Header of the page
Where can I get help using this website?

On the right side of the orientation bar beneath the top banner, there are links to four different types of online assistance:

  1. a Sitemap showing all areas of the site at a glance;
  2. a list of frequently asked questions and answers (FAQs);
  3. video demonstrations of how to use the website and databases (Demos);
  4. a Glossary of terms used in the study of the slave trade.

Additionally, in the Understanding the Database area of The Database section of the site, users can access a guide to understanding and using the online database and the website, including screenshots.

How do I find out what’s available on this website?

The five main sections of the website are listed in the blue banner at the top of the screen: The Database; Assessing the Slave Trade; Resources; Educational Materials; and About the Project. Clicking on the name of one of these sections opens a page with general information about the section and its principal subsections. If you are visiting this site for the first time, you will find it useful to read this introduction. The sitemap, located on the right side of the orientation bar beneath the top banner, provides an at-a-glance list of the sections and subsections of the site.

How do I move from one part of the website to another?

From any page of the website, you can move to another page by clicking on one of the five labels in the top navigation bar (or items in the drop-down menus associated with them). You can also use the sitemap among Help options, or click on part of the path in the orientation bar. Once in a section, you can quickly move to a subsection within it by means of links in the left frame.

What are the optimal settings for viewing the website?

The performance of the Voyages website has been tested for compatibility with Mozilla Firefox 2, Microsoft Internet Explorer 7, and Safari 3.  Interactive features like timelines and maps make extensive use of JavaScript and operate more smoothly on computers not older than three years. The website is designed for a screen resolution of not less than 1024x768 and 32-bit depth. For full display of pages, you may need to disable unnecessary toolbars or side panels in your browser.

Can I reuse or republish any information or materials I find on this website?

The Voyages website supports education and research by making its information available for free. Much of the information is protected by copyright. An Attribution-Non-Commerical Creative Commons license governs much of the content on the site, including historical and imputed data found in the three main databases on the site – the Voyages Database, the Estimates Database, and the African Names Database. This license allows for the non-commercial republication of certain content on the site and the creation of derivate works, provided the Voyages website is appropriately credited as the original source. Some materials on the Voyages website, however, appear by permission of the copyright owners and require their approval before being republished. For a guide to the various content on the site, permissions governing their use, and examples of how to cite the original source, see the "Permissions to Reproduce" section of the "Legal" page.

How do I cite essays and texts found on the website?

That depends on the manual of style you are following. Most citations of materials on a website, however, involve name of author [when given], title of text [when given], name of the website, URL, and date accessed. For example, according to The Chicago Manual of Style Online, the introductory essay by David Eltis in the essays subsection of Assessing the Slave Trade should be cited as follows:

David Eltis, “A Brief Overview of the Trans-Atlantic Slave Trade,” Voyages: The Trans-Atlantic Slave Trade Database, http://www.slavevoyages.org/assessment/essay (accessed April 27, 2008).

For more citation examples, see “Permissions to Reproduce” on the Legal page of this website.

How do I cite a database found on the website?

The Chicago Manual of Style’s “Quick Guide” also provides an example of how to cite an item in an online database. For specific output or data selections, users should cite the URL generated by “Create a link.” Pasting the URL into the website will always generate the same results.

What is the difference between a data variable and an imputed variable?

A data variable is one that is documented directly from one of the primary sources that provide evidence of a slaving voyage. An imputed variable is not documented directly, but is inferred by historians from data variables. The essay, “Construction of the Trans-Atlantic Slave Trade Database: Methods and Sources,” located in “Understanding the Database,” a subsection of “The Database,” explains the assumptions and basis of all imputed variables. On the website, they are indicated by an asterisk following the variable name. Variables with asterisks are imputed. Variables without asterisks are data variables.

What is the difference between basic variables and general variables?

There are two main options for querying the database: a basic search (“Basic variables”) uses a smaller set of variables, and a general search (“General variables”) uses an expanded set of variables. Basic variables are one-third of the total number of variables in the database, and general variables are a more extensive list of variables (though fewer than the over 200 variables available by downloading the full SPSS dataset).

Why is there an asterisk (*) next to some variables?

Variables with an asterisk are imputed. Imputed variables do not refer to information found in a source but to information inferred by historians from information that is found directly in sources. Data variables (variables in the database without asterisks) are documented directly from  primary sources that provide evidence of a slaving voyage. For example, historical documents rarely indicate that a port where slaves disembarked was the principal place of landing, but when documentation exists on the number of slaves disembarked at several ports, the historian can determine where the largest number were disembarked, the principal place of disembarkation for the voyage. In some cases, how many slaves embarked is documented, but not how many disembarked. From the survival rate on voyages with the same characteristics, we impute the number who did so on the voyage with missing information. The essay, “Construction …: Methods and Sources,” explains the assumptions and basis of all imputed variables.

