A rare form of writing upon rolls is that found in the prayers written on the strips which are rolled up inside Buddhist prayer wheels. Such prayers, however, are never read, but are counted as being read through on each revolution of the wheel. Each line of manuscript runs along the entire length of the roll, which is unrolled sideways. The prayer wheels vary immensely in size, the best known being the little hand ones chiefly used in Thibet; they are variously ornamented. [Illustration: FIG. 18.--Roll written upon longitudinally.] The form of writing in rolls that is of most interest so far as books is concerned is a modification of the Thibetan form. Instead of each line running the whole length of the roll, a space limit is now fixed, and the lines of writing follow under each other, so that the page form is at once apparent. This form, a late one, can be seen in the case of the Jewish scrolls of the law. The roll is unrolled sideways, and the rollers at each end are often very handsomely decorated. [Illustration: FIG. 19.--Thibetan prayer wheel.] But writing of this last kind on rolls has suggested another arrangement in which the reading is more easy, and the re-rolling of the roll itself avoided. It will be seen that a blank space is left between each of the written “pages.” Now if the vellum, bark, or paper be folded across these vacant spaces, one after the other, backwards and forwards, like accordion pleating, we shall find that we get a form of book well known in the East and also among primitive nations. [Illustration: FIG. 20.--Roll written upon in page form.] Curious examples of such converted rolls can be seen in most museums, and they are generally kept flat by means of two boards front and back, but not otherwise fastened. The Chinese and Japanese have taken this particular form of evolution from the roll to the book a step further, and by help of the ancient device of “stabbing” the flattened roll along one of its sides, they produce a form called an “Orihon,” easy to consult, strong, and the blank back of the roll so hidden up that its existence is frequently not realised. But if some of the leaves of an Orihon are cut, its real structure becomes at once evident, and a book will be produced with letterpress and blank paper alternately in pairs. A similar kind of alternation shows now and then in the case of MS. rolls that have been cut up, but they are oftener arranged letterpress and blank alternately. [Illustration: FIG. 21.--Sumatran bark book in the form of a folded roll.] [Illustration: FIG. 22.--Orihon.] Without realising it we still preserve this blank and letterpress sequence, found in the converted roll, in official and legal manuscripts as well as in those intended for the printer. When the printing press took the place of the scribe, the blank leaves had no further _raison d’être_, so they dropped out for good.