Measuring the height of the Colossus of Rhodes, engraving by Rubens, from Aguilon, Opticorum, 1613 (Linda Hall Library).
Exterior of the Lycée Louis-le-Grand, facing the rue St Jacques, Paris, France. D'Aguilon studied three years in the Jesuit College de Clermont in Paris (clearly secondardy level for Aguilon).
University of Douai, 1559–1887 (transformed as University of Lille).
A stereographic projection of an armillary sphere, engraving by Rubens, from Aguilon, Opticorum, 1613 (Linda Hall Library).
Dissecting an eyeball, engraving by Rubens, from Aguilon, Opticorum, 1613 (Linda Hall Library).
Francisci Agvilonii e Societate Iesv Opticorvm libri sex, 1567-1617.
A stereographic projection of an armillary sphere, engraving by Rubens, from Aguilon, Opticorum, 1613 (Linda Hall Library).
Engraved title page by Rubens, from Aguilon, Opticorum, 1613 (Linda Hall Library).
Dissecting an eyeball, engraving by Rubens, from Aguilon, Opticorum, 1613 (Linda Hall Library).
Color diagram, from Aguilon, Opticorum, 1613 (Linda Hall Library).
Francisci Agvilonii e Societate Iesv Opticorvm libri sex, 1567-1617.
Exterior of the Lycée Louis-le-Grand, facing the rue St Jacques, Paris, France. D'Aguilon studied three years in the Jesuit College de Clermont in Paris (clearly secondardy level for Aguilon).
University of Douai, 1559–1887 (transformed as University of Lille).
Peter Paul Rubens
Carlo Scribani, c. 1645, Peeter Clouwet (engraver), National Gallery of Victoria, Melbourne Everard Studley Miller Bequest, 1959.
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Ethnicity:
D'Aguilon`s family was a distinguished Spanish noble family.
François d'Aguilon was born on January 4, 1567, in Brussels to Pedro Aguilon, who was secretary to Philip II during an embassy to France. Nothing is known about the economic status of the family. It had to have been affluent at the least.
François De Aguilon studied three years in the Jesuit College de Clermont in Paris (clearly secondary level for Aguilon). He then went to Douai for two years, and having completed the course in humanities, he began to study philosophy. (This would be the beginning of university level study.) After eight months this course of study was interrupted in 1686, and he was sent to Tournai for his novitiate. He returned to Douai in 1588 to study philosophy and mathematics and received the M.A. degree in 1590. He then completed theological studies in Salamanca in 1592.
After having taught syntax and logic, then theology, François d'Aguilon was charged with organizing in Belgium the teaching of the exact sciences, which were useful in commerce, geography, navigation, and architecture, as well as military activities. This project led to the composition of a master treatise on optics that synthesized the works of Euclid, Ibn al-Haytham (Alhazen), Vitellion, Roger Bacon, Pena, Ramus (Pierre de la Ramée), Risner, and Kepler. Its organization into three sections was determined by the manner in which the eye perceives objects (directly, by reflection on polished surfaces, and by refraction through transparent bodies). Aguilon’s death prevented the publication of the second and third sections, on catoptrics, dioptrics, and telescopes. Only the first part exists, with six frontispieces drawn by Rubens: Francisci Aguilonii e Societate Jesu Opticorum libri sex juxta ac mathematicis utiles (1613).
Aguilon's famous book Opticorum libri sex (Six Books on Optics) contained a number of original insights and contributions to the field of geometrical optics even though he was unaware of the optical theories established by Kepler in his Optics which had been published several years previously. What is quite remarkable about this book is the fact that the illustrations at the beginning of each section are works of the greatest Flemish Baroque painter, Peter Paul Rubens. The frontispiece at the beginning of the book shows an eagle, referring to Aguilon's name and a variety of optical and geometrical images. At the beginning of each of six sections are Rubens' drawings describing Aguilon's experiments, one of which is the first known picture of a photometer. This is one of six experiments drawn by Rubens and shows how intensity of light varies with the square of distance from the source. The experiment was later taken up by Mersenne and another Jesuit, Claude de Chales, and eventually led to Bouguer's more famous photometer.
