make in crossing the stream is 12 knots in a northeasterly direction for a distance of 40 miles from the 100-fathom (183 m) curve.

Crossing the Gulf Stream at Jupiter or Fowey Rocks, an average allowance of 21⁄2 knots in a northerly direction should be made for the set of the current.

Crossing the stream from Habana, a fair allowance for the average current between 100-fathom (183 m) curves is 1.1 knots in an east-northeasterly direction.

The approximate mean positions of the inner edge and axis (point) where greatest velocity may be found) are indicated in the following table:

Approximate mean position of the Gulf Stream

Locality

North of Habana, Cuba.
Southeast of Key West, Fla..
East of Fowey Rocks, Fla.
East of Miami Beach, Fla.
East of Palm Beach, Fla..
East of Jupiter Inlet, Fla.
East of Cape Canaveral, Fla..
East of Daytona Beach, Fla.
East of Ormond Beach, Fla..

East of St. Augustine, Fla. (coast line).

East of Jacksonville, Fla. (coast line)

Southeast of Savannah, Ga. (coast line)

Southeast of Charleston, S. C. (coast line).

Southeast of Myrtle Beach, S. C.

Southeast of Cape Fear, N. C. (light).

Southeast of Cape Lookout, N. C. (light).

Southeast of Cape Hatteras, N. C..

Southeast of Virginia Beach, Va.

Southeast of Atlantic City, N. J.

Southeast of Sandy Hook, N. J.

At the western end of the Straits of Florida the limits of the Gulf Stream have not yet been well defined, and for this reason the location of the inner edge has been omitted for Habana, Cuba, and Key West, Fla., in the above table. Between Fowey Rocks and Jupiter Inlet the inner edge is deflected westward and lies very close to the shore line.

Along the Florida Reefs, between Alligator Reef and Dry Tortugas, the distance of the northerly edge of the Gulf Stream from the edge of the reefs gradually increases toward the westward. Off Alligator Reef it is quite close inshore, while off Rebecca Shoal and Dry Tortugas it is possibly 15 to 20 miles south of the 100-fathom (183 m) curve. Between the reefs and the northern edge of the Gulf Stream the currents are ordinarily tidal and are subject at all times to considerable modification by local winds and barometric conditions. This neutral zone varies in both length and breadth; it may extend along the reefs a greater or less distance than stated, and its width varies as the northern edge of the Gulf Stream approaches or recedes from the reefs.

The approximate position of the axis of the Gulf Stream for various regions is shown on the following Coast and Geodetic Survey

charts: No. 1002, Straits of Florida; No. 1003, South Carolina to Cuba; No. 1112, Cape Canaveral to Key West; No. 1113, Alligator Reef to Habana. Chart No. 1001 shows also the position of the inner edge of the Gulf Stream from Chesapeake Bay to Straits of Florida.

WIND CURRENTS

There are given below the results of recent investigations on the currents caused by local winds. These investigations are based on observations made on a number of the lightships along the Atlantic coast from Nantucket Shoals Lightship to Brunswick Lightship. The results, therefore, apply more directly along the route between lightships but are applicable also to the coastal sailing routes farther offshore.

Direction of current due to wind. It is evident that a wind continuing for some time will give rise to a current, the velocity of which increases with an increase in the velocity of the wind; and the mariner has taken it for granted that this current brought about by the wind sets in the same direction as the wind. But the results of careful observations show that this is not the case. Instead of setting with the wind, the current on the Atlantic coast of North America produced by local winds sets on the average about 20° to the right of the wind.

For example, a wind blowing from north will, on the North Atlantic coast, bring about a current that sets not south but about 20° to the right of south, or 200°. Similarly a wind from south will produce a current setting 20° to the right of north, or 20°. It is to be noted that while the current due to the wind will, on the North Alantic coast, set 20° to the right of the wind direction, the current which a vessel experiences at any time is the resultant of the combined actions of the tidal current, the wind current, and any other currents, such as the Gulf Stream or currents due to river discharge. Velocity of current due to wind.-The velocity of the current brought about by winds of different velocities is given in the table below It will be seen that on the Atlantic coast of the United States the velocity of the wind current is about 12 percent of the velocity of the wind.

