Page:Dictionary of National Biography volume 51.djvu/189

 ‘British Palæozoic Fossils in the Geological Museum of the University of Cambridge’ by Professor McCoy (1854), and a preface to ‘A Catalogue of the Cambrian and Silurian Fossils,’ in the same collection, by John William Salter [q. v.] and Professor John Morris [q. v.] (1873). He appears in the ‘Royal Society's Catalogue of Scientific Papers’ as the sole author of forty papers and joint-author of sixteen, published for the most part in the ‘Transactions’ or the ‘Quarterly Journal of the Geological Society,’ the ‘Transactions of the Cambridge Philosophical Society,’ or the ‘Philosophical Magazine.’ Of these the more important can be grouped in five divisions: 1. ‘On the Geology of Cornwall and Devon,’ a subject which was dealt with in the first of his more important communications, read before the Cambridge Philosophical Society in 1820 (Trans. C. P. S. i. 89). Other papers follow, some of them written in conjunction with Murchison. In these the order of the rocks beneath the new red sandstone of the south-west of England was worked out, the stratigraphy of the Carboniferous deposits and of the underlying Devonian system was gradually established, and some valuable contributions were made to the history of the various crystalline masses in Devon and Cornwall, including those in the Lizard peninsula.

2. The next group of papers, small in number, deals with the ‘new red sandstone’ in the northern half of England, giving the results of field work between 1821 and 1824. One of them describes the mineral character and succession of the magnesian and other limestones, the marls, and the sandstones, which extend along the eastern flank of the Pennine range from the south of Northumberland to the north of Derbyshire, dwelling more particularly on the lower part; another deals with the corresponding rocks, breccias and conglomerates, with sandstones, marls and thin calcareous bands, on the western side of the same range, more especially in the valley of the Eden. The part of the new red sandstone more particularly worked out by Sedgwick has since been termed Permian, but his diagnosis of the relations of the strata, their marked discordancy from the underlying carboniferous and their closer affinity with the overlying red rocks, since called Trias, has proved to be correct.

3. A third group deals with a yet more difficult question—the geology of the lake district and its environs. The researches just named were carried downwards through the underlying carboniferous rocks, and then the intricacies of the great central massif were attacked. This task more especially occupied the summers from 1822 to 1824, and its results were published in papers, dating from 1831 to 1857. A more popular account was also given in five letters addressed to Wordsworth, published afterwards in Hudson's ‘Complete Guide to the Lakes’ (1853).

4. A fourth group includes a large number of miscellaneous papers, published at various dates and on different geological topics. Among the more important of these may be noted ‘On Trap Dykes in Yorkshire and Durham’ (1822); ‘On the Association of Trap Rocks with the Mountain Limestone Formation in High Teesdale’ (1823–4); two in 1828, written in conjunction with Murchison—one on the Isle of Arran, another on the secondary rocks in the north of Scotland; one (with the same coadjutor) on the Eastern Alps (1829–30); and last, but not least, the classic paper ‘On the Structure of Large Mineral Masses, &c.,’ read before the Geological Society of London, and published in their ‘Transactions’ (iii. 461).

5. The fifth and largest group deals with the geology of Wales. Sedgwick first took this in hand in the summer of 1831, when he was working for part of his time with Charles Robert Darwin [q. v.] Commencing with the rocks of Anglesey for a base, he worked over Carnarvonshire, and in 1832 carried on his researches into Merionethshire and Cardiganshire. In 1834 he accompanied Murchison over the district on the eastern border of the principality, on which the latter had been engaged. The results of these and of later visits, more especially in 1842 and 1843, were described from time to time in verbal communications to the Cambridge Philosophical Society and to the British Association, but the first systematic papers were read to the Geological Society in 1843 (Proc. Geol. Soc. vol. iv. pt. i. pp. 212; Quart. Journal Geol. Soc. i. 5). Others followed in 1844 and 1846. Soon after Murchison had published his ‘Silurian System,’ in 1839, it became evident that difficulties existed in correlating the work done by the two geologists in their several districts, and a controversy gradually arose concerning the limits of the Cambrian system as established by Sedgwick and of the Silurian system of Murchison (names which were first used about 1835). The general structure of north Wales had been determined by Sedgwick as early as 1832, and subsequent investigation in this region has confirmed the general accuracy of the order in which he placed the beds and of the main divisions which he established; while it has been proved that Murchison had confused together two distinct formations,