Typed letter from Ambrose Swasey to Charles F., Sr., thanking Brush for sending latest gravitation paper, hoping that Brush will continue to work on t Show moreTyped letter from Ambrose Swasey to Charles F., Sr., thanking Brush for sending latest gravitation paper, hoping that Brush will continue to work on the issue and present again at next American Philosophical Society meeting Charles F. Brush, Sr., Papers Series 1: Correspondence Subseries 2: Acknowledgments (1921-1929) Box 2 Folder 14 Show less