Where can I see at a glance variables available for analysis in different sections of the website?

Look in the fourth, fifth, and six columns of the Variable List. The column “Voyages” shows the number of cases that have information coded for each variable in the main database.

How can I observe the values of a variable?

For categorical variables, put the variable into Current query. You will see it there with the notation [nothing selected]. Clicking on select will review the variable’s values. For seeing how many cases, or slave voyages, are coded for the variable, put a mark in the check box and look at Results, at the bottom right of the query box. For numerical variables, one way to observe the range of values is to select the variable for display in the Results tab by using “Configure columns” (top right of main display area, opposite List of voyages) and then sort (clicking on the column heading) to see the top and bottom of its range.

Where do I find bibliographies of studies of the slave trade on the website?

“Published secondary sources,” the fourth part of Sources in Understanding the Database, a subsection of The Database, provides a comprehensive bibliography of scholarly studies of the Atlantic slave trade.

How do I find documentation for a particular voyage?

Your starting point should be the “Sources” for the voyage cited in the Trans-Atlantic Slave Trade database. These are listed in the last of the “Voyage variables” in Voyage detail, accessed by clicking on the row listing a voyage under the Results tab in Search the Database. Pop-up windows explain the short references; but full references are found in Sources in Understanding the Database, where the short references can be used to bring up the full description of the source.

How do I find information about a particular slaving voyage?

“Search the Database” enables you to identify one voyage in particular. If you know the name of the vessel, click on “Vessel name” in the category “Ship, nations, owners” in the query frame. That will open a space in the Current query box to enter the name. Then click on search. As many ships made more than one slaving voyage and others shared the same name, you may well find more than one ship with the name you entered.  Check the year the voyage arrived or other information which permits you to distinguish it from others with the same name. Clicking on a particular voyage in the Results listing will open a window with voyage known details.

How do I limit queries to specific sets of years?

“Select time frame” is the first query box at the top of the left frame in both the Voyages Database and Estimates. In Estimates, the default setting is 1501 to 1866 since evidence points to disembarkation of African slaves in Hispaniola from the beginning of the sixteenth century. For the Voyages Database, the time frame is set by default to the period from 1514, the first year in which a slave voyage can be documented, to 1866, the year of arrival of the last three documented slave voyages. For a single year, specify the same year in both “From” and “To.”

How do I select voyages for examination and analysis?

First, from the set of either basic or general variables, select a variable to limit the search by the criteria represented by its values. You do this by clicking on it in the roll-over menu that lists variables in one of eight categories (Ship, nation, owners; Outcome of voyage; etc.). This will move the variable into the box for “Current query.” Clicking on “Select” here opens a space for limiting the query to certain cases by using the variable. Make your selection and click on OK. You can then further limit the query by using another variable. Again, click on OK once you have made a selection. When you have finished entering criteria of selection, click on “Search” to activate the query. You will see to the right a list of voyages that match your selection criteria.

Is there a way to know how many cases in the database have information relevant to a particular query?

Every choice of criteria limits the query to a smaller number of voyages. As you are making a selection, you can see how many voyages satisfy your criteria by viewing the number after “Results” at the bottom right of the “Current query” Box.

Why do methods of selection differ from variable to variable?

The method of selection depends on the type of variable. If it is numerical, like “Voyage identification number” or “Year arrived with slaves” or “Total slaves embarked,” one is asked to enter a specific number or range of numbers. If it is a name, like that of a ship or its captain or the owner of the venture, one is asked to enter the name or part of it. If the variable consists of a set of categories, such as places or types of outcome of a slaving voyage, then the categories are listed with small check boxes in front of them and one is asked to check those that correspond to categories about which to find information. If there is an arrowhead in front of the checkbox, click on it to reveal further options.

How do I use selection options for numerical variables?

Numerical variables ask the user to choose one of four options and enter a number or numbers after it:

  • Between
  • At most
  • At least
  • is equal to

For percentages and rates, enter “At least ‘0’” to limit the query to voyages for which such measures can be computed.  In general, use whole numbers rather than decimals, for example, "At least 50" rather than "At least .5," for 50% or more.

How does “Previous queries” work?

