come more frequently with easterly and southerly winds; northerly winds clear them away. Southwesterly winds are usually accompanied by haze. (See table of "Hours of operation of fog signals p. 8.)

Ice. In mild winters ice interferes but little with the movements of vessels in Nantucket and Vineyard Sounds. In severe winters drift ice accumulates and renders the movements of sailing vessels hazardous, and sometimes almost completely obstructs their progress for periods of as much as six weeks. During northerly winds which prevail in winter the passage along the north shore through Nantucket Sound will be clear when other parts of the sound are unsafe. Steamers force their way through the ice. Sailing vessels, if caught in a floe while entering by Pollock Rip Channel and Butlers Hole, are almost certain to be carried on the shoals.

It should be borne in mind that the buoys and even lightships are liable to be moved out of their positions by drift ice.

CURRENTS, NANTUCKET AND VINEYARD SOUNDS AND APPROACHES

From Race Point to Chatham Lights the tidal currents are comparatively weak, being on the average not more than 0.5 to 1 knot at time of strength, running approximately parallel to the coast, but the time of current changes rapidly. About 7 miles east of Nauset Beach Light the flood or northerly stream attains its maximum strength about 134 hours after maximum flood at Pollock Rip Channel (approximately 2 hours after low water at Boston) while about 8 miles east of Chatham Light the northerly current is at its strength about 12 hour after maximum flood at Pollock Rip Channel (approximately 34 hour after low water at Boston).

Pollock Rip Channel.-Predicted times of slack water and times and velocities of strength of flood and ebb in advance for every day of the year, are given in the Current Tables, Atlantic Coast, published annually by the United States Coast and Geodetic Survey. At a point midway between lighted buoys Nos. 1 and 2 at the eastern end of the dredged cut in Pollock Rip Channel the flood current sets about 55° true (ENE. 14 E. mag.) and the ebb 225° true (SW. by W. W. mag.) or at an angle of approximately 20° to the axis of the channel.

Stonehorse Shoal Lightship.-The strength of the flood current occurs about 1 hour after maximum flood at Pollock Rip Channel (approximately 114 hours after low water at Boston) and sets 60° true (ENE. 34 E. mg.) with a velocity of about 211⁄2 knots. The strength of ebb occurs about 1 hour after maximum ebb at Pollock Rip Channel (approximately 114 hours after high water at Boston) and sets 240° true (WSW. 34 W. mag.) with a velocity of about 212 knots. Slack waters occur about 1/2 hour after the current turns northeastward and 34 hour after the current turns southwestward at Pollock Rip Channel (approximately 2 hours before the time of low and 11⁄2 hours before the time of high water at Boston). The greatest observed velocity was 3.6 knots.

South end of Great Round Shoal.-The tidal current is rotary, turning clockwise. The strength of the flood occurs about 24 hours after maximum flood at Pollock Rip Channel (approximately 312 hours after low water at Boston) and sets 65° true (E. 34 N. mag.)

161875°-33-4

with a velocity of about 11⁄2 knots. The strength of the ebb occurs about 24 hours after maximum ebb at Pollock Rip Channel (approximately 22 hours after high water at Boston) and sets 245° true (W. 7% S. mag.) with a velocity of about 11⁄2 knots. There is no true slack, since the current is rotary. The minimum currents are about 2 knot and set 335° true (N. % W. mag) about 14 hours after the current turns northeastward at Pollock Rip Channel (approximately 12 hour before low water at Boston) and 155° true (S. 3 E. mag.) about 234 hours after the current turns southwestward at Pollock Rip Channel (approximately 2 hour before high water at Boston). The greatest observed velocity was 2.5 knots in a southwesterly direction, during a gale of 48 to 65 miles an hour.

From the eastern entrance of Nantucket Sound to Hedge Fence Lightship the time of current becomes gradually later; the average velocity at strength varies from about 14 to 2 knots, the flood setting easterly and the ebb westerly.

From Hedge Fence Lightship westward, through Vineyard Sound to Gay Head, the time of current becomes somewhat earlier. The average velocity at time of strength increases from 114 knots at Hedge Fence Lightship to 24 knots off West Chop Light, and then gradually diminishes to 12 knots off Gay Head Light. See "Current diagram Nantucket and Vineyard Sounds," in the Current Tables, Atlantic Coast.

Handkerchief Lightship.-Slack water before flood occurs about 14 hours after the current turns northeastward at Pollock Rip Channel (approximately 1 hour before low water at Boston). Strength of flood occurs about 214 hours after maximum flood at Pollock Rip Channel (approximately 12 hours after low water at Boston) and sets 95° true (ESE. 14 E. mag.) with a velocity of about 134 knots. Slack before ebb occurs about 12 hours after the current turns southwestward at Pollock Rip Channel (approximately 1 hour before high water at Boston). Strength of ebb occurs about 12 hours after maximum ebb at Pollock Rip Channel (approximately 14 hours after high water at Boston) and sets 245° true (W. % S. mag.) with a velocity of about 134 knots. The greatest observed velocity was 2.3 knots set 101° true (SE. by E. 34 E. mag.).

