Typed letter from Sir Robert Hadfield’s secretary to Charles F., Sr., thanking Brush on behalf of Sir Hadfield for sending latest gravitation paper Cha Show moreTyped letter from Sir Robert Hadfield’s secretary to Charles F., Sr., thanking Brush on behalf of Sir Hadfield for sending latest gravitation paper Charles F. Brush, Sr., Papers Series 1: Correspondence Subseries 2: Acknowledgments (1921-1929) Box 2 Folder 13 Show less