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    [Thomas Edison] Charles L. Clarke Diagram Signed and Blueprint Depicting the Carbon Loop of Edison's First Light Bulb. "Chas. L. Clarke." Measuring 13" x 17" (sight) and drawn on linen in black ink, dated March 16, 1880, from "Edison's Laboratory/Note Book 66," the diagram features a drawing of the horseshoe filament of Edison's first light bulb with two semi-circles representing the "near outside edge" and the "opposite inside edge." Clarke, who was made Chief Engineer of the Edison Electric Lighting Co. in 1881, wrote in his personal papers regarding the carbon loop diagram. He says, in part:

    "...By careful measurements and comparison of the dimensions of these with the dimensions after carbonizing...[they] were found to contract 11/15ths of their former length...The loop was drawn on a large scale and the limits of the illuminated portions carefully projected for every fifteen degrees of the half-circle, and the vertical distance between the limits, as projected, gave the true length of the edge as seen from that direction..."

    Below the diagram is the following inscription which reads, in part:

    "The dimensions are given for the loop before carbonizing. All linear dimensions must be multiplied by 11/15 and surfaces by 121/225 to obtain the corresponding dimensions for the carbonized loop...The diagram represents the value of the vertical distance between the projected limits of the edges as seen from any point and it value is determined by the distance from the center to the curve measured on a vector in the direction of that point...The value for outside and inside edges should always be added unless the inside edge is supposed to be exactly behind the outside edge. The sum multiplied by the thickness of the paper before carbonizing and by 121/225 will be the effective illuminating area on the edge corresponding to the given direction."

    Clarke's signature on the bottom right is a later addition as it does not appear in the blueprint. Diagram is matted in cream and framed to an overall size of 19.75" x 23.75". Light toning and some minor soiling.

    The blueprint is an exact copy of the above diagram and measures 12" x 17" (sight), but, as stated, lacks Clarke's signature. Also matted in cream and framed to an overall size of 19.5" x 23.75".

    Charles Lorenzo Clarke was a member of both the American Institute of Electrical Engineers and the American Society of Mechanical Engineers, the Society of Edison Pioneers, the New York Electrical Society, and an honorary fellow of the American Electro-Therapeutic Association.

    Auction Info

    Auction Dates
    December, 2011
    8th-9th Thursday-Friday
    Bids + Registered Phone Bidders: 2
    Lot Tracking Activity: N/A
    Page Views: 2,367

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