Aguilon gave some early hints on perspective geometry which were later used by Desargues, the "Father of projective geometry". Aquilon was the first to use the term horopter, the line CD drawn through the focal point of both eyes and parallel to the line between the eyes.
Aguilon treated, successively, the eye, the object, and the nature of vision; the optic ray and horopter; the general ideas that make possible the knowledge of objects; errors in perception; luminous and opaque bodies; and projections.
His sixth book, Opticorum libri sex (Six Books on Optics), on orthographic, stereographic, and scénographie projections, remains important in the history of science. It accounts for a third of the treatise and was meant for the use of astronomers, cosmographers, architects, military leaders, navigators, painters, and engravers. It places particular emphasis on stereographic projection - a type of projection, used by Ptolemy, in which the portion of the sphere to be represented is projected from the pole onto the plane of the equatorial circle.
D`Aguilon became a Jesuit in 1586 and was ordained in 1596.
In his works D`Aguilon shows the point of view on the balance of the treatise is of interest for the history of optics: description of the eye; controversies on the nature of light and its action; the application of mathematics to optics; the analysis of the concepts of distance, quantity, shape, place, position, continuity, discontinuity, movement, rest, transparency, opacity, shadow, light, resemblance, beauty, and deformity; and explanation of the various errors of perception linked to distance, size, position, shape, place, number, movement, rest, transparency, and opacity.
Book 5, in spite of an Aristotelian concept of light, studies the propagation of light, the limit of its action, the phenomena produced by the combinations of light sources, and the production of shadows. Aguilon proposes an experimental apparatus, drawn by Rubens, that made it possible to study the variations of intensity according to variations in distance and to compare lights of different intensities. This attempt to apply mathematics to the intensity of light was continued by Mersenne, then by Claude Milliet de Chales, and resulted in Bouguer’s photometer.
Quotations:
D'Aguilon expanded on the horopter by saying in his book:
"If objects fall upon different rays it can happen that things at different distances can be seen at equal angles. If point C be directly opposite the eyes, A and B, with a circle drawn through the three points, A, B, and C. By theorem 21 of Euclid's Third book, any other point D on its circumference which lies closer to the observer than C, will subend an angle ADB which will equal angle ACB. Therefore, objects at C and at D are judged equally far from the eye. But this is false, because point C is farther away than D. Therefore a judgment of distance is false when based on the angles between converged axes, quod erat probandum."
Quotes from others about the person
“The horopter is the invention, or rather discovery, of Aguilon; he coined the term and showed how important the horopter is in explaining vision with two eyes; he even demonstrated the horopter in a simple device constructed by him and pictured by Rubens. . . . The theory of Aguilon on the horopter is a large step in the right direction, calling a halt to all previous deficient theories” (Ziggelaar, François Aguilon, 115).
“The designs for the frontispiece and six vignettes reveal Rubens’ knowledge of the actual text. . . . Rubens combined successfully Aguilonius’ references to ancient mythology and allegory into a coherent programme that also includes a connection with the science of optics, for all the various elements on the frontispiece have a direct relationship with the concept of vision” (Held, Rubens and the Book, 52).
Peter Paul Rubens made the illustrations at the beginning of each section of the Opticorum libri sex (Six Books on Optics). The evidence for collaboration is not confined to the words of Aguilon. Rubens himself has provided it in his own language: by his paintings. C. Parkhurst has shown how much Rubens' painting Juno and Argus is in agreement with Aguilon's theory of color and he concludes: Rubens' picture and d'Aguilon's text are important documents for the history of both science and art.
Aguilon dedicated his Opticorum libri to Inigo Borgia, the commander of the Spanish fortress at Antwerp (and a governor of the Spanish Netherlands). Inigo Borgia was the great grandson of St. Francisco de Borgia, the third General of the Society of Jesus.
Within the order, Aguilon's immediate superior, Carlo Scribani, the son of an Italian noble, was Aguilon's friend and may have led the way to Aguilon to succeed him as rector. After some hesitation, I am not listing this as a form of patronage, although it obviously verges on it.
