Portugal, where it fought with distinction at Vimeiro, and afterwards shared in Sir John Moore's Spanish campaign and his disastrous retreat to Corunna. The regiment embarked safely during the night of 16 Jan. 1809, but narrowly escaped shipwreck on the Cornish coast. It remained in England, but in the autumn Murchison went out to Sicily as aide-de-camp to his uncle, General Mackenzie, returning in 1811. The latter was then appointed to a command in Ireland, and took Murchison with him. But the peace of 1814 placed him on half-pay. As it happened, he was in Paris when the news of Napoleon's landing arrived. Murchison then, in hope of seeing active service, and against his uncle's advice, exchanged into a cavalry regiment to no purpose, for his troop remained in England. But as a consolation he met in the Isle of Wight Charlotte, daughter of General and Mrs. Hugonin, whom he married on 29 Aug., and shortly afterwards retired from the army.
This was the turning-point of Murchison's life. 'From this time he came under the influence of a thoughtful, cultivated, and affectionate woman ... to his wife he owed his fame, as he never failed gracefully to record ' (Geikie). It was, however, still some years before he settled down to scientific work. For a brief time he thought of being ordained, but soon gave up the idea, and started with his wife in the spring of 1816 for a leisurely tour on the continent. Here they remained till the summer of 1818, chiefly at Rome and Naples, where Murchison plunged enthusiastically into the study of art and antiquities. On his return to England he sold Tarradale, to the benefit of his income, and settled down at Barnard Castle, devoting himself to field-sports. But about five years afterwards he became acquainted with Sir Humphry Davy, and determined to remove to London in order to pursue science instead of the fox. In the autumn of 1824 he began to attend lectures diligently at the Royal Institution. He was admitted on 7 Jan. 1825 a fellow of the Geological Society, and that science quickly kindled his enthusiasm. The following summer was devoted to field-work around Nursted, Kent (where General Hugonin resided), and to a tour westwards as far as Cornwall. Murchison's first paper, a 'Geological Sketch of the Northwestern extremity of Sussex and the adjoining parts of Hants and Surrey,' was read to the Geological Society at the end of 1825. In 1826 he was elected F.R.S., an honour which at that time indicated social position more than scientific distinction, and spent the summer examining the Jurassic rocks of Yorkshire and on both coasts of Scotland. This was the first of a series of summer journeys for the study of geology, and of a number of papers which quickly made him 'one of the most prominent members of the Geological Society.' In 1827 he travelled with Sedgwick in the highlands; in 1828, accompanied by his wife, with C. Lyell in Auvergne and Northern Italy, the Murchisons returning from Venice across the Tyrol to the Lake of Constance. In 1829 Murchison and Sedgwick wandered through Rhine-Prussia and Germany to Trieste, whence they worked their way through the Eastern Alps to the Salzkammergut, and so back by Constance across France. In 1830 Murchison with his wife revisited the Eastern Alps to continue the last year's work.
After five years of service as secretary of the Geological Society he was elected president in 1831, and almost simultaneously quitted the secondary rocks, hitherto the chief subject of his studies, for those older masses, underlying the carboniferous or the old red sandstone, which were called by Weiner the transition, by some greywacke. These, geologically speaking, were an almost unknown land. In the summer of 1831 Sedgwick attacked the northern part of Wales from Anglesey, Murchison the more southern district from the eastern borderland. At one time a joint tour had been suggested ; but the intention was unfortunately never realised. Murchison devoted the next two summers to similar work, and in the autumn of 1833 determined that his researches should result in a book. In the summer of 1834 the two friends spent some days together in Wales, endeavouring to fit their separate work, but unluckily they parted without discovering that the lower part of Murchison's system of strata (to which in 1835 he assigned the name Silurian) was identical with the upper part of that worked out and called Cambrian by Sedgwick. The preparation of Murchison's book took a long time, but field-work went on in the summer, and in 1836 he made the first of three journeys to Devonshire to unravel another 'greywacke' district. At last, at the end of 1838, 'The Silurian System,' a thick quarto book, with a coloured map and an atlas of plates, of fossils, and sections, was published. It embodied and systematised the results obtained by Murchison himself, or supplied to him by others, which had been already communicated to geologists in numerous papers.
The researches of Sedgwick and Murchison in the west of England were followed by papers in which was proposed the establishment of a Devonian system intermediate
