There are also many curiosities of compilation in auction catalogues. Not to name errors of commission, like giving the authorship of books to the wrong name, and errors of omission, like giving no author's name at all, some catalogues are thickly strewn with the epithets _rare_--and _very rare_, when the books are sufficiently common in one or the other market. Do not be misled by these surface indications. Books are often attributed in catalogues to their editor or translator, and the unwary buyer may thus find himself saddled with a duplicate already in his own collection. There has been much improvement in late years in the care with which auction catalogues are edited, and no important collection at least is offered, without having first passed through the hands of an expert, familiar with bibliography. It is the minor book sales where the catalogues receive no careful editing, and where the dates and editions are frequently omitted, that it is necessary to guard against. It is well to refrain from sending any bids out of such lists, because they furnish no certain identification of the books, and if all would do the same, thus diminishing the competition and the profit of the auctioneer, he might learn never to print a catalogue without date, place of publication, and full name of author of every book offered. Never be too eager to acquire an auction book, unless you are very thoroughly assured that it is one of the kind truly designated _rarissimus_. An eminent and thoroughly informed book collector, with an experience of forty years devoted to book auctions and book catalogues, assured me that it was his experience that almost every book would turn up on the average about every seven years. Of course there are notable exceptions--and especially among the class of books known as _incunabula_, (or cradle-books printed in the infancy of printing) and of early Americana: but it is not these which the majority of libraries are most in search of. Remember always, if you lose a coveted volume, that there will be another chance--perhaps many of them. The private collector, who carries it off against you, has had no former opportunity to get the rare volume, and may never have another. He is therefore justified in paying what is to ordinary judgment an extraordinary price. Individual collectors die, but public libraries are immortal.