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St. Gothard tunnel.
Streams, gauging the flow of.. 80
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Removal of silt from reservoir
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Labor omnia vincit.
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MODERN STEEL AS A STRUCTURAL MATERJAL. By Mr. W.
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RAILWAY NOTES. - Railway Accidents in Germany; Funicular Railway 83; A New Traction Engine: Railway
('ommunication between Paris and Constantinople; Train Blown Over a Precipice, $4.
ENGINEERING MAGAZINE. .
NO. CXLV.-JANUARY, 1881.-VOL. XXIV.
IMPROVEMENT OF RIVERS AND HARBORS ON THE
ATLANTIC COAST OF THE SOUTHERN STATES.
Abstracts of Reports of General Q. A. GILLMORE.*
I. The character and magnitude of the kind, and, under the name of piers or works in progress along our Southern sea-walls, they are found in many imAtlantic border attract attention only portant commercial ports. when the brief summary of the year's The skill of the engineer is exercised work is published, and then excite a when applying such a method, in adaptmomentary interest, only, in the many ing it to the special conditions which who do not know that an engineering confront him in each case. A general problem of great importance is in pro- plan of procedure, when a harbor is to cess of solution.
be constructed at the mouth of a river, To aid, by artificial construction, in is to build piers or jetties out into the the establishment of a way permanently widened mouth of the river in such way open to navigation, and free from the as to continue the current of the stream, danger of accumulations of silt or sand, making the space between them as wide is the end sought. This requires, first as the throat of the harbor or the waterof all, an intimate knowledge of the way of the river; also to carry the jetties character and habits of all currents in up to or above the surface of the water. the neighborhood, so that by properly One effect of this plan is to move the directing them, they may aid, or at least throat of the harbor to the outer exshall not obstruct the end in view. tremity of the works, and to establish
There is a widespread popular notion there the same conditions, so far as the that the method of such improvement deposit of a bar is concerned, as formerby jetties was first successfully applied ly existed nearer the mouth of the river. at the mouth of the Mississippi, whereas In Charleston harbor, where the more such means have been employed, with important of the works covered by the more or less success, for nearly a cen- report are in progress, Gen. Gillmore tury. The improvements at the mouth proposes to construct the jetties lower of the Danube, at Currachee in India, than usual, keeping them entirely below and the harbor of Dublin, are of this low water; also to make the width en
closed between them less than one-half Annual Report upon the Improvement of the the width of the natural throat of the Rivers and Harbors on the coast of South Carolina, Georgia, and the Atlantic Coast of Florida, in charge harbor. The tide will therefore ebb and of Q. A. Gillmore, Lieut.-Col. of Engineers, and Bvt. flow over the tops of the jetties. The Maj. General, U. S. A.
Vol. XXIV.--No. 1.-1.
object sought is to cut a narrow and nor more than six ship channels across deep channel through the bar without the bar at any one time. The greatest moving the bar.
depth of water has sometimes been “The bar which stretches bow-shaped found in one channel and sometimes in
the entrance into Charleston another, being rarely less than 12 feet or Harbor, from Sullivan's Island on the more than 131 feet at mean low tide. north to Folly Island on the south side, “The channels, whether four or more, has not varied much in either location, have always existed in two groups or general direction, or magnitude within clusters, one in the northern and the the period covered by any trustworthy other in the southern curved portion of knowledge which we possess on the sub- the bar, and there has always been a ject.
deep and broad anchorage inside the “In the year 1852 a commission, com- straight reach of the bar abreast of posed of Prof. A. D. Bache, Superintend- Morris Island, ent of the United States Coast Survey; “This anchorage, sometimes called the Lieutenants J. N. Maffitt, M. F. Maury, 'main channel' and sometimes the 'outer and C. H. Davis, United States Navy; harbor,' varies in width from one-third and Lieut. J. D. Kurtz, United States to two-thirds of a mile between the 18 Army, in a report on Charleston Harbor foot curves, and in maximum low-water and Bar, made with special reference to depths from 20 to 45 feet. The direcworks of permanent improvement, stated tion of its central line is about north that a comparison of the chart of 1780, and south, and its length from the throat published in Des Barrés' Atlantic Nep- of the harbor between Morris and Sullitune, with those of 1821, 1825, and van's Islands to its southern terminus, 1851-'52, “shows that according to the where it spreads out in various channels earliest records the bar of Charleston has and shoals in crossing the bar, is fully varied comparatively but little in extent, five miles. At the extremities of this direction, or in distance from the mouth outer harbor or basin, several miles of the harbor.'
apart, are found the two groups of chan“Measured along its crest, or line of nels already mentioned, the most northerleast depths, the bar is ten miles in ly group being directly in front of the length, its north end on Sullivan's Island gorge of the harbor. being close up to the entrance or throat “The bar is essentially a drift-and-wave of the harbor, while its south end, rest- bar, produced in part by the upheaving ing on Folly Island, is six miles distant action of the waves when they approach therefrom. Its average width between the shore, and are converted by break the 18 foot curves is about 14 miles. ing into waves of translation, and in
“In many places the highest points of part by drift material carried along the the bar are only 3 to 4 feet below the coast by surf currents, especially by level of mean low-water, although the those produced by northeast storms. average depths along the crest are con- The peculiar location of the bar, largely siderably greater
to the southward of the gorge of the “The main central body of the bar, 'harbor, and the conditions under which lying near due north and south, is nearly a very large proportion of the ebb-flow is straight for a length of over five miles, diverted from its most direct path, and has its crest parallel to the main shore forced to skirt the main coast for several south of the entrance and at a mean dis- miles before it can find a passage to the tance of about two miles from it, and is sea, indicate the controlling power of not at the present time, and, so far as we these storms. know, never has been traversed by prac "The material composing the surface ticable ship channels.
of the bar closely resembles that usually “The northern and southern extremi- found on the sea shore between high and ties of the bar are formed by rather low water in that section of the country, sharp curves, which connect the straight being shells and fragments of shells, or portion already mentioned with the shore silicious sand, or a mixture of them all. above and below the harbor.
It is easily thrown into suspension by “So far as we can now ascertain there waves, and is moved by a moderate curappear never to have been less than four rent.