This work brought Percival a high reputation as a geologist. He was engaged by the American Mining Company to investigate the lead deposits in Wisconsin and this in turn resulted in his employment by that state to make a geological survey similar to that of Connecticut. He had made his first report and was engaged upon his second when he became ill and in May, 1856, he died and was buried in Hazel Green, Wisconsin. "Eminent as a Poet," runs his epitaph, "rarely accomplished as a Linguist, learned and acute in Science, a Man without Guile." During his employment in Wisconsin his friends had bought a lot and built a house for him in New Haven. It was a queer structure, built after the poet's own plans, with the entrance at the rear, blind windows at the front, and of only one story in height. He was looking forward to spending here his last years, close to his college, with his few intimate friends, surrounded by his books. During an interval in his Wisconsin employment he came to New Haven to inspect his future home and is said to have broken down completely as he was compelled to leave by the duty that called him westward. He was a strange creature, impossible to get along with, handicapped by an over-sensitiveness that led him into resentments that often held the implication of ingratitude, and with a constant grudge against the world. He should have been endowed and relieved of all the detail of life. Even then it is doubtful if he would have produced great poetry, unless he had been rigorously trained by some dominant master to condense, revise and work over again and again his diffuse, sentimental and dreamy verses. A few of them retained for a time a certain vogue and then gradually passed into oblivion. Perhaps the two that were longest remembered were "To Seneca Lake" and "The Coral Grove." It is an odd thing, but some selections from a boyish effort entitled "Seasons of New England," hitherto generally cited as evidence of his youthful absurdities, would make excellent examples of the free verse that nowadays is taken so seriously. In this respect, at least, he was ahead of his time. In his review of the "Life and Letters" Lowell seems rather dogmatic and intolerant, but with his inevitable insight and art of statement he crystalizes into one sentence the whole trouble with Percival. "He appears," writes Lowell, "as striking an example as could be found of the poetic temperament unballasted with those less obvious qualities which make the poetic faculty."