They have all been background spot-cleaned to varying extents.
"Isaac Sprague (1811–1895) was born in Hingham, Massachusetts, and apprenticed with his uncle as a carriage painter. He was a self-taught landscape, botanical and ornithological painter. Sprague served as one of the assistants to John James Audubon on an ornithological expedition up the Missouri River (1843), taking measurements and making sketches. His diary of this expedition is in the Boston Athenæum." [source]
"The Athenæum is fortunate to have seventy-four of Sprague’s watercolor paintings of birds, drawn between 1839 and 1842." [source]
- The 'Art of Isaac Sprague' collection is online at the Boston Athenæum website. [browse all images] [alternative collection landing page]
- The Hunt Institute for Botanical Documentation has a page of biography/resources in relation to Isaac Sprague.
- The Hunt Institute (Carnegie Mellon University) also has a collection of thumbnail images of Sprague's meticulous botanical line sketches in pencil, lithographic and engraved formats.