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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 about 20° to the right of the wind.
For example, a wind blowing from the north will, on the North Atlantic coast, bring about a current that sets not south but about 20° to the right of south, or S. 20° W. Similarly, a wind from south will produce a current setting 20° to the right of north, or N. 20°E. It is to be noted that while the current due to the wind will on the North Atlantic 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.
Table of current direction due to wind—North Atlantic Coast.
S. 20° W. S. 65° W. N. 70° W. N. 25° W. N. 20° E. N. 65° E. S. 70° E. S. 25° E.
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 112 per cent 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 is to multiply the velocity of the wind (in miles per hour) by 112 and point off two places. This will give the velocity of the current in knots. For example, the current due to a 40-mile wind would be 40 by 112=.60, or six-tenths of a knot.
DIRECTIONS, NEW YORK TO STRAITS OF FLORIDA.
NEW YORK TO CAPE HATTERAS.-From Scotland light vessel steer 181° true (S. 7 W. mag.) for 42 miles, or from Ambrose Channel light vessel steer 186° true (S. by W. 38 W. mag.) for 43 miles, to a position 8 miles off Barnegat lighthouse bearing 276o true (WNW. 5/8 W. mag.); then steer 193° 30' true (S. by W. 34 W. mag.) for 287 miles to Diamond Shoal light vessel.
DELAWARE BAY TO CAPE HATTERAS.–From Overfalls light vessel steer 150o true (SSE. mag.) for 251,2 miles to Fenwick Island Shoal light vessel, and then steer 187° 30' true (S. by W. 14 mag.) for 203 miles to Diamond Shoal light vessel.
CHESAPEAKE BAY TO CAPE HATTERAS.–From Chesapeake Bay entrance gas and whistling buoy steer 158o true (S. by E. 12 E. mag.)
for 72 miles to a position with Bodie Island lighthouse bearing 287° true (WNW. mag.) distant 14 miles. Then steer 182o true (s. 578 W. mag.) for 40 miles to Diamond Shoal light vessel, leaving Wimble Shoal gas buoy 31,2 miles to starboard.
The currents may be expected to set with the wind up or down the coast. High velocities of current may occur either with heavy gales or with long-continued gales from one direction, the estimated maximum velocity near the coast being 2 to 3 knots. In depths of 20 fathoms or more, 0.5 to 1 knot is regarded as nearer an average
of what may be expected. Currents produced by on-shore winds set inshore as well as alongshore.
CAPE HATTERAS TO JUPITER.–From Diamond Shoal light vessel there are two routes to the Straits of Florida. Most of the regular lines use the route outside of the Gulf Stream. All vessels bound to any port as far south as St. Johns River follow the coast inside the Stream.
OUTSIDE ROUTE.—From Diamond Shoal light vessel across the Gulf Stream make good the course 191° 30' true (S. by W. 1/2 W. mag.) for 173 miles to latitude 32° 15' N., longitude 76° 00' W. Under ordinary conditions an average allowance should be made for a 1-knot current setting 45° true for the entire run; with northeasterly winds there may be practically no current, while southerly, and especially south west, winds may increase it considerably. Observations should be obtained as often as possible.
From the above latitude and longitude make good the course 212° true (SW. by S. mag.) for 300 miles to latitude 28° 00' N., longitude 79° 00' W. There is uncertainty as to the currents that may be expected on this run. It is probable that a Gulf Stream set of 0.5 knot against the vessel, and as the Bahama Bank is approached possibly some easterly drift also will be experienced. With northeasterly winds it is stated that a southwesterly set of 0.5 knot has been experienced. This and the easterly set mentioned are the dangerous ones to guard against in order not to overrun and get too close to Matanilla Shoal. Observations are the only guide and should be obtained as often as possible. In case of doubt from about latitude 28° N. vessels can stand westward and watch the lead carefully to pick up the edge of the bank on the Florida coast northward of Jupiter.
Matanilla Shoal should be given a wide berth. It is stated that discoloration of the water can not be relied upon to avoid the shoal, the current setting on it not permitting this usual reef warning,
From the position in latitude 28° 00' N., longitude 79° 00' W., the course is shaped across the Gulf Stream for Jupiter Inlet lighthouse. On this course an allowance should be made for a northerly current, averaging about 214 knots for the entire run of about 80 miles. will therefore be necessary to shape the course for a position some 8 or 10 miles southeastward of Jupiter Inlet light to allow for the northerly set. When fixing the position by bearings on the light, keep in mind that while outside the 100-fathom curve the vessel is probably in the full strength of the Gulf Stream, where the northerly current may average a velocity of 4 knots. If the light is on the starboard bow, the vessel will be much closer to it than indicated by the distance run between the successive bearings on it.
