Chapter 6

Mr. Molloy's effort appears to have been, in the first place, directed to a system which could be adapted to any existing apparatus, and in certain cases where water was scarce, to avoid altogether the use of that, in some districts, rare commodity. For the purpose of explanation we select an ordinary amalgamating table fitted with mercury riffles. The surface of the table is in no way interfered with or disturbed. The bed of the riffle, however, is constructed of some porous material, such as leather, non-resinous wood, or cement, which serves as the diaphragm upon which the mercury rests, and separates the fluid metal from the electrolyte beneath. Running the full length of the table is a thin layer of sand, supported and pressing against the diaphragm, and lying in this sand is the anode, formed preferably of lead. A peroxide of that metal is formed by the action of the currents, and may be readily reduced for use over and over again after working for from one to three months. The peroxide of lead, as is well known, is a conductor of electricity, and this fact constitutes an important advantage in the working of the process. The thin layer of sand is saturated with an electrolyte, such as dilute sulphuric acid (H_{2}SO_{4} + 20H_{2}O) to give a simple hydrogen amalgam; (Na_{2}SO_{4} + xH_{2}O) to give a hydrogen sodium amalgam; or (K_{2}SO_{4} + xH_{2}O) to give a hydrogen potassium amalgam. Numerous other electrolytes constituted by acids, alkalies, and salts can be used to form an amalgam permanently maintained in a condition of "quickness" and freed from all liability to "sicken," whatever the components of the ore may be. The mercury is connected with the negative pole of the voltaic battery or other electro-motor, and the lead made with the positive pole of the same source. When the current passes there is formed according to the nature of the electrolyte, a hydrogen amalgam, or an amalgam of hydrogen with a metal electro-positive to hydrogen. The electrolyte, which, it will be understood, is distinct and apart from the body of water passing over the table, will last almost indefinitely, there being no consumption of any of its constituents, excepting hydrogen and oxygen from the water of solution. The quantity of acid or saline material contained in the electrolyte is so very small that there can be no difficulty in finding a supply in any district. The question of the supply of electricity is one which in many mining districts involves considerations of practical importance, since a large supply would necessitate water or steam power. It has been found that two cells having an electromotive force of about two volts each will in this process suffice; if preferred, however, a very small dynamo machine can be used. In connection with the electro-motive force it is requisite to use, it may be observed that an amalgam of sodium containing only a small quantity of this metal would, when constituting a positive element in conjunction with a lead negative and on an aqueous electrolyte, give an opposing electro-motive force of less than three volts. Such an amalgam could therefore be obtained under an electro-motive force of about four volts. The electrical resistance in the circuit constituted by the apparatus being very small, no electrical power is wasted. When water constitutes the electrolyte, as in Barker's system, then the electro-motive force required to obtain a given current would be very much greater than that above specified. The conditions assured under this process appear to be all that can be required, while the amalgams obtained are those most calculated to preserve the "quickness" and prevent the "sickening" of the mercury.

Mr. Molloy has designed a special form of amalgamating machine to be used in conjunction with the above process, and with or without the aid of water. By the employment of this machine, each particle of the ore is slowly rolled in the quickened mercury for from fifteen to thirty or more seconds.

When the extent of the gold and silver mining industries is considered, and when it is borne in mind that a considerable percentage of the precious metal present in the ore is, in the ordinary process of extraction, lost through defective amalgamation--due to insufficient contact with the mercury or to a total absence of contact, as in the case of float gold--it is obvious that the introduction of any system obviating such loss is a matter of very great importance to those who are interested in the above mentioned industries. We expect shortly to hear of the practical introduction on a large scale of Mr. Molloy's process, and we look forward with interest to the results which may be obtained from it.--_The Engineer_.

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TREATMENT OF ORES BY ELECTROLYSIS.

By M. KILIANI.

The author lays down general principles for electrolytic metallurgy. Ores must be distinguished as good and bad conductors; the former may serve directly as anodes, and are easily oxidized by the electro-negative radicals formed at their contact, and dissolve readily in the electrolyte. The bad conductors have to be placed in contact with a conducting anode, formed of an inoxidizable substance, such as platinum, manganese peroxide, or coke. In laboratory experiments a good conducting ore is electrolyzed by suspension from a platinum wire in connection with the source of electricity, and is then immersed in the bath. On an industrial scale the ore, coarsely broken up, is placed in one of the compartments of a trough divided by a diaphragm.

