es au feu, supprimes, ou censures_, etc. Works of
writers of genius and versatile ability were thus proscribed, until it
gave rise to the sarcasm among the scholars of Europe, that if one wanted
to find what were the books best worth reading, he should look in the
Index Expurgatorius. It appears to have been quite forgotten by those in
authority that persecution commonly helps the cause persecuted, and that
the best way to promote the circulation of a book is to undertake to
suppress it. This age finds itself endowed with so many heretics that it
is no longer possible to find purchasers at high prices for books once
deemed unholy. Suppressed passages in later editions lead to a demand for
the uncastrated copies which adds an element of enhanced cost in the
market.

(4) Another source of rarity is the great extent and cost of many works,
outrunning the ability of most collectors to buy or to accommodate them
on their shelves. These costly possessions have been commonly printed in
limited numbers for subscribers, or for distribution by governments under
whose patronage they were produced. Such are some of the notable
collections of early voyages, the great folios of many illustrated
scientific works on natural history, local geography, etc. That great
scholar, Baron von Humboldt, used jocosely to say that he could not
afford to own a set of his own works, most of which are folios
sumptuously printed, with finely engraved illustrations. The collection
known as the "_Grands et petits Voyages_" of De Bry, the former in 13
volumes, relating to America, and finely illustrated with copper-plates
produced in the highest style of that art, are among the rarest sets of
books to find complete. The collection of voyages by Hulsius is equally
difficult to procure. A really perfect set of Piranesi's great
illustrated work on the art and architecture of ancient Rome is very
difficult to acquire. The _Acta Sanctorum_, in the original edition, is
very seldom found. But there is no room to multiply examples.

(5) What adds to the rarity and cost of certain books is the peculiarly
expensive style or condition in which they are produced or preserved.
Some few copies of an edition, for example, are printed on vellum, or on
China or India or other choice paper, in colored ink or bronze, on
colored paper, (rose-tinted, or green, blue or yellow,) on large paper,
with broad margins, etc. Uncut copies always fetch a higher price than
those whose