‘ELDRIDGE’ is a gift

December 2022

By Will Sofrin

I first learned about the remarkable resource called the “Eldridge Tide and Pilot Book” when working as a deckhand on a charter sailboat based out of Newport, R.I. I spent that season sailing as far south as Sandy Hook, N.J, and as far north as Bar Harbor, Maine.

That season, we must have crossed Long Island Sound a half-dozen times in less than six months. Appreciating how strong the tide could rip, depending on where and when we were, meant the difference of an extra half-day’s sail or more. Before departing, our captain would have already memorized the times of the high and low tide at his targeted milestones for the passage and the tidal current diagrams printed in “the Eldridge,” as it became known.

The “Eldridge,” founded by cartographer George Eldridge, will celebrate 150 years in 2024. His first printing, 32 pages long, was a pilot guide for Vineyard Sound and Monomoy Shoals. Included with his observations were compass courses and distances. This volume was the precursor to his “Tide and Pilot Book,” printed 21 years later.

His son, George W., moved to Martha’s Vineyard to sell another of his father’s books, “Compass Test.” While selling the books to anchored vessels out of his catboat, George W. began to observe the changing of the tidal currents and soon developed his first draft of a current table. Soon after that, along with help from his father, George W. began developing current tables for other regions and, in 1875, produced his first tide-table book.

The publication became an indispensable resource for Northeast mariners, and George W. continued to add more pertinent data as it evolved. Initial tables were based on observations made by George W. Some years later, government scientific data became the primary source for developing the tables, and, in cases when not available, the publishers computed the data themselves.

In 1910, George W. transferred the management of the book to his family to free himself up to pursue his interest in developing charts and navigational aids. George died in 1914, and his son-in-law, Wilfrid O. White, president of Kelvin & Wilfrid O. White Co., compass manufacturers, took over as publisher until he died in 1955. Son of Wilfrid, Robert Eldridge White and his wife Molly, took over as publishers and continued expanding readership and coverage.

Robert died in 1990, and Molly continued to manage the publication with her son Ridge and his wife Linda, who modernized the publication after Molly’s death in 2004. The sixth generation, Jenny, and her husband Peter joined her parents in managing the production in 2015.

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The charter boat I worked on was a 70-foot sloop that could average seven to eight knots when under sail or six when under power. Port Jefferson, N.Y., on the north shore of Long Island, south of Bridgeport, Conn., is about 100 miles west of Newport, R.I., making it a perfect stopping point on our passages across Long Island Sound after a long day of sailing.

The deep harbor was ideal for our nine-foot draft, which limited our options for where we could find available transient dockage for a night. Were it not for the overpowering presence of the Port Jefferson Power Station, the beautiful natural harbor would be as iconic as Oyster Bay or Huntington Bay.

We always departed from Newport early in the morning, while it was still dark, sailing west hoping to make it to The Race an hour or two after the flood had begun. The Race is a stretch of water between Fishers and Plum islands that marks the eastern entrance of Long Island Sound. Our captain’s strategy was based on the strength of the tide, which can exceed three knots. It can be so strong that the water’s surface will appear to boil, and patches of spinning whirlpools form at full rip.

According to the 2022 “Eldridge,” the “Avg. Max. Velocity: Flood 3.3 Kts., Ebb 4.2 Kts. Max. Flood 2 hrs. 45 min. after Flood Starts, ±15 min. Max. Ebb 3 hrs. 25 min. after Ebb Starts, ±15 min.” Based on that information, if we were making eight knots heading west at full ebb, our Speed Over Ground (SOG) could be limited to 3.8 knots, whereas our SOG could top out at 11.3 knots at full flood.

On the western end of Long Island Sound is Hell Gate, a narrow tidal strait between Randalls and Wards islands and Astoria, Queens. This is where the water of Long Island Sound meets New York Harbor and the Harlem River. Dutch explorer Adriaen Block – the namesake of Block Island – dubbed this stretch of water Hellegat, which some have loosely, appropriately – and perhaps erroneously – translated as “hell hole.”

