Along with a nephew and another friend, Wilson made a pedestrian tour to the Falls of Niagara, in October 1804, and on his return published in the "Portfolio" a poetical narrative of his journey, entitled "The Foresters,"--a production surpassing his previous efforts, and containing some sublime apostrophes. But his energies were now chiefly devoted to the accomplishment of the grand design he had contemplated. Disappointed in obtaining the co-operation of his friend Mr Lawson, who was alarmed at the extent of his projected adventure, and likewise frustrated in obtaining pecuniary assistance from the President Jefferson, on which he had some reason to calculate, he persevered in his attempts himself, drawing, etching, and colouring the requisite illustrations. In 1806, he was employed as assistant-editor of a new edition of Rees' Cyclopedia, by Mr Samuel Bradford, bookseller in Philadelphia, who rewarded his services with a liberal salary, and undertook, at his own risk, the publication of his "Ornithology." The first volume of the work appeared in September 1808, and immediately after its publication the author personally visited, in the course of two different expeditions, the Eastern and Southern States, in quest of subscribers. These journeys were attended with a success scarcely adequate to the privations which were experienced in their prosecution; but the "Ornithology" otherwise obtained a wide circulation, and, excelling in point of illustration every production that had yet appeared in America, gained for the author universal commendation. In January 1810, his second volume appeared, and in a month after he proceeded to Pittsburg, and from thence, in a small skiff, made a solitary voyage down the Ohio, a distance of nearly six hundred miles. During this lonely and venturous journey he experienced relaxation in the composition of a poem, which afterwards appeared under the title of "The Pilgrim." In 1813, after encountering numerous hardships and perils, which an enthusiast only could have endured, he completed the publication of the seventh volume of his great work. But the sedulous attention requisite in the preparation of the plates of the eighth volume, and the effect of a severe cold, caught in rashly throwing himself into a river to swim in pursuit of a rare bird, brought on him a fatal dysentery, which carried him off, on the 23d of August 1813, in his forty-eighth year. He was interred in the cemetery of the Swedish church, Southwark, Philadelphia, where a plain marble monument has been erected to his memory. A ninth volume was added to the "Ornithology" by Mr George Ord, an intimate friend of the deceased naturalist; and three supplementary volumes have been published, in folio, by Charles Lucien Bonaparte, uncle of the present Emperor of the French.