Readers of the two previous volumes of this series will be aware that Dr. Adrian Fortescue intended to complete it by a third. This volume was to have contained a full treatment of the Uniate Churches corresponding to each of the separated Churches which are treated in his two published works. The book, therefore, must be judged as a fragment. It may be found to lack that finish which it would assuredly have received at the skill full hands of the author. Some inaccuracy may have crept in, which on his revision would have been eliminated. Whatever be its defect, it cannot fail to be of great value to all who are interested in the subject. To ensure that none of the fruits of this study be lost, I have included the author's own copious bibliography for the whole work.