Plotting a Course
Four pairs of dividers were found on the Mary Rose. They are made of brass and would have been used to plot out courses and distances on charts. We didn’t find any maps or charts on the Mary Rose, they most likely rotted away.
The pilot on the Mary Rose might have used a sort of chart called a “Portulan”. This showed the outline of the coast and the names of ports along the coast. Compass roses were drawn on the chart to help the pilot fix his course.
The charts were made of goat or sheepskin as this was more resistant in wet weather than paper.
The pilot would have also had a book of written sailing instructions called a “Rutter”. This would have included lists of landmarks, distances, tide tables and notes about rocks and places to anchor.
Several book covers were found on the Mary Rose, but since the paper didn’t survive, we don’t know if one of them was a Rutter.