THE PLANETARY 1919. AND STELLAR WORLDS. A POPULAR EXPOSITION OF THE GREAT DISCOVERIES AND THEORIES OF MODERN ASTRONOMY. IN A SERIES OF TEN LECTURES. BY 0. M. MITCHEL, A.M., DIRECTOR O.F THE CINCINNATI OBSERVATORY. STANFORD LIBRARY NEW YORK: 21 MURRAY STREET. M/ Pres_87 152012 Mbs2p 580066 Entered according to act of Congress, in the year 1848, by O. M. MITCHEL, In the Clerk's Office of the District Court of the United States for the Southern District of Ol io. PREFACE. A FEW words in explanation of the circumstances under which this volume is presented to the public, may not be unacceptable to the reader. It is now a little more than six years since the writer conceived the idea of erecting a great astronomical observatory in the city of Cincinnati. My attention had been for many years directed to this subject, by the duties of the professorship, which I then held in the college. In attempting to communicate the great truths of astronomy, there were no instruments at hand, to confirm and fix the wonderful facts recorded in the books. Up to that period our country, and the west particularly, had given but little attention to practical astronomy. A few individuals, with a zeal and ardor deserving of all praise, had struggled on to eminence almost without means or instruments. An isolated telescope was found here and there scattered through the country; but no regularly organized observatory with powerful instruments, existed within the limits of the United States, so far as I know. To attempt the building of an observatory of the first class, and to furnish it with instruments of the highest order, withcut any aid from the general or state government, but by the voluntary contribution of all classes of citizens, was an enter prise of no common difficulty. To ascertain whether any interest could be excited in the public mind, in favor of astronomy, in the spring of 1842 a series of lectures was delivered |