In 1664, after taking over the Dutch Colony, the English renamed the body of water the East River, but this dangerous, mile-long, thin stretch of New York City’s East River retained the name Hell Gate.

Hell Gate can be dangerous because of the hidden underwater reef off Wards Island and the giant whirlpools caused by the effects of the tide. According to the 2022 Eldridge: “Avg. Max. Velocity: Flood 3.4 Kts., Ebb 4.6 Kts. Max. Flood 3 hrs. after Flood Starts, ±10 min. Max. Ebb 3 hrs. after Ebb Starts, ±10 min. At City Island, the current turns two hours before Hell Gate. At Throg’s [sic] Neck, the current turns 1 hour before Hell Gate. At Whitestone Pt. the current turns 25 min. before Hell Gate. At College Pt. the current turns 30 min. before Hell Gate.” Understanding that we could have been contending with a 4.6-knot current going in the opposite direction made the difference in the timing of our transit.

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A simple Google search of who first discovered or understood the phenomenon of tides generates a smattering of results. Some seemed accurate, while others were maybe a stretch. Needless to say, the results were staggering and entertaining. For example, I read that the Yolngu, an aggregation of indigenous Aboriginal Australians of Northern Australia, attributed the tides changing to the moon filling and emptying of water.

Pytheas, a Greek explorer and geographer (circa 325 B.C.), observed that the moon had an effect on the tides. Some claim that Plato believed the tides resulted from ocean currents flowing in and out of undersea caverns. In the Middle Ages, Muslim astronomer Abu Ma’shar al-Balkhi theorized in his astrological work “Kitab al-Mudkhal al-Kabīr” (great introduction) that the moon is responsible for the changing of tides.

In 1601, in “De Fundamentis Astrologiae Certioribus” (1601; “Concerning the More Certain Fundamentals of Astrology”), German astronomer Johannes Kepler compared the Earth to a living animal when referencing the tide. In 1608, in “De spiegheling der Ebbenvloet” (The Theory of Ebb and Flood), Simon Stevin argued that the pull of the moon’s gravity is the cause of the tides. In 1616, Galileo Galilei wrote “Discourse on the Tides,” in which he argued that tides are correlated to the Earth’s rotation relative to the sun.

Isaac Newton wrote about his version of tide theory in “Principia,” in which he described a theoretical circumstance in which the planet is uniformly covered by oceans. Unfortunately, his theory did not offer consideration for the continents or varying depths of water. The real breakthrough in tidal theory can be awarded to Pierre-Simon Laplace, who, in 1775, in his “Dynamic Theory of Tides,” considered factors such as the depth and width of the oceans, the Earth’s rotation, friction and rhythmic forces.

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Today, we have a concise and comprehensive understanding of the complex nature of tides thanks to centuries of observations and the help of science and math. We have confirmed that the tide results from the gravitational effect of the moon orbiting the Earth and the Earth’s orbit of the sun and that the gravitational impact of the sun is almost half compared to the moon.

The gravitational effect caused by the moon and sun is called “tidal force.” Where the ocean bulges, there is an opposite bulge. On the side of the Earth facing the moon, gravity is the strongest and pulls the water towards the moon, causing the bulge – high tide. At the farthest side, gravity is weakest, resulting in the second bulge, also high tide. But at the center of the Earth, the gravitational pull is stronger, still pulling the water towards the moon, thus creating the low tides experienced on the sides perpendicular to the moon.

The Earth’s axis of rotation is 23.5 degrees off from the plane of Earth’s orbit around the sun. The moon’s orbit is tilted about five degrees off the plane of Earth’s orbit around the sun. The result is a maximum tidal bulge above or below the Earth’s equator. The timing of the tide changes every day because a lunar day is longer than an earth day; 24 hours and 50 minutes for every rotation of the Earth.

The moon’s orbit around the Earth is 27.322 earth days. The irregularity of the continents on the surface of the Earth restricts the water from freely flowing towards the moon’s pull. These factors are why there are differences in tides depending on when and where you are in the world.

Southern New England experiences a high tide about every 12 hours and 25 minutes, two high tides a day. But this is not the case everywhere, as some parts of the world only have one high tide a day. A “semidiurnal” tide is a tide cycle with two high and two low tides near the same size on the same day. These tides occur in areas such as the Atlantic coast of the United States and the western coast of Europe and Africa.

A “diurnal” tide is a tide cycle with one high and one low tide on the same day. These tides occur in such areas as the Gulf of Mexico and Alaska’s western coast. A “mixed tide” is a tide cycle with two high and two low tides on the same day, but the tides are at different heights. These tides occur along the west coast of the United States as well as in Mexico, the Caribbean Sea and the Arabian Sea.

High tide is when the sea is at its highest level. In most places, the highest high tide usually occurs one to two days after the full moon. Low tide is when the sea is at its lowest level. This occurs in locations on the Earth that are perpendicular to the moon.

Neap tide is the weakest tide and occurs when the moon is in its first or last quarter ­– when the sun and moon are at 90-degree angles. These tides occur twice a month. A spring tide is the largest tide and also occurs twice a month during the full or new moon – when the sun and moon are in alignment.

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A few other tide-related terms should be mentioned. In Alaska, the “bore tide” forms a wave on the leading edge of the flooding tide, with a five-to-10-foot face that can be surfed. This phenomenon can occur twice a day and results from a very low tide colliding with a very high tide.

When I think of large tides, what first comes to mind is the Bay of Fundy. This bay is nearly 45 degrees north of the Earth’s equator, located between the Canadian provinces of New Brunswick and Nova Scotia. At the most inland part of the bay, the high tide can be as much as 56 feet higher than the low tide. The cause for the immense water height differential is a phenomenon known as “tidal resonance.” This occurs when the time it takes for a large wave to travel from one end of a bay to the other is in sync with both high tides.

There are also “red tides” and “brown tides.” They are not actually related to the tide but, instead, are large algae blooms that can change the color of the water. A rip tide is not a tide but rather a strong offshore current. Currents, the motion of water, do play a role in tides. The vertical motion of the tide, causing the ocean water to move toward the shore, is called the flood. The vertical movement of the water when it moves away from the land or out to sea is called the ebb. The ebb and flood can create what is called rectilinear currents.

Then there are tidal currents, which are currents affected by the interactions of the Earth, sun and moon. A tidal current is a type of oceanic current. Tidal currents occur in the oceans, the shore, bays and estuaries along the coast. Just like tides, the velocity of tidal currents can be stronger or weaker depending on the phase of the moon. They are also the only type of currents that change in a regular pattern and can be predicted. The Eldridge has an article on page 36 about how to pilot currents.

Today, we all benefit from the incredible technological innovations of our modern era. That said, I will always have a paper chart on my boat and check the timing of the tides in my “Eldridge Tide and Pilot Book” before getting underway. That’s just good seamanship.

Even with just daysailing out of Clinton Harbor, my brother-in-law has put his copy of the “Eldridge Tide and Pilot Book” to good use. When I told him I was writing this article, he texted me a picture from his “Eldridge” of the current table for The Race, with “Clinton Harbor – 0:38 Min,” written in large letters by a thick black marker at the top of the page. And this is why I gave him a copy of “the Eldridge” upon purchasing his boat.

Will Sofrin is an artist, writer, designer, builder and sailor. After high school, he apprenticed at the IYRS School of Technology & Trades in Newport, R.I., learning wooden-boat building and restoration. Then he became a professional sailor throughout Europe, New England, the Caribbean, Central America and the California coast. In 2014, he launched a firm in Los Angeles that manages the restoration of historic homes and develops ground-up architectural packages for luxury residential homes.