A reference by Hendrie in his edition of Theophilus (1847) led to the discovery of a hitherto unknown manuscript by de Mayerne in the British Museum (manuscript Sloane 1990). In content it resembles the already wellknown de Mayerne manuscript 'Pictoria, Sculpturia et quae subaltemarum artium' (manuscript Sloane 2052) also in the British Museum and already published by Berger and van de Graaf. However there are also sections on the applied arts such as painting and drawing, etching, sculpture, glass, enamelling, ceramics, metalwork and dyeing which give interesting information on the 17th century methods in these fields. There are also references to the preparation of various coloured waxes for modelling, different kinds of cements, methods for making marbled paper and for laying tin foil on paper, also two methods for cleaning paintings. The manuscript is mainly in French with extracts in Latin, English, German and Italian. The first part is undoubtedly almost entirely by de Mayerne himself but the rest is in another hand, probably that of his nephew who inherited the manuscript.