division in accounts4 ,in a general way1 such expenditures1 combined with the proportional charges1 are called revenue expenditure1 as distinguished from the capital1 or suspense1 expenditures4 ,in other words1 revenue expenditures are those involved in the daily turnover of the business and resulting in immediate returns4 ,the inherent difference in character of revenue and capital expenditures is responsible for most of the difficulties in the determination of working costs1 and most of the discussion on the subject4 ,,working ,,costs4--,working costs are a division of expenditure for some unit1--the foot of opening1 ton of ore1 a pound of metal1 cubic yard or fathom of material excavated1 or some other measure4 ,the costs per unit are usually deduced for each month and each year4 ,they are generally determined for each of the different departments of the mine or special works separately4 ,further1 the various sorts of expenditure in these departments are likewise segregated4 ,in metal mining the ton is the universal unit of distribution for administrative purpose1 although the pound of metal is often used to indicate final financial results4 ,the object of determination of working costs is fundamentally for comparative purposes4 ,together with other technical data1 they are the nerves of the administration1 for by comparison of detailed and aggregate results with other mines and internally in the same mine1 over various periods and between different works1 a most valuable check on efficiency is possible4 ,further1 there is one collateral value in all statistical data not to be overlooked1 which is that the knowledge of its existence induces in the subordinate staff both solicitude and emulation4 ,the fact must not be lost sight of1 however1 that the wide variations in physical and economic environment are so likely to vitiate conclusions from comparisons of statistics from two mines or from two detailed works on the same mine1 or even from two different months on the same work1 that the greatest care and discrimination are demanded in their application4 ,moreover1 the inherent difficulties in segregating and dividing the accounts which underlie such data1 render it most desirable to offer some warning regarding the limits to which segregation and division may be carried to advantage4 ,as working costs are primarily for comparisons1 in order that they may have value for this purpose they must include only such items of expenditure as will regularly recur4 ,if this limitation were more generally recognized1 a good deal of dispute and polemics on the subject might be saved4 ,for this reason it is quite impossible that all the expenditure on the mine should be charged into working costs1 particularly some items that arise through capital expenditure4 ,,the ,,dissection ,,of ,,expenditures ,,departmentally4--,the final division in the dissection of the mine expenditure is in the main3-- _/7#a7 ,general ,expenses4 _/ ,ore-breaking4 ,supporting ,stopes4 ,various ,revenue4 7#b7 ,ore ,extraction4 ,trucking ,ore4 expenditures ,hoisting4 for labor1 7#c7 ,pumping4 supplies1 power1 _/ ,shaft-sinking4 repairs1 etc41 ,station-cutting4 worked out per ,crosscutting4 ton or foot _/7#d7 ,development4 ,driving4 advanced ,capital ,rising4 over each or ,winzes4 department4 ,suspense4 ,diamond ,drilling4 _/ 7#e7 ,construction and ,various ,works4 ,equipment4 _/ ,the detailed dissection of expenditures in these various departments with view to determine amount of various sorts of expenditure over the department1 or over some special work in that department1 is full of unsolvable complications4 ,the allocation of the direct expenditure of labor and supplies applied to the above divisions or special departments in them1 is easily accomplished1 but beyond this point two sorts of difficulties immediately arise and offer infinite field for opinion and method4 ,the first of these difficulties arises from supplementary departments on the mine1 such as power1 repairs and maintenance1 sampling and assaying4 ,these departments must be spread over the divisions outlined above1 for such charges are in part or whole a portion of the expense of these divisions4 ,further1 all of these spread departments are applied to surface as well as to underground works1 and must be divided not only over the above departments but also over the surface departments1--not under discussion here4 ,the common method is to distribute power on a basis of an approximation of the amount used in each department2 to distribute repairs and maintenance1 either on a basis of shop returns1 or a distribution over all departments on the basis of the labor employed in those departments1 on the theory that such repairs arise in this proportion2 to distribute sampling and assaying over the actual points to which they relate at the average cost per sample or assay4 ,general expenses1 that is1 superintendence1 etc41 are often not included in the final departments as above1 but are sometimes spread in an attempt to charge a proportion of superintendence to each particular work4 ,as1 however1 such spreading must take place on the basis of the relative expenditure in each department1 the result is of little value1 for such a basis does not truly represent the proportion of general superintendence1 etc41 devoted to each department4 ,if they are distributed over all departments1 capital as well as revenue1 on the basis of total expenditure1 they inflate the capital expenditure departments against a day of reckoning when these charges come to be distributed over working costs4 ,although it may be contended that the capital departments also require supervision1 such a practice is a favorite device for showing apparently low working costs in the revenue departments4 ,the most courageous way is not to distribute general expenses at all1 but to charge them separately and directly to revenue accounts and thus wholly into working costs4 ,the second problem is to reduce the suspense or capital charges to a final cost per ton1 and this is no simple matter4 ,development expenditures bear a relation to the tonnage developed and not to that extracted in any particular period4 ,if it is desired to preserve any value for comparative purposes in the mining costs1 such outlay must be charged out on the basis of the tonnage developed1 and such portion of the ore as is extracted must be written off at this rate2 otherwise one month may see double the amount of development in progress which another records1 and the underground costs would be swelled or diminished thereby in a way to ruin their comparative value from month to month4 ,the ore developed cannot be satisfactorily determined at short intervals1 but it can be known at least annually1 and a price may be deduced as to its cost per ton4 ,in many mines a figure is arrived at by estimating ore-reserves at the end of the year1 and this figure is used during the succeeding year as a redemption of development and as such charged to working costs1 and thus into revenue