€16 REPOET— 1891. 



and establishing a firm basis for the theory that the coal has, for by far the most 

 part, been formed of plants growing where the coal now lies, although some local 

 varieties have arisen from the occasional driftage of floating timber and herbage, 

 and of long-continued maceration of vegetable matter in lakes and pools elsewhere. 



Mr. (afterwards Sir) \V. E. Logan, having for several years worked on the 

 geology of South Wales, in 1837 gave his maps and information to the enthusiastic 

 promoter of the Geological Survey of the British Islands, Mr. (afterwards Sir) 

 H. T. De la Beche, for public use in the construction of the Survey Map and in 

 developing the structure of the country. The first volume of the ' Memoirs of the 

 Geological Survey,' 1846, contains, at p. 145, Sir H. T. De la Beche's acknowledg- 

 ment of Sir (then Mr.) W. E. Logan's gift of the valuable results of his investiga- 

 tions in the Coal-measures and discovery of the nature and meaning of the frequent 

 underclays, an account of which Mr. Logan had already publislied in the ' Annual 

 Report of the Royal Institution of South Wales ' for 18o9 ; in the 'Proceedings 

 of the Geological Society of London,' vol. iii., February 1840, p. '276, and March 

 1842, p. 707, &c. : and ' Transactions of the Geological Society,' second series, 

 vol. vi., 1842, p. 491, &c. 



The hypotheses of the formation of coal offered by earlier writers are carefully 

 reviewed in De la Beche's elaborate memoir ; and the growth of opinion as to 

 coal having been made by plants growing in place is traced from De Luc (1793), 

 Lindley and llutton (1833 and 1835), Adolphe Brongniart (1838), to W. E. I^ogan, 

 by whom, indeed, it was fully established before 1837. Opinions as to the nature 

 of the Stir/maria ficoides, so abundant in the ' underclays,' are also referred to ; 

 and that it is really the root of Sif/illaria is accepted on the good authority of 

 Brongniart and Binney (p. 150). Dr. Buckland's summary (in his Anniversary 

 Addresses to the Geological Society, 1840 and 1841) > of what had been advanced 

 by British geologists in the elucidation of the Coal-measures and their natural 

 history comprised mainly the observations made by Ansted, llawkshaw, Barber, 

 Beaumont, J. E. Bowman, and particularly W. E. Logan. He stated in 

 his Address of 1840 that ' some of the vegetables which foi-med our beds of 

 coal grew on tlie identical banks of sand and silt and mud which, being now 

 indurated to stone and shale, form the strata that accompany the coal ; whilst 

 other portions of these plants have been drifted to various distances from the 

 swamps, savannahs, and forests that gave them birth, particularly those that are 

 dispersed through the sandstones, or mixed with fishes in the shale beds.' 



Dr. Buckland's summary in 1841 is given by De la Beche - ' as expressing his 

 opinion that the Stifftnnriajicoides [which was at that time still regarded by many as 

 an individual floating plant], growing in ponds or lagoons in the localities where we 

 now discover its remains, hj mixture with mud or silts disseminated among them, 

 formed the underbeds, upon which also grew the plants which now form the coal- 

 beds, these latter, by subsidence, being covered by sand or mud, forming sand- 

 stone or shale, between the coal strata, successive coal-beds being formed as the 

 necessary conditions arose.' Sir (then Mr.) G. Lyell's important additions to the 

 subject, then lately given in his ' Travels in North America,' 2 vols., 1845, quoted 

 and applied by De la Beche, were subsequently enlarged in his ' Second Visit,' &e., 

 2 vols., 1849, and in his ' Elements of Geology,' edition of 1851, and subsequently. 



De la Beche's Memoir, after having presented some explanations of geological 

 phenomena, and treated of the general range and occurrence of the Silurian and 

 Devonian rocks in the southern moiety of Wales and the South-western Counties 

 of England, proceeds to describe the Carboniferous strata, and at p. 143 takes up 

 the Coal-measures ; and his work remains a classic autliority on the subject. De 

 la Beche's account of these strata has not been much modified, except by the 

 descriptions of many additional fossils, and details about the special characters of 

 those then known. 



Other information, however, on the past and present conditions of the South- 

 Welsh Coal-field is found in Mr. (now Sir) A. C. Ramsay's paper 'On the Denu- 

 dation of South Wales and the adjacent English Counties,' in the same volume of 



' rroceed. Geol. Son., vol. iii., pp. 229 and 487. 

 2 Mem. Geol. Sitrv., vol. i., 1846, p. 152. 



