But let it now be imagined, that there are no other means of ascertaining the antiquity and genuineness of the classic authors than such as may be collected from the history of existing manuscripts. Our object then will be to discover to what age they may clearly be traced; and to deduce from the facts some sure inference relative to the length of time during which those works have been passing through the hands of copyists. The date of an ancient manuscript may be ascertained by such means as the following:-- 1. Some manuscripts are known to have been carefully preserved in the libraries where they are now found, for several centuries:--for not only have they been mentioned in the catalogues of the depositories to which they belong, but they have been so accurately described by eminent scholars of succeeding ages, that no doubt can remain of their identity. Or even if they have changed hands, the particulars of the successive transfers have been authentically recorded. 2. A large proportion of existing manuscripts are found to be dated by the hand of the copyists, and in such a manner as to leave no question as to the time when the copy was executed. 3. Many manuscripts have marginal notes, added evidently by later hands, which through some incidental allusion to persons, events, or particular customs, or by the use of peculiar forms of expression, indicate clearly the age of the notes, and therefore carry that of the original manuscript somewhat higher. 4. The remote antiquity of a manuscript is often established by the peculiar circumstance of its existing _beneath_ another writing. These re-written manuscripts--palimpsests, or rescripts, as they are termed, afford the most satisfactory proof of antiquity that can be imagined. Parchment, which has always been a costly material, came to be greatly enhanced in price at the time when paper, manufactured from the papyrus of the Nile, began to be scarce, and just before the time when that formed from cotton--called charta bombycina, was brought into general use. At the same period, owing to the general decline of learning, the works of the classic authors fell into very general neglect. Those, therefore, who were copyists by profession, and the monks especially, whose libraries often contained large collections of parchment books, availed themselves of the valuable material which they possessed, by erasing, or washing out, the original writing, and then substituting lives of the saints, religious romances, meditations, or such other inanities as suited the taste of the times. Nevertheless, often, the faithful skin, tenacious of its pristine honours, retained the traces of the original writing with sufficient distinctness to render it still legible. These rescripts, therefore, offer to us a double proof of the antiquity of the work which first occupied the parchment; for in most cases the date of the monkish writing is easily ascertained to be of the twelfth, or even the ninth century.