account in proportion to the tonnage extracted4 ,this matter is further elaborated in some mines1 in that winzes and rises are written off at one rate1 levels and crosscuts at another1 and shafts at one still lower1 on the theory that they lost their usefulness in this progression as the ore is extracted4 ,this course1 however1 is a refinement hardly warranted4 ,plant and equipment constitute another suspense account even harder to charge up logically to tonnage costs1 for it is in many items dependent upon the life of the mine1 which is an unknown factor4 ,most managers debit repairs and maintenance directly to the revenue account and leave the reduction of the construction outlay to an annual depreciation on the final balance sheet1 on the theory that the plant is maintained out of costs to its original value4 ,this subject will be discussed further on4 ,,inherent ,,limitations ,,in ,,accuracy ,,of ,,working ,,costs4--,there are three types of such limitations which arise in the determination of costs and render too detailed dissection of such costs hopeless of accuracy and of little value for comparative purposes4 ,they are1 first1 the difficulty of determining all of even direct expenditure on any particular crosscut1 stope1 haulage1 etc42 second1 the leveling effect of distributing the spread expenditures1 such as power1 repairs1 etc42 and third1 the difficulties arising out of the borderland of various departments4 ,of the first of these limitations the instance may be cited that foremen and timekeepers can indicate very closely the destination of labor expense1 and also that of some of the large items of supply1 such as timber and explosives1 but the distribution of minor supplies1 such as candles1 drills1 picks1 and shovels1 is impossible of accurate knowledge without an expense wholly unwarranted by the information gained4 ,to determine at a particular crosscut the exact amount of steel1 and of tools consumed1 and the cost of sharpening them1 would entail their separate and special delivery to the same place of attack and a final weighing-up to learn the consumption4 ,of the second sort of limitations1 the effect of spread expenditure1 the instance may be given that the repairs and maintenance are done by many men at work on timbers1 tracks1 machinery1 etc4 ,it is hopeless to try and tell how much of their work should be charged specifically to detailed points4 ,in the distribution of power may be taken the instance of air-drills4 ,although the work upon which the drill is employed can be known1 the power required for compression usually comes from a common power-plant1 so that the portion of power debited to the air compressor is an approximation4 ,the assumption of an equal consumption of air by all drills is a further approximation4 ,in practice1 therefore1 many expenses are distributed on the theory that they arise in proportion to the labor employed1 or the machines used in the various departments4 ,the net result is to level down expensive points and level up inexpensive ones4 ,the third sort of limitation of accounting difficulty referred to1 arises in determining into which department are actually to be allocated the charges which lie in the borderland between various primary classes of expenditure4 ,for instance1 in ore won from development1--in some months three times as much development may be in ore as in other months4 ,if the total expense of development work which yields ore be charged to stoping account1 and if cost be worked out on the total tonnage of ore hoisted1 then the stoping cost deduced will be erratic1 and the true figures will be obscured4 ,on the other hand1 if all development is charged to 'capital account' and the stoping cost worked out on all ore hoisted1 it will include a fluctuating amount of ore not actually paid for by the revenue departments or charged into costs4 ,this fluctuation either way vitiates the whole comparative value of the stoping costs4 ,in the following system a compromise is reached by crediting development with an amount representing the ore won from development at the average cost of stoping1 and by charging this amount into stoping4 ,a number of such questions arise where the proper division is simply a matter of opinion4 ,the result of all these limitations is that a point in detail is quickly reached where no further dissection of expenditure is justified1 since it becomes merely an approximation4 ,the writer's own impression is that without an unwarrantable number of accountants1 no manager can tell with any accuracy the cost of any particular stope1 or of any particular development heading4 ,therefore1 aside from some large items1 such detailed statistics1 if given1 are to be taken with great reserve4 ,,working ,,cost ,,sheets4--,there are an infinite number of forms of working cost sheets1 practically every manager having a system of his own4 ,to be of greatest value1 such sheets should show on their face the method by which the spread departments are handled1 and how revenue and suspense departments are segregated4 ,when too much detail is presented1 it is but a waste of accounting and consequent expense4 ,where to draw the line in this regard is1 however1 a matter of great difficulty4 ,no cost sheet is entirely satisfactory4 ,the appended sheet is in use at a number of mines4 ,it is no more perfect than many others4 ,it will be noticed that the effect of this system is to throw the general expenses into the revenue expenditures1 and as little as possible into the suspense account4 ,,general ,,technical ,,data4 ,for the purposes of efficient management1 the information gathered under this head is of equal1 if not superior1 importance to that under working costs4 ,such data fall generally under the following heads3-- ,,labor4--,returns of the shifts worked in the various departments for each day and for the month2 worked out on a monthly basis of footage progress1 tonnage produced or tons handled per man2 also where possible the footage of holes drilled1 worked out per man and per machine4 ,,supplies4--,daily returns of supplies used2 the principal items worked out monthly in quantity per foot of progress1 or per ton of ore produced4 ,,power4--,fuel1 lubricant1 etc41 consumed in steam production1 worked out into units of steam produced1 and this production allocated to the various engines4 ,where electrical power is used1 the consumption of the various motors is set out4 ,,surveys4--,the need of accurate plans requires no discussion4 ,aside from these1 the survey-office furnishes the returns of development footage1 measurements under contracts1 and the like4 ,,sampling ,,and ,,assaying4--,mine sampling and assaying fall under two heads1--the determination of the value of standing ore1 and of products from the mine4 ,the sampling and assaying on a going mine call for the same care and method as in cases of valuation of the mine for purchase1--the details of which have been presented under ,mine ,valuation1--for through it1 guidance must not only be had to the