In view of the frequent discussion of the subject in the past and the still closer attention which it has received in our own times, the author of this collection of desultory studies is fully conscious of their many and serious defects. The question to him was not, however, one of personal interest, but whether, in the absence of any other comprehensive treatise, such a work could be helpful to British students and to the foreign students whose teachers have so feelingly lamented the dearth of scientific writings on this subject. The substance of the present volume was in shape more than ten years ago, but the author found himself unable to give an assured answer to this question. He had indeed already resolved to await the opportunity for further study and revision that only retirement from official life could give, when a circumstance occurred which altered his resolution. A laudable ambition on the part of certain students to produce a much needed Formula Boo/e of official documents8 rendered it desirable, for obvious reasons, that the authority for the arrange ment and conclusions of that work should be forthcoming.