Co c 5 F .3 Sei5 BANCROFT LIBRARY THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA S^^ — =^ 95 THE ADVANTAGES AND NECESSITY OF A DEEP DRAIN TUNNEL i'UK llll*, aHE^T COMSTOCK LEDGE, BY A. SUTRO. .^AiN l^UA.NCibUU, i^ElJKUAKY, 1^05. ^^ ^ ^ i THE ADVANTAGES AND NECESSITY OF A DEEP DRim TUNNEL, FOR THE GRE^T COMSTOCK LEDGE, BY Ar. SUTKO. // SAN FKANCISCO, FEBRUARY, 1865. F ^ 4-t> CONTENTS. Proposition to Mining Companies Introductory Remarks The Great Obstacle in Mining — and its Remedy Necessity of a Grand Drain Tunnel The Tunnell at Gittelde, Brunswick Cost of Pumping in England Cost of Pumping in Nevada Evils of Pumping Advantages of a Drain Tunnel . The Value of the Mines will be Largely Increased Great Depth which Can be Attained Hereafter Report of Baron Richthofen Opinion of Mining Superintendents and Others BANCROFT LIBRARY TO MINING COMPANIES. Tlie undersinrned convinced of the necessity of constructing a deep drain Tunnel to the Comstock ledge, and desirous of seeing this great work speedily carried out, begs leave to lay the fol- lowing proposition before the different Companies of the Com- stock ledge, and is of the opinion that its acceptance will insure the carrying out of this important enterprise. The proposition would be about as follows : i.v,.uo trcfc ihutiexs ui juct, anu no wonaer mat lau «iiierprising American people, particularly the adventurous portion of Cali- fornians, became excited over visions of great wealth and pic- tures of the immense amounts of precious metals produced hy the Spanish-American mines for the last three centuries. The natural consequence was, a great influx of people to these newly discovered regions, and a vigorous prosecution of work, which shortly established the fact that the great Comstock ledge not only contains ores of great value, but that the same ex- tends for miles in length, and r>rnmigfirL truJL.^--..^t^- ^ The Companies will by these means secure to the Tunnel Company a small interest on the capital Invested. They have to pay out nothing until they derive benefit from the drainage of their mines, and then pay nothing, should they have no ore. Should they have ore, the amount to be paid to the Tunnel Company is so small compared to the advantages they will derive, that they will save the amount to be paid per ton, alone in the advantages they would enjoy in extracting the ore from the mines. If the following pages are studied carefully, it will be found that the cost of erecting the necessary pumping machinery, and the cost of maintaining the steam engines, is so immense, that the advantages offered by the tunnel company, must strike the mining companies to be of vital importance to their own interests. The Tunnel Company will have to take all the risk as to the future yield of these mines. They have to embark in an under- taking which involves the outlay of millions for a number of years, before any benefit can be derived from it, and after they complete the work, they only ask a low interest on the capital invested, from those parties who can afford to pay, by being enabled, through their agency, to extract ores from their veins. It may as well be stated here, that some parties are fearful of getting into litigation, by having an outside company construct this tunnel, and striking the Comstock at this great depth ; on this point we would state, that the objects of this Tunnel Com- Danv beins for the purpose of draining: these mines, they would The Tunnell at Gittelde, Brunswick Cost of Pumping in England Cost of Pumping in Nevada Evils of Pumping Advantages of a Drain Tunnel The Value of the Mines will be Largely Increased Great Depth which Can be Attained Hereafter "^j ' "J '^ir-;Ramn Richthofen people at large of the Pacific states, oy st^cuiiu^ mo pciuiaucut working of the Comstock ledge, which in our opinion would be accomplished by constructing a deep drain tunnel, we most cheerfully endorse Mr. Sutro's proposition to the Companies, and shall do all in our power to assist him in carrying out his project. San Francisco ^ March 1, 1865. JOHN PARROTT, LOUIS McLANE, W. C. RALSTON. THE COMSTOCK imES. INTRODUCTORY REMARKS. Over five years have now elapsed since the news of rich silver mines, having been discovered on the eastern slope of the Sierra Nevada mountains, first attracted the attention of the people of California. At first, {he reports of fabulous wealth contained in these mines, were received with some doubt and incredulity, but soon it became patent to the miijds of thinking men, ihat these re- ports were matters of fact, and no wonder