the firm name was changed again to Lea & Blanchard. The publishing house became one of the most successful in America, and was known for publishing items such as The Encyclopedia Americana and a dictionary of German lexicon. In the early 1830s, he became a partner in the Dauphin and Susquehanna Coal Company which owned 42,000 acres on the eastern bank of the Susquehanna River. In 1851, Isaac retired from the publishing business and made his son Henry Charles Lea a full partner and the name was changed to Lea Brothers. Scientific career Lea worked with Lardner Vanuxem during his work on the geology of New York. Many geological histories are defined by mollusk fossils which led Lea to also study living mollusks. In 1815, Lea joined the Academy of Natural Sciences and published his first paper on minerals found in the Philadelphia area in 1817. Lea devoted his leisure time to natural history, both collecting objects and publishing books (some illustrated by his son Henry Charles Lea). He was especially interested in freshwater and land mollusks. He studied mollusks from the Ohio River submitted to the Academy of Natural Sciences by Major Stephen Harriman Long and shells collected by his brother near Cincinnati. Lea described these specimens in the publication Description of Six New Specimens of the Genus Unio which he presented at the American Philosophical Society in 1827 and was the first of multiple papers on Unio. For 50 years he delivered and published 279 scientific articles, books and essays. He named 1,842 species of fifty genera of freshwater and land mollusks, however many of the species he described are not distinct. His publications on geology included a range of topics including coal, earthquakes, fossils and minerals. In 1849, Lea presented a paper on fossilized footprints he discovered in red sandstone in Mount Carbon, Pennsylvania. Lea contended the tracks were reptilian and that due to the strata of rock where the footprints were found, they were from the Devonian Period between 360 and 408 million years old and constituted a new species that he named Sauropus primaevus. The finding sparked a controversy in the geology community and the date of the fossil was challenged by Henry Darwin Rogers, the state geologist of Pennsylvania. Noted geologist Louis Agassiz proposed that the footprints were not those of a reptile but rather those of an amphibian. The footprints have since been