About 2 km off the coast of Madagascar, in the Bay of Antongil, is a small, uninhabited, tropical island called Nosy Mangabe. The island is covered in dense forest and there are no permanent settlements there. But in the 16th and 17th centuries, Dutch ships on their way to the far east, around the Cape of Good Hope, frequently stopped on the island to replenish their supplies of fresh water, repair damaged ship or recover from sickness.

Nosy Mangabe has plenty of fresh water from rains that washes the island practically all round the year. More than 160 inches of it falls on this 1,300-acres island in a year. The abundant fresh water running down the sides of the island’s many peaks and cliffs was too good to pass.

Photo credit: Mark E. Polzer

As ships stopped and restocked their fresh water hold, sailors wandered around the beaches and etched their names on rocks. Some wrote the name of the ship, its captain, their date of arrival and departure. Over time, an ingenious system of messaging began to develop. Sailors began to leave messages, or at times, letters carefully wrapped in canvas and made watertight with tar, which they then buried at the base of the stones. The idea was that the next Dutch ship to anchor on the island would collect the letters or read the message and pass it on to the intended recipient.

In the early 1920s, a French colonial adjunct-inspector of waters and forests, discovered about a dozen of these so-called “postal stones” and managed to read them. In 2012, a team of researchers lead by maritime archaeologist, Wendy van Duivenvoorde, from Flinders University in Australia found more.

Duivenvoorde and her team found about 40 inscriptions, left by officers and sailors of at least 13 different Dutch East India ships that sailed between 1601 and 1657. The inscriptions were carved into several large rock outcrops and the cliff face on a small beach that still carries the name “Plage des Hollandais”, meaning “the beach of the Dutch.”

Photo credit: Mark E. Polzer

Some of these inscription told amazing stories. One inscription reveals that the ship Middleburg reached the island in 1625 after having lost all its mast and sails after a cyclone. It was anchored there for a good seven months while it was being repaired.

“It is quite amazing to think that they managed to reach the bay without masts and sails,” said Duivenvoorde.

Once the Middelburg crew finished building a new mast, the ship continued its voyage back to the Netherlands. Unfortunately, it never reached home. Near the island of Saint Helena in the South Atlantic, it was attacked and sunk—with no survivors—by the Portuguese. However, the Middelburg did stop briefly at Table Bay, South Africa, to deliver a parcel of crew letters. These letters, which are now in the archives of the Dutch East India Company in The Hague, are the last surviving records of the crew and officers.

By the late 1600s, the Dutch had abandoned the system of postal stones because they discovered that the messages didn’t always go to whom they were meant to. Increasingly, crews from rival companies had begun stealing letters from around the rocks and using the information to track the activities of their competitors. So the Dutch ships began employing locals to hold letters.

Postal stones such as those in Nosy Mangabe have also been found on St Helena Island and at the Cape of Good Hope in South Africa. Indeed, postal stones are a unique part of the South African postal history. In 1500, the captain of a Portuguese ship, tucked a letter into the hollow of a tree at Mossel Bay, reporting the loss of several ships in his fleet during a heavy storm over the Atlantic Ocean. Three months later another the crew of another Portuguese ship found the letter and delivered it to Portugal.

You can see these stones at several museums in Cape Town, but Nosy Mangabe is the only place where postal stones can be found in situ.

Photo credit: Mark E. Polzer

Wendy van Duivenvoorde inspects a postal stone in Nosy Mangabe. Photo credit: Mark E. Polzer

A postal stone found on the coast of South Africa with inscription dating from 1632. The inscription translated reads: "Hereunder lie letters from the commander Dirk van der Lee and vice-commander P Crook with the ships Nassau, Frederik Hendrik, Nimegen Wessel and the galliots. Arrived here 9 April 1632 from Batavia and departed 15th ditto." Photo credit: Andrew Massyn/Wikimedia