Table of current velocity due to wind-North Atlantic coast

An easily remembered working rule to get the velocity of the current due to wind along the Atlantic coast is to multiply the velocity of the wind (in miles per hour) by 12 and point off two places. This will give the velocity of the current in knots. For example, to determine the current due to a 40-mile wind we have 40×112=60, and pointing off two decimal places gives 0.60, or six-tenths of a knot.

VARIATION OF THE COMPASS

The magnetic variations for 1936 and annual increase at points mentioned are as follows:

The following data concerning the Intracoastal Waterway, from Boston to the Rio Grande, the Route across Florida, the New York Canal System, the Lakes to Gulf Waterway, and the other river channels tributary to the Mississippi are included for ready refer

ence.

THE INTRACOASTAL WATERWAY

The Intracoastal Waterway affords a protected route, with the exception of various short sections, for vessels between Boston, Mass., and the Rio Grande, a distance of approximately 3,100 miles. No toll is charged for passage as the waterway is under Federal jurisdiction. Navigation is restricted, however, by the limiting depths, and horizontal and vertical clearances in the various sections of the waterway. The controlling horizontal clearance for the entire route is 391/2 feet (12.0 m) at the Palm Valley bridge in Florida. The locks in the alternate route through the Dismal Swamp Canal have a controlling horizontal clearance of 36 feet (11.0 m). The height of the masts of vessels is restricted by the vertical lift bridge at Boynton, Fla., to 42.6 feet (13.0 m).

Boston to New York Harbor.-Between Boston and Long Island Sound it is necessary to pass through comparatively exposed waters and no inland route exists except for the passage through the Cape Cod Canal and its approaches.

The Cape Cod Canal extends from Cape Cod Bay to Buzzards Bay and with its approach channels affords a sea-level waterway 12.6 miles in length. The controlling depth on July 31, 1935, was 24 feet (7.3 m) at mean low water in the canal. Widening and deepening of the canal and the work of constructing two new high-level highway bridges and a vertical lift railroad bridge to replace the existing drawbridges is now nearly completed. The controlling vertical clearance through the canal is 135 feet (41 m) at high water.

(1) THE INTRACOASTAL WATERWAY

51

From the canal, the route generally followed extends from Buzzards Bay to the Atlantic Ocean, thence through Block Island and Long Island Sounds and the East River to upper New York Bay, thence through the more open waters to lower New York Bay. There are numerous harbors on both sides of Long Island Sound.

An inland waterway extends along a portion of the south side of Long Island and affords a protected route from Gardeners Bay to East Rockaway Inlet with a controlling depth of 6 feet (1.8 m) in May 1935 at the south approach of the Shinnecock Canal.

New York Harbor to Delaware Bay.-An outside run between New York Bay and Delaware Bay is now necessary except for vessels whose draft permits use of the New Jersey Inland Waterway. This waterway is entered at its northern end through Manasquan Inlet, 23 miles south of Sandy Hook, and extends for 109 nautical miles to Cape May Inlet at Cape May. The waterway is maintained by the State of New Jersey as a 6-foot (1.8 m) project, but the controlling depth in October 1935 was reported to be 4 feet (1.2 m). Vessels are obliged to run outside from Sandy Hook to Manasquan Inlet, and to round Cape May and cross the lower reaches of Delaware Bay to the Chesapeake and Delaware Canal.

The Intracoastal Waterway formerly extended from New York Bay through the Raritan River, the Delaware and Raritan Canal, and the Delaware River to Delaware Bay. The Delaware and Raritan Canal, now under the jurisdiction of the State of New Jersey, has not been open to navigation since 1933.

Investigation of the New York Bay-Delaware River section of the Intracoastal Waterway is now actively in progress for the purpose of finding and recommending the most desirable route for a sea-level canal of adequate width and a minimum depth of 25 feet (7.6 m) across the State of New Jersey.

