Head-and-shoulders classical-style plaster bust on a round socle, the sitter's head turned slightly to his left, with the robe draped loosely round the neck exposing part of the left breast. The hair is brushed loosely forward, parted on the left, over a balding head.

Raper was the eldest son of an admiral of the same name, who wrote a book on signals in 1828. He served under Murray Maxwell in the 'Alceste' in 1815, taking Lord Amherst on his embassy to China and surviving the 'Alceste's' shipwreck on the way back. From 1822 he was in the Mediterranean under William Henry Smyth in the 'Adventure', being placed in charge of the chronometers, and was commissioned lieutenant in 1823. In 1825, for personal reasons related to his father, he declined becoming first lieutenant in the 'Blossom' under Frederick Beechey on his survey voyage to the Pacific, by which he effectively retired himself from active service. Thereafter, much encouraged by Smyth, he turned to nautical science. He became a fellow of the Royal Geographical and Royal Astronomical societies, and was secretary of the latter from 1839 to 1842.

In 1832 the Admiralty appointed him to a committee on measuring the tonnage of ships and he was principal author of its report. In 1840 he published his 'Practice of Navigation and Nautical Astronomy', for which he was awarded the gold medal of the Royal Geographical Society. It remained a standard text for years, the twenty-first edition being published in 1920.