value of the mine and for reports to owners1 but the detailed development and ore extraction depend on an absolute knowledge of where the values lie4 ,,chapter ,,xviii4 ,,administration 7,concluded74 ,,administrative ,,reports4 ,in addition to financial returns showing the monthly receipts1 expenditures1 and working costs1 there must be in proper administration periodic reports from the officers of the mine to the owners or directors as to the physical progress of the enterprise4 ,such reports must embrace details of ore extraction1 metal contents1 treatment recoveries1 construction of equipment1 and the results of underground development4 ,the value of mines is so much affected by the monthly or even daily result of exploration that reports of such work are needed very frequently1--weekly or even daily if critical work is in progress4 ,these reports must show the width1 length1 and value of the ore disclosed4 ,the tangible result of development work is the tonnage and grade of ore opened up4 ,how often this stock-taking should take place is much dependent upon the character of the ore4 ,the result of exploration in irregular ore-bodies often does not1 over short periods1 show anything tangible in definite measurable tonnage1 but at least annually the ore reserve can be estimated4 ,in mines owned by companies1 the question arises almost daily as to how much of and how often the above information should be placed before stockholders 7and therefore the public7 by the directors4 ,in a general way1 any company whose shares are offered on the stock exchange is indirectly inviting the public to become partners in the business1 and these partners are entitled to all the information which affects the value of their property and are entitled to it promptly4 ,moreover1 mining is a business where competition is so obscure and so much a matter of indifference1 that suppression of important facts in documents for public circulation has no justification4 ,on the other hand1 both the technical progress of the industry and its position in public esteem demand the fullest disclosure and greatest care in preparation of reports4 ,most stockholders' ignorance of mining technology and of details of their particular mine demands a great deal of care and discretion in the preparation of these public reports that they may not be misled4 ,development results may mean little or much1 depending upon the location of the work done in relation to the ore-bodies1 etc41 and this should be clearly set forth4 ,the best opportunity of clear1 well-balanced statements lies in the preparation of the annual report and accounts4 ,such reports are of three parts3-- #a4 ,the profit and loss account1 or the revenue account4 #b4 ,the balance sheet2 that is1 the assets and liabilities statement4 #c4 ,the reports of the directors1 manager1 and consulting engineer4 ,the first two items are largely matters of bookkeeping4 ,they or the report should show the working costs per ton for the year4 ,what must be here included in costs is easier of determination than in the detailed monthly cost sheets of the administration2 for at the annual review1 it is not difficult to assess the amount chargeable to development4 ,equipment expenditure1 however1 presents an annual difficulty1 for1 as said1 the distribution of this item is a factor of the life of the mine1 and that is unknown4 ,if such a plant has been paid for out of the earnings1 there is no object in carrying it on the company's books as an asset1 and most well-conducted companies write it off at once4 ,on the other hand1 where the plant is paid for out of capital provided for the purpose1 even to write off depreciation means that a corresponding sum of cash must be held in the company's treasury in order to balance the accounts1--in other words1 depreciation in such an instance becomes a return of capital4 ,the question then is one of policy in the company's finance1 and in neither case is it a matter which can be brought into working costs and leave them any value for comparative purposes4 ,indeed1 the true cost of working the ore from any mine can only be told when the mine is exhausted2 then the dividends can be subtracted from the capital sunk and metal sold1 and the difference divided over the total tonnage produced4 ,the third section of the report affords wide scope for the best efforts of the administration4 ,this portion of the report falls into three divisions3 7a7 the construction and equipment work of the year1 7b7 the ore extraction and treatment1 and 7c7 the results of development work4 ,the first requires a statement of the plant constructed1 its object and accomplishment2 the second a disclosure of tonnage produced1 values1 metallurgical and mechanical efficiency4 ,the third is of the utmost importance to the stockholder1 and is the one most often disregarded and obscured4 ,upon this hinges the value of the property4 ,there is no reason why1 with plans and simplicity of terms1 such reports cannot be presented in a manner from which the novice can judge of the intrinsic position of the property4 ,a statement of the tonnage of ore-reserves and their value1 or of the number of years' supply of the current output1 together with details of ore disclosed in development work1 and the working costs1 give the ground data upon which any stockholder who takes interest in his investment may judge for himself4 ,failure to provide such data will some day be understood by the investing public as a prima facie index of either incapacity or villainy4 ,by the insistence of the many engineers in administration of mines upon the publication of such data1 and by the insistence of other engineers upon such data for their clients before investment1 and by the exposure of the delinquents in the press1 a more practicable protection of investors can be reached than by years of academic discussion4 ,,chapter ,,xix4 ,the ,amount of ,risk in ,mining ,investments4 ,,risk ,,in ,,valuation ,,of ,,mines2 ,,in ,,mines ,,as ,,compared ,,with ,,other ,,commercial ,,enterprises4 ,from the constant reiteration of the risks and difficulties involved in every step of mining enterprise from the valuation of the mine to its administration as a going concern1 the impression may be gained that the whole business is one great gamble2 in other words1 that the point whereat certainties stop and conjecture steps in is so vital as to render the whole highly speculative4 ,far from denying that mining is1 in comparison with better-class government bonds1 a speculative type of investment1 it is desirable to avow and emphasize the fact4 ,but it is none the less well to inquire what degree of hazard enters in and how it compares with that in other forms of industrial enterprise4 ,mining business1 from an investment view1 is of two sorts1--prospecting ventures and developed mines2 that is1 mines where little or no ore is exposed1 and mines where a definite quantity of ore is measurable or can be reasonably anticipated4 ,the great hazards and likewise the ,aladdin