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Show 1 2 8 4 REPORT OP TIIE CHIEF OP ENGINEERS. of Washoe Lake meandered. The rondezvous- cauip was reached November 25th, and the party disbanded. We were in the field eighty days, dnring which time we traveled in all 1,024 miles, of which 654 were meandered. Seven main triangnlation stations were occupied, and fonrteen secondary. Eight hundred and thirty- four stations were made on meander line, and one hundred and two three- point stations as checks or for the location of important poiuts. One hundred and three cistern- barometer altitudes were observed besides the aneroid determination at each meander station. The highest poiut reached was Freel's Peak, in the eastern summit of the Sierras, 10,862 feet above sea- level, the lowest 4,222 feet, on the Central Pacific Railroad. But few sextant latitude observations were needed as checks, since every important point conld be located by triangulation. The instrumental outfit of the party was the same as that generally allowed and needs no special mention, ( or interesting points concerning the natural history and geology of ihe area visited, I beg to refer to the speoial reports of Messrs. Hensbaw and Conkling. Very respectfully, your obedient servant, M. M. MACOMB, Second Lieutenant Fourth Artillery, U. S. Army. Lieut. GKO. M. WHEELER, Corps of Enginea- 8, in charge. APPENDIX G. PRELIMINARY REPORT ON EXAMINATION AT THE COMSTOCK LODE, BY JOIIN A. CHURCU. VIRGINIA CITY, NEV., June 30, 1877. SIR: I have the honor to submit a fhort report of the woik in the Washoe mining district during the mouth of June, 1877, in accordance with your instructions. Arriving on the gronnd on the 11th day of that month, it was obviously impossible to do more in the short remainder of the fiscal year than to place aud enter upon the prosecution of the work. I find that the period of seven or eight years which have passed since the last extended study of this region has been the period of greatest activity and greatest change the Comstock lode has ever witnessed. The mines have beeu opened a thousand feet deeper than in 1869, and have changed from a vertical to an inclined system of working, in correspondence with the chauge in the dip of the vein. To meet this altered condition of things the mines have all established a separate system of hoisting for the incline; these are being raised to the head of the incline by a " giraffe" and then dumped to a car which is run upon the cage and hoisted as formerly through the vertical shaft. None of them attempt to raise the ore by one continuous hoist through both the inclined aud vertical shafts. Preparations are now completed in one shaft and going on in two others for resuming the extraction through vertical shafts by sinking in the east country- rock of distauces in two cases of more than half a mile from the outcrop of the vein. Changes quite as important have been effected in machinery. The geared pnmping-engines, which were formerly used by all the mines, have been replaced in most of them by very elaborate and expensive direct- acting compound engines, controlled by the Davey valve gear, which has been somewhat modified in this region. The pumps are all of the Cornish pattern and are now raising water from depths of 2,000 and 2,300 feet. Direct- acting hoisting- engines have also been introduced at one shaft, and the speed of hoisting increased in those mines which are extracting great quantities of ore. Self- dumping skeets have taken or will take the place of the ordinary cage and car in two of the deep shafts. These alterations iu the method of working are all important in view of the great depths to which these mines will probably be carried. The machinery now on the ground is sufficient for depths of 3,000 feet, and the method of working the incline and vertical shafts separately adapts it to much deeper sinking. Underground engines are used in considerable numbers for pumping, hoisting, and veutilation, and as these are all worked by compressed air, the mines along this lode ofier probably the most extensive series of air- compressing engines to be found in any district. They are mainly of two types, the Burleigh and a modified Waring. All these changes have produced great effects upon the mining of the district and the financial fortunes of the owners. As now instituted, the mining industry of Washoe preseuts important opportunities for studying the effect and economy of modern mining- machinery. Ventilation and pumping have become questions of especial importance. The heat |