""A Sequel To The First Six Books Of The Elements Of Euclid: Containing An Easy Introduction To Modern Geometry"" is a book written by John Casey and published in 1888. The book is a continuation of Euclid's first six books of geometry, and it aims to provide an easy introduction to modern geometry. The book is divided into two parts: the first part covers the theory of parallels and the second part covers the theory of proportion. The author uses...