Albumen photograph mounted on card depicting Sir David Brewster, identified in period ink below the image as “Sir D. Brewster Physicist.” The portrait shows Brewster standing beside a pedestal with top hat, dressed in formal attire. The photograph likely dates to the mid to late nineteenth century. No photographer’s imprint visible. Approximately 6 by 4 inches. Sir David Brewster (1781–1868) was a Scottish physicist and inventor best known for his work in optics and for the invention of the kaleidoscope in 1816. He conducted pioneering research on the polarization of light and double refraction and was one of the leading scientific figures of nineteenth century Britain. Brewster served as Principal of the United College of St Andrews and later Principal of the University of Edinburgh. He was a founding editor of the Edinburgh Encyclopaedia, an early supporter of photography as a scientific tool, and one of the earliest investigators of stereoscopic vision. Brewster’s research helped establish the scientific principles behind the stereoscope, which became one of the most popular visual technologies of the nineteenth century. He was knighted in 1831 in recognition of his scientific achievements. The mount bears a manuscript identification reading “Sir D. Brewster Physicist.”