those found to hold for Forces, it becomes a purely geometrical entity and can be used with much advantage in Geometry. Being at the same time very elementary, it is a subject which should be introduced in Schools; it will be found not only useful in all possible applications but also of considerable educational value. Having often, and from various quarters, been urged to publish a book on Vectors and having always been prevented from doing so by want of leisure, I asked Mr Turner, who for many years acted as one of my Assistants, to put my lectures into shape for publication. He willingly undertook the task, and the form in which the subject is presented is mainly his. O. HENRICI. July, 1903. 39. Algebraic rules hold for addition 40. Two non-parallel vectors are independent 41. Three coplanar vectors have a relation |