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 234 Thomson, and became a Fellow of the Chemical Society on May 18, 1841, when the Society was barely three months old. He then left London to take up calico printing and dyeing in the neighbourhood of Manchester, but returned south in 1843, at the invitation of Mr Lawes, to assist in the agricultural investigations at Rothamsted, Herts.

Mr John Lawes had begun experiments in 1837 on growing plants in pots with various manures. He discovered the fact that mineral phosphates when treated with sulphuric acid yielded a most effective manure. Taking out his patent for the production of superphosphates in 1842, Lawes soon found himself busy with the establishment of a successful business. Not wishing to give up the agricultural investigations which he had commenced in the fields of Rothamsted he decided to obtain scientific assistance, and remembering the young chemist he had met in Dr Thomson's laboratory, Gilbert was invited in June 1843 to superintend the Rothamsted experiments. Thus began that partnership in investigation which has yielded such a rich harvest of results, and an association with Rothamsted which lasted for fifty-eight years.

Gilbert was elected a Fellow of the Royal Society in 1860, and received a Royal Medal in 1867. He was President of the Chemical Section of the British Association in 1880, and President of the Chemical Society, 1882-3. In 1884 he was appointed Sibthorpian Professor of Rural Economy at Oxford, and held the chair until 1890. He was a member of various foreign academies and societies, and was the recipient of honorary degrees from several home universities, becoming LL.D. of Glasgow (1883), M.A. of Oxford (1884), LL.D. of Edinburgh (1890), and Sc.D. of Cambridge (1894). In 1893 on the occasion of the jubilee of the Rothamsted experiments he received the honour of knighthood.

The character and scope of Gilbert's life-work was well described by Prof. Dewar at a special meeting of the Chemical Society in 1898, when he said, "The work of Gilbert, as we know, was early differentiated into that most complex and mysterious study, the study of organic life. For the last fifty years he has devoted his attention to the physiology of plant