HEAVY TUNNELLING.

Grey River Argus, Volume XV, Issue 1836, 24 June 1874, Page 2

HEAVY TUNNELLING.

("THAMES ADVERTISER.] We have no doubt that most of our readers have heard of the great Comstock lode, which is said to have already yielded the value of L 32,000,000 worth of mineral—probably the most wonderful lode which has been worked «ince the sons of men first began to dig. metals from the bowels of the earth. The lode is in the State of Nevada, about 250 miles from San Francisco, and 20 miles from the Pacific railway, with which it is connected by branch. It is now projected to put in an immense tunnel so as to develop the lode. The tunnel has alreadyibeen entered 1800 yards, and aid is now asked from English capitalists to complete it. It was thought that assistance would be got from Congress, and the mining committee of the House of Representatives recommended the Government to assist by a loan of 2,000,000d0l at 5 per cent. ; , Ooiir gress, however, adjourned before granting the required aid, and it has therefore been determined to seek the funds in the London market. The plan of ;the Sutro Tunnel Company seems something' of the same nature as the Coromandel Tunnel Company. The Sutro Tunnel Company have secured a width of 4000fc, through which the tunnel is to run, and it is expected that important discoveries will be made before, the lode specially in view is reached. Congress has granted the Sutro ■ Tunnel Company the right to claim a royalty of 2dol per ton for ever upon the produce of all the mines benefited by the tunnel. The last number of the Mining Journal contains a number of interesting particulars respecting this important project. Sutro is, it seems, the name of the engineer who has conceived the plan of the tunnel, which is to run in a straight drive for four miles, to a pOint vertically under Virginia City, when it will have a depth of 320 fathoms, or 1920 ft. The surface over the line of the tunnel has heavy undulations, and several intermediate shafts are being put down; so as to have different parts of the tunnel in course of driving simultaneously. Three' of these shafts have been, already com- ; menced. It is estimated that, with ordinary diligence the whole tunnel will be » I completed in' two years • and i tha f writer in the journal from .which' we obtain the particulars states that, considering that in a very short time there will be seven ends driving, and that a large plant of pumps and r machinery is at work, there need be no fearthat the > estimate is over-sanguine. When the ;■* tunnel has been driven four miles, and has reached directly under Virginia City, • it is proposed to drive two branch tunnels, each about a mile and a-half long, east and west, to reach the whole, of the mines on' the Comstock lode, securing perfect drainage, and relieving them from the heavy cost of haulage. The tunnel is to be 12ft high and 16ft wide, is to have a double line of railroad, and a drain for carrying off the water. '■-;

The Sutro tunnel is something: like our Kuranui Hill tunnel, which, however, would give relatively a greater depth in proportion to the length driven. We. are. glad to see that a movement is being made towards its continuation, and the recent encouraging indications from the lodes at and in the vicinity of Punga Flat mast-stimulate those interested to have the tunnel extended. In the recent scheme submitted, when asking a loan from the Government for the extension of this tunnel, statistics were given which showed that the Kuranui HUI tunnelj if carried in a further distance of 6000 ft, would reach to Punga Flat at a depth of 900 ft below the surface in Ruby claim. It would intersect the most prominent lodes, of the district at levels wfcioh would give extraordinary .facility for working them to | advantage, and testing them at depthß n which cannot otherwise be reached, except in a small way and at larger expenditure, by the sinking of shafts. The greatest advantage to be derived from the tunnel would be that, while giving very low levels, it would obviate the necessity for expensive machinery, and in this respect alone, leaving out of the question the ready means of transit afforded, a great : saving of expenditure would be effected.