You can recall the selection criteria in a previous query in the current session by opening the “Previous queries” box and clicking on “restore.” If the box becomes cluttered with too many previous queries, you can remove any of them by clicking on “delete.” This option works only during a single session. When you close the browser window with the website, your previous queries disappear. For a permanent record of a query, use the option “Create a link.”

How does “Create a link” work?

“Create a link” appears in the left frame of “Search the Database” after one has clicked on “Search” to execute a query. It creates a goo.gl URL which users can save and later recreate the query by pasting in the site’s address window.

How do I select variables of names (of the ship, captain, owners) and sources?

Click on the variable in the set of Basic or General variables. It will open a space to enter the name or part of the name. The query program will list all records containing the sequence of letters you enter after click on “Search” to activate the program. Searching for a source is slightly more complicated because it requires one to enter its short reference rather than the full reference. To find voyages described in a particular source, begin by finding it in the bibliography of “Sources” in “Understanding the Database.” Note that the list of sources can be sorted by either short or long reference.

How do I control for certain variables in analyzing data in other variables in the main database and estimates?

A control variable is one that does not change (or is held constant) during analysis of data in order to minimize its effect on results. The reason for doing this is to see more clearly the effects of other variables. Consider the following example. In the Voyages Database, a researcher wishes to examine differences in mortality on slave voyages organized in Great Britain and mainland North American colonies. She begins by setting three criteria in the query frame: a) time frame: 1700-1749; b) place where voyage began: Great Britain (clicking on Great Britain, England, Scotland, and Ireland); and c) outcome of voyage for owners: Delivered slaves for original owners. Time frame is selected because the researcher wants to see if any difference between British and American voyages persisted over time. She plans to obtain results first for the period 1700-49, and then for 1750-99. The second variable, where the voyage began, is the one whose effect on mortality the researcher is interested in. The third variable, outcome for owner, is the control variable. It will not change throughout the analysis. It affects the results, but the researcher is more interested in the effect of the place where the voyage was organized. By limiting the analysis only to voyages completed as the owner of the venture intended, the researcher is able to eliminate the effect on results of other possible outcomes, such as shipwreck or capture at see by an enemy ship.

What does the command “New query” do?

This command resets the query interface to its initial setting, containing all 34,941 voyages in the database. Otherwise, previous specifications remain in effect. If you find less than all voyages or some specifications already set at the beginning of a session, the reason is probably information in your cache from previous sessions which prevents you from making a clean start.

When I begin a new session on the Voyages website, I find that it does not open with default settings, but instead some settings resulting from queries made in the preceding session remain in effect. How do I begin again from default?

First, click on “New query” in the “Current query” box. Normally, it will return you to default settings and to the first page (Results) of Search the Database. If it does not do this, another more roundabout way to get to default settings is to close the browser window (not just a tab since the browser may retain the session state until it is completely exited – indeed, it may be necessary to definitively end a browser session by use of the Task Manager), reopen the browser, clear its cache, and then return to the Voyages website.

How do I extend the range of variables displayed under the “Results Listing”?

Clicking on “Configure columns of the table>” will open a page to choose what to display in “List of Voyages.” Variables are listed in the same categories that are used throughout the website. Select a variable by clicking first on the category under which it is listed in “Choose group of variables” and then on the variable itself in “Available variables.” Your choice will be highlighted. Then click on the arrow to move it to the “Selected variables” box. Note that you can also remove a variable displayed in “List of voyages” by moving it out of the selected variables box. Finally, you can set the order of columns for variables in “List of Voyages” by clicking on any variable and moving it up or down in the selected variables box. When you have finished configuring the list of voyages, click on “Apply configuration.” This returns you to the list of voyages where you will see variables displayed as you have requested.

How do I print results?

One simple way to print results is to use PrtSc (Print Screen). For a table or graph that you would like to print, hit the PrtSc key on your keyboard. This copies an image of the entire page into memory. Then paste the image into a blank screen of an image editing program like Microsoft Paint (one of the accessories) or Adobe Photoshop. From this image, you can then select a part of the image of an entire page, for example, the title and table of Summary Statistics, copy it and paste it into another page which you can print or save. Print screen will not supply a title for a table, graph, or map, nor will it include sources, notes or the details of the query that produced your results. It may be more efficient to download the data into a spreadsheet, construct a table or graph there with title, notes, sources, and desired formatting, and print this instead.

How do I interpret information provided in “Summary Statistics”?

