The Upper Ludlow rocks are mainly soft mudstones and shales with some harder sandy beds capable of being worked as building-stones. These sandy beds are often found covered with ripple-marks and annelid tracks; one of the uppermost sandy layers is known as the “Fucoid bed” from the abundance of the seaweed-like impressions it bears. At the top of this sub-group, near Ludlow, a brown layer occurs, from a quarter of an inch to 4 in. in thickness, full of the fragmentary remains of fish associated with those of Pterygotus and mollusca. This layer, known as the “Ludlow Bone bed,” has been traced over a very large area (see [Bone Bed]). The common fossils include plants (Actinophyllum, Chondrites), ostracods, phyllocarids, eurypterids, trilobites (less common than in the older groups), numerous brachiopods (Lingula minima, Chonetes striatella), gasteropods, pelecypods and cephalopods (Orthoceras bullatum). Fish include Cephalaspis, Cyathaspis, Auchenaspis. The Tilestones, Downton Castle Sandstone and Ledbury shales are occasionally grouped together under the term Downtonian. They are in reality passage beds between the Silurian and Old Red Sandstone, and were originally placed in the latter system by Sir R. I. Murchison. They are mostly grey, yellow or red micaceous, shaly sandstones. Lingula cornea, Platyschisma helicites and numerous phyllocarids and ostracods occur among the fossils.
In Denbighshire and Merionethshire the upper portion of the Denbighshire Grits belongs to this horizon: viz. those from below upwards, the Nantglyn Flags, the Upper Grit beds, the Monograptus leintwardinensis beds and the Dinas Bran beds. In the Silurian area of the Lake district the Coldwell beds, forming the upper part of the Coniston Flags, are the equivalents of the Lower Ludlow; they are succeeded by the Coniston Grits (4000 ft.), the Bannisdale Slates (5200 ft.) and the Kirkby Moor Flags (2000 ft.).
In the Silurian areas of southern Scotland, the Ludlow rocks are represented in the Kirkcudbright Shore and Riccarton district by the Raeberry Castle beds and Balmae Grits (500-750 ft.). In the northern belt—Lanarkshire and the Pentland Hills—the lower portion (or Ludlovian) consists of mudstones, flaggy shales and greywackes; but the upper (or Downtonian) part is made up principally of thick red and yellow sandstones and conglomerates with green mudstones. The Ludlow rocks of Ireland include the “Salrock beds” of County Galway and the “Croagmarhin beds” of Dingle promontory.
See [Silurian], and, for recent papers, the Q. J. Geol. Soc. (London) and Geological Literature (Geol. Soc., London) annual.
LUDOLF (or Leutholf), HIOB (1624-1704), German orientalist, was born at Erfurt on the 15th of June 1624. After studying philology at the Erfurt academy and at Leiden, he travelled in order to increase his linguistic knowledge. While in Italy he became acquainted with one Gregorius, an Abyssinian scholar, and acquired from him an intimate knowledge of the Ethiopian language. In 1652 he entered the service of the duke of Saxe-Gotha, in which he continued until 1678, when he retired to Frankfort-on-Main. In 1683 he visited England to promote a cherished scheme for establishing trade with Abyssinia, but his efforts were unsuccessful, chiefly through the bigotry of the authorities of the Abyssinian Church. Returning to Frankfort in 1684, he gave himself wholly to literary work, which he continued almost to his death on the 8th of April 1704. In 1690 he was appointed president of the collegium imperiale historicum.
The works of Ludolf, who is said to have been acquainted with twenty-five languages, include Sciagraphia historiae aethiopicae (Jena, 1676); and the Historia aethiopica (Frankfort, 1681), which has been translated into English, French and Dutch, and which was supplemented by a Commentarius (1691) and by Appendices (1693-1694). Among his other works are: Grammatica linguae amharicae (Frankfort, 1698); Lexicon amharico-latinum (Frankfort, 1698); Lexicon aethiopico-latinum (Frankfort, 1699); and Grammatica aethiopica (London, 1661, and Frankfort, 1702). In his Grammatik der äthiopischen Sprache (1857) August Dillmann throws doubt on the story of Ludolf’s intimacy with Gregorius.
See C. Juncker, Commentarius de vita et scriptis Jobi Ludolfi (Frankfort, 1710); L. Diestel, Geschichte des alten Testaments in der christlichen Kirche (Jena, 1868); and J. Flemming, “Hiob Ludolf,” in the Beiträge zur Assyriologie (Leipzig, 1890-1891).
LUDWIG, KARL FRIEDRICH WILHELM (1816-1895), German physiologist, was born at Witzenhausen, near Cassel, on the 29th of December 1816. He studied medicine at Erlangen and Marburg, taking his doctor’s degree at Marburg in 1839. He made Marburg his home for the next ten years, studying and teaching anatomy and physiology, first as prosector to F. L. Fick (1841), then as privat-docent (1842), and finally as extraordinary professor (1846). In 1849 he was chosen professor of anatomy and physiology at Zürich, and six years afterwards he went to Vienna as professor in the Josephinum (school for military surgeons). In 1865 he was appointed to the newly created chair of physiology at Leipzig, and continued there until his death on the 23rd of April 1895. Ludwig’s name is prominent in the history of physiology, and he had a large share in bringing about the change in the method of that science which took place about the middle of the 19th century. With his friends H. von Helmholtz, E. W. Brücke and E. Du Bois-Reymond, whom he met for the first time in Berlin in 1847, he rejected the assumption that the phenomena of living animals depend on special biological laws and vital forces different from those which operate in the domain of inorganic nature; and he sought to explain them by reference to the same laws as are applicable in the case of physical and chemical phenomena. This point of view was expressed in his celebrated Text-book of Human Physiology (1852-1856), but it is as evident in his earliest paper (1842) on the process of urinary secretion as in all his subsequent work. Ludwig exercised enormous influence on the progress of physiology, not only by the discoveries he made, but also by the new methods and apparatus he introduced to its service. Thus in regard to secretion, he showed that secretory glands, such as the submaxillary, are more than mere filters, and that their secretory action is attended by chemical and thermal changes both in themselves and in the blood passing through them. He demonstrated the existence of a new class of secretory nerves that control this action, and by showing that if the nerves are appropriately stimulated the salivary glands continue to secrete, even though the animal be decapitated, he initiated the method of experimenting with excised organs. He devised the kymograph as a means of obtaining a written record of the variations in the pressure of the blood in the blood-vessels; and this apparatus not only conducted him to many important conclusions respecting the mechanics of the circulation, but afforded the first instance of the use of the graphic method in physiological inquiries. For the purpose of his researches on the gases in the blood, he designed the mercurial blood-pump which in various modifications has come into extensive use, and by its aid he made many investigations on the gases of the lymph, the gaseous interchanges in living muscle, the significance of oxidized material in the blood, &c. There is indeed scarcely any branch of physiology, except the physiology of the senses, to which he did not make important contributions. He was also a great power as a teacher and the founder of a school. Under him the Physiological Institute at Leipzig became an organized centre of physiological research, whence issued a steady stream of original work; and though the papers containing the results usually bore the name of his pupils only, every investigation was inspired by him and carried out under his personal direction. Thus his pupils gained a practical acquaintance with his methods and ways of thought, and, coming from all parts of Europe, they returned to their own countries to spread and extend his doctrines. Possessed himself of extraordinary manipulative skill, he abhorred rough and clumsy work, and he insisted that experiments on animals should be planned and prepared with the utmost care, not only to avoid the infliction of pain (which was also guarded against by the use of an anaesthetic), but to ensure that the deductions drawn from them should have their full scientific value.