900-foot level shows the above-described ore body to have passed away from this mine into Kentuck; but a quartz seam, varying from four to nine feet in width, has been followed and prospected on this level for several hundred feet, showing, however, only traces of ore. Explorations have been carried 200 feet deeper within the last year, and levels have been opened at 1,000 and 1,100 feet; but cross-sections through the vein show a quartzose mass with only traces of ore. Sulphurets of iron are found thickly disseminated in the porphyries which lie in close contact with the quartz. This can scarcely be regarded as a good sign for finding tractable ore in quantity. In the Yellow Jacket mine, from where ore body No. 3 closed out, south to where ore body No. 4 commenced, (a horizontal distance of over 780 feet,) there had been but little exploration carried on, although the ground was favorable for the existence of ore. The 730-foot level was opened northward, and disclosed a narrow quartz seam with some ore. The 810-foot level was opened and demonstrated eleven feet width of ore, which has been followed for 280 feet, showing from three to eighteen feet width of thirtyfive-dollar mill ore. The 900-foot level was then opened, which showed the newly found ore body of the 810-foot level to be from fourteen to eighteen feet wide, carrying extremely rich seams and bunches of ore. It has been followed for sixty feet, thus far, north and south, and gives forty dollars mill ore. This body does not stand in communication with any ore body heretofore discovered; it has every appearance of being of very large dimensions, and has improved very materially in depth in the last 100 feet explored, so that Yellow Jacket has to all appearances a bright future.

Like the ore found in Alpha 1,000-foot level, and Hale & Norcross 1.037-foot level, this body has also a considerable intermixture of baser metals, which was not the case in the upper ore bodies. Its ores are often in nests, very rich, and alternate abruptly with barren quartz or even porphyry. The same phenomenon was also visible, but not to so great an extent, in ore body No. 6.

From the above description it will be seen that there is a probable reoccurrence of new ore bodies in the Comstock, in depth, so long as the west wall remains firm. Within the last year work has been continued on the formerly discovered eleven bodies of ore, some of which are entirely, and others not quite, exhausted; and two new bodies only have been met with. It is true that explorations, vertical and horizontal, could have been pushed to twice or thrice their actual extent; and had this been done, it is very probable that there would be more ore in sight. Yet, it is certain that the actual value of the Comstock has diminished materially within the past year. The bullion product has been, under the circumstances, large; but it has mainly come from ground on the vein which was known to be valuable before the year commenced, rather than from newly developed ground in depth.

It is very probable that the coming year will give us an equal yield if not a larger one than the foregoing, as railroads, &c., now facilitate all mining and milling operations enormously, and the vast amount of lowgrade ore (estimated, as closely as possible, to amount to 3,500,000 tons of ten-dollar to fourteen-dollar mill ore standing in the eleven old ore bodies, not including new developments made) which yet exists along the vein may be beneficiated hereafter, while hitherto only fifteen-dollar to sixteen-dollar mill ore has been thought worthy of attention.

The two newly discovered ore bodies give every promise of large dimensions and of a quality insuring a handsome revenue to the respective mines in which they are situated. They are not explored sufficiently

to enable me to speak with certainty as to their value, but allowing them their highest probable extent and richness, the fact remains that out of 19,000 feet of length of ground along the course of the vein there were, to an average depth of say 600 feet, about 6,000 feet length of productive ore ground; while between that depth and 1,000 feet, we have at present, though, it is true, explorations have been but partial, only 730 feet length of productive ore ground actually developed.

It has been the experience, thus far, that on this vein the deeper ore bodies are smaller than those near the surface. Their ores occur less uniformly distributed through the gangue, and are more refractory, an evil which unfortunately threatens to increase as greater depths are attained. It is true that nests and small deposits of extreme richness occur at intervals, but not in sufficient quantity to compensate for the increase of cost for their extraction, to say nothing of the inevitable expense of prospective and accessory work which all falls to the cost of mining. On the other hand, the cost of extraction and beneficiation of the ores will hereafter be decreased. The Virginia and Truckee railroad from Virginia to Carson, along the Carson River, began running in November, and milling facilities by water-power will be furnished along the river, reducing the price of reduction probably fifty per cent. below former rates. Many of the shafts, belonging to the leading mines, have attained sufficient depth to be close to the west wall of the vein, or at least not very far from it. Three of them, Gould & Curry, Chollar, and Crownpoint, have already pierced it, and will doubtless be changed to inclines, as the Chollar and Bullion shafts have been. In working through inclines, one-third or one-fourth of the shaft-area (according to the size) becomes useless, which augments the cost of hoisting by one-third or one-fourth of what it is when the main exit of the mine is vertical. This fact will compel, in course of time, the consolidations of several adjoining companies to work through one shaft, a measure which ought to have been adopted long ago.