First, you should be aware that the statistics for slaves embarked, disembarked, and the percentage who died during the Middle Passage are calculated from imputed variables in the data set. Totals are somewhat less, and averages somewhat different, when based on data variables: 331 slaves embarked, 277 disembarked, and 10.9 percent mortality. The other four summary statistics (length of Middle Passage, percentage of children and males, and tonnage) are calculated from data variables.

How can I use “Summary Statistics” in combination with the query frame to the left to compare voyages with different characteristics?

The default for “Search the Database” is the complete database. Thus, when no criteria of selection are specified in the query frame, the summary statistics describe the entirety of the slave trade. While in summary statistics, however, you can select voyages in the query frame at the left to see how they compare with the general average in the entire data set. For example, to answer the question, did the average number of slaves embarked on slave voyages decline or increase in the era of abolition after 1808, simply change the time frame on the left to 1808 to 1866 and click on “Search.” 

What do “averages” calculated in Summary Statistics, Tables, and the Timeline mean?

An average is a value that is typical or representative of all values for the group of persons or things it describes. It is important to remember that the meaning of an average should be judged by the amount of deviation of particular cases around it. For four voyages landing 250, 280, 310, 360 slaves respectively, and for three voyages with 100 slaves and one voyage with 900, the average is the same: 300 slaves. The standard deviation is the clue to how much the average resembles particular cases in the group for which it is calculated. Divide the standard deviation by the average. The smaller the quotient, the closer particular cases are to the average. The larger the quotient, the more variation there is above and below the average.

How do I determine if a slaving voyage is typical or exceptional?

Compare statistics for the voyage, as shown in Voyage detail, to summary statistics for all voyages or voyages of the same type. All voyages are usually too large a reference group to be a meaningful unit of comparison. It is more revealing to determine if a voyage is typical of others under the same flag, or from the same period of time, or following the same route from a region in Africa to a region in the Americas.

Can the data be examined in larger units than single years?

Using the time frame box in the query section, the user can specify periods of any duration, but only one period at a time. In the tables tab in both Estimates and Search the Database, one can choose to display a number of statistics about the slave trade in 5-year, 10-year, 25-year , 50-year, and 100-year periods. Click the desired period in the selection area for table rows. In custom graphs, choices for the x-axis variable include, under voyage dates, year of arrival of slaves by 5-year, 10-year, and 25-year periods.

What can be learned by graphing differences observed in tables?

Graphs can bring to the researcher’s attention patterns that might not be observed simply scanning the statistics contained in a table. Tables also present the danger of tempting the researcher to exaggerate the importance of small differences. If differences are too small, or patterns too indistinct, to be clearly observed in a graph, they are usually not significant.

Custom graphs offer the possibility to construct three kinds of graphs: XY, pie, and bar charts. When should I use each type?

First, read over the answers to the FAQs about how to construct the three kinds of graphs. Each begins with a simple definition of the graph type. In general, bar charts are appropriate for comparing two to ten categories that can be measured numerically; pie charts are appropriate for comparing percentages of a whole; and XY charts show the relationship, or correlation, between two numerical variables.

Is there a technique for making effective graphs?

Remember that a limited number of categories of comparison is necessary for both bar and pie charts. Too many categories make a chart difficult to interpret. If you find this to be the case, use the left query frame to limit the number of categories or values to a manageable number. A bar chart is useful for comparing several categories on a numerical scale, for example, the number of voyages on British and Dutch vessels in the period 1641-1700, when development of sugar colonies in the Caribbean began, or number of slaves embarked in different regions of Africa, or the average size (in tons) of United States and British ships. Number of voyages, slaves embarked, and tonnage are all numerical variables. Flag or nationality and region are categorical variables.  Use of the query frame to limit categories represented in a bar or pie chart is a key to making effective use of the feature.

How do I construct a bar chart?

First, select bar chart as the “Graph type.” Second, choose a categorical variable for the X (horizontal) axis. Third, select for the Y (vertical) axis a variable that can be measured for each category and add it to “Current series.” Several series can be included in the graph if one wishes to do so, but they must be similar. Any series can be removed from “Current series” by checking the box next to it and clicking on “Remove selected.” Once all specifications are made, click on “Show.” If the resulting graph is not satisfactory, rethink your specifications.

How do I make a pie chart?

A pie chart is a circular graph having radii dividing the circle into sectors proportional in area to the relative magnitudes, frequencies or percentages represented. "Voyages" allows users to analyze data using a pie chart in the "Custom graphs" section. Pie charts effectively depict percentages.

