The elements of Euclid, viz. the first six books, together with the eleventh and twelfth. The Errors, by which Theon, or others, have long ago Vitiated these Books, are Corrected, And some of Euclid's Demonstrations are Restored. Also, the book of Euclid's data, in like manner corrected. By Robert Simson, M. D. Emeritus Professor of Mathematics in the University of Glasgow. To this edition are also annexed, elements of plane and spherical trigonometry