caves of mining are mainly confined to the first class4 ,although all mines must pass through the prospecting stage1 the great industry of metal production is based on developed mines1 and it is these which should come into the purview of the non-professional investor4 ,the first class should be reserved invariably for speculators1 and a speculator may be defined as one who hazards all to gain much4 ,it is with mining as an investment1 however1 that this discussion is concerned4 ,,risk ,,in ,,valuation ,,of ,,mines4--,assuming a competent collection of data and efficient management of the property1 the risks in valuing are from step to step3-- #a4 ,the risk of continuity in metal contents beyond sample faces4 #b4 ,the risk of continuity in volume through the blocks estimated4 #c4 ,the risk of successful metallurgical treatment4 #d4 ,the risk of metal prices1 in all but gold4 #e4 ,the risk of properly estimating costs4 #f4 ,the risk of extension of the ore beyond exposures4 #g4 ,the risk of management4 ,as to the continuity of values and volumes through the estimated area1 the experience of hundreds of engineers in hundreds of mines has shown that when the estimates are based on properly secured data for proved ore1 here at least there is absolutely no hazard4 ,metallurgical treatment1 if determined by past experience on the ore itself1 carries no chance2 and where determined by experiment1 the risk is eliminated if the work be sufficiently exhaustive4 ,the risk of metal price is simply a question of how conservative a figure is used in estimating4 ,it can be eliminated if a price low enough be taken4 ,risk of extension in depth or beyond exposures cannot be avoided4 ,it can be reduced in proportion to the distance assumed4 ,obviously1 if no extension is counted1 there is nothing chanced4 ,the risk of proper appreciation of costs is negligible where experience in the district exists4 ,otherwise1 it can be eliminated if a sufficiently large allowance is taken4 ,the risk of failure to secure good management can be eliminated if proved men are chosen4 ,there is1 therefore1 a basic value to every mine4 ,the proved ore taken on known metallurgical grounds1 under known conditions of costs on minimum prices of metals1 has a value as certain as that of money in one's own vault4 ,this is the value previously referred to as the ,a value4 ,if the price 7and interest on it pending recovery7 falls within this amount1 there is no question that the mine is worth the price4 ,what the risk is in mining is simply what amount the price of the investment demands shall be won from extension of the deposit beyond known exposures1 or what higher price of metal must be realized than that calculated in the ,a value4 ,the demands on this ,x1 ,y portion of the mine can be converted into tons of ore1 life of production1 or higher prices1 and these can be weighed with the geological weights and the industrial outlook4 ,,mines ,,compared ,,to ,,other ,,commercial ,,enterprises4--,the profits from a mining venture over and above the bed-rock value ,a1 that is1 the return to be derived from more extensive ore-recovery and a higher price of metal1 may be compared to the value included in other forms of commercial enterprise for good-will4 ,such forms of enterprise are valued on a basis of the amount which will replace the net assets plus 7or minus7 an amount for good-will1 that is1 the earning capacity4 ,this good-will is a speculation of varying risk depending on the character of the enterprise4 ,for natural monopolies1 like some railways and waterworks1 the risk is less and for shoe factories more4 ,even natural monopolies are subject to the risks of antagonistic legislation and industrial storms4 ,but1 eliminating this class of enterprise1 the speculative value of a good-will involves a greater risk than prospective value in mines1 if properly measured2 because the dangers of competition and industrial storms do not enter to such a degree1 nor is the future so dependent upon the human genius of the founder or manager4 ,mining has reached such a stage of development as a science that management proceeds upon comparatively well-known lines4 ,it is subject to known checks through the opportunity of comparisons by which efficiency can be determined in a manner more open for the investor to learn than in any other form of industry4 ,while in mining an estimate of a certain minimum of extension in depth1 as indicated by collateral factors1 may occasionally fall short1 it will1 in nine cases out of ten1 be exceeded4 ,if investment in mines be spread over ten cases1 similarly valued as to minimum of extension1 the risk has been virtually eliminated4 ,the industry1 if reduced to the above basis for financial guidance1 is a more profitable business and is one of less hazards than competitive forms of commercial enterprises4 ,in view of what has been said before1 it may be unnecessary to refer again to the subject1 but the constant reiteration by wiseacres that the weak point in mining investments lies in their short life and possible loss of capital1 warrants a repetition that the ,a1 ,b1 ,c of proper investment in mines is to be assured1 by the ,a value1 of a return of the whole or major portion of the capital4 ,the risk of interest and profit may be deferred to the ,x1 ,y value1 and in such case it is on a plane with good-will4 ,it should be said at once to that class who want large returns on investment without investigation as to merits1 or assurance as to the management of the business1 that there is no field in this world for the employment of their money at over #d4 ,unfortunately for the reputation of the mining industry1 and metal mines especially1 the business is often not conducted or valued on lines which have been outlined in these chapters4 ,there is often the desire to sell stocks beyond their value4 ,there is always the possibility that extension in depth will reveal a glorious ,eldorado4 ,it occasionally does1 and the report echoes round the world for years1 together with tributes to the great judgment of the exploiters4 ,the volume of sound allures undue numbers of the venturesome1 untrained1 and ill-advised public to the business1 together with a mob of camp-followers whose objective is to exploit the ignorant by preying on their gambling instincts4 ,thus a considerable section of metal mining industry is in the hands of these classes1 and a cloud of disrepute hangs ever in the horizon4 ,there has been a great educational campaign in progress during the past few years through the technical training of men for conduct of the industry1 by the example of reputable companies in regularly publishing the essential facts upon which the value of their mines is based1 and through understandable nontechnical discussion in and by some sections of the financial and general press4 ,the real investor is being educated to distinguish between reputable concerns and the counters of gamesters4 ,moreover1 yearly1 men of technical knowledge are taking a stronger and