Sources

Honour, H., and Fleming, J. (1999). A World History of Art.
National Gallery of Art. (2020). The Elements of Art: Line. https://www.nga.gov/education/teachers/lessons-activities/elements-of-art/line.html. Visited 15 October 2020.

Images:

1 Georges Seurat, 1884. Sunday Afternoon on the Island of la Grande Jatte. Image courtesy of Wikimedia Commons.
2 Albert Edelfelt, unknown (part of sketchbook). Image courtesy of Finnish National Gallery.