whose eminent professional standing and intimate familiarity with the physical geography of the whole isthmus. entitle his statement to be taken as authoritative, an opinion of the route now being explored by the Wyse party, he replied that this undertaking would prove to be an utter failure, and took occasion to reiterate an assertion made by him twenty-five years ago, on returning from his own solitary expedition in search of a route in that region, that there is no reason whatever upon which to base a hope of obtaining a favorable line across any portion of the Darien Isthmus. He insists upon his oft-repeated statement that no route exists that could be executed for less than about $300,000,000. He would reject the temporizing policy which deludes itself with the vain hope of new discovery upon ground that has been surveyed and resurveyed, and face the difficulties of the problem. He favors the cutting of a direct line from the Gulf of San Blas, on the Atlantic, to the mouth of the river Bayano, on the Pacific. This is the shortest route that exists, being only about thirty to thirty-five miles long: it would, however, require a ship-tunnel possibly ten miles long.

THE MISSISSIPPI JETTIES.

From the official statements of the government engineers who are commissioned to inspect the work upon the jetties at South Pass, substantial progress appears to have been made during the past year; and everything appears to indicate the complete ultimate success of the undertaking and the triumph of the views of its advocates. From the latest published report of Captain Eads to the South Pass Jetty Company, we abridge the following concerning the more important results obtained. After a preamble relating the difficulties of the task, and affirming that the theories upon which the system of working was undertaken have been fully confirmed, the report announces that the concentration of the water flowing across the sand-bar at the mouth of the Pass by the jetties has created a channel over two hundred feet wide, and in no place less than twenty feet deep, where only about eight feet had previously existed; that the concentration of the water flowing over the shoal in the river at the head of the Pass created a channel over four hundred

feet wide, and in no part less than twenty feet deep, with the central part thirty feet deep, where but fourteen to fifteen feet had previously existed; that the temporary deposit which had formed in the Pass and between the jetties during the time in which a portion of the flow into the Pass had been interrupted by the work at its head has, since the restoration of the normal flow through the new channel at its head, by its removal caused the Pass to enlarge again; an action that has, since this restored flow began, removed from between the jetties in the last three months over half a million cubic yards of deposit, and established through more than half the length of the jetties a much larger and deeper channel than had ever previously existed, the size of which is already, throughout more than two thousand feet, twentyeight feet deep by three hundred feet wide, while for many hundreds of feet it exceeds thirty feet deep by three hundred and fifty feet wide; and, finally, the report affirms-what is of the last importance to the permanent success of the workthat the gulf current athwart the jettied mouth of the Pass effectually prevents the re-formation of the bar in advance of the jetties by deepening the outer slope of the bar, and sweeping away any such portion of the discharged sediment as the river current fails to carry to unknown distances seaward.

The fact is worthy of mention, finally, that on the 1st of November, 1877, the steamship City of Bristol, of the wellknown Inman line, passed through the jetties without detention and without touching. Her draught was twentyone feet eight inches, and the tide at the time was two and a half inches below "average flood-tide," which is the plane of reference established by the United States engi

neers.

OTHER AMERICAN ENGINEERING WORKS.

Concerning the East River Bridge, the Hudson River Tunnel, the New York elevated railroads, and the Poughkeepsie Bridge (which are probably the most noteworthy domestic engineering works in course of construction), we have nothing especially noteworthy to record, save that all are making gradual progress towards completion.

IMPROVEMENT ON THE UPPER MISSISSIPPI.

The last year witnessed, also, the completion of the canal constructed by government engineers with the object of overcoming the obstruction to navigation caused by the Des Moines rapids in the Mississippi at Keokuk, Ia. The following account of the character and importance of this work may be found of interest. The canal extends along the Iowa shore from Keokuk to Nashville a distance of seven and sixtenths miles. It is three hundred feet wide in embankment and two hundred and fifty feet wide in excavation; minimum depth of water, five feet; maximum depth, eight feet, which is sufficient to float the largest steamers that ply the Upper Mississippi. Entire fall in length of canal, 1875 feet. There are two lift-locks and one guard-lock, each three hundred and fifty feet long and eighty feet wide on top, solidly built of cut-stone masonry. Sluices of ample capacity to control the surplus water carried into the canal during the flood season are built around the locks. The cost of the work thus far has been $4,281,000, and $100,000 will still be required to finish it. The Engineering News affirms that this work is of incalculable importance to the navigation of the Mississippi River, as it removes the only obstruction that remained between New Orleans and St. Paul.

