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La dioptrique (in English Dioptrique, Optics, or Dioptrics), is a short treatise published in 1637 included in one of the ''Essays'' written with ''Discourse on the Method'' by Rene Descartes. In this essay Descartes uses various models to understand the properties of light. This essay is known as Descartes' greatest contribution to optics, as it is the first publication of the Law of Refraction. ==First Discourse: On Light== The first discourse captures Descartes' theories on the nature of light. In the first model, he compares light to a stick that allows a blind person to discern his environment through touch. Descartes says: :You have only to consider that the differences which a blind man notes among trees, rocks, water, and similar things through the medium of his stick do not seem less to him than those among red, yellow, green, and all the other colors seem to us; and that nevertheless these differences are nothing other, in all these bodies, than the diverse ways of moving, or of resisting the movements of, this stick. Descartes' second model on light uses his theory of the elements to demonstrate the rectilinear transmission of light as well as the movement of light through solid objects. He uses a metaphor of wine flowing through a vat of grapes, then exiting through a hole at the bottom of the vat. :Now consider that, since there is no vacuum in Nature as almost all the Philosophers affirm, and since there are nevertheless many pores in all the bodies that we perceive around us, as experiment can show quite clearly, it is necessary that these pores be filled with some very subtle and very fluid material, extending without interruption from the stars and planets to us. Thus, this subtle material being compared with the wine in that vat, and the less fluid or heavier parts, of the air as well as of other transparent bodies, being compared with the bunches of grapes which are mixed in, you will easily understand the following: Just as the parts of this wine...tend to go down in a straight line through the hole (other holes in the bottom of the vat )...at the very instant that it is open...without any of those actions being impeded by the others, nor by the resistance of the bunches of grapes in this vat...in the same way, all of the parts of the subtle material, which are touched by the side of the sun that faces us, tend in a straight line towards our eyes at the very instant that we open them, without these parts impeding each other, and even without their being impeded by the heavier particles of transparent bodies which are between the two.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dioptrique」の詳細全文を読む スポンサード リンク
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