Stephen Alexander (astronomer)  Stephen Alexander (September 1, 1806 – June 25, 1883) was a noted astronomer and educator. He was born in Schenectady, New York. He was the brother-in-law of Joseph Henry, the first secretary of the Smithsonian, and worked closely with him. He graduated from Union College in 1824. He became a tutor in mathematics at Princeton University in 1832; he would later become professor of astronomy and mathematics and advocate for the construction of Princeton's first observatory. Alexander relied on the assistance of a free African American man named Alfred Scudder, who worked for him at Princeton during the 1850s. Because of his role as Alexander's assistant on campus, Scudder received the nickname "Assistant Professor of Natural Philosophy" from students. Alexander was elected an Associate Fellow of the American Academy of Arts and Sciences in 1850. In 1860, he was the head of the expedition to observe the solar eclipse in Labrador. He was one of the original members of the National Academy of Sciences in 1862, and a member of the American Philosophical Society, and the American Association for the Advancement of Science. He also served as the president of this last organization in 1859. His principal writings are "Physical Phenomena attendant upon Solar Eclipses", read before the American Philosophical Society in 1848; a paper on the "Fundamental Principles of Mathematics," read before the American Association for the Advancement of Science in 1848; another on the "Origin of the Forms and the Present Condition of some of the Clusters of Stars and several of the Nebulae", read before the American Association in 1850; others on the "Form and Equatorial Diameter of the Asteroid Planets" and "Harmonies in the Arrangement of the Solar System which seem to be Confirmatory of the Nebular Hypothesis of Laplace", presented to the National Academy of Science; and a "Statement and Exposition of Certain Harmonies of the Solar System", which was published by the Smithsonian Institution in 1875.