To make a pie chart in Custom Graphs, click on its button among graph types; enter under X axis the variable whose values will represent slices of the pie; and use the Y axis to choose a variable to determine how the size of each slice will be measured. Click on “Add series” to put it in the “Current series” box. If another variable is there, remove it. Then click on “Show.” Only categorical variables are suitable for a pie chart, and not every categorical variable at that. It is important to choose a variable with a small enough set of values for pieces of the pie to be more than thin slivers. Remember that you can limit the number of values in the query frame on the left.

How do I draw an XY graph?

An X-Y chart consists of a line drawn between the co-ordinates of values of two numerical variables – one on the X (horizontal) axis, the other on the Y (vertical) axis. X-Y charts effectively display changes over time, with a year variable plotted on the x-axis. However, any two numeric variables that might be correlated can be plotted against each other on this type of chart, for example, Middle passage (days) and (Avg)Percentage of slaves embarked who died on voyage. Remember, too, that the query frame on the left can be used to further refine conditions for observing the correlation between two numeric variables.

The Voyages Database and Estimates both have timelines. How do I use them to observe differences over time? Should trends look the same in both sections?

The timeline is a bar graph that functions similarly in Estimates and the Voyages Database. The main difference is that it shows only captives embarked and disembarked per year in Estimates, while it can describe annual change of a larger number of variables in the Voyages Database. For the latter, click on a variable in the selection box and then on the button "Show." The timeline for Estimates includes a chronology which illustrate how this graphic can be used to show the impact of critical events on the slave trade. Moving the cursor from left to right in the main graph area causes a bar to appear indicating year, and information for that year appears below the timeline. To view a segment of time in more detail, click and drag bars on the left and right of the smaller chart area below the main chart area to the beginning and end year of the desired period. Because estimates take into account voyages for which documentation is lacking, the number of embarked and disembarked slaves will be greater in its timeline than in the one for the main database, but trends will be similar.

What kinds of maps are found in the website?

The map on the home page is a historical map in the sense that it is an artifact from the period of the slave trade. It is part of the world map Nova totius terrarium orbis geographica ac hydrographica tabula, drawn by the Dutch cartographer Willem Janszoon Blaeu and first published in 1606. The Introductory maps in the section “Understanding the Database” are historical in another sense. They provide a cartographical view of the history of the slave trade. The nine introductory maps are among more than 150 that will appear in the Atlas of the Slave Trade that will be published soon by Yale University Press. Among the details about a particular voyage provided when one clicks on a row in “List of voyages” on the default page of the Voyages Database is a “Voyage map.” Clicking on the tab of that name in “Voyage detail” displays a map showing the itinerary from where the voyage began to where slaves were purchased to where they landed to where the ship returned to complete an expedition, along with other information when available. Both the Voyages Database and Estimates have maps which allow the user to picture the size and structure of the slave trade as defined by criteria of time, space, national carrier, and other variables in the data set. See the Guide and responses to other FAQs for more information on how to use their interactive features.

Is there any difference between maps in the Voyages Database and in Estimates?

The icons and options for maps in both sections are similar, but there are two important differences. The Voyages Database permits users to put dots on maps corresponding to three levels of detail in labeling: broad regions, regions, and places or ports. In Estimates, only dots for broad and specific regions appear on maps. Embarkation regions in Africa are the same in the two sections, but broad disembarkation regions are slightly different. In the Voyages Database, there are six: Europe, Africa, Brazil, the Caribbean, Spanish Central America, and Mainland North America. In Estimates, the Caribbean is further distinguished by the major powers holding slave colonies there: Great Britain, France, the Netherlands, and Denmark. Colonies in the Guianas are included in the Caribbean. Spanish Americas combines Spain’s Caribbean colonies (Santo Domingo, Cuba, and Puerto Rico) with its mainland colonies, in Central America and in the Rio de la Plata basin. Specific regions within Mainland North America, the British, French, and Danish Caribbean, and the Dutch and Spanish Americas, are also defined somewhat differently in Estimates than in the Voyages Database.

How are interactive maps affected by selections made in the query frame on the left?

Any change in criteria used to select voyages also changes the representation of places of embarkation and disembarkation by yellow and red dots on the map and the meaning of the size of the dots, as shown under the legend “Number of slaves.” For example, in the Voyages Database, use as a point of departure the default map for the entire slave trade from 1514 to 1866. There is only one yellow dot. It is placed over Africa, the continent from which all slaves were taken. The relative sizes of the red dots show that the Caribbean, Brazil, Mainland North America and Spanish Central America, Africa and Europe were recipients of slaves, in that order of importance. The legend shows approximately how many disembarked in each broad region. Rolling over the dots gives exact statistics. Now change the time frame on the left to the period from 1808 to 1866, the era of abolition of the slave trade. You will notice that the number of slaves represented by dots of different sizes is much smaller.

