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 250 the acquaintance of Prof. Lindley, who had for so long known him only as a correspondent and collaborator.

Soon afterwards he was offered the post of naturalist to the Niger expedition, which he refused, and, as it turned out fortunately, for the journey proved disastrous. Stanger, of Stangeria fame, took his place.

In 1842, having then returned to Manchester and started in practice, Williamson made his first attempt at microscopic work, having become interested in the Foraminifera of the Chalk. He also began to examine Confervae, Diatoms and Desmids, finding perhaps, as others have done, that the Freshwater Algae give the best introduction to microscopic biology.

The work on Foraminifera became one of the most important in Williamson's career. In 1845 he wrote his valuable paper on microscopic organisms in the mud of the Levant. His work in this field culminated in his monograph of Foraminifera, issued by the Ray Society in 1857.

In 1851 Williamson was appointed Professor of Natural History, which included Zoology, Botany and Geology, at the new Owens College, Manchester. He tells us, "The botanical portion of my work was that for which I was least prepared"—"of the German language I was utterly ignorant ." The almost insuperable difficulties of a triple Professorship were at first met by spreading the complete course over two years, a sensible plan which was rendered impracticable by the more rigid requirements of examinations. It was not, however, till 1872 that a division of the duties of the chair took place; Williamson was then relieved of the geological teaching by the appointment of Prof. Boyd Dawkins; in 1880 the zoology was taken over by the late Prof. Milnes Marshall, Williamson thus retaining the very subject, botany, with which he had originally been the least familiar.

In addition to his peculiarly arduous duties as Professor, Williamson was a great populariser of science. He was one of the first two members of the Owens' staff to start, in 1854, evening classes for working men. He gave numerous scientific lectures at the Royal Institution in London and elsewhere, his