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Great Sutro Tunnel. -Flying Machine

Not a single bit of the timber used in this bridge but what is at least twelve inches in diameter. The supporting pillars are banded together with ingeniously contrived iron plates. Another wooden trestle bridge is at a place that, from its gloomy character, has been named the Devil's Gate. This is about ten miles from Salt Lake, where the Weber River rushes down a chasm in the Rocky Mountains. On the first opening of this bridge, , the train passed over on a trestle bridge seventy-eight feet above the furious stream. A Government inspector thus reported of the spot: Should a train go down into this fearful gulf all who escaped being crushed would inevitably be drowned." The bridge is a double trestle, one resting on the other, " the supporting timbers standing at an angle of about forty degrees, gradually narrowing from the base to the top. The upper timbers, among other means adopted to prevent their giving way, are secured by large ropes tied around them, and fastened to projecting rocks above." Good trestle -work is supposed to last from fifteen to twenty years, and for viaducts it is ascertained to be much cheaper than embankments. Among famous trestlebridges may be here mentioned that at Pittsburg, 1,172 feet long; the Portage Bridge on the Erie Railroad, 800 feet long, and so constructed that a single timber could be taken out, if needed.

THE GREAT SUTRO TUNNEL. - As this wonderful engineering feat is accomplished, we give a few facts relating to it. This tunnel is intended to render easy the work of mining in the Comstock lode, which had become unprofitably expensive. The mines had reached a depth of over 2,000 feet, and the yearly expense of getting rid of the water, reached nearly $3,000,000. Added to the expense was the fact that the temperature of the lower depths had become almost unendurable. The object of the tunnel from the side of the hill was to tap the mines some 1,800 feet from the opening of the shafts, thus allowing the mines to be drained by natural flowage, and at the same time the heat would be lessened through the ventilation thus obtained. The ore would also be removed by this tunnel. The work has occupied about ten years, and has cost all of $3,000,000. FLYING-MACHINE. - In the year 1833 a model flying-machine was constructed by Rufus Porter, of New Britain, Conn., who kept experimenting, until about fourteen years later he produced a model propelled by steam, which he exhibited at Washington and at the Merchants' Exchange, New York, and a journal of the day declared it made the circuit of the rotunda eleven times like a thing animated with life." Still later he constructed a full working machine, but which he never completed because it was found impossible to procure a varnish or coating for the canvas covering which would prevent the leakage of the gases