THE MADEIRA AND MAMORÉ RAILWAY.

In future commercial possibilities, the work of the building of this railroad (a contract for which was last year given by the agent of the Bolivian Government to certain American capitalists) is doubtless the most important enterprise that has lately been undertaken. The successful accomplishment of this project will have for its practical result the opening of a region of South America vast in extent, and of vast though undeveloped mineral and agricultural resources, but which, by reason of almost insurmountable natural obstacles, has been heretofore practically isolated from commercial intercourse with the world. The object of the proposed improvements, which are on a scale of great magnitude, is, by the construction of a line of railway, to bridge a gap of about one hundred and eighty miles, in which the existence of numerous falls and rapids opposes at present a complete

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barrier to commercial intercourse, and thereby permit the movement of trade down the Madeira and the Amazon to the Atlantic.

The following will give the essential features of this important work: "The road will run along the eastern shore of the Madeira River, in Brazil, from the head of navigation below the rapids to the navigable water of the Mamoré River (a branch of the Madeira) above. The Madeira has its source on the great water-shed of Bolivia, east of the Andes; leaves Bolivia at the northeastern point, and runs across the table-lands of Brazil to the Amazon, which it joins at Barra, about seven hundred miles from the Atlantic. A series of falls, however, render the river useless for a distance of one hundred and eighty miles. The Mamoré is a branch of the Madeira, and begins above the falls on the border of Bolivia."

The object of the proposed railroad, as has been before explained, is to bridge over this gap of one hundred and eighty miles that nature has interposed in this region between it and the commerce of the outer world. The area of country that the road will tap is estimated to be about 480,000 square miles; and of the country itself, the salubrity of its climate, its mineral resources, and agricultural capabilities, the most flattering accounts are given. It is said that silver, gold, lead, copper, salt, and nitre are abundant; and that the soil will produce cotton, sugar-cane, tobacco, coffee, cocoa, indigo, and other important staples in profusion.

The grant received by the Bolivian Navigation Company (under whose auspices the work of improvements is being carried on) from the governments of Brazil and Bolivia embraces a million acres of land, and the navigation of all the waters of Bolivia for the period of ninety-nine years, with the additional concession that no other company shall be accorded the right to build a railroad around the rapids for the next fifty years. The possible value of this monopoly in the future cannot be estimated; and since the contract for the building of the road which is to unite this country in commercial relations with the rest of the world has been accorded to American engineers, the hope is widely expressed that this country may take such measures as will direct

the current of this prospective rich and abundant traffic to our own ports, to the advantage of American manufacturers.

At the time of this writing, the steamer Mercedita had sailed from Philadelphia with a large number of engineers and laborers, and the first load of supplies and machinery, for the scene of operations. This vessel is to be followed by others, and monthly communication between the base of supplies and the Madeira will be kept up.

THE SUTRO TUNNEL.

The latest advices indicate that the great tunnel into the Comstock silver lodes is gradually approaching completion. At the time of this writing it is officially announced that the tunnel-heading had penetrated into paying ore, and had been driven a distance of 18,400 feet into the mountain. This would bring the tunnel, as near as may be estimated, to within less than one hundred feet of the great combination mining-shaft, which, when reached, will practically complete the undertaking and determine its value. The following statements of the nature and history of this enterprise may, in view of the above facts, be of interest:

The object of the Sutro Tunnel is to facilitate mining operations in the Comstock lode, the difficulties and expensiveness of which are very serious. The mines have reached a depth of from 1000 to 2500 feet; and the cost of pumping to keep the workings free from water entails an annual expense of $2,000,000 or $3,000,000. This fact, and the circumstance also that the temperature in the deeper portions of the workings reaches as high as 120°, render mining operations enormously expensive. These difficulties the Sutro Tunnel is designed to obviate by tapping the workings at a depth of about 1800 feet from the surface, creating, therefore, a new surface for ventilation and drainage at the 1800-foot level of the mines, by which it is expected (as the water will be drained off, by the natural flow through the outlet provided, to the depth of 1800 feet) that the cost of pumping will be largely reduced, and that the means of ventilation which it will provide will so far reduce the temperature as to enable the miners to work in comparative comfort. In addition to these obvious advantages which it is expected to realize from the tunnel, there are others of considerable commercial