亥姆霍兹论力的守恒.doc

Introductory Note ? Hermann von Helmholtz; Translated by Edmund Atkinson ? ? HERMANN LUDWIG FERDINAND VON HELMHOLTZ was born at Potsdam, near Berlin, on August 31, 1821. His father was a man of high culture, a teacher in the gymnasium, whose influence ensured to his son the foundations of a broad general education. His mother was a descendant from William Penn, the English Quaker. ??1 ??Helmholtz early showed mathematical ability, and wished to devote his life to the study of physics; but practical considerations led him to take up medicine, and he became a surgeon in the Prussian army. He began the publication of original contributions to science in 1842, and for fifty-two years, till his death in 1894, he continued to produce in an unbroken stream. He held a succession of academic positions, teaching physiology at K?nigsberg, Bonn, and Heidelberg, and for the last twenty-three years of his life filling the chair of physics at Berlin. ??2 ??The titles of his professorships, however, give a very inadequate idea of his range. His contributions to science cover medicine, physiology, optics, acoustics, mathematics, mechanics, and electricity. His interests in science and art came together in his work on esthetics, and he had a lively appreciation of painting, poetry, and music. ??3 ??The practice of popular lecturing on scientific subjects was almost unknown in Germany when Helmholtz began, and he did much to give it dignity and to set a standard. His own lectures, as the reader of the following papers will perceive, are masterpieces of their kind. “The matter,” says a biographer, “is discussed by a master, who brings to bear upon it all his wealth of learning and research, while there is the ever-enduring interest that attaches to an exposition by one who is giving forth from his own treasury.” It is fortunate for the layman when a scientist and thinker of the first order has the skill and the inclination to share with the outside world the rich harvest of hi