As above remarked, two new ore bodies have been discovered within the last year by explorations in depth; one in the northern and one in the southern portion of the vein. The latter promises to be the more valuable. Other and fruitless prospecting work has not inspired much hope of soon discovering fresh ore. On the contrary, we find north of the lately-discovered ore the vein filled principally with feldspathic porphyry in various stages of decomposition up to plastic clay; small, irregularly deposited barren quartz-seams have now and then been encountered; the porphyry is impregnated with iron pyrites; and lime, as both carbonate and sulphate, has been found to increase gradually, and replace the quartz more and more as depth on the vein has been attained. As far as our experience of this vein has gone, the analogy of these phenomena is anything but encouraging in leading us to believe in a speedy recurrence of ore. In the southern portion of the Comstock, beyond the new ore body alluded to, a striking departure from established analogy is observed. Experience on the Comstock has always shown that wherever the vein itself presented large quantities of porphyries imbedded in its matrix, large deposits of quartz were sure to be found at the termini of these intruded masses; and that wherever large quartz-bodies were met, there we were sure to find ore also. Now, developments in Bullion, Imperial, and Crownpoint, from a depth of 1,000 feet to 1,400 feet, have proved the existence of large quartz bodies. The Bullion, at 1,200 feet, shows 63 feet quartz-width; the Imperial 1,000-foot level shows 50 feet quartz and over 87 feet quartzose matter; the Crownpoint 1,000-foot and 1,100-foot levels show from 20 to 60 feet width of quartzose matter; yet in neither mine, in the ground re

ferred to, has ore been found in more than traces. These quartz bodies, and the porphyries accompanying them, show carbonate and sulphate of lime, which neither contained at the upper levels. The waters met with, since limestone made its appearance and the porphyry became so full of pyrites, have been hot-1200 Fahrenheit on June 28 in Crownpoint 1,100-foot level; and ore has never yet been found in paying bodies in this vein where hot water was encountered. The first example of this rule was furnished five years ago in the North Comstock. The Central Company's shaft had attained a depth of 562 feet-162 feet below the terminus of the ore-and hot water was encountered, preventing further explorations. Since that time the Ophir has explored over 400 feet deeper, with a level, and found nothing but limestone and pyrites.

The impression I received last year has not been removed by the history of the present year. All the observed phenomena appear to indicate that the present deepest workings of the Comstock mines are in a comparatively barren zone of the vein, which seems, moreover, to be characterized by a change in the gangue from predominant quartz to predominant carbonate and sulphate of lime. Whether this gradual variation in the gangue is in any way the cause of the diminution of ore, or merely an accidental coincidence, I shall not discuss. The discussion would require the proposition and defense of some particular theory of the processes of the vein formation, which I do not desire to undertake, and an investigation of chemical as well as geological character, for which the facts are not yet sufficient. I must confess, however, that I incline, aside from theoretical reasoning, to believe the appearance of lime in the vein to be connected directly with a change in its metalliferous character. Not that it has prevented the occurrence of ore in depth; but that the character of the ore and its distribution will be found to change if the lime continues. It is quite natural-that is to say, quite a common phenomenon-that the zone between two sorts of gangue should be comparatively barren; and this appearance need not discour age the expectation of finding new metalliferous deposits below it. With regard to the important question, how extensive this zone may be, of course it would be folly to attempt a definite answer, yet the following suggestions may be of value:

1. The barren zone now penetrated by the deeper workings on the Comstock is either one of transition or one of temporary variation. The quartzose gangue has by no means disappeared; it only threatens to do so, or at least to become permanently subordinate. The lime, on the other hand, threatens to become permanently predominant, and has thus far proved unfavorable to the occurrence of ore in the forms and Combinations hitherto characteristic of the vein. In this mixed condition of things, the vein matter being neither one thing nor the other, it is not surprising that the proportion of ore is so greatly diminished. Without meaning to commit myself to any elaborate theory, I may say, for the purpose of illustration, that the calcareous minerals are, as it were, themselves playing the part of ore to the quartz.

2. We may reasonably expect one of two things. Either the unpleas ant admixture of lime will prove to be local and temporary, and the vein will resume again in depth its original matrix, or the change now threatened will continue until the carbonate and sulphate of lime are permanently predominant as gangue.

3. In the former case the chances are in favor of a briefer continuance of the barren interval, and of a subsequent recurrence of ore bodies similar in character and distribution to those already exploited. In favor of this supposition we have the universal prevalence of quartz as vein

H. Ex. Doc. 207—7

material through our silver-bearing regions, and the comparatively infrequent appearance in large quantities, under such conditions, of the carbonate or sulphate of lime. Moreover, there has not been observed, so far as I know, any decided change in the country rock, such as might be expected (though not of absolute necessity) to herald or accompany a complete change in gangue. Again, there is some encouragement for this view, in the fact that the vein of the Occidental and other mines, lying a mile and a half or two miles east of the Comstock, contains in its south portion heavy layers of lime rock, which yield in depth to quartz. (See my former report, p. 50.) This fact has perhaps the more significance, since we may probably look to the east for the principal sources of the materials filling the Comstock lode.

