The work of Ziegelbauer gives in detail the old catalogue of the library of Fulda and those of a number of other abbeys. The estimates of the relative importance of these collections are in the main based upon Ziegelbauer’s statistics. There seems to be no question that these monastery libraries carried on with each other an active correspondence and exchange of books, and that this exchange business developed in not a few cases, as in that of St. Josse-sur-Mer, into what was practically a book-trade. It is the conclusion of Mabillon, as of Montalembert, that during the time in which Christian Europe was covered with active monasteries and convents in which thousands of monks and nuns were engaged in constant transcription, books could hardly have been really rare, at least as compared with the extent of the circle of scholars and readers who required them. Cahier points out that in addition to these great monastery collections, there were libraries of greater or less importance in nearly all the cathedrals, in many of the collegiate churches, and in not a few of the castles. Mabillon is of opinion that the prices of books during the Middle Ages have been very much overestimated, and that the impression as to such prices has been largely based upon isolated and misunderstood instances.[197] Robertson speaks of the collection of Homilies bought in 1056 by Grecia, Countess of Arizon, for two hundred sheep, a measure of wheat, one of millet, one of rye, several marten skins, and four pounds of silver, but Robertson omits to mention that the volumes so purchased were exceptionally beautiful specimens of caligraphy, of painting, and of carving. Maitland points out that it would be as reasonable to quote as examples of prices in the nineteenth century the exorbitant sums paid at special sales by the bibliomaniacs of to-day. “May not some literary historian of the future,” he goes on to say, “at a time when the march of intellect has got past the age of cumbersome and expansive penny magazines and is revelling in farthing cyclopædias, record as an evidence of the scarcity and costliness of books in the nineteenth century, that in the year 1812 an English nobleman gave £2260 and another £1060 for a single volume, and that the next year a Johnson’s Dictionary was sold by public auction for £200. A few such facts would quite set up some future Robertson, whose readers would never dream that we could get better reading, and plenty of it, very much cheaper at that very time.”[198]