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ceeded to the survey of the eastern portion of Lower Canada, where he showed that the rocks, instead of being of a primitive azoic nature as had been supposed, were altered and crystallised palæozoic strata, a fact which, although it is the key to the geology of north-eastern America, had never hitherto been demonstrated. He also declared that the rocks forming the Laurentian and Adirondack mountains, previously regarded as unstratified, were in reality, in his opinion, disturbed and altered sedimentary deposits of vast thickness. The skilful manner in which he traced out the structure of these ancient formations was, according to Sir R. Murchison, perhaps the most remarkable of Logan's achievements. The work of the survey, which Logan steadily continued (until by 1862 he had surveyed over one hundred thousand square miles of territory) was rendered particularly arduous by the absence of any accurate map of the country, so that he was often obliged to make a topographical survey of the country pari passu with a geological one.

In 1851 Logan represented Canada at the Great Exhibition of 1851, forwarding a large collection of the economic minerals of Canada, which was commended as the most interesting and complete mineral exhibit in the exhibition. He was in this year elected F.R.S. In 1855 he was Canadian commissioner at the Paris Exhibition, and was presented by the Emperor Napoleon III with the cross of the Legion of Honour; while on a subsequent visit to England he was awarded the Wollaston medal of the Geological Society, and was, on 29 Jan. 1856, knighted by the queen at Windsor. On his return to Canada an address was presented to him by the Canadian Institute (of which he had been first president), and his portrait was hung in the meeting-hall of the society. He had previously been created LL.D. by the university of Montreal, and an honorary member of numerous scientific societies both British and foreign. Logan again represented Canada at the exhibition of 1862, and in the following year appeared his great work on the ‘Geology of Canada,’ in which his collaborator was his former assistant, Thomas Sterry Hunt. The volume may be described as a generalised summary of the progress of the survey during the first twenty years of its existence; it contains, says Sir A. Geikie (Nature, 1875, ii. 162), ‘the gist of Logan's work, as well as a luminous account of all that was then known of the geology and mineral wealth of the province.’ Later in 1863 he went to London to arrange for the publication of his large geological map of Canada. The publication of a brochure on ‘Eozoon Canadense,’ with notes, by J. W. Dawson and W. B. Carpenter, made known the existence of what were then believed to be organisms—the most ancient relics of life yet discovered—and was followed in 1867 by the award of one of the royal medals of the Royal Society.

Logan resigned his directorship of the survey in 1870, spent the winter of 1874–5 with his sister in Wales, died at Castle Malgwin on 22 June 1875, and was buried in Llechryd Church, Cardiganshire. Logan, who was unmarried, founded in 1872, by a donation of twenty thousand dollars, the ‘Logan chair of geology’ in M'Gill University, Montreal (ib. 1872, i. 448).

Besides his great work on Canadian geology and his annual reports on the progress of the survey, of which the most important is that of 1865, containing a special account of palæozoic fossils, Logan contributed numerous articles to the ‘American Journal of Science and Art’ and to the ‘Proceedings of the British Association.’ He also wrote a brief sketch illustrating the Canadian exhibit at Paris in 1855, which appeared both in French and English. His writings, however, although accurate and precise, are deficient in power of expression, and hardly convey an adequate impression of his vast stores of original information, the product of many years of keen and systematic observation. His distinguishing characteristic as a geologist lay in the power he possessed of grappling with the stratigraphy and structure of the most complicated regions. George Bryce, in his ‘Short History of the Canadian People’ (p. 479), calls him without exaggeration ‘the father of Canadian science.’

[Life by Bernard J. Harrington, Montreal, 1883 (with engraved portrait); Appleton's Cyclopædia of American Biography, iv. 7; Times, 24 July 1862 and 26 June 1875; Nature, 1 July 1875; Geolog. Mag. August 1875, p. 382; Murchison's Siluria, passim; Geolog. Survey of Great Brit., Libr. Cat., p. 195. The proof of this article has been kindly revised by Sir Archibald Geikie.]

T. S.

LOGGAN, DAVID (1635–1700?), artist and engraver, was born at Danzig in 1635. It is said, but on no very certain authority, that he learnt engraving in Denmark from Simon van den Passe, and in Holland from Hendrik Hondius, and that he followed Hondius's two sons to England. The date of his arrival in England is uncertain, but it must have been before 1653, if Vertue be right in assigning his earliest portrait to that year (Walpole, ed. Dallaway, v. 185). In 1665 he was residing at Nuffeild, near Oxford, and had made the acquaintance of Anthony à