Charles Jasper Joly and James Waterhouse

“ Nothing is said about the use of a lens or of solar observations. The second edition, in which he in the same words discloses the use of a convex lens in the aperture as a secret he had intended to keep, was not published till 1589, thirty-one years after the first. In this interval the use of the lens was discovered and clearly described by Daniello Barbaro, a Venetian noble, patriarch of Aquileia, in his work La Pratica della perspettiva (p. 192) , published in 1568, or twenty-one years before Porta’s mention of it. ”

“ He seems to have been well acquainted with the projection of images of objects through small apertures, and to have been the first to show that the arrival of the image of an object at the concave surface of the common nerve—or the retina—corresponds with the passage of light from an object through an aperture in a darkened place, from which it falls upon a surface facing the aperture. ”

“ The account is not very clear, but seems to imply the use of a concave mirror rather than a lens, which might be suggested by the word orbem. He refers to Maurolycus’ work with concave specula.
We now come to Giovanni Battista della Porta, whose account of the camera obscura in the first edition of the Magia Naturalis, in four books (1558, lib. iv. cap. 2) , is very similar to Caesariano’s—a darkened room, a pyramidal aperture towards the sun, and a whitened wall or white paper screens, but no lens. ”

“ The prism a b c is fixed at the top of a small tent furnished with opaque curtains so as to prevent the diffused daylight from overpowering the image on the paper, and in the darkened tent the images of external objects are seen very distinctly. ”

“ He notes the convenience of the method for solar observations and its previous use by some of the observers already mentioned, as well as its advantages for easily and accurately copying on an enlarged or reduced scale, especially for chorographical or topographical documents. ”