Page:Encyclopædia Britannica, Ninth Edition, v. 6.djvu/810

774 the formation of the territory of Wyoming. It began to be colonized in 1859, and its first legislature met in 1862.

DALBERG,, (1744–1817), was the son of a prince of Dalberg who was one of the chief councillors of the elector of Mainz. Having attended the universities of Göttingen and Heidelberg, he devoted himself to the study of canon law, and entered the church. In 1772 he was appointed counsellor and governor of Erfurt by the elector of Mainz, the duties of which position he fulfilled in the most exemplary manner, displaying the highest conscientiousness, and doing all that he could to promote the interests of his people. After other advancements, he became in 1802 archbishop and elector of Mainz. Being obliged by the terms of the peace of Lunéville to give up Worms and Constance, he received Ratisbon, Aschaffenburg, and Wetzlar. In 1804 he visited Paris in order to discuss with Pius VII. the affairs of the Catholic Church of Germany. The result was that he gave way to the wishes of Napoleon, and thereby considerably diminished his popularity at home. The emperor did not fail to reward him; and, on the formation of the Confederation of the Rhine, though he was forced to resign his post as archchancellor of the emperor, he received more than compensating dignities. These, however, on the fall of Napoleon, he was forced to resign; and he died, holding no other office than that of archbishop of Ratisbon (10th February 1817). The friend of Goethe, Schiller, and Wieland, Dalberg was himself a scholar and author.



D'ALEMBERT, (1717–1783), French mathematician and philosopher, was born at Paris in November 1717. He was a foundling, having been exposed in the market near the church of StJean le Rond, Paris, where he was discovered by a commissary of police on the 17th November. It afterwards became known that he was the illegitimate son of the Chevalier Destouches and Madame de Tencin, a lady of somewhat questionable reputation. Whether by secret arrangement with one or other of the parents, or from regard to his exceedingly feeble state, the infant was not taken to the foundling hospital, but intrusted to the wife of a glazier named Rousseau who lived close by. He was called Jean le Rond from the church near which he was found; the surname D'Alembert was added by himself at a later period. His foster-mother brought him up with a kindness that secured his life-long attachment. When, after he was beginning to be famous, Madame Tencin sent for him and acknowledged the relationship between them, he said that she was only a step-mother, and that the glazier's wife was his true mother. His father, without disclosing himself, recognized his natural claims by settling upon him while still an infant an annuity of 1200 francs. Furnished in this way with enough to defray the expense of his education he was sent at four years of age to a boarding school, where he had learned all the master could teach him ere he was ten. In 1730 he entered the Mazarin College under the care of the Jansenists, who soon perceived his exceptional talent, and, prompted perhaps by a commentary on the epistle to the Romans which he produced in the first year of his philosophical course, sought to direct it to theology. They checked his devotion to poetry and mathematics, and in the science in which he was to achieve his greatest distinction he received no instruction at college beyond a few elementary lessons from Caron. His knowledge of the higher mathematics was acquired by his own unaided efforts after he had left the college. This naturally led to his crediting himself with the discovery of many truths which he afterwards found had been already established, often by more direct and elegant processes than his own.

On leaving college he returned to the house of his foster-mother, where he continued to live for thirty years. On the advice of his friends he made two successive efforts to add to his scanty income by qualifying himself for a profession. He studied law, and was admitted as an advocate in 1738, but did not enter upon practice. He next devoted himself to medicine, and in order to detach himself effectually from his favourite subject, sent all his mathematical books to a friend, who was to retain them until he had taken his doctor's degree. His natural inclination, however, proved too strong for him; within a year the books had all been recovered, and he had resolved to content himself with his annuity and give his whole time to mathematics. He led a simple regular life in the house of the glazier, whose circumstances he contrived somewhat to better out of his limited means. His foster-mother continued to show a warm attachment to him, though she took no interest in his pursuits, and professed something like contempt for his fame. &ldquo;You will never,&rdquo; she said, &ldquo;be anything but a philosopher. And what is a philosopher? A fool who plagues himself during his life that men may talk of him after his death.&rdquo;

In 1741 D'Alembert received his first public distinction in being admitted a member of the Academy of Sciences, to which he had previously presented several papers, including a Mémoire sur le calcul integral (1739). In this he pointed out some errors in Reinau's L'Analyse démonstrée, which was regarded as a work of high authority. In his Mémoire sur la réfraction des corps solides (1741) he was the first to give a theoretical explanation of the familiar and curious phenomenon which is witnessed when a body passes from one fluid to another more dense, in a direction not perpendicular to the surface which separates the two fluids. Two years after his election to a place in the Academy he published his Traité de Dynamique. The new principle developed in this treatise, known as D'Alembert's Principle, may be thus stated—&ldquo;If from the forces impressed on any system of bodies, connected in any manner, there be subtracted the forces which, acting alone, would be capable of producing the actual accelerations and retardations of the bodies, the remaining forces must exactly balance each other.&rdquo; The effect of this is greatly to simplify the solution of complex dynamical problems by making them problems of statics.

So early as the year 1744 D'Alembert had applied this principle to the theory of the equilibrium and the motion of fluids; and all the problems before solved by geometricians became in some measure its corollaries. The discovery of this new principle was followed by that of a new calculus, the first trials of which were published in his Réflexions sur le cause générale des Vents, to which the prize medal was adjudged by the Academy of Berlin in the year 1746, and which was a new and brilliant addition to his fame. He availed himself of the favourable circumstance of the king of Prussia having just terminated a glorious campaign by an honourable peace, to dedicate his work to that prince in the following Latin lines:&mdash;

This flattering dedication procured the philosopher a polite letter from Frederick, and a place among his literary 