The Scale of the Universe

This address [Harlow Shapley, Evolution of the Idea of Galactic Size] and the following one by Dr. Heber D. Curtis [Dimensions and Structure of the Galaxy] are adapted from the illustrated lectures given on the Willian Ellery Hale Foundation before the National Academy of Sciences, April 26, 1920. The authors have exchanged papers in preparing them for publication in order that each might have the opportunity of considering the point of view of either.