James Hall, an American geologist and palaeontologist, born at Hingham, Mass., of English parents, Sept. 12, 1811. Destined at first for the medical profession, he soon turned his attention to natural history, which he pursued from 1831 to 1836, under Amos Eaton, in the Rensselaer polytechnic institute, Troy, N. Y., where he has since been for many years professor of geology. Being appointed one of the geologists for the survey of New York, he began in 1837 his explorations of the western district of the state. He published annual reports from 1838 to 1841, and gave in 1843 his final report in a large quarto volume, which forms one of the series of works on the natural history of New York published by the legislature. In this volume he described in a very complete and exhaustive manner the order and succession of the strata, their mineralogical and lithological characters, and the organic remains which they contain. The field work of the survey being then completed, he was appointed palaeontologist to the state, and charged with the work of studying and describing the organic remains of the rocks.

He still holds this post (1874), and has embodied the results of his studies in the "Palaeontology of New York," one of the most remarkable monuments of scientific labor, zeal, and industry which this country has produced. It is as yet incomplete, but some idea of its extent may be given by an account of the volumes already published and those now in progress. Beginning with the lowest member of the New York system of palaeozoic rocks, the first volume of the "Palaeontology " (338 pp. 4to, with 100 plates, 1847) contains descriptions of all the organic remains, both of plants and animals, up to the summit of the so-called Champlain division of the system, which terminates in the Hudson river group, corresponding to the Cambrian of Sedgwick or the Cambrian and lower Silurian of Murchison. The second volume (362 pp., with over 100 plates, 1852) continues the subject up to the base of the Onondaga or Sa-lina formation. The third volume (533 pp., with 128 plates, 1859) includes all the fossil remains of the water lime, the lower Helder-berg, and Oriskany divisions, except the corals and bryozoa.

The fourth (the same, 1867) includes the brachiopoda of the divisions known as the upper Helderberg, Hamilton, Portage, and Chemung, making together the Erian or Devonian. The fifth volume, now in progress (1874), will contain the lamellibranchiates of the last named divisions, besides a review of all the lamellibranchiate forms from the lower formations. The drawings and descriptions for two more volumes are also far advanced, including the gasteropoda, cephalopoda, and Crustacea of the Erian, with the crinoidea, bryozoa, and corals of the same. In addition to these, Prof. Hall has prepared for the "Palaeontology " a complete revision of the palaeozoic brachiopoda of North America, with about 50 plates. This great and comprehensive study of our palaeozoic fauna, which it is proposed to terminate with the base of the coal formation, has demanded researches beyond the limits of New York; and Prof. Hall has extended his investigations westward to the Rocky mountains, tracing out over the region the great divisions of the New York series. It is these identifications which have served as the basis of all our knowledge of the geology of the Mississippi basin.

The general results of these comparative studies will be found in the introduction to the third volume of the "Palaeontology," and more fully in the first volume of the "Report on the Geology of Iowa." Having been in 1855 appointed geologist to this state, he published in 1858, in connection with Whitney and Worthen, a report in two volumes, to which, besides the geological researches just mentioned, he contributed a memoir on the palaeontology of the state, with 34 plates. He subsequently performed for Wisconsin a similar service, the results of which are as yet but partly published. Prof. Hall was about this time called to take charge of the palaeontology of the geological survey of Canada under Sir William Logan. This he declined, but undertook the study of the graptolites of the so-called Quebec group of Canada, which appeared in 18G5 as an exhaustive monograph, with 22 plates. This work was subsequently republished by him, with additions, in the 20th report of the New York state cabinet of natural history.

Various other contributions to palaeontology by him will bo found in most of the reports of the state cabinet and state museum, from No. 3 to No. 25. To these must be added the description of the organic remains given in the government reports of various western surveys, including the reports of Fremont, Stans-bury, and the United States and Mexico boun-dary survey. Besides all these are numerous communications to the " American Journal of Science," and to various scientific societies and academies both at home and abroad, including the geological society of London, of which he is one of the foreign members, and which in 1858 gave him the Wollaston medal. Prof. Hall has also devoted much time to the study of crystalline stratified rocks, and was the first to point out the persistence and the significance of mineralogical character as a guide to their classification, in the manner which has since been developed and extended by Hunt. (See Geology.) While devoting himself to the study of the minute details of organic structures, and discriminating between and classifying these with the utmost precision, Prof. Hall has also successfully traced out and arranged in their true order, over vast areas of North America, the formations to which they belong; thus doing for the stratigraphical geology of our country a work second in importance only to that which he has done for its palaeontology.

Carrying his investigations still further, he has attempted the solution of some of the most difficult questions of dynamical geology, and has laid the grounds for a rational theory of mountains which must be regarded as one of his most important contributions to geological science. (See Mountain.) - In his earlier palaeontological publications Prof. Hall was greatly aided by his wife, who drew the figures of a large portion of the fossils. One of his sons, Charles Edward, is now (1874) engaged in geological investigations in Texas.