ORGANCN 4(1967) L’ANTIQUITÉ CLASSIQUE ET LES DÉBUTS
DE LA SCIENCE MODERNE
Jifi Marek (Czechoslovakia)
THE INFLUENCE OF ANCIENT SCIENCE ON JOANNES MARCUS MARCI’S CONCEPTIONS
ON THE PROPERTIES OF LIGHT
In his scientific w ork Joannes M arcus M arci (1595— 1667) attach ed considerable im portance to problem s connected w ith w hite light and spectral colours.
He lectured a t the medical faculty of P rag ue U niversity. W hile lecturing he w rote several books, not only on m edicine and philosophy, but on m athem atics, mechanics and physical optics as well. In th e firs t half of the 17th century, th a t is at th e beginning of the evolution of physical optics and p rio r to th e w orks of G rim aldi, N ew ton and Huygens, M arci already w rote w orks on physical optics.
He studied, w henever possible, the phenom ena of spectral colours, and so became aw are of the appearance of hues w hen illum inating either narrow slits or edges of a screen or wire, or even a n um ber of various slits, calling them reticula. He also investigated the hues visible on the film of soapbubbles, the colours of the rainbow and the hues appearing in the spectra of prisms. Though M arci observed all these phenom ena, y et th e ir physical properties rem ained unknow n to him.
As early as in 1648 M arci published his most im p ortan t book on rainbow s u nd er th e title Thaumantias, and already in this very y ear he grasped some of the properties of light, by the w ay the same w hich later, in 1672, N ewton described in his famous treatise N ew T heory on L igh t and Colours. M arci already knew, th a t the size of th e angle under w hich light is being refracted from the prism is responsible for the appearance of hues in the spectrum ; he also realized th a t a fu rth e r refraction and reflexion of monochromatic light w ould fail to change th e colour p attern of the light rays used.
1 3 4 J. M arek
In the course of his experim ents M arci very nearly discovered, th a t w hite light is a composition of th e colours of the spectrum . In order to blend the p articu lar spectral colours he not only used prism s of the traditional form, b u t also introduced circular prism s shaped like a bracelet. A nd th is circu lar prism enabled him—in m y opinion quite accidentally—to observe, th a t w hite light appeared w hen the colours of the spectrum are m ixed together.
I t is rem arkable th a t all this knowledge failed to arouse in M arci’s mind th e question as to w h at really happens, w hen all spectral colours are concentrated in one point. Responsible for this is the fact th a t—as far as the properties of w hite light are concerned—M arci adhered to the conceptions advanced by ancient science.
M arci accepted the ideas of A ristotle relating to the four principles (elements) in N ature, and was of th e opinion th a t w hite lig h t is a principle too, y e t a more delicate an d m ore dignified one th an the four common principles of A ristotle. H e even alleged th a t these four common principles had th e ir very origin in the principle of w hite light. He rejected the old idea according to which spectral colours are a product obtained w hen m ixing w hite light w ith darkness. Y et his belief in th e superiority of w hite light over all other principles was the reason, w hy he considered th a t w h ite light is undergoing some kind of contam ination (degeneratio) w hile spectral colours are being formed, this contam ination being caused no t only by the pecularities of w hite light b u t also by th e properties of m atter.
Though M arci generally expressed th e opinion th a t w hite lig h t is a single substance, he also w rote in his w orks about light being a compound of ray s of different kinds—th a t is, of ray s present in th e w hite light which resem ble lum inous or illum inated objects, and of rays capable of being coloured—he calls the la tte r radii colorigeni.
The sum m ing up of all these thoughts and ideas w ould show, th a t the w hite light rem ained for M arci a singular substance, and th a t M arci failed to discover th a t light is a composition of th e spectral colours. He adhered to the ancient doctrines of singular elem ents and believed w hite light to be one of them.
A lthough the concept of an index of refraction w as unknow n to Marci, he nevertheless was—in my opinion—not fa r from discovering the composition of light. Here, in M arci’s reasoning, ancient science was the factor th a t im peded fu rth e r progress.
