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A RARE LACQUERED-BRASS MECHANICO MATHEMATICAL INSTRUMENT, ILLUSTRATING THE RATIO OF THE CIRCLE,
BY JOHN HARRIS, THE VERTICAL RECTANGULAR PLATE ENGRAVED ON THE UPPER EDGE WITH A SCALE DIVIDED 0-10, THE SILVERED-BRASS VERTICAL INSCRIBED ARC DIVIDED FROM THE APEX WITH LINES INSCRIBED 0-10 AT THE LOWER EDGE, MOVEABLE BY RACK AND PINION MOTION, WITH TWO SUB-DIVIDED SCALES 0-10, THE LOWER GEAR WORK WITH WHEEL DRILLED WITH EIGHT VIEWING HOLES TO READ AGAINST THE LOWER SCALE ARC, FIXED TO A RECTANGULAR LACQUERED-BRASS PLATE INSCRIBED WITH THE MAKER'S NAME AND DESCRIPTION OF INSTRUMENT, MOUNTED ON A MAHOGANY PLINTH BASE, OVERALL WIDTH -- 10IN. (25.4CM.)
SEE COLOUR ILLUSTRATION
BY JOHN HARRIS, THE VERTICAL RECTANGULAR PLATE ENGRAVED ON THE UPPER EDGE WITH A SCALE DIVIDED 0-10, THE SILVERED-BRASS VERTICAL INSCRIBED ARC DIVIDED FROM THE APEX WITH LINES INSCRIBED 0-10 AT THE LOWER EDGE, MOVEABLE BY RACK AND PINION MOTION, WITH TWO SUB-DIVIDED SCALES 0-10, THE LOWER GEAR WORK WITH WHEEL DRILLED WITH EIGHT VIEWING HOLES TO READ AGAINST THE LOWER SCALE ARC, FIXED TO A RECTANGULAR LACQUERED-BRASS PLATE INSCRIBED WITH THE MAKER'S NAME AND DESCRIPTION OF INSTRUMENT, MOUNTED ON A MAHOGANY PLINTH BASE, OVERALL WIDTH -- 10IN. (25.4CM.)
SEE COLOUR ILLUSTRATION