Mark Catesby's Natural History of Carolina, Florida and the Bahama Islands, published between 1729 and 1747, is justifiably famous for being the first work in English to describe the natural history of a region of North America. Catesby illustrated this volume himself with engravings of the plants he had seen and collected during his travels in the Carolinas, etc., between 1721 and 1726. Catesby apologized for his deficits as a painter, a trade for which he was untrained, but on the whole did a decent job. The publication of the Natural History was a big deal among western European naturalists; Catesby got elected to the Royal Society in 1733 on the strength of his work, and Linnaeus himself cited a number of Catesby's plates while describing North American species in his Species Plantarum.
But here's the thing - Catesby only painted a small portion of the plants he saw, and only a very small portion of the plants he collected. Of the 432 (or so) vascular plant specimens in the two volumes in the Sloane, 64 of them have corresponding engravings in the Natural History, and many of those are duplicates. That leaves 368 specimens with no paintings. That correspondence is not entirely accurate, either; it's based on notes made on the folio pages by previous scholars who examined the Sloane collections with an interest mainly in their relationship to the Natural History. There are some specimens that do not appear to be exactly what Catesby has painted.
Digitizing these collections makes two new things possible. First, we can now examine the full body of Catesby's scientific work, his actual collected data (a collection that will be fuller once we combine the Sloane materials with the Sherard specimens from Oxford). Second, we can easily examine Natural History engravings and herbarium specimens side by side.
You can see these images side by side here, Alignment of Mark Catesby's Hortus Siccus with his Natural History. We've transcribed the printed descriptions from the Natural History along with any handwritten notes on the specimen pages. There are a few specimens that previous researches linked with different pages in the Natural History from the ones that we identified; in those cases, we've posted both Natural History pages so you can see for yourself what's going on.