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HYDROGRAPHY.

By FRANCIS M. GREEN,
LIEUTENANT-COMMANDER, U.S.N.

During the past year a large amount of work has been performed by hydrographic surveyors in different parts of the world, both in actual surveys and in preparing and publishing the results; although the record of the year's work does not show any one great task either commenced or brought to a conclusion.

As heretofore, the English have accomplished more than any other nation, but American, French, German, Russian, Austrian, and Italian naval officers have also been steadily working to increase and perfect the knowledge of the shores and depths of the ocean.

Owing to the very limited appropriations of money for the maintenance of all branches of the United States government for the past year, the operations of the United States Hydrographic Office and the United States Coast Survey have been very limited.

For this reason no surveys of any consequence have been carried on by the Hydrographic Office.

Forty-one new charts of various parts of the earth's surface have, however, been compiled and published for the use of navigators; sailing directions for the coasts of the Mediterranean Sea, the west coast of Africa, and the West Indies have been prepared and issued; and a very large number of notices of changes in the channels of navigation and of alterations in lights, buoys, and other aids to navigation have been published.

A careful examination of the singular bank discovered by Lieut.-Commander Gorringe, U.S.N., off Cape St. Vincent, has shown that the least depth on it is about thirty fathoms, so that it need not be feared as a danger to navigators.

The late Commander Ryan, in the U.S.S. Huron, carefully determined the latitude and longitude of about twenty

points along the north shore of South America, besides gathering a large amount of valuable information regarding that coast, and, when lost with his ship, was proceeding to correct as many as possible of the discrepancies and errors known to exist in the charts of the island of Cuba.

Commander Schley, U.S.N., is engaged in the U.S.S. Essex in running a line of deep-sea soundings from Liberia, by way of St. Helena, to Rio de Janeiro, a work which will give an entirely new cross-section of the South Atlantic Ocean.

The work of determining by telegraph the differences of longitude between points in the West Indies and the United States having been completed, and the results published by the Hydrographic Office, the same officers of the United States Navy have commenced the measurement in the same way between Lisbon and Pernambuco, Rio de Janeiro, Monte Video, and Buenos Ayres, connecting at the latter point with the chain of longitudes measured by Dr. B. A. Gould from the Cordoba Observatory.

Under the superintendence of the United States Coast Survey the survey of the Gulf of Mexico is steadily progressing. Lieut.-Commander Sigsbee, U.S.N., in the steamer Blake, to whom this extensive work is confided, has during the past season run 6600 miles of soundings, with an average of one sounding for every six and three-tenths miles, and using for all depths over one hundred fathoms the wire sounding-machine devised by himself. Serial temperatures from surface to bottom were taken at two hundred and twenty-two localities, while surface and bottom temperatures were taken at many more. Large numbers of specimens of bottom have been obtained for examination, as well as numerous specimens of water from various depths.

During the coming season Lieut.-Commander Sigsbee will extend the survey to that part of the Florida stream between the Florida reefs and the coast of Cuba, and will be accompanied by Professor Alexander Agassiz.

On the Atlantic coast the Coast Survey have prosecuted hydrographic surveys on the coast of Maine, on the south side of Long Island and in Long Island Sound, in the Currituck, Albemarle, Pamlico, Core, and Bogue sounds, in the Florida channel, and in the Indian and St. Johns rivers, FlorIn the Gulf of Mexico, in addition to the deep-sea work performed by Lieut.-Commander Sigsbee, surveys have been prosecuted on the west coast of Florida, near Cedar Keys, and between St. Andrews and Pensacola, on the coast of Louisiana and in the Mississippi River. At the mouths of the Mississippi observations for currents, volume of discharge, changes of depth, etc., have been continued.

On the Pacific coast work has progressed rapidly on the coasts of California, Oregon, and Washington Territory.

Off-shore tidal-current observations have been continued, and ten tide gauges on shore have been constantly observed and recorded, in addition to those operated by hydrographic parties.

The work of compiling the Coast Pilot for the Atlantic coast and for the coast of Alaska has made steady progress, while a large force in the office has been constantly employed in constructing charts from new surveys, and in the endless work of correcting older chart-plates in accordance with recently discovered changes.

An excellent précis of the work done by English Admiralty Surveyors is given in the Nautical Magazine for July, 1877.

The constant demand for more exact information regarding very many partially surveyed regions, in order to develop new channels of commerce, is very great and is constantly increasing, and the world is indebted to English surveyors for an immense amount of valuable work in this direction.