more influential part in mining finance and in the direction of mining and exploration companies4 ,the net result of these forces will be to put mining on a better plane4 ,,chapter ,,xx4 ,the ,character1 ,training1 and ,obligations of the ,mining ,engineering ,profession4 ,in a discussion of some problems of metal mining from the point of view of the direction of mining operations it may not be amiss to discuss the character of the mining engineering profession in its bearings on training and practice1 and its relations to the public4 ,the most dominant characteristic of the mining engineering profession is the vast preponderance of the commercial over the technical in the daily work of the engineer4 ,for years a gradual evolution has been in progress altering the larger demands on this branch of the engineering profession from advisory to executive work4 ,the mining engineer is no longer the technician who concocts reports and blue prints4 ,it is demanded of him that he devise the finance1 construct and manage the works which he advises4 ,the demands of such executive work are largely commercial2 although the commercial experience and executive ability thus become one pier in the foundation of training1 the bridge no less requires two piers1 and the second is based on technical knowledge4 ,far from being deprecated1 these commercial phases cannot be too strongly emphasized4 ,on the other hand1 ,i am far from contending that our vocation is a business rather than a profession4 ,for many years after the dawn of modern engineering1 the members of our profession were men who rose through the ranks of workmen1 and as a result1 we are to this day in the public mind a sort of superior artisan1 for to many the engine-driver is equally an engineer with the designer of the engine1 yet their real relation is but as the hand to the brain4 ,at a later period the recruits entered by apprenticeship to those men who had established their intellectual superiority to their fellow-workers4 ,these men were nearly always employed in an advisory way--subjective to the executive head4 ,during the last few decades1 the advance of science and the complication of industry have demanded a wholly broader basis of scientific and general training for its leaders4 ,executive heads are demanded who have technical training4 ,this has resulted in the establishment of special technical colleges1 and compelled a place for engineering in the great universities4 ,the high intelligence demanded by the vocation itself1 and the revolution in training caused by the strengthening of its foundations in general education1 has finally1 beyond all question1 raised the work of application of science to industry to the dignity of a profession on a par with the law1 medicine1 and science4 ,it demands of its members equally high mental attainments1--and a more rigorous training and experience4 ,despite all this1 industry is conducted for commercial purposes1 and leaves no room for the haughty intellectual superiority assumed by some professions over business callings4 ,there is now demanded of the mining specialist a wide knowledge of certain branches of civil1 mechanical1 electrical1 and chemical engineering1 geology1 economics1 the humanities1 and what not2 and in addition to all this1 engineering sense1 executive ability1 business experience1 and financial insight4 ,engineering sense is that fine blend of honesty1 ingenuity1 and intuition which is a mental endowment apart from knowledge and experience4 ,its possession is the test of the real engineer4 ,it distinguishes engineering as a profession from engineering as a trade4 ,it is this sense that elevates the possessor to the profession which is1 of all others1 the most difficult and the most comprehensive4 ,financial insight can only come by experience in the commercial world4 ,likewise must come the experience in technical work which gives balance to theoretical training4 ,executive ability is that capacity to cordinate and command the best results from other men1--it is a natural endowment4 which can be cultivated only in actual use4 ,the practice of mine engineering being so large a mixture of business1 it follows that the whole of the training of this profession cannot be had in schools and universities4 ,the commercial and executive side of the work cannot be taught2 it must be absorbed by actual participation in the industry4 ,nor is it impossible to rise to great eminence in the profession without university training1 as witness some of our greatest engineers4 ,the university can do much2 it can give a broad basis of knowledge and mental training1 and can inculcate moral feeling1 which entitles men to lead their fellows4 ,it can teach the technical fundamentals of the multifold sciences which the engineer should know and must apply4 ,but after the university must come a schooling in men and things equally thorough and more arduous4 ,in this predominating demand for commercial qualifications over the technical ones1 the mining profession has differentiated to a great degree from its brother engineering branches4 ,that this is true will be most apparent if we examine the course through which engineering projects march1 and the demands of each stage on their road to completion4 ,the life of all engineering projects in a general way may be divided into five phases399-- ,footnote 993 ,these phases do not necessarily proceed step by step4 ,for an expanding works especially1 all of them may be in process at the same time1 but if each item be considered to itself1 this is the usual progress1 or should be when properly engineered4 #a4 ,determination of the value of the project4 #b4 ,determination of the method of attack4 #c4 ,the detailed delineation of method1 means1 and tools4 #d4 ,the execution of the works4 #e4 ,the operation of the completed works4 ,these various stages of the resolution of an engineering project require in each more or less of every quality of intellect1 training1 and character4 ,at the different stages1 certain of these qualities are in predominant demand3 in the first stage1 financial insight2 in the second1 engineering sense2 in the third1 training and experience2 in the fourth and fifth1 executive ability4 ,a certain amount of compass over the project during the whole five stages is required by all branches of the engineering profession1--harbor1 canal1 railway1 waterworks1 bridge1 mechanical1 electrical1 etc42 but in none of them so completely and in such constant combination is this demanded as in mining4 ,the determination of the commercial value of projects is a greater section of the mining engineer's occupation than of the other engineering branches4 ,mines are operated only to earn immediate profits4 ,no question of public utility enters1 so that all mining projects have by this necessity to be from the first weighed from a profit point of view alone4 ,the determination of this question is one which demands such an amount of technical knowledge and experience that those who are not experts