Delaware Bay to Norfolk.-The Chesapeake and Delaware Canal is a sea-level route which extends for a distance of 19 miles, from Reedy Point on the Delaware River 40 miles below Philadelphia, Pa., to the junction of Back Creek and Elk River, about 4 miles west of Chesapeake City, Md. In June 1934 the controlling depth was 10 feet (3.0 m), although the conditions are such that a draft of 12 feet (3.6 m) can usually be carried through by taking advantage of the tide.

From the junction of the canal into Chesapeake Bay to Norfolk, a distance of 210 miles through Chesapeake Bay, depths in excess of 12 feet (3.6 m) obtain.

Norfolk to Beaufort Entrance.-A sea-level waterway, paralleling the Atlantic coast, with a tidal lock at Great Bridge, Va., is afforded by the route through the Albemarle and Chesapeake Canal, the Alligator River-Pungo River Canal, and the sounds of North Carolina. The project for this waterway provides a depth of 12 feet (3.6 m) at mean low water, but the controlling depth was 11 feet (3.4 m) in the early part of 1935.

The alternate route to Albemarle Sound by way of the Dismal Swamp Canal, a lock canal, has a controlling depth of 9 feet (2.7 m).

Navigation is practicable throughout the year on both of the abovenamed routes.

Beaufort Entrance to Winyah Bay.-In June 1934 there was a controlling depth of 11 feet (3.4 m) from Beaufort Harbor to Swansboro, thence 1012 feet (3.2 m) to the Cape Fear River.

The new cut from Cape Fear River to Winyah Bay has not yet been completed, and vessels whose draft will not permit crossing the bar at Little River Inlet, S. C., are required to go outside from Cape Fear River to Winyah Bay, a distance of about 73 miles.

A depth of 8 feet (2.4 m) is available in the waterway to Little River Inlet from Cape Fear River, a distance of about 28 miles. In August 1935 the low water depth in Little River Inlet was about 412 feet (1.4 m). The channel across the bar, although subject to change, is well buoyed. Navigation, however, should not be attempted except on a rising tide and only after securing local information. The distance from Little River Inlet Lighted Bell Buoy to Winyah Bay Entrance Bell Buoy is 47 nautical miles.

Winyah Bay to Charleston.-Dredging of this section of the waterway to a project depth of 10 feet (3.0 m) is now in progress (April 1935). In September 1935 it was reported that navigation was restricted to a draft of 32 feet (1.1 m) at mean low water at one point and 52 feet (1.7 m) at mean low water through several reaches between Minim Creek and Charleston.

Charleston to the St. Johns River, through the rivers and sounds of South Carolina and Georgia. The project depth through the main waterway is 7 feet (2.1 m). The controlling depth for this section is in Brickyard Creek, north of Beaufort, S. C., where there is a depth of 5 feet (1.5 m) at mean low water.

St. Johns River to Miami.-This section of the waterway extends from the St. Johns River by way of the old Florida East Coast Canal through natural and connecting waterways to Miami on Biscayne Bay. A project depth of 8 feet (2.4 m) at mean low water is being maintained, although the controlling depth may be temporarily reduced by shoaling.

Miami to Key West.-The route north of the Florida Keys has a controlling depth of 4 feet (1.2 m), which occurs in the northern channel through Shell Key Bank.

The route through Hawk Channel has a controlling depth of 10 feet (3.0 m).

Anchorages, sheltered from all ordinary weather, may be found anywhere along these passages, in the lee of reefs and keys.

Key West to the Rio Grande.-The various inside routes and the sections of the Intracoastal Waterway along the Gulf Coast are described in geographical sequence in various parts of this volume and Section No. 34 of this volume, p. 35, gives a résumé of the entire inside route along the Gulf Coast.

Charts covering the routes along the Atlantic Coast and the Gulf of Mexico are published by the United States Coast and Geodetic Survey.

The inland waters are covered in the following publications of the Coast and Geodetic Survey:

United States Coast Pilot, Section B, covering the coast and inland waters from Race Point, Cape Cod, to Sandy Hook, including Long Island Sound, New York Harbor, and tributaries.