In writing this book three questions chiefly interested me. What books and pamphlets did Richard Porson own? From whom did he acquire these materials? What has become of his holdings? Answering the first question was relatively easy. For over two hundred years students have known that, after his death, Porsons library was divided into two unequal parts. The larger portion was sent to auction, the smaller part, together with Porsons papers, was separately sold to Trinity College, Cambridge. To treat the problem I have examined all of the microfilm set of the Sotheby auction catalogues from 1783 to 1808, save when catalogues were not marked or the markings were too faint to decipher: notably Jan. 1, 1785; May 29, 1786; Jan. 22 and May 1, 1797; June 1788; Jan. 13, 1789; May 26, 1791; June 22, 1795; Jan. 1796; 1800; Nov. 14, 1803 through Dec. 3, 1804 (twenty-three catalogues); April 18 and May 29, 1805; April 14-30, May 19, June 5, July 2, 10, 15, 1806...or when the microfilm is imperfect. Likewise, I have seen, in London, most of Christies book catalogues from 1782 to 1808; and, in Los Angeles, much of the Frank Marcham collection at UCLA (coll. 416 boxes 10-34). Finally, I have seen almost all of Porsons books at Trinity and a few other places. From 1786 to 1808, Porson purchased hundreds of books and pamphlets. The records allow us to trace his purchases at forty-seven auctions. Of these, Leigh & Sotheby presented most of the sales. But Porson also bought at sales offered through Edwards, Robson and Clarke, King & Loche, and he at least interested himself in a Stewart sale. In addition, one has to take into account books given to Porson as prizes or gifts; perhaps books entrusted to him for review; and books for which he subscribed. Addressing the second question is complicated by three factors. First, there is the imperfection of the records. The archives of most houses do not sirvive; even the L&S house-files are, on occasion, imperfect or incompletely legible. Secondly, clerks wrote down what they heard. Often enough, they heard Pawson or Pauson, and it was needful to establish identity. Thirdly, there are difficulties in the way of determining specific editions: these range from the existence of multiple editions or impressions to incompleteness of library records and of descriptions of volumes of tracts.