INSIDE ROUTE.-From 1 mile off Diamond Shoal light vessel make good a 229° 30' true (SW. 34 W. mag.) course for 149 miles, which leads close eastward of Cape Lookout Shoals light vessel and 1 mile eastward of Frying Pan Shoals gas, whistling, and submarine bell buoy. From the latter position make good a 234° 30' true (SW. by W. mag.) course for 150 miles to latitude 32° 00' N., longitude 80° 0/' W. Then make good a 203° true (SSW. 18 W. mag.) course for 65 miles to latitude 31° 00' N., longitude 80° 30' W. Then make good a 180° true (S. mag.) course for 90 miles to latitude 29° 30' N., longitude 80° 30' W. Then make good a 169o true (S. by E. mag.) course for 52 miles, which should lead to a position 3 or 4 miles eastward of Hetzel Shoal gas and whistling buoy.
These courses lead in depths of 17 to 20 fathoms. In approaching and passing the shoals off Cape Canaveral care must be exercised; the depth should not be shoaled to less than 13 fathoms.
The current of the Gulf Stream may be expected under ordinary conditions to set against the vessel for the entire run with a velocity of about 0.5 to 0.8 knot, the direction of the current following the curve of the coast. It must be remembered, however, that the effect of winds is almost immediately felt on the currents, and that with northerly, and especially northeasterly, winds a current of about 1 knot will set with it along the coast. Southerly, and especially southwesterly, winds increase the velocity of the Gulf Stream.
Passing 3 or 4 miles eastward of Hetzel Shoal gas and whistling buoy, a 168 true (S. by E. 19 E. mag.) course will lead the same distance eastward of Bethel Shoal gas and whistling buoy, and this course should be continued until Jupiter Inlet lighthouse is made on the starboard bow. Then shape the course to pass from 3 to 6 miles eastward of it. On this run the 15-fathom curve is a good guide. The current of the Gulf Stream may be expected under ordinary conditions to have a velocity of about 0.7 knot off Cape Canaveral, increasing to 1.5 or 2 knots off Jupiter Inlet lighthouse.
STRAITS OF FLORIDA-CAUTION AS TO CURRENTS.—The attention of navigators is called to the fact that most of the wrecks on Florida Reefs occur in the case of vessels bound southward, especially at night; they generally occur on reefs lying about halfway between the lights; and the region of maximum frequency of wrecks is between Carysfort Reef and Alligator Reef, and to a less extent between Fowey Rocks and Carysfort Reef and between Alligator Reef and Sombrero Rey.
From a consideration of the data it can be stated that nearly all casualties are due to one cause—an underestimate of the strength of the Gulf Stream against the vessel. This leads to two errors in navigation: First, the distance made good over the bottom is less than assumed or indicated by the log, and when skirting the reefs the course is changed too soon for the next light and before sighting it; second, the vessel underrunning her log is closer to the reefs than indicated by the four-point bearing, and this error is greater for slow vessels than for fast ones.
At night, when bound southward and navigating at a safe distance from the reefs between Fowey Rocks and Sombrero Key, it is on the side of safety to assume that the vessel is steaming against a 3 or 4 knot current, and from one light to hold a course that will insure
clearing the reefs until the next light is sighted. It is also well to remember that near the reefs there is a tidal current, possibly as much as 0.5 knot in places directly on and off the reefs on the rising and falling tides, respectively.
On the other hand, when bound northward and following Florida Reefs between Sombrero Key and Fowey Rocks it is on the side of safety to underestimate the velocity of the Gulf Stream with the vessel; the courses should be laid well clear of the reefs, which is the usual practice. Vessels are rarely lost on Florida Reefs when bound northward, except when crossing the Stream from Habana and making the reefs in misty or rainy weather.
The following are extracts from a report of a stranding: Rounded Great Isaac Light at a distance of 244 miles, steered by compass and log 227° true for 20 miles, and then steered 224o true. By bow and beam bearing Fowey Rocks light was 12 miles distant when abeam, but on account of the northerly current it was probably about 7 miles. The vessel stranded on the north end of Long Reef, having had a northerly set of 17 miles, or an average of about 244 knots for the crossing from Great Isaac light to Florida Reefs.
Along the keys there is a slight tidal drift, of not more than 0.5 knot, setting on and off the reefs. This current will probably not be noticeable at a greater distance from the reefs than 1 mile. Between the keys, in the passes connecting Hawk Channel and Florida Bay, the current has considerable velocity (3 to 4 knots) in the immediate vicinity of the openings, and is felt to some extent, probably, on and beyond the usual sailing line in Hawk Channel. When not influenced by winds the maximum current northwestward into Florida Bay and southeastward into Hawk Channel through the openings between the keys occurs about 1 hour before high and low waters, respectively, in the straits. The northwesterly current is increased by easterly winds and the southeasterly current by westerly winds, due to the effect of these winds in driving out or piling up, respectively, the water in Florida Bay.