What is the function of icons at the top of maps?

Most of the icons enable the user to zoom in or out. As the zoom level changes, so do labels and geophysical or historical background.

At the far left are pointers to the left and right. Once one begins to move back and forth between zoom levels by icons to the right, these pointers provide an alternative means of changing zoom level.

Next, from left to right, are icons of a hand and an empty magnifying glass. As explained on p. 20 of the Guide, these icons allow you to zoom in a map by defining an area to enlarge: (1) click on the empty magnifying glass icon; (2) using the cross-hair cursor, click and hold the mouse button and then drag the mouse diagonally over the area you wish to enlarge; and (3) release the mouse button.

The middle icons also allow you to zoom in (+) or zoom out (-) between 4 levels or scales: 20, 6, 3, and 1, as shown at the bottom left of the map. Scale 20 shows the largest area, but the least detail. Only broad regions are labeled at this zoom level. Scales 6 and 3 encompass smaller areas of the Atlantic and are suitable for maps with labels of specific regions, but not ports within them. Scale 1 covers the smallest area and shows the most detail. It is meant to be used for viewing maps showing the exact location of ports and places. The bar in between the zoom in and out icons provides another way of moving among the four scales.

Finally, the three icons to the right allow you to set the size of the map on your screen. The lowest setting enables you to view the map display without scrolling. In the navigation box at the bottom right, you will see exactly how much and what part of the entire map of the Atlantic world you can see. At the middle and high size settings, you will have to use scroll bars to see the entire area of the map display.

How do I use the positioning box in the bottom right corner of interactive maps?

The area of the Atlantic world shown in the map area is represented by a white rectangle within the positioning box. Click on the zoom in magnifying glass (+) to observe how the rectangle is reduced as one zooms in. The white rectangle stays in the center of the box. Put the cursor on the map inside the box and move an area of the map you wish to view under the right triangle for it to be displayed on the map.

To the right of the map, “Select map” allows the user to choose between broad regions, regions, and ports. What is the difference between these units?

The Atlantic world is divided, for cartographical purposes, into six or nine broad regions, depending on whether one is in Search the Database or Estimates. In the former, the regions are Europe, Africa, Brazil, the Caribbean, Spanish Central America, and Mainland North America.  In the latter, they are also Europe, Mainland North America, Brazil, and Africa, but further divide the remaining areas of disembarkation into the British Caribbean, French Caribbean, Dutch Americas, Danish West Indies, and Spanish Americas. See the answer to the FAQ about differences between maps in the Voyage Database and Estimates for further information.

Each broad region contains specific regions. They are defined differently for each broad region: nation-states in the case of Europe, segments of the coast for Africa, large geographical areas for Brazil and Spanish Central America, colonies in the Caribbean, and colonies / states on the North American mainland. Specific locations, usually ports, are shown within specific regions.

These categories are the same as those used in the “Voyage Itinerary” category in the Voyages Database search interface.

What is the difference between “visible places” and places labeled on the maps themselves?

Visible places refers to the placement of red and yellow dots on maps. The dots do not themselves contain labels, although rolling over them will open a pop-up box naming the region or place the dot represents and statistics about slaves embarked and/or disembarked there in the period indicated in the time frame. Depending on zoom level, labels of broad regions, regions, or ports will appear on the background map. As a rule, one should select a zoom level that corresponds with the selection of visible places: for ports, for example, select the finest zoom level (1).

“Select map” also allows the user to choose the time period of the map. What is the nature of choices offered here?

First, the user can choose between maps that show only geophysical features for all periods and maps that provide as background boundaries of states and colonies at three points in historical time: around 1650 (1501-1641), 1750 (1642-1807), and 1850 (1808-1867). The dates correspond roughly to three eras in the history of the slave trade: Spanish and Portuguese domination, the apogee of slave trading with the dominance of northern European powers, and the period of its abolition and suppression.

How does selection of an historical map affect the display of data?

In “Select map,” choice of an historical map automatically changes the time frame to the years appropriate to its date (1650, 1750, or 1850) and the range in the number of slaves represented by different size dots.

Places are represented on the map by five different sizes of yellow and red dots? How do I interpret these symbols?

Yellow dots show places of embarkation. Red dots show places of disembarkation. The size of dots shows relative importance, as measured by the number of slaves affected. The larger the dot, the more slaves were embarked or disembarked. For precise numbers, roll over the dots or center the map on a particular place by selecting it in the drop-down menu for “Find visible place.” A pop-up will give the exact number of embarkations and/or disembarkations for the region or location.

