Page:Popular Science Monthly Volume 26.djvu/564

548 was preached in the West Kirk of Edinburgh, one of the largest churches in Scotland, before an unusually crowded congregation; and he preached frequently for some time afterward. His ministrations "seem always to have been most acceptable from the beauty and earnestness of his style, and his well-known gift of creating interest out of the driest subjects." But he was excessively nervous, and his efforts were attended with intense suffering, in the shape of a nervous faintness, which only occurred when he was making a public appearance. For this reason he finally desisted from preaching.

His regular philosophical studies began in 1799, when, at the suggestion of his friend Brougham, he repeated Newton's experiments in the inflection of light, and in connection with them made his first discovery. His after-life was one of almost uninterrupted research. His investigations were to a large extent parallel with those which Malus and Fresnei and others were carrying on during the same period in France, and in some cases room was left for question as to priority of discovery. But in no case is Brewster's claim to independence in research and originality impaired. Professor Forbes has summarized the most important subjects of Brewster's inquiries at this time, as the laws of polarization by reflection and refraction, and other quantitative laws of phenomena; the discovery of the polarizing structure induced by heat and pressure; the discovery of crystals with two axes of double refraction, and many of the laws of their phenomena, including the connection of optical structure and crystalline forms; the laws of metallic refraction, and experiments on the absorption of light. Of his discoveries, primary importance belongs to those of the connection between the refractive index and the polarizing angle, of biaxial crystals, and of the production of double refraction by irregular heating.

In 1816 he devised the kaleidoscope, which became at once very popular, and spread his name widely among all classes of people. The patent which he took out for it was of little value to him, for the authorized manufacturers seem to have wholly failed to supply the demand for the instruments, and the device was speedily patented by enterprising adventurers who made their fortunes out of it. He afterward made earnest and long-continued efforts to promote reforms in the patent laws that should make them more just to inventors.

Several years later, in 1849-'50, he perfected the stereoscope, the principle of which had been discovered and applied by Wheatstone in 1838. Wheatstone employed mirrors to effect the merging of the binocular pictures into one; Brewster substituted lenses for the mirrors, and gave us the instrument substantially as it is.

For the improvements that were made in lighthouses during the second decade of this century, the credit must be divided between Brewster and the Frenchman Fresnei. Both worked independently, and arrived in some cases at nearly identical results. Sometimes Brewster, sometimes the Frenchman, was ahead on a particular point.