The fact that this book is in great part a summary, or selection, from one of mine, as is stated in the Preface, makes it almost a duty for me to do what would in any event be a great pleasure in the case of a work by Professor Chap man. I refer to the duty of writing a few paragraphs by way Of introduction. But, at the same time, this circum stance causes a certain conflict of feelings in me, since no one, unless it be a pedant, can act so freely in self-criticism as he would if he were dealing with the work of another. Fortunately, Professor Chapman has incorporated much of his own harvest in this volume, and to that I may refer with entire lack Of embarrassment.