How is the number of slaves embarked and/or disembarked corresponding with different circle sizes computed?

A simple algorithm has been used to classify the number of embarkations and/or disembarkations for broad regions, regions, or ports, depending on the choice made in “Select map”, into five groups from smallest to largest. The map program looks for the place with the smallest and largest number of embarkations or disembarkations. The difference between the lowest and highest number is then divided by 5, to determine the range represented by each dot size.

In the interactive interface for maps on the right, how does checking or un-checking boxes next to ranges in “Number of slaves” and “Places” of embarkation and disembarkation affect what is displayed on maps?

Only places with a check mark in front of them are displayed on the map. Thus, if one wants only to see dots for the smallest of the five groups of numbers of slaves, one would remove the check mark in front of the four larger circles. Likewise, if one is interested only in places of disembarkation, one would uncheck the box in front of visible places of embarkation.

What is the function of “Refresh”?

Refresh resets the display of dots and time period of maps according to the choices made in “Select map” and the check boxes.

How do I make the map center on a particular place?

“Find visible place,” the tool at the bottom of options to the right of the map, provides a drop down menu of places, regions, or broad regions, depending on the choice made in “Select map” above. Clicking on a place name in this list will center the map on that place, at the second zoom level if not the first, and show statistics related to it. By clicking on the zoom level, you will be able to see its location relative to other places at different scales.

What features are shown on geophysical maps?

Within land masses, one can see rivers (albeit unlabeled) and coastline. Within the North and South Atlantic, the most important ocean currents are traced and labeled. The direction of currents is clockwise in the northern hemisphere and counter-clockwise in the southern hemisphere.

What kinds of detail are displayed on the historical maps?

In Europe, the area of countries were voyages were organized are shaded. Except for Spain, labels of the names of slave trading nations are placed off adjacent coastlines.

In Africa, shaded areas show states, regions, and large population groups. The approximate area covered by each is shown by light grey borders, and the white labels in capital letters are the names of these territorial units. Labels in purple are for so-called ethnic groups not associated with territorial units. Regions of the coast, as defined by Philip Curtin and adopted on this website, are shown in large capital letters adjacent to the coastline to which they refer.

In the Central and South American historical maps of regions and ports, shaded areas represent the extent of colonization around 1650, 1750 and 1850. Boundaries show political changes over the three periods The 1650 historical map for regions of the Caribbean show the small number of islands colonized before the middle of the seventeenth century. Around 1750, close to the apogee of the slave trade, all the larger islands are labeled at level 3 or 6 for regions; and some of the smaller islands are labeled at zoom level 1. Finally, in Mainland North America the historical maps show areas of colonization and the emergence of independent countries in much the same way as for South America.

Can I download results for further analysis using a spreadsheet?

Yes, there are buttons on most pages for downloading information or results from the page in a csv (comma delimited file). Simply click on the button. It will transfer the data file to your computer where you can import it into a spreadsheet program of your choice.

What parts of the Voyages website can I download? How?

First, you can download any PDF file. Click on the link to open it. Acrobat reader provides an option allowing you to save the file to your hard disk. Secondly, data for most tables and graphs can be downloaded as a CSV file by clicking on buttons for this purpose under the display of results in the main area of the page. Thirdly, in the Downloads subsection of the Voyages Database, links are provided to enable you to download the full set of variables in the 2008 edition of the Trans-Atlantic Slave Trade SPSS Database, the version of this database used for the 1999 CD-ROM, the codebook for SPSS versions, the selection of variables for the website in several formats, and a spreadsheet containing the basic calculations used to derive the interactive set of estimates in Assessing the Slave Trade.

What should I do if I find errors in how a variable or variables are coded for a particular voyage or set of voyages?

Correct them using the automatic entry data entry form in Contribute, the fourth subsection under “The Database”. When you receive a user name and password authorizing you to enter this part of the site, you will see that you are first asked to choose between three types of submissions. The second is “Edit an existing voyage.” It has two columns, on the left data as presently entered, on the right the correct data that you propose instead. For variables that are already correct, you just need to click on “copy.” A space is also provided for any notes about your revision of each variable. It is particularly important to provide full information about the sources used to identify mistakes.

How can I contribute new data on slave voyages to the website?

The “Contribute” subsection of the Voyages Database provides a data entry form designed to facilitate submission of new data. Guidelines are provided there on how to use it. In asking for a user name and password to enter this section, you will be put in contact with a specialist in the area and era of the slave trade in which you are interested who will help you with your contribution.

