17 Typed letters between Charles Norton and Charles F., Sr., regarding Norton's desire to attempt to repeat some of Brush's gravitation experiments, p Show more17 Typed letters between Charles Norton and Charles F., Sr., regarding Norton's desire to attempt to repeat some of Brush's gravitation experiments, particularly the pendulum experiments, and further findings and discussions of gravitation between the two. Dated 1921, 1922, 1924, 1926. Charles F. Brush, Sr., Papers Series 1: Correspondence Subseries 3: Business and Professional (1876-1931) Box 5 Folder 9 Show less