American optician, born in Ashfield, MA, on the 8th of March 1804; he was a farmer’s son, and became an engraver for calico printworks (1827–36), then a portrait-painter, and from 1845 a manufacturer of telescopes. He was the first in America to make large achromatic lenses. He and his sons associated themselves in this particular business, their first great order being received from the University of Mississippi for an 18-inch object-glass, which, however, went to Chicago. The next glass, 26 inches, was made for the Naval Observatory at Washington, and was begun in 1870. In 1879 they received an order from Russia for a 30-inch glass for the Imperial Observatory at Pulkova. In 1881 they made the 26-inch glass for the University of Virginia. Then came the order for the Lick Observatory in California, a 36-inch object-glass, commenced in 1886. Alvan Clark died in Cambridge, MA, on the 19th of August 1887.—His son, George Bassett (1827–91), at the age of seventeen became interested in reflecting-telescopes. He attempted to make a speculum five inches in diameter, making his own casting, doing his own grinding, etc., until he so interested his father that the two worked together and succeeded in eliminating the chromatic and spherical aberrations and perfecting a working reflecting-telescope. It was to the aptitude of young George that the house of Alvan Clark and Sons owes its origin and much of its success. He became the mechanician of the firm, and to him fell the task of contriving and experimenting, of designing the models and of bringing to exactitude the essential optical parts of the great instruments produced by the house.—A second son, Alvan Graham, astronomer, born at Fall River, MA, on the 10th of July 1832; discovered double stars, was a member of the expeditions which went to Spain to observe the total eclipse of 1870, and to Wyoming eight years later. He received, in 1862, the gold medal from the Academy of Sciences of France for his discovery of the companion star of Sirius. Mr. Clark has invented several improvements in telescopes. In 1894 he completed the 40-inch glass for the University of Chicago, the telescope which cost $500,000, being located at the Yerkes Observatory, Lake Geneva, WI.
