Handwritten letter from Richard Fay to Charles F., Sr., thanking Brush for latest gravitation paper and commenting on benefit of experimental proof ov Show moreHandwritten letter from Richard Fay to Charles F., Sr., thanking Brush for latest gravitation paper and commenting on benefit of experimental proof over mathematical proof for experimental results Charles F. Brush, Sr., Papers Series 1: Correspondence Subseries 2: Acknowledgments (1921-1929) Box 2 Folder 14 Show less