Following the work of the second summer, Shepard dutifully wrote up his part of the survey and submitted it to the Governor in 1837. Percival, however, had only just begun the work that would consume him for a total of seven years. By 1841 he had surveyed and resurveyed the entire state from east to west at two-mile intervals, coming in contact with every square mile of Connecticut. These surveys were carried out in all seasons, mostly on foot, including one eleven-month period of nearly continuous travel. By this time, the legislature and the new governor, William W. Ellsworth, had tired of waiting for Percival's final report. Further money to support the survey was refused, and Percival was forced to write "a hasty outline ... under circumstances little calculated for cool consideration" - a hasty outline of 495 pages of minute detail and turgid prose!^4>

For the ten years following completion of the survey, Percival lived as a hermit in his New Haven apartment. Few were allowed access to the sanctum of his living quarters, and his own comings and goings were mysterious. Eventually, he was persuaded to carry out a geological survey of Wisconsin. He died in the midst of this pursuit in 1856. His passing brought many epitaphs that attest to the impact this singular man had on his contemporaries: "His eye betokened, even to a casual observer, the presence of rare genius," " . . . he will ever occupy a position shared by few of mortal race," and "We regarded him almost in the light of a sinless being.⁵

Percival's Report on the Geology of Connecticut is one of the landmark works of Connecticut geology. In his survey, Percival delineated all of the major rock types with an accuracy that leaves modern geologists shaking their heads in amazement. His report remained the main source for many areas of the state as late as the 1950s, and is still sometimes used to settle scientific disputes. Although criticized at the time of its publication for not presenting Percival's own theories of rock formation, theories "which we know the accomplished author possesses," it is this omission that makes the report a timeless work.⁶ Nineteenth-century geologists made great advances in mapping, but they were a long way from a comprehensive theory of earth processes. To his enormous credit,

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