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delphia on the 1st of August, 1808, he had not completed his fiftyeighth year.

He was the third in age of four brothers, — only two of whom survive, — who, inspired and guided by their father, Dr. Patrick Kerr Rogers, Professor of Natural Philosophy and Chemistry in William and Mary College, Virginia, — as if by mutual agreement, all gave their lives to the cultivation and teaching of physical science. From his youth, the subject of the present notice evinced so decided a predilection for these studies and became so proficient in them, that, in his twenty-second year, he was made Professor of Physics and Natural History in Dickinson College, at Carlisle, Pennsylvania, where, at the same time, he edited a periodical called a “Messenger of Useful Knowledge.” Here he began his first independent studies in structural and dynamical geology, in which he was destined greatly to excel.

Seeking better opportunities, he soon resigned his chair, and passed a year in England, studying chemistry under the late Professor Turner, and accompanying the late De la Beche in his geological explorations. Returning to Philadelphia, he devoted his whole time to scientific investigations. In conjunction with our other lately deceased associate, Professor Bache, he made and published a valuable series of analyses of the ashes of coal; and he aided his brother, our own William B. Rogers, in experiments upon “the laws of the Voltaic battery” (published in Silliman's Journal), and in preparing two memoirs upon “ the Tertiary Formations of Eastern Virginia,” which were published in the Transactions of the American Philosophical Society. At the request of the Council of the British Association for the Advancement of Science, he prepared a report on the Geology of North America, which was printed in the third Annual Report of that body, and was in part republished in this country in Bradford's edition of Murray's Encyclopædia of Geography

His first systematic geological labor was that of conducting the survey of the State of New Jersey, of which he published a report in 8vo, with a geological map. While thus engaged a similar survey of the great State of Pennsylvania was provided for by the Legislature, and placed under his direction. This, the most important scientific labor of his life, was commenced early in the year 1836, and, with various interruptions and embarrassments growing out of legislative inaction, was completed by him in the spring of 1855. The fruits of these prolonged labors have been given to the world in his great work entitled “ Geology of Pennsylvania, Government Survey ; with a General View of the Geology of the United States, Essays on the Coal Formation and its Fossils, and a Description of the Coal Fields of North America and Great Britain.” This great work is contained in three royal quarto volumes, illustrated by forty-five sketches of scenery, forty-seven geological sections, two plates of columns of strata, twenty-three plates of coal fossils, and seven hundred and seventy-eight wood engravings of views and diagrams of coal-beds, &c., and accompanied by a general geological map of the State, a special map of the anthracite coalbasins, and two large sheets containing the nine general sections, elucidating the geological map.

During the early progress of this work he produced, in conjunction with his brother, William B. Rogers, the well-known memoir “On the Physical Structure of the Appalachian Chain,” unfolding certain dynamical laws which have regulated the elevation of mountain chains. About the same time (1842) he published an elaborate paper on the origin of the Appalachian coal strata, bituminous and anthracitic, containing much original observation and important speculative views ; his brother pursuing a parallel system of investigations in Virginia, where the formations are identical with those of Pennsylvania. The result of the labor of these two brothers, carried on for ten years together, was the grand discovery of the structural unity of central North America, between the Appalachian chain and the Rocky Mountains, the great lakes and the Delta inclusive ; a fact of such importance that it must serve in future as a guide to all general researches ; since it is not reasonable to suppose that so large a portion of the earth's surface should have been formed in any other than the normal mode. Occupying at this time the chair of Geology in the University of Pennsylvania, he gave instruction in that science in the intervals of his labors on the State Survey. He also delivered courses of lectures at the Lowell Institute and elsewhere; on all such occasions showing that readiness and felicity of diction, without the use of notes, for which he had always been remarkable.

He was one of the founders, and an early President, of the American Association of Geologists, which, after an active and most useful career, expanded into the American Association for the Advancement of Science. Although chiefly devoted to geological research, Professor Rogers paid much attention to those sciences of which geology is the extended application, — Natural History, Climatology, and Physical Geography. In 1855 he contributed to Keith Johnson's Physical Atlas the Geological Map of the United States and British North America; and the Chart of the Arctic Basin, with the accompanying letter-press, and the text of the somewhat later Geographical Atlas of North America, is from his pen. The philosophical questions arising from these studies especially interested him ; indeed, the whole bent of his mind was in an eminent degree philosophical rather than technical.

In the year 1857, while in Edinburgh superintending the publication of his Geological Report, he was appointed Regius Professor of Natural History and Geology and Curator of the Hunterian Museum, in the University of Glasgow, and thenceforth became a resident of Scotland. While devoting himself to the duties of his chair, he became associated with Jardine and Balfour in the editorship of the Edinburgh New Philosophical Journal, contributed a paper on “ The Laws of Structure of the more disturbed Zones of the Earth's Crust” to the Transactions of the Royal Society of Edinburgh, and found time for a number of scientific essays, published in Blackwood and Good Words, as well as for occasional lectures on his favorite geological topics in London, Edinburgh, and elsewhere.

