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Rh in the conduct of a large publishing-house, and was only able to give his hours of leisure to science.

was born in Wilmington, Delaware, March 4, 1792. He was descended from ancestors who came over from Gloucestershire, England, with William Penn, and were described as "a couple of noted and valued preachers." He was the fifth son of James Lea, a wholesale merchant, and was at first put in a course of classical instruction at the academy in Wilmington, in preparation for the medical profession. This purpose was afterward given up, and, when he was fifteen years old, Isaac was sent to Philadelphia to engage in mercantile business in association with his brother. He had inherited a strong taste for Nature from his mother, and found a congenial spirit in Professor Vanuxem, then also a youth, with whom he formed the habit of making collecting excursions around the city. The two companions were soon led, by what they found and observed, to inquiry into the composition and structure of the rocks; they had to pursue it at first without any guidance, but in a short time became acquainted with the mineralogical collection of Dr. Adam Seybert. A diversion to their pursuits was given by the occurrence of the war with Great Britain in 1812. They joined a volunteer rifle company, which offered its services to the Governor. Although the company was disbanded without being called into service, young Lea had, by joining it, engaged enough in war to violate the principles of the Society of Friends, and he lost his birthright in it. Among the excursions which the two youths made was one to the coal-mines near Wilkesbarre, where they found slates containing mollusca, which Lea described forty years afterward in the "Journal of the Academy of Natural Sciences." They walked back, over the Pocono Mountain through the Wind-Gap, where Lea found the first trilobite they had ever seen, and down the Delaware River. In 1815 they were both elected members of the Philadelphia Academy of Natural Sciences, and began to take active parts in its proceedings; and in this society Mr. Lea read his first paper, already referred to, embodying the results of many years of close observation which the friends had made upon the rocks during their excursions.

On the publication, in 1818, of Professor Silliman's prospectus of the "American Journal of Science," Mr. Lea procured the names of fourteen subscribers to the journal—an act which Professor Silliman afterward declared "was the turning-point of the scheme"; for, receiving such encouragement from a person with whom he had no personal acquaintance, he was sure the journal would be successful. Mr. Lea contributed several papers to the early numbers of this journal, at the editor's request; but the article of this period which is perhaps most worthy of special mention, is one that he published in 1828 in the "American Quarterly Review," on the Northwest Passage, in which he expressed the opinion that, if the passage were ever made, it must be, as was indicated by the direction of the currents, from west to