On the fragments of the ore which extend up outside of the electrolytic bath is laid a plate of copper connected with the positive wire. Care must be taken that this plate does not plunge into the bath, otherwise the current would not traverse the ore at all. The cathode is preferably formed of the same metal which is to be obtained. The bath should not contain organic acids. In practice the common mineral acids are employed, or their salts, selecting by preference a salt of the metal which is to be isolated. It is convenient to pass the current through the greatest possible number of small decomposition troughs, taking care that the resistance in each is not too great. With a current of one and the same intensity we obtain in n troughs n times as much metal as in a single one. To keep down the resistance of the circuit we employ poles of a large surface, i.e., plenty of ore and baths which are as good conductors as possible.

The state in which the metal is deposited at the negative pole depends on the secondary actions undergone by the electrolyte, and especially of the escape of gas. This is a function of the _density_, of the current, i.e., the proportion of its intensity to the surface of the cathode. If the density is too great there is an escape of hydrogen, and the metal is deposited in a spongy condition. If the density of the current falls below a certain minimum, an oxide is deposited in place of metal. The electrolytic treatment of ores often renders it possible to separate the different metals which may be present. These are deposited in succession, and are sharply separated if the electromotive power is not too great.

1. _Zinc_.--The zinciferous compounds--calamine, blende, and zinc ash--are all poor conductors. They are first dissolved, and the salts obtained are electrolyzed, employing anodes of coke. Blende should be roasted before it is dissolved. The electrolytic bath should be as concentrated as possible to avoid sponginess of the metal and an escape of hydrogen. In a saturated solution the formation of hydrogen decreases as the density of the current augments.

2. _Lead_.--Galena is a good conductor, and may be directly electrolyzed. The best bath is a solution of lead nitrate. The arborescent crystallizations extend rapidly, and must be broken from time to time to prevent the formation of a metallic connection between the anode and the cathode. The sulphur of the galena falls to the bottom of the bath, and may be separated from the gangue by solution in carbon disulphide.

3. _Copper_.--Native copper sulphide, though a good conductor, cannot be directly electrolyzed en account of the presence of iron sulphide, whence iron would be deposited along with the copper. The copper pyrites are roasted, dissolved in dilute sulphuric acid, and the liquid thus obtained is submitted to electrolysis.

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A PEOPLE WITHOUT CONSUMPTION, AND SOME ACCOUNT OF THEIR COUNTRY--THE CUMBERLAND TABLELAND.

By E. M. WIGHT, M.D., Chattanooga, Tenn., Late Professor of Diseases of the Chest and State Medicine, Medical Department University of Tennessee; Late Member of the Tennessee State Board of Health, and ex-President of the Tennessee State Medical Society.

During the ten years that I have practiced medicine in the neighborhood of the Cumberland Tablelands, I have often heard it said that the people on the mountains never had consumption. Occasionally a traveling newspaper correspondent from the North found his way down through the Cumberlands, and wrote back filled with admiration for their grandeur, their climate, their healthfulness, and almost invariably stated that consumption was never known upon these mountains, excepting brought there by some person foreign to the soil, who, if he came soon enough, usually recovered. Similar information came to me in such a variety of ways and number of instances, that I determined some four years ago, when the attempt to get a State Board of Health organized was first discussed by a few medical men of our State, that I would make an investigation of this matter. These observations have extended over that whole time, and have been made with great care and as much accuracy as possible, and to my own astonishment and delight, I have become convinced that pulmonary consumption does not exist among the people native and resident to the Tablelands of the Cumberland Mountains.

In the performance of the work which has enabled me to arrive at this conclusion, I have had the generous assistance of more than twenty physicians, who have been many years in practice in the vicinity of these mountains. Their knowledge of the diseases which had occurred there extended over a, period of more than forty years. Some of these physicians have reported the knowledge of the occurrence of deaths from consumption on the Tablelands, but when carefully inquired into they have invariably found that the person dying was not a native of the mountains, but, a sojourner in search of health. In answer to the question: "How many cases of pulmonary consumption have you known to occur on Walden's Ridge, among the people native to the mountains?" eleven physicians say, "Not one." All of these have been engaged in practice there more than three years, four of them more than ten years, one of them more than twenty, and one of them more than forty years. All the physicians of whom inquiries have been made are now residents, or have been, of the valleys contiguous to Walden's Ridge, and know the mountain people well. Four other physicians in answer to the same question say, that they have known from one to four cases, numbering eleven in all, but had not ascertained whether five of them were born and raised on the mountains or not. The names and place of death of all these cases were given, and I have traced their history and found that but three of them were "natives," or had lived there more than five years, and that one of these was 57 years of age when she died, and had suffered from cancer for three years before her death. The two others died within six months after returning home from long service in the army, where both contracted their disease.

