The foregoing observations prompt to the suggestion that not only the materials upon which a literary production is impressed or imprinted must be capable of easy conveyance or circulation but also that the writing itself must be legible, and that the materials employed must be proof to the utmost attainable extent against the obliterations of use and time. Necessarily, therefore, an achievement so laborious as the transcription of a written volume of whatever form (and especially of the Bible by reason of its size, character, and importance) called for a correspondingly larger concern and care _as to the materials employed_ (including both the ink and the substance written upon) than would be required in the making of a printed book wherein each separate volume but duplicates hundreds and thousands of other volumes made from the same plates. This requirement partly explains the care with which the ancient manuscripts were made or copied. It was this fact that made every copyist's work distinctively individualistic. The permanency and durability of books is largely a matter of relativity and fortuity. We quote from Mr. E. C. Richardson concerning the factors affecting the survival of books: "The average chance of an individual book for long life depends (1) on the intrinsic durability of its material, or its ability to resist hostile environment, (2) on isolation." He says, further: "The enemies to which books are exposed are various: wind, fire, moisture, mold, human negligence, vandalism, and human use. Some materials are naturally more durable than others. Stone and metal inscriptions survive better than wood or clay, vellum than papyrus or paper. On the other hand, however, if isolated or protected from hostile environment, very fragile material may outlast more substantial. Papyrus has survived in the mounds of Egypt, and unbaked clay tablets in the mounds of Babylonia, while millions of stone and metal inscriptions written thousands of years later have already perished. Here the factor of isolation comes in. Fire and pillage, moth and rust, and the bookworm destroy for the most part without respect of persons.... An unbaked tablet which has survived 5,000 years under rubbish may crumble to dust in five years after it has been dug up and exposed to air. The general law is that value tends to preserve, and it has been remarked that all the oldest codices which have survived in free environment are sumptuous copies. Literary value on the other hand is, on the whole, a factor of destruction for the individual rather than for survival. The better a book is the more it is read, and the more it is read, the faster it wears out. The worthless book on the top shelf outlasts all the rest."[18]