This is the title page of Isaac Barrow’s (1630-1677) *Euclide's Elements,* 1660 edition. Barrow was self-taught in geometry. He originally published this book in 1655 as a simplified version of the *Elements*. It became very popular, and for the next half century was the standard English language text on the subject.

Below are pages 10 and 11 of Barrow’s *Euclide's Elements**.* The illustration on page 11 presents Euclid's proof of Proposition I.5 (The base angles of an isosceles triangle are equal). This is the Pons Asinorum [Bridge of Asses] of medieval geometry. If one could prove this proposition, he or she was considered a competent mathematician.

For a text showing the original Latin version of this work, please see Mathematical Treasures: Isaac Barrow’s Euclidean Geometry.