John W. Dawson returned to Joggins in the summer of 1853 without Charles Lyell, who had been hired to work for the 1853 World's Fair in New York City. Dawson continued to investigate the Joggins Formation alone, and on 2 November 1853 sent his completed survey to Lyell. Dawson claimed that his and Lyell's findings matched those made by William Logan, and by 1855 Dawson no longer used his own survey and began to rely only on Logan's for reference. In a 2005 review of their respective surveys, it was determined that Dawson and Lyell's work was more accurate than Logan's. "Hylonomus lyelli" was discovered at the Joggins Cliffs by Dawson and formally described in 1859. Named in honour of his colleague, Charles Lyell, the species would later be recognized as the oldest known reptile and be made the provincial fossil of Nova Scotia. A fossil trackway Dawson discovered in 1866 was at one point believed to have been made by the largest known invertebrate "Arthropleura", but Dawson eventually found the trackway distinct enough to be assigned to its own species: "Diplichnites aenigma". Dawson would devote much of his career to studying the Joggins Formation and again returned in 1877, undertaking an expedition funded by the Royal Society to search for more specimens embedded in the fossil trees. Explosives were detonated at Coal Mine Point, exposing twenty-five lycopsid trees; of these, fifteen contained vertebrate fossils representing over one hundred specimens, the largest single collection of Palaeozoic tetrapods ever found. Dawson and Lyell would come up with many theories over the years to explain why so many animals would assemble there. The first suggestion had been that the creatures had been denning, but it was also suggested that they had died elsewhere and were washed into the trunks by water. Ultimately, Dawson would come to believe that the animals had fallen into the trunk and died there, unable to escape.