that the enterprising American people, particularly the adventurous portion of Cali- fornians, became excited over visions of great wealth and pic- tures of the immense amounts of precious metals produced by the Spanish-American mines for the last three centuries. The natural consequence was, a great influx of people to these newly discovered regions, and a vigorous prosecution of work, which shortly established the fact that the great Comstock ledge not only contains ores of great value, but that the same ex- tends for miles in length, and promised to be of a permanent character. This conclusion has proven correct by experience, and we now have a range of mines which, in all likelihood, will be worked long after our present generation has passed away. But raining for silver was a new thing for our people. "We had no experience at it ; hardly had any idea about the opening and working of such mines, and not the slightest knowledge about the reduction of silver ores. A few persons amongst us^ who had acquired experience at foreign silver mines, readily 6 gave their advice, and work fairly comraeuced. But soon it was found that the methods employed in older countries for reducing ores, would not apply here, for various reasons, such as the cli- mate, expense of labor, fuel, etc., etc. ; and it became a matter of serious doubt, whether these mines could be profitably worked on account of these obstacles. To ship the ores to other countries, could only apply to rich ores, the supply of which w^as limited. To smelt the same was out of question, on account of scarcity of fuel. To roast, by the Freyberg method, was expensive, and the bulk of the ores could not stand the expense. To work them by patio was difficult on account of cold weather the largest portion of the year. These were the only methods known in the world — none of them applicable to our mines. What was to be done ? The inventive genius of the American people soon found a remedy ; a trial was made to work these ores in iron pans, and it was a success. We must admit that considerable loss is occa- sioned in this style of working, but without it our mines could not be worked to any advantage, and it is now generally admit- ted, that this is the only and most profitable method to be em- ployed for average ores, which abound in these mines. From the day of introducing these pans, which, it may be stated, have since been vastly improved, the country commenced to flourish. Cities were built, roads constructed, large reduction works erected, in short, from a state of wilderness, in a few years, a flourishing country sprang up, many millions of bullion are produced an- nually, and many thousands of people find employment. But not only here do we see the eflccts of this new wealth. California, and particularly San Francisco, are directly benefited by it. Every branch of commerce derives benefit from our mines, we being entirely dependent on our sister State for supplies. But will this prosperous state continue ? And how long ? No one doubts the permanency of these mines. One particular claim may run out of its chimney of good ore ; one may have very rich ore at present, next year its neighbor will have it. Thig is the nature of silver mines ; they contain bunches, or chimneys of ore, sometimes producing many millions, but these chimneys are distributed throughout the length of the whole range, horizontally and perpendicularly. For this reason, any particular locality on a mining range like the Comstock, may prove of great value ; but the expense of exploration, and the difficulties to be encountered in prospecting, make many shrink from the undertaking, and give up all hopes of realizing their wishes. As long as mining was carried on comparatively near the sur- face, everything went on well enough ; a small engine of 10, 20, or thirty horse power was erected, at a trifling cost, a shaft sunk. a few galleries opened, plenty of ore extracted, sent to the mills, and silver bars produced, as if by magic. But we are a go ahead people. What takes ten years to accomplish in Mexico or South America, we do in one year ; and, as a natural consequence, after five years' labor, we have attained an average depth in our mines of four hundred feet. And what questions do present themselves to the thinking mind, now ? How long will it take to attain a depth of one thousand, fifteen hundred or two thousand feet ? What obstacles are encountered, at present, and what will be the obstacles to be met at this greater depth ? These are serious questions to he con- sidered by the owners