All these investigations have been made with more particular reference to that part of the Cumberlands known as Walden's Ridge than to the mountains as a whole. This ridge is of equal elevation and of very similar character to the main Cumberland range in the southern part of Tennessee, northwest Georgia, and northwest Alabama, and what is true of this particular part of the great Cumberland table is, in the main, true of the remainder.

Sequatchee Valley lies between Walden's Ridge and what is commonly known in that neighborhood as the Cumberland Mountains, and separates it from the main range for a distance of about one hundred miles, from the Tennessee River below Chattanooga to Grassy Cove, well up toward the center line of the State. Grassy Cove is a small basin valley, which was described to me there as a "sag in the mountains," just above the Sequatchee Valley proper. It is here that the Sequatchee River rises, and flowing under the belt of hills which unites the ridge and the main range, for two miles or more, rises again at the head of Sequatchee Valley. Above Grassy Cove the mountains unite and hold their union firmly on their way north as far as our State reaches.

Topographically considered as a whole, the Cumberland range has its southern terminus in Alabama, and its northern in Pennsylvania. It is almost wholly composed of coal-bearing rocks, resting on Devonian strata, which are visible in many places in the valleys.

But a small portion of the Cumberland lies above a plane of 2,000 feet. Walden's Ridge and Lookout Mountain vary in height from 2,000 to 2,500 feet.

North of Grassy Cove, after the ridges are united, the variation from 2,000 feet is but little throughout the remainder of the State, and the general character of the table changes but little. The great and important difference is in the climate, the winters being much more severe in these mountains in the northern part of the State than in the southern, and the summers much more liable to sudden changes of weather. Scott, Fentress, and Morgan counties comprise this portion of the table, and these have not been included in my examination, excepting as to general features.

In all our southern country, and I may say in our whole country, there is no other large extent of elevated territory which offers mankind a pleasant living place, a comfortable climate--none too cold or too hot--and productive lands. We have east of the upper waters of the great Tennessee River, in our State, and in North Carolina and Georgia, the great Blue Ridge range of mountains, known as the Unaka, or Smoky, Chilhowee, Great and Little Frog, Nantahala, etc., all belonging to the same family of hills. This chain has the same general course as the Cumberlands. It is a much bolder range of mountains, but it is vastly less inhabitable, productive, or convenient of access. The winters there are severely cold, and the nights in summer are too cold and damp for health and comfort, as I know by personal experience of two summers on Nantahala River. But the trout fishing is beyond comparison, and that is one inducement of great value for a stout consumptive _who is a good fellow_. These mountains are much more broken up into branches, peaks, and spurs than the Cumberlands. They afford no table terrritory of any extent. There are some excellent places there for hot summer visits--Ashville, Warm Springs, Franklin, and others.

The Cumberland Mountains, as a whole, are flat, in broad level spaces, broken only by the "divides," or "gulfs," as they are called by the inhabitants, where the streams flow out into the valleys.

Walden's Ridge, of which we come now to speak particularly, is the best located of any part of the Cumberlands as a place for living. From the separation of this ridge from the main range of Grassy Cove to its southern terminus at the Tennessee River, it maintains a remarkably uniform character in every particular. From it access to commerce is easy, having the Tennessee River and the new (now building) Cincinnati Southern Railroad skirting its entire length on the east. It rises very abruptly from both the Tennessee and Sequatchee Valleys, being from 1,200 to 1,500 feet higher than the valleys on each side. Looking from below, on the Tennessee Valley side, the whole extent of the ridge appears securely walled in at the top by a continuous perpendicular wall of sandstone, from 100 to 200 feet high; and from the Sequatchee side the appearance is very similar, excepting that the wall is not so continuous, and of less height.

The top of the ridge is one level stretch of plain, broken only by the "gulfs" before mentioned and an occasional prominent sandstone wall or bowlder. The width on top is, I should judge, 6 or 7 miles. The soil is of uniform character, light, sandy, and less productive for the ordinary crops of the Tennessee farmer than the soil of the lowlands. The grape, apple, and potato grow to perfection, better than in the valleys, and are all never failing crops; so with rye and buckwheat. Corn grows well, very well in selected spots, and where the land is made rich by cultivation. The grasses are rich and luxuriant, even in the wild forests, and when cultivated, the appearance is that of the rich farms of the Ohio or Connecticut Rivers, only here they are green and growing the greater part of the year; so much so that sheep, and in the mild winters the young cattle, live by the wild grasses of the forests the whole year. The great stock raisers of the Sequatchee and Tennessee Valleys make this the summer pasture for their cattle, and drive them to their own farms and barns or to market in winter. The whole Cumberland table, with the exception of that small part which is under cultivation, is one great free, open pasture for all the cattle of the valleys. Thousands of cattle graze there whose owners never pay a dollar for pasturage or own an acre of the range, though, as a rule, most of the well-to-do stock farmers in the valleys own more or less mountain lands. These lands have, until quite recently, been begging purchasers at from 12½ to 25 cents per acre in large tracts of 10,000 acres and upward, and perhaps the same could be said of the present time, leaving out choice tracts and easily accessible places, which are held at from 50 cents to $2 per acre, wooded virgin lands.

