 In 1876, he announced the discovery, later confirmed by other archaeologists, of traces of human presence in the Delaware River Valley dating from the first or "Kansan" ice age, and inferentially from the pre-glacial period when humans are believed to have entered upon the North American continent.However, today the consensus of archaeologists is that most of Abbott's "Trenton Gravel Implements" date from the Middle Woodland period of about A.D. 300–900.From 1876 to 1889, he was assistant curator of the Peabody Museum in Cambridge, Massachusetts, to which he presented a collection of 20,000 archaeological specimens; he freely gave also to other archaeological collections.