Cross Rip Lightship.-Slack water before flood occurs about 2 hours after the current turns northeastward at Pollock Rip Channel (approximately the time of low water at Boston). Strength of flood occurs about 3 hours after maximum flood at Pollock Rip Channel (approximately 314 hours after low water at Boston) and sets 100° true (SE. by E. 34 E. mag.) with a velocity of about 11⁄2 knots. Slack before ebb occurs about 22 hours after the current turns southwestward at Pollock Rip Channel (approximately the time of high water at Boston). Strength of ebb occurs about 234 hours after maximum ebb at Pollock Rip Channel (approximately 3 hours after high water at Boston) and sets 270° true (WNW. 5% W. mag.) with a velocity of 1 knot. The greatest observed velocity was 2.4 knots, setting southeasterly during a northwesterly wind with a velocity of 28 miles an hour.

Muskeget Channel.-The currents through Muskeget Channel are strong, having a velocity of 3 knots or more at strength. The

strength of flood comes about 2 hours after maximum flood at Pollock Rip Channel (approximately 22 hours after low water at Boston) and sets northeasterly. The strength of ebb comes about 2 hours after maximum ebb at Pollock Rip Channel (approximately 212 hours after high water at Boston) and sets southwesterly. Slack water occurs about 2 hours after the slacks at Pollock Rip Channel (approximately 12 hour before time of high or low water at Boston). Hedge Fence Lightship.-Slack water before flood comes about 3 hours after the current turns northeastward at Pollock Rip Channel (approximately 34 hour after low water at Boston). The strength of flood occurs about 311⁄2 hours after maximum flood at Pollock Rip Channel (approximately 21⁄2 hours before high water at Boston) and sets 110° true (SE. 7% E. mag.) with a velocity of about 112 knots. Slack water before ebb occurs about 34 hours after the current turns southwestward at Pollock Rip Channel (approximately 1 hour after high water at Boston). The strength of ebb occurs about 31⁄2 hours after maximum ebb at Pollock Rip Channel (approximately 22 hours before low water at Boston) and sets 270° true (WNW. 5% W. mag.) with a velocity of about 14 knots. The greatest observed velocity was 21⁄2 knots, setting southeasterly during a northwesterly wind with a velocity of 28 miles an hour.

Vineyard Sound Lightship. The tidal current is rotary, turning clockwise. The velocity is small averaging about 1/2 knot at strength; the average minimum is about 1/4 knot. The strength of flood occurs about 3/4 hour before the maximum flood at Pollock Rip Channel (approximately 12 hour before the time of low water at Boston) and sets 325° true (N. by W. 34 W. mag.). The strength of the ebb occurs about 14 hour before maximum ebb at Pollock Rip Channel (approximately the time of high water at Boston) and sets 165° true (S. mag.). Since the tidal currents are small, winds greatly affect them, and the current will generally set with the wind. Observed velocities seldom exceed 1 knot.

DIRECTIONS, NANTUCKET AND VINEYARD SOUNDS

Directions for approaching Vineyard Sound from southward and westward are given on page 24. See also Tables Nos. 2 and 3, Courses and Distances, page 29 and 30.

General remarks.-The numerous shoals, strong tidal currents, at certain seasons thick fog, and the large number of vessels which are often encountered in the narrow parts of the channels, call for more than the ordinary attention of the navigator. In clear weather, in the day time or at night, the aids are readily distinguished and sufficiently numerous to enable a stranger to follow the channel without difficulty.

In clear weather sailing vessels with a favorable current, and with some local knowledge, beat through the sounds against a head wind, and, when they find they are losing ground come to anchor on either side of the prohibited anchorage or under the lee of one of the shoals or in one of the harbors until the wind or current changes. The strongest currents will be encountered in Pollock Rip Channel, between Stonehorse Shoal and Handkerchief Lightships, off East and West Chop, and in Vineyard Sound; in some places the current

sets directly on the shoals and in a calm sailing vessels are sometimes obliged to anchor to prevent going aground. Most of the shoals rise abruptly from deep water, and the soundings are very irregular in depth and can not everywhere be depended on alone for warning of too close an approach to danger.

In thick weather or fog, when the aids can not be seen, sailing vessels and steamers in the vicinity of Pollock Rip Channel desiring to anchor are cautioned against anchoring in the channel or near the buoys or lightships (see "Prohibited anchorages," p. 40). The large number of steamers and tows passing through the slue in thick weather, depending entirely on the sound signals of the aids (making it necessary for them to pass close to the latter), increases the probability of collision for vessels at anchor close to them, and as there is seldom a necessity for such action, sailing vessels should avoid doing so; there is no excuse for a steamer anchoring near the aids.

Vessels when in the vicinity of Pollock Rip entrance lighted whistle buoy, and desiring to anchor (wind and sea permitting), should first be sure of their position and then stand northwestward and anchor west of a line joining Bearses Shoal North End buoy No. 2A and Chatham Bar nun buoy No. 2. Or, run 1 mile to southward and anchor in 5 to 7 fathoms (9 to 13 m) northeastward of Broken Part of Pollock Rip.