of the Comstock ledge, and the people at large of this State, who are entirely dependent on the prosperity of these mines. And these questions, more particularly we intend to answer, with a view of providing means to avoid a calamity which would befall us in a very short number of years, if we do not at once take the matter in hand, and provide timely measures, the nature of which we intend iu this paper further to explain : THE GREAT OBSTACLE IN MINING— AND ITS REMEDY. The great obtade to he enconntered in mines, is vxUer ; this is the fatal agent J which makes it only a question of time, when a mine will have to be abandoned, no matter how rich, on account of the obtacles its removal presents. In every instance, the time must com£ when the cost of drainage will be greater than the produce of the mine ; this may take five, ten, twenty or fifty years, according to the value of the ores and the quantity of the water to be encountered. Now let us examine into our particular instance ; as stated above, the average depth of our mines is about 400 feet ; hardly any water of consequence has been encountered heretofore ; but within the last twelve months, it has become a serious obstacle. The Ophir mine, at present, is flooded in such a manner that their small engine and pump cannot free the mine from water. A new and more powerful engine and pumps are being erected, which, no doubt, will accomplish this desirable result. But how long will this machinery answer the purpose ? Competent engi- neers will tell you, that the power of your machinery will have to be increased by the square, as the depth and quantity of water increases, and that in the course of not many years, at the rate we are progressing, our mines will be worked at a depth where the cost of pumping will nearly, or entirely, consume the net profits derived from them, basing our calculations on the yield et the present time. These are serious reflections and forbode a gloomy future for our young State ; but we will show conclusively, that a work, entirely feasi- ble, practicable, and though of gigantic proportions, can be con- structed without any difficulty, provided all parties inter- ested will cooperate, which will not only remove all anxiety for our future welfare, but which will place our mines into such a position that they may be worked profit-ably, economically and exten- sively for a centvry to come. NECESSITY OF A GRAND DRAIN TUNNEL. This work is the construction of a Grand Drain Tunnel, com- mencing at a point in the foot hills of Carson River Yalley. a little less than four miles or about 20,000 feet from the Corastock ledge, and which Tunnel would strike the Comstock ledge at a depth of 1800 feet below the surface. Works of this kind have by experience been found to be a matter of necessity, and have been carried out wherever nature favored such an undertaking. Now let us see what has been done in other parts of the world in order to obtain drainage in mines. A late writer, speaking of the completion of the great dr-iin tunnel in the Harz mountains in Germany, says : " Already in the beginning of the sixteenth century, the me- chanical appliances for raising water were found to be insufficient, and it was found to be a matter of necessity to construct drain tunnels. The first one, called the Seventy-eight feet Tunnel, was completed in 1525, the Frankensharner Tunnel in 1548, the One Hundred and Fourteen feet Tunnel in 1551 and the Raven Tunnel in 1573. By means of these Tunnels, which were connected with all parts of the mines, it was found possible to work them for about 200 years ; but towards the end of last century it became impossible to master the water, and in consequence it was con- cluded, in the year 1771, to run a still deeper tunnel ; work was commenced in 1777 and the same was completed in 1799. It was called the Deep George Tunnel, and its length, including cross cuts, is 57,000 feet ; it drains the mines under Clausthal to a depth of 900 feet. This relieved the mines from water for a while, but as work progressed and greater depth was attained, the flow of water increased so rapidly that the grandest pump works were found to be insufficient. The topographical features of the country are fcuch that no 2 10 deeper drainage could be obtained, except at an apparently im- practicable distance, and in consequence the danger was imminent, that these mines, which had supported thou-ands of persons for centuries, would shortly have to be abandoned entirely. THE TUNNEL AT GITTELDE, BRUNSWICK. In the year 1850, C. Borchers, a celebrated