The Greek and English Lexicon is his work of greatest labor in the department of classical learning. This alone would entitle him to praise from all who love liberal studies. With the well-thumbed copy of this book, used in college days, now before us, we feel how much we are debtor to his learned toil. Planned early in Mr. Pickering's life, it was begun in 1814. The interruptions of his profession induced him to engage the assistance of the late Dr. Daniel Oliver, Professor of Moral and Intellectual Philosophy at Dartmouth College. The work, proceeding slowly, was not announced by a prospectus until 1820, and not finally published until 1826. It was mainly founded on the well-known Lexicon of Schrevelius, which had received the emphatic commendation of Vicesimus Knox, and was generally regarded as preferable to any other for the use of schools. When Mr. Pickering commenced his labors there was no Greek Lexicon with definitions in our own tongue. The English student obtained his knowledge of Greek through the intervention of Latin. And it is supposed by many, who have not sufficiently regarded other relations of the subject, as we are inclined to believe, that this circuitous and awkward practice is a principal reason why Greek is so much less familiar to us than Latin. In honorable efforts to remove this difficulty our countryman took the lead. Shortly before the last sheets of his Lexicon were printed, a copy of a London translation of Schrevelius reached this country, which proved, however to be "a hurried performance, upon which it would not have been safe to rely."[146] [146] Preface to Pickering's Lexicon.