What should I do if I find two cases describing the same voyage?

In the automatic data entry form in Contribute, one type of submission is “Merge existing voyages.” It shows variables for two or three cases side-by-side for each case, allowing one to determine if they are duplicates. A word of caution: the same ship often made several voyages.

How do I make contributions to features of the website other than the databases (essays, images, bibliographies, links, documents)?

Rather than using the data entry form, contact voyages@emory.edu.

What kinds of essays are published on the website?

Presently, the essays subsection of Understanding the Database contains three types of contributions: interpretative essays, vignettes or biographical sketches about individuals transported on slave ships, and a research note. We will periodically change the contents of this section, adding longer and shorter essays, notes, reports on archives, projects about the slaves, and in general any kind of text for which the Trans-Atlantic Slave Trade Database is a major source. Users are invited to submit manuscripts to voyages@emory.edu.

What is the difference the main database and the estimates database?

Statistics in the Voyages Database are for slaving voyages for which documentary evidence has been found. Evidence of other voyages remains to be discovered. In some cases, it will never be discovered. An attempt has been made to systematically evaluate the completeness of the record of the slave trade for different national carriers in different periods of time. Statistics in Estimates take into account the incomplete nature of historical evidence and adjust figures derived from the Voyages Database upwards to provide an account of the actual volume of the slave trade.

What does the command “Reset to default” do?

In Estimates, each of the boxes for setting criteria of analysis has a “Reset to default” button. Initially, the time frame is set to 1501-1866, the entire period of the slave trade for which estimates are made; and flag (national carrier), embarkation regions, and disembarkation regions are all set to include all values for each. By clicking on “Reset to default” in a box, initial settings are restored for all specifications.

Are embarkation regions in Estimates and the Voyages Database defined differently?

No. Both sections make use of Philip Curtin’s widely used distinction of eight regions of the Africa where slaves were embarked for transportation to the Americas. These regions are segments of the African Atlantic coastline in Africa from Senegambia in the North to West Central Africa in the South, with an eighth region in South-east Africa. In the website, off-shore islands are grouped with the region to which they are closest in proximity: the Cape Verde islands and Madeira with Senegambia, the Banana islands and Bance island with Sierra Leone, the Guinea islands with the Bight of Biafra, St. Helena with West Central Africa (although slaves were only disembarked there), and Indian ocean islands, the Mascarene islands, and Madagascar with Southeast Africa.

Are disembarkation regions in Estimates and the Voyages Database defined differently?

Yes. In the Voyages Database, the Caribbean forms one broad region, and major colonies are specific regions within it, with ports at a third level of analysis of geographical variables. In Estimates, on the other hand, broad regions include five wholly or partly within the Caribbean, broadly distinguished by colonizer nations: the British and French Caribbean, the Danish West Indies, and the Dutch and Spanish Americas. The two last had mainland as well as island colonies. The other broad regions are the same as in Search the database: Europe, Africa, Brazil, and Mainland North America.

How are images linked to other sections of the Voyages website?

In the Images section itself, the caption indicates when an image is relevant to a particular voyage. When one clicks on the image to obtain a larger view with information about it, below the commentary on the right is a link to related voyages. Clicking on it takes you directly to details about the voyage in the Voyages Database. In addition to links from Images to other sections of the website, there are links from other sections like Essays (in Assessing the Slave Trade) to the Images section. One of the three tabs in voyage detail (the page with information on a voyage opened when the row where it appears in the List of voyages is clicked) is to “Related images.”

How does “Search for Images” (the query box in “Images”) function?

Thumbnails of images that match the search criteria (a key term, a period of time, or one of the categories into which the images are organized) will appear in the main part of the window. The user can click on any of them for a full size image and commentary.

What kinds of information are displayed when one clicks on the thumbnail of an image?

Each image includes a brief description of its historical relevance, the creator and location of the original work and its date of creation, and links to related voyages in The Database.

Where do I find information on the website to put voyages into historical context?

Several resources are available on the Voyages website itself: essays and introductory maps in Assessing the slave trade, the chronology of key events in the history of the slave trade below the Estimates timeline, images in Resources, and the glossary with key terms used by historians of the slave trade. In addition, the list of Sources and links on the website, without pretending to be exhaustive, point the user towards some of the most important places beyond the website to look for information.

Can’t find the information you are looking for?

Please address unanswered questions to voyages@emory.edu, and we will attempt to provide this information for you.