In this third edition, the two volumes have been compressed into one; the whole has.been very carefully revised and corrected; the Notes will be found at the foot of the pages, to which they respectively belong; the Questions for Practice, which were omitted in the last edition, have been restored; and though it is scarcely possible to print a mathematical work, of any extent, without some errata; yet it is hoped, that few can be named, which will be found more correct than the present.