material for
receiving impresses, which froze in its very fountains the early
resources of printing.

Some twenty years ago, this view of the case was luminously expounded by
Dr Whately, the present archbishop of Dublin, and with the merit, I
believe, of having first suggested it. Since then, this theory has
received indirect confirmation. Now, out of that original scarcity
affecting all materials proper for durable books, which continued up to
times comparatively modern, grew the opening for palimpsests. Naturally,
when once a roll of parchment or of vellum had done its office, by
propagating through a series of generations what once had possessed an
interest for _them_, but which, under changes of opinion or of taste,
had faded to their feelings or had become obsolete for their
understandings, the whole _membrana_ or vellum skin, the twofold product
of human skill, costly material, and costly freight of thought, which it
carried, drooped in value concurrently--supposing that each were
inalienably associated to the other. Once it had been the impress of a
human mind which stamped its value upon the vellum; the vellum, though
costly, had contributed but a secondary element of value to the total
result. At length, however, this relation between the vehicle and its
freight has gradually been undermined. The vellum, from having been the
setting of the jewel, has risen at length to be the jewel itself; and
the burden of thought, from having given the chief value to the vellum,
has now become the chief obstacle to its value; nay, has totally
extinguished its value, unless it can be dissociated from the connexion.
Yet, if this unlinking _can_ be effected, then--fast as the inscription
upon the membrane is sinking into rubbish--the membrane itself is
reviving in its separate importance; and, from bearing a ministerial
value, the vellum has come at last to absorb the whole value.

Hence the importance for our ancestors that the separation _should_ be
effected. Hence it arose in the middle ages, as a considerable object
for chemistry, to discharge the writing from the roll, and thus to make
it available for a new succession of thoughts. The soil, if cleansed
from what once had been hot-house plants, but now were held to be weeds,
would be ready to receive a fresh and more appropriate crop. In that
object the monkish chemists succeeded; but after fashion which seems
almost incredible; incredible not as regards the extent of thei