The following sketch, in which an attempt is made to cover the history of Arabia from our earliest knowledge down to the entry of Arabs into the Great War, was written to make one fourth part of a volume planned to comprehend also Syria, Mesopotamia, and Persia. The original scheme, however, could not be carried out and my sketch, slight and summary as it is, has to appear by itself. Since I am not an Arabist, it is hardly necessary to say that I owe much to other writers — most, perhaps, to Gaetani, Huart, snouck-hurgronje, and Margoliouth. The last named has laid me under the deepest obliga tion; for he has been so good as to read my book in proof, and to correct in several places my ignorance or my inadvertence. But mine remains the entire responsibility for both the matter and the manner of the following pages. The orthography adopted for Arabic words will be seen to involve a compromise between scientific transliteration and the vulgar spelling of familiar.