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842 spectroscopic observations in connection with the Coast Survey party. While there he made out a catalogue of 273 lines reversed in the chromosphere spectrum, and 104 lines modified in the spectrum of sunspots. In 1874 he went to Peking, China, as assistant astronomer in the party of Professor Watson, which observed the transit of Venus.

While at Hanover Professor Young devoted most of the time which could be spared from college duties to astronomical and spectroscopic observations, and he devised a form of automatic spectroscope which has been very generally adopted, and a description of which was formerly given in "The Popular Science Monthly." He also made a great number of new and instructive observations on the phenomena of solar prominences, and observed some remarkable explosions in the stupendous masses of vapor which are shot out hundreds of thousands of miles from the solar surface. Professor Young also, at this time, established what is known as Doppler's principle as applied to light experimentally, and was enabled to measure the sun's rotation by the displacement of lines in the spectrum.

But, notwithstanding his multifarious labors in the observatory, and at distant places which he visited for observation. Professor Young has also been active as a writer of scientific papers, and as an astronomic teacher. Besides his elaborate courses of instruction to college classes, he has also given courses of popular lectures at Peabody Institute, of Baltimore, and Lowell Institute, at Boston. He has also delivered occasional scientific lectures in different cities, and regular educational courses at Mount Holyoke Seminary, Williams College, St. Paul's School, and several other places. It must be added that he has also found time, within the last few years, to write an excellent popular treatise on "The Sun" for the "International Scientific Series," which is now just issued.

The vigorous movement in the College of New Jersey, at Princeton, for enlarged scientific teaching, which was inspired and directed by President McCosh, led to the choice of Professor Young to take the chair of Astronomy in that institution, and he accepted the invitation in 1877. In 1878 he was in charge of the astronomical expedition organized by the college to observe the eclipse of July 29th of that year, at Denver, Colorado, and in which the party had excellent success. During his residence at Princeton he has maintained his customary activity in pursuing spectroscopic observations in solar physics.

Professor Young has been honored by many recognitions of eminence in his department. He is a member of the National Academy of Sciences, a Fellow and ex-Vice-President of the American Association for the Advancement of Science, an Associate Fellow of the American Academy of Arts and Sciences in Boston, an Honorary Member of the New York Academy of Sciences, and of the Philosophical Society in Philadelphia, and a Foreign Associate of the Royal Astronomical Society of Great Britain.