"This is a facsimile reprint of John Hewlett's 1840 translation of Euler's Algebra and Lagrange's Additions thereto. Most of Euler's contribution is elementary, nothing more advanced than solving quartic equations, but worth having in order to appreciate his leisurely and effective style---would that more great mathematicians wrote so well and to such pedagogic effect. However, one third of the book is his lucid treatment of questions in number theory, and it is this material that drew Lagrange's comments. Here for the first time are the rigorous treatments of continued fractions and "Pell's" equation, and of quadratic forms. The combination of Euler's and Lagrange's tests, of experimental and theoretical research in Weil's description, is justly celebrated by the editors of Euler's Opera omnia, who print the two together, and it is good to see this classic back in print in English. Every library without much Euler should at least have this volume. It is accompanied by an excerpt of Horner's memoir on the life of Euler, and a eulogy by Truesdell, with a useful bibliography." -- MATHEMATICAL REVIEWS