Typed letter from P. Hays to Charles F. Brush, Sr., with Hays thanking Brush for sending him the third paper on Gravitation Charles F. Brush, Sr., Pape Show moreTyped letter from P. Hays to Charles F. Brush, Sr., with Hays thanking Brush for sending him the third paper on Gravitation Charles F. Brush, Sr., Papers Series 1: Correspondence Subseries 2: Acknowledgments (1921-1929) Box 3 Folder 1 Show less