i^^-t PROCEEDINGS 



OF THE 



American PhilosophicaiSoGiety 



HELD AT PHILADELPHIA 



FOR PROMOTING USEFUL KNOWLEDGE 

 Vol. LVIII. 1919. No. 6. 



CONTENTS 



PAGE 



Star Clusters and Their Contribution to Knowledge of the Universe. By 



Harlow Shapley . . . , . . . , -337 



Hydration and Growth. By D. T. MacDougal . . . . -346 



Some Considerations on the Ballistics of a Gun of Seventy-five-mile Range. 



By Arthur Gordon Webster . . . . . . '373 



On a New Method in Exterior Ballistics. Bv Arthur Gordon Web- 

 ster and Mildred Allen ........ 382 



Characters and Restoration of the Sauropod Genus Camarasaurus Cope. 



By Henry Fairfield Osborn and Charles Craig Mook . 386 



PHILADELPHIA 



THE AMERICAN PHILOSOPHICAL SOCIETY 



104 South Fifth Street 



1919 



