Synopsis Differential Equations is the most important branch of modern mathematics. The subject may be considered to occupy a central position from which different lines of development extend in many directions. The object of this set is to give a detailed account of the subject in as simple a form as possible, suitable for those with no previous knowledge of it, and yet at the same time to point out the different directions in which it may be developed. The publication is divided into two parts and three volumes. The first part contains seventeen chapters while the second five, covering all aspects of the subject. A large number of solved examples, definitions and illustrations are provided in every chapter to clarify the concepts with ease, followed by several exercises.