Elements of Quaternions, Part I and Part II

Preface
Part I. On vectors: 1. Fundamental principles respecting vectors
2. Applications to points and lines in a given plane
3. Applications of vectors to space
Part II. On quaternions: 1. Fundamental principles
2. On complanar quaternions
3. On biplanar quaternions
Part III. On quaternions: 1. On the interpretation of a product of vectors
2. On differentials and developments of functions of quaternions
3. On some additional applications.