In the autumn of 1815, Dr. Oliver was appointed to deliver a course of chemical lectures before the medical class at Dartmouth College. Although he had thus far pursued the study of chemistry as a collateral branch of medical science, he felt warranted in accepting the appointment, without, however, proposing to himself a more permanent position in this department.

In 1817, he was married to Miss Mary Robinson Pulling, the only daughter of Edward Pulling, Esq., an eminent barrister of Salem, and almost immediately went again to Philadelphia to avail himself of the advantages of that seat of medical learning, returning to Salem in the spring of 1818.

In the following year he was induced to undertake, in connection with the Hon. John Pickering, the preparation of a Greek lexicon, a work involving much labor and research, and the larger portion of which fell to his lot. Although mainly based on the Latin of Schrevelius, many of the interpretations were new, and there were added more than two thousand new articles. The magnitude of the task and its successful accomplishment at once raised him to a conspicuous rank among the scholars of his day.

In the summer of 1820 he accepted an appointment to the professorship of the Theory and Practice of Medicine, and of Materia Medica and Therapeutics in Dartmouth College, where he delivered his first course of lectures in the following autumn. He was also made Professor of Botany, and his lectures upon Physiology were among his most valuable contributions to medical literature. He took up his permanent residence in Hanover, in August, 1821, and from this time to the close of his connection with the college he was most faithful to all its interests. In 1825 he was appointed to the chair of Intellectual Philosophy in the Academical department of the college, a position which he filled with the ability that distinguished him elsewhere. The address delivered by him on the occasion of his induction into this professorship, upon the "Comparative Importance of the Study of Mental Science," was thus far, perhaps, his most successful literary effort. Clear, comprehensive, and abounding in passages of remarkable beauty and force, it established the reputation of its author both as a writer and a metaphysician.

In 1835 was published his "First Lines in Physiology," a treatise which received the highest commendation both at home and abroad. It passed through three editions, and although the rapid advance in physiological science since its publication has long since led to its disuse, it will still be admired by medical scholars for the purity of its style and the learning it everywhere displays.

In the spring of 1837, Dr. Oliver closed his connection with the college, and returned to Cambridge, where he was temporarily residing at the time of his appointment, again to resume the practice of his profession. He, however, delivered a course of lectures at the Dartmouth Medical School in the autumn of this and the following year. He was also induced, in 1840, after declining professorships both in St. Mary's College, Baltimore, and in Pennsylvania University, to deliver a course of lectures on Materia Medica at the Medical College of Ohio, but he resigned the chair at the close of the session, and returned again to Cambridge, where he resided to the close of his life. Although in declining health at this time, he did not relinquish professional practice until within a few months of his death, which took place on the 1st of June, 1842.

During his comparatively brief career, Dr. Oliver had become widely known as a medical and general scholar. As a teacher in the various departments of medical science with which he was connected he was also eminently successful. His lectures, always prepared with great care, were written with remarkable clearness and elegance, and were often listened to with attention by many outside the ranks of the profession. "His lectures to the under-graduates of the college," says a contemporary,[45] "would be thought, I am persuaded, still more remarkable than those upon Physiology. They were intended to exhibit the present state of mental philosophy. And the singular clearness with which he discriminated the settled points of absolute knowledge in this comprehensive and yet imperfect science, his happy development of intricate and complicated principles, and the beautiful colors which a true poetic spirit enabled him now and then to throw over the bald peaks and angles of this cold region, entitle him to a rank among metaphysicians as eminent as he maintained in his appropriate profession."

[45] Eulogy on Daniel Oliver, delivered by Rev. C. B. Haddock, professor of Belles Lettres.

"The intellectual character of Dr. Oliver," the same writer afterwards adds, in language admirably chosen, "came nearer than it has been my fortune to observe in almost any other instance to the idea of a perfect scholar. He was at once profound, comprehensive, and elegant. Upon no subject which he had considered was his knowledge fragmentary or partial. A philosophic, systematic habit of mind led him always to seek for the principles of things, and to be satisfied only with the truth. The compass of his inquiries was as extraordinary as their depth. He had investigated with care a surprising extent of knowledge. A master of his own language, and minutely acquainted with all its principal productions, he was also thoroughly versed in the Greek, and familiar with the original works which have given to that tongue the first place among human dialects. The German he read with facility, and had pursued his favorite studies in the masters of its profound learning. Of French and Italian he was not ignorant. Music, both as a science and an art, was his delight and recreation. In the arts of painting and sculpture his information was liberal and his taste said to be excellent. Morals and politics he had studied in their theory, and in the history of the world. His acquaintance with civil history was among the most extraordinary of his attainments. The beautiful in Nature, in life, or in art or literature, few men have so exquisitely enjoyed or so justly appreciated.

"Thus, the principal elements of a perfect mind seem to have been singularly united and harmonized in him,—exactness of knowledge, liberal learning, and true taste."