Measurement of magnetic inclination by Leonardo da Vinci. Paris Ms. A, folio 20. dated 1492. The upper word is "Magnet", the lower "Weight". In another sketch on the same folio we see two such boards separated in the landscape. The needles points towards the North Star at the right. After Leonardo the first notice of the inclination was 1542 by Georg Hartmann on a horizontal needle. First builder of a Leonardo like needle (with a horizontal axle) was Robert Norman in 1580. Presented in: Feldhaus, Franz Maria: Leonardo, der Techniker und Erfinder, (1922), p. 119.
/ レオナルド・ダ・ヴィンチ