mining engineer^ first conceived the plan to commence a Tunnel in the Dukedom of Brunswick, at a place called Gittelde, which would give a deeper drainage, of about 300 feet, below the deep George Tunnel, or a depth under the cliurch of Clausthal, of about 1200 feet. Surveys were made and the distance found to be 72,000 feet or about fourteen miles, and the time estimated to complete it, was twenty-two years. On the 2l8t July, 1851 work on this great tunnel called the " Ernst August Tunnel" was com- menced, and on the 22d of June 1864, the last connection was made ; It therefore only took twelve years and eleven months to complete this, the greatest of all mining works." It may as well be stated here, that the mines of the Harz pro- duce about $500,000 in precious metals per annum, an amount taken from the Comstock every fortnight. Now, if they found it a matter of nercessity. and economy to run a tunnel fourteen miles long in the Harz mountains, in order to obtain an addi. tional drainage of 800 feet, in a country where fuel is cheap, how evident must it appear, that a tunnel into the Comstock, less than four miles in length, which will give drainage to a depth of 1800 feet, and which would secure the future working of the richest mine in the world, would not only prove of great benefit, but ought to be commenced and completed without delay. At the place selected for a starting |K)int, the hills form a semi- circle, which brings the distance from the valley within four miles of the Comstock. The formation of the hills on the selected tunnel route, is such that deep ravines exist, from which shafts can be sunk at a comparatively small depth. The formation of 11 rock has been examined by Baron Richthofen, a well known Prussian geologist, who was formerly engaged at the geological survey of Austria, and lately attached as geologist to a Prussian naval expedition to eastern Asia, and who is a European authority in geological matters. This report is annexed, and will be an interestitg document in mining circles. It is proposed to sink four shafts on the tunnel route, which will be about 500, 800, 1,100 and 1,£00 feet deep to the level of the tunnel, on which powerful steam engines and pumps will have to be erected, and from each, two drifts will be run — one towards the mouth of the tunnel, the other towards the Comstock ledge. This would give nine points to work from, and calculating the distance, including shafts, at about 24,000 feet, the distance to be sunk and run, would give an average of 2,666 feet from each point. Work of this kind can be pushed on with great rapidity, pro- vided, short and double shifts of men are employed ; the tunnel will be wide enough to allow three men to work abreast, and it is proposed to employ double that number, so that the moment the men at work with their picks get tired, the other three step in their places, and in this manner change off every fifteen or twenty minutes ; the whole shift to be changed every six or eight hours. A foreman would be employed with each gang, whose duty it would be to see that work is carried on without any interruption, and to discharge all hands who do not perform their task properly. In this manner work can be pushed with consid erable speed, and it is the opinion of competent mining engi neers, that at least an average of three feet per day can be made It would therefore require 888 .days to do the whole work Allowing en extra year to sink partly the deepest of the pro posed shafts, the tunnel can be finished in 3. J years. The shafts will be located in such a manner that the deeper ones will come nearer together, in order to accomplish a connection at as nearly the same time as possible ; with that view, a working survey is being made now, which will require about one month to com- plete. The proposed size of the tunnel will be about 12 feet wide, by 10 in hight, so as to allow of a good sized rail road track,— one to run cars in. the other to run them out. Wherever hard rock is encountered, drilling machinery will be employed, which is at the present time used quite successfully in Europe, and particularly at Mount Ceni?, in the Alps. This drilling machinery is propelled by condensed air, which being discharged at every revolution, replenishes the air in the tunnel. The above facts will at once explain the feasibility of the en- terprise, and in order to more fully understand the difficulties to be encountered in pumping and the advantages to be derived from a drain tunnel, we will more carefully examine into the merits of each. COST OF PUMPING IN