cannot enter the field1--therefore the service of the engineer is always demanded in their satisfactory solution4 ,moreover1 unlike most other engineering projects1 mines have a faculty of changing owners several times during their career1 so that every one has to survive a periodic revaluation4 ,from the other branches of engineering1 the electrical engineer is the most often called upon to weigh the probabilities of financial success of the enterprise1 but usually his presence in this capacity is called upon only at the initial stage1 for electrical enterprises seldom change hands4 ,the mechanical and chemical branches are usually called upon for purely technical service on the demand of the operator1 who decides the financial problems for himself1 or upon works forming but units in undertakings where the opinion on the financial advisability is compassed by some other branch of the engineering profession4 ,the other engineering branches1 even less often1 are called in for financial advice1 and in those branches involving works of public utility the profit-and-loss phase scarcely enters at all4 ,given that the project has been determined upon1 and that the enterprise has entered upon the second stage1 that of determination of method of attack1 the immediate commercial result limits the mining engineer's every plan and design to a greater degree than it does the other engineering specialists4 ,the question of capital and profit dogs his every footstep1 for all mines are ephemeral2 the life of any given mine is short4 ,metal mines have indeed the shortest lives of any4 ,while some exceptional ones may produce through one generation1 under the stress of modern methods a much larger proportion extend only over a decade or two4 ,but of more pertinent force is the fact that as the certain life of a metal mine can be positively known in most cases but a short period beyond the actual time required to exhaust the ore in sight1 not even a decade of life to the enterprise is available for the estimates of the mining engineer4 ,mining works are of no value when the mine is exhausted2 the capital invested must be recovered in very short periods1 and therefore all mining works must be of the most temporary character that will answer4 ,the mining engineer cannot erect a works that will last as long as possible2 it is to last as long as the mine only1 and1 in laying it out1 forefront in his mind must be the question1 ,can its cost be redeemed in the period of use of which ,i am certain it will find employment8 ,if not1 will some cheaper device1 which gives less efficiency1 do8 ,the harbor engineer1 the railway engineer1 the mechanical engineer1 build as solidly as they can1 for the demand for the work will exist till after their materials are worn out1 however soundly they construct4 ,our engineer cousins can1 in a greater degree by study and investigation1 marshal in advance the factors with which they have to deal4 ,the mining engineer's works1 on the other hand1 depend at all times on many elements which1 from the nature of things1 must remain unknown4 ,no mine is laid bare to study and resolve in advance4 ,we have to deal with conditions buried in the earth4 ,especially in metal mines we cannot know1 when our works are initiated1 what the size1 mineralization1 or surroundings of the ore-bodies will be4 ,we must plunge into them and learn1--and repent4 ,not only is the useful life of our mining works indeterminate1 but the very character of them is uncertain in advance4 ,all our works must be in a way doubly tentative1 for they are subject to constant alterations as they proceed4 ,not only does this apply to our initial plans1 but to our daily amendment of them as we proceed into the unknown4 ,mining engineering is1 therefore1 never ended with the initial determination of a method4 ,it is called upon daily to replan and reconceive1 coincidentally with the daily progress of the constructions and operation4 ,weary with disappointment in his wisest conception1 many a mining engineer looks jealously upon his happier engineering cousin1 who1 when he designs a bridge1 can know its size1 its strains1 and its cost1 and can wash his hands of it finally when the contractor steps in to its construction4 ,and1 above all1 it is no concern of his whether it will pay4 ,did he start to build a bridge over a water1 the width or depth or bottom of which he could not know in advance1 and require to get its cost back in ten years1 with a profit1 his would be a task of similar harassments4 ,as said before1 it is becoming more general every year to employ the mining engineer as the executive head in the operation of mining engineering projects1 that is1 in the fourth and fifth stages of the enterprise4 ,he is becoming the foreman1 manager1 and president of the company1 or as it may be contended by some1 the executive head is coming to have technical qualifications4 ,either way1 in no branch of enterprise founded on engineering is the operative head of necessity so much a technical director4 ,not only is this caused by the necessity of executive knowledge before valuations can be properly done1 but the incorporation of the executive work with the technical has been brought about by several other forces4 ,we have a type of works which1 by reason of the new conditions and constant revisions which arise from pushing into the unknown coincidentally with operating1 demands an intimate continuous daily employment of engineering sense and design through the whole history of the enterprise4 ,these works are of themselves of a character which requires a constant vigilant eye on financial outcome4 ,the advances in metallurgy1 and the decreased cost of production by larger capacities1 require yearly larger1 more complicated1 and more costly plants4 ,thus1 larger and larger capitals are required1 and enterprise is passing from the hands of the individual to the financially stronger corporation4 ,this altered position as to the works and finance has made keener demands1 both technically and in an administrative way1 for the highly trained man4 ,in the early stages of ,american mining1 with the moderate demand on capital and the simpler forms of engineering involved1 mining was largely a matter of individual enterprise and ownership4 ,these owners were men to whom experience had brought some of the needful technical qualifications4 ,they usually held the reins of business management in their own hands and employed the engineer subjectively1 when they employed him at all4 ,they were also1 as a rule1 distinguished by their contempt for university-trained engineers4 ,the gradually increasing employment of the engineer as combined executive and technical head1 was largely of ,american development4 ,many ,english and ,european mines still maintain the two separate bureaus1 the technical and the financial4 ,such organization is open to much objection from the point of view of the owner's interests1 and still more from that of the engineer4 ,in such an organization the latter is