A Tapestry of Tastes

The Optics of Giambattista Della Porta (ca. 1535–1615): A Reassessment

“…The rays incident along axes AB and AC thus correspond as perfectly as possible. 18 Thus, in the right-hand diagram of Fig. Accordingly, one image of A will reach the left-hand eye along ray AC to the left of visual axis CH, whereas the other will reach the right-hand eye along ray AB to the right of visual axis BH.…”

“…When speaking of the sphere, he wrote "point of inversion" only to indicate the position in whose vicinity image inversion occurred (DR II 16,18), while avoiding the term when referring to the points where the sphere concentrated rays and could light fires (DR II 22, 23). I have already discussed how ambiguous the notion of "point of inversion" for the mirror was, and it is interesting to note that Della Porta in DR used very little both the term and the notion.…”

“…5.12. 18 Clear and reasonable though it is, Della Porta chose to reject this explanation, presumably because it depends on a more expansive cone of radiation than the pupil will allow. In the left-hand diagram, the axes from both eyes converge on object A, so it will appear to lie straight ahead from both viewpoints C and B.…”

“…Although Sabra recognizes that Descartes never used the word 'speed' in connection with light, his complete analysis of Descartes' proof is based on the assumption incorrectly attributed to Descartes "that the velocity of light is characteristic of the medium it is traversing". 18 Schuster argues, basing himself largely on the Mydorge 'letter', that first Descartes discovered the law, in what he terms the cosecant form, by purely geometrical optical means, based on the traditional image location principle and available data. 14 Shea points out the relevance of Kepler's discussion of such device for Descartes in the Dioptrice of 1611.…”

“…W. Eamon 16 a spectacle of beauty ravished to itself the eyes and hearts of all observers: tongues fell silent, spirits hung suspended." 18 Reading Della Porta's Magia naturalis is to plunge headlong into the cultural world of the Renaissance court. Clarizia imparts an otherworldly sense of beauty, like a miracle.…”