On revisiting, as it proved for the last time, his native country, in 1855, his friends were concerned to see that his health had given way under his prolonged and excessive labors, overtasking a constitution, elastic indeed, but not naturally robust. He returned to Glasgow, reinvigorated it was thought; but we soon heard, with sorrow, that he was no more.

Although the eminent position in geology held by our late associate, and somewhat of the nature and dominant influence of the general views of the associated brothers, may be inferentially gathered from this biographical sketch, yet we are, for obvious reasons, prevented from entering upon their consideration here, nor indeed is it necessary to do so. Of him whom we have lost, suffice it to record, here, in simplest and briefest phrase, that he was a most accomplished investigator, a graceful and persuasive teacher, and fascinating companion ; that to rare powers and attainments he added a lively sympathy in all the interests of humanity, and a courageous devotion to whatever he deemed just and true.

ALEXANDER Dallas Bache, born in Philadelphia on the 19th of July, 1806, was the son of Richard Bache, and grandson of the only daughter of Benjamin Franklin. His mother was Sophia Dallas, daughter of Alexander J. Dallas, of a family also well known in the history of this country. Remarkable from early boyhood for his aptitude in the acquisition of learning, he was appointed a cadet in the National Military Academy at West Point before he had completed the fifteenth year of his age. Here, although the youngest pupil, he soon reached a high grade of scholarship, and maintained it throughout the course, graduating in 1825 at the head of his class ; — a class of such marked ability that it furnished no less than five successful candidates to the corps of Engineers. It has been mentioned as a solitary instance in the history of the Academy, noted for its rigid discipline, that he passed through the entire course of four years without a single mark of demerit, and, what may be hardly less uncommon, without calling forth the least manifestation of envy. Indeed his classmates, as well as the teachers, seem to have taken pride in the high character and scholarship of the youthful cadet. His room-mate, several years his senior, and by no means noted for studious or regular habits, assumed the office of guardian, sedulously protecting him from interruption or intrusion during the hours of study, and, it is said, habitually excused his own shortcomings by pleading the importance of the duty he thus performed. Not that young Bache himself needed a guardian, except for his tender years and to protect him from hindrance on the part of others. Sensible beyond his years of the responsibility which would devolve upon him in the support of his widowed mother and her younger children, and of the obligations incurred in his education at the National School, he resolved from the first to exert his utmost energies, - doubtless not unconscious, moreover, that, as a descendant of Franklin, something more than ordinary might be expected from him. Upon such a mind as his, the adage noblesse oblige could not but have a powerful influence.

Upon his graduation he was selected, on account of his high standing, to remain at the Academy as Assistant Professor, — a position which gave him a desired opportunity to review and extend his studies. But after a year in this service he was, at his own request, assigned to engineering duty at Newport, Rhode Island, under the late General, then Colonel Totten. Here for two years he was engaged in constructing fortifications, devoting his extra hours to the study of physics and chemistry.

The most important event of this period, however, and doubtless the most influential upon his future success, was the acquaintance and

VOL. VII.

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engagement he formed with Miss Fowler, the daughter of an old and highly respected citizen of Newport. The scanty pay of a Lieutenant of Engineers, charged with the support of his mother and the younger, members of her family, forbade all but the remote prospect of marriage; when, fortunately as unexpectedly, he was invited to take the chair of Natural Philosophy and Chemistry in the University of Pennsylvania, at Philadelphia. This, while it opened to him his scientific career, enabled him at once to gratify the warmest wish of his heart, and to secure the companion and helpmate, who, devoting all her thoughts and powers to encourage and assist him, contributed most efficiently to his distinguished usefulness throughout his active life.

Important as was the offered position to his hopes and necessities, and congenial to his tastes, the young officer so far distrusted his ability to fill it, that he prudently retained his connection with the army while the trial was made, – taking a year's leave of absence without pay. But before the year elapsed his fitness for the vocation was assured, and the entire confidence of the authorities and pupils of the University secured. He could now undertake to do something for the advancement of science by researches of his own. He became a member, and soon an active officer of the Franklin Institute, then newly established for the promotion of the mechanic arts, and was thus brought into intimate association with the principal manufacturers, engineers, and artisans of the city, as well as with persons more directly engaged in scientific pursuits; workshops and laboratories were thrown open to him, and other facilities supplied which he could not otherwise have commanded ; and skilful men on every side offered ready assistance in realizing the conceptions of his suggestive mind. No doubt his descent from the illustrious philosopher and statesman, whose name the Institute bears, added somewhat to the commanding influence which he acquired, mainly and worthily, however, by his own industry, ability, courtesy, and rare powers of administration. The volumes of the Journal of the Franklin Institute, from 1828 to 1835 inclusive, abundantly testify to his scientific activity.

The most important of these investigations was that upon the causes of the explosion of steam-boilers, carried on by the Institute under his direction, and soon recognized by the General Government by an appropriation to cover the expense. The results of these elaborate researches and experiments, executed with skill and interpreted with logical discrimination, were embodied in a series of propositions which,

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