Palimpsest (Gr. Palimpsest 13003 , from Palimpsest 13004 , again, and Palimpsest 13005 , to rub), a parchment which has been written upon twice or oftener, the prior writing having been erased and the surface prepared for the new by rubbing. The ancients used the word in this sense, but they also applied it to leaves or books used by authors for a preliminary writing of their works, which were so made that the ink could be wiped off in order to make corrections and revisions. After the conquest of Egypt by the Saracens, western Europe was cut off from the papyrus which it had previously drawn from that country, and the supply of parchment being limited, recourse was had to the erasure of ancient manuscripts. This practice, which prevailed in the "West from the 7th or 8th century throughout the dark ages, and in the East, which was not deprived of papyrus so soon, from about the 11th century, was long supposed to have caused the destruction of a vast amount of classical literature, sacrificed by the monkish transcribers to the needs of missals, antiphonaries, and other religious writings; but it has resulted rather, through the deciphering of the expunged works, in the recovery of important fragments of ancient authors, many of which would otherwise have been lost irrecoverably.

Two processes were used by the mediaeval scribes in the preparation of palimpsests, in the first of which the writing was washed off with a sponge and the parchment smoothed when dry by rubbing with pumice stone; in the second either entire lines were scraped off with a sharp blade, or each letter was erased separately, the surface being afterward rubbed smooth with pumice stone or with a polishing tool. The success of the erasure depended materially on the kind of ink with which the writing was executed. If vegetable, it was easily expunged, as it did not strike into the body of the skin; but if it contained animal or mineral matter, it was impossible to remove entirely the original writing, traces of which could be distinctly seen in many cases even after the surface had been rubbed off. Most of the ancient manuscripts were written with ink composed of lampblack, gum, and vitriol, which so penetrated the skin that it could not be entirely removed; for, if invisible to the eye, its presence can still be detected by proper chemical treatment. - Various means have been adopted in modern times to revive the erased writings of palimpsests. Among the first was to wash the parchment with an infusion of galls and to expose it afterward to the light.

This process frequently reproduced the ancient characters so that they could easily be read; but in some cases it blackened the entire parchment so as to render illegible both the old and the later writing. In 1787 Sir Charles Blagden proposed a "new method of recovering the legibility of decayed writings," viz., to dip the manuscript, after a careful washing in water, into diluted muriatic acid and afterward into a solution of prussiate of potash. A similar treatment was proposed by Prof. Gioberti of the university of Turin, and a preparation founded upon it received the name of tinctura Oiobertina. A preparation of sulphuretted ammonia has also been used with success. When the ink contains some animal substance, such as the blood of the cuttle fish or milk, Prof. Mone recommends that the parchment be immersed in oil in a close vessel and subjected to a heat of 400° R. By means of these and other modes of treatment the ancient writing of many palimpsests has been rendered legible enough to be deciphered by experienced palaeographers; and in several cases two writings have been brought to light under the superficial one. - Among the earliest to make observations on palimpsests was Louis Boivin, who in 1692 discovered under the Syriac text of St. Ephraem, in a manuscript in the royal library at Paris, portions of the Greek Bible 12 or 13 centuries old.

Montfaucon also called attention to the importance of palimpsest manuscripts in his Palceo-graphia Grceca (1708); but it was not until the last half of the 18th century that much progress began to be made in their decipherment. In 1762 F. A. Knittel published a portion of the Epistle to the Romans in the Gothic text of Ulfilas, found under a copy of the Origines of Isidorus in a, manuscript preserved in the library at Wolfenbuttel; and in 1773 P. J. Bruns recovered and published a part of the 91st book of Livy from a palimpsest in the Vatican. But by far the greatest explorer in the field of palimpsest literature was Cardinal Angelo Mai, who published from 1814 to 1853 many invaluable fragments of classic authors before reckoned as lost; among them were the De Republica of Cicero and portions of the histories of Polybius, Diodorus Siculus, Diony-sius of Halicarnassus, Dion Cassius, Appian, and Iamblichus. His success gave zest to the study, and through the labors of Niebuhr and others the greater part of the Institutes of Gaius were recovered from a manuscript at Verona and published in 1820. Other investigators who have rendered important service to literature in this department are Barrett, Blume, Peyron, G. H. Pertz and his son Karl Pertz, Gaupp, F. J. Mone and his son Fridegar Mone, Cureton, Hase, Tregelles, and Tischen-dorf. (See Manuscript).