Letters

Letters Readers’ commentson texts published In Lronurh are welcomed. Ibe Editors reserve tbe rightto shorten letters. Letters should be written in English and sent to the Main Editorial OfIice. Francas le Lionnais Francois le Lionnais died on 13 March 1984, his death almost unnoticed. This good friend of Leonardo was originally a chemicalengineer but since 1950 he had played a vital role in French intellectual life. He was a writer, an organizer, and an incomparable lecturer on French radio and television; but above all he was interested in mathematics, painting, poetry, detective stories and chess. Like many of his friends, I shall always remember his ‘luncheons’ in Boulogne,amidst hundreds of books scattered about his apartment, to which he invited painters like Marcel Duchamp, mathematicians like Stan Ulam or Paul Erdos, not to mention a world chess champion or some fdm maker. The written works of FranGoisle Lionnais were as varied as his guests. After he published “Les Grands Courantsdela Penst MathCmatique” (“Important Trends in Mathematical Thought”), he founded, with Raymond Queneau, POulipo (Workshop for Potential Literature), a group of mathematicians and writers who for the most part are famous today. They began meeting on 24 November 1960 and met every month thereafter to suggest new forms for different kinds of literature. But, above all, le Lionnais considered himself an artist. This led to his founding POupeinpo (Workroomfor Potential Painting), which gathered together a group of painters who were interested in using in their works ideas derived from Combinatorial Theory (such as magic squares), from the theory of numbers, from topology, etc. While le Lionnais was in one of the worst concentration camps, Dora, his passion for art and numbers combined with his unrelenting discipline was the key to his survival: during that period he conducted thorough research into the surprising properties of numbers (which led to the publication in 1982 of the “Dictionaire des Nombres Remarquables” [“Dictionary of Remarkable Numbers”]) and reconstituted from memory all the details of a singlepicture in the Louvre(which led in 1946 to a published text entitled “The Painting at Dora”). His last work, still unpublished, describes him perfectly: It is called “Un Certain DisparatC” (“A Certain Incongruity”). Claude Berge Centre de Mathematique Sociale 54. Boulevard Raspail Paris, 75270France Comments on “Photographic Images and Optical Effects Using Birefringent Materials” I was interested to read in Mr Semenoffs article (Leonardo 17, 180 (1984)), that birefringent displays have been used as introductions to a number of television programmes. It was difficult to appreciate the prints in the article as they were reproduced in monochrome but I find it disappointing that the majority of users of this medium resort to the abstract. The range of colours available using one or even two types of cellophane is fairly limited and consequently the colour sensations produced in these abstract prints, although at first a novelty, soon become repetitive. As the transmitted colours are very similar to those produced in stained glass windows I am surprised that few artists have developed this concept. I have observed only one exhibit in this form, at the British Science Museum in London. One error of fact in Mr Semenoffsarticle is the claim that the colours are of a single wavelength. In fact the analyser blocks a single wavelength completely and greatly reduces neighboring wavelengths and therefore the colours produced do not have the purity of single wavelength colours. In our own work (Colour Research andApplication 4,164 (1979)) we did not obtain purities above 50% but we did calculate that purities of approximately 85% were possible. S . J. Edwards School of Applied Physics Leicester Polytechnic P.O. Box 143 Leicester L E I 9BH U.K. Reply to Mr S. J. Edwards Of course Mr Edwards is right. As a physicist devoted to research into the phenomena, he obviously understands it much better than an artist who is more concerned with the possibilities in its use. In an attempt to make a point, I have oversimplifiedadifticult concept. It is also true that the range of colors available are not the full spectrum ofthe rainbow. While some colors are rich, others are not so saturated. This could be caused by the thickness of the...