When in the vicinity of Stonehorse Shoal Lightship, and desiring to anchor, steer 136° true (SSE. 1⁄2 E. mag.) for 12 miles from the lightship and anchor in about 412 fathoms (8 m) and about 14 miles southward of the sailing line.

Vessels when between Butlers Hole and Handkerchief Lightship, or when in the vicinity of the latter can anchor anywhere southwestward of Stonehorse Shoal in 44 to 62 fathoms (7.7 to 11.9 m), taking care to keep Stonehorse Shoal lighted bell buoy No. 9 bearing westward of 35° true (NE. 1⁄2 E. mag.), and to be 1 to 12 miles southeastward of the sailing line, so as to keep outside of the prohibited anchorage. Or they may anchor northwestward of Handkerchief Lightship and on the west side of Handkerchief Shoal. (See also "Anchorages," preceding.)

Great Round Shoal Channel is used mostly by the very deep draft vessels passing through the sounds and sometimes by sailing vessels that are headed by the wind so as to prevent their working through Pollock Rip Channel. In thick weather a vessel may anchor (wind and sea permitting) anywhere in this channel and wait for clear weather; the bottom is generally sand, gravel, pebbles, or a combination of these. The tidal currents are not as strong as in Pollock Rip Channel, nor is the danger from collision as great as in the former. The sound signals are not as numerous as in Pollock Rip Channel. Easterly winds make high tides and strong westerly currents. Westerly winds make low tides and strong easterly cur

rents.

See Tables Nos. 4 and 5, pages 31 and 32, for courses and distances. The directions are good for a depth of 29 feet (8.8 m) at low water through Pollock Rip Channel and through Great Round Shoal Channel. These channels are subject to change, and vessels drawing over 27 feet (8.2 m) should wait for a favorable tide.

With southerly or westerly gales there is a heavy sea in the westerly entrance of Vineyard Sound, and a heavy, ugly sea occurs at times in Vineyard Sound off the entrance of Quicks Hole. To avoid this sea, tows especially, frequently use Quicks Hole.

DIRECTIONS ALONG THE NORTH SHORE

This passage has broken ground with depths of 16 and 17 feet (4.9 and 5.2 m) in places, and is not recommended at low water for a greater draft than about 14 feet (4.3 m). Strangers should not attempt it at night.

To pass southward of Bishop and Clerks. From a position close westward of Handkerchief Lightship make good a 292° true (NW. 5% W. mag.) course for 1134 miles, passing 134 miles southwestward of Bishop and Clerks Lighthouse and 1/2 mile northeastward of Broken Ground black buoy; Hyannis Breakwater Light and lighted bell buoy No. 14 should then be in range, and Bishop and Clerks Lighthouse should bear 74° true (E. % N. mag.). Then steer 254° true (W. % S. mag.) for 534 miles, with Bishop and Clerks Lighthouse astern, to close southward of Wreck Shoal spar buoy No. 18.

To pass northward of Bishop and Clerks. From a position. close westward of Handkerchief Lightship make good a 307° true (NW. 5% N. mag.) course for 10 miles, and pass northeastward and northward of Bishop and Clerks Lighthouse, rounding it at a distance of 3/4 mile. Then steer 262° true (W. 5% N. mag.), pass about 3% mile southward of Hallets Rock buoy and 1/2 mile southward of West Southwest Ledge lighted bell buoy. When the lighted bell buoy is in range with Hyannis Breakwater Light, steer 238° true (WSW. 12 W. mag.) for 41⁄2 miles to a position midway between the buoy at the eastern end of Wreck Shoal and the buoy on the northwest end of Horseshoe Shoal. Then steer 256° true (W. % N. mag.) for 2 miles to Wreck Shoal Spar buoy No. 18.

Wreck Shoal to Nobska Point.-Pass close southward of Wreck Shoal Spar buoy No. 18, steer 267° true (W. by N. mag.) for 7 miles, passing 300 yards northward of a horizontally striped buoy, about 3⁄4 mile northward of the eastern end of L'Hommedieu Shoal and about 1/4 mile southward of Davis Neck Shoal red buoy. When about 1 mile westward of the latter buoy and West Chop Lighthouse bears 184° true (S. by W. 5% W. mag.), steer 235° true (WSW. 14 W. mag.) for 21/2 miles to a position 1 mile southward of Nobska Point light and bell buoys, passing about 1/4 mile northward of the black buoy at the western end of New Shoal. For directions through Vineyard Sound from Nobska Point light and bell buoys, see tables Nos. 4 and 5, pages 31 and 32.

NANTUCKET ISLAND (CHART 1209)

on the south side of Nantucket Sound, is about 13 miles long, hilly, highest (about 100 feet (30 m)) in the eastern part, and partly wooded, with steep sand bluffs on the eastern and southern sides. The northern shore is fringed with shoals to a distance of about 1 mile. There is a prominent water tank about 12 miles westward of Nantucket.