An Amplitude Compass Brazilian rosewood double box bronze gimbal with two freedom degrees, interior with polychrome decoration, compass rose black-printed on paper, bronze transportation handles Portuguese 19th C. (1st decade) signs of use, two loose corners, maintenance required marked JOZÉ DA CRUS A FES EM LISBOA NO ANNO DE 1808 Dimensões (altura x comprimento x largura) - 19 x 32 x 32 cm Notes: used by Portuguese navigators to measure the magnetic bearing of the Sun’s rising or setting, to compare its value with the true bearing, in order to establish the magnetic variation of the compass.
Used with the latitude, the knowledge of the compass variation allowed the ships much safer landings.