"In Franeker, the Uffenbach brothers are visiting the collection of Willem Loré. Uffenbach describes the use of his portable, rotatable skymap. It was made in Amsterdam by one "Van der Molen" under the title "Onderwijs in het gebruyk van hemels plyn". Loré shows them also models of fortifications; Uffenbach explains how these were produced. Loré and the Uffenbach brothers discuss the production of glass sphaeren for the microscope."