The forest growth of Walden's Ridge is almost entirely oak and chestnut. Hickory, perhaps, comes next in frequency, and pine after. There is but little undergrowth, and where the forests have never been molested there are but few small trees. This is due to the annual fires which occur every autumn, or some time in winter, almost without exception, and overrun the whole ridge. It does not rage like a prairie fire. Its progress is usually slow, the material consumed being only the dry forest leaves and grasses. The one thing essential to its progress is these dry leaves, hence it cannot march into the clearings. Nearly all the small shrubs are killed by these fires, otherwise they are harmless, and are greatly valued by the stock men for the help they render in the growth of the wild grasses. The free circulation of air through these great unbroken forests is certainly much facilitated by these fires, since they destroy every year what would soon become impediments. The destruction of this undergrowth leaves the woods open, and the lands are mainly so level that a carriage may be driven for miles, regardless of roads, through the forests in every direction.

The shrubs about the fields and places where the forests have been interrupted by civilization and other causes are blackberry, huckleberry, raspberry, sumac, and their usual neighbors, with the azalia, laurel, and rhododendron on the slopes and in the shade of the cliffs.

The kinds of wild grasses, I regret to say, I have not noted, and the same of the rich and varied display of wild flowers.

The whole ridge is well supplied with clean, soft running water, even in the driest of the season. There are no marshes, swamps, or bogs, no still water--not even a "puddle" for long--for the soil is of such a character, that surface water quickly filters away into the sands and mingles with the streams in the gulfs. Springs of mineral water are abundant everywhere. Probably there is not a square mile of Walden's Ridge which does not furnish chalybeate water abundantly. Sulphur springs with Epsom salts in combination are nearly as common.

The entire extent of Walden's Ridge is underlaid with veins of coal, and iron ore is plentiful, especially in the foot hills. The coal and iron are successfully mined in many places on the eastern slope; on the western they are nearly untouched for the want of transportation. I find that the impression prevails that the minerals of the Cumberlands are largely controlled by land agents and speculators. This is only true as applied to a very small part of the whole, not more than 1 per cent. The mineral ownership remains with the lands almost entirely.

The prevailing winds on Walden's Ridge are from the southwest; northers and northeasters are of rare occurrence. One old lady who had resided there for forty years, in answer to my query upon this subject, said: "Nine days out of ten, the year round, I can smell Alabama in the air." This was the usual testimony of the residents. Winds of great velocity never occur there. In summer there is always an evening breeze, commencing at 4 to 6 o'clock, and continuing until after sunrise the next morning. In times of rain, clouds hang low over the ridge occasionally, but they never have fogs there.

The range of the thermometer is less on the Tablelands than in the adjacent valleys. I have had access to the carefully taken observations of the Lookout Mountain Educational Institute, such published accounts as have been made by Professor Safford, State Geologist, Mr. Killebrew, the thorough and painstaking private record of Captain John P. Long, of Chattanooga, and many more of less length of time. From all these I deduce the fact that the summer days are seven or eight degrees cooler on the mountains than in the Tennessee Valley at Chattanooga, and five or six degrees cooler than in the Sequatchee Valley, as far up as Dunlay and Pikeville. The nights on the table are cooler than in the lower lands by several more degrees than the days; how much I have thus far not been able to state. The late fall months, the winter, and early spring are not so much colder than the valleys as the summer months, the difference between the average temperature of the mountains and valleys being at that time four or five degrees less than in the summer. There is no record of so hot a day ever having occurred on the Cumberladd Mountains as to cause mercury to run so high as 95° F., or so cold a day as to cause it to run so low as 10° below zero.

In the average winter the ground rarely freezes to a greater depth than 2 or 3 inches, and it remains frozen but a few days at a time. Ice has been known to form 8 inches thick, but in ordinary winters, 3 or 4 is the maximum. Snow falls every winter, more or less, and sometimes remains for a week. Old people have a remembrance of a foot of snow which lasted for a week.