JUPITER TO FOWEY ROCKS.—Vessels follow the coast as close as safety permits—in the daytime at a distance of 1 to 142 miles to Hillsboro Inlet lighthouse, then 112 to 2 miles off until abreast Biscayne Shoal buoy, and pass 1 mile eastward of Florida Reefs North End gas buoy and Fowey Rocks lighthouse. Close attention should be given to the lead, and courses not depended upon entirely, and checked frequently. From Jupiter to Lake Worth Inlet the depth should not be shoaled to less than 13 fathoms, and then keep in over 15 fathoms. Southward of Lake Worth Inlet the depths increase so rapidly offshore that the hand lead can not be depended upon to insure safety for deep-draft vessels.
A narrow ridge, on which least depths of 7 to 12 fathoms were found and with somewhat deeper water inside it, lies from 1 to 11/2 miles from this coast. This ridge has not been closely developed, and should be avoided by deep-draft vessels. A vessel with a draft of 23 feet reports striking at a point 142 miles from shore and 6 miles southward of Jupiter Inlet light, and another with a draft of 19 feet at a point 134 miles from shore and 1812 miles northward of Fowey Rocks light. It is suspected that the reported grounding of several steamers on ridges south of New River Inlet is in a measure attributable to the indistinct shore line for which the line of trees
along the west edge of the marsh is mistaken, which would place a vessel 1 to 142 miles inshore of her intended position.
The current of the Gulf Stream may be expected to have a velocity of 1.5 knots from well northward of Jupiter until southward of West Palm Beach, then 1 knot to Hillsboro Inlet, and then 0.7 knot to Fowey Rocks. The velocity increases rapidly offshore.
At night, from a position 6 miles off Jupiter Inlet light, make good a 183° true (S. 178 W.mag.) course for 82 miles, passing 242 miles off the coast southward of Lake Worth Inlet, 312 miles off Hillsboro Inlet lighthouse, 3 miles off Biscayne Shoal gas and bell buoy, 212 miles off Florida Reefs North End gas and bell buoy, and 2 miles off Fowey Rocks lighthouse. The 15-fathom curve is a safe guide between Jupiter and Lake Worth Inlet. On this course the current of the Gulf Stream should be assumed to have a velocity of 2 knots in determining the distance off the lights by bow and beam bearings, and more if farther offshore than the distances stated.
FOWEY ROCKS TO SAND KEY.-Vessels follow the Florida Reefs from 1 to 2 miles off in the daytime and 2 to 4 miles off at night. The position should be checked on the aids as passed and on the lights and sectors at night. Care must be taken not to get inside of the line of reefs, beacons (spindles), buoys, or lighthouses, especially when passing parts of the reef that lie well back of the edge and do not break or show near the surface. The color of the water does not always mark the edge of the reefs.
Except in the vicinity of Fowey Rocks, where the 100-fathom curve is only about 2 miles outside the reef, the 50-fathom curve lies from 2 to 3 miles from Florida Reefs, and this is about the least depth that can be depended upon to insure safety in skirting them. The hand lead is practically of no value as an aid and should not be depended on.
The reefs are fringed in places with broken ground, which as a measure of safety should be avoided by deep-draft vessels where the depths are less than 10 or 12 fathoms.
Any crossing of the Gulf Stream should be regarded as difficult, on account of the strong current of variable velocity for which it may not be possible to make a proper allowance and the abrupt shoaling inside the 100-fathom curve. The axis of the Gulf Stream is nearest the reefs from about 10 miles northward of Carysfort Reef lighthouse to Molasses Reef lighthouse.
Vessels bound for Habana generally shape the course for that port when abreast of Alligator Reef lighthouse.
The following courses may serve as a check, and the distances at which they are laid from the reefs should be regarded as a minimum to insure safety :
In the daytime. From 1 mile off Fowey Rocks lighthouse make good the course 187o true (S. 1/2 W. mag.) for 7 miles to 1 mile off Triumph Reef beacon “O”; then 193o true ($. by W. mag:), for 642 miles to 1 mile off Pacific Reef lighthouse; then 203° true (S. by W.78 W. mag.) for 10 miles, passing 12 mile off Turtle Harbor buoy (nun, No. 2), and to a position 1 mile off Carysfort Reef lighthouse.
From 1 mile off Carysfort Reef lighthouse make good the course 207° true (SSW. 1/4 W. mag.) for 6 miles to 114 miles off The Elbow beacon “J”; then 219o true (SW. 58 S. mag.) for 10 miles to 114