Alexander, Stephen, 1806-1883

Stephen Alexander was an astronomer, mathematician, author, and educator, under whose influence astronomy first developed as a separate discipline at Princeton University. He graduated with honors from Union College at the age of eighteen.

A cousin and also a brother-in-law of Joseph Henry, he collaborated with Henry in his scientific investigations at Albany Academy and accompanied him to Princeton in 1832, when Henry became professor of natural philosophy. Appointed tutor in mathematics in 1833 and professor of astronomy in 1840, Alexander's association with Princeton continued for fifty years. Alexander gave Princeton's first discrete course in astronomy. The College's first astronomy building, the Halsted Observatory, which stood on University Place from 1869 to 1932, was built through his influence and from his plans; however, a telescope was not installed until after his retirement. Working with only his own small telescope, he carried on a steady program of research, published many papers, and studied comets, including the great comet of 1843, whose sudden appearance excited American interest in astronomy. He also studied the atmospheres of Venus, Mercury, and Jupiter, led expeditions for the Coast and Geodetic Survey and the National Academy of Sciences to observe solar eclipses, and in collaboration with Henry, conducted experiments on the relative heat of sunspots. He was president of the American Association for the Advancement of Science in 1859 and was chosen as one of the original fifty members of the National Academy of Sciences in 1862.