The manuscripts of the twelfth and thirteenth centuries are distinguished by a degeneracy in the mode of writing, and by a growing abuse of the principle of celerity and facility. To these symptoms of the influence of a mercantile motive, put into activity by an increasing demand for books, may be added the practice of discharging the writing of old parchments, which prevailed at the same period more extensively than heretofore. A vast number of books of this sort, written upon erased parchments, are to be met with, executed in the twelfth, thirteenth, and fourteenth centuries. In most instances, the first writing is utterly obliterated; yet the marks of the erasure are still evident. Thus in a MS. above described, not a letter, not a point, of the ancient writing remains; but on many of the leaves may be discerned ruled lines, either transverse or perpendicular, which having been deeply impressed upon the parchment could not be effaced; so that those old lines often crossed the new writing. Other pages of the same MS. present no such indications; the leaves having probably been taken from different books. In another MS., executed in the year 1186, though the ancient writing is generally obliterated, yet in a few places, if closely inspected, the ends of the letters may be perceived. In a word, if all the books of the thirteenth and fourteenth centuries are examined, there will appear to be almost as many written upon erased, as upon new parchments.[1] I am of opinion, that many authors extant in the time of Photius, and even in that of Porphyrogenitus, were utterly destroyed by the prevalence of this pernicious practice. This plague, as it may be termed, spread its devastation among ancient books first in the twelfth century, and continued its ravages during the thirteenth and fourteenth. The same thing is rarely to be observed in bombycine manuscripts: I have met with one book only of this material in which the first writing had been erased, and a second induced. The Greek writers of these times ordinarily erased a better work for the sake of substituting a worse; either one of their own inane productions, or those works of which there is no scarcity among MSS. The extremest ignorance must certainly have pervaded Greece in those times, when what related to ancient history, or to polite learning, was not valued a straw by the writers, who rather than purchase new parchment, destroyed, without scruple, ancient books.