Page:Popular Science Monthly Volume 77.djvu/453

Rh

HERE has been a revolution in the physical science of to-day compared with the physical science of twenty-five years ago. In the first place there has been a revolution in the methods of teaching science. The physics laboratory of the University of Berlin was founded in 1863, the Cavendish Laboratory, of Cambridge, in 1874. In 1871 Professor Trowbridge, of Harvard, was obliged to borrow certain electrical measuring instruments, as the university had none of its own. It is not surprising, then, that twenty-five years ago there were in the United States very few physics laboratories worthy of the name. Physics teaching in college and high school was chiefly from the textbook. To-day a college which would offer work in physics without a laboratory would be considered a joke; and in order to be commissioned to enter its students into the freshman class of a college, a high school must have a certain minimum of laboratory equipment and the physics teacher must devote a part of his time to laboratory instruction.

In the second place there has been a complete change in the attitude of men of affairs toward the physics professor and his students. No longer do they consider us theoretical, and therefore impractical. No longer do they look with distrust or contempt on laboratory methods and data. No longer do they hold that apprenticeship and experience are sufficient for their needs. To-day the large industrial concerns are establishing laboratories of their own and employing in them the best trained men they can command.

In the third place there has been a revolution in some of our physical theories. By the term revolution I do not mean a destructive upheaval in which the work of the past has been repudiated and destroyed and a new order of things established. I mean that some of our ideas have undergone such a complete and rapid change that what some might term an evolution is really a revolution. Indeed, we have had two revolutionary periods within the past twenty-five years.

The first came in 1887 with the epoch-making researches of Heinrich Hertz. Faraday had given us his theory of lines of force and the mathematicians had attacked it. Young and Fresnel had given us the undulatory theory of light and Laplace and Poisson had "befuddled us with their objections." Ampère had given a theory of magnetism, but Poisson and Weber had given two others. To explain an electric charge we could resort to the one-fluid theory, the two-fluid theory, the potential theory, the energy theory, the ether strain theory. Maxwell