The little known window design and corresponding glass cartoon kept in the Municipal Archives of Leiden are the remains of a now lost window with the representation of Pallas Athena and her owl, given by the Board of Governors of Leiden University to the Pieterskerk. They have been first published by Pelinck in I943 with the correct destination, donor's name and even the date, I629 (note 2). He was able to do so by linking the drawings with a description from c. I630 by the Utrecht antiquarian Arnoldus Buchelius and the published resolution of the Cu-rators taken on I4 May I629 (notes 6, 9). The Curators offered a gift of glass to the former churchmaster Heinrick Egbertsz. van der Hal, whereby no artist's name or subject matter are mentioned, only the obligatory inclusion of the city arms. The practical arrangement for the commission was left to the Burgomasters of Leyden, who were all members of the Board of Governors. The small-scale drawing, severely damaged, concentrates on the architectural and heraldic design (fig. i). An aedicule supported by Corinthian columns and crowned by a pediment offers room below to the city arms of Leiden and the university flag, with a still life of books and globes in front, covering the floor. Two more coats of arms are depicted on either side of the pediment: on the left the arms of Holland held by the Dutch lion, and on the right those of Prince William of Orange, founding father of the university, held by Fame. The drawing provided with scale indications and an unfinished, alternative design on the reverse is apparantly not a vidimus, but a working document to facilitate the elaboration of the cartoon. The latter consists of two long segments for the first two lights and two shorter ones, with the missing information added either on the reverse of the same strip or of the corresponding second (for the third) and first (for the fourth) lights (figs. 2-9). The working method is so far similar to that of the Gouda cartoons, of which the latest pieces date from the early I7th century. With the repetition of parts of the architecture in mirror image the Leiden cartoon is now considered, contrary to Pelinck, complete. It represents minor improvements in composition and ornament with respect to the small drawing, but most important, it depicts the figures in the second and third lights, still missing in the small design. Pallas Athena, goddess of wisdom and protector of science and the arts is standing on a pedestal in the aedicule, paging in a book placed on the cathedra on her leftside. Her attributes, the owl and the shield with Medusa head, are nearby. Below her feet four children are engaged in writing and reading. They are identified now as personifications of the four then faculties of the young university: on the left theology, distinguished by a piece of paper inscribed with Hebrew-like characters bound to the figure's head, and medicine, depicted as a naked child, only the head covered by a drapery. The two helmeted boys on the right represent law and philosophy. The donation can not be linked to any special occasion, in I629 the university existed just 54 years. The old attribution by Pelinck on presumed stylistic ground of design and cartoon to the Utrecht painter and glass-painter Jan Gerritsz. van Bronchorst (c. I603-I66I) was already rejected in the past in the artist's biography on the same ground (note 25). A new candidate is proposed now in the person of the Leiden artist Pieter Kouwenhorn (I599/I600-I654), who originated from Haarlem and was inscribed in I6I9 as master glass-painter in the rolls of the Leiden Guild of St. Luke. Although he has already been studied in the past in some detail, more information is given now on his life and the small œuvre of his drawings (notes 29-30, 56). The Burgomasters of Leiden, responsible for commissioning the artist, were familiar with him, as Kouwenhorn has just finished in I628 a documented window in the Aldermen's Chamber of the City Hall (fig. II). Although the figural scenes of this cartoon are smaller and they are therefore executed in the favourite technique of the artist in pen, grey and brown ink and wash instead of black and white chalk, they also present certain parallels in support of the attribution. More stylistic arguments are provided by Kouwenhorn's signed drawing with a related subject matter, Minerva and Mercury from I635 in the Album Amicorum of the Leiden scholar Petrus Scriverius (fig. I5). The new attribution is finally substantiated by documents. The artist's correct Christian name, mis-spelled surname and his qualification as a glass-painter occur in the church administration, when he was paid on 25th of March I630 the sum of f 6 s I4, without precising his services; on 30th December of the same year payment of f I0 s I6 is recorded again to him as Pieter Pieters. (notes 5I, 52). The first item most probably concerns the customary gratuity given by the churchwardens after installment of the window in the Pieterskerk, with payment perhaps for additional work in December. Completion of the glass within a year, announced by the Curators of the university on I4th May I629 is reasonable, and full payment was due from the latter. The question remains, if Kouwenhorn was only the glass-painter or also the author of the window's design and the draftsman of the cartoon with figures of exceptional quality, which are executed more carefully than the protagonists of the smaller cartoon for the Aldermen's Chamber. His oeuvre of independent drawings made in a variety of techniques (figs. I0, I2, I4, I6, I7), the reference made to him shortly after his death as an excellent draftsman, and his involvement in giving drawing lessons leave no doubt as to his capacities in this field (notes 36-38). Together with Bronchorst, Kouwenhorn follows in the footsteps of such famous I6th-century glass-painters as the Crabeths from Gouda and Willem Tybout from Haarlem, who all worked from own design. As to Kouwenhorn, unfortunately none of his windows is preserved. The exact location of the university glass in the Pieterskerk is unknown, just like the date when it fell into decay and was removed.