One finds in this many changes from former editions. Much new matter has been added and much of the old has been thoroughly revised and rewritten. Of the greatest value are the four hundred illustrations. Most of these are new and they have been so well executed that they convey clearly the ideas intended. There can not be too many good illustrations, but poor ones are worse than none. The subdivision of the subject is a natural one and the subheads under the chapters have been conspicuously typed so that one may quickly turn to the particular point desired. The work is well arranged and published and, as the author's views are sound, it must take its place as one of the best text-books on the subject.