The camera obscura was bought on 25 March 1739 for Giovanni Poleni’s Cabinet of Physics

Date: 1st half 18th century

Description

In December 1738, right after the creation of a chair of Experimental Philosophy at the University of Padua, Giovanni Francesco Morosini, one of the Venetian magistrates in charge of the University of Padua, decided to buy some instruments for the new chair, and he started negotiating the acquisition of some devices from the heirs of a Venetian patrician, Cristino Martinelli. He was advised by Bernardino Zendrini, public mathematician and Venice Water Superintendent. Then, as soon as he was assigned the new chair, in early February 1739, Giovanni Poleni started supervising the acquisition. The scholar chose the objects and dealt with all the related practical questions, from the restoration to the transport, but always in collaboration with Zendrini, who actually stayed in Venice. Five instruments, among which this camera obscura, were thus officially bought on 25 March 1739 for the new course of Experimental Philosophy. Giovanni Poleni mentioned this camera in his "Indice delle Machine”, the catalogue where he noted every new instrument he bought, describing it as “A camera obscura twenty-four inches long, twelve inches and four lines high, in walnut. With two plane mirrors, one made of metal and the other one of crystal, and with a convex lens. V.1. His Excellency the Magistrate bought it from the noble Martinelli family”. Within the camera, a metallic mirror is fixed with an angle of 25° with respect to the horizontal and, above the mirror, a glass sheet is fixed with an angle of 50° with respect to the mirror (the glass is not original). When the light enters the camera, it is reflected by the mirror on the glass sheet and, by laying a sheet of paper on the glass, one can observe and draw the image of the external objects and landscape. To focus the image, a convex lens is inserted into a tube made of cardboard and wood, through which the light enters the camera. Another lens is fixed on the cover of the camera, to verify the focus when the camera is closed. One of the lateral wooden panels is not original.

Materials and techniques: walnut wood/cardboard/glass/speculum

Dimensions: height 33 cm, width 32 cm, length 62 cm

Related scholars: Giovanni Poleni (b.1683 - d.1761). Professor of Experimental Philosophy at the University of Padua from 1739 to 1761 / Cristino Martinelli (b.1653 - d.1732)

Keywords: optics, pre-cinema

University of Padua, Museum of the History of Physics

Cat. Number: 5

Exhibitions

• "La curiosità e l'ingegno - Collezionismo scientifico e metodo sperimentale a Padova nel Settecento", Padua, Botanical garden, May-December 2000

Bibliography

• Adolphe Ganot, Trattato elementare di fisica sperimentale ed applicata e di meteorologia: con una numerosa raccolta di problemi, Milano, 1859
• Pierre-Adolphe Daguin, Traité élémentaire de physique théorique et expérimentale: avec les applications à la météorologie et aux arts industriels, 2 ed., Paris,1862
• Giovanni Poleni, Indice delle macchine, Biblioteca Nazionale Marciana di Venezia, mss.it., cl. III, 54-55 = 4969-4970, cl. IV, 626 = 5488, 636 = 5497 [It was written by Giovanni Poleni from 1740 to 1761]