This volume collects my shorter articles on the history of mechanics, some already published in various places, some revised from earlier papers, and some never published before. All of them began as lectures, and here they are printed as such, little changed from the last times I read them out to an audience. While the several articles concern different aspects of mechanics, overlap and even some repetition could not be avoided, since mechanics is one great science, and the same original oftentimes served more than one end in its growth. My three major historical treatises, which were published in Volumes (II) 11 , 2 12, and 13 of L. Euleri Opera Omnia, are not included. To simplify the printing I have also mostly omitted detailed reference to sources discussed more fully in those treatises, but of course I have added to the texts of the lectures citations of other sources, some notes in answer to questions a reader might ask, and biblio­ graphical notes at the end of each. I am grateful to the U.S. National Science Foundation for its support of this work through a grant to The Johns Hopkins University.