Owing to the sandy nature of the bottom at the mouths of several of the rivers and estuaries on the shores of Great Britain, it is necessary at frequent intervals to re-survey them.

In Yarmouth harbor, at the mouth of the river Thames, in the Solway Firth, at the mouth of the river Tay, and at the mouth of the river Shannon, marked changes were found during the past year to have taken place in the channels and shoals.

In the Mediterranean, Captain Wharton, R.N., in H.M.S. Fawn, has continued the examination of the mouth of the Nile and the entrance to the Suez Canal.

A considerable advance of the land is shown to have taken place at the Damietta mouth of the Nile, as compared with its condition in 1856. A careful examination of the depths in the canal showed that the reports of its decrease in depth were without foundation.

Captain Wharton states that at the season of highest Nile, the water at the Damietta mouth is so charged with mud that it forms a sort of breakwater for the region to leeward of it, the wind being powerless to raise it into waves.

Passing into the Red Sea, Captain Wharton has done very valuable work in surveying an inshore route along the Atrican coast, by which small vessels may avoid the stormy southerly winds and heavy sea prevalent during the summer months.

At Mauritius, Lieutenant Coghlan, R.N., has commenced a much-needed survey of the shores of that island, no hydrographic survey ever having been made.

In the China Sea, Commander Napier, in H. M. S. Nassau, has done a large amount of work in Carimata and Hai-tan straits, as well as in the labyrinth of shoals and channels in the Strait of Malacca.

On the coasts of Corea and Japan, Captain St. John, R.N., and the officers of H. M. S. Sylvia, have surveyed and connected the numerous groups of islands lying between Japan and the northern parts of China.

A party under command of Staff-Commander Maxwell have divided their labors between Placentia Bay and the northeast coast of Labrador, which work can only be done in midsummer.

Lieutenant Pullen, R.N., has energetically pushed the survey of the island of Jamaica.

The surveys of the shore of Australia have been carried on by four fully organized parties, and a large amount of work has been accomplished.

The general survey of the Fiji group under charge of Lieutenant Moore, R.N., has made marked progress.

A detailed survey of the Gettysburg bank discovered last year by Lieut.-Commander Gorringe, U.S.N., has been made by Commander Egerton, R.N., who, however, failed to find a less depth on it than had been found by its discoverer-viz., thirty fathoms.

Besides the direction of all these surveys, the British Hydrographic Office has published 167 notices to mariners, consisting of notifications of changes in lights, buoys, etc. ; 350

pages of hydrographic notices; new editions of sailing directions for the Mediterranean; directions for the Dardanelles and Black Sea, the west coast of Scotland, and the “ Australia Directory;" 62 new charts have been published, 1896 have been corrected, and 180,000 have been printed and disposed of for the use of navigators.

Under the direction of the Indian Government, English nayal officers have also been busily at work on the surveys of the coasts of India and Burmah, extending the incompleted charts of the coast, and re-surveying those ports and harbors in which natural and artificial changes are constantly being effected.

Under the direction of the French Ministry of Marine, extended surveys have been made on the coasts of France, especially of the approaches to the ports of Boulogne, Rochelle, and St. Jean de Luz, to determine the changes in depth and position of the various channels.

In the Gulf of Siam, French surveyors are busily at work in exploring and surveying; here, as elsewhere, increased commerce being accompanied by an urgent need of exact knowledge of the shores.

Detailed charts will soon be published of the recently completed surveys by MM. Herand and Bouillet in 1873-4-5 of the delta of Tong-kin.

Charts of the coasts of Tunis and Tripoli from the survey recently completed by Captain Mouchez are in course of preparation, and will be shortly published on a scale of zodoo.

In addition to these surveys, the French Dépôt de la Marine has continued, as heretofore, the publication of corrected charts and nautical books. Eighty-two charts have been published of various parts of the globe, and a number of most valuable nautical books, including the" Annales Hydrographiques,” issued quarterly; the “Livret des Phares;" "Récherches Chronométriques;" sailing directions for the north coast of France, for New Caledonia, and for the mainland of America from Guiana along the shores of the Caribbean Sea and Gulf of Mexico to the south point of Florida.

Under the auspices of the Imperial German Hydrographic Office, a re-survey of the shores of the German Empire has been commenced.

In the Baltic Sea the hydrographic portion of this work is

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