STOPING is universally conducted by opening a level below the body of ore to be extracted, and working upward on the vein. On the Comstock, the openings made in mining the ore are so large that a complicated system of timbering is requisite to replace the material extracted. A rectangular system of timbers is usually adopted, the posts being about seven feet in length, 12 inches square, and placed about five feet apart from centre to centre. These are retained in their places by "caps" and "sills," and further to secure the mine each floor, as far as practicable, is filled up with waste material as soon as it is worked out. In early days too little attention was paid to this last precaution, resulting in extensive caves" or giving way of the ground from the superincumbent pressure. If a body of ore is entirely extracted the result is not serious; but should any remain untouched, the cost and difficulty of securing it after a "cave" has occurred in its vicinity is usually greatly increased from the broken and shattered condition of the ground. The quantity of timber used in these stopes is immense, as will be seen by the details of the annual consumption on a future page. Any means which would diminish its price would be a great gain to the entire community.

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PROSPECTING for new ore bodies forms a serious item in the cost of mining on the Comstock. When the great and irregular width of the vein, the irregular distribution of the ore bodies, the uncertainty of their occurrence, and our imperfect knowledge of the structure of the vein are taken into consideration, the difficulty of laying out prospecting works to the best advantage becomes apparent. Immense sums of money are spent annually in this kind of work, which must be taken entirely from the pockets of the shareholders when a mine is unproductive. If only moderately productive the entire revenue may be consumed in looking for more valuable bodies of ore; at the same time, the certainty of being richly rewarded for years of waiting if they are found, induces the continuation of work on mines which have not yielded a dollar for years. They are known on the main fissure of the Comstock to be surrounded by good property, and may become valuable at any moment. The Hale and Norcross mine is a good illustration. The following extract is taken from the annual report of the president of the company, for 1866:

Heretofore the entire expense of opening the mine, erecting machinery, &c., had to be borne from money collected by assessments, until they aggregated the sum of $350,000, equal to $875 per foot. For the year just ended the trustees have been enabled to return to the stockholders, in dividends, the sum of $490,000, equal to $1,225 per foot, or, in one year to repay the assessments collected in five years, with the handsome sum of $350 per foot in addition, besides carrying over the large surplus in cash of $133,288 99, equal to a further sum of $333 22 per foot, making altogether the handsome profit, in one year, of $1,558 22 per foot, or 155 per cent. on the par value of the stock.

In this connection the advantages of a community of knowledge and interest among the mining superintendents would be of immense value, the experience of all becoming available by each, thus reducing the cost of explorations by showing in what portion of the different mines deposits of ore are most likely to be found, and thus directing attention more particularly to them. Every dollar spent on an unproductive mine is so much taken out of the aggregate net profits of the mining interest, and every dollar which can be saved would be equal to the same amount distributed in dividends. But because a mine on the Comstock is unproductive to-day, is no reason why it should be abandoned. The only point to be considered is how it may be developed in the most economical manner, and the plan suggested above appears to afford a solution of the difficulty. The inefficient character of the results obtained by many companies working on the Comstock lode, when compared with the money expended, is well known to persons familiar with our mines, and can only be remedied by some such organization.

These engines were almost universally, in early times, attached to friction hoisting gear, but the increase of depth attained has almost banished this mode of operation, the great weight of the rope and car rendering it unsafe. Flat wire ropes have almost entirely superseded the hemp ropes originally employed. For hoisting ore cages are employed in all instances, buckets being used only for sinking in the shafts. These cages are fitted with a variety of appliances to insure safety in case of accident to the ropes or hoisting machinery.

PUMPS. The largest pumps in use are 14 inches in diameter; the greater number, however, range from 10 to 12 inches. The amount of water to contend with varies greatly in different mines, being, as a whole, more abundant in the north end of the lode. The Ophir Mexican pump throws about 300 gallons per minute, and must be run steadily to keep the mine free of water. The Bullion mine, about one mile to the southward, is comparatively dry, and in most cases a few hours' pumping daily is sufficient to rid it of water. Small pumping machinery would generally be sufficient was there not always a risk of tapping bodies of water dammed up by the clay seams in the vein already spoken of. These reservoirs generally yield a large volume when first struck, but rapidly diminish to a small stream. The machinery must be adequate, however, to the duty imposed upon it at such times, otherwise serious detention and damage may be the result.

AMOUNT OF ORE RAISED FROM THE MINES.-The amount of ore raised from the mines on the Comstock lode may be put down at the present time at about 1,500 tons daily, and the total amount raised since the commencement of operations at about 2,000,000 tons. The following table, compiled by S. H. Marlette, the surveyor general of Nevada, from returns made to the assessor, for the year 1866, shows the number of tons produced quarterly by the several mines which yielded more than $20 per ton. Some mines, owning mills of their own, work rock yielding as low as $15 per ton, but no record of this becomes public, and is very difficult to obtain, chiefly owing to disinclination on the part of owners of unincorporated mines to make their operations public. The table also shows the yield of the ore per ton.

YIELD OF ORE PER TON.-From information furnished by the superintendents of the following mines, the yield per ton appears to be

Savage mine-30,250 tons produced in the last six months of 1866, yielded an average of $42 93 per ton.

Hale and Norcross mine-16,836 tons produced in the same time, yielded an average of $50 33 per ton.

Gould and Curry mine-62,425 tons produced in 1866, yielded an average of $28 64 per ton.

The following table shows the number of tons of ore, worth more than $20 per ton, produced quarterly by mines on the Comstock lode, names of the mines, and yield of some of the ores: