Recently I visited the Saugerties Lighthouse, a time-worn red brick structure that has stood just off the shore of the Hudson at the mouth of Esopus Creek since 1869. It replaced the original fire-decimated one built in 1835 — engraved by William Wade, who produced a remarkable picture of the length of the Hudson from New York to Albany.
Its grand days past, its light automated, the Saugerties Lighthouse fell into disuse in the 1950s but was restored and put on the National Register of Historical Places in 1979. In 1990 it was officially recommissioned with a solar-powered beacon.
Most amazing, it’s the only lighthouse along the river that also serves as a bed and breakfast. If you’re lucky enough to book a spot, you can fall asleep listening to the Hudson’s waves slap against the structure’s massive, circular stone base.
When we visited, we wound down half a mile along the shore, through wetlands and over wooden bridges, to get to the jetty that led out to the lighthouse. Water chestnut pods lay at our feet in abundance, drifts of them. like the black and spiny ectoskeletons of tiny prehistoric monsters,.
It was a damp day, chilly and foggy. The river spread out all around.
I used to live along the same stretch of river as the lighthouse, a half hour further south, in Ulster Park. In the middle of an apple orchard. The farmer who owned the trees favored McIntosh apples but there were a few stretches of the storied Ida Reds, a deep crimson on the outside with snow-white meat. As good in the hand as they were for the pie. The arthritic limbs of the trees were probably forty or fifty years old and stood massed in winter under a hush of snow that was a kind of bookend to the white pink blossoms of early spring. The Hudson Valley had been a majestic apple growing region for hundreds of years.
We would walk down a winding hill along River Road to the beach on the Hudson and collect water chestnut pods, strewn here across the mud flats as they cover the beach at Saugerties. It was said that the bay at Esopus once was meadow, grazed by cows. Cows in the river. Imagine. There was a lighthouse, the Esopus Lighthouse, that was distinguished by the image of a cat in one window.
These lighthouses are concrete evidence of a much different time on the river. They guarded against wrecks when Kingston became a bustling riverport in the nineteenth century. Kingston had its own lighthouse since 1837; one of its first keepers was a woman named Catherine Murdock. She stayed in service for 50 years.
In 1826, lighthouses started going up along the river. Eventually there were 14. Today, conservationists have preserved seven. The most famous perhaps, featured in a children’s book, is the little red lighthouse beneath the George Washington Bridge, which was deactivated when the blazing lights of the span made it superfluous in 1947 but can still be visited. Farther north are the 1883 Lighthouse at Sleepy Hollow, the oldest one, at Stony Point, the Esopus Lighthouse and the one at the Rondout in Kingston. The Hudson-Athens Lighthouse farther north has been guiding ships safely since 1874. Its fog bell is one of the last remaining on the river.
I wass mostly silent at Saugerties Lighthouse when we visited. The tides tossed up mysterious objects.
Sometimes you can find a kind of conglomerate of pulverized shells (probably clam) and mud that hardens into a rock, similar to what is called coquina on the beaches of St. Augustine, Florida, that the Spanish built forts out of.
If you get to stay overnight at the Saugerties Lighthouse, you can do some beachcombing after your coffee in the morning.
Jean Zimmerman 
Thanks for the background, a layered analysis.
Amazing plants, though, spiny as they are.
Thousands of years ago, the tiny coquina clam donax variabilis lived in the shallow waters of coastal Florida, as they still do today. These are the small pink, lavender, yellow, or white shells one sees along the beach at the waterline. As the resident clam died, the shells accumulated in layers, year after year, century after century, for thousands of years forming submerged deposits several feet thick.
During the last ice age, sea levels dropped, exposing these shell layers to air and rain. Eventually, the shell became covered with soil, then trees and other vegetation.
Although found in very few places in the world, conditions were just right that several deposits of this shell rock formed along the east coast of Florida. The Spanish knew about this rock, and while they might have picked up loose chunks, the people of St. Augustine were primarily soldiers, not stone masons, and so this rock sat mostly unused and unappreciated for years. Wood was more plentiful, at first, and easier to work with.
But then the British, settling to the north, edged into the Carolinas. Spanish Florida was only a short sail away. Something more than a wooden fort was needed to protect St. Augustine and to keep the
water percolating through the dead vegetation and soil picked up carbon dioxide and became carbonic acid, the same ingredient that makes soda pop fizz.
As this weak acid soaked downward, it dissolved some of the calcium in the shells, producing calcium carbonate, which solidified in lower layers much like flowstone and stalactites are formed in caves. This material “glued” the shell fragments together into a porous type of limestone we now call coquina, Spanish for “tiny shell”.
Re the beachcombing, you’ve got to do it during low tide, which varies day to day… As for the water chestnut, they are the invasive Euroasian variety, originally released in a garden pond near Schenectady in the late 19th century, and now spreading all over the Hudson River. The plant’s black pods, known as devil’s heads, are pointy so watch where you walk. When they dry out on shore, they smell like rotten garbage. FWIW….