ENGLAND. In order that we may get a correct idea of the cost of pumping from a great depth, and the machinery required to do so, we will take the statistics of a celebrated mine in Europe, the "Consoli- dated United Copper Mines," of Cornwall : They employ nine steam engines ; three of 90 inch cylinder ; three of 85 ; one of 80 ; and two of 65 ; and a water wheel 48 feet in diamater, all employed in pumping ; the water discharged per minute is from 2,000 to 3,000 gallons. The water is raised at an average of 170 fathoms. The average cost for drainage in ten^ears, has been, per year, £12,700 sterling. The stream of water, which would be encountered at a depth of 1,800 feet, draining the Comstock ledge from the Siena Ne- vada Mine to the Uncle Sam, has been variously estimated at 8, 4, 5, and as high as 10 square feet, and the rapidity with which it would flow out of the tunnel, at from 5 to 6 miles per hour. Now let us take the lowest figures 3 square feet, and the stream to flow 6 miles per hour ; that is to say, the stream would 13 fill a trough or canal 2 feet wide, and li feet high, and the water would flow 5 miles per hour. We would then get the following figures : 5 miles contain 26,300 feet ; each foot in length would give 3 cubic feet or 78,900 cubic feet of water per hour. This amount reduced to minutes gives 1,315 cubic feet of water per minute, or 8,195 imperial gallons. The cost of draining the "C. U. Copper Mines," of Cornwall, per annum, is $63,500, at a depth of 1,020 feet; at 1,450 feet, (allowing for tunnels in existence now,) the cost would be at least one-half more, or $95,250. Now the quantity of water to be raised here, according to the above estimate, is 3.28 times as much, which would give an annual cost of performing this work in England, of $312,420. The difference in cost of fuel, labor, etc., between the state of Nevada and Cornwall, has variously been estimated to be from ten to fifteen times as much here, but taking the lower figures, we would get an annual cost of draining these mines here, of $3,124,200. The number of engines required at theabove][mines named in Cornwall is nine, of an average diameter of cylinder of 82 inches ; we would require 3.28 times as many on account of the greater quantity of water and again one half as many more on account the greater depth ; we would therefore require 4.92 times as many engines, or say 44 of 82 inch cylinder. The cost of engines of this size, including setting up, pumps, pipes, etc., has been estimated to be from $100,000 to $150,000 each. Let us base our calculations on the first named estimate : Forty -four engines at $100,000 would give a total cost of $4,400,000. The additional interest, current here above that in England, would be say 1 J per cent, per month, or on the whole outlay for machinery $66,000 per month. We have now the following amounts : Cost of pumping per month, $260,350 Interest on capital invested, 66,000 Or a monthly expense of $326,350 for drainage by pumping. 14 Estimating the number of tons produced by these mines to be 1000 tons per day, or 30,000 tons per month, the cost of drainage per ton of ore raised, would be $10.88. COST OF PUMPING IN NEVADA. In making the above estimate, we have taken estimates of an English mine as our basis. Now let us figure the cost of pumping, taking the quantity of water as above stated and make our calculations from the statements made by pumping works and mills in Nevada. Most estimates are made that the cost of running a steam engine for twenty-four hours is from $2,00 to $2,50 per horse power. Some are made as low as $1,50. We will again take the lower figures. The ordinary way of calculating, is to count 33,000 pounds, to be lifted one foot high per minute, as one horse power. We have 8195 gallons, or 1315 cubic feet, at 62.32 pounds per cubic foot, we get 81,950 lbs to be lifted per minute ; divided by 33,000, this would give 27.80 horse powers, to lift the given quantity one foot high ; in order to lift it 1450 feet, we have to multiply by that number, which would give 4039 horse powers. Now it takes just double the given power, to overcome the friction of water in pipes, the friction of engine, etc., etc., which would give 8078 horse powers, to raise the given quantity of water 1450 feet. Calculating the cost of running the pump- ing machinery, as stated above at $1,50 per day per horse power, we would have an expense of $12,117 per day, or $363,510 per month, or on every ton of ore raised an expense of $12,12. Some statistics have been furnished by Capt. Taylor of the Best