Brillisour & Moline Dip Needle Compass by Municipal Instrument Co. (of Berwyn, Illinois). Compass is composed entirely of brass, with original glass lenses. Encased and sold in it's handsome original felt-lined leather case. American made. Mid-20th Century.
Dipping compasses were used as navigational aides primarily around the North and South poles. Earth's magnetic field is parallel to the surface at the equator, where traditional compasses are most reliable (measuring horizontal magnetic deflection) . The closer one is to the poles, the more vertical Earth's magnetic field is to the surface. Dip Needle compasses are used vertically to align with the direction of the magnetic field (measuring vertical magnetic inclination).
SN: 60534
Weight: 2 lbs. 4.8 oz.
Dimensions: 15” x 5” x 1.75”