About this project

From Concept to Blog

The blog was divided into three separate components:

  1. The map page, including a contemporary map and a modern map, both showing The Unity’s voyage.
  2. The daily account, including the daily posts of the key players.
  3. The menu with background information about the various stages of the voyage and the MCC as a company and as a builder of the ship The Unity.

A time bar was added below the map and daily account pages, which could be dragged sideways to change the date. A ‘dashboard’ can be found below the bar, showing ‘current’ data on the weather, the nautical position, the distance traveled, the number of Africans on board and the number of crew members on board.

Due to the international nature of the trans-Atlantic trade in enslaved Africans, the blog is available in both Dutch and English.

1. The map page

A special 17th century map was used for the map page, which shows both sides of the Atlantic Ocean, as well as both hemispheres. Such nautical maps were used up to the 18th century for sea navigation. After the 18th century, more use was made of map sections which showed sections of coastal and oceanic regions.

The 17th century map is a rare, colored map drawn on parchment. This ‘West-Indian plain chart’ was published in 1669 in Amsterdam, by Hendrick Doncker (1626-1699). The map and the rights of reproduction belong to the owner, the Norman B. Leventhal Map Center in the Boston Public Library. The Zeeland Archives would like to thank the Norman B. Leventhal Map Center for permission to incorporate the map into the blog.

The voyage of The Unity can also be followed on a modern OpenStreetMap. Both maps can be zoomed in and out.

2. The Daily Account

The daily account page opens with the most current post of the first mate. Other contributions from other key players can be found under separate icons at the top of the page.

Visitors can leave a comment on each daily post, or add a tag. Tags help to unfold the contents the blog further.

Transcriptions and translations

The Dutch texts have been transcribed, but not translated – each text is given in the original 18th century Dutch.  Difficult terms are given a short explanation, and to the right of the post the authentic archive documents can be found. These documents can also be enlarged.

The Zeeland Archives have chosen to display the Dutch archive texts without any interpretation. This way, visitors can engage with the material as objectively as possible. The menu pages (see Stages of the Voyage) however, give an overview of the voyage. The texts have been transcribed by volunteers of the Zeeland Archives, part of the group PaiZ (Paleography in Zeeland).

For the English translation the texts have been ‘modernized’. One unique aspect of Dutch historic logbooks is the use of sail names to indicate the strength and speed of the wind. Although this is unusual in English historic logbooks, the Zeeland Archives have chosen to translate the Dutch terms literally. The texts have been translated by students of the University College Roosevelt (UCR) in Middelburg.

Locating the ship

The nautical location of The Unity is shown on the map and with the degrees of latitude and longitude on the dashboard below the map. The data for this was gathered from the first mate’s logbook, who noted the ship’s exact location using coastal or sea navigation.

For coastal navigation the first mate described two landmarks which were visible from the ship. These descriptions were used to determine modern-day latitude and longitude degrees.

For sea navigation, the first mate calculated the position at sea using the estimated compound course and the navigational instruments. However, the coordinates noted in the logbook do not coincide with modern coordinates.

Calculating the traveled distance was done using Google Maps.

Correcting the coordinates of sea navigation

Sea navigation was used for 161 days to determine the ship’s position. In the logbook, degrees of longitude were expressed in 360 degrees counted from the prime meridian, instead of 180 degrees eastern and 180 degrees western longitude.  The coordinates from the logbook were corrected accordingly.

The prime meridian of that time ran through the Canary Islands – the Greenwich line did not come about until the 19th century.  On comparing various positions of historic locations which still exists, the prime meridian of the logbook was determined at 16º40’, in line with the prime meridian used by the 17th century mapmaker Joan Willemsz Blaeu (1596-1673). This meridian could be found at approximately 16º45’: running through Tenerife, called El Pico by the locals.

Another often-used meridian is the 18º10’ line, running through the island Ferro (El Hiero), the western-most island of the Canary Islands.

The longitude coordinates of the logbook were corrected using the 16º40’.

The approach outlined above had good results, except in the following cases:

  • Three days in which the positions did not concur with other information given in the logbook. For example: according to the logbook, the ship should only be a few miles away from Cape Ortegal, while the distance according to the (re)calculated coordinates amounts to over 100 miles. These kind of days have been corrected by hand, based on information given in the logbook.
  • The trans-Atlantic crossing. Together, the coordinates certainly did provide a good overview of the set course, but they were located too closely together. For example, when the logbook reports a visual sighting of the American coast, the coordinates show that the ship was still 1500 miles away from the coast. Data from CLIWOC (Climatological Database for the World’s Oceans 1750-1850) was used to correct this. CLIWOC gathers meteorological data from the logbooks of a variety of European nations, with the aim of mapping climate changes. MCC voyages were also included in this project. Computer calculations were used to determine positions at sea.

The aforementioned determining of the ship’s position has been applied to the modern map of OpenStreetMaps, one of two maps which document the geographical voyage of the Unity. The blog opens automatically on the other map, an old West-Indian plain chart from the Norman B. Leventhal Center collection. Naturally, this 17th century map deviates from modern maps. The voyage of The Unity has been corrected as much as possible on the basis of geographical names on the map.

Number of people on board

The number of crew members on board has been determined using the logbook, the payroll and the muster roll. Unfortunately the logbook could not provide a decisive answer regarding the number of enslaved Africans on board.

The first mate lost track of the number early on. An actual number is mentioned for the last time on January 28, 1762, when ‘slave nr. 82 and 83’, a boy and a man, were brought on board. After that date, the first mate would leave a blank space to fill in the number later – though that never happened. Apparently it was not seen as necessary by the time the ship returned or the first mate was unable to reconstruct the voyage. He did mention how many people were brought on board every time, indicating whether it concerned men, women, boys or girls. These numbers do not coincide with the trade book however.

The date of purchase of the enslaved Africans also does not necessarily coincide with the date on which they came on board. The latter could happen a day later, or several weeks later. This was because trade was conducted simultaneously from the ship and the from the boat. Crew members could be gone for weeks to trade with the boat.

The trade book doesn’t always give the exact date of purchase, but a period of several days or weeks. In addition, in some cases it was clear that the dates were simply incorrect.

The numbers mentioned in the blog of the purchased and deceased slaves coincides with the numbers given in the final accounts of the ship’s administration. These accounts can be found in the trade book and in the ship’s book.

The African children formed a separate category on board, since they were not counted in the administration. They stayed with their (step)mother. We know how many children were brought on board, and how many were born on board, since the logbook mentions it. The numbers agree with the accounts of sold (step)mothers and their children in Guyana.

3. The Menu

The menu is located at the top of the page. Here, you can find:

  • An Introduction: introduces the voyage of the Unity, including a short video, as well as giving some explanations about the blog
  • Stages of the Voyage: gives information on the various stages of the voyage
  • Middelburgse Commercie Compagnie: gives information on the MCC as a company and constructer of The Unity
  • About this Project: a menu concerning the creation of the blog


Complex information about the ship The Unity and the voyage is made transparent by means of infographics.

Using data gathered from the MCC archive and other sources, the Zeeland Archives have constructed a 3D-drawing of The Unity. A longitudinal and a cross section have been added as well. The reconstruction clearly reveals how little room there was on board, and where exactly the enslaved Africans were held prisoner.

Other infographics visualize the data from the trade book. For example: Where were most of the Africans bought? What was the average price paid for an enslaved African? How was the cargo composed?