always subordinate to the financial control1--hence the least paid and least respected4 ,when two bureaus exist1 the technical lacks that balance of commercial purpose which it should have4 ,the ambition of the theoretical engineer1 divorced from commercial result1 is complete technical nicety of works and low production costs without the regard for capital outlay which the commercial experience and temporary character of mining constructions demand4 ,on the other hand1 the purely financial bureau usually begrudges the capital outlay which sound engineering may warrant4 ,the result is an administration that is not comparable to the single head with both qualifications and an even balance in both spheres4 ,in ,america1 we still have a relic of this form of administration in the consulting mining engineer1 but barring his functions as a valuer of mines1 he is disappearing in connection with the industry1 in favor of the manager1 or the president of the company1 who has administrative control4 ,the mining engineer's field of employment is therefore not only wider by this general inclusion of administrative work1 but one of more responsibility4 ,while he must conduct all five phases of engineering projects coincidentally1 the other branches of the profession are more or less confined to one phase or another4 ,they can draw sharper limitations of their engagements or specialization and confine themselves to more purely technical work4 ,the civil engineer may construct railway or harbor works2 the mechanical engineer may design and build engines2 the naval architect may build ships2 but given that he designed to do the work in the most effectual manner1 it is no concern of his whether they subsequently earn dividends4 ,he does not have to operate them1 to find the income1 to feed the mill1 or sell the product4 ,the profit and loss does not hound his footsteps after his construction is complete4 ,although it is desirable to emphasize the commercial side of the practice of the mining engineer's profession1 there are other sides of no less moment4 ,there is the right of every red-blooded man to be assured that his work will be a daily satisfaction to himself2 that it is a work which is contributing to the welfare and advance of his country2 and that it will build for him a position of dignity and consequence among his fellows4 ,there are the moral and public obligations upon the profession4 ,there are to-day the demands upon the engineers which are the demands upon their positions as leaders of a great industry4 ,in an industry that lends itself so much to speculation and chicanery1 there is the duty of every engineer to diminish the opportunity of the vulture so far as is possible4 ,where he can enter these lists has been suggested in the previous pages4 ,further than to the investor in mines1 he has a duty to his brothers in the profession4 ,in no profession does competition enter so obscurely1 nor in no other are men of a profession thrown into such terms of intimacy in professional work4 ,from these causes there has arisen a freedom of disclosure of technical results and a comradery of members greater than that in any other profession4 ,no profession is so subject to the capriciousness of fortune1 and he whose position is assured to-day is not assured to-morrow unless it be coupled with a consideration of those members not so fortunate4 ,especially is there an obligation to the younger members that they may have opportunity of training and a right start in the work4 ,the very essence of the profession is that it calls upon its members to direct men4 ,they are the officers in the great industrial army4 ,from the nature of things1 metal mines do not1 like our cities and settlements1 lie in those regions covered deep in rich soils4 ,our mines must be found in the mountains and deserts where rocks are exposed to search4 ,thus they lie away from the centers of comfort and culture1--they are the outposts of civilization4 ,the engineer is an officer on outpost duty1 and in these places he is the camp leader4 ,by his position as a leader in the community he has a chieftainship that carries a responsibility besides mere mine management4 ,his is the responsibility of example in fair dealing and good government in the community4 ,in but few of its greatest works does the personality of its real creator reach the ears of the world2 the real engineer does not advertise himself4 ,but the engineering profession generally rises yearly in dignity and importance as the rest of the world learns more of where the real brains of industrial progress are4 ,the time will come when people will ask1 not who paid for a thing1 but who built it4 ,to the engineer falls the work of creating from the dry bones of scientific fact the living body of industry4 ,it is he whose intellect and direction bring to the world the comforts and necessities of daily need4 ,unlike the doctor1 his is not the constant struggle to save the weak4 ,unlike the soldier1 destruction is not his prime function4 ,unlike the lawyer1 quarrels are not his daily bread4 ,engineering is the profession of creation and of construction1 of stimulation of human effort and accomplishment4 ,,index4 ,accounts4 ,administration4 ,administrative reports4 ,air-compression4 -drills4 ,alteration1 secondary4 ,alternative shafts to inclined deposit4 ,amortization of capital and interest4 ,animals for underground transport4 ,annual demand for base metals4 report4 ,artificial pillars4 ,assay foot4 inch4 of samples4 plans4 ,assaying4 ,a value of mine4 ,averages1 calculation4 ,bailing4 ,balance sheet4 ,basic price4 value of mine4 ,benches4 ,bend in combined shafts4 ,bins4 ,blocked-out ore4 ,blocks4 ,bonanzas1 origin4 ,bonus systems1 of work4 ,breaking ore4 ,broken ,hill1 levels4 ore-pillars4 ,bumping-trough4 ,cable-ways4 ,cages4 ,calculation of averages4 of quantities of ore4 ,capital expenditure4 ,caving systems4 ,churn-drills4 ,chutes1 loading1 in vertical shaft4 ,classification of ore in sight4 ,combined shaft4 stopes4 ,commercial value of projects1 determination4 ,compartments for shaft4 ,compressed-air locomotives4 -air pumps4 vs4 electricity for drills4 ,content1 average metal1 determining4 metal1 differences4 ,contract work4 ,copper1 annual demand4 deposits4 ores1 enrichment4 ,cost of entry into mine4 of equipment4 production4 per foot of sinking4 working4 ,cribs4 ,crosscuts4 ,cross-section of inclined deposit which must be attacked in depth4 showing auxiliary vertical outlet4 ,crouch1 ,j4 ,j4 ,cubic feet per ton of ore4 foot contents of block4 ,deep-level mines4 ,demand for metals4 ,departmental dissection of expenditures4 ,deposits1 in situ4 ore1 classes4 regularity4 size4 structure4 ,depth of exhaustion4 ,determination of average metal contents of ore4 ,development in early prospecting stage4 in neighboring mines4 of mines4 ,diamond-drilling4 ,diluting narrow samples to a stoping width4 ,dip4 ,direct-acting steam-pumps4 ,distribution of values4 ,dividend1 annual1 present value4 ,dommeiler4 ,down holes4 ,drainage4 comparison of different systems4 systems4 ,drifts4 ,drill1 requirements4 ,drilling4 ,drives4 ,dry walling with timber caps4 ,efficiency1 factors of4 of mass4 ,electrical haulage4 pumps4 ,electricity for drills4 ,engine1 size for winding appliances4 ,engineer1 mining1 as executive4 ,engineering projects1 phases of4 ,enrichment4 at cross-veins4 ,entry1 to mine4 to vertical or horizontal deposits4 ,equipment1 cost4 improvements4 mechanical4 ,erosion4 ,error1 percentage in estimates from sampling4 ,escape4 ,examination of mining property4 ,excavation1 supporting4 ,exhaustion1 depth4 ,expenditures1 departmental dissection4 mine4 ,extension in depth4 ,factor of safety in calculating averages of samples4 ,filling4 system combined with square-setting4 with broken ore subsequently withdrawn4 waste4 ,fissure veins4 ,fissuring4 depth4 ,fixed charges4 ,flat-back stope4 ,flexibility in drainage system4 ,floors4 ,folding4 ,foot-drilled system of contract work4 -hole system of contract work4 of advance system of contract work4 value4 ,fraud1 precautions against in sampling4 ,general expenses4 ,gold deposits4 deposits1 alteration4 enrichment4 ,hammer type of drill4 ,hand-drilling4 -trucking4 ,haulage1 electrical4 equipment in shaft4 mechanical4 ,hole system of contract work4 ,horizons of ore-deposits4 ,horizontal deposits1 entry4 stope4 filled with waste4 ,hydraulic pumps4 ,impregnation deposits4 ,inch1 assay4 ,inclined deposits to be worked from outcrop or near it4 deposits which must be attacked in depth4 shaft4 ,inclines4 capacity4 ,infiltration type of deposits4 ,intelligence as factor of skill4 ,interest calculations in mine valuation4 ,intervals1 level4 ,inwood's tables4 ,iron hat4 leaching4 ,ivanhoe mine1 ,west ,australia4 ,kibble4 ,labor1 general technical data4 handling4 unions4 ,lateral underground transport4 ,le ,roi mine4 ,lead1 annual demand4 deposits4 enriching4 prices1 #ahhd-aijh4 -zinc ores1 enrichment4 ,lenses4 ,levels4 intervals4 of ,broken ,hill4 protection4 ,life1 in sight4 of mine4 ,locomotives1 compressed-air4 ,lode mines1 valuation4 ,lodes4 ,long-wall stope4 ,machine-drill1 performance4 drilling4 vs4 hand-drilling4 ,management1 mine4 ,matte4 ,mechanical efficiency of drainage machinery4 equipment4 ,men for underground transport4 ,metal content1 determining4 contents1 differences4 demand for4 mine1 value4 price4 ,mines compared to other commercial enterprises4 equipment4 expenditures4 ,mines--continued4 life of4 metal1 value of4 of moderate depths4 to be worked to great depths4 valuation4 ,mining engineering profession4 ,mt4 ,cenis tunnel4 ,morgan gold mine4 ,normal price4 ,obligations of engineering profession4 ,openings1 position in relation to secondary alteration4 ,ore1 average width in block4 blocked-out4 -bodies4 shapes4 -breaking1 methods4 calculation of quantities of4 -chutes in shrinkage-stoping4 -deposits1 classes4 determination of average metal contents4 developed4 developing4 expectant4 in sight4 sight1 classification4 -pillars4 support in narrow stopes4 -shoots4 weight of a cubic foot4 width for one sample4 ,origin of deposit4 ,outcrop mines4 ,output1 factors limiting4 giving least production cost4 maximum1 determination4 ,overhand stapes4 ,overproduction of base metal4 ,oxidation4 ,patchwork plant1 mechanical inefficiency of4 ,pay areas1 formation4 ,pillars1 artificial4 ,positive ore4 value of metal mine4 ,possible ore4 ,power conditions4 general technical data4 sources4 transmission4 ,preliminary inspection4 ,previous yield4 ,price of metals4 ,probable ore4 ,producing stage of mine4 ,production1 cost4 ,profit and loss account4 factors determining4 in sight4 ,proportional charges4 ,prospecting stage of mine4 ,prospective ore4 value4 ,protection of levels4 ,proved ore4 ,pumping systems4 ,pumps1 compressed-air4 electrical4 hydraulic4 rod-driven4 ,ratio of output to mine4 ,recoverable percentage of gross assay value4 ,recovery of ore4 ,rectangular shaft4 ,redemption of capital and interest4 ,reduction of output4 ,regularity of deposit4 ,reliability of drainage system4 ,replacement4 ,reports4 administrative4 ,resuing4 ,revenue account4 ,rill-cut overhand stope4 method of incline cuts4 -stopes4 filled with waste4 -stoping4 ,rises4 ,risk in mining investments4 in valuation of mines4 ,roadways1 protecting in shrinkage-stoping4 ,rod-driven pumps4 ,rotary steam-pumps4 ,round vertical shafts4 ,runs of value4 test-treatment4 ,safety1 factor of1 in calculating averages of samples4 ,sample1 assay of4 average value4 narrow1 diluting to a stoping width4 sections4 taking1 physical details4 manner of taking4 ,sampling4 accuracy4 percentage of error in estimates from4 precautions against fraud4 ,saving of fixed charges4 ,secondary alteration4 enrichment4 ,security of investment4 ,self-dumping skip4 ,sets4 ,shafts4 arrangement for very deep inclined shafts4 compartments4 different depths4 haulage4 location4 number4 output capacity4 shape4 size4 ,shrinkage-stope4 -stoping4 advantages4 disadvantages4 when applicable4 ,silver deposits4 deposits1 enrichment4 prices4 ,sinking1 speed4 ,size of deposit4 ,skill1 effect on production cost4 ,skips4 balanced4 haulage in vertical shaft4 ,sollars4 ,solubility of minerals4 ,specific volume of ores4 ,speculative values of metal mine4 value of mine4 ,spelter1 annual demand4 ,square-set4 -set timbering4 ,stations4 arrangement for skip haulage in vertical shaft4 ,steam-pumps1 direct4 ,steepening winzes and ore passes4 ,stope filled with broken ore4 minimum width4 ,stoping4 contract systems4 ,storing metal4 ,structural character of deposit4 ,structure of deposit4 ,stull and waste pillars4 support with waste renforcement4 -supported stope4 ,stulls4 wood4 ,subheading4 ,sublevel caving system4 ,subsidiary development4 ,superficial enrichment4 ,supplies1 general technical data4 ,support by pillars of ore4 ,supporting excavation4 ,surveys4 ,suspense charges4 ,test parcels4 sections4 -treatment runs4 ,timber1 cost4 ,timbered shaft design4 ,timbering4 ,tin1 annual demand4 deposits4 ore1 migration and enrichment4 ,tools4 ,top slicing4 ,tracks4 ,transport in stopes4 ,tunnel entry4 feet paid for in #aj years4 size4 ,underhand stopes4 ,uppers4 ,valuation1 mine4 of lode mines4 mines1 risk in4 mines with little or no ore in sight4 on second-hand data4 ,value1 average1 of samples4 discrepancy between estimated and actual4 distribution4 of extension in depth1 estimating4 positive1 of metal mine4 present1 of an annual dividend4 of #a or #a1 payable in -- years4 runs of4 speculative1 of metal mine4 ,valuing ore in course of breaking4 ,ventilation4 ,vertical deposits1 entry4 interval between levels4 shafts4 capacity4 ,volume1 specific1 of ores4 ,waste-filled stope4 ,water-power4 ,weight per cubic foot of ore4 ,weindel1 ,caspar4 ,whiting hoist4 ,width of ore for one sample4 ,winding appliances4 ,winzes4 in shrinkage-stoping4 to be used for filling4 ,working cost4 inherent limitations in accuracy of4 sheets4 ,workshops4 ,yield1 previous4 ,years of life required to yield -- interest4 ,zinc deposits4 leaching4