4. In case of the complete change of the gangue and the permanent prevalence of lime, the character of the ores and the manner of their distribution would probably suffer a complete change also. As a mere illustration, I may say that the ores in depth would have to bear the same relation to lime that the present ores bear to quartz. This relation science cannot now exactly define; it is surmised to be partly chemical, partly electrical, and partly mechanical; and it is certainly dependent also upon the manner in which the vein-fissure was filled, and the succession and relative duration of the different entrances of vein-matter. The nature of the ore that might be expected in a lime gangue on the Comstock is, however, practically indicated by the modifications already observed in those parts of the vein where lime forms a considerable proportion of the gangue; and judging from this hint we might anticipate more widely disseminated ore, of lower grade, containing more base metal and more difficult of treatment than has been the case in general heretofore.

It is impossible to predict which of the two contingencies thus described will arise. With regard to the latter it may be said that the analogies of other veins in the neighborhood, or even in the whole silver belt of the United States, afford no argument, since none of them are opened to such a depth. The probability of the change alluded to will increase with every new depth attained in working on the barren zone.

5. The most difficult and costly labor on this vein has always been, and is now more than ever, the exploration of the vein for new bodies of ore; and the expense of this necessary work has increased with increasing depth until it is now crushing. The reduction in milling rates affords no relief to those companies which have no ores to be milled, though it will enable work to be prosecuted in many cases where for merly the high cost of treatment prevented the extraction of low-grade ores. The present crying necessity is a cheapening of the mine expenses. The Virginia and Truckee railroad, by reducing the prices of timber, and to some extent of supplies, has effected a considerable improvement; but much remains to be done before the explorations in depth can be economically carried on to the extent which the circumstances encourage and demand.

Foremost among the necessary reforms is the consolidation of companies, and the consequent reduction of the cost of administration. This movement is already beginning among the small proprietorships, and by another year I expect to find the aggregate number of companies on the vein greatly reduced.

The systems of ventilation by machinery, of drainage by pumps, and of hoisting through vertical shafts, though great improvements on the ruder methods of natural ventilation, (or no ventilation,) hoisting water in buckets, and dragging out ore through inclines, are, nevertheless,

fast approaching their economical limit of application in these mines. In a foot note to my previous report, (page 52,) I pointed out the great advantage of utilizing the enormous "head" afforded by the depth of the shafts, in the employment of hydraulic power. This is not possible until an outlet is created below for the water so employed; and this consideration alone renders the construction of a deep tunnel an economical necessity. It is reported that operations have been commenced on the Sutro Tunnel, and that the laboring miners themselves have subscribed a large sum, "as a first installment," toward the enterprise. Whoever builds this tunnel, it seems to be of vital importance to the industry of mining on the Comstock that it should be completed. The calculation, quoted in my last report, that fifty gallons of water per second, with a fall of two thousand feet, create a working capacity of 1,800 horse-power, is slightly exaggerated, as the power thus created would be more exactly 1,516 horse-power;* but the fact remains as a forcible argument, justifying my assertion that "if the Sutro Tunnel is completed to the lode, and connected with deep shafts, the conditions for explorations to still greater depths will be more favorable than they were at the very surface; since the immense power of the hydraulic column will be at the service of the miner."

MINES ON THE CONTINUATIONS OF THE COMSTOCK.

So many of the Comstock mines proper have been compelled to extract from their old workings ores once cast aside, as not worth enough to pay for treatment, that the mills, as well as the mines, have found their advantage in reducing the prices of custom-work, to enable these operations to be continued; and this reduction of prices has in turn caused the resumption of active work on many a mining claim beyond the limits of the recognized Comstock ledge, though on the extensions north and south of its supposed course. South of the Overmann are three or four claims which have lain idle for years. Under the present favorably low milling rates, ore is extracted from them on contract by small companies of miners. It is principally found near the surface, contains a comparatively large proportion of gold, and yields from $11 to $14 a ton. The amount thus obtained is, however, quite limited. North of the Utah, work has been done for some time on small claims; and, it is said, with profit. There are a good many places on and around the Comstock lodes where it would not pay a large company to operate, but where small associations of miners, not burdened with costly organizations and administrations, can labor with profit.

The Sacramento mine appears to occupy the northern continuation of the Comstock; and in this mine a larger amount of work has been per-. formed than in any other of the similar locations coming under this head. The ores run as high as $20 per ton, and may be called, on the average, twelve-dollar mill rock; the mean production is 50 tons per day.

*A gallon of water contains 231 inches, and weighs 8.3388822 avoirdupois pounds. To compute the power of a fall of water, it is necessary to multiply the amount in pounds falling per minute, by the height in feet through which it falls. The product is the number of foot-pounds per minute exerted by the fall. As 33,000 foot-pounds per minute constitute one horse-power, it is easy to obtain the number of horse-powers. Thus:

30×60×8.3388822×2000 33,000

tion as above supposed.

1,516.16 horse-powers, exerted by the column of water in mo