ould meet the first demand--massive pyramids
of covered earth or of solid masonry, or chambers hewn from the heart
of some granitic hill. In low latitudes, where glacial action is not
to be feared, the pyramidal form might be preferable: in more northern
regions the rock-cut chamber would probably be at once cheaper and
more durable. In either case, an elevated site should be chosen as a
safeguard against submergence.

To secure the permanence of the records would be more difficult.
Ordinary books and papers would clearly be unsuitable for long
keeping; though for comparatively limited periods they might answer if
securely packed in airtight waterproof cases. Nothing liable to
spontaneous decay should be admitted. Stereotype plates of metal would
be even more open to objection than printed sheets. The noble metals
would be too costly, the baser would corrode; and with either the
value of the plates as metal would be a standing danger to the
deposit. The material basis of the library must be, as nearly as
possible, worthless for other uses (to insure them against the natural
greed of man), yet such as will hold the records sharply and
faithfully under all circumstances. The _terra cotta_ tablets of
ancient Assyria are instructive in this connection. Possibly plates of
artificial stone, or sheets of a _papier-mache_-like preparation of
asbestos, might be less bulky and equally durable.

Having determined this point, and dug from the solid rock a chamber
for the reception of our legacy, the next step would be the selection
of its contents. Obviously the books to be preserved should embrace
first of all lexicons and grammars of every known form of speech,
since it is impossible to tell which of the dialects of to-day will be
the parents of the dominant tongue of any distant future time; while
we may be practically certain that some one or more of the languages
of to-day will furnish a key to any language that men will ever use.
Next in order would come encyclopaedias, the most comprehensive and
complete that there might be room for. The sacred books of all nations
might come next; then the works of the great poets, historians and
novelists; after them, the best obtainable records of art, science,
the various industries, and so on, with specimens of the best and most
typical of our works of art, manufacture, and the like.

The spaces between the various articles should be filled in with some
insoluble and neutral substanc