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    Augustin-Jean Fresnel. Autograph Letter Signed.
    "A. Fresnel." One page in French, 7.25" x 8.5", Rennes; [circa 1816-1818]. In this letter to the French scientist François Arago in Paris, Fresnel, at the time posted in Rennes, comments on the possibility of developing a "mechanical theory of light waves" based on studies of light reflecting off various surfaces, and proposes that in this way the movement of light could be subsumed within the laws of motion, or physics. Arago must have made a proposition to Fresnel's uncle about working with Fresnel and the latter accepts with gratitude. The English translation of Fresnel's letter is presented here.

    "It is possible that the discord happening in the other directions, in opposition to the movement, makes it so that the light necessarily propagates in the direction that forms an angle equal to the angle of incidence. In this way we can conceive of how light loses as little intensity as it does when it reflects off a polished surface. If we could measure with precision the intensity of light reflected off polished surfaces versus the intensity of scattered light, we might be able to establish a mechanical theory of light waves and to subsume all light phenomena within general laws of motion. Eyesight would not suffice to pursue these observations; it would be necessary to consult a thermometer in order to observe the change in temperature of the mirror as the light rays hit it and thereby calculate the quantity of motion that has heated the mirror. My uncle has informed me of the kind offers you have made for me; I accept with equal parts pleasure and gratitude. Pray request a few months' extension of my leave on my behalf. I will go to Paris as soon as my 'Directeur Général' permits me to do so. I hope we will obtain it easily, especially at a time when road building faces such inactivity....PS: You must have received my previous letter containing the experimental results you requested."

    Augustin-Jean Fresnel (1788-1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light from the late 1830s until the end of the 19th century. He is best known for inventing the catadioptric (reflective/refractive) Fresnel lens and for pioneering the use of "stepped" lenses to extend the visibility of lighthouses, saving countless lives at sea. He died of tuberculosis at the young age of 39.

    Dominique François Jean Arago (1786-1853), known as François Arago, was a French mathematician, physicist, astronomer, and politician. Arago was an ardent supporter of Fresnel's optical theories, helping to confirm Fresnel's wave theory of light. The two worked together from 1815 to 1821 on experiments on the polarization of light, which led to the inference that the vibrations of the luminiferous ether were transverse to the direction of motion, and that polarization consisted of a resolution of rectilinear propagation into components at right angles to each other.

    Condition: Letter has the usual folds and a weakening of the paper where letter was sealed; otherwise good.

    Auction Info

    Auction Dates
    September, 2019
    4th Wednesday
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