Siberch’s fifth book, _Erasmus De conscribendis epistolis_, was issued in October 1521. This is a more important book in point of size than any which preceded it, containing eighty leaves, whereas the largest of the others only ran to twenty. It also shows certain marks of advance. We find for the first time a frequent use of fine initial letters, and it is the first book for which the printer obtained a privilege, unfortunately not printed in full. Four copies of this book are known, two in the British Museum, and two in Cambridge College Libraries, St John’s and Corpus. The last copy has the additional interest of being bound by a contemporary Cambridge stationer, Nicholas Speryng, and bears his mark and initials on the binding. The Erasmus was followed by Galen _De Temperamentis_, translated from the Greek by Linacre. This is the commonest of Siberch’s books, at least twelve copies being known, but some of these show important variations. The first intention seems to have been to issue the _De Temperamentis_ alone, and it was so printed off on sixty-six leaves, with the signatures A⁴, Q⁶. Later it was determined to add another small treatise _De inequali intemperie_, so the last two leaves of the first issue, containing the end of the _De Temperamentis_ were cancelled, and two new sheets R⁴ and S⁶ added. Finally a preliminary quire of eight leaves was printed, making the complete book consist of seventy-four leaves. One copy of the first state is known, first noticed by Mr Bowes in the library of Trinity College, Dublin, in 1894. On the verso of the penultimate leaf is a woodcut of the Adoration of the Shepherds and the colophon, on the verso of the last leaf the small block of the Royal arms and the date 1521. A transitional copy, containing the first issue with the end uncancelled, but the additional sheets added, is in the library of the Royal College of Physicians. All the remaining copies are of the revised issue. In it the last two leaves are mainly occupied with a list of the errata which had been found in the _De Temperamentis_, and on the verso of the last leaf is the device of the Royal arms. The woodcut of the Shepherds found in the early copies has not as yet been traced to an earlier source. It is apparently Low Country work of the fifteenth century; Sir Martin Conway ascribes it to about the year 1485.