The best return in my power for the favourable re ception the reading public, and many writers in the periodical press, have accorded to this book, is to take care that the Edition I am now about to issue Shall be as little unworthy as I can make it of the continuance of their favour; though, indeed, this which they have a right to expect, is no more than I ought to be glad to do for my own sake. I have, therefore, carefully revised the whole volume. In this/revision I have, without omitting, or modifying, a Single statement of fact, or of opinion, introduced as much new matter as nearly equals in bulk a fourth of the old. These additions include a few reminiscences of my Egyptian tour, which had not re curred to me while engaged on the original work; but, in the main, they consist of fuller developments of some of its more important investigations and views.